(2022) 28:27
Zhang et al. Molecular Medicine
https://doi.org/10.1186/s10020-022-00455-y

Molecular Medicine

Open Access

REVIEW

Molecular hydrogen is a potential protective
agent in the management of acute lung injury
Yan Zhang, Jin Zhang and Zhiling Fu*

Abstract
Acute lung injury (ALI) and acute respiratory distress syndrome, which is a more severe form of ALI, are life-threatening clinical syndromes observed in critically ill patients. Treatment methods to alleviate the pathogenesis of ALI have
improved to a great extent at present. Although the efficacy of these therapies is limited, their relevance has increased
remarkably with the ongoing pandemic caused by the novel coronavirus disease 2019 (COVID-19), which causes
severe respiratory distress syndrome. Several studies have demonstrated the preventive and therapeutic effects ofmolecular hydrogen in the various diseases. The biological effects of molecular hydrogen mainly involve anti-inflammation, antioxidation, and autophagy and cell death modulation. This review focuses on the potential therapeutic
effects of molecular hydrogen on ALI and its underlying mechanisms and aims to provide a theoretical basis for theclinical treatment of ALI and COVID-19.
Keywords: Acute lung injury, COVID-19, Molecular hydrogen, ROS, Inflammation, Autophagy, Apoptosis, Pyroptosis
Background
The lungs not only are the primary location where gas
exchange occurs in mammals but also have the largest epithelial surface in that is direct contact with theexternal environment. Therefore, the lungs are the primary target for many airborne pathogens, toxicants,
and allergens that cause pneumonia, acute lung injury(ALI), and acute respiratory distress syndrome (ARDS)(Kumar 2020). ALI and its more severe form, ARDS, arelife-threatening clinical syndromes that occur in criticallyill patients (Hughes and Beasley 2017); these syndromes
manifest as increased microvascular permeability, alveolar and interstitial edema with normal cardiac fillingpressures, hyaline membrane formation, and atelectasis.
Patients with ALI and ARDS exhibit symptoms such asacute hypoxic respiratory insufficiency or respiratory
failure (Slutsky 2001). Despite advances in the treatmentof preclinical and clinical conditions, the morbidity and*Correspondence: fuzl323@sj-hospital.org
Department of Anesthesiology, Shengjing Hospital of China Medical
University, Shenyang 110004, People’s Republic of China

mortality associated with ALI and ARDS are alarmingly
high (Hayes et al. 2012), particularly since the outbreak ofcoronavirus disease 2019 (COVID-19) caused by severe
acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
on December 31, 2019, in Wuhan, China, which subsequently resulted in a pandemic. Therefore, finding anddeveloping new drugs so as to effectively treat ALI/ARDS
is imperative; these may also be useful in the treatment of
COVID-19.
In recent times, treatment to alleviate the pathogenesis of ALI has improved to a great extent, and existing
therapies can be divided into supportive intervention
and pharmacological treatment. Supportive intervention,such as lung-protective mechanical ventilation, together
with adjunctive approaches, such as prone positioning and the use of neuromuscular blocking agents, hasdecreased mortality (Slutsky and Ranieri 2013). Pharmacological treatments involve the use of corticosteroids, antioxidants, neuromuscular blocking agents, fluid
management, and stem cell-based therapeutics for treating influenza- and coronavirus-induced ALI (Shafeeq
and Lat 2012; Du et al. 2020; Mrityunjaya et al. 2020);© The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which
permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to theoriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images orother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line
to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory
regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of thislicence, visit http://creativecommons.org/licenses/by/4.0/.

Zhang et al. Molecular Medicine(2022) 28:27

however, most have been unsuccessful till date (Villar
et al. 2019).
Molecular hydrogen is colorless and odorless and thelightest chemical element in the earth’s atmosphere.
For a long time, it was accepted that molecular hydrogen remains inert in mammalian cells. In 2007, Ohsawa
et al. discovered that molecular hydrogen could selectively reduce hydroxyl radicals (·OH) and peroxynitrite­(ONOO−), which are highly strong oxidants, in cells,
thereby suppressing brain injury in ischemia/reperfusion (I/R) injury and stroke in a rat model (Ohsawa et al.
2007). In 2001, studies demonstrated that high-pressure
molecular hydrogen gas has anti-inflammatory properties that can cure parasite-induced animal liver inflammation (Gharib et al. 2001). Subsequent cellular andanimal studies as well as clinical experiments in diverse
biomedical fields have demonstrated the preventive andtherapeutic effects of molecular hydrogen in variousorgans, including the brain, heart, lung, pancreas, andliver, through its antioxidative stress, anti-inflammatory,
antiapoptotic, and various other biological effects (Qiu
et al. 2011; Hou et al. 2012; Xie et al. 2012; Luo et al. 2015;
Liu et al. 2020b). The action of molecular hydrogen in the
body is moderate and no side effects have been identified so far. It can be conveniently administered throughvarious modes, including gas inhalation, hydrogen-richsaline (HRS) injection, hydrogen-rich water (HW), andas nanocrystals to achieve targeted delivery and controlled release (Kawamura et al. 2020). A simple methodof administering molecular hydrogen is inhalation using
a ventilator circuit, face mask, or nasal cannula. Hydrogen-dissolved water or HW is portable, safe, and easily
administered. Molecular hydrogen can easily penetrate
the skin, and a warm HW bath can be used therapeutically in daily life (Koyama et al. 2014; Ohta 2014). HRS
injections may deliver more accurate molecular hydrogendoses (Ge et al. 2017). Molecular hydrogen utilized as
nanoparticles exhibits high bio-reductivity and effective
scavenging of cytotoxic OH (Zhang et al. 2019).
So far, the preventive and therapeutic effects of molecular hydrogen for various lung diseases, such as ALI,
chronic obstructive pulmonary disease, asthma, andpulmonary arterial hypertension, have been extensively
investigated (Kishimoto et al. 2015; Audi et al. 2017;
Wang et al. 2020). China’s National Health Commission(7th trial ed NHC: Bejing, 2020) and the Chinese Center
for Disease Control and Prevention (6th ed. CDCP:
Bejing, 2020) have recommended effective oxygen therapy as a component of the general treatment for patientswith COVID-19; they have also stated that a mixture ofmolecular hydrogen and oxygen (66.6% molecular hydrogen to 33.3% ­O2) for inhalation yields better results thanoxygen alone (Conti et al. 2020; Ostojic 2020).

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In this article, we summarize the most recently published literature concerning the application of molecular hydrogen for ALI caused by various pathologicalprocesses and briefly discuss the potential mechanisms
underlying the action of molecular hydrogen in ALI. We
hope that this review will facilitate our understandingof the therapeutic and preventive activities of molecular hydrogen and provide information that can be used
to further the treatment of ALI and COVID-19 in the
future.

Pathophysiology of acute lung injury (ALI)
ALI/ARDS is characterized by a proteinaceous alveolar
exudate, lung edema, endothelial and epithelial injury
induced by dysregulated inflammation, and the destruction of alveolar/capillary barrier. It is also accompanied
by an influx of neutrophils into the interstitium andbronchoalveolar space (Grommes and Soehnlein 2011)(Fig. 1). Based on the severity of hypoxemia, the 2012
Berlin Conference proposed the following three categories of ARDS: mild (200 mm Hg < ­PaO2/FiO2 ≤ 300 mmHg), moderate (100 mm Hg < ­PaO2/FiO2 ≤ 200 mm Hg),and severe (­PaO2/FiO2 ≤ 100 mm Hg) (Ranieri et al.
2012). ALI can be caused by a plethora of direct or indirect insults to the lung (Sharp et al. 2015). Direct factors include severe pulmonary infection, pulmonary
embolism, and lung contusion, which can lead to serious alveolar lesions, whereas indirect factors include
sepsis, trauma, massive transfusion, pancreatitis, fatembolism, and major surgery, which can initially trigger
uncontrolled systemic inflammation, followed by multiple inflammatory cell infiltration and eventually, vascularendothelial injury (Bayat and Sachs 2012; Su et al. 2012)
The pathogenesis of ALI includes a dysregulated inflammatory response, excessive oxidative stress, and dysregulated cell apoptosis and autophagy.
Inflammation

An inflammatory response is the physiological responseof the body to various stimuli and damages. However,uncontrolled inflammation in the lungs or the wholebody contributes to the main pathogenesis of ALI/ARDS(Fan and Fan 2018). Different types of cells in the lungtissues, including neutrophils, macrophages, endothelial
cells (ECs), and alveolar epithelial cells (AECs), participate in the inflammatory process; these are accompaniedby the release of a cascade of inflammatory mediatorsfrom inflammatory cells (Herold et al. 2013; Nieman et al.
2015).
Neutrophils are the first to be recruited to the site of
inflammation, and neutrophil recruitment into the lungis characteristic of ALI. Generally, neutrophils havea potent antimicrobial armor that includes oxidants,

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Fig. 1 The pathogenesis of acute lung injury involves dysregulated inflammation and alveolar and endothelial barrier dysfunction

proteinases, and cationic peptides. However, the dysregulated release of these microbicidal compounds into theextracellular space can also paradoxically damage hosttissues (Grommes and Soehnlein 2011).
Macrophages are highly plastic cells. The common
inflammatory response involves the accumulation of proinflammatory M1 macrophages at the site of injury, followed by the appearance of anti-inflammatory/wound
repair M2 macrophages; the balance in the activity ofthese macrophage subpopulations determines the outcome of the pathogenic response (Laskin et al. 2019).
Macrophages recognize pathogen-associated molecularpatterns (PAMPs) and trigger innate immune responses
to activate host defenses (Wu et al. 2015), thereby playing
an important role in the pathogenesis of ALI/ARDS bymodulating inflammatory responses and repairing damaged lung tissues (Huang et al. 2018).
The pulmonary endothelium is an active continuous
monolayer comprising ECs that internally line the bloodvessels and mediates key processes in lung homeostasis.
ECs play a major role in ALI/ARDS pathogenesis by altering hemostasis, weakening barrier function, and mediating intercellular signalling (Orfanos et al. 2004). EC
dysfunction is also an important feature of hospitalized
patients with COVID-19. In patients with COVID-19,
the level of von Willebrand factor, which is a circulating
adhesive glycoprotein secreted by ECs, is considerably
elevated (Panigada et al. 2020), directing both endothelial infection with SARS-CoV-2 and the indirect damage caused by inflammation in COVID-19-associatedcoagulopathy (Iba et al. 2020). In addition, SARS-CoV-2
binds to and downregulates angiotensin-converting
enzyme 2, resulting in remarkably increased vascularpermeability in the lungs (Amraei and Rahimi 2020).
Moreover, a common complication of COVID-19 is the“cytokine storm.” Cytokines can cause vascular leaks in
the lung alveolar–endothelial interface and promote ALI(Vassiliou et al. 2020).
AECs can be categorized into two types: types I and II.
Type I AECs are involved in facilitating gaseous exchange
and can recognize pathogens. Type II AECs serve as
innate immune cells and secrete surfactant proteins on
their apical side. AECs are also potent regulators of the
primary immune response against invading pathogens
and act by releasing various immune mediators, suchas antimicrobial peptides and cytokines, and by directlyinteracting with macrophages and neutrophils. However,the prolonged activation of AECs may harm the hostthrough the release of a large amount of proinflammatory
cytokines and chemokines and increase apoptosis (Hippenstiel et al. 2006; Kumar 2020).
There are several signal transduction pathways modulating the inflammatory process in ALI/ARDS such as
nuclear factor kappa-B (NF-κB); the nucleotide-binding oligomerization domain-, leucine-rich repeat, andpyrin domain-containing 3 (NLRP3); mitogen-activatedprotein kinase (MAPK); and Toll-like receptor (TLR)
signaling. NF-κB is considered the master regulatorof inflammatory responses. It activates a series of proinflammatory transcriptional programs to shape theZhang et al. Molecular Medicine(2022) 28:27

inflammatory response. Animal studies have establishedthat this transcription factor is an important mediator in ALI/ARDS (Rahman and Fazal 2011). In addition,
the high-mobility group box-1 protein (HMGB1), a lateinflammatory mediator, can induce ALI by promoting
NF-kB nuclear translocation, which can result in therelease of inflammatory cytokines that further promote
the release of HMGB1, resulting in a positive feedback
loop that amplifies the inflammatory cascade (Entezari
et al. 2014; Lee et al. 2018). The NF-κB pathway offersa variety of potential molecular targets for therapeuticintervention, and agents aimed at modulating the NF-κB
pathway may alleviate ALI/ARDS (Wright and Christman 2003).
The NLRP3 inflammasome can be activated by theassembly of the NLRP3/apoptosis-associated speck–like
protein/pro-caspase 1 protein complex, leading to therelease of interleukin (IL)-1β (Martinon et al. 2002; Grosset al. 2011). Both the NLRP3 inflammasome and IL-1β
mediate inflammation and contribute to inflammasomeassociated pyroptosis (a mode of cell death) during ALI
and ARDS (Ganter et al. 2008; Lee et al. 2016). NLRP3
activation is also involved in the pathogenesis of severe
COVID-19, particularly in the formation of a cytokine
storm. Therefore, targeting this pathway may provide
insights for the treatment of severe COVID-19 (Freeman
and Swartz 2020; Saeedi-Boroujeni et al. 2021).
p38 MAPK involves cell growth, differentiation, proliferation, migration, apoptosis, and inflammation (Pearson et al. 2001) and is upregulated in ALI (Ma et al. 2015;
Xiong et al. 2016). Blocking of p38 MAPK signaling
pathway alleviated the expression of proinflammatory
cytokines and NLRP3 inflammasome in LPS-induced
ALI (Li et al. 2018), bearing a potential for ALI therapy.
TLRs are an ancient evolutionarily family of patternrecognition receptors that play a central role in immune
response by identifying PAMPs from pathogens anddamage-associated molecular patterns from dying or
injured cells. In lipopolysaccharide (LPS)-induced ALI,LPS binds to Toll-like receptor 4 (TLR4) and stimulates
the TLR4-dependent inflammatory responses, including
the activation of the TLR4/MyD88/NF-kB and TLR4/
TRIF/IRF3 pathways (Togbe et al. 2007; Kuzmich et al.
2017). Blocking the TLR4 pathway is a potential strategy
to alleviate LPS-induced ALI.
Oxidative stress

Reactive oxygen species (ROS) include free radicals, such
as ·OH, superoxide anion radicals ­(O2·−), and non-freeradical species such as singlet oxygen (1O2) and hydrogen
peroxide ­(H2O2). They are generated inside the body by
aerobic organism as a byproduct of energy metabolism
through oxidative phosphorylation (Sies 2015). Normally,

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there are antioxidant defense systems in the cells that
protect the biological systems from free radical toxicity
such as superoxide dismutase (SOD), catalase (CAT),glutathione peroxidase (GSH-Px), and heme oxygenase-1(HO-1) (Birben et al. 2012; Kellner et al. 2017). The dysregulation of ROS due to an imbalance in ROS generation and local antioxidant defenses results in oxidative
stress, which causes oxidative damage to proteins, lipids,and nucleic acids (Ornatowski et al. 2020). During thepathogenesis of ALI/ARDS, the activation of neutrophilssequestered in pulmonary circulation can result in therelease of free radicals and ROS, which leads to endothelial dysfunction and disruption, and is responsible forthe principal clinical manifestations of this syndrome(Chabot et al. 1998). Recent studies suggest that oxidative stress plays an important role in viral infections, suchas those caused by severe acute respiratory syndrome
coronavirus and SARS-CoV-2, particularly in the morecritical ARDS phase of infection (Cecchini and Cecchini
2020; Muhoberac 2020; Ntyonga-Pono 2020).
The transcription factor nuclear factor erythroid
2-related factor 2 (Nrf2) is a major regulator of the cytoprotective antioxidative protein expression products. The
activation of Nrf2 signaling plays an essential role in preventing injury induced by oxidative stress to cells and tissues. The redox balance maintained by Nrf2 is important
for the airways, and Nrf2 activation confers protective
effects on various lung disorders including ALI/ARDS(Liu et al. 2019; Lee et al. 2021). Moreover, Nrf2 contributes to the regulation of the HO-1 axis and NF-κB pathway, both of which are potent anti-inflammatory targets.
Nrf2 also participates in macrophage metabolism and theexpression of inflammatory mediators (Saha et al. 2020).
Therapeutic intervention using reductants and chelators could be employed for ALI/ARDS. In both in vitro
and in vivo experimental models, natural anti-oxidants,
such as curcumin and garlic extract, decreased inflammation by activating Nrf2 and inducing Nrf2-regulated
gene expression. However, these therapies remain to betranslated into actual changes for patients with ARDS,
and systematic studies must be conducted in human trials (Patel et al. 2018). Recently, vitamin C has been studied as a potential antioxidant to treat sepsis. Patients withsepsis have been found to be deficient in vitamin C, andhigh-dose intravenous vitamin C administration had adose-dependent effect on the prevention of multiorgan
failure and ARDS. However, considering its safety profile,current treatment is only justified for compassionate use(Kashiouris et al. 2020).
Dysregulated autophagy and apoptosis

Autophagy is a highly conserved proteostatic process
involving the degradation of cellular components such

Zhang et al. Molecular Medicine(2022) 28:27

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as lipids and misfolded proteins. This process helps
maintain cellular and tissue homeostasis in response
to numerous cellular stressors (Wang et al. 2019a).
Autophagy plays a protective role in ALI/ARDS triggered by LPS, sepsis, and hyperoxia by regulating inflammatory-oxidative stress, apoptosis, pathogen clearance
mechanisms, and balancing immune regulation, thereby
avoiding recurrent exacerbations and disease progression
in lungs (Yuan et al. 2012; Deretic et al. 2013; Junkins
et al. 2013; Liu et al. 2013a).
Dysfunctional autophagy gives rise to various pathological states (Zhu et al. 2017; Mo et al. 2018). Recently,
evidence suggested that SARS-CoV-2 inhibits autophagolysosomal formation and autophagy flux with impaired
viral clearance and immune dysfunction. Therefore, targeting autophagy may prevent the replication of SARSCoV-2 as a treatment for COVID-19 and allow a bettertuning of inflammatory responses (Pehote and Vij 2020).
Autophagy is a complex process that can be harmful in excess. For instance, LPS-induced autophagy ofalveolar macrophages in ALI promotes their transformation from type M2 to M1, which enhances apoptosis(Qiu et al. 2021). In addition, inhibition of autophagy intype II AECs is associated with alleviated inflammation
and apoptosis (Zhang et al. 2015). Studies have foundthat autophagy in the septic lung represents a protective
response; however, excessive accumulation of autophagosomes may play a maladaptive role in the late stage ofsepsis, thus leading to ALI. Therefore, autophagy flux isa novel therapeutic target for the management of sepsisinduced ALI (Lo et al. 2013).

of apoptosis and pulmonary vascular permeability (Gillet al. 2015). In addition, increased apoptosis of AECs andalveolar macrophages can be observed, which results in
the release of tumor necrosis factor-α (TNF-α) and transforming growth factor-β1, resulting in inflammation andprogression from ARDS to fibrosis (Chapman 1999; Yanget al. 2018; Cui et al. 2020; Zhou et al. 2020a). Therefore,
interventions targeting apoptosis may be instrumental
for ALI/ARDS therapy.
Pyroptosis is a form of programmed necrosis triggeredby inflammasomes, which detect cytosolic perturbations
and drive the activation of caspase-1 or caspase-11/4/5.
This causes cleavage of gasdermin D, separating its
N-terminal pore-forming domain from the C-terminal
repressor domain. Thereafter, the pore-forming domain
oligomerizes, forming large pores in the membrane anddriving swelling and membrane rupture (Kovacs andMiao 2017). Pyroptosis can occur in different cell types
in ALI in a mouse model, including macrophages, neutrophils, and ECs, and plays an important role in thedevelopment of ALI (Liu et al. 2021). Inflammasomes areindispensable in the process of caspase-induced pyroptosis. The NLRP3 inflammasome is the most studied
inflammasome, and it is involved in the activation of caspase-1 in the caspase-1-dependent pyroptosis pathway.
At present, the inhibition of the NLRP3 inflammasome
is an attractive and effective treatment for ALI caused byvarious pathogenetic factors such as LPS-induced ALI,
ventilator-induced lung injury (VILI), and hyperoxiainduced ALI (HILI) (Kuipers et al. 2012; Hong et al. 2019;
Wang et al. 2019b).

Apoptosis and pyroptosis in ALI

Biological effects of molecular hydrogen
The potential mechanisms underlying the biologicaleffects of molecular hydrogen remain unclear. Molecular oxygen may exert anti-inflammatory and antioxidant
activities and modulate autophagy pathways and cell
death pathways (apoptosis and pyroptosis) (Table 1).

Apoptosis is important in developmental biology and tissue remodeling during repair (Majno and Joris 1995). It
is triggered by the two following fundamental signaling
pathways: the extrinsic death receptor-mediated pathway and the intrinsic mitochondria-dependent pathway(Olson and Kornbluth 2001; Thorburn 2004).
Emerging evidence has suggested that the upregulation of pulmonary cell apoptosis is a pathophysiological consequence of various environmental stresses suchas hypoxia, hyperoxia, oxidants, and LPS; these contribute to the initiation and progression of ALI and
ARDS (Chopra et al. 2009). For instance, a clinical trial
showed that excessive pulmonary EC apoptosis damages
endothelial integrity and subsequently results in pulmonary endothelial barrier dysfunction, which has been
observed in patients with severe ARDS (Abadie et al.
2005). Animal studies have demonstrated that inflammation and apoptosis are interrelated. For instance, p38
MAPK activation is linked to the initiation of the apoptotic cascade and plays a critical role in the development

Anti‑inflammatory action

Molecular hydrogen exhibits anti-inflammatory activities
in various injury models. In animal experiments, it downregulates the expression of proinflammatory and inflammatory cytokines, such as IL-1β, IL-6, TNF-α, HMGB-1,
and intercellular cell adhesion molecule-1 (ICAM-1)(Buchholz et al. 2008; Tian et al. 2017). It also modulates the function of various inflammatory cells during
inflammation, e.g., in LPS-induced injury, molecularhydrogen treatment substantially inhibited the increasein M1 cells, increasing M2 polarization of macrophages(Ning et al. 2018; Qiu et al. 2021); molecular hydrogencan inhibit the recruitment of neutrophils to lesion sites(Liu et al. 2015a), particularly inhibiting the adhesion

Zhang et al. Molecular Medicine(2022) 28:27

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Table 1 The proposed biological effects of molecular hydrogen
Biological effects

Main mechanisms

References

Anti-inflammation

Inhibits IL-1β, IL-6, TNF-α, HMGB-1, ICAM-1;
Inhibits M1 polarization, increases M2 polarization of macrophages;
Inhibits the recruitment of neutrophils to lesion sites, inhibits
adhesion of polymorphonuclear neutrophils to ECs;
The involved pathways: NF-κB, NLRP3, TLR4, Nrf2

Buchholz et al. (2008), Kawamura et al. (2013), Xiao et al. (2013),
Ren et al. (2014), Chen et al. (2015b), Liu et al. (2015a), Shi et al.
(2015), Xie et al. (2015), Zhai et al. (2015), Tian et al. (2017), Ninget al. (2018), Yu et al. (2019), Zou et al. (2019), Ming et al. (2020),
Yang et al. (2020), Qiu et al. (2021)

Anti-oxidation

Directly scavenges ·OH and ­ONOO−;
activates Nrf-2/ HO-1;
upregulates the expression of SOD, CAT, GSH-Px, downregulates NADPH oxidase; hormesis through increasing ROS

Ohsawa et al. (2007), Yu and Zheng (2012), Shinbo et al. (2013),
Hirayama et al. (2018), Zhao et al. (2019)

Modulates autophagy Promotes autophagy when autophagy is insufficient; inhibits
autophagy when excessive autophagy disrupts cell homeostasis

Zhang et al. (2015), Yao et al. (2019), Chen et al. (2020a), Zhuang
et al. (2020), Qiu et al. (2021)

Modulates cell death

Cai et al. (2008), Kawamura et al. (2010), Du et al. (2016), Nieet al. (2021), Zhang et al. (2021)

Antiapoptosis: inhibiting Bax, caspase-3, and caspase-8,
upregulating Bcl-xl and Bcl-2
Inhibits pyroptosis by inhibiting oxidative stress, NLRP3 and­mitoKATP/ERK1/2/p38 MAPK signaling pathwaysof polymorphonuclear neutrophils to ECs to modulate
the permeability of the vascular endothelium (Xie et al.
2015).
The anti-inflammatory effect of molecular hydrogen
may involve inhibiting several inflammatory pathways,
including the NF-κB pathway. Molecular hydrogen inhibits NF-κB activity, decreasing inflammatory factors in avariety of pathological models in rats or mice, such as
cecal ligation and puncture-induced ALI, hepatectomyinduced postoperative cognitive dysfunction, ovalbumin-induced asthma, smoke inhalation injury, sodium
taurocholate-induced acute pancreatitis induced acuterenal injury (Xiao et al. 2013; Chen et al. 2015b; Shi et al.
2015; Zhai et al. 2015; Tian et al. 2017). HRS downregulated the expression of NLRP3 that is involved in lungand limb and intestinal I/R injuries, as well as in acutepancreatitis in rats (Ren et al. 2014; Zou et al. 2019; Yanget al. 2020). Molecular hydrogen inhibits the TLR4-mediated inflammatory pathway, improving hyperglycemia inrats with type 2 diabetes mellitus (Ming et al. 2020). It
also regulates Nrf2 pathways, inhibiting oxidative stressinduced inflammatory lung disease in rats (Kawamura
et al. 2013).
Antioxidative action

Molecular hydrogen can directly scavenge the strongoxidants ·OH and O­ NOO− (Ohsawa et al. 2007; Shinbo
et al. 2013). Owing to its intrinsic characteristics, suchas nonpolarity and a small molecular weight, molecularhydrogen can easily penetrate the membrane and accumulate in the lipid phase; however, it does not affectnormal metabolic redox reactions. In addition, molecular hydrogen can indirectly reduce oxidative stress byregulating gene expression. For instance, it can activate

Nrf-2, enhancing the expression of HO-1, which is adownstream antioxidant of Nrf-2. It can also upregulate
the expression of SOD, CAT, and GSH-Px and downregulate the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in rats (Yu and Zheng
2012; Zhao et al. 2019).
In most cases, molecular hydrogen demonstrated anantioxidative activity. However, a clinical trial showedthat inhaling a mixture of 1.2–1.4% molecular hydrogen–air increased urinary 8-hydroxy-2′-deoxyguanosine,a marker of oxidative stress, levels. This phenomenon ofincreasing ROS is associated with hormesis (Hirayama
et al. 2018). In the process of hormesis, mitochondrial
stress activates signaling pathways in cells to make themless susceptible to oxidative damage (Yun and Finkel2014). The effect of increasing ROS on molecular hydrogen is similar to that induced by short and mildly strenuous exercise, and this may facilitate activating the Nrf2
anti-oxidative pathway (Hirayama et al. 2018).
Action on autophagy

Besides having a direct anti-inflammatory effect, molecular hydrogen can modulate autophagy by downregulating
the expression of NF-κB and MAPK and upregulating
HO-1 activity (Liu and Zhang 2017; Ohta 2021; Slezak
et al. 2021), suggesting that there is an intimate crosstalk
between autophagy, inflammation, and ROS.
Molecular hydrogen promotes autophagy in conditions
in which it is activated but not sufficient to overcome
stress. For instance, in sepsis, an increase in endoplasmic reticulum stress (ERS) impaired autophagy. By
activating the autophagy pathway, molecular hydrogen
alleviated ERS and mitigated inflammation and organ
injury in mice (Chen et al. 2020a). Similarly, through theZhang et al. Molecular Medicine(2022) 28:27

mTOR-autophagy signaling pathway, molecular hydrogen activated autophagy and attenuated sepsis-induced
neuroinflammation in both in vivo and in vitro experiments (Zhuang et al. 2020). Furthermore, molecularhydrogen can activate selective autophagy pathways suchas mitophagy (sequestration of damaged mitochondria tolysosomes). Through phosphatase and tensin homologinduced kinase 1 (PINK1)/Parkin-induced mitophagy,
HRS could alleviate the inflammation response and apoptosis in in vivo and in vitro experiments in myocardial I/R
injury (Yao et al. 2019). In these studies, autophagy represents an inducible response to stress and acts as an initialprotective response to cell death (Ryter and Choi 2010).
Impaired functioning of autophagy, such as impaired
autophagosome-lysosome fusion, may cause the accumulation of autophagosomes (Lo et al. 2013). In such a situation, molecular hydrogen may help promote autophagy
and increase the flow of autophagy to alleviate the harmful effect of stress.
In contrast, molecular hydrogen exerts an antiautophagy effect when excessive autophagy disrupts cellhomeostasis. For instance, in an LPS-induced ALI rat
model, molecular hydrogen was shown to protect type
II AECs by reducing the expression of autophagy-related
proteins, thus decreasing the number of autophagosomes(Zhang et al. 2015). It also suppressed the autophagy ofalveolar macrophages, thus regulating their polarization
and apoptosis (Qiu et al. 2021). Molecular hydrogen may
alter cell fate by regulating the balance between apoptosis
and autophagy.
This dual effect of molecular hydrogen on autophagy
may be explained by different levels of autophagy due
to different stresses and treatment durations (Qiu et al.
2021). Autophagy is a double-edged sword; while it protects cells from stress-induced injury, when excessive,it disrupts cellular homeostasis and results in abnormal
pathological conditions.
Detailed mechanisms of molecular hydrogen on
autophagy still need to be clarified. Nonetheless, molecular hydrogen exerts protective effects by modulating
autophagy and can harness autophagy pathways to maintain body hemostasis and protect cells from harmful
stresses.
Action on cell death

In most conditions, molecular hydrogen exerts antiapoptotic effects by modulating the expression of apoptosisassociated proteins, such as inhibiting the expression of
the proapoptotic proteins, such as B-cell lymphoma-2-associated X-protein (Bax), caspase-3, and caspase-8, andupregulating the expression of antiapoptotic proteins,
such as B-cell lymphoma-extra-large (Bcl-xl) and B-cell
lymphoma-2 (Bcl-2) (Cai et al. 2008; Kawamura et al.

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2010; Du et al. 2016). Additionally, molecular hydrogencan inhibit apoptosis by reducing inflammation and oxidative damage but activating autophagy (Yao et al. 2019;
Qiu et al. 2020).
Molecular hydrogen can affect pyroptosis in various
animal models by inhibiting oxidative stress and NLRP3mediated pyroptosis, alleviating myocardial I/R injury
in rats (Nie et al. 2021). Post-conditioning with hydrogen gas ameliorated subarachnoid hemorrhage-induced
neuronal pyroptosis through the m­ itoKATP/ERK1/2/p38
MAPK signaling pathway in rats (Zhang et al. 2021). In
the lung, the inflation of 3% molecular hydrogen during the cold ischemia phase alleviated lung I/R injury byinhibiting pyroptosis and improving graft function in rats
(Zheng et al. 2021a). It is conceivable that modulating
pyroptosis is an important mechanism by which molecular hydrogen plays a protective role in ALI.

Effect of molecular hydrogen on ALI
Molecular hydrogen protects and restores epithelial
and endothelial barrier function in the lung

Through its anti-inflammatory and antioxidative effects
and by modulating autophagy and cell death, molecular hydrogen markedly alleviates tissue damage in thelung; in particular, it helps in restoring the lung barrier
function.
As mentioned above, type I AECs are highly specialized for the gas exchange between alveoli and capillary
blood in the lung. They are also involved in ion and watertransport, the regulation of cell proliferation, and peptide
metabolism signaling pathways in the peripheral lungs(Herzog et al. 2008). Type I AECs have ion channels andpumps for transcellular sodium transport (Johnson et al.
2002). Among these, aquaporins (AQPs) facilitate water
flux across cell membranes and provide a transcellularroute for water transport across epithelia (Wittekindt
and Dietl 2019). Therefore, AQPs, particularly AQP1 and
AQP5, are of tremendous significance in lung pathophysiology, such as in that of ALI (Yadav et al. 2020).
Molecular hydrogen has been shown to protect epithelial function in ALI in animal experiments. It alleviated
AEC apoptosis (Shi et al. 2012), which potentially helps
maintain the integrity of the epithelial barrier. It also protects AQP function. In our studies, we demonstrated thatin LPS-induced ALI, the expression of AQP1 and AQP5
in the rat lung was downregulated. HRS treatment inhibited the activation of p38 MAPK and c-Jun N-terminal
kinase, decreasing the inhibitory effect of LPS on AQP1and AQP5 (Liu et al. 2016; Tao et al. 2016). These effects
of molecular hydrogen help to keep the alveolar space
relatively free from fluid overload, improving alveolar gas
exchange to alleviate ALI.

Zhang et al. Molecular Medicine(2022) 28:27

In addition, HRS can protect type II AECs in LPSinduced ALI by inhibiting excessive autophagy (Zhang
et al. 2015), and type II AECs are involved in the metabolism of pulmonary surfactants and help maintain a sufficient respiratory surface area of the lungs at the end of
expiration (Lopez-Rodriguez and Pérez-Gil 2014) (Fig. 2).
In addition to the epithelial barrier dysfunction, severe
disturbances to the endothelial barrier are involvedin ALI and ARDS (Ware and Matthay 2000). Restoring endothelial barrier function can effectively improve
ALI outcomes. Endothelial permeability is maintainedby transcellular and paracellular routes. The transcellular route is moderated by caveolae-mediated vesiculartransport, whereas the paracellular route is supported
by interendothelial junctions (including tight junctions(TJs) and adherens junctions (AJs)), which connect
adjacent ECs with the monolayer (Komarova and Malik2010). Occludin and vascular endothelial (VE)-cadherin
are major components of TJ and AJ components, respectively. Occludin and claudins are linked to the zonula
occludens and other protein complexes, mediating theinteraction between adhesion molecules and actin filaments (Balda and Matter 2016). VE-cadherin maintains
firm EC–EC junctions by binding its cytoplasmic domain
to α-catenin and β-catenin (Dejana et al. 1995). In ALI,
TJs and AJs in pulmonary microvascular endothelial cells(PMVECs) are damaged first, leading to a high endothelial permeability (Li et al. 2020). In addition to interendothelial junctions, another critical factor that influences
endothelial permeability is the endothelial cytoskeleton,
which maintains endothelial cell–cell adhesion by delicately regulating endothelial contractility and junctionalorganization. It is mainly regulated by small guanosine
triphosphatases (GTPases) RhoA, Rac1, Cdc42) or Rap1
(Spindler et al. 2010). RhoA, the most studied proteinin the Rho family, is activated in ALI, leading to the

Page 8 of 18

activation of Rho kinases (ROCK) and myosin light chain
kinase, which phosphorylates the light chain of myosin
and induces actomyosin contractility, leading to a weakening of endothelial cell–cell adhesion (Shen et al. 2010;
Schnittler 2016; Yin et al. 2019).
In vitro studies showed that molecular hydrogen alleviates the hyperpermeability of the vascular endothelium in ALI, represented by decreasing the fluorescein
isothiocyanate-dextran flux and increasing the transendothelial electrical resistance of EC (Xie et al. 2015; Yu
et al. 2015). In LPS-induced endothelial injury, molecularhydrogen could increase the expression of VE-cadherin
and influence its distribution (as manifested by comparatively even and complete at the cell joints (Yu et al. 2015),
recover the reduced expression of occludin, and ameliorate the excessive expression of ROCK and RhoA (Yanget al. 2016; Li et al. 2020). Molecular hydrogen can also
reduce the expression of ICAM-1 and its release from thecell, in addition to inhibiting the adhesion of monocytes
to EC (Chen et al. 2015a; Xie et al. 2015; Yu et al. 2015).
Physically, EC apoptosis is beneficial because it replaces
damaged ECs infected with intracellular pathogens byhealthy cells. However, under stress conditions, apoptosis may become a pathophysiological consequenceof these stimuli (Chambers et al. 2018) and cause detrimental effects on the body. For instance, it disrupts theintegrity of the endothelium and contributes to vascular leakage (Hotchkiss et al. 2002). Molecular hydrogencan prevent LPS-induced EC apoptosis by inhibiting theactivity of RhoA or activating the Nrf2-mediated HO-1
pathway in in vitro experiments (Chen et al. 2015a; Liet al. 2020). In our study, we found that molecular hydrogen activated mTOR/transcription factor EB (TFEB)mediated autophagy and inhibited HPMEC apoptosis in
LPS-induced ALI (Fu et al. 2020). Through the inhibitionof apoptosis, molecular hydrogen improves cell viability
and suppresses the release of the cell adhesion molecules,
such as vascular cell adhesion molecule-1 and ICAM-1,
and pro-inflammatory cytokines, such as TNF-α, IL-1β,
and HMGB1, potentially alleviating endothelial injury(Fig. 3).
Molecular hydrogen confers a protective effecton extrapulmonary organs

Fig. 2 Protective effects of molecular hydrogen on AECs. Molecularhydrogen alleviates AEC apoptosis, decreasing the inhibitory effectof LPS on AQP1 and AQP5, and protects type II AECs in LPS-induced
injury by inhibiting excessive autophagy

ALI/ARDS is a severe lung disease involving the respiratory system and extrapulmonary distal organs (Del Sorbo
and Slutsky 2011). For instance, although COVID-19 iswell known for causing a substantial respiratory pathology, it can also cause thrombotic complications, neurologic illnesses, myocardial dysfunction and arrhythmia,
acute coronary syndromes, acute kidney injury, hepatocellular injury, hyperglycemia and ketosis, and dermatological complications (Gupta et al. 2020). An intimate

Zhang et al. Molecular Medicine(2022) 28:27

Page 9 of 18

Fig. 3 Molecular hydrogen alleviates the hyperpermeability of the vascular endothelium in ALI. The interendothelial junctions of ECs include
tight junctions and adherens junctions. Occludin and claudins are linked to the zonula occludens. The cytoplasmic domain of VE-cadherin binds
to α-catenin and β-catenin to firmly maintain EC–EC junctions. RhoA activates Rho kinases and myosin light chain kinase, which phosphorylates
the myosin light chain, inducing actomyosin contractility and weakening endothelial cell–cell adhesion. Molecular hydrogen could increase theexpression of VE-cadherin and occludin. It also inhibits the expression of RhoA, reduces the expression of ICAM-1 and its release from the cell, andinhibits the adhesion of monocytes to ECs

crosstalk occurs between the lungs and other organs thatcoordinate to provide the host immunity against infection and maintain homeostasis (Wang et al. 2021b). It
was concluded that the predominant cause of death inpatients with ARDS is not severe hypoxemia but multiple organ failure (Del Sorbo and Slutsky 2011); thishighlights the importance of protecting extrapulmonaryorgans.
Molecular hydrogen has preventive and therapeutic
effects on various organs. Its action in sepsis-induced
lung injury and multiple organ dysfunction in animal
experiments is most well studied. Molecular hydrogen reduces the damage to various organ functions andimproves the survival rate (Xie et al. 2014; Zheng and
Zhu 2016; Qiu et al. 2019; Qi et al. 2021), which may
alleviate ALI. In sepsis-induced brain injury, molecular hydrogen can attenuate the disruption of the blood–
brain barrier and decrease its permeability, thereby
reducing sepsis-associated encephalopathy and improving cognitive function (Yu et al. 2020). Chronic exposure
to molecular hydrogen prevents memory loss in patientswith sepsis, whereas acute molecular hydrogen inhalation decreases neuroinflammation in memory-relatedareas and increases the activity of Nrf2 (Jesus et al. 2020).
In sepsis-induced liver injury in mice model, molecular hydrogen activated the Fun14 domain-containing
protein 1-induced mitophagy pathway, decreased theliver histological score, and decreased the levels of alanine aminotransferase and aspartate aminotransferase.

Therefore, it may serve as an effective therapeutic strategy for sepsis-induced liver injury (Yan et al. 2019). In
myocardial tissues with severe sepsis, molecular hydrogen gas treatment led to upregulated HO-1 and theexpression of mitofusin-2 (Mfn2) and peroxisome proliferator-activated receptor-gamma coactivator-1α, while
limiting severe sepsis-related mitochondrial dysfunction (Zhang et al. 2020) and restoring cardiac fatty acidoxidation by increasing cardiac energy in sepsis (Taoet al. 2015). In the kidney, molecular hydrogen remarkably reduces serum levels of blood urea nitrogen and Cr(Li et al. 2013), and it is considered useful in alleviating
structural damage to the kidney and protecting renal
function. In the septic intestine, the luminal administration of HRS prevented intestinal dysbiosis, hyperpermeability, and bacterial translocation, which is a major causeof multiple organ dysfunction syndrome in critical illness(Ikeda et al. 2018). Collectively, these results suggest thatin addition to its direct protective effects on the lungs,
molecular hydrogen can indirectly protect lung tissues
via a mechanism that underlies its protective effects onother tissues and organs.

Application of molecular hydrogen in ALI caused
by various etiological factors
Sepsis‑induced ALI

Sepsis is a serious systemic inflammatory response syndrome that causes life-threatening organ dysfunction
due to a dysfunctional host response to infection, which

Zhang et al. Molecular Medicine(2022) 28:27

is a leading cause of ALI (Sessler et al. 1996). Molecularhydrogen has been widely used in studies focusing on
sepsis in recent years and has yielded beneficial effects.
As mentioned above, oxidative stress plays an important role in the process of ALI/ARDS; however, data
demonstrating the clinical improvements of antioxidant
therapy remain limited. Molecular hydrogen has antioxidant capacity, and the main mechanism underlying
this is the activation of the Nrf2/HO-1-dependent pathway, which reduces oxidative stress (Xie et al. 2012) anddownregulates the expression and reduces the release of
HMGB1 in the serum and lung tissues of septic mice.
Mitochondrial dysfunction plays an important rolein sepsis-induced organ damage. In sepsis, molecularhydrogen therapy effectively improved mitochondrial
function, reflected by the blocking of mitochondrial
permeability transition pore openings, and an increasein mitochondrial-membrane potential and adenosine
triphosphate (ATP) levels, respiration control ratio,
mitochondrial–respiration complex activities, and Mfn2
expression along with a decrease in the histological scoreand dynamin-related protein 1 levels (Dong et al. 2018).
Molecular hydrogen can also inactivate the NLRP3
inflammasome through the activation of autophagy andmitigation of mitochondrial dysfunction and cytokine
release in septic mice (Chen et al. 2019).
When molecular hydrogen is combined with othertherapies in sepsis, it can synergistically enhance their
therapeutic effect. For instance, the combination ofmolecular hydrogen inhalation with early fluid resuscitation considerably reduced the increase in oxidative
stress in the lung tissue, decreasing the degree of inflammation in septic rats (Liu et al. 2013b). The combinationof inhaling molecular hydrogen and hyperoxia produced
beneficial effects on organs in zymosan-induced septic
mice (Hong et al. 2016). In addition, the combination ofmolecular hydrogen with propofol improved the survival
rate of septic mice and reduced tissue damage (Honget al. 2017).
LPS is a component of the outer membrane of gramnegative bacteria. It binds to TLR4, stimulating TLR4dependent systemic inflammatory responses andtriggering the host innate immune system. Molecular hydrogen treatment can reduce the degree of LPSinduced inflammation in lung tissues of experimental
animals. It inhibits NF-κB signaling pathway-mediatedinflammation and apoptosis in the lung (Xie et al. 2012),
reduces p38 MAPK expression and inhibits p38 MAPK
activation (Liang et al. 2012), inhibits the RhoA mediatedpathway (Yang et al. 2016), and modulates autophagy
through the mTOR/TFEB signaling pathway and thePINK1/Parkin mitophagy pathway (Fu et al. 2020; Chenet al. 2021). Recently, molecular hydrogen was found to

Page 10 of 18

activate thioredoxin 1 and decrease tissue factor expression, alleviating inflammatory and coagulation cascade
reactions (Li et al. 2021). Through these mechanisms,
molecular hydrogen considerably improved the survival
rate of mice with LPS and reduced lung edema and hemorrhage, inflammatory cell infiltration, and inflammatory
cytokine secretion.
COVID‑19

COVID-19 often manifests with mild cold-like symptoms, but severe disease with complications occurs in
15% of the cases (Zhou et al. 2020b). Respiratory failure
occurring in severe cases is characterized by a systemic
inflammatory reaction with inflammatory cytokine
release (Zhu et al. 2020). At present, the only available
therapeutic remedies are restricted to alleviating theside effects caused by the virus, such as inflammationand pulmonary fibrosis, which are recognized as the firstcauses of death.
A high level of IL-6 closely correlates with SARSCoV-2 infection and the vital signs of COVID-19 patients(Chen et al. 2020b; Liu et al. 2020a). Microbes are known
to bind to TLR, inducing IL-1, a highly inflammatory
mediator of fever and fibrosis (Conti et al. 2020). Moreover, SARS-CoV-2 infection causing ARDS involves the
NLRP3 inflammasome pathway and the release of its
products, the proinflammatory cytokines IL-6 and IL-1β(Freeman and Swartz 2020). Treatments inhibiting theexpression of IL-6 and IL-1 and targeting the NLRP3
inflammasome pathway would be a viable approach to
reduce SARS-CoV-2-induced inflammatory cytokine
signaling. Accumulating evidence has also suggested that
COVID-19 induces oxidative stress by producing a substantial ROS load, especially in the more critical ARDS
phase (Muhoberac 2020). Therefore, interventions using
reductants may help treat COVID-19.
Clinical trials and animal experiments showed thatmolecular hydrogen can attenuate inflammation andoxidative stress in the airways and lungs in infective
pulmonary diseases by inhibiting the proinflammatory cytokines MCP-1, IL-6, and IL-1β and the NLRP3
pathway, as well as modulating the Nrf2 signaling pathway (Chen et al. 2019; Niu et al. 2020; Wang et al. 2020).
Molecular hydrogen may provide an effective and novel
adjuvant treatment against COVID-19 and may be beneficial in preventing a COVID-19-associated cytokine
storm and multiple organ failure (Wang et al. 2021a).
Ischemia/reperfusion (I/R)‑induced ALI

I/R-induced injury is associated with serious clinicaloutcomes. Its pathophysiology involves ROS, aseptic
inflammation, and cell death pathways. I/R-induced ALI
usually occurs after cardiac bypass surgery and lung

Zhang et al. Molecular Medicine(2022) 28:27

transplantation (den Hengst et al. 2010), leading to primary graft dysfunction. So far, no effective therapy isavailable to prevent I/R injury and treatment strategies
are mainly restricted to supportive care. At present, dataon the application of molecular hydrogen molecules inclinical I/R-induced ALI are limited, but studies in animal models suggest that molecular hydrogen can reduce
oxidative stress, inflammation, and apoptosis and alleviate I/R injury in lung transplantation.
During I/R, mounting ROS stimulate tissue inflammation and mitochondrial dysfunction and induce NLRP3
inflammasome activation, eventually hampering cellular
homeostasis (Minutoli et al. 2016). In lung transplantation in rat models, when donors are ventilated usinghydrogen gas, hydrogen-induced HO-1 (Kawamura et al.
2011) and inflation with hydrogen gas during the cold
ischemia phase inhibited pyroptosis (Zheng et al. 2021a).
Molecular hydrogen inhibits the inflammatory
response pathways, including the p38 MAPK and NF-κB
pathways, thereby decreasing the levels of IL-8, IL-1β,
and TNF-α in the recipient lung and decreasing myeloperoxidase (MPO) levels in a PMVECs lung transplantation model and a rat lung transplantation model (Liuet al. 2015b; Zhang et al. 2018; Saito et al. 2020).
Molecular hydrogen could also considerably inhibit
apoptosis in rat lung transplantation and inhibit theexpression of proapoptotic proteins caspase-3 and caspase-8 in lung grafts, but activate the antiapoptotic
proteins Bcl-2 and Bcl-xL, thus stabilizing the mitochondrial outer membrane and terminating the release ofcytochrome c into the cytosol via the intrinsic apoptotic
pathway (Kawamura et al. 2010; Liu et al. 2015b). Additionally, pretreatment of rat donor lungs with molecularhydrogen can induce several lung surfactant-related, ATPsynthase, and stress-response genes (Tanaka et al. 2012).
Hyperoxia‑induced acute lung injury

The administration of oxygen in high concentration isrequired to maintain sufficient blood oxygenation insome critically ill patients, but prolonged exposure toit can result in HILI, even leading to respiratory failure.
HILI is mainly caused by excessive ROS generated duringhyperoxic conditions (Altemeier and Sinclair 2007). So
far, there are no effective prevention or treatment methods for HILI. An animal study found that HRS ameliorated HILI by reducing oxidative stress and inflammatorycascades, inhibiting apoptosis in lung tissues (Sun et al.
2011). The mechanism involved the Nrf2/HO-1-dependent pathway, prolonging survival against lethal hyperoxia
in rats (Kawamura et al. 2013). Another study found thatmolecular hydrogen could reduce HILI-related ERS byincreasing a master regulator of ERS-silent information

Page 11 of 18

regulator type-1 (SIRT1) expression in rats (Sun et al.
2017).
To further understand the molecular mechanisms
underlying molecular hydrogen effects in HILI, quantitative proteomics in vitro revealed that molecularhydrogen can protect AECIIs from hyperoxic injury
by modulating a range of protein expression levels andbiological processes, such as VEGFA, PDGFB, IGFBP3,
EDN1, NADPH oxidase levels, and the coagulation cascade (Lu et al. 2018). These findings provide a theoreticalbasis for the clinical application of molecular hydrogen intreating oxygen toxicity.
VILI

Ventilator support is often required in the intensive careunit for critically ill patients with respiratory failure,but it can also induce lung injury and even exacerbate
it (Tremblay and Slutsky 2006). Through its antioxidant,
anti-inflammatory, and antiapoptotic effects, molecularhydrogen effectively reduced the inflammatory response
in VILI at the local and systemic levels in mice (Huang
et al. 2010). Interestingly, molecular hydrogen increased
the early activation of NF-κB, which correlated withelevated levels of the antiapoptotic protein Bcl-2 anddecreased levels of Bax, and contributed to the epithelial
protective effects of molecular hydrogen against apoptosis and the activation of the inflammatory signaling pathway during VILI in a mouse model (Huang et al. 2011).
Radiation‑induced lung injury

Radiation is used in medical diagnosis and cancer treatment. However, damage can also occur during radiation
therapy. ROS generated in therapy are one of factors contributing to the side effects of radiation therapy (Ward1988; Shao et al. 2014). Extensive studies have revealed
that molecular hydrogen exerts radioprotective effects
as an antioxidant and intracellular response modulator(Hirano et al. 2021). In the human lung epithelial cellline A549 undergoing irradiation, molecular hydrogen
reduced the amount of radiation-induced ROS and apoptosis while enhancing cell viability (Terasaki et al. 2011).
In an in vivo mouse model, molecular hydrogen similarly attenuated oxidative stress and apoptosis that act asmeasures of acute damage. It also reduced late damagepulmonary fibrosis as observed on alleviated chest computed tomography, Ashcroft score, and type III collagendeposition (Terasaki et al. 2011).
Burn‑induced ALI

Major burns can cause massive tissue destruction andactivate a cytokine-mediated inflammatory response,
which leads to dramatic pathophysiological effects at

Zhang et al. Molecular Medicine(2022) 28:27

sites both local to and distant from the burn (Bittner
et al. 2015).
In an extensive rat model for burns, severe burns withdelayed resuscitation caused impaired oxygenation andlung edema. Intraperitoneal HRS ameliorated theseeffects, substantially attenuated pulmonary oxidative
products, and reduced the levels of pulmonary inflammation mediators and myeloperoxidase (Fang et al. 2011).
Similarly, Qin et al. found that at an early stage of severeburns in mice, molecular hydrogen considerably alleviated the infiltration of inflammatory cells and improved
pathological lesions of the lung tissue, thus increasing thesurvival rates of mice (Qin et al. 2017).
SIRT1 expression in rat lung after burn injury presented an increasing trend after a short period of
suppression. SIRT1 might provide protection from burninduced remote ALI by attenuating PMVEC apoptosis
via p38 MAPK signaling; thus, SIRT1 exhibits a potential
therapeutic effect on burn-induced ALI (Bai et al. 2015).
Molecular hydrogen can increase SIRT1 expression in
hyperoxia ALI. Therefore, although further investigationis needed, molecular hydrogen may modulate SIRT1 inburn-induced ALI.
ALI induced by other causes

In seawater instillation-induced ALI in rabbits, molecularhydrogen inhalation alleviated histopathological changes
and cell apoptosis; decreased the malondialdehyde content and MPO activity in lung tissues; decreased thePage 12 of 18

levels of TNF-α, IL-1β, and IL-6 in bronchoalveolar lavage fluid; and markedly improved lung endothelial permeability. These protective effects may be related to theactivation of the Nrf2 pathway (Diao et al. 2016).
In addition, molecular hydrogen attenuates gefitinibinduced exacerbation of naphthalene-evoked ALI (Terasaki et al. 2019) and oleic acid-induced ALI (Ying et al.
2017) in animal experiments. A combination of molecular hydrogen and hyperoxia improved the survival rate
and reduced the organ damage in a zymosan-induced
generalized inflammation mouse model. This combination showed a more marked beneficial effect against
lung, liver, and kidney damage (Hong et al. 2016). It canbe concluded that molecular hydrogen has a wide therapeutic application spectrum in the treatment of ALI
caused by various pathogenetic factors. The applicationof molecular hydrogen in ALI is summarized in Table 2.

Perspective
Molecular hydrogen is easily applicable because it
exhibits remarkable efficacy on nearly all pathogenic
states that are involved in inflammation and oxidative
stress. In this study, we reviewed the protective effects
and underlying mechanism of molecular hydrogenin ALI caused by different pathogenetic factors. The
anti-ALI effects of molecular hydrogen were mainly
attributed to its anti-inflammatory, antioxidative, antiapoptotic, and autophagy-modulating effects. However,the potential molecular mechanisms still need further

Table 2 Application of molecular hydrogen in ALI caused by various etiological factors
Etiological factors

Effect of molecular hydrogen

References

Sepsis-induced ALI

Inhibits HMGB1 by activating Nrf2/HO-1; improves
mitochondrial function; decreases NLRP3 inflammasome
through activating autophagy
Inhibits NF-κB; inhibits p38 MAPK; inhibits RhoA;
modulates mTOR/TFEB autophagy and PINK1/Parkinmitophagy; activates thioredoxin 1 and decreases tissue
factor expression

Xie et al. (2010, 2012), Liang et al. (2012), Li et al. (2015,2021), Yang et al. (2016), Dong et al. (2018), Chen et al.
(2019, 2021), Yu et al. (2019), Fu et al. (2020)

COVID-19

Inhibits MCP-1, IL-6, IL-1β; inhibits NLRP3 pathway, modu- Chen et al. (2019), Niu et al. (2020), Wang et al. (2020)
lates Nrf2 signaling pathway

I/R induced ALI

Induces HO-1, inhibits p38 MAPK and NF-κB, decreases
IL-8, IL-1β, TNF-α; inhibits apoptosis and pyroptosis

Kawamura et al. (2010, 2011), Liu et al. (2015b), Zhang et al.
(2018), Saito et al. (2020), Zheng et al. (2021a)

HILI

Activates Nrf2/HO-1; increases SIRT1; protects AECIIs by
modulating related proteins expression and biologicalprocesses

Kawamura et al. (2013), Sun et al. (2017), Lu et al. (2018)

VILI

Reduces inflammatory responses at local and systemiclevel; increases the early activation of NF-κB

Huang et al. (2010, 2011)

Irradiation-induced lung injury Reduces ROS and apoptosis in A549 cells; reduces lungfibrosis

Terasaki et al. (2011)

Burn induced ALI

Attenuates oxidative stress and inflammation; may
modulate SIRT1Fang et al. (2011), Bai et al. (2015), Qin et al. (2017)

ALI induced by other causes

The protective effects are mainly by inhibiting oxidative
stress, inflammation, apoptosis

Diao et al. (2016), Hong et al. (2016), Ying et al. (2017),
Terasaki et al. (2019)

Zhang et al. Molecular Medicine(2022) 28:27

exploration, and some results remain controversial,
warranting further research. Although none have beenfound till date, it is unlikely that there are no adverse
effects of molecular hydrogen. Additional research is
required to confirm whether molecular hydrogen has
undetected potential adverse effects to provide better
clinical guidance.
Most current research is based on animal experiments; additional clinical trials are needed. Until now,
inhalation of molecular hydrogen at a concentrationof 1.3–4% has been employed as a form of treatment
in clinical trials; however, the optimal dose of molecular hydrogen varies depending on the type of expectedbiological effect. Recently, a prospective, open-label,rater-blinded clinical pilot study in patients experiencing ST-elevation myocardial infarction demonstrated
that molecular hydrogen gas inhalation during percutaneous coronary intervention is feasible and safe andmay also promote left ventricular reverse remodeling at
6 months after ST-elevated myocardial infarction (Katsumata et al. 2017). Another multicenter, randomized,
controlled clinical trial showed that the administrationof a molecular hydrogen and oxygen mixture was superior to oxygen to improve symptoms in patients withacute exacerbation of chronic obstructive pulmonary
disease (Zheng et al. 2021b).
For COVID-19, which has led to an urgent demand fortherapeutic agents to alleviate and prevent the pandemic,
many therapeutics and interventions have been investigated to combat the viral infection-induced inflammationand oxidative stress that contribute to its etiology andpathogenesis; however, these have not yielded any significantly improved treatment outcomes, In China, Nanshan et al. applied ­H2/O2 inhalation for the treatment of
COVID-19 in more than 2000 patients and yielded positive and effective outcomes (Alwazeer et al. 2021). ­H2/O2
inhalation therapy can be performed in general wards orat home using portable ­H2/O2 generating and inhalation
devices. This will ease the pressure on hospitals, reduce
hospitalization time, and prevent severe illness caused by
COVID-19. Currently, several clinical trials of molecular hydrogen on COVID-19 are registered in the Clinical
Trial Registry (Alwazeer et al. 2021).
Till date, the reported benefits of molecular hydrogentherapy in patients with ALI are still limited to symptomatic descriptions. To expand the utility of molecular hydrogen therapy in ALI, further understanding ofmolecular hydrogen pharmacokinetics and its biologicalmechanisms of action will facilitate the clinical applications of this important molecule. We believe that this will
generate standard clinical practice in the near future, andmolecular hydrogen may provide strategies for ALI.

Page 13 of 18

Abbreviations
8-OHdG: 8-Hydroxy-2′-deoxyguanosine; AECs: Alveolar epithelial cells; AJ:
Adherens junctions; ARD: Acute respiratory distress syndrome; ALI: Acutelung injury; AQPs: Aquaporins; ATP: Adenosine triphosphate; Bax: B-cell
lymphoma-2-associated X-protein; Bcl-2: B-cell lymphoma-2; Bcl-xl: B-cell
lymphoma-extra-large; CAT​: Catalase; COVID-19: Coronavirus disease 2019;
ECs: Endothelial cells; ERS: Endoplasmic reticulum stress; GSH-Px: Glutathione
peroxidase; GTPases: Guanosine triphosphatases; HO-1: Heme oxygenase-1;
HILI: Hyperoxia-induced ALI; HMGB1: High-mobility group box-1 protein;
HRS: Hydrogen-rich saline; I/R: Ischemia/reperfusion; ICAM-1: Intercellular celladhesion molecule-1; ICU: Intensive care unit; IL: Interleukin; LPS: Lipopolysaccharide; MAPK: Mitogen-activated protein kinase; Mfn2: Mitofusin-2; MPO:
Myeloperoxidase; NADPH: Nicotinamide adenine dinucleotide phosphate;
NF-κB: Nuclear factor kappa-B; NLRP3: Nucleotide-binding oligomerization
domain-, leucine-rich repeat- and pyrin domain-containing 3; Nrf2: Nuclear
factor erythroid 2-related factor 2; PAMPs: Pathogen-associated molecularpatterns; PINK1: Phosphatase and tensin homolog-induced kinase 1; PMVECs:
Pulmonary microvascular endothelial cells; ROCK: Rho kinases; ROS: Reactive
oxygen species; SARS-CoV-2: Severe acute respiratory syndrome coronavirus
2; SIRT1: Silent information regulator type-1; SOD: Superoxide dismutase; TLR:
Toll-like receptor; TNF-α: Tumor necrosis factor-α; TJ: Tight junction; VE: Vascularendothelial; VILI: Ventilator-induced lung injury.
Acknowledgements
Special thanks to Pro. Xiuying Wu (Department of Anesthesiology, Shengjing
Hospital of China Medical University, Shenyang) for reviewing and helpful suggestions for our manuscript.
Authors’ contributions
ZF formulated the idea and collect the literatures; YZ organized the paper andconceived the figures; ZF wrote the manuscript. JZ reviewed the manuscript.
All authors read and approved the final manuscript.
Funding
This work was supported by the Technology Bureau of Liaoning Province(Grant No. 17-230-9-45).
Availability of data and materials
Not applicable.

Declarations
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Received: 26 October 2021 Accepted: 14 February 2022

References
Abadie Y, Bregeon F, Papazian L, Lange F, Chailley-Heu B, Thomas P, Duvaldestin
P, Adnot S, Maitre B, Delclaux C. Decreased VEGF concentration in lungtissue and vascular injury during ARDS. Eur Respir J. 2005;25(1):139–46.
Altemeier WA, Sinclair SE. Hyperoxia in the intensive care unit: why more is notalways better. Curr Opin Crit Care. 2007;13(1):73–8.
Alwazeer D, Liu FF, Wu XY, LeBaron TW. Combating oxidative stress and inflammation in COVID-19 by molecular hydrogen therapy: mechanisms andperspectives. Oxid Med Cell Longev. 2021;2021:5513868.
Amraei R, Rahimi N. COVID-19, renin-angiotensin system and endothelial
dysfunction. Cells. 2020;9(7):1652.
Audi SH, Jacobs ER, Zhang X, Camara AKS, Zhao M, Medhora MM, Rizzo B,
Clough AV. Protection by inhaled hydrogen therapy in a rat modelZhang et al. Molecular Medicine(2022) 28:27

of acute lung injury can be tracked in vivo using molecular imaging.
Shock. 2017;48(4):467–76.
Bai X, Fan L, He T, Jia W, Yang L, Zhang J, Liu Y, Shi J, Su L, Hu D. SIRT1 protects
rat lung tissue against severe burn-induced remote ALI by attenuating
the apoptosis of PMVECs via p38 MAPK signaling. Sci Rep. 2015;5:10277.
Balda MS, Matter K. Tight junctions as regulators of tissue remodelling. Curr
Opin Cell Biol. 2016;42:94–101.
Bayat B, Sachs UJ. Transfusion-related acute lung injury: an overview. Curr
Pharm Des. 2012;18(22):3236–40.
Birben E, Sahiner UM, Sackesen C, Erzurum S, Kalayci O. Oxidative stress andantioxidant defense. World Allergy Organ J. 2012;5(1):9–19.
Bittner EA, Shank E, Woodson L, Martyn JA. Acute and perioperative care of theburn-injured patient. Anesthesiology. 2015;122(2):448–64.
Buchholz BM, Kaczorowski DJ, Sugimoto R, Yang R, Wang Y, Billiar TR, McCurry
KR, Bauer AJ, Nakao A. Hydrogen inhalation ameliorates oxidative
stress in transplantation induced intestinal graft injury. Am J Transplant.
2008;8(10):2015–24.
Cai J, Kang Z, Liu WW, Luo X, Qiang S, Zhang JH, Ohta S, Sun X, Xu W, Tao H, Li
R. Hydrogen therapy reduces apoptosis in neonatal hypoxia-ischemia
rat model. Neurosci Lett. 2008;441(2):167–72.
Cecchini R, Cecchini AL. SARS-CoV-2 infection pathogenesis is relatedto oxidative stress as a response to aggression. Med Hypotheses.
2020;143:110102.
Chabot F, Mitchell JA, Gutteridge JM, Evans TW. Reactive oxygen species inacute lung injury. Eur Respir J. 1998;11(3):745–57.
Chambers E, Rounds S, Lu Q. Pulmonary endothelial cell apoptosis inemphysema and acute lung injury. Adv Anat Embryol Cell Biol.
2018;228:63–86.
Chapman HA. A Fas pathway to pulmonary fibrosis. J Clin Invest.
1999;104(1):1–2.
Chen H, Xie K, Han H, Li Y, Liu L, Yang T, Yu Y. Molecular hydrogen protects miceagainst polymicrobial sepsis by ameliorating endothelial dysfunction via an Nrf2/HO-1 signaling pathway. Int Immunopharmacol.
2015a;28(1):643–54.
Chen X, Liu Q, Wang D, Feng S, Zhao Y, Shi Y, Liu Q. Protective effects ofhydrogen-rich saline on rats with smoke inhalation injury. Oxid Med
Cell Longev. 2015b;2015:106836.
Chen H, Mao X, Meng X, Li Y, Feng J, Zhang L, Zhang Y, Wang Y, Yu Y, Xie K.
Hydrogen alleviates mitochondrial dysfunction and organ damage via
autophagy-mediated NLRP3 inflammasome inactivation in sepsis. Int J
Mol Med. 2019;44(4):1309–24.
Chen HG, Han HZ, Li Y, Yu YH, Xie KL. Hydrogen alleviated organ injury anddysfunction in sepsis: the role of cross-talk between autophagy andendoplasmic reticulum stress: experimental research. Int Immunopharmacol. 2020a;78:106049.
Chen X, Zhao B, Qu Y, Chen Y, Xiong J, Feng Y, Men D, Huang Q, Liu Y, Yang
B, Ding J, Li F. Detectable serum severe acute respiratory syndrome
coronavirus 2 viral load (RNAemia) is closely correlated with drasticallyelevated interleukin 6 level in critically ill patients with coronavirus
disease 2019. Clin Infect Dis. 2020b;71(8):1937–42.
Chen H, Lin H, Dong B, Wang Y, Yu Y, Xie K. Hydrogen alleviates cell damage
and acute lung injury in sepsis via PINK1/Parkin-mediated mitophagy.
Inflamm Res. 2021;70(8):915–30.
Chopra M, Reuben JS, Sharma AC. Acute lung injury:apoptosis and signalingmechanisms. Exp Biol Med (Maywood). 2009;234(4):361–71.
Conti P, Gallenga CE, Tetè G, Caraffa A, Ronconi G, Younes A, Toniato E, Ross R,
Kritas SK. How to reduce the likelihood of coronavirus-19 (CoV-19 or
SARS-CoV-2) infection and lung inflammation mediated by IL-1. J Biol
Regul Homeost Agents. 2020;34(2):333–8.
Cui J, Ding H, Yao Y, Liu W. Inhibition Mir-92a alleviates oxidative stressand apoptosis of alveolar epithelial cells induced by lipopolysaccharide exposure through TLR2/AP-1 pathway. Biomed Res Int.
2020;2020:9673284.
Dejana E, Corada M, Lampugnani MG. Endothelial cell-to-cell junctions. FASEB
J. 1995;9(10):910–8.
Del Sorbo L, Slutsky AS. Acute respiratory distress syndrome and multiple
organ failure. Curr Opin Crit Care. 2011;17(1):1–6.
den Hengst WA, Gielis JF, Lin JY, Van Schil PE, De Windt LJ, Moens AL. Lungischemia-reperfusion injury: a molecular and clinical view on acomplex pathophysiological process. Am J Physiol Heart Circ Physiol.
2010;299(5):H1283-1299.

Page 14 of 18

Deretic V, Saitoh T, Akira S. Autophagy in infection, inflammation and immunity. Nat Rev Immunol. 2013;13(10):722–37.
Diao M, Zhang S, Wu L, Huan L, Huang F, Cui Y, Lin Z. Hydrogen gas inhalation
attenuates seawater instillation-induced acute lung injury via the Nrf2
pathway in rabbits. Inflammation. 2016;39(6):2029–39.
Dong A, Yu Y, Wang Y, Li C, Chen H, Bian Y, Zhang P, Zhao Y, Yu Y, Xie K. Protective effects of hydrogen gas against sepsis-induced acute lung injury
via regulation of mitochondrial function and dynamics. Int Immunopharmacol. 2018;65:366–72.
Du H, Sheng M, Wu L, Zhang Y, Shi D, Weng Y, Xu R, Yu W. Hydrogen-rich saline
attenuates acute kidney injury after liver transplantation via activating
p53-mediated autophagy. Transplantation. 2016;100(3):563–70.
Du J, Li H, Lian J, Zhu X, Qiao L, Lin J. Stem cell therapy: a potential approachfor treatment of influenza virus and coronavirus-induced acute lunginjury. Stem Cell Res Ther. 2020;11(1):192.
Entezari M, Javdan M, Antoine DJ, Morrow DM, Sitapara RA, Patel V, Wang
M, Sharma L, Gorasiya S, Zur M, Wu W, Li J, Yang H, Ashby CR, Thomas
D, Wang H, Mantell LL. Inhibition of extracellular HMGB1 attenuates hyperoxia-induced inflammatory acute lung injury. Redox Biol.
2014;2:314–22.
Fan EKY, Fan J. Regulation of alveolar macrophage death in acute lung inflammation. Respir Res. 2018;19(1):50.
Fang Y, Fu XJ, Gu C, Xu P, Wang Y, Yu WR, Sun Q, Sun XJ, Yao M. Hydrogen-richsaline protects against acute lung injury induced by extensive burn in
rat model. J Burn Care Res. 2011;32(3):e82-91.
Freeman TL, Swartz TH. Targeting the NLRP3 inflammasome in severe COVID19. Front Immunol. 2020;11:1518.
Fu Z, Zhang Z, Wu X, Zhang J. Hydrogen-rich saline inhibits lipopolysaccharide-induced acute lung injury and endothelial dysfunction by regulating autophagy through mTOR/TFEB signaling pathway. Biomed Res Int.
2020;2020:9121894.
Ganter MT, Roux J, Miyazawa B, Howard M, Frank JA, Su G, Sheppard D, VioletteSM, Weinreb PH, Horan GS, Matthay MA, Pittet JF. Interleukin-1beta
causes acute lung injury via alphavbeta5 and alphavbeta6 integrindependent mechanisms. Circ Res. 2008;102(7):804–12.
Ge L, Yang M, Yang NN, Yin XX, Song WG. Molecular hydrogen: a preventive and therapeutic medical gas for various diseases. Oncotarget.
2017;8(60):102653–73.
Gharib B, Hanna S, Abdallahi OM, Lepidi H, Gardette B, De Reggi M. Antiinflammatory properties of molecular hydrogen: investigation on parasite-induced liver inflammation. C R Acad Sci III. 2001;324(8):719–24.
Gill SE, Rohan M, Mehta S. Role of pulmonary microvascular endothelial cell
apoptosis in murine sepsis-induced lung injury in vivo. Respir Res.
2015;16(1):109.
Grommes J, Soehnlein O. Contribution of neutrophils to acute lung injury. Mol
Med. 2011;17(3–4):293–307.
Gross O, Thomas CJ, Guarda G, Tschopp J. The inflammasome: an integrated
view. Immunol Rev. 2011;243(1):136–51.
Gupta A, Madhavan MV, Sehgal K, Nair N, Mahajan S, Sehrawat TS, Bikdeli B,
Ahluwalia N, Ausiello JC, Wan EY, Freedberg DE, Kirtane AJ, Parikh SA,
Maurer MS, Nordvig AS, Accili D, Bathon JM, Mohan S, Bauer KA, Leon
MB, Krumholz HM, Uriel N, Mehra MR, Elkind MSV, Stone GW, Schwartz
A, Ho DD, Bilezikian JP, Landry DW. Extrapulmonary manifestations of
COVID-19. Nat Med. 2020;26(7):1017–32.
Hayes M, Curley G, Ansari B, Laffey JG. Clinical review: stem cell therapies for
acute lung injury/acute respiratory distress syndrome—hope or hype?
Crit Care. 2012;16(2):205.
Herold S, Gabrielli NM, Vadász I. Novel concepts of acute lung injury andalveolar-capillary barrier dysfunction. Am J Physiol Lung Cell Mol
Physiol. 2013;305(10):L665-681.
Herzog EL, Brody AR, Colby TV, Mason R, Williams MC. Knowns and unknownsof the alveolus. Proc Am Thorac Soc. 2008;5(7):778–82.
Hippenstiel S, Opitz B, Schmeck B, Suttorp N. Lung epithelium as a sentineland effector system in pneumonia–molecular mechanisms of pathogen recognition and signal transduction. Respir Res. 2006;7(1):97.
Hirano SI, Ichikawa Y, Sato B, Yamamoto H, Takefuji Y, Satoh F. Molecular hydrogen as a potential clinically applicable radioprotective agent. Int J Mol
Sci. 2021;22(9):4566.
Hirayama M, Ito M, Minato T, Yoritaka A, LeBaron TW, Ohno K. Inhalation ofhydrogen gas elevates urinary 8-hydroxy-2′-deoxyguanine in Parkinson’s disease. Med Gas Res. 2018;8(4):144–9.

Zhang et al. Molecular Medicine(2022) 28:27

Hong Y, Sun LI, Sun R, Chen H, Yu Y, Xie K. Combination therapy of molecularhydrogen and hyperoxia improves survival rate and organ damage ina zymosan-induced generalized inflammation model. Exp Ther Med.
2016;11(6):2590–6.
Hong Y, Chen H, Yu Y, Xie K. Effect of combination therapy with propofol
and hydrogen-rich saline on organ damage and cytokines in amurine model of sepsis. Zhonghua Wei Zhong Bing Ji Jiu Yi Xue.
2017;29(4):316–20.
Hong CY, Zhang HD, Liu XY, Xu Y. Attenuation of hyperoxic acute lung injury
by Lycium barbarum polysaccharide via inhibiting NLRP3 inflammasome. Arch Pharm Res. 2019;42(10):902–8.
Hotchkiss RS, Tinsley KW, Swanson PE, Karl IE. Endothelial cell apoptosis insepsis. Crit Care Med. 2002;30(5 Suppl):S225-228.
Hou Z, Luo W, Sun X, Hao S, Zhang Y, Xu F, Wang Z, Liu B. Hydrogen-rich saline
protects against oxidative damage and cognitive deficits after mild
traumatic brain injury. Brain Res Bull. 2012;88(6):560–5.
Huang CS, Kawamura T, Lee S, Tochigi N, Shigemura N, Buchholz BM, Kloke
JD, Billiar TR, Toyoda Y, Nakao A. Hydrogen inhalation ameliorates
ventilator-induced lung injury. Crit Care. 2010;14(6):R234.
Huang CS, Kawamura T, Peng X, Tochigi N, Shigemura N, Billiar TR, Nakao A,
Toyoda Y. Hydrogen inhalation reduced epithelial apoptosis in ventilator-induced lung injury via a mechanism involving nuclear factor-kappa
B activation. Biochem Biophys Res Commun. 2011;408(2):253–8.
Huang X, Xiu H, Zhang S, Zhang G. The role of macrophages in the pathogenesis of ALI/ARDS. Mediat Inflamm. 2018;2018:1264913.
Hughes KT, Beasley MB. Pulmonary manifestations of acute lung injury:
more than just diffuse alveolar damage. Arch Pathol Lab Med.
2017;141(7):916–22.
Iba T, Connors JM, Levy JH. The coagulopathy, endotheliopathy, and vasculitis
of COVID-19. Inflamm Res. 2020;69(12):1181–9.
Ikeda M, Shimizu K, Ogura H, Kurakawa T, Umemoto E, Motooka D, Nakamura
S, Ichimaru N, Takeda K, Takahara S, Hirano SI, Shimazu T. Hydrogen-richsaline regulates intestinal barrier dysfunction, dysbiosis, and bacterialtranslocation in a murine model of sepsis. Shock. 2018;50(6):640–7.
Jesus AA, Passaglia P, Santos BM, Rodrigues-Santos I, Flores RA, Batalhão ME,
Stabile AM, Cárnio EC. Chronic molecular hydrogen inhalation mitigates
short and long-term memory loss in polymicrobial sepsis. Brain Res.
2020;1739:146857.
Johnson MD, Widdicombe JH, Allen L, Barbry P, Dobbs LG. Alveolar epithelial
type I cells contain transport proteins and transport sodium, supporting an active role for type I cells in regulation of lung liquid homeostasis. Proc Natl Acad Sci USA. 2002;99(4):1966–71.
Junkins RD, Shen A, Rosen K, McCormick C, Lin TJ. Autophagy enhances
bacterial clearance during P. aeruginosa lung infection. PLoS ONE.
2013;8(8):e72263.
Kashiouris MG, L’Heureux M, Cable CA, Fisher BJ, Leichtle SW, Fowler AA.
The emerging role of vitamin C as a treatment for sepsis. Nutrients.
2020;12(2):292.
Katsumata Y, Sano F, Abe T, Tamura T, Fujisawa T, Shiraishi Y, Kohsaka S, Ueda I,
Homma K, Suzuki M, Okuda S, Maekawa Y, Kobayashi E, Hori S, Sasaki J,
Fukuda K, Sano M. The effects of hydrogen gas inhalation on adverse
left ventricular remodeling after percutaneous coronary intervention
for ST-elevated myocardial infarction—first pilot study in humans. Circ
J. 2017;81(7):940–7.
Kawamura T, Huang CS, Tochigi N, Lee S, Shigemura N, Billiar TR, Okumura M,
Nakao A, Toyoda Y. Inhaled hydrogen gas therapy for prevention of lungtransplant-induced ischemia/reperfusion injury in rats. Transplantation.
2010;90(12):1344–51.
Kawamura T, Huang CS, Peng X, Masutani K, Shigemura N, Billiar TR, Okumura
M, Toyoda Y, Nakao A. The effect of donor treatment with hydrogen onlung allograft function in rats. Surgery. 2011;150(2):240–9.
Kawamura T, Wakabayashi N, Shigemura N, Huang CS, Masutani K, Tanaka
Y, Noda K, Peng X, Takahashi T, Billiar TR, Okumura M, Toyoda Y,
Kensler TW, Nakao A. Hydrogen gas reduces hyperoxic lung injury
via the Nrf2 pathway in vivo. Am J Physiol Lung Cell Mol Physiol.
2013;304(10):L646-656.
Kawamura M, Imamura R, Kobayashi Y, Taniguchi A, Nakazawa S, Kato T,
Namba-Hamano T, Abe T, Uemura M, Kobayashi H, Nonomura N.
Oral administration of Si-based agent attenuates oxidative stress andischemia-reperfusion injury in a rat model: a novel hydrogen administration method. Front Med (Lausanne). 2020;7:95.

Page 15 of 18

Kellner M, Noonepalle S, Lu Q, Srivastava A, Zemskov E, Black SM. ROS signaling in the pathogenesis of acute lung injury (ALI) and acute respiratory
distress syndrome (ARDS). Adv Exp Med Biol. 2017;967:105–37.
Kishimoto Y, Kato T, Ito M, Azuma Y, Fukasawa Y, Ohno K, Kojima S. Hydrogenameliorates pulmonary hypertension in rats by anti-inflammatory andantioxidant effects. J Thorac Cardiovasc Surg. 2015;150(3):645-654.e643.
Komarova Y, Malik AB. Regulation of endothelial permeability via paracellular and transcellular transport pathways. Annu Rev Physiol.
2010;72:463–93.
Kovacs SB, Miao EA. Gasdermins: effectors of pyroptosis. Trends Cell Biol.
2017;27(9):673–84.
Koyama Y, Taura K, Hatano E, Tanabe K, Yamamoto G, Nakamura K, Yamanaka K,
Kitamura K, Narita M, Nagata H, Yanagida A, Iida T, Iwaisako K, Fujinawa
H, Uemoto S. Effects of oral intake of hydrogen water on liver fibrogenesis in mice. Hepatol Res. 2014;44(6):663–77.
Kuipers MT, Aslami H, Janczy JR, van der Sluijs KF, Vlaar AP, Wolthuis EK, Choi G,
Roelofs JJ, Flavell RA, Sutterwala FS, Bresser P, Leemans JC, van der Poll T,
Schultz MJ, Wieland CW. Ventilator-induced lung injury is mediated by
the NLRP3 inflammasome. Anesthesiology. 2012;116(5):1104–15.
Kumar V. Pulmonary innate immune response determines the outcome of
inflammation during pneumonia and sepsis-associated acute lunginjury. Front Immunol. 2020;11:1722.
Kuzmich NN, Sivak KV, Chubarev VN, Porozov YB, Savateeva-Lyubimova TN,
Peri F. TLR4 signaling pathway modulators as potential therapeutics ininflammation and sepsis. Vaccines (Basel). 2017;5(4):34.
Laskin DL, Malaviya R, Laskin JD. Role of macrophages in acute lung injury
and chronic fibrosis induced by pulmonary toxicants. Toxicol Sci.
2019;168(2):287–301.
Lee S, Suh GY, Ryter SW, Choi AM. Regulation and function of the nucleotide
binding domain leucine-rich repeat-containing receptor, pyrin domaincontaining-3 inflammasome in lung disease. Am J Respir Cell Mol Biol.
2016;54(2):151–60.
Lee S, Piao C, Kim G, Kim JY, Choi E, Lee M. Production and application of
HMGB1 derived recombinant RAGE-antagonist peptide for anti-inflammatory therapy in acute lung injury. Eur J Pharm Sci. 2018;114:275–84.
Lee J, Jang J, Park SM, Yang SR. An update on the role of Nrf2 in respiratory
disease: molecular mechanisms and therapeutic approaches. Int J Mol
Sci. 2021;22(16):8406.
Li GM, Ji MH, Sun XJ, Zeng QT, Tian M, Fan YX, Li WY, Li N, Yang JJ. Effects ofhydrogen-rich saline treatment on polymicrobial sepsis. J Surg Res.
2013;181(2):279–86.
Li Y, Xie K, Chen H, Wang G, Yu Y. Hydrogen gas inhibits high-mobility groupbox 1 release in septic mice by upregulation of heme oxygenase 1. J
Surg Res. 2015;196(1):136–48.
Li D, Ren W, Jiang Z, Zhu L. Regulation of the NLRP3 inflammasome and macrophage pyroptosis by the p38 MAPK signaling pathway in a mousemodel of acute lung injury. Mol Med Rep. 2018;18(5):4399–409.
Li Y, Chen H, Shu R, Zhang X, Yu Y, Liu X, Xu K. Hydrogen treatment prevents
lipopolysaccharide-induced pulmonary endothelial cell dysfunction through RhoA inhibition. Biochem Biophys Res Commun.
2020;522(2):499–505.
Li Q, Hu L, Li J, Yu P, Hu F, Wan B, Xu M, Cheng H, Yu W, Jiang L, Shi Y, Li J, Duan
M, Long Y, Liu WT. Hydrogen attenuates endotoxin-induced lung injury
by activating thioredoxin 1 and decreasing tissue factor expression.
Front Immunol. 2021;12:625957.
Liang C, Liu X, Liu L, He D. Effect of hydrogen inhalation on p38 MAPK activation in rats with lipopolysaccharide-induced acute lung injury. Nan
Fang Yi Ke Da Xue Xue Bao. 2012;32(8):1211–3.
Liu Y, Zhang J. Saturated hydrogen saline ameliorates lipopolysaccharideinduced acute lung injury by reducing excessive autophagy. Exp Ther
Med. 2017;13(6):2609–15.
Liu QP, Zhou DX, Lin P, Gao XL, Pan L, Jin FG. Participation of autophagyin acute lung injury induced by seawater. Exp Lung Res.
2013a;39(10):441–52.
Liu W, Shan LP, Dong XS, Liu XW, Ma T, Liu Z. Combined early fluid resuscitationand hydrogen inhalation attenuates lung and intestine injury. World J
Gastroenterol. 2013b;19(4):492–502.
Liu H, Liang X, Wang D, Zhang H, Liu L, Chen H, Li Y, Duan Q, Xie K. Combination therapy with nitric oxide and molecular hydrogen in a murine
model of acute lung injury. Shock. 2015a;43(5):504–11.

Zhang et al. Molecular Medicine(2022) 28:27

Liu R, Fang X, Meng C, Xing J, Liu J, Yang W, Li W, Zhou H. Lung inflation withhydrogen during the cold ischemia phase decreases lung graft injury inrats. Exp Biol Med (Maywood). 2015b;240(9):1214–22.
Liu LD, Wu XY, Tao BD, Wang N, Zhang J. Protective effect and mechanism ofhydrogen treatment on lung epithelial barrier dysfunction in rats withsepsis. Genet Mol Res. 2016. https://​doi.​org/​10.​4238/​gmr.​15016​050.
Liu Q, Gao Y, Ci X. Role of Nrf2 and its activators in respiratory diseases. Oxid
Med Cell Longev. 2019;2019:7090534.
Liu B, Li M, Zhou Z, Guan X, Xiang Y. Can we use interleukin-6 (IL-6) blockade
for coronavirus disease 2019 (COVID-19)-induced cytokine release
syndrome (CRS)? J Autoimmun. 2020a;111:102452.
Liu B, Xue J, Zhang M, Wang M, Ma T, Zhao M, Gu Q, Qin S. Hydrogen inhalation alleviates nonalcoholic fatty liver disease in metabolic syndrome
rats. Mol Med Rep. 2020b;22(4):2860–8.
Liu B, He R, Zhang L, Hao B, Jiang W, Wang W, Geng Q. Inflammatory caspases
drive pyroptosis in acute lung injury. Front Pharmacol. 2021;12:631256.
Lo S, Yuan SS, Hsu C, Cheng YJ, Chang YF, Hsueh HW, Lee PH, Hsieh YC. Lc3
over-expression improves survival and attenuates lung injury throughincreasing autophagosomal clearance in septic mice. Ann Surg.
2013;257(2):352–63.
Lopez-Rodriguez E, Pérez-Gil J. Structure-function relationships in pulmonary
surfactant membranes: from biophysics to therapy. Biochim Biophys
Acta. 2014;1838(6):1568–85.
Lu X, Wang C, Wu D, Zhang C, Xiao C, Xu F. Quantitative proteomics reveals
the mechanisms of hydrogen-conferred protection against hyperoxia-induced injury in type II alveolar epithelial cells. Exp Lung Res.
2018;44(10):464–75.
Luo ZL, Cheng L, Ren JD, Fang C, Xiang K, Xu HT, Tang LJ, Wang T, Tian FZ.
Hydrogen-rich saline protects against ischemia/reperfusion injury ingrafts after pancreas transplantations by reducing oxidative stress inrats. Mediat Inflamm. 2015;2015:281985.
Ma L, Zhao Y, Wang R, Chen T, Li W, Nan Y, Liu X, Jin F. 3,5,4′-Tri-O-acetylresveratrol attenuates lipopolysaccharide-induced acute respiratory distress syndrome via MAPK/SIRT1 pathway. Mediat Inflamm.
2015;2015:143074.
Majno G, Joris I. Apoptosis, oncosis, and necrosis. An overview of cell death.
Am J Pathol. 1995;146(1):3–15.
Martinon F, Burns K, Tschopp J. The inflammasome: a molecular platform
triggering activation of inflammatory caspases and processing of proILbeta. Mol Cell. 2002;10(2):417–26.
Ming Y, Ma QH, Han XL, Li HY. Molecular hydrogen improves type 2 diabetes
through inhibiting oxidative stress. Exp Ther Med. 2020;20(1):359–66.
Minutoli L, Puzzolo D, Rinaldi M, Irrera N, Marini H, Arcoraci V, Bitto A, Crea
G, Pisani A, Squadrito F, Trichilo V, Bruschetta D, Micali A, Altavilla
D. ROS-mediated NLRP3 inflammasome activation in brain, heart,kidney, and testis ischemia/reperfusion injury. Oxid Med Cell Longev.
2016;2016:2183026.
Mo Y, Lou Y, Zhang A, Zhang J, Zhu C, Zheng B, Li D, Zhang M, Jin W, Zhang L,
Wang J. PICK1 deficiency induces autophagy dysfunction via lysosomal
impairment and amplifies sepsis-induced acute lung injury. Mediat
Inflamm. 2018;2018:6757368.
Mrityunjaya M, Pavithra V, Neelam R, Janhavi P, Halami PM, Ravindra PV.
Immune-boosting, antioxidant and anti-inflammatory food supplements targeting pathogenesis of COVID-19. Front Immunol.
2020;11:570122.
Muhoberac BB. What can cellular redox, iron, and reactive oxygen species suggest about the mechanisms and potential therapy of COVID-19? Front
Cell Infect Microbiol. 2020;10:569709.
Nie C, Ding X, Rong A, Zheng M, Li Z, Pan S, Yang W. Hydrogen gas inhalation
alleviates myocardial ischemia-reperfusion injury by the inhibitionof oxidative stress and NLRP3-mediated pyroptosis in rats. Life Sci.
2021;272:119248.
Nieman GF, Gatto LA, Habashi NM. Impact of mechanical ventilation on
the pathophysiology of progressive acute lung injury. J Appl Physiol.
2015;119(11):1245–61.
Ning K, Liu WW, Huang JL, Lu HT, Sun XJ. Effects of hydrogen on polarization of macrophages and microglia in a stroke model. Med Gas Res.
2018;8(4):154–9.
Niu Y, Nie Q, Dong L, Zhang J, Liu SF, Song W, Wang X, Wu G, Song D. Hydrogen attenuates allergic inflammation by reversing energy metabolic
pathway switch. Sci Rep. 2020;10(1):1962.

Page 16 of 18

Ntyonga-Pono MP. COVID-19 infection and oxidative stress: an under-exploredapproach for prevention and treatment? Pan Afr Med J. 2020;35(Suppl2):12.
Ohsawa I, Ishikawa M, Takahashi K, Watanabe M, Nishimaki K, Yamagata K,
Katsura K, Katayama Y, Asoh S, Ohta S. Hydrogen acts as a therapeutic
antioxidant by selectively reducing cytotoxic oxygen radicals. Nat Med.
2007;13(6):688–94.
Ohta S. Molecular hydrogen as a preventive and therapeutic medical gas: initiation, development and potential of hydrogen medicine. Pharmacol
Ther. 2014;144(1):1–11.
Ohta S. Direct targets and subsequent pathways for molecular hydrogen toexert multiple functions: focusing on interventions in radical reactions.
Curr Pharm Des. 2021;27(5):595–609.
Olson M, Kornbluth S. Mitochondria in apoptosis and human disease. Curr Mol
Med. 2001;1(1):91–122.
Orfanos SE, Mavrommati I, Korovesi I, Roussos C. Pulmonary endothelium inacute lung injury: from basic science to the critically ill. Intensive CareMed. 2004;30(9):1702–14.
Ornatowski W, Lu Q, Yegambaram M, Garcia AE, Zemskov EA, Maltepe E, Fineman JR, Wang T, Black SM. Complex interplay between autophagy andoxidative stress in the development of pulmonary disease. Redox Biol.
2020;36:101679.
Ostojic SM. COVID-19 and molecular hydrogen inhalation. Ther Adv Respir Dis.
2020;14:1753466620951051.
Panigada M, Bottino N, Tagliabue P, Grasselli G, Novembrino C, Chantarangkul
V, Pesenti A, Peyvandi F, Tripodi A. Hypercoagulability of COVID-19
patients in intensive care unit: a report of thromboelastography
findings and other parameters of hemostasis. J Thromb Haemost.
2020;18(7):1738–42.
Patel VJ, Biswas Roy S, Mehta HJ, Joo M, Sadikot RT. Alternative and natural
therapies for acute lung injury and acute respiratory distress syndrome.
Biomed Res Int. 2018;2018:2476824.
Pearson G, Robinson F, Beers Gibson T, Xu BE, Karandikar M, Berman K, Cobb
MH. Mitogen-activated protein (MAP) kinase pathways: regulation andphysiological functions. Endocr Rev. 2001;22(2):153–83.
Pehote G, Vij N. Autophagy augmentation to alleviate immune response
dysfunction, and resolve respiratory and COVID-19 exacerbations. Cells.
2020;9(9):1952.
Qi B, Yu Y, Wang Y, Wang Y, Yu Y, Xie K. Perspective of molecular hydrogen in thetreatment of sepsis. Curr Pharm Des. 2021;27(5):667–78.
Qin C, Bian YX, Feng TT, Zhang JH, Yu YH. Effects of hydrogen on the lungdamage of mice at early stage of severe burn. Zhonghua Shao Shang
Za Zhi. 2017;33(11):682–7.
Qiu X, Li H, Tang H, Jin Y, Li W, YuSun W, Pingfeng W, Sun X, Xia Z. Hydrogen
inhalation ameliorates lipopolysaccharide-induced acute lung injury inmice. Int Immunopharmacol. 2011;11(12):2130–7.
Qiu P, Liu Y, Zhang J. Recent advances in studies of molecular hydrogen
against sepsis. Int J Biol Sci. 2019;15(6):1261–75.
Qiu X, Dong K, Guan J, He J. Hydrogen attenuates radiation-induced intestinal
damage by reducing oxidative stress and inflammatory response. Int
Immunopharmacol. 2020;84:106517.
Qiu P, Liu Y, Chen K, Dong Y, Liu S, Zhang J. Hydrogen-rich saline regulates thepolarization and apoptosis of alveolar macrophages and attenuates
lung injury via suppression of autophagy in septic rats. Ann Transl Med.
2021;9(12):974.
Rahman A, Fazal F. Blocking NF-κB: an inflammatory issue. Proc Am Thorac Soc.
2011;8(6):497–503.
Ranieri VM, Rubenfeld GD, Thompson BT, Ferguson ND, Caldwell E, Fan E,
Camporota L, Slutsky AS. Acute respiratory distress syndrome: the Berlin
Definition. JAMA. 2012;307(23):2526–33.
Ren JD, Ma J, Hou J, Xiao WJ, Jin WH, Wu J, Fan KH. Hydrogen-rich saline inhibits NLRP3 inflammasome activation and attenuates experimental acutepancreatitis in mice. Mediat Inflamm. 2014;2014:930894.
Ryter SW, Choi AM. Autophagy in the lung. Proc Am Thorac Soc.
2010;7(1):13–21.
Saeedi-Boroujeni A, Mahmoudian-Sani MR, Bahadoram M, Alghasi A. COVID19: a case for inhibiting NLRP3 inflammasome, suppression of inflammation with curcumin? Basic Clin Pharmacol Toxicol. 2021;128(1):37–45.
Saha S, Buttari B, Panieri E, Profumo E, Saso L. An overview of Nrf2 signaling
pathway and its role in inflammation. Molecules. 2020;25(22):5474.

Zhang et al. Molecular Medicine(2022) 28:27

Saito M, Chen-Yoshikawa TF, Takahashi M, Kayawake H, Yokoyama Y,
Kurokawa R, Hirano SI, Date H. Protective effects of a hydrogen-richsolution during cold ischemia in rat lung transplantation. J Thorac
Cardiovasc Surg. 2020;159(5):2110–8.
Schnittler H. Contraction of endothelial cells: 40 years of research, but thedebate still lives. Histochem Cell Biol. 2016;146(6):651–6.
Sessler CN, Bloomfield GL, Fowler AA 3rd. Current concepts of sepsis andacute lung injury. Clin Chest Med. 1996;17(2):213–35.
Shafeeq H, Lat I. Pharmacotherapy for acute respiratory distress syndrome.
Pharmacotherapy. 2012;32(10):943–57.
Shao L, Luo Y, Zhou D. Hematopoietic stem cell injury induced by ionizing
radiation. Antioxid Redox Signal. 2014;20(9):1447–62.
Sharp C, Millar AB, Medford AR. Advances in understanding of thepathogenesis of acute respiratory distress syndrome. Respiration.
2015;89(5):420–34.
Shen Q, Rigor RR, Pivetti CD, Wu MH, Yuan SY. Myosin light chain kinase
in microvascular endothelial barrier function. Cardiovasc Res.
2010;87(2):272–80.
Shi J, Yao F, Zhong C, Pan X, Yang Y, Lin Q. Hydrogen saline is protective for
acute lung ischaemia/reperfusion injuries in rats. Heart Lung Circ.
2012;21(9):556–63.
Shi Q, Liao KS, Zhao KL, Wang WX, Zuo T, Deng WH, Chen C, Yu J, Guo WY,
He XB, Abliz A, Wang P, Zhao L. Hydrogen-rich saline attenuates
acute renal injury in sodium taurocholate-induced severe acutepancreatitis by inhibiting ROS and NF-κB pathway. Mediat Inflamm.
2015;2015:685043.
Shinbo T, Kokubo K, Sato Y, Hagiri S, Hataishi R, Hirose M, Kobayashi H.
Breathing nitric oxide plus hydrogen gas reduces ischemia-reperfusion injury and nitrotyrosine production in murine heart. Am J
Physiol Heart Circ Physiol. 2013;305(4):H542-550.
Sies H. Oxidative stress: a concept in redox biology and medicine. Redox
Biol. 2015;4:180–3.
Slezak J, Kura B, LeBaron TW, Singal PK, Buday J, Barancik M. Oxidative stressand pathways of molecular hydrogen effects in medicine. Curr Pharm
Des. 2021;27(5):610–25.
Slutsky AS. The acute respiratory distress syndrome, mechanical ventilation,and the prone position. N Engl J Med. 2001;345(8):610–2.
Slutsky AS, Ranieri VM. Ventilator-induced lung injury. N Engl J Med.
2013;369(22):2126–36.
Spindler V, Schlegel N, Waschke J. Role of GTPases in control of microvascular permeability. Cardiovasc Res. 2010;87(2):243–53.
Su CF, Kao SJ, Chen HI. Acute respiratory distress syndrome and lung injury:
pathogenetic mechanism and therapeutic implication. World J Crit
Care Med. 2012;1(2):50–60.
Sun Q, Cai J, Liu S, Liu Y, Xu W, Tao H, Sun X. Hydrogen-rich saline
provides protection against hyperoxic lung injury. J Surg Res.
2011;165(1):e43-49.
Sun Q, Han W, Hu H, Fan D, Li Y, Zhang Y, Lv Y, Li M, Pan S. Hydrogen alleviates
hyperoxic acute lung injury related endoplasmic reticulum stress in rats
through upregulation of SIRT1. Free Radic Res. 2017;51(6):622–32.
Tanaka Y, Shigemura N, Kawamura T, Noda K, Isse K, Stolz DB, Billiar TR, Toyoda
Y, Bermudez CA, Lyons-Weiler J, Nakao A. Profiling molecular changes
induced by hydrogen treatment of lung allografts prior to procurement. Biochem Biophys Res Commun. 2012;425(4):873–9.
Tao B, Liu L, Wang N, Tong D, Wang W, Zhang J. Hydrogen-rich saline attenuates lipopolysaccharide-induced heart dysfunction by restoring fatty
acid oxidation in rats by mitigating C-Jun N-terminal kinase activation.
Shock. 2015;44(6):593–600.
Tao B, Liu L, Wang N, Wang W, Jiang J, Zhang J. Effects of hydrogen-rich saline
on aquaporin 1, 5 in septic rat lungs. J Surg Res. 2016;202(2):291–8.
Terasaki Y, Ohsawa I, Terasaki M, Takahashi M, Kunugi S, Dedong K, Urushiyama
H, Amenomori S, Kaneko-Togashi M, Kuwahara N, Ishikawa A, Kamimura
N, Ohta S, Fukuda Y. Hydrogen therapy attenuates irradiation-induced
lung damage by reducing oxidative stress. Am J Physiol Lung Cell Mol
Physiol. 2011;301(4):L415-426.
Terasaki Y, Suzuki T, Tonaki K, Terasaki M, Kuwahara N, Ohsiro J, Iketani M,
Takahashi M, Hamanoue M, Kajimoto Y, Hattori S, Kawaguchi H, Shimizu
A, Ohsawa I. Molecular hydrogen attenuates gefitinib-induced exacerbation of naphthalene-evoked acute lung injury through a reduction inoxidative stress and inflammation. Lab Invest. 2019;99(6):793–806.
Thorburn A. Death receptor-induced cell killing. Cell Signal. 2004;16(2):139–44.

Page 17 of 18

Tian Y, Guo S, Zhang Y, Xu Y, Zhao P, Zhao X. Effects of hydrogen-rich saline on
hepatectomy-induced postoperative cognitive dysfunction in old mice.
Mol Neurobiol. 2017;54(4):2579–84.
Togbe D, Schnyder-Candrian S, Schnyder B, Doz E, Noulin N, Janot L, Secher T,
Gasse P, Lima C, Coelho FR, Vasseur V, Erard F, Ryffel B, Couillin I, Moser
R. Toll-like receptor and tumour necrosis factor dependent endotoxininduced acute lung injury. Int J Exp Pathol. 2007;88(6):387–91.
Tremblay LN, Slutsky AS. Ventilator-induced lung injury: from the bench to thebedside. Intensive Care Med. 2006;32(1):24–33.
Vassiliou AG, Kotanidou A, Dimopoulou I, Orfanos SE. Endothelial damage inacute respiratory distress syndrome. Int J Mol Sci. 2020;21(22):8793.
Villar J, Zhang H, Slutsky AS. Lung repair and regeneration in ARDS: role of
PECAM1 and Wnt signaling. Chest. 2019;155(3):587–94.
Wang K, Chen Y, Zhang P, Lin P, Xie N, Wu M. Protective features of autophagyin pulmonary infection and inflammatory diseases. Cells. 2019a;8(2):123.
Wang YC, Liu QX, Zheng Q, Liu T, Xu XE, Liu XH, Gao W, Bai XJ, Li ZF. Dihydromyricetin alleviates sepsis-induced acute lung injury through inhibiting
NLRP3 inflammasome-dependent pyroptosis in mice model. Inflammation. 2019b;42(4):1301–10.
Wang ST, Bao C, He Y, Tian X, Yang Y, Zhang T, Xu KF. Hydrogen gas (XEN) inhalation ameliorates airway inflammation in asthma and COPD patients.
QJM. 2020;113(12):870–5.
Wang M, Peng J, Hui J, Hou D, Li W, Yang J. Hydrogen therapy as aneffective and novel adjuvant treatment against COVID-19. QJM.
2021a;114(1):74–5.
Wang Z, Pu Q, Huang C, Wu M. Crosstalk between lung and extrapulmonary organs in infection and inflammation. Adv Exp Med Biol.
2021b;1303:333–50.
Ward JF. DNA damage produced by ionizing radiation in mammalian cells:
identities, mechanisms of formation, and reparability. Prog Nucleic Acid
Res Mol Biol. 1988;35:95–125.
Ware LB, Matthay MA. The acute respiratory distress syndrome. N Engl J Med.
2000;342(18):1334–49.
Wittekindt OH, Dietl P. Aquaporins in the lung. Pflugers Arch.
2019;471(4):519–32.
Wright JG, Christman JW. The role of nuclear factor kappa B in the pathogenesis of pulmonary diseases: implications for therapy. Am J Respir Med.
2003;2(3):211–9.
Wu DD, Pan PH, Liu B, Su XL, Zhang LM, Tan HY, Cao Z, Zhou ZR, Li HT, Li HS,
Huang L, Li YY. Inhibition of alveolar macrophage pyroptosis reduces
lipopolysaccharide-induced acute lung injury in mice. Chin Med J(Engl). 2015;128(19):2638–45.
Xiao M, Zhu T, Wang T, Wen FQ. Hydrogen-rich saline reduces airway remodeling via inactivation of NF-κB in a murine model of asthma. Eur Rev
Med Pharmacol Sci. 2013;17(8):1033–43.
Xie K, Yu Y, Pei Y, Hou L, Chen S, Xiong L, Wang G. Protective effects of hydrogen gas on murine polymicrobial sepsis via reducing oxidative stressand HMGB1 release. Shock. 2010;34(1):90–7.
Xie K, Yu Y, Huang Y, Zheng L, Li J, Chen H, Han H, Hou L, Gong G, Wang G.
Molecular hydrogen ameliorates lipopolysaccharide-induced acutelung injury in mice through reducing inflammation and apoptosis.
Shock. 2012;37(5):548–55.
Xie K, Liu L, Yu Y, Wang G. Hydrogen gas presents a promising therapeuticstrategy for sepsis. Biomed Res Int. 2014;2014:807635.
Xie K, Wang W, Chen H, Han H, Liu D, Wang G, Yu Y. Hydrogen-rich medium
attenuated lipopolysaccharide-induced monocyte-endothelial celladhesion and vascular endothelial permeability via rho-associatedcoiled-coil protein kinase. Shock. 2015;44(1):58–64.
Xiong LL, Tan Y, Ma HY, Dai P, Qin YX, Yang RA, Xu YY, Deng Z, Zhao W, Xia QJ,
Wang TH, Zhang YH. Administration of SB239063, a potent p38 MAPK
inhibitor, alleviates acute lung injury induced by intestinal ischemia
reperfusion in rats associated with AQP4 downregulation. Int Immunopharmacol. 2016;38:54–60.
Yadav E, Yadav N, Hus A, Yadav JS. Aquaporins in lung health and disease:
emerging roles, regulation, and clinical implications. Respir Med.
2020;174:106193.
Yan M, Yu Y, Mao X, Feng J, Wang Y, Chen H, Xie K, Yu Y. Hydrogen gas inhalation attenuates sepsis-induced liver injury in a FUNDC1-dependent
manner. Int Immunopharmacol. 2019;71:61–7.
Yang T, Wang L, Sun R, Chen H, Zhang H, Yu Y, Wang Y, Wang G, Yu Y, Xie K.
Hydrogen-rich medium ameliorates lipopolysaccharide-induced

Zhang et al. Molecular Medicine(2022) 28:27

barrier dysfunction via RhoA-mDia1 signaling in CACO-2 cells. Shock.
2016;45(2):228–37.
Yang L, Zhang Z, Zhuo Y, Cui L, Li C, Li D, Zhang S, Cui N, Wang X, Gao H.
Resveratrol alleviates sepsis-induced acute lung injury by suppressing
inflammation and apoptosis of alveolar macrophage cells. Am J Transl
Res. 2018;10(7):1961–75.
Yang L, Guo Y, Fan X, Chen Y, Yang B, Liu KX, Zhou J. Amelioration of coagulation disorders and inflammation by hydrogen-rich solution reduces
intestinal ischemia/reperfusion injury in rats through NF-κB/NLRP3
pathway. Mediat Inflamm. 2020;2020:4359305.
Yao L, Chen H, Wu Q, Xie K. Hydrogen-rich saline alleviates inflammation andapoptosis in myocardial I/R injury via PINK-mediated autophagy. Int J
Mol Med. 2019;44(3):1048–62.
Yin J, Lv L, Zhai P, Long T, Zhou Q, Pan H, Botwe G, Wang L, Wang Q, Tan L,
Kuebler WM. Connexin 40 regulates lung endothelial permeability inacute lung injury via the ROCK1-MYPT1- MLC20 pathway. Am J Physiol
Lung Cell Mol Physiol. 2019;316(1):L35-l44.
Ying Y, Xu H, Yao M, Qin Z. Protective effect of hydrogen-saturated salineon acute lung injury induced by oleic acid in rats. J Orthop Surg Res.
2017;12(1):134.
Yu YS, Zheng H. Chronic hydrogen-rich saline treatment reduces oxidative
stress and attenuates left ventricular hypertrophy in spontaneous
hypertensive rats. Mol Cell Biochem. 2012;365(1–2):233–42.
Yu Y, Wang WN, Han HZ, Xie KL, Wang GL, Yu YH. Protective effects of hydrogen-rich medium on lipopolysaccharide-induced monocytic adhesion
and vascular endothelial permeability through regulation of vascularendothelial cadherin. Genet Mol Res. 2015;14(2):6202–12.
Yu Y, Yang Y, Yang M, Wang C, Xie K, Yu Y. Hydrogen gas reduces HMGB1 releasein lung tissues of septic mice in an Nrf2/HO-1-dependent pathway. Int
Immunopharmacol. 2019;69:11–8.
Yu Y, Feng J, Lian N, Yang M, Xie K, Wang G, Wang C, Yu Y. Hydrogen gas
alleviates blood–brain barrier impairment and cognitive dysfunctionof septic mice in an Nrf2-dependent pathway. Int Immunopharmacol.
2020;85:106585.
Yuan K, Huang C, Fox J, Laturnus D, Carlson E, Zhang B, Yin Q, Gao H, Wu M.
Autophagy plays an essential role in the clearance of Pseudomonas
aeruginosa by alveolar macrophages. J Cell Sci. 2012;125(Pt 2):507–15.
Yun J, Finkel T. Mitohormesis. Cell Metab. 2014;19(5):757–66.
Zhai Y, Zhou X, Dai Q, Fan Y, Huang X. Hydrogen-rich saline ameliorates lunginjury associated with cecal ligation and puncture-induced sepsis inrats. Exp Mol Pathol. 2015;98(2):268–76.
Zhang Y, Liu Y, Zhang J. Saturated hydrogen saline attenuates endotoxininduced lung dysfunction. J Surg Res. 2015;198(1):41–9.
Zhang G, Li Z, Meng C, Kang J, Zhang M, Ma L, Zhou H. The anti-inflammatory
effect of hydrogen on lung transplantation model of pulmonary microvascular endothelial cells during cold storage period. Transplantation.
2018;102(8):1253–61.
Zhang L, Zhao P, Yue C, Jin Z, Liu Q, Du X, He Q. Sustained release of bioactivehydrogen by Pd hydride nanoparticles overcomes Alzheimer’s disease.
Biomaterials. 2019;197:393–404.
Zhang Y, Dong A, Xie K, Yu Y. Protective effects of hydrogen on myocardial mitochondrial functions in septic mice. Biomed Res Int.
2020;2020:1568209.
Zhang CS, Han Q, Song ZW, Jia HY, Shao TP, Chen YP. Hydrogen gas postconditioning attenuates early neuronal pyroptosis in a rat model ofsubarachnoid hemorrhage through the mitoK(ATP) signaling pathway.
Exp Ther Med. 2021;22(2):836.
Zhao YS, An JR, Yang S, Guan P, Yu FY, Li W, Li JR, Guo Y, Sun ZM, Ji ES. Hydrogenand oxygen mixture to improve cardiac dysfunction and myocardial
pathological changes induced by intermittent hypoxia in rats. Oxid
Med Cell Longev. 2019;2019:7415212.
Zheng Y, Zhu D. Molecular hydrogen therapy ameliorates organ damage
induced by sepsis. Oxid Med Cell Longev. 2016;2016:5806057.
Zheng P, Kang J, Xing E, Zheng B, Wang X, Zhou H. Lung inflation withhydrogen during the cold ischemia phase alleviates lung ischemiareperfusion injury by inhibiting pyroptosis in rats. Front Physiol.
2021a;12:699344.
Zheng ZG, Sun WZ, Hu JY, Jie ZJ, Xu JF, Cao J, Song YL, Wang CH, Wang J, Zhao
H, Guo ZL, Zhong NS. Hydrogen/oxygen therapy for the treatmentof an acute exacerbation of chronic obstructive pulmonary disease:

Page 18 of 18

results of a multicenter, randomized, double-blind, parallel-groupcontrolled trial. Respir Res. 2021b;22(1):149.
Zhou H, Wang X, Zhang B. Depression of lncRNA NEAT1 antagonizes LPSevoked acute injury and inflammatory response in alveolar epithelial
cells via HMGB1-RAGE signaling. Mediat Inflamm. 2020a;2020:8019467.
Zhou P, Yang XL, Wang XG, Hu B, Zhang L, Zhang W, Si HR, Zhu Y, Li B, Huang
CL, Chen HD, Chen J, Luo Y, Guo H, Jiang RD, Liu MQ, Chen Y, Shen XR,
Wang X, Zheng XS, Zhao K, Chen QJ, Deng F, Liu LL, Yan B, Zhan FX,Wang YY, Xiao GF, Shi ZL. A pneumonia outbreak associated with a newcoronavirus of probable bat origin. Nature. 2020b;579(7798):270–3.
Zhu Q, Wang H, Wang H, Luo Y, Yu Y, Du Q, Fei A, Pan S. Protective effectsof ethyl pyruvate on lipopolysaccharide-induced acute lung injury
through inhibition of autophagy in neutrophils. Mol Med Rep.
2017;15(3):1272–8.
Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, Zhao X, Huang B, Shi W, Lu R,
Niu P, Zhan F, Ma X, Wang D, Xu W, Wu G, Gao GF, Tan W. A novel coronavirus from patients with pneumonia in China, 2019. N Engl J Med.
2020;382(8):727–33.
Zhuang X, Yu Y, Jiang Y, Zhao S, Wang Y, Su L, Xie K, Yu Y, Lu Y, Lv G. Molecularhydrogen attenuates sepsis-induced neuroinflammation throughregulation of microglia polarization through an mTOR-autophagydependent pathway. Int Immunopharmacol. 2020;81:106287.
Zou R, Wang MH, Chen Y, Fan X, Yang B, Du J, Wang XB, Liu KX, Zhou J.
Hydrogen-rich saline attenuates acute lung injury induced by limb
ischemia/reperfusion via down-regulating chemerin and NLRP3 in rats.
Shock. 2019;52(1):134–41.

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