bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Na/K‐ATPase Non‐Enzymatic Function in Proximal Tubule Sodium Handling
Authors: Mukherji Shreya Tapan , Mayes Isabella W , Liu Jiang , McDermott Jeff Paul , Blanco Gustavo , Pierre Sandrine V , Xie Zijian
Published: June 2021

Systemic levels of endogenous cardiotonic steroids (CTS) increase markedly during salt loading, volume expansion and renal insufficiency, suggesting a physiological role in the regulation of renal Na+ handling. CTS are classically known as specific inhibitors of Na/K‐ATPase (NKA) α1 ion‐pumping function, which is critical for Na+ and water reabsorption in the renal proximal tubule (PT). At much lower concentrations, closer to the range of those reported for endogenous CTS in the blood, they also initiate NKA/Src‐mediated signaling in renal cell cultures. To investigate the respective roles of PT NKA α1/Src signaling and ion‐pumping function in physiological salt handling, we developed a PT‐specific NKA α1 knockout (RPTα1−/−) mouse with PT‐specific rescue by wild‐type NKA α1 (RPT α1WT) or a mutant NKA α1 with intact ion‐pumping function and blunted NKA/Src signaling (RPTα1Y260A).

The PT‐specific NKA α1 knockout mouse was generated by crossing SGLT2 (sodium glucose co‐transporter 2)‐Cre mice with Floxed ATP1a1 mice. A SGLT2‐Cre/Rosa 26 system was then used to re‐introduce α1WT or α1Y260A expression at the Rosa26 locus. Mice were born with the expected Mendelian ratio and appeared phenotypically normal, with no detectable change in water and food intake, or body weight. Renal phenotyping was further assessed using metabolic cages in 2–4 month‐old male and female mice.

PT‐specific KO and rescue was confirmed by immunohistochemistry in PT cells isolated from RPTα1−/−, RPTα1WT, and RPTα1Y260A mice. Kidney size, morphology and structure appeared overall normal following periodic acid shift (PAS) and trichrome staining. Functionally, in contrast with the predicted outcome based solely on the classical enzymatic function of NKA, a significant decrease in daily urine output (0.55±0.2 vs 1.76±0.3 mL/24h in RPTα1+/+, n=8–10, p<0.01) and absolute Na+ excretion (0.13±0.07 vs 0.35±0.0.5 mmol/24h in RPTα1+/+, n=6, p<0.01) were observed in the absence of PT NKA. The urinary clearance of lithium was significantly decreased in RPTα1−/− (1.42±0.3 vs 4.13±0.5 mL/min in RPTα1+/+, n=3, p<0.05), suggesting that the observed increase in Na+ reabsorption originated in the PT. The urinary output was rescued in the RPTα1WT (2.12±0.3 vs 2.16±0.4 mL/24h in RPTα1WTcontrol, n=7–10, p>0.05) but not in the RPTα1Y260A (0.42±0.1 vs 1.56±0.2 mL/24h in RPTα1Y260Acontrol, n=6–8, p<0.01), which supported the role of NKA α1/Src signaling in the PT Na+ reabsorption.

These results support a previously unascertained physiological role of NKA/Src signaling in PT Na+ and water reabsorption, and warrant further investigation to assess the mechanism and possible impact on blood pressure regulation.

Support or Funding Information

Marshall Institute of Interdisciplinary Research Funds

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sodium self‐inhibition and proton sensitivity do not correlate with proteolytic processing in epithelial sodium channels containing the δ‐subunit
Authors: Althaus Mike , Gettings Sean Michael , Wichmann Lukas , Krasteva‐Christ Gabriela , Maxeiner Stephan
Published: June 2021

The epithelial sodium channel (ENaC) is the only constitutively‐active ion channel of the DEG/ENaC protein family and evolved as a mechanism for sodium conservation during tetrapod evolution. We recently characterised a Xenopus laevis ENaC isoform which consists of the δ‐, β‐and γ‐ENaC subunits (Wichmann et al. J Biol Chem 4;293(18):6647–6658). Currents generated by these δβγ‐ENaCs have a slow transient nature due to a pronounced sodium self‐inhibition (SSI). In contrast to canonical ENaCs composed of the α‐, β‐ and γ‐subunits, δβγ‐ENaCs are not stimulated by proteases. The δ‐subunit is not proteolytically processed during intracellular maturation and the presence of the δ‐subunit prevents cleavage of the γ‐subunit at the cell surface. We therefore hypothesised that a lack of proteolytic processing might explain the transient nature of currents generated by Xenopus δβγ‐ENaCs and might indicate an evolutionary prerequisite towards constitutive ENaC activity.

We expressed αβγ‐ or δβγ‐ENaC from guinea pigs (Cavia porcellus) as well as Xenopus laevis in Xenopus oocytes and measured currents generated by those isoforms as well as their degree of SSI, response to extracellular chymotrypsin (2 μg/ml) and extracellular acidification (pH 6.0), by two‐electrode voltage‐clamp electrophysiology.

In contrast to Xenopus laevis δβγ‐ENaC, currents generated by Cavia porcellus δβγ‐ENaC did not have a transient form and had a profoundly reduced SSI compared to the Cavia porcellus αβγ‐ENaC isoform. Like our previous observations using Xenopus laevis ENaCs, Cavia porcellus αβγ‐ENaC was robustly activated by extracellular chymotrypsin, whereas Cavia porcellus δβγ‐ENaC was insensitive to extracellular protease. Xenopus laevis δβγ‐ENaC was strongly activated by extracellular acidification due to inhibition of SSI, whereas Cavia porcellus δβγ‐ENaC was insensitive to extracellular acidification.

We conclude that the absence of proteolytic ENaC activation is not directly linked to a transient ion channel activity. By contrast, a strong SSI and proton sensitivity correlate with a more transient ENaC activity, whereas a lack of SSI and proton insensitivity renders ENaC constitutively‐open. These findings might suggest that changes in the kinetics of SSI and proton sensitivity rather than proteolytic processing determined ENaC evolution towards a constitutively‐active ion channel.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Aging Increases Physiological Function of TRPC3 Channels in Female Arterial Smooth Muscle
Authors: Goldsmith Jacob A. , Evanson Kirk W.
Published: June 2021

Cardiovascular function declines with age, but patterns of vascular aging differ between the sexes across lifespan. In arterial smooth muscle, transient receptor potential canonical 3 (TRPC3) channels participate in the regulation of intracellular calcium and smooth muscle contractility. The effects of aging on TRPC3 function in female arterial smooth muscle is poorly understood. Here, we investigated physiological function of TRPC3 channels in pressurized, endothelium‐denuded middle cerebral arteries from young (~2 months) and old (~ 20 months) female CD (Sprague Dawley) IGS rats. Myogenic tone (60 mmHg) was similar between young and old cerebral resistance size arteries, however membrane depolarization‐induced vasoconstriction (60 mM K+) was reduced with age. Application of the selective TRPC3 channel inhibitor, Pyr3 (10 μM), elicited vasodilation in both young and old, however Pyr3‐mediated vasodilation was substantially larger in aged females. Application of 1‐oleoyl‐2‐acetyl‐sn‐glycerol (OAG, 50 μM), a diacylglycerol analog, enhanced myogenic tone to a greater degree in old females as compared to young, while administration of Pyr3+OAG resulted in a greater loss in developed tone in old females. In conclusion, physiological function of TRPC3 channels is elevated with age in female arterial smooth muscle, which could be an important compensatory mechanism to maintain myogenic tone in cerebral resistance size arteries.

Support or Funding Information

Florida State University

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
BIN1 clusters CaV1.2 channels in vascular smooth muscle
Authors: O'Dwyer Samantha , Moreno Claudia , Klug Nicholas , Santana Luis Fernando
Published: June 2021

Resistance vessel such as mesenteric arteries respond to increases in intravascular pressure by constricting. Ca2+ influx via voltage‐gated CaV1.2 channels in the smooth muscle surrounding these vessels is critical for the development of myogenic tone and thus the regulation of arterial dimeter and blood flow. Our group discovered that CaV1.2 channels have an inherent ability to form clusters and functionally couple in response to local elevations in [Ca2+]i. The consequence of these channels coming together is that they amplify Ca2+ influx during depolarization. However, the mechanisms dictating the arrangement of CaV1.2 channels in smooth muscle cells are unknown. BIN1, a member of the BAR (Bin1‐Amphiphysin‐Rvs) domain superfamily, has been implicated in the trafficking of CaV1.2 channels but has not yet been studied in smooth muscle. In this study, we test the hypothesis that BIN1 promotes the formation of CaV1.2 clusters enhancing overall Ca2+ influx into the vascular smooth muscle and shaping arterial diameter. We report that BIN1 is expressed and translated in arterial smooth muscle while ground state depletion (GSD) super‐resolution imaging suggest that smooth muscle specific down‐regulation of BIN1 diminishes CaV1.2 cluster formation. Using patch clamp electrophysiology and pressurized arteriography, we observed that loss of BIN1 substantially diminishes ICa and attenuates arterial tone. Overall, these results suggest that BIN1 is a critical component in shaping CaV1.2 clustering and plays a physiological role in vascular smooth muscle Ca2+ entry and arterial diameter.

Support or Funding Information

This work is supported by NIH R01 HL085870 (LFS), T32GM099608 (SO), and 18PRE33960249 (SO)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Malignant Hyperthermia: A secondary factor, i.e., intense peripheral vasoconstriction, drives heat retention
Authors: Williams Charles H
Published: June 2021

MH is a lethal genetic disease at the sodium channel which allows an influx of sodium ions into muscle cells that must be pumped back out by the Na+K+ATPase, thus expending copious amounts of ATP, i.e. a futile cycle, which produces high body temperature. The metabolic rate goes from 5ml/O2/Kg to over 50ml/O2/Kg.

A peripheral vasoconstriction develops which shuts down heat loss via radiation thru the skin. This produces a purplish mottled skin color in the skin of a white pig. It also holds the heat internally and raises core temperature up to 118oF. The vasoconstriction is so severe that it increases arterial blood pressure to over 400 mm Hg. Heart rate increases to over 200 bpm and the heart function rapidly degrades resulting in heart failure due to the excessive workload on the heart.

Preliminary data suggests that norepinephrine release drives the vasoconstriction and the increased heart rate.

All the deleterious effects can be prevented by pretreatment with Organon 9426, a non‐depolarizing muscle relaxant. Sevoflurane, a new general gaseous anesthetic, is a weaker triggering agent than Halothane and can be used for 2–3 hours with minimal MH triggering effect.

Succinylcholine is a very potent MH triggering agent and should not be used for human surgery cases.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Interferon alpha/beta receptor 1 inhibition results in delayed onset increased blood pressure and altered vascular remodeling
Authors: Brown Isola A.M. , Good Miranda E. , Peruri Alekhya , Isakson Brant E.
Published: June 2021

Emerging studies have begun to recognize a role for the immune system in mediating blood pressure, where the depletion or inhibition of immune cells attenuates increased blood pressure in animal models of hypertension. What is less clear, however, is how immunosuppression and the downregulation of specific signaling pathways contributes to the regulation of blood pressure in the absence of a hormonal or other stimulus. The increased incidence of new‐onset hypertension in patients who are prescribed immunosuppressants suggests a relationship between decreased immune activity and hypertension. We investigated this relationship and tested the hypothesis that the suppression of the innate and adaptive immune systems alters vascular structure and blood pressure homeostasis. We induced immunosuppression by treating 11‐week old male C57Bl/6 mice with 4mg of purified anti‐interferon alpha/beta receptor 1 (IFNAR1) antibody via intra‐peritoneal injection. Blood pressure was measured continuously via a radiotelemetry transmitter implanted in the left carotid artery for up to 11 weeks post anti‐IFNAR1 treatment. Following blood pressure recordings, animals were sacrificed and blood vessels including the aorta, renal artery and mesenteric vessel pairs were isolated and analyzed by histology for changes in vascular protein expression and vessel remodeling. Beginning ~10 days post anti‐IFNAR1 treatment, immunosuppressed mice developed increased mean arterial pressure (MAP) during their active period (night), that was attributable to both increased diastolic and systolic blood pressures. Comparatively, only diastolic pressures increased during the rest period (day), resulting in a MAP that was not significantly increased. These changes in pressure were sustained up to 25 days post anti‐IFNAR1 treatment. At 6, 8 and 11 weeks post anti‐IFNAR1, daytime blood pressures in immunosuppressed animals were comparable to control mice while nighttime systolic, diastolic and MAPs remained elevated. Histological analysis of vessels collected 11 weeks after anti‐IFNAR1 treatment showed altered lumen diameter and medial thickness in the aorta and renal arteries. Our findings show a role for immunosuppression in regulating blood pressure homeostasis and vascular structure, and begin to identify mechanisms of remodeling that may be involved. Future work will how investigate key vascular signaling pathways and how they are altered during immunosuppression and the resulting hypertension.

Support or Funding Information

Ford Foundation Postdoctoral Grant (IAMB), HL 088554 R01 (BEI)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Cerebral Vascular Function in a Murine Model of Experimental Cerebral Malaria
Authors: Brooks Steven D , Da Silva Moreira Aline , Carvalho Leonardo , Ackerman Hans
Published: June 2021

Cerebral Malaria (CM) is among the most severe complications of malarial infection, with a mortality rate of 15–20%. Many survivors of CM develop lasting neurological sequalae, cognitive and behavioral impairments, or epilepsy. However, the etiology of CM is poorly defined, and treatment strategies are limited.

Studies in the murine model of experimental cerebral malaria (ECM) have demonstrated cerebral blood flow (CBF) impairments that are associated with decreased nitric oxide (NO) bioavailability, blood brain barrier disruption, endothelial activation, impaired pial vessel reactivity, and cerebral ischemia. While these complications have been observed in vivo, cerebral artery function has not specifically been evaluated in ECM. Therefore, the aim of this study was to interrogate vasoreactivity and NO bioavailability in cerebral arteries (CAs) isolated from ECM mice, with the hypothesis that arterial vasodilatory function would be impaired by ECM.

ECM was induced by Plasmodium berghei ANKA (PbA) infection in 10–12 week old C57Bl/6J mice and confirmed by murine coma score. On day 6 post‐infection, CBF was measured by laser speckle imaging. Cerebral arteries (CAs) were dissected from the brain into a modified Krebs buffer. Cerebral vasoreactivity was assessed by ex vivo pressure myography in middle cerebral arteries (MCA) obtained from control (n=4) and ECM (n=7) mice. NO production from dissected vessels was measured in an ex vivo Daf‐2 fluorescence assay (n=6, n=6).

As expected, ECM mice had a significant, 25% reduction in CBF. However, ex vivo MCAs from ECM mice maintained robust endothelium‐dependent vasodilation to methacholine (MCh), which was inhibited by L‐NAME. ECM MCAs also exhibited normal dose responses to serotonin‐induced vasoconstriction and nitroprusside‐induced vasodilation, suggesting normal vasoreactivity of ECM cerebral arteries. Similarly, the results of the ex vivo Daf‐2 assay showed that the MCh‐induced NO production from ECM arteries was comparable to controls. To test whether ECM plasma would induce vascular dysfunction in ex vivo CAs, we incubated CAs obtained from ECM (n=2) and control (n=6) mice in plasma collected from ECM or control animals. Surprisingly, we found that plasma from ECM mice increased NO production of both ECM and control CAs.

These unexpected results indicate that NO bioavailability and vasoreactivity are preserved in cerebral vessels in ECM, and that circulating factors in the plasma during PbA infection actively stimulate NO production. Our next focus will be on reconciling decreased CBF with preserved vascular function, as well as identifying the NO‐stimulating mediator(s) present within ECM plasma.

Support or Funding Information

Research and funding support from NIAID Division of Intramural Research.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Chronic Intracerebroventricular Leptin Infusion Attenuates Cardiac Dysfunction After Myocardial Infarction
Authors: Gava Fabio N. , da Silva Alexandre A. , Ashraf Sadia , Omoto Ana C.M. , Dai Xuemei , Pullman Mallory , Harmancey Romain , Hall John E. , do Carmo Jussara M.
Published: June 2021

Leptin is an important regulator of energy balance and substrate utilization in various tissues including the heart. In the present study we tested whether activation of leptin receptors in the central nervous system (CNS) confers protection against cardiac dysfunction after myocardial infarction (MI) induced by permanent ligation of the left anterior descending coronary artery (LAD). Male Sprague‐Dawley rats at 12 weeks of age were implanted with BP telemetry transmitters and an intracerebroventricular (ICV) cannula was inserted into the lateral ventricle. After 10 days of recovery, mean arterial pressure (MAP) and heart rate (HR) were measured 24‐hrs/day by telemetry and cardiac function was assessed by echocardiography (VisualSonics‐VEVO3100®). After stable baseline measurements for 4 days, the LAD was permanently ligated and saline vehicle (0.5 μL/hr, n=6) or leptin (15 μg/day, n=7) were infused ICV via osmotic minipump for 28 consecutive days. Compared to vehicle treatment, chronic ICV leptin infusion for 4 weeks markedly attenuated cardiac dysfunction caused by MI as evidenced by normalization of global cardiac radial strain (39±4 to 36±5 vs. 37±4 to 25±3 %), cardiac output (92±5 to 110±10 vs. 105±6 to 83±9 ml/min) and left atrium to aorta ratio, an index of cardiac congestion, (1.6±0.1 to 1.6±0.1 vs. 1.7±0.1 to 2.3±0.1). Central leptin administration also significantly improved ejection fraction (from 35±3 to 49±2 %) and fractional shortening (from 12.4±0.8 to 18.6±1.4 %, for week 1 and week 4 post‐MI, respectively), whereas no improvement was observed in vehicle‐treated rats (from 36±4 to 30±2 %, and from 12.2±1.7 to 10.1±1.3 %, respectively). In addition, ICV leptin infusion prevented the bradycardia observed in vehicle‐treated rats (354±3 to 370±6 vs. 360±7 to 323±6 bpm) but did not attenuate the reduction in MAP evoked by MI (101±4 to 94±3 vs. 102±3 to 97±2 mmHg). There was no difference in infarcted area between groups (30±3 vs. 29±5 %). These results indicate that leptin can improve cardiac function and attenuate progression of heart failure after MI via a CNS‐mediated mechanism.

Support or Funding Information

NHLBI PO1HL51971, NIGMS P20GM104357 and NIGMS U54GM115428

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
RAGE‐DIAPH1 modulates hyperglycemia driven induction of Serum response factor target genes in cardiac cells
Authors: Sreejit Gopalkrishna , Quadri Nosirudeen , Ananthakrishnan Radha , Schmidt Ann Marie , Ramasamy Ravichandran
Published: June 2021

The mammalian Diaphanous‐related formin diaphanous 1 (DIAPH1) is a canonical effector for Rho small GTP‐binding proteins. When activated by GTP‐bound RhoA, DIAPH1 relies upon its formin homology‐2 domain to elongate linear actin filaments by adding actin monomers to their barbed ends. As a consequence, DIAPH1 also signals to the nucleus via the myocardin‐related transcription factor/serum response factor (MRTF/SRF) axis to effect gene expression. DIAPH1 interacts with the cytoplasmic domain of the receptor for advanced glycation end products (RAGE) through its poly‐proline‐rich formin homology‐1 domain. In response to RAGE ligand stimulation, DIAPH1 participates in signal transduction in smooth muscle cells, macrophages, immune cells, and transformed cells. While RAGE is known to be an essential component of the in vivo response to myocardial stress in diabetes, role of DIAPH1 in diabetic hearts has not been investigated. The goal of this study is to investigate the role of cardiac DIAPH1 in the physiological response to diabetes in mice. In wild type littermate (WT) mice and Diaph1 deleted mice diabetes was induced using low doses of streptozotocin and hearts harvested after 3 months of diabetes. Myocardial Diaph1 expression was significantly increased in diabetic WT mice vs non‐diabetic WT mice (p<0.05). In H9C2 cells, treatment with high glucose (20 mM) and RAGE ligands significantly increased Diaph1 expression. We observed significant increases in expression of a sub‐set of SRF target genes in response to high glucose and that these SRF target genes were attenuated in Diaph1 silenced cells. SRF target genes c‐Fos, Egr‐1, Mmp‐2, Mmp‐9 and Sm‐22, increased in response to high glucose in a DIAPH1 dependent manner, while Tgf‐β1, Tgf‐β2, Atp2a and Cofilin did not show any changes in response to high glucose treatment. We observed that high glucose and RAGE ligands induces DIAPH1 driven changes in SRF target gene expression via ERK1 and PKC αβ signaling mechanisms. We posit that DIAPH1, by its impact on SRF and SRF target genes may play an important role in mediating diabetic cardiomyopathy.

Support or Funding Information

NIH HL60901

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
A Single High Sodium Meal Impairs Dynamic Cerebral Autoregulation
Authors: Migdal Kamila U , Robinson Austin T , Watso Joseph C , Babcock Matthew C , Serrador Jorge M , Farquhar William B
Published: June 2021

The ability for the brain to maintain cerebral blood flow despite changes in arterial blood pressure is termed cerebral autoregulation (CA). CA is known to be impaired in patients with cognitive decline and in patients that have suffered a stroke. Dysfunctional CA is also predictive of strokes and all‐cause mortality. Excess dietary sodium (Na+) consumption has been implicated in increased stroke risk. However, the effects of a high dietary Na+ consumption on cerebral autoregulation is unknown.

Purpose

We tested the hypothesis that a single high‐ vs low‐Na+ meal impairs CA in healthy young adults.

Methods

Twenty healthy, normotensive adults (11F/9M; age: 26±5 yrs; BMI: 24.7±3.5 kg/m2; BP: 105±6/58±4 mmHg, mean±SD) participated in this crossover design study. We provided participants with high‐ (HS: 1,495 mg) and low‐(LS: 138 mg) Na+ meals in a randomized order. Visits were separated by one week for males. We tested females in the early follicular phase of their menstrual cycle (~four weeks apart). Right middle cerebral artery (MCA) velocity (via transcranial Doppler ultrasound) and beat‐to‐beat blood pressure (via photoplethysmography) was assessed while participants lay supine for ten minutes. Dynamic CA was measured using transfer function analysis (coherence, gain, and phase) between spontaneous changes in mean arterial pressure to MCA velocity. Transfer function analysis was calculated in the 0.03–0.15 Hz range which reflects cerebral autoregulatory processes. Dynamic CA was measured prior to‐ and 60 minutes post‐meal. Biochemical data from venous blood samples were analyzed using two‐way repeated measures ANOVA (meal x time). Tukey post hoc comparisons were used when appropriate. The change in dynamic CA from baseline was analyzed using paired, two‐tailed, t‐tests.

Results

Serum Na+ was elevated on the high‐ vs low‐Na+ meal 60 minutes post‐meal (HS=141.7±0.8 vs LS=140.2±0.6 mmol/L, p<0.001). Brachial mean blood pressure 60 minutes post‐meal was not different between the conditions (HS=78±5 vs LS=78±7 mmHg, p>0.05). Coherence, gain and phase were not different in the very low frequency band (0.03–0.07 Hz) (p>0.05 for all). The change in gain from baseline in the low frequency band (0.07–0.15 Hz) was significantly elevated following the high‐Na+ meal vs the low‐Na+ meal, implying impaired dynamic CA (HS= Δ0.14±0.46 vs LS=Δ−0.17±0.43 %/mmHg, p=0.02). The change in phase and coherence from baseline was not different between the high‐ and low‐Na+ meals (p=0.33 and p=0.17, respectively).

Conclusion

These preliminary data suggest that a high sodium meal may impair dynamic cerebral autoregulation in healthy young adults.

Support or Funding Information

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sodium Nitrite Supplementation Improves Vascular Endothelial Function but not Motor or Cognitive Function in Middle‐Aged and Older Adults
Authors: Woodward Kayla A. , Santos‐Parker Jessica R. , Lubieniecki Kara L. , Nagy Erzsebet , Bryan Nathan S. , Chonchol Michel , Justice Jamie N. , Seals Douglas R. , Rossman Matthew J.
Published: June 2021

We previously observed improvements in vascular endothelial function as well as exploratory measures of motor and cognitive function in a pilot study of sodium nitrite supplementation in middle‐aged and older (MA/O) adults. Here, we sought to establish the efficacy of sodium nitrite for improving endothelial function (primary outcome) while also taking advantage of the opportunity to confirm our motor and cognitive function findings in a larger randomized, placebo‐controlled, double‐blind, parallel group study with 12 weeks of sodium nitrite (80 mg/day) vs. placebo in healthy MA/O adults (n = 49, 68±1 yr) with impaired endothelial function (baseline brachial artery flow‐mediated dilation [FMD] <6%). Sodium nitrite increased plasma levels of nitrite acutely (10‐fold, p<0.05 vs placebo) and chronically (p<0.05) and was well‐tolerated over the 12‐week supplementation period. Vascular endothelial function, measured by brachial artery FMD, was increased by 28% vs. baseline (p<0.05) after 12 weeks of supplementation (3.9±1.2 to 5.0±1.8%, p<0.05), but unchanged with placebo (3.8±1.4 to 4.0±1.5%, p>0.05). There were no differences in secondary outcomes of motor or cognitive function assessed with measures of the NIH Toolbox and other standardized tests between the sodium nitrite and placebo group after 12 weeks (all p>0.05). There were no differences in subject characteristics, body composition or circulating markers of inflammation and oxidative stress with sodium nitrite or placebo (all p>0.05). Collectively, these results indicate that sodium nitrite supplementation for 12 weeks improves endothelial function but does not affect motor or cognitive function in healthy, high‐functioning MA/O adults. These findings suggest therapeutic strategies to enhance nitrite levels may hold promise for treating age‐related vascular endothelial dysfunction.

Clinicaltrials.gov Identifier: NCT02393742

Support or Funding Information

NIH R01 AG013038, K01 DK115524 and NIH/NCATS Colorado CTSA Grant Number UL1 TR002535; American Physiology Society UGREF Award

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
MG53 Protein Protects Aortic Valve Interstitial Cells from Membrane Injury and Fibrocalcific Remodeling
Authors: Adesanya T.M. Ayodele , Russell Melanie , Park Ki Ho , Zhou Xinyu , Sermersheim Matthew A , Gumpper Kristyn N , Koenig Sara N , Tan Tao , Whitson Bryan A , Janssen Paul M.L. , Lincoln Joy , Zhu Hua , Ma Jianjie
Published: June 2021

The aortic valve of the heart experiences constant mechanical stress under physiological conditions. Maladaptive valve injury responses contribute to the development of valvular heart disease (VHD). Here we test the hypothesis that MG53, an essential cell membrane repair protein, can protect valvular cells from injury and fibrocalcific remodeling processes associated with VHD. We found that MG53 is expressed in pig and human patient aortic valves and observed aortic valve disease in aged Mg53−/− mice. Aortic valves of Mg53−/− mice showed compromised cell membrane integrity. In vitro studies demonstrated that recombinant human MG53 (rhMG53) protein protects primary valve interstitial cells (VICs) from mechanical injury and that, in addition to mediating membrane repair, rhMG53 can enter VICs and suppress transforming growth factor‐b‐dependent activation of fibrocalcific signaling. Given the preserved contractile function of Mg53−/− mouse hearts under physiological conditions, the observation that aged Mg53−/− mice display hemodynamic and histological signs of aortic valve disease highlights a critical in vivo mechanism of MG53‐mediated valvular protection. Overall, our work revealed a dual function for MG53 in maintaining the integrity of the VICs and in controlling TGF‐β‐mediated fibrotic remodeling associated with VHD.

Support or Funding Information

Research Support: RO1 grants (HL069000 and AR070752) from NIH to J.M.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Augmented Survival, Angiogenic Properties and Mobilization of Human Endothelial Progenitor Cells Following Exposure to Sevoflurane
Authors: Vlad Adelina , Niculescu Loredan , Stancu Camelia , Popescu Mihaela , Stanca Ionut , Corneci Dan , Ceafalan Laura , Gilca Marilena , Surcel Mihaela , Popescu Andreea , Dimulescu Doina
Published: June 2021

Anesthetic preconditioning (APC) with volatile agents has cardiac anti‐ischemic virtues that may be linked to stimulating effects of volatile anesthetics on stem cells biology. We investigated the influence of sevoflurane (Sevo) on apoptosis, proliferation, incorporation in tube‐like structure and mobilization of human endothelial progenitor cells (EPCs). 7‐days old cultured EPCs derived from human cord blood mononuclear cells were exposed in vitro to sevoflurane 2% or 4% in air/5% CO2, or only to air/5% CO2 (sham control) for 2 hrs in a modular chamber. Proliferation, apoptosis and incorporation of EPCs into tube‐like structures of HUVEC was evaluated 24 hrs later. EPCs plasma levels were evaluated by flow‐cytometry and in vitro culture assay before exposure to sevoflurane (1 MAC in 50% O2) or only to 50% O2 (sham control) and 24 hrs afterwards, in blood samples collected from coronary artery disease patients. Values are expressed as means ± SEM, compared by ANOVA. In the in vitro preconditioning setting, sevoflurane stimulated EPCs proliferation estimated by the MTS assay (n = 12, p < 0.01 for 2% Sevo, p < 0.001 for 4% Sevo) and by counting adherent DilAcLDL+/ FITC‐UEAI+ cells (n = 4, p < 0.01 for 2% Sevo, p < 0.001 for 4% Sevo), diminished apoptosis measured by annexin V/ propidium iodide assay (n = 5, p < 0.05 for both 2% and 4% Sevo), and raised the number of incorporated DiIAcLDL‐EPCs into HUVEC tube‐like structures (n = 4, p < 0.01 for 2% Sevo, p < 0.001 for 4% Sevo) when compared to control. Plasma CD45dim/CD34+/CD309+ and CD45dim/CD34+/CD309+/CD133+ mononuclear cell populations were increased in Sevo treated patients (n = 15) vs. the control group (n = 10) at 24 h post‐exposure vs. baseline (p < 0.01), and the number of adherent DilAcLDL+/FITC‐UEAI+ cells in 7 days old EPCs cultures was significantly higher in the study group vs. control between the same time points (p < 0.05). Our data prove that sevoflurane positively influences the biology of EPCs both in vivo and vitro, and may have an important cardioprotective impact in various interventional and surgical heart procedures by improving angiogenesis and ischemic tissue repair.

Support or Funding Information

The financial support was provided by UEFISCDI Romania, research grant PN‐II‐RUTE‐2012‐3‐0463.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Impact of Salt Restriction on Central and Peripheral Hemodynamics During Exercise in Essential Hypertension: A Systematic Investigation
Authors: Ratchford Stephen M , Broxterman Ryan R , LaSalle David Taylor , Kwon Oh‐Sung , Hopkins Paul N , Richardson Russell S , Trinity Joel D
Published: June 2021

Background

Dietary salt restriction is a well‐established approach to lower blood pressure and reduce cardiovascular disease risk in hypertensive individuals. While high blood pressure increases the risk of cardiovascular events in hypertensive individuals during exercise, little is known regarding the effects of salt restriction on central and peripheral hemodynamic responses to exercise in individuals with hypertension.

Purpose

Therefore, this study sought to determine the impact of salt restriction on central and peripheral hemodynamic responses to handgrip and knee extension exercise, exercise modalities which circumvent the central limitations to whole body exercise.

Methods

Hypertensive patients (14M/8F, 51±10y, 173±11cm, 99±23kg) forwent antihypertensive medication use for at least 2 weeks prior to cross‐sectional enrollment on a 5‐d liberal salt (LS: 200mmol/d) followed by a 5‐d restricted salt (RS: 10mmol/d) diet. Patients were studied prior to and during: supine static intermittent handgrip (HG) exercise at 15, 30, 45% MVC (MVC: 20±4kg) and seated knee extension (KE) exercise at 40, 60, 80% KE Max (KE Max: 35±17W).

Results

Salt restriction lowered resting systolic blood pressure (SBP) (supine: −12±3mmHg, seated: −14±3mmHg, P<0.05), diastolic blood pressure (DBP) (supine: −3±2mmHg, seated: −5±1mmHg, P<0.05), and mean arterial pressure (MAP) (supine: −8±2mmHg, seated: −8±2mmHg, P<0.05). Similar reductions in SBP, DBP, and MAP were maintained during HG and KE exercise (all p<0.05). Despite lower blood pressure during exercise, peripheral blood flow and vascular conductance, were similar between groups during HG and KE exercise.

Conclusions

Salt restriction appears to be an effective means to ameliorate blood pressure and reduce the risk of a cardiovascular event during exercise in hypertensive individuals without altering blood flow and vasodilatory ability during either arm or leg exercise.

Support or Funding Information

Veteran Affairs Rehabilitation Research and Development Grant, 1KRX001215 CDA2, JD Trinity and Merit Grants, E1697R and E6910R, RS Richardson; American Heart Association Grant, 14SDG1850039, JD Trinity; National Heart, Lung, Blood Institute Grant, P01‐HL‐091830, RS Richardson.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Leptin induces hypertension acting via Transient Receptor Potential channel subfamily M member 7 (Trpm7) in the carotid bodies
Authors: Shin Mi Kyung , Caballero Candela , Tang Winnie Yan‐Yee , Yeung Bonnie Ho‐yee , Gu Chenjuan , Sham James S.K. , Shirahata Machiko , Polotsky Vsevolod Y.
Published: June 2021

RATIONALE

Obesity leads to cardiovascular morbidity and mortality acting via multiple mechanisms including increased prevalence and severity of hypertension. Obesity leads to high levels of leptin which is produced in adipocytes. Increased leptin levels have also been implicated in increased sympathetic activity and the pathogenesis of hypertension in obesity. However, mechanisms for the effects of leptin on blood pressure are unclear. The carotid bodies (CB) express leptin receptor (LepR), but the mechanisms and consequences of leptin action in CB are unknown. We have previously demonstrated that leptin enhances carotid sinus nerve activity in response to hypoxia and this effect is abolished by non‐selective blockers of transient receptor potential (TRP) channels (Shirahata et al., 2015). We have performed a retrospective analysis of the CB transcriptome in mice and found that trpm7 is the most abundant TRP channel. We hypothesized that high levels of circulating leptin signal via LepR in CB leading to hypertension and this effect will be abolished by trpm7 shRNA.

METHODS

1) We developed a novel technique allowing us to express LepR in mouse CB using an adenoviral vector suspended in Matrigel. LepR deficient male db/db mice were implanted with telemetry in the left femoral artery for blood pressure monitoring. Blood pressure measurements were performed before and after CB infection with adenovirus carrying the LepR gene (Ad‐LepR, n=5) or luciferase (control, Ad‐Laz, n=6); 2) Male C57BL/6J mice (n=13) were implanted with telemetry for blood pressure monitoring at baseline, during leptin infusion (120ug/day for 3 days via a SC pump) with adenoviral vector which contained trpm7 shRNA (N=6) or control shRNA (N=7);

RESULTS

1) LepR expression in CB of db/db mice significantly increased mean arterial pressure by 6 mmHg during the day and by 13 mmHg during at night (p < 0.005), whereas CB infection with a control virus had no effect (p=0.585). 2) In C57BL/6J mice, leptin infusion increased mean arterial pressure by 11 mm Hg during the day (p<0.001) and by 15 mm Hg at night (p <0.001). Adenoviral trpm7 shRNA completely abolished leptin‐induced hypertension (p < 0.001).

CONCLUSIONS

Leptin increases blood pressure acting via LepR in the CB. Leptin‐induced hypertension is abolished by trpm7 shRNA suggesting that leptin may act via TRPM7.

Support or Funding Information

HL 133100, HL128970

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Amino Acid‐Based Oral Rehydration Solution Mitigates Exertional Heat Stroke Severity but Does Not Alter the Innate Immune Response
Authors: King Michelle Ann , Dineen Shauna , Ward Jermaine , Mayer Thomas , Plamper Mark , Grosche Astrid , Xu XiaoDong , Sasidharan Anusree , Ward Matthew , Clanton Thomas , Vidyasagar Sadasivan , Leon Lisa
Published: June 2021

Theadverse sequelae following exertional heat stroke (EHS) is hypothesized to be aconsequence of heat cytotoxicity and endotoxin leakage secondary to increasesin gut permeability. Administration ofspecific amino acids has been shown to tighten the mucosal barrier, reduceparacellular permeability, decrease endotoxin leakage, and suppress the subsequentinflammatory response. The primaryobjective of this study was to determine if an amino acid based oralrehydration solution (AA‐ORS) would increase performance in the heat and dampenthe innate immune response following an EHS protocol when compared to a watercontrol (H2O). To explorethis, C57 BL/6J mice were implanted with temperature transmitters and underwentfour familiarization sessions. On the evening prior to EHS, mice were gavaged with 150 μl of either the AA‐ORS or H2O. The EHS protocol was conducted in an environmental chamber at a temperature of 37.5°C with 30% relative humidity and utilized a forced incremental running protocol. TheEHS protocol continued until neurological symptoms were limiting (core temperature(Tc) 42.2°C ± 0.2 H2O and AA‐ORS). Tissue and blood samples were collected at 0.5, 3, and 24 h post EHS. All mice survived until tissue collection. Performance in the heat was similar between groups as determined by percent dehydration, max speed, distance, time to Tc max, and thermal load (P>0.05). The extent of hypothermia during recovery, a marker of EHS severity, was mitigated with AA‐ORS (P=0.0054). Minimum Tc (AA‐ORS:32.9°C ± 0.4; H2O: 32.1°C ± 0.8; P=0.0020), hypothermia depth (AA‐ORS: 33.3 ±0.5 min; H2O: 32.5 ± 0.8 min; P=0.0024), and hypothermia length (AA‐ORS: 186.9 ± 47.3 min; H2O: 243.6 ± 42.3 min; P=0.0017) were all significantly improved by AA‐ORS. Although AA‐ORS reduced paracellular permeability (4 kDa FITC, Ussing chamber) at both the 30 min and 3 h timepoints (P<0.05), it did not affect the cytokine or chemokine profile (25 plex Luminex panel) in response to EHS at any time point (P>0.05). Inflammation in hypothalamus was alsomeasured as an indication of EHS severity. No differences were seen between AA‐ORS and H2O in mRNA upregulation of IL‐1β, IL‐6, TNFα, MCP‐1, MIP‐1α, MIP‐1β or pattern recognition receptors TLR‐4 and CD14 at the 0.5 or 3 h time points. Further, corticosterone, a hormone that has been shown to suppress the innate immuneresponse, did not differ between treatment groups at any time point. These results suggest that an AA‐ORS improves Tc regulation during EHS recovery, but this dosage had no effect on the systemic inflammatory response that isc haracteristic of EHS. Author views not official US Army or Do Dpolicy.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Impact of repeated local heat stress on skeletal muscle structure and function in humans
Authors: Kim Kyoungrae , Trewin Adam , Petersen Aaron C. , Gavin Timothy P. , Roseguini Bruno T.
Published: June 2021

Introduction

Short‐term exposure to heat stress has been shown to enhance muscle strength and elicit mitochondrial adaptations in human skeletal muscle. We recently documented that exposure to five sessions of heat therapy (HT) accelerates the recovery of fatigue resistance following exercise‐induced muscle damage in humans. However, the long‐term impact of repeated exposure to local heat stress on contractile function and skeletal muscle structure remains unknown. The purpose of the present study was to examine the effects of 8 weeks of daily treatment with local HT on muscle strength, fatigability, fiber size and mitochondrial content in humans.

Methods

Twelve healthy young adults (23.6±1.4 years, BMI 24.9±0.9 kg/m2) had one randomly selected thigh treated with daily HT for 8 consecutive weeks while the opposite thigh served as a control. A water‐circulating garment perfused with water at ~52ºC was used to apply HT for 90 min daily. Knee extensor strength (single peak torque during 3 repetition maximums at 180°/s and 60°/s) and fatigue resistance (total work during 40 repetition maximums at 180°/s) were assessed using isokinetic dynamometry before and after 4 and 8 weeks of treatment. Biopsies were obtained from the vastus lateralis muscle for the determination of myofiber cross‐sectional area and maximal citrate synthase activity.

Results

Treatment with HT elicited an increase in thigh skin temperature (39.8±0.1ºC), while skin temperature remained at baseline levels in the control thigh (32.4± 0.1ºC). A significant treatment effect was observed for the changes from baseline in peak isokinetic torque at 180º/s (p=0.04). On average, the changes in peak isokinetic torque from baseline for HT were ~2 fold higher than control at week 4 (Control: 4.1±3.7 Nm vs. HT: 9±4.6 Nm) and ~4 fold higher at week 8 (Control: 1.7±2.7 Nm vs. HT: 7.7±2.9 Nm). There were no differences between treatments for peak isokinetic torque at 60º/s, myofiber cross‐sectional area and citrate synthase activity.

Conclusion

These results indicate that daily exposure to HT for 8 weeks enhances muscle strength in humans. Local HT may be a practical therapeutic approach to improve muscle function in individuals with limited mobility and skeletal muscle weakness.

Support or Funding Information

Support: American College of Sports Medicine Research Endowment

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Mechanisms Underlying the Stimulatory Effect of Inhaled Sulfur Dioxide on Rat Vagal Bronchopulmonary Sensory Nerves
Authors: Lin An‐Hsuan , Hsu Chun‐Chun , Lin You‐Shuei , Lin Ruei‐Lung , Lee Lu‐Yuan
Published: June 2021

Chronic exposure to sulfur dioxide (SO2), an air pollutant, can cause airway injury and lung diseases. Acute exposure to SO2 triggers cough and reflex bronchoconstriction, indicating a stimulatory effect of SO2 on airway sensory nerves. Indeed, a recent study in our lab has demonstrated that vagal bronchopulmonary C‐fibers are the primary target of inhaled SO2. This study was carried out to investigate the underlying mechanism of this stimulatory effect of SO2 on bronchopulmonary C‐fibers. Our results showed: 1) Inhalation of SO2 (1,000–2,000 ppm, 10 breaths) evoked a pronounced and reproducible stimulatory effect on pulmonary C‐fibers in anesthetized rats. 2) Pretreatment with an intravenous infusion of sodium bicarbonate (120 μmol/kg) raised the baseline arterial pH by 0.08 units, which profoundly diminished the stimulatory effect of SO2 on pulmonary C‐fibers by 83.9%. 3) This stimulatory effect of SO2 was also significantly attenuated by a pretreatment with amiloride (a blocker of acid‐sensing ion channels, ASICs; 11 μmol/kg) alone (Δ = 70.7%); AMG9810 (an antagonist of transient receptor potential vanilloid type‐1, TRPV1; 10 μmol/kg) alone (Δ = 76.7%); and by a combination of amiloride and AMG9810 (Δ = 91.4%). 4) To further investigate if this stimulatory effect is generated by a direct action of SO2 on sensory nerves, the change in intracellular Ca2+ concentration, [Ca2+]i, was measured in isolated rat vagal pulmonary sensory neurons. Perfusion with extracellular fluid saturated with SO2 (1,000 and 2,000 ppm) evoked a significant increase in [Ca2+]i in a concentration‐dependent manner in these neurons, and these responses to SO2 were markedly suppressed by a combined pretreatment with amiloride and AMG9810. 5) In addition, inhalation of SO2 (300 and 600 ppm for 5 min) evoked cough reflex responses consistently in awake mice in a concentration‐dependent manner; the cough responses were almost completely prevented by a pretreatment with amiloride aerosol inhalation (5 mM for 4 min) in TRPV1‐knockout mice. In conclusion, this study suggested that inhalation of SO2 lowered the pH in airway/lung tissues, which exerted a stimulatory effect on vagal bronchopulmonary C‐fibers by activating both ASICs and TRPV1 channels.

Support or Funding Information

NIH grants AI123832 & UL1TR001998

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.