bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen metabolic competition in the lactic acidotic diabetic kidney: A point of no return?
Authors: Laustsen Christoffer , Lipsø Kasper , Østergaard Jakob Appel , Mose Per , Flyvbjerg Allan , Pedersen Michael , Palm Fredrik , Ardenkjaer‐Larsen Jan Henrik 
Published: November 2023

Diabetic nephropathy is directly related to renal hypoxia, with an increased mitochondrial uncoupling and increased energy demand to maintain normal renal function. Lowering the oxygen content in inspired air has shown to worsen the prognostic outcome of diabetic patients independent of glycemic control. We therefore tested the hypothesis that acutely altered renal oxygen availability alters metabolic pathways related to cellular energy production.Methods and materialsHyperpolarized 13C‐MRI and blood oxygenation level‐dependent (BOLD) 1H‐MRI were used to investigate the renal metabolic changes following acute changes in oxygen content in the inspired air in control and streptozotocin‐induced insulinopenic rats with and without insulin treatment.ResultsThe severe lactic acidosis phenotype of diabetes, show a negative sensitivity towards oxygen changes, with a 12% and 16% reduction in the lactate‐to‐total carbon ratio change in both treated and untreated animals, however with no response differences between the treated and untreated group.DiscussionThe negative response to changes in oxygen availability can be the result of an increased lactate pool size masking the Pasteur effect, thus highlighting a key event in the development of kidney disease. The inability of insulin to normalize the lactate‐to‐pyruvate conversion in the present study indicates maintained elevated metabolic flux in these kidneys.Support or Funding InformationThe study was supported by The Simon Spies Foundation and the Danish National Research Foundation. Sascha Gude and Line Nielsen are acknowledged for their laboratory assistance.
(Pro)Renin Receptor Mediates Antidiuretic Action of Vasopressin/Prostaglandin EP4 Subtype
Authors: Yang Tianxin , Lu Xiaohan , Peng Kexin , Wang Fei 
Published: November 2023

Within the kidney, (pro)renin receptor (PRR) is predominantly expressed in the collecting duct (CD), particularly in intercalated cells and is regulated by the EP4 subtype. Here we investigated the function of CD PRR during antidiuresis and defined its relationship with the EP4 subtype as well as vasopressin (VP). Water deprivation (WD) elevated renal PRR expression and urinary soluble PRR (sPRR) excretion in rats. Intrarenal infusion of a PRR decoy peptide PRO20 to rats partially attenuated the decrease in urine volume and the increase in urine osmolality in response to 48‐h WD, in parallel with suppressed aquaporin‐2 expression; a similar effect was seen with EP4 antagonism. The mice lacking PRR in the CD exhibited increased urine volume and decreased urine osmolality at basal condition and exhibited impaired urine concentrating capability after WD, accompanied with severe volume loss and a dangerous level of plasma hyperosmolality. In primary culture of rat inner medullary collecting duct (IMCD) cells, exposure to 10 nM prorenin for 24 h remarkably induced AQP2 protein expression, which was blunted by a PRR decoy inhibitor PRO20 and PRR siRNA. VP treatment for 24 h similarly induced aquaporin‐2 (AQP2) expression, accompanied with increased release of PGE2 and sPRR; the AQP2 upregulation was blunted by antagonism of EP4 or PRR. Overall, we have defined a VP/PGE2/EP4/PRR/AQP2 pathway that appears to play an important role in regulation of urine concentrating capability.Support or Funding InformationThis work was supported by National Institutes of Health Grants DK104072 and DK094956, VA Merit Review from the Department of Veterans Affairs, and National Natural Science Foundation of China Grant No. 91439205 and No. 31330037. T. Yang is a Research Career Scientist in the Department of Veterans Affairs.
Lack of adenylyl cyclase 6 induces alkalosis and enhances urinary acidification
Authors: Poulsen Søren Brandt , Fenton Robert A , Rieg Timo 
Published: November 2023

Adenylyl cyclase isoform 6 (AC6) is expressed along the entire nephron, catalyzes the synthesis of cyclic adenosine monophosphate (cAMP) and contributes to the regulation of various aspects of renal transport. Recent in vitro and ex vivo studies identified that cAMP regulates Cl−/HCO3− exchanger (pendrin) trafficking to the apical plasma membrane of type B intercalated cells. However, the isoforms of AC involved in the regulation of urinary pH are not known. To gain insight in this regard, we studied AC6 knockout (AC6−/−) and littermate wild‐type (WT) mice. As a model of metabolic alkalosis and to test for a defect in urinary alkalinization, mice were supplied sodium‐bicarbonate in their drinking water for 8 days. Baseline urinary pH was significantly lower in AC6−/− mice (AC6−/−: 6.5 ± 0.2; WT: 7.7 ± 0.2, P < 0.05), which was associated with a more alkaline blood pH (AC6−/−: 7.44 ± 0.01; WT: 7.41 ± 0.01, P < 0.05). While blood pH was unaffected in both genotypes after bicarbonate administration compared to baseline conditions, urinary pH was increased in AC6−/− mice during bicarbonate administration, and pendrin abundance was higher compared to WT mice (AC6−/−: 225 ± 16%; WT: 100 ± 6%, P < 0.001). Immunohistochemistry showed a comparable subcellular pendrin distribution and number of pendrin‐positive cells/mm2 cortex in AC6−/− compared to WT mice (AC6−/−: 121.2 ± 8.7; WT: 108.3 ± 6.6, NS), thus possibly indicating intact pendrin regulation. Proton pump (H+‐ATPase B1 subunit) abundance was higher in AC6−/− mice both under baseline conditions (AC6−/−: 175 ± 25 %; WT: 100 ± 7%, P < 0.05) and after bicarbonate administration (AC6−/−: 196 ± 16%; WT: 100 ± 15%, P < 0.01). Furthermore, the number of H+‐ATPase B1 subunit‐positive cells/mm2 was higher after bicarbonate administration both in the cortex/outer stripe outer medulla (AC6−/−: 192.8 ± 10.5; WT: 161.0 ± 9.3, P < 0.05) and in the inner stripe outer medulla (AC6−/−: 312.6 ± 23.5; WT: 224.1 ± 11.3, P < 0.01). In conclusion, our results suggest that lack of AC6 induces mild metabolic alkalosis and enhances urinary acidification under baseline conditions. Stable blood pH after alkaline loading in AC6−/− may require a higher pendrin and H+‐ATPase B1 subunit abundance.Support or Funding InformationThis work was supported by the O'Brien Center for Acute Kidney Injury Research Grant P30DK079337, Diabetes Endocrinology Research Center P30DK063491, American Heart Association 15BGIA22410018, Satellite Healthcare (a not‐for‐profit renal care provider), Department of Veterans Affairs Merit Review Award, and Center on Genetics of Transport and Epithelial Biology at University of Cincinnati. Further funding is provided by the Lundbeck Foundation, the Danish Medical Research Council, and the Novo Nordisk Foundation.
The Sex‐Specific Adaptation of the Mitochondrial Lon protease in the model organism, Drosophila Melanogaster
Authors: Pomatto Laura Corrales‐Diaz , Shen Brenda , Carney Caroline , Tower John , Davies Kelvin J. A. 
Published: November 2023

Due to the maternal inheritance of mitochondria, many of the mitochondrial genes and targeted proteins are optimized in a sex‐dependent manner, favoring females. In turn, this generates a biological power‐play between the sexes. One example is the mitochondrial stress response protein, the Lon protease. Our work in the model organism Drosophila melanogaster, has uncovered a sexual difference in Lon expression. A major hallmark of this sexual dimorphism is the ability of females, pre‐treated with hydrogen peroxide to adapt (measured by increased survival time) compared to non‐pretreated females, when subsequently exposed to a lethal dose of hydrogen peroxide. In contrast males, regardless if they are pre‐treated or only challenged, show no adaptation. As well, the removal of Lon from females prevents adaptation, with no impact upon males. In addition, Lon protein expression and activity is only inducible in a sex‐dependent manner. Based on our findings, we attribute these differences to the unique Lon protein banding variation that we have identified in males and females.Support or Funding InformationNational Science Foundation Graduate Research Fellowship; NIH/NIEHS RO1ES003598 (PI Davies, K.J.A.)
Increased O‐GlcNAcylation Attenuates Autophagic Flux, Induces Mitochondrial Dysfunction and Leads to Accumulation of Alpha‐Synuclein in Neurons
Authors: Wani Willayat Yousuf , Benavides Gloria , Ahmad Israr , Shacka John , Chacko Balu , Chatham John C , Paterson Andrew J , Darley‐Usmar Victor M , Zhang Jianhua 
Published: November 2023

Alpha‐synuclein accumulation and mitochondrial dysfunction are prominent in Parkinson's disease (PD). To determine how autophagy, the cellular protein homeostasis and mitochondrial quality control process is regulated by a nutrient sensing post‐translational modification pathway, the O‐linked attachment of β‐N‐acetyl‐glucosamine on protein S/T residues (O‐GlcNAcylation), we first performed western blot analyses of lysates from postmortem temporal cortex of controls and PD patients, and found significantly increased O‐GlcNAcylation levels in PD brains compared to control. Whether increased O‐GlcNAcylation affects neuronal function and survival was then tested in rat primary cortical neurons. We found that thiamet G, a highly selective inhibitor of the O‐GlcNAcase (OGA) that removes O‐GlcNAc modification, significantly increased protein O‐GlcNAcylation, decreased autophagic flux, decreased mitochondrial complex IV activities, increased accumulation of mitochondrial peroxynitrite, and led to an increased α‐synuclein accumulation. To confirm our results in vivo, we assessed cortical synaptosomal characteristics in wildtype and dnOGA transgenic (CaMKIIα‐tTA::Tet‐dnOGA, dominant negative OGA with a catalytic site deletion) mice. We found that dnOGA synaptosomes exhibited increased O‐GlcNAcylation, decreased mitochondrial function, increased α‐synuclein, and accumulation of autophagosomes. Taken together we proposed that a significant increase of O‐GlcNAcylation levels in PD brains may contribute to impairment of neuronal bioenergetics and attenuation of autophagic activities and accumulation of α‐synuclein.Support or Funding InformationUAB School of Medicine Multi‐Investigator Pilot Grant and NIH R01‐NS064090 (JZ)
S‐nitrosylation of Mitochondrial Proteins Preserves Skeletal Muscle Function From Ischemia‐Reperfusion‐Induced Injury
Authors: Wilson Rebecca June , Zhang Mei , Murphy Michael P. , Yan Zhen 
Published: November 2023

Ischemia‐reperfusion (IR) injury in skeletal muscle is a common complication in many diseases and clinical settings that leads to loss of muscle mass and function. Unfortunately, there are currently no preemptive treatments to reduce IR injury in skeletal muscle. Generation of mitochondrial reactive oxygen species (ROS) during rapid re‐establishment of oxidative phosphorylation in mitochondria upon reperfusion has been identified as a major mediator of IR injury in skeletal muscle. We hypothesized that reversible suppression of mitochondrial respiration by covalently linking nitric oxide moieties to protein thiols (S‐nitrosylation or SNO), which is known to inhibit enzyme activities, may mitigate IR injury to skeletal muscle. We subjected C57BL/6 mice to 1 hour of unilateral ischemia by application of a rubber‐band tourniquet or to a sham procedure (Con). Five minutes prior to tourniquet removal, we performed intramuscular injection of an endogenous s‐nitrosothiol (S‐nitrosoglutathione, GSNO group), a mitochondria‐specific S‐nitrosothiol (MitoSNO1 group) or the respective vehicles (IR group). We assessed muscle weight and maximal specific force production 14 days following IR injury. The IR group had significantly less muscle force than Con mice (~50% reduction), while GSNO injection led to a moderate, but not statistically significant improvement of muscle force compared to the IR group (~10% improvement). Treatment with MitoSNO1 resulted in a complete recovery of muscle force. Gastrocnemius and tibialis anterior muscle masses were significantly reduced by ~40% and ~20%, respectively, in the IR and GSNO groups, but preserved in the MitoSNO1 group. Taken together, targeted S‐nitrosylation of mitochondrial proteins profoundly protects skeletal muscle against IR injury‐induced loss in muscle mass and function. Therefore, mitochondria targeted interventions may provide an efficacious means for protection of skeletal muscle against IR injury.Support or Funding InformationAHA Predoctoral Award #14PRE20380254
PKD Translocation to the Outer Mitochondrial Membrane Induces Mitochondrial Fragmentation and Cell Death via DLP1 Phosphorylation in Cardiomyocytes
Authors: Jhun Bong Sook , O‐Uchi Jin , Mishra Jyotsna , Xu Xiaole , Hurst Stephen , Mende Ulrike , Sheu Shey‐Shing 
Published: November 2023

Heart failure (HF) occurs in response to various types of stimulus including Gq‐protein coupled receptor (GqPCR) stimulation. GqPCR‐mediated mitochondrial dysfunction is frequently observed in HF animal models, but the molecular mechanism remains unclear. Recently, Protein kinase D (PKD) located at GqPCR downstream has been recognized as a key signaling nodal point affecting various cardiac functions. Therefore, we hypothesize that PKD acts as a mitochondrial signaling component and induces mitochondrial dysfunctions under GqPCR‐mediated HF. Using the outer mitochondrial membrane (OMM)‐targeted CFP (mt‐CFP), we found that the value of the Förster resonance energy transfer (FRET) between mt‐CFP and YFP‐tagged PKD significantly increases upon GqPCR stimulation, indicating PKD translocation from cytosol to the OMM. Next, using the FRET‐based OMM‐targeted PKD‐activity sensor, we observed that PKD is activated at the OMM after GqPCR stimulation. Furthermore, we found that GqPCR‐mediated PKD activation at the OMM induced mitochondrial fragmentation, increased reactive oxygen species generation and mitochondrial permeability transition pore opening, followed by caspase‐3 activation in cardiomyocytes. These morphological and functional alterations in cardiac mitochondria were mediated via PKD‐dependent phosphorylation of Dynamin‐Like Protein 1 (DLP1) at S637. Importantly, PKD‐dependent DLP1 phosphorylation concurrent with abnormal mitochondrial morphology and apoptotic signaling were also observed in ventricular tissue from transgenic mice with cardiac‐specific overexpression of constitutively active Gaq. In summary, we conclude that GqPCR stimulation induces PKD translocation to the OMM and induces mitochondrial fragmentation and dysfunction, which likely contributes to cardiomyocyte dysfunction during HF.Support or Funding InformationThis work was partly supported by American Heart Association (AHA) grant (14BGIA18830032 to J.O.‐U.), Medical Research Grant from W.W. Smith Charitable Trust (H1403 to J.O.‐U.) and NIH grants (2R01HL093671 and 1R01HL122124 to SSS).
Denervation alters micro‐RNA expression profiles of microvesicles released by cultured muscle fibers
Authors: Hamidi Sayyed , De Gasperi Rita , Harlow Lauren M. , Ksiezak‐Reding Hana , Bauman William A. , Cardozo Christopher P. 
Published: November 2023

OBJECTIVESSkeletal muscle releases a wide variety of substances that signal to distant tissues to integrate physiologic responses to physical activity or immobilization. Microvesicles have been the focus of intense study for their ability to signal from cell to cell. We tested whether skeletal muscle fibers produce microvesicles and examined their microRNA composition.METHODSThese studies were conducted using fibers isolated from gastrocnemius muscle from mice at 7 days after sciatic nerve transection or sham surgery. Skeletal muscle fibers were maintained in culture for 48 hours and the released microvesicles collected by ultracentrifugation. The microvesicles were characterized by electron microscopy and labeled with PHK67 to evaluate their uptake by C2C12 cells. The microRNA expression profiles of fibers and corresponding microvesicles were analyzed by Nanostrings microRNA microarrays.RESULTSSkeletal muscle fibers maintained in culture for 48 hours released microvesicles which, by electron microscopy, were ~100 nm in diameter, had a bilamellar membrane, and were labeled by anti‐CD63. Vesicles labeled with PHK67, a fluorescent dye taken up by vesicle membranes, were avidly taken up by C2C12 cells. We observed high‐levels of microRNA expression in sham fibers for let7‐d, miR‐1, miR‐133a, miR‐125‐5p and miR‐22. In microvesicles, there was high‐level expression of miR‐1, 133a, 133b, and 378. When comparing miR expression in microvesicles from denervated versus sham muscle fibers, miR 1, 133a, and 145 were downregulated while miR‐206 was greatly up‐regulated. A similar though less dramatic pattern of changes was observed when comparing denervated and sham fibers. These studies reveal that skeletal muscle fibers release microvesicles that contain microRNA, the relative expression levels of these microRNAs is similar to that observed in skeletal muscle, these vesicles can be transferred to other cells, and paralysis resulting from nerve transection alters the microRNA expression profiles in vesicles in a manner similar to the parent muscle fibers.CONCLUSIONSThese findings have important implications for understanding the mechanisms by which skeletal muscle fibers signal locally to adjacent muscle cells, as well other more distant cell types, including those found in bone.Support or Funding InformationNA
Chronic alcohol ingestion induces alveolar macrophage oxidative stress and phagocytic dysfunction by down‐regulating NADPH oxidase‐related microRNAs
Authors: Yeligar Samantha M. , Harris Frank L. , Hart C. Michael , Brown Lou Ann S. 
Published: November 2023

ObjectiveCompared to non‐alcoholics, chronic alcohol abusers are 2–4 times as likely to develop respiratory infections and acute respiratory distress syndrome (ARDS). Alcohol abuse increases susceptibility to lung infections in alcoholics through enhanced oxidative stress and impaired alveolar macrophage (AM) phagocytic function. NADPH oxidases (Nox) are primary sources of oxidative stress in AMs, and the Nox isoforms, Nox1 and Nox2, are required for Nox4 expression and activity. We hypothesize that alcohol attenuates Nox1‐ and Nox2‐associated microRNAs (miRs) to up‐regulate Nox1, Nox2, Nox4, oxidative stress, and phagocytic dysfunction.MethodsAMs were obtained from the bronchoalveolar lavage (BAL) fluid of C57BL/6J mice fed ± ethanol (20% w/v) in the drinking water for 12 wks. In parallel, MH‐S cells, a mouse AM cell line, were transfected ± 50 nM miR mimics and treated ± 0.08% ethanol for 3 d. Levels of Nox1‐related miRs (miR‐1264 and ‐1982), which bind to the Nox1 3′UTR to decrease Nox1 levels, and Nox2‐related miRs (miR‐103 and ‐107), which bind to the Nox2 3′UTR to decrease Nox2 levels, were assessed by qRT‐PCR. Nox1, Nox2, and Nox4 mRNA and protein expression were measured by qRT‐PCR and western blot. Oxidative stress was measured with DCFH‐DA and Amplex Red assays. AM function was evaluated by phagocytosis assay (S. aureus internalization).ResultsIn vivo and in vitro studies demonstrated that ethanol: 1) decreased AM levels of Nox1‐related miR‐1264 and Nox2‐related miR‐107; 2) increased Nox1, Nox2, and Nox4 mRNA and protein expression; 3) enhanced oxidative stress; and 4) impaired phagocytic capacity. miR mimics reversed these ethanol‐induced AM derangements.ConclusionsChronic alcohol ingestion enhances AM Nox expression, oxidative stress, and phagocytic dysfunction by down‐regulating Nox‐related miRs. Our studies suggest that targeting Nox‐related miR expression may attenuate alcohol‐induced AM derangements and decrease susceptibility to respiratory infections in patients with a history of alcohol use disorders.Support or Funding InformationResearch Funding Source: AHA SDG 13SDG13930003 (SMY), NIAAA 1K99AA021803 (SMY), Emory Alcohol & Lung Biology Center 1P50AA135757 (LAB & CMH), and Merit Review Funding from the Atlanta VA Medical Center (CMH).
Microglial Inflammatory Responses to Systemic Immune Challenge are Attenuated over the Course of Chronic Intermittent Hypoxia Exposure
Authors: Ouellette Jonathan N. , Smith Stephanie M.C. , Watters Jyoti J. 
Published: November 2023

Intermittent hypoxia (IH) is a hallmark of sleep disordered breathing that causes significant neuronal death, in part, via elevated levels of neuroinflammatory molecules. We previously identified microglia as one cellular source of these pro‐inflammatory molecules in the CNS within 1–2 weeks of IH exposure. However, microglial responses during IH to a concomitant inflammatory challenge are not yet known, an important consideration given that sleep disordered breathing and systemic inflammation are common co‐morbidities. Toll‐like receptor 4 (TLR4) is an innate immune receptor whose activation mediates inflammation in response to gram‐negative bacterial lipopolysaccharide (LPS) and endogenous molecules released from injured/dying cells prevalent in the CNS during IH. We found that TLR4 activation was necessary for microglial pro‐inflammatory responses to IH in vitro, and that TLR4 mRNA and activated cell surface protein levels increase and remain elevated in microglia for at least 28 days of IH in vivo, suggesting that microglia in the brains of IH‐exposed mice may be primed for greater responsiveness to subsequent inflammatory challenges. To test this hypothesis, we evaluated inflammatory gene expression in immunomagnetically‐isolated microglia from adult male C57Bl/6 mice that received 7–14 days of either normoxia (room air) or IH (60–90 second intervals of 6.5–10.5% O2 for 8–12 hours) followed by intraperitoneal injection of LPS (1 mg/kg; 14 hours) or vehicle (HBSS). Surprisingly, we found that LPS‐stimulated microglial pro‐inflammatory gene expression (COX‐2, IL‐1β, TNFα and CCL3) was significantly attenuated in IH‐exposed mice, whereas microglial expression of anti‐inflammatory/trophic factors (IFNβ and BDNF) was increased by IH alone (and unaltered by LPS in either O2 condition). Studies to investigate microglial responses to other forms of systemic inflammation during IH are ongoing. These data suggest that microglial responses are not exaggerated during IH, despite chronically elevated TLR4 levels. Further, they support the idea that microglia undergo a phenotypic transition during chronic exposure to IH that dampens their ability to respond to inflammatory stimuli, perhaps as an adaptive or compensatory response to protect the CNS against continued IH insult.Support or Funding InformationSupported by R01 HL111598 and R01 NS085226