bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uncovering the role of GPR39 in the kidney
Authors: Pluznick Jennifer , Kui Mackenzie 
Published: May 2024

G protein-coupled receptors (GPCRs) constitute the largest class of proteins in the mammalian genome. Upon activation by a specific ligand, these receptors initiate downstream cellular responses that regulate various physiological processes. One such receptor under investigation in our lab is the ghrelin family receptor GPR39. Unlike its relatives, GPR39 does not respond to peptide hormones or neuropeptides. Initial studies suggested zinc as the endogenous ligand, but recent research indicates that zinc functions as an allosteric potentiator for another unidentified endogenous ligand. To date, synthetic agonists for GPR39 have revealed functions for GPR39 in the heart, bone, skin, pancreas, and gastrointestinal tract. However, GPR39’s role in renal physiology is currently unknown, despite relatively high kidney expression. To address this gap in knowledge, we first worked to localize GPR39 within the kidney. As a reliable antibody for GPR39 is not available, we utilized a combination of RNAScope (Gpr39) and immunofluorescence (AQP2). We find that GPR39 is expressed in the renal collecting duct, with the highest expression in AQP2-positive cells (principal cells) in the inner medullary collecting duct, and lesser expression in the cortical collecting duct. To determine if GPR39 is expressed apically or basolaterally, we then cloned GPR39 with a C-terminal EGFP tag and observed basolateral targeting of GPR39 in polarized MDCK cells grown on filters. In order to query the function of GPR39 in principal cells, we used murine principal kidney cortical collecting duct cells (mpkCCD). As others have shown, we find that mpkCCD express and traffc AQP2 to the apical plasma membrane only in the presence of the vasopressin analog dDAVP. Furthermore, we observe that treatment of mpkCCD with the GPR39-specific agonist cpd1324 induces internalization of AQP2 into cytoplasmic vesicles, even in the continued presence of dDAVP. Under vehicle conditions (dDAVP + vehicle), 80.9±7.7% (mean±SD) of AQP2 stain colocalized with an apical membrane marker (WGA staining). In contrast, when mpkCCD cells were co-treated ddAVP+cpd1324, only 58.3±6.02% of AQP2 stain colocalized with the apical membrane (p < 0.001, t-test). These results indicate that GPR39 activation may act to antagonize vasopressin-induced AQP2 traffcking in mpkCCD cells. NHLBIT32HL007534 (MK) and American Heart Association Established Investigator Award (JLP). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Strategies for protecting lung health after spinal cord injury and gastric reflux
Authors: Sunshine Michael , Devine Caroline , Waters Christopher , Alilain Warren 
Published: May 2024

Spinal cord injuries have a significant and far-reaching impact, affecting more than 300,000 people in the United States alone. Among these injuries, cervical-level injuries are the most common, accounting for approximately 60% of all spinal cord injuries. Pulmonary complications, specifically aspiration-related pneumonia, rank as the primary cause of death in individuals with these injuries. Notably, those with cervical spinal cord injuries have an elevated risk of experiencing acute lung injury and acute respiratory distress syndrome. Moreover, spinal cord injuries, regardless of their location, often lead to gastric dysmotility, a condition frequently linked with gastroesophageal reflux disease. This research aims to untangle the intricate relationship between these interconnected health issues and their collective impact on pulmonary function. Here we tested the hypotheses 1) that cervical spinal cord injury increases the susceptibility for developing acute lung injury associated with gastric juice aspiration and 2) that TRPV4 inhibitors will mitigate gastric fluid/SCI-induced lung injury. These studies employed a rat model of spinal cord injury, C2 hemisection (C2Hx). This model mimics the reduced inspiratory tidal volume observed in individuals with cervical spinal cord injuries and has more recently been shown to recapitulate certain aspects of lung injury associated with spinal cord injuries. Additionally, to produce the effects of gastric reflux, gastric juices were introduced into the trachea in a subset of animals following spinal cord injury. Furthermore, TRPV4 inhibitors were administered to assess their potential to mitigate lung damage after spinal injury, gastric juice instillation or at both times. Preliminary data suggest that C2Hx and low levels of gastric juice increase inflammatory markers in the lung and circulation above even high levels of gastric instillation. Further, preliminary data supports the hypothesis that TRVP4 inhibition may protect the lung. The outcomes of these investigations will provide valuable insights into how spinal cord injuries might predispose individuals to lung injury. Additionally, they will evaluate the effcacy of a promising therapeutic approach using TRPV4 inhibitors to restore lung barrier function, potentially reversing this susceptibility. R21NS121966-01. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
ERMP1 Increases NAFLD Severity by Increasing Mitochondrial Bioenergetics
Authors: Rahman Afra , Kumar Talari Noble , Mattam Ushodaya , Chella Krishnan Karthickeyan 
Published: May 2024

Non-alcoholic fatty liver disease (NAFLD) is a condition where there is a buildup of fat in the liver cells that is not caused by alcohol use. It is estimated that 20-30% of the population worldwide are affected by NAFLD but to this day, there are no current treatment options. Previous studies in our lab have shown “key driver” genes regulating NAFLD. Follow-up studies have shown mitochondrial dysfunction as a key mechanistic driver of NAFLD and have identified Endoplasmic Reticulum Metallopeptidase 1 (ERMP1) as a candidate gene. ERMP1 is a zinc-binding protease and is highly expressed in several cancers. We found that Ermp1 expression was positively associated with NAFLD progression and hepatic TG accumulation using liver transcriptome from ~100 different mouse strains called hybrid mouse diversity panel (HMDP). Follow-up network enrichment analysis revealed mitochondrial, endoplasmic reticulum, cell cycle, and circadian rhythm enrichments, as well as liver-related disease traits including fatty liver disease, steatohepatitis, liver cirrhosis and neoplasms. Unfortunately, there still isn’t a complete understanding of factors governing the progression of NAFLD, or the effect ERMP1 gene has on the liver. But since mitochondrial dysfunction has been shown to play a causal role in liver fat buildup during NAFLD, we started our investigation here. We hypothesize that there is a direct relationship between NAFLD severity and ERMP1 gene, which is mediated by enhanced mitochondrial activity. We found that when downregulating the ERMP1 gene, there was a reduction in mitochondrial respiration under lipid stress conditions in a mouse liver cell line (AML12). The same was also seen when decreasing the expression of ERMP1 in a diet-induced obesity model. This was accompanied by reduced mitochondrial OXPHOS subunits, specifically Complex II. Taken together, we conclude that ERMP1 increases NAFLD severity by increasing mitochondrial activity. R00DK120875. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Population Studies Revealed Sex-Specific Roles of MIC25/CHCHD6 in Promoting NAFLD
Authors: Mattam Ushodaya , Kumar Talari Noble , Rahman Afra , Stiles Linsey , Péterfy Miklós , Divakaruni Ajit S. , Lusis Aldons J. 
Published: May 2024

One of the major complications of metabolic syndrome affecting the liver, in the absence of excessive alcohol, is non-alcoholic fatty liver disease (NAFLD). It is estimated that 20-30% of the population worldwide are affected by NAFLD. Recent studies have revealed that NAFLD is more prevalent in men than women, with men exhibiting severe NAFLD symptoms. As of now, there are no prevention and/or treatment options for NAFLD other than reducing the risk factors such as weight reduction. To this end, we used our ~100 diverse inbred strains of mice and identified MIC25 or CHCHD6, a core component of MICOS (mitochondrial contact site and cristae organizing system) complex, as a causal gene in mediating NAFLD. We also observed dramatic differences in the regulation and functions of MIC25 between sexes. Specifically, MIC25 expression was downregulated in females via estrogen and is strongly associated with NAFLD severity. We followed up by investigating the mechanistic roles of MIC25 using loss- and gain-of-function mouse models. In a steatosis mouse model, MIC25 silencing ameliorates plasma cholesterol levels, insulin resistance, and intrahepatic triglyceride accumulation, while MIC25 overexpression exacerbates them. Stable isotope tracing analyses revealed that MIC25 also regulated carbon flux through mitochondrial pyruvate carboxylase and glucose anaplerosis, thereby affecting de novo lipogenesis, fat and glutamine oxidation, and gluconeogenesis accompanied by mitochondrial dysfunction/maladaptation. Given the need for a promising NAFLD drug candidate with personalized therapeutic potential, we feel that our novel findings will be of considerable interest to the liver scientific community. R00DK120875. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Site-Directed Mutagenesis Reveals P2XR7 Extracellular Domain Residues That Facilitate Channel Activation by Histone Proteins
Authors: Al-Aqtash Rua'a , Collier Daniel 
Published: May 2024

Seven mammalian ionotropic purinergic receptors (P2XRs) have been identified (P2XR1-7). All P2XRs have a large extracellular domain containing a conserved extracellular ATP binding pocked, however, P2XRs vary widely in ATP affnity and desensitization kinetics. P2XR7 is unique in that it has the lowest ATP affnity (mM), does not desensitize to ATP, and has a large intracellular C-terminal domain. In our recent work, we demonstrated that histone proteins activate P2XR7 current. However, histone-evoked currents are not inhibited by selective inhibitors of P2XR7 ATP-evoked current. We hypothesized that histone proteins may bind to a distinct allosteric site in the P2XR7 extracellular domain. To test this, we expressed mouse and human P2X receptors (m.- and h.P2XR1-7) in heterologous cells (Xenopus oocytes) and measured inward cation currents using a two-electrode voltage clamp (TEVC). This allowed us to determine which P2XR channels are suffcient for histone-induced currents and provided a strategy to determine the P2XR7 residues involved in histone- and ATP-evoked currents. Histone proteins induced large inward cation currents in oocytes expressing m.P2XR7 and m.P2XR4, but not in those expressing m.P2XR1. Because histone proteins are highly alkaline, we aligned the extracellular domains of m.P2XR7, -4, and -1, and looked for acidic residues that were conserved in P2XR7 and -4 but absent in P2XR1. This approach identified 12 possible histone binding residues, of which three (D156N, E175K, and E240Q) were found to be silent mutations. Mutations at these sites decreased histone-evoked current but did not decrease ATP-evoked current. These results provide functional insight into a new allosteric mechanism of P2XR7 channel activation by histone proteins which may be used to guide the development of new pharmacologic and therapeutic strategies. NIH R00HL133451 and R01HL155180. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Seabird Spread in the Sarasota Bay
Authors: Haas Sydney 
Published: May 2024

Seabirds are marvels that exist all along Florida coasts. However, very little has been done to study how they are spread in the Sarasota Bay. The interactions between different species and how they are spread in the Sarasota Bay is very important for this ever-changing ecosystem. Having biodiversity of all species in the Bay is very important so that this ecosystem can survive and thrive. This Bay is consistently impacted by red tide, hurricanes, rip current, and many other climate disasters. Seeing how seabirds are impacted by these occurrences is important for measuring the biodiversity of the Bay. The spread of 6 seabird species (cormorant, brown pelican, anhinga, ibis, spoonbill, and osprey) were measured for 14 different test sites in the Sarasota Bay, while also taking into account other species that were observed. One boat trip was taken each month in June, July, and August to observe the 6 seabird species, and the others sighted, at the 14 different test sites. At these 14 test sites over the three months, the most observed bird species were gulls. The least observed species were spoonbills. The most observed species for the targeted species were cormorants. However, no bird species was statistically significantly above or below one another. Therefore, the biodiversity in the Sarasota Bay seems to be at healthy levels, even with the climate disasters that have occurred. Support was provided by Dr. Toro-Farmer, including funding for the boat trips and access to GIS software. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Pharmacological and genetic inhibition of transient receptor potential melastatin-subfamily member 7 (Trpm7) channel in the carotid body attenuated intermittent hypoxia-induced hypertension
Authors: Shin Mi-Kyung , Sun Boran , Cui Honggang , Tang Wan-Yee , Polotsky Vsevolod 
Published: May 2024

RATIONALE: Obesity causes hypertension and sleep disordered breathing (SDB). Intermittent hypoxia (IH), a cardinal feature of SDB, also causes hypertension contributing to cardiovascular sequelae of obesity. The carotid body plays a role in the IH-induced hypertension. We have previously shown that obesity increases expression of the transient receptor potential melastatin-subfamily member 7 (TRPM7) channel in CB glomus cells and that knockdown of TRPM7 in CB treats hypertension in diet-induced obese mice. Our data in cell culture indicate that hypoxia increases TRPM7 expression. Therefore, we hypothesized that IH increases TRPM7 expression in CB and that pharmacological and genetic inhibition of Trpm7 in CB will treat IH-induced hypertension. Methods: 1) Pharmacological inhibition: We exposed male C57BL/6J mice to IH (n = 9) or air (n = 9) for 5 days and obtained continuous BP telemetry recording prior and after the exposure. Then we applied a long-acting TRPM7 inhibitor FTY720 or placebo to the CB area and repeated BP measurements before and after the 5-day IH or air exposure.2) Genetic inhibition: In another experiment, we knocked out Trpm7 gene expression in CB of male Trpm7 flox/flox mice by administering adenovirus carrying Cre-recombinase to the CB followed by BP recording during the 5-day IH or air exposure. RESULTS: We found that IH induced > 20-fold increase in Trpm7 mRNA expression in CB. IH increased BP from 102.9 ± 1.0 mmHg to 111.7 ± 1.1 mmHg. FTY720 hydrogel abolished the BP increase induced by IH. In Trpm7 flox/flox mice, IH also markedly increased BP prior to the adenoviral treatment from 101.9 ± 1.6 mmHg to 110.2 ± 4.0 mmHg. CB-specific Trpm7 knockout abolished IH-induced hypertension. CONCLUSION: We conclude that IH-induced upregulation of Trpm7 in CB contributes to the development of hypertension in IH and that IH-induced hypertension can be treated by pharmacological and genetic inhibition of Trpm7. 19CDA34700025, R01HL133100, R01HL128970. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Skeletal muscle preservation in arctic ground squirrels during hibernation season
Authors: Goropashnaya Anna V. , Confides Amy L. , Yoldi Bergua Inigo , Drew Kelly L. , Dupont-Versteegden Esther E. , Fedorov Vadim B. 
Published: May 2024

Reduced skeletal loading leads to muscle atrophy in humans and most mammals. By contrast, hibernating mammals demonstrate limited loss of skeletal muscle mass and strength by the end of winter after being physically inactive for several months. The present study objective was to establish potential underlying processes for the lack of muscle loss during the hibernation season of arctic ground squirrels (AGS). Our hypothesis was that early in the the hibernation season, protective mechanisms of AGS are not yet mobilized and muscles show signs of atrophy, while compensatory processes for preventing muscle loss appear at a later time point. Quadriceps muscles of juvenile male AGS were collected shortly before hibernation, and on 2, 6, 10-12 and 16-22 weeks during hibernation. Pre-hibernating animals were used as controls. Fiber cross-sectional area (CSA) and fiber type composition were determined with immunohistochemistry. Amount of total RNA, ribosomal RNA content and expression levels of genes involved in 2 pathways of protein degradation, ubiquitination and autophagy, were analyzed by real-time PCR, to evaluate molecular mechanisms of muscle maintenance. One-Way ANOVA was used to statistically analyze the group differences. We found that CSA was not different between the groups (P > 0.05). CSA frequency distribution curves did not reveal any shift to a smaller or larger size range. No difference was detected in myofiber composition between the hibernation groups compared to the control. Total RNA and ribosomal RNA content were not significantly different between the groups during hibernation. Muscle atrophy marker FBXO32 (Atrogin-1, MAFBX) and autophagy related genes MAP1LC3A and BECN1 did not show different level of expression between the groups. Only another muscle atrophy marker TRIM63 (MURF-1, Iris Ring Finger Protein) was significantly over-expressed at the time point of 2 weeks of hibernation. These results indicate that throughout the hibernation season, AGS preserve muscle fiber CSA showing limited signs of muscle atrophy only during the first weeks of hibernation, and yet-to-be determined processes exist to suppress protein degradation in AGS muscles during hibernation. The work was supported by Center of Biomedical Research Excellence under grant number [P20GM130443]. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Enteric and Systemic Postprandial Lactate Shuttle Phases and Dietary Carbohydrate Carbon Flow
Authors: Leija Robert , Curl Casey , Arevalo Jose , Osmond Adam , Duong Justin , Huie Melvin , Masharani Umesh 
Published: May 2024

We interrogated the hypothesis of a Postprandial Lactate Shuttle (PLS) in young, healthy men and women (n=15). Participants reported to the lab (5:00 AM) following an overnight fast and had the forearm vein catheterized for primed continuous infusions of [6,6-2H]glucose and [3-13C]lactate stable isotope tracers. The contralateral hand vein was warmed and catharized for arterialized blood sampling. After a 90-minute (min) equilibration period participants underwent a 75 g oral glucose tolerance test (OGTT). Arterialized [lactate] rose from baseline (0.60sup>). We estimate carbon flow from the OGTT from the rates of appearance of glucose, lactate and GNG from lactate. At 120-min the 75 g load was accounted for as follows: 29 g as blood lactate, 24 g of glucose from hepatic glucose release, 8 g of glucose from GNG, and 14 g withheld in the liver. Because blood [lactate] and Ra rose before [glucose] and Ra, evidence of an Enteric PLS is provided. Because secondary increments in blood [lactate] and Ra coincided with those of glucose, results are interpreted to indicate presence of a larger, secondary Systemic PLS phase. Antiquated ideas of lactate production due to hypoxia in skeletal muscles need to be supplanted because glycolysis proceeds to lactate in fully aerobic tissues, and because dietary carbohydrate is processed via lactate shuttling. In humans, lactate is a major vehicle for carbohydrate carbon distribution and metabolis. NIH grant R01 AG059715. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.