bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex-dependent polymorphism in urinary output is reversed upon deletion of exchange protein directly activated by cAMP (Epac)
Authors: Atamanchuk Anna , Pyrsev Kyrylo , Kordysh Mariya , Zaika Oleg , Pochynyuk Oleh
Published: May 2024

It is well-described that there are notable sex-dependent differences in urinary production with females having a smaller volume and greater urinary concentrating ability. Apart from contribution of the androgenic inputs, the underlying signaling intermediates remain largely unexplored. We previously showed that exchange protein directly activated by cAMP (Epac) is a critical regulator of water-solute transport in the proximal tubule and collecting duct. Deletion of either Epac1 or Epac2 isoforms increases urinary output and Na+ excretion. Here, we used metabolic cage balance studies to test whether Epac signaling mediates sex-dependent differences in urinary production. We found that concomitant deletion of Epac1&2 moderately increases 24h urinary volume by 38% (from 1.82+/-0.13 to 2.52+/-0.21 ml) in males, but drastically augment urinary production in females by 320% (from 1.39+/-0.10 to 4.45+/-0.37 ml). This was associated with only a mild though significant reduction in urinary osmolarity in males by 35%, whereas urine osmolarity was markedly decreased from 2511+/-5 to 977+/-60 mOsm in females. Consistently, plasma osmolarity was not different in EpacWT versus Epac1&2−/− males, but became significantly more hypertonic in Epac1&2−/− females. We further determine the functional consequences of impaired Epac cascade on fluid reabsorption in the proximal tubule and collecting duct in males and females. Deletion of Epac1 and Epac2 decreases NHE-3 expression in the proximal tubule in an additive manner. In addition, Na+/H+-dependent recovery after acidification was drastically reduced in freshly isolated split-opened proximal tubules from Epac1&2−/− mice when compared to EpacWT. Interestingly, the reduction of NHE-3 expression was more pronounced in Epac1&2−/− females (by 89%) than in males (by 59%). Immunofluorescence confocal images revealed much more diffuse intracellular distribution of AQP2 water channel in Epac1&2−/− females when compared to males. Furthermore, osmotically-driven water influx was reduced in principal cells within split-opened collecting ducts of Epac1&2−/− females but not males, when compared to respective EpacWT. In summary, our results reveal a substantially greater role of Epac signaling in renal water handling in females than in males. Interestingly, Epac1&2 deletion leads to a reversed pattern of sexual dimorphism in urinary production with females excreting larger volumes of hypotonic urine than males.

This research was supported by NIH-NIDDK DK117865, DK119170, AHA EIA35260097 (to O. Pochynyuk).

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.
Roles of mitofusin-2 in mouse neutrophil adhesion and development
Authors: Fan Zhichao , Pulikkot Sunitha , Liu Wei , Deng Qing
Published: May 2024

Neutrophils play a critical role in inflammation and innate immunity. A crucial step in neutrophil recruitment is their adhesion to vascular endothelium. Previous research demonstrated the necessity of mitofusin-2 (MFN2) for integrin activation, adhesion, and the development of neutrophil-like HL60 cells. However, it remains unknown whether this holds true for primary neutrophils. Additionally, neutrophil adhesion is closely associated with their development, making it challenging to independently investigate the roles of MFN2 in regulating mouse neutrophil adhesion and development. In this study, we successfully addressed these challenges by utilizing two distinct conditional knockout mouse models. Our findings revealed that blood neutrophils from MFN2flox/flox LysM-cre mice exhibited approximately a 50% reduction in MFN2 expression. Remarkably, these MFN2 knockdown (KD) mice did not display any defects in neutrophil development. In contrast, blood neutrophils from MFN2flox/flox Vav-iCre mice showed a substantial (>90%) reduction in MFN2 expression. These MFN2 knockout mice exhibited a notable defect in the maturation of band cells into polymorphonuclear neutrophils. We further investigated the neutrophil adhesion using MFN2 knockdown mice and identified the neutrophil adhesion defect using microfluidics, the integrin activation defect using soluble ligand binding, and the Ca2+ flux defect using time-lapse flow cytometry. These findings provide valuable insights into the role of MFN2 in leukocyte adhesion and development and offer potential new perspectives for understanding and treating MFN2-deficiency-related diseases.

This research was supported by grants from the National Institutes of Health, National Heart, Lung, and Blood Institute, USA (R01HL145454), National Institute of General Medical Sciences (R35GM119787), National Institute on Aging (P30AG024832), a Career re-entry fellowship from the American Association of Immunologists (G602182), and a startup fund from UConn Health.

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.
Beneficial Effect of Heat Treatment on the Exercise Pressor Reflex in Hindlimb Ischemia-Reperfusion: Potential Role of P2X3
Authors: Qin Lu , Li Qin , Li Jianhua
Published: May 2024

PURPOSE: In peripheral artery disease (PAD), a greater blood pressure (BP) response during exercise causes cardiovascular and cerebrovascular risks. The exercise pressor reflex (EPR) is a key factor for why BP is exaggerated in PAD patients. Thus, we examined the effect of heat treatment (HT) with two temperature increments in skeletal muscle: 1.5 and 3oC on the EPR response following limb ischemia-reperfusion (IR) injury, one of the most common pathological conditions seen in PAD. In addition, the P2X3 (an ATP-sensitive receptor) in the muscle afferent dorsal root ganglion (DRG) was also evaluated. We hypothesized that IR upregulates the BP response to static muscle contraction and the protein expression of P2X3 in muscle afferent nerves. HT attenuates those exaggerated responses. METHODS: An experimental IR model was induced by 6 hours of ischemia followed by 18 hours of reperfusion in rats (IR rats). For HT groups, three HT sessions (muscle temperature increased by 1.5 or 3oC) for 30 mins/each time were applied. EPR response was evoked by static muscle contraction (30s). Protein expression of the P2X3 receptor in DRGs was examined. Data are presented as mean ± standard deviation. Results: The mean arterial pressure (MAP) response to the static muscle contraction was significantly exaggerated in rats of IR 18h (vs. Sham, P=0.018). With increasing Tm by 1.5°C, there was a promising trend that thus exaggerated BP response was attenuated (IR 18h + HT 1.5°C, n=5 vs. IR 18h rats, n=5, P=0.08). Meanwhile, the exaggerated BP response was significantly attenuated with the Tm increasing by 3°C (IR 18h + HT 3°C, n=5, vs. IR 18h rats, n=5, P=0.032). The expression of the P2X3 receptor was significantly enhanced in the DRGs of IR 18h rats (n=4, p<0.01 vs. sham, n=6). The upregulated P2X3 was suppressed in the DRGs of IR 18h rats +HT of 1.5°C (n=3, p<0.01 vs. IR 18h, n=4) and there was a promising trend that upregulated P2X3 was suppressed in the DRGs of IR 18h rats +HT of 3°C (n=3, P=0.079 vs. IR 18h, n=4). CONCLUSION: IR injury leads to upregulation of EPR response and this effect was attenuated by HT. The P2X3 signaling pathways are likely involved in the beneficial regulatory effect of HT on EPR in IR. Further data collection will be performed to test this conclusion.

Supported by NIH R01 HL141198 & HL164571; AHA GRANT # 940567/Lu Qin/2022; and College of Medicine DOM Innovation and Inspiration Award. The authors sincerely thank Chunying Yang for the excellent technical assistance.

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.
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.
The distribution and structural plasticity of excitatory synapses along interneuron dendrites in the adult hippocampus
Authors: Chirillo Michael , Weisberg Seth , Parker Patrick , Bourne Jennifer , Harris Kristen
Published: May 2024

Hippocampal interneurons form a large, heterogeneous group with differing structural, physiological, and chemical phenotypes. Most CA1 interneuron dendrites, however, lack spines. To investigate structural synaptic plasticity along interneuron dendrites, we generated three-dimensional (3D) reconstructions from serial section electron microscopy (EM) of excitatory synapses along aspiny dendrites in CA1 stratum radiatum of young adult rats under control conditions and at 2 h during LTP induced with theta-burst stimulation. In total, 43 aspiny dendritic segments and their synapses were identified and reconstructed in 3D. Aspiny dendrites were categorized as smooth or varicose based on dendritic volume contours along each segment. We further sub-segmented varicose dendrites varicosities and inter-varicose regions using automated and manual methods. We found synapses and total synaptic input per length were distributed uniformly along smooth dendrites. Synapses along varicose dendrites, however, occurred preferentially at varicosities. While synaptic input per length along varicosities was similar to that along smooth dendrites, both synapse number and total synaptic input per length along inter-varicose regions were lower. Dendritic segments were also analyzed for mitochondria and glycogen content. We found that mitochondria and glycogen were also distributed uniformly along smooth dendrites. In varicose dendrites, however, mitochondrial volume and glycogen granule numbers were highest in varicosities, while inter-varicose regions were comparatively devoid of these resources. The spatial distribution of synapses and dendritic resources in both smooth and varicose dendrites was preserved at 2 h during LTP when compared to control conditions. These findings suggest that synapses occur along interneuron dendrites where dendritic resources are most available. When dendritic resources are distributed uniformly throughout the dendrite, as occurs in smooth dendrites, synapse distribution is also uniform. Varicosities, on the other hand, represent resource-rich sites along varicose dendrites where synaptic clustering occurs.

This work was supported by the National Science Foundation (NSF 1707356, NSF 2014862) and the National Institutes of Health (R01 5R01MH09598).

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.
Quantitative EEG Microstates Predict Correct Responses During Visuo-Spatial Working Memory Task
Authors: Nayyar Madhavi , Soni Sunaina , Sharma Ratna , Sood Mamta , Prakash Suriya , Kaur Simran , Tayade Prashant
Published: May 2024

Hypothesis: EEG microstate maps during pre-response period of Visuo-Spatial Working Memory (VSWM) Task can predict correct or incorrect response in healthy population and patients with schizophrenia. Methods: After taking informed consent, 30 patients diagnosed with schizophrenia (as per DSM-5 criteria) and 30 controls (both age and gender matched) were recruited. Thereafter, 128 channel EEG was recorded during eyes closed and eyes open states as well as during VSWM task performance. The VSWM task entails matching pairs of identical multicolored abstract pictures hidden in arrays of different cognitive loads after an initial encoding. Following the acquisition; EEG pre-processing, down sampling, average referencing, and Independent Component Analysis were done. Epoch of 100 milliseconds just before each response was taken and grouped into either correct or incorrect trials following which they were subjected to microstate analysis. Statistical analysis was done to compare temporal microstate parameters (Global explained variance, mean duration, time coverage, and segment count density) of each microstate map found between correct and incorrect trials. Data and Results: Microstate maps of pre-response state during correct and incorrect trials were compared in patients with schizophrenia and controls taken together as well as separately. Global explained variance of Microstate Map A (RA-LP, Right Anterior- Left Posterior orientation) was found to be significantly more during pre-response period when the responses were correct as compared to incorrect trials. GEV of Map A emerged out to be the key predictor of correct response in all three groups: overall Correct versus incorrect trials (patients and controls taken together), among patients with schizophrenia, and among controls. Conclusions: Global Explained Variance of EEG microstates Map A is a good predictor of correct response in VSWM task.

Department of Physiology, All India Institute of Medical Sciences, New Delhi.

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.
Metabolic-Dysfunction Associated Liver Disease Progresses Independent of Weight in a Rodent Model
Authors: Skinner Roy , Alawadi Ayad , Warren Derek , Benedito Vagner , Tou Janet
Published: May 2024

Background: Metabolic dysfunction associated steatotic liver disease (MASLD) is the most prevalent liver disease worldwide with an estimated 25% of U.S. adults having MASLD. MASLD is typically regarded as a diet driven disease, with the Western diet (high fat, high sugar, low fiber) being a major driver. Recently, evidence suggests MASLD can be present regardless of body weight. There is not good evidence on how prevalent this is, but reports suggest it could be as high as nearly 30% of MASLD patients. As such, there is a critical need to better understand MASLD independent of weight to ensure all individuals with the disease are receiving proper diagnosis and treatment. Methods: Young female rats were fed either a Control (AIN-93G) or Western (45% fat, 34% sugar) diet for 8 weeks. Histology, RT-qPCR, and standard biological assays were performed to analyze differences in hepatic function and fatty acid analysis was used to analyze fatty acid deposition in the liver, adipose tissue, and brain. Results: There were no statistically significant differences in the weights of rats consuming a Control or Western diet. However, consuming a Western diet had increased histological evidence of fat deposition and inflammation compared to Control. Rats consuming a Western diet also displayed increased ( p<0.05) hepatic triglyceride content and relative expression of several key genes involved in lipogenesis and oxidative stress. Fatty acid analysis found Western diet rats to have increased (p<0.05) hepatic monounsaturated fatty acid (MUFA) content, while adipose tissue of those same animals had decreased (p<0.05) MUFAs. Conclusions: The Western diet plays a significant role in the development of MASLD independent of differences in weight. This model may serve to better elucidate mechanisms at play in lean MASLD. We are currently conducting additional experiments on the role of alcohol in this phenomenon.

WVU Davis College Dean's Opportunity Fund and the UVM Food Systems Research Center.

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.
Characterisation of a Novel Osmosensitive Pathway from the Supraoptic Nucleus to the Median Preoptic Nucleus
Authors: Nedelkoska Teodora , Burke Peter , Hildreth Cara
Published: May 2024

The Supraoptic Nucleus (SON) is well regarded for the neuroendocrine release of vasopressin and oxytocin through the posterior pituitary gland. Evidence also exists for extra-pituitary efferent projections of SON neurons, mainly collaterals to the lateral hypothalamus and central amygdala. The objective of this study was to examine the existence of a central SON projection to the median preoptic nucleus (MnPO) of the hypothalamus. Microinjections of the retrograde tracer Cholera Toxin B Subunit (CTb) into the MnPO of male Wistar rats (n = 3) retrogradely labelled SON neurons. Fluorescence immunohistochemistry revealed equal involvement of vasopressin (AVP) and oxytocin (OXT) — producing SON neurons (n = 107 AVP+/CTb+, n = 110 OXT+/ CTb+, n = 417 total CTb+ neurons). This major collateral projection was also examined in an animal model of Polycystic Kidney Disease, the Lewis Polycystic Kidney (LPK) rat (n = 3 animals; n = 104 AVP+/CTb+, n = 41 OXT+/CTb+, n = 372 total CTb+ neurons) and its healthy Lewis control (n = 3 animals; n = 115 AVP+/CTb+, n = 100 OXT+/CTb+, n = 430 total CTb+ neurons). Although the function of this projection is currently unclear, preliminary data in a subset of LPKs shows these SON neurons with MnPO collateral projections are activated by osmotic stressors (e.g., hypertonic saline). In summary, we report a major collateral projection from the SON to MnPO that is activated by osmotic stress. Given the well-known role of the MnPO in drinking behaviour, we suggest this SON-MnPO circuit may be involved in the coordination of fluid regulation and drinking behaviour.

This project was funded by Macquarie University.

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.
Boldine Promotes Recovery of Function After Motor-Incomplete Spinal Cord Injury in Mice
Authors: Toro Carlos A. , Siddiq Mustafa , Hansen Jens , Zhao Wei , Iyengar Ravi , Cardozo Christopher
Published: May 2024

Membrane channels such as connexins (Cx) and pannexins (Panx) are permeable to calcium ions and other small molecules such as ATP and glutamate. Release of ATP and glutamate through these channels is a key mechanism driving tissue response to traumas such as spinal cord injury (SCI). Boldine, an alkaloid isolated from the Chilean boldo tree, blocks both Cx hemichannels (HC) and Panx. To test if boldine could improve function after SCI, boldine or vehicle was administered to treat mice with a moderate severity contusion-induced SCI. Boldine led to greater spared white matter and increased locomotor function as determined by the Basso Mouse Scale and horizontal ladder rung walk tests. Boldine treatment reduced immunostaining for markers of activated microglia (Iba1) and astrocytic (GFAP) markers while increasing that for axon growth and neuroplasticity (GAP-43). RT-qPCR studies showed that boldine treatment reduced expression of chemokine Ccl2, cytokine IL-6 and microglial gene CD68, while increasing expression of the neurotransmission genes Snap25 and Grin2b, and Gap-43. Bulk RNA sequencing revealed that boldine modulated a large number of genes involved in neurotransmission in spinal cord tissue just caudal from the lesion epicenter at 14 days after SCI. Numbers of genes regulated by boldine was much lower at 28 days after injury. Furthermore, physical activity through treadmill training together with boldine showed an additive effect in recovery of function after SCI. Overall, our results indicate that boldine treatment ameliorates injury and spares tissue to increase locomotor function.

DOD SCIRP SC170315; VA RR&D Service Grant B-2020-C; NIH GM54508 and GM137056.

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.
Deletion of ADAM17 on microglia attenuates salt-sensitive hypertension
Authors: Mohan Uma Priya , Scarborough Amy , Restivo Luke , Xia Huijing , Lazartigues Eric
Published: May 2024

Previous work from our group identified ADAM17-mediated shedding as a major mechanism responsible for ACE2 shedding, thus impairing ACE2 compensatory activity and contributing to the development of salt sensitive hypertension. While microglia have been shown to contribute to salt sensitive hypertension, the mechanisms responsible are unknown. Accordingly, we hypothesize that ADAM17 promotes microglia priming, sympatho-excitation and neuro-inflammation in salt sensitive hypertension, and thus targeting ADAM17 or its maturation, via iRhom2, provides a multi-pronged strategy to normalize BP. Here, we aimed to evaluate whether deletion of ADAM17 on microglia attenuates hypertension. Uninephrectomized male and female mice (14–16-week-old, n=10/group) with selective deletion of ADAM17 in microglia (Cx3CR1-ADAM17tom) or with global deletion of iRhom2 (iRhom2-KO) and littermate controls (Cx3CR1-Cretom) mice were used to monitor blood pressure (BP telemetry, DSI) at baseline and following the initiation of salt sensitive hypertension (DOCA 1mg/g body weight sc + 1% saline po for 3 weeks). Following the establishment of hypertension (7 days post DOCA implantation) mice were injected with tamoxifen (200 nl ICV) and monitored for 2 more weeks. At the end of the treatment, mice were euthanized, and their brains were collected. Baseline mean arterial pressure (MAP) was not different in Cx3CR1-ADAM17tom, iRhom2-KO compared to controls (102±1, 106±1 and 104±1 mmHg, respectively). Surprisingly, all mice developed hypertension following DOCA implantation, including iRhom2 KO (Cx3CR1-ADAM17tom: 131±1, iRhom2 KO: 131±1, control: 126±1 mmHg, respectively. p<0.05). Interestingly, following tamoxifen injection Cx3CR1-ADAM17tom mice showed a blunted hypertension compared to the control group (MAP: 122±0.2 vs. 146±0.5 mmHg, one way ANOVA, p<0.05) suggesting that ADAM17 in microglia contributes to salt sensitive hypertension. In vitro, human microglia cells (iCell microglia — hIPSC) were shown to express lower ACE2 protein (0.03 ± 0.1 vs. 1.18 ± 0.3, Student’s t test, p<0.05) when exposed to Ang-II (100 ng) with a trend for ADAM17 upregulation (1.5 ± 0.3 vs. 1.1 ± 0.1, p<0.05). Together, our data suggest that overactivity of the renin-angiotensin system is associated with overexpression of ADAM17 in microglia and a simultaneous downregulation of ACE2. In addition, knockdown of ADAM17 specifically on microglia blunted the development of hypertension. We conclude that ADAM17 expression in microglia plays a pivotal role in salt sensitive hypertension.

This work was supported in part by a research grant from the National Institutes of Health (HL163588).

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.
Chronic Hypoxia during Gestation Disrupts Spontaneous Ca2+ Oscillations in Middle Cerebral Arterial Myocytes of Fetal Sheep
Authors: Boskind Madison , Nelapudi Nikitha , Romero Monica , Albert-Minckler Eris , Chan Michelle , Zhang Lubo , Blood Arlin
Published: May 2024

Long Term Hypoxic (LTH) stress is associated with an elevated risk of intracranial hemorrhage and stroke in newborns. Existing evidence illustrates that fetal sheep subjected to LTH conditions exhibit compromised cerebrovascular reactivity and arterial development, leading to perturbations in cerebral blood flow. Given the critical role of whole-cell Ca2+ waveforms in the contraction of middle cerebral arterial (MCA) myocytes and the regulation of cerebral blood flow, a comprehensive understanding of Ca2+ signaling patterns can provide insight into hypoxia-related cerebrovascular disease in neonates. This study was designed to test the hypothesis that intrauterine LTH disrupts whole-cell Ca2+ oscillations in fetal MCA myocytes. The hypothesis was addressed using MCAs isolated from term fetal sheep (approximately 140 days of gestation) delivered by cesarean section. These fetuses were carried by ewes residing at low-altitude (700 m) or high-altitude conditions (3801 m) for over 100 days of gestation. Ca2+ oscillatory activity was recorded using confocal fluorescence imaging techniques in an en face myocyte preparation. Spontaneous Ca2+ oscillations were evaluated in the presence and absence of 30 mM K+ to depolarize the myocytes, with or without 10 μM ryanodine, which blocks ryanodine receptor mediated Ca2+ release. The results of the study reveal that LTH decreases oscillatory activity and restricts the augmentation of activity following membrane depolarization. Furthermore, LTH induces dysregulation in spatial and temporal Ca2+ signals, manifesting as reduced event amplitude, shortened event duration, and decreased area under the curve (AUC). These findings highlight the impact of gestational hypoxia on multiple aspects of Ca2+ signaling in fetal lamb MCA, which may contribute to cerebrovascular dysfunction in the newborn.

R01HL155295, R01HL149608, Advanced Imaging and Microscopy Core Loma Linda University School of Medicine.

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.