bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Cardiac Myocytes the SGLT2 Inhibitor Ertugliflozin Attenuates Cytosolic Ca2+ Peaks After Adrenergic Stimulation
Authors: Dixit Mihir , Alam Sifat , Zhao Tengteng , Nguyen Quoc , Gierden Kyle , Yuan Jason , Vallon Volker 
Published: May 2024

A novel class of antidiabetic drugs, called gliflozins, inhibit sodium-glucose cotransporter 2 (SGLT2i) to lower blood glucose levels in patients with Type 2 diabetes (T2DM). Gliflozins reduce mortality and heart failure (HF) hospitalizations in HF patients with or without T2DM, but the molecular mechanisms are unclear. We hypothesize that modulating effects on cardiac calcium homeostasis are involved in SGLT2i-induced benefits during HF, and that the SGLT2i ertugliflozin (ERTU) will alter cytosolic calcium concentration ([Ca2+]cyt) in contracting cardiomyocytes after adrenergic stimulation. Cardiomyocytes were isolated from 0–2-day old C57BL/6J mice, treated for 72 hours with either ERTU (100 nM, and 1 μM), the NHE-1 inhibitor cariporide (CARI, 10 μM), ERTU and CARI, or vehicle (Ctrl). After 72 hours, cells were either A) loaded with Fura-2, baseline cytosolic calcium levels ([Ca2+]cyt) recorded, cells stimulated with phenylephrine (PE, 100 μM), and [Ca2+]cyt recorded for additional 30 minutes, B) lysed and protein isolated for analysis by immunoblotting, or C) fixed for immunohistochemical assessment. Results: 100 nM and 1 uM ERTU reduced [Ca2+]cyt peaks after PE, but 100 nM ERTU to a lesser degree. In contrast, 72-hour-long NHE1 inhibition with CARI increased [Ca2+]cyt at baseline when compared to vehicle and ERTU, and further enhanced [Ca2+]cyt peaks after PE. Immunoblotting revealed increased protein levels of S16 phosphorylated phospholamban, decreased total phospholamban, and upregulated sarcomeric α-actinin post-ERTU. Immunohistochemical assessment of sarcomeric α-actinin localization revealed improved sarcomeric Z-line organization after ERTU administration. Sustained exposure to the SGLT2i ERTU reduced, but the NHE-1 inhibitor CARI increased [Ca2+]cyt in contracting cardiac myocytes. These data indicate that ERTU’s beneficial effect on [Ca2+]cyt homeostasis is independent of NHE1 inhibition. Since disturbed calcium handling and calcium overload are hallmarks of HF, reduced [Ca2+]cyt levels after sympathetic stimulation may contribute to the cardioprotective effect of SGLT2i. Further studies are needed to unravel the molecular mechanisms behind ERTU’s influence on cardiac calcium homeostasis. This study was funded by Merck & Co., Inc. (Kenilworth, NJ). 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.
Chaos in the Colon: Unlocking the Puzzle of DRA (SLC26A3) Downregulation with IL-1α and p38 MAPK Amidst Brachyspira Turmoil
Authors: Challa Nitin , Enns Cole , Keith Brandon , Harding John , Loewen Matthew 
Published: May 2024

This study examines the impact of Brachyspira hyodysenteriae and Brachyspira hampsonii infection on chloride (36Cl−) transport within the porcine colon. Utilizing 3H-mannitol and 36Cl−, we evaluated the bidirectional flux across colonic tissues from both healthy and infected pigs. We observed no change in 3H-mannitol flux, indicating unaffected paracellular movement. However, we observed a significant decrease in mucosal-serosal 36Cl− flux (Jm-s) in the apical segment of the spiral colon of infected pigs, suggesting a compromised chloride absorption due to the downregulation of DRA (SLC26A3), confirmed by reduced mRNA and protein levels. To dissect the molecular dynamics in vitro, we exposed polarized Caco-2 cells to B. hampsonii lysate. This model recapitulated the in vivo responses, including the downregulation of DRA and the concomitant IL-1α upregulation. This in vitro model demonstrated that B. hampsonii lysate upregulates IL-1α expression through p38 MAPK phosphorylation. More importantly, in vitro studies with B. hampsonii lysate, recombinant IL-1α, SB 203580 (p38 MAPK inhibitor), and blocking IL-1α signalling with IL-1 receptor antagonist (IL-1RA) revealed that IL-1α has a dose-dependent negative effect on DRA expression and a positive effect on IL-1α expression. Furthermore, inhibiting IL-1α expression with SB 203580 and blocking IL-1α signalling with IL-1RA not only prevented this downregulation of DRA but also promoted its upregulation, highlighting the regulatory role of IL-1α in chloride absorption. In summary, this study presents an in-depth understanding by which Brachyspira infections can impede chloride absorption in the colon and offers potential intervention targets for conditions involving impaired DRA-mediated Cl− transport. This research was supported by Alberta Livestock Meat Association (ALMA 2013R054R) and Natural Sciences and Engineering Research Council of Canada Discovery Grant 02743-2021 (to M. E. Loewen). 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 effects of Type 2 Diabetes mellitus might be mitigated by grape pomace flour
Authors: Monteiro Rodrigues Luis , Nicolai Marisa , Piccoli Raphaela , Pereira Paula , Spanevello Roselia , Stefanello Francieli , Palma Maria Lidia 
Published: May 2024

Type 2 diabetes mellitus (T2DM) is a multifaceted metabolic disorder characterized by insulin resistance and pancreatic β-cell dysfunction, leading to varying metabolic insults. Grape pomace, a byproduct of the winemaking industry, is under investigation as a potential therapy for T2DM due to its abundant content of bioactive polyphenols and dietary fiber. Within the current backdrop of environmental concerns, the conversion of grape pomace into a safe and applicable form, with the aim of promoting sustainable management of environmental waste, acts as a catalyst for the emergence of viable alternatives. Grape pomace flour (GPF) represents an economical and feasible solution. We hypothesized that dietary supplementation of GPF would improve the glycemic control and the associated risk factors in T2DM-induced animals. In this sense, the present study, approved by CEUA UFPel No 033578/2022-14, aimed to evaluate the effect of the GPF from ‘Arinto’ and ‘Touriga Nacional’ grape varieties on biochemical and histopathological parameters in an animal model of T2DM. To induce T2DM, rats were given a high-fat diet and a Streptozotocin (STZ) injection (35 mg/kg). The rats were divided into five groups: Control (CT), T2DM, T2DM+Metformin (Met) (250 mg/kg), T2DM+'Arinto' GPF 10% (WGPF), and T2DM+'Touriga Nacional' GPF 10% (RGPF). Results showed that Met, WGPF, and RGPF groups had significantly lower blood glucose ( p<0.05, P<0.001, and p<0.01, respectively) and triglyceride levels ( p<0.001) compared to the T2DM group. Also, we observed a significant increase in serum cholesterol levels in the T2DM when compared to the CT ( p<0.01), that was reversed in the treated groups. Additionally, the T2DM+RGPF group had higher levels of high-density lipoprotein (HDL) compared to the control group ( p<0.05). Histopathological analysis revealed structural changes in the pancreas in the T2DM animals, while tissue damage was not observed in the Met and GPF supplementation groups. In conclusion, both 'Arinto' and 'Touriga Nacional' GPF demonstrated protective effects against increased blood glucose, triglycerides, and cholesterol levels in a T2DM animal model. 'Touriga Nacional' GPF also increased HDL levels and showed protective effects on pancreatic cell structure. This suggests that GPF could be a promising dietary option for T2DM and its complications. FCT-Foundation for Science and Technology (UIDB/04567/2020 CBIOS, and UIDP/04567/2020 CBIOS), Pelotas Federal University (UFPel), and Brazil's Federal Government (CNPq). 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.
Angiotensin-(1-7) Mas Receptors are Highly Colocalized to GABAergic Proopiomelanocortin Neurons in the Arcuate Nucleus of the Hypothalamus
Authors: Vernail Victoria , Bingaman Sarah , Silberman Yuval , Arnold Amy 
Published: May 2024

Previous studies from our laboratory have shown that circulating levels of angiotensin (Ang)-(1-7), a protective hormone of the renin-angiotensin system, are greatly reduced in obese hypertensive mice. Additionally, restoration of this hormone reduces cardiovascular sympathetic tone and lowers blood pressure in this model suggesting a central mechanism of action. In support of this, our recent data show that the sympatho-inhibitory and blood pressure lowering effects of Ang-(1-7) involve activation of mas receptors (masR) within the arcuate nucleus of the hypothalamus (ARC). More specifically, we have found that masR are highly colocalized to proopiomelanocortin (POMC) neurons in the ARC. Due to the heterogeneous nature of POMC neuron subtypes, we wanted to explore the neurotransmitter phenotype of these POMCmasR neurons. We hypothesized that due to the blood pressure lowering effects of Ang-(1-7), POMCmasR are likely colocalized to inhibitory GABAergic neurons. To test this, we performed RNAscope in-situ hybridization in male C57Bl/6J mice after twelve weeks of either a 60% high fat diet (HFD) or matched control diet (n=12-18/group). We used RNAscope to colocalize expression of POMC, masR, and the vesicular GABA transporter, Vgat, mRNA transcripts within the ARC. Colocalization of POMCmasR and Vgat was quantified and percent-colocalization compared between control and HFD groups. We found that POMCmasR are highly colocalized with the GABAergic marker, Vgat, to a similar extent in control and HFD groups (84±4 vs. 90±2% of neurons, respectively; p=0.294 unpaired t-test). The population of POMC neurons that did not express masR also did not colocalize with Vgat. As an initial step to determine if masR modulates GABAergic signaling in the ARC, we assessed gene expression of glutamate decarboxylase 2 (Gad2; a GABA synthetic enzyme) in the ARC following chronic six-week treatment with systemic Ang-(1-7) versus saline infusion in male mice fed a control diet versus HFD (n=9-13/group). We found that Ang-(1-7) increases ARC Gad2 mRNA in HFD mice (1.03±0.09 control diet vs. 0.93±0.07 HFD vs. 1.23±0.07 HFD plus Ang-(1-7); p=0.023 one-way ANOVA). Supporting specificity of these actions, Ang-(1-7) did not alter POMC mRNA in the ARC. These overall data suggest that masR primarily localize to GABA-expressing POMC neurons in the ARC, and Ang-(1-7) may directly modulate GABA synthesis pathways in this brain region. Further studies are needed to elucidate the functional importance of these ARC POMC GABAergic neurocircuits to the depressor effects of Ang-(1-7) in obesity. Funding: NIH R01 HL156986. 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.
Renin-Angiotensin System Signaling in Parietal Epithelial Cells
Authors: Fedoriuk Mykhailo , Stefanenko Mariia , Van Beusecum Justin , Palygin Oleg 
Published: May 2024

INTRODUCTION. Bowman's capsule surrounds the kidney glomerular tuft and consists of a monolayer of parietal epithelial cells (PECs) creating a physiologically functioning barrier between the urinary space and the renal interstitium. Pathophysiological PEC activation describes the phenotypic switch from their normal quiescent state to one of proliferation and migration to the glomerular tuft, leading to glomerular injury. The development of several proteinuric kidney diseases is closely associated with PEC activation, however, the mechanisms of functional receptor signaling in these cells are not well described. This study investigates the functional presence of renin-angiotensin system (RAS) components and corresponding intracellular mechanisms in PECs. Methods. The vibrodissociation method was utilized to obtain freshly isolated Bowman’s capsules from discarded adult male human transplant tissues and 12-week old Wistar male and female rats. Confocal fluorescent microscopy of freshly isolated Bowman’s capsule PECs was performed using Fluo-8 or DAF-FM fluorescent dyes to detect changes in intracellular Ca2+ concentrations and nitric oxide (NO) response to the variety of RAS peptides. RESULTS. In separate experiments on freshly isolated rodent and human Bowman’s capsule PECs, we demonstrate the changes in redox response to the stimulation of RAS components. In particular, the acute application of Ang II peptide caused a rapid increase in NO production. Interestingly, we did not indicate significant changes in intracellular Ca2+ influx. To find out which receptor is responsible for the NO release we preincubated PECs with AT1R and AT2R blockers (Losartan and PD123319 respectively). Our data indicate that RAS mediates NO production through the AT2R activation. There is no sex difference was observed in these experiments. Further experiments with the variety of nitric oxide synthase (NOS) pharmacology reveal the functional distribution of NOS in rodent PECs. CONCLUSION. Our study provides an overview of the RAS signaling within PECs. For the first time, we present evidence demonstrating a direct connection between Ang II and redox homeostasis in PECs. Further investigation using the developed approach will be essential for understanding the role of Bowman's capsule cells in the glomerulus and the development of potential treatment against the hyperplasia of activated PECs and corresponding chronic kidney pathologies. Funding Sources: R01 DK129227, R01 DK126720, VA CDA-2 1IK2BX005605-01. 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.
Chronic Intermittent Hypoxia Alters GABAergic Inhibition in Median Preoptic Nucleus (MnPO) Neurons of Rats
Authors: Farmer George , Little Joel , Cunningham J Thomas 
Published: May 2024

Chronic intermittent hypoxia (CIH) is an animal model simulating the hypoxemia associated with obstructive sleep apnea (OSA) in humans. Male rats exposed to CIH exhibit increased sympathetic tone and persistent elevations in blood pressure similar to that observed in patients with. In MnPO neurons, CIH reduces GABAa inhibition and, in some neurons, GABAa activation produces excitation. Here, loose patch and perforated patch recordings were conducted in MnPO neurons in response to optogenetic stimulation of GABAergic SFO (efferent) and MnPO (local) neurons to assess the role of GABAergic signaling in these nuclei on MnPO excitability. Our working hypothesis was that CIH would diminish the inhibitory effects of optogenetic stimulation of GABA neurons. This hypothesis was tested using an AAV vector that selectively expresses channel rhodopsin in GABA neurons Using isoflurane (2-3%) anesthesia, male Sprague-Dawley rats (250-350g) received infusions (0.2 μL) of pAAV-mDlx-ChR2-mCherry-Fishell-3 in the SFO or MnPO. After recovery, rats were subjected to 7 days of CIH (0800-1600 hr) or normoxia (Norm). CIH consisted of 6 min cycles (3 min 21% O2, 3 min 10% O2) repeated 10x/hr for 8 hours (during the normal inactive/sleep phase) on 7 consecutive days. For in vitro recordings, rats were anesthetized with isoflurane (2-3%), and sagittal or coronal slices (300 μm) containing MnPO were cut using standard slice procedures. Voltage-clamp loose patch or perforated patch recordings using gramicidin (100 ug/ml in 140 mM K-gluconate) were collected in MnPO neurons in response to optogenetic stimulation of GABAergic neurons (2 ms pulse, 20 Hz, 1 sec). MnPO neurons from CIH-treated rats showed differing responses to GABAergic stimulation while MnPO neurons from Norm-treated rats predominantly exhibited GABAergic inhibition. MnPO neurons from Norm rats exhibited mIPSCs and outward currents in response to muscimol. MnPO neurons from CIH-treated rats show variable mIPSC frequencies and heterogeneous responses to GABAergic neuronal activation in the SFO and MnPO. The results demonstrate that CIH alters the Cl− homeostasis in some MnPO neurons altering their response to GABAa stimulation. These changes may contribute to the increased sympathetic tone and reactivity, as well as the persistent hypertension associated with CIH. Supported by R01 HL155977. 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 stiffness is altered by age and fatigue at the cellular level
Authors: Privett Grace , Ricci Austin , Callahan Damien 
Published: May 2024

Advanced age is associated with increased skeletal muscle stiffness at the cellular and whole-tissue levels. In older adults, fatigue increases falls risk. Our lab has previously observed fatigue-induced reductions in skeletal muscle cellular stiffness in younger adults, prompting the question of whether the same occurs in older adults. If so, it is possible that fatigue-induced reduction in cellular stiffness of older adults would reduce the rate of tendon loading and/or increase tissue compliance, ultimately contributing to increased falls risk. Therefore, the OBJECTIVE of the present study is to measure cellular passive and active stiffness in younger and older adults across fatigue conditions to test the hypothesis that fatigue induces tissue compliance that predisposes older adults to falls. Methods: 11 untrained males and females (7 younger, 20±1 yrs.; 4 older, 74±4 yrs.) performed unilateral knee extensions to fatigue, followed by bilateral biopsy of the Vastus Lateralis providing fatigued (F) and non-fatigued (NF) samples. Single fibers (146 younger, 130 older) were passively stretched to 156% initial length and passive modulus was calculated as the slope of the resulting stress-strain curve. Separately, Residual Force Enhancement (RFE) was measured in a subset of fibers (9 younger, 40 older) to assess passive contributions (titin) to active (actin-myosin) stretch. Main effects (age/fatigue) on passive modulus and RFE were tested via linear mixed model and t-tests, respectively. Results: Passive modulus was increased with age (p=0.04) and reduced by fatigue in both the younger (p<0.01) and older (p<0.01) participants. In a subset of fibers, RFE was increased in older women compared to younger (p<0.01) and older men (p<0.01). No main effect of fatigue on RFE was detected (p=0.49). However, RFE trended towards reduction with fatigue in a younger male (p=0.13) and was significantly reduced by fatigue in myosin heavy chain (MHC) I fibers from an older male (p=0.02). CONCLUSION: In agreement with existing literature, cellular passive modulus was higher in older versus younger adults. Additionally, fatigue reduced passive modulus in skeletal muscle fibers from both older and younger adults. Though no main effect of fatigue on RFE was detected, these results suggest that cellular RFE measures are age- and fiber-type specific. This work was supported by funds from the Wu Tsai Human Performance Alliance. 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.
Effect of CaSR Deletion in the Esophagus on Gene Expression and Immune Function
Authors: Abdulnour-Nakhoul Solange , Kolls Jay , Flemington Erik , Ungerleider Nathan , Nakhoul Hani , Song Kejing , Nakhoul Nazih 
Published: May 2024

Background: The calcium sensing receptor (CaSR) regulates Ca2+ concentration in plasma by regulating parathyroid hormone secretion. In other tissues, CaSR plays roles in cellular differentiation and migration, and in secretion and absorption. We reported previously that CaSR can be conditionally deleted in the mouse esophagus. This conditional knock-out ( EsoCaSR−/−) model showed significant reduction in levels of adherens and tight junction proteins and had significant build-up of bacteria on the luminal esophageal surface. Objectives: We aimed to further understand the role of CaSR and to examine the modification in gene expression induced by CaSR deletion in the esophagus. Methods: We performed mRNA sequencing and bioinformatic analyses of mice esophageal tissues. Gene expression was characterized using an unbiased pathway approach in EsoCaSR−/− and control mouse esophageal mucosae. Next generation sequencing was used to obtain a profile of the differences in RNA expression between tissues. RNA expression data was used to analyze differences in pathways and functional networks between EsoCaSR−/− and control esophageal tissues. Results: Our data indicated significant upregulation of gene sets involved in DNA replication and cell cycle in EsoCaSR−/−. This is accompanied by marked downregulation of gene sets involved in the innate immune response and in protein homeostasis including peptide elongation and protein traffcking. Ingenuity Pathway Analysis (IPA) demonstrated that these genes are mapped to important biological networks including Calcium and RhoA signaling pathways. Conclusions: The major findings of this study are that CaSR impacts important pathways of cell proliferation, differentiation, cell cycle and innate immune response in esophageal epithelium. The disruption of these pathways also causes significant modifications of the microbiome. Funding: U54 GM104940 grant from NIH, VA Merit grant, Paul Teschan Research grant, Carol Lavin Bernick grant, Tulane institutional grant. 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.