bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal NHE1 is required for regulation of intracellular pH in principal cells and type B intercalated cells
Authors: Xue Jianxiang , Thomas Linto , Rieg Jessica Dominguez , Tomilin Viktor , Pochynyuk Oleh , Rieg Timo
Published: May 2023

The sodium-hydrogen exchanger isoform 1 (NHE1) is a plasma membrane transporter with roles in transepithelial Na+/H+ transport, intracellular pH (pHi) and cell volume regulation. Within the kidney, NHE1 is previously documented to be expressed in all nephron segments. However, recent transcriptomic and proteomic analyses, and our staining results in mice, consistently find no expression of NHE1 in the proximal tubule or thick ascending limb, but in the distal nephron, including distal convoluted tubule, connecting tubule, and collecting duct (principal and intercalated cells, PC and IC, respectively). We hypothesized that basolateral NHE1 in IC (co-labelling with H+-ATPase B1 subunit, labeling all 3 types of IC: type A, B, and non-A-non-B) plays an important role in acid-base homeostasis. Due to lack of a suitable animal model, we generated kidney-specific NHE1 knockout (NHE1KS-KO) mice. NHE1KS-KO mice completely lack renal NHE1 protein expression compared to their control littermates (n=6 male mice/genotype). No differences were observed in body weight, food and water intake (determined in their home cages) or concentrations of blood Na+, K+, Ca2+, pH or HCO3-. Urine analysis showed no significant differences in electrolytes, minerals of pH. To mechanistically determine the role of NHE1 for pHi regulation in IC and PC we used confocal microscopy of acutely-split open cortical collecting ducts. This method allows for the analysis of a vast number of PC/IC simultaneously. To study the role of NHE1 we employed a NH4Cl pre-pulse (40 mM) and measured pHi recovery after switching back to a physiological solution. Intracellular pH recovery in PC (n=171) was significantly slower (~50%) in NHE1KS-KO mice compared to controls (n=85). Similar to PC, pHi recovery in type B IC of NHE1KS-KO mice (n=38) was significantly slower (~35%) compared to controls (n=40). No differences in type A IC were observed between NHE1KS-KO mice (n=35) and controls (n=29). Inhibition of ClC-K2 via NPPB (Cl-channel blocker) was used to confirm cell types: PC did not respond with a change in pHi but NPPB increased pHi in type A and decreased pHi in type B ICs. In summary, our results identify for the first time an important role of NHE1 for pHi regulation particularly in PCs and type B ICs.

Funding to Dr. Rieg was provided by the NIDDK grant 1R01DK110621, VA Merit Review Award IBX004968A, AHA Transformational Research Award 19TPA34850116, and NIDDK Diabetic Complications Consortium grants DK076169 and DK115255. DK095029 and DK117865 (both to O. Pochynyuk). Dr. Thomas was supported by an AHA postdoctoral grant (828731), V. Tomilin by an AHA Career Development Award 19CDA34660148.

This is the full abstract presented at the American Physiology Summit 2023 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.
Subcutaneous white adipose tissue expression of HuR mediates cardiac pathology via adipose tissue-derived extracellular vesicles
Authors: Desarapu Rohan , Anthony Sarah , Guarnieri Adrienne , Parkins Sharon , Kuhnell Damaris , Langevin Scott , Tranter Michael
Published: May 2023

Obesity is a rapidly growing epidemic worldwide, especially in the United States, and is associated with cardiovascular disease (CVD), diabetes, cancer, and a multitude of other comorbidities. Adipose tissue has been shown to act as an endocrine organ in the body and to mediate cardiac physiology. We have previously shown that deletion of HuR specifically in adipocytes (Adipo-HuR KO) induces cardiac fibrosis in mice, independent of traditional adipose/obesity co-morbidities (dyslipidemia, hypertension, diabetes).​ Deletion of HuR in the adipocyte affects both brown adipose tissue (BAT) depots as well as subcutaneous white adipose tissue (scWAT) depots. We have shown that HuR deletion in BAT (using a UCP1-driven cre model) maintains normal cardiac function compared to Adipo-HuR KO mice. This points toward scWAT being the primary mediator of cardiac pathology from adipose tissue, which is consistent with our previously published bioinformatic analysis suggesting HuR-dependent adipose tissue-derived extracellular vesicles (Ad-EVs) as the mechanism by which this occurs.The goal of this work is to identify the mechanisms by which HuR expression in subcutaneous white adipose tissue (scWAT) mediates cardiac function via Ad-EVs. Here, we show that Ad-EVs isolated from scWAT depots of our Adipo-HuR KO model induce significant hypertrophic signaling in vitro, compared to wild-type littermates. We also show that expression of HuR in scWAT specifically is decreased with obesity and age, suggesting a potential mechanistic link between obesity, HuR expression in scWAT, and CVD.In conclusion, our results demonstrate that loss of HuR expression in scWAT is sufficient to induce cardiac hypertrophy and fibrosis, in part through endocrine-mediated Ad-EV signaling. In addition, we are beginning to identify HuR-dependent gene expression patterns in human scWAT which may potentially play a significant role in this signaling axis.

This work was supported by NIH grants R01-HL132111 and HL158671 (MT). RD is supported by a Peter Lauf Travel Award from the Ohio Physiological Society. SP is supported by an NIH Training grant T32HL125204 (PIs: Molkentin and Kranias). ARG was supported by American Heart Association Predoctoral Fellowship (916812).

This is the full abstract presented at the American Physiology Summit 2023 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.
TRPV4 expression in the renal tubule is necessary for maintaining whole body K+ homeostasis
Authors: Stavniichuk Anna , Pyrshev Kyrylo , Zaika Oleg , Tomilin Viktor , Pochynyuk Oleh
Published: May 2023

Distal segments of the renal tubule have a major role in controlling whole body K+ homeostasis by performing flow-induced K+ secretion (FIKS) during K+ load and K+ reabsorption in response to systemic K+ deficiency. The transient receptor potential vanilloid type 4 (TRPV4) Ca2+-permeable channel serves as the sensor of tubular flow thus being well-suited to govern K+ transport in the distal renal tubule. In the current manuscript, we directly tested whether TRPV4 function in the renal tubule is significant in affecting K+ balance. For this, we employed balance metabolic cage studies and systemic measurements with different K+ feeding regimens: high (5% K+), regular (0.9% K+), and low (<0.01% K+) in newly created transgenic mice with selective TRPV4 deletion in the renal tubule (TRPV4fl/fl-Pax8Cre) and their littermate genetic controls (TRPV4fl/fl). Successful deletion was verified by the absence of TRPV4 protein expression in renal homogenates and the lack of TRPV4-mediated Ca2+ influx in freshly-isolated split-opened collecting ducts. There were no differences in plasma electrolytes, baseline urinary volume, and K+ levels when both strains were fed regular K+ intake. In contrast, plasma K+ levels were significantly elevated in TRPV4fl/fl-Pax8Cre mice on both high and low K+ intake. This was associated with a marked decrease in 24 h urinary K+ levels in the knockout, whereas urinary volume and aldosterone levels were indistinguishable from the control TRPV4fl/fl littermates suggesting a direct decrease in the distal tubule K+ transport. Interestingly, we also detected significant differences in urinary pH levels indicative of the altered K+ reabsorption via H+-K+ ATPase in the collecting duct. Indeed, we detected a significantly faster pHi recovery after intracellular acidification with ammonium pulse in both acid secreting A- and base-secreting B-types of intercalated cells and to a lesser degree in principal cells in split-opened collecting ducts from TRPV4fl/fl-Pax8Cre mice on low but not regular K+ intake, which is consistent with augmented H+-K+ ATPase activity and K+ reabsorption in the knockouts. In summary, our results demonstrate an indispensable pro-kaliuretic role of TRPV4 in the renal tubule in controlling K+ balance and urinary K+ excretion during variations in dietary K+ intake

This research was supported by NIH-NIDDK DK117865, DK119170, AHA EIA35260097 (to O. Pochynyuk) and AHA-19CDA34660148 (to V. N. Tomilin).

This is the full abstract presented at the American Physiology Summit 2023 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.
Postnatal Inhibition of TrkB Kinase Reduces the Number of Phrenic Motor Neurons
Authors: Brandenburg Joline , Fogarty Matthew , Zhan Wen-Zhi , Sieck Gary
Published: May 2023

During embryonic development, the number of phrenic motor neurons (PhMNs) declines precipitously during the final trimester and continues into the early postnatal period. When BDNF/TrkB signaling is absent in utero, animals do not survive after birth, most likely due to excessive loss of vital motor neurons (e.g., PhMNs). Far less is known about the early postnatal effect of BDNF/TrkB signaling. We have shown that BDNF/TrkB signaling is important in promoting PhMN neuroplasticity in mature rodents. Taken together, we hypothesized that inhibition of BDNF/TrkB signaling during early postnatal development results in fewer PhMNs. Chemo-genetic TrkBF616A mutant mice were used to induce inhibition of TrkB kinase activity in response to oral administration (via drinking water) of a phosphoprotein phosphatase 1 inhibitor derivative (1NMPP1). 1NMPP1-induced TrkB kinase inhibition was initiated at P0 and continued until P21 and compared to untreated control mice. At P28, PhMNs were retrogradely labeled via rhodamine phrenic nerve dip. One day later, mice were euthanized, perfused with 4% paraformaldehyde, and the cervical spinal cord was excised and processed for longitudinal cryosectioning (70 μm). Labeled PhMNs were imaged by 3D high resolution confocal microscopy. The number of PhMNs were counted. PhMN somal surface area and number of primary dendrites were also determined. 1NMPP1-induced inhibition of TrkB kinase resulted in 24% fewer PhMNs (P=0.01) and 21% more primary dendrites (P=0.0002) than control mice. The distribution of PhMN somal surface areas was not affected. We conclude that BDNF/TrkB signaling is essential in promoting survival of PhMNs in the early postnatal period. BDNF/TrkB signaling during postnatal development also plays a role in paring primary dendrites. While inhibition of TrkB kinase did not significantly alter the distribution of PhMN somal surface areas at P28, it is possible that further growth of PhMNs into maturity might have been altered as larger PhMNs emerge as a result of disproportionate growth beyond this age in mice.

Supported by National Institutes of Health grants R01-AG044615 (GCS), R01-HL96750 (GCS).

This is the full abstract presented at the American Physiology Summit 2023 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.
Effects of wetted inner clothing on heat strain while wearing ventilation garments in hot-dry and warm-humid environments
Authors: Tokizawa Ken
Published: May 2023

The present study examined 1) the effect of wearing a water-soaked inner t-shirt with a ventilation garment on heat strain in undertaking moderate-intensity exercise (metabolic rate: 200 W/m2) in heat (37 °C, 50% RH, 2.8 kPa) in study 1, and 2) whether the cooling was effective in hot-dry (40 °C, 30% RH, 2.2 kPa) and warm-humid (32 °C, 80% RH, 3.8 kPa) environments in study 2. It was hypothesized that 1) wearing a water-soaked t-shirt in combination with a ventilation garment would attenuate heat and cardiovascular strain compared with a dry t-shirt/ventilation garment combination; and 2) mitigation of heat and cardiovascular strain would be greater in the warm-humid condition.In the study 1, while intermittent walking in the heat for 60 min, eight male subjects wore a dry inner t-shirt without fanning of a ventilation jacket as a control (CON). Meanwhile, under a fanned ventilation jacket, the subject wore a dry inner t-shirt (DRY) or an inner t-shirt soaked with 350 mL of tap water (WET). Increases in rectal temperature in the WET trial (0.7 ± 0.2 °C) were lower than in the CON (1.3 ± 0.3 °C) and DRY (1.1 ± 0.2 °C) (both p<0.05) trials. Heart rate and sweat loss were lowest in the WET, followed by DRY, and then CON (all p<0.05).In the study 2, the attenuation in elevation of rectal temperature, heart rate, and sweat loss in WET was observed in both hot-dry and warm-humid environments. There was no difference in the attenuation between the hot-dry and warm-humid conditions.These findings demonstrate that wearing a water-soaked inner t-shirt while using a ventilation garment is an effective and practical cooling strategy to mitigate heat strain during moderate-intensity exercise in hot occupations.

Public (The project research of National Institute of Occupational Safety and Health, Japan)

This is the full abstract presented at the American Physiology Summit 2023 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.
Contribution of the tachykinergic receptors of the respiratory parafacial region on breathing activity
Authors: Maia Octávio , Oliveira Luiz , Takakura Ana , Moreira Thiago
Published: May 2023

Ventilation is a process initiated in the central nervous system, essential for maintaining the body’s homeostasis, especially to regulate O2 and CO2 levels in blood and tissues. Based on functional and anatomical characteristics, the respiratory parafacial region was subdivided into two distinct populations, the ventral (pFV) and lateral (pFL) parafacial regions. Evidence suggests that both regions express high levels tachykinergic receptors and have an impact on breathing. However, little is known about the tachykinergic modulation of the tachykinergic signaling to control breathing output. In the present study, we pharmacologically investigated the respiratory effects elicited by the injection of substance P (SP) within the parafacial region as well as the role of NK1 receptors in the baseline and in the ventilatory response to hypercapnia (7% CO2). External intercostal muscle activity (IntEMG) was recorded in urethane-anesthetized male or female adult C57Bl6J mice. SP injections (1 μM - 30 nL) in the pFV elicited a significant increase in the IntEMG frequency (18.3 ± 5.3, vs. saline: -1.2 ± 0.8%), IntEMG amplitude (38.3 ± 11.6 vs. saline: -1.95 ± 2.5%) and IntEMG minute volume (62.4 ± 12.4 vs. saline: -3.1 ± 2.7%). In contrast, SP injections in the pFL elicited a significant reduction in the IntEMG frequency (-18.4 ± 4.5, vs. saline: -0.42 ± 0.42%) and an increase in the IntEMG amplitude (43.7 ± 15.2 vs. saline: 1.8 ± 1.8%). Bilateral blockade of NK1 receptors (GR82334 - 100 mM - 30 nL) in the pFV region was able to reduce the increase in the IntEMG amplitude (13.4 ± 5.5, vs. saline: 58.1 ± 24.5%), IntEMG frequency (5.1 ± 5.1, vs. saline: 13.6 ± 10.3%,) and IntEMG minute volume (19 ± 8, vs. saline: 77.6 ± 27.1%) induced by hypercapnia and completely eliminate the excitatory effect elicited by SP. Our results suggest that tachycinergic signaling exerts different effects on respiratory rate depending on the site of injections in the parafacial region and NK1 receptors within the pFV region are involved in the hypercapnia ventilatory response.

FAPESP, CNPq, CAPES-PROEX.

This is the full abstract presented at the American Physiology Summit 2023 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.
Breathing irregularities in spontaneously hypertensive neonate rats
Authors: Zoccal Daniel , Vieira Beatriz , Mendes Letícia , Leirão Isabela
Published: May 2023

An excessive sympathetic drive is commonly observed in hypertensive patients and critically contributes to increasing arterial pressure levels. The quality of postnatal life can impact sympathetic control in adulthood. Spontaneously hypertensive (SH) rats, an experimental model of neurogenic hypertension, exhibit breathing irregularities in adult life. In this study, we investigated whether SH rats display breathing abnormalities after birth, which could be a risk factor for developing sympathetic overactivity. Using head-out plethysmography, we found that the neonate (P0-2, male and female) SH rats (n=9) exhibited lower minute ventilation than age-matched normotensive rats (NT, n=14; 816±177 vs 1261±189 ml/min/kg, P<0.05) under resting conditions, mainly due to reductions in respiratory frequency (93±15 vs 132±13 cpm, P<0.05). The reduced baseline ventilation in the SH group was accompanied by a greater prevalence of periods of apneas and respiratory irregularities (P<0.05). Under hypoxia conditions (10% O2, 10 min), SH and NT rats (n=9/each) mounted similar transient increases in minute ventilation during the initial period of exposure due to increments in tidal volume. In contrast, the respiratory frequency in the SH rats decreased progressively below baseline levels during hypoxia exposure (42% reduction, P<0.05), while it remained similar to pre-hypoxia values in the control group. In rhythmic in vitro preparations from neonate SH rats (n=2), we identified ectopic bursts in the hypoglossal activity and prolonged inspiratory-related bursts in the preBötzinger complex compared to preparations from NT rats (n=2). Our findings indicate that breathing irregularities in SH rats are present from birth and could be linked to dysfunctions in the inspiratory rhythm-generating network.

Financial support: FAPESP, CNPq.

This is the full abstract presented at the American Physiology Summit 2023 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.
AT1a receptor knockout selectively in renomedullary interstitial cells of the kidney lowers basal blood pressure, impairs urine concentration, and attenuates angiotensin II-induced hypertension in RMIC-Agtr1a-/- mice
Authors: Li Xiao , Hassan Rumana , Hao Chuan-Ming , Zhang Ming-Zhi , Harris Raymond , Zhuo Jia
Published: May 2023

We previously reported that global deletion of angiotensin II (Ang II) AT1a receptors significantly lowered basal blood pressure and impaired urine concentration in mice. As we also demonstrated that renomedullary interstitial cells (RMICs) of the kidney expressed a high level of AT1 (AT1a) receptors, we hypothesized that AT1a receptors in RMICs may play an important physiological role in maintaining basal blood pressure and urine concentration homeostasis. To test the hypothesis, we generated a novel mouse model with deletion of AT1a receptors selectively in the RMICs of the kidney medulla using inducible Tenascin-C-CreER2/Agtr1af/f recombination approach (RMIC- Agtr1a-/- ) in the present study. Adult male wildtype (WT) and RMIC- Agtr1a-/- mice (n=10-18 per group) were phenotyped under basal conditions and treated with or without a slow pressor dose of Ang II infusion via an osmotic minipump (~500 μg/kg/day, i.p.) for 2 weeks to determine the roles of AT1a receptors in RMICs in maintaining basal blood pressure and urine concentration homeostasis and in the development of Ang II-induced hypertension. Under basal conditions, telemetry systolic blood pressure was significantly lower in adult male RMIC- Agtr1a-/- than WT mice (WT: 122 ± 4 mmHg vs. RMIC-Agtr1a-/-: 102 ± 3 mmHg, P<0.01). This hypotensive phenotype in RMIC- Agtr1a-/- mice was associated with significant decreases in 24 h urine output (WT: 1.56 ± 0.15 mL/24 h vs. RMIC- Agtr1a-/- : 0.98 ± 0.13 mL/24 h, P<0.01), urinary sodium (WT: 207.9 ± 7.3 μmol/24 h vs. RMIC- Agtr1a-/- : 145.2 ± 5.4 μmol/24 h, P<0.01), and potassium excretion (WT: 221.0 ± 6.7 μmol/24 h vs. RMIC-Agtr1a-/-: 160.8 ± 10.6 μmol/24 h, P<0.01), respectively. Moreover, urine osmolality was markedly decreased in RMIC- Agtr1a-/- mice even though 24 h urine output was lowered (WT: 1724 ± 335 mOsm/Kg H2O vs. RMIC- Agtr1a-/- : 1128 ± 102 mOsm/Kg H2O, P<0.01). In response to Ang II infusion, telemetry systolic blood pressure increased to 148 ± 5 mmHg in WT mice, but it increased only to 129 ± 8 mmHg in RMIC- Agtr1a-/- mice ( P<0.01). Furthermore, Ang II infusion for 2 weeks failed to alter urine osmolality in RMIC- Agtr1a-/- mice (1226 ± 110 mOsm/Kg H2O, n.s.). In conclusion, we demonstrated for the 1st time that AT1a receptors in RMICs of the kidney medulla play a key role in physiologically maintaining basal blood pressure homeostasis and urine concentration, as well as in the development of Ang II-induced hypertension.

R01DK123144, R01DK067299, R01DK102429

This is the full abstract presented at the American Physiology Summit 2023 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.
Intravenous injection of fentanyl in adult awake goats increases arterial blood pressure and reduces heart rate without affecting metabolic rate or temperature
Authors: Forster Hubert , Grams Kirstyn , Neumueller Suzanne , Buiter Nicole , Hilbert Grace , Pan Lawrence , Lewis Stephen , Hodges Matthew
Published: May 2023

At high doses, synthetic opioids are thought to slow heart rate and reduce mean arterial blood pressures in humans and rodents and could create a life-threatening situation. Herein, we report dose-dependent effects of intravenous (IV) injection of fentanyl on systolic (SYS), diastolic (DIA), and mean (MAP) arterial blood pressure, heart rate (HR) metabolic rate and body temperatures in adult female goats (n=7). Variables were measured 30 min before, during and up to 90 min after IV injection of vehicle (saline) or 25, 50, 75, 100, and 125 mcg/kg fentanyl. Baseline averages for SYS, DIA, MAP was 102, 73, 83 mmHg, respectively, and HR was 84 beats/minute (bpm). There were no significant changes in these values over 90 minutes when saline was injected. Between 8 and 10 minutes after fentanyl injection, SYS, DIA, and MAP increased substantially from control by about 40, 25, and 30 mmHg, respectively. These increases did not appear dose independent, but by 90 minutes post-injection SYS, DIA, and MAP decreased toward control at the lowest dose (25 mcg/kg). The fentanyl induced arterial hypertension was partially compensated by a ~15 bpm decrease in heart rate which changed minimally between 10 and 90 minutes after fentanyl injection. The sustained increase in arterial blood pressure indicates a sustained excitatory effect of fentanyl consistent with the excitatory effect of fentanyl on tidal volume and respiratory muscle activity (see additional abstracts from our group). This excitatory effect is not due to changes in metabolic rate and/or body temperature as we found no consistent effect of fentanyl injections on these variables. This excitatory effect of fentanyl appears species-dependent as opioid agonists injected into rats and humans typically induces arterial hypotension. Species dependency of fentanyl may reflect species variation in effects of fentanyl on vagal nerve endings, brainstem control centers, and/or cardiac receptors (J. Car.Pharm, 1985), or alternatively may reflect differences in fentanyl metabolism whereby metabolites may have differential effects on blood pressure among these species.

NIH DA050571

This is the full abstract presented at the American Physiology Summit 2023 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.
Neuronostatin induces gluconeogenic enzyme expression and glucose release in hepatocytes
Authors: Mahmood Ammar , Grote Stephen , Kolar Grant , Samson Willis , Yosten Gina
Published: May 2023

Hepatic glucose production (HGP) is regulated by a complex system of hormones, receptors, signaling mechanisms, glycolytic and gluconeogenic enzymes, and many overlapping transcription factors. The proteins involved in HGP are attractive targets for antidiabetic therapy, and thus it is critical to identify and characterize new targets within the regulation of HGP. We identified a novel peptide, neuronostatin (NST), encoded in the somatostatin preprohormone that exerts its effects in the central nervous system, the heart, and the pancreas. NST is produced in the delta cells of the pancreatic islets and plays an important role in maintaining glucose homeostasis through enhancing glucagon secretion from the α cell and reducing insulin release from the β cell. In male rats, a bolus injection of NST significantly increased blood glucose over 30 minutes after administration. Likewise, the peptide delayed glucose clearance and diminished the insulin response to hyperglycemia in a glucose tolerance test. Our group also identified the orphan GPCR, GPR107, as a cognate receptor for the peptide. GPR107 is expressed in numerous tissues, including the liver. In searching for the role of NST in hepatic physiology, we observed that hepatocellular carcinoma cell line HEPG2 expressed GPR107. Thus, we hypothesized that NST would elicit hepatic glucose production. We found that treatment of HEPG2 cells with NST significantly elevated cFos mRNA expression, indicating that HEPG2 cells respond to the peptide. In addition, NST induced expression of key gluconeogenic enzymes and enhanced glucose release in HepG2 cells. In vivo, antagonism of the glucagon receptor in rats did not attenuate elevated blood glucose levels in response to treatment of NST, supporting a direct, glucagon-independent action of NST on HGP. Thus, our results suggest that NST could play a physiologically relevant role in the liver and that GPR107 could be a potential new target to modulate HGP.

National Institute of Health (NIH)

This is the full abstract presented at the American Physiology Summit 2023 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.
Carotid Body O2 Sensing requires H2S-dependent Persulfidation of Olfactory Receptor 78
Authors: Peng Ying-Jie , Nanduri Jayasri , Wang Ning , Bindokas Vytautas , Fox Aaron , Vignane Thibaut , Filipovic Milos , Prabhakar Nanduri
Published: May 2023

Hydrogen sulfide (H2S) is implicated in O2 sensing by the carotid body(CB) to stimulate breathing response to hypoxia. Present study shows hydrogen sulfide-dependent persulfidation (S-sulfhydration) of olfactory receptor 78 (Olfr78) as an integral component of carotid body O2 sensing. H2S increased cAMP production (index of Olfr78 activation) in HEK-293 cells expressing Olfr78 as measured by cAMP fluorescent biosensor, in a dose-dependent manner with an ED50 of 25μM. H2S as well as hypoxia increased persulfidation in the carotid body glomus cells and these responses were absent in cells Olfr78 as well as CTH (CSE) null mice. MS/MS analysis showed that persulfidation of Cys240 increased in a time-dependent manner with H2S. Alpha fold modelling of Olfr78 showed Cys240 in the interface of the cytosol and the membrane facilitating water accessibility of sulfur atom in cysteine. Substituting Cys240 with alanine blocked Olfr78 activation by H2S as indicated by absence of increased cAMP fluorescence in HEK-293 cells and impaired trafficking of Olfr78 protein to the cell membrane, consistent with the Alpha fold model prediction of Cys240 location near the surface of the Olfr78. Hypoxia and H2S stimulated ex vivo CB sensory activity and elevated intracellular calcium of glomus cells in wild type but not Olfr78 mutants. Intravenous administration of H2S increased efferent phrenic nerve activity in a dose-dependent manner, and the responses were absent in Olfr78 mutants. These results suggest that H2S through redox modification of Cys240 of Olfr78 participates in O2 sensing by the CB to regulate breathing.

Supported by NIH-HLBI P01-HL-44454

This is the full abstract presented at the American Physiology Summit 2023 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.
Loss of Kir5.1 disturbs acid-base homeostasis in Dahl salt-sensitive rats
Authors: Xu Biyang , Staruschenko Alexander
Published: May 2023

Renal basolateral inwardly-rectifying potassium (Kir) channels contribute to the maintenance of the resting membrane potential and potassium homeostasis. Heteromeric Kir4.1/Kir5.1 channels are more sensitive to intracellular acidification than homomeric Kir4.1 channels. Our previous study demonstrated that genetic mutation of Kcnj16 (the gene encodes Kir5.1) causes chronic metabolic acidosis with lower blood pH and bicarbonate levels in Dalh salt-sensitive (SS) rats. Here, we aim to investigate the underlying mechanisms. We hypothesized that loss of Kir5.1 disturbs acid-base homeostasis in SS rats by impairing ammoniagenesis in the proximal tubule and HCO3- reabsorption in the distal convoluted tubule (DCT).12-week-old male SSWT and SSKcnj16-/- rats were separated into two groups (N=5 per group). At the end of the experiment, kidneys were flushed and processed for blood pH and Western blot analysis.Western blot analysis indicated that knock out of Kir5.1 causes lower expression of sodium-coupled neutral amino acid transporter 3 (SNAT3), which may indicate defective ammoniagenesis in the proximal tubule. On the other hand, increased expression of NBCe1 and NHE3 suggests enhanced HCO3- reabsorption and H+ excretion. Additionally, the expression of vacuolar ATPase (V-ATPase), which is a proton pump responsible for controlling the intracellular and extracellular pH of cells, remained the same. In the following experiments, we will further investigate the ammoniagensis in the proximal tubule as well as key bicarbonate transporters in DCT and collecting duct.

Funding sources: National Institute of Health Grants R35 HL135749 (to AS), Department of Veterans Affairs grant I01 BX004024 (to AS).

This is the full abstract presented at the American Physiology Summit 2023 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.
S1928 Phosphorylation Control CaV1.2 Spatial Distribution and Function During Angiotensin II Signaling: Implications for Hypertension
Authors: Flores Tamez Victor , Baudel Miguel , Hong Junyoung , Singhrao Navid , Ramer Victoria , Reddy Gopireddy , Man Kwun Nok Mimi , Hell Johannes , Nieves-Cintron Madeline , Navedo Manuel
Published: May 2023

The L-type calcium channel CaV1.2 (LTCC) is essential for vascular smooth muscle (VSM) contraction and blood pressure control. Increased vascular contractility, blood pressure, and enhanced angiotensin II (angII) signaling are hallmarks of hypertension (HTN). It has been proposed that spatial redistribution of CaV1.2 channels at the sarcolemma of VSM contributes to the potentiation of LTCC function and vascular dysfunction during HTN. However, the mechanisms underlying the spatiotemporal regulation of the CaV1.2 channels during angII signaling and HTN are poorly understood. Here, we hypothesize that CaV1.2 phosphorylation at the S1928 site is a key event mediating increased CaV1.2 channel clustering, which in turn leads to an increase in LTCC activity and vascular reactivity during angII signaling and HTN. We first demonstrated that angII-treated wild-type (WT) mesenteric arteries display increased phosphorylation at the S1928 site. Molecularly, angII redistributed CaV1.2 into larger clusters. This was correlated with elevated VSM whole-cell L-type channel currents, global intracellular Ca2+ and contraction, increased arterial tone ex vivo and in vivo in mesenteric arteries, and altered mesenteric blood flow in arteries from WT mice. These changes were prevented or significantly ameliorated in mesenteric VSM cells and arteries from a knock-in mouse expressing a mutant CaV1.2 in which serine was replaced with alanine at position 1928 (S1928A mouse) and by PKC inhibition. In angII-induced hypertensive mice, increased CaV1.2 cluster size and channel activity, enhanced arterial tone, and mean arterial pressure in WT mice were prevented or significantly reduced in S1928A mice. Altogether, these results suggest a key role for the phosphorylation of vascular CaV1.2 at S1928 in regulating LTCC spatial distribution, activity and vascular function during angII signaling and HTN. Phosphorylation of this single amino acid could be an essential regulatory mechanism that could be exploited for therapeutic intervention.

This work was supported by NIH grants R01HL149127, R01HL121059, and R01HL161872 (to MFN).

This is the full abstract presented at the American Physiology Summit 2023 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.
Oxidation in a respiratory brainstem area of an Alzheimer's rat model
Authors: Schmitz Hailey , Le Andy , Koogler Alicia , Ostrowski Daniela , Ostrowski Tim
Published: May 2023

Alzheimer’s disease (AD) is a progressive neurodegenerative disease affecting more than 50 million individuals worldwide. Sporadic AD comprises 95% of all cases and is most commonly known for its hallmark symptoms of cognitive decline and memory degradation. In addition, respiratory dysfunction is found in up to 80% of AD patients and often manifests as sleep-disordered breathing. In the early stages of AD, increased reactive oxygen species cause widespread oxidative stress, which can damage cellular components and severely impact neuronal activity. While the respiratory dysfunction and oxidative stress is well known, there is little known about the underlying mechanisms and their potential intersection in AD patients. This study used the Streptozotocin (STZ)-AD rat model, which is the only well-established model mimicking sporadic AD with its multifactorial presentations including AD hallmark symptoms and respiratory dysfunction. Two weeks after induction of the STZ-AD rat model (2 mg/kg STZ), we analyzed targets of oxidative stress in a critical respiratory control area in the brainstem, the nucleus Tractus Solitarii (nTS). Immunohistochemistry was used to fluorescently stain brainstem sections in order to analyze for oxidation of lipids (4-hydroxynonenal, 4-HNE), DNA (8-hydroxyguanine, 8-OHG), and protein sulfhydryl groups (dimedone-tagged sulfenic acid). While there was no pronounced lipid peroxidation, the STZ-AD group had significantly increased levels of DNA oxidation when compared to the control (CTL). In addition, sulfhydryl groups, which are present on many cellular proteins, also had a significantly increased baseline oxidation in the STZ-AD group when compared to CTL. Oxidation of these sulfhydryl groups is known to be responsible for altering ion channel function and thus neuronal activity. Reducing agent Dithiothreitol (DTT) was able to revert sulfhydryl oxidation in STZ-AD to its reduced form, while CTL rats did not change from baseline. On the other hand, addition of the oxidizing agent hydrogen peroxide increased sulfhydryl oxidation in CTL, but not in STZ-AD. Overall, our results show that STZ-AD causes increased oxidation throughout a key brainstem area of respiration. This oxidation also affects protein components important for neuronal activity, which could be an underlying cause for the respiratory dysfunction in AD.

Funding sources include the Kirksville College of Osteopathic Medicine Biomedical Sciences Graduate Program and the National Institutes of Health (R15AG065927).

This is the full abstract presented at the American Physiology Summit 2023 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.
Highlighting the role of glial-specific miR-92 on synaptogenesis of developing Drosophila melanogaster
Authors: Moe Simon , McNeill Elizabeth
Published: May 2023

The objective of this study was to investigate the glial specific role of miR-92 in the developing nervous system. micro-RNA (miRNA) have been implicated in many neurological and neurodegenerative disease states. Glial tissue provides a wealth of supporting roles in nervous tissue function, however their ability to mediate nervous system development through epigenetic factors is poorly understood. We predict that miR-92 expression is necessary in glial tissue for both proper development and physiology at the developing larval neuromuscular junction. Using a combination UAS/Gal4 system, highly human conserved miR-92b expression was competitively inhibited in various tissues within the third instar larval nervous system of Drosophila melanogaster. We measured developmental parameters of the nervous tissue, electrophysiological features, and explored potential genetic targets in recapitulating the loss-of-function phenotypes. Amongst the tissues encompassing the neuromuscular junction (NMJ) of larval Drosophila, loss of miR-92b expression in glial tissue recapitulates global loss phenotypes. These NMJ were characterized by fewer glutamate-releasing synaptic boutons and an increased count of underdeveloped ghost boutons. These same flies have a decreased mEJP frequency in abdominal muscles 6/7, but a normal EJP. Inhibition of miR-92b in the subperineurial glia subtype, which function as the blood-brain barrier, can mimic these synaptic phenotypes. Administration of a dextran dye show that the subperineurial glia of the CNS have increased permeability in miR-92b inhibited flies. Target analysis predicted a V-ATPase gene (Vha55) downstream may be driving these phenotypes. Future work will explore Vha55 as a possible candidate driving these neuronal phenotypes. The importance of glial specific miRNA in modifying neurological systems is very promising for both therapeutic markers and potential treatments.

This is the full abstract presented at the American Physiology Summit 2023 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.
Brief angiotensin converting enzyme inhibition early in life delays the onset of albuminuria in sheep born with a solitary functioning kidney
Authors: Denton Kate , McArdle Zoe , Moritz Karen , Schreuder Michiel
Published: May 2023

Children with solitary functioning kidney (SFK) have an increased risk of hypertension and kidney injury from early in life. Hypertrophy and hyperfiltration are compensatory adaptations in the remaining kidney that may contribute to kidney injury over time. Angiotensin-converting enzyme inhibitors (ACEi) have reno-protective and blood pressure (BP) lowering properties. This study examined if brief ACEi early in life in sheep born with a SFK altered compensatory kidney hypertrophy and prevented elevation in BP and albuminuria. SFK was induced by unilateral nephrectomy in male fetal sheep at 100 days gestation (term=150 days; n=19) or sham surgery performed (n=10). Between 4 to 8 weeks, some SFK lambs received enalapril (n=10; 0.5mg/kg/day, once daily, orally) and others received vehicle (water; n=9). At 2, 6 and 20 months kidney volume was assessed using magnetic resonance imaging. At 8, 14 and 20 months, BP, renal functional reserve and albuminuria were examined. In SFK sheep, kidney volume was lower (~20%) than sham at 2 and 6 months but similar at 20 months. ACEi in SFK sheep reduced kidney volume at 2 months (~13%) but not at 6 or 20 months. SFK sheep had higher BP than sham at all ages and ACEi did not prevent the rise in BP. SFK sheep had higher urinary albumin and reduced RFR at all ages compared with sham. ACEi increased RFR and prevented albuminuria at 8 months in sheep with SFK but not at 14 and 20 months. In conclusion, brief and early ACEi in sheep with SFK did not prevent elevations in BP but delayed the onset of kidney injury in the short-term. This was likely associated with a reduction in the level of kidney hypertrophy early in life. Brief postnatal ACEi may delay loss of renal function in children born with one kidney and warrants further investigation.

The Netherlands Organization for Health Research and Development (ZonMW Vidi 016.156.454)

This is the full abstract presented at the American Physiology Summit 2023 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.
Evaluation of gastrocnemius motor evoked potentials induced by trans-spinal magnetic stimulation following tibial nerve crush in rats
Authors: Vinit Stephane , Michel-Flutot Pauline , Jesus Isley , Bonay Marcel , Auré Karine , Lee Kun-Ze , Mansart Arnaud
Published: May 2023

Peripheral nerve injuries induce long-lasting physiological and severe functional impairment due to motor, sensory, and autonomic denervation. Preclinical models allow us to study the process of nerve damage, evaluate the capacity of the peripheral nervous system for spontaneous recovery, and test diagnostic tools to assess the damage and subsequent recovery. Methods: In this study on Sprague-Dawley rats, we: 1) compared the use of two different anesthetics (isoflurane and urethane) for the evaluation of motor evoked potentials (MEPs) induced by trans-spinal magnetic stimulation (TSMS) in gastrocnemius and brachioradialis muscles; 2) monitored the evolution of gastrocnemius MEPs by applying paired-pulse stimulation to evaluate the neuromuscular junction activity; and 3) evaluated the MEP amplitude before and after left tibialis nerve crush (up to 7 days post-injury under isoflurane anesthesia). The results showed that muscle MEPs had higher amplitudes under isoflurane anesthesia as compared with urethane anesthesia in the rats, demonstrating higher motoneuronal excitability under isoflurane anesthesia evaluated by TSMS. Following tibial nerve crush, a significant reduction in gastrocnemius MEP amplitude was observed on the injured side, mainly due to axonal damage from the initial crush. No spontaneous recovery of MEP amplitude in gastrocnemius muscles was observed up to 7 days post-crush; even a nerve section did not induce any variation in residual MEP amplitude, suggesting that the initial crush effectively severed axonal fibers. These observations were confirmed histologically by a drastic reduction in the remaining myelinated fibers in the crushed tibial nerve. These data demonstrate that TSMS can be reliably used to noninvasively evaluate peripheral nerve function in rats. This method could therefore readily be applied to evaluate nerve conductance in the clinical environment.

This research was funded by the Chancellerie des Universités de Paris (Legs Poix) (SV, MB), the Fondation de France (SV), the Fondation Médisite (SV), INSERM (MB, SV, AM), Université de Versailles Saint-Quentin-en-Yvelines (SV, AM) and Ministry of Science and Technology 109-2636-B-110-001 (KZL).

This is the full abstract presented at the American Physiology Summit 2023 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.
Hemodynamic response to different contractile speeds of resistance exercise in adults with sarcopenic obesity
Authors: Hsu Kuo-Jen , Huang Sheng-Yun , Chen Chiao-Nan
Published: May 2023

This study aimed to compare the effects of high-speed and low-speed resistance exercise on hemodynamics in adults with sarcopenic obesity. We hypothesized that high-speed resistance exercise induces greater/longer cardiovascular stress than low-speed resistance exercise. Forty-five individuals with sarcopenic obesity (64.0±6.0 years) were randomized to the low-speed resistance exercise group (LSRE; n=24) and the high-speed resistance exercise group (HSRE; n=21). All participants performed one-session of resistance exercises [squatting, chest press, and upright row; 3 sets of 10 repetitions at 60% of 1 repeated maximum]. Participants in the LSRE group performed the exercises with a 4:4 second concentric-eccentric contraction cycle controlled by a metronome while participants in the HSRE group performed the exercise with a 1:4 second concentric-eccentric contraction cycle. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and arterial stiffness (brachial-ankle pulse wave velocity; baPWV) were determined before exercise (resting), immediately after exercise (P0), 15-min after exercise (P15), and 30-min after exercise (P30). Two-way repeated measure analysis of variance was used to examine the effect of different contractile speeds of resistance exercise on outcome variables. The significant level was set at 0.05. We found that the HR at P0 was higher than the resting values for both groups, with 10.9 bpm and 14.0 bpm of increases for the LSRE group and HSRE group, respectively. HR was back to the resting level at P15 in the LSRE group; however, HR was back to the resting level until P30 in the HSRE group. For both groups, SBP was significantly higher at P0 compared to resting (12.5 mmHg of increase for the LSRE group and 11.9 mmHg of increase for the HSRE group) and back to the resting level at P15. PWV at P0 was higher than the resting and back to the resting level at P15 in the LSRE group. PWV levels did not change with exercise in the HSRE group (p>0.05). DBP did not change significantly with exercise in both groups (p>0.05). In conclusion, the influence of HSRE on HR is longer than that of LSRE. LSRE, but not HSRE, results in transient changes in arterial stiffness in adults with sarcopenic obesity.

This study was supported by the Ministry of Science and Technology, Taiwan [grant numbers: MOST-109-2314-B-010 -036 -MY3 (Chen, C.N.)].

This is the full abstract presented at the American Physiology Summit 2023 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.