bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypoxemia in individuals with mild-to-moderate obesity at simulated altitude: implications for an exaggerated ventilatory response
Authors: Balmain Bryce , Ri-Li Ge , Levine Benjamin , Babb Tony
Published: May 2023

Introduction: Individuals with obesity are more hypoxemic (lower PaO2) relative to those without obesity. Rapid ascent to high altitude also causes hypoxemia. However, the magnitude of hypoxemia in individuals with obesity at high altitude is unknown but could be more severe compared with those without obesity due to the additive effects of obesity- and altitude-related causes of hypoxemia. To test this hypothesis, we compared PaO2 in individuals with vs. without obesity at a simulated altitude of 12,000ft. Methods: 19 younger otherwise healthy individuals were studied for 24 hours in a hypobaric environmental chamber: 10 without obesity (age: 35±7yr; BMI: 25.0±3.8 kg/m2) and 9 with mild-to-moderate obesity (age: 35±6yr; BMI: 37.3±4.2kg/m2). PaO2 (arterial puncture), ventilation (V̇E, pneumotachograph), and self-reported symptoms of acute mountain sickness (AMS, Lake Louise score) were measured at sea level (Pb: ~760mmHg) and at a simulated altitude of 12,000ft (Pb: ~483mmHg). Results: PaO2 was lower (p<0.001) in those with (84.5±8.0mmHg) vs. without obesity (96.1±6.8 mmHg) at sea level; however, PaO2 was not significantly different between groups at 12,000ft (with obesity: 47.8±6.0mmHg; without obesity: 51.2±5.6mmHg, p=0.265). While V̇E was similar between groups at sea level (with obesity: 14.8±5.0L/min; without obesity: 11.3±3.3L/min, p=0.114), V̇E was higher (p=0.029) in those with (58.3±8.4L/min) vs. without (47.2±9.0L/min) obesity at 12,000ft, which may reflect a greater hypoxic ventilatory response in those with obesity relative to those without obesity. Lastly, seven individuals with obesity and four individuals without obesity had AMS scores of ≥4 at 12,000ft. Conclusion: We demonstrated that the magnitude of hypoxemia at high altitude was similar between those with and without obesity, but this was at the expense of an exaggerated ventilatory response in those with obesity. While perhaps an appropriate compensatory ventilatory response to a hypoxic stimulus, this finding could have implications for younger healthy individuals with mild-to-moderate obesity traveling to higher elevations where they could be more likely to develop severe dyspnea and/or AMS. Further investigation of the degree of hypoxemia at high altitude is required in older individuals with a greater magnitude of obesity.

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.
What is the role of ATP in the hypertensive carotid body?
Authors: Felippe Igor , Pen Dylan , Bose Aabharika , Moraes Davi , Ponnampalam Anna , Paton Julian
Published: May 2023

ATP acting on P2X2/3 receptors within carotid bodies (CBs) underpins chemoreflex hyperreflexia and hypertonicity of sympathetic activity in Spontaneously Hypertensive rats (SHR). As the exact mechanisms remain elusive, we hypothesized either a greater release and/or decreased breakdown of ATP in CBs of SHR versus Wistar rats, and that high concentrations of exogenous ATP in the CB of normotensive rats would produce the sensitised motor responses portrayed by SHRs. Three experiments were performed to investigate the generation, breakdown and physiological responses of ATP in the CB: First, we sought to quantify the amount of ATP released from CBs of male Wistar and SHRs (N=10 for each strain; 4-5 weeks old) using an in vitro colorimetric technique; second, in both strains (Wistar, N=10; SHR, N=12), we used digital droplet polymerase chain reaction (ddPCR) for quantitative analysis of gene expression of six enzymes, which are all involved with the extracellular metabolism of ATP (Enpp1-3, Entpd 2-3, and Nt5e); we also quantified the levels of gene expression for tyrosine hydroxylase (TH) and Panx-1 channel, which are markers for CB type I (or glomus cells) and type-II cells, respectively. Third, we used the working heart-brainstem preparation (WHBP) for analysis of the CB chemoreflex responses evoked by ATP stimulation in Wistar rats (N= 25, 60-80g). Stimulation of CBs was carried out with local intra-arterial injection of potassium cyanide (KCN 20-100 μL, 0.04%; i.a.), and direct intra-CB injection of ATP (10-100 μL, 50 μM - 5 mM) or α, β-methylene ATP (10 μM, 450 μM, and 5mM).Although no rat strain differences in Enpp1 and Entpd2-3 were detected, Enpp2-3 and Nt5e expression were increased in SHR (p<0.05) versus Wistar rats suggesting greater breakdown of ATP in SHR CBs. However, ATP released from the CB at baseline and with KCN stimulation was two-fold greater in SHR (P<0.05). KCN stimulation of the CB, evoked hyperpnoea, bradycardia and sympathoexcitation in Wistar rats, whereas ATP produced hypopnoea/apnoea, repetitive burst discharge of post-inspiratory activity and elevations in both abdominal motor activity and SNA. We found that the ATP-induced hyponoea/apnoea was prevented by ipsilateral nodosectomy suggesting activation of non-CB afferent/s. Microinjecting either ATP or α, β-methylene ATP directly into the CB produced hyperpnoea and sympathoexcitation. Despite upregulation of some ATP degrading enzymes in the SHR, CB release of ATP is higher in this strain and produces activation of respiratory and sympathetic systems.

Health Research Council of New Zealand

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.
Effect of Dohongsamul-tang on Cardiac Function in Chronic Myocardial Infarction Rats
Authors: Jang Youn Jae , Hong Mi Hyeon , Yang Sun Ryo , Lee Ho Sub , Kang Dae Gill
Published: May 2023

Myocardial infarction (MI) is a frequent and severe manifestation of ischemic heart disease. We investigated the changes of protein in chronic MI which was occurred with long-term ischemia, without reperfusion. Guaruhaebaekbaekju-tang(瓜蔞薤白白酒湯, GHT) is an established traditional Chinese medicine that is widely used for the treatment of cardiac function, although its mechanisms remain unclear. GHT (100 or 200 mg/kg/day) was administered to rats immediately after coronary artery ligation for 8 weeks. After being sacrificed, the effect of GHT on cardiac fibrosis was confirmed by cardiac function and histological studies. As a result, the biomarker for detecting MI, lactate dehydrogenase (LDH), creatine kinase myocardial band (CK-MB) and Creatine Phosphokinase (CPK) enzymes, were significantly decreased by GHT. Heart function was evaluated by cardiac ultrasound to determine the effect of GHT on left ventricular dysfunction. MI group have decreased EF (Ejection fraction) as well as FS (Fractional shortening), compared to HT group. Additionally, left-ventricular (LV) dysfunction and dilatation were attenuated in the GHT group compared with MI group. In addition, protein expression levels the effect of GRT on cardiac fibrosis was confirmed by reducing the expression of transforming growth factor β (TGF-β) and collagen 1. This is thought to appear through inhibition of the TGF-β/p-Smad 2 pathway. Additionally, GHT reduced the Masson's trichrome and picrosirius red staining intensity in left ventricle of the MI group. Therefore, these findings suggest tha GHT has protective effects via inhibition of TGF-β/p-Smad 2 pathway, which is associated with improvement of myocardial fibrosis in rats with MI. These results suggest that GHT has a protective effect on heart failure by alleviating cardiac hypertrophy, myocardial fibrosis, cardiac dysfunction caused in MI model.

This study was supported by a National Research Foundation of Korea (NRF) Grant funded by the Korean government (MSIP) (2017R1A5A2015805) (2021R1A2C1010859).

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.
Investigating respiratory simplification caused by prenatal RAGE upregulation
Authors: Clarke Derek , Curtis Katrina , Wendt Ryan , Stapley Brendan , Clark Evan , Campbell Kennedy , Black Joe , Hill Nate , Arroyo Juan , Reynolds Paul
Published: May 2023

Receptors for advanced glycation end-products (RAGE) are multi-ligand cell surface receptors of the immunoglobulin superfamily predominantly expressed by lung epithelium. Previous experiments showed that RAGE upregulation throughout pregnancy caused significant fetal lung hypoplasia via elevated apoptosis and misregulation of the transcription factors thyroid transcription factor 1 (TTF1) and forkhead box protein A2 (Fox-A2). Our current research focused on characterizing the contributors to these abnormalities. We confirmed poor development of murine lungs through a time course of RAGE upregulation from conception to sacrifice on embryonic day (E)15.5, E16.5, E17.5, E18.5, and specific upregulation from E15.5 to E18.5 only. H&E staining confirmed significant simplification. We hypothesized that this malformation was in part due to aberrant levels of inflammation and apoptosis. Blotting revealed significantly increased levels of phosphorylated AKT and ERK1/2 in RAGE TG pups which cause NF-κB mediated transcription of inflammatory genes. Due to potential roles for these signaling intermediates, we sought to assess RAGE-mediated impact on mitochondrial efficiency. Oxidative phosphorylation was assessed in lungs from RAGE TG pups and controls by measuring oxygen consumption per unit mass when lungs were exposed to the substrates malate, glutamate, ADP, succinate, and FCCP which activate sequential components of the electron transport chain. We discovered significantly increased levels of oxidative phosphorylation in transgenic pups compared to controls. Levels of ATP and reactive oxidative species (ROS) in relation to altered oxidative phosphorylation and inflammation provided additional mechanistic clarity. These results support the importance of proper RAGE regulation in the development of lung tissue and elucidate mechanisms possibly causing such damage.

This work was supported by funding from the National Institutes of Health (NIH 1R15-HL152257, PRR and JAA).

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.
Reciprocal Regulation of Na/K-ATPase and Sodium Glucose Co-Transporter 2
Authors: Gao Yingnyu , Correa Pessoa Marco Tulio , Liu Jiang , Pierre Sandrine , Tian Jiang
Published: May 2023

Sodium Glucose Co-Transporter 2 (SGLT2) is the major driving force for glucose reabsorption and inhibition of SGLT2 improves renal and cardiac function in patients with chronic kidney disease (CKD). Since SGLT2 uses the sodium gradient established by Na/K-ATPase (NKA) for glucose reabsorption, we hypothesize that there is link between SGLT2 and NKA in regulation of renal and cardiac functions. To demonstrate this hypothesis, we measured the SGLT2 expression level in LLC-PK1 cells (a porcine proximal tubule cell line), PY-17 cells (a cell line derived from LLC-PK1 cells with NKA α1 knockdown), and AAC-19 cells (a cell line that re-introduce a rat NKA α1 into the PY17 cells). The RT-PCR result showed that reduction of NKA in PY17 causes significant increase in SGLT2 expression (about 1.7-fold change compared to that in LLC-PK1 cells), while reintroduction of NAK in AAC-19 cells brought down the SGLT2 expression level that comparable to LLC-PK1 cells. Reciprocally, we found that inhibition of SGLT2 blocked NKA related signaling pathway. Specifically, treatment of LLC-PK1 cells with ouabain at 10 or 100 nM induced Src activation while pretreatment of the cells by 1 μM EMP (a specific SGLT2 inhibitor) for 24h blocked ouabain-induced Src activation. Our previous work has demonstrated that the plasmalemmal NKA/Src complex serves a scaffolding and signaling function beyond its well-known ion pumping role and blocking NKA/Src signaling attenuates cardiac hypertrophy and improves heart function in animal model of CKD. Based on these findings, we demonstrated a functional link between SGLT2 and NKA and postulate that the renal and cardiovascular benefit of SGLT2 inhibition may reside within their capacity for regulation of NKA signaling, which need to be further validated in animal models.

Marshall Start up Funding to Jiang Tian, NIH R15HL164682-01 to Jiang Liu and Jiang Tian, NIH R01 DK129937 to Sandrine Pierre and Jiang Liu.

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.
Mitochondrial Rieske iron-sulfur protein is a crucial molecule in COPD-associated pulmonary hypertension
Authors: Truong Lillian , Zheng Yun-Min , Wang Yong-Xiao
Published: May 2023

Pulmonary hypertension (PH) often occurs in chronic obstructive pulmonary disease (COPD) and is the major cause of death in COPD patients. Molecular mechanisms for PH in COPD remain poorly understood, and clinical treatments are neither specific nor effective. Cigarette and e-cigarette smoking (CS) account for up to 90% of COPD cases, in which nicotine is the major active component and causes COPD-like cellular responses; moreover, hypoxia is a known key factor in the development of PH. In this study, we aim to develop a PH in COPD animal model and determine the underlying molecular mechanisms. Our findings revealed that co-exposure of nicotine (or CS) and hypoxia synergistically elevated PH (i.e., right ventricular pressure and weight) compared to nicotine, CS, or hypoxia alone. We also found that mitochondrial reactive oxygen species ([ROS]m), assessed using mitochondrial-specific ROS indicator MitoSOX, was significantly increased in pulmonary artery smooth muscle cells (PASMCs) from CS patients with COPD compared to normal PASMCs from non-CS patients. The increased [ROS]m was blocked by lentiviral short hairpin RNA (shRNA)-mediated knockdown of Rieske iron-sulfur protein (RISP) in mitochondrial complex III. More importantly, SMC-specific RISP gene knockout blocked nicotine/hypoxia exposure-induced PA remodeling and hypertension, whereas SMC-specific RISP overexpression exacerbated PH in mice. We further discovered that RISP regulated DNA damage following nicotine/hypoxia co-exposure via ataxia telangiectasia-mutated (ATM) signaling. RISP also mediated nuclear factor (NF)-κB inflammatory signaling. Together, our studies for the first time demonstrate that nicotine/hypoxia co-exposure leads to RISP-dependent [ROS]m, ATM-mediated DNA damage-dependent NF-κB-associated inflammation, PA vasoremodeling and PH in COPD in a sex-dependent manner. Moreover, RISP, ATM, and NF-κB may serve as novel and effective molecular targets in treating COPD and its associated PH.

NIH R01 HL122865, NIH R03AG070784, and NIH R01 HL108232

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.
Aerobic exercise training improves left ventricular chamber compliance in Göttingen minipigs
Authors: Duncker Dirk , Heinonen Ilkka , van Drie Ruben , Zandbergen Lotte , van der Velden Jolanda , Merkus Daphne , Sorop Oana
Published: May 2023

Introduction: Exercise training is known to improve left ventricular (LV) function, but the mechanisms remain incompletely understood. Here we investigated the structural and functional adaptations in the LV in response to 2-months of aerobic exercise training in Göttingen minipigs. Methods: Adult male Göttingen minipigs were randomized to an aerobic exercise training regimen of running on a treadmill 3 times per week (N=8, EX) or sedentary housing (N=8, untrained, UT). Structural, functional and molecular measurements were performed in the LV of pigs from both groups at the end of the 2-months period. Results: EX did not affect body weight (35±1 kg vs 37±2 kg EX vs UT) but improved endurance running capacity (75±6 min vs 38±4 min until exhaustion in EX vs UT, P<0.05 by t-test) at the end of the 2-month period, which was associated with enhanced endothelium-dependent vasodilation to bradykinin of small arteries isolated from skeletal small arteries (AUC: 438±46 in EX vs 292±37 in UT, P <0.05 by t-test). EX had no significant effect on LV systolic function (data not shown), but resulted in an increase in LV end-diastolic compliance as the slope of the end-diastolic pressure-volume relationship was lower in EX vs UT ( P<0.05 by 2-way ANOVA). This increase in LV chamber compliance was not due to changes in LV structure as the LV weight to body weight ratio (3.10±0.17 vs 3.15±0.10 g/kg), cardiomyocyte cross-sectional area (100±10 vs 104±8 mm2) and collagen content (7.6±0.3 vs 6.6±0.4% myocardium area) were not significantly different between UT and EX. In contrast, single LV cardiomyocyte stiffness was reduced in EX compared to UT ( P<0.05 by 2-way ANOVA), likely caused by a shift in titin isoform towards the more compliant N2BA isoform (N2BA/N2B ratio: 1.22±0.03 vs 0.95±0.05; P<0.05 by t-test). Conclusion: Two months of aerobic exercise training 3 times per week increased LV diastolic chamber compliance, which was mediated, at least in part, through a titin isoform shift and a decreased myocyte stiffness, in the absence of LV structural changes.

Dutch CardioVascular Alliance: An initiative with support of the Dutch Heart Foundation (Grants 2017B018 ARENA-PRIME and 2020B008 RECONNEXT)

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.
Activation of urotensin II receptor induces podocyte injury via TRPC6-mediated endoplasmic reticulum stress
Authors: Kanthakumar Praghalathan , Adebiyi Adebowale
Published: May 2023

Podocytes are essential for the glomerular filtration barrier in the kidney. Podocyte injury can lead to chronic kidney disease (CKD). One of the leading causes of CKD is diabetes mellitus. Plasma urotensin II (UII) levels and renal tissue expression of UII and its receptor UT are increased in diabetic kidney disease. However, the role of the UII system in podocyte derangement is unexplored. In this study, we report for the first time that UT is expressed in mouse podocytes in culture and glomerular explants. UII increased intracellular Ca2+ levels ([Ca2+]i) in cultured podocytes bathed in zero Ca2+ solution, an effect abolished by ER Ca2+ ATPase inhibitor thapsigargin. Subsequent restoration of extracellular Ca2+ increased [Ca2+]i despite the blockade of voltage-gated Ca2+ channels, suggesting a store-operated Ca2+ entry (SOCE) mechanism activated by UII. UII precipitated ER injury in cultured podocytes, as indicated by an increase in ER stress marker GRP78. GSK1562590, a UT antagonist, reversed this effect. Next, we tested two putative SOCE pathways previously reported in podocytes, i.e., TRPC5 and TRPC6 ion channels. Activation of UT by UII significantly increased TRPC6 but not TRPC5 mRNA in cultured podocytes. Whole-cell patch-clamp recordings of cultured podocytes showed that UII stimulates cation currents, which SAR 7443, a selective TRPC6 blocker, attenuated. By contrast, UII-induced cation currents were not sensitive to AC 1903, a selective TRPC5 blocker. In line with patch-clamp experiments, Ca2+ imaging studies showed that TRPC6 blockade with SAR 7443 mitigated UII-induced increase in [Ca2+]i. Super-resolution microscopy of cultured podocytes revealed that activation of UT caused a significant increase in the fragmentation of actin filaments, as indicated by a decrease in the percentage of long filaments and an increase in short filaments. Together these findings suggest that: (1) UT is expressed in native and cultured podocytes. (2) UT activation in podocytes triggers ER Ca2+ release, activates SOCE pathways and leads to the development of ER stress. (3) TRPC6 is a probable SOCE pathway stimulated by UII in podocytes. (4) UII might cause podocyte injury by disrupting the actin cytoskeleton.

Dr. Adebiyi: NIH R01 HL151735 and R01 DK127625; APS 2020 John F. Perkins, Jr. Research Career Enhancement Award. Dr. Kanthakumar: American Heart Association Postdoctoral Fellowship (830462).

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.
Estrogen regulates myogenic tone in hippocampal arterioles by enhanced basal release of nitric oxide and endothelial SK channel activity
Authors: Dabertrand Fabrice
Published: May 2023

Arteries and arterioles exhibit myogenic tone, a partially constricted state that allows further constriction or dilation in response to moment-to-moment fluctuations in blood pressure. The vascular endothelium that lines the internal surface of all blood vessels controls a wide variety of essential functions, including the contractility of the adjacent smooth muscle cells by providing a tonic vasodilatory influence. Studies conducted on large (pial) arteries on the surface of the brain have shown that estrogen lowers myogenic tone in female mice by enhancing nitric oxide (NO) release from the endothelium, however, whether this difference extends to the intracerebral microcirculation remains ambiguous. The existing incomplete picture of sex differences in cerebrovascular physiology combined with a deficiency in treatments that fully restore cognitive function after cerebrovascular accidents places heavy emphasis on the necessity to investigate myogenic tone regulation in the microcirculation from both male and female mice. We hypothesized that sex-linked hormone regulation of myogenic tone extends its influence to the microcirculation level, and sought to characterize it in isolated arterioles from the hippocampus, a major cognitive brain area. Using diameter measurements in pressure myography experiments, we measured lower myogenic tone responses in hippocampal arterioles from female than male mice at physiologically relevant pressures. By using a combined surgical and pharmacological approach, we found myogenic tone in ovarectomized (OVX) female mice matches that of males, as well as in endothelium-denuded arterioles. Interestingly, eNOS inhibition induced a larger constriction in female arterioles but only partially abolished the difference in tone. We identified that the remnant difference was mediated by a higher activity of the small-conductance Ca2+-sensitive K+ (SK) channels. Collectively, these data indicate that eNOS and SK channels exert greater vasodilatory influence over myogenic tone in female mice at physiological pressures.

R01HL136636; RF1NS129022

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.
DNA methylation inhibitor regulates guanylyl cyclase/natriuretic peptide receptor-A gene expression via 5'-untranslated region in mesangial and smooth muscle cells
Authors: Kumar Prerna , Neerukonda Smitha , Bloodworth Meaghan , N. Peters Whitney , N. Pandey Kailash
Published: May 2023

Guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) is activated by cardiac hormones atrial and brain natriuretic peptides (ANP, BNP) and produces intracellular second messenger cGMP. The physiological actions of ANP/NPRA/cGMP signaling cascade largely include diuresis, natriuresis, vasorelaxation, and organ protection, which maintains blood pressure and opposed renal, cardiac, and vascular injury and remodeling. However, the mechanisms that contribute to the activation of Npr1 (coding for GC-A/NPRA) expression is not well understood. The present study was aimed at understanding the epigenetic mechanisms of DNA methyltransferase (DNMT) inhibitor, 5-Azacytidine (5-Aza)-mediated Npr1 gene transcription. The studies were carried out in mouse mesangial cells (MMCs) and rat thoracic aortic smooth muscle (RTASM) cells, cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum and ITS (insulin, transferrin, and sodium selenite) and treated with 5-Aza for 24 h. Western blot analysis showed that 5-Aza enhanced NPRA protein levels by 5-fold and 7-fold in a dose-dependent manner in MMCs and RTASM cells, respectively, and greatly stimulated intracellular accumulation of cGMP in ANP-treated cells. Treatment with 5-Aza attenuated DNMT activity and repressed DNMT1 protein levels in cells. The MethPrimer search result showed the presence of three cytosine-phosphate-guanine (CpG) islands in the Npr1 full length promoter and 5'-untranslated region (UTR), namely island 1 (-886 to -752, 134 bp), island 2 (-310 to -158, 152 bp), and island 3 (-154 to +310, 464 bp) from the transcription start site. Addition of 5'-UTR encompassing +56 to +359 bp region to the Npr1 promoter constructs, (-1982/+55) and proximal promoter (-356/+55), was inhibitory to Npr1 transcriptional activity, independent of the cell type. Furthermore, treatment with 5-Aza distinctly induced Npr1 promoter activity of the construct -356/5'-UTR by 10-fold in MMCs suggesting that the repressive effect of DNA methylation on Npr1 gene transcription might be via 5'-UTR. The results demonstrate that 5-Aza acts as a potent inducer of Npr1 expression and signaling and provides new insights in the epigenetic control of Npr1, an important player in the control of hypertension and cardiorenal axis.

Supported by the NIH grants (HL062147 and DK133833).

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.
Actin Polymerization Increases in The Ductus Arteriosus During The Developmental Transition to Lung Ventilation
Authors: Werra Hakeem , Dzialowski Edward , Rippamonti Jessica
Published: May 2023

The Ductus Arteriosus (DA) is an embryonic blood vessel that connects the descending aorta and the pulmonary artery during fetal development. It functions as a right-to-left shunt diverting blood away from the nonventilated lungs and to the descending aorta. The DA serves a comparable physiological role in all terrestrial vertebrates during their embryonic development. Following birth or hatching, the DA constricts in response to increase in arterial oxygen tension brought on by initiation of lung ventilation, and it closes to stop the embryonic shunt. We examined the extent of actin polymerization in the DA during the transition to lung ventilation at hatching in the chicken. We isolated and fixed DA from developing chickens on embryonic days 15 and 19 (ED15 and ED19), during internal pipping (IP) and external pipping (EP), and in hatchlings. Vessel sections were fluorescently stained with Alexa Fluor 488 (DNase 1) for G-actin, Alexa Fluor 568 (Phalloidin) for F-actin, and TOPRO-3 for nuclei staining. Fluorescence microscopy was used to image the sections and quantify F-actin to G-actin levels within the DA for each age. From the images, F-actin to G-actin ratios were determined. Embryonic stages exhibited strong G-actin staining with minimal F-actin staining. During hatching, F-actin staining became more pronounced, exhibiting clearer fiber patterns in the tunica media. F-actin to G-actin ratios increased significantly in the DA from ED15 through hatching, suggesting actin polymerization in the DA increased as the chickens progressed from day 19 to external pipping (EP). These results suggest that increases in actin polymerization play a role in ductus arteriosus constriction at hatching in chickens.

This research is funded by grant R15HL14887 from the NIH-NHLBI.

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.
Role of TRPV4 in superficial cervical lymphatic vessel contractile function
Authors: Polk Felipe , Pires Paulo
Published: May 2023

Collecting cervical lymphatic vessels pump lymph and macromolecules drained by brain meningeal lymphatics to the cervical lymph nodes. Collecting lymphatics vessels rely on spontaneous contractions to propel lymph against a pressure gradient to re-enter the venous circulation. The calcium permeable transient receptor potential vanilloid 4 channel (TRPV4) has been shown to mediate intraluminal pressure-induced vasodilatory responses in small arteries. However, whether TRPV4 participates in pressure-dependent contractile responses in lymphatic vessels remains unclear. We hypothesized that increases in intraluminal pressure leads to TRPV4-dependent increases in lymphatic pump function. TRPV4 expression was assessed by PCR assay in isolated superficial cervical lymphatic vessels (sCLV). Using pressure myography, contractile function of isolated sCLV was assessed in the presence of TRPV4 antagonist (1μM HC-067047) or vehicle (DMSO). To quantify lymphatic pump function (FPF), the product of contractile frequency (FREQ) and ejection fraction (EF) was analyzed using repeated end-diastolic and end-systolic diameter measurements. We detected TRPV4 mRNA expression following PCR amplification from isolated sCLV tissue of young C57Bl/6J mice (4-6 months). In pressurized sCLV, TRPV4 activation with GSK 1016790A (10 nM) abolished spontaneous rhythm contractions by causing a sustained constriction, consequently leading to a significant decrease in lymphatic pump function (FPF: 4.67±0.58 vs 1.17±0.86, Vehicle vs GSK 1016790A, n=8, p<0.05) at baseline intraluminal pressure (3 cm H2O). TRPV4 antagonism (HC-067047, 1 μM) did not affect basal sCLV contractility (FPF: 5.15±0.6 vs 3.44±0.43, Vehicle vs HC 067047, n=5, p>0.05). Further, when HC-067047 was applied to the bath and intraluminal pressure was maintained at 2 cm H2O, no changes were observed in FREQ (9.3±1.4 vs 11.7±1.3 Hz, Vehicle vs. HC-067047, n=7 / 9, p>0.05), EF (0.253±0.040 vs 0.268±0.037, Vehicle vs. HC-067047, n=7 / 9, p>0.05), or contractile amplitude (22.54±6.769 vs 26.76±3.028 μm, Vehicle vs HC-067047, n=7 / 9, p>0.05). Similarly, TRPV4 blockade did not alter FREQ (12.4±1.3 vs 14.3±1.4 Hz, Vehicle vs. HC-067047, n=7 / 9, p>0.05), EF (0.090±0.024 vs 0.092±0.019, Vehicle vs HC-067047) or contractile amplitude (7.98±2.814 vehicle vs 9.27±1.88 μm, Vehicle vs HC-067047) at the higher intraluminal pressure of 7 cm H2O. Collectively, these data suggest that TRPV4 channels are not involved in pressure-dependent contractile responses of sCLV in mice, despite inducing a robust constriction upon pharmacological activation.

National Institutes of Health (R01 AG073230) and the Alzheimer's Association (AARGD-21-850835)

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.
Adolescent is more susceptible to tuft cell hyperplasia with increased mast cell infiltration and enhanced FFA2/5-HT mediated anion secretion in mouse duodenum and jejunum
Authors: Ito Suguru , Akiba Yasutada , Kaunitz Jonathan
Published: May 2023

Though one of the primary functions of intestinal tuft cells us the sensing of the luminal content, the contribution of tuft cells to epithelial secretion has not been previously studied. We have found that in adult mice, induced tuft cell hyperplasia enhances the secretory responses to luminal short-chain fatty acids (SCFA) due to increased jejunal cholinergic signaling, whereas mast cell-mediated serotonergic signaling is predominant in the duodenum. Since mast cell density is higher in children with functional dyspepsia (FD) than in adults, we hypothesized that mast cell density and 5-HT signals may be increased by tuft cell hyperplasia more in adolescent (7-week-old; 7 wk) than in adult mice (15-week-old; 15 wk). Tuft cell hyperplasia was induced by oral sodium succinate (NaSuc, 100 mM) in the drinking water for 7 days in 7 wk or 15 wk mice, then assessed at 8 or 16 wk (8 w/16 w). Using Ussing chambers mounted with muscle-stripped mouse proximal duodenum or jejunum, the succinate receptor agonist cis-epoxy succinic acid (cESA, 1-30 mM) was applied to the mucosal bath whereas the selective free fatty acid receptor 2 (FFA2) agonist 4-CMTB (10 μM) was added to the serosal bath. Tuft cell doublecortin-like kinase 1 (DCLK1), mast cell protease 1 (MCPT1), and tryptophan hydroxylase 1 (TPH1/5-HT), used to measure tuft cell, mast cell, and enterochromaffin (EC) cell density, respectively, were assessed by real-time PCR and immunostaining.NaSuc treatment significantly increased the number of DCLK1-positive tuft cells and MCPT1-positive mast cells with no change in EC cell density in the duodenal and jejunal villi; density was higher at 8 w than at 16 w. mRNA expression of DCLK1 was increased in the duodenal and jejunal mucosa at both ages, whereas MCPT1, TPH1 and FFA2 were increased in both mucosæ at 8 w, but choline acetyltransferase (ChAT) was increased in the jejunal mucosa at 16 w. Luminal cESA increased atropine-inhibitable Isc in the jejunal mucosa, whereas 4-CMTB increased 5-HT3/5-HT4-mediated duodenal Isc. The Isc response to cESA in jejunum was enhanced at 16 w, whereas the response to 4-CMTB was enhanced at 8 w.These results suggest that NaSuc differentially enhances secretory responses, with jejunal serotonergic signals predominating at 8 w and cholinergic signals at 16 w. These data suggest that younger mice are more susceptible to tuft cell hyperplasia with resultant enhanced 5-HT signals with mast cell infiltration, consistent with clinical data.

Supported by VA Merit Review

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.
Crosstalk between hepatic uridine biosynthesis and ER stress in obesity and type 2 diabetes
Authors: Deng Yingfeng , Fu Ling , Kebrom Leah , Jang Chelsea , Kalkum Markus , Scherer Philipp
Published: May 2023

Pathologically elevated hepatic glucose production is one of the most important etiologies of type 2 diabetes mellitus (T2DM). The underlying molecular mechanism remains ill-defined. Uridine is the most abundant nucleoside in circulation. Blood uridine level is stably maintained in mammals since excess uridine promotes spontaneous tumorigenesis. We recently showed that adipose tissue is a novel site to supply uridine in addition to the liver (Deng Y, et al., Science, 2017). Obesity, a condition with increased fat mass, is therefore associated with a higher supply of uridine from adipose tissue. To maintain homeostatic circulating uridine level in obesity, de novo uridine synthesis in hepatocytes will need to be reduced. Consistent with this notion, we found that Cad, the rate-limiting enzyme for uridine synthesis, is decreased in the liver by HFD feeding. Aspartate (Asp) is a key substrate for hepatic uridine synthesis. Importantly, Asp is also an essential substrate for hepatic glucose production. Therefore, the reduction of uridine biosynthesis in obesity (more Asp is available) may increase hepatic glucose production. Conversely, upregulation of uridine synthesis may suppress glucose output and type 2 diabetes. Based on this rationale, we hypothesize that hepatic uridine synthesis and glucose production are reciprocally regulated and reduced liver uridine synthesis is a main cause for elevated hepatic glucose production in obesity and T2DM. To test this hypothesis, we engineered a mouse model in which Cad is deleted in hepatocytes. Preliminary data showed that liver gluconeogenetic pathway was upregulated by Cad deletion. Consistently, PALA, an inhibitor of uridine synthesis, caused an acute elevation in blood glucose (hyperglycemia), again supporting a role of uridine synthesis in hepatic glycemic control. We further showed that XBP1s, the most conserved branch of ER stress and the UPR (unfolded protein response), is a key regulator of de novo uridine synthesis via upregulation of Cad expression. Hepatocyte overexpression of XBP1s leads to hypoglycemia and lipolysis. Taken together, our study uncovers a novel link of uridine homeostasis and hepatic glycemic control through cellular response to ER stress, which provides potential targets for therapeutic design against obesity and T2D.

Supported by the American Diabetes Association and NIDDK.

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.
Comparison of shear-wave elastography to state-of-the-art respiratory function testing to measure the range of forces generated by the diaphragm muscle
Authors: Gransee Heather , Smith Joshua , Johnston Jessica , Knoll Kate , Lee Hyungkyi , Jiang Lai , Urban Matthew , Johnson Bruce , Mantilla Carlos
Published: May 2023

The diaphragm muscle is important in both sustaining ventilation and performing higher-force behaviors necessary for maintaining airway patency. Ventilatory behaviors (i.e., eupnea and response to hypoxia-hypercapnia) require only ~20% of maximal force generation, whereas coughing requires forces ~60% of maximal. Existing techniques to measure the full range of forces generated by respiratory muscles are limited by their invasiveness (e.g., balloon manometry for transdiaphragmatic pressure (Pdi) measurements), requirements for training, supervision and subjectivity (e.g., maximal inspiratory and expiratory pressures). Ultrasound-based shear-wave elastography (SWE) assesses muscle stiffness and has shown promising results in being used as a surrogate for Pdi to evaluate diaphragm muscle force. Previous literature has demonstrated a correlation between diaphragm SWE and Pdi at lower force behaviors and the goal of the present study was to evaluate the efficacy of SWE-based measurements of the diaphragm in correlating with Pdi measurements across the range of forces generated by the diaphragm. In this pilot study, we recruited 6 male and 5 female healthy volunteers. Subjects were positioned in a seated position with their torso unsupported. Pdi was measured during graded inspiratory threshold loading trials using a POWERbreathe Plus commercial inspiratory loading device, as well as during maximal inspiratory pressure (MIP). Simultaneously, SWE was performed at the zone of apposition in the right anterior axillary line, and diaphragm Young’s modulus and shear wave speed were subsequently measured. The average Pdi during MIP testing was 149 ± 66 cm H2O. Pdi during inspiratory loading at a low resistance was 39 ± 14 cm H2O and at a high resistance was 78 ± 29 cm H2O. Subjects were able to generate an average Pdi range of 39 ± 19 cm H2O across the graded resistance levels, and the average percent of MIP obtained was 54 ± 13%. Average Young’s modulus as measured with SWE during inspiratory loading at a low resistance was 46 ± 19 kPa and at a high resistance was 104 ± 19 kPa. From low to high resistance, Pdi, Young’s modulus, and shear wave speed increased by an average of 100%, 126%, and 59%, respectively. Taken together, SWE is a promising method of non-invasive assessment of diaphragm muscle forces across a range of voluntary behaviors.

Support from NIH grant R21 DA055848 and the Mayo Clinic.

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.
Identification of novel changes in skeletal muscle proteome after sildenafil treatment
Authors: Wu Linda , Garcia Luis , Lipinski Austin , Langlais Paul , Coletta Dawn
Published: May 2023

Insulin Resistance (IR) is associated with increased matrix proteins, including collagens, fibronectins, and laminins in the endomysium surrounding skeletal muscle. The increased ECM deposition in skeletal muscle IR results in ECM stiffening that decreases muscle integrity and cellular signaling. Recent evidence has shown that Sildenafil, a phosphodiesterase 5a inhibitor, improves insulin sensitivity in humans, and in high fat diet mice, reduces collagen deposition in the matrix surrounding skeletal muscle. In addition, data shows that a short-term treatment of Sildenafil for 7 days increases protein synthesis and decreases muscle fatigue in humans, which may mitigate the effects of IR. However, very few studies have examined the molecular mechanisms and metabolic signaling directly associated with Sildenafil’s influence on skeletal muscle. The aim of our study was to perform an unbiased proteomic analysis on Sildenafil’s effects on skeletal muscle in C2C12 myotubes. We hypothesized that Sildenafil would alter the abundance of proteins in metabolic pathways that are involved in communicating with the ECM. We performed a dose response (n = 3 for each dose; 0.5 μM, 1 μM, 2.5 μM, 5 μM, and 10 μM) and time response (n = 3 for each time; 30 min, 1 hour, 4 hour, 6 hour) curve. Proteomic analyses revealed that the highest number of proteins significantly changing was at 1 μM for 30 min (n = 423). Analysis of the significant proteins revealed 396 and 27 proteins that increased and decreased, respectively. KEGG analysis revealed that 20% of the total changing proteins (n = 83) were in metabolic pathways. The top 10 metabolic protein increasers, represented as a fold change of abundance compared to vehicle, were ASCL3 (1.27 ± 0.08), GT251 (1.12 ± 0.10), ODPA (1.15 ± 0.03), PCKGM (1.08 ± 0.04), PCY1A (1.23 ± 0.04), PGM1 (1.06 ± 0.04), PTG1S (1.21 ± 0.05), PYR1 (1.37 ± 0.09). SAHH (1.19 + 0.07), and THIM (1.13 ± 0.08). Of the 83 metabolic proteins, only 6 were decreasing, P5CR2 (0.78 ± 0.04), ALD1 (0.82 ± 0.11), P4K2A (0.67 ± 0.05), DGAT1 (0.27 ± 0.19), SCLY (0.77 ± 0.15), and PLCD3 (0.61 ± 0.16). The results from this preliminary study conclude that Sildenafil affects proteins involved in metabolic pathways. Further analysis will be performed to confirm the roles of these proteins in relation to ECM signaling/communication in these metabolic pathways.

University of Arizona's Research, Innovation & Impact Faculty Seed Grant

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.
Purinergic receptor activation attenuates pilocarpine-induced water intake
Authors: De Paula Patricia , Gois Pedro A. , Menani José V.
Published: May 2023

Intraperitoneal (ip) injection of pilocarpine (PILO, muscarinic cholinergic agonist) induces salivation, water intake and changes in body temperature. These effects are due to a direct action on the salivary glands and central nervous system (CNS). ATP (adenosine 5'-triphosphate) is a neurotransmitter in the peripheral and CNS and is responsible for activating purinergic receptors located in various regions including the salivary glands. Preliminary results from our laboratory showed that ATP injected intraperitoneally (ip) reduced PILO-induced salivation, suggesting the participation of peripheral purinergic receptors in salivary secretion. The aim of the present study was to investigate the effects of ip injection of ATP (a natural agonist of purinergic receptors) on water intake and changes in body temperature induced by PILO also administered ip. Male Holtzman rats (300-350 g, n=18) were used. The experimental protocols were approved by the Ethical Committee for Animal Care and Use – CEUA from the Dentistry School of Araraquara, UNESP (Proc. CEUA nº 11/2019). A group of 10 rats received ip injection of PILO (1 mg/kg of body weight) to induce water intake. Ten minutes before, half of the group received an ip injection of ATP (200 mg/kg of body weight) and the other half received saline. Then water was offered in graduated burettes fitted with metal drinking spouts. The results showed that ip injections of ATP (200 mg/kg of body weight) reduced PILO-induced water intake (0.2 ± 0.1 ml/15 min, vs. saline + pilocarpine: 2.2 ± 0.6 ml/15 min, p<0.05). Another group of 8 rats was submitted to a median laparotomy for the placement of body temperature sensors in the abdominal cavity. The results showed that ip injection of PILO did not alter body temperature (0.3 ± 0.1 °C, vs. saline: 0.3 ± 0.1 °C) and the combination of ATP + PILO also did not change body temperature (0.2 ± 0.1 °C). Thus, the results suggest that ip injection of ATP reduced PILO-induced water intake, but PILO alone or combined with ATP did not change body temperature in rats

CNPq, PROPE UNESP, FAPESP

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.