bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondrial and Microvascular Impairments in a Novel Swine Model of Peripheral Artery Disease
Authors: Anderson Cody , Allen Michael , Hakim Ali , Tian Yukian , Al-Gahmi Al-Murtadha , Kim Kyung-Soo , Carlson Mark
Published: May 2024

Introduction: Impaired skeletal muscle mitochondria and microvascular function have been reported in human peripheral artery disease (PAD). However, no large animal models of PAD have mimicked these impairments. Purpose: The purpose of this study was to examine the skeletal muscle microvasculature and mitochondria in a novel swine model of PAD. Hypothesis: We hypothesized that hindlimb ischemia leads to dysfunction of skeletal muscle microvessels and mitochondria. Methods: Ossabaw swine (n=5) with metabolic syndrome underwent endovascular coil occlusion of the right external iliac artery to generate hindlimb ischemia (ISC). The left leg served as a non-ischemic control (CON). After 4-weeks, biopsies were collected from both legs (lateral gastrocnemius). Skeletal muscle arterioles were assessed using video microscopy. Microvascular vasodilatory function was assessed in response to flow (Shear stress), acetylcholine (ACh), and sodium nitroprusside (SNP). Skeletal muscle mitochondrial function was assessed using high-resolution respirometry. Substrates were administered as follows: malate (M) & glutamate (G), adenosine diphosphate (ADP), succinate (S), oligomycin, and ascorbate (Asc) & N,N,N,N-tetramethyl-phenylenediamine (TMPD). Complex I state 2 (CI-S2) was assessed as M+G, complex I state 3 (CI-S3) was assessed as (M+G+ADP)-(M+G), complex II state 3 (CII-S3) was assessed as (M+G+ADP+S)-(M+G+ADP), complex I&II state 3 (CI&II S3) was assessed as (M+G+ADP+S)-(M+G), state 4 (S4) was assessed after oligomycin, and complex IV (CIV) respiration was assessed after Asc+TMPD. The respiratory control ratio (RCR) was calculated as CI&II-S3/S4. Results: Vasodilation in response to flow was reduced in ISC vs. CON (Δ-13.1±13.7%, p=0.01). but not in response to ACh (Δ-6.2±17.7%, p=0.23) or SNP (Δ1.7±11.0%, p=0.53). Additionally, CI-S2 (Δ-0.3±3.7 pmolO2·s−1·mg−1, p=0.65), S4 (Δ-1.7±4.4 pmolO2·s−1·mg−1, p=0.14), and CIV (Δ-2.8±20.9 pmolO2·s−1·mg−1, p=0.65) were not different between ISC and CON. However, CI-S3 (Δ-4.7±5.0 pmolO2·s−1·mg−1, p<0.01), CII-S3 (Δ-3.5±5.0 pmolO2·s−1·mg−1, p=0.02), CI&II-S3 (Δ-8.5±8.7 pmolO2·s−1·mg−1, p<0.01), and RCR (Δ-0.8±1.3 pmolO2·s−1·mg−1, p=0.04) were all reduced in ISC vs. CON. Conclusions: We found that skeletal muscle microvessels and mitochondria were impaired in our swine model. Based on the present findings, we conclude that our novel porcine model closely replicates the pathophysiology PAD, making it a promising large animal model for studying human PAD.

This research was supported by the National Institutes of Health (R01HD106911, R01AG062198, R01AG0778031) and the Great Plains IdeA-CTR (U54 GM115458).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Ganglionic blockade modulates sympathetic neural discharge and neurocirculatory regulation in humans
Authors: Lynn Cameron , Limberg Jacqueline , Nicholson Wayne , Curry Timothy , Iannarelli Nathan , Shoemaker Kevin , Joyner Michael
Published: May 2024

This study investigated the impact of integrated muscle sympathetic nerve activity (MSNA) discharge patterns on human neurocirculatory regulation. In 13 healthy females (42 ± 15 years), the transduction of integrated MSNA (peroneal microneurography) into mean arterial pressure (MAP; arterial catheter) was studied during an intravenous infusion of a nicotinic ganglionic antagonist (trimethaphan camsylate, 1-7 mg/min). Neurovascular transduction (signal averaging) was studied based on the overall response, burst sequence (singlet, doublet, and triplet+), and burst amplitude (binned into tertials: small, medium, and large bursts). Data (mean ± SD) are reported for a 10-minute baseline (BSL), the one-minute period at the midpoint of the trimethaphan infusion with integrated MSNA bursts (TM-Mid), and the last minute of trimethaphan infusion with integrated MSNA bursts (TM-Last). During BSL, the MAP transduction responses were greatest for triplets+ (singlets: 0.9 ± 0.2 mmHg, doublets: 2.0 ± 0.6 mmHg, triplet+: 2.6 ± 0.9 mmHg; P < 0.01) and large bursts (small: 1.0 ± 0.3 mmHg, medium: 1.7 ± 0.5 mmHg, large: 2.2 ± 0.7 mmHg; P < 0.01). Trimethaphan infusion reduced integrated MSNA burst frequency resulting in a greater proportion of singlets (BSL: 45 ± 18 %, TM-Mid: 75 ± 23 %, TM-Last: 94 ± 20 %; P < 0.01), a lower proportion of doublets, and a lower proportion of triplets+ (BSL: 23 ± 19 %, TM-Mid: 9 ± 18 %, TM-Last: 0 ± 0 %; P < 0.01). Trimethaphan infusion reduced integrated MSNA burst amplitude resulting in a greater proportion of small bursts (BSL: 33 ± 0.2 %, TM-Mid: 60 ± 26 %, TM-Last: 78 ± 37 %; P < 0.01), a lower proportion of medium bursts, and a lower proportion of large bursts (BSL: 34 ± 1 %, TM-Mid: 17 ± 26 %, TM-Last: 1 ± 5 %; P < 0.01). Trimethaphan-mediated changes in MSNA burst frequency and amplitude were associated with reduced overall MAP transduction responses (BSL: 1.6 ± 0.5 mmHg, TM-Mid: 0.5 ± 0.2 mmHg, TM-Last: 0.3 ± 0.3 mmHg; P < 0.01). Linear regression analyses demonstrated that the trimethaphan-mediated reduction in the proportion of large bursts ( β = 0.02 ± 0.008 mmHg/%, R2 = 0.13, P = 0.03) more strongly affected sympathetic neurovascular transduction responses than reductions in the proportion of triplet+ burst sequences (P = 0.91). These findings suggest that time varying MSNA discharge patterns, particularly variations in burst amplitude, support human neurocirculatory regulation.

This work was supported by the National Institutes of Health and the Natural Sciences and Engineering Research Council of Canada.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Investigating the Impact of Circulating miRNAs on Cardiovascular System Remodeling During Pregnancy
Authors: Khan Inzar , Raggio Max , Hetherington Isabella , Totary-Jain Hana
Published: May 2024

During pregnancy, women undergo significant remodeling of their cardiovascular system, a complex process involving various physiological adaptations to ensure an adequate blood supply to the developing fetus. An intriguing area of research focuses on the role of circulating microRNAs, particularly the primate-specific chromosome 19 miRNA cluster (C19MC) and the rodent-specific chromosome 2 miRNA cluster (C2MC), both of which exhibit high expression levels in the placenta. Extracellular vesicles, such as exosomes, play a crucial role in intercellular communication and may carry microRNAs that contribute to the physiological changes observed during pregnancy. However, the influence of circulating C19MC and C2MC microRNAs on maternal cardiovascular system remodeling remains unexplored. We hypothesized that the increased levels of circulating C2MC or C19MC microRNAs during pregnancy might play a role in the maternal cardiovascular system adaptations. To investigate this hypothesis, we conducted a study to determine whether circulating exosomes during pregnancy lead to elevated expression levels of C19MC or C2MC microRNAs in various organs, including the heart, kidney, liver, spleen, lungs, and brain. In our investigation, we utilized three distinct mouse models: wild-type (WT) mice expressing only C2MC, C2MC knock-out (KO) mice, and a novel humanized mouse model, which combined C2MC KO with either a single or double copy of the human C19MC. We extracted total RNA from the organs of these mice and performed cDNA synthesis. Subsequently, we measured the expression levels of two representative microRNAs, miR-517a and miR-466a, corresponding to C19MC and C2MC, respectively, in the organs of pregnant and non-pregnant mice using TaqMan RT-qPCR. Our results indicated no significant differences in the expression levels of miR-517a and miR-466a when normalized to the housekeeping gene snoRNA-202 across different organs in pregnant and non-pregnant mice. To comprehensively assess the expression patterns of all microRNAs within the C19MC and C2MC clusters in various organs of pregnant and non-pregnant mice, further investigation with a larger sample size and small RNA-Seq analysis is warranted. This approach will enable us to explore a broader spectrum of microRNAs and potentially identify specific candidates that may play a crucial role in the essential physiological process of maternal cardiovascular system remodeling.

This study is supported by USF Cardiovascular Summer Undergraduate Research Fellowship (SURF) sponsored by the American Heart Association.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
SERCA mediated thermogenesis during contraction-relaxation cycle in rat skeletal muscle in vivo
Authors: Tabuchi Ayaka , Tanaka Yoshinori , C Poole David , Kano Yutaka
Published: May 2024

BACKGROUND: Across the lifespan, body temperature homeostasis is tightly regulated and impacts various physiological phenomena. In skeletal muscle, heat is produced via contraction-dependent (shivering) and independent (nonshivering) mechanisms, regulating the body temperature and muscle physiology including contractile properties. PURPOSE: In this study, we aimed to reveal the intracellular temperature dynamics in skeletal muscle in vivo during the contraction-relaxation cycle. Additionally, we tested the hypothesis that calcium ion (Ca2+) handling mediated by sarcoplasmic reticulum Ca2+ ATPase (SERCA) is involved in the thermogenesis process during contraction-relaxation cycle in skeletal muscle fibers. METHOD: The spinotrapezius muscle of anesthetized adult male Wistar rats (n = 18) was exteriorized and subjected to microinjection of fluorescent probe Cellular Thermoprobe for Fluorescence Ratio (49.3 μM) for intracellular temperature imaging in vivo. The fluorescence ratio (R: 580 nm / 515 nm) was measured in vivo during temperature increases induced by an external heater for thermoprobe calibration. R was also measured following Ca2+ injection (3.9 nL, 2.0 mM), and Ca2+ injection with SERCA inhibition by cyclopiazonic acid (CPA, 100 μM). RESULTS: The fluorescence ratio linearly increased with the increase of the muscle surface temperature from 25 °C to 40 °C (r2 = 0.97, P < 0.01). The intracellular temperature in muscle was increased and sustained following the Ca2+ injection and this thermogenetic response was significantly suppressed with SERCA inhibition (Ca2+: 38.3 ± 1.4 °C vs Ca2++CPA: 28.3 ± 2.8 °C, P < 0.01 at 1 min following injection). Importantly, elevated muscle temperature occurred predominantly in the muscle relaxation phase that followed the muscle shortening: That shortening occurred immediately and transiently after the Ca2+ injection. CONCLUSION: In this investigation, we demonstrated a novel technique for in vivo intracellular temperature imaging of skeletal muscle. Herein we demonstrate that substantial heat is generated concomitantly with SERCA mediated Ca2+ handling and muscle relaxation.

This work was supported by JSPS KAKENHI Grant Numbers 20H04074, 19K22800.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Sex-dependent impairment of kidney function in megalin knockout mice
Authors: Youm Elynna , Albalawy Wafaa N. , Marciszyn Allison , Rbaibi Youssef , Shipman Katherine , Boyd-Shiwarski Cary , Tan Roderick
Published: May 2024

Megalin ( Lrp2) is a multiligand receptor that drives endocytic flux in the kidney proximal tubule (PT) and is necessary for the recovery of albumin and other filtered proteins that escape the glomerular filtration barrier. We previously found that knocking out Lrp2 in the opossum kidney (OK) PT cell line leads to differential expression of genes involved in mitochondrial and metabolic function. Additionally, we observed large reductions in sodium glucose co-transporter 2 (Sglt2) transcript (>80%) and protein (~40%) expression levels. While Sglt2 transcript and protein levels in Lrp2 KO in mice were more modestly reduced, male and female KO mice fed regular chow or a Western diet (WD) had increased tolerance to a high glucose challenge compared with control mice. Surprisingly, male Lrp2 KO mice fed a WD developed substantial kidney injury, while female KO mice had significantly less injury. In metabolic studies, Lrp2 KO mice preferentially utilized fatty acid oxidation compared to control mice. We hypothesize that compromised endocytic flux in Lrp2 KO mice impairs mitochondrial and metabolic function to worsen kidney damage in a sex-dependent manner. Current studies are focused on a variety of approaches to test how reduced endocytic capacity impacts mitochondrial function and metabolism in Lrp2 KO cells and control OK cells. We will confirm our findings in age-matched male and female control and Lrp2 KO mice. These studies will help to determine the role of megalin expression and function on PT metabolism, function, and overall health.

National Institutes of Health: T32DK061296, T32AG021885-20, RO1 DK125049, RO1 DK118726, S10 OD028596, U54 DK137329.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Proteomic profiling of Botryllus schlosseri, an emerging model organism
Authors: Dong Weizhen , Luu Brenda , Lin Mandy , Enriquez Isabel , Hamar Jens , Kültz Dietmar
Published: May 2024

Botryllus schlosseri is a colonial chordate species that exhibits robust stem cell-mediated regeneration capacities throughout life. It grows through a process of colonial budding known as blastogenesis, in addition to its sexual reproduction mode, embryogenesis. In natural conditions, colony growth peaks in the summer and drastically decreases in the winter due to various seasonal factors. We have established and optimized a method to rear B. schlosseri animals in landlocked laboratories where the controlled conditions allow colonies to grow continuously and exponentially through asexual reproduction under constant temperature, salinity, light, and nutrient conditions. During the weekly blastogenic cycle, all asexually derived parental zooids synchronously regress within one day and are replaced by a new generation. To enable comprehensive molecular phenotyping of this species we established a quantitative proteomics workflow and spectral library for Liquid chromatography/Tandem mass spectrometry (LCMS) data-independent acquisition (DIA). In this study, we quantified the relative abundances of several thousand proteins representing molecular phenotypes of B. schlosseri. This workflow enables us to use proteomics to characterize zooid development during its regenerative cycle, including the short critical period of the takeover stage, during which degenerating zooids undergo massive apoptosis while succeeding buds quickly mature and migrate into place. From this data, protein networks associated with regeneration and degeneration can be created, offering insights into tissue developmental pathways in vivo and future cell immortalization strategies in vitro. Furthermore, the establishment of quantitative proteomics workflows for B. schlosseri coupled with its unique life cycle features promotes the use of this model organism for the study of phenotypic plasticity and evolution of aging, stem cells, and mechanisms of regeneration and cell differentiation.

This project is funded by NSF Grant MCB — 2127516.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Use of Function Diagrams in Physiology Education: Nessie the Nephron and Navigating the Lochs
Authors: Wilson Thad , Jackson Brian , Sawaya B. Peter
Published: May 2024

Function diagrams focus on physiological concepts rather than associated structures and can serve as elaboration tools and mnemonic aids. A function diagram prototype of the gastrointestinal system was recently described (Wilson & Barrett, Adv Physiol Educ, 45:264–268, 2021). Currently, a functional diagram of the glomerulus, nephron, urinary system, and bladder is proposed. Colloquially named “Nessie the Nephron” to loosely capture the looping structure and illusive understanding of renal blood flow, glomerular filtration, and epithelial transport for the student, not to mention the nearly mythical countercurrent multiplier. “Navigating the Lochs” references Nessie’s possible habitat and more importantly the movement and storage of the modified ultrafiltrate from the nephron. The primary analogies that form the structure of this function diagram are: Rain Barrel, Soaker Hose, & Hose Nozzle (afferent and efferent blood flow and filtration pressure); Water Purification System (glomerular filtration barrier forming multiple step filtration process involving the capillary, basement membrane, and podocytes); Mixed Recycling Machine (proximal tubule individual, co-, and bulk transport); Desiccator & Briner (thin descending limb removal of water and thin/thick ascending limb movement of salt); Conveyor Belt Picker (distal nephron selective ion transport); and Concentrator (collecting duct water and urea transport). The primary analogies that elaborate “Navigating the Lochs” are Aqueduct & Cistern System (fluid movement and collection); and Pressure Gauge, Syringe Bulb, and Two-valve Plumbing (bladder storage and micturition). Complimenting these analogies is the rich potential for inclusion of clinical and comparative applications and examples to link previous knowledge and strengthen memories for future retrieval.

University of Kentucky College of Medicine.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Alteration of Piezo1 signaling in type 2 diabetic mice: Focus on endothelium and BKca channel
Authors: Haam Chae Eun , Choi Sooyeon , Oh Eun Yi , Byeon Seonhee , Choi Soo-Kyoung , Lee Young-Ho
Published: May 2024

Aim: Piezo1, a mechanosensitive ion channel, plays a significant role in vascular physiology and disease. This study aimed to elucidate the altered signaling elicited by Piezo1 activation in the arteries of type 2 diabetes. Methods: Ten-to 12-week-old male C57BL/6 (control) and type 2 diabetic mice (db−/db−) were used. The second-order mesenteric arteries (~150 mm) were used for isometric tension experiments. Western blot analysis and immunofluorescence staining were performed to observe protein expression. Results: Piezo1 was significantly decreased in mesenteric arteries of type 2 diabetic mice compared to control mice, as analyzed by western blot and immunofluorescence staining. Piezo1 agonist, Yoda1, concentration-dependently induced relaxation of mesenteric arteries in both groups. Interestingly, the relaxation response was significantly greater in control mice than in db−/db− mice. The removal of endothelium reduced relaxation responses induced by Yoda1, which was greater in control mice than db−/db− mice. Furthermore, the relaxation response was reduced by pre-treatment with various types of K+ channel blockers in endothelium-intact arteries in control mice. In endothelium-denuded arteries, pre-incubation with charybdotoxin, an Ca2+-activated K+ channel (BKCa channel) blocker, significantly attenuated Yoda1-induced relaxation in db−/db− mice, while there was no effect in control mice. Co-immunofluorescence staining showed more structural coupling between Piezo1 and BKCa channel was observed in db−/db− mice than in control mice. Conclusions: The present study is the first report on the distinct aspects of vascular response induced by Piezo1 activation in the mesenteric resistance arteries in type 2 diabetic mice.

National Research Foundation of Korea (RS-2023-00272628).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Targeting Melanocortin 4 Receptor to Treat Sleep-Disordered Breathing
Authors: Amorim Mateus R. , Aung O , Anokye-Danso Frederick , de Deus Junia L. , Xiong Jiali , Dergacheva Olga , Bevans-Fonti Shannon
Published: May 2024

There is no effective pharmacotherapy for sleep-disordered breathing (SDB). A melanocortin receptor 4 (MCR4) agonist, setmelanotide (SET), is used to treat genetic obesity caused by abnormal melanocortin and leptin signaling. We hypothesized that SET can treat SDB in diet-induced obese mice. We performed a proof-of-concept randomized crossover trial of a single dose of SET vs vehicle and a two-week daily SET vs vehicle trial in obese mice. We also examined co-localization of Mcr4 mRNAs with a marker of CO2 sensing neurons PHOX2b in the brainstem and performed chemogenetic studies expressing Cre-dependent designer receptors exclusively activated by designer drugs (DREADD) in Mcr4-Cre mice. SET increased minute ventilation across sleep/wake states, greatly enhanced the hypercapnic ventilatory response (HCVR), and abolished apneas during sleep. PHOX2b+ neurons in the nucleus of the solitary tract (NTS) and the parafacial region expressed Mc4r. Chemogenetic stimulation of the MC4R+ neurons in the parafacial region, but not in the NTS, augmented the HCVR without any changes in metabolism. Parafacial MC4R neurons projected to the respiratory pre-motor neurons expressing cholera toxin B after C3-C4 spinal cord injections. In conclusion, MC4R agonists enhance the HCVR and treat SDB by acting on the parafacial MC4R+ neurons.

NIH (R01 HL128970, R01 HL133100, and R01 HL138932), AHA (#915167).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Modulation of Endothelial Cell Mitochondrial Phenotype and Angiogenesis by TRPV4
Authors: Dalal Kesha , Katari Venkatesh , Kondapalli Narendra , Paruchuri Sailaja , Thodeti Charles
Published: May 2024

Transient receptor potential vanilloid type 4 (TRPV4) is a mechanically activated ion channel implicated in the regulation of endothelial cell (EC) proliferation, migration, and angiogenesis. However, the molecular mechanism(s) by which TRPV4 regulates EC functions remains underexplored. Here, we investigated if TRPV4 channels mediate endothelial function via modulation of mitochondria. Confocal microscopy showed a peri-nuclear localization of mitochondria in normal EC (NEC), while they were localized throughout the cell in TRPV4 knockout EC (KOEC). Furthermore, transmission electron microscopy confirmed clear round mitochondria in NEC compared to elongated mitochondria with distinct cristae in KOEC. Importantly, we found increased distribution of mitochondria in KOEC with increasing stiffness, when cultured on extracellular matrix (ECM) gels of varying stiffness that mimic the stiffness of matrix in pathophysiological conditions such as tumor or heart failure (0.2, 8, and 50 kPa). Mechanistically, western blot analysis showed increased fusion/fission protein ratio (Optic Atrophy 1 (OPA1)/mitochondrial fission factor (MFF)), in KOEC compared to NEC. Seahorse flux analyzer analysis demonstrated increased basal oxygen consumption rate (OCR), maximal OCR, ATP-linked OCR, and spare capacity in KOEC compared to NEC, which were significantly attenuated by a small molecule inhibitor of OPA1, MYLS22. Finally, MYLS22 normalized TRPV4-knockout mediated abnormal proliferation, migration, and angiogenesis ex vivo. Taken together, these findings indicate that mechanosensitive TRPV4 channels regulate mitochondrial phenotype and function during angiogenesis through OPA1.

This work was supported by the National Institutes of Health (and R01HL148585 and AHA-TPA-971237) to CKT.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Protection from hypertension phenotype by a mitochondrial division inhibitor in mice infused with angiotensin II
Authors: Nakayama Yuki , J. Preston Kyle , Kawai Tatsuo , Torimoto Keiichi , Eguchi Satoru
Published: May 2024

Mitochondrial dysfunction has been implicated in various types of cardiovascular diseases including hypertension. Mitochondrial fission fusion balance is critical for mitochondrial quality control, whereas enhanced fission has been reported in several models of cardiovascular diseases. However, limited information is available regarding the contribution of mitochondrial fission in hypertension. Here, we have tested our hypothesis that inhibition of mitochondrial fission attenuates development of hypertension and associated vascular remodeling. C57BL6 mice were infused with angiotensin II for 2 weeks with or without treatment of mitochondrial fission inhibitor mdivi1. Cultured vascular endothelial cells and adventitial fibroblasts from rat aortas were stimulated with angiotensin II in the presence or absence of mdivi1. In C57BL6 mice infused with angiotensin II for 2 weeks, co-treatment of mitochondrial fission inhibitor mdivi1 significantly inhibited angiotensin II-induced development of hypertension assessed by telemetry. Histological assessment of hearts and aortas demonstrated that mdivi1 inhibited vessel fibrosis and hypertrophy induced by angiotensin II. This was associated with attenuation of angiotensin II-induced decline in mitochondrial aspect ratio seen in both endothelium and media of aortas. Mdivi1 also mitigated angiotensin II-induced cardiac hypertrophy assessed by heart weight body weight ratio as well as by echocardiogram. Proteomic analysis on endothelial cell culture media with angiotensin II and/or mdivi1 treatment revealed that mdivi1 inhibited endothelial cell hypersecretory phenotype induced by angiotensin II. In addition, mdivi1 attenuated angiotensin II-induced protein induction of periostin, a myofibroblast marker in cultured vascular fibroblasts. In conclusion, these data suggest that mdivi1 prevented angiotensin II-induced hypertension and cardiovascular remodeling via multicellular mechanisms in the vasculature.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Postmenopausal Women with Obesity have Reduced Leg Endothelial Function and Exercise Vasodilatory Capacity
Authors: Martinez Mauricio , Fischer Stephen , Maharaj Arun , Kang Yejin , Dillon Katherine , Figueroa Arturo
Published: May 2024

Background: Obesity (OB) is highly prevalent in postmenopausal women; particularly increased abdominal visceral adipose tissue contributes to endothelial dysfunction and cardiovascular risk. The endothelium plays an important role on blood flow (BF) and pressure control at rest and during exercise. However, it is unknown how different body mass index (BMI) categories influence upper and lower limb endothelial function and BF responses to exercise in postmenopausal women. Purpose: The purpose was to examine upper and lower limb endothelial function at rest and BF regulation during low-intensity exercises in OB, overweight (OW), and lean (LN) postmenopausal women. We hypothesized that endothelial function and BF responses to submaximal exercise in both limbs will be attenuated in OB compared to the OW and LN groups. Methods: Women were classified as OB (30.0-39.9 kg/m2; n = 13), OW (25.0-29.9 kg/m2; n = 15), and LN (18.5-24.9 kg/m2; n = 11) by BMI. Flow-mediated dilation (FMD) of the brachial (BA-FMD) and superficial femoral arteries (FA-FMD) were measured using ultrasound. BF and vascular conductance (VC) in the brachial (BA-BF and BA-VC) and femoral (FA-BF and FA-VC) arteries were measured during separate 3-stage incremental rhythmic handgrip and plantarflexion exercises (PFE) at 5, 15, and 30 % of maximal strength and calculated 1-repetition max (1RM), respectively. Results: No differences in BA-FMD were observed among the groups. FA-FMD was significantly lower in OB (2.6 ± 1.4%) compared to OW (4.3 ± 1.9%) and LN (4.2 ± 0.7%) groups (P < 0.05). Increases in FA-BF (OB: 462 ± 229 vs. OW: 616 ± 173 vs. LN: 640 ± 141 mL/min; P < 0.001) and FA-VC (OB: 410 ± 176 vs. OW: 585 ± 155 vs LN: 623 ± 153 mL/min*100mmHg; P < 0.001) were attenuated during PFE at 30% of 1RM in OB compared to OW and LN. Upper-body exercise vasodilation was not attenuated by OB. FA-BF and FA-VC during PFE at 30% of 1RM were correlated with FA-FMD (FA-BF: r = 0.423, P = 0.007, FA-VC: r = 0.367, P = 0.021) and BMI (FA-BF: r = -.386, P = 0.015, FA-VC: r = -.456, P = 0.004). Conclusion: Postmenopausal women with OB have blunted leg endothelial function and exercise vasodilator function during submaximal dynamic plantarflexion exercise compared to LN and OW. These findings suggest that OB may contribute to reduce leg endothelial function, and vasodilator function during exercise in postmenopausal women.

No support of funding information to disclose.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Undergraduates have few science instructor role models with concealable stigmatized identities
Authors: Brownell Sara , Busch Carly , Cooper Katelyn
Published: May 2024

Concealable stigmatized identities (CSIs) are identities that can be kept hidden and carry negative stereotypes depending on the culture of a particular context; common examples of CSIs in the U.S. are struggling with mental health and LGBTQ+ identities. In order to understand the potential influence instructors have as role models for their students based on CSIs, we must first explore the identities instructors have and whether they disclose those identities to their students. To address this gap in the literature, we conducted a study to examine (1) to what extent science instructors hold concealable identities, (2) whether they reveal those identities to undergraduates, and (3) how the prevalence of CSIs among science instructors compares to their prevalence among science undergraduates. We contacted every science instructor whose email we could find from very high research activity (R1) institutions and a subset completed the survey (N = 1,248); the survey began with a suite of demographic questions, including potential CSIs. For each CSI reported, instructors indicated the extent to which they revealed these identities to undergraduates. We surveyed a national sample of science undergraduate students from R1 institutions (N = 2,428) and asked whether they identified as having any of the CSIs included on the instructor survey. The most common CSIs among instructors were currently or previously having anxiety (35.4%) and being a first-generation college student (29.0%). Across all CSIs, relatively few instructors revealed their identities to students. When compared to the prevalence of the CSIs among undergraduates, we found the largest mismatches, calculated by subtracting the percent of undergraduates from the percent of instructors with each CSI, in reporting struggling academically in college (-30%), anxiety (-25%), and depression (-24%). For all identities, the mismatch between instructors and undergraduates grew when accounting for whether instructors revealed the CSI to their students. Given the potential for instructors to act as role models for students, understanding what identities instructors hold and the extent to which they share them with students is important to consider as we work toward creating a more diverse and inclusive scientific community.

National Science Foundation.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Effect of the bacterial lipopolysaccharide (LPS) on vitamin B1 (thiamin) uptake along the intestinal tract: inhibition mediated via reduction in level of expression of thiamin transporter-1 & -2 proteins at the cell membrane
Authors: Anthonymuthu Selvaraj , Sabui Subrata , Manzon Kameron Isaiah , Said Hamid
Published: May 2024

Background: LPS is a potent bacterial virulence factor and is a source of considerable clinical morbidity and mortality. This endotoxin is a predominant component of the outer membrane of Gram-negative bacteria. The gut is exposed to high levels of LPS in conditions like Inflammatory Bowel Diseases, necrotizing enterocolitis, sepsis, and following infection with enteric pathogens. Studies have shown that exposure of gut epithelial/other cells to LPS exerts profound and differential effects on membrane transport processes. Nothing, however, is known about the effect of LPS on uptake of free thiamin in the small intestine (where absorption of dietary thiamin occurs), and the large intestine (where absorption of the microbiota-generated thiamin occurs). Aim: To examine the effect of LPS on the small and large intestinal uptake of free thiamin and to determine the mechanism(s) involved. Methods: We used in vitro (human duodenum-derived HuTu 80 cells and colon-derived non-transformed NCM460 cells), ex vivo (human differentiated polarized enteroid and colonoid monolayers), and in vivo (mouse) models in our studies. Uptake studies were performed using 3H-thiamin as substrate. Results: Treating intestinal HuTu 80 and colonic NCM460 epithelial cells with LPS led to a significant inhibition in carrier-mediated 3H-thiamin uptake. Similar results were obtained when human differentiated enteroid and colonoid monolayers ex vivo, and mouse in vivo were treated with LPS. No changes in total cellular levels of thiamin transporter-1 & -2 (THTR-1 and THTR-2, respectively) proteins and mRNAs were observed upon LPS treatments; however, a significant decrease in the fraction of the THTR-1 & THTR-2 proteins that are expressed at the cell membrane were observed. These findings suggest that the LPS inhibitory effect on thiamin uptake in the small and large intestine is likely mediated via a decrease in the fraction of the thiamin transporters that are expressed at the cell membrane. Conclusion: This study shows that bacterial LPS inhibits thiamin uptake along the intestinal tract, and that this inhibition is likely mediated via reduction in level of the THTR-1 & THTR-2 proteins at the cell membrane.

Supported by NIH grants DK-56061 and AA-018071, and VA grants 101BX001142 & IK6BX006189.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
cAMP enriched EVs mediates hypoxic pulmonary hypertension
Authors: Bhadra Aritra , Hewes Jenny , Lee Ji Young , Zhou Chun , Bonnie Frederic , Bauer Natalie
Published: May 2024

Our lab reported the novel finding that stimulation of pulmonary endothelial cells with a beta-agonist and a phosphodiesterase inhibitor induced enrichment of cyclic adenosine monophosphate (cAMP) in EVs. cAMP protects the pulmonary vasculature by regulation of permeability, vasoreactivity and proliferation. Extracellular vesicles provide a protected environment for circulating cAMP. Thus, we hypothesized that administration of cAMP, in the protected environment of an EV, could deliver cAMP to improve outcomes in pulmonary hypertension. Briefly, male Sprague Dawley rats, maintained in normoxic or hypoxic conditions for 3 weeks, received 50 ug of cAMP-enriched EVs (cAMP-EVs) per day over 3 days via tail vein injection. cAMP-EV injections improved the Fulton index (non-injected hypoxia rat 0.37 ± 0.039 versus injected hypoxia rat 0.32 ± 0.019, p value 0.032 n = 5) and echocardiography revealed PH rats that received cAMP-EVs had a significant increase in PAAT/PAET ratio compared to those that did not (non-injected hypoxia rat 0.27 ± 0.056 versus injected hypoxia rat 0.32 ± 0.04, p value 0.04, n = 6). Using IVIS analysis of isolated tissues to detect PKH-labeled EVs we found that cAMP-enriched EVs accumulated in the lung but were not detectable in the heart. To confirm this was not strictly a vasoreactivity effect, we also examined PCNA, a marker of proliferation, in histological sections and found it was decreased in the presence of cAMP-EVs. Pulmonary arterial thickness was also significantly improved in the presence of cAMP-EVs. To understand the underlying mechanism for cAMP-EV based signaling, we studied the phosphorylation status of endothelial nitric oxide synthase (eNOS) in isolated paraffn fixed lung slices. We found increased phosphorylation of eNOS in PH rats which received cAMP EVs compared to non-injected PH or control rats. Combined these data suggest that cAMP-EVs may decrease right ventricular hypertrophy, improve pulmonary arterial function, and repair hypoxic vascular injury. Future investigations will determine whether the observed response is cAMP dependent and further evaluate the specificity of pulmonary vascular uptake of cAMP-EVs.

1R01HL133066-01A1 (Bauer).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Quantifying in vivo Mitochondrial Effciency at Rest and during Exercise in Human Skeletal Muscle
Authors: Erol Muhammet Enes , Bannon Sean T. , Matias Alexs A. , Siokas Triantafyllia , Nagarajan Rajakumar , Le fur Yann , Park Song-Young
Published: May 2024

Introduction: Mitochondrial effciency provides an additional mechanism to fine-tune oxidative phosphorylation rate to match ATP demand in skeletal muscle with far-reaching consequences on exercise tolerance. However, the direct measurement of both oxygen consumption (VO2) and ATP production from the same region of the contracting muscle in vivo remains a technical challenge. Purpose: Using an innovative approach combining noninvasive phosphorus and proton magnetic resonance spectroscopy (31P/1H-MRS), the present study aimed to characterize skeletal muscle ATP synthesis rate and muscle VO2 at rest and during a graded dynamic plantar flexion exercise to determine mitochondrial effciency in the gastrocnemius muscle. Method: We assessed mitochondrial effciency in the gastrocnemius muscles of 12 healthy adults (21± 1 yrs.). 31P and 1H magnetic resonance spectroscopy (MRS) was performed using a whole-body 3T MR system (Skyra, Siemens) at rest and during a series of constant workloads coupled to brief transient ischemia to quantify both oxidative ATP synthesis (ATPox) rate and myoglobin-derived oxygen consumption (Mb-derived VO2). The MRS data were acquired with a dual-tuned 31P/1H surface coil with linear polarization positioned over the gastrocnemius muscle. Results: As expected, the end-exercise PCr concentration decreased from 29 ± 2 mM of WRmax to 18 ± 1 mM with increasing workload. Likewise, the end-exercise Mb oxygenation level declined linearly with increasing workload. As the exercise workload increased, the ATPox synthesis rate increased linearly (r2 = 0.45), whereas there was no significant change in Mb-derived VO2. At rest, the estimated P/O ratio in the gastrocnemius muscle was 1.95 ± 0.68, whereas non-physiological values were obtained during exercise. Conclusion: During exercise, Mb-derived VO2 was likely limited by O2 availability with the methodology employed (30-sec occlusion, spectrum time resolution of 10 sec), which precluded the accurate quantification of mitochondrial effciency. However, mitochondrial effciency calculated at rest is in agreement with previously documented values ex vivo and thus provides an additional parameter to evaluate mitochondrial function in vivo.

This work was funded in part by National Heart, Lung, and Blood Institute Grant R00HL125756.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) improves lipid utilization but not survival following prolonged hemorrhagic shock
Authors: Calderon Alfredo , Kennard Cianna , Klemke Harold , Marshall Stephanie , Meledeo Michael , Xiang Lusha
Published: May 2024

Hemorrhagic shock induces insulin resistance and cellular ATP depletion, the initial step for cell death and organ injury. AMPK is a fuel-sensing enzyme that maintains ATP production by facilitating glucose and fatty acid uptake and oxidation. Using a previously developed rat model of AKI induced by prolonged hemorrhagic shock, we tested the hypothesis that AICAR, an AMPK activator, can enhance fuel consumption, delay onset of AKI, and increase survival following prolonged hemorrhagic shock. Additionally, we hypothesized that AICAR requires 7.5% polyethylene glycol-20k (PEG) to elicit the catabolism effect, as PEG enhances the capillary perfusion in the absence of resuscitation, and thus, in theory, facilitates AICAR delivery into ischemic tissues. Rats were randomized into 4 groups (n=8/group) based on treatment: saline (vehicle), AICAR, PEG, and AICAR+PEG. Trauma was induced in (Inactin) anesthetized rats with muscle injury and fibula fracture, followed by pressure-controlled hemorrhagic shock (MAP = 55 mmHg) for 45 minutes. Animals then received an intravenous injection of saline (vehicle), AICAR, PEG, or AICAR+PEG. MAP, blood gases, RBF, renal oxygen delivery, capillary perfusion and tissue oxygen levels in the skeletal muscle were monitored for another 2 hours. GFR and mortality were recorded at the end of the experiment. The saline group exhibited impaired tissue perfusion and GFR with 100% mortality. AICAR alone showed no effect on hemodynamics, renal function, or mortality (100%). PEG and AICAR+PEG similarly improved MAP, capillary perfusion in the skeletal muscle, renal blood flow, renal oxygen delivery, and GFR. Compared to PEG, free FA levels were further decreased in AICAR+PEG, which was concomitant with elevated lactate levels and blunted oxygen partial pressure in the skeletal muscle despite the improved capillary perfusion. The mortality was 12.5% in PEG and 50% in AICAR+PEG. Our results suggest that AICAR+PEG does enhance fuel utilization but fails to further improve the tolerance to hemorrhagic shock, possibly due to a shift of oxygen consumption from vital organs to peripheral tissue. Importantly, the catabolism effect of AICAR relies on suffcient tissue perfusion, suggesting that PEG might be potentially considered as a routine therapeutic tool to optimize drug delivery during hemorrhagic shock.

DoD disclaimer: The views expressed in this article are those of the author(s) and do not reflect the offcial policy or position of the U.S. Army Medical Department, Department of the Army, DoD, or the U.S. Government. Funding: This study was funded by US Army Medical Research and Development Command.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Vascular Smooth Muscle Cell Mechanical Stretch Modulates Tissue Transglutaminase Activity and Cytoskeletal Dynamics
Authors: Lateef Olubodun M. , Foote Christopher A. , Ramirez-Perez Francisco I. , Augenreich Marc A. , Power Gavin , Padilla Jaume , Martinez-Lemus Luis A.
Published: May 2024

Vascular smooth muscle cells (VSMCs) are exposed to a wide range of mechanical stimuli in both physiological and pathological conditions. These mechanical stimuli are converted into biochemical signals that regulate VSMC contractility and cytoskeletal structures in a process known as mechanotransduction. Thus, the ability of VSMCs to sense and respond to mechanical signals is essential for proper regulation of their structural characteristics and the modulation of vascular tone. We had previously shown that increased tissue transglutaminase 2 (TG2) activity modulates actin dynamics via alterations of the phosphorylation state of cofilin leading to VSMC stiffening and remodeling of the vascular wall. However, whether mechanical forces act through TG2 to modulate VSMC stiffness remains unknown. Herein, we tested the hypothesis that mechanical stretch increases VSMC stiffness by increasing TG2 activity, reducing cofilin activity, and increasing actin cytoskeletal stress fiber formation. To this end, immortalized human aortic vascular smooth muscle cells (HAoSMCs) were cultured and seeded on Uniflex culture plates. HAoSMCs were left unstretched or exposed to cyclic uniaxial stretch using a Flexcell tension system with 11% elongation at 1 Hz for 6 hrs. HAoSMCs were treated without or with the nitric oxide (NO) donor s-nitrosoglutathione (400μmol/L) or cystamine (200μmol/L) under stretched and unstretched conditions, as NO and cystamine are known inhibitors of TG2. All differences reported herein are significant at p<0.05. Our results show that cyclic uniaxial stretch for 6 hrs increases VSMC TG2 content and activity, actin stress fibers (polymerization), and phospho-cofilin/cofilin ratios (cofilin inactivation), relative to the unstretched condition. Notably, the increase in TG2 activity and F-actin content occurring in response to stretch was inhibited by the NO donor or cystamine. As it has been previously shown that cellular stiffness is associated with stress fiber formation, this work suggests that stretch-induced cellular stiffening is potentially mediated by TG2 activity in VSMC.

National Institutes of Health grant: R01HL153264 to LM-L and JP.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.