bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparing Nitric Oxide Generation Pathways using Dietary L-Arginine and Dietary Nitrate: A 15N tracer study in Wistar Rats
Authors: Brown Haleigh , Piknova Barbora , Park Ji Won , Tunau-Spencer Khalid J , Schechter Alan N 
Published: May 2024

Mammals generate nitric oxide (NO) through two main pathways. In the direct production pathway, endogenous nitric oxide synthase (NOS) enzymes catalyze the reaction of L-arginine with oxygen, producing nitric oxide and citrulline. When oxygen accessibility is low, the reductive pathway supplies nitric oxide through the nitrate-nitrite-NO reduction cascade. Additional research is needed to understand whether the two NO generation pathways interact and what effects the two pathways have on the body and each other. We investigated how dietary supplementation of 15N-L-arginine (0.5 g/kg), 15N-nitrate (0.013 g/kg), or a combination of L-arginine and nitrate influences nitrate concentrations in plasma, skeletal muscle, and liver tissue from Wistar rats. We administered treatments via oral gavage. Two hours after treatment administration, we euthanized the rats and collected tissue samples. The nitrate concentrations were measured using chemiluminescence, and future mass spectrometry analysis for 15N/14N ratios will be performed. The calculated concentrations were compared between treatment groups using single factor analysis of variance. Firstly, we observed that nitrate administration significantly increased total nitrate levels in plasma, liver, and muscle tissues compared to the control group. Interestingly, L-arginine alone did not result in a significant rise in total nitrate concentrations. Notably, liver tissue from the L-arginine-treated group had slightly lower concentrations of nitrate than the control group. The combination of L-arginine and nitrate showed no statistically significant difference when compared with the nitrate-treated group in all three tissues. These results suggest that a bolus of L-arginine does not have a substantial short-term effect (within 2 hours after ingestion) on total nitrate concentrations in rat tissues. Future mass spectrometry analysis will indicate how the tissues handle acute ingestion of two different NO sources: L-arginine and nitrate. Further research must be performed for a more detailed understanding of the kinetics of arginine and nitrate, as well as for the effects of these dietary supplements on improving NO homeostasis. This work was supported by intramural NIDDK/NIH grant ZIA DK 025104-15 to Alan N. Schechter. 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.
Effects of Myocardial Infarction-induced Heart Failure on Diaphragm Arteriolar Vasorelaxation
Authors: Behnke Bradley , Horn Andrew , C Poole David , Musch Timothy 
Published: May 2024

INTRODUCTION: Diaphragm atrophy and contractile dysfunction are prevalent in heart failure (HF), diminishing physical capacity and quality of life. The delivery of blood flow and oxygen necessary to support the metabolic demand of contractions is largely governed by the resistance vasculature (i.e., arterioles) with the endothelium playing a central role in arteriolar vasorelaxation. Adequate perfusion and blood flow distribution, and thus resistance vessel vasodilation, is a major determinate of diaphragm contractile function. While the mechanistic bases of HF-induced diaphragm dysfunction continue to be elucidated, the impact of HF on diaphragm vasomotor control has not been investigated. METHODS: Adult (6 mo) Sprague-Dawley rats (n=7) were divided into two groups: 1) Healthy Control (HC; n=4) and 2) MI-induced heart failure (HF; n=3). First-order arterioles (1A) from the medial costal diaphragm were isolated, cannulated, and pressurized at 90 cmH2O and allowed to equilibrate for 60 min to develop spontaneous tone. Thereafter, endothelium-dependent and -independent vasorelaxation responses to cumulative doses of acetylcholine (ACh; 10−9 to 10−4M) and sodium nitroprusside (SNP; 10−9 to 10−4M) were determined. RESULTS: There were no differences in spontaneous development (%) or maximal diameter (μm) between HC (20 ± 4%; 178 ± 11 μm) and HF (18 ± 2%; 184 ± 29 μm) diaphragm 1As ( P > 0.05). Maximal ACh-mediated relaxation (%) was significantly reduced in HF rats compared to HC rats (52 ± 2 versus 68 ± 5%; P < 0.05). Maximal endothelial-independent vasorelaxation with SNP, was not different between HC and HF rats (71 ± 3 versus 73 ± 1%; P > 0.05). CONCLUSION: The preliminary data herein demonstrate that HF impaired endothelial function and vasomotor function in the medial costal diaphragm resistance vasculature. This suggests that, in HF, there may be a redistribution of blood flow to less effcient regions of the diaphragm (e.g., ventral costal) to sustain contractile function and compensate for the diminished medial costal vasomotor function demonstrated herein. Studies including a larger sample size are warranted to investigate the impact of HF on regional blood flow distribution and resistance vessel function in the diaphragm. Such investigations would yield novel mechanistic insights into HF-induced diaphragm dysfunction. National Institute of Aging 1R15AG078060, Ruth L. Kirschstein National Research Service Awards from the National Heart, Lung, and Blood Institute 1F31HL167618-01, and Sustained Momentum for Investigators with Laboratories Established (SMILE) Grants at Kansas State University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Thick Ascending Limbs (TALs)-specific deletion of ALMS1 (Alstrom syndrome 1) increases surface NKCC2 expression and NaCl reabsorption in the TAL
Authors: Maskey Dipak , Ortiz Pablo 
Published: May 2024

The regulation of NKCC2 mediated NaCl reabsorption in Thick Ascending Libs (TALs) is essential to salt homeostasis and blood pressure regulation. Previously, our lab showed that NKCC2 activity is regulated by membrane traffcking and inhibiting endocytosis enhanced surface NKCC2 expression and NaCl reabsorption. We also found that ALMS1, a protein mutated in Alström syndrome, is expressed in TALs. Whole animal gene deletion of ALMS1 caused hypertension, and inhibits NKCC2 endocytosis, increasing its surface expression and renal NaCl reabsorption. Little is known about additional functions of ALMS1, however, global gene deletion of ALMS1 induces obesity, and that, in turn may affect TAL and NKCC2 function. We hypothesized that ALMS1 is a part of protein complex that binds apical NKCC2 in TALs and promotes its endocytosis. To dissect the specific role of ALMS1 in TALs, without interference of systemic effects, we studied surface NKCC2 expression and TAL mediated Na transport after inducible deletion of ALMS1 in TALs. To do this, we generated a loxP flanked exon 7 ALMS1 transgenic mouse line, that we crossed with TAL specific inducible Umod-ERT2 Cre mice (Umod-ALMS1 KO). 3 weeks after inducing Cre expression with tamoxifen, ALMS1 expression in TAL suspensions decreased by 85% (p<0.01) (n=5). In Umod-ALMS1 KO TALs the surface to total NKCC2 ratio, was increased by 37±15% compared to control floxed ALMS1 (p<0.01) (n=5). Recombinant ALMS1 (GST-Carboxyl terminus-ALMS1), or immunoprecipitation of ALMS1, pulled down NKCC2 from TAL lysates (n=3), suggesting that the mechanism by which ALMS1 regulates surface NKCC2 involves protein-protein interactions. Three weeks after inducing ALMS1 deletion, we measured bumetanide-induced natriuresis (4h) as an index of NKCC2-mediated NaCl absorption. We found that bumetanide induced UNa excretion was enhanced in Umod-ALMS1 KO, compared to control (control: 110±7 vs Umod-ALMS1 KO: 173±26 μmols Na/4h, p<0.01). We conclude that ALMS1, binds NKCC2 to regulate its surface expression. Depletion of ALMS1, specifically in the TAL enhances surface NKCC2 and TAL NaCl reabsorption. Our data indicate that regulation of the ALMS1-NKCC2 interaction in the TAL is important for renal NaCl reabsorption. Decreased ALMS1 function or expression increased TAL NaCl reabsorption and this may contribute to the hypertension and kidney disease that is associated with SNPs in the ALMS1 gene in the general population, or in patients with Alstrom Syndrome. NIH R01, Henry Ford Fund. 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.
Sirtuin 4 regulates nutrient-stimulated insulin secretion by modulating GLP-1 secretion
Authors: Penney Magan C. , Do Evan , Luong Amy , Huynh Frank K. 
Published: May 2024

Sirtuin 4 (SIRT4) is a mitochondrial enzyme that can remove several novel post-translational modifications (PTMs) on target proteins and thereby modify their activity. We and others have previously shown that young mice lacking SIRT4 (SIRT4KO mice) have elevated glucose, leucine, and glutamine-stimulated insulin secretion. As these mice aged, they developed insulin resistance and glucose intolerance. We hypothesize that when these mice are young and eat a mixed nutrient diet, they secrete elevated amounts of insulin in response to each meal and this hyperinsulinemia drives the development of insulin resistance in old age. However, while insulin secretion in response to glucose, leucine, and glutamine individually has been reported in these mice, it has not been shown how much insulin these mice secrete in response to combinations of these nutrients, which would more closely resemble a normal meal. Thus, we sought to characterize insulin secretion in SIRT4KO mice in response to mixed nutrient challenges. Indeed, SIRT4KO mice secrete more insulin response to different combinations of glucose, leucine, and glutamine. In most cases, these increases in insulin secretion were synergistic, rather than just an additive effect of each individual nutrient. In particular, when leucine and glucose were administered together in aged SIRT4KO males, plasma insulin levels were synergistically increased more than 3-fold over glucose or leucine alone. Remarkably, treating aged SIRT4KO mice with leucine during a glucose tolerance test resulted in so much insulin secretion that glucose intolerance was normalized. Importantly, despite these extremely high insulin levels, there were no signs of dangerous hypoglycemia. To determine whether these synergistic effects of glucose and leucine on insulin secretion were due to effects of SIRT4 on pancreatic beta-cells, we treated beta-cell specific SIRT4KO mice with glucose and leucine and found no differences in insulin secretion compared to wild-type mice, suggesting that SIRT4 affects insulin secretion by acting indirectly on the beta-cell. To determine whether SIRT4 may affect insulin secretion by altering incretin secretion, we measured GLP-1 secretion in response glucose and leucine in combination and found that GLP-1 secretion was elevated in SIRT4KO mice compared to wild-type controls. Taken together, our data show that SIRT4 may be a key regulator of insulin secretion in response to mixed nutrients via effects on GLP-1 secretion. NIH Support of Competitive Research (SCORE) Pilot Project Award #SC2GM141997 San Jose State University Department of Biological Sciences Start-up Funds. 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.
Identification of Vasopressin-Regulated Aquaporin-2 Traffcking Mechanism with Proximity-Labeling Proteomics
Authors: Liu Chin-Fu , Lin Yi-Jiun , Yu Ming-Jiun 
Published: May 2024

Vasopressin controls collecting duct water permeability in part by regulating traffcking of aquaporin-2 to and from the apical plasma membrane in the principal cells. Evidence have shown that aquaporin-2 resides in Rab11-positive recycling endosomes where its PDZ motif is phosphorylated at serine 269, leading to apical aquaporin-2 localization in response to vasopressin. Here, we employed Rab11-conjugated biotin ligase (TurboID) to biotinylate kinases and traffcking machineries recruited to Rab11-positive endosomes in the mpkCCD cells in response to vasopressin vs. vehicle. The biotin-labeled proteins were purified with streptavidin-affnity chromatography and identified with protein mass spectrometry. A total of 2,948 proteins were quantified in three independent repeats of which 119 proteins showed increases in the Rab11-positive endosomes in response to vasopressin while 104 proteins showed decreases. GO term analysis of the 119 increased proteins showed enriched biological processes including transport, protein transport, and vesicle-mediated transport. Microtubule affnity regulating kinase 2 stood out from our Bayes theorem probability analysis as a candidate kinase for aquaporin-2 serine 269 phosphorylation. Purified microtubule affnity regulating kinase 2 phosphorylated a synthetic aquaporin-2 peptide at serine 269 in vitro. Among the 119 proteins is the PDZ-domain containing Rho GTPase-activating protein 21 involved in F-actin dynamics. Switching between GTP- and GDP-bound state, Rho GTPase-activating protein 21 promotes F-actin polymerization and depolymerization, respectively. Our preliminary observations are indicative of a hypothetical model where vasopressin recruits microtubule affnity regulating kinase 2 to the Rab11-positive endosomes where it phosphorylates aquaporin-2 PDZ motif at serine 269. The phosphorylated PDZ motif recruits and activates Rho GTPase-activating protein 21, resulting in the GDP-bound state that promotes F-actin depolymerization. The depolymerized F-actin would facilitate fusion of the aquaporin-2 vesicles with the apical plasma membrane. National Science and Technology Council, TAIWAN, MOST 111-2320-B-002-084-MY3. 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.
Sesamin Enhances Apoptosis of Activated T cells by physically Interacting with MCL-1 and Shows Therapeutic Effect on Allergic Dermatitis
Authors: Park Hee-Suk , Lee Hyun-Su 
Published: May 2024

Sesamin is lignans mainly found in sesame seeds and oil. Previous studies have demonstrated that sesamin has potent pharmacological activities including anti-inflammatory, antioxidative, and cholesterol-and lipid-lowering. Detailed studies performed with sesamin revealed that it possesses anti-proliferative and pro-apoptotic properties that could potentially be used to kill tumors. Nevertheless T cell-mediated disorders usually occur when over-activated T cells are proliferative and less apoptotic, however, it is unknown whether sesamin suppresses T cell activation with underlying mechanism related to proliferation and apoptosis. In the present study, we evaluate whether sesamin upregulates apoptosis on activated T cells and improves T cell-mediated disease. First of all, we confirmed that sesamin suppresses IL-2 production and CD69 expression from activated T cells by quantitative PCR, ELISA and flow cytometry. In silico analysis showed that Myeloid cell leukemia 1 (MCL-1) is predicted to physically interact with sesamin in T cells. According to the in silico prediction, pulldown assay using sepharose4B beads and western blot results showed that treatment with sesamin physically binds to MCL-1 in T cells and regulates S56 phosphorylation level of MCL-1 which represents activity of MCL-1 in activated T cells. Moreover, inhibition of MCL-1 activity by sesamin blocked heterodimer interaction between MCL-1 and BAK in activated T cells by co-immunoprecipitation assay. These results led sesamin to selectively induce cell death pathway only in activated T cells. Oral administration of sesamin alleviated the symptoms of dinitrochlorobenzene (DNCB)/mite extract-induced AD, including ear thickness, mRNA levels of pro-atopic cytokines on the ear lesions of sesamin-treated AD mice. Therefore, these results suggest that sesamin has a therapeutic potential for treating T-cell mediated disease through modulating MCL-1 activity on activated T cells. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2021R1I1A1A01059119). 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.
Mitochondria control IP3-evoked Ca2+ release triggered by voltage-dependent Ca2+ entry in intact resistance arteries
Authors: Zhang Xun , Lee Matthew , Buckley Charlotte , Wilson Calum , McCarron John 
Published: May 2024

The contractility of vascular smooth muscle cells (VSMCs) is a major contributor of vascular tone and blood pressure. In VSMCs, intracellular Ca2+ level determines the contractile activity that generates the force to contract arteries. A major source of Ca2+ is via influx through voltage dependent Ca2+ channels (VDCCs). While mitochondria are now recognised as key regulators of intracellular Ca2+ homeostasis in several cell types, their role in modulating Ca2+ signalling mediated by VDCC in VSMCs is unresolved. Given the potential physiological significance, and unclarified interaction between mitochondria and VDCCs in VSMCs, we hypothesize that mitochondria directly regulate Ca2+ signalling mediated by VDCCs. The interplay between mitochondria and VDCCs was investigated by imaging and analysing intracellular Ca2+ signals in smooth muscle cells in intact arteries from rat mesentery. Depolarization of the plasma membrane potential, by high potassium (20 mM) physiological saline solution, triggered Ca2+ influx through VDCCs and a sustained increase in intracellular Ca2+ on which repetitive Ca2+ oscillations occurred. All Ca2+ signals were abolished by removal of external Ca2+ and by dihydropyridine inhibitors of VDCCs. Significantly, the repetitive Ca2+ oscillations, but not the sustained Ca2+ signals, were blocked by the IP3 receptor inhibitor 2-APB and SERCA inhibitor cyclopiazonic acid. Neither the repetitive Ca2+ oscillations or the sustained Ca2+ signals were altered by the ryanodine receptor inhibitors ryanodine and dantrolene. These results suggest that Ca2+ influx via VDCC triggers Ca2+-induced Ca2+ release at IP3 receptors in intact mesenteric arteries. Depolarization of the mitochondrial membrane potential (ψm), with the uncoupler CCCP or complex I inhibitor rotenone, but not ATP deprivation with the ATP synthesis blocker oligomycin, inhibited VDCC evoked IP3 mediated Ca2+ oscillations but not the sustained Ca2+ signals. Furthermore, in intact arteries, depolarization of ψm directly suppressed inositol triphosphate receptors (IP3Rs) mediated Ca2+ release from the internal Ca2+ store evoked by photolysis of caged IP3. These results suggest that mitochondria regulate Ca2+ release via IP3R triggered by Ca2+ entry via VDCC. In return, Ca2+ entry via VDCCs did not alter ψm, but upregulated ROS production. Together, these results suggest that mitochondria regulate Ca2+-induced Ca2+ release at IP3 receptors triggered by Ca2+ influx via VDCCs but do not directly regulate VDCC activity. British Heart Foundation (RG/F/20/110007; PG/20/9/34859). 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.
Increases in cardiac vagal modulation following a single session of passive calf stretching
Authors: Lehnen Georgia , Araujo Marcela , Rocha Igor , Vianna Lauro , Trajano Gabriel 
Published: May 2024

Autonomic cardiovascular responses to mechanoreflex activation by passive muscle stretching have been shown in numerous investigations. These cardiovascular adjustments include cardiac vagal inhibition, sympathetic activation, pressor response, and baroreflex resetting. However, it is currently unclear how the autonomic system responds after a single session of passive muscle stretching. Therefore, we aimed to test the hypothesis that there would be parasympathetic dominance after stretching cessation. Twenty-four volunteers (14 men; 22±3 yr) performed two protocols: 1) five sets of 1 minute of unilateral passive calf stretching with 15 s of rest; and 2) control condition (six minutes of resting at the same position). The autonomic cardiac responses of both control and experimental conditions were assessed before, and immediately, 15 minutes and 30 minutes after stretching cessation. Passive stretching was performed on an isokinetic dynamometer (Biodex System 4, USA). Heart rate, systolic and diastolic blood pressure were continuously measured on a beat-to-beat basis using lead II electrocardiography (BioAmp, MLA2540) and finger photoplethysmography (Human NIBP, Australia). Brachial arterial blood pressure was also measured with an automated digital sphygmomanometer (Dixtal, DX2022, Brazil). Heart rate variability (HRV) was determined following the guidelines of the Task Force of the European Society of Cardiology and the North American Society of Pacing. With regards to the hemodynamics variables, there was no significant difference in the heart rate before and after passive stretching, while mean blood pressure (MBP) was slightly higher (±2mmHg) 30 min following both protocols (control, p=0.027 and stretch, p=0.035). Regarding HRV analysis, in the time domain, RMSSD was significantly increased 30 min following passive stretching (+15%; p=0.029), and this effect was also detected when using the frequency domain (high frequency: +37%, p=0.039). Of note, our major findings were not affected by sex. In conclusion, autonomic cardiovascular control shifts to a parasympathetic dominant state following passive calf stretch, and the effect peaks around 30 minutes after stretching. Passive stretching seems to be a safe, easy, and effective form of exercise that evokes autonomic cardiovascular responses during and following its cessation, even if it is performed in a single session of stretch. CNPq 307764/2022-2; CAPES (001) QUT South America Scholarship. 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.