Vasorelaxant Responses Research Articles

Apelin from Perivascular Adipose Tissue Is Involved in the Regulation of Vasorelaxation and Renal Function in Metabolic Syndrome

The perivascular adipose tissue (PVAT) regulates the arterial tone by releasing vasoactive molecules. PVAT dysfunction favoring the vasorelaxation response could contribute to the development of kidney disease in metabolic syndrome (MetS). Previously, we demonstrated that overactivation of angiotensin II signaling in the PVAT deteriorates the compensatory PVAT effects in rats with MetS (SHRSP.Z-Leprfa/IzmDmcr (SPZF) and SHR/NDmcr-cp (CP) rats). Apelin is an endogenous regulator of angiotensin II. Therefore, we investigated whether changes in apelin levels in the PVAT alter PVAT function and impair kidney function in MetS. Twenty-three-week-old male and female SPZF and CP rats were used. In the female CP rats, apelin mRNA levels in renal arterial PVAT, enhancing effects of the PVAT on acetylcholine-induced relaxation in renal arteries, and estimated glomerular filtration rate (eGFR) were the highest, and urine protein levels and homeostasis model assessment of insulin resistance (HOMA-IR) were the lowest. Apelin mRNA levels were positively correlated with the enhancing effects of the PVAT on vasorelaxation and eGFR but negatively correlated with urine protein levels and HOMA-IR. Moreover, apelin levels positively correlated with mRNA levels of angiotensin-converting enzyme 2 and angiotensin II type 1 receptor-associated protein, which are negative regulators of angiotensin II. This study suggests that a decline in apelin levels in the PVAT, probably owing to angiotensin II, is associated with PVAT dysfunction on vascular tone, resulting in impaired kidney function in MetS.

101 5-HT4 receptor-mediated vasorelaxation occurs through a cyclic mononucleotide-dependent mechanism in the isolated bovine lateral saphenous vein

Abstract Serotonin (5-HT)-mediated vasorelaxation of the isolated bovine lateral saphenous vein occurs primarily through 5-HT4 receptor activation. Vasorelaxation responses mediated through 5-HT4 have only been documented to occur in cattle and sheep and thus, may represent a novel vasorelaxation mechanism that is specific to ruminants. In tissues from other species, the 5-HT4 receptor and its associated G protein couple with adenylate cyclase. However, the mechanisms contributing to 5-HT4-mediated vasorelaxation in vascular tissue remain undefined. To better understand the mechanisms of 5-HT4-mediated vasorelaxation, lateral saphenous veins from cattle (n = 4) were collected and assessed for vasoactivity in response to increasing concentrations of a selective 5-HT4 receptor agonist (BIMU-8) in the absence and presence of selective inhibitors of downstream proteins involved with cyclic mononucleotide-mediated signaling. Isolated vessel segments were suspended in chambers of a multi-myograph containing 5 mL of continuously oxygenated Krebs-Henseleit buffer and equilibrated to 1 g tension for 90 min. After the equilibration period, vessels were exposed to dimethyl sulfoxide (DMSO; vehicle control) or selective inhibitors of downstream protein targets dissolved in DMSO (1×10-5 M) for 5 min. Vessels were pre-contracted with 1×10-4 M phenylephrine for 10 min to achieve a sustained increase in tension. After the 10-min pre-contraction period, vessels were exposed to increasing concentrations (1×10-9 to 1×10-4) of BIMU-8 non-cumulatively. Vasoactive response data were normalized as a percentage of the maximum contractile response induced by the phenylephrine pre-contraction. In the absence of selective inhibitors (control), BIMU-8 induced (P < 0.01) dose-dependent relaxations (mean -log EC50 = 6.30 M) with a 112% increase in maximal vasorelaxation activity occurring at 1×10-4 M. In the presence of the selective inhibitors for adenylate cyclase (NKY80) or guanylate cyclase (NS2028), 66% and 86% of the vasorelaxation responses to BIMU-8 were attenuated (P < 0.01), respectively. In the presence of the selective inhibitors for protein kinase A [protein kinase A inhibitor fragment (6-22) amide] or protein kinase G (Rp-8-bromo-PET-Cyclic GMPS), 66% and 97% of the maximal vasorelaxation responses to BIMU-8 were attenuated (P < 0.01), respectively. In the presence of non-selective inhibitors for Ca2+ channels and K+ channels, vasorelaxation responses to BIMU-8 were attenuated (P < 0.01). In the presence of selective inhibitors for the protein phosphatase 1 and 2A subunits of myosin light chain (calyculin A) and heat shock protein synthesis (quercetin), vasorelaxation responses to BIMU-8 were attenuated (P < 0.01). The findings of the current study demonstrate that 5-HT4-receptor mediated vasorelaxation occurs through a cyclic mononucleotide-dependent mechanism involving cross-activation of protein kinase A and G signaling. Downstream proteins involved in the signaling cascade leading to vasorelaxation include Ca2+ channels, K+ channels, myosin light chain phosphatase, and heat shock proteins. More research is needed to fully describe the cellular and molecular mechanisms responsible for 5-HT4 receptor-mediated vasorelaxation.

Oxysterol Sensing Through GPR183 Triggers Endothelial Senescence in Hypertension.

Despite endothelial dysfunction being an initial step in the development of hypertension and associated cardiovascular/renal injuries, effective therapeutic strategies to prevent endothelial dysfunction are still lacking. GPR183 (G protein-coupled receptor 183), a recently identified G protein-coupled receptor for oxysterols and hydroxylated metabolites of cholesterol, has pleiotropic roles in lipid metabolism and immune responses. However, the role of GPR183 in the regulation of endothelial function remains unknown. Endothelial-specific GPR183 knockout mice were generated and used to examine the role of GPR183 in endothelial senescence by establishing 2 independent hypertension models: desoxycorticosterone acetate/salt-induced and Ang II (angiotensin II)-induced hypertensive mice. Echocardiography, transmission electron microscopy, blood pressure measurement, vasorelaxation response experiments, flow cytometry analysis, and chromatin immunoprecipitation analysis were performed in this study. Endothelial GPR183 was significantly induced in hypertensive mice, which was further confirmed in renal biopsies from subjects with hypertensive nephropathy. Endothelial-specific deficiency of GPR183 markedly alleviated cardiovascular and renal injuries in hypertensive mice. Moreover, we found that GPR183 regulated endothelial senescence in both hypertensive mice and aged mice. Mechanistically, GPR183 disrupted circadian signaling by inhibiting PER1 (period circadian regulator 1) expression, thereby facilitating endothelial senescence and dysfunction through the cAMP (cyclic adenosine monophosphate)/PKA (protein kinase A)/CREB (cAMP-response element binding protein) signaling pathway. Importantly, pharmacological inhibition of the oxysterol-GPR183 axis by NIBR189 or clotrimazole ameliorated endothelial senescence and cardiovascular/renal injuries in hypertensive mice. This study discovers a previously unrecognized role of GPR183 in promoting endothelial senescence. Pharmacological targeting of GPR183 may be an innovative therapeutic strategy for hypertension and its associated complications.

Abstract P338: Impaired Endothelial-Dependent Vasorelaxation and Myogenic Response in Renal Afferent Arterioles of Diabetic mice: Role of Endothelial NOX1, and New Gene Pathways.

Diabetes increases the risk of cardiovascular disease and hypertension, in part, by decreasing arterial vasodilation through decreased NO bioavailability and increased superoxide. In the kidney, type 1 diabetes induces a decrease in renal filtration, proteinuria, inflammation, and fibrosis, increasing the incidence of kidney disease. In diabetic rats and rabbits, prone to renal disease, diabetes blunts acetylcholine (Ach)-induced vasorelaxation of afferent arterioles, in part, by enhancing endothelial superoxide. However, it is unclear whether diabetes affects afferent arteriole vasodilation and myogenic response in mice. We hypothesize that diabetes increases endothelial NOX1 mediated superoxide production in mouse afferent arterioles, decreasing Ach-induced vasodilation. We dissected and perfused afferent arterioles from male diabetic Akita mice 12-14 weeks of age and measured the effect Ach (10 -7 -10 -5 M) on luminal diameter after pre-constriction with norepinephrine. Diabetic Akita mice had a largely reduced Ach-induced dilation at all doses of Ach (80±6% average inhibition in dilation, p<0.025, n=6). To study the role of NOX1, we used the inhibitor ML171 (5µM). When added to the endothelial lumen, NOX1 inhibition completely restored Ach-induced dilation of diabetic Akita mice, which was not different from WT controls. In Control C57 mice, ML171 did not change Ach-induced dilation in Aff-Art (n=6). We then examined the myogenic response in diabetic mice by measuring lumen diameter after step increases in perfusion pressure (60-140 mmHg). Afferent arterioles of diabetic Akita mice did not constrict when pressure was increased, even at 140 mmHg, whereas WT mice showed normal myogenic response (delta constriction 60-140 mmHg WT: 2.15±0.41 vs Akita: 0.37±0.32 µm, WT p<0.01 from baseline, Akita n.s from baseline). To understand the mechanisms behind these effects we performed RNAseq in manually micro-dissected afferent arterioles from 12-week-old Akita and WT mice. Bioinformatics analysis showed 530 DEGs (FDR pAdj<0.05, n=6). Most of the DEGs are involved in endothelial cell function/metabolism, smooth muscle cell contractility, activated inflammatory pathways, and free radical/NO production. We conclude that early diabetes has a large effect on renal afferent arteriole reactivity by affecting the expression of hundreds of genes. These effects are likely involved in hypertension and kidney damage progression in type 1 diabetes.

Role of L-type Ca2+-channels in the vasorelaxing response to finerenone in arteries of human visceral adipose tissue.

Inadequate blood supply to the expanding adipose tissue (AT) is involved in the unhealthy AT remodeling and cardiometabolic consequences of obesity. Because of the pathophysiological role of upregulated mineralocorticoid receptor (MR) signaling in the complications of obesity, this study tested the vasoactive properties of finerenone, a nonsteroidal MR antagonist, in arteries of human AT. Arteries isolated from the visceral AT of obese subjects were studied in a wire myograph. Finerenone resulted in a concentration-dependent relaxation of arteries precontracted with either the thromboxane-A2 analog U46619, ET-1, or high-K+ solution; the steroidal MR antagonist potassium canrenoate, by contrast, did not relax arteries contracted with either U46619 or high-K+ solution. Finerenone-induced relaxation after precontraction with U46619 was greater in the arteries of obese versus nonobese subjects. Mechanistically, the vasorelaxing response to finerenone was not influenced by preincubation with the nitric oxide synthase inhibitor L-NAME or by endothelium removal. Interestingly, finerenone, like the dihydropyridine Ca2+-channel blocker nifedipine, relaxed arteries contracted with the L-type Ca2+-channel agonist Bay K8644. In conclusion, finerenone relaxes arteries of human visceral AT, likely through antagonism of L-type Ca2+ channels. This finding identifies a novel mechanism by which finerenone may improve AT perfusion, hence protecting against the cardiometabolic complications of obesity.

The vasodilator effect of Eugenol on uterine artery – potential therapeutic applications in pregnancy-associated hypertension

Preeclampsia, a gestational associated hypertension, has been reported in 6–8% of pregnant women worldwide leading to premature delivery and low birth weight of newborn due to reduced blood flow to placenta. Although several vasodilators (Methyl dopa, hydralazine, β-blockers and diuretics) are currently in use to treat preeclampsia, still there is a search for safer drugs with better efficacy. Lately, antihypertensive vasodilators from natural sources are gaining importance in treating preeclampsia. Eugenol (Eug), a natural essential oil, has been traditionally used in health and food products without any risk. In the present study, ex vivo experiments were designed to examine the vasorelaxation effect of Eug and its signaling pathways in a middle uterine artery (MUA) of pregnant Capra hircus (Ch). In presence of different blockers (L-NAME, indomethacin, ODQ, Ouabain, glibenclamide, 4-AP, Ba2, Carbenoxolone and 18β Glycyrrhetinic acid), Eug-induced concentration-dependent vasorelaxation response was elicited. The results showed that Eug caused a greater vasorelaxation effect in the MU of pregnant animals, which is mediated by potential activation of eNOS, KATP channels, and Kir channels with moderate activation of Na+- K+- ATPase and sGC and MEGJ. These findings provide a strong basis for developing Eug as a therapeutic candidate in the treatment of pregnancy-associated hypertension.

Role of L-type Ca2+-channels in the vasorelaxing response to finerenone in arteries of human visceral adipose tissue

Role of L-type Ca2+-channels in the vasorelaxing response to finerenone in arteries of human visceral adipose tissue

Vasorelaxant mechanisms of the antidiabetic anagliptin in rabbit aorta: roles of Kv channels and SERCA pump.

The present study investigated the vasorelaxant mechanisms of an oral antidiabetic drug, anagliptin, using phenylephrine (Phe)-induced pre-contracted rabbit aortic rings. Arterial tone measurement was performed in rabbit thoracic aortic rings. Anagliptin induced vasorelaxation in a dose-dependent manner. Pre-treatment with the classical voltagedependent K+ (Kv) channel inhibitors 4-aminopyridine and tetraethylammonium significantly decreased the vasorelaxant effect of anagliptin, whereas pre-treatment with the inwardly rectifying K+ (Kir) channel inhibitor Ba2+, the ATP-sensitive K+ (KATP) channel inhibitor glibenclamide, and the large-conductance Ca2+-activated K+ (BKCa) channel inhibitor paxilline did not attenuate the vasorelaxant effect. Furthermore, the vasorelaxant response of anagliptin was effectively inhibited by pre-treatment with the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump inhibitors thapsigargin and cyclopiazonic acid. Neither cAMP/protein kinase A (PKA)-related signaling pathway inhibitors (adenylyl cyclase inhibitor SQ 22536 and PKA inhibitor KT 5720) nor cGMP/protein kinase G (PKG)-related signaling pathway inhibitors (guanylyl cyclase inhibitor ODQ and PKG inhibitor KT 5823) reduced the vasorelaxant effect of anagliptin. Similarly, the anagliptin-induced vasorelaxation was independent of the endothelium. Based on these results, we suggest that anagliptin-induced vasorelaxation in rabbit aortic smooth muscle occurs by activating Kv channels and the SERCA pump, independent of other vascular K+ channels, cAMP/PKA- or cGMP/PKG-related signaling pathways, and the endothelium.

NONO2P, a novel nitric oxide donor, causes vasorelaxation through NO/sGC/PKG pathway, K+ channels opening and SERCA activation

Background & aimsThe treatment of cardiovascular diseases (CVD) could greatly benefit from using nitric oxide (NO) donors. This study aimed to investigate the mechanisms of action of NONO2P that contribute to the observed responses in the mesenteric artery. The hypothesis was that NONO2P would have similar pharmacological actions to sodium nitroprusside (SNP) and NO. MethodsMale Wistar rats were euthanized to isolate the superior mesenteric artery for isometric tension recordings. NO levels were measured using the DAF-FM/DA dye, and cyclic guanosine monophosphate (cGMP) levels were determined using a cGMP-ELISA Kit. ResultsNONO2P presented a similar maximum efficacy to SNP. The free radical of NO (NO•) scavengers (PTIO; 100 μM and hydroxocobalamin; 30 μM) and nitroxyl anion (NO−) scavenger (L-cysteine; 3 mM) decreased relaxations promoted by NONO2P. The presence of the specific soluble guanylyl cyclase (sGC) inhibitor (ODQ; 10 μM) nearly abolished the vasorelaxation. The cGMP-dependent protein kinase (PKG) inhibition (KT5823; 1 μM) attenuated the NONO2P relaxant effect. The vasorelaxant response was significantly attenuated by blocking inward rectifying K+ channels (Kir), voltage-operated K+ channels (KV), and large conductance Ca2+-activated K+ channels (BKCa). NONO2P-induced relaxation was attenuated by cyclopiazonic acid (10 μM), indicating that sarcoplasmic reticulum Ca2+-ATPase (SERCA) activation is involved in this relaxation. Moreover, NONO2P increased NO levels in endothelial cells and cGMP production. ConclusionsNONO2P induces vasorelaxation with the same magnitude as SNP, releasing NO• and NO−. Its vasorelaxant effect involves sGC, PKG, K+ channels opening, and SERCA activation, suggesting its potential as a therapeutic option for CVD.

Glyphosate, the active ingredient of RoundUp, promotes gut dysbiosis, vascular dysfunction and hypertension

Introduction: Glyphosate was developed and marketed as an herbicide by Monsanto, USA, in the 1970s. Since then, multiple studies have documented its adverse effects on human health, whereby the use of glyphosate is banned in Europe and its renewal is currently under discussion by European policy. However, glyphosate remains the most widely used herbicide in the United States. Glyphosate exposure can occur through consumption of genetically modified crops tolerant to glyphosate. Glyphosate targets 5-enolpyruvylshikimate-3-phosphate synthase, which is only present in plants and microbes. Therefore, glyphosate is considered safe for humans. However, humans are holobionts with symbiotic gut microbiota, which can be targeted by glyphosate to result in gut dysbiosis. Because our previous studies demonstrate that gut microbiota dysbiosis causes hypertension, we hypothesized that exposure to glyphosate aggravates gut dysbiosis-mediated hypertension. Methods: Two groups of adult (8–10 week old) genetically hypertensive Dahl salt-sensitive (S) male rats were surgically implanted with radiotelemetry transmitters to monitor blood pressure (BP) and administered with or without glyphosate (175 mg/kg body weight per day) in drinking water for 3 weeks (Glyphosate-treated group, n=8; control, n=6). Fecal 16S rRNA gene sequencing and Oxford Nanopore whole genome sequencing were performed for microbiota analyses. Vascular function was examined ex vivo in isolated mesenteric arteries using wire myography. Results: As early as 1 week of exposure to glyphosate was suffcient to significantly increase systolic (173 mmHg vs. 160 mmHg, p<0.0001) and mean arterial pressure (148 mmHg vs 141 mmHg, p<0.0002), but not diastolic BP of S rats. Diastolic BP (142 mmHg vs 135 mmHg, p<0.0001), systolic BP (195 mmHg vs 176 mmHg, p<0.0001), and mean arterial pressure (168 mmHg vs 155 mmHg, p<0.0001) were all significantly increased by week 3, indicating a temporally sustained detrimental effect of glyphosate on BP. The elevation in BP was accompanied by increased contractility of isolated mesenteric resistance arteries as determined by their increased vasocontractile response to phenylephrine (p=0.034), and decreased vasorelaxant response to acetylcholine (p=0.047). 16S metagenomics data revealed distinct rearrangement of gut microbiota composition in the glyphosate-treated group compared to control. Significant shifts in both α-diversity (Shannon entropy; p=0.049) and β-diversity (R=0.24, p<0.032) were observed in the glyphosate-treated group. Bacterial genera such as Candidatus, Erysipelatoclostridium, and Ruminicoccus were more abundant in the glyphosate group whereas Bifidobacterium that produces short-chain fatty acids, was depleted. Summary: Oral glyphosate exposure resulted in elevated BP, increased vascular contractility, and altered gut microbiota composition. Conclusion: This is the first proof-of-concept study to demonstrate that glyphosate is harmful for human health as it contributes to the escalation of hypertension. While more mechanistic studies are warranted, our study supports the reasoning that the unabated use of glyphosate could be a contributor to the rising incidence of hypertension in the western society. NHLBI to Bina Joe (R01HL1430820). 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

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.

Sulforaphane improves vasodilatory reactivity in diaphragm arterioles from rats with pulmonary hypertension

Pulmonary hypertension (PH) is a chronic, progressive disease characterized by pulmonary vascular remodeling, respiratory muscle and cardiac impairments, and exercise intolerance. Specifically, the diaphragm displays compromised contractile and vascular function, precluding it from meeting the increased metabolic demands of PH-induced chronic hyperpnea. Oxidative stress has been implicated in vascular dysfunction and PH pathology, therefore our objective was to target the antioxidant mediator Nrf2 (Nuclear factor erythroid 2-related factor 2) using sulforaphane (SFN) to determine whether this could improve vascular function in the diaphragm. We hypothesized that incubation with SFN would increase vasodilatory responsiveness in diaphragm arterioles from PH rats. Methods: Female Sprague-Dawley rats were administered monocrotaline (MCT; 50 mg/kg, i.p.) to induce PH. Disease progression was monitored via echocardiography. Once animals developed PH (~3 wks), the diaphragm was removed and first-order arterioles from the medial costal diaphragm were isolated, cannulated, and pressurized at 90 cmH2O. After a 60 min equilibration period and spontaneous tone development, endothelium-dependent and -independent vasorelaxation responses to cumulative doses of acetylcholine (ACh) and sodium nitroprusside (SNP) (10−9 to 10−4 M) were determined. These vessels were subsequently incubated with SFN (10 μM, 20 min), then ACh and SNP dose-response measurements were repeated. Results: All PH rats displayed morphometric and echocardiographic criteria for disease (i.e., right ventricular hypertrophy and reduced pulmonary artery acceleration time). Incubation with SFN improved endothelium-dependent and -independent vasodilation (p<0.05). Maximal vasodilatory responses with SFN were 14% and 16% higher for ACh (30±2 vs 34±3%; P=0.02) and SNP (52±2 vs 60±2%; P=0.03), respectively. However, vasodilatory reactivity remains substantially lower than that of healthy animals. Conclusions: These findings suggest that Nrf2 activation using SFN may improve vascular function in the diaphragm with PH. Future investigations will focus on chronic administration of SFN to PH rats to determine the therapeutic potential of this compound in vivo. The results of these studies provide insight into novel pharmacological strategies to improve diaphragm vascular and contractile function, with the potential to help mitigate dyspnea and exercise intolerance and enhance life quality for PH patients. Sustained Momentum for Investigators with Laboratories Established Grants (TIM & DCP); National Institute on Aging 1R15AG078060 (BJB & DCP); Ruth L. Kirschstein National Research Service Awards 1F31HL167618-01 (AGH) and 1F31HL170643-01 (KMS). 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.

Cross-sexual Effects of Testosterone on Mesenteric Arterial Reactivity in Ovariectomized Female Rats

The number of transgender individuals is on the rise in the United States. Although there are studies on the effects of sex hormones on cardiovascular function of cisgender male and female, still much is not known about the effects of cross-sex hormone therapy (CSHT) on cardiovascular function in transgender individuals. It has been shown that the risk factors of cardiovascular diseases (CVD) are increased in transgenders after they undergo CSHT. Epidemiological studies suggest that transgender females (male to female, MtF) on estrogen therapy develop higher risk of CVD compared to transgender males (female to male, FtM) taking testosterone. This study investigates the effects of testosterone or estrogen treatment on the third branch of mesenteric arterial reactivity in ovariectomized female rats. Briefly, 8-10 weeks old female Sprague Dawley (SD) rats were ovariectomized (OVX) and subcutaneously implanted with placebo (OVX + PL) or testosterone (OVX + T, 7.5 mg) or 17β- estradiol (OVX + E2, 1.5 mg) pellets for about 35 days. Age matched intact female SD rats were also included in the experimental groups. Endothelium-dependent vasorelaxation (EDV) to acetylcholine (ACh) was measured in the precontracted mesenteric arteries with phenylephrine (PE), using wire myography. Responses to sodium nitroprusside (SNP)-induced vasorelaxation, and PE- and endothelin-1 (ET-1) induced vasocontraction were also determined. We demonstrated that the responses to ACh in rat mesenteric arteries were not altered by either ovariectomy or estrogen treatment. However, testosterone treatment of OVX female rats significantly enhanced the sensitivity to ACh-induced vasorelaxation compared with those in other experimental groups. Moreover, the mesenteric arteries of OVX + T exhibited a trend of reduced sensitivity to PE responses compared to other groups. Furthermore, the maximum tension to ET-1 was significantly reduced in mesenteric arteries of OVX + T compared to OVX+E2 and OVX+PL groups. The vasorelaxation responses to SNP were not altered in any of experimental groups studied. These data suggest that elevated sensitivity to ACh in testosterone-treated ovariectomized female rats might be, in part, due to reduced vessel responses to contractile agents, but not altered sensitivity of smooth muscle to nitric oxide (NO) in this group. Additional studies are needed to investigate the underlying mechanisms and document the consequences for the improvement of EDV observed in OVX + T rats. NIDA/NIGMS, 1SC1DA052120-01 to MF, Bridge Grant from University of the Pacific to RR. 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.

Novel Role of YAP1 in Regulating Blood Pressure and Vascular Tone

Introduction: Hypertension is a major risk factor for occlusive vascular diseases, myocardial infarction, heart failure, stroke, and chronic kidney disease. In the U.S., ~30% of adults suffer from hypertension. Merely half of the individuals with hypertension have their blood pressure under control, despite the wide range of antihypertensive medications available, indicating an urgent need for a better understanding of the underlying causes of hypertension to identify novel therapeutic strategies for its treatment and prevention. Recent genome-wide association study (GWAS) has identified an unexpected association between a loss-of-function SNP in the YAP1 gene locus and decreased blood pressure (BP). Moreover, de novo analysis of publicly available RNAseq data revealed that the vascular tissues of hypertensive mice treated with Ang-II exhibit increased YAP1 expression. Suggesting a novel role of YAP1 in blood pressure regulation. However, whether Vascular smooth muscle cell (VSMC) expressed YAP1 has a specific role in VSMC contraction and BP regulation remains completely unknown. Therefore, we hypothesized that YAP1 could play a key role in regulating blood pressure. Methodology: We have generated a novel inducible SM-specific- Yap1 Knockout ( YAP1 iKO) mouse model and employed a pharmacological inhibitor of YAP1, Verteporfin, to delineate the functional role of VSMC-expressed YAP1 in hypertension in regulating vascular tone and BP. Vascular reactivity experiments were performed using wire myography. BP was measured in ambulant mice via radiotelemetry. In vitro gain- and loss-of-function studies utilizing human coronary artery SMCs were conducted to examine the impact of YAP1 on contractility signaling components using western blotting. Results: Consistent with GWAS and RNAseq data, we found that YAP1 is upregulated in vascular tissues of spontaneously hypertensive rats (SHRs). Using aortic rings from WT mice, we discovered that Verteporfin significantly reduced vasoconstrictive responses to Phenylephrine or Serotonin but did not alter endothelium-dependent vasorelaxant responses to Acetylcholine, suggesting a specific role of YAP1 in VSMCs. Consistently, YAP1 iKO exhibited attenuated responses to vasoconstrictors in isolated conduit and resistance vessels. Importantly, radiotelemetry studies demonstrated for the first time that YAP1 iKO mice exhibit a hypotensive phenotype. Mechanistically, YAP1 gain- and loss-of-function studies in human VSMCs showed that YAP1 activates multiple signaling pathways that play a key role in VSMC contractility including RhoA/ROCK1/actin polymerization and PKC/ERK signaling pathways. Summary/Conclusion: This is the first study to demonstrate that inhibition of SM-specific-Yap1 expression regulates BP and vascular tone, likely via the regulation of contractile machinery components. Together, our data suggest that YAP1 is a promising novel therapeutic target for ameliorating hypertension. This work is supported by a grant from National Heart, Lung, and Blood Institute (R00HL153896). 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.

The antihypertensive action of C-phycocyanin is related to the prevention of angiotensin II-caused vascular dysfunction in chronic kidney disease.

C-phycocyanin (CPC) is a photosynthetic protein found in Arthrospira maxima with a nephroprotective and antihypertensive activity that can prevent the development of hemodynamic alterations caused by chronic kidney disease (CKD). However, the complete nutraceutical activities are still unknown. This study aims to determine if the antihypertensive effect of CPC is associated with preventing the impairment of hemodynamic variables through delaying vascular dysfunction. Twenty-four normotensive male Wistar rats were divided into four groups: (1) sham + 4 mL/kg/d vehicle (100 mM of phosphate buffer, PBS) administered by oral gavage (og), (2) sham + 100 mg/kg/d og of CPC, (3) CKD induced by 5/6 nephrectomy (CKD) + vehicle, (4) CKD + CPC. One week after surgery, the CPC treatment began and was administrated daily for four weeks. At the end treatment, animals were euthanized, and their thoracic aorta was used to determine the vascular function and expression of AT1, AT2, and Mas receptors. CKD-induced systemic arterial hypertension (SAH) and vascular dysfunction by reducing the vasorelaxant response of angiotensin 1-7 and increasing the contractile response to angiotensin II. Also, CKD increased the expression of the AT1 and AT2 receptors and reduced the Mas receptor expression. Remarkably, the treatment with CPC prevented SAH, renal function impairment, and vascular dysfunction in the angiotensin system. In conclusion, the antihypertensive activity of CPC is associated with avoiding changes in the expression of AT1, AT2, and Mas receptors, preventing vascular dysfunction development and SAH in rats with CKD.

Sodium Hydrosulfide Reverts Chronic Stress-Induced Cardiovascular Alterations by Reducing Oxidative Stress.

Chronic stress induces a group of unrecognized cardiovascular impairments, including elevated hemodynamic variables and vascular dysfunction. Moreover, hydrogen sulfide (H 2 S), a gasotransmitter that regulates the cardiovascular system decreases under chronic stress. Thus, this study assessed the impact of sodium hydrosulfide (NaHS) (H 2 S donor) on chronic restraint stress (CRS)-induced cardiovascular changes. For that purpose, male Wistar rats were restrained for 2 hours a day in a transparent acrylic tube over 8 weeks. Then, body weight, relative adrenal gland weight, serum corticosterone, H 2 S-synthesizing enzymes, endothelial nitric oxide synthetize expression, reactive oxygen species levels, lipid peroxidation, and reduced glutathione-to-oxidized glutathione (GSH 2 :GSSG) ratio were determined in the thoracic aorta. The hemodynamic variables were measured in vivo by the plethysmograph method. The vascular function was evaluated in vitro as vasorelaxant responses induced by carbachol or sodium nitroprusside, and norepinephrine (NE)-mediated vasocontractile responses in the thoracic aorta. CRS increased (1) relative adrenal gland weight; (2) hemodynamic variables; (3) vasoconstrictor responses induced by NE, (4) reactive oxygen species levels, and (5) lipid peroxidation in the thoracic aorta. In addition, CRS decreased (1) body weight; (2) vasorelaxant responses induced by carbachol; (3) GSH content, and (4) GSH 2 :GSSG ratio. Notably, NaHS administration (5.6 mg/kg) restored hemodynamic variables and lipid peroxidation and attenuated the vasoconstrictor responses induced by NE in the thoracic aorta. In addition, NaHS treatment increased relative adrenal gland weight and the GSH 2 :GSSG ratio. Taken together, our results demonstrate that NaHS alleviates CRS-induced hypertension by reducing oxidative stress and restoring vascular function in the thoracic aorta.

Oral curcumin phytosome supplementation improves anthropometric measures of adiposity and enhances endothelial function in rats on a high-fat-diet regimen

Objectives: Curcumin has a protective role in endothelial function and nitric oxide (NO) production in animal models of different diseases; however, the role of curcumin on aortic reactivity in rats placed on a high-fat diet (HFD) remains unclear. This study aims to determine whether oral curcumin phytosome supplementation can reduce adiposity and enhance endothelial function. Materials and Methods: Rats were assigned to one of three groups: normal diet (ND), HFD for 20 weeks, and HFD supplemented with curcumin phytosome (HFD + Curcumin). Anthropometric measures were recorded weekly for the three groups, until the end of the feeding regimen. After 20 weeks of feeding on HFD, myographic investigations were conducted on thoracic aortic rings dissected from HFD and HFD + Curcumin rats. The response to high potassium chloride (KCl), incremental doses of phenylephrine (Phe) before and after L-NAME treatment, acetylcholine (ACh), or sodium nitroprusside (SNP), was evaluated. ACh-induced relaxation was also assessed in HFD + Curcumin rats, after preincubation with chromium III-mesoporhyrin. Results: HFD rats exhibited increased adiposity measures, some of which were negatively correlated with vasorelaxation response to ACh. HFD + Curcumin rats had reduced anthropometric measures, compared to HFD rats. Aortic rings from HFD and HFD + Curcumin rats exhibited comparable contractile responses to KCl and Phe. The difference in contractile response to Phe before and after L-NAME incubation was greater for HFD + Curcumin rats. ACh induced greater vasorelaxant responses in HFD + Curcumin rats. There was no group difference in the relaxant response to SNP. In HD + Curcumin rats, chromium III mesoporphyrin significantly reduced ACh-induced relaxations. Conclusion: Oral curcumin phytosome supplementation could reduce adiposity in rats placed on an HFD and may have enhanced basal and stimulated NO release from the endothelium, and heme oxygenase-1 may partly mediate this curcumin protective role. This study provides evidence that this curcumin formulation, taken as a daily supplement, may be effective in providing some protection against adiposity-associated adverse cardiovascular disorders.

The roles of NADPH oxidase and PKC pathways in the modulation of GLP-1 induced-vasorelaxation in diabetic rat aorta

A hormone of the incretin system known as glucagon-like peptide-1 (GLP-1) is important for a number of glucoregulatory functions. This study aimed to investigate the effect of inhibitors on the vasorelaxant response of GLP-1 in T1D rats. A single subcutaneous injection of 50 mg/kg of streptozotocin (STZ) was used to develop diabetes mellitus. Eighty aortic rings from twenty male albino rats were prepared. An Automatic Organ Bath was used. In our study, apocynin increased vascular response to GLP- 1 in the non-diabetic group with (Emax:72.40±0.350) and (pD2: -9.923±0.444). In induced diabetes, the NADPH oxidase inhibitor decreased GLP-1 vasodilatation property with (Emax; 68.91±2.002) and (pD2: -9.480±0.138). The results show that bisindolylmaleimide IX (RO31-8220) has an increased effect on GLP-1 vasodilation in non-diabetic groups with (Emax:88.45±38.18) and (pD2: -10.81±0.281). While in induced diabetic rat’s vascular relaxation of GLP-1 decreased with (Emax: 77.73±2.801) and (pD2: - 10.28±0.203). The data analysis demonstrated that rotenone with (Emax: 63.69±35.10) (pD2: - 9.612±0.246), and in diabetic rats with (Emax:69.98±22.94) and (pD2: -9.612±0.246). In our study oxypurinol with (Emax: 82.16±16.10) and (pD2: - 9.434±0.443), and in diabetic rats with (Emax: 58.03±8.350) and (pD2: -9.612±0.246). We concluded that inhibitors could increase the vasorelaxant response of GLP-1 in non-diabetic rats, while this vasorelaxant response of GLP-1 diminished in diabetic-induced rats.

Psiguanol, a novel α-pyrone derivative from Psidium guajava leaves and vasorelaxant activity in rat aorta cells through intracellular cGMP-dependent opening of calcium channels

The phytochemical investigation of Psidium guajava leaves led to the isolation of total nineteen compounds which belongs to meroterpenoids, flavonoid, phenolics, and triterpenoids. The compounds were isolated using extensive chromatography techniques and identified as psiguanol (4), as new compound along with guajadial (1), psidial A (2), β-caryophyllene (3), quercetin (5), avicularin (6), guaijaverin (7), hyperin (8), rutin (9), ursolic acid (10), corosolic acid (11), asiatic acid (12), β-sitosterol (13), β-sitosterol-D-glucoside (14), ellagic acid (15), 3,3',4'-trimethylellagic acid 4-O-glucoside (16), protocatechuic acid (17), gallic acid (18), and tricosanoic acid (19) as known molecules. The compound 16 was isolated for the first time from this plant. The isolated compounds were evaluated for vasorelaxation activity in rat aorta cells and it was observed that compound 4 exhibited the most potent vasorelaxation response in the ex-vivo model in isolated rat aorta cells. Mechanistically, the vasorelaxation activity of 4 was mediated through cGMP-dependent BKCa channel opening.

Vasorelaxant effect of a phenylethylamine analogue based on schwarzinicine A an alkaloid isolated from the leaves of Ficus schwarzii

N-Phenethyl-1-phenyl-pentan-3-amine (1) is a new compound synthesised as a simplified analogue of schwarzinicine A (2), a natural compound extracted from Ficus schwarzii. Compound 1 differs from compound 2 due to its structural simplification, featuring two phenyl rings without methoxy substitution, as opposed to compound 2, which possesses three 3,4-dimethoxy aromatic rings. Our previous research findings highlighted the calcium-inhibitory effects of compound 2, but the mechanism of action for compound 1 remains unexplored, serving as the primary focus of this study. Building upon our earlier research, this study aimed to elucidate compound 1's calcium-modulating potential by using rat-isolated aortae in an organ bath set-up and HEK cells expressing hTRPC channels with the fluorometric assay to measure calcium influx. Compound 1 elicited a vasorelaxation response (Emax 111.4%) similar to its parent compound 2 (Emax 123.1%), and inhibited hTRPC3-, hTRPC4-, hTRPC5-, and hTRPC6-mediated calcium influx into HEK cells with IC50 values of 6, 2, 2, 5 µM, respectively. Compound 1 has a similar pharmacological profile as its parent compound 2, whereby it exerts a vasorelaxant effect by attenuating calcium influx and inhibits multiple TRPC channels.