Vascular Function In Hypertension Research Articles

Current topic of vascular function in hypertension in 2023–2024

AbstractNoninvasive tests of vascular function are useful for assessing the severity of atherosclerosis and risk of cardiovascular events, understanding the pathophysiology of cardiometabolic disorders, and investigating the effects of therapeutic interventions on cardiovascular morbidity and mortality, all of which can provide additional information for the management of patients with cardiovascular risk factors or a history of cardiovascular disease. In 2023–2024, many excellent articles on vascular function were published in Hypertension Research and other major cardiovascular and hypertension journals, and we summarize the emerging evidence on vascular function in this review. We hope that this review will be helpful for the management of patients with cardiovascular risk factors in clinical practice and for future basic and clinical research on vascular function.

Vascular function in hypertension: does gender dimension matter?

Blood pressure and vascular ageing trajectories differ between men and women. These differences develop due to sex-related factors, attributable to sex chromosomes or sex hormones, and due to gender-related factors, mainly related to different sociocultural behaviors. The present review summarizes the relevant facts regarding gender-related differences in vascular function in hypertension. Among sex-related factors, endogenous 17ß-estradiol plays a key role in protecting pre-menopausal women from vascular ageing. However, as vascular ageing (preceding and inducing hypertension) has a steeper increase in women than in men starting already from the third decade, it is likely that gender-related factors play a prominent role, especially in the young. Among gender-related factors, psychological stress (including that one related to gender-based violence and discrimination), depression, some psychological traits, but also low socioeconomic status, are more common in women than men, and their impact on vascular ageing is likely to be greater in women. Men, on the contrary, are more exposed to the vascular adverse consequences of alcohol consumption, as well as of social deprivation, while "toxic masculinity" traits may result in lower adherence to lifestyle and preventive strategies. Unhealthy diet habits are more prevalent in men and smoking is equally prevalent in the two sexes, but have a disproportional negative effect on women's vascular health. In conclusion, given the major and complex role of gender-related factors in driving vascular alterations and blood pressure patterns, gender dimension should be systematically integrated into future research on vascular function and hypertension and to tailor cardiovascular prevention strategies.

Current topic of vascular function in hypertension.

Vascular function assessment is useful for the evaluation of atherosclerosis severity, which may provide additional information for cardiovascular risk stratification. In addition, vascular function assessment is helpful for a better understanding of pathophysiological associations between vascular dysfunction and cardiometabolic disorders. In 2020 and 2021, although coronavirus disease 2019 (COVID-19) was still a worldwide challenge for health care systems, many excellent articles regarding vascular function were published in Hypertension Research and other major cardiovascular and hypertension journals. In this review, we summarize new findings on vascular function and discuss the association between vascular function and COVID-19, the importance of lifestyle modifications for the maintenance of vascular function, and the usefulness of vascular function tests for cardiovascular risk assessment. We hope this review will be helpful for the management of cardiovascular risk factors, including hypertension and cardiovascular diseases, in clinical practice.

Oxidative Regulation of Vascular Cav1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders.

Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca2+ (Cav1.2) channel in small arteries and arterioles plays an essential role in regulating Ca2+ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Cav1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Cav1.2 and potential roles of ROS-mediated Cav1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.

Swimming Exercise Alleviates Endothelial Mitochondrial Fragmentation via Inhibiting Dynamin-Related Protein-1 to Improve Vascular Function in Hypertension.

Regular exercise has been recommended clinically for all individuals to protect against hypertension but the underlying mechanisms are not fully elucidated. We recently found a significant mitochondrial fragmentation in the vascular endothelium of hypertensive human subjects. In this study, we investigated whether exercise could restore endothelial mitochondrial dynamics and thus improve vascular function in hypertension. Vascular endothelial mitochondrial morphological alterations were examined in patients with hypertension and hypertensive animal models. Furthermore, swimming exercise-induced endothelial mitochondrial dynamics and vascular function changes were investigated in spontaneously hypertensive rats (SHRs). Mitochondrial fragmentation with an elevated mitochondrial fission mediator Drp1 (dynamin-related protein-1) was observed in the mesenteric artery endothelium from hypertensive patients. A similar mitochondrial fragmentation with increased Drp1 expression were exhibited in the aortic endothelium of angiotensin II-induced hypertensive mice and SHRs. Interestingly, swimming exercise significantly reduced vascular Drp1 expression and alleviated endothelial mitochondrial fragmentation, thus improving blood pressure in SHRs. In cultured endothelial cells, angiotensin II exposure induced Drp1 upregulation, mitochondrial fragmentation and dysfunction, and reduced nitric oxide production, which was blunted by Drp1 genetic reduction or its inhibitor Mdivi-1. Mdivi-1 administration also ameliorated endothelial mitochondrial fragmentation, vascular dysfunction and blood pressure elevation in SHRs while swimming exercise plus Mdivi-1 treatment provided no additional benefits, suggesting that Drp1 inhibition may partially contribute to swimming exercise-conferred anti-hypertensive effects. These findings suggest that swimming exercise alleviates endothelial mitochondrial fragmentation via inhibiting Drp1, which may contribute to exercise-induced improvement of vascular function and blood pressure in hypertension.

Berberine Improves Vascular Dysfunction by Inhibiting Trimethylamine-N-oxide via Regulating the Gut Microbiota in Angiotensin II-Induced Hypertensive Mice

Berberine (BBR) has been demonstrated to exert cardiovascular protective effects by regulating gut microbiota. However, few studies examine the effect of BBR on the gut microbiota in hypertension. This study aims to investigate the role of BBR in regulating microbial alterations and vascular function in hypertension. C57BL/6 J mice were infused with Ang II (0.8 mg/kg/day) via osmotic minipumps and treated with BBR (150 mg/kg/day) or choline (1%) for 4 weeks. Blood pressure was detected by tail-cuff measurement once a week. Abdominal aorta pulse wave velocity (PWV) and endothelium dependent vasodilatation were measured to evaluate vascular function. Vascular remodeling was assessed by histological staining of aortic tissue. The fecal microbiota was profiled using 16S ribosomal DNA (rDNA) sequencing. Plasma trimethylamine (TMA)/trimethylamine-N-oxide (TMAO) and hepatic FMO3 expression were measured. We found that BBR treatment significantly alleviated the elevated blood pressure, vascular dysfunction, and pathological remodeling in Ang II-induced hypertensive mice, while choline treatment aggravated hypertension-related vascular dysfunction. 16S rDNA gene sequencing results showed that BBR treatment altered gut microbiota composition (reduced the Firmicutes/Bacteroidetes (F/B) ratio and increased the abundances of Lactobacillus). Moreover, BBR inhibited FMO3 expression and plasma TMA/TMAO production in hypertensive mice. TMAO treatment increased the apoptosis and oxidative stress of human aortic endothelial cells (HAECs) and aggravated Ang II-induced HAECs dysfunction in vitro. These results indicate that the protective effect of BBR in hypertension might be attributed (at least partially) to the inhibition of TMAO production via regulating the gut microbiota.

Abstract MP54: Pro-resolving Lipid Mediators Ameliorate Endothelium Dysfunction In Arteries From Hypertensive Rats

Resolution of inflammation is an active phenomenon to switch off the inflammatory processes andfacilitate the return to homeostasis. Increasing the levels of pro-resolving lipid mediators topromote the resolution of inflammation is emerging as a novel therapeutic approach. Arachidonicacid (AA) and docosahexaenoic acid (DHA) are substrates to produce the pro-resolving lipidmediators lipoxin A4 (LXA4) and resolvin D1 (RvD1), respectively. However, it is unknown if thesemediators can ameliorate dysfunction in arteries from hypertensive animals. Therefore, wehypothesized that pro-resolving lipid mediators decrease acetylcholine-induced contractions inarteries from spontaneously hypertensive rats (SHR). Mesenteric resistance arteries from maleSHR and Wistar Kyoto (WKY) (14-weeks old, n=6-8) were used for vascular function via wiremyograph. MRA were incubated with either RvD1 or LXA4 (10 nM, 1 hour) or vehicle prior toconcentration response curves to acetylcholine or phenylephrine (1 nM - 3 μM). We alsoperformed lipidomic analysis on plasma from WKY and SHR. As expected, low concentrations (≤100 nM) of acetylcholine induced relaxation in arteries from both groups, however highconcentrations (≥ 1 μM) of acetylcholine induced contraction in arteries from SHR, but not in WKY[Relaxation to acetylcholine [Area Under the curve (AUC)]: WKY: 396.6 ± 17.7 vs. SHR-control:296.0 ± 26.7*, t-test *vs. WKY, p=0.03). Treatment with the mediators did not change relaxationin arteries from WKY (AUC: Vehicle: 396.6 ±17.7 vs. RvD1: 402.8 ± 18.0; LXA4: 399.0 ± 18.4,p>0.05). However, incubation with RvD1 or LXA4 reduced acetylcholine induced-contraction inarteries from SHR (AUC: Vehicle: 296.0 ± 26.7 vs. RvD1: 372.5 ± 18.5*; LXA4: 376.8 ± 23.6*, t-test *vs. vehicle, p<0.05). Lipidomic analysis showed that precursors for pro-resolving lipidmediators are decreased in SHR [DHA (pmol/mL): WKY: 5637.5 ± 275.3 vs. SHR: 4509.2 ±453.9*, AA: WKY:16018.3 ± 351.3 vs. SHR: 13928.5 ± 959.5 *vs. WKY, p<0.05]. Overall, theseresults suggest that resolution of inflammation and the pro-resolving lipid mediators, RvD1 orLXA4, may be used as a new therapeutic tool to improve vascular function in hypertension.

Pro‐Resolving Lipid Mediators Reduce Acetylcholine‐Induced Contractions in Resistance Arteries from Hypertensive Rats

Aims It is well known that low-grade chronic inflammation induces vascular dysfunction and contributes to hypertension. On the other hand, resolution of inflammation is an active phenomenon to switch off the inflammatory processes once the harmful stimuli is removed and facilitate the return to homeostasis. Increasing the levels of pro-resolving mediators to promote the resolution of inflammation is emerging as a novel therapeutic approach. Arachidonic acid, docosahexaenoic acid, and eicosapentaenoic acid produce pro-resolving lipid mediators lipoxin A4 (LXA4), resolvin D1 (RvD1), and resolvin E1 (RvE1), respectively, through the 5-lipoxygenase enzymatic pathway. However, it is unknown if pro-resolving lipid mediators can ameliorate dysfunction in arteries from hypertensive animals. Therefore, we hypothesized that pro-resolving lipid mediators decrease acetylcholine-induced contractions in arteries from spontaneously hypertensive rats (SHR). Methods Mesenteric resistance arteries (MRA) (lumen diameter ~ 250 µm) from male SHR and Wistar Kyoto (WKY) (14-weeks old, n=3) were collected to assess vascular function via wire myograph. After testing vascular smooth muscle cell integrity, MRA were incubated with either RvD1, RvE1, or LXA4 (10 nM, 1 hour) or vehicle prior to concentration response curves to acetylcholine (1 nM - 3 µM). Phenylephrine (10 µM) was used to contract the arteries prior relaxation curves. Results As expected, low concentrations (≤ 100 nM) of acetylcholine induced relaxation in arteries from both groups, however high concentrations (≥ 1 µM) of acetylcholine induced contraction in arteries from SHR, but not in WKY [Maximum response (Emax): WKY: 94.5 ± 3.3 vs. SHR-control: 44.9 ± 12.5* %, t-test *vs. WKY, p=0.01). Treatment with the pro-resolving lipid mediators did not change acetylcholine-induced relaxation in arteries from WKY (Vehicle: 94.5 ±3.3 vs. RvD1: 95.8 ± 0.8; RvE1: 90.1 ± 7.1; LXA4: 93.5 ± 3.9 %, p>0.05). However, incubation with RvE1 abolished acetylcholine induced-contraction in arteries from SHR and promoted relaxation (Vehicle: 44.9 ± 12.5 vs. RvE1: 94.1 ± 3.5%,* t-test *vs. vehicle, p<0.05). While acetylcholine-induced contraction abolishment from incubation with RvD1 and LXA4 did not reach significance due to small sample size in arteries from SHR, we did observe a tendency towards improvement. Conclusion Overall, these results suggest that pro-resolving lipid mediators biosynthesized from the 5-lipoxygenase enzymatic pathway improved endothelium-dependent relaxation in arteries from hypertensive animals. As docosahexaenoic acid and eicosapentaenoic acid are already recommended to protect against many cardiovascular diseases, our work suggests that RvD1, RvE1, or LXA4 may also be used as a new therapeutic tool to specifically improve vascular function in hypertension.

Effects of Enhanced Intracranial Pressure on Blood Pressure and the Cardio-Ankle Vascular Index in Rabbits.

Aim: Stroke is well known to lead to hypertension; nevertheless, the role of vascular function in hypertension remains unclear. In this study, we aimed to clarify the mechanism underlying increased arterial stiffness following stroke. Methods: The cardio-ankle vascular index (CAVI) was measured in five New Zealand White rabbits. Under general anesthesia, intracranial pressure (ICP) was increased by injecting saline (15 mL) into the cisterna magna. ICP was monitored using a catheter inserted into the subarachnoid space via right frontal bone craniotomy. Blood pressure (BP), CAVI, and common carotid flow (CCF) were evaluated, and the responses of these parameters to increased ICP were analyzed. Results: Saline injection into the cisterna magna increased the ICP by over 20 mmHg. Both BP and CAVI increased from 63.2±4.84 to 128.8±14.68 mmHg and from 4.02±0.28 to 4.9±0.53, respectively. Similarly, BP and CCF increased. When hexamethonium was administered before the increase in ICP, the increase in BP (132.2±9.41 mmHg with 10 mg/kg hexamethonium vs. 105.6±11.01 mmHg with 100 mg/kg hexamethonium) and CAVI (5.02±0.64 with 10 mg/kg hexamethonium vs. 4.82±0.42 with 100 mg/kg hexamethonium) were suppressed in a dose-dependent manner. Conclusion: Increased ICP causes an increase in BP and CAVI, suggesting that enhanced stiffness of the muscular arteries contributes to high BP. Blocking the autonomic nervous system with hexamethonium suppresses the increase in BP and CAVI, indicating that these increases are mediated by activation of the autonomic nervous system.

Influence of dietary inorganic nitrate on blood pressure and vascular function in hypertension: prospective implications for adjunctive treatment.

Dietary inorganic nitrate (nitrate) is a promising adjunctive treatment to reduce blood pressure and improve vascular function in hypertension. However, it remains unknown if the efficacy of nitrate is dependent upon an elevated blood pressure or altered by medication in patients with hypertension. Therefore, blood pressure and vascular function, measured by passive leg movement (PLM) and flow-mediated dilation (FMD), were assessed following 3 days of placebo (nitrate-free beetroot juice) and nitrate (nitrate-rich beetroot juice) administration in 13 patients (age: 53 ± 12 yr) with hypertension taking antihypertensive medications (study 1) and in 14 patients (49 ± 13 yr) with hypertension not taking antihypertensive medications (study 2). In study 1, plasma nitrite concentration was greater for nitrate than placebo (341 ± 118 vs. 308 ± 123 nmol/L, P < 0.05), yet blood pressure and vascular function were unaltered. In study 2, plasma nitrite concentration was greater for nitrate than placebo (340 ± 102 vs. 295 ± 93 nmol/L, P < 0.01). Systolic (136 ± 16 vs. 141 ± 19 mmHg), diastolic (84 ± 13 vs. 88 ± 12 mmHg), and mean (101 ± 12 vs. 106 ± 13 mmHg) blood pressures were lower (P < 0.05), whereas the PLM change in leg vascular conductance (6.0 ± 3.0 vs. 5.1 ± 2.6 mL·min-1·mmHg-1) and FMD (6.1 ± 2.4% vs. 4.1 ± 2.7%) were greater (P < 0.05) for nitrate than placebo. The changes in systolic blood pressure (r = -0.60) and FMD (r = -0.48) induced by nitrate were inversely correlated (P < 0.05) to the respective baseline values obtained in the placebo condition. Thus, the efficacy of nitrate to improve blood pressure and vascular function in hypertension appears to be dependent on the degree of blood pressure elevation and vascular dysfunction and not antihypertensive medication status, per se.NEW & NOTEWORTHY Dietary nitrate (nitrate) is a promising intervention to improve blood pressure and vascular function in hypertension. We demonstrate that these beneficial effects of nitrate are inversely related to the baseline value in a continuous manner with no distinction between antihypertensive medication status. Thus, the efficacy of nitrate to improve blood pressure and vascular function in hypertension appears to be dependent on the degree of blood pressure elevation and vascular dysfunction and not antihypertensive mediation status.

Resistin Mediates Sex-Dependent Effects of Perivascular Adipose Tissue on Vascular Function in the Shrsp

Premenopausal women are relatively protected from developing hypertension compared to men. Perivascular adipose tissue (PVAT) has been shown to mediate vasoactive effects; however, a sex-dependent difference in PVAT function in the setting of hypertension has not yet been explored. We investigated the effect of PVAT on resistance vessel biology in male and female 16 week old stroke prone spontaneously hypertensive rats (SHRSP). This preclinical model of hypertension exhibits a sex-dependent difference in the development of hypertension similar to humans. Wire myography was used to assess vascular function in third-order mesenteric arteries. KATP channel-mediated vasorelaxation by cromakalim was significantly impaired in vessels from SHRSP males + PVAT relative to females (maximum relaxation: male + PVAT 46.9 ± 3.9% vs. female + PVAT 97.3 ± 2.7%). A cross-over study assessing the function of male PVAT on female vessels confirmed the reduced vasorelaxation response to cromakalim associated with male PVAT (maximum relaxation: female + PVATfemale90.6 ± 1.4% vs. female + PVATmale65.8 ± 3.5%). In order to explore the sex-dependent differences in PVAT at a molecular level, an adipokine array and subsequent western blot validation identified resistin expression to be increased approximately 2-fold in PVAT from male SHRSP vessels. Further wire myography experiments showed that pre-incubation with resistin (40 ng/ml) significantly impaired the ability of female + PVAT vessels to relax in response to cromakalim (maximum relaxation: female + PVAT 97.3 ± 0.9% vs. female + PVAT + resistin[40ng/ml]36.8 ± 2.3%). These findings indicate a novel role for resistin in mediating sex-dependent vascular function in hypertension through a KATP channel-mediated mechanism.

Metformin prevents vascular damage in hypertension through the AMPK/ER stress pathway.

Metformin is an antidiabetic drug. However, the pleiotropic beneficial effects of metformin in nondiabetic models still need to be defined. The objective of this study is to investigate the effect of metformin on angiotensin II (Ang II)-induced hypertension and cardiovascular diseases. Mice were infused with Ang II (400 ng/kg per min) with or without metformin for 2 weeks. Mice infused with angiotensin II displayed an increase in blood pressure associated with enhanced vascular endoplasmic reticulum (ER) stress markers, which were blunted after metformin treatment. Moreover, hypertension-induced reduction in phosphorylated AMPK, endothelial nitric oxide synthase (eNOs) phosphorylation, and endothelium-dependent relaxation (EDR) in mesenteric resistance arteries (MRA) were rescued after metformin treatment. Infusion of ER stress inducer (tunicamycin, Tun) in control mice induced ER stress in MRA and reduced phosphorylation of AMPK, eNOS synthase phosphorylation, and EDR in MRA without affecting systolic blood pressure (SBP). All these factors were reversed subsequently with metformin treatment. ER stress inhibition by metformin improves vascular function in hypertension. Therefore, metformin could be a potential therapy for cardiovascular diseases in hypertension independent of its effects on diabetes.

A9595 Crosstalk Between Vascular Redox and Calcium Signalling in Hypertension Involves Transient Receptor Potential Melastatin 2 Channel Activation

Objectives: ROS regulates Ca2+ homeostasis by mechanisms still not fully understood. TRPM2, a redox-sensitive channel permeable to Ca2+ and Na+, is activated by H2O2 via oxidation or ADPR production. We tested the hypothesis that TRPM2 is a molecular target of ROS leading to regulation of Ca2+ levels and vascular function in hypertension. Methods: VSMCs from normotensive and hypertensive subject were used. Ca2+ and Na+ influx was assessed by fluorescence microscopy. Results: O2- (1.65 fold) and H2O2 (1.88 fold) generation were enhanced in VSMCs from hypertensive subjects (p < 0.05). Ca2+ (AUC: 1.36 fold) and Na+ influx (AUC: 1.2 fold) were also increased in cells from hypertensive subjects (p < 0.05), an effect blocked by PEG-catalase and, 2-APB, 8-br or olaparib (TRPM2 inhibitors). Additionally, in the absence of Na+, [Ca2+]i was reduced to levels detected in cells from normotensive subjects. TRPM2-induced Na+ influx may influence the sodium-calcium exchanger (NCX), which in reverse mode, promotes Ca2+ influx. Benzamil, KB-R7943 and YM244769 (NCX inhibitors) also ameliorated the increased Ca2+ influx observed in hypertension. MLC20 activation, a marker of cell contraction, was increased in VSMCs from hypertensive subjects (1.72 fold), an effect reversed by TRPM2 and NCX inhibitors (p < 0.05). Arteries from hypertensive mice exhibit increased TRPM2 (1.5 fold) and NCX (1.9 fold) mRNA expression and increased U46619-induced vasoconstriction (Emax: 7.6 ± 0.2 vs 10.21 ± 0.3), effect reversed by TRPM2 and NCX inhibitors (p < 0.05). Conclusion: In conclusion, activation of redox-dependent TRPM2 channel contributes to increased calcium and sodium influx, partially through NCX activation. The results highlight a novel pathway linking ROS to Ca2+ and Na+ signalling through TRPM2/NCX, leading to vascular dysfunction in hypertension.

Vascular Nox (NADPH Oxidase) Compartmentalization, Protein Hyperoxidation, and Endoplasmic Reticulum Stress Response in Hypertension.

Vascular Nox (NADPH oxidase)-derived reactive oxygen species and endoplasmic reticulum (ER) stress have been implicated in hypertension. However, relationships between these processes are unclear. We hypothesized that Nox isoforms localize in a subcellular compartment-specific manner, contributing to oxidative and ER stress, which influence the oxidative proteome and vascular function in hypertension. Nox compartmentalization (cell fractionation), O2- (lucigenin), H2O2 (amplex red), reversible protein oxidation (sulfenylation), irreversible protein oxidation (protein tyrosine phosphatase, peroxiredoxin oxidation), and ER stress (PERK [protein kinase RNA-like endoplasmic reticulum kinase], IRE1α [inositol-requiring enzyme 1], and phosphorylation/oxidation) were studied in spontaneously hypertensive rat (SHR) vascular smooth muscle cells (VSMCs). VSMC proliferation was measured by fluorescence-activated cell sorting, and vascular reactivity assessed in stroke-prone SHR arteries by myography. Noxs were downregulated by short interfering RNA and pharmacologically. In SHR, Noxs were localized in specific subcellular regions: Nox1 in plasma membrane and Nox4 in ER. In SHR, oxidative stress was associated with increased protein sulfenylation and hyperoxidation of protein tyrosine phosphatases and peroxiredoxins. Inhibition of Nox1 (NoxA1ds), Nox1/4 (GKT137831), and ER stress (4-phenylbutyric acid/tauroursodeoxycholic acid) normalized SHR vascular reactive oxygen species generation. GKT137831 reduced IRE1α sulfenylation and XBP1 (X-box binding protein 1) splicing in SHR. Increased VSMC proliferation in SHR was normalized by GKT137831, 4-phenylbutyric acid, and STF083010 (IRE1-XBP1 disruptor). Hypercontractility in the stroke-prone SHR was attenuated by 4-phenylbutyric acid. We demonstrate that protein hyperoxidation in hypertension is associated with oxidative and ER stress through upregulation of plasmalemmal-Nox1 and ER-Nox4. The IRE1-XBP1 pathway of the ER stress response is regulated by Nox4/reactive oxygen species and plays a role in the hyperproliferative VSMC phenotype in SHR. Our study highlights the importance of Nox subcellular compartmentalization and interplay between cytoplasmic reactive oxygen species and ER stress response, which contribute to the VSMC oxidative proteome and vascular dysfunction in hypertension.

Abstract P504: Resistin Mediates Sex-dependent Effects of Perivascular Adipose Tissue on Vascular Function in the SHRSP

Background: Premenopausal women are relatively protected against hypertension compared to males. Estrogen levels have been identified as a potential underlying cause, but the pathophysiological mechanisms remain incompletely understood. We hypothesised that sex-dependent effects of perivascular adipose tissuePVAT mediate altered vascular function in hypertension. Methods: The effect of PVAT was investigated on resistance vessels of 16 week old male and female stroke-prone spontaneously hypertensive rats (SHRSP). Results: Wire myography was used on 3 rd -order mesenteric vessels (maximum contraction: male +PVAT 113.3±1.1 vs. female +PVAT 91.4±11.36 %). Noradrenaline mediated vasoconstriction was increased in SHRSP males compared to females. K ATP channel-mediated vasorelaxation by cromakalim was impaired in males compared to females (maximum relaxation: male +PVAT 46.9±3.9 % vs. female +PVAT 97.3±2.7 %) A cross-over study assessing function of male PVAT on female vessels and vice versa confirmed the reduced K ATP mediated vasorelaxation induced by male PVAT (maximum relaxation: female +PVAT female 90.6±1.4 % vs. female +PVAT male 65.8±3.5 %). An adipokine array with subsequent western blot validation identified resistin as a potential modifier of vascular reactivity. Resistin was increased by approximately 2-fold in SHRSP male PVAT. Male and female vessels pretreated with resistin (40ng/ml) showed no difference in response to noradrenaline. However, vasorelaxation in response to cromakalim was significantly impaired in resistin treated female vessels, similar to levels observed in male vessels (maximum relaxation: female +PVAT 97.3±0.9 % vs. female +PVAT +resistin 36.8 ±2.3 %). Conclusion: We identified a novel role for resistin in sex-dependent PVAT mediated vascular function in hypertension through a K ATP channel mediated mechanism.

Abstract P219: Vascular Cross-talk Between Redox and Calcium Signaling in Hypertension Involves Transient Receptor Potential Melastatin 2 Channel Activation

The transient receptor potential melastatin 2 cation channel (TRPM2) is redox-sensitive and promotes Ca 2+ influx after H 2 O 2 activation through oxidative modification and PARP-ADPR-dependent mechanisms. TRPM2 also regulates Na + influx, and by increasing [Na + ]i interferes with the Na + -Ca 2+ exchanger (NCX) inducing reverse mode action, promoting Ca 2+ influx. These processes may be driven by Nox4-derived H 2 O 2. We tested the hypothesis that vascular dysfunction in hypertension involves oxidative stress-induced TRPM2 activation through H 2 O 2 production, which in turn promotes Ca 2+ influx. Mesenteric arteries isolated from wildtype (WT), LinA3 (mice expressing human renin with Ang II-dependent hypertension), Nox4 -/- and LinA3/Nox4 -/- mice and vascular smooth muscle cells (VSMCs) from hypertensive and normotensive patients were used. Arteries from hypertensive LinA3 mice, exhibit increased U46619-induced vasoconstriction versus WT mice (Emax - LinA3 vs WT: 9.37 ± 0.51 vs 6.79 ± 0.29), an effect attenuated by olaparib (PARP-ADPR inhibitor) and 2-APB (TRPM2 blocker) and also increased mRNA expression (Fold change - related to control) of NOX4 (3.05 ± 0.30), TRPM2 (1.38 ± 0.24), NCX (1.973 ± 0.34) and salt inducible kinase 1 (1.833 ± 0.12) and sodium-potassium pump (1.43 ± 0.16), which are activated when intracellular levels of Na + rise beyond a critical point. These events seem to be regulated by NOX4, since they were not observed in mesenteric arteries from LinA3/Nox4 -/- mice. Ang II-induced Ca 2+ influx is potentiated in VSMCs from hypertensive patients (AUC-Ex490/Em535: normotensive: 15400±917.5 vs hypertensive - 22460±2388), a response followed by increased generation of O 2 - and H 2 O 2 in cells from hypertensive patients. These ROS effects were attenuated by catalase, and 2-APB, 8-br and olaparib (TRPM2 inhibitors) and benzamil, KB-R7943 and YM244769 (NCX inhibitors). Our data indicate that TRPM2 ion channel activation contributes to redox-sensitive vascular dysfunction in hypertension. These findings suggest that dysregulation of TRPM2-NOX4-derived ROS and NCX may contribute to redox- and Ca 2+ signalling important in vascular function in hypertension. TRPM2 may be a point of cross-talk between ROS and Ca 2+ signalling.

PP.22.23] VASCULAR ENDOTHELIAL GROWTH FACTOR RECEPTOR INHIBITION INDUCES VASCULAR DYSFUNCTION VIA REDOX-SENSITIVE AND NITRIC OXIDE-DEPENDENT PATHWAYS

Objective: Vascular endothelial growth factor (VEGF)/ VEGF receptor (VEGFR) inhibitors, used as anti-angiogenic drugs to treat cancer, induce severe hypertension. Molecular mechanisms whereby VEGF inhibitors cause hypertension are unclear, but nitric oxide (NO) and oxidative stress may be involved. We questioned whether reactive oxygen species (ROS), important regulators of vascular function in hypertension, also play a role in VEGF inhibitor-induced vascular dysfunction. Design and method: Human microvascular endothelial cells (HMECs) were stimulated with vatalanib (VEGFR inhibitor) and gefitinib (EGFR inhibitor). Normotensive male SV-129 mice were treated with Vatalanib (100 mg/Kg/day) or Gefitinib (100 mg/Kg/day). Vascular reactivity was performed in mesenteric arteries. Phosphorylation of eNOS was assessed by immunoblotting. ROS were measured by amplex red, lucigenin and nitrotyrosine elisa. TBARS levels were measured by lipid peroxidation assay kit and catalase activity by amplex red. Nox and antioxidant enzymes mRNA was analysed by qPCR. Results: No changes in blood pressure were observed in animals treated with vatalanib on this dose. However acetylcholine-induced vasodilatation was impaired in those mice and phosphorylation of eNOS activation site (Ser1177) was decreased, while no changes were observed after exposure of HMECs to gefitinib. Hydrogen peroxide (H2O2) levels were reduced in HMECs stimulated with vatalanib and in aorta and heart from vatalanib-treated mice. This effect was followed by an increase in catalase activity and a decrease in Nox 4 mRNA expression while Nox5 mRNA levels were increase by vatalanib. VEGF inhibition also increased peroxynitrite levels in aorta and kidney and increased plasma TBARS levels. In kidney vatalanib increased H2O2 and superoxide anion production which was followed by a decrease in catalase activity and Nrf2 nuclear translocation. mRNA levels of antioxidant enzymes in HMECs, kidney and heart were decreased after exposure to vatalanib. Gefitinib only increased catalase activity and peroxynitrite levels in heart as well as decreased Nrf2 nuclear translocation in kidney from mice. Conclusions: In conclusion, our data identify novel mechanisms whereby VEGFR inhibition modulates NO signalling, antioxidant defences and ROS production in tissues and endothelial cells. These molecular processes may contribute to reduced vasorelaxation and may play a role on VEGFRI-induced hypertension.

224 Vascular endothelial growth factor receptor inhibition induces vascular dysfunction via redox-sensitive processes

Vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) inhibitors, used as anti-angiogenic drugs to treat cancer, induce severe hypertension. Molecular mechanisms whereby VEGF inhibitors cause hypertension are unclear, but nitric oxide...

6 Resistin mediates sex-dependent effects of perivascular adipose tissue on vascular function in the shrsp

Introduction Premenopausal women are relatively protected against hypertension compared to males. Oestrogen levels have been identified as a potential underlying cause, but many of the pathophysiological mechanisms remain to be determined. Altered perivascular adipose tissue (PVAT) function has been identified to have vasoactive effects. However, in hypertension, sex-dependent differences of PVAT have not yet been explored. Hypothesis Sex-dependent effects of PVAT mediate altered vascular function in hypertension. Approach and result The effect of PVAT was investigated on resistance vessels of 16 week old male and female stroke-prone spontaneously hypertensive rats (SHRSP). This preclinical model of hypertension presents with a sex-difference in the development of hypertension comparable to humans. Wire-myography was used on 3rd order mesenteric vessels to assess vascular function. Noradrenaline mediated vasoconstriction was increased in SHRSP males compared to females (maximum contraction: male +PVAT 113.3±1.1% vs female +PVAT 91.4%±11.36%). KATP channel-mediated vasorelaxation by cromakalim was impaired in males compared to females (maximum relaxation: male +PVAT 46.9±3.9% vs female +PVAT 97.3%±2.7%). A cross-over study assessing function of male PVAT on female vessels and vice versa confirmed the reduced KATP mediated vasorelaxation induced by male PVAT (maximum relaxation: female +PVATfemale 90.6±1.4% vs female +PVATmale 65.8%±3.5%). To explore the cause of sex-dependent differences in PVAT an adipokine array with subsequent western blot validation was carried out. This identified resistin as a potential modifier of vascular reactivity. Resistin was increased by approximately 2-fold in SHRSP male mesenteric PVAT. Further wire-myography experiments with male and female vessels pre-treated with resistin (40 ng/ml) showed no difference in response to noradrenaline. However, vasorelaxation in response to cromakalim was significantly impaired in resistin treated female vessels, similar to levels observed in male vessels (maximum relaxation: female +PVAT 97.3±0.9% vs female +PVAT +resistin[40 ng/ml] 36.8%±2.3%). Conclusion These findings indicate a novel role for resistin in sex-dependent PVAT mediated vascular function in hypertension through a KATP channel mediated mechanism.

Interlobular Arteries From 2-Kidney, 1-Clip Goldblatt Hypertensive Rats’ Exhibit-Impaired Vasodilator Response to Epoxyeicosatrienoic Acids

BackgroundSmall renal arteries have a significant role in the regulation of renal hemodynamics and blood pressure (BP). To study potential changes in the regulation of vascular function in hypertension, we examined renal vasodilatory responses of small arteries from nonclipped kidneys of the 2-kidney, 1-clip Goldblatt hypertensive rats to native epoxyeicosatrienoic acids (EETs) that are believed to be involved in the regulation of renal vascular function and BP. A total of 2 newly synthesized EET analogues were also examined. Materials and MethodsRenal interlobular arteries isolated from the nonclipped kidneys on day 28 after clipping were preconstricted with phenylephrine, pressurized and the effects of a 14,15-EET analogue, native 14,15‐EET and 11,12‐ether-EET‐8ZE, an analogue of 11,12-EET, on the vascular diameter were determined and compared to the responses of arteries from the kidneys of sham-operated rats. ResultsIn the arteries from nonclipped kidneys isolated in the maintenance phase of Goldblatt hypertension, the maximal vasodilatory response to 14,15-EET analogue was 30.1 ± 2.8% versus 49.8 ± 7.2% in sham-operated rats; the respective values for 11,12-ther-EET-8ZE were 31.4 ± 6.4% versus 80.4 ± 6%, and for native EETs they were 41.7 ± 6.6% versus 62.8 ± 4.4% (P ≤ 0.05 for each difference). ConclusionsWe propose that reduced vasodilatory action and decreased intrarenal bioavailability of EETs combined with intrarenal angiotensin II levels that are inappropriately high for hypertensive rats underlie functional derangements of the nonclipped kidneys of 2-kidney, 1-clip Goldblatt hypertensive rats. These derangements could play an important role in pathophysiology of sustained BP elevation observed in this animal model of human renovascular hypertension.