Vascular Function In Hypertension Research Articles

Low-salt diet increases NO bioavailability and COX-2 vasoconstrictor prostanoid production in spontaneously hypertensive rats

AimsThe ability of dietary sodium restriction to reduce the incidence of cardiovascular mortality and improve vascular function in hypertension still remains poorly understood. The aim of this study was to observe the effects of a long period of salt restriction on the vascular reactivity of mesenteric resistance arteries of SHRs. MethodsMale SHRs received either standard-salt diet (0.3% NaCl) or low-salt diet (0.03% NaCl) for 28weeks. Vascular reactivity was studied in mesenteric artery segments and the influence of cyclooxygenase-2 (COX-2), reactive oxygen species (ROS) and participation of the renin-angiotensin system were analyzed. Key findingsDecreased salt intake did not affect phenylephrine-induced vasoconstriction but increased acetylcholine-induced vasodilatation and also increased the response to phenylephrine after inhibition of NO synthase by L-NAME (100μM) and iNOS protein expression was elevated. Cyclooxygenase inhibitor indomethacin (10μM) and COX-2 inhibitor NS 398 (1μM) decreased the reactivity to phenylephrine in low-salt-treated group, and COX-2 protein expression was elevated in low-salt group. The effects of apocynin (10μM); superoxide anion scavenger, tiron (1mM); hydrogen peroxide scavenger, catalase (1000UmL−1); and ACE and AT1 receptor blockers, enalapril (10μM) and losartan (10μM) on vascular reactivity were not different between two groups. The levels of AT1 protein expression were similar in both groups. SignificanceLow-salt diet modulates mesenteric vascular responses via increased NO bioavailability suggested by increased iNOS protein expression and vasoconstrictor prostanoid production via COX-2 pathway, in SHRs. Neither ROS nor the local renin-angiotensin system is involved in these responses.

Heme oxygenase-1 suppresses a pro-inflammatory phenotype in monocytes and determines endothelial function and arterial hypertension in mice and humans.

Heme oxygenase-1 (HO-1) confers protection to the vasculature and suppresses inflammatory properties of monocytes and macrophages. It is unclear how HO-1 determines the extent of vascular dysfunction in mice and humans. Decreased HO-1 activity and expression was paralleled by increased aortic expression and activity of the nicotinamide dinucleotide phosphate oxidase Nox2 in HO-1 deficient Hmox1⁻/⁻ and Hmox1(⁺/⁻) compared with Hmox1⁺/⁺ mice. When subjected to angiotensin II-infusion, streptozotocin-induced diabetes mellitus and aging, HO-1 deficient mice showed increased vascular dysfunction inversely correlated with HO activity. In a primary prevention population-based cohort, we assessed length polymorphisms of the HMOX1 promoter region and established a bipolar frequency pattern of allele length (long vs. short repeats) in 4937 individuals. Monocytic HMOX1 mRNA expression was positively correlated with flow-mediated dilation and inversely with CD14 mRNA expression indicating pro-inflammatory monocytes in 733 hypertensive individuals of this cohort. Hmox1⁻/⁻ mice showed drastically increased expression of the chemokine receptor CCR2 in monocytes and the aorta. Angiotensin II-infused Hmox1⁻/⁻ mice had amplified endothelial inflammation in vivo, significantly increased aortic infiltration of pro-inflammatory CD11b⁺ Ly6C(hi) monocytes and Ly6G⁺ neutrophils and were marked by Ly6C(hi) monocytosis in the circulation and an increased blood pressure response. Finally, individuals with unfavourable HMOX1 gene promoter length had increased prevalence of arterial hypertension and reduced cumulative survival after a median follow-up of 7.23 years. Heme oxygenase-1 is a regulator of vascular function in hypertension via determining the phenotype of inflammatory circulating and infiltrating monocytes with possible implications for all-cause mortality.

Abstract P097: Molecular Mechanisms of VEGFR Inhibition-induced Endothelial Cell Damage

VEGF/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) and Ang II, important regulators of vascular function in hypertension, also play a role in VEGF inhibitor-induced vascular dysfunction. Human microvascular endothelial cells (HMECs) were stimulated with vatalanib (VAT-VEGFR inhibitor) and gefitinib (GEF-EGFR inhibitor) in the absence/presence of Ang II. Activation of eNOS and MAPKs were assessed by immunoblotting. Antioxidant enzyme mRNA was analysed by qPCR. Microparticle levels were measured by flow cytometry. Endothelial microparticles, biomarkers of endothelial damage, tend to increase in subjects treated with VEGFR inhibitors. Phosphorylation of eNOS activation site (Ser1177) (28.3% ± 7.1) was decreased by VAT, while no changes were observed after exposure of HMECs to GEF (p<0.05). VAT decreased mRNA expression of Nox4 (0.5 ± 0.2) and H2O2-regulating antioxidants enzymes such as catalase (0.4 ± 0.1) and glutathione peroxidase (0.4 ± 0.1), while increased mRNA levels of Nox5 (3.35±1.1) (p<0.05 vs. veh). Ang II stimulation increased eNOS (171.2% ± 17.4) and ERK1/2 (177.5% ± 38.5) activation (p<0.05); all effects were blocked only by GEF. Inhibition of VEGFR also blocked Ang II effects on SOD1 (1.33 ± 0.1), HO-1 (1.6 ± 0.3) and NQO1 (1.6 ± 0.3) mRNA levels (p<0.05). In addition, Ang II increased Nox4 mRNA expression through VEGFR-dependent mechanisms. VEGFR1/2 and AT2R, but not AT1R, were expressed in HMEC. Ang II effects on eNOS phosphorylation were inhibited by PD123319 (AT2R antagonist) but not by losartan (AT1R antagonist). In conclusion, our data identify novel mechanisms whereby AngII, possibly through AT2R-dependent VEGFR transactivation, regulates eNOS activation, MAPK signalling and H2O2-related antioxidant enzymes. In addition to changes in NO availability, VEGFR inhibition may interfere with the redox status of endothelial cells, leading to vascular dysfunction and hypertension.

Increased plasma neopterin levels are associated with reduced endothelial function and arterial elasticity in hypertension.

Inflammation has been shown to play a pivotal role in the pathogenesis and development of hypertensive vascular injury. Neopterin is a novel marker of immune activation produced mainly by activated macrophages. Few data are available to show the association between neopterin and vascular function in hypertension. The present study was designed to investigate the relationship between neopterin levels related to arterial stiffness and endothelial function in patients with hypertension, and their changes after blood pressure-lowering treatment. Twenty-four hypertensive patients and 30 age- and gender-matched healthy volunteers were recruited. Plasma neopterin levels were higher in hypertensive patients compared with their counterparts (log-neopterin: 0.77±0.18 versus 0.61±0.16, P=0.003). Increased neopterin levels were correlated with increased brachial-ankle pulse wave velocity (baPWV; control: r=0.659, P<0.001; hypertension: r=0.487, P=0.021), and inversely associated with impaired brachial flow-mediated dilation (FMD; control: r=-0.735, P<0.001; hypertension: r=-0.557, P=0.005). Fifteen hypertensives received 3 months of standard antihypertensive treatment. Three months later, their plasma neopterin levels decreased (log-neopterin: 0.63±0.17 versus 0.50±0.19, P=0.001), whereas arterial elasticity (baPWV: 1764±101 versus 1685±96 cm s(-1), P=0.272) and endothelial function (FMD: 5.92±1.43% versus 7.73±1.31%, P<0.05) were improved. The decline in neopterin levels was linearly correlated with baPWV decrease (r=0.800, P<0.001), FMD improvement (r=0.670, P=0.006) and blood pressure reduction (r=0.548, P=0.042). Our present study demonstrated for the first time that neopterin is closely correlated with vascular dysfunctions, and measurement of plasma neopterin levels might be used as a surrogate biomarker for the clinical evaluation of vascular damage and risk stratification of future atherosclerotic cardiovascular disease in patients with hypertension.

Abstract 18540: Heme Oxygenase 1 Activity and Expression Suppresses a Proinflammatory Phenotype in Monocytes and Correlates With Endothelial Function in Mice and Humans

Background: Heme oxygenase-1 (HO-1) confers protection to the vasculature and suppresses inflammatory properties of monocytes and macrophages. It is unclear how HO-1 activity and expression determine the extent of vascular dysfunction in mice and humans. Methods and results: Decreasing HO activity was parallelled by decreasing aortic HO-1, eNOS and phospho-eNOS (ser1177) protein expression in HO-1 deficient mice, whereas aortic expression of nox2 showed a stepwise increase in HO-1+/- and HO-1-/- mice as compared to HO-1+/+ controls. Aortic superoxide formation increased depending on the extent of HO-1 deficiency and was blunted by the PKC inhibitor chelerythrine, indicating activation of the NADPH oxidase. When subjected to disease models of vascular dysfunction - angiotensin II-infusion (ATII, 0.1mg/kg/d for 7d), streptozotocin-induced diabetes mellitus and aging - HO-1 deficient mice showed an increased vascular dysfunction (shown by isometric tension studies) that was inversely correlated with HO activity. In a primary prevention population based cohort (the Gutenberg Health Study, GHS), we assessed length polymorphisms of the HO-1 promoter region, established a bipolar frequency pattern of allele length (long vs short repeats) in 4937 individuals and found a moderately significant association with flow mediated dilation of the brachial artery (FMD) in individuals with arterial hypertension. Monocytic HO-1 mRNA expression was positively correlated with CD14 expression indicating proinflammatory monocytes (p&lt;0.001) and inversely with FMD in 733 hypertensive individuals of the GHS. ATII-infused HO-1+/+ mice had a significant infiltration of proinflammatory CD11b+Ly6Chi monocytes into the aortic wall, which was sharpely increased in HO-1+/- and HO-1-/- mice, providing a mechanistic link of the monocyte phenotype determined by HO-1 and vascular dysfunction in arterial hypertension. Conclusions: We here present evidence that HO activity and expression and inversely correlates with vascular dysfunction and NADPH oxidase mediated oxidative stress in mice and humans. We conclude, that HO-1 is a regulator of vascular function in hypertension via determining the phenotype of inflammatory circulating and infiltrating monocytes.

Abstract 340: Novel Molecular Mechanisms Involved In VEGFR Inhibition In Human Endothelial Cells

VEGF/VEGFR inhibitors are increasingly being used as anti-angiogenic drugs to treat cancer. However these drugs are limited by the development of severe hypertension. Molecular mechanisms whereby VEGF inhibitors cause hypertension are unclear, but nitric oxide (NO) signalling may be involved. We questioned whether reactive oxygen species (ROS) and Ang II, important regulators of vascular function in hypertension, also play a role in VEGF inhibitor-induced vascular dysfunction. Human microvascular endothelial cells (HMECs) were stimulated with vatalanib (VAT-VEGFR inhibitor) and gefitinib (GEF-EGFR inhibitor) in the absence/presence of Ang II. Activation of eNOS and MAPKs were assessed by immunoblotting. Antioxidant enzyme mRNA was analyzed by qPCR. Phosphorylation of eNOS activation site (Ser1177) (28.3% ± 7.1) and p38 MAPK (55.4% ± 2.4) was decreased by VAT, while no changes were observed after exposure of HMECs to GEF (p&lt;0.05). VAT also decreased mRNA expression of Nox4 (0.5 ± 0.2), and H2O2-related antioxidants enzymes such as catalase (0.4 ± 0.1) and glutathione peroxidase (0.4 ± 0.1). Ang II stimulation increased eNOS (171.2% ± 17.4), ERK1/2 (177.5% ± 38.5), p38 MAPK (186.9% ± 36.6) activation (p&lt;0.05); an effect blocked by VAT and GEF. Inhibition of VEGFR also blocked Ang II effects on SOD1 (1.33 ± 0.1), HO-1 (1.6 ± 0.3) and NQO1 (1.6 ± 0.3) mRNA levels (p&lt;0.05). In addition, Ang II increased Nox4 mRNA expression through VEGFR-dependent mechanisms. Interestingly, VEGFR1/2 and AT2R were expressed in HMEC, but not AT1R. Ang II effects on eNOS phosphorylation were inhibited by PDE123 (AT2R antagonist) but not by losartan (AT1R antagonist). In conclusion, our data elucidate novel mechanisms whereby AngII, possibly through AT2R-dependent VEGFR transactivation, regulates eNOS activation, MAPK signalling and H2O2-related antioxidant enzymes. In addition to changes in NO availability, VEGFR inhibition may interfere with the redox status of endothelial cells, leading to vascular dysfunction and hypertension.

Atrial natriuretic peptide and regulation of vascular function in hypertension and heart failure

Atrial natriuretic peptide (ANP) plays a pivotal role in modulation of vascular function and it is also involved in the pathophysiology of several cardiovascular diseases. We provide an updated overview of the current appraisal of ANP vascular effects in both animal models and humans. We describe the physiological implications of ANP vasomodulatory properties as well as the involvement of ANP, through its control of vascular function, in hypertension and heart failure. The principal molecular mechanisms underlying regulation of vascular tone, that is natriuretic peptide receptor type A/cyclic guanylate monophosphate, natriuretic peptide receptor type C, nitric oxide system, are discussed. We review the literature on therapeutic implications of ANP in hypertension and heart failure, examining the potential use of ANP analogues, neutral endopeptidase (NEP) inhibitors, ACE/NEP inhibitors, angiotensin receptor blocker (ARB)/NEP inhibitors, the new dual endothelin-converting enzyme (ECE)/NEP inhibitors and ANP-based gene therapy. The data discussed support the role of ANP in different pathological conditions through its vasomodulatory properties. They also indicate that ANP may represent an optimal therapeutic agent in cardiovascular diseases.

Wy14643 improves vascular function in the aorta of the spontaneously hypertensive rat mainly by activating peroxisome proliferator-activated receptors alpha

Experiments were designed to determine if Wy14643 ([[4-chloro-6-[(2,3-dimethylphenyl)amino]-2-pyrimidinyl]thio]-acetic acid), a preferential agonist at peroxisome proliferator-activated receptors (PPAR) α, improves vascular function in hypertension, and if so, the mechanism(s) involved. Isometric tension was measured in isolated thoracic aorta of spontaneously hypertensive rats (SHR). Wy14643-induced relaxations in SHR aortic rings were greater than those induced by fenofibrate or rosiglitazone (PPARα or PPARγ agonists, respectively) and were larger in rings with endothelium than those without. Both MK886 [(1-[(4-chlorophenyl)methyl]-3-1,1-dimethylethyl)thio]-(α,α-dimethyl-5-1-methylethyl)-1H-indole-2-propanoic acid (PPARα antagonist) and GW9662 (2-chloro-5-nitrobenzanilide) (PPARγ antagonists) inhibited Wy14643-induced relaxations. The inhibitory effect of MK886 was more pronounced in rings with endothelium than those without. In SHR aortic rings with endothelium, L-NAME (Nω-nitro-L-arginine methyl ester, nitric oxide synthase inhibitor), ODQ (1H-1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one, soluble guanylyl cyclase inhibitor) and compound C [adenosine monophosphate-activated protein kinase (AMPK) inhibitor] reduced Wy14643-induced relaxations. Western blotting studies indicated that Wy14643 and fenofibrate, but not rosiglitazone, increased the phosphorylation of endothelial nitric oxide synthase and AMPK; these effects were abolished by compound C but not L-NAME. Endothelium-dependent contractions evoked by acetylcholine in quiescent SHR aorta in the presence of L-NAME were reduced by Wy14643 and fenofibrate but not by rosiglitazone. MK886, but not GW9662, prevented this effect. Wy14643 and fenofibrate inhibited acetylcholine-induced prostanoid release to the same extent. These findings suggest that PPARα agonists induce nitric oxide-mediated relaxation through activation of AMPK and reduce the release of endothelium-dependent contracting factors. Because also of the ability to activate smooth muscle PPARγ to induce relaxation, Wy14643 offers additional protection against vascular dysfunction of spontaneous hypertension.

Abstract 33: Endoplasmic Reticulum Stress and Vascular Dysfunction in Hypertension

Objective: Cardiac damage and vascular dysfunction are major causes of morbidity and mortality in hypertension. In this study, we explored the beneficial therapeutic effect of endoplasmic reticulum (ER) stress inhibition on cardiac damage and vascular dysfunction in hypertension. Methods &amp; results: Mice were infused with angiotensin II (Ang-II, 400 ng/kg/min) with or without ER stress inhibitors (Tudca and PBA) for two weeks. Mice infused with Ang-II displayed an increase in blood pressure, cardiac hypertrophy and fibrosis associated with enhanced collagen-I content, TGFβ1 activity, and ER stress markers, which were blunted after ER stress inhibition. Hypertension induced ER stress in aorta and mesenteric resistance arteries (MRA), enhanced TGFβ1 activity in aorta but not in MRA, and reduced eNOS phosphorylation and endothelium-dependent relaxation (EDR) in aorta and MRA. The inhibition of ER stress significantly reduced TGFβ1 activity, enhanced eNOS phosphorylation and improved EDR. The inhibition of TGFβ1 pathway improved EDR in aorta but not in MRA, while the reduction in ROS levels ameliorated EDR in MRA only. Infusion of tunicamycin in control mice induced ER stress in aorta and MRA, and reduced EDR by a TGFβ1-dependent mechanism in aorta and ROS-dependent mechanism in MRA. Conclusion: ER stress inhibition reduces cardiac damage and improves vascular function in hypertension. Therefore ER stress could be a potential target for cardiovascular diseases.

Endoplasmic Reticulum Stress Is Involved in Cardiac Damage and Vascular Endothelial Dysfunction in Hypertensive Mice

Cardiac damage and vascular dysfunction are major causes of morbidity and mortality in hypertension. In the present study, we explored the beneficial therapeutic effect of endoplasmic reticulum (ER) stress inhibition on cardiac damage and vascular dysfunction in hypertension. Mice were infused with angiotensin II (400 ng/kg per minute) with or without ER stress inhibitors (taurine-conjugated ursodeoxycholic acid and 4-phenylbutyric acid) for 2 weeks. Mice infused with angiotensin II displayed an increase in blood pressure, cardiac hypertrophy and fibrosis associated with enhanced collagen I content, transforming growth factor-β1 (TGF-β1) activity, and ER stress markers, which were blunted after ER stress inhibition. Hypertension induced ER stress in aorta and mesenteric resistance arteries (MRA), enhanced TGF-β1 activity in aorta but not in MRA, and reduced endothelial NO synthase phosphorylation and endothelium-dependent relaxation (EDR) in aorta and MRA. The inhibition of ER stress significantly reduced TGF-β1 activity, enhanced endothelial NO synthase phosphorylation, and improved EDR. The inhibition of TGF-β1 pathway improved EDR in aorta but not in MRA, whereas the reduction in reactive oxygen species levels ameliorated EDR in MRA only. Infusion of tunicamycin in control mice induced ER stress in aorta and MRA, and reduced EDR by a TGF-β1-dependent mechanism in aorta and reactive oxygen species-dependent mechanism in MRA. ER stress inhibition reduces cardiac damage and improves vascular function in hypertension. Therefore, ER stress could be a potential target for cardiovascular diseases.

Effects of long‐term aerobic exercise on vascular function mediated by insulin and insulin‐like growth factor‐1 in hypertension

Hypertension induces vascular dysfunction and decreases nitric oxide (NO) bioavailability. However, whether exercise influences insulin‐ and insulin‐like growth factor‐1 (IGF‐1)‐mediated vascular function in hypertension remains unclear. Thus, we aimed to investigate the effects of long‐term aerobic exercise on vascular function mediated by insulin and IGF‐1 in spontaneously hypertensive rats (SHR). Three groups of rats were used: SHR with aerobic exercise (SHR‐EX), SHR, and Wistar‐Kyoto rats (WKY) as the normotensive control group. The exercise group ran on the treadmill at moderate intensity for 1 hr/day, 5 days/week for 8 weeks. Vasorelaxant responses of rat aortas were analyzed in the organ baths. The aortic protein expression, such as insulin and IGF‐1 receptors, was also examined by Western blot. We found that, compared with the WKY, the SHR group had significantly (p&lt;0.05) lower vasorelaxant responses to insulin and IGF‐1. However, the aerobic exercise significantly (p&lt;0.05) improved the adverse effects in the SHR‐EX group. After treating the inhibitors of NO synthase and phosphatidylinositol‐3 kinase (PI3K), the differences of vascular responses among three groups were eliminated. In addition, the protein expression of insulin and IGF‐1 receptors was significantly (p&lt;0.05) increased in the SHR‐EX group. Our results suggested that long‐term aerobic exercise ameliorated hypertension‐induced vascular dysfunction mediated by insulin and IGF‐1.

Contributory role of endothelium and voltage-gated potassium channels in apocynin-induced vasorelaxations

Although apocynin, the nicotinamide adenine dinucleotide phosphate oxidase inhibitor improves vascular function in hypertension, its specificity has been questioned. The present study examined whether apocynin-induced vasorelaxations involve endothelium and/or K channels in vascular cells. Aortas from Sprague-Dawley rats were suspended in organ baths for functional studies. Changes in intracellular calcium ([Ca]i) and nitric oxide ([NO]i) in rat endothelial cells were detected by fluorescence imaging. Whole-cell voltage-gated K (Kv) currents were recorded in vascular smooth muscle cells. Apocynin-induced aortic relaxations were attenuated by the absence of endothelium, endothelial nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester, or nitric oxide-dependent soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one. 4-Aminopyridine (4-AP, voltage-gated potassium channels blocker) attenuated apocynin-induced relaxations, its combined treatment with 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) did not cause further inhibition. Apocynin increased [Ca]i and [NO]i in endothelial cells, which were abolished by 4-AP, indicating the involvement of voltage-gated potassium channels in endothelial cells. In addition, apocynin-stimulated increase in endothelial nitric oxide synthase phosphorylation at Ser depended on the presence of extracellular Ca. Notably, 4-AP also reduced apocynin-induced relaxations in the absence of endothelium and apocynin increased 4-AP-sensitive voltage-gated potassium channel currents in vascular smooth muscle cells. This study provides novel data showing that apocynin-induced relaxations of rat aortas are mediated by 4-AP-sensitive stimulation of [Ca]i and [NO]i increases in endothelium and by activation of voltage-gated potassium channels in vascular smooth muscle cells.

Improving vascular function in hypertension: potential benefits of combination therapy with amlodipine and renin–angiotensin–aldosterone system blockers

Hypertension is characterized by endothelial dysfunction and increased risk for adverse cardiovascular outcomes. In addition to lowering blood pressure, the calcium-channel blocker amlodipine and blockers of the renin-angiotensin-aldosterone system (angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers) may further reduce cardiovascular risk by improving endothelial function when used alone or in combination. In fact, the beneficial effects of the combination of amlodipine and a renin-angiotensin-aldosterone system blocker on endothelial function have been found to be greater than the effect of either drug alone, likely due to additive effects on nitric oxide activity. This review summarizes the observed effects of these agents on endothelial function and the complementary mechanisms by which they act, thus providing rationale (beyond blood pressure benefits) for their use in combination.

The Soluble Epoxide Hydrolase Inhibitor AR9281 Decreases Blood Pressure, Ameliorates Renal Injury and Improves Vascular Function in Hypertension.

Soluble epoxide hydrolase inhibitors (sEHIs) are demonstrating promise as potential pharmaceutical agents for the treatment of cardiovascular disease, diabetes, inflammation, and kidney disease. The present study determined the ability of a first-in-class sEHI, AR9281, to decrease blood pressure, improve vascular function, and decrease renal inflammation and injury in angiotensin hypertension. Rats were infused with angiotensin and AR9281 was given orally during the 14-day infusion period. Systolic blood pressure averaged 180 ± 5 mmHg in vehicle treated and AR9281 treatment significantly lowered blood pressure to 142 ± 7 mmHg in angiotensin hypertension. Histological analysis demonstrated decreased injury to the juxtamedullary glomeruli. Renal expression of inflammatory genes was increased in angiotensin hypertension and two weeks of AR9281 treatment decreased this index of renal inflammation. Vascular function in angiotensin hypertension was also improved by AR9281 treatment. Decreased afferent arteriolar and mesenteric resistance endothelial dependent dilator responses were ameliorated by AR9281 treatment of angiotensin hypertensive rats. These data demonstrate that the first-in-class sEHI, AR9281, lowers blood pressure, improves vascular function and reduces renal damage in angiotensin hypertension.

Effects of acute severe exercise on insulin‐ and insulin‐like growth factor‐1‐mediated vasorelaxation in spontaneously hypertensive rats

Exercise enhances the vascular function mainly by improving endothelial function. The way of exercise influences on hypertension‐induced vascular dysfunction remains unclear. Thus, the aim of this study was to examine the effects of acute severe exercise on insulin‐ and insulin‐like growth factor‐1 (IGF‐1)‐mediated vasorelaxation in spontaneously hypertensive rats (SHR). Three groups of rats were used in this study: SHR with exercise, SHR, and Wistar‐Kyoto rats (WKY) as control. The SHR with acute severe exercise group ran on treadmill at the speed of 28‐30 m/min until exhausted. Thoracic aortas were isolated to analyze vascular responses in organ baths. Selective inhibitors were used to examine the roles of endothelial nitric oxide synthase (eNOS) and phosphatidylinositol‐3 kinase (PI3K) in the vasorelaxation. Furthermore, the vascular response induced by sodium nitroprusside (SNP, a NO donor) was examined. Our results showed that, 1) insulin‐ and IGF‐1‐mediated vasorelaxation was significantly lower in SHR than WKY; 2) acute exercise ameliorated these adverse effects in SHR; 3) after treating either wortmannin (a PI3K inhibitor) or L‐NAME (a eNOS inhibitor), the differences of vascular responses among three groups were eliminated; 4) no significant differences of the SNP‐induced vasorelaxation were found among three groups. Our findings suggested that acute severe exercise could reverse the impairments of vascular function in hypertension.

Increased Activation of Stromal Interaction Molecule-1/Orai-1 in Aorta From Hypertensive Rats

Disturbances in the regulation of cytosolic calcium (Ca 2+ ) concentration play a key role in the vascular dysfunction associated with arterial hypertension. Stromal interaction molecules (STIMs) and Orai proteins represent a novel mechanism to control store-operated Ca 2+ entry. Although STIMs act as Ca 2+ sensors for the intracellular Ca 2+ stores, Orai is the putative pore-forming component of Ca 2+ release–activated Ca 2+ channels at the plasma membrane. We hypothesized that augmented activation of Ca 2+ release–activated Ca 2+ /Orai-1, through enhanced activity of STIM-1, plays a role in increased basal tonus and vascular reactivity in hypertensive animals. Endothelium-denuded aortic rings from Wistar-Kyoto and stroke-prone spontaneously hypertensive rats were used to evaluate contractions because of Ca 2+ influx. Depletion of intracellular Ca 2+ stores, which induces Ca 2+ release–activated Ca 2+ activation, was performed by placing arteries in Ca 2+ free-EGTA buffer. The addition of the Ca 2+ regular buffer produced greater contractions in aortas from stroke-prone spontaneously hypertensive rats versus Wistar-Kyoto rats. Thapsigargin (10 μmol/L), an inhibitor of the sarcoplasmic reticulum Ca 2+ ATPase, further increased these contractions, especially in stroke-prone spontaneously hypertensive rat aorta. Addition of the Ca 2+ release–activated Ca 2+ channel inhibitors 2-aminoethoxydiphenyl borate (100 μmol/L) or gadolinium (100 μmol/L), as well as neutralizing antibodies to STIM-1 or Orai-1, abolished thapsigargin-increased contraction and the differences in spontaneous tone between the groups. Expression of Orai-1 and STIM-1 proteins was increased in aorta from stroke-prone spontaneously hypertensive rats when compared with Wistar-Kyoto rats. These results support the hypothesis that both Orai-1 and STIM-1 contribute to abnormal vascular function in hypertension. Augmented activation of STIM-1/Orai-1 may represent the mechanism that leads to impaired control of intracellular Ca 2+ levels in hypertension.

Endogenous ouabain in cardiovascular function and disease

An endogenous ouabain has been isolated and conclusively identified from several mammalian tissues, including human plasma, by a number of independent laboratories. Substantial evidence from independent laboratories in several continents is consistent with an adrenal source for most if not all of the circulating endogenous ouabain. Accumulating evidence suggests that circulating levels of endogenous ouabain in humans are modulated by dietary salt and chronic volume status. Endogenous ouabain is linked significantly with vascular function in hypertension and likely impacts the pathogenesis of heart and renal failure. Moreover, the molecular mechanism of endogenous ouabain-linked hypertension involves the sodium pump/sodium-calcium exchange duet. The outstanding analytical issues include the elucidation of distal events in the biosynthetic pathway for endogenous ouabain and identification of molecular mechanisms that regulate its secretion and clearance.

Sex steroids and vascular responses in hypertension and aging

Sex hormones play a significant role in human physiology. Estrogen may have protective effects in the cardiovascular system, as evidenced by the decreased incidence of cardiovascular disease (CVD) in premenopausal compared with postmenopausal women. This review highlights the acute and long-term effects of sex hormones on the vascular endothelium and vascular smooth muscle (VSM) in adults. Changes in the sex hormone mix, their receptors, and their effects on vascular function in hypertension and aging are also discussed. Literature collected from the National Centers for Biotechnology Information as identified by a PubMed database search, as well as our experimental work, was used to highlight current knowledge regarding vascular responses to sex hormones in hypertension and in aging. Experiments in adult female animals have shown that estrogen induces endothelium-dependent vascular relaxation via the nitric oxide (NO), prostacyclin, and hyperpolarization pathways. Also, surface membrane estrogen receptors (ERs) decrease intracellular free Ca2+ concentration and perhaps protein kinase C-dependent VSM contraction. However, clinical trials such as the Heart and Estrogen/progestin Replacement Study (HERS), HERS-II, and the Women's Health Initiative did not support the experimental findings and demonstrated adverse cardiovascular events of hormone therapy (HT) in aging women. The lack of vascular benefits of HT may be related to the hormone used, the ER, or the patient's cardiovascular condition or age. Experiments on vascular strips from aging (16-month-old) female spontaneously hypertensive rats have shown reduced ER-mediated NO production from endothelial cells and decreased inhibitory effects of estrogen on Ca2+ entry mechanisms of VSM contraction. The age-related decrease in ER-mediated vascular relaxation may explain the decreased effectiveness of HT on CVD in aging women. New HT strategies should further examine the benefits of natural estrogens and phytoestrogens. Transdermal estrogen may be more effective than the oral form, and specific ER modulators may maximize the vascular benefits and reduce the risk of invasive breast cancer. Variants of vascular ERs should be screened for genetic polymorphisms and postmenopausal decrease in the amount of downstream signaling mechanisms. HT may be more effective during the menopausal transition than in late menopause. Progesterone, testosterone, or their specific modulators may be combined with estrogen to provide alternative HT strategies. Thus, HT type, dose, route of administration, and timing should be customized, depending on the patient's cardiovascular condition and age, thereby enhancing the vascular benefits of HT in aging women.

O76. Role of the T cell in modulation of blood pressure and vascular function in hypertension

O76. Role of the T cell in modulation of blood pressure and vascular function in hypertension

Translocation of endothelial nitric oxide synthase: Another feat of amlodipine, a cardiovascular jack-of-all-trades

See article by Batova et al. [12] (pages 478–485) in this issue. The antihypertensive drug amlodipine (Norvasc®) is a long-acting, third-generation Ca2+ channel blocker that has been shown to limit the progression of atherosclerosis and to decrease the incidence of cardiovascular events in humans [1]. It is generally well tolerated and often used in combination with diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists and statins [2–4]. Amlodipine exhibits nanomolar affinity to dihydropyridine as well as benzothiazepine and phenylalkylamine binding sites of voltage-dependent L-type Ca2+ channels [5]. It is several-fold more lipophilic than the first- and second-generation Ca2+ channel blockers and adopts a well-defined position in the bilayer membrane [6]. It has been suggested that partitioning of amlodipine to membranes results in beneficial modification of the structure of cholesterol-rich membranes of vascular smooth muscle cells, an effect that might contribute to atheroprotection [7]. Besides the well-documented inhibition of L-type Ca2+ channels, amlodipine exerts additional effects that contribute to the improvement of vascular function in hypertension and ischemic heart disease [8]. There is both in vitro and in vivo evidence indicating that dihydropyridines including amlodipine act as antioxidants preventing the progression of atherosclerosis by interfering with lipid peroxidation. However, amlodipine has pharmacological properties distinct from other Ca2+ channel blockers. Probably most relevant to the antihypertensive and antiplatelet effects of the drug is the release of endothelium-derived nitric oxide (NO). …