Aortic Nitric Oxide Production Research Articles

Vascular protein disulfide isomerase A1 mediates endothelial dysfunction induced by angiotensin II in mice.

Protein disulfide isomerases (PDIs) are involved in platelet aggregation and intravascular thrombosis, but their role in regulating endothelial function is unclear. Here, we characterized the involvement of vascular PDIA1 in angiotensin II (Ang II)-induced endothelial dysfunction in mice. Endothelial dysfunction was induced in C57BL/6JCmd male mice via Ang II subcutaneous infusion, and PDIA1 was inhibited with bepristat. Endothelial function was assessed invivo with magnetic resonance imaging and exvivo with a myography, while arterial stiffness was measured as pulse wave velocity. Nitric oxide (NO) bioavailability was measured in the aorta (spin-trapping electron paramagnetic resonance) and plasma (NO2 - and NO3 - levels). Oxidative stress, eNOS uncoupling (DHE-based aorta staining), and thrombin activity (thrombin-antithrombin complex; calibrated automated thrombography) were evaluated. The inhibition of PDIA1 by bepristat in Ang II-treated mice prevented the impairment of NO-dependent vasodilation in the aorta as evidenced by the response to acetylcholine invivo, increased systemic NO bioavailability and the aortic NO production, and decreased vascular stiffness. Bepristat's effect on NO-dependent function was recapitulated exvivo in Ang II-induced endothelial dysfunction in isolated aorta. Furthermore, bepristat diminished the Ang II-induced eNOS uncoupling and overproduction of ROS without affecting thrombin activity. In Ang II-treated mice, the inhibition of PDIA1 normalized the NO-ROS balance, prevented endothelial eNOS uncoupling, and, thereby, improved vascular function. These results indicate the importance of vascular PDIA1 in regulating endothelial function, but further studies are needed to elucidate the details of the mechanisms involved.

Chronic Stress Produces Persistent Increases in Plasma Corticosterone, Reductions in Brain and Cardiac Nitric Oxide Production, and Delayed Alterations in Endothelial Function in Young Prehypertensive Rats.

This study was designed to investigate whether oxidative stress, nitric oxide (NO) deficiency and/or endothelial dysfunction (ED) are present in young borderline hypertensive rats (BHR) and whether these pathologies can be causally involved in the initiation of blood pressure (BP) increases. Additionally, we tested the hypothesis that crowding stress, experienced during the peripubertal period, may produce persistent or delayed disorders in corticosterone release, NO synthesis, oxidative status and/or endothelial function that could accelerate BP increases. To test these hypotheses, 5-week-old male BHR and normotensive Wistar-Kyoto rats (WKY) were either kept in control conditions (for 2 and 4 weeks, respectively) or exposed to social stress produced by crowding for 2 weeks (stress). After cessation of crowding, a group of rats of each phenotype was kept in control conditions for the next 2 weeks (post-stress). Systolic BP of 5-week-old BHR was significantly increased vs. age-matched WKY (127 ± 3 vs. 104 ± 3 mmHg, p < 0.01) and remained significantly higher throughout the course of the experiment. Despite elevated BP, no signs of oxidative damage to plasma lipids, NO deficiency or ED were observed in control BHR vs. age-matched WKY. Crowding stress elevated plasma corticosterone and accelerated BP increases only in BHR; these effects persisted 2 weeks post-stress. Crowding failed to induce oxidative damage to plasma lipids in either phenotype, but it produced persistent decreases in NO production in the hypothalamus and brainstem of both strains of rats, as well as in the hearts of BHR. In contrast, crowding failed to reduce NO production in the aortae or acetylcholine-induced relaxations of the femoral arteries in both strains investigated. However, significantly reduced aortic NO production was observed in BHR 2 weeks post-stress vs. age-matched controls, which was in agreement with reduced NO-dependent components of vasorelaxation. In conclusion, this study’s data showed that oxidative stress, NO deficiency and ED are not causally involved in initiation of blood pressure increase in BHR. However, exposure to stressful environments produced persistent increases in plasma corticosterone and reductions of brain and cardiac NO production followed by a delayed decrease in the NO-dependent component of endothelium-dependent relaxation—changes that collectively accelerated BP increases only in BHR.

Perivascular adipose tissue inhibits endothelial function of rat aortas via caveolin-1.

Perivascular adipose tissue (PVAT)-derived factors have been proposed to play an important role in the pathogenesis of atherosclerosis. Caveolin-1 (Cav-1), occupying the calcium/calmodulin binding site of endothelial NO synthase (eNOS) and then inhibiting nitric oxide (NO) production, is also involved in the development of atherosclerosis. Thus, we investigated whether PVAT regulated vascular tone via Cav-1 and/or endothelial NO pathways. Isometric tension studies were carried out in isolated thoracic aortas from Wistar rats in the presence and absence of PVAT. Concentration-response curves of phenylephrine, acetylcholine, and sodium nitroprusside were illustrated to examine the vascular reactivity and endothelial function. The protein expressions of eNOS and Cav-1 were also examined in aortic homogenates. Our results demonstrated that PVAT significantly enhanced vasoconstriction and inhibited vasodilatation via endothelium-dependent mechanism. The aortic NO production was diminished after PVAT treatment, whereas protein expression and activity of eNOS were not significantly affected. In addition, Cav-1 protein expression was significantly increased in aortas with PVAT transfer. Furthermore, a caveolae depleter methyl-β-cyclodextrin abolished the effect of PVAT on the enhancement of vasoconstriction, and reversed the impairment of aortic NO production. In conclusion, unknown factor(s) released from PVAT may inhibit endothelial NO production and induce vasocontraction via an increase of Cav-1 protein expression.

Uncoupled Endothelial Nitric Oxide Synthase and Oxidative Stress in a Rat Model of Pregnancy-Induced Hypertension

Preeclampsia is a human pregnancy-associated syndrome associated with hypertension, proteinuria, and endothelial dysfunction. We tested whether increased reactive oxygen species (superoxide and peroxynitrite) production and decreased bioavailability of the endothelial nitric oxide (NO) synthase (eNOS) cofactor tetrahydrobiopterin (BH4) contributes to maternal endothelial dysfunction in rats with pregnancy-induced hypertension and several characteristics of preeclampsia. Nonpregnant (DS) and pregnant (PDS) rats were treated with deoxycorticosterone acetate and 0.9% saline for approximately 3 weeks and nonpregnant (Con) and pregnant (P) rats received tap water. Blood pressure, urinary protein levels, mesenteric vascular reactivity, aortic protein expression, and aortic reactive oxygen species levels were compared between the four groups. The PDS rats had significantly decreased mesenteric endothelium-dependent relaxation responses and aortic NO production compared to Con, DS, and P rats despite increased aortic eNOS expression. Aortic superoxide and peroxynitrite levels were increased in PDS rats compared with Con, DS, and P rats. Scavenging of reactive oxygen species or increasing tetrahydrobiopterin levels normalized mesenteric endothelium-dependent relaxation responses, aortic NO production, and aortic superoxide and peroxynitrite levels in PDS rats. These data suggest that increased superoxide production by NADPH oxidase, peroxynitrite degradation of BH4, and uncoupled eNOS contribute to endothelial dysfunction in a rat model of pregnancy-induced hypertension.

Chronic Ethanol Ingestion Increases Aortic Endothelial Nitric Oxide Synthase Expression and Nitric Oxide Production in the Rat

Chronic alcohol consumption perturbs cellular function in a variety of organ systems. Previous studies have suggested that moderate alcohol consumption reduces vascular disease, whereas heavier alcohol consumption may worsen it. The mechanisms for these vascular effects of chronic alcohol ingestion continue to be defined and constitute the focus of this study. Male Sprague Dawley rats were fed an isocaloric, Lieber-Decarli liquid diet containing either ethanol (36% calories) or Maltose-Dextrin (substituted for ethanol) for 6 weeks. Telemetric blood pressure measurements were taken before and after ethanol feeding. After the rats were killed, the aortas were analyzed for endothelial nitric oxide (NO) synthase expression and NO production. Chronic ethanol ingestion decreased mean arterial pressure and increased aortic NO production as demonstrated by direct ex vivo measurements using iron diethyldithio-carbamic acid as well as analysis of nitrosyl-hemoglobin (NO-Hb) levels. Consistent with these assays of vascular NO production, endothelium-dependent relaxation responses to acetycholine (Ach) were enhanced in ethanol-fed animals. Aortic endothelial nitric oxide synthase expression was also increased by chronic ethanol ingestion. These findings demonstrate that a regimen of chronic alcohol ingestion in the rat produced generally salutary effects in the systemic vasculature following a 6-week treatment regimen. These findings extend previous in vitro studies to demonstrate that alcohol has potent effects on vascular endothelial nitric oxide synthase expression, NO production, and vascular function. Consistent with previous reports, these findings confirm that alcohol-induced alterations in the production of reactive nitrogen species play an important role in the pathogenesis of alcohol-mediated tissue effects.

Anti-atherogenic Effects of the Methanol Extract of Sorbus Cortex in Atherogenic-Diet Rats

The present study was designed to examine whether the methanol extract of Sorbus commixta cortex (MSC) could prevent the development of atherosclerosis through regulating the vascular nitric oxide (NO) and endothelin-1 (ET-1) systems in atherogenic-diet rats. Our findings show that aortic NO production as well as endothelial nitric oxide synthase (ecNOS) expression was significantly decreased in atherogenic-diet rats compared with those in the control group. Aortic ET-1 expression was augmented in rats fed an atherogenic-diet while NF-kappaB p65 was upregulated. Treatment of atherogenic-diet rats with either low (100 mg/kg/d) or high (200 mg/kg/d) doses of MSC led not only to significant increases in the aortic NOS/NO system, but also to decreases in aortic ET-1 expression. The aortic expression level of NF-kappaB p65 was also attenuated in atherogenic-diet rats by chronic treatment with low or high doses of MSC. Atherogenic-diet induced increases in the expression of adhesion molecules including intercellular adhesion molecules-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin were markedly decreased by treatment with MSC. From the histopathological examination, MSC treatment was shown to lessen the thickening noted in the aortic intima and media of the atherogenic-diet rats. These results suggest that MSC affects the atherogenic process via the suppression of proinflammatory and adhesion molecules in atherogenic-diet rats, which may be, at least in part, causally related with the regulation of vasoactive systems such as the NO and ET-1 systems.

Exercise conditioning attenuates the hypertensive effects of nitric oxide synthase inhibitor in rat.

Many individuals with cardiovascular diseases undergo periodic exercise conditioning with or with out medication. Therefore, this study investigated the interaction of exercise training and chronic nitric oxide synthase (NOS) inhibitor (Nitro-L-Arginine Methyl Ester, L-NAME) treatment on blood pressure and its correlation with aortic nitric oxide (NO), antioxidant defense system and oxidative stress parameters in rats. Fisher 344 rats were divided into four groups: (1) sedentary control, (2) exercise training (ET) for 8 weeks, (3) L-NAME (10 mg/kg, subcutaneous for 8 weeks) and (4) ET + L-NAME. Blood pressure (BP) was monitored weekly for 8 weeks with tail-cuff method. The animals were sacrificed 24 h after last treatments and thoracic aortic rings were isolated and analyzed. Exercise conditioning resulted in a significant increase in respiratory exchange ratio (RER), aortic NO production, NO synthase activity and inducible iNOS protein expression. Training significantly enhanced aortic GSH levels, GSH/GSSG ratio and up-regulation of aortic CuZn-SOD, Mn-SOD, catalase (CAT), glutathione peroxidase (GSH-Px) activity and protein expression and significantly decreased aortic lipid peroxidation. Chronic L-NAME administration resulted in a significant depletion of aortic NO, NOS activity, endothelial (eNOS) and iNOS protein expression, GSH level, GSH/GSSG ratio, down-regulation of aortic antioxidant enzyme activities and protein expressions. Aortic xanthine oxidase (XO) activity significantly increased with increased lipid peroxidation and protein oxidation after L-NAME administration. The biochemical changes were accompanied by increased in BP. Interaction of training and chronic NOS inhibitor treatment resulted in normalization of BP and aortic antioxidant enzyme activity and protein expression, up-regulation of aortic GSH/GSSG ratio, NO levels, Mn-SOD protein expression, depletion of GSSG, protein oxidation and lipid peroxidation. The data suggest that training attenuated the oxidative injury caused by chronic NOS inhibitor treatment by up-regulating the NO and antioxidant systems and lowering the BP in rats.