Oxidative Stress and Vascular Damage in Hypertension: Role of Angiotensin II

Reactive oxygen species are oxygen derivates and play an active role in vascular biology. These compounds are generated within the vascular wall, at the level of endothelial and vascular smooth muscle cells, as well as by adventitial fibroblasts. In healthy conditions, ROS are produced in a controlled manner at low concentrations and function as signaling molecules regulating vascular contraction-relaxation and cell growth. Physiologically, the rate of ROS generation is counterbalanced by the rate of elimination. In hypertension, an enhanced ROS generation occurs, which is not counterbalanced by the endogenous antioxidant mechanisms, leading to a state of oxidative stress. In the present paper, major angiotensin II-induced vascular ROS generation within the vasculature, and relative sources, will be discussed. Recent development of signalling pathways whereby angiotensin II-driven vascular ROS induce and accelerate functional and structural vascular injury will be also considered

Adipocytokine levels mark endothelial function in normotensive individuals

BACKGROUND: Endothelial dysfunction is an independent risk factor for cardiovascular events. Inflammatory mediators released by the adipose tissue can lead to local insulin resistance and endothelial dysfunction. This study addressed the relationship of adipocytokines with endothelial function and blood pressure. METHODS: In 92 newly diagnosed, drug-naïve essential hypertensive patients (HT, mean age 49 yrs) without organ damage and 66 normotensive subjects (NT, mean age 47 yrs), by an automated system, we measured endothelium-dependent and -independent vasodilation as brachial artery flow-mediated dilation before and after administration of glyceryl-trinitrate. Retinol binding protein-4 (RBP4) and resistin levels were determined by ELISA and RIA, respectively. Oxidative stress was evaluated by measuring serum malondyaldehyde (MDA). RESULTS: Flow-mediated dilation was significantly (p = 0.03) lower in HT (5.3 ± 2.6%) than NT (6.1 ± 3.1%), while response to glyceryl-trinitrate (7.5 ± 3.7% vs 7.9 ± 3.4%) was similar. RBP4 (60.6 ± 25.1 vs 61.3 ± 25.9 μg/ml), resistin (18.8 ± 5.3 vs 19.9 ± 6.1 ng/ml) and MDA levels (2.39 ± 1.26 vs 2.08 ± 1.17 nmol/ml) were not different in HT and NT. RBP4 (r = −0.25; p = 0.04) and resistin levels (r = −0.29; p = 0.03) were related to flow-mediated dilation in NT, but not in HT (r = −0.03 and r = −0.10, respectively). In NT, multivariate analysis including RBP4 and confounders showed that only BMI or waist circumference remained related to flow- mediated dilation. In the multivariate model including resistin and confounders, BMI, age and resistin were significantly related to flow-mediated dilation, while only age significant correlated with this parameter when BMI was replaced by waist circumference. CONCLUSIONS: Adipocytokine levels may be independent predictors of endothelial dysfunction in the peripheral circulation of healthy subjects, providing a pathophysiological link between inflammation from adipose tissue and early vascular alterations

Vascular Dysfunction in a Mouse Model of Rett Syndrome and Effects of Curcumin Treatment

Mutations in the coding sequence of the X-linked gene MeCP2 (Methyl CpG–binding protein) are present in around 80% of patients with Rett Syndrome, a common cause of intellectual disability in female and to date without any effective pharmacological treatment. A relevant, and so far unexplored feature of RTT patients, is a marked reduction in peripheral circulation. To investigate the relationship between loss of MeCP2 and this clinical aspect, we used the MeCP2 null mouse model B6.129SF1-MeCP2tm1Jae for functional and pharmacological studies. Functional experiments were performed on isolated resistance mesenteric vessels, mounted on a pressurized myograph. Vessels from female MeCP2(+/−) mice show a reduced endothelium-dependent relaxation, due to a reduced Nitric Oxide (NO) availability secondary to an increased Reactive Oxygen Species (ROS) generation. Such functional aspects are associated with an intravascular increase in superoxide anion production, and a decreased vascular eNOS expression. These alterations are reversed by curcumin administration (5% (w/w) dietary curcumin for 21 days), which restores endothelial NO availability, decreases intravascular ROS production and normalizes vascular eNOS gene expression. In conclusion our findings highlight alterations in the vascular/endothelial system in the absence of a correct function of MeCP2, and uncover related cellular/molecular mechanisms that are rescued by an anti-oxidant treatment

Early treatment with hydroxychloroquine prevents the development of endothelial dysfunction in a murine model of systemic lupus erythematosus

INTRODUCTION: Accelerated atherosclerosis is one of the major causes of morbidity in patients with systemic lupus erythematosus (SLE). Endothelial dysfunction (ED) is considered an early marker of atherosclerosis. It is a reversible alteration, thus representing an attractive target for prevention strategies against cardiovascular disease. Studies have shown that ED occurs in patients with SLE even in the absence of severe, active disease. Hydroxychloroquine (HCQ) is widely used in SLE to control disease activity, but its use is also associated with an improvement in long-term prognosis. Beyond the beneficial effect in well-established disease, our hypothesis is that treatment with HCQ might have a beneficial impact on ED prevention in SLE. The aim of this study was to assess the impact of early treatment with HCQ on ED in a murine model of SLE. METHODS: Twelve-week-old NZB/W F1 (NZ) and C57BL/6 J mice (controls) were allocated to receive HCQ or vehicle for 6, 12, or 18 weeks. Proteinuria and anti-double-stranded DNA autoantibodies were determined. ED was assessed in mesenteric arteries (pressurized myography). Nitric oxide (NO) availability and reactive oxygen species (ROS) production were evaluated. Vascular ROS production was measured with dihydroethidium (DHE) fluorescent dye. RESULTS: Starting from 18 weeks of age, NZ mice showed a progressive reduction in NO availability, which was normalized by ascorbic acid and apocynin in the up to 24-week-old group, and partly ameliorated in older animals. HCQ administration normalized the NO availability in the up to 24-week-old group, with a partial amelioration in the 30-week-old group. DHE analysis revealed a progressive increment of vascular ROS generation among NZ groups, which was prevented by apocynin. Similarly, in the NZ HCQ-treated group, vascular ROS production was abrogated. CONCLUSIONS: The ED that characterizes this mouse model of SLE is caused by the nicotinamide adenine dinucleotide phosphate oxidase-driven ROS excess. Very early treatment with HCQ is able to exert vascular protection via an antioxidant effect

Luteolin Prevents Cardiometabolic Alterations and Vascular Dysfunction in Mice With HFD-Induced Obesity

Purpose: Luteolin exerts beneficial effects against obesity-associated comorbidities, although its influence on vascular dysfunction remains undetermined. We examined the effects of luteolin on endothelial dysfunction in a mouse model of diet-induced obesity. Methods: Standard diet (SD) or high-fat diet (HFD)-fed mice were treated daily with luteolin intragastrically. After 8 weeks, body and epididymal fat weight, as well as blood cholesterol, glucose, and triglycerides were evaluated. Endothelium-dependent relaxations of resistance mesenteric vessels was assessed by a concentration-response curve to acetylcholine, repeated upon Nw-nitro-L-arginine methylester (L-NAME) or ascorbic acid infusion to investigate the influence of nitric oxide (NO) availability and reactive oxygen species (ROS) on endothelial function, respectively. Intravascular ROS production and TNF levels were measured by dihydroethidium dye and ELISA, respectively. Endothelial NO synthase (eNOS) and superoxide dismutase 1 (SOD1), as well as microRNA-214-3p expression were examined by Western blot and RT-PCR assays, respectively. Results: HFD animals displayed elevated body weight, epididymal fat weight and metabolic indexes. Endothelium-dependent relaxation was resistant to L-NAME and enhanced by ascorbic acid, which restored also the inhibitory effect of L-NAME, suggesting a ROS-dependent reduction of NO availability in HFD vessels. Moreover, media-lumen ratio, intravascular superoxide anion and TNF levels were increased, while vascular eNOS, SOD1, and microRNA-214-3p expression were decreased. In HFD mice, luteolin counteracted the increase in body and epididymal fat weight, and metabolic alterations. Luteolin restored vascular endothelial NO availability, normalized the media-lumen ratio, decreased ROS and TNF levels, and normalized eNOS, SOD1 and microRNA-214-3p expression. Conclusion: Luteolin prevents systemic metabolic alterations and vascular dysfunction associated with obesity, likely through antioxidant and anti-inflammatory mechanisms

The flavonoid compound apigenin prevents colonic inflammation and motor dysfunctions associated with high fat diet-induced obesity

When compared to SD mice, HFD animals displayed increased body weight, epididymal fat weight and metabolic indexes. HFD mice showed increments in colonic MDA, IL-1 beta and IL-6 levels, as well as a decrease in let-7f expression in both colonic and epididymal tissues. HFD mice displayed an increase in colonic eosinophil infiltration. Immunohistochemistry revealed an increase in SP and iNOS expression in myenteric ganglia of HFD mice. In preparations from HFD mice, electrically evoked contractions upon NOS blockade or mediated by tachykininergic stimulation were enhanced. In HFD mice, Apigenin counteracted the increase in body and epididymal fat weight, as well as the alterations of metabolic indexes. Apigenin reduced also MDA, IL-1 beta and IL-6 colonic levels as well as eosinophil infiltration, SP and iNOS expression, along with a normalization of electrically evoked tachykininergic and nitrergic contractions. In addition, apigenin normalized let-7f expression in epididymal fat tissues, but not in colonic specimens

Cyclooxygenase-2 inhibition improves vascular endothelial dysfunction in a rat model of endotoxic shock: Role of inducible nitric-oxide synthase and oxidative

ABSTRACT We investigated whether cyclooxygenase (COX) isoforms (COX-1 and COX-2) and decreased NO availability contribute to endothelial dysfunction in endotoxemic rats. The involvement of reactive oxygen species (ROS) was also evaluated. Rats were injected with Salmonella-derived lipopolysaccharide or saline. After 6 h, endothelial function of mesenteric resistance arteries was evaluated. In controls, acetylcholine (ACh)-induced relaxation was inhibited by the nitric-oxide synthase inhibitor N G -monomethyl-L-arginine (L-NMMA) and unaffected by 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)-phenyl-2(5H)-furanone (DFU) (COX-2 inhibitor). In lipopolysaccharide (LPS)-treated rats, the response to ACh was blunted compared with controls, less sensitive to L-NMMA, and enhanced by DFU. COX-2 blockade also improved the inhibitory effect of L-NMMA on cholinergic relaxation. SC-560 [5-(4-clorophenyl)-1-(4-metoxyphenyl)-3-trifluoromethylpirazole] (COX-1 inhibitor) did not modify the response to ACh in both groups. LPS-induced endothelial dysfunction was unaffected by the thromboxane A 2 (TxA 2 ) receptor antagonist SQ-29548 (7-[3-[[2-[(phenylamino) hept-2-yl]-[1S(1alpha,2alpha(Z),3alpha,4alpha)]-5-heptenoic acid). In vivo inducible nitric-oxide synthase (iNOS) inhibition by S-methylisothiourea partly attenuated LPS-induced endothelial dysfunction. The antioxidants ascorbic acid and superoxide dismutase normalized endothelium-dependent relaxation and restored the inhibitory action of L-NMMA on ACh. Responses to sodium nitroprusside were similar in both groups. In LPS-treated rats, reverse transcription-polymerase chain reaction showed a marked increase in mesenteric iNOS and COX-2 expressions, whereas endothelial nitric-oxide synthase and COX-1 were unchanged. LPS-induced COX-2 overexpression was reduced but not abrogated by S-methylisothiourea. LPS-induced COX-2 upregulation was also documented by immunohistochemistry. In conclusion, mesenteric resistance vessels from endotoxemic rats show impaired endothelial function due to reduced NO availability, a condition that is partly ascribable to an iNOS-dependent enhanced COX-2 expression, whereas TxA 2 does not seem to be involved. Oxidative stress is the main mechanism responsible for reduced NO availability, and COX-2 might act as a source of ROS

Targeting SIRT1 Rescues Age- and Obesity-Induced Microvascular Dysfunction in Ex Vivo Human Vessels

ackground: Experimental evidence suggests a key role of SIRT1 (silent information regulator 1) in age- and metabolic-related vascular dysfunction. Whether these effects hold true in the human microvasculature is unknown. We aimed to investigate the SIRT1 role in very early stages of age- and obesity-related microvascular dysfunction in humans. Methods: Ninety-five subjects undergoing elective laparoscopic surgery were recruited and stratified based on their body mass index status (above or below 30 kg/m2) and age (above or below 40 years) in 4 groups: Young Nonobese, Young Obese, Old Nonobese, and Old Obese. We measured small resistance arteries' endothelial function by pressurized micromyography before and after incubation with a SIRT1 agonist (SRT1720) and a mitochondria reactive oxygen species (mtROS) scavenger (MitoTEMPO). We assessed vascular levels of mtROS and nitric oxide availability by confocal microscopy and vascular gene expression of SIRT1 and mitochondrial proteins by qPCR. Chromatin immunoprecipitation assay was employed to investigate SIRT1-dependent epigenetic regulation of mitochondrial proteins. Results: Compared with Young Nonobese, obese and older patients showed lower vascular expression of SIRT1 and antioxidant proteins (FOXO3 [forkhead box protein O3] and SOD2) and higher expression of pro-oxidant and aging mitochondria proteins p66Shc and Arginase II. Old Obese, Young Obese and Old Nonobese groups endothelial dysfunction was rescued by SRT1720. The restoration was comparable to the one obtained with mitoTEMPO. These effects were explained by SIRT1-dependent chromatin changes leading to reduced p66Shc expression and upregulation of proteins involved in mitochondria respiratory chain. Conclusions: SIRT1 is a novel central modulator of the earliest microvascular damage induced by age and obesity. Through a complex epigenetic control mainly involving p66Shc and Arginase II, it influences mtROS levels, NO availability, and the expression of proteins of the mitochondria respiratory chain. Therapeutic modulation of SIRT1 restores obesity- and age-related endothelial dysfunction. Early targeting of SIRT1 might represent a crucial strategy to prevent age- and obesity-related microvascular dysfunction. Keywords: aging; endothelial cells; microcirculation; mitochondria; obesity; sirtuin