Essential hypertension and oxidative stress: New insights

Reactive oxygen species: key regulators in vascular health and diseases

ROS are a group of small reactive molecules that play critical roles in the regulation of various cell functions and biological processes. In the vascular system, physiological levels of ROS are essential for normal vascular functions including endothelial homeostasis and smooth muscle cell contraction. In contrast, uncontrolled overproduction of ROS resulting from an imbalance of ROS generation and elimination leads to the development of vascular diseases. Excessive ROS cause vascular cell damage, the recruitment of inflammatory cells, lipid peroxidation, activation of metalloproteinases and deposition of extracellular matrix, collectively leading to vascular remodelling. Evidence from a large number of studies has revealed that ROS and oxidative stress are involved in the initiation and progression of numerous vascular diseases including hypertension, atherosclerosis, restenosis and abdominal aortic aneurysm. Furthermore, considerable research has been implemented to explore antioxidants that can reduce ROS production and oxidative stress in order to ameliorate vascular diseases. In this review, we will discuss the nature and sources of ROS, their roles in vascular homeostasis and specific vascular diseases and various antioxidants as well as some of the pharmacological agents that are capable of reducing ROS and oxidative stress. The aim of this review is to provide information for developing promising clinical strategies targeting ROS to decrease cardiovascular risks.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Chronic PARP-1 inhibition reduces carotid vessel remodeling and oxidative damage of the dorsal hippocampus in spontaneously hypertensive rats

Vascular remodeling during chronic hypertension may impair the supply of tissues with oxygen, glucose and other compounds, potentially unleashing deleterious effects. In this study, we used Spontaneously Hypertensive Rats and normotensive Wistar-Kyoto rats with or without pharmacological inhibition of poly(ADP-ribose)polymerase-1 by an experimental compound L-2286, to evaluate carotid artery remodeling and consequent damage of neuronal tissue during hypertension. We observed elevated oxidative stress and profound thickening of the vascular wall with fibrotic tissue accumulation induced by elevated blood pressure. 32 weeks of L-2286 treatment attenuated these processes by modulating mitogen activated protein kinase phosphatase-1 cellular levels in carotid arteries. In hypertensive animals, vascular inflammation and endothelial dysfunction was observed by NF-κB nuclear accumulation and impaired vasodilation to acetylcholine, respectively. Pharmacological poly(ADP-ribose)polymerase-1 inhibition interfered in these processes and mitigated Apoptosis Inducing Factor dependent cell death events, thus improved structural and functional alterations of carotid arteries, without affecting blood pressure. Chronic poly(ADP-ribose)polymerase-1 inhibition protected neuronal tissue against oxidative damage, assessed by nitrotyrosine, 4-hydroxinonenal and 8-oxoguanosine immunohistochemistry in the area of Cornu ammonis 1 of the dorsal hippocampus in hypertensive rats. In this area, extensive pyramidal cell loss was also attenuated by treatment with lowered poly(ADP-ribose)polymer formation. It also preserved the structure of fissural arteries and attenuated perivascular white matter lesions and reactive astrogliosis in hypertensive rats. These data support the premise in which chronic poly(ADP-ribose)polymerase-1 inhibition has beneficial effects on hypertension related tissue damage both in vascular tissue and in the hippocampus by altering signaling events, reducing oxidative/nitrosative stress and inflammatory status, without lowering blood pressure.

Streptococcus thermophilus fermented milk reduces serum MDA-LDL and blood pressure in healthy and mildly hypercholesterolaemic adults

Low-density lipoprotein (LDL)-cholesterol, malondialdehyde-modified low-density lipoprotein (MDA-LDL), MDA-LDL/LDL-cholesterol in serum, and blood pressure are considered useful risk markers of cardiovascular diseases. This study aimed to examine whether a fermented milk containing Streptococcus thermophilus YIT 2001 (ST), which has high anti-oxidative activity, would benefit healthy and mildly hyper-LDL-cholesterolaemic adults via a randomised, double-blind, placebo-controlled trial. ST-fermented milk or non-fermented placebo milk (PC) was consumed once a day for 12 weeks by 29 and 30 subjects, respectively, with average serum LDL-cholesterol levels of about 140 mg/dl. Serum levels of LDL-cholesterol and MDA-LDL and blood pressure were analysed before (baseline) and after consumption. Comparisons of the responses between both groups were assessed using analysis of covariance (ANCOVA, with the baseline value as the covariate). ANCOVA demonstrated that the ST group had significant reductions in MDA-LDL, MDA-LDL/LDL-cholesterol, systolic blood pressure (SBP), and diastolic blood pressure (DBP) compared with the PC group during the consumption period (P<0.05). Moreover, stratified analysis revealed that there were significant reductions in MDA-LDL, MDA-LDL/LDL-cholesterol, SBP, and DBP in the ST group compared with the PC group during the consumption period in subjects who had above median (65 U/l) levels of oxidative stress marker MDA-LDL at baseline (P<0.05), but not in subjects with levels below the median. These findings suggest that daily consumption of ST-fermented milk may be beneficial in healthy or mildly hyper-LDL cholesterolaemic subjects through reductions in risk marker values of oxidative stress and/or cardiovascular diseases. The benefits were particularly remarkable in subjects who had higher levels of MDA-LDL.

Chronic exposure to low doses of estradiol-17ß increases blood pressure in young female rats: A possible role for central Endothelin-1

Previously, we demonstrated that chronic exposure to low levels of estradiol-17β (E2) increases mean arterial pressure (MAP) in young female Sprague-Dawley (SD) rats, however, the underlying mechanisms are unclear. Since endothelin-1 (ET-1) is implicated in blood pressure (BP) regulation, we hypothesized that E2’s effects on MAP are mediated through central ET-1. To test this, young female SD rats were either sham implanted or implanted s.c. with slow-release E2 pellets (20 ng/day for 90 days). BP was monitored by telemetry. After 75 days of E2 exposure, ET_A antagonist or vehicle was administered i.c.v. After 90 days of E2 exposure, rats were sacrificed, and the paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) were microdissected for gene expression and protein analysis of ET-1 and its receptors. E2 exposure increased MAP after pellet implantation. Gene expression of ET-1 and ET_A but not ET_B receptors were upregulated in the PVN and RVLM of E2 treated animals. Further, the protein levels of ET_A receptor were also increased in the PVN of E2 treated animals. However, i.c.v. infusion of the ET_A antagonist did not completely block the increase in blood pressure. Our results suggest that increases in central ET-1 activity could possibly play a role in chronic E2-induced increase in BP but further studies are needed to completely understand the contribution of ET-1 in this phenomenon.

Effects of green tea supplementation on inflammation markers, antioxidant status and blood pressure in NaCl-induced hypertensive rat model

Background: Recent studies indicate the important role of chronic inflammation and oxidative stress in the pathogenesis of hypertension. Green tea, due to the high content of catechins, shows high antioxidant activity. Objective: To determine the effect of supplementation with green tea extract on the blood pressure, on the concentration of selected parameters of inflammation and antioxidant status in the model of high-sodium-diet induced hypertension. Design: The study lasted 42 days. The experimental population consisted of 30 rats. The rats were divided into three groups. The rats in the control group were fed a standard diet with 35 g of NaCl per kg of diet, in the second group hypertensive rats were fed a standard diet with NaCl (35 g/kg diet) and with an extract of green tea (2 g/kg diet). The third group consisted of hypertensive rats fed a standard diet with NaCl (35 g/kg diet), and 4 g of green tea extract/kg diet. Results: Supplementation with green tea had no effect on body mass of rats on a high-sodium diet. At the end of the experiment systolic blood pressures in SH2 and SH4 groups were significantly lower than in the control group SK. The SH4 group was characterized by a significantly lower diastolic blood pressure value and concentration of TNF-α in comparison to the SK group. The rats from both SH2 and SH4 groups were characterized by higher total antioxidant status values compared to the control group. Discussion: The mechanism of the beneficial effects of green tea on blood pressure is not clear, but it is believed that it is related to its omnidirectional properties. Conclusions: Supplementation of green tea has a beneficial effect on blood pressure, markers of inflammation and antioxidant status in an experimental model of hypertension.

Vochysia rufa Stem Bark Extract Protects Endothelial Cells against High Glucose Damage

Background: Increased oxidative stress by persistent hyperglycemia is a widely accepted factor in vascular damage responsible for type 2 diabetes complications. The plant Vochysia rufa (Vr) has been used in folk medicine in Brazil for the treatment of diabetes. Thus; the protective effect of a Vr stem bark extract against a challenge by a high glucose concentration on EA.hy926 (EA) endothelial cells is evaluated. Methods: Vegetal material is extracted with distilled water by maceration and evaporated until dryness under vacuum. Then; it is isolated by capillary electrophoresis-tandem mass spectrometry. Cell viability is evaluated on EA cells treated with 0.5-100 µg/mL of the Vr extract for 24 h. The extract is diluted at concentrations of 5, 10 and 25 µg/mL and maintained for 24 h along with 30 mM of glucose to evaluate its protective effect on reduced glutathione (GSH); glutathione peroxidase (GPx) and reductase (GR) and protein carbonyl groups. Results:V. rufa stem bark is composed mainly of sugars; such as inositol; galactose; glucose; mannose; sacarose; arabinose and ribose. Treatment with Vr up to 100 µg/mL for 24 h did not affect cell viability. Treatment of EA cells with 30 mM of glucose for 24 h significantly increased the cell damage. EA cells treated with 30 mM of glucose showed a decrease of GSH concentration and increased Radical Oxygen Species (ROS) and activity of antioxidant enzymes and protein carbonyl levels; compared to control. Co-treatment of EA with 30 mM glucose plus 1-10 μg/mL Vr significantly reduced cell damage while 5-25 μg/mL Vr evoked a significant protection against the glucose insult; recovering ROS; GSH; antioxidant enzymes and carbonyls to baseline levels. Conclusion:V. rufa extract protects endothelial cells against oxidative damage by modulating ROS; GSH concentration; antioxidant enzyme activity and protein carbonyl levels.

Evaluation of the relationship between T663A polymorphism in the alpha-epithelial sodium channel gene and essential hypertension

Objectives:

To evaluate the relationship between alpha epithelial sodium channel (alpha-ENaC) T663A polymorphism and the risk of essential hypertension.

Methods:

This meta-analysis was conducted between November 2014 and February 2015 in Shanghai Medical Instrumentation College, Shanghai, China. We collected all published available case-control data (N=12) identified through PubMed, Web of Science, Scopus, and Chinese National Knowledge Infrastructure (CNKI) up to December 2014. The pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using the fixed- or random-effect model.

Results:

Although subgroup analysis showed that alpha-ENaC T663A polymorphism was associated with essential hypertension in North American individuals (OR=1.55, 95% CI=1.22-1.98, p=0.0003), our meta-analysis results did not confirm such association overall (OR=1.03, 95% CI=0.92-1.15, p=0.62). The lack of association was further confirmed by the non-superiority test (p<0.0001).

Conclusion:

Alpha-ENaC T663A polymorphism might not be a risk factor for essential hypertension.

Beneficial effects of grape seed proanthocyanidin extract on arterial remodeling in spontaneously hypertensive rats via protecting against oxidative stress

Arterial remodeling is a pathogenic occurrence during hypertension and, in turn, is closely associated with the development and complications of hypertension. Grape seed proanthocyanidin extract (GSPE) has been reported to exhibit a protective effect on cardiovascular disease, however its effect on arterial remodeling remains to be fully elucidated. In the present study, the effects of GSPE on arterial remodeling were analyzed by treating spontaneously hypertensive rats (SHRs) with GSPE (250 mg/kg·day). Arterial remodeling was quantified through morphological methods; thoracic aortas were stained with hematoxylin-eosin or sirius red‑victoria blue. The arterial ultrastructure was imaged using transmission electron microscopy. The content of nitric oxide (NO) and endothelin‑1 (ET‑1) were examined to determine endothelial function. Oxidative stress was assessed by malondialdehyde (MDA) levels and the activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Administration of GSPE markedly alleviated hypertension‑induced arterial remodeling, which was not associated with blood pressure control. ET‑1 production was reduced, while NO production was increased in the GSPE group, which exhibited improved endothelial function. In addition, treatment with GSPE significantly ameliorated oxidative stress by improving SOD and CAT activities and reducing MDA formation. In conclusion, GSPE may attenuate hypertension‑induced arterial remodeling by repressing oxidative stress and is recommended as a potential anti‑arterial remodeling agent for patients with hypertensive vascular diseases.

The impact of grape seed extract treatment on blood pressure changes: A meta-analysis of 16 randomized controlled trials

BACKGROUNDS AND OBJECTIVE

Several clinical trials have shown that grape seed extract can reduce blood pressure, but the results are often irreproducible. We therefore sought to systematically evaluate the impact of grape seed extract treatment on the changes of systolic/diastolic blood pressure (SBP/DBP) by meta-analyzing available randomized controlled trials.

METHODS

Trial selection and data extraction were completed independently by 2 investigators. Effect-size estimates were expressed as weighted mean difference (WMD) and 95% confidence interval (CI).

RESULTS

Twelve articles involving 16 clinical trials and 810 study subjects were analyzed. Overall analyses found significant reductions for SBP (WMD = -6.077; 95% CI: -10.736 to -1.419; P = 0.011) and DBP (WMD = -2.803; 95% CI: -4.417 to -1.189; P = 0.001) after grape seed extract treatment. In subgroup analyses, there were significant reductions in younger subjects (mean age < 50 years) for SBP (WMD = -6.049; 95% CI: -10.223 to -1.875; P = 0.005) and DBP (WMD = -3.116; 95% CI: -4.773 to -1.459; P < 0.001), in obese subjects (mean body mass index ≥ 25 kg/m) for SBP (WMD = -4.469; 95% CI: -6.628 to -2.310; P < 0.001), and in patients with metabolic syndrome for SBP (WMD = -8.487; 95% CI: -11.869 to -5.106; P < 0.001). Further meta-regression analyses showed that age, body mass index, and baseline blood pressure were negatively associated with the significant reductions of SBP and DBP after treatment. There was no indication of publication bias.

CONCLUSION

Our findings demonstrate that grape seed extract exerted a beneficial impact on blood pressure, and this impact was more obvious in younger or obese subjects, as well as in patients with metabolic disorders. In view of the small sample size involved, we agree that confirmation of our findings in a large-scale, long-term, multiple-dose randomized controlled trial, especially among hypertensive patients is warranted.

(-)-Epicatechin in vitro ameliorates erythrocyte protein carbonyl content in hypertensive patients: comparison with L-ascorbic acid

CONTEXT

Oxidative stress plays a key role in the patho-physiology of hypertension. (-)-Epicatechin has many important biological properties.

OBJECTIVE

The present study was undertaken to evaluate effect of (-)-epicatechin on protein carbonyl content in gender-based hypertensive patients and normal subjects.

METHODS

The study was carried out on 83 normal (male: 42; female: 41) and 62 hypertensive subjects (male: 32; female: 30). In vitro effect on (-)-epicatechin and L-ascorbic acid was estimated on protein carbonyl content.

RESULTS

Result showed a significant (p < 0.001) increase in protein carbonyl content in hypertensive patients but no gender-based difference was observed. (-)-epicatechin shows significant (p < 0.001) dose-dependent effect as compared to L-ascorbic acid, which is manifested as decrease in protein carbonyl content.

CONCLUSION

We hypothesizes that a higher intake of (-)-epicatechin may provide protection against hypertension in males and females.

Identification of Serum Metabolites Associated With Incident Hypertension in the European Prospective Investigation into Cancer and Nutrition-Potsdam Study

Metabolomics is a promising tool to gain new insights into early metabolic alterations preceding the development of hypertension in humans. We therefore aimed to identify metabolites associated with incident hypertension using measured data of serum metabolites of the European Prospective Investigation Into Cancer and Nutrition (EPIC)-Potsdam study. Targeted metabolic profiling was conducted on serum blood samples of a randomly drawn EPIC-Potsdam subcohort consisting of 135 cases and 981 noncases of incident hypertension, all of them being free of hypertension and not on antihypertensive therapy at the time of blood sampling. Mean follow-up was 9.9 years. A validated set of 127 metabolites was statistically analyzed with a random survival forest backward selection algorithm to identify predictive metabolites of incident hypertension taking into account important epidemiological hypertension risk markers. Six metabolites were identified to be most predictive for the development of hypertension. Higher concentrations of serine, glycine, and acyl-alkyl-phosphatidylcholines C42:4 and C44:3 tended to be associated with higher and diacyl-phosphatidylcholines C38:4 and C38:3 with lower predicted 10-year hypertension-free survival, although visualization by partial plots revealed some nonlinearity in the above associations. The identified metabolites improved prediction of incident hypertension when used together with known risk markers of hypertension. In conclusion, these findings indicate that metabolic alterations occur early in the development of hypertension. However, these alterations are confined to a few members of the amino acid or phosphatidylcholine metabolism, respectively.

Hypertension as an autoimmune and inflammatory disease

Hypertension that is considered idiopathic is called essential hypertension and accordingly has no clear culprit for its cause. However, basic research and clinical studies in recent years have expanded our understanding of the mechanisms underlying the development of essential hypertension. Of these, increased oxidative stress, both in the kidney and arterial wall, closely coupled with inflammatory infiltration now appear to have a prominent role. Discovery of regulatory and interleukin-17-producing T cells has enabled us to better understand the mechanism by which inflammation and autoimmunity, or autoinflammation, lead to the development of hypertension. Despite achieving considerable progress, the intricate interactions between oxidative stress, the immune system and the development of hypertension remain to be fully elucidated. In this review, we summarize recent developments in the pathophysiology of hypertension with a focus on the oxidant stress-autoimmunity-inflammation interaction.

Effect of sour tea (Hibiscus sabdariffa L.) on arterial hypertension: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Hibiscus sabdariffa L. is a tropical wild plant rich in organic acids, polyphenols, anthocyanins, polysaccharides, and volatile constituents that are beneficial for the cardiovascular system. Hibiscus sabdariffa beverages are commonly consumed to treat arterial hypertension, yet the evidence from randomized controlled trials (RCTs) has not been fully conclusive. Therefore, we aimed to assess the potential antihypertensive effects of H. sabdariffa through systematic review of literature and meta-analysis of available RCTs.

METHODS

The search included PUBMED, Cochrane Library, Scopus, and EMBASE (up to July 2014) to identify RCTs investigating the efficacy of H. sabdariffa supplementation on SBP and DBP values. Two independent reviewers extracted data on the study characteristics, methods, and outcomes. Quantitative data synthesis and meta-regression were performed using a fixed-effect model, and sensitivity analysis using leave-one-out method. Five RCTs (comprising seven treatment arms) were selected for the meta-analysis. In total, 390 participants were randomized, of whom 225 were allocated to the H. sabdariffa supplementation group and 165 to the control group in the selected studies.

RESULTS

Fixed-effect meta-regression indicated a significant effect of H. sabdariffa supplementation in lowering both SBP (weighed mean difference -7.58 mmHg, 95% confidence interval -9.69 to -5.46, P < 0.00001) and DBP (weighed mean difference -3.53 mmHg, 95% confidence interval -5.16 to -1.89, P < 0.0001). These effects were inversely associated with baseline BP values, and were robust in sensitivity analyses.

CONCLUSION

This meta-analysis of RCTs showed a significant effect of H. sabdariffa in lowering both SBP and DBP. Further well designed trials are necessary to validate these results.

Assessment of Oxidative DNA Damage by Alkaline Comet Assay in Human Essential Hypertension

The objective of the present study was to investigate the antioxidant status and the extent of oxidative DNA damage in lymphocytes and their relation with essential hypertension (EHT). A total of 100 South Indian subjects aged 30-65 were included for the study. Of these 50 were normotensive controls (group-1) with blood pressure ≥120/80 mm Hg, 50 were newly diagnosed (group-2) and were not on any antihypertensive drugs, but had systolic blood pressure ranging between 140 and 160 mmHg and diastolic blood pressure 95-100 mmHg and 50 newly diagnosed essential hypertensive patients underwent drug therapy for 1 year was considered as group-3. Enzymatic and non-enzymatic antioxidants significantly decreased and lymphocyte DNA damage was significantly increased in newly diagnosed hypertensive patients compared with control group. The major decrease in DNA damage and significant improvement in enzymatic and non-enzymatic antioxidants were observed after 1 year of antihypertensive therapy in treated group compared with newly diagnosed hypertensive patients. Total antioxidant status and lymphocyte DNA damage showed a strong negative correlation in all the three groups. Essential hypertension associated with oxidative stress which in turn causes genotoxic susceptibility to variety of disease including cancer. In the absence of DNA repair process and DNA checkpoint mechanisms, the genomic integrity is susceptible to extensive damage. In our study, increased oxidative DNA damage and decreased antioxidant levels were frequently observed in the newly diagnosed essential hypertensive patients, suggesting that oxidative stress is important in the pathogenesis of EHT. Therefore, the present study has additional clinical implication. Further investigations with large number of patients along with antioxidant supplement are highly warranted.

Are increased oxidative stress and asymmetric dimethylarginine levels associated with masked hypertension?

OBJECTIVE

In this study, our aim was to determine total oxidative stress and asymmetric dimethylarginine (ADMA) levels in patients with masked hypertension (MHT) and to examine their association with blood pressure.

METHODS

Fifty patients diagnosed with MHT and 48 healthy volunteers without any known chronic diseases have been included in this study.

RESULTS

When compared to the control group, patients with MHT had higher levels of mean ADMA (p < 0.001), total oxidant status (TOS) (p < 0.001), and oxidative stress index (OSI) (p < 0.001), and a lower mean total antioxidant status (TAS) (p < 0.001) level. While a positive correlation was determined between the systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels with ADMA, TOS, and OSI levels, a negative correlation was determined with the TAS level. During the stepwise multivariable logistic regression analysis, age (OR = 1.221; p = 0.003), body mass index (OR = 1.512; p = 0.005), low density lipoprotein (OR = 0.925; p = 0.016), ADMA (OR = 1.200; p = 0.002), and OSI (OR = 3.750; p = 0.002) levels were determined to be the predictors of MHT. During the linear regression analysis, it was determined that the independent risk factors of SBP and DBP are ADMA and OSI, and the independent risk factor of TOS, OSI, and ADMA is SBP. Our study found out that oxidative stress and ADMA levels of patients with MHT are higher than those of the control group. ADMA and OSI were determined to be predictors of MHT.

CONCLUSION

Based on these results, it could be said that oxidative stress, and therefore the ADMA level, could have an effect on the etiopathogenesis of MHT.

The Level of Selenium and Oxidative Stress in Workers Chronically Exposed to Lead

The possible beneficial role of selenium (Se) on the oxidative stress induced by lead (Pb) is still unclear in humans. Therefore, the aim of the present study was to explore the associations among the Se levels, chronic Pb exposure, oxidative stress parameters, and parameters characterizing the function of the antioxidant defense system in men who are occupationally exposed to Pb. Based on the median serum Se concentrations, the 324 study subjects were divided into two subgroups: a subgroup with a low Se level (L-Se) and a subgroup with a high Se level (H-Se). The levels of lead (PbB) and zinc protoporphyrin (ZPP) in the blood and the delta-aminolevulinic acid (ALA) level in the urine served as indices of Pb exposure. The PbB level was significantly lower in the H-Se group compared to that in the L-Se group by 6 %. The levels of 8-hydroxyguanosine and lipofuscin (LPS) and the activity of superoxide dismutase were significantly lower in the H-Se group compared to that in the L-Se group by 17, 19, and 11 %, respectively. However, the glutathione level (GSH) and the activities of glutathione peroxidase (GPx) and catalase were significantly higher by 9, 23, and 3 %. Spearman correlations showed positive associations between the Se level and GPx activity and GSH level. A lower serum Se level in chronically Pb-exposed subjects is associated with higher Pb blood levels and an elevated erythrocyte LPS level, which reflects the intensity of oxidative stress. Besides, in a group of Pb-exposed subjects with lower serum Se level, depleted GSH pool and decreased activity of GPx in erythrocytes were reported. However, the present results are inadequate to recommend Se supplementation for chronic lead exposure at higher doses than would be included in a normal diet except for selenium deficiency.

The acute impact of polyphenols from Hibiscus sabdariffa in metabolic homeostasis: an approach combining metabolomics and gene-expression analyses

We explored the acute multifunctional effects of polyphenols from Hibiscus sabdariffa in humans to assess possible consequences on the host's health. The expected dynamic response was studied using a combination of transcriptomics and metabolomics to integrate specific functional pathways through network-based methods and to generate hypotheses established by acute metabolic effects and/or modifications in the expression of relevant genes. Data were obtained from healthy male volunteers after 3 hours of ingestion of an aqueous Hibiscus sabdariffa extract. The data were compared with data obtained prior to the ingestion, and the overall findings suggest that these particular polyphenols had a simultaneous role in mitochondrial function, energy homeostasis and protection of the cardiovascular system. These findings suggest beneficial actions in inflammation, endothelial dysfunction, and oxidation, which are interrelated mechanisms. Among other effects, the activation of the heme oxygenase-biliverdin reductase axis, the systemic inhibition of the renin-angiotensin system, the inhibition of the angiotensin-converting enzyme, and several actions mirroring those of the peroxisome proliferator-activated receptor agonists further support this notion. We also found concordant findings in the serum of the participants, which include a decrease in cortisol levels and a significant increase in the active vasodilator metabolite of bradykinin (des-Arg(9)-bradykinin). Therefore, our data support the view that polyphenols from Hibiscus sabdariffa play a regulatory role in metabolic health and in the maintenance of blood pressure, thus implying a multi-faceted impact in metabolic and cardiovascular diseases.

Urotensin-ⅡReceptor Antagonist SB-710411 Protects Rat Heart against Ischemia-Reperfusion Injury via RhoA/ROCK Pathway

Aim

SB-710411 is a rat selective urotensin-II (U-II) receptor antagonist, which can block U-II-induced contraction of the aorta and inhibit U-II-induced myocardial fibrosis in rats. However, the effect of SB-710411 on myocardial ischemia-reperfusion (I/R) injury is unclear. The present study was designed to investigate whether SB-710411 has a protective effect on myocardial I/R injury in rats and the possible mechanisms.

Methods and Results

Myocardial I/R injury was induced by occluding the left anterior descending coronary artery in adult male Sprague-Dawley rats. Hemodynamic parameters, electrocardiogram (ECG), infarct size, histological alteration, lactate dehydrogenase (LDH), creatine phosphokinase-MB (CK-MB), cardiac troponin I (cTnI), RhoA, and the protein expressions of U-II receptor (UTR), ROCK₁ and ROCK₂ were evaluated. Cardiac I/R injury significantly up-regulated the expressions of UTR, ROCK₁ and ROCK₂ proteins in rat myocardium. SB-710411 1.0 and 2.0 μg/kg significantly reduced cardiac I/R-induced the infarct size and histological damage in rat myocardium, markedly inhibited the changes of hemodynamic parameters and the increases of ST-segment in ECG, the serum LDH and CK-MB activities and cTnI level in rats subjected to myocardial I/R injury. Furthermore, SB-710411 obviously prevented myocardial I/R-increased RhoA activity and UTR, ROCK₁ and ROCK₂ protein expressions.

Conclusions

Our results indicate that cardiac I/R injury increases myocardial UTR expression, and SB-710411 has a potent protective effect on myocardial I/R injury in rats. The cardioprotection may be associated with the inhibition of UTR-RhoA/ROCK pathway.

Nitric oxide and the cardiovascular system

Nitric oxide (NO) generated by endothelial cells to relax vascular smooth muscle is one of the most intensely studied molecules in the past 25 years. Much of what is known about NO regulation of NO is based on blockade of its generation and analysis of changes in vascular regulation. This approach has been useful to demonstrate the importance of NO in large scale forms of regulation but provides less information on the nuances of NO regulation. However, there is a growing body of studies on multiple types of in vivo measurement of NO in normal and pathological conditions. This discussion will focus on in vivo studies and how they are reshaping the understanding of NO's role in vascular resistance regulation and the pathologies of hypertension and diabetes mellitus. The role of microelectrode measurements in the measurement of [NO] will be considered because much of the controversy about what NO does and at what concentration depends upon the measurement methodology. For those studies where the technology has been tested and found to be well founded, the concept evolving is that the stresses imposed on the vasculature in the form of flow-mediated stimulation, chemicals within the tissue, and oxygen tension can cause rapid and large changes in the NO concentration to affect vascular regulation. All these functions are compromised in both animal and human forms of hypertension and diabetes mellitus due to altered regulation of endothelial cells and formation of oxidants that both damage endothelial cells and change the regulation of endothelial nitric oxide synthase.

Longitudinal Association between Selenium Levels and Hypertension in a Rural Elderly Chinese Cohort

OBJECTIVES

Results from previous studies have been inconsistent on the association between selenium and hypertension, and very few studies on this subject have focused on the elderly population. The purpose of this study is to examine the relationship between selenium level and hypertension in a rural elderly Chinese cohort.

DESIGN

A longitudinal study was implemented and data were analyzed using logistic regression models and Cox proportional hazards regression model adjusting for potential confounders. The associations between selenium level and prevalent hypertension at baseline and between selenium and incident hypertension were examined.

SETTING

Community-based setting in four rural areas in China.

SUBJECTS

A total of 2000 elderly aged 65 years and over (mean 71.9±5.6 years) participated in this study.

MEASUREMENTS

Nail selenium levels were measured in all subjects at baseline. Blood pressure measures and self-reported hypertension history were collected at baseline, 2.5 years and 7 years later. Hypertension was defined as systolic blood pressure 140 mmHg or higher, diastolic blood pressure 90 mmHg or higher, or reported use of anti-hypertensive medication.

RESULTS

The rate of baseline hypertension was 63.50% in this cohort and the mean nail selenium level is 0.413±0.183μg/g. Multi-covariate adjusted cross-sectional analyses indicated that higher selenium level was associated with higher blood pressure measures at baseline and higher rates of hypertension. For the 635 participants with normal blood pressure at baseline, 360 had developed hypertension during follow-up. The incidence rate for hypertension was 45.83%, 52.27%, 62.50%, 70.48%, and 62.79% from the first selenium quintile to the fifth quintile respectively. Comparing to the lowest quintile group, the hazard ratios were 1.41 (95%CI: 1.03 to1.94), 1.93 (95%CI: 1.40 to 2.67), 2.35 (95%CI: 1.69 to 3.26) and 1.94 (95%CI: 1.36 to 22.77) for the second selenium quintile to the fifth quintile respectively.

CONCLUSIONS

Our findings suggest that high selenium may play a harmful role in the development of hypertension. Future studies are needed to confirm our findings and to elucidate a plausible biological mechanism.

Dynamic thiol/disulphide homeostasis in patients with newly diagnosed primary hypertension

We aimed to investigate the thiol/disulphide homeostasis in patients with newly diagnosed primary hypertension with a novel and automated method. Blood thiol/disulphide homeostasis, which consists of native thiol/disulphide exchanges, was investigated in 45 patients with primary hypertension and 45 healthy controls. The levels of native thiol, total thiol, and native thiol/total thiol ratio were lower while the disulphide level and disulphide/native thiol and disulphide/total thiol ratios were higher in patients with primary hypertension when compared with those in the control group. Positive correlation was detected between 24-hour systolic and diastolic blood pressure levels and disulphide/native thiol ratio. With reference to the stepwise multiple linear regression model; increase in disulphide/native thiol ratio and log(24-hour urine microalbumin) and decrease in native thiol/total thiol ratio are independent predictors of 24-hour systolic and diastolic blood pressure. This study demonstrated that thiol/disulphide homeostasis was shifted toward disulphide formation in patients with primary hypertension.

Hypercholesterolemia and Hypertension: Two Sides of the Same Coin

The aim of this review article is to summarize the current knowledge about mechanisms that connect blood pressure regulation and hypercholesterolemia, the mutual interaction between hypertension and hypercholesterolemia, and their influence on atherosclerosis development. Our research shows that at least one-third of the population of Western Europe has hypertension and hypercholesterolemia. Several biohumoral mechanisms could explain the relationship between hypertension and hypercholesterolemia and the association between these risk factors and accelerated atherosclerosis. The most investigated mechanisms are the renin-angiotensin-aldosterone system, oxidative stress, endothelial dysfunction, and increased production of endothelin-1. Arterial hypertension is frequently observed in combination with hypercholesterolemia, and this is related to accelerated atherosclerosis. Understanding the mechanisms behind this relationship could help explain the benefits of therapy that simultaneously reduce blood pressure and cholesterol levels.

7, 8-Dihydroxyflavone Protects an Endothelial Cell Line from H2O2 Damage

7, 8-dihydroxyflavone (7, 8-DHF), a selective agonist for TrkB receptors, has been well studied for its neurotrophic functions. However, its roles outside the neural tissues have scarcely been studied as yet. In this study, we investigated the protecting roles of 7, 8-DHF in EA.hy926 cells, a human umbilic vein endothelial cell line which was exposed to hydrogen peroxide (H2O2). We found that 7, 8-DHF significantly protected the cells from being damaged by H2O2 through suppression of apoptosis, attenuation of inflammatory factor releasing and inhibition of reactive oxygen species generation. The potent biological effects of 7, 8-DHF were probably executed via its binding to TrkB receptors because the receptor specific antagonist ANA-12 significantly blocked its protecting effects. The protecting roles of 7, 8-DHF in EA.hy926 cells suggest that it will be a promising compound to be developed into a health product that definitely benefits endothelial functions and prevents cardiovascular diseases.

Glutathione Supplementation Attenuates Oxidative Stress and Improves Vascular Hyporesponsiveness in Experimental Obstructive Jaundice

We investigated the protective effects and mechanism of glutathione (GSH) on vascular hyporesponsiveness induced by bile duct ligation (BDL) in a rat model. Seventy-two male Sprague-Dawley rats were randomly divided into four groups: a NS group, a GSH group, a BDL + NS group, and a BDL + GSH group. GSH was administrated into rats in the GSH and BDL + GSH groups by gastric gavage. An equal volume of normal saline was, respectively, given in the NS group and BDL + NS group. Blood was gathered for serological determination and thoracic aorta rings were isolated for measurement of isometric tension. Obstructive jaundice led to a significant increase in the serum total bilirubin, AST, and ALT levels. The proinflammatory cytokines levels (TNF-α and IL-1β), concentration of NO, and oxidative stress markers (MDA and 3-NT) were increased as well. All of those were reduced by the treatment of GSH. Meanwhile, contraction of aorta rings to NA and vasorelaxation to ACh or SNP in the BDL group rats were markedly decreased, while GSH administration reversed this change. Our findings suggested that GSH supplementation attenuated overexpressed ONOO(−) from the reaction of excessive NO with O₂^∙- and protected against obstructive jaundice-induced vascular hyporesponsiveness in rats.

Oxidative stress, oxidative balance score, and hypertension among a racially diverse population

Hypertension is a risk factor for several vascular diseases. Evidence suggests that oxidative stress (OS) plays a significant role in its pathophysiology. Human studies have shown inconsistent results, varying based on the OS biomarker and study population. In a racially diverse population, examine the association between: (1) blood pressure or hypertension and four markers of OS and (2) blood pressure or hypertension and oxidative balance score (OBS). Using data (n = 317) from the cross-sectional study on race, stress, and hypertension, an OBS was constructed from various measures of pro-oxidant and antioxidant exposures. OS was assessed by four biomarkers: fluorescence oxidative products, F2-isoprostanes, mitochondrial DNA copy number, and gamma tocopherol. Multivariate linear and logistic regression analyses were used to estimate the associations of interest. None of the adjusted associations between hypertension and OS markers was statistically significant. OBS was inversely associated with hypertension after adjusting for study covariates. Persons with higher OBS have lower odds of having hypertension; however, the evidence on the relationship between OS markers and blood pressure remains unconvincing.

Mechanisms and consequences of endothelial nitric oxide synthase dysfunction in hypertension

Reduced nitric oxide bioavailability contributes to endothelial dysfunction and hypertension. The endothelial isoform of nitric oxide synthase (eNOS) is responsible for the production of nitric oxide within the endothelium. Loss of eNOS cofactor tetrahydrobiopterin to initial increase in oxidative stress leads to uncoupling of eNOS, in which the enzyme produces superoxide anion rather than nitric oxide, further substantiating oxidative stress to induce vascular pathogenesis. The current review focuses on recent advances on the molecular mechanisms and consequences of eNOS dysfunction in hypertension, and potential novel therapeutic strategies restoring eNOS function to treat hypertension.

Clinical implication of hematological indices in the essential hypertension

Prognostic value of haematological indices, especially red cell distribution width, neutrophil lymphocyte ratio and mean platelet volume, was reported with numerous investigations in miscellaneous cardiovascular settings. Their major prognostic value was linked to oxidative stress and inflammation since their level was correlated with major inflammatory markers such as high sensitive C-reactive protein and interleukins. Oxidative stress and chronic inflammation are also postulated as the main pathophysiologic mechanism of essential hypertension (HT) and its vascular complication. Recently, correlation between HT and haematological parameters was searched in numerous studies, which has made the topic more popular. Herein, we reveal the correlation between haematological indices and HT and we also demonstrate the clinical implication of this correlation. Impaired haematological parameters may strongly indicate hypertensive end-organ damage.

An assessment of oxidized LDL in the lipid profiles of patients with obstructive sleep apnea and its association with both hypertension and dyslipidemia, and the impact of treatment with CPAP

OBJECTIVE

Obstructive sleep apnea (OSA) has been linked to increased oxidative stress, lipid peroxidation and worsening atherosclerosis. This study investigated oxidized low-density lipoprotein (oxLDL) as a marker of lipid peroxidation, and total LDL cholesterol (direct LDL-C), as a marker of the lipid profile among individuals with OSA, and its association with hypertension (HYP) and dyslipidemia (DYS). The impact of one year of continuous positive airway pressure (CPAP) was also assessed.

METHODS

Blood was collected after 12 h of fasting from 99 consecutive patients who were diagnosed with OSA via polysomnography, and were also diagnosed with both HYP and DYS via clinical and laboratory studies. The patients were classified into the following three groups: GI [OSA with comorbidities (HYP or DYS)], GII [OSA without comorbidities], and GIII [control]. Thirty-five patients with an apnea/hypopnea index >20 per hour of sleep were randomized to groups that received either Sham-CPAP or CPAP treatments over 12 months.

RESULTS

In a binary regression controlled for sex, age, body mass index, and glycemia, model 1 which analyzed direct LDL-C, demonstrated significant levels of risk in the setting of DYS but not in the settings of HYP and OSA. In model 2, which analyzed oxLDL, DYS (p = 0.01), HYP (p = 0.032), and OSA (p = 0.039) were statistically significant. Significant alterations were observed in only the sleep parameters following one year of CPAP.

CONCLUSIONS

Based on the statistical regression model, only the presence of DYS (p = 0.001) was associated with the levels of direct LDL-C. The remaining comorbidities (OSA and HYP) were not significantly related to the levels of direct LDL-C. Regarding oxLDL, OSA, HYP and DYS each added significant score values to the levels of oxLDL. These findings are suggestive of the importance of assessing oxLDL among patients presenting with OSA, both with and without comorbidities.

Mitochondrial and genomic ancestry are associated with etiology of heart failure in Brazilian patients

There is a high prevalence of heart failure (HF) in the general population, but it is more common in black people. We evaluated the association between genomic ancestry and mitochondrial haplogroups (mt-haplogroups) with HF etiology in 503 Brazilian patients. We elicited Mt-haplogroups by analyzing the control region of mitochondrial DNA, and genomic ancestry, by using 48 autosomal insertion-deletion ancestry informative markers. Hypertensive (28.6%, n=144) and ischemic (28.4%, n=143) etiologies of HF were the most prevalent herein. Our results showed that 233 individuals (46.3%) presented African mitochondrial (mt)-haplogroups, and the major contribution in the genomic ancestry analysis was the European ancestry (57.5% (±22.1%)). African mt-haplogroups were positively associated with a diagnosis of hypertensive cardiomyopathy (odds ratio, OR 1.55, confidence interval, CI 95% 1.04-2.44, P=0.04) when compared with European mt-haplogroups. Regarding the genomic ancestry, the African ancestry variant had higher risks (OR 7.84, 95% CI 2.81-21.91, P<0.001), whereas the European ancestry variant had lower risks (OR 0.14, 95% CI 0.04-5.00, P<0.001) for developing the hypertensive etiology. In addition, European ancestry showed an OR of 4.05 (CI 95% 1.53-10.74, P=0.005), whereas African ancestry showed an OR of 0.17 (CI 95% 0.06-0.48, P=0.001) for developing ischemic etiology. In conclusion, this study supports the importance of using ancestry informative markers and mitochondrial DNA to study the genetics of complex diseases in admixed populations to improve the management, treatment and prevention of these illnesses. Therefore, the ancestry informative markers and mt-haplogroups could provide new biomarkers to be associated with HF etiologies and be used as a premise for more specific management.

Selenium and its supplementation in cardiovascular disease--what do we know?

The trace element selenium is of high importance for many of the body’s regulatory and metabolic functions. Balanced selenium levels are essential, whereas dysregulation can cause harm. A rapidly increasing number of studies characterizes the wide range of selenium dependent functions in the human body and elucidates the complex and multiple physiological and pathophysiological interactions of selenium and selenoproteins. For the majority of selenium dependent enzymes, several biological functions have already been identified, like regulation of the inflammatory response, antioxidant properties and the proliferation/differentiation of immune cells. Although the potential role of selenium in the development and progression of cardiovascular disease has been investigated for decades, both observational and interventional studies of selenium supplementation remain inconclusive and are considered in this review. This review covers current knowledge of the role of selenium and selenoproteins in the human body and its functional role in the cardiovascular system. The relationships between selenium intake/status and various health outcomes, in particular cardiomyopathy, myocardial ischemia/infarction and reperfusion injury are reviewed. We describe, in depth, selenium as a biomarker in coronary heart disease and highlight the significance of selenium supplementation for patients undergoing cardiac surgery.