Vascular oxidative stress precedes high blood pressure in spontaneously hypertensive rats

The Association Between 24-Hour Blood Pressure Profiles and Dementia

Midlife hypertension increases risk for dementia. Around one third of adults have diagnosed hypertension; however, many adults are undiagnosed, or remain hypertensive despite diagnosis or treatment. Since blood pressure (BP) follows a circadian rhythm, ambulatory BP monitoring allows for the assessment of BP over a 24-hour period and provides an important tool for improving the diagnosis and management of hypertension. The measurement of 24-hour BP profiles, especially nocturnal BP, demonstrate better predictive ability for cardiovascular disease and mortality than office measurement. However, few studies have examined 24-hour BP profiles with respect to dementia risk. This is an important topic since improvements in BP management could facilitate the primary prevention of vascular cognitive impairment and dementia. Therefore, this review discusses the evidence linking BP to dementia, with a focus on whether the implementation of 24-hour BP measurements can improve risk prediction and prevention strategies. Pathways linking nocturnal BP to dementia are also discussed as are risk reduction strategies. Overall, limited research suggests an association between 24-hour BP elevation and poorer cognition, cerebral small vessel disease, and dementia. However, most studies were cross-sectional. Further evidence is needed to substantiate 24-hour BP profiles, over and above office BP, as predictors of vascular cognitive impairment and incident dementia.

Association between oxidative balance score and new-onset hypertension in adults: A community-based prospective cohort study

Introduction

Oxidative stress plays a key role in the pathophysiology of hypertension development. The oxidative balance score (OBS) comprises dietary and lifestyle pro- and anti-oxidant components and reflects the overall oxidative stress burden. We aimed to evaluate the association between the OBS and new-onset hypertension (HTN) using large, community-based, prospective Korean cohort data.

Methods

Among 10,030 participants aged 40-69 years included in the Korean Genome and Epidemiology Study, the data of 5,181 participants were analyzed. The hazard ratio (HR) and 95% confidence interval (CI) for new-onset HTN according to sex-specific OBS quartile groups were calculated using univariable and multivariable Cox proportional hazard regression analyses.

Results

During the mean 13.6-year follow-up period, 1,157 men and 1,196 women developed new-onset HTN. Compared to the Q1 group, the adjusted HRs (95%CI) for new-onset HTN in the Q2, Q3, and Q4 groups were 0.96 (0.82-1.16), 0.85 (0.72-0.99), and 0.71 (0.59-0.86) in men and 0.81 (0.69-0.95), 0.81(0.68-0.95), and 0.70 (0.57-0.84) in women, respectively.

Discussion

Individuals with high OBS are at lower risk of developing HTN. This study suggests that a healthy lifestyle and antioxidant rich diet could be a preventive strategy for HTN.

Involvement of AGE and Its Receptors in the Pathogenesis of Hypertension in Elderly People and Its Treatment

Both systolic and diastolic blood pressures increase with age up to 50 to 60 years of age. After 60 years of age systolic pressure rises to 84 years of age but diastolic pressure remains stable or even decreases. In the oldest age group (85-99 years), the systolic blood pressure (SBP) is high and diastolic pressure (DBP) is the lowest. Seventy percent of people older than 65 years are hypertensive. This paper deals with the role of advanced glycation end products (AGE) and its cell receptor (RAGE) and soluble receptor (sRAGE) in the development of hypertension in the elderly population. Plasma/serum levels of AGE are higher in older people as compared with younger people. Serum levels of AGE are positively correlated with age, arterial stiffness, and hypertension. Low serum levels of sRAGE are associated with arterial stiffness and hypertension. Levels of sRAGE are negatively correlated with age and blood pressure. Levels of sRAGE are lower in patients with arterial stiffness and hypertension than patients with high levels of sRAGE. AGE could induce hypertension through numerous mechanisms including, cross-linking with collagen, reduction of nitric oxide, increased expression of endothelin-1, and transforming growth factor-β (TGF-β). Interaction of AGE with RAGE could produce hypertension through the generation of reactive oxygen species, increased sympathetic activity, activation of nuclear factor-kB, and increased expression of cytokines, cell adhesion molecules, and TGF- β. In conclusion, the AGE-RAGE axis could be involved in hypertension in elderly people. Treatment for hypertension in elderly people should be targeted at reduction of AGE levels in the body, prevention of AGE formation, degradation of AGE in vivo, downregulation of RAGE expression, blockade of AGE-RAGE interaction, upregulation of sRAGE expression, and use of antioxidants.

Gao-Zi-Yao improves learning and memory function in old spontaneous hypertensive rats

Aims

Gao-Zi-Yao has long been a unique way for treating various diseases. The present study is to explore the effect of Gao-Zi-Yao on learning and memory function in old spontaneous hypertensive rats (SHR) and its possible mechanism.

Method

Male old SHR were received different doses of Gao-Zi-Yao for 4 weeks. Systolic blood pressure (SBP) and heart rate were monitored. Serum levels of nitric oxide (NO), interleukin (IL)-1β, IL-2, and tumor necrotic factor (TNF)-α were measured. Morris water maze was performed to test the learning and memory function of the rats. Number of neurons in hippocampus was counted by Nissl staining. Western blot was applied to detect the expressions of learning and memory function related proteins, N-methyl-d-aspartate receptor 2B (NMDAR 2B), glutamate receptor 1 (GluR1), phosphorylated-calmodulin-dependent protein kinase II (p-CaMK II), and phosphorylated-cAMP responsive element-binding protein (p-CREB) in rat hippocampus.

Results

Data showed that Gao-Zi-Yao reduced SBP in old SHR, elevated NO level, and suppressed levels of IL-1β, IL-2, TNF-α. The results of Morris water maze experiment showed that Gao-Zi-Yao dose-dependently improved learning and memory function. Number of neurons in the hippocampal dentate gyrus (DG) region of the old SHR was increased by Gao-Zi-Yao treatment. In addition, Gao-Zi-Yao elevated the protein expressions of NMDAR 2B, GluR1, p-CaMK II, and p-CREB in hippocampus.

Conclusion

Gao-Zi-Yao decreases SBP and improves the learning and memory function of the old SHR by regulation of oxidative stress, inflammatory factors and neuron number in hippocampal DG area and the expression of learning and memory function related proteins.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03630-0.

Age- and Phenotype-Dependent Changes in Circulating MMP-2 and MMP-9 Activities in Normotensive and Hypertensive Rats

Matrix metalloproteinases (MMPs) are important in the pathogenesis of numerous diseases. The present study aimed to monitor the activation of MMP-2 and MMP-9 in spontaneously hypertensive rats (SHR) and their normotensive counterparts-Wistar-Kyoto rats (WKY). The animals were divided according to age (7, 20, and 52 weeks) and phenotype into: WKY-7, WKY-20, WKY-52, SHR-7, SHR-20 and SHR-52 groups. MMP plasma activities were determined by gelatine zymography. We monitored selected parameters of oxidative stress and antioxidant status. N-terminal pro-brain natriuretic peptide (NT-proBNP) was determined as a marker of heart function and neurohumoral activation. SHR-7 showed higher MMP-2 activity compared with WKY-7, while SHR-52 showed lower MMP-2 and MMP-9 activities compared with WKY-52. Examining age-dependent changes in MMP activities, we found a decrease in MMP-2 activity and increase in MMP-9 activity with increasing age in both phenotypes. Parameters of oxidative stress and antioxidant status as well as NT-proBNP levels were not significantly worsened due to aging in SHR. Our results suggest that hypertension is accompanied by varying MMP activation during aging. The results of our study may indicate that MMP-2 inhibition is therapeutically applicable during the development of hypertension, while in developed, stabilized and uncomplicated hypertension, systemic MMP-2 and MMP-9 inhibition may not be desirable.

LC-MS-Based Lipidomic Analysis of Serum Samples from Spontaneously Hypertensive Rats Treated with an Extract of Acanthopanax sessiliflorus Fruits

Recently, lipidomics has revealed that many diseases are highly associated with altered lipid metabolism, as in the case of hypertension affecting serum lipid metabolism. In this study, an LC-MS-based lipidomic approach was used to profile serum lipids in spontaneously hypertensive rats (SHRs) treated with an extract of Acanthopanax sessiliflorus fruits (ASF), to elucidate the serum lipid metabolism alteration by hypertension and the treatment of a drug or ASF. First, UPLC-QTOF/MS profiled a total of 208 lipids from six pooled samples of normal controls, SHR, SHR + 100 mg/kg of drug, and SHR + ASF 200, 400, or 600 mg/kg. These six groups were differentiated by the PCA and sPLS-DA, and 120 lipid species were identified as differentially regulated lipids (DRLs) by ANOVA (p values < 0.05). Second, UPLC-QqQ/MS was used for the target profiling of 120 DRLs from individual samples of the six groups. Using an ANOVA, 67 lipids (38 TGs, 4 DGs, 17 PCs, 2 PEs, and 6 LPCs) were selected as validated DRLs. The mostly altered lipids, such as TG (62:13), TG (60:13), PC (34:4), PC (36:5), and PC (38:2), were decreased in SHR compared to the normal control, and received little by treatment with ASF. These results demonstrated the correlation between hypertension and serum lipid metabolism. Furthermore, both drug and ASF treatment similarly altered the lipid profiles of SHRs. Finally, we found that DRLs have the potential to help us to interpret the lipid metabolism of hypertension.

Antioxidant and vasorelaxant effects of aqueous extract of large cardamom in L-NAME induced hypertensive rats

PURPOSE

The present work aimed to study the effect of aqueous extract of large cardamom (AELC) to prevent vascular remodeling and oxidative stress in N^ω-Nitro-L-arginine methyl ester (L-NAME)-induced hypertension.

METHOD

Male Wistar rats were administered with L-NAME 40 mg/kg/day for 28 days by oral gavage. The treatments included captopril (20 mg/kg/day) or AELC (100, 200 and 400 mg/kg/day) along with L-NAME administration.

RESULTS

L-NAME treated rats showed high systolic, diastolic and mean arterial pressure, decreased nitric oxide level, increased level of malondialdehyde in plasma, heart, aorta and kidney, hypertrophy of the vascular wall and reduced vascular response to acetylcholine in phenylephrine-precontracted aorta. Treatment with AELC markedly reduced the blood pressure, restored the nitric oxide level, reduced the malondialdehyde level, alleviated the hypertrophy in L-NAME-induced hypertensive rats. Additionally, it also improved the vascular response to acetylcholine in phenylephrine pre-contracted aorta.

CONCLUSION

In conclusion, our results demonstrate the preventive effect of AELC in L-NAME-induced hypertensive model, which is possibly related to antioxidant activities and restoration of nitric oxide level.

Chronic NOS Inhibition Affects Oxidative State and Antioxidant Response Differently in the Kidneys of Young Normotensive and Hypertensive Rats

Deficiency of nitric oxide (NO) and oxidative stress can be a cause, a consequence, or, more often, a potentiating factor for hypertension and hypertensive renal disease. Both NO and superoxide anions are radical molecules that interact with each other, leading to oxidative damage of such organs as the kidney. In the present study, we investigated the effect of chronic-specific (neuronal NOS inhibition) and nonspecific NOS inhibition on the oxidative state and antioxidant response and associated oxidative damage of the kidney of young normotensive and hypertensive rats. Young male normotensive Wistar rats (WRs, age 4 weeks) and spontaneously hypertensive rats (SHRs, age 4 weeks) were divided into three groups for each strain by the type of administered compounds. The first group was treated with 7-nitroindazole (WR+7-NI; SHR+7-NI), the second group was treated with N(G)-nitro-L-arginine-methyl ester (WR+L-NAME; SHR+L-NAME), and the control group was treated with pure drinking water (WR; SHR) continuously for up to 6 weeks. Systolic blood pressure increased in WR+L-NAME after the first week of administration and increased slightly in SHR+L-NAME in the third week of treatment. 7-NI had no effect on blood pressure. While total NOS activity was not affected by chronic NOS inhibition in any of the WR groups, it was attenuated in SHR+7-NI and SHR+L-NAME. Nitration of proteins (3-nitrotyrosine expression) was significantly reduced in WR+7NI but not in WR+L-NAME and increased in SHR+7-NI and SHR+L-NAME. Immunoblotting analysis of SOD isoforms showed decreased SOD2 and SOD3 expressions in both WR+7-NI and WR+L-NAME followed by increased SOD activity in WR+L-NAME. Conversely, increased expression of SOD2 and SOD3 was observed in SHR+L-NAME and SHR+7-NI, respectively. SOD1 expression and total activity of SOD did not change in the SHR groups. Our results show that the antioxidant defense system plays an important role in maintaining the oxidative state during NO deficiency. While the functioning antioxidant system seeks to balance the oxidation state in the renal cortex of normotensive WRs, the impaired antioxidant activity leads to the development of oxidative damage of proteins in the kidney induced by peroxynitrite in SHRs.

Antihypertensive and antioxidant activities of enzymatic wheat bran protein hydrolysates

Bioactive peptides from plant protein sources have been continuously identified as nutrient supplements for low toxicity but multiple physiological activities such as antihypertensive, antioxidant, and anti-inflammatory. In this study, wheat bran protein isolate was digested with alcalase to produce wheat bran protein hydrolysate (WPH) that was then separated into different peptide fractions (<1, 1-3, 3-5, and 5-10 kDa) by membrane ultrafiltration. WPH and the peptide fractions were evaluated for in vitro activities such as antioxidant, renin inhibition, and angiotensin-converting enzyme (ACE) inhibition. In addition, the blood pressure-lowering effects of WPH and the <1 kDa peptides were determined by oral administration to spontaneously hypertensive rats (SHRs). Results showed that the ACE and renin inhibitions were significantly (p < .05) higher for the <1 kDa fraction (84.25% ± 2.45%, 75.19% ± 1.75%, respectively) when compared to the WPH and >1 kDa fractions. The <1 kDa fraction also showed significantly (p < .05) higher oxygen radical antioxidant activity with 2044.73 ± 37.45 (μM TE/g protein) when compared to lower values obtained for the >1 kDa membrane fractions and WPH. Oral administration (100 mg/kg body weight) of the <1 kDa membrane fraction to SHRs resulted in a better decrease (-35 mmHg) in the systolic blood pressure when compared to the WPH (-20 mmHg) after 6 hr. And seven peptides (NL, QL, FL, HAL, AAVL, AKTVF, and TPLTR) were identified and amino acid sequence was determined by tandem mass spectrometry. We conclude that the WPH could be considered as a suitable natural antihypertensive and antioxidant resource. PRACTICAL APPLICATIONS: The results of the present study indicate that WPH and its ultrafiltration fractions possess potential as a source of antihypertensive and strong antioxidant peptides. It has been proved that wheat bran has a good blood pressure lowering and antioxidation and other biological activities, and the <1 kDa fraction showing high oxygen radical absorbance capacity level also has better in vitro ACE inhibition and renin-inhibitory activity. The higher antihypertensive efficiency of the <1 kDa fraction may be because the peptides can be better absorbed from the gastrointestinal tract or an increased ability to interact with the enzyme (ACE or renin) protein structure to change the active conformation and lead to decreased catalysis. The results of this study indicate that WPH, especially <1 kDa peptide, can be used as a component in formulating antihypertensive functional foods and nutraceuticals, thus improving the industrial production efficiency and bioavailability of wheat bran.

Calcimimetic R-568 vasodilatory effect on mesenteric vascular beds from normotensive (WKY) and spontaneously hypertensive (SHR) rats. Potential involvement of vascular smooth muscle cells (vSMCs)

The potential role of calcimimetics as vasculotropic agents has been suggested since the discovery that calcium sensing receptors (CaSRs) are expressed in cardiovascular tissues. However, whether this effect is CaSR-dependent or -independent is still unclear. In the present study the vascular activity of calcimimetic R-568 was investigated in mesenteric vascular beds (MVBs) isolated from Spontaneously Hypertensive rats (SHR) and the relative age-matched Wistar-Kyoto (WKY) control rats. Pre-constricted MBVs were perfused with increasing concentrations of R-568 (10 nM– 30 μM) resulting in a rapid dose-dependent vasodilatation. However, in MVBs from SHR this was preceded by a small but significant vasoconstriction at lowest nanomolar concentrations used (10–300 nM). Pre-treatment with pharmacological inhibitors of nitric oxide (NO) synthase (NOS, L-NAME), K_Ca channels (CTX), cyclo-oxygenase (INDO) and CaSR (Calhex) or the endothelium removal suggest that NO, CaSR and the endothelium itself contribute to the R-568 vasodilatory/vasoconstrictor effects observed respectively in WKY/SHR MVBs. Conversely, the vasodilatory effects resulted by highest R-568 concentration were independent of these factors. Then, the ability of lower R-568 doses (0.1–1 μM) to activate endothelial-NOS (eNOS) pathway in MVBs homogenates was evaluated. The Akt and eNOS phosphorylation levels resulted increased in WKY homogenates and Calhex significantly blocked this effect. Notably, this did not occur in the SHR. Similarly, vascular smooth muscle cells (vSMCs) stimulation with lower R-568 doses resulted in Akt activation and increased NO production in WKY but not in SHR cells. Interestingly, in these cells this was associated with the absence of the biologically active dimeric form of the CaSR thus potentially contributing to explain the impaired vasorelaxant effect observed in response to R-568 in MVB from SHR compared to WKY. Overall, these findings provide new insight on the mechanisms of action of the calcimimetic R-568 in modulating vascular tone both in physiological and pathological conditions such as hypertension.

Radical Scavenger Capacity of Jabuticaba Fruit (Myrciaria cauliflora) and Its Biological Effects in Hypertensive Rats

Jabuticaba is an exotic fruit native to Brazil that has been arousing medicinal interest. Using chemical (HPLC-PDA, resonance mass spectra, and NMR), electroanalytical (differential pulse voltammetry, radical scavenging assay), and pharmacological (in vivo and in vitro) approaches, we have identified its bioactive compounds and hypotensive effects on hypertensive rats. The hydroalcoholic extract of jabuticaba (HEJ) presents a great quantity of phenolic compounds, and several molecules with hydroxyl groups present high efficiency as an antioxidant. The treatment with HEJ (100 and 300 mg/kg/day, for four weeks) presented hypotensive effects on L-NAME-induced hypertensive rats, possibly improving the nitric oxide bioavailability because of its high antioxidant potential. Furthermore, renal and cardiac hypertrophies were also attenuated after the HEJ treatment. Moreover, the vascular responses to contractile and dilating agonists were improved with the HEJ treatment, which is also able to induce nitric oxide production in endothelial cells.

Resveratrol did not alter blood pressure in rats with nitric oxide synthase-inhibited hypertension

Background:

Inhibition of nitric oxide synthase (NOS) is a well-known experimental model of hypertension (HT). It was shown that oxidative stress contributes to the pathogenesis of HT. Resveratrol is a potent anti-oxidant that is found in red grapes, peanuts and red wine. It improves the NO response and increases endothelial NOS expression, which causes endothelium-dependent vasorelaxation as well as renal vasodilation. We aimed to explore the effects of resveratrol on blood pressure, the water–salt balance and sodium excretion as a reflection of renal function in NOS-inhibited rat models.

Methods:

Thirty-five male Sprague-Dawley rats (200–250g) were used in this study. In order to obtain hypertension models, an NOS inhibitor, N-nitro-L-arginin (L-NNA) was used. The rats were randomly divided into five groups: controls (given water and 0.8% salty diet) and four groups [given L-NNA, resveratrol (RSV) eluent, RSV, and L-NNA + RSV]. Blood pressures were measured indirectly by the tailcuff method on the first, seventh and 10th days. At the end of the study protocol (10th day), fluid balance, glomerular filtration rate, fractional sodium excretion, and blood and urinesodium and creatinine levels were measured.

Results:

At the end of the study protocol, blood pressures were higher in only the L-NNA group (117.8 ± 3.5 vs 149.5 ± 2.1 mmHg; p < 0.05), as expected. Additional applications of RSV with L-NNA could not prevent the increase in blood pressure (122.8 ± 7.3 vs 155.4 ± 4.4 mmHg; p < 0.05). There were no remarkable changes in water–salt balance and renal function with the application of resveratrol.

Conclusion:

Resveratrol was unable to prevent or reverse blood pressure increase in NOS-inhibited rats.

Moringa oleifera Seeds Attenuate Vascular Oxidative and Nitrosative Stresses in Spontaneously Hypertensive Rats

Moringa oleifera (MOI) is a tree currently used in traditional medicine in tropical Africa, America, and Asia for therapeutic applications in several disorders including arterial hypertension. We previously described a cardiac protective role of a treatment with MOI seeds in spontaneously hypertensive rats (SHR). Here, we investigated the effects of this treatment on oxidative and nitrosative vascular stresses in SHR, with normotensive Wistar Kyoto rats used as controls. Oxidative and nitrosative stresses detected in SHR aortas using the fluorescent dye dihydroethidine and protein nitrotyrosine staining were reduced in MOI-treated SHR aortas. This was associated with a decrease of free 8-isoprostane circulating level, vascular p22^phox and p47^phox expressions, and SOD2 upregulation. Moreover, circulating nitrites and C-reactive protein, increased in SHR, were both reduced in SHR receiving MOI. This was associated to decrease iNOS and NF-κB protein expressions after MOI treatment. In functional studies, the endothelium-dependent carbachol-induced relaxation was improved in MOI-treated SHR resistance arteries. Oral administration of MOI seeds demonstrates vascular antioxidant, anti-inflammatory, and endothelial protective effects in SHR. Our data support the use of MOI seeds in diet against cardiovascular disorders associated with oxidative stress and inflammation such as hypertension, scientifically validating the use of these seeds in Malagasy traditional medicine.

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.

Moringa oleiferaSeeds Attenuate Vascular Oxidative and Nitrosative Stresses in Spontaneously Hypertensive Rats

Moringa oleifera(MOI) is a tree currently used in traditional medicine in tropical Africa, America, and Asia for therapeutic applications in several disorders including arterial hypertension. We previously described a cardiac protective role of a treatment with MOI seeds in spontaneously hypertensive rats (SHR). Here, we investigated the effects of this treatment on oxidative and nitrosative vascular stresses in SHR, with normotensive Wistar Kyoto rats used as controls. Oxidative and nitrosative stresses detected in SHR aortas using the fluorescent dye dihydroethidine and protein nitrotyrosine staining were reduced in MOI-treated SHR aortas. This was associated with a decrease of free 8-isoprostane circulating level, vascular p22phoxand p47phoxexpressions, and SOD2 upregulation. Moreover, circulating nitrites and C-reactive protein, increased in SHR, were both reduced in SHR receiving MOI. This was associated to decrease iNOS and NF-κB protein expressions after MOI treatment. In functional studies, the endothelium-dependent carbachol-induced relaxation was improved in MOI-treated SHR resistance arteries. Oral administration of MOI seeds demonstrates vascular antioxidant, anti-inflammatory, and endothelial protective effects in SHR. Our data support the use of MOI seeds in diet against cardiovascular disorders associated with oxidative stress and inflammation such as hypertension, scientifically validating the use of these seeds in Malagasy traditional medicine.

Effect of Nigella sativa supplementation over a one-year period on lipid levels, blood pressure and heart rate in type-2 diabetic patients receiving oral hypoglycemic agents: nonrandomized clinical trial

BACKGROUND

Diabetic patients with hypertension and dyslipidemia are at a high risk of cardiovascular complications.

OBJECTIVES

To determine the effect of Nigella sativa supplementation on the lipid profile, mean arterial pressure, and heart rate in persons with type 2 diabetes on oral hypoglycemic agents (OHA).

DESIGN

Single-blind, nonrandomized.

SETTING

Diabetes clinic of a university hospital in Saudi Arabia.

PATIENTS AND METHODS

Type-2 diabetic patients were recruited by purposive sampling and assigned to treatment or control at the discretion of the investigator with the patient blinded to treatment. Before the in.tervention and every 3 months thereafter until the end of the treatment period, the following parameters were measured: triglycerides (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), and body mass index (BMI). Results at the baseline and each subsequent visit were compared between the two groups.

MAIN OUTCOME MEASURE(S)

Lipid and cardiovascular parameters, and BMI.

RESULTS

Fifty-seven patients were assigned to receive N sativa 2 g daily for one year and 57 were assigned to receive an identical regimen of placebo, along with OHA. A significant decrease in HDL-C and increase in the TC/HDL-C and LDL-C/HDL-C ratios were seen in the control group. The N sativa group had a signifi.cant decline in TC, LDL-C, TC/HDL-C and LDL-C/HDL-C ratios, compared with the respective baseline data and the control group. HDL-C was significantly elevated in the N sativa group. The control group showed a significant elevation in MAP. The N sativa group had a significant reduction in SBP, DBP, MAP and HR and a significant decrease in DBP, MAP and HR as compared with the control group.

CONCLUSION

N sativa supplementation improves total cholesterol, mean arterial pressure and heart rate in type 2 diabetes patients on oral hypoglycemic agents.

LIMITATIONS

There were 9 subjects in each group lost to follow up; thus the sample size could not be maintained as per the sample size calculation. The study was nonrandomized and thus there was a possibility of allocation bias. (Clinical trial registration number: CTRI/2013/06/003781, Clinical Trial Registry of India).

Evaluation of anti-hypertensive activity of Ulmus wallichiana extract and fraction in SHR, DOCA-salt- and L-NAME-induced hypertensive rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ulmus wallichiana Planchon (Himalayan Elm), a traditional medicinal plant, used in fracture healing in folk tradition of Uttarakhand, Himalaya, India. It is also used as diuretic. U. rhynchophylla, native to China, known as Gou Teng in Chinese medicine, is used for hypertension (WHO). U. macrocarpa has antihypertensive and vasorelaxant activity. However, no detailed studies related to hypertension have been reported previously, so we have explored the antihypertensive activity of U. wallichiana.

AIM OF THE STUDY

To investigate the pharmacological effect of ethanolic extract (EE) and butanolic fraction (BF) of U. wallichiana in hypertensive rats.

MATERIALS AND METHODS

SHR, DOCA-salt- and L-NAME-induced hypertension models were used. Treatment was performed by oral administration of EE and BF of U. wallichiana (500mg/kg/day and 50mg/kg/day) for 14 days. Then blood pressure was measured by non-invasive blood pressure (NIBP) measurement technique. Invasive blood pressure (IBP) was also reported to support the NIBP data. Concentrations of plasma renin, angiotensin II (Ang II), nitrate/nitrite (NO), cGMP were estimated. Angiotensin-converting enzyme (ACE) activity and ROS activity were also estimated.

RESULTS

Blood pressure was significantly higher in SHR as compared to normotensive wistar group (170.59±0.83mmHg vs 121.54±1.24mmHg, respectively). SBP was increased in DOCA-salt induced group compared to their control (132.77±3.90mmHg vs 107.85±5.95mmHg, respectively) and L-NAME-induced group compared to their control (168.55±5.07mmHg vs 113.03±4.13mmHg, respectively). The treatment of extract and fraction of U. wallichiana significantly decreased the blood pressure in SHR+EE (151.26±1.85mmHg, p<0.001), SHR+BF (140.44±1.16mmHg, p<0.001); DOCA+EE (113.43±5.44mmHg, p<0.05), DOCA+BF (105.09±5.12mmHg, p<0.05) and L-NAME+EE (119.76±4.39mmHg, p<0.001), L-NAME+BF (117.50±7.27mmHg, p<0.001) compared to their respective diseased control groups. The plasma renin, Ang II and ACE activity were also significantly decreased and augmented the NO and cGMP levels. It also down regulated the expression of Renin, ACE, NOS3 and TGF-β1 at mRNA levels.

CONCLUSIONS

The EE and BF probably reducing the BP via Renin-angiotensin-aldosterone system and NO/cGMP signaling pathway. The decrease in blood pressure may be due to presence of quercetin analogue flavonoids (2S,3S)-(+)-3',4',5,7-tetrahydroxydihydroflavonol-6-C-β-D-glucopyranoside; 6-Glucopyranosyl-3,3',4',5,7-pentahydroxyflavone; 6-Glucopyranosyl-4',5,7-trihydroxyflavanone and (2S,3S)-(+)-4',5,7-trihydroxydihydroflavonol-6-C-β-D-glucopyranoside, may be due to its antioxidant activity. Thus EE and BF of U. wallichiana found to have the potential ability to be used as herbal medicament to treat hypertension.

Oxidant Mechanisms in Renal Injury and Disease

SIGNIFICANCE

A common link between all forms of acute and chronic kidney injuries, regardless of species, is enhanced generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during injury/disease progression. While low levels of ROS and RNS are required for prosurvival signaling, cell proliferation and growth, and vasoreactivity regulation, an imbalance of ROS and RNS generation and elimination leads to inflammation, cell death, tissue damage, and disease/injury progression.

RECENT ADVANCES

Many aspects of renal oxidative stress still require investigation, including clarification of the mechanisms which prompt ROS/RNS generation and subsequent renal damage. However, we currently have a basic understanding of the major features of oxidative stress pathology and its link to kidney injury/disease, which this review summarizes.

CRITICAL ISSUES

The review summarizes the critical sources of oxidative stress in the kidney during injury/disease, including generation of ROS and RNS from mitochondria, NADPH oxidase, and inducible nitric oxide synthase. The review next summarizes the renal antioxidant systems that protect against oxidative stress, including superoxide dismutase and catalase, the glutathione and thioredoxin systems, and others. Next, we describe how oxidative stress affects kidney function and promotes damage in every nephron segment, including the renal vessels, glomeruli, and tubules.

FUTURE DIRECTIONS

Despite the limited success associated with the application of antioxidants for treatment of kidney injury/disease thus far, preventing the generation and accumulation of ROS and RNS provides an ideal target for potential therapeutic treatments. The review discusses the shortcomings of antioxidant treatments previously used and the potential promise of new ones. Antioxid. Redox Signal. 25, 119-146.

Antihypertensive Properties of a Pea Protein Hydrolysate during Short- and Long-Term Oral Administration to Spontaneously Hypertensive Rats

This study investigated short-term (24 h) and long-term (5 wk) systolic blood pressure (SBP)-lowering effects in spontaneously hypertensive rats (SHR) of a 5 kDa membrane pea protein hydrolysate permeate (PPH-5) produced through thermoase hydrolysis of pea protein isolate (PPI). Amino acid analysis showed that the PPH-5 had lower contents of sulfur-containing amino acids than the PPI. Size-exclusion chromatography indicated mainly low molecular weight (<10 kDa) peptides in PPH-5 but not in the PPI. The PPH-5 had renin and angiotensin converting enzyme inhibition IC50 values of 0.57 and 0.10 mg/mL (P < 0.05), respectively, and consisted mainly of peptides with 2 to 6 amino acids. Mass spectrometry analysis revealed mainly hydrophilic tetrapeptide sequences. After a single oral administration (100 mg/kg body weight) to SHR, the unheated PPI showed weakest (P < 0.05) SBP-lowering effect with a -4 mm Hg maximum when compared to -25 mm Hg for heat-treated PPI and -36 mm Hg for PPH-5. Incorporation of the PPH-5 as 0.5% or 1% (w/w) casein substitute in the SHR diet produced maximum SBP reductions of -22 or -26 mm Hg (P < 0.05), respectively after 3 wk. In comparison, the unhydrolyzed PPI produced a maximum SBP reduction of -17 mm Hg also after 3 wk. Potency of the pea products decreased in the 4th and 5th wk, though SBP values of the treated rats were still lower than the untreated control. We conclude that the antihypertensive potency of PPH-5 may have been due to the presence of easily absorbed hydrophilic peptides.

Effects of a novel ACE inhibitor, 3-(3-thienyl)-l-alanyl-ornithyl-proline, on endothelial vasodilation and hepatotoxicity in l-NAME-induced hypertensive rats

Nitric oxide (NO) is a widespread biological mediator involved in many physiological and pathological processes, eg, in the regulation of vascular tone and hypertension. Chronic inhibition of NO synthase by N^G-nitro-l-arginine methyl ester (l-NAME) hydrochloride results in the development of hypertension accompanied by an increase in vascular responsiveness to adrenergic stimuli. Recently, we developed a novel sulfur-containing angiotensin-converting enzyme inhibitor: 3-(3-thienyl)-l-alanyl-ornithyl-proline (TOP). Our previous studies indicated a superior nature of the molecule as an antihypertensive agent in spontaneously hypertensive rats (showing the involvement of renin–angiotensin–aldosterone system) in comparison to captopril. The aim of the present study was to investigate the effect of TOP on NO pathway in l-NAME-induced hypertensive rats, and captopril was included as the standard treatment group. Treatment with both TOP (20 mg/kg) and captopril (40 mg/kg) prevented the development of hypertension in l-NAME model, but TOP showed better restoration of NO and normal levels of angiotensin-converting enzyme. In addition, in vitro vasorelaxation assay showed an improvement in endothelium-dependent vasodilation in both the cases. Further, the biochemical (malondialdehyde, alanine aminotransferase, and aspartate aminotransferase) and the histopathological effects of TOP on rat liver tissues revealed a protective nature of TOP in comparison to captopril in the l-NAME model. In conclusion, TOP at 50% lesser dose than captopril was found to be better in the l-NAME model.

Hypertension and aging

Hypertension is a highly prevalent condition with numerous health risks, and the incidence of hypertension is greatest among older adults. Traditional discussions of hypertension have largely focused on the risks for cardiovascular disease and associated events. However, there are a number of collateral effects, including risks for dementia, physical disability, and falls/fractures which are increasingly garnering attention in the hypertension literature. Several key mechanisms--including inflammation, oxidative stress, and endothelial dysfunction--are common to biologic aging and hypertension development and appear to have key mechanistic roles in the development of the cardiovascular and collateral risks of late-life hypertension. The objective of the present review is to highlight the multi-dimensional risks of hypertension among older adults and discuss potential strategies for treatment and future areas of research for improving overall care for older adults with hypertension.

Probiotics Blunt the Anti-Hypertensive Effect of Blueberry Feeding in Hypertensive Rats without Altering Hippuric Acid Production

Previously we showed that feeding polyphenol-rich wild blueberries to hypertensive rats lowered systolic blood pressure. Since probiotic bacteria produce bioactive metabolites from berry polyphenols that enhance the health benefits of berry consumption, we hypothesized that adding probiotics to a blueberry-enriched diet would augment the anti-hypertensive effects of blueberry consumption. Groups (n = 8) of male spontaneously hypertensive rats were fed one of four AIN '93G-based diets for 8 weeks: Control (CON); 3% freeze-dried wild blueberry (BB); 1% probiotic bacteria (PRO); or 3% BB + 1% PRO (BB+PRO). Blood pressure was measured at weeks 0, 2, 4, 6, and 8 by the tail-cuff method, and urine was collected at weeks 4 and 8 to determine markers of oxidative stress (F2-isoprostanes), nitric oxide synthesis (nitrites), and polyphenol metabolism (hippuric acid). Data were analyzed using mixed models ANOVA with repeated measures. Diet had a significant main effect on diastolic blood pressure (p = 0.046), with significantly lower measurements in the BB- vs. CON-fed rats (p = 0.035). Systolic blood pressure showed a similar but less pronounced response to diet (p = 0.220), again with the largest difference between the BB and CON groups. Absolute increase in blood pressure between weeks 0 and 8 tended to be smaller in the BB and PRO vs. CON and BB+PRO groups (systolic increase, p = 0.074; diastolic increase, p = 0.185). Diet had a significant main effect on hippuric acid excretion (p<0.0001), with 2- and ~1.5-fold higher levels at weeks 4 and 8, respectively, in the BB and BB+PRO vs. PRO and CON groups. Diet did not have a significant main effect on F2-isoprostane (p = 0.159) or nitrite excretion (p = 0.670). Our findings show that adding probiotics to a blueberry-enriched diet does not enhance and actually may impair the anti-hypertensive effect of blueberry consumption. However, probiotic bacteria are not interfering with blueberry polyphenol metabolism into hippuric acid.

A novel hemp seed meal protein hydrolysate reduces oxidative stress factors in spontaneously hypertensive rats

This report shows the antioxidant effects of a hemp seed meal protein hydrolysate (HMH) in spontaneously hypertensive rats (SHR). Defatted hemp seed meal was hydrolyzed consecutively with pepsin and pancreatin to yield HMH, which was incorporated into rat feed as a source of antioxidant peptides. Young (8-week old) SHRs were divided into three groups (8 rats/group) and fed diets that contained 0.0%, 0.5% or 1.0% (w/w) HMH for eight weeks; half of the rats were sacrificed for blood collection. After a 4-week washout period, the remaining 20-week old SHRs were fed for an additional four weeks and sacrificed for blood collection. Plasma total antioxidant capacity (TAC) and superoxide dismutase (SOD), catalase (CAT) and total peroxides (TPx) levels were determined. Results showed that plasma TAC, CAT and SOD levels decreased in the older 20-week old SHRs when compared to the young SHRs. The presence of HMH in the diets led to significant (p < 0.05) increases in plasma SOD and CAT levels in both young and adult SHR groups; these increases were accompanied by decreases in TPx levels. The results suggest that HMH contained antioxidant peptides that reduced the rate of lipid peroxidation in SHRs with enhanced antioxidant enzyme levels and total antioxidant capacity.

Effect of treatment with the antioxidant alpha-lipoic (thioctic) acid on heart and kidney microvasculature in spontaneously hypertensive rats

Endothelial cells represent an important vascular site of signaling and development of damage during ischemia, inflammation and other pathological conditions. Excessive reactive oxygen species production causes pathological activation of endothelium including exposure of cell to adhesion molecules. Intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and platelet-endothelial cell adhesion molecule-1 (PECAM-1) are members of the immunoglobulin super-family which are present on the surface of endothelial cells. These molecules represent important markers of endothelial inflammation. The present study was designed to investigate, with immunochemical and immunohistochemical techniques, the effect of treatment with (+/-)-alpha lipoic (thioctic) acid and its enantiomers on heart and kidney endothelium in spontaneously hypertensive rats (SHR). Arterial hypertension is accompanied by an increased oxidative stress status in the heart characterized by thiobarbituric acid reactive substances (TBARS) and nucleic acid oxidation increase. The higher oxidative stress also modifies adhesion molecules expression. In the heart VCAM-1, which was higher than ICAM-1 and PECAM-1, was increased in SHR. ICAM-1, VCAM-1 and PECAM-1 expression was significantly greater in the renal endothelium of SHR. (+/-)-Alpha lipoic acid and (+)-alpha lipoic acid treatment significantly decreased TBARS levels, the nucleic acid oxidation and prevented adhesion molecules expression in cardiac and renal vascular endothelium. These data suggest that endothelial molecules may be used for studying the mechanisms of vascular injury on target organs of hypertension. The effects observed after treatment with (+)-alpha lipoic acid could open new perspectives for countering heart and kidney microvascular injury which represent a common feature in hypertensive end-organs damage.

Protein disulfide isomerase expression increases in resistance arteries during hypertension development. Effects on Nox1 NADPH oxidase signaling

NADPH oxidases derived reactive oxygen species (ROS) play an important role in vascular function and remodeling in hypertension through redox signaling processes. Previous studies demonstrated that protein disulfide isomerase (PDI) regulates Nox1 expression and ROS generation in cultured vascular smooth muscle cells. However, the role of PDI in conductance and resistance arteries during hypertension development remains unknown. The aim of the present study was to investigate PDI expression and NADPH oxidase dependent ROS generation during hypertension development. Mesenteric resistance arteries (MRA) and thoracic aorta were isolated from 6, 8, and 12 week-old spontaneously hypertensive (SHR) and Wistar rats. ROS production (dihydroethidium fluorescence), PDI (WB, imunofluorescence), Nox1 and NOX4 (RT-PCR) expression were evaluated. Results show a progressive increase in ROS generation in MRA and aorta from 8 to 12 week-old SHR. This effect was associated with a concomitant increase in PDI and Nox1 expression only in MRA. Therefore, suggesting a positive correlation between PDI and Nox1 expression during the development of hypertension in MRA. In order to investigate if this effect was due to an increase in arterial blood pressure, pre hypertensive SHR were treated with losartan (20 mg/kg/day for 30 days), an AT1 receptor antagonist. Losartan decreased blood pressure and ROS generation in both vascular beds. However, only in SHR MRA losartan treatment lowered PDI and Nox1 expression to control levels. In MRA PDI inhibition (bacitracin, 0.5 mM) decreased Ang II redox signaling (p-ERK 1/2). Altogether, our results suggest that PDI plays a role in triggering oxidative stress and vascular dysfunction in resistance but not in conductance arteries, increasing Nox1 expression and activity. Therefore, PDI could be a new player in oxidative stress and functional alterations in resistance arteries during the establishment of hypertension.

Prehypertension: Underlying pathology and therapeutic options

Prehypertension (PHTN) is a global major health risk that subjects individuals to double the risk of cardiovascular disease (CVD) independent of progression to overt hypertension. Its prevalence rate varies considerably from country to country ranging between 21.9% and 52%. Many hypotheses are proposed to explain the underlying pathophysiology of PHTN. The most notable of these implicate the renin-angiotensin system (RAS) and vascular endothelium. However, other processes that involve reactive oxygen species, the inflammatory cytokines, prostglandins and C-reactive protein as well as the autonomic and central nervous systems are also suggested. Drugs affecting RAS have been shown to produce beneficial effects in prehypertensives though such was not unequivocal. On the other hand, drugs such as β-adrenoceptor blocking agents were not shown to be useful. Leading clinical guidelines suggest using dietary and lifestyle modifications as a first line interventional strategy to curb the progress of PHTN; however, other clinically respected views call for using drugs. This review provides an overview of the potential pathophysiological processes associated with PHTN, abridges current intervention strategies and suggests investigating the value of using the "Polypill" in prehypertensive subjects to ascertain its potential in delaying (or preventing) CVD associated with raised blood pressure in the presence of other risk factors.

Aqueous extract of dioscorea opposita thunb. normalizes the hypertension in 2K1C hypertensive rats

BACKGROUND

Dioscorea opposita Thunb. (Huai Shan Yao, DOT), a common staple food in China, has been used for more than 2000 years in traditional Chinese medicine (TCM) to treat different systemic diseases including hypertension. The objective of this study was to investigate the possible antihypertensive effects of the aqueous extract of (DOT) in renovascular hypertensive rats as well as the mechanism in reducing blood pressure.

METHODS

The two-kidney one-clip (2K1C) Goldblatt model of renovascular hypertension was used in Wistar rats. Rats with captopril, low-dose DOT and high-dose DOT treated 2K1C groups for 6 weeks. The blood pressure, cardiac mass index (heart weight/body weight), plasma level of angiotensin-II (Ang-II), endothelin-1(ET-1), superoxide dismutase (SOD) and malondialdehyde (MDA) were evaluated.

RESULTS

DOT significantly reduced mean systolic and diastolic blood pressure after treatment. DOT also significantly increased plasma SOD activity but decreased plasma MDA concentration. Renal function was improved with captopril and DOT. DOT reduced plasma Ang-II activity and plasma ET concentration. They couldalso significantly reduce the left ventricular hypertrophy and cardiac mass index.

CONCLUSIONS

Our results suggest that DOT may have an antihypertensive effect on hypertension by inhibit ET-converting enzyme and antioxidant activity, which warrant further exploration.

Impact of exercise training on redox signaling in cardiovascular diseases

Reactive oxygen and nitrogen species regulate a wide array of signaling pathways that governs cardiovascular physiology. However, oxidant stress resulting from disrupted redox signaling has an adverse impact on the pathogenesis and progression of cardiovascular diseases. In this review, we address how redox signaling and oxidant stress affect the pathophysiology of cardiovascular diseases such as ischemia-reperfusion injury, hypertension and heart failure. We also summarize the benefits of exercise training in tackling the hyperactivation of cellular oxidases and mitochondrial dysfunction seen in cardiovascular diseases.

Antihypertensive effects of extract from Picrasma quassiodes (D. Don) Benn. in spontaneously hypertensive rats

ETHNOPHARMACOLOGICA RELEVANCE: Picrasma quassiodes (D. Don) Benn. (PQB) is a widely used herbal medicine used for gastroenteritis, snakebite, infection and hypertension in China. The aim of the study was to investigate the possible antihypertensive mechanisms on spontaneously hypertensive rats (SHR) of the extract from Picrasma quassiodes (D. Don) Benn.

MATERIALS AND METHODS

In the in vivo study, extract from Picrasma quassiodes (D. Don) Benn. at the dose of 50, 100, 200mg/kg and captopril (12.5mg/kg) were administrated to different group of SHR rats by gavage for six consecutive weeks after the blood pressures were firstly measured. At the end of the study, rats serum nitric oxide (NO) was measured by the nitrate reductase method; superoxide dismutase (SOD) and malondialdehyde (MDA) activities were measured by the colorimetric method; the expression of aorta endothelial nitric oxide synthase (eNOS) was measured by immunohistochemical analysis.

RESULTS

The results showed that the oral administration of PQB could lower the systolic blood pressure (SBP) of SHR rats. In addition, the serum level of NO in SHR treated with PQB (100 and 200mg/kg) was increased dramatically (P<0.05, P<0.01), but administration with captopril had no significant effect. The expression of aorta eNOS was markedly increased when treated with PQB. The serum SOD levels were increased with treatment of PQB (100 and 200mg/kg; P<0.05, P<0.01). All the effects of these parameters were comparable to that of the SHR control group.

CONCLUSIONS

Our results disclosed that PQB is effective to lower blood pressure of SHR, its antihypertensive effect is probably associated with lowering oxidative stress by reducing SOD activity, preserving endothelial function and increasing the expression of eNOS to regulate NO and directly relax artery.

Prevention of γ-radiation induced cellular genotoxicity by tempol: protection of hematopoietic system

Tempol (TPL) under in vitro conditions reduced the extent of gamma radiation induced membrane lipid peroxidation and disappearance of covalently closed circular form of plasmid pBR322. TPL protected cellular DNA from radiation-induced damage in various tissues under ex vivo and in vivo conditions as evidenced by comet assay. TPL also prevented radiation induced micronuclei formation (in peripheral blood leucocytes) and chromosomal aberrations (in bone marrow cells) in whole body irradiated mice. TPL enhanced the rate of repair of cellular DNA (blood leucocytes and bone marrow cells) damage when administered immediately after radiation exposure as revealed from the increased Cellular DNA Repair Index (CRI). The studies thus provided compelling evidence to reveal the effectiveness of TPL to protect hematopoietic system from radiation injury.

The onset of left ventricular diastolic dysfunction in SHR rats is not related to hypertrophy or hypertension

Left ventricular (LV) diastolic dysfunction, particularly relaxation abnormalities, are known to be associated with the development of LV hypertrophy (LVH). Preliminary human and animal studies suggested that early LV diastolic dysfunction may be revealed independently of LVH. However, whether LV diastolic dysfunction is compromised before the onset of hypertension and LVH remains unknown. We therefore evaluated LV diastolic function in spontaneously hypertensive rats (SHR) at different ages and tested whether LV diastolic dysfunction is associated with abnormal intracellular calcium homeostasis. LV systolic and diastolic functions were evaluated by invasive and echocardiographic methods in 3-week-old (without hypertension) and 5-week-old (with hypertension) SHR and Wistar-Kyoto control rats. Basal intracytoplasmic calcium and sarcoplasmic reticulum (SR) Ca2+ contents were measured in cardiomyocytes using fura-2 AM. Sarco(endo)plasmic Ca2+-ATPase isoform 2a (SERCA 2a) and phospholamban (PLB) expressions were quantified by Western blot and quantitative RT-PCR techniques. LV relaxation dysfunction was observed in 3-week-old SHR rats before onset of hypertension and LVH. An increase in basal intracytoplasmic Ca2+ and a decrease in SR Ca2+ release were demonstrated in SHR. Decreased expression of SERCA 2a and Ser16 PLB (p16-PLB) protein levels was also observed in SHR rats, whereas mRNA expression was not decreased. For the first time, we have shown that LV myocardial dysfunction precedes hypertension in 3-week-old SHR rats. This LV myocardial dysfunction was associated with high diastolic [Ca2+]i possibly due to decreased SERCA 2a and p16-PLB protein levels. Diastolic dysfunction may be a potential predictive marker of arterial hypertension in genetic hypertension syndromes.

Chronic exercise preserves renal structure and hemodynamics in spontaneously hypertensive rats

AIMS

Exercise training (ExT) is a recommended adjunct to many pharmaceutical antihypertensive therapies. The effects of chronic ExT on the development of hypertension-induced renal injury remain unknown. We examined whether ExT would preserve renal hemodynamics and structure in the spontaneously hypertensive rat (SHR), and whether these effects were mediated by improved redox status and decreased inflammation. Normotensive WKY rats and SHR underwent moderate-intensity ExT for 16 weeks. One group of SHR animals was treated with hydralazine to investigate the pressure-dependent/independent effects of ExT. Acute renal clearance experiments were performed prior to sacrifice. Tissue free radical production rates were measured by electron paramagnetic resonance; gene and protein expression were measured by real time RT-PCR and Western blot or immunofluorescence, respectively. Plasma angiotensin II levels and kidney antioxidants were assessed. Training efficacy was assessed by citrate synthase activity assay in hind-limb muscle.

RESULTS

ExT delayed hypertension, prevented oxidative stress and inflammation, preserved antioxidant status, prevented an increase in circulating AngII levels, and preserved renal hemodynamics and structure in SHR. In addition, exercise-induced effects, at least, in part, were found to be pressure-independent.

INNOVATION

This study is the first to provide mechanistic evidence for the renoprotective benefits of ExT in a model of hypertension. Our results demonstrate that initiation of ExT in susceptible patients can delay the development of hypertension and provide renoprotection at the functional and ultrastructural level.

CONCLUSION

Chronic ExT preserves renal hemodynamics and structure in SHR; these effects are partially mediated by improved redox status and decreased inflammation.

Perivascular Fat and the Microcirculation: Relevance to Insulin Resistance, Diabetes, and Cardiovascular Disease

Type 2 diabetes and its major risk factor, obesity, are a growing burden for public health. The mechanisms that connect obesity and its related disorders, such as insulin resistance, type 2 diabetes, and hypertension, are still undefined. Microvascular dysfunction may be a pathophysiologic link between insulin resistance and hypertension in obesity. Many studies have shown that adipose tissue-derived substances (adipokines) interact with (micro)vascular function and influence insulin sensitivity. In the past, research focused on adipokines from perivascular adipose tissue (PVAT). In this review, we focus on the interactions between adipokines, predominantly from PVAT, and microvascular function in relation to the development of insulin resistance, diabetes, and cardiovascular disease.

Oxidative stress and hypertension: current concepts

Hypertension is a major contributor to the development of renal failure, cardiovascular disease, and stroke. These pathologies are associated with vascular functional and structural changes including endothelial dysfunction, altered contractility, and vascular remodeling. Central to these phenomena is oxidative stress. Factors that activate pro-oxidant enzymes, such as NADPH oxidase, remain poorly defined, but likely involve angiotensin II, mechanical stretch, and inflammatory cytokines. Reactive oxygen species influence vascular, renal, and cardiac function and structure by modulating cell growth, contraction/dilatation, and inflammatory responses via redox-dependent signaling pathways. Compelling data from molecular and cellular experiments, together with animal studies, implicate a role for oxidative stress in hypertension. However, the clinical evidence is still controversial. This review provides current insights on the mechanisms of the generation of reactive oxygen species and the vascular effects of oxidative stress and discusses the significance of oxidative damage in experimental and clinical hypertension.

Drag reduction by polyethylene glycol in the tail arterial bed of normotensive and hypertensive rats

This study was designed to evaluate the effect of drag reducer polymers (DRP) on arteries from normotensive (Wistar) and spontaneously hypertensive rats (SHR). Polyethylene glycol (PEG 4000 at 5000 ppm) was perfused in the tail arterial bed with (E+) and without endothelium (E-) from male, adult Wistar (N = 14) and SHR (N = 13) animals under basal conditions (constant flow at 2.5 mL/min). In these preparations, flow-pressure curves (1.5 to 10 mL/min) were constructed before and 1 h after PEG 4000 perfusion. Afterwards, the tail arterial bed was fixed and the internal diameters of the arteries were then measured by microscopy and drag reduction was assessed based on the values of wall shear stress (WSS) by computational simulation. In Wistar and SHR groups, perfusion of PEG 4000 significantly reduced pulsatile pressure (Wistar/E+: 17.5 ± 2.8; SHR/E+: 16.3 ± 2.7%), WSS (Wistar/E+: 36; SHR/E+: 40%) and the flow-pressure response. The E- reduced the effects of PEG 4000 on arteries from both groups, suggesting that endothelial damage decreased the effect of PEG 4000 as a DRP. Moreover, the effects of PEG 4000 were more pronounced in the tail arterial bed from SHR compared to Wistar rats. In conclusion, these data demonstrated for the first time that PEG 4000 was more effective in reducing the pressure-flow response as well as WSS in the tail arterial bed of hypertensive than of normotensive rats and these effects were amplified by, but not dependent on, endothelial integrity. Thus, these results show an additional mechanism of action of this polymer besides its mechanical effect through the release and/or bioavailability of endothelial factors.

Resveratrol prevents endothelial nitric oxide synthase uncoupling and attenuates development of hypertension in spontaneously hypertensive rats

Endothelial dysfunction is a hallmark of hypertension and vascular oxidative stress can contribute to endothelial dysfunction and hypertension development. Resveratrol is an antioxidant polyphenol which improves endothelium dependent relaxation, the mechanisms of which are unknown. Also, the role of resveratrol in hypertension remains to be established. The purpose of this study was to investigate the mechanisms of resveratrol induced improvement of endothelial function and establish its role in hypertension. SHR and WKY rats, 3-4 weeks old, were treated with resveratrol in drinking water for 10 weeks, untreated SHR and WKY rats served as controls. At the end of the treatment, control SHR exhibited increased blood pressure, oxidative stress and attenuated endothelium dependent relaxation in comparison to WKY rats. The impaired endothelium function in SHR was associated with lower nitrite/nitrate levels, elevated nitrotyrosine content and eNOS uncoupling. Resveratrol treatment attenuated hypertension development in SHR as indicated by lower blood pressure in resveratrol treated SHR (SHR-R) compared to control SHR. SHR-R also exhibited reduced H(2)O(2) content and elevated superoxide dismutase activity. Resveratrol treatment normalized endothelium dependent vasorelaxation in SHR. In parallel, resveratrol restored nitrite/nitrate levels and normalized nitrotyrosine content in SHR. SHR exhibited increased l-arginine dependent superoxide production which was blocked by NOS inhibitor l-NNA, suggesting eNOS uncoupling. eNOS uncoupling was prevented by resveratrol treatment. In conclusion, early treatment with resveratrol lowers oxidative stress, preserves endothelial function and attenuates development of hypertension in SHR. More importantly, prevention of eNOS uncoupling and NO scavenging could represent novel mechanisms for resveratrol-mediated antihypertensive effects.

Oxidative stress and endothelial dysfunction in hypertension

Systemic arterial hypertension is a highly prevalent cardiovascular risk factor that causes significant morbidity and mortality, and is becoming an increasingly common health problem because of the increasing longevity and prevalence of predisposing factors such as sedentary lifestyle, obesity and nutritional habits. Further complicating the impact of this disease, mild and moderate hypertension are usually asymptomatic, and their presence (and the subsequent increase in cardiovascular risk) is often unrecognized. The pathophysiology of hypertension involves a complex interaction of multiple vascular effectors including the activation of the sympathetic nervous system, of the renin-angiotensin-aldosterone system and of the inflammatory mediators. Subsequent vasoconstriction and inflammation ensue, leading to vessel wall remodeling and, finally, to the formation of atherosclerotic lesions as the hallmark of advanced disease. Oxidative stress and endothelial dysfunction are consistently observed in hypertensive subjects, but emerging evidence suggests that they also have a causal role in the molecular processes leading to hypertension. Reactive oxygen species (ROS) may directly alter vascular function or cause changes in vascular tone by several mechanisms including altered nitric oxide (NO) bioavailability or signaling. ROS-producing enzymes involved in the increased vascular oxidative stress observed during hypertension include the NADPH oxidase, xanthine oxidase, the mitochondrial respiratory chain and an uncoupled endothelial NO synthase. In the current review, we will summarize our current understanding of the molecular mechanisms in the development of hypertension with an emphasis on oxidative stress and endothelial dysfunction.

Lisinopril attenuates renal oxidative injury in L-NAME-induced hypertensive rats

Hypertension and related oxidative stress are involved in the pathogenesis of any renal diseases. Angiotensin-converting enzyme inhibitors have multi-directional renoprotective effects. In this study, we aimed to investigate whether lisinopril treatment has any biochemical alterations on renal tissue in L-NAME (Nε-nitro-L-arginine methyl ester) induced hypertension model. Twenty-eight Sprague-Dawley rats were included in this study and divided into four equal groups (n = 7): control group, L-NAME treated group (75 mg/kg/day), L-NAME plus lisinopril treated group and only lisinopril treated group (10 mg/kg/day). L-NAME and lisinopril were continued for 6 weeks. Systolic blood pressures were measured by using tail cuff method. In biochemical analysis, malondialdehyde (MDA, an index of lipid peroxidation) levels, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in renal tissues were used as markers of oxidative stress-induced renal impairment. Microalbumin and N-acetyl-β-D-glucosaminidase (NAG) in urine were determined as markers of renal tubular damage related to hypertension. Chronic L-NAME administration resulted in a significant depletion of serum nitric oxide (NO). When compared with control group, serum creatinine, microalbumin, urine NAG, renal tissue MDA level, and CAT activities were significantly high, while renal tissue SOD and GSH-Px activities low in L-NAME group. In the L-NAME plus lisinopril treated group, serum creatinine, microalbumin and urine NAG, renal MDA level and CAT activity decreased, whereas SOD, GSH-Px activities in renal tissue and serum NO levels were increased. Thus, lisinopril treatment reversed these effects. There were not any significant difference between L-NAME plus lisinopril treated group and control group concerning serum creatinine, renal tissue MDA level and SOD, GSH-Px, CAT activities. These results suggest that lisinopril could diminish biochemical alterations in L: -NAME induced hypertensive renal damage that occurs by oxidative stress.

Differential responses to blood pressure and oxidative stress in streptozotocin-induced diabetic Wistar-Kyoto rats and spontaneously hypertensive rats: effects of antioxidant (honey) treatment

Oxidative stress is implicated in the pathogenesis and/or complications of hypertension and/or diabetes mellitus. A combination of these disorders increases the risk of developing cardiovascular events. This study investigated the effects of streptozotocin (60 mg/kg; ip)-induced diabetes on blood pressure, oxidative stress and effects of honey on these parameters in the kidneys of streptozotocin-induced diabetic Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Diabetic WKY and SHR were randomized into four groups and received distilled water (0.5 mL) and honey (1.0 g/kg) orally once daily for three weeks. Control SHR had reduced malondialdehyde (MDA) and increased systolic blood pressure (SBP), catalase (CAT) activity, and total antioxidant status (TAS). SBP, activities of glutathione peroxidase (GPx) and glutathione reductase (GR) were elevated while TAS was reduced in diabetic WKY. In contrast, SBP, TAS, activities of GPx and GR were reduced in diabetic SHR. Antioxidant (honey) treatment further reduced SBP in diabetic SHR but not in diabetic WKY. It also increased TAS, GSH, reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio, activities of GPx and GR in diabetic SHR. These data suggest that differences in types, severity, and complications of diseases as well as strains may influence responses to blood pressure and oxidative stress.

Vascular BDNF expression and oxidative stress during aging and the development of chronic hypertension

Brain-derived neurotrophic factor (BDNF) and TrK receptors play an important role in vascular development and response to injury. In this study, we investigated the participation of the BDNF/TrK pathway and oxidative stress during the development of hypertension in spontaneously hypertensive rats (SHR). In SHR and normotensive rats (WKY) at 6 and 13 weeks of age, we studied (i) plasma antioxidant capacity, (ii) production of superoxide and NAD(P)H oxidase activity in aorta (iii) plasma BDNF and vascular expression of BDNF, TrKB, NAD(P)H oxidase subunits, AT1 receptor, and MCP-1. In 6- and 13-week-old SHR aorta, superoxide level was twice than in WKY aorta. At 13 weeks, when blood pressure in SHR was 60 mmHg higher in SHR than in WKY, an enhancement of NAD(P)H oxidase activity in SHR was associated with an increase in p47phox, AT1, and BDNF expression in vessels. MCP-1 expression increased with blood pressure. Our study demonstrated that in SHR rats, an increase in levels of vascular oxidative stress and in aortic BDNF and TrKB expression occurs prior to the rise in blood pressure, while a reinforcement of vascular and circulating oxidative stress markers is brought about later by hypertension.

The thromboxane/endoperoxide receptor (TP): the common villain

The stimulation of thromboxane/endoperoxide receptors (TP) elicits diverse physiological/pathophysiological reactions, including platelet aggregation and contraction of vascular smooth muscle. Furthermore, the activation of endothelial TP promotes the expression of adhesion molecules and favors adhesion and infiltration of monocytes/macrophages. In various cardiovascular diseases, endothelial dysfunction is predominantly the result of the release of endothelium-derived contracting factors that counteract the vasodilator effect of nitric oxide produced by the endothelial nitric oxide synthase. Endothelium-dependent contractions involve the activation of cyclooxygenases, the production of reactive oxygen species along with that of endothelium-derived contracting factors, which diffuse toward the vascular smooth muscle cells and activate their TP. TP antagonists curtail the endothelial dysfunction in diseases such as hypertension and diabetes, are potent antithrombotic agents, and reduce vascular inflammation. Therefore, TP antagonists, because of this triple activity, may have a unique potential for the treatment of cardiovascular disorders.

Intrinsic nitric oxide and superoxide production regulates descending vasa recta contraction

Descending vasa recta (DVR) are 12- to 15-μm microvessels that supply the renal medulla with blood flow. We examined the ability of intrinsic nitric oxide (NO) and reactive oxygen species (ROS) generation to regulate their vasoactivity. Nitric oxide synthase (NOS) inhibition with N(ω)-nitro-l-arginine methyl ester (l-NAME; 100 μmol/l), or asymmetric N(G),N(G)-dimethyl-l-arginine (ADMA; 100 μmol/l), constricted isolated microperfused DVR by 48.82 ± 4.34 and 27.91 ± 2.91%, respectively. Restoring NO with sodium nitroprusside (SNP; 1 mmol/l) or application of 8-Br-cGMP (100 μmol/l) reversed DVR vasoconstriction by l-NAME. The superoxide dismutase mimetic Tempol (1 mmol/l) and the NAD(P)H inhibitor apocynin (100, 1,000 μmol/l) also blunted ADMA- or l-NAME-induced vasoconstriction, implicating a role for concomitant generation of ROS. A role for ROS generation was also supported by an l-NAME-associated rise in oxidation of dihydroethidium that was prevented by Tempol or apocynin. To test whether H(2)O(2) might play a role, we examined its direct effects. From 1 to 100 μmol/l, H(2)O(2) contracted DVR whereas at 1 mmol/l it was vasodilatory. The H(2)O(2) scavenger polyethylene glycol-catalase reversed H(2)O(2) (10 μmol/l)-induced vasoconstriction; however, it did not affect l-NAME-induced contraction. Finally, the previously known rise in DVR permeability to (22)Na and [(3)H]raffinose that occurs with luminal perfusion was not prevented by NOS blockade. We conclude that intrinsic production of NO and ROS can modulate DVR vasoactivity and that l-NAME-induced vasoconstriction occurs, in part, by modulating superoxide concentration and not through H(2)O(2) generation. Intrinsic NO production does not affect DVR permeability to hydrophilic solutes.

PPARalpha stimulation exerts a blood pressure lowering effect through different mechanisms in a time-dependent manner

Peroxisome proliferator activated receptors (PPARs) are a family of nuclear receptors that, upon activation with selective ligands, work as transcription factors. Recently, these have been related with the cardiovascular system. Our aim was to study PPARalpha-stimulation and its effects on blood pressure in rats with aortic coarctation, and to explore the role of the antioxidant system. Male Wistar rats (250-280 g) were distributed into the following groups: 1) sham; 2) aortic coarctated-vehicle-treated (AoCo-V), and 3) AoCo-clofibrate (100mg/kg) treated (AoCo-C). Rats were treated for 1 or 21 days. Clofibrate lowered blood pressure in both 1- and 21-day treatments. Renal reactive oxygen species increased after 1 day in AoCo-V, while clofibrate prevented this effect. Superoxide dismutase (SOD)-1 expression increased 3.6-fold upon PPARalpha stimulation (1 day) and returned to normal values by day 21. SOD-1 activity increased slightly in response to clofibrate. Renal activity of catalase increased in AoCo-C (1 day) and returned to normal (21 days). eNOS expression was not modified acutely (1 day) but increased at 21 days of treatment with clofibrate. Angiotensin II AT(1)-receptor expression as well as angiotensin II decreased in clofibrate-treated rats, while angiotensin II AT(2)-receptor expression increased, in both treatment periods. Angiotensin-(1-7) increased at 21 days. Our results suggest that in the early development of AoCo-induced hypertension, stimulation of PPARalpha increases the antioxidant defenses, leading to improvement in endothelial factors while in the sub-chronic phase (21 days), eNOS and angiotensin II receptors appear to play major roles in controlling blood pressure.