Oxidative stress and hypertension

Antioxidant-based therapies for angiotensin II-associated cardiovascular diseases

Cardiovascular diseases, including hypertension and heart failure, are associated with activation of the renin-angiotensin system (RAS) and increased circulating and tissue levels of ANG II, a primary effector peptide of the RAS. Through its actions on various cell types and organ systems, ANG II contributes to the pathogenesis of cardiovascular diseases by inducing cardiac and vascular hypertrophy, vasoconstriction, sodium and water reabsorption in kidneys, sympathoexcitation, and activation of the immune system. Cardiovascular research over the past 15-20 years has clearly implicated an important role for elevated levels of reactive oxygen species (ROS) in mediating these pathophysiological actions of ANG II. As such, the use of antioxidants, to reduce the elevated levels of ROS, as potential therapies for various ANG II-associated cardiovascular diseases has been intensely investigated. Although some antioxidant-based therapies have shown therapeutic impact in animal models of cardiovascular disease and in human patients, others have failed. In this review, we discuss the benefits and limitations of recent strategies, including gene therapy, dietary sources, low-molecular-weight free radical scavengers, polyethylene glycol conjugation, and nanomedicine-based technologies, which are designed to deliver antioxidants for the improved treatment of cardiovascular diseases. Although much work has been completed, additional research focusing on developing specific antioxidant molecules or proteins and identifying the ideal in vivo delivery system for such antioxidants is necessary before the use of antioxidant-based therapies for cardiovascular diseases become a clinical reality.

Targeting mitochondrial reactive oxygen species as novel therapy for inflammatory diseases and cancers

There are multiple sources of reactive oxygen species (ROS) in the cell. As a major site of ROS production, mitochondria have drawn considerable interest because it was recently discovered that mitochondrial ROS (mtROS) directly stimulate the production of proinflammatory cytokines and pathological conditions as diverse as malignancies, autoimmune diseases, and cardiovascular diseases all share common phenotype of increased mtROS production above basal levels. Several excellent reviews on this topic have been published, but ever-changing new discoveries mandated a more up-to-date and comprehensive review on this topic. Therefore, we update recent understanding of how mitochondria generate and regulate the production of mtROS and the function of mtROS both in physiological and pathological conditions. In addition, we describe newly developed methods to probe or scavenge mtROS and compare these methods in detail. Thorough understanding of this topic and the application of mtROS-targeting drugs in the research is significant towards development of better therapies to combat inflammatory diseases and inflammatory malignancies.

Evaluation of the antihypertensive properties of yellow passion fruit pulp (Passiflora edulis Sims f. flavicarpa Deg.) in spontaneously hypertensive rats

Various species of the genus Passiflora have been extensively used in traditional medicine as sedatives, anxiolytics, diuretics and analgesics. In the present study, after the identification and quantification of phytochemical compounds from yellow passion fruit pulp by liquid chromatography-photodiode array-mass spectrometry (HPLC-PDA-MS/MS), its antihypertensive effect was investigated on spontaneously hypertensive rats. Additionally, the renal function, evaluated by kidney/body weight, serum creatinine, proteinuria, urinary flow, reduced glutathione (GSH) levels and thiobarbituric acid-reactive substances (TBARS) and mutagenicity in bone marrow cells were assessed to evaluate the safety of passion fruit consumption. Yellow passion fruit pulp (5, 6 or 8 g/kg b.w.) was administered by gavage once a day for 5 consecutive days. HLPC-PDA-MS/MS analysis revealed that yellow passion fruit pulp contains phenolic compounds, ascorbic acid, carotenoids and flavonoids. The highest dose of passion fruit pulp significantly reduced the systolic blood pressure, increased the GSH levels and decreased TBARS. There were no changes in renal function parameters or the frequency of micronuclei in bone marrow cells. In conclusion, the antihypertensive effect of yellow passion fruit pulp, at least in part, might be due to the enhancement of the antioxidant status. The exact mechanisms responsible by this effect need further investigation.

D5 dopamine receptor decreases NADPH oxidase, reactive oxygen species and blood pressure via heme oxygenase-1

D5 dopamine receptor (D5R) knock-out mice (D5(-/-)) have a higher blood pressure (BP) and higher reactive oxygen species (ROS) production than their D5R wild-type littermates (D5(+/+)). We tested the hypothesis that the high BP and increased ROS production in D5(-/-) mice may be caused by decreased heme oxygenase-1 (HO-1) expression and activity. We found that renal HO-1 protein expression and HO enzyme activity were decreased (65 and 50%, respectively) in D5(-/-) relative to D5(+/+) mice. A 24 h of administration of hemin, an HO-1 inducer, increased HO-1 expression and HO activity (6.8- and 1.9-fold, respectively) and normalized the increased ROS production and BP in D5(-/-) mice. Expression of HO-1 protein and HO activity were increased (2.3- and 1.5-fold, respectively) in HEK cells that heterologously expressed human wild-type D5R (HEK-hD5R), but not the empty vector-transfected HEK-293 cells. Fenoldopam (Fen), a D5R agonist, increased HO activity (3 h), HO-1 protein expression, HO-1 and D5R colocalization and co-immunoprecipitation in HEK-hD5R cells. Cellular NADPH oxidase activity was decreased by 35% in HEK-hD5R that was abrogated with silencing of the heme oxygenase 1 gene (HMOX1). HMOX1 siRNA also impaired the ability of Fen to decrease NADPH oxidase activity in HEK-hD5R cells. In summary, the D5R positively regulates HO-1 through direct protein/protein interaction in the short-term and by increasing HO-1 protein expression in the long-term. The impaired D5R regulation of HO-1 and ROS production contributes to the pathogenesis of hypertension in D5(-/-) mice.

Black-white blood pressure disparities: depressive symptoms and differential vulnerability to blood lead

BACKGROUND

Blacks have higher hypertension rates than whites, but the reasons for these disparities are unknown. Differential vulnerability, through which stress alters vulnerability to the effects of environmental hazards, is an emergent notion in environmental health that may contribute to these disparities.

OBJECTIVES

We examined whether blacks and whites exhibit different associations between blood lead (BPb) and blood pressure (BP) and whether depressive symptoms may play a role.

METHODS

Using the National Health and Nutrition Examination Survey 2005-2008, we regressed BP on the three-way interaction among race/ethnicity, BPb, and depressive symptoms in blacks and whites ≥ 20 years of age.

RESULTS

Blacks but not whites showed a positive association between BPb and systolic blood pressure (SBP). The disparity in this association between blacks and whites appeared to be specific to the high depressive symptoms group. In the low depressive symptoms group, there was no significant black-white disparity (βinteraction = 0.9 mmHg; 95% CI: -0.9, 2.7). However, of those with high depressive symptoms, blacks and whites had 5.6 mmHg (95% CI: 2.0, 9.2) and 1.2 mmHg (95% CI: -0.5, 2.9) increases in SBP, respectively, in association with each doubling of BPb (βinteraction = 4.4 mmHg; 95% CI: 0.5, 8.3). The pattern of results was similar for diastolic blood pressure.

CONCLUSIONS

Our results suggest that depressive symptoms may contribute to the black-white disparity in the association between BPb and BP. Depressive symptoms may result, in part, from psychosocial stress. Our results support the notion that stress increases vulnerability to the health effects of environmental hazards and suggest that stress-related vulnerability may be an important determinant of racial/ethnic health disparities.

Vanin-1 T26I polymorphism, hypertension and cardiovascular events in two large urban-based prospective studies in Swedes

BACKGROUND AND AIMS

Vanin-1 (gene name VNN1) is an enzyme with pantetheinase activity generating the amino-thiol cysteamine which is implicated in the regulation of red-ox status through its effect on glutathione. We tested the hypothesis that the rs2294757 VNN1 T26I polymorphism could affect blood pressure (BP) levels, hypertension prevalence, and risk of incident cardiovascular events.

METHODS AND RESULTS

The VNN1 T26I polymorphism was genotyped in 5664 participants of the cardiovascular cohort of the "Malmö Diet and Cancer" (MDC-CVA) study and successively in 17874 participants of the "Malmö Preventive project"(MPP). The incidence of cardiovascular events was monitored for an average of nearly 12 years of follow-up in the MDC-CVA and for 25 years in the MPP. Both before and after adjustment for sex, age and BMI in the MDC-CVA the polymorphism had a mild lowering effect on diastolic BP and hypertension, especially in females. However in MPP no effect on BP phenotypes was detectable. Before and after adjustment for major cardiovascular risk factors, the hazard ratio for incident ischemic stroke and coronary events in the MDC-CVA was not significantly different in carriers of different genotypes.

CONCLUSIONS

Our data do not support a major role for the VNN1 T26I variant in determining BP level and incident ischemic events.

Consumption of healthy foods at different content of antioxidant vitamins and phytochemicals and metabolic risk factors for cardiovascular disease in men and women of the Moli-sani study

BACKGROUND/OBJECTIVES

To categorize healthy food groups into categories of low-antioxidant (LAC) or high-antioxidant vitamins and phytochemicals content (HAC) and comparatively associate them with metabolic risk factors for cardiovascular disease (CVD).

SUBJECTS/METHODS

A total of 6879 women (55±12 years) and 6892 men (56 ± 12 years) were analyzed from the Moli-sani cohort, randomly recruited from the general population. The European Prospective Investigation into Cancer and Nutrition Food Frequency Questionnaire was used for dietary assessment. The antioxidant content of each food group was evaluated using Istituto Nazionale di Ricerca per gli Alimenti e la Nutrizione and United States Department of Agriculture (USDA) food composition tables. Healthy foods, according to a Mediterranean dietary pattern, were categorized into HAC or LAC; total food antioxidant content (FAC) score was constructed for a comparative evaluation of the consumption of these two groups.

RESULTS

In men, an increase in FAC score, which represents an increased consumption of HAC with respect to LAC foods, was associated with a decrease in systolic blood pressure, diastolic blood pressure and C-reactive protein (CRP) (β=-0.5, P=0.02, β=-0.3, P=0.02 and β=-0.03, P=0.03, respectively). Logistic regression analyses showed that in men 15% (30 units) increase in FAC score was associated with 6% decrease in the likelihood of having hypertension (odds ratio (OR)=0.94, 95% confidence interval (CI) 0.91-0.98) and 3% decrease in the likelihood of having a high CRP risk level (OR=0.97, 95% CI 0.94-0.99). No significant associations were observed in women.

CONCLUSIONS

A possible greater protective role of healthy HAC as compared with healthy LAC foods on hypertension and inflammation was detected in men. These results stress the importance of studying healthy foods according to their content in antioxidant vitamins and phytochemicals, in primary prevention of CVD.

Role of the NADPH oxidases in the subfornical organ in angiotensin II-induced hypertension

Reactive oxygen species and the NADPH oxidases contribute to hypertension via mechanisms that remain undefined. Reactive oxygen species produced in the central nervous system have been proposed to promote sympathetic outflow, inflammation, and hypertension, but the contribution of the NADPH oxidases to these processes in chronic hypertension is uncertain. We therefore sought to identify how NADPH oxidases in the subfornical organ (SFO) of the brain regulate blood pressure and vascular inflammation during sustained hypertension. We produced mice with loxP sites flanking the coding region of the NADPH oxidase docking subunit p22(phox). SFO-targeted injections of an adenovirus encoding cre-recombinase markedly diminished p22(phox), Nox2, and Nox4 mRNA in the SFO, as compared with a control adenovirus encoding red-fluorescent protein injection. Increased superoxide production in the SFO by chronic angiotensin II infusion (490 ng/kg min(-1) × 2 weeks) was blunted in adenovirus encoding cre-recombinase-treated mice, as detected by dihydroethidium fluorescence. Deletion of p22(phox) in the SFO eliminated the hypertensive response observed at 2 weeks of angiotensin II infusion compared with control adenovirus encoding red-fluorescent protein-treated mice (mean arterial pressures=97 ± 15 versus 154 ± 6 mm Hg, respectively; P=0.0001). Angiotensin II infusion also promoted marked vascular inflammation, as characterized by accumulation of activated T-cells and other leukocytes, and this was prevented by deletion of the SFO p22(phox). These experiments definitively identify the NADPH oxidases in the SFO as a critical determinant of the blood pressure and vascular inflammatory responses to chronic angiotensin II, and further support a role of reactive oxygen species in central nervous system signaling in hypertension.

A novel look at racial health disparities: the interaction between social disadvantage and environmental health

OBJECTIVES

We explored the notion that social disadvantage increases vulnerability to the health effects of environmental hazards. Specifically, we examined (1) whether race modifies the association between blood lead and blood pressure and (2) whether socioeconomic status (SES) plays a role in this modifying effect.

METHODS

Using the National Health and Nutrition Examination Survey (2001-2008) and linear regression, we estimated the association between blood lead and blood pressure. Using interactions among race, SES, and lead, we estimated this association by levels of social disadvantage.

RESULTS

Black men and women showed a 2.8 (P < .001) and 4.0 (P < .001) millimeters mercury increase in SBP, respectively, for each doubling of blood lead. White adults showed no association. This lead-SBP association exhibited by Blacks was primarily isolated to Blacks of low SES. For example, poor but not nonpoor Black men showed a 4.8 millimeters mercury (P < .001) increase in SBP for each doubling of blood lead.

CONCLUSIONS

Our results suggest that social disadvantage exacerbates the deleterious health effects of lead. Our work provides evidence that social and environmental factors must be addressed together to eliminate health disparities.

Identification of novel antioxidant peptides generated in Spanish dry-cured ham

The objective of this study was to purify and identify antioxidant peptides present in a water soluble extract of Spanish dry-cured ham. The initial extract was loaded into a Sephadex G25 column and fractions showing antioxidant activity were collected, pooled together and subjected to reversed-phase chromatography for further purification. Using a nano-LC-MS/MS analysis, 27 peptides were identified in these fractions. Several key peptides were selected for synthesis and the determination of their antioxidant properties using the DPPH radical-scavenging assay and reducing power analysis. The strongest radical-scavenging activity was observed with peptide SAGNPN which showed 50% antioxidant activity at a concentration of 1.5mg/ml. On the other hand, the peptide GLAGA showed the higher reducing power with 0.5 units of absorbance at 700 nm at a concentration of 1mg/ml. Other synthesised sequences showed lower antioxidant activity. The results indicate the potential of Spanish dry-cured ham as a source of antioxidant peptides naturally generated during the dry-curing process.

Angiotensin-(1-7) modulates renin-angiotensin system associated with reducing oxidative stress and attenuating neuronal apoptosis in the brain of hypertensive rats

Angiotensin-(1-7) [Ang-(1-7)] has beneficial effects against hypertension-induced damage in heart and kidney, but its effects in brain are not clear as yet. The present study aimed to investigate the protective effects of Ang-(1-7) on the physiopathologic changes caused by hypertension in brain of spontaneously hypertensive rats (SHRs). Wistar-Kyoto rats received intracerebroventricular (I.C.V.) infusion of artificial cerebrospinal fluid (aCSF) while SHRs received I.C.V. infusion of Ang-(1-7), Mas receptor antagonist A-779 and aCSF for 4 weeks. Brain tissues were collected and analyzed by western blot, enzyme immunoassay, spectrophotometric assays and terminal deoxynucleotidyl transferase-mediated dUTP end-labeling (TUNEL) staining. Our study showed that infusion of Ang-(1-7) for 4 weeks significantly reduced the expression of Angiotensin II and Angiotensin II type 1 receptors in SHR brain. Additionally, it decreased the levels of malondialdehyde and elevated total superoxide dismutase activity, which was accompanied by reductions of NADPH oxidase subunit gp91(phox) and inducible nitric oxide synthase in the brain of SHR. The increases of the percentage of TUNEL-positive neurons and Bax to Bcl-2 ratio in SHR brain were also attenuated by Ang-(1-7). The anti-oxidative and anti-apoptosis effects of Ang-(1-7) are independent of blood pressure reduction and can be partially abolished by A-779. These findings suggest that chronic treatment with Ang-(1-7) is beneficial to attenuate hypertension-induced physiopathologic changes in brain and may be helpful to prevent hypertension-related cerebrovascular diseases.

Ceruloplasmin (ferroxidase) oxidizes hydroxylamine probes: deceptive implications for free radical detection

Ceruloplasmin (ferroxidase) is a copper-binding protein known to promote Fe(2+) oxidation in plasma of mammals. In addition to its classical ferroxidase activity, ceruloplasmin is known to catalyze the oxidation of various substrates, such as amines and catechols. Assays based on cyclic hydroxylamine oxidation are used to quantify and detect free radicals in biological samples ex vivo and in vitro. We show here that human ceruloplasmin promotes the oxidation of the cyclic hydroxylamine 1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine hydrochloride (CPH) and related probes in Chelex-treated phosphate buffer and rat serum. The reaction is suppressed by the metal chelators DTPA, EDTA, and desferal, whereas heparin and bathocuproine have no effect. Catalase or superoxide dismutase additions do not interfere with the CPH-oxidation yield, demonstrating that oxygen-derived free radicals are not involved in the CPH oxidation mediated by ceruloplasmin. Plasma samples immunodepleted of ceruloplasmin have lower levels of CPH oxidation, which confirms the role of ceruloplasmin (ferroxidase) as a biological oxidizing agent of cyclic hydroxylamines. In conclusion, we show that the ferroxidase activity of ceruloplasmin is a possible biological source of artifacts in the cyclic hydroxylamine-oxidation assay used for reactive oxygen species detection and quantification.

Proteomic response to acupuncture treatment in spontaneously hypertensive rats

Previous animal and clinical studies have shown that acupuncture is an effective alternative treatment in the management of hypertension, but the mechanism is unclear. This study investigated the proteomic response in the nervous system to treatment at the Taichong (LR3) acupoint in spontaneously hypertensive rats (SHRs). Unanesthetized rats were subject to 5-min daily acupuncture treatment for 7 days. Blood pressure was monitored over 7 days. After euthanasia on the 7^th day, rat medullas were dissected, homogenized, and subject to 2D gel electrophoresis and MALDI-TOF analysis. The results indicate that blood pressure stabilized after the 5th day of acupuncture, and compared with non-acupoint treatment, Taichong-acupunctured rat’s systolic pressure was reduced significantly (P<0.01), though not enough to bring blood pressure down to normal levels. The different treatment groups also showed differential protein expression: the 2D images revealed 571±15 proteins in normal SD rats’ medulla, 576±31 proteins in SHR’s medulla, 597±44 proteins in medulla of SHR after acupuncturing Taichong, and 616±18 proteins in medulla of SHR after acupuncturing non-acupoint. In the medulla of Taichong group, compared with non-acupoint group, seven proteins were down-regulated: heat shock protein-90, synapsin-1, pyruvate kinase isozyme, NAD-dependent deacetylase sirtuin-2, protein kinase C inhibitor protein 1, ubiquitin hydrolase isozyme L1, and myelin basic protein. Six proteins were up-regulated: glutamate dehydrogenase 1, aldehyde dehydrogenase 2, glutathione S-transferase M5, Rho GDP dissociation inhibitor 1, DJ-1 protein and superoxide dismutase. The altered expression of several proteins by acupuncture has been confirmed by ELISA, Western blot and qRT-PCR assays. The results indicate an increase in antioxidant enzymes in the medulla of the SHRs subject to acupuncture, which may provide partial explanation for the antihypertensive effect of acupuncture. Further studies are warranted to investigate the role of oxidative stress modulation by acupuncture in the treatment of hypertension.

The new role of LOX-1 in hypertension induced neuronal apoptosis

Lectin-like oxidized low-density lipoprotein (oxLDL) receptor-1 (LOX-1) was originally identified as a receptor for oxLDL predominantly expressed in endothelial cells. Recently up-regulation of LOX-1 has been implicated in oxidative stress and cell apoptosis in many cell types. However, LOX-1 expression in neurons or regulation of neuronal apoptosis by LOX-1 has not been reported. To investigate the possible roles of LOX-1 in hypertension induced brain damage, we examined the distribution of LOX-1 in cortex and hippocampus and compared its expression in 32-week-old SHR and WKY rats. Immunofluorescence revealed that LOX-1 positive cells were located principally at the cortex involved in sensory information processing and were mainly expressed in neurons. We also found up-regulated mRNA expression of LOX-1, Bax and caspase-3 and down-regulated mRNA expression of Bcl-2 in SHR group. Compared with WKY group, SHR group showed increased LOX-1 positive cells and TUNEL positive cells. Furthermore, double-labeling method indicated that LOX-1 expression was colocalized with TUNEL positive cells, which means that LOX-1 expression was involved in hypertension related cell apoptosis. These findings indicated that LOX-1 expression was up-regulated in the cortex of SHR and its expression has implication in neuronal apoptosis. Elevated Bax/Bcl-2 ratio may be involved under this event.

Role of copper transport protein antioxidant 1 in angiotensin II-induced hypertension: a key regulator of extracellular superoxide dismutase

Extracellular superoxide dismutase (SOD3) is a secretory copper enzyme involved in protecting angiotensin II (Ang II)-induced hypertension. We found previously that Ang II upregulates SOD3 expression and activity as a counterregulatory mechanism; however, underlying mechanisms are unclear. Antioxidant 1 (Atox1) is shown to act as a copper-dependent transcription factor, as well as a copper chaperone, for SOD3 in vitro, but its role in Ang II-induced hypertension in vivo is unknown. Here we show that Ang II infusion increases Atox1 expression, as well as SOD3 expression and activity, in aortas of wild-type mice, which are inhibited in mice lacking Atox1. Accordingly, Ang II increases vascular superoxide production, reduces endothelium-dependent vasodilation, and increases vasoconstriction in mesenteric arteries to a greater extent in Atox1(-/-) than in wild-type mice. This contributes to augmented hypertensive response to Ang II in Atox1(-/-) mice. In cultured vascular smooth muscle cells, Ang II promotes translocation of Atox1 to the nucleus, thereby increasing SOD3 transcription by binding to Atox1-responsive element in the SOD3 promoter. Furthermore, Ang II increases Atox1 binding to the copper exporter ATP7A, which obtains copper from Atox1, as well as translocation of ATP7A to plasma membranes, where it colocalizes with SOD3. As its consequence, Ang II decreases vascular copper levels, which is inhibited in Atox1(-/-) mice. In summary, Atox1 functions to prevent Ang II-induced endothelial dysfunction and hypercontraction in resistant vessels, as well as hypertension, in vivo by reducing extracellular superoxide levels via increasing vascular SOD3 expression and activity.

Central cardiovascular circuits contribute to the neurovascular dysfunction in angiotensin II hypertension

Hypertension, a powerful risk factor for stroke and dementia, has damaging effects on the brain and its vessels. In particular, hypertension alters vital cerebrovascular control mechanisms linking neural activity to cerebral perfusion. In experimental models of slow-developing hypertension, free radical signaling in the subfornical organ (SFO), one of the forebrain circumventricular organs, is critical for the hormonal release and sympathetic activation driving the elevation in arterial pressure. However, the contribution of this central mechanism to the cerebrovascular alterations induced by hypertension remains uncertain. We tested the hypothesis that free radical production in the SFO is involved in the alterations in cerebrovascular regulation produced by hypertension. In a mouse model of gradual hypertension induced by chronic administration of subpressor doses of angiotensin II (AngII), suppression of free radicals in the SFO by overexpression of CuZn-superoxide dismutase (CuZnSOD) prevented the alteration in neurovascular coupling and endothelium-dependent responses in somatosensory cortex induced by hypertension. The SFO mediates the dysfunction via two signaling pathways. One involves SFO-dependent activation of the paraventricular hypothalamic nucleus, elevations in plasma vasopressin, upregulation of endothelin-1 in cerebral resistance arterioles and activation of endothelin type A receptors. The other pathway depends on activation of cerebrovascular AngII type 1 (AT1) receptors by AngII. Both pathways mediate vasomotor dysfunction by inducing vascular oxidative stress. The findings implicate for the first time the SFO and its efferent hypothalamic pathways in the cerebrovascular alterations induced by AngII, and identify vasopressin and endothelin-1 as potential therapeutic targets to counteract the devastating effects of hypertension on the brain.

Peroxisome proliferator-activated receptor-γ activation reduces cyclooxygenase-2 expression in vascular smooth muscle cells from hypertensive rats by interfering with oxidative stress

AIMS

Hypertension is associated with increased plasma inflammatory markers such as cytokines and increased vascular cyclooxygenase-2 (COX-2) expression. The ability of peroxisome proliferator-activated receptor-γ (PPARγ) agonists to reduce oxidative stress seems to contribute to their anti-inflammatory properties. This study analyzes the effect of pioglitazone, a PPARγ agonist, on interleukin-1β-induced COX-2 expression and the role of reactive oxygen species (ROS) on this effect.

METHODS AND RESULTS

Vascular smooth muscle cells from hypertensive rats stimulated with interleukin-1β (10 ng/ml, 24 h) were used. Interleukin-1β increased: 1) COX-2 protein and mRNA levels; 2) protein and mRNA levels of the NADPH oxidase subunit NOX-1, NADPH oxidase activity and ROS production; and 3) phosphorylation of inhibitor of nuclear factor kappa B (IκB) kinase (IKK) nuclear expression of the p65 nuclear factor kappa B (NF-κB) subunit and cell proliferation, all of which were reduced by apocynin (30 μmol/l). Interleukin-1β-induced COX-2 expression was reduced by apocynin, tempol (10 μmol/l), catalase (1000 U/ml) and lactacystin (5 μmol/l). Moreover, H2O2 (50 μmol/l, 90 min) induced COX-2 expression, which was reduced by lactacystin. Pioglitazone (10 μmol/l) reduced the effects of interleukin-1β on: 1) COX-2 protein and mRNA levels; 2) NOX-1 protein and mRNA levels, NADPH oxidase activity and ROS production; and 3) p-IKK, p65 expressions and cell proliferation. Pioglitazone also reduced the H2O2-induced COX-2 expression and increased Cu/Zn and Mn-superoxide dismutase protein expression. PPARγ small interfering RNA (5 nmol/l) further increased interleukin-1β-induced COX-2 and NOX-1 mRNA levels. In addition, pioglitazone increased the interleukin-1β-induced PPARγ mRNA levels.

CONCLUSION

PPARγ activation with pioglitazone reduces interleukin-1β-induced COX-2 expression by interference with the redox-sensitive transcription factor NF-κB.

Novel concepts in the genesis of hypertension: role of LOX-1

Hypertension is a common disease and a potent risk factor for cardiovascular disease. Tremendous strides have been made in understanding its genesis in the last 2 decades. Hypertension is often clustered with other cardiovascular risk factors, such as dyslipidemia and diabetes. The state of hypertension is often associated with increased vascular oxidative stress. Oxidative stress promotes proliferation and hypertrophy of vascular smooth muscle cell and collagen deposition, leading to thickening of the vascular media and narrowing of the vascular lumen. Oxidative stress also injures endothelium, impairs endothelium-dependent vascular relaxation and increases vascular contractile activity. Further, oxidative stress also oxidizes LDL-cholesterol. It has been shown that oxidized low-density lipoprotein (ox-LDL) activates renin-angiotensin system (RAS) and angiotensin II via its type 1 receptor activates ox-LDL receptor LOX-1. This mutually facilitative cross-talk between ox-LDL and RAS may be an important component in the development of hypertension. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a receptor for ox-LDL. This review summarizes the role of LOX-1 in the pathogenesis of hypertension.

Structural mechanism of disulphide bond-mediated redox switches

The oxidation of cysteine sulphydryl in proteins produces sulphenic acid that can form a reversible disulphide bond with another cysteine. The disulphide bond formation often triggers switches in protein structure and activity, especially when the distance between the two cysteine sulphur atoms is longer than the resulting disulphide bond distance. As an early example for the reversible disulphide bond-mediated functional switches, the reduced and oxidized forms of the bacterial transcription factor OxyR were characterized by X-ray crystallography. Recently, the Drosophila vision signalling protein, the association of inactivation-no-afterpotential D (INAD) was analysed by structural and functional methods. The two conserved cysteines of INAD were found to cycle between reduced and oxidized states during the light signal processing in Drosophila eyes, which was achieved by conformation dependent modulation of the disulphide bond redox potential. The production of the hypertension control peptide angiotensins was also shown to be controlled by the reversible disulphide bond in the precursor protein angiotensinogen. The crystal structure of the complex of angiotensiongen with its processing enzyme renin elucidated the role of the disulphide bond in stabilizing the precursor-enzyme complex facilitating the production of angiotensins. The increasing importance of the disulphide bond-mediated redox switches in normal and diseased states has implications in the development of novel antioxidant-based therapeutic approaches.

The Heart and Medicine: Exploring the Interconnectedness of Cardiometabolic-related Concerns Through a Systems Biology Approach

Patients do not just wake up one morning with cardiac disease. Instead there is an extended preclinical phase during which lifestyle choices determine outcome. Recent advances in our understanding of oxidative stress, endocrine signaling, immune/inflammatory balance, and energy production illuminate opportunities for efficacious intervention. A thorough exploration of these pathophysiologies will allow physicians the opportunity to offer their patients a journey away from illness and disease to optimal wellness.

No effect of creatine supplementation on oxidative stress and cardiovascular parameters in spontaneously hypertensive rats

Background

Exacerbated oxidative stress is thought to be a mediator of arterial hypertension. It has been postulated that creatine (Cr) could act as an antioxidant agent preventing increased oxidative stress. The aim of this study was to investigate the effects of nine weeks of Cr or placebo supplementation on oxidative stress and cardiovascular parameters in spontaneously hypertensive rats (SHR).

Findings

Lipid hydroperoxidation, one important oxidative stress marker, remained unchanged in the coronary artery (Cr: 12.6 ± 1.5 vs. Pl: 12.2 ± 1.7 nmol·mg^-1; p = 0.87), heart (Cr: 11.5 ± 1.8 vs. Pl: 14.6 ± 1.1 nmol·mg^-1; p = 0.15), plasma (Cr: 67.7 ± 9.1 vs. Pl: 56.0 ± 3.2 nmol·mg^-1; p = 0.19), plantaris (Cr: 10.0 ± 0.8 vs. Pl: 9.0 ± 0.8 nmol·mg^-1; p = 0.40), and EDL muscle (Cr: 14.9 ± 1.4 vs. Pl: 17.2 ± 1.5 nmol·mg^-1; p = 0.30). Additionally, Cr supplementation affected neither arterial blood pressure nor heart structure in SHR (p > 0.05).

Conclusions

Using a well-known experimental model of systemic arterial hypertension, this study did not confirm the possible therapeutic effects of Cr supplementation on oxidative stress and cardiovascular dysfunction associated with arterial hypertension.

Molecular mechanisms of hypertension--reactive oxygen species and antioxidants: a basic science update for the clinician

Many factors have been implicated in the pathophysiology of hypertension such as upregulation of the renin-angiotensin-aldosterone system, activation of the sympathetic nervous system, perturbed G protein-coupled receptor signalling, inflammation, and altered T-cell function. Common to these processes is increased bioavailability of reactive oxygen species (ROS) (termed oxidative stress) due to excess ROS generation, decreased nitric oxide (NO) levels, and reduced antioxidant capacity in the cardiovascular, renal, and nervous systems. Although oxidative stress may not be the sole etiology of hypertension, it amplifies blood pressure elevation in the presence of other prohypertensive factors. In the cardiovascular system ROS play a physiological role in controlling endothelial function, vascular tone, and cardiac function, and a pathophysiological role in inflammation, hypertrophy, proliferation, apoptosis, migration, fibrosis, angiogenesis, and rarefaction, all of which are important processes contributing to endothelial dysfunction and cardiovascular remodelling in hypertension. A major source for cardiovascular ROS is a family of nonphagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox1, Nox2, Nox4, and Nox5). Other sources include mitochondrial enzymes, xanthine oxidase, and uncoupled NO synthase (NOS). Although convincing data from animal studies support a causative role for oxidative stress in the pathogenesis of hypertension, there is still no solid evidence that oxidative stress causes hypertension in humans. However, biomarkers of excess ROS are increased in patients with hypertension and oxidative damage is important in the molecular mechanisms associated with cardiovascular and renal injury in hypertension. Although clinical trials failed to show beneficial antihypertensive effects of antioxidants, strategies that combat oxidative stress by targeting Noxs in an isoform-specific manner may have therapeutic potential.

NOX5: from basic biology to signaling and disease

In mammals, the NADPH oxidase family of enzymes comprises seven members: NOXs 1-5, DUOX1, and DUOX2. All of these enzymes function to move an electron across cellular membranes, transferring it to oxygen to generate the superoxide anion. This generation of reactive oxygen species has important physiological and pathophysiological roles. NOX5 is perhaps the least well understood of these NOX isoforms, in part because the gene is not present in mice or rats. In recent years, however, there has been a rapid increase in our understanding of the NOX5 gene, the structural and biochemical aspects of the NOX5 enzyme, the role NOX5 plays in health and disease, and the development of novel NOX inhibitors. This review takes a look back at some historical aspects of the discovery of NOX5 and summarizes our current understanding of the enzyme.

Effects of tempol and candesartan on neural control of the kidney

We compared the effects of tempol (300 μmol kg(-1) plus 300 μmol kg(-1) h(-1), n=14) and candesartan (10 μg kg(-1) plus 10 μg kg(-1) h(-1), n=14) on renal haemodynamics, excretory function, and responses to electrical stimulation of the renal nerves (RNS) in lean and obese rabbits under pentobarbitone anaesthesia. Depressor responses to tempol (-16 ± 2 mmHg) and candesartan (-12 ± 1 mmHg) were similar. Candesartan, but not tempol, significantly increased basal renal blood flow (RBF; +36 ± 7%). Tempol, but not candesartan, significantly reduced glomerular filtration rate (GFR; -30 ± 10%) and sodium excretion (U(Na)V; -44 ± 14%). RNS induced frequency-dependent reductions in RBF (-20 ± 3% at 1 Hz), GFR (-28 ± 6% at 1 Hz) and U(Na)V (-55 ± 6% at 1 Hz). Candesartan blunted these responses. Tempol did not significantly alter RBF and GFR responses to RNS but blunted the U(Na)V response. Responses to RNS, and the effects of tempol and candesartan, were similar in lean compared with obese rabbits. Unlike candesartan, tempol did not induce renal vasodilatation, maintain GFR and U(Na)V during reductions in arterial pressure, or blunt neurally-mediated vasoconstriction. In conclusion, unlike the AT(1)-receptor antagonist candesartan, tempol does not blunt the effects of RNS on renal haemodynamic function. Furthermore, under the current experimental conditions superoxide appears to make little contribution to the actions of endogenous angiotensin II on baseline renal haemodynamics or excretory function, or their responses to RNS.

Inhibition of sevoflurane postconditioning against cerebral ischemia reperfusion-induced oxidative injury in rats

The volatile anesthetic sevoflurane is capable of inducing preconditioning and postconditioning effects in the brain. In this study, we investigated the effects of sevoflurane postconditioning on antioxidant and immunity indexes in cerebral ischemia reperfusion (CIR) rats. Rats were randomly assigned to five separate experimental groups I–V. In the sham group (I), rats were subjected to the same surgery procedures except for occlusion of the middle cerebral artery and exposed to 1.0 MAC sevoflurane 90 min after surgery for 30 min. IR control rats (group II) were subjected to middle cerebral artery occlusion (MCAO) for 90 min and exposed to O₂ for 30 min at the beginning of reperfusion. Sevoflurane 0.5, 1.0 and 1.5 groups (III, IV, V) were all subjected to MCAO for 90 min, but at the beginning of reperfusion exposed to 0.5 MAC, 1.0 MAC or 1.5 MAC sevoflurane for 30 min, respectively. Results showed that sevoflurane postconditioning can decrease serum tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), nitric oxide (NO), nitric oxide synthase (NOS) and increase serum interleukin-10 (IL-10) levels in cerebral ischemia reperfusion rats. In addition, sevoflurane postconditioning can still decrease blood lipid, malondialdehyde (MDA) levels, infarct volume and increase antioxidant enzymes activities, normal pyramidal neurons density in cerebral ischemia reperfusion rats. It can be concluded that sevoflurane postconditioning may decrease blood and brain oxidative injury and enhance immunity indexes in cerebral ischemia reperfusion rats.

Angiotensin II-derived reactive oxygen species underpinning the processing of the cardiovascular reflexes in the medulla oblongata

The brainstem is a major site in the central nervous system involved in the processing of the cardiovascular reflexes such as the baroreflex and the peripheral chemoreflex. The nucleus tractus solitarius and the rostral ventrolateral medulla are 2 important brainstem nuclei, and they play pivotal roles in autonomic cardiovascular regulation. Angiotensin II is one of the neurotransmitters involved in the processing of the cardiovascular reflexes within the brainstem. It is well-known that one of the mechanisms by which angiotensin II exerts its effect is via the activation of pathways that generate reactive oxygen species (ROS). In the central nervous system, ROS are reported to be involved in several pathological diseases such as hypertension, heart failure and sleep apnea. However, little is known about the role of ROS in the processing of the cardiovascular reflexes within the brainstem. The present review mainly discussed some recent findings documenting a role for ROS in the processing of the baroreflex and the peripheral chemoreflex in the brainstem.

Oxidative stress and lectin-like ox-LDL-receptor LOX-1 in atherogenesis and tumorigenesis

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as a major receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, monocytes, platelets, cardiomyocytes, and vascular smooth muscle cells. Its expression is minimal under physiological conditions but can be induced under pathological conditions. The upregulation of LOX-1 by ox-LDL appears to be important for physiologic processes, such as endothelial cell proliferation, apoptosis, and endothelium remodeling. Pathophysiologic effects of ox-LDL in atherogenesis have also been firmly established, including endothelial cell dysfunction, smooth muscle cell growth and migration, monocyte transformation into macrophages, and finally platelet aggregation-seen in atherogenesis. Recent studies show a positive correlation between increased serum ox-LDL levels and an increased risk of colon, breast, and ovarian cancer. As in atherosclerosis, ox-LDL and its receptor LOX-1 activate the inflammatory pathway through nuclear factor-kappa B, leading to cell transformation. LOX-1 is important for maintaining the transformed state in developmentally diverse cancer cell lines and for tumor growth, suggesting a molecular connection between atherogenesis and tumorigenesis.

Regulation of endothelial function by mitochondrial reactive oxygen species

Mitochondria are well known for their central roles in ATP production, calcium homeostasis, and heme and steroid biosynthesis. However, mitochondrial reactive oxygen species (ROS), including superoxide and hydrogen peroxide, once thought to be toxic byproducts of mitochondrial physiologic activities, have recently been recognized as important cell-signaling molecules in the vascular endothelium, where their production, conversion, and destruction are highly regulated. Mitochondrial reactive oxygen species appear to regulate important vascular homeostatic functions under basal conditions in a variety of vascular beds, where, in particular, they contribute to endothelium-dependent vasodilation. On exposure to cardiovascular risk factors, endothelial mitochondria produce excessive ROS in concert with other cellular ROS sources. Mitochondrial ROS, in this setting, act as important signaling molecules activating prothrombotic and proinflammatory pathways in the vascular endothelium, a process that initially manifests itself as endothelial dysfunction and, if persistent, may lead to the development of atherosclerotic plaques. This review concentrates on emerging appreciation of the importance of mitochondrial ROS as cell-signaling molecules in the vascular endothelium under both physiologic and pathophysiologic conditions. Future potential avenues of research in this field also are discussed.

Role of T lymphocytes in angiotensin II-mediated microvascular thrombosis

Clinical trials and animal studies have revealed a role for the renin-angiotensin system in the enhanced thrombus development that is associated with hypertension. Because T lymphocytes have been implicated in the vascular dysfunction and blood pressure elevation associated with increased angiotensin II (Ang II) levels, we evaluated the role of the adaptive immune system in mediating the enhanced thrombosis during Ang II-induced hypertension. Light/dye-induced thrombosis was induced in cremaster arterioles of wild-type, immunodeficient Rag-1(-/-), CD8(+), or CD4(+) lymphocyte-deficient and NADPH oxidase (gp91(phox))-deficient mice implanted with an Ang II-loaded pump for 2 weeks. Chronic Ang II infusion enhanced arteriolar thrombosis in wild-type mice but not in Rag-1(-/-), CD4(+) T-cell-deficient, or gp91(phox-/-) mice. CD8(+) T-cell(-/-) mice exhibited partial protection. Adoptive transfer of T cells derived from wild-type or gp91(phox-/-) mice into Rag-1(-/-) restored the prothrombotic phenotype induced by Ang II. T lymphocytes (CD4(+) and, to a lesser extent, CD8(+)) play a major role in mediating the accelerated microvascular thrombosis associated with Ang II-induced hypertension. NADPH oxidase-derived reactive oxygen species, produced by cells other than T lymphocytes, also appear critical for the Ang II-enhanced, T cell-dependent thrombosis response.

The mitochondrial paradigm for cardiovascular disease susceptibility and cellular function: a complementary concept to Mendelian genetics

While there is general agreement that cardiovascular disease (CVD) development is influenced by a combination of genetic, environmental, and behavioral contributors, the actual mechanistic basis of how these factors initiate or promote CVD development in some individuals while others with identical risk profiles do not, is not clearly understood. This review considers the potential role for mitochondrial genetics and function in determining CVD susceptibility from the standpoint that the original features that molded cellular function were based upon mitochondrial-nuclear relationships established millions of years ago and were likely refined during prehistoric environmental selection events that today, are largely absent. Consequently, contemporary risk factors that influence our susceptibility to a variety of age-related diseases, including CVD were probably not part of the dynamics that defined the processes of mitochondrial-nuclear interaction, and thus, cell function. In this regard, the selective conditions that contributed to cellular functionality and evolution should be given more consideration when interpreting and designing experimental data and strategies. Finally, future studies that probe beyond epidemiologic associations are required. These studies will serve as the initial steps for addressing the provocative concept that contemporary human disease susceptibility is the result of selection events for mitochondrial function that increased chances for prehistoric human survival and reproductive success.

ACE2-mediated reduction of oxidative stress in the central nervous system is associated with improvement of autonomic function

Oxidative stress in the central nervous system mediates the increase in sympathetic tone that precedes the development of hypertension. We hypothesized that by transforming Angiotensin-II (AngII) into Ang-(1–7), ACE2 might reduce AngII-mediated oxidative stress in the brain and prevent autonomic dysfunction. To test this hypothesis, a relationship between ACE2 and oxidative stress was first confirmed in a mouse neuroblastoma cell line (Neuro2A cells) treated with AngII and infected with Ad-hACE2. ACE2 overexpression resulted in a reduction of reactive oxygen species (ROS) formation. In vivo, ACE2 knockout (ACE2^−/y) mice and non-transgenic (NT) littermates were infused with AngII (10 days) and infected with Ad-hACE2 in the paraventricular nucleus (PVN). Baseline blood pressure (BP), AngII and brain ROS levels were not different between young mice (12 weeks). However, cardiac sympathetic tone, brain NADPH oxidase and SOD activities were significantly increased in ACE2^−/y. Post infusion, plasma and brain AngII levels were also significantly higher in ACE2^−/y, although BP was similarly increased in both genotypes. ROS formation in the PVN and RVLM was significantly higher in ACE2^−/y mice following AngII infusion. Similar phenotypes, i.e. increased oxidative stress, exacerbated dysautonomia and hypertension, were also observed on baseline in mature ACE2^−/y mice (48 weeks). ACE2 gene therapy to the PVN reduced AngII-mediated increase in NADPH oxidase activity and normalized cardiac dysautonomia in ACE2^−/y mice. Altogether, these data indicate that ACE2 gene deletion promotes age-dependent oxidative stress, autonomic dysfunction and hypertension, while PVN-targeted ACE2 gene therapy decreases ROS formation via NADPH oxidase inhibition and improves autonomic function. Accordingly, ACE2 could represent a new target for the treatment of hypertension-associated dysautonomia and oxidative stress.

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.

Calcific aortic valve stenosis: methods, models, and mechanisms

Calcific aortic valve stenosis (CAVS) is a major health problem facing aging societies. The identification of osteoblast-like and osteoclast-like cells in human tissue has led to a major paradigm shift in the field. CAVS was thought to be a passive, degenerative process, whereas now the progression of calcification in CAVS is considered to be actively regulated. Mechanistic studies examining the contributions of true ectopic osteogenesis, nonosseous calcification, and ectopic osteoblast-like cells (that appear to function differently from skeletal osteoblasts) to valvular dysfunction have been facilitated by the development of mouse models of CAVS. Recent studies also suggest that valvular fibrosis, as well as calcification, may play an important role in restricting cusp movement, and CAVS may be more appropriately viewed as a fibrocalcific disease. High-resolution echocardiography and magnetic resonance imaging have emerged as useful tools for testing the efficacy of pharmacological and genetic interventions in vivo. Key studies in humans and animals are reviewed that have shaped current paradigms in the field of CAVS, and suggest promising future areas for research.

Uric acid levels and atrial fibrillation in hypertensive patients

OBJECTIVE

Uric acid (UA) is a cardiovascular risk marker associated with oxidative stress and inflammation. Recently, atrial fibrillation (AF) has been associated with inflammation and oxidative stress. The objective of this observational study was to investigate the association between UA levels and AF in hypertensive patients.

METHODS

Consecutive patients with hypertension were screened. We excluded subjects with coronary artery disease, congestive heart failure, diabetes, valvular heart disease, congenital heart disease, cardiomyopathy, renal failure, inflammatory conditions, thyroid dysfunction, respiratory diseases, and those who were taking drugs that affect UA metabolism (apart from diuretics). The final study population consisted of 451 patients. Fifty of them (11%) had AF (paroxysmal: 38; persistent: 8; permanent: 4). Demographic, clinical, laboratory, and echocardiographic characteristics were carefully recorded.

RESULTS

After univariate analysis, age, duration of hypertension, serum creatinine, serum UA, left atrial diameter (LAD), interventricular septum thickness, and left ventricular posterior wall thickness were significantly increased in patients with AF compared with non-AF patients, while the estimated glomerular filtration (eGFR) level was much lower in patients with AF than in those without AF. After multivariate logistic regression analysis, the independent predictors of AF were UA (OR: 1.008; 95% CI: 1.003-1.013, p=0.002) and LAD (OR: 1.160; 95% CI: 1.068-1.260; p<0.001).

CONCLUSION

We demonstrated an independent association between increased serum UA levels and AF in hypertensive patients. Undoubtedly, larger studies in different populations should further examine this potential association as well as the underlying pathophysiological mechanisms.

Losartan protects mesenteric arteries from ROS-associated decrease in myogenic constriction following 5/6 nephrectomy

BACKGROUND

Chronic renal failure (CRF) is associated with hypertension, proteinuria, loss of myogenic constriction (MC) of mesenteric arteries and increased production of reactive oxygen species (ROS) under experimental conditions. Previous results showed that ACE (angiotensin-converting enzyme activity) inhibitor therapy is effective in slowing down the progression of disease. Therefore, we wanted to study whether the inverse AT(1) (angiotensin II type 1) receptor agonist, losartan (LOS) was effective in preventing loss of MC in a rat model of CRF and whether acute ROS scavengers could improve MC.

METHODS

Rats underwent 5/6 nephrectomy (5/6 Nx) and were treated with vehicle or LOS (20 mg/kg/day; 5/6 Nx + LOS) for 12 weeks. Thereafter, the MC of the mesenteric arteries were measured in the presence and/or absence of tempol and catalase. Systolic blood pressure and proteinuria were measured weekly.

RESULTS

Systolic blood pressure and proteinuria in the 5/6 Nx + LOS group were significantly lower than in the 5/6 Nx group. Moreover, the MC of 5/6 Nx + LOS arteries was significantly increased compared with the untreated 5/6 Nx group (maximum MC, 32.3 ± 6.9 vs 8.9 ± 3.8% (p < 0.01)). Tempol + catalase significantly increased the MC in the 5/6 Nx group, but not in the 5/6 Nx + LOS group (increase in MC, 59.7 ± 13.0 (p < 0.05) vs. 17.0 ± 15.1%).

CONCLUSION

These results support the roles of the RAAS (renin-angiotensin-aldosterone system) and ROS in the vascular dysfunction of systemic vessels in CRF.

Role of galloylation and polymerization in cytoprotective effects of polyphenolic fractions against hydrogen peroxide insult

Byproducts and wastes generated by agricultural, food, and forestry industries contain large amounts of polyphenols, which can be potentially used as sources of natural or semisynthetic antioxidants. This study examined and compared the protection against peroxidative damage induced in erythrocytes and 3T3 cell line of polyphenolic fractions from white grape pomace, pine bark, and witch hazel bark. The work pays special attention to the different degrees of polymerization and galloylation of the extracts to contribute to the understanding of their mechanisms of action. Fractions demonstrated different protections against erythrocyte lipid peroxidation, hemolysis, and 3T3 cytotoxicity caused by H(2)O(2). Galloylation is claimed to be related to antioxidant protective capacity, and it is also responsible for the pro-oxidant effect observed at high doses. The results show that not only the percentage of galloylation but also the degree of polymerization are important modulators of their antioxidant capacity. In this sense, it is crucial that novel polyphenolic fractions were prepared attending a value of 3 for the mean degree of polymerization and did not exceed a 30% of galloylation to reach the highest antioxidant capacity with the lowest cytotoxic effects. For this reason, the grape extracts appear to be the best strategy to fight against hydrogen peroxide cell damage.

Plasma reactive carbonyl species: Potential risk factor for hypertension

To study the role of oxidative stress in hypertension and pre-hypertension, this study analysed plasma levels of reactive carbonyl species (RCS) in 1204 Chinese Han adults. Results showed a statistically significant positive correlation (p < 0.001) between blood pressure and plasma RCS levels with or without being adjusted for covariates. Multivariate-adjusted odds ratio (OR) illustrated that, compared with the lowest quartile of plasma RCS levels, the highest quartile subjects had a 59% and a 130% increase in the risk for developing pre-hypertension and hypertension, respectively. The multi-interaction analysis manifested that the underlying mechanism of the increase of hypertensive risk or pre-hypertensive risk by overweight and unhealthy lifestyles might, at least in part, be through oxidative stress. In conclusion, these findings suggest that oxidative stress, as indicated by plasma RCS levels, are not the necessary consequence of pre-hypertension or hypertension, but reliable risk factors for developing pre-hypertension or hypertension in Chinese Han adults.

Temporal relation of cardiac hypertrophy, oxidative stress, and fatty acid metabolism in spontaneously hypertensive rat

Left ventricular hypertrophy is an adaptive response to hypertension, and an independent clinical risk factor for cardiac failure, sudden death, and myocardial infarction. As regression of cardiac hypertrophy is associated with a lower likelihood of cardiovascular events, it is recognized as a target of antihypertensive therapy. This necessitates identification of factors associated with the initiation and progression of hypertrophy. Oxidative stress and metabolic shift are intimately linked with myocardial hypertrophy, but their interrelationship is not clearly understood. This study proposes to identify the temporal sequence of events so as to distinguish whether oxidative stress and metabolic shift are a cause or consequence of hypertrophy. Spontaneously hypertensive rat (SHR) was used as the experimental model. Cardiac hypertrophy was apparent at 2 months of age, as assessed by hypertrophy index and brain natriuretic peptide gene expression. Enhanced myocardial lipid peroxidation accompanied by nuclear factor-kappa B gene expression in one-month-old SHR suggests that oxidative stress precedes the development of hypertrophy. Metabolic shift identified by reduction in the expression of peroxisome proliferator-activated receptor-alpha, medium chain acyl CoA dehydrogenase, and carnitine palmitoyltransferase 1β was seen at 4 months of age, implying that reduction of fatty acid oxidation is a consequence of hypertrophy. Information on the temporal sequence of events associated with hypertrophy will help in the prevention and reversal of cardiac remodeling. Investigations aimed at prevention of hypertrophy should address reduction of oxidative stress. Both, oxidative stress and metabolic modulation have to be considered for studies that focus on the regression of hypertrophy.

The role of oxidative stress in the pathophysiology of hypertension

Hypertension is considered to be the most important risk factor in the development of cardiovascular disease. An increasing body of evidence suggests that oxidative stress, which results in an excessive generation of reactive oxygen species (ROS), has a key role in the pathogenesis of hypertension. The modulation of the vasomotor system involves ROS as mediators of vasoconstriction induced by angiotensin II, endothelin-1 and urotensin-II, among others. The bioavailability of nitric oxide (NO), which is a major vasodilator, is highly dependent on the redox status. Under physiological conditions, low concentrations of intracellular ROS have an important role in the normal redox signaling maintaining vascular function and integrity. However, under pathophysiological conditions, increased levels of ROS contribute to vascular dysfunction and remodeling through oxidative damage. In human hypertension, an increase in the production of superoxide anions and hydrogen peroxide, a decrease in NO synthesis and a reduction in antioxidant bioavailability have been observed. In turn, antioxidants are reducing agents that can neutralize these oxidative and otherwise damaging biomolecules. The use of antioxidant vitamins, such as vitamins C and E, has gained considerable interest as protecting agents against vascular endothelial damage. Available data support the role of these vitamins as effective antioxidants that can counteract ROS effects. This review discusses the mechanisms involved in ROS generation, the role of oxidative stress in the pathogenesis of vascular damage in hypertension, and the possible therapeutic strategies that could prevent or treat this disorder.

Inflammation and reactive oxygen species in cardiovascular disease

Reactive oxygen species (ROS) have long been proposed to be mediators of experimental cardiovascular pathology. There is also a wealth of data indicating that ROS are involved in clinical cardiovascular pathology. However, multiple clinical studies have shown little benefit from anti-oxidant treatments, whereas nearly all experimental studies have shown a marked effect of anti-oxidant therapy. One reason for this discrepancy is that ROS are produced through multiple different mechanisms of which some are clinically beneficial; thus, in a defined experimental system where predominately pathological ROS are generated does not mimic a clinical setting where there are likely to be multiple ROS generating systems producing beneficial and pathological ROS. Simple inhibition of ROS would not be expected to have the same result in these two situations; ergo, it is important to understand the molecular mechanism underlying the production of ROS so that clinical treatments can be tailored to target the pathological production of ROS. One such example of this in cardiovascular biology is tissue specific inflammation-mediated ROS generation. This and the following series of articles discuss the current understanding of the role of ROS in cardiovascular disease, specifically focusing on the molecular mechanisms of ROS generation and the actions of ROS within the cardiovascular system. Although there are still many areas with regard to the effects of ROS in the cardiovascular system that are not completely understood, there is a wealth of data suggesting that blocking pathological ROS production is likely to have beneficial clinical effects compared to traditional anti-oxidants.