Pleiotropic Effects of Hydrogen Peroxide in Arteries and Veins From Normotensive and Hypertensive Rats

NADPH oxidase 4-derived hydrogen peroxide counterbalances testosterone-induced endothelial dysfunction and migration

High levels of testosterone (Testo) are associated with cardiovascular risk by increasing reactive oxygen species (ROS) formation. NADPH oxidases (NOX) are the major source of ROS in the vasculature of cardiovascular diseases. NOX4 is a unique isotype, which produces hydrogen peroxide (H2O2), and its participation in cardiovascular biology is controversial. So far, it is unclear whether NOX4 protects from Testo-induced endothelial injury. Thus, we hypothesized that supraphysiological levels of Testo induce endothelial NOX4 expression to attenuate endothelial injury. Human mesenteric vascular endothelial cells (HMECs) and human umbilical vein endothelial cells (HUVEC) were treated with Testo (10-7 M) with or without a NOX4 inhibitor [GLX351322 (10-4 M)] or NOX4 siRNA. In vivo, 10-wk-old C57Bl/6J male mice were treated with Testo (10 mg/kg) for 30 days to study endothelial function. Testo increased mRNA and protein levels of NOX4 in HMECs and HUVECs. Testo increased superoxide anion (O2-) and H2O2 production, which were abolished by NOX1 and NOX4 inhibition, respectively. Testo also attenuated bradykinin-induced NO production, which was further impaired by NOX4 inhibition. In vivo, Testo decreased H2O2 production in aortic segments and triggered endothelial dysfunction [decreased relaxation to acetylcholine (ACh)], which was further impaired by GLX351322 and by a superoxide dismutase and catalase mimetic (EUK134). Finally, Testo led to a dysregulated endothelial cell migration, which was exacerbated by GLX351322. These data indicate that supraphysiological levels of Testo increase the endothelial expression and activity of NOX4 to counterbalance the deleterious effects caused by Testo in endothelial function.NEW & NOTEWORTHY By inducing ROS formation, high levels of testosterone play a major role in the pathogenesis of cardiovascular disease. NOXs are the major sources of ROS in the vasculature of cardiovascular diseases. Herein, we describe a novel compensatory mechanism by showing that NOX4 is a protective oxidant enzyme and counterbalances the deleterious effects of testosterone in endothelial cells by modulating hydrogen peroxide formation.

GPX8 regulates clear cell renal cell carcinoma tumorigenesis through promoting lipogenesis by NNMT

BACKGROUND

Clear cell renal cell carcinoma (ccRCC), with its hallmark phenotype of high cytosolic lipid content, is considered a metabolic cancer. Despite the implication of this lipid-rich phenotype in ccRCC tumorigenesis, the roles and regulators of de novo lipid synthesis (DNL) in ccRCC remain largely unexplained.

METHODS

Our bioinformatic screening focused on ccRCC-lipid phenotypes identified glutathione peroxidase 8 (GPX8), as a clinically relevant upstream regulator of DNL. GPX8 genetic silencing was performed with CRISPR-Cas9 or shRNA in ccRCC cell lines to dissect its roles. Untargeted metabolomics, RNA-seq analyses, and other biochemical assays (e.g., lipid droplets staining, fatty acid uptake, cell proliferation, xenograft, etc.) were carried out to investigate the GPX8's involvement in lipid metabolism and tumorigenesis in ccRCC. The lipid metabolic function of GPX8 and its downstream were also measured by isotope-tracing-based DNL flux measurement.

RESULTS

GPX8 knockout or downregulation substantially reduced lipid droplet levels (independent of lipid uptake), fatty acid de novo synthesis, triglyceride esterification in vitro, and tumor growth in vivo. The downstream regulator was identified as nicotinamide N-methyltransferase (NNMT): its knockdown phenocopied, and its expression rescued, GPX8 silencing both in vitro and in vivo. Mechanically, GPX8 regulated NNMT via IL6-STAT3 signaling, and blocking this axis suppressed ccRCC survival by activating AMPK. Notably, neither the GPX8-NNMT axis nor the DNL flux was affected by the von Hippel Lindau (VHL) status, the conventional regulator of ccRCC high lipid content.

CONCLUSIONS

Taken together, our findings unravel the roles of the VHL-independent GPX8-NNMT axis in ccRCC lipid metabolism as related to the phenotypes and growth of ccRCC, which may be targeted for therapeutic purposes.

Venous endothelial function in cardiovascular disease

The essential role of the endothelium in vascular homeostasis is associated with the release of endothelium-dependent relaxing and contractile factors (EDRF and EDCF, respectively). Different from arteries, where these factors are widely studied, the vasoactive factors derived from the venous endothelium have been given less attention. There is evidence for a role of the nitric oxide (NO), endothelium-dependent hyperpolarization (EDH) mechanism, and cyclooxygenase (COX)-derived metabolites as EDRFs; while the EDCFs need to be better evaluated since no consensus has been reached about their identity in venous vessels. The imbalance between the synthesis, bioavailability, and/or action of EDRFs and/or EDCFs results in a pathological process known as endothelial dysfunction, which leads to reduced vasodilation and/or increased vasoconstriction. In the venous system, endothelial dysfunction is relevant since reduced venodilation may increase venous tone and decrease venous compliance, thus enhancing mean circulatory filling pressure, which maintains or modify cardiac workload contributing to the etiology of cardiovascular diseases. Interestingly, some alterations in venous function appear at the early stages (or even before) the establishment of these diseases. However, if the venous endothelium dysfunction is involved in these alterations is not yet fully understood and requires further studies. In this sense, the present study aims to review the current knowledge on venous endothelial function and dysfunction, and the general state of the venous tone in two important cardiovascular diseases of high incidence and morbimortality worldwide: hypertension and heart failure.

Chronic Iron Overload Restrains the Benefits of Aerobic Exercise to the Vasculature

Physical exercise is a well-recognized effective non-pharmacological therapy for cardiovascular diseases. However, because iron is essential element in many physiological processes including hemoglobin and myoglobin synthesis, thereby playing a role on oxygen transport, many athletes use iron supplement to improve physical performance. Regarding this, iron overload is associated with oxidative stress and damage to various systems, including cardiovascular. Thus, we aimed to identify the vascular effects of aerobic exercise in a rat model of iron overload. Male Wistar rats were treated with 100 mg/kg/day iron-dextran, i.p., 5 days a week for 4 weeks, and then underwent aerobic exercise protocol on a treadmill at moderate intensity, 60 min/day, 5 days a week for 8 weeks. Exercise reduced vasoconstrictor response of isolated aortic rings by increasing participation of nitric oxide (NO) and reducing oxidative stress, but these benefits to the vasculature were not observed in rats previously subjected to iron overload. The reduced vasoconstriction in the exercised group was reversed by incubation with superoxide dismutase (SOD) inhibitor, suggesting that increased SOD activity by exercise was lost in iron overload rats. Iron overload groups increased serum levels of iron, transferrin saturation, and iron deposition in the liver, gastrocnemius muscle, and aorta, and the catalase was overexpressed in the aorta probably as a compensatory mechanism to the increased oxidative stress. In conclusion, despite the known beneficial effects of aerobic exercise on vasculature, our results indicate that previous iron overload impeded the anticontractile effect mediated by increased NO bioavailability and endogenous antioxidant response due to exercise protocol.

Postoperative Tetraplegia to a Child after Cerebellar Pilocytic Astrocytoma Excision at Prone Position: Case Report and Literature Review

BACKGROUND Various factors have been implicated in the pathogenesis of infarction after posterior fossa surgery such as venous air embolism, patient's position (seated or prone), hyperflexion of the neck, excessive spinal cord traction, cervical canal stenosis, and systemic arterial hypotension. The main aim of this case report was to elucidate a case in which hydrogen peroxide was implicated in a major and systemic complication after a neurosurgical procedure. CASE REPORT We describe the case of a 5-year-old female patient who was admitted to our hospital because of a cerebellar hemispheric astrocytoma associated with obstructive hydrocephalus and accompanied by 2 syringomyelic cavities in the cervicothoracic portion of the spinal cord. Immediately after gross total resection of the lesion, impaired mobility of the upper and lower extremities was observed, a finding that was not consistent with intraoperative neurophysiologic monitoring data. Hydrogen peroxide had been judiciously used to irrigate the resection tumor cavity. In the next few postoperative days, the patient suffered from transient diabetes insipidus and hyperpyrexia, indicative of hypothalamic injury. CONCLUSIONS Neurological evaluation of the patient, after stabilization of her medical condition, revealed residual spasticity of upper and lower extremities, rendering her able to mobilize via the aid of wheelchair only. The most possible pathophysiologic explanation of her neurological deterioration, including hypothalamic dysfunction, was analyzed. The role of hydrogen peroxide as a source of free radical formation, and its co-responsibility for vascular platelet aggregation and vasoconstriction was considered, upon case review, the main responsible etiologic factor.

Uterine perivascular adipose tissue is a novel mediator of uterine artery blood flow and reactivity in rat pregnancy

KEY POINTS

In vivo, uterine perivascular adipose tissue (PVAT) potentiates uterine artery blood flow in pregnant rats, although not in non-pregnant rats. In isolated preparations, uterine PVAT has pro-contractile and anti-dilatory effects on uterine arteries. Pregnancy induces changes in uterine arteries that makes them responsive to uterine PVAT signalling.

ABSTRACT

An increase in uterine artery blood flow (UtBF) is a common and necessary feature of a healthy pregnancy. In the present study, we tested the hypothesis that adipose tissue surrounding uterine arteries (uterine perivascular adipose tissue; PVAT) is a novel local mediator of UtBF and uterine artery tone during pregnancy. In vivo experiments in anaesthetized Sprague-Dawley rats showed that pregnant animals (gestational day 16, term = 22--23 days) had a three-fold higher UtBF compared to non-pregnant animals. Surgical removal of uterine PVAT reduced UtBF only in pregnant rats. In a series of ex vivo bioassays, we demonstrated that uterine PVAT had pro-contractile and anti-dilatory effects on rat uterine arteries. In the presence of PVAT-conditioned media, isolated uterine arteries from both pregnant and non-pregnant rats had reduced vasodilatory responses. In non-pregnant rats, these responses were mediated at the level of uterine vascular smooth muscle, whereas, in pregnant rats, PVAT-media reduced endothelium-dependent relaxation. Pregnancy increased adipocyte size in ovarian adipose tissue but had no effect on uterine PVAT adipocyte morphology. In addition, pregnancy down-regulated the gene expression of metabolic adipokines in uterine but not in aortic PVAT. In conclusion, this is the first study to demonstrate that uterine PVAT plays a regulatory role in UtBF, at least in part, as a result of its actions on uterine artery tone. We propose that the interaction between the uterine vascular wall and its adjacent adipose tissue may provide new insights for interventions in pregnancies with adipose tissue dysfunction and abnormal UtBF.

Multivessel analysis of progressive vascular aging in the rat: Asynchronous vulnerability among vascular territories

Aging induces vascular dysfunction, representing the major risk factor for cardiovascular disease. Our aim was to ascertain specific vulnerability of vascular territories to aging by evaluating the progressive impact of aging on vascular function in four different vascular beds: aorta, mesenteric artery (MA), coronary artery (CA), and penile corpus cavernosum (CC) from 3, 6, 9, 12, 20 or 24 months-old male rats. Contractile/relaxant responses were evaluated in organ chambers (A/CC) and wire myographs (MA/CA). Relationships of systemic biomarkers with endothelial function impairment were also determined. Although all vessels manifested aging-related impairment in endothelial vasodilation, CA was the most impacted by aging considering the onset (at 6 months) and magnitude of endothelial dysfunction (reduction by 1.5 log units in the concentration required for 50% of maximal relaxation for acetylcholine). H₂O₂-induced vasodilations were progressively reduced by aging in aorta, CC and CA while NO-donor-induced vasodilation was impaired by aging only in CA. Serum asymmetric dimethylarginine significantly correlated to endothelial decline in aorta, MA, and CC, while HOMA-IR was significantly associated with endothelial dysfunction in CA and MA. CA are especially vulnerable to aging-related vascular dysfunction. Correlations of vascular dysfunction with systemic biomarkers differ among vessels, further suggesting heterogeneity in aging-induced vascular impact.

Thrombospondin-1, Free Radicals, and the Coronary Microcirculation: The Aging Conundrum

SIGNIFICANCE

Successful matching of cardiac metabolism to perfusion is accomplished primarily through vasodilation of the coronary resistance arterioles, but the mechanism that achieves this effect changes significantly as aging progresses and involves the contribution of reactive oxygen species (ROS). Recent Advances: A matricellular protein, thrombospondin-1 (Thbs-1), has been shown to be a prolific contributor to the production and modulation of ROS in large conductance vessels and in the peripheral circulation. Recently, the presence of physiologically relevant circulating Thbs-1 levels was proven to also disrupt vasodilation to nitric oxide (NO) in coronary arterioles from aged animals, negatively impacting coronary blood flow reserve.

CRITICAL ISSUES

This review seeks to reconcile how ROS can be successfully utilized as a substrate to mediate vasoreactivity in the coronary microcirculation as "normal" aging progresses, but will also examine how Thbs-1-induced ROS production leads to dysfunctional perfusion and eventual ischemia and why this is more of a concern in advancing age.

FUTURE DIRECTIONS

Current therapies that may effectively disrupt Thbs-1 and its receptor CD47 in the vascular wall and areas for future exploration will be discussed. Antioxid. Redox Signal. 27, 785-801.

Pro-contractile effects of perivascular fat in health and disease

Perivascular adipose tissue (PVAT) is now recognized as an active player in vascular homeostasis. The expansion of PVAT in obesity and its possible role in vascular dysfunction have attracted much interest. In terms of the regulation of vascular tone and blood pressure, PVAT has been shown to release vasoactive mediators, for instance, angiotensin peptides, reactive oxygen species, chemokines and cytokines. The secretory profile of PVAT is altered by obesity, hypertension and other cardiovascular diseases, leading to an imbalance between its pro-contractile and anti-contractile effects. PVAT adipocytes represent an important source of the mediators, but infiltrating immune cells may become more important under conditions of hypoxia and inflammation. This review describes recent advances in the effects of PVAT on the regulation of vascular tone, highlighting the evidence for a pro-contractile action in health and disease. The role of the endothelium, vascular smooth muscle, immune cells and probably perivascular nerves in PVAT function is also discussed.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

c-Src, ERK1/2 and Rho kinase mediate hydrogen peroxide-induced vascular contraction in hypertension: role of TXA2, NAD(P)H oxidase and mitochondria

AIM

: The aim of this study was to analyse the signalling pathways involved in H2O2 vascular responses in hypertension.

METHODS

Vascular function, thromboxane A2 (TXA2) production, oxidative stress and protein expression were determined in mesenteric resistance arteries (MRAs) from hypertensive (spontaneously hypertensive rats, SHR) and normotensive Wistar Kyoto (WKY) rats.

RESULTS

H2O2 and the TP agonist U46619 induced greater contractile responses in MRA from SHR than WKY. Moreover, H2O2 increased TXA2 production more in SHR than in WKY. The c-Src inhibitor PP1 reduced H2O2 and U46619-induced contraction and TXA2 release in both strains. The ERK1/2 inhibitor PD98059 reduced H2O2 but not U46619-induced contraction only in SHR arteries. The Rho kinase inhibitor Y26372 reduced H2O2 and U46619-induced contractions only in SHR arteries. Basal c-Src, ERK1/2 and Rho kinase expression were greater in MRA from SHR than WKY. In SHR, the combination of PD98059 with the TP antagonist SQ29548 but not with Y27632 inhibited the H2O2 contraction more than each inhibitor alone. H2O2 and U46619 increased NAD(P)H oxidase activity and O2 production and decreased mitochondrial membrane potential in vessels from SHR. The effects induced by H2O2 were abolished by inhibitors of TXA2 synthase, ERK1/2 and c-Src. The mitochondrial antioxidant mitoTEMPO reduced H2O2-induced contraction and NAD(P)H oxidase activation.

CONCLUSION

In arteries from WKY, c-Src mediates H2O2 contractile responses by modulating TXA2 release and TXA2 effect. In SHR, H2O2 induces c-Src dependent TXA2 release that provokes vascular contractile responses through Rho kinase, c-Src and O2 from NAD(P)H Oxidase and mitochondria. Moreover, ERK1/2 activation contributes to H2O2 contraction in SHR through effects on mitochondria/NAD(P)H Oxidase.

Chronic iron overload in rats increases vascular reactivity by increasing oxidative stress and reducing nitric oxide bioavailability

AIMS

Iron overload in animal models and humans increases oxidative stress and induces cardiomyopathy. It has been suggested that the vasculature is also damaged, but the impacts on vascular reactivity and the underlying mechanisms remain poorly understood. In this study, we aimed to identify possible changes in the vascular reactivity of aortas from iron overloaded rats and investigate the underlying mechanisms.

MAIN METHODS

Rats were treated with 100mg/kg/day iron-dextran, ip, five days a week for four weeks and compared to a saline-injected group.

KEY FINDINGS

Chronic iron administration increased serum iron and transferrin saturation with significant deposition in the liver. Additionally, iron overload significantly increased the vasoconstrictor response in aortic rings as assessed in vitro, with reduced influence of endothelial denudation or l-NAME incubation on the vascular reactivity. In vitro assay with DAF-2 indicated reduced NO production in the iron overload group. Iron overload-induced vascular hyperactivity was reversed by incubation with tiron, catalase, apocynin, allopurinol and losartan. Moreover, malondialdehyde was elevated in the plasma, and O2(•-) generation and NADPH oxidase subunit (p22phox) expression were increased in the aortas of iron-loaded rats.

SIGNIFICANCE

Our results demonstrated that chronic iron overload is associated with altered vascular reactivity and the loss of endothelial modulation of the vascular tone. This iron loading-induced endothelial dysfunction and reduced nitric oxide bioavailability may be a result of increased production of reactive oxygen species and local renin-angiotensin system activation.

Chronic lead exposure decreases the vascular reactivity of rat aortas: the role of hydrogen peroxide

We investigated whether exposure to small concentrations of lead alters blood pressure and vascular reactivity. Male Wistar rats were sorted randomly into the following two groups: control (Ct) and treatment with 100 ppm of lead (Pb), which was added to drinking water, for 30 days. Systolic blood pressure (BP) was measured weekly. Following treatment, aortic ring vascular reactivity was assessed. Tissue samples were properly stored for further biochemical investigation. The lead concentration in the blood reached approximately 8 μg/dL. Treatment increased blood pressure and decreased the contractile responses of the aortic rings to phenylephrine (1 nM–100 mM). Following N-nitro-L arginine methyl ester (L-NAME) administration, contractile responses increased in both groups but did not differ significantly between them. Lead effects on R_max were decreased compared to control subjects following superoxide dismutase (SOD) administration. Catalase, diethyldithiocarbamic acid (DETCA), and apocynin increased the vasoconstrictor response induced by phenylephrine in the aortas of lead-treated rats but did not increase the vasoconstrictor response in the aortas of untreated rats. Tetraethylammonium (TEA) potentiated the vasoconstrictor response induced by phenylephrine in aortic segments in both groups, but these effects were greater in lead-treated rats. The co-incubation of TEA and catalase abolished the vasodilatory effect noted in the lead group. The present study is the first to demonstrate that blood lead concentrations well below the values established by international legislation increased blood pressure and decreased phenylephrine-induced vascular reactivity. The latter effect was associated with oxidative stress, specifically oxidative stress induced via increases in hydrogen peroxide levels and the subsequent effects of hydrogen peroxide on potassium channels.

Hydrogen peroxide induces vasorelaxation by enhancing 4-aminopyridine-sensitive Kv currents through S-glutathionylation

Hydrogen peroxide (H₂O₂) is an endothelium-derived hyperpolarizing factor. Since opposing vasoactive effects have been reported for H₂O₂ depending on the vascular bed and experimental conditions, this study was performed to assess whether H₂O₂ acts as a vasodilator in the rat mesenteric artery and, if so, to determine the underlying mechanisms. H₂O₂ elicited concentration-dependent relaxation in mesenteric arteries precontracted with norepinephrine. The vasodilatory effect of H₂O₂ was reversed by treatment with dithiothreitol. H₂O₂-elicited vasodilation was significantly reduced by blocking 4-aminopyridine (4-AP)-sensitive Kv channels, but it was resistant to blockers of big-conductance Ca²⁺-activated K⁺ channels and inward rectifier K⁺ channels. A patch-clamp study in mesenteric arterial smooth muscle cells (MASMCs) showed that H₂O₂ increased Kv currents in a concentration-dependent manner. H₂O₂ speeded up Kv channel activation and shifted steady state activation to hyperpolarizing potentials. Similar channel activation was seen with oxidized glutathione (GSSG). The H₂O₂-mediated channel activation was prevented by glutathione reductase. Consistent with S-glutathionylation, streptavidin pull-down assays with biotinylated glutathione ethyl ester showed incorporation of glutathione (GSH) in the Kv channel proteins in the presence of H₂O₂. Interestingly, conditions of increased oxidative stress within MASMCs impaired the capacity of H₂O₂ to stimulate Kv channels. Not only was the H₂O₂ stimulatory effect much weaker, but the inhibitory effect of H₂O₂ was unmasked. These data suggest that H₂O₂ activates 4-AP-sensitive Kv channels, possibly through S-glutathionylation, which elicits smooth muscle relaxation in rat mesenteric arteries. Furthermore, our results support the idea that the basal redox status of MASMCs determines the response of Kv currents to H₂O₂.

DJ-1/park7 modulates vasorelaxation and blood pressure via epigenetic modification of endothelial nitric oxide synthase

AIMS

DJ-1/park7, a multifunctional protein, may play essential roles in the vascular system. However, the function of DJ-1/park7 in vascular contractility has remained unclear. The present study was designed to investigate whether the DJ-1/park7 is involved in the regulation of vascular contractility and systolic blood pressure (SBP).

METHODS AND RESULTS

Norepinephrine (NE) elevated contraction in endothelium-intact vessels in a dose-dependent manner, to a greater extent in DJ-1/park7 knockout (DJ-1/park7(-/-)) mice than in wild-type (DJ-1/park7(+/+)) mice. Acetylcholine inhibited NE-evoked contraction in endothelium-intact vessels, and this was markedly impaired in DJ-1/park7(-/-) mice compared with DJ-1/park7(+/+). Nitric oxide (NO) production (82.1 ± 2.8% of control) and endothelial NO synthase (eNOS) expression (61.7 ± 8.9%) were lower, but H2O2 production (126.4 ± 8.6%) was higher, in endothelial cells from DJ-1/park7(-/-) mice than in those from DJ-1/park7(+/+) controls; these effects were reversed by DJ-1/park7-overexpressing endothelial cells from DJ-1/park7(-/-) mice. Histone deacetylase (HDAC)-1 recruitment and H3 histone acetylation at the eNOS promoter were elevated and diminished, respectively, in DJ-1/park7(-/-) mice compared with DJ-1/park7(+/+) controls. Moreover, SBP was significantly elevated in DJ-1/park7(-/-) mice compared with DJ-1/park7(+/+) controls, but this elevation was inhibited in mice treated with valproic acid, an inhibitor of Class I HDACs including HDAC-1.

CONCLUSION

These results demonstrate that DJ-1/park7 protein may be implicated in the regulation of vascular contractility and blood pressure, probably by the impairment of NO production through H2O2-mediated epigenetic inhibition of eNOS expression.

Role of H(2)O(2) in hypertension, renin-angiotensin system activation and renal medullary disfunction caused by angiotensin II

BACKGROUND AND PURPOSE

Activation of the intrarenal renin-angiotensin system (RAS) and increased renal medullary hydrogen peroxide (H(2) O(2) ) contribute to hypertension. We examined whether H(2) O(2) mediated hypertension and intrarenal RAS activation induced by angiotensin II (Ang II).

EXPERIMENTAL APPROACH

Ang II (200 ng·kg(-1) ·min(-1) ) or saline were infused in Sprague Dawley rats from day 0 to day 14. Polyethylene glycol (PEG)-catalase (10 000 U·kg(-1) ·day(-1) ) was given to Ang II-treated rats, from day 7 to day 14. Systolic blood pressure was measured throughout the study. H(2) O(2) , angiotensin AT(1) receptor and Nox4 expression and nuclear factor-κB (NF-κB) activation were evaluated in the kidney. Plasma and urinary H(2) O(2) and angiotensinogen were also measured.

KEY RESULTS

Ang II increased H(2) O(2) , AT(1) receptor and Nox4 expression and NF-κB activation in the renal medulla, but not in the cortex. Ang II raised plasma and urinary H(2) O(2) levels, increased urinary angiotensinogen but reduced plasma angiotensinogen. PEG-catalase had a short-term antihypertensive effect and transiently suppressed urinary angiotensinogen. PEG-catalase decreased renal medullary expression of AT(1) receptors and Nox4 in Ang II-infused rats. Renal medullary NF-κB activation was correlated with local H(2) O(2) levels and urinary angiotensinogen excretion. Loss of antihypertensive efficacy was associated with an eightfold increase of plasma angiotensinogen.

CONCLUSIONS AND IMPLICATIONS

The renal medulla is a major target for Ang II-induced redox dysfunction. H(2) O(2) appears to be the key mediator enhancing intrarenal RAS activation and decreasing systemic RAS activity. The specific control of renal medullary H(2) O(2) levels may provide future grounds for the treatment of hypertension.

Effects of glutathione-depleting drug buthionine sulfoximine and aging on activity of endothelium-derived relaxing and contracting factors in carotid artery of Sprague-Dawley rats

The role of the antioxidant glutathione (GSH) in mediating endothelial (dys)function, and how that role may depend on age, is unclear. The main purpose of the current study was to investigate the effect of 10-day treatment with the GSH-depleting drug l-buthionine sulfoximine (BSO) on endothelium-derived relaxing factor and endothelium-derived contracting factor activities in the isolated common carotid artery (CCA) of Adult and Aging animals. CCA blood pressure and flow were unaffected by age or BSO. Endothelium-derived relaxing factor activity, examined in precontracted CCA as relaxation to cumulative acetylcholine (ACh), was largely nitric oxide synthase (NOS) mediated and was not different between Adult and Aging animals at lower ACh; however, at higher ACh, relaxation was blunted in Aging CCA, an effect abolished by cyclooxygenase (COX) inhibition but not by NOS inhibition nor by the reactive oxygen species (ROS) inhibitors 4-hydroxy-TEMPO or Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin,tetratosylate,hydroxide. Specific examination of endothelium-derived contracting factor activity in quiescent NOS-inhibited CCA established that higher ACh elicited a contractile response, ∼3.5-fold greater in Aging versus Adult CCA, which was abolished by COX-1-specific inhibition but unaffected by ROS inhibitors. Aging was unrelated to changes in liver or vascular tissue GSH or ROS content. BSO was effective in significantly decreasing GSH and increasing ROS content in both animal cohorts. However, NOS-mediated endothelium-derived relaxing factor activity was well preserved and age-related COX-mediated endothelium-derived contracting factor activity was unaffected in response to these BSO-induced perturbations, as were exogenous H2O2-stimulated NOS/non-NOS-mediated relaxation and COX-mediated contractile activities. These data suggest that, regardless of age, chronic partial depletion of GSH in vivo does not necessarily cause endothelium-dependent vasomotor dysfunction.

Angiotensin II upregulates Ca(V)1.2 protein expression in cultured arteries via endothelial H(2)O(2) production

BACKGROUND

We previously reported that angiotensin II caused an endothelial-dependent increase in L-type voltage-dependent Ca(2+) channel (Ca(V)1.2) in cultured arteries, but the signaling pathways are not clear.

METHODS

Endothelial damage was generated by brief intra-arterial perfusion with 0.3% CHAPS. Ca(V)1.2 expression, function and H(2)O(2) were measured by Western blot, tension recording and Amplex Red H(2)O(2) assay kit, respectively.

RESULTS

Angiotensin II dose-dependently upregulated Ca(V)1.2 expression in endothelium-intact arteries. The angiotensin II upregulation of Ca(V)1.2 expression in endothelium-intact arteries was blocked by NAD(P)H oxidase inhibitor diphenyleneiodonium (DPI), apocynin, a more specific NAD(P)H oxidase inhibitor gp91ds-tat and also by catalase. H(2)O(2) similarly upregulated Ca(V)1.2 expression in endothelium-intact and endothelium-damaged arteries, and the latter effect was also blocked by DPI and apocynin. Angiotensin II increased H(2)O(2) production by endothelium-intact but not by endothelium-damaged arteries, and this effect was blocked by apocynin, catalase and gp91ds-tat. The upregulation of Ca(V)1.2 by angiotensin II and H(2)O(2) is accompanied by an increased tension response to KCl and the Ca(2+) channel activator FPL 64176, and this effect was also attenuated by gp91ds-tat.

CONCLUSION

These results suggest that angiotensin II stimulates endothelial NAD(P)H oxidase-produced H(2)O(2,) which may additionally act through vascular smooth muscle NAD(P)H oxidase, to upregulate vascular Ca(V)1.2 protein.

Effects of Melothria maderaspatana leaf extract on antioxidant status in sham-operated and uninephrectomized DOCA-salt hypertensive rats

The present study was designed to investigate the antihypertensive and antioxidant effect of Melothria maderaspatana leaf extract (MME) on sham-operated and DOCA-salt (deoxycorticosterone acetate) induced hypertensive rats. Administration of DOCA-salt significantly increased the systolic (from 127 to 212 mm Hg) and diastolic (from 91 to 174 mm Hg) blood pressure compared to sham-operated control rats, while treatment with MME significantly reduced the systolic (from 212 to 135 mm Hg) and diastolic (from 174 to 96 mm Hg) blood pressure compared to hypertensive control. In DOCA-salt rats, the plasma and tissue concentration of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxide (LOOH) significantly increased and administration of MME significantly reduced these parameters towards the levels in sham-operated control. In hypertensive rats, activities of the enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and levels of non-enzymatic antioxidants such as vitamin C, vitamin E and reduced glutathione (GSH) decreased significantly in the plasma and tissues. Administration of MME returned the enzymatic and non-enzymatic antioxidants towards sham-operated control. MME shows both antihypertensive and antioxidant properties in DOCA-salt hypertensive rats and, among the three different doses tested, 200 mg/kg caused the maximum effect.

Superoxide dismutase mimetic drug tempol aggravates anti-GBM antibody-induced glomerulonephritis in mice

Oxidative stress plays an important role in the pathogenesis of anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM-GN). Superoxide dismutase (SOD) is the first line of defense against oxidative stress by converting superoxide to hydrogen peroxide (H(2)O(2)). We investigated the effect of the SOD mimetic drug tempol on anti-GBM-GN in mice. 129/svJ mice were challenged with rabbit anti-mouse-GBM sera to induce GN and subsequently divided into tempol (200 mg.kg(-1).day(-1), orally) and vehicle-treated groups. Routine histology, SOD and catalase activities, malondialdehyde (MDA), H(2)O(2), and immunohistochemical staining for neutrophils, lymphocytes, macrophages, p65-NF-kappaB, and osteopontin were performed. Mice with anti-GBM-GN had significantly reduced renal SOD and catalase activities and increased H(2)O(2) and MDA levels. Unexpectedly, tempol administration exacerbated anti-GBM-GN as evidenced by intensification of proteinuria, the presence of severe crescentic GN with leukocyte influx, and accelerated mortality in the treated group. Tempol treatment raised SOD activity and H(2)O(2) level in urine, upregulated p65-NF-kappaB and osteopontin in the kidney, but had no effect on renal catalase activity. Thus tempol aggravates anti-GBM-GN by increasing production of H(2)O(2) which is a potent NF-kappaB activator and as such can intensify inflammation and renal injury. This supposition is supported by increases seen in p65-NF-kappaB, osteopontin, and leukocyte influx in the kidneys of the tempol-treated group.

Diminished expression of dihydropteridine reductase is a potent biomarker for hypertensive vessels

To identify the new targets for hypertension, we analyzed the protein expression profiles of aortic smooth muscle in spontaneously hypertensive rats (SHR) of various ages during the development of hypertension, as well as in age-matched normotensive Wistar-Kyoto (WKY) rats, using a proteomic analysis. The expressions of seven proteins were altered in SHR compared with WKY rats. Of these proteins, NADH dehydrogenase 1alpha, GSTomega1, peroxi-redoxin I and transgelin were upregulated in SHR compared with WKY rats. On the other hand, the expression of HSP27 and Ran protein decreased in SHR. The diminution of dihydrobiopterin reductase, an enzyme located in the regeneration pathways of tetrahydrobiopterin (BH4), was also prominent in SHR. The results from a PCR analysis revealed that the expression of BH4 biosynthesis enzymes - GTP cyclohydrolase-1 and sepiapterin reductase - decreased and increased, respectively, in SHR compared with WKY rats. The level of BH4 was less in aortic strips from SHR than from WKY rats. Moreover, treatment with BH4 inhibited aortic smooth muscle contraction induced by serotonin. These results suggest that the deficiency in BH4 regeneration produced by diminished dihydrobiopterin reductase expression is involved in vascular disorders in hypertensive rats.

Intrarenal artery superoxide is mainly NADPH oxidase-derived and modulates endothelium-dependent dilation in elderly patients

AIMS

The present study was performed to investigate the contribution of NADPH oxidases (Nox) to superoxide formation in human renal proximal resistance arteries and to test whether superoxide formation contributes to acute vasoconstrictor responses and endothelium-dependent vasodilation in these vessels.

METHODS AND RESULTS

Arcuate and proximal interlobular artery segments were from patients who underwent nephrectomy because of a renal tumour. Vessels were dissected from tumour-free parts of the kidneys. Additional intrarenal arteries were obtained from rats. Superoxide formation was measured by lucigenin-enhanced chemiluminescence, expression of Nox isoforms was analysed by RT-PCR, and functional studies were performed by small vessel wire myography. Sixty per cent of superoxide formation in human arcuate and proximal interlobular arteries was due to Nox activity. mRNA expression analyses revealed the presence of Nox2 and Nox4 but not Nox1. Phenylephrine and endothelin-1 induced powerful concentration-dependent vasoconstrictions that were unaffected by superoxide scavengers. Vasopressin elicited small and variable vasoconstrictions with signs of tachyphylaxis. Endothelium-dependent vasodilation was blunted by tiron and Nomega-nitro-L-arginine methyl ester but not by superoxide dismutase or catalase. Exogenous hydrogen peroxide elicited vasoconstriction.

CONCLUSION

Nox activity is the major source of superoxide formation in renal proximal resistance arteries from elderly patients. Acute vasoconstrictor responses to alpha1-adrenoreceptor activation and to endothelin-1 do not depend on superoxide formation, while endothelium-dependent vasodilation in intrarenal arteries is reactive oxygen species-dependent.

Effect of N-epsilon-(carboxymethyl)lysine on coronary vasoconstriction in isolated perfused hearts from control and streptozotocin-induced diabetic rats

Advanced glycation end products (AGEs) derived from glucose are implicated in the pathogenesis of diabetic vascular disease. However, their direct modulatory effects on coronary vascular tone remain unclear. We previously reported that coronary vasoconstriction was induced by acetylcholine (ACh) infusion of the isolated perfused rat heart and that sensitivity was greater in perfused hearts from streptozotocin (STZ)-induced diabetic rats than in those from age-matched controls (Kamata et al., 2008). Here, we investigated the effect of N(epsilon)-(carboxymethyl)lysine (CML), which has one of the main AGE structures, on ACh-induced vasoconstriction in perfused hearts isolated from control and diabetic rats. ACh-induced vasoconstriction was significantly greater in the STZ-induced diabetic group than in the age-matched controls. CML enhanced the ACh-induced vasoconstriction in coronary arteries from control rats, but not in those from STZ-induced diabetic rats. In the controls, the vasoconstriction induced by the calcium-channel activator Bay K 8644 was also enhanced by CML. These CML-mediated enhancements of the vasoconstrictions induced by ACh and Bay K 8644 were significantly suppressed by tempol, a superoxide dismutase mimetic. The plasma CML and glucose levels were each significantly elevated in STZ-induced diabetic rats. These findings suggest (a) that CML augments ACh-induced coronary vasoconstriction, an effect that may be attributable to increased superoxide and to activation of voltage-gated Ca(2+) channels and (b) that this modulating effect may be desensitized in the STZ-induced diabetic heart.

Sustained contraction and endothelial dysfunction induced by reactive oxygen species in porcine coronary artery

A combination of purine and xanthine oxidase (XOD) dose-dependently elicited sustained contraction of porcine coronary arterial rings and resulted in increased concentrations of superoxide anions and hydrogen peroxide. These contractile responses appeared, with a delay, after the application of purine and XOD, used as a reactive oxygen species (ROS)-generating system. Coronary arteries precontracted with prostaglandin F(2alpha) failed to relax in response to substance P after exposing the arterial preparation to this ROS-generating system. The contractile response of the coronary artery to the ROS-generating system was almost completely inhibited by catalase (130 U/ml), and was partially inhibited by superoxide dismutase (60 U/ml), or mannitol (30 mM). A voltage-dependent L-type Ca(2+) channel antagonist, nicardipine, had no effect on contraction. Dysfunction of endothelial cells was completely prevented by catalase, but not by superoxide dismutase or mannitol. These results suggest that superoxide anions, hydrogen peroxide and hydroxyl radicals might be involved in eliciting sustained, delayed-onset coronary artery contraction, which is not related to L-type Ca(2+) channels. They also suggest that hydrogen peroxide might play a major role in endothelial dysfunction of the porcine coronary artery.

A comparison of reactive oxygen species metabolism in the rat aorta and vena cava: focus on xanthine oxidase

Reactive oxygen species (ROS) are important mediators in vascular biology. Venous function, although relevant to cardiovascular disease, is still understudied. We compared aspects of ROS metabolism between a major artery (the aorta) and a major vein (the vena cava, VC) of the rat, with the hypothesis that venous ROS metabolism would be overall increased compared with its arterial counterpart. Superoxide and hydrogen peroxide (H2O2) release in basal conditions was higher in VC compared with aorta. The antioxidant capacity for H2O2 was also higher in VC than in aorta. Exogenous superoxide induced a higher contraction in VC compared with aorta. Protein expression of three major ROS metabolizing enzymes, xanthine oxidase (XO), CuZn-SOD, and catalase, was higher in VC compared with aorta. Because XO seemed a likely source of the higher VC ROS levels, we examined it further and found higher mRNA expression and activity of XO in VC compared with aorta. We also investigated the impact of XO inhibition by allopurinol on aorta and VC functional responses to norepinephrine, ANG II, ET-1, and ACh. Maximal ET-1-mediated contraction was decreased by allopurinol in VC but not in the aorta. Our results suggest that there are overall differences in ROS metabolism between aorta and VC, with the latter operating normally at a higher set point, releasing but also being able to handle, higher ROS levels. We propose XO to be an important source for these differences. The result of this particular comparison may be reflective of a general arteriovenous contrast.

Reactive oxygen species participate in acute renal vasoconstrictor responses induced by ETAand ETBreceptors

Reactive oxygen species (ROS) play important roles in renal vasoconstrictor responses to acute and chronic stimulation by angiotensin II and norepinephrine, as well as in long-term effects of endothelin-1 (ET-1). Little is known about participation of ROS in acute vasoconstriction produced by ET-1. We tested the influence of NAD(P)H oxidase inhibition by apocynin [4 mg·kg−1·min−1, infused into the renal artery (ira)] on ETAand ETBreceptor signaling in the renal microcirculation. Both receptors were stimulated by ET-1, ETAreceptors by ET-1 during ETBantagonist BQ-788, and ETBby ETBagonist sarafotoxin 6C. ET-1 (1.5 pmol injected ira) reduced renal blood flow (RBF) 17 ± 4%. Apocynin raised baseline RBF (+10 ± 1%, P < 0.001) and attenuated the ET-1 response to 10 ± 2%, i.e., 35 ± 9% inhibition ( P < 0.05). Apocynin reduced ETA-induced vasoconstriction by 42 ± 12% ( P < 0.05) and that of ETBstimulation by 50 ± 8% ( P < 0.001). During nitric oxide (NO) synthase inhibition ( Nω-nitro-l-arginine methyl ester), apocynin blunted ETA-mediated vasoconstriction by 60 ± 8% ( P < 0.01), whereas its effect on the ETBresponse (by 87 ± 8%, P < 0.001) was even larger without than with NO present ( P < 0.05). The cell-permeable superoxide dismutase mimetic tempol (5 mg·kg−1·min−1ira), which reduces O2−and may elevate H2O2, attenuated ET-1 responses similar to apocynin (by 38 ± 6%, P < 0.01). We conclude that ROS, O2−rather than H2O2, contribute substantially to acute renal vasoconstriction elicited by both ETAand ETBreceptors and to basal renal vasomotor tone in vivo. This physiological constrictor action of ROS does not depend on scavenging of NO. In contrast, scavenging of O2−by NO seems to be more important during ETBstimulation.

Redox regulation in the extracellular environment

The oxidizing nature of the extracellular environment is vastly different from the highly reducing nature of the intracellular compartment. The redox potential of the cytosolic compartment of the intracellular environment limits disulfide bond formation, whereas the oxidizing extracellular environment contains proteins rich in disulfide bonds. If not for an extracellular antioxidant system to eliminate reactive oxygen and nitrogen species, lipid peroxidation and protein oxidation would become excessive, resulting in cellular damage. Many reviews have focused on the role of intracellular antioxidants in the elimination of oxidative stress, but this one will focus on the coordinated action of both intracellular and extracellular antioxidants in limiting cellular oxidant stress.

Comparison of H2O2-induced vasoconstriction in the abdominal aorta and mesenteric artery of the mouse

Hydrogen peroxide (H(2)O(2)) is generally perceived as an arterial vasodilator. Due to the emerging importance of H(2)O(2) as a possible vasoconstrictor, we examined whether H(2)O(2) constricts both the abdominal aorta and superior mesenteric artery and postulated that H(2)O(2) is a ubiquitous constrictor of quiescent mouse arteries. Moreover, we postulated that KCl depolarization discloses and/or exaggerates H(2)O(2)-induced constriction. Under quiescent conditions, H(2)O(2) constricted the mouse abdominal aorta but not the mesenteric artery. Vessel depolarization (a) exaggerated this constrictor response in the aorta, and (b) unmasked a contractile response in the mesenteric artery. Our final hypothesis tested whether tyrosine kinases, mitogen-activated protein kinases (MAPKs), and/or Rho-kinase are uniformly involved in H(2)O(2)-induced vasoconstriction. We observed a marked difference in the ability of tyrosine kinase inhibitor to block H(2)O(2)-induced vasoconstriction. p38 and ERK 1/2MAPK inhibitors reduced the maximal response to H(2)O(2), whereas JNK inhibitor had no effect. Finally, Rho-kinase inhibitor decreased the H(2)O(2) response in the mesenteric artery but not in the aorta. These data demonstrate a variable yet tightly regulated H(2)O(2) vasoconstrictor effect. Furthermore, we found that p38, ERK 1/2 and Rho-kinase play a role in H(2)O(2) constriction, which may be critical pathways involved in H(2)O(2)-induced constriction across vascular beds.

Analysis of peroxiredoxin decreasing oxidative stress in hypertensive aortic smooth muscle

To determine the role of peroxiredoxin (Prx) in response to oxidative stress and during hypertension in the vasculature, we identified Prx proteins and analyzed their antioxidant effects. Rat aortic smooth muscle contains all six Prxs (I-VI). Prx I, II, and VI shifted to its acidic site on two-dimensional polyacrylamide gel electrophoresis after exposure to H(2)O(2). The total expression of Prx I and VI was increased in response to H(2)O(2). The expression of Prx I, but not that of Prx II and VI, increases and the acidic form of Prx I and the sulfonic acid form of Prx (SO(3)H-Prx) are more strongly expressed in the aortic smooth muscle of hypertensive rats than in that of normotensive control rats. Prxs were also found in the mesenteric artery, heart, and kidney. The expression levels of Prx I and VI were increased in mesenteric artery, but not heart and kidney, from hypertensive rats compared with that from normotensive rats. These results suggest that Prxs play a crucial role against oxidative stress in vascular smooth muscles during hypertension.

Enoxaparin reduces H2O2-induced activation of human endothelial cells by a mechanism involving cell adhesion molecules and nuclear transcription factors

There are data that document the anti-inflammatory effect of enoxaparin (EP) and its possible antioxidant potential. This study was designed to search for the antioxidant mechanism(s) of EP directly on endothelial cells exposed to an oxidant stimulus. For this purpose cultured human endothelial cells were exposed to nontoxic concentrations of hydrogen peroxide in the presence or absence of EP, and the adhesion of monocytes, the expression of cell adhesion molecules and transcription factors possibly involved in the process were tested. Adhesion assays, ELISA and Western blot analysis revealed that EP reduced monocyte adhesion, ICAM-1 and P-selectin expression, decreased the nuclear levels of c-Jun and p65 proteins, and diminished the phosphorylation of c-Jun protein, MAPK p38 and JNK. Together, the data demonstrate the antioxidant effect of EP and the involvement of ICAM-1, P-selectin, MAPK p38, JNK and the transcription factors NF-kappaB and AP-1 in the mechanism of action of this drug.

Cyclooxygenase, p38 Mitogen-Activated Protein Kinase (MAPK), Extracellular Signal-Regulated Kinase MAPK, Rho Kinase, and Src Mediate Hydrogen Peroxide-Induced Contraction of Rat Thoracic Aorta and Vena Cava

In hypertension, blood vessels exhibit increased reactive oxygen species production that may alter vascular tone. We previously observed that H2O2 contracted rat thoracic vena cava under resting tone and aorta contracted with KCl. In arteries but not veins, H2O2-induced contraction required extracellular Ca2+ influx. Because of this difference in Ca2+ utilization, we hypothesized that signaling pathways mediating H2O2-induced contraction in vena cava under resting tone differed from those mediating H2O2-induced contraction in aorta contracted with KCl. Inhibitors of cyclooxygenase (COX) 1 and 2 (indomethacin, 10 microM), thromboxane A2 (TXA2) receptors [ICI185282 (2RS,4RS,5SR-4-o-hydroxyphenyl-2-trifluoromethyl-1,3-dioxan-5-yl heptenoic acid), 10 microM], p38 mitogen-activated protein kinase (MAPK) [SB203580 (4-[5-(4-fluorophenyl)-2-[4-(methylsulfonyl)phenyl]-1H-imidazol-4-yl]pyridine), 10 microM], extracellular signal-regulated kinase (Erk) [PD98059 (2'-amino-3'-methoxyflavone), 10 microM], src [PP1 (4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, 10 microM], and rho kinase [Y27632 (trans-4-[(1R)-1-aminoethyl]-N-4-pyridinylcyclohexanecarboxamide dihydrochloride), 10 microM], significantly reduced H2O2-induced contraction in vena cava under resting tone and aorta after KCl (30 mM) contraction. In contrast, the phosphatidylinositol 3-kinase (PI3-K) inhibitor LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one, 20 microM] did not reduce aortic or venous H2O2-induced contraction. p38 MAPK, Erk MAPK, and src inhibition did not reduce aortic or venous contraction to the TXA2 receptor agonist U46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy PGF(2alpha), 1 microM), whereas rho kinase inhibition significantly reduced aortic and venous contraction to U46619, and PI3-K inhibition reduced venous contraction to U46619. Our data suggest that, in rat thoracic aorta and vena cava, a COX-derived metabolite is one important mediator of H2O2 contraction, possibly via rho kinase activation, and that H2O2-induced contraction via p38 and Erk MAPK probably occurs independently of TXA2 receptor activation.