Background-Angiotensin II (ATII), a potent vasoconstrictor, causes hypertension, promotes infiltration of myelomonocytic cells into the vessel wall, and stimulates both vascular and inflammatory cell NADPH oxidases. Clinical Perspective on p 1381Primary sources of ROS in the cardiovascular system are the Nox-based, multisubunit enzymes NADPH oxidases. 3 Several Nox isoforms are expressed and functional in phagocytic cells like monocytes, macrophages, and neutrophils (myelomonocytic cells); T cells; endothelial cells; vascular smooth muscle cells; and adventitial fibroblasts. All of these have been suggested to contribute to cardiovascular pathology, 3,4 although the importance of individual cell types and their relative impact on the development of cardiovascular disease remain unclear.The phagocytic NADPH oxidase is a major source of ROS elicited by angiotensin II (ATII). 5 In ApoE Ϫ/Ϫ mice fed a high-fat diet, the extent of atherosclerotic lesions is attenuated by limiting the burden of superoxide generated by myelomonocytes. 6 Leukocyte activation by ATII involving the phagocyte-type NADPH oxidase had been demonstrated in

The correlation between mtROS formation and acetylcholine-dependent relaxation revealed that mitochondrial radical formation significantly contributes to age-dependent endothelial dysfunction.

Chronic nitroglycerin treatment results in development of nitrate tolerance associated with endothelial dysfunction (ED). We sought to clarify how mitochondria- and NADPH oxidase (Nox)-derived reactive oxygen species (ROS) contribute to nitrate tolerance and nitroglycerin-induced ED. Nitrate tolerance was induced by nitroglycerin infusion in male Wistar rats (100 microg/h/4 day) and in C57/Bl6, p47(phox/) and gp91(phox/) mice (50 microg/h/4 day). Protein and mRNA expression of Nox subunits were unaltered by chronic nitroglycerin treatment. Oxidative stress was determined in vascular rings and mitochondrial fractions of nitroglycerin-treated animals by L-012 enhanced chemiluminescence, revealing a dominant role of mitochondria for nitrate tolerance development. Isometric tension studies revealed that genetic deletion or inhibition (apocynin, 0.35 mg/h/4 day) of Nox improved ED, whereas nitrate tolerance was unaltered. Vice versa, nitrate tolerance was attenuated by co-treatment with the respiratory chain complex I inhibitor rotenone (100 microg/h/4 day) or the mitochondrial permeability transition pore blocker cyclosporine A (50 microg/h/4 day). Both compounds improved ED, suggesting a link between mitochondrial and Nox-derived ROS. Mitochondrial respiratory chain-derived ROS are critical for the development of nitrate tolerance, whereas Nox-derived ROS mediate nitrate tolerance-associated ED. This suggests a crosstalk between mitochondrial and Nox-derived ROS with distinct mechanistic effects and sites for pharmacological intervention.

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OBJECTIVEDiabetes is associated with vascular oxidative stress, activation of NADPH oxidase, and uncoupling of nitric oxide (NO) synthase (endothelial NO synthase [eNOS]). Pentaerithrityl tetranitrate (PETN) is an organic nitrate with potent antioxidant properties via induction of heme oxygenase-1 (HO-1). We tested whether treatment with PETN improves vascular dysfunction in the setting of experimental diabetes.RESEARCH DESIGN AND METHODSAfter induction of hyperglycemia by streptozotocin (STZ) injection (60 mg/kg i.v.), PETN (15 mg/kg/day p.o.) or isosorbide-5-mononitrate (ISMN; 75 mg/kg/day p.o.) was fed to Wistar rats for 7 weeks. Oxidative stress was assessed by optical methods and oxidative protein modifications, vascular function was determined by isometric tension recordings, protein expression was measured by Western blotting, RNA expression was assessed by quantitative RT-PCR, and HO-1 promoter activity in stable transfected cells was determined by luciferase assays.RESULTSPETN, but not ISMN, improved endothelial dysfunction. NADPH oxidase and serum xanthine oxidase activities were significantly reduced by PETN but not by ISMN. Both organic nitrates had minor effects on the expression of NADPH oxidase subunits, eNOS and dihydrofolate reductase (Western blotting). PETN, but not ISMN, normalized the expression of GTP cyclohydrolase-1, extracellular superoxide dismutase, and S-glutathionylation of eNOS, thereby preventing eNOS uncoupling. The expression of the antioxidant enzyme, HO-1, was increased by STZ treatment and further upregulated by PETN, but not ISMN, via activation of the transcription factor NRF2.CONCLUSIONSIn contrast to ISMN, the organic nitrate, PETN, improves endothelial dysfunction in diabetes by preventing eNOS uncoupling and NADPH oxidase activation, thereby reducing oxidative stress. Thus, PETN therapy may be suited to treat patients with cardiovascular complications of diabetes.

Abstract-The organic nitrate pentaerythritol tetranitrate is devoid of nitrate tolerance, which has been attributed to the induction of the antioxidant enzyme heme oxygenase (HO)-1. With the present study, we tested whether chronic treatment with pentaerythritol tetranitrate can improve angiotensin II-induced vascular oxidative stress and dysfunction. In contrast to isosorbide-5 mononitrate (75 mg/kg per day for 7 days), treatment with pentaerythritol tetranitrate (15 mg/kg per day for 7 days) improved the impaired endothelial and smooth muscle function and normalized vascular and cardiac reactive oxygen species production (mitochondria, NADPH oxidase activity, and uncoupled endothelial NO synthase), as assessed by dihydroethidine staining, lucigenin-enhanced chemiluminescence, and quantification of dihydroethidine oxidation products in angiotensin II (1 mg/kg per day for 7 days)-treated rats. The antioxidant features of pentaerythritol tetranitrate were recapitulated in spontaneously hypertensive rats. In addition to an increase in HO-1 protein expression, pentaerythritol tetranitrate but not isosorbide-5 mononitrate normalized vascular reactive oxygen species formation and augmented aortic protein levels of the tetrahydrobiopterin-synthesizing enzymes GTPcyclohydrolase I and dihydrofolate reductase in angiotensin II-treated rats, thereby preventing endothelial NO synthase uncoupling. Haploinsufficiency of HO-1 completely abolished the beneficial effects of pentaerythritol tetranitrate in angiotensin II-treated mice, whereas HO-1 induction by hemin (25 mg/kg) mimicked the effect of pentaerythritol tetranitrate. Improvement of vascular function in this particular model of arterial hypertension by pentaerythritol tetranitrate largely depends on the induction of the antioxidant enzyme HO-1 and identifies pentaerythritol tetranitrate, in contrast to isosorbide-5 mononitrate, as an organic nitrate able to improve rather than to worsen endothelial function. (Hypertension. 2010;55:897-904.)Key Words: pentaerythritol tetranitrate Ⅲ isosorbide-5-mononitrate Ⅲ angiotensin-II Ⅲ SHR Ⅲ endothelial dysfunction Ⅲ vascular oxidative stress B oth arterial hypertension and coronary artery disease are associated with an activation of the circulating and local renin-angiotensin system and increased oxidative stress within the vascular wall. 1,2 Angiotensin-II (AT-II) treatment has been shown to cause endothelial dysfunction, which is at least in part mediated by increased vascular reactive oxygen species (ROS) levels. 3,4 ROS sources involved may include the NADPH oxidases, 3 an uncoupled endothelial NO synthase (NOS; eNOS), 4 and mitochondrial superoxide sources. 5 The crucial role of the NADPH oxidase as an important superoxide source was further substantiated by the demonstration that NADPH oxidase 1 overexpression in transgenic mice potentiates AT-II-induced hypertension, 6 whereas blood pressure responses to AT-II were reduced in NADPH oxidase 1-deficient mice. 7 Increased vascular ROS production and endothelial dysfunction ...

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