NADH/NADPH Oxidase and Enhanced Superoxide Production in the Mineralocorticoid Hypertensive Rat

Abstract

Abstract-We previously reported increased aortic reactive oxygen species (ROS) production in mineralocorticoid (deoxycorticosterone acetate [DOCA]-salt) hypertensive rats. In the present study, we tested the hypothesis that NADH/NADPH oxidase is responsible for increased ROS production, namely superoxide (O 2 Ϫ ), in aorta from the DOCA-salt rat. Treatment of aortic rings from DOCA-salt rats with the NO synthase inhibitor N-nitro-L-arginine and the xanthine oxidase inhibitor allopurinol did not significantly change O 2 Ϫ production. Furthermore, de-endothelialization of aorta from DOCA-salt rats did not affect O 2 Ϫ production compared with that of sham-operated rats. Thus, xanthine oxidase and uncoupled endothelial NO synthase were not responsible for increased O 2 Ϫ production in the DOCA-salt rats. In contrast, treatment with the NADPH oxidase inhibitor apocynin significantly decreased O 2 Ϫ production in aortic rings from DOCA-salt rats compared with sham-operated rats. Moreover, long-term administration of apocynin (in drinking water, 1.5 mmol/L, 28 days) to DOCA-salt rats significantly decreased systolic blood pressure compared with that of rats treated with DOCA-salt alone. Furthermore, O 2 Ϫ production in aortic rings from DOCA-salt rats treated with apocynin for 28 days was reduced compared with that of untreated DOCA-salt rats. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated that DOCA-salt rats have significantly greater mRNA levels of the NADPH oxidase subunit p22phox than do sham-operated rats. These findings suggest that NADPH oxidase is increased and is responsible for increased O 2 Ϫ production and possibly contributes to increased blood pressure in the DOCA-salt hypertensive rat. Key Words: deoxycorticosterone acetate Ⅲ NADH/NADPH Ⅲ mineralocorticoids Ⅲ hypertension, mineralocorticoid H ypertension, atherosclerosis, and mechanical injury exert common pathological effects on the vessel wall, such as vascular smooth muscle cell (VSMC) proliferation, monocyte/macrophage infiltration, endothelial dysfunction, and increased connective tissue deposition. 1 In addition, these vascular diseases have been shown to be associated with oxidative stress, and there is good evidence implicating angiotensin II in the oxidative stress associated with hypertension. 2,3 However, we 4 and others 5 have reported increased oxidative stress in mineralocorticoid (deoxycorticosterone acetate [DOCA]) hypertension, which is characterized by low angiotensin II levels. We also found that oxidative stress causes increased transcription of genes responsible for the early inflammatory response in the DOCA-salt hypertensive rat. 4 Moreover, a potentially significant consequence of oxidative stress is vascular smooth muscle cell proliferation 6 and NO inactivation, 7 which could play an important role in the vascular changes and causes of hypertension. However, the source of the oxidative (reactive oxygen species [ROS]) stress is not known. Early studies have identified endothelial xanthine oxidase ...

Endothelin-1 Increases Vascular Superoxide via Endothelin A –NADPH Oxidase Pathway in Low-Renin Hypertension

“…2 In DOCA-salt hypertensive rats, aortic NADPH oxidase activity was significantly increased compared with their normotensive controls. 7,8 In the present study, we examined (1) the effect of ET-1 on superoxide production both in vitro in normal rats and in vivo in DOCA-salt hypertensive rats and (2) whether this effect is mediated by NADPH oxidase, xanthine oxidase, or uncoupled NOS. Our results indicate that (1) ET-1 stimulates arterial O 2 Ϫ production in a concentration-dependent manner in normal rats; (2) apocynin but not L-NAME or allopurinol inhibits the O 2 Ϫ production in both ET-1-stimulated arteries of normal rats and arteries of DOCA-salt rats; and (3) the selective ET A receptor antagonist ABT-627 suppresses superoxide production in vitro in ET-1-treated arteries of normal rats and in vivo in arteries of DOCA-salt hypertensive rats.…”

“…The selectivity of apocynin, a methoxy-substituted catechol, on NADPH oxidase has been well characterized, because it impedes the assembly of the p47phox and p67phox subunits within the membrane NADPH oxidase complex. 8,24 There are at least 2 vascular ET-1 receptors, ET A and ET B . 15 ET-1 exerts its vasoactive effects mainly through the activation of the G protein-coupled ET A receptors on vascular smooth muscle cells, 16 whereas ET B may exert protective effects in DOCA-salt hypertension.…”

Mechanisms of H2O2-induced oxidative stress in endothelial cells

“…These include: xanthine oxidase (Miyachi et al 1986;Satoh et al 1998;Fleming et al 2001), NADPH oxidase (Meyer et al 1999;Hohler et al 2000;Barry-Lane et al 2001;Beswick et al 2001;Seno et al 2001;Brandes et al 2002;Li et al 2002;Lassegue et al 2003;Parinandi et al 2003), and uncoupled NOS (Beretta et al 2003;Landmesser et al 2003). NADPH oxidase and uncoupled NOS are thought to be major…”

Long-chain polyunsaturated fatty acids interact with nitric oxide, superoxide anion, and transforming growth factor-β to prevent human essential hypertension

“…This suggests that NAD(P)H oxidase assembly occurs de novo in vivo (Rey et al, 2001). Activation of NAD(P)H oxidase is seen not only in SHR, and patients with essential hypertension but also in mineralocorticoid (deoxycorticosterone acetate, DOCA,-salt) hypertensive rats (Beswick et al, 2001). Thus, NAD(P)H oxidase activation could be a general mechanism by which hypertension develops irrespective of the mode of induction of hypertension.…”