Heme oxygenase (HO-1, encoded by Hmox1) is an inducible protein activated in systemic inflammatory conditions by oxidant stress. Vascular injury is characterized by a local reparative process with inflammatory components, indicating a potential protective role for HO-1 in arterial wound repair. Here we report that HO-1 directly reduces vasoconstriction and inhibits cell proliferation during vascular injury. Expression of HO-1 in arteries stimulated vascular relaxation, mediated by guanylate cyclase and cGMP, independent of nitric oxide. The unexpected effects of HO-1 on vascular smooth muscle cell growth were mediated by cell-cycle arrest involving p21Cip1. HO-1 reduced the proliferative response to vascular injury in vivo; expression of HO-1 in pig arteries inhibited lesion formation and Hmox1-/- mice produced hyperplastic arteries compared with controls. Induction of the HO-1 pathway moderates the severity of vascular injury by at least two adaptive mechanisms independent of nitric oxide, and is a potential therapeutic target for diseases of the vasculature.

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 ...

Augmentation of nitric oxide (NO) production in vivo decreases lesions in a variety of models of arterial injury, and inhibition of NO synthase exacerbates experimental intimal lesions. Both vascular smooth muscle cell (VSMC) proliferation and migration contribute to lesion formation. Although NO inhibits VSMC proliferation, its effects on VSMC migration are unknown. To test the hypothesis that NO inhibits VSMC migration independent of inhibition of proliferation, we examined migration of rat aortic VSMCs after wounding of a confluent culture in the presence of chemical donors of NO. Hydroxyurea was used to eliminate any confounding effect of NO on proliferation. Three NO donors, diethylamine NONOate, spermine NONOate, and S-nitrosoglutathione, exhibited concentration-dependent inhibition of both number of migrating VSMCs and maximal distance migrated. Inhibition of migration was also seen with 8-Br-cGMP, suggesting that activation of guanylate cyclase may play a role in mediating the antimigratory effects of NO. Migration resumed after removal of NO donors, as evidenced by an increase in distance migrated. Measurement of VSMC protein synthesis and mitochondrial respiration indicated that inhibition of migration by NO donors was not due to metabolic cytostasis. These findings indicate that NO reversibly inhibits VSMC migration independent of proliferation or cytotoxicity, a novel mechanism by which both endogenous and pharmacological NO may alter vascular pathology.

Abstract-We previously reported increased monocyte/macrophage infiltration, reactive oxygen species accumulation, and nuclear factor-B (NF-B) activation in mineralocorticoid (deoxycorticosterone acetate [DOCA]) hypertensive rats. We tested the hypothesis that prolonged antioxidant administration inhibits superoxide accumulation, lowers blood pressure, and reduces NF-B activation in DOCA-salt hypertensive rats. DOCA rats exhibited a significant increase in systolic blood pressure compared with sham rats. Aortic rings from DOCA rats exhibited increased superoxide (O 2 Ϫ ) production compared with sham rats. In addition, the treatment of DOCA rats with pyrrolidinedithiocarbamate (PDTC) or 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (Tempol) caused a significant decrease in systolic blood pressure and aortic superoxide accumulation. Monocyte/macrophage infiltration was also significantly decreased in DOCA rats treated with PDTC or Tempol compared with untreated DOCA rats. NF-B-binding activity was significantly greater in untreated DOCA rats than in either sham rats or PDTC-or Tempol-treated DOCA rats. Also, DOCA rats treated with Tempol exhibited no significant difference in NF-B-binding activity compared with sham. These results suggest that antioxidants attenuate systolic blood pressure, suppress renal NF-B-binding activity, and partly alleviate renal monocyte/macrophage infiltration in DOCA-salt hypertension. Key Words: Tempol Ⅲ pyrrolidinedithiocarbamate Ⅲ hypertension, mineralocorticoid Ⅲ nuclear factor-B Ⅲ monocyte/macrophage H ypertension imparts an increased risk of myocardial infarction, stroke, renal damage, and blindness. 1 Although at least10 genes have been shown to increase blood pressure, the pathogenesis of steroid hypertension has been shown to be primarily linked to mutations that result in ectopic production of the adrenal corticosterone, or aldosterone. 2 Hypertension has also been shown to have proinflammatory actions, which increase the formation of hydrogen peroxide (H 2 O 2 ) and superoxide (O 2 Ϫ ) within tissue and blood. [3][4][5] Furthermore, superoxide accumulation has been implicated in the activation of nuclear factor-B (NF-B). 6 NF-B transcriptionally regulates many cellular genes implicated in early immune, acute phase, and inflammatory responses, including interleukin (IL)-1␤, tumor necrosis factor-␣, IL-2, IL-6, IL-8, inducible NO synthase (iNOS), cyclooxygenase (COX)-2, intracellular adhesion molecules, and many antioxidant systems. 7 Free radicals and other reactive oxygen species (ROS) are generated by all aerobic cells and have been shown to participate in many deleterious reactions, in particular, reduced formation of endothelial NO synthase (eNOS) 8,9 and increased oxidative stress. 10 Endogenous NO plays an important role in the regulation of blood pressure by maintaining vascular smooth muscle in a partially relaxed state. During hypertension, the endogenous vasodilatory effect of NO is prevented due to interaction with ROS, specifically superoxide, thus resulting in incre...

Platelet-derived growth factor (PDGF) is a potent mitogen for vascular smooth muscle cells that has been implicated in the pathogenesis of atherosclerosis. The potential role of PDGF in the altered vasoreactivity of atherosclerotic vessels has been studied through an examination of its effects on contractility in the rat aorta. PDGF caused a concentration-dependent contraction of aortic strips and was significantly more potent on a molar basis than the classic vasoconstrictor peptide angiotensin II. Furthermore, PDGF increased the cytosolic free calcium concentration in cultured rat aortic smooth muscle cells. These observations suggest a new biological activity for PDGF that may contribute to the enhanced vasoreactivity of certain atherosclerotic vessels.

Helical strips of rat tail artery were observed to relax in response to potassium after contraction induced by 10^–7 g/ml norepinephrine in potassium-free solution. After several minutes of relaxation, the strips showed an abrupt redevelopment of tension. The amplitude of the potassium-induced relaxation was employed as an index of the activity of the electrogenic sodium-potassium pump and hence of the Na⁺-K⁺ ATPase. This assumption seemed justified because the observed amplitude of potassium-induced relaxation paralleled known effects of the following variables on Na⁺-K⁺ ATPase: (1) intracellular sodium concentration; (2) ouabain administration; (3) magnesium; (4) temperature, and (5) potassium concentration. The relaxation that occurred in response to potassium is suggested to be due to an enhanced Na⁺-K⁺ ATPase resulting in increased electrogenic transport of sodium and potassium and, consequently, hyperpolarization. We propose that potassium-induced relaxation of rat tail artery may be used as a functional indicator of Na⁺-K⁺ ATPase activity in vascular smooth muscle.

Previous studies suggest that epoxyeicosatrienoic acids (EETs) are vasodilators of the mesenteric artery; however, the production and regulation of EETs in the mesenteric artery remain unclear. The present study was designed 1) to determine which epoxygenase isoform may contribute to formation of EETs in mesenteric arteries and 2) to determine the regulation of mesenteric artery cytochrome P-450 (CYP) enzymes in obese Zucker rats. Microvessels were incubated with arachidonic acid, and CYP enzyme activity was determined. Mesenteric arteries demonstrate detectable epoxygenase and hydroxylase activities. Next, protein and mRNA expressions were determined in microvessels. Although renal microvessels express CYP2C23 mRNA and protein, mesenteric arteries lacked CYP2C23 expression. CYP2C11 and CYP2J mRNA and protein were expressed in mesenteric arteries and renal microvessels. In addition, mesenteric artery protein expression was evaluated in lean and obese Zucker rats. Compared with lean Zucker rats, mesenteric arterial CYP2C11 and CYP2J proteins were decreased by 38 and 43%, respectively, in obese Zucker rats. In contrast, soluble epoxide hydrolase mRNA and protein expressions were significantly increased in obese Zucker rat mesenteric arteries. In addition, nitric oxide-independent dilation evoked by acetylcholine was significantly attenuated in mesenteric arteries of obese Zucker rats. These data suggest that the main epoxygenase isoforms expressed in mesenteric arteries are different from those expressed in renal microvessels and that decreased epoxygenases and increased soluble epoxide hydrolase are associated with impaired mesenteric artery dilator function in obese Zucker rats.

Introduction-Thirty million men in the United States suffer from erectile dysfunction (ED) and this number is expected to double by 2025. Considered a major public health problem, which seriously affects the quality of life of patients and their partners, ED becomes increasingly prevalent with age and chronic smoking is a major risk factor in the development of ED.