Pro-atherogenic role of smooth muscle Nox4-based NADPH oxidase

Abstract

Nox4-based NADPH oxidase is a major reactive oxygen species-generating enzyme in the vasculature, but its role in atherosclerosis remains controversial. Objective Our goal was to investigate the role of smooth muscle Nox4 in atherosclerosis. Approach and results Atherosclerosis-prone conditions (disturbed blood flow and Western diet) increased Nox4 mRNA level in smooth muscle of arteries. To address whether upregulated smooth muscle Nox4 under atherosclerosis-prone conditions was directly involved in the development of atherosclerosis, mice carrying a human Nox4 P437H dominant negative mutation (Nox4DN), specifically in smooth muscle, were generated on a FVB/N ApoE deficient genetic background to counter the effect of increased smooth muscle Nox4. Nox4DN significantly decreased aortic stiffness and atherosclerotic lesions, with no effect on blood pressure. Gene analysis indicated that soluble epoxide hydrolase 2 (sEH) was significantly downregulated in Nox4DN smooth muscle cells (SMC), at both mRNA and protein levels. Downregulation of sEH by siRNA decreased SMC proliferation and migration, and suppressed inflammation and macrophage adhesion to SMC. Conclusions Downregulation of smooth muscle Nox4 inhibits atherosclerosis by suppressing sEH, which, at least in part, accounts for inhibition of SMC proliferation, migration and inflammation.

Redox control of vascular smooth muscle cell function and plasticity

“…Furthermore, studies by Tong et al[41] in mice with TAGLN-driven overexpression of a human dominant negative mutant of NOX4 showed decreased carotid wire-injury-induced neointima formation, as compared to controls. These same mice also had reduced atherosclerotic lesion sizes after 12 weeks of Western diet feeding [42]. These data would support the hypothesis that SMC NOX4 expression may contribute to maintenance of SMC in a quiescent contractile state.…”

NOX4-derived reactive oxygen species limit fibrosis and inhibit proliferation of vascular smooth muscle cells in diabetic atherosclerosis

“…Recent studies by Tong et al [42] have explored the effects of SMC-NOX4 on atherosclerosis induced by western diet and partial left common carotid artery (LCA) ligation in FVB/N Apoe −/− mice that overexpress a human dominant negative (DN) form of NOX4 specifically in SMCs. Contrary to the atherogenic effects previously observed in C57/Bl6J Apoe −/− mice with genetic deletion of Nox4 and rendered diabetic [9] or subjected to Western-diet with subsequent partial LCA ligation [8], these authors showed an attenuation of atherosclerosis in DN mice linked to reduced inflammation, proliferation and migration via downregulation of soluble epoxide hydrolase 2.…”

Reactive Oxygen Species Generation and Atherosclerosis

“…24 SMC-specific expression of a human-dominant negative form of NOX4 (NOX4 P437H) resulted in decreased neointima formation after carotid artery denudation in FVB/N mice 25 or lower atherosclerosis in Apoe −/− mice. 72 Protective effect of dominant negative NOX4 in Apoe −/− mice was also associated with lower numbers of infiltrating macrophages. Overexpression of NOX4 P437H resulted in inhibition of soluble epoxide hydroxylase-2 expression and decreased proinflammatory signaling and levels of VCAM1, MCP1, and ICAM1, what was mirrored by lower macrophage adhesion.…”

“…Overexpression of NOX4 P437H resulted in inhibition of soluble epoxide hydroxylase-2 expression and decreased proinflammatory signaling and levels of VCAM1, MCP1, and ICAM1, what was mirrored by lower macrophage adhesion. 72 Importantly, soluble epoxide hydroxylase-2 downregulation reduced the expression of thrombospondin-1, 72 which was crucial for the observed effects of NOX4 P437H on proliferation and migration in Apoe +/+ mice. 25 On the other hand, Nox4 in Apoe −/− mice had a protective effect both in mice with spontaneous atherosclerosis development or after partial carotid artery ligation.…”