NOXA1-dependent NADPH oxidase regulates redox signaling and phenotype of vascular smooth muscle cell during atherogenesis

Increased reactive oxygen species (ROS) production and inflammation are key factors in the pathogenesis of atherosclerosis. We previously reported that NOX activator 1 (NOXA1) is the critical functional homolog of p67phox for NADPH oxidase activation in mouse vascular smooth muscle cells (VSMC). Here we investigated the effects of systemic and SMC-specific deletion of Noxal on VSMC phenotype during atherogenesis in mice. Neointimal hyperplasia following endovascular injury was lower in Noxa1 -deficient mice versus the wild-type following endovascular injury. Noxal deletion in Apoe(-/-) or Ldlr(-/-) mice fed a Western diet showed 50% reduction in vascular ROS and 30% reduction in aortic atherosclerotic lesion area and aortic sinus lesion volume (P < 0.01). SMC-specific deletion of Noxa1 in Apoe(-/-) mice (Noxa1(SMC-/-)/Apoe(-/-)) similarly decreased vascular ROS levels and atherosclerotic lesion size. TNF alpha-induced ROS generation, proliferation and migration were significantly attenuated in Noxal -deficient versus wild-type VSMC. Immunofluorescence analysis of atherosclerotic lesions showed a significant decrease in cells positive for CD68 and myosin11 (22% versus 9%) and Mac3 and a-actin (17% versus 5%) in the Noxa1(SMC-/-)/Apoe(-/-) versus Apoe(-/-) mice. The expression of transcription factor KLF4, a modulator of VSMC phenotype, and its downstream targets - VCAM1, CCL2, and MMP2 - were significantly reduced in the lesions of Noxa1(SMC-/-)/Apoe(-/-) versus Apoe(-/-) mice as well as in oxidized phospholipids treated Noxa1(SMC-/- )versus wild-type VSMC. Our data support an important role for NOXA1-dependent NADPH oxidase activity in VSMC plasticity during restenosis and atherosclerosis, augmenting VSMC proliferation and migration and KLF4-mediated transition to macrophage-like cells, plaque inflammation, and expansion.