Abstract 1215: Reactive Oxygen Species-Mediated Regulation of CD44 and Hyaluronic Acid in Vascular Smooth Muscle Proliferation, Migration and Atherosclerosis
Proliferation and migration of vascular smooth muscle cells (VSMC) are important events in the development of restenosis and atherosclerosis. These processes are initiated by a number of agonists including thrombin and involve generation of reactive oxygen species (ROS) by NAD(P)H oxidases. NAD(P)H oxidase-deficient apoE−/ −/p47phox−/ − mice had lower levels of aortic ROS generation and less atherosclerosis than apoE−/ − mice. Recently we showed that thrombin induced expression of a number of genes including CD44 antigen in VSMC in NAD(P)H oxidase-dependent manner and immunoreactive CD44 expression was significantly less in atherosclerotic lesions of apoE−/ −/p47phox−/ − mice than in apoE−/ − mice. In this study we investigated redox-sensitive regulation of thrombin-induced CD44 gene expression, its effect on proliferation and migration in VSMC and its functional relevance in atherogenesis. Thrombin-induced CD44 transcription was blocked by pretreatment with DPI, an inhibitor of NAD(P)H oxidase and was attenuated in p47phox−/ − VSMC. CD44 expression was mediated by the stimulation of ERK1/2 and consequent activation of transcription factor AP1. Expression of hyaluronic acid (HA), a ligand for CD44, was increased in atherosclerotic lesions of apoE−/ −mice compared with apoE−/ −/p47phox−/ − mice. Consistent with this, expression of hyaluronan synthase increased significantly in wild-type but not p47phox−/ − VSMC in response to thrombin treatment. Low molecular weight HA (LMW-HA) stimulated proliferation of wild-type, but not p47phox−/ −VSMC and pretreatment with thrombin further enhanced LMW-HA-induced VSMC proliferation. LMW-HA also stimulated ROS generation in wild-type but not in p47phox−/ − VSMC and this effect was further increased by pretreatment with thrombin. Thrombin enhanced haptotactic migration of VSMC towards HA and this effect was attenuated by incubation with CD44 antibody. In conclusion, our data indicate that ROS mediate the regulation of CD44 and HA expression in atherosclerotic lesions and the interaction of CD44 antigen receptor and its ligand play an important role in the development of atherosclerosis under pathophysiological conditions.