Abstract 11170: Induction of NADPH Oxidase 4 by Metabolic Stress Enhances Monocyte Adhesion and Chemotaxis: Role of Redox Signaling in Early Macrophage Recruitment of Atherosclerosis
Monocyte adhesion and chemotaxis are the initial steps of macrophage recruitment to sites of arterial injury and atherosclerosis. We showed that metabolic stress (hyperlipidemia and hyperglycemia) accelerates these processes in a thiol oxidation-dependent manner, but the source of ROS involved in thiol oxidation and the molecular mechanism underlying accelerated macrophage recruitment were not known. Here we tested the hypothesis that Nox4, an inducible source of intracellular ROS we recently identified in monocytes and macrophages, regulates monocyte adhesion and chemotaxis, and thus macrophage recruitment to atherosclerotic lesions. We found that metabolic stress (mimicked by 100 μg/ml LDL plus 25 mM glucose) induced Nox4 expression, increased intracellular ROS production, and enhanced both MCP-1-induced adhesion and chemotaxis of THP-1 monocytes (n=4; P<0.05). Nox4 siRNA knockdown prevented acceleration of monocyte adhesion and chemotaxis by metabolic stress (n=4; P<0.05). Adenovirus-mediated Nox4 over-expression promoted monocyte adhesion and chemotaxis, mimicking the effects of metabolic stress (n=4; P<0.05). To investigate the molecular mechanism through which Nox4-derived ROS regulate monocyte adhesion and chemotaxis, we determined the sub-cellular localization of Nox4. Various membranous sub-cellular compartments were studied. Interestingly, Nox4 localized to focal adhesions and the F-actin cytoskeleton by fluorescent confocal microscopy (Pearson coefficient>0.7). Co-immunoprecipitation studies confirmed the association of Nox4 with phospho-FAK, paxillin and actin. Importantly, metabolic stress promoted the association of Nox4 with actin (n=3; P<0.05), and actin associated with Nox4 was S-glutathionylated, a redox-sensitive, reversible post-translational modification previously reported to regulate actin polymerization. In summary, induction of Nox4 mediates metabolic stress-enhanced macrophage recruitment by generating localized ROS to migration machineries, and thus promoting the rate of monocyte adhesion and migration. We showed that monocyte adhesion and chemotaxis are redox-regulated processes and identified a novel role of Nox4 in the early macrophage recruitment of atherosclerosis.
- © 2011 by American Heart Association, Inc.