Abstract 20169: A Novel Role for NADPH oxidase 4 in Monocyte Migration and Macrophage Recruitment in Atherosclerosis
Hyperlipidemia and hyperglycemia enhance the responsiveness of monocytes to MCP-1-induced chemotaxis in vivo, increase macrophage recruitment and accelerate atherosclerotic lesion formation in LDL-receptor-deficient mice (Qiao et al., ATVB 2009). In this study, we investigated the molecular details underlying monocyte hyperresponsiveness to MCP-1 induced by metabolic stress and report that culturing THP-1 monocytes for 24 h in the presence of 0.1 mg/ml human LDL plus 25 mM glucose induced Nox4 expression, increased intracellular H2O2 production and accelerated chemotaxis in response to MCP−1. Adenovirus-mediated Nox4 overexpression alone sensitized THP-1 monocytes to MCP-1 and accelerated cell migration, mimicking the effects of metabolic stress. Conversely, siRNA-mediated knockdown of Nox4 protected monocytes against metabolic stress-induced hypersensitivity to MCP-1 and prevented exaggerated chemotactic responses. Confocal microscopy and immunoprecipitation studies in human monocyte-derived macrophages revealed that Nox4 co-localizes with its dimerization partner, p22phox, and associates with proteins involved in the formation of active focal adhesions, including phospho-FAK, paxillin, and the F-actin cytoskeleton. Importantly, actin associated with Nox4 was S-glutathionylated, suggesting that Nox4-derived H2O2 may regulate macrophages migration through post-translational modification of protein thiols. Finally, induction of hypercholesterolemia and hyperglycemia in C57BL/6 mice increased both protein-S-glutathionylation in macrophages and macrophage recruitment into MCP-1-loaded Matrigel plugs implanted subcutaneous in these mice. Compared to Matrigel plug-derived macrophages from healthy control mice, macrophages from metabolically-stressed mice showed a 4.9-fold increase in Nox4 expression. In summary, we identified a novel mechanism involving monocytic Nox4 that appears to contribute to increased macrophage recruitment and accelerated atherosclerosis associated with metabolic disorders
- © 2010 by American Heart Association, Inc.