NADPH oxidase 4 (Nox4) mediates metabolic stress‐induced hyper‐responsiveness of monocytes to MCP‐1

We previously showed that metabolic stress (MS) promotes thiol oxidative stress and increases the responsiveness of monocytes to chemotactic stimuli, resulting in accelerated atherogenesis in LDLR‐null mice. Macrophages isolated from MS‐mice showed increased Nox4 expression and protein‐S‐glutathionylation. We therefore hypothesized that Nox4 mediates MS‐induced monocyte hyper‐responsiveness to chemokines, like MCP‐1. Exposure of THP‐1 monocytes to MS in vitro (high levels of LDL and glucose) induced Nox4 expression and intracellular ROS, and increased MCP‐1‐mediated chemotaxis. Nox4 over‐expression sensitized monocytes to MCP‐1, mimicking the effect of MS. Conversely, Nox4 siRNA suppressed MS‐accelerated chemotaxis. Confocal microscopy showed that Nox4 localized to focal adhesions and the F‐actin cytoskeleton, structures that are crucial for cell motility. Co‐immunoprecipitation confirmed that Nox4 associated with both activated‐FAK and actin. Furthermore, Nox4‐associated actin was S‐glutathionylated. MS enhanced Nox4‐actin association, and MCP‐1‐induced monocyte adhesion to fibronectin, which was partially prevented by Nox4 siRNA, supporting a role for Nox4 in cytoskeletal dynamics and adhesion. Our results suggested that Nox4‐derived ROS mediate MS‐accelerated monocyte chemotaxis in thiol redox‐dependent manner. AHA 10PRE3460002 (CFL), NIH HL070963 & AHA 0855011F (RA).