NADPH Oxidase 4 Regulates Inflammation in Ischemic Heart Failure: Role of Soluble Epoxide Hydrolase

Oxidative stress is implicated in cardiomyocyte cell death and cardiac remodeling in the failing heart. The role of NADPH oxidase 4 (NOX4) in cardiac adaptation to pressure overload is controversial, but its function in myocardial ischemic stress has not been thoroughly elucidated. The present study examined the function of NOX4 in the pathogenesis of ischemic heart failure, utilizing mouse models, cell culture, and human heart samples. Results: Nox4‐/‐ mice showed a protective phenotype in response to permanent left anterior descending (LAD) coronary artery ligation with smaller infarction area, lower cardiomyocyte cross‐sectional area, higher capillary density, and less cell death versus wild‐type mice. Nox4‐/‐ mice had lower activity of soluble epoxide hydrolase (sEH), a potent regulator of inflammation. Nox4‐/‐ mice also showed a 50% reduction in the number of infiltrating CD68+ macrophages in the peri‐infarct zone versus wild‐type mice. Adenoviral overexpression of NOX4 in cardiomyoblast cells increased sEH expression and activity and CCL4 and CCL5 levels; inhibiting sEH activity in NOX4 overexpressing cells attenuated the cytokine levels. Human hearts with ischemic cardiomyopathy showed adverse cardiac remodeling, increased NOX4 and sEH protein expression and CCL4 and CCL5 levels compared to control nonfailing hearts. Innovation and Conclusion: These data from Nox4‐/‐ mouse model and human heart tissues show for the first time that oxidative stress from increased NOX4 expression has a functional role in ischemic heart failure. One mechanism by which NOX4 contributes to ischemic heart failure is by increasing inflammatory cytokine production via enhanced sEH activity.