NOX1/NADPH oxidase is involved in endotoxin-induced cardiomyocyte apoptosis

Abstract The functional significance of NOX1/NADPH oxidase in the heart has not been explored due to its low expression relative to other NOX homologs identified so far. We aimed to clarify the role of NOX1/NADPH oxidase in the septic heart by utilizing mice deficient in the Nox1 gene (Nox1 −/Y ). Sepsis was induced by intraperitoneal administration of lipopolysaccharides (LPS: 25 mg/kg) or cecal ligation and puncture (CLP) surgery. A marked elevation of NOX1 mRNA was demonstrated in cardiac tissue, which was accompanied by increased production of reactive oxygen species (ROS). In Nox1 −/Y treated with LPS, cardiac dysfunction and survival were significantly improved compared with wild-type mice (Nox1 +/Y ) treated with LPS. Concomitantly, LPS-induced cardiomyocyte apoptosis and activation of caspase-3 were alleviated in Nox1 −/Y . The level of phosphorylated Akt in cardiac tissue was significantly lowered in Nox1 +/Y but not in Nox1 −/Y treated with LPS or that underwent CLP surgery. Increased oxidation of cysteine residues of Akt and enhanced interaction of Akt with protein phosphatase 2A (PP2A), a major phosphatase implicated in the dephosphorylation of Akt, were demonstrated in LPS-treated Nox1 +/Y . These responses to LPS were significantly attenuated in Nox1 −/Y . Taken together, ROS derived from NOX1/NADPH oxidase play a pivotal role in endotoxin-induced cardiomyocyte apoptosis by increasing oxidation of Akt and subsequent dephosphorylation by PP2A. Marked up-regulation of NOX1 may affect the risk of mortality under systemic inflammatory conditions.