Abstract 12263: Loss of p47phox Subunit of NADPH Oxidase Enhances Susceptibility to Biomechanical Stress: Novel Role Of p47phox in the Regulation of Cortactin and Actin Filaments
Background: The classical phagocyte NADPH oxidase (gp91phox or Nox2) is expressed in cardiomyocytes, fibroblasts and vasculature. Nox2 activation requires membrane translocation of the p47phox subunit leading to the generation of superoxide. Activation of NADPH oxidase, initiated by phosphorylation of p47phox, has been linked to the progression of heart failure.
Hypothesis: We hypothesize that loss of p47phox subunit will result in decreased ROS production and resistance to the development of heart failure in response to pressure-overload.
Methods and Results: We randomized 8 weeks old male p47phox null (p47phoxKO) mice and age matched wildtype (WT) male mice to transverse aortic constriction (TAC) induced pressure-overload cardiomyopathy. Lack of p47phox blunted the increase in reactive oxygen species (ROS) levels in response to pressure-overload. However, p47phoxKO mice showed marked systolic dysfunction in response to pressure-overload at 5 weeks (EF: 22.7±3.1 vs 47.5±2.5; p<0.001) and 9 weeks (EF: 13.8±1.2 vs 34.8±3.2; p<0.001) post-TAC, which resulted in higher mortality rate compared to WT mice (25.8% vs 7.5%; p<0.01). p47phoxKO TAC hearts also displayed markedly elevated cardiac fibrosis despite equivalent phosphorylation of Akt and ERK1/2, compared with WT hearts. Biomechanical stress resulted in upregulation of N-cadherin and β-catenin in p47phoxKO hearts but disrupted the actin filament cytoskeleton and reduced phosphorylation of FAK. p47phox was found to interact with cortactin by co-immunoprecipitation and double immunofluorescence staining. The interaction of cortactin with p47phox was predominantly cytosolic in WT hearts and translocated to the membrane upon biomechanical stress where cortactin interacted with N-cadherin resulting in adaptive cytoskeletal remodeling. However, p47phoxKO hearts showed deficient interaction of cortactin with N-cadherin resulting in loss of biomechanical stress induced actin polymerization and cytoskeletal remodeling.
Conclusions: Loss of p47phox subunit of NADPH oxidase leads to a paradoxical enhanced susceptibility to biomechanical stress. We identified a novel role of p47phox as a regulator of cortactin and adaptive cytoskeletal remodeling during biomechanical stress.
- © 2012 by American Heart Association, Inc.