Role of oxidative stress in cardiac dysfunction of PPARα−/− mice

Abstract

This study was designed to determine the effects of PPARα lack on cardiac mechanical performance and to identify potential intracellular mechanisms linking PPARα pathway deficiency to cardiac contractile dysfunction. Echocardiography, ex vivo papillary muscle assays, and in vitro motility assays were used to assess global, intrinsic ventricular muscle performance and myosin mechanical properties, respectively, in PPARα−/− and age-matched wild-type mice. Three-nitrotyrosine formation and 4-hydroxy-2-nonenal protein-adducts, both markers of oxidative damage, were analyzed by Western blot analysis and immunolabeling. Radical scavenging capacity was analyzed by measuring protein levels and/or activities of the main antioxidant enzymes, including catalase, glutathione peroxidase, and manganese and copper-zinc superoxide dismutases. Echocardiographic left ventricular fractional shortening in PPARα−/− was 16% lower than that in wild-type. Ex vivo left ventricular papillary muscle exhibited reduced shortening velocity and isometric tension (three- and twofold, respectively). In vitro myosin-based velocity was ≈20% slower in PPARα−/−, indicating that myosin itself was involved in the contractile dysfunction. Staining of 3-nitrotyrosine was more pronounced in PPARα−/−, and myosin heavy chain was the main nitrated protein. Formation of 3-nitrotyrosine myosin heavy chain was twofold higher in PPARα−/− and 4-hydroxy-2-nonenal protein-adducts were threefold higher. The expression and activity of manganese superoxide dismutase were respectively 33% and 50% lower in PPARα−/−, with no changes in copper-zinc superoxide dismutase, catalase, or glutathione peroxidase. These findings demonstrate that PPARα pathway deficiency impairs cardiac function and also identify oxidative damage to myosin as a link between PPARα deficiency and contractile dysfunction.