Cardiac-specific overexpression of catalase rescues ventricular myocytes from ethanol-induced cardiac contractile defect

Oxidative stress is intimately involved in alcoholic cardiomyopathy. Catalase is responsible for detoxification of hydrogen peroxide (H₂O₂) and may interfere with ethanol-induced cardiac toxicity. To test this hypothesis, a transgenic mouse line was produced to overexpress catalase (∼50-fold) in the heart, ranging from sarcoplasm, the nucleus and peroxisomes within myocytes. Mechanical and intracellular Ca²⁺ properties were evaluated in ventricular myocytes from catalase transgenic (CAT) and wild-type FVB mice. Protein abundance of sarco (endo) plasmic reticulum Ca²⁺-ATPase (SERCA), phospholamban (PLB), Na⁺/Ca²⁺ exchanger (NCX), dihydropyridine Ca²⁺ receptor (DHPR), ryanodine receptor (RyR), Akt and phosphorylated Akt (pAkt) were measured by western blot. CAT itself did not alter body and organ weights, as well as myocyte contractile properties. Acute exposure of ethanol elicited a concentration-dependent depression in cell shortening and intracellular Ca²⁺ in FVB mice with maximal inhibitions of 65.4% and 35.8%, respectively. The ethanol-induced cardiac depression was significantly attenuated in myocytes from CAT with maximal inhibitions of 42.4% and 27.3%. CAT also abrogated the ethanol-induced inhibition of maximal velocity of shortening/relengthening, prolongation of relengthening duration and intracellular Ca²⁺ clearing time. Cell shortening at different extracellular Ca²⁺ revealed stronger myocyte-shortening amplitude under lower (0.5 mM) Ca²⁺ in CAT mice. Protein expression of NCX, RyR, Akt and pAkt were elevated in myocytes from CAT mice, while those of SERCA, PLB and DHPR were not affected. In conclusion, our data suggest that catalase overexpression may protect cardiac myocytes from ethanol-induced contractile defect, partially through improved intracellular Ca²⁺ handling and Akt signaling.