Abstract
Catalase is an antioxidative enzyme that converts hydrogen peroxide (H2 O2 ) produced by superoxide dismutase from highly reactive superoxide (O2- ) to water and oxygen molecules. Although recent findings demonstrate that catalase, autophagy and the nuclear factor κB (NF-κB) signalling pathway are centrally involved in diabetic cardiomyopathy (DCM), the interplay between the three has not been fully characterized. Thus, the mechanism responsible for catalase-mediated protection against heart injury in diabetic mice was investigated in this study, as well as the role of NF-κB-p65 in the regulation of autophagic flux was investigated in this study. Western blot analysis revealed that catalase inhibited NF-κB activity and decreased LC3-II (microtubule-associated protein 1 light chain 3) and beclin-1 (Atg6) expression. Furthermore, up-regulation of autophagy was detrimental for cardiac function in diabetic mice. Catalase overexpression reduced the level of NF-κB subunit in the nucleus, where it initiates autophagy through activation of the key autophagy gene BECN1. To evaluate the role of the NF-κB pathway in diabetes-induced autophagy, Bay11-7082, an NF-κB inhibitor, was injected into diabetic mice, which suppressed NF-κB and attenuated diabetes-induced autophagy and myocardial apoptosis. In agreement with the in vivo results, Bay11-7082 also inhibited high-glucose-induced activation of NF-κB and the up-regulation of LC3-II and beclin-1 expression in H9c2 cells. In addition, high-glucose-induced activation of autophagic flux and apoptosis were largely attenuated by p65 siRNA, suggesting that catalase ameliorates diabetes-induced autophagy, at least in part by increasing the activity of the NF-κB pathway and p65-mediated transcription of BECN1.