Abstract 1990: Decreased Complex I Activity and Increased Oxidative Stress as Mechanisms for Adverse Effects of Pressure Overload in Mice Expressing Activated GSK-33
We reported that, under pressure overload (PO), GSK-3áS21A knock in mice (αKI) developed more severe cardiac dysfunction, apoptosis, and fibrosis than wild type mice (WT), in contrast to GSK-3βS9A knock in mice. In order to elucidate the molecular mechanism by which activated GSK-3α enhances pathological hypertrophy, we performed microarray analysis and pathway analysis, which revealed that the expression of genes of the mitochondrial electron transport chain, including several subunits of NADH-ubiquinone oxidoreductase (Complex I), was significantly lower in αKI than in WT under PO. Transcription factor binding site analysis revealed that E2F-mediated transcription was significantly lower in αKI than in WT subjected to PO. In fact, E2F binding sites are present in the promoter region of the subunits of Complex I. We subsequently studied the activity of Complex I and the expression of its subunits in order to find mechanisms for the adverse effects of activated GSK-3áin the heart subjected to PO. After PO, the expression of the NDUFS1 subunit of Complex I was increased by 2.6 fold in WT hearts but was decreased by 26% in áKI hearts. The myocardial Complex I activity was significantly increased after PO in WT, but was significantly decreased by 30% in áKI. These results suggest that activated GSK-3ádiminished the compensatory increase in Complex I after PO. Adenovirus harboring cyclin D1 with a nuclear localization signal, which activates E2F signaling, injected into áKI myocardium increased NDUFS1 expression and Complex I activity and rescued the PO-induced cardiac dysfunction, fibrosis, and apoptosis, indicating that Complex I is involved in the protective effects provided by E2F activation induced by cyclin D1 located in the nucleus. The mitochondrial aconitase activity in áKI hearts was significantly decreased by 21% at baseline and significantly decreased by 25% under PO, compared to that in WT hearts, indicating increased oxidative stress in áKI hearts. In summary, activated GSK-3áattenuated the increase in the expression of Complex I subunits and Complex I activity and enhanced oxidative stress under PO. Activated GSK-3ádecreases Complex I expression and activity by inhibiting the Cyclin D-E2F pathway, thereby causes adverse effects of PO in áKI.
This research has received full or partial funding support from the American Heart Association, National Center.