Abstract 2973: Effects Of Cardiac Resynchronization Therapy On The Mitochondrial Proteome In A Canine Model Of Heart Failure
Cardiac resynchronization therapy (CRT) is a procedure used in the clinics to ameliorate the symptoms associated with heart failure-induced conduction disturbances and ventricular dyssynchrony. The molecular modifications underlying the beneficial effects of CRT have not been completely clarified. Recent investigations suggest that CRT may reduce apoptosis of cardiac myocytes. Mitochondria are likely to be major players in this benign transition due to their role in both energy production and apoptosis regulation. Therefore the proteome of cardiac mitochondria was investigated in a canine model for heart failure alternatively submitted to CRT.
Methods and results: Mitochondria-enriched fractions obtained from sections of the left ventricular free wall of dyssynchrony-induced heart failure (DHF) dogs alternatively submitted to CRT were analyzed through two-dimensional gel electrophoreisis (2DE). Roughly 1200 protein spots were visualized on the 2D gels after silver staining. Software-assisted differential display analysis indicated that the density of almost 50 protein spots was significantly changed upon CRT. These spots were selected and identified through mass spectrometry. Among other changes six forms of ATP synthase beta subunit were decreased 2- to 3-fold (0.0001≤p≤0.047), as well as four forms of cytochrome C (2-fold decrease, 0.002≤p≤0.047). The existence of multiple forms of a protein suggests for the presence of post-translational modifications (PTM). Therefore the phosphorylation (a common PTM) status of mitochondrial proteome was also monitored by combining the differential-in-gel electrophoresis (DIGE) technology with alkaline phosphatase teatment. ATP synthase beta subunit was differently phosphorylated in CRT samples comparing to DHF as indicated by the change in its isoelectric point upon treatment with alkaline phosphatase.
Conclusions: The proteomic investigation of mitochondria revealed a previously unseen presence of PTM mechanisms at the mitochondria level in heart failure and CRT. Phosphorylation mechanisms in the mitochondria may play a prominent role in modulating cardiac function, as observed for the beneficial effects of CRT.