Abstract 162: c-fos Protects the Myocardium from Ischemic Injury and Improves Cardiac Function

Abstract

Background: c-fos is an immediate early response gene. c-Fos proteins form heterodimers with Jun family proteins, and the resulting AP-1 complexes regulate transcription by binding to the AP-1 sequence found in many cellular genes. c-fos is activated in cardiomyocytes following myocardial infarction. However, the role of c-fos in regulating cardiomyocyte survival and cardiac function post myocardial infarction (MI) is not known. In the present study, we hypothesized that c-fos protects the myocardium from ischemic injury and improves cardiac function. Methods and Results: The generation of mice with cardiomyocyte specific c-fos −/ − was achieved by crossing the floxed c-fos mice with mice over-expressing Cre recombinase under the control of α-myosin heavy chain. Wild-type (WT) littermates were used as controls. MI was induced by coronary artery ligation. Infarct size, myocardial apoptosis and cardiac function were determined at 2 days post-MI. While area at risk was similar between the 2 groups, infarct size was significantly increased in c-fos −/ − compared to WT mice (58 ± 4% vs. 44 ± 3%, P< 0.05). Myocardial caspase-3 activity and cytosolic DNA fragments in the peri-infarct region were significantly increased while Bcl-2/Bax protein ratio was significantly decreased in c-fos −/− mice ( P< 0.05). LV pressure volume relationship was assessed in vivo using a Millar pressure conductance catheter. LV end-systolic elastance ( E es ) and +d P /dt max were significantly decreased in c-fos −/− compared to WT mice (1.7 ± 0.4 vs. 5.1 ± 1.0 mmHg/μL; 4776 ± 567 vs. 7006 ± 319 mmHg/s, P< 0.01). Conclusions: Deficiency in c-fos increases infarct size and myocardial apoptosis leading to impaired cardiac function post-MI. Our results suggest that c-fos protects the myocardium from ischemic injury and improves cardiac function.