Abstract 15901: Adverse Post-Ischemic Cardiac Remodeling in Chronic Hindlimb Ischemia: Proteomic Identification of a Novel Molecular Mechanism
Peripheral arterial disease is an important manifestation of atherosclerosis, commonly complicated by myocardial infarction or stroke. In this study we investigated whether chronic hindlimb ischemia might activate detrimental signalling pathways in the heart. To test this, cardiac function and signalling were analyzed in mice undergoing: 1) unilateral hindlimb ischemia induced by ligation of the left common femoral artery (L); 2) myocardial infarction by ligation of the left descending coronary artery (MI); 3) MI after five weeks of hindlimb ischemia (L+MI); 4) sham operation (SHAM). Cardiac function, evaluated by transthoracic echocardiography at baseline and seven days after MI, was significantly decreased in L+MI mice compared to MI (% fractional shortening, MI: 47.2±1.9; L+MI: 38.5± 0.8, p<0.05), and this was associated with a significant increase in % cardiomyocyte apoptotic death as shown by TUNEL assay (MI: 10.5±2.2, L+MI: 54.3±2.5, p<0.05) and p53 activation. Importantly, 5 weeks of hindlimb ischemia did not significantly affect the levels of the pro-inflammatory cytokines TNF-α, IL-1β and IL-6. To determine whether a soluble factor might be responsible for such differences, rat neonatal cardiomyocytes were incubated with the serum of MI and L+MI mice for 4 hours under low oxygen conditions, and the apoptotic cell death was then evaluated. Interestingly, only serum from L+MI mice induced marked positivity to TUNEL staining and p53 protein levels in cardiomyocytes (p53 protein levels fold over SHAM: MI: 1.3±0.4; PL5: 5.9±1.0 p<0.05 vs. SHAM). With the use of high-pressure liquid chromatography and mass spectrometry, a peptide of approximately 10 kDa inducing apoptosis in cardiomyocytes was isolated and identified in L+MI serum. This peptide was characterized by intrinsic apoptotic function, and was able to potentiate the detrimental effects of low oxygen conditions in cardiomyocytes. In conclusion, chronic hindlimb ischemia plays a direct role in the modulation of cardiomyocyte survival under low oxygen conditions, promoting the systemic release of a pro-apoptotic factor; this effect is independent from atherosclerosis or systemic inflammation.
- © 2011 by American Heart Association, Inc.