Regulatory effect of Bcl-2 family proteins in CPB-induced cardiomyocyte apoptosis in dog hearts

Abstract

Whether conventional hypothermic CPB induces myocyte apoptosis in dog hearts and modulation of bcl-2, bcl-xl, bax, bad, and caspase-3 pathways in this setting was investigated. Ten healthy adult dogs were randomized into sham-operated and CPB groups. Samples of left ventricle were obtained before, during and 3 h after CPB. In situ TUNEL was used to detect apoptotic myocytes. Immunohistochemistry and flow cytometry were employed for detection of expressions of bcl-2, bcl-xl, bax and bad proteins. Z-DEVD-AMC substrate cleavage and TBARS methods were used to measure the activity of caspase-3 and the content of lipid peroxide in LV myocardium, respectively. After CPB, the number of apoptotic myocytes in CPB group was significantly increased. The results of immunohistochemistry demonstrated that bcl-2, bcl-xl, bax and bad proteins were constitutionally present on the sarcolemma of the LV myocytes. FACS results showed that, after CPB, expressions of bax and bad in CPB group were significantly upregulated, while the expressions of bcl-2 and bcl-xl were not significantly changed in both groups. The activity of caspase-3 and the content of lipid peroxide in LV myocardium in CPB group were also significantly increased after CPB. The present study shows that there exists myocardiocyte apoptosis in dog hearts undergoing conventional hypothermic CPB and the myocyte apoptosis is initiated by ischemia and performed during reperfusion. Moreover, the CPB-induced myocyte apoptosis was associated with upregulation of expressions of bax and bad proteins, activation of caspase-3 and increase of oxidative stress.

Novel Functional Role of Heat Shock Protein 90 in Mitochondrial Connexin 43-Mediated Hypoxic Postconditioning

“…Accumulating studies have shown that the pro-apoptotic (Bax) and anti-apoptotic (Bcl-2) proteins of the Bcl-2 family play a pivotal role in this apoptotic process [38] The balance between pro- and anti-apoptotic members of the Bcl-2 family is critical in determining cell fate. Apart from their localization at the mitochondria and the cytoplasm, Bcl-2 and Bax proteins are also constitutionally present on the sarcolemma of the cardiomyocytes [39]. Currently, the anti-apoptotic role of cytosolic Bcl-2 in postconditioning cardioprotection has been well investigated in both in vivo and in vitro [38, 40], but little is known regarding the role of Bcl-2 family members in the sarcolemma and mitochondria.…”