beta-Adrenergic receptor-stimulated apoptosis in adult cardiac myocytes involves MMP-2-mediated disruption of beta1 integrin signaling and mitochondrial pathway.

Stimulation of beta-adrenergic receptors (beta-AR) induces apoptosis in adult rat ventricular myocytes (ARVMs) via the JNK-dependent activation of mitochondrial death pathway. Recently, we have shown that inhibition of matrix metalloproteinase-2 (MMP-2) inhibits beta-AR-stimulated apoptosis and that the apoptotic effects of MMP-2 are possibly mediated via its interaction with beta1 integrins. Herein we tested the hypothesis that MMP-2 impairs beta1 integrin-mediated survival signals, such as activation of focal adhesion kinase (FAK), and activates the JNK-dependent mitochondrial death pathway. Inhibition of MMP-2 using SB3CT, a selective gelatinase inhibitor, significantly increased FAK phosphorylation (Tyr-397 and Tyr-576). TIMP-2, tissue inhibitor of MMP-2, produced a similar increase in FAK phosphorylation, whereas treatment of ARVMs with purified active MMP-2 significantly inhibited FAK phosphorylation. Inhibition of MMP-2 using SB3CT inhibited beta-AR-stimulated activation of JNKs and levels of cytosolic cytochrome c. Treatment of ARVMs with purified MMP-2 increased cytosolic cytochrome c release. Furthermore, inhibition of MMP-2 using SB3CT and TIMP-2 attenuated beta-AR-stimulated decreases in mitochondrial membrane potential. Overexpression of beta1 integrins using adenoviruses expressing the human beta1A-integrin decreased beta-AR-stimulated cytochrome c release and apoptosis. Overexpression of beta1 integrins also inhibited apoptosis induced by purified active MMP-2. These data suggest that MMP-2 interferes with the beta1 integrin survival signals and activates JNK-dependent mitochondrial death pathway leading to apoptosis.