Matrix metalloproteinases mediate -adrenergic receptor-stimulated apoptosis in adult rat ventricular myocytes

metalloproteinases mediate -adrenergic receptor-stimulated apop-tosis in adult rat ventricular myocytes. Am J Physiol Cell Physiol 289: C168 –C176, 2005. First published February 23, 2005; doi:10.1152/ajpcell.00606.2004.—Changes in the synthesis and activ-ity of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are associated with myocardial remodeling. Here we measured the expression and activity of MMPs and TIMPs, and tested the hypoth-esis that increased MMP activity plays a proapoptotic role in -ad-renergic receptor (-AR)-stimulated apoptosis of adult rat ventricular myocytes (ARVMs). -AR stimulation (isoproterenol, 24 h) increased mRNA levels of MMP-2 and TIMP-1 while it decreased TIMP-2 mRNA levels as analyzed by real-time PCR. Western blot analysis, immunocytochemical analysis, in-gel zymography, and MMP-2 ac-tivity assay confirmed -AR-stimulated increases in MMP-2 protein levels and activity. Inhibition of MMPs using GM-6001 (a broad-spectrum inhibitor of MMPs), SB3CT (inhibitor of MMP-2), and purified TIMP-2 inhibited -AR-stimulated apoptosis as determined by TdT-mediated dUTP nick end labeling staining. Treatment with active MMP-2 alone increased the number of apoptotic cells. This increase in MMP-2-mediated apoptosis was inhibited by GM-6001 and SB3CT pretreatment. Coimmunoprecipitation studies indicated increased physical association of MMP-2 with 1-integrins after -AR stimulation. Inhibition of MMP-2 using SB3CT or stimulation of 1-integrin signaling using laminin inhibited the increased associ-ation of MMP-2 with 1-integrins. -AR stimulation increased poly-ADP-ribose-polymerase cleavage, which was inhibited by inhibition of MMP-2. These data suggest the following: 1) -AR stimulatio