Influence of ischemia/reperfusion and modulation of PI3K/Akt kinase pathway on matrix metalloproteinase-2 in rat hearts.

Matrix metalloproteinases (MMPs) are enzymes that play an important role in degradation and remodeling of extracellular matrix and MMP-2 has been also shown as a primary mediator of the acute mechanical dysfunction of the heart immediately after ischemia/reperfusion (I/R). The aims of the study were to investigate the influence of I/R on MMP-2 and to study the effects of wortmannin on modulation of MMP-2 activities after cycle of short I/R procedures (ischemic preconditioning, IP). Wortmannin is a specific inhibitor of PI3K/Akt kinase pathway activation of which was found to play a role in infarct size limiting mechanisms in the rat heart. In the study isolated Langendorff-perfused rat hearts subjected to protocols of prolonged (test) I/R and/or IP were used. Wortmannin was infused before and during the reperfusion phase of IP. The levels and activation of proteins were determined by immunoblot assay. The MMP-2 activities were measured by zymography. We found that ischemia induced time-dependent activation of tissue pro-MMP-2. Strong activation occurred after 15 min ischemia, during prolonged ischemia and following reperfusion the activities of this form of MMP-2 declined. The specific activities of both 72 and 63 kDa forms of MMP-2 were increased in perfusates collected during reperfusion after 30 min ischemia and these activities peaked in the first minute of reperfusion. Cycle of short ischemia and reperfusion that led to increased cardiac tolerance against prolonged I/R reduced 72 kDa MMP-2 activities and induced also an activation of Akt kinase. The application of wortmannin was connected with inhibition of IP-mediated Akt kinase activation. Moreover, the actions of wortmannin were linked with modulation of MMP-2 activities. Our results suggest that MMP-2 may be involved in the responses of rat hearts to ischemia and point to possible relationship between Akt kinase and modulation of MMP-2 activities in rat hearts.