Aim: 

Inhibition of GSK-3ß was shown to protect the reperfused heart against reperfusion injury. We showed in previous studies that reperfusion causes hypercontracture and necrosis of cardiomyocytes. The aim of the present study is to investigate whether inhibition of GSK-3ß protects reperfused cardiac myocytes against hypercontracture and necrosis and whether this is due to inhibition of mitochondrial permeability transition pore (MPTP).

Methods: 

To simulate ischemia and reperfusion, isolated cardiac myocytes from adult rats were superfused anoxically (pH 6.4) and then reperfused with a normoxic puffer (pH 7.4). Opening of MPTP was detected by monitoring the mitochondrial membrane potential with JC-1, and necrosis by use of propidium iodide staining.

Results: 

Simulated ischemia led to mitochondrial depolarization and to a decrease in pH_i. During the first two minutes of reperfusion Dy recovered, but collapsed after 5 min of reperfusion indicating MPTP Opening. Concomitantly, reperfused cells developed hypercontracture. Application of the GSK- 3ß inhibitor SB 216763 (5mM), or MPTP inhibitor cyclosporine (0.5 mM) at the time of reperfusion significantly prevented the collapse in Dy, hypercontracture and cell necrosis (p<0.05 vs. control). Treatment of reperfused cells with both inhibitors (SB 216763+cyclosporine) did not significantly improve collapse in Dy, hypercontracture, or cell necrosis in comparison to SB 216763, or cyclosporine alone.

Conclusions: 

Inhibition of GSK-3ß protects reperfused cardiac myocytes against development of hypercontracture and necrosis via inhibition of MPTP.