Selective Pharmacological Blockade of GPR39 Markedly Reduces No Reflow and Infarct Volumes in a Rat Acute Myocardial Infarction When Administered Prior to Reperfusion

Our aim was to determine whether selective pharmacological blockade of GPR39 by the novel drug, VC108, reduces no reflow (NRV) and infarct (INV) volumes during acute myocardial infarction (AMI). Immuocytochemistry and qPCR of isolated rat cardiac cells as well as immunohistochemistry and western blot of rat myocardium was performed for presence of GPR39. Rats underwent 1 h of coronary occlusion and 1 h of reperfusion. Groups 1 and 2 animals received drug/vehicle prior to or during coronary occlusion. Groups 3 and 4 received drug/vehicle 5 min prior to or 30 min after reperfusion. Readouts also included tissue pO 2 , hemodynamics, and wall thickening. In Groups 5 and 6 animals, drug was injected for measurement of plasma and tissue levels. Immunocytochemistry and qPCR of cells and immunohistochemistry and western blot of tissue revealed GPR39 expression in all cardiac cells analyzed as well as entire myocardial tissue. There was marked reduction in NRV and INV in groups 1 and 3 animals where both were measured and in Group 2 where INV was measured. In contrast, Group 4 animals failed to show reduction in NRV and INV with the drug. The reduction in NRV in all animals was associated with higher tissue pO 2 in VC108 compared to vehicle treated animals. Similar results were obtained for INV in only in Group 2 animals. In Group 3 animals direct cardiomyocyte effect of VC108 was seen in myocardium as evidenced by reduced necrosis and apoptosis. We conclude that VC108 is very effective in reducing INV and NRV in an AMI model when given before coronary occlusion or just prior to reperfusion (the latter being clinically more relevant) both in male and female rats. This effect is not seen after reperfusion. VC108 acts by blocking GPR39, resulting in vasodilation through pericyte and VSMC relaxation. It also directly protects cardiomyocytes by preventing downstream effects of GPR39 stimulation.