Expression of lectin-like oxidized low-density lipoprotein receptor-1 in allografted hearts

The pathogenesis of posttransplant coronary artery disease, which is thought to be a major form of chronic rejection after cardiac transplantation, is not fully understood. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) on endothelial cells induces reduction of NO release and up-regulation of adhesion molecules, thereby contributing to the development of vascular atherosclerosis. Herein, we investigated the expression of LOX-1 mRNA in murine allografted hearts that develop diffuse coronary obstruction. Allogeneic (C57BL/6 to BALB/c) and syngeneic (C57BL/6 to C57BL/6) heterotopic cardiac transplants were removed the 10th posttransplant day. LOX-1 mRNA expression was measured by RT-PCR. The heartbeat of the allografts gradually weakened and was almost stopped on day 10, whereas syngeneic hearts continued to pulsate throughout the experiment. Histologically, allografts showed fibrous luminal narrowing of the coronary arteries with severe mononuclear cell infiltration. In contrast, the vascular architecture of syngeneic grafts was almost normal. Marked increase in LOX-1 mRNA expression was observed only in allografts. The results indicate that alloimmune responses induce up-regulation of LOX-1 mRNA in transplanted hearts. Increased LOX-1 may be involved in the progression of obstructive vascular changes.