TRAIL expression in vascular smooth muscle

TRAIL is a cell-associated tumor necrosis factor-related apoptosis-inducing ligand originally identified in immune cells. The ligand has the capacity to induce apoptosis after binding to cell surface receptors. To examine TRA IL expression in murine vascular tissue, we employed in situ hybridization and immunohistochemistry. In these studies, we found that TRAIL mRNA and pr otein were specifically localized throughout the medial smooth muscle cell layer of the pulmonary artery. Notably, a similar pattern of expression was observed in the mouse aorta. Consistent with these findings, we found that cultures of primary human aorta and pulmonary artery smooth muscle cells e xpress abundant TRAIL mRNA and protein. We also found that these cells and endothelial cells undergo cell lysis in response to exogenous addition of T RAIL. Last, we confirmed that TRAIL specifically activated a death program by confirming poly(ADP ribose) polymerase cleavage. Overall, we believe tha t these findings are relevant to understanding the factors that regulate ce ll turnover in the vessel wall.