부산대학교 도서관

Thrombin, an important mediator of thrombosis and inflammation, may also enhance vascular cytoprotection. Thus thrombin induces expression of the complement-inhibitory protein decay-accelerating factor (DAF) in human umbilical vein endothelial cells (HUVECs), thus increasing protection against complement-mediated injury. Using PKC isozyme-specific peptide antagonists and adenoviral constructs, we have shown in the present study that PKC-[member of] is the primary isozyme involved in DAF induction by thrombin. Experiments with proteinase-activated receptor-1 (PAR1) and PAR2 activating peptides (APs) showed that DAF expression induced by PA[R.sub.1]-AP was PKC-[alpha]-dependent; in contrast, PA[R.sub.2]-AP induction of DAF required activation of PKC-[member of]. PA[R.sub.1]-AP and PA[R.sub.2]-AP in combination exerted an additive effect on DAF protein expression, which was equivalent to that observed with thrombin alone. These data implied a specific role for PA[R.sub.2] in DAF induction, which was supported by the observation that upregulation of endothelial cell (EC) PA[R.sub.2]-enhanced DAF induction by thrombin. ERK1/2, p38, and JNK MAPK were also involved in thrombin-induced DAF upregulation, with evidence of interdependence between ERK1/2 and JNK. A role for transactivation of PAR2 by PA[R.sub.1] was suggested by partial inhibition of thrombininduced DAF expression by the PA[R.sub.1] signaling antagonists BMS200261 and SCH79797, whereas inhibition of thrombin-induced cleavage of PA[R.sub.1] by specific MAbs or hirudin completely abrogated the response. Together, these data imply that the predominant pathway for thrombin-induced DAF expression involves transactivation of PA[R.sub.2] by PA[R.sub.1] and signaling via PKC-[member of]/MAPK. This may represent an important, novel pathway for endothelial cytoprotection during inflammation and angiogenesis and suggests that PA[R.sub.2] may play a central role in some thrombin-induced responses. cytoprotection; proteinase-activated receptor 1