Riewald Matthias, Petrovan Ramona J, Donner Aaron, Ruf Wolfram
Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.
J Endotoxin Res. 2003;9(5):317-21. doi: 10.1179/096805103225002584.
The anti-inflammatory effects of activated protein C (APC) have lead to its recent approval for the treatment of sepsis. Although the endothelial cell protein C receptor (EPCR) plays a crucial role in APC's protective roles in septicemia, the precise signaling mechanism of the protease APC remains unclear. In fibroblast overexpression systems, we find that APC activates protease activated receptors (PAR) 1 and 2 in an EPCR-dependent manner. Human endothelial cells (HUVECs) express PAR1, PAR2 and EPCR. Stimulation of HUVECs with either APC, or specific receptor activating peptides for PAR1 or PAR2, show that all three agonists induce a very similar set of early response genes as assessed by high density microarray analysis. Only the transcript for monocyte chemo-attractant protein-1 (MCP-1) was selectively induced by APC and the PAR1 agonist, but not by the PAR2 agonist. APC-mediated MAP kinase phosphorylation and gene induction were inhibited by cleavage blocking antibodies to PAR1, demonstrating that APC signals exclusively through PAR1 in endothelial cells. MCP-1 is protective in animal models of endotoxemia, suggesting that APC may prevent lethality in sepsis by inducing MCP-1 expression through EPCR-dependent activation of endothelial cell PAR1. These data demonstrate unexpected protective functions of the major thrombin receptor PAR1 in endothelial cells.
活化蛋白C（APC）的抗炎作用使其最近被批准用于治疗败血症。尽管内皮细胞蛋白C受体（EPCR）在APC对败血症的保护作用中起着关键作用，但蛋白酶APC的确切信号传导机制仍不清楚。在成纤维细胞过表达系统中，我们发现APC以EPCR依赖的方式激活蛋白酶激活受体（PAR）1和2。人内皮细胞（HUVECs）表达PAR1、PAR2和EPCR。用APC或PAR1或PAR2的特异性受体激活肽刺激HUVECs，结果显示，通过高密度微阵列分析评估，所有这三种激动剂均诱导出一组非常相似的早期反应基因。只有单核细胞趋化蛋白-1（MCP-1）的转录本被APC和PAR1激动剂选择性诱导，而未被PAR2激动剂诱导。APC介导的MAP激酶磷酸化和基因诱导被PAR1的切割阻断抗体抑制，这表明APC在内皮细胞中仅通过PAR1发出信号。MCP-1在动物内毒素血症模型中具有保护作用，这表明APC可能通过EPCR依赖的内皮细胞PAR1激活诱导MCP-1表达，从而预防败血症中的致死率。这些数据证明了主要凝血酶受体PAR1在内皮细胞中具有意想不到的保护功能。
