Center for Vascular and Inflammatory Diseases, Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
J Clin Invest. 2010 Jun;120(6):1971-80. doi: 10.1172/JCI40380. Epub 2010 May 10.
Activated protein C (APC), the only FDA-approved biotherapeutic drug for sepsis, possesses anticoagulant, antiinflammatory, and barrier-protective activities. However, the mechanisms underlying its anti-inflammatory functions are not well defined. Here, we report that the antiinflammatory activity of APC on macrophages is dependent on integrin CD11b/CD18, but not on endothelial protein C receptor (EPCR). We showed that CD11b/CD18 bound APC within specialized membrane microdomains/lipid rafts and facilitated APC cleavage and activation of protease-activated receptor-1 (PAR1), leading to enhanced production of sphingosine-1-phosphate (S1P) and suppression of the proinflammatory response of activated macrophages. Deletion of the gamma-carboxyglutamic acid domain of APC, a region critical for its anticoagulant activity and EPCR-dependent barrier protection, had no effect on its antiinflammatory function. Genetic inactivation of CD11b, PAR1, or sphingosine kinase-1, but not EPCR, abolished the ability of APC to suppress the macrophage inflammatory response in vitro. Using an LPS-induced mouse model of lethal endotoxemia, we showed that APC administration reduced the mortality of wild-type mice, but not CD11b-deficient mice. These data establish what we believe to be a novel mechanism underlying the antiinflammatory activity of APC in the setting of endotoxemia and provide clear evidence that the antiinflammatory function of APC is distinct from its barrier-protective function and anticoagulant activities.
活化蛋白 C（APC）是唯一获得 FDA 批准用于败血症的生物治疗药物，具有抗凝、抗炎和屏障保护作用。然而，其抗炎功能的机制尚未完全明确。在这里，我们报告 APC 对巨噬细胞的抗炎活性依赖于整合素 CD11b/CD18，而不依赖于内皮蛋白 C 受体（EPCR）。我们表明，CD11b/CD18 在特殊的膜微区/脂筏内结合 APC，并促进 APC 裂解和蛋白酶激活受体-1（PAR1）的激活，导致鞘氨醇-1-磷酸（S1P）的产生增加和激活的巨噬细胞的促炎反应受到抑制。APC 的 γ-羧基谷氨酸结构域缺失，该区域对其抗凝活性和 EPCR 依赖性屏障保护至关重要，但对其抗炎功能没有影响。APC 的 CD11b、PAR1 或鞘氨醇激酶-1 的基因失活，但不是 EPCR，消除了 APC 抑制体外巨噬细胞炎症反应的能力。使用 LPS 诱导的致命性内毒素血症小鼠模型，我们表明 APC 给药降低了野生型小鼠的死亡率，但不能降低 CD11b 缺陷型小鼠的死亡率。这些数据确立了我们认为是内毒素血症中 APC 抗炎活性的一种新机制，并提供了明确的证据表明 APC 的抗炎功能与其屏障保护功能和抗凝活性不同。
