Activated protein C as a proteolytically activable antioxidant, anticoagulant protein

Abstract number: P0001

Yamaji K., Abeyama K., Kawahara K., Wang Y., Liu Y., Hashiguchi T., Maruyama I.

Kagoshima University, Japan

Activated protein C (APC), is an important natural anticoagulant, which is proteolytically generated from protein C (PC) by the modulation of the thrombin activity in the presence of thrombomodulin on endothelial surface. Recent studies have demonstrated that APC had anti-inflammatory and cytoprotective properties, beyond its anticoagulant activities. Consistent with these evidences, the clinically applied APC is effective in the treatment of DIC and endotoxemia. However, the mechanisms underlying these APCs cytostatic effects (i.e. anti-inflammation and cytoprotection) still remain uncertain. Thus, the goal of this study is to clarify the molecular mechanism of the APCs cytostatic effects. Using macrophage line, RAW264.7, we first examined the effect of APC on proinflammatory signaling (i.e. NF-kappaB and cytokine production). APC at a range of 0.1–1 mM, but not PC, could reduce LPS-induced NF-kappaB activity and resultant proinflammatory cytokine production (i.e. TNF-a, IL-1b, and IL-6). In this context, several experiments using antioxidants revealed that reactive oxygen intermediates (ROI) generation was required in the mechanism of LPS-induced proinflammatory signalings. Furthermore, APC, but not PC, could reduce LPS-induced ROI generation. These results thus, led to hypothesize that APC might act as an antioxidant protein. To validate our hypothesis, we next examined whether APC protein chemically had antioxidant property. Cell-free experiments revealed that physiologically effective range (0.1–1 mM) of APC, but not PC, had inhibitory effects on chemically induced lipid peroxidation and on protein glycation (Schiff base formation), suggesting APCs antioxidant property. These finding suggest that APC, via its intrinsic antioxidant properties, may exert important cytoprotective and anti-inflammatory effects in settings of oxidant stress distinct from its anticoagulant activity.