Inhibitory effect of curcumin, a food spice from turmeric, on platelet-activating factor- and arachidonic acid-mediated platelet aggregation through inhibition of thromboxane formation and Ca 2+ signaling

Abstract

Curcumin, a dietary spice from turmeric, is known to be anti-inflammatory, anticarcinogenic, and antithrombotic. Here, we studied the mechanism of the antiplatelet action of curcumin. We show that curcumin inhibited platelet aggregation mediated by the platelet agonists epinephrine (200 μM), ADP (4 μM), platelet-activating factor (PAF; 800 nM), collagen (20 μg/mL), and arachidonic acid (AA: 0.75 mM). Curcumin preferentially inhibited PAF- and AA-induced aggregation ( ic 50; 25–20 μM), whereas much higher concentrations of curcumin were required to inhibit aggregation induced by other platelet agonists. Pretreatment of platelets with curcumin resulted in inhibition of platelet aggregation induced by calcium ionophore A-23187 ( ic 50; 100 μM), but curcumin up to 250 μM had no inhibitory effect on aggregation induced by the protein kinase C (PKC) activator phorbol myrsitate acetate (1 μM). Curcumin (100 μM) inhibited the A-23187-induced mobilization of intracellular Ca 2+ as determined by using fura-2 acetoxymethyl ester. Curcumin also inhibited the formation of thromboxane A 2 (TXA 2) by platelets ( ic 50; 70 μM). These results suggest that the curcumin-mediated preferential inhibition of PAF- and AA-induced platelet aggregation involves inhibitory effects on TXA 2 synthesis and Ca 2+ signaling, but without the involvement of PKC.