Tanshinone IIA, a major component of Salvia milthiorriza Bunge. inhibits platelet activiation via ErK-2 signaling pathway

Ethnopharmacological relevance: The roots of Salvia milthorriza Bunge (Lamiaceae) known as "Danshen", are used in Traditional Chinese Medicine as a remedy for activating blood and eliminating stasis. TIIA, a diterpenoid of Salvia milthorriza, is one of active components in Danshen that exhibits a significant improvement of the blood flow in the coronary circulatory system and a reduction of myocardial infarction. However, its effect on platelet and underlying mechanism remains largely unknown. On this basis, this compound could be a promising agent to improve blood viscosity and microcirculation and to prevent CVD. Materials and methods: In order to investigate the effects of TIIA on platelet functionality and its interaction with various platelet activation pathways, rat PRP were incubated with TIIA for 1 min at 37 degrees C prior the addition of the stimuli (ADP or collagen). Aggregation was monitored in a light transmission aggregometer measuring changes in turbidity with continuous observation up to 10 min after the addition of the stimuli. MAPK signaling pathway and tubulin acetylation were analyzed by a Western blot technique. The effect of the TIIA was also studied in vivo on bleeding time in mice. Results: TIIA selectively inhibited rat platelet aggregation induced by reversible ADP stimuli (3 mu M) in a concentration-dependent manner (0.5-50 mu M). Nevertheless, TIIA was less active against the irreversible stimuli induced by ADP (10 mu M) and collagen (10 mu g/mL). Moreover, experiments performed on platelet lysates collected at different time-point after the addition of the stimuli shown that TIIA modulated tubulin acetylation and inhibited Erk-2 phosphorylation. Concomitantly, TIIA administrated i.p. at 10 mg/kg significantly amplified the mice bleeding time with an increase of 58% compared to its control (2.06 +/- 0.29 min vs 1.30 +/- 0.07). ASA was used as reference drug for in vitro and in vivo experiments. Conclusions: This study clarifies the intracellular signaling pathway involved in antiplatelet action of TIIA and also gives preliminary evidences for its anticoagulant activity. On this basis, this compound could be a promising agent to improve blood viscosity and microcirculation and to prevent CVD