The Effect of Tanshinone-IIa on IL-1β Induced-Thrombocytosis in an Immune Vasculitis Model

Inflammation cytokines may be involved in the pathogenesis of thrombocytosis with vasculitis. Our previous study showed that inflammation cytokine IL-1β plays an important role on in-vitro megakaryopoiesis (Yang M et al, Br J Haematol 2000). The role of IL-1β and Tanshinone IIA (TIIA) (Isolated from Danshen, Radix Salviae Miltiorrhiza Bge) on platelets and megakaryocytes (MKs) in immune vasculitis model was investigated in this study. Rabbit model with immune vasculitis was established by injection (iv) of BSA. After treatment with BSA for 7 days, the platelet count, platelet aggregation and the expression of AnnexinⅤ were significantly increased in this vasculitis model group compared with normal control group (n=7). IL-1β levels was also significantly higher in vasculitis model. There were positive correlations between platelet count and IL-1β levels (R=0.65), platelet aggregation and IL-1β levels (R=0.60). Treatment with TIIA (5 mg/kg/day, iv) and aspirin significantly decreased all these parameters. MKs and CFU-MK number were also significantly increased in vasculitis group as compared to normal group. Treatment with TIIA and aspirin significantly reduced the number of MKs and CFU-MK in this model. Study further demonstrated that IL-1β alone or in combination with TPO induced in-vitro CFU-MK formation. The mRNA of of IL-1 type I and type II receptors (IL-1 RI and RII) were detected in cultured MK (CD61+ CD41+) cells. The expression of IL-1 RI and RII was also confirmed by immunofluorescence staining in bone marrow MKs. Moreover, the IL-1R bloker can reduced IL-1β induced megakaryopoiesis. TIIA on in-vitro megakaryopoiesis was also investigated. TIIA at 10-30 ug/ml significantly inhibited CFU-MK formation. TIIA also induced the apoptosis of MKs in a dose dependent manner by Anexin V assay. Caspase 3 assay showed the activation of Caspase 3 increased from 5% to 16%. Using JC-1 assay found that the depolarized cells increased from 9% to 17% suggesting the involvement of intrinsic apoptotic pathway. IL-1β may play an important role in the thrombocytosis of immune vasculitis by inducing megakaryopoiesis. TIIA has anti-platelet effect in this model which may be mediated via inhibiting IL-1β induced-megakaryopoiesis.