IL-1β Plays An Important Role On Thrombocytosis In An Immune Vasculitis Model Via Promoting Megakaryopoiesis

Thrombocytosis and inflammation cytokines may be involved in the pathogenesis of vasculitis. Our previous study have showed that major inflammation cytokine IL-1β play an important role on in-vitro megakaryopoiesis (Yang M et al, Br J Haematol 2000). In this study, we investigated the changes of IL-1β and megakaryopoiesis and the effect of aspirin in an immune vasculitis model. Rabbit immune vasculitis model was established by intravenous injection of bovine serum albumin. In this model, platelet number and function of periphery blood, megakaryocyte number and the CFU-MK formation of the bone marrow, and serum levels of inflammatory cytokines were investigated. 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=6). The serum levels of inflammatory cytokine IL-1β was also significantly higher in vasculitis model. There were positive correlations between platelet count and IL-1β levels (R=0.55), platelet aggregation and IL-1β levels (R=0.603). Treatment with aspirin (100 mg/kg/d) significantly decreased all these parameters, showing aspirin had anti-platelets and anti-inflammation effects. Our results also demonstrated that megakaryocyte number and the formation of CFU-MK were significantly increased in vasculitis group as compared to those in normal group. Treatment with aspirin significantly reduced the number of megakaryocytes and the formations of CFU-MK in bone marrow in this immune vasculitis model. Our study further demonstrated that IL-1β alone or in combination with TPO induced in-vitro CFU-MK formation. Using RT-PCR techniques, the mRNA of of IL-1 type I and type II receptors (IL-1 RI and RII) were detected in cultured CD61+ CD41+ cells and four megakaryocytic cell lines. The expression of IL-1 RI and RII was also confirmed by flow cytometry and immunofluorescence staining in bone marrow megakaryocytes. Moreover, the IL-1R bloker can reduced IL-1β induced megakaryopoiesis. This sudy showed that IL-1β may play an important role in the pathogenesis of immune vasculitis. Aspirin has anti-inflammation effects in this model which may be mediated via inhibiting megakaryopoiesis and platelet formation.