Splenocyte apoptosis in Plasmodium berghei ANKA infection: possible role of TNF-α and TGF-β

Cerebral malaria is associated with the circulating levels of tumour necrosis factor alpha (TNF-a) and transforming growth factor beta (TGF-beta), but association between these two cytokines and implications in splenocyte apoptosis remain largely obscured. We have evaluated the outcome of TGF-beta and TNF-a production in the context of splenocyte apoptosis during Plasmodium berghei ANKA (PbA) infection. Blood-stage PbA infection confirmed bloodbrain barrier disruption, disarray of white pulp, increase in percentage of sub-G0/G1 and splenocyte apoptosis. Flow cytometric analysis reveals up-regulation of Fas-L followed by caspase-8 and caspase-3 activation and signifies possible involvement of Fas-L-mediated splenocyte apoptosis. We have observed down-regulation of TGF-beta and up-regulation of TNF-a in tissue and serum level, respectively, during PbA infection. Association between the production of TGF-beta and the severity of malaria infection in splenocytes was verified with TGF-beta inhibitor that exacerbated the apoptotic process. In contrary, TNF-a inhibitor causes significant delay in apoptotic process, but could not alter the lethality of parasite. Thus, results from this study suggest that the critical balance between TGF-beta and TNF-a might have a key role on Fas-L-mediated splenocyte apoptosis during experimental cerebral malaria.