Enhanced metabolic activation of and platelet response to clopidogrel in T cell-deficient mice through induction of Cyp2c and Cyp3a and inhibition of Ces1

Background: T cells and platelets reciprocally coordinate mutual functions through crosstalk or interaction. However, it is not known whether metabolic activation of and platelet response to clopidogrel could be changed if T cells were deficient or impaired in some cases and, if any, how it would work. Objectives: The objective of this study was to dissect the potential changes in platelet responses to and metabolic activation of clopidogrel in the case of T cell deficiency and to elucidate their mechanisms involved. Methods: BALB/c athymic nude mice or euthymic mice (controls) pretreated with cyclosporine A (CsA), thymosin & alpha;1 (T & alpha;1), or their combination were used to investigate the changes in ADP-induced platelet activation and aggregation, systemic exposure of clopidogrel and its metabolites, and mRNA/protein expression and activity levels of clopidogrel-metabolizing enzymes in the liver, respectively. Results: Nude mice exhibited significantly enhanced antiplatelet effects of clopidogrel due to increased formation of clopidogrel active metabolite in the liver, where the enzyme activity levels of Cyp2c and Cyp3a were significantly elevated compared with control mice. Furthermore, the effects of CsA pretreatment on the metabolism of clopidogrel in euthymic mice were identical to those seen in athymic mice. As expected, concomitant use of T & alpha;1 reversed all the observed effects of CsA on clopidogrel metabolism and relevant metabolic enzymes. Conclusions: T cell deficiency or suppression enhances the antiplatelet effects of clopidogrel due to the boosted metabolic activation of clopidogrel in the liver through a dramatic induction of Cyp2c and Cyp3a in mice, suggesting that the metabolism of substrate drugs of Cyp2c and Cyp3a may be enhanced by T cell impairment.