In Vitro Evaluation of Inhibitory Effect of Artemisinin and Dihydroartemisinin on Calcineurin Enzyme

Artimisinin (an anti-malaria drug) is extracted from Artemisia annua and its water soluble derivative is dihydroartimisinin. Previous in vivo and in vitro studies showed that it has an inhibitory effect on T cells. It is also useful for immunosuppression of immune system. The stable state kinetic for comparison of inhibitory effect of artimisinin, dihydroartimisinin and cyclosporine A on calcineurin activation was used in this study. First, the best inhibitory concentration of artimisinin, dihydroartimisinin and cyclosporine A was calculated. Afterwards, the km and Vmax of them in the presence of substrate, paranitrophenylphosphate (P-NPP) were measured. The KI was calculated in the presence of cyclosporine A, artemisinin and dihydroartemisinin. In this study, we used distilled water instead of sample in blank and cyclosporinA as a positive control group. The Vmax in the control group was 81.97 M/min and in the presence of cyclosporine A and artemisinin or dihydroartemisinin were 81.97 M/min and 66.225 M/min, respectively. The Km in the absence of inhibitors was 1.886 M and in the presence of cyclosporine A and artemisinin or dihydroartemisinin was 2.819 M and 1.736, respectively. Also, ­KI in the presence of artimisinin and dihydroartimisinin was 4.219 ×10-5 M and in the presence of cyclosporine A was 2.021×10-5 M. This study indicates that the inhibitory power of artimisinin and dihydroartimisinin is almost equal and they inhibited calcineurin competitively, while inhibitory effect of cyclosporine A is non-competitive.