INCREASE IN GLUTATHIONE-PEROXIDASE ACTIVITY IN MALARIA PARASITE AFTERSELENIUM SUPPLEMENTATION

Glutathione peroxidase (GPx), a key enzyme involved in the detoxificat ion of many peroxides, has been investigated in two malaria parasite s pecies: P. yoelii in vivo (murine malaria) and P. falciparum in vitro (human malaria). We demonstrate the presence of an endogenous GPx acti vity in these two Plasmodia species. Enzymatic assays and the use of s pecific substrates and inhibitors allowed us to determine that the act ivity is selenium dependent. As this activity was shown to be lower in P. falciparum than in P. yoelii, and selenium levels were found to be low in culture medium and culture red blood cells, we hypothesized th at a severe selenium deficiency could be responsible for this differen ce. After selenium supplementation, with either sodium selenite or sel enocystine, we observed an increase in growth of P. falciparum only in with sodium selenite, whereas higher GPx activities were noted in par asites grown in media supplemented with both. An increase in GPx activ ities was also observed in parasites that had undergone an experimenta l oxidative stress with TBOOH. As the erythrocyte is unable to synthes ize new proteins, these results provide further evidence for the exist ence of an endogenous parasitic selenium-dependent glutathione peroxid ase.