Glutathione protects macrophages and Leishmania major against nitric oxide-mediated cytotoxicity

The aim of this investigation was to examine whether macrophage and Leishma nia major glutathione were involved in either host or parasite protection a gainst NO cytotoxicity. Buthionine sulfoximine (BSO), an inhibitor of gamma -glutamylcysteine synthase, caused a complete and irreversible depletion of macrophage glutathione, but only a 20 % and reversible decrease in L. majo r glutathione. Glutathione-depleted macrophages, when activated with IFN-ga mma/LPS, released less than 60 % of the NO produced by untreated macrophage s, resulting in a corresponding decrease in their leishmanicidal activity. BSO-treated macrophages were more susceptible to the cytotoxic effects of t he NO donor SNAP. Treatment of macrophages with 1,3-bis(chloroethyl)-1-nitr osourea (BCNU), an inhibitor of glutathione reductase and trypanothione red uctase or with Br-Octane, a glutathione-S-transferase substrate, resulted i n a transient decrease in glutathione levels and did not increase the susce ptibility of the macrophages to SNAP. Treatment of the promastigote forms o f L. major with BCNU resulted in an 80 % decrease in total glutathione conc entration with no concomitant change in viability. However, this treatment rendered the parasites more susceptible to SNAP. Finally, macrophage glutat hione protected the internalized L, major from SNAP. Overall, these results demonstrate that glutathione is an essential protective component against NO cytotoxicity on both macrophages and parasites.