Glutathione and the redox control system trypanothione/trypanothione reductase are involved in the protection of Leishmania spp. against nitrosothiol-induced cytotoxicity
Romão, P.R.T.; Tovar, J.; Fonseca, S.G.; Moraes, R.H.; Cruz, A.K.; Hothersall, J.S.; Noronha-Dutra, A.A.; Ferreira, S.H.; Cunha, F.Q.
Glutathione is the major intracellular antioxidant thiol protecting mammalian cells against oxidative stress induced by oxygen- and nitrogen-derived reactive species. In trypanosomes and leishmanias, trypanothione plays a central role in parasite protection against mammalian host defence systems by recycling trypanothione disulphide by the enzyme trypanothione reductase. Although Kinetoplastida parasites lack glutathione reductase, they maintain significant levels of glutathione. The aim of this study was to use iLeishmania donovani trypanothione reductase/i gene mutant clones and different iLeishmania /ispecies to examine the role of these two individual thiol systems in the protection mechanism against S-nitroso-iN/i-acetyl-D,L-penicillamine (SNAP), a nitrogen-derived reactive species donor. We found that the resistance to SNAP of different species of iLeishmania /iwas inversely correlated with their glutathione concentration but not with their total low-molecular weight thiol content (about 0.18 nmol/10sup7/sup parasites, regardless iLeishmania /ispecies). The glutathione concentration in iL. amazonensis/i, iL. donovani/i, iL./i imajor/i, and iL. braziliensis/i were 0.12, 0.10, 0.08, and 0.04 nmol/10sup7/sup parasites, respectively. iL. amazonensis/i, that have a higher level of glutathione, were less susceptible to SNAP (30 and 100 µM). The ICsub50/subvalues of SNAP determined to iL. amazonensis/i, iL. donovani/i, iL. major/i, and iL. braziliensis /iwere 207.8, 188.5, 160.9, and 83 µM, respectively. We also observed that iL. donovani /imutants carrying only one itrypanothione reductase/i allele had a decreased capacity to survive (~40%) in the presence of SNAP (30-150 µM). In conclusion, the present data suggest that both antioxidant systems, glutathione and trypanothione/trypanothione reductase, participate in protection of iLeishmania/i against the toxic effect of nitrogen-derived reactive species.
Keywords: Leishmania; Glutathione; Trypanothione; Trypanothione reductase; Nitric oxide; Free radicals.