Abstract:
Chemotherapy is, together with vector control, an essential tool for the control of visceral leishmaniasis (VL), but its efficacy is jeopardized by the growing resistance and treatment failure against first-line drugs. To delay the emergence of resistance, the use of drug combinations of existing antileishmanial agents has been tested systematically in clinical trials for the treatment of visceral leishmaniasis (VL). In vitro, Leishmania donovani promastigotes are able to develop experimental resistance to several combinations of different antileishmanial drugs, after 10 weeks of drug pressure. With an untargeted LC-MS metabolomics approach, we identified metabolic changes in lines experimentally resistant to drug combinations and their respective single-resistant lines. This highlighted both collective metabolic changes (found in all combination therapy-resistant (CTR) lines) and specific ones (found in certain CTR lines). We demonstrated that single-resistant and CTR parasite cell lines show distinct metabolic adaptations, which all converge on the same defensive mechanisms that were experimentally validated: protection against drug-induced and external oxidative stress and changes in membrane fluidity. The latter was only accompanied by changes in drug uptake in the lines resistant against drug combinations with antimonials and surprisingly, drug accumulation was higher in these lines. Altogether, these results highlight the importance and the central role of protection to oxidative stress in the different resistant lines. Ultimately, these phenotypic changes could interfere with the mode of action of all drugs that are currently used for the treatment of VL and should be taken into account for drug development.
