Estudo do mecanismo de resistência a compostos derivados da classe das tiossemicarbazonas em tripanosomatídeos, com ênfase na glicoproteína-P e na nitrorredutase do tipo I / Study class of compounds derived from the resistance mechanism of thiosemicarbazones in trypanosomatids, with emphasis on P-glycoprotein and type I nitroreductase

Os tratamentos disponíveis para a doença de Chagas e as leishmanioses não são eficientes e apresentam alta toxicidade. Diversos estudos mostram que há possibilidade de indução de resistência de Trypanosoma cruzi ao Benznidazol (BZ) o que pode interferir na eficácia do tratamento. O mesmo tem sido relatado com relação aos fármacos utilizados para o tratamento das leishmanioses, embora não exista um mecanismo de ação definido para a resistência a drogas nestes protozoários. Neste trabalho foram focalizados dois potenciais mecanismos: 1) atividade da glicoproteína-P (Pgp), uma proteína de membrana que atua como uma bomba de efluxo dependente de energia e associada ao fenótipo de resistência a múltiplas drogas (MDR); 2) a enzima nitrorredutase presente em T. cruzi (TcNTR), reponsável pela redução de nitroderivados, como BZ, para obter o efeito tripanocida. Na busca de novos compostos seletivos contra T. cruzi e Leishmania amazonensis, nosso grupo vem estudando derivados da classe das tiossemicarbazonas. Em estudos prévios foi observado que o derivado 4-N-(2-metoxi-estiril)-tiossemicarbazona (2-MEOTIO) foi o composto mais efetivo sobre diferentes formas de T. cruzi, enquanto 4-N-(4’-hidroxi-3’-metoxi-estiril)-tiossemicarbazona (3-MEOTIO) se mostrou o mais eficiente contra L. amazonensisO mecanismo de resistência a estes compostos foi avaliado, e nossos resultados mostram a participação da Pgp na resistência a 2-MEOTIO e BZ em T. cruzi, e a 3-MEOTIO em L. amazonensis...

The available drugs for the treatment of Chagas disease and leishmaniasisare not efficient and cause toxic side effects. Several studies show the possibilityof drug resistance induction to Benznidazol (BZ) in Trypanosoma cruzi, whichmay interfere with the treatment efficacy. The same has been observed regardingcompounds used to treat leishmaniasis, although more studies on drug resistancemechanism are needed. In the present study we focused on two potential drugresistance mechanisms: 1) P-glycoprotein (Pgp) activity, a membrane proteinwhich acts as an efflux pump energy-dependent and is associated with themultidrug resistance fenotype (MDR); 2) the enzyme nitroreductase (TcNTR)found in T. cruzi, which is responsible for the reduction of nitroheterocyclicderivatives, such as Bz and Nifurtimox, generating metabolites with trypanocidalactivity. In the search for new selective drugs for the treatment of Chagas diseaseand leishmaniasis, our group has been studying compounds from the class of thethiosemicarbazones. Previous studies showed that the 4-N-(2-methoxy-styryl)-thiosemicarbazone (2-MEOTIO) was the most efficient compound on differentforms of T. cruzi, whereas 4-N-(4’-hidroxy-3’-methoxy styryl)-thiosemicarbazone(3-MEOTIO) was the most active on Leishmania amazonensis. Here weevaluated the drug resistance mechanism to both thiosemicarbazone derivatives,as well as, to BZ which was used as reference drug for T. cruzi. Our results showthe participation of Pgp in the resistance to both 2-MEOTIO and BZ in T. cruzi, aswell as in the resistance in L. amazonensis to the compound 3-MEOTIO.Interestingly, in T. cruzi the participation of Pgp is related to its localization notonly in the plasma membrane but also in the mithocondrion...

P-glycoprotein efflux pump plays an important role in Trypanosoma cruzi drug resistance.

Drug resistance in protozoan parasites has been associated with the P-glycoprotein (Pgp), an energy-dependent efflux pump that transports substances across the membrane. Interestingly, the genes TcPGP1 and TcPGP2 have been described in Trypanosoma cruzi, although the function of these genes has not been fully elucidated. The main goal of this work was to investigate Pgp efflux pump activity and expression in T. cruzi lines submitted to in vitro induced resistance to the compounds 4-N-(2-methoxy styryl)-thiosemicarbazone (2-Meotio) and benznidazole (Bz) and to verify the stability of the resistant phenotypes during the parasite life cycle. We observed that the EC50 values for the treatment of epimastigotes with 2-Meotio or Bz were increased at least 4.7-fold in resistant lines, and this phenotype was maintained in metacyclic trypomastigotes, cell-derived trypomastigotes, and intracellular amastigotes. However, in epimastigotes, 2-Meotio resistance is reversible, but Bz resistance is irreversible. When compared with the parental line, the resistant lines exhibited higher Pgp efflux activity, reversion of the resistant phenotypes in the presence of Pgp inhibitors, cross-resistance with Pgp modulators, higher basal Pgp ATPase activity, and overexpression of the genes TcPGP1 and TcPGP2. In conclusion, the resistance induced in T. cruzi by the compounds 2-Meotio and Bz is maintained during the entire parasite life cycle. Furthermore, our data suggest the participation of the Pgp efflux pump in T. cruzi drug resistance.