Influência dos tratamentos com Lactonas Sesquiterpênicas isoladas de Tithonia diversifolia, em monoterapia e combinadas ao benznidazol, durante infecção aguda experimental por Trypanosoma cruzi

Abstract

According to the World Health Organization, Chagas' disease, caused by the protozoan Trypanosoma cruzi, is still part of the neglected diseases group, since investments for research into new drug development are scarce, therapeutic options are limited. Thus, the need for studies with the purpose of developing new drugs effective in the chemotherapy of the disease is evident. The Tithonia diversifolia species, daisy, is a plant considered invasive in Brazil, being found along highways and in vacant lots. The sesquiterpene lactones (STLs) isolated from this plant have anti-inflammatory and anti-parasitic action, among other pharmacological actions. In this sense, the objective of this work was to evaluate the trypanocidal activity of foliar lavage extract in STLs (ELF) and tagitinin C (TC) extracted from T. diversifolia, isolated and in combination with benznidazole (Bz). In addition, the potential of monotherapy and combined treatments in relation to the ability to induce parasitological cure, and to prevent or reduce the myocarditis index and its influences on the cellular and humoral immune response of experimentally infected animals by T.cruzi Y strain were evaluated. The results demonstrated that both the ELF and the isolated TC have trypanocidal activity in vitro, presenting the IC50 of 0.6426 μg/mL and 0.4022 μg/mL, respectively. These results were considered promising when compared to the IC50 of 9.32 μg/mL of the reference drug Bz. It was also observed that ELF and TC reduced the rate of infection by amastigotes in H9c2 cells by 32% and 51%, respectively, while Bz inhibited 36%. In the in vivo experiments, it was verified that both ELF and TC could suppress the parasitemia of the animals experimentally infected by strain Y, being observed a potentiation of this activity when the STLs were combined with Bz, once the treatment with ELF + Bz induced 70% cure in the animals, the same rate was observed in the treatment with Bz monotherapy. The TC + Bz combination could completely suppress the parasitaemia and the tests of the curing criterion confirmed a cure rate of 100% among the animals submitted to this treatment. Through dosing of cytokines has been observed that combination therapy inhibited the production of IFN-γ and TNF-α, important inflammatory cytokines related to tissue injury associated with Chagas’ disease, and was also found that animals subjected to treatments containing the STLs, presented higher IL-10 cytokine productions, suggesting a modulation of the immune response induced by the anti-inflammatory activity of the STLs. The benefit of modulation of the immune response was also evidenced by the absence and / or reduction of myocarditis in the animals receiving combined treatment with ELF + Bz and TC + Bz. In general, our results demonstrate that the combined treatment between TC and Bz is promising, since in addition to inducing the cure rate superior to Bz in monotherapy, it still prevented the myocarditis in the animals. In addition, the STLs are capable of interfering in the immune response of the host, and this interference may be related to a better prognosis of the disease.