Crotoxin stimulates an M1 activation profile in murine macrophages during Leishmania amazonensis infection

Federal University of Para. Institute of Biological Sciences. Laboratory of Parasitology and Laboratory of Structural Biology. Bel?m, PA, Brazil / National Institute of Science and Technology in Structural Biology and Bioimaging. Rio de Janeiro, RJ, Brazil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil / National Institute of Science and Technology in Structural Biology and Bioimaging. Rio de Janeiro, RJ, Brazil. Federal University of Para. Institute of Biological Sciences. Laboratory of Parasitology and Laboratory of Structural Biology. Bel?m, PA, Brazil. University of S?o Paulo. Department,Institute of Biomedical Sciences. Cell and Developmental Biology. S?o Paulo, SP, Brazil. Butantan Institute. Laboratory of Pathophysiology. S?o Paulo, SP, Brazil / University of S?o Paulo. Institute of Biomedical Sciences. Department of Pharmacology. S?o Paulo, SP, Brazil. Federal University of Para. Institute of Biological Sciences. Laboratory of Parasitology and Laboratory of Structural Biology. Bel?m, PA, Brazil / National Institute of Science and Technology in Structural Biology and Bioimaging. Rio de Janeiro, RJ, Brazil. American tegumentary leishmaniasis is caused by different species of Leishmania. This protozoan employs several mechanisms to subvert the microbicidal activity of macrophages and, given the limited efficacy of current therapies, the development of alternative treatments is essential. Animal venoms are known to exhibit a variety of pharmacological activities, including antiparasitic effects. Crotoxin (CTX) is the main component of Crotalus durissus terrificus venom, and it has several biological effects. Nevertheless, there is no report of CTX activity during macrophage - Leishmania interactions. Thus, the main objective of this study was to evaluate whether CTX has a role in macrophage M1 polarization during Leishmania infection murine macrophages, Leishmania amazonensis promastigotes and L. amazonensis-infected macrophages were challenged with CTX. MTT [3-(4,5dimethylthiazol-2-yl)-2,5-diphenyl tetrasodium bromide] toxicity assays were performed on murine macrophages, and no damage was observed in these cells. Promastigotes, however, were affected by treatment with CTX (IC50 = 22?86 ?g mL-1) as were intracellular amastigotes. Macrophages treated with CTX also demonstrated increased reactive oxygen species production. After they were infected with Leishmania, macrophages exhibited an increase in nitric oxide production that converged into an M1 activation profile, as suggested by their elevated production of the cytokines interleukin-6 and tumour necrosis factor-? and changes in their morphology. CTX was able to reverse the L. amazonensis-mediated inhibition of macrophage immune responses and is capable of polarizing macrophages to the M1 profile, which is associated with a better prognosis for cutaneous leishmaniasis treatment.