The trans-sialidase, the major Trypanosoma cruzi virulence factor: Three decades of studies.

Chagas' disease is a potentially life-threatening disease caused by the protozoan parasite Trypanosoma cruzi. Since the description of Chagas'disease in 1909 extensive research has identified important events in the disease in order to understand the biochemical mechanism that modulates T. cruzi-host cell interactions and the ability of the parasite to ensure its survival in the infected host. Exactly 30 years ago, we presented evidence for the first time of a trans-sialidase activity in T. cruzi (T. cruzi-TS). This enzyme transfers sialic acid from the host glycoconjugates to the terminal ß-galactopyranosyl residues of mucin-like molecules on the parasite's cell surface. Thenceforth, many articles have provided convincing data showing that T. cruzi-TS is able to govern relevant mechanisms involved in the parasite's survival in the mammalian host, such as invasion, escape from the phagolysosomal vacuole, differentiation, down-modulation of host immune responses, among others. The aim of this review is to cover the history of the discovery of T. cruzi-TS, as well as some well-documented biological effects encompassed by this parasite's virulence factor, an enzyme with potential attributes to become a drug target against Chagas disease.

Leishmanicidal effects of piperine, its derivatives, and analogues on Leishmania amazonensis.

Leishmaniasis is a tropical disease caused by protozoan parasites of the genus Leishmania which affects 12 million people worldwide. The discovery of drugs for the treatment of leishmaniasis is a pressing concern in global health programs. The aim of this study aim was to evaluate the leishmanicidal effect of piperine and its derivatives/analogues on Leishmania amazonensis. Our results showed that piperine and phenylamide are active against promastigotes and amastigotes in infected macrophages. Both drugs induced mitochondrial swelling, loose kinetoplast DNA, and led to loss of mitochondrial membrane potential. The promastigote cell cycle was also affected with an increase in the G1 phase cells and a decrease in the S-phase cells, respectively, after piperine and phenylamide treatment. Lipid analysis of promastigotes showed that piperine reduced triglyceride, diacylglycerol, and monoacylglycerol contents, whereas phenylamide only reduced diacylglycerol levels. Both drugs were deemed non toxic to macrophages at 50 µM as assessed by XTT (sodium 2,3,-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)-carbonyl]-2H-tetrazolium inner salt), Trypan blue exclusion, and phagocytosis assays, whereas low toxicity was noted at concentrations higher than 150 µM. None of the drugs induced nitric oxide (NO) production. By contrast, piperine reduced NO production in activated macrophages. The isobologram analysis showed that piperine and phenylamide acted synergistically on the parasites suggesting that they affect different target mechanisms. These results indicate that piperine and its phenylamide analogue are candidates for development of drugs for cutaneous leishmaniasis treatment.