Trypanosoma cruzi proliferate and differentiate inside different compartments of triatomines gut that is the first environment encountered by T. cruzi. Due to its complex life cycle, the parasite is constantly exposed to reactive oxygen species (ROS). We tested the influence of the pro-oxidant molecules H₂O₂ and the superoxide generator, Paraquat, as well as, metabolism products of the vector, with distinct redox status, in the proliferation and metacyclogenesis. These molecules are heme, hemozoin and urate. We also tested the antioxidants NAC and GSH. Heme induced the proliferation of epimastigotes and impaired the metacyclogenesis. β-hematin, did not affect epimastigote proliferation but decreased parasite differentiation. Conversely, we show that urate, GSH and NAC dramatically impaired epimastigote proliferation and during metacyclogenesis, NAC and urate induced a significant increment of trypomastigotes and decreased the percentage of epimastigotes. We also quantified the parasite loads in the anterior and posterior midguts and in the rectum of the vector by qPCR. The treatment with the antioxidants increased the parasite loads in all midgut sections analyzed. In vivo, the group of vectors fed with reduced molecules showed an increment of trypomastigotes and decreased epimastigotes when analyzed by differential counting. Heme stimulated proliferation by increasing the cell number in the S and G2/M phases, whereas NAC arrested epimastigotes in G1 phase. NAC greatly increased the percentage of trypomastigotes. Taken together, these data show a shift in the triatomine gut microenvironment caused by the redox status may also influence T. cruzi biology inside the vector. In this scenario, oxidants act to turn on epimastigote proliferation while antioxidants seem to switch the cycle towards metacyclogenesis. This is a new insight that defines a key role for redox metabolism in governing the parasitic life cycle.

Heme is a ubiquitous molecule that has a number of physiological roles. The toxic effects of this molecule have been demonstrated in various models, based on both its pro-oxidant nature and through a detergent mechanism. It is estimated that about 10 mM of heme is released during blood digestion in the blood-sucking bug's midgut. The parasite Trypanosoma cruzi, the agent of Chagas' disease, proliferates in the midgut of the insect vector; however, heme metabolism in trypanosomatids remains to be elucidated. Here we provide a mechanistic explanation for the proliferative effects of heme on trypanosomatids. Heme, but not other porphyrins, induced T. cruzi proliferation, and this phenomenon was accompanied by a marked increase in reactive oxygen species (ROS) formation in epimastigotes when monitored by ROS-sensitive fluorescent probes. Heme-induced ROS production was time-and concentration-dependent. In addition, lipid peroxidation and the formation of 4-hydroxy-2-nonenal (4-HNE) adducts with parasite proteins were increased in epimastigotes in the presence of heme. Conversely, the antioxidants urate and GSH reversed the heme-induced ROS. Urate also decreased parasite proliferation. Among several protein kinase inhibitors tested only specific inhibitors of CaMKII, KN93 and Myr-AIP, were able to abolish heme-induced ROS formation in epimastigotes leading to parasite growth impairment. Taken together, these data provide new insight into T. cruzi- insect vector interactions: heme, a molecule from the blood digestion, triggers epimastigote proliferation through a redox-sensitive signalling mechanism.

Trypanosoma cruzi, the protozoan responsible for Chagas disease, has a complex life cycle comprehending two distinct hosts and a series of morphological and functional transformations. Hemoglobin degradation inside the insect vector releases high amounts of heme, and this molecule is known to exert a number of physiological functions. Moreover, the absence of its complete biosynthetic pathway inT. cruziindicates heme as an essential molecule for this trypanosomatid survival. Within the hosts,T. cruzihas to cope with sudden environmental changes especially in the redox status and heme is able to increase the basal production of reactive oxygen species (ROS) which can be also produced as byproducts of the parasite aerobic metabolism. In this regard, ROS sensing is likely to be an important mechanism for the adaptation and interaction of these organisms with their hosts. In this paper we discuss the main features of heme and ROS susceptibility inT. cruzibiology.

Plant derived compounds have been shown to be important sources of several anti-cancer agents. As cell cycle deregulation and tumor growth are intimately linked, the discovery of new substances targeting events in this biochemical pathway would be of great value. The anti-leukemic effect of an ethanolic extract of Pterodon pubescens seeds (EEPp) has been previously demonstrated and now we show that a terpenic subfraction (SF5) of EEPp containing farnesol, geranylgeraniol and vouacapan derivatives induces apoptosis in the human chronic myelogenous leukemia cell line K562. This work addresses SF5’s antiproliferative mechanisms in these cells since they are still unclear.

Trypanosoma cruzi, the causative agent of Chagas disease, faces changes in redox status and nutritional availability during its life cycle. However, the influence of oxygen fluctuation upon the biology of T. cruzi is unclear. The present work investigated the response of T. cruzi epimastigotes to hypoxia. The parasites showed an adaptation to the hypoxic condition, presenting an increase in proliferation and a reduction in metacyclogenesis. Additionally, parasites cultured in hypoxia produced more reactive oxygen species (ROS) compared to parasites cultured in normoxia. The analyses of the mitochondrial physiology demonstrated that hypoxic condition induced a decrease in both oxidative phosphorylation and mitochondrial membrane potential (ΔΨm) in epimastigotes. In spite of that, ATP levels of parasites cultivated in hypoxia increased. The hypoxic condition also increased the expression of the hexokinase and NADH fumarate reductase genes and reduced NAD(P)H, suggesting that this increase in ATP levels of hypoxia-challenged parasites was a consequence of increased glycolysis and fermentation pathways. Taken together, our results suggest that decreased oxygen levels trigger a shift in the bioenergetic metabolism of T. cruzi epimastigotes, favoring ROS production and fermentation to sustain ATP production, allowing the parasite to survive and proliferate in the insect vector.