Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, presents a variable clinical course, varying from asymptomatic to serious debilitating pathologies with cardiac, digestive or cardio-digestive impairment. Previous studies using two clonal T. cruzi populations, Col1.7G2 (T. cruzi I) and JG (T. cruzi II) demonstrated that there was a differential tissue distribution of these parasites during infection in BALB/c mice, with predominance of JG in the heart. To date little is known about the mechanisms that determine this tissue selection. Upon infection, host cells respond producing several factors, such as reactive oxygen species (ROS), cytokines, among others. Herein and in agreement with previous data from the literature we show that JG presents a higher intracellular multiplication rate when compared to Col1.7G2. We also showed that upon infection cardiomyocytes in culture may increase the production of oxidative species and its levels are higher in cultures infected with JG, which expresses lower levels of antioxidant enzymes. Interestingly, inhibition of oxidative stress severely interferes with the intracellular multiplication rate of JG. Additionally, upon H2O2-treatment increase in intracellular Ca2+ and oxidants were observed only in JG epimastigotes. Data presented herein suggests that JG and Col1.7G2 may sense extracellular oxidants in a distinct manner, which would then interfere differently with their intracellular development in cardiomyocytes.

Chagas disease (CD), caused by the protozoa , is a chronic illness in which parasites persist in the host-infected tissues for years. invasion in cardiomyocytes elicits the production of pro-inflammatory mediators [TNF-α, IL-1β, IFN-γ; nitric oxide (NO)], leading to mitochondrial dysfunction with increased superoxide radical (O), hydrogen peroxide (HO) and peroxynitrite generation. We hypothesize that these redox mediators may control parasite proliferation through the induction of intracellular amastigote programmed cell death (PCD). In this work, we show that (CL-Brener strain) infection in primary cardiomyocytes produced an early (24 h post infection) mitochondrial dysfunction with HO generation and the establishment of an oxidative stress evidenced by FoxO3 activation and target host mitochondrial protein expression (MnSOD and peroxiredoxin 3). TNF-α/IL-1β-stimulated cardiomyocytes were able to control intracellular amastigote proliferation compared with unstimulated cardiomyocytes. In this condition leading to oxidant formation, an enhanced number of intracellular apoptotic amastigotes were detected. The ability of HO to induce PCD was further confirmed in the epimastigote stage of the parasite. HO treatment induced parasite mitochondrial dysfunction together with intra-mitochondrial O generation. Importantly, parasites genetically engineered to overexpress mitochondrial Fe-superoxide dismutase (Fe-SODA) were more infective to TNF-α/IL-1β-stimulated cardiomyocytes with less apoptotic amastigotes; this result underscores the role of this enzyme in parasite survival. Our results indicate that cardiomyocyte-derived diffusible mediators are able to control intracellular amastigote proliferation by triggering PCD and that parasite Fe-SODA tilts the process toward survival as part of an antioxidant-based immune evasion mechanism.

No abstract

Trypanosoma cruzi enters host cells by subverting the mechanism of cell membrane repair. In this process, the parasite induces small injuries in the host cell membrane leading to calcium entry and lysosomal exocytosis, which are followed by compensatory endocytosis events that drive parasites into host cells. We have previously shown that absence of both LAMP-1 and 2, major components of lysosomal membranes, decreases invasion of T. cruzi into host cells, but the mechanism by which they interfere with parasite invasion has not been described. Here we investigated the role of these proteins in parasitophorous vacuole morphology, host cell lysosomal exocytosis, and membrane repair ability. First, we showed that cells lacking only LAMP-2 present the same invasion phenotype as LAMP1/2-/- cells, indicating that LAMP-2 is an important player during T. cruzi invasion process. Second, neither vacuole morphology nor lysosomal exocytosis was altered in LAMP-2 lacking cells (LAMP2-/- and LAMP1/2-/- cells). We then investigated the ability of LAMP-2 deficient cells to perform compensatory endocytosis upon lysosomal secretion, the mechanism by which cells repair their membrane and T. cruzi ultimately enters cells. We observed that these cells perform less endocytosis upon injury when compared to WT cells. This was a consequence of impaired cholesterol traffic in cells lacking LAMP-2 and its influence in the distribution of caveolin-1 at the cell plasma membrane, which is crucial for plasma membrane repair. The results presented here show the major role of LAMP-2 in caveolin traffic and membrane repair and consequently in T. cruzi invasion.

Purpose The purpose of this paper is to analyse how a company’s orientation enables sustainable practices in its supply chains. Specifically, it focusses on how the strategic orientation of a company may stimulate new behaviours in supply chains. Design/methodology/approach Two in-depth qualitative case studies were conducted. Each company’s orientation to sustainable supply chains was studied using cross-case analysis. Findings The organisations in this study have a market-driving (i.e. proactive) orientation instead of market-driven (i.e. responsive) behaviour. Using analysis from the process of change for sustainability and explaining some challenges faced by both organisations, findings indicate that a corporate strategy of sustainability modified the companies’ management processes, even for the company that changed its orientation during the time (i.e. sustainability was not the main strategy at first). Practical examples of actions are provided to illustrate the study’s conclusion that a corporate orientation towards sustainability is an enabling factor in developing sustainable supply chain management (SCM). Research limitations/implications Strategic management plays an important role in a company’s orientation towards sustainability – internally and throughout its supply chains. Based on the findings, future research should measure the effect of a company’s orientation on sustainable SCM. Practical implications This study contributes to the understanding of companies’ strategic orientations and explores ways to introduce sustainability into supply chains. Originality/value The paper examines an underexplored debate regarding to how strategic orientations are related to sustainable SCM, focussing on both market-driving (i.e. proactive) and market-driven (i.e. responsive) orientations.