Trypanosoma cruzi is a protozoan responsible for Chagas disease and has a complex life cycle including vertebrate (mammals) and invertebrate (insects) hosts. The parasite presents proliferative and infective forms that are challenged throughout their cycle as different sources of nutrients, pH, immune system, and levels of reactive oxygen species (ROS). Although ROS cause damage to cells and tissues when their levels are controlled, they are involved in signal transduction pathways involved in cell growth and differentiation. Curiously, the proliferation of epimastigote inside the bug insect is favored by high levels of ROS from the digestion of blood meal, and it is regulated by a cellular signaling mechanism involving heme and CaMKII. On the other hand, the differentiation of epimastigote into metacyclic trypomastigote in the rectum occurs in the reduced state. Interestingly, when the parasite infects the vertebrate, the immune system recognizes this pathogen and macrophages become activated. Thus, NADPH oxidase produces ROS that helps the parasite enter the mammalian cells, improving the infection. The parasite thrives inside the mammalian cells also involving ROS. Thus, the life cycle of Trypanosoma cruzi obeys a fine tuning of the redox state, not affecting the host cells and being helpful to the parasite.
Part of the book: Biology of Trypanosoma cruzi