The effects of endoplasmic reticulum stressors, tunicamycin and dithiothreitol on Trypanosoma cruzi

In higher eukaryotic cells, pertubations in ER environment, called ER stress, usually activate unfolded protein response (UPR) pathway in an attempt to re-stablish the ER homeostasis and prevent cell death. Because trypanosomatids appear to lack the classical UPR, it is not clear how these parasites respond to ER stress. Thus, the aim of this work was to evaluate the effects of ER stressors tunicamycin (TM) or dithiothreitol (DTT) on Trypanosoma cruzi. The TM treatment showed strong trypanostatic effect. At 2.5 μg/mL of TM, the mRNA levels of both binding protein (BiP) and calreticulin (CRT) increased significantly, whereas the protein levels of BiP remained stable. TM treatment induced ultrastructural changes compatible with an autophagic process. The DTT treatment inhibited the cell growth, induced drastic morphological changes, mitochondrial membrane depolarization and increased ROS production. The expression of BiP apparently was not affected by DTT, whereas the mRNA levels of BiP and CRT were significantly reduced. Our results suggest that TM induces autophagy/ER-phagy without causing substantial injury to the parasite. Conversely, the DTT treatment seems to rupture the mitochondrion homeostasis leading to parasite death. The comprehension of the mechanisms behind the susceptibility of T. cruzi to ER stress open perspectives for the development of chemotherapeutic agents addressed to these pathways.