cruzi developmental forms were susceptible to the melittin peptide; the epimastigotes (the proliferative insect vector-borne stage), the trypomastigotes (the infective, non-proliferative form), and the intracellular amastigotes (the infective, proliferative form) were found to be sensitive to the venom. The different IC50/1 day or LD50/1 day values indicated that low doses were mainly effective against these infective forms. The electron microscopy data, together with the fluorimetry and flow cytometry analyses, strongly suggested that the T. cruzi parasites were being killed via different cell death mechanisms, which is similar to what we observed with the A. mellifera
venom treatment ( Adade et al., 2012). Programmed cell death (PCD) is a genetically regulated process and is pivotal to the homeostasis of metazoan organisms. This process has been characterized based on morphological criteria and environmental conditions HSP inhibitor and classified into three different types: apoptosis
Belnacasan (I-PCD type), autophagy (II-PCD type) and programmed necrosis (III-PCD type) (Kroemer et al., 2009). Once triggered, apoptosis is characterized by cytoplasmic retraction, chromatin condensation, chromosomal DNA fragmentation, mitochondrial swelling with alterations in the membrane potential and permeability, exposure of phosphatidylserine residues at the outer plasma membrane, the activation of caspases, blebbing of the plasma membrane, and the packaging of cellular constituents into apoptotic vesicles
(Guimarães and Linden, 2004). In contrast, Metalloexopeptidase autophagy is a complex signaling pathway involving more than 30 well-conserved Atg proteins that function to remove or remodel damaged cellular structures. It is morphologically characterized by the formation of autophagosomes (double-membrane vesicles) that are responsible for the engulfment of cytoplasmic constituents, the development of concentric membrane structures in the cytosol and surrounding organelles (Tsujimoto and Shimizu, 2005; Meijer et al., 2007). Here, we showed that melittin-treated parasites exhibited several morphological alterations that could be characterized as autophagy and apoptosis, predominantly. The treated epimastigotes exhibited mitochondrial damage without alterations of the kDNA networks. The most remarkable feature detected was the endoplasmic reticulum profile that surrounded various structures, resembling autophagosomes. These alterations were confirmed by the decrease in the mitochondrial potential and the increase in monodansyl cadaverine staining. Furthermore, the lack of TUNEL staining among treated epimastigotes reinforced the notion of an autophagic cell death phenotype. The morphological changes observed in melittin-treated epimastigotes were in agreement with our previous studies that described autophagy-mediated epimastigote cell death upon A. mellifera venom treatment ( Adade et al., 2012).