title: Caspase-3-like protease influences but is not essential for DNA fragmentation in Blastocystis undergoing apoptosis.
abstract: Blastocystis hominis undergo apoptosis after treatment with a cytotoxic monoclonal antibody (MAb), 1D5, by mechanisms that are not fully understood, although our previous study demonstrated that caspase-3-like protease activity is involved. To elucidate the mechanism of MAb 1D5-induced apoptosis, we inhibited Blastocystis caspase-3-like protease to investigate if there would be a concomitant decrease in in situ DNA fragmentation. However, MAb 1D5-induced apoptosis, evidenced by DNA fragmentation, was not completely blocked by pretreating with specific caspase-3 inhibitor, Ac-DEVD-CHO, indicating that caspase-independent apoptotic pathways might also be involved. Our results also revealed that the treatment with MAb 1D5 resulted in the loss of mitochondrial membrane potential (deltapsim), independent of Ac-DEVD-CHO pretreatment. In conclusion, this study demonstrates that MAb 1D5-induced apoptosis in B. hominis is not wholly dependent on caspase-3-like protease activity and is associated with mitochondrial dysregulation. This is the first report showing evidence for complex apoptotic pathways in a unicellular parasite.
authors.affiliation: Laboratory of Molecular and Cellular Parasitology, Department of Microbiology, Faculty of Medicine, National University of Singapore, Singapore.
authors.forename: A M A
authors.initials: AM
authors.lastname: Nasirudeen
authors.forename: Kevin S W
authors.initials: KS
authors.lastname: Tan
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D016845:Blastocystis hominis / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D048429:Cell Size / Q000187:drug effects; D004247:DNA / Q000187:drug effects*; D053938:DNA Fragmentation / Q000187:drug effects*; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D061945:Caspase Inhibitors; D009842:Oligopeptides; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; D004247:DNA; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases