title: Metronidazole induces programmed cell death in the protozoan parasite Blastocystis hominis.
abstract: Previous studies by the authors have shown that the protozoan parasite Blastocystis hominis succumbed to a cytotoxic monoclonal antibody with a number of cellular and biochemical features characteristic of apoptosis in higher eukaryotes. The present study reports that apoptosis-like features are also observed in growing cultures of axenic B. hominis upon exposure to metronidazole, a drug commonly used for the treatment of blastocystosis. Upon treatment with the drug, B. hominis cells displayed key morphological and biochemical features of programmed cell death (PCD), viz. nuclear condensation and nicked DNA in nucleus, reduced cytoplasmic volume, externalization of phosphatidylserine and maintenance of plasma membrane integrity with increasing permeability. This present study also supports the authors' previously postulated novel function for the B. hominis central vacuole in PCD; it acts as a repository where apoptotic bodies are stored before being released into the extracellular space. The implications and possible roles of PCD in B. hominis are discussed.
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117597.
authors.forename: A M A
authors.initials: AMA
authors.lastname: Nasirudeen
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117597.
authors.forename: Yap Eu
authors.initials: YE
authors.lastname: Hian
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117597.
authors.forename: Mulkit
authors.initials: M
authors.lastname: Singh
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, 5 Science Drive 2, Singapore 117597.
authors.forename: Kevin S W
authors.initials: KSW
authors.lastname: Tan
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D016845:Blastocystis hominis / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D053938:DNA Fragmentation; D008795:Metronidazole / Q000494:pharmacology*; D008854:Microscopy, Electron; D010718:Phosphatidylserines / Q000378:metabolism
chemical_list: D000981:Antiprotozoal Agents; D010718:Phosphatidylserines; D008795:Metronidazole