title: Strain-dependent induction of human enterocyte apoptosis by blastocystis disrupts epithelial barrier and ZO-1 organization in a caspase 3- and 9-dependent manner.
abstract: Blastocystis is an emerging protistan parasite colonizing the human intestine. It is frequently reported to cause general intestinal symptoms of vomiting, diarrhea, and abdominal pain. We recently demonstrated that Blastocystis rearranged cytoskeletal proteins and induced intestinal epithelial barrier compromise. The effect of Blastocystis on enterocyte apoptosis is unknown, and a possible link between microbially induced enterocyte apoptosis and increased epithelial permeability has yet to be determined. The aim of this study is to assess if Blastocystis induces human enterocyte apoptosis and whether this effect influences human intestinal epithelial barrier function. Monolayers of polarized human colonic epithelial cell-line Caco-2 were incubated with Blastocystis subtype 7 and subtype 4. Assays for both early and late markers of apoptosis, phosphatidylserine externalization, and nuclear fragmentation, respectively, showed that Blastocystis ST-7, but not ST-4, significantly increased apoptosis in enterocytes, suggesting that Blastocystis exhibits host specificity and strain-to-strain variation in pathogenicity. ST-7 also activated Caco-2 caspases 3 and 9 but not 8. ST-7 induced changes in epithelial resistance, permeability, and tight junction (ZO-1) localization. Pretreatment of Caco-2 monolayers with a pan-caspase inhibitor z-VAD-fmk significantly inhibited these changes. This suggests a role for enterocyte apoptosis in Blastocystis-mediated epithelial barrier compromise in the human intestine.
authors.affiliation: Laboratory of Molecular and Cellular Parasitology, Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science, Drive 2, Singapore 117596.
authors.forename: Zhaona
authors.identifier: 0000-0003-3518-4017
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Laboratory of Molecular and Cellular Parasitology, Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science, Drive 2, Singapore 117596.
authors.forename: Haris
authors.identifier: 0000-0002-0007-9658
authors.initials: H
authors.lastname: Mirza
authors.affiliation: Laboratory of Molecular and Cellular Parasitology, Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science, Drive 2, Singapore 117596.
authors.forename: Joshua D W
authors.initials: JD
authors.lastname: Teo
authors.affiliation: Laboratory of Molecular and Cellular Parasitology, Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science, Drive 2, Singapore 117596.
authors.forename: Kevin S W
authors.initials: KS
authors.lastname: Tan
mesh_terms: D017209:Apoptosis; D016844:Blastocystis / Q000502:physiology*; D018938:Caco-2 Cells; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D002467:Cell Nucleus; D020895:Enterocytes / Q000166:cytology / Q000469:parasitology; D006790:Host-Parasite Interactions / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000469:parasitology; D062826:Zonula Occludens-1 Protein / Q000378:metabolism*
chemical_list: C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D020169:Caspases