title: Is Trichomonas tenax a Parasite or a Commensal?
abstract: Trichomonas tenax is considered a commensal organism found under poor oral hygiene conditions. T. tenax presents morphological similarities with T. vaginalis, and there are doubts concerning whether this protist is a parasite and whether it is a genetic variant of T. vaginalis. This study aimed to investigate the capacity of T. tenax to cause mammalian cell damage and compare its cytotoxicity with that of T. vaginalis. Protozoan-host cell interaction assays were performed with Madin-Darby canine kidney, HeLa, and gum cells and 3D spheroids, which were examined by scanning electron and transmission electron microscopy. Cellular viability experiments were also performed. T. tenax attached and had different forms when interacting with mammalian cells and caused damage with time-dependent host-cell viability. We observed that T. tenax produced plasma membrane projections and phagocytosed portions of the mammalian cells. In addition, T. tenax caused membrane blebbing and apoptotic bodies in HeLa cells, thus inducing cell death. Spheroids were also used in interaction assays with T. tenax and they were damaged by these cells. This study shows that T. tenax fulfills the requisites of a parasite, causing damage to different mammalian cells and behaving similarly to T. vaginalis when in contact with target cells in vitro.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil; Instituto Nacional de Metrologia e Qualidade Ambiental, Inmetro, Rio de Janeiro, Brazil.
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Ribeiro
authors.affiliation: Instituto Nacional de Metrologia e Qualidade Ambiental, Inmetro, Rio de Janeiro, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Santos
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil; UNIGRANRIO - Universidade do Grande Rio, Rio de Janeiro, Brazil; INBEB -Instituto Nacional de Biologia Estrutural e Bioimagem, Brazil. Electronic address: marlenebenchimol@gmail.com.
authors.forename: Marlene
authors.initials: M
authors.lastname: Benchimol
mesh_terms: D000818:Animals; D016923:Cell Death; D002462:Cell Membrane / Q000378:metabolism; D002477:Cells / Q000469:parasitology* / Q000648:ultrastructure; D004285:Dogs; D000067128:Extracellular Vesicles / Q000378:metabolism; D006367:HeLa Cells; D006790:Host-Parasite Interactions; D006801:Humans; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010587:Phagocytosis; D014244:Trichomonas / Q000502:physiology* / Q000648:ultrastructure*
keywords: 3D spheroids; Cell cytotoxicity; Trichomonas vaginalis.