title: Acidic extracellular pH shifts colorectal cancer cell death from apoptosis to necrosis upon exposure to propionate and acetate, major end-products of the human probiotic propionibacteria.
abstract: The human probiotic Propionibacterium freudenreichii kills colorectal adenocarcinoma cells through apoptosis in vitro via its metabolites, the short chain fatty acids (SCFA), acetate and propionate. However, the precise mechanisms, the kinetics of cellular events and the impact of environmental factors such as pH remained to be specified. For the first time, this study demonstrates a major impact of a shift in extracellular pH on the mode of propionibacterial SCFA-induced cell death of HT-29 cells, in the pH range 5.5 to 7.5 prevailing within the colon. Propionibacterial SCFA triggered apoptosis in the pH range 6.0 to 7.5, a lethal process lasting more than 96 h. Indeed at pH 7.5, SCFA induced cell cycle arrest in the G2/M phase, followed by a sequence of cellular events characteristic of apoptosis. By contrast, at pH 5.5, the same SCFA triggered a more rapid and drastic lethal process in less than 24 h. This was characterised by sudden mitochondrial depolarisation, inner membrane permeabilisation, drastic depletion in ATP levels and ROS accumulation, suggesting death by necrosis. Thus, in digestive cancer prophylaxis, the observed pH-mediated switch between apoptosis and necrosis has to be taken into account in strategies involving SCFA production by propionibacteria to kill colon cancer cells.
authors.affiliation: UMR 1253 INRA Agrocampus, Science & Technologie du Lait et de l'Oeuf, Rennes cedex, France.
authors.forename: Annaïg
authors.initials: A
authors.lastname: Lan
authors.forename: Dominique
authors.initials: D
authors.lastname: Lagadic-Gossmann
authors.forename: Christophe
authors.initials: C
authors.lastname: Lemaire
authors.forename: Catherine
authors.initials: C
authors.lastname: Brenner
authors.forename: Gwénaël
authors.initials: G
authors.lastname: Jan
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D002458:Cell Fractionation; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D048430:Cell Shape; D002843:Chromatin / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation; D005232:Fatty Acids, Volatile / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008928:Mitochondria / Q000378:metabolism; D009336:Necrosis; D019936:Probiotics; D011422:Propionates / Q000378:metabolism*; D011424:Propionibacterium / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D002843:Chromatin; D005232:Fatty Acids, Volatile; D011422:Propionates; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D020169:Caspases; C029658:propionic acid; D019342:Acetic Acid