title: IL-8 release and neutrophil activation by Clostridium difficile toxin-exposed human monocytes.
abstract: Neutrophil infiltration is central to the pathogenesis of Clostridium difficile toxin A-induced enterocolitis. This study examines whether monocyte activation by C. difficile toxins is instrumental in initiating neutrophil activation and recruitment. Human monocytes were exposed to low concentrations of highly purified C. difficile toxins, and the conditioned media were harvested for cytokine and functional assays. Monocytes exposed to C. difficile toxin A (10(-10) M) or toxin B (10(-12) M) released 100 and 20 times basal levels, respectively, of the neutrophil chemoattractant interleukin-8 (IL-8). Reverse transcriptase-polymerase chain reaction demonstrated a marked increase in IL-8 mRNA expression by monocytes 3 h after toxin exposure. Conditioned media from toxin A- and toxin B-treated monocytes stimulated neutrophil migration (324 and 245% of control, respectively). This effect was completely blocked by IL-8 antiserum. These media also upregulated neutrophil CD11b/CD18 and endothelial cell intercellular adhesion molecule-1 expression. C. difficile toxins, at low concentrations, potently activate monocytes to release factors, including IL-8, that facilitate neutrophil extravasation and tissue infiltration. Our findings indicate a major role for toxin-mediated monocyte and macrophage activation in C. difficile colitis.
authors.affiliation: Section of Gastroenterology, Department of Veterans Affairs Medical Center, Boston 02130, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Linevsky
authors.forename: C
authors.initials: C
authors.lastname: Pothoulakis
authors.forename: S
authors.initials: S
authors.lastname: Keates
authors.forename: M
authors.initials: M
authors.lastname: Warny
authors.forename: A C
authors.initials: AC
authors.lastname: Keates
authors.forename: J T
authors.initials: JT
authors.lastname: Lamont
authors.forename: C P
authors.initials: CP
authors.lastname: Kelly
mesh_terms: D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000633:toxicity; D018821:CD18 Antigens / Q000096:biosynthesis; D002478:Cells, Cultured; D016360:Clostridioides difficile; D017077:Culture Media, Conditioned; D004768:Enterotoxins / Q000633:toxicity*; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis; D016209:Interleukin-8 / Q000096:biosynthesis*; D007700:Kinetics; D016177:Macrophage-1 Antigen / Q000096:biosynthesis; D009000:Monocytes / Q000187:drug effects* / Q000502:physiology; D018375:Neutrophil Activation / Q000187:drug effects / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D018821:CD18 Antigens; D017077:Culture Media, Conditioned; D004768:Enterotoxins; D007106:Immune Sera; D016209:Interleukin-8; D016177:Macrophage-1 Antigen; D012333:RNA, Messenger; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; D018799:Intercellular Adhesion Molecule-1