title: Clostridium difficile toxins A and B directly stimulate human mast cells.
abstract: Clostridium difficile toxins A and B (TcdA and TcdB) are the causative agents of antibiotic-associated pseudomembranous colitis. Mucosal mast cells play a crucial role in the inflammatory processes underlying this disease. We studied the direct effects of TcdA and TcdB on the human mast cell line HMC-1 with respect to degranulation, cytokine release, and the activation of proinflammatory signal pathways. TcdA and TcdB inactivate Rho GTPases, the master regulators of the actin cytoskeleton. The inactivation of Rho GTPases induced a reorganization of the actin cytoskeleton accompanied by morphological changes of cells. The TcdB-induced reorganization of the actin cytoskeleton in HMC-1 cells reduced the number of electron-dense mast cell-specific granules. Accordingly, TcdB induced the release of hexosaminidase, a marker for degranulation, in HMC-1 cells. The actin rearrangement was found to be responsible for degranulation since latrunculin B induced a comparable hexosaminidase release. In addition, TcdB as well as latrunculin B induced the activation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase 1/2 and also resulted in a p38 MAPK-dependent increased formation of prostaglandins D(2) and E(2). The autocrine stimulation of HMC-1 cells by prostaglandins partially contributed to the degranulation. Interestingly, TcdB-treated HMC-1 cells, but not latrunculin B-treated HMC-1 cells, showed a strong p38 MAPK-dependent increase in interleukin-8 release. Differences in the mast cell responses to TcdB and latrunculin B are probably due to the presence of functionally inactive Rho GTPases in toxin-treated cells. Thus, the HMC-1 cell line is a promising model for studying the direct effects of C. difficile toxins on mast cells independently of the tissue context.
authors.affiliation: Department of Toxicology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Gesa K A
authors.initials: GK
authors.lastname: Meyer
authors.forename: Anne
authors.initials: A
authors.lastname: Neetz
authors.forename: Gudrun
authors.initials: G
authors.lastname: Brandes
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Tsikas
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Butterfield
authors.forename: Ingo
authors.initials: I
authors.lastname: Just
authors.forename: Ralf
authors.initials: R
authors.lastname: Gerhard
mesh_terms: D001426:Bacterial Proteins / Q000276:immunology*; D001427:Bacterial Toxins / Q000276:immunology*; D015550:Cell Degranulation; D002460:Cell Line; D016360:Clostridioides difficile / Q000472:pathogenicity*; D016207:Cytokines / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004768:Enterotoxins / Q000276:immunology*; D005947:Glucose / Q000378:metabolism; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology; D008407:Mast Cells / Q000276:immunology* / Q000382:microbiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D011457:Prostaglandins D / Q000096:biosynthesis; D011458:Prostaglandins E / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D016207:Cytokines; D004768:Enterotoxins; D016209:Interleukin-8; D011457:Prostaglandins D; D011458:Prostaglandins E; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D006596:Hexosaminidases; D020741:rho GTP-Binding Proteins; D005947:Glucose