title: Human neutrophils are activated by a peptide fragment of Clostridium difficile toxin B presumably via formyl peptide receptor.
abstract: Clostridium difficile may induce antibiotic-associated diarrhoea and, in severe cases, pseudomembranous colitis characterized by tremendous neutrophil infiltration. All symptoms are caused by two exotoxins: TcdA and TcdB. We describe here the activation of isolated human blood neutrophils by TcdB and, moreover, by toxin fragments generated by limited proteolytical digestion. Kinetics and profiles of TcdB-induced rise in intracellular-free Ca(2+) and reactive oxygen species production were similar to that induced by fMLF, which activates the formyl peptide receptor (FPR) recognizing formylated bacterial peptide sequences. Transfection assays with the FPR-1 isoform hFPR26 in HEK293 cells, heterologous desensitization experiments and FPR inhibition via cyclosporine H strongly suggest activation of cells via FPR-1. Domain analyses revealed that the N-terminal glucosyltransferase domain of TcdB is a potent activator of FPR pointing towards an additional mechanism that might contribute to pathogenesis. This pro-inflammatory ligand effect can be triggered even by cleaved and, thus, non-cytotoxic toxin. In summary, we report (i) a ligand effect on neutrophils as completely new molecular mode of action, (ii) pathogenic potential of truncated or proteolytically cleaved 'non-cytotoxic' fragments and (iii) an interaction of the N-terminal glucosyltransferase domain instead of the C-terminal receptor binding domain of TcdB with target cells.
authors.affiliation: Institute of Toxicology, Hannover Medical School, Germany.
authors.forename: Sebastian D
authors.initials: SD
authors.lastname: Goy
authors.affiliation: Institute of Toxicology, Hannover Medical School, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Olling
authors.affiliation: Institute of Pharmacology, Hannover Medical School, Germany.
authors.forename: Detlef
authors.initials: D
authors.lastname: Neumann
authors.affiliation: Institute of Toxicology, Hannover Medical School, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Pich
authors.affiliation: Institute of Toxicology, Hannover Medical School, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Gerhard
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D016360:Clostridioides difficile / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D009504:Neutrophils / Q000276:immunology* / Q000382:microbiology*; D010446:Peptide Fragments / Q000378:metabolism*; D044042:Receptors, Formyl Peptide / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C469986:FPR1 protein, human; D010446:Peptide Fragments; D044042:Receptors, Formyl Peptide; C031815:toxB protein, Clostridium difficile