Toxin B of Clostridium difficile activates human VIP submucosal neurons, in part via an IL-1beta-dependent pathway.
This study investigated whether toxin B of Clostridium difficile can activate human submucosal neurons and the involved pathways. Isolated segments of human colon were placed in organ culture for 3 h in the presence of toxin B or IL-1beta. Whole mounts of internal submucosal plexus were stained with antibodies against c-Fos, neuron-specific enolase (NSE), vasoactive intestinal polypeptide (VIP), and substance P (SP). The membrane potential (Vm) response of submucosal neurons to local application of toxin B and IL-1beta was determined by a multisite optical recording technique. Toxin B (0.1 to 10 ng/ml) increased the proportion of c-Fos-positive neurons dose dependently compared with the control. In the presence of toxin B (10 ng/ml), most c-Fos-positive neurons were immunoreactive for VIP (79.8 +/- 22.5%) but only 19.4 +/- 14.0% for SP. Toxin B induced a rapid rise in IL-1beta mRNA level and a sixfold increase in IL-1beta protein in supernatant after 3 h of incubation. c-Fos expression induced by toxin B was reduced dose dependently by IL-1 receptor antagonist (0.1-10 ng/ml). IL-1beta significantly increased c-Fos expression in submucosal neurons compared with the control (34.2 +/- 10.1 vs. 5.1 +/- 1.3% of NSE neurons). Microejection of toxin B had no effect on the Vm of enteric neurons. Evidence of a direct excitatory effect of IL-1beta on Vm was detected in a minority of enteric neurons. Therefore, toxin B of C. difficile activates VIP-positive submucosal neurons, at least in part, via an indirect IL-1beta-dependent pathway.
Neunlist
M
M
Institut National de la Santé et de la Recherche Médicale U539; Hôtel-Dieu Hospital, 1, place Alexis Ricordeau, 44035 Nantes, France. michel.neunlist@sante.univ-nantes.fr
Barouk
J
J
Michel
K
K
Just
I
I
Oreshkova
T
T
Schemann
M
M
Galmiche
J P
JP
D000368:Aged; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology*; D003106:Colon / Q000294:innervation*; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D013368:Submucous Plexus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D007375:Interleukin-1; D016760:Proto-Oncogene Proteins c-fos; C031815:toxB protein, Clostridium difficile; D014660:Vasoactive Intestinal Peptide