Toxin B of Clostridium difficile activates human VIP submucosal neurons, in part via an IL-1[beta]-dependent pathway

Neunlist, M., J. Barouk, K. Michel, I. Just, T. Oreshkova, M. Schemann, and J. P. Galmiche. Toxin B of Clostridium difficile activates human VIP submucosal neurons, in part via an IL-1[beta]-dependent pathway. Am J Physiol Gastrointest Liver Physiol 285: G1049-G1055, 2003. First published June 11, 2003; 10.1152/ajpgi.00487.2002.--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-1[beta]. 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 ([V.sub.m]) response of submucosal neurons to local application of toxin B and IL-1[beta] 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 [+ or -] 22.5%) but only 19.4 [+ or -] 14.0% for SP. Toxin B induced a rapid rise in IL-1[beta] mRNA level and a sixfold increase in IL-1[beta] 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-1[beta] significantly increased c-Fos expression in submucosal neurons compared with the control (34.2 [+ or -] 10.1 vs. 5.1 [+ or -] 1.3% of NSE neurons). Microejection of toxin B had no effect on the [V.sub.m] of enteric neurons. Evidence of a direct excitatory effect of IL-1[beta] on [V.sub.m] 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-1[beta]-dependent pathway. c-Fos; voltage-sensitive dyes; cytokines; human submucosal plexus