Toxin A (TcdA) and toxin B (
TcdB) are the major
virulence factors of Clostridium difficile and are the causative agents for clinical symptoms, such as secretory diarrhoea and
pseudomembranous colitis. Mast cells are essentially involved in the toxin-induced colonic inflammatory processes. To study the direct effects of these toxins on the expression of inflammatory genes, a
DNA microarray containing evaluated probes of 90 selected inflammatory genes was applied to the immature mast cell line HMC-1. TcdA and
TcdB induced up-regulation of only a limited number of genes within the early phase of cell treatment.
Interleukin-8 (IL-8),
transcription factor c-jun and
heme oxygenase-1 messenger RNA (
mRNA) increased more than 2-fold. In contrast,
IL-16, known as a CD4(+) T-cell
chemoattractant factor and the
chemokine receptor cKit were down-regulated. Stimulation of HMC-1 cells with
IL-8 had no effect on
IL-16 mRNA level, indicating that both
cytokines were independently affected by the toxins. Regulation of both
cytokines, however, depended on glucosylation of
Rho GTPases as tested by application of
enzyme-deficient TcdA or
TcdB. Down-regulation of total and secreted
IL-16 protein was checked by
enzyme-linked
immunosorbent assay. The data implicate that TcdA and
TcdB affect lymphocyte migration by modulating release of the
chemoattractant factor
IL-16 from mast cells. In addition, this is the first report showing that
Rho GTPases are involved in the regulation of
IL-16 expression.