EFFECT OF CLOSTRIDIUM-DIFFICILE TOXIN-A ON HUMAN INTESTINAL EPITHELIAL-CELLS - INDUCTION OF INTERLEUKIN-8 PRODUCTION AND APOPTOSIS AFTER CELL DETACHMENT

Clostridium difficile is the aetiological agent of pseudomembranous co litis, and animal studies suggest the essential role of secreted toxin A in inducing disease. This study examined the biological responses t o toxin A by human intestinal epithelial cells. Confluent monolayers o f Caco2, HT29, and T84 cells and primary epithelial cells in organ cul tures of human colonic biopsy specimens and after detachment with EDTA were studied. Interleukin 8 was assayed using enzyme linked immunosor bent assay (ELISA). Purified C difficile toxin A induced cell rounding and detachment of monolayers of the epithelial cell lines. Cells in d etached monolayers initially remained viable while adherent to each ot her. Subsequently, an increasing number of apoptotic cells appeared in suspension. Exposure to toxin A for 24 hours induced interleukin 8 pr oduction in T84 and HT29 cells. Toxin A also induced epithelial cell r ounding, detachment, and apoptosis in organ cultures of human colonic biopsy specimens. During culture (in medium only), EDTA detached colon ic epithelial cells produced interleukin 8 and cell death occurred by apoptosis. Colonic disease by C difficile may be initiated by toxin A mediated induction of epithelial cell interleukin 8 production and apo ptosis after cell detachment from the basement membrane. Studies on is olated (toxin untreated) colonic epithelial cells suggest that interle ukin 8 production and apoptosis occur as a consequence of cell injury and detachment.