COLONIC EPITHELIAL-CELL LINES AS A SOURCE OF INTERLEUKIN-8 - STIMULATION BY INFLAMMATORY CYTOKINES AND BACTERIAL LIPOPOLYSACCHARIDE

Cytokines produced by intestinal epithelial cells may function as sign als to neighbouring immune and inflammatory cells. We investigated pro duction of the neutrophil and T-lymphocyte chemotactic cytokine interl eukin-8 (IL-8) by intestinal epithelial cells using four colonic adeno carcinoma cell lines, T84, CaCo-2 HT29 and SW620, as a model system. T hese cell lines secreted substantial amounts of IL-8 if stimulated wit h IL-1 beta, tumour necrosis factor-alpha (TNF-alpha) or interferon-ga mma (IFN-gamma), except CaCo-2 cells, which responded only to IL-1 bet a. Bacterial lipopolysaccharide (LPS) was also an efficient stimulus o f IL-8 release in SW620 and HT29 cells, whereas T84 and CaCo-2 cells w ere completely unresponsive to LPS. IL-8 secretion was greatest at 4 h r after stimulation and was accompanied by induction of IL-8 messenger RNA. In T84 cells IFN-gamma and epidermal growth factor (EGF) stimula ted IL-8 secretion synergistically with TNF-alpha, whereas in SW620 ce lls this synergism occurred only between IFN-gamma and TNF-alpha. IL-4 , IL-10 and transforming growth factor-beta (TGF-beta), which can down -regulate IL-8 production in macrophages, had no effect on IL-8 genera tion by our cell lines. Adenocarcinoma cell culture supernatants also induced rapid transients of intracellular calcium in neutrophils. Depe nding on cell line and stimulus, supernatant bioactivity was completel y or partially abrogated by neutralizing antibodies to IL-8, indicatin g that the cell lines investigated also generate other neutrophil-acti vating factors. IL-8 and possibly other chemokines generated by coloni c adenocarcinomas may help to attract tumour-infiltrating leucocytes. Possibly, normal intestinal epithelial cells also have the potential t o secrete this potent chemoattractant and thus might contribute to inf lammatory responses of the intestinal mucosa, for example in inflammat ory bowel disease.