EXPRESSION OF FUNCTIONAL ICAM-1 AND VCAM-1 ADHESION MOLECULES BY AN IMMORTALIZED EPITHELIAL-CELL CLONE DERIVED FROM THE SMALL-INTESTINE

The role of small bowel-derived epithelial cells in regulating the acc umulation of inflammatory cells within the inflamed gut epithelium is poorly understood because of the difficulties in culturing the epithel ial cells in vitro. We have recently developed a cloned epithelial cel l line (IEC-4.1) derived from the small intestine of BALB/c mice. In t he present study, we examined whether IEC-4.1 cells could express adhe sion molecules ICAM-1 and VCAM-1 and the molecular basis of macrophage adhesion to the epithelial cells. Northern blot analysis demonstrated that IEC-4.1 cells constitutively expressed ICAM-1 and VCAM-1 mRNA at low levels. Stimulation with LPS (12 mu g/ml) or TNF-alpha (2.5 ng/ml ) markedly upregulated ICAM-1 and VCAM-1 gene expression in IEC-4.1 ce lls. ICAM-1 mRNA started to increase 2 hr after LPS stimulation, peake d at 4 hr, and then decreased rapidly to the basal level at 8 hr. VCAM -1 mRNA had the similar pattern of upregulation but the increased VCAM -1 mRNA sustained over a longer period of time and did not return to t he basal level until 24 hr after the stimulation. IEC-4.1 cells expres sed very low basal levels of ICAM-1 and VCAM-1 on the cell surface as demonstrated by immunofluorescence staining and FACS analysis, Stimula tion of IEC-4.1 cells with LPS or TNF-alpha markedly increased the sur face expression of both ICAM-1 and VCAM-1, which correlated with the i ncreased binding of macrophages to the stimulated IEC-4.1 cells. Adher ence of macrophages to the IEC-4.1 cells was mediated by both LFA-1/IC AM-1 and VLA-4/VCAM-1 since blocking both adhesion pathways inhibited macrophage adhesion by about 90%. These findings suggest that small bo wel-derived epithelial cells may be capable of expressing a defined se t of functional adhesion molecules during mucosal inflammation. (C) 19 97 Academic Press