Studies have indicated that intestinal epithelial cells (IEC) may play an important role in mucosal inflammations by producing inflammatory cytokines and chemokines which can amplify local responses. However, IEC also must adhere to a basement membrane of extracellular matrix (ECM) proteins which can provide signals to the cell through the cell surface integrins. Yet little is known of the effect of ECM proteins and integrins on cytokine responses by IEC. We have found that culturing Caco-2 human colonic carcinoma cells on laminin type 5 (LN-5) can result in a significant suppression, as compared to cells on fibronectin, in IL-1 stimulated IL-6 and monocyte chemoattractant protein-1 (MCP- 1) production. In addition, activation of the alpha3beta1 integrin, which mediates adherence to LN-5, by treating cells with an anti-alpha3 integrin antibody can also suppress IL-1 stimulated IL-6, IL-8 and MCP- 1 responses as compared to cells treated with normal IgG. These results suggest that integrin-ECM signals may be able to modify the capacity of IEC to produce cytokines. Furthermore, as ECM proteins in the basement membrane change through the progress of inflammation and wound healing, IEC may be capable of sensing these changes and responding accordingly. This suggests an important role for ECM proteins and integrins in inflammatory responses at mucosal surfaces. Therefore, we propose to further characterize the mechanism of this novel effect on IL-1 induced cytokine responses by examining the regulatory effect of LN-5 or the alpha3 integrin on (1) IL-1 stimulated activation of the transcription factor NF-kappaB, (2) the late events of the IL-1 intracellular signaling pathway leading to the activation of NF-KB, (3) the events in the IL-1 signaling pathway leading to the activation of AP-1, and (4) the early events of the IL-1 signal transduction pathway associated with the IL-1 receptor. Insight into the mechanism of this suppression will help to understand the role of integrins in regulating cytokine responses by IEC during inflammation and wound healing. In addition, an identification of sites in the IL-1 signaling pathway which are affected by LN-5 or the alpha3 integrin may suggest potential targets for future drug therapies to limit the contribution of the IEC in mucosal inflammatory diseases.
