Studies have indicated that intestinal epithelial cells (IEC) may play an important role in mucosal inflammations by producing inflammatory cytokines which can amplify local responses. However, I EC 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 colonic carcinoma cells on laminin type 5 (LN-5) or activating the alpha3beta1 integrin with an anti-alpha3 integrin antibody can result in a significant suppression in IL-1 stimulated pro-inflammatory cytokine production. This suggests an important role for ECM proteins and integrins in inflammatory responses at mucosal surfaces. In addition, activation of the alpha3beta1 integrin, results in a suppression in the distal portions of the IL-1 intracellular signaling pathways leading to NF-kappaB and AP-1 activation. These results suggest that integrin-ECM signals may be able to modify the capacity of IEC to produce cytokines by altering the IL-1 signaling pathway. 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. Therefore, we propose to identify the mechanism of this novel effect on the IL-1 intracellular signaling pathway by examining the regulatory effect of LN-5 or the alpha3beta1 integrin on (1) the IL-1 stimulated function of the TAK1 complex, (2) the role of TRAF6 in the suppression of the IL-1 intracellular signaling pathway, and (3) the effect on IRAK-1 and IRAK- 4. 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 alpha3beta1 integrin may suggest potential targets for future drug therapies to limit the contribution of the IEC in mucosal inflammatory diseases. ? ?
