Modulation of membrane type 1 matrix metalloproteinase by LPS and gamma interferon bound to extracellular matrix in intestinal crypt cells.

Membrane type 1 matrix metalloproteinase (MT1-MMP) is an integral membrane protein that participates in the processing and degradation of cell surface proteins and the extracellular matrix (ECM). This enzyme regulates ECM turnover in wound repair, promotes cell migration and activates other MMPs, such as MMP-2, which is involved in angiogenesis, cell migration and tumoral metastasis. An increase in pro-inflammatory cytokine expression, such as gamma interferon (IFN-gamma), has been associated with chronic wounds in inflammatory bowel diseases. However, the extent to which cytokines modulate MT1-MMP has not been totally defined. In this report, the effects of the bacterial lipopolysaccharide (LPS) and ECM-bound IFN-gamma on MT1-MMP expression and MMP-2 activity were evaluated by Western blot, RT-PCR and zymography in isolated intestinal epithelial and cultured HT-29 cells. In the presence of LPS, ECM-bound IFN-gamma, but not soluble IFN-gamma, reduced the enterocyte MT1-MMP protein expression. In addition, the active form of MMP-2 was also decreased in the presence of both LPS and IFN-gamma, indicating that lower MMP-2 activity accompanied the decrease in MT1-MMP expression. These results suggest the possibility that endotoxin and ECM-bound IFN-gamma may affect matrix remodeling by modulating matrix metalloproteinase in enterocytes during wound healing.

Interferon gamma bound to extracellular matrix changes the hyporesponsiveness to LPS in crypt but not villous intestinal epithelial cells.

Intestinal epithelial cells (IEC) are hyporesponsive to LPS. Responsiveness to luminal bacteria has been implicated in the pathogenesis of inflammatory bowel diseases (IBD). In support of this, previous studies have demonstrated that some intestinal epithelial cell lines are induced by IFN-gamma to respond to LPS. However, both the responsiveness to LPS and the effect of IFN-gamma in intestinal cell lines are heterogeneous. In addition, IFN-gamma may be sequestered in the extracellular matrix (ECM) compartment. The ECM-bound form is more effective than soluble IFN-gamma in producing its biological effects in several experimental models. We investigated the effect of ECM-bound and soluble IFN-gamma treatment on interleukin-8 (IL-8) secretion in response to LPS in freshly isolated villous and crypt cells. We demonstrate that ECM-bound, but not soluble IFN-gamma, induced an increase in IL-8 secretion in response to LPS in undifferentiated crypt cells. This effect was associated with an increase in TLR4 expression. In contrast, mature villous cells did not modify their response to LPS when treated with IFN-gamma (ECM-bound or soluble). These results suggest that selective changes in immature crypt cells induced by IFN-gamma bound to extracellular matrix could contribute to inappropriate responsiveness to commensal bacteria in IBD.