Expression and Role of Anaphylatoxin Receptors on Human Colonic Epithelial Cells
Human colonic epithelial cell lines (T84, Caco2 and HT-29) were used to address the question of whether intestinal epithelial cells can detect and respond to activated complement via the anaphylatoxin receptors, considering the gut is host to large numbers of bacteria. All cell lines possess C3aR, C5aR and C5L2. Confocal microscopy confirmed that cells express apical C5aR and C5L2. C3a and C5a up-regulated CXCL8 and CXCL10 mRNA but not secreted protein levels within 48 hours. Protein levels were not increased using simultaneous treatment with subthreshold concentrations of LPS or TNF plus anaphylatoxin. C3a and C5a also increased the permeability of polarized monolayers. Anaphylatoxins also promoted the proliferation of T84 and HT-29. Inhibition of ERK signaling abolished these effects of anaphylatoxins. Our findings that multiple human cell lines possess functional anaphylatoxin receptors indicates that the colonic epithelium likely responds to the activation of complement in the lumen with an inflammatory outcome.