P001 Autonomous cure of damaged human colon epithelial FPCK-1-1 cells by IL-22
Introduction It is known that inflammatory bowel disease results from the malfunction of the barrier system of the intestinal epithelium. In order to study the mechanism of intestinal inflammation, we established an in vitro culture system using FPCK-1-1 epithelial cells with quasi-normal chromosomes derived from human adenoma. In the previous model, Caco-2 cells were used instead of FPCK-1-1 cells. Caco-2 cells were co-cultured with THP-1 cells stimulated with phorbol myristate acetate (PMA). The condition of this co-culture system is different from actual events occurred in vivo in many ways. Caco-2 cells are adenocarcinoma cells with tetraploid nuclei. It is reported that peptidoglycans (PGN) from Staphylococcus aureus (S. aureus) cause inflammation and organ injury by inducing TNF-α, IL-6, and IL-10.We co-cultured FPCK-1-1 cells with PGN-stimulated THP-1 cells. Methods FPCK-1-1 cells derived from a tubular adenoma developing in a male familial polyposis coli patient have a normal karyotype with neither a point mutation on codon 12 of K-ras gene nor the amplification of myc, c-H-ras, and/or c-K–ras genes. Using a new in vitro co-culture model of intestinal inflammation, we showed the decrease of transepithelial electrical resistance (TER) and the increase in FITC-dextran permeability of FPCK-1-1 monolayer cells by co-culturing with THP-1 cells stimulated with PGN of S. aureus. As a curing reagent of this damage of tight junction, complex polysaccharides from Spirulina pacifica were used. Roles of TLR2, TLR4, and IL-22 were analyzed by using antibodies against them. Results Using a newly established model, we found Spirulina complex polysaccharides not only inhibit the injuring of epithelial cells but also recover the decreased TER of FPCK-1-1 monolayer cells after FPCK-1-1 cells were damaged by co-culturing with PGN-stimulated THP-1 cells. These results suggest that Spirulina complex polysaccharides have both defensive and therapeutic potency. Recovery of the expression level of claudin-2 is a sign of the recovery from the early stage of injury of the tight junction, but not that from the late phase injury. Interestingly, we found that curative effect of Spirulina complex polysaccharides on the early and the late phase damages of human colon epithelial cells was abolished by anti-IL-22 antibodies, suggesting that IL-22 is necessary for the recovery from these damages. Signals of Spirulina complex polysaccharides through both TLR2 and TLR4 are indispensable for the production of IL-22. We found that IL-22 was produced from FPCK-1-1 cells in response to Spirulina complex polysaccharides in the absence of THP-1 cells. Furthermore, we found that FPCK-1-1 cells produced IL-22 in response to IL-1β + IL-6 + IL-23. Conclusion In conclusion, our data suggest that damages of human colon epithelial cells are cured, at least in part, by the autonomous production of IL-22.