Protective effect of oligochitosan on LPS-induced inflammation of the intestinal epithelial cells

Objective To investigate the protective effect of oligochitosan on lipopolysaccharide (LPS) induced inflammation of the intestinal epithelial cells. Methods intestinal epithelial cells Caco-2 were divided into five groups: normal control group, model group, high-, medium-and low-level oligochitosan groups. In the oligochitosan groups, the cells were pre-treated with 0.25, 0.5 and 1.0 g/L oligochitosan, respectively, at 2 h before LPS stimulation. MTT method was used for cell viability assay. ELISA was used to measure the levels of inflammation related cytokines, such as tumor necrotizing factor-related factor alpha (TNF-α) , interleukin-8 (IL-8) and prostaglandin E2 (PGE2) , in the cell culture supernatant. Western blotting was used to detect the changes in expression of Toll-like receptor 4 (TLR4) , nuclear factor κB (NF-κB) and cyclooxygenase 2 (COX-2). Results The Caco-2 cell viability was not affected by treatment with oligochitosan and/or LPS. Compared with the model group, 0.25, 0.5 and 1.0 g/L oligochitosan reduced the production of TNF-α (352.5±21.6, 298.4±25.1, 203.4±20.0 vs 436 .8±38.7 μg/L, P<0.05) and PGE2 (632.2±35.6, 522.6±26.7, 402.4±30.2 vs 822.3±23.5 μg/L, P<0.01) in Caco-2 cells in a dose dependent manner; 0.5 and 1.0 g/L oligochitosan reduced COX 2 expression (P<0.05 and P<0.01) ; medium-and high-level oligochitosan was significantly associated with lowered expression of TLR4 compared with the model group (P<0.05) ; the expression of NF-κB in each group of oligochitosan dosage was significantly lowered (P<0.05; P<0.01). Conclusion Oligochitosan may reverse LPS-induced inflammation of the intestinal epithelial cells and therefore may be potentially protective against inflammatory bowel diseases. The underlysing mechanism of this action may be related to inhibition of TLR4/NF-κB signaling pathway. Key words: Inflammation; Intestinal epithelial cells; Lipopolysaccharide; Oligochitosan; TLR4