Chitooligosaccharides Attenuate Lipopolysaccharideinduced Inflammation and Apoptosis of Intestinal Epithelial Cells: Possible Involvement of TLR4/NF-κB Pathway

Abstract:

Marine-derived chitooligosaccharides (CHOS) are a new class of anti-inflammatory natural products characterized by its nontoxity, low-cost and small-molecule. But whether CHOS exert a protective action against inflammatory bowel diseases (IBDs) is not yet fully understood. This paper studied the effect of CHOS on the inflammation and apoptosis of intestinal epithelial cells (IECs) using lipopolysaccharides (LPS)-stimulated Caco-2 cells as an in vitro model of IBD. Caco-2 cells were pre-incubated with various concentrations of CHOS (0.25, 0.5 and 1.0 mg/ml) for 2 h prior to being co-stimulated or not with LPS at a concentration of 1μg/mL for 48h. Cell apoptosis was measured with Annexin V-FITC and propidium iodide (PI) assay by flow cytometry. The levels of proinflammatory mediators including tumor necrosis factor (TNF)-α, interleukin-8 and prostaglandin (PG) E2 were analyzed using Enzyme-linked Immunosorbent Assay. And the cell expression of toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), caspase-3, bcl-2, and cyclooxygenase (COX)-2 was examined by western blot. We observed that CHOS significantly and concentration-dependently inhibited the LPS-induced inflammatory response and apoptosis of IECs, which was evidenced by the reduction in the release of proinflammatory mediators TNF-α, PGE2, the expression of COX-2, apoptotic (Annexin V⁺/PI^-) cell populations, the pro-apoptotic caspase-3 expression, and the enhancement of the expression level of anti-apoptotic bcl-2. And CHOS treatment significantly reduced the protein expressions of TLR4 and NF-κB in LPS-stimulated Caco-2 cells. Thus, the present study suggests the potential medical use of CHOS in the control of IBDs, which may be due to the downregulation of TLR4/NF-κB pathway.

Key words: Chitooligosaccharides, Inflammatory bowel diseases, Lipopolysaccharides, Intestinal epithelial cells.