Inhibitory effects of chitooligosaccharides on degranulation and cytokine generation in rat basophilic leukemia RBL-2H3 cells

Chitooligosaccharides (COS) of three different molecular weight ranges (1-3 kDa, 3-5 kDa and 5-10 kDa) were investigated for their abilities against allergic reactions in RBL-2H3 cells. At the high concentration of 1000 μg/ml, COS with molecular weights of 1-3 kDa greatly attenuated the histamine and β-hexosaminidase release and intracellular Ca2+ elevation induced by calcium ionophore A23187, at the rates of 32% and 34% release and 37% elevation, respectively. Furthermore, the inhibitory activities of COS on calcium ionophore A23187 plus phorbol 12-myristate 13-acetate (PMA)-induced production as well as mRNA expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-4, and IL-6 were evidenced. Notably, the suppressive effects on the phosphorylation of extracellular signal-regulated kinases (MEK/ERK) and p38 kinase by COS were confirmed. These results indicate that COS could be used as an inhibitor in regulating mast cell-mediated allergic inflammatory responses.