Gallic acid-grafted chitooligosaccharides suppress antigen-induced allergic reactions in RBL-2H3 mast cells.

In this study, a bioactive derivative of chitooligosaccharides (3-5 kDa) was synthesized via grafting of gallic acid onto chitooligosaccharides (G-COS) to enhance anti-allergic activity. Hence, G-COS was evaluated for its capabilities against allergic reactions in RBL-2H3 mast cells sensitized with dinitrophenyl-specific immunoglobulin E antibody and stimulated by antigen dinitrophenyl-bovine serum albumin. It was revealed that G-COS exhibited significant inhibition on histamine release and production as well as intracellular Ca(2+) elevation at the concentration of 200μg/ml. Likewise, the suppressive effects of G-COS on expression and production of interleukin (IL)-4 and tumor necrosis factor (TNF)-α were evidenced. Moreover, G-COS treatment caused a remarkable blockade on degradation of inhibitory κB-α (IκB-α) protein, translocation of nuclear factor (NF)-κB, and phosphorylation of mitogen-activated protein kinases (MAPKs). Notably, the inhibitory activities of G-COS on allergic reactions were found as a consequence of suppression of FcεRI expression in antigen-stimulated cells. Accordingly, G-COS was suggested to be a promising candidate of novel inhibitors against allergic reactions.