Chitosan, a deacetylated chitin, has been reported to accelerate the wound healing and exert anti-inflammatory effect but the possible mechanisms involved are still unclear. Enhanced production of prostaglandin E-2 (PGE(2)) and pro-inflammatory cytokines has been shown to contribute to immunosuppression and cytotoxicity during wound healing. In this study, we examined the effect of chitosan on cyclooxygenase pathway and cytokines production in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. Our results first demonstrated that chitosans (MW = 50,000, 150,000 or 300,000) significantly inhibit the overproduction of PGE(2) as well as cyclooxygenase-2 (COX-2) protein expression and activity accompanied by attenuation of pro-inflammatory cytokines production such as tumor necrosis factor-alpha and interleukin-1beta formation but increase of the anti-inflammatory cytokine, IL-10, formation in LPS-treated RAW 264.7 macrophages. These results suggest that the beneficial effect of chitosan on wound healing may be associated, at least partly, with the inhibition of PGE(2) production by suppressing COX-2 induction and activity as well as attenuation of pro-inflammatory/anti-inflammatory cytokines ratio in activated macrophages. (C) 2003 Elsevier Inc. All rights reserved.