Chitosan, naturally occuring biopolymer, has received considerable attention as a phamaceutical applications because of biocompatible, biodegradable and less toxic nature. In this study, chemically modified chitosans, aminoethyl-chitosans (AECs), were prepared in order to improve both water-solubility and bioactivity, and the effects of AECs on lipopolysaccharides (LPS)-induced inflammation in RAW264.7 mouse macrophages were investigated. AEC90 derived from 90% deacetylated chitosan showed strong inhibition capacity with regard to nitric oxide (NO) production than that of AEC50 derived from 50% deacetylated chitosan. Therefore further studies were coducted using AEC90. The production of prostaglandin E(2) (PGE(2)) also inhibited by pretreatment of AEC90 in a dose-dependent manner which suggest the possibility of down-regulating their respective genes, inducible nitric oxide synthases (iNOS) and cyclooxygenase-2 (COX-2). Reverse transcrition-polymerase chain reaction (RT-PCR) and Western blot analysis revealed that AEC90 can affect both transcriptional and translational levels of iNOS and COX-2 expression via NF-kappa B pathway. Furthermore, AEC90 also suppressed the production of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6), and the transcriptional and translational levels of such cytokines were also inhibited by AEC90 treatment. (C) 2010 Elsevier Ltd. All rights reserved.