Immunostimulatory effects of sulfated chitosans on RAW 264.7 mouse macrophages via the activation of PI3 K/Akt signaling pathway

To investigate the immunostimulatory effects of chitosan sulfates, we prepared alpha- and beta-chitosan sulfates with different molecular weights and compared their immunostimulatory activities in RAW 264.7 macrophages. Results suggest that beta-chitosan sulfates were more active than alpha-chitosan in promoting nitric oxide (NO) production. Further study show that beta-chitosan sulfate significantly promoted the production of NO, prostaglandin E-2, tumor necrosis factor (TNF)-alpha, interleukin-6 and interleukin-1 beta at the levels of transcription and translation. Moreover, Western blots revealed that it induced the phosphorylation of p85 and Akt, and the nuclear translocation of p50/p65 and c-Fos/c-Jun. The luciferase activity of cells pretreated with I3-chitosan sulfate further confirmed the nuclear translocation of p50/p65 and c-Fosic-Jun. Determination of Toll-like receptor (TLR) 4 expression suggested that beta-chitosan sulfate at least partly bound to TLR4. In conclusion, beta-chitosan sulfates activate RAW 264.7 cells through the PI3K-Akt pathway, which is dependent on activator protein-1 and nuclear factor-kappa B activation. (C) 2017 Elsevier B.V. All rights reserved.