Immunostimulatory effects of sulfated chitosans on RAW 264.7 mouse macrophages via the activation of PI3K/Akt signaling pathway.

To investigate the immunostimulatory effects of chitosan sulfates， we prepared α- and β-chitosan sulfates with different molecular weights and compared their immunostimulatory activities in RAW 264.7 macrophages. Results suggest that β-chitosan sulfates were more active than α-chitosan in promoting nitric oxide (NO) production. Further study show that β-chitosan sulfate significantly promoted the production of NO， prostaglandin E， tumor necrosis factor (TNF)-α， interleukin-6 and interleukin-1β 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 β-chitosan sulfate further confirmed the nuclear translocation of p50/p65 and c-Fos/c-Jun. Determination of Toll-like receptor (TLR) 4 expression suggested that β-chitosan sulfate at least partly bound to TLR4. In conclusion， β-chitosan sulfates activate RAW 264.7 cells through the PI3K-Akt pathway， which is dependent on activator protein-1 and nuclear factor-κB activation.