Effects of the molecular weight and protein and sulfate content of Chlorella ellipsoidea polysaccharides on their immunomodulatory activity

We investigated the effects of the protein and sulfate content, as well as the molecular weight (Mw), of green alga Chlorella ellipsoidea polysaccharides on their immunomodulatory activity. The deproteinized (DP1-3), desulfated (DS1-3), and hydrolyzed (DH1-3) derivatives of C. ellipsoidea polysaccharides were prepared by enzymatic hydrolysis, desulfation, and acid hydrolysis, respectively, of differing durations, resulting in preparations containing various amounts of proteins (2.41%-8.97%), sulfates (1.36%-4.89%), and Mw (51.5-193.4 kDa). The DH1-3-induced production of nitric oxide (NO) by RAW264.7 cells, decreased as the Mw of DH1-3 decreased. In addition, the sulfate content and Mw of DS1-3 affected the release of NO. However, lower protein content did not affect DP1-3-induced NO release and cytokine mRNA expression in RAW264.7 cells. Based on a multiple regression analysis of the effects of protein content, sulfate content, and Mw, on NO release, we found that Mw was a key factor for the stimulation of RAW264.7 cells, as it affected cytokine production, and activation of the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Therefore, the Mw of C. ellipsoidea polysaccharides played an important role in their immunomodulatory activities.