The immunomodulatory effect of docosahexaenoic acid (DHA) on the RAW264.7 cells by modification of membrane structure and function
Background: DHA can regulate various physiological functions of cells, as our group has clarified the immunomodulatory activity and molecular mechanism of DHA on RAW264.7 cells. However, the effect of DHA on the alters of membrane fatty acid environment and the activation of signaling pathways on the cell membrane were still not clear. Methods: In this study, we evaluated the fluidity, potential and the fatty acids, phos-pholipids and protein composition of RAW264.7 cell membrane by DHA treatment. Results: The fluidity of RAW264.7 cell membrane was increased by DHA treatment. The results of membrane potential suggested that DHA (2.4 μM) significantly reduced the surface potential of the cell membrane, which might influence the fluidity of cell membranes. In addition, the fatty acids and phospholipids were measured and the re-sults indicated that DHA treatment (2.4 μM) altered the lipid environment and com-position of phospholipids in RAW264.7 cell membrane. Then the LC-MS/MS-based label free quantitative proteomics approach was applied to identify a total of 86 dif-ferential proteins between 2.4 μM DHA and control (>2.0-fold change or <0.5-fold change), which are most frequently related to cell response to stimulus and response to stress. These results suggested that DHA could alter the fluidity, potential, the fatty acids and phospholipids composition of RAW264.7 cell membrane, eventually affect the proteins of cell membrane, especially the changes in Siglec 1, iNOS, GPR120, Ras and MEK expressions (validated by Western blot analysis), which were likely to be associated with the activation of intracellular signaling pathway in RAW264.7 cells by DHA treatment.