Immunostimulatory effect of ethanol extract of Chondracanthus tenellus in RAW 264.7 macrophages in vitro

Objective: To investigate whether ethanol extracts of Chondracanthus tenellus (EECT) could improve immunomodulatory property of murine monocyte/macrophage RAW 264.7 cells. Methods: Cell viability, phagocytic ability, and nitric oxide were measured. The levels of prostaglandin E2 and cytokines were determined using enzyme-linked immunosorbent assay kits. Expression of immunoregulatory response protein was detected by Western blotting assay. Results: As the concentration of EECT increased, the morphology of the cells changed to a typical active macrophage shape, and the phagocytic activity increased significantly. EECT also effectively enhanced the production and secretion of immunomodulatory mediators, such as nitric oxide and prostaglandin E2, and cytokines. In addition, compared with the control group, EECT markedly stimulated the expression of Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88, one of the TLR4 adapter molecules. Furthermore, EECT promoted the nucleus translocation of nuclear factor-kappa B (NF-κB) by increasing the phosphorylation and degradation of the inhibitor of NF-κB-α, indicating activation of the NF-κB signaling pathway. Meanwhile, similar trends were found in cells treated with lipopolysaccharide as a positive control. Conclusions: Taken together, the results indicate that EECT has an immunomodulatory effect by increasing the production of immunomodulatory mediators and cytokines through activation of the TLR4/NF-κB signaling pathway. EECT could be used as a potential candidate for medication or dietary supplements to increase immune activity.