Dual Effect of the Extract from the Fungus on Lipopolysaccharide-Induced Cytokine Production in RAW 264.7 Macrophages Depending on the Lipopolysaccharide Concentration.

PURPOSE

Extract from the fungus (CV) is classified as an immunological response modifier. Previously, we have shown that this extract induces interleukin 6 (IL-6)-related extension of lipopolysaccharide (LPS)-induced fever. This study investigated the effect of CV extract on the production of pro-inflammatory cytokines and the expression of components of signal transduction pathways leading to the secretion of cytokines from RAW 264.7 macrophages stimulated with different doses of LPS.

METHODS

RAW 264.7 cells were stimulated with CV extract alone or co-treated with CV extract and LPS. The level of IL-6 and tumour necrosis factor α (TNF-α) in the culture media was measured using ELISA. Protein expression of Toll-like receptor (TLR) 4, phosphorylated IκB (p-IκB), CD14 glycoprotein and phospho-phosphatidylinositol 3-kinase (p-PI3K) was evaluated using Western blot. The effects of TLR4, nuclear factor κB (NF-κB) and p-PI3K on cytokine secretion were estimated using inhibitors: TAK-242, JSH-23 and LY294002.

RESULTS

CV extract itself stimulates the secretion of IL-6 and TNF-α and increases the expression of TLR4, p-IκB and p-PI3K. The presence of CV extract during the treatment of cells with lower concentrations of LPS (10 and 100 ng/mL) increases the cytokine production. Co-stimulation of cells with CV extract and LPS at a higher dose (500 ng/mL) decreases the secretion of cytokines. This effect is related to the changes in the expression of TLR4, CD14 glycoprotein, p-IκB and p-PI3K.

CONCLUSION

This is the first report showing that the CV extract-induced production of cytokines is mediated by the PI3K signalling pathway. This extract acts antagonistically or additively with LPS on the production of IL-6 and TNF-α, depending on the LPS concentration. Our results are helpful for illustrating the mechanisms for the immunostimulatory effect of CV extract in inflammatory processes.