Induction of IL-8 expression by Cordyceps militaris grown on germinated soybeans through lipid rafts formation and signaling pathways via ERK and JNK in A549 cells.

AIM OF THE STUDY

In order to elucidate immunoregulatory mechanisms of Cordyceps militaris, a methanol extract of Cordyceps militaris grown on germinated soybeans was prepared and its immunoregulatory effect in the human lung epithelial cells was investigated by examining its ability to induce IL-8 expression.

MATERIALS AND METHODS

Cordyceps militaris grown on germinated soybeans was extracted with 80% methanol (GSC4M) and used for stimulation of a human lung epithelial cell-line, A549. An enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction were performed to examine the production of IL-8 protein and its mRNA, respectively. For the analysis of transcription factors regulating IL-8 transcriptional activation, the nuclear fraction was extracted from GSC4M-treated A549 cells and subjected to electrophoretic mobility shift assay.

RESULTS

GSC4M induced IL-8 protein secretion and its mRNA expression from A549 cells in a dose- and time-dependent manner. GSC4M-induced IL-8 expression was inhibited by an inhibitor for lipid rafts formation but not by that for clathrin-coated pits. In addition, signaling pathways for GSC4M-induced IL-8 expression were mediated through ERK and JNK but hardly through p38 kinase. Furthermore, GSC4M augmented the DNA-binding activity of the transcription factors AP-1, NF-IL6, and NF-kappaB, all of which are involved in the transcriptional activation of the IL-8 gene.

CONCLUSION

Cordyceps militaris grown on germinated soybeans stimulates lung epithelial cells to produce IL-8 through lipid rafts formation and signaling pathways via ERK and JNK.