Investigating the function of a novel protein from Anoectochilus formosanus which induced macrophage differentiation through TLR4-mediated NF-κB activation.

Anoectochilus formosanus is a therapeutic orchid appreciated as a traditional Chinese medicine in Asia. The extracts of A. formosanus have been reported to possess hepatoprotective, anti-inflammatory, and anti-tumor activates. A novel protein was isolated from A. formosanus, and its immunomodulatory effect on murine peritoneal macrophage was investigated. Macrophages obtained from ascites of thioglycollate-induced BALB/c were co-cultured with IPAF (0-20 μg/ml) for 24 h and then harvested for flow cytometry analysis. The cytokine/chemokine production was measured by real time PCR and ELISA. The interaction between IPAF and toll like receptors (TLRs) was investigated by TLR gene knockout (KO) mice and fluorescence labeled IPAF. The activation of NF-κB was assessed by EMSA. IPAF stimulated the TNF-α and IL-1β production, upregulated the CD86 and MHC II expression, and enhanced the phagocytic activity of macrophages. IPAF induced gene expression of IL-12 and Th1-assosiated cytokines/chemokines. The stimulating effect of IPAF was impaired, and the IPAF-macrophage interaction was reduced in TLR4(-/-) C57BL/10ScNJ mice. In addition, IPAF stimulated expressions of TLR signal-related genes and the activation of NF-κB. IPAF could induce classical activated macrophage differentiation via TLR4-dependent NF-κB activation and had potential of IPAF to modulate the Th1 response. These findings provided valuable information regarding the immune modulatory mechanism of A. formosanus, and indicated the possibility of IPAF as a potential peptide drug.