Lipopolysaccharide (LPS) regulates TLR4 signal transduction in nasopharynx epithelial cell line 5-8F via NFκB and MAPKs signaling pathways

The lipopolysaccharide (LPS) of Gram-negative bacteria induces the expression of cytokines and proinflammatory genes via the TLR4 signaling pathway in diverse cell types. The purpose of the present study was to test the hypothesis that the nasopharynx epithelial cells (NECs) could recognize and respond to LPS. The underlying molecular mechanisms were further elucidated in the NEC line 5-8F for its ability to activate the NFκB and TNF-α reporter genes, in response to LPS. After LPS stimulation, the TNF-α promoter activity and the relevant production of TNF-α were significantly increased in 5-8F cells. Moreover, LPS activated NFκB p65, ERK1/2 and JNK1/2 and induced their translocation to the nucleus. Western blot analysis showed that the expression of NFκB p65, MEK1, ERK1/2, JNK1/2, phospho-ERK1/2 and phospho-JNK1/2 proteins also was increased in NEC 5-8F cells, following the LPS stimulation. Additionally, the expression of TLR1-6, MD2 and CD14 was examined by RT-PCR, and the CD14 expression was determined by flow cytometry analysis. We demonstrated that the expression of CD14, TLR4 and MD2 was crucial for the NEC responses to LPS. In conclusion, our results provide novel mechanisms for the response of nasopharnyx epithelial cells to LPS stimulation, through NFκB and MAPKs signaling pathways.