Porphyromonas gingivalis lipopolysaccharide induces over production of CC chemokine ligand 2 via toll-like receptor-4 in oral lichen planus

Background We recently reported that the CC chemokine ligand 2 (CCL2)-CC receptor 2 (CCR2) axis was involved in the pathogenesis of oral lichen planus (OLP). However, the exact mechanism for the high expression of CCL2 in OLP specimens is not clear. Therefore, this study was designed to investigate the potential role of the toll-like receptor 4 (TLR-4) pathway in overproduction of CCL2 in OLP lesions. Methods Immunohistochemical staining and real-time RT-PCR were used to detect TLR-4, CCL2, and CCR2 expression in OLP lesions. Then, gingival epithelial cells from OLP lesions were established and treated with Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS). CCL2 expression in epithelial cells was determined by Western blotting and real-time RT-PCR. In some experiments, TAK-242, a specific inhibitor of TLR-4, was used to block the TLR-4 pathway before cells were stimulated with LPS. Results We found that TLR-4 was significantly increased in the epithelium of OLP specimens, compared with controls. Moreover, LPS can induce the over production of CCL2 in epithelial cells of OLP, in vitro. TAK-242 effectively eliminated the increase in CCL2 expression induced by LPS by blocking the TLR-4/NF-κB pathway. In addition, we again confirmed that expression of CCL2 and CCR2 was increased in OLP specimens. Conclusion Increased TLR-4 expression contributes to the upregulated expression of CCL2 in the epithelium of OLP lesions, which suggests that oral bacteria participate in the pathogenesis of OLP via the TLR-4 pathway.