Porphyromonas gingivalis lipopolysaccharide induces interleukin-6 and c-c motif chemokine ligand 2 expression in cultured hCMEC/D3 human brain microvascular endothelial cells

Objective This paper describes the effect of Porphyromonas gingivalis (P gingivalis) lipopolysaccharide (LPS) on the expression of interleukin-6 (IL-6) and C-C motif chemokine ligand 2 (CCL2) in cultured hCMEC/D3 human brain microvascular endothelial cells. Background P gingivalis is one of the important pathogens in periodontitis, and periodontitis is a risk factor for brain disorders including cerebrovascular diseases and Alzheimer's disease. However, the mechanisms underlying the pathogenesis of P gingivalis-mediated brain diseases are incompletely understood. Effects of P gingivalis LPS on brain endothelial cells are not known well. Methods The hCMEC/D3 human brain microvascular endothelial cells were cultured and treated with P gingivalis LPS. The expression of IL-6 and CCL2 mRNA and protein was examined using quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Effect of inhibitors of Toll-like receptor (TLR) 2, TLR4, nuclear factor-kappa B (NF-kappa B), p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) was also investigated. Phosphorylation of NF-kappa B p65, p38 MAPK and JNK was examined using Western blotting. Results P gingivalis LPS-induced mRNA and protein expression of IL-6 and CCL2 in hCMEC/D3 cells in a concentration-dependent manner at the concentration of 0.5-50 mu g/mL. Maximal mRNA expression of IL-6 and CCL2 was found 2 and 4 hours after stimulation, respectively. Induction of IL-6 and CCL2 by P gingivalis LPS was almost completely inhibited by pretreatment of cells with TLR4 inhibitor but not by TLR2 inhibitor. Treatment of cells with P gingivalis LPS for up to 2 hours induced phosphorylation of NF-kappa B p65, p38 MAPK and JNK. IL-6 induction was decreased by pretreatment of cells with NF-kappa B inhibitor SN50 or p38 MAPK inhibitor SB203580, while CCL2 induction was reduced by SN50 or JNK inhibitor SP600125. Conclusions IL-6 and CCL2 produced upon P gingivalis LPS stimulation may contribute to the inflammatory reactions in brain endothelial cells and subsequent neurological disorders such as cerebrovascular and Alzheimer's diseases.