Purpose: To investigate the effects of lipopolysaccharides (LPS) extracted from Porphyromonas endodontalis (P.e) on the expression of interleukin-34 (IL-34) mRNA in MC3T3-E1 cells and the role of p38MAPK, ERK1/2, NF-κB and SIRT1 in the process.
Methods: MC3T3-E1 cells were treated with different concentrations of P.e-LPS(0-50 mg/L) and 20 mg/L P.e-LPS for different time (0-24 h). The expression of IL-34 mRNA was detected by real-time reverse transcription-polymerase chain reaction (real time RT-PCR). MC3T3-E1 cells were pretreated with inhibitor of NF-κB(BAY 11-7082),inhibitor of p38MAPK (SB203580), inhibitor of ERK1/2 (PD98059), agonist of sirtuin1 (SIRT1) [resveratrol (RES)] and inhibitor of SIRT1 (EX-527) for 1 h, and then were treated with 20 mg/L P.e-LPS. The expression of IL-34 mRNA was detected by real time RT-PCR. Statistical analysis was performed using one-way ANOVA and Dunnett t test with SPSS 13.0 software package.
Results: The level of IL-34 mRNA increased significantly after treatment with different concentrations of P.e-LPS(0-50 mg/L)，which indicated that P.e-LPS induced osteoblasts to express IL-34 mRNA in a dose-dependent manner. Maximal induction of IL-34 mRNA expression was observed in MC3T3-E1 cells treated with 20 mg/L P.e-LPS for 24 h.At 48 h, the expression of IL-34 mRNA decreased gradually. The mRNA of IL-34 decreased significantly after pretreatment with 10 μmol/L BAY-117082, SB203580 and PD98059 for 1 h. P.e-LPS-induced IL-34 upregulation was attenuated by pretreatment with RES, but increased by EX-527.
Conclusions: These results suggest that P.e-LPS may mediate IL-34 mRNA expression in MC3T3-E1 cells. This process is dependent, at least in part, on p38MAPK, ERK1/2, NF-κB and SIRT1 signaling pathways.