BACKGROUND: Toothache often occurs with pulpitis. Lipopolysaccharide (LPS) is produced by gram-negative bacteria, and its accumulation is related to clinical symptoms of pain. MicroRNAs (miRNAs) display anti-inflammatory potential due to their direct regulation of cellular protein expression, which can promote inflammatory changes in dental pulp tissues. However, the mechanism of LPS-induced pulpitis is still unclear.

MATERIAL AND METHODS: In this study, dental pulp stem cells (DPSCs) were separated and cultured from rat dental pulp tissues; then, LPS was administered to induce inflammation and activate the TLR4 pathway.

RESULTS: It was found that miR-506 was upregulated following LPS treatment in DPSCs. The inhibition of miR-506 in LPS-treated DPSCs led to attenuated inflammation and deactivation of the TLR4 pathway. Furthermore, the bioinformatic analysis and dual-luciferase reporter gene assay indicated that miR-506 could target the 3’-UTR of sirtuin 1 (SIRT1). Additionally, SIRT1 decreased in LPS-treated DPSCs, and miR-506 transfection resulted in SIRT1 upregulation. SIRT1 overexpression showed a similar inhibitory effect as that of miR-506 downregulation on inflammation and TLR4 activation in DPSCs.

CONCLUSIONS: In brief, miR-506 can protect dental pulp in LPS-induced inflammation by inhibiting the SIRT1-mediated TLR4 pathway.

Keywords: Lipopolysaccharides, Pulpitis, Dental Pulp, Sirtuin 1, Stem Cells, Toll-Like Receptor 4