Context: Shikonin (SHI), an active component extracted from Radix Arnebiae, has been reported to possess anti-inflammatory properties in various cells. However, its effect on lipopolysaccharide (LPS)-stimulated human periodontal ligament cells (hPDLCs) is unknown. Objective: To investigate the effects of SHI on the expression of inflammatory related cytokines in LPSstimulated hPDLCs. Materials and methods: The effects of SHI (0.125, 0.25, 0.5, 1, and 2 lg/mL) on hPDLCs proliferation for 1, 3 and 7 days were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression of interleukin-1 (IL-1), IL-6, tumor necrosis factor-a (TNF-a), matrix metalloproteinase-2 (MMP-2), MMP-9 and cyclooxygenase-2 (COX-2) were detected in hPDLCs following SHI treatment (0.25 and 0.5 lg/mL) using Quantitative Reverse Transcriptase Polymerase Chain Reaction (qRT-PCR). The signaling pathways triggered by SHI in hPDLC were evaluated using western blotting. Results: LD50 of SHI is 1.7 lg/mL (day 1) and 1.1 lg/mL (day 3 and 7) in hPDLCs. No morphological changes were observed when hPDLCs were treated with LPS only (1 lg/mL) or LPS with SHI (0.25 and 0.5 lg/mL). Data from qRT-PCR suggests that SHI attenuates LPS-induced increases of IL-1, IL-6, TNF-a, MMP-2, MMP-9 and COX-2 in hPDLCs. Down-regulation of phosphorylated extracellular signal-regulated kinase (ERK) and nuclear factor-jB (NF-jB), and up-regulation of I-jB, were observed in LPS-stimulated hPDLCs after exposed to SHI at 0.25 or 0.5 lg/mL. Discussion and conclusions: SHI possesses anti-inflammatory effects in LPS-stimulated hPDLCs via phospho-ERK and NF-jB/I-jB signaling pathways; this suggests that SHI may hold potential as an anti-inflammatory agent against periodontitis.