Abstract
Background and Objective: It has been found that human periodontal ligament (hPDL) cells express cannabinoid receptor CB2. However, the functional importance of CB2 in hPDL cells exposed to bacterial endotoxins is not known. Here we investigate if the inflammation promoter lipopolysaccharide (LPS) affects CB2 expression and if activation of CB2 regulates LPS-induced pro-inflammatory cytokine production and osteoclastogenic gene expression in hPDL cells. Methods: The hPDL cells were obtained from extracted teeth of periodontally healthy subjects. CB2 expression in hPDL cells exposed to LPS was deter- mined by quantitative real-time PCR analysis. Then, the cells were incubated with or without CB2-specific agonist HU-308 before further stimulation with LPS. In some experiments, the cells were pre-treated with CB2-specific antagonist SR144528. The production of pro-inflammatory cytokines interleukin-1 beta (IL- 1β), interleukin-6 (IL-6) and tumor necrosis factoralpha (TNF-α) was assessed by enzyme-linked immunosorbent assay (ELISA). The mRNA expression of osteoclastogenic genes osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) was examined using quantitative real-time PCR analysis. Results: CB2 expression in hPDL cells was markedly enhanced by LPS. HU-308 significantly suppressed the production of IL-1β, IL-6 and TNF-α exposed to LPS, whereas SR144528 attenuated this effect. The OPG/RANKL ratio decreased when exposed to LPS, furthermore increased significantly with the addition of HU-308 and finally decreased markedly after pretreatment with SR144528. Conclusion: Our study demonstrated that activation of CB2 had anti-inflammatory and anti-resorptive effects on LPS-stimulated hPDL cells. These findings suggest that activation of CB2 might be an effective therapeutic strategy for the treatment of inflammation and alveolar bone resorption in periodontitis.
Highlights
Periodontitis is a chronic inflammatory disease characterized by periodontal inflammation and alveolar bone resorption
These findings suggest that activation of CB2 might be an effective therapeutic strategy for the treatment of inflammation and alveolar bone resorption in periodontitis
When the human periodontal ligament (hPDL) cells growing from the tissue fragments reached confluence, the cell layer was rinsed with phosphate-buffered saline (PBS) and the cells were released with 0.25% trypsin—0.1% EDTA solution
Summary
Periodontitis is a chronic inflammatory disease characterized by periodontal inflammation and alveolar bone resorption. Lipopolysaccharides (LPS) play a key role in the destruction of periodontal tissues, including the gingiva, periodontal ligament (PDL), and alveolar bone, through the production of pro-inflammatory mediators, such as interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α) and prostaglandin (PG) [1]. The PDL cells modulate osteoclastogenesis by expression of osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) [4,5]. We investigate if the inflammation promoter lipopolysaccharide (LPS) affects CB2 expression and if activation of CB2 regulates LPS-induced pro-inflammatory cytokine production and osteoclastogenic gene expression in hPDL cells. CB2 expression in hPDL cells exposed to LPS was determined by quantitative real-time PCR analysis. The mRNA expression of osteoclastogenic genes osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) was examined using quantitative real-time PCR analysis. The OPG/RANKL ratio decreased when exposed to LPS, increased significantly with the addition of HU-308 and decreased markedly after pre-
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