PPARγ inhibits inflammation and RANKL expression in epoxy resin-based sealer-induced osteoblast precursor cells E1 cells.

OBJECTIVES: The AH26 of epoxy resin-based sealer is used widely owing to its excellent physical characteristics but it induces oxidative stress and cytotoxicity at the periapical tissues. AH26 exhibited cytotoxicity towards MC-3T3-E1 cells, which resulted in mitochondria-mediated apoptosis. Peroxisome proliferator-activated receptor (PPARγ) has an anti-inflammatory effect in several tissue and cells, but its action of AH26-related inflammation is not completely understood. The aim of this study is to investigate the anti-inflammatory and anti-osteoclastic mechanisms of PPARγ in AH26-induced MC-3T3 E1 cells. METHODS: AH26 was prepared according to the manufacturer's instructions. The 1-day extraction sample, which was diluted by 30%, was tested in this experiment. Recombinant deficiency adenoviral PPARγ (Ad/PPARγ) was used to examine PPARγ over-expression in MC-3T3 E1 cells. AH26-induced reactive oxygen species (ROS) formation was analysed using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) with fluorescence-activated cell sorting (FACS), and the expression of receptor activator of nuclear factor-κB ligand (RANKL) and inflammatory molecules was determined by immunoblotting. The anti-inflammatory and anti-osteoclastic mechanisms of the PPARγ-involved signal pathway was examined by immunoblotting. RESULTS: The AH26 elutes induced inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), RANKL expression and ROS formation. In addition, the AH26 elutes suppressed the expression of PPARγ. However, the recovery of PPARγ expression with Ad/PPARγ resulted in the inhibition of iNOS, COX-2, RANKL and ROS formation despite the AH26 treatment in MC-3T3 E1 cells. The mechanism of PPARγ was confirmed by the blocking of nuclear factor kappa B (NF-κB) translocation to the nucleus after the suppression of ERK1/2, SAPK/JNK and AP-1 in AH26-induced MC-3T3 E1 cells. CONCLUSION: From this result, PPARγ acts to inhibit bone destruction in AH26-induced bone cells. Therefore, the anti-inflammatory and anti-osteoclastic character of PPARγ might be applicable for healing periapical lesions more rapidly or reducing the induction of cellular inflammation caused by some endodontic sealers.

Reactive oxygen species removal activity of davallialactone reduces lipopolysaccharide-induced pulpal inflammation through inhibition of the extracellular signal-regulated kinase 1/2 and nuclear factor kappa b pathway.

INTRODUCTION: Davallialactone, hispidin analogues derived from the mushroom Inonotus xeranticus, has antioxidant properties. This study examined whether the reactive oxygen species (ROS) removal activity of davallialactone affects the lipopolysaccharide (LPS)-induced anti-inflammatory activity in human dental pulp cells. METHODS: The LPS-induced formation of ROS was analyzed by using dichlorofluorescein diacetate with fluorescence-activated cell sorter, and the expression of inflammatory molecules in primary cultured human dental pulp cells was determined by immunoblotting. The inflammatory mechanism of the davallialactone-involved signal pathway was examined by immunoblotting. RESULTS: Davallialactone acted as an antioxidant to confirm the elimination of ROS formation and elevation of Cu/Zn superoxide dismutase and Mn superoxide dismutase expression in LPS-induced pulp cells. The antioxidant activity of davallialactone leads to inhibition of LPS-induced inflammation by blocking the extracellular signal-regulated kinase (ERK1/2) and nuclear factor kappa B (NF-κB) pathway, which decreases the expression of inflammatory molecules such as intercellular adhesion molecule-1, vascular cell adhesion molecule-1, matrix metalloproteinase-2, matrix metalloproteinase-9, inducible nitric oxide synthase, and cyclooxygenase-2. The character of davallialactone was more effective in comparison with N-acetylcysteine as the control antioxidant in this study. CONCLUSIONS: Davallialactone has antioxidant activity and anti-inflammatory effects in LPS-induced human dental pulp cells through the suppression of ERK1/2 activation followed by blockage of NF-κB translocation from cytosol into nuclear. Therefore, the good anti-inflammatory capacity of davallialactone might be used for oral diseases such as pulpitis and periodontitis.