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.