Identification of hop polyphenolic components which inhibit prostaglandin E₂ production by gingival epithelial cells stimulated with periodontal pathogen

Chronic marginal periodontitis is a destructive inflammatory disease caused by an imbalance between bacterial virulence and host defense ability, resulting in eventual tooth exfoliation. Porphyromonas gingivalis, a major periodontal pathogen, triggers a series of cellular inflammatory responses including the production of prostaglandin E₂ (PGE₂), which causes periodontal destruction; thus, anti-inflammatory reagents are considered beneficial for periodontal therapy. In the present study, we examined whether hop- and apple-derived polyphenols (HBP and ACT, respectively) inhibit PGE ₂ production by human gingival epithelial (HGE) cells stimulated with P. gingivalis components. HGE cells were stimulated with P. gingivalis membrane vesicles, and the effects of HBP, ACT and epigallocatechin gallate (EGCg) on PGE₂ production by HGE cells were evaluated using an enzyme-linked immunosorbent assay. HBP and EGCg significantly inhibited PGE₂ production, whereas ACT did not. By further fractionation steps of HBP to identify the effective components, 3 components of HBP, 2-[(2-methylpropanoyl)- phloroglucinol]1-O-β-D-glucopyranoside (MPPG), quercetin 3-O-β-D-glucopyranoside (isoquercitrin), and kaempferol 3-O-β-glucopyranoside (astragalin), were found to be elements which significantly inhibited cellular PGE₂ production. These results suggest that HBP is a potent inhibitor of cellular PGE₂ production induced by P. gingivalis, and HBP may be useful for the prevention and attenuation of periodontitis.