Protective effects of paeoniflorin on alveolar bone resorption and soft-tissue breakdown in experimental periodontitis

Background and Objective Paeoniflorin is the main active ingredient in Radix Paeoniae and has been reported to exhibit obvious anti-inflammatory and immune-regulatory activities. This study aimed to investigate the protective effects of paeoniflorin on alveolar bone destruction and soft-tissue breakdown in experimental periodontitis. As supplementary evidence, we evaluated the related expression of MMP-2, MMP-9, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Material and Methods Twenty-eight rats were randomly placed into the following four groups: healthy group; periodontitis group; periodontitis plus 30 mg/kg of paeoniflorin (P30) group; and periodontitis plus 60 mg/kg of paeoniflorin (P60) group. Periodontitis was induced in rats by placing ligatures around the lower first molars. The body weight of each rat was measured and recorded before and after the experiment. Bone resorption was evaluated using micro-computed tomography. Soft-tissue destruction and collagen fiber degradation were assessed by histologic analysis and picrosirius red staining. The expression levels of MMP-2, MMP-9, iNOS and COX-2 in gingiva were detected by western blotting. Results Periodontal tissues were intact in the healthy group. Alveolar bone level was significantly reduced, and evident inflammation of soft tissues was observed in the periodontitis group. Paeoniflorin significantly prevented alveolar bone loss and inflammatory infiltration in a dose-dependent manner. The collagen fiber fractions were significantly higher in the P30 and P60 groups than in the periodontitis group. The results of the western blot analyses revealed that both 30 and 60 mg/kg of paeoniflorin significantly down-regulated the levels of MMP-2, MMP-9, iNOS and COX-2. Conclusion This study provides the first evidence that paeoniflorin significantly down-regulates inflammatory infiltration and prevents alveolar bone loss and soft-tissue destruction in experimental periodontitis. The anti-inflammatory mechanism of paeoniflorin was further supported, in part, by its inhibitory effect on MMP-2, MMP-9, iNOS and COX-2.