Effects and mechanisms of plant antioxidants in periodontitis and osteoporosis

Associated with the aging of the world population, periodontitis and osteoporosis are regarded as two major public health problems nowadays. Osteoporosis and periodontitis-induced alveolar bone loss are the most common bone degeneration pathologies. Although the pathological conditions of both diseases are different, they have mechanistically quite some similarities. Oxidative stress (OS), resulting from their pathological conditions, plays an important role in the bone loss of periodontitis and osteoporosis. Development of effective treatment requires a better understanding of the detrimental conditions and the related potential treatment approaches. In this thesis, we investigated the relationship between oxidative damage and periodontal tissue destruction in periodontitis, as well as the role of three plant antioxidants (silibinin (SB), curcumin (Cur), and notoginsenoside R1 (NGR1)) in periodontitis or osteoporosis. We found that: 1. Enhanced local and systemic oxidative damages are associated with more severe levels of periodontal tissue destruction. The downregulation of Nrf2 in periodontal tissues plays a key role in diabetes mellites-induced periodontal tissue destruction aggravation. 2. SB administration can down-regulate periodontitis-induced OS and inflammation, so as to attenuate periodontal tissue destruction in experimental periodontitis. 3. Cur significantly prevented the OS-induced damage of osteoblasts through activating GSK3β-Nrf2 signaling pathway and scavenging reactive oxygen species. 4. NGR1 significantly attenuates OS-induced mitochondrial damage and restores osteogenic differentiation of osteoblast through the blockage of JNK signaling pathway. In conclusion, plant antioxidants (Cur, NGR1, SB) effectively inhibit cellular oxidative damage-induced bone loss in osteoporosis and periodontitis, thus bearing potential therapeutic value to these diseases.