2011 Volume 54 Issue 1 Pages 10-19
Cigarette smoking is one of most significant risk factor for periodontitis. The characteristics of smoking-associated periodontitis are loss of periodontal attachment, loss of alveolar bone and a higher rate of tooth loss. These characteristics result from tobacco products changing the host immune response. Nicotine is a major component and the most pharmacologically active agent in tobacco. Porphyromonas gingivalis (P. gingivalis) is the most representative periodontopathic bacteria. In this study, we investigate the immunological effects of nicotine and P. gingivalis LPS on cytokine production in the human gingival fibroblast cell line Gin-1. Gin-1 cells were exposed for 24-72 hours at the indicated concentrations (0, 1, 10, 100μg/ml, 1mg/ml) of nicotine and/or 1μg/ml P. gingivalis LPS. The cell morphology and viability of Gin-1 cells was assessed by micro-photo examination and cell viability test. The expression and production of cytokines were examined using Real-time RT-PCR and ELISA, respectively. In addition, mitogen-activated protein kinase (MAPK) inhibitor for p-38, extracellular signal-regulated kinase (ERK) and the c-Jun N-terminal kinase (JNK) pathway were used to identify the signal transduction pathway (s). A high concentration of nicotine (1mg/ml) changed the morphology and reduced the cell viability of Gin-1 cells. However, an intermediate concentration of nicotine (10, 100μg/ml) did not induce any morphological change or reduce the viability of Gin-1 cells, but did increase the expression and production of inflammatory cytokines in a dose-dependent manner, and decreased the OPG expression and production level in Gin-1 cells. Moreover, nicotine and P. gingivalis LPS in combination can additively up-regulate IL-6 production. A low concentration of nicotine (1μg/ml) had no effect on Gin-1 cells. Specific inhibitors of p-38 and the ERK pathway, but not that of the JNK pathway, could significantly suppress nicotine-induced up-regulation of IL-6 and IL-8 production. These findings demonstrate that cigarette smoking may exacerbate periodontitis by augmenting inflammatory cytokine production induced by periodontopathic bacteria. Moreover, cigarette smoking may augment alveolar bone loss as a feature of smoking-associated periodontitis by increasing inflammatory cytokine production and decreasing OPG production leading to osteoclastogenesis via p-38 and the ERK pathway.
