Increased MMP-9 and t-PA expression in human osteoblasts by nicotine

Objectives: Cigarette smoking is a major risk factor in the development and further progression of periodontal diseases. The proteolysis of extracellular matrix by matrix metalloproteinases (MMPs) and plasminogen activators (PAs) seems to be a key initiating event for the progression of the periodontal inflammatory process. However, there is little information about the proteolytic enzymes in smoking-associated periodontal disease. The aim of this study was to investigate the effects of nicotine on the expression of MMPs and PAs in human osteoblast cell line U2OS cells. Methods: Various concentrations of nicotine (0, 0.125, 0.25, 0.5, and 1 mM) without cytotoxicity were used to evaluate the gelatinolytic and caseinolytic activities in U2OS cells by using gelatin and casein zymography. Results: The gelatin zymograms revealed that MMP-2 (72 kDa) and MMP-9 (92 kDa) were secreted by U2OS cells. MMP-2 was released in much higher amounts than MMP-9. Secretion of MMP-9 was dose-dependent by treatment with nicotine (p<0.05). Casein zymography exhibited a caseinolytic band with a molecular weight of 70 kDa, indicative of the presence of tissue type plasminogen activators (t-PA). t-PA was also found to be upregulated by nicotine in a dose-dependent manner (p<0.05). Conclusions: Nicotine increased human osteoblast-mediated proteolytic enzymes, in part through the activation of MMP-9 and t-PA. The activation of MMP-9 and t-PA by nicotine suggests a potential role for nicotine in the pathogenesis of smoking-associated periodontal disease. This study was supported by NSC 96-2314-B-040-034.