Reduction of plasminogen activator activity stimulated by lipopolysaccharide from periodontal pathogen in human gingival fibroblasts by low-energy laser irradiation

Human gingival fibroblasts (hGF) reside in gingival tissues which are challenged frequently by oral bacteria. Lipopolysaccharide (LPS) from periodontal pathogens can penetrate gingival tissues and stimulate plasminogen activator (PA) activity which is implicated in the PA/plasmin proteolytic system. The PA/plasmin system plays an important role in the degradation of the extracellular matrix and synthesis of kinin in the process of inflammation. Anti-inflammatory effects by low-energy laser irradiation have been reported. However, the mechanisms of biostimulatory effects have not been elucidated in detail. The primarily cultured hGF cells were challenged with LPS isolated from Campylobacter rectus which was known as a periodontal pathogen and Ga-AI-As diode low energy laser was irradiated (830 nm, 7.90 J/cm(2)). The cultured medium of hGF cells showed a marked elevation in PA activity by LPS, which was significantly inhibited by the laser irradiation in a dose-dependent manner. This effect was involved in the reduction of tPA mRNA levels.