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 chall enged frequently by oral bacteria. Lipopolysaccharide (LPS) from periodonta l pathogens can penetrate gingival tissues and stimulate plasminogen activa tor (PA) activity which is implicated in the PA/plasmin proteolytic system. The PA/plasmin system plays an important role in the degradation of the ex tracellular matrix and synthesis of kinin in the process of inflammation. A nti-inflammatory effects by low-energy laser irradiation have been reported . However, the mechanisms of biostimulatory effects have not been elucidate d in detail. The primarily cultured hGF cells were challenged with LPS isol ated from Campylobacter rectus which was known as a periodontal pathogen an d Ga-AI-As diode low energy laser was irradiated (830 nm, 7.90 J/cm(2)). Th e 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-d ependent manner. This effect was involved in the reduction of tPA mRNA leve ls.