Stimulation of plasminogen activator/plasmin system in gingival fibroblast cells by oxygen radicals

The effect of extracellular oxygen radicals on cultured gingival fibroblast cells (Gin cells) was investigated in the plasminogen activator (PA)/plasmin system. The activation of the PA/plasmin system in Gin cells exposed to a sublethal oxygen radical [hypoxanthine (HX) 0.1 mg ml-1/xanthine oxidase (XOD) 5 munit ml-1] system was examined. Following a 1 h exposure, washed cells were cultured for up to 24 h in fresh medium containing 2% fetal calf serum. The exogenous addition of superoxide dismutase, an oxygen radical scavenger, abolished the PA/plasmin activity enhanced by the HX/XOD system. The PA produced by Gin cells was found to be urokinase-type PA (uPA), as preincubation of Gin cell-conditioned medium with anti-uPa serum completely inhibited PA activity. These findings suggest that extracellular oxidant targetting to Gin cells may be involved in the progression of inflammation and the invasion of periodontium through stimulation of the PA/plasmin system.