Oxidative stress induces urokinase-type plasminogen activator in RC-K8 human malignant lymphoma cells and H69 human small cell lung carcinoma cells

Abstract

Reactive oxygen species act as second messengers in the signal transduction induced by inflammatory stimuli such as interleukin-1 (IL-1), tumor necrosis factor-α (TNFα), and lipopolysaccharide (LPS). We have previously shown that both IL-1 and LPS induce the urokinase-type plasminogen activator (uPA) gene expression in RC-K8 human malignant lymphoma cells. Here, we provide evidence that an oxidative stimulation by eit her hydrogen peroxide (H₂O₂) or menadione (2-methyl-1,4-naphthoquinone (MQ)), a quinone compound that generates reactive oxygen species, causes the up-regulation of uPA expression in both RC-K8 cells and H69 human small cell lung carcinoma cells. uPA accumulation in their conditio ned media was significantly increased after treatment with H₂O₂or MQ and it was dose-dependent of the stimulus. Northern blotting analysis revealed that uPA mRNA levels in both RC-K8 and H69 cells were increased approximately 2-fold 9h after treatment with H₂O₂. The half-lives of uPA mRNA were not changed before and after H₂O₂stimulation. A synthetic antioxidant, N-acetylcysteine (NAC), completely inhibited the H₂O₂-induced uPA mRNA accumulation. The inhibition of the on-going protein synthesis by cycloheximide (CHX) did not inhibit the H₂O₂-induced uPA mRNA accumulation. These results suggest that the oxidative stress induces uPA accumulation through activating uPA gene transcription. Therefore, the stimuli that generate reactive oxygen species may influence many biological cell-functions mediated by the uPA/plasmin system by regulating uPA expression in malignant cells.