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

Reactive oxygen species act as second messengers in the signal transduction induced by inflammatory stimuli such as interleukin-1 (IL-1), tumor necros is factor-alpha (TNF alpha), and lipopolysaccharide (LPS). We have previous ly shown that both IL-l and LPS induce the urokinase-type plasminogen activ ator (uPA) gene expression in RC-K8 human malignant lymphoma cells. Here, w e provide evidence that an oxidative stimulation by either hydrogen peroxid e (H2O2) Or menadione (2-methyl-1,4-naphthoquinone (MQ)), a quinone compoun d that generates reactive oxygen species, causes the up-regulation of uPA e xpression in both RC-K8 cells and H69 human small cell lung carcinoma cells . uPA accumulation in their conditioned media was significantly increased a fter treatment with H2O2 or MQ and it was dose-dependent of the stimulus. N orthern blotting analysis revealed that uPA mRNA levels in both RC-K8 and H 69 cells were increased approximately 2-fold 9h after treatment with H2O2. The half-lives of uPA mRNA were not changed before and after H2O2 stimulati on. A synthetic antioxidant, N-acetylcysteine (NAC), completely inhibited t he H2O2-induced uPA mRNA accumulation. The inhibition of the on-going prote in synthesis by cycloheximide (CHX) did not inhibit the H2O2-induced uPA mR NA accumulation. These results suggest that the oxidative stress induces uP A accumulation through activating uPA gene transcription. Therefore, the st imuli that generate reactive oxygen species may influence many biological c ell-functions mediated by the uPA/plasmin system by regulating uPA expressi on in malignant cells. (C) 2000 Harcourt Publishers Ltd.