ABSTRACT: Role of oxidative, AP-1, and hypoxia-responsive signaling pathways in induction of plasminogen activator inhibitor-1 (PAI-1) by nickel.

Human epidemiological and animal studies have associated inhalation of nickel dusts with increased incidence of pulmonary fibrosis. At the cellular level, we have shown that non-cytotoxic levels of particulate nickel subsulfide inhibit fibrinolysis by transcriptionally inducing expression of PAI-1, an inhibitor of urokinase-type plasminogen activator. Therefore, the current studies examined whether nickel stimulated the PAI-1 promoter though an oxidant-sensitive, AP-1 or a hypoxia-like, HIF-1a signaling pathway. Addition of nickel to BEAS-2B human airway epithelial cells stimulated intracellular oxidation, measured as DCF fluorescence, increased both HIF-1a and c-Jun protein levels, and elevated PAI-1 mRNA levels. Pre-treatment of the cells with either the antioxidant N-acetyl-L-cysteine (NAC) or the DPH oxidase inhibitor apocyanin blocked nickel stimulated DCF fluorescence, but did not affect the increased HIF- 1a protein of PAI-1 mRNA levels. Nickel enhanced expression of a transiently transfected AP-1-luciferase reporter construct, and expression of the dominant-negative inhibitor of AP-1, TAM67, prevented induction of PAI-1 mRNA levels by nickel. Pre-treating cells with antisense oligonucleotides to HIFa also abolished nickel-stimulated PAI-1 gene transcription. These data indicate that nickel-stimulated reactive oxygen species and NADPH oxidase are not involved in nickel-induced transcriptional activation of PAI-1. However, this induction requires both AP-1 and HIF-1a signaling pathways. Supported by SBRP grant ES07373.

Andrew AS, Klei LR, Barchowsky A. Role of oxidative, AP-1, and hypoxia-responsive signaling pathways in induction of plasminogen activator inhibitor-1 (PAI-1) by nickel. Free Radical Biology and Medicine. 29:S53, 2001