Hydrogen peroxide activates activator protein-1 and mitogen-activated protein kinases in pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) are implicated in the pathogenesis of pancreatic inflammation and fibrosis, where oxidative stress is thought to play a key role. Reactive oxygen species such as hydrogen peroxide (H2O2) may act as a second messenger to mediate the actions of growth factors and cytokines. But the role of reactive oxygen species in the activation and regulation of cell functions in PSCs remains largely unknown. We here examined the effects of H2O2 on the activation of signal transduction pathways and cell functions in PSCs. PSCs were isolated from the pancreas of male Wistar rats, and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. Activation of transcription factors was examined by electrophoretic mobility shift assay and luciferase assay. Activation of mitogen-activated protein (MAP) kinases was assessed by Western blotting using anti-phosphospecific antibodies. The effects of H2O2 on proliferation, alpha(1)(I)procollagen gene expression, and monocyte chemoattractant protein-1 production were evaluated. The effect of H2O2 on the transformation of freshly isolated PSCs in culture was also assessed. H2O2 at non-cytotoxic concentrations (up to 100 mu M) induced oxidative stress in PSCs. H2O2 activated activator protein-1, but not nuclear factor kappa B. In addition, H2O2 activated three classes of MAP kinases: extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAP kinase. H2O2 induced alpha(1)(I)procollagen gene expression but did not induce proliferation or monocyte chemoattractant protein-1 production. H2O2 did not initiate the transformation of freshly isolated PSCs to myofibroblast-like phenotype. Specific activation of these signal transduction pathways and collagen gene expression by H2O2 may play a role in the pathogenesis of pancreatic fibrosis.