PANCREATIC STELLATE CELL NADPH OXIDASE SYSTEM AND ITS ROLE IN MEDIATING PANCREATIC STELLATE CELL PROLIFERATION BY PLATELET DERIVED GROWTH FACTOR (PDGF)

Abstract

Activated stellate cells are considered the key mediator in chronic pancreatitis and hepatic cirrhosis. Recently, studies in hepatic stellate cells demonstrated that the reactive oxygen species (ROS) producing enzyme system, NADPH oxidase, regulates proliferation and activation of hepatic stellate cells to produce fibrosis. The aims of this study were to determine whether NADPH oxidase system is present in pancreatic stellate cells, whether growth factors such as PDGF regulate this system and the role of ROS produced by this system in PDGF-mediated pancreatic stellate cell proliferation. We found NADPH oxidase components Nox1, Nox2, Nox4, p22phox, p47phox and p67phox were present at mRNA level in cultured pancreatic stellate cells, Furthermore; Western blot analysis demonstrated the presence of subunits for Nox2, p22phox, p47phox and p67phox in the membrane fraction of pancreatic stellate cells. The NADPH oxidase activity was confined to the membrane fraction of the stellate cells. PDGF treatment significantly increased NADPH oxidase activity in cultured pancreatic stellate cells in a time and dose-dependent manner. PDGF treatment at concentration of 10 ng/ml for 24 hours increased the NADPH oxidase activity by 42% and 260% in serum-enriched (15% FBS) and serum-starved (0.5% FBS) conditions, respectively. These effects were blocked by the NADPH oxidase inhibitor, diphenylene iodonium (DPI). Importantly, PDGF-mediated PSC proliferation was blocked by antioxidant N-acetyl-L-cysteine; ROS scavenger, Tiron and NADPH oxidase inhibitors, DPI and apocynin. Conclusions: NADPH oxidase system is present in pancreatic stellate cells. The activity of NADPH oxidase is modulated by the growth factor, PDGF. NADPH oxidase plays an important role in PDGF-mediated PSC proliferation. These results may provide new insights into mechanisms of pancreatic fibrosis as well as potential molecular target for therapy.