Activated pancreatic stellate cells (PSCs) play an important role in pancreatic 
fibrosis and inflammation, where oxidative stress is implicated in the 
pathogenesis. NADPH oxidase might be a source of reactive oxygen species (ROS) 
in the injured pancreas. This study aimed to clarify the expression and 
regulation of cell functions by NADPH oxidase in PSCs. PSCs were isolated from 
rat and human pancreas tissues. Expression of NADPH oxidase was assessed by 
reverse transcription-PCR and immunostaining. Intracellular ROS production was 
assessed using 2',7'-dichlorofluorescin diacetate. The effects of diphenylene 
iodonium (DPI) and apocynin, inhibitors of NADPH oxidase, on key parameters of 
PSC activation were evaluated in vitro. In vivo, DPI (at 1 mg.kg body 
wt(-1).day(-1)) was administered in drinking water to 10-wk-old male Wistar 
Bonn/Kobori rats for 10 wk and to rats with chronic pancreatitis induced by 
dibutyltin dichloride (DBTC). PSCs expressed key components of NADPH oxidase 
(p22(phox), p47(phox), NOX1, gp91(phox)/NOX2, NOX4, and NOX activator 1). 
PDGF-BB, IL-1beta, and angiotensin II induced ROS production, which was 
abolished by DPI and apocynin. DPI inhibited PDGF-induced proliferation, 
IL-1beta-induced chemokine production, and expression of alpha-smooth muscle 
actin and collagen. DPI inhibited transformation of freshly isolated cells to a 
myofibroblast-like phenotype. In addition, DPI inhibited the development of 
pancreatic fibrosis in Wistar Bonn/Kobori rats and in rats with DBTC-induced 
chronic pancreatitis. In conclusion, PSCs express NADPH oxidase to generate ROS, 
which mediates key cell functions and activation of PSCs. NADPH oxidase might be 
a potential target for the treatment of pancreatic fibrosis.