Submitted on January 8, 2007
Accepted on August 23, 2007
Externally-applied pressure activates pancreatic stellate cells through the generation of intracellular reactive oxygen species
Hiroshi Asaumi1, Shiro Watanabe2, Masashi Taguchi3, Mitsuo Tashiro3, and Makoto Otsuki1*
1 Third Department of Internal Medicine, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan
2 Third Department of Internal Medicine, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan; Kitakyushu, United States
3 Third Department of Internal Medicine, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan; Kitakyushu, Japan
* To whom correspondence should be addressed. E-mail: mac-otsk{at}med.uoeh-u.ac.jp.
Introduction: Local tissue pressure is higher in chronic pancreatitis than in the normal pancreas. We reported recently that pressure application induces synthesis of extracellular matrix (ECM) and cytokines in pancreatic stellate cells (PSCs), and that epigallocatechin gallate (EGCG), a potent antioxidant, inhibits the transformation of PSCs from quiescent to activated phenotype and ethanol-induced synthesis of ECM and cytokines in PSCs. These results suggest that oxidative stress and reactive oxygen species (ROS) are important in PSC activation. The aim of this study was to clarify the effects of ROS on activation and functions of pressure-stimulated PSCs.
Methods: We used freshly isolated rat PSCs and culture activated PSCs. Pressure was applied on rat cultured PSCs by adding compressed helium gas into a pressure loading apparatus. PSCs were cultured with or without antioxidants (EGCG and NAC) under normal or elevated pressure.
Results: Externally-applied high pressure (80 mmHg) resulted in a gradual decrease of SOD activity in PSCs and increased intracellular ROS generation as early as 30 sec, reaching a peak level at 1 h. Antioxidants significantly inhibited ROS generation. Pressure increased the expression levels of 
-smooth muscle actin, type I procollagen 1 and transforming growth factor-
1 in PSCs. EGCG suppressed these alterations, abolished pressure-induced phosphorylation of p38 mitogen-activated protein kinase, and suppressed pressure-induced PSC transformation to activated phenotype.
Conclusion: Our results indicated that ROS is a key player in pressure-induced PSC activation and ECM synthesis. Antioxidants could be potentially effective against the development of pancreatic fibrosis in patients with chronic pancreatitis.
