Involvement of Angiotensin II and Reactive Oxygen Species in Pancreatic Fibrosis

Background: Pancreatic cancers often develop in the context of pancreatic fibrosis caused by chronic pancreas inflammation, which also results in the accumulation of reactive oxygen species (ROS), pancreatic parenchymal cell death, and stellate cell activation. Angiotensin II, which is converted from angiotensin I bytheangiotensin-converting enzyme (ACE), stimulates ROS production via NADPH oxidase. In stellate cells, angiotensin II activates the stress-activated protein kinase p38. However, the molecular mechanism by which angiotensin II regulates pancreatic inflammation and fibrosis remains to be determined. Methods: Wistar Bonn/Kobori (WBN/Kob) rats spontaneously develop chronic pancreatic inflammation. To examine whether blockade of the renin-angiotensin system affects the development of pancreatic fibrosis, WBN/Kob rats were given angiotensin II type 1 receptor (AT1R) blocker or ACE inhibitor (ACEI). Next, we assessed the role of angiotensin II and its possible downstream target p38α in stellate cell activation using primary stellate cells. Results: Treatment with AT1R blocker and ACEI prevented the development of chronic pancreatitis and fibrosis. In stellate cells, angiotensin II upregulated the expression of angiotensin II receptors, α-smooth muscle actin (SMA) and transforming growth factor-β. In addition, p38α was found to be essential to collagen type I production and α-SMA expression. ROS accumulation is enhanced in chronic pancreatic inflammation, which increases the risk of pancreatic cancer. Conclusions: Inhibition of the angiotensin II signaling pathway might be a promising strategy to prevent pancreatic fibrogenesis and subsequent carcinogenesis.