Inhibition of cyclooxygenase-2 reduces the protective effect of hepatocyte growth factor in experimental pancreatitis

Hepatocyte growth factor (HGF) overexpression is observed in experimental and clinical acute pancreatitis. Moreover, previous studies have shown that administration of HGF reduces pancreatic damage in experimental pancreatitis. The aim of our studies was to determine the role of cyclooxygenase-1 and cyclooxygenase-2 in the protective effect of HGF administration against caerulein-induced pancreatitis. Acute pancreatitis was induced in rats by infusion of caerulein. HGF was administered twice at the dose 10 microg/kg s.c. The activity of cyclooxygenase-1 and cyclooxygenase-2 was inhibited by resveratrol and rofecoxib, respectively (10 mg/kg). Immediately after cessation of caerulein or saline infusion, pancreatic blood flow, pancreatic cell proliferation, pancreatic prostaglandin E(2) generation, plasma lipase activity, plasma interleukin-1 beta and interleukin-10 concentration were measured and morphological signs of pancreatitis were examined. Expression of cyclooxygenase-1 and cyclooxygenase-2 mRNA transcripts was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Cyclooxygenase protein production was analyzed by Western blot. Administration of HGF or caerulein alone, or their combination, was without effect on cyclooxygenase-1 mRNA expression in pancreatic tissue. Expression of cyclooxygenase-2 mRNA was increased by HGF and caerulein. The maximal increase in cyclooxygenase-2 mRNA expression was observed when HGF administration was combined with caerulein infusion. A similar effect was observed when we studied the influence of HGF and caerulein on pancreatic cyclooxygenase-2 production, as determined by Western blot. Administration of HGF without induction of acute pancreatitis increased pancreatic prostaglandin E(2) generation and plasma interleukin-10, and this effect was abolished by the cyclooxygenase-2 inhibitor, rofecoxib. Treatment with HGF, during the development of pancreatitis, increased the plasma interleukin-10 concentration and attenuated pancreatic damage, as evidenced by: (a) histological improvement of pancreatic integrity; (b) the partial reversal of the decrease in DNA synthesis and pancreatic blood flow; (c) the reduction in pancreatitis-evoked increase in plasma lipase and interleukin-1 beta. Administration of resveratrol and rofecoxib alone was without effect on the development of pancreatitis. Combination of rofecoxib with HGF reduced the HGF-evoked increase in plasma interleukin-10 concentration and pancreatic prostaglandin E(2) generation, and abolished the protective effect of HGF against pancreatic damage in pancreatitis. Resveratrol did not affect the protective effect of HGF. We conclude that: (1) HGF induces cyclooxygenase-2 but not cyclooxygenase-1 expression; (2) inhibition of cyclooxygenase-2 in HGF-treated rats decreases the release of anti-inflammatory interleukin-10, increases the production of pro-inflammatory interleukin-1 beta and reduces pancreatic blood flow; (3) cyclooxygenase-2 activity is necessary for the protective effect of HGF in acute pancreatitis.