Macrophage-derived transforming growth factor-beta 1 induces hepatocellular injury via apoptosis in rat severe acute pancreatitis

Background. The mechanism of acute pancreatitis-induced hepatocellular inju ry is unclear We have observed hepatocyte apoptosis in rat acute necrotizin g pancreatitis. These studies were designed to deter mine the mediator(s) r esponsible for hepatocyte apoptosis and to clarify the significance of macr ophages as its source. Methods. A mt sodium deoxycholate-induced pancreatitis model was used. Immu nohistochemical studies for apoptosis-inducing mediators on hepatocytes wer e examined in the liver and on the peritoneal macrophages. The levels of tr ansforming growth factor-beta 1 (TGF-beta 1) were also evaluated quantitati vely with an enzyme-linked immunosorbent assay. Induction of apoptosis on t he hepatocytes was evaluated by in situ nick-end labeling and tissue DNA fr agmentation enzyme-linked immunosorbent assay. Finally, the effects of TGF- beta 1 neutralization and macrophage depletion were examined. Results. In the liver and the peritoneal macrophages, strong expression of TGF-beta 1 was defected ea, lv in the course of pancreatitis. in sodium deo xycholate-induced pancreatitis, the levels of TGP-beta 1 were also elevated in the plasma (9.2 +/- 0.8 ng/mL), in the pancreatitis-associated ascitic fluid (11.5 +/- 0.6 ng/mL), and in the liver homogenate (2.8 +/- 0.3 ng/g o f liver tissue). Moreover the amount of fragmented DNA of the liver with pa ncreatitis was 290% +/- 20% of that with a sham operation and serum alanine aminotransferase levels elavated to 248.2 +/- 67.0 IU/L. TGF-beta 1 neutra lization partly blocked the positive labeling on the nuclei of the hepatocy tes, the elevation of the amounts of fragmented DNA (205% +/- 10% of sham o peration), and the serum in alanine aminotransferase level (144.2 +/- 14.9 IU/L). On the other hand, the macrophage depletion caused a marked decrease in the TGF-beta 1 protein level in the plasma (4.8 +/- 1.2 ng/mL) or in th e pancreatitis-associated ascitic fluid (8.0 +/- 1.0 ng/mL). Moreover, the macrophage depletion completely inhibited the elevation of the TGF-beta 1 p rotein level in the liver homogenate (1.5 +/- 0.4 ng/g of liver tissue), an d thereafter decreased the amounts of the positive labeling on the nuclei o f the hepatocytes and decreased the amount of fragmented DNA (120% +/- 18% of sham operation) and the serum alanine aminotransferase elevation (119.2 +/- 24.2 IU/L). Conclusions. In a model of sodium deoxycholate-induced pancreatitis, macrop hages are responsible for pancreatitis-induced hepatocellular injury by mea ns of apoptosis, and macrophage-derived TGF-beta 1 is one of the major fact ors inducing the hepatocyte apoptosis.