Pancreatic and pulmonary mast cells activation during experimental acute pancreatitis

Abstract

Aim: To study the activation of pancreatic and pulmonary mast cells and the effect of mast cell inhibition on the activation of peritoneal and alveolar macrophages during acute pancreatitis.

Methods: Pancreatitis was induced by intraductal infusion of 5% sodium taurodeoxycholate in rats. The mast cell inhibitor cromolyn was administered intraperitoneally (i.p.) 30 min before pancreatitis induction. The pancreatic and pulmonary tissue damage was evaluated histologically and mast cells and their state of activation were evaluated. Peritoneal and alveolar macrophages were obtained and the expression of tumor necrosis factor alpha was determined. Myeloperoxidase activity was measured to evaluate the effect of mast cell inhibition on the progression of the inflammatory process. Finally, the effect of plasma on cultured mast cells or macrophages was evaluated in vitro.

Results: The mast cell stabilizer significantly reduced inflammation in the pancreas and lung and the activation of alveolar macrophages but had no effect on peritoneal macrophages. Mast cell degranulation was observed in the pancreas during pancreatitis but no changes were observed in the lung. Plasma from rats with pancreatitis could activate alveolar macrophages but did not induce degranulation of mast cells in vitro.

Conclusion: Pancreatic mast cells play an important role in triggering the local and systemic inflammatory response in the early stages of acute pancreatitis. In contrast, lung mast cells are not directly involved in the inflammatory response related to pancreatic damage.

Figure 1

Presence of mast cells in pancreas (A-C) and lung (D-F), in control (A and D). Three hours after induction of pancreatitis (B and E) and under cromolyn treatment (C and F). Degranulating mast cells were observed in the pancreas after pancreatitis induction (B). Cromolyn treatment prevented mast cell degranulation (C). In contrast, no evident degranulation was observed in lung after induction of pancreatitis. Toluidine blue, × 40.

Figure 2

Effect of mast cell inhibitor, cromolyn. Three hours after pancreatitis induction, increased levels of lipase and histamine were detected in plasma. Cromolyn treatment had no effect on lipase, which is related to acinar cell damage, but prevented the increase in histamine. In tissue, leukocyte infiltration was evaluated by measuring myeloperoxidase (MPO) activity. Pancreatitis resulted in increased MPO activity in both pancreas and lung. Cromolyn treatment partially prevented these increases. ^aP < 0.05 vs C; ^cP < 0.05 vs AP. C: Control; AP: Acute pancreatitis.

Figure 3

Both peritoneal and alveolar macrophages were activated after induction of pancreatitis, but the expression of tumor necrosis factor α mRNA in peritoneal macrophages was one order of magnitude higher than that observed in alveolar macrophages. Tumor necrosis factor (TNF)α release was induced in peritoneal cells, while in alveolar cells the observed increase was not statistically significant. Cromolyn treatment completely prevented the activation of alveolar macrophages. In contrast, peritoneal macrophages remained activated under cromolyn treatment. ^aP < 0.05 vs C; ^cP < 0.05 vs AP. C: Control; AP: Acute pancreatitis.

Figure 4

The effect of plasma on cultured mast cell line RBL-2H3 and alveolar macrophages. Mast cells were not activated by plasma from animals with pancreatitis. In contrast, the expression of tumor necrosis factor (TNF)α in alveolar macrophages was induced by plasma from animals with pancreatitis. This induction was not observed when animals were treated with cromolyn. ^aP < 0.05 vs C; ^cP < 0.05 vs AP. C: Control; AP: Acute pancreatitis.