Dexamethasone down-regulates the inflammatory mediators but fails to reduce the tissue injury in the lung of acute pancreatitis rat models.

Pulmonary complications are frequent in the course of acute pancreatitis. We investigate the effects of dexamethasone on lung injury in mild and severe AP. Mild and severe acute pancreatitis was induced in rats by bile-pancreatic duct obstruction and infusion of 3.5% sodium taurocholate into the bile-pancreatic duct, respectively. Dexamethasone (1 mg/kg) was given by intramuscular injection 1 h after acute pancreatitis. Plasma amylase activity was measured to evaluate the pancreas damage. Lungs were harvested for analysing mRNA expression of monocyte chemoattractant protein-1 (MCP-1), cytokine-induced neutrophil chemoattractant (CINC), P-selectin and intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO) activity (as index of neutrophil infiltration) and histological examination. Dexamethasone reduced the hyperamylasemia and hindered the pulmonary upregulation of MCP-1, CINC, P-selectin and ICAM-1, in both mild and severe acute pancreatitis. Despite this, dexamethasone treatment failed to reduce MPO activity and histological alterations developed in lungs during acute pancreatitis, either in bile-pancreatic duct obstruction or sodium taurocholate model. We conclude that pulmonary local factors different from inflammatory mediators contribute to leukocyte recruitment, so that although dexamethasone down-regulated the lung expression of chemokines and adhesion molecules during acute pancreatitis it was not able to prevent leukocyte infiltration, which could be responsible for maintaining the lung injury in either mild or severe acute pancreatitis.

Signal transduction of MCP-1 expression induced by pancreatitis-associated ascitic fluid in pancreatic acinar cells.

Pancreatitis-associated ascitic fluid (PAAF) is known to contribute to the progression of acute pancreatitis (AP). We have investigated the capability of PAAF to activate the expression of MCP-1 in pancreatic acinar cells and the involvement of MAPK, NF-kappaB and STAT3 as downstream signalling transduction pathways. The actions of dexamethasone (Dx) and N-acetylcysteine (NAC) on the PAAF's acinar effects have also been evaluated. Acinar cells were incubated for 1 hr with PAAF collected from rats with severe AP induced by sodium taurocholate in the absence or presence of Dx (10(-7) M) or NAC (30 mM). MCP-1 mRNA expression, phospho-p38-MAPK, IkappaB alpha, nuclear p65 levels and nuclear translocation of STAT3 were analysed. In response to PAAF, overexpression of MCP-1, phosphorylation of p38-MAPK, degradation of IkappaB alpha and increases in p65 nuclear levels and STAT3 activity were found in acinar cells. PAAF-mediated MCP-1 up-regulation was completely suppressed by Dx and NAC. MAPK activation was only inhibited by NAC, NF-kappaB activation was repressed by Dx and NAC, and STAT3 pathway was strongly blocked by Dx and significantly reduced by NAC. In conclusion, acinar cells were activated by PAAF to produce MCP-1, mainly via NF-kappaB and STAT3 pathways. Both downstream pathways were targeted by Dx and NAC to repress the PAAF-mediated acinar MCP-1 up-regulation.

ICAM-1 and CD11b/CD18 expression during acute pancreatitis induced by bile-pancreatic duct obstruction: effect of N-acetylcysteine.

Different molecules are involved in the recruitment of leukocytes during inflammation. The aim was to investigate (i) the contribution of acinar cells to the overall production of ICAM-1 and (ii) the kinetics of leukocyte CD11b/CD18 expression during acute pancreatitis (AP) induced by bile-pancreatic duct obstruction (BPDO) to evaluate the contribution of both molecules to leukocyte homing. The role of reactive oxygen species (ROS) as mediators in the expression of ICAM-1 and CD11b/CD18 was examined by using N-acetylcysteine (NAC) as an antioxidant treatment. By mechanisms resistant to NAC treatment, acinar cells were able to produce ICAM-1 at first onset of AP; other cell sources contribute to maintaining increased ICAM-1 plasma levels during AP. By contrast, CD11b/CD18 was overexpressed in leukocytes in the course of AP by oxidant-dependent mechanisms. Since NAC treatment reduced neutrophil infiltration in the pancreas, we conclude that CD11b/CD18 over-expression is required for leukocyte recruitment; however, other adhesion molecules in addition to ICAM-1 seem to contribute to leukocyte homing during BPDO-induced AP.

Pro- and anti-inflammatory response of acinar cells during acute pancreatitis. Effect of N-acetyl cysteine.

We investigate the ability of acinar cells to produce tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) at different stages of acute pancreatitis (AP). Since oxidative stress is involved in the inflammatory response, the effect of N-acetyl cysteine (NAC) has also been evaluated. AP was induced in rats by bile-pancreatic duct obstruction (BPDO). NAC (50 mg/kg) was administered 1h before and 1h after BPDO. Acinar cells were incubated for 4 h at 37 degrees C in 5% CO2 atmosphere in absence and presence of 24-h BPDO-PAAF (20%, v/v) as stimulant agent. Acinar production of TNF-alpha and IL-10 was analysed by flow cytometry. Plasma amylase activity and histological studies of the pancreas indicated the severity of AP. PAAF significantly stimulated the acinar production of TNF-alpha and IL-10 in control rats. TNF-alpha production was also significantly stimulated in acinar cells of rats with AP, although a decrease in the pro-inflammatory response was found from 6 h after BPDO onwards. However, acinar cells failed to produce IL-10 from 3 h after BPDO. The protective effect of NAC treatment against oxidative cell damage reduced the pancreatic injury and maintained and enhanced the ability of acinar cells to produce IL-10 at early AP stages. As long as acinar cells were not severely damaged in the course of AP, greater ability to produce cytokines in response to PAAF was found in those with higher forward scatter (R2 cells). We suggest that the capability of acinar cells to maintain an appropriate balance between the production of pro- and anti-inflammatory mediators could contribute to determine the degree of severity of AP.

Low enzyme content in the pancreas does not reduce the severity of acute pancreatitis induced by bile-pancreatic duct obstruction.

Enzyme load in pancreas has been considered a risk factor in the development of acute pancreatitis. In order to confirm this hypothesis our aim was to analyze the development and evolution of acute pancreatitis (AP) induced by bile-pancreatic duct obstruction (BPDO) after reducing the pancreatic enzyme content. L-364,718 - a potent CCK-receptor antagonist - was administered (0.1 mg/kg/day) for 7 days before inducing AP by BPDO. The course of AP was evaluated at different times from 1.5-48 h after BPDO. Amylase and trypsinogen contents and cytosolic calcium levels were measured by flow cytometry using specific antisera against pancreatic enzymes labelled with isothiocyanate of fluorescein and Fluo 3, respectively. The severity of the disease at the different stages was evaluated by measurements of amylase activity in ascites and plasma, percentage of pancreatic fluid and haematocrit. Electron microscopy study of the pancreas showed an increased number of zymogen granules spread through the acinar cells of control rats treated with L-364,718 for 7 days, however, total enzyme content in individual acinar cells was significantly (p < 0.01) diminished. AP significantly increased intracellular amylase and trypsinogen load from 3-12 h after BPDO, and prior L-364,718 treatment enhanced the blockade of enzyme secretion. As a result, acinar enzyme content was significantly increased from earlier stages (1.5 h after BPDO). In parallel, increased cytosolic calcium levels observed up to 24 h after BPDO appeared earlier in L-364,718-treated rats than in those not treated. The severity of AP seems to have been higher in rats previously treated with the CCK-receptor antagonist as indicated by the significantly higher pancreatic fluid and amylase activity in ascites and plasma observed at different times after BPDO. Our results indicate that there is no correlation between the severity of pancreatitis and the amount of enzymes accumulated in the pancreas before the disease is induced.