Pancreatic and pulmonary mast cells activation during experimental acute pancreatitis

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 α 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 signif icantly 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.

Role of macrophages in the progression of acute pancreatitis

In addition to pancreatic cells,other inflammatory cell populations contribute to the generation of inflammatory mediators during acute pancreatitis.In particular,macrophages could be activated by mediators released during pancreatitis by a damaged pancreas.It has been reported that peritoneal macrophages,alveolar macrophages and Kupffer cells become activated in different stages of severe acute pancreatitis.However,macrophages display remarkable plasticity and can change their physiology in response to environmental cues.Depending on their microenvironmental stimulation,macrophages could follow different activation pathways resulting in marked phenotypic heterogeneity.This ability has made these cells interesting therapeutical targets and several approaches have been assayed to modulate the progression of inflammatory response secondary to acute pancreatitis.However,despite the recent advances in the modulation of macrophage function in vivo,the therapeutical applications of these strategies require a better understanding of the regulation of gene expression in these cells.

Peroxisome proliferator-activated receptor γ agonist reduces the severity of post-ERCP pancreatitis in rats

AIM: To determine the effects of prophylactic peroxi-some proliferator-activated receptor (PPARγ) agonist administration in an experimental model of post-endoscopic retrograde cholangiopancreatography (post-ERCP) acute pancreatitis.METHODS: Post-ERCP pancreatitis was induced in male Wistar rats by infusion of contrast medium into the pancreatic duct. In additional group, rosiglitazone, a PPARγ agonist, was administered 1 h before infusion of contrast medium. Plasma and pancreas samples were obtained 6 h after the infusion.RESULTS: Infusion of contrast medium into the pan-creatic duct resulted in an inflammatory process characterized by increased lipase levels in plasma, and edema and myeloperoxidase activity (MPO) in pancreas. This result correlated with the activation of nuclear factor κB (NFκB) and the inducible NO synthase (iNOS) expression in pancreatic cells. Rosiglitazone reduced the increase in lipase and the level of edema and the increase in myeloperoxidase as well as the activation of NFκB and iNOS expression.CONCLUSION: A single oral dose of rosiglitazone, given 1 h before post-ERCP pancreatitis induction is effective in reducing the severity of the subsequent inflammatory process. The protective effect of rosiglitazone was associated with NFκB inhibition and the blockage of leukocyte infiltration in pancreas.

Pancreatitis-associated protein:From a lectin to an anti-inflammatory cytokine

Pancreatitis-associated protein (PAP) was discovered in the pancreatic juice of rats with acute pancreatitis. PAP is a 16 kDa secretory protein structurally related to the C-type lectins although classical lectin-related function has not been reported yet. Then, it was demonstrated that PAP expression may be activated in some tissues in a constitutive or injury- and inflammation-induced manner. More recently, it has been found that PAP acts as an anti-inflammatory factor in vitro and in vivo. PAP expression can be induced by several pro- and anti-inflammatory cytokines and by itself through a JAK/STAT3-dependent pathway. PAP is able to activate the expression of the anti-inflammatory factor SOCS3 through the JAK/STAT3-dependent pathway. The JAK/STAT3/SOCS3 pathway seems to be a common point between PAP and several cytokines. Therefore, it is reasonable to propose that PAP is a new anti- inflammatory cytokine.