Sabrina Gea-Sorlí

Release of inflammatory mediators by adipose tissue during acute pancreatitis.

Obesity and lipid metabolism are associated with the severity of acute pancreatitis. Fat necrosis appears in the severe acute pancreatitis as a consequence of the release of lipolytic enzymes, but its potential role on the progression of the disease is unclear. In this study, we have examined the role of white adipose tissue as a source of inflammatory mediators that can promote systemic inflammation during experimental taurocholate‐induced acute pancreatitis in rats. The inflammatory status and the expression of TNFα, iNOS, adiponectin and IL‐10 were determined in necrotic and non‐necrotic areas of adipose tissue. Samples of adipose tissue were also used to induce the activation of macrophages in vitro. Finally, the release of TNFα to mesenterial vessels surrounded by necrotic or non‐necrotic fat was evaluated in ex vivo perfused mesenterium. A strong inflammatory infiltrate was observed in the border between necrotic and non‐necrotic areas of adipose tissue. In these areas, high expression of TNFα and iNOS and a reduced expression of IL‐10 were observed, while adiponectin showed only a moderate increase. Necrotic fat strongly activates peritoneal macrophages in vitro. Mesenterial areas with fat necrosis release to the vascular vessels significantly increased amounts of TNFα when compared to vessels without necrosis. Altogether, these results indicate that adipose tissue inflammation is a process secondary to acute pancreatitis but also contributes to the generation of mediators potentially involved in the induction of the systemic inflammatory response. In particular, the areas of fat necrosis are important sources of inflammatory mediators. Copyright

In vitro, but not in vivo, reversibility of peritoneal macrophages activation during experimental acute pancreatitis

BackgroundSystemic inflammatory response syndrome is one of the major pathobiologic processes underlying severe acute pancreatitis and the degree of macrophage activation could be one of the factors that finally determine the severity of the disease. We evaluated the activation phenotype in peritoneal macrophages during the progression of an experimental model of acute pancreatitis induced in rats by intraductal administration of 5% sodium taurocholate and the effect of IL-4 and IL-13 to modulate this activation.Samples of pancreas, lung and adipose tissue as well as plasma were also obtained. In some animals IL4 and IL13 were injected 1 h after induction in order to modulate macrophage activation. The expressions of TNFα and Mannose Receptor, as indicators of classical and alternative macrophage activation, were evaluated. Levels of myeloperoxidase and plasma lipase were determined to evaluate the severity of the inflammatory process. The stability of IL-4 in ascitic fluid and plasma was evaluated.ResultsPeritoneal macrophages showed a classical M1 activation clearly induced 3 h after pancreatitis induction and maintained until 18 h. Treatment with IL-4 and IL-13 reversed the activation of macrophages from a classical M1 to alternative M2 in vitro, but failed to modulate the response of peritoneal macrophages in vivo despite a reduction in inflammation was observed in lung and adipose tissue. Finally, IL-4 shows a short half-live in ascitic fluid when compared with plasma.ConclusionPeritoneal macrophages adopt a pro-inflammatory activation early during acute pancreatitis. Treatment with M2 cytokines could revert in vitro the pancreatitis-induced activation of macrophages but fails to modulate its activation in vivo. This treatment has only a moderate effect in reducing the systemic inflammation associated to acute pancreatitis. Hydrolytic enzymes presents in ascitic fluid could be involved in the degradation of cytokines, strongly reducing its utility to modulate peritoneal macrophages in pancreatitis.

Activation of lung macrophage subpopulations in experimental acute pancreatitis

Pulmonary macrophages exist in two different anatomical compartments in the lower respiratory tract: alveolar macrophages in the alveoli and interstitial macrophages in the interstitium. Depending on the micro‐environmental stimulation, macrophages follow different activation pathways. According to their inflammatory response pattern, activated macrophages have been characterized as pro‐inflammatory (M1), wound‐healing (M2a) and regulatory (M2b). Since acute pancreatitis occurs in parallel with acute lung injury, the profile of the different macrophage subpopulations could be relevant in the progression of the disease. The activation of lung alveolar and interstitial macrophages was assessed in an experimental model of severe acute pancreatitis induced in rats by intraductal infusion of 3.5% sodium taurocholate. Alveolar and interstitial macrophages were obtained and the expression of markers of different activations was evaluated. Activation of nuclear factors PPARγ and NF‐κB, which are involved in the acquisition of different phenoytpes, was also measured. Alveolar macrophages acquired an early M1 phenotype characterized by the expression of inflammatory cytokines and NF‐κB activation. In contrast, interstitial macrophages followed the inhibitory M2b pathway. In these macrophages, PPARγ became activated and the anti‐inflammatory cytokine IL‐10 was expressed. These results suggest that alveolar and interstitial macrophages play different roles in acute lung injury associated with acute pancreatitis. Alveolar macrophages promote an early inflammatory response, whereas interstitial macrophages help resolve inflammation. Copyright

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.

Differences in the Inflammatory Response Induced by Acute Pancreatitis in Different White Adipose Tissue Sites in the Rat

Background There is increasing evidence of the role of adipose tissue on the systemic effects of acute pancreatitis. Patients with higher body mass index have increased risk of local and systemic complications and patients with android fat distribution and higher waist circumference are at greater risk for developing the severe form of the disease. Here we evaluated the changes on different areas of adipose tissue and its involvement on the inflammatory response in an experimental model of acute pancreatitis. Methods Pancreatitis was induced in male Wistar rats by intraductal administration of sodium taurocholate. Orlistat was administered to inhibit lipase activity. Activation of peritoneal macrophages was evaluated by measuring IL1β and TNFα expression. Inflammation was evaluated by measuring myeloperoxidase activity in mesenteric, epididymal and retroperitoneal areas of adipose tissue. Changes in the expression of inflammatory mediator in these areas of adipose tissue were also evaluated by RT-PCR. Results Pancreatitis induces the activation of peritoneal macrophages and a strong inflammatory response in mesenteric and epididymal sites of adipose tissue. By contrast, no changes were found in retroperitoneal adipose tissue. Inhibition of lipase prevented the activation of macrophages and the local inflammation in adipose tissue. Conclusions Our results confirm the involvement of adipose tissue on the progression of systemic inflammatory response during acute pancreatitis. However, there is a considerable diversity in different adipose tissue sites. These differences need to be taken into account in order to understand the progression from local pancreatic damage to systemic inflammation during acute pancreatitis.

New Roles for Corticosteroid Binding Globulin and Opposite Expression Profiles in Lung and Liver

Corticosteroid-binding globulin (CBG) is the specific plasma transport glycoprotein for glucocorticoids. Circulating CBG is mainly synthesized in liver but, its synthesis has been located also in other organs as placenta, kidney and adipose tissue with unknown role. Using an experimental model of acute pancreatitis in cbg-/- mice we investigated whether changes in CBG affect the progression of the disease as well as the metabolism of glucocorticoids in the lung. Lack of CBG does not modify the progression of inflammation associated to pancreatitis but resulted in the loss of gender differences in corticosterone serum levels. In the lung, CBG expression and protein level were detected, and it is noteworthy that these showed a sexual dimorphism opposite to the liver, i.e. with higher levels in males. Reduced expression of 11β-HSD2, the enzyme involved in the deactivation of corticosterone, was also observed. Our results indicate that, in addition to glucocorticoids transporter, CBG is involved in the gender differences observed in corticosteroids circulating levels and plays a role in the local regulation of corticosteroids availability in organs like lung.

Minocycline inhibits peritoneal macrophages but activates alveolar macrophages in acute pancreatitis

Minocycline is a tetracycline antibiotic that, in addition to its antimicrobial function, has been reported to possess a relevant anti-inflammatory activity. Its effects have been extensively evaluated in inflammatory-related neurological diseases. Here, we evaluate its effect on the systemic inflammatory response in a model of experimental acute pancreatitis. Minocycline treatment significantly reduced the inflammation in pancreas and mesenterium, had no effect on the adipose tissue inflammation, and increased the inflammatory response in the lung. These differences seem to be related with different effects exerted on peritoneal and alveolar macrophages. In vitro, minocycline reduced the expression of IL-1β and inhibit the activation of nuclear factor kappa B (NF-κB) on peritoneal macrophages, while it had no effect on alveolar macrophages. Our data indicates that although minocycline may be useful as a tool to control some inflammatory processes, differences on its effects depending on the population of macrophages involved in the process can be expected. In the particular case of acute pancreatitis, it could promote or potentiate inflammation in the lung so that its use does not appear to be recommended.

Role of protease-activated receptor 2 in lung injury development during acute pancreatitis in rats

Objective The objective of this study was to evaluate whether an uncontrolled activation of mast cells and macrophages through protease-activated receptor-2 (PAR-2) during acute pancreatitis could develop lung injury. Methods Pancreatitis was induced in rats by intraductal infusion of sodium taurocholate. In a group of animals, PAR-2 antagonist or trypsin (TRP) inhibitor was intravenously administered before the pancreatitis induction. In additional groups, the animals were treated with PAR-2–activating peptide or pancreatic TRP. The myeloperoxidase (MPO) activity was measured to evaluate the progression of inflammation. Results Plasma from the animals with pancreatitis and pancreatic TRP induced the secretion of mast cells and alveolar macrophages as well as increased the density of PAR-2 in the plasma membrane. The treatment of alveolar macrophages with TRP, tryptase, as well as PAR-1– and PAR-2–activating peptide led to an increase in calcium-triggered exocytosis. Similar results were obtained in acinar cells. The intravenous injection of PAR-2–activating peptide and TRP induced an increase in MPO activity in the lung. The intravenous injection of PAR-2 antagonist or TRP inhibitor before the pancreatitis induction could prevent the increase in MPO activity in the pancreas and the lung. Conclusions The TRP generated during acute pancreatitis could be involved in the progression of lung injury through the activation of PAR-2 in alveolar macrophages.