Systemic delivery of AAV-GCDH ameliorates HLD-induced phenotype in a glutaric aciduria type I mouse model.

Glutaric aciduria type 1 (GA1) is a rare inherited metabolic disorder caused by a deficiency of glutaryl-coenzyme A dehydrogenase (GCDH), with accumulation of neurotoxic metabolites, resulting in a complex movement disorder, irreversible brain damage, and premature death in untreated individuals. While early diagnosis and a lysine restricted diet can extend survival, they do not prevent neurological damage in approximately one-third of treated patients, and more effective therapies are required. Here we report the efficacy of adeno-associated virus 9 (AAV9)-mediated systemic delivery of human GCDH at preventing a high lysine diet (HLD)-induced phenotype in Gcdh -/- mice. Neonatal treatment with AAV-GCDH restores GCDH expression and enzyme activity in liver and striatum. This treatment protects the mice from HLD-aggressive phenotype with all mice surviving this exposure; in stark contrast, a lack of treatment on an HLD triggers very high accumulation of glutaric acid, 3-hydroxyglutaric acid, and glutarylcarnitine in tissues, with about 60% death due to brain accumulation of toxic lysine metabolites. AAV-GCDH significantly ameliorates the striatal neuropathology, minimizing neuronal dysfunction, gliosis, and alterations in myelination. Magnetic resonance imaging findings show protection against striatal injury. Altogether, these results provide preclinical evidence to support AAV-GCDH gene therapy for GA1.

Aberrant TIMP-1 overexpression in tumor-associated fibroblasts drives tumor progression through CD63 in lung adenocarcinoma.

Tissue inhibitor of metalloproteinase-1 (TIMP-1) is an important regulator of extracellular matrix turnover that has been traditionally regarded as a potential tumor suppressor owing to its inhibitory effects of matrix metalloproteinases. Intriguingly, this interpretation has been challenged by the consistent observation that increased expression of TIMP-1 is associated with poor prognosis in virtually all cancer types including lung cancer, supporting a tumor-promoting function. However, how TIMP-1 is dysregulated within the tumor microenvironment and how it drives tumor progression in lung cancer is poorly understood. We analyzed the expression of TIMP-1 and its cell surface receptor CD63 in two major lung cancer subtypes: lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC), and defined the tumor-promoting effects of their interaction. We found that TIMP-1 is aberrantly overexpressed in tumor-associated fibroblasts (TAFs) in ADC compared to SCC. Mechanistically, TIMP-1 overexpression was mediated by the selective hyperactivity of the pro-fibrotic TGF-ß1/SMAD3 pathway in ADC-TAFs. Likewise, CD63 was upregulated in ADC compared to SCC cells. Genetic analyses revealed that TIMP-1 secreted by TGF-ß1-activated ADC-TAFs is both necessary and sufficient to enhance growth and invasion of ADC cancer cells in culture, and that tumor cell expression of CD63 was required for these effects. Consistently, in vivo analyses revealed that ADC cells co-injected with fibroblasts with reduced SMAD3 or TIMP-1 expression into immunocompromised mice attenuated tumor aggressiveness compared to tumors bearing parental fibroblasts. We also found that high TIMP1 and CD63 mRNA levels combined define a stronger prognostic biomarker than TIMP1 alone. Our results identify an excessive stromal TIMP-1 within the tumor microenvironment selectively in lung ADC, and implicate it in a novel tumor-promoting TAF-carcinoma crosstalk, thereby pointing to TIMP-1/CD63 interaction as a novel therapeutic target in lung cancer.

Inhibition of miR-222 by Oncolytic Adenovirus-Encoded miRNA Sponges Promotes Viral Oncolysis and Elicits Antitumor Effects in Pancreatic Cancer Models.

Oncolytic adenoviruses (OA) are envisioned as a therapeutic option for patients with cancer, designed to preferentially replicate in cancer cells. However, the high number of genetic alterations in tumors can generate a context in which adenoviruses have difficulties replicating. Abnormal miRNAs expression is a trademark of pancreatic cancer, with several oncogenic miRNAs playing essential roles in cancer-associated pathways. The perturbed miRNome induces reprogramming of gene expression in host cells that can impact the complex interplay between cellular processes and viral replication. We have studied the effects of overexpressed miRNAs on oncolytic adenoviral activity and identified miRNAs modulators of adenoviral oncolysis in pancreatic cancer cells. Inhibition of the highly upregulated miR-222 sensitized cancer cells to oncolysis. To provide a therapeutic application to this insight, we engineered the oncolytic adenovirus AdNuPARmE1A with miR-222 binding sites, working as sponges to withdraw the miRNA from the cellular environment. AdNuPAR-E-miR222-S mediated-decrease of miR-222 expression in pancreatic cancer cells strongly improved the viral yield and enhanced the adenoviral cytotoxic effects. Antitumoral studies confirmed a high activity for AdNuPARmE1A-miR222-S in vivo, controlling tumor progression more effectively than the scrambled control virus in xenografts. We demonstrated that the increased antitumor potency of the novel oncolytic virus resulted from the combinatory effects of miR-222 oncomiR inhibition and the restoration of miR-222 target genes activity enhancing viral fitness.

Epigenetic SMAD3 Repression in Tumor-Associated Fibroblasts Impairs Fibrosis and Response to the Antifibrotic Drug Nintedanib in Lung Squamous Cell Carcinoma.

The tumor-promoting fibrotic stroma rich in tumor-associated fibroblasts (TAF) is drawing increased therapeutic attention. Intriguingly, a trial with the antifibrotic drug nintedanib in non-small cell lung cancer reported clinical benefits in adenocarcinoma (ADC) but not squamous cell carcinoma (SCC), even though the stroma is fibrotic in both histotypes. Likewise, we reported that nintedanib inhibited the tumor-promoting fibrotic phenotype of TAFs selectively in ADC. Here we show that tumor fibrosis is actually higher in ADC-TAFs than SCC-TAFs in vitro and patient samples. Mechanistically, the reduced fibrosis and nintedanib response of SCC-TAFs was associated with increased promoter methylation of the profibrotic TGFß transcription factor SMAD3 compared with ADC-TAFs, which elicited a compensatory increase in TGFß1/SMAD2 activation. Consistently, forcing global DNA demethylation of SCC-TAFs with 5-AZA rescued TGFß1/SMAD3 activation, whereas genetic downregulation of SMAD3 in ADC-TAFs and control fibroblasts increased TGFß1/SMAD2 activation, and reduced their fibrotic phenotype and antitumor responses to nintedanib in vitro and in vivo. Our results also support that smoking and/or the anatomic location of SCC in the proximal airways, which are more exposed to cigarette smoke particles, may prime SCC-TAFs to stronger SMAD3 epigenetic repression, because cigarette smoke condensate selectively increased SMAD3 promoter methylation. Our results unveil that the histotype-specific regulation of tumor fibrosis in lung cancer is mediated through differential SMAD3 promoter methylation in TAFs and provide new mechanistic insights on the selective poor response of SCC-TAFs to nintedanib. Moreover, our findings support that patients with ADC may be more responsive to antifibrotic drugs targeting their stromal TGFß1/SMAD3 activation. SIGNIFICANCE: This study implicates the selective epigenetic repression of SMAD3 in SCC-TAFs in the clinical failure of nintedanib in SCC and supports that patients with ADC may benefit from antifibrotic drugs targeting stromal TGFß1/SMAD3.

Mutations in TIMM50 cause severe mitochondrial dysfunction by targeting key aspects of mitochondrial physiology.

3-Methylglutaconic aciduria (3-MGA-uria) syndromes comprise a heterogeneous group of diseases associated with mitochondrial membrane defects. Whole-exome sequencing identified compound heterozygous mutations in TIMM50 (c.[341 G>A];[805 G>A]) in a boy with West syndrome, optic atrophy, neutropenia, cardiomyopathy, Leigh syndrome, and persistent 3-MGA-uria. A comprehensive analysis of the mitochondrial function was performed in fibroblasts of the patient to elucidate the molecular basis of the disease. TIMM50 protein was severely reduced in the patient fibroblasts, regardless of the normal mRNA levels, suggesting that the mutated residues might be important for TIMM50 protein stability. Severe morphological defects and ultrastructural abnormalities with aberrant mitochondrial cristae organization in muscle and fibroblasts were found. The levels of fully assembled OXPHOS complexes and supercomplexes were strongly reduced in fibroblasts from this patient. High-resolution respirometry demonstrated a significant reduction of the maximum respiratory capacity. A TIMM50-deficient HEK293T cell line that we generated using CRISPR/Cas9 mimicked the respiratory defect observed in the patient fibroblasts; notably, this defect was rescued by transfection with a plasmid encoding the TIMM50 wild-type protein. In summary, we demonstrated that TIMM50 deficiency causes a severe mitochondrial dysfunction by targeting key aspects of mitochondrial physiology, such as the maintenance of proper mitochondrial morphology, OXPHOS assembly, and mitochondrial respiratory capacity.

Preparation for a first-in-man lentivirus trial in patients with cystic fibrosis.

We have recently shown that non-viral gene therapy can stabilise the decline of lung function in patients with cystic fibrosis (CF). However, the effect was modest, and more potent gene transfer agents are still required. Fuson protein (F)/Hemagglutinin/Neuraminidase protein (HN)-pseudotyped lentiviral vectors are more efficient for lung gene transfer than non-viral vectors in preclinical models. In preparation for a first-in-man CF trial using the lentiviral vector, we have undertaken key translational preclinical studies. Regulatory-compliant vectors carrying a range of promoter/enhancer elements were assessed in mice and human air-liquid interface (ALI) cultures to select the lead candidate; cystic fibrosis transmembrane conductance receptor (CFTR) expression and function were assessed in CF models using this lead candidate vector. Toxicity was assessed and 'benchmarked' against the leading non-viral formulation recently used in a Phase IIb clinical trial. Integration site profiles were mapped and transduction efficiency determined to inform clinical trial dose-ranging. The impact of pre-existing and acquired immunity against the vector and vector stability in several clinically relevant delivery devices was assessed. A hybrid promoter hybrid cytosine guanine dinucleotide (CpG)- free CMV enhancer/elongation factor 1 alpha promoter (hCEF) consisting of the elongation factor 1α promoter and the cytomegalovirus enhancer was most efficacious in both murine lungs and human ALI cultures (both at least 2-log orders above background). The efficacy (at least 14% of airway cells transduced), toxicity and integration site profile supports further progression towards clinical trial and pre-existing and acquired immune responses do not interfere with vector efficacy. The lead rSIV.F/HN candidate expresses functional CFTR and the vector retains 90-100% transduction efficiency in clinically relevant delivery devices. The data support the progression of the F/HN-pseudotyped lentiviral vector into a first-in-man CF trial in 2017.

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 11ß-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-1Beta and inhibit the activation of nuclear factor kappa B (NF-kappaB) 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

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-1ß 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.

Repeated nebulisation of non-viral CFTR gene therapy in patients with cystic fibrosis: a randomised, double-blind, placebo-controlled, phase 2b trial.

BACKGROUND: Lung delivery of plasmid DNA encoding the CFTR gene complexed with a cationic liposome is a potential treatment option for patients with cystic fibrosis. We aimed to assess the efficacy of non-viral CFTR gene therapy in patients with cystic fibrosis. METHODS: We did this randomised, double-blind, placebo-controlled, phase 2b trial in two cystic fibrosis centres with patients recruited from 18 sites in the UK. Patients (aged ≥12 years) with a forced expiratory volume in 1 s (FEV1) of 50-90% predicted and any combination of CFTR mutations, were randomly assigned, via a computer-based randomisation system, to receive 5 mL of either nebulised pGM169/GL67A gene-liposome complex or 0.9% saline (placebo) every 28 days (plus or minus 5 days) for 1 year. Randomisation was stratified by % predicted FEV1 (<70 vs ≥70%), age (<18 vs ≥18 years), inclusion in the mechanistic substudy, and dosing site (London or Edinburgh). Participants and investigators were masked to treatment allocation. The primary endpoint was the relative change in % predicted FEV1. The primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01621867. FINDINGS: Between June 12, 2012, and June 24, 2013, we randomly assigned 140 patients to receive placebo (n=62) or pGM169/GL67A (n=78), of whom 116 (83%) patients comprised the per-protocol population. We noted a significant, albeit modest, treatment effect in the pGM169/GL67A group versus placebo at 12 months' follow-up (3.7%, 95% CI 0.1-7.3; p=0.046). This outcome was associated with a stabilisation of lung function in the pGM169/GL67A group compared with a decline in the placebo group. We recorded no significant difference in treatment-attributable adverse events between groups. INTERPRETATION: Monthly application of the pGM169/GL67A gene therapy formulation was associated with a significant, albeit modest, benefit in FEV1 compared with placebo at 1 year, indicating a stabilisation of lung function in the treatment group. Further improvements in efficacy and consistency of response to the current formulation are needed before gene therapy is suitable for clinical care; however, our findings should also encourage the rapid introduction of more potent gene transfer vectors into early phase trials. FUNDING: Medical Research Council/National Institute for Health Research Efficacy and Mechanism Evaluation Programme.

Lipids generated during acute pancreatitis increase inflammatory status of macrophages by interfering with their M2 polarization.

BACKGROUND: Necrosis of adipose tissue is a common complication of acute pancreatitis. The areas of steatonecrosis become a source of inflammatory mediators, including chemically modified fatty acids which could influence the progression of the systemic inflammation. In an experimental model of acute pancreatitis we analyzed the effects of lipids generated by two representative areas of adipose tissue on the switch to the M1 phenotype in macrophages. METHODS: Pancreatitis was induced in rats by intraductal administration of 5% taurocholate and after 6 h, lipids from retroperitoneal, mesenteric or epididymal adipose tissues were collected. Lipid uptake, phenotype polarization and the activation of PPARγ and NFκB were evaluated in macrophages treated with these lipids. RESULTS: After induction of pancreatitis, lipids from visceral adipose tissue promote the switch to an increased pro-inflammatory phenotype in macrophages. This effect is not related with a higher activation of NFκB but with an interfering effect on the activation of M2 phenotype. CONCLUSIONS: During acute pancreatitis, lipids generated by some areas of adipose tissue interfere on the M2 polarization of macrophages, thus resulting in a more intense pro-inflammatory M1 response.

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.

Fat necrosis generates proinflammatory halogenated lipids during acute pancreatitis.

OBJECTIVE: To evaluate the generation of halogenated fatty acids in the areas of fat necrosis during acute pancreatitis and to evaluate the effects of these molecules on the ensuing inflammatory process. BACKGROUND: Lipid mediators derived from adipose tissue have been implicated in the progression of acute pancreatitis, although their precise role remains unknown. METHODS: Acute pancreatitis was induced in rats by intraductal infusion of 3.5% sodium taurocholate. Fatty acid chlorohydrins (FA-Cl) were measured in adipose tissue, ascitic fluid, and plasma by mass spectrometry. Chlorohydrins were also instilled in the rats' peritoneal cavity, and their effects on peritoneal macrophages activation and in systemic inflammation were evaluated. Finally, they have also been measured in plasma from human patients with acute pancreatitis. RESULTS: Induced acute pancreatitis results in a substantial release not only of free fatty acids but also of the chlorohydrins of both oleic and linoleic acids from adipose tissue. In plasma, only the chlorohydrin of oleic acid was detected. Administration of 250-µM lipid chlorohydrins, which is the concentration found in ascitic fluid, induces the expression of TNFα and interleukin-1ß in peritoneal macrophages and increases the systemic inflammatory response in pancreatitis. Finally, increased concentrations of oleic acid chlorohydrin have been found in plasma of human patients with pancreatitis. CONCLUSIONS: During acute pancreatitis, adipose tissue release FA-Cl, which exacerbate the systemic inflammatory response.

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 IL1ß 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.

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.

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 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.

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 TNFalpha, 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 TNFalpha 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 TNFalpha 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 TNFalpha 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.

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.

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

BACKGROUND: Systemic 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 TNFalpha 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. RESULTS: Peritoneal 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. CONCLUSION: Peritoneal 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.