Role of P-selectin and ICAM-1 in pancreatitis-induced lung inflammation in rats: significance of oxidative stress

Biosensing Platform for the Detection of Biomarkers for ALI/ARDS in Bronchoalveolar Lavage Fluid of LPS Mice Model

Acute respiratory distress syndrome (ARDS) is a worldwide health concern. The pathophysiological features of ALI/ARDS include a pulmonary immunological response. The development of a rapid and low-cost biosensing platform for the detection of ARDS is urgently needed. In this study, we report the development of a paper-based multiplexed sensing platform to detect human NE, PR3 and MMP-2 proteases. Through monitoring the three proteases in infected mice after the intra-nasal administration of LPS, we showed that these proteases played an essential role in ALI/ARDS. The paper-based sensor utilized a colorimetric detection approach based on the cleavage of peptide-magnetic nanoparticle conjugates, which led to a change in the gold nanoparticle-modified paper sensor. The multiplexing of human NE, PR3 and MMP-2 proteases was tested and compared after 30 min, 2 h, 4 h and 24 h of LPS administration. The multiplexing platform of the three analytes led to relatively marked peptide cleavage occurring only after 30 min and 24 h. The results demonstrated that MMP-2, PR3 and human NE can provide a promising biosensing platform for ALI/ARDS in infected mice at different stages. MMP-2 was detected at all stages (30 min-24 h); however, the detection of human NE and PR3 can be useful for early- (30 min) and late-stage (24 h) detection of ALI/ARDS. Further studies are necessary to apply these potential diagnostic biosensing platforms to detect ARDS in patients.

Role of Hydrogen Sulfide, Substance P and Adhesion Molecules in Acute Pancreatitis

Inflammation is a natural response to tissue injury. Uncontrolled inflammatory response leads to inflammatory disease. Acute pancreatitis is one of the main reasons for hospitalization amongst gastrointestinal disorders worldwide. It has been demonstrated that endogenous hydrogen sulfide (H₂S), a gasotransmitter and substance P, a neuropeptide, are involved in the inflammatory process in acute pancreatitis. Cell adhesion molecules (CAM) are key players in inflammatory disease. Immunoglobulin (Ig) gene superfamily, selectins, and integrins are involved at different steps of leukocyte migration from blood to the site of injury. When the endothelial cells get activated, the CAMs are upregulated which leads to them interacting with leukocytes. This review summarizes our current understanding of the roles H₂S, substance P and adhesion molecules play in acute pancreatitis.

P-Selectin-Based Dual-Model Nanoprobe Used for the Specific and Rapid Visualization of Early Detection toward Severe Acute Pancreatitis in Vivo

Identifying severe acute pancreatitis (SAP) as soon as possible is critical for achieving optimal outcomes and saving lives. In this study, a novel P-selectin-targeted, NIR fluorescent dye (Cy 5.5)-labeled dual-modal nanoprobe based on diethylenetriaminepentaacetic chelates (Gd-DTPA-Cy5.5-PsLmAb) was constructed for the bimodal imaging of SAP at the early stage. Gd-DTPA-Cy5.5-PsLmAb was prepared, and its structure was characterized by Fourier transform infrared spectroscopy, UV-vis spectroscopy, and fluorescence spectroscopy, and its stability was evaluated. Biocompatibility was evaluated by the hemolysis and cytotoxicity assays. The enzyme-linked immunosorbent assay was used to detect and evaluate the expression of P-selectin in the peripheral blood of 11 patients with acute pancreatitis (AP) and 5 healthy volunteers. The bimodal imaging ability of Gd-DTPA-Cy5.5-PsLmAb nanoprobes was evaluated via near-infrared fluorescence (NIRF) and magnetic resonance imaging (MRI) in AP animal models in vivo. Gd-DTPA-Cy5.5-PsLmAb showed low toxicity to human embryonic kidney cells (293T cells) and good blood compatibility. The P-selectin levels of humans and rats in the mild acute pancreatitis (MAP)/SAP stage were significantly higher than those in the control group and reached the highest level at the SAP stage. Furthermore, Gd-DTPA-Cy5.5-PsLmAb nanoprobes showed clear NIRF imaging of mouse pancreas at the MAP stage and SAP stage by a fluorescence signal at 6.09 × 10⁸ and 1.95 × 10⁹, respectively. Meanwhile, Gd-DTPA-Cy5.5-PsLmAb nanoprobes also successfully showed the T1-weighted MR signal of rat pancreas at the MAP stage, but Gd-DTPA seldom showed any signal increase at the MAP stage; Gd-DTPA-Cy5.5-PsLmAb and Gd-DTPA could show an increasing MR signal of rat pancreas at the SAP stage. Gd-DTPA-Cy5.5-PsLmAb proved to offer a stronger signal than Gd-DTPA.Our findings indicate that Gd-DTPA-Cy5.5-PsLmAb is an effective and specific MR/NIRF dual nanoprobe for bimodal imaging, providing a promising diagnostic approach for early SAP in clinic.

Protective effects of Coenzyme Q10 against acute pancreatitis

Acute pancreatitis (AP) refers to inflammation in the pancreas, which may lead to death in severe cases. Coenzyme Q10 (Q10), generally known to generate energy, plays an important role as an anti-oxidant and anti-inflammatory effector. Here, we showed the effect of Q10 on inflammatory response in murine AP model. For this study, we induced AP by injection of cerulein intraperitoneally or pancreatic duct ligation (PDL) in mice. The level of cytokines and digestive enzymes were measured in pancreas, and blood. All pancreatic tissues were excised for investigation such as histological changes, infiltration of immune cells. Administration of Q10 attenuated the severity of AP and its associated pulmonary complication as shown by reduction of acinar cell death, parenchymal edema, inflammatory cell infiltration and alveolar thickening in both cerulein-induced AP and PDL-induced AP. Moreover, reduction of the cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were observed in pancreas and pancreatic acinar cells by Q10. Furthermore, Q10 reduced the infiltration of immune cells such as monocytes and neutrophils and augmentation of chemokines such as CC chemokine-2 (CCL2) and C-X-C chemokine-2 (CXCL2) in pancreas of AP mice. In addition, Q10 deactivates the phosphorylation of extracellular signal-regulated kinase (ERK) and c-jun NH₂-terminal kinase (JNK) in pancreas. In conclusion, these observations suggest that Q10 could attenuate the pancreatic damage and its associated pulmonary complications via inhibition of inflammatory cytokines and inflammatory cell infiltration and that the deactivation of ERK and JNK by Q10 might contribute to the attenuation of AP.

Pulmonary complications of acute pancreatitis

Introduction: Acute pancreatitis is an inflammatory condition of the pancreas, which runs a severe course in 20% of patients, wherein it is associated with high mortality. It is associated with several pleuro-pulmonary complications with variable severity that may occur either in isolation but are frequently present in combination. Clinicians need to be aware of these complications for early and appropriate management.Areas covered: We performed a systematic search of the PUBMED database (1970-2019) to identify relevant articles focusing on pleuro-pulmonary complications that may occur in patients with acute pancreatitis. We also retrieved articles describing the pathophysiological mechanisms and treatment approach of the various complications.Expert opinion: Acute pancreatitis is usually a self-limiting disease, but the development of organ failure during the course worsens the clinical outcome. Pulmonary complications usually occur early in the course of acute pancreatitis. Clinicians need to recognize the various pulmonary complications of acute pancreatitis, early during the disease, and manage them appropriately and aggressively to improve outcomes.

Adhesion molecules and pancreatitis

Acute and chronic pancreatitises are gastrointestinal inflammatory diseases, the incidence of which is increasing worldwide. Most (~ 80%) acute pancreatitis (AP) patients have mild disease, and about 20% have severe disease, which causes multiple organ failure and has a high mortality rate. Chronic pancreatitis (CP) is characterized by chronic inflammation and destruction of normal pancreatic parenchyma, which leads to loss of exocrine and endocrine tissues. Patients with CP also have a higher incidence of pancreatic ductal adenocarcinoma. Although a number of factors are associated with the development and progression of AP and CP, the underlying mechanism is unclear. Adhesion molecules play important roles in cell migration, proliferation, and signal transduction, as well as in development and tissue repair. Loosening of cell-cell adhesion between pancreatic acinar cells and/or endothelial cells increases solute permeability, resulting in interstitial edema, which promotes inflammatory cell migration and disrupts tissue structure. Oxidative stress, which is one of the important pathogenesis of pancreatitis, leads to upregulation of adhesion molecules. Soluble adhesion molecules are reportedly involved in AP. In this review, we focus on the roles of tight junctions (occludin, tricellulin, claudin, junctional adhesion molecule, and zonula occludin), adherens junctions (E-cadherin and p120-, α-, and β-catenin), and other adhesion molecules (selectin and intercellular adhesion molecules) in the progression of AP and CP. Maintaining the normal function of adhesion molecules and preventing their abnormal activation maintain the structure of the pancreas and prevent the development of pancreatitis.

E and P Selectins as Potential Markers in the Assessment of the Severity of Acute Pancreatitis

OBJECTIVES

Acute pancreatitis (AP) is commonly associated with the release of adhesion molecules such as E and P selectins. We designed the present study to evaluate the role of selectins as potential markers that could reflect the severity of the disease.

METHODS

One hundred fifty patients with AP constituted the patient group, whereas 70 healthy volunteers established the control group. In both groups, blood samples were taken for measurements of E selectin, P selectin, caspase-cleaved cytokeratin 18, and total soluble cytokeratin 18 levels on admission and days 1, 2, 4, and 6.

RESULTS

Values of E and P selectins on admission were both elevated compared with control subjects (P < 0.01). The nonsurvivors had higher values of E selectin (P < 0.04) and P selectin (P < 0.03) on admission. Levels of E and P selectin showed positive correlation with the length of stay (P < 0.05). E selectin on admission yielded a sensitivity of 75% and 78% specificity, whereas P selectin had a sensitivity of 67% and 91% specificity.

CONCLUSIONS

Selectin values in the early course of AP may play a role as indicators of overall prognosis, which may help physicians in better understanding the pathophysiology of a benign disease that may have serious and detrimental complications.

Elevation of GPRC5A expression in colorectal cancer promotes tumor progression through VNN-1 induced oxidative stress

The clearance of oxidative stress compounds is critical for the protection of the organism from malignancy, but how this key physiological process is regulated is not fully understood. Here, we found that the expression of GPRC5A, a well-characterized tumor suppressor in lung cancer, was elevated in colorectal cancer tissues in patients. In both cancer cell lines and a colitis-associated cancer model in mice, we found that GPRC5A deficiency reduced cell proliferation and increased cell apoptosis as well as inhibited tumorigenesis in vivo. Through RNA-Seq transcriptome analysis, we identified oxidative stress associated pathways were dysregulated. Moreover, in GPRC5A deficient cells and mouse tissues, the oxidative agents were reduced partially due to increased glutathione (GSH) level. Mechanistically, GPRC5A regulates NF-κB mediated Vanin-1 expression which is the predominant enzyme for cysteamine generation. Administration of cystamine (the disulfide form of cysteamine) in GPRC5A deficient cell lines inhibited γ-GCS activity, leading to reduction of GSH level and increase of cell growth. Taken together, our studies suggest that GPRC5a is a potential biomarker for colon cancer and promotes tumorigenesis through stimulation of Vanin-1 expression and oxidative stress in colitis associated cancer. This study revealed an unexpected oncogenic role of GPRC5A in colorectal cancer suggesting there are complicated functional and molecular mechanism differences of this gene in distinct tissues.

Perfluorocarbon reduces cell damage from blast injury by inhibiting signal paths of NF-κB, MAPK and Bcl-2/Bax signaling pathway in A549 cells

Background and objective

Blast lung injury is a common type of blast injury and has very high mortality. Therefore, research to identify medical therapies for blast injury is important.

Perfluorocarbon (PFC) is used to improve gas exchange in diseased lungs and has anti-inflammatory functions in vitro and in vivo. The aim of this study was to determine whether PFC reduces damage to A549 cells caused by blast injury and to elucidate its possible mechanisms of action.

Study design and methods

A549 alveolar epithelial cells exposed to blast waves were treated with and without PFC. Morphological changes and apoptosis of A549 cells were recorded. PCR and enzyme-linked immunosorbent assay (ELISA) were used to measure the mRNA or protein levels of IL-1β, IL-6 and TNF-α. Malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity levels were detected. Western blot was used to quantify the expression of NF-κB, Bax, Bcl-2, cleaved caspase-3 and MAPK cell signaling proteins.

Results

A549 cells exposed to blast wave shrank, with less cell-cell contact. The morphological change of A549 cells exposed to blast waves were alleviated by PFC. PFC significantly inhibited the apoptosis of A549 cells exposed to blast waves. IL-1β, IL-6 and TNF-α cytokine and mRNA expression levels were significantly inhibited by PFC. PFC significantly increased MDA levels and decreased SOD activity levels. Further studies indicated that NF-κB, Bax, caspase-3, phospho-p38, phosphor-ERK and phosphor-JNK proteins were also suppressed by PFC. The quantity of Bcl-2 protein was increased by PFC.

Conclusion

Our research showed that PFC reduced A549 cell damage caused by blast injury. The potential mechanism may be associated with the following signaling pathways:

1) the signaling pathways of NF-κB and MAPK, which inhibit inflammation and reactive oxygen species (ROS); and 2) the signaling pathways of Bcl-2/Bax and caspase-3, which inhibit apoptosis.

Abdominal paracentesis drainage protects rats against severe acute pancreatitis-associated lung injury by reducing the mobilization of intestinal XDH/XOD

Our previous study showed that abdominal paracentesis drainage (APD) benefits patients with severe acute pancreatitis (SAP) by delaying or avoiding multiple organ failure. However, the role of APD treatment in SAP-associated lung injury (PALI) remains unclear. Therefore, we investigated the impact of APD on PALI in rats to explore the mechanisms underlying its potential treatment benefits. A drainage tube was inserted into the right lower quadrant of rats immediately after SAP induction via the retrograde infusion of 5% sodium taurocholate into the biliopancreatic duct. Mortality rates, histological scores, wet-to-dry weight (W/D) ratios, inflammatory infiltration and oxidative stress in lung tissues were then examined. Xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) activities in the sera, intestines and lungs were assessed, as was P-selectin expression. APD treatment significantly decreased pathological damage scores, oxidative stress and neutrophil infiltration in lung tissues, indicating that APD has protective effects against PALI in rats. Moreover, APD decreased the levels of serum α-amylase and trypsin and resulted in a significant decrease in XDH mobilization from the intestines, which suppressed P-selectin expression in lung tissues following SAP induction. APD treatment exerts a significant protective effect against lung injury secondary to SAP by reducing the mobilization of intestinal XDH or XOD (XDH/XOD) and the expression of P-selectin in the lungs. These findings provide novel insights into the mechanisms underlying the effectiveness of APD in patients with SAP.

Hyperbaric oxygen preconditioning protects the lung against acute pancreatitis induced injury via attenuating inflammation and oxidative stress in a nitric oxide dependent manner

This study aimed to investigate the protective effects of hyperbaric oxygen preconditioning (HBO-PC) on acute pancreatitis AP associated acute lung injury (ALI) and the potential mechanisms. Rats were randomly divided into sham group, AP group, HBO-PC + AP group and HBO-PC + L-NAME group. Rats in HBO-PC + AP group received HBO-PC once daily for 3 days, and AP was introduced 24 h after last HBO-PC. In HBO-PC + L-NAME group, L-NAME (40 mg/kg) was intraperitoneally injected before each HBO-PC. At 24 h after AP, the blood lipase and amylase activities were measured; the lung and pancreas were harvested for pathological examination; the bronchoalveolar lavage fluid was collected for the detection of lactate dehydrogenase (LDH) and proteins; inflammatory factors, superoxide dismutase (SOD) activity and malonaldehyde content were measured in the lung and blood; the Nrf2, SOD-1 and haem oxygenase-1 (HO-1) protein expression was measured in the lung. The lung nitric oxide (NO) and NO synthase activity increased significantly after HBO-PC. HBO-PC was able to reduce blood lipase and amylase activities, improve lung and pancreatic pathology, decrease LDH and proteins in BALF, inhibit the production of inflammatory factors, reduce malonaldehyde content and increase SOD activity in the lung and blood as well as increase protein expression of Nrf2, SOD-1 and HO-1 in the lung. However, L-NAME before HBO-PC significantly attenuated protective effects of HBO-PC. HBO-PC is able to protect the lung against AP induced injury by attenuating inflammation and oxidative stress in the lung via a NO dependent manner.

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.

Effects of Local Pancreatic Renin-Angiotensin System on the Microcirculation of Rat with Severe Acute Pancreatitis

Severe acute pancreatitis (SAP) is normally related to multiorgan dysfunction and local complications. Studies have found that local pancreatic renin-angiotensin system (RAS) was significantly upregulated in drug-induced SAP. The present study aimed to investigate the effects of angiotensin II receptors inhibitor valsartan on dual role of RAS in SAP in a rat model and to elucidate the underlying mechanisms. 3.8% sodium taurocholate (1 ml/kg) was injected to the pancreatic capsule in order for pancreatitis induction. Rats in the sham group were injected with normal saline in identical locations. We also investigated the regulation of experimentally induced SAP on local RAS expression in the pancreas through determination of the activities of serum amylase, lipase and myeloperoxidase, histological and biochemical analysis, radioimmunoassay, fluorescence quantitative PCR and Western blot analysis. The results indicated that valsartan could effectively suppress the local RAS to protect against experimental acute pancreatitis through inhibition of microcirculation disturbances and inflammation. The results suggest that pancreatic RAS plays a critical role in the regulation of pancreatic functions and demonstrates application potential as AT1 receptor antagonists. Moreover, other RAS inhibitors could be a new therapeutic target in acute pancreatitis.

Pancreatic ascites hemoglobin contributes to the systemic response in acute pancreatitis

Upon hemolysis extracellular hemoglobin causes oxidative stress and cytotoxicity due to its peroxidase activity. Extracellular hemoglobin may release free hemin, which increases vascular permeability, leukocyte recruitment, and adhesion molecule expression. Pancreatitis-associated ascitic fluid is reddish and may contain extracellular hemoglobin. Our aim has been to determine the role of extracellular hemoglobin in the local and systemic inflammatory response during severe acute pancreatitis in rats. To this end we studied taurocholate-induced necrotizing pancreatitis in rats. First, extracellular hemoglobin in ascites and plasma was quantified and the hemolytic action of ascitic fluid was tested. Second, we assessed whether peritoneal lavage prevented the increase in extracellular hemoglobin in plasma during pancreatitis. Third, hemoglobin was purified from rat erythrocytes and administered intraperitoneally to assess the local and systemic effects of ascitic-associated extracellular hemoglobin during acute pancreatitis. Extracellular hemoglobin and hemin levels markedly increased in ascitic fluid and plasma during necrotizing pancreatitis. Peroxidase activity was very high in ascites. The peritoneal lavage abrogated the increase in extracellular hemoglobin in plasma. The administration of extracellular hemoglobin enhanced ascites; dramatically increased abdominal fat necrosis; upregulated tumor necrosis factor-α, interleukin-1β, and interleukin-6 gene expression; and decreased expression of interleukin-10 in abdominal adipose tissue during pancreatitis. Extracellular hemoglobin enhanced the gene expression and protein levels of vascular endothelial growth factor (VEGF) and other hypoxia-inducible factor-related genes in the lung. Extracellular hemoglobin also increased myeloperoxidase activity in the lung. In conclusion, extracellular hemoglobin contributes to the inflammatory response in severe acute pancreatitis through abdominal fat necrosis and inflammation and by increasing VEGF and leukocyte infiltration into the lung.

Thalidomide Inhibits Adhesion Molecules in Experimental Acute Pancreatitis-Associated Lung Injury

Preclinical Research The study evaluated the effect of thalidomide on adhesion molecule expression in acute pancreatitis-associated lung injury in rats. Acute pancreatitis was induced in rats by retrograde infusion of 5% sodium taurocholate into the bile-pancreatic duct, and thalidomide (100 mg/kg) was given daily by intragastric route for 8 days before this treatment. Serum lipase (LPS), protein levels in bronchoalveolar lavage fluid (BALF), superoxide dismutase (SOD), glutathione peroxidase (GSHpx), and malondialdehyde (MDA) levels in lung were measured. Compared with the acute pancreatitis- group, lung histopathology, serum LPS, protein levels in BALF, SOD, GSHpx, and MDA levels, and the expression levels of intercellular adhesion molecule-1 and E-selectin mRNA and protein in rats given thalidomide were improved (P < 0.01). Thus, thalidomide may reduce the expression of adhesion molecules via inhibition of oxidative stress to alleviate acute pancreatitis-associated lung injury in a rat model. Drug Dev Res, 2014. © 2014 Wiley Periodicals, Inc.

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.

Free radicals and acute pancreatitis: much ado about … something

There is a convincing body of evidence that oxidative stress is involved in the pathogenesis of acute pancreatitis. The effects of different radical scavengers suggested that reactive oxygen metabolites are generated at very early stage of disease and contribute to amplify the pancreatic damage. Oxidative stress is also involved in the progression of the disease from a local damage to a systemic organ failure. However, therapeutic use of antioxidants failed to clearly show a clinical benefit in different trials. Therefore, although antioxidants alone seem to be not enough for the treatment of severe acute pancreatitis, future combined therapeutic strategies should include antioxidants in its composition.

Sodium Hydrosulphide alleviates remote lung injury following limb traumatic injury in rats

Hydrogen sulphide (H2S) was found to attenuate ventilator or oleic acid induced lung injury. The aim of this study was to explore the effects of exogenous H2S donor, sodium Hydrosulphide (NaHS), on lung injury following blast limb trauma and the underlying mechanisms. For in vitro experiments, pulmonary micro-vessel endothelial cells (PMVECs) were cultured and treated with NaHS or vehicle in the presence of TNF-α. For in vivo, blast limb traumatic rats, induced by using chartaceous electricity detonators, were randomly treated with NaHS, cystathionine gamma-lyase inhibitor (PAG) or vehicle. In vitro, NaHS (100 µM) treatment increased PMVECs viability and decreased LDH release into culture media after tumor necrosis factor (TNF) α challenge. In addition, NaHS treatment prevented the increase of nitric oxide, Intercellular Adhesion Molecule 1(ICAM-1) and interleukin (IL)-6 production and inducible nitric oxide synthase activation induced by TNF-α. Knock-down of NF-E2-Related Factor 2 (Nrf2) partially abolished the protective effect of NaHS. In vivo, NaHS treatment significantly alleviated lung injury following blast limb trauma, demonstrated by a decreased histopathological score and lung water content. Furthermore, NaHS treatment reversed the decrease of H2S concentration in plasma, prevented the increase of TNF-α, IL-6, malondialdehyde and myeloperoxidase, increased the Nrf2 downstream effector glutathione in both plasma and lungs, and reversed the decrease of superoxide dismutase in both plasma and lungs induced by blast limb trauma. Our data indicated that NaHS protects against lung injury following blast limb trauma which is likely associated with suppression of the inflammatory and oxidative response and activation of Nrf2 cellular signal.

Obese rats exhibit high levels of fat necrosis and isoprostanes in taurocholate-induced acute pancreatitis

BACKGROUND

Obesity is a prognostic factor for severity in acute pancreatitis in humans. Our aim was to assess the role of oxidative stress and abdominal fat in the increased severity of acute pancreatitis in obese rats.

METHODOLOGY

Taurocholate-induced acute pancreatitis was performed in lean and obese Zucker rats. Levels of reduced glutathione, oxidized glutathione, L-cysteine, cystine, and S-adenosylmethionine were measured in pancreas as well as the activities of serine/threonine protein phosphatases PP1 and PP2A and tyrosin phosphatases. Isoprostane, malondialdehyde, triglyceride, and free fatty acid levels and lipase activity were measured in plasma and ascites. Lipase activity was measured in white adipose tissue with and without necrosis and confirmed by western blotting.

FINDINGS

Under basal conditions obese rats exhibited lower reduced glutathione levels in pancreas and higher triglyceride and free fatty acid levels in plasma than lean rats. S-adenosyl methionine levels were markedly increased in pancreas of obese rats. Acute pancreatitis in obese rats led to glutathione oxidation and lower reduced glutathione levels in pancreas together with decreased activities of redox-sensitive phosphatases PP1, and PP2A. S-adenosyl methionine levels decreased but cystine levels increased markedly in pancreas upon pancreatitis. Acute pancreatitis triggered an increase in isoprostane levels in plasma and ascites in obese rats. Free fatty acid levels were extremely high in pancreatitis-associated ascitic fluid from obese rats and lipase was bound with great affinity to white adipose tissue, especially to areas of necrosis.

CONCLUSIONS

Our results show that oxidative stress occurs locally and systemically in obese rats with pancreatitis favouring inactivation of protein phosphatases in pancreas, which would promote up-regulation of pro-inflammatory cytokines, and the increase of isoprostanes which might cause powerful pulmonary and renal vasoconstriction. Future studies are needed to confirm the translational relevance of the present findings obtained in a rat model of taurocholate-induced pancreatic damage and necrosis.

Evaluation of N-acetylcysteine treatment in acute pancreatitis-induced lung injury

OBJECTIVE

Pulmonary complications are frequent during acute pancreatitis (AP). We investigate the effects of N-acetylcysteine (NAC) on lung injury in mild and severe AP. ANIMALS AND TREATMENT: Mild and severe AP was induced in rats by bile-pancreatic duct obstruction (BPDO) and infusion of 3.5 % sodium taurocholate (NaTc) into the bile-pancreatic duct, respectively. NAC (50 mg/kg) was given 1 h before and 1 h after AP.

METHODS

Amylase activity was measured in plasma. Lungs were harvested for mRNA expression analysis of monocyte chemoattractant protein-1 (MCP-1), cytokine-induced neutrophil chemoattractant (CINC), P-selectin and intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO) activity and histological examination.

RESULTS

Hyperamylasemia was reduced by NAC in both AP models. NAC down-regulated MCP-1, CINC and P-selectin in BPDO- but not in NaTc-induced AP. Pulmonary insults did not vary in mild AP and were exacerbated in severe AP by NAC treatment. NAC reduced lung MPO activity in mild but not in severe AP.

CONCLUSIONS

Although NAC treatment down-regulated inflammatory mediators in lungs during AP it did not prevent leukocyte infiltration, which could be responsible for maintaining the lung injury. As a result, NAC aggravated the lung damage in severe AP and failed to exert beneficial effects in the mild disease model.

Antioxidant therapy in acute pancreatitis: experimental and clinical evidence

SIGNIFICANCE

Oxidative stress plays an important role in the pathogenesis of both acute and chronic pancreatitis. Although its impact is well investigated and has been studied clinically in chronic pancreatitis, it is less well defined for acute pancreatitis.

RECENT ADVANCES

Pathophysiological aspects of oxidative stress in acute pancreatitis have shown that reactive oxidative species (ROS) participate in the inflammatory cascade, and mediate inflammatory cell adhesion and consecutive tissue damage. Furthermore, ROS are involved in the generation of pain as another important clinical feature of patients suffering from acute pancreatitis.

CRITICAL ISSUES

Despite sufficient basic and experimental knowledge and evidence, the step from bench to bedside has not been successfully performed. Only a limited number of clinical studies are available that can give convincing evidence for the use of antioxidants in the clinical setting of acute pancreatitis.

FUTURE DIRECTIONS

Future studies are required to evaluate potential benefits of antioxidative substances to attenuate the severity of acute pancreatitis. Special focus should be put on the aspect of pain generation and the progression from mild to severe acute pancreatitis in the clinical setting.

The Renin-angiotensin system and reactive oxygen species: implications in pancreatitis

SIGNIFICANCE

The renin-angiotensin system (RAS) is a circulating hormonal system involved in the regulation of blood pressure and circulating fluid electrolytes. Recent findings have revealed that locally generated angiotensin (Ang) II plays a pivotal role in normal physiology as well as pathophysiology in various tissues and organs, including the pancreas. This review article summarizes current progress that has been made in elucidating the putative roles of Ang II in both acute and chronic pancreatitis.

RECENT ADVANCES

A convergence of evidence suggests that the underlying mechanism may involve reactive oxygen species (ROS)-generating systems, such as nicotinamide adenine dinucleotide phosphate oxidase, and subsequent elevation of proinflammatory and profibrogenic gene expression as well as protein activity. More importantly, Ang II-induced ROS interacts with other ROS-generating systems to positively feed-forward the ROS-induced signaling.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Advances in basic research indicate that RAS blockers may provide potential therapeutic role for the management of pancreatic inflammation and, more importantly, pancreatitis-associated complications. Genetic alterations resulting from a malfunction in the epigenetic control of pancreatic RAS could be a causative factor in the development of pancreatitis.

Oxidative and nitrosative stress in acute pancreatitis. Modulation by pentoxifylline and oxypurinol

Reactive oxygen species are considered mediators of the inflammatory response and tissue damage in acute pancreatitis. We previously found that the combined treatment with oxypurinol - as inhibitor of xanthine oxidase- and pentoxifylline - as inhibitor of TNF-α production-restrained local and systemic inflammatory response and decreased mortality in experimental acute pancreatitis. Our aims were (1) to determine the time-course of glutathione depletion and oxidation in necrotizing pancreatitis in rats and its modulation by oxypurinol and pentoxifylline; (2) to determine whether TNF-α is responsible for glutathione depletion in acute pancreatitis; and (3) to elucidate the role of oxidative stress in the inflammatory cascade in pancreatic AR42J acinar cells. We report here that oxidative stress and nitrosative stress occur in pancreas and lung in acute pancreatitis and the co-treatment with oxypurinol and pentoxifylline prevents oxidative stress in both tissues. Oxypurinol was effective in preventing glutathione oxidation, whereas pentoxifylline abrogated glutathione depletion. This latter effect was independent of TNF-α since glutathione depletion occurred in mice deficient in TNF-α or its receptors after induction of pancreatitis. The beneficial effects of oxypurinol in the inflammatory response may also be ascribed to a partial inhibition of MEK1/2 activity. Pentoxifylline markedly reduced the expression of Icam1 and iNos induced by TNF-α in vitro in AR42J cells. Oxidative stress significantly contributes to the TNF-α-induced up-regulation of Icam and iNos in AR42J cells. These results provide new insights into the mechanism of action of oxypurinol and pentoxifylline as anti-inflammatory agents in acute pancreatitis.

Targeting P-selectin in acute pancreatitis

IMPORTANCE OF THE FIELD

Acute pancreatitis (AP) is a multifactorial disorder not fully understood yet. In particular, the pathogenetic pathways promoting a severe life-threatening course of AP are the subject of ongoing investigations. P-selectin has been shown to play a central role in the complex pathophysiology in AP as well as various other inflammatory conditions.

AREAS COVERED IN THIS REVIEW

P-selectin function in AP is reviewed with focus on its dual function as a mediator of leukocyte recruitment and cell adhesion, which implies the unique effect of linking both inflammation and coagulation, especially in the progression from mild to severe necrotizing AP. Potential therapeutic aspects are discussed with regard to the clinical situation.

WHAT THE READER WILL GAIN

A better understanding of the pathogenic role of P-selectin in AP and of the rationale for a therapeutic blockade.

TAKE HOME MESSAGE

P-selectin is a glycoprotein that mediates the adhesion of activated platelets and leukocytes to the vessel wall in various inflammatory conditions. Both pathophysiological steps are closely linked and play a key role in the course of severe AP. A treatment approach by inhibition of P-selectin could be of distinct interest as a therapeutic option in severe AP.

Effects of dexamethasone on intercellular adhesion molecule 1 expression and inflammatory response in necrotizing acute pancreatitis in rats

OBJECTIVES

Adhesion molecules are involved in the inflammatory response during acute pancreatitis (AP). We investigated the effect of dexamethasone (Dx) on intercellular adhesion molecule 1 (ICAM-1) expression during AP and its consequences on leukocyte recruitment and pancreatic damage.

METHODS

Acute pancreatitis was induced in rats by 3.5% sodium taurocholate for 3 hours and 6 hours. Dexamethasone (1 mg/kg) was administered either 30 minutes before or 1 hour after inducing AP. Messenger RNA ICAM-1 expression in pancreas and lung, membrane-bound ICAM-1 in acinar cells, and ICAM-1 plasma levels were analyzed. Histological examination of the pancreas and neutrophil infiltration in pancreas and lung were also measured.

RESULTS

Prophylactic and therapeutic administration of Dx down-regulated ICAM-1 expression in pancreas and lung from early AP. Dexamethasone given before AP reduced the pancreatic damage, but lung inflammation was not prevented. Therapeutic Dx treatment was ineffective in avoiding leukocyte recruitment into the pancreas and lung in rats with AP. High ICAM-1 concentration was found in plasma during AP, which was not reduced by Dx treatments.

CONCLUSIONS

Dexamethasone down-regulates ICAM-1 expression, but it does not completely prevent leukocyte recruitment during sodium taurocholate-induced AP.

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 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.

Alpha1G T-type calcium channel selectively regulates P-selectin surface expression in pulmonary capillary endothelium

Regulated P-selectin surface expression provides a rapid measure for endothelial transition to a proinflammatory phenotype. In general, P-selectin surface expression results from Weibel-Palade body (WPb) exocytosis. Yet, it is unclear whether pulmonary capillary endothelium possesses WPbs or regulated P-selectin surface expression and, if so, how inflammatory stimuli initiate exocytosis. We used immunohistochemistry, immunofluorescence labeling, ultrastructural assessment, and an isolated perfused lung model to demonstrate that capillary endothelium lacks WPbs but possesses P-selectin. Thrombin stimulated P-selectin surface expression in both extra-alveolar vessel and alveolar capillary endothelium. Only in capillaries was the thrombin-stimulated P-selectin surface expression considerably mitigated by pharmacologic blockade of the T-type channel or genetic knockout of the T-type channel alpha(1G)-subunit. Depolarization of endothelial plasma membrane via high K(+) perfusion capable of eliciting cytosolic Ca(2+) transients also provoked P-selectin surface expression in alveolar capillaries that was abolished by T-type channel blockade or alpha(1G) knockout. Our findings reveal an intracellular WPb-independent P-selectin pool in pulmonary capillary endothelium, where the regulated P-selectin surface expression is triggered by Ca(2+) transients evoked through activation of the alpha(1G) T-type channel.

Effect of baicalin and octreotide on the expression levels of P-selectin protein in multiple organs of rats with severe acute pancreatitis

AIM

To investigate the effect of baicalin and octreotide on the expression levels of P-selectin protein in multiple organs of rats with severe acute pancreatitis and explore the underlying mechanism.

METHODS

Rats were randomly divided into sham-operated, model control, baicalin-treated and octreotide-treated groups. At 3, 6 and 12 h after operation, the mortality rates of rats, the contents of plasma endotoxin as well as serum NO and ET-1, the pathological changes in multiple organs, and the expression levels of P-selectin protein in each group were observed.

RESULTS

At 12 h after operation, the mortality rates of rats in treated groups were significantly lower than that in the model control group (P < 0.05), and the pathological severity scores in multiple organs in treated groups were also significantly lower than those in the model control group (P < 0.05). The contents of plasma endotoxin, serum PLA(2) (at 6 and 12 h after operation), ET-1 and NO (at 3 and 12 h after operation) in treated groups were significantly lower than those in the model control group (P < 0.05, P < 0.01 or P < 0.001). In the baicalin-treated group, the expression levels of P-selectin protein in liver (at 3 h after operation), kidney (at 3 and 6 h after operation), pancreas, lung and spleen were significantly lower than those in the model control group (P < 0.01). In the octreotide-treated group, the expression levels of this protein in lung, intestinal mucosa (at 6 and 12 h after operation), lymph nodes (at 3 and 6 h after operation), spleen and thymus were significantly lower than those in the model control group (P < 0.05). Additionally, the products of the staining intensity and positive rate of P-selectin protein in pancreas, spleen (at 3 h after operation), intestinal mucosa (at 6 h after operation), thymus (at 6 h after operation) and lung (at 6 h after operation) in treated groups were significantly lower than those in the model control group (P < 0.05).

CONCLUSION

Both baicalin and octreotide can exert some protective effects on multiple organs and the former is superior to the latter in protecting pancreas. Furthermore, decreasing the expression levels of P-selectin protein in these organs is one of the possible mechanisms.

Inter-individual variability of plasma PAF-acetylhydrolase activity in ARDS patients and PAFAH genotype

BACKGROUND

Platelet activating factor (PAF), a pro-inflammatory phospholipid, stimulates cytokine secretion from polymorphonuclear leukocytes expressing the transmembrane G-protein coupled PAF receptor. Elevated PAF levels are associated with acute respiratory distress syndrome (ARDS) and sepsis severity. The pro-inflammatory effects of PAF are terminated by PAF acetylhydrolase (PAF-AH).

OBJECTIVE

We sought to determine whether allelic variants in the human PAFAH gene (Arg92His, Ile198Thr, and Ala379Val) contribute to variability in PAF-AH activity in patient plasma obtained within 72 h of ARDS diagnosis.

RESULTS

Plasma PAF-AH activity (mean +/- SD) was higher in patients homozygous for the Arg92 allele compared to His92 allele carriers (2.21 +/- 0.77 vs. 1.64 +/- 0.68 U/min; P < 0.01; n = 31 and 21 respectively). Baseline plasma PAF-AH activity was higher among day 7 survivors vs. day 7 non-survivors (2.05 +/- 0.75 vs. 1.27 +/- 0.63, P = 0.05).

CONCLUSION

These data demonstrate an association between PAF-AH allelic variation, plasma activity, and outcome in ARDS.

Treatment of acute pancreatitis: focus on medical care

Acute pancreatitis has an incidence of about 300 per 1 million individuals per year, of which 10-15% of patients develop the severe form of the disease. Novel management options, which have the potential to improve outcome, include initial proper fluid resuscitation, which maintains microcirculation and thereby potentially decreases ischaemia and reperfusion injury. The traditional treatment concept in acute pancreatitis, fasting and parenteral nutrition, has been challenged and early initiation of enteral feeding in severe pancreatitis and oral intake in mild acute pancreatitis is both feasible and provides some benefits. There are at present no data supporting immunonutritional supplements and probiotics should be avoided in patients with acute pancreatitis. There is also no evidence of any benefits provided by prophylactic antibacterials in patients with predicted severe acute pancreatitis. A variety of specific medical interventions have been investigated (e.g. intense blood glucose monitoring by insulin) but none has become clinically useful. Lessons can probably be learned from critical care in general, but studies are needed to verify these interventions in acute pancreatitis.

Hypertonic saline reduces metalloproteinase expression in liver during pancreatitis

1. We recently demonstrated that hypertonic saline reduces inflammation and mortality in acute pancreatitis. The present study investigated the effects of hypertonic saline in metalloproteinase (MMP) regulation and pancreatitis-associated hepatic injury. 2. Wistar rats were divided into four groups: (i) control, not subjected to insult or treatment; (ii) no treatment (NT), induction of pancreatitis (retrograde infusion of 2.5% sodium taurocholate (1.0 mL/kg)), but no further treatment; (iii) normal saline (NS), induction of pancreatitis and treatment with normal saline (0.9% NaCl, 34 mL/kg, i.v. bolus, 1 h after the induction of pancreatitis); and (iv) hypertonic saline (HS), induction of pancreatitis and treatment with hypertonic saline (7.5% NaCl, 4 mL/kg administered over a period of 5 min, 1 h after the induction of pancreatitis). In all four groups, 4, 12 and 24 h after the induction of pancreatitis, liver tissue samples were assayed to determine levels of MMP-2, MMP-9, 47 kDa heat shock protein (HSP47) and collagen (Type I and III). 3. Compared with the control group, MMP-9 expression and activity was increased twofold in the NS and NT groups 4 and 12 h after the induction of pancreatitis, but remained at basal levels in the HS group. In contrast, MMP-2 expression was increased twofold 12 h after the induction of pancreatitis only in the NS group, whereas the expression of HSP47 was increased 4 h after the induction of pancreatitis in the NS and NT groups. Greater extracellular matrix remodelling occurred in the NS and NT groups compared with the HS group, probably as a result of the hepatic wound-healing response to repeated injury. However, the collagen content in hepatic tissue remained at basal levels in the HS group. 4. In conclusion, the results of the present study indicate that hypertonic saline is hepatoprotective and reduces hepatic remodelling, maintaining the integrity of the hepatic extracellular matrix during pancreatitis. Hypertonic saline-mediated regulation of MMP expression may have clinical relevance in pancreatitis-associated liver injury.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

Reactive oxygen species and endothelial activation

Endothelial activation refers to a specific change in endothelial phenotype, characterized most notably by an increase in endothelial-leukocyte interactions and permeability, which is pivotal to inflammatory responses in both physiologic and pathologic settings. An increasing body of evidence indicates an important role for reactive oxygen species (ROS)-mediated modulation of signal-transduction pathways in many of the processes involved in endothelial activation. ROS generated by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family of enzymes may be especially important in this regard. We discuss the evidence implicating redox signaling pathways in the molecular and cellular processes underlying endothelial activation and the role in cardiovascular diseases, and also provide a detailed description of NADPH oxidase regulation in endothelial cells, in view of its likely importance in this context.

Redox status of acute pancreatitis as measured by cyclic voltammetry: initial rodent studies to assess disease severity

OBJECTIVE

To determine whether serum antioxidant capacity as measured by the electrochemical technique cyclic voltammetry could be used to resolve differences in the severity of an inflammatory disease such as acute pancreatitis.

DESIGN

Experimental animal study.

SETTING

Animal laboratory, Department of Surgery, Faculty of Medical and Health Sciences, University of Auckland, New Zealand.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

A total of 48 inbred male Wistar rats were studied in five experimental groups. Group 1 (baseline reference, immediate euthanasia, n = 14) had no surgical intervention. Group 2 (sham, n = 9) had identical surgical procedures to the pancreatitis groups except for the intraductal infusion. Groups 3-5 (n = 9, n = 10, and n = 6, respectively) had acute pancreatitis induced by the pancreatic intraductal infusion of 3%, 4%, or 5% sodium taurocholate, respectively. Groups 2-5 were killed after 12 hrs.

MEASUREMENTS AND MAIN RESULTS

Cyclic voltammetry involves scanning the voltage of a working electrode while recording the anodic current produced as the low molecular weight antioxidants in the solution are oxidized on the surface of the working electrode. The current produced is proportional to the combined concentration of the antioxidants. There was a significant positive correlation of the first cyclic voltammetric peak maximum with pancreatic histologic severity (Spearman's r = .51, p = .007) and with a number of other markers of systemic severity, notably bicarbonate (r = -.57, p = .002), base excess (r = -.65, p < .001), urea (r = .68, p < .001), and calcium (r = -.60, p = .008). The first cyclic voltammetric peak maximum was superior at indicating the severity of the disease state compared with a standard method of total antioxidant capacity measurement.

CONCLUSIONS

In experimental pancreatitis, the first cyclic voltammetric peak maximum showed significant correlations with histologic and systemic indices of severity. Further clinical studies are now needed to define the role of cyclic voltammetry in monitoring the progression of this and other severe illness in the critical care setting.

The inflammatory cascade in acute pancreatitis: relevance to clinical disease

Acute pancreatitis is an inflammatory condition that is initiated by the intra pancreatic activation of proteases. Pancreatic enzyme activation triggers a local and systemic inflammatory response that is associated with recruitment of inflammatory cells into the pancreas and a widespread up-regulation of inflammatory markers in distant tissues.

The role of inflammatory and parenchymal cells in acute pancreatitis

The infiltration of inflammatory cells into the pancreas is an early and central event in acute pancreatitis that promotes local injury and systemic complications of the disease. Recent research has yielded the important finding that resident cells of the pancreas (particularly acinar and pancreatic stellate cells) play a dynamic role in leukocyte attraction via secretion of chemokines and cytokines and expression of adhesion molecules. Significant progress has been made in recent years in our understanding of the role of leukocyte movement (adhesion to the blood vessel wall, transmigration through the blood vessel wall and infiltration into the parenchyma) in the pathophysiology of acute pancreatitis. This review discusses recent studies and describes the current state of knowledge in the field. It is clear that detailed elucidation of the numerous processes in the inflammatory cascade is an essential step towards the development of improved therapeutic strategies in acute pancreatitis. Studies to date suggest that combination therapy targeting different steps of the inflammatory cascade may be the treatment of choice for this disease.

Role of tumor necrosis factor-alpha in acute pancreatitis: from biological basis to clinical evidence

Tumor necrosis factor (TNF)-alpha is a pleiotropic cytokine that exerts host-damaging effects in different autoimmune and inflammatory diseases. It is a key regulator of other proinflammatory cytokines and of leukocyte adhesion molecules, and it is a priming activator of immune cells. In recent years, several research lines-mostly derived from animal models and in vitro studies-suggested that TNF-alpha plays a pivotal role in the pathogenesis of acute pancreatitis. In particular, it contributes to the systemic progression of the inflammatory response and to the end-organ dysfunction often observed in severe disease. Current clinical applications of TNF-alpha in acute pancreatitis include the assessment of blood concentrations to predict disease severity and to identify individuals prone to develop complications such as multiple organ failure and septic shock. However, TNF-alpha is rapidly cleared from the bloodstream, and sensitivity and overall accuracy of its measurement seem strictly time dependent, thereby being of potential prognostic value only in the first days after the onset of the disease. In parallel, TNF-alpha has been evaluated as a novel pharmacologic target for treating pancreatitis. Although promising results have been observed in the laboratory, transition to clinical practice seems problematic, in particular, in the light of divergent results obtained in sepsis trials. Therefore, in future clinical trials pertaining to TNF-alpha neutralization in acute pancreatitis, timing of intervention should be related to changes in TNF-alpha serum levels, and inclusion and exclusion criteria should be accurately selected to better define the population most likely to benefit.

Cell-based Angiopoietin-1 Gene Therapy for Acute Lung Injury

RATIONALE

The acute respiratory distress syndrome is a significant cause of morbidity and mortality in critically ill patients. Angiopoietin-1 (Ang-1), a ligand for the endothelial Tie2 receptor, is an endothelial survival and vascular stabilization factor that reduces endothelial permeability and inhibits leukocyte-endothelium interactions.

OBJECTIVES

We hypothesized that Ang-1 counteracts vascular inflammation and pulmonary vascular leak in experimental acute lung injury.

METHODS

We used cell-based gene therapy in a rat model of ALI. Transgenic mice overexpressing Ang-1 or deficient in the Tie2 receptor were also studied to better elucidate the mechanisms of protection.

MEASUREMENTS AND MAIN RESULTS

The present report provides data that support a strong protective role for the Ang-1/Tie2 system in two experimental models of LPS-induced acute lung injury. In a rat model, cell-based Ang-1 gene transfer improved morphological, biochemical, and molecular indices of lung injury and inflammation. These findings were confirmed in a gain-of-function conditional, targeted transgenic mouse model, in which Ang-1 reduced endothelial cell activation and the expression of adhesion molecules, associated with a marked improvement in airspace inflammation and intraalveolar septal thickening. Moreover, heterozygous Tie2-deficient mice demonstrated enhanced evidence of lung injury and increased early mortality.

CONCLUSIONS

These results support a critical role for the Ang-1/Tie2 axis in modulating the pulmonary vascular response to lung injury and suggest that Ang-1 therapy may represent a potential new strategy for the treatment and/or prevention of acute respiratory distress syndrome in critically ill patients.

Especies reactivas de oxígeno en las enfermedades inflamatorias del páncreas: ¿una posible diana terapéutica?

Chronic and acute pancreatitis can be understood as distinct stages of an inflammatory spectrum in the pancreas. Although its pathogenesis is not well defined, oxidative stress seems to be clearly involved in its development. During acute pancreatitis, there is an extraordinary and rapid formation of reactive oxygen species that leads to the extinction of pancreatic antioxidant reserves, causes direct tissue damage and activates oxidative cellular mediators, giving rise to the lesion. However, classical antioxidants have not been shown to have clear benefits in patients with acute pancreatitis. Chronic pancreatitis seems to be the result of a recurrent lesion and defective repair, leading to pancreatic atrophy and fibrosis. In this process, oxidative stress is an efficient stimulus to maintain pancreatic stellar cells active, the fibrogenic motor of chronic pancreatitis. Although antioxidant supplements relieve abdominal pain in these patients, the direction of future antioxidant therapies lies in identifying oxidative mechanisms with the potential for intervention.

Circulating TNF-alpha and its soluble receptors during experimental acute pancreatitis

Clinical and experimental studies have shown increased concentrations of TNF-alpha and its soluble receptors in serum of patients with acute pancreatitis. In this work, we have investigated the time-course of TNF-alpha and its soluble receptors during taurocholate-induced acute pancreatitis. In addition, since TNF-alpha itself could mediate the shedding of its receptors, we have assessed the effect of inhibiting TNF-alpha production on the release of soluble TNF-alpha receptors in experimental acute pancreatitis. Our results indicate that soluble receptors are released in the early stages of the disease and this increase is concomitant with the release of TNF-alpha, which is mainly bound to specific proteins. The increased concentrations of its receptors strongly suggest that they could be these binding proteins. Inhibition of TNF-alpha generation with pentoxifylline abrogated the shedding of sTNF-alphaR1, but had no effect on sTNF-alphaR2. This finding suggests that the shedding of sTNF-alphaR1 is induced by TNF-alpha itself, but in the case of sTNF-alphaR2, the shedding appears to be induced by another mechanism.

Potential role of reactive oxygen species in pancreatitis-associated multiple organ dysfunction

BACKGROUND

Severe acute pancreatitis is still associated with substantial morbidity and mortality. Experimental and clinical studies have demonstrated that reactive oxygen species (ROS) represent early occurring inflammatory mediators contributing to cell dysfunction, both locally in the pancreas and remote organs.

METHOD

A systematic literature review was conducted to investigate the potential roles of intra- and intercellular, as well as interorgan signaling of ROS in the development of pancreatitis-associated multiple organ dysfunction syndrome (MODS). A text word search of the Medline, PubMed and Cochrane databases, and a manual search of the citations from these references, was performed.

RESULTS

ROS directly compromise cellular damage and regulate intercellular signals in pancreatitis-associated MODS. ROS are involved in leukocyte activation, production of cytokines, endothelial barrier dysfunction, and microcirculatory barrier dysfunction in acute pancreatitis. Beside effects on intercellular signaling, ROS also affect intracellular events and activate the transcription factor nuclear factor kappa B that regulates inflammatory cytokine expression.

CONCLUSION

ROS is a critical factor responsible for the development of pancreatitis-induced remote organ dysfunction via intercellular and interorgan signaling. The role of antioxidant treatment, included as a part of multimodal management, remains to be investigated.

Vascular physiology and pathology of circulating xanthine oxidoreductase: from nucleotide sequence to functional enzyme

The evolutionarily conserved, cofactor-dependent, enzyme xanthine oxidoreductase exists in both cell-associated and circulatory forms. The exact role of the circulating form is not known; however, several putative physiological and pathological functions have been suggested that range from purine catabolism to a mediator of acute respiratory distress syndrome. Regulation of gene expression, cofactor synthesis and insertion, post-translational conversion, entry into the circulation, and putative physiological and pathological roles for human circulating xanthine oxidoreductase are discussed.

Oxygen in the alveolar air space mediates lung inflammation in acute pancreatitis

During the early stages of acute pancreatitis, acute respiratory distress syndrome often occurs. This is associated with the release of proinflammatory mediators into the blood, but it remains unclear why these mediators induce inflammation especially in the lung. One of the first events occurring during the progression of acute pancreatitis is the induction of P-selectin expression in the endothelial cells of the lung. This expression has been associated with the generation of superoxide radicals by circulating xanthine oxidase. Because this enzyme needs molecular oxygen to perform the reaction, we have hypothesized that oxygen present in the alveolar space favors the generation of free radicals by xanthine oxidase and explains why P-selectin is expressed only in the lung. For this purpose, we evaluated the progression of the inflammatory process in rats with induced acute pancreatitis and one lung breathing nitrogen while the other lung continued breathing air. Acute pancreatitis was induced by intraductal administration of taurocholate and myeloperoxidase; P-selectin expression was measured 3 h after induction. Results indicated that, in the absence of oxygen in the alveolar space, the xanthine oxidase-dependent P-selectin expression did not occur and lung inflammation was significantly reduced.

Extracellular superoxide dismutase attenuates lipopolysaccharide-induced neutrophilic inflammation

Extracellular superoxide dismutase (EC-SOD) is an abundant antioxidant in the lung and vascular walls. Previous studies have shown that EC-SOD attenuates lung injury in a diverse variety of lung injury models. In this study, we examined the role of EC-SOD in mediating lipopolysaccharide (LPS)-induced lung inflammation. We found that LPS-induced neutrophilic lung inflammation was exaggerated in EC-SOD-deficient mice and diminished in mice that overexpressed EC-SOD specifically in the lung. Similar patterns were seen for bronchoalveolar lavage cytokines, such as tumor necrosis factor-alpha, keratinocyte-derived chemokines, and macrophage inflammatory protein-2 as well as expression of lung intercellular adhesion molecule-1, vascular cell adhesion molecule-1, endothelial cell selectin, and platelet selectin. In a macrophage cell line, EC-SOD inhibited LPS-induced macrophage cytokine release, but did not alter expression of intercellular adhesion molecules in endothelial cells. These results suggest that EC-SOD plays an important role in attenuating the inflammatory response in the lung most likely by decreasing release of proinflammatory cytokines from phagocytes.

Effect of simultaneous inhibition of TNF-alpha production and xanthine oxidase in experimental acute pancreatitis: the role of mitogen activated protein kinases

OBJECTIVE

To assess the effects of inhibiting both tumor necrosis factor (TNF)-alpha production and xanthine oxidase activity on the inflammatory response, mitogen-activated protein kinase (MAPK) activation and mortality in necrotizing acute pancreatitis in rats.

SUMMARY BACKGROUND DATA

Pancreatic injury triggers 2 major pathways involved in the systemic effects of severe acute pancreatitis: pro-inflammatory cytokines and oxidative stress.

METHODS

Pancreatitis was induced by intraductal infusion of 3.5% sodium taurocholate. We examined whether treatment with oxypurinol, a specific inhibitor of xanthine oxidase, and/or pentoxifylline, an inhibitor of TNF-alpha production, affects pancreatic damage, ascites, lung inflammation, and MAPK phosphorylation.

RESULTS

Oxypurinol prevented p38 phosphorylation in the pancreas and partially avoided the rise in lung myeloperoxidase activity. Pentoxifylline prevented erk 1/2 and JNK phosphorylation in the pancreas, and it partially reduced ascites and the rise in lung myeloperoxidase activity. Combined treatment with oxypurinol and pentoxifylline almost completely abolished ascites, MAPK phosphorylation in the pancreas, and the increase in lung myeloperoxidase activity. Histology revealed a reduction in pancreatic and lung damage. These changes were associated with a significant improvement of survival.

CONCLUSIONS

: Simultaneous inhibition of TNF-alpha production and xanthine oxidase activity greatly reduced local and systemic inflammatory response in acute pancreatitis and decreased mortality rate. These effects were associated with blockade of the 3 major MAPKs.

Pulmonary endothelium in acute lung injury: from basic science to the critically ill

BACKGROUND

Pulmonary endothelium is an active organ possessing numerous physiological, immunological, and metabolic functions. These functions may be altered early in acute lung injury (ALI) and further contribute to the development of acute respiratory distress syndrome (ARDS). Pulmonary endothelium is strategically located to filter the entire blood before it enters the systemic circulation; consequently its integrity is essential for the maintenance of adequate homeostasis in both the pulmonary and systemic circulations. Noxious agents that affect pulmonary endothelium induce alterations in hemodynamics and hemofluidity, promote interactions with circulating blood cells, and lead to increased vascular permeability and pulmonary edema formation.

OBJECTIVE

We highlight pathogenic mechanisms of pulmonary endothelial injury and their clinical implications in ALI/ARDS patients.

Mobilization of xanthine oxidase from the gastrointestinal tract in acute pancreatitis

Background

Xanthine oxidoreductase has been proposed to play a role in the development of local and systemic effects of acute pancreatitis. Under physiologic conditions, the enzyme exists mainly as xanthine dehydrogenase (XDH) but can be converted by proteolytic cleavage to its superoxide-generating form xanthine oxidase (XOD). In addition to its intracellular location XDH/XOD is also associated to the polysaccharide chains of proteoglycans on the external endothelial cell membrane.

In the early stages of acute pancreatitis, this enzyme seems to be arising from its mobilization from the gastrointestinal endothelial cell surface. Taking into account the ability of α-amylase to hydrolyze the internal α-1,4 linkages of polysaccharides, we wanted to elucidate the involvement of α-amylase in XDH/XOD mobilization from the gastrointestinal endothelial cell surface and the relevance of the ascitic fluid (AF) as the source of α-amylase in experimental acute pancreatitis.

Methods

Acute pancreatitis was induced in male Wistar rats by intraductal administration of 5% sodium taurocholate. In another experimental group 3000 U/Kg α-amylase was i.v. administered. The concentrations of XDH, XOD and α-amylase in plasma and AF and myeloperoxidase (MPO) in lung have been evaluated. In additional experiments, the effect of peritoneal lavage and the absorption of α-amylase present in the AF by an isolated intestine have been determined.

Results

Similar increase in XDH+XOD activity in plasma was observed after induction of acute pancreatitis and after i.v. administration of α-amylase. Nevertheless, the conversion from XDH to XOD was only observed in the pancreatitis group. Lung inflammation measured as MPO activity was observed only in the pancreatitis group. In addition peritoneal lavage prevented the increase in α-amylase and XDH+XOD in plasma after induction of pancreatitis. Finally, it was observed that α-amylase is absorbed from the AF by the intestine.

Conclusions

During the early stages of acute pancreatitis, α-amylase absorbed from AF through the gastrointestinal tract could interfere with the binding of XDH/XOD attached to glycoproteins of the endothelial cells. Proteolytic enzymes convert XDH into its oxidase form promoting an increase in circulating XOD that has been reported to be one of the mechanisms involved in the triggering of the systemic inflammatory process.