N-acetylcysteine decreases severity of acute pancreatitis in mice

N-acetylcysteine prevents intra-acinar oxygen free radical production in pancreatic duct obstruction-induced acute pancreatitis

Although oxygen free radicals (OFR) are considered to be one of the pathophysiological mechanisms involved in acute pancreatitis (AP), the contribution of acinar cells to their production is not well established. The aim of the present study was to determine the effect of N-acetylcysteine (NAC) in the course of AP induced by pancreatic duct obstruction (PDO) in rats, directly analysing by flow cytometry the quantity of OFR generated in acinar cells. NAC (50 mg/kg) was administered 1 h before and 1 h after PDO. Measurements by flow cytometry of OFR generated in acinar cells were taken at different PDO times over 24 h, using dihydrorhodamine-123 as fluorescent dye. Histological studies of pancreas and measurements of neutrophil infiltration in the pancreas, pancreatic glutathione (GSH), malondialdehyde (MDA) levels, plasma amylase activity and hemoconcentration were carried out in order to assess the severity of AP at different stages. NAC effectively blunted GSH depletion at early AP stages and prevented OFR generation found in acinar cells as a consequence of AP induced by PDO. This attenuation of the redox state impairment reduced cellular oxidative damage, as reflected by less severe pancreatic lesions, normal pancreatic MDA levels, as well as diminished neutrophil infiltration in pancreas. Hyperamylasemia and hemoconcentration following AP induction were ameliorated by NAC administration at early stages, when oxidative stress seems to be critical in the development of pancreatitis. In conclusion, NAC reinforces the antioxidant defences in acinar cells, preventing OFR generation therefore attenuating oxidative damage and subsequently reducing the severity of PDO-induced AP at early stages of the disease.

N-acetylcysteine induces beneficial changes in the acinar cell cycle progression in the course of acute pancreatitis

Oxygen free radicals (OFR) are produced in the course of acute pancreatitis (AP). In addition to injurious oxidative effects, they are also involved in the regulation of cell growth. The aim of the present study was to examine the relationship between the effectiveness of N-acetyl-l-cysteine (NAC) to prevent the generation of OFR and the changes in the cell-cycle pattern of acinar cells in the course of AP induced in rats by pancreatic duct obstruction (PDO). NAC (50 mg/kg) was administered 1 h before and 1 h after PDO. Flow-cytometric measurement of OFR generation in acinar cells was carried out using dihydrorhodamine as fluorescent dye. Plasma amylase activity, pancreatic glutathione (GSH) content and TNF-alpha plasma levels were also measured. The distribution of acinar cells throughout the different cell-cycle phases was analysed at different AP stages by flow cytometry using propidium iodide staining. NAC administration reduced the depletion of pancreatic GSH content and prevented OFR generation in acinar cells of rats with PDO-induced acute pancreatitis. As a result, AP became less severe as reflected by the significant improvement of hyper-amylasaemia and maintenance of plasma TNF-alpha levels at values not significantly different from controls were found. NAC administration inhibited progression of cell-cycle phases, maintaining acinar cells in quiescent state at early PDO times. The protection from oxidative damage by NAC treatment during early AP, allows the pancreatic cell to enter S-phase actively at later stages, thereby allowing acinar cells to proliferate and preventing the pancreatic atrophy provoked by PDO-induced AP. The results provide evidence that OFR play a critical role in the progression of acinar cell-cycle phases. Prevention of OFR generation of acinar cells in rats with PDO-induced AP through NAC treatment, not only protects pancreas from oxidative damage but also promotes beneficial changes in the cell cycle progression which reduce the risk of pancreatic atrophy.

Pancreatic gene expression during the initiation of acute pancreatitis: identification of EGR-1 as a key regulator

We hypothesized that genes expressed in pancreatic acinar cells during the initiation of acute pancreatitis determine the severity of the disease. Therefore, we utilized microarrays to identify those genes commonly induced in rat pancreatic acinar cells within 1-4 h in two in vivo models, caerulein and taurocholate administration. This strategy yielded 51 known genes representing a complex array of molecules, including those that are likely to either reduce or increase the severity of the disease. Novel genes identified in the current study included ATF3, BRF1, C/EBPbeta, CGRP, EGR-1, ephrinA1, villin2, ferredoxin, latexin, lipocalin, MKP-1, NGFI-B, RhoA, tissue factor (TF), and syndecan. To validate these microarray results, the role of EGR-1 was further investigated using quantitative RT-PCR, Western blotting, and immunocytochemistry. EGR-1 expression occurred within acinar cells and correlated with the development of caerulein-induced acute pancreatitis in rats. Furthermore, the levels of the inflammation-related genes MCP-1, PAI, TF, IL-6, and ICAM-1 and the extent of lung inflammation were reduced during the initiation of caerulein-induced acute pancreatitis in EGR-1-deficient mice. Thus this study identified EGR-1 and several other novel genes likely to be important in the development and severity of acute pancreatitis.

Saralasin, a nonspecific angiotensin II receptor antagonist, attenuates oxidative stress and tissue injury in cerulein-induced acute pancreatitis

INTRODUCTION

Free radical-mediated pancreatic injury is believed to play a key role in the pathogenesis of acute pancreatitis. Most of these studies have focused on the effects of antioxidant enzymes and free radical scavengers on improving the pancreatic injury. Recent findings showed that cerulein-induced acute pancreatitis was associated with an upregulation of a local pancreatic renin-angiotensin system in the pancreas. In the current study we hypothesized that inhibition of this renin-angiotensin system by saralasin, a nonspecific antagonist for angiotensin II receptor, could attenuate the severity of cerulein-induced pancreatitis.

METHODOLOGY

The effects of saralasin on oxidative stress and tissue injury in cerulein-induced pancreatitis were assessed by histopathologic analysis and on the basis of biochemical changes of plasma alpha-amylase level, pancreatic glutathione status, oxidative modification of protein, and lipid peroxidation.

RESULTS

Data from the biochemical analysis showed that intravenous injections of saralasin at doses of 10 microg/kg to 50 microg/kg 30 minutes before the induction of acute pancreatitis significantly reduced pancreatic injury, as indicated by a decrease in plasma alpha-amylase activity in comparison with the cerulein-treated control. The effect of saralasin was further manifested by significant suppressions of glutathione depletion, oxidative modification of proteins, and lipid peroxidation in cerulein-treated rat pancreas. Histopathologic examination findings were in agreement with the biochemical data.

CONCLUSIONS

These data suggest that prophylactic administration of saralasin can ameliorate the oxidative stress and tissue injury in cerulein-induced pancreatitis. Such a protective effect may provide new insight into the potential value of angiotensin II receptor antagonists in the clinical therapy for acute pancreatitis.

The role of the intestine in the pathophysiology and management of severe acute pancreatitis

BACKGROUND

The outcome of severe acute pancreatitis has scarcely improved in 10 years. Further impact will require new paradigms in pathophysiology and treatment. There is accumulating evidence to support the concept that the intestine has a key role in the pathophysiology of severe acute pancreatitis which goes beyond the notion of secondary pancreatic infection. Intestinal ischaemia and reperfusion and barrier failure are implicated in the development of multiple organ failure.

DISCUSSION

Conventional management of severe acute pancreatitis has tended to ignore the intestine. More recent attempts to rectify this problem have included 1) resuscitation aimed at restoring intestinal blood flow through the use of appropriate fluids and splanchnic-sparing vasoconstrictors or inotropes; 2) enteral nutrition to help maintain the integrity of the intestinal barrier; 3) selective gut decontamination and prophylactic antibiotics to reduce bacterial translocation and secondary infection. Novel therapies are being developed to limit intestinal injury, and these include antioxidants and anti-cytokine agents. This paper focuses on the role of the intestine in the pathogenesis of severe acute pancreatitis and reviews the implications for management.

Curcumin ameliorates ethanol and nonethanol experimental pancreatitis

Treatments for pancreatitis are limited. Activation of transcription factor NF-kappaB, a key regulator of inflammatory molecule expression, is an early event in experimental pancreatitis and correlates with the inflammatory response. We report here that curcumin, a natural phytochemical known to inhibit NF-kappaB and activator protein (AP)-1, another important proinflammatory transcription factor, ameliorates pancreatitis in two rat models. In both cerulein pancreatitis and pancreatitis induced by a combination of ethanol diet and low-dose CCK, curcumin improved the severity of the disease as measured by a number of parameters (histology, serum amylase, pancreatic trypsin, and neutrophil infiltration). Curcumin markedly inhibited NF-kappaB and AP-1 activation, assessed by DNA binding and degradation of inhibitory IkappaB proteins, and the induction of mRNAs for cytokines IL-6 and TNF-alpha, the chemokine KC, and inducible nitric oxide synthase in pancreas. Curcumin also blocked CCK-induced NF-kappaB and AP-1 activation in isolated pancreatic acini. Our findings indicate that blocking key signals of the inflammatory response ameliorates pancreatitis in both ethanol and nonethanol models. They suggest that curcumin, which is currently in clinical trials for cancer prevention, may be useful for treatment of pancreatitis.

The role of monocyte chemoattractant protein-1 in experimental chronic pancreatitis model induced by dibutyltin dichloride in rats

INTRODUCTION

Recently, dibutyltin dichloride (DBTC) was reported to induce pancreatic fibrosis within 28 days in rats, but it is not clear that the induced condition should be considered chronic pancreatitis.

AIM AND METHODOLOGY

The aim of this study was to clarify whether the pancreatic fibrosis induced by DBTC can be regarded as chronic pancreatitis. Furthermore, we examined the relation of monocyte chemoattractant protein-1 (MCP-1) to the development of pancreatic fibrosis in this model. DBTC solution was injected into the right jugular vein in rats, and biochemical and histologic changes were measured at days 1, 3, 7, 14, and 28.

RESULTS

Microscopically, inflammatory cell infiltration was evident in the pancreas at days 1 and 3, mononuclear cell infiltration was observed at days 7, 14, and 28, and pancreatic fibrosis was pronounced 7 days later. At day 28, interstitial fibrosis and atrophy of the gland and ductlike tubular complex had progressed. DBTC produced a significant decrease in the contents of pancreatic protein and amylase, whereas the pancreatic hydroxyproline content increased. Serum and pancreatic MCP-1 concentration significantly increased compared with the control group. Furthermore, the expression of PDGF mRNA in the pancreas increased following the MCP-1 elevation.

CONCLUSIONS

These results suggest that this experimental model of pancreatic fibrosis induced by DBTC in rats was useful as a chronic pancreatitis model and that MCP-1 may play an important role in the development of pancreatic fibrosis.

Absence of endogenous interleukin-6 enhances the inflammatory response during acute pancreatitis induced by cerulein in mice

Interleukin-6 (IL-6) exerts a wide spectrum of regulatory activities during immune and inflammatory responses. The aim of this study was to investigate the role of endogenous IL-6 in the inflammatory response associated with acute pancreatitis. Acute pancreatitis was induced by hourly (x5) i.p. injections of cerulein (50 microg/kg, suspended in saline solution) in IL-6 deficient mice (IL-6-KO) and wild-type (IL-6WT) littermates. IL-6KO mice exhibited a more severe tissue injury and a higher rate of mortality and when compared to IL-6WT mice. Acute pancreatitis was characterized by edema, neutrophil infiltration, tissue hemorrhage and cell necrosis, upregulation of P-selectin and intercellular adhesion molecule-1 (ICAM-1), as well as increases in the serum levels of amylase and lipase. The degree of oxidative and nitrosative tissue damage was significantly greater in IL-6KO mice than in wild-type littermates, as indicated by higher tissue levels of malondialdehyde and nitrosylated proteins. Plasma levels of the inflammatory cytokines tumour necrosis factor-alpha and interleukin-1beta were also greatly enhanced in IL-6KO mice when compared to wild-type mice. These events were correlated with an increase in the staining (immunoreactivity) for poly (ADP-ribose) polymerase (PARP) in the pancreas of cerulein-treated IL-6WT. The staining for PARP was more pronounced in IL-6KO mice subjected to acute pancreatitis than in the corresponding WT mice. These data demonstrate that endogenous IL-6 exerts an anti-inflammatory role during acute pancreatitis, possibly by regulating the expression of adhesion molecules, the subsequent adhesion and activation of neutrophils and finally the generation of cytokine and reactive oxygen or nitrogen species.

NF-kappaB activation in pancreas induces pancreatic and systemic inflammatory response

BACKGROUND & AIMS

The role of nuclear factor kappaB (NF-kappaB) activation in acute pancreatitis is uncertain. The transcription factor NF-kappaB is activated early in acute pancreatitis, and NF-kappaB is widely considered a key element in inflammatory responses based on its ability to regulate the expression of inflammatory mediators in vitro. However, its role in vivo in specific diseases remains unclear, and the current data on the role of NF-kappaB in acute pancreatitis is primarily correlative.

METHODS

In this study, NF-kappaB was directly activated within the pancreas using adenoviral-mediated transfer of an active subunit, RelA/p65 (Adp65), delivered by intraductal injection.

RESULTS

Administration of Adp65 led to the infection of a population of acinar cells within the pancreas, the activation of NF-kappaB, the expression of NF-kappaB target genes, and an inflammatory response. Administration of Adp65 increased the infiltration of neutrophils to the pancreas and lung and caused widespread damage to pancreatic acinar cells. In contrast, at the same titer, control adenovirus (AdGFP) had no effect on these parameters. The level of NF-kappaB activation and the severity of inflammation were reduced when an adenovirus bearing the inhibitory subunit IkappaB-alpha was coadministered with Adp65.

CONCLUSIONS

Thus, activation of NF-kappaB within the pancreas was sufficient for the initiation of an inflammatory response in this model. These results help define the specific role of NF-kappaB activation in acute pancreatitis.

Towards a novel treatment strategy for acute pancreatitis. 1. Reappraisal of the evidence on aetiogenesis

Despite more than a century of research endeavour, there is no specific medical treatment for acute pancreatitis and early mortality is high - 20% of fatalities by the day after admission. I do not see any realistic prospect that today's focus on immunomodulation will provide a breakthrough either. The signs are that the outcome of acute pancreatitis is determined almost at its inception, and that those unfortunate individuals in whom the seeds for a precipitous course are sewn do not declare themselves until it is too late. This reappraisal of the evidence on disease aetiogenesis has been undertaken in an effort to fathom why this might be.

Rethinking cystic fibrosis pathology: the critical role of abnormal reduced glutathione (GSH) transport caused by CFTR mutation

Though the cause of cystic fibrosis (CF) pathology is understood to be the mutation of the CFTR protein, it has been difficult to trace the exact mechanisms by which the pathology arises and progresses from the mutation. Recent research findings have noted that the CFTR channel is not only permeant to chloride anions, but other, larger organic anions, including reduced glutathione (GSH). This explains the longstanding finding of extracellular GSH deficit and dramatically reduced extracellular GSH:GSSG (glutathione disulfide) ratio found to be chronic and progressive in CF patients. Given the vital role of GSH as an antioxidant, a mucolytic, and a regulator of inflammation, immune response, and cell viability via its redox status in the human body, it is reasonable to hypothesize that this condition plays some role in the pathogenesis of CF. This hypothesis is advanced by comparing the literature on pathological phenomena associated with GSH deficiency to the literature documenting CF pathology, with striking similarities noted. Several puzzling hallmarks of CF pathology, including reduced exhaled NO, exaggerated inflammation with decreased immunocompetence, increased mucus viscoelasticity, and lack of appropriate apoptosis by infected epithelial cells, are better understood when abnormal GSH transport from epithelia (those without anion channels redundant to the CFTR at the apical surface) is added as an additional explanatory factor. Such epithelia should have normal levels of total glutathione (though perhaps with diminished GSH:GSSG ratio in the cytosol), but impaired GSH transport due to CFTR mutation should lead to progressive extracellular deficit of both total glutathione and GSH, and, hypothetically, GSH:GSSG ratio alteration or even total glutathione deficit in cells with redundant anion channels, such as leukocytes, lymphocytes, erythrocytes, and hepatocytes. Therapeutic implications, including alternative methods of GSH augmentation, are discussed.