Activation of proteases in cerulein-induced pancreatitis

A system for in vivo on-demand ultra-low field Overhauser-enhanced 3D-Magnetic resonance imaging

Development of very-low field MRI is an active area of research. It aims at reducing operating costs and improve portability. However, the signal-to-noise issue becomes prominent at ultra-low field (<1 mT), especially for molecular imaging purposes that addresses specific biochemical events. In the context of preclinical molecular MRI of abnormal proteolysis the paper describes a MRI system able to produce Overhauser-enhanced MR images in living rats through in situ Dynamic Nuclear Polarization at 206 µT using stable and non-toxic nitroxides. In parallel conventional images are generated at 206 µT following pre-polarization at 20 mT. Results show that nitroxides are visualized in 3D within a few minutes in the lungs, kidneys and bladder post-administration. This system will be used for molecular imaging of inflammation using protease-specific nitroxide probes.

Detection of Lipase Activity in Cells by a Fluorescent Probe Based on Formation of Self-Assembled Micelles

Reliable and sensitive detection of lipase activity is essential for the early diagnosis and monitoring of acute pancreatitis or progression of digestive diseases. However, the available fluorescent probes for detection of lipase activity are only implemented in a hexane-water two-phase system due to the nature of heterogeneous catalysis of lipase, thus limiting their applications in direct imaging of lipase activity in living cells and tissues. Here we designed and synthesized a "turn on" fluorescent probe CPP based on self-assembled micelles for hydrolysis of lipase. The CPP probe exhibits high selectivity and excellent sensitivity for the detection of lipase in such a homogeneous system and is successfully applied for monitoring lipase activity in pancreatic AR42J cells, tissues, and serums. Taken together, the fluorescent CPP probe not only provides a tool for diagnostic potential in pancreatic disease but also demonstrates an application potential for micelle self-assembly-based development of biological probes.

The Regulatory Effect of the Kinase Inhibitor PD98059 on Autophagic Flux During Trypsinogen Activation in Pancreatic Acinar Cells

OBJECTIVES

To study the role of kinase inhibitor PD98059 on autophagy flow in the process of trypsinogen activation in pancreatic acinar cell and its related mechanism.

METHODS

In the present study, bioinformatics analysis was used to predict kinases and their most relevant inhibitor (PD98059) which participates in autophagy of acute pancreatitis (AP). The rat pancreatic acini AR42J cells were divided into 4 groups: control group, sodium taurocholate hydrate (TLC) group, PD98059 group, and TLC + PD group. Twenty-seven Sprague-Dawley rats were divided into 3 groups (n = 9), including control group, severe AP (SAP) group, and SAP + PD group. We detected trypsinogen activation, autophagic activation, lysosome pH, and cathepsin-L activity in vivo and in vitro.

RESULTS

Results revealed trypsinogen activation was significantly inhibited in mitogen-activated protein kinase 1, JAK2, LYN, and their common inhibitor was PD98059. The trypsinogen activation, Beclin1, and light chain 3 II expressions were reduced, whereas the expressions of lysosomal-associated membrane protein 2, cathepsin L1, and cathepsin-L activity is upregulated after the PD98059 pretreatment, both in vivo and in vitro.

CONCLUSIONS

Lysosomal dysfunction blocked autophagy flux, accompanied by increasing pancreatic acinar cell autophagy in the process of trypsinogen activation. PD98059 inhibited AP occurrence and pancreatic injury via improving the blocked autophagic pathway and reducing trypsinogen activation.

Withaferin A, a novel compound of Indian ginseng (Withania somnifera), ameliorates Cerulein-induced acute pancreatitis: Possible role of oxidative stress and inflammation

Acute pancreatitis is an inflammatory disorder of the pancreas that may precipitate due to various reasons such as chronic alcoholism, gall stone obstruction, and life style. Current treatment options offer limited efficacy, as they provide only symptomatic relief. This study is an attempt to study the effects of Withaferin A (WFA) against Cerulein-induced acute pancreatitis in mice. Animals were pretreated with WFA via intraperitoneal route, for 7 days. Plasma amylase and lipase, tissue malondialdehyde (MDA), and glutathione were evaluated for all groups. Western blot analysis; haematoxylin and eosin staining of the liver, lung, and pancreas; immunohistochemistry for nitrotyrosine; and myeloperoxidase activity were performed. Haematoxylin and eosin stained sections significantly revealed the altered architecture and thereby damage in the pancreas, lungs, and liver that has been low in treatment groups. Increased myeloperoxidase and nitrotyrosine have also been reduced upon treatment with WFA. Increased levels of MDA, NO, and expression of myeloperoxidase and nitrotyrosine in the parameters estimated add evidence to the role of oxidative stress and inflammation in acute pancreatitis. WFA evidently altered these conditions upon pretreatment. Our study shows that this novel steroidal compound has potent anti-inflammatory property. Natural compounds can therefore be good remedies against many diseases if incorporated in routine diet as dietary supplement.

Cerulein-Induced Acute Pancreatitis Affects Sphingomyelin Signaling Pathway in Rats

OBJECTIVES

Acute pancreatitis (AP) is a common and severe gastrointestinal inflammatory disease with poorly understood pathogenesis. We adopted cerulein-induced pancreatitis, a well-established rat model shearing similarities with human AP, to determine the disease background. Special interest was placed on sphingolipids, because their signaling pathways are involved in many pathological states including hepatic steatosis, heart infarction, or pancreatic origin type 1 diabetes.

METHODS

Sphingolipid levels in the blood and pancreas were determined by the means of chromatography (thin-layer and high-performance liquid chromatography).

RESULTS

We found that AP leads to activation of ceramide de novo synthesis pathway, as evidenced by a significant increment in sphinganine, that is, ceramide synthesis precursor, content (+3.8-fold). Surprisingly, despite the reported growth in sphinganine concentration, we observed a reduced (-38%) ceramide level in the pancreas of rats with AP. The results could be explained by subsequent hydrolysis of ceramide to other secondary messengers, that is, sphingosine (+4-fold) or sphingosine-1-phosphate (+3-fold).

CONCLUSIONS

Because it is known that sphingosine-1-phosphate and some of its analogs could have a protective role against AP complications, our findings may contribute to elaboration of new therapeutic strategies in the management of this severe medical condition.

Visualization, Quantification and Characterization of Caerulein-Induced Acute Pancreatitis in Rats by 3.0T Clinical MRI, Biochemistry and Histomorphology

Purpose: To investigate whether Caerulein-induced acute pancreatitis (AP) in rats could be noninvasively studied by clinical magnetic resonance imaging (MRI) techniques and validated by enzymatic biochemistry and histomorphology. Materials and Methods: The study was approved by the institutional animal ethical committee. The AP was induced in 26 rats by intraperitoneal injections of Caerulein, as compared to 6 normal rats. T2-weighted 3D MRI, T2 relaxation measurement and contrast enhanced T1-weighted MRI were performed at 3 Tesla. Pancreatic volume and contrast ratio of pancreas against surrounding tissues were measured by MRI. Animals were scarified at 3, 8, 24 and 48-hr respectively for analyses of serum lipase and amylase levels, and biliopancreatic perfusion-assisted histomorphology. Results: The AP could be observed on MRI 3-hr onwards after Caerulein-administration. T2 relaxation within the pancreas was prolonged due to high water content or edema. Increase of vascular permeability was indicated by T1 contrast enhancement. Both edema and vascular permeability gradually recovered afterwards (p<0.05/0.01), paralleled by declining serum enzyme levels (p<0.05). Microscopy revealed cell vacuolization and edema for early stage, and increased inflammatory cell infiltration and acinar cell loss after 24 and 48-hr. Conclusion: Multiparametric MRI techniques at 3.0T could facilitate noninvasive diagnosis and characterization of Caerulein induced AP in rats, as validated by a novel ex vivo method.

Nucleotide-binding oligomerization domain 1 acts in concert with the cholecystokinin receptor agonist, cerulein, to induce IL-33-dependent chronic pancreatitis

Nucleotide-binding oligomerization domain 1 (NOD1) fulfills important host-defense functions via its responses to a variety of gut pathogens. Recently, however, we showed that in acute pancreatitis caused by administration of cholecystokinin receptor (CCKR) agonist (cerulein) NOD1 also has a role in inflammation via its responses to gut commensal organisms. In the present study, we explored the long-term outcome of such NOD1 responsiveness in a new model of chronic pancreatitis induced by repeated administration of low doses of cerulein in combination with NOD1 ligand. We found that the development of chronic pancreatitis in this model requires intact NOD1 and type I IFN signaling and that such signaling mediates a macrophage-mediated inflammatory response that supports interleukin (IL)-33 production by acinar cells. The IL-33, in turn, has a necessary role in the induction of IL-13 and TGF-β1, factors causing the fibrotic reaction characteristic of chronic pancreatitis. Interestingly, the Th2 effects of IL-33 were attenuated by the concomitant type I IFN response since the inflammation was marked by clear increases in IFN-γ and TNF-α production but only marginal increases in IL-4 production. These studies establish chronic pancreatitis as an IL-33-dependent inflammation resulting from synergistic interactions between the NOD1 and CCKR signaling pathways.

Valproic Acid Limits Pancreatic Recovery after Pancreatitis by Inhibiting Histone Deacetylases and Preventing Acinar Redifferentiation Programs

The mechanisms by which drugs induce pancreatitis are unknown. A definite cause of pancreatitis is due to the antiepileptic drug valproic acid (VPA). On the basis of three crucial observations-that VPA inhibits histone deacetylases (HDACs), HDACs mediate pancreas development, and aspects of pancreas development are recapitulated during recovery of the pancreas after injury-we hypothesized that VPA does not cause injury on its own, but it predisposes patients to pancreatitis by inhibiting HDACs and provoking an imbalance in pancreatic recovery. In an experimental model of pancreatic injury, we found that VPA delayed recovery of the pancreas and reduced acinar cell proliferation. In addition, pancreatic expression of class I HDACs (which are the primary VPA targets) increased in the midphase of pancreatic recovery. VPA administration inhibited pancreatic HDAC activity and led to the persistence of acinar-to-ductal metaplastic complexes, with prolonged Sox9 expression and sustained β-catenin nuclear activation, findings that characterize a delay in regenerative reprogramming. These effects were not observed with valpromide, an analog of VPA that lacks HDAC inhibition. This is the first report, to our knowledge, that VPA shifts the balance toward pancreatic injury and pancreatitis through HDAC inhibition. The work also identifies a new paradigm for therapies that could exploit epigenetic reprogramming to enhance pancreatic recovery and disorders of pancreatic injury.

Apigenin inhibits pancreatic stellate cell activity in pancreatitis

BACKGROUND

Chronic pancreatitis (CP) is characterized by recurrent pancreatic injury, resulting in inflammation, necrosis, and fibrosis. There are currently no drugs limiting pancreatic fibrosis associated with CP, and there is a definite need to fill this void in patient care.

MATERIALS AND METHODS

Pancreatitis was induced in C57/BL6 mice using supraphysiologic doses of cerulein, and apigenin treatment (once daily, 50 μg per mouse by oral gavage) was initiated 1 wk into the recurrent acute pancreatitis (RAP) protocol. Pancreata were harvested after 4 wk of RAP. Immunostaining with fibronectin antibody was used to quantify the extent of pancreatic fibrosis. To assess how apigenin may decrease organ fibrosis, we evaluated the effect of apigenin on the proliferation and apoptosis of human pancreatic stellate cells (PSCs) in vitro. Finally, we assessed apigenin's effect on the gene expression in PSCs stimulated with parathyroid hormone-related protein, a profibrotic and proinflammatory mediator of pancreatitis, using reverse transcription-polymerase chain reaction.

RESULTS

After 4 wk of RAP, apigenin significantly reduced the fibrotic response to injury while preserving acinar units. Apigenin inhibited viability and induced apoptosis of PSCs in a time- and dose-dependent manner. Finally, apigenin reduced parathyroid hormone-related protein-stimulated increases in the PSC messenger RNA expression levels of extracellular matrix proteins collagen 1A1 and fibronectin, proliferating cell nuclear antigen, transforming growth factor-beta, and interleukin-6.

CONCLUSIONS

These in vivo and in vitro studies provide novel insights regarding apigenin's mechanism(s) of action in reducing the severity of RAP. Additional preclinical testing of apigenin analogs is warranted to develop a therapeutic agent for patients at risk for CP.

Models of acute and chronic pancreatitis

Animal models of acute and chronic pancreatitis have been created to examine mechanisms of pathogenesis, test therapeutic interventions, and study the influence of inflammation on the development of pancreatic cancer. In vitro models can be used to study early stage, short-term processes that involve acinar cell responses. Rodent models reproducibly develop mild or severe disease. One of the most commonly used pancreatitis models is created by administration of supraphysiologic concentrations of caerulein, an ortholog of cholecystokinin. Induction of chronic pancreatitis with factors thought to have a role in human disease, such as combinations of lipopolysaccharide and chronic ethanol feeding, might be relevant to human disease. Models of autoimmune chronic pancreatitis have also been developed. Most models, particularly of chronic pancreatitis, require further characterization to determine which features of human disease they include.

Differential effects of endothelins on histological and ultrastructural changes and trypsinogen activation in the secretagogue-induced acute pancreatitis in rats

The role of endothelins in acute pancreatitis remains obscure. To assess the effects of endothelins (ETs) in early (4 h) caerulein-induced acute pancreatitis (AP) in rats, ET-1, ET-2 and ET-3 (0.5 or 1.0 nmol/kg) were applied twice with i.p. caerulein (2×40 μg/kg) at 1h interval. Histological and ultrastructural examinations of pancreases and the assay of trypsinogen activation in whole homogenate were performed. All ETs, especially ET-1 at the higher dose, decreased inflammatory cell infiltration despite an increase in the edema score. The vacuolization and necrosis of acinar cells were slightly increased after the lower dose of ET-1 and ET-2. Ultrastructural changes were generally improved after the higher dose of ETs. Trypsinogen activation increased from 4.8±1.3% in control to 18.4±3.8% in AP (p<0.01). It was attenuated to 6.4±1.3% (p<0.01) by the higher dose of ET-1 and to 8.8±1.5% (p<0.05) by the lower dose of ET-3. In summary, ETs, especially ET-1 at the higher dose, were found to have some beneficial effects on morphological changes and trypsinogen activation in the pancreas in early caerulein-induced AP.

Effect of proton pump inhibitor on amylase release from isolated pancreatic acini

Proton pump inhibitors (PPIs) could inhibit the secretion of gastric acid. Meanwhile, it could also decrease the secretion of other digestive glands besides gastric parietal cell. As we know, PPIs have been widely used to treat acute pancreatitis, and it is effective in clinical practice. However, research showed the side effect of PPIs on acute pancreatitis. The direct effect of PPI on pancreatic secretion is still unknown. Our experiment investigated the direct effect of PPIs on pancreatic exocrine by isolated pancreatic acini. In our study, isolated pancreatic acini were prepared as previously described by Williams, and cerulein was added to stimulate its secretion. The amylase release in the suspension was determined after the administration of different concentrations of omeprazole and Sandostatin; and its activity was also observed in different time phases. In our in vitro study, all results suggest that omeprazole has no direct repression on amylase release from isolated pancreatic acini.

Biochemistry and biology of SPINK-PSTI and monitor peptide

This article summarizes structural and functional properties of pancreatic secretory trypsin inhibitor (PSTI), which has been identified in many species. Its prominent role is to protect the pancreas from prematurely activated trypsinogen before entry into the duodenum. In the rat there are two isoforms, one of which is PSTI-I, a 61-amino acid peptide involved in the feedback regulation of pancreatic enzymes. Independent investigations in neoplastic diseases led to the discovery of tumor-associated trypsin inhibitor,which is identical to PSTI.

Extracellular cleavage of E-cadherin by leukocyte elastase during acute experimental pancreatitis in rats

BACKGROUND & AIMS

Cadherins play an important role in cell-cell contact formation at adherens junctions. During the course of acute pancreatitis, adherens junctions are known to dissociate-a requirement for the interstitial accumulation of fluid and inflammatory cells-but the underlying mechanism is unknown.

METHODS

Acute pancreatitis was induced in rats by supramaximal cerulein infusion. The pancreas and lungs were either homogenized for protein analysis or fixed for morphology. Protein sequencing was used to identify proteolytic cleavage sites and freshly prepared acini for ex vivo studies with recombinant proteases. Results were confirmed in vivo by treating experimental pancreatitis animals with specific protease inhibitors.

RESULTS

A 15-kilodalton smaller variant of E-cadherin was detected in the pancreas within 60 minutes of pancreatitis, was found to be the product of E-cadherin cleavage at amino acid 394 in the extracellular domain that controls cell-contact formation, and was consistent with E-cadherin cleavage by leukocyte elastase. Employing cell culture and ex vivo acini leukocyte elastase was confirmed to cleave E-cadherin at the identified position, followed by dissociation of cell contacts and the internalization of cleaved E-cadherin to the cytosol. Inhibition of leukocyte elastase in vivo prevented E-cadherin cleavage during pancreatitis and reduced leukocyte transmigration into the pancreas.

CONCLUSIONS

These data provide evidence that polymorphonuclear leukocyte elastase is involved in, and required for, the dissociation of cell-cell contacts at adherens junctions, the extracellular cleavage of E-cadherin, and, ultimately, the transmigration of leukocytes into the epithelial tissue during the initial phase of experimental pancreatitis.

Manifestations of experimental acute pancreatitis in young and old rats

Two kinds of experimental pancreatitis were induced in young (4-6 month) and old (25-27 month) female Wistar rats: acute edematous pancreatitis was induced by intraperitoneal administration of a high dose of cerulein (40 micro/kg x 2) and acute hemorrhagic pancreatitis was intraductal injection of 1% deoxycholic acid. After these treatments, the plasma amylase concentration and pancreatic wet weight were determined and the pancreas was examined histologically. In the groups with cerulein induced pancreatitis one of eight old rats died, whereas all five young rats survived. There was no specific finding macroscopically in the liver, kidney, lung or heart of old rats at autopsy after cerulein injection. The plasma amylase concentration and the pancreatic wet weight were significantly increased by administration of cerulein or deoxycholic acid in both young and old rats. There was no significant difference in the plasma amylase concentrations in young and old rats after the induction of acute pancreatitis. The increase in pancreatic wet weight was less in old rats than in young ones after deoxycholic acid treatment, but similar in the two groups after cerulein injection. The extents of histological changes were also similar in young and old rats. Thus, no evidence that aging increases susceptibility to pancreatitis was obtained.

Effect of endothelin-1 receptor antagonists on histological and ultrastructural changes in the pancreas and trypsinogen activation in the early course of caerulein-induced acute pancreatitis in rats

AIM: To assess the effect of non-selective ET_A/B (LU 302872) and selective ET_A (LU 302146) antagonist on pancreatic histology and ultrastructure of acinar cells in connection with trypsinogen activation in early caerulein-induced AP.

METHODS: Male Wistar rats with caerulein-induced AP, lasting 4 h, were treated i.p. with 10 and 20 mg/kg b.w. of each antagonist. Edema, inflammatory infiltration, necrosis and vacuolization of acinar cells in the pancreas were scored at 0-3 scale. Free active trypsin (FAT), total potential trypsin (TPT) after activation with enterokinase, and index of trypsinogen activation (%FAT/TPT) were assayed in pancreatic homogenates.

RESULTS: In untreated AP, the edema, inflammatory infiltration, necrosis and vacuolization increased as compared to control healthy rats (P<0.01). None of the treatment exerted any meaningful effect on the edema and inflammatory infiltration. The selective antagonist increased slightly the necrosis score to 0.82±0.06 at higher dose (P<0.05) vs 0.58±0.06 in untreated AP. The non-selective antagonist increased slightly the vacuolization score to 2.41±0.07 at higher dose (P<0.01) vs 1.88±0.08 in untreated AP. The decrease in the number of zymogen granules, disorganization of endoplasmic reticulum, autophagosomes and cytoplasmic vacuoles were more prominent in treated AP than in untreated AP groups. %FAT/TPT in untreated AP increased about four times (18.4±3.8 vs 4.8±1.3 in control group without AP, P<0.001). Treatment of AP with both antagonists did not affect significantly augmented trypsinogen activation.

CONCLUSION: The treatment with endothelin-1 receptors (non-selective ET_A/B and selective ET_A) antagonists has essential effect neither on the edema and inflammatory infiltration nor on trypsinogen activation observed in the early course of caerulein-induced AP. Nevertheless a slight increase of the necrosis and vacuolization score and some of the ultrastructural data could suggest the possibility of their undesired effects in caerulein-induced AP at investigated doses.

The secretagogue effect of the poison from Centruroides limpidus limpidus on the pancreas of mice and the antagonistic action of the Bouvardia ternifolia extract

In Mexican traditional medicine the plant species Bouvardia ternifolia is used as remedy to treat patients who have been stung by scorpions. In the preceding study, the methanol extract from the roots of this plant was capable of reducing the poisonous effect of Centruroides limpidus limpidus on mice. The poisoning from scorpion C. limpidus limpidus includes manifestations associated with the pancreatitis. This study evaluated the effect produced by the hexane and methanol extract from the root of B. ternifolia upon the acutely inflamed pancreas induced by the venom of C. limpidus limpidus on rats, and the release of amylase in the isolated pancreas of mice. The intravenous administration of venom induced the extravasation of labelled albumin, in a dose dependant manner. The pre-administration of both extracts of Bouvardia ternifolia reduced significantly (p < 0.05) the extravasation by 60%. Upon measuring the secretagogue effect of the venom in the isolated pancreas of mice, the EC50 of the venom was 3.76 x 10(-3) mg ml(-1), whilst in the presence of the methanol and hexane extracts, this EC50 was 9.13 x 10(-3) mg ml(-1) and 0.01629 mg ml(-1). In conclusion, the C. limpidus limpidus venom possesses a secretagogue effect of amylase on the pancreas of mice and produces an inflamed pancreas which is effectively antagonised by the hexane and methanol extracts from the roots of B. ternifolia.

Protective effects of rhubarb on experimental severe acute pancreatitis

AIM: To investigate the effects of rhubarb on severe acute pancreatitis (SAP) in rats.

METHODS: Severe acute pancreatitis was induced by two intraperitoneal injections of cerulein (40 μg/kg body weight) plus 5-h restraint water-immersion stress. Rhubarb (75-150 mg/kg) was orally fed before the first cerulein injection. The degree of pancreatic edema, serum amylase level, local pancreatic blood flow (PBF), and histological alterations were investigated. The effects of rhubarb on pancreatic exocrine secretion in this model were evaluated by comparing with those of somatostatin.

RESULTS: In the Cerulein + Stress group, severe edema and diffuse hemorrhage in the pancreas were observed, the pancreatic wet weight (11.60 ± 0.61 g/Kg) and serum amylase (458 490 ± 43 100 U/L) were markedly increased (P < 0.01 vs control). In the rhubarb (150 mg/kg) treated rats, necrosis and polymorphonuclear neutrophil (PMN) infiltration in the pancreas were significantly reduced (P < 0.01), and a marked decrease (50%) in serum amylase levels was also observed (P < 0.01). PBF dropped to 38% (93 ± 5 mL/min per 100 g) of the control in the Cerulein + Stress group and partly recovered in the Cerulein + Stress + Rhubarb 150 mg group (135 ± 12 mL/min per 100 g) (P < 0.01). The pancreatic exocrine function was impaired in the SAP rats. The amylase levels of pancreatic juice were reduced in the rats treated with rhubarb or somatostatin, comparing with that of untreated SAP group. The bicarbonate concentration of pancreatic juice was markedly elevated only in the rhubarb-treated group (P < 0.01).

CONCLUSION: Rhubarb can exert protective effects on SAP, probably by inhibiting the inflammation of pancreas, improving pancreatic microcirculation, and altering exocrine secretion.

The endothelin-1 receptor antagonists ameliorate histology and ultrastructural alterations in the pancreas and decrease trypsinogen activation in severe taurocholate pancreatitis in rats

The role of potent vasoconstrictor endothelin-1 (ET-1) in acute pancreatitis (AP) remains controversial. The aim was to compare the effect of nonselective ET RA/B (LU-302872) and selective ET RA (LU-302146) antagonists on pancreatic histology, ultrastructure and trypsinogen activation in severe taurocholate AP in rats. Male Wistar rats with AP were treated with an intraperitoneous injection of 1, 5 and 10 mg/kg of body weight of each antagonist at 0, 6, 12 and 18 h after taurocholate administration. After 24 h, the samples of pancreases were taken for histological and ultrastructural examinations and for assessment of trypsinogen activation. Both antagonists, at all investigated doses, decreased the damage to the acinar cells detected in the light microscope and ultrastructurally. Trypsinogen activation increased to 29.7 +/- 3.9% in the AP untreated in comparison to the control group [12.7 +/- 1.4% (P<0.001)]. This increase was attenuated to 13.8 +/- 2.2% in AP treated with a high dose of the nonselective antagonist and to 8.4 +/- 1.7% with low dose of selective antagonist. The obtained results indicate that ET-1 could participate in the damage to the pancreas during AP. Both antagonists of ET-1 receptors exerted a similar beneficial effect on the morphological changes of the pancreas in AP. One of the probable mechanism could be the attenuation of trypsinogen activation.

The effect of endothelin-1 receptor antagonists in acute experimental pancreatitis in the rats

The relative role of endothelin-1 receptors, ET(A) and ET(B) blockade in acute pancreatitis (AP) remains controversial. The aim of the study was to compare the effect of nonselective ET(A/B) antagonist (LU 302872) and selective ET(A)antagonist (LU 302146) in severe taurocholate AP in rats. Male Wistar rats with AP were treated with increasing doses: 1, 5 or 10 mg/kg b.w. of antagonists i.p. at 0, 6, 12, 18 h after induction of AP. In 24 h survivors, free active trypsin (FAT) and total potential trypsin (TPT), chymotrypsin and lipase in 12,000 x g supernatants of the pancreases were assayed. The index of trypsinogen activation (% FAT/TPT) was elevated in untreated AP to 29.2 +/- 5.0 vs 5.4 +/- 0.9 in the control (p < 0.001). ET(A/B) antagonist at increasing doses, diminished this index to 9.8 +/- 2.7, 10.3 +/- 1.6 and 10.1 +/- 2.0 respectively (p < 0.005). ET(A) antagonist reduced % FAT/TPT ratio to 10.6 +/- 1.9 (p < 0.005), 13.4 +/- 0.5 (p < 0.001) and 10.2 +/- 2.4 (p < 0.005) at respective doses. Both antagonists to a similar degree reduced the histological scores of inflammation, hemorrhages and necrosis. The increase in chymotrypsin and lipase activities after 24 h was not significant. In conclusion, both nonselective ET(A/B) and selective ET(A) antagonists attenuated to similar degree the augmented trypsinogen activation and pancreatic injury in taurocholate acute experimental pancreatitis in rats. Endothelin-1 receptor antagonists could be beneficial in the course of acute pancreatitis by the attenuation of trypsinogen activation.

Mechanisms of Chinese herb emodin and somatostatin analogs on pancreatic regeneration in acute pancreatitis in rats

INTRODUCTION

Studies have revealed that emodin is a potent agent in the management of clinical and experimental acute pancreatitis, but the molecular mechanisms by which emodin produces its biologic effects, especially on pancreatic regeneration after acute pancreatitis, remain unknown. Numerous experimental and clinical studies have shown that somatostatin analogs have favorable effects on acute pancreatitis, but their role in the management of acute pancreatitis remains controversial.

AIM

To investigate mechanisms of the Chinese herb emodin and somatostatin analogs (SSa; Sandostatin) in acute pancreatitis of rats by analyzing the changes in pancreatic tissue cytokine transforming growth factor beta1 (TGFbeta1) and epidermal growth factor (EGF) gene expression, DNA synthesis, total protein content, and the relations between them.

METHODOLOGY

Acute pancreatitis was induced by intraperitoneal infusion of cerulein in rats. Emodin was administered intravenously and Sandostatin was administered subcutaneously at the time of induction of pancreatitis and 24, 48, and 72 hours afterward. Rats were killed at 6, 24, 48, 72, and 96 hours after the operation. The mRNA expression of TGFbeta1 and EGF were evaluated by reverse transcription polymerase chain reaction, and pancreatic tissue DNA synthesis was measured by the 3H-thymidine incorporation method in vitro. Total protein content was detected by Lowry's method.

RESULTS

The serum amylase level was decreased significantly in the emodin-treated and Sandostatin-treated groups in comparison with the nontreated group. Pancreatic tissue DNA synthesis was significantly decreased at 72 hours after the induction of pancreatitis, and a marked increase was observed at 96 hours after treatment with emodin and Sandostatin. Within 48 hours of the induction of pancreatitis, the total protein content in pancreatic tissue declined, but there was a remarkable increase in the emodin-treated group at 96 hours and Sandostatin-treated group at 48 hours. Expression of TGFbeta1 mRNA and EGF mRNA were undetectable in normal pancreas and the nontreated group at 6 hours but was observed from 24 hours to 96 hours after the induction of pancreatitis and reached its maximum at 72 hours. TGFbeta1 mRNA could be detected 6 hours after treatment with emodin and Sandostatin, and its expression was significantly higher in the emodin-treated and Sandostatin-treated groups than in the nontreated group at 24 and 48 hours. The expression of EGF mRNA was significantly higher in the emodin-treated and Sandostatin-treated group than in the nontreated group at 48 hours.

CONCLUSION

It was concluded that mechanisms of the Chinese herb emodin and somatostatin analogs in the management of acute pancreatitis in rats might be ascribed to the upregulation of TGFbeta1 and EGF gene expression, which subsequently increases DNA synthesis and protein content and thus accelerates pancreatic repair and regeneration.

Pathophysiological effects of nicotine on the pancreas: an update

Epidemiological evidence strongly suggests an association between cigarette smoking and pancreatic diseases. It is well recognized that nicotine, a major component in cigarette smoke, is an addictive agent and, therefore, reinforces smoking behavior. The current review update focuses on the genetics of nicotine dependence and its role on the development of pancreatic diseases. The role of smoking and nicotine in pancreatitis and pancreatic cancer development is also discussed. Exposure of laboratory animals to nicotine clearly supports the notion that nicotine can induce pancreatic injury. The mechanism by which nicotine induces such effects is perhaps mediated via signal transduction pathways in the pancreatic acinar cell, leading to enhanced levels of intracellular calcium release, resulting in cytotoxicity and eventual cell death. The induction of pancreatic injury by nicotine may also involve activation and expression of protooncogene, H-ras, which can increase cytosolic calcium via second messenger pathways. Development of pancreatic carcinoma in cigarette smokers as observed in human populations may be the result of activation and mutation of the H-ras gene. A possible pathogenetic mechanism of nicotine in the pancreas activating multiple signal transduction pathways is schematically summarized in Figure 1.

Coordinate regulation of secretory stress proteins (PSP/reg, PAP I, PAP II, and PAP III) in the rat exocrine pancreas during experimental acute pancreatitis

BACKGROUND

Pancreatic stone protein (PSP/reg) is a constitutively secreted protein in pancreatic juice. Pancreatitis-associated protein (PAP) belongs to the same family of proteins. PAP is highly increased during acute pancreatitis, while no exact data exist regarding PSP/reg protein synthesis and secretion. Recently, an attempt to determine PSP/reg and PAP levels in sera of rats with acute pancreatitis showed a significant increase in PAP but failed to demonstrate changes in PSP/reg. Others reported that surgical manipulation of the pancreas, including sham controls, affected mRNA levels of PSP/reg. Neither report determined protein levels of PSP/reg.

METHODS

Rats were treated intraperitoneally with a supramaximal dose of caerulein to induce pancreatitis, a physiological dose of caerulein, or a saline injection. Pancreata were analyzed for PAP and PSP/reg using ELISAs. RNA was extracted for Northern blot analysis of PAP I, II, and III and PSP/reg mRNA.

RESULTS

Experimental induction of acute pancreatitis caused a coordinate increase in both PSP/reg and PAP. PAP showed an acute response and returned to low levels within 48 h while PSP/reg exhibited a more sustained response. Intraperitoneal application of a physiological dose of caerulein and even a saline injection caused an increase in PSP/reg.

CONCLUSION

PSP/reg and PAP levels are increased through similar mechanisms by physiological and supramaximal doses of caerulein. However, PSP/reg regulation appears to sustain high levels while PAP levels are more transient. Since the regulation of this protein family is affected even under mild stress, we define them as secretory stress proteins.

C1-inhibitor: an anti-inflammatory reagent with therapeutic potential

Excessive activation of the protein cascade systems often leads to severe inflammatory tissue destruction with potential life-threatening outcome. These include clinical disorders, such as capillary leak syndrome, septic shock, myocardial infarction and other ischaemia/reperfusion injuries, trauma, burns, multiple organ failure, as well as graft rejection. A therapeutic substitution of appropriate regulators appears to be a reasonable approach to reduce undesirable inflammatory reactions. C1-inhibitor, a multifunctional regulator of the various kinin-generating cascade systems, is frequently reduced in patients suffering from severe inflammation. C1-inhibitor concentrate has been used for decades as a substitution therapy to treat acute attacks in patients with hereditary angioedema. Studies including pathophysiologically relevant animal models now provide sufficient evidence that C1-inhibitor may also serve as an effective means to protect against inflammatory tissue injury. Promising clinical results are emerging which support C1-inhibitor as a candidate for therapy in severe inflammatory disorders. Although treatment with C1-inhibitor is regarded as safe, recent reports on possible side effects in certain clinical situations emphasise the importance of controlled clinical studies. The following review will focus on the impact of C1-inhibitor treatment on diseases, where complement contributes to the pathogenesis.

Plasma and urinary trypsinogen activation peptide in healthy dogs, dogs with pancreatitis and dogs with other systemic diseases

OBJECTIVE

To determine the specificity and sensitivity of plasma and urinary trypsinogen activation peptide (TAP) concentrations in diagnosing pancreatitis in dogs.

DESIGN

Retrospective analysis of clinical cases.

PROCEDURE

Dogs were classified into three groups: healthy animals, dogs with confirmed pancreatitis and dogs with nonpancreatic disease, which clinically or biochemically resembled pancreatitis. This last group was further subdivided into dogs with renal and those with nonrenal disease. The plasma and urinary TAP concentration was determined by a competitive enzyme immunoassay. Clinical cases additionally had serum trypsin-like immunoreactivity concentration measured, as well as radiography and ultrasound of the abdomen and further diagnostic procedures. Nonparametric analysis of variance (Kruskal-Wallis test) was performed using Statistix 4.0 program.

RESULTS

There was a wide range of urinary TAP concentration in healthy dogs (mean 52.30 nmol/L, standard deviation 55.25) that made interpretation of urinary TAP concentrations difficult in the other groups. There was a narrow reference range for plasma TAP (mean 2.67 nmol/L, standard deviation 0.93). Plasma and urinary TAP concentrations, as well as urinary TAP to creatinine ratio, were all increased in dogs that died with necrotising pancreatitis. Values were not increased in mild, interstitial pancreatitis. Increased plasma TAP concentrations were also present in dogs with severe renal disease.

CONCLUSION

Plasma TAP concentration is a good prognostic indicator in naturally occurring pancreatitis in dogs. The failure of TAP to increase in mild pancreatitis, and the increase present in severe renal disease, suggests its measurement has limited application as a sole diagnostic tool for canine pancreatitis. Further investigations are required in order to explain the large variability of urinary TAP concentration and the presence of circulating TAP in healthy dogs.

Alterations in the glycoconjugates of pancreatic cell membrane induced by acute pancreatitis

The alterations that progressively appear in plasma membrane glycoconjugates of rat pancreatic cells at different stages of acute pancreatitis induced by duct obstruction have been analyzed on individual cells by flow cytometry using the fluoresceinated lectins, wheat germ agglutinin (WGA), Tetragonolobus purpureus agglutinin (TP) and Concanavalin A (Con A), which specifically bind to N-acetyl D-glucosamine, L-fucose and D-mannose, respectively. Two populations of pancreatic cells were differentiated according to the forward scatter (size), which showed different density of saccharidic terminals located at external positions in the glycoconjugates of the plasma membrane. A significant increase in WGA and TP binding was found 1.5 h after pancreatic obstruction, which could be due to the fusion of zymogen granules with the plasma membrane as suggested by the basolateral exocytosis observed by electron microscopy at this stage. The most external sugar residues of membrane glycoconjugates are removed 12 h after pancreatic duct obstruction as a consequence of an advanced state of pancreatitis. The hydrolytic process reaches greater depths in the membrane 48 h after obstruction. At this stage a significant decrease in WGA, TP and ConA binding was found in all pancreatic cells, indicating the loss of N-acetyl D-glucosamine and/or sialic acid, L-fucose and even D-mannose which is located in the core of the glycan. The results provide information about the progressive degradation induced by acute pancreatitis in pancreatic cell membrane glycoconjugates.

The recovery of acute pancreatitis depends on the enzyme amount stored in zymogen granules at early stages

Little is known about the changes in pancreatic enzyme storage in acute pancreatitis. We have performed flow cytometric studies of zymogen granules from rats with acute pancreatitis induced by hyperstimulation with caerulein. A comparison was made with rats treated with hydrocortisone (10 mg/kg/day) over 7 days before inducing pancreatitis in order to find out whether the amount of enzymes stored in the pancreas plays a key role in the development of pancreatitis. The potentially therapeutic effect of L-364,718 (0.1 mg/kg/day, for 7 days), a CCK receptor antagonist, was assayed in the rats with caerulein-induced pancreatitis which had previously received the hydrocortisone treatment. A significant increase in the intragranular enzyme content was observed 5 h after hyperstimulation with caerulein. The highest values were reached in the rats previously treated with hydrocortisone. The greatest pancreatic enzyme load was parallel to the highest values in plasma amylase, edema and haematocrit observed. Acute pancreatitis was reversed seven days later. At this stage smaller granules appeared in the pancreas whose enzyme content was similar to that of controls when no treatment was applied after pancreatitis. In contrast, L-364,718 administration prevented the favourable evolution of pancreatitis since the antagonism exerted on CCK receptors induced a blockade of secretion of the large amounts of enzymes stored in the pancreas. Moreover, the enzyme content in zymogen granules was below normal values since the stimulatory CCK action on enzyme synthesis can be inhibited by L-364,718. Our results suggest that the efficiency of CCK antagonists, as potential therapy, would also depend on the load of enzymes in the pancreas when acute pancreatitis is produced.

Trypsin activates pancreatic duct epithelial cell ion channels through proteinase-activated receptor-2

Proteinase-activated receptor-2 (PAR-2) is a G protein-coupled receptor that is cleaved by trypsin within the NH2-terminus, exposing a tethered ligand that binds and activates the receptor. We examined the secretory effects of trypsin, mediated through PAR-2, on well-differentiated nontransformed dog pancreatic duct epithelial cells (PDEC). Trypsin and activating peptide (AP or SLIGRL-NH2, corresponding to the PAR-2 tethered ligand) stimulated both an 125I- efflux inhibited by Ca2+-activated Cl- channel inhibitors and a 86Rb+ efflux inhibited by a Ca2+-activated K+ channel inhibitor. The reverse peptide (LRGILS-NH2) and inhibited trypsin were inactive. Thrombin had no effect, suggesting absence of PAR-1, PAR-3, or PAR-4. In Ussing chambers, trypsin and AP stimulated a short-circuit current from the basolateral, but not apical, surface of PDEC monolayers. In monolayers permeabilized basolaterally or apically with nystatin, AP activated apical Cl- and basolateral K+ conductances. PAR-2 agonists increased [Ca2+]i in PDEC, and the calcium chelator BAPTA inhibited the secretory effects of AP. PAR-2 expression on dog pancreatic ducts and PDEC was verified by immunofluorescence. Thus, trypsin interacts with basolateral PAR-2 to increase [Ca2+]i and activate ion channels in PDEC. In pancreatitis, when trypsinogen is prematurely activated, PAR-2-mediated ductal secretion may promote clearance of toxins and debris.

Trypsinogen activation and glutathione content are linked to pancreatic injury in models of biliary acute pancreatitis

CONCLUSION

In models of biliary acute pancreatitis, which might resemble the situation in humans, premature activation of trypsinogen inside the pancreas ("autodigestion") occurs and is correlated with the extent of ductal and parenchymal injury. It is accompanied by a critical spending of protease inhibitors and glutathione, compromising important acinar cell defense and maintenance mechanisms.

BACKGROUND

Premature activation of pancreatic digestive enzymes and profound changes of levels of certain biochemical compounds have been implicated in the pathophysiology of acute pancreatitis. Hitherto, little information on their role in biliary acute pancreatitis has been available.

METHODS

Three types of injury to the pancreaticobiliary duct system of various severity were induced in rats--ligation of the common bile-pancreatic duct, retrograde infusion of electrolyte, or retrograde infusion of taurocholate solution--and were compared to sham-operated animals. Trypsin, trypsin inhibitory capacity (TIC), reduced glutathione (GSH), and other compounds were measured in pancreatic tissue. Histopathology, as well as serum amylase, lipase, and gamma-glutamyl transferase (gamma GT) were assessed.

RESULTS

Histopathology and elevated activity of gamma GT in the serum revealed increasing severity of pancreatic injury from sham operation through retrograde duct infusion with taurocholate. GSH was diminished even in macroscopically normal-appearing tissue, but significantly lower in altered (hemorrhagic)-looking sections. Conversely, tissue levels of trypsin were significantly increased. TIC was elevated only in the duct obstruction model, whereas it was reduced in the retrograde duct infusion models.

Codistribution of TAP and the granule membrane protein GRAMP-92 in rat caerulein-induced pancreatitis

The pathological activation of zymogens within the pancreatic acinar cell plays a role in acute pancreatitis. To identify the processing site where activation occurs, antibodies to the trypsinogen activation peptide (TAP) were used in immunofluorescence studies using frozen sections from rat pancreas. Saline controls or animals receiving caerulein in amounts producing physiological levels of pancreatic stimulation demonstrated little or no TAP immunoreactivity. However, after caerulein hyperstimulation (5 micrograms. kg-1. h-1) for 30 min and the induction of pancreatitis, TAP immunoreactivity appeared in a vesicular, supranuclear compartment that demonstrated no overlap with zymogen granules. The number of vesicles and their size increased with time. After 60 min of hyperstimulation with caerulein, most of the TAP reactivity was localized within vacuoles >/=1 micrometer that demonstrated immunoreactivity for the granule membrane protein GRAMP-92, a marker for lysosomes and recycling endosomes. Pretreatment with the protease inhibitor FUT-175 blocked the appearance of TAP after hyperstimulation. These studies provide evidence that caerulein hyperstimulation stimulates trypsinogen processing to trypsin in distinct acinar cell compartments in a time-dependent manner.

Intra-acinar cell activation of trypsinogen during caerulein-induced pancreatitis in rats

Supramaximal stimulation of the pancreas with the CCK analog caerulein causes acute edematous pancreatitis. In this model, active trypsin can be detected in the pancreas shortly after the start of supramaximal stimulation. Incubation of pancreatic acini in vitro with a supramaximally stimulating caerulein concentration also results in rapid activation of trypsinogen. In the current study, we have used the techniques of subcellular fractionation and both light and electron microscopy immunolocalization to identify the site of trypsinogen activation and the subsequent fate of trypsin during caerulein-induced pancreatitis. We report that trypsin activity and trypsinogen-activation peptide (TAP), which is released on activation of trypsinogen, are first detectable in a heavy subcellular fraction. This fraction is enriched in digestive enzyme zymogens and lysosomal hydrolases. Subsequent to trypsinogen activation, both trypsin activity and TAP move to a soluble compartment. Immunolocalization studies indicate that trypsinogen activation occurs in cytoplasmic vacuoles that contain the lysosomal hydrolase cathepsin B. These observations suggest that, during the early stages of pancreatitis, trypsinogen is activated in subcellular organelles containing colocalized digestive enzyme zymogens and lysosomal hydrolases and that, subsequent to its activation, trypsin is released into the cytosol.

Protective effect of a pancreatic elastase inhibitor against a variety of acute pancreatitis in rats

Protective effect of trifluoroacetyl-L-lysyl-L-alaninanilide hydrochloride (compound 1), a pancreatic elastase inhibitor, on three types of acute pancreatitis models was examined in rats. Mild, moderate and severe acute pancreatitis were induced by cerulein, the closed duodenal loop method and retrograde injection of a taurocholate plus trypsin solution into the pancreatic duct, respectively. Intravenous infusion of compound 1 at a dose of 30 mg/kg/hr resulted in lower increases in serum amylase, lipase, blood urea nitrogen (BUN) and creatinine levels in rats with mild cerulein-induced edematous pancreatitis. Compound 1 had no beneficial effect on pancreatitis in rats with moderate pancreatitis. In rats with severe pancreatitis, prophylactic treatment of compound 1 (30 mg/kg/hr) reduced both elevated serum BUN level and ascitic volume, and it histologically inhibited the extent of pancreatic edema and hemorrhage. These results suggest that pancreatic elastase is partially responsible for pancreatic edema and hemorrhage exhibited by rats with severe acute pancreatitis.

Acute-phase response of the rat pancreas protects against further aggression with severe necrotizing pancreatitis

OBJECTIVE

To test the hypothesis that the specific acute-phase response program of the pancreas is a powerful emergency defense mechanism that is beneficial during acute pancreatitis.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Research laboratory in a university medical school.

SUBJECTS

Female Wistar rats, weighing 250 to 300 g.

INTERVENTIONS

An acute-phase response was induced in rats subjected to hyperstimulation with cerulein. The development of the acute-phase reaction was monitored by the expression of the pancreatitis-associated protein I. In control animals, no acute-phase response was induced. After the first experimental procedure at periods of 2, 48, or 168 hrs, the pancreas was challenged by inducing severe necrotizing pancreatitis with retrograde infusion of taurocholate into the pancreatic duct. The course of necrohemorrhagic pancreatitis and survival of the rats to the challenge was monitored with time.

MEASUREMENTS AND MAIN RESULTS

Forty-eight hours after the onset of edematous pancreatitis, the acute-phase response was strong, as judged by the overexpression of mRNA, which encoded the pancreatitis-associated protein I, and the resulting increase in concentrations of this protein in the pancreas. When necrotizing pancreatitis was induced, the survival rate was significantly higher than in the corresponding control group. In contrast, expression of the pancreatitis-associated protein I was not detectable after 2 hrs, indicating that the acute phase had not fully developed, nor after 168 hrs when the acute phase had ended. In both cases, challenge by necrotizing pancreatitis led to similar survival rates in cerulein-treated and control rats.

CONCLUSIONS

The acute-phase response of the pancreas seems to be a powerful emergency defense mechanism against further pancreatic aggression, as shown by the improved survival of the animals. The factors mediating this protection are unknown. Due to the strong overexpression of the pancreatitis-associated protein I during the climax of the acute phase, this protein might be involved in the defense mechanism.

The effect of ethanol on pancreatic enzymes--a dietary artefact?

The effects of ethanol on pancreatic digestive and lysosomal enzymes may be relevant to the pathogenesis of alcoholic pancreatitis since pancreatic enzymes are thought to play an important role in the development of pancreatic injury. Previous studies, using the Lieber-DeCarli pair-feeding model of ethanol administration, have demonstrated that ethanol significantly increases the content and gene expression of pancreatic enzymes. However, these findings have been questioned because, in the Lieber-DeCarli model, ethanol-fed rats have a lower carbohydrate intake than their pair-fed controls, making it difficult to ascribe any observed changes to ethanol alone. This study was designed to distinguish between the effects of ethanol and those of reduced dietary carbohydrate on pancreatic enzymes, using a quartet-feeding model of ethanol administration. Rats were fed liquid diets containing low (11%) and high (47%) amounts of carbohydrate, with and without ethanol, for four weeks. The effects of ethanol on pancreatic content and messenger RNA levels for digestive enzymes (trypsinogen, chymotrypsinogen and lipase) and a lysosomal enzyme (cathepsin B) were assessed. Ethanol feeding resulted in a significant increase in glandular content with a corresponding increase in mRNA levels for all four enzymes studied. By contrast, a reduction in dietary carbohydrate intake alone did not alter pancreatic content or gene expression for the above enzymes. These results indicate that (i) ethanol significantly increases the capacity of the acinar cells to synthesise digestive enzymes and the lysosomal enzyme cathepsin B, and (ii) these changes are due to ethanol itself and are not due to variations in dietary carbohydrate intake.

Subcellular kinetics of early trypsinogen activation in acute rodent pancreatitis

To investigate the debated role of intracellular trypsinogen activation and its relation to lysosomal enzyme redistribution in the pathogenesis of acute pancreatitis, rats were infused with the cholecystokinin analog caerulein at 5 micrograms.kg-1.h-1 for intervals up to 3 h, and the changes were contrasted with those in animals receiving saline or 0.25 microgram.kg-1.h-1 caerulein. Saline or 0.25 microgram.kg-1.h-1 caerulein did not induce significant changes. In contrast, 5 micrograms.kg-1.h-1 caerulein caused significant hyperamylasemia and pancreatic edema within 30 min. Pancreatic content of trypsinogen activation peptide (TAP) increased continuously (significant within 15 min). TAP generation was predominantly located in the zymogen fraction during the first hour but expanded to other intracellular compartments thereafter. Cathepsin B activity in the zymogen compartment increased continuously throughout the experiments and correlated significantly with TAP generation in the same compartment. Total trypsinogen content increased to 143% with marked interstitial trypsinogen accumulation after 3 h. Supramaximal caerulein stimulation causes trypsinogen activation by 15 min that originates in the zymogen compartment and is associated with increasing cathepsin B activity in this subcellular compartment. However, a much larger pool of trypsinogen survives and accumulates in the extracellular space and may become critical in the evolution of necrotizing pancreatitis.

Trypsinogen activation in rat pancreatic acinar cells hyperstimulated by caerulein

Inappropriate trypsinogen activation is discussed as an early intracellular event in the secretagogue-induced model of acute pancreatitis. However, the mechanisms by which trypsinogen is activated are not well characterized. In the present work, trypsinogen activation was studied in intact acinar cells using bis-(CBZ-arginyl)-Rhodamine 110 [(CBZ-Arg)2-Rho 110] as a cell-permeant substrate for trypsin and also independently via the formation of trypsinogen activation peptide (TAP). Preincubation with 10 nM caerulein increased the Rho 110-substrate cleavage more than threefold. This proteolytic activity was fully sensitive to a benzamidine (BA)-type serine protease inhibitor. The appearance of enzymatic activity was paralleled by the formation of TAP. The lack of effect of the high-molecular soybean trypsin inhibitor indicates an intracellular substrate cleavage. The cathepsin B inhibitor CA-074 prevented neither the caerulein-induced formation of TAP nor the (CBZ-Arg)2-Rho 110-cleaving activity. BA inhibited the Rho 110-substrate cleavage and significantly reduced the TAP formation. These results show that trypsinogen activation in caerulein-hyperstimulated acinar cells may occur independently of the activity of cathepsin B. On the contrary, the effect of BA suggests the role of a serine protease in trypsinogen activation.

Cloning and expression of the rat p8 cDNA, a new gene activated in pancreas during the acute phase of pancreatitis, pancreatic development, and regeneration, and which promotes cellular growth

To characterize at the molecular level the pancreatic emergency program set up by the pancreatic cells in response to pancreatitis, we have developed a strategy in which the phenotype of the pancreatitis affected pancreas is established by characterization of a large number of its transcripts. Herein, we describe the cloning, sequence, and expression of a new gene, named p8, which is strongly activated in pancreatic acinar cells during the acute phase of pancreatitis, in developing pancreas and during pancreatic regeneration. In acinar cells, p8 mRNA is expressed rapidly and specifically in response to cellular pancreatitis-induced injury; its induction occurred almost similarly in edematous and necrohemorrhagic pancreatitis, indicating that p8 mRNA is maximally activated even in response to a mild pancreatic injury. Furthermore, in vitro studies suggest that p8 mRNA is induced in pancreatic and non-pancreatic cells in response to some apoptotic stimuli. p8 acts as a promoter of cellular growth factor when its cDNA is transfected into COS-7 and AR4-2J cells. Although we failed to identify p8-related sequences, analysis of its primary and secondary structure suggests that p8 is a basic helix-turn-helix-containing gene with slight homology to several homeotic genes and sufficient signal to be targeted to the nucleus. We therefore propose p8 as a putative transcriptional factor which can regulate pancreatic growth.

Role of hypertriglyceridemia in the pathogenesis of experimental acute pancreatitis in rats

CONCLUSION

The pancreatic damage initiated via different pathogenetic pathways can be increased by triglycerides. Thus, triglycerides seem to play an important role in the pathogenesis of acute pancreatitis.

BACKGROUND

Lipolytic enzymes and their substrates may play a role in the pathogenesis of acute necrotizing pancreatitis. We investigated, therefore, whether triglycerides alter the course of acute pancreatitis in three experimental models of rats.

METHODS

1. Edematous acute pancreatitis induced by repeated sc injections of cerulein; 2. Necrotizing acute pancreatitis by retrograde duct injection of sodium taurocholate; and 3. Pancreatic edema by ligation of: a. The bile duct at the liver hilus; b. The common bile/pancreatic duct close to the duodenal wall; or c. A combination of a. and b. Six hours later, rats were sacrificed and the isolated perfused pancreas prepared. The pancreases were perfused with either HEPES/Ringer/HAES alone or in combination with various concentrations of triglycerides (1-5% wt/vol). The activities of lipase and amylase in the portal venous effluents were regarded as a marker of pancreatic injury. In addition, the pancreases were evaluated by light microscopy.

RESULTS

In both cerulein and taurocholate acute pancreatitis, amylase/lipase activities were significantly higher compared to controls during 45 min of perfusion. In both models, addition of triglycerides caused a dose-dependent marked elevation of enzymes. Ligation (a) did not cause any rise in enzymes in the venous effluent; triglycerides had no effect. Ligation (b) or (c) caused a significant increase of pancreatic enzymes, which was further increased by triglycerides. Histology showed various degrees of severity of tissue damage depending on the model used. The additional damaging effect of a 45-min perfusion with triglycerides, however, could not be detected by histology.

Release of nonesterified fatty acids during cerulein-induced pancreatitis in rats

During acute pancreatitis, data obtained in vitro suggest that pancreatic lipase, acting on circulating or tissular triglycerides, might generate nonesterified fatty acids (NEFA) that could promote pancreatic and fat tissue necrosis. This work determined whether NEFA were actually produced in vivo in pancreatic tissue and in blood during cerulein-induced pancreatitis in rats. Intraperitoneal injections of cerulein induced pancreatitis. To promote the possible NEFA release by pancreatic lipase, a venous infusion of human very low density lipoprotein (VLDL) was used to cause hypertriglyceridemia. NEFA were measured in portal and aortic blood and in tissue extracts prepared from pancreas homogenates. NEFA did not increase either in peripheral or in portal blood. In pancreatic tissue, NEFA levels did not differ from controls. The major hypertriglyceridemia produced by human VLDL intravenous infusion neither altered the course of the disease nor promoted plasma NEFA release. The role commonly attributed to NEFA in acute pancreatitis seems questionable.

Effects of high-dose intraperitoneal aprotinin treatment on complement activation and acute phase response in acute severe pancreatitis

Forty-eight patients with severe acute pancreatitis were treated with intraperitoneal lavage in a double-blind randomized multi-center trial. One group (aprotinin group, n = 22) was also treated intraperitoneally with high doses of the protease inhibitor aprotinin. In the group not treated with aprotinin (control group), 6 patients were operated on because of pancreatic necrosis, compared with none in the treated group. Complement activation and the acute phase response were studied with measurements of anaphylatoxin C3a, C1 inhibitor (C1 Inh), interleukin 6 (IL-6), and C-reactive protein (CRP). The control group had higher plasma levels of C3a and lower levels of C1 Inh compared with the aprotinin group. The differences were statistically significant for C3a but not for C1 Inh. Both groups had high plasma levels of IL-6 and CRP. There were no differences between the groups in CRP levels, but the control group had higher IL-6 levels (not statistically significant) than the aprotinin group. This was caused by very high levels in the 6 patients operated on because of pancreatic necrosis, indicating that IL-6 could be a good plasma marker of pancreatic necrosis. The results also show that massive antiprotease treatment reduces complement activation, as illustrated by the lower C3a levels in the aprotinin group. The lower C1 Inh levels in the control group could have been caused by an increased consumption of the inhibitor.

Exocrine function of caerulein-induced acute pancreatitis in anesthetized rats

Exocrine function was studied in anesthetized rats that had received two specific doses of caerulein (maximal stimulation and supramaximal stimulation). Male Wistar rats (body weight, 200-250 g) were divided into three groups: the control group (4-h saline infusion), the maximal stimulation group (0.25 microgram/kg per h caerulein for 4 h), and the caerulein pancreatitis group (10 micrograms/kg per h for 4h). Histologically, interstitial edema and cytoplasmic vacuolization were observed only in the caerulein pancreatitis group, with no abnormal findings in the other groups. The volume of pancreatic juice was significantly increased in both the maximal stimulation group and the caerulein pancreatitis group. The protein output and the amylase output in the 1st h of caerulein infusion were also significantly increased, to 459% and 338% in the maximal stimulation group, and to 925% and 1430% respectively, in the caerulein pancreatitis compared to the baseline values. We also found that the pancreatic juice of the caerulein pancreatitis group contained precipitated protein, and high trypsin activity, and protein degradation was confirmed by electrophoresis. These findings were not observed in the other groups. These results strongly suggest that hypersecretion and the appearance of trypsin activity in pancreatic juice plays an important role in the induction of histological changes in this pancreatitis model in anesthetized rats.

Acute pancreatitis induced by hypercalcaemia associated with adult T-cell leukaemia: a case report

A 44 year old Japanese woman with adult T-cell leukaemia (ATL) was admitted to Kyushu University hospital to receive a course of alpha-interferon treatment. She experienced a sudden onset of hypercalcaemia and epigastric pain associated with an increase in the level of pancreatic enzymes. Her serum parathyroid hormone related protein level was above normal although her high sensitive PTH level was within the normal range. Ultrasonography and computed tomography (CT) of the abdomen showed enlargement of the pancreas with indistinct margins and massive accumulation of extrapancreatic fluid. Cullen's sign was observed. A few days after the onset of acute pancreatitis, the serum amylase level increased to 3400 IU/L, and the serum calcium level fell to 4.2 mg/dL from 13.3 mg/dl. Her fasting blood glucose level increased to 242 mg/dL. Although the first episode of pancreatitis appeared to respond to treatment, she experienced a second episode of pancreatitis accompanied by an elevation of the serum calcium level. These findings suggest that acute pancreatitis was caused by hypercalcaemia associated with ATL.

Protease-antiprotease interactions and the rationale for therapeutic protease inhibitors

A number of pancreatic enzymes have been suggested as the initiating factor for acute pancreatitis. In particular, the relationship between proteases and antiproteases has been examined extensively, based on the suspicion that an imbalance between them is the central factor in the pathogenesis of acute pancreatitis. Animal studies with antiproteolytic agents in models of acute pancreatitis have shown an improvement in outcome. However, more recently, prospective, randomized, multicentre trials treating human acute pancreatitis with antiproteolytic drugs (aprotinin, gabexate mesilate, and even fresh frozen plasma) have failed to show any benefit in the clinical setting. Thus, clinically, it seems likely that antiproteolytic therapy has no effect on the course of severe acute pancreatitis. Today, the mortality in severe acute pancreatitis is determined by septic complications due to infected pancreatic necroses in the late phase 2-3 weeks after the onset of the disease. Death in the early phase of the disease has become increasingly rare where an imbalance between proteases and antiproteases may be involved.

Infusion of C1-inhibitor plasma concentrate prevents hyperamylasemia induced by endoscopic sphincterotomy

Hyperamylasemia after endoscopic sphincterotomy is a common event, occurring in about 70% of cases. Clinical acute pancreatitis may also develop in 1% to 6% of cases. Previous attempts to prevent this reaction with inhibitors of exocrine pancreatic secretion (somatostatin and octreotide) provided conflicting and often disappointing results. Kallikrein is one of the proteases that sustain the inflammatory process in acute pancreatitis; the C1 inhibitor is the only physiologic inhibitor of the first component of the human complement cascade and is a major inactivator of kallikrein and Factor XII. Therefore, we tested the C1 inhibitor in the prevention of hyperamylasemia in 40 consecutive patients undergoing endoscopic sphincterotomy for common bile duct stones or benign papillary stenosis. They were given either C1 inhibitor (20 cases) or placebo (20 cases) before the procedure. Serum amylase levels were determined at baseline and 2, 4, 8, and 24 hours thereafter. Significant differences in serum amylase levels between groups were observed at 2 hours (p < .01), 4 hours (p < .0005), and 8 hours (p < .005) after sphincterotomy. The differences in amylase levels were also significant among the 24 subjects with pancreatic ductal filling (2 hours, p < .05; 4 hours, p < .005; 8 hours, p < .01) and the 9 patients with previous episodes of acute pancreatitis (4 hours, p < .05; 8 hours, p < .05; 24 hours, p < .05). The infusion of C1-inhibitor plasma concentrate resulted in a 50% increase in functional levels of C1 inhibitor (in the 8 cases for whom they were assayed), which persisted throughout the observation period.

Nitric oxide modulates pancreatic edema formation in rat caerulein-induced pancreatitis

This study was designed to investigate the role of nitric oxide (NO) in the formation of pancreatic edema in caerulein-induced pancreatitis in rats. Pancreatitis was produced by two intraperitoneal injections of caerulein, and plasma amylase concentration, pancreatic edema index (pancreatic wet weight/body weight), and Evans blue extravasation (as a measure of vascular permeability) were evaluated 5 h after the first injection. Four doses (1, 2.5, 5, and 10 mg/kg) of NG-nitro-L-arginine (L-NNA), an NO synthase inhibitor, were subcutaneously administered at -0.5, 0.5, 1.5, 2.5, and 3.5 h after the first injection of caerulein. L-NNA significantly lowered the edema index, the wet/dry weight ratio of the pancreas, and Evans blue extravasation in the rats with pancreatitis. The maximal effect was obtained by L-NNA at a dose of 2.5 mg/kg; this inhibited the increase in pancreatic edema formation from the control value by 60%-70%. Intraperitoneal injections (20 mg/kg, five times) of L-arginine, a substrate for NO production, partly reversed the L-NNA-induced inhibition of pancreatic edema formation, but D-arginine, an enantiomer of L-arginine, did not show any effect. Plasma amylase concentrations were not significantly affected by any dose of L-NNA, nor were they affected by L- or D-arginine. These findings strongly suggest that endogenous NO plays an important role in the formation of pancreatic edema in caerulein-induced pancreatitis in rats, probably by increasing vascular permeability and protein extravasation.

Cholecystokinin-8 induces edematous pancreatitis in dogs associated with short burst of trypsinogen activation

To study the early pathogenesis of acute edematous pancreatitis in dogs, we examined the relationship of pancreatic hyperstimulation with cholecystokinin-8 (10 micrograms/kg/hr intravenously for 6 hr) to alterations in circulating pancreatic enzymes and pancreatic morphology with special reference to trypsinogen activation. Cholecystokinin-8 infusion was associated with increases in plasma amylase, lipase, trypsin-like immunoreactivity, and plasma and urine trypsinogen activation peptide. Pancreatic parenchymal swelling and interlobular and subcapsular fluid accumulations were detected ultrasonographically within 2 hr of cholecystokinin-8. Circulating trypsin-like immunoreactivity and trypsinogen activation peptide in urine reached a peak at 2 and 4 hr, respectively, then declined despite progressive increases in circulating amylase and lipase and intrapancreatic fluid. No significant changes were observed in dogs receiving a saline infusion. This study illustrates that cholecystokinin-8 induces edematous pancreatitis in dogs that is associated with a short-lived burst of trypsinogen activation.

Protective effect of nitric oxide on development of acute pancreatitis in rats

Nitric oxide (NO) has been implicated to regulate pancreatic circulation, promote capillary integrity, and inhibit leukocyte adhesion. We investigated the role of NO in the development of pancreatitis. Nitro-L-arginine, an inhibitor of NO synthase, in total dose of 35 mg/kg body wt was infused in the rats with edematous pancreatitis induced by two intraperitoneal injections of cerulein (20 micrograms/kg). L-Arginine (125 or 250 mg/kg), a NO donor was intravenously administered twice in the rats with hemorrhagic pancreatitis induced by water-immersion stress plus two intraperitoneal injections of cerulein (40 micrograms/kg). The degree of pancreas edema, serum amylase levels, and histologic alterations were investigated. Nitro-L-arginine exacerbated cerulein-induced pancreatitis and caused a decrease in pancreatic blood flow. L-Arginine ameliorated the severity of hemorrhagic pancreatitis dose dependently and improved the pancreatic blood flow. These findings suggest that NO could confer protection against the development of hemorrhagic pancreatitis, probably through improvement of the pancreatic microcirculation.