Interstitial trypsinogen release and its relevance to the transformation of mild into necrotizing pancreatitis in rats

Bibliometric Analysis of Cathepsin B Research From 2011 to 2021

Cathepsin B (CTSB) is a lysosomal protease implicated in the progression of various diseases. A large number of CTSB-related studies have been conducted to date. However, there is no comprehensive bibliometric analysis on this subject. In our study, we performed quantitative analysis of CTSB-related publications retrieved from the Science Citation Index Expanded (SCIE) of the Web of Science Core Collection (reference period: 2011–2021). A total of 3,062 original articles and reviews were retrieved. The largest number of publications were from USA (n = 847, 27.66%). The research output of each country showed positive correlation with gross domestic product (GDP) (r = 0.9745, P < 0.0001). Active collaborations between countries/regions were also observed. Reinheckel T and Sloane BF were perhaps the most impactful researchers in the research landscape of CTSB. Plos ONE was the most prevalent (119/3,062, 3.89%) and cited journal (3,021 citations). Comprehensive analysis of the top citations, co-citations, and keywords was performed to acquire the theoretical basis and hotspots of CTSB-related research. The main topics included CTSB-related cancers and inflammatory diseases, CTSB-associated cell death pattern, and the applications of CTSB. These results provide comprehensive insights into the current status of global CTSB-related research especially in pancreas, which is worthy of continued follow-up by practitioners and clinicians in this field.

The Global Status and Trends of Enteropeptidase: A Bibliometric Study

Background

Enteropeptidase (EP) is a type II transmembrane serine protease and a physiological activator of trypsinogen. Extensive studies related to EP have been conducted to date. However, no bibliometric analysis has systematically investigated this theme. Our study aimed to visualize the current landscape and frontier trends of scientific achievements on EP, provide an overview of the past 120 years and insights for researchers and clinicians to facilitate future collaborative research and clinical intervention.

Methods

Quantitative analysis of publications relating to EP from 1900 to 2020 was interpreted and graphed through the Science Citation Index Expanded of Web of Science Core Collection (limited to SCIE). Microsoft office 2019, GraphPad Prism 8, VOSviewer, and R-bibliometrix were used to conduct the bibliometric analysis.

Results

From 1900 to 2020, a total of 1,034 publications were retrieved. The USA had the largest number of publications, making the greatest contribution to the topic (n = 260, 25.15%). Active collaborations between countries/regions were also enrolled. Grant and Hermontaylor were perhaps the most impactful researchers in the landscape of EP. Protein Expression and Purification and the Journal of Biological Chemistry were the most prevalent (79/1,034, 7.64%) and cited journals (n = 2,626), respectively. Using the top 15 citations and co-citations achievements clarified the theoretical basis of the EP research field. Important topics mainly include the structure of EP, the affective factors for activating substrates by EP, EP-related disorders, and inhibitors of EP.

Conclusion

Based on the bibliometric analysis, we have gained a comprehensive analysis of the global status and research frontiers of studies investigating EP, which provides some guidance and reference for researchers and clinicians engaged in EP research.

Pancreatitis-Induced Depletion of Syntaxin 2 Promotes Autophagy and Increases Basolateral Exocytosis

BACKGROUND & AIMS

Pancreatic acinar cells are polarized epithelial cells that store enzymes required for digestion as inactive zymogens, tightly packed at the cell apex. Stimulation of acinar cells causes the zymogen granules to fuse with the apical membrane, and the cells undergo exocytosis to release proteases into the intestinal lumen. Autophagy maintains homeostasis of pancreatic acini. Syntaxin 2 (STX2), an abundant soluble N-ethyl maleimide sensitive factor attachment protein receptor in pancreatic acini, has been reported to mediate apical exocytosis. Using human pancreatic tissues and STX2-knockout (KO) mice, we investigated the functions of STX2 in zymogen granule-mediated exocytosis and autophagy.

METHODS

We obtained pancreatic tissues from 5 patients undergoing surgery for pancreatic cancer and prepared 80-μm slices; tissues were exposed to supramaximal cholecystokinin octapeptide (CCK-8) or ethanol and a low concentration of CCK-8 and analyzed by immunoblot and immunofluorescence analyses. STX2-KO mice and syntaxin 2+/+ C57BL6 mice (controls) were given intraperitoneal injections of supramaximal caerulein (a CCK-8 analogue) or fed ethanol and then given a low dose of caerulein to induce acute pancreatitis, or saline (controls); pancreata were isolated and analyzed by histology and immunohistochemistry. Acini were isolated from mice, incubated with CCK-8, and analyzed by immunofluorescence microscopy or used in immunoprecipitation experiments. Exocytosis was quantified using live-cell exocytosis and Ca2+ imaging analyses and based on formation of exocytotic soluble N-ethyl maleimide sensitive factor attachment protein receptor complexes. Dysregulations in autophagy were identified using markers, electron and immunofluorescence microscopy, and protease activation assays.

RESULTS

Human pancreatic tissues and dispersed pancreatic acini from control mice exposed to CCK-8 or ethanol plus CCK-8 were depleted of STX2. STX2-KO developed more severe pancreatitis after administration of supramaximal caerulein or a 6-week ethanol diet compared with control. Acini from STX2-KO mice had increased apical exocytosis after exposure to CCK-8, as well as increased basolateral exocytosis, which led to ectopic release of proteases. These increases in apical and basolateral exocytosis required increased formation of fusogenic soluble N-ethyl maleimide sensitive factor attachment protein receptor complexes, mediated by STX3 and STX4. STX2 bound ATG16L1 and prevented it from binding clathrin. Deletion of STX2 from acini increased binding of AT16L1 to clathrin, increasing formation of pre-autophagosomes and inducing autophagy. Induction of autophagy promoted the CCK-8-induced increase in autolysosome formation and the activation of trypsinogen.

CONCLUSIONS

In studies of human pancreatic tissues and pancreata from STX2-KO and control mice, we found STX2 to block STX3- and STX4-mediated fusion of zymogen granules with the plasma membrane and exocytosis and prevent binding of ATG16L1 to clathrin, which contributes to induction of autophagy. Exposure of pancreatic tissues to CCK-8 or ethanol depletes acinar cells of STX2, increasing basolateral exocytosis and promoting autophagy induction, leading to activation of trypsinogen.

TRO40303 Ameliorates Alcohol-Induced Pancreatitis Through Reduction of Fatty Acid Ethyl Ester-Induced Mitochondrial Injury and Necrotic Cell Death

OBJECTIVES

Mitochondrial permeability transition pore inhibition is a promising approach to treat acute pancreatitis (AP). We sought to determine (i) the effects of the mitochondrial permeability transition pore inhibitor 3,5-seco-4-nor-cholestan-5-one oxime-3-ol (TRO40303) on murine and human pancreatic acinar cell (PAC) injury induced by fatty acid ethyl esters (FAEEs) or taurolithocholic acid-3-sulfate and (ii) TRO40303 pharmacokinetics and efficacy in experimental alcoholic AP (FAEE-AP).

METHODS

Changes in mitochondrial membrane potential (Δψm), cytosolic Ca ([Ca]c), and cell fate were examined in freshly isolated murine or human PACs by confocal microscopy. TRO40303 pharmacokinetics were assessed in cerulein-induced AP and therapeutic efficacy in FAEE-AP induced with palmitoleic acid and ethanol. Severity of AP was assessed by standard biomarkers and blinded histopathology.

RESULTS

TRO40303 prevented loss of Δψm and necrosis induced by 100 μM palmitoleic acid ethyl ester or 500 μM taurolithocholic acid-3-sulfate in murine and human PACs. Pharmacokinetic analysis found TRO40303 accumulated in the pancreas. A single dose of 3 mg/kg TRO40303 significantly reduced serum amylase (P = 0.043), pancreatic trypsin (P = 0.018), and histopathology scores (P = 0.0058) in FAEE-AP.

CONCLUSIONS

TRO40303 protects mitochondria and prevents necrotic cell death pathway activation in murine and human PACs, ameliorates the severity of FAEE-AP, and is a candidate drug for human AP.

Depletion of the membrane-fusion regulator Munc18c attenuates caerulein hyperstimulation-induced pancreatitis

Epithelial pancreatic acinar cells perform crucial functions in food digestion, and acinar cell homeostasis required for secretion of digestive enzymes relies on SNARE-mediated exocytosis. The ubiquitously expressed Sec1/Munc18 protein mammalian uncoordinated-18c (Munc18c) regulates membrane fusion by activating syntaxin-4 (STX-4) to bind cognate SNARE proteins to form a SNARE complex that mediates exocytosis in many cell types. However, in the acinar cell, Munc18c's functions in exocytosis and homeostasis remain inconclusive. Here, we found that pancreatic acini from Munc18c-depleted mice (Munc18c^+/-) and human pancreas (lenti-Munc18c-shRNA-treated) exhibit normal apical exocytosis of zymogen granules (ZGs) in response to physiologic stimulation with the intestinal hormone cholecystokinin (CCK-8). However, when stimulated with supraphysiologic CCK-8 levels to mimic pancreatitis, Munc18c-depleted (Munc18c^+/-) mouse acini exhibited a reduction in pathological basolateral exocytosis of ZGs resulting from a decrease in fusogenic STX-4 SNARE complexes. This reduced basolateral exocytosis in part explained the less severe pancreatitis observed in Munc18c^+/- mice after hyperstimulation with the CCK-8 analog caerulein. Likely as a result of this secretory blockade, Munc18c-depleted acini unexpectedly activated a component of the endoplasmic reticulum (ER) stress response that contributed to autophagy induction, resulting in downstream accumulation of autophagic vacuoles and autolysosomes. We conclude that Munc18c's role in mediating ectopic basolateral membrane fusion of ZGs contributes to the initiation of CCK-induced pancreatic injury, and that blockade of this secretory process could increase autophagy induction.

Ex vivo human pancreatic slice preparations offer a valuable model for studying pancreatic exocrine biology

A genuine understanding of human exocrine pancreas biology and pathobiology has been hampered by a lack of suitable preparations and reliance on rodent models employing dispersed acini preparations. We have developed an organotypic slice preparation of the normal portions of human pancreas obtained from cancer resections. The preparation was assessed for physiologic and pathologic responses to the cholinergic agonist carbachol (Cch) and cholecystokinin (CCK-8), including 1) amylase secretion, 2) exocytosis, 3) intracellular Ca²⁺ responses, 4) cytoplasmic autophagic vacuole formation, and 5) protease activation. Cch and CCK-8 both dose-dependently stimulated secretory responses from human pancreas slices similar to those previously observed in dispersed rodent acini. Confocal microscopy imaging showed that these responses were accounted for by efficient apical exocytosis at physiologic doses of both agonists and by apical blockade and redirection of exocytosis to the basolateral plasma membrane at supramaximal doses. The secretory responses and exocytotic events evoked by CCK-8 were mediated by CCK-A and not CCK-B receptors. Physiologic agonist doses evoked oscillatory Ca²⁺ increases across the acini. Supraphysiologic doses induced formation of cytoplasmic autophagic vacuoles and activation of proteases (trypsin, chymotrypsin). Maximal atropine pretreatment that completely blocked all the Cch-evoked responses did not affect any of the CCK-8-evoked responses, indicating that rather than acting on the nerves within the pancreas slice, CCK cellular actions directly affected human acinar cells. Human pancreas slices represent excellent preparations to examine pancreatic cell biology and pathobiology and could help screen for potential treatments for human pancreatitis.

Central role of neutrophil in the pathogenesis of severe acute pancreatitis

Severe acute pancreatitis (SAP) is an acute abdominal disease with the strong systemic inflammatory response, and rapidly progresses from a local pancreatic damage into multiple organ dysfunction. For many decades, the contributions of neutrophils to the pathology of SAP were traditionally thought to be the chemokine and cytokine cascades that accompany inflammation. In this review, we focus mainly on those recently recognized aspects of neutrophils in SAP processes. First, emerging evidence suggests that therapeutic interventions targeting neutrophils significantly lower tissue damage and protect against the occurrence of pancreatitis. Second, trypsin activation promotes the initial neutrophils recruitment into local pancreas, and subsequently neutrophils infiltration in turn triggers trypsin production. Finally, neutrophils have the unique ability to release neutrophil extracellular traps even in the absence of pathogens.

Effects of ethanol metabolites on exocytosis of pancreatic acinar cells in rats

BACKGROUND & AIMS

During development of alcoholic pancreatitis, oxidative (acetaldehyde) and nonoxidative metabolites (ethyl palmitate, ethyl oleate), rather than ethanol itself, mediate toxic injury. Exposure of pancreatic acini to ethanol blocks cholecystokinin (CCK)-8-stimulated apical exocytosis and redirects exocytosis to the basolateral plasma membrane, causing interstitial pancreatitis. We examined how each ethanol metabolite contributes to these changes in exocytosis.

METHODS

Rat pancreatic acini were incubated with concentrations of ethanol associated with alcoholic pancreatitis (20-50 mmol/L) or ethanol metabolites (1-3 mmol/L) and then stimulated with CCK-8. We performed single zymogen granule (ZG) exocytosis assays, Ca(2+) imaging studies, ultrastructural analyses (with electron microscopy), and confocal microscopy to assess the actin cytoskeleton and track the movement of vesicle-associated membrane protein (VAMP)-8-containing ZGs. Coimmunoprecipitation assays were used to identify complexes that contain the distinct combinations of Munc18 and the soluble N-ethylmaleimide sensitive factor attachment protein receptor proteins, which mediate apical (ZG-apical plasma membrane) and basolateral exocytosis and fusion between ZGs (ZG-ZG).

RESULTS

The ethanol metabolites acetaldehyde, ethyl palmitate, and ethyl oleate reduced CCK-8-stimulated apical exocytosis and formation of apical exocytotic complexes (between Munc18b and Syntaxin-2, synaptosomal-associated protein of 23 kilodaltons [SNAP23], and VAMP2) in rat pancreatic acini. Acetaldehyde and ethyl oleate redirected CCK-8-stimulated exocytosis to the basal and lateral plasma membranes and translocation of VAMP8-containing ZGs toward the basolateral plasma membrane. This process was mediated primarily via formation of basolateral exocytotic complexes (between Munc18c and Syntaxin-4, SNAP23, and VAMP8). Exposure of the acini to acetaldehyde and ethyl oleate followed by CCK-8 stimulation mildly perturbed the actin cytoskeleton and Ca(2+) signaling; exposure to ethyl palmitate severely affected Ca(2+) signaling. Acetaldehyde, like ethanol, promoted fusion between ZGs by the formation of ZG-ZG exocytotic complexes (between Munc18b and Syntaxin-3, SNAP23, and VAMP8), whereas ethyl palmitate and ethyl oleate reduced ZG-ZG fusion and formation of these complexes.

CONCLUSIONS

The ethanol metabolites acetaldehyde, ethyl palmitate, and ethyl oleate perturb exocytosis processes in cultured rat pancreatic acini (apical blockade, basolateral exocytosis, and fusion between ZGs). Acetaldehyde and, to a lesser degree, ethyl oleate produce many of the same pathologic effects of ethanol on CCK-8-stimulated exocytosis in pancreatic acini.

Multidrug strategies are effective in the treatment of severe experimental pancreatitis

BACKGROUND

Trypsinogen activation, oxygen radicals, cytokines, leukocyte infiltration, and pancreatic ischemia are important steps in the pathogenesis of necrotizing pancreatitis and associated systemic complications. Several drugs that inhibit those pathogenetic steps attenuated biochemical and histologic changes, while survival remained low. The aim of the present study was to evaluate the benefit of multidrug approaches compared to monotherapies on organ injury and survival in acute experimental pancreatitis in the rat model of retrograde bile injection combined with intravenous cerulein.

METHODS

Necrotizing pancreatitis was induced in rats. After a therapy-free interval of 6 hours, 10 treatment regimens were evaluated: multidrug regimen 1, which contained the protease inhibitor gabexate mesilate, oxygen-free radical scavengers, nitric oxide donor L-arginine, a platelet-activating factor antagonist, and antibodies against intracellular adhesion molecule-1 (ICAM-1) dissolved in dextran, was compared to multidrug regimen 2 (dextran, acetylcysteine, L-arginine, and anti-ICAM-1), monotherapies of each of the drugs, and standard intravascular volume replacement.

RESULTS

Both multidrug regimens significantly reduced pancreatic and systemic injury and microcirculatory disturbances compared to any of the monotherapies. Treatment with regimen 1 decreased 24-hour mortality to 0% and increased long-term survival to 85% (standard therapy, 70% and 15%, respectively). Multidrug regimen 2 was as effective as regimen 1.

CONCLUSION

Treatment of acute necrotizing pancreatitis with multidrug regimens significantly decreases short-term mortality compared to monotherapies. Moreover, multidrug strategies are still effective after a wide therapeutic window. Key to this effective therapy is the inhibition of microcirculatory disturbances and of the systemic inflammatory response. The experimental superiority of the multidrug approach should be confirmed in a clinical trial.

Pharmacotherapy for acute pancreatitis

Our knowledge of acute pancreatitis is still far from complete and there is no unanimous agreement concerning the pathophysiological processes leading to typical alterations during the course of acute pancreatitis. We reviewed the paper published in the last decade on the pathophysiology and treatment of acute pancreatitis. It is difficult to translate the experimental therapeutic results into clinical practice. For example, lexipafant was efficacious in decreasing the severity and mortality of lethal pancreatitis in rats, but seems to have no effect on severe acute pancreatitis in humans. Thus, the main problem in acute pancreatitis, especially in the severe form of the disease, is the difficulty of designing clinical studies capable of giving reliable statistically significant answers regarding the benefits of the various proposed therapeutic agents previously tested in experimental settings. Thus, analgesia, supportive care, and treatment of the pulmonary and renal complications remain the cornerstones of the treatment of acute pancreatitis, especially in the severe form of the disease.

Nafamostat for Prophylaxis against Post-Endoscopic Retrograde Cholangiopancreatography Pancreatitis Compared with Gabexate

BACKGROUND/AIMS

The protease inhibitors, nafamostat and gabexate, have been used to prevent pancreatitis related to endoscopic retrograde cholangiopancreatography (ERCP). In vitro, nafamostat inhibits the pancreatic protease activities 10-100 times more potently than gabexate. We evaluated the efficacy of nafamostat for prophylaxis against post-ERCP pancreatitis in comparison with gabexate.

METHODS

Five hundred patients (208 patients in the nafamostat-treated group and 292 in the gabexate-treated group) were analyzed retrospectively after selective exclusion. The incidences of pancreatitis and hyperamylasemia after the ERCP were compared between the nafamostat and gabexate groups.

RESULTS

The incidences of acute pancreatitis and hyperamylasemia were 9.1% and 40.9%, respectively, in the nafamostat-treated group, and 8.6% and 39.4% in the gabexate-treated group. The frequencies of post-ERCP pancreatitis and hyperamylasemia did not differ significantly between the two groups, Post-ERCP pancreatitis in two group did not vary according to the different ERCP procedures. The mean serum amylase level at 6 h after ERCP was significantly lower in the nafamostat-treated group than in the gabexate-treated group (p=0.020). However, the difference in serum amylase level did not persist at 18 h and 36 h post-ERCP.

CONCLUSIONS

Administration of nafamostat before ERCP was not inferior to gabexate in protecting against the development of pancreatitis.

Probiotic agent Saccharomyces boulardii reduces the incidence of lung injury in acute necrotizing pancreatitis induced rats

BACKGROUND

Acute necrotizing pancreatitis is a severe acute inflammatory disease of the pancreas that can lead to extrapancreatic organ involvement. Supervening lung injury is an important clinical entity determining the prognosis of the patient. Probiotics are dietary supplements known to reduce or alter inflammation and inflammatory cytokines. In the present study, we hypothesize that probiotics may reduce lung injury by reducing bacterial translocation, which results in reduced infection, inflammation, and generation of proinflammatory cytokines in an experimental model of acute necrotizing pancreatitis.

METHODS

Pancreatitis was induced by concomitant intravenous infusion of cerulein and glycodeoxycholic acid infusion into the biliopancreatic duct. Saccharomyces boulardii was used as the probiotic agent. Rats were divided into three groups: sham, pancreatitis-saline, which received saline via gavage at 6 and 24 h following the pancreatitis, pancreatitis-probiotics, which received probiotics via gavage method at 6 and 24 h following the pancreatitis. The rats were sacrificed at 48 h, venous blood, mesenteric lymph node, pancreatic and lung tissue samples were obtained for analysis.

RESULTS

Serum pancreatic amylase, lactate dehydrogenase, secretory phospholipase A(2), and IL-6 were found to be increased in pancreatitis-saline group compared with the other groups (P < 0.05). Histological analyses revealed that edema, inflammation, and vacuolization as well as polymorphonuclear leukocyte infiltration in the lung tissue was significantly reduced in the probiotic treated group. Bacterial translocation was significantly reduced in the probiotic treated group compared with the other groups (P < 0.05).

CONCLUSION

These results suggest that Saccharomyces boulardii reduce the bacterial translocation. As a result of this, reduced proinflammatory cytokines and systemic inflammatory response was observed, which may be the reason underlying reduced lung injury in acute necrotizing pancreatitis.

Protease activation, pancreatic leakage, and inflammation in acute pancreatitis: differences between mild and severe cases and changes over the first three days

BACKGROUND/AIMS

The pathophysiology of acute pancreatitis (AP) may be studied using markers of protease activation (active carboxypeptidase B (aCAP), the activation peptide of carboxypeptidase B (CAPAP)), leakage of pancreatic enzymes (trypsinogen-2, procarboxypeptidase B (proCAP), amylase), and inflammation (monocyte chemoattractant protein-1 (MCP-1), CRP).

METHODS

This prospective study included 140 cases of AP. Mild (n = 124) and severe (n = 16) cases were compared with respect to serum levels of trypsinogen-2, proCAP, amylase, aCAP, CAPAP (serum/urine), MCP-1 (serum/urine) and CRP on days 1, 2 and 3 from onset of symptoms. All patients with information on all 3 days were included in a time-course analysis (n = 44-55, except amylase: n = 27).

RESULTS

High levels in severe versus mild cases were seen for trypsinogen-2, CAPAP in serum and urine, and MCP-1 in serum on days 1-3. No differences were seen for proCAP, amylase and aCAP. MCP-1 in urine was significantly elevated on day 1-2, and CRP on day 2-3. CAPAP and MCP-1 levels peaked early and stayed elevated for 48 h in serum.

CONCLUSION

Protease activation and inflammation are early events in AP, with high levels of these markers within 24 h. Protease activation declines after 48 h, whereas inflammation is present for a longer time.

A novel animal model of severe pancreatitis in mice and its differences to the rat

BACKGROUND

A noninvasive model of necrohemorrhagic pancreatitis induced by simultaneous intravenous cerulein/enterokinase (EK) infusion has recently been established in rats. The aim of the present study was to establish this new model in mice and to compare it with the rat model.

METHODS

Male Balb/C mice (20 to 25 g) were used for the experiments. Pancreatitis was induced by simultaneous intravenous infusion of cerulein and EK. Controls were infused with either 0.9% NaCl, cerulein, or EK. Animals were humanely killed 6 hours after start of infusions. Pancreatic and pulmonary injury was assessed by histology, wet-to-dry weight ratio, and myeloperoxidase activity. Systemic cytokine, amylase, and lactate dehydrogenase (LDH) levels in blood were measured to assess pancreatic and systemic inflammatory response. To evaluate the role of protease activity in this model, trypsin, cathepsin B, and elastase activity were measured in pancreatic tissue. Survival experiments were performed to determine survival time and tissue injury in the later course of the disease.

RESULTS

Mice with simultaneous cerulein/EK infusion developed marked local and systemic organ injury compared with those animals who received cerulein or EK alone. Pancreatic and pulmonary injury increased with high concentrations of cerulein/EK infusions. Survival decreased in these animals. Whereas acinar cell apoptosis was an early finding, pancreatic necrosis was observed later in the course of the disease. Serum levels of LDH, interleukin (IL)-1 alpha, and IL-1 beta reflected cell damage and the systemic inflammatory response. Protease activity in pancreatic tissue was greatest in animals with simultaneous cerulein/EK infusion.

CONCLUSIONS

Using intravenous cerulein/EK infusions, a model of lethal acute pancreatitis has been established in mice. Major pancreatic edema, acinar cell apoptosis and necrosis, and pulmonary leukocyte sequestration are characteristic findings in this model. Although pancreatic injury was not as strong as in the rat model, this model may prove useful for future studies in transgenic mice.

Inhibition of Rac1 decreases the severity of pancreatitis and pancreatitis-associated lung injury in mice

Pancreatitis is a disease with high morbidity and mortality. In vitro experiments on pancreatic acini showed that supramaximal but not submaximal cholecystokinin (CCK) stimulation induces effects in the acinar cell that can be correlated with acinar morphological changes observed in the in vivo experimental model of cerulein-induced pancreatitis. The GTPase Rac1 was previously reported to be involved in CCK-evoked amylase release from pancreatic acinar cells. Here, we demonstrate that pretreatment with the Rac1 inhibitor NSC23766 (100 microM, 2 h) effectively blocked Rac1 translocation and activation in CCK-stimulated pancreatic acini, without affecting activation of its closely related GTPase, RhoA. This specific Rac1 inhibition decreased supramaximal (10 nM) CCK-stimulated acinar amylase release (27.% reduction), which seems to be connected to the reduction observed in serum amylase (46.6% reduction) and lipase levels (46.1% reduction) from cerulein-treated mice receiving NSC23766 (100 nmol h(-1)). The lack of Rac1 activation also reduced formation of reactive oxygen species (ROS; 20.8% reduction) and lactate dehydrogenase release (LDH; 24.3% reduction), but did not alter calcium signaling or trypsinogen activation in 10 nM CCK-stimulated acini. In the in vivo model, the cerulein-treated mice receiving NSC23766 also presented a decrease in both pancreatic and lung histopathological scores (reduction in oedema, 32.4 and 66.4%; haemorrhage, 48.3 and 60.2%; and leukocyte infiltrate, 53.5 and 43.6%, respectively; reduction in pancreatic necrosis, 65.6%) and inflammatory parameters [reduction in myeloperoxidase, 52.2 and 38.9%; nuclear factor kappaB (p65), 61.3 and 48.6%; and nuclear factor kappaB (p50), 46.9 and 44.9%, respectively], together with lower serum levels for inflammatory (TNF-alpha, 40.4% reduction) and cellular damage metabolites (LDH, 52.7% reduction). Collectively, these results suggest that pharmacological Rac1 inhibition ameliorates the severity of pancreatitis and pancreatitis-associated lung injury through the reduction of pancreatic acinar damage induced by pathological digestive enzyme secretion and overproduction of ROS.

Effects of nafamostat mesilate on the prevention of cerulein-induced acute pancreatitis

OBJECTIVES

Protease inhibitors showed protective effects on animal models of acute pancreatitis when administered before induction of pancreatitis, and results when administered after induction are uncertain. We assessed the effects of nafamostat mesilate in a mouse model of cerulein-induced pancreatitis comparing results of before and after induction.

METHODS

Cerulein was injected to mice intraperitoneally to induce pancreatitis, and they received intravenous nafamostat mesilate before and after induction. Serum concentrations of amylase and lipase, histological changes, and tissue expression of myeloperoxidase were measured. In addition, tissue activation of p38 mitogen-activated protein kinase (MAPK) and interleukin-6 was evaluated.

RESULTS

Development of pancreatitis was prevented by pretreatment with nafamostat mesilate. However, such effect was not shown when given after induction, although it partially suppressed myeloperoxidase expression and infiltration of inflammatory cells. Tissue expression of phospho-p38 MAPK was prominent in mice with pancreatitis and suppressed by pretreatment with nafamostat mesilate. Interleukin-6 expression was not influenced by either cerulein or nafamostat mesilate.

CONCLUSIONS

The development of pancreatitis was prevented by treating mice with nafamostat mesilate before induction, however, this finding was not observed if administered after injection of cerulein. Pretreatment with nafamostat mesilate suppressed activation of p38 MAPK.

Mitochondrial injury in pancreatitis

Pancreatitis is an increasingly common disease that carries a significant mortality and which lacks specific therapy. Pathological calcium signalling is an important contributor to the initiating cell injury, caused by or acting through mitochondrial inhibition. A principal effect of disordered cell signalling and impaired mitochondrial function is cell death, either by apoptosis that is primarily protective, or by necrosis that is deleterious, both locally and systemically. Mitochondrial calcium overload is particularly important in necrotic injury, which may include damage mediated by the mitochondrial permeability transition pore. The role of reactive oxygen species remains controversial. Present understanding of the part played by disordered pancreatic acinar calcium signalling and mitochondrial inhibition offers several new potential therapeutic targets.

Enterokinase induces severe necrosis and rapid mortality in cerulein pancreatitis: Characterization of a novel noninvasive rat model of necro-hemorrhagic pancreatitis

BACKGROUND

Unlike edematous pancreatitis, induction of severe necrotizing pancreatitis in rats generally requires an invasive laparotomy with infusion and/or ligation of the pancreatic duct or duodenal or arterial occlusion. The aim of this study was to establish and characterize a noninvasive model of severe acute pancreatitis in rats.

METHODS

Wistar rats were infused intravenously with cerulein or a combination of cerulein and enterokinase. Saline (154-mmol/L NaCl) or enterokinase only was infused in controls. In a first set of experiments, intrapancreatic protease activation and the release of cytokines were correlated with the severity of organ injury. Pancreatic and pulmonary injuries were determined at 6 h. In a second set of experiments, we assessed 24-h survival, serum parameters possibly reflecting the course of the disease, and morphologic changes later in the course of the disease.

RESULTS

The severity of pancreatic injury and survival were correlated strongly with the amount of enterokinase infused simultaneously with cerulein. Trypsin as well as elastase and cathepsin B activity in pancreatic tissue samples were increased markedly in these animals. Marked pancreatic hemorrhage, necrosis, and leukocyte infiltration were present in animals with the greatest amounts of enterokinase infused. IL-6 and LDH, but not IL-1beta, CRP, and amylase, in serum correlated with the severity of pancreatitis.

CONCLUSIONS

This noninvasive rat model of acute pancreatitis is characterized by major pancreatic necrosis, hemorrhage, and fatality. The simple and noninvasive induction technique may have advantages for future studies on inflammatory changes and sepsis in necrotizing pancreatitis compared with other currently available invasive models.

Recent insights into the cellular mechanisms of acute pancreatitis

In acute pancreatitis, initiating cellular events causing acinar cell injury includes co-localization of zymogens with lysosomal hydrolases, leading to premature enzyme activation and pathological exocytosis of zymogens into the interstitial space. This is followed by processes that accentuate cell injury; triggering acute inflammatory mediators, intensifying oxidative stress, compromising the microcirculation and activating a neurogenic feedback. Such localized events then progress to a systemic inflammatory response leading to multiorgan dysfunction syndrome with resulting high morbidity and mortality. The present review discusses some of the most recent insights into each of these cellular processes postulated to cause or propagate the process of acute pancreatitis, and also the role of alcohol and genetics.

Chronic alcohol consumption is a major risk factor for pancreatic necrosis in acute pancreatitis

BACKGROUND

Much of the late morbidity and mortality of acute pancreatitis (AP) is attributed to complications of pancreatic necrosis (PNEC). Early diagnosis of PNEC in high-risk patients is critical to management. Hemoconcentration is one risk factor for PNEC, but additional risk factors are likely implicated.

AIMS

(1) To evaluate a series of preselected clinical factors in a prospectively collected cohort with AP to identify risk factors for PNEC and (2) to verify the relative risk of any newly identified factor(s) by retrospective analysis of a large patient cohort.

METHODS

Phase I: 102 AP patients were prospectively ascertained, of which 77 (mean age 49 yr; 35 women, 42 men) underwent contrast-enhanced computerized tomography (CECT) and were studied. Eleven subjects developed PNEC (14%). Binary logistic regression was performed to identify any clinical factors associated with PNEC. Phase II: 1,474 anonymized patients admitted to the hospital with a diagnosis of AP were electronically reviewed to identify 359 subjects (mean age 54 yr; 157 women, 202 men) with AP and CECT. Seventy-six of these patients (21%) exhibited CECT evidence of PNEC. The associations found in the Phase I group were compared with Phase II by logistic regression analysis.

RESULTS

In Phase I, only chronic alcohol consumption was identified as a significant new risk factor for the development of PNEC (6/19 vs 5/58, p= 0.02, OR 4.8, CI 1.27-18.2). In Phase II, it was verified that excessive alcohol consumption was a significant risk factor for PNEC (18/52 vs 58/307, p= 0.012, OR 2.27, CI 1.19-4.30).

CONCLUSION

Chronic alcohol consumption seems to constitute a strong risk factor for PNEC.

Cathepsin B activates human trypsinogen 1 but not proelastase 2 or procarboxypeptidase B

BACKGROUND/AIMS

Activation of trypsinogen to trypsin is a crucial step in the development of acute pancreatitis. The cause of this activation is not known although suggested explanations include autoactivation, cathepsin B-mediated activation and activation by mast cell tryptase. The aim of this study was to investigate cathepsin B and tryptase activation of pancreatic zymogens.

METHODS

Trypsinogen-1, proelastase, and procarboxypeptidase B were purified from human pancreatic juice. Human cathepsin B and betaI-tryptase are commercial products. Activation and degradation of zymogens were measured by activity towards specific substrates for trypsin and pancreatic elastase, ELISAs for procarboxypeptidase B and its activation peptide, and a radioimmunoassay for the trypsinogen activation peptide.

RESULTS

Cathepsin B caused activation of trypsinogen-1 with a trypsin yield of about 30% of that produced by enterokinase. Proelastase and procarboxypeptidase B was not activated by cathepsin B. None of the zymogens were inactivated by cathepsin B. Neither monomeric nor tetrameric tryptase could activate any of the examined zymogens.

CONCLUSION

Cathepsin B is a competent activator of trypsinogen-1, although not as efficient as enterokinase. If cathepsin B is to play a role in protease activation in acute pancreatitis, this most probably occurs by activation of trypsinogen.

Pancreatic proteases in serum induce leukocyte-endothelial adhesion and pancreatic microcirculatory failure

BACKGROUND

Neutrophil-mediated tissue injury in acute pancreatitis includes a severe reduction of the functional microcirculation via interaction of adhesion molecules on leukocytes (MAC-1) and endothelium (ICAM-1). The hypothesis of the study was that trypsin and elastase in serum alone lead to the expression of these complementary adhesion molecules and result in increased leukocyte-endothelial interaction (LEI). In addition we evaluated the preventative benefit of protease inhibition on these mechanisms.

MATERIALS AND METHODS

In vitro: Cultured endothelial cells (HUVEC) and human leukocytes (PMN) were stimulated with increasing doses of trypsin and elastase. In addition, pre-treatment of PMN or HUVEC was performed with protease inhibitors (Nafamostat mesilate, FUT and gabexate mesilate, FOY). The expression of ICAM-1 or MAC-1 was evaluated by flow cytometry. In vivo: Severe pancreatitis was induced in rats. Microcirculatory disturbances were evaluated by real-time confocal microscopy at 9 h in controls and acute pancreatitis with or without anti-protease treatment. Additionally, the effect of continuous trypsin and elastase infusion on pancreatic microcirculation and LEI were evaluated by intravital fluorescence videomicroscopy.

RESULTS

Up-regulation of MAC-1 and ICAM-1 expression requires the presence of serum. The maximal increase of MAC-1 and ICAM-1 expression was found at concentrations of trypsin or elastase characteristic for acute pancreatitis. FUT or FOY significantly reduced protease-induced expression of MAC-1 and ICAM-1. Real-time in-vivo microscopy revealed that functional capillary density in acute pancreatitis was significantly reduced (267.1 +/- 2.95/mm2 vs. 91.29 +/- 12.81/mm2) and treatment with FUT significantly reduced this effect (134.6 +/- 4.6/mm2; p < 0.05 vs. untreated pancreatitis). Infusion of trypsin or elastase alone increased LEI in vivo and reduced pancreatic perfusion.

CONCLUSION

Both trypsin and elastase up-regulate the expression of adhesion molecules on leukocytes and endothelial cells in the presence of serum. Increased LEI and reduced perfusion of the pancreas, characteristic of acute pancreatitis, is induced in vivo by infusion of pancreatic proteases and this effect is partially abrogated by their inhibitors. These results support the role of circulating trypsin and elastase in promoting pancreatic microcirculatory failure in experimental acute pancreatitis.

Degradation and inactivation of plasma tumor necrosis factor-alpha by pancreatic proteases in experimental acute pancreatitis

BACKGROUND

Release of TNFalpha is thought to play an important role in mediating systemic effects in acute pancreatitis (AP). We have been unable to find an elevation of plasma TNFalpha in AP and hypothesize that it is susceptible to catabolism by circulating pancreatic proteases.

METHODS

(1) AP was induced in Sprague-Dawley rats by cerulein hyperstimulation preceded by intraductal infusion of saline (mild) or glycodeoxycholic acid (severe). Healthy and sham-operated animals served as controls. Severity of pancreatitis was confirmed by histology. Plasma TNFalpha levels were measured at various time points after induction of AP with competitive ELISA. (2) Recombinant rat TNFalpha (rrTNFalpha) was incubated with trypsin, elastase, chymotrypsin and pepsin. Western Blot was performed to visualize TNF degradation. (3) RrTNFalpha was incubated in a concentration and time-dependant manner with proteases and TNF bioactivity was evaluated with a cytotoxicity assay.

RESULTS

(1) Plasma TNFalpha levels in severe pancreatitis were significantly lower than in sham-operated controls after 0.5 and 6 h. (2) Incubation with proteases showed degradation in the presence of trypsin, elastase and chymotrypsin and no effect of pepsin. (3) There was a concentration dependent inactivation of rrTNFalpha in the presence of pancreatic proteases and a complete time-dependent inactivation in the presence of trypsin.

CONCLUSION

Plasma TNFalpha does not rise in experimental AP, and levels are significantly lower in severe pancreatitis compared to sham-operated controls. Our study demonstrates degradation and inactivation of TNFalpha by pancreatic proteases, suggesting that it is unlikely it plays an important role in the development of distant organ failure.

Membrane-bound ICAM-1 is upregulated by trypsin and contributes to leukocyte migration in acute pancreatitis

In acute pancreatitis, ICAM-1 is upregulated in various organs and contributes to the development of organ injury. To investigate the effects of pancreatic proteases on ICAM-1 expression and their role in the early process of leukocyte migration, human umbilical vein endothelial cells (HUVECs) were incubated with serum subjected to limited trypsin digestion and Wistar rats were injected with trypsin. Significant upregulation of membrane-bound ICAM-1 was seen on HUVECs incubated with trypsinated serum. Likewise, soluble ICAM-1 increased in the supernatant of HUVECs. Changes of membrane-bound ICAM-1 and soluble ICAM-1 were maximal with high concentrations of trypsin. HUVECs incubated with TNF-alpha (positive control) showed similar changes. In the pancreas and lungs of animals infused with trypsin, ICAM-1 and leukocyte sequestration were increased compared with controls. Reflecting the relevance of protease-induced ICAM-1 expression in leukocyte migration, leukocyte-endothelium interaction, as assessed by intravital microscopy, was markedly increased by trypsin. Inhibition of ICAM-1 ameliorated these changes significantly. In conclusion, trypsinated serum induces the upregulation of both membrane-bound ICAM-1 on endothelial cells and soluble ICAM-1. These changes contribute to the early steps of leukocyte migration in acute pancreatitis. The role of soluble ICAM-1 remains to be investigated.

Continuous regional application of protease inhibitor in the treatment of acute pancreatitis. An experimental study using closed duodenal obstruction model in dogs

In clinical settings, the effectiveness of protease inhibitors in the treatment of acute pancreatitis has been still controversial. With the concept that sufficient tissue concentration of protease inhibitor in the pancreas has to be included to achieve its potent inhibitory effect, we applied a continuous regional intra-arterial (CRI) application of low-molecular-weight protease inhibitor, nafamostat mesilate (FUT-175), for closed duodenal loop obstruction model in mongrel dogs. The use of CRI application led to a higher concentration of FUT-175 in the pancreatic tissue (4,453 +/- 758 ng/g) when compared with that applied intravenously (905 +/- 48 ng/g). Consequently, pancreatic parenchyma in CRI application animals was remarkably preserved, as assessed by the lower extent of pancreatic necrosis (12.4 +/- 2.6% in CRI vs. 25.6 +/- 1.9% in intravenous). Additionally, the elevation of trypsin-like activity in the pancreas was significantly inhibited in CRI animals. Based on these findings, the dose as well as the route of protease inhibitors should be carefully considered to achieve its beneficial effect.

Site-specific therapeutic effects of protease inhibitors: effect of route of administration in experimental pancreatitis

Inappropriate local and systemic activation of trypsin arising from trypsinogen mediates key steps in the pathogenesis of acute pancreatitis. Trypsin presumably causes direct injury to cells, but also activates other proteases and causes secondary effects such as inducing the expression of adhesion molecules on endothelium and leukocytes, and stimulating leukocytes to secrete cytokines, tissue-damaging enzymes, oxygen radicals and matrix metalloproteinases. Protease inhibition interferes with this cascade of events. Here we review experimental studies on protease inhibition and their potential application and report our findings of site-specific therapeutic effects of the novel protease inhibitor nafamostat (FUT-175) in experimental acute pancreatitis.

Acute pancreatitis in Soweto, South Africa: relationship between trypsinogen load, trypsinogen activation, and fibrinolysis

OBJECTIVE

It is not known why acute pancreatitis in Soweto, South Africa, pursues an aggressive course. We sought clues from circulating trypsinogen load at admission as marker of initial acinar injury, trypsinogen activation using the carboxypeptidase B activation peptide as surrogate, proteinase inhibitors, the coagulation-fibrinolysis axis, indicators of inflammation, oxidative stress markers, and antioxidant status. This article reports on the first four aspects.

METHODS

The study involved 24 consecutive patients with a first attack. All of them were admitted within 24 h, and 22 were alcoholic. Urine was analyzed for anionic trypsinogen and the carboxypeptidase B activation peptide. Serum was tested for anionic and cationic trypsinogen, alpha1 proteinase inhibitor and alpha2 macroglobulin. Plasma from a subset was assayed for soluble fibrin, cross-linked fibrin degradation products (surrogates for thrombin and plasmin activity, respectively), and tissue-type plasminogen activator and inhibitor.

RESULTS

Soweto controls had higher serum anionic trypsinogen (p = 0.004) and plasminogen activator:inhibitor ratio (p = 0.047) than U.K. controls. The outcome of acute pancreatitis was mild in 17 but severe in seven with three deaths, two on day 2. In mild pancreatitis, intense plasmin activity (p < 0.001) accompanied the surge in trypsinogen, especially anionic (p < 0.001), but without increased thrombin activity and in five patients without trypsinogen activation. In severe pancreatitis, further significant increments in plasmin activity and trypsinogens were accompanied by increased thrombin activity (p = 0.013) and trypsinogen activation (p = 0.046). There was no correlation between surrogates of plasmin and thrombin activity, or between either and the carboxypeptidase B activation peptide, which showed a curvilinear relationship to total serum trypsinogen.

CONCLUSIONS

The aggressive nature of alcoholic acute pancreatitis in Soweto seems to reflect early profound fibrinolysis, which precedes coagulation and is initially independent of trypsin. Subclinical acinar-cell injury and a profibrinolytic diathesis in outwardly healthy Sowetans may predispose to this problem.

Matrix metalloproteinase-9 promotes neutrophil migration and alveolar capillary leakage in pancreatitis-associated lung injury in the rat

BACKGROUND & AIMS

In pancreatitis-associated lung injury, neutrophils (PMN) access the lung by migration through endothelial basement membranes. We hypothesize that degeneration of the basement membrane by specific PMN-produced matrix metalloproteinases (MMPs) may facilitate this process.

METHODS

Mild or severe pancreatitis was induced in rats and the consequent pulmonary injury characterized. MMP-2 and MMP-9 activity in supernatant of PMN cultures and homogenates of lungs were assessed by zymography and Western blot. Congruence of PMN and MMP expression in lung tissue was evaluated by neutrophil depletion and fluorescent immunohistochemistry (IHC). The contribution of MMPs to PMN transmigration and lung injury was tested with the MMP inhibitor batimastat (BB-94) in vitro (PMN transmigration across matrigel chambers) and in vivo (myeloperoxidase activity and Evans blue in broncho-alveolar lavage fluid).

RESULTS

MMP-9 was highly expressed in lungs and supernatant of neutrophil cultures in severe pancreatitis, and, to a lesser degree, in mild pancreatitis. Lung IHC showed colocalization of MMP-9 and PMN. PMN depletion simultaneously reduced neutrophil infiltration and MMP-9 levels in lung tissue. Trypsin, interleukin 1 beta, and tumor necrosis factor (TNF)-alpha all potently stimulated MMP-9 release from PMN. BB-94 significantly reduced TNF-alpha-induced PMN transmigration across matrigel and ameliorated transendothelial PMN migration and protein leak in severe pancreatitis.

CONCLUSIONS

MMP-9 secretion by PMN can be stimulated by trypsin and proinflammatory cytokines and increases in pancreatitis in proportion to its severity. MMP inhibition reduces PMN transmigration and reduces resultant alveolar-capillary leakage. These findings suggest an important role for MMP-9 from PMN in the pathogenesis of pancreatitis-associated lung injury.

Supramaximal cholecystokinin displaces Munc18c from the pancreatic acinar basal surface, redirecting apical exocytosis to the basal membrane

Exocytosis at the apical surface of pancreatic acinar cells occurs in the presence of physiological concentrations of cholecystokinin (CCK) but is inhibited at high concentrations. Here we show that Munc18c is localized predominantly to the basal membranes of acinar cells. Supramaximal but not submaximal CCK stimulation caused Munc18c to dissociate from the plasma membrane, and this displacement was blocked by protein kinase C (PKC) inhibitors. Conversely, whereas the CCK analog CCK-OPE alone failed to displace Munc18c from the membrane, this agent caused Munc18c displacement following minimal PKC activation. To determine the physiological significance of this displacement, we used the fluorescent dye FM1-43 to visualize individual exocytosis events in real-time from rat acinar cells in culture. We showed that supramaximal CCK inhibition of secretion resulted from impaired apical secretion and a redirection of exocytic events to restricted basal membrane sites. In contrast, CCK-OPE evoked apical exocytosis and could only induce basolateral exocytosis following activation of PKC. Infusion of supraphysiological concentrations of CCK in rats, a treatment that induced tissue changes reminiscent of mild acute pancreatitis, likewise resulted in rapid displacement of Munc18c from the basal membrane in vivo.

Review of feline pancreatitis part one: the normal feline pancreas, the pathophysiology, classification, prevalence and aetiologies of pancreatitis

The cellular mechanisms involved once pancreatitis has been initiated are reasonably well understood. The events leading up to this process are less well established. Much of our current understanding of pancreatitis in cats has been determined from experiments in cats or extrapolated from other species. The normal anatomy and function of the pancreas and a review of the current state of knowledge about the pathophysiology of pancreatitis is discussed. The current prevalence of feline pancreatitis is unknown, but the disease is being reported with increasing frequency. The aetiology of pancreatitis and the types of pancreatic inflammation present in cats is different from other species, such as the dog, a species where the disease is considered more common. Concurrent diseases are often present that may be more serious than the pancreatic inflammation and the treatment of these diseases is often complicated by pancreatitis.

Stress kinase inhibition modulates acute experimental pancreatitis

AIM: To examine the role of p38 during acute experimental cerulein pancreatitis.

METHODS: Rats were treated with cerulein with or without a specific JNK inhibitor (CEP1347) and/or a specific p38 inhbitor (SB203580) and pancreatic stress kinase activity was determined. Parameters to assess pancreatitis included trypsin, amylase, lipase, pancreatic weight and histology.

RESULTS: JNK inhibition with CEP1347 ameliorated pancreatitis, reducing pancreatic edema. In contrast, p38 inhibition with SB203580 aggravated pancreatitis with higher trypsin levels and, with induction of acinar necrosis not normally found after cerulein hyperstimulation. Simultaneous treatment with both CEP1347 and SB203580 mutually abolished the effects of either compound on cerulein pancreatitis.

CONCLUSION: Stress kinases modulate pancreatitis differentially. JNK seems to promote pancreatitis development, possibly by supporting inflammatory reactions such as edema formation while its inhibition ameliorates pancreatitis. In contrast, p38 may help reduce organ destruction while inhibition of p38 during induction of cerulein pancreatitis leads to the occurrence of acinar necrosis.

Expression of the adhesion molecules Mac-1 and L-selectin on neutrophils in acute pancreatitis is protease- and complement-dependent

OBJECTIVE

To examine the effect of pancreatic proteases on the expression of the adhesion molecules Mac-1 and l-selectin on neutrophils, and the role of complement activation in this process.

SUMMARY BACKGROUND DATA

Sequestration of neutrophils in the pancreatic and pulmonary microvasculature characterizes acute pancreatitis.

METHODS

Serum was collected from inbred rats after induction of necrotizing pancreatitis; trypsinogen activation peptide was measured to quantify trypsin activation. Normal rat serum was also collected and subjected to limited trypsin digestion with and without the addition of complement inhibitor. Both groups of sera were incubated in vitro with healthy leukocytes. Expression of Mac-1 and L-selectin on neutrophils was measured quantitatively by flow cytometry. To assess the consequences of these events in vivo, trypsinated serum with or without complement inhibition or control serum was infused intravenous into rats. Soybean trypsin inhibitor was added to serum before injections to block residual trypsin activity. Pancreatic and pulmonary injury was quantitated by histology, measurement of edema, and myeloperoxidase activity.

RESULTS

Mac-1 expression on neutrophils incubated with pancreatitis serum was increased compared with controls, whereas L-selectin was decreased. Neutrophils incubated with trypsinated serum also showed upregulation of Mac-1 and downregulation of L-selectin, particularly with trypsin at 10(-4) mol/L. Addition of soluble complement receptor 1 abrogated both Mac-1 upregulation and L-selectin downregulation. Lungs of animals injected with trypsinated serum showed increased edema and myeloperoxidase activity, which were reduced by soluble complement receptor 1.

CONCLUSIONS

Trypsin-generated complement activation participates in the upregulation of Mac-1 and shedding of L-selectin on neutrophils in acute pancreatitis. Protease or complement inhibition may be effective in preventing leukocyte migration and subsequent local and remote organ injury.