Mechanisms of intracellular zymogen activation

Roles of Autophagy and Pancreatic Secretory Trypsin Inhibitor in Trypsinogen Activation in Acute Pancreatitis

The focus of the review is on roles of autophagy and pancreatic secretory trypsin inhibitor (PSTI), an endogenous trypsin inhibitor, in trypsinogen activation in acute pancreatitis. Acute pancreatitis is a disease in which tissues in and around the pancreas are autodigested by pancreatic digestive enzymes. This reaction is triggered by the intrapancreatic activation of trypsinogen. Autophagy causes trypsinogen and cathepsin B, a trypsinogen activator, to colocalize within the autolysosomes. Consequently, if the resultant trypsin activity exceeds the inhibitory activity of PSTI, the pancreatic digestive enzymes are activated, and they cause autodigestion of the acinar cells. Thus, autophagy and PSTI play important roles in the development and suppression of acute pancreatitis, respectively.

Eupatilin Ameliorates Cerulein-Induced Pancreatitis Via Inhibition of the Protein Kinase D1 Signaling Pathway In Vitro

OBJECTIVE

The aim of this study was to investigate the effects of eupatilin on protein kinase D1 (PKD1) and nuclear factor kappa B (NF-κB) signaling pathways in cerulein-induced in vitro pancreatitis.

METHODS

We used collagenase digestion to isolate pancreatic acinar cells from male C57BL/6 mice. In vitro acute pancreatitis was induced by treatment with a supramaximal dose of cerulein. Eupatilin was pretreated before stimulation with cerulein.

RESULTS

Eupatilin significantly reduced cerulein-induced amylase release in pancreatic acini. Eupatilin treatment downregulated cerulein-induced expression of interleukin (IL)-1β, IL-6, and CC chemokine ligands 2 and 5, but it upregulated expression of IL-4 and IL-10. We demonstrated that eupatilin pretreatment attenuated cerulein-induced necrosis in isolated pancreatic acinar cells. This effect of eupatilin was confirmed by lactic dehydrogenase assay, fluorescence-activated cell sorting analysis, and cytopathologic analysis. Eupatilin inhibited cerulein-induced activation of PKD1/NF-κB and the nuclear translocation of NF-κB.

CONCLUSIONS

Our data demonstrated that eupatilin is a potential therapeutic candidate for the treatment of pancreatitis through its ability to reduce cellular necrosis and inflammatory responses by inhibition of the PKD1/NF-κB signaling pathway.

Proteomic analysis of oxidized proteins in the brain and liver of the Nile tilapia (Oreochromis niloticus) exposed to a water-accommodated fraction of Maya crude oil

Crude oil (CO) is a super mixture of chemical compounds whose toxic effects are reported in fish species according to international guidelines. In the current study a proteomic analysis of oxidized proteins (ox) was performed on the brain and liver of Nile tilapia exposed to WAF obtained from relevant environmental loads (0.01, 0.1 and 1.0 g/L) of Maya CO. Results have shown that oxidation of specific proteins was a newly discovered organ-dependent process able to disrupt key functions in Nile tilapia. In control fish, enzymes involved on aerobic metabolism (liver aldehyde dehydrogenase and brain dihydrofolate reductase) and liver tryptophan--tRNA ligase were oxidized. In WAF-treated liver specimens, fructose-bisphosphate aldolase (FBA), β-galactosidase (β-GAL) and dipeptidyl peptidase 9 (DPP-9) were detected in oxidized form. oxDPP-9 could be favorable by reducing the risk associated with altered glucose metabolism, the opposite effects elicited by oxFBA and oxβ-GAL. oxTrypsin showed a clear adverse effect by reducing probably the hepatocyte capacity to achieve proteolysis of oxidized proteins as well as for performing the proper digestive function. Additionally, enzyme implicated in purine metabolism adenosine (deaminase) was oxidized. Cerebral enzymes of mitochondrial respiratory chain complex (COX IV, COX5B), of glycosphingolipid biosynthesis (β-N-acetylhexosaminidase), involved in catecholamines degradation (catechol O-methyltransferase), and microtubule cytoskeleton (stathmin) were oxidized in WAF-treated specimens. This response suggests, in the brain, an adverse scenario for the mitochondrial respiration process and for ATP provision as for ischemia/reoxygenation challenges. Proteomic analysis of oxidized proteins is a promising tool for monitoring environmental quality influenced by hydrocarbons dissolved in water.

Enzyme Development for Human Islet Isolation: Five Decades of Progress or Stagnation?

In comparison to procedures used for the separation of individual cell types from other organs, the process of human pancreatic islet isolation aims to digest the pancreatic exocrine matrix completely without dispersing the individual cells within the endocrine cell cluster. This objective is unique within the field of tissue separation, and outlines the challenge of islet isolation to balance two opposing priorities. Although significant progress has been made in the characterization and production of enzyme blends for islet isolation, there are still numerous areas which require improvement. The ultimate goal of enzyme production, namely the routine production of a consistent and standardized enzyme blend, has still not been realized. This seems to be mainly the result of a lack of detailed knowledge regarding the structure of the pancreatic extracellular matrix and the synergistic interplay between collagenase and different supplementary proteases during the degradation of the extracellular matrix. Furthermore, the activation of intrinsic proteolytic enzymes produced by the pancreatic acinar cells, also impacts on the chance of a successful outcome of human islet isolation. This overview discusses the challenges of pancreatic enzymatic digestion during human islet isolation, and outlines the developments in this field over the past 5 decades.

Src kinases play a novel dual role in acute pancreatitis affecting severity but no role in stimulated enzyme secretion

In pancreatic acinar cells, the Src family of kinases (SFK) is involved in the activation of several signaling cascades that are implicated in mediating cellular processes (growth, cytoskeletal changes, apoptosis). However, the role of SFKs in various physiological responses such as enzyme secretion or in pathophysiological processes such as acute pancreatitis is either controversial, unknown, or incompletely understood. To address this, in this study, we investigated the role/mechanisms of SFKs in acute pancreatitis and enzyme release. Enzyme secretion was studied in rat dispersed pancreatic acini, in vitro acute-pancreatitis-like changes induced by supramaximal COOH-terminal octapeptide of cholecystokinin (CCK). SFK involvement assessed using the chemical SFK inhibitor (PP2) with its inactive control, 4-amino-7-phenylpyrazol[3,4-d]pyrimidine (PP3), under experimental conditions, markedly inhibiting SFK activation. In CCK-stimulated pancreatic acinar cells, activation occurred of trypsinogen, various MAP kinases (p42/44, JNK), transcription factors (signal transducer and activator of transcription-3, nuclear factor-κB, activator protein-1), caspases (3, 8, and 9) inducing apoptosis, LDH release reflective of necrosis, and various chemokines secreted (monocyte chemotactic protein-1, macrophage inflammatory protein-1α, regulated on activation, normal T cell expressed and secreted). All were inhibited by PP2, not by PP3, except caspase activation leading to apoptosis, which was increased, and trypsin activation, which was unaffected, as was CCK-induced amylase release. These results demonstrate SFK activation is playing a dual role in acute pancreatitis, inhibiting apoptosis and promoting necrosis as well as chemokine/cytokine release inducing inflammation, leading to more severe disease, as well as not affecting secretion. Thus, our studies indicate that SFK is a key mediator of inflammation and pancreatic acinar cell death in acute pancreatitis, suggesting it could be a potential therapeutic target in acute pancreatitis.

Renofemoral shunt for protection of abdominal allografts during emergency abdominal aortic surgery

Emergency aortic surgery can be a daunting task in patients with functioning kidney and pancreas allografts because it poses the risk of allograft loss due to prolonged warm ischemia created by aortic cross-clamping. We present a case in which dual allografts, both originating from the right iliac arterial system, were protected from warm ischemia during aortic cross-clamping by creation of a temporary renofemoral shunt between the native left renal artery and right femoral artery. This simple technique maintained pulsatile allograft perfusion during aortic reconstruction for treatment of a ruptured mycotic aortic aneurysm complicated by an aortocolonic fistula.

Phylogenetic distribution of protease inhibitors of the Kazal-family within the Arthropoda

In mammalian pancreatic cells, the pancreatic secretory trypsin inhibitor (PSTI) belonging to the Kazal-family prevents the premature activation of digestive enzymes and thus plays an important role in a protective mechanism against tissue destruction by autophagy. Although a similar protective mechanism exists in Arthropoda, the distribution of these inhibitors in this phylum remains obscure. A comprehensive in silico search of nucleotide databases, revealed the presence of members of the Kazal-family in the four major subphyla of the Arthropoda. Especially in the Hexapoda and the Crustacea these inhibitors are widespread, while in the Chelicerata and Myriapoda only a few Kazal-like protease inhibitors were found. A sequence alignment of inhibitors retrieved in the digestive system of insects revealed a conservation of the PSTI characteristics and strong resemblance to vertebrate PSTI. A phylogenetic analysis of these inhibitors showed that they generally cluster according to their order. The results of this data mining study provide new evidence for the existence of an ancient protective mechanism in metazoan digestive systems. Kazal-like inhibitors, which play an important protective role in the pancreas of vertebrates, also seem to be present in Arthropoda.

Altered gene expression in cerulein-stimulated pancreatic acinar cells: pathologic mechanism of acute pancreatitis

Acute pancreatitis is a multifactorial disease associated with the premature activation of digestive enzymes. The genes expressed in pancreatic acinar cells determine the severity of the disease. The present study determined the differentially expressed genes in pancreatic acinar cells treated with cerulein as an in vitro model of acute pancreatitis. Pancreatic acinar AR42J cells were stimulated with 10(-8) M cerulein for 4 h, and genes with altered expression were identified using a cDNA microarray for 4,000 rat genes and validated by real-time PCR. These genes showed a 2.5-fold or higher increase with cerulein: lithostatin, guanylate cyclase, myosin light chain kinase 2, cathepsin C, progestin-induced protein, and pancreatic trypsin 2. Stathin 1 and ribosomal protein S13 showed a 2.5-fold or higher decreases in expression. Real-time PCR analysis showed time-dependent alterations of these genes. Using commercially available antibodies specific for guanylate cyclase, myosin light chain kinase 2, and cathepsin C, a time-dependent increase in these proteins were observed by Western blotting. Thus, disturbances in proliferation, differentiation, cytoskeleton arrangement, enzyme activity, and secretion may be underlying mechanisms of acute pancreatitis.

Relationship between carbachol hyperstimulation-induced pancreatic intracellular trypsinogen and NF-kappa B activation in rats in vitro

The relationship between intracellular trypsinogen activation and NF-kappa B activation in rat pancreatic acinar cells induced by M3 cholinergic receptor agonist (carbachol) hyperstimulation was studied. Rat pancreatic acinar cells were isolated, cultured and treated with carbachol, the active protease inhibitor (pefabloc) and NF-kappa B inhibitor (PDTC) in vitro. Intracellular trypsin activity was measured by using a fluorogenic substrate. The activity of NF-kappa B was monitored by using electrophoretic mobility shift assay. The results showed that after pretreatment with 2 mmol/L pefabloc, the activities of trypsin and NF-kappa B in pancreatic acinar cells treated with high concentrations of carbachol (10(-3) mol/L) in vitro was significantly decreased as compared with control group (P<0.01). The addition of 10(-2) mol/L PDTC resulted in a significant decrease of NF-kappa B activities in pancreatic acinar cells after treated with high concentrations of carbachol (10(-3) mol/L) in vitro, but the intracellular trypsinogen activity was not obviously inhibited (P>0.05). It was concluded that intracellular trypsinogen activation is likely involved in the regulation of high concentrations of carbachol-induced NF-kappa B activation in pancreatic acinar cells in vitro. NF-kappa B activation is likely not necessary for high concentrations of carbachol-induced trypsinogen activation in pancreatic acinar cells in vitro.

From acute pancreatitis to end-organ injury: mechanisms of acute lung injury

BACKGROUND

Multi-organ dysfunction, and in particular lung injury, is often responsible for the unfavorable outcome of patients with severe acute pancreatitis. Understanding of the mechanisms by which local inflammation in the pancreas leads to end-organ injury is crucial for the development of new therapeutic strategies.

METHODS

A MEDLINE search was performed with the terms "acute pancreatitis," "lung injury," "inflammatory response," "SIRS," and "multi-organ dysfunction." Pertinent articles were selected for analysis.

RESULTS

Modulation of the inflammatory response using a combination of immunomodulatory agents may decrease the incidence of severe pancreatitis-related acute lung injury and acute respiratory distress syndrome.

CONCLUSION

Clinical trials are of utmost importance to establish the validity of such strategies.

Zerumbone exerts a beneficial effect on inflammatory parameters of cholecystokinin octapeptide-induced experimental pancreatitis but fails to improve histology

OBJECTIVE

Our experiments were designed to investigate the effects of zerumbone pretreatment on cholecystokinin octapeptide (CCK-8)-induced acute pancreatitis in rats.

METHODS

Male Wistar rats weighing 240 to 280 g were divided into a control group, a group treated with CCK-8, a group receiving 20 mg/kg zerumbone before CCK-8 administration, and a group treated with zerumbone only.

RESULTS

The serum amylase and lipase activities and the pancreatic weight-body weight ratio were significantly reduced by zerumbone pretreatment, but the drug failed to influence the histological parameters of pancreatitis. The anti-inflammatory effects of the drug were manifested in decreases in the cytosolic interleukin 6 and tumor necrosis factor alpha concentrations and an elevation in the I-kappaB concentration, whereas the antioxidant ability of zerumbone was demonstrated by reductions in inducible nitric oxide synthase, Mn- and Cu/Zn-superoxide dismutase activities in the zerumbone-treated rats.

CONCLUSION

Zerumbone ameliorated the changes of several parameters of acute pancreatitis probably by interfering with I-kappaB degradation, but in the applied dose, it failed to influence the histology of the disease.

[Inflammatory pancreatic disease due to enzyme autodigestion: an exceptional model of glandular crinophagy]

The exocrine pancreas is a functionally dangerous structure since it is exposed to digestion by its most aggressive enzymes (proteases, etc) despite self-protective measures such as the synthesis of some of these enzymes in the form of inactive zymogens (trypsinogen, etc.). We review inflammatory pancreatic disease by separately analyzing its classical forms of onset: acute and chronic pancreatitis (AP and CP). There is general consensus that the initial pathogenic event in AP is intraacinar activation of trypsinogen into trypsin, followed by that of the remaining proenzymes, giving rise to an unusual model of autophagic inflammation. In contrast, consensus is lacking on the initial pathogenic event in CP (toxic-metabolic lesion, oxidative stress, ductal hypertension, etc.?), although in some cases a <<necrosis-fibrosis>> sequence due to recurrent episodes of AP seems evident. The pathogenic features shared by both forms of the disease and which justify some recent attempts to formulate an overall explanation of the pathogenesis of pancreatitis are discussed. Such an explanation would place both forms of pancreatitis within the conceptual framework of an <<inflammatory pancreatic disease due to enzyme autodigestion>>.

K+-induced ion-exchanges trigger trypsin activation in pancreas acinar zymogen granules

Trypsin premature activation has been thought to be a key event in the initiation phase of acute pancreatitis. Here we test a hypothesis that a sustained increase of cytosolic Ca(2+) concentration ([Ca(2+)](C)) can trigger K(+) influx into pancreas acinar zymogen granules (ZGs) via a Ca(2+)-activated K(+) channel (K(Ca)), and this influx of K(+) then mobilizes bound-Ca(2+) by K(+)/Ca(2+) ion-exchange to increase free Ca(2+) concentration in the ZGs ([Ca(2+)](G)) and release bound-H(+) by K(+)/H(+) ion-exchange to decrease the pH in ZGs (pH(G)). Both the increase of [Ca(2+)](G) and the decrease of pH(G) will facilitate trypsinogen autoactivation and stabilize active trypsin inside ZGs that could lead to acute pancreatitis. The experimental results are consistent with our hypothesis, suggesting that K(+) induced ion-exchanges play a critical role in the initiation of trypsin premature activation in ZGs.

Role of CCK/gastrin receptors in gastrointestinal/metabolic diseases and results of human studies using gastrin/CCK receptor agonists/antagonists in these diseases

In this paper, the established and possible roles of CCK1 and CCK2 receptors in gastrointestinal (GI) and metabolic diseases are reviewed and available results from human agonist/antagonist studies are discussed. While there is evidence for the involvement of CCK1R in numerous diseases including pancreatic disorders, motility disorders, tumor growth, regulation of satiety and a number of CCK-deficient states, the role of CCK1R in these conditions is not clearly defined. There are encouraging data from several clinical studies of CCK1R antagonists in some of these conditions, but their role as therapeutic agents remains unclear. The role of CCK2R in physiological (atrophic gastritis, pernicious anemia) and pathological (Zollinger-Ellison syndrome) hypergastrinemic states, its effects on the gastric mucosa (ECL cell hyperplasia, carcinoids, parietal cell mass) and its role in acid-peptic disorders are clearly defined. Furthermore, recent studies point to a possible role for CCK2R in a number of GI malignancies. Current data from human studies of CCK2R antagonists are presented and their potential role in the treatment of these conditions reviewed. Furthermore, the role of CCK2 receptors as targets for medical imaging is discussed.

Ethanol augments elevated-[Ca2+]C induced trypsin activation in pancreatic acinar zymogen granules

It has been long recognized that significant percentage of patients with acute pancreatitis often presents with a history of excessive alcohol consumption; however, the patho-physiological effect of ethanol on acute pancreatitis remains poorly understood. Abnormally elevated cytosolic Ca2+ ([Ca2+]C) has been found to be a shared phenomenon in acute pancreatitis that could induce trypsin premature activation. Here, we present the effects of ethanol to sensitize zymogen granules (ZGs) of pancreas acinar cells to elevated [Ca2+]C leading to zymogen premature activation that could result in acute pancreatitis. The pH fluctuations ([pH]G), Ca2+ concentration ([Ca2+]G), and premature trypsin activation inside the ZGs were monitored directly with specific fluorescence indicators. Our results showed that ethanol could act directly on ZGs and cause ZGs more receptive to elevated [Ca2+]C that could induce premature activation of zymogen (trypsin). This alcohol-induced effect is concentration dependent and strongly influenced by the surrounding [Ca2+]C. The K+ channels on ZGs membranes are required in the sensitization process. Our observations provide a mechanistic understanding of the role of ethanol in the initiation phase of alcoholic pancreatitis.

Effects of pancreatic duct ligation on pancreatic response to bombesin

To examine mechanisms that might be related to biliary pancreatitis, we examined the effects of pancreatic duct ligation (PDL) with pancreatic stimulation in vivo. PDL alone caused no increase in pancreatic levels of trypsinogen activation peptide (TAP), trypsin, or chymotrypsin and did not initiate pancreatitis. Although bombesin caused zymogen activation within the pancreas, the increases were slight and it did not cause pancreatitis. However, the combination of PDL with bombesin resulted in prominent increases in pancreatic TAP, trypsin, chymotrypsin, and the appearance of TAP in acinar cells and caused pancreatitis. Disruption of the apical actin network in the acinar cell was observed when PDL was combined with bombesin but not with PDL or bombesin alone. These studies suggest that when PDL is combined with pancreatic acinar cell stimulation, it can promote zymogen activation, the retention of active enzymes in acinar cells, and the development of acute pancreatitis.

Intracellular activation of trypsinogen in rat pancreatic acini after supramaximal secretagogue stimulation: cysteine protease and serine protease activity

OBJECTIVE

The aim of the study was to explore the mechanism by which trypsinogen becomes activated during acute pancreatitis.

METHODS

Given the ability of cholecystokinin (CCK) to induce pancreatitis in vivo, the effects of high-dose CCK on preparations of isolated pancreatic acini were examined using immunofluorescence techniques for the detection of trypsinogen activation. Acini were pretreated with weak base or serine or cysteine protease inhibitors before CCK hyperstimulation.

RESULTS

CCK was found to stimulate the generation of trypsinogen activation peptide (TAP), a marker for trypsinogen processing. The generation of TAP was inhibited by pretreatment with a weak base, chloroquine (40 micromol/L). TAP generation was also inhibited by pretreatment with serine protease inhibitor FUT-175 (1 micromol/L) but not cysteine protease inhibitor E64 (0.1 mmol/L) or E64-d (0.1 mmol/L). Although treatment with a high dose of E64-d (1 mmol/L) reduced activation, it also caused cell injury.

CONCLUSIONS

High-dose CCK stimulated the intracellular activation of trypsinogen within isolated pancreatic acini. This event appears to require an acidic subcellular compartment and serine protease activity. The role for thiol proteases in this model remains unclear.

Altered posttranslational processing of glycoproteins in cerulein-induced pancreatitis

Acute pancreatitis is an auto-digestive disease resulting in inflammation. At the cellular level, acute pancreatitis disrupts posttranslational protein processing and traffic in the secretory pathway, and zymogens become activated in the acinar cell. To better understand the disruption of the secretory pathway in pancreatitis, pulse-chase [(35)S]met/cys analysis was used to study the effects of supramaximal cerulein stimulation on posttranslational modification in the secretory pathway of the major sulfated glycoprotein of the mouse pancreas, pro-Muclin, and the lysosomal membrane protein LAMP1. Maximal cerulein or high concentration bombesin stimulation had little effect on glycoprotein processing. By contrast, supramaximal cerulein stimulation strongly inhibited pro-Muclin processing as measured by the failure of Muclin to attain its normal mature size of 300 kDa and to become highly sulfated and decreased proteolytic cleavage of pro-Muclin to produce apactin. Digestion of immunoprecipitated [35S]met/cys-labeled Muclin and LAMP1 with endoglycosidase H demonstrated that the supramaximal cerulein-induced block in processing occurred before the medial Golgi compartment. With supramaximal cerulein stimulation, vacuoles formed which contained Muclin, amylase, and LAMP1. Earlier autoradiographic studies showed that newly synthesized proteins end up in pancreatitis-associated vacuoles, so it is likely that glycoproteins with incomplete posttranslational processing are also present in vacuoles. Because glycoproteins are believed to protect the membranes of lysosomes and zymogen granules, when they are not correctly processed, their defensive mechanisms may be impaired, and this could contribute to vacuole fragility in pancreatitis.

Melatonin protects against pancreaticobiliary inflammation and associated remote organ injury in rats: role of neutrophils

Although the role of oxidative stress in acute pancreatitis (AP) has been studied in several animal models, little data are available regarding AP induced by pancreatic duct obstruction. We characterized the protective effects of melatonin on pancreaticobiliary inflammation and associated remote organ injury. In Sprague-Dawley rats, either the common pancreaticobiliary duct (PBDL; n = 28) or bile duct (BDL; n = 28) was ligated or a sham operation was applied (n = 14). Either melatonin (10 mg/kg) or vehicle (saline; 1 mL/kg) was administered intraperitoneally (i.p.) immediately before the surgery and twice a day until the rats were decapitated at 6 or 72 h. The pancreas, liver, kidneys and lungs were removed and tissue samples were stored for the determination of malondialdehyde (MDA) and glutathione (GSH) levels and myelopreoxidase activity. The results demonstrate that pathogenesis of acute obstructive pancreatitis involves not only the oxidative damage of the pancreatic and hepatic tissues, as assessed by increased MDA and reduced GSH levels, but the lungs and kidneys are also challenged by oxidant injury. Similarly, hepatic oxidative injury caused by cholestasis was also accompanied by pulmonary, renal and even pancreatic damage. The biochemical findings were also verified histologically. Melatonin, probably because of its free-radical scavenging and antioxidant activity, which involves an inhibitory effect on tissue neutrophil infiltration, protected all the affected tissues.

VMP1 expression correlates with acinar cell cytoplasmic vacuolization in arginine-induced acute pancreatitis

BACKGROUND

Recently, we described the cloning of VMP1 (vacuole membrane protein 1). In vitro expression of VMP1 promotes formation of cytoplasmic vacuoles followed by cell death. In order to test if VMP1 expression is related to the cytoplasmic vacuolization of the acinar cells during acute pancreatitis, we studied the in vivo expression of the new gene during arginine-induced acute pancreatitis.

METHODS

Male Wistar rats injected with 500 mg/100 g of L-arginine were time-course sacrificed and pancreas tissue removed.

RESULTS

Northern blot analysis showed maximal induction of VMP1 after 24 h remaining high after 48 h of arginine administration. Significant increase in the number of TUNEL-stained cells were found at those periods. After 24 and 48 h of arginine administration, light micrographs from thin plastic toluidine blue sections revealed numerous vacuoles in the cytoplasm of acinar cells. In situ hybridization studies showed high expression of VMP1 in acinar cells with cytoplasmic vacuolization. VMP1 mRNA highly and significantly correlated with vacuole formation.

CONCLUSION

These results suggest that VMP1 expression may be involved in the cytoplasmic vacuolization of acinar cells during the early stage of acute pancreatitis.

The pH modulator chloroquine blocks trypsinogen activation peptide generation in cerulein-induced pancreatitis

INTRODUCTION AND AIMS

We examined the effects of a weak base, chloroquine, on the trypsinogen processing in cerulein-induced pancreatitis.

METHODOLOGY

Immunofluorescence studies were performed using newly generated affinity-purified antibodies to the trypsinogen activation peptide (TAP).

RESULTS

The present study showed that chloroquine pretreatment blocked intracellular TAP generation in cerulein-induced pancreatitis.

CONCLUSION

These results indicate that intracellular trypsinogen activation, which plays an important role in acute pancreatitis, requires a low-pH compartment, as well as serine protease activity.

Involvement of cholecystokinin/gastrin-related peptides and their receptors in clinical gastrointestinal disorders

In this paper the possible roles of cholecystokinin (CCK), gastrin, or gastrin-related peptides and their receptors in human gastrointestinal diseases are reviewed. For CCK/CCK(A) receptors (CCK(A)-R), the evidence for their proposed involvement in diseases caused by impaired CCK release or CCK(A)-R mutations, pancreatic disorders (acute/chronic pancreatitis), gastrointestinal motility disorders (gallbladder disease, irritable bowel syndrome), pancreatic tumor growth and satiety disorders, is briefly reviewed. The evidence that has established the involvement of gastrin/CCK(B)-R in mediating the action of hypergastrinaemic disorders, mediating hypergastrinaemic effects on the gastric mucosa (ECL hyperplasia, carcinoids, parietal cell mass), and acid-peptic diseases, is reviewed. The evidence for their possible involvement in mediating growth of gastric and pancreatic tumours and possible involvement of gastrin-related peptides in colon cancers, is reviewed briefly.

Cholecystokinin induces caspase activation and mitochondrial dysfunction in pancreatic acinar cells. Roles in cell injury processes of pancreatitis

Apoptosis and necrosis are critical parameters of pancreatitis, the mechanisms of which remain unknown. Many characteristics of pancreatitis can be studied in vitro in pancreatic acini treated with high doses of cholecystokinin (CCK). We show here that CCK stimulates apoptosis and death signaling pathways in rat pancreatic acinar cells, including caspase activation, cytochrome c release, and mitochondrial depolarization. The mitochondrial dysfunction is mediated by upstream caspases (possibly caspase-8) and, in turn, leads to activation of caspase-3. CCK causes mitochondrial alterations through both permeability transition pore-dependent (cytochrome c release) and permeability transition pore-independent (mitochondrial depolarization) mechanisms. Caspase activation and mitochondrial alterations also occur in untreated pancreatic acinar cells; however, the underlying mechanisms are different. In particular, caspases protect untreated acinar cells from mitochondrial damage. We found that caspases not only mediate apoptosis but also regulate other parameters of CCK-induced acinar cell injury that are characteristic of pancreatitis; in particular, caspases negatively regulate necrosis and trypsin activation in acinar cells. The results suggest that the observed signaling pathways regulate parenchymal cell injury and death in CCK-induced pancreatitis. Protection against necrosis and trypsin activation by caspases can explain why the severity of pancreatitis in experimental models correlates inversely with the extent of apoptosis.