Proinflammatory role of trypsin and protease-activated receptor-2 in a rat model of acute pancreatitis

In vitro, in silico and crystallographic-based identification of serine protease inhibitors

Serine proteases are involved in various ailments, including pancreatitis, and colon cancer. Based on substrate recognition serine proteases are classified into different groups. Trypsin and trypsin-like serine proteases are among most studied group of serine proteases. Trypsin is among the chief hydrolysing enzyme involved in the pathogenesis of pancreatitis. Its inhibition can help to manage the disease. Herein, we investigated the trypsin inhibitory effect of some arginine-based small molecules, through in vitro, in silico, and crystallographic methods. Compounds 1-3 were evaluated against bovine pancreatic trypsin (BPT). Compound 1 was found to be active against trypsin with IC50 value of 247.98 ± 2.44 μM. Molecular docking studies were used to investigate the binding energy and binding conformation of inhibitor. All three compounds were subjected to crystallisation with trypsin. Compounds 1-2 were successfully crystallised with BPT The crystal structures of trypsin in complexed with compounds 1, and 2 were determined at 2.30 and 2.50 Å resolution, respectively. Both molecules showed their binding affinity with the active site residues of trypsin. This study will provide insight into the binding mechanism of E-64 and arginine and might be useful in designing effective inhibitors of serine proteases.

Network meta-analysis on the mechanisms underlying alcohol augmentation of acute pancreatitis and diabetes type II

BACKGROUND

Pancreatitis is a severe inflammatory pathology that occurs from pancreatic duct and exocrine acinar injury, leading to improper secretion of digestive enzymes, auto-digestion of the pancreas, and subsequent inflammation. Clinical reports show that 60%-90% of pancreatitis patients have a history of chronic alcohol use. More recent studies reveal that exocrine pancreas disorders like acute pancreatitis can precede diabetes type II onset, though mechanisms are not yet fully known. This study identified molecules and key signaling pathways underlying alcohol-induced acute pancreatitis and their effects on diabetes type II onset.

METHODS

Data on human peripheral blood samples with or without acute pancreatitis were retrieved from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (accession number GSE194331). Acute pancreatitis-mediated differentially expressed genes (DEGs) were generated from GSE194331 using CLC Genomics Workbench 12. Molecules associated with ethanol (EtOH), acute pancreatitis, and diabetes type II were collected from QIAGEN Knowledge Base (QKB). The relationship between the molecules and signaling pathways associated with EtOH, acute pancreatitis, or diabetes type II was examined using various Ingenuity Pathway Analysis (IPA) tools.

RESULTS

Our investigation showed that acute pancreatitis-mediated DEGs were closely associated with EtOH by revealing that EtOH-induced acute pancreatitis appears to lead to the onset of diabetes type II. We found that diabetes type II onset was mediated by pro-inflammatory and metabolic mechanisms underlying EtOH-induced acute pancreatitis, involving increased expression of cytokines including macrophage migration inhibitory factor (MIF), and decreased expression of hormones such as insulin.

CONCLUSIONS

Exposure to alcohol may promote diabetes type II by affecting the activity of key inflammatory and metabolic mediators involved in acute pancreatitis. These findings call for further investigation into the role of pro-inflammatory and metabolic mediators like resistin, IL-6, and insulin in EtOH-induced diabetes type II associated with acute pancreatitis pathologies.

PAR2: The Cornerstone of Pancreatic Diseases

It has been 30 years since the first member of the protease-activated receptor (PAR) family was discovered. This was followed by the discovery of three other receptors, including PAR2. PAR2 is a G protein-coupled receptor activated by trypsin site-specific proteolysis. The process starts with serine proteases acting between arginine and serine, creating an N-terminus that functions as a tethered ligand that binds, after a conformational change, to the second extracellular loop of the receptor, leading to activation of G-proteins. The physiological and pathological functions of this ubiquitous receptor are still elusive. This review focuses on PAR2 activation and its distribution under physiological and pathological conditions, with a particular focus on the pancreas, a significant producer of trypsin, which is the prototype activator of the receptor. The role in acute or chronic pancreatitis, pancreatic cancer, and diabetes mellitus will be highlighted.

Expression of Proteinase-Activated Receptor 2 During Colon Volvulus in the Horse

Large colon volvulus in horses is associated with a poor prognosis, especially when ischemic-reperfusion injury of the affected intestinal tract develops. Proteinase-activated receptor 2 (PAR₂) plays an important role in the pathogenesis of inflammation in the gastrointestinal tract. The aim of this study was to evaluate the distribution and expression of PAR₂ in colonic pelvic flexure of horses spontaneously affected by large colon volvulus (CVH group). Eight horses admitted for severe abdominal colon volvolus and which underwent surgery were included. Colon samples were collected after enterotomy. Data previously obtained from healthy horses were used as a control group. Histologic evaluation was carried out to grade the severity of the colon lesions. Immunofluorescence, western blot and quantitative polymerase chain reaction (RT-qPCR) were carried out on colon samples to evaluate PAR₂ expression. In addition, the transcriptional profile of cytokines and chemokines was evaluated using RT² Profiler™ PCR Array Horse Cytokines & Chemokines. Three out of the eight patients were euthanised due to clinical deterioration. Immunostaining for PAR² was observed in the enterocytes, intestinal glands and neurons of the submucosal and myenteric plexi. In the CVH horses, the expression of PAR₂ mesenger RNA (mRNA) did not differ significantly from that of the healthy animals; western blots of the mucosa of the colon tracts showed a clear band of the expected molecular weight for PAR₂ (~44 kDa) and a band smaller than the expected molecular weight for PAR₂ (25kDa), suggesting its activation. The gene expressions for C-X-C motif ligand 1 (CXCL1); interleukin 8 (IL8), macrophage inflammatory protein 2 beta (MIP-2BETA) were upregulated in the colic horses as compared with the colons of the healthy horses. Therefore, in the present study, the expression and activation of PAR₂ in the colons of horses in the presence of an inflammatory reaction like that occurring in those with spontaneous colon volvulus was confirmed.

Intestinal barrier damage, systemic inflammatory response syndrome, and acute lung injury: A troublesome trio for acute pancreatitis

Severe acute pancreatitis (SAP), a serious inflammatory disease of the pancreas, can easily lead to systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndromes (MODS). Acute lung injury (ALI) is one of the most serious complications of SAP. However, the specific pathogenesis of SAP-associated ALI is not fully understood. Crosstalk and multi-mechanisms involving pancreatic necrosis, bacteremia, intestinal barrier failure, activation of inflammatory cascades and diffuse alveolar damage is the main reason for the unclear pathological mechanism of SAP-associated ALI. According to previous research on SAP-associated ALI in our laboratory and theories put forward by other scholars, we propose that the complex pattern of SAP-associated ALI is based on the "pancreas-intestine-inflammation/endotoxin-lung (P-I-I/E-L) pathway". In this review, we mainly concentrated on the specific details of the "P-I-I/E-L pathway" and the potential treatments or preventive measures for SAP-associated ALI.

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.

PAR2 regulates regeneration, transdifferentiation, and death

Understanding the mechanisms by which cells sense and respond to injury is central to developing therapies to enhance tissue regeneration. Previously, we showed that pancreatic injury consisting of acinar cell damage+β-cell ablation led to islet cell transdifferentiation. Here, we report that the molecular mechanism for this requires activating protease-activated receptor-2 (PAR2), a G-protein-coupled receptor. PAR2 modulation was sufficient to induce islet cell transdifferentiation in the absence of β-cells. Its expression was modulated in an islet cell type-specific manner in murine and human type 1 diabetes (T1D). In addition to transdifferentiation, PAR2 regulated β-cell apoptosis in pancreatitis. PAR2's role in regeneration is broad, as mice lacking PAR2 had marked phenotypes in response to injury in the liver and in digit regeneration following amputation. These studies provide a pharmacologically relevant target to induce tissue regeneration in a number of diseases, including T1D.

Role of protease-activated receptor 2 in lung injury development during acute pancreatitis in rats

OBJECTIVE

The objective of this study was to evaluate whether an uncontrolled activation of mast cells and macrophages through protease-activated receptor-2 (PAR-2) during acute pancreatitis could develop lung injury.

METHODS

Pancreatitis was induced in rats by intraductal infusion of sodium taurocholate. In a group of animals, PAR-2 antagonist or trypsin (TRP) inhibitor was intravenously administered before the pancreatitis induction. In additional groups, the animals were treated with PAR-2-activating peptide or pancreatic TRP. The myeloperoxidase (MPO) activity was measured to evaluate the progression of inflammation.

RESULTS

Plasma from the animals with pancreatitis and pancreatic TRP induced the secretion of mast cells and alveolar macrophages as well as increased the density of PAR-2 in the plasma membrane. The treatment of alveolar macrophages with TRP, tryptase, as well as PAR-1- and PAR-2-activating peptide led to an increase in calcium-triggered exocytosis. Similar results were obtained in acinar cells. The intravenous injection of PAR-2-activating peptide and TRP induced an increase in MPO activity in the lung. The intravenous injection of PAR-2 antagonist or TRP inhibitor before the pancreatitis induction could prevent the increase in MPO activity in the pancreas and the lung.

CONCLUSIONS

The TRP generated during acute pancreatitis could be involved in the progression of lung injury through the activation of PAR-2 in alveolar macrophages.

Autocrine extra-pancreatic trypsin 3 secretion promotes cell proliferation and survival in esophageal adenocarcinoma

Trypsin or Tumor associated trypsin (TAT) activation of Protease-activated receptor 2 (PAR-2) promotes tumor cell proliferation in gastrointestinal cancers. The role of the trypsin/PAR-2 network in esophageal adenocarcinoma (EA) development has not yet been investigated. The aim of this study is to investigate the role of trypsin/PAR-2 activation in EA tumorogenesis and therapy. We found that esophageal adenocarcinoma cells (EACs) and Barrett’s Metaplasia (BART) expressed high levels of type 3 extra-pancreatic trypsinogen (PRSS3), a novel type of TAT. Activity of secreted trypsin was detected in cultured media from EA OE19 and OE33 cultures but not from BART culture. Surface PAR-2 expression in BART and EACs was confirmed by both flow cytometry and immunofluorescence. Trypsin induced cell proliferation (∼ 2 fold; P<0.01) in all tested cell lines at a concentration of 10 nM. Inhibition of PAR-2 activity in EACs via the PAR-2 antagonist ENMD (500 µM), anti-PAR2 antibody SAM-11 (2 µg/ml), or siRNA PAR-2 knockdown, reduced cell proliferation and increased apoptosis by up to 4 fold (P<0.01). Trypsin stimulation led to phosphorylation of ERK1/2, suggesting involvement of MAPK pathway in PAR-2 signal transduction. Inhibition of PAR-2 activation or siRNA PAR-2 knockdown in EACs prior to treatment with 5 FU reduced cell viability of EACs by an additional 30% (P<0.01) compared to chemotherapy alone. Our data suggest that extra-pancreatic trypsinogen 3 is produced by EACs and activates PAR-2 in an autocrine manner. PAR-2 activation increases cancer cell proliferation, and promotes cancer cell survival. Targeting the trypsin activated PAR-2 pathway in conjunction with current chemotherapeutic agents may be a viable therapeutic strategy in EA.

Chloroquine relieves acute lung injury in rats with acute hemorrhagic necrotizing pancreatitis

This study preliminarily investigated the mechanism by which chloroquine (CQ) relieves acute lung injury (ALI) complicated in acute hemorrhagic necrotizing pancreatitis (AHNP). Sixty male Wistar rats were randomized into sham-operated group (group A, n=10), AHNP group (group B, n=10), L-arginine-treated group (group C, n=10), L-N-nitro-L-arginine methyl ester (NAME)-treated group (group D, n=10), CQ-treated group (group E, n=10) and CQ+L-NAME-treated group (group F, n=10). TLR4 expression was measured by using real time-PCR and Western blotting respectively. The results showed that, in the group B, the expression of TLR4 and the levels of TNF-α and IL-6 in the lungs were significantly increased, and the nitric oxide (NO) concentration was reduced, as compared with those in the group A (P<0.05 or P<0.01). Lung injury was aggravated with the increased expression of TLR4. When the inhibitor and stimulator of TLR4, namely L-Arg and L-NAME, were added respectively, lung injury was correspondingly relieved or aggravated (P<0.05 or P<0.01). In the group E, TLR4 expression was substantially lower and NO concentration higher than those in the group B (P<0.05 or P<0.01). However, in the group F, NO concentration was markedly decreased, and the inhibitory effect of CQ on TLR4 expression and the relief of lung injury were weakened when compared with those in the group E (P<0.05 or P<0.01). It was concluded that TLR4 may play an important role in the pathogenesis and development of ALI complicated in AHNP. CQ could relieve ALI by decreasing the TLR4 expression and increasing the NO release.

Modulating human proteinase activated receptor 2 with a novel antagonist (GB88) and agonist (GB110)

BACKGROUND AND PURPOSE

Many cells express proteinase activated receptor 2 (PAR2) on their plasma membrane. PAR2 is activated by proteolytic enzymes, such as trypsin and tryptase that cleave the receptor N-terminus, inititating signalling to intracellular G proteins. Studies on PAR2 have relied heavily upon activating effects of proteases and peptide agonists that lack stability and bioavailability in vivo.

EXPERIMENTAL APPROACH

A novel small molecule agonist GB110 and an antagonist GB88 were characterized in vitro against trypsin, peptide agonists, PAR2 antibody, PAR1 agonists and flow cytometry,in seven cell lines using intracellular Ca(2+) mobilization and examined in vivo against PAR2- and PAR1-induced rat paw oedema.

KEY RESULTS

GB110 is a potent non-peptidic agonist activating PAR2-mediated Ca(2+) release in HT29 cells (EC(50) ∼200 nM) and six other human cell lines, inducing PAR2 internalization. GB88 is a unique PAR2 antagonist, inhibiting PAR2 activated Ca(2+) release (IC(50) ∼2 µM) induced by native (trypsin) or synthetic peptide and non-peptide agonists. GB88 was a competitive and surmountable antagonist of agonist 2f-LIGRLO-NH(2), a competitive but insurmountable antagonist of agonist GB110, and a non-competitive insurmountable antagonist of trypsin. GB88 was orally active and anti-inflammatory in vivo, inhibiting acute rat paw oedema elicited by agonist GB110 and proteolytic or peptide agonists of PAR2 but not by corresponding agonists of PAR1 or PAR4.

CONCLUSIONS AND IMPLICATIONS

The novel PAR2 agonist and antagonist modulate intracellular Ca(2+) and rat paw oedema, providing novel molecular tools for examining PAR2-mediated diseases.

High-throughput sequence analysis of turbot (Scophthalmus maximus) transcriptome using 454-pyrosequencing for the discovery of antiviral immune genes

Background

Turbot (Scophthalmus maximus L.) is an important aquacultural resource both in Europe and Asia. However, there is little information on gene sequences available in public databases. Currently, one of the main problems affecting the culture of this flatfish is mortality due to several pathogens, especially viral diseases which are not treatable. In order to identify new genes involved in immune defense, we conducted 454-pyrosequencing of the turbot transcriptome after different immune stimulations.

Methodology/Principal Findings

Turbot were injected with viral stimuli to increase the expression level of immune-related genes. High-throughput deep sequencing using 454-pyrosequencing technology yielded 915,256 high-quality reads. These sequences were assembled into 55,404 contigs that were subjected to annotation steps. Intriguingly, 55.16% of the deduced protein was not significantly similar to any sequences in the databases used for the annotation and only 0.85% of the BLASTx top-hits matched S. maximus protein sequences. This relatively low level of annotation is possibly due to the limited information for this specie and other flatfish in the database. These results suggest the identification of a large number of new genes in turbot and in fish in general. A more detailed analysis showed the presence of putative members of several innate and specific immune pathways.

Conclusions/Significance

To our knowledge, this study is the first transcriptome analysis using 454-pyrosequencing for turbot. Previously, there were only 12,471 EST and less of 1,500 nucleotide sequences for S. maximus in NCBI database. Our results provide a rich source of data (55,404 contigs and 181,845 singletons) for discovering and identifying new genes, which will serve as a basis for microarray construction, gene expression characterization and for identification of genetic markers to be used in several applications. Immune stimulation in turbot was very effective, obtaining an enormous variety of sequences belonging to genes involved in the defense mechanisms.

Serine proteases mediate inflammatory pain in acute pancreatitis

Acute pancreatitis is a life-threatening inflammatory disease characterized by abdominal pain of unknown etiology. Trypsin, a key mediator of pancreatitis, causes inflammation and pain by activating protease-activated receptor 2 (PAR(2)), but the isoforms of trypsin that cause pancreatitis and pancreatic pain are unknown. We hypothesized that human trypsin IV and rat P23, which activate PAR(2) and are resistant to pancreatic trypsin inhibitors, contribute to pancreatic inflammation and pain. Injections of a subinflammatory dose of exogenous trypsin increased c-Fos immunoreactivity, indicative of spinal nociceptive activation, but did not cause inflammation, as assessed by measuring serum amylase and myeloperoxidase activity and by histology. The same dose of trypsin IV and P23 increased some inflammatory end points and caused a more robust effect on nociception, which was blocked by melagatran, a trypsin inhibitor that also inhibits polypeptide-resistant trypsin isoforms. To determine the contribution of endogenous activation of trypsin and its minor isoforms, recombinant enterokinase (ENK), which activates trypsins in the duodenum, was administered into the pancreas. Intraductal ENK caused nociception and inflammation that were diminished by polypeptide inhibitors, including soybean trypsin inhibitor and a specific trypsin inhibitor (type I-P), and by melagatran. Finally, the secretagogue cerulein induced pancreatic nociceptive activation and nocifensive behavior that were reversed by melagatran. Thus trypsin and its minor isoforms mediate pancreatic pain and inflammation. In particular, the inhibitor-resistant isoforms trypsin IV and P23 may be important in mediating prolonged pancreatic inflammatory pain in pancreatitis. Our results suggest that inhibitors of these isoforms could be novel therapies for pancreatitis pain.

Proteinase-activated receptor 2 mediates thermal hyperalgesia and is upregulated in a rat model of chronic pancreatitis

OBJECTIVES

The mechanism of pain in chronic pancreatitis (CP) has yet to be explored. Proteinase-activated receptor 2 (PAR2) plays a pronociceptive role in visceral pain. The study aimed to assess the expression of PAR2 in dorsal root ganglia (DRGs) and validate its role of thermal hyperalgesia in CP.

METHODS

Chronic pancreatitis model was induced by trinitrobenzene sulfonic acid infusion into rat pancreatic ducts. Abdominal hyperalgesia was measured by thermal withdrawal latencies. The expression of PAR2 and transient receptor potential vanilloid 1 (TRPV1) were analyzed by immunofluorescence and Western blot. The messenger RNA encoding PAR2 was quantitated by real-time polymerase chain reaction. The effects of short-term and long-term ulinastatin treatment on abdominal thermal hyperalgesia of rats with CP were measured.

RESULTS

Rats with CP showed a decreased thermal withdrawal latency. Proteinase-activated receptor 2 and TRPV1 were significantly upregulated in DRGs. The increased PAR2 protein expression was tightly correlated with thermal withdrawal latencies and TRPV1 expression. Short-term ulinastatin treatment inhibited the development of thermal hyperalgesia of rats with CP in a dose-dependent manner.

CONCLUSIONS

The thermal hyperalgesia in CP is associated with an up-regulation of the PAR2 in DRGs. Proteinase-activated receptor 2 was involved in the pain generation in rats with CP.

The protective effects of Lipoxin A4 during the early phase of severe acute pancreatitis in rats

OBJECTIVE

Our aim was to investigate the protective effects of a Lipoxin A(4) analogue (LXA4) in the early phase of acute pancreatitis in rats.

MATERIALS AND METHODS

Severe acute pancreatitis (SAP) was induced by injection of 5% sodium taurocholate into the pancreatic duct. Rats with SAP were treated with LXA4 (0.1 mg/kg), 10 min after the 5% sodium taurocholate injection, after which LXA4 was administrated every 8 hours, three times (LXA4 group). The sham group was only given the vehicle after operation. Plasma amylase activity, serum levels of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α) were measured at 4, 12, and 24 h after induction of SAP. The pancreatic index and histopathologic observations were evaluated and the expression of intercellular adhesion molecule-1 (ICAM-1) and NF-κB p65 in the pancreas, and the expression of ICAM-1 in the lungs were detected by immunohistochemistry.

RESULTS

LXA4 treated rats had lower serum levels of TNF-α, IL-1, and IL-6 at all time points measured (p < 0.05), but significantly differed in plasma amylase activity only at 24 h as compared with the SAP group. The pancreatic index and the scores of pancreatitic histopathologic evaluations were lower in the LXA4 group as compared to the SAP group. Immunohistochemistry showed that LXA4 attenuated the expression of ICAM-1 and NF-κB p65 in the pancreas, as well as the expression of ICAM-1 in the lungs in animals with pancreatitis (p < 0.05).

CONCLUSIONS

We demonstrate that LXA4 has protective effects in experimental SAP, which may be achieved by inhibiting the NF-κB signalling pathway, thereby reducing the production of proinflammatory cytokines.

Profiling gene expression induced by protease-activated receptor 2 (PAR2) activation in human kidney cells

Protease-Activated Receptor-2 (PAR2) has been implicated through genetic knockout mice with cytokine regulation and arthritis development. Many studies have associated PAR2 with inflammatory conditions (arthritis, airways inflammation, IBD) and key events in tumor progression (angiogenesis, metastasis), but they have relied heavily on the use of single agonists to identify physiological roles for PAR2. However such probes are now known not to be highly selective for PAR2, and thus precisely what PAR2 does and what mechanisms of downstream regulation are truly affected remain obscure. Effects of PAR2 activation on gene expression in Human Embryonic Kidney cells (HEK293), a commonly studied cell line in PAR2 research, were investigated here by comparing 19,000 human genes for intersecting up- or down-regulation by both trypsin (an endogenous protease that activates PAR2) and a PAR2 activating hexapeptide (2f-LIGRLO-NH(2)). Among 2,500 human genes regulated similarly by both agonists, there were clear associations between PAR2 activation and cellular metabolism (1,000 genes), the cell cycle, the MAPK pathway, HDAC and sirtuin enzymes, inflammatory cytokines, and anti-complement function. PAR-2 activation up-regulated four genes more than 5 fold (DUSP6, WWOX, AREG, SERPINB2) and down-regulated another six genes more than 3 fold (TXNIP, RARG, ITGB4, CTSD, MSC and TM4SF15). Both PAR2 and PAR1 activation resulted in up-regulated expression of several genes (CD44, FOSL1, TNFRSF12A, RAB3A, COPEB, CORO1C, THBS1, SDC4) known to be important in cancer. This is the first widespread profiling of specific activation of PAR2 and provides a valuable platform for better understanding key mechanistic roles of PAR2 in human physiology. Results clearly support the development of both antagonists and agonists of human PAR2 as potential disease modifying therapeutic agents.

The proteinase/proteinase-activated receptor-2/transient receptor potential vanilloid-1 cascade impacts pancreatic pain in mice

AIMS

Proteinase-activated receptor-2 (PAR2) and transient receptor potential vanilloid-1 (TRPV1) are co-localized in the primary afferents, and the trans-activation of TRPV1 by PAR2 activation is involved in processing of somatic pain. Given evidence for contribution of PAR2 to pancreatic pain, the present study aimed at clarifying the involvement of TRPV1 in processing of pancreatic pain by the proteinase/PAR2 pathway in mice.

MAIN METHODS

Acute pancreatitis was created by repeated administration of cerulein in conscious mice, and the referred allodynia/hyperalgesia was assessed using von Frey filaments. Injection of PAR2 agonists into the pancreatic duct was achieved in anesthetized mice, and expression of Fos in the spinal cord was determined by immunohistochemistry.

KEY FINDINGS

The established referred allodynia/hyperalgesia following cerulein treatment was abolished by post-treatment with nafamostat mesilate, a proteinase inhibitor, and with capsazepine, a TRPV1 antagonist, in mice. Injection of trypsin, an endogenous PAR2 agonist, or SLIGRL-NH(2), a PAR2-activating peptide, into the pancreatic duct caused expression of Fos protein in the spinal superficial layers at T8-T10 levels in the mice. The spinal Fos expression caused by trypsin and by SLIGRL-NH(2) was partially blocked by capsazepine, the former effect abolished by nafamostat mesilate.

SIGNIFICANCE

Our data thus suggest that the proteinase/PAR2/TRPV1 cascade might impact pancreatic pain, in addition to somatic pain, and play a role in the maintenance of pancreatitis-related pain in mice.

Plasma concentrations of growth arrest-specific protein 6 and protein S in patients with acute pancreatitis

BACKGROUND

The aim of the present study was to clarify the changes in plasma concentrations of growth arrest-specific protein 6 (Gas6) and protein S (PS) in patients with mild or severe acute pancreatitis (AP).

METHODS

The study group comprised 29 consecutive patients with AP (24 males, five females; mean age, 54.8 +/- 15.0 years) and 20 healthy controls (10 males, 10 females; mean age, 53.0 +/- 15.3 years). Plasma concentrations of Gas6 and PS were measured by enzyme-linked immunosorbent assay.

RESULTS

The concentration of Gas6 was significantly higher in both severe and mild AP than in healthy controls, and was significantly correlated with two of the multiple organ failure assessment scores. Furthermore, when compared with survivors, the concentrations of Gas6 in non-survivors of severe AP were significantly increased. The concentrations of free PS and total PS were significantly decreased compared with normal controls, but there was no difference between cases and controls in the concentrations of C4 binding protein-PS.

CONCLUSION

Plasma concentrations of Gas6 and PS correlate with disease severity. High concentrations of Gas6 reflect microcirculatory abnormalities, and phagocytosis of dying cells in sepsis associated with severe AP.

Intervention of pyrrolidine dithiocarbamate and tetrandrine on cellular calcium overload of pancreatic acinar cells induced by serum and ascitic fluid from rats with acute pancreatitis

BACKGROUND AND AIM

To investigate the effects of serum and ascitic fluid from rats with acute pancreatitis (AP) on cellular free calcium concentration ([Ca(2+)]i) of isolated rat pancreatic acinar cells, and the intervention of pyrrolidine dithiocarbamate (PDTC) and tetrandrine (Tet) to cellular calcium overload in AP.

METHODS

AP was induced in Sprague-Dawley rats with a retrograde pancreatic duct injection of 3% sodium deoxycholate, and confirmed by histopathological examination and amylase activity assay. The rat serum and ascitic fluid were collected at 1, 5 and 10 h after AP induction, and used as irritants on isolated rat pancreatic acinar cells. The effects on intracellular [Ca(2+)]i, and cell viability were examined. Then, the antagonistic effects of different concentrations of PDTC and Tet were assessed.

RESULTS

The irritation with AP serum and ascitic fluid reduced the survival rate of the isolated rat pancreatic acinar cells and increased the cellular [Ca(2+)]i significantly (P < 0.05). As AP induction course prolonged, the stimulation effect of the AP serum and ascitic fluid intensified. In the pretreated acinar cells with PDTC or Tet, the decreased cell vitality reverted. The elevation of [Ca(2+)]i in the acinar cells significantly ameliorated (significant, P < 0.05; very significant, P < 0.01).

CONCLUSION

The serum and ascitic fluid from AP rats drastically elevate the [Ca(2+)]i in isolated pancreatic acinar cells and decrease cell vitality, while the pretreatment of cells with PDTC and Tet offsets the calcium overload irritated by the AP serum and ascitic fluid and protects these isolated acinar cells.

PAR2 exerts local protection against acute pancreatitis via modulation of MAP kinase and MAP kinase phosphatase signaling

During acute pancreatitis, protease-activated receptor 2 (PAR2) can be activated by interstitially released trypsin. In the mild form of pancreatitis, PAR2 activation exerts local protection against intrapancreatic damage, whereas, in the severe form of pancreatitis, PAR2 activation mediates some systemic complications. This study aimed to identify the molecular mechanisms of PAR2-mediated protective effects against intrapancreatic damage. A mild form of acute pancreatitis was induced by an intraperitoneal injection of caerulein (40 microg/kg) in rats. Effects of PAR2 activation on intrapancreatic damage and on mitogen-activated protein (MAP) kinase signaling were assessed. Caerulein treatment activated extracellular signal-regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK) within 15 min and maintained phosphorylation of ERK and JNK for 2 h in the rat pancreas. Although PAR2 activation by the pretreatment with PAR2-activating peptide (AP) itself increased ERK phosphorylation in rat pancreas, the same treatment remarkably decreased caerulein-induced activation of ERK and JNK principally by accelerating their dephosphorylation. Inhibition of ERK and JNK phosphorylation by the pretreatment with MAP/ERK kinase (MEK) or JNK inhibitors decreased caerulein-induced pancreatic damage that was similar to the effect induced by PAR2-AP. Notably, in caerulein-treated rats, PAR2-AP cotreatment highly increased the expression of a group of MAP kinase phosphatases (MKPs) that deactivate ERK and JNK. The above results imply that downregulation of MAP kinase signaling by MKP induction is a key mechanism involved in the protective effects of PAR2 activation on caerulein-induced intrapancreatic damage.

A phase I study of full-dose gemcitabine and regional arterial infusion of nafamostat mesilate for advanced pancreatic cancer

BACKGROUND

The primary end points of this study were to determine the dose-limiting toxic effects (DLTs), maximum tolerated dose, and a recommended phase II dose of a synthetic serine protease inhibitor, nafamostat mesilate, in combination with full-dose gemcitabine in patients with unresectable locally advanced or metastatic pancreatic cancer. The secondary end point was to assess therapeutic response.

PATIENTS AND METHODS

Patients with previously untreated pancreatic cancer received gemcitabine (1 000 mg/m(2) i.v. for 30 min) on days 1, 8, and 15, with nafamostat mesilate (continuous regional arterial infusion for 24 h through a port-catheter system) on days 1, 8, and 15; this regimen was repeated at 28-day intervals. The initial dose of nafamostat mesilate was 2.4 mg/kg and was escalated in increments of 1.2 mg/kg until a dose of 4.8 mg/kg was achieved. A standard '3+3' phase I dose-escalation design was used. Therapeutic response and clinical benefit response were assessed.

RESULTS

Twelve patients were enrolled in this study. None of the patients experienced DLTs, and nafamostat mesilate was well tolerated at doses up to 4.8 mg/kg in combination with full-dose gemcitabine. This combination chemotherapy yielded a reduction of a high serum level of the tumor marker CA19-9. Pain was reduced in three of seven patients without oral morphine sulfate. Overall survival was 7.1 months for all patients.

CONCLUSION

This phase I study was carried out safely. This combination chemotherapy showed beneficial improvement in health-related quality of life. The recommended phase II dose of nafamostat mesilate in combination with full-dose gemcitabine is 4.8 mg/kg.

Proteinase-activated receptor 2 (PAR-2) in gastrointestinal and pancreatic pathophysiology, inflammation and neoplasia

Of all the body systems, the gastrointestinal (GI) tract is the most exposed to proteinases. Proteolytic activity must thus be tightly regulated in the face of diverse environmental challenges, because unrestrained or excessive proteolysis leads to pathological GI conditions. The protease-activated receptor-2 (PAR-2) is expressed in numerous cell types within the GI tract, suggesting both multiple functions and numerous modes of receptor activation. Although best known as a pancreatic digestive enzyme, trypsin has also been found in other tissues and various cancers. Of interest, trypsin and PAR-2 act together in an autocrine loop that promotes proliferation, invasion and metastasis in neoplasia through various mechanisms. Trypsin and PAR-2 seem to act both directly and indirectly through activation of other proteinase cascades, including metalloproteinases. PAR-2 activation can participate in inflammatory reactions, be protective to mucosal surfaces, send or inhibit nociceptive messages, modify gut motility or secretory functions, and stimulate cell proliferation and motility. Several studies point to a role for the PARs in disease processes of the GI tract and pancreas ranging from inflammatory bowel disease, symptoms associated with irritable bowel syndrome, pain in pancreatitis, development of colon and other GI cancers, and even infectious colitis. Proteinases should not only be considered from the traditional view as digestive or degradative enzymes in the gut, but additionally as signalling molecules that actively participate in the spectrum of physiology and diseased states of the GI tract.

A small interfering RNA targeting proteinase-activated receptor-2 is effective in suppression of tumor growth in a Panc1 xenograft model

Proteinase-activated receptor-2 (PAR-2), which is a G protein-coupled receptor, is activated in inflammatory processes and cell proliferation. We previously demonstrated that an anti-PAR-2 antibody suppresses proliferation of human pancreatic cells in vitro. However, there have been no studies of PAR-2 signaling pathways in vivo. The aim of this study was to determine whether blockade of PAR-2 by RNA interference influences pancreatic tumor growth. We originally constructed small interfering RNAs (siRNAs) targeting human PAR-2, and performed cell proliferation assays of Panc1 human pancreatic cancer cell line with these siRNAs. Intratumoral treatment with these PAR-2 siRNAs and atelocollagen was also performed in a xenograft model with nude mice and Panc1 cells. siRNAs against human PAR-2 inhibited proliferation of Panc1 cells, whereas control scramble siRNAs had no effect on proliferation. The PAR-2 siRNAs dramatically suppressed tumor growth in the xenograft model. PAR-2-specific siRNA inhibited growth of human pancreatic cancer cells both in vitro and in vivo. Blockade of PAR-2 signaling by siRNA may be a novel strategy to treat pancreatic cancer.

Role of PAR2 in murine pulmonary pseudomonal infection

Proteinases can influence lung inflammation by various mechanisms, including via cleavage and activation of protease-activated receptors (PAR) such as PAR2. In addition, proteinases such as neutrophil and/or Pseudomonas-derived elastase can disarm PAR2 resulting in loss of PAR2 signaling. Currently, the role of PAR2 in host defense against bacterial infection is not known. Using a murine model of acute Pseudomonas aeruginosa pneumonia, we examined differences in the pulmonary inflammatory response between wild-type and PAR2(-/-) mice. Compared with wild-type mice, PAR2(-/-) mice displayed more severe lung inflammation and injury in response to P. aeruginosa infection as indicated by higher bronchoalveolar lavage fluid neutrophil numbers, protein concentration, and TNF-alpha levels. By contrast, IFN-gamma levels were markedly reduced in PAR2(-/-) compared with wild-type mice. Importantly, clearance of P. aeruginosa was diminished in PAR2(-/-) mice. In vitro testing revealed that PAR2(-/-) neutrophils killed significantly less bacteria than wild-type murine neutrophils. Further, both neutrophils and macrophages from PAR2(-/-) mice displayed significantly reduced phagocytic efficiency compared with wild-type phagocytes. Stimulation of PAR2 on macrophages using a PAR2-activating peptide resulted in enhanced phagocytosis directly implicating PAR2 signaling in the phagocytic process. We conclude that genetic deletion of PAR2 is associated with decreased clearance of P. aeruginosa. Our data suggest that a deficiency in IFN-gamma production and impaired bacterial phagocytosis are two potential mechanisms responsible for this defect.

Gastrointestinal roles for proteinase-activated receptors in health and disease

It has been almost a decade since the molecular cloning of all four members of the proteinase-activated receptor (PAR) family was completed. This unique family of G protein-coupled receptors (GPCRs) mediates specific cellular actions of various endogenous proteinases including thrombin, trypsin, tryptase, etc. and also certain exogenous enzymes. Increasing evidence has been clarifying the emerging roles played by PARs in health and disease. PARs, particularly PAR1 and PAR2, are distributed throughout the gastrointestinal (GI) tract, modulating various GI functions. One of the most important GI functions of PARs is regulation of exocrine secretion in the salivary glands, pancreas and GI mucosal epithelium. PARs also modulate motility of GI smooth muscle, involving multiple mechanisms. PAR2 appears to play dual roles in pancreatitis and related pain, being pro-inflammatory/pro-nociceptive and anti-inflammatory/anti-nociceptive. Similarly, dual roles for PAR1 and PAR2 have been demonstrated in mucosal inflammation/damage throughout the GI tract. There is also fundamental and clinical evidence for involvement of PAR2 in colonic pain. PARs are thus considered key molecules in regulation of GI functions and targets for development of drugs for treatment of various GI diseases.

Suppression of pancreatitis-related allodynia/hyperalgesia by proteinase-activated receptor-2 in mice

1 Proteinase-activated receptor-2 (PAR2), a receptor activated by trypsin and tryptase, is abundantly expressed in the gastrointestinal tract including the C-fiber terminal, and might play a role in processing of visceral pain. In the present study, we examined and characterized the roles of PAR2 in pancreatitis-related abdominal hyperalgesia/allodynia in mice. 2 Caerulein, administered i.p. once, caused a small increase in abdominal sensitivity to stimulation with von Frey hairs, without causing pancreatitis, in PAR2-knockout (KO) mice, but not wild-type (WT) mice. 3 Caerulein, given hourly six times in total, caused more profound abdominal hyperalgesia/allodynia in PAR2-KO mice, as compared with WT mice, although no significant differences were detected in the severity of pancreatitis between the KO and WT animals. 4 The PAR2-activating peptide, 2-furoyl-LIGRL-NH(2), coadministered repeatedly with caerulein six times in total, abolished the caerulein-evoked abdominal hyperalgesia/allodynia in WT, but not PAR2-KO, mice. Repeated doses of 2-furoyl-LIGRL-NH(2) moderately attenuated the severity of caerulein-induced pancreatitis in WT animals. 5 Our data from experiments using PAR2-KO mice provide evidence that PAR2 functions to attenuate pancreatitis-related abdominal hyperalgesia/allodynia without affecting pancreatitis itself, although the PAR2AP applied exogenously is not only antinociceptive but also anti-inflammatory.

The proteinase inhibitor camostat mesilate suppresses pancreatic pain in rodents

Camostat mesilate, an orally available proteinase inhibitor, is clinically used for treatment of pancreatitis. Given recent evidence that pancreatic proteinases including trypsin and/or proteinase-activated receptor-2 (PAR2) might be involved in pancreatic pain, we examined if camostat mesilate could suppress spinal Fos expression, a marker for neuronal activation, following specific application of trypsin to the pancreas, and pancreatitis-related referred allodynia. Trypsin, administered into the pancreatic duct, caused delayed expression of Fos proteins in the superficial layer of the bilateral T8 and T9 spinal dorsal horns in rats. The trypsin-induced spinal Fos expression was completely abolished by oral pre-administration of camostat mesilate at 300 mg/kg. After hourly repeated (6 times in total) administration of caerulein, mice showed typical symptoms of pancreatitis, accompanied by mechanical allodynia in the upper abdomen (i.e., referred hyperalgesia/allodynia), as assessed by use of von Frey filaments. Camostat mesilate at 100-300 mg/kg, given orally twice before the 1st and 4th doses of caerulein, abolished the pancreatitis-related abdominal allodynia, while it partially prevented the inflammatory signs. The same doses of camostat mesilate, when administered once after the final dose of caerulein, also revealed significant anti-allodynic effect. These data suggest that camostat mesilate prevents and/or depresses pancreatitis-induced pain and/or referred hyperalgesia/allodynia, in which proteinases including trypsin would play a critical role.

New developments in the relationship between protease activated recerptor-2 and alimentary system diseases

Protease-activated receptor-2 (PAR-2) is a G-protein-coupled receptor, and its special molecule structure and activation way are similar to other protease-activated receptors. PAR-2 is widely distributed in alimentary system and series of effects are produced when it is activated by certain proteases. For example, PAR-2 exerts gastric mucosal cytoprotective effect, influences the secretion of digestive glands and movement of gastrointestinal tract, participates in the development of pancreatitis, and associates closely with malignant tumors in alimentary system. More and more researches are now focusing on the relationship between PAR-2 and alimentary system diseases.

A mouse model of hereditary pancreatitis generated by transgenic expression of R122H trypsinogen

BACKGROUND & AIMS

Missense mutations in human cationic trypsinogen PRSS1 are frequently detected in patients with hereditary pancreatitis, a rare genetic disease of the pancreas characterized by autodigestive necrosis, chronic inflammation, and fibrosis. To examine the link between PRSS1 mutations and the initiation and progression of hereditary pancreatitis, we have sought to generate a transgenic mouse that carries a missense mutation in the PRSS1 that is most frequently observed in patients.

METHODS

A transgenic mouse was generated in which the expression of the mouse PRSS1 mutant R122H (R122H_mPRSS1) is targeted to pancreatic acinar cells by fusion to the elastase promoter. The expression of the mutant trypsinogen was assessed by immunohistochemical staining and real-time reverse transcription polymerase chain reaction analysis. The relationship between transgene expression and inflammation was analyzed by morphologic assessment of H&E-stained tissue sections, responsiveness to cerulein-induced pancreatitis, and immunohistochemical identification of cellular and biochemical components of the inflammatory response.

RESULTS

Pancreata from transgenic mice display early-onset acinar cell injury and inflammatory cell infiltration. With progressing age, the transgenic mice develop pancreatic fibrosis and display acinar cell dedifferentiation. Moreover, the expression of R122H_mPRSS1 transgene is associated with enhanced response to cerulein-induced pancreatitis. Finally, cell-specific activation of the inflammation-associated signaling pathways, c-jun-N-terminal kinase and extracellular signal-regulated kinase, was observed in response to expression of R122H_mPRSS1.

CONCLUSIONS

These results underscore the importance of PRSS1 mutations as pathogenic mediators of hereditary pancreatitis and indicate that persistent pancreatic injury might be causally linked to chronic pancreatitis.

The role of trypsin, trypsin inhibitor, and trypsin receptor in the onset and aggravation of pancreatitis

Trypsin activity is properly suppressed in the pancreatic acinar cells under normal conditions. A small amount of trypsinogen is converted to active trypsin and inactivated by pancreatic secretory trypsin inhibitor (PSTI), thereby preventing damage to pancreatic acinar cells as a first line of defense. However, if trypsin activation (due to excessive stimulation of pancreatic acinar cells) exceeds the capacity of PSTI, a subsequent cascade of events leads to the activation of various proteases that damage cells. This can be interpreted as the main causative event of pancreatitis onset. Trypsin produced in and secreted from the pancreatic acinar cells activates protease activated receptor-2 (PAR-2), which is present at high densities on the luminal surfaces of pancreatic acinar cells and duct cells. Results of PAR-2 activation are the production of cytokines and the regulation of exocrine function via a negative feedback loop. Thus, the actions of trypsin, trypsin inhibitor (PSTI), and trypsin receptor (PAR-2) in the pancreas are strongly interconnected.

The Dose of Nafamostat Mesilate During Plasma Exchange With Continuous Hemodiafiltration in the Series-Parallel Circuit

We studied nafamostat mesilate (NM) and interleukin (IL)-18 levels to determine whether the dose of NM is reduced during plasma exchange (PE) with continuous hemodiafiltration (CHDF) when the series-parallel circuit is used. The subjects of the current study included four patients with acute hepatic failure who underwent PE with CHDF. The four patients underwent a total 15 PE + CHDF procedures, and for each procedure, they were randomized to receive either a half-dose of NM or no NM in the CHDF circuit. Eight procedures were carried out with NM administration, and seven were carried out without NM administration. The dose of NM in the NM group was significantly higher than that in the non-NM group (P = 0.040). No significant differences were observed between the two groups in the inlet NM concentration, the outlet NM concentration, or the rate of IL-18 removal. No statistical correlation was observed between the IL-18 level and the NM dose, the inlet NM concentration, or the outlet NM concentration. There was no blood access difficulty such as catheter failure or clotting of the filter. Thus, it might be possible to carry out PE and CHDF with the series-parallel method without administration of NM in the CHDF circuit.

Applicability of disseminated intravascular coagulation parameters in the assessment of the severity of acute pancreatitis

OBJECTIVES

To evaluate the clinical applicability of the determination of disseminated intravascular coagulation (DIC) parameters in acute pancreatitis.

METHODS

The subjects for this study were 139 consecutive patients with acute pancreatitis. DIC parameters were assessed at the initial observation of these patients.

RESULTS

The levels of the DIC parameters at admission were significantly associated with the severity and the prognosis of acute pancreatitis. Antithrombin III (AT-III), fibrin/fibrinogen degradation products-E, platelet count, D-dimer, and thrombin-AT-III complex at admission showed better area under the receiver operating characteristics curve values compared with C-reactive protein. An AT-III value of 69% at admission was the best cut-off value to predict fatal outcome (sensitivity, 81%; specificity, 86%).

CONCLUSIONS

The aggravated coagulation parameters predict a fatal outcome in patients with acute pancreatitis. AT-III level (<69%) was the most accurate marker for poor outcome of acute pancreatitis at admission.