The protective effects of long-acting recombinant human pancreatic secretory trypsin inhibitor (R44S-PSTI) in a rat model of cerulein-induced pancreatitis

Analysis of humoral immune response in experimental autoimmune pancreatitis in mice

OBJECTIVES

To study the autoimmune response in MRL/Mp mice, which spontaneously develop pancreatitis in the exocrine pancreatic tissue.

METHODS

Six-week-old female mice were injected intraperitoneally with polyinosinic polycytidylic acid at a dose of 5 mg/kg of body weight twice a week for up to 12 weeks. The mice were serially killed, and the severity of their pancreatitis was graded with a histological scoring system. Immunohistological examinations were performed, and the serum levels of autoantibodies were measured by enzyme-linked immunosorbent assay.

RESULTS

The administration of polyinosinic polycytidylic acid accelerated the development of pancreatitis, with abundant infiltration of B220 B cells and CD138 plasmacytes. Various autoantibodies directed against autoantigens, including carbonic anhydrase II and lactoferrin, were detected but none against glutamic acid decarboxylase. Of these, autoantibodies directed against the pancreatic secretory trypsin inhibitor (PSTI; 91.7%) were more prevalent than those against carbonic anhydrase II (33.3%) or lactoferrin (45.8%). Determination of the epitope of the anti-PSTI antibody showed that most immunoreactivity was directed at the site on PSTI that is active in the suppression of trypsin activity.

CONCLUSIONS

The autoimmune response to PSTI protein may induce a failure of PSTI activity, resulting in the activation of trypsinogen and the subsequent disease progression.

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.

Identification of a novel autoantibody against pancreatic secretory trypsin inhibitor in patients with autoimmune pancreatitis

OBJECTIVES

Although autoimmune pancreatitis (AIP) has been recently recognized as a new disease entity of chronic pancreatitis, the clinical diagnosis of the disease remains disputed. Autoantibodies against carbonic anhydrase II and lactoferrin are detected in most patients with AIP, but not in about 10%. We undertook this study to determine whether additional autoantibodies are present in the serum level of AIP patients.

METHODS

We recruited 26 patients with AIP for the study. For comparison, we also recruited 53 patients with various pancreatic diseases and 12 healthy subjects. We immunoscreened human pancreatic cDNA library using patients' sera. Positive clones were analyzed by DNA sequencing and were constructed into a pGEX-4T-1 expression vector. The recombinant proteins were used as antigens in enzyme-linked immunosorbent assay to screen the subjects' sera for autoantibodies.

RESULTS

We cloned a cDNA encoding the pancreatic secretory trypsin inhibitor (PSTI). Among 26 patients with AIP, autoantibodies against PSTI were significantly positive in 11 (42.3%) by western blotting and in 8 (30.8%) by enzyme-linked immunosorbent assay, respectively. However, none of control subjects was positive for anti-PSTI antibodies.

CONCLUSIONS

These findings suggest that PSTI may be related to the pathogenesis of AIP, and autoantibodies against PSTI can be a useful diagnostic marker for the disease.

Pancreatic secretory trypsin inhibitor (SPINK1) gene mutations in patients with acute pancreatitis

OBJECTIVES

Mutations in the secretory trypsin inhibitor (SPINK1) gene have been found to be associated with hereditary and chronic pancreatitis. There are no previous reports on SPINK1 mutations in patients with acute pancreatitis (AP).

METHODS

The study population consists of 371 patients with AP, of which 207 patients had mild and 164 had a severe form of the disease. The etiologies of AP were identified. Four hundred fifty-nine blood donors served as controls. SPINK1 N34S and P55S mutations were detected by minisequencing and confirmed by direct sequencing.

RESULTS

The N34S mutation was found in 29 (7.8%) of the patients and in 12 (2.6%) of the controls (P < 0.0001, Fisher exact test). There was no difference in the frequency of the P55SS mutation between the groups. A majority of the patients (n = 229; 61.7%) had alcohol-induced AP. The frequency of the N34S mutation was higher in the subgroups of severe AP (15/164; 9.1%) and alcohol-induced AP (21/229; 9.2%), but the differences were not statistically significant. No differences in age at admission and number of attacks of AP were observed between the groups.

CONCLUSION

SPINK1 N34S mutation enhances the susceptibility of AP.

Transgenic expression of pancreatic secretory trypsin inhibitor-I ameliorates secretagogue-induced pancreatitis in mice

BACKGROUND & AIMS

Endogenous trypsin inhibitors are believed to inhibit protease activity if trypsin becomes inadvertently activated within the acinar cell. However, this action remains unproven, and the role of endogenous pancreatic trypsin inhibitors in acute pancreatitis is unknown. In this study, we tested whether increased levels of pancreatic secretory trypsin inhibitor-I (PSTI-I) in mice could prevent secretagogue-induced pancreatitis.

METHODS

Rat PSTI-I expression was targeted to pancreatic acinar cells in transgenic mice by creating a minigene driven by the rat elastase I enhancer/promoter. Secretagogue-induced pancreatitis was achieved by 12 hourly intraperitoneal injections of caerulein. The severity of pancreatitis was assessed by measurements of serum amylase, histologic grading, and pancreas wet weight-to-body weight ratio. Trypsinogen activation and trypsin activity were measured in pancreatic extracts.

RESULTS

Targeted expression of PSTI-I to the pancreas increased endogenous trypsin inhibitor capacity by 190% (P <.01) in transgenic vs. nontransgenic mice. Caerulein administration to nontransgenic mice produced histologic evidence of acute pancreatitis, and significantly elevated serum amylase and pancreas weight ratio. In caerulein-treated transgenic mice, the histologic severity of pancreatitis was significantly reduced. There was no difference in trypsinogen activation peptide levels between caerulein-treated transgenic and nontransgenic mice. However, trypsin activity was significantly lower in transgenic mice receiving caerulein compared with nontransgenic mice.

CONCLUSIONS

These data demonstrate that the severity of secretagogue-induced pancreatitis is significantly ameliorated in mice with higher pancreatic levels of trypsin inhibitor. We propose that PSTI-I prevents pancreatitis by inhibiting the activity of trypsin, rather than by reducing trypsinogen activation.

Expression of proteinase-activated receptor 2 during taurocholate-induced acute pancreatic lesion development in Wistar rats

BACKGROUND

Proteinase-activated receptor 2 (PAR-2) is a G-protein coupled transmembrane receptor activated by trypsin by site-specific cleavage. Its presence on pancreatic structures was demonstrated in the past. PAR-2 physiologically involves in duct/acinary cells secretion, arterial tonus regulation or capillary liquid turnover. During development of acute pancreatitis/acute pancreatic lesion (APL) these mentioned structures are influenced by very high concentration of trypsin due to its increased basolateral secretion into the interstitium. The aim of our study as presented was to investigate whether PAR-2 is also involved in APL following changes of PAR-2 expression.

METHODS

APL was investigated in Wistar rats after injection of 0.1 mL taurocholate into the ductus choledochus. Anatomy, histology, reverse transcriptase polymerase chain reaction (RT PCR) as well as immunohistochemistry and Western-blot analysis of pancreatic tissue were performed using antibody mapping of the new NH2 terminal of PAR-2 after trypsin cleavage. Results from control rats and d 1 or d 4 rats after taurocholate injection were compared.

RESULTS

Much higher positivity on acinary/duct cells was observed in APL induced animals than in controls. Similar findings were noticed on arterial smooth muscle cells. Surprisingly, parallel to the exocrine pancreas and vessel findings, enhanced Langerhans' islet cell positivity was observed in experimental animals.

CONCLUSIONS

Based on these results, we have demonstrated that during APL development PAR-2 expression increases. This effect is caused by conformational changes after PAR-2 activation, and the new NH2 terminal of activated receptor presentation. We suggest that PAR-2 physiological functions are enhanced during APL development.

Expression of proteinase-activated receptor 2 during taurocholate-induced acute pancreatic lesion development in Wistar rats

BACKGROUND

Proteinase-activated receptor 2 (PAR-2) is a G-protein coupled transmembrane receptor activated by trypsin by site-specific cleavage. Its presence on pancreatic structures was demonstrated in the past. PAR-2 physiologically involves in duct/acinary cells secretion, arterial tonus regulation or capillary liquid turnover. During development of acute pancreatitis/acute pancreatic lesion (APL) these mentioned structures are influenced by very high concentration of trypsin due to its increased basolateral secretion into the interstitium. The aim of our study as presented was to investigate whether PAR-2 is also involved in APL following changes of PAR-2 expression.

METHODS

APL was investigated in Wistar rats after injection of 0.1 mL taurocholate into the ductus choledochus. Anatomy, histology, reverse transcriptase polymerase chain reaction (RT PCR) as well as immunohistochemistry and Western-blot analysis of pancreatic tissue were performed using antibody mapping of the new NH2 terminal of PAR-2 after trypsin cleavage. Results from control rats and d 1 or d 4 rats after taurocholate injection were compared.

RESULTS

Much higher positivity on acinary/duct cells was observed in APL induced animals than in controls. Similar findings were noticed on arterial smooth muscle cells. Surprisingly, parallel to the exocrine pancreas and vessel findings, enhanced Langerhans' islet cell positivity was observed in experimental animals.

CONCLUSIONS

Based on these results, we have demonstrated that during APL development PAR-2 expression increases. This effect is caused by conformational changes after PAR-2 activation, and the new NH2 terminal of activated receptor presentation. We suggest that PAR-2 physiological functions are enhanced during APL development.

Increased secretion of the pancreatic secretory trypsin inhibitor (PSTI-I, monitor peptide) during development of chronic pancreatitis in the WBN/Kob rat

BACKGROUND

Recent genetic investigations into cationic trypsinogen and pancreatic secretory trypsin inhibitor (PSTI) led to the conclusion that mutations in either gene can contribute to the development of (hereditary) chronic pancreatitis. Since genetic animal models are not available yet, we have studied the Wistar-Bonn/Kobori (WBN/Kob) rat, a model for chronic pancreatitis (CP). To explore the possibility that PSTI may be secreted at lower levels or contain a mutation in the WBN/Kob rat, we investigated the masses of PSTI-I and -II and asked whether the ratio of PSTI/trypsinogen is decreased in animals with CP.

METHODS

We collected pancreatic juice from WBN/Kob and Wistar rats aged 6-36 weeks and measured PSTI-I (ELISA) and trypsin.

RESULTS

PSTI-I and -II were identified in Wistar and WBN/Kob rats by mass spectrometry and N-terminal sequencing. Using a newly developed PSTI-I ELISA, we can show that the PSTI-I/trypsinogen ratio is not decreased but rather increased in WBN/Kob rats compared to healthy Wistar rats. No evidence for a PSTI mutation was found.

CONCLUSION

Our data does not support the hypothesis that a dysbalance of PSTI/trypsinogen ratio is a causative factor for CP.

Predicting the reactivity of proteins from their sequence alone: Kazal family of protein inhibitors of serine proteinases

An additivity-based sequence to reactivity algorithm for the interaction of members of the Kazal family of protein inhibitors with six selected serine proteinases is described. Ten consensus variable contact positions in the inhibitor were identified, and the 19 possible variants at each of these positions were expressed. The free energies of interaction of these variants and the wild type were measured. For an additive system, this data set allows for the calculation of all possible sequences, subject to some restrictions. The algorithm was extensively tested. It is exceptionally fast so that all possible sequences can be predicted. The strongest, the most specific possible, and the least specific inhibitors were designed, and an evolutionary problem was solved.

Predicting the reactivity of proteins from their sequence alone: Kazal family of protein inhibitors of serine proteinases

An additivity-based sequence to reactivity algorithm for the interaction of members of the Kazal family of protein inhibitors with six selected serine proteinases is described. Ten consensus variable contact positions in the inhibitor were identified, and the 19 possible variants at each of these positions were expressed. The free energies of interaction of these variants and the wild type were measured. For an additive system, this data set allows for the calculation of all possible sequences, subject to some restrictions. The algorithm was extensively tested. It is exceptionally fast so that all possible sequences can be predicted. The strongest, the most specific possible, and the least specific inhibitors were designed, and an evolutionary problem was solved.

Base variant of human pancreatic secretory trypsin inhibitor in healing of stress-induced gastric lesions in rats

Pancreatic secretory trypsin inhibitor (PSTI) is an inhibitor of serine-proteinases including pancreatic trypsin that prevents excessive digestion of the gastrointestinal mucus, but its role in the mechanism of mucosal defense has been little studied. This study was designed to determine the effect of base variant of human PSTI (R44S-PSTI) on gastric secretion, healing of gastric lesions induced by stress and the expression of PSTI during mucosal recovery from stress lesions. Recombinant R44S-PSTI was obtained using by site-directed mutagenesis due to replacement of arginine by serine that led to longer half life of this peptide than its natural form. Stress ulcerations were induced by exposure of rats to a standard 3.5 h of water immersion and restraint stress with or without pretreatment with vehicle or R44S-PSTI (0.1 mg/kg) applied s.c. 30 min before and immediately after the end of stress. Rats were then sacrificed immediately (time 0) and at 6 h or 12 h after the termination of stress. The gastric blood flow (GBF) was measured by H2-gas clearance technique at each time period and gastric mucosal samples were excised for assessment of PSTI immunohistochemical expression and PSTI messenger RNA by reverse transcriptase polymerase chain reaction (RT-PCR) and Southern hybridization. Stress produced numerous gastric lesions and decreased the GBF by about 30% as compared to the respective value in vehicle-treated non-stressed gastric mucosa. R44S-PSTI given s.c. in graded doses (0.01-1 mg/kg) inhibited dose-dependently gastric acid and pepsin outputs, in rats with gastric fistula and accelerated the healing of stress-induced gastric lesions significantly. The healing effects of R44S-PSTI (0.1 mg/kg s.c.) recorded at 6 h and 12 h after the end of stress were accompanied by a significant rise in the GBF. The expression of PSTI mRNA in the intact mucosa was weak, but following exposure to stress it was significantly augmented to reach the highest observed value at 6 h after the stress. We conclude that (1) base variant of human PSTI accelerates healing of stress-induced gastric lesions probably due to its antisecretory activity and enhancement of mucosal blood flow and (2) the expression of genes for PSTI plays an important role in the mechanism of mucosal recovery from gastric lesions induced by stress.