Local administration of human pancreatic secretory trypsin inhibitor prevents the development of experimental acute pancreatitis in rats and dogs

Hepatic steatosis depresses alpha-1-antitrypsin levels in human and rat acute pancreatitis

Hepatic steatosis (HS) can exacerbate acute pancreatitis (AP). This study aimed to investigate the relation between α1-antitrypsin (AAT) and acute pancreatitis when patients have HS. Using proteomic profiling, we identified 18 differently expressed proteins pots in the serum of rats with or without HS after surgical establishment of AP. AAT was found to be one of the significantly down-regulated proteins. AAT levels were significantly lower in hepatic steatosis acute pancreatitis (HSAP) than in non-HSAP (NHSAP) (P < 0.001). To explore the clinical significance of these observations, we measured the levels of AAT in the serum of 240 patients with HSAP, NHSAP, fatty liver disease (FLD), or no disease. Compared with healthy controls, serum AAT levels in patients with NHSAP were significantly higher (P < 0.01), while in patients with HSAP serum AAT levels were significantly lower (P < 0.01). Further studies showed that acute physiology and chronic health evaluation (APACHE-II) scores were negatively correlated with serum AAT levels (r = −0.85, P < 0.01). In conclusion, low serum levels of AAT in patients with HSAP are correlated with disease severity and AAT may represent a potential target for therapies aiming to improve 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 thalidomide in experimental models of post-endoscopic retrograde cholangiopancreatography pancreatitis

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) plays a central role in the pathogenesis of acute pancreatitis and related systemic complications. The authors hypothesized that it may also play an important role in the development of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP). The aim of the study was to evaluate the effectiveness of thalidomide, an immunomodulator that exerts an inhibitory action on TNF-alpha by enhancing mRNA degradation, in reducing post-ERCP pancreatitis in a rat model.

METHODS

A total of 200 mg/kg thalidomide was given intragastric once a day (total 8 days) before the experimental models of post-ERCP pancreatitis were established. After 24 h, histology and edema of pancreas, serum amylase, and TNF-alpha mRNA in the pancreatic tissue were evaluated.

RESULTS

Intraductal contrast infusion caused increases in serum amylase, edema, histological grade, and TNF-alpha mRNA of pancreas. The prophylactic use of thalidomide significantly reduced serum amylase, pancreatic edema and the histologic grade of pancreatitis accompanied by a decrease in mRNA expression of TNF-alpha in the pancreatic tissue.

CONCLUSIONS

Prophylactic intragastric administration of thalidomide provides a protective effect in post-ERCP pancreatitis. The mechanism of the protective effects of thalidomide seems to be the reduction of expression of TNF-alpha mRNA in pancreatic tissue.

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.

Pancreas graft thrombosis: is there a role for trypsin

PURPOSE

Thrombosis of the pancreas graft is the main cause of early graft loss in pancreas transplantation. We investigated whether hypercoagulability develops locally in the pancreas and contributes to thrombosis formation because of ischemia or reperfusion injury. It was further hypothesized that this might be induced by excessive intravascular trypsin activity.

METHODS

Ten Patients undergoing pancreas transplantation were studied. In addition to the standard operation a 14 French catheter was inserted in the distal part of the splenic vein of the pancreas graft. After reperfusion blood samples were drawn simultaneously from the splenic vein of the pancreas graft (local samples) and the radial artery (systemic samples) at 0,1,2,5,10,30, and 60 minutes after reperfusion.

RESULTS

After reperfusion a progressive hypercoagulability developed locally in the pancreas as seen by an increase of thrombin-antithrombin complexes and only a transient increase of plasmin-antiplasmin complexes. In addition antithrombin 3 and protein c decreased systemically. The alterations seem not to be triggered by trypsin because trypsin activity locally remained low despite trypsinogen release and activation as assessed by trypsinogen activation peptides.

CONCLUSION

Local hypercoagulability might contribute to the development of graft thrombosis, however, the mechanism seems not to be related to ectopic trypsin activation.

Intraductal administration of an NK1 receptor antagonist attenuates the inflammatory response to retrograde infusion of radiological contrast in rats: implications for the pathogenesis and prevention of ERCP-induced pancreatitis

INTRODUCTION

The neurogenic inflammatory mediator, substance P (SP), has been implicated in the pathogenesis of acute secretagogue-induced pancreatitis. We hypothesized that it may also play an important role in the development of acute pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP). AIMS Our aim was to evaluate the effectiveness of CP-96345, a NK1 receptor antagonist, in diminishing post-ERCP pancreatitis in a rat model.

METHODS

The effects of CP-96345, when mixed with the contrast agent, were studied in a rat model of pancreatitis caused by retrograde contrast infusion. After 24 hours, histology, edema, and myeloperoxidase activity (MPO) of pancreas, plasma amylase, and NK1 receptor endocytosis in pancreatic acinar cells were evaluated.

RESULTS

Intraductal contrast infusion caused increases in plasma amylase, edema, histologic grade, and MPO of pancreas, and NK1 receptor internalization in pancreatic acinar cells. The addition of CP-96345 to the infusate significantly reduced pancreatic edema, MPO activity, and the histologic grade of pancreatitis accompanied by a decrease in NK1 receptor internalization.

CONCLUSIONS

When an NK1 receptor antagonist is delivered along with the contrast media there is significant reduction in the pancreatic inflammation caused by intraductal contrast infusion. These results provide some insight into the pathogenesis of ERCP induced pancreatitis as well as present novel pharmacological targets for its prevention.

Randomized, placebo-controlled trial of lazaroid effects on severe acute pancreatitis in rats

OBJECTIVES

To evaluate the therapeutic potential of lazaroids in severe necrotizing acute pancreatitis and to investigate the association between oxidative stress, protease activation, and local production of proinflammatory cytokines and the severity and lethality of the disease.

BACKGROUND

Oxidative stress is a crucial factor in the pathophysiology of acute pancreatitis and its systemic complications. Treatment with antioxidants, however, failed to improve survival in most studies performed so far. Lazaroids are a novel class of antioxidants that potently protect pancreatic acinar cells against oxidant attack in vitro.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

University research laboratory.

SUBJECTS

Seventy-five anesthetized male Wistar rats (300-350 g).

INTERVENTIONS

Severe acute pancreatitis was induced by retrograde injection of 3.5% taurocholate-sodium into the common bile-pancreatic duct. Interventions were performed to mimic the clinical situation, including continuous intravenous fluid substitution and administration of lazaroids in a therapeutic protocol. Therapy was started 1 hr after injection of the bile salt by using three different lazaroids, lactated Ringer's solution (placebo), and methylprednisolone as a corticosteroid control (n = 15 in each group). All the substances were given by continuous intravenous infusion throughout the 20-hr trial period.

MEASUREMENTS AND MAIN RESULTS

Pancreatic homogenates and ascites were analyzed for indicators of oxidative stress, antioxidants, proteases, and proinflammatory cytokines. Pancreatic edema, morphologic pancreatitis severity, and pancreatic histopathology also were assessed. All three lazaroids and methylprednisolone diminished pancreatic tumor necrosis factor-alpha concentrations. Lethality was 33% in the placebo group. Neither the lazaroids nor methylprednisolone influenced survival. The local pancreatic and peritoneal concentrations of lipid peroxidation products, antioxidants, and proteases did not differ among the five groups. Nonsurviving rats, however, had a higher total protease activity in the pancreas and higher concentrations of trypsinogen activation peptide in ascites, as compared with surviving animals. There were no differences between survivors and nonsurvivors with regard to variables of oxidative stress and cytokines.

CONCLUSIONS

Lazaroid application under clinically relevant conditions (i.e., after induction of fulminant acute pancreatitis) does not influence lethality or biochemical variables relevant to this disease. Protease activation rather than oxidative stress or local pancreatic cytokine production is an important determinant of disease severity and survival in acute pancreatitis. In experimental studies evaluating novel therapeutics, the same strict criteria should be applied as in the human setting.

Proteases and protease inhibitors in cerulein-induced acute pancreatitis in rats

BACKGROUND

Proteases and protease inhibitors are important in acute pancreatitis (AP), although little is known about the time course in cerulein-induced AP in the rat.

MATERIALS AND METHODS

AP was induced by supramaximal stimulation of cerulein, 10 microgram/kg/h, and during 72 h we measured lipase, amylase, albumin, prekallikrein, factor X, alpha(1)-protease inhibitor, alpha(1)-macroglobulin, alpha(2)-antiplasmin, antithrombin III (all in plasma) and macroscopic and histologic variables.

RESULTS

Within 12 h an edematous pancreatitis was evident with peak values of peritoneal exudate, pancreatic wet weight ratio, and plasma amylase and lipase activities. Histologically, edema and vacuolization were prominent already after 3 and 6 h, respectively, while inflammation, necrosis, and total histological score gradually increase to reach peak levels at 48 h. Proenzymes and most plasma protease inhibitors decreased to low levels after 6-12 h followed by a gradual increase. The sequential changes over time indicate that kallikrein - kinin activation, and plasminogen activation are probably early events in cerulein-induced AP in rats. alpha(1)-Macroglobulin and alpha(1)-protease inhibitor gradually decreased during the whole study period, probably being "second line" defense inhibitors. Levels above normal were seen for alpha(2)-antiplasmin and factor X at 48 h, normalizing at 72 h.

CONCLUSIONS

These results suggest that protease activation and protease inhibitor consumption occur in cerulein-induced AP in the rat.

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

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

Intrapancreatic turnover of recombinant human pancreatic secretory trypsin inhibitor in experimental porcine pancreatitis

Experimental porcine pancreatitis was induced by the injection of taurocholate into the pancreatic duct. Recombinant human pancreatic secretory trypsin inhibitor (25 mg) was administered to each animal in one of three different ways: into the pancreatic duct (n = 5), into the abdominal cavity adjacent to the pancreas (n = 2) or intravenously (n = 2). The intrapancreatic turnover was assessed during 6 h using a microdialysis technique. The intraglandular concentration, measured by enzyme-linked immunosorbent assay, was highest after injection of rhPSTI into the pancreatic duct and substantially lower after intravenous and intraperitoneal administration. The intrapancreatic half-life of the inhibitor after intraductal administration was considerably longer (3-6 times) in pigs with pancreatitis than has previously been found in the normal gland. These facts argue in favour of the intraductal administration route in future trials of antiprotease treatment in acute pancreatitis.

Nonesterified fatty acids in acute cerulein-induced pancreatitis in the rat. Are they really deleterious in vivo?

During acute pancreatitis, experimental data obtained in vitro suggested that pancreatic lipase generates nonesterified fatty acids (NEFA), noxious for acinar cells, by hydrolysis of pancreatic or circulating triglycerides. The purpose of this work was to determine whether experimentally induced high plasma NEFA levels do indeed aggravate in vivo cerulein-induced pancreatitis. Anesthetized Sprague-Dawley rats received cerulein and were simultaneously infused intravenously with either saline or a triglyceride + heparin mixture (TGH) in order to increase the amount of circulating NEFA. Plasma NEFA increased about fourfold (3.02 +/- 0.28 mumol/liter) in animals infused with TGH with respect to controls (0.75 +/- 0.05 mumol/liter). In rats receiving cerulein + TGH, pancreatic enzyme levels in plasma, ascites, and histological alterations of the pancreas did not differ from those observed in the rats receiving cerulein + saline. There was less macroscopic pancreatic edema (P < 0.01) in the cerulein + TGH group than in the cerulein + saline group. Separate infusion of either heparin alone or of triglycerides alone had no effect. We conclude that high levels of circulating NEFA do not aggravate cerulein pancreatitis in rats and may even induce a protective effect.

Prevention of trypsin-induced shock in rats by the pancreatic secretory trypsin inhibitor

Intravenously infused bovine trypsin, 75 mg kg-1 during 3 h, induced shock in rats which proved lethal. After 5 h, all the rats had died. In another group of rats receiving trypsin, the pancreatic secretory trypsin inhibitor, 75 mg kg-1, was infused during 5 h. These rats all survived. After about 1 h, alpha 1-macroglobulin was found to be saturated in both groups, while kininogen cleavage, coinciding with a decline in arterial blood pressure, only occurred in the untreated group. Trypsin complex formation with alpha 1-inhibitor 3 and alpha 1-proteinase inhibitor was more pronounced in untreated rats. It is concluded that the pancreatic secretory trypsin inhibitor may function as an effective trypsin inhibitor in plasma.

High-dose intraperitoneal aprotinin treatment of acute severe pancreatitis: a double-blind randomized multi-center trial

A multi-center double-blind trial was performed on 48 patients with severe acute pancreatitis. All patients were treated with intraperitoneal lavage. One group (n = 22) was also treated with high doses of the protease inhibitor, aprotinin (Trasylol; Bayer AG, Leverkusen, Germany) administered intraperitoneally. Eight patients died, giving a total mortality of 16.6%. No difference was observed between the two groups. Altogether, 12 patients were operated on, corresponding to 25%. In the group not treated with aprotinin, 6 patients were operated on because of pancreatic necrosis, compared with none in the treated group. The difference was statistically significant. There were no significant differences between the two groups with regard to organ failure or other complications. It was concluded that aprotinin counteracts the development of pancreatic necrosis when given intraperitoneally in high doses to patients with severe acute pancreatitis, thus reducing the need for surgical intervention in these patients.

Human pancreatic proenzymes are activated at different rates in vitro

The rates of activation of procolipase, prophospholipase (proPLA2), chymotrypsinogen, and trypsinogen were studied after incubation of human pancreatic juice with porcine enterokinase in vitro. Under the conditions chosen procolipase was fully activated within 10 min of incubation. Full activation of phospholipase (PLA2) was seen within 15 min, whereas complete activation of chymotrypsin and trypsin was not seen until after 30 to 60 min, respectively. The different proenzymes probably differ in their suitability as substrates for trypsin. A physiologic consequence of a differentiated activation of the pancreatic proenzymes in vivo could be a delayed proteolytic degradation of the lipolytic enzymes in the intestine.

Absence of trypsinogen autoactivation and immunolocalization of pancreatic secretory trypsin inhibitor in acinar cells in vitro

To establish the significance of the addition of trypsin inhibitors to pancreatic acinar cells maintained in vitro, cells were cultured in the presence or absence of soybean trypsin inhibitor. Both cultures exhibited similar growth pattern, ultrastructural appearance, as well as secretory properties. Moreover, there was no evidence of trypsinogen activation in the culture medium. Using the immunocytochemical approach, pancreatic secretory trypsin inhibitor antigenic sites were revealed with specific polyclonal and monoclonal antibodies. The results obtained demonstrated that this trypsin inhibitor is in fact a typical pancreatic secretory protein being processed through the endoplasmic reticulum-Golgi-granule secretory pathway of the acinar cells in rat and human tissues. While the polyclonal antibody yield labelings of increasing intensities along the secretory pathway, the monoclonal one probably due to the molecular nature of its specific antigenic determinant, gave higher labelings in the endoplasmic reticulum. In conclusion the present study has shown that pancreatic acinar cells secrete a specific pancreatic trypsin inhibitor which most probably is involved in the mechanism to prevent trypsinogen activation.

Influence of plasma proteinase inhibitors and the secretory leucocyte proteinase inhibitor on pancreatic elastase-induced degradation of some plasma proteins

Pancreatic elastase-induced degradation of some plasma proteins was studied in an in vitro model. The digestion was correlated with the degree of saturation of the alpha 1-proteinase inhibitor (alpha 1PI) and also with varying amounts of secretory leucocyte proteinase inhibitor (SLPI). SLPI was found to inhibit pancreatic elastase showing a Ki of about 10(-7) M for the complex. On the addition of human pancreatic elastase to plasma cleavage of C3, kininogen, fibrinogen and fibronectin was observed when the alpha 1PI approached saturation. In the present in vitro model it was possible to block the cleavage of the four plasma proteins, mentioned above completely with SLPI. Addition of the inhibitor also decreased the consumption of alpha 1PI.

Release of immunoreactive canine leukocyte elastase normally and in endotoxin and pancreatitic shock

A specific ELISA has been developed for the determination of alpha 1-proteinase inhibitor-bound leukocyte elastase in canine plasma and tissue fluids. Comparison of the sequence of the first 16 N-terminal amino acids of the isolated canine leukocyte elastase to other elastases indicated moderate homology with porcine pancreatic elastase and pronounced identity with human leukocyte elastase. Normal canine plasma contains about 66 micrograms/l leukocyte elastase measured as elastase alpha 1-proteinases inhibitor complexes. This represents about 70% of the total amount of leukocyte elastase released in plasma. The remaining 30% is bound by alpha 1 alpha 2-macroglobulin. Blood coagulation leads to a rapid release of elastase from the leukocytes. Slow intravenous infusion of a lethal dose of endotoxin into dogs is followed by a marked drop in leukocyte count and a simultaneous rapid increase in plasma leukocyte elastase concentration reaching a plateau level of 2-3 mg/l plasma. Bile-induced pancreatitis in dogs is accompanied by successive increases in leukocyte elastase levels in plasma as well as in peritoneal exudates, reaching a level of about 15 mg/l in the exudates during the late stages of disease.