Effect of a new synthetic trypsin inhibitor on taurocholate-induced acute pancreatitis in rats

Recent advances on plasmin inhibitors for the treatment of fibrinolysis-related disorders

Growing evidence suggests that plasmin is involved in a number of physiological processes in addition to its key role in fibrin cleavage. Plasmin inhibition is critical in preventing adverse consequences arising from plasmin overactivity, e.g., blood loss that may follow cardiac surgery. Aprotinin was widely used as an antifibrinolytic drug before its discontinuation in 2008. Tranexamic acid and ε-aminocaproic acid, two small molecule plasmin inhibitors, are currently used in the clinic. Several molecules have been designed utilizing covalent, but reversible, chemistry relying on reactive cyclohexanones, nitrile warheads, and reactive aldehyde peptidomimetics. Other major classes of plasmin inhibitors include the cyclic peptidomimetics and polypeptides of the Kunitz and Kazal-type. Allosteric inhibitors of plasmin have also been designed including small molecule lysine analogs that bind to plasmin's kringle domain(s) and sulfated glycosaminoglycan mimetics that bind to plasmin's catalytic domain. Plasmin inhibitors have also been explored for resolving other disease states including cell metastasis, cell proliferation, angiogenesis, and embryo implantation. This review highlights functional and structural aspects of plasmin inhibitors with the goal of advancing their design.

Selected biochemical parameters and ultrastructural picture of pancreas due to Ulinastatin treatment of experimental acute pancreatitis

Urinary trypsin inhibitor (UTI, Ulinastatin) is a protease inhibitor that has not been yet used in Europe in any experimental trial of severe acute pancreatitis. We have combined the experimental model of severe, hemorrhagic form of acute pancreatitis, and pharmacological treatment with a protease inhibitor. Male Wistar rats were divided into four experimental groups: healthy controls, operated, operated with experimentally induced acute pancreatitis, and animals with acute pancreatitis--treated with UTI preparations. Subjects in the last group were administered UTI intraperitoneally 1 h after pancreatitis induction in an average standard dose of 3000 units/animal. Additionally, four subgroups were created in this treated group, based on the UTI administration time--number of standard doses received: 2 h - 1 standard dose, 6 h - 5 standard doses, 12 h - 11 doses, 24 and 48 h - 15 doses. Statistically significant differences in the serum amylase and lipase activity between the UTI-treated and non-treated subjects were found. In the group of non-treated animals, there a profound destruction of cellular organelles was observed with a total degradation of nuceli, endoplasmatic reticulum and zymogen granules. However, in the UTI-treated subjects, pathological processes proceeded with the significantly slower pace and in much smaller quantities.

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.

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.

CCK independently activates intracellular trypsinogen and NF-kappaB in rat pancreatic acinar cells

In the cholecystokinin (CCK) hyperstimulation model of acute pancreatitis, two early intracellular events, activation of trypsinogen and activation of nuclear factor-kappaB (NF-kappaB), are thought to be important in the development of the disease. In this study, the relationship between these two events was investigated. NF-kappaB activity was monitored by using a DNA binding assay and mob-1 chemokine gene expression. Intracellular trypsin activity was measured by using a fluorogenic substrate. Protease inhibitors including FUT-175, Pefabloc, and E-64d prevented CCK stimulation of intracellular trypsinogen and NF-kappaB activation. Likewise, the NF-kappaB inhibitors pyrrolidine dithiocarbamate and N-acetyl-L-cysteine inhibited CCK stimulation of NF-kappaB and intracellular trypsinogen activation. These results suggested a possible codependency of these two events. However, CCK stimulated NF-kappaB activation in Chinese hamster ovary-CCK(A) cells, which do not express trypsinogen, indicating that trypsin is not necessary for CCK activation of NF-kappaB. Furthermore, adenovirus-mediated expression in acinar cells of active p65 subunits to stimulate NF-kappaB, or of inhibitory kappaB-alpha molecules to inhibit NF-kappaB, did not affect either basal or CCK-mediated trypsinogen activation. Thus trypsinogen and NF-kappaB activation are independent events stimulated by CCK.

Urinary excretion of trypsinogen activation peptide (TAP) in taurocholate-induced pancreatitis in rats

Trypsinogen activation peptide (TAP) is a useful marker of severe acute pancreatitis. However, it is sometimes difficult to detect an elevation of plasma TAP in patients with acute pancreatitis because TAP is rapidly cleared from plasma. Therefore, urine TAP has been evaluated to provide an accurate prediction of the outcome of pancreatitis. In the present study, we examined the time course of plasma and urine TAP simultaneously after induction of taurocholate-induced pancreatitis in rats. Plasma TAP levels peaked at 1 hour after the induction of pancreatitis and then gradually decreased, but was still higher than prepancreatitis levels at 48 hours. Significant increases in urine TAP levels were seen at 0-6, 6-12, and 30-36 hours after induction of pancreatitis. The peak level of urine TAP output and TAP/creatinine ratio was observed at 6-12 and 30-36 hours, respectively. Urine TAP concentration showed a significant correlation with both urine TAP/creatinine ratio and TAP output in urine (p < 0.01). In conclusion, plasma TAP increased immediately after the induction of pancreatitis, but excretion of TAP into urine was delayed several hours in taurocholate-induced pancreatitis in rats. The measurement of urine TAP concentration alone sufficiently can reflect the amount of TAP liberated in the pancreas at initial stage of acute pancreatitis.

Long-term effects of nafamostat and imipenem on experimental acute pancreatitis in rats

Long-term effects of nafamostat mesylate, a protease inhibitor, and imipenem, an antibiotic, on trypsintaurocholate-induced acute pancreatitis were studied in rats. Sham-operated rats infused with a buffer solution into the pancreatic duct served as controls. Nafamostat (1 mg/kg), imipenem (10 mg/kg), or imipenem + nafamostat in saline was injected subcutaneously 0.25, 3, 24, and 48 hours after the induction of pancreatitis. In untreated rats and control rats, saline was injected at the same intervals as in the treated rats. All rats in an untreated group died within 3.5 days (median survival, 1.25 day) after the induction of pancreatitis. The 2-week survival rate was significantly (p < 0.05) improved by a combination of nafamostat and imipenem (42%), but not by nafamostat (17%), or imipenem (8%) alone. Bacterial culture at 24 hours revealed infection of necrotic pancreatic tissues and ascites by intestinal bacteria in all untreated rats but not in control rats. Bacterial counts were significantly reduced by imipenem, but not by nafamostat. In conclusion, bacterial infection occurred within 24 hours after the induction of trypsintaurocholate pancreatitis in rats. Early treatment with nafamostat + imipenem, but not nafamostat or imipenem alone, improves long-term survival.

Do plasma and urine trypsinogen activation peptides (TAP) really increase in trypsin-taurocholate-induced pancreatitis?

Plasma and urine levels of trypsinogen activation peptides (TAP) reflect the severity of acute pancreatitis in experimental and clinical acute pancreatitis. In trypsin-taurocholate-induced pancreatitis in rats, the extrinsic bovine trypsin used for the induction of pancreatitis might influence on the TAP levels after induction of pancreatitis. The aim of the present study was to elucidate whether infused trypsin itself affects TAP levels in trypsin-taurocholate-induced pancreatitis. Rats were divided into three groups. In the pancreatitis group, acute pancreatitis was induced by a retrograde infusion of bovine trypsin and sodium taurocholate into the pancreatic duct. In the duct infusion group and peritoneal injection group, a mixture of bovine trypsin and trypsin inhibitor, ONO-3403, was infused into the pancreatic duct or the peritoneal cavity. Plasma and urine TAP concentration significantly increased in trypsin-taurocholate-induced pancreatitis but not in the duct infusion and peritoneal injection groups for 6 hours after the infusion of trypsin. Serum rat immunoreactive trypsin (IRT) and amylase significantly increased in the pancreatitis and duct infusion groups but not in the peritoneal injection group. Serum levels of bovine IRT in the pancreatitis group was significantly lower than those in duct infusion and peritoneal injection groups. In conclusion, an intraductal infusion of bovine trypsin itself into pancreatic duct does not influence the levels of plasma and urine TAP in trypsin-taurocholate-induced pancreatitis.

Relationship of plasma CCK to acinar cell regeneration in acute pancreatitis as studied by proliferating cell nuclear antigen

In order to elucidate the relationship of cholecystokinin to acinar cell regeneration, the current study examined the changes in plasma cholecystokinin and immunostaining of proliferating cell nuclear antigen in the pancreas of rats with acute necrotizing pancreatitis. Proliferating cell nuclear antigen immunohistochemistry has been used to examine the proliferation of cells in several types of tissues. We compared the usefulness of proliferating cell nuclear antigen immunostaining and the incorporation of 5-bromodeoxyuridine to demonstrate acinar cell proliferation in the pancreas of rats with acute necrotizing pancreatitis. We also examined the relationship between these labeling indices and plasma cholecystokinin concentrations. The labeling index of paraformaldehyde-fixed specimens stained with proliferating cell nuclear antigen showed biphasic peaks at 12 hr and day 7. On the other hand, the methanol-fixed specimens stained with proliferating cell nuclear antigen and specimens stained with bromodeoxyuridine showed monophasic peaks in their labeling indices on day 5. There was a linear correlation (r = 0.808, P < 0.001) between the labeling index of bromodeoxyuridine and that of methanol-fixed proliferating cell nuclear antigen during the entire experimental period. During the regenerating phase, plasma cholecystokinin bioactivity showed positive correlations with the labeling index of bromodeoxyuridine and that of methanol-fixed proliferating cell nuclear antigen, r = 0.555 and 0.566, respectively (P < 0.001). Immunostaining of methanol-fixed proliferating cell nuclear antigen may be a useful tool for analyzing proliferating acinar cells. Acinar cell proliferation correlates with the bioactivity of plasma cholecystokinin during the regenerating phase of acute pancreatitis.

Serum alpha 2-macroglobulin-trypsin complex and early recognition of severe acute pancreatitis after endoscopic retrograde pancreatography

Serum alpha 2-macroglobulin-trypsin complex (alpha 2M-T) was measured to differentiate the elevation of serum pancreatic enzymes caused by severe acute pancreatitis from simple elevation after endoscopic retrograde pancreatography (ERP). A patient with severe acute pancreatitis demonstrated marked elevation of serum alpha 2M-T. In patients without severe acute pancreatitis, serum alpha 2M-T did not rise in spite of elevated serum pancreatic enzymes. In conclusion, abdominal pain with elevated serum alpha 2M-T can be an early diagnostic clue to severe acute pancreatitis after ERP.