Effect of FOY-305 (camostate) on severe acute pancreatitis in two experimental animal models

No role for protease inhibitors as a mitigation strategy for postpancreatectomy acute pancreatitis (PPAP): Propensity score matching analysis

BACKGROUND

While the use of protease inhibitor gabexate mesylate (GM) is still controversial in acute pancreatitis, it has never been tested for postpancreatectomy acute pancreatitis (PPAP). This study aims to assess the impact of GM on postoperative serum hyperamylasaemia (POH) or PPAP after pancreatoduodenectomy (PD).

METHODS

Consecutive patients developing POH after PD between 2016 and 2021 were included. According to GM administration, patients were divided into GM-treated and control (CTR) groups. GM was administered from postoperative day 1-3 in POH patients who underwent surgery before 2017. A 2:1 propensity matching was used to minimize the risk of bias.

RESULTS

Overall, 264 patients with POH were stratified in the GM (59 patients) and CTR (104 patients) cohorts, which showed balanced baseline characteristics after matching. No difference in postoperative complications was observed between the groups (all p > 0.05), except for PPAP occurrence, which was significantly higher in the GM group (37% vs. 22%, p = 0.037). A total of 45 patients (28%) evolved to PPAP. Comparing PPAP patients in the GM and CTR groups, no significant differences in POPF, relaparotomy, and mortality (all p > 0.09) were found. No difference in intravenous crystalloid administration was found in patients with PPAP, whether or not they developed major complications or pancreatic fistula (p > 0.05) CONCLUSION: Protease inhibitor seems ineffective in preventing a PPAP after PD once a POH has occurred. Further studies are needed to achieve benchmarks for treating PPAP and identify mitigation strategies to prevent the evolution of POH into additional morbidity.

Preclinical testing of dabigatran in trypsin-dependent pancreatitis

Pancreatitis, the inflammatory disorder of the pancreas, has no specific therapy. Genetic, biochemical, and animal model studies revealed that trypsin plays a central role in the onset and progression of pancreatitis. Here, we performed biochemical and preclinical mouse experiments to offer proof of concept that orally administered dabigatran etexilate can inhibit pancreatic trypsins and shows therapeutic efficacy in trypsin-dependent pancreatitis. We found that dabigatran competitively inhibited all human and mouse trypsin isoforms (Ki range 10-79 nM) and dabigatran plasma concentrations in mice given oral dabigatran etexilate well exceeded the Ki of trypsin inhibition. In the T7K24R trypsinogen mutant mouse model, a single oral gavage of dabigatran etexilate was effective against cerulein-induced progressive pancreatitis, with a high degree of histological normalization. In contrast, spontaneous pancreatitis in T7D23A mice, which carry a more aggressive trypsinogen mutation, was not ameliorated by dabigatran etexilate, given either as daily gavages or by mixing it with solid chow. Taken together, our observations showed that benzamidine derivatives such as dabigatran are potent trypsin inhibitors and show therapeutic activity against trypsin-dependent pancreatitis in T7K24R mice. Lack of efficacy in T7D23A mice is probably related to the more severe pathology and insufficient drug concentrations in the pancreas.

Trypsin activity governs increased susceptibility to pancreatitis in mice expressing human PRSS1R122H

Currently, an effective targeted therapy for pancreatitis is lacking. Hereditary pancreatitis (HP) is a heritable, autosomal-dominant disorder with recurrent acute pancreatitis (AP) progressing to chronic pancreatitis (CP) and a markedly increased risk of pancreatic cancer. In 1996, mutations in PRSS1 were linked to the development of HP. Here, we developed a mouse model by inserting a full-length human PRSS1R122H gene, the most commonly mutated gene in human HP, into mice. Expression of PRSS1R122H protein in the pancreas markedly increased stress signaling pathways and exacerbated AP. After the attack of AP, all PRSS1R122H mice had disease progression to CP, with similar histologic features as those observed in human HP. By comparing PRSS1R122H mice with PRSS1WT mice, as well as enzymatically inactivated Dead-PRSS1R122H mice, we unraveled that increased trypsin activity is the mechanism for R122H mutation to sensitize mice to the development of pancreatitis. We further discovered that trypsin inhibition, in combination with anticoagulation therapy, synergistically prevented progression to CP in PRSS1R122H mice. These animal models help us better understand the complex nature of this disease and provide powerful tools for developing and testing novel therapeutics for human pancreatitis.

Acute Pancreatitis: Work-up and Management

Acute pancreatitis is still a common clinical entity that causes significant morbidity and mortality. The most common etiological associations include chronic al coholism, biliary tract disease, iatrogenic (e.g., endo scopic retrograde cholangiopancreatography-induced), hypertriglyceridemia, and idiopathic varieties. New radiological techniques such as dynamic pancreatog raphy appear to be useful in diagnosing and determin ing the extent of necrotizing pancreatitis. Biochem ical variables such as the C-reactive protein and the trypsinogen-activated peptide seem promising in de tecting severe disease within the first few days of hospi talization. Computed tomographic-guided percutane ous aspiration of phlegmonous pancreatitis may be helpful in differentiating infected from noninfected masses. Although current studies have not identified any pharmacological agent as efficacious in improving sur vival, emergency sphincterotomy and removal of im pacted gallstones in severe gallstone pancreatitis may be beneficial in this regard. Prolonged (i.e., 7 day) perito neal dialysis may reduce the severity of pancreatic sep sis. Surgical drainage of infected fluid collections such as abscesses is a well-accepted adjunct to medical therapy. Surgical necrosectomy for necrotizing pancreatitis, however, which is advocated in some aggressive surgi cal units, is not yet commonplace and its role needs to be determined in controlled studies.

Comparison of the efficacy of continuous i.v. infusion versus continuous regional arterial infusion of nafamostat mesylate for severe acute pancreatitis

Aim

Continuous regional arterial infusion (CRAI) of protease inhibitors may be effective in the treatment of severe acute pancreatitis (SAP), but it is more invasive than i.v. infusion. The purpose of this study was to examine the effectiveness of continuous i.v. infusion (CIVI) for SAP compared with CRAI by unifying the dose and the administration period of nafamostat mesylate.

Methods

This study comprised 32 patients with SAP who were divided into two groups: the CRAI group and the CIVI group. The protease inhibitor, nafamostat mesylate, was continuously infused at a rate of 200 mg/day for 5 days in both groups. Clinical outcomes including in-hospital mortality were examined.

Results

There were no significant between-group differences in in-hospital mortality and 90-day mortality. The duration from admission to treatment was significantly shorter in the CIVI group (median, 7 h vs. 2 h, P = 0.0001; CRAI group vs. CIVI group). The rate of mechanical ventilation was significantly less in the CIVI group than in the CRAI group (93% vs. 47%, P = 0.007). The CIVI group showed a tendency toward decreased length of intensive care unit stay (median, 13 days vs. 4 days, P = 0.085) and hospital stay (median, 19 days vs. 11 days, P = 0.072). Total costs during hospitalization were significantly lower in the CIVI group (median, $18,320 vs. $11,641, P = 0.049).

Conclusion

The effectiveness of CIVI with early nafamostat mesylate treatment after the development of SAP could be equivalent to, or better than, that of CRAI.

The oncogenic microRNA miR-21 promotes regulated necrosis in mice

MicroRNAs (miRNAs) regulate apoptosis, yet their role in regulated necrosis remains unknown. miR-21 is overexpressed in nearly all human cancer types and its role as an oncogene is suggested to largely depend on its anti-apoptotic action. Here we show that miR-21 is overexpressed in a murine model of acute pancreatitis, a pathologic condition involving RIP3-dependent regulated necrosis (necroptosis). Therefore, we investigate the role of miR-21 in acute pancreatitis injury and necroptosis. miR-21 deficiency protects against caerulein- or L-arginine-induced acute pancreatitis in mice. miR-21 inhibition using locked-nucleic-acid-modified oligonucleotide effectively reduces pancreatitis severity. miR-21 deletion is also protective in tumour necrosis factor-induced systemic inflammatory response syndrome. These data suggest that miRNAs are critical participants in necroptosis and miR-21 enhances cellular necrosis by negatively regulating tumour suppressor genes associated with the death-receptor-mediated intrinsic apoptosis pathway, and could be a therapeutic target for preventing pathologic necrosis.

Role of bone marrow cells in the development of pancreatic fibrosis in a rat model of pancreatitis induced by a choline-deficient/ethionine-supplemented diet

Bone marrow cell (BMC)-derived myofibroblast-like cells have been reported in various organs, including the pancreas. However, the contribution of these cells to pancreatic fibrosis has not been fully discussed. The present study examined the possible involvement of pancreatic stellate cells (PSCs) originating from BMCs in the development of pancreatic fibrosis in a clinically relevant rat model of acute pancreatitis induced by a choline-deficient/ethionine-supplemented (CDE) diet. BMCs from female transgenic mice ubiquitously expressing green fluorescent protein (GFP) were transplanted into lethally irradiated male rats. Once chimerism was established, acute pancreatitis was induced by a CDE diet. Chronological changes in the number of PSCs originating from the donor BMCs were examined using double immunofluorescence for GFP and markers for PSCs, such as desmin and alpha smooth muscle actin (αSMA), 1, 3 and 8 weeks after the initiation of CDE feeding. We also used immunohistochemical staining to evaluate whether the PSCs from the BMCs produce growth factors, such as platelet-derived growth factor (PDGF) and transforming growth factor (TGF) β1. The percentage of BMC-derived activated PSCs increased significantly, peaking after 1 week of CDE treatment (accounting for 23.3±0.9% of the total population of activated PSCs) and then decreasing. These cells produced both PDGF and TGFβ1 during the early stage of pancreatic fibrosis. Our results suggest that PSCs originating from BMCs contribute mainly to the early stage of pancreatic injury, at least in part, by producing growth factors in a rat CDE diet-induced pancreatitis model.

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.

The effect of continuous arterial infusion of gabexate mesilate (FOY-007) on experimental acute pancreatitis

The effectiveness of continuous arterial infusion of Gabexate Mesilate (FOY-007) on experimental acute pancreatitis was investigated. Acute necrotizing pancreatitis was induced by an injection of 10% Na-taurocholate (1ml/kg) into the main pancreatic duct of mongrel dogs. Animals were divided into three groups; Group A: non-treated control, Group B: after the induction of pancreatitis, injected with FOY-007 intravenously (5mg/kg/hr), Group C: after the induction of pancreatitis, injected with FOY-007 via the celiac artery. The changes in the values of amylase and lipase in serum and ascites etc. were examined. A histological examination was done and the FOY-007 concentration of the pancreas was measured. In both groups B and C, the serum levels of amylase and lipase reached significantly to low levels compared with those in group A. The extents of pancreatic parenchyma necrosis in each group were 36.1, 25.3 and 19.5%, respectively, and were significantly improved in group C. In addition, the FOY-007 levels in pancreas specimens in the intraarterial infusion group exceeded those in the intravenous infusion group by 32 times. The results suggest that continuous FOY-007 arterial infusion therapy is useful as a local treatment for severe acute pancreatitis.

Role of nonesterified fatty acids in necrotizing pancreatitis: an in vivo experimental study in rats

INTRODUCTION

In acute pancreatitis, nonesterified fatty acids (NEFA) might be released by lipase and cause tissue necrosis by their detergent properties, but this has not been established in vivo.

AIMS

To measure the release of NEFA in the blood stream, pancreatic tissue, and peritoneal cavity during taurocholate-induced acute necrotizing pancreatitis in rats.

METHODOLOGY

Ascites and blood were repeatedly sampled; after 24 hours, pancreatic lesions were scored, and NEFA were measured in the pancreas. The effects of a specific lipase inhibitor (Tetrahydrolipstatin [THL]) were also studied.

RESULTS

A slight transient increase (22%) of NEFA concentration was observed in systemic circulation but did not parallel the time course of lipase activity, arguing against an intravascular production of NEFA by circulating lipase. Pancreatic NEFA did not differ between rats with pancreatitis and control rats. NEFA in ascites increased to threefold the basal value immediately after taurocholate and decreased rapidly thereafter, whereas lipase increased later in ascites and remained elevated during the 24-hour duration of the experiment. Lipase inhibition by THL neither modified the early increase of NEFA in ascites, nor altered the macroscopic, enzymatic, and histologic evolution of pancreatitis.

CONCLUSION

This in vivo study does not confirm the hypothetical role of NEFA produced by pancreatic lipase in the necrotic process and its systemic complications, up to now mainly suggested on the basis of ex vivo experiments.

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.

Alcohol and the pancreas

Alcoholic pancreatitis is a major, often lethal complication of alcohol abuse. Until recently it was generally accepted that alcoholic pancreatitis was a chronic disease from the outset. However, there is now emerging evidence in favour of the necrosis-fibrosis hypothesis that alcoholic pancreatitis begins as an acute process and that repeated acute attacks lead to chronic pancreatitis, resulting in exocrine and endocrine failure. Over the past 10-15 years, the focus of research into the pathogenesis of alcoholic pancreatitis has shifted from possible sphincteric and ductular abnormalities to the acinar cell itself which has increasingly been implicated as the initial site of injury. Recent studies have shown that the acinar cell can metabolize alcohol at rates comparable to those observed in hepatocytes. In addition, it has been demonstrated that alcohol and its metabolites exert direct effects on the pancreatic acinar cell which may promote premature digestive enzyme activation and oxidant stress. The challenge remains to identify predisposing and triggering factors in this disease.

Evaluation of anti-influenza effects of camostat in mice infected with non-adapted human influenza viruses

The anti-influenza effects of camostat, a serine protease inhibitor, on in vivo influenza infections were evaluated. Mice which received non-adapted human influenza viruses intranasally, developed a reproducible infection with very low mortality. The infection was readily detected by the recovery of the virus from an oropharyngeal swab. Five-week-old ICR mice received intraperitoneal injections of saline (control), amantadine (known positive drug), or camostat, after infection with influenza A/Taiwan/1/86 virus. Virus detection was performed on day 1, 2, 3, 5, and 7 of postinfection. Both camostat and amantadine were effective in ameliorating mouse influenza. On day 5, mice injected with camostat (45%) or amantadine (50%) showed a lower virus secreting rate than those receiving saline (90%). Additionally, camostat showed strong anti-influenza effects on an amantadine-resistant type A virus and a type B virus infection in vitro. The results show that blocking the hemagglutinin cleavage is an effective target for development of an anti-influenza agent. They also demonstrate that virus detection from the oropharynx of mice, infected with non-adapted virus, is a useful in vivo influenza model.

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.

Gabexate mesilate vs aprotinin in human acute pancreatitis (GA.ME.P.A.). A prospective, randomized, double-blind multicenter study

The authors report the results of a randomized, double-blind multicenter clinical trial on the use of gabexate mesilate vs aprotinin in the therapy of acute pancreatitis. The size of the study sample and the end points chosen for evaluation of the early systemic complications of the pancreatitis--carefully selected targets for reliable assessment of the efficacy of any protease inhibitor--lead to the conclusion that gabexate mesilate is more efficacious than aprotinin in reducing the early complications of necrotizing acute pancreatitis, if administered within 72 h of onset of symptoms. Its good tolerability means that it can be used safely even at the dose of 3 g/24 h.

Protective effect of AA-861 (5-lipoxygenase inhibitor) on experimental acute necrotizing pancreatitis in rats

The effect of the 5-lipoxygenase inhibitor AA-861 on acute necrotizing pancreatitis was studied in an experimental model. Pancreatitis was induced in rats by retrograde injection of 0.4 mL/kg body wt of 6% taurocholic acid into the pancreatic duct. The animals were divided into three groups: control group; administered AA-861 in a single dose of 30 mg/kg; and administered AA-861 in a single dose of 60 mg/kg. The following parameters were examined: serum amylase, lipase, trypsin, blood sugar, and survival rate. Histology of the pancreas was also studied. The serum amylase and lipase activities in groups 2 and 3 were lower than those in group 1 in the early phase after induction of pancreatitis. The elevation of serum trypsin was not suppressed by AA-861. Blood sugar was more efficiently controlled in groups 2 and 3 than in group 1. The survival rates in groups 2 and 3 were better than that in group 1, but there were no significant differences among the three groups. Histologically, massive tissue necrosis with hemorrhage, edema, and inflammatory cell infiltration was prominent in group 1, whereas such changes were obviously suppressed in groups 2 and 3. The results suggest that AA-861 may prove useful in the treatment of acute pancreatitis.

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.

Comparison of different treatment modalities in experimental pancreatitis in rats

Lipolytic enzymes may play a role in the pathogenesis of acute pancreatitis. Therefore, the effects of a lipase inhibitor, THL (tetrahydrolipstatin), a protease inhibitor, FUT (nafamostat mesilate), and albumin under different conditions in rats were investigated. (a) Isolated pancreatic acini were incubated with pancreatic homogenates and triglycerides or lecithin with or without albumin and the degree of cellular destruction quantitated. (b) Taurocholate was injected into the pancreatic duct of isolated pancreas and the organ continuously perfused with either FUT, THL, or albumin. Organ damage was evaluated by measurement of pancreatic enzymes in the portal effluence. (c) Necrotizing pancreatitis was induced in vivo via retrograde taurocholate injection. FUT, THL, or albumin was applied either intravenously or injected into the pancreatic parenchyma. (a) Albumin prevented the cellular damage caused by both fatty acids and lysolecithin. (b) THL was ineffective, FUT lowered the release of pancreatic enzymes into the portal effluence, and albumin was most effective. (c) Albumin prevented the development of panlobular necrosis and lowered the degree of extrapancreatic fat necrosis. Albumin, via its ability to bind detergents, may have therapeutic implications.

Influence of a platelet-activating factor antagonist on severe pancreatitis in two experimental models

This study investigates the role of platelet-activating factor (PAF) in experimental pancreatitis. The concentration of PAF quantified in ascites of bile-induced pancreatitis by radioimmunoassay (RIA) ranged from 3.67 +/- 0.39 pmol/mL 2 h to 0.954 +/- 0.39 pmol/mL 10 h after injection of taurocholate. Administration of a potent PAF antagonist, WEB-2170, prior to injection of taurocholate prolonged mean survival time in rats receiving i.v. camostate and albumin (46.4 h, n = 15, vs controls 38.3 h, n = 13). However, the survival rate after 72 h was not improved. The histologically estimated severity of pancreatitis and pancreatic enzymes in blood, tissue, or ascites was not affected. WEB-2170 had no effect on survival when injected simultaneously with taurocholate into the pancreatic duct or given i.v. after induction of pancreatitis (1, 0.1, or 0.01 mg/kg WEB-2170 vs controls). Subcutaneous injection of 10 mg/kg WEB-2170 also did not improve survival in pancreatitis induced by choline-deficient, ethionine-supplemented diet in mice. It is concluded that administration of a PAF antagonist after the onset of severe experimental pancreatitis does not influence its outcome, although activation of PAF may play a role in the pathogenesis of pancreatitis.

Participation of GABAergic systems in the production of antinociception by various stresses in mice

Based on the data that diazepam, a benzodiazepine (BZP) receptor agonist, antagonized psychological (PSY)-stress induced analgesia (SIA) without prominent action on footshock (FS)- and forced swimming (SW)-SIA and that BZP receptors are coupled with GABA receptors, we examined how the GABAergic system participates in the production of various SIAs. Muscimol, a GABAA receptor agonist, at doses of 0.25 to 1.0 mg/kg, affected each SIA differently, suppressed PSY-SIA at 0.25 mg/kg but tended to potentiate it at 1.0 mg/kg, potentiated SW-SIA dose-dependently and did not affect FS-SIA at the doses employed. Both bicuculline, a GABAA receptor antagonist, 0.5 to 2.0 mg/kg, and picrotoxin, a Cl- channel blocker, 0.25 to 1.0 mg/kg, dose-dependently suppressed PSY- and FS-SIA. Meanwhile, the effects of both drugs on SW-SIA were less than those on PSY- and FS-SIA, namely, bicuculline slightly inhibited it only at 2.0 mg/kg, and picrotoxin did not produce any appreciable effect even at the highest dose. Baclofen, a GABAB receptor agonist, at 5.0 and 10.0 mg/kg had no influence on each SIA. On the contrary, CGP 35348, a GABAB receptor antagonist at 20 to 100 mg/kg caused the dose-dependent blockade of FS-SIA, but affected neither PSY- nor SW-SIA. The production of PSY- and SW-SIA is attributable to the GABAA receptors/Cl- channel mediated mechanism alone, while that of FS-SIA involves both GABAA and GABAB receptor mediated systems. Thus, GABAergic systems play an important role in the production of each SIA; however, the participation of the receptor subtypes in the mechanism was different from each other.

Cytoprotective effects of prostaglandins and a new potent protease inhibitor in acute pancreatitis

The redistribution of cathepsin B, a lysosomal enzyme, from the lysosomal pellet to the zymogen pellet in the subcellular fractionation, the colocalization of cathepsin B with digestive enzyme, and increased cellular, lysosomal, and mitochondrial fragility within acinar cells have been found during the early stages of caerulein-induced acute pancreatitis in rats. In the present study, the authors investigated the protective effects of prostaglandin E1 and E2, a combined therapy of these prostaglandins, and a new, synthetic, low molecular weight protease inhibitor, ONO3307, on the exocrine pancreas in this noninvasive model of experimental pancreatitis in vivo and in vitro. Prostaglandin E2, but not E1, prevented hyperamylasemia, congestion of amylase and trypsinogen in the acinar cells, redistribution of cathepsin B, and amylase and lactate dehydrogenase discharge from the dispersed acini. It also prevented cathepsin B leakage from the lysosomes and malate dehydrogenase leakage from the mitochondria in an almost dose-dependent manner, particularly at the dose of 100 micrograms/kg/hr continuous infusion. Furthermore, the combined therapy of prostaglandin E2 with ONO3307 strongly inhibited all the parameters tested in this study. This combination therapy seems to be the most effective against secretagogue-induced pancreatic injuries. These results indicate that cellular and subcellular organellar fragility seem to be closely involved in the pathogenesis of acute pancreatitis. Prostaglandin E2 seems to have important cytoprotective effects on the biologic membranes, such as a stabilizer of lysosomal or mitochondrial membranes. In addition, these findings also suggest the crucial roles of some unknown proteases in the etiology of acute pancreatitis, and indicate the clinical effectiveness of prostaglandins and this type of low molecular weight protease inhibitor for acute pancreatitis.

Protective effect of antithrombin III in acute experimental pancreatitis in rats

In the present study we investigated the therapeutic action of antithrombin III (AT III) in taurocholate-induced experimental pancreatitis with high lethality in rats. High-dose AT III treatment greatly improved the survival rate not only when given as pretreatment but also when given 2 hr after induction. No favorable effect on survival rate was observed on administration after 5 hr. Both intravascular and intraperitoneal AT III administration locally restored decreased AT III levels in the peritoneal cavity and increased plasma AT III to supranormal levels. The primary pancreatic insult seemed to be unaffected by the treatment, because neither the rise in plasma lipase nor the development of ascites or the extension of the pancreatic necrosis were diminished. Because heparin pretreatment of the rats was also effective, the mechanism of the beneficial action was probably mediated by inhibition of the proteases of the coagulation cascade, thereby preventing intravascular coagulation in the pancreas and distant organs and subsequent systemic complications. The high efficacy of AT III treatment in this experimental model may stimulate clinical studies evaluating the efficacy of AT III treatment in an early stage of acute pancreatitis.

Influence of the CCK-antagonist loxiglumide on bile-induced experimental pancreatitis

The present study investigates the effect of CCK-receptor blockade on taurocholate-induced pancreatitis in rats using the potent antagonist loxiglumide. Intraperitoneal administration (50 mg/kg) of loxiglumide began 3 h before, or 10 min or 3 h after induction of pancreatitis. Mean survival times of the experimental groups were 31.2, 23.6, and 20.5 h, respectively, compared to 18.2 h for controls. Survival for 24 h after induction of pancreatitis was significantly improved when the antagonist was given 3 h before, but not in the time periods after induction. After 72 h, survival time was not significantly altered in any of the groups. Furthermore, amylase and lipase levels quantified 10 h after induction of pancreatitis in ascites, blood, or tissue did not indicate a significant difference, nor was improvement in survival seen when the CCK-antagonist was tested in rats receiving a basal treatment with intravenous volume substitution, peritoneal lavage, and protease inhibition. We conclude that CCK-receptor blockade does not improve the final outcome of bile-induced pancreatitis in the rat, even if treatment is started before induction of pancreatitis.

Camostate (FOY-305) improves the therapeutic effect of peritoneal lavage on taurocholate induced pancreatitis

The effect of peritoneal lavage with the addition of camostate to the lavage fluid on the outcome of taurocholate pancreatitis in rats was studied. Camostate is a low molecular weight protease inhibitor which has been developed recently. Peritoneal lavage was performed for 12 hours and camostate was added to the lavage fluid in five concentrations. At 0.1 mg/ml the survival rate increased significantly (11 of 20 v controls 4 of 20, p less than 0.05); the maximal effect was observed at 0.2 mg/ml, and no effect was seen at 0.01 and 0.05 mg/ml. Adverse effects occurred at 0.5 mg/ml. The addition of 0.1 mg/ml camostate significantly reduced the acidosis in arterial blood: mean (SD) pH 7.30 (0.035) v controls 7.23 (0.054) (n = 9, p less than 0.01) and arterial base excess: -15.4 (1.26) mmol/l v controls: -17.4 (2.51) mmol/l (n = 9, p less than 0.05). There was no difference, however, in plasma amylase activity and in the histological degree of specific tissue damage to the pancreas. A combination of intravenous camostate and lavage with the addition of camostate to the lavage fluid yielded a significantly improved survival compared with treatment with intravenous camostate alone (10 out of 16 animals v intravenous camostate alone, two out of 16, p greater than 0.01). We conclude that lavage with camostate significantly improves the prognosis of severe necrotising pancreatitis in rats.