Clinical relevance of experimental acute pancreatitis

Epidural anesthesia improves pancreatic perfusion and decreases the severity of acute pancreatitis

AIM: To study the safety of epidural anesthesia (EA), its effect on pancreatic perfusion and the outcome of patients with acute pancreatitis (AP).

METHODS: From 2005 to August 2010, patients with predicted severe AP [Ranson score ≥ 2, C-reactive protein > 100 or necrosis on computed tomography (CT)] were prospectively randomized to either a group receiving EA or a control group treated by patient controlled intravenous analgesia. Pain management was evaluated in the two groups every eight hours using the visual analog pain scale (VAS). Parameters for clinical severity such as length of hospital stay, use of antibiotics, admission to the intensive care unit, radiological/clinical complications and the need for surgical necrosectomy including biochemical data were recorded. A CT scan using a perfusion protocol was performed on admission and at 72 h to evaluate pancreatic blood flow. A significant variation in blood flow was defined as a 20% difference in pancreatic perfusion between admission and 72 h and was measured in the head, body and tail of the pancreas.

RESULTS: We enrolled 35 patients. Thirteen were randomized to the EA group and 22 to the control group. There were no differences in demographic characteristics between the two groups. The Balthazar radiological severity score on admission was higher in the EA group than in the control group (mean score 4.15 ± 2.54 vs 3.38 ± 1.75, respectively, P = 0.347) and the median Ranson scores were 3.4 and 2.7 respectively (P = NS). The median duration of EA was 5.7 d, and no complications of the epidural procedure were reported. An improvement in perfusion of the pancreas was observed in 13/30 (43%) of measurements in the EA group vs 2/27 (7%) in the control group (P = 0.0025). Necrosectomy was performed in 1/13 patients in the EA group vs 4/22 patients in the control group (P = 0.63). The VAS improved during the first ten days in the EA group compared to the control group (0.2 vs 2.33, P = 0.034 at 10 d). Length of stay and mortality were not statistically different between the 2 groups (26 d vs 30 d, P = 0.65, and 0% for both respectively).

CONCLUSION: Our study demonstrates that EA increases arterial perfusion of the pancreas and improves the clinical outcome of patients with AP.

Immune cells and immune-based therapy in pancreatitis

Alcohol and gallstones are the most common etiologic factors in acute pancreatitis (AP). Recurrent AP can lead to chronic pancreatitis (CP). Although the underlying pathophysiology of the disease is complex, immune cells are critical in the pathogenesis of pancreatitis and determining disease severity. In this review, we discuss the role of innate and adaptive immune cells in both AP and CP, potential immune-based therapeutic targets, and animal models used to understand our knowledge of the disease. The relative difficulty of obtaining human pancreatic tissue during pancreatitis makes animal models necessary. Animal models of pancreatitis have been generated to understand disease pathogenesis, test therapeutic interventions, and investigate immune responses. Although current animal models do not recapitulate all aspects of human disease, until better models can be developed available models are useful in addressing key research questions. Differences between experimental and clinical pancreatitis need consideration, and when therapies are tested, models with established disease ought to be included.

Immune-modulating therapy in acute pancreatitis: Fact or fiction

Acute pancreatitis (AP) is one of the most common diseases of the gastrointestinal tract, bearing significant morbidity and mortality worldwide. Current treatment of AP remains unspecific and supportive and is mainly targeted to aggressively prevent systemic complications and organ failure by intensive care. As acute pancreatitis shares an indistinguishable profile of inflammation with sepsis, therapeutic approaches have turned towards modulating the systemic inflammatory response. Targets, among others, have included pro- and anti-inflammatory modulators, cytokines, chemokines, immune cells, adhesive molecules and platelets. Even though, initial results in experimental models have been encouraging, clinical implementation of immune-regulating therapies in acute pancreatitis has had a slow progress. Main reasons include difficulty in clinical translation of experimental data, poor understanding of inflammatory response time-course, flaws in experimental designs, need for multimodal approaches and commercial drawbacks. Whether immune-modulation in acute pancreatitis remains a fact or just fiction remains to be seen in the future.

A review of animal models of nonneoplastic pancreatic diseases

The nonneoplastic diseases of the human pancreas generally comprise the inflammatory and degenerative conditions that include acute and chronic pancreatitis, with cystic fibrosis being arguably one of the most important diseases that induce the condition. Both acute and chronic conditions vary in severity, but both can be life threatening; and because of this fact, the study of their progression, and their responsiveness to therapy, is largely conducted by indirect means using serum markers of damage and repair such as amylase and lipase activities that normally occur at very low levels in the circulation but can be significantly increased during inflammatory episodes. Progress in the understanding the pathogenesis of both conditions has therefore been largely due to time course studies in animal models of pancreatitis, and it is in this context that animal model development has been so significant. In general terms, the animal models can be divided into the invasive, surgical procedures, and those induced by the administration of chemical secretagogues that induce hypersecretion of the pancreatic enzymes. The former include ligation and/or cannulation of the biliopancreatic ducts with infusion of solutions of various kinds, or the formation of closed duodenal loops. Secretagogue administration includes administration of caerulein or l-arginine in various protocols. An additional model involves administration of dibutyltin dichloride, which induces a partial blockage of the pancreatic ducts to induce pancreatic disease through enzymic reflux into the gland. The models have been invaluable in generating testable hypotheses for the human diseases. These hypotheses for the production of cellular damage as the initiating events in the disease include (1) intracellular chemical activation, (2) pancreatic secretion reflux, (3) intracellular production of reactive oxygen species, and (4) intracellular production of free radicals.

The clinical course of acute pancreatitis and the inflammatory mediators that drive it

Acute pancreatitis (AP) is a common emergency condition. In the majority of cases, it presents in a mild and self-limited form. However, about 20% of patients develop severe disease with local pancreatic complications (including necrosis, abscess, or pseudocysts), systemic organ dysfunction, or both. A modern classification of AP severity has recently been proposed based on the factors that are causally associated with severity of AP. These factors are both local (peripancreatic necrosis) and systemic (organ failure). In AP, inflammation is initiated by intracellular activation of pancreatic proenzymes and/or nuclear factor-κB. Activated leukocytes infiltrate into and around the pancreas and play a central role in determining AP severity. Inflammatory reaction is first local, but may amplify leading to systemic overwhelming production of inflammatory mediators and early organ failure. Concomitantly, anti-inflammatory cytokines and specific cytokine inhibitors are produced. This anti-inflammatory reaction may overcompensate and inhibit the immune response, rendering the host at risk for systemic infection. Currently, there is no specific treatment for AP. However, there are several early supportive treatments and interventions which are beneficial. Also, increasing the understanding of the pathogenesis of systemic inflammation and the development of organ dysfunction may provide us with future treatment modalities.

Epidural anaesthesia restores pancreatic microcirculation and decreases the severity of acute pancreatitis

AIM: To investigate the effect of epidural anaesthesia (EA) on pancreatic microcirculation during acute pancreatitis (AP).

METHODS: AP was induced by injection of sodium taurocholate into the pancreatic duct of Sprague-Dawley rats. To realize EA, a catheter was introduced into the epidural space between T7 and T9 and bupivacaine was injected. Microcirculatory flow was measured by laser Doppler flowmetry. Arterial blood gas analyses were performed. At the end of the experiment (≤ 5 h), pancreas was removed for histology. The animals were divided into three groups: Group 1 (n = 9), AP without EA; Group 2 (n = 4), EA without AP; and Group 3 (n = 6), AP treated by EA.

RESULTS: In Group 1, pancreatic microcirculatory flow prior to AP was 141 ± 39 perfusion units (PU). After AP, microcirculatory flow obviously decreased to 9 ± 6 PU (P < 0.05). Metabolic acidosis developed with base excess (BE) of - 14 ± 3 mmol/L. Histology revealed extensive edema and tissue necrosis. In Group 2, EA did not significantly modify microcirculatory flow. BE remained unchanged and histological analysis showed normal pancreatic tissue. In Group 3, AP initially caused a significant decrease in microcirculatory flow from 155 ± 25 to 11 ± 7 PU (P < 0.05). After initiation of EA, microcirculatory flow obviously increased again to 81 ± 31 PU (P < 0.05). BE was -6 ± 4 mmol/L, which was significantly different compared to Group 1 (P < 0.05). Furthermore, histology revealed less extensive edema and necrosis in pancreatic tissue in Group 3 than that in Group 1.

CONCLUSION: AP caused dramatic microcirculatory changes within the pancreas, with development of metabolic acidosis and tissue necrosis. EA allowed partial restoration of microcirculatory flow and prevented development of tissue necrosis and systemic complications. Therefore, EA should be considered as therapeutic option to prevent evolution from edematous to necrotic AP.

Acute phase response in acute pancreatitis: a comparison with abdominal sepsis

BACKGROUND

Increased knowledge on the underlying pathophysiological mechanisms in acute pancreatitis (AP) and abdominal sepsis (AS) is essential, not least for the development of novel ways of treatment. The present study aims at determining dynamic changes in the systemic inflammatory response in AP and AS.

METHODS

AP was induced by the intraductal injection of sodium taurodeoxycholate in the rat, while AS was induced by caecal ligation and puncture. The animals were killed 1, 3, 6 and 9 h after challenge. Plasma exudation of radiolabelled albumin, myeloperoxidase (MPO), TNF-alpha, MCP-1, superoxide and hydrogen peroxide was measured.

RESULTS

Leakage index of human serum albumin showed a significant increase early (I h) after induction of AP and later (9h) in AS compared to controls (P < 0.05). Hydrogen peroxide generation by circulating monocytes/macrophages was high early (1 h) in AP and after 3 and 6h in AS. Superoxide generation increased by time after both challenges. MPO activity increased significantly, starting at 3 h in both AP and AS (P < 0.05). TNF-alpha increased significantly at 6 and 9 h in both models.

CONCLUSION

Our results indicate differences in the release of systemic inflammatory mediators and cellular response in AP and AS. However, potential similarities in end-effect, such as the development of remote organ injury (lungs), may exist as implied by the MPO results. Further investigations of the mechanisms are crucial.

Deferoxamine and meropenem combination therapy in experimental acute pancreatitis

INTRODUCTION

Recent data from the experimental clinical studies suggest that antibiotics having good penetration to pancreas may reduce mortality by preventing pancreatic infection, which is the most important prognostic factor in acute pancreatitis (AP). Deferoxamine is an active free oxygen radical scavenger, which has been shown to have a protective role in development of acute pancreatitis.

AIM

To determine the effects of combination of deferoxamine and meropenem in acute necrotizing pancreatitis.

METHODOLOGY

One hundred male Sprague-Dawley rats were randomly divided into 5 groups. All rats underwent laparotomy with cannulation of biliopancreatic duct. Group 1 received intraductal saline injection. Acute necrotizing pancreatitis was induced in group 2, 3, 4, and 5 by intraductal injection of 3% taurocholate. Group 1 (sham operated) and group 2 were injected with saline of 0.3 mL/kg intraperitoneally (i.p). Group 3 was injected with meropenem 60 mg/kg/d i.p, group 4 with deferoxamine 80 mg/kg/d s.c and group 5 with combination of these 2 agents at the same doses. While meropenem was started 2 hours later, all treatments were started immediately after the induction of pancreatitis. All rats were killed at the 48th hour of the treatment and blood and tissue samples were collected for amylase determinations, pathologic examinations, and culture.

RESULTS

There was no difference in serum amylase levels between AP induced groups (P > 0.05). Pancreatic histology scores were significantly low in rats treated with deferoxamine (group 4), and combination regimen (group 5) (P < 0.001). Meropenem significantly reduced the incidence of pancreatic infection. Although combination of deferoxamine with meropenem showed better effects than meropenem alone in terms of pancreatic infection, the difference did not reach to statistical significance.

CONCLUSIONS

Meropenem treatment reduces secondary pancreatic infections in acute pancreatitis. Treatment with deferoxamine and meropenem combination may be more beneficial than single therapies in reducing the severity of pancreatitis. Further studies investigating the effects of this combination on survival are needed.

Peptide YY improves local and systemic parameters and prevents death in lethal necrotizing pancreatitis

INTRODUCTION

Peptide YY (PYY) is a gastrointestinal hormone with multiple inhibitory effects on the proximal digestive tract, including suppression of secretion by the exocrine pancreas.

AIM

To determine whether peptide YY would reduce mortality in a lethal model of necrotizing pancreatitis by improving local and systemic parameters of this disease.

METHODOLOGY

Necrotizing pancreatitis was induced in three groups of 30 mice by feeding a choline-deficient ethionine-supplemented diet. Osmotic pumps placed in 10 control mice delivered normal saline. In the two study groups, PYY was delivered at 200 pmol/kg/hr. The prophylactic group received PYY pumps at the onset; the therapeutic group received pumps 24 hours later. Ten mice from each group were followed to assess survival. Remaining mice were killed at 24, 48, 72, and 96 hours. Pancreata were graded on a nine-point histologic scale. Amylasemia was quantified by kinetic determination. Serum interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) values were determined by ELISA.

RESULTS

Both prophylactic and therapeutic PYY significantly reduced mortality compared with that seen in controls ( p = 0.05 and p = 0.007). Five-day survival was 33% in controls, 80% in those receiving prophylactic PYY, and 100% in the therapeutic group. Amylasemia was reduced in the therapeutic group by day 3 ( p < 0.02) and in the prophylactic group by day 4 ( p < 0.01). Histologic changes mirrored those in serum amylase. Prophylactic and therapeutic administration of PYY suppressed early circulating levels of IL-6.

CONCLUSION

PYY reduces mortality and improves local and systemic parameters in this murine model and may be of clinical benefit in the management of human necrotizing pancreatitis, particularly as this study demonstrates a clear survival benefit when PYY is given after the onset of disease.

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.

Hyperlipaemia intensifies the course of acute oedematous and acute necrotising pancreatitis in the rat

BACKGROUND

Serum triglyceride concentrations higher than 10 to 20 mmol/l are probably a risk factor for developing acute pancreatitis in humans.

AIMS

To therefore analyse the influence of hyperlipaemia on the course of acute oedematous and acute necrotising pancreatitis in rats.

SUBJECTS

Male Wistar rats were used in all experiments.

METHODS

Six different groups of animals were used: two groups without pancreatitis (controls), two with acute oedematous pancreatitis, and two with acute necrotising pancreatitis. One group from each pair was treated with Triton WR 1339, which induces endogenous hyperlipaemia. Blood samples were taken from all subjects to measure triglyceride, cholesterol, amylase, and lipase. Pancreatic tissue samples were taken and the degree of pancreatic damage was judged microscopically.

RESULTS

In the control groups no significant changes occurred, either in serum enzyme activities or in histology. The hyperlipaemic subgroup of animals with acute oedematous pancreatitis developed significantly higher (p < 0.001) serum amylase activities and a greater degree of histological damage (p < 0.01) than the animals of the non-hyperlipaemic acute oedematous pancreatitis group. In the animals with necrotising pancreatitis, serum lipase activity and the histological degree of pancreatic damage were significantly higher in the hyperlipaemic animals than in the non-hyperlipaemic animals.

CONCLUSION

This study shows that hyperlipaemia intensifies the course of acute oedematous and acute necrotising pancreatitis in rats.

Effects of the cholecystokinin receptor antagonist L-364,718 on pancreatitis induced by a deficient in choline and supplemented with ethionine (CDE) diet in the rat

The role of cholecystokinin (CCK) in the development of a necrotizing acute pancreatitis induced by a diet deficient in choline and supplemented with ethionine (CDE) has been evaluated in the rat by using a potent CCK receptor antagonist L-364,718. Acute pancreatitis was induced by administration of CDE diet for 14 days. L-364,718 administration was carried out by subcutaneous injections at dose of 0.1 mg/kg/day. Pancreatic exocrine secretion (flow, protein, amylase and trypsin outputs) in resting and under infusion of 1.25 microgram/kg/h of CCK-8 were used to evaluate the pancreatic functionality. Others parameters (serum amylase, percentage fluid in pancreas, haematocrit and mortality) evaluated the severity of pancreatitis. L-364,718 slightly reduced the mortality and the increases of percentage of fluid accumulated in pancreas in CDE diet acute pancreatitis. Basal and CCK stimulated pancreatic secretion was significantly depressed 36 hours after L-364,718 treatment. A slight response to CCK was observed. Nevertheless it was lower than usually observed in control rats. Our results demonstrate that in the rat, chronic L-364,718 treatment did not completely restore pancreatic activity in acute pancreatitis induced by CDE diet. Hence CCK cannot be considered as the main factor involved in the development of this pancreatitis model.

Nafamostat mesilate on the course of acute pancreatitis. Protective effect on peritoneal permeability and relation with supervening pulmonary distress

Three hundred sixty Sprague-Dawley rats were allocated into four groups, according to different content of a 24-h i.v. infusion performed 1 h after intrabiliary injection of enterokinase/sodium taurocholate to induce acute pancreatitis (AP): (1) Saline; (2) 5 micrograms/kg/h nafamostat mesilate (FUT-175); (3) 10 micrograms/kg/h FUT-175; and (4) 25 micrograms/kg/h FUT-175. Peritoneal fluid was removed and exchanged with 1 mL 3.33 M fluorescein-isothiocyanate-conjugated (FITC) dextrans of 4000-40,000 Dalton. Serial blood samples were withdrawn and examined for FITC-dextrans, phospholipase A2 (PLA2), blood gases, amylase, and lipase. As compared to control (55%), FUT-175 brought about a lower (5 micrograms/kg/h: 25%) or no mortality (10 and 25 micrograms/kg/h), and a milder histological and biochemical evidence of AP. Untreated animals with PLA2 values over two times the standard deviation showed a respiratory distress. Further, unlike group 1, FUT-175 doses as low as 5 micrograms/kg prevented the increase in peritoneal permeability to small-size molecules (up to 20,000 Dalton). In a second experiment under the same drug protocol, 1000 U/mL of PLA2 and 2 mL of pancreatitis ascites were instilled ip. Peritoneal permeability to FITC-dextrans up to 30,000 Dalton and to PLA2 significantly increased in the saline group and in the 5 micrograms/kg FUT-175 group. However, 10 micrograms/kg and 25 micrograms/kg FUT-175 doses prevented such phenomenon. In conclusion, FUT-175 proves to be a potent antiprotease molecule with a biochemical activity also against PLA2 in vivo and prevents significant transperitoneal-blood access of pancreatic enzymes.

Experimental models of acute pancreatitis

Various models of experimental acute pancreatitis are described. An ideal model would be reproducible, have a similar natural history to that of the human disease and a similar response to treatment. Furthermore, it should be relatively cheap and simple. Few, if any, of the available experimental models completely satisfy these criteria. The appropriate choice of model is discussed, as are possible future developments in this field.