The association of type II pneumocytes and endothelial permeability with the pulmonary custocyte system in experimental acute pancreatitis

Review of experimental animal models of biliary acute pancreatitis and recent advances in basic research

Acute pancreatitis (AP) is a formidable disease, which, in severe forms, causes significant mortality. Biliary AP, or gallstone obstruction-associated AP, accounts for 30-50% of all clinical cases of AP. In biliary AP, pancreatic acinar cell (PAC) death (the initiating event in the disease) is believed to occur as acinar cells make contact with bile salts when bile refluxes into the pancreatic duct. Recent advances have unveiled an important receptor responsible for the major function of bile acids on acinar cells, namely, the cell surface G-protein-coupled bile acid receptor-1 (Gpbar1), located in the apical pole of the PAC. High concentrations of bile acids induce cytosolic Ca(2+) overload and inhibit mitochondrial adenosine triphosphate (ATP) production, resulting in cell injury to both PACs and pancreatic ductal epithelial cells. Various bile salts are employed to induce experimental AP, most commonly sodium taurocholate. Recent characterization of taurolithocholic acid 3-sulphate on PACs has led researchers to focus on this bile salt because of its potency in causing acinar cell injury at relatively low, sub-detergent concentrations, which strongly implicates action via the receptor Gpbar1. Improved surgical techniques have enabled the infusion of bile salts into the pancreatic duct to induce experimental biliary AP in mice, which allows the use of these transgenic animals as powerful tools. This review summarizes recent findings using transgenic mice in experimental biliary AP.

Influence of Qingyitang on surfactant protein A expression in severe acute pancreatitis-induced lung injury in rats

AIM: To investigate the expression of surfactant protein A (SP-A) in the lungs of rats with severe acute pancreatitis (SAP), and the effect of Qingyitang on acute lung injury (ALI) induced by SAP.

METHODS: SD rats were randomly divided into sham-operation group (SO, n = 10), SAP model group (SAP, n = 10) and Qingyitang group (QYT, n = 10). Severe acute pancreatitis was induced in the SAP and QYT groups. Sham operations were only performed on rats in the SO group. QYT (10 mL/kg) was intragastrically administered 30 min and 12 hours after SAP was induced in the QYT group. Serum amylase (AMY) levels, PaO2 and lung wet/dry ratio (W/D) were determined. The level of SP-A mRNA expression in lung was detected by reverse transcription polymerase chain reaction (RT-PCR). SP-A protein in lung was detected by Western blotting. Pathological changes in the pancreas, lung and alveolar type II cells were observed 24 hours after the establishment of the model.

RESULTS: The serum levels of AMY (7144.19 U/L ± 727.91 U/L) in rats of the SAP group were remarkably higher than those in rats of the QYT (4283.51 U/L ± 527.52 U/L) and SO (1193.41 U/L ± 192.54 U/L, P < 0.01) groups. The levels of PaO2 in rats of the SAP group (79.24 mmHg ± 5.84 mmHg) were lower than those in rats of the SO (96.78 mmHg ± 3.81 mmHg) and QYT (88.16 mmHg ± 5.07 mmHg, P < 0.01) groups. The expression levels of SP-A mRNA and SP-A in the rat lungs of the SAP group were significantly decreased compared with those in rats in the SO and QYT groups (P < 0.01). The pathologic changes of the pancreas, lung and alveolar type II cells in rats of the QYT and SO groups were milder than those in rats of the SAP group.

CONCLUSION: The levels of SP-A decrease remarkably in rats with ALI induced by SAP. Administration of QYT reduces injury of lung by protecting alveolar type II cells and increasing the expression of SP-A.

From acute pancreatitis to end-organ injury: mechanisms of acute lung injury

BACKGROUND

Multi-organ dysfunction, and in particular lung injury, is often responsible for the unfavorable outcome of patients with severe acute pancreatitis. Understanding of the mechanisms by which local inflammation in the pancreas leads to end-organ injury is crucial for the development of new therapeutic strategies.

METHODS

A MEDLINE search was performed with the terms "acute pancreatitis," "lung injury," "inflammatory response," "SIRS," and "multi-organ dysfunction." Pertinent articles were selected for analysis.

RESULTS

Modulation of the inflammatory response using a combination of immunomodulatory agents may decrease the incidence of severe pancreatitis-related acute lung injury and acute respiratory distress syndrome.

CONCLUSION

Clinical trials are of utmost importance to establish the validity of such strategies.

Influence of mast cells on the expression of adhesion molecules on circulating and migrating leukocytes in acute pancreatitis-associated lung injury

Pancreatitis-associated lung injury is an early-occurring and severe complication, still associated with substantial mortality. A number of inflammatory cells and their products are involved in the initiation and progress of the condition. In the present study, acute pancreatitis (AP) was induced by the intraductal infusion of 5% sodium taurodeoxycholate in the rat. Pulmonary endothelial barrier dysfunction was measured by plasma exudation of radiolabeled albumin. Expression of PECAM-1, ICAM-1, and L: -selectin on neutrophils (CD11b(+)) and monocytes/macrophages (CD11b/c(+)), obtained from circulation and lung tissue, was measured 1 and 6 hours after AP induction (n = 10 rats/time point/group). Plasma levels of histamine and serotonin were determined. The role of mast cells was evaluated by pretreatment with the mast cell stabilizer cromolyn. Intraperitoneal administration of cromolyn downregulated pancreatitis-induced systemic increase of histamine at 1 hour (513 +/- 82 vs. 309 +/- 50, p < 0.05). Cromolyn prevented a decreased expression of PECAM-1 on circulatory neutrophils and monocytes/macrophages and against an increased expression of ICAM-1 and PECAM-1 on pulmonary neutrophils and monocytes/macrophages 6 hours after AP induction (about 40% vs. 10%, p < 0.01). The mast cell stabilizer also prevented pancreatitis-induced pulmonary endothelial barrier dysfunction at 6 hours. Thus, our data indicate that mast cells may play a critical role in the activation of leukocytes during the initiation of pancreatitis-associated lung injury by altering phenotypes of adhesion molecules.

Neutral Endopeptidase Determines the Severity of Pancreatitis-Associated Lung Injury1

BACKGROUND

Neutral endopeptidase (NEP) is a cell-surface metalloprotease that degrades proinflammatory peptides such as substance P, neurokinin A, and bradykinin. Inhibition of NEP exacerbates both experimental pancreatitis and the associated lung injury. It is unclear if worsened lung injury is the indirect result of more severe pancreatitis or if it is a direct effect of NEP inhibition in the lung.

MATERIALS AND METHODS

We used a model of pancreatitis-associated lung injury (PALI) to test the hypothesis that antagonism or genetic deletion of NEP augments PALI inflammation and pulmonary damage irregardless of the degree of pancreatitic inflammation.

RESULTS

In NEP(+/+) mice, intraperitoneal injection of porcine pancreatic elastase (elastase, 0.085 U/g at t = 0 h and t = 1 h) caused a 7-fold increase in lung myeloperoxidase (MPO) activity and marked pulmonary edema, neutrophil infiltration, and hemorrhage at 4 h as compared to control animals. The pattern of lung injury induced by elastase mimicked that observed among a separate group of animals with PALI induced by cerulein but was not associated with pancreatitis. Both NEP(-/-) mice and NEP(+/+) mice pretreated with the NEP antagonist phosphoramidon (10 mg/kg s.c.) had significant elevations of lung MPO and worsened lung histology compared to NEP(+/+) mice given elastase alone. Antagonism of either the vanilloid receptor transient receptor vanilloid 1 or the substance P receptor NK1-R had no effect on elastase-mediated lung injury in NEP-deficient mice.

CONCLUSIONS

NEP is an inhibitor of pancreatic elastase-induced lung injury, presumably via degradation of proinflammatory mediators.

Angiogenesis, endothelial cell functions, and tumor cell growth in biodegradable and nonbiodegradable devices

Development of tissue engineering creates multiple potentials for clinical treatment and scientific research. Biodegradable collagen matrices have been found to support simultaneous autotransplantation of hepatocytes after major liver resection. Dynamic angiogenesis in biodegradable devices (BDD) and nondegradable devices (NDD) transplanted into the renal subcapsule and subcutaneous tissue was measured by the distribution of radiolabeled red blood cells and serum albumin. The circulation, microvascular integrity, and capacities of endothelial cells (adhesion, proliferation, and migration) were investigated within 2 weeks after subcutaneous transplantation of both devices. Patterns of tumor cell growth in both devices were morphologically studied. After subcutaneous transplantation, significant angiogenesis was noted at 1 week in BDD implants and from 2 weeks and on in NDD implants, with an increase in implant blood and plasma volumes. Leakage index of radiolabeled albumin in NDD implants was significantly higher than in BDD implants, while the leakage index 2 weeks after BDD implant was similar to that in subcutaneous tissues. Adhesion, proliferation and migration rates of endothelial cells isolated from both devices were higher than from subcutaneous tissues. Endothelial proliferation and migration rates in BDD implants were significantly higher at 1 week, while in NDD at 2 weeks. Tumor cells migrated and grew on the top surface of NDD with a flattened shape, while growing within the BDD forming a round mass. Endothelial capacities, angiogenetic procedure, and biological and physical characteristics of the device contribute to patterns of tumor cell growth in the device. Biodegradable collagen matrix with three-dimensional structure is suitable for simultaneous transplantation with cells without prevascularization.

Alterations of Adhesion Molecule Expression and Inflammatory Mediators in Acute Lung Injury Induced by Septic and Non-septic Challenges

The lung is frequently the first failing organ during the sequential development of multiple organ dysfunction under both septic or non-septic conditions. The present study compared polymorphisms of tumor necrosis factor (TNFalpha), monocyte chemoattractant protein-1 (MCP-1), and adhesion molecule (AM) expression on circulating, recruited, and migrating leukocytes in the development of lung injury after induction of acute pancreatitis (AP) or abdominal sepsis by cecal ligation and puncture (CLP). Pulmonary alveolar barrier and endothelial barrier permeability dysfunction were measured. The expression of AMs (CD11b, CD11b/c, CD31, CD54 and CD62L) on leukocytes isolated from blood, lung tissue, and bronchoalveolar space were measured by flowcytometry. Plasma exudation to the interstitial tissue and the bronchoalveolar space significantly increased 1 and 3 hours after induction of pancreatitis and to the bronchoalveolar space from 6 hours after sepsis. Bronchoalveolar levels of MCP-1 significantly increased earlier than plasma exudation to the alveoli in both pancreatitis and sepsis. Alterations in expression of adhesion molecules on bronchoalveolar lavage (BAL) leukocytes can represent a marker reflecting leukocyte activation in the lung tissue, since both BAL and lung tissue leukocytes showed similar patterns of changes. Expression of adhesion molecules on circulating leukocytes increased 1 hour after induction of pancreatitis. Activating phenotypes of circulating, lung tissue and bronchoalveolar leukocytes may thus be responsible for the-development and severity of secondary lung injury.

Multimodal management - of value in fulminant acute pancreatitis?

BACKGROUND

The multiple organ dysfunction syndrome (MODS) is the major cause of morbidity and mortality associated with acute pancreatitis. Presently, therapy is merely organ supportive as no effective therapy against underlying causative pathophysiological mechanisms exists.

AIMS

To evaluate the effect of treatment with a platelet-activating factor inhibitor (PAFI), a monoclonal antibody against platelet endothelial cell adhesion molecule 1 (PECAM-1-MAb) and an oxygen free radical scavenger (N-acetylcystein; NAC), alone or in combination, on systemic organ dysfunction in experimental acute pancreatitis.

METHODS

Severe acute pancreatitis was induced in rats by the intraductal administration of taurodeoxycholate. Treatment was given after 1 or 3 h, and evaluations were performed 6 h after induction. Organ dysfunction was evaluated by means of endothelial integrity impairment expressed as endothelial barrier leakage index.

RESULTS

Severe acute pancreatitis caused a significant impairment in endothelial integrity in all organs studied and decreased levels of protease inhibitors compared to controls. The endothelial barrier impairment was significantly ameliorated by all treatment modalities, either given early or later. Combinations of NAC and the PECAM-1-MAb or the PECAM-1-MAb and the PAFI were the only schedules to restore endothelial barrier integrity to normal levels in most of the organs studied.

CONCLUSION

Combination therapy with NAC and PECAM-1-MAb and/or PAFI may offer effective, causative-directed supplements to organ-supportive therapy of MODS in severe acute pancreatitis.

Relationship between overexpression of NK-1R, NK-2R and intestinal mucosal damage in acute necrotizing pancreatitis

AIM: To study the expression of neurokinin-1 receptor (NK-1R) and neurokinin-2 receptor (NK-2R) in distal ileum of acute necrotizing pancreatitis (ANP) and to evaluate the relationship between expression of these two receptors and intestinal mucosal damage.

METHODS: A total of 130 adult Sprague-Dawley rats were randomly divided into two groups: the rats in ANP group (n = 80) were induced by the retrograde intraductal infusion of 30 g·L^-1 sodium taurocholate. And the rats in normal control group (n = 50) received laparotomy only. Sacrifices were made 6 h, 12 h, 24 h and 48 h later in ANP and normal control group after induction respectively. Intestinal mucosal permeability was studied by intrajejunal injection of 1.5mCi radioactive isotope ^99mTc-diethlene triamine pentacetic acid (DTPA) and the radioactivity of ^99mTc-DTPA content in urine was measured 6 h, 12 h, 24 h and 48 h after induction. Then the pancreas and intestine were prepared for pathology. Reverse transcription polymerase chain reaction (RT-PCR) was used to determine the mRNA expression of NK-1R and NK-2R, and Western blot was used to investigate the protein level of NK-1R and NK-2R.

RESULTS: In ANP rats, serious histologic damages in intestinal mucosa were observed, and the radioactivity of ^99mTc-DTPA in urine increased significantly in the ANP group. RT-PCR revealed that NK-1R and NK-2R mRNA level was overexpressed in the distal ileum of ANP as compared with the normal control group. Western blot discovered stronger NK-1R (14-fold increase) and NK-2R (9-fold increase) immunoreactivity in the intestinal mucosa of ANP rats. Moreover, the overexpression of NK-1R was associated with mucosal pathological score (r = 0.77, P < 0.01) and intestinal permeability (r = 0.68, P < 0.01) in ANP rats.

CONCLUSION: NK-1R and NK-2R contribute to disrupted neuropeptides loop balance, deteriorate intestinal damage, and are involved in pathophysiological changes in ANP.