In vivo evidence for the role of GM-CSF as a mediator in acute pancreatitis-associated lung injury. (49/463)

Severe pancreatitis is frequently associated with acute lung injury (ALI) and the respiratory distress syndrome. The role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in mediating the ALI associated with secretagogue-induced experimental pancreatitis was evaluated with GM-CSF knockout mice (GM-CSF -/-). Pancreatitis was induced by hourly (12x) intraperitoneal injection of a supramaximally stimulating dose of the cholecystokinin analog caerulein. The resulting pancreatitis was similar in GM-CSF-sufficient (GM-CSF +/+) control animals and GM-CSF -/- mice. Lung injury, quantitated by measuring lung myeloperoxidase activity (an indicator of neutrophil sequestration), alveolar-capillary permeability, and alveolar membrane thickness was less severe in GM-CSF -/- than in GM-CSF +/+ mice. In GM-CSF +/+ mice, pancreas, lung and serum GM-CSF levels increase during pancreatitis. Lung levels of macrophage inflammatory protein (MIP)-2 are also increased during pancreatitis, but, in this case, the rise is less profound in GM-CSF -/- mice than in GM-CSF +/+ controls. Administration of anti-MIP-2 antibodies was found to reduce the severity of pancreatitis-associated ALI. Our findings indicate that GM-CSF plays a critical role in coupling pancreatitis to ALI and suggest that GM-CSF may act indirectly by regulating the release of other proinflammatory factors including MIP-2.  (+info)

Cathepsin B inhibition prevents trypsinogen activation and reduces pancreatitis severity. (50/463)

Intrapancreatic activation of trypsinogen is believed to play a critical role in the initiation of acute pancreatitis, but mechanisms responsible for intrapancreatic trypsinogen activation during pancreatitis have not been clearly defined. In previous in vitro studies, we have shown that intra-acinar cell activation of trypsinogen and acinar cell injury in response to supramaximal secretagogue stimulation could be prevented by the cell permeant cathepsin B inhibitor E64d (Saluja A, Donovan EA, Yamanaka K, Yamaguchi Y, Hofbauer B, and Steer ML. Gastroenterology 113: 304-310, 1997). The present studies evaluated the role of intrapancreatic trypsinogen activation, this time under in vivo conditions, in two models of pancreatitis by using another highly soluble cell permeant cathepsin B inhibitor, L-3-trans-(propylcarbamoyl)oxirane-2-carbonyl-L-isoleucyl-L-proline methyl ester (CA-074me). Intravenous administration of CA-074me (10 mg/kg) before induction of either secretagogue-elicited pancreatitis in mice or duct infusion-elicited pancreatitis in rats markedly reduced the extent of intrapancreatic trypsinogen activation and substantially reduced the severity of both pancreatitis models. These observations support the hypothesis that, during the early stages of pancreatitis, trypsinogen activation in the pancreas is mediated by the lysosomal enzyme cathepsin B. Our findings also suggest that pharmacological interventions that inhibit cathepsin B may prove useful in preventing acute pancreatitis or reducing its severity.  (+info)

Primary sensory neurons: a common final pathway for inflammation in experimental pancreatitis in rats. (51/463)

We hypothesized that neurogenic inflammation is a common final pathway for parenchymal inflammation in pancreatitis and evaluated the role of primary sensory neurons in secretagogue-induced and obstructive pancreatitis. Neonatal rats received either the primary sensory neuron-denervating agent capsaicin (50 mg/kg s.c.) or vehicle. At 8 wk of age, pancreatitis was produced by six hourly injections of caerulein (50 microg/kg i.p.) or by common pancreaticobiliary duct ligation (CPBDL). The severity of pancreatitis was assessed by serum amylase, pancreatic myeloperoxidase (MPO) activity, histological grading, pancreatic plasma extravasation, and wet-to-dry weight ratio. Caerulein significantly increased MPO activity and wet-to-dry weight ratio, produced histological evidence of edematous pancreatitis, induced plasma extravasation, and caused hyperamylasemia. CPBDL increased MPO activity and produced histological evidence of pancreatitis. Neonatal capsaicin administration significantly reduced tissue MPO levels, histological severity scores, and wet-to-dry weight ratio and abolished plasma extravasation. These results demonstrate that primary sensory neurons play a significant role in the inflammatory cascade in experimental pancreatitis and appear to constitute a common final pathway for pancreatic parenchymal inflammation.  (+info)

Studies on caerulein (FI6934). Absorption, distribution, metabolism and excretion of caerulein. (52/463)

35S-Caerulein (35S-FI6934) was administered intramuscularly into rats (280 mug/kg), rabbits (380 mug/kg) and mice (3.3 mg/kg). Blood level of radioactivity in rats and rabbits reached the maximum at 5 and 15 min after administration, respectively, and then decreased rapidly. In both rats and rabbits, the radioactivities were excreted mainly into the urine. The physiological activity of FI6934 was detected in the blood of rats and rabbits collected within 15 and 30 min after injection respectively, and in the bile of rats collected within the first 2 hr. In rats, the radioactivities were densely distributed in kidney, liver, pancreas, and intestine. Four metabolites of 35S-FI6934 were isolated by paper chromatography from rat urine (i.m., 500 mug/kg). The main metabolites, F-I and F-II, were negative to nynhydrin and to the Ehrlich reagent and carried no physiological activity. 35S-Chym-I, which was prepared by digesting 35S-FI6934 with chymotrypsin, was injected to rats (i.m. 16 or 8 mg/kg/. The metabolite, C-I, isolated from the urine was considered to have a very similar structure to F-I from the results of paper chromatography and paper electrophoresis. By amino acid analysis, the structure of C-I was estimated to be as follows: Pyr-Gln (or Glu)-Asp-Tyr-Thr-Gly. (see article).  (+info)

Pancreatic microcirculatory impairment in experimental acute pancreatitis in rats. (53/463)

AIM: To study the feature of pancreatic microcirculatory impairment, especially the initial changes, in caerulein-induced experimental acute pancreatitis (AP). METHODS: The pancreatic microcirculation of caerulein-induced AP model was studied by intravital fluorescence microscopy with FITC-labeled erythrocytes (FITC-RBC), scanning electron microscopy of vascular corrosion casts, and light microscopy of Chinese ink-injected/cleared tissues. RESULTS: Animals in caerulein-treated group showed hyperamylemia (X2), pancreatic oedema, infiltration of inflammatory cells in pancreas. Constrictions of intralobular arteriolar sphincters, presence of vacuoles in all layers of sphincter, and gross irregularity in capillary network of acini were found in the AP specimens. The decrease of pancreatic capillary blood flow (0.34+/-0.10 nl x min(-1) vs 0.91+/-0.06 nl x min(-1) of control, P<0.001), reduction of functional capillary density(277+/-13 cm(-1) vs 349+/-8 cm(-1) of control, P<0.001), and irregular intermittent perfusion were observed in caerulein-induced groups. CONCLUSION: Impairment and constriction of pancreatic intralobular arteriolar sphincter are the initial microcirculatory lesions in the early phase of acute pancreatitis, and play a key role in the pancreatic ischaemia and pancreatic microvascular failure in acute pancreatitis.  (+info)

Inhibition of cyclooxygenase-2 ameliorates the severity of pancreatitis and associated lung injury. (54/463)

Cyclooxygenase-2 (COX-2), a widely distributed enzyme, plays an important role in inflammation. We have studied the role of COX-2 in acute pancreatitis and pancreatitis-associated lung injury using both the pharmacological inhibition of COX-2 and genetic deletion of COX-2. Pancreatitis was induced in mice by 12 hourly injections of cerulein. The severity of pancreatitis was assessed by measuring serum amylase, pancreatic trypsin activity, intrapancreatic sequestration of neutrophils, and acinar cell necrosis. The severity of lung injury was evaluated by measuring lactate dehydrogenase levels in the bronchoalveolar lavage fluid and by quantitating neutrophil sequestration in the lung. In both the pharmacologically inhibited and genetically altered mice, the severity of pancreatitis and pancreatitis-associated lung injury was reduced compared with the noninhibited strains of COX-2-sufficient mice. This reduction in injury indicates that COX-2 plays an important proinflammatory role in pancreatitis and its associated lung injury. Our findings support the concept that COX-2 inhibitors may play a beneficial role in the prevention of acute pancreatitis or in the reduction of its severity.  (+info)

Expression and functional analysis of rat P23, a gut hormone-inducible isoform of trypsin, reveals its resistance to proteinaceous trypsin inhibitors. (55/463)

Rat P23 is an isoform of trypsin (ogens) synthesized by rat acinar cells. Expression of P23 is stimulated strongly by caerulein, an analogue of cholecystokinin (CCK). However, the physiological relevance of rat P23 in healthy and pathological conditions such as caerulein-induced pancreatitis is largely unknown. Using recombinant P23 trypsinogen and reconstitution analysis of zymogen autoactivation, unique inhibitor-resistance characteristics of P23 were elucidated. P23 cDNA was expressed in Escherichia coli periplasm, yielding recombinant P23 trypsinogen. Autoactivation of zymogen granule contents from caerulein-induced rat pancreas was also studied. Activation kinetics of P23 by enterokinase was similar to those of rat anionic trypsinogen, which is a major isoform of trypsinogen. Interestingly, rat pancreatic secretory trypsin inhibitor (PSTI), which protects against deleterious activation of trypsinogens in zymogen granules, failed to inhibit P23 trypsin even with four-fold molar excess, at which concentration it effectively inhibited rat anionic trypsin to almost 100%. P23 trypsin also showed marked resistance to proteinaceous trypsin inhibitors such as soybean trypsin inhibitor and aprotinin. P23 trypsin activated by enterokinase dramatically accelerated the cascade of autoactivation of anionic trypsinogen even in the presence of PSTI. Taken together with a previous observation that P23 is specifically upregulated 14-fold by 24-h caerulein infusion, these results suggest that elevated levels of P23 should be taken into consideration in the mechanism of trypsinogens within the pancreas in pathological conditions.  (+info)

Role of S-adenosylmethionine in two experimental models of pancreatitis. (56/463)

Severe necrotizing pancreatitis occurs in young female mice fed a choline-deficient and ethionine-supplemented (CDE) diet. Although the mechanism of the pancreatitis is unknown, one consequence of this diet is depletion of hepatic S-adenosylmethionine (SAM). SAM formation is catalyzed by methionine adenosyltransferases (MATs), which are encoded by liver-specific (MAT1A) and non-liver-specific (MAT2A) genes. In this work, we examined changes in pancreatic SAM homeostasis in mice receiving the CDE diet and the effect of SAM treatment. We found that both MAT forms are expressed in normal pancreas and pancreatic acini. After 48 h of the CDE diet, SAM levels decreased 50% and MAT1A-encoded protein disappeared via post-translational mechanisms, whereas MAT2A-encoded protein increased via pretranslational mechanisms. CDE-fed mice exhibited extensive necrosis, edema, and acute pancreatic inflammatory infiltration, which were prevented by SAM treatment. However, old female mice consuming the CDE diet that do not develop pancreatitis showed a similar fall in pancreatic SAM level. SAM was also protective in cerulein-induced pancreatitis in the rat, but the protection was limited. Although the pancreatic SAM level fell by more than 80% in the MAT1A knockout mice, no pancreatitis developed. This study thus provides several novel findings. First, the so-called liver-specific MAT1A is highly expressed in the normal pancreas and pancreatic acini. Second, the CDE diet causes dramatic changes in the expression of MAT isozymes by different mechanisms. Third, in contrast to the situation in the liver, where absence of MAT1A and decreased hepatic SAM level can lead to spontaneous tissue injury, in the pancreas the roles of SAM and MAT1A appear more complex and remain to be defined.  (+info)