Glutathione monoethyl ester ameliorates caerulein-induced pancreatitis in the mouse

Diurnal variability of cysteine and glutathione content in the pancreas and liver of the mouse

The sensitivity of organs such as the liver to injury by certain drugs is modulated by the endogenous capacity to synthesize glutathione during periods of increased demand. Recent experimental evidence suggests that glutathione availability could also play an important role in preventing pancreatic injury as well. To better understand the role of cysteine availability in regulating glutathione homeostasis in the pancreas and liver under normal conditions, the diurnal variation in cysteine in mouse pancreas and liver was measured and compared with corresponding measurements of organ glutathione content. Pancreatic cysteine varied significantly over a 24-hr period, dropping to 21 nmol/g at 2 P.M. and rising to 68 nmol/g at 10 P.M. Fasting prevented this diurnal variation in pancreatic cysteine. Pancreatic glutathione was at its lowest at 10 P.M. and rose sharply to a peak at 2 A.M. Fasting had no effect on this diurnal pattern. In contrast to the pancreas, fasting did not prevent the diurnal change in liver cysteine, whereas it caused substantial depletion of liver glutathione. Together, these findings suggest that under normal conditions, pancreatic and liver glutathione content are not determined solely by tissue cysteine availability. Moreover, basal glutathione content is under differing homeostatic mechanisms in the pancreas and the liver.

Acute ethanol administration induces oxidative changes in rat pancreatic tissue

BACKGROUND

There is mounting clinical evidence that ethanol toxicity to the pancreas is linked with glutathione depletion from oxidative stress but there is not experimental proof that this occurs.

AIMS AND METHODS

The effect of acute ethanol ingestion (4 g/kg) on the pancreatic content of reduced (GSH) and oxidised (GSSG) glutathione, malondialdehyde (MDA), and carbonyl proteins were therefore studied in the rat.

RESULTS

Ethanol caused a significant reduction in GSH (p < 0.02) and an increase in GSSG (p < 0.005), MDA (p < 0.05), and carbonyl proteins (p < 0.05) in the rat pancreas. The GSH/GSSG ratios were significantly decreased after ethanol, especially in rats pretreated with diethylmaleate (DEM), a GSH blocker. Administration of ethanol after DEM further increased the rate of lipid and protein oxidation. Pretreatment with cyanamide (an inhibitor of aldehyde dehydrogenase) but not with 4-methylpyrazole (an alcohol dehydrogenase inhibitor) caused higher production of GSSG and MDA.

CONCLUSIONS

These findings indicate that acute ethanol reduces the pancreatic content of GSH, which seems to be protective against ethanol toxicity, since its depletion is accompanied by increased oxidative damage to cell structures. The further increase of lipid peroxidation and GSSG production in the presence of cyanamide suggests that acetaldehyde might be responsible for the oxidative changes that occur in pancreatic cells after ethanol administration.

Antioxidants in pediatric gastrointestinal disease

Oxidant stress seems to be involved in the pathogenesis of several important gastroenterologic disorders in infants and children. The question can still be asked, in most circumstances, whether the oxidant stress precedes, and therefore is involved in, tissue or cellular injury or is a result of injury and not of clinical importance. The data favor the former situation in several inflammatory conditions of the bowel and in a variety of liver diseases. Experimental and clinical testing of this possible basic mechanism of tissue injury over the next few years will shed light on the role of antioxidants in treating gastrointestinal disorders.

Role of oxidative stress in the pathogenesis of acute pancreatitis

During the last 10 years, the role of oxidative stress in pancreatitis and the benefits or otherwise of antioxidants has been the subject of numerous research papers. There is general agreement that glutathione and other sulphydryl compounds are depleted while lipid peroxidation is increased in pancreatic tissue during the development of acute pancreatitis. Treatment with antioxidants has been shown to reduce acinar cell injury and oedema in various animal models of pancreatitis, suggesting that the sustained generation of reactive oxygen species depletes cellular antioxidant defences. Evidence for a role for bradykinin and nitric oxide in pancreatitis has been conflicting with some studies suggesting these agents might ameliorate pancreatic dysfunction by enhancing pancreatic blood flow and secretion in response to bradykinin-stimulated generation of nitric oxide from endothelium, while other studies suggest that nitric oxide potentiates pancreatic oxidative stress. Thus, there is clearly a need for well-designed clinical trials to evaluate the protective role of antioxidant therapy in acute pancreatitis.

Cerulein-induced acute pancreatitis diminished vitamin E concentration in plasma and increased in the pancreas

Redistribution of vitamin E in the rat body was studied during acute pancreatitis induced by two intraperitoneal doses of cerulein 40 micrograms/kg of body weight at 1-hr intervals. Hyperamylasemia (2064 +/- 521 vs 6419 +/- 129 U/dL) and pancreatic edema (pancreatic water content, 71 +/- 1.2% vs 78 +/- 2%) were observed. In this model the increased level of lipid soluble fluorophore was also observed (274 +/- 18 vs 120 +/- 9.0 relative fluorescence per g dry wt). Parallel with these changes was a decrease in the level of vitamin E in the serum and an increase in the pancreas. The concentration of vitamin E in the pancreas after 6 h was 162 +/- 8.5 ng/mg dry mass vs 128.1 +/- 6.1 ng/mg dry mass in control animals. The effect of heparin on vitamin E redistribution induced by acute pancreatitis was also investigated. It was found that heparin at a dose of 100 U/kg body mass prevents the drop of the vitamin E level in the serum as well as the increases in the concentration in the pancreas tissue. It was concluded that acute pancreatitis induced redistribution of vitamin E in the rat body. Moreover, we studied the effects of heparin treatment on oxidative stress in the pancreas tissue. Acute pancreatitis caused an increase in lipofuscin accumulation, and a decrease in protein sulfhydryl groups in citrate synthetase (CS) and in malate dehydrogenase (MDH) activity. Heparin treatment that protected vitamin E accumulation in the pancreas tissue did not influence the changes in the level of lipofuscin and proteins sulfhydryl.(ABSTRACT TRUNCATED AT 250 WORDS)

The endogenous scavengers in cerulein-induced acute pancreatitis

Studies in animal models suggest that oxygen radicals are important in the pathogenesis of acute pancreatitis. Cerulein, a decapeptide isolated from the skin of the frog, Hyla caerula, is closely related to the C-terminus of cholecystokinin and it is a potent stimulant of pancreatic exocrine secretion. The aim of the present study was to measure the activity of endogenous scavengers, superoxide dismutase, catalase and glutathione levels in cerulein-induced acute pancreatitis in rats. We found that the plasma amylase and ribonuclease levels in the pancreatitis group were both significantly high (p < 0.01, p < 0.05, respectively) when compared with the control group. Although superoxide dismutase and glutathione levels of pancreatic tissue were decreased significantly (p < 0.01, p < 0.01 respectively), we observed a significant increase (p < 0.01) in catalase activity in the cerulein treated group compared to the control group. Therefore, we concluded that the profound alteration of the activities of endogenous scavengers (superoxide dismutase, catalase) and glutathione depletion occurring after cerulein-induced pancreatitis seemed to be important in tissue injury and may provide the basis for successful therapy of the disease.

Interleukin-4 suppresses the expression of macrophage NADPH oxidase heavy chain subunit (gp91-phox)

The production of superoxide anion by NADPH oxidase is a principal nonspecific bactericidal activity of macrophages and neutrophils in host defense. However, exuberant production of superoxide anion also damages host tissues. Cloning and DNA sequencing of the 91 kDa subunit (gp91-phox) open reading frame indicated a high degree of sequence conservation, greater than 90% in nucleotide and amino acid sequences, between the porcine and human cDNAs. We show in pigs that interleukin-4 (IL-4), a T lymphocyte cytokine which plays a major role in mediating antibody responses to pathogens, suppresses superoxide anion production in macrophages by specifically reducing the level of mRNA encoding gp91-phox. Messenger RNA levels are suppressed approx. 70% within 4 h and persist for 24 h without any change in the rate of mRNA turnover. Nuclear run-on analysis showed that IL-4 did not alter the rate of gp91-phox gene transcription under conditions in which IL-1 beta transcription was inhibited. These results indicate that IL-4 suppresses the inflammatory response of macrophages by mechanisms that include post-transcriptional regulation of the 91 kDa catalytic subunit of NADPH oxidase, and transcriptional regulation of inflammatory cytokine expression.

Evidence for early oxidative stress in acute pancreatitis. Clues for correction

Pancreatic oxidative stress with depletion of pancreatic glutathione is an early feature in all tested models of acute pancreatitis, and sooner or later the problem extends to the lung, irrespective of disease severity, whether toward spontaneous recovery or death from multisystem organ failure. We, therefore, sought evidence of oxidative stress in the human disease by analyzing admission blood samples. We found it from high concentrations of oxidatively altered linoleic acid in serum and vitamin C in plasma (p < 0.001 vs controls or a group of other acute abdominal crises where the proportion of patients with admission Apache II scores < or > 8 was similar). These changes were accompanied by subnormal levels of ascorbic acid in plasma (p < 0.001); selenium (p < 0.001), beta-carotene (p < 0.001), and alpha-tocopherol in serum (p = 0.005 for its molar ratio to cholesterol). Paradoxically, the plasma concentration of S-adenosylmethionine was elevated (p = 0.02), suggesting that this proximate bioactive metabolite of the essential amino acid had backtracked because its intracellular metabolism down the methionine trans-sulfuration pathway toward glutathione synthesis was disrupted. The aberrations transcended putative etiological factor, duration of symptoms, or disease severity. We conclude: (1) that oxidative stress has pervaded the vascular compartment by the time of admission in patients with acute pancreatitis, and, (2) that blood micronutrient antioxidant profiles at this stage are consistent not only with compromised intracellular capacity to synthesize/refurbish glutathione, but also vulnerability of intra- and extracellular lipid targets.

Cloning and expression of the gene encoding the porcine NADPH oxidase light-chain subunit (p22-phox)

In previous studies, we showed that interleukin-4 (IL-4) suppressed porcine (p) macrophage superoxide production and that the mechanism of suppression involved down-regulation of the superoxide-generating enzyme NADPH oxidase heavy-chain 91-kDa subunit mRNA (gp91-phox) expression. In order to examine the effect of IL-4 on expression of the gene encoding the porcine NADPH oxidase light-chain 22-kDa subunit (p22-phox), we cloned the p22-phox cDNA from a macrophage library. The p22-phox cDNA is 786 bp in length and contains a 576-bp open reading frame which predicts a primary translation product of 192 amino acids (aa). Comparison of the porcine and human 22-phox cDNAs showed a high degree of similarity between the two species in their nucleotide (85%) and deduced aa (83%) sequences. as well as in their hydropathy profiles. Notable features, including a high proline content and an iron-coordinating His94, are conserved in both the porcine and human 22-Phox. A single species of mRNA of about 1 kb was detected in macrophages. The mRNA levels remained unchanged in cells treated with lipopolysaccharide (LPS) or with IL-4 at various concentrations from 0-50 ng/ml. Prolonged treatment with LPS or IL-4 did not enhance the effect of these substances on p22-phox mRNA expression. The effect of IL-4 on p22-phox mRNA expression was also compared with another immunosuppressive cytokine, transforming growth factor-beta 1 (TGF beta 1). No change in mRNA expression was found in the cells with or without TGF beta 1 treatment. The results indicated that the heavy and light chains of NADPH oxidase are independently regulated by IL-4 in macrophages.

Cerulein-induced pancreatic cysteine depletion: prevention does not diminish acute pancreatitis in the mouse

BACKGROUND/AIMS

Induction of acute necrotizing pancreatitis with cerulein causes profound pancreatic glutathione depletion in the mouse. Because cysteine availability can be rate-limiting for glutathione synthesis, the pancreatic content of cysteine during cerulein treatment was measured and the potential benefit of augmenting pancreatic cysteine was determined.

METHODS

Female Swiss-Webster mice were treated with cerulein with and without simultaneous administration of the cysteine prodrug, L-2-oxothiazolidine 4-carboxylic acid. Pancreatic cysteine and glutathione content were measured, and serum amylase levels and pancreatic histology were assessed.

RESULTS

Pancreatic cysteine content decreased to 42% of normal after 4 hours of cerulein treatment. L-2-oxothiazolidine 4-carboxylic acid more than doubled pancreatic cysteine content at 4 hours and prevented pancreatic cysteine depletion when administered with cerulein. Cerulein caused pancreatic glutathione depletion despite this normalization of cysteine. Moreover, the biochemical and histological evidence of cerulein-induced pancreatitis was unaltered by preventing cysteine depletion.

CONCLUSIONS

Pancreatic cysteine is depleted during induction of acute pancreatitis with cerulein in parallel with depletion of pancreatic glutathione. Because preventing pancreatic cysteine depletion with L-2-oxothiazolidine 4-carboxylic acid did not prevent glutathione loss, causes of pancreatic glutathione depletion other than insufficiency of this critical precursor must also play an important role in cerulein-induced glutathione depletion.

Effect of antioxidant treatment in rats with acute hemorrhagic pancreatitis

The purpose of this study was to evaluate the effect of free radical ablation therapy in acute hemorrhagic pancreatitis. Acute pancreatitis was induced in 64 rats by retrograde injection of 5% sodium taurocholate. Thirty animals were pretreated with 100,000 units/kg/hr of superoxide dismutase (SOD) and 400,000 units/kg catalase within the first 3 hr. After 0.5, 3.5, and 12 hr of observation time, serum enzymes and the tissue content of conjugated dienes, malondialdehyde, reduced and oxidized glutathione, as well as ATP, ADP and AMP were measured. In addition, tissue samples were examined by light microscopy. Untreated rats (N = 34) developed within 12 hr an acute hemorrhagic necrotizing pancreatitis with a concomitant increase in serum enzyme levels and a decrease in reduced glutathione and ATP. Within the 12-hr observation period, 57% of the animals died. Scavenger treatment improved the tissue damage and attenuated the increase of the serum enzyme levels and the decrease in reduced glutathione and ATP. Moreover, the lethality rate was significantly lower. Oxygen radicals seem to be instrumental for the development of acute hemorrhagic pancreatitis. Thereby, antioxidant treatment reduces tissue damage, biochemical alterations and extrapancreatic complications, thus improving the final outcome.

Glutathione and ATP levels, subcellular distribution of enzymes, and permeability of duct system in rabbit pancreas following intravenous administration of alcohol and cerulein

In order to reproduce what might occur during the initial phase in some cases of acute alcohol-induced pancreatitis, rabbits were infused with diluted ethanol and low-dose cerulein. The duct permeability was assessed by recovery of fluoresceinated dextran (molecular weight 19,500) in central venous blood following orthograde duct perfusion with this substance in the anesthetized animal. Serum ethanol, lipase, and amylase were measured; pancreatic duct morphology was examined by light microscopy and electron microscopy. ATP and glutathione were measured, as were amylase, trypsinogen/trypsin, cathepsin B, and DNA levels in differential centrifugates. As expected, acinar amylase and trypsinogen showed a significant decrease in the experimental group; cathepsin B activity was similarly diminished. Compared with the control group, the activity of serum amylase and lipase in the experimental group demonstrated a significant increase. However, no differences between saline-infused control animals and the treated group regarding pancreatic duct permeability, continuity of lumen-lining epithelium, ATP and glutathione levels, and the relative subcellular distribution of pancreatic digestive and lysosomal enzymes were observed. Thus, our findings do not support the relevance of some of the most common hypotheses on the pathophysiology of acute pancreatitis in its early stage for at least a certain subgroup of patients with acute alcohol-induced pancreatitis.

Platelet-activating factor: a mediator of pancreatic inflammation during cerulein hyperstimulation

Hyperstimulation of the exocrine pancreas with cerulein causes acute pancreatitis, characterized by intensive interstitial edema, acinar vacuolization, leukocytic infiltration, and hyperamylasemia. Whereas the pathogenesis of cerulein-induced pancreatitis is not well-defined, a local inflammatory response may contribute to the full expression of acute pancreatitis. Platelet-activating factor (PAF) seems to be an important mediator of the inflammatory response. The present evidence includes: 1) pancreatic PAF levels increased in rats in which cerulein-induced pancreatitis was initiated, concomitant with an increase in calcium concentrations in the pancreatic tissue; 2) treatment of rats exposed to cerulein with WEB2170, a PAF receptor antagonist, was shown to reduce inflammatory injury, as demonstrated by decreases in pancreatic weight, Evan's blue extravasation, and myeloperoxidase activity and an improvement in pancreatic histology. In an idealized in vitro experiment mimicking cerulein-induced acute pancreatitis, in which pancreatic acini were employed, cerulein induced amylase release, an increase in [Ca2+]i, and an increase in PAF synthesis. Whereas amylase release was induced by low concentrations of cerulein (10(-11) mol/L), relatively high concentrations of cerulein (10(-9) mol/L) were required for the observed increases in PAF synthesis and the [Ca2+]i, indicating that these two responses may not occur under physiological conditions. The present study suggests that the pancreatic accumulation of PAF coupled with Ca2+ overload are important biochemical components of the pathophysiology of cerulein-induced acute pancreatitis. In fact, PAF production may serve as a primary mediator of inflammation observed during pancreatic hyperstimulation. This is an important observation that will allow a more detailed characterization of the molecular basis of cerulein-induced acute pancreatitis.