Glutathione metabolism in the pancreas compared with that in the liver, kidney, and small intestine

Dietary glycine supplementation enhances glutathione availability in tissues of pigs with intrauterine growth restriction

This study tested the hypothesis that dietary supplementation with glycine enhances the synthesis and concentrations of glutathione (GSH, a major antioxidant) in tissues of pigs with intrauterine growth restriction (IUGR). At weaning (21 d of age), IUGR pigs and litter mates with normal birth weights (NBW) were assigned randomly to one of two groups, representing supplementation with 1% glycine or 1.19% l-alanine (isonitrogenous control) to a corn- and soybean meal-based diet. Blood and other tissues were obtained from the pigs within 1 wk after the feeding trial ended at 188 d of age to determine GSH, oxidized GSH (GSSG), and activities of GSH-metabolic enzymes. Results indicated that concentrations of GSH + GSSG or GSH in plasma, liver, and jejunum (P < 0.001) and concentrations of GSH in longissimus lumborum and gastrocnemius muscles (P < 0.05) were lower in IUGR pigs than in NBW pigs. In contrast, IUGR increased GSSG/GSH ratios (an indicator of oxidative stress) in plasma (P < 0.001), jejunum (P < 0.001), both muscles (P < 0.05), and pancreas (P = 0.001), while decreasing activities of γ-glutamylcysteine synthetase and GSH synthetase in liver (P < 0.001) and jejunum (P < 0.01); and GSH reductase in jejunum (P < 0.01), longissimus lumborum muscle (P < 0.01), gastrocnemius muscle (P < 0.05), and pancreas (P < 0.01). In addition, IUGR pigs had greater (P < 0.001) concentrations of thiobarbituric acid reactive substances (TBARS; an indicator of lipid peroxidation) in plasma, jejunum, muscles, and pancreas than NBW pigs. Compared with isonitrogenous controls, dietary glycine supplementation increased concentrations of GSH plus GSSG and GSH in plasma (P < 0.01), liver (P < 0.001), jejunum (P < 0.001), longissimus lumborum muscle (P = 0.001), and gastrocnemius muscle (P < 0.05); activities of GSH-synthetic enzymes in liver (P < 0.01) and jejunum (P < 0.05), while reducing GSSG/GSH ratios in plasma (P < 0.001), jejunum (P < 0.001), longissimus lumborum muscle (P < 0.001), gastrocnemius muscle (P = 0.01), pancreas (P < 0.05), and kidneys (P < 0.01). Concentrations of GSH plus GSSG, GSH, and GSSG/GSH ratios in kidneys were not affected (P > 0.05) by IUGR. Furthermore, glycine supplementation reduced (P < 0.001) TBARS concentrations in plasma, jejunum, muscles, and pancreas. Collectively, IUGR reduced GSH availability and induced oxidative stress in pig tissues, and these abnormalities were prevented by dietary glycine supplementation in a tissue-specific manner.

Is System xc- a Suitable Target for Tumour Detection and Response Assessment with Imaging?

System xc- is upregulated in cancer cells and can be imaged using novel radiotracers, most commonly with (4S)-4-(3-[18F]fluoropropyl)-L-glutamic acid (18F-FSPG). The aim of this review was to summarise the use of 18F-FSPG in humans, explore the benefits and limitations of 18F-FSPG, and assess the potential for further use of 18F-FSPG in cancer patients. To date, ten papers have described the use of 18F-FSPG in human cancers. These studies involved small numbers of patients (range 1-26) and assessed the use of 18F-FSPG as a general oncological diagnostic agent across different cancer types. These clinical trials were contrasting in their findings, limiting the scope of 18F-FSPG PET/CT as a purely diagnostic agent, primarily due to heterogeneity of 18F-FSPG retention both between cancer types and patients. Despite these limitations, a potential further application for 18F-FSPG is in the assessment of early treatment response and prediction of treatment resistance. Animal models of cancer have shown that changes in 18F-FSPG retention following effective therapy precede glycolytic changes, as indicated by 18F-FDG, and changes in tumour volume, as measured by CT. If these results could be replicated in human clinical trials, imaging with 18F-FSPG PET/CT would offer an exciting route towards addressing the currently unmet clinical needs of treatment resistance prediction and early imaging assessment of therapy response.

Molecular Genetics of Abnormal Redox Homeostasis in Type 2 Diabetes Mellitus

Numerous studies have shown that oxidative stress resulting from an imbalance between the production of free radicals and their neutralization by antioxidant enzymes is one of the major pathological disorders underlying the development and progression of type 2 diabetes (T2D). The present review summarizes the current state of the art advances in understanding the role of abnormal redox homeostasis in the molecular mechanisms of T2D and provides comprehensive information on the characteristics and biological functions of antioxidant and oxidative enzymes, as well as discusses genetic studies conducted so far in order to investigate the contribution of polymorphisms in genes encoding redox state-regulating enzymes to the disease pathogenesis.

Laying performance, egg quality, fertility, nutrient digestibility, digestive enzymes activity, gut microbiota, intestinal morphology, antioxidant capacity, mucosal immunity, and cytokine levels in meat-type Japanese quail breeders fed different phytogenic levels

A total of 180 female Japanese quail breeders were allocated to 5 treatments with 6 replicates of 6 birds and fed a diet supplemented with 0, 125, 250, 500, or 1000 mg/kg of a phytogenic feed additive (PFA) in a 9-wk experiment. Egg weight, feed efficiency, shell breaking strength and calcium content, specific gravity, Haugh unit, and percentages of fertile eggs increased with increasing PFA levels (P < 0.05). Increasing of PFA levels increased nutrient digestibility, dietary AMEn, and activities of digestive enzymes in the pancreas and intestinal digesta (P < 0.05). Supplementation of PFA reduced Escherichia coli (P < 0.05), Clostridium spp. (P < 0.05) and Salmonella spp. counts (P < 0.05), while increased Lactobacillus and Bifidobacterium spp. counts in the ileal and cecal contents (P < 0.05). Dietary PFA increased jejunal villus height and decreased ileal crypt depth (P < 0.05). Serum diamine oxidase activity and D-lactate level were decreased with increase in PFA level (P < 0.05). Increasing PFA levels increased glutathione peroxidase activity in the pancreas, small intestine, and cecal tonsil, but decreased malondialdehyde contents (P < 0.05). Birds fed PFA exhibited increased levels of secretory IgA in the intestinal mucosa (P < 0.05), and increased the percentage of CD3+ T cells, ratio of CD4+/CD8+ T cells, and cytokine concentrations in the cecal tonsils (P < 0.05). In conclusion, PFA could improve gut health and nutrient utilization and, therefore, benefit productivity, egg quality, and fertility in quails.

The Link between Type 2 Diabetes Mellitus and the Polymorphisms of Glutathione-Metabolizing Genes Suggests a New Hypothesis Explaining Disease Initiation and Progression

The present study investigated whether type 2 diabetes (T2D) is associated with polymorphisms of genes encoding glutathione-metabolizing enzymes such as glutathione synthetase (GSS) and gamma-glutamyl transferase 7 (GGT7). A total of 3198 unrelated Russian subjects including 1572 T2D patients and 1626 healthy subjects were enrolled. Single nucleotide polymorphisms (SNPs) of the GSS and GGT7 genes were genotyped using the MassArray-4 system. We found that the GSS and GGT7 gene polymorphisms alone and in combinations are associated with T2D risk regardless of sex, age, and body mass index, as well as correlated with plasma glutathione, hydrogen peroxide, and fasting blood glucose levels. Polymorphisms of GSS (rs13041792) and GGT7 (rs6119534 and rs11546155) genes were associated with the tissue-specific expression of genes involved in unfolded protein response and the regulation of proteostasis. Transcriptome-wide association analysis has shown that the pancreatic expression of some of these genes such as EDEM2, MYH7B, MAP1LC3A, and CPNE1 is linked to the genetic risk of T2D. A comprehensive analysis of the data allowed proposing a new hypothesis for the etiology of type 2 diabetes that endogenous glutathione deficiency might be a key condition responsible for the impaired folding of proinsulin which triggered an unfolded protein response, ultimately leading to beta-cell apoptosis and disease development.

Boosting GSH Using the Co-Drug Approach: I-152, a Conjugate of N-acetyl-cysteine and β-mercaptoethylamine

Glutathione (GSH) has poor pharmacokinetic properties; thus, several derivatives and biosynthetic precursors have been proposed as GSH-boosting drugs. I-152 is a conjugate of N-acetyl-cysteine (NAC) and S-acetyl-β-mercaptoethylamine (SMEA) designed to release the parent drugs (i.e., NAC and β-mercaptoethylamine or cysteamine, MEA). NAC is a precursor of L-cysteine, while MEA is an aminothiol able to increase GSH content; thus, I-152 represents the very first attempt to combine two pro-GSH molecules. In this review, the in-vitro and in-vivo metabolism, pro-GSH activity and antiviral and immunomodulatory properties of I-152 are discussed. Under physiological GSH conditions, low I-152 doses increase cellular GSH content; by contrast, high doses cause GSH depletion but yield a high content of NAC, MEA and I-152, which can be used to resynthesize GSH. Preliminary in-vivo studies suggest that the molecule reaches mouse organs, including the brain, where its metabolites, NAC and MEA, are detected. In cell cultures, I-152 replenishes experimentally depleted GSH levels. Moreover, administration of I-152 to C57BL/6 mice infected with the retroviral complex LP-BM5 is effective in contrasting virus-induced GSH depletion, exerting at the same time antiviral and immunomodulatory functions. I-152 acts as a pro-GSH agent; however, GSH derivatives and NAC cannot completely replicate its effects. The co-delivery of different thiol species may lead to unpredictable outcomes, which warrant further investigation.

Prophylactic Administration of Silybin Ameliorates L-Arginine-Induced Acute Pancreatitis

Background

Oxidative stress have been shown to play a role in the pathogenesis of acute pancreatitis. The aim of this study was to investigate the potential effect of silybin, a potent antioxidant, on L-arginine-induced acute pancreatitis in an experimental rat model.

Material/Methods

Forty female Wistar Albino rats were divided into 5 groups as follows: Group 1 (C): control group (n=8), Group 2 (SL): silybin group (n=8), Group 3 (LA): acute pancreatitis group (n=8), Group 4 (SLLA): prophylaxis group (n=8), and Group 5 (LASL): treatment group (n=8). Group C (control) received 2 intraperitoneal (i.p.) injections of physiological saline at an interval of 1 h. Group SL received only a single i.p. injection of silybin. The SLLA group received a single i.p. injection of silybin before the induction of acute pancreatitis with L-arginine, whereas the LASL group received the same injection after the induction of acute pancreatitis with L-arginine. Pancreatic tissues were histopathologically examined. Levels of amylase and oxidative stress markers (total oxidant status and total anti-oxidant status) were determined in the blood samples. Oxidative stress index was calculated.

Results

In comparison to the LA, the prophylaxis and treatment groups showed significant improvements in serum oxidative stress parameters (p=0.001 and p=0.005, respectively). Histopathological analysis showed that the treatment group had significant improvements in edema scores only (p=0.006), whereas the prophylaxis group had the same improvements in inflammation and necrosis scores as well as in total scores (p=0.004, 0.006, and 0.004, respectively).

Conclusions

When used for prophylactic rather than therapeutic purposes, silybin ameliorates serum oxidative stress parameters and improves histopathological results via its antioxidant and anti-inflammatory properties.

The effects of cocaine on different redox forms of cysteine and homocysteine, and on labile, reduced sulfur in the rat plasma following active versus passive drug injections

The aim of the present studies was to evaluate cocaine-induced changes in the concentrations of different redox forms of cysteine (Cys) and homocysteine (Hcy), and products of anaerobic Cys metabolism, i.e., labile, reduced sulfur (LS) in the rat plasma. The above-mentioned parameters were determined after i.p. acute and subchronic cocaine treatment as well as following i.v. cocaine self-administration using the yoked procedure. Additionally, Cys, Hcy, and LS levels were measured during the 10-day extinction training in rats that underwent i.v. cocaine administration. Acute i.p. cocaine treatment increased the total and protein-bound Hcy contents, decreased LS, and did not change the concentrations of Cys fractions in the rat plasma. In turn, subchronic i.p. cocaine administration significantly increased free Hcy and lowered the total and protein-bound Cys concentrations while LS level was unchanged. Cocaine self-administration enhanced the total and protein-bound Hcy levels, decreased LS content, and did not affect the Cys fractions. On the other hand, yoked cocaine infusions did not alter the concentration of Hcy fractions while decreased the total and protein-bound Cys and LS content. This extinction training resulted in the lack of changes in the examined parameters in rats with a history of cocaine self-administration while in the yoked cocaine group an increase in the plasma free Cys fraction and LS was seen. Our results demonstrate for the first time that cocaine does evoke significant changes in homeostasis of thiol amino acids Cys and Hcy, and in some products of anaerobic Cys metabolism, which are dependent on the way of cocaine administration.

Chronic pancreatitis is associated with hyperhomocysteinemia and derangements in transsulfuration and transmethylation pathways

OBJECTIVES

Homocysteine has been implicated in vascular dysfunction and thrombosis, as well as inflammatory conditions. This study was aimed to find out whether chronic pancreatitis (CP) is associated with hyperhomocysteinemia and derangements of transmethylation and transsulfuration pathways.

METHODS

We estimated homocysteine and its metabolites in 45 alcoholic CP patients, 45 tropical CP patients, and 48 healthy controls.

RESULTS

Significant increases in plasma total homocysteine and decreases in red blood cell folate, reduced glutathione, plasma methionine, cysteine, and urinary inorganic sulfate/creatinine ratio were observed in both alcoholic and tropical CP patients in comparison with healthy controls. Red blood cell glutathione and plasma cysteine levels were significantly lower in alcoholic than in tropical CP patients. However, plasma vitamin B12 levels were comparable between CP patients and controls. No significant differences in these parameters were observed between diabetic patients and nondiabetic patients. Multivariate regression analysis showed a significant negative correlation between homocysteine and folate (r = -0.415, P = 0.001) and a positive correlation between glutathione and cysteine levels (r = 0.37, P = 0.003).

CONCLUSIONS

Chronic pancreatitis is associated with hyperhomocysteinemia and derangements in transmethylation and transsulfuration pathways. Low folate levels observed in these patients seem to have a key role in this derangement.

Trypsinogen activation and glutathione content are linked to pancreatic injury in models of biliary acute pancreatitis

CONCLUSION

In models of biliary acute pancreatitis, which might resemble the situation in humans, premature activation of trypsinogen inside the pancreas ("autodigestion") occurs and is correlated with the extent of ductal and parenchymal injury. It is accompanied by a critical spending of protease inhibitors and glutathione, compromising important acinar cell defense and maintenance mechanisms.

BACKGROUND

Premature activation of pancreatic digestive enzymes and profound changes of levels of certain biochemical compounds have been implicated in the pathophysiology of acute pancreatitis. Hitherto, little information on their role in biliary acute pancreatitis has been available.

METHODS

Three types of injury to the pancreaticobiliary duct system of various severity were induced in rats--ligation of the common bile-pancreatic duct, retrograde infusion of electrolyte, or retrograde infusion of taurocholate solution--and were compared to sham-operated animals. Trypsin, trypsin inhibitory capacity (TIC), reduced glutathione (GSH), and other compounds were measured in pancreatic tissue. Histopathology, as well as serum amylase, lipase, and gamma-glutamyl transferase (gamma GT) were assessed.

RESULTS

Histopathology and elevated activity of gamma GT in the serum revealed increasing severity of pancreatic injury from sham operation through retrograde duct infusion with taurocholate. GSH was diminished even in macroscopically normal-appearing tissue, but significantly lower in altered (hemorrhagic)-looking sections. Conversely, tissue levels of trypsin were significantly increased. TIC was elevated only in the duct obstruction model, whereas it was reduced in the retrograde duct infusion models.

Control of gamma-glutamyl transpeptidase expression by glucocorticoids in the rat pancreas. Correlation with granule formation

Glucocorticoids are known to promote the formation of zymogen granules in acinar cells of the exocrine pancreas in vivo as well as in vitro. To gain insight into the mechanism of this regulation, we studied the effects of glucocorticoids on the synthesis of two components of the secretory granule membrane, the glycoprotein 2 (GP-2) and the gamma-glutamyl transpeptidase (GGT). It was demonstrated that following adrenalectomy, degranulation of pancreatic acinar cells is accompanied by a sharp decrease in GGT and GP-2 synthesis as measured by mRNA and protein accumulation. The decline of GGT synthesis was prevented by glucocorticoid replacement therapy, whereas GP-2 synthesis could be maintained with either glucocorticoid or estradiol treatment. These in vivo observations were corroborated and extended in an in vitro study using AR42J pancreatic cells. With this cell line, it was demonstrated that dexamethasone induces the formation of zymogen granules and the accumulation of a specific GGT transcript (mRNA III) by decreasing its degradation rate. At the same time, the GP-2 mRNA level was not modified by the hormonal treatment. These data demonstrate that glucocorticoids exert a positive control on the GGT expression in pancreatic cells at a post-transcriptional level. GGT, an enzyme of the glutathione metabolism, could play a significant role in protein packaging in secretory cells.

Altered lipid peroxidation/glutathione ratio in experimental extrahepatic cholestasis

1. Lipid peroxidation can occur in the presence of a cellular antioxidant-oxidant imbalance, but the role of lipid peroxides in cholestasis is not well understood. 2. This study was undertaken in order to: (i) evaluate the behaviour of a product of lipid peroxidation (thiobarbituric acid-reactive species), and of an important antioxidant tripeptide, reduced glutathione, in the course of experimental extrahepatic cholestasis; and (ii) ascertain whether there was a link between this aspect and the alterations in liver morphology. 3. Forty-five male Sprague-Dawley rats (250-300 g) were double bile duct ligated and followed from 1 to 28 days. At the end of each experimental period, blood and liver samples were collected for thiobarbituric acid-reactive species and glutathione determinations. 4. Bile duct ligated rats showed a marked increase in liver weight which was related to cholestasis duration and to some anatomical alterations such as bile duct proliferation and dilation and liver fibrosis (periportal, perivenular, perineoductular and parenchymal). 5. An increase in serum lipid peroxidation was also observed but this was not linked to hepatic thiobarbituric acid-reactive species. Erythrocyte and hepatic glutathione decreased in relation to cholestasis duration. Serum lipid peroxides and erythrocyte glutathione were correlated with liver cell necrosis. 6. In conclusion, experimental extrahepatic cholestasis determines bile duct proliferation and fibrosis, the degree of which is directly related to the duration of cholestasis itself and to liver cell necrotic phenomena.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Mouse pancreatic acinar/ductular tissue gives rise to epithelial cultures that are morphologically, biochemically, and functionally indistinguishable from interlobular duct cell cultures

Most of the pancreatic exocrine epithelium consists of acinar and intralobular duct (ductular) cells, with the balance consisting of interlobular and main duct cells. Fragments of mouse acinar/ductular epithelium can be isolated by partial digestion with collagenase and purified by Ficoll density gradient centrifugation. We investigated whether previously developed culture conditions used for duct epithelium would result in the selective survival and proliferation of ductular cells from the acinar/ductular fragments. The fragments were cultured on nitrocellulose filters coated with extracellular matrix. After 2 to 4 wk the filters were covered with proliferating cells resembling parallel cultures of duct epithelium by the following criteria: protein/DNA ratio, light and electron microscopic appearance, the presence of duct markers (carbonic anhydrase [CA] activity, CA II mRNA, the cystic fibrosis transmembrane conductance regulator), the near absence of acinar cell markers (amylase and chymotrypsin), a similar polypeptide profile after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the presence of spontaneous and secretin-stimulated electrogenic ion transport. Both duct and ductular epithelia formed fluid-filled cysts in collagen gels and both could be subcultured. We conclude that acinar/ductular tissue gives rise to ductular cells in culture by some combination of acinar cell death and/or transdifferentiation to a ductular phenotype, accompanied by proliferation of these cells and preexisting ductular cells. These cultures may be used to investigate the properties of this part of the pancreatic duct system, from which most of the pancreatic juice water and electrolytes probably originates.

Glutathione monoethyl ester ameliorates caerulein-induced pancreatitis in the mouse

Studies in animal models suggest that oxygen radicals may be important in the pathogenesis of acute pancreatitis. Because glutathione is an essential component of the defense against radical-mediated cellular injury, we investigated whether pancreatic glutathione content is influenced by inducing acute pancreatitis and whether augmenting the intracellular supply of glutathione would alter the course of pancreatitis. Caerulein, a decapeptide cholecystokinin analogue, induces acute necrotizing pancreatitis in mice when given in high doses (50 micrograms/kg per h) over a period of 6 h. The pancreatic glutathione content (total, GSH + GSSG) in mice treated with high-dose caerulein fell to 17% of normal within 4 h of beginning caerulein and recovered toward normal after discontinuing caerulein treatment. Mice treated with glutathione monoethyl ester (20 mmol/kg 1 h before caerulein, 10 mmol/kg 3 and 7 h after starting caerulein) were found to have blunted depletion of pancreatic glutathione, diminished histologic evidence of pancreatitis (necrosis, inflammation, and vacuolization), and lower serum amylase values compared with mice treated with caerulein alone. These findings suggest that the profound depletion of pancreatic glutathione caused by hyperstimulation of the pancreas with caerulein is critically important in the pathogenesis of acute caerulein-induced pancreatitis.