Effect of nonprotein thiols on protein synthesis in isolated rat hepatocytes

Sulfur amino acid restriction-induced changes in redox-sensitive proteins are associated with slow protein synthesis rates

The mechanisms underlying life span extension by sulfur amino acid restriction (SAAR) are unclear. Cysteine and methionine are essential for the biosynthesis of proteins and glutathione (GSH), a major redox buffer in the endoplasmic reticulum (ER). We hypothesized that SAAR alters protein synthesis by modulating the redox milieu. Male F344-rats were fed control (CD: 0.86% methionine without cysteine) and SAAR diets (0.17% methionine without cysteine) for 12 weeks. Growth rates, food intake, cysteine and GSH levels, proteins associated with redox status and translation, and fractional protein synthesis rates (FSRs) were determined in liver. Despite a 40% higher food intake, growth rates for SAAR rats were 27% of those fed CD. Hepatic free cysteine in SAAR rats was 55% compared with CD rats. SAAR altered tissue distribution of GSH, as hepatic and erythrocytic levels were 56% and 196% of those in CD rats. Lower GSH levels did not induce ER stress (i.e., unchanged expression of Xbp1_s , Chop, and Grp78), but activated PERK and its substrates eIF2-α and NRF2. SAAR-induced changes in translation-initiation machinery (higher p-eIF2-α and 4E-BP1, and lower eIF4G-1) resulted in slower protein synthesis rates (53% of CD). Proteins involved in the antioxidant response (NRF2, KEAP1, GCLM, and NQO1) and protein folding (PDI and ERO1-α) were increased in SAAR. Lower FSR and efficient protein folding might be improving proteostasis in SAAR.

The effect of polyphenolic extract from pine bark, Pycnogenol on the level of glutathione in children suffering from attention deficit hyperactivity disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) belongs to the neurodevelopmental disorders characterized by impulsivity, distractibility and hyperactivity. In the pathogenesis of ADHD genetic and non-genetic factors play an important role. It is assumed that one of non-genetic factors should be oxidative stress. Pycnogenol, an extract from the pine bark, consists of bioflavonoids, catechins, procyanidins and phenolic acids. Pycnogenol acts as powerful antioxidant, chelating agent; it stimulates the activities of some enzymes, like SOD, eNOS, and exhibits other biological activities.

AIM

The aim of this randomized, double-blind, placebo-controlled trial was to investigate the influence of administered Pycnogenol or placebo on the level of reduced (GSH) and oxidized (GSSG) glutathione in children suffering from ADHD and on total antioxidant status (TAS). This is the first investigation of the redox glutathione state in relation to ADHD.

RESULTS

One month of Pycnogenol administration (1 mg/kg body weight/day) caused a significant decrease in GSSG and a highly significant increase in GSH levels as well as improvement of GSH/GSSG ratio in comparison to a group of patients taking a placebo. TAS in children with ADHD was decreased in comparison with reference values. Pycnogenol administration normalizes TAS of ADHD children.

Rethinking cystic fibrosis pathology: the critical role of abnormal reduced glutathione (GSH) transport caused by CFTR mutation

Though the cause of cystic fibrosis (CF) pathology is understood to be the mutation of the CFTR protein, it has been difficult to trace the exact mechanisms by which the pathology arises and progresses from the mutation. Recent research findings have noted that the CFTR channel is not only permeant to chloride anions, but other, larger organic anions, including reduced glutathione (GSH). This explains the longstanding finding of extracellular GSH deficit and dramatically reduced extracellular GSH:GSSG (glutathione disulfide) ratio found to be chronic and progressive in CF patients. Given the vital role of GSH as an antioxidant, a mucolytic, and a regulator of inflammation, immune response, and cell viability via its redox status in the human body, it is reasonable to hypothesize that this condition plays some role in the pathogenesis of CF. This hypothesis is advanced by comparing the literature on pathological phenomena associated with GSH deficiency to the literature documenting CF pathology, with striking similarities noted. Several puzzling hallmarks of CF pathology, including reduced exhaled NO, exaggerated inflammation with decreased immunocompetence, increased mucus viscoelasticity, and lack of appropriate apoptosis by infected epithelial cells, are better understood when abnormal GSH transport from epithelia (those without anion channels redundant to the CFTR at the apical surface) is added as an additional explanatory factor. Such epithelia should have normal levels of total glutathione (though perhaps with diminished GSH:GSSG ratio in the cytosol), but impaired GSH transport due to CFTR mutation should lead to progressive extracellular deficit of both total glutathione and GSH, and, hypothetically, GSH:GSSG ratio alteration or even total glutathione deficit in cells with redundant anion channels, such as leukocytes, lymphocytes, erythrocytes, and hepatocytes. Therapeutic implications, including alternative methods of GSH augmentation, are discussed.

Some chemical properties and biological role of thiazolidine compounds

In this study we have investigated some chemical properties and the biological role of thiazolidine compounds, obtained by condensation of aminothiols (L- or D-cysteine, cysteamine) with pyridoxal-5'-phosphate. These products have been tested in presence of rat liver extracts (supernatant and mitochondria); bacterial suspensions and enzymes (L- or D-aminoacid oxidase, xanthine oxidase) with interesting results which gives evidence to a biological role. Their formation in vivo may represent the regulation of intracellular levels of pyridoxal-5'-phosphate and aminothiols. Moreover, we have analysed the two diastereoisomers of the thiazolidine compounds derived from L-cysteine and D-cysteine: we have succeeded to distinguish by NMR analysis the cis and the trans forms, concluding that the interconversion of the free forms is extremely rapid at pH 7: thus, it may be relevant for the protein bound forms.

Cooperation between glutathione depletion and protein synthesis inhibition against naturally occurring neuronal death

It is generally agreed that naturally-occurring neuronal death in developing animals is dependent on the synthesis of proteins. Oxidative stress, as when intracellular concentrations of free radicals are raised or when cell constituents such as membrane lipids or protein thiols are oxidized, is also involved in various types of neuronal death. In the present report, we show that the number of naturally dying retinal cells in the chick embryo can be reduced by intraocular injections of cycloheximide, an inhibitor of protein synthesis. L-buthionine-[S,R]-sulfoximine, an inhibitor of glutathione synthesis, can either enhance or diminish the cell death, depending on the conditions of treatment. Moreover, when the two inhibitors are combined, L-buthionine-[S,R]-sulfoximine potentiates the neuroprotective effects of cycloheximide. Measurements of retinal glutathione concentration and protein synthesis show the specificity of the treatments: buthionine-sulfoximine diminishes glutathione concentrations but not protein synthesis whereas cycloheximide inhibits protein synthesis without decreasing glutathione concentrations. Naturally-occurring neuronal death thus seems to involve the synthesis of proteins, and is also influenced by oxidative phenomena. Our results extend previous data in tectal-lesioned embryos, and suggest that a moderate, non-lethal oxidative stress can enhance the resistance of ganglion cells that might otherwise have died (spontaneously or following axotomy) owing to insufficient retrograde trophic support.