Capillary electrophoresis of glutathione to monitor oxidative stress and response to antioxidant treatments in an animal model

Rapid capillary electrophoresis analysis of glutathione and glutathione disulfide in roots and shoots of plants exposed to copper

INTRODUCTION

Glutathione and glutathione disulfide can be determined by capillary zone electrophoresis; however, the frequent use of acidic precipitation of protein from samples prior to analysis generates an acidic matrix of strength and pH that may cause changes in the method sensitivity, comigration of species or changes in the equilibria that relate both species in cells or fluids.

OBJECTIVE

To optimise electrophoretic conditions for glutathione and glutathione disulfide determination, and to improve pre-analytical treatment for better visualization of the signals of both peptides in an acidic matrix.

METHODOLOGY

The method consisted of direct photometric detection at 185 nm and 300 mm borate at pH 7.6 as background electrolyte. The variables under study were voltage applied, injection time, capillary length and electrolyte pH. Seedlings were hydroponically grown and the peptides were extracted with metaphosphoric acid.

RESULTS

The resulting acidic matrix was previously treated with the same background electrolyte to prevent comigration and to improve signal resolution. The optimised method showed good reproducibility and linearity, with correlation coefficients above 0.999 and detection limits below 3 microM, and determination of both analytes in less than 3 min. Analyte recovery in the process was in the 88-104% range. The concentration range found in hydroponically grown tomato plants, irrespective of copper level, was 45-100 nmol/g fresh weight for glutathione and below 56 nmol/g fresh weight for glutathione disulfide.

CONCLUSION

The results obtained here support the applicability of the method to the fast and simultaneous determination of glutathione and glutathione disulfide in tissue of shoots and roots of plants grown under either normal or stressful conditions.

Evolution of oxidative stress parameters and response to oral vitamins E and C in streptozotocin-induced diabetic rats

Type I diabetes in humans and streptozotocin (STZ)-induced diabetes in rats has been associated with oxidative stress, but antioxidant therapy has given contradictory results, in part related to the absence of common conditions used to evaluate in-vivo antioxidant properties. This prompted the study of an experimental model of antioxidant therapy in STZ-treated rats. Adult female rats received STZ (50 mgkg(-1)) and were studied 7 or 14 days later. Adipose tissue weight progressively decreased with the time of treatment, whereas plasma triglycerides increased at 7 days, before returning to control values at 14 days after STZ treatment. STZ diabetic rats had increased plasma thiobarbituric acid reacting substances and alpha-tocopherol levels, but the latter variable was decreased when corrected for total lipids. STZ diabetic rats showed a higher GSSG/GSH ratio at Day 14 and lower GSH + GSSG at Day 7 in liver. To evaluate the effect of short-term antioxidant therapy, rats received 5 doses of vitamins C and E over 3 days before being killed on Day 14. Treatment with antioxidants decreased plasma lactic acid and thiobarbituric acid reacting substances, as well as urine 8-isoprostane, and decreased plasma uric acid in controls. Vitamins increased the plasma alpha-tocopherol/lipids ratio only in control rats, although the plasma and liver alpha-tocopherol concentration increased in both groups. STZ diabetic rats showed moderate oxidative stress and treatment with antioxidant vitamins caused a significant change in a selected group of oxidative stress markers, which reflected an improvement in some of the complications associated with this disease. The present experimental conditions can be used as a sensitive experimental model to study the responsiveness of diabetes to other antioxidant interventions.

New perspective of diabetes response to an antioxidant treatment through metabolic fingerprinting of urine by capillary electrophoresis

Benefits of capillary electrophoresis to provide a comprehensive snapshot of multiple metabolites in biological samples have been exploited. Afterwards, multivariate statistical methods can be employed in order to mine additional information from the data. Urine fingerprints of control and diabetic rats have shown the clear effects of an antioxidant treatment on diabetic animals, which were not seen in controls, in a rapid, simple and cost-effective way without identifying a single marker. The procedure involves the measurement of samples with a relatively inexpensive tool such as CE-UV, without any previous treatment other than filtration and the application of chemometric tools [PCA (principal components analysis) and PLS-DA (partial least squares discriminant analysis)]. Data pre-treatment of electrophoretic profiles (alignment, normalization and baseline correction) has shown to be key for further chemometric treatment. Once developed, the methodology can easily be applied for a rapid in vivo screening of extracts with potential in vitro activity. Classification was supported by that produced after PCA and PLS-DA of target variables obtained with selectively designed, time and reagent consuming methods.

Recent developments in CE and CEC of peptides

The article brings a comprehensive survey of recent developments and applications of high-performance capillary electromigration methods, zone electrophoresis, ITP, IEF, affinity electrophoresis, EKC, and electrochromatography, to analysis, preparation, and physicochemical characterization of peptides. New approaches to the theoretical description and experimental verification of electromigration behavior of peptides and to methodology of their separations, such as sample preparation, adsorption suppression, and detection, are presented. Novel developments in individual CE and CEC modes are shown and several types of their applications to peptide analysis are presented: conventional qualitative and quantitative analysis, purity control, determination in biomatrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid and sequence analysis, and peptide mapping of proteins. Some examples of micropreparative peptide separations are given and capabilities of CE and CEC techniques to provide important physicochemical characteristics of peptides are demonstrated.

Oxidized Forms of Glutathione in Peripheral Blood as Biomarkers of Oxidative Stress

Background: Reduced glutathione (GSH) and its redox forms, glutathione disulfide (GSSG) and glutathionylated proteins (PSSG), are biomarkers of oxidative stress, but methodologic artifacts can interfere with their measurement. We evaluated the importance of correct sample handling during the preanalytical phase for GSH, GSSG, and PSSG measurement.

Methods: We used human blood for in vitro experiments with oxidants [tert-butylhydroperoxide (t-BOOH), diamide, and menadione]. For in vivo experiments, we used rats in which we cannulated the jugular and femoral veins for both oxidant administration and blood collection. We measured GSH, GSSG, and PSSG with HPLC with or without sample pretreatment with N-ethylmaleimide (NEM) to prevent artifacts. We also measured malondialdehyde (MDA) with HPLC, and protein carbonyls (PCO) with spectrophotometric procedures.

Results: When methodologic artifacts were prevented by pretreatment with NEM, GSSG results increased up to 3-fold over the basal concentrations, even in the presence of 5 μmol/L t-BOOH or diamide and 20 μmol/L menadione. PSSG increased by ∼50% at 20 μmol/L t-BOOH or diamide and at 50 μmol/L menadione. PCO and MDA remained unchanged. In vivo oxidation treatments elicited immediate and significant increases in GSSG and PSSG over basal values (up to 200-fold), whereas PCO and MDA showed only slight variation 120 or 180 min after treatment.

Conclusions: With the use of artifact-free measurement methods, GSH, GSSG, and PSSG are potentially powerful and reliable biomarkers of oxidative stress status and can be used to evaluate whether, and to what extent, oxidative stress may be involved in various diseases.

Liquid chromatography–tandem mass spectrometry assay of reduced and oxidized glutathione and main precursors in mice liver

A liquid chromatography/tandem mass spectrometry assay of glutathione (GSH), glutathione disulfide (GSSG) and of precursors (gamma-glutamyl-cysteine, cysteinyl-glycine, cysteine, cystine, homocysteine and homocystine) was developed to study glutathione synthesis in mice liver. After iodoacetic acid derivatization, the analytes were analyzed using reversed-phase gradient HPLC and detected using multiple reaction monitoring. Linear calibrations were performed over the concentrations range of 100-10,000 ng/mL for the thiol-containing precursors and extended up to 100,000 ng/mL for GSH and GSSG. The method was validated for each compound with inter-day accuracy below 11.9% and with precision below 15%. The method showed low limits of quantitation of 100 ng/mL for each thiol-containing compound and GSSG and of 200 ng/mL for other disulfides.

Comparison of the stability of glutathione and related synthetic tetrapeptides by HPLC and capillary electrophoresis

Glutathione and related peptides are interesting targets as protectors of biological systems against an oxidative injury. Two novel glutathione analogues, UPF1 and UPF15, have been designed and synthesised. As a result of different reactions taking place, the thiol-containing compounds oxidise to disulfides. In this study, the stability of UPF1, UPF15 and glutathione in various solutions was investigated by using HPLC and CE. The results showed that UPF1 and UPF15 are powerful hydroxyl radical scavengers and their dimerisation process velocity is higher than that of glutathione.