Proteomic analysis of glutathione S-transferase isoforms in mouse liver mitochondria

Sigma-Class Glutathione Transferases (GSTσ): A New Target with Potential for Helminth Control

Glutathione transferases (GSTs EC 2.5.1.18) are critical components of phase II metabolism, instrumental in xenobiotics' metabolism. Their primary function involves conjugating glutathione to both endogenous and exogenous toxic compounds, which increases their solubility and enables their ejection from cells. They also play a role in the transport of non-substrate compounds and immunomodulation, aiding in parasite establishment within its host. The cytosolic GST subfamily is the most abundant and diverse in helminths, and sigma-class GST (GSTσ) belongs to it. This review focuses on three key functions of GSTσ: serving as a detoxifying agent that provides drug resistance, functioning as an immune system modulator through its involvement in prostaglandins synthesis, and acting as a vaccine antigen.

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells

Glutathione S-transferase is heterogeneously expressed in breast cancer cells and is therefore emerging as a potential diagnostic biomarker for studying the heterogeneity of breast cancers. However, available fluorescent probes for GSTs depend heavily on GSTs-catalyzed glutathione (GSH) nucleophilic substitution reactions, making them susceptible to interference by the high concentration of nucleophilic species in the cellular environment. Moreover, the functions of subcellular GSTs are generally overlooked due to the lack of suitable luminescence probes. Herein, we report a highly selective affinity-based luminescence probe 1 for GST in breast cancer cells through tethering a GST inhibitor, ethacrynic acid, to an iridium(III) complex. Compared to activity-based probes which require the use of GSH, this probe could image GST-pi in the mitochondria by directly adducting to GST-pi (or potentially GST-pi/GS) in living cells. Probe 1 possesses desirable photophysical properties including a lifetime of 911 ns, a Stokes shift of 343 nm, and high photostability. The "turn on" luminescence mode of the probe enables highly selective detection of the GST with a limit of detection of 1.01 μM, while its long emission lifetime allows sensitive detection in organic dye-spiked autofluorescence samples by a time-resolved mode. The probe was further applied to specifically and quantitatively visualize MDA-MB-231 cells via specific binding to mitochondrial GST, and could differentiate breast cell lines based on their expression levels of GST. To the best of our knowledge, this probe is the first affinity-based iridium(III) imaging probe for the subcellular GST. Our work provides a valuable tool for unmasking the diverse roles of a subcellular GST in living systems, as well as for studying the heterogeneity of breast cancers.

Global Quantification of Glutathione S-Transferases in Human Serum Using LC-MS/MS Coupled with Affinity Enrichment

The members of the glutathione S-transferase (GST) superfamily often exhibit functional overlap and can compensate for each other. Their concentrations in serum are considered as disease biomarkers. A global and quantitative evaluation of serum GSTs is therefore urgent, but there is a lack of efficient approaches due to technological limitations. GSH magnetic beads were examined for their affinity to enrich GSTs in serum, and the enriched GSTs were quantitatively targeted using a Q Exactive HF-X mass spectrometer in parallel reaction monitoring (PRM) mode. To optimize the quantification of GST peptides, sample types, trypsin digestion, and serum loading were carefully assessed; a biosynthetic method was employed to generate isotope-labeled GST peptides, and instrumental parameters were systematically optimized. A total of 134 clinical sera were collected for GST quantification from healthy donors and patients with four liver diseases. Using the new approach, GSTs in healthy sera were profiled: 14 GST peptides were quantified, and the abundance of five GST families was ranked GSTM > GSTP > GSTA > MGST1 > GSTT1, ranging from 0.1 to 4 pmol/L. Furthermore, combining the abundance of multiple GST peptides could effectively distinguish different types of liver diseases. Quantification of serum GSTs through targeted proteomics, therefore, has apparent clinical potential for disease diagnosis.

Activity of glutathione S-transferase and its π isoenzyme in the context of single nucleotide polymorphism in the GSTP1 gene (rs1695) and tobacco smoke exposure in the patients with acute pancreatitis and healthy subjects

Oxidative stress associated with the course of acute pancreatitis (AP) can cause changes in the involvement of antioxidants, which can result in the increased production of free radicals with pro-inflammatory potential. Through its noncatalytic activity, the glutathione S-transferase and its π isoenzyme (GST-π), apart from cellular xenobiotics detoxification, are involved in the regulation of cellular signalling, metabolism and apoptosis. This study aimed to evaluate the impact of SNP rs1695 in the GSTP1 gene on GST and GST-π activity in healthy subjects and patients with acute pancreatitis (AP). The concentration of glutathione (GSH) as an important component of the antioxidant system, necessary for environmental xenobiotics detoxification by GST, and malonyldialdehyde (MDA) as a marker of oxidative stress induced by inflammation were also assessed. SNP was examined in 39 AP patients and 51 healthy subjects using PCR-RFLP methods. GST activity (in plasma and erythrocyte lysate) and GST-π activity (in erythrocyte lysate) were measured using the spectrophotometric method with 1-chloro-2,4-dinitrobenzene and ethacrynic acid as substrate, respectively. Blood GSH concentration was measured using the Patterson method. Concentrations of high-sensitive C-reactive protein (hs-CRP) and MDA were measured using commercial tests. In the blood of non-smoking AP patients with GG genotypes for SNP rs1695 in the GSTP1 gene, the lowest GST-π activity was shown. It was accompanied by the lowest hsCRP concentration in this group. In the blood of smoking healthy subjects with AG genotype, a decrease in GST-π activity was noted compared to non-smokers from this group. However, in the blood of smokers with AP, a gradually decreasing GST-π activity was noted in individuals with AA genotype, which was associated with the increasing MDA concentration. It confirms the role of GST-π in the neutralization of oxidative stress induced by the exposure to smoke xenobiotics.

Proteome and transcriptome analysis revealed florfenicol via affected drug metabolism and lipid metabolism induce liver injury of broilers

In order to explore the mechanism of liver injury induced by florfenicol (FFC) in broilers. Sixty broilers were randomly divided into 2 groups: control group: normal drinking water and feed were given every d; FFC group: tap water containing FFC (0.15g/L) was given every d and feed was taken freely; each group was given 5 dd of continuous medication and feed was taken freely. The results showed that compared with the control group, FFC could significantly inhibit the weight gain of broilers (P < 0.05), and significantly inhibit the expression of CYP1A1 and CYP2H1 in liver tissue (P < 0.05). It was found that the expression of genes related to the effect of cytochrome P450 on the metabolism of exogenous substances, the peroxisome proliferators-activated receptors signal pathway, peroxisome pathway and glutathione metabolic pathway in the liver of broilers. The results of qPCR of UDP glucuronosyltransferase family 2A1 (UGT2A1), glutathione S-transferase-like 2 (GSTAL2), hematopoietic prostaglandin D synthase (HPGDS), glutathione S-transferase theta 1(GSTT1), isocitrate dehydrogenase (NADP(+)) 1 (IDH1), acyl-CoA oxidase 2 (ACOX2), fatty acid binding protein 1 (FABP1), adenylosuccinate lyase (ADSL), and phosphoribosyl aminoim idazolesuccino carboxamide synthase (PAICS) genes which were randomly selected from the most significant genes were consistent with those of RNA-seq. The results showed that FFC can affect the drug metabolism and lipid synthesis in the liver of broiler, thus impairing the normal function of liver and the growth and development of broiler.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

In vitro and In vivo Antioxidant Activity of Flavonoid Extracted from Mulberry Fruit (Morus alba L.)

Background:

Many plants possess antioxidants that exhibit additive or synergistic activities.

Objective:

In this study, an ethanol-extracted flavonoid extracted from mulberry fruit (FEM) was evaluated for the antioxidant activity in vitro and the hemolysis in red blood cell (RBC) and lipid peroxidation in liver in vivo.

Materials and Methods:

Antioxidant activities in vitro were measured by quantifying its 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, reducing power, and Fe²⁺-chelating ability. FEM inhibits hemolysis in RBCs and effects of lipid peroxidation in the liver were estimated.

Results:

The total content of flavonoid compounds was 187.23 mg of quercetin equivalents per grams dried material. In the in vitro assays, FEM demonstrated a strong antioxidant effect, especially in DPPH scavenging activity and reducing power. Mouse RBC hemolysis induced by H₂O₂ was significantly inhibited by FEM in a dose- and time-dependent manner. The effects of FEM on lipid peroxidation in liver, mitochondria, and microsome were investigated. The percentage of inhibition at high concentration (100 μg/mL) of FEM was 45.51%, 39.36%, and 42.78% for liver, mitochondria, and microsomes, respectively. These results suggest that the FEM possesses a strong antioxidant activity both in vivo and in vitro.

SUMMARY

The total content of flavonoid compounds in mulberry fruit was 187.23 mg/g dried material

FEM showed a strong antioxidant effect, especially in 2,2-diphenyl-1-picrylhydrazyl scavenging activity and reducing power

Mouse red blood cell hemolysis induced by H₂O₂ was significantly inhibited by FEM in a dose- and time-dependent manner

The inhibition percentage at high concentration of FEM was 45.51%, 39.36%, and 42.78% for mouse’s liver, mitochondrial, and microsomes, respectively.

Abbreviations used: FEM: Flavonoid Extracted from Mulberry fruit, H₂O₂: Hydrogen peroxide, DPPH: 2,2-diphenyl-1-picrylhydrazyl, EDTA: Ethylene diamine tetraacetic acid, MDA: malondialdehyde, TBA: 2-thiobarbituric acid, RBC: Red blood cells, DNJ: 1-deoxynojirimycin, LDL: low density lipoprotein, ROS: reactive oxygen species, EDTA2Na: Ethylenediaminetetraacetic acid disodium salt.

Glutathione-S-transferase-pi (GST-pi) expression in renal cell carcinoma

Multidrug resistance correlates with unfavourable treatment outcomes in numerous cancers including renal cell carcinoma. The expression and clinical relevance of Glutathione-S-transferase-pi (GST-pi), a multidrug resistance factor, in kidney tumors remain controversial. We analyzed the expression of GST-pi in 60 formalin-fixed, paraffin-embedded renal cell carcinoma samples by immunohistochemistry and compared them with matched normal regions of the kidney. A significantly higher expression of GST-pi was observed in 87% of clear cell carcinoma and 50% of papillary subtypes. GST-pi expression did not correlate with tumor grade or patient survival. GST-pi is unlikely to be a prognostic factor for renal cell carcinoma. However, further studies with large number of samples are warranted to establish the role of GST-pi, if any, in intrinsic or acquired resistance of renal cell carcinoma to conventional treatments.

Mitochondria in metabolic disease: getting clues from proteomic studies

Mitochondria play a key role as major regulators of cellular energy homeostasis, but in the context of mitochondrial dysfunction, mitochondria may generate reactive oxidative species and induce cellular apoptosis. Indeed, altered mitochondrial status has been linked to the pathogenesis of several metabolic disorders and specially disorders related to insulin resistance, such as obesity, type 2 diabetes, and other comorbidities comprising the metabolic syndrome. In the present review, we summarize information from various mitochondrial proteomic studies of insulin-sensitive tissues under different metabolic states. To that end, we first focus our attention on the pancreas, as mitochondrial malfunction has been shown to contribute to beta cell failure and impaired insulin release. Furthermore, proteomic studies of mitochondria obtained from liver, muscle, and adipose tissue are summarized, as these tissues constitute the primary insulin target metabolic tissues. Since recent advances in proteomic techniques have exposed the importance of PTMs in the development of metabolic disease, we also present information on specific PTMs that may directly affect mitochondria during the pathogenesis of metabolic disease. Specifically, mitochondrial protein acetylation, phosphorylation, and other PTMs related to oxidative damage, such as nitrosylation and carbonylation, are discussed.

Optimization of storage and stability of camel liver glutathione S-transferase

Glutathione S-transferases (GSTs) are multifunctional enzymes and play an important role in cellular detoxification. Besides this, GSTs act as cytosolic carrier proteins that bind hydrophobic compounds such as heme, bilirubin, steroids, and polycyclic hydrocarbons. GST has great importance in biotechnology, as it is a target for vaccine and drug development and biosensors development for xenobiotics. Moreover, the GST tag has been extensively used for protein expression and purification. Until now, biophysical properties of camel liver GST have not been characterized. In the present study we have purified camel (Camelus dromedarius) liver GST to homogeneity in a single step by affinity chromatography with 23.4-fold purification and 60.6% yield. Our results showed that maximal activity of GST was at pH 6.5 and it was stable in the pH range of 5 to 10. The optimum temperature was 55°C and the Tm was 57°C. The chemical chaperone glycerol (3.3 M) was able to protect GST activity and aggregation against thermal denaturation by stabilizing the protein structure at 50 and 57°C, respectively. However, L-arginine (125 mM) did not protect GST against thermal stress. Far-ultraviolet circular dichroism (CD) spectra showed that glycerol protected the secondary structure of GST while L-arginine induced conformational changes under thermal stress. In conclusion, our studies on the GST stability suggest that glycerol works as a stabilizer and L-arginine acts as a destabilizer.

The effect of melaxen on the activity of caspases and the glutathione antioxidant system in toxic liver injury

A comparative study of the activity of caspase-1 and caspase-3, the glutathione antioxidant system and NADPH-generating enzymes (glucose-6-phosphate dehydrogenase and NADP-isocitrate dehydrogenase) and a study of DNA fragmentation in the blood serum of patients with chronic alcoholic hepatitis during basic treatment and combination therapy including melaxen have been carried out. It was found that the blood serum level of reduced glutathione, which decreases in pathology, increased more significantly in patients receiving melaxen as compared to the group of patients receiving the standard treatment. More significant changes in the activity of caspase-1 and caspase-3, glutathione reductase, glutathione peroxidase, glutathione-S-transferase, glucose-6-phosphate dehydrogenase and NADP-isocitrate dehydrogenase toward the control values were observed during the combination therapy. The correction in the melatonin level under the influence of melaxen apparently had a positive effect on the free-radical homeostasis in patients, which resulted in more pronounced changes in the investigated parameters towards the normal values as compared to the basic treatment. KEY WORD S chronic alcoholic hepatitis; glutathione peroxidase; glutathione reductase; reduced glutathione; glutathione-S-transferase; caspases; melaxen.