Human cytosolic glutathione transferases: structure, function, and drug discovery

The role of glutathione S-transferases in human disease pathogenesis and their current inhibitors

Glutathione S-transferases (GSTs) are a family of enzymes detoxifying various harmful compounds by conjugating them with glutathione. While primarily beneficial, dysregulation of GST activity or specific isoforms can contribute to disease pathogenesis. The intricate balance of detoxification processes regulated by GSTs is pivotal in cellular homeostasis, whereby dysregulation in these mechanisms can have profound implications for human health. Certain GSTs neutralize carcinogens, shielding cells and potentially preventing tumorigenesis. Polymorphisms in specific GSTs may result in the accumulation of toxic metabolites, exacerbating oxidative stress, inflammation, and DNA damage, notably observed in neurodegenerative diseases like Parkinson's disease. They can also modulate signaling pathways involved in cell proliferation, survival, and apoptosis, with aberrant activity potentially contributing to uncontrolled cell growth and resistance to cell death, thus promoting cancer development. They may also contribute to autoimmune diseases and chronic inflammatory conditions. This knowledge is useful for designing therapeutic interventions and understanding chemoresistance due to GST polymorphisms. A variety of GST inhibitors have been developed and investigated, with researchers actively working on new inhibitors aimed at preventing off-target effects. By leveraging knowledge of the involvement of specific GST isoforms in disease pathogenesis across different populations, more effective and targeted therapeutics can be designed to enhance patient care and improve treatment outcomes.

Unravelling selectivity discrepancies of protoporphyrin binding to glutathione transferase: A comparative analysis of molecular dynamic simulated versus implicit solvent-minimized protein models

Schistosomiasis is a neglected tropical disease caused by parasitic trematodes, which are an ongoing global health and veterinary concern owing to their acquired drug resistance pressure to available treatment. There is a need for a new generation of effective anthelmintics for preventive and therapeutic purposes. Natural products, such as porphyrins, have been reported to inhibit the main detoxification enzymes in these parasites, called glutathione transferases, which help them evade immune response and drug therapy, thus making them good drug targets. Computational modelling was used to screen potential inhibitors out of 461 protoporphyrin IX-like compounds, including a potent known inhibitor called bromosulfophthalein. However, unlike traditional docking, where the stable energy-minimized structure is used, a short molecular dynamic simulation step was added to yield the most averaged protein structure conformation as the starting point of high throughput virtual screening. Here, it was shown that the starting point is crucial as the results suggested different lead compounds; for the 26-kDa japonicum GST, the top-scoring compounds were CID: 122690402 for the minimized structure and CID: 137797052 for the MD-simulated structure. Similarly, for the 28-kDa haematobium GST, the lead compounds were CID: 70415734 and CID: 69301914, respectively. These results highlight the importance of incorporating protein dynamics into structure-based drug design and provide valuable insights into the development of porphyrin-based therapeutics against schistosomiasis and other helminthic infections.

Isozyme-specific inhibition of GSTP1-1: a crucial element in cancer-targeting drugs

Selectively targeting cancer cells has been a main challenge in cancer therapy. The purpose is to spare normal cells and minimize side effects. Targeting the antioxidant enzymes (i.e. GST) for the purpose of selectively killing cancer cells has attracted much attention in the past few decades. The intention of lowering the antioxidant enzymes is "tipping" the ROS concentrations to levels above the cytotoxic threshold. This would result in extensive damage to the cellular macromolecules and organelles leading to cell death. Here we focused on the glutathione S-transferase pi 1 (GSTP1), because it is one of the overexpressed antioxidant enzymes in cancer and has been targeted for the purpose of killing cancer cells. However, most available GSTP1 inhibitors do not show selectivity towards the isozyme. This can potentially lead to many side effects. Therefore, the search for optimal selective GSTP1 inhibitors is still underway. The novelty of this review stems from highlighting the significance of selectively targeting GSTP1. We also addressed the structural feature of the enzyme which challenges the design of novel selective GSTP1 inhibitors. We then provide guidelines to help resolve these challenges to help design future compounds. The first objective of this review is to present a brief literature review to highlight the importance of selectively targeting GSTP1. Briefly, the lack of selectivity towards GSTP1 has resulted in extensive side effects which limited reaching advanced clinical trials. We screened publications on many potential inhibitors, including some that reached phase I and II clinical trials, for their ability to bind with GSTP1, GSTM, and GSTA. All compounds appear to bind different GST isozymes (at least to some extent). The second objective is to present differences in the structures of GST isotypes (GSTP1, GSTM, GSTA) which could allow selectively targeting a certain isotype. Our modelling results highlight the importance of certain structural moieties for better selective binding to GSTP1.

Brain Fog: a Narrative Review of the Most Common Mysterious Cognitive Disorder in COVID-19

It has been more than three years since COVID-19 impacted the lives of millions of people, many of whom suffer from long-term effects known as long-haulers. Notwithstanding multiorgan complaints in long-haulers, signs and symptoms associated with cognitive characteristics commonly known as "brain fog" occur in COVID patients over 50, women, obesity, and asthma at excessive. Brain fog is a set of symptoms that include cognitive impairment, inability to concentrate and multitask, and short-term and long-term memory loss. Of course, brain fog contributes to high levels of anxiety and stress, necessitating an empathetic response to this group of COVID patients. Although the etiology of brain fog in COVID-19 is currently unknown, regarding the mechanisms of pathogenesis, the following hypotheses exist: activation of astrocytes and microglia to release pro-inflammatory cytokines, aggregation of tau protein, and COVID-19 entry in the brain can trigger an autoimmune reaction. There are currently no specific tests to detect brain fog or any specific cognitive rehabilitation methods. However, a healthy lifestyle can help reduce symptoms to some extent, and symptom-based clinical management is also well suited to minimize brain fog side effects in COVID-19 patients. Therefore, this review discusses mechanisms of SARS-CoV-2 pathogenesis that may contribute to brain fog, as well as some approaches to providing therapies that may help COVID-19 patients avoid annoying brain fog symptoms.

Identification of Boc2Lys-Linked Ethacrynic Acid and Its Analogues As Efficient Glutathione S-Transferase Degraders

Targeted protein degradation has been emerging as a promising strategy for drug design and a useful tool for the research of intracellular protein function by specifically downregulating the protein level via promoted degradation. Aside from proteolysis targeting chimeras (PROTAC) that utilize a specific E3 ligase ligand as a tag to recruit polyubiquitin onto the targeted protein and subsequently induce degradation, Boc3Arg was also reported an efficient tag to induce degradation through directly localizing the protein to the 20S proteasome. Based on the similarity of Boc2Lys and Boc3Arg, we identified that Boc2Lys also efficiently induced targeted protein degradation, taking glutathione S-transferase as an example. We found that Boc2Lys-linked ethacrynic acid was able to dose-dependently downregulate the target protein in a mechanism distinct to Boc3Arg.

GSTT1/GSTM1 deficiency aggravated cisplatin-induced acute kidney injury via ROS-triggered ferroptosis

Introduction

Cisplatin is a widely used chemotherapeutic agent prescribed to treat solid tumors. However, its clinical application is limited because of cisplatin- induced nephrotoxicity. A known complication of cisplatin is acute kidney injury (AKI). Deletion polymorphisms of GSTM1 and GSTT1, members of the glutathione S-transferase family, are common in humans and are presumed to be associated with various kidney diseases. However, the specific roles and mechanisms of GSTM1 and GSTT1 in cisplatin induced AKI remain unclear.

Methods

To investigate the roles of GSTM1 and GSTT1 in cisplatin-induced AKI, we generated GSTM1 and GSTT1 knockout mice using CRISPR-Cas9 technology and assessed their kidney function under normal physiological conditions and cisplatin treatment. Using ELISA kits, we measured the levels of oxidative DNA and protein damage, along with MDA, SOD, GSH, and the GSH/GSSG ratio in wild-type and GSTM1/GSTT1 knockout mice following cisplatin treatment. Additionally, oxidative stress levels and the expression of ferroptosis-related proteins in kidney tissues were examined through Western blotting, qPCR, immunohistochemistry, and immunofluorescence techniques.

Results

Here, we found that GSTT1 and GSTM1 were downregulated in the renal tubular cells of AKI patients and cisplatin-treated mice. Compared with WT mice, Gstm1/Gstt1-DKO mice were phenotypically normal but developed more severe kidney dysfunction and exhibited increased ROS levels and severe ferroptosis after injecting cisplatin.

Discussion

Our study revealed that GSTM1 and GSTT1 can protect renal tubular cells against cisplatin-induced nephrotoxicity and ferroptosis, and genetic screening for GSTM1 and GSTT1 polymorphisms can help determine a standard cisplatin dose for cancer patients undergoing chemotherapy.

Glutathione transferase P1 is modified by palmitate

Glutathione transferase P1 (GSTP1) is a multi-functional protein that protects cells from electrophiles by catalyzing their conjugation with glutathione, and contributes to the regulation of cell proliferation, apoptosis, and signalling. GSTP1, usually described as a cytosolic enzyme, can localize to other cell compartments and we have reported its strong association with the plasma membrane. In the current study, the hypothesis that GSTP1 is palmitoylated and this modification facilitates its dynamic localization and function was investigated. Palmitoylation is the reversible post-translational addition of a 16-C saturated fatty acid to proteins, most commonly on Cys residues through a thioester bond. GSTP1 in MCF7 cells was modified by palmitate, however, GSTP1 Cys to Ser mutants (individual and Cys-less) retained palmitoylation. Treatment of palmitoylated GSTP1 with 0.1 N NaOH, which cleaves ester bonds, did not remove palmitate. Purified GSTP1 was spontaneously palmitoylated in vitro and peptide sequencing revealed that Cys48 and Cys102 undergo S-palmitoylation, while Lys103 undergoes the rare N-palmitoylation. N-palmitoylation occurs via a stable NaOH-resistant amide bond. Analysis of subcellular fractions of MCF7-GSTP1 cells and a modified proximity ligation assay revealed that palmitoylated GSTP1 was present not only in the membrane fraction but also in the cytosol. GSTP1 isolated from E. coli, and MCF7 cells (grown under fatty acid free or regular conditions), associated with plasma membrane-enriched fractions and this association was not altered by palmitoyl CoA. Overall, GSTP1 is modified by palmitate, at multiple sites, including at least one non-Cys residue. These modifications could contribute to regulating the diverse functions of GSTP1.

Persistent Post COVID-19 Endothelial Dysfunction and Oxidative Stress in Women

The assessment of endothelial dysfunction and free radical homeostasis parameters were performed in 92 women, aged 45 to 69 years, divided into the following groups: women without COVID-19 (unvaccinated, no antibodies, control); women with acute phase of COVID-19 infection (main group, COVID-19+); 12 months post COVID-19+; women with anti-SARS-CoV-2 IgG with no symptoms of COVID-19 in the last 12 months (asymptomatic COVID-19). Compared to the control, patients of the main group had lower glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities, decreased advanced glycation end products (AGEs) level, higher glutathione reductase (GR) activity, and higher glutathione S transferases pi (GSTpi), thiobarbituric acid reactants (TBARs), endothelin (END)-1, and END-2 concentrations (all p ≤ 0.05). The group with asymptomatic COVID-19 had lower 8-OHdG and oxidized glutathione (GSSG) levels, decreased total antioxidant status (TAS), and higher reduced glutathione (GSH) and GSH/GSSG levels (all p ≤ 0.05). In the group COVID-19+, as compared to the group without clinical symptoms, we detected lower GPx and SOD activities, decreased AGEs concentration, a higher TAS, and greater GR activity and GSTpi and TBARs concentrations (all p ≤ 0.05). The high content of lipid peroxidation products 12 months post COVID-19+, despite decrease in ENDs, indicates long-term changes in free radical homeostasis. These data indicate increased levels of lipid peroxidation production contribute, in part, to the development of free radical related pathologies including long-term post COVID syndrome.

The Role of Glutathione Transferase Omega-Class Variant Alleles in Individual Susceptibility to Ovarian Cancer

The tumor microenvironment is affected by reactive oxygen species and has been suggested to have an important role in ovarian cancer (OC) tumorigenesis. The role of glutathione transferases (GSTs) in the maintenance of redox balance is considered as an important contributing factor in cancer, including OC. Furthermore, GSTs are mostly encoded by highly polymorphic genes, which further highlights their potential role in OC, known to originate from accumulated genetic changes. Since the potential relevance of genetic variations in omega-class GSTs (GSTO1 and GSTO2), with somewhat different activities such as thioltransferase and dehydroascorbate reductase activity, has not been clarified as yet in terms of susceptibility to OC, we aimed to investigate whether the presence of different GSTO1 and GSTO2 genetic variants, individually or combined, might represent determinants of risk for OC development. Genotyping was performed in 110 OC patients and 129 matched controls using a PCR-based assay for genotyping single nucleotide polymorphisms. The results of our study show that homozygous carriers of the GSTO2 variant G allele are at an increased risk of OC development in comparison to the carriers of the referent genotype (OR1 = 2.16, 95% CI: 0.88-5.26, p = 0.08; OR2 = 2.49, 95% CI: 0.93-6.61, p = 0.06). Furthermore, individuals with GST omega haplotype H2, meaning the concomitant presence of the GSTO1*A and GSTO2*G alleles, are more susceptible to OC development, while carriers of the H4 (*A*A) haplotype exhibited lower risk of OC when crude and adjusted haplotype analysis was performed (OR1 = 0.29; 95% CI: 0.12-0.70; p = 0.007 and OR2 = 0.27; 95% CI: 0.11-0.67; p = 0.0054). Overall, our results suggest that GSTO locus variants may confer OC risk.

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.

Overexpression of Glutathione S-Transferases in Human Diseases: Drug Targets and Therapeutic Implications

Glutathione S-transferases (GSTs) are a major class of phase II metabolic enzymes. Besides their essential role in detoxification, GSTs also exert diverse biological activities in the occurrence and development of various diseases. In the past few decades, much research interest has been paid to exploring the mechanisms of GST overexpression in tumor drug resistance. Correspondingly, many GST inhibitors have been developed and applied, solely or in combination with chemotherapeutic drugs, for the treatment of multi-drug resistant tumors. Moreover, novel roles of GSTs in other diseases, such as pulmonary fibrosis and neurodegenerative diseases, have been recognized in recent years, although the exact regulatory mechanisms remain to be elucidated. This review, firstly summarizes the roles of GSTs and their overexpression in the above-mentioned diseases with emphasis on the modulation of cell signaling pathways and protein functions. Secondly, specific GST inhibitors currently in pre-clinical development and in clinical stages are inventoried. Lastly, applications of GST inhibitors in targeting cell signaling pathways and intracellular biological processes are discussed, and the potential for disease treatment is prospected. Taken together, this review is expected to provide new insights into the interconnection between GST overexpression and human diseases, which may assist future drug discovery targeting GSTs.

Intracellular spatiotemporal metabolism in connection to target engagement

The metabolism in eukaryotic cells is a highly ordered system involving various cellular compartments, which fluctuates based on physiological rhythms. Organelles, as the smallest independent sub-cell unit, are important contributors to cell metabolism and drug metabolism, collectively designated intracellular metabolism. However, disruption of intracellular spatiotemporal metabolism can lead to disease development and progression, as well as drug treatment interference. In this review, we systematically discuss spatiotemporal metabolism in cells and cell subpopulations. In particular, we focused on metabolism compartmentalization and physiological rhythms, including the variation and regulation of metabolic enzymes, metabolic pathways, and metabolites. Additionally, the intricate relationship among intracellular spatiotemporal metabolism, metabolism-related diseases, and drug therapy/toxicity has been discussed. Finally, approaches and strategies for intracellular spatiotemporal metabolism analysis and potential target identification are introduced, along with examples of potential new drug design based on this.

Junction of the redox dynamic, orchestra of signaling, and altered metabolism in regulation of T- cell lymphoma

T-cell lymphoma is a hematologic neoplasm derived from the lymphoid lineage. It belongs to a diverse group of malignant disorders, mostly affecting the young population worldwide, that vary with respect to molecular features as well as genetic and clinical complexities. Cancer cells rewire the cellular metabolism, persuading it to meet new demands of growth and proliferation. Furthermore, the metabolic alterations and heterogeneity are aberrantly driven in cancer by a combination of genetic and non-genetic factors, including the tumor microenvironment. New insight into cancer metabolism highlights the importance of nutrient supply to tumor development and therapeutic responses. Importantly, oxidative stress due to an imbalance in the redox status of reactive species via exogenous and/or endogenous factors is closely related to multiple aspects of cancer. This alters the signaling pathways governed through the multiple intracellular signal transduction and transcription factors, leading to tumor progression. These oncogenic signaling molecules are regulated through different redox sensors, including nuclear factor-erythroid 2 related factor 2 (Nrf2), phase-II antioxidant enzyme, and NQO1 (NADPH quinone oxidoreductase (1). The existing understanding of the molecular mechanisms of T-cell lymphoma regulation through the cross-talk of redox sensors under the influence of metabolic vulnerability is not well explored. This review highlights the role of the redox dynamics, orchestra of signaling, and genetic regulation involved in T-cell lymphoma progression in addition to the challenges to their etiology, treatment, and clinical response in light of recent updates.

The Multifaceted Role of Glutathione S-Transferases in Health and Disease

In humans, the cytosolic glutathione S-transferase (GST) family of proteins is encoded by 16 genes presented in seven different classes. GSTs exhibit remarkable structural similarity with some overlapping functionalities. As a primary function, GSTs play a putative role in Phase II metabolism by protecting living cells against a wide variety of toxic molecules by conjugating them with the tripeptide glutathione. This conjugation reaction is extended to forming redox sensitive post-translational modifications on proteins: S-glutathionylation. Apart from these catalytic functions, specific GSTs are involved in the regulation of stress-induced signaling pathways that govern cell proliferation and apoptosis. Recently, studies on the effects of GST genetic polymorphisms on COVID-19 disease development revealed that the individuals with higher numbers of risk-associated genotypes showed higher risk of COVID-19 prevalence and severity. Furthermore, overexpression of GSTs in many tumors is frequently associated with drug resistance phenotypes. These functional properties make these proteins promising targets for therapeutics, and a number of GST inhibitors have progressed in clinical trials for the treatment of cancer and other diseases.

Molecular dynamics-derived pharmacophores of Schistosoma glutathione transferase in complex with bromosulfophthalein: Screening and analysis of potential inhibitors

Schistosoma glutathione transferases (GSTs) have been identified as attractive drug targets for the design of novel antischistosomals. Here, we used in silico methods to validate the discriminative inhibitory properties of bromosulfophthalein (BSP) against the 26-kDa GST from S. japonicum (Sj26GST), and the 28-kDa GST from S. haematobium (Sh28GST), versus human GST (hGST) isoforms alpha (hGSTA), mu (hGSTM) and pi (hGSTP). The use of BSP as an archetypal selective inhibitor was harnessed to produce molecular dynamics-derived pharmacophores of the two targets. Pharmacophore-based screening using a large dataset of experimental and approved drug compounds was performed to produce a shortlist of candidates. The top candidate for each target was prioritised via molecular docking, yielding guanosine-3'-monophosphate-5'-diphosphate (G3D) for Sj26GST, and quercetin-3'-O-phosphate (Q3P) for Sh28GST. Comparative molecular dynamics studies of both candidates compared to BSP showed similar characteristics of binding stability and strength, suggesting their potential to emulate the inhibitory effects of BSP.

The antioxidant glutathione

Reduced glutathione (GSH) is an essential non-enzymatic antioxidant in mammalian cells. GSH can act directly as an antioxidant to protect cells against free radicals and pro-oxidants, and as a cofactor for antioxidant and detoxification enzymes such as glutathione peroxidases, glutathione S-transferases, and glyoxalases. Glutathione peroxidases detoxify peroxides by a reaction that is coupled to GSH oxidation to glutathione disulfide (GSSG). GSSG is converted back to GSH by glutathione reductase and cofactor NADPH. GSH can regenerate vitamin E following detoxification reactions of vitamin E with lipid peroxyl radicals (LOO). GSH is a cofactor for GST during detoxification of electrophilic substances and xenobiotics. Dicarbonyl stress induced by methylglyoxal and glyoxal is alleviated by glyoxalase enzymes and GSH. GSH regulates redox signaling through reversible oxidation of critical protein cysteine residues by S-glutathionylation. GSH is involved in other cellular processes such as protein folding, protecting protein thiols from oxidation and crosslinking, degradation of proteins with disulfide bonds, cell cycle regulation and proliferation, ascorbate metabolism, apoptosis and ferroptosis.

Glutathione and Its Metabolic Enzymes in Gliomal Tumor Tissue and the Peritumoral Zone at Different Degrees of Anaplasia

This research was aimed at investigating the features of free radical activity and the parameters of glutathione metabolism in tumor tissues and the peritumoral zone at different degrees of glial tumor anaplasia. We analyzed postoperative material from 20 patients with gliomas of different degrees of anaplasia. The greatest differences compared to adjacent noncancerous tissues were found in the tumor tissue: an increased amount of glutathione and glutathione-related enzymes at Grades I and II, and a decrease of these parameters at Grades III and IV. For the peritumoral zone of Grades I and II, the indices changed in different directions, while for Grades III and IV, they occurred synchronously with the tumor tissue changes. For Low Grade and High Grade gliomas, opposite trends were revealed regarding changes in the level of glutathione and the enzymes involved in its metabolism and in the free radical activity in the peritumoral zone. The content of glutathione and the enzymes involved in its metabolism decreased with the increasing degree of glioma anaplasia. In contrast, free radical activity increased. The glutathione system is an active participant in the antioxidant defense of the body and can be used to characterize the cell condition of gliomas at different stages of tumor development.

Relationship between Glutathione-Dependent Enzymes and the Immunohistochemical Profile of Glial Neoplasms

This research aimed to investigate the relationships between the parameters of glutathione metabolism and the immunohistochemical characteristics of glial tumors. Postoperative material from 20 patients with gliomas of different grades of anaplasia was analyzed. Bioinformatic analysis of the interactions between the gliomas’ immunohistochemical markers and their glutathione-dependent enzymes was carried out using the STRING, BioGrid, while Signor databases revealed interactions between such glioma markers as IDH and p53 and the glutathione exchange enzymes (glutathione peroxidase, glutathione reductase, glutathione S-transferase). The most pronounced relationship with glutathione metabolism was demonstrated by the level of the nuclear protein Ki67 as a marker of proliferative activity, and the presence of the IDH1 mutation as one of the key genetic events of gliomagenesis. The glutathione system is an active participant in the body’s antioxidant defense, involving the p53 markers and MGMT promoter methylation. It allows characterization of the gliomal cells’ status at different stages of tumor development.

An updated analysis on the association of GSTM1 polymorphism and smoking exposure with the increased risk of coronary heart disease

Objective

To undertake a meta-analysis to investigate if there is an association between the glutathione S-transferase mu 1 (GSTM1) gene polymorphism, coronary artery disease (CAD) susceptibility and smoking.

Methods

Electronic databases, including PubMed®, Web of Science and Embase®, were searched for relevant case–control studies. Data were extracted and the odds ratio (OR) was calculated and appropriate statistical methods were used for the meta-analysis.

Results

The analysis included eight studies with a total of 1880 cases with CAD and 1758 control subjects. The results of this meta-analysis demonstrated that there is no association between the GSTM1 null and CAD (OR 1.24, 95% confidence interval [CI] 1.00, 1.55). An increased risk of CAD was observed in the smoking population with the GSTM1 null genotype (OR 1.48, 95% CI 1.02, 2.15). Subgroup analyses of geographical region, genotyping method and publication language category demonstrated potential relationships among gene polymorphism, smoking and CAD.

Conclusions

Based on the current literature, the GSTM1 null genotype was associated to CAD in the smoking population. The interaction between smoking and GSTM1 polymorphism may contribute to the susceptibility of CAD.

Ursolic acid alleviates tetrandrine-induced hepatotoxicity by competitively binding to the substrate-binding site of glutathione S-transferases

BACKGROUND

Tetrandrine (TET), a bisbenzylisoquinoline alkaloid isolated from Stephania tetrandra S. Moore, is the only approved medicine in China for silicosis. However, TET-induced hepatotoxicity has raised safety concerns. The underlying toxic targets and mechanism induced by TET remain unclear; there are no targeted detoxification strategies developed for TET-induced hepatotoxicity. Ursolic acid (UA), a pentacyclic triterpene with liver protective effects, may have detoxification effects on TET-induced hepatotoxicity.

PURPOSE

This study aims to explore toxic targets and mechanism of TET and present UA as a potential targeted therapy for alleviating TET-induced hepatotoxicity.

METHODS

A TET-induced liver-injury model was established to evaluate TET toxicity and the potential UA detoxification effect. Alkenyl-modified TET and UA probes were designed to identify potential liver targets. Pharmacological and molecular biology methods were used to explore the underlying toxicity/detoxification mechanism.

RESULTS

TET induced liver injury by covalently binding to the substrate-binding pocket (H-site) of glutathione S-transferases (GSTs) and inhibiting GST activity. The covalent binding led to toxic metabolite accumulation and caused redox imbalance and liver injury. UA protected the liver from TET-induced damage by competitively binding to the GST H-site.

CONCLUSION

The mechanism of TET-induced hepatotoxicity is related to irreversible binding with the GST H-site and GST-activity inhibition. UA, a natural antidote, competed with TET on H-site binding and reversed the redox imbalance. This study revealed the hepatotoxic mechanism of TET and provided a targeted detoxifying agent, UA, to alleviate hepatotoxicity caused by GST inhibition.

The suppressive role of phytochemical-induced glutathione S-transferase Mu 2 in human urothelial carcinoma cells

Glutathione S-transferases (GSTs) belong to one class of phase 2 detoxification enzymes which are important in metabolism and/or detoxification of various electrophilic endogenous metabolites and xenobiotics. From the available database, we found that GSTM2 gene expression is lower in high stages of bladder urothelial carcinoma than in stage 1 and normal bladder tissue. GSTM2 overexpression retards invasion, migration and tumor sphere formation of bladder cancer cells. Analysis of GSTM2 promoter activity shows that one SP1 site located at - 48 to - 40 bp is important for GSTM2 gene expression in BFTC 905 cells. An SP1 inhibitor, mithramycin A, inhibits GSTM2 promoter activity and protein expression. SP1 overexpression also increases GSTM2 expression in BFTC 905 and 5637 cells. Eight potential phytochemicals were analyzed for GSTM2 promoter activation, and results indicated that baicalein, berberrubine, chalcone, curcumin, resveratrol, and wogonin can increase promoter activity. In endogenous GSTM2 expression, berberrubine and resveratrol activated GSTM2 mRNA and protein expression the most. A DNA methylation inhibitor, 5-aza-deoxycytidine, can decrease GSTM2 gene methylation level and then increase its gene expression; 50 μM berberrubine decreased the GSTM2 gene methylation level, providing a mechanism for activating GSTM2 gene expression. Berberrubine and resveratrol also increased SP1 protein expression as one of the mechanisms for GSTM2 gene expression. In summary, berberrubine and resveratrol activates GSTM2 expression which inhibits cell proliferation, migration, and invasion of bladder cancer cells. The GSTM2 expression mechanism is partially via SP1 activation, and the effect of berberrubine is also partly via DNA CpG demethylation.

Evolutionary Adaptations of Parasitic Flatworms to Different Oxygen Tensions

During the evolution of the Earth, the increase in the atmospheric concentration of oxygen gave rise to the development of organisms with aerobic metabolism, which utilized this molecule as the ultimate electron acceptor, whereas other organisms maintained an anaerobic metabolism. Platyhelminthes exhibit both aerobic and anaerobic metabolism depending on the availability of oxygen in their environment and/or due to differential oxygen tensions during certain stages of their life cycle. As these organisms do not have a circulatory system, gas exchange occurs by the passive diffusion through their body wall. Consequently, the flatworms developed several adaptations related to the oxygen gradient that is established between the aerobic tegument and the cellular parenchyma that is mostly anaerobic. Because of the aerobic metabolism, hydrogen peroxide (H₂O₂) is produced in abundance. Catalase usually scavenges H₂O₂ in mammals; however, this enzyme is absent in parasitic platyhelminths. Thus, the architecture of the antioxidant systems is different, depending primarily on the superoxide dismutase, glutathione peroxidase, and peroxiredoxin enzymes represented mainly in the tegument. Here, we discuss the adaptations that parasitic flatworms have developed to be able to transit from the different metabolic conditions to those they are exposed to during their life cycle.

Antioxidant Genetic Profile Modifies Probability of Developing Neurological Sequelae in Long-COVID

Understanding the sequelae of COVID-19 is of utmost importance. Neuroinflammation and disturbed redox homeostasis are suggested as prevailing underlying mechanisms in neurological sequelae propagation in long-COVID. We aimed to investigate whether variations in antioxidant genetic profile might be associated with neurological sequelae in long-COVID. Neurological examination and antioxidant genetic profile (SOD2, GPXs and GSTs) determination, as well as, genotype analysis of Nrf2 and ACE2, were conducted on 167 COVID-19 patients. Polymorphisms were determined by the appropriate PCR methods. Only polymorphisms in GSTP1AB and GSTO1 were independently associated with long-COVID manifestations. Indeed, individuals carrying GSTP1 Val or GSTO1 Asp allele exhibited lower odds of long-COVID myalgia development, both independently and in combination. Furthermore, the combined presence of GSTP1 Ile and GSTO1 Ala alleles exhibited cumulative risk regarding long-COVID myalgia in carriers of the combined GPX1 LeuLeu/GPX3 CC genotype. Moreover, individuals carrying combined GSTM1-null/GPX1LeuLeu genotype were more prone to developing long-COVID “brain fog”, while this probability further enlarged if the Nrf2 A allele was also present. The fact that certain genetic variants of antioxidant enzymes, independently or in combination, affect the probability of long-COVID manifestations, further emphasizes the involvement of genetic susceptibility when SARS-CoV-2 infection is initiated in the host cells, and also months after.

Many hands make light work: CNV of GSTM1 effect on the oral carcinoma risk

BACKGROUND

Genetic alterations of oral squamous cell carcinoma (OSCC) allow the understanding of the oral carcinogenesis and the identification of molecular biomarkers that aid the early diagnosis of the disease. The copy number variation (CNV) of GSTM1 and GSTT1 are promising targets because these two genes codify enzymes that perform the inactivation of tobacco carcinogens, which are the main risk factor of OSCC. However, the different levels of - detoxification mechanism in relation to each copy of the genes are unknown. Therefore, this study aimed to investigate the possible association of the CNV of GSTM1 and GSTT1 with the risk of development of OSCC.

METHODS

A total of 234 OSCC patients and 422 patients without any cancer diagnoses were recruited from Heliópolis Hospital from 2000 to 2011. The CNV was determined by TaqMan real-time PCR and the CopyCaller software. Odds ratio (OR) and 95% confidence interval (95% CI) values were calculated by Multiple Logistic Regression.

RESULTS

Most OSCC patients reported they continued smoking high amounts of cigarettes despite the tumor diagnosis. The CNV of GSTM1 varied from zero to two copies and the analysis revealed that two copies of GSTM1 decreased by 53% the OSCC risk (OR 0.47; 95% CI 0.24-0.92) and the risk of the tumor was modified according to the interaction of the CNV of GSTM1 and the cigarette smoking consumption, which for the amount of 40 packs-year of cigarettes the OSCC risk diminished progressively according to the increase of copies of GSTM1. Although the GSTT1 gene varied from zero to three copies, none of them were associated with the tumor risk.

CONCLUSION

The findings suggest that the CNV of GSTM1 might be applied as a tool for the surveillance of patients and the early detection of OSCC.

Ligandability Assessment of Human Glutathione Transferase M1-1 Using Pesticides as Chemical Probes

Glutathione transferases (GSTs; EC 2.5.1.18) form a group of multifunctional enzymes that are involved in phase II of the cellular detoxification mechanism and are associated with increased susceptibility to cancer development and resistance to anticancer drugs. The present study aims to evaluate the ligandability of the human GSTM1-1 isoenzyme (hGSTM1-1) using a broad range of structurally diverse pesticides as probes. The results revealed that hGSTM1-1, compared to other classes of GSTs, displays limited ligandability and ligand-binding promiscuity, as revealed by kinetic inhibition studies. Among all tested pesticides, the carbamate insecticide pirimicarb was identified as the strongest inhibitor towards hGSTM1-1. Kinetic inhibition analysis showed that pirimicarb behaved as a mixed-type inhibitor toward glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). To shine a light on the restricted hGSTM1-1 ligand-binding promiscuity, the ligand-free crystal structure of hGSTM1-1 was determined by X-ray crystallography at 1.59 Å-resolution. Comparative analysis of ligand-free structure with the available ligand-bound structures allowed for the study of the enzyme's plasticity and the induced-fit mechanism operated by hGSTM1-1. The results revealed important structural features of the H-site that contribute to xenobiotic-ligand binding and specificity. It was concluded that hGSTM1-1 interacts preferentially with one-ring aromatic compounds that bind at a discrete site which partially overlaps with the xenobiotic substrate binding site (H-site). The results of the study form a basis for the rational design of new drugs targeting hGSTM1-1.

The metabolism and biotransformation of AFB1: Key enzymes and pathways

Aflatoxins B₁ (AFB₁) is a hepatoxic compound produced by Aspergillus flavus and Aspergillus parasiticus, seriously threatening food safety and the health of humans and animals. Understanding the metabolism of AFB₁ is important for developing detoxification and intervention strategies. In this review, we summarize the AFB₁ metabolic fates in humans and animals and the key enzymes that metabolize AFB₁, including cytochrome P450s (CYP450s) for AFB₁ bioactivation, glutathione-S-transferases (GSTs) and aflatoxin-aldehyde reductases (AFARs) in detoxification. Furthermore, AFB₁ metabolism in microbes is also summarized. Microorganisms specifically and efficiently transform AFB₁ into less or non-toxic products in an environmental-friendly approach which could be the most desirable detoxification strategy in the future. This review provides a wholistic insight into the metabolism and biotransformation of AFB₁ in various organisms, which also benefits the development of protective strategies in humans and animals.

Combined GSTT1 Null, GSTM1 Null and XPD Lys/Lys Genetic Polymorphisms and Their Association with Increased Risk of Chronic Myeloid Leukemia

Purpose

Glutathione S-transferases (GSTT1 and GSTM1) are instrumental in detoxification process of activated carcinogens. Nucleotide excision repair is carried out by DNA helicase encoded by xeroderma pigmentosum group D (XPD) genes and aberrations in the XPD gene predisposes to increased risk of cancer. The present study aimed to investigate GSTT1, GSTM1 and XPD polymorphisms in newly diagnosed chronic myeloid leukemia (CML) patients and to examine the association of these polymorphisms with the risk of developing CML.

Patients and Methods

This case–control study was carried out from June 2019 to August 2021 involving 150 newly diagnosed patients with CML and an equal number of randomly selected age- and sex-matched healthy individuals. A multiplex-PCR assay was used to genotype GSTT1 null and GSTM1 null polymorphisms. XPD gene polymorphism was detected by PCR-RFLP using predesigned gene-specific primers.

Results

GSTT1 and GSTM1 null polymorphisms were detected in 42.7% and 61.3% of cases, respectively, compared to 18% and 35.3% for controls. The combination of both GST null polymorphisms revealed a significant association with CML. Frequencies of XPD Lys751Gln genotypes in cases were 62.7% heterozygous Lys/Gln, 24% homozygous Lys/Lys and 13.3% homozygous Gln/Gln, while in the controls were 74.7%, 20%, and 5.3%, respectively. Significant differences were also noted regarding the combination of GSTT1/GSTM1 null with XPD Lys/Lys, and GSTM1 null with XPD Lys/Lys.

Conclusion

In conclusion, GSTT1 null, GSTM1 null and XPD polymorphisms showed positive association with the risk of development of CML. Furthermore, age and gender did not exhibit any association with the studied polymorphisms, while CML phases were associated with GSTT1 null polymorphism.

GSTpi reduces DNA damage and cell death by regulating the ubiquitination and nuclear translocation of NBS1

Glutathione S-transferase pi (GSTpi) is an important phase II detoxifying enzyme that participates in various physiological processes, such as antioxidant, detoxification, and signal transduction. The high expression level of GSTpi has been reported to be related to drug-resistant and anti-inflammatory and it functioned via its non-catalytic ligandin. However, the previous protection mechanism of GSTpi in DNA damage has not been addressed so far. Nijmegen breakage syndrome 1 (NBS1) is one of the most important sensor proteins to detect damaged DNA. Here, we investigated the interaction between GSTpi and NBS1 in HEK-293 T cells and human breast adenocarcinoma cells during DNA damage. Our results showed that overexpression of GSTpi in cells by transfecting DNA vector decreased the DNA damage level after methyl methanesulfonate (MMS) or adriamycin (ADR) treatment. We found that cytosolic GSTpi could increase NBS1 ubiquitin-mediated degradation in unstimulated cells, which suggested that GSTpi could maintain the basal level of NBS1 during normal conditions. In response to DNA damage, GSTpi can be phosphorylated in Ser184 and inhibit the ubiquitination degradation of NBS1 mediated by Skp2 to recover NBS1 protein level. Phosphorylated GSTpi can further enhance NBS1 nuclear translocation to activate the ATM-Chk2-p53 signaling pathway. Finally, GSTpi blocked the cell cycle in the G2/M phase to allow more time for DNA damage repair. Thus, our finding revealed the novel mechanism of GSTpi via its Ser184 phosphorylation to protect cells from cell death during DNA damage and it enriches the function of GSTpi in drug resistance.

Matching chemical properties to molecular biological activities opens a new perspective on L-ergothioneine

L-ergothioneine is a low-molecular weight natural product, the chemical structure of which comprises oxygen-, nitrogen- and sulfur-containing functional groups. This gives L-ergothioneine specific physicochemical properties and allows to better understanding its chemical reactivity, which is primarily due to the 2-thio-imidazole group. Here, I review how different modes of chemical reactivity account for the reported molecular biological activities of L-ergothioneine. By matching the physicochemical properties to the biological properties of L-ergothioneine, a new perspective of the function and the mode of action of this enigmatic molecule emerges into the limelight.

Association of GSTO1, GSTO2, GSTP1, GPX1 and SOD2 polymorphism with primary open angle glaucoma

It is becoming increasingly evident that oxidative stress has a supporting role in pathophysiology and progression of primary open angle glaucoma (POAG). The aim of our study was to assess the association between polymorphisms in genes encoding enzymes involved in redox homeostasis, mitochondrial superoxide dismutase (SOD2), glutathione peroxidase (GPX1) and glutathione transferases (GSTs) with susceptibility to POAG. Single nucleotide polymorphisms in GST omega (GSTO1rs4925, GSTO2 rs156697), pi 1 (GSTP1 rs1695), as well as GPX1 (rs1050450) and SOD2 (rs4880) were determined by quantitative polymerase chain reaction (qPCR) in 102 POAG patients and 302 respective controls. The risk for POAG development was noted in carriers of both GSTO2*GG and GSTO1*AA variant genotypes (OR = 8.21, p = 0.002). Individuals who carried GPX1*TT and SOD2*CC genotypes had also an increased risk of POAG development but without significance after Bonferroni multiple test correction (OR = 6.66, p = 0.005). The present study supports the hypothesis that in combination, GSTO1/GSTO2, modulate the risk of primary open angle glaucoma.

Protective effect of glutathione S-transferase enzyme activity against aflatoxin B1 in poultry species: relationship between glutathione S-transferase enzyme kinetic parameters, and resistance to aflatoxin B1

Comparative studies designed to investigate the role of glutathione S-transferase (GST) activity on the enzyme catalyzed trapping of aflatoxin B1-8,9-epoxide (AFBO) with glutathione, and the relationship with aflatoxin B1 (AFB1) resistance have not been conducted in poultry. Hepatic cytosolic fractions of chickens, quail, turkeys and ducks were used to measure in vitro the enzymatic parameters maximal velocity (Vmax), Michaelis-Menten constant (Km) and intrinsic clearance (CLint) for GST activity. AFB1 used ranged from 2.0 to 157.5 µM and the AFB1-GSH produced was identified and quantitated by HPLC. Significant differences were found in GST Vmax values, being the highest in chickens, followed by quail, ducks and turkeys. The Km values were also significantly different, with chickens < ducks < turkeys < quail. Chickens had the higher CLint value in contrast to ducks. Differences by sex showed that duck females had a higher CLint value than the turkey and quail, whereas duck males had a CLint close to that of turkey. The ratio "AFBO production /AFB1-GSH production" follows the order duck>turkey>quail>chicken, in agreement with the known poultry sensitivity. The extremely high "AFB1 epoxidation activity/ GST activity" ratio observed in ducks might be the explanation for the development of hepatocellular carcinoma in this species.

Glutathione S-Transferase M3 Is Associated with Glycolysis in Intrinsic Temozolomide-Resistant Glioblastoma Multiforme Cells

Glioblastoma multiforme (GBM) is a malignant primary brain tumor. The 5-year relative survival rate of patients with GBM remains <30% on average despite aggressive treatments, and secondary therapy fails in 90% of patients. In chemotherapeutic failure, detoxification proteins are crucial to the activity of chemotherapy drugs. Usually, glutathione S-transferase (GST) superfamily members act as detoxification enzymes by activating xenobiotic metabolites through conjugation with glutathione in healthy cells. However, some overexpressed GSTs not only increase GST activity but also trigger chemotherapy resistance and tumorigenesis-related signaling transductions. Whether GSTM3 is involved in GBM chemoresistance remains unclear. In the current study, we found that T98G, a GBM cell line with pre-existing temozolomide (TMZ) resistance, has high glycolysis and GSTM3 expression. GSTM3 knockdown in T98G decreased glycolysis ability through lactate dehydrogenase A activity reduction. Moreover, it increased TMZ toxicity and decreased invasion ability. Furthermore, we provide next-generation sequencing-based identification of significantly changed messenger RNAs of T98G cells with GSTM3 knockdown for further research. GSTM3 was downregulated in intrinsic TMZ-resistant T98G with a change in the expression levels of some essential glycolysis-related genes. Thus, GSTM3 was associated with glycolysis in chemotherapeutic resistance in T98G cells. Our findings provide new insight into the GSTM3 mechanism in recurring GBM.

Biofunctional Feed Supplemented With By-products of Olive Oil Production Improves Tissue Antioxidant Profile of Lambs

BACKGROUND/AIM

Olive mill wastewater (OMW) is a byproduct of olive oil production. The aim of the study was to estimate the redox profile of lambs' vital organs after consumption of an OMW-supplemented feed.

MATERIALS AND METHODS

Twenty-four lambs received breast milk until day 15. Then, they were divided in two groups: control and OMW, n=12 each. The control group received standard ration, while the OMW group received OMW enriched feed along with mother's milk until day 42 and animals (n=6 per group) were sacrificed. The remaining 12 received the feeds until day 70 and sacrificed. Tissue samples were collected at day 42 and 70 and specific redox biomarkers were assessed.

RESULTS

Overall, the OMW feed improved tissue redox profile by affecting the glutathione S-transferase (GST) activity and γ-glutamate-cysteine ligase (γ-GCL) expression in all tested tissues. Superoxide dismutase (SOD) activity was not affected.

CONCLUSION

The polyphenol-rich byproduct reinforced lamb redox profile and may putatively improve their wellness and productivity.

Interactions Between Odorants and Glutathione Transferases in the Human Olfactory Cleft

Xenobiotic metabolizing enzymes and other proteins, including odorant-binding proteins located in the nasal epithelium and mucus, participate in a series of processes modulating the concentration of odorants in the environment of olfactory receptors (ORs) and finely impact odor perception. These enzymes and transporters are thought to participate in odorant degradation or transport. Odorant biotransformation results in 1) changes in the odorant quantity up to their clearance and the termination of signaling and 2) the formation of new odorant stimuli (metabolites). Enzymes, such as cytochrome P450 and glutathione transferases (GSTs), have been proposed to participate in odorant clearance in insects and mammals as odorant metabolizing enzymes. This study aims to explore the function of GSTs in human olfaction. Using immunohistochemical methods, GSTs were found to be localized in human tissues surrounding the olfactory epithelium. Then, the activity of 2 members of the GST family toward odorants was measured using heterologously expressed enzymes. The interactions/reactions with odorants were further characterized using a combination of enzymatic techniques. Furthermore, the structure of the complex between human GSTA1 and the glutathione conjugate of an odorant was determined by X-ray crystallography. Our results strongly suggest the role of human GSTs in the modulation of odorant availability to ORs in the peripheral olfactory process.

Glutathione S-transferases and their implications in the lung diseases asthma and chronic obstructive pulmonary disease: Early life susceptibility?

Our lungs are exposed daily to airborne pollutants, particulate matter, pathogens as well as lung allergens and irritants. Exposure to these substances can lead to inflammatory responses and may induce endogenous oxidant production, which can cause chronic inflammation, tissue damage and remodeling. Notably, the development of asthma and Chronic Obstructive Pulmonary Disease (COPD) is linked to the aforementioned irritants. Some inhaled foreign chemical compounds are rapidly absorbed and processed by phase I and II enzyme systems critical in the detoxification of xenobiotics including the glutathione-conjugating enzymes Glutathione S-transferases (GSTs). GSTs, and in particular genetic variants of GSTs that alter their activities, have been found to be implicated in the susceptibility to and progression of these lung diseases. Beyond their roles in phase II metabolism, evidence suggests that GSTs are also important mediators of normal lung growth. Therefore, the contribution of GSTs to the development of lung diseases in adults may already start in utero, and continues through infancy, childhood, and adult life. GSTs are also known to scavenge oxidants and affect signaling pathways by protein-protein interaction. Moreover, GSTs regulate reversible oxidative post-translational modifications of proteins, known as protein S-glutathionylation. Therefore, GSTs display an array of functions that impact the pathogenesis of asthma and COPD.

In this review we will provide an overview of the specific functions of each class of mammalian cytosolic GSTs. This is followed by a comprehensive analysis of their expression profiles in the lung in healthy subjects, as well as alterations that have been described in (epithelial cells of) asthmatics and COPD patients. Particular emphasis is placed on the emerging evidence of the regulatory properties of GSTs beyond detoxification and their contribution to (un)healthy lungs throughout life. By providing a more thorough understanding, tailored therapeutic strategies can be designed to affect specific functions of particular GSTs.

LanCLs add glutathione to dehydroamino acids generated at phosphorylated sites in the proteome

Enzyme-mediated damage repair or mitigation, while common for nucleic acids, is rare for proteins. Examples of protein damage are elimination of phosphorylated Ser/Thr to dehydroalanine/dehydrobutyrine (Dha/Dhb) in pathogenesis and aging. Bacterial LanC enzymes use Dha/Dhb to form carbon-sulfur linkages in antimicrobial peptides, but the functions of eukaryotic LanC-like (LanCL) counterparts are unknown. We show that LanCLs catalyze the addition of glutathione to Dha/Dhb in proteins, driving irreversible C-glutathionylation. Chemo-enzymatic methods were developed to site-selectively incorporate Dha/Dhb at phospho-regulated sites in kinases. In human MAPK-MEK1, such "elimination damage" generated aberrantly activated kinases, which were deactivated by LanCL-mediated C-glutathionylation. Surveys of endogenous proteins bearing damage from elimination (the eliminylome) also suggest it is a source of electrophilic reactivity. LanCLs thus remove these reactive electrophiles and their potentially dysregulatory effects from the proteome. As knockout of LanCL in mice can result in premature death, repair of this kind of protein damage appears important physiologically.

Glutathione S-Transferases in Cancer

In humans, the glutathione S-transferases (GST) protein family is composed of seven members that present remarkable structural similarity and some degree of overlapping functionalities. GST proteins are crucial antioxidant enzymes that regulate stress-induced signaling pathways. Interestingly, overactive GST proteins are a frequent feature of many human cancers. Recent evidence has revealed that the biology of most GST proteins is complex and multifaceted and that these proteins actively participate in tumorigenic processes such as cell survival, cell proliferation, and drug resistance. Structural and pharmacological studies have identified various GST inhibitors, and these molecules have progressed to clinical trials for the treatment of cancer and other diseases. In this review, we discuss recent findings in GST protein biology and their roles in cancer development, their contribution in chemoresistance, and the development of GST inhibitors for cancer treatment.

Polymorphisms in Genes Encoding Glutathione Transferase Pi and Glutathione Transferase Omega Influence Prostate Cancer Risk and Prognosis

Considering the pleiotropic roles of glutathione transferase (GST) omega class members in redox homeostasis, we hypothesized that polymorphisms in GSTO1 and GSTO2 might contribute to prostate cancer (PC) development and progression. Therefore, we performed a comprehensive analysis of GSTO1 and GSTO2 SNPs' role in susceptibility to PC, as well as whether they might serve as prognostic biomarkers independently or in conjunction with other common GST polymorphisms (GSTM1, GSTT1, and GSTP1). Genotyping was performed in 237 PC cases and 236 age-matched controls by multiplex PCR for deletion of GST polymorphisms and quantitative PCR for SNPs. The results of this study, for the first time, demonstrated that homozygous carriers of both GSTO1*A/A and GSTO2*G/G variant genotypes are at increased risk of PC. This was further confirmed by haplotype analysis, which showed that H2 comprising both GSTO1*A and GSTO2*G variant alleles represented a high-risk combination. However, the prognostic relevance of polymorphisms in GST omega genes was not found in our cohort of PC patients. Analysis of the role of other investigated GST polymorphisms (GSTM1, GSTT1, and GSTP1) in terms of PC prognosis has shown shorter survival in carriers of GSTP1*T/T (rs1138272) genotype than in those carrying at least one referent allele. In addition, the presence of GSTP1*T/T genotype independently predicted a four-fold higher risk of overall mortality among PC patients. This study demonstrated a significant prognostic role of GST polymorphism in PC.

Influence of Proteome Profiles and Intracellular Drug Exposure on Differences in CYP Activity in Donor-Matched Human Liver Microsomes and Hepatocytes

Human liver microsomes (HLM) and human hepatocytes (HH) are important in vitro systems for studies of intrinsic drug clearance (CLint) in the liver. However, the CLint values are often in disagreement for these two systems. Here, we investigated these differences in a side-by-side comparison of drug metabolism in HLM and HH prepared from 15 matched donors. Protein expression and intracellular unbound drug concentration (Kpuu) effects on the CLint were investigated for five prototypical probe substrates (bupropion-CYP2B6, diclofenac-CYP2C9, omeprazole-CYP2C19, bufuralol-CYP2D6, and midazolam-CYP3A4). The samples were donor-matched to compensate for inter-individual variability but still showed systematic differences in CLint. Global proteomics analysis outlined differences in HLM from HH and homogenates of human liver (HL), indicating variable enrichment of ER-localized cytochrome P450 (CYP) enzymes in the HLM preparation. This suggests that the HLM may not equally and accurately capture metabolic capacity for all CYPs. Scaling CLint with CYP amounts and Kpuu could only partly explain the discordance in absolute values of CLint for the five substrates. Nevertheless, scaling with CYP amounts improved the agreement in rank order for the majority of the substrates. Other factors, such as contribution of additional enzymes and variability in the proportions of active and inactive CYP enzymes in HLM and HH, may have to be considered to avoid the use of empirical scaling factors for prediction of drug metabolism.

The Interaction of the Flavonoid Fisetin with Human Glutathione Transferase A1-1

Glutathione transferases (GSTs) are a family of Phase II detoxification enzymes that are involved in the development of the multidrug resistance (MDR) mechanism in cancer cells and therefore affect the clinical outcome of cancer chemotherapy. The discovery of nontoxic natural compounds as inhibitors for GSTs is a promising approach for chemosensitizing and reversing MDR. Fisetin (7,3′,4′-flavon-3-ol) is a plant flavonol present in many plants and fruits. In the present work, the interaction of fisetin with human glutathione transferase A1-1 (hGSTA1-1) was investigated. Kinetic analysis revealed that fisetin is a reversible inhibitor for hGSTA1-1 with IC₅₀ 1.2 ± 0.1 μΜ. It functions as a mixed-type inhibitor toward glutathione (GSH) and as a noncompetitive inhibitor toward the electrophile substrate 1-chloro-2,4-dinitrobenzene (CDNB). In silico molecular modeling and docking predicted that fisetin binds at a distinct location, in the solvent channel of the enzyme, and occupies the entrance of the substrate-binding sites. Treatment of proliferating human epithelial colorectal adenocarcinoma cells (CaCo-2) with fisetin causes a reduction in the expression of hGSTA1-1 at the mRNA and protein levels. In addition, fisetin inhibits GST activity in CaCo-2 cell crude extract with an IC₅₀ (2.5 ± 0.1 μΜ), comparable to that measured using purified recombinant hGSTA1-1. These actions of fisetin can provide a synergistic role toward the suppression and chemosensitization of cancer cells. The results of the present study provide insights into the development of safe and effective GST-targeted cancer chemosensitizers.

The role of glutathione S-transferase omega gene polymorphisms in childhood acute lymphoblastic leukemia: a case-control study

Background

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Glutathione-S-methyl transferase (GSTs) enzymes’ family is known to catalyze carcinogens detoxification. Overexpression of (GSTO) omega class was reported in cancer occurrence. The purpose of the study was to investigate the association of GSTO1*A140D (rs4925) and GSTO2*N142D (rs156697) polymorphisms with the susceptibility to childhood ALL and to evaluate their prognostic impact. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism technique in 96 Egyptian pediatric ALL patients and 99 controls.

Results

No statistically significant different GSTO1*A140D genotype and allele distribution was observed among ALL cases and controls; however, a statistically significant different GSTO1*A140D genotype distribution was found between de novo ALL cases and controls [CC (37% vs. 56.6%), CA (47.8% vs. 40.4%), and AA (15.2% vs. 3.0%), respectively] (0.008). GSTO1*A140D variant genotypes’ frequency was significantly higher in de novo cases than in controls (63% vs. 43.4%) (0.028). The minor allele frequency (MAF) of GSTO1*A140D-A was significantly higher in de novo cases compared to controls (0.39 vs. 0.23) (0.005). Genotyping of GSTO2*N142D revealed a statistically significant difference of genotype distribution between ALL patients and controls [AA (26% vs. 36.3%), AG (62.5% vs. 61.6%), and GG (11.4% vs. 2.0%), respectively] (0.017) and between de novo ALL cases and controls [AA (37% vs. 36.3%), AG (45.7% vs. 61.6%), and GG (17.3% vs. 2.0%), respectively] (0.002). The MAF of GSTO2*N142D-G was significantly higher in ALL patients than in controls (0.42 vs. 0.32) (0.046). The high-risk ALL group had a higher frequency of GSTO1*A140D and GSTO2*N142D variant genotypes compared to corresponding wild genotypes and a higher frequency of combined polymorphisms compared to single polymorphisms and wild genotypes but with no statistically significant difference.

Conclusion

A statistically significant difference of GSTO1*A140D and GSTO2*N142D genotype distribution was detected between de novo ALL cases and controls. Compared to the control group, the MAF of GSTO1*A140D-A was overexpressed in de novo ALL cases and that of GSTO2*N142D-G was significantly higher in ALL patients. These findings suggest that the studied polymorphisms might play a significant role in the susceptibility to de novo childhood ALL in Egypt; however, GSTO1*A140D and/or GSTO2*N142D polymorphisms have no impact on ALL prognosis.

Glutathione S transferase T1 gene polymorphism and its promoter methylation are associated with breast cancer susceptibility in Egyptian women

BACKGROUND

Breast cancer (BC) is one of the leading causes of cancer mortality in women. Glutathione S-transferase (GSTT1) is involved in activation of detoxification reactions and catalysis of chemicals conjugation with glutathione. GSTT1 genotype is a limiting factor for some environmental diseases. Epigenetic changes have an essential role in BC through inappropriate interaction between genomic and environmental risk factors.

AIM

This study was directed to explore the association of BC risk with GSTT1 genetic variations and its methylation status in Egyptian women.

DESIGN AND METHODS

This study included 100 healthy women as the control group and 100 patients were clinically and histologically diagnosed with breast cancer. All blood samples were used for genomic DNA extraction. GSTT1 genotyping was accomplished by multiplex PCR and methylation-specific PCR was used to analyze the GSTT1 promoter methylation status.

RESULTS

Breast cancer patients showed significant incidence of null GSTT1 in relation to controls (p = 0.004). GSTT1 gene promoter methylation status showed significant difference between hypermethylated and unmethylated patients when compared with healthy subjects (p = 0.005). GSTT1 promoter methylation status was not significantly associated with null genotype. There was no significant association between GSTT1-null genotypes and BC stage in cases with or without family history, but for promotor methylation, there was significant association with stage III and IV breast cancer disease.

CONCLUSION

GSTT1 null genetic variant and promoter hypermethylation in the GSTT region of the gene may be considered as critical risk factors for BC in Egyptian women.

Monitoring of pollution in the western Black Sea coast of Turkey by striped red mullet (Mullus surmuletus)

The striped red mullet (Mullus surmuletus) is an economically important demersal fish species. In this study, our aim was to monitor the pollution in the western Black Sea coast of Turkey using striped red mullet as a bioindicator species. Fish samples were caught from four different locations in the western Black Sea coast of Turkey in 2006, 2009-2011, and 2016. Highly elevated cytochrome P4501A (CYP1A)-related 7-ethoxyresorufin O-deethylase (EROD) activities were measured in striped red mullet caught from Zonguldak Harbor in all of the sampling years. The lowest EROD activities were measured in fish samples caught from Kefken. In addition to the EROD activity measurements, glutathione S-transferase (GST), glutathione reductase, and catalase activities were also measured in the striped red mullet samples. Higher GST and catalase activities were measured in the striped red mullet samples caught from Zonguldak Harbor than from Kefken in 2016. These results indicate that the striped red mullet is responsive to CYP1A inducer pollutants. This study covers intermittent measurements of the biomonitoring data from the striped red mullet caught around the western Black Sea coast of Turkey, over a 10-year period.

The effect of co-administration of berberine, resveratrol, and glibenclamide on xenobiotic metabolizing enzyme activities in diabetic rat liver

It is possible to use plant-derived antioxidant molecules in the form of dietary supplements. However, dietary supplement-drug interaction pattern has not been well defined for most of these products. The aim of this study was to determine the effects of berberine, resveratrol, and glibenclamide on xenobiotic metabolizing enzyme activities in diabetic rats. Streptozotocin was administered to create experimental diabetes. Resveratrol (5 mg/kg) (R), glibenclamide (5 mg/kg) (G), and berberine (10 mg/kg) (B) were administered individually or in combinations in DMSO by intraperitoneal administration route to the diabetic rats. DMSO was also given to non-diabetic control (C) and diabetic control (D) groups. Livers of rats were taken under anesthesia at the end of the treatment period (12 days). Ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-depentylase (PROD), aniline 4-hydroxylase (A4H), erythromycin N-demethylase (ERND), glutathione S-transferase (GST), catalase (CAT), and glutathione reductase (GR) activities were measured in microsomes and cytosols. In addition, histomorphological studies were also performed in the liver tissues. EROD activity of D+R was significantly higher than C and D+R+B. PROD activity of D+R was significantly higher than C, D, D+R+G, D+R+B, and D+R+B+ G. PROD activity of D+B was significantly higher than C and D+R+B. ERND activity of D+R was significantly higher than D+R+G and D+R+B. GST activity of D+R was significantly higher than D+R+G. CAT activity of D+B was significantly lower than C. It is clear that co-administration of resveratrol, berberine, and glibenclamide modifies some of the important xenobiotic metabolizing enzyme activities. Resveratrol and berberine have the potential to cause dietary supplement-drug interaction.

Optimized Fluorescent Probe for Specific Imaging of Glutathione S-Transferases in Living Cells and Mice

GSTP1 has been considered to be a marker for malignancy in many tissues. However, the existing GST fluorescent probes are unfavorable for in vivo imaging because of the limited emission wavelength or insufficient fluorescence enhancement (six-fold). The limited fluorescence enhancement of GST fluorescent probes is mainly ascribed to the high background signals resulting from the spontaneous reaction between GSH and the probes. In this work, a highly specific GST probe with NIR emission has been successfully developed through optimization of the essential unit of the probe to repress the spontaneous reaction. The novel GST probe exhibits over 100-fold fluorescence enhancement upon incubation with GSTP1/GSH and high selectivity over other potential interference. In addition, the probe has been proved to be capable of tracking endogenous GST in A549 cells. Finally, the in vivo imaging results demonstrate that the probe can be used for effective imaging of endogenous GST activity in subcutaneous tumor mouse with high contrast.

An integrated approach to unravel a crucial structural property required for the function of the insect steroidogenic Halloween protein Noppera-bo

Ecdysteroids are the principal steroid hormones essential for insect development and physiology. In the last 18 years, several enzymes responsible for ecdysteroid biosynthesis encoded by Halloween genes were identified and genetically and biochemically characterized. However, the tertiary structures of these proteins have not yet been characterized. Here, we report the results of an integrated series of in silico, in vitro, and in vivo analyses of the Halloween GST protein Noppera-bo (Nobo). We determined crystal structures of Drosophila melanogaster Nobo (DmNobo) complexed with GSH and 17β-estradiol, a DmNobo inhibitor. 17β-Estradiol almost fully occupied the putative ligand-binding pocket and a prominent hydrogen bond formed between 17β-estradiol and Asp-113 of DmNobo. We found that Asp-113 is essential for 17β-estradiol–mediated inhibition of DmNobo enzymatic activity, as 17β-estradiol did not inhibit and physically interacted less with the D113A DmNobo variant. Asp-113 is highly conserved among Nobo proteins, but not among other GSTs, implying that this residue is important for endogenous Nobo function. Indeed, a homozygous nobo allele with the D113A substitution exhibited embryonic lethality and an undifferentiated cuticle structure, a phenocopy of complete loss-of-function nobo homozygotes. These results suggest that the nobo family of GST proteins has acquired a unique amino acid residue that appears to be essential for binding an endogenous sterol substrate to regulate ecdysteroid biosynthesis. To the best of our knowledge, ours is the first study describing the structural characteristics of insect steroidogenic Halloween proteins. Our findings provide insights relevant for applied entomology to develop insecticides that specifically inhibit ecdysteroid biosynthesis.