Phospholipid hydroperoxide glutathione peroxidase activity of human glutathione transferases

Glutathione and glutathione-dependent enzymes: From biochemistry to gerontology and successful aging

The tripeptide glutathione (GSH), namely γ-L-glutamyl-L-cysteinyl-glycine, is an ubiquitous low-molecular weight thiol nucleophile and reductant of utmost importance, representing the central redox agent of most aerobic organisms. GSH has vital functions involving also antioxidant protection, detoxification, redox homeostasis, cell signaling, iron metabolism/homeostasis, DNA synthesis, gene expression, cysteine/protein metabolism, and cell proliferation/differentiation or death including apoptosis and ferroptosis. Various functions of GSH are exerted in concert with GSH-dependent enzymes. Indeed, although GSH has direct scavenging antioxidant effects, its antioxidant function is substantially accomplished by glutathione peroxidase-catalyzed reactions with reductive removal of H2O2, organic peroxides such as lipid hydroperoxides, and peroxynitrite; to this antioxidant activity also contribute peroxiredoxins, enzymes further involved in redox signaling and chaperone activity. Moreover, the detoxifying function of GSH is basically exerted in conjunction with glutathione transferases, which have also antioxidant properties. GSH is synthesized in the cytosol by the ATP-dependent enzymes glutamate cysteine ligase (GCL), which catalyzes ligation of cysteine and glutamate forming γ-glutamylcysteine (γ-GC), and glutathione synthase, which adds glycine to γ-GC resulting in GSH formation; GCL is rate-limiting for GSH synthesis, as is the precursor amino acid cysteine, which may be supplemented as N-acetylcysteine (NAC), a therapeutically available compound. After its cell export, GSH is degraded extracellularly by the membrane-anchored ectoenzyme γ-glutamyl transferase, a process occurring, as GSH synthesis and export, in the γ-glutamyl cycle. GSH degradation occurs also intracellularly by the cytoplasmic enzymatic ChaC family of γ-glutamyl cyclotransferase. Synthesis and degradation of GSH, together with its export, translocation to cell organelles, utilization for multiple essential functions, and regeneration from glutathione disulfide by glutathione reductase, are relevant to GSH homeostasis and metabolism. Notably, GSH levels decline during aging, an alteration generally related to impaired GSH biosynthesis and leading to cell dysfunction. However, there is evidence of enhanced GSH levels in elderly subjects with excellent physical and mental health status, suggesting that heightened GSH may be a marker and even a causative factor of increased healthspan and lifespan. Such aspects, and much more including GSH-boosting substances administrable to humans, are considered in this state-of-the-art review, which deals with GSH and GSH-dependent enzymes from biochemistry to gerontology, focusing attention also on lifespan/healthspan extension and successful aging; the significance of GSH levels in aging is considered also in relation to therapeutic possibilities and supplementation strategies, based on the use of various compounds including NAC-glycine, aimed at increasing GSH and related defenses to improve health status and counteract aging processes in humans.

Structure-activity analysis suggests an olfactory function for the unique antennal delta glutathione transferase of Apis mellifera

Glutathione transferases (GST) are detoxification enzymes that conjugate glutathione to a wide array of molecules. In the honey bee Apis mellifera, AmGSTD1 is the sole member of the delta class of GSTs, with expression in antennae. Here, we structurally and biochemically characterized AmGSTD1 to elucidate its function. We showed that AmGSTD1 can efficiently catalyse the glutathione conjugation of classical GST substrates. Additionally, AmGSTD1 exhibits binding properties with a range of odorant compounds. AmGSTD1 has a peculiar interface with a structural motif we propose to call 'sulfur sandwich'. This motif consists of a cysteine disulfide bridge sandwiched between the sulfur atoms of two methionine residues and is stabilized by CH…S hydrogen bonds and S…S sigma-hole interactions. Thermal stability studies confirmed that this motif is important for AmGSTD1 stability and, thus, could facilitate its functions in olfaction.

Gcm counteracts Toll-induced inflammation and impacts hemocyte number through cholinergic signaling

Hemocytes, the myeloid-like immune cells of Drosophila, fulfill a variety of functions that are not completely understood, ranging from phagocytosis to transduction of inflammatory signals. We here show that downregulating the hemocyte-specific Glial cell deficient/Glial cell missing (Glide/Gcm) transcription factor enhances the inflammatory response to the constitutive activation of the Toll pathway. This correlates with lower levels of glutathione S-transferase, suggesting an implication of Glide/Gcm in reactive oxygen species (ROS) signaling and calling for a widespread anti-inflammatory potential of Glide/Gcm. In addition, our data reveal the expression of acetylcholine receptors in hemocytes and that Toll activation affects their expressions, disclosing a novel aspect of the inflammatory response mediated by neurotransmitters. Finally, we provide evidence for acetylcholine receptor nicotinic acetylcholine receptor alpha 6 (nAchRalpha6) regulating hemocyte proliferation in a cell autonomous fashion and for non-cell autonomous cholinergic signaling regulating the number of hemocytes. Altogether, this study provides new insights on the molecular pathways involved in the inflammatory response.

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.

Role of Insect and Mammal Glutathione Transferases in Chemoperception

Glutathione transferases (GSTs) are ubiquitous key enzymes with different activities as transferases or isomerases. As key detoxifying enzymes, GSTs are expressed in the chemosensory organs. They fulfill an essential protective role because the chemosensory organs are located in the main entry paths of exogenous compounds within the body. In addition to this protective function, they modulate the perception process by metabolizing exogenous molecules, including tastants and odorants. Chemosensory detection involves the interaction of chemosensory molecules with receptors. GST contributes to signal termination by metabolizing these molecules. By reducing the concentration of chemosensory molecules before receptor binding, GST modulates receptor activation and, therefore, the perception of these molecules. The balance of chemoperception by GSTs has been shown in insects as well as in mammals, although their chemosensory systems are not evolutionarily connected. This review will provide knowledge supporting the involvement of GSTs in chemoperception, describing their localization in these systems as well as their enzymatic capacity toward odorants, sapid molecules, and pheromones in insects and mammals. Their different roles in chemosensory organs will be discussed in light of the evolutionary advantage of the coupling of the detoxification system and chemosensory system through GSTs.

Antioxidant, anti-inflammatory and beneficial metabolic effects of botryosphaeran [(1→3)(1→6)-β-d-glucan] are responsible for its anti-tumour activity in experimental non-obese and obese rats bearing Walker-256 tumours

Botryosphaeran, a (1→3)(1→6)-β-d-glucan, presents several beneficial activities, such as antiproliferative, hypoglycemic and antitumoural activities. This study evaluated the effects of botryosphaeran on oxidative stress, inflammation and metabolic activities in Walker-256 tumour-bearing non-obese and obese rats. Wistars rats were divided into four groups: control tumour (CT); control tumour + botryosphaeran (CTB); obese tumour (OT), and obese tumour + botryosphaeran (OTB). In ninth week, obese and non-obese rats were inoculated with 1 × 107 Walker-256 tumour cells and treated with botryosphaeran (30 mg/kg/d for 15 days). In 11th week, the following parameters were evaluated glycogen, glucose and lactate levels, pro-oxidant (TBARS) and antioxidant markers (superoxide dismutase [SOD]; catalase [CAT]; glutathione-S-transferase [GST]; reduced glutathione [GSH]; vitamin C) and cytokines. Obesity presented oxidative stress and inflammation, as demonstrated by high levels of TBARS, SOD and TNF-α, and lower levels of CAT, GSH and interleukin-10 (IL-10). Botryosphaeran significantly decreased TBARS and TNF-α and increased GST, GSH, vitamin C and IL-10 in the liver; increased SOD and vitamin C in tumour tissue; decreased TBARS in adipose tissue, and notably decreased the levels of glycogen and lactate in the tumour of CTB rats. Botryosphaeran promoted significant antioxidant, anti-inflammatory, and beneficial metabolic effects in Walker-256 tumour-bearing non-obese and obese rats, which contributed to its antitumour activity.

Structural and Functional Characterization of Camelus dromedarius Glutathione Transferase M1-1

Glutathione transferases (GSTs; EC. 2.5.1.18) are a large family of multifunctional enzymes that play crucial roles in the metabolism and inactivation of a broad range of xenobiotic compounds. In the present work, we report the kinetic and structural characterization of the isoenzyme GSTM1-1 from Camelus dromedarius (CdGSTM1-1). The CdGSΤM1-1 was expressed in E. coli BL21 (DE3) and was purified by affinity chromatography. Kinetics analysis showed that the enzyme displays a relative narrow substrate specificity and restricted ability to bind xenobiotic compounds. The crystal structures of CdGSΤM1-1 were determined by X-ray crystallography in complex with the substrate (GSH) or the reaction product (S-p-nitrobenzyl-GSH), providing snapshots of the induced-fit catalytic mechanism. The thermodynamic stability of CdGSTM1-1 was investigated using differential scanning fluorimetry (DSF) in the absence and in presence of GSH and S-p-nitrobenzyl-GSH and revealed that the enzyme’s structure is significantly stabilized by its ligands. The results of the present study advance the understanding of camelid GST detoxification mechanisms and their contribution to abiotic stress adaptation in harsh desert conditions.

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.

The Potential of Biologically Active Brazilian Plant Species as a Strategy to Search for Molecular Models for Mosquito Control

Natural products are a valuable source of biologically active compounds and continue to play an important role in modern drug discovery due to their great structural diversity and unique biological properties. Brazilian biodiversity is one of the most extensive in the world and could be an effective source of new chemical entities for drug discovery. Mosquitoes are vectors for the transmission of dengue, Zika, chikungunya, yellow fever, and many other diseases of public health importance. These diseases have a major impact on tropical and subtropical countries, and their incidence has increased dramatically in recent decades, reaching billions of people at risk worldwide. The prevention of these diseases is mainly through vector control, which is becoming more difficult because of the emergence of resistant mosquito populations to the chemical insecticides. Strategies to provide efficient and safe vector control are needed, and secondary metabolites from plant species from the Brazilian biodiversity, especially Cerrado, that are biologically active for mosquito control are herein highlighted. Also, this is a literature revision of targets as insights to promote advances in the task of developing active compounds for vector control. In view of the expansion and occurrence of arboviruses diseases worldwide, scientific reviews on bioactive natural products are important to provide molecular models for vector control and contribute with effective measures to reduce their incidence.

Qing-Yu-Mu, an Herbal Formula, Reduces Hepatic Oxidative Stress in Rats Fed a High-Frying Oil Diet and Ameliorates Carbon Tetrachloride-Induced Liver Injury

Qing-Yu-Mu (QYM) is an herbal formula used to prevent and treat liver disease in Taiwan. In this study, the hepatoprotective effects of QYM were evaluated in two experimental models. First, rats were fed a high-frying oil (FO) diet containing 1.25% QYM for 5 weeks to investigate effects of QYM on hepatic oxidative stress and antioxidant enzyme activities. Then, protective effects of QYM on carbon tetrachloride (CCl₄)-induced chronic liver injury were evaluated. Results show that QYM treatment reduced FO diet-induced hepatic lipid peroxidation and reactive oxygen species levels and increased glutathione (GSH) S-transferase activity. A higher reduced GSH/oxidized GSH (GSSG) ratio was observed after QYM treatment. Furthermore, QYM ameliorated CCl₄-induced liver injury by reducing the activity of plasma alanine aminotransferase and histological lesions in the liver. QYM also increased the level of hepatic GSH and activities of GSH peroxidase and superoxide dismutase. Finally, chlorogenic acid, chrysophanol, and apigenin were found to be present in relative abundance in QYM. Results show that QYM may exhibit a hepatoprotective effect by reducing oxidative stress and increasing antioxidant activity in the liver.

Association of combined genetic variations in SOD3, GPX3, PON1, and GSTT1 with hypertension and severity of coronary artery disease

Oxidative stress plays a critical role in the pathophysiology of hypertension (HT) and the progression of atherosclerotic coronary artery disease (CAD). Genetic variations in superoxide dismutase (SOD), glutathione peroxidase 3 (GPX3), paraoxonase 1 (PON1) and glutathione S-transferase theta 1 (GSTT1) may modulate their gene functions, affecting protein functions. These changes could have an impact on the pathogenesis of HT and progression of CAD. The present study investigated the associations of individual and combined antioxidant-related gene polymorphisms with the incidence of HT and severity of CAD. Two study populations were enrolled. The HT-associated study comprised 735 control and 735 hypertensive subjects (mean age 59.3 ± 9.0 years), matched for age and sex. The CAD study, hospital-based subjects (mean age 62.1 ± 9.5 years), included 279 CAD patients and 165 non-CAD subjects. Gene polymorphisms were identified in genomic DNA using polymerase chain reaction (PCR)-based technique. Genetic variations were assessed for their associations with HT and severity of CAD. Antioxidant gene variants, SOD3 rs2536512-GG, GPX3 rs3828599-GG, PON1 rs705379-TT, and GSTT1^{-/- and +/-}, were independently associated with the incidence of HT. A combination of four HT-associated genotypes, as a genetic risk score (GRS), revealed an association of GRS 5 and GRS ≥ 6 with increased susceptibility to HT and CAD, and further with multivessel coronary atherosclerosis (multivessel CAD) compared with GRS 0-2 [respective ORs(95% CI) for GRS ≥ 6 = 2.37 (1.46-3.85), 3.26 (1.29-8.25), and 4.36 (1.36-14.0)]. Combined polymorphisms in these four antioxidant-related genes were associated with the incidences of HT and CAD, and with the severity of coronary atherosclerosis.

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.

Characterization of Xi-class mycothiol S-transferase from Corynebacterium glutamicum and its protective effects in oxidative stress

Background

Oxidative stress caused by inevitable hostile conditions during fermentative process was the most serious threat to the survival of the well-known industrial microorganism Corynebacterium glutamicum. To survive, C. glutamicum developed several antioxidant defenses including millimolar concentrations of mycothiol (MSH) and protective enzymes. Glutathione (GSH) S-transferases (GSTs) with essentially defensive role in oxidative stress have been well defined in numerous microorganisms, while their physiological and biochemical functions remained elusive in C. glutamicum thus far.

Results

In the present study, we described protein NCgl1216 belonging to a novel MSH S-transferase Xi class (MstX), considered as the equivalent of GST Xi class (GSTX). MstX had a characteristic conserved catalytic motif (Cys-Pro-Trp-Ala, C-P-W-A). MstX was active as thiol transferase, dehydroascorbate reductase, mycothiolyl-hydroquinone reductase and MSH peroxidase, while it showed null activity toward canonical GSTs substrate as 1-chloro-2,4-dinitrobenzene (CDNB) and GST Omega’s specific substance glutathionyl-acetophenones, indicating MstX had some biochemical characteristics related with mycoredoxin (Mrx). Site-directed mutagenesis showed that, among the two cysteine residues of the molecule, only the residue at position 67 was required for the activity. Moreover, the residues adjacent to the active Cys67 were also important for activity. These results indicated that the thiol transferase of MstX operated through a monothiol mechanism. In addition, we found MstX played important role in various stress resistance. The lack of C. glutamicum mstX gene resulted in significant growth inhibition and increased sensitivity under adverse stress condition. The mstX expression was induced by stress.

Conclusion

Corynebacterium glutamicum MstX might be critically involved in response to oxidative conditions, thereby giving new insight in how C. glutamicum survived oxidative stressful conditions.

Association of genetic polymorphisms in SOD2, SOD3, GPX3, and GSTT1 with hypertriglyceridemia and low HDL-C level in subjects with high risk of coronary artery disease

Background

Oxidative stress modulates insulin resistant-related atherogenic dyslipidemia: hypertriglyceridemia (HTG) and low high-density lipoprotein cholesterol (HDL-C) level. Gene polymorphisms in superoxide dismutase (SOD2 and SOD3), glutathione peroxidase-3 (GPX3), and glutathione S-transferase theta-1 (GSTT1) may enable oxidative stress-related lipid abnormalities and severity of coronary atherosclerosis. The present study investigated the associations of antioxidant-related gene polymorphisms with atherogenic dyslipidemia and atherosclerotic severity in subjects with high risk of coronary artery disease (CAD).

Methods

Study population comprises of 396 subjects with high risk of CAD. Gene polymorphisms: SOD2 rs4880, SOD3 rs2536512 and rs2855262, GPX rs3828599, and GSTT1 (deletion) were evaluated the associations with HTG, low HDL-C, high TG/HDL-C ratio, and severity of coronary atherosclerosis.

Results

SOD2 rs4880-CC, SOD3 rs2536512-AA, rs2855262-CC, and GPX3 rs3828599-AA, but not GSTT1^-/- individually increased risk of HTG combined with low HDL-C level. With a combination of five risk-genotypes as a genetic risk score (GRS), GRS ≥ 6 increased risks of low HDL-C, high TG/HDL-C ratio, and HTG combined with low HDL-C, comparing with GRS 0–2 [respective adjusted ORs (95% CI) = 2.70 (1.24–5.85), 3.11 (1.55–6.23), and 5.73 (2.22–14.77)]. Gene polymorphisms, though, were not directly associated with severity of coronary atherosclerosis; high TG/HDL-C ratio was associated with coronary atherosclerotic severity [OR = 2.26 (95% CI [1.17–4.34])].

Conclusion

Combined polymorphisms in antioxidant-related genes increased the risk of dyslipidemia related to atherosclerotic severity, suggesting the combined antioxidant-related gene polymorphisms as predictor of atherogenic dyslipidemia.

Characterization of rat glutathione transferases in olfactory epithelium and mucus

The olfactory epithelium is continuously exposed to exogenous chemicals, including odorants. During the past decade, the enzymes surrounding the olfactory receptors have been shown to make an important contribution to the process of olfaction. Mammalian xenobiotic metabolizing enzymes, such as cytochrome P450, esterases and glutathione transferases (GSTs), have been shown to participate in odorant clearance from the olfactory receptor environment, consequently contributing to the maintenance of sensitivity toward odorants. GSTs have previously been shown to be involved in numerous physiological processes, including detoxification, steroid hormone biosynthesis, and amino acid catabolism. These enzymes ensure either the capture or the glutathione conjugation of a large number of ligands. Using a multi-technique approach (proteomic, immunocytochemistry and activity assays), our results indicate that GSTs play an important role in the rat olfactory process. First, proteomic analysis demonstrated the presence of different putative odorant metabolizing enzymes, including different GSTs, in the rat nasal mucus. Second, GST expression was investigated in situ in rat olfactory tissues using immunohistochemical methods. Third, the activity of the main GST (GSTM2) odorant was studied with in vitro experiments. Recombinant GSTM2 was used to screen a set of odorants and characterize the nature of its interaction with the odorants. Our results support a significant role of GSTs in the modulation of odorant availability for receptors in the peripheral olfactory process.

Protective Role of Freshwater and Marine Rotifer Glutathione S-Transferase Sigma and Omega Isoforms Transformed into Heavy Metal-Exposed Escherichia coli

Glutathione S-transferases (GSTs) play an important role in phase II of detoxification to protect cells in response to oxidative stress generated by exogenous toxicants. Despite their important role in defense, studies on invertebrate GSTs have mainly focused on identification and characterization. Here, we isolated omega and sigma classes of GSTs from the freshwater rotifer Brachionus calyciflorus and the marine rotifer Brachionus koreanus and explored their antioxidant function in response to metal-induced oxidative stress. The recombinant Bc- and Bk-GSTs were successfully transformed and expressed in Escherichia coli. Their antioxidant potential was characterized by measuring kinetic properties and enzymatic activity in response to pH, temperature, and chemical inhibitor. In addition, a disk diffusion assay, reactive oxygen species assay, and morphological analysis revealed that GST transformed into E. coli significantly protected cells from oxidative stress induced by H₂O₂ and metals (Hg, Cd, Cu, and Zn). Stronger antioxidant activity was exhibited by GST-S compared to GST-O in both rotifers, suggesting that GST-S plays a prominent function as an antioxidant defense mechanism in Brachionus spp. Overall, our study clearly shows the antioxidant role of Bk- and Bc-GSTs in E. coli and provides a greater understanding of GST class-specific and interspecific detoxification in rotifer Brachionus spp.

Glutathione S-Transferase Protein Expression in Different Life Stages of Zebrafish (Danio rerio)

Zebrafish is a widely used animal model in biomedical sciences and toxicology. Although evidence for the presence of phases I and II xenobiotic defense mechanisms in zebrafish exists on the transcriptional and enzyme activity level, little is known about the protein expression of xenobiotic metabolizing enzymes. Given the important role of glutathione S-transferases (GSTs) in phase II biotransformation, we analyzed cytosolic GST proteins in zebrafish early life stages and different organs of adult male and female fish, using a targeted proteomics approach. The established multiple reaction monitoring-based assays enable the measurement of the relative abundance of specific GST isoenzymes and GST classes in zebrafish through a combination of proteotypic peptides and peptides shared within the same class. GSTs of the classes alpha, mu, pi and rho are expressed in zebrafish embryo as early as 4 h postfertilization (hpf). The majority of GST enzymes are present at 72 hpf followed by a continuous increase in expression thereafter. In adult zebrafish, GST expression is organ dependent, with most of the GST classes showing the highest expression in the liver. The expression of a wide range of cytosolic GST isoenzymes and classes in zebrafish early life stages and adulthood supports the use of zebrafish as a model organism in chemical-related investigations.

Functional, Structural and Biochemical Features of Plant Serinyl-Glutathione Transferases

Glutathione transferases (GSTs) belong to a ubiquitous multigenic family of enzymes involved in diverse biological processes including xenobiotic detoxification and secondary metabolism. A canonical GST is formed by two domains, the N-terminal one adopting a thioredoxin (TRX) fold and the C-terminal one an all-helical structure. The most recent genomic and phylogenetic analysis based on this domain organization allowed the classification of the GST family into 14 classes in terrestrial plants. These GSTs are further distinguished based on the presence of the ancestral cysteine (Cys-GSTs) present in TRX family proteins or on its substitution by a serine (Ser-GSTs). Cys-GSTs catalyze the reduction of dehydroascorbate and deglutathionylation reactions whereas Ser-GSTs catalyze glutathione conjugation reactions and eventually have peroxidase activity, both activities being important for stress tolerance or herbicide detoxification. Through non-catalytic, so-called ligandin properties, numerous plant GSTs also participate in the binding and transport of small heterocyclic ligands such as flavonoids including anthocyanins, and polyphenols. So far, this function has likely been underestimated compared to the other documented roles of GSTs. In this review, we compiled data concerning the known enzymatic and structural properties as well as the biochemical and physiological functions associated to plant GSTs having a conserved serine in their active site.

Analysis of the Effect of Intestinal Ischemia and Reperfusion on the Rat Neutrophils Proteome

Intestinal ischemia and reperfusion injury is a model system of possible consequences of severe trauma and surgery, which might result into tissue dysfunction and organ failure. Neutrophils contribute to the injuries preceded by ischemia and reperfusion. However, the mechanisms by which intestinal ischemia and reperfusion stimulate and activate circulating neutrophils is still not clear. In this work, we used proteomics approach to explore the underlying regulated mechanisms in Wistar rat neutrophils after ischemia and reperfusion. We isolated neutrophils from three different biological groups; control, sham laparotomy, and intestinal ischemia/reperfusion. In the workflow, we included iTRAQ-labeling quantification and peptide fractionation using HILIC prior to LC-MS/MS analysis. From proteomic analysis, we identified 2,045 proteins in total that were grouped into five different clusters based on their regulation trend between the experimental groups. A total of 417 proteins were found as significantly regulated in at least one of the analyzed conditions. Interestingly, the enzyme prediction analysis revealed that ischemia/reperfusion significantly reduced the relative abundance of most of the antioxidant and pro-survival molecules to cause more tissue damage and ROS production whereas some of the significantly up regulated enzymes were involved in cytoskeletal rearrangement, adhesion and migration. Clusters based KEGG pathways analysis revealed high motility, phagocytosis, directional migration, and activation of the cytoskeletal machinery in neutrophils after ischemia and reperfusion. Increased ROS production and decreased phagocytosis were experimentally validated by microscopy assays. Taken together, our findings provide a characterization of the rat neutrophil response to intestinal ischemia and reperfusion and the possible mechanisms involved in the tissue injury by neutrophils after intestinal ischemia and reperfusion.

Histone Methyltransferase Setd7 Regulates Nrf2 Signaling Pathway by Phenethyl Isothiocyanate and Ursolic Acid in Human Prostate Cancer Cells

SCOPE

This study aims to investigate the role of the epigenetic regulator SET domain-containing lysine methyltransferase 7 (Setd7) in regulating the antioxidant Nrf2 pathway in prostate cancer (PCa) cells and examines the effects of two phytochemicals, phenethyl isothiocyanate (PEITC) and ursolic acid (UA).

METHODS AND RESULTS

Lentivirus-mediated shRNA knockdown of Setd7 in LNCaP and PC-3 cells decreases the expression of downstream Nrf2 targets, such as NAD(P)H: quinone oxidoreductase 1 (Nqo1) and glutathione S-transferase theta 2 (Gstt2). Downregulation of Setd7 decreases soft agar colony formation ability of PCa cells. Knockdown of Setd7 increases reactive oxygen species (ROS) generation. Furthermore, Setd7 knockdown attenuates Nqo1 and Gstt2 expression in response to H2 O2 challenge, whereas increased DNA damage is observed in Setd7 knockdown cells in comet assay. Interestingly, Setd7 expression could be induced by the dietary phytochemicals PEITC and UA. Chromatin immunoprecipitation (ChIP) assays show that Setd7 knockdown decreased H3K4me1 enrichment in the Nrf2 and Gstt2 promoter regions, while PEITC and UA treatments elevated the enrichment.

CONCLUSION

Taken together, these results indicate that Setd7 knockdown decreases Nrf2 and Nrf2-target genes expression and that PEITC and UA induce Setd7 expression, which activates the Nrf2/antioxidant response element (ARE) signaling pathway and protects DNA from oxidative damage.

Characterization of a Drosophila glutathione transferase involved in isothiocyanate detoxification

Glutathione transferases (GSTs) are ubiquitous key enzymes that catalyse the conjugation of glutathione to xenobiotic compounds in the detoxification process. GSTs have been proposed to play a dual role in the signal termination of insect chemodetection by modifying odorant and tasting molecules and by protecting the chemosensory system. Among the 40 GSTs identified in Drosophila melanogaster, the Delta and Epsilon groups are insect-specific. GSTs Delta and Epsilon may have evolved to serve in detoxification, and have been associated with insecticide resistance. Here, we report the heterologous expression and purification of the D. melanogaster GST Delta 2 (GSTD2). We investigated the capacity of GSTD2 to bind tasting molecules. Among them, we found that isothiocyanates (ITC), insecticidal compounds naturally present in cruciferous plant and perceived as bitter, are good substrates for GSTD2. The X-ray structure of GSTD2 was solved, showing the absence of the classical Ser catalytic residue, conserved in the Delta and Epsilon GSTs. Using molecular dynamics, the interaction of ITC with the GSTD2 three-dimensional structure is analysed and discussed. These findings allow us to consider a biological role for GSTD2 in chemoperception, considering GSTD2 expression in the chemosensory organs and the potential consequences of insect exposure to ITC.

Influence of chemotherapeutic drug-related gene polymorphisms on toxicity and survival of early breast cancer patients receiving adjuvant chemotherapy

BACKGROUND

We investigated whether GSTT1 ("null" allele), GSTM1 ("null"allele), GSTP1 (A313G), RFC1 (G80A), MTHFR (C677T), TS (2R/3R) polymorphisms were associated with toxicity and survival in patients with early breast cancer (EBC) treated with adjuvant chemotherapy (CT).

METHODS

This prospective trial included patients with stage I-III BC subjected to CT with CMF or FEC regimens. PCR-RFLP was performed for MTHFR, RFC1 and GSTP1, while PCR for TS, GSTT1 and GSTM1 genes.

RESULTS

Among the 244 patients consecutively enrolled, 48.7% were treated with FEC and 51.3% with CMF. Patients with TS2R/3R genotype showed less frequently severe neutropenia (G3/G4) than those with TS2R/2R and 3R/3R genotype (p = 0.038). Patients with MTHFRCT genotype had a higher probability of developing severe neutropenia than those with MTHFR CC genotype (p = 0.043). Patients with RFC1GG or GSTT1-null genotype or their combination (GSTT1-null/RFC1GG) were significantly associated with a shorter disease free survival (DFS) (p = 0.009, p = 0.053, p = 0.003, respectively) and overall survival (OS) (p = 0.036, p = 0.015, p = 0.005, respectively). Multivariate analysis confirmed the association of RFC1GG genotype with a shorter DFS (p = 0.018) and of GSTT1-null genotype of a worse OS (p = 0.003), as well as for the combined genotypes GSTT1-null/RFC1GG, (DFS: p = 0.004 and OS: p = 0.003).

CONCLUSIONS

Our data suggest that TS2R/2R and 3R/3R or MTHFR CT genotypes have a potential role in identifying patients with greater risk of toxicity to CMF/FEC and that RFC1 GG and GSTT1-null genotypes alone or in combination could be important markers in predicting clinical outcome in EBC patients.

Ecotoxicological assessment of the anticancer drug cisplatin in the polychaete Nereis diversicolor

Anticancer drugs are designed to inhibit tumor cell proliferation by interacting with DNA and altering cellular growth factors. When released into the waterbodies of municipal and hospital effluents these pharmaceutical compounds may pose a risk to non-target aquatic organisms, due to their mode of action (cytotoxic, genotoxic, mutagenic and teratogenic). The present study aimed to assess the ecotoxicological potential of the alkylating agent cisplatin (CisPt) to the polychaete Nereis diversicolor, at a range of relevant environmental concentrations (i.e. 0.1, 10 and 100ngPtL-1). Behavioural impairment (burrowing kinetic impairment), ion pump effects (SR Ca2+-ATPase), neurotoxicity (AChE activity), oxidative stress (SOD, CAT and GPXs activities), metal exposure (metallothionein-like proteins - MTLP), biotransformation (GST), oxidative damage (LPO) and genotoxicity (DNA damage), were selected as endpoints to evaluate the sublethal responses of the ragworms after 14-days of exposure in a water-sediment system. Significant burrowing impairment occurred in worms exposed to the highest CisPt concentration (100ngPtL-1) along with neurotoxic effects. The activity of antioxidant enzymes (SOD, CAT) and second phase biotransformation enzyme (GST) was inhibited but such effects were compensated by MTLP induction. Furthermore, LPO levels also increased. Results showed that the mode of action of cisplatin may pose a risk to this aquatic species even at the range of ngL-1.

Interactive effects of temperature, ultraviolet radiation and food quality on zooplankton alkaline phosphatase activity

Ultraviolet Radiation (UVR) is a stressor for aquatic organisms affecting enzyme activities in planktonic populations because of the increase in reactive oxygen species. In addition, UVR exposure combined with other environmental factors (i.e. temperature and food quality) could have even higher detrimental effects. In this work, we aimed to determine the effect of UVR on somatic Alkaline Phosphatase Activity (APA) and Glutathione S-Transferase (GST) activity on the cladoceran Daphnia commutata under two different temperatures (10 °C and 20 °C) and under three food qualities (carbon:phosphorus ratios: 1150, 850 and 550). APA is a biomarker that is considered as a P deficiency indicator in zooplankton. Since recovery from UVR damage under dark conditions is an ATP depending reaction we also measured APA during recovery phases. We carried out a laboratory experiment combining different temperatures and food qualities with exposition to UVR followed by luminic and dark phases for recovery. In addition, we exposed organisms to H2O2, to establish if the response on APA to UVR was a consequence of the reactive oxygen species produced these short wavelengths. Our results showed that somatic APA was negatively affected by UVR exposure and this effect was enhanced under high temperature and low food quality. Consistently, GST activity was higher when exposed to UVR under both temperatures. The H2O2 experiments showed the same trend as UVR exposure, indicating that APA is affected mainly by oxidative stress than by direct effect of UVR on the enzyme. Finally, APA was affected in the dark phase of recovery confirming the P demands. These results enlighten the importance of food quality in the interacting effect of UVR and temperature, showing that C:P food ratio could determine the success or failure of zooplanktonic populations in a context of global change.

Gene-environment interactions in esophageal cancer

Esophageal cancer (EC) is one of the most common malignancies in low- and medium-income countries and represents a disease of public health importance because of its poor prognosis and high mortality rate in these regions. The striking variation in the prevalence of EC among different ethnic groups suggests a significant contribution of population-specific environmental and dietary factors to susceptibility to the disease. Although individuals within a demarcated geographical area are exposed to the same environment and share similar dietary habits, not all of them will develop the disease; thus genetic susceptibility to environmental risk factors may play a key role in the development of EC. A wide range of xenobiotic-metabolizing enzymes are responsible for the metabolism of carcinogens introduced via the diet or inhaled from the environment. Such dietary or environmental carcinogens can bind to DNA, resulting in mutations that may lead to carcinogenesis. Genes involved in the biosynthesis of these enzymes are all subject to genetic polymorphisms that can lead to altered expression or activity of the encoded proteins. Genetic polymorphisms may, therefore, act as molecular biomarkers that can provide important predictive information about carcinogenesis. The aim of this review is to discuss our current knowledge on the genetic risk factors associated with the development of EC in different populations; it addresses mainly the topics of genetic polymorphisms, gene-environment interactions, and carcinogenesis. We have reviewed the published data on genetic polymorphisms of enzymes involved in the metabolism of xenobiotics and discuss some of the potential gene-environment interactions underlying esophageal carcinogenesis. The main enzymes discussed in this review are the glutathione S-transferases (GSTs), N-acetyltransferases (NATs), cytochrome P450s (CYPs), sulfotransferases (SULTs), UDP-glucuronosyltransferases (UGTs), and epoxide hydrolases (EHs), all of which have key roles in the detoxification of environmental and dietary carcinogens. Finally, we discuss recent advances in the study of genetic polymorphisms associated with EC risk, specifically with regard to genome-wide association studies, and examine possible challenges of case-control studies that need to be addressed to better understand the interaction between genetic and environmental factors in esophageal carcinogenesis.

Glutathione transferases and neurodegenerative diseases

There is substantial agreement that the unbalance between oxidant and antioxidant species may affect the onset and/or the course of a number of common diseases including Parkinson's and Alzheimer's diseases. Many studies suggest a crucial role for oxidative stress in the first phase of aging, or in the pathogenesis of various diseases including neurological ones. Particularly, the role exerted by glutathione and glutathione-related enzymes (Glutathione Transferases) in the nervous system appears more relevant, this latter tissue being much more vulnerable to toxins and oxidative stress than other tissues such as liver, kidney or muscle. The present review addresses the question by focusing on the results obtained by specimens from patients or by in vitro studies using cells or animal models related to Parkinson's and Alzheimer's diseases. In general, there is an association between glutathione depletion and Parkinson's or Alzheimer's disease. In addition, a significant decrease of glutathione transferase activity in selected areas of brain and in ventricular cerebrospinal fluid was found. For some glutathione transferase genes there is also a correlation between polymorphisms and onset/outcome of neurodegenerative diseases. Thus, there is a general agreement about the protective effect exerted by glutathione and glutathione transferases but no clear answer about the mechanisms underlying this crucial role in the insurgence of neurodegenerative diseases.

Glutathione S-transferase expression in upper urinary tract urothelial carcinomas: a Taiwan study

OBJECTIVES

Glutathione S-transferase (GST) isoenzymes play important roles in resistance to cell apoptosis and carcinogenesis. We aimed to establish the relationship between GST expression and the prognosis of upper urinary tract urothelial carcinoma (UTT-UC) in Taiwan.

METHODS

This study retrospectively reviewed 46 patients with pathologically confirmed UUT-UC at Kaohsiung Medical University Hospital. In each patient, expression of GSTT1 and GSTP1 was compared between urothelial carcinoma and normal urothelial cells by Western blotting.

RESULTS

GSTP1 expression in the UUT-UC cells was significantly higher than that in normal urothelial cells (1.6 fold, p<0.001). Expression of GSTT1 was significantly associated with the invasiveness of the carcinoma (p=0.006).

CONCLUSIONS

In UUT-UC, GSTP1 might be a potential tumor marker, whereas high GSTT1 expression could be used as an indicator of cancer progression. This study is the first to demonstrate potential applications of different GST isoenzymes for biomolecular analysis of UUT-UCs in Taiwan.

The still mysterious roles of cysteine-containing glutathione transferases in plants

Glutathione transferases (GSTs) represent a widespread multigenic enzyme family able to modify a broad range of molecules. These notably include secondary metabolites and exogenous substrates often referred to as xenobiotics, usually for their detoxification, subsequent transport or export. To achieve this, these enzymes can bind non-substrate ligands (ligandin function) and/or catalyze the conjugation of glutathione onto the targeted molecules, the latter activity being exhibited by GSTs having a serine or a tyrosine as catalytic residues. Besides, other GST members possess a catalytic cysteine residue, a substitution that radically changes enzyme properties. Instead of promoting GSH-conjugation reactions, cysteine-containing GSTs (Cys-GSTs) are able to perform deglutathionylation reactions similarly to glutaredoxins but the targets are usually different since glutaredoxin substrates are mostly oxidized proteins and Cys-GST substrates are metabolites. The Cys-GSTs are found in most organisms and form several classes. While Beta and Omega GSTs and chloride intracellular channel proteins (CLICs) are not found in plants, these organisms possess microsomal ProstaGlandin E-Synthase type 2, glutathionyl hydroquinone reductases, Lambda, Iota and Hemerythrin GSTs and dehydroascorbate reductases (DHARs); the four last classes being restricted to the green lineage. In plants, whereas the role of DHARs is clearly associated to the reduction of dehydroascorbate to ascorbate, the physiological roles of other Cys-GSTs remain largely unknown. In this context, a genomic and phylogenetic analysis of Cys-GSTs in photosynthetic organisms provides an updated classification that is discussed in the light of the recent literature about the functional and structural properties of Cys-GSTs. Considering the antioxidant potencies of phenolic compounds and more generally of secondary metabolites, the connection of GSTs with secondary metabolism may be interesting from a pharmacological perspective.

Quantitative proteomics analysis of altered protein expression in the placental villous tissue of early pregnancy loss using isobaric tandem mass tags

Many pregnant women suffer miscarriages during early gestation, but the description of these early pregnancy losses (EPL) can be somewhat confusing because of the complexities of early development. Thus, the identification of proteins with different expression profiles related to early pregnancy loss is essential for understanding the comprehensive pathophysiological mechanism. In this study, we report a gel-free tandem mass tags- (TMT-) labeling based proteomic analysis of five placental villous tissues from patients with early pregnancy loss and five from normal pregnant women. The application of this method resulted in the identification of 3423 proteins and 19647 peptides among the patient group and the matched normal control group. Qualitative and quantitative proteomic analysis revealed 51 proteins to be differentially abundant between the two groups (≥1.2-fold, Student's t-test, P < 0.05). To obtain an overview of the biological functions of the proteins whose expression levels altered significantly in EPL group, gene ontology analysis was performed. We also investigated the twelve proteins with a difference over 1.5-fold using pathways analysis. Our results demonstrate that the gel-free TMT-based proteomic approach allows the quantification of differences in protein expression levels, which is useful for obtaining molecular insights into early pregnancy loss.

Renal injury and Nrf2 modulation in mouse kidney following chronic exposure to TiO₂ nanoparticles

TiO₂ nanoparticles (NPs) are used in the food industry but have potential toxic effects in humans and animals. TiO₂ NPs impair renal function and cause oxidative stress and renal inflammation in mice, associated with inhibition of nuclear factor erythroid-2-related factor 2 (Nrf2), which regulates genes encoding many antioxidants and detoxifying enzymes. This study determined whether TiO₂ NPs activated the Nrf2 signaling pathway. Mice exhibited accumulation of reactive oxygen species and peroxidation of lipid, protein, and DNA in the kidney, coupled with renal dysfunction, glutathione depletion, inflammatory cell infiltration, fatty degeneration, and apoptosis. These were associated with increased expression of NOX4, cyclooxygenase-2, and nuclear factor-κB. Oxidative stress and inflammation were accompanied by decreased expression of Nrf2 and down-regulation of its target gene products including heme oxygenase 1, glutamate-cysteine ligase catalytic subunit, and glutathione S-transferase. Chronic TiO₂ NP exposure is associated with suppression of Nrf2, which contributes to the pathogenesis of oxidative stress and inflammation.

The role of metal coordination complexes in cytosolic cellular defense

The metal coordination complexes are known to induce cytotoxic effects on various cell lines and shown to have great potential for therapeutic interventions. Their main mechanism of action is through the mediation of enzyme activities in signaling pathways essential for cellular functioning. The overall cellular responses are dose-dependent and require high exposure levels and duration to overcome cellular defense against external toxicants. However, their effect through signal transduction components is limited due to the conferred drug resistance associated with glutathione transferase (GST)-mediated mechanisms. The GST family of enzymes is not only related to anticancer drug resistance, but also associated with cancer development where they may also contribute kinase signaling events including non-receptor protein tyrosine kinase (PTK)-related pathways. In the current study, we evaluated the effect of symmetrical and mononuclear complexes of Pd(II), Pt(II), and Ni(II) with organic ligands on cytosolic targets involved in glutathione utilization, antioxidant defense, and kinase signaling by virtue of acellular in vitro analyses.

Inhibition and induction of glutathione S-transferases by flavonoids: possible pharmacological and toxicological consequences

Many studies reviewed herein demonstrated the potency of some flavonoids to modulate the activity and/or expression of glutathione S-transferases (GSTs). Because GSTs play a crucial role in the detoxification of xenobiotics, their inhibition or induction may significantly affect metabolism and biological effects of many drugs, industrials, and environmental contaminants. The effect of flavonoids on GSTs strongly depends on flavonoid structure, concentration, period of administration, as well as on GST isoform and origin. Moreover, the results obtained in vitro are often contrary to the vivo results. Based on these facts, the revelation of important flavonoid-drug or flavonoid-pollutant interaction has been complicated. However, it should be borne in mind that ingestion of certain flavonoids in combination with drugs or pollutants (e.g., acetaminophen, simvastatin, cyclophosphamide, cisplatine, polycyclic aromatic hydrocarbons, chlorpyrifos, acrylamide, and isocyanates), which are GST substrates, could have significant pharmacological and toxicological consequences. Although reasonable consumptions of a flavonoids-rich diet (that may lead to GST induction) are mostly beneficial, the uncontrolled intake of high concentrations of certain flavonoids (e.g., quercetin and catechins) in dietary supplements (that may cause GST inhibition) may threaten human health.

Induction of detoxification enzymes by quercetin in the silkworm

Quercetin is one of the most abundant flavonoids and the defense secondary metabolites in plants. In this study, the effect of quercetin on the growth of the silkworm larvae was investigated. Cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs), and carboxylesterases (COE) were assayed after exposure to different concentrations of quercetin for 3 d (short-term) and 7 d (long-term), respectively. The results showed that the weight gain of the silkworm larvae significantly decreased after the larvae were treated by different concentrations of quercetin except for the treatment with 0.5% quercetin. Activities of P450, GST, and COE were induced by 0.5 or 1% concentration of quercetin. In the midgut, the induction activity of P450s was reached to the highest level (2.3-fold) by 1% quercetin for 7 d, the highest induction activities of GSTs toward CHP and CDNB were 4.1-fold and 2.6-fold of controls by 1% quercetin after 7 d exposure, respectively. For COEs, the highest activity (2.3-fold) was induced by 0.5% quercetin for 7 d. However, P450s in whole body were higher inducible activities in short-term treatment than those in long-term treatment. The responses of eight cytochrome P450 (CYP) genes belonged to CYP6 and CYP9 families and seven GST genes were detected with real-time polymerase chain reaction. In addition, the genes induced by quercetin significantly were confirmed by qRT-PCR. CYP6AB5, CYP6B29, and GSTe8 were identified as inducible genes, of which the highest induction levels were 10.9-fold (0.5% quercetin for 7 d), 6.2-fold (1% quercetin for 7 d), and 7.1-fold (1% quercetin for 7 d), respectively.

A custom rat and baboon hypertension gene array to compare experimental models

One challenge in understanding the polygenic disease of hypertension is elucidating the genes involved and defining responses to environmental factors. Many studies focus on animal models of hypertension; however, this does not necessarily extrapolate to humans. Current technology and cost limitations are prohibitive in fully evaluating hypertension within humans. Thus, we have designed a single-array platform that allows direct comparison of genes relevant to hypertension in animal models and non-human primates/human hypertension. The custom array is targeted to 328 genes known to be potentially related to blood pressure control. Studies compared gene expression in the kidney from normotensive rats and baboons. We found 74 genes expressed in both the rat and baboon kidney, 41 genes expressed in the rat kidney that were not detected in the baboon kidney and 34 genes expressed in the baboon kidney that were not detected in the rat kidney. To begin the evaluation of the array in a pathological condition, kidney gene expression was compared between the salt-sensitive deoxycorticosterone acetate (DOCA) rat model of hypertension and sham animals. Gene expression in the renal cortex and medulla from hypertensive DOCA compared with sham rats revealed three genes differentially expressed in the renal cortex: annexin A1 (up-regulated; relative intensity: 1.316 ± 0.321 versus 2.312 ± 0.283), glutamate-cysteine ligase (down-regulated; relative intensity: 3.738 ± 0.174 versus 2.645 ± 0.364) and glutathione-S transferase (down-regulated; relative intensity: 5.572 ± 0.246 versus 4.215 ± 0.411) and 21 genes differentially expressed in the renal medulla. Interestingly, few genes were differentially expressed in the kidney in the DOCA-salt model of hypertension; this may suggest that the complexity of hypertension may be the result of only a few gene-by-environment responsive events.

Impact of glutathione transferase M1, T1, and P1 gene polymorphisms in the genetic susceptibility of North Indian population to renal cell carcinoma

In this study, we investigated the association of GSTP1, GSTM1, and GSTP1 genetic variants with renal cell carcinoma (RCC) among North Indian patients. The difference in frequency of the GSTT1 null genotype between cases and control subjects was statistically significant (active ver. null, odds ratio [OR]=0.368; confidence intervals [CI] 95%=0.243-0.557, p=0.001). The differences in the frequency of GSTP1 genotypes were statistically significant (AA ver. AG/GG, OR=1.879; CI 95%=0.355-0.797, p=0.002). Higher allelic frequency of the GSTP1 G allele was associated with RCC cases (G ver. A allele, OR=1.534; 95% CI=1.159-2.030, p=0.003). The gene-gene interaction in terms of three-way combination of GSTM1 null, GSTT1 null, and GSTP1 (AG/GG) resulted in 4.5-fold increase in RCC risk (OR=4.452; 95% CI=2.220-9.294). Similarly, our study revealed that GST polymorphism might be a vital determinant of advancement to higher pathological stages and histological grades of RCC. Our findings suggest that genetic variability in members of the GST gene family may be associated with an increased susceptibility to RCC and its progression.

Impact of polyphenol metabolites produced by colonic microbiota on expression of COX-2 and GSTT2 in human colon cells (LT97)

Polyphenols may play an important role in colon cancer prevention. After entering the colon, they are subjected to metabolism by the human gut microbiota. The objective of the present study was to analyze the impact of selected intestinal metabolites on modulation of enzymes involved in detoxification and inflammation in human adenoma cells LT97. LT97 cells were incubated with 3,4-dihydroxyphenylacetic acid (ES) and 3-(3,4-dihydroxyphenyl)-propionic acid (PS), metabolites of quercetin and chlorogenic acid/caffeic acid, respectively. The effect on cell number was analyzed using 4'- 6-diamino-2-phenylindole-dihydrochloride (DAPI)-staining. Modulation of glutathione S-transferase T2 (GSTT2) and cyclooxygenase-2 (COX-2) was measured by real-time PCR and Western blot. Comet assay was performed to assess the impact on DNA damage caused by the GSTT2 substrate cumene hydroperoxide (CumOOH). Polyphenol metabolites did not affect cell number but significantly upregulated GSTT2 expression and decreased COX-2. The latter was confirmed via Western blot. CumOOH-induced DNA damage was significantly reduced compared to the control. An upregulation of GSTT2 and downregulation of COX-2 could possibly contribute to the chemopreventive potential of polyphenols after degradation in the gut. Working with polyphenol metabolites is an important prerequisite to better understand the in vivo effects of pure polyphenols.

Leishmania-macrophage interactions: insights into the redox biology

Leishmaniasis is a neglected tropical disease that affects about 350 million individuals worldwide. The protozoan parasite has a relatively simple life cycle with two principal stages: the flagellated mobile promastigote living in the gut of the sandfly vector and the intracellular amastigote within phagolysosomal vesicles of the vertebrate host macrophage. This review presents a state-of-the-art overview of the redox biology at the parasite-macrophage interface. Although Leishmania species are susceptible in vitro to exogenous superoxide radical, hydrogen peroxide, nitric oxide, and peroxynitrite, they manage to survive the endogenous oxidative burst during phagocytosis and the subsequent elevated nitric oxide production in the macrophage. The parasite adopts various defense mechanisms to cope with oxidative stress: the lipophosphoglycan membrane decreases superoxide radical production by inhibiting NADPH oxidase assembly and the parasite also protects itself by expressing antioxidant enzymes and proteins. Some of these enzymes could be considered potential drug targets because they are not expressed in mammals. In respect to antileishmanial therapy, the effects of current drugs on parasite-macrophage redox biology and its involvement in the development of drug resistance and treatment failure are presented.

The cytoprotective role of the Keap1-Nrf2 pathway

An elaborate network of highly inducible proteins protects aerobic cells against the cumulative damaging effects of reactive oxygen intermediates and toxic electrophiles, which are the major causes of neoplastic and chronic degenerative diseases. These cytoprotective proteins share common transcriptional regulation, through the Keap1-Nrf2 pathway, which can be activated by various exogenous and endogenous small molecules (inducers). Inducers chemically react with critical cysteine residues of the sensor protein Keap1, leading to stabilisation and nuclear translocation of transcription factor Nrf2, and ultimately to coordinate enhanced expression of genes coding for cytoprotective proteins. In addition, inducers inhibit pro-inflammatory responses, and there is a linear correlation spanning more than six orders of magnitude of concentrations between inducer and anti-inflammatory activity. Genetic deletion of transcription factor Nrf2 renders cells and animals much more sensitive to the damaging effects of electrophiles, oxidants and inflammatory agents in comparison with their wild-type counterparts. Conversely, activation of the Keap1-Nrf2 pathway allows survival and adaptation under various conditions of stress and has protective effects in many animal models. Cross-talks with other signalling pathways broadens the role of the Keap1-Nrf2 pathway in determining the fate of the cell, impacting fundamental biological processes such as proliferation, apoptosis, angiogenesis and metastasis.

The glutathione transferase kappa family

Glutathione transferase (GST) kappa, also named mitochondrial GST, is a very ancient protein family with orthologs in bacteria and eukaryotes. Both the structure and the subcellular localization of GSTK1-1, in mitochondria and peroxisomes, make this enzyme distinct from cytosolic GSTs. Rodent and human GSTK1 exhibit activity towards a number of model GST substrates and, in Caenorhabditis elegans, this enzyme may be involved in energy and lipid metabolism, two functions related to mitochondria and peroxisomes. Interestingly, GST kappa is also a key regulator of adiponectin biosynthesis and multimerization suggesting that it might function as a chaperone to facilitate correct folding and assembly of proteins. Since adiponectin expression has been correlated with insulin resistance, obesity and diabetes, GSTK1 expression level which is negatively correlated with obesity in mice and human adipose tissues may be an important factor in these metabolic disorders. Furthermore, a polymorphism in the hGSTK1 promoter has been associated with insulin secretion and fat deposition.

Effect of organophosphate phoxim exposure on certain oxidative stress biomarkers in the silkworm

Organophosphorus (OP) insecticides are widely used in agriculture, which are toxic to insect pests and nontarget organisms. The current study mainly assessed the effect of the pesticide phoxim on oxidative stress by certain biomarkers in the fat body and midgut of the silkworm, Bombyx mori (L.), after exposure to 50% lethal concentration (LC50) of phoxim for 2 h. Malondialdehyde (MDA) content, activity of glutathione transferase (GST), and expression of GST at transcriptional level were assayed. LC50 value of phoxim was 2.5 mg/liter at 2-h exposure for the day 3 of the fifth-instar larvae. After exposure of phoxim, MDA content in the fat body significantly increased at 4-20 h posttreatment (p.t.),the highest increase was approximately 4.11-fold from 0.451 +/- 0.053 to 1.854 +/- 0.113 nmol/mg protein compared with corresponding control. In the midgut, significant increase in the MDA content (from 1.40- to 3.16-fold) was observed at 8-42 h p.t. The activity of GSTs increased to 1.48-2.00-fold at 24-42 h p.t. and 1.33-1.48-fold at 20-24 h p.t. in the fat body and midgut, respectively. The peroxidase activity of GSTs also was induced, which increased to 1.46-2.06-fold and 1.31-1.50-fold in the fat body and midgut, respectively. BmGSTe8 showed a late up-regulation of transcripts at 24-42 h after exposure to phoxim, which might contribute to the improved phoxim tolerance of silkworm larvae. These results indicated that phoxim could trigger oxidative stress and that MDA content and GST activity might be used as biomarkers of OP insecticide exposure. In addition, activity of GSTs were more inducible in the fat body than in midgut.

Nuclear shield: a multi-enzyme task-force for nucleus protection

BACKGROUND

In eukaryotic cells the nuclear envelope isolates and protects DNA from molecules that could damage its structure or interfere with its processing. Moreover, selected protection enzymes and vitamins act as efficient guardians against toxic compounds both in the nucleoplasm and in the cytosol. The observation that a cytosolic detoxifying and antioxidant enzyme i.e. glutathione transferase is accumulated in the perinuclear region of the rat hepatocytes suggests that other unrecognized modalities of nuclear protection may exist. Here we show evidence for the existence of a safeguard enzyme machinery formed by an hyper-crowding of cationic enzymes and proteins encompassing the nuclear membrane and promoted by electrostatic interactions.

METHODOLOGY/PRINCIPAL FINDINGS

Electron spectroscopic imaging, zeta potential measurements, isoelectrofocusing, comet assay and mass spectrometry have been used to characterize this surprising structure that is present in the cells of all rat tissues examined (liver, kidney, heart, lung and brain), and that behaves as a "nuclear shield". In hepatocytes, this hyper-crowding structure is about 300 nm thick, it is mainly formed by cationic enzymes and the local concentration of key protection enzymes, such as glutathione transferase, catalase and glutathione peroxidase is up to seven times higher than in the cytosol. The catalytic activity of these enzymes, when packed in the shield, is not modified and their relative concentrations vary remarkably in different tissues. Removal of this protective shield renders chromosomes more sensitive to damage by oxidative stress. Specific nuclear proteins anchored to the outer nuclear envelope are likely involved in the shield formation and stabilization.

CONCLUSIONS/SIGNIFICANCE

The characterization of this previously unrecognized nuclear shield in different tissues opens a new interesting scenario for physiological and protection processes in eukaryotic cells. Selection and accumulation of protection enzymes near sensitive targets represents a new safeguard modality which deeply differs from the adaptive response which is based on expression of specific enzymes.

Cellular effects of photogenerated oxidants and long-lived, reactive, hydroperoxide photoproducts

Reaction of radicals and singlet oxygen ((1)O(2)) with proteins results in both direct damage and the formation of long-lived reactive hydroperoxides. Elevated levels of protein hydroperoxide-derived products have been detected in multiple human pathologies, suggesting that these secondary oxidants contribute to tissue damage. Previous studies have provided evidence for protein hydroperoxide-mediated inhibition of thiol-dependent enzymes and modulation of signaling processes in isolated systems. In this study (1)O(2) and hydroperoxides have been generated in J774A.1 macrophage-like cells using visible light and the photosensitizer rose bengal, with the consequences of oxidant formation examined both immediately and after subsequent (dark-phase) incubation. Significant losses of GSH (≤50%), total thiols (≤20%), and activity of thiol-dependent proteins (GAPDH, thioredoxin, protein tyrosine phosphatases, creatine kinase, and cathepsins B and L; 10-50% inhibition) were detected after 1 or 2 min photo-oxidation. Non-thiol-dependent enzymes were not affected. In contrast, NADPH levels increased, together with the activity of glutathione reductase, glutathione peroxidase, and thioredoxin reductase; these increases may be components of a rapid global cytoprotective cellular response to stress. Neither oxidized thioredoxin nor radical-mediated protein oxidation products were detected at significant levels. Further decreases in thiol levels and enzyme activity occurred during dark-phase incubation, with this accompanied by decreased cell viability. These secondary events are ascribed to the reactions of long-lived hydroperoxides, generated by (1)O(2)-mediated reactions. Overall, this study provides novel insights into early cellular responses to photo-oxidative damage and indicates that long-lived hydroperoxides can play a significant role in cellular damage.

Oxidant-NO dependent gene regulation in dogs with type I diabetes: impact on cardiac function and metabolism

Background

The mechanisms responsible for the cardiovascular mortality in type I diabetes (DM) have not been defined completely. We have shown in conscious dogs with DM that: 1) baseline coronary blood flow (CBF) was significantly decreased, 2) endothelium-dependent (ACh) coronary vasodilation was impaired, and 3) reflex cholinergic NO-dependent coronary vasodilation was selectively depressed. The most likely mechanism responsible for the depressed reflex cholinergic NO-dependent coronary vasodilation was the decreased bioactivity of NO from the vascular endothelium. The goal of this study was to investigate changes in cardiac gene expression in a canine model of alloxan-induced type 1 diabetes.

Methods

Mongrel dogs were chronically instrumented and the dogs were divided into two groups: one normal and the other diabetic. In the diabetic group, the dogs were injected with alloxan monohydrate (40-60 mg/kg iv) over 1 min. The global changes in cardiac gene expression in dogs with alloxan-induced diabetes were studied using Affymetrix Canine Array. Cardiac RNA was extracted from the control and DM (n = 4).

Results

The array data revealed that 797 genes were differentially expressed (P < 0.01; fold change of at least ±2). 150 genes were expressed at significantly greater levels in diabetic dogs and 647 were significantly reduced. There was no change in eNOS mRNA. There was up regulation of some components of the NADPH oxidase subunits (gp91 by 2.2 fold, P < 0.03), and down-regulation of SOD1 (3 fold, P < 0.001) and decrease (4 - 40 fold) in a large number of genes encoding mitochondrial enzymes. In addition, there was down-regulation of Ca²⁺ cycling genes (ryanodine receptor; SERCA2 Calcium ATPase), structural proteins (actin alpha). Of particular interests are genes involved in glutathione metabolism (glutathione peroxidase 1, glutathione reductase and glutathione S-transferase), which were markedly down regulated.

Conclusion

our findings suggest that type I diabetes might have a direct effect on the heart by impairing NO bioavailability through oxidative stress and perhaps lipid peroxidases.

Isoenzyme profile of glutathione transferases in transitional cell carcinoma of upper urinary tract

Upregulated glutathione S-transferase P1 (GSTP1) plays an important role in the resistance to apoptosis in transitional cell carcinoma (TCC) of the urinary bladder (UB) and represents a potential target for chemotherapeutic agents. Our aim was to perform a systematic investigation of a glutathione S-transferase (GST) isoenzyme profile (GSTM, GSTP1, and GSTT1) in the upper urinary tract (UUT) TCC and compare it with the GST isoenzyme pattern of the UB TCC and normal urothelium. We examined GST activity spectrophotometrically by using substrates for the overall GST activity, GSTP1, and GSTT1 in the cytosolic fraction. GSTP1 and GSTM expression was analyzed by Western blotting. The results obtained have shown that the overall GST activity was significantly higher in UUT TCC in comparison with urothelium (P<0.001), which gradually increases with tumor grade (P<0.05). The mean GSTP1 and GSTT1 activities in UUT TCC were 2- and 3.6-fold higher, respectively, than in the normal urothelium (P<0.001), and these values did not differ significantly from activities found in the UB TCC. GSTM was expressed in 42% of the UUT TCC and 50% of the UB TCC specimens. The level of GSTM expression was slightly increased in the UUT TCC specimens in comparison with normal urothelium (P>0.05). We conclude that 3 major cytosolic GST classes, GSTM, GSTP1, and GSTT1, are expressed in the UUT TCC. The isoenzyme profile of GST in the UUT TCC is similar to that observed in the UB TCC; it shows essentially the same alteration of the GST phenotype in the course of cancerization. The association of GSTT1 and GSTP1 upregulation with the malignant phenotype of the UUT TCC might result in resistances to both chemotherapy and apoptosis.

Effect of chitosan on hepatic drug-metabolizing enzymes and oxidative stress in rats fed low- and high-fat diets

Chitosan is sold worldwide as a lipid-lowering functional food and may be taken with certain medications. To investigate the effect of chitosan on drug-metabolizing enzymes and oxidative stress in the liver, male Wistar rats were fed a low- or high-fat diet with cellulose or chitosan for 4 weeks. A significant decrease in cytochrome P450 (CYP) 3A-catalyzed testosterone 6beta-hydroxylation in liver microsomes was observed in rats fed the chitosan with low- and high-fat diets. The expression of CYP 3A1 and 3A2, however, was suppressed by chitosan in rats fed the low-fat diet only. Furthermore, rats fed the low-fat diet with chitosan had lower hepatic glutathione S-transferase (GST) activity and superoxide dismutase activity and higher total tissue and microsomal lipid hydroperoxides. Hepatic alpha-tocopherol was lower in rats fed the chitosan-containing diet. The results suggest that chitosan is likely to modulate CYP 3A activity and protein expression and GST activity partially in a dietary fat-dependent manner. This change may cause a decrease in the metabolism of drugs catalyzed by these enzymes in liver tissues. Moreover, decrease of alpha-tocopherol level and SOD activity by chitosan partly accounts for the increase of hepatic lipid peroxidation.