Differential effects of iron overload on GST isoform expression in mouse liver and kidney and correlation between GSTA4 induction and overproduction of free radicles

Investigation of ferroptosis-associated molecular subtypes and immunological characteristics in lupus nephritis based on artificial neural network learning

BACKGROUND

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) with poor treatment outcomes. The role and underlying mechanisms of ferroptosis in LN remain largely unknown. We aimed to explore ferroptosis-related molecular subtypes and assess their prognostic value in LN patients.

METHODS

Molecular subtypes were classified on the basis of differentially expressed ferroptosis-related genes (FRGs) via the Consensus ClusterPlus package. The enriched functions and pathways, immune infiltrating levels, immune scores, and immune checkpoints were compared between the subgroups. A scoring algorithm based on the subtype-specific feature genes identified by artificial neural network machine learning, referred to as the NeuraLN, was established, and its immunological features, clinical value, and predictive value were evaluated in patients with LN. Finally, immunohistochemical analysis was performed to validate the expression and role of feature genes in glomerular tissues from LN patients and controls.

RESULTS

A total of 10 differentially expressed FRGs were identified, most of which showed significant correlation. Based on the 10 FRGs, LN patients were classified into two ferroptosis subtypes, which exhibited significant differences in immune cell abundances, immune scores, and immune checkpoint expression. A NeuraLN-related protective model was established based on nine subtype-specific genes, and it exhibited a robustly predictive value in LN. The nomogram and calibration curves demonstrated the clinical benefits of the protective model. The high-NeuraLN group was closely associated with immune activation. Clinical specimens demonstrated the alterations of ALB, BHMT, GAMT, GSTA1, and HAO2 were in accordance with bioinformatics analysis results, GSTA1 and BHMT were negatively correlated with the severity of LN.

CONCLUSION

The classification of ferroptosis subtypes and the establishment of a protective model may form a foundation for the personalized treatment of LN patients.

Animal models of kidney iron overload and ferroptosis: a review of the literature

In recent years, it has been identified that excess iron contributes to the development of various pathologies and their complications. Kidney diseases do not escape the toxic effects of iron, and ferroptosis is identified as a pathophysiological mechanism that could be a therapeutic target to avoid damage or progression of kidney disease. Ferroptosis is cell death associated with iron-dependent oxidative stress. To study the effects of iron overload (IOL) in the kidney, numerous animal models have been developed. The methodological differences between these models should reflect the IOL-generating mechanisms associated with human IOL diseases. A careful choice of animal model should be considered for translational purposes.

Aspects regarding renal morphophysiology of fruit-eating and vampire bats

Bats have adapted to many different feeding habits, which are known to induce morphophysiological adaptations in several tissues, especially those particularly involved with absorption, metabolism and excretion. The common vampire bat (Desmodus rotundus) has a very unique diet (blood), which, among other challenges, seems to pose a risk to their kidneys, due to the increased nitrogen excretion imposed by their remarkably high protein meal. Fruit-eating bats (Artibeus lituratus) consume a high carbohydrate diet and may be taken as a suitable species for this dietary comparative study. Here we aimed at investigating the renal morphology and stereology, kidneys antioxidant capacity, and plasma antidiuretic hormone (ADH) concentrations in adult fruit-eating and vampire bats. Sixteen animals were captured and used in this study, being 8 adult males from each species. Our results showed higher morphological standards of glomerular area, volumetric density of glomeruli, and renal somatic index for vampire bats, as well as higher reactive species of oxygen (ROS) production, such as nitric oxide (NO), higher plasma iron reduction ability (FRAP), higher activity of the antioxidant enzyme glutathione-S-transferase (GST) and a higher malondialdehyde production (MDA) in vampires' kidneys, compared to the fruit-eating species. The activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were higher in fruit-eating bats. Plasma ADH concentrations were not different between species. Taken together, the renal morphophysiology conditions presented by vampire bats might be associated with a high demand for nitrogenous products excretion imposed by protein and iron overload. These features may play an important role on preventing protein-overload nephropathy, allowing vampires to survive under such a unique diet.

Age-associated changes in GSH S-transferase gene/proteins in livers of rats

OBJECTIVES

Glutathione S-transferases (GSTs) are phase-II metabolic enzymes playing important roles in drug metabolism, anti-oxidative stress and anti-aging. Age is a key factor influencing GSTs expression. Thus, age-related changes of 10 GSTs were examined.

METHODS

Livers from male Sprague-Dawley rats at fetus (-2 d), neonates (1, 7, 14 and 21 d), puberty (28 and 35 d), adulthood (60 and 180 d), and aging (540 and 800 d), were collected and subjected to qPCR analysis. Liver proteins from 14, 28, 60, 180, 540 and 800 d were also extracted for selected protein analysis by Western-blot.

RESULTS

The expression of GSTA1 and GSTP1 increased over the life span and the expression of GSTA4, GSTO1 and GSTZ1 gradually increased until adulthood, and slightly decreased at 800 days. The expression of GSTM1, GSTM3, GSTT1, GSTT2 and GSTK1 gradually increased until adulthood, but significantly decreased during aging of 540 and 800 days. There is a small peak at 7-14 d for GSTA1, GSTP1 and GSTZ1. The protein expression of GSTA1, GSTM1 and GSTP1 followed the trend of mRNA changes.

DISCUSSION

This study characterized three expression patterns of 10 GSTs during development and aging in rat liver, adding to our understanding of anti-aging role of GSTs.

Effect of diet on expression of genes involved in lipid metabolism, oxidative stress, and inflammation in mouse liver-insights into mechanisms of hepatic steatosis

Nutritional intake is a fundamental determinant of health. Many studies have correlated excess caloric intake, as well as a high ratio of n-6:n-3 fatty acids, with detrimental health outcomes, such as the metabolic syndrome. In contrast, low-calorie diets have beneficial health effects. Despite these associations, our understanding of the causal relationship between diet and health remains largely elusive. The present study examined the molecular changes elicited by nine diets with varying fat, sugar, cholesterol, omega-3 fatty acids, omega-6 fatty acids, and calories in C57BL/6 male mice. Microarray analyses were conducted on liver samples from three mice per diet and detected 20,449 genes of which 3,734 were responsive to changes in dietary components. Principal component analysis showed that diet restriction correlated the least with the other diets and also affected more genes than any other diet. Interestingly, Gene Set Enrichment Analysis (GSEA) identified gene sets involved in glutathione metabolism, immune response, fatty acid metabolism, cholesterol metabolism, ABC transporters, and oxidative phosphorylation as being highly responsive to changes in diet composition. On the gene level, this study reveals novel findings such as the induction of the drug efflux pump Abcb1a (p-glycoprotein) by diet restriction and an atherogenic diet, as well as the suppression of the rate limiting step of bile acid synthesis, Cyp7a1, by a high fructose diet. This study provides considerable insight into the molecular changes incurred by a variety of diets and furthers our understanding of the causal relationships between diet and health.

Mechanism of chronic dietary iron overload-induced liver damage in mice

Chronic iron overload may result in hepatic fibrosis and even neoplastic transformation due to a burst of reactive oxygen species (ROS). Mitochondria have been proposed to be important in the production of ROS. The purpose of this study was to investigate the role of the mitochondrial permeability transition pore (mPTP) in the burst of ROS, and to clarify the mechanism whereby ROS induced by iron overload results in hepatic damage. It has been demonstrated that when ferrocene-induced iron-overloaded mice were fed the cyclosporin A (CsA), a specific inhibitor of the mPTP, diet (10 mg/kg/day) for 50 days, liver-to-body weight ratio, serum levels of alanine transaminase (ALT) and aspartate transaminase (AST), ROS production, mitochondrial swelling, loss of mitochondrial membrane potential (Δψ) and hepatocyte apoptosis decreased. However, the total antioxidant status, including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase activities, increased. The protective effect of CsA on the liver of iron-overloaded mice may be due to inhibition of the ROS burst and a successive antioxidant effect. To the best of our knowledge, these data provide the first support for the theory that ROS-induced ROS release (RIRR) may be involved in the burst of ROS in the liver and greatly contribute to the hepatic damage initiated by iron overload.

Biochemical and molecular mechanisms of N-acetyl cysteine and silymarin-mediated protection against maneb- and paraquat-induced hepatotoxicity in rats

Oxidative stress is one of the major players in the pathogenesis of maneb (MB) and paraquat (PQ)-induced disorders. N-acetyl cysteine (NAC), a glutathione (GSH) precursor and silymarin (SIL), a naturally occurring antioxidant, encounter oxidative stress-mediated cellular damage. The present study was aimed to investigate the effects of NAC and SIL against MB and/or PQ-induced hepatotoxicity in rats. The levels of hepatotoxicity markers - alanine aminotransaminase (ALT), aspartate aminotransaminase (AST) and total bilirubin, histological changes, oxidative stress indices, phase I and phase II xenobiotic metabolizing enzymes - cytochrome P450 (CYP) and glutathione S-transferase (GST) and pro-inflammatory molecules - inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were measured in animals treated with MB and/or PQ in the presence or absence of NAC and SIL. MB and/or PQ augmented ALT, AST, total bilirubin, lipid peroxidation and nitrite contents and catalytic activities of superoxide dismutase and glutathione peroxidase however, the GSH content was attenuated. NAC and SIL restored the above-mentioned alterations towards basal levels but the restorations were more pronounced in SIL treated groups. Similarly, MB and/or PQ-mediated histopathological symptoms and changes in the catalytic activities/expressions of CYP1A2, CYP2E1, iNOS, TNF-α, and IL-1β were alleviated by NAC and SIL. Conversely, MB and/or PQ-induced GSTA4-4 expression/activity was further increased by NAC/SIL and glutathione reductase activity was also increased. The results obtained thus suggest that NAC and SIL protect MB and/or PQ-induced hepatotoxicity by reducing oxidative stress, inflammation and by modulating xenobitic metabolizing machinery and SIL seems to be more effective.

Combined Stimulation with the Tumor Necrosis Factor α and the Epidermal Growth Factor Promotes the Proliferation of Hepatocytes in Rat Liver Cultured Slices

The culture liver slices are mainly used to investigate drug metabolism and xenobiotic-mediated liver injuries while apoptosis and proliferation remain unexplored in this culture model. Here, we show a transient increase in LDH release and caspase activities indicating an ischemic injury during the slicing procedure. Then, caspase activities decrease and remain low in cultured slices demonstrating a low level of apoptosis. The slicing procedure is also associated with the G0/G1 transition of hepatocytes demonstrated by the activation of stress and proliferation signalling pathways including the ERK1/2 and JNK1/2/3 MAPKinases and the transient upregulation of c-fos. The cells further progress up to mid-G1 phase as indicated by the sequential induction of c-myc and p53 mRNA levels after the slicing procedure and at 24 h of culture, respectively. The stimulation by epidermal growth factor induces the ERK1/2 phosphorylation but fails to activate expression of late G1 and S phase markers such as cyclin D1 and Cdk1 indicating that hepatocytes are arrested in mid-G1 phase of the cell cycle. However, we found that combined stimulation by the proinflammatory cytokine tumor necrosis factor α and the epidermal growth factor promotes the commitment to DNA replication as observed in vivo during the liver regeneration.

Maneb and paraquat-induced modulation of toxicant responsive genes in the rat liver: comparison with polymorphonuclear leukocytes

Experimental studies have shown that toxicant responsive genes, cytochrome P450s (CYPs) and glutathione S-transferases (GSTs) play a critical role in pesticide-induced toxicity. CYPs play pro-oxidant role and GSTs offer protection in maneb (MB) and paraquat (PQ)-induced brain and lung toxicities. The present study aimed to investigate the effect of repeated exposures of MB and/or PQ on lipid peroxidation (LPO), glutathione content (GSH) and toxicant responsive genes, i.e., CYP1A1, 1A2, 2E1, GSTA4-4, GSTA1-1 and GSTA3-3 in the liver and to correlate the same with polymorphonuclear leukocytes (PMNs). A significant augmentation in LPO and reduction in GSH content was observed in a time of exposure dependent manner in the liver and PMNs of MB and/or PQ treated animals. The expression and catalytic activity of CYP2E1 and GSTA4-4 were significantly increased following MB and/or PQ exposure both in the liver and PMNs. Although the expression of GSTA3-3 was increased, the expression of GSTA1-1 was unaltered after MB and/or PQ treatment in both the liver and PMNs. MB augmented the expression and catalytic activity of CYP1A1 in the liver, however, CYP1A2 was unaffected. PQ, on the other hand, significantly increased hepatic CYP1A2 expression and catalytic activity. MB and/or PQ did not produce any significant changes in CYP1A1 and CYP1A2 in PMNs. The results of the study thus demonstrate that MB and PQ differentially regulate hepatic CYP1A1 and CYP1A2 while LPO, GSH, CYP2E1, GSTA4-4 and GSTA3-3 are modulated in the similar fashions both in the liver and PMNs.

Protective role of glutathione S-transferase A4 induced in copper/zinc-superoxide dismutase knockout mice

Copper/zinc-superoxide dismutase (SOD1) plays a protective role in cells by catalyzing the conversion of the superoxide anion into molecular oxygen and hydrogen peroxide. Although SOD1 knockout (KO) mice exhibit a reduced life span and an elevated incidence of dysfunctions in old age, young SOD1 KO mice grow normally and exhibit no abnormalities. This fact leads to the hypothesis that other antioxidative proteins prevent oxidative stress, compensating for SOD1. Differently expressed genes in 3-week-old SOD1 KO and littermate wild-type mice were explored. A gene remarkably elevated in SOD1 KO mouse kidneys was identified as the glutathione S-transferase Alpha 4 gene (Gsta4), which encodes the GSTA4 subunit. The GSTA4 protein level and activity were also significantly increased in SOD1 KO mouse kidneys. The administration of an iron complex, a free radical generator, induced GSTA4 expression in wild-type mouse kidneys. Iron deposition detected in SOD1 KO mouse kidney is thought to be an inducer of GSTA4. In addition, overexpression of mouse GSTA4 cDNA in human embryonic kidney cells decreased cell death caused by both 4-hydroxynonenal and hydrogen peroxide. These findings suggest that compensatory induced GSTA4 plays a protective role against oxidative stress in young SOD1 KO mouse kidneys.

Association between polymorphisms in the GSTA4 gene and risk of lung cancer: a case-control study in a Southeastern Chinese population

GST Alpha 4 (GSTA4) has an important role in the protection against oxidative stress induced by carcinogens such as tobacco smoke. However, few studies investigated the association between GSTA4 polymorphisms and lung cancer risk. We genotyped three selected GSTA4 SNPs (rs182623 - 1718:T > A, rs3798804 + 5034:G > A and rs316141 + 13984:C > T) in a case-control study of 500 lung cancer patients and 517 cancer-free controls and evaluated the association between these SNPs and risk of lung cancer in this Han Chinese population. We found that there was a significant difference in genotype and allele frequency distributions of GSTA4 -1718 between the cases and the controls (P = 0.006 and P = 0.003, respectively). Compared with the GSTA4 -1718TT genotype, individuals with the TA + AA genotypes had a significantly decreased risk of lung cancer (adjusted OR, 0.63; 95% CI, 0.47-0.84; P = 0.006). Although there were no such statistical differences between the cases and controls at the loci +5034 and +13984, nor for histological types, individuals carrying the genotypes of -1718TA, +5034GG and +13984CT had a significantly decreased lung cancer risk (OR, 0.37; 95% CI, 0.23-0.61; P < 0.0001), especially for those smokers who smoked </=25 pack-years (P < 0.000001). These results need to be confirmed in larger studies with different ethnic groups.

Expression of genes for redox-dependent glutathione S-transferase isoforms GSTP1-1 and GSTA4-4 in tumor cell during the development doxorubicin resistance

Expression of genes for redox-dependent glutathione S-transferase isoforms GSTP1-1 and GSTA4-4 in tumor cells K562, MCF-7, and SKOV-3 was studied during the development of resistance to doxorubicin. It was found that the development of resistance was accompanied by predominant increase in the expression of hGSTP1 gene in MCF-7 cells, and hGSTA4 gene in resistant K562/DOX and SKVLB cells.

Novel selenoorganic compounds as modulators of oxidative stress in blood platelets

Many selenoorganic compounds play an important role in biochemical processes and act as antioxidants, enzyme inhibitors, or drugs. The effects of five new synthesized selenoorganic compounds (2-(5-chloro-2-pyridyl)-7-azabenzisoselenazol-3(2H)-one; 2-phenyl-7-azabenzisoselenazol-3(2H)-one; 2-(pyridyl)-7-azabenzisoselenazol-3(2H)-one; 7-azabenzisoselenazol-3(2H)-one; bis(2-aminophenyl) diselenide) on oxidative changes in human blood platelets and in plasma were studied in vitro and compared with those of ebselen, a well known antioxidant. Our studies demonstrated that bis(2-aminophenyl) diselenide has distinctly protective effects against oxidative stress in blood platelets and in plasma. It might have greater biological relevance and stronger pharmacological effects than ebselen.

Proteomic identification of alterations in metabolic enzymes and signaling proteins in hypokalemic nephropathy

Hypokalemic nephropathy caused by prolonged K(+) deficiency is associated with metabolic alkalosis, polydipsia, polyuria, growth retardation, hypertension, and progressive tubulointerstitial injury. Its pathophysiology, however, remains unclear. We performed gel-based, differential proteomics analysis of kidneys from BALB/c mice fed with high-normal-K(+) (HNK), low-normal-K(+) (LNK), or K(+)-depleted diet for 8 wk (n = 6 in each group). Plasma K(+) levels were 4.62 +/- 0.35, 4.46 +/- 0.23, and 1.51 +/- 0.21 mmol/L for HNK, LNK, and KD mice, respectively (p < 0.0001; KD vs. others). With comparable amounts of food intake, the KD mice drank significantly more water than the other two groups and had polyuria. Additionally, the KD mice had growth retardation, metabolic alkalosis, markedly enlarged kidneys, renal tubular dilation, intratubular deposition of amorphous and laminated hyaline materials, and tubular atrophy. A total of 33 renal proteins were differentially expressed between the KD mice and others, whereas only eight proteins were differentially expressed between the HNK and LNK groups, as determined by quantitative intensity analysis and ANOVA with Tukey's post hoc multiple comparisons. Using MALDI-MS and/or quadrupole-TOF MS/MS, 30 altered proteins induced by K(+)-depletion were identified as metabolic enzymes (e.g., carbonic anhydrase II, aldose reductase, glutathione S-transferase GT41A, etc.), signaling proteins (14-3-3 epsilon, 14-3-3 zeta, and cofilin 1), and cytoskeletal proteins (gamma-actin and tropomyosin). Some of these altered proteins, particularly metabolic enzymes and signaling proteins, have been demonstrated to be involved in metabolic alkalosis, polyuria, and renal tubular injury. Our findings may lead to a new road map for research on hypokalemic nephropathy and to better understanding of the pathophysiology of this medical disease when the functional and physiological significances of these altered proteins are defined.

Activation of C-Jun N-terminal kinase is required for glutathione transferase A4 induction during oxidative stress, not during cell proliferation, in mouse hepatocytes

Expression of the mouse glutathione transferase Alpha 4 (mGSTA4) has been studied during hepatocyte isolation and in cultured hepatocytes. Transient mGSTA4 induction during liver disruption correlated to strong oxidative stress and induction of the Jun N-terminal kinase (JNK) pathway. Similarly, tumor necrosis factor alpha induced both JNK phosphorylation and mGSTA4 expression while specific JNK inhibitor JNKI1 prevented these two events and JNK activator anisomycin strongly induced mGSTA4 expression. We also found that endogenous JNK and mGSTA4 co-immunoprecipitate. A second mGSTA4 induction occurred 2 days after cell seeding concomitantly to DNA replication and was prevented by treatment with mitogen-activated protein kinase (MEK) inhibitor U0126. Our data demonstrate that mGSTA4 is strongly increased during oxidative stress possibly via JNK pathway and during proliferation via MEK/extracellular signal-regulated kinase pathway, and suggest that mGSTA4 might be an endogenous regulator of JNK activity by direct binding.

Microarray analysis of altered gene expression in murine fibroblasts transformed by nickel(II) to nickel(II)-resistant malignant phenotype

B200 cells are Ni(II)-transformed mouse BALB/c-3T3 fibroblasts displaying a malignant phenotype and increased resistance to Ni(II) toxicity. In an attempt to find genes whose expression has been altered by the transformation, the Atlas Mouse Stress/Toxicology cDNA Expression Array (Clontech Laboratories, Inc., Palo Alto, CA) was used to analyze the levels of gene expression in both parental and Ni(II)-transformed cells. Comparison of the results revealed a significant up- or downregulation of the expression of 62 of the 588 genes present in the array (approximately 10.5%) in B200 cells. These genes were assigned to different functional groups, including transcription factors and oncogenes (9/14; fractions in parentheses denote the number of up-regulated versus the total number of genes assigned to this group), stress and DNA damage response genes (11/12), growth factors and hormone receptors (6/9), metabolism (7/7), cell adhesion (2/7), cell cycle (3/6), apoptosis (3/4), and cell proliferation (2/3). Among those genes, overexpression of beta-catenin and its downstream targets c-myc and cyclin D1, together with upregulated cyclin G, points at the malignant character of B200 cells. While the increased expression of glutathione (GSH) synthetase, glutathione-S-transferase A4 (GSTA4), and glutathione-S-transferase theta (GSTT), together with high level of several genes responding to oxidative stress, suggests the enforcement of antioxidant defenses in Ni-transformed cells.

Phosphorylation enhances mitochondrial targeting of GSTA4-4 through increased affinity for binding to cytoplasmic Hsp70

Recently we showed that three different isoforms of cytosolic glutathione S-transferases (GST), including GSTA4-4, are also localized in the mitochondrial compartment. In this study, we have investigated the mechanism of mouse GSTA4-4 targeting to mitochondria, using a combination of in vitro mitochondrial import assay and in vivo targeting in COS cells transfected with cDNA. Our results show that the mitochondrial GSTA4-4 is more heavily phosphorylated compared with its cytosolic counterpart. Protein kinase activators (cAMP, forskolin, or phorbol-12-myristate-13-acetate) markedly increased GSTA4-4 targeting to mitochondria, whereas kinase inhibitors caused its retention in the cytosol. Immunoinhibition and immunodepletion studies showed that the Hsp70 chaperone is required for the efficient translation of GSTA4-4 as well as its translocation to mitochondria. Co-immunoprecipitation studies showed that kinase inhibitors attenuate the affinity of GSTA4-4 for cytoplasmic Hsp70 suggesting the importance of phosphorylation for binding to the chaperone. Mutational analysis show that the putative mitochondrial targeting signal resides within the C-terminal 20 amino acid residues of the protein and that the targeting signal requires activation by phosphorylation at the C-terminal-most protein kinase A (PKA) site at Ser-189 or protein kinase C (PKC) site at Thr-193. We demonstrate for the first time that PKA and PKC modulate the cytoplasmic and mitochondrial pools of GSTA4-4.

Pro-inflammatory cytokines tumor necrosis factor alpha and interleukin-6 and survival factor epidermal growth factor positively regulate the murine GSTA4 enzyme in hepatocytes

We hypothesized that glutathione transferases could be induced and may participate to cellular defenses against the oxidative stress occurring during liver regeneration. Here, we evidenced that murine GSTA1 (mGSTA1), A4, Pi, and Mu are up-regulated during mouse liver regeneration, exhibiting a biphasic pattern of induction correlating early G(1) phase and G(1)/S transition of the cell cycle. Using confocal microscopy immunolocalization and subcellular fractionation, mGSTA4 was demonstrated in both mitochondria and cytosol and found preferentially increased in cytosol during liver regeneration. In addition, mGSTA4 was induced in vivo and in cultured hepatocytes by tumor necrosis factor alpha (TNFalpha), interleukin-6 (IL-6), and epidermal growth factor (EGF), factors that play crucial roles in hepatocyte survival and proliferation during liver regeneration. However, the mitogenic effect of EGF was not responsible for the induction of mGSTA4. In transient transfections, IL-6 and EGF, but not TNFalpha, transactivated the human GSTA4 (hGSTA4) promoter cloned upstream of the luciferase reporter gene suggesting that IL-6 and EGF up-regulated hGSTA4 at a transcriptional level, whereas TNFalpha could rather act at a post-transcriptional level. The inhibition of phosphoinositide 3-kinase, p38 MAPK, and MEK/ERK signaling pathways, using specific inhibitors, prevented EGF-dependent induction of mGSTA4 and transactivation of hGSTA4 promoter. Altogether, these data favor the conclusion that, in regenerating hepatocytes, several GST isoforms are induced and that cytokines TNFalpha and IL-6 and survival factor EGF positively regulate mGSTA4 via survival signaling pathways.