Immunohistologic localization of alpha, mu, and pi class glutathione S-transferases in human tissues

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.

Glutathione S-transferase A1 suppresses tumor progression and indicates better prognosis of human primary hepatocellular carcinoma

Glutathione S-transferase (GST) family members play an important role in detoxification, metabolism and carcinogenesis. The aim of this study is to investigate the effect of Glutathione S-transferase A1 (GSTA1) on the prognosis of HCC and to understand its role in tumor progression and the possible mechanism. GSTA1 in HCC was assessed using immunohistochemical staining, and it was found that HCC patients with better pathological differentiation had higher GSTA1 abundance. Further, high GSTA1 expression was correlated with low AFP, absent PVTT, and early stage TNM for HCC patients. Higher GSTA1 indicated longer overall survival and disease-free survival, while lower GSTA1 indicated poorer prognosis. Subsequently, lentiviral vector carrying GSTA1 gene was successfully constructed and maintained high expression in 97H and SNU449 liver cancer cells. We found that high GSTA1 restrained liver cancer cell proliferation, migration and invasion in vitro. Western blot showed that LKB1 and p-AMPK were upregulated while p-mTOR, p-p70 S6 Kinase and MMP-9 were downregulated in high GSTA1 groups. Taken together, high GSTA1 correlated with satisfactory prognosis of HCC. Additionally, GSTA1 may act as a protective factor through suppression of tumorigenesis by targeting AMPK/mTOR in HCC.

A Comparison of the Effects of Prolonged (>10 Hour) Low-flow Sevoflurane, High-flow Sevoflurane, and Low-flow Isoflurane Anaesthesia on Hepatorenal Function in Orthopaedic Patients

This study compared the effects of low-flow sevoflurane, high-flow sevoflurane and low-flow isoflurane on hepatorenal function during and after more than 10 hours of anaesthesia. Twenty-five patients scheduled for elective orthopaedic surgery were categorized into three groups; low-flow sevoflurane (fresh gas flow at 1 litre/min, n=9), high-flow sevoflurane (5 l/min, n=7), or low-flow isoflurane (1 l/min, n=9). Inspiratory compound A concentrations were measured. The groups had similar duration of anaesthesia and exposure to anaesthetic agents. The area under the curve of concentration (mean, SD) of compound A in the low-flow sevoflurane group (359.8, 106.1 ppm.h) was greater than that in the high-flow sevoflurane group (61.1, 29.3 ppm.h; P<0.01). All groups showed normal plasma creatinine and creatinine clearance, and transient postoperative increases in plasma alanine aminotrans-ferase and alpha glutathione-S-transferase, as well as urinary glucose and alpha glutathione-S-transferase, with no significant differences between groups. There were no significant relationships between the area under the curve of concentration of compound A and the biomarkers. These findings suggest that prolonged anaesthesia with low-flow sevoflurane has similar effects on hepatorenal function to prolonged anaesthesia with high-flow sevoflurane and low-flow isoflurane.

Fluorescence detection of glutathione S-transferases in a low GSH level environment

Glutathione S-transferases (GSTs) play crucial roles in the detoxification process and the development of drug-resistance and are proved to be important markers for various tumors.

Diagnostic accuracy of novel serological biomarkers to detect acute mesenteric ischemia: a systematic review and meta-analysis

Laparotomy remains the gold standard for diagnosis of acute mesenteric ischemia (AMI), but is often unhelpful or too late due to non-specific clinical and radiological signs. This systematic review and meta-analysis aims to evaluate the diagnostic accuracy of the novel serological biomarkers intestinal fatty acid-binding protein (I-FABP), α-glutathione S-transferase (α-GST), D-lactate, ischemia modified albumin (IMA), and citrulline to detect AMI. A systematic search of electronic databases was performed to identify all published diagnostic accuracy studies on I-FABP, α-GST, D-lactate, IMA, and citrulline. Articles were selected based on pre-defined inclusion and exclusion criteria. Risk of bias and applicability were assessed. Two-by-two contingency tables were constructed to calculate accuracy standards. Summary estimates were computed using random-effects models. The search yielded 1925 papers, 21 were included in the final analysis. Pooled sensitivity and specificity for investigated biomarkers were: I-FABP (Uden); 79.0 (95% CI 66.5-88.5) and 91.3 (87.0-94.6), I-FABP (Osaka); 75.0 (67.9-81.2) and 79.2 (76.2-82.0), D-lactate; 71.7 (58.6-82.5) and 74.2 (69.0-79.0), α-GST; 67.8 (54.2-79.5) and 84.2 (75.3-90.9), IMA; 94.7 (74.0-99.9) and 86.4 (65.1-97.1), respectively. One study investigated accuracy standards for citrulline: sensitivity 39% and specificity 100%. The novel serological biomarkers I-FABP, α-GST, IMA, and citrulline may offer improved diagnostic accuracy of acute mesenteric ischemia; however, further research is required to specify threshold values and accuracy standards for different aetiological forms.

Predicting acute kidney injury: current status and future challenges

Acute kidney injury (AKI) is characterized by an acute decline in renal function and is associated to increased mortality rate, hospitalization time, and total health-related costs. The severity of this ‘fearsome’ clinical complication might depend on, or even be worsened by, the late detection of AKI, when the diagnosis is based on the elevation of serum creatinine (SCr). For these reasons, in recent years a great number of new tools, biomarkers and predictive models have been proposed to clinicians in order to improve diagnosis and prevent the development of AKI. The purpose of this narrative paper is to review the current state of the art in prediction and early detection of AKI and outline future challenges.

Glutathione S Transferases Polymorphisms Are Independent Prognostic Factors in Lupus Nephritis Treated with Cyclophosphamide

OBJECTIVE

To investigate association between genetic polymorphisms of GST, CYP and renal outcome or occurrence of adverse drug reactions (ADRs) in lupus nephritis (LN) treated with cyclophosphamide (CYC). CYC, as a pro-drug, requires bioactivation through multiple hepatic cytochrome P450s and glutathione S transferases (GST).

METHODS

We carried out a multicentric retrospective study including 70 patients with proliferative LN treated with CYC. Patients were genotyped for polymorphisms of the CYP2B6, CYP2C19, GSTP1, GSTM1 and GSTT1 genes. Complete remission (CR) was defined as proteinuria ≤0.33g/day and serum creatinine ≤124 µmol/l. Partial remission (PR) was defined as proteinuria ≤1.5g/day with a 50% decrease of the baseline proteinuria value and serum creatinine no greater than 25% above baseline.

RESULTS

Most patients were women (84%) and 77% were Caucasian. The mean age at LN diagnosis was 41 ± 10 years. The frequency of patients carrying the GST null genotype GSTT1-, GSTM1-, and the Ile→105Val GSTP1 genotype were respectively 38%, 60% and 44%. In multivariate analysis, the Ile→105Val GSTP1 genotype was an independent factor of poor renal outcome (achievement of CR or PR) (OR = 5.01 95% CI [1.02-24.51]) and the sole factor that influenced occurrence of ADRs was the GSTM1 null genotype (OR = 3.34 95% CI [1.064-10.58]). No association between polymorphisms of cytochrome P450s gene and efficacy or ADRs was observed.

CONCLUSION

This study suggests that GST polymorphisms highly impact renal outcome and occurrence of ADRs related to CYC in LN patients.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

Trichloroethylene biotransformation and its role in mutagenicity, carcinogenicity and target organ toxicity

Metabolism is critical for the mutagenicity, carcinogenicity, and other adverse health effects of trichloroethylene (TCE). Despite the relatively small size and simple chemical structure of TCE, its metabolism is quite complex, yielding multiple intermediates and end-products. Experimental animal and human data indicate that TCE metabolism occurs through two major pathways: cytochrome P450 (CYP)-dependent oxidation and glutathione (GSH) conjugation catalyzed by GSH S-transferases (GSTs). Herein we review recent data characterizing TCE processing and flux through these pathways. We describe the catalytic enzymes, their regulation and tissue localization, as well as the evidence for transport and inter-organ processing of metabolites. We address the chemical reactivity of TCE metabolites, highlighting data on mutagenicity of these end-products. Identification in urine of key metabolites, particularly trichloroacetate (TCA), dichloroacetate (DCA), trichloroethanol and its glucuronide (TCOH and TCOG), and N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NAcDCVC), in exposed humans and other species (mostly rats and mice) demonstrates function of the two metabolic pathways in vivo. The CYP pathway primarily yields chemically stable end-products. However, the GST pathway conjugate S-(1,2-dichlorovinyl)glutathione (DCVG) is further processed to multiple highly reactive species that are known to be mutagenic, especially in kidney where in situ metabolism occurs. TCE metabolism is highly variable across sexes, species, tissues and individuals. Genetic polymorphisms in several of the key enzymes metabolizing TCE and its intermediates contribute to variability in metabolic profiles and rates. In all, the evidence characterizing the complex metabolism of TCE can inform predictions of adverse responses including mutagenesis, carcinogenesis, and acute and chronic organ-specific toxicity.

Regulation of biotransformation systems and ABC transporters by benznidazole in HepG2 cells: involvement of pregnane X-receptor

Background

Benznidazole (BZL) is the only antichagasic drug available in most endemic countries. Its effect on the expression and activity of drug-metabolizing and transporter proteins has not been studied yet.

Methodology/Principal Findings

Expression and activity of P-glycoprotein (P-gp), Multidrug resistance-associated protein 2 (MRP2), Cytochrome P450 3A4 (CYP3A4), and Glutathione S-transferase (GST) were evaluated in HepG2 cells after treatment with BZL. Expression was estimated by immunoblotting and real time PCR. P-gp and MRP2 activities were estimated using model substrates rhodamine 123 and dinitrophenyl-S-glutathione (DNP-SG), respectively. CYP3A4 and GST activities were evaluated through their abilities to convert proluciferin into luciferin and 1-chloro-2,4-dinitrobenzene into DNP-SG, respectively. BZL (200 µM) increased the expression (protein and mRNA) of P-gp, MRP2, CYP3A4, and GSTπ class. A concomitant enhancement of activity was observed for all these proteins, except for CYP3A4, which exhibited a decreased activity. To elucidate if pregnane X receptor (PXR) mediates BZL response, its expression was knocked down with a specific siRNA. In this condition, the effect of BZL on P-gp, MRP2, CYP3A4, and GSTπ protein up-regulation was completely abolished. Consistent with this, BZL was able to activate PXR, as detected by reporter gene assay. Additional studies, using transporter inhibitors and P-gp-knock down cells, demonstrated that P-gp is involved in BZL extrusion. Pre-treatment of HepG2 cells with BZL increased its own efflux, as a consequence of P-gp up-regulation.

Conclusions/Significance

Modifications in the activity of biotransformation and transport systems by BZL may alter the pharmacokinetics and efficiency of drugs that are substrates of these systems, including BZL itself.

Chagas disease is an endemic infection caused by Trypanosoma cruzi. Benznidazole (BZL) is the only antichagasic drug available in most endemic countries. The liver plays a major role in disposition of endogenous and exogenous compounds and their excretion is mainly mediated by transporter proteins (such as P-gp and MRP2) that act coordinately with biotransformation enzymes (such as CYP3A4 and GST). At present there is no information on whether BZL may modulate major biotransformation systems and transporters, with potential impact on its disposition or on disposition of other therapeutic agents co-administered with BZL. BZL (200 µM) altered the expression (protein and mRNA) and activity of P-gp, MRP2, CYP3A4, and GSTπ in HepG2 cells (a cell model that retains many biochemical, morphological and functional properties of the human hepatocytes), being the nuclear receptor PXR a key mediator. Additional studies demonstrated that P-gp is involved in BZL extrusion. Alterations in the pharmacokinetics and efficiency of drugs that are substrates of these systems, including BZL itself, would be expected.

A performance evaluation of three drug-induced liver injury biomarkers in the rat: alpha-glutathione S-transferase, arginase 1, and 4-hydroxyphenyl-pyruvate dioxygenase

Alanine aminotransferase (ALT) activity is the most frequently relied upon reference standard for monitoring liver injury in humans and nonclinical species. However, limitations of ALT include a lack of specificity for diagnosing liver injury (e.g., present in muscle and the gastrointestinal tract), its inability to monitor certain types of hepatic injury (e.g., biliary injury), and ambiguity with respect to interpretation of modest or transient elevations (< 3× upper limit of normal). As an initial step to both understand and qualify additional biomarkers of hepatotoxicity that may add value to ALT, three novel candidates have been evaluated in 34 acute toxicity rat studies: (1) alpha-glutathione S-transferase (GSTA), (2) arginase 1 (ARG1), and (3) 4-hydroxyphenylpyruvate dioxygenase (HPD). The performance of each biomarker was assessed for its diagnostic ability to accurately detect hepatocellular injury (i.e., microscopic histopathology), singularly or in combination with ALT. All three biomarkers, either alone or in combination with ALT, improved specificity when compared with ALT alone. Hepatocellular necrosis and/or degeneration were detected by all three biomarkers in the majority of animals. ARG1 and HPD were also sensitive in detecting single-cell necrosis in the absence of more extensive hepatocellular necrosis/degeneration. ARG1 showed the best sensitivity for detecting biliary injury with or without ALT. All the biomarkers were able to detect biliary injury with single-cell necrosis. Taken together, these novel liver toxicity biomarkers, GSTA, ARG1, and HPD, add value (both enhanced specificity and sensitivity) to the measurement of ALT alone for monitoring drug-induced liver injury in rat.

Urinary α-GST and π-GST for prediction of dialysis requirement or in-hospital death in established acute kidney injury

CONTEXT

Urinary α-glutathione S-transferase (α-GST) and π-glutathione S-transferase (π-GST) are promising proximal and distal tubular leakage markers for early detection of acute kidney injury (AKI).

OBJECTIVE

To examine the performance of these markers for predicting the composite of dialysis requirement or in-hospital death in patients with an established diagnosis of AKI.

MATERIALS AND METHODS

Prospective cohort study of 245 adults with AKI. A single urinary α-GST and π-GST measurement was obtained at time of nephrology consultation.

RESULTS

Overall, urinary π-GST performed better than α-GST for prediction of dialysis requirement (AUC 0.59 vs. 0.56), and the composite outcome (AUC 0.58 vs. 0.56). In subgroup analyses, π-GST displayed better discrimination for prediction of dialysis requirement in patients with baseline eGFR <60 mL/min/1.73 m(2) (AUC 0.61) and oliguria (AUC 0.72). Similarly, α-GST performed better in patients with stage-1 (AUC 0.66) and stage-2 AKI (AUC 0.80).

CONCLUSIONS

In patients with an established diagnosis of AKI, a single urinary π-GST measurement performed better than α-GST at predicting dialysis requirement or death, but neither marker had good prognostic discrimination.

Non-invasive markers of gut wall integrity in health and disease

The intestinal mucosa is responsible for the absorption of nutrients from the lumen and for the separation of the potentially toxic luminal content (external environment) from the host (internal environment). Disruption of this delicate balance at the mucosal interface is the basis for numerous (intestinal) diseases. Experimental animal studies have shown that gut wall integrity loss is involved in the development of various inflammatory syndromes, including post-operative or post-traumatic systemic inflammatory response syndrome, sepsis, and multiple organ failure. Assessment of gut wall integrity in clinical practice is still a challenge, as it is difficult to evaluate the condition of the gut non-invasively with currently available diagnostic tools. Moreover, non-invasive, rapid diagnostic means to assess intestinal condition are needed to evaluate the effects of treatment of intestinal disorders. This review provides a survey of non-invasive tests and newly identified markers that can be used to assess gut wall integrity.

Non-invasive markers of gut wall integrity in health and disease

The intestinal mucosa is responsible for the absorption of nutrients from the lumen and for the separation of the potentially toxic luminal content (external environment) from the host (internal environment). Disruption of this delicate balance at the mucosal interface is the basis for numerous (intestinal) diseases. Experimental animal studies have shown that gut wall integrity loss is involved in the development of various inflammatory syndromes, including post-operative or post-traumatic systemic inflammatory response syndrome, sepsis, and multiple organ failure. Assessment of gut wall integrity in clinical practice is still a challenge, as it is difficult to evaluate the condition of the gut non-invasively with currently available diagnostic tools. Moreover, non-invasive, rapid diagnostic means to assess intestinal condition are needed to evaluate the effects of treatment of intestinal disorders. This review provides a survey of non-invasive tests and newly identified markers that can be used to assess gut wall integrity.

Redox control systems in the nucleus: mechanisms and functions

Proteins with oxidizable thiols are essential to many functions of cell nuclei, including transcription, chromatin stability, nuclear protein import and export, and DNA replication and repair. Control of the nuclear thiol-disulfide redox states involves both the elimination of oxidants to prevent oxidation and the reduction of oxidized thiols to restore function. These processes depend on the common thiol reductants, glutathione (GSH) and thioredoxin-1 (Trx1). Recent evidence shows that these systems are controlled independent of the cytoplasmic counterparts. In addition, the GSH and Trx1 couples are not in redox equilibrium, indicating that these reductants have nonredundant functions in their support of proteins involved in transcriptional regulation, nuclear protein trafficking, and DNA repair. Specific isoforms of glutathione peroxidases, glutathione S-transferases, and peroxiredoxins are enriched in nuclei, further supporting the interpretation that functions of the thiol-dependent systems in nuclei are at least quantitatively distinct, and probably also qualitatively distinct, from similar processes in the cytoplasm. Elucidation of the distinct nuclear functions and regulation of the thiol redox pathways in nuclei can be expected to improve understanding of nuclear processes and also to provide the basis for novel approaches to treat aging and disease processes associated with oxidative stress in the nuclei.

Protective effect of Jasonia montana against ethinylestradiol-induced cholestasis in rats

Estrogens, and particularly glucuronides such as ethinylestradiol (EE), have been shown to cause cholestasis in animal studies, by reducing bile acid uptake by hepatocytes. The aim of the present article is to investigate anticholestatic activity of the ethanolic extract of the aerial parts of Jasonia montana against liver cholestasis induced by EE in adult female rats in an attempt to understand its mechanism of action, which may pave the way for possible therapeutic applications. Subcutaneous administration of 100 μg/kg b.w. ethinylestradiol to rats induced hepatocellular cholestasis with a significant decrease in serum cholesterol, bile acids and bilirubin levels as well as in hepatic superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) activities and hepatic total, protein-bound and non-protein sulfhydryl groups. Also, treatment with EE produced significant increase in serum Pi-glutathione-s-transferase (Pi-GST), gamma glutamyl transpeptidase (γ-GT) and alpha-glutathione-s-transferase (α-GST) activities as well as serum nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) level and hepatic malondialdehyde (MDA) level as compare to control group. Oral administration of the aerial parts of ethanolic extract at a concentration of 150 mg/kg b.w. daily to rats treated with EE for 15 days showed a significant protection against-induced decrease in serum cholesterol, bile acids and bilirubin levels. The treatment also resulted in a significant increase in hepatic SOD, GPx and GR activities as well as hepatic total, protein-bound and non-protein sulfhydryl groups. In addition, the extract could inhibit serum Pi-GST, γ-GT and α-GST activities as well as reduce serum TNF-α, NO and hepatic MDA as compare to ethinylestradiol treated rats. High content of flavonoids and phenolic compounds was found in ethanolic extract, which may be responsible for free radical activity. The results clearly suggest that the aerial parts of J. montana extract may effectively normalize the impaired antioxidant status in ethinylestradiol (EE)-cholestatic model. Thus the extract may have a therapeutic value in drug-induced biliary cholestasis as well as in hormonal therapy.

Proteomics identification of azaspiracid toxin biomarkers in blue mussels, Mytilus edulis

Azaspiracids are a class of recently discovered algae-derived shellfish toxins. Their distribution globally is on the increase with mussels being most widely implicated in azaspiracid-related food poisoning events. Evidence that these toxins were bound to proteins in contaminated mussels has been shown recently. In the present study characterization of these proteins in blue mussels, Mytilus edulis, was achieved using a range of advanced proteomics tools. Four proteins present only in the hepatopancreas of toxin-contaminated mussels sharing identity or homology with cathepsin D, superoxide dismutase, glutathione S-transferase Pi, and a bacterial flagellar protein have been characterized. Several of the proteins are known to be involved in self-defense mechanisms against xenobiotics or up-regulated in the presence of carcinogenic agents. These findings would suggest that azaspiracids should now be considered and evaluated as potential tumorigenic compounds. The presence of a bacterial protein only in contaminated mussels was an unexpected finding and requires further investigation. The proteins identified in this study should assist with development of urgently required processes for the rapid depuration of azaspiracid-contaminated shellfish. Moreover they may serve as early warning indicators of shellfish exposed to this family of toxins.

The depletion of nuclear glutathione impairs cell proliferation in 3t3 fibroblasts

Background

Glutathione is considered essential for survival in mammalian cells and yeast but not in prokaryotic cells. The presence of a nuclear pool of glutathione has been demonstrated but its role in cellular proliferation and differentiation is still a matter of debate.

Principal Findings

We have studied proliferation of 3T3 fibroblasts for a period of 5 days. Cells were treated with two well known depleting agents, diethyl maleate (DEM) and buthionine sulfoximine (BSO), and the cellular and nuclear glutathione levels were assessed by analytical and confocal microscopic techniques, respectively. Both agents decreased total cellular glutathione although depletion by BSO was more sustained. However, the nuclear glutathione pool resisted depletion by BSO but not with DEM. Interestingly, cell proliferation was impaired by DEM, but not by BSO. Treating the cells simultaneously with DEM and with glutathione ethyl ester to restore intracellular GSH levels completely prevented the effects of DEM on cell proliferation.

Conclusions

Our results demonstrate the importance of nuclear glutathione in the control of cell proliferation in 3T3 fibroblasts and suggest that a reduced nuclear environment is necessary for cells to progress in the cell cycle.

Urinary excretion of α‐GST and albumin in rheumatoid arthritis patients treated with methotrexate or other DMARDs alone or in combination with NSAIDs

OBJECTIVE

To evaluate the effect of methotrexate (MTX) and other disease-modifying anti-rheumatic drugs (DMARDs) alone or in combination with non-steroidal anti-inflammatory drugs (NSAIDs) on the urinary excretion of alpha-glutathione S-transferase (alpha-GST) and albumin in rheumatoid arthritis (RA) patients.

METHODS

Nineteen RA patients starting treatment with MTX were followed for 1 year with measurements of urinary alpha-GST, urinary albumin, and urinary and plasma creatinine at the start of treatment, and after 16, 28, and 52 weeks. A larger group of RA patients (n = 72) undergoing long-term treatment with different DMARDs was compared with 79 healthy controls regarding urinary alpha-GST and albumin. alpha-GST was quantified by an enzyme immunoassay. Urine albumin was measured turbidimetrically.

RESULTS

The urine-alpha-GST/urine-creatinine ratio and the urine-albumin/urine-creatinine ratio did not change during 52 weeks of treatment with MTX. The long-term DMARD-treated RA patients and the healthy controls were comparable with regard to the urine-alpha-GST/urine-creatinine ratio and the urine-albumin/urine-creatinine ratio. All patients had preserved renal function as assessed by plasma creatinine, and none had proteinuria using urine dipstick methods.

CONCLUSION

DMARD-treated RA patients with normal serum creatinine had no detectable renal injuries assessed by the urinary excretions of alpha-GST and albumin.

Biomarkers of kidney integrity in children and adolescents with dental amalgam mercury exposure: findings from the Casa Pia children's amalgam trial

Mercury is toxic to the kidney, and dental amalgam is a source of mercury exposure. Few studies have evaluated the effects of dental amalgam on kidney function in a longitudinal context in children. Here, we evaluated urinary concentrations of glutathione S-transferases (GSTs) alpha and pi as biomarkers of renal proximal and distal tubular integrity, respectively, and albumin as a biomarker of glomerular integrity in children and adolescents 8-18 years of age over a 7-year course of dental amalgam treatment. Five hundred seven children, 8-12 years of age at baseline, participated in a clinical trial to evaluate the neurobehavioral and renal effects of dental amalgam in children. Subjects were randomized to either dental amalgam or resin composite treatments. Urinary GSTs alpha and pi, albumin, and creatinine concentrations were measured at baseline and annually in all subjects. Results were evaluated using linear regression analysis. GST-alpha concentrations were similar between treatment groups and in each sex and race (white vs. non-white) group in each follow-up year. GST-pi levels tended upward over the course of follow-up by four- to six-fold. This increase was seen in all groups irrespective of the treatment, race, or gender. Females had GST-pi levels approximately twice those of males at all ages. Albumin concentrations were constant throughout the follow-up period and did not differ by treatment, although females had 39% higher albumin levels than males. Additionally, we found no significant effects of amalgam treatment on the proportion of children with microalbuminuria (>30 mg/g creatinine). These findings are relevant within the context of children's health risk assessment as relates to the safety of mercury exposure from dental amalgam on kidney function. These data also provide normative values for sensitive indices of renal functional integrity that may serve in the evaluation of children and adolescents with renal disorders.

Antioxidant enzyme immunoreactivity in rat von Ebner gland after nickel treatment

Our study was designed to clarify the role of antioxidant enzymes in the rat von Ebner gland during acute nickel toxicity. After treatment with nickel acetate, we monitored ultrastructural alterations in acinar and ductal cells, immunohistochemical staining for glutathione peroxidase (GPx) and glutathione S-transferases (GST mu and GST pi), and immunoreactivity for malondialdehyde (MDA). Immunoreactivity for MDA was present only in the acinar cells, and it was enhanced at 3 h after Ni treatment. In contrast, immunoreactivities for GPx and GSTs did not change in acinar cells but significantly increased in ductal cells after Ni treatment. Cytoplasmic vacuoles increased in acinar cells at 3 h after Ni treatment, but they almost completely disappeared at 24 h. No morphological changes were observed in taste bud cells from Ni-treated rats. Because lipid peroxidation, as monitored by immunoreactivity for MDA, was only transiently increased in the acinar cells, the enhanced antioxidant enzyme immunoreactivity in ductal cells of the von Ebner gland plays a crucial role in the self-defense system against nickel toxicity in the rat oral cavity.

Drug metabolism enzyme expression and activity in primary cultures of human proximal tubular cells

We previously catalogued expression and activity of organic anion and cation, amino acid, and peptide transporters in primary cultures of human proximal tubular (hPT) cells to establish them as a cellular model to study drug transport in the human kidney [Lash, L.H., Putt, D.A., Cai, H., 2006. Membrane transport function in primary cultures of human proximal tubular cells. Toxicology 228, 200-218]. Here, we extend our analysis to drug metabolism enzymes. Expression of 11 cytochrome P450 (CYP) enzymes was determined with specific antibodies. CYP1B1, CYP3A4, and CYP4A11 were the only CYP enzymes readily detected in total cell extracts. These same CYP enzymes, as well as CYP3A5 and possibly CYP2D6, were detected in microsomes from confluent hPT cells, although expression levels varied among kidney samples. In agreement with Western blot data, only activity of CYP3A4/5 was detected among the enzyme activities measured. Expression of all three glutathione S-transferases (GSTs) known to be found in hPT cells, GSTA, GSTP, and GSTT, was readily detected. Variable expression of three sulfotransferases (SULTs), SULT1A3, SULT1E, and SULT2A1, and three UDP-glucuronosyltransferases (UGTs), UGT1A1, UGT1A6, and UGT2B7, was also detected. When examined over the course of cell growth to confluence, expression of all enzymes was generally maintained at readily measurable levels, although they were often lower than in fresh tissue. These results indicate that primary cultures of hPT cells possess significant capacity to metabolize many classes of drugs, and can be used as an effective model to study drug metabolism.

Enhanced invasive and metastatic potential induced by transforming growth factor-beta1 might be correlated with glutathione-S-transferase-pi, cofilin and heat shock protein 27 in SGC-7901 gastric cancer cells

In our previous study, we found that the transforming growth factor (TGF)-beta1 enhanced the metastatic and invasive potential of gastric cancer cells. Proteomics was employed in this study to further illustrate the underlying molecular mechanisms. After two-dimensional electrophoresis, image analysis, spot identification, protein identification and database analysis, three proteins, namely, glutathione-S-transferase-pi (GST-pi), cofilin and heat shock protein 27 (HSP27), were found to be up-regulated in TGF-beta1 treated SGC-7901 cells. The findings were further confirmed by Western blot analysis. These results suggested that GST-pi, cofilin and HSP27 might participate in enhanced invasive potential induced by TGF-beta1.

Electrostatic Association of Glutathione Transferase to the Nuclear Membrane

The possible nuclear compartmentalization of glutathione S-transferase (GST) isoenzymes has been the subject of contradictory reports. The discovery that the dinitrosyl-diglutathionyl-iron complex binds tightly to Alpha class GSTs in rat hepatocytes and that a significant part of the bound complex is also associated with the nuclear fraction (Pedersen, J. Z., De Maria, F., Turella, P., Federici, G., Mattei, M., Fabrini, R., Dawood, K. F., Massimi, M., Caccuri, A. M., and Ricci, G. (2007) J. Biol. Chem. 282, 6364-6371) prompted us to reconsider the nuclear localization of GSTs in these cells. Surprisingly, we found that a considerable amount of GSTs corresponding to 10% of the cytosolic pool is electrostatically associated with the outer nuclear membrane, and a similar quantity is compartmentalized inside the nucleus. Mainly Alpha class GSTs, in particular GSTA1-1, GSTA2-2, and GSTA3-3, are involved in this double modality of interaction. Confocal microscopy, immunofluorescence experiments, and molecular modeling have been used to detail the electrostatic association in hepatocytes and liposomes. A quantitative analysis of the membrane-bound Alpha GSTs suggests the existence of a multilayer assembly of these enzymes at the outer nuclear envelope that could represent an amazing novelty in cell physiology. The interception of potentially noxious compounds to prevent DNA damage could be the possible physiological role of the perinuclear and intranuclear localization of Alpha GSTs.

Tissue and species distribution of the glutathione pathway transcriptome

The goal of this study was to compare and contrast the basal gene expression levels of the various enzymes involved in glutathione metabolism among tissues and genders of the rat, mouse and canine. The approach taken was to use Affymetrix GeneChip microarray data for rat, mouse and canine tissues, comparing intensity levels for individual probes between tissues and genders. As was hypothesized, the relative expression in liver, lung, heart, kidney and testis varied from gene to gene, with differences of expression between tissues sometimes greater than a 1000-fold. The pattern of differential expression was usually similar between male and female animals, but varied greatly between the three species. Gstp1 appears to be expressed at high levels in male mouse liver, reasonable levels in canine liver, but very low levels in male rat liver. In all species examined, Gstp1 expression was below detectable levels in testis. Gsta3/Yc2 expression appeared high in rodent liver and female canine liver, but not male canine liver. Finally, Mgst1 and Gpx3 expression appeared to be lower in canine heart and testis than seen in rodents. Given the critical role of the glutathione pathway in the detoxification of many drugs and xenobiotics, the observed differences in basal tissue distribution among mouse, rat and canine has far-reaching implications in comparing responses of these species in safety testing.

Renal function and cardiopulmonary bypass in pediatric cardiac surgical patients

We studied prospectively the perioperative changes of renal function in nine children undergoing cardiac surgery with cardiopulmonary bypass (CPB). Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured with inulin and (131)I-hippuran clearances before CPB, during hypo and normothermic CPB, following sternal closure and 1 h postoperatively. Urinary alpha glutathione S-transferase (alpha GS-T) was measured pre- and postoperatively as a marker for tubular cellular damage. Plasma and urine creatinine and electrolytes were measured. Free water, osmolal and creatinine clearances, as well as fractional excretion of sodium (FeNa) and potassium transtubular gradient (TTKG) were calculated. GFR was normal before and after surgery. ERPF was low before and after surgery; it increased significantly immediately after CPB. Filtration fraction (FF) was abnormally elevated before and after surgery; however, a significant decrease during normothermic CPB and sternal closure was found. Alpha GS-T presented a moderate, but nonsignificant increase postoperatively. FeNa also increased in this period, but not significantly. Creatinine, osmolal, free water clearances, as well as TTKG, were normal in all patients pre- and postoperatively. We conclude that there is no evidence of clinically significant deterioration of renal function in children undergoing repair of cardiac lesions under CPB. Minor increases of alpha GS-T in urine postoperatively did not confirm cellular tubular damage. There was no tubular dysfunction at that time.

Alpha glutathione S-transferase: a potential marker of ischemia-reperfusion injury of the intestine after cardiac surgery?

BACKGROUND

The aim of the study was to assess the utility of alpha glutathione S-transferase (alphaGST) as a potential marker of intestinal ischemia-reperfusion injury in children after cardiac surgery.

METHODS

Twenty-six patients undergoing cardiac surgery were enrolled in this longitudinal experimental study. Blood samples were drawn for analysis at specified time points during surgery and analyzed for alphaGST levels. Clinical indices of splanchnic morbidity were assessed up to discharge from hospital. Results were analyzed using Mann-Whitney tests and linear mixed effects models.

RESULTS

Two groups were identified. Group 1 (n = 16) showed no intestinal morbidity and group 2 (n = 10) had signs of intestinal morbidity. Statistical differences were shown between the 2 groups with respect to time with aortic cross-clamp (ACC) in situ, time on cardiac bypass, duration of operation, time to enteral feeding and full feeding, time on mechanical ventilation, and time in the intensive care unit postoperatively. The serum concentration of alphaGST was significantly higher for group 2 and this rise was greatest after removal of the ACC.

CONCLUSIONS

AlphaGST showed significant elevation in patients with prolonged bypass times and ACC times. These patients also displayed signs of intestinal morbidity, suggesting that this marker may be useful in screening patients at risk for intestinal pathology. This rise in alphaGST was associated with a prolonged ischemia time, and was greatest after the cross-clamp was released, suggesting that it is a postischemic reperfusion phenomenon leading to its elevation. A low alphaGST level appears to exclude significant intestinal ischemia.

Chemopreventive effects of aloe against genotoxicity induced by benzo[a]pyrene

Chemopreventive effects of aloe against benzo[a]pyrene (BaP) mutagenicity were investigated in the Salmonella typhimurium bacterial mutation assay, the chromosome aberration assay using Chinese hamster ovary (CHO) cells, and the mouse micronuclei test using bone-marrow cells. In the bacterial assay, aloe produced a concentration-dependent decrease in the number of mutant colonies induced by BaP. The chromosome-damaging responses of BaP in CHO cells were abolished by treatment with aloe, approximately to the level seen in control. In the in vivo mouse bone-marrow micronuclei test, pretreatment of aloe 24 h prior to BaP treatment reduced the frequency of micronucleated polychromatic erythrocytes. In the cells of CHO and bone marrow treated with aloe, glutathione (GSH) levels were shown to be higher and extracellular discharge rate increased as incubation time with aloe rose. MDR1 and MRP2 gene were more expressed in Hepa c cells than in NTCC cells, but there was no change in BCRP gene expression. The antimutagenic effects of aloe were statistically significant and concentration dependent. These results demonstrated that aloe might exert chemopreventive effects against BaP-induced mutagenicity.

Alpha-gluthathione S-transferase as an early marker of hepatic ischemia/reperfusion injury after liver resection

Organ dysfunction following liver resection is one of the major postoperative complications of liver surgery. The Pringle maneuver is often applied during liver resection to minimize bleeding, which in turn complicates the postoperative course owing to liver ischemia and reperfusion. Routinely, hepatocellular damage is diagnosed by, for example, abnormal aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and the prothrombin time (PT). The cytosolic liver enzyme alpha-glutathione S-transferase (alpha-GST) has recently been shown to have good sensitivity for detecting hepatic injury after acetaminophen poisoning or liver transplantation, but its role in non-transplantation liver surgery has not been assessed. In this prospective randomized clinical study, the diagnostic role of plasma alpha-GST following warm ischemia and reperfusion is reported. A total of 75 patients who underwent liver resection were randomly assigned to three groups: (1) without Pringle (NPR); (2) with Pringle (PR); (3) with ischemic preconditioning by 10 minutes of ischemia and reperfusion each prior to the Pringle manuever (IPC). The major findings are as follows: (1) ALT, AST, and alpha-GST increased upon liver manipulation as early as prior to resection, with a rapid return of alpha-GST values to preoperative levels, whereas ALT and AST further increased on the first postoperative day. (2) In the PR group, alpha-GST, but not ALT and AST, was significantly elevated compared with that in the NPR group at 15 and 30 minutes and 2 hours after resection/reperfusion. In addition, only levels of alpha-GST significantly correlated with the Pringle duration. (3) The ischemia/reperfusion-induced early rise in alpha-GST was completely prevented by ischemic preconditioning. Moreover, only alpha-GST concentrations (> 490 microg L(-1)) determined early after resection (2 hours) predicted postoperative liver dysfunction (24 hours PT < 60%) with a positive predictive value of 74% and a negative predictive value of 76%. Thus alpha-GST seems to be a sensitive, predictive marker of ischemia/reperfusion-induced hepatocellular injury and postoperative liver dysfunction.

The response to cyclophosphamide in steroid-sensitive nephrotic syndrome is influenced by polymorphic expression of glutathion-S-transferases-M1 and -P1

Glutathione-S-transferases (GST) play a central role in the inactivation of toxic drugs like cyclophosphamide (CP). These enzymes depict several polymorphisms with altered activity, and it has been shown that different polymorphisms influence the risk of malignancies and the outcome after chemotherapy. To prove the hypothesis that CP efficacy in children with nephrotic syndrome is influenced by polymorphic expression of GSTs, the genotype of 26 patients was analyzed and correlated with the outcome after CP treatment. All 26 children with steroid-sensitive nephrotic syndrome and frequent relapses or steroid dependency were treated with CP at a mean age of 6.7+/-4.0 years. CP was given in a dose of 2 mg/kg/day for 12+/-1 week. GST-M1, GST-P1 and GST-T1 polymorphisms were detected by PCR. In patients with GST-M1 null polymorphism, a significantly better rate of sustained remission was seen than in patients with the heterozygous or homozygous GST-M1 wildtype (0 versus 29%, P <0.01). In contrast, children with GST-P heterozygous or homozygous polymorphism had a significantly lower rate of sustained remission compared to homozygous wildtype (7 versus 38%, P <0.02). The GST-T1 genotype did not influence the outcome after CP treatment (P =0.32). Patients with the combination of GST-M1 null and GST-P1 wildtype did not relapse in 50%, compared to 6% in other children (P <0.01). We conclude that the polymorphic expression of GST-M1 and -P1 did significantly influence the long-term remission rate after CP treatment of steroid-sensitive nephrotic syndrome in children. Whereas GST-M1 null will increase cyclophosphamide efficacy, GST-P1 polymorphism seems to be related to enhanced susceptibility to further relapses.

Oxidative stress and cyclooxygenase activity in prostate carcinogenesis: targets for chemopreventive strategies

Over the last decade, epidemiological, experimental and clinical studies have implicated oxidative stress in the development and progression of prostate cancer. Oxidative stress may be linked to the effects of androgens, anti-oxidant systems and the pre-malignant condition, high-grade prostatic intraepithelial neoplasia. Cyclooxygenase-2 activity has been linked with prostate carcinogenesis. Evidence suggests that oxidative stress and cyclo-oxygenase-2 activity may be mechanistically linked. Agents such as anti-oxidants and cyclo-oxgenase-2 inhibitors may be of value in the chemoprevention of prostate cancer. The feasibility of intervention with such agents will depend on the development and validation of biomarkers for clinical trials, particularly markers of oxidative damage caused by reactive oxygen species (ROS). A greater understanding of the molecular events associated with oxidative stress will enhance the development of such biomarkers and should result in better strategies for the chemoprevention of prostate cancer.

Improvement of postischemic hepatic microcirculation after endothelinA receptor blockade--endothelin antagonism influences platelet-endothelium interactions

Endothelin (ET) contributes to disturbances of hepatic microcirculation after ischemia/reperfusion (I/R) by causing vasoconstriction and enhancing leukocyte- and platelet-endothelium interactions. The aim of this study was to investigate a possible protective role of a selective endothelin(A) receptor antagonist (ET(A)-RA) in this setting. In a rat model, warm ischemia of the left lateral liver lobe was induced for 90 minutes under intraperitoneal anesthesia with xylazine and ketamine. Groups of rats consisted of sham-operated (SO, n=14), untreated ischemia (n=14), and treatment with BSF208075 (5 mg/kg body weight IV, n=14). The effect of the ET(A)-RA on I/R was assessed by in vivo microscopy 20 to 90 minutes after reperfusion; by measurement of local tissue Po(2), serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and glutathione S-transferase alpha levels, and by histologic investigation. In the untreated group, sinusoidal constriction to 69.4+/-6.7% of diameters of SO rats was observed, leading to a significant decrease in perfusion rate (74.3+/-2.1% of SO) and liver tissue Po(2) (43.5+/-3.2% of SO) (P < 0.05). In addition, we found an increased percentage of stagnant leukocytes (142.9+/-11.9%) and platelets (450.1+/-62.3%) in sinusoids and in postsinusoidal venules (P < 0.05). Hepatocellular damage (AST and ALT increase to 1330+/-157 U/L and 750+/-125 U/L respectively; previously, 27.1+/-3.5 U/L and 28.5+/-3.6 U/L) was detected 6 hours after reperfusion (P < 0.05). Administration of the ET(A)-RA before reperfusion significantly reduced I/R injury. Sinusoidal diameters were maintained (108.5+/-6.6%), and perfusion rate (93.1+/-1.8%) and tissue Po(2) (95.3+/-5.7%) were significantly increased (P < 0.05). According to reduced leukocyte-endothelium interactions after therapy, both platelet rolling and adhesion were significantly reduced (P < 0.05). The number of stagnant platelets in sinusoids was 199.5+/-12.3% of 50 (P < 0.05). After treatment, hepatocellular damage was decreased (AST and ALT levels after 6 hours of reperfusion: 513+/-106 U/L and 309+/-84 U/L, respectively; P < 0.05), and histologic changes were reduced in the long term. Our results provide evidence that the new therapeutic approach with an ET(A)-RA is effective in reducing hepatic I/R injury. In addition to reduced leukocyte-endothelium interactions, the number of stagnant and rolling platelets in sinusoids and venules was significantly reduced. The reduction in microcirculatory damages is responsible for better organ outcome.

Kidney slices of human and rat to characterize cisplatin-induced injury on cellular pathways and morphology

Kidney slices represent an in vitro model that has the cellular complexity of in vivo tissue to provide insights into mechanisms of organ injury, as shown in this study with the model nephrotoxicant cisplatin. Cell pathways altered by cisplatin exposure are assessed by gene expression analysis, cell function, and morphology in human and rat kidney slices in comparison to rat kidney from an in vivo study. The acute nephrosis of the tubular epithelium induced by cisplatin in vivo was reproduced in both human and rat kidney slices, while the glomerulus appeared resistant even at high concentrations. Kidney gene expression changes of in vivo and in vitro samples were indicative of transcription, DNA damage, cell cycle, proliferation, and apoptosis that are in agreement with the mechanism of cisplatin causing DNA damage, growth arrest, and apoptosis; while genes indicative of protein damage, the disruption of transport and calcium homeostasis, cellular metabolism, and oxidative stress are pathways linked with cisplatin binding to various cellular proteins and macromolecules. Both concentration and time-dependent gene expression changes evident in the in vitro model preceded a change in tissue morphology. Functional assays confirming cell dysfunction and increased apoptosis revealed the rat kidney to be more sensitive to the effects of cisplatin than human kidney as demonstrated by significant decreases in slice ATP and GSH levels, significant increases in caspase 9 and 3 activity, p53 protein levels, and increased DNA laddering. The regional markers of proximal and distal tubular injury, alpha- and pi-glutathione S-transferases, were shown for the human kidney slices to be significantly increased by cisplatin. In this study, cisplatin-induced nephrotoxicity was demonstrated morphologically in rat and human kidney slices, and the associated gene expression and functional changes characterized the cellular pathways involved.

Does glutathione S-transferase Pi (GST-Pi) a marker protein for cancer?

Glutathione S-transferases (GSTs, EC 2.5.1.18) are multifunctional and multigene products. They are versatile enzymes and participate in the nucleophilic attack of the sulphur atom of glutathione on the electrophilic centers of various endogenous and xenobiotic compounds. Out of the five, alpha, micro, pi, sigma and theta, major classes of GSTs, GST-pi has significance in the diagnosis of cancers as it is expressed abundantly in tumor cells. This protein is a single gene product, coded by seven exons, that is having 24 kDa mass and pI value of 7.0. Four upstream elements such as two enhancers, and one of each of AP-1 site and GC box regulate pi gene. During chemical carcinogenesis because of jun/fos oncogenes (AP-1) regulatory elements, specifically GST-pi is expressed in liver. Therefore this gene product could be used as marker protein for the detection of chemical toxicity and carcinogenesis.

Developmental changes in glutathione S-transferase isoforms expression and activity in intrasplenic fetal liver tissue transplants in rats

The aim of the present study was to characterise developmental changes in glutathione S-transferase (GST) isoforms expression and in glutathione conjugation capacity in intrasplenic liver tissue transplants. For this purpose, syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fischer 344 rats. Three days, 1, 2, 4 weeks, 2, 4, 6 months and 1 year later, transplant-recipients and control animals were sacrificed and class alpha, mu and pi GST isoforms expression and GST activities using the substrates o-dinitrobenzene and 1-chloro-2,4-dinitrobenzene were assessed in livers and spleens. In the hepatocytes of the adult livers no class pi, but a distinct class alpha and mu GST expression was seen. The bile duct epithelia were class pi GST positive. Fetal livers displayed almost no class alpha and mu, but a slight class pi GST expression. The same pattern was seen in 3-day-old intrasplenic liver tissue transplants. Up to 2 weeks after surgery the class alpha and mu GST expression increased in the hepatocytes of the transplants, whereas the immunostaining for class pi GST disappeared. No remarkable changes were seen thereafter. Normal conjugation capacities were observed with the livers of both groups of rats. Control spleens displayed only low GST activities. From 2 months after transplantation on activities were significantly higher in transplant-containing spleens than in respective control organs with a further increase up to one year after grafting. These results show that intrasplenically transplanted fetal liver cells proliferate and differentiate into mature cells displaying a GST expression pattern with respective enzyme activities similar to adult liver.

Evaluation of 2-year-old intrasplenic fetal liver tissue transplants in rats

Liver cell transplantation into host organs like the spleen may possibly provide a temporary relief after extensive liver resection or severe liver disease or may enable treatment of an enzyme deficiency. With time, however, dedifferentiation or malignant transformation of the ectopically transplanted cells may be possible. Thus, in the present study syngenic fetal liver tissue suspensions were transplanted into the spleen of adult male rats and evaluated 2 years thereafter in comparison to orthotopic livers for histopathological changes and (as markers for preneoplastic transformation) for cytochrome P450 (P450) and glutathione S-transferase (GST) isoform expression. Because inducibility of P450 and GST isoforms may be changed in preneoplastic foci, prior to sacrifice animals were additionally treated either with beta-naphthoflavone, phenobarbital, dexamethasone, or the respective solvent. In the 2-year-old grafts more than 70% of the spleen mass was occupied by the transplant. The transplanted hepatocytes were arranged in cord-like structures. Also few bile ducts were present. Morphologically, no signs of malignancy were visible. With all rats, transplant recipients as well as controls, however, discrete nodular structures were seen in the livers. Due to age, both livers and transplants displayed only a low P450 2B1 and 3A2 and GST class alpha and mu isoform expression. No immunostaining for P450 1A1 was visible. At both sites, beta-naphthoflavone, phenobarbital, or dexamethasone treatment enhanced P450 1A1, P450 2B1 and 3A2, or P450 3A2 expression, respectively. No immunostaining for GST class pi isoforms was seen in the transplants. The livers of both transplant recipients and control rats, however, displayed GST pi-positive foci, corresponding to the nodular structures seen histomorphologically. Compared to the surrounding tissue, these foci also exhibited a more pronounced staining for GST class alpha and mu isoforms and a stronger inducibility of the P450 1A1 expression due to beta-naphthoflavone. In conclusion, in contrast to the livers, no preneoplastic foci seem to appear in the intrasplenic transplants even 2 years after transplantation. This may be due either to the protection of these transplants by the orthotopic livers or to the different humoral and nerval influences at the ectopic site.

The ABCs of drug transport in intestine and liver: efflux proteins limiting drug absorption and bioavailability

Many orally administered drugs must overcome several barriers before reaching their target site. The first major obstacle to cross is the intestinal epithelium. Although lipophilic compounds may readily diffuse across the apical plasma membrane, their subsequent passage across the basolateral membrane and into blood is by no means guaranteed. Efflux proteins located at the apical membrane, which include P-glycoprotein (Pgp; MDR1) and MRP2, may drive compounds from inside the cell back into the intestinal lumen, preventing their absorption into blood. Drugs may also be modified by intracellular phase I and phase II metabolising enzymes. This process may not only render the drug ineffective, but it may also produce metabolites that are themselves substrates for Pgp and/or MRP2. Drugs that reach the blood are then passed to the liver, where they are subject to further metabolism and biliary excretion, often by a similar system of ATP-binding cassette (ABC) transporters and enzymes to that present in the intestine. Thus a synergistic relationship exists between intestinal drug metabolising enzymes and apical efflux transporters, a partnership that proves to be a critical determinant of oral bioavailability. The effectiveness of this system is optimised through dynamic regulation of transporter and enzyme expression; tissues have a remarkable capacity to regulate the amounts of protein both at transcriptional and post-transcriptional levels in order to maintain homeostasis. This review addresses the progress to date on what is known about the role and regulation of drug efflux mechanisms in the intestine and liver.

Effect of cyclosporine therapy in transplanted patients-diagnostic values of tubular markers

The introduction of cyclosporine A (CsA) into the clinical practice has resulted in a major improvement in the short-term outcomes of solid organ transplantation and treatment of autoimune diseases. Chronic ScA nephrotoxicity has been described in kidneys of recepients of renal and other organ allografts. However, the exact mechanism underlying the development of fibrosis in chronic CsA nephrotoxicity has remained poorly understood. Evaluation with the validation data set showed that noninvasive urine protein differentiation might be a useful diagnostic strategy in nephrology. Over the past decade numerous studies in patients after transplantation have demonstrated that renal tubular cell injury after a toxic insult, results in sloughing of tubular debris and cell into the tubular lumen with eventual obstruction of tubular flow, increased intratubular pressure and backleak of glomerular filtrate out of the tubule. Urinary enzymes and low molecular proteins have been recommended as useful markers for the detection of changes in the kidney tissue in cases after renal transplantation. The aim of our study was to monitor the concentration and eventual nephrotoxic effect of Cyclosporine A using the concentration of low molecular proteins α-1-microglobulin and β−2-microglobulin, serum Cystatin C, as well as the concentration of isoform of GST-α and π.

Mercapturate metabolism of 4-hydroxy-2-nonenal in rat and human cerebrum

4-Hydroxy-2-nonenal (HNE), a potent toxin formed in the brain from oxidation of polyunsaturated fatty acids, is increased in Alzheimer disease (AD), where it is a proposed effector of amyloid beta peptide-mediated neurotoxicity. Detoxification of HNE via the mercapturic acid pathway (MAP) is the primary means by which other organs, such as liver, limit its toxic effects. Here we examined the distribution and activity of MAP detoxification for HNE in cerebrum. Our results showed that rat cerebral cortex and especially synaptosomes were less well equipped to detoxify HNE via the MAP than liver. Glutathione transferases (GSTs) catalyze the committed step in the MAP; GST-mu and GST-pi, but not OST-alpha, were detected in neurons and astrocytes in cerebrum from AD patients and controls. MAP activity in frontal cortex of AD patients was modestly but significantly increased compared to controls. These data suggest that lipid peroxidation may present a greater toxic burden to cerebrum than to other organs, and that a component of response to injury in late stage AD is a slight increase in MAP activity.

Mu class glutathione S-transferase mRNA isoform expression in acute lymphoblastic leukaemia

Glutathione S-transferases (GSTs) are implicated in cytotoxic drug resistance in leukaemia. In a previous study, expression of mu class GST (GSTM) was associated with poor prognosis in childhood acute lymphoblastic leukaemia (ALL), however, that study did not differentiate between individual GSTM isoforms. This study, therefore, investigated individual GSTM isoform expression in ALL blasts at the mRNA level. Leukaemic blasts from 21 children with ALL were studied. Interindividual variation in the pattern of GSTM mRNA isoform expression was demonstrated. GSTM2 transcript was expressed in all patients in contradistinction to GSTM5, which was not detected in any sample. GSTM3 and GSTM4 expression varied between individuals, with GSTM3 expressed in 62% and GSTM4 in 24% of patients. Lymphoblast expression of GSTM3 was positively related to good prognosis whereas expression of GSTM4 was not related to clinical outcome in this small cohort. No relationship was demonstrated with established indicators of prognosis, including sex, age, immunophenotype and presenting white cell count. The results suggest that expression of GSTM3 may play a role in determining prognosis in childhood ALL and could provide more information for accurate stratification of treatment. Further studies are required to determine whether there is a causal relationship between GSTM3 expression and clinical outcome.

Enhanced immunocytochemical expression of antioxidant enzymes in rat submandibular gland after normobaric oxygenation

In order to clarify the role of antioxidant enzymes in the male rat submandibular gland against short-term normobaric oxygenation, we performed immunocytochemical staining of manganese-containing superoxide dismutase (Mn-SOD), copper- and zinc-containing SOD (Cu/Zn-SOD), catalase (CAT), glutathione peroxidase, and glutathione S-transferases (GST alpha, GST mu, and GST pi) between days 1 and 7 after normobaric oxygenation. Ultrastructural alterations and immunoreactivities for malondialdehyde (MDA), a lipid peroxidation-related molecule, of the acinar and ductal cells after the oxygenation were also investigated. Immunoreactivity for MDA was exhibited in the acinar cells throughout the experiment. On the other hand, immunoreactivity for the SODs, CAT, and GSTs was not altered, when compared to that of controls, but was significantly elevated in the granular, striated, and excretory ductal cells. Since an increase of lipid peroxidation as indicated by enhanced immunoreactivity for MDA was detected in the acinar and intercalated ductal cells, the results indicate that the enhanced antioxidant enzymes in the granular, striated, and excretory ductal cells play a crucial role in the self-defense system of the male rat submandibular gland against normobaric oxygenation.

Dopamine thioethers: formation in brain and neurotoxicity

Dopamine (DA) oxidation is proposed to be a significant contributor to some forms of neurodegeneration, although the mechanisms are not fully resolved. Recent results from in vitro and in vivo models have suggested that some products of oxidized DA metabolized along the mercapturic acid pathway (MAP) may contribute to dopaminergic neurodegeneration. Here we review recent findings on the localization of MAP enzymes in human brain, as well as the concentration and neurotoxicity of their DA thioether products.

Glutathione S-transferase: a potential new marker of intestinal ischemia

BACKGROUND/PURPOSE

The accurate and early diagnosis of intestinal ischemia remains difficult chiefly because of a lack of a suitable marker that is noninvasive and easy to use. The glutathione S-transferases (GST) are a family of cytosolic enzymes involved in detoxification and released from a variety of cells when the cell membrane is damaged. The enzymes are distributed widely in the intestine and show isoform specificity in their distribution throughout the intestinal tract. Several previous reports have shown the utility of these enzymes in the diagnosis of liver and renal graft damage during and after organ transplantation. The object of this study was to determine if GST levels correlated with histologic changes of intestinal ischemia in a controlled animal model of mesenteric intestinal ischemia.

METHODS

Control and experimental male Sprague-Dawley rats underwent laparotomy and ligation of the Superior Mesenteric Artery (SMA) and both control and experimental animals were studied at 30, 60, 90, 120, and 240 minutes. Blood taken from the Inferior Vena Cava (IVC) and Portal Vein (PV) and jejunal and ileal perfusates were assayed for alpha and mu isoforms of GST using a commercially available enzyme immunoassay. In addition, jejunal and ileal segments were sampled and reviewed by a histopathologist blinded to the group being studied.

RESULTS

A reproducible pattern of intestinal ischemia was noted with worsening grades of injury observed with greater ligation times. Luminal alpha and mu GST release (as measured by the appearance in luminal perfusate) increased with increasing ischemia times. Increased ischemia times resulted in increased levels of alpha and mu GST in both portal and systemic venous samples but lagged behind the appearance of raised luminal GST values.

CONCLUSIONS

The results suggest that GST may be an interesting and useful marker in the early detection of intestinal ischemia. Its detection in peripheral blood has implications for a more detailed study design to determine the sensitivity and specificity of this marker in more diverse clinical conditions such as necrotizing enterocolitis and superior mesenteric artery occlusion.

Immunohistochemical localization and activity of glutathione transferase zeta (GSTZ1-1) in rat tissues

Glutathione transferase zeta (GSTZ1-1) catalyzes the biotransformation of a range of alpha-haloacids, including dichloroacetic acid (DCA), and the penultimate step in the tyrosine degradation pathway. DCA is a rodent carcinogen and a common drinking water contaminant. DCA also causes multiorgan toxicity in rodents and dogs. The objective of this study was to determine the expression and activities of GSTZ1-1 in rat tissues with maleylacetone and chlorofluoroacetic acid as substrates. GSTZ1-1 protein was detected in most tissues by immunoblot analysis after immunoprecipitation of GSTZ1-1 and by immunohistochemical analysis; intense staining was observed in the liver, testis, and prostate; moderate staining was observed in the brain, heart, pancreatic islets, adrenal medulla, and the epithelial lining of the gastrointestinal tract, airways, and bladder; and sparse staining was observed in the renal juxtaglomerular regions, skeletal muscle, and peripheral nerve tissue. These patterns of expression corresponded to GSTZ1-1 activities in the different tissues with maleylacetone and chlorofluoroacetic acid as substrates. Specific activities ranged from 258 +/- 17 (liver) to 1.1 +/- 0.4 (muscle) nmol/min/mg of protein with maleylacetone as substrate and from 4.6 +/- 0.89 (liver) to 0.09 +/- 0.01 (kidney) nmol/min/mg of protein with chlorofluoroacetic acid as substrate. Rats given DCA had reduced amounts of immunoreactive GSTZ1-1 protein and activities of GSTZ1-1 in most tissues, especially in the liver. These findings indicate that the DCA-induced inactivation of GSTZ1-1 in different tissues may result in multiorgan disorders that may be associated with perturbed tyrosine metabolism.