Increased sensitivity of glutathione S-transferase P-null mice to cyclophosphamide-induced urinary bladder toxicity

Cyclophosphamide Pharmacogenomic Variation in Cancer Treatment and Its Effect on Bioactivation and Pharmacokinetics

Cyclophosphamide (Cy) is a prodrug that is mainly bioactivated by cytochrome P450 (CYP) 2B6 enzyme. Several other enzymes are also involved in its bioactivation and affect its kinetics. Previous studies have shown the effect of the enzymes' genetic polymorphisms on Cy kinetics and its clinical outcome. These results were controversial primarily because of the involvement of several interacting enzymes in the Cy metabolic pathway, which can also be affected by several clinical factors as well as other drug interactions. In this review article, we present the effect of CYP2B6 polymorphisms on Cy kinetics since it is the main bioactivating enzyme, as well as discussing all previously reported enzymes and clinical factors that can alter Cy efficacy. Additionally, we present explanations for key Cy side effects related to the nature and site of its bioactivation. Finally, we discuss the role of busulphan in conditioning regimens in the Cy metabolic pathway as a clinical example of drug-drug interactions involving several enzymes. By the end of this article, our aim is to have provided a comprehensive summary of Cy pharmacogenomics and the effect on its kinetics. The utility of these findings in the development of new strategies for Cy personalized patient dose adjustment will aid in the future optimization of patient specific Cy dosages and ultimately in improving clinical outcomes. In conclusion, CYP2B6 and several other enzyme polymorphisms can alter Cy kinetics and consequently the clinical outcomes. However, the precise quantification of Cy kinetics in any individual patient is complex as it is clearly under multifactorial genetic control. Additionally, other clinical factors such as the patient's age, diagnosis, concomitant medications, and clinical status should also be considered.

GSTP alleviates acute lung injury by S-glutathionylation of KEAP1 and subsequent activation of NRF2 pathway

Oxidative stress plays an important role in the pathogenesis of acute lung injury (ALI). As a typical post-translational modification triggered by oxidative stress, protein S-glutathionylation (PSSG) is regulated by redox signaling pathways and plays diverse roles in oxidative stress conditions. In this study, we found that GSTP downregulation exacerbated LPS-induced injury in human lung epithelial cells and in mice ALI models, confirming the protective effect of GSTP against ALI both in vitro and in vivo. Additionally, a positive correlation was observed between total PSSG level and GSTP expression level in cells and mice lung tissues. Further results demonstrated that GSTP inhibited KEAP1-NRF2 interaction by promoting PSSG process of KEAP1. By the integration of protein mass spectrometry, molecular docking, and site-mutation validation assays, we identified C434 in KEAP1 as the key PSSG site catalyzed by GSTP, which promoted the dissociation of KEAP1-NRF2 complex and activated the subsequent anti-oxidant genes. In vivo experiments with AAV-GSTP mice confirmed that GSTP inhibited LPS-induced lung inflammation by promoting PSSG of KEAP1 and activating the NRF2 downstream antioxidant pathways. Collectively, this study revealed the novel regulatory mechanism of GSTP in the anti-inflammatory function of lungs by modulating PSSG of KEAP1 and the subsequent KEAP1/NRF2 pathway. Targeting at manipulation of GSTP level or activity might be a promising therapeutic strategy for oxidative stress-induced ALI progression.

Fine particulate matter air pollution and aortic perivascular adipose tissue: Oxidative stress, leptin, and vascular dysfunction

Exposure to fine particulate matter (PM2.5 ) air pollution increases blood pressure, induces vascular inflammation and dysfunction, and augments atherosclerosis in humans and rodents; however, the understanding of early changes that foster chronic vascular disease is incomplete. Because perivascular adipose tissue (PVAT) inflammation is implicated in chronic vascular diseases, we investigated changes in aortic PVAT following short-term air pollution exposure. Mice were exposed to HEPA-filtered or concentrated ambient PM2.5 (CAP) for 9 consecutive days, and the abundance of inflammatory, adipogenic, and adipokine gene mRNAs was measured by gene array and qRT-PCR in thoracic aortic PVAT. Responses of the isolated aorta with and without PVAT to contractile (phenylephrine, PE) and relaxant agonists (acetylcholine, ACh; sodium nitroprusside, SNP) were measured. Exposure to CAP significantly increased the urinary excretion of acrolein metabolite (3HPMA) as well as the abundance of protein-acrolein adducts (a marker of oxidative stress) in PVAT and aorta, upregulated PVAT leptin mRNA expression without changing mRNA levels of several proinflammatory genes, and induced PVAT insulin resistance. In control mice, PVAT significantly depressed PE-induced contractions-an effect that was dampened by CAP exposure. Pulmonary overexpression of extracellular dismutase (ecSOD-Tg) prevented CAP-induced effects on urinary 3HPMA levels, PVAT Lep mRNA, and alterations in PVAT and aortic function, reflecting a necessary role of pulmonary oxidative stress in all of these deleterious CAP-induced changes. More research is needed to address how exactly short-term exposure to PM2.5 perturbs PVAT and aortic function, and how these specific genes and functional changes in PVAT could lead over time to chronic inflammation, endothelial dysfunction, and atherosclerosis.

Urinary levels of the acrolein conjugates of carnosine are associated with inhaled toxicants

OBJECTIVE

The inhalation of air-borne toxicants is associated with adverse health outcomes which can be somewhat mitigated by enhancing endogenous anti-oxidant capacity. Carnosine is a naturally occurring dipeptide (β-alanine-L-histidine), present in high abundance in skeletal and cardiac muscle. This multi-functional dipeptide has anti-oxidant properties, can buffer intracellular pH, chelate metals, and sequester aldehydes such as acrolein. Due to these chemical properties, carnosine may be protective against inhaled pollutants which can contain metals and aldehydes and can stimulate the generation of electrophiles in exposed tissues. Thus, assessment of carnosine levels, or levels of its acrolein conjugates (carnosine-propanal and carnosine-propanol) may inform on level of exposure and risk assessment.

METHODS

We used established mass spectroscopy methods to measure levels of urinary carnosine (n = 605) and its conjugates with acrolein (n = 561) in a subset of participants in the Louisville Healthy Heart Study (mean age = 51 ± 10; 52% male). We then determined associations between these measures and air pollution exposure and smoking behavior using statistical modeling approaches.

RESULTS

We found that higher levels of non-conjugated carnosine, carnosine-propanal, and carnosine-propanol were significantly associated with males (p < 0.02) and those of Caucasian ethnicity (p < 0.02). Levels of carnosine-propanol were significantly higher in never-smokers (p = 0.001) but lower in current smokers (p = 0.037). This conjugate also demonstrated a negative association with mean-daily particulate air pollution (PM_2.5) levels (p = 0.01).

CONCLUSIONS

These findings suggest that urinary levels of carnosine-propanol may inform as to risk from inhaled pollutants.

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.

Histone methyltransferase G9a protects against acute liver injury through GSTP1

Acute liver injury is commonly caused by bacterial endotoxin/lipopolysaccharide (LPS), and by drug overdose such as acetaminophen (APAP). The exact role of epigenetic modification in acute liver injury remains elusive. Here, we investigated the role of histone methyltransferase G9a in LPS- or APAP overdose-induced acute liver injury. Under d-galactosamine sensitization, liver-specific G9a-deficient mice (L-G9a^−/−) exhibited 100% mortality after LPS injection, while the control and L-G9a^+/− littermates showed very mild mortality. Moreover, abrogation of hepatic G9a or inhibiting the methyltransferase activity of G9a aggravated LPS-induced liver damage. Similarly, under sublethal APAP overdose, L-G9a^−/− mice displayed more severe liver injury. Mechanistically, ablation of G9a inhibited H3K9me1 levels at the promoters of Gstp1/2, two liver detoxifying enzymes, and consequently suppressed their transcription. Notably, treating L-G9a^−/− mice with recombinant mouse GSTP1 reversed the LPS- or APAP overdose-induced liver damage. Taken together, we identify a novel beneficial role of G9a-GSTP1 axis in protecting against acute liver injury.

Glutathione S-transferase P deficiency induces glucose intolerance via JNK-dependent enhancement of hepatic gluconeogenesis

Hepatic glutathione S-transferases (GSTs) are dysregulated in human obesity, nonalcoholic fatty liver disease, and diabetes. The multifunctional GST pi-isoform (GSTP) catalyzes the conjugation of glutathione with acrolein and inhibits c-Jun NH₂-terminal kinase (JNK) activation. Herein, we tested whether GSTP deficiency disturbs glucose homeostasis in mice. Hepatic GST proteins were downregulated by short-term high-fat diet in wild-type (WT) mice concomitant with increased glucose intolerance, JNK activation, and cytokine mRNAs in the liver. Genetic deletion of GSTP did not affect body composition, fasting blood glucose levels, or insulin levels in mice maintained on a normal chow diet; however, compared with WT mice, the GSTP-null mice were glucose intolerant. In GSTP-null mice, pyruvate intolerance, reflecting increased hepatic gluconeogenesis, was accompanied by elevated levels of activated JNK, cytokine mRNAs, and glucose-6-phosphatase proteins in the liver. Treatment of GSTP-null mice with the JNK inhibitor 1,9-pyrazoloanthrone (SP600125) significantly attenuated pyruvate-induced hepatic gluconeogenesis and significantly altered correlations between hepatic cytokine mRNAs and metabolic outcomes in GSTP-null mice. Collectively, these findings suggest that hepatic GSTP plays a pivotal role in glucose handling by regulating JNK-dependent control of hepatic gluconeogenesis. Thus, hepatic GSTP-JNK dysregulation may be a target of new therapeutic interventions during early stages of glucose intolerance to prevent the worsening metabolic derangements associated with human obesity and its relentless progression to diabetes.

Electronic cigarette-generated aldehydes: The contribution of e-liquid components to their formation and the use of urinary aldehyde metabolites as biomarkers of exposure

Electronic cigarettes (e-cigarette) have emerged as a popular electronic nicotine delivery system (ENDS) in the last decade. Despite the absence of combustion products and toxins such as carbon monoxide (CO) and tobacco-specific nitrosamines (TSNA), carbonyls including short-chain, toxic aldehydes have been detected in e-cigarette-derived aerosols up to levels found in tobacco smoke. Given the health concerns regarding exposures to toxic aldehydes, understanding both aldehyde generation in e-cigarette and e-cigarette exposure is critical. Thus, we measured aldehydes generated in aerosols derived from propylene glycol (PG):vegetable glycerin (VG) mixtures and from commercial e-liquids with flavorants using a state-of-the-art carbonyl trap and mass spectrometry. To track e-cigarette exposure in mice, we measured urinary metabolites of 4 aldehydes using ULPC-MS/MS or GC-MS. Aldehyde levels, regardless of abundance (saturated: formaldehyde, acetaldehyde >> unsaturated: acrolein, crotonaldehyde), were dependent on the PG:VG ratio and the presence of flavorants. The metabolites of 3 aldehydes - formate, acetate and 3-hydroxypropyl mercapturic acid (3-HPMA; acrolein metabolite) -- were increased in urine after e-cigarette aerosol and mainstream cigarette smoke (MCS) exposures, but the crotonaldehyde metabolite (3-hydroxy-1-methylpropylmercapturic acid, HPMMA) was increased only after MCS exposure. Interestingly, exposure to menthol-flavored e-cigarette aerosol increased the levels of urinary 3-HPMA and sum of nicotine exposure (nicotine, cotinine, trans-3'-hydroxycotinine) relative to exposure to a Classic Tobacco-flavored e-cigarette aerosol. Comparing these findings with aerosols of other ENDS and by measuring aldehyde-derived metabolites in human urine following exposure to e-cigarette aerosols will further our understanding of the relationship between ENDS use, aldehyde exposure and health risk.

GSTA1 diplotypes affect busulfan clearance and toxicity in children undergoing allogeneic hematopoietic stem cell transplantation: a multicenter study

Busulfan (BU) dose adjustment following therapeutic drug monitoring contributes to better outcome of hematopoietic stem cell transplantation (HSCT). Further improvement could be achieved through genotype-guided BU dose adjustments. To investigate this aspect, polymorphism within glutathione S transferase genes were assessed. Particularly, promoter haplotypes of the glutathione S transferase A1 (GSTA1) were evaluated in vitro, with reporter gene assays and clinically, in a pediatric multi-center study (N =138) through association with BU pharmacokinetics (PK) and clinical outcomes. Promoter activity significantly differed between the GSTA1 haplotypes (p<0.001) supporting their importance in capturing PK variability. Four GSTA1 diplotype groups that significantly correlated with clearance (p=0.009) were distinguished. Diplotypes underlying fast and slow metabolizing capacity showed higher and lower BU clearance (ml/min/kg), respectively. GSTA1 diplotypes with slow metabolizing capacity were associated with higher incidence of sinusoidal obstruction syndrome, acute graft versus host disease and combined treatment-related toxicity (p<0.0005). Among other GST genes investigated, GSTP1 313GG correlated with acute graft versus host disease grade 1-4 (p=0.01) and GSTM1 non-null genotype was associated with hemorrhagic cystitis (p=0.003). This study further strengthens the hypothesis that GST diplotypes/genotypes could be incorporated into already existing population pharmacokinetic models for improving first BU dose prediction and HSCT outcomes. (N^o Clinicaltrials.gov identifier: NCT01257854. Registered 8 December 2010, retrospectively registered).

Biomarkers of Chronic Acrolein Inhalation Exposure in Mice: Implications for Tobacco Product-Induced Toxicity

Exposure to tobacco smoke, which contains several harmful and potentially harmful constituents such as acrolein increases cardiovascular disease (CVD) risk. Although high acrolein levels induce pervasive cardiovascular injury, the effects of low-level exposure remain unknown and sensitive biomarkers of acrolein toxicity have not been identified. Identification of such biomarkers is essential to assess the toxicity of acrolein present at low levels in the ambient air or in new tobacco products such as e-cigarettes. Hence, we examined the systemic effects of chronic (12 weeks) acrolein exposure at concentrations similar to those found in tobacco smoke (0.5 or 1 ppm). Acrolein exposure in mice led to a 2- to 3-fold increase in its urinary metabolite 3-hydroxypropyl mercapturic acid (3-HPMA) with an attendant increase in pulmonary levels of the acrolein-metabolizing enzymes, glutathione S-transferase P and aldose reductase, as well as several Nrf2-regulated antioxidant proteins. Markers of pulmonary endoplasmic reticulum stress and inflammation were unchanged. Exposure to acrolein suppressed circulating levels of endothelial progenitor cells (EPCs) and specific leukocyte subsets (eg, GR-1+ cells, CD19+ B-cells, CD4+ T-cells; CD11b+ monocytes) whilst other subsets (eg, CD8+ cells, NK1.1+ cells, Ly6C+ monocytes) were unchanged. Chronic acrolein exposure did not affect systemic glucose tolerance, platelet-leukocyte aggregates or microparticles in blood. These findings suggest that circulating levels of EPCs and specific leukocyte populations are sensitive biomarkers of inhaled acrolein injury and that low-level (<0.5 ppm) acrolein exposure (eg, in secondhand smoke, vehicle exhaust, e-cigarettes) could increase CVD risk by diminishing endothelium repair or by suppressing immune cells or both.

The Association of Combined GSTM1 and CYP2C9 Genotype Status with the Occurrence of Hemorrhagic Cystitis in Pediatric Patients Receiving Myeloablative Conditioning Regimen Prior to Allogeneic Hematopoietic Stem Cell Transplantation

Hemorrhagic cystitis (HC) is one of the complications of busulfan-cyclophosphamide (BU-CY) conditioning regimen during allogeneic hematopoietic stem cell transplantation (HSCT) in children. Identifying children at high risk of developing HC in a HSCT setting could facilitate the evaluation and implementation of effective prophylactic measures. In this retrospective analysis genotyping of selected candidate gene variants was performed in 72 children and plasma Sulfolane (Su, water soluble metabolite of BU) levels were measured in 39 children following treatment with BU-CY regimen. The cytotoxic effects of Su and acrolein (Ac, water soluble metabolite of CY) were tested on human urothelial cells (HUCs). The effect of Su was also tested on cytochrome P 450 (CYP) function in HepaRG hepatic cells. Cumulative incidences of HC before day 30 post HSCT were estimated using Kaplan–Meier curves and log-rank test was used to compare the difference between groups in a univariate analysis. Multivariate Cox regression was used to estimate hazard ratios with 95% confidence intervals (CIs). Multivariate analysis included co-variables that were significantly associated with HC in a univariate analysis. Cumulative incidence of HC was 15.3%. In the univariate analysis, HC incidence was significantly (p < 0.05) higher in children older than 10 years (28.6 vs. 6.8%) or in children with higher Su levels (>40 vs. <11%) or in carriers of both functional GSTM1 and CYP2C9 (33.3 vs. 6.3%) compared to the other group. In a multivariate analysis, combined GSTM1 and CYP2C9 genotype status was associated with HC occurrence with a hazards ratio of 4.8 (95% CI: 1.3–18.4; p = 0.02). Ac was found to be toxic to HUC cells at lower concentrations (33 μM), Su was not toxic to HUC cells at concentrations below 1 mM and did not affect CYP function in HepaRG cells. Our observations suggest that pre-emptive genotyping of CYP2C9 and GSTM1 may aid in selection of more effective prophylaxis to reduce HC development in pediatric patients undergoing allogeneic HSCT.

Article summary:

(1) Children carrying functional alleles in GSTM1 and CYP2C9 are at high risk for developing hemorrhagic cystitis following treatment with busulfan and cyclophosphamide based conditioning regimen.

(2) Identification of children at high risk for developing hemorrhagic cystitis in an allogeneic HSCT setting will enable us to evaluate and implement optimal strategies for its prevention.

Trial registration: This study is a part of the trail “clinicaltrials.gov identifier: NCT01257854.”

Cyclophosphamide leads to persistent deficits in physical performance and in vivo mitochondria function in a mouse model of chemotherapy late effects

Fatigue is the symptom most commonly reported by long-term cancer survivors and is increasingly recognized as related to skeletal muscle dysfunction. Traditional chemotherapeutic agents can cause acute toxicities including cardiac and skeletal myopathies. To investigate the mechanism by which chemotherapy may lead to persistent skeletal muscle dysfunction, mature adult mice were injected with a single cyclophosphamide dose and evaluated for 6 weeks. We found that exposed mice developed a persistent decrease in treadmill running time compared to baseline (25.7±10.6 vs. 49.0±16.8 min, P = 0.0012). Further, 6 weeks after drug exposure, in vivo parameters of mitochondrial function remained below baseline including maximum ATP production (482.1 ± 48.6 vs. 696.2 ± 76.6, P = 0.029) and phosphocreatine to ATP ratio (3.243 ± 0.1 vs. 3.878 ± 0.1, P = 0.004). Immunoblotting of homogenized muscles from treated animals demonstrated a transient increase in HNE adducts 1 week after exposure that resolved by 6 weeks. However, there was no evidence of an oxidative stress response as measured by quantitation of SOD1, SOD2, and catalase protein levels. Examination of mtDNA demonstrated that the mutation frequency remained comparable between control and treated groups. Interestingly, there was evidence of a transient increase in NF-ĸB p65 protein 1 day after drug exposure as compared to saline controls (0.091±0.017 vs. 0.053±0.022, P = 0.033). These data suggest that continued impairment in muscle and mitochondria function in cyclophosphamide-treated animals is not linked to persistent oxidative stress and that alternative mechanisms need to be considered.

Recent Progress in Analytical Methods for Determination of Urinary 3-Hydroxypropylmercapturic Acid, a Major Metabolite of Acrolein

3-Hydroxypropylmercapturic acid (3-HPMA), a major metabolite of acrolein in urine, has been recognized as a noninvasive biomarker of exposure to cigarette smoke. Since acrolein is formed endogenously from polyamines and is also formed during oxidative stress and aggravates tissue damage by changing protein activity through its conjugation in pathological lesions, it is thought that the urinary 3-HPMA level is useful as a biomarker to monitor the severity of several diseases related to acrolein. To study the correlation between 3-HPMA and disease severity, it is important to understand the properties of analytical methods for determination of 3-HPMA. In this article, we summarize the analytical methods for determination of urinary 3-HPMA and discuss the utility of 3-HPMA as one of the biomarkers for the diagnosis of brain infarction.

Protective Effects of Essential Oils as Natural Antioxidants against Hepatotoxicity Induced by Cyclophosphamide in Mice

Clinical application of cyclophosphamide (CP) as an anticancer drug is often limited due to its toxicity. CP is metabolized mainly in the liver by cytochrome P450 system into acrolein which is the proximate toxic metabolite. Many different natural antioxidants were found to alleviate the toxic effects of various toxic agents via different mechanisms. Therefore, the present study aimed at investigating the role of essential oils extracted from fennel, cumin and clove as natural antioxidants in the alleviation of hepatotoxicity induced by CP through assessment of hepatotoxicity biomarkers (AST, ALT, ALP), histopathology of liver tissues as well as other biochemical parameters involved in the metabolism of CP. The data of the present study showed that treatment of male mice with cyclophosphamide (2.5 mg/Kg BW) as repeated dose for 28 consecutive days was found to induce hepatotoxicity through the elevation in the activities of AST, ALT, and ALP. Combined administration of any of these oils with CP to mice partially normalized the altered hepatic biochemical markers caused by CP, whereas administration of fennel, clove or cumin essential oils alone couldn't change liver function indices. Moreover, CP caused histological changes in livers of mice including swelling and dilation in sinusoidal space, inflammation in portal tract and hepatocytes, as well as, hyperplasia in Kuppfer cells. However, co-administration of any of the essential oils with CP alleviated to some extent the changes caused by CP but not as the normal liver. CP was also found to induce free radical levels (measured as thiobarbituric acid reactive substances) and inhibited the activities of superoxide dismutase, glutathione reductase, and catalase as well as activities and protein expressions of both glutathione S-transferase (GSTπ) and glutathione peroxidase. Essential oils restored changes in activities of antioxidant enzymes (SOD, CAT, GR, GST, and GPx) caused by CP to their normal levels compared to control group. In addition, treatment of mice with CP was found to induce the protein expression of CYP 3A4, 2B1/2, 2C6, 2C23. Moreover, the present study showed that essential oils reduced the expression of CYPs 2E1, 3A4 but could not restore the expression of CYP 2C6 and 2C23 compared to CP-treated mice. Interestingly, pretreatment of mice with essential oil of clove was found to restore activities of DMN-dI, AHH, and ECOD which were induced by CP to their normal control levels. It is concluded that EOs showed a marked hepatoprotective effect against hepatotoxicity induced by CP. In addition, co-administration of CP with any of these oils might be used as a new strategy for cancer treatment to alleviate the hepatotoxicity induced by CP.

Attenuation of lung fibrosis in mice with a clinically relevant inhibitor of glutathione-S-transferase π

Idiopathic pulmonary fibrosis (IPF) is a debilitating lung disease characterized by excessive collagen production and fibrogenesis. Apoptosis in lung epithelial cells is critical in IPF pathogenesis, as heightened loss of these cells promotes fibroblast activation and remodeling. Changes in glutathione redox status have been reported in IPF patients. S-glutathionylation, the conjugation of glutathione to reactive cysteines, is catalyzed in part by glutathione-S-transferase π (GSTP). To date, no published information exists linking GSTP and IPF to our knowledge. We hypothesized that GSTP mediates lung fibrogenesis in part through FAS S-glutathionylation, a critical event in epithelial cell apoptosis. Our results demonstrate that GSTP immunoreactivity is increased in the lungs of IPF patients, notably within type II epithelial cells. The FAS-GSTP interaction was also increased in IPF lungs. Bleomycin- and AdTGFβ-induced increases in collagen content, α-SMA, FAS S-glutathionylation, and total protein S-glutathionylation were strongly attenuated in Gstp-/- mice. Oropharyngeal administration of the GSTP inhibitor, TLK117, at a time when fibrosis was already apparent, attenuated bleomycin- and AdTGFβ-induced remodeling, α-SMA, caspase activation, FAS S-glutathionylation, and total protein S-glutathionylation. GSTP is an important driver of protein S-glutathionylation and lung fibrosis, and GSTP inhibition via the airways may be a novel therapeutic strategy for the treatment of IPF.

Ginseng alleviates cyclophosphamide-induced hepatotoxicity via reversing disordered homeostasis of glutathione and bile acid

Cyclophosphamide (CP), a chemotherapeutic agent, is restricted due to its side effects, especially hepatotoxicity. Ginseng has often been clinically used with CP in China, but whether and how ginseng reduces the hepatotoxicity is unknown. In this study, the hepatoprotective effects and mechanisms under the combined usage were investigated. It was found that ginseng could ameliorate CP-induced elevations of ALP, ALT, ALS, MDA and hepatic deterioration, enhance antioxidant enzymes’ activities and GSH’s level. Metabolomics study revealed that 33 endogenous metabolites were changed by CP, 19 of which were reversed when ginseng was co-administrated via two main pathways, i.e., GSH metabolism and primary bile acids synthesis. Furthermore, ginseng could induce expression of GCLC, GCLM, GS and GST, which associate with the disposition of GSH, and expression of FXR, CYP7A1, NTCP and MRP 3, which play important roles in the synthesis and transport of bile acids. In addition, NRF 2, one of regulatory elements on the expression of GCLC, GCLM, GS, GST, NTCP and MRP3, was up-regulated when ginseng was co-administrated. In conclusion, ginseng could alleviate CP-induced hepatotoxicity via modulating the disordered homeostasis of GSH and bile acid, which might be mediated by inducing the expression of NRF 2 in liver.

Genetic Deficiency of Glutathione S-Transferase P Increases Myocardial Sensitivity to Ischemia-Reperfusion Injury

RATIONALE

Myocardial ischemia-reperfusion (I/R) results in the generation of oxygen-derived free radicals and the accumulation of lipid peroxidation-derived unsaturated aldehydes. However, the contribution of aldehydes to myocardial I/R injury has not been assessed.

OBJECTIVE

We tested the hypothesis that removal of aldehydes by glutathione S-transferase P (GSTP) diminishes I/R injury.

METHODS AND RESULTS

In adult male C57BL/6 mouse hearts, Gstp1/2 was the most abundant GST transcript followed by Gsta4 and Gstm4.1, and GSTP activity was a significant fraction of the total GST activity. mGstp1/2 deletion reduced total GST activity, but no compensatory increase in GSTA and GSTM or major antioxidant enzymes was observed. Genetic deficiency of GSTP did not alter cardiac function, but in comparison with hearts from wild-type mice, the hearts isolated from GSTP-null mice were more sensitive to I/R injury. Disruption of the GSTP gene also increased infarct size after coronary occlusion in situ. Ischemia significantly increased acrolein in hearts, and GSTP deficiency induced significant deficits in the metabolism of the unsaturated aldehyde, acrolein, but not in the metabolism of 4-hydroxy-trans-2-nonenal or trans-2-hexanal; on ischemia, the GSTP-null hearts accumulated more acrolein-modified proteins than wild-type hearts. GSTP deficiency did not affect I/R-induced free radical generation, c-Jun N-terminal kinase activation, or depletion of reduced glutathione. Acrolein exposure induced a hyperpolarizing shift in INa, and acrolein-induced cell death was delayed by SN-6, a Na(+)/Ca(++) exchange inhibitor. Cardiomyocytes isolated from GSTP-null hearts were more sensitive than wild-type myocytes to acrolein-induced protein crosslinking and cell death.

CONCLUSIONS

GSTP protects the heart from I/R injury by facilitating the detoxification of cytotoxic aldehydes, such as acrolein.

Mercapturic Acids Derived from the Toxicants Acrolein and Crotonaldehyde in the Urine of Cigarette Smokers from Five Ethnic Groups with Differing Risks for Lung Cancer

The Multiethnic Cohort epidemiology study has clearly demonstrated that, compared to Whites and for the same number of cigarettes smoked, African Americans and Native Hawaiians have a higher risk for lung cancer whereas Latinos and Japanese Americans have a lower risk. Acrolein and crotonaldehyde are two important constituents of cigarette smoke which have well documented toxic effects and could play a role in lung cancer etiology. Their urinary metabolites 3-hydroxypropylmercapturic acid (3-HPMA) and 3-hydroxy-1-methylpropylmercapturic acid (HMPMA), respectively, are validated biomarkers of acrolein and crotonaldehyde exposure. We quantified levels of 3-HPMA and HMPMA in the urine of more than 2200 smokers from these five ethnic groups, and also carried out a genome wide association study using blood samples from these subjects. After adjusting for age, sex, creatinine, and total nicotine equivalents, geometric mean levels of 3-HPMA and HMPMA were significantly different in the five groups (P < 0.0001). Native Hawaiians had the highest and Latinos the lowest geometric mean levels of both 3-HPMA and HMPMA. Levels of 3-HPMA and HMPMA were 3787 and 2759 pmol/ml urine, respectively, in Native Hawaiians and 1720 and 2210 pmol/ml urine in Latinos. These results suggest that acrolein and crotonaldehyde may be involved in lung cancer etiology, and that their divergent levels may partially explain the differing risks of Native Hawaiian and Latino smokers. No strong signals were associated with 3-HPMA in the genome wide association study, suggesting that formation of the glutathione conjugate of acrolein is mainly non-enzymatic, while the top significant association with HMPMA was located on chromosome 12 near the TBX3 gene, but its relationship to HMPMA excretion is not clear.

Induction of the pi class of glutathione S-transferase by carnosic acid in rat Clone 9 cells via the p38/Nrf2 pathway

Induction of phase II enzymes is important in cancer chemoprevention. We compared the effect of rosemary diterpenes on the expression of the pi class of glutathione S-transferase (GSTP) in rat liver Clone 9 cells and the signaling pathways involved. Culturing cells with 1, 5, 10, or 20 μM carnosic acid (CA) or carnosol (CS) for 24 h in a dose-dependent manner increased the GSTP expression. CA was more potent than CS. The RNA level and the enzyme activity of GSTP were also enhanced by CA treatment. Treatment with 10 μM CA highly induced the reporter activity of the enhancer element GPEI. Furthermore, CA markedly increased the translocation of nuclear factor erythroid-2 related factor 2 (Nrf2) from the cytosol to the nucleus after 30 to 60 min. CA the stimulated the protein induction of p38, nuclear Nrf2, and GSTP was diminished in the presence of SB203580 (a p38 inhibitor). In addition, SB203580 pretreatment or silencing of Nrf2 by siRNA suppressed the CA-induced GPEI-DNA binding activity and GSTP protein expression. Knockdown of p38 or Nrf2 by siRNA abolished the activation of p38 and Nrf2 as well as the protein induction and enzyme activity of GSTP by CA. These results suggest that CA up-regulates the expression and enzyme activity of GSTP via the p38/Nrf2/GPEI pathway.

Glutathione S-transferase P protects against cyclophosphamide-induced cardiotoxicity in mice

High-dose chemotherapy regimens using cyclophosphamide (CY) are frequently associated with cardiotoxicity that could lead to myocyte damage and congestive heart failure. However, the mechanisms regulating the cardiotoxic effects of CY remain unclear. Because CY is converted to an unsaturated aldehyde acrolein, a toxic, reactive CY metabolite that induces extensive protein modification and myocardial injury, we examined the role of glutathione S-transferase P (GSTP), an acrolein-metabolizing enzyme, in CY cardiotoxicity in wild-type (WT) and GSTP-null mice. Treatment with CY (100-300 mg/kg) increased plasma levels of creatine kinase-MB isoform (CK · MB) and heart-to-body weight ratio to a significantly greater extent in GSTP-null than WT mice. In addition to modest yet significant echocardiographic changes following acute CY-treatment, GSTP insufficiency was associated with greater phosphorylation of c-Jun and p38 as well as greater accumulation of albumin and protein-acrolein adducts in the heart. Mass spectrometric analysis revealed likely prominent modification of albumin, kallikrein-1-related peptidase, myoglobin and transgelin-2 by acrolein in the hearts of CY-treated mice. Treatment with acrolein (low dose, 1-5 mg/kg) also led to increased heart-to-body weight ratio and myocardial contractility changes. Acrolein induced similar hypotension in GSTP-null and WT mice. GSTP-null mice also were more susceptible than WT mice to mortality associated with high-dose acrolein (10-20 mg/kg). Collectively, these results suggest that CY cardiotoxicity is regulated, in part, by GSTP, which prevents CY toxicity by detoxifying acrolein. Thus, humans with low cardiac GSTP levels or polymorphic forms of GSTP with low acrolein-metabolizing capacity may be more sensitive to CY toxicity.

Inflammation and pyroptosis mediate muscle expansion in an interleukin-1β (IL-1β)-dependent manner

Muscle inflammation is often associated with its expansion. Bladder smooth muscle inflammation-induced cell death is accompanied by hyperplasia and hypertrophy as the primary cause for poor bladder function. In mice, DNA damage initiated by chemotherapeutic drug cyclophosphamide activated caspase 1 through the formation of the NLRP3 complex resulting in detrusor hyperplasia. A cyclophosphamide metabolite, acrolein, caused global DNA methylation and accumulation of DNA damage in a mouse model of bladder inflammation and in cultured bladder muscle cells. In correlation, global DNA methylation and NLRP3 expression was up-regulated in human chronic bladder inflammatory tissues. The epigenetic silencing of DNA damage repair gene, Ogg1, could be reversed by the use of demethylating agents. In mice, demethylating agents reversed cyclophosphamide-induced bladder inflammation and detrusor expansion. The transgenic knock-out of Ogg1 in as few as 10% of the detrusor cells tripled the proliferation of the remaining wild type counterparts in an in vitro co-culture titration experiment. Antagonizing IL-1β with Anakinra, a rheumatoid arthritis therapeutic, prevented detrusor proliferation in conditioned media experiments as well as in a mouse model of bladder inflammation. Radiation treatment validated the role of DNA damage in the NLRP3-associated caspase 1-mediated IL-1β secretory phenotype. A protein array analysis identified IGF1 to be downstream of IL-1β signaling. IL-1β-induced detrusor proliferation and hypertrophy could be reversed with the use of Anakinra as well as an IGF1 neutralizing antibody. IL-1β antagonists in current clinical practice can exploit the revealed mechanism for DNA damage-mediated muscular expansion.

Attenuation of cystitis and pain sensation in mice lacking fatty acid amide hydrolase

Endocannabinoids, such as N-arachidonoylethanolamine (AEA, also called anandamide), exert potent analgesic and anti-inflammatory effects. Fatty acid amide hydrolase (FAAH) is primarily responsible for degradation of AEA, and deletion of FAAH increases AEA content in various tissues. Since FAAH has been shown to be present in the bladder of various species, we compared bladder function, severity of experimental cystitis, and cystitis-associated referred hyperalgesia in male wild-type (WT) and FAAH knock-out (KO) mice. Basal concentrations of AEA were greater, and the severity of cyclophosphamide (CYP)-induced cystitis was reduced in bladders from FAAH KO compared to WT mice. Cystitis-associated increased peripheral sensitivity to mechanical stimuli and enhanced bladder activity (as reflected by increased voiding frequency) were attenuated in FAAH KO compared to WT mice. Further, abundances of mRNA for several pro-inflammatory compounds were increased in the bladder mucosa after CYP treatment of WT mice, and this increase was inhibited in FAAH KO mice. These data indicate that endogenous substrates of FAAH, including the cannabinoid AEA, play an inhibitory role in bladder inflammation and subsequent changes in pain perception. Therefore, FAAH could be a therapeutic target to treat clinical symptoms of painful inflammatory bladder diseases.

Glutathione S-transferase and MRP1 form an integrated system involved in the storage and transport of dinitrosyl-dithiolato iron complexes in cells

Nitrogen monoxide (NO) is vital for many essential biological processes as a messenger and effector molecule. The physiological importance of NO is the result of its high affinity for iron in the active sites of proteins such as guanylate cyclase. Indeed, NO possesses a rich coordination chemistry with iron and the formation of dinitrosyl-dithiolato iron complexes (DNICs) is well documented. In mammals, NO generated by cytotoxic activated macrophages has been reported to play a role as a cytotoxic effector against tumor cells by binding and releasing intracellular iron. Studies from our laboratory have shown that two proteins traditionally involved in drug resistance, namely multidrug-resistance protein 1 and glutathione S-transferase, play critical roles in intracellular NO transport and storage through their interaction with DNICs (R.N. Watts et al., Proc. Natl. Acad. Sci. USA 103:7670-7675, 2006; H. Lok et al., J. Biol. Chem. 287:607-618, 2012). Notably, DNICs are present at high concentrations in cells and are biologically available. These complexes have a markedly longer half-life than free NO, making them an ideal "common currency" for this messenger molecule. Considering the many critical roles NO plays in health and disease, a better understanding of its intracellular trafficking mechanisms will be vital for the development of new therapeutics.

Acrolein exposure is associated with increased cardiovascular disease risk

Background

Acrolein is a reactive aldehyde present in high amounts in coal, wood, paper, and tobacco smoke. It is also generated endogenously by lipid peroxidation and the oxidation of amino acids by myeloperoxidase. In animals, acrolein exposure is associated with the suppression of circulating progenitor cells and increases in thrombosis and atherogenesis. The purpose of this study was to determine whether acrolein exposure in humans is also associated with increased cardiovascular disease (CVD) risk.

Methods and Results

Acrolein exposure was assessed in 211 participants of the Louisville Healthy Heart Study with moderate to high (CVD) risk by measuring the urinary levels of the major acrolein metabolite—3‐hydroxypropylmercapturic acid (3‐HPMA). Generalized linear models were used to assess the association between acrolein exposure and parameters of CVD risk, and adjusted for potential demographic confounders. Urinary 3‐HPMA levels were higher in smokers than nonsmokers and were positively correlated with urinary cotinine levels. Urinary 3‐HPMA levels were inversely related to levels of both early (AC133⁺) and late (AC133⁻) circulating angiogenic cells. In smokers as well as nonsmokers, 3‐HPMA levels were positively associated with both increased levels of platelet–leukocyte aggregates and the Framingham Risk Score. No association was observed between 3‐HPMA and plasma fibrinogen. Levels of C‐reactive protein were associated with 3‐HPMA levels in nonsmokers only.

Conclusions

Regardless of its source, acrolein exposure is associated with platelet activation and suppression of circulating angiogenic cell levels, as well as increased CVD risk.

Mice lacking three Loci encoding 14 glutathione transferase genes: a novel tool for assigning function to the GSTP, GSTM, and GSTT families

Glutathione S-transferases (GSTs) form a superfamily defined by their ability to catalyze the conjugation of glutathione with electrophilic substrates. These enzymes are proposed to play a critical role in protection of cellular components from damage mediated by reactive metabolites. Twenty-two cytosolic GSTs, grouped into seven families, are recognized in mice. This complexity hinders the assignment of function to a subset or family of these genes. We report generation of a mouse line in which the locus encoding three GST gene families is deleted. This includes the four Gstt genes spanning 65 kb on chromosome 10 and the seven Gstm genes found on a 150 kb segment of DNA chromosome 3. In addition, we delete two Gstp genes on chromosome 19 as well as a third related gene located 15 kb telomeric to Gstp1 and Gstp2, which we identify as a potential new member of this gene family. We show that, despite the loss of up to 75% of total GST activity in some tissues from these animals, the mice are healthy and fertile, with normal life expectancy. The normal development and health of these animals make them an appropriate model for defining the role of these families in redox homeostasis and metabolism of drugs and environmental pollutants.

Diphenylmethyl selenocyanate attenuates malachite green induced oxidative injury through antioxidation & inhibition of DNA damage in mice

BACKGROUND & OBJECTIVES

Malachite green (MG), an environmentally hazardous material, is used as a non permitted food colouring agent, especially in India. Selenium (Se) is an essential nutritional trace element required for animals and humans to guard against oxidative stress induced by xenobiotic compounds of diverse nature. In the present study, the role of the selenium compound diphenylmethyl selenocyanate (DMSE) was assessed on the oxidative stress (OS) induced by a food colouring agent, malachite green (MG) in vivo in mice.

METHODS

Swiss albino mice (Mus musculus) were intraperitoneally injected with MG at a standardized dose of 100 μg/ mouse for 30 days. DMSE was given orally at an optimum dose of 3 mg/kg b.w. in pre (15 days) and concomitant treatment schedule throughout the experimental period. The parameters viz. ALT, AST, LPO, GSH, GST, SOD, CAT, GPx, TrxR, CA, MN, MI and DNA damage have been evaluated.

RESULTS

The DMSE showed its potential to protect against MG induced hepatotoxicity by controlling the serum alanine aminotransferase and aspartate amino transferase (ALT and AST) levels and also ameliorated oxidative stress by modulating hepatic lipid peroxidation and different detoxifying and antioxidative enzymes such as glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and also the selenoenzymes such as glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) and reduced glutathione level which in turn reduced DNA damage.

INTERPRETATION & CONCLUSIONS

The organo-selenium compound DMSE showed significant protection against MG induced heptotoxicity and DNA damage in murine model. Better protection was observed in pretreatment group than in the concomitant group. Further studies need to be done to understand the mechanism of action.

Activation of cannabinoid receptor 2 inhibits experimental cystitis

Cannabinoids have been shown to exert analgesic and anti-inflammatory effects, and the effects of cannabinoids are mediated primarily by cannabinoid receptors 1 and 2 (CB1and CB2). Both CB1 and CB2 are present in bladders of various species, including human, monkey, and rodents, and it appears that CB2 is highly expressed in urothelial cells. We investigated whether treatment with the CB2 agonist GP1a alters severity of experimental cystitis induced by acrolein and referred mechanical hyperalgesia associated with cystitis. We also investigated whether the mitogen-activated protein kinases (MAPK), ERK1/2, p38, and JNK are involved in the functions of CB2. We found that treatment with the selective CB2 agonist GP1a (1-10 mg/kg, ip) inhibited the severity of bladder inflammation 3 h after intravesical instillation of acrolein in a dose-dependent manner, and inhibition reached significance at a dose of 10 mg/kg (P < 0.05). Treatment with GP1a (10 mg/kg) inhibited referred mechanical hyperalgesia associated with cystitis (P < 0.05). The inhibitory effects of the CB2 agonist were prevented by the selective CB2 antagonist AM630 (10 mg/kg, sc). We further demonstrated the inhibitory effects of CB2 appear to be at least partly mediated by reducing bladder inflammation-induced activation of ERK1/2 MAPK pathway. The results of the current study indicate that CB2 is a potential therapeutic target for treatment of bladder inflammation and pain in patients.

Glutathione transferases, regulators of cellular metabolism and physiology

BACKGROUND

The cytosolic glutathione transferases (GSTs) comprise a super family of proteins that can be categorized into multiple classes with a mixture of highly specific and overlapping functions.

SCOPE OF REVIEW

The review covers the genetics, structure and function of the human cytosolic GSTs with particular attention to their emerging roles in cellular metabolism.

MAJOR CONCLUSIONS

All the catalytically active GSTs contribute to the glutathione conjugation or glutathione dependant-biotransformation of xenobiotics and many catalyze glutathione peroxidase or thiol transferase reactions. GSTs also catalyze glutathione dependent isomerization reactions required for the synthesis of several prostaglandins and steroid hormones and the catabolism of tyrosine. An increasing body of work has implicated several GSTs in the regulation of cell signaling pathways mediated by stress-activated kinases like Jun N-terminal kinase. In addition, some members of the cytosolic GST family have been shown to form ion channels in intracellular membranes and to modulate ryanodine receptor Ca(2+) channels in skeletal and cardiac muscle.

GENERAL SIGNIFICANCE

In addition to their well established roles in the conjugation and biotransformation of xenobiotics, GSTs have emerged as significant regulators of pathways determining cell proliferation and survival and as regulators of ryanodine receptors that are essential for muscle function. This article is part of a Special Issue entitled Cellular functions of glutathione.

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

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

Increased skin papilloma formation in mice lacking glutathione transferase GSTP

The glutathione S-transferase GSTP is overexpressed in many human cancers and chemotherapy-resistant cancer cells, where there is evidence that GSTP may have additional functions beyond its known catalytic role. On the basis of evidence that Gstp-deficient mice have a comparatively higher susceptibility to skin carcinogenesis, we investigated whether this phenotype reflected an alteration in carcinogen detoxification or not. For this study, Gstp(-/-) mice were interbred with Tg.AC mice that harbor initiating H-ras mutations in the skin. Gstp(-/-)/Tg.AC mice exposed to the proinflammatory phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) exhibited higher tumor incidence and multiplicity with a significant thickening of skin after treatment, illustrating hyperproliferative growth. Unexpectedly, we observed no difference in cellular proliferation or apoptosis or in markers of oxidative stress, although higher levels of the inflammatory marker nitrotyrosine were found in Gstp(-/-)/Tg.AC mice. Instead, gene set enrichment analysis of microarray expression data obtained from skin revealed a more proapoptotic and proinflammatory environment shortly after TPA treatment. Within 4 weeks of TPA treatment, Gstp(-/-)/Tg.AC mice displayed altered lipid/sterol metabolism and Wnt signaling along with aberrant processes of cytoskeletal control and epidermal morphogenesis at both early and late times. In extending the evidence that GSTP has a vital role in normal homeostatic control and cancer prevention, they also strongly encourage the emerging concept that GSTP is a major determinant of the proinflammatory character of the tumor microenvironment. This study shows that the GSTP plays a major role in carcinogenesis distinct from its role in detoxification and provides evidence that the enzyme is a key determinant of the proinflammatory tumor environment.

Acrolein-induced dyslipidemia and acute-phase response are independent of HMG-CoA reductase

SCOPE

Aldehydes are ubiquitous natural constituents of foods, water and beverages. Dietary intake represents the greatest source of exposure to acrolein and related aldehydes. Oral acrolein induces dyslipidemia acutely and chronically increases atherosclerosis in mice, yet the mechanisms are unknown. Because lipid synthesis and trafficking are largely under hepatic control, we examined hepatic genes in murine models of acute and chronic oral acrolein exposure.

METHODS AND RESULTS

Changes in hepatic gene expression were examined using a Steroltalk microarray. Acute acrolein feeding modified plasma and hepatic proteins and increased plasma triglycerides within 15  min. By 6  h, acrolein altered hepatic gene expression including Insig1, Insig2 and Hmgcr genes and stimulated an acute-phase response (APR) with up-regulation of serum amyloid A genes (Saa) and systemic hypoalbuminemia. To test if decreased HMG-CoA reductase activity could modify acrolein-induced dyslipidemia or the APR, mice were pretreated with simvastatin. Statin treatment, however, did not alter acrolein-induced dyslipidemia or hypoalbuminemia associated with an APR. Few hepatic genes were dysregulated by chronic acrolein feeding in apoE-null mice. These studies confirmed that acute acrolein exposure altered expression of hepatic genes involved with lipid synthesis and trafficking and APR, and thus, indicated a hepatic locus of acrolein-induced dyslipidemia and APR that was independent of HMG CoA-reductase.

CONCLUSION

Dietary intake of acrolein could contribute to cardiovascular disease risk by disturbing hepatic function.

Protein modification by acrolein: relevance to pathological conditions and inhibition by aldehyde sequestering agents

Acrolein (ACR) is a toxic and highly reactive α,β-unsaturated aldehyde widely distributed in the environment as a common pollutant and generated endogenously mainly by lipoxidation reactions. Its biological effects are due to its ability to react with the nucleophilic sites of proteins, to form covalently modified biomolecules which are thought to be involved as pathogenic factors in the onset and progression of many pathological conditions such as cardiovascular and neurodegenerative diseases. Functional impairment of structural proteins and enzymes by covalent modification (crosslinking) and triggering of key cell signalling systems are now well-recognized signs of cell and tissue damage induced by reactive carbonyl species (RCS). In this review, we mainly focus on the in vitro and in vivo evidence demonstrating the ability of ACR to covalently modify protein structures, in order to gain a deeper insight into the dysregulation of cellular and metabolic pathways caused by such modifications. In addition, by considering RCS and RCS-modified proteins as drug targets, this survey will provide an overview on the newly developed molecules specifically tested for direct or indirect ACR scavenging, and the more significant studies performed in the last years attesting the efficacy of compounds already recognized as promising aldehyde-sequestering agents.

Knockout and transgenic mice in glutathione transferase research

Glutathione transferases (GSTs) are a multigene family of ubiquitously expressed, polymorphic enzymes responsible for the metabolism of a wide range of both endogenous and exogenous substrates, play a central role in the adaptive response to chemical and oxidative stress, and are subject to regulation by a range of structurally unrelated chemicals. In this review, we present a current summary of knockout mouse models in the GST field, discussing some of the issues pertaining to orthologous proteins between mice and humans, the potential confounding issues related to genetic background, and also cover new transgenic models in the increasingly important area of humanization.

Synthesis, quantification, characterization, and signaling properties of glutathionyl conjugates of enals

Oxidation of lipids generates large quantities of highly reactive alpha,beta-unsaturated aldehydes (enals). Enals and their protein adducts accumulate in the tissues of several pathologies. In vitro, low concentrations of enals such as HNE (4-hydroxy trans-2-nonenal) affect cell signaling whereas high concentrations of enals are cytotoxic. Direct conjugation of the C2-C3 double bond of enals with the sulfhydryl group of GSH is a major route for the metabolism and detoxification of enals. Recently, we found that glutathionyl conjugate of HNE (GS-HNE) enhances the peritoneal leukocyte infiltration and stimulates the formation of proinflammatory lipid mediators. Moreover, the reduced form of the glutathione conjugate of HNE (GS-DHN) elicits strong mitogenic signaling in smooth muscle cells. In this chapter we discuss the methods to study the metabolism of enals and the redox signaling properties of glutathionyl conjugates of HNE.

Postischemic deactivation of cardiac aldose reductase: role of glutathione S-transferase P and glutaredoxin in regeneration of reduced thiols from sulfenic acids

Aldose reductase (AR) is a multifunctional enzyme that catalyzes the reduction of glucose and lipid peroxidation-derived aldehydes. During myocardial ischemia, the activity of AR is increased due to the oxidation of its cysteine residues to sulfenic acids. It is not known, however, whether the activated, sulfenic form of the protein (AR-SOH) is converted back to its reduced, unactivated state (AR-SH). We report here that in perfused mouse hearts activation of AR during 15 min of global ischemia is completely reversed by 30 min of reperfusion. During reperfusion, AR-SOH was converted to a mixed disulfide (AR-SSG). Deactivation of AR and the appearance of AR-SSG during reperfusion were delayed in hearts of mice lacking glutathione S-transferase P (GSTP). In vitro, GSTP accelerated glutathiolation and inactivation of AR-SOH. Reduction of AR-SSG to AR-SH was facilitated by glutaredoxin (GRX). Ischemic activation of AR was increased in GRX-null hearts but was attenuated in the hearts of cardiospecific GRX transgenic mice. Incubation of AR-SSG with GRX led to the regeneration of the reduced form of the enzyme. In ischemic cardiospecific AR transgenic hearts, AR was co-immunoprecipitated with GSTP, whereas in reperfused hearts, the association of AR with GRX was increased. These findings suggest that upon reperfusion of the ischemic heart AR-SOH is converted to AR-SSG via GSTP-assisted glutathiolation. AR-SSG is then reduced by GRX to AR-SH. Sequential catalysis by GSTP and GRX may be a general redox switching mechanism that regulates the reduction of protein sulfenic acids to cysteines.