Regulation of 4‐Hydroxynonenal Mediated Signaling By Glutathione S‐Transferases

Acetaminophen-induced liver injury: Molecular mechanism and treatments from natural products

Acetaminophen (APAP) is a widely used analgesic and antipyretic over-the-counter medicine worldwide. Hepatotoxicity caused by APAP overdose is one of the leading causes of acute liver failure (ALF) in the US and in some parts of Europe, limiting its clinical application. Excessive APAP metabolism depletes glutathione and increases N-acetyl-p-benzoquinoneimide (NAPQI) levels, leading to oxidative stress, DNA damage, and cell necrosis in the liver, which in turn leads to liver damage. Studies have shown that natural products such as polyphenols, terpenes, anthraquinones, and sulforaphane can activate the hepatocyte antioxidant defense system with Nrf2 as the core player, reduce oxidative stress damage, and protect the liver. As the key enzyme metabolizing APAP into NAPQI, cytochrome P450 enzymes are also considered to be intriguing target for the treatment of APAP-induced liver injury. Here, we systematically review the hepatoprotective activity and molecular mechanisms of the natural products that are found to counteract the hepatotoxicity caused by APAP, providing reference information for future preclinical and clinical trials of such natural products.

Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4

High concentrations of electrophilic lipid alkenals formed during oxidative stress are implicated in cytotoxicity and disease. However, low concentrations of alkenals are required to induce antioxidative stress responses. An established clearance pathway for lipid alkenals includes conjugation to glutathione (GSH) via Michael addition, which is catalyzed mainly by glutathione transferase isoform A4 (GSTA4-4). Based on the ability of GSTs to catalyze hydrolysis or retro-Michael addition of GSH conjugates, and the antioxidant function of low concentrations of lipid alkenals, we hypothesize that GSTA4-4 contributes a homeostatic role in lipid metabolism. Enzymatic kinetic parameters for retro-Michael addition with trans-2-Nonenal (NE) reveal the chemical competence of GSTA4-4 in this putative role. The forward GSTA4-4-catalyzed Michael addition occurs with the rapid exchange of the C2 proton of NE in D₂O as observed by NMR. The isotope exchange was completely dependent on the presence of GSH. The overall commitment to catalysis, or the ratio of first order k_cat,f for 'forward' Michael addition to the first order k_cat,ex for H/D exchange is remarkably low, approximately 3:1. This behavior is consistent with the possibility that GSTA4-4 is a regulatory enzyme that contributes to steady-state levels of lipid alkenals, rather than a strict 'one way' detoxication enzyme.

Electrophilic Aldehyde 4-Hydroxy-2-Nonenal Mediated Signaling and Mitochondrial Dysfunction

Reactive oxygen species (ROS), a by-product of aerobic life, are highly reactive molecules with unpaired electrons. The excess of ROS leads to oxidative stress, instigating the peroxidation of polyunsaturated fatty acids (PUFA) in the lipid membrane through a free radical chain reaction and the formation of the most bioactive aldehyde, known as 4-hydroxynonenal (4-HNE). 4-HNE functions as a signaling molecule and toxic product and acts mainly by forming covalent adducts with nucleophilic functional groups in proteins, nucleic acids, and lipids. The mitochondria have been implicated as a site for 4-HNE generation and adduction. Several studies clarified how 4-HNE affects the mitochondria's functions, including bioenergetics, calcium homeostasis, and mitochondrial dynamics. Our research group has shown that 4-HNE activates mitochondria apoptosis-inducing factor (AIFM2) translocation and facilitates apoptosis in mice and human heart tissue during anti-cancer treatment. Recently, we demonstrated that a deficiency of SOD2 in the conditional-specific cardiac knockout mouse increases ROS, and subsequent production of 4-HNE inside mitochondria leads to the adduction of several mitochondrial respiratory chain complex proteins. Moreover, we highlighted the physiological functions of HNE and discussed their relevance in human pathophysiology and current discoveries concerning 4-HNE effects on mitochondria.

GSTM1 Gene, Diet, and Kidney Disease: Implication for Precision Medicine?: Recent Advances in Hypertension

In the United States, the prevalence of chronic kidney disease in adults is ≈14%. The mainstay of therapy for chronic kidney disease is angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, but many patients with chronic kidney disease still progress to end-stage kidney disease. Increased oxidative stress is a major molecular underpinning of chronic kidney disease progression. In humans, a common deletion variant of the glutathione-S-transferase μ-1 (GSTM1) gene, the GSTM1 null allele (GSTM1(0)), results in decreased GSTM1 enzymatic activity and is associated with higher levels of oxidative stress. GSTM1 belongs to the superfamily of GSTs that are phase II antioxidant enzymes and are regulated by Nrf2 (nuclear factor erythroid 2-related factor 2). Cruciferous vegetables in general, and broccoli in particular, are rich in glucoraphanin, a precursor of sulforaphane that has been shown to have protective effects against oxidative damage through the activation of Nrf2. This review will highlight recent human and animal studies implicating the role of GSTM1 deficiency in hypertension and kidney disease, and its impact on the effects of cruciferous vegetables on kidney injury and disease progression, illustrating the significance of gene and environment interaction and a potential for targeted precision medicine in the treatment of kidney disease.

Age-Related Neuronal Deterioration Specifically Within the Dorsal CA1 Region of the Hippocampus in a Mouse Model of Late Onset Alzheimer's Disease

BACKGROUND

Neuronal damage resulting from increased oxidative stress is important in the development of late onset/age-related Alzheimer's disease (LOAD). We have developed an oxidative stress-related mouse model of LOAD based on gene deletion of aldehyde dehydrogenase 2 (ALDH2), an enzyme important for the detoxification of endogenous aldehydes arising from lipid peroxidation. Compared to wildtype (WT) mice, the knockout (KO) mice exhibit AD-like pathologies and a progressive decline in recognition and spatial memory. This progression presumably has a morphological basis induced by oxidative damage.

OBJECTIVE

We performed morphometric analyses in the dorsal hippocampal CA1 region (dCA1) to determine if altered neuronal structure can help account for the progressive cognitive impairment in 3- to 12-month-old KO mice.

METHODS

Dendritic morphology was quantitatively analyzed by branched structured analysis and Sholl analysis following Golgi-Cox staining in WT mice (148 neurons) versus KO mice (180 neurons).

RESULTS

The morphology and complexity of dCA1 pyramidal neurons were similar at age 3 months in WTs and KOs. However, by 6 months there were significant reductions in apical and basal dendritic length, dendrite complexity, and spine density in KO versus WT mice that were maintained through ages 9 and 12 months. Immunostaining for protein adducts of the lipid peroxidation product 4-hydroxynonenal revealed significant increases in staining in dCA1 (but not ventral CA1) by 3 months, increasing through 12 months.

CONCLUSION

This specific and progressive increase in dCA1 oxidative damage preceded detectable synaptic trimming in KO mice, in keeping with studies showing that lesions to dorsal hippocampus primarily impair cognitive memory.

Activating p53 function by targeting RLIP

Aberrations in RLIP, p53, and PKCα represent essentially the entire spectrum of all human neoplasms. Elevated PKCα expression, failure of the cell cycle checkpoint (p53 dysfunction), and abnormal glutathione (GSH) metabolism are fundamental hallmarks of carcinogenesis and drug/radiation resistance. However, a lack of investigations into the interactions between these important regulatory nodes has fundamentally limited our understanding of carcinogenesis and the development of effective interventions for cancer prevention and therapy. Loss of p53, perhaps the most powerful tumor suppressor gene, predisposes rodents to spontaneous cancer and humans to familial, as well as acquired, cancers. Until recently, no genetic manipulation of any oncogene had been reported to abrogate spontaneous carcinogenesis in p53^-/- rodent models. However, the overexpression of RLIP, a GSH-electrophile conjugate (GS-E) transporter, has been found to enhance cancer cell proliferation and confer drug/radiation resistance, whereas its depletion causes tumor regression, suggesting its importance in cancer and drug/radiation resistance. Indeed, RLIP is an essential effector of p53 that is necessary for broad cancer-promoting epigenetic remodeling. Interestingly, through a haploinsufficiency mechanism, the partial depletion of RLIP in p53^-/- mice provides complete protection from neoplasia. Furthermore, RLIP^-/- mice exhibit altered p53 and PKCα function, marked deficiency in clathrin-dependent endocytosis (CDE), and almost total resistance to chemical carcinogenesis. Based on these findings, in this review, we present a novel and radical hypothesis that expands our understanding of the highly significant cross-talk between p53, PKCα, and GSH signaling by RLIP in multiple tumor models.

Alteration of retinal metabolism and oxidative stress may implicate myopic eye growth: Evidence from discovery and targeted proteomics in an animal model

Myopia, the most common cause of impaired vision, may induce sight- threatening diseases or ocular complications due to axial elongation. The exact mechanisms underlying myopia development have received much attention and understanding of these is necessary for clinical prevention or therapeutics. In this study, quantitative proteomics using Isotope Coded Protein Label (ICPL) was applied to identify differentially regulated proteins in the retinas of myopic chicks and, from their presence, infer the possible pathogenesis of excessive ocular elongation. Newly hatched white leghorn chicks (n = 15) wore -10D and + 10D lenses bilaterally for 3 and 7 days, respectively, to develop progressive lens-induced myopia (LIM) and hyperopia (LIH). Retinal proteins were quantified with nano-liquid chromatography electrospray ionization coupled with tandem mass spectrometry (nanoLC-ESI-MS/MS). Bioinformatics analysis of differentially regulated proteins revealed that the majority originated from the cytoplasmic region and were related to various metabolic, glycolytic, or oxidative processes. The fold changes of four proteins of interest (vimentin, apolipoprotein A1, interphotoreceptor retinoid binding protein, and glutathione S-transferase) were further confirmed by a novel high-resolution multiple reaction monitoring mass spectrometry (MRM-HR) using a label-free approach. SIGNIFICANCE: Discovery of effective protein biomarkers of myopia has been extensively studied to inhibit myopia progression. This study first applied lens-induced hyperopia and myopia in the same chick to maximize the inter-ocular differences, aiming to discover more protein biomarker candidates. The findings provided new evidence that myopia was metabolism related, accompanied by altered energy generation and oxidative stress at retinal protein levels. The results in the retina were also compared to our previous study in vitreous using ICPL quantitative technology. We have now presented the protein changes in these two adjacent tissues, which may provide extra information of protein changes during ocular growth in myopia.

Protective effect of inducible aldo-keto reductases on 4-hydroxynonenal- induced hepatotoxicity

4-Hydroxynonenal (HNE), an end-product of lipid peroxidation generated in response to oxidative stress, has been implicated in the pathophysiology of chronic liver diseases. HNE is very reactive that forms Michael adducts with nucleophilic sites in DNA, lipids and proteins. At high concentrations, HNE causes rapid cell death associated with depletion of sulfhydryl groups and inhibition of key metabolic enzymes. At low concentrations, HNE stimulates expression of genes that are part of an adaptive response. In this study, we show that sub-lethal concentrations of HNE induce mRNA expression levels of heme oxygenase-1 (HO-1) (2.5-fold), NADPH:quinone oxidoreductase (NQO1) (4.5-fold), AKR1C3 (2-fold) and AKR7A2 (3-fold) enzymes. Protein expression levels of AKR1C and AKR7A2 are induced by 2- and 1.5-fold following exposure to HNE. The role of AKR1C3 and AKR7A2 in protecting HepG2 cells against HNE toxicity was investigated through using RNAi. Results show that AKR7A2, but not AKR1C3 contributes to the protection against HNE toxicity in HepG2 cells. Moreover, transcriptional factor nuclear factor erythroid 2 p45-related factor 2 (Nrf2) is activated by HNE through translocation to the nucleus. Overexpressing AKR7A2 could rescue the effect of knocking down Nrf2 on HNE-induced cytotoxicity. Furthermore, a natural compound 7-hydroxycoumain, an AKR7A2 inducer, shows hepatoprotection against HNE via AKR7A2 induction. Hence, the inducible AKR7A2 has provided a new therapeutic target to treat chronic liver disease.

Characterisation of a diazinon-metabolising glutathione S-transferase in the silkworm Bombyx mori by X-ray crystallography and genome editing analysis

Previously, we found an unclassified glutathione S-transferase 2 (bmGSTu2) in the silkworm Bombyx mori that conjugates glutathione to 1-chloro-2,4-dinitrobenzene and also metabolises diazinon, an organophosphate insecticide. Here, we provide a structural and genome-editing characterisation of the diazinon-metabolising glutathione S-transferase in B. mori. The structure of bmGSTu2 was determined at 1.68 Å by X-ray crystallography. Mutation of putative amino acid residues in the substrate-binding site showed that Pro13, Tyr107, Ile118, Phe119, and Phe211 are crucial for enzymatic function. bmGSTu2 gene disruption resulted in a decrease in median lethal dose values to an organophosphate insecticide and a decrease in acetylcholine levels in silkworms. Taken together, these results indicate that bmGSTu2 could metabolise an organophosphate insecticide. Thus, this study provides insights into the physiological role of bmGSTu2 in silkworms, detoxification of organophosphate insecticides, and drug targets for the development of a novel insecticide.

Effect of fluoride on photosynthetic pigment content and antioxidant system of Hydrilla verticillata

Fluoride can either inhibit or enhance the growth of aquatic macrophytes, depending upon fluoride concentration and exposure time. To investigate fluoride toxicity, the submerged plant Hydrilla verticillata was treated with various concentrations of fluoride (F) (0, 10, 20, and 40 mg/L) for different lengths of time (7, 14, 21, and 28 days). At exposure to 10 mg/L F, the content of chlorophyll, protein, and carbohydrates content increased in leaves of H. verticillata, and the activity of guaiacol peroxidase (POD) and superoxide dismutase (SOD) slightly increased in plants compared with the control. When fluoride concentration increased to 20 mg/L, the toxic effect generated by fluoride led to a reduction of chlorophyll, protein, and carbohydrates in H. verticillata, but the activity of guaiacol peroxidase and SOD and the amount of ascorbic acid (AsA) and glutathione (GSH) were enhanced significantly. After exposure to fluoride at 40 mg/L for a long period, these physiological parameters showed a sharp decrease, and inactivation was observed in H. verticillata. These results suggested that a certain concentration of fluoride induced antioxidant response, and excess fluoride induced metabolism imbalance and oxidative damage in H. verticillata.

Identification of a diazinon-metabolizing glutathione S-transferase in the silkworm, Bombyx mori

The glutathione S-transferase superfamily play key roles in the metabolism of numerous xenobiotics. We report herein the identification and characterization of a novel glutathione S-transferase in the silkworm, Bombyx mori. The enzyme (bmGSTu2) conjugates glutathione to 1-chloro-2,4-dinitrobenzene, as well as metabolizing diazinon, one of the organophosphate insecticides. Quantitative reverse transcription–polymerase chain reaction analysis of transcripts demonstrated that bmGSTu2 expression was induced 1.7-fold in a resistant strain of B. mori. Mutagenesis of putative amino acid residues in the glutathione-binding site revealed that Ile54, Glu66, Ser67, and Asn68 are crucial for enzymatic function. These results provide insights into the catalysis of glutathione conjugation in silkworm by bmGSTu2 and into the detoxification of organophosphate insecticides.

Mitochondrial bioenergetics and oxidative status disruption in brainstem of weaned rats: Immediate response to maternal protein restriction

Mitochondrial bioenergetics dysfunction has been postulated as an important mechanism associated to a number of cardiovascular diseases in adulthood. One of the hypotheses is that this is caused by the metabolic challenge generated by the mismatch between prenatal predicted and postnatal reality. Perinatal low-protein diet produces several effects that are manifested in the adult animal, including altered sympathetic tone, increased arterial blood pressure and oxidative stress in the brainstem. The majority of the studies related to nutritional programming postulates that the increased risk levels for non-communicable diseases are associated with the incompatibility between prenatal and postnatal environment. However, little is known about the immediate effects of maternal protein restriction on the offspring's brainstem. The present study aimed to test the hypothesis that a maternal low-protein diet causes tissue damage immediately after exposure to the nutritional insult that can be assessed in the brainstem of weaned offspring. In this regard, a series of assays was conducted to measure the mitochondrial bioenergetics and oxidative stress biomarkers in the brainstem, which is the brain structure responsible for the autonomic cardiovascular control. Pregnant Wistar rats were fed ad libitum with normoprotein (NP; 17% casein) or low-protein (LP; 8% casein) diet throughout pregnancy and lactation periods. At weaning, the male offsprings were euthanized and the brainstem was quickly removed to assess the mitochondria function, reactive oxygen species (ROS) production, mitochondrial membrane electric potential (ΔΨm), oxidative biomarkers, antioxidant defense and redox status. Our data demonstrated that perinatal LP diet induces an immediate mitochondrial dysfunction. Furthermore, the protein restriction induced a marked increase in ROS production, with a decrease in antioxidant defense and redox status. Altogether, our findings suggest that LP-fed animals may be at a higher risk for oxidative metabolism impairment throughout life than NP-fed rats, due to the immediate disruption of the mitochondrial bioenergetics and oxidative status caused by the LP diet.

Mitochondrial Dysfunction in Cancer and Neurodegenerative Diseases: Spotlight on Fatty Acid Oxidation and Lipoperoxidation Products

In several human diseases, such as cancer and neurodegenerative diseases, the levels of reactive oxygen species (ROS), produced mainly by mitochondrial oxidative phosphorylation, is increased. In cancer cells, the increase of ROS production has been associated with mtDNA mutations that, in turn, seem to be functional in the alterations of the bioenergetics and the biosynthetic state of cancer cells. Moreover, ROS overproduction can enhance the peroxidation of fatty acids in mitochondrial membranes. In particular, the peroxidation of mitochondrial phospholipid cardiolipin leads to the formation of reactive aldehydes, such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA), which are able to react with proteins and DNA. Covalent modifications of mitochondrial proteins by the products of lipid peroxidation (LPO) in the course of oxidative cell stress are involved in the mitochondrial dysfunctions observed in cancer and neurodegenerative diseases. Such modifications appear to affect negatively mitochondrial integrity and function, in particular energy metabolism, adenosine triphosphate (ATP) production, antioxidant defenses and stress responses. In neurodegenerative diseases, indirect confirmation for the pathogenetic relevance of LPO-dependent modifications of mitochondrial proteins comes from the disease phenotypes associated with their genetic alterations.

Antioxidant role of glutathione S-transferases: 4-Hydroxynonenal, a key molecule in stress-mediated signaling

4-Hydroxy-2-trans-nonenal (4HNE), one of the major end products of lipid peroxidation (LPO), has been shown to induce apoptosis in a variety of cell lines. It appears to modulate signaling processes in more than one way because it has been suggested to have a role in signaling for differentiation and proliferation. It has been known that glutathione S-transferases (GSTs) can reduce lipid hydroperoxides through their Se-independent glutathione-peroxidase activity and that these enzymes can also detoxify LPO end-products such as 4HNE. Available evidence from earlier studies together with results of recent studies in our laboratories strongly suggests that LPO products, particularly hydroperoxides and 4HNE, are involved in the mechanisms of stress-mediated signaling and that it can be modulated by the alpha-class GSTs through the regulation of the intracellular concentrations of 4HNE. We demonstrate that 4HNE induced apoptosis in various cell lines is accompanied with c-Jun-N-terminal kinase (JNK) and caspase-3 activation. Cells exposed to mild, transient heat or oxidative stress acquire the capacity to exclude intracellular 4HNE at a faster rate by inducing GSTA4-4 which conjugates 4HNE to glutathione (GSH), and RLIP76 which mediates the ATP-dependent transport of the GSH-conjugate of 4HNE (GS-HNE). The balance between formation and exclusion promotes different cellular processes - higher concentrations of 4HNE promote apoptosis; whereas, lower concentrations promote proliferation. In this article, we provide a brief summary of the cellular effects of 4HNE, followed by a review of its GST-catalyzed detoxification, with an emphasis on the structural attributes that play an important role in the interactions with alpha-class GSTA4-4. Taken together, 4HNE is a key signaling molecule and that GSTs being determinants of its intracellular concentrations, can regulate stress-mediated signaling, are reviewed in this article.

Epsilon glutathione transferases possess a unique class-conserved subunit interface motif that directly interacts with glutathione in the active site

Epsilon class glutathione transferases (GSTs) have been shown to contribute significantly to insecticide resistance. We report a new Epsilon class protein crystal structure from Drosophila melanogaster for the glutathione transferase DmGSTE6. The structure reveals a novel Epsilon clasp motif that is conserved across hundreds of millions of years of evolution of the insect Diptera order. This histidine-serine motif lies in the subunit interface and appears to contribute to quaternary stability as well as directly connecting the two glutathiones in the active sites of this dimeric enzyme.

Cytotoxic and Antitumor Activity of Sulforaphane: The Role of Reactive Oxygen Species

According to recent estimates, cancer continues to remain the second leading cause of death and is becoming the leading one in old age. Failure and high systemic toxicity of conventional cancer therapies have accelerated the identification and development of innovative preventive as well as therapeutic strategies to contrast cancer-associated morbidity and mortality. In recent years, increasing body of in vitro and in vivo studies has underscored the cancer preventive and therapeutic efficacy of the isothiocyanate sulforaphane. In this review article, we highlight that sulforaphane cytotoxicity derives from complex, concurring, and multiple mechanisms, among which the generation of reactive oxygen species has been identified as playing a central role in promoting apoptosis and autophagy of target cells. We also discuss the site and the mechanism of reactive oxygen species' formation by sulforaphane, the toxicological relevance of sulforaphane-formed reactive oxygen species, and the death pathways triggered by sulforaphane-derived reactive oxygen species.

Perinatal low-protein diet alters brainstem antioxidant metabolism in adult offspring

BACKGROUND AND OBJECTIVES

Studies in humans and animal models have established a close relationship between early environment insult and subsequent risk of development of non-communicable diseases, including the cardiovascular. Whereas experimental evidences highlight the early undernutrition and the late cardiovascular disease relation, the central mechanisms linking the two remain unknown. Owing to the oxidative balance influence in several pathologies, the aim of the present study was to evaluate the effects of maternal undernutrition (i.e. a low-protein (LP) diet) on oxidative balance in the brainstem.

METHODS AND RESULTS

Male rats from mothers fed with an LP diet (8% casein) throughout the perinatal period (i.e. gestation and lactation) showed 10× higher lipid peroxidation levels than animals treated with normoprotein (17% casein) at 100 days of age. In addition, we observed the following reductions in enzymatic activities: superoxide dismutase, 16%; catalase, 30%; glutathione peroxidase, 34%; glutathione-S-transferase, 51%; glutathione reductase, 23%; glucose-6-phosphate dehydrogenase, 31%; and in non-enzymatic glutathione system, 46%.

DISCUSSION

This study is the first to focus on the role of maternal LP nutrition in oxidative balance in a central nervous system structure responsible for cardiovascular control in adult rats. Our data observed changes in oxidative balance in the offspring, therefore, bring a new concept related to early undernutrition and can help in the development of a new clinical strategy to combat the effects of nutritional insult. Wherein the central oxidative imbalance is a feasible mechanism underlying the hypertension risk in adulthood triggered by maternal LP diet.

NADP(+)-dependent dehydrogenase activity of carbonyl reductase on glutathionylhydroxynonanal as a new pathway for hydroxynonenal detoxification

An NADP(+)-dependent dehydrogenase activity on 3-glutathionyl-4-hydroxynonanal (GSHNE) was purified to electrophoretic homogeneity from a line of human astrocytoma cells (ADF). Proteomic analysis identified this enzymatic activity as associated with carbonyl reductase 1 (EC 1.1.1.184). The enzyme is highly efficient at catalyzing the oxidation of GSHNE (KM 33 µM, kcat 405 min(-1)), as it is practically inactive toward trans-4-hydroxy-2-nonenal (HNE) and other HNE-adducted thiol-containing amino acid derivatives. Combined mass spectrometry and nuclear magnetic resonance spectroscopy analysis of the reaction products revealed that carbonyl reductase oxidizes the hydroxyl group of GSHNE in its hemiacetal form, with the formation of the corresponding 3-glutathionylnonanoic-δ-lactone. The relevance of this new reaction catalyzed by carbonyl reductase 1 is discussed in terms of HNE detoxification and the recovery of reducing power.

Identification of candidate odorant degrading gene/enzyme systems in the antennal transcriptome of Drosophila melanogaster

The metabolism of volatile signal molecules by odorant degrading enzymes (ODEs) is crucial to the ongoing sensitivity and specificity of chemoreception in various insects, and a few specific esterases, cytochrome P450s, glutathione S-transferases (GSTs) and UDP-glycosyltransferases (UGTs) have previously been implicated in this process. Significant progress has been made in characterizing ODEs in Lepidoptera but very little is known about them in Diptera, including in Drosophila melanogaster, a major insect model. We have therefore carried out a transcriptomic analysis of the antennae of D. melanogaster in order to identify candidate ODEs. Virgin male and female and mated female antennal transcriptomes were determined by RNAseq. As with the Lepidoptera, we found that many esterases, cytochrome P450 enzymes, GSTs and UGTs are expressed in D. melanogaster antennae. As olfactory genes generally show selective expression in the antennae, a comparison to previously published transcriptomes for other tissues has been performed, showing preferential expression in the antennae for one esterase, JHEdup, one cytochrome P450, CYP308a1, and one GST, GSTE4. These largely uncharacterized enzymes are now prime candidates for ODE functions. JHEdup was expressed heterologously and found to have high catalytic activity against a chemically diverse group of known ester odorants for this species. This is a finding consistent with an ODE although it might suggest a general role in clearing several odorants rather than a specific role in clearing a particular odorant. Our findings do not preclude the possibility of odorant degrading functions for other antennally expressed esterases, P450s, GSTs and UGTs but, if so, they suggest that these enzymes also have additional functions in other tissues.

Glutathione-binding site of a bombyx mori theta-class glutathione transferase

The glutathione transferase (GST) superfamily plays key roles in the detoxification of various xenobiotics. Here, we report the isolation and characterization of a silkworm protein belonging to a previously reported theta-class GST family. The enzyme (bmGSTT) catalyzes the reaction of glutathione with 1-chloro-2,4-dinitrobenzene, 1,2-epoxy-3-(4-nitrophenoxy)-propane, and 4-nitrophenethyl bromide. Mutagenesis of highly conserved residues in the catalytic site revealed that Glu66 and Ser67 are important for enzymatic function. These results provide insights into the catalysis of glutathione conjugation in silkworm by bmGSTT and into the metabolism of exogenous chemical agents.

An integrated medical treatment for type-2 diabetes

This paper tries to emphasize two relevant concepts: the first is that type 2 diabetes is a chronic diseases characterized by both a dysmetabolism and a chronic oxidative stress. A variety of orthodox drugs are somewhat able to correct the metabolic alterations, but do not deal with the chronic inflammation. Consequently, as the validity of precisely treating blood with therapeutic ozone concentrations in restoring a redox homeostasis has been now demonstrated, the integration of ozone therapy appears essential for a rational treatment of type 2 diabetes. Such a combination may be able to reduce the diabetic epidemic.

Cell death and diseases related to oxidative stress: 4-hydroxynonenal (HNE) in the balance

During the last three decades, 4-hydroxy-2-nonenal (HNE), a major α,β-unsaturated aldehyde product of n-6 fatty acid oxidation, has been shown to be involved in a great number of pathologies such as metabolic diseases, neurodegenerative diseases and cancers. These multiple pathologies can be explained by the fact that HNE is a potent modulator of numerous cell processes such as oxidative stress signaling, cell proliferation, transformation or cell death. The main objective of this review is to focus on the different aspects of HNE-induced cell death, with a particular emphasis on apoptosis. HNE is a special apoptotic inducer because of its abilities to form protein adducts and to propagate oxidative stress. It can stimulate intrinsic and extrinsic apoptotic pathways and interact with typical actors such as tumor protein 53, JNK, Fas or mitochondrial regulators. At the same time, due to its oxidant status, it can also induce some cellular defense mechanisms against oxidative stress, thus being involved in its own detoxification. These processes in turn limit the apoptotic potential of HNE. These dualities can imbalance cell fate, either toward cell death or toward survival, depending on the cell type, the metabolic state and the ability to detoxify.

Catalytic function of an ε-class glutathione S-transferase of the silkworm

The glutathione S-transferase (GST) superfamily is involved in the detoxification of various xenobiotics. A silkworm GST, belonging to a previously reported Epsilon-class GST family, was identified, named bmGSTE, cloned, and produced in Escherichia coli. Investigation of this enzyme's properties showed that it was able to catalyse glutathione (GSH) with 1-chloro-2,4-dinitrobenzene and ethacrynic acid, and also that it possessed GSH-dependent peroxidase activity. The enzyme's highly conserved amino acid residues, including Ser11, His53, Val55, Ser68 and Arg112, were of interest regarding their possible involvement in its catalytic activity. These residues were replaced with alanine by site-directed mutagenesis and subsequent kinetic analysis of bmGSTE mutants indicated that His53, Val55, and Ser68 were important for enzyme function.

4-Hydroxynonenal induces G2/M phase cell cycle arrest by activation of the ataxia telangiectasia mutated and Rad3-related protein (ATR)/checkpoint kinase 1 (Chk1) signaling pathway

4-Hydroxynonenal (HNE) has been widely implicated in the mechanisms of oxidant-induced toxicity, but the detrimental effects of HNE associated with DNA damage or cell cycle arrest have not been thoroughly studied. Here we demonstrate for the first time that HNE caused G2/M cell cycle arrest of hepatocellular carcinoma HepG2 (p53 wild type) and Hep3B (p53 null) cells that was accompanied with decreased expression of CDK1 and cyclin B1 and activation of p21 in a p53-independent manner. HNE treatment suppressed the Cdc25C level, which led to inactivation of CDK1. HNE-induced phosphorylation of Cdc25C at Ser-216 resulted in its translocation from nucleus to cytoplasm, thereby facilitating its degradation via the ubiquitin-mediated proteasomal pathway. This phosphorylation of Cdc25C was regulated by activation of the ataxia telangiectasia and Rad3-related protein (ATR)/checkpoint kinase 1 (Chk1) pathway. The role of HNE in the DNA double strand break was strongly suggested by a remarkable increase in comet tail formation and H2A.X phosphorylation in HNE-treated cells in vitro. This was supported by increased in vivo phosphorylation of H2A.X in mGsta4 null mice that have impaired HNE metabolism and increased HNE levels in tissues. HNE-mediated ATR/Chk1 signaling was inhibited by ATR kinase inhibitor (caffeine). Additionally, most of the signaling effects of HNE on cell cycle arrest were attenuated in hGSTA4 transfected cells, thereby indicating the involvement of HNE in these events. A novel role of GSTA4-4 in the maintenance of genomic integrity is also suggested.

Emerging treatments in lung cancer - targeting the RLIP76 molecular transporter

Multidrug resistance in lung cancer cells is a significant obstacle in the treatment of lung cancer. Resistance to chemotherapeutic agents is often the result of efflux of the drugs from cancer cells, mediated by adenosine triphosphate (ATP)-dependent drug transport across the plasma membrane. Thus, identifying molecular targets in the cancer cell transport machinery could be a key factor in successful combinatorial therapy, along with chemotherapeutic drugs. The transport protein Ral-interacting protein of 76 kDa (RLIP76), also known as Ral-binding protein 1 (RalBP1), is a highly promising target for lung cancer treatment. RLIP76 is an ATP-dependent non-ATP-binding cassette (ABC) transporter, responsible for the major transport function in many cells, including many cancer cell lines, causing efflux of glutathione-electrophile conjugates of both endogenous metabolites and environmental toxins. RLIP76 is expressed in most human tissues, and is overexpressed in non-small-cell lung cancer cell lines and in many tumor types. The blockade of RLIP76 by various approaches has been shown to increase the sensitivity to radiation and chemotherapeutic drugs, and leads to apoptosis in cells. In xenograft tumor models in mice, RLIP76 blockade or depletion results in complete and sustained regression across many cancer cell types, including lung cancer cells. In addition to its transport function, RLIP76 has many other cellular and physiological functions based on its domain structure, which includes a unique Ral-binding domain and a Rho GTPase activating protein (RhoGAP)-catalytic domain as well as docking sites for multiple signaling proteins. As a Ral effector, RhoGAP, and adapter protein, RLIP76 has been shown to play important roles in endocytosis, mitochondrial fission, cell spreading and migration, actin dynamics during gastrulation, and Ras-induced tumorigenesis. Additionally, RLIP76 is also important for stromal cell function in tumors, as it was recently shown to be required for efficient endothelial cell function and angiogenesis in solid tumors. However, RLIP76 knockout mice are viable, and blockade effects appear to be selective for implanted tumors in mice, suggesting the possibility that RLIP76-targeting drugs may be successful in clinical trials. In this review, we outline the many cellular and physiological functions of RLIP76 in normal and cancer cells, and discuss the potential for RLIP76-based therapeutics in lung cancer treatment.

Glutathione-s-transferases as determinants of cell survival and death

SIGNIFICANCE

The family of glutathione S-transferases (GSTs) is part of a cellular Phase II detoxification program composed of multiple isozymes with functional human polymorphisms that have the capacity to influence individual response to drugs and environmental stresses. Catalytic activity is expressed through GST dimer-mediated thioether conjugate formation with resultant detoxification of a variety of small molecule electrophiles.

RECENT ADVANCES

More recent work indicates that in addition to the classic catalytic functions, specific GST isozymes have other characteristics that impact cell survival pathways in ways unrelated to detoxification. These characteristics include the following: regulation of mitogen-activated protein kinases; facilitation of the addition of glutathione to cysteine residues in certain proteins (S-glutathionylation); as a novel cellular partner of the human papilloma virus-16 E7 oncoprotein playing a pivotal role in preventing cell death in infected human cells; mitogenic influence in myeloproliferative pathways; participant in the process of cocaine addiction.

CRITICAL ISSUES

Some of these functions have provided a platform for targeting GST with novel small molecule therapeutics, particularly in cancer where evidence of clinical applications is emerging.

FUTURE DIRECTIONS

Our evolving understanding of the GST superfamily and their divergent expression patterns in individuals make them attractive candidates for translational studies in a variety of human pathologies. In addition, their role in regulating cell fate in signaling and cell death pathways has opened up a significant functional complexity that extends well beyond standard detoxification reactions.

Anti-oxidative stress regulator NF-E2-related factor 2 mediates the adaptive induction of antioxidant and detoxifying enzymes by lipid peroxidation metabolite 4-hydroxynonenal

BACKGROUND

NF-E2-related factor 2 (NRF2) regulates a battery of antioxidative and phase II drug metabolizing/detoxifying genes through binding to the antioxidant response elements (ARE). NRF2-ARE signaling plays a central role in protecting cells from a wide spectrum of reactive toxic species including reactive oxygen/nitrogen species (RONS). 4-hydroxylnonenal (4-HNE) is a major end product from lipid peroxidation of omega-6 polyunsaturated fatty acids (PUFA) induced by oxidative stress, and it is highly reactive to nucleophilic sites in DNA and proteins, causing cytotoxicity and genotoxicity. In this study, we examined the role of NRF2 in regulating the 4-HNE induced gene expression of antioxidant and detoxifying enzymes.

RESULTS

When HeLa cells were treated with 4-HNE, NRF2 rapidly transloated into the nucleus, as determined by the distribution of NRF2 tagged with the enhanced green fluorescent protein (EGFP) and increased NRF2 protein in the nuclear fraction. Transcriptional activity of ARE-luciferase was significantly induced by 0.01-10 μM of 4-HNE in a dose-dependent manner, and the induction could be blocked by pretreatment with glutathione (GSH). 4-HNE induced transcriptional expression of glutathione S-transferase (GST) A4, aldoketone reductase (AKR) 1C1 and heme oxygenase-1 (HO-1), and the induction was attenuated by knocking down NRF2 using small interfering RNA.

CONCLUSIONS

NRF2 is critical in mediating 4-HNE induced expression of antioxidant and detoxifying genes. This may account for one of the major cellular defense mechanisms against reactive metabolites of lipids peroxidation induced by oxidative stress and protect cells from cytotoxicity.

Protein carbonylation and metabolic control systems

Oxidative stress is linked to the production of reactive lipid aldehydes that non-enzymatically alkylate cysteine, histidine, or lysine residues in a reaction termed protein carbonylation. Reactive lipid aldehydes and their derivatives are detoxified via a variety of phase I and phase II systems, and when antioxidant defenses are compromised or oxidative conditions are increased, protein carbonylation is increased. The resulting modification has been implicated as causative in a variety of metabolic states including neurodegeneration, muscle wasting, insulin resistance, and aging. Although such modifications usually result in loss of protein function, protein carbonylation may be regulatory and activate signaling pathways involved in antioxidant biology and cellular homeostasis.

Role of 4-hydroxynonenal in chemopreventive activities of sulforaphane

Chemoprevention of cancer via herbal and dietary supplements is a logical approach to combating cancer and currently it is an attractive area of research investigation. Over the years, isothiocyanates, such as sulforaphane (SFN) found in cruciferous vegetables, have been advocated as chemopreventive agents, and their efficacy has been demonstrated in cell lines and animal models. In vivo studies with SFN suggest that in addition to protecting normal healthy cells from environmental carcinogens, it also exhibits cytotoxicity and apoptotic effects against various cancer cell types. Among several mechanisms for the chemopreventive activity of SFN against chemical carcinogenesis, its effect on drug-metabolizing enzymes that cause activation/neutralization of carcinogenic metabolites is well established. Recent studies suggest that SFN exerts its selective cytotoxicity to cancer cells via reactive oxygen species-mediated generation of lipid peroxidation products, particularly 4-hydroxynonenal (HNE). Against the background of the known biochemical effects of SFN on normal and cancer cells, in this article we review the underlying molecular mechanisms responsible for the overall chemopreventive effects of SFN, focusing on the role of HNE in these mechanisms, which may also contribute to its selective cytotoxicity to cancer cells.

How a calculated oxidative stress can yield multiple therapeutic effects

It is proposed to discuss how ozonetherapy acts on patients affected by vascular and degenerative diseases. Ozone is a strong oxidant but, if used in small dosages on human blood ex vivo, acts as an acceptable stressor. By instantly reacting with PUFA bound to albumin, ozone is entirely consumed but generates two messengers acting in an early and in a late phase: the former is due to hydrogen peroxide, which triggers biochemical pathways on blood cells and the latter is due to alkenals which are infused into the donor patient. After undergoing a partial catabolism, alkenals enter into a great number of body's cells, where they react with Nrf2-Keap1 protein: the transfer of activated Nrf2 into the nucleus and its binding to antioxidant response element (ARE) is the crucial event able to upregulate the synthesis of antioxidant proteins, phase II enzymes and HO-1. With the progress of ozonetherapy, these protective enzymes are able to reverse the oxidative stress induced by chronic inflammation. Consequently, the repetition of graduated stresses induces a multiform adaptive response able to block the progress of the disease and to improve the quality of life.

Ozone: a new therapeutic agent in vascular diseases

In this article, we scientifically evaluate the bio-oxidative procedure known as oxygen-ozone therapy. Research over a decade has established a comprehensive framework for understanding and recommending this type of autohemotherapy in vascular diseases. In contrast, a non-specific immunomodulation therapy, using heavily oxidized and denatured blood, has been recently used in studies involving a total of approximately 3000 patients and has led to 'disappointing' results. Such a treatment appears to be an inappropriate example of the so-called minor autohemotherapy, and its poor outcomes may discourage any further studies. Therefore it appears necessary to clarify that the use of only a minimal ozone dose and a valid experimental protocol is likely to produce beneficial results. Millions of people suffer from chronic limb, brain, and heart ischemia, and such patients may benefit if appropriate ozone therapy could be implemented. Accordingly, we propose the need for a well designed, multicenter, clinical trial to be conducted.

A preliminary characterization of the cytosolic glutathione transferase proteome from Drosophila melanogaster

The cytosolic GST (glutathione transferase) superfamily has been annotated in the Drosophila melanogaster genome database. Of 36 genes, four undergo alternative splicing to yield a total of 41 GST proteins. In the present study, we have obtained the 41 transcripts encoding proteins by RT (reverse transcription)-PCR using RNA template from Drosophila S2 cells, an embryonic cell line. This observation suggests that all of the annotated DmGSTs (D. melanogaster GSTs) in the proteome are expressed in the late embryonic stages of D. melanogaster. To avoid confusion in naming these numerous DmGSTs, we have designated them following the universal GST nomenclature as well as previous designations that fit within this classification. Furthermore, in the cell line, we identified an apparent processed pseudogene, gste8, in addition to two isoforms from the Delta class that have been published previously. Only approximately one-third of the expressed DmGSTs could be purified by conventional GSH affinity chromatography. The diverse kinetic properties as well as physiological substrate specificity of the DmGSTs are such that each individual enzyme displayed a unique character even compared with members from the same class.

Reliable and effective oxygen-ozone therapy at a crossroads with ozonated saline infusion and ozone rectal insufflation

OBJECTIVES

This review aims to highlight the advantages and safety of oxygen-ozone therapy (OOT) and to suggest ways to enhance its acceptance.

KEY FINDINGS

The treatment of a herniated disk by injecting a gaseous oxygen-ozone mixture inside the nucleus pulposus is a great clinical success. However, the use of OOT lags for a number of reasons, including lack of standardization, the need for numerous treatments, lack of knowledge and even denial. Anecdotally, several million treatments by OOT have been performed worldwide indicating its usefulness, mainly in peripheral arterial diseases and age-related macular degeneration. The scepticism that accompanies the systemic use of ozone can only be overcome by demonstrating the validity of OOT in controlled and randomized clinical trials. Cheaper and quicker methods, such as ozonating physiological saline with successive infusion as well as ozone rectal insufflations, are becoming popular, however, such alternative procedures are erratic, unstable and liable to be toxic, with deleterious consequences, and are likely to discredit the beneficial use of ozone.

SUMMARY

The approval of ozone in terms of both therapeutic efficacy and safety will depend on the results achieved by authoritative clinical trials.

Mechanisms of Action Involved in Ozone Therapy: Is healing induced via a mild oxidative stress?

The potential mechanisms of action of ozone therapy are reviewed in this paper. The therapeutic efficacy of ozone therapy may be partly due the controlled and moderate oxidative stress produced by the reactions of ozone with several biological components. The line between effectiveness and toxicity of ozone may be dependent on the strength of the oxidative stress. As with exercise, it is well known that moderate exercise is good for health, whereas excessive exercise is not.Severe oxidative stress activates nuclear transcriptional factor kappa B (NFκB), resulting in an inflammatory response and tissue injury via the production of COX2, PGE2, and cytokines. However, moderate oxidative stress activates another nuclear transcriptional factor, nuclear factor-erythroid 2-related factor 2 (Nrf2). Nrf2 then induces the transcription of antioxidant response elements (ARE). Transcription of ARE results in the production of numerous antioxidant enzymes, such as SOD, GPx, glutathione-s-transferase(GSTr), catalase (CAT), heme-oxygenase-1 (HO-1), NADPH-quinone-oxidoreductase (NQO-1), phase II enzymes of drug metabolism and heat shock proteins (HSP). Both free antioxidants and anti-oxidative enzymes not only protect cells from oxidation and inflammation but they may be able to reverse the chronic oxidative stress. Based on these observations, ozone therapy may also activate Nrf2 via moderate oxidative stress, and suppress NFκB and inflammatory responses. Furthermore, activation of Nrf2 results in protection against neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Mild immune responses are induced via other nuclear transcriptional factors, such as nuclear factor of activated T-cells (NFAT) and activated protein-1 (AP-1).Additionally, the effectiveness of ozone therapy in vascular diseases may also be explained by the activation of another nuclear transcriptional factor, hypoxia inducible factor-1α (HIF-1a), which is also induced via moderate oxidative stress. Recently these concepts have become widely accepted. The versatility of ozone in treating vascular and degenerative diseases as well as skin lesions, hernial disc and primary root carious lesions in children is emphasized. Further researches able to elucidate whether the mechanisms of action of ozone therapy involve nuclear transcription factors, such as Nrf2, NFAT, AP-1, and HIF-1α are warranted.

Modulation of aldehyde dehydrogenase activity affects (±)-4-hydroxy-2E-nonenal (HNE) toxicity and HNE-protein adduct levels in PC12 cells

Oxidative stress is known to be one of the major factors underlying Parkinson's disease (PD). One of the consequences of oxidative stress is lipid peroxidation. A toxic product of lipid peroxidation, (±)-4-hydroxy-2E-nonenal (HNE) leads to membrane disruption and formation of HNE-protein adducts and such adducts have been detected in PD brain tissues. Aldehyde dehydrogenases (ALDHs) are involved in metabolizing HNE and other endogenous aldehydes. Interestingly, the cytosolic aldehyde dehydrogenase 1A1 (ALDH1A1) has been reported to be down-regulated in brain tissues affected in PD which could result in enhancement of HNE toxicity. We sought to first establish the role of ALDH1A1 in mediating HNE toxicity in PC12 cells by overexpressing ALDH1A1 and by using disulfiram, an ALDH inhibitor. Overexpression and inhibition of ALDH1A1 activity resulted in reduced and increased HNE toxicity, respectively. We then established conditions for detecting HNE-protein adducts following HNE treatment and showed that overexpression and inhibition of ALDH activity resulted in reduced and increased formation of HNE-protein adducts, respectively. We also show that 6-methyl-2-(phenylazo)-3-pyridinol, previously identified as an activator of ALDH1A1, can protect PC12 cells against HNE-mediated toxicity and can cause a small but significant decrease in levels of HNE-protein adducts. Our results should encourage identification of more potent ALDH activators and their testing in the PC12-HNE model. Such cytoprotective compounds could then be tested for their neuroprotective activity in in vivo models of oxidative stress-induced PD.

N-acetylcysteine reduces markers of differentiation in 3T3-L1 adipocytes

Oxidative stress plays a critical role in the pathogenesis of diabetes, hypertension and atherosclerosis. Some authors reported that fat accumulation correlates to systemic oxidative stress in humans and mice, but the relationship of lipid production and oxidative metabolism is still unclear. In our laboratory we used 3T3-L1 preadipocytes, which are able to differentiate into mature adipocytes and accumulate lipids, as obesity model. We showed that intracellular reactive oxygen species (ROS) and antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities increased in parallel with fat accumulation. Meanwhile N-acetylcysteine (NAC), a well known antioxidant and Glutathione (GSH) precursor, inhibited ROS levels as well as fat accumulation in a concentration-dependent manner. NAC also inhibited both adipogenic transcription factors CCAAT/enhancer binding protein beta (C/EBP β) and peroxisomal proliferator activated receptor gamma (PPAR γ) expression; we suggested that intracellular GSH content could be responsible for these effects.

The Role of PPAR Ligands in Controlling Growth-Related Gene Expression and their Interaction with Lipoperoxidation Products

Peroxisome proliferators-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear hormone receptor superfamily. The three PPAR isoforms (α, γ and β/δ) have been found to play a pleiotropic role in cell fat metabolism. Furthermore, in recent years, evidence has been found regarding the antiproliferative, proapoptotic, and differentiation-promoting activities displayed by PPAR ligands, particularly by PPARγ ligands. PPAR ligands affect the expression of different growth-related genes through both PPAR-dependent and PPAR-independent mechanisms. Moreover, an interaction between PPAR ligands and other molecules which strengthen the effects of PPAR ligands has been described. Here we review the action of PPAR on the control of gene expression with particular regard to the effect of PPAR ligands on the expression of genes involved in the regulation of cell-cycle, differentiation, and apoptosis. Moreover, the interaction between PPAR ligands and 4-hydroxynonenal (HNE), the major product of the lipid peroxidation, has been reviewed.

Ozone acting on human blood yields a hormetic dose-response relationship

The aim of this paper is to analyze why ozone can be medically useful when it dissolves in blood or in other biological fluids. In reviewing a number of clinical studies performed in Peripheral Arterial Diseases (PAD) during the last decades, it has been possible to confirm the long-held view that the inverted U-shaped curve, typical of the hormesis concept, is suitable to represent the therapeutic activity exerted by the so-called ozonated autohemotherapy. The quantitative and qualitative aspects of human blood ozonation have been also critically reviewed in regard to the biological, therapeutic and safety of ozone. It is hoped that this gas, although toxic for the pulmonary system during prolonged inhalation, will be soon recognized as a useful agent in oxidative-stress related diseases, joining other medical gases recently thought to be of therapeutic importance. Finally, the elucidation of the mechanisms of action of ozone as well as the obtained results in PAD may encourage clinical scientists to evaluate ozone therapy in vascular diseases in comparison to the current therapies.

Oxygen/ozone as a medical gas mixture. A critical evaluation of the various methods clarifies positive and negative aspects

Besides oxygen, several other gases such as NO, CO, H₂, H₂S, Xe and O₃ have come to age over the past few years. With regards to O₃, its mechanisms of action in medicine have been clarified during the last two decades so that now a comprehensive framework for understanding and recommending ozone therapy in various pathologies is available. O₃ used within the determined therapeutic window is absolutely safe and more effective than golden standard medications in numerous pathologies, like vascular diseases. However, ozone therapy is mostly in practitioners' hands and some recent developments for increasing cost effectiveness and speed of treatment are neither standardized, nor evaluated toxicologically. Hence, the aim of this article is to emphasize the need to objectively assess the pros and cons of oxygen/ozone as a medical gas mixture in the hope that ozone therapy will be accepted by orthodox medicine in the near future.

Clair DK. p53 Regulates oxidative stress-mediated retrograde signaling: a novel mechanism for chemotherapy-induced cardiac injury

The side effects of cancer therapy on normal tissues limit the success of therapy. Generation of reactive oxygen species (ROS) has been implicated for numerous chemotherapeutic agents including doxorubicin (DOX), a potent cancer chemotherapeutic drug. The production of ROS by DOX has been linked to DNA damage, nuclear translocation of p53, and mitochondrial injury; however, the causal relationship and molecular mechanisms underlying these events are unknown. The present study used wild-type (WT) and p53 homozygous knock-out (p53^−/−) mice to investigate the role of p53 in the crosstalk between mitochondria and nucleus. Injecting mice with DOX (20 mg/kg) causes oxidative stress in cardiac tissue as demonstrated by immunogold analysis of the levels of 4-hydroxy-2′-nonenal (4HNE)-adducted protein, a lipid peroxidation product bound to proteins. 4HNE levels increased in both nuclei and mitochondria of WT DOX-treated mice but only in nuclei of DOX-treated p53^(−/−) mice, implicating a critical role for p53 in causing DOX-induced oxidative stress in mitochondria. The stress-activated protein c-Jun amino-terminal kinase (JNKs) was activated in response to increased 4HNE in WT mice but not p53^(−/−) mice receiving DOX treatment, as determined by co-immunoprecipitation of HNE and pJNK. The activation of JNK in DOX treated WT mice was accompanied by Bcl-2 dissociation from Beclin in mitochondria and induction of type II cell death (autophagic cell death), as evidenced by an increase in LC3-I/LC-3-II ratio and γ-H2AX, a biomarker for DNA damage. The absence of p53 significantly reduces mitochondrial injury, assessed by quantitative morphology, and decline in cardiac function, assessed by left ventricular ejection fraction and fraction shortening. These results demonstrate that p53 plays a critical role in DOX-induced cardiac toxicity, in part, by the induction of oxidative stress mediated retrograde signaling.

Interactions of glutathione transferases with 4-hydroxynonenal

Electrophilic products of lipid peroxidation are important contributors to the progression of several pathological states. The prototypical α,β-unsaturated aldehyde, 4-hydroxynonenal (HNE), triggers cellular events associated with oxidative stress, which can be curtailed by the glutathione-dependent elimination of HNE. The glutathione transferases (GSTs) are a major determinate of the intracellular concentration of HNE and can influence susceptibility to toxic effects, particularly when HNE and GST levels are altered in disease states. In this article, we provide a brief summary of the cellular effects of HNE, followed by a review of its GST-catalyzed detoxification, with an emphasis on the structural attributes that play an important role in the interactions with alpha-class GSTs. Some of the key determining characteristics that impart high alkenal activity reside in the unique C-terminal interactions of the GSTA4-4 enzyme. Studies encompassing both kinetic and structural analyses of related isoforms will be highlighted, with additional attention to stereochemical aspects that demonstrate the capacity of GSTA4-4 to detoxify both enantiomers of the biologically relevant racemic mixture while generating a select set of diastereomeric products with subsequent implications. A summary of the literature that examines the interplay between GSTs and HNE in model systems relevant to oxidative stress will also be discussed to demonstrate the magnitude of importance of GSTs in the overall detoxification scheme.

Mechanisms of 4-hydroxy-2-nonenal induced pro- and anti-apoptotic signaling

In recent years, 4-hydroxy-2-nonenal (4-HNE) has emerged as an important second messenger in cell cycle signaling. Here, we demonstrate that 4-HNE induces signaling for apoptosis via both the Fas-mediated extrinsic and the p53-mediated intrinsic pathways in HepG2 cells. 4-HNE induces a Fas-mediated DISC independent apoptosis pathway by activating ASK1, JNK, and caspase-3. Parallel treatment of 4-HNE to HepG2 cells also induces apoptosis by the p53 pathway through activation of Bax, p21, JNK, and caspase-3. Exposure of HepG2 cells to 4-HNE leads to the activation of both Fas and Daxx, promotes the export of Daxx from the nucleus to cytoplasm, and facilitates Fas-Daxx binding. Depletion of Daxx by siRNA results in the potentiation of apoptosis, indicating that Fas-Daxx binding in fact is inhibitory to Fas-mediated apoptosis in cells. 4-HNE-induced translocation of Daxx is also accompanied by the activation and nuclear accumulation of HSF1 and up-regulation of heat shock protein Hsp70. All these effects of 4-HNE in cells can be attenuated by ectopic expression of hGSTA4-4, the isozyme of glutathione S-transferase with high activity for 4-HNE. Through immunoprecipitation and liquid chromatography-tandem mass spectrometry, we have demonstrated the covalent binding of 4-HNE to Daxx. We also demonstrate that 4-HNE modification induces phosphorylation of Daxx at Ser668 and Ser671 to facilitate its cytoplasmic export. These results indicate that while 4-HNE exhibits toxicity through several mechanisms, in parallel it evokes signaling for defense mechanisms to self-regulate its toxicity and can simultaneously affect multiple signaling pathways through its interactions with membrane receptors and transcription factors/repressors.

NGF induced differentiated PC12 cells as in vitro tool to study 4-hydroxynonenal induced cellular damage

Investigations were carried out to examine the suitability of PC12 cells as an in vitro tool to examine 4-hydroxynonenal (4-HNE)-induced toxicity in nervous tissue. On day 8 of differentiation, markers of neural effects and oxidative stress were measured following exposure of PC12 cells to 1-50 microM 4-HNE for 1-8h. Endpoints included dopamine DA-D(2) receptor and glutathione S-transferase (GSTP1-1) protein levels, 4-HNE-protein binding, glutathione (GSH) concentrations and intracellular calcium levels. GSH levels were maximally depleted after 4h. 4-HNE also induced depletion of GSTP1-1 and increased intracellular Ca(++), with the latter seen as early as 1h after exposure. Responses at 8h were not greater than responses at earlier times. The experiments suggest that PC12 cells could be an in vitro tool for understanding toxicant-cell interactions, especially those that result in oxidative stress.