Detoxification Of Reactive Aldehydes Research Articles

A novel aldo-keto reductase gene, OsAKR1, from rice confers higher tolerance to cadmium stress in rice by an in vivo reactive aldehyde detoxification

Elevated levels of cadmium (Cd) have the ability to impede plant development. Aldo-keto reductases (AKRs) have been demonstrated in a number of plant species to improve tolerance to a variety of abiotic stresses by scavenging cytotoxic aldehydes; however, only a few AKRs have been identified to improve Cd tolerance. The OsAKR1 gene was extracted and identified from rice here. After being exposed to Cd, the expression of OsAKR1 dramatically rose in both roots and shoots, although more pronounced in roots. According to a subcellular localization experiment, the nucleus and cytoplasm are where OsAKR1 is primarily found. Mutants lacking OsAKR1 exhibited Cd sensitive phenotype than that of the wild-type (WT) Nipponbare (Nip), and osakr1 mutants exhibited reduced capacity to scavenge methylglyoxal (MG). Furthermore, osakr1 mutants exhibited considerably greater hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels, and increased catalase (CAT) activity in comparison to Nip. The expression of three isomeric forms of CAT was found to be considerably elevated in osakr1 mutants during Cd stress, as demonstrated by quantitative real-time PCR analysis, when compared to Nip. These results imply that OsAKR1 controlled rice's ability to withstand Cd by scavenging harmful aldehydes and turning on the reactive oxygen species (ROS) scavenging mechanism.

Mitochondrial aldehyde dehydrogenase-2 coordinates the hydrogen sulfide - AMPK axis to attenuate high glucose-induced pancreatic β-cell dysfunction by glutathione antioxidant system

Progression of β-cell loss in diabetes mellitus is significantly influenced by persistent hyperglycemia. At the cellular level, a number of signaling cascades affect the expression of apoptotic genes, ultimately resulting in β-cell failure; these cascades have not been elucidated. Mitochondrial aldehyde dehydrogenase-2 (ALDH2) plays a central role in the detoxification of reactive aldehydes generated from endogenous and exogenous sources and protects against mitochondrial deterioration in cells. Here we report that under diabetogenic conditions, ALDH2 is strongly inactivated in β-cells through CDK5-dependent glutathione antioxidant imbalance by glucose-6-phosphate dehydrogenase (G6PD) degradation. Intriguingly, CDK5 inhibition strengthens mitochondrial antioxidant defense through ALDH2 activation. Mitochondrial ALDH2 activation selectively preserves β-cells against high-glucose-induced dysfunction by activating AMPK and Hydrogen Sulfide (H2S) signaling. This is associated with the stabilization and enhancement of the activity of G6PD by SIRT2, a cytoplasmic NAD+-dependent deacetylase, and is thereby linked to an elevation in the GSH/GSSG ratio, which leads to the inhibition of mitochondrial dysfunction under high-glucose conditions. Furthermore, treatment with NaHS, an H2S donor, selectively preserves β-cell function by promoting ALDH2 activity, leading to the inhibition of lipid peroxidation by high-glucose concentrations. Collectively, our results provide the first direct evidence that ALDH2 activation enhances H2S-AMPK-G6PD signaling, leading to improved β-cell function and survival under high-glucose conditions via the glutathione redox balance.

Repurposing of Strychnine as the Potential Inhibitors of Aldo-keto Reductase Family 1 Members B1 and B10: Computational Modeling and Pharmacokinetic Analysis.

AKR1B1 and AKR1B10 are important members of aldo-keto reductase family which plays a significant role in cancer progression by modulating cellular metabolism. These enzymes are involved in various metabolic processes, including the synthesis and metabolism of hormones, detoxification of reactive aldehydes, and the reduction of various endogenous and exogenous compounds. This study aimed to explore the potential of strychnine as an anticancer agent by targeting AKR1B1 and AKR1B10 via drug repurposing approach. To assess the drug-like properties of strychnine, a physiologically based pharmacokinetic (PKPB) model and High Throughput Pharmacokinetics (HTPK) approach were employed. The obtained results fell within the expected range for drug molecules, confirming its suitability for further investigation. Additionally, density functional theory (DFT) studies were conducted to gain insight into the electronic properties contributing to the drug molecule's reactivity. Building upon the promising DFT results, molecular docking analysis using the AutoDock tool was performed to examine the binding interactions between strychnine and the proposed targets, AKR1B1 and AKR1B10. Findings from the molecular docking studies suggested a higher probability of strychnine acting as an inhibitor of AKR1B1 and AKR1B10 with docking scores of - 30.84 and - 29.36kJ/mol respectively. To validate the stability of the protein-ligand complex, Molecular Dynamic Simulation (MDS) studies were conducted, revealing the formation of a stable complex between the enzymes and strychnine. This comprehensive approach sheds light on the potential effectiveness of strychnine as a treatment for breast, lung, liver, and pancreatic cancers, as well as related malignancies. The novel insights gained from the physiologically based pharmacokinetic modeling, density functional theory, molecular docking, and molecular dynamics simulations collectively support the prospect of strychnine as a promising molecule for anticancer therapy. Further investigations are warranted to validate these findings and explore the therapeutic potential of strychnine in preclinical and clinical settings.

Discovery of novel small-molecule aldehyde dehydrogenase 2 activators based on drug repurposing

Aldehyde dehydrogenase 2 (ALDH2) plays an important role in the detoxification of reactive aldehydes under oxidative stress. Because an estimated 50% of East Asians carry a common ALDH2 deficient variant with decreased enzyme activity and are more susceptible to toxic aldehydes, more recent findings have highlighted the therapeutic potential of ALDH2 activators in aldehyde-related diseases such as cardiovascular injury. Drug repurposing has unique advantages in providing new lead compounds with good drug-like properties. Herein, we identified Tadalafil from DrugBank as a novel ALDH2 activator using a combination strategy of docking-based and pharmacophore-based virtual screening based on exploring the activation mechanism. Then a hit-based substructure search was completed and has led to the discovery of 5 hits, among which A1 showed better ALDH2 activation activity than Tadalafil. This study provides a good basis for the further research of ALDH2 activators.

Novel silkworm (Bombyx mori) sulfotransferase swSULT ST3 is involved in metabolism of polyphenols from mulberry leaves.

Polyphenols in plants are important for defense responses against microorganisms, insect herbivory, and control of feeding. Owing to their antioxidant, anti-cancer, and anti-inflammatory activities, their importance in human nutrition has been acknowledged. However, metabolism of polyphenols derived from mulberry leaves in silkworms (Bombyx mori) remains unclear. Sulfotransferases (SULT) are involved in the metabolism of xenobiotics and endogenous compounds. The purpose of this study is to investigate the metabolic mechanism of polyphenols mediated by B. mori SULT. Here, we identified a novel SULT in silkworms (herein, swSULT ST3). Recombinant swSULT ST3 overexpressed in Escherichia coli effectively sulfated polyphenols present in mulberry leaves. swSULT ST3 showed high specific activity toward genistein among the polyphenols. Genistein-7-sulfate was produced by the activity of swSULT ST3. Higher expression of swSULT ST3 mRNA was observed in the midgut and fat body than in the hemocytes, testis, ovary, and silk gland. Polyphenols inhibited the aldo-keto reductase detoxification of reactive aldehydes from mulberry leaves, and the most noticeable inhibition was observed with genistein. Our results suggest that swSULT ST3 plays a role in the detoxification of polyphenols, including genistein, and contributes to the effects of aldo-keto reductase in the midgut of silkworms. This study provides new insight into the functions of SULTs and the molecular mechanism responsible for host plant selection in lepidopteran insects.

Detoxification of Reactive Aldehydes by Alda-1 Treatment Ameliorates Experimental Autoimmune Encephalomyelitis in Mice

Reactive aldehydes are generated as a toxic end-product of lipid peroxidation under inflammatory oxidative stress condition which is a well-established phenomenon in the pathogenesis of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Alda-1, a selective agonist of mitochondrial aldehyde dehydrogenase 2 (ALDH2), is known to detoxify the reactive aldehydes. In this study, we investigated the effect of Alda-1 on CNS myelin pathology associated with reactive aldehydes and mitochondrial/peroxisomal dysfunctions in a mouse model of EAE. Daily treatment of EAE mice with Alda-1, starting at the peak of disease, ameliorated the clinical manifestation of disease along with the improvement of motor functions. Accordingly, Alda-1 treatment improved demyelination and neuroaxonal degeneration in EAE mice. EAE mice had increased levels of reactive aldehyde species, such as 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and acrolein (ACL) in the spinal cords and these levels were significantly reduced in Alda-1-treated EAE mice. Furthermore, Alda-1 treatment improved the loss of mitochondrial (OXPHOS) and peroxisomal (PMP70 and catalase) proteins as well as mitochondrial/peroxisomal proliferation factors (PGC-1α and PPARs) in the spinal cords of EAE mice. Taken together, this study demonstrates the therapeutic efficacy of ALDH2-agonist Alda-1 in the abatement of EAE disease through the detoxification of reactive aldehydes, thus suggesting Alda-1 as a potential therapeutic intervention for MS.

Aberrant reactive aldehyde detoxification by aldehyde dehydrogenase-2 influences endometriosis development and pain-associated behaviors.

Endometriosis affects ∼176 million women worldwide, yet on average, women experience pain ∼10 years from symptom onset before being properly diagnosed. Standard treatments (drugs or surgery) often fail to provide long-term pain relief. Elevated levels of reactive aldehydes such as 4-hydroxynonenal (4-HNE) have been implicated in the peritoneal fluid of women with endometriosis and upon accumulation, reactive aldehydes can form protein-adducts and/or generate pain. A key enzyme in detoxifying reactive aldehydes to less reactive forms is the mitochondrial enzyme aldehyde dehydrogenase-2 (ALDH2). Here, we tested the hypothesis that aberrant reactive aldehyde detoxification by ALDH2 underlies endometriosis and its associated pain. We determined, in the eutopic and ectopic endometrium of women with severe (stage IV) peritoneal endometriosis, that ALDH2 enzyme activity was decreased, which was associated with decreased ALDH2 expression and increased 4-HNE adduct formation compared to the eutopic endometrium of controls in the proliferative phase. Using a rodent model of endometriosis and an ALDH2*2 knock-in mouse with decreased ALDH2 activity, we determined that increasing ALDH2 activity with the enzyme activator Alda-1 could prevent endometriosis lesion development as well as alleviate pain-associated behaviors in proestrus. Overall, our findings suggest that targeting the ALDH2 enzyme in endometriosis may lead to better treatment strategies and in the proliferative phase, that increased 4-HNE adduct formation within the endometrium may serve as a less invasive diagnostic biomarker to reduce years of suffering in women.

Exogenous methylglyoxal enhances the reactive aldehyde detoxification capability and frost-hardiness of wheat

Cold-acclimation is essential for the development of adequate frost-hardiness in cereals and therefore sudden freezes can cause considerable damage to the canopy. However, timely adding of an appropriate signal in the absence of cold acclimation may also harden wheat for the upcoming freeze. The feasibility of the promising signal molecule methylglyoxal was tested here for such applications and the signal mechanism was studied in bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. ssp. durum). Spraying with 10 mM methylglyoxal did not decrease the fresh weight and photosynthetic parameters in most wheat varieties at growth temperature (21 °C). Photosynthetic parameters even improved and chlorophyll content increased in some cases. Increased transcript level of glutathione-S-transferases and omega-3 fatty acid desaturases was detected by qPCR 6 h after the last methylglyoxal spray. Aldo-keto reductase and glyoxalase enzyme activities, as well as sorbitol content of wheat plants increased 24 h after the last 10 mM methylglyoxal spray in most of the cultivars. These mechanisms may explain the increased freezing survival of methylglyoxal pretreated wheat plants from less than 10% to over 30%. Our results demonstrate that exogenous methylglyoxal treatment can be safely added to wheat plants as preparatory treatment without detrimental effects but inducing some of the stress-protective mechanisms, which contribute to frost-hardiness.

Glucose Metabolism in Cardiac Hypertrophy and Heart Failure.

Glucose Metabolism in Cardiac Hypertrophy and Heart Failure.

Mitochondrial Aldehyde Dehydrogenase in Myocardial Ischemic and Ischemia-Reperfusion Injury.

Myocardial ischemia-reperfusion (IR) injury during acute myocardial infarction or open-heart surgery would promote oxidative stress, leading to the accumulation of reactive aldehydes that cause cardiac damage. It has been well demonstrated that aldehyde dehydrogenase (ALDH)-2 is an important cardioprotective enzyme for its central role in the detoxification of reactive aldehydes. ALDH2 activation by small molecule activators is a promising approach for cardioprotection for myocardial IR injury.

Aldehyde Dehydrogenase 2 (ALDH2) and Aging: Is There a Sensible Link?

Aging is a complex irreversible biological process associated with increased prevalence of chronic disease and high healthcare burden. Several theories have been proposed for the biology of aging including free radical accumulation, DNA damage, apoptosis, telomere shortening, autophagy failure, and disturbed autonomic response. Aging is also closely associated with progressive deterioration of cardiovascular and neurological functions. Linkage, genome-wide association (GWAS), and next-generation sequencing analysis have confirmed a number of susceptibility loci for aging, in particular, Alzheimer's disease. Recent evidence from our group and others also revealed a tie between genetic mutation of mitochondrial aldehyde dehydrogenase (ALDH2) and life span as well as cardiovascular aging. ALDH2 represents the single most gene with the greatest number of human genetic polymorphism and is deemed an important enzyme for detoxification of reactive aldehydes. Here, we will briefly review the tie between ALDH2 and cardiovascular aging process. While recent work on ALDH2 research has broadened the pathogenic mechanisms of ALDH2 mutation or deficiency, therapeutic potential targeting ALDH2 in the elderly still remains debatable.

Surveillance of Cancer Stem Cell Plasticity Using an Isoform-Selective Fluorescent Probe for Aldehyde Dehydrogenase 1A1.

Cancer stem cells (CSCs) are progenitor cells that contribute to treatment-resistant phenotypes during relapse. CSCs exist in specific tissue microenvironments that cell cultures and more complex models cannot mimic. Therefore, the development of new approaches that can detect CSCs and report on specific properties (e.g., stem cell plasticity) in their native environment have profound implications for studying CSC biology. Herein, we present AlDeSense, a turn-on fluorescent probe for aldehyde dehydrogenase 1A1 (ALDH1A1) and Ctrl-AlDeSense, a matching nonresponsive reagent. Although ALDH1A1 contributes to the detoxification of reactive aldehydes, it is also associated with stemness and is highly elevated in CSCs. AlDeSense exhibits a 20-fold fluorescent enhancement when treated with ALDH1A1. Moreover, we established that AlDeSense is selective against a panel of common ALDH isoforms and exhibits exquisite chemostability against a collection of biologically relevant species. Through the application of surface marker antibody staining, tumorsphere assays, and assessment of tumorigenicity, we demonstrate that cells exhibiting high AlDeSense signal intensity have properties of CSCs. Using these probes in tandem, we have identified CSCs at the cellular level via flow cytometry and confocal imaging, as well as monitored their states in animal models.

Mice deficient in aldo-keto reductase 1a (Akr1a) are resistant to thioacetamide-induced liver injury

Aldehyde reductase (Akr1a) has been reported to be involved in detoxification of reactive aldehydes as well as in the synthesis of bioactive compounds such as ascorbic acid (AsA). Because Akr1a is expressed at high levels in the liver and is involved in xenobiotic metabolism, our objective was to investigate the hepato-protective role of Akr1a in a thioacetamide (TAA)-induced hepatotoxicity model using Akr1a-deficient (Akr1a−/−) mice. Wild-type (WT) and Akr1a−/− mice were injected intraperitoneally with TAA and the extent of liver injury in the acute phase was assessed. Intriguingly, the extent of TAA-induced liver damage was less in the Akr1a−/− mice than in the WT mice. Biomarkers for the ER stress-induced apoptosis pathway were markedly decreased in the livers of Akr1a−/− mice, whereas AsA levels in plasma did not change significantly in any of the mice. In the liver, TAA is converted to reactive metabolites such as TAA S-oxide and then to TAA S, S-dioxide via the action of CYP2E1. In Akr1a−/− mice, CYP2E1 activity was relatively lower than WT mice at the basal level, leading to reactive TAA metabolites being produced at lower levels after the TAA treatment. The levels of liver proteins that were modified with these metabolites were also lower in the Akr1a−/− mice than the WT mice after the TAA treatment. Furthermore, after a lethal dose of a TAA challenge, the WT mice all died within 36 h, whereas almost all of the Akr1a−/− mice survived. These collective results suggest that Akr1a−/− mice are resistant to TAA-induced liver injury, and it follows that the absence of Akr1a might modulate TAA bioactivation.

178 - Acetaldehyde Dehydrogenase 2(ALDH2) in Atherosclerosis: Beyond Detoxification of Reactive Aldehydes

Previous studies have linked human polymorphisms of ALDH2 to cardiovascular diseases but the underlying mechanisms remain elusive. Here we investigated the role of ALDH2 in atherosclerosis using a murine model of low density lipoprotein receptor (LDLR) and ALDH2 double knockout mice. Surprisingly, we found that double KO mice had significantly decreased areas of atherosclerotic plaque and less macrophages in mouse aorta comparing to LDLR KO mice. Bone marrow transplant experiments also supported an important role of macrophages in this phenotype. Moreover, in vitro experiments using bone marrow derived macrophages (BMDM) showed that macrophages from ALDH2 KO had decreased uptake of ox-LDL through downregulation of phagocytic genes in LDLR-/-background. CO-IP, IF experiments, and RNA-seq in macrophages demonstrated that LDLR regulated ALDH2 entering into nucleus and regulated genes related to autophagy, AMPK activation, and mitochondrial functions. Our findings shed light on novel roles of ALDH2 in the pathogenesis of atherosclerosis through modulating macrophages functions by interactions of LDLR and AMPK - beyond the conventional roles of detoxification of reactive aldehydes.

Identification of activation of tryptophan‐NAD+ pathway as a central metabolic response to chemical stress from feeding thermally‐oxidized soybean oil in mouse through metabolomics‐based biochemical analysis

Consumption of thermally‐oxidized lipids is associated with metabolic disorders and cardiovascular disease. However, the specific metabolic events induced by thermally‐oxidized lipids and their underlying mechanisms are not well defined. In this study, the metabolic responses to consuming thermally‐oxidized vegetable oil were examined through metabolomics‐guided biochemical analysis. The control diet containing 7% (w/w) fresh soybean oil diet (CSO) and the treatment diet containing 7% (w/w) heated soybean oil (HSO) were fed to two groups of C57BL/6 mice for 4 weeks, respectively. Liquid chromatography‐mass spectrometry (LC‐MS)‐based metabolomic analysis indicated that HSO greatly altered the composition of metabolomes in serum, urine, and liver samples. A group of hydroxylalkenoic acids in urine were identified as newly formed metabolites from HSO treatment. HSO altered the lipidome, which was indicated by the increases of phospholipids containing saturated fatty acids and the decrease of phospholipids containing polyunsaturated fatty acids in the liver and serum. In the liver, HSO‐induced disruption of redox balance was reflected by the decrease of glutathione (GSH) and ascorbic acid and the upregulation of detoxifying gene expression. Moreover, the levels of several microbial metabolites in urine were affected by HSO, suggesting the changes in microflora. Above all, the most prominent metabolic changes induced by HSO occurred in the tryptophan‐NAD+ pathway since multiple metabolites in this pathway were affected, including the decrease of serum tryptophan, the increases of NAD+ and adenosine metabolites in the liver, and the increases of kynurenic acid, nicotinamide, and nicotinamide N‐oxide in urine. The activation of tryptophan‐NAD+ pathway was confirmed by observing the upregulation of tryptophan 2,3‐dioxygenase, kynureninase, and quinolinate phosphoribosyl transferase expression in this pathway, likely contributed by the activation of peroxisome proliferator‐activated receptor α (PPARα), as suggested by the upregulation of PPARα target genes in the liver and the decreases of triacylglycerols in both serum and liver. Since NAD+ and its metabolites are the indispensable cofactors or substrates of major metabolic events induced by HSO, including the detoxification of reactive aldehydes through aldehyde dehydrogenase, sustaining redox balance and DNA repair activities, and PPARα–mediated metabolic reactions, such as fatty acid β‐oxidation, the activation of tryptophan‐NAD+ pathway is deemed to be a central metabolic event induced by thermally‐oxidized lipids.Support or Funding InformationNIFA project MIN‐18‐092

Characterizing Sirtuin 3 Deacetylase Affinity for Aldehyde Dehydrogenase 2

Mitochondrial aldehyde dehydrogenase (ALDH2) plays a central role in the detoxification of reactive aldehydes generated through endogenous and exogenous sources. The biochemical regulation of enzyme activity through post-translational modification provides an intricate response system regulating mitochondrial detoxification pathways. ALDH2 is a known target of lysine acetylation, which arises as a consequence of mitochondrial bioenergetic flux and sirtuin deacetylase activity. The mitochondrial deacetylase Sirtuin 3 (SIRT3) has been reported to alter ALDH2 lysine acetylation status, yet the mechanism and consequence of this interaction remain unknown. The in vitro results presented here provide a novel biochemical approach using stable-isotope dilution mass spectrometry to elucidate which lysine residues are targeted by SIRT3 for deacetylation. Furthermore, HPLC-MS/MS and computational modeling elucidate a potential role for acetyl-Lys369 on ALDH2 in perturbing normal β-nicotinamide adenine dinucleotide (NAD+) cofactor binding.

Lipoic acid protects gastric mucosa from ethanol-induced injury in rat through a mechanism involving aldehyde dehydrogenase 2 activation

Numerous studies demonstrate that reactive aldehydes are highly toxic and aldehyde dehydrogenase 2 (ALDH2)-mediated detoxification of reactive aldehydes is thought as an endogenous protective mechanism against reactive aldehydes-induced cell injury. This study aims to explore whether lipoic acid, a potential ALDH2 activator, is able to protect gastric mucosa from ethanol-induced injury through a mechanism involving clearance of reactive aldehydes. The rats received 60% of acidified ethanol through intragastric administration and held for 1h to establish a mucosal injury model. Lipoic acid (10 or 30mg/kg) or Alda-1 (a positive control, 10mg/kg) was given 45min before the ethanol treatment. The gastric tissues were collected for analysis of gastric ulcer index, cellular apoptosis, 4-hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA) contents, and ALDH2 activity. The results showed that acute administration of ethanol led to an increase in gastric ulcer index, cellular apoptosis, 4-HNE and MDA contents concomitant with a decrease in ALDH2 activity; these phenomena were reversed by lipoic acid or Alda-1. The gastric protection of lipoic acid was attenuated in the presence of ALDH2 inhibitor. Based on these observations, we conclude that lipoic acid exerts the beneficial effects on ethanol-induced injury through a mechanism involving, at least in part, ALDH2 activation. As a dietary supplement or a medicine already in some countries, lipoic acid can be used to treat the ethanol - induced gastric mucosal injury.

A novel aldo-keto reductase from Jatropha curcas L. (JcAKR) plays a crucial role in the detoxification of methylglyoxal, a potent electrophile

Abiotic stress leads to the generation of reactive oxygen species (ROS) which further results in the production of reactive carbonyls (RCs) including methylglyoxal (MG). MG, an α, β-dicarbonyl aldehyde, is highly toxic to plants and the mechanism behind its detoxification is not well understood. Aldo-keto reductases (AKRs) play a role in detoxification of reactive aldehydes and ketones. In the present study, we cloned and characterised a putative AKR from Jatropha curcas (JcAKR). Phylogenetically, it forms a small clade with AKRs of Glycine max and Rauwolfia serpentina. JcAKR was heterologously expressed in Escherichia coli BL-21(DE3) cells and the identity of the purified protein was confirmed through MALDI-TOF analysis. The recombinant protein had high enzyme activity and catalytic efficiency in assays containing MG as the substrate. Protein modelling and docking studies revealed MG was efficiently bound to JcAKR. Under progressive drought and salinity stress, the enzyme and transcript levels of JcAKR were higher in leaves compared to roots. Further, the bacterial and yeast cells expressing JcAKR showed more tolerance towards PEG (5%), NaCl (200mM) and MG (5mM) treatments compared to controls. In conclusion, our results project JcAKR as a possible and potential target in crop improvement for abiotic stress tolerance.

Detoxification of Carbonyl Compounds by Carbonyl Reductase in Neurodegeneration.

Oxidative stress in the brain is the major cause of neurodegenerative disorders, including Alzheimer's, Parkinson's, Huntington's, and Creutzfeldt-Jakob diseases or amyotrophic lateral sclerosis. Under conditions of oxidative stress, the production of highly reactive oxygen species (ROS) overwhelms antioxidant defenses, resulting in the modification of macromolecules and their deposition in neuronal cell tissues. ROS plays an important role in neuronal cell death that they generate reactive aldehydes from membrane lipid peroxidation. Several neuronal diseases are associated with increased accumulation of abnormal protein adducts of reactive aldehydes, which mediate oxidative stress-linked pathological events, including cell growth inhibition and apoptosis induction. Combining findings on neurodegeneration and oxidative stress in Drosophila with studies on the metabolic characteristics of the human enzyme CBR1, it is clear now that CBR1 has a potential physiological role of neuroprotection in humans. Several studies suggest that CBR1 represents a significant pathway for the detoxification of reactive aldehydes derived from lipid peroxidation and that CBR1 in humans is essential for neuronal cell survival and to confer protection against oxidative stress-induced brain degeneration. Recently, it was discovered that HIF1alpha, AP-1, and Nrf2 could all regulate CBR1 at the transcriptional level. Nrf2 is known to regulate the transcription of antioxidant enzymes, and CBR1 functions as an antioxidant enzyme, suggesting that transcriptional regulation of CBR1 is a major contributor to the control of oxidative stress in neurodegeneration.

Deletion of GSTA4-4 results in increased mitochondrial post-translational modification of proteins by reactive aldehydes following chronic ethanol consumption in mice

Chronic alcohol consumption induces hepatic oxidative stress resulting in production of highly reactive electrophilic α/β-unsaturated aldehydes that have the potential to modify proteins. A primary mechanism of reactive aldehyde detoxification by hepatocytes is through GSTA4-driven enzymatic conjugation with GSH. Given reports that oxidative stress initiates GSTA4 translocation to the mitochondria, we hypothesized that increased hepatocellular damage in ethanol (EtOH)-fed GSTA4−/− mice is due to enhanced mitochondrial protein modification by reactive aldehydes. Chronic ingestion of EtOH increased hepatic protein carbonylation in GSTA4−/− mice as evidenced by increased 4-HNE and MDA immunostaining in the hepatic periportal region. Using mass spectrometric analysis of biotin hydrazide conjugated carbonylated proteins, a total of 829 proteins were identified in microsomal, cytosolic and mitochondrial fractions. Of these, 417 were novel to EtOH models. Focusing on mitochondrial fractions, 1.61-fold more carbonylated proteins were identified in EtOH-fed GSTA4−/− mice compared to their respective WT mice ingesting EtOH. Bioinformatic KEGG pathway analysis of carbonylated proteins from the mitochondrial fractions revealed an increased propensity for modification of proteins regulating oxidative phosphorylation, glucose, fatty acid, glutathione and amino acid metabolic processes in GSTA4−/− mice. Additional analysis revealed sites of reactive aldehyde protein modification on 26 novel peptides/proteins isolated from either SV/GSTA4−/− PF or EtOH fed mice. Among the peptides/proteins identified, ACSL, ACOX2, MTP, and THIKB contribute to regulation of fatty acid metabolism and ARG1, ARLY, and OAT, which regulate nitrogen and ammonia metabolism having direct relevance to ethanol-induced liver injury. These data define a role for GSTA4-4 in buffering hepatic oxidative stress associated with chronic alcohol consumption and that this GST isoform plays an important role in protecting against carbonylation of mitochondrial proteins.