Identification and characterization of a novel microsomal enzyme with glutathione-dependent transferase and peroxidase activities

Deciphering Staphylococcus aureus-host dynamics using dual activity-based protein profiling of ATP-interacting proteins

The utilization of ATP within cells plays a fundamental role in cellular processes that are essential for the regulation of host-pathogen dynamics and the subsequent immune response. This study focuses on ATP-binding proteins to dissect the complex interplay between Staphylococcus aureus and human cells, particularly macrophages (THP-1) and keratinocytes (HaCaT), during an intracellular infection. A snapshot of the various protein activity and function is provided using a desthiobiotin-ATP probe, which targets ATP-interacting proteins. In S. aureus, we observe enrichment in pathways required for nutrient acquisition, biosynthesis and metabolism of amino acids, and energy metabolism when located inside human cells. Additionally, the direct profiling of the protein activity revealed specific adaptations of S. aureus to the keratinocytes and macrophages. Mapping the differentially activated proteins to biochemical pathways in the human cells with intracellular bacteria revealed cell-type-specific adaptations to bacterial challenges where THP-1 cells prioritized immune defenses, autophagic cell death, and inflammation. In contrast, HaCaT cells emphasized barrier integrity and immune activation. We also observe bacterial modulation of host processes and metabolic shifts. These findings offer valuable insights into the dynamics of S. aureus-host cell interactions, shedding light on modulating host immune responses to S. aureus, which could involve developing immunomodulatory therapies.

IMPORTANCE

This study uses a chemoproteomic approach to target active ATP-interacting proteins and examines the dynamic proteomic interactions between Staphylococcus aureus and human cell lines THP-1 and HaCaT. It uncovers the distinct responses of macrophages and keratinocytes during bacterial infection. S. aureus demonstrated a tailored response to the intracellular environment of each cell type and adaptation during exposure to professional and non-professional phagocytes. It also highlights strategies employed by S. aureus to persist within host cells. This study offers significant insights into the human cell response to S. aureus infection, illuminating the complex proteomic shifts that underlie the defense mechanisms of macrophages and keratinocytes. Notably, the study underscores the nuanced interplay between the host's metabolic reprogramming and immune strategy, suggesting potential therapeutic targets for enhancing host defense and inhibiting bacterial survival. The findings enhance our understanding of host-pathogen interactions and can inform the development of targeted therapies against S. aureus infections.

Mutant p53 protects triple-negative breast adenocarcinomas from ferroptosis in vivo

The TP53 tumor suppressor gene is mutated early in most of the patients with triple-negative breast cancer (TNBC). The most frequent TP53 alterations are missense mutations that contribute to tumor aggressiveness. Here, we used an autochthonous somatic TNBC mouse model, in which mutant p53 can be toggled on and off genetically while leaving the tumor microenvironment intact and wild-type for p53 to identify physiological dependencies on mutant p53. In TNBCs that develop in this model, deletion of two different hotspot p53R172H and p53R245W mutants triggers ferroptosis in vivo, a cell death mechanism involving iron-dependent lipid peroxidation. Mutant p53 protects cells from ferroptosis inducers, and ferroptosis inhibitors reverse the effects of mutant p53 loss in vivo. Single-cell transcriptomic data revealed that mutant p53 protects cells from undergoing ferroptosis through NRF2-dependent regulation of Mgst3 and Prdx6, which encode two glutathione-dependent peroxidases that detoxify lipid peroxides. Thus, mutant p53 protects TNBCs from ferroptotic death.

UBL3 Interaction with α-Synuclein Is Downregulated by Silencing MGST3

Ubiquitin-like 3 (UBL3) is a membrane-anchored protein that plays a crucial role in sorting proteins into small extracellular vesicles. Aggregations of alpha-synuclein (α-syn) are associated with the pathology of neurodegenerative diseases such as Parkinson's disease. Recently, the interaction between UBL3 and α-syn was discovered, with potential implications in clearing excess α-syn from neurons and its role in disease spread. However, the regulator that can mediate the interaction between UBL3 and α-syn remains unclear. In this study, using the split gaussian luciferase complementation assay and RNA interference technology, we identified that QSOX2, HTATIP2, UBE3C, MGST3, NSF, HECTD1, SAE1, and ATG3 were involved in downregulating the interaction between UBL3 and α-syn. Notably, silencing MGST3 had the most significant impact. Immunocytochemistry staining confirmed the impact of MGST3 silencing on the co-localization of UBL3 and α-syn in cells. MGST3 is a part of the antioxidant system, and silencing MGST3 is believed to contribute to oxidative stress. We induced oxidative stress with hydrogen peroxide, observing its effect on the UBL3-α-syn interaction, and showing that 800 µM of H2O2 downregulated this interaction. In conclusion, silencing MGST3 downregulates the interaction between UBL3 and α-syn.

Cardiomyocyte-Specific Wt1 Is Involved in Cardiac Metabolism and Response to Damage

The Wilms tumor suppressor gene (Wt1) encodes a C2H2-type zinc-finger transcription factor that participates in transcriptional regulation, RNA metabolism, and protein-protein interactions. WT1 is involved in the development of several organs, including the kidneys and gonads, heart, spleen, adrenal glands, liver, diaphragm, and neuronal system. We previously provided evidence of transient WT1 expression in about 25% of cardiomyocytes of mouse embryos. Conditional deletion of Wt1 in the cardiac troponin T lineage caused abnormal cardiac development. A low expression of WT1 has also been reported in adult cardiomyocytes. Therefore, we aimed to explore its function in cardiac homeostasis and in the response to pharmacologically induced damage. Silencing of Wt1 in cultured neonatal murine cardiomyocytes provoked alterations in mitochondrial membrane potential and changes in the expression of genes related to calcium homeostasis. Ablation of WT1 in adult cardiomyocytes by crossing αMHC^MerCreMer mice with homozygous WT1-floxed mice induced hypertrophy, interstitial fibrosis, altered metabolism, and mitochondrial dysfunction. In addition, conditional deletion of WT1 in adult cardiomyocytes increased doxorubicin-induced damage. These findings suggest a novel role of WT1 in myocardial physiology and protection against damage.

Biosynthesis of prostaglandin 15dPGJ2 -glutathione and 15dPGJ2-cysteine conjugates in macrophages and mast cells via MGST3

Inhibition of microsomal prostaglandin E synthase-1 (mPGES-1) results in decreased production of proinflammatory PGE₂ and can lead to shunting of PGH₂ into the prostaglandin D₂ (PGD₂)/15-deoxy-Δ^12,14-prostaglandin J₂ (15dPGJ₂) pathway. 15dPGJ₂ forms Michael adducts with thiol-containing biomolecules such as GSH or cysteine residues on target proteins and is thought to promote resolution of inflammation. We aimed to elucidate the biosynthesis and metabolism of 15dPGJ₂ via conjugation with GSH, to form 15dPGJ₂-glutathione (15dPGJ₂-GS) and 15dPGJ₂-cysteine (15dPGJ₂-Cys) conjugates and to characterize the effects of mPGES-1 inhibition on the PGD₂/15dPGJ₂ pathway in mouse and human immune cells. Our results demonstrate the formation of PGD₂, 15dPGJ₂, 15dPGJ₂-GS, and 15dPGJ₂-Cys in RAW264.7 cells after lipopolysaccharide stimulation. Moreover, 15dPGJ₂-Cys was found in lipopolysaccharide-activated primary murine macrophages as well as in human mast cells following stimulation of the IgE-receptor. Our results also suggest that the microsomal glutathione S-transferase 3 is essential for the formation of 15dPGJ₂ conjugates. In contrast to inhibition of cyclooxygenase, which leads to blockage of the PGD₂/15dPGJ₂ pathway, we found that inhibition of mPGES-1 preserves PGD₂ and its metabolites. Collectively, this study highlights the formation of 15dPGJ₂-GS and 15dPGJ₂-Cys in mouse and human immune cells, the involvement of microsomal glutathione S-transferase 3 in their biosynthesis, and their unchanged formation following inhibition of mPGES-1. The results encourage further research on their roles as bioactive lipid mediators.

Blockade of Platelet CysLT1R Receptor with Zafirlukast Counteracts Platelet Protumoral Action and Prevents Breast Cancer Metastasis to Bone and Lung

Metastases are the main cause of death in cancer patients, and platelets are largely known for their contribution in cancer progression. However, targeting platelets is highly challenging given their paramount function in hemostasis. Using a high-throughput screening and platelet-induced breast tumor cell survival (PITCS) assay as endpoint, we identified the widely used anti-asthmatic drugs and cysteinyl leukotriene receptor 1 (CysLT1R) antagonists, zafirlukast and montelukast, as new specific blockers of platelet protumoral action. Here, we show that human MDA-B02 breast cancer cells produce CysLT through mechanisms involving microsomal glutathione-S-transferase 1/2/3 (MGST1/2/3) and that can modulate cancer cell–platelet interactions via platelet–CysLT1R. CysLT1R blockade with zafirlukast decreased platelet aggregation and adhesion on cancer cells and inhibited PITCS, migration, and invasion in vitro. Zafirlukast significantly reduced, by 90%, MDA-B02 cell dissemination to bone in nude mice and reduced by 88% 4T1 spontaneous lung metastasis formation without affecting primary tumor growth. Combined treatment of zafirlukast plus paclitaxel totally inhibited metastasis of 4T1 cells to the lungs. Altogether, our results reveal a novel pathway mediating the crosstalk between cancer cells and platelets and indicate that platelet CysLT1R represents a novel therapeutic target to prevent metastasis without affecting hemostasis.

Recent, full-length gene retrocopies are common in canids

Gene retrocopies arise from the reverse transcription and insertion into the genome of processed mRNA transcripts. Although many retrocopies have acquired mutations that render them functionally inactive, most mammals retain active LINE-1 sequences capable of producing new retrocopies. New retrocopies, referred to as retro copy number variants (retroCNVs), may not be identified by standard variant calling techniques in high-throughput sequencing data. Although multiple functional FGF4 retroCNVs have been associated with skeletal dysplasias in dogs, the full landscape of canid retroCNVs has not been characterized. Here, retroCNV discovery was performed on a whole-genome sequencing data set of 293 canids from 76 breeds. We identified retroCNV parent genes via the presence of mRNA-specific 30-mers, and then identified retroCNV insertion sites through discordant read analysis. In total, we resolved insertion sites for 1911 retroCNVs from 1179 parent genes, 1236 of which appeared identical to their parent genes. Dogs had on average 54.1 total retroCNVs and 1.4 private retroCNVs. We found evidence of expression in testes for 12% (14/113) of the retroCNVs identified in six Golden Retrievers, including four chimeric transcripts, and 97 retroCNVs also had significantly elevated F ST across dog breeds, possibly indicating selection. We applied our approach to a subset of human genomes and detected an average of 4.2 retroCNVs per sample, highlighting a 13-fold relative increase of retroCNV frequency in dogs. Particularly in canids, retroCNVs are a largely unexplored source of genetic variation that can contribute to genome plasticity and that should be considered when investigating traits and diseases.

Model systems for studying lipid oxidation associated with muscle foods: Methods, challenges, and prospects

Lipid oxidation is a complex process in muscle-based foods (red meat, poultry and fish) causing severe quality deterioration, e.g., off-odors, discoloration, texture defects and nutritional loss. The complexity of muscle tissue -both composition and structure- poses as a formidable challenge in directly clarifying the mechanisms of lipid oxidation in muscle-based foods. Therefore, different in vitro model systems simulating different aspects of muscle have been used to study the pathways of lipid oxidation. In this review, we discuss the principle, preparation, implementation as well as advantages and disadvantages of seven commonly-studied model systems that mimic either compositional or structural aspects of actual meat: emulsions, fatty acid micelles, liposomes, microsomes, erythrocytes, washed muscle mince, and muscle homogenates. Furthermore, we evaluate the prospects of stem cells, tissue cultures and three-dimensional printing for future model system development. Based on this reviewing of oxidation models, tailoring correct model to different study aims could be facilitated, and readers are becoming acquainted with advantages and shortcomings. In addition, insight into recent technology developments, e.g., stem cell- and tissue-cultures as well as three-dimensional printing could provide new opportunities to overcome the current bottlenecks of lipid oxidation studies in muscle.

Mapping the Proteoform Landscape of Five Human Tissues

A functional understanding of the human body requires structure-function studies of proteins at scale. The chemical structure of proteins is controlled at the transcriptional, translational, and post-translational levels, creating a variety of products with modulated functions within the cell. The term "proteoform" encapsulates this complexity at the level of chemical composition. Comprehensive mapping of the proteoform landscape in human tissues necessitates analytical techniques with increased sensitivity and depth of coverage. Here, we took a top-down proteomics approach, combining data generated using capillary zone electrophoresis (CZE) and nanoflow reversed-phase liquid chromatography (RPLC) hyphenated to mass spectrometry to identify and characterize proteoforms from the human lungs, heart, spleen, small intestine, and kidneys. CZE and RPLC provided complementary post-translational modification and proteoform selectivity, thereby enhancing the overall proteome coverage when used in combination. Of the 11,466 proteoforms identified in this study, 7373 (64%) were not reported previously. Large differences in the protein and proteoform level were readily quantified, with initial inferences about proteoform biology operative in the analyzed organs. Differential proteoform regulation of defensins, glutathione transferases, and sarcomeric proteins across tissues generate hypotheses about how they function and are regulated in human health and disease.

Oxidative Stress Modulation by Carnosine in Scaffold Free Human Dermis Spheroids Model: A Proteomic Study

Carnosine is an endogenous β-alanyl-L-histidine dipeptide endowed with antioxidant and carbonyl scavenger properties, which is able to significantly prevent the visible signs of aging and photoaging. To investigate the mechanism of action of carnosine on human skin proteome, a 3D scaffold-free spheroid model of primary dermal fibroblasts from a 50-year-old donor was adopted in combination with quantitative proteomics for the first time. The label free proteomics approach based on high-resolution mass spectrometry, integrated with network analyses, provided a highly sensitive and selective method to describe the human dermis spheroid model during long-term culture and upon carnosine treatment. Overall, 2171 quantified proteins allowed the in-depth characterization of the 3D dermis phenotype during growth and differentiation, at 14 versus 7 days of culture. A total of 485 proteins were differentially regulated by carnosine at 7 days, an intermediate time of culture. Of the several modulated pathways, most are involved in mitochondrial functionality, such as oxidative phosphorylation, TCA cycle, extracellular matrix reorganization and apoptosis. In long-term culture, functional modules related to oxidative stress were upregulated, inducing the aging process of dermis spheroids, while carnosine treatment prevented this by the downregulation of the same functional modules. The application of quantitative proteomics, coupled to advanced and relevant in vitro scaffold free spheroids, represents a new concrete application for personalized therapies and a novel care approach.

Genome-Wide Association and Mendelian Randomization Analysis Reveal the Causal Relationship Between White Blood Cell Subtypes and Asthma in Africans

Background: White blood cell (WBC) traits and their subtypes such as basophil count (Bas), eosinophil count (Eos), lymphocyte count (Lym), monocyte count (Mon), and neutrophil counts (Neu) are known to be associated with diseases such as stroke, peripheral arterial disease, and coronary heart disease. Methods: We meta-analyze summary statistics from genome-wide association studies in 17,802 participants from the African Partnership for Chronic Disease Research (APCDR) and African ancestry individuals from the Blood Cell Consortium (BCX2) using GWAMA. We further carried out a Bayesian fine mapping to identify causal variants driving the association with WBC subtypes. To access the causal relationship between WBC subtypes and asthma, we conducted a two-sample Mendelian randomization (MR) analysis using summary statistics of the Consortium on Asthma among African Ancestry Populations (CAAPA: n cases = 7,009, n control = 7,645) as our outcome phenotype. Results: Our metanalysis identified 269 loci at a genome-wide significant value of (p = 5 × 10-9) in a composite of the WBC subtypes while the Bayesian fine-mapping analysis identified genetic variants that are more causal than the sentinel single-nucleotide polymorphism (SNP). We found for the first time five novel genes (LOC126987/MTCO3P14, LINC01525, GAPDHP32/HSD3BP3, FLG-AS1/HMGN3P1, and TRK-CTT13-1/MGST3) not previously reported to be associated with any WBC subtype. Our MR analysis showed that Mon (IVW estimate = 0.38, CI: 0.221, 0.539, p < 0.001), Neu (IVW estimate = 0.189, CI: 0.133, 0.245, p < 0.001), and WBCc (IVW estimate = 0.185, CI: 0.108, 0.262, p < 0.001) are associated with increased risk of asthma. However, there was no evidence of causal relationship between Lym and asthma risk. Conclusion: This study provides insight into the relationship between some WBC subtypes and asthma and potential route in the treatment of asthma and may further inform a new therapeutic approach.

The roles of lipid mediators in type I hypersensitivity

Type I hypersensitivity is an immediate immune reaction that involves IgE-mediated activation of mast cells. Activated mast cells release chemical mediators, such as histamine and lipid mediators, which cause allergic reactions. Recent developments in detection devices have revealed that mast cells simultaneously release a wide variety of lipid mediators. Mounting evidence has revealed that mast cell-derived mediators exert both pro- and anti-inflammatory functions and positively and negatively regulate the development of allergic inflammation. This review presents the roles of major lipid mediators released from mast cells. Author believes this review will be helpful for a better understanding of the pathogenesis of allergic diseases and provide a new strategy for the diagnosis and treatment of allergic reactions.

Emerging role of cysteinyl LTs in cancer

Cysteinyl leukotrienes (CysLTs) are inflammatory lipid mediators that play a central role in the pathophysiology of several inflammatory diseases. Recently, there has been an increased interest in determining how these lipid mediators orchestrate tumour development and metastasis through promoting a pro-tumour micro-environment. Up-regulation of CysLTs receptors and CysLTs production is found in a number of cancers and has been associated with increased tumorigenesis. Understanding the molecular mechanisms underlying the role of CysLTs and their receptors in cancer progression will help investigate the potential of targeting CysLTs signalling for anti-cancer therapy. This review gives an overview of the biological effects of CysLTs and their receptors, along with current knowledge of their regulation and expression. It also provides a recent update on the molecular mechanisms that have been postulated to explain their role in tumorigenesis and on the potential of anti-CysLTs in the treatment of cancer.

First evidence of transcriptional modulation by chlorothalonil in mussels Perna perna

Gills are considered a key player in organism defenses against environmental pollutants. Since it is the major site of uptake of waterborne chemicals, the modulation of important cellular defenses is expected in this tissue. Chlorothalonil, a fungicide presented in herbicides and antifouling paints, might be responsible for toxicity in marine biota. In this context, mussels were exposed to 0.1 μgL^-1 and 10 μgL^-1 of chlorothalonil for 24 h and 96 h. Genes from biotransformation and antioxidant defense pathways were investigated. Overall, we report, for the first time, an increase in the transcripts of the AhR-like, SULT1A1-like, CYP1A2-like, GSTO-like, MGST-like and SOD-like genes in the gills of the brown mussel Perna perna. This up-regulation was observed mostly after 96 h of exposure to chlorothalonil. Those results reinforce the important role of gills in xenobiotic metabolism and suggest the involvement of the mentioned genes in the detoxification of the compound. Throughout biotransformation and antioxidant defenses pathway, mussels exposed to chlorothalonil are activating mechanisms of defense against this contaminant.

Integral Membrane Enzymes in Eicosanoid Metabolism: Structures, Mechanisms and Inhibitor Design

Eicosanoids are potent lipid mediators involved in central physiological processes such as hemostasis, renal function and parturition. When formed in excess, eicosanoids become critical players in a range of pathological conditions, in particular pain, fever, arthritis, asthma, cardiovascular disease and cancer. Eicosanoids are generated via oxidative metabolism of arachidonic acid along the cyclooxygenase (COX) and lipoxygenase (LOX) pathways. Specific lipid species are formed downstream of COX and LOX by specialized synthases, some of which reside on the nuclear and endoplasmic reticulum, including mPGES-1, FLAP, LTC4 synthase, and MGST2. These integral membrane proteins are members of the family "membrane-associated proteins in eicosanoid and glutathione metabolism" (MAPEG). Here we focus on this enzyme family, which encompasses six human members typically catalyzing glutathione dependent transformations of lipophilic substrates. Enzymes of this family have evolved to combat the topographical challenge and unfavorable energetics of bringing together two chemically different substrates, from cytosol and lipid bilayer, for catalysis within a membrane environment. Thus, structural understanding of these enzymes are of utmost importance to unravel their molecular mechanisms, mode of substrate entry and product release, in order to facilitate novel drug design against severe human diseases.

Systematic characterization of glutathione S-transferases in common marmosets

The common marmoset is an important primate species used in drug metabolism studies. However, glutathione S-transferases (GSTs), essential drug-metabolizing enzymes involved in the conjugation of various endogenous and exogenous substrates, have not been identified or characterized in this species. In this study, 20 GSTs [including 3 microsomal GSTs (MGSTs)] were identified and characterized in marmosets. Marmoset GSTs had amino acid sequences highly identical (86-99%) to human GSTs, except for GSTA4L, which had lower identities (59-62%) with human GSTAs. Phylogenetic analysis revealed that marmoset GSTs were closely clustered with their human counterparts. Marmoset GSTs had gene and genomic structures generally similar to their human counterparts, with some differences in GSTA, GSTM, and GSTT clusters. Marmoset GST mRNAs exhibited distinct tissue expression patterns: GSTA1, GSTA3, GSTA4L, GSTK1, GSTT1, GSTZ1, and MGST1 mRNAs were expressed most abundantly in liver. Other GST mRNAs were expressed most abundantly in small intestine, lung, brain, or kidney. Expression of GSTT4 and GSTT4L mRNAs was detected only in testis. Among all 20 marmoset GST mRNAs, the most abundant mRNAs were GSTA1 mRNA in liver, small intestine, and kidney; GSTM3 mRNA in testis; and MSGT3 mRNA in brain and lung. All 20 GSTs mediated the conjugation of GST substrates 1-chloro-2,4-dinitrobenzene; 1,2-epoxy-3-(p-nitrophenoxy)propane; styrene 7,8-oxide; and/or 1-iodohexane, but with different activity levels. Kinetic analyses showed that marmoset GSTM2/GSTM5 and GSTM5/GSTT1 effectively conjugated styrene 7,8-oxide and 1-iodohexane, respectively, with the highest affinity. These results suggest that the 20 newly identified marmoset GSTs were functional drug-metabolizing enzymes able to conjugate typical GST substrates.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Roles of cysteinyl leukotrienes and their receptors in immune cell-related functions

The cysteinyl leukotrienes (cys-LTs), leukotriene C₄, (LTC₄), LTD₄, and LTE₄, are lipid mediators of inflammation. LTC₄ is the only intracellularly synthesized cys-LT through the 5-lipoxygenase and LTC₄ synthase pathway and after transport is metabolized to LTD₄ and LTE₄ by specific extracellular peptidases. Each cys-LT has a preferred functional receptor in vivo; LTD₄ to the type 1 cys-LT receptor (CysLT₁R), LTC₄ to CysLT₂R, and LTE₄ to CysLT₃R (OXGR1 or GPR99). Recent studies in mouse models revealed that there are multiple regulatory mechanisms for these receptor functions and each receptor plays a distinct role as observed in different mouse models of inflammation and immune responses. This review focuses on the integrated host responses to the cys-LT/CysLTR pathway composed of sequential ligands with preferred receptors as seen from mouse models. It also discusses potential therapeutic targets for LTC₄ synthase, CysLT₂R, and CysLT₃R.

Tissue-specific contributions of Tmem79 to atopic dermatitis and mast cell-mediated histaminergic itch

Atopic dermatitis (AD) is the most common skin disease in children. It is characterized by relapsing inflammation, skin-barrier defects, and intractable itch. However, the pathophysiology of itch in AD remains enigmatic. Here, we examine the contribution of Tmem79, an orphan transmembrane protein linked to AD in both mice and humans. We show that Tmem79 is expressed by both keratinocytes and sensory neurons, but that loss of keratinocytic Tmem79 is sufficient to elicit robust scratching. Tmem79 ^-/- mice demonstrate an accumulation of dermal mast cells, which are diminished following chronic treatment with cyclooxygenase inhibitors and an EP3 receptor antagonist. In Tmem79 ^-/- mice, mast cell degranulation produces histaminergic itch in a histamine receptor 1/histamine receptor 4 (H4R/H1R)-dependent manner that may involve activation of TRPV1^- afferents. TMEM79 has limited sequence homology to a family of microsomal glutathione transferases and confers protection from cellular accumulation of damaging reactive species, and may thus play a role in regulating oxidative stress. In any case, mechanistic insights from this model suggest that therapeutics targeting PGE₂ and/or H1R/H4R histaminergic signaling pathways may represent useful avenues to treat Tmem79-associated AD itch. Our findings suggest that individuals with mutations in Tmem79 develop AD due to the loss of protection from oxidative stress.

Leukotriene biosynthetic enzymes as therapeutic targets

Leukotrienes are powerful immune-regulating lipid mediators with established pathogenic roles in inflammatory allergic diseases of the respiratory tract - in particular, asthma and hay fever. More recent work indicates that these lipids also contribute to low-grade inflammation, a hallmark of cardiovascular, neurodegenerative, and metabolic diseases as well as cancer. Biosynthesis of leukotrienes involves oxidative metabolism of arachidonic acid and proceeds via a set of soluble and membrane enzymes that are primarily expressed by cells of myeloid origin. In activated immune cells, these enzymes assemble at the endoplasmic and perinuclear membrane, constituting a biosynthetic complex. This Review describes recent advances in our understanding of the components of the leukotriene-synthesizing enzyme machinery, emerging opportunities for pharmacological intervention, and the development of new medicines exploiting both antiinflammatory and pro-resolving mechanisms.

Nrf2-Mediated Antioxidant Defense and Peroxiredoxin 6 Are Linked to Biosynthesis of Palmitic Acid Ester of 9-Hydroxystearic Acid

Fatty acid esters of hydroxy fatty acids (FAHFAs) are lipid mediators with promising antidiabetic and anti-inflammatory properties that are formed in white adipose tissue (WAT) via de novo lipogenesis, but their biosynthetic enzymes are unknown. Using a combination of lipidomics in WAT, quantitative trait locus mapping, and correlation analyses in rat BXH/HXB recombinant inbred strains, as well as response to oxidative stress in murine models, we elucidated the potential pathway of biosynthesis of several FAHFAs. Comprehensive analysis of WAT samples identified ∼160 regioisomers, documenting the complexity of this lipid class. The linkage analysis highlighted several members of the nuclear factor, erythroid 2 like 2 (Nrf2)-mediated antioxidant defense system (Prdx6, Mgst1, Mgst3), lipid-handling proteins (Cd36, Scd6, Acnat1, Acnat2, Baat), and the family of flavin containing monooxygenases (Fmo) as the positional candidate genes. Transgenic expression of Nrf2 and deletion of Prdx6 genes resulted in reduction of palmitic acid ester of 9-hydroxystearic acid (9-PAHSA) and 11-PAHSA levels, while oxidative stress induced by an inhibitor of glutathione synthesis increased PAHSA levels nonspecifically. Our results indicate that the synthesis of FAHFAs via carbohydrate-responsive element-binding protein-driven de novo lipogenesis depends on the adaptive antioxidant system and suggest that FAHFAs may link activity of this system with insulin sensitivity in peripheral tissues.

The Incomplete Glutathione Puzzle: Just Guessing at Numbers and Figures?

SIGNIFICANCE

Glutathione metabolism is comparable to a jigsaw puzzle with too many pieces. It is supposed to comprise (i) the reduction of disulfides, hydroperoxides, sulfenic acids, and nitrosothiols, (ii) the detoxification of aldehydes, xenobiotics, and heavy metals, and (iii) the synthesis of eicosanoids, steroids, and iron-sulfur clusters. In addition, glutathione affects oxidative protein folding and redox signaling. Here, I try to provide an overview on the relevance of glutathione-dependent pathways with an emphasis on quantitative data. Recent Advances: Intracellular redox measurements reveal that the cytosol, the nucleus, and mitochondria contain very little glutathione disulfide and that oxidative challenges are rapidly counterbalanced. Genetic approaches suggest that iron metabolism is the centerpiece of the glutathione puzzle in yeast. Furthermore, recent biochemical studies provide novel insights on glutathione transport processes and uncoupling mechanisms.

CRITICAL ISSUES

Which parts of the glutathione puzzle are most relevant? Does this explain the high intracellular concentrations of reduced glutathione? How can iron-sulfur cluster biogenesis, oxidative protein folding, or redox signaling occur at high glutathione concentrations? Answers to these questions not only seem to depend on the organism, cell type, and subcellular compartment but also on different ideologies among researchers.

FUTURE DIRECTIONS

A rational approach to compare the relevance of glutathione-dependent pathways is to combine genetic and quantitative kinetic data. However, there are still many missing pieces and too little is known about the compartment-specific repertoire and concentration of numerous metabolites, substrates, enzymes, and transporters as well as rate constants and enzyme kinetic patterns. Gathering this information might require the development of novel tools but is crucial to address potential kinetic competitions and to decipher uncoupling mechanisms to solve the glutathione puzzle. Antioxid. Redox Signal. 27, 1130-1161.

Nrf2 Activation by 5-lipoxygenase Metabolites in Human Umbilical Vascular Endothelial Cells

5-hydroxyeicosatetraenoic acid (5-HETE) and 5-hydroxyeicosapentaenoic acid (5-HEPE) are major metabolites produced by 5-lipoxygenase (5-LOX) from arachidonic acid (AA) and eicosapentaenoic acid (EPA). Effects of hydroxides on endothelial cells are unclear, although 5-LOX is known to increase at arteriosclerotic lesions. To investigate the effects of hydroxides on human umbilical vein endothelial cells (HUVECs), the cells were treated with 50 μM each of AA, EPA, 5-HETE, and 5-HEPE. Treatment of HUVECs with 5-HETE and 5-HEPE, rather than with AA and EPA, increased the nuclear translocation of NF-E2 related factor 2 (Nrf2) and upregulated the expression of heme oxygenase-1 and cystine/glutamate transporter regulated by Nrf2. Reactive oxygen species (ROS) generation was markedly elevated in HUVECs after treatment with 5-HETE and 5-HEPE, and the pretreatment with α-tocopherol abrogated ROS levels similar to those in the vehicle control. However, ROS generation was independent of Nrf2 activation induced by 5-HETE and 5-HEPE. 5-HETE was converted to 5-oxo-eicosatetraenoic acid (5-oxo-ETE) in HUVECs, and 5-oxo-ETE increased Nrf2 activation. These results suggest that 5-HETE works as an Nrf2 activator through the metabolite 5-oxo-ETE in HUVECs. Similarly, 5-HEPE works in the same way, because 5-HEPE is metabolized to 5-oxo-eicosapentaenoic acid through the same pathway as that for 5-HETE.

Adaptations to High Salt in a Halophilic Protist: Differential Expression and Gene Acquisitions through Duplications and Gene Transfers

The capacity of halophiles to thrive in extreme hypersaline habitats derives partly from the tight regulation of ion homeostasis, the salt-dependent adjustment of plasma membrane fluidity, and the increased capability to manage oxidative stress. Halophilic bacteria, and archaea have been intensively studied, and substantial research has been conducted on halophilic fungi, and the green alga Dunaliella. By contrast, there have been very few investigations of halophiles that are phagotrophic protists, i.e., protozoa. To gather fundamental knowledge about salt adaptation in these organisms, we studied the transcriptome-level response of Halocafeteria seosinensis (Stramenopiles) grown under contrasting salinities. We provided further evolutionary context to our analysis by identifying genes that underwent recent duplications. Genes that were highly responsive to salinity variations were involved in stress response (e.g., chaperones), ion homeostasis (e.g., Na⁺/H⁺ transporter), metabolism and transport of lipids (e.g., sterol biosynthetic genes), carbohydrate metabolism (e.g., glycosidases), and signal transduction pathways (e.g., transcription factors). A significantly high proportion (43%) of duplicated genes were also differentially expressed, accentuating the importance of gene expansion in adaptation by H. seosinensis to high salt environments. Furthermore, we found two genes that were lateral acquisitions from bacteria, and were also highly up-regulated and highly expressed at high salt, suggesting that this evolutionary mechanism could also have facilitated adaptation to high salt. We propose that a transition toward high-salt adaptation in the ancestors of H. seosinensis required the acquisition of new genes via duplication, and some lateral gene transfers (LGTs), as well as the alteration of transcriptional programs, leading to increased stress resistance, proper establishment of ion gradients, and modification of cell structure properties like membrane fluidity.

Global Proteome Changes in the Rat Diaphragm Induced by Endurance Exercise Training

Mechanical ventilation (MV) is a life-saving intervention for many critically ill patients. Unfortunately, prolonged MV results in the rapid development of diaphragmatic atrophy and weakness. Importantly, endurance exercise training results in a diaphragmatic phenotype that is protected against ventilator-induced diaphragmatic atrophy and weakness. The mechanisms responsible for this exercise-induced protection against ventilator-induced diaphragmatic atrophy remain unknown. Therefore, to investigate exercise-induced changes in diaphragm muscle proteins, we compared the diaphragmatic proteome from sedentary and exercise-trained rats. Specifically, using label-free liquid chromatography-mass spectrometry, we performed a proteomics analysis of both soluble proteins and mitochondrial proteins isolated from diaphragm muscle. The total number of diaphragm proteins profiled in the soluble protein fraction and mitochondrial protein fraction were 813 and 732, respectively. Endurance exercise training significantly (P<0.05, FDR <10%) altered the abundance of 70 proteins in the soluble diaphragm proteome and 25 proteins of the mitochondrial proteome. In particular, key cytoprotective proteins that increased in relative abundance following exercise training included mitochondrial fission process 1 (Mtfp1; MTP18), 3-mercaptopyruvate sulfurtransferase (3MPST), microsomal glutathione S-transferase 3 (Mgst3; GST-III), and heat shock protein 70 kDa protein 1A/1B (HSP70). While these proteins are known to be cytoprotective in several cell types, the cyto-protective roles of these proteins have yet to be fully elucidated in diaphragm muscle fibers. Based upon these important findings, future experiments can now determine which of these diaphragmatic proteins are sufficient and/or required to promote exercise-induced protection against inactivity-induced muscle atrophy.

Catalytic Conversion of Lipophilic Substrates by Phase constrained Enzymes in the Aqueous or in the Membrane Phase

Both soluble and membrane-bound enzymes can catalyze the conversion of lipophilic substrates. The precise substrate access path, with regard to phase, has however, until now relied on conjecture from enzyme structural data only (certainly giving credible and valuable hypotheses). Alternative methods have been missing. To obtain the first experimental evidence directly determining the access paths (of lipophilic substrates) to phase constrained enzymes we here describe the application of a BODIPY-derived substrate (PS1). Using this tool, which is not accessible to cytosolic enzymes in the presence of detergent and, by contrast, not accessible to membrane embedded enzymes in the absence of detergent, we demonstrate that cytosolic and microsomal glutathione transferases (GSTs), both catalyzing the activation of PS1, do so only within their respective phases. This approach can serve as a guideline to experimentally validate substrate access paths, a fundamental property of phase restricted enzymes. Examples of other enzyme classes with members in both phases are xenobiotic-metabolizing sulphotransferases/UDP-glucuronosyl transferases or epoxide hydrolases. Since specific GSTs have been suggested to contribute to tumor drug resistance, PS1 can also be utilized as a tool to discriminate between phase constrained members of these enzymes by analyzing samples in the absence and presence of Triton X-100.

Effect of nine diets on mRNAs of phase-II conjugation enzymes in livers of mice

1. Phase-II enzymes are important in metabolizing many xenobiotics including prescription drugs and chemical carcinogens. Whereas it is known that diet can alter the expression of phase-II conjugation enzymes, the previous studies are limited in using only two or three diets and examining only a few enzymes. 2. Adult male C57BL6 mice were fed one of nine diets for 3 weeks. Of the 87 genes encoding major hepatic phase-II enzymes, approximately one-half (43) were altered by at least one diet. Diet restriction altered the hepatic expression of the most genes encoding phase-II enzymes (27), followed by lab chow (15), atherogenic diet (13), high-fat diet (10), western diet (7), high-fructose diet (5), and essential fatty acid-deficient diet (3), whereas the low n-3 fatty acid diet had no effect on the hepatic expression of these phase-II enzymes. 3. This comprehensive study provides detailed information on which conjugation enzymes are changed by these diets, and these data can be used to further investigate the mechanism for these changes in messenger RNAs, and whether these changes result in alterations in enzyme activity and drug action.

Orphan proteins of unknown function in the mitochondrial intermembrane space proteome: New pathways and metabolic cross-talk

The mitochondrial intermembrane space (IMS) is involved in protein transport, lipid homeostasis and metal ion exchange, while further acting in signalling pathways such as apoptosis. Regulation of these processes involves protein modifications, as well as stress-induced import or release of proteins and other signalling molecules. Even though the IMS is the smallest sub-compartment of mitochondria, its redox state seems to be tightly regulated. However, the way in which this compartment participates in the cross-talk between the multiple organelles and the cytosol is far from understood. Here we focus on newly identified IMS proteins that may represent future challenges in mitochondrial research. We present an overview of the import pathways, the recently discovered new components of the IMS proteome and how these relate to key aspects of cell signalling and progress made in stem cell and cancer research.

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A brief overview of the classic mitochondrial import pathways is featured

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Recent studies assigning a number of new proteins to the mitochondrial IMS are discussed

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Analysis of the expanded IMS proteomes can provide insights into organelle cross-talk and signalling pathways

V-PYRRO/NO downregulates mRNA expression levels of leukotriene C4 synthase during hepatic ischemia reperfusion injury in rats via inhibition of the nuclear factor-κB activation pathway

The aim of the present study was to explore the mechanism underlying the effects of a selective liver nitric oxide (NO) donor, O²-vinyl1-(pyrrolidin-1-yl)-diazen-1-ium-1,2-diolate (V-PYRRO/NO), on the gene expression of leukotriene C4 synthase (LTC4S) during hepatic ischemia/reperfusion (I/R). Adult male Sprague-Dawley rats were divided into 3 groups: Sham (control), I/R and V-PYRRO/NO + I/R groups. The liver was subjected to 1 h of partial hepatic ischemia followed by 5 h of reperfusion, saline or V-PYRRO/NO (1.06 µmol/kg/h) administered intravenously. The mRNA expression levels of LTC4S in rat liver tissue were examined by the reverse transcription-polymerase chain reaction method, the protein expression levels of nuclear factor-κB (NF-κB) p65, p50 and IκBα in liver cell lysates and nuclear extracts were detected by western blot analysis. Hepatic mRNA expression of LTC4S was lower in V-PYRRO/NO + I/R group compared to the I/R group. In addition, the protein expression levels of NF-κB p65 and p50 in the nucleus extract were lower in the V-PYRRO/NO + I/R group when compared with the I/R group. However, the IκBα protein in the 3 groups was not changed. Immunohistochemistry staining revealed that the I/R liver exhibited strong cytoplasmic and nuclear staining for NF-κB p65; however, the V-PYRRO/NO + I/R group liver presented slight cytoplasmic and nuclear staining. In conclusion, V-PYRRO/NO may downregulate LTC4S mRNA expression by inhibiting NF-κB activation independent of IκBα during hepatic I/R injury.

Detoxification of insecticides, allechemicals and heavy metals by glutathione S-transferase SlGSTE1 in the gut of Spodoptera litura

Insect glutathione S-transferases (GSTs) play important roles in detoxifying toxic compounds and eliminating oxidative stress caused by these compounds. In this study, detoxification activity of the epsilon GST SlGSTE1 in Spodoptera litura was analyzed for several insecticides and heavy metals. SlGSTE1 was significantly up-regulated by chlorpyrifos and xanthotoxin in the midgut of S. litura. The recombinant SlGSTE1 had Vmax (reaction rate of the enzyme saturated with the substrate) and Km (michaelis constant and equals to the substrate concentration at half of the maximum reaction rate of the enzyme) values of 27.95 ± 0.88 μmol/min/mg and 0.87 ± 0.028 mmol/L for glutathione, respectively, and Vmax and Km values of 22.96 ± 0.78 μmol/min/mg and 0.83 ± 0.106 mmol/L for 1-chloro-2,4-dinitrobenzene, respectively. In vitro enzyme indirect activity assay showed that the recombinant SlGSTE1 possessed high binding activities to the insecticides chlorpyrifos, deltamethrin, malathion, phoxim and dichloro-diphenyl-trichloroethane (DDT). SlGSTE1 showed higher binding activity to toxic heavy metals cadmium, chromium and lead than copper and zinc that are required for insect normal growth. Western blot analysis showed that SlGSTE1 was induced in the gut of larvae fed with chlorpyrifos or cadmium. SlGSTE1 also showed high peroxidase activity. All the results together indicate that SlGSTE1 may play an important role in the gut of S. litura to protect the insect from the toxic effects of these compounds and heavy metals.

Characterization of glutathione transferases involved in the pathogenicity of Alternaria brassicicola

BACKGROUND

Glutathione transferases (GSTs) represent an extended family of multifunctional proteins involved in detoxification processes and tolerance to oxidative stress. We thus anticipated that some GSTs could play an essential role in the protection of fungal necrotrophs against plant-derived toxic metabolites and reactive oxygen species that accumulate at the host-pathogen interface during infection.

RESULTS

Mining the genome of the necrotrophic Brassica pathogen Alternaria brassicicola for glutathione transferase revealed 23 sequences, 17 of which could be clustered into the main classes previously defined for fungal GSTs and six were 'orphans'. Five isothiocyanate-inducible GSTs from five different classes were more thoroughly investigated. Analysis of their catalytic properties revealed that two GSTs, belonging to the GSTFuA and GTT1 classes, exhibited GSH transferase activity with isothiocyanates (ITC) and peroxidase activity with cumene hydroperoxide, respectively. Mutant deficient for these two GSTs were however neither more susceptible to ITC nor less aggressive than the wild-type parental strain. By contrast mutants deficient for two other GSTs, belonging to the Ure2pB and GSTO classes, were distinguished by their hyper-susceptibility to ITC and low aggressiveness against Brassica oleracea. In particular AbGSTO1 could participate in cell tolerance to ITC due to its glutathione-dependent thioltransferase activity. The fifth ITC-inducible GST belonged to the MAPEG class and although it was not possible to produce the soluble active form of this protein in a bacterial expression system, the corresponding deficient mutant failed to develop normal symptoms on host plant tissues.

CONCLUSIONS

Among the five ITC-inducible GSTs analyzed in this study, three were found essential for full aggressiveness of A. brassicicola on host plant. This, to our knowledge is the first evidence that GSTs might be essential virulence factors for fungal necrotrophs.

Joint genetic analysis of hippocampal size in mouse and human identifies a novel gene linked to neurodegenerative disease

BACKGROUND

Variation in hippocampal volume has been linked to significant differences in memory, behavior, and cognition among individuals. To identify genetic variants underlying such differences and associated disease phenotypes, multinational consortia such as ENIGMA have used large magnetic resonance imaging (MRI) data sets in human GWAS studies. In addition, mapping studies in mouse model systems have identified genetic variants for brain structure variation with great power. A key challenge is to understand how genetically based differences in brain structure lead to the propensity to develop specific neurological disorders.

RESULTS

We combine the largest human GWAS of brain structure with the largest mammalian model system, the BXD recombinant inbred mouse population, to identify novel genetic targets influencing brain structure variation that are linked to increased risk for neurological disorders. We first use a novel cross-species, comparative analysis using mouse and human genetic data to identify a candidate gene, MGST3, associated with adult hippocampus size in both systems. We then establish the coregulation and function of this gene in a comprehensive systems-analysis.

CONCLUSIONS

We find that MGST3 is associated with hippocampus size and is linked to a group of neurodegenerative disorders, such as Alzheimer's.

Genetic variation in antioxidant enzymes, cigarette smoking, and longitudinal change in lung function

Antioxidant enzymes play an important role in the defense against oxidative stress in the lung and in the pathogenesis of chronic obstructive pulmonary disease (COPD). Sequence variation in genes encoding antioxidant enzymes may alter susceptibility to COPD by affecting longitudinal change in lung function in adults. We genotyped 384 sequence variants in 56 candidate genes in 1281 African American and 1794 European American elderly adults in the Health, Aging, and Body Composition study. Single-marker associations and gene-by-smoking interactions with rate of change in FEV₁ and FEV₁/FVC were evaluated using linear mixed-effects models, stratified by race/ethnicity. In European Americans, rs17883901 in GCLC was statistically significantly associated with rate of change in FEV₁/FVC; the recessive genotype (TT) was associated with a 0.9% per year steeper decline (P = 4.50 × 10(-5)). Statistically significant gene-by-smoking interactions were observed for variants in two genes in European Americans: the minor allele of rs2297765 in mGST3 attenuated the accelerated decline in FEV₁/FVC in smokers by 0.45% per year (P = 1.13 × 10(-4)); for participants with greater baseline smoking pack-years, the minor allele of rs2073192 in IDH3B was associated with an accelerated decline in FEV₁/FVC (P = 2.10 × 10(-4)). For both genes, nominally significant interactions (P < 0.01) were observed at the gene level in African Americans (P = 0.007 and 4.60 × 10(-4), respectively). Nominally significant evidence of association was observed for variants in SOD3 and GLRX2 in multiple analyses. This study identifies two novel genes associated with longitudinal lung function phenotypes in both African and European Americans and confirms a prior finding for GCLC. These findings suggest novel mechanisms and molecular targets for future research and advance the understanding of genetic determinants of lung function and COPD risk.

Modulation of oxidative stress by twist oncoproteins

Expression of developmental genes Twist1 and Twist2 is reactivated in many human tumors. Among their oncogenic activities, induction of epithelial to mesenchymal transition is believed to increase cell motility and invasiveness and may be related to acquisition of cancer stem cell phenotype. In addition, Twist proteins promote malignant conversion by overriding two oncogene-induced failsafe programs: senescence and apoptosis. Reactive oxygen species (ROS) are also important mediators of apoptosis, senescence and motility and are tightly linked to disease, notably to cancer. We report here that Twist factors and ROS are functionally linked. In wild type cells both Twist1 and Twist2 exhibit antioxidant properties. We show that Twist-driven modulation of oncogene-induced apoptosis is linked to its effects on oxidative stress. Finally, we identify several targets that mediate Twist antioxidant activity. These findings unveil a new function of Twist factors that could be important in explaining their pleiotropic role during carcinogenesis.

Genome evolution in the cold: Antarctic icefish muscle transcriptome reveals selective duplications increasing mitochondrial function

Antarctic notothenioids radiated over millions of years in subzero waters, evolving peculiar features, such as antifreeze glycoproteins and absence of heat shock response. Icefish, family Channichthyidae, also lack oxygen-binding proteins and display extreme modifications, including high mitochondrial densities in aerobic tissues. A genomic expansion accompanying the evolution of these fish was reported, but paucity of genomic information limits the understanding of notothenioid cold adaptation. We reconstructed and annotated the first skeletal muscle transcriptome of the icefish Chionodraco hamatus providing a new resource for icefish genomics (http://compgen.bio.unipd.it/chamatusbase/, last accessed December 12, 2012). We exploited deep sequencing of this energy-dependent tissue to test the hypothesis of selective duplication of genes involved in mitochondrial function. We developed a bioinformatic approach to univocally assign C. hamatus transcripts to orthology groups extracted from phylogenetic trees of five model species. Chionodraco hamatus duplicates were recorded for each orthology group allowing the identification of duplicated genes specific to the icefish lineage. Significantly more duplicates were found in the icefish when transcriptome data were compared with whole-genome data of model species. Indeed, duplicated genes were significantly enriched in proteins with mitochondrial localization, involved in mitochondrial function and biogenesis. In cold conditions and without oxygen-carrying proteins, energy production is challenging. The combination of high mitochondrial densities and the maintenance of duplicated genes involved in mitochondrial biogenesis and aerobic respiration might confer a selective advantage by improving oxygen diffusion and energy supply to aerobic tissues. Our results provide new insights into the genomic basis of icefish cold adaptation.

RNA-sequencing quantification of hepatic ontogeny and tissue distribution of mRNAs of phase II enzymes in mice

Phase II conjugating enzymes play key roles in the metabolism of xenobiotics. In the present study, RNA sequencing was used to elucidate hepatic ontogeny and tissue distribution of mRNA expression of all major known Phase II enzymes, including enzymes involved in glucuronidation, sulfation, glutathione conjugation, acetylation, methylation, and amino acid conjugation, as well as enzymes for the synthesis of Phase II cosubstrates, in male C57BL/6J mice. Livers from male C57BL/6J mice were collected at 12 ages from prenatal to adulthood. Many of these Phase II enzymes were expressed at much higher levels in adult livers than in perinatal livers, such as Ugt1a6b, -2a3, -2b1, -2b5, -2b36, -3a1, and -3a2; Gsta1, -m1, -p1, -p2, and -z1; mGst1; Nat8; Comt; Nnmt; Baat; Ugdh; and Gclc. In contrast, hepatic mRNA expression of a few Phase II enzymes decreased during postnatal liver development, such as mGst2, mGst3, Gclm, and Mat2a. Hepatic expression of certain Phase II enzymes peaked during the adolescent stage, such as Ugt1a1, Sult1a1, Sult1c2, Sult1d1, Sult2as, Sult5a1, Tpmt, Glyat, Ugp2, and Mat1a. In adult mice, the total transcripts for Phase II enzymes were comparable in liver, kidney, and small intestine; however, individual Phase II enzymes displayed marked tissue specificity among the three organs. In conclusion, this study unveils for the first time developmental changes in mRNA abundance of all major known Phase II enzymes in mouse liver, as well as their tissue-specific expression in key drug-metabolizing organs. The age- and tissue-specific expression of Phase II enzymes indicate that the detoxification of xenobiotics is highly regulated by age and cell type.

The leukotrienes: immune-modulating lipid mediators of disease

The leukotrienes are important lipid mediators with immune modulatory and proinflammatory properties. Classical bioactions of leukotrienes include chemotaxis, endothelial adherence, and activation of leukocytes, chemokine production, as well as contraction of smooth muscles in the microcirculation and respiratory tract. When formed in excess, these compounds play a pathogenic role in several acute and chronic inflammatory diseases, such as asthma, rheumatoid arthritis, and inflammatory bowel disease. An increasing number of diseases have been linked to inflammation implicating the leukotrienes as potential mediators. For example, recent investigations using genetic, morphological, and biochemical approaches have pointed to the involvement of leukotrienes in cardiovascular diseases including atherosclerosis, myocardial infarction, stroke, and abdominal aortic aneurysm. Moreover, new insights have changed our previous notion of leukotrienes as mediators of inflammatory reactions to molecules that can fine-tune the innate and adaptive immune response. Here, we review the most recent understanding of the leukotriene cascade with emphasis on recently identified roles in immune reactions and pathophysiology.

Regulation of leukotriene and 5oxoETE synthesis and the effect of 5-lipoxygenase inhibitors: a mathematical modeling approach

BACKGROUND

5-lipoxygenase (5-LO) is a key enzyme in the synthesis of leukotrienes and 5-Oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (oxoETE). These inflammatory signaling molecules play a role in the pathology of asthma and so 5-LO inhibition is a promising target for asthma therapy. The 5-LO redox inhibitor zileuton (Zyflo IR/CR(®)) is currently marketed for the treatment of asthma in adults and children, but widespread use of zileuton is limited by its efficacy/safety profile, potentially related to its redox characteristics. Thus, a quantitative, mechanistic description of its functioning may be useful for development of improved anti-inflammatory targeting this mechanism.

RESULTS

A mathematical model describing the operation of 5-LO, phospholipase A2, glutathione peroxidase and 5-hydroxyeicosanoid dehydrogenase was developed. The catalytic cycles of the enzymes were reconstructed and kinetic parameters estimated on the basis of available experimental data. The final model describes each stage of cys-leukotriene biosynthesis and the reactions involved in oxoETE production. Regulation of these processes by substrates (phospholipid concentration) and intracellular redox state (concentrations of reduced glutathione, glutathione (GSH), and lipid peroxide) were taken into account. The model enabled us to reveal differences between redox and non-redox 5-LO inhibitors under conditions of oxidative stress. Despite both redox and non-redox inhibitors suppressing leukotriene A4 (LTA4) synthesis, redox inhibitors are predicted to increase oxoETE production, thus compromising efficacy. This phenomena can be explained in terms of the pseudo-peroxidase activity of 5-LO and the ability of lipid peroxides to transform 5-LO into its active form even in the presence of redox inhibitors.

CONCLUSIONS

The mathematical model developed described quantitatively different mechanisms of 5-LO inhibition and simulations revealed differences between the potential therapeutic outcomes for these mechanisms.

Cloning of a novel glutathione S-transferase 3 (GST3) gene and expressionanalysis in pearl oyster, Pinctada martensii

Microsomal glutathione S-transferase (MGST) functions in cellular defense against xenobiotics and provides protection against the action of lipid hydroperoxides produced as a consequence of oxidative stress. In this study, a full-length cDNA encoding MGST3 (referred to as PmMGST3) was identified from the pearl oyster, Pinctada martensii by a combination of expressed sequence tag (EST) analysis and rapid amplification of cDNA ends (RACE). The full-length cDNA of PmMGST3 is 971 bp and contains a 5' UTR of 39 bp, a 3' UTR of 491 bp with a canonical polyadenylation signal sequence (AATAAA), and an open reading frame (ORF) of 447 bp encoding a polypeptide of 146 residues. The deduced polypeptide contains a conserved motif (FNCx(1)QRx(2)H) characteristic of the MGST3 subfamily. The PmMGST3 transcript could be detected in all tissues tested, with highest transcript level seen in hepatopancreas. Cadmium treatment significantly increased PmMGST3 mRNA levels in gill and hepatopancreas, while bacterial challenge initially depressed mRNA levels and then increased its level in haemocytes, gill and hepatopancreas in a time-dependent manner. In an assay using cumene hydroperoxide as a substrate, we demonstrated that PmMGST3 possesses glutathione-dependent peroxidase activity. These results suggest that PmMGST3 plays an important role in cellular defense against oxidative stress caused by cadmium and bacteria.

Glutathione s-transferases in pediatric cancer

The glutathione S-transferases (GSTs) are a family of ubiquitously expressed polymorphic enzymes important for detoxifying endogenous and exogenous compounds. In addition to their classic activity of detoxification by conjugation of compounds with glutathione, many other functions are now found to be associated with GSTs. The associations between GST polymorphisms/functions and human disease susceptibility or treatment outcome, mostly in adults, have been extensively studied and reviewed. This mini review focuses on studies related to GST epidemiology and functions related to pediatric cancer. Opportunities to exploit GST in pediatric cancer therapy are also discussed.

Mechanisms of induction of cytosolic and microsomal glutathione transferase (GST) genes by xenobiotics and pro-inflammatory agents

Glutathione transferase (GST) isoezymes are encoded by three separate families of genes (designated cytosolic, microsomal and mitochondrial transferases), with distinct evolutionary origins, that provide mammalian species with protection against electrophiles and oxidative stressors in the environment. Members of the cytosolic class Alpha, Mu, Pi and Theta GST, and also certain microsomal transferases (MGST2 and MGST3), are up-regulated by a diverse spectrum of foreign compounds typified by phenobarbital, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, pregnenolone-16α-carbonitrile, 3-methylcholanthrene, 2,3,7,8-tetrachloro-dibenzo-p-dioxin, β-naphthoflavone, butylated hydroxyanisole, ethoxyquin, oltipraz, fumaric acid, sulforaphane, coumarin, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole, 12-O-tetradecanoylphorbol-13-acetate, dexamethasone and thiazolidinediones. Collectively, these compounds induce gene expression through the constitutive androstane receptor (CAR), the pregnane X receptor (PXR), the aryl hydrocarbon receptor (AhR), NF-E2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor-γ (PPARγ) and CAATT/enhancer binding protein (C/EBP) β. The microsomal T family includes 5-lipoxygenase activating protein (FLAP), leukotriene C(4) synthase (LTC4S) and prostaglandin E(2) synthase (PGES-1), and these are up-regulated by tumour necrosis factor-α, lipopolysaccharide and transforming growth factor-β. Induction of genes encoding FLAP, LTC4S and PGES-1 is mediated by the transcription factors C/EBPα, C/EBPδ, C/EBPϵ, nuclear factor-κB and early growth response-1. In this article we have reviewed the literature describing the mechanisms by which cytosolic and microsomal GST are up-regulated by xenobiotics, drugs, cytokines and endotoxin. We discuss cross-talk between the different induction mechanisms, and have employed bioinformatics to identify cis-elements in the upstream regions of GST genes to which the various transcription factors mentioned above may be recruited.

Microsomal glutathione transferase 1: mechanism and functional roles

Microsomal glutathione transferase 1 (MGST1) belongs to a superfamily named MAPEG (membrane-associated proteins in eicosanoid and glutathione metabolism). This family is represented in all life forms, except archae. Of the six human members, three are specialized in the synthesis of leukotrienes and prostaglandin E, whereas the others (MGST1-3) have potential roles in drug metabolism. MGST1 has a well-established role in the conjugation of electrophiles and oxidative stress protection, whereas MGST2 and 3 have been less studied. Here, we review the recent advances regarding the structure, mechanism, and functional roles of MGST1. Emerging data show that the enzyme is overexpressed in certain tumors and support a role for the enzyme in protecting cells from cytostatic drugs.