Role of Glyoxalase 1 (Glo1) and methylglyoxal (MG) in behavior: recent advances and mechanistic insights

G2A as a key modulator of carbonyl stress and apoptosis resistance in glucose-loaded cancer cells

Cancer cells exhibit high glycolytic activity, metabolizing glucose as their primary energy substrate. Toxic metabolites produced during glycolysis, such as methylglyoxal, induce carbonyl stress (CS), promoting inflammation and oxidative stress. The elevated glucose metabolism in cancer cells creates this toxic environment. However, little research has focused on the molecules mediating these reactions and stresses, and their role in selecting and enriching apoptosis-resistant cells. This study investigated the impact of constitutively suppressing oxidized lipid receptor G2A (GPR132) expression on the relationship between CS and oxidative stress in glucose-loaded cancer cells. G2A has recently attracted attention as a tumor promoter. However, our study shows that G2A suppression under glucose loading significantly reduces CS and associated oxidative stress, thereby enhancing cancer cell survival. This suggests a new mechanism contrary to conventional thinking, involving the acute induction of glyoxalase 1 (Glo1). G2A may thus play a role in selecting and enriching apoptosis-resistant cell populations under high glucose conditions by regulating Glo1 expression. These findings improve our understanding of the adaptive capacity of cancer cells to glucose toxicity.

Genomic Analysis Identifies Risk Factors in Restless Legs Syndrome

OBJECTIVE

Restless legs syndrome (RLS) is a neurological condition that causes uncomfortable sensations in the legs and an irresistible urge to move them, typically during periods of rest. The genetic basis and pathophysiology of RLS are incompletely understood. We sought to identify additional novel genetic risk factors associated with RLS susceptibility.

METHODS

We performed a whole-genome sequencing and genome-wide association meta-analysis of RLS cases (n = 9,851) and controls (n = 38,957) in 3 population-based biobanks (All of Us, Canadian Longitudinal Study on Aging, and CARTaGENE).

RESULTS

Genome-wide association analysis identified 9 independent risk loci, of which 8 had been previously reported, and 1 was a novel risk locus (LMX1B, rs35196838, OR 1.14, 95% CI 1.09-1.19, p value = 2.2 × 10-9). Furthermore, a transcriptome-wide association study also identified GLO1 and a previously unreported gene, ELFN1. A genetic correlation analysis revealed significant common variant overlaps between RLS and neuroticism (rg = 0.40, se = 0.08, p value = 5.4 × 10-7), depression (rg = 0.35, se = 0.06, p value = 2.17 × 10-8), and intelligence (rg = -0.20, se = 0.06, p value = 4.0 × 10-4).

INTERPRETATION

Our study expands the understanding of the genetic architecture of RLS, and highlights the contributions of common variants to this prevalent neurological disorder. ANN NEUROL 2024;96:994-1005.

Antioxidative and Antiglycative Stress Activities of Selenoglutathione Diselenide

The damage caused by oxidative and glycative stress to cells accumulates on a daily basis and accelerates aging. Glutathione (GSH), a major antioxidant molecule in living organisms, plays a crucial role in detoxifying the stress-causing substances inherent in cells, such as H2O2 and methylglyoxal (MG), an important intermediate of advanced glycation end-products (AGEs). In this study, we focused on the enhanced antioxidant capacity of the selenium analog of GSH, i.e., selenoglutathione (GSeH), compared to GSH, and examined its effects on the detoxification of stress-causing substances and improvement in cell viability. In cell-free systems, GSeH (1 mM) generated in situ from GSeSeG in the presence of NADPH and glutathione reductase (GR) rapidly reduced more than 80% of 0.1 mM H2O2, indicating the significant glutathione peroxidase (GPx)-like antioxidant activity of GSeSeG. Similarly, around 50% of 0.5 mM MG was degraded by 0.5 mM GSeH within 30 min through a non-enzymatic mechanism. It was also found that GSeSeG (0.05-0.5 mM) showed glutathione S-transferase (GST)-like activity against 1-chloro-2,4-dinitrobenzene (CDNB), a model substance of oxidative stress-causing toxic materials in cells. Meanwhile, HeLa cells that had been pre-treated with GSeSeG exhibited increased viability against 1.2 mM H2O2 (at [GSeSeG] = 0.5-50 μM) and 4 mM MG (at [GSeSeG] = 3 μM), and the latter effect was maintained for two days. Thus, GSeSeG is a potential antioxidant and antiglycative stress agent for cells.

Endogenous Cellular Metabolite Methylglyoxal Induces DNA-Protein Cross-Links in Living Cells

Methylglyoxal (MGO) is an electrophilic α-oxoaldehyde generated endogenously through metabolism of carbohydrates and exogenously due to autoxidation of sugars, degradation of lipids, and fermentation during food and drink processing. MGO can react with nucleophilic sites within proteins and DNA to form covalent adducts. MGO-induced advanced glycation end-products such as protein and DNA adducts are thought to be involved in oxidative stress, inflammation, diabetes, cancer, renal failure, and neurodegenerative diseases. Additionally, MGO has been hypothesized to form toxic DNA-protein cross-links (DPC), but the identities of proteins participating in such cross-linking in cells have not been determined. In the present work, we quantified DPC formation in human cells exposed to MGO and identified proteins trapped on DNA upon MGO exposure using mass spectrometry-based proteomics. A total of 265 proteins were found to participate in MGO-derived DPC formation including gene products engaged in telomere organization, nucleosome assembly, and gene expression. In vitro experiments confirmed DPC formation between DNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), as well as histone proteins H3.1 and H4. Collectively, our study provides the first evidence for MGO-mediated DNA-protein cross-linking in living cells, prompting future studies regarding the relevance of these toxic lesions in cancer, diabetes, and other diseases linked to elevated MGO levels.

Molecular Assessment of Methylglyoxal-Induced Toxicity and Therapeutic Approaches in Various Diseases: Exploring the Interplay with the Glyoxalase System

This comprehensive exploration delves into the intricate interplay of methylglyoxal (MG) and glyoxalase 1 (GLO I) in various physiological and pathological contexts. The linchpin of the narrative revolves around the role of these small molecules in age-related issues, diabetes, obesity, cardiovascular diseases, and neurodegenerative disorders. Methylglyoxal, a reactive dicarbonyl metabolite, takes center stage, becoming a principal player in the development of AGEs and contributing to cell and tissue dysfunction. The dual facets of GLO I-activation and inhibition-unfold as potential therapeutic avenues. Activators, spanning synthetic drugs like candesartan to natural compounds like polyphenols and isothiocyanates, aim to restore GLO I function. These molecular enhancers showcase promising outcomes in conditions such as diabetic retinopathy, kidney disease, and beyond. On the contrary, GLO I inhibitors emerge as crucial players in cancer treatment, offering new possibilities in diseases associated with inflammation and multidrug resistance. The symphony of small molecules, from GLO I activators to inhibitors, presents a nuanced understanding of MG regulation. From natural compounds to synthetic drugs, each element contributes to a molecular orchestra, promising novel interventions and personalized approaches in the pursuit of health and wellbeing. The abstract concludes with an emphasis on the necessity of rigorous clinical trials to validate these findings and acknowledges the importance of individual variability in the complex landscape of health.

Clinical validation of electrochemical biosensor for the detection of methylglyoxal in subjects with type-2 diabetes mellitus

Methylglyoxal (MG), a highly reactive by-product of glycolysis, is involved in the formation of advanced glycation end-products (AGEs). Elevated levels of MG have been correlated with micro-and macro-angiopathic complications in diabetes, including neuropathy, kidney disease, retinopathy, and cardiovascular disease. Therefore, point-of-care devices for detecting MG may be of great use in the screening of diabetes complications. This study was designed to determine the utility of the developed electrochemical biosensor to measure the level of MG in human plasma from type-2 diabetes mellitus patients. Electrochemical studies were carried out with optimized experimental parameters using the modified Platinum-electrode. Subsequently, clinical studies using 350 blood plasma samples were conducted and the results were validated against the ELISA kit, Normal Glucose Tolerance (NGT), and glycosylated haemoglobin (HbA1c). The MG sensor exhibited a linear range of 1.0-7.5 μM concentration with a sensitivity of 1.02 mA µM-1, a limit of detection of 0.21 µM, a limit of quantification of 0.70 µM and a response time less than 10 s. The sensor showed 90% correlation with ELISA data. The developed biosensor showed a significant correlation with HbA1c and fasting plasma glucose suggesting that it can be used as a point-of-care device to screen for diabetes.

Sex-specific interactions between stress axis and redox balance are associated with internalizing symptoms and brain white matter microstructure in adolescents

Adolescence is marked by the maturation of systems involved in emotional regulation and by an increased risk for internalizing disorders (anxiety/depression), especially in females. Hypothalamic-pituitary-adrenal (HPA)-axis function and redox homeostasis (balance between reactive oxygen species and antioxidants) have both been associated with internalizing disorders and may represent critical factors for the development of brain networks of emotional regulation. However, sex-specific interactions between these factors and internalizing symptoms and their link with brain maturation remain unexplored. We investigated in a cohort of adolescents aged 13-15 from the general population (n = 69) whether sex-differences in internalizing symptoms were associated with the glutathione (GSH)-redox cycle homeostasis and HPA-axis function and if these parameters were associated with brain white matter microstructure development. Female adolescents displayed higher levels of internalizing symptoms, GSH-peroxidase (GPx) activity and cortisol/11-deoxycortisol ratio than males. There was a strong correlation between GPx and GSH-reductase (Gred) activities in females only. The cortisol/11-deoxycortisol ratio, related to the HPA-axis activity, was associated with internalizing symptoms in both sexes, whereas GPx activity was associated with internalizing symptoms in females specifically. The cortisol/11-deoxycortisol ratio mediated sex-differences in internalizing symptoms and the association between anxiety and GPx activity in females specifically. In females, GPx activity was positively associated with generalized fractional anisotropy in widespread white matter brain regions. We found that higher levels of internalizing symptoms in female adolescents than in males relate to sex-differences in HPA-axis function. In females, our results suggest an important interplay between HPA-axis function and GSH-homeostasis, a parameter strongly associated with brain white matter microstructure.

Genomic analysis identifies risk factors in restless legs syndrome

Restless legs syndrome (RLS) is a neurological condition that causes uncomfortable sensations in the legs and an irresistible urge to move them, typically during periods of rest. The genetic basis and pathophysiology of RLS are incompletely understood. Here, we present a whole-genome sequencing and genome-wide association meta-analysis of RLS cases (n = 9,851) and controls (n = 38,957) in three population-based biobanks (All of Us, Canadian Longitudinal Study on Aging, and CARTaGENE). Genome-wide association analysis identified nine independent risk loci, of which eight had been previously reported, and one was a novel risk locus (LMX1B, rs35196838, OR = 1.14, 95% CI = 1.09-1.19, p-value = 2.2 × 10-9). A genome-wide, gene-based common variant analysis identified GLO1 as an additional risk gene (p-value = 8.45 × 10-7). Furthermore, a transcriptome-wide association study also identified GLO1 and a previously unreported gene, ELFN1. A genetic correlation analysis revealed significant common variant overlaps between RLS and neuroticism (rg = 0.40, se = 0.08, p-value = 5.4 × 10-7), depression (rg = 0.35, se = 0.06, p-value = 2.17 × 10-8), and intelligence (rg = -0.20, se = 0.06, p-value = 4.0 × 10-4). Our study expands the understanding of the genetic architecture of RLS and highlights the contributions of common variants to this prevalent neurological disorder.

Cerebrospinal fluid exploratory proteomics and ketamine metabolite pharmacokinetics in human volunteers after ketamine infusion

Ketamine is a treatment for both refractory depression and chronic pain syndromes. In order to explore ketamine's potential mechanism of action and whether ketamine or its metabolites cross the blood brain barrier, we examined the pharmacokinetics of ketamine and its metabolites-norketamine (NK), dehydronorketamine (DHNK), and hydroxynorketamines (HNKs)-in cerebrospinal fluid (CSF) and plasma, as well as in an exploratory proteomic analysis in the CSF of nine healthy volunteers who received ketamine intravenously (0.5 mg/kg IV). We found that ketamine, NK, and (2R,6R;2S,6S)-HNK readily crossed the blood brain barrier. Additionally, 354 proteins were altered in the CSF in at least two consecutive timepoints (p < 0.01). Proteins in the classes of tyrosine kinases, cellular adhesion molecules, and growth factors, including insulin, were most affected, suggesting an interplay of altered neurotransmission, neuroplasticity, neurogenesis, synaptogenesis, and neural network functions following ketamine administration.

Local low-frequency vibration accelerates healing of full-thickness wounds in a hyperglycemic rat model

AIMS/INTRODUCTION

Local low-frequency vibration (LLFV) promotes vasodilation and blood flow, enhancing wound healing in diabetic foot ulcers with angiopathy. However, vibration-induced vasodilation does not occur, owing to chronic hyperglycemia and inflammation. We hypothesized that LLFV improves glycometabolism and inflammation, leading to vasodilation and angiogenesis in diabetic wounds. Therefore, this study investigated the effect of LLFV on wound healing in hyperglycemic rats, primarily focusing on glycometabolism, inflammation, vasodilation, and angiogenesis.

MATERIALS AND METHODS

Streptozotocin-induced hyperglycemic Sprague-Dawley rats were used in this study. We applied LLFV to experimentally-induced wounds at 50 Hz and 0, 600, 1,000 or 1,500 mVpp for 40 min/day from post-wounding days (PWD) 1-14.

RESULTS

The relative wound areas in the 600 and 1,000 mVpp groups on PWD 5-7 were significantly smaller than those at 0 mVpp. The expression of Glo-1 (1,500 mVpp) and Slc2A4 (1,000 and 1,500 mVpp) was upregulated on PWD 4 and 14, respectively. However, there was no difference in methylglyoxal expression levels in any group until PWD 14. At 1,000 mVpp, the expression of Tnfa on PWD 4, and that of Ptx3 and Ccl2 on PWD 14 was downregulated. Furthermore, the M1/M2 macrophage ratio was considerably decreased on both days. The expression of Nos3, Vegfa and vascular endothelial growth factor A was upregulated on PWD 4. In addition, vasodilation and angiogenesis were more obvious on PWD 14 with 1,000 mVpp.

CONCLUSIONS

The results suggest that LLFV promotes wound healing, improves glycometabolism and inflammation, and enhances vasodilation and angiogenesis in hyperglycemic wounds.

Advanced maternal age leads to changes within the insulin/IGF system and lipid metabolism in the reproductive tract and preimplantation embryo: insights from the rabbit model

Reproductive potential in women declines with age. The impact of ageing on embryo-maternal interactions is still unclear. Rabbits were used as a reproductive model to investigate maternal age-related alterations in reproductive organs and embryos on Day 6 of pregnancy. Blood, ovaries, endometrium, and blastocysts from young (16-20 weeks) and advanced maternal age phase (>108 weeks, old) rabbits were analysed at the mRNA and protein levels to investigate the insulin-like growth factor (IGF) system, lipid metabolism, and stress defence system. Older rabbits had lower numbers of embryos at Day 6 of pregnancy. Plasma insulin and IGF levels were reduced, which was accompanied by paracrine regulation of IGFs and their receptors in ovaries and endometrium. Embryos adapted to hormonal changes as indicated by reduced embryonic IGF1 and 2 levels. Aged reproductive organs increased energy generation from the degradation of fatty acids, leading to higher oxidative stress. Stress markers, including catalase, superoxide dismutase 2, and receptor for advanced glycation end products were elevated in ovaries and endometrium from aged rabbits. Embryonic fatty acid uptake and β-oxidation were increased in both embryonic compartments (embryoblast and trophoblast) in old rabbits, associated with minor changes in the oxidative and glycative stress defence systems. In summary, the insulin/IGF system, lipid metabolism, and stress defence were dysregulated in reproductive tissues of older rabbits, which is consistent with changes in embryonic metabolism and stress defence. These data highlight the crucial influence of maternal age on uterine adaptability and embryo development.

Epigenetic meets metabolism: novel vulnerabilities to fight cancer

Histones undergo a plethora of post-translational modifications (PTMs) that regulate nucleosome and chromatin dynamics and thus dictate cell fate. Several evidences suggest that the accumulation of epigenetic alterations is one of the key driving forces triggering aberrant cellular proliferation, invasion, metastasis and chemoresistance pathways. Recently a novel class of histone "non-enzymatic covalent modifications" (NECMs), correlating epigenome landscape and metabolic rewiring, have been described. These modifications are tightly related to cell metabolic fitness and are able to impair chromatin architecture. During metabolic reprogramming, the high metabolic flux induces the accumulation of metabolic intermediate and/or by-products able to react with histone tails altering epigenome homeostasis. The accumulation of histone NECMs is a damaging condition that cancer cells counteracts by overexpressing peculiar "eraser" enzymes capable of removing these modifications preserving histones architecture. In this review we explored the well-established NECMs, emphasizing the role of their corresponding eraser enzymes. Additionally, we provide a parterre of drugs aiming to target those eraser enzymes with the intent to propose novel routes of personalized medicine based on the identification of epi-biomarkers which might be selectively targeted for therapy. Video Abstract.

Methylglyoxal-derived hydroimidazolone, MG-H1, increases food intake by altering tyramine signaling via the GATA transcription factor ELT-3 in Caenorhabditis elegans

The Maillard reaction, a chemical reaction between amino acids and sugars, is exploited to produce flavorful food ubiquitously, from the baking industry to our everyday lives. However, the Maillard reaction also occurs in all cells, from prokaryotes to eukaryotes, forming advanced glycation end-products (AGEs). AGEs are a heterogeneous group of compounds resulting from the irreversible reaction between biomolecules and α-dicarbonyls (α-DCs), including methylglyoxal (MGO), an unavoidable byproduct of anaerobic glycolysis and lipid peroxidation. We previously demonstrated that Caenorhabditis elegans mutants lacking the glod-4 glyoxalase enzyme displayed enhanced accumulation of α-DCs, reduced lifespan, increased neuronal damage, and touch hypersensitivity. Here, we demonstrate that glod-4 mutation increased food intake and identify that MGO-derived hydroimidazolone, MG-H1, is a mediator of the observed increase in food intake. RNAseq analysis in glod-4 knockdown worms identified upregulation of several neurotransmitters and feeding genes. Suppressor screening of the overfeeding phenotype identified the tdc-1-tyramine-tyra-2/ser-2 signaling as an essential pathway mediating AGE (MG-H1)-induced feeding in glod-4 mutants. We also identified the elt-3 GATA transcription factor as an essential upstream regulator for increased feeding upon accumulation of AGEs by partially controlling the expression of tdc-1 gene. Furthermore, the lack of either tdc-1 or tyra-2/ser-2 receptors suppresses the reduced lifespan and rescues neuronal damage observed in glod-4 mutants. Thus, in C. elegans, we identified an elt-3 regulated tyramine-dependent pathway mediating the toxic effects of MG-H1 AGE. Understanding this signaling pathway may help understand hedonistic overfeeding behavior observed due to modern AGE-rich diets.

Genome insight and probiotic potential of three novel species of the genus Corynebacterium

Three bacterial strains, B5-R-101^T, TA-R-1^T, and BL-R-1^T, were isolated from the feces of a healthy Korean individual. Cells of these strains were Gram-stain-positive, facultatively anaerobic, oxidase-negative, catalase-positive, rod-shaped, and non-motile. They were able to grow within a temperature range of 10-42°C (optimum, 32-37°C), at a pH range of 2.0-10.0 (optimum, pH 5.5-8.0), and at NaCl concentration of 0.5-10.5% (w/v). All the three strains exhibited 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities ranging from 58 ± 1.62 to 79 ± 1.46% (% inhibition). These strains survived in lower pH (2.0) and in 0.3% bile salt concentration for 4 h. They did not show hemolytic activity and exhibited antimicrobial activity against pathogenic bacteria, such as Escherichia coli, Acinetobacter baumannii, Staphylococcus aureus, and Salmonella enterica. The genomic analysis presented no significant concerns regarding antibiotic resistance or virulence gene content, indicating these strains could be potential probiotic candidates. Phylogenetic analysis showed that they belonged to the genus Corynebacterium, with 98.5-99.0% 16S rRNA gene sequence similarities to other members of the genus. Their major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The abundant cellular fatty acids were C_16:0, C_18:1ω9c, and anteiso-C_19:0. Genomic analysis of these isolates revealed the presence of genes necessary for their survival and growth in the gut environment, such as multi-subunit ATPases, stress response genes, extracellular polymeric substance biosynthesis genes, and antibacterial genes. Furthermore, the genome of each strain possessed biosynthetic gene clusters with antioxidant and antimicrobial potentials, including terpenes, saccharides, polyketides, post-translationally modified peptides (RIPPs), and non-ribosomal peptides (NRPs). In silico DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values were lower than the thresholds to distinguish novel species. Based on phenotypic, genomic, phylogenomic, and phylogenetic analysis, these potential probiotic strains represent novel species within the genus Corynebacterium, for which the names Corynebacterium intestinale sp. nov. (type strain B5-R-101^T = CGMCC 1.19408^T = KCTC 49761^T), Corynebacterium stercoris sp. nov. (type strain TA-R-1^T = CGMCC 1.60014^T = KCTC 49742^T), and Corynebacterium faecium sp. nov. (type strain BL-R-1^T = KCTC 49735^T = TBRC 17331^T) are proposed.

Glyoxalase 1 inhibitor BBGC suppresses the progression of chronic lymphocytic leukemia and promotes the efficacy of Palbociclib

Chronic lymphocytic leukemia (CLL) is a highly heterogeneous disease. Despite recent tremen-dous progress in managing CLL, the disease remains incurable with clinical therapies, and relapse is inevitable. To overcome this, new diagnostic and prognostic markers need to be investigated. We thus screened through the public database for genes with diagnostic, prognostic, and therapeutic implications in CLL. We further performed RT-qPCR and Western blot analysis to measure the candidate gene and protein expression levels, respectively, in peripheral blood mononuclear cells. Our results indicated that Glyoxalase 1 (GLO1) expression was significantly higher in patients with CLL than in healthy controls. Furthermore, cell proliferation, apoptosis, and cell cycle assay results together indicated that S-p-bromobenzylglutathione cyclopentyl diester (BBGC), an effective inhibitor of GLO1, suppresses the progression of CLL. Bioinformatics analysis revealed that GLO1 expression is closely associated with CDK4 expression in a wide variety of cancer types, and inhibition of CDK4 through silencing of genes or inhibitors can downregulate GLO1 expression. Subsequent validation experiments demonstrated that GLO1 protein levels were downregulated in MEC-1 and Jurkat cell lines after palbociclib exposure, and combination treatment of palbociclib with GLO1 inhibitor BBGC effectively delayed the growth of tumor cell lines.

The expanding impact of methylglyoxal on behavior-related disorders

Methylglyoxal (MGO) is a reactive dicarbonyl compound formed as a byproduct of glycolysis. MGO is a major cell-permeant precursor of advanced glycation end products (AGEs), since it readily reacts with basic phospholipids and nucleotides, as well as amino acid residues of proteins, such as arginine, cysteine, and lysine. The AGEs production induced by MGO are widely associated with several pathologies, including neurodegenerative diseases. However, the impact of MGO metabolism and AGEs formation in the central nervous system (particularly in neurons, astrocytes and oligodendrocytes) on behavior and psychiatric diseases is not fully understood. Here, we briefly present background information on the biological activity of MGO in the central nervous system. It was gathered the available information on the role of MGO metabolism at the physiological processes, as well as at the neurobiology of psychiatry diseases, especially pain-related experiences, anxiety, depression, and cognition impairment-associated diseases. To clarify the role of MGO on behavior and associated diseases, we reviewed primarily the main findings at preclinical studies focusing on genetic and pharmacological approaches. Since monoamine neurotransmitter systems are implicated as pivotal targets on the pathophysiology and treatment of psychiatry and cognitive-related diseases, we also reviewed how MGO affects these neurotransmission systems and the implications of this phenomenon for nociception and pain; learning and cognition; and mood. In summary, this review highlights the pivotal role of glyoxalase 1 (Glo1) and MGO levels in modulating behavioral phenotypes, as well as related cellular and molecular signaling. Conclusively, this review signals dopamine as a new neurochemical MGO target, as well as highlights how MGO metabolism can modulate the pathophysiology and treatment of pain, psychiatric and cognitive-related diseases.

Methylglyoxal in the Brain: From Glycolytic Metabolite to Signalling Molecule

Advances in molecular biology technology have piqued tremendous interest in glycometabolism and bioenergetics in homeostasis and neural development linked to ageing and age-related diseases. Methylglyoxal (MGO) is a by-product of glycolysis, and it can covalently modify proteins, nucleic acids, and lipids, leading to cell growth inhibition and, eventually, cell death. MGO can alter intracellular calcium homeostasis, which is a major cell-permeant precursor to advanced glycation end-products (AGEs). As side-products or signalling molecules, MGO is involved in several pathologies, including neurodevelopmental disorders, ageing, and neurodegenerative diseases. In this review, we demonstrate that MGO (the metabolic side-product of glycolysis), the GLO system, and their analogous relationship with behavioural phenotypes, epigenetics, ageing, pain, and CNS degeneration. Furthermore, we summarise several therapeutic approaches that target MGO and the glyoxalase (GLO) system in neurodegenerative diseases.

Resolving Enantiomers of 2-Hydroxy Acids by Nuclear Magnetic Resonance

Biologically important 2-hydroxy carboxylates such as lactate, malate, and 2-hydroxyglutarate exist in two enantiomeric forms that cannot be distinguished under achiral conditions. The D and L (or R, S) enantiomers have different biological origins and functions, and therefore, there is a need for a simple method for resolving, identifying, and quantifying these enantiomers. We have adapted and improved a chiral derivatization technique for nuclear magnetic resonance (NMR), which needs no chromatography for enantiomer resolution, with greater than 90% overall recovery. This method was developed for 2-hydroxyglutarate (2HG) to produce diastereomers resolvable by column chromatography. We have applied the method to lactate, malate, and 2HG. The limit of quantification was determined to be about 1 nmol for 2HG with coefficients of variation of less than 5%. We also demonstrated the method on an extract of a renal carcinoma bearing an isocitrate dehydrogenase-2 (IDH2) variant that produces copious quantities of 2HG and showed that it is the D enantiomer that was exclusively produced. We also demonstrated in the same experiment that the lactate produced in the same sample was the L enantiomer.

Formation and metabolism of 6-(1-acetol)-8-(1-acetol)-rutin in foods and in vivo, and their cytotoxicity

Methylglyoxal (MGO) is a highly reactive precursor which forms advanced glycation end-products (AGEs) in vivo, which lead to metabolic syndrome and chronic diseases. It is also a precursor of various carcinogens, including acrylamide and methylimidazole, in thermally processed foods. Rutin could efficiently scavenge MGO by the formation of various adducts. However, the metabolism and safety concerns of the derived adducts were paid less attention to. In this study, the optical isomers of di-MGO adducts of rutin, namely 6-(1-acetol)-8-(1-acetol)-rutin, were identified in foods and in vivo. After oral administration of rutin (100 mg/kg BW), these compounds reached the maximum level of 15.80 μg/L in plasma at 15 min, and decreased sharply under the quantitative level in 30 min. They were detected only in trace levels in kidney and fecal samples, while their corresponding oxidized adducts with dione structures presented as the predominant adducts in kidney, heart, and brain tissues, as well as in urine and feces. These results indicated that the unoxidized rutin-MGO adducts formed immediately after rutin ingestion might easily underwent oxidation, and finally deposited in tissues and excreted from the body in the oxidized forms. The formation of 6-(1-acetol)-8-(1-acetol)-rutin significantly mitigated the cytotoxicity of MGO against human gastric epithelial (GES-1), human colon carcinoma (Caco-2), and human umbilical vein endothelial (HUVEC) cells, which indicated that rutin has the potential to be applied as a safe and effective MGO scavenger and detoxifier, and AGEs inhibitor.

GLO1 Contributes to the Drug Resistance of Escherichia coli Through Inducing PER Type of Extended-Spectrum β-Lactamases

Background

Escherichia coli-associated antimicrobial resistance (AMR) issue so far needs urgent considerations. This study aims to screen the potent genes associated with extended-spectrum β-lactamases (ESBLs) in drug-resistant Escherichia coli and elucidate the specific drug-resistant mechanism.

Methods

Clinical ESBLs-EC samples were obtained based on the microbial identification, and the whole genome was sequenced. In combination with the significantly enriched pathways, several differently expressed genes were screened and verified by RT-PCR. Furthermore, through knocking out glyoxalase 1 (GLO1) gene and transfecting overexpressed plasmids, the potential relationship between GLO1 and ESBLs was then investigated. Lastly, the concentrations of β-lactamases in bacteria and supernatant from different groups were examined by enzyme-linked immunosorbent assay (ELISA).

Results

After successful isolation and identification of ESBLs-EC, the whole genome and eighteen differential metabolic pathways were analyzed to select differently expressed genes, including add, deoD, guaD, speG, GLO1, VNN1, etc. RT-PCR results showed that there were no differences in these genes between the standard bacteria and susceptible Escherichia coli. Remarkably, the relative levels of four genes including speG, Hdac10, GLO1 and Ppcdc were significantly increased in ESBLs-EC in comparison with susceptible strains, whereas other gene expression was decreased. Further experiments utilizing gene knockout and overexpression strains confirmed the role of GLO1. At last, a total of 10 subtypes of β-lactamases were studied using ELISA, including BES-, CTX-M1-, CTX-M2-, OXA1-, OXA2-, OXA10-, PER-, SHV-, TEM-, and VEB-ESBLs, and results demonstrated that GLO1 gene expression only affected PER-β-lactamases but had no effects on other β-lactamases.

Conclusion

SpeG, Hdac10, GLO1 and Ppcdc might be associated with the drug-resistant mechanism of Escherichia coli. Of note, this study firstly addressed the role of GLO1 in the drug resistance of ESBLs-EC, and this effect may be mediated by increasing PER-β-lactamases.

With No Lysine Kinase 1 Promotes Metabolic Derangements and RV Dysfunction in Pulmonary Arterial Hypertension

Small molecule inhibition of with no lysine kinase 1 (WNK1) (WNK463) signaling activates adenosine monophosphate-activated protein kinase signaling and mitigates membrane enrichment of glucose transporters 1 and 4, which decreases protein O-GlcNAcylation and glycation. Quantitative proteomics of right ventricular (RV) mitochondrial enrichments shows WNK463 prevents down-regulation of several mitochondrial metabolic enzymes. and metabolomics analysis suggests multiple metabolic processes are corrected. Physiologically, WNK463 augments RV systolic and diastolic function independent of pulmonary arterial hypertension severity. Hypochloremia, a condition of predicted WNK1 activation in patients with pulmonary arterial hypertension, is associated with more severe RV dysfunction. These results suggest WNK1 may be a druggable target to combat metabolic dysregulation and may improve RV function and survival in pulmonary arterial hypertension.

Microarray profiling and identification of core promoter sequence in Gordonia

Gordonia are Gram-positive bacteria which have immense biotechnological potential. Genomes of several Gordonia spp. have been sequenced but a detailed analysis of the differentially expressed genes during growth, the promoters which drive their expression and the information on the core promoter sequence is lacking. Here, we report the identification of core promoter sequence in Gordonia sp. IITR100. The GC content of the promoters was found to be within a range of 62-65%. The 5'-UTR length in the genes was also analysed and about 56% promoters were found to have long 5'-UTR. The functionality of the promoters was validated by microarray profiling. Based on the differential expression of genes, two growth phase dependent promoters PdsbA and Pglx were isolated and analysed. They add to the existing repertoire of the promoters functional in both Gram-negative and Gram-positive bacteria. Our results suggest that the core promoter sequence identified is conserved in members of Gordonia spp. and is similar to that of other members of Actinobacteria.

Inosine mitigated diabetic peripheral neuropathy via modulating GLO1/AGEs/RAGE/NF-κB/Nrf2 and TGF-β/PKC/TRPV1 signaling pathways

Inosine is a dietary supplement that is widely used for managing numerous central neurological disorders. Interestingly, recent experimental investigation of inosine revealed its potential to promote peripheral neuroprotection after sciatic nerve injury. Such investigation has guided the focus of the current study to expose the potential of inosine in mitigating diabetic peripheral neuropathy (DPN) in rats and to study the possible underlying signaling pathways. Adult male Wistar rats were arbitrarily distributed into four groups. In the first group, animals received saline daily for 15 days whereas rats of the remaining groups received a single injection of both nicotinamide (50 mg/Kg/i.p.) and streptozotocin (52.5 mg/Kg/i.p.) for DPN induction. Afterward, inosine (10 mg/Kg/p.o.) was administered to two groups, either alone or in combination with caffeine (3.75 mg/Kg/p.o.), an adenosine receptor antagonist. As a result, inosine showed a hypoglycemic effect, restored the sciatic nerve histological structure, enhanced myelination, modulated conduction velocities and maintained behavioral responses. Furthermore, inosine increased GLO1, reduced AGE/RAGE axis and oxidative stress which in turn, downregulated NF-κB p65 and its phosphorylated form in the sciatic nerves. Inosine enhanced Nrf2 expression and its downstream molecule HO-1, resulting in increased CAT and SOD along with lowered MDA. Moreover, pain was relieved due to suppression of PKC and TRPV1 expression, which ultimately lead to reduced SP and TGF-β. The potential effects of inosine were nearly blocked by caffeine administration; this emphasizes the role of adenosine receptors in inosine-mediated neuroprotective effects. In conclusion, inosine alleviated hyperglycemia-induced DPN via modulating GLO1/AGE/RAGE/NF-κB p65/Nrf2 and TGF-β/PKC/TRPV1/SP pathways.

Eugenol and its liposome-based nano carrier reduce anxiety by inhibiting glyoxylase-1 expression in mice

The most common form of psycho-social dysfunction is anxiety with depression being related closely without any age bar. They are present with combined state of sadness, confusion, stress, fear etc. Glyoxalase system contains enzyme named glyoxalase 1 (GLO1).It is a metabolic pathway which detoxifies alpha-oxo-aldehydes, particularly methylglyoxal (MG). Methylglyoxal is mainly made by the breakdown of the glycolytic intermediates, glyceraldehyde-3-phosphates and dihydroxyacetone phosphate. Glyoxylase-1 expression is also related with anxiety behavior. A casual role or GLO-1 in anxiety behavior by using viral vectors for over expression in the anterior cingulate cortex was found and it was found that local GLO-1 over expression increased anxiety behavior. The present study deals with the molecular mechanism of protective activity of eugenol against anxiolytic disorder. A pre-clinical animal study was performed on 42 BALB/c mice. Animals were given stress through conventional restrain model. The mRNA expression of GLO-1 was analyzed by real time RT-PCR. Moreover, the GLO-1 protein expression was also examined by immunohistochemistry in whole brain and mean density was calculated. The mRNA and protein expressions were found to be increased in animals given anxiety as compared to the normal control. Whereas, the expressions were decreased in the animals treated with eugenol and its liposome-based nanocarriers in a dose dependent manner. However, the results were better in animals treated with nanocarriers as compared to the compound alone. It is concluded that the eugenol and its liposome-based nanocarriers exert anxiolytic activity by down-regulating GLO-1 protein expression in mice.

Single Cell Gene Expression Analysis in a 3D Microtissue Liver Model Reveals Cell Type-Specific Responses to Pro-Fibrotic TGF-β1 Stimulation

3D cell culture systems are widely used to study disease mechanisms and therapeutic interventions. Multicellular liver microtissues (MTs) comprising HepaRG, hTERT-HSC and THP-1 maintain multicellular interactions and physiological properties required to mimic liver fibrosis. However, the inherent complexity of multicellular 3D-systems often hinders the discrimination of cell type specific responses. Here, we aimed at applying single cell sequencing (scRNA-seq) to discern the molecular responses of cells involved in the development of fibrosis elicited by TGF-β1. To obtain single cell suspensions from the MTs, an enzymatic dissociation method was optimized. Isolated cells showed good viability, could be re-plated and cultured in 2D, and expressed specific markers determined by scRNA-seq, qRT-PCR, ELISA and immunostaining. The three cell populations were successfully clustered using supervised and unsupervised methods based on scRNA-seq data. TGF-β1 led to a fibrotic phenotype in the MTs, detected as decreased albumin and increased αSMA expression. Cell-type specific responses to the treatment were identified for each of the three cell types. They included HepaRG damage characterized by a decrease in cellular metabolism, prototypical inflammatory responses in THP-1s and extracellular matrix remodeling in hTERT-HSCs. Furthermore, we identified novel cell-specific putative fibrosis markers in hTERT-HSC (COL15A1), and THP-1 (ALOX5AP and LAPTM5).

Methylglyoxal-Mediated Dopamine Depletion, Working Memory Deficit, and Depression-Like Behavior Are Prevented by a Dopamine/Noradrenaline Reuptake Inhibitor

Methylglyoxal (MGO) is an endogenous toxin, mainly produced as a by-product of glycolysis that has been associated to aging, Alzheimer's disease, and inflammation. Cell culture studies reported that MGO could impair the glyoxalase, thioredoxin, and glutathione systems. Thus, we investigated the effect of in vivo MGO administration on these systems, but no major changes were observed in the glyoxalase, thioredoxin, and glutathione systems, as evaluated in the prefrontal cortex and the hippocampus of mice. A previous study from our group indicated that MGO administration produced learning/memory deficits and depression-like behavior. Confirming these findings, the tail suspension test indicated that MGO treatment for 7 days leads to depression-like behavior in three different mice strains. MGO treatment for 12 days induced working memory impairment, as evaluated in the Y maze spontaneous alternation test, which was paralleled by low dopamine and serotonin levels in the cerebral cortex. Increased DARPP32 Thr75/Thr34 phosphorylation ratio was observed, suggesting a suppression of phosphatase 1 inhibition, which may be involved in behavioral responses to MGO. Co-treatment with a dopamine/noradrenaline reuptake inhibitor (bupropion, 10 mg/kg, p.o.) reversed the depression-like behavior and working memory impairment and restored the serotonin and dopamine levels in the cerebral cortex. Overall, the cerebral cortex monoaminergic system appears to be a preferential target of MGO toxicity, a new potential therapeutic target that remains to be addressed.

Glyoxalase 1 Inhibitor Alleviates Autism-like Phenotype in a Prenatal Valproic Acid-Induced Mouse Model

Autism spectrum disorder (ASD) is a severe neurological and developmental disorder that impairs a person's ability to socialize and communicate and affects behavior. The number of patients diagnosed with ASD has risen rapidly. However, the pathophysiology of ASD is poorly understood, and drugs for ASD treatment are strikingly limited. This study aims to evaluate the roles of glyoxalase 1 (GLO1)-methylglyoxal (MG)-γ-aminobutyric acid (GABA) signaling in ASD using a valproic acid (VPA)-induced animal model of autism. The GLO1 levels were analyzed by RT-qPCR and Western blot assay, and MG levels were measured with a Methylglyoxal Assay Kit. The open-field and sniff duration tests were used to assess the interest and anxiety of VPA mice. The three-chamber, marble-burying, and tail-flick tests were applied to determine the sociability, repetitive behavior, and nociceptive threshold of VPA mice. Our results demonstrated that increased GLO1 and decreased MG were observed in VPA mice. Administration of S-p-bromobenzylglutathione cyclopentyl diester (BrBzGCp2), a GLO1 inhibitor, was beneficial for alleviating anxiety, reducing repetitive behavior, and improving the impaired sociability and nociceptive threshold of VPA mice. BrBzGCp2 treatment may be developed as a promising therapeutic strategy for patients with ASD.

Non-enzymatic covalent modifications: a new link between metabolism and epigenetics

Epigenetic modifications, including those on DNA and histones, have been shown to regulate cellular metabolism by controlling expression of enzymes involved in the corresponding metabolic pathways. In turn, metabolic flux influences epigenetic regulation by affecting the biosynthetic balance of enzyme cofactors or donors for certain chromatin modifications. Recently, non-enzymatic covalent modifications (NECMs) by chemically reactive metabolites have been reported to manipulate chromatin architecture and gene transcription through multiple mechanisms. Here, we summarize these recent advances in the identification and characterization of NECMs on nucleic acids, histones, and transcription factors, providing an additional mechanistic link between metabolism and epigenetics.

Oxidative-Antioxidant Imbalance and Impaired Glucose Metabolism in Schizophrenia

Schizophrenia is a neurodevelopmental disorder featuring chronic, complex neuropsychiatric features. The etiology and pathogenesis of schizophrenia are not fully understood. Oxidative-antioxidant imbalance is a potential determinant of schizophrenia. Oxidative, nitrosative, or sulfuric damage to enzymes of glycolysis and tricarboxylic acid cycle, as well as calcium transport and ATP biosynthesis might cause impaired bioenergetics function in the brain. This could explain the initial symptoms, such as the first psychotic episode and mild cognitive impairment. Another concept of the etiopathogenesis of schizophrenia is associated with impaired glucose metabolism and insulin resistance with the activation of the mTOR mitochondrial pathway, which may contribute to impaired neuronal development. Consequently, cognitive processes requiring ATP are compromised and dysfunctions in synaptic transmission lead to neuronal death, preceding changes in key brain areas. This review summarizes the role and mutual interactions of oxidative damage and impaired glucose metabolism as key factors affecting metabolic complications in schizophrenia. These observations may be a premise for novel potential therapeutic targets that will delay not only the onset of first symptoms but also the progression of schizophrenia and its complications.

Synthesis of an Alkynyl Methylglyoxal Probe to Investigate Nonenzymatic Histone Glycation

Methylglyoxal (MGO) is a reactive dicarbonyl metabolite that modifies histones in vivo and induces changes in chromatin structure and function. Here we report the synthesis and application of a chemical probe for investigating MGO-glycation. A two-step synthesis of a Cu-click compatible alkynyl oxoaldehyde probe (AlkMGO) via sequential Dess-Martin and Riley oxidations is presented. This synthesis elevates the accessibility and utility of an important tool for tracking, enriching, and studying MGO-glycation to aid in understanding its underlying biochemical functions.

Glyoxalase 1 gene improves the antistress capacity and reduces the immune inflammatory response

BACKGROUND

Fish immunity is not only affected by the innate immune pathways but is also triggered by stress. Transport and loading stress can induce oxidative stress and further activate the immune inflammatory response, which cause tissue damage and sudden death. Multiple genes take part in this process and some of these genes play a vital role in regulation of the immune inflammatory response and sudden death. Currently, the key genes regulating the immune inflammatory response and the sudden death caused by stress in Coilia nasus are unknown.

RESULTS

In this study, we studied the effects of the Glo1 gene on stress, antioxidant expression, and immune-mediated apoptosis in C. nasus. The full-length gene is 4356 bp, containing six exons and five introns. Southern blotting indicated that Glo1 is a single-copy gene in the C. nasus genome. We found two single-nucleotide polymorphisms (SNPs) in the Glo1 coding region, which affect the three-dimensional structure of Glo1 protein. An association analysis results revealed that the two SNPs are associated with stress tolerance. Moreover, Glo1 mRNA and protein expression of the heterozygous genotype was significantly higher than that of the homozygous genotype. Na+ and sorbitol also significantly enhanced Glo1 mRNA and protein expression, improved the fish's antioxidant capacity, and reduced the immune inflammatory response, thus sharply reducing the mortality caused by stress.

CONCLUSIONS

Glo1 plays a potential role in the stress response, antioxidant capacity, and immune-mediated apoptosis in C. nasus.

Repeated Methylglyoxal Treatment Depletes Dopamine in the Prefrontal Cortex, and Causes Memory Impairment and Depressive-Like Behavior in Mice

Methylglyoxal (MGO) is a highly reactive dicarbonyl molecule that promotes the formation of advanced glycation end products (AGEs), which are believed to play a key role in a number of pathologies, such as diabetes, Alzheimer's disease, and inflammation. Here, Swiss mice were treated with MGO by intraperitoneal injection to investigate its effects on motor activity, mood, and cognition. Acute MGO treatment heavily decreased locomotor activity in the open field test at higher doses (80-200 mg/kg), an effect not observed at lower doses (10-50 mg/kg). Several alterations were observed 4 h after a single MGO injection (10-50 mg/kg): (a) plasma MGO levels were increased, (b) memory was impaired (object location task), (c) anxiolytic behavior was observed in the open field and marble burying test, and (d) depressive-like behavior was evidenced as evaluated by the tail suspension test. Biochemical alterations in the glutathione and glyoxalase systems were not observed 4 h after MGO treatment. Mice were also treated daily with MGO at 0, 10, 25 and 50 mg/kg for 11 days. From the 5th to the 11th day, several behavioral end points were evaluated, resulting in: (a) absence of motor impairment as evaluated in the open field, horizontal bars and pole test, (b) depressive-like behavior observed in the tail suspension test, and (c) cognitive impairments detected on working, short- and long-term memory when mice were tested in the Y-maze spontaneous alternation, object location and recognition tests, and step-down inhibitory avoidance task. An interesting finding was a marked decrease in dopamine levels in the prefrontal cortex of mice treated with 50 mg/kg MGO for 11 days, along with a ~ 25% decrease in the Glo1 content. The MGO-induced dopamine depletion in the prefrontal cortex may be related to the observed memory deficits and depressive-like behavior, an interesting topic to be further studied as a potentially novel route for MGO toxicity.

High expression of GLO1 indicates unfavorable clinical outcomes in glioma patients

BACKGROUNDS

Glyoxalase I (GLO1), a ubiquitous enzyme involved in the process of detoxification of methylglyoxal in the cellular glycolysis pathway, was reported to be highly expressed in human tumor. It has also been found that GLO1 is associated with tumor cell survival and proliferation in some types of cancer, such as pancreatic cancer, hepatocellular carcinoma and gastric cancer. However, the role of GLO1 in glioma has not been clarified. The purpose of present study is to explore the expression pattern of GLO1 and whether the expression level of GLO1 is associated with the unfavorable clinical outcomes of patients with glioma.

METHODS

Quantitative RT-PCR and immunohistochemistry staining were used to investigate the mRNA and protein level of GLO1 in glioma tissues together with normal brain tissues. The prognostic role of GLO1 in glioma patients was assessed using univariate and multivariate analyses. Clinical outcomes were estimated by using the Kaplan-Meier analysis and the log-rank test. The function of GLO1 in glioma cell lines were investigated by in vitro experiments.

RESULTS

Expression level of GLO1 was higher in glioma tissues than that in normal brain tissues. High GLO1 expression was significantly correlated with WHO grade and the poor overall survival time in glioma patients. Moreover, GLO1 was also defined as an unfavorable prognosis factor. Overexpression of GLO1 in the glioma cell line U87 can enhance the tumor cell proliferation, migration and invasion. Whereas, knockdown of GLO1 can suppress those abilities.

CONCLUSIONS

Our studies demonstrated that GLO1 was highly expressed in glioma tissues and significantly correlated with the poor prognosis of glioma patients. It indicated that GLO1 might serve as a new prognostic predictor and therapeutic target for glioma treatment.

Rapid and persistent loss of TXNIP in HT22 neuronal cells under carbonyl and hyperosmotic stress

Thioredoxin interacting protein (TXNIP) binds to thioredoxin thereby limiting its activity, but it also promotes internalization of glucose transporters, participates in inflammasome activation, and controls autophagy. Published data and this work demonstrate that TXNIP responds to a number of apparently unrelated stresses, such as serum deprivation, pH change, and oxidative, osmotic and carbonyl stress. Interestingly, we noticed that hyperosmotic (NaCl) and carbonyl (methylglyoxal, MGO) stresses in HT22 neuronal cells produced a rapid loss of TXNIP (half-life ∼12 min), prompting us to search for possible mechanisms controlling this TXNIP loss, including pH change, serum deprivation, calcium metabolism and inhibition of the proteasome and other proteases, autophagy and MAPKs. None of these routes stopped the TXNIP loss induced by hyperosmotic and carbonyl stress. Besides transcriptional, translational and microRNA regulation, there is evidence indicating that mTOR and AMPK also control TXNIP expression. Indeed, AMPK-deficient mouse embryonic fibroblasts failed to respond to phenformin (AMPK activator) and compound C (AMPK inhibitor), while rapamycin induced a marked increase in TXNIP levels, confirming the known AMPK/mTOR control over TXNIP. However, the TXNIP loss induced by NaCl or MGO were observed even in AMPK deficient MEFs or after mTOR inhibition, indicating AMPK/mTOR does not participate in this rapid TXNIP loss. These results suggest that rapid TXNIP loss is a general and immediate response to stress that can improve energy availability and antioxidant protection, eventually culminating in better cell survival.

Indole-4-carboxaldehyde Isolated from Seaweed, Sargassum thunbergii, Attenuates Methylglyoxal-Induced Hepatic Inflammation

Glucose degradation is aberrantly increased in hyperglycemia, which causes various harmful effects on the liver. Glyoxalase-1 (Glo-1) is a ubiquitous cellular enzyme that participates in the detoxification of methylglyoxal (MGO), a cytotoxic byproduct of glycolysis that induces protein modification (advanced glycation end-products, AGEs) and inflammation. Here, we investigated the anti-inflammatory effect of indole-4-carboxaldehyde (ST-I4C), which was isolated from the edible seaweed Sargassum thunbergii, on MGO-induced inflammation in HepG2 cells, a human hepatocyte cell line. ST-I4C attenuated the MGO-induced expression of inflammatory-related genes, such as tumor necrosis factor (TNF)-α and IFN-γ by activating nuclear factor-kappa B (NF-κB) without toxicity in HepG2 cells. In addition, ST-I4C reduced the MGO-induced AGE formation and the expression of the receptor for AGE (RAGE). Interestingly, both the mRNA and protein expression levels of Glo-1 increased following ST-I4C treatment, and the decrease in Glo-1 mRNA expression caused by MGO exposure was rescued by ST-I4C pretreatment. These results suggest that ST-I4C shows anti-inflammatory activity against MGO-induced inflammation in human hepatocytes by preventing an increase in the pro-inflammatory gene expression and AGE formation. Therefore, it represents a potential therapeutic agent for the prevention of hepatic steatosis.

Effect of dietary vitamin E on oxidative stress-related gene-mediated differences in anxiety-like behavior in inbred strains of mice

It has been reported that the degree of anxiety-like behavior differs between inbred strains of mice, and that this phenomenon was linked to the expression levels of the oxidative stress-related genes glyoxalase 1 (Glo1) and glutathione reductase 1 (Gsr) in the brain. Therefore, we investigated whether antioxidative activity in the brain affects the Glo1 and Gsr mRNA expressions and strain-dependent anxiety-like behavior using mice fed different amounts of vitamin E. First, we measured brain Glo1 and Gsr mRNA levels and evaluated the anxiety-like behaviors presented by C57BL/6J (B6) and DBA/2C (D2) mice. We demonstrated that D2 mice presented both significantly elevated Glo1 and Gsr mRNA levels as well as more prominent anxiety-like behavior in elevated plus-maze and open field tests. Next, we fed mice from these two strains either a control, vitamin E-free, or vitamin E-supplemented diet for four weeks. Plasma, liver, and brain α-tocopherol concentrations changed in a dose-dependent manner. However, neither brain Glo1 and Gsr mRNA levels nor anxiety-like behavior were affected by dietary vitamin E intake. These results demonstrated that while strain-dependent anxiety-like behavior in mice was related to oxidative stress-related gene expression, the regulatory mechanisms for these genes and anxiety-like behaviors were independent of antioxidative activity in the brain. Strain-dependent differences of the anxiety in mice are probably related to the anxiolytic effects of methylglyoxal, a substrate for Glo1 and Gsr.

Methylglyoxal Disrupts Paranodal Axoglial Junctions via Calpain Activation

Nodes of Ranvier and associated paranodal and juxtaparanodal domains along myelinated axons are essential for normal function of the peripheral and central nervous systems. Disruption of these domains as well as increases in the reactive carbonyl species methylglyoxal are implicated as a pathophysiology common to a wide variety of neurological diseases. Here, using an ex vivo nerve exposure model, we show that increasing methylglyoxal produces paranodal disruption, evidenced by disorganized immunostaining of axoglial cell-adhesion proteins, in both sciatic and optic nerves from wild-type mice. Consistent with previous studies showing that increase of methylglyoxal can alter intracellular calcium homeostasis, we found upregulated activity of the calcium-activated protease calpain in sciatic nerves after methylglyoxal exposure. Methylglyoxal exposure altered clusters of proteins that are known as calpain substrates: ezrin in Schwann cell microvilli at the perinodal area and zonula occludens 1 in Schwann cell autotypic junctions at paranodes. Finally, treatment with the calpain inhibitor calpeptin ameliorated methylglyoxal-evoked ezrin loss and paranodal disruption in both sciatic and optic nerves. Our findings strongly suggest that elevated methylglyoxal levels and subsequent calpain activation contribute to the disruption of specialized axoglial domains along myelinated nerve fibers in neurological diseases.

Streptozotocin causes acute responses on hippocampal S100B and BDNF proteins linked to glucose metabolism alterations

Streptozotocin (STZ) is a glucosamine-nitrosourea commonly used to induce long-lasting models of diabetes mellitus and Alzheimer's disease. Direct toxicity of STZ on the pancreas and kidneys has been well characterized, but the acute effect of this compound on brain tissue has received less attention. Herein, we investigated the acute and direct toxicity of STZ on fresh hippocampal slices, measuring changes in BDNF and S100B secretion (two widely-used peripheral markers of brain injury), as well as glucose metabolism. Moreover, we investigated in vivo changes of these proteins in the hippocampus, 48 h after intracerebroventricular STZ administration. Transverse hippocampal slices (0.3 mm thick) were obtained using a McIlwain tissue chopper and target proteins were measured in the incubation medium by ELISA. STZ decreased S100B secretion, but increased BDNF secretion as well as causing impairment in glucose uptake in hippocampal slices, measured using [³H] deoxy-glucose. Glucose levels and glucose metabolism differentially modulated S100B secretion in astrocytes and BDNF secretion in neurons, when evaluated under specific conditions (high-potassium medium, presence of tetrodotoxin or fluorocitrate). Moreover, at 48 h after intracerebroventricular STZ, hippocampal BDNF content, but not S100B, was reduced. Our results indicate that BDNF and S100B are useful and sensitive markers of glucose metabolism disturbance and reinforce these proteins as general acute markers of brain disorders.

Metal-Binding Pharmacophore Library Yields the Discovery of a Glyoxalase 1 Inhibitor

Anxiety and depression are common, highly comorbid psychiatric diseases that account for a large proportion of worldwide medical disability. Glyoxalase 1 (GLO1) has been identified as a possible target for the treatment of anxiety and depression. GLO1 is a Zn²⁺-dependent enzyme that isomerizes a hemithioacetal, formed from glutathione and methylglyoxal, to a lactic acid thioester. To develop active inhibitors of GLO1, fragment-based drug discovery was used to identify fragments that could serve as core scaffolds for lead development. After screening a focused library of metal-binding pharmacophores, 8-(methylsulfonylamino)quinoline (8-MSQ) was identified as a hit. Through computational modeling and synthetic elaboration, a potent GLO1 inhibitor was developed with a novel sulfonamide core pharmacophore. A lead compound was demonstrated to penetrate the blood-brain barrier, elevate levels of methylglyoxal in the brain, and reduce depression-like behavior in mice. These findings provide the basis for GLO1 inhibitors to treat depression and related psychiatric illnesses.

An electrochemical sensor with a copper oxide/gold nanoparticle-modified electrode for the simultaneous detection of the potential diabetic biomarkers methylglyoxal and its detoxification enzyme glyoxalase

Highly sensitive electro-oxidation of the MGO and GLO biomarkers at the CuO/Au/GCE sensor employing the AdSDPV method.

Striatal transcriptome of a mouse model of ADHD reveals a pattern of synaptic remodeling

Despite the prevalence and high heritability of Attention-Deficit/Hyperactivity Disorder (ADHD), genetic etiology remains elusive. Clinical evidence points in part to reduced function of the striatum, but which specific genes are differentially expressed and how they sculpt striatal physiology to predispose ADHD are not well understood. As an exploratory tool, a polygenic mouse model of ADHD was recently developed through selective breeding for high home cage activity. Relative to the Control line, the High-Active line displays hyperactivity and motor impulsivity which are ameliorated with amphetamine. This study compared gene expression in the striatum between Control and High-Active mice to develop a coherent hypothesis for how genes might affect striatal physiology and predispose ADHD-like symptoms. To this end, striatal transcriptomes of High-Active and Control mice were analyzed after mice were treated with saline or amphetamines. The pseudogene Gm6180 for n-cofilin (Cfl1) displayed 20-fold higher expression in High-Active mice corresponding with reduced Cfl1 expression suggesting synaptic actin dysregulation. Latrophilin 3 (Lphn3), which is associated with ADHD in human populations and is involved in synapse structure, and its ligand fibronectin leucine rich transmembrane protein 3 (Flrt3), were downregulated in High-Active mice. Multiple genes were altered in High-Active mice in a manner predicted to downregulate the canonical Wnt pathway. A smaller and different set of genes including glyoxalase (Glo1) were differentially regulated in High-Active as compared to Control in response to amphetamine. Together, results suggest genes involved in excitatory synapse regulation and maintenance are downregulated in ADHD-like mice. Consistent with the molecular prediction, stereological analysis of the striatum from a separate set of mice processed for imunohistochemical detection of synaptophysin revealed approximately a 46% reduction in synaptophysin immunoreactivity in High-Active relative to Control. Results provide a new set of molecular targets related to synapse maintenance for the next generation of ADHD medicines.

Autism-related behaviors in the cyclooxygenase-2-deficient mouse model

Prostaglandin E2 (PGE2) is an endogenous lipid molecule involved in normal brain development. Cyclooxygenase-2 (COX2) is the main regulator of PGE2 synthesis. Emerging clinical and molecular research provides compelling evidence that abnormal COX2/PGE2 signaling is associated with autism spectrum disorder (ASD). We previously found that COX2 knockout mice had dysregulated expression of many ASD genes belonging to important biological pathways for neurodevelopment. The present study is the first to show the connection between irregular COX2/PGE2 signaling and autism-related behaviors in male and female COX2-deficient knockin, (COX)-2^- , mice at young (4-6 weeks) or adult (8-11 weeks) ages. Autism-related behaviors were prominent in male (COX)-2^- mice for most behavioral tests. In the open field test, (COX)-2^- mice traveled more than controls and adult male (COX)-2^- mice spent less time in the center indicating elevated hyperactive and anxiety-linked behaviors. (COX)-2^- mice also buried more marbles, with males burying more than females, suggesting increased anxiety and repetitive behaviors. Young male (COX)-2^- mice fell more frequently in the inverted screen test revealing motor deficits. The three-chamber sociability test found that adult female (COX)-2^- mice spent less time in the novel mouse chamber indicative of social abnormalities. In addition, male (COX)-2^- mice showed altered expression of several autism-linked genes: Wnt2, Glo1, Grm5 and Mmp9. Overall, our findings offer new insight into the involvement of disrupted COX2/PGE2 signaling in ASD pathology with age-related differences and greater impact on males. We propose that (COX)-2^- mice might serve as a novel model system to study specific types of autism.

Intermittent hypoxia, brain glyoxalase-1 and glutathione reductase-1, and anxiety-like behavior in mice

OBJECTIVE

Sleep apnea has been associated with anxiety, but the mechanisms of the sleep apnea-anxiety relationship are unresolved. Sleep apnea causes oxidative stress, which might enhance anxiety-like behavior in rodents. To clarify the apnea-anxiety connection, we tested the effect of intermittent hypoxia, a model of sleep apnea, on the anxiety behavior of mice.

METHODS

The rodents were exposed daily to 480 one-minute cycles of intermittent hypoxia to a nadir of 7±1% inspiratory oxygen fraction or to a sham procedure with room air. After 7 days, the mice from both groups were placed in an elevated plus maze and were video recorded for 10 min to allow analysis of latency, frequency, and duration in open and closed arms. Glyoxalase-1 (Glo1) and glutathione reductase-1 (GR1) were measured in the cerebral cortex, hippocampus, and striatum by Western blotting.

RESULTS

Compared to controls, the intermittent hypoxia group displayed less anxiety-like behavior, perceived by a statistically significant increase in the number of entries and total time spent in open arms. A higher expression of GR1 in the cortex was also observed.

CONCLUSION

The lack of a clear anxiety response as an outcome of intermittent hypoxia exposure suggests the existence of additional layers in the anxiety mechanism in sleep apnea, possibly represented by sleepiness and irreversible neuronal damage.

Sodium benzoate induced developmental defects, oxidative stress and anxiety-like behaviour in zebrafish larva

Sodium benzoate (SB) is a common food preservative. Its FDA described safety limit is 1000 ppm. Lately, increased use of SB has prompted investigations regarding its effects on biological systems. Data regarding toxicity of SB is divergent and controversial with studies reporting both harmful and beneficial effects. Therefore, we did a systematic dose dependent toxicity study of SB using zebrafish vertebrate animal model. We also investigated oxidative stress and anxiety-like behaviour in zebrafish larva treated with SB. Our results indicate that SB induced developmental (delayed hatching), morphological (pericardial edema, yolk sac edema and tail bending), biochemical (oxidative stress) and behavioural (anxiety-like behaviour) abnormalities in developing zebrafish larva. LC₅₀ of SB induced toxicity was approximately 400 ppm after 48 h of SB exposure. Our study strongly supports its harmful effects on vertebrates at increasing doses. Thus, we suggest caution in the excessive use of this preservative in processed and convenience foods.

Neuroprotection through flavonoid: Enhancement of the glyoxalase pathway

The glyoxalase pathway functions to detoxify reactive dicarbonyl compounds, most importantly methylglyoxal. The glyoxalase pathway is an antioxidant defense mechanism that is essential for neuroprotection. Excessive concentrations of methylglyoxal have deleterious effects on cells, leading to increased levels of inflammation and oxidative stress. Neurodegenerative diseases - including Alzheimer's, Parkinson's, Aging and Autism Spectrum Disorder - are often induced or exacerbated by accumulation of methylglyoxal. Antioxidant compounds possess several distinct mechanisms that enhance the glyoxalase pathway and function as neuroprotectants. Flavonoids are well-researched secondary plant metabolites that appear to be effective in reducing levels of oxidative stress and inflammation in neural cells. Novel flavonoids could be designed, synthesized and tested to protect against neurodegenerative diseases through regulating the glyoxalase pathway.

Conflicting Effects of Methylglyoxal and Potential Significance of miRNAs for Seizure Treatment

According to an update from the World Health Organization, approximately 50 million people worldwide suffer from epilepsy, and nearly one-third of these individuals are resistant to the currently available antiepileptic drugs, which has resulted in an insistent pursuit of novel strategies for seizure treatment. Recently, methylglyoxal (MG) was demonstrated to serve as a partial agonist of the gamma-aminobutyric acid type A (GABA_A) receptor and to play an inhibitory role in epileptic activities. However, MG is also a substrate in the generation of advanced glycation end products (AGEs) that function by activating the receptor of AGEs (RAGE). The AGE/RAGE axis is responsible for the transduction of inflammatory cascades and appears to be an adverse pathway in epilepsy. This study systematically reviewed the significance of GABAergic MG, glyoxalase I (GLO1; responsible for enzymatic catalysis of MG cleavage) and downstream RAGE signaling in epilepsy. This work also discussed the potential of miRNAs that target multiple mRNAs and introduced a preliminary scheme for screening and validating miRNA candidates with the goal of reconciling the conflicting effects of MG for the future development of seizure treatments.

Identification of a novel, fast-acting GABAergic antidepressant

Current pharmacotherapies for depression exhibit slow onset, side effects and limited efficacy. Therefore, identification of novel fast-onset antidepressants is desirable. GLO1 is a ubiquitous cellular enzyme responsible for the detoxification of the glycolytic byproduct methylglyoxal (MG). We have previously shown that MG is a competitive partial agonist at GABA-A receptors. We examined the effects of genetic and pharmacological inhibition of GLO1 in two antidepressant assay models: the tail suspension test (TST) and the forced swim test (FST). We also examined the effects of GLO1 inhibition in three models of antidepressant onset: the chronic FST (cFST), chronic mild stress (CMS) paradigm and olfactory bulbectomy (OBX). Genetic knockdown of Glo1 or pharmacological inhibition using two structurally distinct GLO1 inhibitors (S-bromobenzylglutathione cyclopentyl diester (pBBG) or methyl-gerfelin (MeGFN)) reduced immobility in the TST and acute FST. Both GLO1 inhibitors also reduced immobility in the cFST after 5 days of treatment. In contrast, the serotonin reuptake inhibitor fluoxetine (FLX) reduced immobility after 14, but not 5 days of treatment. Furthermore, 5 days of treatment with either GLO1 inhibitor blocked the depression-like effects induced by CMS on the FST and coat state, and attenuated OBX-induced locomotor hyperactivity. Finally, 5 days of treatment with a GLO1 inhibitor (pBBG), but not FLX, induced molecular markers of the antidepressant response including brain-derived neurotrophic factor (BDNF) induction and increased phosphorylated cyclic-AMP response-binding protein (pCREB) to CREB ratio in the hippocampus and medial prefrontal cortex (mPFC). Our findings indicate that GLO1 inhibitors may provide a novel and fast-acting pharmacotherapy for depression.