The glyoxalase system in health and disease

Glyoxalase System in Breast and Ovarian Cancers: Role of MEK/ERK/SMAD1 Pathway

The glyoxalase system, comprising GLO1 and GLO2 enzymes, is integral in detoxifying methylglyoxal (MGO) generated during glycolysis, with dysregulation implicated in various cancer types. The MEK/ERK/SMAD1 signaling pathway, crucial in cellular processes, influences tumorigenesis, metastasis, and angiogenesis. Altered GLO1 expression in cancer showcases its complex role in cellular adaptation and cancer aggressiveness. GLO2 exhibits context-dependent functions, contributing to both proapoptotic and antiapoptotic effects in different cancer scenarios. Research highlights the interconnected nature of these systems, particularly in ovarian cancer and breast cancer. The glyoxalase system's involvement in drug resistance and its impact on the MEK/ERK/SMAD1 signaling cascade underscore their clinical significance. Furthermore, this review delves into the urgent need for effective biomarkers, exemplified in ovarian cancer, where the RAGE-ligand pathway emerges as a potential diagnostic tool. While therapeutic strategies targeting these pathways hold promise, this review emphasizes the challenges posed by context-dependent effects and intricate crosstalk within the cellular milieu. Insights into the molecular intricacies of these pathways offer a foundation for developing innovative therapeutic approaches, providing hope for enhanced cancer diagnostics and tailored treatment strategies.

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.

Aldehyde-mediated inhibition of asparagine biosynthesis has implications for diabetes and alcoholism

Patients with alcoholism and type 2 diabetes manifest altered metabolism, including elevated aldehyde levels and unusually low asparagine levels. We show that asparagine synthetase B (ASNS), the only human asparagine-forming enzyme, is inhibited by disease-relevant reactive aldehydes, including formaldehyde and acetaldehyde. Cellular studies show non-cytotoxic amounts of reactive aldehydes induce a decrease in asparagine levels. Biochemical analyses reveal inhibition results from reaction of the aldehydes with the catalytically important N-terminal cysteine of ASNS. The combined cellular and biochemical results suggest a possible mechanism underlying the low asparagine levels in alcoholism and diabetes. The results will stimulate research on the biological consequences of the reactions of aldehydes with nucleophilic residues.

Comparison of the methylglyoxal scavenging effects of kaempferol and glutathione and the consequences for the toxicity of methylglyoxal in SH-SY5Y cells

This study aimed to characterize the methylglyoxal (MGO) scavenging capacity of glutathione (GSH) and kaempferol in more detail with special emphasis on the possible reversible nature of the adduct formation and their competition for MGO, and the safety consequences of their MGO-scavenging effects. GSH showed immediate and concentration-dependent MGO-scavenging effects, while the scavenging effects by kaempferol appeared concentration- but also time-dependent, with stable adducts formed over time. The GSH adduct gradually disappeared in a competition reaction with kaempferol, and kaempferol became the preferred scavenger over time. Furthermore, the scavenging of MGO by kaempferol provided better protection than GSH against extracellular MGO in SH-SY5Y cells. It is concluded that flavonoids like kaempferol provide better scavengers for food-borne MGO than thiol-based scavengers such as GSH, while, given the endogenous concentrations of both scavengers and the detoxification of the GSH-MGO adduct by the glyoxalase system, GSH will be dominant for intracellular MGO protection.

Mining the Penicillium expansum Genome for Virulence Genes: A Functional-Based Approach to Discover Novel Loci Mediating Blue Mold Decay of Apple Fruit

Blue mold, a postharvest disease of pome fruits, is caused by the filamentous fungus Penicillium expansum. In addition to the economic losses caused by P. expansum, food safety can be compromised, as this pathogen is mycotoxigenic. In this study, forward and reverse genetic approaches were used to identify genes involved in blue mold infection in apple fruits. For this, we generated a random T-DNA insertional mutant library. A total of 448 transformants were generated and screened for the reduced decay phenotype on apples. Of these mutants, six (T-193, T-275, T-434, T-588, T-625, and T-711) were selected for continued studies and five unique genes were identified of interest. In addition, two deletion mutants (Δt-625 and Δt-588) and a knockdown strain (t-434KD) were generated for three loci. Data show that the ∆t-588 mutant phenocopied the T-DNA insertion mutant and had virulence penalties during apple fruit decay. We hypothesize that this locus encodes a glyoxalase due to bioinformatic predictions, thus contributing to reduced colony diameter when grown in methylglyoxal (MG). This work presents novel members of signaling networks and additional genetic factors that regulate fungal virulence in the blue mold fungus during apple fruit decay.

Chemical probes and methods for the study of protein arginine methylation

Protein arginine methylation is a widespread post-translational modification (PTM) in eukaryotic cells. This chemical modification in proteins functionally modulates diverse cellular processes from signal transduction, gene expression, and DNA damage repair to RNA splicing. The chemistry of arginine methylation entails the transfer of the methyl group from S-adenosyl-l-methionine (AdoMet, SAM) onto a guanidino nitrogen atom of an arginine residue of a target protein. This reaction is catalyzed by about 10 members of protein arginine methyltransferases (PRMTs). With impacts on a variety of cellular processes, aberrant expression and activity of PRMTs have been shown in many disease conditions. Particularly in oncology, PRMTs are commonly overexpressed in many cancerous tissues and positively correlated with tumor initiation, development and progression. As such, targeting PRMTs is increasingly recognized as an appealing therapeutic strategy for new drug discovery. In the past decade, a great deal of research efforts has been invested in illuminating PRMT functions in diseases and developing chemical probes for the mechanistic study of PRMTs in biological systems. In this review, we provide a brief developmental history of arginine methylation along with some key updates in arginine methylation research, with a particular emphasis on the chemical aspects of arginine methylation. We highlight the research endeavors for the development and application of chemical approaches and chemical tools for the study of functions of PRMTs and arginine methylation in regulating biology and disease.

A Role for Advanced Glycation End Products in Molecular Ageing

Ageing is a composite process that involves numerous changes at the cellular, tissue, organ and whole-body levels. These changes result in decreased functioning of the organism and the development of certain conditions, which ultimately lead to an increased risk of death. Advanced glycation end products (AGEs) are a family of compounds with a diverse chemical nature. They are the products of non-enzymatic reactions between reducing sugars and proteins, lipids or nucleic acids and are synthesised in high amounts in both physiological and pathological conditions. Accumulation of these molecules increases the level of damage to tissue/organs structures (immune elements, connective tissue, brain, pancreatic beta cells, nephrons, and muscles), which consequently triggers the development of age-related diseases, such as diabetes mellitus, neurodegeneration, and cardiovascular and kidney disorders. Irrespective of the role of AGEs in the initiation or progression of chronic disorders, a reduction in their levels would certainly provide health benefits. In this review, we provide an overview of the role of AGEs in these areas. Moreover, we provide examples of lifestyle interventions, such as caloric restriction or physical activities, that may modulate AGE formation and accumulation and help to promote healthy ageing.

Catalytic Reaction Mechanism of Glyoxalase II: A Quantum Mechanics/Molecular Mechanics Study

Methylglyoxal (MG) is a reactive and toxic compound produced in carbohydrate, lipid, and amino acid metabolism. The glyoxalase system is the main detoxifying route for MG and consists of two enzymes, glyoxalase I (GlxI) and glyoxalase II (GlxII). GlxI catalyzes the formation of S-d-lactoylglutathione from hemithioacetal, and GlxII converts this intermediate to d-lactate. A relationship between the glyoxalase system and some diseases like diabetes has been shown, and inhibiting enzymes of this system may be an effective means of controlling certain diseases. A detailed understanding of the reaction mechanism of an enzyme is essential to the rational design of competitive inhibitors. In this work, we use quantum mechanics/molecular mechanics (QM/MM) calculations and energy refinement utilizing the big-QM and QM/MM thermodynamic cycle perturbation methods to propose a mechanism for the GlxII reaction that starts with a nucleophilic attack of the bridging OH^- group on the substrate. The coordination of the substrate to the Zn ions places its electrophilic center close to the hydroxide group, enabling the reaction to proceed. Our estimated reaction energies are in excellent agreement with experimental data, thus demonstrating the reliability of our approach and the proposed mechanism. Additionally, we examined alternative protonation states of Asp-29, Asp-58, Asp-134, and the bridging hydroxide ion in the catalytic process. However, these give less favorable reactions, a poorer reproduction of the crystal structure geometry of the active site, and higher root-mean-squared deviations of the active site residues in molecular dynamics simulations.

Methylglyoxal: a novel upstream regulator of DNA methylation

BACKGROUND

Aerobic glycolysis, also known as the Warburg effect, is predominantly upregulated in a variety of solid tumors, including breast cancer. We have previously reported that methylglyoxal (MG), a very reactive by-product of glycolysis, unexpectedly enhanced the metastatic potential in triple negative breast cancer (TNBC) cells. MG and MG-derived glycation products have been associated with various diseases, such as diabetes, neurodegenerative disorders, and cancer. Glyoxalase 1 (GLO1) exerts an anti-glycation defense by detoxifying MG to D-lactate.

METHODS

Here, we used our validated model consisting of stable GLO1 depletion to induce MG stress in TNBC cells. Using genome-scale DNA methylation analysis, we report that this condition resulted in DNA hypermethylation in TNBC cells and xenografts.

RESULTS

GLO1-depleted breast cancer cells showed elevated expression of DNMT3B methyltransferase and significant loss of metastasis-related tumor suppressor genes, as assessed using integrated analysis of methylome and transcriptome data. Interestingly, MG scavengers revealed to be as potent as typical DNA demethylating agents at triggering the re-expression of representative silenced genes. Importantly, we delineated an epigenomic MG signature that effectively stratified TNBC patients based on survival.

CONCLUSION

This study emphasizes the importance of MG oncometabolite, occurring downstream of the Warburg effect, as a novel epigenetic regulator and proposes MG scavengers to reverse altered patterns of gene expression in TNBC.

Glycation Interferes with the Activity of the Bi-Functional UDP-N-Acetylglucosamine 2-Epimerase/N-Acetyl-mannosamine Kinase (GNE)

Mutations in the gene coding for the bi-functional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), the key enzyme of the sialic acid biosynthesis, are responsible for autosomal-recessive GNE myopathy (GNEM). GNEM is an adult-onset disease with a yet unknown exact pathophysiology. Since the protein appears to work adequately for a certain period of time even though the mutation is already present, other effects appear to influence the onset and progression of the disease. In this study, we want to investigate whether the late onset of GNEM is based on an age-related effect, e.g., the accumulation of post-translational modifications (PTMs). Furthermore, we also want to investigate what effect on the enzyme activity such an accumulation would have. We will particularly focus on glycation, which is a PTM through non-enzymatic reactions between the carbonyl groups (e.g., of methylglyoxal (MGO) or glyoxal (GO)) with amino groups of proteins or other biomolecules. It is already known that the levels of both MGO and GO increase with age. For our investigations, we express each domain of the GNE separately, treat them with one of the glycation agents, and determine their activity. We demonstrate that the enzymatic activity of the N-acetylmannosamine kinase (GNE-kinase domain) decreases dramatically after glycation with MGO or GO-with a remaining activity of 13% ± 5% (5 mM MGO) and 22% ± 4% (5 mM GO). Whereas the activity of the UDP-N-acetylglucosamine 2-epimerase (GNE-epimerase domain) is only slightly reduced after glycation-with a remaining activity of 60% ± 8% (5 mM MGO) and 63% ± 5% (5 mM GO).

Glutathione-Related Enzymes and Proteins: A Review

The tripeptide glutathione is found in all eukaryotic cells, and due to the compartmentalization of biochemical processes, its synthesis takes place exclusively in the cytosol. At the same time, its functions depend on its transport to/from organelles and interorgan transport, in which the liver plays a central role. Glutathione is determined as a marker of the redox state in many diseases, aging processes, and cell death resulting from its properties and reactivity. It also uses other enzymes and proteins, which enables it to engage and regulate various cell functions. This paper approximates the role of these systems in redox and detoxification reactions such as conjugation reactions of glutathione-S-transferases, glyoxylases, reduction of peroxides through thiol peroxidases (glutathione peroxidases, peroxiredoxins) and thiol-disulfide exchange reactions catalyzed by glutaredoxins.

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.

Glutathione: Pharmacological aspects and implications for clinical use in non-alcoholic fatty liver disease

Glutathione is a tripeptide synthesized at cytosolic level, that exists in cells in a reduced form (thiol-reduced-GSH-) and in an oxidized form (disulfide-oxidized). The antioxidant function of GSH has led to speculation about its therapeutic role in numerous chronic diseases characterized by altered redox balance and reduced GSH levels, including, for instance, neurodegenerative disorders, cancer, and chronic liver diseases. Among these latter, non-alcoholic fatty liver disease (NAFLD), characterized by lipid accumulation in hepatocytes, in the absence of alcohol abuse or other steatogenic factors, is one of the most prevalent. The umbrella term NAFLD includes the pure liver fat accumulation, the so-called hepatic steatosis or non-alcoholic fatty liver, and the progressive form with inflammation, also known as non-alcoholic steatohepatitis, which is related to the increase in oxidative stress and reactive oxygen species, eventually leading to liver fibrosis. Although the pathogenetic role of oxidative stress in these diseases is well established, there is still limited evidence on the therapeutic role of GSH in such conditions. Hence, the aim of this review is to depict the current molecular and pharmacological knowledge on glutathione, focusing on the available studies related to its therapeutic activity in NAFLD.

RAGE-Dependent Effect of Exogenous Methylglyoxal Intake on Lung Biomechanics in Mice

Methylglyoxal (MG) is a known highly reactive dicarbonyl and precursor to free radicals and advanced glycation end-products (AGEs). It is discussed to be involved in tissue aging and in the pathogenesis of different degenerative diseases. The effect of long-term oral administration of MG, simulating dietary MG intake, on the lung biomechanics of wild type (WT) and receptor for advanced glycation end-products knockout (RAGE-KO) mice was studied using an ex vivo ventilation system starting at the age of 6 months and after feeding for 6 and 12 months with MG. Our results showed that MG was taken up in the circulation and efficiently excreted with urine. The amount of free urinary MG measured after 12 months of feeding was lowered. After 12 months feeding, a significant airway resistance increase accompanied by a decrease of the maximal inspiratory airflow was observed in WT animals. No effect of MG in lung function of RAGE-KO mice could be detected. Despite the evidence that MG entered the systemic circulation, no MG-derived AGE accumulation was detected in the lung lysates in dependency on MG-feeding. Our data indicate that the short-term feeding of MG has little effect in vivo. Only after long-term treatment was MG secretion reduced, leading to tissue impairment.

Loss of glyoxalase 2 alters the glucose metabolism in zebrafish

Glyoxalase 2 is the second enzyme of the glyoxalase system, catalyzing the detoxification of methylglyoxal to d-lactate via SD-Lactoylglutathione. Recent in vitro studies have suggested Glo2 as a regulator of glycolysis, but if Glo2 regulates glucose homeostasis and related organ specific functions in vivo has not yet been evaluated. Therefore, a CRISPR-Cas9 knockout of glo2 in zebrafish was created and analyzed. Consistent with its function in methylglyoxal detoxification, SD-Lactoylglutathione, but not methylglyoxal accumulated in glo2^-/- larvae, without altering the glutathione metabolism or affecting longevity. Adult glo2^-/- livers displayed a reduced hexose concentration and a reduced postprandial P70-S6 kinase activation, but upstream postprandial AKT phosphorylation remained unchanged. In contrast, glo2^-/- skeletal muscle remained metabolically intact, possibly compensating for the dysfunctional liver through increased glucose uptake and glycolytic activity. glo2^-/- zebrafish maintained euglycemia and showed no damage of the retinal vasculature, kidney, liver and skeletal muscle. In conclusion, the data identified Glo2 as a regulator of cellular energy metabolism in liver and skeletal muscle, but the redox state and reactive metabolite accumulation were not affected by the loss of Glo2.

The Human Glyoxalase Gene Family in Health and Disease

The glyoxalase gene family consists of six structurally and functionally diverse enzymes with broad roles in metabolism. The common feature that defines this family is based on structural motifs that coordinate divalent cations which are required for activity. These family members have been implicated in a variety of physiological processes, including amino-acid metabolism (4-hydroxyphenylpyruvate dioxygenase; HPD), primary metabolism (methylmalonyl-CoA epimerase; MCEE), and aldehyde detoxication (glyoxalase 1; GLO1) and therefore have significant associations with disease. A central function of this family is the detoxification of reactive dicarbonyls (e.g., methylglyoxal), which react with cellular nucleophiles, resulting in the modification of lipids, proteins, and DNA. These damaging modifications activate canonical stress responses such as heat shock, unfolded protein, antioxidant, and DNA damage responses. Thus, glyoxalases serve an important role in homeostasis, preventing the pathogenesis of metabolic disease states, including obesity, diabetes, cardiovascular disease, renal failure, and aging. This review presents a thorough overview of the literature surrounding this diverse enzyme class. Although extensive literature exists for some members of this family (e.g., GLO1), little is known about the physiological role of glyoxalase domain-containing protein 4 (GLOD4) and 5 (GLOD5), paving the way for exciting avenues for future research.

Glyoxylase-1 combats dicarbonyl stress and right ventricular dysfunction in rodent pulmonary arterial hypertension

Background

Heightened glycolytic flux is associated with right ventricular (RV) dysfunction in pulmonary arterial hypertension (PAH). Methylglyoxal, a glycolysis byproduct, is a highly reactive dicarbonyl that has toxic effects via non-enzymatic post-translational modifications (protein glycation). Methylglyoxal is degraded by the glyoxylase system, which includes the rate-limiting enzyme glyoxylase-1 (GLO1), to combat dicarbonyl stress. However, the potential consequences of excess protein glycation on RV function are unknown.

Methods

Bioinformatics analysis of previously identified glycated proteins predicted how protein glycation regulated cardiac biology. Methylglyoxal treatment of H9c2 cardiomyocytes evaluated the consequences of excess protein glycation on mitochondrial respiration. The effects of adeno-associated virus serotype 9-mediated (AAV9) GLO1 expression on RV function in monocrotaline rats were quantified with echocardiography and hemodynamic studies. Immunoblots and immunofluorescence were implemented to probe the effects of AAV-Glo1 on total protein glycation and fatty acid oxidation (FAO) and fatty acid binding protein levels.

Results

In silico analyses highlighted multiple mitochondrial metabolic pathways may be affected by protein glycation. Exogenous methylglyoxal minimally altered mitochondrial respiration when cells metabolized glucose, however methylglyoxal depressed FAO. AAV9-Glo1 increased RV cardiomyocyte GLO1 expression, reduced total protein glycation, partially restored mitochondrial density, and decreased lipid accumulation. In addition, AAV9-Glo1 increased RV levels of FABP4, a fatty acid binding protein, and hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunits alpha and beta (HADHA and HADHB), the two subunits of the mitochondrial trifunctional protein for FAO. Finally, AAV9-Glo1 blunted RV fibrosis and improved RV systolic and diastolic function.

Conclusion

Excess protein glycation promotes RV dysfunction in preclinical PAH, potentially through suppression of FAO.

Role of the Glyoxalase System in Breast Cancer and Gynecological Cancer-Implications for Therapeutic Intervention: a Review

Methyglyoxal (MGO), an essential endogenous dicarbonyl metabolite, can lead to multiple physiological problems including hyperglycemia, kidney diseases, malignant tumors, beyond its normal concentration range. The glyoxalase system, making MGO maintained at a low level, links glycation to carcinogenesis, growth, metastasis, and cancer chemotherapy. The glyoxalase system comprises glyoxalase 1 (Glo1) and glyoxalase 2 (Glo2), which is often overexpressed in various tumor tissues. However, very little is known about the glyoxalase system in breast cancer and gynecological cancer. In this review, we introduce the role of the glyoxalase system in breast cancer, endometrial cancer, ovarian cancer and cervical cancer, and highlight the potential of the glyoxalase system to be both as a marker for diagnosis and a novel target for antitumor therapy. However, the intrinsic molecular biology and mechanisms of the glyoxalase system in breast cancer and gynecological cancer need further exploration.

Methylglyoxal-induces multiple stable changes in human serum albumin before forming nephrotoxic advanced glycation end-products: Injury demonstration in human embryonic kidney cells

The minor fraction of methylglyoxal that is not metabolized in healthy humans reacts with macromolecules to form AGEs. In diabetics, the formation of MG is accelerated; its level may be enhanced multifold. The glyoxalase enzymes responsible for the regular and effective clearance of excess methylglyoxal may become defective in diabetes mellitus leading to its retention in cells and plasma. The methylglyoxal-modified-HSA was prepared, characterised by multiple biophysical techniques and biochemical (s) and its damaging effect was examined on embryonic kidney cell line HEK 293. The UV results showed hyperchromicity in MG-modified-HSA while nitroblue tetrazolium and fluorescence data suggested AGEs formation in comparison to control HSA. Upward shift of negative peaks in CD suggested reduction in α-helicity. Accelerated mobility and diffused broad bands observed in native and SDS polyacrylamide gel, respectively suggest neutralization of some of the positive charges on MG-modified-HSA as well as generation of cross-links. As observed by trypan blue assay, MTT, LDH activity assay, acridine orange, propidium iodide, ethidium bromide, 4',6-diamidino-2-phenylindole (DAPI) staining and ROS measurements, the MG-HSA AGEs caused damage to human embryonic kidney cells. The data suggest that MG-HSA AGEs may trigger powerful inflammatory responses at cellular level which might set the stage for nephrotoxicity in diabetics.

Elevated plasma level of the glycolysis byproduct methylglyoxal on admission is an independent biomarker of mortality in ICU COVID-19 patients

Biomarkers to identify ICU COVID-19 patients at high risk for mortality are urgently needed for therapeutic care and management. Here we found plasma levels of the glycolysis byproduct methylglyoxal (MG) were 4.4-fold higher in ICU patients upon admission that later died (n = 33), and 1.7-fold higher in ICU patients that survived (n = 32),compared to uninfected controls (n = 30). The increased MG in patients that died correlated inversely with the levels of the MG-degrading enzyme glyoxalase-1 (r² = - 0.50), and its co-factor glutathione (r² = - 0.63), and positively with monocytes (r² = 0.29). The inflammation markers, SSAO (r² = 0.52), TNF-α (r² = 0.41), IL-1β (r² = 0.25), CRP (r² = 0.26) also correlated positively with MG. Logistic regression analysis provides evidence of a significant relationship between the elevated MG upon admission into ICU and death (P < 0.0001), with 42% of the death variability explained. From these data we conclude that elevated plasma MG on admission is a novel independent biomarker that predicts mortality in ICU COVID-19 patients.

Metabolic Shades of S-D-Lactoylglutathione

S-D-lactoylglutathione (SDL) is an intermediate of the glutathione-dependent metabolism of methylglyoxal (MGO) by glyoxalases. MGO is an electrophilic compound that is inevitably produced in conjunction with glucose breakdown and is essentially metabolized via the glyoxalase route. In the last decades, MGO metabolism and its cytotoxic effects have been under active investigation, while almost nothing is known about SDL. This article seeks to fill the gap by presenting an overview of the chemistry, biochemistry, physiological role and clinical importance of SDL. The effects of intracellular SDL are investigated in three main directions: as a substrate for post-translational protein modifications, as a reservoir for mitochondrial reduced glutathione and as an energy currency. In essence, all three approaches point to one direction, namely, a metabolism-related regulatory role, enhancing the cellular defense against insults. It is also suggested that an increased plasma concentration of SDL or its metabolites may possibly serve as marker molecules in hemolytic states, particularly when the cause of hemolysis is a disturbance of the pay-off phase of the glycolytic chain. Finally, SDL could also represent a useful marker in such metabolic disorders as diabetes mellitus or ketotic states, in which its formation is expected to be enhanced. Despite the lack of clear-cut evidence underlying the clinical and experimental findings, the investigation of SDL metabolism is a promising field of research.

Substrate Protein Interactions and Methylglyoxal Modifications Reduce the Aggregation Propensity of Human Alpha-A-Crystallin G98R Mutant

The G98R mutation in αA-crystallin is associated with presenile cataract development in humans. Previous studies have indicated that mutant proteins altered structure, decreased stability, increased oligomeric size, loss of chaperone-like activity, and susceptibility to proteolysis could be contributing factors to cataract formation. To evaluate the effect of substrate protein interactions with the mutant protein on cataract formation, we have performed chaperone assays with alcohol dehydrogenase (ADH), citrate synthase (CS), and βB2-crystallin (βB2), and analyzed the reaction mixtures by multi-angle light scattering (MALS) analysis. It appears that αAG98R protein initially gets stabilized upon interaction with substrate proteins. Analysis of the chaperone-client protein complexes revealed that wild-type αA-crystallin interacts with substrate proteins to form compact complexes leading to a slight increase in oligomeric mass, whereas αAG98R forms less compact and high molecular weight complexes with the substrate, and the resulting complexes continue to increase in size over time. As a result, the soluble complexes formed initially by the mutant protein begin to scatter light and precipitate. We found that the stability and chaperone activity of the αAG98R can be improved by modifying the protein with low concentrations (50 µM) of methylglyoxal (MGO). Incubation of αAG98R protein (1 mg/ml) under aseptic conditions for 30 days at 37°C resulted in precipitation of the mutant protein. In contrast, mutant protein incubations carried out with 50 µM MGO remained soluble and transparent. SDS-PAGE analysis showed gradual autolysis of the mutant protein in the absence of MGO. The average molar mass of the mutant protein oligomers changed from 7,258 ± 12 kDa to 3,950 ± 08 kDa within 60 min of incubation with MGO. There was no further significant change in the molar mass of mutant protein when tested on day 7 of MGO treatment. Our data suggest that the initial stabilization of αAG98R by substrate proteins could delay congenital cataracts' appearance, and the uncontrolled long-term interaction amongst mutant subunits and substrate proteins could be the rationale behind presenile cataracts formation. The results also demonstrate the potential benefit of low concentrations of MGO in stabilizing mutant chaperone protein(s).

The Influence of Intracellular Glutathione Levels on the Induction of Nrf2-Mediated Gene Expression by α-Dicarbonyl Precursors of Advanced Glycation End Products

α-Dicarbonyl compounds, particularly methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG), are highly reactive precursors for the formation of advanced glycation end products (AGEs). They are formed in vivo and during food processing. This study aimed to investigate the role of intracellular glutathione (GSH) levels in the induction of Nrf2-mediated gene expression by α-dicarbonyl compounds. The reactions between α-dicarbonyl compounds (MGO, GO, and 3-DG) and GSH were studied by LC-MS in a cell-free system. It was shown that these three α-dicarbonyl compounds react instantaneously with GSH, with the GSH-mediated scavenging decreasing in the order MGO > GO > 3DG. Furthermore, in a cell-based reporter gene assay MGO, GO, and 3-DG were able to induce Nrf2-mediated gene expression in a dose-dependent manner. Modulation of intracellular GSH levels showed that the cytotoxicity and induction of the Nrf2-mediated pathway by MGO, GO and 3-DG was significantly enhanced by depletion of GSH, while a decrease in Nrf2-activation by MGO and GO but not 3-DG was observed upon an increase of the cellular GSH levels. Our results reveal subtle differences in the role of GSH in protection against the three typical α-dicarbonyl compounds and in their induction of Nrf2-mediated gene expression, and point at a dual biological effect of the α-dicarbonyl compounds, being reactive toxic electrophiles and -as a consequence- able to induce Nrf2-mediated protective gene expression, with MGO being most reactive.

Elucidating the degradation mechanism of a self-degradable dextran-based medical adhesive

We developed a self-degradable medical adhesive, LYDEX, consisting of periodate-oxidized aldehyde-functionalized dextran (AD) and succinic anhydride-treated ε-poly-l-lysine (SAPL). After gelation and adhesion of LYDEX by Schiff base bond formation between the AD aldehyde groups and SAPL amino groups, molecular degradation associated with the Maillard reaction is initiated, but the detailed degradation mechanism remains unknown. Herein, we elucidated the degradation mechanism of LYDEX by analyzing the main degradation products under typical solution conditions in vitro. The degradation of the LYDEX gel with a sodium periodate/dextran content of 2.5/20 was observed using gel permeation chromatography and infrared and ¹H NMR spectroscopy. The AD ratio in the AD-SAPL mixture increased as the molecular weight decreased with the degradation time. This discovery of LYDEX self-degradability is useful for clarifying other polysaccharide hydrogel degradation mechanisms, and valuable for the use of LYDEX in medical applications, such as hemostatic or sealant materials.

A Dunaliella salina Extract Counteracts Skin Aging under Intense Solar Irradiation Thanks to Its Antiglycation and Anti-Inflammatory Properties

Glycation, and the resulting buildup of advanced glycation end products (AGEs), is recognized as a key driver of cumulative skin damage and skin aging. Dunaliella salina is a halophile microalga adapted to intense solar radiation through the production of carotenoids. We present a natural supercritical CO₂ extract of Dunaliella salina rich in the colorless carotenoids phytoene and phytofluene. The extract exhibited antiglycation and anti-inflammatory activities in ex vivo testing, showing strongly reduced formation of N-ε-carboxy-methyl-lysine with exposure to methylglyoxal, reduced AGE receptor levels, and significantly reduced interleukins 6 and 8. In a placebo-controlled clinical study under intense solar exposure, the extract significantly reduced the skin’s glycation scores and its sensitivity to histamine; key skin aging parameters were also significantly improved vs. placebo, including wrinkle counts and spots. These results demonstrate the value of this Dunaliella salina extract, rich in colorless carotenoids, as an antiglycative, anti-inflammatory, and antiaging active ingredient, including in high-irradiation contexts.

Pyramiding of γ-TMT and gly I transgenes in Brassica juncea enhances salinity and drought stress tolerance

We previously generated Brassica juncea lines overexpressing either glyoxalase I (gly I) or γ-tocopherol methyltransferase (γ-TMT) involved in the glyoxalase system and tocopherol biosynthesis, respectively. These transgenic plants showed tolerance to multiple abiotic stresses. As tolerance is a complex trait that can be improved by pyramiding of several characteristics in a single genotype, we generated in this study B. juncea plants coexpressing gly I and γ-TMT by crossing the previously generated stable transgenic lines. The performance of the newly generated B. juncea lines coexpressing gly I and γ-TMT was compared with that of wild-type and the single transgenic lines under non-stressed and NaCl and mannitol stress conditions. Our results show a more robust antioxidant response of B. juncea plants coexpressing gly I and γ-TMT compared to the other lines in terms of higher chlorophyll retention, relative water content, antioxidant enzyme and proline levels, and photosynthetic efficiency and lower oxidative damage. The differences in response to the stress of the different lines were reflected in their yield parameters. Overall, we demonstrate that the pyramiding of multiple genes involved in antioxidant pathways could be a viable and useful approach for achieving higher abiotic stress tolerance in crop plants.

The activity of glyoxylase 1 is regulated by glucose-responsive phosphorylation on Tyr136

OBJECTIVE

Methylglyoxal (MG) is a highly reactive α-oxoaldehyde that glycates proteins. MG has been linked to the development of diabetic complications: MG is the major precursor of advanced glycation end products (AGEs), a risk marker for diabetic complications in humans. Furthermore, flies and fish with elevated MG develop insulin resistance, obesity, and hyperglycemia. MG is detoxified in large part through the glyoxalase system, whose rate-limiting enzyme is glyoxalase I (Glo1). Hence, we aimed to study how Glo1 activity is regulated.

METHODS

We studied the regulation and effect of post-translational modifications of Glo1 in tissue culture and in mouse models of diabetes.

RESULTS

We show that Glo1 activity is promoted by phosphorylation on Tyrosine 136 via multiple kinases. We find that Glo1 Y136 phosphorylation responds in a bimodal fashion to glucose levels, increasing in cell culture from 0 mM to 5 mM (physiological) glucose, and then decreasing at higher glucose concentrations, both in cell culture and in mouse models of hyperglycemia.

CONCLUSIONS

These data, together with published findings that elevated MG leads to hyperglycemia, suggest the existence of a deleterious positive feedback loop whereby hyperglycemia leads to reduced Glo1 activity, contributing to elevated MG levels, which in turn promote hyperglycemia. Hence, perturbations elevating either glucose or MG have the potential to start an auto-amplifying feedback loop contributing to diabetic complications.

A Link Between Methylglyoxal and Heart Failure During HIV-1 Infection

Early-onset heart failure (HF) continues to be a major cause of morbidity and mortality in people living with human immunodeficiency virus type one (HIV-1) infection (PLWH), yet the molecular causes for this remain poorly understood. Herein NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ humanized mice (Hu-mice), plasma from PLWH, and autopsied cardiac tissues from deceased HIV seropositive individuals were used to assess if there is a link between the glycolysis byproduct methylglyoxal (MG) and HF in the setting of HIV-1 infection. At five weeks post HIV infection, Hu-mice developed grade III-IV diastolic dysfunction (DD) with an associated two-fold increase in plasma MG. At sixteen-seventeen weeks post infection, cardiac ejection fraction and fractional shortening also declined by 26 and 35%, and plasma MG increased to four-fold higher than uninfected controls. Histopathological and biochemical analyses of cardiac tissues from Hu-mice 17 weeks post-infection affirmed MG increase with a concomitant decrease in expression of the MG-degrading enzyme glyoxalase-1 (Glo1). The endothelial cell marker CD31 was found to be lower, and coronary microvascular leakage and myocardial fibrosis were prominent. Increasing expression of Glo1 in Hu-mice five weeks post-infection using a single dose of an engineered AAV2/9 (1.7 × 10¹² virion particles/kg), attenuated the increases in plasma and cardiac MG levels. Increasing Glo1 also blunted microvascular leakage, fibrosis, and HF seen at sixteen weeks post-infection, without changes in plasma viral loads. In plasma from virally suppressed PLWH, MG was also 3.7-fold higher. In autopsied cardiac tissues from seropositive, HIV individuals with low viral log, MG was 4.2-fold higher and Glo1 was 50% lower compared to uninfected controls. These data show for the first time a causal link between accumulation of MG and HF in the setting of HIV infection.

Diet and Obesity-Induced Methylglyoxal Production and Links to Metabolic Disease

The obesity rate in the United States is 42.4% and has become a national epidemic. Obesity is a complex condition that is influenced by socioeconomic status, ethnicity, genetics, age, and diet. Increased consumption of a Western diet, one that is high in processed foods, red meat, and sugar content, is associated with elevated obesity rates. Factors that increase obesity risk, such as socioeconomic status, also increase consumption of a Western diet because of a limited access to healthier options and greater affordability of processed foods. Obesity is a public health threat because it increases the risk of several pathologies, including atherosclerosis, diabetes, and cancer. The molecular mechanisms linking obesity to disease onset and progression are not well understood, but a proposed mechanism is physiological changes caused by altered lipid peroxidation, glycolysis, and protein metabolism. These metabolic pathways give rise to reactive molecules such as the abundant electrophile methylglyoxal (MG), which covalently modifies nucleic acids and proteins. MG-adducts are associated with obesity-linked pathologies and may have potential for biomonitoring to determine the risk of disease onset and progression. MG-adducts may also play a role in disease progression because they are mutagenic and directly impact protein stability and function. In this review, we discuss how obesity drives metabolic alterations, how these alterations lead to MG production, the association of MG-adducts with disease, and the potential impact of MG-adducts on cellular function.

Defining the landscape of metabolic dysregulations in cancer metastasis

Metastasis is the primary cause of cancer related deaths due to the limited number of efficient druggable targets. Signatures of dysregulated cancer metabolism could serve as a roadmap for the determination of new treatment strategies. However, the metabolic signatures of metastatic cells remain vastly elusive. Our aim was to determine metabolic dysregulations associated with high metastatic potential in breast cancer cell lines. We have selected 5 triple negative breast cancer (TNBC) cell lines including three with high metastatic potential (HMP) (MDA-MB-231, MDA-MB-436, MDA-MB-468) and two with low metastatic potential (LMP) (BT549, HCC1143). The normal epithelial breast cell line (hTERT-HME1) was also investigated. The untargeted metabolic profiling of cells and growth media was conducted and total of 479 metabolites were quantified. First we characterized metabolic features differentiating TNBC cell lines from normal cells as well as identified cell line specific metabolic fingerprints. Next, we determined 92 metabolites in cells and 22 in growth medium that display significant differences between LMP and HMP. The HMP cell lines had elevated level of molecules involved in glycolysis, TCA cycle and lipid metabolism. We identified metabolic advantages of cell lines with HMP beyond enhanced glycolysis by pinpointing the role of branched chain amino acids (BCAA) catabolism as well as molecules supporting coagulation and platelet activation as important contributors to the metastatic cascade. The landscape of metabolic dysregulations, characterized in our study, could serve as a roadmap for the identification of treatment strategies targeting cancer cells with enhanced metastatic potential.

Generation of a GLO-2 deficient mouse reveals its effects on liver carbonyl and glutathione levels

OBJECTIVE

Hydroxyacylglutathione hydrolase (aka as GLO-2) is a component of the glyoxalase pathway involved in the detoxification of the reactive oxoaldehydes, glyoxal and methylglyoxal. These reactive metabolites have been linked to a variety of pathological conditions, including diabetes, cancer and heart disease and may be involved in the aging process. The objective of this study was to generate a mouse model deficient in GLO-2 to provide insight into the function of GLO-2 and to determine if it is potentially linked to endogenous oxalate synthesis which could influence urinary oxalate excretion.

METHODS

A GLO-2 knock out mouse was generated using CRISPR/Cas 9 techniques. Tissue and 24-h urine samples were collected under baseline conditions from adult male and female animals for biochemical analyses, including chromatographic measurement of glycolate, oxalate, glyoxal, methylglyoxal, D-lactate, ascorbic acid and glutathione levels.

RESULTS

The GLO-2 KO animals developed normally and there were no changes in 24-h urinary oxalate excretion, liver levels of methylglyoxal, glyoxal, ascorbic acid and glutathione, or plasma d-lactate levels. GLO-2 deficient males had lower plasma glycolate levels than wild type males while this relationship was not observed in females.

CONCLUSIONS

The lack of a unique phenotype in a GLO-2 KO mouse model under baseline conditions is consistent with recent evidence, suggesting a functional glyoxalase pathway is not required for optimal health. A lower plasma glycolate in male GLO-2 KO animals suggests glyoxal production may be a significant contributor to circulating glycolate levels, but not to endogenous oxalate synthesis.

Methylglyoxal Forms Diverse Mercaptomethylimidazole Crosslinks with Thiol and Guanidine Pairs in Endogenous Metabolites and Proteins

Methylglyoxal (MGO) is a reactive byproduct formed by several metabolic precursors, the most notable being triosephosphates in glycolysis. While many MGO-mediated adducts have been described, the reactivity and specific biomolecular targets of MGO remain incompletely mapped. Based on our recent discovery that MGO can form stable mercaptomethylimidazole crosslinks between cysteine and arginine (MICA) in proteins, we hypothesized that MGO may participate in myriad reactions with biologically relevant guanidines and thiols in proteins, metabolites, and perhaps other biomolecules. Herein, we performed steady-state and kinetic analyses of MGO reactivity with several model thiols, guanidines, and biguanide drugs to establish the plausible and prevalent adducts formed by MGO in proteins, peptides, and abundant cellular metabolites. We identified several novel, stable MICA metabolites that form in vitro and in cells, as well as a novel intermolecular post-translational MICA modification of surface cysteines in proteins. These data confirm that kinetic trapping of free MGO by thiols occurs rapidly and can decrease formation of more stable imidazolone (MG-H1) arginine adducts. However, reversible hemithioacetal adducts can go on to form stable MICA modifications in an inter- and intramolecular fashion with abundant or proximal guanidines, respectively. Finally, we discovered that intracellular MICA-glutathione metabolites are recognized and exported by the efflux pump MRP1, providing a parallel and perhaps complementary pathway for MGO detoxification working alongside the glyoxalase pathway. These data provide new insights into the plausible reactions involving MGO in cells and tissues, as well as several new molecular species in proteins and metabolites for further study.

Evaluation of Immunomodulatory Responses and Changed Wound Healing in Type 2 Diabetes-A Study Exploiting Dermal Fibroblasts from Diabetic and Non-Diabetic Human Donors

The dermis is the connective layer between the epidermis and subcutis and harbours nerve endings, glands, blood vessels, and hair follicles. The most abundant cell type is the fibroblast. Dermal fibroblasts have a versatile portfolio of functions within the dermis that correspond with different types of cells by either direct contact or by autocrine and paracrine signalling. Diabetic skin is characterized by itching, numbness, ulcers, eczema, and other pathophysiological changes. These pathogenic phenotypes have been associated with the effects of the reactive glucose metabolite methylglyoxal (MGO) on dermal cells. In this study, dermal fibroblasts were isolated from diabetic and non-diabetic human donors. Cultured dermal fibroblasts from diabetic donors exhibited reduced insulin-induced glucose uptake and reduced expression of the insulin receptor. This diabetic phenotype persists under cell culture conditions. Secretion of IL-6 was increased in fibroblasts from diabetic donors. Increased secretion of IL-6 and MIF was also observed upon the treatment of dermal fibroblasts with MGO, suggesting that MGO is sufficient for triggering these immunomodulatory responses. Remarkably, MIF treatment resulted in decreased activity of MGO-detoxifying glyoxalase-1. Given that reduced glyoxalase activity results in increased MGO levels, these findings suggested a positive-feedback loop for MGO generation, in which MIF, evoked by MGO, in turn blocks MGO-degrading glyoxalase activity. Finally, secretion of procollagen Type I C-Peptide (PICP), a marker of collagen production, was reduced in fibroblast from diabetic donors. Remarkably, treatment of fibroblasts with either MGO or MIF was sufficient for inducing reduced PICP levels. The observations of this study unravel a signalling network in human dermal fibroblasts with the metabolite MGO being sufficient for inflammation and delayed wound healing, hallmarks of T2D.

Glyoxalase-I Is Upregulated in Acute Cerulein-Induced Pancreatitis: A New Mechanism in Pancreatic Inflammation?

Inflammation caused by oxidative stress (ROS) demonstrates an essential mechanism in the pathogenesis of acute pancreatitis (AP). Important sources for ROS comprise the reactive compound methylglyoxal (MGO) itself and the MGO-derived formation of advanced glycation end-products (AGEs). AGEs bind to the transmembrane receptor RAGE and activate NF-κB, and lead to the production of pro-inflammatory cytokines. MGO is detoxified by glyoxalase-I (Glo-I). The importance of Glo-I was shown in different models of inflammation and carcinogenesis. Nevertheless, the role of Glo-I and MGO in AP has not been evaluated so far. This study analyzed Glo-I in cerulein-(CN)-induced AP and determined the effects of Glo-I knockdown, overexpression and pharmacological modulation. Methods: AP was induced in C57BL6/J mice by i.p. injection of CN. Glo-I was analyzed in explanted pancreata by Western Blot, qRT-PCR and immunohistochemistry. AR42J cells were differentiated by dexamethasone and stimulated with 100 nM of CN. Cells were simultaneously treated with ethyl pyruvate (EP) or S-p-bromobenzylglutathione-cyclopentyl-diester (BrBz), two Glo-I modulators. Knockdown and overexpression of Glo-I was achieved by transient transfection with Glo-I siRNA and pEGFP-N1-Glo-I-Vector. Amylase secretion, TNF-α production (ELISA) and expression of Glo-I, RAGE and NF-κB were measured. Results: Glo-I was significantly upregulated on protein and mRNA levels in CN-treated mice and AR42J cells. Dexamethasone-induced differentiation of AR42J cells increased the expression of Glo-I and RAGE. Treatment of AR42J cells with CN and EP or BrBz resulted in a significant reduction of CN-induced amylase secretion, NF-κB, RAGE and TNF-α. Overexpression of Glo-I led to a significant reduction of CN-induced amylase levels, NF-κB expression and TNF-α, whereas Glo-I knockdown revealed only slight alterations. Measurements of specific Glo-I activity and MGO levels indicated a complex regulation in the model of CN-induced AP. Conclusion: Glo-I is overexpressed in a model of CN-induced AP. Pharmacological modulation and overexpression of Glo-I reduced amylase secretion and the release of pro-inflammatory cytokines in AP in vitro. Targeting Glo-I in AP seems to be an interesting approach for future in vivo studies of AP.

The possible role of methylglyoxal metabolism in cancer

Tumours reprogram their metabolism to acquire an evolutionary advantage over normal cells. However, not all such metabolic pathways support energy production. An example of these metabolic pathways is the Methylglyoxal (MG) one. This pathway helps maintain the redox state, and it might act as a phosphate sensor that monitors the intracellular phosphate levels. In this work, we discuss the biochemical step of the MG pathway and interrelate it with cancer.

Chitosan Displays a Potent Caloric Restriction Mimetic Effect in Senescent Rats

Chitosan is a polysaccharide made up of β1,4-linked d-glucosamine (GlcN) and N-acetyl-GlcN. In this study, we evaluated the possible caloric restriction mimetic (CRM) effect of dietary chitosan on systemic redox status, inflammatory biomarkers, and lipid profile in plasma and erythrocyte samples of d-galactose-induced mimetically aged rats. We found a significant increase (p < 0.05) in the reactive oxygen species, protein carbonyl, fasting glucose, body weight, cholesterol, triglyceride, inflammatory markers-interleukin-6 and tumor necrosis factor-alpha in an accelerated senescent rat model. There was also a significant decrease (p < 0.05) in glutathione, advanced glycation end product in senescent rats. Chitosan treatment increased ferric-reducing antioxidant potential, glutathione, plasma membrane-reduced system in accelerated senescent model of rats. Our finding suggests that chitosan has properties similar to a CRM and can effectively maintain the redox homeostasis during the aging process in rat erythrocytes.

NMR-Based Metabolomics in Investigation of the Radiation Induced Changes in Blood Serum of Head and Neck Cancer Patients and Its Correlation with the Tissue Volumes Exposed to the Particulate Doses

In the present study, we analyze the nuclear magnetic resonance (NMR) blood serum metabolic profiles of 106 head and neck squamous cell carcinoma (HNSCC) patients during radio (RT) and concurrent radio-chemotherapy (CHRT). Four different fractionation schemes were compared. The blood samples were collected weekly, from the day before the treatment until the last week of CHRT/RT. The NMR spectra were acquired on A Bruker 400 MHz spectrometer at 310 K and analyzed using multivariate methods. Seven metabolites were found significantly to be altered solely by radiotherapy: N-acetyl-glycoprotein (NAG), N-acetylcysteine, glycerol, glycolate and the lipids at 0.9, 1.3 and 3.2 ppm. The NMR results were correlated with the tissue volumes receiving a particular dose of radiation. The influence of the irradiated volume on the metabolic profile is weak and mainly limited to sparse correlations with the inflammatory markers, creatinine and the lymphocyte count in RT and the branched-chain amino-acids in CHRT. This is probably due to the optimal planning and delivery of radiotherapy improving sparing of the surrounding normal tissues and minimizing the differences between the patients (caused by the tumor location and size).

Dysregulation of post-transcriptional modification by copy number variable microRNAs in schizophrenia with enhanced glycation stress

Previously, we identified a subpopulation of schizophrenia (SCZ) showing increased levels of plasma pentosidine, a marker of glycation and oxidative stress. However, its causative genetic factors remain largely unknown. Recently, it has been suggested that dysregulated posttranslational modification by copy number variable microRNAs (CNV-miRNAs) may contribute to the etiology of SCZ. Here, an integrative genome-wide CNV-miRNA analysis was performed to investigate the etiology of SCZ with accumulated plasma pentosidine (PEN-SCZ). The number of CNV-miRNAs and the gene ontology (GO) in the context of miRNAs within CNVs were compared between PEN-SCZ and non-PEN-SCZ groups. Gene set enrichment analysis of miRNA target genes was further performed to evaluate the pathways affected in PEN-SCZ. We show that miRNAs were significantly enriched within CNVs in the PEN-SCZ versus non-PEN-SCZ groups (p = 0.032). Of note, as per GO analysis, the dysregulated neurodevelopmental events in the two groups may have different origins. Additionally, gene set enrichment analysis of miRNA target genes revealed that miRNAs involved in glycation/oxidative stress and synaptic neurotransmission, especially glutamate/GABA receptor signaling, were possibly affected in PEN-SCZ. To the best of our knowledge, this is the first genome-wide CNV-miRNA study suggesting the role of CNV-miRNAs in the etiology of PEN-SCZ, through effects on genes related to glycation/oxidative stress and synaptic function. Our findings provide supportive evidence that glycation/oxidative stress possibly caused by genetic defects related to the posttranscriptional modification may lead to synaptic dysfunction. Therefore, targeting miRNAs may be one of the promising approaches for the treatment of PEN-SCZ.

The Role of Glyoxalase in Glycation and Carbonyl Stress Induced Metabolic Disorders

Glycation refers to the covalent binding of sugar molecules to macromolecules, such as DNA, proteins, and lipids in a non-enzymatic reaction, resulting in the formation of irreversibly bound products known as advanced glycation end products (AGEs). AGEs are synthesized in high amounts both in pathological conditions, such as diabetes and under physiological conditions resulting in aging. The body's anti-glycation defense mechanisms play a critical role in removing glycated products. However, if this defense system fails, AGEs start accumulating, which results in pathological conditions. Studies have been shown that increased accumulation of AGEs acts as key mediators in multiple diseases, such as diabetes, obesity, arthritis, cancer, atherosclerosis, decreased skin elasticity, male erectile dysfunction, pulmonary fibrosis, aging, and Alzheimer's disease. Furthermore, glycation of nucleotides, proteins, and phospholipids by α-oxoaldehyde metabolites, such as glyoxal (GO) and methylglyoxal (MGO), causes potential damage to the genome, proteome, and lipidome. Glyoxalase-1 (GLO-1) acts as a part of the anti-glycation defense system by carrying out detoxification of GO and MGO. It has been demonstrated that GLO-1 protects dicarbonyl modifications of the proteome and lipidome, thereby impeding the cell signaling and affecting age-related diseases. Its relationship with detoxification and anti-glycation defense is well established. Glycation of proteins by MGO and GO results in protein misfolding, thereby affecting their structure and function. These findings provide evidence for the rationale that the functional modulation of the GLO pathway could be used as a potential therapeutic target. In the present review, we summarized the newly emerged literature on the GLO pathway, including enzymes regulating the process. In addition, we described small bioactive molecules with the potential to modulate the GLO pathway, thereby providing a basis for the development of new treatment strategies against age-related complications.

Pleiotropic Actions of Aldehyde Reductase (AKR1A)

We provide an overview of the physiological roles of aldehyde reductase (AKR1A) and also discuss the functions of aldose reductase (AKR1B) and other family members when necessary. Many types of aldehyde compounds are cytotoxic and some are even carcinogenic. Such toxic aldehydes are detoxified via the action of AKR in an NADPH-dependent manner and the resulting products may exert anti-diabetic and anti-tumorigenic activity. AKR1A is capable of reducing 3-deoxyglucosone and methylglyoxal, which are reactive intermediates that are involved in glycation, a non-enzymatic glycosylation reaction. Accordingly, AKR1A is thought to suppress the formation of advanced glycation end products (AGEs) and prevent diabetic complications. AKR1A and, in part, AKR1B are responsible for the conversion of d-glucuronate to l-gulonate which constitutes a process for ascorbate (vitamin C) synthesis in competent animals. AKR1A is also involved in the reduction of S-nitrosylated glutathione and coenzyme A and thereby suppresses the protein S-nitrosylation that occurs under conditions in which the production of nitric oxide is stimulated. As the physiological functions of AKR1A are currently not completely understood, the genetic modification of Akr1a could reveal the latent functions of AKR1A and differentiate it from other family members.

Molecular docking and dynamic studies of a potential therapeutic target inhibiting glyoxalase system: Metabolic action of the 3, 3 '- [3- (5-chloro-2-hydroxyphenyl) -3-oxopropane-1, 1-diyl] - Bis-4-hydroxycoumarin leads overexpression of the intracellular level of methylglyoxal and induction of a pro-apoptotic phenomenon in a hepatocellular carcinoma model

Methylglyoxal is a dicarbonyl compound recruited as a potential cytotoxic marker, initially presents in cells and considered as a metabolite of the glycolytic pathway. Our aim is to demonstrate the inhibitory effect of 3, 3'-[3-(5-chloro-2-hydroxyphenyl)-3-oxopropane-1, 1-diyl] Bis (4-hydroxycoumarin) on the glyoxalase system, and indirectly its anticancer activity. The docking of OT-55 was conducted by using Flexible docking protocol, ChiFlex and libdock tools inside the active site of Glo-I indicated that both hydrogen bonding and hydrophobic interactions contributed significantly in establishing potent binding with the active site which is selected as a strong inhibitor with high scoring values and maximum Gibbs free energy. Coumarin-liposome formulation was characterized and evaluated in vivo against chemically induced hepatocarcinoma in Wistar rats. After Diethylnitrosamine (DEN) induction, microscopic assessment was realized; precancerous lesions were developed showing an increase of both tumor-associated lymphocyte and multiple tumor acini supported by the blood investigation. Our finding also suggested a preferential uptake of liposomes respectively in liver, kidney, lung, brain and spleen in the DEN-treated animals. OT-55 has also been shown to inhibit the activity of Glo-I in vitro as well as in DEN-treated rats. An abnormal high level of MGO of up to 50% was recorded followed by a reduction in glucose consumption and lactate dehydrogenase production validated in the positive control. MGO generates apoptosis as depicted by focal hepatic lesions. Also, no deleterious effects in the control group were observed after testing our coumarin but rather a vascular reorganization leading to nodular regenerative hyperplasia. Involved in the detoxification process, liver GSH is restored in intoxicated rats, while no changes are seen between controls. At the endothelial cell, OT-55 appears to modulate the release of NO only in the DEN-treated group. OT-55 would behave both as an anticancer agent but also as an angiogenic factor regarding results obtained.

Phosphorylation of T107 by CamKIIδ Regulates the Detoxification Efficiency and Proteomic Integrity of Glyoxalase 1

The glyoxalase system is a highly conserved and ubiquitously expressed enzyme system, which is responsible for the detoxification of methylglyoxal (MG), a spontaneous by-product of energy metabolism. This study is able to show that a phosphorylation of threonine-107 (T107) in the (rate-limiting) Glyoxalase 1 (Glo1) protein, mediated by Ca²⁺/calmodulin-dependent kinase II delta (CamKIIδ), is associated with elevated catalytic efficiency of Glo1 (lower K_M; higher V_max). Additionally, we observe proteasomal degradation of non-phosphorylated Glo1 via ubiquitination does occur more rapidly as compared with native Glo1. The absence of CamKIIδ is associated with poor detoxification capacity and decreased protein content of Glo1 in a murine CamKIIδ knockout model. Therefore, phosphorylation of T107 in the Glo1 protein by CamKIIδ is a quick and precise mechanism regulating Glo1 activity, which is experimentally linked to an altered Glo1 status in cancer, diabetes, and during aging.

Role of protein S-Glutathionylation in cancer progression and development of resistance to anti-cancer drugs

The survival, functioning and proliferation of mammalian cells are highly dependent on the cellular response and adaptation to changes in their redox environment. Cancer cells often live in an altered redox environment due to aberrant neo-vasculature, metabolic reprogramming and dysregulated proliferation. Thus, redox adaptations are critical for their survival. Glutathione plays an essential role in maintaining redox homeostasis inside the cells by binding to redox-sensitive cysteine residues in proteins by a process called S-glutathionylation. S-Glutathionylation not only protects the labile cysteine residues from oxidation, but also serves as a sensor of redox status, and acts as a signal for stimulation of downstream processes and adaptive responses to ensure redox equilibrium. The present review aims to provide an updated overview of the role of the unique redox adaptations during carcinogenesis and cancer progression, focusing on their dependence on S-glutathionylation of specific redox-sensitive proteins involved in a wide range of processes including signalling, transcription, structural maintenance, mitochondrial functions, apoptosis and protein recycling. We also provide insights into the role of S-glutathionylation in the development of resistance to chemotherapy. Finally, we provide a strong rationale for the development of redox targeting drugs for treatment of refractory/resistant cancers.

Low glucose and high pyruvate reduce the production of 2-oxoaldehydes, improving mitochondrial efficiency, redox regulation, and stallion sperm function†

Energy metabolism in spermatozoa is complex and involves the metabolism of carbohydrate fatty acids and amino acids. The ATP produced in the electron transport chain in the mitochondria appears to be crucial for both sperm motility and maintaining viability, whereas glycolytic enzymes in the flagella may contribute to ATP production to sustain motility and velocity. Stallion spermatozoa seemingly use diverse metabolic strategies, and in this regard, a study of the metabolic proteome showed that Gene Ontology terms and Reactome pathways related to pyruvate metabolism and the Krebs cycle were predominant. Following this, the hypothesis that low glucose concentrations can provide sufficient support for motility and velocity, and thus glucose concentration can be significantly reduced in the medium, was tested. Aliquots of stallion semen in four different media were stored for 48 h at 18°C; a commercial extender containing 67 mM glucose was used as a control. Stallion spermatozoa stored in media with low glucose (1 mM) and high pyruvate (10 mM) (LG-HP) sustained better motility and velocities than those stored in the commercial extender formulated with very high glucose (61.7 ± 1.2% in INRA 96 vs 76.2 ± 1.0% in LG-HP media after 48 h of incubation at 18°C; P < 0.0001). Moreover, mitochondrial activity was superior in LG-HP extenders (24.1 ± 1.8% in INRA 96 vs 51.1 ± 0.7% in LG-HP of spermatozoa with active mitochondria after 48 h of storage at 18°C; P < 0.0001). Low glucose concentrations may permit more efficient sperm metabolism and redox regulation when substrates for an efficient tricarboxylic acid cycle are provided. The improvement seen using low glucose extenders is due to reductions in the levels of glyoxal and methylglyoxal, 2-oxoaldehydes formed during glycolysis; these compounds are potent electrophiles able to react with proteins, lipids, and DNA, causing sperm damage.

Methylglyoxal induces p53 activation and inhibits mTORC1 in human umbilical vein endothelial cells

Methylglyoxal (MGO), a precursor of advanced glycation end products (AGEs), is regarded as a pivotal mediator of vascular damage in patients with diabetes. We have previously reported that MGO induces transcriptional changes compatible with p53 activation in cultured human endothelial cells. To further substantiate this finding and to explore the underlying mechanisms and possible consequences of p53 activation, we aimed (1) to provide direct evidence for p53 activation in MGO-treated human umbilical vein endothelial cells (HUVECs), (2) to assess putative mechanisms by which this occurs, (3) to analyze down-stream effects on mTOR and autophagy pathways, and (4) to assess the potential benefit of carnosine herein. Exposure of HUVECs to 800 µM of MGO for 5 h induced p53 phosphorylation. This was paralleled by an increase in TUNEL and γ-H2AX positive cells, indicative for DNA damage. Compatible with p53 activation, MGO treatment resulted in cell cycle arrest, inhibition of mTORC1 and induction of autophagy. Carnosine co-treatment did not counteract MGO-driven effects. In conclusion, our results demonstrate that MGO elicits DNA damage and p53 activation in HUVECs, resulting in modulation of downstream pathways, e.g. mTORC1.

The Dual-Role of Methylglyoxal in Tumor Progression - Novel Therapeutic Approaches

One of the hallmarks of cancer cells is their metabolic reprogramming, which includes the preference for the use of anaerobic glycolysis to produce energy, even in presence of normal oxygen levels. This phenomenon, known as “Warburg effect”, leads to the increased production of reactive intermediates. Among these Methylglyoxal (MGO), a reactive dicarbonyl known as the major precursor of the advanced glycated end products (AGEs), is attracting great attention. It has been well established that endogenous MGO levels are increased in several types of cancer, however the MGO contribution in tumor progression is still debated. Although an anti-cancer role was initially attributed to MGO due to its cytotoxicity, emerging evidence has highlighted its pro-tumorigenic role in several types of cancer. These apparently conflicting results are explained by the hormetic potential of MGO, in which lower doses of MGO are able to establish an adaptive response in cancer cells while higher doses cause cellular apoptosis. Therefore, the extent of MGO accumulation and the tumor context are crucial to establish MGO contribution to cancer progression. Several therapeutic approaches have been proposed and are currently under investigation to inhibit the pro-tumorigenic action of MGO. In this review, we provide an overview of the early and latest evidence regarding the role of MGO in cancer, in order to define its contribution in tumor progression, and the therapeutic strategies aimed to counteract the tumor growth.

Ellagic acid: A potent glyoxalase-I inhibitor with a unique scaffold

The glyoxalase system, particularly glyoxalase-I (GLO-I), has been approved as a potential target for cancer treatment. In this study, a set of structurally diverse polyphenolic natural compounds were investigated as potential GLO-I inhibitors. Ellagic acid was found, computationally and experimentally, to be the most potent GLO-I inhibitor among the tested compounds which showed an IC50 of 0.71 mmol L-1. Its binding to the GLO-I active site seemed to be mainly driven by ionic interaction via its ionized hydroxyl groups with the central Zn ion and Lys156, along with other numerous hydrogen bonding and hydrophobic interactions. Due to its unique and rigid skeleton, it can be utilized to search for other novel and potent GLO-I inhibitors via computational approaches such as pharmacophore modeling and similarity search methods. Moreover, an inspection of the docked poses of the tested compounds showed that chlorogenic acid and dihydrocaffeic acid could be considered as lead compounds worthy of further optimization.

Studies of binding by sulfonylureas with glyoxal- and methylglyoxal-modified albumin by immunoextraction using affinity microcolumns

Diabetes is characterized by elevated levels of blood glucose, which can result in the modification of serum proteins. The modification of a protein by glucose, or glycation, can also lead to the formation of advanced glycated end-products (AGEs). One protein that can be modified through glycation and AGE formation is human serum albumin (HSA). In this study, immunoextraction based on polyclonal anti-HSA antibodies was used with high-performance affinity microcolumns to see how AGE-related modifications produced by glyoxal (Go) and methylglyoxal (MGo) affected the binding of HSA to several first- and second-generation sulfonylureas, a class of drugs used to treat type II diabetes and known to bind to HSA. With this approach, it was possible to use a single platform to examine drug interactions with several preparations of HSA. Each applied protein sample could be used over 20-50 experiments, and global affinity constants for most of the examined drugs could be obtained in less than 7.5 min. The binding constants measured for these drugs with normal HSA gave good agreement with global affinities based on the literature. Both Go- and MGo-related modifications at clinically relevant levels were found by this method to create significant changes in the binding by some sulfonylureas with HSA. The global affinities for many of the drugs increased by 1.4-fold or more; gliclazide and tolazamide had no significant change with some preparations of modified HSA, and a small-to-moderate decrease in binding strength was noted for glibenclamide and gliclazide with Go-modified HSA. This approach can be adapted for the study of other drug-protein interactions and alternative modified proteins by altering the antibodies that are employed for immunoextraction and within the affinity microcolumn.