Advances in glyoxalase research. Glyoxalase expression in malignancy, anti-proliferative effects of methylglyoxal, glyoxalase I inhibitor diesters and S-D-lactoylglutathione, and methylglyoxal-modified protein binding and endocytosis by the advanced glycation endproduct receptor

Glyoxal

The Expert Panel for Cosmetic Ingredient Safety reviewed information that has become available since their year 2000 assessment, along with updated information regarding product types, and frequency and concentrations of use, and reaffirmed their original conclusion that Glyoxal is safe for use in products intended to be applied to the nail at concentrations ≤1.25% and that the available data are insufficient to support the safety for other uses.

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.

An Introduction to the Special Issue "Protein Glycation in Food, Nutrition, Health and Disease"

On 20-24 September 2021, leading researchers in the field of glycation met online at the 14th International Symposium on the Maillard Reaction (IMARS-14), hosted by the authors of this introductory editorial, who are from Doha, Qatar [...].

Emerging Glycation-Based Therapeutics-Glyoxalase 1 Inducers and Glyoxalase 1 Inhibitors

The abnormal accumulation of methylglyoxal (MG) leading to increased glycation of protein and DNA has emerged as an important metabolic stress, dicarbonyl stress, linked to aging, and disease. Increased MG glycation produces inactivation and misfolding of proteins, cell dysfunction, activation of the unfolded protein response, and related low-grade inflammation. Glycation of DNA and the spliceosome contribute to an antiproliferative and apoptotic response of high, cytotoxic levels of MG. Glyoxalase 1 (Glo1) of the glyoxalase system has a major role in the metabolism of MG. Small molecule inducers of Glo1, Glo1 inducers, have been developed to alleviate dicarbonyl stress as a prospective treatment for the prevention and early-stage reversal of type 2 diabetes and prevention of vascular complications of diabetes. The first clinical trial with the Glo1 inducer, trans-resveratrol and hesperetin combination (tRES-HESP)-a randomized, double-blind, placebo-controlled crossover phase 2A study for correction of insulin resistance in overweight and obese subjects, was completed successfully. tRES-HESP corrected insulin resistance, improved dysglycemia, and low-grade inflammation. Cell permeable Glo1 inhibitor prodrugs have been developed to induce severe dicarbonyl stress as a prospective treatment for cancer-particularly for high Glo1 expressing-related multidrug-resistant tumors. The prototype Glo1 inhibitor is prodrug S-p-bromobenzylglutathione cyclopentyl diester (BBGD). It has antitumor activity in vitro and in tumor-bearing mice in vivo. In the National Cancer Institute human tumor cell line screen, BBGD was most active against the glioblastoma SNB-19 cell line. Recently, potent antitumor activity was found in glioblastoma multiforme tumor-bearing mice. High Glo1 expression is a negative survival factor in chemotherapy of breast cancer where adjunct therapy with a Glo1 inhibitor may improve treatment outcomes. BBGD has not yet been evaluated clinically. Glycation by MG now appears to be a pathogenic process that may be pharmacologically manipulated for therapeutic outcomes of potentially important clinical impact.

Methylglyoxal Levels in Human Colorectal Precancer and Cancer: Analysis of Tumor and Peritumor Tissue

Colorectal cancer (CRC) is one of the most common cancers worldwide and its incidence is increasing; therefore, an understanding of its oncogenic mechanisms is critical for improving its treatment and management. Methylglyoxal (MGO) has a highly reactive aldehyde group and has been suggested to play a role in oncogenesis. However, no standardized data are currently available on MGO levels in colorectal precancerous and cancerous lesions. We collected 40 matched colorectal tumor and peritumor tissues from patients with low-grade dysplasia (LGD), high-grade dysplasia (HGD), and invasive cancer (IC). MGO levels increased between LGD, HGD, and IC tumor tissues (215.25 ± 39.69, 267.45 ± 100.61, and 587.36 ± 123.19 μg/g protein, respectively; p = 0.014). The MGO levels in peritumor tissue increased and were significantly higher than MGO levels in tumor tissue (197.99 ± 49.40, 738.09 ± 247.87, 933.41 ± 164.83 μg/g protein, respectively; p = 0.002). Tumor tissue MGO levels did not correlate with age, sex, underlying disease, or smoking status. These results suggest that MGO levels fluctuate in progression of CRC and warrants further research into its underlying mechanisms and function in tumor biology.

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.

Interplay among Oxidative Stress, Methylglyoxal Pathway and S-Glutathionylation

Reactive oxygen species (ROS) are produced constantly inside the cells as a consequence of nutrient catabolism. The balance between ROS production and elimination allows to maintain cell redox homeostasis and biological functions, avoiding the occurrence of oxidative distress causing irreversible oxidative damages. A fundamental player in this fine balance is reduced glutathione (GSH), required for the scavenging of ROS as well as of the reactive 2-oxoaldehydes methylglyoxal (MGO). MGO is a cytotoxic compound formed constitutively as byproduct of nutrient catabolism, and in particular of glycolysis, detoxified in a GSH-dependent manner by the glyoxalase pathway consisting in glyoxalase I and glyoxalase II reactions. A physiological increase in ROS production (oxidative eustress, OxeS) is promptly signaled by the decrease of cellular GSH/GSSG ratio which can induce the reversible S-glutathionylation of key proteins aimed at restoring the redox balance. An increase in MGO level also occurs under oxidative stress (OxS) conditions probably due to several events among which the decrease in GSH level and/or the bottleneck of glycolysis caused by the reversible S-glutathionylation and inhibition of glyceraldehyde-3-phosphate dehydrogenase. In the present review, it is shown how MGO can play a role as a stress signaling molecule in response to OxeS, contributing to the coordination of cell metabolism with gene expression by the glycation of specific proteins. Moreover, it is highlighted how the products of MGO metabolism, S-D-lactoylglutathione (SLG) and D-lactate, which can be taken up and metabolized by mitochondria, could play important roles in cell response to OxS, contributing to cytosol-mitochondria crosstalk, cytosolic and mitochondrial GSH pools, energy production, and the restoration of the GSH/GSSG ratio. The role for SLG and glyoxalase II in the regulation of protein function through S-glutathionylation under OxS conditions is also discussed. Overall, the data reported here stress the need for further studies aimed at understanding what role the evolutionary-conserved MGO formation and metabolism can play in cell signaling and response to OxS conditions, the aberration of which may importantly contribute to the pathogenesis of diseases associated to elevated OxS.

DNA Adducts as Biomarkers To Predict, Prevent, and Diagnose Disease-Application of Analytical Chemistry to Clinical Investigations

Characterization of the chemistry, structure, formation, and metabolism of DNA adducts has been one of the most significant contributions to the field of chemical toxicology. This work provides the foundation to develop analytical methods to measure DNA adducts, define their relationship to disease, and establish clinical tests. Monitoring exposure to environmental and endogenous toxicants can predict, diagnose, and track disease as well as guide therapeutic treatment. DNA adducts are one of the most promising biomarkers of toxicant exposure owing to their stability, appearance in numerous biological matrices, and characteristic analytical properties. In addition, DNA adducts can induce mutations to drive disease onset and progression and can serve as surrogate markers of chemical exposure. In this perspective, we highlight significant advances made within the past decade regarding DNA adduct quantitation using mass spectrometry. We hope to expose a broader audience to this field and encourage analytical chemistry laboratories to explore how specific adducts may be related to various pathologies. One of the limiting factors in developing clinical tests to measure DNA adducts is cohort size; ideally, the cohort would allow for model development and then testing of the model to the remaining cohort. The goals of this perspective article are to (1) provide a summary of analyte levels measured using state-of-the-art analytical methods, (2) foster collaboration, and (3) highlight areas in need of further investigation.

Methylglyoxal modification reduces the sensitivity of hen egg white lysozyme to stress-induced aggregation: Insight into the anti-amyloidogenic property of α-dicarbonyl compound

The reactive α-oxoaldehyde, methylglyoxal reacts with different proteins to form Advanced Glycation End Products (AGEs) through Maillard reaction. Its level increases significantly in diabetic condition. Here, we have investigated the effect of different concentrations of methylglyoxal (200-400 µM) on the monomeric protein, hen egg white lysozyme (HEWL) following incubation for 3 weeks. Reaction of methylglyoxal with HEWL induced considerable changes in tertiary structure of the protein, but no significant alteration in secondary structure, as evident from different spectroscopic and biophysical studies. Interestingly, methylglyoxal modification was found to enhance the thermal stability of the protein and reduce its sensitivity to stress-induced aggregation. Finally, peptide mass fingerprinting revealed modification of arginine (Arg-45, Arg-14, Arg-68 or Arg-72) and lysine (Lys-116) residues of the protein to AGE adducts, namely, hydroimidazolone, tetrahydropyrimidine, and carboxyethyllysine. Methylglyoxal-derived AGE adducts (MAGE) appear to be responsible for the observed changes in protein. As demonstrated in the present study, the findings may highlight a possible therapeutic potential of the α-oxoaldehyde against protein misfolding and conformational disorder.Communicated by Ramaswamy H. Sarma.

Recent advances in the discovery and development of glyoxalase I inhibitors

Glyoxalase I (GLO1) is a homodimeric Zn²⁺-metalloenzyme that catalyses the transformation of methylglyoxal (MG) to d-lacate through the intermediate S-d-lactoylglutathione. Growing evidence indicates that GLO1 has been identified as a potential target for the treatment cancer and other diseases. Various inhibitors of GLO1 have been discovered or developed over the past several decades including natural or natural product-based inhibitors, GSH-based inhibitors, non-GSH-based inhibitors, etc. The aim of this review is to summarize recent achievements of concerning discovery, design strategies, as well as pharmacological aspects of GLO1 inhibitors with the target of promoting their development toward clinical application.

Glyoxalase 1 expression is downregulated in preimplantation blastocysts of diabetic rabbits

In a diabetic pregnancy, an altered maternal metabolism led to increased formation of reactive α-dicarbonyls such as glyoxal (GO) and methylglyoxal (MGO) in the reproductive organs and embryos. The enzyme glyoxalase (GLO) 1 detoxifies reactive α-dicarbonyls thus protecting cells against malfunction or modifications of proteins by advanced glycated end products (AGEs). The aim of this study was to analyse the influence of a maternal insulin-dependent diabetes mellitus (IDD) on GLO1 expression and activity in preimplantation embryos in vivo and human trophoblast cells (Ac-1M88) in vitro. Maternal diabetes was induced in female rabbits by alloxan before conception and maintained during the preimplantation period. GLO1 expression and activity were investigated in 6-day-old blastocysts from healthy and diabetic rabbits. Furthermore, blastocysts and human trophoblast cells were exposed in vitro to hyperglycaemia, GO and MGO and analysed for GLO1 expression and activity. During gastrulation, GLO1 was expressed in all compartments of the rabbit blastocyst. Maternal diabetes decreased embryonic GLO1 protein amount by approx. 30 per cent whereas the enzymatic activity remained unchanged, indicating that the specific GLO1 activity increases along with metabolic changes. In in vitro cultured embryos, neither hyperglycaemia nor MGO and GO had an effect on GLO1 protein amount. In human trophoblast cells, a stimulating effect on the GLO1 expression was shown in the highest GO concentration, only. Our data show that maternal diabetes mellitus affects the specific activity of GLO1, indicating that GLO1 was post-translationally modified due to changes in metabolic processes in the preimplantation embryos.

Synthesis and metabolism of methylglyoxal, S-D-lactoylglutathione and D-lactate in cancer and Alzheimer's disease. Exploring the crossroad of eternal youth and premature aging

Both cancer and Alzheimer's disease (AD) are emerging as metabolic diseases in which aberrant/dysregulated glucose metabolism and bioenergetics occur, and play a key role in disease progression. Interestingly, an enhancement of glucose uptake, glycolysis and pentose phosphate pathway occurs in both cancer cells and amyloid-β-resistant neurons in the early phase of AD. However, this metabolic shift has its adverse effects. One of them is the increase in methylglyoxal production, a physiological cytotoxic by-product of glucose catabolism. Methylglyoxal is mainly detoxified via cytosolic glyoxalase route comprising glyoxalase 1 and glyoxalase 2 with the production of S-D-lactoylglutathione and D-lactate as intermediate and end-product, respectively. Due to the existence of mitochondrial carriers and intramitochondrial glyoxalase 2 and D-lactate dehydrogenase, the transport and metabolism of both S-D-lactoylglutathione and D-lactate in mitochondria can contribute to methylglyoxal elimination, cellular antioxidant power and energy production. In this review, it is supposed that the different ability of cancer cells and AD neurons to metabolize methylglyoxal, S-D-lactoylglutathione and D-lactate scores cell fate, therefore being at the very crossroad of the "eternal youth" of cancer and the "premature death" of AD neurons. Understanding of these processes would help to elaborate novel metabolism-based therapies for cancer and AD treatment.

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.

Multiple roles of glyoxalase 1-mediated suppression of methylglyoxal glycation in cancer biology-Involvement in tumour suppression, tumour growth, multidrug resistance and target for chemotherapy

Glyoxalase 1 (Glo1) is part of the glyoxalase system in the cytoplasm of all human cells. It catalyses the glutathione-dependent removal of the endogenous reactive dicarbonyl metabolite, methylglyoxal (MG). MG is formed mainly as a side product of anaerobic glycolysis. It modifies protein and DNA to form mainly hydroimidazolone MG-H1 and imidazopurinone MGdG adducts, respectively. Abnormal accumulation of MG, dicarbonyl stress, increases adduct levels which may induce apoptosis and replication catastrophe. In the non-malignant state, Glo1 is a tumour suppressor protein and small molecule inducers of Glo1 expression may find use in cancer prevention. Increased Glo1 expression is permissive for growth of tumours with high glycolytic activity and is thereby a biomarker of tumour growth. High Glo1 expression is a cause of multi-drug resistance. It is produced by over-activation of the Nrf2 pathway and GLO1 amplification. Glo1 inhibitors are antitumour agents, inducing apoptosis and necrosis, and anoikis. Tumour stem cells and tumours with high flux of MG formation and Glo1 expression are sensitive to Glo1 inhibitor therapy. It is likely that MG-induced cell death contributes to the mechanism of action of current antitumour agents. Common refractory tumours have high prevalence of Glo1 overexpression for which Glo1 inhibitors may improve therapy.

Formation of Pentosidine Cross-Linking in Myoglobin by Glyoxal: Detection of Fluorescent Advanced Glycation End Product

Glyoxal, a reactive α-oxoaldehyde, increases in diabetic condition and reacts with proteins to form advanced glycation end products (AGEs) following Maillard-like reaction. Considering the significance of protein modification by glyoxal-derived AGEs, we investigated the in vitro effect of glyoxal (200 μM) on the monomeric heme protein myoglobin (Mb) (100 μM) after incubation for one week at 25 °C. Glyoxal-treated Mb exhibited increased absorbance around the Soret region, decreased α-helicity and thermal stability compared to control Mb. Intrinsic fluorescence spectrum of the treated Mb showed an additional signal in the 400-500 nm region on excitation at 280 nm that was absent in control Mb. When excited at 335 nm, the glyoxal-treated sample gave a strong fluorescence indicating AGE formation. Mass spectrometric studies revealed formation of glyoxal-derived fluorescent AGE adduct pentosidine between Lys-145 and Arg-139 residues of Mb. Other than pentosidine, additional AGE adducts, namely, carboxymethyllysine at Lys-133, hydroimidazolone at Arg-31 and pyrrolidone-carboxymethyllysine at Lys-145 were also detected. Lys-145 was thus found to contain two different types of AGE adducts, indicating the heterogeneous nature of in vitro glycation reaction. AGE-induced protein modifications might be associated with complications in disease conditions.

Dicarbonyls and glyoxalase in disease mechanisms and clinical therapeutics

The reactive dicarbonyl metabolite methylglyoxal (MG) is the precursor of the major quantitative advanced glycation endproducts (AGEs) in physiological systems - arginine-derived hydroimidazolones and deoxyguanosine-derived imidazopurinones. The glyoxalase system in the cytoplasm of cells provides the primary defence against dicarbonyl glycation by catalysing the metabolism of MG and related reactive dicarbonyls. Dicarbonyl stress is the abnormal accumulation of dicarbonyl metabolites leading to increased protein and DNA modification contributing to cell and tissue dysfunction in ageing and disease. It is produced endogenously by increased formation and/or decreased metabolism of dicarbonyl metabolites. Dicarbonyl stress contributes to ageing, disease and activity of cytotoxic chemotherapeutic agents. It contributes to ageing through age-related decline in glyoxalase 1 (Glo-1) activity. Glo-1 has a dual role in cancer as a tumour suppressor protein prior to tumour development and mediator of multi-drug resistance in cancer treatment, implicating dicarbonyl glycation of DNA in carcinogenesis and dicarbonyl-driven cytotoxicity in mechanism of action of anticancer drugs. Glo-1 is a driver of cardiovascular disease, likely through dicarbonyl stress-driven dyslipidemia and vascular cell dysfunction. Dicarbonyl stress is also a contributing mediator of obesity and vascular complications of diabetes. There are also emerging roles in neurological disorders. Glo-1 responds to dicarbonyl stress to enhance cytoprotection at the transcriptional level through stress-responsive increase of Glo-1 expression. Small molecule Glo-1 inducers are in clinical development for improved metabolic, vascular and renal health and Glo-1 inhibitors in preclinical development for multidrug resistant cancer chemotherapy.

Evaluation of potential flavonoid inhibitors of glyoxalase-I based on virtual screening and in vitro studies

Glyoxalase-I (GLO-I) is a component of the ubiquitous detoxification system involved in the conversion of methylglyoxal (MG) to d-lactate in the glycolytic pathway. MG toxicity arises from its ability to form advanced glycation end products. GLO-I has been reported to be frequently overexpressed in various types of cancer cells. In this study, we performed structure-based virtual screening of focused flavonoids commercial library to identify potential and specific inhibitors of GLO-I. The compounds were ranked based on Glide extra precision docking score and five hits (curcumin, quercetin, morin, naringin and silibinin) were selected on the basis of their interaction with active site amino acid residues of GLO-I. Mixed mode QM/MM calculation was performed on the top-scoring hit to ascertain the role of zinc ion in ligand binding. In addition, the identified hits were subjected to MM/GBSA binding energy prediction, ADME prediction and similarity studies. The hits were tested in vitro for cell viability, and GLO-I inhibition. Naringin (ST072162) was found to be most potent inhibitor of GLO-I among the identified hits with highest glide XP dock score of -14.906. These findings suggest that naringin could be a new scaffold for designing inhibitors against GLO-I with potential application as anticancer agents.

Potential prognostic, diagnostic and therapeutic markers for human gastric cancer

The high incidence of gastric cancer (GC) and its consequent mortality rate severely threaten human health. GC is frequently not diagnosed until a relatively advanced stage. Surgery is the only potentially curative treatment. Thus, early screening and diagnosis are critical for improving prognoses in patients with GC. Gastroscopy with biopsy is an appropriate method capable of aiding the diagnosis of specific early GC tumor types; however, the stress caused by this method together with it being excessively expensive makes it difficult to use it as a routine method for screening for GC on a population basis. The currently used tumor marker assays for detecting GC are simple and rapid, but their use is limited by their low sensitivity and specificity. In recent years, several markers have been identified and tested for their clinical relevance in the management of GC. Here, we review the serum-based tumor markers for GC and their clinical significance, focusing on discoveries from microarray/proteomics research. We also review tissue-based GC tumor markers and their clinical application, focusing on discoveries from immunohistochemical research. This review provides a brief description of various tumor markers for the purposes of diagnosis, prognosis and therapeutics, and we include markers already in clinical practice and various forthcoming biomarkers.

Pathophysiological importance of aggregated damaged proteins

Reactive oxygen species (ROS) are formed continuously in the organism even under physiological conditions. If the level of ROS in cells exceeds the cellular defense capacity, components such as RNA/DNA, lipids, and proteins are damaged and modified, thus affecting the functionality of organelles as well. Proteins are especially prominent targets of various modifications such as oxidation, glycation, or conjugation with products of lipid peroxidation, leading to the alteration of their biological function, nonspecific interactions, and the production of high-molecular-weight protein aggregates. To ensure the maintenance of cellular functions, two proteolytic systems are responsible for the removal of oxidized and modified proteins, especially the proteasome and organelles, mainly the autophagy-lysosomal systems. Furthermore, increased protein oxidation and oxidation-dependent impairment of proteolytic systems lead to an accumulation of oxidized proteins and finally to the formation of nondegradable protein aggregates. Accordingly, the cellular homeostasis cannot be maintained and the cellular metabolism is negatively affected. Here we address the current knowledge of protein aggregation during oxidative stress, aging, and disease.

Advanced glycoxidation and lipoxidation end products (AGEs and ALEs): an overview of their mechanisms of formation

Advanced lipoxidation end products (ALEs) and advanced glycation end products (AGEs) have a pathogenetic role in the development and progression of different oxidative-based diseases including diabetes, atherosclerosis, and neurological disorders. AGEs and ALEs represent a quite complex class of compounds that are formed by different mechanisms, by heterogeneous precursors and that can be formed either exogenously or endogenously. There is a wide interest in AGEs and ALEs involving different aspects of research which are essentially focused on set-up and application of analytical strategies (1) to identify, characterize, and quantify AGEs and ALEs in different pathophysiological conditions; (2) to elucidate the molecular basis of their biological effects; and (3) to discover compounds able to inhibit AGEs/ALEs damaging effects not only as biological tools aimed at validating AGEs/ALEs as drug target, but also as promising drugs. All the above-mentioned research stages require a clear picture of the chemical formation of AGEs/ALEs but this is not simple, due to the complex and heterogeneous pathways, involving different precursors and mechanisms. In view of this intricate scenario, the aim of the present review is to group the main AGEs and ALEs and to describe, for each of them, the precursors and mechanisms of formation.

Where does plasma methylglyoxal originate from?

The elevation of plasma methylglyoxal levels in diabetic humans is widely observed, but it is unknown to what extent different sources of methylglyoxal contribute to its plasma concentration. A retrospective analysis of clinical findings has been undertaken. There is controversy about the correlation of plasma methylglyoxal concentrations with fasting or postprandial glucose levels, and the relationship with HbA1c. There is only one study in which plasma ketone body levels have been monitored in parallel with methylglyoxal and a positive correlation between plasma methylglyoxal and β-hydroxybutyrate was observed. There are no reports on plasma aminoacetone levels and methylglyoxal in diabetic humans. This paper suggests that although there is a close association between methylglyoxal and carbohydrate metabolism, the presence of this 1,2-dicarbonyl in the plasma is mainly due to other mechanisms. Protein glycation and aminoacetone degradation are proposed to be the major and the minor sources of plasma methylglyoxal under normal conditions.

Glyoxalase-I is a novel prognosis factor associated with gastric cancer progression

Glyoxalase I (GLO1), a methylglyoxal detoxification enzyme, is implicated in the progression of human malignancies. The role of GLO1 in gastric cancer development or progression is currently unclear. The expression of GLO1 was determined in primary gastric cancer specimens using quantitative polymerase chain reaction, immunohistochemistry (IHC), and western blotting analyses. GLO1 expression was higher in gastric cancer tissues, compared with that in adjacent noncancerous tissues. Elevated expression of GLO1 was significantly associated with gastric wall invasion, lymph node metastasis, and pathological stage, suggesting a novel role of GLO1 in gastric cancer development and progression. The 5-year survival rate of the lower GLO1 expression groups was significantly greater than that of the higher expression groups (log rank P = 0.0373) in IHC experiments. Over-expression of GLO1 in gastric cancer cell lines increases cell proliferation, migration and invasiveness. Conversely, down-regulation of GLO1 with shRNA led to a marked reduction in the migration and invasion abilities. Our data strongly suggest that high expression of GLO1 in gastric cancer enhances the metastasis ability of tumor cells in vitro and in vivo, and support its efficacy as a potential marker for the detection and prognosis of gastric cancer.

Flow cytometric analysis of glyoxalase-1 expression in human leukocytes

Altered glyoxalase-1 (GLO-1) activity and expression is associated with the development of late diabetic complications, malignancy and oxidative stress- and aging-related diseases. In the present study, we developed a flow cytometry method for GLO-1 detection in human leukocytes isolated from peripheral blood samples to investigate GLO-1 expression in leukocyte subsets from type 1 and 2 diabetes mellitus patients (n = 11) and healthy subjects (n = 8). The flow cytometry analysis of GLO-1 in leukocytes showed that expression index of GLO-1-positive cells was slightly increased in mononuclear leukocytes from diabetic patients. This result correlated with the increase in GLO-1 activity in the whole blood samples of type 2 diabetes patients. In conclusion, the present study demonstrates that flow cytometry is suitable for the detection of the GLO-1 enzyme in human leukocytes and that this method could be used to investigate the fast adaptation of the glyoxalase system related to the pathogenesis of late complications of diabetes mellitus and other glycation stress-related disorders.

A study of D-lactate and extracellular methylglyoxal production in lactate re-utilizing CHO cultures

In large-scale mammalian cell culture, the key toxic by-products assessed and monitored are lactate and ammonia. Often no distinction between the two isoforms of lactate is made. Here, we present profiles of both D- and L-lactate. D-Lactate is the end molecule of the methylglyoxal pathway. D-Lactate unlike L-lactate is not re-utilized, and although during normal culture time frames it represents one-tenth of total lactate, during lactate re-use it represents nearly 35%. This indicates significant carbon flow through pathways not associated with primary metabolites. We have observed that the behavior of D-lactate is radically different from that of L-lactate with the level of one isoform changing, whilst the concentration of the other remains constant. This is an example of an alternate carbon flow pathway containing metabolic intermediates that may potentially have a detrimental effect on cells. The activity of the methylglyoxal pathway when measured as a proportion of glucose consumption in this study far exceeds any previously reported. This highlights the potential importance of "non-primary" metabolisms to long lifespan mammalian fermentation practices.

Converting GLX2-1 into an active glyoxalase II

Arabidopsis thaliana glyoxalase 2-1 (GLX2-1) exhibits extensive sequence similarity with GLX2 enzymes but is catalytically inactive with SLG, the GLX2 substrate. In an effort to identify residues essential for GLX2 activity, amino acid residues were altered at positions 219, 246, 248, 325, and 328 in GLX2-1 to be the same as those in catalytically active human GLX2. The resulting enzymes were overexpressed, purified, and characterized using metal analyses, fluorescence spectroscopy, and steady-state kinetics to evaluate how these residues affect metal binding, structure, and catalysis. The R246H/N248Y double mutant exhibited low level S-lactoylglutathione hydrolase activity, while the R246H/N248Y/Q325R/R328K mutant exhibited a 1.5-2-fold increase in k(cat) and a decrease in K(m) as compared to the values exhibited by the double mutant. In contrast, the R246H mutant of GLX2-1 did not exhibit glyoxalase 2 activity. Zn(II)-loaded R246H GLX2-1 enzyme bound 2 equiv of Zn(II), and (1)H NMR spectra of the Co(II)-substituted analogue of this enzyme strongly suggest that the introduced histidine binds to Co(II). EPR studies indicate the presence of significant amounts a dinuclear metal ion-containing center. Therefore, an active GLX2 enzyme requires both the presence of a properly positioned metal center and significant nonmetal, enzyme-substrate contacts, with tyrosine 255 being particularly important.

GLO1 overexpression in human malignant melanoma

Glyoxalase I [lactoylglutathione lyase (EC 4.4.1.5) encoded by GLO1] is a ubiquitous cellular defense enzyme involved in the detoxification of methylglyoxal, a cytotoxic byproduct of glycolysis. Accumulative evidence suggests an important role of GLO1 expression in protection against methylglyoxal-dependent protein adduction and cellular damage associated with diabetes, cancer, and chronological aging. On the basis of the hypothesis that GLO1 upregulation may play a functional role in glycolytic adaptations of cancer cells, we examined GLO1 expression status in human melanoma tissue. Quantitative reverse transcription polymerase chain reaction analysis of a cDNA tissue array containing 40 human melanoma tissues (stages III and IV) and 13 healthy controls revealed pronounced upregulation of GLO1 expression at the mRNA level. Immunohistochemical analysis of a melanoma tissue microarray confirmed upregulation of glyoxalase I protein levels in malignant melanoma tissue versus healthy human skin. Consistent with an essential role of GLO1 in melanoma cell defense against methylglyoxal cytotoxicity, siRNA interference targeting GLO1-expression (siGLO1) sensitized A375 and G361 human metastatic melanoma cells towards the antiproliferative, apoptogenic, and oxidative stress-inducing activity of exogenous methylglyoxal. Protein adduction by methylglyoxal was increased in siGLO1-transfected cells as revealed by immunodetection using a monoclonal antibody directed against the major methylglyoxal-derived epitope argpyrimidine that detected a single band of methylglyoxal-adducted protein in human LOX, G361, and A375 total cell lysates. Using two-dimensional proteomics followed by mass spectrometry the methylglyoxal-adducted protein was identified as heat shock protein 27 (Hsp27; HSPB1). Taken together, our data suggest a function of GLO1 in the regulation of detoxification and target adduction by the glycolytic byproduct methylglyoxal in malignant melanoma.

Human glyoxalase II contains an Fe(II)Zn(II) center but is active as a mononuclear Zn(II) enzyme

Human glyoxalase II (Glx2) was overexpressed in rich medium and in minimal medium containing zinc, iron, or cobalt, and the resulting Glx2 analogues were characterized using metal analyses, steady-state and pre-steady-state kinetics, and NMR and EPR spectroscopies to determine the nature of the metal center in the enzyme. Recombinant human Glx2 tightly binds nearly 1 equiv each of Zn(II) and Fe. In contrast to previous reports, this study demonstrates that an analogue containing 2 equiv of Zn(II) cannot be prepared. EPR studies suggest that most of the iron in recombinant Glx2 is Fe(II). NMR studies show that Fe(II) binds to the consensus Zn(2) site in Glx2 and that this site can also bind Co(II) and Ni(II), suggesting that Zn(II) binds to the consensus Zn(1) site. The NMR studies also reveal the presence of a dinuclear Co(II) center in Co(II)-substituted Glx2. Steady-state and pre-steady-state kinetic studies show that Glx2 containing only 1 equiv of Zn(II) is catalytically active and that the metal ion in the consensus Zn(2) site has little effect on catalytic activity. Taken together, these studies suggest that Glx2 contains a Fe(II)Zn(II) center in vivo but that the catalytic activity is due to Zn(II) in the Zn(1) site.

Arabidopsis thaliana GLX2-1 contains a dinuclear metal binding site, but is not a glyoxalase 2

In an effort to probe the structure and function of a predicted mitochondrial glyoxalase 2, GLX2-1, from Arabidopsis thaliana, GLX2-1 was cloned, overexpressed, purified and characterized using metal analyses, kinetics, and UV-visible, EPR, and (1)H-NMR spectroscopies. The purified enzyme was purple and contained substoichiometric amounts of iron and zinc; however, metal-binding studies reveal that GLX2-1 can bind nearly two equivalents of either iron or zinc and that the most stable analogue of GLX2-1 is the iron-containing form. UV-visible spectra of the purified enzyme suggest the presence of Fe(II) in the protein, but the Fe(II) can be oxidized over time or by the addition of metal ions to the protein. EPR spectra revealed the presence of an anti-ferromagnetically-coupled Fe(III)Fe(II) centre and the presence of a protein-bound high-spin Fe(III) centre, perhaps as part of a FeZn centre. No paramagnetically shifted peaks were observed in (1)H-NMR spectra of the GLX2-1 analogues, suggesting low amounts of the paramagnetic, anti-ferromagnetically coupled centre. Steady-state kinetic studies with several thiolester substrates indicate that GLX2-1 is not a GLX2. In contrast with all of the other GLX2 proteins characterized, GLX2-1 contains an arginine in place of one of the metal-binding histidine residues at position 246. In order to evaluate further whether Arg(246) binds metal, the R246L mutant was prepared. The metal binding results are very similar to those of native GLX2-1, suggesting that a different amino acid is recruited as a metal-binding ligand. These results demonstrate that Arabidopsis GLX2-1 is a novel member of the metallo-beta-lactamase superfamily.

Advanced glycation end products, diabetes and ageing

Advanced glycation end products (AGEs) are formed in vivo by a non-enzymatic reaction of proteins with carbohydrates and accumulate in many tissues during ageing. They are discussed as being responsible for many age- and diabetes-related diseases. On the other hand, AGEs are formed by the heating of food and are taken up by the nutrition. The contribution of endogenously formed versus exogenous intake of AGEs to age-related diseases is still under discussion.

Protein and nucleotide damage by glyoxal and methylglyoxal in physiological systems--role in ageing and disease

Glycation of proteins, nucleotides and basic phospholipids by glyoxal and methylglyoxal--physiological substrates of glyoxalase 1--is potentially damaging to the proteome, genome and lipidome. Glyoxalase 1 suppresses glycation by these alpha-oxoaldehyde metabolites and thereby represents part of the enzymatic defence against glycation. Albert Szent-Györgyi pioneered and struggled to understand the physiological function of methylglyoxal and the glyoxalase system. We now appreciate that glyoxalase 1 protects against dicarbonyl modifications of the proteome, genome and lipome. Latest research suggests there are functional modifications of this process--implying a role in cell signalling, ageing and disease.

A possible regulatory role of 17beta-estradiol and tamoxifen on glyoxalase I and glyoxalase II genes expression in MCF7 and BT20 human breast cancer cells

The glutathione-dependent glyoxalases system, composed of glyoxalase I (GloI) and glyoxalase II (GloII) enzymes, is involved in the detoxification of methylglyoxal, a by-product of cell metabolism. Aberrations in the expression of glyoxalase genes in several human cancers have been reported. Sometimes, these aberrations seem to differ depending on the organs and on the sensitivity of the tumours to estrogens, as we previously detected in the hormone-responsive breast cancer compared to the hormone-independent bladder cancer. To investigate a possible regulatory role of estrogens, as well as antiestrogens, on glyoxalases system, estrogen receptor (ER)-positive MCF7 and ER-negative BT20 human breast cancer cells were cultured in the presence of 17beta-estradiol (E2) and tamoxifen (TAM) performing two independent experiments. After a 24 h or 4 days treatment, we evaluated GloI and GloII mRNA levels, by Ribonuclease Protection Assay (RPA), enzymatic activities spectrophotometrically and cell proliferation by [3H]thymidine incorporation. We found that both steroid molecules affected glyoxalases gene expression and proliferation in a different manner in the cell lines. The modifications in mRNA levels were accompanied by parallel changes in the enzymatic activities. The possibility that modulation of glyoxalase genes by E2 and TAM are due to the presence of estrogen response elements (ERE) or cross-talk mechanisms by proteins of the estrogen signal transduction pathways are discussed. Knowledge regarding the regulation of glyoxalases by E2 and TAM may provide insights into the importance of this enzymes in human breast carcinomas in vivo.

Molecular basis of formaldehyde detoxification. Characterization of two S-formylglutathione hydrolases from Escherichia coli, FrmB and YeiG

The Escherichia coli genes frmB (yaiM) and yeiG encode two uncharacterized proteins that share 54% sequence identity and contain a serine esterase motif. We demonstrated that purified FrmB and YeiG have high carboxylesterase activity against the model substrates, p-nitrophenyl esters of fatty acids (C2-C6) and alpha-naphthyl acetate. However, both proteins had the highest hydrolytic activity toward S-formylglutathione, an intermediate of the glutathione-dependent pathway of formaldehyde detoxification. With this substrate, both proteins had similar affinity (Km = 0.41-0.43 mM), but FrmB was almost 5 times more active. Alanine replacement mutagenesis of YeiG demonstrated that Ser145, Asp233, and His256 are absolutely required for activity, indicating that these residues represent a serine hydrolase catalytic triad in this protein and in other S-formylglutathione hydrolases. This was confirmed by inspecting the crystal structure of the Saccharomyces cerevisiae S-formylglutathione hydrolase YJG8 (Protein Data Bank code 1pv1), which has 45% sequence identity to YeiG. The structure revealed a canonical alpha/beta-hydrolase fold and a classical serine hydrolase catalytic triad (Ser161, His276, Asp241). In E. coli cells, the expression of frmB was stimulated 45-75 times by the addition of formaldehyde to the growth medium, whereas YeiG was found to be a constitutive enzyme. The simultaneous deletion of both frmB and yeiG genes was required to increase the sensitivity of the growth of E. coli cells to formaldehyde, suggesting that both FrmB and YeiG contribute to the detoxification of formaldehyde. Thus, FrmB and YeiG are S-formylglutathione hydrolases with a Ser-His-Asp catalytic triad involved in the detoxification of formaldehyde in E. coli.

Thioester hydrolysis reactivity of zinc hydroxide complexes: investigating reactivity relevant to glyoxalase II enzymes

A recently reported binuclear zinc hydroxide complex [(L(1)Zn(2))(mu-OH)](ClO(4))(2) (, L(1) = 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenolate monoanion) containing a single bridging hydroxide was examined for thioester hydrolysis reactivity. Treatment of it with hydroxyphenylthioacetic acid S-methyl ester in dry CD(3)CN results in no reaction after approximately 65 h at 45(1) degrees C. Binuclear zinc hydroxide complexes of the N-methyl-N-((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine (L(2)) and N-methyl-N-((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)ethyl)amine (L(3)) chelate ligands were prepared by treatment of each ligand with molar equivalent amounts of Zn(ClO(4))(2).6H(2)O and KOH in methanol. These complexes, [(L(2)Zn)(2)(mu-OH)(2)](ClO(4))(2) and [(L(3)Zn)(2)(mu-OH)(2)](ClO(4))(2) (), which have been structurally characterized by X-ray crystallography, behave as 1 : 1 electrolytes in acetonitrile, indicating that the binuclear cations dissociate into monomeric zinc hydroxide species in solution. Treatment of them with one equivalent of hydroxyphenylthioacetic acid S-methyl ester per zinc center in acetonitrile results in the formation of a zinc alpha-hydroxycarboxylate complex, [(L(2))Zn(O(2)CCH(OH)Ph)]ClO(4).1.5H(2)O or [(L(3))Zn(O(2)CCH(OH)Ph)]ClO(4).1.5H(2)O, and CH(3)SH. These reactions, to our knowledge, are the first reported examples of thioester hydrolysis mediated by zinc hydroxide complexes. The results of this study suggest that a terminal Zn-OH moiety may be required for hydrolysis reactivity with a thioester substrate.

Structural studies on a mitochondrial glyoxalase II

Glyoxalase 2 is a beta-lactamase fold-containing enzyme that appears to be involved with cellular chemical detoxification. Although the cytoplasmic isozyme has been characterized from several organisms, essentially nothing is known about the mitochondrial proteins. As a first step in understanding the structure and function of mitochondrial glyoxalase 2 enzymes, a mitochondrial isozyme (GLX2-5) from Arabidopsis thaliana was cloned, overexpressed, purified, and characterized using metal analyses, EPR and (1)H NMR spectroscopies, and x-ray crystallography. The recombinant enzyme was shown to bind 1.04 +/- 0.15 eq of iron and 1.31 +/- 0.05 eq of Zn(II) and to exhibit k(cat) and K(m) values of 129 +/- 10 s(-1) and 391 +/- 48 microm, respectively, when using S-d-lactoylglutathione as the substrate. EPR spectra revealed that recombinant GLX2-5 contains multiple metal centers, including a predominant Fe(III)Z-n(II) center and an anti-ferromagnetically coupled Fe(III)Fe(II) center. Unlike cytosolic glyoxalase 2 from A. thaliana, GLX2-5 does not appear to specifically bind manganese. (1)H NMR spectra revealed the presence of at least eight paramagnetically shifted resonances that arise from protons in close proximity to a Fe(III)Fe(II) center. Five of these resonances arose from solvent-exchangeable protons, and four of these have been assigned to NH protons on metal-bound histidines. A 1.74-A resolution crystal structure of the enzyme revealed that although GLX2-5 shares a number of structural features with human GLX2, several important differences exist. These data demonstrate that mitochondrial glyoxalase 2 can accommodate a number of different metal centers and that the predominant metal center is Fe(III)Zn(II).

Toxic concentrations of exogenously supplied methylglyoxal in hybridoma cell culture

Concentrations at which methylglyoxal, a by-product of cellular metabolism, can be toxic to hybridoma cell cultures were determined using exogenously supplied doses. Trypan blue cell counts of 6-well cultures incubated for 24 h with various methylglyoxal concentrations revealed inhibition of cell growth at 300 muM and higher, with a median inhibitory concentration of 490+/-20 muM. The primary mode of death was apoptosis, as assessed by chromatin condensation, and the effects of methylglyoxal were observed to be complete by approximately eight hours. Yet, the impact of methylglyoxal was a function of the rate of dosing; stepwise addition of MG during the first 6 h of incubation inhibited growth but caused much less cell death than a comparable bolus dose. Inhibition of cellular metabolism by MG was found to coincide with inhibition of cell growth, with a comparable median inhibitory concentration of 360+/-20 muM. The effects on viable cell density and metabolism were both linear at doses approaching zero, with lowest observable effect levels of 54 and 77 muM, respectively. These results provide quantitative estimates for concentrations of methylglyoxal that may be inhibitory to biopharmaceutical-producing cell lines.

Antimelanoma activity of apoptogenic carbonyl scavengers

Therapeutic induction of apoptosis is an important goal of anticancer drug design. Cellular carbonyl stress mediated by endogenous reactive carbonyl species (RCS) such as glyoxal and methylglyoxal (MG) affects proliferative signaling and metastasis of human tumor cells. Recent research suggests that RCS produced constitutively during increased tumor cell glycolysis may be antiapoptotic survival factors and thus represent a novel molecular target for anticancer intervention. Here, we demonstrate the tumor cell-specific apoptogenicity of carbonyl scavengers, which act by covalently trapping RCS, against human (A375, G361, and LOX) and murine (B16) melanoma cell lines. A structure-activity relationship study identified nucleophilic carbonyl scavenger pharmacophores as the functional determinants of apoptogenic antimelanoma activity of structurally diverse agents such as 3,3-dimethyl-D-cysteine and aminoguanidine. Previous work has demonstrated that covalent adduction of protein-arginine residues in the mitochondrial permeability transition (MPT) pore and heat shock protein 27 by intracellular MG produced in tumor cell glycolysis inhibits mitochondrial apoptosis and enhances cancer cell survival. Indeed, in various melanoma cell lines, carbonyl scavenger-induced apoptosis was antagonized by pretreatment with the membrane-permeable RCS phenylglyoxal (PG). Carbonyl scavenger-induced apoptosis was associated with early loss of mitochondrial transmembrane potential, and cyclosporin A antagonized the effects of carbonyl scavengers, suggesting a causative role of MPT pore opening in carbonyl scavenger apoptogenicity. Consistent with RCS inhibition of mitochondrial apoptosis in melanoma cells, staurosporine-induced apoptosis also was suppressed by PG pretreatment. Our results suggest that carbonyl scavengers acting as direct molecular antagonists of RCS are promising apoptogenic prototype agents for antimelanoma drug design.

Reversal of anticancer drug resistance by COTC based on intracellular glutathione and glyoxalase I

Suppression of resistance to anticancer drugs by COTC of glyoxalase I (GloI) inhibitor targeting intracellular glutathione (GSH) and GloI was studied. Depletion of the cellular GSH content and inhibition of GloI by COTC increased chemotherapy-mediated apoptosis in apoptosis-resistant pancreatic adenocarcinoma AsPC-1 cells.

Modification of Permeability Transition Pore Arginine(s) by Phenylglyoxal Derivatives in Isolated Mitochondria and Mammalian Cells

Methylglyoxal and synthetic glyoxal derivatives react covalently with arginine residue(s) on the mitochondrial permeability transition pore (PTP). In this study, we have investigated how the binding of a panel of synthetic phenylglyoxal derivatives influences the opening and closing of the PTP. Using both isolated mitochondria and mammalian cells, we demonstrate that the resulting arginine-phenylglyoxal adduct can lead to either suppression or induction of permeability transition, depending on the net charge and hydrogen bonding capacity of the adduct. We report that phenylglyoxal derivatives that possess a net negative charge and/or are capable of forming hydrogen bonds induced permeability transition. Derivatives that were overall electroneutral and cannot form hydrogen bonds suppressed permeability transition. When mammalian cells were incubated with low concentrations of negatively charged phenylglyoxal derivatives, the addition of oligomycin caused a depolarization of the mitochondrial membrane potential. This depolarization was completely blocked by cyclosporin A, a PTP opening inhibitor, indicating that the depolarization was due to PTP opening. Collectively, these findings highlight that the target arginine(s) is functionally linked with the opening/closing mechanism of the PTP and that the electric charge and hydrogen bonding of the resulting arginine adduct influences the conformation of the PTP. These results are consistent with a model where the target arginine plays a role as a voltage sensor.

Proteomic studies identified a single nucleotide polymorphism in glyoxalase I as autism susceptibility factor

Autism is a neurodevelopmental disability characterized by deficits in verbal communications, impairments in social interactions, and repetitive behaviors. Several studies have indicated strong involvement of multigenic components in the etiology of autism. Linkage analyses and candidate gene search approaches so far have not identified any reliable susceptibility genes. We are using a proteomic approach to identify protein abnormalities due to aberrant gene expression in autopsied autism brains. In four of eight autism brains, we have found an increase in polarity (more acidic) of glyoxalase I (Glo1) by two-dimensional gel electrophoresis. To identify the molecular change resulting in the shift of Glo1 polarity, we undertook sequencing of GLO1 gene. Direct sequencing of GLO1 gene/mRNA in these brains, has identified a single nucleotide polymorphism (SNP), C419A. The SNP causes an Ala111Glu change in the protein sequence. Population genetics of GLO1 C419A SNP studied in autism (71 samples) and normal and neurological controls (49 samples) showed significantly higher frequency for the A419 (allele frequency 0.6 in autism and 0.4 in controls, one-tailed Fisher's test P < 0.0079). Biochemical measurements have revealed a 38% decrease in Glo1 enzyme activity in autism brains (one-tailed t-test P < 0.026). Western blot analysis has also shown accumulation of advanced glycation end products (AGE's) in autism brains. These data suggest that homozygosity for A419 GLO1 resulting in Glu111 is a predisposing factor in the etiology of autism.

Methotrexate inhibits the glyoxalase system in vivo in children with acute lymphoid leukaemia

The inhibition of glyoxalase I leads to antitumour activity through the accumulation of methylglyoxal. Our earlier observations suggested that methotrexate (MTX) may affect the glyoxalase system. This prompted a serial study of the drug on this metabolic pathway. Ten children with acute lymphoid leukaemia (ALL), admitted to our department between January 2002 and July 2003, were enrolled. Plasma D-lactate was assayed before, 24 and 72 h after the start of four consecutive MTX infusions (5 g/m(2)/24 h) in each patient. Inhibition of glyoxalase I was tested in vitro, using human erythrocyte lysates and yeast enzyme. The elevated initial plasma D-lactate levels (P<0.02) fell significantly (P<0.001) in response to 24 h MTX infusions. In vitro, MTX, folic and folinic acids inhibited the activity of glyoxalase I. Thus, MTX seems to affect the alpha-oxoaldehyde metabolism in vivo, as a likely consequence of glyoxalase I inhibition. This action probably contributes to the anticancer activity and toxicity of the drug.