Aging-dependent reduction in glyoxalase 1 delays wound healing

Glycation modulates superoxide dismutase 1 aggregation and toxicity in models of sporadic amyotrophic lateral sclerosis

Different SOD1 proteoforms are implicated## in both familial and sporadic cases of Amyotrophic Lateral Sclerosis (ALS), an aging-associated disease that affects motor neurons. SOD1 is crucial to neuronal metabolism and health, regulating the oxidative stress response and the shift between oxidative-fermentative metabolism, which is important for astrocyte-neuron metabolic cooperation. Neurons have a limited capacity to metabolize methylglyoxal (MGO), a potentially toxic side product of glycolysis. MGO is highly reactive and can readily posttranslationally modify proteins, in a reaction known as glycation, impacting their normal biology. Here, we aimed to investigate the effect of glycation on the aggregation and toxicity of human SOD1WT (hSOD1WT). Cells with deficiency in MGO metabolism showed increased levels of hSOD1WT inclusions, displaying also reduced hSOD1WT activity and viability. Strikingly, we also found that the presence of hSOD1WT in stress granules increased upon MGO treatment. The treatment of recombinant hSOD1WT with MGO resulted in the formation of SDS-stable oligomers, specially trimers, and thioflavin-T positive aggregates, which can promote cell toxicity and TDP-43 pathology. Together, our results suggest that glycation may play a still underappreciated role on hSOD1WT and TDP-43 pathologies in sporadic ALS, which could open novel perspectives for therapeutic intervention.

Decreased methylglyoxal-mediated protein glycation in the healthy aging mouse model of ectopic expression of UCP1 in skeletal muscle

Mice with ectopic expression of uncoupling protein-1 (UCP1) in skeletal muscle exhibit a healthy aging phenotype with increased longevity and resistance to impaired metabolic health. This may be achieved by decreasing protein glycation by the reactive metabolite, methylglyoxal (MG). We investigated protein glycation and oxidative damage in skeletal muscle of mice with UCP1 expression under control of the human skeletal actin promoter (HSA-mUCP1) at age 12 weeks (young) and 70 weeks (aged). We found both young and aged HSA-mUCP1 mice had decreased advanced glycation endproducts (AGEs) formed from MG, lysine-derived Nε(1-carboxyethyl)lysine (CEL) and arginine-derived hydroimidazolone, MG-H1, whereas protein glycation by glucose forming Nε-fructosyl-lysine (FL) was increased ca. 2-fold, compared to wildtype controls. There were related increases in FL-linked AGEs, Nε-carboxymethyl-lysine (CML) and 3-deoxylglucosone-derived hydroimidazolone 3DG-H, and minor changes in protein oxidative and nitration adducts. In aged HSA-mUCP1 mice, urinary MG-derived AGEs/FL ratio was decreased ca. 60% whereas there was no change in CML/FL ratio - a marker of oxidative damage. This suggests that, normalized for glycemic status, aged HSA-mUCP1 mice had a lower flux of whole body MG-derived AGE exposure compared to wildtype controls. Proteomics analysis of skeletal muscle revealed a shift to increased heat shock proteins and mechanoprotection and repair in HSA-mUCP1 mice. Decreased MG-derived AGE protein content in skeletal muscle of aged HSA-mUCP1 mice is therefore likely produced by increased proteolysis of MG-modified proteins and increased proteostasis surveillance of the skeletal muscle proteome. From this and previous transcriptomic studies, signaling involved in enhanced removal of MG-modified protein is likely increased HSPB1-directed HUWE1 ubiquitination through eIF2α-mediated, ATF5-induced increased expression of HSPB1. Decreased whole body exposure to MG-derived AGEs may be linked to increased weight specific physical activity of HSA-mUCP1 mice. Decreased formation and increased clearance of MG-derived AGEs may be associated with healthy aging in the HSA-mUCP1 mouse.

Methylglyoxal in the Brain: From Glycolytic Metabolite to Signalling Molecule

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

The Glyoxalase System Is a Novel Cargo of Amniotic Fluid Stem-Cell-Derived Extracellular Vesicles

The glyoxalase system is a ubiquitous cellular metabolic pathway whose main physiological role is the removal of methylglyoxal (MG). MG, a glycolysis byproduct formed by the spontaneous degradation of triosephosphates glyceraldehyde-3-phosphate (GA3P) and dihydroxyacetonephosphate (DHAP), is an arginine-directed glycating agent and precursor of the major advanced glycation end product arginine-derived, hydroimidazolone (MG-H1). Extracellular vesicles (EVs) are a heterogeneous family of lipid-bilayer-vesicular structures released by virtually all living cells, involved in cell-to-cell communication, specifically by transporting biomolecules to recipient cells, driving distinct biological responses. Emerging evidence suggests that included in the EVs cargo there are different metabolic enzymes. Specifically, recent research has pointed out that EVs derived from human amniotic fluid stem cell (HASC-EVs) contain glycolytic pay-off phase enzymes, such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Since GAPDH catalyzes the sixth step of glycolysis using as a substrate GA3P, from which MG spontaneously origins, we wanted to investigate whether MG-derived MG-H1, as well as glyoxalases, could be novel molecule cargo in these EVs. By using immunoassays and spectrophotometric methods, we found, for the first time ever, that HASC-EVs contain functional glyoxalases and MG-H1, pioneering research to novel and exciting roles of these eclectic proteins, bringing them to the limelight once more.

Glyoxalase 1 knockdown induces age-related β-cell dysfunction and glucose intolerance in mice

Tight control of glycemia is a major treatment goal for type 2 diabetes mellitus (T2DM). Clinical studies indicated that factors other than poor glycemic control may be important in fostering T2DM progression. Increased levels of methylglyoxal (MGO) associate with complications development, but its role in the early steps of T2DM pathogenesis has not been defined. Here, we show that MGO accumulation induces an age-dependent impairment of glucose tolerance and glucose-stimulated insulin secretion in mice knockdown for glyoxalase 1 (Glo1KD). This metabolic alteration associates with the presence of insular inflammatory infiltration (F4/80-positive staining), the islet expression of senescence markers, and higher levels of cytokines (MCP-1 and TNF-α), part of the senescence-activated secretory profile, in the pancreas from 10-month-old Glo1KD mice, compared with their WT littermates. In vitro exposure of INS832/13 β-cells to MGO confirms its casual role on β-cell dysfunction, which can be reverted by senolytic treatment. These data indicate that MGO is capable to induce early phenotypes typical of T2D progression, paving the way for novel prevention approaches to T2DM.

Pyridoxamine ameliorates methylglyoxal-induced macrophage dysfunction to facilitate tissue repair in diabetic wounds

Methylglyoxal (MGO) is a highly reactive dicarbonyl compound formed during hyperglycaemia. MGO combines with proteins to form advanced glycation end products (AGEs), leading to cellular dysfunction and organ damage. In type 2 diabetes mellitus (T2DM), the higher the plasma MGO concentration, the higher the lower extremity amputation rate. Here, we aimed to identify the mechanisms of MGO-induced dysfunction. We observed that the accumulation of MGO-derived AGEs in human diabetic wounds increased, whereas the expression of glyoxalase 1 (GLO1), a key metabolic enzyme of MGO, decreased. We show for the first time that topical application of pyridoxamine (PM), a natural vitamin B6 analogue, reduced the accumulation of MGO-derived AGEs in the wound tissue of type-2 diabetic mice, promoted the influx of macrophages in the early stage of tissue repair, improved the dysfunctional inflammatory response, and accelerated wound healing. In vitro, MGO damaged the phagocytic functions of M1-like macrophages induced by lipopolysaccharide (LPS), but not those of M0-like macrophages induced by PMA or of M2-like macrophages induced by interleukins 4 (IL-4) and 13 (IL-13); the impaired phagocytosis of M1-like macrophages was rescued by PM administration. These findings suggest that the increase in MGO metabolism in vivo might contribute to macrophage dysfunction, thereby affecting wound healing. Our results indicate that PM may be a novel therapeutic approach for treating diabetic wounds. MGO forms protein adducts that cause macrophage dysfunction. These adducts cause cell and organ dysfunction that is common in diabetes. Pyridoxamine scavenges MGO to ameliorate this dysfunction, promoting wound healing. Pyridoxamine could be used therapeutically to treat non-healing diabetic wounds.

Consequences of Dicarbonyl Stress on Skeletal Muscle Proteins in Type 2 Diabetes

Skeletal muscle is the largest organ in the body and constitutes almost 40% of body mass. It is also the primary site of insulin-mediated glucose uptake, and skeletal muscle insulin resistance, that is, diminished response to insulin, is characteristic of Type 2 diabetes (T2DM). One of the foremost reasons posited to explain the etiology of T2DM involves the modification of proteins by dicarbonyl stress due to an unbalanced metabolism and accumulations of dicarbonyl metabolites. The elevated concentration of dicarbonyl metabolites (i.e., glyoxal, methylglyoxal, 3-deoxyglucosone) leads to DNA and protein modifications, causing cell/tissue dysfunctions in several metabolic diseases such as T2DM and other age-associated diseases. In this review, we recapitulated reported effects of dicarbonyl stress on skeletal muscle and associated extracellular proteins with emphasis on the impact of T2DM on skeletal muscle and provided a brief introduction to the prevention/inhibition of dicarbonyl stress.

Carbonyl Stress in Red Blood Cells and Hemoglobin

The paper overviews the peculiarities of carbonyl stress in nucleus-free mammal red blood cells (RBCs). Some functional features of RBCs make them exceptionally susceptible to reactive carbonyl compounds (RCC) from both blood plasma and the intracellular environment. In the first case, these compounds arise from the increased concentrations of glucose or ketone bodies in blood plasma, and in the second-from a misbalance in the glycolysis regulation. RBCs are normally exposed to RCC-methylglyoxal (MG), triglycerides-in blood plasma of diabetes patients. MG modifies lipoproteins and membrane proteins of RBCs and endothelial cells both on its own and with reactive oxygen species (ROS). Together, these phenomena may lead to arterial hypertension, atherosclerosis, hemolytic anemia, vascular occlusion, local ischemia, and hypercoagulation phenotype formation. ROS, reactive nitrogen species (RNS), and RCC might also damage hemoglobin (Hb), the most common protein in the RBC cytoplasm. It was Hb with which non-enzymatic glycation was first shown in living systems under physiological conditions. Glycated HbA1c is used as a very reliable and useful diagnostic marker. Studying the impacts of MG, ROS, and RNS on the physiological state of RBCs and Hb is of undisputed importance for basic and applied science.

Glyoxalase System in the Progression of Skin Aging and Skin Malignancies

Dicarbonyl compounds, including methylglyoxal (MGO) and glyoxal (GO), are mainly formed as byproducts of glucose metabolism. The main glyoxalase system consists of glyoxalase I and II (Glo1 and Glo2) and is the main enzyme involved in the detoxification of dicarbonyl stress, which occurs as an accumulation of MGO or GO due to decreased activity or expression of Glo1. Dicarbonyl stress is a major cause of cellular and tissue dysfunction that causes various health issues, including diabetes, aging, and cancer. The skin is the largest organ in the body. In this review, we discuss the role of the glyoxalase system in the progression of skin aging, and more importantly, skin malignancies. We also discuss the future prospects of the glyoxalase system in other skin abnormalities such as psoriasis and vitiligo, including hyperpigmentation. Finally, in the present review, we suggest the role of glyoxalase in the progression of skin aging and glyoxalase system as a potential target for anticancer drug development for skin cancer.

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

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

Methylglyoxal, a Highly Reactive Dicarbonyl Compound, in Diabetes, Its Vascular Complications, and Other Age-Related Diseases

The formation and accumulation of methylglyoxal (MGO), a highly reactive dicarbonyl compound, has been implicated in the pathogenesis of type 2 diabetes, vascular complications of diabetes, and several other age-related chronic inflammatory diseases such as cardiovascular disease, cancer, and disorders of the central nervous system. MGO is mainly formed as a byproduct of glycolysis and, under physiological circumstances, detoxified by the glyoxalase system. MGO is the major precursor of nonenzymatic glycation of proteins and DNA, subsequently leading to the formation of advanced glycation end products (AGEs). MGO and MGO-derived AGEs can impact on organs and tissues affecting their functions and structure. In this review we summarize the formation of MGO, the detoxification of MGO by the glyoxalase system, and the biochemical pathways through which MGO is linked to the development of diabetes, vascular complications of diabetes, and other age-related diseases. Although interventions to treat MGO-associated complications are not yet available in the clinical setting, several strategies to lower MGO have been developed over the years. We will summarize several new directions to target MGO stress including glyoxalase inducers and MGO scavengers. Targeting MGO burden may provide new therapeutic applications to mitigate diseases in which MGO plays a crucial role.

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.

Ameliorating Methylglyoxal-Induced Progenitor Cell Dysfunction for Tissue Repair in Diabetes

Patient-derived progenitor cell (PC) dysfunction is severely impaired in diabetes, but the molecular triggers that contribute to mechanisms of PC dysfunction are not fully understood. Methylglyoxal (MGO) is one of the highly reactive dicarbonyl species formed during hyperglycemia. We hypothesized that the MGO scavenger glyoxalase 1 (GLO1) reverses bone marrow-derived PC (BMPC) dysfunction through augmenting the activity of an important endoplasmic reticulum stress sensor, inositol-requiring enzyme 1α (IRE1α), resulting in improved diabetic wound healing. BMPCs were isolated from adult male db/db type 2 diabetic mice and their healthy corresponding control db/+ mice. MGO at the concentration of 10 µmol/L induced immediate and severe BMPC dysfunction, including impaired network formation, migration, and proliferation and increased apoptosis, which were rescued by adenovirus-mediated GLO1 overexpression. IRE1α expression and activation in BMPCs were significantly attenuated by MGO exposure but rescued by GLO1 overexpression. MGO can diminish IRE1α RNase activity by directly binding to IRE1α in vitro. In a diabetic mouse cutaneous wound model in vivo, cell therapies using diabetic cells with GLO1 overexpression remarkably accelerated wound closure by enhancing angiogenesis compared with diabetic control cell therapy. Augmenting tissue GLO1 expression by adenovirus-mediated gene transfer or with the small-molecule inducer trans-resveratrol and hesperetin formulation also improved wound closure and angiogenesis in diabetic mice. In conclusion, our data suggest that GLO1 rescues BMPC dysfunction and facilitates wound healing in diabetic animals, at least partly through preventing MGO-induced impairment of IRE1α expression and activity. Our results provide important knowledge for the development of novel therapeutic approaches targeting MGO to improve PC-mediated angiogenesis and tissue repair in diabetes.

Wound-Healing Markers Revealed by Proximity Extension Assay in Tears of Patients following Glaucoma Surgery

Tears are a constantly available and highly valuable body fluid collectable by non-invasive techniques. Although it can give information on ocular status and be used for follow-ups, tear analysis is challenging due to the low amount of sample that is available. Proximity extension assay (PEA) allows for a sensitive and scalable analysis of multiple proteins in a single run from a one-µL sample, so we applied this technique and examined the amount of 184 proteins in tears collected at different time points after trabeculectomy. The success rate of this surgical intervention highly depends on proper wound healing; therefore, information on the process is indispensable. We observed significantly higher levels of IL-6 and MMP1 at the early time points (day one, two, and four) following trabeculectomy, and the protein amounts went back to the level observed before the surgery three months after the intervention. Patients with or without complications were tested, and proteins that have roles in the immune response and wound healing could be observed with altered frequency and amounts in the cases of patients with complications. Our results highlight the importance of inflammation in wound-healing complications, and at the same time, indicate the utility of PEA in tear analysis.

Hyperglycaemia-induced methylglyoxal accumulation potentiates VEGF resistance of diabetic monocytes through the aberrant activation of tyrosine phosphatase SHP-2/SRC kinase signalling axis

Diabetes mellitus (DM) is a major cardiovascular risk factor contributing to cardiovascular complications by inducing vascular cell dysfunction. Monocyte dysfunction could contribute to impaired arteriogenesis response in DM patients. DM monocytes show blunted chemotactic responses to arteriogenic stimuli, a condition termed as vascular endothelial growth factor (VEGF) resistance. We hypothesize that methylglyoxal (MG), a glucose metabolite, induces monocyte dysfunction and aimed to elucidate the underlying molecular mechanisms. Human monocytes exposed to MG or monocytes from DM patients or mice (db/db) showed VEGF-resistance secondary to a pro-migratory phenotype. Mechanistically, DM conditions or MG exposure resulted in the upregulation of the expression of SHP-2 phosphatase. This led to the enhanced activity of SHP-2 and aided an interaction with SRC kinase. SHP-2 dephosphorylated the inhibitory phosphorylation site of SRC leading to its abnormal activation and phosphorylation of cytoskeletal protein, paxillin. We demonstrated that MG-induced molecular changes could be reversed by pharmacological inhibitors of SHP-2 and SRC and by genetic depletion of SHP-2. Finally, a SHP-2 inhibitor completely reversed the dysfunction of monocytes isolated from DM patients and db/db mice. In conclusion, we identified SHP-2 as a hitherto unknown target for improving monocyte function in diabetes. This opens novel perspectives for treating diabetic complications associated with impaired monocyte function.

Mechanistic targeting of advanced glycation end-products in age-related diseases

Glycative stress, caused by the accumulation of cytotoxic and irreversibly-formed sugar-derived advanced glycation end-products (AGEs), contributes to morbidity associated with aging, age-related diseases, and metabolic diseases. In this review, we summarize pathways leading to formation of AGEs, largely from sugars and glycolytic intermediates, and discuss detoxification of AGE precursors, including the glyoxalase system and DJ-1/Park7 deglycase. Disease pathogenesis downstream of AGE accumulation can be cell autonomous due to aggregation of glycated proteins and impaired protein function, which occurs in ocular cataracts. Extracellular AGEs also activate RAGE signaling, leading to oxidative stress, inflammation, and leukostasis in diabetic complications such as diabetic retinopathy. Pharmaceutical agents have been tested in animal models and clinically to diminish glycative burden. We summarize existing strategies and point out several new directions to diminish glycative stress including: plant-derived polyphenols as AGE inhibitors and glyoxalase inducers; improved dietary patterns, particularly Mediterranean and low glycemic diets; and enhancing proteolytic capacities of the ubiquitin-proteasome and autophagy pathways that are involved in cellular clearing of AGEs.

Nicotine induces apoptosis in human osteoblasts via a novel mechanism driven by H2O2 and entailing Glyoxalase 1-dependent MG-H1 accumulation leading to TG2-mediated NF-kB desensitization: Implication for smokers-related osteoporosis

Nicotine contained in cigarette smoke contributes to the onset of several diseases, including osteoporosis, whose emerging pathogenic mechanism is associated with osteoblasts apoptosis. Scanty information is available on the molecular mechanisms of nicotine on osteoblasts apoptosis and, consequently, on an important aspect of the pathogenesis of smokers-related osteoporosis. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a major precursor of advanced glycation end products (AGEs), potent pro-apoptotic agents. Hydroimidazolone (MG-H1) is the major AGE derived from the spontaneous MG adduction of arginine residues. The aim of this study was to investigate whether, and by means of which mechanism, the antiglycation defence Glo1 was involved in the apoptosis induced by 0.1 and 1µM nicotine in human primary osteoblasts chronically exposed for 11 and 21 days. By using gene overexpression/silencing and scavenging/inhibitory agents, we demonstrated that nicotine induces a significant intracellular accumulation of hydrogen peroxide (H₂O₂) that, by inhibiting Glo1, drives MG-H1 accumulation/release. MG-H1, in turn, triggers H₂O₂ overproduction via receptor for AGEs (RAGE) and, in parallel, an apoptotic mitochondrial pathway by inducing Transglutaminase 2 (TG2) downregulation-dependent NF-kB desensitization. Measurements of H₂O₂, Glo1 and MG-H1 circulating levels in smokers compared with non-smokers or in smokers with osteoporosis compared with those without this bone-related disease supported the results obtained in vitro. Our findings newly pose the antiglycation enzymatic defense Glo1 and MG-H1 among the molecular events involved in nicotine-induced reactive oxygen species-mediated osteoblasts apoptosis, a crucial event in smoker-related osteoporosis, and suggest novel exposure markers in health surveillance programmes related to smokers-associated osteoporosis.

Silymarin Attenuates ELMO-1 and KIM-1 Expression and Oxidative Stress in the Kidney of Rats with Type 2 Diabetes

Chronic diabetes mellitus is accompanied with overexpression of ELMO1 and KIM1 and enhanced oxidative stress. This study was aimed to evaluate the effects of administration of silymarin on oxidative stress markers and ELMO1 and KIM1 expression in the kidney tissue of type 2 diabetic rats. In this experimental study, 36 male Wistar rats were divided into 6 groups: Control, silymarin-treated control (60 and 120 mg/kg/day), diabetic, and silymarin-treated diabetic groups (60 and 120 mg/kg/day). Tissue levels of oxidative stress and biochemical parameters were measured by spectrophotometric methods. Lipid peroxidation levels in the kidney tissue were measured by fluorometric method. Insulin was determined using immunoassay. Gene expression analysis was determined by qPCR technique. The level of expression of ELMO1 and KIM1 in the diabetic groups treated with silymarin was significantly reduced (P < 0.001). Total antioxidant levels and thiol groups contents increased (P < 0.001) dramatically in treated groups. A significant decrease in tissue levels of malondialdehyde and total oxidant were observed in the silymarin treated diabetic rats (P < 0.001). The results showed that the urinary amount of protein in the treatment groups was significantly lower than of diabetic control (P < 0.001). These results indicate that silymarin has a blood glucose lowering effect and, due to its antioxidant properties, increases the antioxidant parameters and reduces the oxidant markers. The administration of silymarin has beneficial effects on kidney of diabetic rats with reduction of ELMO1 and KIM1expression.

Methylglyoxal-induced dicarbonyl stress in aging and disease: first steps towards glyoxalase 1-based treatments

Dicarbonyl stress is the abnormal accumulation of dicarbonyl metabolites leading to increased protein and DNA modification contributing to cell and tissue dysfunction in aging and disease. It is produced by increased formation and/or decreased metabolism of dicarbonyl metabolites. MG (methylglyoxal) is a dicarbonyl metabolite of relatively high flux of formation and precursor of the most quantitatively and functionally important spontaneous modifications of protein and DNA clinically. Major MG-derived adducts are arginine-derived hydroimidazolones of protein and deoxyguanosine-derived imidazopurinones of DNA. These are formed non-oxidatively. The glyoxalase system provides an efficient and essential basal and stress-response-inducible enzymatic defence against dicarbonyl stress by the reduced glutathione-dependent metabolism of methylglyoxal by glyoxalase 1. The GLO1 gene encoding glyoxalase 1 has low prevalence duplication and high prevalence amplification in some tumours. Dicarbonyl stress contributes to aging, disease and activity of cytotoxic chemotherapeutic agents. It is found at a low, moderate and severe level in obesity, diabetes and renal failure respectively, where it contributes to the development of metabolic and vascular complications. Increased glyoxalase 1 expression confers multidrug resistance to cancer chemotherapy and has relatively high prevalence in liver, lung and breast cancers. Studies of dicarbonyl stress are providing improved understanding of aging and disease and the basis for rational design of novel pharmaceuticals: glyoxalase 1 inducers for obesity, diabetes and cardiovascular disease and glyoxalase 1 inhibitors for multidrug-resistant tumours. The first clinical trial of a glyoxalase 1 inducer in overweight and obese subjects showed improved glycaemic control, insulin resistance and vascular function.

Characteristic Variations and Similarities in Biochemical, Molecular, and Functional Properties of Glyoxalases across Prokaryotes and Eukaryotes

The glyoxalase system is the ubiquitous pathway for the detoxification of methylglyoxal (MG) in the biological systems. It comprises two enzymes, glyoxalase I (GLYI) and glyoxalase II (GLYII), which act sequentially to convert MG into d-lactate, thereby helping living systems get rid of this otherwise cytotoxic byproduct of metabolism. In addition, a glutathione-independent GLYIII enzyme activity also exists in the biological systems that can directly convert MG to d-lactate. Humans and Escherichia coli possess a single copy of GLYI (encoding either the Ni- or Zn-dependent form) and GLYII genes, which through MG detoxification provide protection against various pathological and disease conditions. By contrast, the plant genome possesses multiple GLYI and GLYII genes with a role in abiotic stress tolerance. Plants possess both Ni²⁺- and Zn²⁺-dependent forms of GLYI, and studies on plant glyoxalases reveal the various unique features of these enzymes distinguishing them from prokaryotic and other eukaryotic glyoxalases. Through this review, we provide an overview of the plant glyoxalase family along with a comparative analysis of glyoxalases across various species, highlighting similarities as well as differences in the biochemical, molecular, and physiological properties of these enzymes. We believe that the evolution of multiple glyoxalases isoforms in plants is an important component of their robust defense strategies.

Methylglyoxal in Metabolic Disorders: Facts, Myths, and Promises

Glucose and fructose metabolism originates the highly reactive byproduct methylglyoxal (MG), which is a strong precursor of advanced glycation end products (AGE). The MG has been implicated in classical diabetic complications such as retinopathy, nephropathy, and neuropathy, but has also been recently associated with cardiovascular diseases and central nervous system disorders such as cerebrovascular diseases and dementia. Recent studies even suggested its involvement in insulin resistance and beta-cell dysfunction, contributing to the early development of type 2 diabetes and creating a vicious circle between glycation and hyperglycemia. Despite several drugs and natural compounds have been identified in the last years in order to scavenge MG and inhibit AGE formation, we are still far from having an effective strategy to prevent MG-induced mechanisms. This review summarizes the endogenous and exogenous sources of MG, also addressing the current controversy about the importance of exogenous MG sources. The mechanisms by which MG changes cell behavior and its involvement in type 2 diabetes development and complications and the pathophysiological implication are also summarized. Particular emphasis will be given to pathophysiological relevance of studies using higher MG doses, which may have produced biased results. Finally, we also overview the current knowledge about detoxification strategies, including modulation of endogenous enzymatic systems and exogenous compounds able to inhibit MG effects on biological systems.

Methylglyoxal-Glyoxalase 1 Balance: The Root of Vascular Damage

The highly reactive dicarbonyl methylglyoxal (MGO) is mainly formed as byproduct of glycolysis. Therefore, high blood glucose levels determine increased MGO accumulation. Nonetheless, MGO levels are also increased as consequence of the ineffective action of its main detoxification pathway, the glyoxalase system, of which glyoxalase 1 (Glo1) is the rate-limiting enzyme. Indeed, a physiological decrease of Glo1 transcription and activity occurs not only in chronic hyperglycaemia but also with ageing, during which MGO accumulation occurs. MGO and its advanced glycated end products (AGEs) are associated with age-related diseases including diabetes, vascular dysfunction and neurodegeneration. Endothelial dysfunction is the first step in the initiation, progression and clinical outcome of vascular complications, such as retinopathy, nephropathy, impaired wound healing and macroangiopathy. Because of these considerations, studies have been centered on understanding the molecular basis of endothelial dysfunction in diabetes, unveiling a central role of MGO-Glo1 imbalance in the onset of vascular complications. This review focuses on the current understanding of MGO accumulation and Glo1 activity in diabetes, and their contribution on the impairment of endothelial function leading to diabetes-associated vascular damage.

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.

Cutaneous wound healing in aging small mammals: a systematic review

As the elderly population grows, so do the clinical and socioeconomic burdens of nonhealing cutaneous wounds, the majority of which are seen among persons over 60 years of age. Human studies on how aging effects wound healing will always be the gold standard, but studies have ethical and practical hurdles. Choosing an animal model is dictated by costs and animal lifespan that preclude large animal use. Here, we review the current literature on how aging effects cutaneous wound healing in small animal models and, when possible, compare healing across studies. Using a literature search of MEDLINE/PubMed databases, studies were limited to those that utilized full-thickness wounds and compared the wound-healing parameters of wound closure, reepithelialization, granulation tissue fill, and tensile strength between young and aged cohorts. Overall, wound closure, reepithelialization, and granulation tissue fill were delayed or decreased with aging across different strains of mice and rats. Aging in mice was associated with lower tensile strength early in the wound healing process, but greater tensile strength later in the wound healing process. Similarly, aging in rats was associated with lower tensile strength early in the wound healing process, but no significant tensile strength difference between young and old rats later in healing wounds. From studies in New Zealand White rabbits, we found that reepithelialization and granulation tissue fill were delayed or decreased overall with aging. While similarities and differences in key wound healing parameters were noted between different strains and species, the comparability across the studies was highly questionable, highlighted by wide variability in experimental design and reporting. In future studies, standardized experimental design and reporting would help to establish comparable study groups, and advance the overall knowledge base, facilitating the translatability of animal data to the human clinical condition.

RAGE and glyoxalase in kidney disease

Glycation is an important reaction in the regulation of physiological state. When poorly controlled, however, glycation can also result in the accumulation of glycated proteins (advanced glycation endproducts; AGEs) in the body. This AGE accumulation is termed glycative stress, and is an established pathological factor: to date, glycative stress has been closely associated with not only kidney diseases, but also kidney aging. Accumulating evidence demonstrates that the progression of renal tubular damage and tubular aging are often correlated with activation of the receptor for the AGE (RAGE)-AGE pathway or decreased activity of glyoxalase 1, which is an anti-glycation enzyme to lower glycative stress. Further, glycative stress exacerbates the derangement of protein homeostasis: the posttranslationally modified proteins by glycation often lose or gain their functions. Such deranged protein homeostasis leads to endoplasmic reticulum (ER) stress, a state of ER dysfunction in which the quality control of proteins is defective, as well as to induction of its stress signal, the unfolded protein response (UPR), in the kidney. The lowering of glycative stress via modulation of RAGE-AGE axis or glyoxalase 1 activity is beneficial for tubular homeostasis and the subsequent prevention and treatment of kidney disease, suggesting the possibility of novel therapeutic approaches which target glycative stress. In this review, we focused on the impact of glycative stress in the kidney, especially the role of RAGE and glyoxalase 1. Further we also discuss the crosstalk between glycative stress and ER stress in their effect on protein homeostasis.

A Glyoxalase-1 Knockdown Does Not Have Major Short Term Effects on Energy Expenditure and Atherosclerosis in Mice

Objective. Glyoxalase-1 is an enzyme detoxifying methylglyoxal (MG). MG is a potent precursor of advanced glycation endproducts which are regarded to be a key player in micro- and macrovascular damage. Yet, the role of Glo1 in atherosclerosis remains unclear. In this study, the effect of Glo1 on mouse metabolism and atherosclerosis is evaluated. Methods. Glo1 knockdown mice were fed a high fat or a standard diet for 10 weeks. Body weight and composition were investigated by Echo MRI. The PhenoMaster system was used to measure the energy expenditure. To evaluate the impact of Glo1 on atherosclerosis, Glo1(KD) mice were crossed with ApoE-knockout mice and fed a high fat diet for 14 weeks. Results. Glo1 activity was significantly reduced in heart, liver, and kidney lysates derived from Glo1(KD) mice. Yet, there was no increase in methylglyoxal-derived AGEs in all organs analyzed. The Glo1 knockdown did not affect body weight or body composition. Metabolic studies via indirect calorimetry did not show significant effects on energy expenditure. Glo1(KD) mice crossed to ApoE(-/-) mice did not show enhanced formation of atherosclerosis. Conclusion. A Glo1 knockdown does not have major short term effects on the energy expenditure or the formation of atherosclerotic plaques.

Impact of intensive treatment on serum methylglyoxal levels among individuals with screen-detected type 2 diabetes: the ADDITION-Denmark study

AIMS

Methylglyoxal (MG) has been implicated in the development of micro- and macrovascular diabetic complications, but it remains unclear how current treatments of type 2 diabetes affect its circulating levels.

METHODS

In the Danish arm of the ADDITION trial, we (a) described serum MG levels at baseline and at 6-year follow-up among individuals with screen-detected type 2 diabetes, (b) examined the effect of intensive multifactorial treatment compared with routine care on MG, (c) examined the associations between MG and risk factors at baseline and at follow-up and (d) examined the associations between changes in MG and changes in risk factors.

RESULTS

Patients in both treatment arms experienced a significant decline in MG from baseline to follow-up, with no effect of allocation to intensive treatment. In cohort analyses, MG was associated with smoking and fasting glucose at baseline and smoking and LDL cholesterol at follow-up. Compared with patients receiving no lipid-lowering treatment, patients receiving lipid-lowering treatment had higher MG at follow-up, and those initiating lipid-lowering treatment experienced a less pronounced decline in MG.

CONCLUSIONS

Further studies are required to explore any possible effects of the observed decrease in MG in type 2 diabetes patients as well as the potential interplay between MG, lipids, lipid-lowering treatment and smoking.

Peroxynitrite-mediated glyoxalase I epigenetic inhibition drives apoptosis in airway epithelial cells exposed to crystalline silica via a novel mechanism involving argpyrimidine-modified Hsp70, JNK, and NF-κB

Glyoxalase I (Glo1) is a cellular defense enzyme involved in the detoxification of methylglyoxal (MG), a cytotoxic by-product of glycolysis, and MG-derived advanced glycation end products (AGEs). Argpyrimidine (AP), one of the major AGEs coming from MG modification of protein arginines, is a proapoptotic agent. Crystalline silica is a well-known occupational health hazard, responsible for a relevant number of pulmonary diseases. Exposure of cells to crystalline silica results in a number of complex biological responses, including apoptosis. The present study was aimed at investigating whether, and through which mechanism, Glo1 was involved in Min-U-Sil 5 crystalline silica-induced apoptosis. Apoptosis, by TdT-mediated dUTP nick-end labeling assay, and transcript and protein levels or enzymatic activity, by quantitative real-time PCR, Western blot, and spectrophotometric methods, respectively, were evaluated in human bronchial BEAS-2B cells exposed or not (control) to crystalline silica and also in experiments with appropriate inhibitors. Reactive oxygen species were evaluated by coumarin-7-boronic acid or Amplex red hydrogen peroxide/peroxidase methods for peroxynitrite (ONOO(-)) or hydrogen peroxide (H2O2) measurements, respectively. Our results showed that Min-U-Sil 5 crystalline silica induced a dramatic ONOO(-)-mediated inhibition of Glo1, leading to AP-modified Hsp70 protein accumulation that, in a mechanism involving JNK and NF-κB, triggered an apoptotic mitochondrial pathway. Inhibition of Glo1 occurred at both functional and transcriptional levels, the latter occurring via ERK1/2 MAPK and miRNA 101 involvement. Taken together, our data demonstrate that Glo1 is involved in the Min-U-Sil 5 crystalline silica-induced BEAS-2B cell mitochondrial apoptotic pathway via a novel mechanism involving Hsp70, JNK, and NF-κB. Because maintenance of an intact respiratory epithelium is a critically important determinant of normal respiratory function, the knowledge of the mechanisms underlying its disruption may provide insight into the genesis, and possibly the prevention, of a number of pathological conditions commonly occurring in silica dust occupational exposure.

Glycative stress and glyoxalase in kidney disease and aging

Glycation is one of the important reactions regulating physiological state, and glycative stress, namely an overwhelming and unfavourable glycation state, is established as a pathological factor. Glycative stress is closely associated with not only various kidney diseases, but also kidney aging. Accumulating evidence, including studies in my laboratory, demonstrates that progression of renal tubular damage and its aging is correlated with the decrease in the activity of anti-glycative stress enzyme Glo1 (glyoxalase I) in the kidney. The reduction of glycative and oxidative stresses by Glo1 overexpression is beneficial for prevention of kidney disease and treatment, suggesting the novel therapeutic approaches targeting Glo1. The present review is focused on the impact of glycative stress and Glo1 on protein homoeostasis and discusses further the cross-talk between glycative stress and UPR (unfolded protein response), which controls the protein homoeostasis state.

Prevention of dicarbonyl-mediated advanced glycation by glyoxalases: implication in skin aging

Skin aging is the result of intrinsic chronological aging and photoaging, due to UV exposure, that both share important histological modifications and molecular features, including alterations of proteins. One of the main damage is glycation that occurs when reducing sugars react non-enzymatically with proteins. This reaction also happens when the dicarbonyl compounds GO (glyoxal) and MG (methylglyoxal), which are glucose derivatives, react with proteins. These compounds can be detoxified by the glyoxalase system composed of two enzymes, Glo1 (glyoxalase I) and Glo2 (glyoxalase II). The aims of the present mini-review are to briefly summarize our current knowledge of the biological roles of these enzymes in aging and then discuss the relevance of studying the role of glycation and of detoxifying systems in human skin aging.

The role of methylglyoxal and the glyoxalase system in diabetes and other age-related diseases

The formation and accumulation of advanced glycation endproducts (AGEs) are related to diabetes and other age-related diseases. Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is the major precursor in the formation of AGEs. MGO is mainly formed as a byproduct of glycolysis. Under physiological circumstances, MGO is detoxified by the glyoxalase system into D-lactate, with glyoxalase I (GLO1) as the key enzyme in the anti-glycation defence. New insights indicate that increased levels of MGO and the major MGO-derived AGE, methylglyoxal-derived hydroimidazolone 1 (MG-H1), and dysfunctioning of the glyoxalase system are linked to several age-related health problems, such as diabetes, cardiovascular disease, cancer and disorders of the central nervous system. The present review summarizes the mechanisms through which MGO is formed, its detoxification by the glyoxalase system and its effect on biochemical pathways in relation to the development of age-related diseases. Although several scavengers of MGO have been developed over the years, therapies to treat MGO-associated complications are not yet available for application in clinical practice. Small bioactive inducers of GLO1 can potentially form the basis for new treatment strategies for age-related disorders in which MGO plays a pivotal role.

Antiglycation therapy: Discovery of promising antiglycation agents for the management of diabetic complications

CONTEXT

During diabetes mellitus, non-enzymatic reaction between amino groups of protein and carbonyl of reducing sugars (Millard reaction) is responsible for the major diabetic complications. Various efforts have been made to influence the process of protein glycation.

OBJECTIVES

This review article provides an extensive survey of various studies published in scientific literature to understand the process of protein glycation and its measurement. Moreover, evaluation and identification of potential inhibitors (antiglycation agents) of protein glycation from natural and synthetic sources and their mechanism of action in vitro and in vivo are also addressed.

METHOD

In this review article, the mechanism involved in the formation of advanced glycation end products (AGEs) is discussed, while in second and third parts, promising antiglycation agents of natural and synthetic sources have been reviewed, respectively. Finally, in vivo studies have been addressed. This review is mainly compiled from important databases such as Science, Direct, Chemical Abstracts, SciFinder, and PubMed.

RESULTS

During the last two decades, various attempts have been made to inhibit the process of protein glycation. New potent inhibitors of protein glycation belonging to different classes such as flavonoids, alkaloids, terpenes, benzenediol Schiff bases, substituted indol, and thio compounds have been identified.

CONCLUSION

Antiglycation therapy will be an effective strategy in future to prevent the formation of AGEs for the management of late diabetic complications Current review article highlighted various compounds of natural and synthetic origins identified previously to inhibit the protein glycation and formation of AGEs in vitro and in vivo.

Resveratrol-Dependent Down-regulation of Receptor for Advanced Glycation End-products and Oxidative Stress in Kidney of Rats With Diabetes

BACKGROUND

Millions of people in the world have diabetes mellitus and its prevalence is growing. Oxidative stress, advanced glycation end-products (AGEs) and receptor for advanced glycation end-products (RAGE) play key role in the pathogenesis of diabetes. New and safe strategies of remedy are needed for this disease.

OBJECTIVES

We hypothesized that resveratrol may exert a renal protective effect on diabetic rats.

MATERIALS AND METHODS

Male rats with diabetes were treated with or without resveratrol as 1, 5, 10 mg/kg of body weight for 30 days. The total AGEs and malondialdehyde levels in kidney tissues were determined by spectrofluorimetric method and the insulin level was assayed using ELISA. The total antioxidant capacity contents in kidney and the glucose in plasma were measured by a colorimetric assay. The expression of RAGE was assayed in kidneys of all animals using quantitative PCR.

RESULTS

In resveratrol-treated rats with diabetes, malondialdehyde levels, plasma glucose and expression of RAGE were significantly reduced compared with the untreated group. Moreover, the total antioxidant and insulin levels significantly increased in treated rats. There was no significant difference in the AGEs contents among all the groups.

CONCLUSIONS

These results revealed that resveratrol has beneficial effects on kidney by extenuating the oxidative stress and down-regulation of RAGE expression.

Dicarbonyl stress in cell and tissue dysfunction contributing to ageing and disease

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. Enzymes metabolising dicarbonyls, glyoxalase 1 and aldoketo reductases, provide an efficient and stress-response enzyme defence against dicarbonyl stress. Dicarbonyl stress is produced by increased formation and/or decreased metabolism of dicarbonyl metabolites, and by exposure to exogenous dicarbonyls. It contributes to ageing, disease and activity of cytototoxic chemotherapeutic agents.

High tissue glucose alters intersomitic blood vessels in zebrafish via methylglyoxal targeting the VEGF receptor signaling cascade

Hyperglycemia causes micro- and macrovascular complications in diabetic patients. Elevated glucose concentrations lead to increased formation of the highly reactive dicarbonyl methylglyoxal (MG), yet the early consequences of MG for development of vascular complications in vivo are poorly understood. In this study, zebrafish were used as a model organism to analyze early vascular effects and mechanisms of MG in vivo. High tissue glucose increased MG concentrations in tg(fli:EGFP) zebrafish embryos and rapidly induced several additional malformed and uncoordinated blood vessel structures that originated out of existing intersomitic blood vessels (ISVs). However, larger blood vessels, including the dorsal aorta and common cardinal vein, were not affected. Expression silencing of MG-degrading enzyme glyoxalase (glo) 1 elevated MG concentrations and induced a similar vascular hyperbranching phenotype in zebrafish. MG enhanced phosphorylation of vascular endothelial growth factor (VEGF) receptor 2 and its downstream target Akt/protein kinase B (PKB). Pharmacological inhibitors for VEGF receptor 2 and Akt/PKB as well as MG scavenger aminoguanidine and glo1 activation prevented MG-induced hyperbranching of ISVs. Taken together, MG acts on smaller blood vessels in zebrafish via the VEGF receptor signaling cascade, thereby describing a new mechanism that can explain vascular complications under hyperglycemia and elevated MG concentrations.

Increased peritoneal damage in glyoxalase 1 knock-down mice treated with peritoneal dialysis

BACKGROUND

Peritoneal dialysis (PD) is limited by peritoneal fibrosis and ultrafiltration failure. This is in part caused by the high concentration of glucose degradation products (GDPs) present in PD fluids (PDF) as a consequence of heat sterilization. Existing research in long-term PD has mainly dealt with the toxicity induced by GDPs and the development of therapeutic strategies to reduce the cellular burden of GDPs. Currently, there are few data regarding the potential role of detoxification systems of GDP in PD. In this study, the role of glyoxalase 1 (Glo1), the major detoxification pathway for dicarbonyl-derived GD such as methylglyoxal (MG) and glyoxal (Gx), was investigated in vivo using heterozygous knock-down mice for Glo1 (Glo1(-/+)).

METHODS

Wild-type (WT) and Glo1(-/+) mice were repeatedly treated with PDF containing low and high amounts of GDP, particularly with respect to the content of dicarbonyls. After 12 weeks of treatment with PDF, peritoneal damage and function were evaluated.

RESULTS

Glo1(-/+) mice treated with PDF showed increased formation of advanced glycation endproduct (AGE) when compared with WT mice, particularly the Gx-derived AGE, carboxymethyl-lysine. This was associated with increased inflammation, neovascularization, increased peritoneal fibrosis and impaired peritoneal function.

CONCLUSIONS

This study suggests a pivotal and underestimated role for Glo1 as a detoxifying enzyme in GDP-associated peritoneal toxicity in PD. The indirect and direct modulation of Glo1 may therefore offer a new therapeutic option in prevention of GDP-induced peritoneal damage in PD.

Glyoxalase I inhibition induces apoptosis in irradiated MCF-7 cells via a novel mechanism involving Hsp27, p53 and NF-κB

BACKGROUND

Glyoxalase I (GI) is a cellular defence enzyme involved in the detoxification of methylglyoxal (MG), a cytotoxic byproduct of glycolysis, and MG-derived advanced glycation end products (AGEs). Argpyrimidine (AP), one of the major AGEs coming from MG modifications of proteins arginines, is a pro-apoptotic agent. Radiotherapy is an important modality widely used in cancer treatment. Exposure of cells to ionising radiation (IR) results in a number of complex biological responses, including apoptosis. The present study was aimed at investigating whether, and through which mechanism, GI was involved in IR-induced apoptosis.

METHODS

Apoptosis, by TUNEL assay, transcript and protein levels or enzymatic activity, by RT-PCR, western blot and spectrophotometric methods, respectively, were evaluated in irradiated MCF-7 breast cancer cells, also in experiments with appropriate inhibitors or using small interfering RNA.

RESULTS

Ionising radiation induced a dramatic reactive oxygen species (ROS)-mediated inhibition of GI, leading to AP-modified Hsp27 protein accumulation that, in a mechanism involving p53 and NF-κB, triggered an apoptotic mitochondrial pathway. Inhibition of GI occurred at both functional and transcriptional levels, the latter occurring via ERK1/2 MAPK and ERα modulation.

CONCLUSIONS

Glyoxalase I is involved in the IR-induced MCF-7 cell mitochondrial apoptotic pathway via a novel mechanism involving Hsp27, p53 and NF-κB.

Bleomycin hydrolase and hyperhomocysteinemia modulate the expression of mouse proteins involved in liver homeostasis

The liver is the major contributor to homocysteine (Hcy) metabolism and fatty liver disease is associated with hyperhomocysteinemia. Bleomycin hydrolase (Blmh) is an aminohydrolase that also participates in Hcy metabolism by hydrolyzing Hcy-thiolactone. To gain insight into hepatic functions of Blmh, we analyzed the liver proteome of Blmh(-/-) and Blmh(+/+) mice in the absence and presence of diet-induced (high methionine) hyperhomocysteinemia using 2D IEF/SDS-PAGE gel electrophoresis and MALDI-TOF mass spectrometry. We identified eleven liver proteins whose expression was significantly altered as a result of the Blmh gene inactivation. The differential expression (Blmh(-/-) vs. Blmh(+/+)) of four liver proteins was lower, of two proteins was higher, and was further modified in mice fed with a hyperhomocysteinemic high-Met diet. The down-regulated proteins are involved in lipoprotein metabolism (ApoA1, ApoE), antigen processing (Psme1), energy metabolism (Atp5h, Gamt), methylglyoxal detoxification (Glo1), oxidative stress response (Sod1), and inactivation of catecholamine neurotransmitters (Comt). The two up-regulated proteins are involved in nitric oxide generation (Ddah1) and xenobiotic detoxification (Sult1c1). We also found that livers of Blmh(-/-) mice expressed a novel variant of glyoxalase domain-containing protein 4 (Glod4) by a post-transcriptional mechanism. Our findings suggest that Blmh interacts with diverse cellular processes-from lipoprotein metabolism, nitric oxide regulation, antigen processing, and energy metabolism to detoxification and antioxidant defenses-that are essential for liver homeostasis and that modulation of these interactions by hyperhomocysteinemia underlies the involvement of Hcy in fatty liver disease.