Methylglyoxal Research Articles

An integrated proteomics and metabolomics analysis of methylglyoxal-induced neurotoxicity in a human neuroblastoma cell line

This study aimed to highlight the molecular and biochemical changes induced by methylglyoxal (MGO) exposure in SH-SY5Y human neuroblastoma cells, and to explore how these changes contribute to its neurotoxicity, utilizing an integrated proteomics and metabolomics approach. Using label-free quantitative nanoLC-MS/MS proteomics and targeted LC-TQ-MS/MS-based metabolomics, the results revealed that MGO exposure, particularly at cytotoxic levels, significantly altered the proteome and metabolome of SH-SY5Y cells. Analysis of proteomics data showed significant alterations in cellular functions including protein synthesis, cellular structural integrity, mitochondrial function, and oxidative stress responses. Analysis of metabolomics and integration of metabolomics and proteomics data highlighted significant changes in key metabolic pathways including arginine biosynthesis, glutathione metabolism, cysteine and methionine metabolism, and the tricarboxylic acid cycle. These results suggest that MGO exposure induced both toxic effects and adaptive responses in cells. MGO exposure led to increased endoplasmic reticulum stress, disruptions in cellular adhesion and extracellular matrix integrity, mitochondrial dysfunction, and amino acid metabolism disruption, contributing to cellular toxicity. Conversely, cells exhibited adaptive responses by upregulating protein synthesis, activating the Nrf2 pathway, and reprogramming metabolism to counteract dicarbonyl stress and maintain energy levels. Furthermore, a set of key proteins and metabolites associated with these changes were shown to exhibit a significant concentration-dependent decrease or increase in their expression levels with increasing MGO concentrations, suggesting their potential as biomarkers for MGO exposure. Taken together, these findings provide insight into the molecular mechanisms underlying MGO-induced neurotoxicity and potential targets for therapeutic intervention.

Methylglyoxal-Induced Modifications in Human Triosephosphate Isomerase: Structural and Functional Repercussions of Specific Mutations

Triosephosphate isomerase (TPI) dysfunction is a critical factor in diverse pathological conditions. Deficiencies in TPI lead to the accumulation of toxic methylglyoxal (MGO), which induces non-enzymatic post-translational modifications, thus compromising protein stability and leading to misfolding. This study investigates how specific TPI mutations (E104D, N16D, and C217K) affect the enzyme’s structural stability when exposed to its substrate glyceraldehyde 3-phosphate (G3P) and MGO. We employed circular dichroism, intrinsic fluorescence, native gel electrophoresis, and Western blotting to assess the structural alterations and aggregation propensity of these TPI mutants. Our findings indicate that these mutations markedly increase TPI’s susceptibility to MGO-induced damage, leading to accelerated loss of enzymatic activity and enhanced protein aggregation. Additionally, we observed the formation of MGO-induced adducts, such as argpyrimidine (ARGp), that contribute to enzyme inactivation and aggregation. Importantly, the application of MGO-scavenging molecules partially mitigated these deleterious effects, highlighting potential therapeutic strategies to counteract MGO-induced damage in TPI-related disorders.

Sll1019 and slr1259 encoding glyoxalase II improve tolerance of Synechocystis sp. PCC 6803 to methylglyoxal- and ethanol- induced oxidative stress by glyoxalase pathway.

The glyoxalase pathway is the primary detoxification mechanism for methylglyoxal (MG), a ubiquitous toxic metabolite that disrupts redox homeostasis. In the glyoxalase pathway, glyoxalase II (GlyII) can completely detoxify MG. Increasing the activity of the glyoxalase system can enhance the resistance of plants or organisms to abiotic stress, but the relevant mechanism remains largely unknown. In this study, we investigated the physiological functions of GlyII genes (sll1019 and slr1259) in Synechocystis sp. PCC 6803 under MG or ethanol stress based on transcriptome and metabolome data. High-performance liquid chromatography (HPLC) results showed that proteins Sll1019 and Slr1259 had GlyII activity. Under stress conditions, sll1019 and slr1259 protected the strain against oxidative stress by enhancing the activity of the glyoxalase pathway and raising the contents of antioxidants such as glutathione and superoxide dismutase. In the photosynthetic system, sll1019 and slr1259 indirectly affected the light energy absorption by strains, synthesis of photosynthetic pigments, and activities of photosystem I and photosystem II, which was crucial for the growth of the strain under stress conditions. In addition, sll1019 and slr1259 enhanced the tolerance of strain to oxidative stress by indirectly regulating metabolic networks, including ensuring energy acquisition, NADH and NADPH production, and phosphate and nitrate transport. This study reveals the mechanism by which sll1019 and slr1259 improve oxidative stress tolerance of strains by glyoxalase pathway. Our findings provide theoretical basis for breeding, seedling, and field production of abiotic stress tolerance-enhanced variety.IMPORTANCEThe glyoxalase system is present in most organisms, and it is the primary pathway for eliminating the toxic metabolite methylglyoxal. Increasing the activity of the glyoxalase system can enhance plant resistance to environmental stress, but the relevant mechanism is poorly understood. This study revealed the physiological functions of glyoxalase II genes sll1019 and slr1259 in Synechocystis sp. PCC 6803 under abiotic stress conditions and their regulatory effects on oxidative stress tolerance of strains. Under stress conditions, sll1019 and slr1259 enhanced the activity of the glyoxalase pathway and the antioxidant system, maintained photosynthesis, ensured energy acquisition, NADH and NADPH production, and phosphate and nitrate transport, thereby protecting the strain against oxidative stress. This study lays a foundation for further deciphering the mechanism by which the glyoxalase system enhances the tolerance of cells to abiotic stress, providing important information for breeding, seedling, and selection of plants with strong stress resistance.

Genomic identification, characterization, and stress-induced expression profiling of glyoxalase and D-lactate dehydrogenase gene families in Capsicum annuum

BackgroundCapsicum annuum, a significant agricultural and nutritional crop, faces production challenges due to its sensitivity to various abiotic stresses. Glyoxalase (GLY) and D-lactate dehydrogenase (D-LDH) enzymes play vital roles in mitigating these stresses by detoxifying the stress-induced cytotoxin, methylglyoxal (MG).MethodsA genome-wide study was conducted to identify and characterize glyoxalase I (GLYI), glyoxalase II (GLYII), unique glyoxalase III or DJ-1 (GLYIII), and D-LDH gene candidates in Capsicum annuum. The identified members were evaluated based on their evolutionary relationships with known orthologues, as well as their gene and protein features. Their expression patterns were examined in various tissues, developmental stages, and in response to abiotic stress conditions using RNA-seq data and qRT-PCR.ResultsA total of 19 GLYI, 9 GLYII, 3 DJ-1, and 11 D-LDH members were identified, each featuring characteristic domains: glyoxalase, metallo-β-lactamase, DJ-1_PfpI, and FAD_binding_4, respectively. Phylogenetic analysis revealed distinct clades depending on functional diversification. Expression profiling demonstrated significant variability under stress conditions, underscoring their potential roles in stress modulation. Notably, gene-specific responses were observed with CaGLYI-2, CaGLYI-7, CaGLYII-6, CaDJ-1 A, and CaDLDH-1 showed upregulation under salinity, drought, oxidative, heat, and cold stresses, while downregulation were shown for CaGLYI-3, CaGLYII-1, CaDJ-1B, and CaDJ-1 C. Remarkably, CaGLYI-1 presented a unique expression pattern, upregulated against drought and salinity but downregulated under oxidative, heat, and cold stress.ConclusionThe identified GLY and D-LDH gene families in Capsicum annuum exhibited differential expression patterns under different abiotic stresses. Specifically, CaGLYI-2, CaGLYI-7, CaGLYII-6, CaDJ-1 A, and CaDLDH-1 were upregulated in response to all five analyzed abiotic stressors, highlighting their critical role in stress modulation amidst climate change. This study enhances our understanding of plant stress physiology and opens new avenues for developing stress-resilient crop varieties, crucial for sustainable agriculture.

Increased Levels of Circulating Methylglyoxal Have No Consequence for Cerebral Microvascular Integrity and Cognitive Function in Young Healthy Mice.

Diabetes and other age-related diseases are associated with an increased risk of cognitive impairment, but the underlying mechanisms remain poorly understood. Methylglyoxal (MGO), a by-product of glycolysis and a major precursor in the formation of advanced glycation end-products (AGEs), is increased in individuals with diabetes and other age-related diseases and is associated with microvascular dysfunction. We now investigated whether increased levels of circulating MGO can lead to cerebral microvascular dysfunction, blood-brain barrier (BBB) dysfunction, and cognitive impairment. Mice were supplemented or not with 50mM MGO in drinking water for 13weeks. Plasma and cortical MGO and MGO-derived AGEs were measured with UPLC-MS/MS. Peripheral and cerebral microvascular integrity and inflammation were investigated. Cerebral blood flow and neurovascular coupling were investigated with laser speckle contrast imaging, and cognitive tests were performed. We found a 2-fold increase in plasma MGO and an increase in MGO-derived AGEs in plasma and cortex. Increased plasma MGO did not lead to cerebral microvascular dysfunction, inflammation, or cognitive decline. This study shows that increased concentrations of plasma MGO are not associated with cerebral microvascular dysfunction and cognitive impairment in healthy mice. Future research should focus on the role of endogenously formed MGO in cognitive impairment.

Molecular mechanism of ectopic lipid accumulation induced by methylglyoxal via activation of the NRF2/PI3K/AKT pathway implicates renal lipotoxicity caused by diabetes mellitus.

Patients with chronic kidney disease (CKD) have a high incidence of dyslipidemia comprising high triglyceride (TG) and low high-density lipoprotein (HDL)-cholesterol levels. An abnormal increase of TGs within cells can lead to intracellular lipid accumulation. In addition to dyslipidemia, hyperglycemia in diabetes may elicit ectopic lipid deposition in non-adipose tissues. Hyperglycemia increases intracellular levels of methylglyoxal (MG) leading to cellular dysfunction. A deficit of glyoxalase I (GLO1) contributes to dicarbonyl stress. Whether dicarbonyl stress induced by MG causes renal lipotoxicity through alteration of lipid metabolism signaling is still unknown. In this study, mice with high fat diet-induced diabetes were used to investigate the renal pathology induced by MG. NRK52E cells treated with MG were further used in vitro to delineate the involvement of lipogenic signaling. After treatment with MG for 12 weeks, plasma TG levels, renal fatty changes, and tubular injuries were aggravated in diabetic mice. In NRK52E cells, MG activated the nuclear factor erythroid 2-related factor 2 (Nrf2)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and sterol regulatory element-binding protein 1 (SREBP1), resulting in stimulation of fatty acid synthase. The intracellular accumulation of lipid droplets was mainly contributed by TGs, which increased the oxidative stress accompanied by high Nrf2 expression. In addition, MG time-dependently activated cyclin D, cyclin-dependent kinase 4 (CDK4), and cleaved caspase-3, evidencing that G0/G1 arrest was associated with apoptosis of NRK52E cells. In conclusion, our studies revealed the mechanism of lipotoxicity caused by MG. The target of such dicarbonyl stress may become a promising therapy for diabetic CKD.

The Maize Gene ZmGLYI-8 Confers Salt and Drought Tolerance in Transgenic Arabidopsis Plants.

Methylglyoxal (MG), a highly reactive and cytotoxic α-oxoaldehyde compound, can over-accumulate under abiotic stress, consequently injuring plants or even causing death. Glyoxalase I (GLYI), the first enzyme of the glyoxalase pathway, plays multiple roles in the detoxification of MG and in abiotic stress responses. However, the GLY1 gene in maize has been little studied in response to abiotic stress. In this study, we screened a glyoxalase I gene (ZmGLYI-8) and overexpressed in Arabidopsis. This gene was localized in the cytoplasm and can be induced in maize seedlings under multiple stress treatments, including salt, drought, MG, ABA, H2O2 and high temperature stress. Phenotypic analysis revealed that after MG, salt and drought stress treatments, overexpression of ZmGLYI-8 increased the tolerance of transgenic Arabidopsis to MG, salt and drought stress. Furthermore, we demonstrated that the overexpression of ZmGLYI-8 scavenges accumulated reactive oxygen species, detoxifies MG and enhances the activity of antioxidant enzymes to improve the resistance of transgenic Arabidopsis plants to salt and drought stress. In summary, this study preliminarily elucidates the molecular mechanism of the maize ZmGLYI-8 gene in transgenic Arabidopsis and provides new insight into the breeding of salt- and drought-tolerant maize varieties.

Selective activation of PPARα by pemafibrate mitigates peritoneal inflammation and fibrosis through suppression of NLRP3 inflammasome and modulation of inflammation

Peritoneal inflammation and fibrosis remain major challenges to the long-term maintenance of peritoneal dialysis. Pemafibrate, a selective peroxisome proliferator-activated receptor α (PPARα) modulator, has been implicated in the management of fibrosis-related disorders. We investigated whether pemafibrate ameliorates peritoneal inflammation and fibrosis and explored the underlying mechanisms in mice with methylglyoxal (MGO)-induced peritoneal fibrosis (MGO mice). MGO mice exhibited peritoneal fibrosis with increased expression of mesenchymal markers, transforming growth factor-β1 (TGF-β1), and substantial deposition of extracellular matrix (ECM) proteins. Additionally, MGO mice exhibited peritoneal inflammation as indicated by elevated tumor necrosis factor-α expression and macrophage infiltration in peritoneal tissue. These effects were mitigated by pemafibrate treatment, which also restored peritoneal membrane function. Furthermore, pemafibrate promoted anti-inflammatory macrophage polarization in both mice and THP-1 cells. In human peritoneal mesothelial cells (HPMCs), pemafibrate effectively inhibited interferon-γ-induced production of TGF-β1 and ECM while suppressing the proinflammatory cytokines nuclear factor-κB (NF-κB) and activator protein 1. The NF-κB inhibitory effect of pemafibrate involved stabilization of the NF-κB inhibitory protein IkBα. Notably, pemafibrate hindered activation of the NLR family pyrin domain containing 3/caspase-1 axis in interferon-γ-stimulated THP-1 cells. These findings suggest that pemafibrate ameliorates peritoneal inflammation and fibrosis, making it a promising candidate for peritoneal fibrosis therapy.

Elucidating the Antiglycation Effect of Creatine on Methylglyoxal-Induced Carbonyl Stress In Vitro.

Advanced glycation end products (AGEs) with multiple structures are formed at the sites where carbonyl groups of reducing sugars bind to free amino groups of proteins through the Maillard reaction. In recent years, it has been highlighted that the accumulation of AGEs, which are generated when carbonyl compounds produced in the process of sugar metabolism react with proteins, is involved in various diseases. Creatine is a biocomponent that is homeostatically present throughout the body and is known to react nonenzymatically with α-dicarbonyl compounds. This study evaluated the antiglycation potential of creatine against methylglyoxal (MGO), a glucose metabolite that induces carbonyl stress with formation of AGEs in vitro. Further, to elucidate the mechanism of the cytoprotective action of creatine, its effect on the accumulation of carbonyl proteins in the cells and the MGO-induced cellular damage were investigated using neuroblastoma cells. The results revealed that creatine significantly inhibits protein carbonylation by directly reacting with MGO, and creatine added to the culture medium suppressed MGO-derived carbonylation of intracellular proteins and exerted a protective effect on MGO-induced cytotoxicity. These findings suggest that endogenous and supplemented creatine may contribute to the attenuation of carbonyl stress in vivo.

Gas-liquid interfacial reaction mechanisms of typical small α-dicarbonyls in the neutral and acidic droplets: Implications for secondary organic aerosol formation

Small α-dicarbonyls (SαDs) are well-known as the important precursors of secondary organic aerosol (SOA). Hence, it is imperative to understand the atmospheric chemistry of SαDs to contribute to SOA formation. In this work, we investigated the interfacial chemistry of typical SαDs, including methylglyoxal (MG) and biacetyl (BA) in the neutral and acidic droplets by combined molecular dynamics and quantum chemical calculations. The trans configurations of MG and BA are found to be the favorable configurations at the interfaces and are prone to stay at the gas-liquid interface of the acidic droplet. The C=O group exhibits a preferential uptake orientation towards the interface because the carbonyl-O atom has a strong interaction with interfacial H2O. The uptakes and accumulations of MG and BA at the interfaces are promoted by the acidic condition. Subsequent interfacial hydrations of MG and BA in the acidic droplet are beneficial to yield diols, which can engage in oligomerization in the droplet interior to contribute SOA formation. Our results provide the theoretical insight into the interfacial chemistry of SαDs and their role in SOA formation.

Comparative Evaluation of Aminoguanidine, Semicarbazide and Thiosemicarbazide Treatment for Methylglyoxal-Induced Neurological Toxicity in Experimental Models

Background: Advanced glycation end products (AGEs) are complex compounds that play a critical role in neurological disorders, including the pathogenesis of Alzheimer's disease. Methylglyoxal (MG) is recognized as the primary precursor of AGEs. Methylglyoxal is produced endogenously and also introduced through dietary exposures. Objectives: This study aimed to investigate and compare the effects of aminoguanidine (AG), semicarbazide (SC), and thiosemicarbazide (TSC) on MG-induced neurological toxicity in rats. Methods: Male Wistar rats were exposed orally to MG, MG + AG, MG + SC, and MG + TSC for 70 days. Neurobehavioral, biochemical, and histopathological changes were evaluated. Results: The findings indicated that oral administration of MG for 70 days resulted in memory impairment and increased anxiety in neurobehavioral tests. Additionally, MG elevated protein carbonylation in brain tissues. Semicarbazide was found to prevent MG-induced memory problems, while both SC and AG reduced carbonyl content in brain tissues. Advanced glycation and TSC were effective in alleviating anxiety induced by MG exposure. Histopathological analysis revealed that MG caused cell damage and neuronal necrosis in the hippocampus, particularly in the cornu ammonis 1 (CA1) and dentate gyrus (DG) regions. However, AG, SC, and TSC improved neuronal survival in these areas. Conclusions: The data suggest that SC, AG, and TSC may offer neuroprotective effects against MG-induced neurobehavioral toxicity. Further studies are required to explore the mechanisms of action of these compounds.

Use of physiologically based kinetic modeling to predict neurotoxicity and genotoxicity of methylglyoxal in humans

This study aimed to evaluate human neurotoxicity and genotoxicity risks from dietary and endogenous methylglyoxal (MGO), utilizing physiologically based kinetic (PBK) modeling-facilitated reverse dosimetry as a new approach methodology (NAM) to extrapolate in vitro toxicity data to in vivo dose-response predictions. A human PBK model was defined based on a newly developed and evaluated mouse model enabling the translation of in vitro toxicity data for MGO from human stem cell-derived neurons and WM-266-4 melanoma cells into quantitative human in vivo toxicity data and subsequent risk assessment by the margin of exposure (MOE) approach. The results show that the MOEs resulting from daily dietary intake did not raise a concern for endpoints for neurotoxicity including mitochondrial function, cytotoxicity, and apoptosis, while those for DNA adduct formation could not exclude a concern over genotoxicity. Endogenous MGO formation, especially under diabetic conditions, resulted in MOEs that raised concern not only for genotoxicity but also for some of the neurotoxicity endpoints evaluated. Thus, the results also point to the importance of taking the endogenous levels into account in the risk assessment of MGO.

Crosstalk of methylglyoxal and calcium signaling in maize (Zea mays L.) thermotolerance through methylglyoxal-scavenging system

Methylglyoxal (MG) and calcium ion (Ca2+) can increase multiple-stress tolerance including plant thermotolerance. However, whether crosstalk of MG and Ca2+ exists in the formation of maize thermotolerance and underlying mechanism still remain elusive. In this paper, maize seedlings were irrigated with MG and calcium chloride alone or in combination, and then exposed to heat stress (HS). The results manifested that, compared with the survival percentage (SP, 45.3%) of the control seedlings, the SP of MG and Ca2+ alone or in combination was increased to 72.4%, 74.2%, and 83.4% under HS conditions, indicating that Ca2+ and MG alone or in combination could upraise seedling thermotolerance. Also, the MG-upraised SP was separately weakened to 42.2%, 40.3%, 52.1%, and 39.4% by Ca2+ chelator (ethylene glycol tetraacetic acid, EGTA), plasma membrane Ca2+ channel blocker (lanthanum chloride, LaCl3), intracellular Ca2+ channel blocker (neomycin, NEC), and calmodulin (CaM) antagonist (trifluoperazine, TFP). However, significant effect of MG scavengers N-acetylcysteine (NAC) and aminoguanidine (AG) on Ca2+-induced thermotolerance was not observed. Similarly, an endogenous Ca2+ level in seedlings was increased by exogenous MG under non-HS and HS conditions, while exogenous Ca2+ had no significant effect on endogenous MG. These data implied that Ca2+ signaling, at least partly, mediated MG-upraised thermotolerance in maize seedlings. Moreover, the activity and gene expression of glyoxalase system (glyoxalase I, glyoxalase II, and glyoxalase III) and non-glyoxalase system (MG reductase, aldehyde reductase, aldo-keto reductase, and lactate dehydrogenase) were up-regulated to a certain extent by Ca2+ and MG alone in seedlings under non-HS and HS conditions. The up-regulated MG-scavenging system by MG was enhanced by Ca2+, while impaired by EGTA, LaCl3, NEC, or TFP. These data suggest that the crosstalk of MG and Ca2+ signaling in maize thermotolerance through MG-scavenging system. These findings provided a theoretical basis for breeding climate-resilient maize crop and developing smart agriculture.

Intracellular Methylglyoxal Accumulation in Classically Activated Mouse Macrophages is Mediated by HIF-1α.

Approximately one million cases of sepsis in the U.S.A. occur annually. The early phase of sepsis features dramatic changes in host metabolism and inflammation. While examining the effects of metabolic pathways on inflammation, we discovered that the highly reactive glycolytic metabolite, methylglyoxal (MG), accumulates intracellularly during classical activation of macrophages. Herein, we explored the role of glycolysis and the master regulator of glycolysis, Hypoxia-Inducing Factor-1α (HIF-1α), in inflammation and MG accumulation in mouse and human macrophages. To determine how HIF-1α regulates the inflammatory response of macrophages, we correlated HIF-1α stabilization with proinflammatory gene expression and MG-adduct accumulation in WT vs HIF1a-deficient macrophages treated with LPS or LPS+IFN-γ. A nearly complete loss of HIF-1α protein expression in response to the hypoxia mimetic, cobalt chloride, confirmed the phenotype of the HIF1a-deficient macrophages. Moreover, absence of HIF-1α was also associated with decreased MG accumulation. Increasing the glucose concentration in cultured macrophages was sufficient to cause accumulation of endogenous MG-adducts which correlated with increased Tnf and Il1b expression during classical activation. Use of the MG antagonist, aminoguanidine, led to a significant decrease in Tnf and Il1b expression in both mouse macrophages and in the THP-1 human macrophage cell line. Although off-target effects cannot be ruled out, these results are consistent with the possibility that MG regulates cytokine expression in classically activated macrophages. Collectively, this work suggests that HIF-1α stabilization is upstream of MG accumulation and that targeting the activity of HIF-1α in macrophages may be therapeutic during sepsis by limiting endogenous MG accumulation.

Aging of mineral dusts and proxies by uptake of methylglyoxal: A Knudsen cell study

This study investigates interactions between methylglyoxal (MGL) and 29 different samples, such as clays, proxies and natural dusts from the arid regions of the planet. Initial and quasi steady state uptake coefficients (ɣ0 and ɣqss) of MGL are determined using a Knudsen cell at concentration of 70 ppb, under dry conditions. Remarkably high ɣ0 values for MGL, ranging from 0.05 to 0.67, are determined, close to those of radical species, suggesting a high affinity for dusts. ɣ0 is evidenced to be linearly correlated with the Al/Si ratio of dust samples, indicating a specific initial affinity of MGL with aluminum surface sites. Ɣqss, determined after 40 minutes of exposure, ranges from 2.9 × 10-7 to 5.9 × 10-6. Ɣqss is linearly correlated with Ti/Si ratio, highlighting specific affinity of MGL with titanium. The impact of concentration on ɣqss is investigated on Gobi dust with MGL concentrations ranging from 0.1 ppt to 2.2 ppm. Ɣqss increases when MGL concentration decreases. Under typical dust storm conditions, MGL uptake competes with gas phase removal by OH radicals or photolysis. In addition, the maximum storage capacity of MGL by samples is determined at 2 ppm with Knudsen cell. MGL uptake does not exceed a compact monolayer on natural dust samples, whereas on some surrogates multilayer uptake is reached. Comparison of ɣ0 and ɣqss of glyoxal and MGL shows that MGL generally exhibits higher affinity with samples. The maximum number of molecules taken up by Gobi dust (Nmax) of MGL is compared with those for isoprene, isopropanol and acetic acid retrieved from literature. It points at the dependance of Nmax on chemical functionality of VOCs: oxygenated compounds exhibit higher interactions with dust. Data are available to increase the representativeness of modeling.

Generation of affinity maps for thiazolidinediones with human serum albumin using affinity microcolumns. II. Effects of advanced glycation end products on multisite drug binding

Multisite protein interactions by the thiazolidinedione-class drugs pioglitazone and rosiglitazone were examined by using high-performance affinity microcolumns that contained normal human serum albumin (HSA) vs HSA that had been modified to form advanced glycation end products by glyoxal (Go) or methylglyoxal (MGo). The results were used to generate an affinity map for these drugs at several key regions on HSA. Strong binding (∼105 M−1) by these drugs was seen at both Sudlow sites I and II. About a 50 % decrease in the affinities at Sudlow site II was observed for pioglitazone for Go-modified HSA, while either a 47 % decrease or 1.6-fold increase in affinity was seen for MGo-modified HSA, depending on the extent of modification. The binding affinity for rosiglitazone at Sudlow site II had a 40–83 % decrease for Go-modified HSA and either a non-significant change or 1.4-fold increase for MGo-modified HSA. At Sudlow site I, pioglitazone gave a 41 % decrease in affinity for either Go or MGo-modified HSA, and for rosiglitazone up to a 55 % decrease or 1.3-fold increase in affinity was noted. Positive allosteric effects were seen by these drugs with the tamoxifen site of HSA, and neither drug had any notable binding at the digitoxin site for the normal or modified forms of HSA. Rosiglitazone also had weak interactions at a site in subdomain IB, which increased in affinity by up to 5.0-fold with the Go- or MGo-modified HSA. This study illustrated how affinity microcolumns can be used to provide a detailed analysis of solute-protein systems that involve complex interactions. The data obtained should also be valuable in providing a better understanding of how drug interactions with HSA and other proteins can be altered by modifications of these binding agents in diseases such as diabetes.

Pseudomonas aeruginosa LasR-deficient mutants have increased methylglyoxal and hydrogen peroxide sensitivity due to low intracellular glutathione.

Methylglyoxal is a highly reactive metabolite that is detected in various disease states, including those where Pseudomonas aeruginosa is present and MG resistance requires the glutathione-dependent glyoxalase enzyme GloA3 enzyme. This study reveals that P . aeruginosa strains with LasR mutations, which are commonly found in clinical isolates, are more sensitive to methylglyoxal (MG) and hydrogen peroxide due to lower intracellular glutathione levels and high activity of the CbrAB-Crc regulatory pathway. This could be significant for understanding the selective pressures that drive P. aeruginosa evolution in infection sites, as well as a better understanding of LasR-strain metabolism in infections such as those associated with cystic fibrosis.

Glyoxalase 1 overexpression improves neurovascular coupling and limits development of mild cognitive impairment in a mouse model of type 1 diabetes.

Diabetes is associated with cognitive impairment, but the underlying mechanism remains unclear. Methylglyoxal (MGO), a precursor to advanced glycation endproducts (AGEs), is elevated in diabetes and linked to microvascular dysfunction. In this study, overexpression of the MGO-detoxifying enzyme glyoxalase 1 (Glo1) was used in a mouse model of diabetes to explore whether MGO accumulation in diabetes causes cognitive impairment. Diabetes was induced with streptozotocin. Fasting blood glucose, cognitive function, cerebral blood flow, neurovascular coupling (NVC), Glo1 activity, MGO and AGEs were assessed. In diabetes, MGO-derived hydroimidazolone-1 increased in the cortex, and was decreased in Glo1-overexpressing mice compared to controls. Visuospatial memory was decreased in diabetes, but not in Glo1/diabetes. NVC response time was slightly increased in diabetes, and normalised in the Glo1-overexpressing group. No impact of diabetes or Glo1 overexpression on blood-brain barrier integrity or vascular density was observed. Diabetes induced a mild visuospatial memory impairment and slightly reduced NVC response speed and these effects were mitigated by Glo1. This study shows a link between MGO-related AGE accumulation and cerebrovascular/cognitive functions in diabetes. Modulation of the MGO-Glo1 pathway may be a novel intervention strategy in patients with diabetes who have cerebrovascular complications. KEY POINTS: Diabetes is associated with an increased risk of stroke, cognitive decline, depression and Alzheimer's disease, but the underlying mechanism remains unclear. Methylglyoxal (MGO), a highly reactive by-product of glycolysis, plays an important role in the development of diabetes-associated microvascular dysfunction in the periphery and is detoxified by the enzyme glyoxalase 1. Diabetes reduced visuospatial memory in mice and slowed the neurovascular coupling response speed, which was improved by overexpression of glyoxalase 1. MGO formation and MGO-derived advanced glycation endproduct (AGE) accumulation in the brain of diabetic mice are associated with a slight reduction in neurovascular coupling and mild cognitive impairment. The endogenous formation of MGO, and the accumulation of MGO-derived AGEs, might be a potential target in reducing the risk of vascular cognitive impairment in people with diabetes.

Methylglyoxal mediates the association between 2-hour plasma glucose and HbA1c with inflammation: The Maastricht Study.

Glucose excursions in persons with diabetes may drive chronic inflammation. Methylglyoxal (MGO) is formed from glucose, is elevated in persons with diabetes, and is a potent glycating agent linked with inflammation. We investigated whether glucose excursions are associated with low-grade inflammation and whether MGO mediates this association. We used data from The Maastricht Study, an extensive phenotyping study into the etiology of type 2 diabetes and its complications. Data of 3017 participants, who underwent an oral glucose tolerance test and where data on MGO levels and inflammation were available, were used. Linear regression analyses, adjusted for potential confounders, evaluated associations between fasting plasma glucose (FPG), 2-hours plasma glucose (2h-PG) and HbA1c and low-grade inflammation (stdβ, [95% confidence interval]), calculated from plasma concentrations of C-reactive protein, serum amyloid A, interleukin-6, interleukin-8, tumor necrosis factor and soluble intercellular adhesion molecule-1. Mediation analyses investigated whether MGO mediated these associations. 2h-PG (0.172 [0.110; 0.234]) and HbA1c (0.148 [0.101; 0.196]), but not FPG (0.049 [-0.002; 0.100]), were associated with low-grade inflammation. 2h-PG and HbA1c were also associated with 2h-MGO (0.471 [0.407; 0.534], and 0.244 [0.195; 0.294], respectively). Furthermore, 2h-MGO was independently and positively associated with low-grade inflammation (0.078 [0.037, 0.120]). 2h-MGO mediated 23% of the association between 2h-PG and inflammation, and 16% of the association between HbA1c and inflammation. MGO mediates the association between post-load glucose excursions and HbA1c with inflammation, providing evidence for a role of postprandial MGO formation to hyperglycemia-induced low-grade inflammation.

Monascus pigments suppress fructose-mediated BSA glycation by trapping methylglyoxal and covalent binding to proteins

In this study, four Monascus pigments (ankaflavin, AK; monascin MS; rubropunctatin, O1; monascorubrin, O2) were proved to exhibit considerable anti-glycation properties in bovine serum albumin (BSA)-fructose model. AK (40.62 %) and MS (48.38 %) were found to exert lower inhibitory effects on the formation of fluorescent advanced glycation end products (AGEs) than aminoguanidine (59.4 %), while O1 (90.64 %) and O2 (93.82 %) displayed much stronger abilities. AK and MS could trap methylglyoxal (MGO) with maximum capture rates of 85.67 % and 84.90 %, respectively, and only mono-MGO adducts of them were detected. LC-Orbitrap MS/MS analysis revealed that four pigments significantly altered the type and reduced the number of the glycated sites and they all covalently bound to BSA, with O1 and O2 possessing high reactivity. Altogether, AK and MS suppressed fluorescent AGEs formation mainly via trapping MGO and covalently interacting with BSA, and blocking free amino groups was the dominant mechanism for O1 and O2. These findings presented new insights into Monascus pigments as dietary supplement for inhibiting protein glycation.