Concentrations Of Methylglyoxal Research Articles

Rhizobium inoculation and exogenous melatonin synergistically increased thermotolerance by improving antioxidant defense, photosynthetic efficiency, and nitro-oxidative homeostasis in Medicago truncatula

Global warming negatively affects plant growth due to the detrimental effects of high temperature-induced heat stress. Rhizobium inoculation (RI) and exogenous melatonin (MT) have shown a positive role in resisting abiotic stress. However, their synergistic effect on avoiding heat-induced damages in Medicago truncatula has not been studied yet. Hence, the objective of the present study was to evaluate the impact of these amendments (RI and MT) to ameliorate the heat damages in Medicago truncatula. The study was comprised of two factors: (1) heat-induced stress: (i) optimum temperature (26 ± 1°C): (23 ± 1°C) (day: night), (ii) moderate heat (35 ± 1°C): (28 ± 1°C), and (iii) severe heat (41 ± 1°C): (35 ± 1°C) for 72 h, and (2) amendments: (i) no RI + no MT (NRI + NMT), (ii) Rhizobium inoculation (RI), (iii) 60 μM melatonin (MT), and (iii) RI + MT. Results showed that the combined application of RI and MT was better than their individual applications, as it prevented heat-induced membrane damages by declining the hydrogen peroxide (34.22% and 29.78%), superoxide anion radical (29.49% and 26.71%), malondialdehyde contents (26.43% and 21.96%), and lipoxygenase activity (44.75% and 25.51%) at both heat stress levels as compared to NRI + NMT. Moreover, RI + MT treated plants showed higher antioxidative and methylglyoxal detoxification enzymes (Gly I and Gly II) activities under heat stress. While, NRI + NMT treated plants showed a higher level of methylglyoxal contents (47.99% and 46.71%) under both levels of heat stress. Relative to NRI + NMT plants, RI + MT pretreated plants exhibited improved heat tolerance as indicated by higher chlorophyll (37.42% and 43.52%), carotenoid contents (32.41% and 47.08%), and photosynthetic rate (42.62% and 64.63%), under moderate and severe heat stress, respectively. Furthermore, RI + MT pretreated plants had considerably higher indole-3 acetic acid and abscisic acid concentrations under moderate (54.02% and 53.92%) and severe (68.36% and 64.61%) heat stress conditions. Similarly, plant dry biomass, NPK uptake, nitric oxide, and nitrate reductase activity were high in RI + MT treated plants, under both levels of stress. Therefore, this study advocates the positive synergistic effect of RI and MT pretreatment against moderate and severe heat-induced stress and for possible maintenance of plant growth under changing scenarios of global warming.

Formation Priority of Pyrazines and 2-Acetylthiazole Dependent on the Added Cysteine and Fragments of Deoxyosones during the Thermal Process of the Glycine-Ribose Amadori Compound.

In this study, it was found that extra-added cysteine (Cys) became involved in volatile compound formation during the Maillard reaction of the glycine-ribose Amadori rearrangement product (GR-ARP). The priority of the Cys reaction with different α-dicarbonyls and its dependence on the Cys dosage were investigated. At the same concentrations of methylglyoxal (MGO) and glyoxal (GO), it was found that 2-acetylthiazole was the dominant product when the molar ratio of Cys to MGO was 1:1, while formation of pyrazines was improved when the Cys percentage increased. Cys preferentially reacted with MGO first rather than GO to exclusively generate 2-acetylthiazole at a high yield. The concentration of 2-acetylthiazole quickly increased up to a plateau and remained stable during further heat treatment. When MGO was totally consumed, remaining Cys began to react with GO through the predominant pathway where the keto form of carbonylcysteimine derived from Cys and GO was hydrolyzed to recover GO with cysteamine formation, whereas the hydrolysis reactivity of enolized carbonylcysteimine as the Strecker pathway for generation of pyrazines was relatively low. During the heat treatment of GR-ARP, the constantly lower ratios of α-dicarbonyls to Cys led to inhibited formation of 2-aminopropanal, which accounted for the decreased methylpyrazine yields.

The Detriment of Salicylic Acid to the Pseudomonas savastanoi pv. phaseolicola Proteome.

Salicylic acid (SA), a natural product, is the major hormonal regulator of the plant immune system. SA also has antibacterial activity that is not completely elucidated. To gain a better understanding of this, Pseudomonas savastanoi pv. phaseolicola, a bacterial pathogen of beans, was exposed to sub-inhibitory amounts of SA and was then examined using quantitative mass spectrometry. Among the 2,185 proteins quantified, there were pronounced increases in p-hydroxybenzoic acid efflux pumps and multidrug efflux pumps. By contrast there were significant decreases in porin proteins, high-osmolarity response proteins, and protein components of the type VI secretion system. In addition, there were alterations in enzymes likely affecting the production of alginate, which is needed for infection. Furthermore, there was a decrease in an enzyme needed to detoxify methylglyoxal. Assays confirmed a reduction in alginate production and an increase in cellular methylglyoxal concentrations after SA treatment. Culture assays demonstrated that SA altered bacterial growth curves more so than other hydroxylated benzoic acid isomers. These data reveal that SA is antibiotic and that P. savastanoi pv. phaseolicola significantly alters its proteome in response to SA in vitro. Similar alterations to the bacterial proteome occur in beans during an immune reaction when SA increases at the site of infection. Thus, in beans, SA likely deters bacterial infection by adversely altering the bacterial proteome. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022.

Mineralocorticoid interaction with glycated albumin downregulates NRF – 2 signaling pathway in renal cells: Insights into diabetic nephropathy

In diabetic nephropathy, hyperglycemia elevates albumin glycation and also results in increased plasma aldosterone. Both glycation and aldosterone are reported to cause oxidative stress by downregulating the NRF-2 pathway and thereby resulting in reduced levels of antioxidants and glycation detoxifying enzymes. We hypothesize that an interaction between aldosterone and glycated albumin may be responsible for amplified oxidative stress and concomitant renal cell damage. Hence, human serum albumin was glycated by methylglyoxal (MGO) in presence of aldosterone. Different structural modifications of albumin, functional modifications and aldosterone binding were analyzed. HEK-293 T cells were treated with aldosterone+glycated albumin along with inhibitors of receptors for mineralocorticoid (MR) and advanced glycation endproducts (RAGE). Cellular MGO content, antioxidant markers (nitric oxide, glutathione, catalase, superoxide dismutase, glutathione peroxidase), detoxification enzymes (aldose reductase, Glyoxalase I, II), their expression along with NRF-2 and Keap-1 were measured. Aldosterone binds to albumin with high affinity which is static and spontaneous. Cell treatment by aldosterone+glycated albumin increased intracellular MGO, MR and RAGE expression; hampered antioxidant, detoxification enzyme activities and reduced NRF-2, Keap-1 expression. Thus, the glycated albumin-aldosterone interaction and its adverse effect on renal cells were confirmed. The results will help in developing better pharmacotherapeutic strategies for diabetic nephropathy.

Foliar application of procyanidins enhanced the biosynthesis of 2-acetyl-1-pyrroline in aromatic rice (Oryza sativa L.)

BackgroundProcyanidins is a polyphenolic compound with multiple properties. However, the application of exogenous procyanidins in crops has not been reported. Aromatic rice is a high-quality rice with a special aroma and popular with consumers. The 2-acetyl-1-pyrroline (2-AP) is a key compound of aromatic rice aroma. In the current study, aromatic rice plants were sprayed with procyanidins solutions at 0.25 (Pr0.25), 0.50 (Pr0.50), 1.00 (Pr1.00), 2.00 (Pr2.00) g L−1, respectively and treatment sprayed with distilled water was taken as control (CK). The effects of exogenous procyanidins on growth and 2-AP biosynthesis of aromatic rice plants were explored.ResultsCompared with CK, Pr1.00 and Pr2.00 treatments significantly increased 2-AP content by 16.67% and 37.68%, respectively. Higher proline, 1-pyrroline-5-carboxylic acid (P5C), 1-pyrroline, methylglyoxal contents, and lower γ- aminobutyric acid (GABA) content were recorded in Pr1.00 and Pr2.00 treatments than CK. Compared with CK, Pr1.00 and Pr2.00 treatments significantly improved the activities of P5CS and OAT and diminished the activity of BADH. Furthermore, compared with CK, Pr1.00 and Pr2.00 treatments significantly up-regulated the transcript levels of P5CS2, P5CR, OAT, DAO4 and down-regulated the transcript levels of BADH2. Exogenous procyanidins had no substantial effects on plant height, stem diameter, fresh weight, and dry weight of aromatic rice plants.ConclusionsIn conclusion, our findings reported the increment of 2-AP content in aromatic rice under exogenous procyanidins. Our results indicated that the application of exogenous procyanidins enhanced 2-AP biosynthesis by improving proline biosynthesis and inhibiting GABA formation.

Correlation of the antibacterial activity of commercial manuka and Leptospermum honeys from Australia and New Zealand with methylglyoxal content and other physicochemical characteristics.

Variation in the antibacterial potency of manuka honey has been reported in several published studies. However, many of these studies examine only a few honey samples, or test activity against only a few bacterial isolates. To address this deficit, a collection of 29 manuka/Leptospermum honeys was obtained, comprising commercial manuka honeys from Australia and New Zealand and several Western Australian Leptospermum honeys obtained directly from beekeepers. The antibacterial activity of honeys was quantified using several methods, including the broth microdilution method to determine minimum inhibitory concentrations (MICs) against four species of test bacteria, the phenol equivalence method, determination of antibacterial activity values from optical density, and time kill assays. Several physicochemical parameters or components were also quantified, including methylglyoxal (MGO), dihydroxyacetone (DHA), hydroxymethylfurfural (HMF) and total phenolics content as well as pH, colour and refractive index. Total antioxidant activity was also determined using the DPPH* (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing-antioxidant power) assays. Levels of MGO quantified in each honey were compared to the levels stated on the product labels, which revealed mostly minor differences. Antibacterial activity studies showed that MICs varied between different honey samples and between bacterial species. Correlation of the MGO content of honey with antibacterial activity showed differing relationships for each test organism, with Pseudomonas aeruginosa showing no relationship, Staphylococcus aureus showing a moderate relationship and both Enterococcus faecalis and Escherichia coli showing strong positive correlations. The association between MGO content and antibacterial activity was further investigated by adding known concentrations of MGO to a multifloral honey and quantifying activity, and by also conducting checkerboard assays. These investigations showed that interactions were largely additive in nature, and that synergistic interactions between MGO and the honey matrix did not occur.

Preparation and Characterisation of a Cyclodextrin-Complexed Mānuka Honey Microemulsion for Eyelid Application.

Honey has been widely purported as a natural remedy due to its antimicrobial and anti-inflammatory effects. In recent years, several studies have suggested that the considerably high methylglyoxal (MGO) concentration in Mānuka honey (MH) makes it particularly effective to manage bacterial overload, such as that observed in blepharitis. However, the poor solubility, high viscosity, and osmolarity of aqueous honey solutions, especially at the high MGO concentrations studied in the literature, render the formulation of an acceptable dosage form for topical application to the eyelids challenging. Here, the antibacterial properties of raw MH and alpha-cyclodextrin (α-CD)-complexed MH were evaluated at relatively low MGO concentrations, and a liquid crystalline-forming microemulsion containing α-CD-complexed MH was formulated. After determining pH and osmolarity, ocular tolerability was assessed using human primary corneal epithelial cells and chorioallantoic membranes, while the antibacterial efficacy was further evaluated in vitro. The α-CD–MH complex had significantly greater antibacterial activity against Staphylococcus aureus than either constituent alone, which was evident even when formulated as a microemulsion. Moreover, the final formulation had a physiologically acceptable pH and osmolarity for eyelid application and was well-tolerated when diluted 1:10 with artificial tear fluid, as expected to be the case after accidental exposure to the ocular surface in the clinical setting. Thus, a safe and efficient MH dosage form was developed for topical application to the eyelids, which can potentially be used to support optimal eyelid health in the management of blepharitis.

Methylglyoxal and high glucose inhibit VEGFR2 phosphorylation at specific tyrosine residues.

Diabetes is characterized by hyperglycemia and a significant risk of vascular complications. Vascular endothelial growth factor (VEGF) and its main receptor VEGFR2 (KDR), which is highly expressed in vascular endothelial cells, are essential mediators of vascular maintenance and angiogenesis. During glycolysis after high calorie food intake, methylglyoxal (MGO) is formed and MGO blood levels are elevated in diabetes. MGO reacts with arginine residues to generate MG-H1 or with lysine residues to carboxyethyl lysine which are common components of advanced glycation end-products. Therefore, the question arises whether hyperglycemic conditions affect VEGF signaling via a ligand-independent direct modification of signaling components. As a first step, the effect of MGO on VEGFR2 activation was investigated in cultured endothelial cells from human umbilical vein by determination of VEGFR2 phosphorylation at selected tyrosine residues by ELISA and immunoblotting using phospho-specific antibodies. Phosphorylation of VEGFR2-Y996, VEGFR2-Y1054, or VEGFR2-Y1175 reached a maximum 5min after stimulation of endothelial cells with VEGF. Phosphorylation wassignificantly inhibited by 100µM MGO and to a lesserextent by high glucose treatment. 2,3-Pentanedione and glyoxal were investigated for comparison. In summary, VEGFR2 phosphorylation is sensitive to MGO or high glucose concentrations which may be relevant in the pathophysiology of microvascular disease in diabetes.

ORAL ADMINISTRATION OF METHYLGLYOXAL ELEVATES BLOOD PRESSURE, BUT NOT ARTERIAL STIFFNESS, IN MICE

Objective: Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is associated with diabetes and other age-related diseases such as hypertension. In these diseases, MGO may accelerate arterial stiffening. In the present study, we investigated the effect of elevated plasma MGO concentrations on arterial stiffness measured in- and ex vivo. Design and method: Eight-week-old male C57BL/6 mice were randomly allocated to control (n = 22) and treatment (n = 22) groups. Treatment started at age 10 weeks and consisted of 50 mM MGO in the drinking water for 13 weeks. Blood pressure (tail-cuff) and tonometric carotid-to-femoral pulse wave velocity (PWV) were recorded after 0, 5, and 11 weeks. After 15 weeks, mice were euthanised and their left common carotid arteries (CCAs) harvested for ex vivo bi-axial biomechanical testing. First, CCAs were stretched to in vivo length and exposed to quasi-static pressure inflation from 0–200 mmHg. Second, a 5 Hz pulsatile pressure of 120/80 mmHg was applied, to enable calculation of single-point PWV (Bramwell-Hill). Third, a structural axial stiffness coefficient was determined by performing quasi-static axial stretch sweeps at constant pressures of 60/100/140/200 mmHg. Finally, a four-fibre family strain energy function was fitted to the dataset to allow for calculation of material stiffness variables. Results: Plasma MGO levels at 15 weeks in the treatment group were 2.2-fold higher than the control group (879 ± 274 nM vs. 399 ± 45 nM, mean ± standard deviation, p < 0.001). After 11 weeks, systolic and diastolic blood pressures were elevated in the treatment group (systolic 110 ± 3 vs 105 ± 7 mmHg, p = 0.015, diastolic 85 ± 3 vs 80 ± 7 mmHg, p = 0.019). No differences in carotid-to-femoral PWV were observed at any time point (Figure). Ex vivo PWVs were not significantly different; neither were the axial stiffness coefficients. CCAs from treated mice showed a non-significant smaller inner radius and thickness than controls. Material stiffness, as assessed by constitutive modelling at a reference pressure of 100 mmHg, did not show any difference between groups. Conclusions: Higher plasma MGO levels are associated with an increase in blood pressure, but not an increase in arterial stiffness.

Dicarbonyl Stress in Diabetic Vascular Disease.

Late vascular complications play a prominent role in the diabetes-induced increase in morbidity and mortality. Diabetes mellitus is recognised as a risk factor driving atherosclerosis and cardiovascular mortality; even after the normalisation of blood glucose concentration, the event risk is amplified—an effect called “glycolytic memory”. The hallmark of this glycolytic memory and diabetic pathology are advanced glycation end products (AGEs) and reactive glucose metabolites such as methylglyoxal (MGO), a highly reactive dicarbonyl compound derived mainly from glycolysis. MGO and AGEs have an impact on vascular and organ structure and function, contributing to organ damage. As MGO is not only associated with hyperglycaemia in diabetes but also with other risk factors for diabetic vascular complications such as obesity, dyslipidaemia and hypertension, MGO is identified as a major player in the development of vascular complications in diabetes both on micro- as well as macrovascular level. In diabetes mellitus, the detoxifying system for MGO, the glyoxalase system, is diminished, accounting for the increased MGO concentration and glycotoxic load. This overview will summarise current knowledge on the effect of MGO and AGEs on vascular function.

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

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

Acrylamide causes neurotoxicity by inhibiting glycolysis and causing the accumulation of carbonyl compounds in BV2 microglial cells

Acrylamide is a potent neurotoxin produced during industrial production or food processing at high temperatures, and its effect on glycolytic processes may be critical in triggering neurotoxicity. Our work investigated the neurotoxic effects of acrylamide based on glycolysis using immortalized mouse microglia cell line BV2. The results showed that 1.5 mM acrylamide significantly inhibited the expression and activity of triphosphate isomerase and 3-phosphoglyceraldehyde dehydrogenase. Moreover, acrylamide limited the expression of pyruvate kinase and the decrease of pyruvate and lactate content of glycolysis products. In addition, acrylamide could increase intracellular methylglyoxal content and further affect its detoxification system. Not only that, subsequent cellular responses resulting from methylglyoxal accumulation, such as oxidative stress, activation of ERK, upregulation of NF-κB inflammatory signaling pathway, and elevated pro-inflammatory factor TNF-α, were found in the acrylamide-treated cell model. Therefore, we suggest that acrylamide's perturbation of the glycolytic process leads to methylglyoxal accumulation, which may be responsible for its key to neurotoxicity.

Free L-Lysine and Its Methyl Ester React with Glyoxal and Methylglyoxal in Phosphate Buffer (100 mM, pH 7.4) to Form Nε-Carboxymethyl-Lysine, Nε-Carboxyethyl-Lysine and Nε-Hydroxymethyl-Lysine

Glyoxal (GO) and methylglyoxal (MGO) are highly reactive species formed in carbohydrate metabolism. Nε-Carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL) are considered to be the advanced glycation end-products (AGEs) of L-lysine (Lys) with GO and MGO, respectively. Here, we investigated the reaction of free L-lysine (Lys) with GO and MGO in phosphate buffer (pH 7.4) at 37 °C and 80 °C in detail in the absence of any other chemicals which are widely used to reduce Schiff bases. The concentrations of Lys, GO and MGO used in the experiments were 0.5, 2.5, 5.0, 7.5 and 10 mM. The reaction time ranged between 0 and 240 min. Experiments were performed in triplicate. The concentrations of remaining Lys and of CML and CEL formed in the reaction mixtures were measured by stable-isotope dilution gas chromatography-mass spectrometry (GC-MS). Our experiments showed that CML and CEL were formed at higher concentrations at 80 °C compared to 37 °C. CML was found to be the major reaction product. In mixtures of GO and MGO, MGO inhibited the formation of CML from Lys (5 mM) in a concentration-dependent manner. The highest CML concentration was about 300 µM corresponding to a reaction yield of 6% with respect to Lys. An addition of Lys to GO, MGO and their mixtures resulted in strong reversible decreases in the Lys concentration up to 50%. It is assumed that free Lys reacts rapidly with GO and MGO to form many not yet identified reaction products. Reaction mixtures of Lys and MGO were stronger colored than those of Lys and GO, notably at 80 °C, indicating higher reactivity of MGO towards Lys that leads to polymeric colored MGO species. We have a strong indication of the formation of Nε-(hydroxymethyl)-lysine (HML) as a novel reaction product of Lys methyl ester with MGO. A mechanism is proposed for the formation of HML from Lys and MGO. This mechanism may explain why Lys and GO do not react to form a related product. Preliminary analyses show that HML is formed at higher concentrations than CEL from Lys methyl ester and MGO. No Schiff bases or their hydroxylic precursors were identified as reaction products. In their reactions with Lys, GO and MGO are likely to act both as chemical oxidants on the terminal aldehyde group to a carboxylic group (i.e., R-CHO to R-COOH) and as chemical reductors on labile Schiff bases (R-CH=N-R to R-CH2-NH-R) presumably via disproportionation and hydride transfer. Our study shows that free non-proteinic Lys reacts with GO and MGO to form CML, CEL and HML in very low yield. Whether proteinic Lys also reacts with MGO to form HML residues in proteins remains to be investigated. The physiological occurrence and concentration of HML in biological fluids and tissues and its relation to CML and CEL are elusive and warrant further investigations in health and disease. Chemical synthesis and structural characterization of HML are expected to advance and accelerate the scientific research in this topic.

The Effect of Microwave Baking Conditions on the Quality of Biscuits and the Control of Thermal Processing Hazards in the Maillard Reaction.

To reduce thermal processing hazards (TPHs), microwave baking has been extensively used in food thermal processing. In this study, the influence of microwave power and microwave time on the formation of TPHs and their precursors was explored in microwave-baked biscuits. The results indicated that the content of acrylamide, 5-hydroxymethylfurfural, methylglyoxal, and 3-deoxyglucosone increased linearly with the extension of microwave time (2, 2.5, and 3 min) and microwave power (440, 480, and 520 W). There was a significant correlation between the four TPHs. 3-Deoxyglucosone may directly or indirectly participate in the formation of the other three TPHs. The relationship between TPH levels with some heat-induced sensory characteristics was analyzed. The correlation between the sensory characteristics and the content of TPHs is L* > a* > hardness > Water activity (AW). The correlation coefficients between L* value and the four TPHs are −0.950, −0.891, −0.803, and −0.985. Furthermore, the content of TPHs produced by traditional baking and microwave baking under the same texture level was compared. Compared with traditional baking (190°C, 7 min), microwave baking at 440 W for 3 min successfully decrease methylglyoxal, 3-Deoxyglucosone, acrylamide, and 5-hydroxymethylfurfural content by 60.75, 30.19, 30.87, and 61.28%, respectively. Traditionally baked biscuits, which had a more obvious color, as characterized by lower L* value, larger a* and b* values, are more susceptible to the formation of TPHs. Therefore, microwave baking can reduce the generation of TPHs.

Rapid increase in atmospheric glyoxal and methylglyoxal concentrations in Lhasa, Tibetan Plateau: Potential sources and implications

Glyoxal (Gly) and methylglyoxal (Mgly) are the intermediate products of several volatile organic compounds (VOCs) as well as the precursors of brown carbon and may play key roles in photochemical pollution and regional climate change in the Tibetan Plateau (TP). However, their sources and atmospheric behaviors in the TP remain unclear. During the second Tibetan Plateau Scientific Expedition and Research in the summer of 2020, the concentrations of Gly (0.40 ± 0.30 ppbv) and Mgly (0.57 ± 0.16 ppbv) observed in Lhasa, the most densely populated city in the TP, had increased by 20 and 15 times, respectively, compared to those measured a decade previously. Owing to the strong solar radiation, secondary formations are the dominant sources of both Gly (71%) and Mgly (62%) in Lhasa. In addition, primary anthropogenic sources also play important roles by emitting Gly and Mgly directly and providing abundant precursors (e.g., aromatics). During ozone pollution episodes, local anthropogenic sources (industries, vehicles, solvent usage, and combustion activities) contributed up to 41% and 45% in Gly and Mgly levels, respectively. During non-episode periods, anthropogenic emissions originating from the south of Himalayas also have non-negligible contributions. Our results suggest that in the previous decade, anthropogenic emissions have elevated the levels of Gly and Mgly in the TP dramatically. This study has important implications for understanding the impact of human activities on air quality and climate change in this ecologically fragile area.

Nanoencapsulated Lippia origanoides essential oil: physiochemical characterisation and assessment of its bio‐efficacy against fungal and aflatoxin contamination as novel green preservative

SummaryThe study explores in vitro antifungal and aflatoxin B1 inhibitory potency of chemically characterised Lippia origanoides EO (LOEO) encompassed in chitosan nanoparticle (CS‐LOEO‐Np). CS‐LOEO‐Np was physico‐chemically characterised through XRD, SEM and FTIR analyses. CS‐LOEO‐Np exhibited improved antifungal and AFB1 inhibitory efficacy (0.05 and 0.045 µl mL−1, respectively) in contrast to LOEO (0.30 and 0.25 µl mL−1, respectively). Bioactivity of LOEO loaded nanoparticle was enhanced as reflected by depletion in ergosterol content, rapid cellular ion release and reduced methylglyoxal content. IC50 value equivalent to 4.17 µl mL−1 displayed better antioxidant potency of CS‐LOEO‐Np as compared to LOEO (IC50 = 6.20 µl mL−1). CS‐LOEO‐Np preserved sensorial attributes of stored Nigella sativa (model food matrix) samples and have higher lethal toxicity dose, that is LD50 = 8832 mg kg−1. Hence, CS‐LOEO‐Np could serve as novel green candidate to ensure food security with better nutritional and sensorial features.

Дикарбонільний стрес: гіпотеза клітинного пошкодження в умовах гіпоксії. Пусковий механізм розвитку мультиорганної дисфункції

Актуальність. Різноманітні критичні стани організму часто асоційовані з розвитком гіпоксії, у результаті чого активуються механізми гліколізу, під впливом звільнення стресових гормонів розвивається гіперглікемія. Показано, що в умовах анаеробного гліколізу на тлі гіперглікемії в клітинах продукуються токсичні речовини, що викликають гліколізування протеїнів та нуклеїнових кислот. Разом із порушенням функції клітинних білків виникає мітохондріальна дисфункція, що призводить до енергетичного дефіциту та порушення функціонування органів. Мета дослідження: виявити провідні механізми дикарбонільного стресу, їх значення для формування критичних станів організму та визначити найбільш перспективні способи корекції для фахівців у галузі інтенсивної терапії. Матеріали та методи. Детальне вивчення результатів сучасних наукових досліджень процесів вуглеводного обміну при патологічних станах на підставі інформації, поданої в Інтернеті. Результати. Провідна роль у пошкодженні клітинних структур організму при дикарбонільному стресі належить гліоксалю та метилгліоксалю. Ці хімічні сполуки утворюються як побічні продукти анаеробного гліколізу. Збільшенню їх синтезу сприяють активація анаеробного гліколізу та гіперглікемія. Дикарбонільні сполуки вступають у хімічні реакції з амінними групами протеїнів, нуклеїнових кислот та інших біологічно активних сполук, порушуючи їх функціонування. Природна детоксикація здійснюється гліоксалазною системою за участю відновленого глутатіону, що є основним компонентом антиоксидантної системи. Прогресування окислювального стресу та поява антиоксидантного дефіциту зумовлюють збільшення тяжкості пошкоджень, що викликає підвищене утворення гліоксалю та метилгліоксалю. Профілактика дикарбонільного стресу здійснюється за допомогою збільшення потужності антиоксидантної системи, насамперед за рахунок зростання утворення відновленого глутатіону. Для нейтралізації токсичних дикарбонільних метаболітів можуть бути використані препарати, що виконують функцію «пасток». Перспективне застосування терапії, що спрямована на усунення мітохондріальної дисфункції. Висновки. Нова проблема пошкодження організму в умовах дикарбонільного стресу диктує необхідність аналізу та переоцінки численної кількості заходів інтенсивної терапії. Докладне вивчення особливостей вуглеводного обміну при різних критичних станах, включаючи визначення концентрації гліоксалю та метилгліоксалю, моніторинг рівня глікемії та кліренсу лактату в поєднанні з поверненням до оцінювання стану компенсації функції прооксидантної/антиоксидантної системи організму, є одним із перспективних напрямів наукових досліджень у клініці, що має розпочатися. Фахівці з інтенсивної терапії щоденно стикаються із ситуаціями, коли дикарбонільний стрес може виступати як один із дійсних механізмів формування органної та мультиорганної дисфункції й визначає розвиток декомпенсації життєво важливих функцій. Навчитися протистояти йому є актуальною найближчою задачею.

Folic acid deficiency increases sensitivity to DNA damage by glucose and methylglyoxal.

Type 2 diabetes (T2D) is associated with elevated frequencies of micronuclei (MNi) and other DNA damage biomarkers. Interestingly, individuals with T2D are more likely to be deficient in micronutrients (folic acid, pyridoxal-phosphate, cobalamin) that play key roles in one-carbon metabolism and maintaining genomic integrity. Furthermore, it has recently been shown that deficiencies in these nutrients, in particular folic acid leaves cells susceptible to glucose-induced DNA damage. Therefore, we sought to investigate if the B lymphoblastoid WIL2-NS cell line cultured under folic acid-deficient conditions was more sensitive to DNA damage induced by glucose, or the reactive glycolytic byproduct methylglyoxal (MGO) and subsequent advanced glycation endproduct formation. Here, we show that only WIL2-NS cultured under folic acid-deficient conditions (23 nmol/l) experience an increase in MNi frequency when exposed to high concentrations of glucose (45 mmol/l) or MGO (100 µmol/l). Furthermore, we showed aminoguanidine, a well-validated MGO and free radical scavenger was able to prevent further MNi formation in folic acid-deficient cells exposed to high glucose, which may be due to a reduction in MGO-induced oxidative stress. Interestingly, we also observed an increase in MGO and other dicarbonyl stress biomarkers in folic acid-deficient cells, irrespective of glucose concentrations. Overall, our evidence shows that folic acid-deficient WIL2-NS cells are more susceptible to glucose and/or MGO-induced MNi formation. These results suggest that individuals with T2D experiencing hyperglycemia and folic acid deficiency may be at higher risk of chromosomal instability.

Design of an activatable NIR-II nanoprobe for the in vivo elucidation of Alzheimer's disease-related variations in methylglyoxal concentrations

Clear elucidation of the changes in Alzheimer's disease (AD)-related methylglyoxal (MGO) levels in vivo is significant yet highly challenging. Fluorescence imaging in the second near-infrared region (NIR-II, 1000-1700 nm) has gained increasing attention as an observation method in living organisms, but an MGO-activatable fluorescent probe that emits in this region for in vivo brain imaging is lacking because of the existence of the blood-brain barrier (BBB). Herein, a biocompatible Fe3O4 nanoparticle (IONP)-conjugated MGO-activatable NIR-II fluorescent probe (MAM) modified with the peptide T7 (HAIYPRH) (named TM-IONP) is reported for the in situ detection of MGO in a transgenic AD mouse model. In this system, the T7 peptide enhances BBB crossing and brain accumulation by specifically targeting transferrin receptors on the BBB. Due to the MAM probe, TM-IONPs emit fluorescence in the NIR-II region and display high selectivity with an MGO detection limit of 72 nM and a 10-fold increase in the fluorescence signal. After intravenous administration, the TM-IONPs are easily delivered to the brain and pass through the BBB without intervention, and as a result, the brains of AD mice can be noninvasively imaged for the first time by the in situ detection of MGO with a 24.2-fold enhancement in NIR-II fluorescence intensity compared with wild-type mice. Thus, this MGO-activated NIR-II-emitting nanoprobe is potentially useful for early AD diagnosis in clinic.

Multifloral white honey outclasses manuka honey in methylglyoxal content: assessment of free and encapsulated methylglyoxal and anti-microbial peptides in liposomal formulation against toxigenic potential of Bacillus subtilis Subsp spizizenii strain.

The therapeutic virtues of honey no longer need to be proven. Honey, which is rich in nutrients, is an excellent nutritional food because of its many properties; however, honey has been diverted from this primary function and used in clinical research. Evidence has shown that honey still possesses unknown properties and some of these aspects have never been addressed. In this work, two bioactive compounds found in honey (methylglyoxal and antimicrobial peptides) were evaluated for their anti-Bacillus subtilis activity with particular attention to their dilution factor. Although this bacterial strain does not possess an indigenous virulence factor gene, it becomes virulent by transferring plasmids with B. thuringiensis or expression of toxins from Bordetella pertussis. As is known, methylglyoxal is a toxic electrophile present in many eukaryotic and prokaryotic cells, which is generated by enzymatic and non-enzymatic reactions. Its overexpression successfully kills bacteria by inducing membrane disruption. Also, AMPs show potent inhibitory action against Gram-positive bacteria. Because of the lack of information concerning the main ingredients of honey, the microencapsulation process was used. Both methylglyoxal (MGO) and peptide-loaded liposomes were synthesized, characterized and compared to their free forms. The liposomal formulations contained a mixture of eggPC, cholesterol, and octadecylamine and their particle sizes were measured and their encapsulation efficacy calculated. The results revealed that Algerian multifloral white honey contained higher levels of MGO compared to manuka honey, which prevented bacterial growth and free MGO was relatively less effective. In fact, MGO killed BS in the loaded form with the same bacteriostatic and bactericidal index. However, the action of AMPs was different. Indeed, the investigation into the reactivity of MGO in the solvent indicated that regardless of the level of water added, honey is active at a fixed dilution. This data introduces the notion of dilution and abolishes the concept of concentration. Moreover, the synergistic antibacterial effect of the compounds in honey was diminished by the matrix effect. The degree of liposome-bacteria-fusion and the delay effect observed could be explain by both the composition and nature of the lipids used. Finally, this study reinforces the idea that under certain conditions, the metalloproteinases in honey produce AMPs.