Role of methylglyoxal and glyoxalase in the regulation of plant response to heavy metal stress.

KEY MESSAGE: Methylglyoxal and glyoxalase function a significant role in plant response to heavy metal stress. We update and discuss the most recent developments of methylglyoxal and glyoxalase in regulating plant response to heavy metal stress. Methylglyoxal (MG), a by-product of several metabolic processes, is created by both enzymatic and non-enzymatic mechanisms. It plays an important role in plant growth and development, signal transduction, and response to heavy metal stress (HMS). Changes in MG content and glyoxalase (GLY) activity under HMS imply that they may be potential biomarkers of plant stress resistance. In this review, we summarize recent advances in research on the mechanisms of MG and GLY in the regulation of plant responses to HMS. It has been discovered that appropriate concentrations of MG assist plants in maintaining a balance between growth and development and survival defense, therefore shielding them from heavy metal harm. MG and GLY regulate plant physiological processes by remodeling cellular redox homeostasis, regulating stomatal movement, and crosstalking with other signaling molecules (including abscisic acid, gibberellic acid, jasmonic acid, cytokinin, salicylic acid, melatonin, ethylene, hydrogen sulfide, and nitric oxide). We also discuss the involvement of MG and GLY in the regulation of plant responses to HMS at the transcriptional, translational, and metabolic levels. Lastly, considering the current state of research, we present a perspective on the future direction of MG research to elucidate the MG anti-stress mechanism and offer a theoretical foundation and useful advice for the remediation of heavy metal-contaminated environments in the future.

Pyramiding D-lactate dehydrogenase with the glyoxalase pathway enhances abiotic stress tolerance in plants.

Methylglyoxal is a common cytotoxic metabolite produced in plants during multiple biotic and abiotic stress. To mitigate the toxicity of MG, plants utilize the glyoxalase pathway comprising glyoxalase I (GLYI), glyoxalase II (GLYII), or glyoxalase III (GLYIII). GLYI and GLYII are the key enzymes of glyoxalase pathways that play an important role in abiotic stress tolerance. Earlier research showed that MG level is lower when both GLYI and GLYII are overexpressed together, compared to GLYI or GLYII single gene overexpressed transgenic plants. D-lactate dehydrogenase (D-LDH) is an integral part of MG detoxification which metabolizes the end product (D-lactate) of the glyoxalase pathway. In this study, two Arabidopsis transgenic lines were constructed using gene pyramiding technique: GLYI and GLYII overexpressed (G-I + II), and GLYI, GLYII, and D-LDH overexpressed (G-I + II + D) plants. G-I + II + D exhibits lower MG and D-lactate levels and enhanced abiotic stress tolerance than the G-I + II and wild-type plants. Further study explores the stress tolerance mechanism of G-I + II + D plants through the interplay of different regulators and plant hormones. This, in turn, modulates the expression of ABA-dependent stress-responsive genes like RAB18, RD22, and RD29B to generate adaptive responses during stress. Therefore, there might be a potential correlation between ABA and MG detoxification pathways. Furthermore, higher STY46, GPX3, and CAMTA1 transcripts were observed in G-I + II + D plants during abiotic stress. Thus, our findings suggest that G-I + II + D has significantly improved MG detoxification, reduced oxidative stress-induced damage, and provided a better protective mechanism against abiotic stresses than G-I + II or wild-type plants.

Lactoylglutathione promotes inflammatory signaling in macrophages through histone lactoylation.

Chronic, systemic inflammation is a pathophysiological manifestation of metabolic disorders. Inflammatory signaling leads to elevated glycolytic flux and a metabolic shift towards aerobic glycolysis and lactate generation. This rise in lactate corresponds with increased generation of lactoylLys modifications on histones, mediating transcriptional responses to inflammatory stimuli. Lactoylation is also generated through a non-enzymatic S-to-N acyltransfer from the glyoxalase cycle intermediate, lactoylglutathione (LGSH). Here, we report a regulatory role for LGSH in mediating histone lactoylation and inflammatory signaling. In the absence of the primary LGSH hydrolase, glyoxalase 2 (GLO2), RAW264.7 macrophages display significant elevations in LGSH and histone lactoylation with a corresponding potentiation of the inflammatory response when exposed to lipopolysaccharides. An analysis of chromatin accessibility shows that lactoylation is associated with more compacted chromatin than acetylation in an unstimulated state; upon stimulation, however, regions of the genome associated with lactoylation become markedly more accessible. Lastly, we demonstrate a spontaneous S-to-S acyltransfer of lactate from LGSH to CoA, yielding lactoyl-CoA. This represents the first known mechanism for the generation of this metabolite. Collectively, these data suggest that LGSH, and not intracellular lactate, is the primary driving factor facilitating histone lactoylation and a major contributor to inflammatory signaling.

Application of biochar and humic acid improves the physiological and biochemical processes of rice (Oryza sativa L.) in conferring plant tolerance to arsenic-induced oxidative stress.

Biochar (BC) and humic acid (HA) are well-documented in metal/metalloid detoxification, but their regulatory role in conferring plant oxidative stress under arsenic (As) stress is poorly understood. Therefore, we aimed at investigating the role of BC and HA (0.2 and 0.4 g kg-1 soil) in the detoxification of As (0.25 mM sodium arsenate) toxicity in rice (Oryza sativa L. cv. BRRI dhan75). Arsenic exhibited an increased lipid peroxidation, hydrogen peroxide, electrolyte leakage, and proline content which were 32, 30, 9, and 89% higher compared to control. In addition, the antioxidant defense system of rice consisting of non-enzyme antioxidants (18 and 43% decrease in ascorbate and glutathione content) and enzyme activities (23-50% reduction over control) was decreased as a result of As toxicity. The damaging effect of As was prominent in plant height, biomass acquisition, tiller number, and relative water content. Furthermore, chlorophyll and leaf area also exhibited a decreasing trend due to toxicity. Arsenic exposure also disrupted the glyoxalase system (23 and 33% decrease in glyoxalase I and glyoxalase II activities). However, the application of BC and HA recovered the reactive oxygen species-induced damages in plants, upregulated the effectiveness of the ascorbate-glutathione pool, and accelerated the activities of antioxidant defense and glyoxalase enzymes. These positive roles of BC and HA ultimately resulted in improved plant characteristics with better plant-water status and regulated proline content that conferred As stress tolerance in rice. So, it can be concluded that BC and HA effectively mitigated As-induced physiology and oxidative damage in rice plants. Therefore, BC and HA could be used as potential soil amendments in As-contaminated rice fields.

Association between GLO1 variants and gestational diabetes mellitus susceptibility in a Chinese population: a preliminary study.

Background: Glyoxalase 1 (GLO1) plays a crucial role in defending against glycation. Single nucleotide polymorphism (SNP) variants in the GLO1 gene may affect gene expression and alter enzyme activity. However, there have been limited studies evaluating the association between GLO1 and diabetes, especially gestational diabetes mellitus (GDM). Therefore, this study is the first to explore the association of GLO1 SNPs and GDM risk. Methods: The study included a total of 500 GDM patients and 502 control subjects. The SNPscan™ genotyping assay was used to genotype rs1781735, rs4746 and rs1130534. To assess the disparities in genotype, allele, and haplotype distributions and their correlation with GDM risk, the independent sample t-test, logistic regression, and chi-square test were employed during the data processing phase. Furthermore, one-way ANOVA was conducted to determine the differences in genotype and blood glucose and methylglyoxal(MG) levels. Results: Significant differences were observed in prepregnancy body mass index (pre-BMI), age, systolic blood pressure (SBP), diastolic blood pressure (DBP), and parity between GDM and healthy subjects (P < 0.05). After adjusting for these factors, GLO1 rs1130534 TA remained associated with an increased risk of GDM (TA vs. TT + AA: OR = 1.320; 95% CI: 1.008-1.728; P = 0.044), especially in the pre-BMI ≥ 24 subgroup (TA vs. TT + AA: OR = 2.424; 95% CI: 1.048-5.607; P = 0.039), with fasting glucose levels being significantly elevated in the TA genotype compared to the TT genotype (P < 0.05). Conversely, the GLO1 rs4746 TG was associated with a decreased risk of GDM (TG vs. TT: OR = 0.740; 95% CI: 0.548-0.999; P = 0.049; TG vs. TT + GG: OR = 0.740; 95% CI: 0.548-0.998; P = 0.048). Additionally, the haplotype T-G-T of rs1781735, rs4746 and rs1130534 was associated with a decreased risk of GDM among individuals with a pre-BMI ≥ 24 (OR = 0.423; 95% CI: 0.188-0.955; P = 0.038). Furthermore, the rs1781735 GG genotype was found to be more closely related to maternal MG accumulation and neonatal weight gain (P < 0.05). Conclusion: Our findings suggested that GLO1 rs1130534 was associated with an increased susceptibility to GDM and higher blood glucose levels, but GLO1 rs4746 was associated with a decreased risk of GDM. The rs1781735 has been associated with the accumulation of maternal MG and subsequent weight gain in neonates.

MiR-205-3p suppresses bladder cancer progression via GLO1 mediated P38/ERK activation.

MicroRNAs (miRNAs) have been reported to serve as potential biomarkers in bladder cancer and play important roles in cancer progression. This study aimed to investigate the biological role of miR-205-3p in bladder cancer. We showed that miR-205-3p was significantly down-regulated in bladder cancer tissues and cells. Moreover, overexpression of miR-205-3p inhibited bladder cancer progression in vitro. Then we confirmed that GLO1, a downstream target of miR-205-3p, mediated the effect of miR-205-3p on bladder cancer cells. In addition, we found that miR-205-3p inhibits P38/ERK activation through repressing GLO1. Eventually, we confirmed that miR-205-3p inhibits the occurrence and progress of bladder cancer by targeting GLO1 in vivo by nude mouse tumorigenesis and immunohistochemistry. In a word, miR-205-3p inhibits proliferation and metastasis of bladder cancer cells by activating the GLO1 mediated P38/ERK signaling pathway and that may be a potential therapeutic target for bladder cancer.

Proline-mediated activation of glyoxalase II improve methylglyoxal detoxification in Oryza sativa L. under chromium injury: Clarification via vector analysis of enzymatic activities and gene expression.

Environmental factors affect plants in several ways including the excessive accumulation of methylglyoxal (MG), resulting in dysfunctions of many biological processes. Exogenous proline (Pro) application is one of the successful strategies to increase plant tolerance against various environmental stresses, including chromium (Cr). This study highlights the alleviation role of exogenous Pro on MG detoxification in rice plants induced by Cr(Vl) through modifying the expression of glyoxalase I (Gly I)- and glyoxalase II (Gly II)-related genes. The MG content in rice roots was significantly reduced by Pro application under Cr(VI) stress, however, there was little effect on the MG content in shoots. In this connection, the vector analysis was used to compare the involvement of Gly l and Gly II on MG detoxification in 'Cr(VI)' and 'Pro+Cr(VI)' treatments. Results exhibited that vector strength in rice roots increased with an increase in Cr concentrations, while there was a negligible difference in the shoots. The comparative analysis demonstrated that the vector strengths in roots under 'Pro+Cr(VI)' treatments were higher than 'Cr(VI)' treatments, suggesting that Pro improved Gly II activity more efficiently to reduce MG content in roots. Calculation of the gene expression variation factors (GEFs) indicated a positive effect of Pro application on the expression of Gly I and Gly ll-related genes, wherein a stronger impact was in roots than the shoots. Together, the vector analysis and gene expression data reveal that exogenous Pro chiefly improved Gly ll activity in rice roots which subsequently enhanced MG detoxification under Cr(VI) stress.

Overexpressing glyoxalase 1 attenuates acute hyperglycemia-exacerbated neurological deficits of ischemic stroke in mice.

Stress-induced hyperglycemia (SIH) is associated with poor functional recovery and high mortality in patients with acute ischemic stroke (AIS). However, intensive controlling of blood glucose by using insulin was not beneficial in patients with AIS and acute hyperglycemia. This study investigated the therapeutic effects of the overexpression of glyoxalase I (GLO1), a detoxifying enzyme of glycotoxins, on acute hyperglycemia-aggravated ischemic brain injury.  In the present study, adeno-associated viral (AAV)-mediated GLO1 overexpression reduced infarct volume and edema level but did not improve neurofunctional recovery in the mice with middle cerebral artery occlusion (MCAO). AAV-GLO1 infection significantly enhanced neurofunctional recovery in the MCAO mice with acute hyperglycemia but not in the mice with normoglycemia. Methylglyoxal (MG)-modified proteins expression significantly increased in the ipsilateral cortex of the MCAO mice with acute hyperglycemia. AAV-GLO1 infection attenuated the induction of MG-modified proteins, ER stress formation, and caspase 3/7 activation in MG-treated Neuro-2A cells, and reductions in synaptic plasticity and microglial activation were mitigated in the injured cortex of the MCAO mice with acute hyperglycemia. Treatment with ketotifen, a potent GLO1 stimulator, after surgery, alleviated neurofunctional deficits and ischemic brain damage in the MCAO mice with acute hyperglycemia.  Altogether, our data substantiate that, in ischemic brain injury, GLO1 overexpression can alleviate pathologic alterations caused by acute hyperglycemia. Upregulation of GLO1 may be a therapeutic strategy for alleviating SIH-aggravated poor functional outcomes in patients with AIS.

Metformin inhibits methylglyoxal-induced retinal pigment epithelial cell death and retinopathy via AMPK-dependent mechanisms: Reversing mitochondrial dysfunction and upregulating glyoxalase 1.

Diabetic retinopathy (DR) is a major cause of blindness in adult, and the accumulation of advanced glycation end products (AGEs) is a major pathologic event in DR. Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is a precursor of AGEs. Although the therapeutic potential of metformin for retinopathy disorders has recently been elucidated, possibly through AMPK activation, it remains unknown how metformin directly affects the MGO-induced stress response in retinal pigment epithelial cells. Therefore, in this study, we compared the effects of metformin and the AMPK activator A769662 on MGO-induced DR in mice, as well as evaluated cytotoxicity, mitochondrial dynamic changes and dysfunction in ARPE-19 cells. We found MGO can induce mitochondrial ROS production and mitochondrial membrane potential loss, but reduce cytosolic ROS level in ARPE-19 cells. Although these effects of MGO can be reversed by both metformin and A769662, we demonstrated that reduction of mitochondrial ROS production rather than restoration of cytosolic ROS level contributes to cell protective effects of metformin and A769662. Moreover, MGO inhibits AMPK activity, reduces LC3II accumulation, and suppresses protein and gene expressions of MFN1, PGC-1α and TFAM, leading to mitochondrial fission, inhibition of mitochondrial biogenesis and autophagy. In contrast, these events of MGO were reversed by metformin in an AMPK-dependent manner as evidenced by the effects of compound C and AMPK silencing. In addition, we observed an AMPK-dependent upregulation of glyoxalase 1, a ubiquitous cellular enzyme that participates in the detoxification of MGO. In intravitreal drug-treated mice, we found that AMPK activators can reverse the MGO-induced cotton wool spots, macular edema and retinal damage. Functional, histological and optical coherence tomography analysis support the protective actions of both agents against MGO-elicited retinal damage. Metformin and A769662 via AMPK activation exert a strong protection against MGO-induced retinal pigment epithelial cell death and retinopathy. Therefore, metformin and AMPK activator can be therapeutic agents for DR.

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

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

The thioesterase APT1 is a bidirectional-adjustment redox sensor.

The adjustment of cellular redox homeostasis is essential in when responding to environmental perturbations, and the mechanism by which cells distinguish between normal and oxidized states through sensors is also important. In this study, we found that acyl-protein thioesterase 1 (APT1) is a redox sensor. Under normal physiological conditions, APT1 exists as a monomer through S-glutathionylation at C20, C22 and C37, which inhibits its enzymatic activity. Under oxidative conditions, APT1 senses the oxidative signal and is tetramerized, which makes it functional. Tetrameric APT1 depalmitoylates S-acetylated NAC (NACsa), and NACsa relocates to the nucleus, increases the cellular glutathione/oxidized glutathione (GSH/GSSG) ratio through the upregulation of glyoxalase I expression, and resists oxidative stress. When oxidative stress is alleviated, APT1 is found in monomeric form. Here, we describe a mechanism through which APT1 mediates a fine-tuned and balanced intracellular redox system in plant defence responses to biotic and abiotic stresses and provide insights into the design of stress-resistant crops.

Supplementation with Ascophyllum nodosum extracts mitigates arsenic toxicity by modulating reactive oxygen species metabolism and reducing oxidative stress in rice.

Ascophyllum nodosum extract (ANE) is considered as an effective source of biostimulants that have the potential of ameliorating the negative impact of different abiotic stresses in plants. Considering the growth-promoting ability and other regulatory roles of ANE, the present investigation was executed to evaluate the role of ANE in conferring arsenic (As) tolerance in rice (Oryza sativa L. cv. BRRI dhan89). Rice seedlings (35-d-old) were exposed to two doses of sodium arsenate (As1 - 50 mg As kg-1 soil; As2 - 100 mg As kg-1 soil) at 25 days after transplanting through irrigation, whereas only water was applied to the control. Foliar application of 0.1% ANE was also supplemented under control as well as As-stressed conditions at 7 days intervals for 5 times. Arsenic-induced oxidative stress was evident through a sharp increase in lipid peroxidation, hydrogen peroxide, methylglyoxal, and electrolyte leakage in the As-treated plants. As a consequence, plant growth and biomass, leaf relative water content, as well as yield attributes were reduced noticeably. On the other hand, ANE supplemented plants accumulated enhanced levels of ascorbate and glutathione, their redox balance, and the activities of antioxidant and glyoxalase enzymes viz. ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, catalase, glutathione peroxidase, and activities of glyoxalase I and glyoxalase II, respectively. Furthermore, relative water content, plant growth, yield attributes and yield were increased in the As-treated rice plants with ANE supplementation. The results reflected that foliar spray with ANE alleviated As-induced oxidative stress in rice plants by modulating the antioxidative defense and glyoxalase system.

Genome-Wide Identification and Functional Characterization of Stress Related Glyoxalase Genes in Brassica napus L.

Rapeseed (Brassica napus L.) is not only one of the most important oil crops in the world, but it is also an important vegetable crop with a high value nutrients and metabolites. However, rapeseed is often severely damaged by adverse stresses, such as low temperature, pathogen infection and so on. Glyoxalase I (GLYI) and glyoxalase II (GLYII) are two enzymes responsible for the detoxification of a cytotoxic metabolite methylglyoxal (MG) into the nontoxic S-D-lactoylglutathione, which plays crucial roles in stress tolerance in plants. Considering the important roles of glyoxalases, the GLY gene families have been analyzed in higher plans, such as rice, soybean and Chinese cabbage; however, little is known about the presence, distribution, localizations and expression of glyoxalase genes in rapeseed, a young allotetraploid. In this study, a total of 35 BnaGLYI and 30 BnaGLYII genes were identified in the B. napus genome and were clustered into six and eight subfamilies, respectively. The classification, chromosomal distribution, gene structure and conserved motif were identified or predicted. BnaGLYI and BnaGLYII proteins were mainly localized in chloroplast and cytoplasm. By using publicly available RNA-seq data and a quantitative real-time PCR analysis (qRT-PCR), the expression profiling of these genes of different tissues was demonstrated in different developmental stages as well as under stresses. The results indicated that their expression profiles varied among different tissues. Some members are highly expressed in specific tissues, BnaGLYI11 and BnaGLYI27 expressed in flowers and germinating seed. At the same time, the two genes were significantly up-regulated under heat, cold and freezing stresses. Notably, a number of BnaGLY genes showed responses to Plasmodiophora brassicae infection. Overexpression of BnGLYI11 gene in Arabidopsis thaliana seedlings confirmed that this gene conferred freezing tolerance. This study provides insight of the BnaGLYI and BnaGLYII gene families in allotetraploid B. napus and their roles in stress resistance, and important information and gene resources for developing stress resistant vegetable and rapeseed oil.

Role of lactoyl-glutathione lyase of Salmonella in the colonization of plants under salinity stress.

Salmonella, a foodborne human pathogen, can colonize the members of the kingdom Plantae. However, the basis of the persistence of Salmonella in plants is largely unknown. Plants encounter various biotic and abiotic stress agents in soil. We conjectured that methylglyoxal (MG), one of the common metabolites that accumulate in plants during both biotic and abiotic stress, plays a role in regulating the plant-Salmonella interaction. The interaction of Salmonella Typhimurium with plants under salinity stress was investigated. It was observed that wild-type Salmonella Typhimurium can efficiently colonize the root, but mutant bacteria lacking MG detoxifying enzyme, lactoyl-glutathione lyase (Lgl), showed lower colonization in roots exclusively under salinity stress. This colonization defect is due to the poor viability of the mutated bacterial strains under these conditions. This is the first report to prove the role of MG-detoxification genes in the colonization of stressed plants and highlights the possible involvement of metabolic genes in the evolution of the plant-associated life of Salmonella.

Nitric oxide and spermidine alleviate arsenic-incited oxidative damage in Cicer arietinum by modulating glyoxalase and antioxidant defense system.

Anthropogenic activities such as mining, fossil fuel combustion, fertilisers and pesticides utilisation in agriculture, metallurgic processes and disposal of industrial wastes have contributed an exponential rise in arsenic content in environment. The present paper deals with arsenate (AsV) incited stress in chickpea (Cicer arietinum L.) plants and its alleviation through the application of nitric oxide (NO) and spermidine (SPD). The exposure of C. arietinum to AsV reduced seedling length, biomass, relative water content and biochemical constituents. All the above-mentioned parameters were escalated when sodium nitroprusside (SNP) or SPD were utilised alone or in combination with AsV. The electrolyte leakage and malondialdehyde content were increased in chickpea treated with AsV, but reduced in combine treatment (As+SNP+SPD). In chickpea seedlings, 89.4, 248.4 and 333.3% stimulation were recorded in sugar, proline and glycine betaine contents, respectively, with As+SNP+SPD treatment in comparison to control. SNP and SPD modulated function of glyoxalase enzymes by which methylglyoxal (MG) was significantly detoxified in C. arietinum . Maximum reduction 45.2% was observed in MG content in SNP+SPD treatment over AsV stress. Hence, synergistic application of NO and SPD protected chickpea plants against AsV-generated stress by strengthening the antioxidant defence and glyoxalase system, which helped in regulation of biochemical pathways.

Loss of glyoxalase 2 alters the glucose metabolism in zebrafish.

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

H3K27 acetylation activated long noncoding RNA RP11-162G10.5 promotes breast cancer progression via the YBX1/GLO1 axis.

PURPOSE: Long noncoding RNAs (lncRNAs) orchestrate critical roles in human tumorigenesis. However, the regulatory mechanism of lncRNAs in tissue-specific expressions in breast cancer (BC) remains poorly understood. This study aims to investigate lncRNA role and mechanisms in BC. METHODS: RNA sequencing was used to explore differentially expressed lncRNAs in BC and adjacent tissues. H3K27 acetylation (H3K27ac) chromatin immune-precipitation sequencing (ChIP-seq) data of BC cells from the GEO dataset (GSE85158) was retrieved to identify the H3K27ac activated lncRNAs that were involved in tumorigenesis. RP11-162G10.5 was selected as the target lncRNA for further functional and mechanism study. RESULTS: In this study, we identified a novel lncRNA RP11-162G10.5, whose overexpression was specifically driven by H3K27ac in luminal breast cancer. And increased RP11-162G10.5 in BC is correlated with poor patient outcomes. RP11-162G10.5 promotes tumor cell proliferation in vitro and in vivo. Mechanistically, RP11-162G10.5 recruits transcriptional factor YBX1 to the GLO1 promoter, consequently activating GLO1 transcription to modulate the progression of BC. CONCLUSIONS: Our findings suggest that the histone modification-activated lncRNA contributes to the oncogenesis of BC. Also, our data reveal a role for RP11-162G10.5 in BC tumorigenesis and may supply a strategy for targeting the RP11-162G10.5 as a potential biomarker and a therapeutic target for breast cancer patients.

Role of glyoxalase I and II in somatic and spermatogenic testicular cells during the postnatal development of the domestic cat.

Like humans, many felid species suffer from teratozoospermia and frequently produce low numbers of normal spermatozoa. Male fertility can be affected by oxidative and dicarbonyl stress. Because of the high level of glycolytic activity in testes, reactive dicarbonyl metabolites may arise as side-products of glycolysis; their generation is further promoted by oxidative stress. Alpha-oxoaldehydes, including methylglyoxal (MG), are reactive dicarbonyl metabolites and substrates for the formation of advanced glycation end products. Elevated levels of both may lead to dicarbonyl stress and cause cellular dysfunction. However, MG and other α-oxoaldehydes can be converted to less dangerous molecules via the glyoxalase pathway. In this pathway, α-oxoaldehydes react with glutathione (GSH), forming a thioacetal, which becomes metabolized by glyoxalase I (GLO I) to S-D-lactoyl-glutathione (SLG). Glyoxalase II (GLO II) converts SLG to d-lactate upon the release of GSH. Nothing is known about the glyoxalase system in the feline testis and its capacity to mitigate an excess of dicarbonyl metabolites. To study whether GLO I and GLO II are present and have a specific function in the testis of the domestic cat, the gene expression of both enzymes were analyzed in testis samples of different developmental stages (prepubertal, pubertal, postpubertal). Furthermore, the presence of GLO I and GLO II proteins was investigated via immunohistochemistry. The GLO I gene expression does not change between developmental stages. Immunohistochemistry revealed strong signals for GLO I in the cytoplasm and nuclei of Sertoli and Leydig cells during all developmental stages. GLO I was described as catalyzing the rate-limiting step in the glyoxalase pathway. This implies a function on the part of this enzyme of sustaining the homeostasis of somatic testicular cells. For GLO II, we observed stage-dependent mRNA expression, which was significantly increased after puberty. In accordance with this observation, clear immunohistochemical GLO II signals were observed in nuclei of individual germ cells. The most intense signals were visible in spermatocytes. The different localizations of the strong GLO I and GLO II signals indicate that GLO II, in addition to the classical glyoxalase pathway, may have additional functions in meiotic germ cells, for example, providing lactate as an energy substrate and/or GSH as an antioxidant. Moreover, protein functions may be modulated via S-glutathionylation.

Viridiplantae-specific GLXI and GLXII isoforms co-evolved and detoxify glucosone in planta.

Reactive carbonyl species (RCS) such as methylglyoxal (MGO) and glyoxal (GO) are highly reactive, unwanted side-products of cellular metabolism maintained at harmless intracellular levels by specific scavenging mechanisms.MGO and GO are metabolized through the glyoxalase (GLX) system, which consists of two enzymes acting in sequence, GLXI and GLXII. While plant genomes encode a number of different GLX isoforms, their specific functions and how they arose during evolution are unclear. Here, we used Arabidopsis (Arabidopsis thaliana) as a model species to investigate the evolutionary history of GLXI and GLXII in plants and whether the GLX system can protect plant cells from the toxicity of RCS other than MGO and GO. We show that plants possess two GLX systems of different evolutionary origins and with distinct structural and functional properties. The first system is shared by all eukaryotes, scavenges MGO and GO, especially during seedling establishment, and features Zn2+-type GLXI proteins with a metal cofactor preference that were present in the last eukaryotic common ancestor. GLXI and GLXII of the second system, featuring Ni2+-type GLXI, were acquired by the last common ancestor of Viridiplantae through horizontal gene transfer from proteobacteria and can together metabolize keto-D-glucose (KDG, glucosone), a glucose-derived RCS, to D-gluconate. When plants displaying loss-of-function of a Viridiplantae-specific GLXI were grown in KDG, D-gluconate levels were reduced to 10%-15% of those in the wild type, while KDG levels showed an increase of 48%-67%. In contrast to bacterial GLXI homologs, which are active as dimers, plant Ni2+-type GLXI proteins contain a domain duplication, are active as monomers, and have a modified second active site. The acquisition and neofunctionalization of a structurally, biochemically, and functionally distinct GLX system indicates that Viridiplantae are under strong selection to detoxify diverse RCS.

A glutathione-independent DJ-1/PfpI domain-containing tomato glyoxalaseIII2, SlGLYIII2, confers enhanced tolerance under salt and osmotic stresses.

In plants, glyoxalase enzymes are activated under stress conditions to mitigate the toxic effects of hyperaccumulated methylglyoxal (MG), a highly reactive carbonyl compound. Until recently, a glutathione-dependent bi-enzymatic pathway involving glyoxalase I (GLYI) and glyoxalase II (GLYII) was considered the primary MG-detoxification system. Recently, a new glutathione-independent glyoxalase III (GLYIII) mediated direct route was also reported in plants. However, the physiological significance of this new pathway remains to be elucidated across plant species. This study identified the full complement of 22 glyoxalases in tomato. Based on their strong induction under multiple abiotic stresses, SlGLYI4, SlGLYII2 and SlGLYIII2 were selected candidates for further functional characterisation. Stress-inducible overexpression of both glutathione-dependent (SlGLYI4 + SlGLYII2) and independent (SlGLYIII2) pathways led to enhanced tolerance in both sets of transgenic plants under abiotic stresses. However, SlGLYIII2 overexpression (OE) plants outperformed the SlGLYI4 + SlGLYII2 OE counterparts for their stress tolerance under abiotic stresses. Further, knockdown of SlGLYIII2 resulted in plants with exacerbated stress responses than those silenced for both SlGLYI4 and SlGLYII2. The superior performance of SlGLYIII2 OE tomato plants for better growth and yield under salt and osmotic treatments could be attributed to better GSH/GSSG ratio, lower reactive oxygen species levels, and enhanced antioxidant potential, indicating a prominent role of GLYIII MG-detoxification pathway in abiotic stress mitigation in this species.