Showing papers on "Lactoylglutathione lyase published in 2012"

Molecular Mechanism of Heavy Metal Toxicity and Tolerance in Plants: Central Role of Glutathione in Detoxification of Reactive Oxygen Species and Methylglyoxal and in Heavy Metal Chelation

Abstract: Heavy metal (HM) toxicity is one of the major abiotic stresses leading to hazardous effects in plants. A common consequence of HM toxicity is the excessive accumulation of reactive oxygen species (ROS) and methylglyoxal (MG), both of which can cause peroxidation of lipids, oxidation of protein, inactivation of enzymes, DNA damage and/or interact with other vital constituents of plant cells. Higher plants have evolved a sophisticated antioxidant defense system and a glyoxalase system to scavenge ROS and MG. In addition, HMs that enter the cell may be sequestered by amino acids, organic acids, glutathione (GSH), or by specific metal-binding ligands. Being a central molecule of both the antioxidant defense system and the glyoxalase system, GSH is involved in both direct and indirect control of ROS and MG and their reaction products in plant cells, thus protecting the plant from HM-induced oxidative damage. Recent plant molecular studies have shown that GSH by itself and its metabolizing enzymes—notably glutathione S-transferase, glutathione peroxidase, dehydroascorbate reductase, glutathione reductase, glyoxalase I and glyoxalase II—act additively and coordinately for efficient protection against ROS- and MG-induced damage in addition to detoxification, complexation, chelation and compartmentation of HMs. The aim of this review is to integrate a recent understanding of physiological and biochemical mechanisms of HM-induced plant stress response and tolerance based on the findings of current plant molecular biology research.

Human DJ-1 and its homologs are novel glyoxalases

Abstract: Human DJ-1 is a genetic cause of early-onset Parkinson's disease (PD), although its biochemical function is unknown. We report here that human DJ-1 and its homologs of the mouse and Caenorhabditis elegans are novel types of glyoxalase, converting glyoxal or methylglyoxal to glycolic or lactic acid, respectively, in the absence of glutathione. Purified DJ-1 proteins exhibit typical Michaelis-Menten kinetics, which were abolished completely in the mutants of essential catalytic residues, consisting of cysteine and glutamic acid. The presence of DJ-1 protected mouse embryonic fibroblast and dopaminergically derived SH-SY5Y cells from treatments of glyoxals. Likewise, C. elegans lacking cDJR-1.1, a DJ-1 homolog expressed primarily in the intestine, protected worms from glyoxal-induced death. Sub-lethal doses of glyoxals caused significant degeneration of the dopaminergic neurons in C. elegans lacking cDJR-1.2, another DJ-1 homolog expressed primarily in the head region, including neurons. Our findings that DJ-1 serves as scavengers for reactive carbonyl species may provide a new insight into the causation of PD.

Exogenous Selenium Pretreatment Protects Rapeseed Seedlings from Cadmium-Induced Oxidative Stress by Upregulating Antioxidant Defense and Methylglyoxal Detoxification Systems

Abstract: The protective effect of selenium (Se) on antioxidant defense and methylglyoxal (MG) detoxification systems was investigated in leaves of rapeseed (Brassica napus cv. BINA sharisha 3) seedlings under cadmium (Cd)-induced oxidative stress. Two sets of 11-day-old seedlings were pretreated with both 50 and 100 μM Se (Na2SeO4, sodium selenate) for 24 h. Two concentrations of CdCl2 (0.5 and 1.0 mM) were imposed separately or on the Se-pretreated seedlings, which were grown for another 48 h. Cadmium stress at any levels resulted in the substantial increase in malondialdehyde and H2O2 levels. The ascorbate (AsA) content of the seedlings decreased significantly upon exposure to Cd stress. The amount of reduced glutathione (GSH) increased only at 0.5 mM CdCl2, while glutathione disulfide (GSSG) increased at any level of Cd, with concomitant decrease in GSH/GSSG ratio. The activities of ascorbate peroxidase (APX) and glutathione S-transferase (GST) increased significantly with increased concentration of Cd (both at 0.5 and 1.0 mM CdCl2), while the activities of glutathione reductase (GR) and glutathione peroxidase (GPX) increased only at moderate stress (0.5 mM CdCl2) and then decreased at 1.0 mM severe stress (1.0 mM CdCl2). Monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon exposure to any levels of Cd. Selenium pretreatment had little effect on the nonenzymatic and enzymatic components of seedlings grown under normal conditions; i.e., they slightly increased the GSH content and the activities of APX, GR, GST, and GPX. On the other hand, Se pretreatment of seedlings under Cd-induced stress showed a synergistic effect; it increased the AsA and GSH contents, the GSH/GSSG ratio, and the activities of APX, MDHAR, DHAR, GR, GPX, CAT, Gly I, and Gly II which ultimately reduced the MDA and H2O2 levels. However, in most cases, pretreatment with 50 μM Se showed better results compared to pretreatment with 100 μM Se. The results indicate that the exogenous application of Se at low concentrations increases the tolerance of plants to Cd-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.

A novel mechanism of methylglyoxal cytotoxicity in prostate cancer cells.

Abstract: Methylglyoxal is one of the most powerful glycating agents of proteins and other important cellular components and has been shown to be toxic to cultured cells. Methylglyoxal cytotoxicity appears to occur through cell-cycle arrest but, more often, through induction of apoptosis. In this study we examined whether, and through which molecular mechanism, methylglyoxal affects the growth of poorly aggressive LNCaP and invasive PC3 human prostate cancer cells, where its role has not been exhaustively investigated yet. We demonstrated that methylglyoxal is cytotoxic on LNCaP and PC3 and that such cytotoxicity occurs not via cell proliferation but apoptosis control. Moreover, we demonstrated that methylglyoxal cytotoxicity, potentiated by the silencing of its major scavenging enzyme Glyoxalase I, occurred via different apoptotic responses in LNCaP and PC3 cells that also showed a different susceptibility to this metabolite. Finally, we showed that the observed methylglyoxal apoptogenic role involved different molecular pathways, specifically mediated by methylglyoxal or methylglyoxal-derived argpyrimidine intracellular accumulation and NF-kB signaling-pathway. In particular, in LNCaP cells, methylglyoxal, through the accumulation of argpyrimidine, desensitized the key cell survival NF-kB signaling pathway, which was consistent with the modulation of NF-kB-regulated genes, triggering a mitochondrial apoptotic pathway. The results suggest that this physiological compound merits investigation as a potential chemo-preventive/-therapeutic agent, in differently aggressive prostate cancers.

Methylglyoxal mediates adipocyte proliferation by increasing phosphorylation of Akt1.

Abstract: Methylglyoxal (MG) is a highly reactive metabolite physiologically presented in all biological systems. The effects of MG on diabetes and hypertension have been long recognized. In the present study, we investigated the potential role of MG in obesity, one of the most important factors to cause metabolic syndrome. An increased MG accumulation was observed in the adipose tissue of obese Zucker rats. Cell proliferation assay showed that 5–20 µM of MG stimulated the proliferation of 3T3-L1 cells. Further study suggested that accumulated-MG stimulated the phosphorylation of Akt1 and its targets including p21 and p27. The activated Akt1 then increased the activity of CDK2 and accelerated the cell cycle progression of 3T3-L1 cells. The effects of MG were efficiently reversed by advanced glycation end product (AGE) breaker alagebrium and Akt inhibitor SH-6. In summary, our study revealed a previously unrecognized effect of MG in stimulating adipogenesis by up-regulation of Akt signaling pathway and this mechanism might offer a new approach to explain the development of obesity.

Glyoxalase-I Is a Novel Prognosis Factor Associated with Gastric Cancer Progression

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

Glyoxalase I (GLO1) is Up-regulated in Pancreatic Cancerous Tissues Compared with Related Non-cancerous Tissues

Abstract: Background Glyoxalase I (GLO1), an enzyme involved in the detoxification of methylglyoxal in the glycolysis pathway, has been found to be frequently overexpressed in various types of cancer. Recent studies showed that GLO1 is related to proliferation and apoptosis in human cancer cells. However, expression of GLO1 in pancreatic cancer (PC) has not been precisely defined. Since PC is one of the most malignant types of cancer, we investigated the levels of GLO1 in tissues from patients with PC. Materials and methods We examined the expression of GLO1 in tumors from patients with PC and adjacent normal tissues by western blotting. Results Western blotting demonstrated that GLO1 was significantly overexpressed in pancreatic cancerous tissues compared with adjacent non-cancerous tissues (n=20, p Conclusion GLO1 could be a clinically useful target in the therapy of PC.

Inhibition of Advanced Glycation End Product Formation by Pu-erh Tea Ameliorates Progression of Experimental Diabetic Nephropathy

Abstract: Accumulation of advanced glycation end products (AGEs) has been implicated in the development of diabetic nephropathy. We investigated the effects of Pu-erh tea on AGE accumulation associated with diabetic nephropathy. Although it did not affect blood glucose levels and insulin sensitivy, Pu-erh tea treatment for 8 weeks attenuated the increases in urinary albumin, serum creatinine, and mesangial matrix in db/db mice. We found that Pu-erh tea prevented diabetes-induced accumulation of AGEs and led to a decreased level of receptor for AGE expression in glomeruli. Both production and clearance of carbonyl compounds, the main precursor of AGE formation, were probably attenuated by Pu-erh tea in vivo independent of glyoxalase I expression. In vitro, HPLC assay demonstrated Pu-erh tea could trap methylglyoxal in a dose-dependent manner. Our study raises the possibility that inhibition of AGE formation by carbonyl trapping is a promising approach to prevent or arrest the progression of diabetic complications.

Potential of a γ-glutamyl-transpeptidase-stable glutathione analogue against amyloid-β toxicity.

Abstract: The antioxidant properties of glutathione (GSH) and their relevance to oxidative stress induced pathological states such as Alzheimer's disease is well-established. The utility of GSH itself as a pharmacotherapeutic agent for such disorders is limited because of the former's lability to breakdown through amide cleavage by the ubiquitous enzyme γ-glutamyl transpeptidase (γ-GT). In the present study, a GSH analogue, Ψ-GSH, where the γ-glutamylcysteine amide linkage is replaced with a ureide linkage, was synthesized. Ψ-GSH was found to be stable toward γ-GT mediated breakdown. Ψ-GSH fulfilled four cardinal properties of GSH, namely, traversing across the blood brain barrier (BBB) via the GSH active uptake machinery, replacing GSH in the glyoxalase-I mediated detoxification of methylglyoxal, protecting cells against chemical oxidative insult, and finally lowering the cytotoxicity of amyloid-β peptide. These results validate Ψ-GSH as a viable metabolically stable replacement for GSH and establish it as a potential preclinical candidate for treatment of oxidative stress mediated pathology.

Glyoxalase 1 and glyoxalase 2 activities in blood and neuronal tissue samples from experimental animal models of obesity and type 2 diabetes mellitus.

Abstract: The glyoxalase enzymes catalyse the conversion of reactive glucose metabolites into non-toxic products as a part of the cellular defence system against glycation. This study investigated changes in glyoxalase 1 and glyoxalase 2 activities and the development of diabetic complications in experimental animal models of obesity (Zucker fa/fa rats) and type 2 diabetes mellitus (Goto-Kakizaki rats). In contrast to Zucker rats, in Goto-Kakizaki rats the glyoxalase 1 activities in brain, spinal cord and sciatic nerve tissues were significantly reduced by 10, 32 and 36 %, respectively. Lower glyoxalase 1 activity in the neuronal tissues was associated with a higher blood glucose concentration and impaired endothelium-dependent relaxation to acetylcholine in aortic rings in Goto-Kakizaki rats. This study provides evidence for disturbed neuronal glyoxalase 1 activity under conditions of hyperglycaemia in the presence of impaired endothelium-dependent relaxation and cognitive function.

Methylglyoxal alters glucose metabolism and increases AGEs content in C6 glioma cells

Abstract: Methylglyoxal is a dicarbonyl compound that is physiologically produced by enzymatic and non-enzymatic reactions. It can lead to cytotoxicity, which is mainly related to Advanced Glycation End Products (AGEs) formation. Methylglyoxal and AGEs are involved in the pathogenesis of Neurodegenerative Diseases (ND) and, in these situations, can cause the impairment of energetic metabolism. Astroglial cells play critical roles in brain metabolism and the appropriate functioning of astrocytes is essential for the survival and function of neurons. However, there are only a few studies evaluating the effect of methylglyoxal on astroglial cells. The aim of this study was to evaluate the effect of methylglyoxal exposure, over short (1 and 3 h) and long term (24 h) periods, on glucose, glycine and lactate metabolism in C6 glioma cells, as well as investigate the glyoxalase system and AGEs formation. Glucose uptake and glucose oxidation to CO2 increased in 1 h and the conversion of glucose to lipids increased at 3 h. In addition, glycine oxidation to CO2 and conversion of glycine to lipids increased at 1 h, whereas the incorporation of glycine in proteins decreased at 1 and 3 h. Methylglyoxal decreased glyoxalase I and II activities and increased AGEs content within 24 h. Lactate oxidation and lactate levels were not modified by methylglyoxal exposure. These data provide evidence that methylglyoxal may impair glucose metabolism and can affect glyoxalase activity. In periods of increased methylglyoxal exposure, such alterations could be exacerbated, leading to further increases in intracellular methylglyoxal and AGEs, and therefore triggering and/or worsening ND.

Nephrotoxin-induced renal cell injury involving biochemical alterations and its prevention with antioxidant.

Abstract: Background: Although nephrotoxic agents or nephrotoxins are known to induce acute renal cell injury, their cytotoxic action is not fully elucidated. It is thus crucial to explore such a cytotoxic mechanism and the increasing volume of reports indicated a significant involvement of oxidative stress. To test this possibility, we investigated if a nephrotoxin would exert oxidative stress, leading to renal cell injury accompanied by certain biochemical alterations. We also examined if specific antioxidant might help prevent such oxidative cell injury. These studies may then help establish a prophylactic or preventive modality for renal cell injury induced by nephrotoxins. Methods: As glycerol has been commonly used for studying acute renal failure in animals, whether it would induce cellular injury was tested in renal proximal tubular OK cells in vitro . Cells were exposed to the varying concentrations of glycerol and cell number / viability was determined in 24 hours. Severity of oxidative stress was assessed by lipid peroxidation assay. Possible effects of glycerol on biochemical parameters were also examined on glyoxalase I activity and heat shock protein 90 using spectrophotometric (enzymatic) assay and Western blot analysis. Results: Glycerol (2.5%) was highly cytotoxic to OK cells, inducing 95% cell death in 24 hours. Lipid peroxidation assay indicated that nearly 3-fold greater oxidative stress was exerted by this glycerol. Concurrently, glyoxalase I activity was drastically lost by 75% and heat shock protein 90 was partially degraded following glycerol exposure. However, N-acetylcysteine, a potent glutathione-based antioxidant, was capable of almost completely preventing the glycerol-mediated adverse outcomes, such as cell death, glyoxalase I inactivation, and heat shock protein 90 degradation. Conclusions: Glycerol is cytotoxic, capable of inducing specific biochemical alterations such as inactivation of glyoxalase I and degradation of heat shock protein 90, which may reflect a breakdown of the cellular detoxification and defense systems, leading ultimately to OK cell death. Nevertheless, as N-acetylcysteine can provide full cytoprotection against such glycerol toxicity, it could be considered a prophylactic modality for nephrotoxin-induced oxidative renal cell injury and death. doi:10.4021/jocmr833w

Insights to Sequence Information of Lactoylglutathione Lyase Enzyme from Different Source Organisms

Abstract: Lactoylglutathione lyases (also known as glyoxalase I) are widely distributed enzymes among plants, fungi and bacteria. It is an enzyme that catalyzes the isomerization of hemithioacetal adducts, which are formed in a spontaneous reaction between a glutathionyl group and aldehydes such as methylglyoxal. In the present study, thirty full- length amino acid sequences of lactoylglutathione lyases from bacteria, fungi, and plants were collected and subjected to multiple sequence alignment (MSA), pattern identification, domain identification discovering individual amino acid composition, and phylogenetic tree construction. MSA revealed that one tyrosine residue were identically found in all analyzed species, two tyrosine, one arginine, one leucine, one glycine, one histidine, one phenylalanine, one proline, one aspartic acid and one glutamic acid residues were identically found in all the bacterial and fungal sources, one phenylalanine, one tyrosine, one histidine, one proline, and one glycine residues were identically found in all bacterial and plant sources while two glycine, two tyrosine, two aspartic acid and one proline residues were identically found in all plants and fungal lactoylglutathione lyases. Two major sequence clusters were constructed by phylogenetic analysis. One cluster contains ten species of fungi, five species of plant, and two species of bacteria, whereas the other one contains eight species of bacteria, four species of plant and one species of plant was outgrouped from both clusters . The amino acid composition result revealed that the average frequency of amino acid glycine is 7.86 percent that is very high in comparison to other amino acids and an average frequency of is 1.07 that is very low in all analyzed species. In addition, nine motifs which were unique for their groups were also identified.