Methylglyoxal induces DNA crosslinks in ECV304 cells via a reactive oxygen species-independent protein carbonylation pathway

Methylglyoxal disrupts the functionality of rat liver mitochondria

Methylglyoxal (MG) is a reactive metabolite derived from different physiological pathways. Its production can be harmful to cells via glycation reactions of lipids, DNA, and proteins. But, the effects of MG on mitochondrial functioning and bioenergetic responses are still elusive. Then, the effects of MG on key parameters of mitochondrial functionality were examined here. Isolated rat liver mitochondria were exposed to 0.1-10 mM of MG to determine its toxicity in the mitochondrial viability, membrane potential (Δψm), swelling and the superoxide (O2•-) production. Besides, mitochondrial oxidative phosphorylation parameters were analyzed by high-resolution respiratory (HRR) assay. In this set of experiments, routine state, PM state (pyruvate/malate), oxidative phosphorylation (OXPHOS), LEAK respiration, electron transport system (ETS) and oxygen residual (ROX) states were evaluated. HRR showed that PM state, OXPHOS CI-Linked, LEAK respiration, ETS CI/CII-Linked and ETS CII-Linked/ROX were significantly inhibited by MG exposure. MG also inhibited the complex II activity, and decreased Δψm and the viability of mitochondria. Taken together, our data indicates that MG is an inductor of mitochondrial dysfunctions and impairs important steps of respiratory chain, effects that can alter bioenergetics responses.

Diet and Obesity-Induced Methylglyoxal Production and Links to Metabolic Disease

The obesity rate in the United States is 42.4% and has become a national epidemic. Obesity is a complex condition that is influenced by socioeconomic status, ethnicity, genetics, age, and diet. Increased consumption of a Western diet, one that is high in processed foods, red meat, and sugar content, is associated with elevated obesity rates. Factors that increase obesity risk, such as socioeconomic status, also increase consumption of a Western diet because of a limited access to healthier options and greater affordability of processed foods. Obesity is a public health threat because it increases the risk of several pathologies, including atherosclerosis, diabetes, and cancer. The molecular mechanisms linking obesity to disease onset and progression are not well understood, but a proposed mechanism is physiological changes caused by altered lipid peroxidation, glycolysis, and protein metabolism. These metabolic pathways give rise to reactive molecules such as the abundant electrophile methylglyoxal (MG), which covalently modifies nucleic acids and proteins. MG-adducts are associated with obesity-linked pathologies and may have potential for biomonitoring to determine the risk of disease onset and progression. MG-adducts may also play a role in disease progression because they are mutagenic and directly impact protein stability and function. In this review, we discuss how obesity drives metabolic alterations, how these alterations lead to MG production, the association of MG-adducts with disease, and the potential impact of MG-adducts on cellular function.

Nerolidol inhibits proliferation of leiomyoma cells via reactive oxygen species-induced DNA damage and downregulation of the ATM/Akt pathway

Nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol), a sesquiterpene alcohol present in aromatic essential oils of numerous plants, has been reported to possess anticancer activity. The potential therapeutic effect of nerolidol on uterine fibroids (UF), the most common benign tumor of the uterus worldwide, is unknown. In this study, we examined the anti-UF potential of nerolidol in ELT3 cells, a rat leiomyoma cell line widely used as an in vitro model, to identify the potential therapeutic agents for UF. We observed that treatment with cis- or trans-nerolidol inhibited cell proliferation in a dose-dependent manner and induced cell cycle arrest in the G1 phase, which was accompanied by reduction in Akt phosphorylation and downregulation of cyclin D1, cyclin-dependent kinase 4 (CDK4), and CDK6 protein expression. The proliferation-inhibiting activity of nerolidol correlated with the generation of intracellular reactive oxygen species (ROS), which was suppressed by N-acetyl-l-cysteine, a ROS inhibitor. Nerolidol treatment also increased the percentage of cells for which tail moment could be calculated using an alkaline comet assay, and induced p-γH2AX^ser139 expression, which indicated induction of DNA damage. We also observed downregulation of ATM and its phosphorylation after nerolidol treatment; furthermore, treatment with KU-55933, an ATM kinase inhibitor, mimicked the inhibitory effects of nerolidol treatment on cell proliferation and Akt phosphorylation. In conclusion, nerolidol displayed anti-UF activity in a leiomyoma cell model via ROS-induced DNA damage and G1 phase cell cycle arrest by inhibiting the expression and activation of the ATM/Akt pathway. Our data suggests that nerolidol is a potential therapeutic agent for UF.

Molecular docking and dynamic studies of a potential therapeutic target inhibiting glyoxalase system: Metabolic action of the 3, 3 '- [3- (5-chloro-2-hydroxyphenyl) -3-oxopropane-1, 1-diyl] - Bis-4-hydroxycoumarin leads overexpression of the intracellular level of methylglyoxal and induction of a pro-apoptotic phenomenon in a hepatocellular carcinoma model

Methylglyoxal is a dicarbonyl compound recruited as a potential cytotoxic marker, initially presents in cells and considered as a metabolite of the glycolytic pathway. Our aim is to demonstrate the inhibitory effect of 3, 3'-[3-(5-chloro-2-hydroxyphenyl)-3-oxopropane-1, 1-diyl] Bis (4-hydroxycoumarin) on the glyoxalase system, and indirectly its anticancer activity. The docking of OT-55 was conducted by using Flexible docking protocol, ChiFlex and libdock tools inside the active site of Glo-I indicated that both hydrogen bonding and hydrophobic interactions contributed significantly in establishing potent binding with the active site which is selected as a strong inhibitor with high scoring values and maximum Gibbs free energy. Coumarin-liposome formulation was characterized and evaluated in vivo against chemically induced hepatocarcinoma in Wistar rats. After Diethylnitrosamine (DEN) induction, microscopic assessment was realized; precancerous lesions were developed showing an increase of both tumor-associated lymphocyte and multiple tumor acini supported by the blood investigation. Our finding also suggested a preferential uptake of liposomes respectively in liver, kidney, lung, brain and spleen in the DEN-treated animals. OT-55 has also been shown to inhibit the activity of Glo-I in vitro as well as in DEN-treated rats. An abnormal high level of MGO of up to 50% was recorded followed by a reduction in glucose consumption and lactate dehydrogenase production validated in the positive control. MGO generates apoptosis as depicted by focal hepatic lesions. Also, no deleterious effects in the control group were observed after testing our coumarin but rather a vascular reorganization leading to nodular regenerative hyperplasia. Involved in the detoxification process, liver GSH is restored in intoxicated rats, while no changes are seen between controls. At the endothelial cell, OT-55 appears to modulate the release of NO only in the DEN-treated group. OT-55 would behave both as an anticancer agent but also as an angiogenic factor regarding results obtained.

Wound Healing Activity of the Essential Oil of Bursera morelensis, in Mice

Bursera morelensis is used in Mexican folk medicine to treat wounds on the skin. It is an endemic tree known as “aceitillo”, and the antibacterial and antifungal activity of its essential oil has been verified; it also acts as an anti-inflammatory. All of these reported biological activities make the essential oil of B. morelensis a candidate to accelerate the wound-healing process. The objective was to determine the wound-healing properties of B. morelensis’ essential oil on a murine model. The essential oil was obtained by hydro-distillation, and the chemical analysis was performed by gas chromatography-mass spectrometry (GC-MS). In the murine model, wound-healing efficacy (WHE) and wound contraction (WC) were evaluated. Cytotoxic activity was evaluated in vitro using peritoneal macrophages from BALB/c mice. The results showed that 18 terpenoid-type compounds were identified in the essential oil. The essential oil had remarkable WHE regardless of the dose and accelerated WC and was not cytotoxic. In vitro tests with fibroblasts showed that cell viability was dose-dependent; by adding 1 mg/mL of essential oil (EO) to the culture medium, cell viability decreased below 80%, while, at doses of 0.1 and 0.01 mg/mL, it remained around 90%; thus, EO did not intervene in fibroblast proliferation, but it did influence fibroblast migration when wound-like was done in monolayer cultures. The results of this study demonstrated that the essential oil was a pro-wound-healing agent because it had good healing effectiveness with scars with good tensile strength and accelerated repair. The probable mechanism of action of the EO of B. morelensis, during the healing process, is the promotion of the migration of fibroblasts to the site of the wound, making them active in the production of collagen and promoting the remodeling of this collagen.

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

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

CYP450-mediated mitochondrial ROS production involved in arecoline N-oxide-induced oxidative damage in liver cell lines

BACKGROUND

IARC has classified the betel nut as a human environmental carcinogen. Previous studies have found that arecoline (AR) is the major alkaloid present in the saliva of betel quid chewers. Saliva contains a large content of AR which has been further shown to cause mutation of oral mucosa cells, resulting in oral cancer. Whereas, to date, there are only few studies reported the hepatotoxicity associated with arecoline and betel nut chewing. Therefore, the main purpose of this study was to determine the toxic effects of AR and its oxidative metabolite, arecoline N-oxide (ARNO), in normal liver cell lines.

METHODS

The cytotoxic, genotoxic, and mutagenic effects were detected by crystal violet staining, alkaline comet assay, and Salmonella mutagenicity test, respectively. Measurement of intracellular reactive oxygen species (ROS) generation was determined using the H2-DCFDA assay.

RESULTS

Our results demonstrated that ARNO exerted higher cytotoxicity, DNA damage, and mutagenicity than its parent compound arecoline in liver cells. Antioxidants, such as N-acetylcysteine, Trolox, and penicillamine, strongly protected liver cells from ARNO-induced DNA damage and ROS production. Furthermore, co-treatment with Mito-TEMPO also effectively blocked ARNO-induced ROS production in liver cells. Besides antioxidants, co-treatment with 1-aminobenzotriazole and methimazole nearly completely suppressed ARNO-induced ROS production in liver cells.

CONCLUSIONS

Our data suggest that arecoline ingested from the habit of chewing betel quid can be primarily oxidized to ARNO, thereby enhancing its toxicity through increased ROS production. Considering the excellent protective effects of both mitochondria-targeted antioxidant and CYP450 inhibitor on ARNO-induced ROS production in liver cells, mitochondria CYP450-mediated metabolism of ARNO may be a key mechanism. Collectively, our results provide novel cellular evidence for the positive connection between habitual betel quid chewing and the risk for liver damage.

Electronic cigarette: A recent update of its toxic effects on humans

Electronic cigarettes (e-cigarettes), battery-powered and liquid-vaporizing devices, were invented to replace the conventional cigarette (c-cigarette) smoking for the sake of reducing the adverse effects on multiple organ systems that c-cigarettes have induced. Although some of the identified harmful components in e-cigarettes were alleged to be measured in lower quantity than those in c-cigarettes, researchers unveiled that the toxic effects of e-cigarettes should not be understated. This review is sought for an attempt to throw light on several typical types of e-cigarette components (tobacco-specific nitrosamines, carbonyl compounds, and volatile organic compounds) by revealing their possible impacts on human bodies through different action mechanisms characterized by alteration of specific biomarkers on cellular and molecular levels. In addition, this review is intended to draw the limelight that like c-cigarettes, e-cigarettes could also be accompanied with toxic effects on whole human body, which are especially apparent on respiratory system. From head to foot, from physical aspect to chemical aspect, from genotype to phenotype, potential alterations will take place upon the intake of the liquid aerosol.

Healthy brain aging: Interplay between reactive species, inflammation and energy supply

Brains' high energy expenditure with preferable utilization of glucose and ketone bodies, defines the specific features of its energy homeostasis. The extensive oxidative metabolism is accompanied by a concomitant generation of high amounts of reactive oxygen, nitrogen, and carbonyl species, which will be here collectively referred to as RONCS. Such metabolism in combination with high content of polyunsaturated fatty acids creates specific problems in maintaining brains' redox homeostasis. While the levels of products of interaction between RONCS and cellular components increase slowly during the first two trimesters of individuals' life, their increase is substantially accelerated towards the end of life. Here we review the main mechanisms controlling the redox homeostasis of the mammalian brain, their age-dependencies as well as their adaptive potential, which might turn out to be much higher than initially assumed. According to recent data, the organism seems to respond to the enhancement of aging-related toxicity by forming a new homeostatic set point. Therefore, further research will focus on understanding the properties of the new set point(s), the general nature of this phenomenon and will explore the limits of brains' adaptivity.

Synthesis, structural studies and stability of model cysteine containing DNA–protein cross-links

In the presence of N^α-acetyllysine, cross-links of aldehydic adenine nucleoside adducts with N-acetylcysteine lose an N-acetylcysteine moiety undergoing transformation into amino derivatives.

Copper-induced oxidative damage to the prophenoloxidase-activating system in the freshwater crayfish Procambarus clarkii

Previous studies have demonstrated copper-induced proteins damage in gill and hepatopancreas of the freshwater crayfish Procambarus clarkii, but little information is available about its effects on key component of the innate defense in haemolymph. In the present study, we evaluated the relationship between oxidative carbonylation and prophenoloxidase-activating system (proPO-AS) activity, by exposing P. clarkii to sub-lethal concentrations (1/50, 1/12, 1/6 and 1/3 of the 96 h LC50) Cu(2+) up to 96 h. Six biomarkers of oxidative stress, i.e. reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), protein carbonyl (PC), malondialdehyde (MDA) and DNA-protein crosslinks (DPCs), and six indicators of immune status, i.e. total hemocyte counts (THCs), differential hemocyte counts (DHCs), hemocyanin (HC), prophenoloxidase (proPO), serine protease (SP) and phenoloxidase (PO), were determined in haemolymph. The results indicated that there was a significant increase (P < 0.05) in the levels of ROS, PC, MDA and DPCs accompanied by markedly decreased (P < 0.05) activities of proPO, SP, PO and HC in a dose and time dependent manner. The significant and positive correlations (P < 0.01) between ROS production and the formation of PC, MDA and DPCs were observed in crayfish at 96 h. There was a significant negative correlation (P < 0.01) between the levels of protein carbonyls and the activities of proPO and SP in hemocyte lysate supernatant and PO and HC in haemolymph. Carbonylated proteins may be recognized not merely as a specific signal in oxidative stress pathways but also as a "non-self" molecule in proPO-AS. In crayfish species, copper-catalyzed protein carbonylation may be one of the main mechanisms for immunity dysfunction in proPO-AS.

Oxidative stress and glyoxalase I activity mediate dicarbonyl toxicity in MCF-7 mamma carcinoma cells and a tamoxifen resistant derivative

BACKGROUND

Acquired tamoxifen resistance is a significant problem in estrogen receptor positive breast cancer. In a cellular model, tamoxifen resistance was associated with increased sensitivity towards toxic dicarbonyls and reduced free sulfhydryl group content. We here analyzed the role of oxidative stress and glyoxalase I activity on dicarbonyl resistance and the significance of glyoxalase I expression for survival.

METHODS

Reactive oxygen species were determined by 2,7-dihydrochlorofluorescein diacetate. Inhibitors for NADPH-oxidase (diphenyleneiodonium), p38 MAPK (SB203580) and ERK1/2 (UO126) were applied to investigate interactions of these signaling molecules. N-acetyl cysteine was used to evaluate the effect of oxidative stress on cell viability, which was assessed by the resazurin assay. Gene expression was analyzed by real time qRT-PCR. Glyoxalase activity was inhibited by the specific inhibitor CS-0683 and siRNA. The relevance of glyoxalase 1 mRNA abundance on survival of breast cancer patients was evaluated by the KM-plotter web interface.

RESULTS

α-Oxo-aldehydes caused an immediate increase in reactive oxygen species where the tamoxifen resistant cell line (TamR) responded at lower concentrations than the MCF-7 parental cell line. Inhibitor studies placed ROS production by NADPH-oxidase downstream of p38 MAPK. The antioxidant N-acetyl cysteine (NAC) increased survival, whereas glyoxalase (GLO1) inhibition increased dicarbonyl toxicity. GLO1 mRNA abundance was correlated with unfavorable prognosis of breast cancer patients.

CONCLUSIONS

Dicarbonyl toxicity was mediated by oxidative stress and GLO1 activity determines aldehyde toxicity in tamoxifen resistant cells.

GENERAL SIGNIFICANCE

Glyoxalases might be predictive biomarkers for tamoxifen resistance and a putative target for the treatment of tamoxifen resistant breast cancer patients.

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

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

Characterization of the deoxyguanosine-lysine cross-link of methylglyoxal

Methylglyoxal is a mutagenic bis-electrophile that is produced endogenously from carbohydrate precursors. Methylglyoxal has been reported to induce DNA-protein cross-links (DPCs) in vitro and in cultured cells. Previous work suggests that these cross-links are formed between guanine and either lysine or cysteine side chains. However, the chemical nature of the methylglyoxal induced DPC have not been determined. We have examined the reaction of methylglyoxal, deoxyguanosine (dGuo), and Nα-acetyllysine (AcLys) and determined the structure of the cross-link to be the N2-ethyl-1-carboxamide with the lysine side chain amino group (1). The cross-link was identified by mass spectrometry and the structure confirmed by comparison to a synthetic sample. Further, the cross-link between methylglyoxal, dGuo, and a peptide (AcAVAGKAGAR) was also characterized. The mechanism of cross-link formation is likely to involve an Amadori rearrangement.