Cytotoxic molecular mechanisms and cytoprotection by enzymic metabolism or autoxidation for glyceraldehyde, hydroxypyruvate and glycolaldehyde

Qualitative and Quantitative Profiling of Fructose Degradation Products Revealed the Formation of Thirteen Reactive Carbonyl Compounds and Higher Reactivity Compared to Glucose

Fructose occurs in foods and as a metabolite in vivo. It can be degraded, leading to the formation of reactive carbonyl compounds, which may influence food properties and have an impact on health. The present study performed an in-depth qualitative and quantitative profiling of fructose degradation products. Thus, the α-dicarbonyl compounds 3-deoxyglucosone, glucosone, methylglyoxal, glyoxal, hydroxypyruvaldehyde, threosone, 3-deoxythreosone, and 1-desoxypentosone and the monocarbonyl compounds formaldehyde, acetaldehyde, glycolaldehyde, glyceraldehyde, and dihydroxyacetone were detected in fructose solutions incubated at 37 °C. Quantitative profiling after 7 days revealed 4.6-271.6-fold higher yields of all degradation products from fructose compared to glucose. Except for 3-deoxyglucosone, the product formation appeared to be metal dependent, indicating oxidative pathways. CaCl2 and MgCl2 partially reduced fructose degradation. Due to its high reactivity compared to glucose, particularly toward metal-catalyzed pathways, fructose may be a strong contributor to sugar degradation and Maillard reaction in foods and in vivo.

Constructing Protein-Scaffolded Multienzyme Assembly Enhances the Coupling Efficiency of the P450 System for Efficient Daidzein Biosynthesis from (2S)-Naringenin

Daidzein is a major isoflavone compound with an immense pharmaceutical value. This study applied a novel P450 CYP82D26 which can biosynthesize daidzein from (2S)-naringenin. However, the recombinant P450 systems often suffer from low coupling efficiency, leading to an electron transfer efficiency decrease and harmful reactive oxygen species release, thereby compromising their stability and catalytic efficiency. To address these challenges, the SH3-GBD-PDZ (SGP) protein scaffold was applied to assemble a multienzyme system comprising CYP82D26, P450 reductase, and NADP+-dependent aldehyde reductase in desired stoichiometric ratios. Results showed that the coupling efficiency of the P450 system was significantly increased, primarily attributed to the channeling effect of NADPH resulting from the proximity of tethered enzymes and the electrostatic interactions between NADPH and SGP. Assembling this SGP-scaffolded assembly system in Escherichia coli yielded a titer of 240.5 mg/L daidzein with an 86% (2S)-naringenin conversion rate, which showed a 9-fold increase over the free enzymes of the P450 system. These results underscore the potential application of the SGP-scaffolded multienzyme system in enhancing the coupling and catalytic efficiency of the P450 system.

Metabolic Syndrome: Lessons from Rodent and Drosophila Models

Overweight and obesity are health conditions tightly related to a number of metabolic complications collectively called “metabolic syndrome” (MetS). Clinical diagnosis of MetS includes the presence of the increased waist circumference or so-called abdominal obesity, reduced high density lipoprotein level, elevated blood pressure, and increased blood glucose and triacylglyceride levels. Different approaches, including diet-induced and genetically induced animal models, have been developed to study MetS pathogenesis and underlying mechanisms. Studies of metabolic disturbances in the fruit fly Drosophila and mammalian models along with humans have demonstrated that fruit flies and small mammalian models like rats and mice have many similarities with humans in basic metabolic functions and share many molecular mechanisms which regulate these metabolic processes. In this paper, we describe diet-induced, chemically and genetically induced animal models of the MetS. The advantages and limitations of rodent and Drosophila models of MetS and obesity are also analyzed.

Glycolaldehyde, an Advanced Glycation End Products Precursor, Induces Apoptosis via ROS-Mediated Mitochondrial Dysfunction in Renal Mesangial Cells

Glycolaldehyde (GA) is a reducing sugar and a precursor of advanced glycation end products (AGEs). The role of precursor and precursor-derived AGEs in diabetes and its complications have been actively discussed in the literature. This study aimed to elucidate the mechanism of GA-induced apoptosis in renal cells. Immunoblotting results showed that GA (100 μM) caused cytotoxicity in murine renal glomerular mesangial cells (SV40 MES 13) and induced apoptosis via major modulators, decreasing Bcl-2 and increasing Bax, cytochrome c, and cleaved caspase-3/-9 expression. GA-derived AGE accumulation and receptor for AGE (RAGE) expression increased in mesangial cells; however, cells that were cotreated with aminoguanidine (AG) showed no increase in GA-derived AGE concentration. Furthermore, reactive oxygen species (ROS) production was increased by GA, while AG inhibited AGE formation, leading to a decrease in ROS levels in mesangial cells. We evaluated apoptosis through fluorescence-activated cell sorting, and used TUNEL staining to study DNA fragmentation. Additionally, we measured ATP generation and used MitoTracker staining to access changes in mitochondrial membrane potential. This study showed that GA increased AGE concentration, RAGE expression, and excessive ROS generation, leading to renal mesangial cell damage via GA-induced apoptosis pathway caused by mitochondrial dysfunction.

Synthetic Formatotrophs for One-Carbon Biorefinery

The use of CO2 as a carbon source in biorefinery is of great interest, but the low solubility of CO2 in water and the lack of efficient CO2 assimilation pathways are challenges to overcome. Formic acid (FA), which can be easily produced from CO2 and more conveniently stored and transported than CO2, is an attractive CO2-equivalent carbon source as it can be assimilated more efficiently than CO2 by microorganisms and also provides reducing power. Although there are native formatotrophs, they grow slowly and are difficult to metabolically engineer due to the lack of genetic manipulation tools. Thus, much effort is exerted to develop efficient FA assimilation pathways and synthetic microorganisms capable of growing solely on FA (and CO2). Several innovative strategies are suggested to develop synthetic formatotrophs through rational metabolic engineering involving new enzymes and reconstructed FA assimilation pathways, and/or adaptive laboratory evolution (ALE). In this paper, recent advances in development of synthetic formatotrophs are reviewed, focusing on biological FA and CO2 utilization pathways, enzymes involved and newly developed, and metabolic engineering and ALE strategies employed. Also, future challenges in cultivating formatotrophs to higher cell densities and producing chemicals from FA and CO2 are discussed.

A Comprehensive Review on Source, Types, Effects, Nanotechnology, Detection, and Therapeutic Management of Reactive Carbonyl Species Associated with Various Chronic Diseases

Continuous oxidation of carbohydrates, lipids, and amino acids generate extremely reactive carbonyl species (RCS). Human body comprises some important RCS namely hexanal, acrolein, 4-hydroxy-2-nonenal, methylglyoxal, malondialdehyde, isolevuglandins, and 4-oxo-2- nonenal etc. These RCS damage important cellular components including proteins, nucleic acids, and lipids, which manifests cytotoxicity, mutagenicity, multitude of adducts and crosslinks that are connected to ageing and various chronic diseases like inflammatory disease, atherosclerosis, cerebral ischemia, diabetes, cancer, neurodegenerative diseases and cardiovascular disease. The constant prevalence of RCS in living cells suggests their importance in signal transduction and gene expression. Extensive knowledge of RCS properties, metabolism and relation with metabolic diseases would assist in development of effective approach to prevent numerous chronic diseases. Treatment approaches for RCS associated diseases involve endogenous RCS metabolizers, carbonyl metabolizing enzyme inducers, and RCS scavengers. Limited bioavailability and bio efficacy of RCS sequesters suggest importance of nanoparticles and nanocarriers. Identification of RCS and screening of compounds ability to sequester RCS employ several bioassays and analytical techniques. Present review describes in-depth study of RCS sources, types, properties, identification techniques, therapeutic approaches, nanocarriers, and their role in various diseases. This study will give an idea for therapeutic development to combat the RCS associated chronic diseases.

Role of Aldehyde Dehydrogenases in Physiopathological Processes

Many different diseases are associated with oxidative stress. One of the main consequences of oxidative stress at the cellular level is lipid peroxidation, from which toxic aldehydes may be generated. Below their toxicity thresholds, some aldehydes are involved in signaling processes, while others are intermediaries in the metabolism of lipids, amino acids, neurotransmitters, and carbohydrates. Some aldehydes ubiquitously distributed in the environment, such as acrolein or formaldehyde, are extremely toxic to the cell. On the other hand, aldehyde dehydrogenases (ALDHs) are able to detoxify a wide variety of aldehydes to their corresponding carboxylic acids, thus helping to protect from oxidative stress. ALDHs are located in different subcellular compartments such as cytosol, mitochondria, nucleus, and endoplasmic reticulum. The aim of this review is to analyze, and highlight, the role of different ALDH isoforms in the detoxification of aldehydes generated in processes that involve high levels of oxidative stress. The ALDH physiological relevance becomes evident by the observation that their expression and activity are enhanced in different pathologies that involve oxidative stress such as neurodegenerative disorders, cardiopathies, atherosclerosis, and cancer as well as inflammatory processes. Furthermore, ALDH mutations bring about several disorders in the cell. Thus, understanding the mechanisms by which these enzymes participate in diverse cellular processes may lead to better contend with the damage caused by toxic aldehydes in different pathologies by designing modulators and/or protocols to modify their activity or expression.

Daring metabolic designs for enhanced plant carbon fixation

Increasing agricultural productivity is one of the major challenges our society faces. While multiple strategies to enhance plant carbon fixation have been suggested, and partially implemented, most of them are restricted to relatively simple modifications of endogenous metabolism, i.e., "low hanging fruit". Here, I portray the next generation of metabolic solutions to increase carbon fixation rate and yield. These strategies involve major rewiring of central metabolism, including dividing Rubisco's catalysis between several enzymes, replacing Rubisco with a different carboxylation reaction, substituting the Calvin Cycle with alternative carbon fixation pathways, and engineering photorespiration bypass routes that do not release carbon. While the barriers for implementing these elaborated metabolic architectures are quite significant, if we truly want to revolutionize carbon fixation, only daring engineering efforts will lead the way.

The role of the baroreflex and parasympathetic nervous system in fructose-induced cardiac and metabolic alterations

It is well-established that baroreflex sensitivity is essential for blood pressure control, and also plays a key role in the modulation of disease-induced metabolic alterations. In order to investigate the role of the baroreflex in the cardiometabolic and inflammatory derangements promoted by fructose overload, Wistar rats underwent sinoaortic denervation (SAD) or sham surgery and were studied 90 days after receiving tap water (Den and Ctrl) or a 10% fructose solution (Fruc and Den-Fruc). All experimental groups showed marked and similar degree of baroreflex impairment compared to Ctrl. As expected, fructose overload effectively induced metabolic syndrome; however, when it was associated with SAD, several alterations were attenuated. While Fruc rats displayed increased sympathetic modulation and tone and reduced vagal modulation compared to Ctrl animals, Den-Fruc rats showed greater vagal tone and modulation when compared to the Fruc group. Moreover, the Den-Fruc group showed augmented expression of β1 adrenergic receptors and TNF/IL-10 ratio and reduction of β2 in the left ventricle. The increase in vagal function was correlated with improved insulin sensitivity (r² = 0.76), and decreased abdominal fat (r² = -0.78) and β2 receptors (r² = -0.85). Our results showed that: (1) chronic fructose overload induced severe baroreflex impairment, i.e. in a similar magnitude to that observed in SAD rats, which is accompanied by cardiometabolic dysfunctions; (2) the compensatory enhancement in parasympathetic function in SAD rats submitted to fructose intake may point out the possibility of use of approaches that improve vagal function as therapeutic target to attenuate fructose-induced cardiometabolic dysfunctions.

Dark Hydrazone Fluorescence Labeling Agents Enable Imaging of Cellular Aldehydic Load

Aldehydes are key intermediates in many cellular processes, from endogenous metabolic pathways like glycolysis to undesired exogenously induced processes such as lipid peroxidation and DNA interstrand cross-linking. Alkyl aldehydes are well documented to be cytotoxic, affecting the functions of DNA and protein, and their levels are tightly regulated by the oxidative enzyme ALDH2. Mutations in this enzyme are associated with cardiac damage, diseases such as Fanconi anemia (FA), and cancer. Many attempts have been made to identify and quantify the overall level of these alkyl aldehydes inside cells, yet there are few practical methods available to detect and monitor these volatile aldehydes in real time. Here, we describe a multicolor fluorogenic hydrazone transfer ("DarkZone") system to label alkyl aldehydes, yielding up to 30-fold light-up response in vitro. A cell-permeant DarkZone dye design was applied to detect small-molecule aldehydes in the cellular environment. The new dye design also enabled the monitoring of cellular acetaldehyde production from ethanol over time by flow cytometry, demonstrating the utility of the DarkZone dyes for measuring and imaging the aldehydic load related to human disease.

S-nitrosomycothiol reductase and mycothiol are required for survival under aldehyde stress and biofilm formation in Mycobacterium smegmatis

We show that Mycobacterium smegmatis mutants disrupted in mscR, coding for a dual function S-nitrosomycothiol reductase and formaldehyde dehydrogenase, and mshC, coding for a mycothiol ligase and lacking mycothiol (MSH), are more susceptible to S-nitrosoglutathione (GSNO) and aldehydes than wild type. MSH is a cofactor for MscR, and both mshC and mscR are induced by GSNO and aldehydes. We also show that a mutant disrupted in egtA, coding for a γ-glutamyl cysteine synthetase and lacking in ergothioneine, is sensitive to nitrosative stress but not to aldehydes. In addition, we find that MSH and S-nitrosomycothiol reductase are required for normal biofilm formation in M. smegmatis, suggesting potential new therapeutic pathways to target to inhibit or disrupt biofilm formation. © 2016 IUBMB Life, 68(8):621-628, 2016.

Fructose-Induced Carbonyl/Oxidative Stress in S. cerevisiae: Involvement of TOR

The TOR (target of rapamycin) signaling pathway first described in the budding yeast Saccharomyces cerevisiae is highly conserved in eukaryotes effector of cell growth, longevity, and stress response. TOR activation by nitrogen sources, in particular amino acids, is well studied; however its interplay with carbohydrates and carbonyl stress is poorly investigated. Fructose is a more potent glycoxidation agent capable of producing greater amounts of reactive carbonyl (RCS) and oxygen species (ROS) than glucose. The increased RCS/ROS production, as a result of glycoxidation in vivo, is supposed to be involved in carbonyl/oxidative stress, metabolic disorders, and lifespan shortening of eukaryotes. In this work we aim to expand our understanding of how TOR is involved in carbonyl/oxidative stress caused by reducing monosaccharides. It was found that in fructose-grown compared with glucose-grown cells the level of carbonyl/oxidative stress markers was higher. The defects in the TOR pathway inhibited metabolic rate and suppressed generation of glycoxidation products in fructose-grown yeast.

Identification and detoxification of glycolaldehyde, an unattended bioethanol fermentation inhibitor

Although there have been approximately 60 chemical compounds identified as potent fermentation inhibitors in lignocellulose hydrolysate, our research group recently discovered glycolaldehyde as a key fermentation inhibitor during second generation biofuel production. Accordingly, we have developed a yeast S. cerevisiae strain exhibiting tolerance to glycolaldehyde. During this glycolaldehyde study, we established novel approaches for rational engineering of inhibitor-tolerant S. cerevisiae strains, including engineering redox cofactors and engineering the SUMOylation pathway. These new technical dimensions provide a novel platform for engineering S. cerevisiae strains to overcome one of the key barriers for industrialization of lignocellulosic ethanol production. As such, this review discusses novel biochemical insight of glycolaldehyde in the context of the biofuel industry.

Glycolaldehyde induces endoplasmic reticulum stress and apoptosis in Schwann cells

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Glycolaldehyde induces endoplasmic reticulum stress in Schwann cells.

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Glycolaldehyde causes apoptosis in Schwann cells.

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Nrf2 activated by glycolaldehyde plays a protective role in the cytotoxicity.

Schwann cell injury is caused by diabetic neuropathy. The apoptosis of Schwann cells plays a pivotal role in diabetic nerve dysfunction. Glycolaldehyde is a precursor of advanced glycation end products that contribute to the pathogenesis of diabetic neuropathy. In this study, we examined whether glycolaldehyde induces endoplasmic reticulum (ER) stress and apoptosis in rat Schwann cells. Schwann cells treated with 500 μM glycolaldehyde showed morphological changes characteristic of apoptosis. Glycolaldehyde activated apoptotic signals, such as caspase-3 and caspase-8. Furthermore, it induced ER stress response involving RNA-dependent protein kinase-like ER kinase (PERK), inositol-requiring ER-to-nucleus signal kinase 1α (IRE1α), and eukaryotic initiation factor 2α (eIF2α). In addition, glycolaldehyde activated CCAAT/enhancer-binding homologous protein (CHOP), an ER stress response factor crucial to executing apoptosis. Knockdown of nuclear factor E2-related factor 2 (Nrf2), which is involved in the promotion of cell survival following ER stress, enhanced glycolaldehyde-induced cytotoxicity, indicating that Nrf2 plays a protective role in the cytotoxicity caused by glycolaldehyde. Taken together, these findings indicate that glycolaldehyde is capable of inducing apoptosis and ER stress in Schwann cells. The ER stress induced by glycolaldehyde may trigger the glycolaldehyde-induced apoptosis in Schwann cells. This study demonstrated for the first time that glycolaldehyde induced ER stress.

AllR Controls the Expression of Streptomyces coelicolor Allantoin Pathway Genes

Streptomyces species are native inhabitants of soil, a natural environment where nutrients can be scarce and competition fierce. They have evolved ways to metabolize unusual nutrients, such as purines and its derivatives, which are highly abundant in soil. Catabolism of these uncommon carbon and nitrogen sources needs to be tightly regulated in response to nutrient availability and environmental stimulus. Recently, the allantoin degradation pathway was characterized in Streptomyces coelicolor. However, there are questions that remained unanswered, particularly regarding pathway regulation. Here, using a combination of proteomics and genetic approaches, we identified the negative regulator of the allantoin pathway, AllR. In vitro studies confirmed that AllR binds to the promoter regions of allantoin catabolic genes and determined the AllR DNA binding motif. In addition, effector studies showed that allantoic acid, and glyoxylate, to a lesser extent, inhibit the binding of AllR to the DNA. Inactivation of AllR repressor leads to the constitutive expression of the AllR regulated genes and intriguingly impairs actinorhodin and undecylprodigiosin production. Genetics and proteomics analysis revealed that among all genes from the allantoin pathway that are upregulated in the allR mutant, the hyi gene encoding a hydroxypyruvate isomerase (Hyi) is responsible of the impairment of antibiotic production.

Reactive carbonyl species in vivo: generation and dual biological effects

Reactive carbonyls are widespread species in living organisms and mainly known for their damaging effects. The most abundant reactive carbonyl species (RCS) are derived from oxidation of carbohydrates, lipids, and amino acids. Chemical modification of proteins, nucleic acids, and aminophospholipids by RCS results in cytotoxicity and mutagenicity. In addition to their direct toxicity, modification of biomolecules by RCS gives rise to a multitude of adducts and cross links that are increasingly implicated in aging and pathology of a wide range of human diseases. Understanding of the relationship between metabolism of RCS and the development of pathological disorders and diseases may help to develop effective approaches to prevent a number of disorders and diseases. On the other hand, constant persistence of RCS in cells suggests that they perform some useful role in living organisms. The most beneficial effects of RCS are their establishment as regulators of cell signal transduction and gene expression. Since RCS can modulate different biological processes, new tools are required to decipher the precise mechanisms underlying dual effects of RCS.

Fructose compared with glucose is more a potent glycoxidation agent in vitro, but not under carbohydrate-induced stress in vivo: potential role of antioxidant and antiglycation enzymes

The contribution of carbohydrates to non-enzymatic processes such as glycation/autoxidation has been extensively investigated over the last decades. This may be attributed to either beneficial or detrimental effects of reducing carbohydrates, and most studies in the field of glycoxidation are focused on glucose. Non-enzymatic reactions of fructose have not been as thoroughly investigated as those of glucose. To compare glucose and fructose involvement in the generation of glycoxidation products under experimental conditions close to the physiological situation, we used intact Saccharomyces cerevisiae cells as in vivo model and cell-free extracts prepared from whole yeast cells as in vitro model. Both intact cells and cell-free extracts were incubated with glucose or fructose. It was shown that: (i) in vitro fructose was more reactive than glucose and produced higher level of autoxidation and glycation products; (ii) no substantive differences were observed for the effect of glucose and fructose on the intracellular level of glycoxidation products, when intact yeast cells were exposed to the high concentration of hexoses; (iii) the activity of defensive enzymes (superoxide dismutase, catalase, glyoxalases, and glutathione reductase) was increased in both glucose- and fructose-stressed yeasts, indicating the development of oxidative/carbonyl stress; (iv) glucose-6-phosphate dehydrogenase activity significantly dropped in yeast exposed to both hexoses, demonstrating its high sensitivity to reactive oxygen and carbonyl species; and (v) fructose more markedly activated glyoxalases than glucose. Involvement of glucose and fructose in the glycoxidation reactions as well as potential role of antioxidant and antiglycation enzymes in yeast protection against glycoxidation are discussed.

Fructation in vivo: detrimental and protective effects of fructose

There is compelling evidence that long-term intake of excessive fructose can have deleterious side effects in different experimental models. However, the role of fructose in vivo remains controversial, since acute temporary application of fructose is found to protect yeast as well as animal tissues against exogenous oxidative stress. This review suggests the involvement of reactive carbonyl and oxygen species in both the cytotoxic and defensive effects of fructose. Potential mechanisms of the generation of reactive species by fructose in the nonenzymatic reactions, their implication in the detrimental and protective effects of fructose are discussed.

Glycolaldehyde impairs neutrophil biochemical parameters by an oxidative and calcium-dependent mechanism--protective role of antioxidants astaxanthin and vitamin C

AIM

The present study examined the effects of glycolaldehyde (GC) on biochemical parameters of human neutrophils and whether the antioxidant astaxanthin associated with vitamin C can modulate these parameters.

METHODS

Neutrophils from healthy subjects were treated with GC (1mM) followed or not by the antioxidants astaxanthin (2 μM) and vitamin C (100 μM). We examined the phagocytic capacity, hypochlorous acid, myeloperoxidase (MPO) and glucose-6-phosphate dehydrogenase (G6PDH) activities, cytokines and [Ca(2+)](i). Also, superoxide anion, hydrogen peroxide, nitric oxide production, antioxidant enzyme activities and glutathione-recycling system were evaluated.

RESULTS

GC promoted a marked reduction on the phagocytic capacity, maximal G6PDH and MPO activities, hypochlorous acid production and release of IL-1β, IL-6 and TNF-α cytokines. Some impairment in the neutrophils biochemical parameters appears to be mediated by oxidative stress through ROS/RNS production and calcium reduction. Oxidative stress was evidenced by reduction in the activities of the main antioxidant enzymes, GSH/GSSG ratio and in the increment of O(2)(-) and H(2)O(2) and NO.

CONCLUSIONS

Treatment of cells with the combination of the antioxidants astaxanthin and vitamin C was able to restore some neutrophils function mainly by decreasing ROS/RNS production and improving the redox state. Overall, our findings demonstrate that GC modulates several neutrophils biochemical parameters in vitro.

Fructose protects baker's yeast against peroxide stress: potential role of catalase and superoxide dismutase

The negative effects of fructose due to its chronic consumption are well documented, while short-term application of fructose is found to protect different types of cells against oxidative stress. Reactive oxygen species (ROS) are suggested to mediate both the cytotoxic and defensive effects. Here, we compare the influence of glucose and fructose on yeast under H(2)O(2)-induced stress. Under control conditions, fructose-grown comparing with glucose-grown yeast demonstrated higher metabolic activity and ROS level. Therefore, fructose was suggested to provoke a mild stress that resulted in the acquisition of cellular resistance to lethal challenges, which explained the higher survival of fructose-grown yeast under H(2)O(2)-induced shock. Exposure to H(2)O(2) increased ROS level in glucose-grown cells, whereas it decreased the ROS level in fructose-grown cells. Hydrogen peroxide activated superoxide dismutase (SOD) and catalase in both the cell types studied, but glucose-grown cells demonstrated a sharp rise of the activities, while cells grown on fructose showed a broad peak of activation. Thus, fructose is likely to protect the antioxidant enzymes against their inactivation by H(2)O(2). Despite a different type of the enzyme activation in both the studied cell types (glucose- and fructose-grown), a strong positive correlation between SOD and catalase was found. The physiological meaning of this relationship and possible mechanisms of the fructose protective effect are discussed.