Reactive Carbonyl Species Research Articles

Efficient scavenging of reactive carbonyl species in chloroplasts is required for light acclimation and fitness of plants.

Reactive carbonyl species (RCS) derived from lipid peroxides can act as critical damage or signaling mediators downstream of reactive oxygen species by modifying target proteins. However, their biological effects and underlying mechanisms remain largely unknown in plants. Here, we have uncovered the mechanism by which the RCS 4-hydroxy-(E)-2-nonenal (HNE) participates in photosystem II (PSII) repair cycle of chloroplasts, a crucial process for maintaining PSII activity under high and changing light conditions. High Light Sensitive 1 (HLT1) is a potential NADPH-dependent reductase in chloroplasts. Deficiency of HLT1 had no impact on the growth of Arabidopsis plants under normal light conditions but increased sensitivity to high light, which resulted from a defective PSII repair cycle. In hlt1 plants, the accumulation of HNE-modified D1 subunit of PSII was observed, which did not affect D1 degradation but hampered the dimerization of repaired PSII monomers and reassembly of PSII supercomplexes on grana stacks. HLT1 is conserved in all photosynthetic organisms and has functions in overall growth and plant fitness in both Arabidopsis and rice under naturally challenging field conditions. Our work provides the mechanistic basis underlying RCS scavenging in light acclimation and suggests a potential strategy to improve plant productivity by manipulating RCS signaling in chloroplasts.

Saccharomyces cerevisiae DJ-1 paralogs maintain genome integrity through glycation repair of nucleic acids and proteins.

Reactive carbonyl species (RCS) such as methylglyoxal and glyoxal are potent glycolytic intermediates that extensively damage cellular biomolecules leading to genetic aberration and protein misfolding. Hence, RCS levels are crucial indicators in the progression of various pathological diseases. Besides the glyoxalase system, emerging studies report highly conserved DJ-1 superfamily proteins as critical regulators of RCS. DJ-1 superfamily proteins, including the human DJ-1, a genetic determinant of Parkinson's disease, possess diverse physiological functions paramount for combating multiple stressors. Although S. cerevisiae retains four DJ-1 orthologs (Hsp31, Hsp32, Hsp33, and Hsp34), their physiological relevance and collective requirement remain obscure. Here, we report for the first time that the yeast DJ-1 orthologs function as novel enzymes involved in the preferential scavenge of glyoxal and methylglyoxal, toxic metabolites, and genotoxic agents. Their collective loss stimulates chronic glycation of the proteome, and nucleic acids, inducing spectrum of genetic mutations and reduced mRNA translational efficiency. Furthermore, the Hsp31 paralogs efficiently repair severely glycated macromolecules derived from carbonyl modifications. Also, their absence elevates DNA damage response, making them vulnerable to various genotoxins. Interestingly, yeast DJ-1 orthologs preserve functional mitochondrial content, maintain ATP levels, and redistribute into mitochondria to alleviate the glycation damage of macromolecules. Together, our study uncovers a novel glycation repair pathway in S. cerevisiae and a possible neuroprotective mechanism of how hDJ-1 confers mitochondrial health during glycation toxicity.

Cysteine carbonylation with reactive carbonyl species from lipid peroxidation induce local structural changes on thioredoxin active site

Protein oxidative modifications with reactive carbonyl species (RCS) is directly linked to metabolic processes in premature aging, cancer, neurodegenerative and infectious diseases. RCS as 4-Hydroxy-2-nonal (HNE), 4-Hydroxy-2-hexenal (HHE), 4-Oxo-2-nonenal (ONE) and Malondialdehyde (MDA) attack nucleophilic amino acids residues forming irreversible adducts with proteins as Thioredoxins (Trx). This is a class of small thiol oxide-reductases playing a key role in redox signaling and oxidative stress responses in mammals. Although proteomic studies have identified to Cys-32 residue as a target of HNE attack that inhibit its enzymatic activity, how this carbonylation affects its structure and dynamic behavior at the atomic level is unknown. Even more, the molecular bases for the atomistic behavior of these modified proteins have not been completely understood. We present molecular dynamics simulations of Trx-modified with four different RCS to analyze its global and local structural effects. For this, parameters supported in the AMBER force fields were built and validated for three non-natural cysteine residues modified with HHE, ONE and MDA. Results obtained showed a slight change in the global conformational stability of Trx modified with HNE and MDA, establishing that all modified proteins presented local regions of high mobility in the modified catalytic site and some regions far from the modification area. In addition, essential domain movement modes evidences that proteins modified with the RCS assayed induce changes in conformational flexibility. Finally, these data showed that the given conformational changes did not caused global changes in proteins but rather localized changes in particular regions.

Phytohormones and arbuscular mycorrhizal Rhizoglomus intraradices together modulate defense mechanisms in mungbean to reduce Ni toxicity

The roles of Salicylic acid (SA), Nitric Oxide (NO) and Rhizoglomus intraradices in imparting tolerance to Vigna radiata (mungbean) in Nickel (Ni) contaminated soil have been studied individually but not cumulatively. In this study, pot experiments were conducted to compare the individual and synergistic role of phytohormones, with/without R. intraradices in modulating soil properties and curbing the generation of reactive carbonyl species, reactive oxygen species in mungbean plants subjected to Ni (0, 150 mgkg−1) stress. Ni had a negative correlation with growth and productivity potential of plants. Application of phytohormones and arbuscular mycorrhiza (AM) improved the yielding potential by successfully boosting the functioning of enzymes involved in glyoxalase pathway and antioxidant defense system. AM improved the functional efficiency of plants by modulating soil properties and various defense mechanisms to a maximum extent followed by SA and least by NO. Moreover, exogenous application of phytohormones to AM inoculated plants increased the colonisation capacity of fungal partner significantly, which in turn enhanced the synthesis of glomalin and improved the activity of soil enzymes responsible for nutrient cycling. However, combined application of SA with AM functioned in a more synergistic manner than the combined application of NO with AM. Interestingly, the cumulative treatment of the two phytohormones along with R. intraradices was the most efficient in re-establishing mungbean plants under Ni-stress. The study suggested the use of this cost-effective ameliorative strategy involving the combined use of phytohormones with AM to improve the agricultural outputs of mungbean cultivation even under Ni-stressed environments. The study recommends combined applications of phytohormones with AM to impart Ni tolerance to mungbean plants. However, field studies are suggested to be carried out for the authentication of present result findings.

LC-MS Profiling of Kakkonto and Identification of Ephedrine as a Key Component for Its Anti-Glycation Activity.

A total of 147 oral Kampo prescriptions, which are used clinically in Japan, were evaluated for their anti-glycation activity. Kakkonto demonstrated significant anti-glycation activity, prompting further analysis of its chemical constituents using LC-MS, which revealed the presence of two alkaloids, fourteen flavonoids, two but-2-enolides, five monoterpenoids, and four triterpenoid glycosides. To identify the components responsible for its anti-glycation activity, the Kakkonto extract was reacted with glyceraldehyde (GA) or methylglyoxal (MGO) and analyzed using LC-MS. In LC-MS analysis of Kakkonto reacted with GA, the peak intensity of ephedrine was attenuated, and three products from ephedrine-scavenging GA were detected. Similarly, LC-MS analysis of Kakkonto reacted with MGO revealed two products from ephedrine reacting with MGO. These results indicated that ephedrine was responsible for the observed anti-glycation activity of Kakkonto. Ephedrae herba extract, which contains ephedrine, also showed strong anti-glycation activity, further supporting ephedrine's contribution to Kakkonto's reactive carbonyl species' scavenging ability and anti-glycation activity.

HDL Function and Atherosclerosis: Reactive Dicarbonyls as Promising Targets of Therapy.

Epidemiologic studies detected an inverse relationship between HDL (high-density lipoprotein) cholesterol (HDL-C) levels and atherosclerotic cardiovascular disease (ASCVD), identifying HDL-C as a major risk factor for ASCVD and suggesting atheroprotective functions of HDL. However, the role of HDL-C as a mediator of risk for ASCVD has been called into question by the failure of HDL-C-raising drugs to reduce cardiovascular events in clinical trials. Progress in understanding the heterogeneous nature of HDL particles in terms of their protein, lipid, and small RNA composition has contributed to the realization that HDL-C levels do not necessarily reflect HDL function. The most examined atheroprotective function of HDL is reverse cholesterol transport, whereby HDL removes cholesterol from plaque macrophage foam cells and delivers it to the liver for processing and excretion into bile. Indeed, in several studies, HDL has shown inverse associations between HDL cholesterol efflux capacity and ASCVD in humans. Inflammation plays a key role in the pathogenesis of atherosclerosis and vulnerable plaque formation, and a fundamental function of HDL is suppression of inflammatory signaling in macrophages and other cells. Oxidation is also a critical process to ASCVD in promoting atherogenic oxidative modifications of LDL (low-density lipoprotein) and cellular inflammation. HDL and its proteins including apoAI (apolipoprotein AI) and PON1 (paraoxonase 1) prevent cellular oxidative stress and LDL modifications. Importantly, HDL in humans with ASCVD is oxidatively modified rendering HDL dysfunctional and proinflammatory. Modification of HDL with reactive carbonyl species, such as malondialdehyde and isolevuglandins, dramatically impairs the antiatherogenic functions of HDL. Importantly, treatment of murine models of atherosclerosis with scavengers of reactive dicarbonyls improves HDL function and reduces systemic inflammation, atherosclerosis development, and features of plaque instability. Here, we discuss the HDL antiatherogenic functions in relation to oxidative modifications and the potential of reactive dicarbonyl scavengers as a therapeutic approach for ASCVD.

A robust activatable two-photon fluorescent probe for endogenous formaldehyde biomarker visualization diagnosis and evaluation of diabetes mellitus

Diabetes mellitus and its complications are one of the largest healthcare burdens in the world and are increasing every year. However, the lack of effective biomarkers and non-invasive real-time monitoring tools remains a great challenge for the early diagnosis of diabetes mellitus. Endogenous formaldehyde (FA) represents a key reactive carbonyl species in biological systems, and altered metabolism and functions of FA have been closely related to the pathogenesis and maintenance of diabetes. Among various noninvasive biomedical imaging techniques, the identification-responsive fluorescence (FL) imaging could greatly benefit the comprehensive multi-scale assessment of some diseases such as diabetes. Herein, we have designed a robust activatable two-photon probe DM-FA for the first highly selective monitoring of fluctuations in FA levels during diabetes mellitus. Through the density functional theory (DFT) theoretical calculations, we elucidated the rationality of the activatable fluorescent probe DM-FA turning on the FL before and after the reaction with FA. In addition, DM-FA has excellent high selectivity, high growth factor and good photostability in the process of recognizing FA. Due to the brilliant two-photon and one-photon FL imaging capabilities of DM-FA, it has been successfully used to visualize of exogenous and endogenous FA in cells and mice. Remarkably, as a powerful FL imaging visualization tool, DM-FA was introduced for the first time to visually diagnose and explore diabetes through the fluctuation of FA content. The successful application of DM-FA in two-photon and one-photon FL imaging experiments found elevated FA levels in high glucose-stimulated diabetic cell models. We successfully visualized upregulation of FA levels in diabetic mice and decreased of FA levels in diabetic mice scavenged by NaHSO3 from multiple perspectives using multiple imaging modalities. This work may provide a novel strategy for the initial diagnosis of diabetes mellitus and the evaluation of the efficacy of drug therapy for treating diabetes mellitus, which will likely have a positive impact on clinical medicine.

Anti-Glucotoxicity Effect of Phytoconstituents via Inhibiting MGO-AGEs Formation and Breaking MGO-AGEs.

The therapeutic benefits of phytochemicals in the treatment of various illnesses and disorders are well documented. They show significant promise for the discovery and creation of novel medications for treating a variety of human diseases. Numerous phytoconstituents have shown antibiotic, antioxidant, and wound-healing effects in the conventional system. Traditional medicines based on alkaloids, phenolics, tannins, saponins, terpenes, steroids, flavonoids, glycosides, and phytosterols have been in use for a long time and are crucial as alternative treatments. These phytochemical elements are crucial for scavenging free radicals, capturing reactive carbonyl species, changing protein glycation sites, inactivating carbohydrate hydrolases, fighting pathological conditions, and accelerating the healing of wounds. In this review, 221 research papers have been reviewed. This research sought to provide an update on the types and methods of formation of methylglyoxal-advanced glycation end products (MGO-AGEs) and molecular pathways induced by AGEs during the progression of the chronic complications of diabetes and associated diseases as well as to discuss the role of phytoconstituents in MGO scavenging and AGEs breaking. The development and commercialization of functional foods using these natural compounds can provide potential health benefits.

A lysosomal localized fluorescence probe for the detection of formaldehyde and its cell imaging

Formaldehyde (FA) is one of reactive carbonyl species (RCS), which is involved in various physiological and pathological processes of organisms. Herein, a novel fluorescent probe (FAP1) containing lysosomal localization group for the detection of FA was designed and synthesized. The probe exhibited good fluorescence recognition performances for FA, such as large Stokes shift (130 nm), specific selectivity, good anti-interference ability, and low minimum detection limit (16 nM). It is worth mentioning that the probe has good biocompatibility and could be applied to the imaging detection of FA in lysosome.

Biochar-Mediated Control of Metabolites and Other Physiological Responses in Water-Stressed Leptocohloa fusca.

We investigated biochar-induced drought tolerance in Leptocohloa fusca (Kallar grass) by exploring the plant defense system at physiological level. L. fusca plants were exposed to drought stress (100%, 70%, and 30% field capacity), and biochar (BC), as an organic soil amendment was applied in two concentrations (15 and 30 mg kg-1 soil) to induce drought tolerance. Our results demonstrated that drought restricted the growth of L. fusca by inhibiting shoot and root (fresh and dry) weight, total chlorophyll content and photosynthetic rate. Under drought stress, the uptake of essential nutrients was also limited due to lower water supply, which ultimately affected metabolites including amino and organic acids, and soluble sugars. In addition, drought stress induced oxidative stress, which is evidenced by the higher production of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), superoxide ion (O2-), hydroxyl ion (OH-), and malondialdehyde (MDA). The current study revealed that stress-induced oxidative injury is not a linear path, since the excessive production of lipid peroxidation led to the accumulation of methylglyoxal (MG), a member of reactive carbonyl species (RCS), which ultimately caused cell injury. As a consequence of oxidative-stress induction, the ascorbate-glutathione (AsA-GSH) pathway, followed by a series of reactions, was activated by the plants to reduce ROS-induced oxidative damage. Furthermore, biochar considerably improved plant growth and development by mediating metabolites and soil physio-chemical status.

Deciphering peroxisomal reactive species interactome and redox signalling networks.

Plant peroxisomes are highly dynamic organelles with regard to metabolic pathways, number and morphology and participate in different metabolic processes and cell responses to their environment. Peroxisomes from animal and plant cells house a complex system of reactive oxygen species (ROS) production associated to different metabolic pathways which are under control of an important set of enzymatic and non enzymatic antioxidative defenses. Nitric oxide (NO) and its derivate reactive nitrogen species (RNS) are also produced in these organelles. Peroxisomes can regulate ROS and NO/RNS levels to allow their role as signalling molecules. The metabolism of other reactive species such as carbonyl reactive species (CRS) and sulfur reactive species (SRS) in peroxisomes and their relationship with ROS and NO have not been explored in depth. In this review, we define a peroxisomal reactive species interactome (PRSI), including all reactive species ROS, RNS, CRS and SRS, their interaction and effect on target molecules contributing to the dynamic redox/ROS homeostasis and plasticity of peroxisomes, enabling fine-tuned regulation of signalling networks associated with peroxisome-dependent H2O2. Particular attention will be paid to update the information available on H2O2-dependent peroxisomal retrograde signalling and to discuss a specific peroxisomal footprint.

Supplementation-induced change in muscle carnosine is paralleled by changes in muscle metabolism, protein glycation and reactive carbonyl species sequestering.

Carnosine is a performance-enhancing food supplement with a potential to modulate muscle energy metabolism and toxic metabolites disposal. In this study we explored interrelations between carnosine supplementation (2 g/day, 12 weeks) induced effects on carnosine muscle loading and parallel changes in (i) muscle energy metabolism, (ii) serum albumin glycation and (iii) reactive carbonyl species sequestering in twelve (M/F=10/2) sedentary, overweight-to-obese (BMI: 30.0+/-2.7 kg/m2) adults (40.1+/-6.2 years). Muscle carnosine concentration (Proton Magnetic Resonance Spectroscopy; 1H-MRS), dynamics of muscle energy metabolism (Phosphorus Magnetic Resonance Spectroscopy; 31P-MRS), body composition (Magnetic Resonance Imaging; MRI), resting energy expenditure (indirect calorimetry), glucose tolerance (oGTT), habitual physical activity (accelerometers), serum carnosine and carnosinase-1 content/activity (ELISA), albumin glycation, urinary carnosine and carnosine-propanal concentration (mass spectrometry) were measured. Supplementation-induced increase in muscle carnosine was paralleled by improved dynamics of muscle post-exercise phosphocreatine recovery, decreased serum albumin glycation and enhanced urinary carnosine-propanal excretion (all p<0.05). Magnitude of supplementation-induced muscle carnosine accumulation was higher in individuals with lower baseline muscle carnosine, who had lower BMI, higher physical activity level, lower resting intramuscular pH, but similar muscle mass and dietary protein preference. Level of supplementation-induced increase in muscle carnosine correlated with reduction of protein glycation, increase in reactive carbonyl species sequestering, and acceleration of muscle post-exercise phosphocreatine recovery.

Predicting the formation of 2-amino-3-methyl-imidazole[4,5-f]quinoline (IQ) in the Maillard reaction model system under various reaction conditions

The 2-amino-3-methyl-imidazole [4,5-f] quinoline (IQ) is a compound generated during the Maillard reaction while heating protein-rich foods and has been classified as a class 2A possible human carcinogen that has attracted ongoing public concern. However, the formation mechanism of IQ remains unknown. Herein, we investigated the formation mechanism of IQ in the Maillard reaction model system under various reaction conditions (temperature, time, and pH). The results showed that various conditions significantly influenced the precursors, reactive carbonyl species, and IQ formation (P < 0.05). There was regularity between IQ and various conditions, and the R2 in the fitting curves were between 0.90 and 0.99. To further explore the relationship between IQ and various conditions, a partial least squares (PLS) prediction model was constructed. The model indicates that temperature is a significant contributor to the formation of IQ during the Maillard reaction. Further analysis indicated that crotonaldehyde plays a vital role. Crotonaldehyde could promote IQ formation at low addition levels but inhibit its formation at high addition levels. Possible effects of crotonaldehyde on the formation of IQ were proposed. Overall, this research will help to identify more effective ways to reduce the formation of IQ in meat products, which can improve their safety for human consumption.

Effect of acrolein on the formation of harman and norharman in chemical models and roast beef patties

Harman and norharman were the most abundant β-carboline-type heterocyclic amines (HCAs) detected in various foodstuffs. Unsaturated fatty acids in foods may undergo rapid oxidative deterioration during transportation, storage and heat treatment, forming reactive carbonyl species (RCS). This work studied the effects of acrolein, a highly reactive RCS, on the formation of harman and norharman in the tryptophan model system. Results showed that 0.005, 0.01, 0.015, 0.02, 0.05, 0.1 and 0.2 mmol of acrolein led to harman production increased by 528 %, 752 %, 981 %, 1172 %, 1375 %, 1288 % and 768 % respectively, and led to norharman formation increased by 116 %, 129 %, 152 %, 169 %, and 197 %, 185 % and 157 %, respectively. Furthermore, acrolein addition reduced the residue of tryptophan (up to 63.19 %), but increased the level of the intermediates including formaldehyde (up to 352 %), acetaldehyde (up to 491 %), (1S,3S)-1-Methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA, up to 1936 %), and 1,2,3,4-tetrahydro-β-carboline-3-carboxylicacid (THCA, up to 2142 %) in the tryptophan model system. Acrolein might react with tryptophan, harman and norharman to eliminate them directly. These data suggested that acrolein may contribute to harman and norharman formation through participating in the above complex chemical reactions. In addition, the content of harman and norharman produced in roast beef patties made of minced beef oxidized for 2, 4, 6, 8, and 10 days increased by 118 %, 188 %, 267 %, 137 %, and 48 %, respectively, and led to norharman formation increased by 140 %, 132 %, 90 %, 86 %, and 74 %, respectively compared with those made of fresh minced beef, which further illustrated that lipid oxidation products potentially contributed to harman and norharman formation.

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine.

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.

Chlamydomonas reinhardtii mutants deficient for Old Yellow Enzyme 3 exhibit increased photooxidative stress.

Old Yellow Enzymes (OYEs) are flavin-containing ene-reductases that have been intensely studied with regard to their biotechnological potential for sustainable chemical syntheses. OYE-encoding genes are found throughout the domains of life, but their physiological role is mostly unknown, one reason for this being the promiscuity of most ene-reductases studied to date. The unicellular green alga Chlamydomonas reinhardtii possesses four genes coding for OYEs, three of which we have analyzed biochemically before. Ene-reductase CrOYE3 stood out in that it showed an unusually narrow substrate scope and converted N-methylmaleimide (NMI) with high rates. This was recapitulated in a C. reinhardtii croye3 mutant that, in contrast to the wild type, hardly degraded externally added NMI. Here we show that CrOYE3-mediated NMI conversion depends on electrons generated photosynthetically by photosystem II (PSII) and that the croye3 mutant exhibits slightly decreased photochemical quenching in high light. Non-photochemical quenching is strongly impaired in this mutant, and it shows enhanced oxidative stress. The phenotypes of the mutant suggest that C. reinhardtii CrOYE3 is involved in the protection against photooxidative stress, possibly by converting reactive carbonyl species derived from lipid peroxides or maleimides from tetrapyrrole degradation.

Characterization of the action of the lipid oxidation product 4-hydroxyhexenal on Lactiplantibacillus plantarum, the dominant bacterium in dry-cured fish

(E)-4-Hydroxyhexenal (HHE) is receiving widespread attention as a representative reactive carbonyl species (RCS) derived from n-3 polyunsaturated fatty acids peroxidation due to its health hazard. However, few studies have addressed the potential effects of lipid oxidation products on microbial growth in food products. Therefore, this study attempted to elucidate the action of HHE on Lactiplantibacillus plantarum (L. plantarum), the dominant bacteria in dry-cured fish. The results showed that the minimum inhibitory concentration (MIC) of HHE was 250 μg/mL. Time-kill curves confirmed the strong inhibitory activity of HHE. Lactate dehydrogenase (LDH) assay indicated that HHE disrupted the integrity of cell wall. Scanning electron microscopy (SEM) and flow cytometry analysis revealed that HHE induced changes in cell morphology, compromised cell membrane permeability, and thus disrupted intracellular homeostasis. Based on untargeted metabolomic analysis, HHE disrupted multiple metabolic pathways in L. plantarum involving amino acid metabolism, lipid metabolism, protein biosynthesis, nucleic acid metabolism and energy metabolism. This research provide new insights into the HHE inhibition mechanism and theoretical support for studying the effects of lipid oxidation products on microorganisms in food matrix.

Proteome-wide analysis of hydrogen peroxide-induced protein carbonylation in Arabidopsis thaliana.

Protein carbonylation is a non-enzymatic and irreversible post-translational modification that occurs naturally in living organisms under the direct or indirect effect of reactive oxygen species (ROS). In animals, signaling pathways involving numerous carbonylated proteins have been identified, highlighting the dual role of these molecules in ROS signal transduction. In plants, studies on phytohormone signaling (auxin, methyl jasmonate, abscisic acid) have shown that reactive carbonyl species (RCS: acrolein, malondialdehyde, 4-hydroxynonenal, etc.), derived from the action of ROS on lipids, play important roles in secondary root formation and stomatal closure. However, the carbonylated proteins involved in these signaling pathways remain to be identified. In this study, we analyzed proteins responsive to carbonylation by exogenous hydrogen peroxide (H2O2) by profiling the carbonyl proteome extracted from Arabidopsis thaliana leaves after H2O2 treatment. Carbonylated proteins were enriched at the peptide level and analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). We identified 35 and 39 uniquely carbonylated proteins in the untreated and the H2O2-treated plant samples, respectively. In comparison to the control treatment, gene ontology enrichment analysis revealed that most of the carbonylated proteins identified in the H2O2-treated plant samples are related to sulfate adenylyl transferases and amidophosphoribosyl transferases involved in the immune system response, defense response, and external stimulus-response. These results indicated that exogenous H2O2 caused a change in the pattern of protein carbonylation in A. thaliana leaves. Protein carbonylation may thus influence the plant transcriptome and metabolism in response to H2O2 and ROS-triggering external stimuli.

Inhibitory effects of rooibos (Aspalathus linearis) against reactive carbonyl species and advanced glycation end product formation in a glucose-bovine serum albumin model and cookies.

In thermally processed foods, several heat-induced toxicants are potentially formed due to the Maillard reaction, such as α-dicarbonyls and advanced glycation end products (AGEs). In the present work, we found that the methylglyoxal (MGO)-trapping and antiglycative activities of the herbal tea samples correlated strongly with their total phenolic and flavonoid contents. Among the tested herbal tea samples, rooibos exhibited the strongest MGO-trapping and antiglycative activities against AGEs formation. Aspalathin, orientin and isoorientin were further identified as the major bioactive compounds of rooibos that scavenged MGO to form the corresponding mono-MGO adducts. Moreover, the contents of dicarbonyls and AGEs in the cookie were remarkably reduced by fortification with rooibos. Altogether, our current findings suggested that rooibos might serve as a functional ingredient to reduce intake of dietary reactive carbonyl species (RCS) and AGEs from thermally processed foods, especially bakery products.

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.