Measurement of 4-hydroxynonenal in small volume blood plasma samples: modification of a gas chromatographic-mass spectrometric method for clinical settings

Lipid peroxidation: Reactive carbonyl species, protein/DNA adducts, and signaling switches in oxidative stress and cancer

Under the exposure of lipids to reactive oxygen species (ROS), lipid peroxidation proceeds non-enzymatically and generates an extremely heterogeneous mixture of reactive carbonyl species (RCS). Among them, HNE, HHE, MDA, methylglyoxal, glyoxal, and acrolein are the most studied and/or abundant ones. Over the last decades, significant progress has been achieved in understanding mechanisms of RCS generation, protein/DNA adduct formation, and their identification and quantification in biological samples. In our review, we critically discuss the advancements in understanding the roles of RCS-induced protein/DNA modifications in signaling switches to provide adaptive cell response under physiological and oxidative stress conditions. At non-toxic concentrations, RCS modify susceptible Cys residue in c-Src to activate MAPK signaling and Cys, Lys, and His residues in PTEN to cause its reversible inactivation, thereby stimulating PI3K/PKB(Akt) pathway. RCS toxic concentrations cause irreversible Cys modifications in Keap1 and IKKβ followed by stabilization of Nrf2 and activation of NF-κB, respectively, for their nuclear translocation and antioxidant gene expression. Dysregulation of these mechanisms causes diseases including cancer. Alterations in RCS, RCS detoxifying enzymes, RCS-modified protein/DNA adducts, and signaling pathways have been implicated in various cancer types.

Plasma biomarkers of endothelial function, inflammation and oxidative stress in individuals with non-freezing cold injury

NEW FINDINGS

What is the central question of this study? Are biomarkers of endothelial function, oxidative stress and inflammation altered by non-freezing cold injury (NFCI)? What is the main finding and its importance? Baseline plasma [interleukin-10] and [syndecan-1] were elevated in individuals with NFCI and cold-exposed control participants. Increased [endothelin-1] following thermal challenges might explain, in part, the increased pain/discomfort experienced with NFCI. Mild to moderate chronic NFCI does not appear to be associated with either oxidative stress or a pro-inflammatory state. Baseline [interleukin-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosis of NFCI.

ABSTRACT

Plasma biomarkers of inflammation, oxidative stress, endothelial function and damage were examined in 16 individuals with chronic NFCI (NFCI) and matched control participants with (COLD, n = 17) or without (CON, n = 14) previous cold exposure. Venous blood samples were collected at baseline to assess plasma biomarkers of endothelial function (nitrate, nitrite and endothelin-1), inflammation [interleukin-6 (IL-6), interleukin-10 (IL-10), tumour necrosis factor alpha and E-selectin], oxidative stress [protein carbonyl, 4-hydroxy-2-nonenal (4-HNE), superoxide dismutase and nitrotyrosine) and endothelial damage [von Willebrand factor, syndecan-1 and tissue type plasminogen activator (TTPA)]. Immediately after whole-body heating and separately, foot cooling, blood samples were taken for measurement of plasma [nitrate], [nitrite], [endothelin-1], [IL-6], [4-HNE] and [TTPA]. At baseline, [IL-10] and [syndecan-1] were increased in NFCI (P < 0.001 and P = 0.015, respectively) and COLD (P = 0.033 and P = 0.030, respectively) compared with CON participants. The [4-HNE] was elevated in CON compared with both NFCI (P = 0.002) and COLD (P < 0.001). [Endothelin-1] was elevated in NFCI compared with COLD (P < 0.001) post-heating. The [4-HNE] was lower in NFCI compared with CON post-heating (P = 0.032) and lower than both COLD (P = 0.02) and CON (P = 0.015) post-cooling. No between-group differences were seen for the other biomarkers. Mild to moderate chronic NFCI does not appear to be associated with a pro-inflammatory state or oxidative stress. Baseline [IL-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosing NFCI, but it is likely that a combination of tests will be required.

Lipid peroxidation derived reactive carbonyl species in free and conjugated forms as an index of lipid peroxidation: limits and perspectives

Reactive carbonyl species (RCS) formed by lipidperoxidation as free forms or as enzymatic and non-enzymatic conjugates are widely used as an index of oxidative stress. Besides general measurements based on derivatizing reactions, more selective and sensitive MS based analyses have been proposed in the last decade. Untargeted and targeted methods for the measurement of free RCS and adducts have been described and their applications to in vitro and ex vivo samples have permitted the identification of many biological targets, reaction mechanisms and adducted moieties with a particular relevance to RCS protein adducts. The growing interest in protein carbonylation can be explained by considering that protein adducts are now recognized as being involved in the damaging action of oxidative stress so that their measurement is performed not only to obtain an index of lipid peroxidation but also to gain a deeper insight into the molecular mechanisms of oxidative stress. The aim of the review is to discuss the most novel analytical approaches and their application for profiling reactive carbonyl species and their enzymatic and non-enzymatic metabolites as an index of lipid-oxidation and oxidative stress. Limits and perspectives will be discussed.

Age-related alteration in HNE elimination enzymes

4-hydroxynonenal (HNE, 4-hydroxy-2-nonenal) is a primary α,β-unsaturated aldehyde product of lipid peroxidation. The accumulation of HNE increases with aging and the mechanisms are mainly attributable to increased oxidative stress and decreased capacity of HNE elimination. In this review article, we summarize the studies on age-related change of HNE concentration and alteration of HNE metabolizing enzymes (GCL, GST, ALDHs, aldose reductase, and 20S-proteasome), and discuss potential mechanism of age-related decrease in HNE-elimination capacity by focusing on Nrf2 redox signaling.

Carotenoids and Markers of Oxidative Stress in Human Observational Studies and Intervention Trials: Implications for Chronic Diseases

Carotenoids include C30, C40 and C50 terpenoid-based molecules, many of which constitute coloured pigments. However, >1100 of these are known to occur in nature and only about a dozen are known to play a role in our daily diet. Carotenoids have received much attention due to their proposed health benefits, including reducing the incidence of chronic diseases, such as cardiovascular disease and diabetes. Many of these diseases are characterized by chronic inflammation co-occurring with oxidative stress, characterized by, for example, enhanced plasma F2-isoprostane concentrations, malondialdehyde, and 8-hydroxyguanosine. Though carotenoids can act as direct antioxidants, quenching, for example, singlet oxygen and peroxide radicals, an important biological function appears to rest also in the activation of the body's own antioxidant defence system, related to superoxide-dismutase, catalase, and glutathione-peroxidase expression, likely due to the interaction with transcription factors, such as nuclear-factor erythroid 2-related factor 2 (Nrf-2). Though mostly based on small-scale and observational studies which do not allow for drawing conclusions regarding causality, several supplementation trials with isolated carotenoids or food items suggest positive health effects. However, negative effects have also been reported, especially regarding beta-carotene for smokers. This review is aimed at summarizing the results from human observational studies/intervention trials targeting carotenoids in relation to chronic diseases characterized by oxidative stress and markers thereof.

Lipoxidation in cardiovascular diseases

Lipids can go through lipid peroxidation, an endogenous chain reaction that consists in the oxidative degradation of lipids leading to the generation of a wide variety of highly reactive carbonyl species (RCS), such as short-chain carbonyl derivatives and oxidized truncated phospholipids. RCS exert a wide range of biological effects due to their ability to interact and covalently bind to nucleophilic groups on other macromolecules, such as nucleic acids, phospholipids, and proteins, forming reversible and/or irreversible modifications and generating the so-called advanced lipoxidation end-products (ALEs). Lipoxidation plays a relevant role in the onset of cardiovascular diseases (CVD), mainly in the atherosclerosis-based diseases in which oxidized lipids and their adducts have been extensively characterized and associated with several processes responsible for the onset and development of atherosclerosis, such as endothelial dysfunction and inflammation. Herein we will review the current knowledge on the sources of lipids that undergo oxidation in the context of cardiovascular diseases, both from the bloodstream and tissues, and the methods for detection, characterization, and quantitation of their oxidative products and protein adducts. Moreover, lipoxidation and ALEs have been associated with many oxidative-based diseases, including CVD, not only as potential biomarkers but also as therapeutic targets. Indeed, several therapeutic strategies, acting at different levels of the ALEs cascade, have been proposed, essentially blocking ALEs formation, but also their catabolism or the resulting biological responses they induce. However, a deeper understanding of the mechanisms of formation and targets of ALEs could expand the available therapeutic strategies.

4-hydroxynonenal-mediated signaling and aging

4-Hydroxy-2-nonenal (HNE), one of the major α, β-unsaturated aldehydes produced during lipid peroxidation, is a potent messenger in mediating signaling pathways. Lipid peroxidation and HNE production appear to increase with aging. Although the cause and effect relation remains arguable, aging is associated with significant changes in diverse signaling events, characterized by enhanced or diminished responses of specific signaling pathways. In this review we will discuss how HNE may contribute to aging-related alterations of signaling pathways.

Signaling by 4-hydroxy-2-nonenal: Exposure protocols, target selectivity and degradation

4-hydroxy-2-nonenal (HNE), a major non-saturated aldehyde product of lipid peroxidation, has been extensively studied as a signaling messenger. In these studies a wide range of HNE concentrations have been used, ranging from the unstressed plasma concentration to far beyond what would be found in actual pathophysiological condition. In addition, accumulating evidence suggest that signaling protein modification by HNE is specific with only those proteins with cysteine, histidine, and lysine residues located in certain sequence or environments adducted by HNE. HNE-signaling is further regulated through the turnover of HNE-signaling protein adducts through proteolytic process that involve proteasomes, lysosomes and autophagy. This review discusses the HNE concentrations and exposure modes used in signaling studies, the selectivity of the HNE-adduction site, and the turnover of signaling protein adducts.

4-Hydroxy-7-oxo-5-heptenoic Acid (HOHA) Lactone is a Biologically Active Precursor for the Generation of 2-(ω-Carboxyethyl)pyrrole (CEP) Derivatives of Proteins and Ethanolamine Phospholipids

2-(ω-Carboxyethyl)pyrrole (CEP) derivatives of proteins were previously shown to have significant pathological and physiological relevance to age-related macular degeneration, cancer and wound healing. Previously, we showed that CEPs are generated in the reaction of ε-amino groups of protein lysyl residues with 1-palmityl-2-(4-hydroxy-7-oxo-5-heptenoyl)-sn-glycero-3-phosphatidylcholine (HOHA-PC), a lipid oxidation product uniquely generated by oxidative truncation of docosahexanenate-containing phosphatidylcholine. More recently, we found that HOHA-PC rapidly releases HOHA-lactone and 2-lyso-PC (t1/2 = 30 min at 37 °C) by nonenzymatic transesterification/deacylation. Now we report that HOHA-lactone reacts with Ac-Gly-Lys-OMe or human serum albumin to form CEP derivatives in vitro. Incubation of human red blood cell ghosts with HOHA-lactone generates CEP derivatives of membrane proteins and ethanolamine phospholipids. Quantitative analysis of the products generated in the reaction HOHA-PC with Ac-Gly-Lys-OMe showed that HOHA-PC mainly forms CEP-dipeptide that is not esterified to 2-lysophosphatidycholine. Thus, the HOHA-lactone pathway predominates over the direct reaction of HOHA-PC to produce the CEP-PC-dipeptide derivative. Myleoperoxidase/H2O2/NO2(-) promoted in vitro oxidation of either 1-palmityl-2-docosahexaneoyl-sn-glycero-3-phosphatidylcholine (DHA-PC) or docosahexaenoic acid (DHA) generates HOHA-lactone in yields of 0.45% and 0.78%, respectively. Lipid oxidation in human red blood cell ghosts also releases HOHA-lactone. Oxidative injury of ARPE-19 human retinal pigmented epithelial cells by exposure to H2O2 generated CEP derivatives. Treatment of ARPE-19 cells with HOHA-lactone generated CEP-modified proteins. Low (submicromolar), but not high, concentrations of HOHA-lactone promote increased vascular endothelial growth factor (VEGF) secretion by ARPE-19 cells. Therefore, HOHA-lactone not only serves as an intermediate for the generation of CEPs but also is a biologically active oxidative truncation product from docosahexaenoate lipids.

4-Hydroxynonenal in the pathogenesis and progression of human diseases

Metastable aldehydes produced by lipid peroxidation act as 'toxic second messengers' that extend the injurious potential of free radicals. 4-hydroxy 2-nonenal (HNE), a highly toxic and most abundant stable end product of lipid peroxidation, has been implicated in the tissue damage, dysfunction, injury associated with aging and other pathological states such as cancer, Alzheimer, diabetes, cardiovascular and inflammatory complications. Further, HNE has been considered as a oxidative stress marker and it act as a secondary signaling molecule to regulates a number of cell signaling pathways. Biological activity of HNE depends on its intracellular concentration, which can differentially modulate cell death, growth and differentiation. Therefore, the mechanisms responsible for maintaining the intracellular levels of HNE are most important, not only in the defense against oxidative stress but also in the pathophysiology of a number of disease processes. In this review, we discussed the significance of HNE in mediating various disease processes and how regulation of its metabolism could be therapeutically effective.

Oxidative stress and antioxidant defence in a healthy nonagenarian population

Results on oxidative markers during ageing are not consistent throughout the scientific literature; however, successful ageing may depend on better ability to cope with oxidative stress. A previous study of ours showed that successful ageing could actually be related to enhanced response to oxidatively modified proteins. In this study, a healthy nonagenarian population (OVER-90) was examined for various blood oxidative biomarkers and compared with a healthy population of blood donors (age range, 23-66 years). Blood glutathione, both total (tGSH) and oxidised (GSSG), and total plasmatic antioxidant status were maintained in the OVER-90 at a level similar to the control population. Sulphydryl (sulfhydryl) groups and glutathione peroxidase (GPx) were instead decreased. The results are discussed in a possible unifying view: the OVER-90 population could possess a globally preserved antioxidant ability, though some signs of oxidative damage are present and some structures could be 'sacrificed' in order to keep the redox equilibrium.

Cardiovascular redox and ox stress proteomics

SIGNIFICANCE

Oxidative post-translational modifications (OPTMs) have been demonstrated as contributing to cardiovascular physiology and pathophysiology. These modifications have been identified using antibodies as well as advanced proteomic methods, and the functional importance of each is beginning to be understood using transgenic and gene deletion animal models. Given that OPTMs are involved in cardiovascular pathology, the use of these modifications as biomarkers and predictors of disease has significant therapeutic potential. Adequate understanding of the chemistry of the OPTMs is necessary to determine what may occur in vivo and which modifications would best serve as biomarkers.

RECENT ADVANCES

By using mass spectrometry, advanced labeling techniques, and antibody identification, OPTMs have become accessible to a larger proportion of the scientific community. Advancements in instrumentation, database search algorithms, and processing speed have allowed MS to fully expand on the proteome of OPTMs. In addition, the role of enzymatically reversible OPTMs has been further clarified in preclinical models.

CRITICAL ISSUES

The identification of OPTMs suffers from limitations in analytic detection based on the methodology, instrumentation, sample complexity, and bioinformatics. Currently, each type of OPTM requires a specific strategy for identification, and generalized approaches result in an incomplete assessment.

FUTURE DIRECTIONS

Novel types of highly sensitive MS instrumentation that allow for improved separation and detection of modified proteins and peptides have been crucial in the discovery of OPTMs and biomarkers. To further advance the identification of relevant OPTMs in advanced search algorithms, standardized methods for sample processing and depository of MS data will be required.

Dietary regulation of catabolic disposal of 4-hydroxynonenal analogs in rat liver

Our previous work in perfused rat livers has demonstrated that 4-hydroxynonenal (HNE) is catabolized predominantly via β oxidation. Therefore, we hypothesized that perturbations in β oxidation, such as diet-altered fatty acid oxidation activity, could lead to changes in HNE levels. To test our hypothesis, we (i) developed a simple and sensitive GC/MS method combined with mass isotopomer analysis to measure HNE and HNE analogs, 4-oxononenal (ONE) and 1,4-dihydroxynonene (DHN), and (ii) investigated the effects of four diets (standard, low-fat, ketogenic, and high-fat mix) on HNE, ONE, and DHN concentrations in rat livers. Our results showed that livers from rats fed the ketogenic diet or high-fat mix diet had high ω-6 polyunsaturated fatty acid concentrations and markers of oxidative stress. However, high concentrations of HNE (1.6 ± 0.5 nmol/g) and ONE (0.9 ± 0.2 nmol/g) were found only in livers from rats fed the high-fat mix diet. Livers from rats fed the ketogenic diet had low HNE (0.8 ± 0.1 nmol/g) and ONE (0.4 ± 0.07 nmol/g), similar to rats fed the standard diet. A possible explanation is that the predominant pathway of HNE catabolism (i.e., β oxidation) is activated in the liver by the ketogenic diet. This is consistent with a 10-fold decrease in malonyl-CoA in livers from rats fed a ketogenic diet compared to a standard diet. The accelerated catabolism of HNE lowers HNE and HNE analog concentrations in livers from rats fed the ketogenic diet. On the other hand, rats fed the high-fat mix diet had high rates of lipid synthesis and low rates of fatty acid oxidation, resulting in the slowing down of the catabolic disposal of HNE and HNE analogs. Thus, decreased HNE catabolism from a high-fat mix diet induces high concentrations of HNE and HNE analogs. The results of this work suggest a potential causal relationship to metabolic syndrome induced by Western diets (i.e., high-fat mix), as well as the effects of a ketogenic diet on the catabolism of lipid peroxidation products in liver.

Advances in methods for the determination of biologically relevant lipid peroxidation products

Lipid peroxidation is recognized to be an important contributor to many chronic diseases, especially those of an inflammatory pathology. In addition to their value as markers of oxidative damage, lipid peroxidation products have also been shown to have a wide variety of biological and cell signalling effects. In view of this, accurate and sensitive methods for the measurement of lipid peroxidation products are essential. Although some assays have been described for many years, improvements in protocols are continually being reported and, with recent advances in instrumentation and technology, highly specialized and informative techniques are increasingly used. This article gives an overview of the most currently used methods and then addresses the recent advances in some specific approaches. The focus is on analysis of oxysterols, F(2)-isoprostanes and oxidized phospholipids by gas chromatography or liquid chromatography mass spectrometry techniques and immunoassays for the detection of 4-hydroxynonenal.

Beneficial effects of growth hormone-releasing peptide on myocardial oxidative stress and left ventricular dysfunction in dilated cardiomyopathic hamsters

BACKGROUND

Growth hormone-releasing peptide (GHRP) may act directly on the myocardium and improve left ventricular (LV) function, suggesting a potential new approach to the treatment of cardiomyopathic hearts. The present study tested the hypothesis that the beneficial cardiac effects of GHRP might include attenuation of myocardial oxidative stress.

METHODS AND RESULTS

Dilated cardiomyopathic TO-2 hamsters were injected with GHRP-2 (1 mg/kg) or saline from 6 to 12 weeks of age. F1B hamsters served as controls. Untreated TO-2 hamsters progressively developed LV dilation, wall thinning, and systolic dysfunction between 6 and 12 weeks of age. Marked myocardial fibrosis was apparent in untreated hamsters at 12 weeks of age in comparison with F1B controls. The ratio of reduced to oxidized glutathione (GSH/GSSG) was decreased and the concentration of 4-hydroxynonenal (4-HNE) was increased in the hearts of untreated TO-2 hamsters. Treatment with GHRP-2 attenuated the progression of LV remodeling and dysfunction, as well as myocardial fibrosis, in TO-2 hamsters. GHRP-2 also inhibited both the decrease in the GSH/GSSG ratio and the increase in the concentration of 4-HNE in the hearts of TO-2 hamsters.

CONCLUSIONS

GHRP-2 can suppress the increase in the level of myocardial oxidative stress, leading to attenuation of progressive LV remodeling and dysfunction in dilated cardiomyopathic hamsters. (Circ J 2010; 74: 163 - 170).

Differential distribution of 4-hydroxynonenal adducts to sulfur and nitrogen residues in blood proteins as revealed using Raney nickel and gas chromatography-mass spectrometry

Quantification of 4-hydroxy-2-nonenal (HNE) bound to circulating proteins may prove to be useful in evaluating the role of this bioactive lipoperoxidation by-product in the pathogenesis of various diseases. Recently, we developed a quantitative gas chromatography-mass spectrometry (GCMS) assay of total protein-bound HNE (HNE-P) in blood after reduction with NaB(2)H(4) and cleavage with Raney nickel. Whereas it has been assumed that Raney nickel cleaves only Michael adducts of HNE to cysteine via a thioether bond (HNE-SP), results from this study demonstrate that our GCMS method also detects with precision picomoles of HNE adducts via nitrogen residues (HNE-NP). Specifically, evidence was obtained using various study models, including polyamino acids consisting of cysteine, lysine, and histidine and a biologically relevant molecule, albumin. Furthermore, we show that dinitrophenylhydrazine treatment before Raney nickel treatment can be used to discriminate and quantify the various HNE-P molecular species in plasma and blood samples from normal rats, which range between 0.15 and 3 pmol/mg protein or 10 to 600 nM. However, whereas HNE-SP predominated in whole blood, we detected HNE-NP only in plasma. We also identified another significant MS signal, which we attribute to protein-bound 1,4-dihydroxynonane (DHN-P) presumably formed from the enzymatic reduction of HNE-P. The distribution profile of all these species in plasma differed from that observed when physiologically relevant concentrations of albumin and HNE were incubated in vitro. Furthermore, interestingly, hypercholesterolemic rabbits showed higher plasma levels of HNE-NP, but not of DHN-P. Beyond documenting the presence of various types of HNE-P in circulating proteins, our results emphasize the importance of enzymatic mechanisms in situ as a factor determining their distribution in the various blood compartments under various conditions.

Alpha,beta-unsaturated aldehydes adducts to actin and albumin as potential biomarkers of carbonylation damage

Reactive carbonyl species (RCS) generated by lipid peroxidation, leading to protein carbonylation, are involved in several human diseases. Protein carbonylation constitutes one of the best characterised biomarker of oxidative damage to proteins. Albumin and actin have been identified, through different proteomic approaches, as the main protein targets for RCS in plasma and tissues, respectively. By a combined LC-MS/MS and computational approach, we have demonstrated their high reactivity towards alpha,beta-unsaturated aldehydes, and established the stoichiometry of reaction with HNE and acrolein, as well as the amino acid residues more susceptible to carbonyl attack. A new mass spectrometric approach, based on LC-MS/MS analysis of tag HNE/ACR-modified peptides of carbonylated albumin and actin is proposed, and the advantages over the conventional methods for RCS and RCS-adducted protein analyses discussed.

Enzyme-linked immunosorbent assay for 4-hydroxynonenal-histidine conjugates

Highly reactive aldehyde 4-hydroxynonenal (HNE) is the final product of lipid peroxidation, known as a second messenger of free radicals and a signaling molecule. It forms protein conjugates involved in pathology of various diseases. To determine cellular HNE-protein conjugates we developed indirect ELISA based on well-known, monoclonal antibody against HNE-histidine (HNE-His) adducts. The method was calibrated using HNE-albumin conjugates as standards (R(2) = 0.999) and validated on human osteosarcoma cell cultures (HOS). The ELISA showed good sensitivity (8.1 pmol HNE-His/mg of protein), precision ( +/- 8% intra-assay and +/- 12% inter-assay) and spiking recovery ( +/- 9%). The assay revealed 60-fold increase of cellular HNE-His adducts upon copper-induced lipid peroxidation of HOS. The ELISA matched HNE-immunocytochemistry of HNE-treated HOS cells and quantified the increase of cellular HNE-His conjugates in parallel to the decrease of free HNE in culture medium. The ELISA was developed as ELISA Stress for severe lipid peroxidation and ELISA Fine for studies on HNE physiology.

Life span and stress resistance of Caenorhabditis elegans are differentially affected by glutathione transferases metabolizing 4-hydroxynon-2-enal

The lipid peroxidation product 4-hydroxynon-2-enal (4-HNE) forms as a consequence of oxidative stress, and acts as a signaling molecule or, at superphysiological levels, as a toxicant. The steady-state concentration of the compound reflects the balance between its generation and its metabolism, primarily through glutathione conjugation. Using an RNAi-based screen, we identified in Caenorhabditis elegans five glutathione transferases (GSTs) capable of catalyzing 4-HNE conjugation. RNAi knock-down of these GSTs (products of the gst-5, gst-6, gst-8, gst-10, and gst-24 genes) sensitized the nematode to electrophilic stress elicited by exposure to 4-HNE. However, interference with the expression of only two of these genes (gst-5 and gst-10) significantly shortened the life span of the organism. RNAi knock-down of the other GSTs resulted in at least as much 4-HNE adducts, suggesting tissue specificity of effects on longevity. Our results are consistent with the oxidative stress theory of organismal aging, broadened by considering electrophilic stress as a contributing factor. According to this extended hypothesis, peroxidation of lipids leads to the formation of 4-HNE in a chain reaction which amplifies the original damage. 4-HNE then acts as an "aging effector" via the formation of 4-HNE-protein adducts, and a resulting change in protein function.

Attenuation of oxidative stress and cardiac dysfunction by bisoprolol in an animal model of dilated cardiomyopathy

Oxidative stress is an important susceptibility factor for dilated cardiomyopathy. We have investigated the effects of bisoprolol, a beta1-selective adrenoceptor blocker, on oxidative stress and the development of cardiac dysfunction in a model of dilated cardiomyopathy. Male TO-2 and control hamsters at 8 weeks of age were treated with bisoprolol (5 mg/kg per day) or vehicle for 4 weeks. Treatment with bisoprolol prevented the progression of cardiac dysfunction in TO-2 hamsters. This drug did not affect the increase in NADPH oxidase activity but prevented the reduction in activity and expression of mitochondrial manganese-dependent superoxide dismutase as well as the increases in the concentrations of interleukin-1beta and tumor necrosis factor-alpha in the left ventricle of TO-2 hamsters. Attenuation of the development of cardiac dysfunction by bisoprolol may thus result in part from normalization of the associated increases in the levels of oxidative stress and pro-inflammatory cytokines in the left ventricle.

Mass spectrometric characterization of covalent modification of human serum albumin by 4-hydroxy-trans-2-nonenal

Several pieces of evidence indicate that albumin modified by HNE is a promising biomarker of systemic oxidative stress and that HNE-modified albumin may contribute to the immune reactions triggered by lipid peroxidation-derived antigens. In this study, we found by HPLC analysis that HNE is rapidly quenched by human serum albumin (HSA) because of the covalent adduction to the different accessible nucleophilic residues of the protein, as demonstrated by electrospray ionization mass spectrometry (ESI-MS) direct infusion experiments (one to nine HNE adducts, depending on the molar ratio used, from 1:0.25 to 1:5 HSA:HNE). An LC-ESI-MS/MS approach was then applied to enzymatically digested HNE-modified albumin, which permitted the identification of 11 different HNE adducts, 8 Michael adducts (MA) and 3 Schiff bases (SB), involving nine nucleophilic sites, namely: His67 (MA), His146 (MA), His242 (MA), His288 (MA), His510 (MA), Lys 195 (SB), Lys 199 (MA, SB), Lys525 (MA, SB) and Cys34 (MA). The most reactive HNE-adduction site was found to be Cys34 (MA) followed by Lys199, which primarily reacts through the formation of a Schiff base, and His146, giving the corresponding HNE Michael adduct. These albumin modifications are suitable tags of HNE-adducted albumin and could be useful biomarkers of oxidative and carbonylation damage in humans.

Circulating 4-hydroxynonenal-protein thioether adducts assessed by gas chromatography-mass spectrometry are increased with disease progression and aging in spontaneously hypertensive rats

Oxidative stress has been implicated in numerous degenerative diseases of aging, including heart diseases. However, there is still a need to identify biomarkers of oxidative stress-related events, such as protein modification by the lipid peroxidation product 4-hydroxynonenal (HNE) in these diseases in humans. The objective of this study was to assess if circulating levels of HNE-protein adducts (i) can be assessed with precision by GCMS and (ii) vary with disease progression and aging in a model of cardiomyopathy that displays enhanced oxidative stress, namely the spontaneously hypertensive rats (SHR). We modified a previously published isotope dilution GCMS method that quantifies HNE and its inactive metabolite, 1,4-dihydroxynonene (DHN), bound to thiol proteins following treatment with NaB(2)H(4) and Raney nickel, to increase its sensitivity (20-fold), precision, and robustness. Levels of these adducts were measured in blood and plasma collected from SHR and control Wistar rats at 7, 15, 22, and 30 weeks of age. Levels of protein-bound HNE, which were quantitated with good precision in the nanomolar range in blood, but not in plasma, were significantly increased by disease (SHR) and age (P < 0.0001 for both). Compared to Wistar rats, SHR showed greater blood levels of HNE-protein adducts at 22 and 30 weeks. Levels of protein-bound DHN, which were detected in blood and in plasma, were not affected by disease or age. Collectively, the results of this study conducted in an animal model of cardiomyopathy demonstrate that changes in blood HNE-protein thioether adducts with disease progression and aging can be assessed with good precision by the described GCMS method. This method may prove to be useful in evaluating the occurrence and impact of oxidative stress-related events involving bioactive HNE in heart diseases and aging in humans.

Analysis of Derivatized Biogenic Aldehydes by LC Tandem Mass Spectrometry

Lipid peroxidation has been linked to the etiology of several diseases, including Alzheimer's disease (AD). End products of this phenomenon include low molecular weight, water-soluble aldehydes, compounds that covalently modify proteins and nucleic acids, thereby altering function. Aliphatic aldehydes (C3-C10) are generated during lipid peroxidation, along with alpha,beta-unsaturated aldehydes, including acrolein and 4-hydroxynonenal (HNE). The Hantzsch reaction was used to produce heterocyclic aldehyde derivatives that can be conveniently analyzed with mass spectrometry. Liquid chromatographic analyses revealed increasing retention times from derivatized methanal to octanal. HNE derivatives were observed to elute between heptanal and octanal derivatives, while the acrolein derivatives had a retention time similar to the propanal derivative. Smaller aliphatic aldehyde derivatives fragmented in a similar manner to produce a base peak of m/z 273, while the larger derivatives yielded m/z 274 as the base peak. Acrolein and HNE derivatives fragmented in a slightly different manner compared to their aliphatic counterparts. Calibration plots of aliphatic and unsaturated aldehydes were linear (r2 >/= 0.99) in the concentration range explored (approximately 5-1500 pg on column). The LC-MS/MS methodology developed here will be used in subsequent studies to determine aldehyde concentrations for comparing age-matched controls to AD tissues from human subjects.

High sensitivity of plasma membrane ion transport ATPases from human neutrophils towards 4-hydroxy-2,3-trans-nonenal

Lipid peroxidation results in release of 4-hydroxy-2,3-trans-nonenal (HNE), which is known to conjugate to specific amino acids of proteins and may alter their function. The effect of HNE on the activities of Na(+)/K(+)-ATPase, Mg(2+)-ATPase, Ca(2+)-ATPase, and calmodulin-stimulated Ca(2+)-ATPase has been studied both in erythrocyte ghosts and in neutrophil membrane preparations. Neutrophil Ca(2+)-ATPase was strongly inhibited by micromolar concentrations of HNE (IC(50) = 12 microM), that means in the range of pathophysiologically relevant HNE levels. The IC(50) value for neutrophil Na(+)/K(+)-ATPase was about 40 microM. HNE was considerably less effective against neutrophil Mg(2+)-ATPase and the erythrocyte ghost enzymes (IC(50) values range from 91 to 240 microM). The data suggest that HNE may play a specific role in the regulation of neutrophil calcium homeostasis in response to oxidative stress.