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Validation of methyl malondialdehyde as internal standard for malondialdehyde detection by capillary electrophoresis.

The aim of this study was to validate, by capillary electrophoresis, the use of synthesized methyl malondialdehyde as the internal standard for the direct quantification of free and total (free+bound) malondialdehyde in biological samples. All analyses were performed in 20 cm x 50 microm uncoated capillaries at 20 degrees C, using 25 mmol/L borax (pH 9.3) and 5 mmol/L tetradecyltrimethylammonium bromide as running buffer. The applied voltage was -4kV (about 8 microA), the detector being set at 260 nm for a total run time of 8 min per sample. Free malondialdehyde was evaluated after acetonitrile extraction, while the samples evaluated for total malondialdehyde were, before extraction, hydrolyzed for 1h at 60 degrees C in the presence of 1 mol/L NaOH. The detection threshold was 0.2 micromol/L in microsomes and 0.4 micromol/L in plasma. As an application of the method, three pools of rat liver microsomes were quantified before (0.35+/-0.1 and 1.1+/-0.5 nmol/mg protein, free and total malondialdehyde, respectively, mean+/-SD) and after lipoperoxidation induction using systems able to generate oxygen free radicals (18.4+/-3.2 and 19.7+/-2.0 nmol/mg protein). The results were confirmed by isotopic dilution gas chromatography-mass spectrometry, used as the reference method. The feasibility of capillary electrophoresis for malondialdehyde determination in normal and pathological human plasma was also investigated.

Acetonitriles↗

Cell-biology of ageing. III. Malondialdehyde as an index of free radical reactions in the early senescent mutants of Neurospora crassa and study of the effect of free radical scavengers on malondialdehyde contents.

Malondialdehyde - a product of lipid peroxidation due to free radical reaction was estimated in the culture filtrates of early senescent mutants of Neurospora crassa and the effects of vitamin E, vitamin C and Sodium selenite (free radical scavengers) in malondialdehyde contents were studied. From the results obtained, it could not be established that increased free radical reaction was the sole factor for the early senescence of all the mutants; and the free radical scavengers had very little effect on the malondialdehyde content of the selected early senescent mutants.

Ascorbic Acid↗

Methyl malondialdehyde is not suitable as an internal standard for malondialdehyde detection in urine after derivatisation with 2,4-dinitrophenylhydrazine.

A previously described method of measurement of malondialdehyde (MDA) in human urine after derivatisation with 2,4-dinitrophenylhydrazine (DNPH) was tested for a possibility of using methyl malondialdehyde (MeMDA) as an internal standard. Despite structural similarity, those compounds were found to produce different yields of derivatisation under the same conditions depending on urine matrix. We conclude, that MeMDA is not suitable as an internal standard for the measurement of MDA in urine under previously reported conditions when DNPH is used as a deriviatising agent.

Calibration↗

Methyl malondialdehyde as an internal standard for the determination of malondialdehyde.

Methyl malondialdehyde (Me-MDA) is suggested as an internal standard for the determination of the lipid peroxidation product, malondialdehyde (MDA). A procedure for synthesising the Me-MDA sodium salt is described in detail. The purity and identity of the synthesised Me-MDA have been confirmed using nuclear magnetic resonance and UV spectroscopy, and by micellar electrokinetic chromatography. The applicability of Me-MDA as an internal standard has been demonstrated for rat brain homogenate samples. These samples were purified solely through ultrafiltration. The preferred analytical technique was capillary zone electrophoresis (CZE) with UV detection at 267 nm. The limits of detection (3 S/N) for the CZE separations of Me-MDA and MDA were 0.5 and 0.2 microM, respectively, and the total analysis time was approximately 10 min. Details of separations are also presented using high-performance liquid chromatography (HPLC) with UV detection at 245 nm, and gas chromatography, together with either electron capture or mass spectrometric detection. The GC separations require derivatisation of MDA and Me-MDA with pentafluorophenylhydrazine while the CZE and HPLC separations can be performed on the native molecules.

Chromatography, Gas↗

Mutagenicity of the malondialdehyde oligomerization products 2-(3'-oxo-1'-propenyl)-malondialdehyde and 2,4-dihydroxymethylene-3-(2,2-dimethoxyethyl)glutaraldehyde in Salmonella.

Malondialdehyde (MDA), a byproduct of non-enzymatic lipid peroxidation and prostaglandin biosynthesis, has been shown to be a weak frameshift mutagen in Salmonella mutagenicity assays. Because it is a dialdehyde, MDA can undergo self condensation to form polymeric products. It is possible that these condensation products are highly mutagenic and have contributed to previously reported estimates of MDA mutagenicity. We synthesized two major MDA polymerization products, (1) 2-(3'-oxo-1'-propenyl)-malondialdehyde [(MDA)2] and (2) 2,4-dihydroxymethylene-3-(2,2-dimethoxyethyl)glutaraldehyde [(MDA)3Me2] and tested their mutagenicity in the Salmonella frameshift tester strains hisD3052 and TA94 (hisD3052/pKM101). Analysis of the reversion rates revealed both (MDA)2 and (MDA)3Me2 to be weak mutagens, approximately equipotent to MDA. Although both (MDA)2 and (MDA)3Me2 are mutagenic, the fact that their formation is thermodynamically unfavorable under physiological conditions suggests they do not contribute significantly to the mutagenicity of MDA solutions.

Dose-Response Relationship, Drug↗

Improved method for plasma malondialdehyde measurement by high-performance liquid chromatography using methyl malondialdehyde as an internal standard.

Measurement of malondialdehyde (MDA) is an important contribution to the assessment of oxidative stress. We report a sensitive and reproducible high-performance liquid chromatography (HPLC) method for measurement of plasma MDA in the assessment of lipid peroxidation. Using methyl malondialdehyde (Me-MDA) as an internal standard with reversed-phase HPLC and UV detection and derivatisation with 2,4 dinitrophenylhydrazine (DNPH), we obtained maximum MDA values with 60-min incubation of 10% plasma with 1 M NaOH at 60 degrees C. The dilution of the plasma and a longer incubation time in the alkaline hydrolysis step greatly improved recovery of MDA from its bound form. Ratios of peak height of MDA/Me-MDA were linear over a range of 0-100 microM with correlation coefficients >0.99. The recovery was 88.5%. Within and between run variations were <4 and <7%, respectively. The mean MDA value measured in 20 healthy volunteers was 13.8 microM (+/-1.32).

Calibration↗

Reaction of malondialdehyde-DNA adducts with hydrazines-development of a facile assay for quantification of malondialdehyde equivalents in DNA.

Malondialdehyde is a ubiquitous product of lipid peroxidation that reacts with DNA to form premutagenic lesions. Principal among them is pyrimido-[1,2-alpha]purin-10(3H)-one (M(1)G). M(1)G has recently been found to be a reactive electrophile in DNA that couples with amines at basic pH or hydroxylamines at neutral pH. We explored the reaction of M(1)G with hydrazines because of the possibility that the latter could act as bifunctional nucleophiles to strip the malondialdehyde equivalent from DNA. Pentafluorophenylhydrazine reacted rapidly with M(1)G to form a hydrazone conjugate. This hydrazone was stable at room temperature and did not cyclize to form the corresponding pyrazole. In contrast, phenylhydrazine and benzylhydrazine reacted with M(1)G to form phenylpyrazole and benzylpyrazole, respectively. Pentafluorobenzylhydrazine reacted rapidly with M(1)G to form pentafluorobenzylpyrazole and dG in near quantitative yield. This reaction formed the basis for a quantitative assay for the presence of M(1)G or M(1)G equivalents in DNA or protein that utilized gas chromatography/negative chemical ionization mass spectrometry. The assay was extended to the oxopropenyl donors, M(1)A, base propenal, and N(epsilon)-3-oxopropenyl-lysine. Analysis of DNA treated with bleomycin demonstrated a linear increase in the level of oxopropenyl groups that plateaued at approximately 1 oxopropenyl group/100 bases at a bleomycin concentration of 200 microM. Parallel analysis of M(1)G in the samples revealed that this adduct represents a small fraction of the total oxopropenyl units generated in DNA by treatment with bleomycin.

Adenine↗

Excretion of malondialdehyde, formaldehyde, acetaldehyde, acetone and methyl ethyl ketone in the urine of rats given an acute dose of malondialdehyde.

A high pressure liquid chromatographic system (HPLC) has recently been developed for the simultaneous detection of malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT) and acetone (ACON). We have examined the urinary excretion of these four lipid metabolites in the urine of rats following the acute oral administration of MDA (158 mg/kg body weight). During the first 12 h, increases in the urinary excretion of MDA and ACT of approximately 192- and 70-fold, respectively, were observed. The urinary excretion of both MDA and ACT decreased thereafter. An increase in FA excretion was observed only 12-24 h after MDA administration. A significant decrease in ACON relative to control values was observed 12-48 h after MDA treatment. Two new peaks were present in the HPLC chromatograms of urine samples 0-24 h after MDA administration. Both peaks were shown to be due to methyl ethyl ketone (MEK) which appears to be formed as a result of MDA metabolism. The results demonstrate that orally administered MDA is rapidly excreted in the urine, and alters the metabolism and excretion of other lipid metabolites.

Acetaldehyde↗

Dissociation between prostaglandin and malondialdehyde formation in exudate and increased levels of malondialdehyde in plasma and liver during granulomatous inflammation in the rat.

During kaolin-induced granuloma pouch inflammation in the rat the concentration of malondialdehyde (MDA) in the exudate, measured by the 2-thiobarbiturate method, steadily increased and this increase was correlated with the increase in granuloma weight. There was a complete lack of correlation between the concentrations of MDA and prostaglandin (PG)-like material in the inflammatory exudate. Whereas the concentration of PGs reached a maximum 1 day after the induction of inflammation and returned to control levels on day 4, the MDA concentration continuously increased from the initiation of inflammation up to day 16. During granuloma development the concentration of MDA in the plasma reached a maximum on day 2 in parallel with the concentration in the liver, then both plasma and liver MDA decreased to levels observed in control rats. Between day 2 and 8 of the inflammatory process homogenates of livers from inflamed rats showed an increased formation of MDA on incubation, the amount formed being maximal on day 4. The results of the present study are discussed in view of a possible involvement of lipid peroxidation in inflammation.

Animals↗

The importance of lipid-derived malondialdehyde in diabetes mellitus.

Malondialdehyde (MDA) is a highly toxic by-product formed in part by lipid oxidation derived free radicals. Many studies have shown that its concentration is increased considerably in diabetes mellitus. Malondialdehyde reacts both irreversibly and reversibly with proteins and phospholipids with profound effects. In particular, the collagen of the cardiovascular system is not only stiffened by cross-links mediated by malondialdehyde but then becomes increasingly resistant to remodelling. It is important in diabetes mellitus because the initial modification of collagen by sugar adducts forms a series of glycation products which then stimulate breakdown of the lipids to malondialdehyde and hence further cross-linking by malondialdehyde of the already modified collagen. Some progress is being made into the mechanisms of formation and the nature of the intermolecular cross-links induced by malondialdehyde which result in the stiffening of the collagenous tissues. Our recent studies indicate the formation of pyridyl cross-links. Malondialdehyde has been shown to react several orders of magnitude faster with the pre-existing collagen enzymic cross-links than the amino acid side-chains. Malondialdehyde modification of basic amino-acid side-chains also results in a change in properties, for example, in the charge profile of the molecule resulting in modified cell-matrix interactions. Although aspects of the biochemistry of malondialdehyde are still not fully understood its complex chemistry is being unravelled and this should lead to ways of preventing its damaging reactions, for example, through antioxidant therapy.

Amino Acids↗

Immunogenicity of malondialdehyde-modified low density lipoproteins. Studies with monoclonal antibodies.

Malondialdehyde (MDA)-modified low density lipoprotein (LDL) can stimulate the accumulation of cholesteryl esters in cultured macrophages through its interaction with specific scavenger receptors. It has been speculated that such interaction occurs in vivo thus contributing to the formation of foam cells within atherosclerotic lesions. This report describes the development of new tools in the form of a specific assay for MDA-LDL to investigate this hypothesis. We have immunized BALB/c mice with malondialdehyde mouse low density lipoproteins and antibodies against malondialdehyde human low density lipoproteins were generated. Monoclonal antibodies were produced using hybridoma techniques and one particular clone (EB 7-3) was expanded for further studies. The immunoreactivity of several antigens was tested using antibody EB 7-3 in an enzyme-linked immunosorbent assay (ELISA). In a typical assay malondialdehyde human LDL (with at least 40% of lysines modified) was coated (2 micrograms/ml, 100 microliter) in 96-well microtiter plates. Antibody plus one of several antigens were then added and the interaction between the antibody and coated antigen was measured using alkaline phosphatase-conjugated affinity purified goat anti-mouse immunoglobulin. The binding of antibody EB 7-3 to wells coated with malondialdehyde-LDL was competitively inhibited by malondialdehyde-LDL added in solution, with half maximal inhibition occurring at 150 +/- 80 ng/ml. In addition, the ability of malondialdehyde-LDL to inhibit this interaction was proportional to the degree of modification: the more lysines were modified the more did malondialdehyde-LDL inhibit the binding of antibody EB 7-3 to coated malondialdehyde-LDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗

The significance of measuring the time course of serum malondialdehyde concentration in patients with torsion of the testis.

PURPOSE: We determined the time course of malondialdehyde, a measure of free radical damage, in patients undergoing standard surgical treatment for testicular torsion. MATERIALS AND METHODS: Patients presenting with testicular torsion were studied prospectively. Blood samples were obtained after administering general anesthesia but before surgical incision, and 10 minutes, 30 minutes and 24 hours after detorsion. Orchiopexy was performed in patients with viable testes (group 1) and orchiectomy was performed in those with nonviable testes (group 2). Further blood samples were obtained 1 and 3 months after surgery. Similar blood samples were taken from controls, including patients younger than 40 years undergoing other operations involving manipulation of the testis, such as hydrocelectomy or orchiopexy (group 3). The level of malondialdehyde in each serum sample was determined by the thiobarbituric acid reaction. RESULTS: A total of 65 patients were studied, including 56 with testicular torsion and 9 controls (group 3). Of the 56 patients 11 (19.6%) with testicular torsion underwent ipsilateral orchiectomy and contralateral orchiopexy (group 2). The remaining 45 patients (80.4%) underwent bilateral orchiopexy (group 1). However serum malondialdehyde was estimated in only 34 of the 56 patients with torsion. Mean malondialdehyde at 0, 10 and 30 minutes, 24 hours, and 3 and 6 months was 3.3, 3.69, 3.69, 2.9, 2.65 and 2.39 nmol./ml. on the 24 group 1 patients, 3.53, 4.56, 3.87, 2.87, 2.82 and 2.64 nmol./ml. in the 10 group 2 patients, and 3.6, 3.08, 3.18, 2.95, 2.88 and 2.65 nmol./ml. in the 9 group 3 controls, respectively. The highest serum malondialdehyde was at 10 minutes after detorsion in groups 1 and 2. There was a statistically significant difference in malondialdehyde between groups 1 and 2 compared with group 3 at 10 minutes (p <0.04). Serum malondialdehyde returned to baseline at 24 hours in all patients. CONCLUSIONS: The results of this study indicate that testicular torsion and its treatment with detorsion is an example of ischemia-reperfusion injury, producing measurable changes in malondialdehyde in humans. Thus, serum malondialdehyde could be used to determine the extent of injury.

Adolescent↗

Inhibition of mitochondrial aldehyde dehydrogenase by malondialdehyde.

Rat liver mitochondria contain an aldehyde dehydrogenase (ALDH, EC 1.2.1.3) with a low Km for acetaldehyde (2 microM) which is susceptible to inhibition by a variety of agents including p-chloromercuribenzoate and arsenite. This low Km ALDH isozyme has been shown to be decreased in activity following CCl4 treatment in vivo and by lipid peroxidation in vitro. Malondialdehyde, the most studied product of lipid peroxidation, was investigated for possible inhibitory effects on the low Km ALDH for rat liver mitochondria. Malondialdehyde was found to be a potent inhibitor of the enzyme. The enzyme was equally sensitive to inhibition when intact mitochondrial preparations were compared with disrupted mitochondria. The extent of enzyme inhibition was dependent on malondialdehyde concentration and time of incubation. High concentrations of malondialdehyde completely inhibited low Km mitochondrial ALDH activity. Malondialdehyde was found to inhibit the low Km ALDH irreversibly. The rate of ALDH inactivation exhibited two phases, one a rapid rate phase (5-15 s) and a second slower rate phase, both of which showed rates which were dependent on malondialdehyde concentration. These data show that malondialdehyde is a potent, high affinity, irreversible inhibitor of the low Km ALDH of rat liver mitochondria. This ALDH isozyme is considered to be the most important enzyme in acetaldehyde metabolism. Malondialdehyde inhibition of the low Km ALDH may be important since both ethanol and acetaldehyde are thought to stimulate hepatic lipid peroxidation.

Aldehyde Dehydrogenase↗

Increased serum malondialdehyde and decreased nitric oxide within 24 hours of thrombotic stroke onset.

BACKGROUND AND PURPOSE: Ischemia/reperfusion generates free oxygen radicals, which react with the unsaturated lipids of biomembranes resulting in the generation products such as malondialdehyde. Malondialdehyde could be a sensor for tissue damage and reperfusion. Nitric oxide, released due to the early arrival of leukocytes in the brain parenchyma, could be a sensor for nonflow phenomenon. Thereby, the purpose of this research was to evaluate the behavior of malondialdehyde and nitric oxide within the 24 hours after the stroke onset. METHODS: Fifteen patients up to an age of 49 years, admitted to the emergency of University Hospital and Chiquinquirá Hospital in Maracaibo, Venezuela, were examined by a neurologist and underwent 12-lead electrocardiograms and computed tomography for the diagnosis of thrombotic stroke. Serum malondialdehyde and nitric oxide were measured as thiobarbituric acid adducts and total nitrites. Data were collected within the 24 hours after the stroke onset. RESULTS: Malondialdehyde for patients with stroke had a significant increase (P<0.001) when compared with healthy controls (47.9 +/- 7.1 vs. 1.7 +/- 0.2 micromol/L). Conversely, serum nitric oxide for patients with stroke had a significant decrease (P<0.001) when compared with the control group (14.5 +/- 1.4 vs. 41.3 +/- 3.7 micromol/L). The lowest values of malondialdehyde and the highest values of nitric oxide were observed in two patients, who died. CONCLUSIONS: Serum levels of malondialdehyde increase, and serum levels of nitric oxide diminish within 24 hours after the onset of thrombotic stroke onset. This suggests that serum malondialdehyde level could be used as potentially reliable and sensitive marker for reperfusion, whereas nitric oxide levels could acts as potential biochemical sensor for nonreflow phenomenon.

Aged↗

Ionotropic glutamate receptors are involved in malondialdehyde production in anesthetized rat brain cortex: a microdialysis study.

Elevated extracellular glutamate levels can increase malondialdehyde production in the brains of anesthetized rats. Thus, we investigated whether ionotropic glutamate receptors are involved in glutamate-induced malondialdehyde production. A microdialysis probe was implanted in the brain cortex of anesthetized rats. The malondialdehyde level in microdialysates was analyzed using an HPLC system. Three different ionotropic glutamate receptor agonists were used. At a concentration of 1.5 mM alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrobromide (AMPA, a selective AMPA receptor agonist) induced a dramatic increase in extracellular malondialdehyde production (as much as 14-fold relative to the basal value). N-Methyl-D-aspartic acid (NMDA, a selective NMDA receptor agonist) also induced an increase in extracellular malondialdehyde production; however, the increase was not as much as that observed in the perfusion of AMPA receptor agonist. Kainic acid (a selective kainate receptor agonist) did not significantly increase malondialdehyde production. When co-perfused with L-trans-pyrrolidine-2,4-dicarboxylate (PDC; 31.4 mM), a glutamate uptake transport inhibitor that can increase the extracellular glutamate levels, AMPA receptor antagonist [1-(4-aminophenyl)4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride, 1.0 mM] can significantly reduce PDC-induced malondialdehyde production. Although NMDA receptor antagonist [(5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate, MK801] also can decrease the PDC-induced malondialdehyde production, it was not as effective as the AMPA receptor antagonist. These results suggest that ionotropic receptors are involved in the glutamate-induced increase in malondialdehdye production. Specifically, AMPA receptor seems to be predominant in the glutamate-induced malondialdehdye production in anesthetized rat brain cortex.

Anesthesia↗

Hepatic mitochondrial malondialdehyde metabolism in rats with chronic iron overload.

Peroxidative decomposition of mitochondrial membrane phospholipids with subsequent mitochondrial dysfunction is a postulated mechanism of liver cell injury in parenchymal iron overload. Malondialdehyde is formed when polyunsaturated fatty acids of membrane phospholipids undergo peroxidative decomposition, and it is metabolized by aldehyde dehydrogenase. We studied mitochondrial metabolism of malondialdehyde in rats with chronic dietary iron overload. Hepatic malondialdehyde concentrations were significantly increased in iron-loaded livers, and mitochondrial respiratory control ratios using glutamate as a substrate were decreased by 47% largely owing to reductions in state 3 respiration. When exogenous malondialdehyde was added to mitochondrial fractions, there was significantly less metabolism of malondialdehyde in mitochondria of iron-loaded livers as compared with controls. In addition, there was a 28% decrease in mitochondrial aldehyde dehydrogenase in iron-loaded livers but no change in cytosolic aldehyde dehydrogenase. Increased hepatic malondialdehyde in chronic iron overload may result from a combination of increased production and decreased metabolism of malondialdehyde, both of which may be due to iron-induced mitochondrial lipid peroxidation.

Aldehyde Dehydrogenase↗

Diminished susceptibility to proteolysis after protein modification by the lipid peroxidation product malondialdehyde: inhibitory role for crosslinked and noncrosslinked adducted proteins.

The lipid peroxidation product malondialdehyde forms adducts with proteins that are detected during routine assays for protein carbonylation. To test whether this damage alters the susceptibility of a protein to proteolysis, we treated bovine serum albumin with various concentrations of malondialdehyde and examined its susceptibility to digestion by alpha-chymotrypsin. In keeping with findings concerning the consequences of protein damage by other carbonyl products of lipid peroxidation, we found that malondialdehyde-modified protein was resistant to proteolysis. Since significant protein crosslinking occurred during modification with malondialdehyde, we investigated the possibility that crosslinked proteins were acting as proteolytic inhibitors. Malondialdehyde-modified proteins were resolved into crosslinked and noncrosslinked forms and the effectiveness of both species as proteolytic antagonists was examined. While both forms of malondialdehyde-adducted proteins were more potent proteolytic inhibitors than unmodified albumin, there were no significant differences in inhibitory potency between crosslinked and noncrosslinked proteins. Our findings suggest that malondialdehyde-modification produces protease-resistant proteins without an obligatory role for crosslinking.

Animals↗