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PubMed2005

Kinetics of ethanol and acetaldehyde release suggest a role for acetaldehyde production in tolerance of rice seedlings to micro-aerobic conditions.

BACKGROUND AND AIMS: This paper examines the basis of the greater tolerance of an indica rice cultivar FR13A to complete submergence compared with relatively intolerant japonica rice CT6241. We study whether this superior tolerance is related to its greater tolerance to O2 shortage and to an ability to run a more favourable rate of alcoholic fermentation during and after O2 deprivation. METHODS Fermentation products were analysed using sensitive laser-based photoacoustics at high time resolution to establish patterns and rates of ethanol and acetaldehyde emission by intact rice seedlings exposed to micro-aerobic (0.05-0.5 % O2) or zero O2 supply, and also during their return to air. Oxygen and CO2 emission or uptake was also quantified. KEY RESULTS: In the dark, no acetaldehyde and ethanol emission was observed until external O2 concentration in a gas phase decreased to <or=0.3% O2. The ethanol production rate was maximal in 0% O2, similar in both cultivars and gradually diminished with increasing O2 concentration. Lag time for induction of fermentation increased with O2 up to 0.3% and was shorter in CT6241. Light strongly suppressed fermentation. In contrast to that of ethanol, emission of acetaldehyde in the dark under micro-aerobic conditions (<or=0.15% O2 gas phase) exceeded that under anaerobiosis, was maximal in 0.05% O2 and was greater in FR13A than in CT6241. A drop in acetaldehyde emission to about half its value immediately followed a switch to anaerobic conditions after 6.5 h treatment under 0.05% O2, while ethanol release showed a further increase. A large peak in acetaldehyde emission immediately followed the return of seedlings to air after treatment with <or=0.15% O2. The emission from FR13A was up to three times larger than from CT6241. CONCLUSIONS: Tolerance to submergence in FR13A appears not to be connected to its rate of ethanol production during anaerobiosis, but to the increased acetaldehyde output during and after experiencing micro-aerobic conditions (0.05-0.15% O2). Extra acetaldehyde production from ethanol may be a consequence of diversion of the reactive oxygen species away from the damaging lipid peroxidation pathway.

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PubMed1990

In vivo accelerated acetaldehyde metabolism using acetaldehyde dehydrogenase-loaded erythrocytes.

Human erythrocytes were loaded with homogeneous acetaldehyde dehydrogenase (AcDH) purified from Alcaligenes Eutrophus (an enzyme species with an apparent Km for acetaldehyde similar to the mitochondrial enzyme), using an encapsulation procedure based on hypotonic haemolysis, isotonic resealing and reannealing. The AcDH-overloaded erythrocytes contained 1.55 +/- 0.25 I.U. of AcDH activity per ml of packed erythrocytes, a value 12-15 times higher than that of corresponding unloaded or native red cells. The AcDH-loaded erythrocytes were found to metabolize 4 +/- 0.8 mumol of acetaldehyde/hr/ml of red blood cells, whereas the glycolytic activity was almost unmodified. Estimates of intracellular adenine nucleotides showed 50% ATP decay in the AcDH-loaded cells when incubated in the presence of acetaldehyde concentrations higher than 50 microM, whereas the [NAD+]/[NADH] ratio was strongly decreased but to the same extent as in control cells, suggesting that this was due to the acetaldehyde itself and not to the presence of encapsulated AcDH. Similar results were obtained using mouse erythrocytes. AcDH-overloaded mouse red blood cells from donor animals were also injected intraperitoneally into compatible recipients (Balb/C) and 80 to 85% of these were found to enter into circulation within 24 hr and to circulate with a half-life of 6-7.3 days (normal half-life 11 days). Following an acute dose of ethanol (2g/kg intraperitoneally), blood levels of acetaldehyde were significantly lower in mice receiving the AcDH-loaded erythrocytes than in controls. Blood levels of ethanol were also lower in the treated mice compared to controls. These results show that AcDH-overloaded erythrocytes can perform in vitro and in vivo as bioreactors improving alcohol and acetaldehyde metabolism, and suggest that administration of these cells to alcoholic patients could be of value in restoring to normal, or improving, alcohol and acetaldehyde metabolism.

Acetaldehyde↗

PubMed1995

Structural analysis of peptide-acetaldehyde adducts by mass spectrometry and production of antibodies directed against nonreduced protein-acetaldehyde adducts.

Acetaldehyde can form protein-acetaldehyde adducts (AAs) in vivo and may play a role in the genesis of alcoholic liver disease. The nature of the chemical modification of proteins by acetaldehyde in vivo has not been elucidated. In vitro, acetaldehyde can form reversible adducts including a Schiff's base with lysine (K) and imidazolidinone with terminal amino groups of proteins such as human hemoglobin (Hb). In this study, we used FAB/MS to analyze the products of peptide-AAs (pep-AAs) formed by incubating acetaldehyde with Hb peptides. We then used an octabranched multiple antigen peptide (MAP) system containing Hb peptide-AAs to raise antibodies. Three Hb peptides [i.e., 8-pep consisting of 8 residues (V1HLTPVEK8) at the N-terminus of beta-chain of human sickle-cell Hb, 11-pep-gly consisting of 11 residues (G56NPKVKAHGKK66) in a segment of beta-chain rich in lysine, and 11-pep-pro that consists of the same sequence as 11-pep-gly, except G56 was replaced by proline (P)] were incubated with 1 mM acetaldehyde at 4 degrees C for 7d without NaCNBH3 (nonreduced conditions). Analysis by FAB/MS showed that 8-pep formed an imidazolidinone at the N-terminal valine, 11-pep-gly formed a Schiff's base and imidazolidinone at the N-terminus, whereas 11-pep-pro that lacks a free alpha-amino group formed only a Schiff's base at K59. By contrast, incubation of these Hb peptides with 250 mM acetaldehyde and NaCNBH3 at 37 degrees C for 1 hr (reduced conditions) produced mono- and diethylated modifications of all available K residues, as well as the N-terminal amino group.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1996

Metabolism of acetaldehyde to acetate by rat hepatic P-450s: presence of different metabolic pathway from acetaldehyde dehydrogenase system.

NADPH-dependent activity of acetaldehyde oxidation was investigated in microsomes by assaying [14C]acetic acid produced from [14C]acetaldehyde with ion-exchange column. Rat hepatic microsomes exhibited acetaldehyde oxidation activity in the presence of NADPH. This activity was induced 2-fold by the treatment of rats with ethanol. We designated this NADPH-dependent oxidation system as microsomal acetaldehyde-oxidizing system (MAOS), to distinguish from the NAD-dependent acetaldehyde oxidation system by acetaldehyde in mitochondria and cytsol. We further investigated essential enzymes contributing to MAOS activity. Acetaldehyde oxidation activity was investigated in eight forms of purified P-450 in a reconstituted system. Cytochrome P-450 (CYP) 2E1 had the highest oxidation activity and CYP1A2 and CYP4A2 had the next highest activity. Other forms had low activity. To assess the contribution of these forms to MAOS activity, immunoblot was done. CYP2E1 was induced 2-fold by ethanol treatment, but CYP1A2 and CYP4A2 were not reflecting the MAOS activity increased by ethanol treatment. These results suggest that CYP2E1 is the essential enzyme in the MAOS of rats.

Acetaldehyde↗

PubMed1997

Stable acetaldehyde adducts: structural characterization of acetaldehyde adducts of human hemoglobin N-terminal beta-globin chain peptides.

Acetaldehyde is the first oxidation product of ethanol in vivo. Our earlier work showed that with sufficient acetaldehyde, five of the six possible sites of the peptide pentalysine were modified as a Schiff base (Braun KP, et al: J Biol Chem 270:11263-11266, 1995). However, we were unable to deduce unequivocally which site was unmodified. Lysine residues, as well as the amine terminal valine residues, in hemoglobin have been implicated as target structures for acetaldehyde adducts resulting from ethanol consumption. Hemoglobin adducts of acetaldehyde have been used clinically as a marker of ethanol consumption, but the chemical nature of these adducts remains undefined. As part of our continuing structural characterization of acetaldehyde-protein adduct formation, we studied the peptides Val-His-Leu-Thr-Pro and Val-His-Leu-Thr-Pro-Val-Glu-Lys, from the amine terminus of the beta-globin chain of hemoglobin, in vitro. Both peptides have at least one potential site for adduct formation. In the octapeptide, the N-terminal amine group of Val as well as the epsilon-amine group of the lysine sidechain can potentially be modified by acetaldehyde. We used mass spectrometry, carbon-13 nuclear magnetic resonance, and Raman spectroscopy and characterized stable Schiff base acetaldehyde adducts of these two peptides at both reactive sites. The identification of stable Schiff base adducts with the N-terminal peptides of the beta-chain of hemoglobin as well as with epsilon-amino groups of lysine provides another possible means of monitoring ethanol consumption. The functional implications of these stable Schiff bases remains undefined.

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PubMed1988

Acetaldehyde adducts with haemoglobin: determination of acetaldehyde released from haemoglobin by acid hydrolysis.

Acetaldehyde, the first metabolite of ethanol, reacts with haemoglobin in vitro to produce acetaldehyde-haemoglobin adducts. Some clinical studies on the minor haemoglobins have suggested that these adducts may be formed in people abusing alcohol. Under hydrolysis of haemoglobin, with oxalic acid at 100 degrees C in sealed vials, some acetaldehyde was released and then specifically determined by HPLC. The kinetics of hydrolysis were studied using haemoglobin previously labelled with 14[C] acetaldehyde. The maximum liberation of 14 [C] acetaldehyde was obtained after 3 hr 30 min hydrolysis and this time factor was then utilized in the analysis of alcoholic and control haemoglobin. Thus, we have confirmed the formation of acetaldehyde haemoglobin adducts in vivo. It must be noted that the released acetaldehyde corresponds only to an index of the stable adducts. The levels were higher in alcoholics than in controls (1.417 +/- 0.171 and 1.295 +/- 0.139 nmol/mg Hb, respectively, P less than 0.001). In conclusion, this marker is not a convenient tool for the monitoring of alcohol exposure levels because of the low differences between alcoholic and control haemoglobins.

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PubMed1985

Gas-liquid chromatographic analysis of ethanol and acetaldehyde in blood with minimal artifactual acetaldehyde formation.

A gas-liquid chromatographic procedure utilizing headspace gas analysis is described for the determination of ethanol and its metabolite, acetaldehyde, in a 100-microliters sample of blood from the rat, guinea pig, sheep, or human. Artifactual formation of ethanol-derived acetaldehyde is minimized during sample preparation by using a chemical solution containing perchloric acid and sodium azide in saline, and thiourea. Aqueous standards of ethanol and acetaldehyde are used to calibrate the procedure, and 1-propanol is used as the internal standard of the method. The recovery of ethanol and acetaldehyde from spiked blood samples is quantitative and reproducible, with a within-day coefficient of variation of less than 7% for ethanol and less than 9% for acetaldehyde. The lower limit of quantitative sensitivity is 0.006 mg/ml ethanol and 0.10 microgram/ml acetaldehyde. The instrumental analysis time is less than 3 min, which enables high sample throughput.

Acetaldehyde↗

PubMed1984

Subcellular aldehyde dehydrogenase activity and acetaldehyde oxidation by isolated intact mitochondria of rat brain and liver after acetaldehyde treatment.

The effect of treatment of rats with acetaldehyde on the subcellular NAD+-aldehyde dehydrogenase (EC 1.2.1.3, ALDH) activities and acetaldehyde oxidation by isolated intact mitochondria of the liver and the brain was studied. Inhalation of acetaldehyde caused a significant decrease in the liver mitochondrial low Km-ALDH activity, while brain mitochondrial ALDH activity remained unchanged. Acetaldehyde oxidation by isolated intact liver mitochondria decreased significantly but that by brain mitochondria remained unchanged after acetaldehyde inhalation. These findings raise the possibility that the brain enzyme may be exposed to lower concentration of acetaldehyde than the liver enzyme.

Acetaldehyde↗

PubMed1988

The metabolism of acetaldehyde and not acetaldehyde itself is responsible for in vivo ethanol-induced lipid peroxidation in rats.

A single oral administration of ethanol (5 g/kg) to rats induced a marked increase in lipid peroxidation, in the liver and kidney within 9 hr, as assessed by malondialdehyde accumulation. The pretreatment with alcohol dehydrogenase (ADH) inhibitor, 4-methylpyrazole (1 mmol/kg) caused approximately 50% inhibition of the hepatic ADH activity and abolished this ethanol-induced lipid peroxidation. The disulfiram treatment (100 mg/kg) significantly inhibited 63% of the hepatic low Km aldehyde dehydrogenase (ALDH) but not the high Km ALDH. The cyanamide treatment (15 mg/kg) effectively decreased 83% of the low Km and 70% of the high Km ALDH in the liver. Although there was more than a 20-fold elevation of acetaldehyde levels by the inhibition of acetaldehyde metabolism with disulfiram or cyanamide, the ethanol-induced lipid peroxidation was significantly suppressed by pretreatment with these drugs. More than 90% inhibition of xanthine oxidase and dehydrogenase by the pretreatment with allopurinol (100 mg/kg), with no effect on the hepatic ADH and ALDH activities, did not alter the enhancement of lipid peroxidation following ethanol administration. We propose that the metabolism of acetaldehyde (probably via the low Km ALDH) and not acetaldehyde itself is responsible for the ethanol-induced lipid peroxidation in vivo and that the contribution of xanthine oxidase, as an initiator of lipid peroxidation through acetaldehyde oxidation is minute during acute intoxication.

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PubMed2005

Dissociation between the locomotor and anxiolytic effects of acetaldehyde in the elevated plus-maze: evidence that acetaldehyde is not involved in the anxiolytic effects of ethanol in mice.

Acetaldehyde, the first product of ethanol metabolism, has been suggested to play a major role in many behavioral effects of ethanol. However, very few studies have directly tested the behavioral effects of the acute administration of acetaldehyde. In particular, the role of this metabolite in ethanol-induced anxiolytic effects has never been extensively tested. The aim of the present study was to characterize the anxiolytic effects of acetaldehyde in two strains of mice, C57BL/6J and CD1 mice with the elevated plus-maze procedure. The results show that acute injections of ethanol (1-2 g/kg) induced significant dose-dependent anxiolytic effects in both strains of mice. In contrast, acetaldehyde failed to produce any anxiolytic effect, although it induced a significant hypolocomotor effect at the highest doses. In an independent experiment, cyanamide, an aldehyde dehydrogenase inhibitor, prevented the locomotor stimulant effects of ethanol, although it failed to alter its anxiolytic effects. Together, the results of the present study indicate that acetaldehyde is not involved in ethanol-induced anxiolytic effects, although it may be involved in its sedative/hypolocomotor effects.

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PubMed1988

Acetaldehyde oxidation in rat liver mitochondria, action of Mg2+, ATP and rotenone on acetaldehyde oxidation in intact mitochondria, and on some purified aldehyde dehydrogenase isozymes.

In intact rat liver mitochondria acetaldehyde is oxidized by three functionally distinct dehydrogenase systems. Two of these reduce intramitochondrial nicotinamide adenine dinucleotide (NAD): one is operative with micromolar acetaldehyde concentrations and is stimulated by Mg2+, the other is operative with millimolar acetaldehyde concentrations and is stimulated by adenosine 5'-triphosphate (ATP). The third system reduces added NAD and is stimulated by rotenone. Connected to these systems, three aldehyde dehydrogenase isozymes (ALDH) have been purified: a low-Km ALDH activated by Mg2+, a high-Km ALDH activated by ATP and Mg2+, a high-Km ALDH activated by rotenone. The properties of some isozymes are affected by detergents. Thus, deoxycholate augments the stimulation of low-Km isozyme by Mg2+ and confers sensitivity to Mg2+ and ATP on one of the high-Km isozymes. A fourth isozyme has been purified. Its affinity for acetaldehyde is so low that it is very unlikely that acetaldehyde is the physiological substrate.

Acetaldehyde↗

PubMed1981

Determination of acetaldehyde in human blood by a gas chromatographic method with negligible artefactual acetaldehyde formation.

A method is described for determination of acetaldehyde in blood by head space gas chromatography. The method utilizes sodium nitrite-sulfosalicylic acid as an inhibitor of the ethanol oxidizing systems by means of which the interference of ethanol is reduced considerably. The detection limit was 0.4 mumol/l, the recovery 101.5 +/- 5.2% and the coefficient of variation was 7.8% (1.5 mumol/1 acetaldehyde). There was no disappearance of acetaldehyde if the head space vials were kept at -20 degree C for 24 h. In the comparison study with the semicarbazide method our results were 0.7-4.1 mumol/l lower. The values for acetaldehyde in blood after ethanol ingestion (0.5 g/kg) by volunteers were 0.5-1.3 mumol/l.

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PubMed1990

Cross-reactivity of antibodies raised against acetaldehyde adducts of protein with acetaldehyde adducts of phosphatidyl-ethanolamine: possible role in alcoholic cirrhosis.

This study measured the possible cross-reactivity of hapten-specific IgG antibodies purified from the sera of rabbits sensitized to an albumin-acetaldehyde conjugate [N-ethyl-rabbit serum albumin (N-ethyl-RSA)] with acetaldehyde-phosphatidylethanolamine adducts. The N-ethyl-RSA was coupled to an Affigel-10 column to affinity purify the IgG (anti-N-ethyl-RSA IgG). Dioleoyl-phosphatidylethanolamine (DOPE) was reacted with acetaldehyde to form a Schiff base, which was reduced to N-ethyl-DOPE, purified by high pressure liquid chromatography, and analyzed with direct chemical ionization mass spectrometry. Lamellar liposomes containing either 5% by weight N-ethyl-DOPE and 95% egg phosphatidylcholine or a mixture of 5% N-ethyl-DOPE, 71% DOPE, and 24% dioleoylphosphatidylcholine, as well as hexagonal phase micelles containing 5% N-ethyl-DOPE and 95% DOPE, were prepared by sonication. Anti-N-ethyl-RSA IgG was then incubated with each of these lipid mixtures for 30 min, a fluorescein-conjugated goat anti-rabbit IgG was added for an additional 30 min, and then binding of anti-N-ethyl-RSA IgG to N-ethyl-DOPE in the liposomes or micelles was measured by flow cytometry. Anti-N-ethyl-RSA IgG bound to N-ethyl-DOPE in both vesicles and hexagonal phase micelles, but the affinity was 16 times greater for the hapten in the hexagonal phase. This result demonstrates that physical presentation of the hapten can affect antibody recognition and that antibodies raised against N-ethyl-RSA can cross-react with acetaldehyde-phospholipid adducts.

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PubMed1991

Binding of anti-acetaldehyde IgG antibodies to hepatocytes with an acetaldehyde-phosphatidylethanolamine adduct on their surface.

We have previously shown that antibodies raised against acetaldehyde adducts of protein cross-react with an acetaldehyde adduct of dioleoylphosphatidylethanolamine, N-ethyl-dioleoylphosphatidylethanolamine, when the latter is incorporated into hexagonal phase phospholipid micelles. In the present study we demonstrate that these same IgG antibodies cross-react with N-ethyl-dioleoylphosphatidylethanolamine when this adduct is incorporated into the surface of hepatocytes. Hapten-specific IgG antibodies were purified from the sera of rabbits sensitized to an albumin-acetaldehyde conjugate that had been reduced with sodium cyanoborohydride (N-ethyl-RSA). The N-ethyl-RSA was coupled to an Affi-Gel-10 column to affinity purify the IgG. Liposomes containing N-ethyl-dioleoylphosphatidylethanolamine were fused with isolated hepatocytes, the affinity purified primary IgG antibodies were added, then fluorescein-conjugated second antibodies were added, and antibody binding to hepatocytes was measured by flow cytometry. The fluorescence of these hepatocytes was significantly greater (p less than 0.01) than control hepatocytes prepared with (1) pre-immune primary IgG antibodies with fluorescein-conjugated second antibodies, (2) no primary antibody but with fluorescein-conjugated second antibodies, and (3) no fluorescein-conjugated second antibodies.

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PubMed1994

Macrophages are a major source of acetaldehyde in circulating acetaldehyde-albumin complexes formed after exposure of mice to ethanol.

C57BL mice were depleted of macrophages by an intravenous injection of liposome-encapsulated dichloromethylene diphosphonate (DCMDP), and control mice were uninjected or injected with empty liposomes. One day after injection, a proportion of the DCMDP-treated and control mice was continuously exposed to ethanol vapor for 4 days. Albumin fractions were separated from the sera of both ethanol-unexposed and ethanol-exposed animals and tested for cytotoxicity against a monolayer of A9 cells using two indicators of cytotoxicity: detachment of adherent cells and a decrease in the ability of cells to reduce tetrazolium. The results show that, in mice exposed to ethanol, macrophages are a major source of the acetaldehyde in circulating cytotoxic acetaldehyde-albumin complexes and presumably also of free acetaldehyde.

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PubMed2024

Engineering a probiotic Bacillus subtilis for acetaldehyde removal: A hag locus integration to robustly express acetaldehyde dehydrogenase.

We have addressed critical challenges in probiotic design to develop a commercially viable bacterial strain capable of removing the intestinal toxin, acetaldehyde. In this study, we report the engineering of the hag locus, a σD-dependent flagellin expression site, as a stable location for robust enzyme production. We demonstrate constitutive gene expression in relevant conditions driven by the endogenous hag promoter, following a deletion of the gene encoding a post-translational regulator of σD, FlgM, and a point mutation to abrogate the binding of the translational inhibitor CsrA. Reporter constructs demonstrate activity at the hag locus after germination, with a steady increase in heterologous expression throughout outgrowth and vegetative growth. To evaluate the chassis as a spore-based probiotic solution, we identified the physiologically relevant ethanol metabolic pathway and the subsequent accumulation of gut-derived acetaldehyde following alcohol consumption. We integrated a Cupriavidus necator aldehyde dehydrogenase gene (acoD) into the hag locus under the control of the flagellin promoter and observed a rapid reduction in acetaldehyde levels in gut-simulated conditions post-germination. This work demonstrates a promising approach for the development of genetically engineered spore-based probiotics.

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PubMed1994

Anti-acetaldehyde adduct antibodies generated by ethanol-fed rats react with reduced and unreduced acetaldehyde-modified proteins.

We have previously shown that rats fed ethanol for prolonged periods generate antibodies reactive with proteins modified by acetaldehyde in vitro. In this report we demonstrate that these antibodies react with two groups of adducts: those formed when acetaldehyde reacts with proteins at 37 degrees C for 24 hr ('unreduced' adducts) and those formed by a 1 hr incubation followed by the addition of sodium cyanoborohydride (a reducing agent specific for Schiff bases) to the reaction mixture ('reduced' adducts). These data suggest that adducts from both of these groups are formed in vivo as a result of ethanol ingestion by rats.

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PubMed1993

Heterogeneity of hepatic acetaldehyde adducts in guinea-pigs after chronic ethanol administration: an immunohistochemical analysis with monoclonal and polyclonal antibodies against acetaldehyde-modified protein epitopes.

The formation of acetaldehyde (AcH) adducts was immunohistochemically demonstrated in the livers of experimental animals after chronic ethanol consumption. Recently, we established a hybridoma producing monoclonal antibody against the adduct. Although the polyclonal antibody obtained from a rabbit immunized with adducts had affinities for AcH adducts produced with 20 microM, 1 mM and 10 mM of AcH, the monoclonal antibody could recognize only those produced with 1 and 10 mM of AcH, suggesting that there is a difference of antigenicity between the adducts formed with a high concentration of AcH and those modified with a low concentration of AcH. AcH adducts in the liver of guinea-pigs fed ethanol for 90 days were detected by immunohistochemical staining with the polyclonal and monoclonal antibodies. The staining of liver specimens with polyclonal antibody was observed around both the portal and perivenular areas, whereas the reactions to monoclonal antibody were localized only in the perivenular area. These data suggest that AcH adducts are able to be formed around both portal and perivenular areas in the liver and that the perivenular area might be exposed to a higher concentration of AcH than the portal area after ethanol intake.

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