Addition Of Acetaldehyde Research Articles

The role of cellular oxidases and catalytic iron in the pathogenesis of ethanol-induced liver injury

Free radical generation and catalytic iron have been implicated in the pathogenesis of alcohol-induced liver injury but the source of free radicals is a subject of controversy. The mechanism of ethanol-induced liver injury was investigated in isolated hepatocytes from a rodent model of iron loading in which free radical generation was measured by the determination of alkane production (ethane and pentane). Iron loading (125mg/kg i.p.) increased hepatic non-heme iron 3-fold, increased the prooxidant activity of cytosolic ultrafiltrates 2-fold and doubled ethanol-induced alkane production. The addition of desferrioxamine (20μM), a tight chelator of iron, completely abolished alkane production indicating the importance of catalytic iron. The role of cellular oxidases as a source of ethanol induced free radicals was studied through the use of selective inhibitors. In both the presence and absence of iron loading, selective inhibition of xanthine oxidase with oxipurinol(20μM) diminished ethanol-induced alkane production 0–40%, inhibition of aldehyde oxidase with menadione (20μM) diminished alkane production 36–75%, while the inhibition of aldehyde and xanthine oxidase by feeding tungstate (100mg/kg/day) virtually abolished alkane production. Addition of acetaldehyde(50μM) to hepatocytes generated alkanes at rates comparable to those achieved with ethanol indicating the importance of acetaldehyde metabolism in free radical generation. The cellular oxidases (aldehyde and xanthine oxidase) along with catalytic iron play a fundamental role in the pathogenesis of free radical injury due to ethanol.

Preparation of (9Z, 11Z) - Vitamin A

Starting from (7E,9Z)-C 15-aldehyde 4, the syntheses of (9Z, 11Z)-vitamin A acetate and palmitate are reported. The construction strategy is based on treatment of 4 with Zn-PPh 3/CBr 4, addition of acetaldehyde followed by a Wittig-Horner reaction to give the (9Z, 11Z)-C 20-nitrile 7 which was reduced with DIBAH to the corresponding aldehyde 8 and then to the title compound 1. The thermal instability of 1 is discussed.

Aldehyde-enhanced photon emission from crude extracts of soybean seedlings

The photon emission from a soybean seedling was remarkably enhanced with the addition of acetaldehyde. The emission spectrum in a seedling had peaks at around 670 and 610–615 nm, with a shoulder at 530–540 nm. In the crude extracts of seedlings, enhancement of photon emission depended on the aldehyde chain length; acetaldehyde gave a maximal photon emission intensity. The photon emission intensity in crude extracts reduced by hydrosulfite showed an initial rapid increase followed by a quick decay in the first phase and a slow decay in the second phase, in the presence of oxygen and aldehyde. The emission spectrum in a whole soybean seedling was observed similarly in crude extracts, with the addition of acetaldehyde. Since a similar photon emission pattern appears in the supernatants of autoclaved extracts, concomitant with the same emission spectra, it is concluded that this photon emission occurs nonenzymatically. Furthermore, when the sample has decayed once photon emission is reduced, the photon emission appears again, upon mixing the sample with oxygen and aldehyde. This result suggests that a hydroperoxide intermediate is an emitter reacting with aldehyde. An energy transfer from triplet carbonyl may not be involved in this reaction.

Effect of Acetaldehyde on Growth, Substrates, and Products by Leuconostoc mesenteroides ssp cremoris

AbstractAddition of 5.6 mmol/L of acetaldehyde to glucose broth led to an increase in the specific growth rate, a decrease in the specific glucose consumption rate, and an increase in the specific lactate production rate of Leuconostoc mesenteroides ssp cremoris. The amount of acetate produced was enhanced. For cells growing in broth containing glucose plus citrate, addition of acetaldehyde did not stimulate growth and did not significantly change the maxima of specific consumption rate of citrate and glucose; however, a change in kinetics was observed: the maxima appeared earlier in the presence of acetaldehyde than in its absence. In the absence of acetaldehyde, the specific citrate utilization rate was higher than the specific glucose consumption rate.

Acetaldehyde selectively stimulates collagen production in cultured rat liver fat-storing cells but not in hepatocytes

Hepatocytes and fat-storing cells have been implicated in the production of collagen, under both normal and pathological conditions. In this study, short-term primary cultures of rat hepatocytes, maintained in a serum-free, hormonally defined medium without dexamethasone and cultured on a fibronectin-collagen type IV substratum, were used. Primary and passage 1 and 2 cultures of fat-storing cells maintained on tissue culture plastic were also studied. Hepatocytes produced significant amounts of collagen type III, but formation of collagen type I was not detectable. Laminin and collagen type IV production were very low. Hepatocytes maintained their ability to metabolize ethanol (at levels comparable to those observed at 2 hr) for at least 48 hr after plating and this metabolism was inhibited 86% to 95% by 4-methylpyrazole (1 mmol/L). Neither ethanol (50 mmol/L) nor acetaldehyde (175 mumol/L, initial concentration) had any effect on the production of collagen type III or laminin. Fat-storing cells (95% to 100% desmin-positive) produced significant amounts of both type I and type III collagen. Production of collagen type IV and laminin was very low. Metabolism of ethanol by these cultures was not detected. Addition of ethanol had no effect on collagen or laminin production in fat-storing cells. In contrast, acetaldehyde significantly increased the production of collagen type I, but did not alter the production of collagen type III, IV or laminin. Incorporation of 3H-proline into total protein was not affected by addition of ethanol or acetaldehyde to fat-storing cells or hepatocytes. Exposure of fat-storing cells to ethanol or acetaldehyde did not change 3H-collagen degrading activity in the media.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of aldehyde oxidase in ethanol-induced hepatic lipid peroxidation in the rat

Hepatic lipid peroxidation has been implicated in the pathogenesis of alcohol-induced liver injury, but the mechanism(s) by which ethanol metabolism or resultant free radicals initiate lipid peroxidation is not fully defined. The role of the molybdenum-containing enzymes aldehyde oxidase and xanthine oxidase in the generation of such free radicals was investigated by measuring alkane production (lipoperoxidation products) in isolated rat hepatocytes during ethanol metabolism. Inhibition of aldehyde oxidase and xanthine oxidase (by feeding tungstate at 100 mg/day per kg) decreased alkane production (80-95%), whereas allopurinol (20 mg/kg by mouth), a marked inhibitor of xanthine oxidase, inhibited alkane production by only 35-50%. Addition of acetaldehyde (0-100 microM) (in the presence of 50 microM-4-methylpyrazole) increased alkane production in a dose-dependent manner (Km of aldehyde oxidase for acetaldehyde 1 mM); menadione, an inhibitor of aldehyde oxidase, virtually inhibited alkane production. Desferrioxamine (5-10 microM) completely abolished alkane production induced by both ethanol and acetaldehyde, indicating the importance of catalytic iron. Thus free radicals generated during the metabolism of acetaldehyde by aldehyde oxidase may be a fundamental mechanism in the initiation of alcohol-induced liver injury.

Alterations in the Regulatory Properties of Hepatic Fatty Acid Oxidation and Carnitine Palmitoyltransferase I Activity after Ethanol Feeding and Withdrawal

The effects of prolonged ethanol feeding on the regulatory properties of both hepatic fatty acid oxidation and carnitine palmitoyltransferase I activity (CPT-I) were studied in rats fed a high-fat diet containing 36% of total calories as ethanol (ethanol group) or an isocaloric amount of carbohydrate (control group). Prolonged ethanol feeding progressively decreased CPT-I activity and increased enzyme sensitivity and sensitization to inhibition by malonyl-CoA in liver mitochondria. Similarly, long-term ethanol feeding progressively increased the sensitivity of CPT-I, as well as that of fatty acid oxidation, to inhibition by 4-hydroxyphenylglyoxylate. Short-term addition of ethanol or acetaldehyde to the incubations markedly increased the sensitivity of CPT-I to inhibition by malonyl-CoA in a subsequent assay in hepatocytes isolated from ethanol-treated rats, but not in cells from control animals. This effect may be mediated by the ethanol- or acetaldehyde-induced increase of intracellular malonyl-CoA levels. The present results show that ethanol feeding to rats leads to profound alterations in the regulatory properties of hepatic CPT-I, which seem to be determinant for the decreased capacity of fatty acid oxidation by the liver in this state. Nevertheless, all the above-mentioned alterations of the fatty acid oxidative system were reversible, disappearing after 2 to 4 days of ethanol withdrawal.

Deuterium D(V/K) Isotope Effects on Ethanol Oxidation in Hepatocytes: Importance of the Reverse ADH‐Reaction

The kinetic deuterium isotope effect, D(V/K), on ethanol oxidation was measured on hepatocytes from rat and pig by the radiometric competitive method using 14C-labelled ethanol containing deuterium in the (1-R)-position. The corrected D(V/K) values of 2.68 and 2.80 for rat and pig hepatocytes respectively were significantly different, suggesting differences in the amount of non-ADH ethanol oxidizing activity. The apparent isotope effects declined rapidly with time when acetaldehyde was present in the medium as a result of the reduction to ethanol of the [14C]-acetaldehyde formed from the double labelled ethanol by alcohol dehydrogenase (ADH). Fructose and cyanamide caused the acetaldehyde concentration during ethanol oxidation to increase by entirely different mechanisms, and the isotope effect to decrease with time, as did also the addition of acetaldehyde. The apparent first order rate constant for the reverse ADH reaction, assuming the reactants to be acetaldehyde and the ADH-NADH complex, was determined by two methods giving comparable results. In the presence of semicarbazide, which removes acetaldehyde, the isotope effect was nearly constant. This was the case also when the acetaldehyde concentration was very low (less than 1 microM) for other reasons, as in hepatocytes from starved animals. A mathematical formula describing the expected decrease of the apparent isotope effect with time was derived. The different response of pig and rat hepatocytes to addition of fructose (the 'fructose effect') is suggested to be caused by differences in activity of aldehyde dehydrogenases in the two species.

ChemInform Abstract: Radiation‐Initiated Addition of Acetaldehyde to Allyl Alcohol and Conversion of the 1:2‐Telomer into 1‐Methyl‐2,8‐dioxabicyclo(4,2,1)nonane.

AbstractThe title reaction leads to the products (III), (IV) and to the 1:2‐telomer (V).

Synthesis of Nectriafurone, an Isofuranonaphthoquinone Isolated from the Fungus Nectria haematococca

Syntheses of 5-methoxy-4,7-dihydroxynaphtho[2,3-C]8,9-furandione (2) and of 4,7-dihydroxynaphtho[2,3-c]8,9-furandione (3) were carried out by a rapid Friedel-Crafts reaction using the dry method. The addition of acetaldehyde on 2 in presence of LDA gave the (±)-nectriafurone (1), thus confirming the proposed structure of 3-(1'-hydroxyethyl)-5-methoxy-4,7-dihydroxynaphtho[2,3-c]8,9-furandione

DNA cleavage during ethanol metabolism: Role of superoxide radicals and catalytic iron

The generation of superoxide and related free radicals and the mobilization of catalytic iron due to ethanol metabolism have been suggested as mechanisms of alcohol-induced liver injury as well as of the increased risk of cancer observed in alcoholics. Cleavage of double stranded DNA is produced by both free radicals as well as by catalytic iron. The effects of ethanol metabolism on DNA cleavage were therefore studied in vitro as well as in vivo in isolated hepatocytes. Intactness of double stranded DNA was studied by measuring ethidium bromide fluorescence after DNA electrophoresis. In vitro , the metabolism of acetaldehyde by aldehyde oxidase caused cleavage of Lambda phage DNA. Cleavage was inhibited by both superoxide dismutase and desferrioxamine indicating the role of superoxide radicals and catalytic iron respectively. Studies with HIND III digests of the Lambda phage indicate a lack of specificity in the breaks with respect to nucleotide sequences. Addition of EDTA greatly enhanced cleavage. In vivo , ethanol metabolism caused minimal breakage in hepatocyte DNA and addition of acetaldehyde (100μM) markedly enhanced cleavage; all cleavage was inhibited by desferrioxamine. Themetabolism of ethanol to acetaldehyde and the further metabolism of acetaldehyde by aldehyde oxidase generates free radicals and mobilizes iron; these may contribute to alcohol-induced injury and carcinogenesis.

“An efficient and mild entry to 1,4-dicarbonyl compounds via photochemical addition of acyl radical to electron-deficient olefins”

Photoehcmical addition of acetaldehyde to electron-deficient olefins in the presence of molecular oxygen provides an efficient and mild method for the synthesis of 1,4-functionallzed compounds. Some considerations about the mechanism and the substituent effects are outlined.

Non-enzymic activation of the fifth component of human complement, by oxygen radicals. Some properties of the activation product, C5b-like C5

Purified human C5 was converted non-enzymically to an activated form as defined by its ability to participate in reactive lysis. This conversion occurred following exposure to systems that generate oxygen radicals, namely addition of H 2O 2 in the presence of ascorbic acid and iron or the addition of xanthine oxidase, acetaldehyde and iron. The conversion of C5 to a functionally active species was iron-dependent and inhibited by hydroxyl radical scavengers such as DMSO. The findings suggest that OH is the active oxygen species that converts C5. The conversion product of C5, termed C5(H 2O 2), is C5b-like due to its ability to bind C6 and cause reactive lysis. C5(H 2O 2) is much more stable than C5b obtained by complement convertases. Although C5(H 2O 2) has lost the binding site of native C5 for C3b it can be cleaved by complement-derived convertases; the cleavage is, however, less efficient than in the case of native C5. The resulting cleavage product, which is C5a-like, is chemotactic although C5(H 2O 2) is not chemotactic. C5(H 2O 2) serves as a better substrate for plasma kallikrein than native C5, resulting in the generation of a C5a-like chemotactic product. These data indicate that oxygen radicals can bring about a conformational change in C5, causing it to behave as a functionally activated molecule of the complement system. This may have implications for the role of complement and its activation in the inflammatory response.

Effect of hydrogen acceptors on D‐xylose fermentation by anaerobic culture of immobilized Pachysolen tannophilus cells

The effect of hydrogen acceptors on the kinetic parameters of D-xylose fermentation under anaerobic conditions was studied in a transient culture of immobilized Pachysolen tannophilus cells. Addition of oxygen to a steady-state culture resulted in a rapid increase (up to fivefold) in the rates of ethanol production and D-xylose uptake, but the rate of xylitol production was unaffected. Furthermore, the molar ethanol yield increased from 0.97 to 1.43 in the presence of oxygen. The moles of ethanol produced per moles of oxygen utilized were considerably greater than would be predicted from the stoichiometry of D-xylose fermentation, which suggests that the organism required oxygen for other functions in addition to its role as a hydrogen acceptor in D-xylose metabolism. When the artificial hydrogen acceptors acetone, acetaldehyde, and acetoin were added to the culture, the rate of ethanol production increased while the xylitol production rate decreased but the rate of xylose uptake was unaffected. The molar ethanol yields increased from 1.03 to 1.63, 1.43, and 1.24 upon addition of acetaldehyde, acetone, and acetoin, respectively, at the expense of the molar xylitol yields. The hydrogen acceptors sodium acetate, methylene blue, benzyl viologen, phenazine methosulfate, indigo carmine, and tetrazolium chloride had no effect on ethanol production.

Effect of Additives on Selective Formation of Isobutene from the CO–H2 Reaction over ZrO2

Abstract The CO–H2 reaction over ZrO2 was carried out in the presence of various organic additives. The addition of dimethyl ether, methylal, acetaldehyde, and dimethyl acetal showed the marked enhancement effects on the hydrocarbon formation keeping the high selectivity for isobutene. Ethylene was little effective. The addition of acetone, propanal, and propylene resulted in the decrease in the formation of isobutene and the increase in that of n-butenes. The presence of CO and H2 was essential to the selective formation of isobutene. The formation pathways of isobutene and the other hydrocarbons are discussed.

Radiation-initiated addition of acetaldehyde to allylalcohol and conversion of the 1:2-telomer into 1-methyl-2,8-dioxabicyclo[4,2,1]nonane

Radiation-initiated addition of acetaldehyde to allyl alcohol gave a mixture of 5-hydroxy-2-pentanone (1:1-adduct I), 2-methyl-2-(4-oxopentyloxy)tetrahydrofuran (II), 7-hydroxy-4-hydroxymethyl-2-heptanone (1:2-telomer III) and 1,1-bis(4-oxopentyloxy)ethane (IV). The telomer III was dehydrated to afford 3-acetonyltetrahydropyran (IV), 1-methyl-2,8-dioxabicyclo[4.2.1]nonane (VI) and 3,10-dimethyl-4,11,16,17-tetraoxatricyclo[8.4.2.23,8]octadecane (VII).

The influence of oxygen and organic hydrogen acceotors on glycolytic dioxide production in Brettanomyces anomalus

AbstractThe yeast Brettanomyces anomalus showed the Custers effect in that under strictly anaerobic conditions, in the presence of glucose, CO2 production was negligble. CO2 production was stimulated by mixing anaerobic cell suspensions with an aerated glucose solution in astopped‐flow cell. Glycolytic CO2 production continued even after oxygen exhaustion. Studies using an open reaction vessel showed that the rate of glycolytic CO2 production could be increased to a maximum level by exposing the anaerobic cell suspension to brief pulses of O2. A cell suspension CO2 at a maximal rate demonstrated the Pasteur effect on switching the mobile gas to a mixture conatining oxygen (5.05 KPa). In contrast to glycolytic CO2 production in vivo nicotinamide pool responded rapidly to changes in oxygen concentration. The addition of acetaldehyde, acetone, or 3‐hydroxy‐butan‐2‐one led to a temprorary production of CO2 at an initial rate depending on the concentration of substance added according to the Michaelis–Menten equation. The maximal rates were equal with all three substances, whereas tha apparent Km values were different. The total amount of CO2 produced was 22‐fold greater than the amount of acetaldehyde added. Added organic hydrogen acceptors modulated the intracellular reedox balance of B. anomalus under conditions. These results are discussed in relation to the current hypothesis of the Custers effect.

Effects of ethanol feeding on the activity and regulation of hepatic carnitine palmitoyltransferase I

The effects of ethanol administration on activity and regulation of carnitine palmitoyltransferase I (CPT-I) were studied in hepatocytes isolated from rats fed a liquid, high-fat diet containing 36% of total calories as ethanol or an isocaloric amount of sucrose. Cells were isolated at several time points in the course of a 5-week experimental period. Ethanol consumption markedly decreased CPT-I activity and increased enzyme sensitivity to inhibition by exogenously added malonyl-CoA. Changes in enzyme activity occurred sooner than those in enzyme sensitivity. Fatty acid oxidation to CO 2 and ketone bodies was depressed in hepatocytes from ethanol-fed animals during the first part of the treatment. At the end of the 35-day period, there were no longer differences in the rate of ketogenesis between the two groups. At that time, however, the rate of CO 2 formation was still impaired in the ethanol-fed animals. Furthermore, addition of ethanol or acetaldehyde to the incubation medium strongly depressed CPT-I activity and rates of fatty acid oxidation in hepatocytes from ethanol-treated rats, whereas these effects were much less pronounced in cells from control animals. The response of CPT-I activity to insulin, glucagon, vasopressin, and phorbol ester was blunted in cells derived from ethanol-fed rats. These changes in the regulation of CPT-I activity corresponded with those observed in the rate of fatty acid oxidation. It is concluded that CPT-I may play a role in the generation of the ethanol-induced fatty liver.

Uv-light- and radiation-initiated addition of acetaldehyde to allyl alkanoates

UV-light- and γ-60Co-initiated addition of acetaldehyde to allyl formate (I) and allyl acetate (II) yielded the 1:1 adducts - 4-oxopentyl formate (III) and 4-oxopentyl acetate (IV), respectively, together with the 1:2 telomers - 7-formyloxy-4-formyloxymethyl-2-heptanone (V) and 7-acetoxy-4-acetoxymethyl-2-heptanone (VI). The initial radiation yields are: G(III) = 200·8, G(IV) = 211·3, G(V) = 39·5, G(VI) = 37·9. Base-catalyzed transesterification of oxopentyl alkanoates III and IV afforded 5-hydroxy-2-pentanone (XIV), the same reaction of dialkylalkanoates VI and VII gave 5-hydroxy-4-hydroxymethyl-2-heptanone (XV).

Acetaldehyde increases collagen gene transcription in cultured human fibroblasts.

Acetaldehyde, the first metabolite of ethanol, mediates many of the biological effects of ethanol. We have previously shown that acetaldehyde, but not ethanol, stimulates collagen production in cultured human fibroblasts (Holt, K., Bennett, M., and Chojkier, M. (1984) Hepatology 4, 843-848). Here, we examined the effects of acetaldehyde on collagen gene expression. Confluent human fetal fibroblasts were incubated for up to 4 h in the presence of ascorbate (0.2 mM) alone or with the addition of either ethanol (12 mM) or acetaldehyde (200 microM). Acetaldehyde induced the production of collagen (up to 2.5-fold) and had a small inhibitory effect on procollagen secretion (-20%). The steady-state levels of mRNAs were measured by hybridizing total cellular RNA to specific cDNA probes at high stringency. Acetaldehyde increased the steady-state level of collagen alpha 1(I) and collagen alpha 2(I) mRNAs about 3-fold and had small effects on beta-actin mRNA (+50%) and collagenase mRNA (-50%). Northern blots revealed that the RNAs were intact and that acetaldehyde preferentially increased the abundance of the longer of the two collagen alpha 1(I) transcripts. Acetaldehyde increased both collagen alpha 1(I) and collagen alpha 1(III) transcriptional activity by 2.5-fold and had small effects on beta-actin and collagenase gene transcription. The increase in both collagen production and collagen mRNA levels induced by acetaldehyde was blocked by methylene blue, a scavenger of reducing equivalents. These data indicate that reducing equivalents, which enhance the formation and stability of acetaldehyde-protein adducts, may be required for acetaldehyde-stimulated collagen production. Thus, this study suggests that acetaldehyde increases collagen production by increasing collagen gene transcription in cultured human fibroblasts.