The effect of acetaldehyde on mitochondrial function

Electronic structures and dielectric function of (5, 5) CNT-C2H4O system: A first-principles study on the detection capability of CNT for gas sensing applications

Carbon nanotubes (CNTs) are known to have a wide range of applications in various fields of discipline. In this research, the ability of metallic armchair (5, 5) CNT to detect acetaldehyde (C2H4O) was investigated using first-principles density functional theory (DFT) as implemented in Quantum ESPRESSO with the Generalized Gradient Approximation (GGA). Accordingly, it was found that C2H4O preserved the metallic behavior of the CNT. However, some bands are found to have overlapped in both the valence and conduction regions of the electronic structures of the resulting system that are mainly caused by the p orbitals of the oxygen and carbon atoms of the compound. These are further confirmed by the projected density of states (pDOS). Moreover, optical transitions are observed in both the real and imaginary parts of the dielectric function caused by the interband transitions between the Van Hove singularities of the electronic structures. In all circumstances, this research has provided more insights into the potential gas sensing applications of metallic CNTs.

Chemical Adducts of Reactive Flavor Aldehydes Formed in E-Cigarette Liquids Are Cytotoxic and Inhibit Mitochondrial Function in Respiratory Epithelial Cells

Introduction

Flavor aldehydes in e-cigarettes, including vanillin, ethyl vanillin (vanilla), and benzaldehyde (berry/fruit), rapidly undergo chemical reactions with the e-liquid solvents, propylene glycol, and vegetable glycerol (PG/VG), to form chemical adducts named flavor aldehyde PG/VG acetals that can efficiently transfer to e-cigarette aerosol. The objective of this study was to compare the cytotoxic and metabolic toxic effects of acetals and their parent aldehydes in respiratory epithelial cells.

Aims and Methods

Cell metabolic assays were carried out in bronchial (BEAS-2B) and alveolar (A549) epithelial cells assessing the effects of benzaldehyde, vanillin, ethyl vanillin, and their corresponding PG acetals on key bioenergetic parameters of mitochondrial function. The potential cytotoxic effects of benzaldehyde and vanillin and their corresponding PG acetals were analyzed using the LIVE/DEAD cell assay in BEAS-2B cells and primary human nasal epithelial cells (HNEpC). Cytostatic effects of vanillin and vanillin PG acetal were compared using Click-iT EDU cell proliferation assay in BEAS-2B cells.

Results

Compared with their parent aldehydes, PG acetals diminished key parameters of cellular energy metabolic functions, including basal respiration, adenosine triphosphate production, and spare respiratory capacity. Benzaldehyde PG acetal (1–10 mM) increased cell mortality in BEAS-2B and HNEpC, compared with benzaldehyde. Vanillin PG acetal was more cytotoxic than vanillin at the highest concentration tested while both diminished cellular proliferation in a concentration-dependent manner.

Conclusions

Reaction products formed in e-liquids between flavor aldehydes and solvent chemicals have differential toxicological properties from their parent flavor aldehydes and may contribute to the health effects of e-cigarette aerosol in the respiratory system of e-cigarette users.

Implications

With no inhalation toxicity studies available for acetals, data from this study will provide a basis for further toxicological studies using in vitro and in vivo models. This study suggests that manufacturers’ disclosure of e-liquid ingredients at time of production may be insufficient to inform a comprehensive risk assessment of e-liquids and electronic nicotine delivery systems use, due to the chemical instability of e-liquids over time and the formation of new compounds.

Phylogenetic and functional diversity of aldehyde-alcohol dehydrogenases in microalgae

The study shows the biochemical and enzymatic divergence between the two aldehyde-alcohol dehydrogenases of the alga Polytomella sp., shedding light on novel aspects of the enzyme evolution amid unicellular eukaryotes. Aldehyde-alcohol dehydrogenases (ADHEs) are large metalloenzymes that typically perform the two-step reduction of acetyl-CoA into ethanol. These enzymes consist of an N-terminal acetylating aldehyde dehydrogenase domain (ALDH) and a C-terminal alcohol dehydrogenase (ADH) domain. ADHEs are present in various bacterial phyla as well as in some unicellular eukaryotes. Here we focus on ADHEs in microalgae, a diverse and polyphyletic group of plastid-bearing unicellular eukaryotes. Genome survey shows the uneven distribution of the ADHE gene among free-living algae, and the presence of two distinct genes in various species. We show that the non-photosynthetic Chlorophyte alga Polytomella sp. SAG 198.80 harbors two genes for ADHE-like enzymes with divergent C-terminal ADH domains. Immunoblots indicate that both ADHEs accumulate in Polytomella cells growing aerobically on acetate or ethanol. ADHE1 of ~ 105-kDa is found in particulate fractions, whereas ADHE2 of ~ 95-kDa is mostly soluble. The study of the recombinant enzymes revealed that ADHE1 has both the ALDH and ADH activities, while ADHE2 has only the ALDH activity. Phylogeny shows that the divergence occurred close to the root of the Polytomella genus within a clade formed by the majority of the Chlorophyte ADHE sequences, next to the cyanobacterial clade. The potential diversification of function in Polytomella spp. unveiled here likely took place after the loss of photosynthesis. Overall, our study provides a glimpse at the complex evolutionary history of the ADHE in microalgae which includes (i) acquisition via different gene donors, (ii) gene duplication and (iii) independent evolution of one of the two enzymatic domains.

Protective Effects of Ligularia fischeri and Aronia melanocarpa Extracts on Alcoholic Liver Disease (In Vitro and In Vivo Study)

Hepatic protective effects of Ligularia fischeri (LF) and Aronia melanocarpa (AM) against alcohol were investigated in vitro and in vivo test. LF, AM, and those composed mixing material (LF+AM) were treated in HepG2 cell. Alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities were significantly increased in each singleness extract and mixed composite. The protective effect on alcoholic liver damage was investigated by animal models. Serum alcohol level and acetaldehyde level were significantly decreased by LF+AM treatment in acute experimental model. In the chronic mouse model study, we had found that the increased plasma liver damage index (alkaline phosphatase) by alcohol treatment was declined by oral administration of LF+AM extraction composite. As well as, it was identified that the protection effect was induced by increasing catalase activity and suppressing COX-2, TNF-α, MCP-1, and IL-6 mRNA expressions. CYP2E1 mRNA expression was also increased. These results suggest that oral ingestion of LF and AM mixed composite is able to protect liver against alcohol-induced injury by increasing alcohol metabolism activity and antioxidant system along with decreasing inflammatory responses.

Cinnamaldehyde in flavored e-cigarette liquids temporarily suppresses bronchial epithelial cell ciliary motility by dysregulation of mitochondrial function

Aldehydes in cigarette smoke (CS) impair mitochondrial function and reduce ciliary beat frequency (CBF), leading to diminished mucociliary clearance (MCC). However, the effects of aldehyde e-cigarette flavorings on CBF are unknown. The purpose of this study was to investigate whether cinnamaldehyde, a flavoring agent commonly used in e-cigarettes, disrupts mitochondrial function and impairs CBF on well-differentiated human bronchial epithelial (hBE) cells. To this end, hBE cells were exposed to diluted cinnamon-flavored e-liquids and vaped aerosol and assessed for changes in CBF. hBE cells were subsequently exposed to various concentrations of cinnamaldehyde to establish a dose-response relationship for effects on CBF. Changes in mitochondrial oxidative phosphorylation and glycolysis were evaluated by Seahorse Extracellular Flux Analyzer, and adenine nucleotide levels were quantified by HPLC. Both cinnamaldehyde-containing e-liquid and vaped aerosol rapidly yet transiently suppressed CBF, and exposure to cinnamaldehyde alone recapitulated this effect. Cinnamaldehyde impaired mitochondrial respiration and glycolysis in a dose-dependent manner, and intracellular ATP levels were significantly but temporarily reduced following exposure. Addition of nicotine had no effect on the cinnamaldehyde-induced suppression of CBF or mitochondrial function. These data indicate that cinnamaldehyde rapidly disrupts mitochondrial function, inhibits bioenergetic processes, and reduces ATP levels, which correlates with impaired CBF. Because normal ciliary motility and MCC are essential respiratory defenses, inhalation of cinnamaldehyde may increase the risk of respiratory infections in e-cigarette users.

Ethanol-induced oxidative stress: basic knowledge

After a general introduction, the main pathways of ethanol metabolism (alcohol dehydrogenase, catalase, coupling of catalase with NADPH oxidase and microsomal ethanol-oxidizing system) are shortly reviewed. The cytochrome P(450) isoform (CYP2E1) specifically involved in ethanol oxidation is discussed. The acetaldehyde metabolism and the shift of the NAD/NADH ratio in the cellular environment (reductive stress) are stressed. The toxic effects of acetaldehyde are mentioned. The ethanol-induced oxidative stress: the increased MDA formation by incubated liver preparations, the absorption of conjugated dienes in mitochondrial and microsomal lipids and the decrease in the most unsaturated fatty acids in liver cell membranes are discussed. The formation of carbon-centered (1-hydroxyethyl) and oxygen-centered (hydroxyl) radicals during the metabolism of ethanol is considered: the generation of hydroxyethyl radicals, which occurs likely during the process of univalent reduction of dioxygen, is highlighted and is carried out by ferric cytochrome P(450) oxy-complex (P(450)-Fe(3+)O(2) (.-)) formed during the reduction of heme-oxygen. The ethanol-induced lipid peroxidation has been evaluated, and it has been shown that plasma F(2)-isoprostanes are increased in ethanol toxicity.

The role of acetaldehyde in pregnancy outcome after prenatal alcohol exposure

It is not known why some heavy-drinking women give birth to children with alcohol-related birth defects (ARBD) whereas others do not. The objective of this study was to determine whether the frequency of elevated maternal blood acetaldehyde levels among alcoholics is in the range of ARBD among alcoholic women. MEDLINE was searched from 1980 to 2000 using the key words acetaldehyde, pharmacokinetics, and alcoholism for controlled trials reporting blood or breath acetaldehyde levels in alcoholics and nonalcoholics. Separately, using the key words fetal alcohol syndrome, epidemiology, prevalence, incidence, and frequency, articles were identified reporting ARBD incidences among the offspring of heavy drinkers. Of 23 articles reporting acetaldehyde levels in alcoholics, four met the inclusion criteria. Forty-three studies reported on the rate of ARBD in heavy drinkers, and 14 were accepted. Thirty-four percent of heavy drinkers had a child with ARBD, and 43% of chronic alcoholics had high acetaldehyde levels. The similar frequencies of high acetaldehyde levels among alcoholics and the rates of ARBD among alcoholic women provide epidemiologic support to the hypothesis that acetaldehyde may play a major role in the cause of ARBD.

Cytotoxicity of short-chain alcohols

Ethanol and other short-chain alcohols elicit a number of cellular responses that are potentially cytotoxic and, to some extent, independent of cell type. Aberrations in phospholipid and fatty acid metabolism, changes in the cellular redox state, disruptions of the energy state, and increased production of reactive oxygen metabolites have been implicated in cellular damage resulting from acute or chronic exposure to short-chain alcohols. Resulting disruptions of intracellular signaling cascades through interference with the synthesis of phosphatidic acid, decreases in phosphorylation potential and lipid peroxidation are mechanisms by which solvent alcohols can affect the rate of cell proliferation and, consequently, cell number. Nonoxidative metabolism of short-chain alcohols, including phospholipase D-mediated synthesis of alcohol phospholipids, and the synthesis of fatty acid alcohol esters are additional mechanisms by which alcohols can affect membrane structure and compromise cell function.

Inhibition of plasma membrane and mitochondrial transmembrane potentials by ethanol

The actions of ethanol and its primary oxidative metabolite, acetaldehyde, on plasma membrane and mitochondrial transmembrane potentials were examined in rat brain using fluorescence techniques. Subchronic treatment of adult rats with ethanol resulted in a significant depolarization of both the plasma and mitochondrial membranes when the mean blood ethanol level of the rats was 59 +/- 11 mM (mean +/- SEM, n = 6). Acute dosing of animals (4.5 g/kg, i.p.) failed to show any significant alterations. Various concentrations of ethanol, added in vitro to a crude synaptosomal preparation isolated from the rat cerebrocortex (P2) from untreated animals, depolarized both the plasma and mitochondrial transmembrane potentials in a dose-related manner. Addition of acetaldehyde in vitro did not reveal any significant effects on plasma or mitochondrial transmembrane potential.

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.

Ethanol-induced inhibition of ventricular protein synthesis in vivo and the possible role of acetaldehyde

We have determined the extent to which acute ethanol administration perturbs the synthesis of ventricular contractile and non-contractile proteins in vivo. Male Wistar rats were treated with a standard dose of ethanol (75 mmol kg-1 body weight; i.p.). Controls were treated with isovolumetric amounts of saline (0.15 mol l-1 NaCl). Two metabolic inhibitors of ethanol metabolism were also used namely 4-methylpyrazole (alcohol dehydrogenase inhibitor) and cyanamide (acetaldehyde dehydrogenase inhibitor) which in ethanol-dosed rats have been shown to either decrease or increase acetaldehyde formation, respectively. After 2.5 h, fractional rates of protein synthesis (i.e. the percentage of tissue protein renewed each day) were measured with a large (i.e. 'flooding') dose of L-[4-3H]phenylalanine (150 mumol (100 g)-1 body weight into a lateral vein). This dose of phenylalanine effectively floods all endogenous free amino acid pools so that the specific radioactivity of the free amino acid at the site of protein synthesis (i.e. the amino acyl tRNA) is reflected by the specific radioactivity of the free amino acid in acid-soluble portions of cardiac homogenates. The results showed that ethanol alone and ethanol plus 4-methylpyrazole decreased the fractional rates of mixed, myofibrillar (contractile) and sarcoplasmic (non-contractile) protein synthesis to the same extent (by approx. 25 per cent). Profound inhibition (i.e. 80 per cent) in the fractional rates of mixed, myofibrillar and sarcoplasmic protein synthesis occurred when cyanamide was used to increase acetaldehyde formation. There was also a significant decrease in cardiac DNA content. The results suggest that acute ethanol-induced cardiac injury in the rat may be mediated by both acetaldehyde and ethanol.

The identification and partial characterization of acetaldehyde adducts of hemoglobin occurring in vivo: a possible marker of alcohol consumption

Chromatographic, peptide mapping and mass spectrometric analysis were used to examine hemoglobin (Hb) from heavy drinkers and abstainers for alcohol consumption-related modifications. Heavy drinker and abstainer hemoglobin samples contained similar amounts of glycosylated Hb and significantly different (p < 0.05) amounts of "fast" hemoglobin. The presence of higher amounts of "fast" Hb in heavy drinker relative to abstainer samples suggested the presence of alcohol-consumption related modifications. To further examine Hb for modifications, tryptic peptides of the "fast" hemoglobin HbA1c were isolated and analyzed by plasma desorption mass spectrometry (PDMS). [14C]acetaldehyde (AcH)-Hb was synthesized in vivo for use as a standard. Specific peptides were chosen based on co-migration with radiolabeled peptides from a tryptic digest of the [14C]acetaldehyde-Hb. The masses obtained by PDMS for two heavy drinker peptides were identical to two radiolabeled peptides; the two pairs of peptides co-migrated on HPLC. A comparison of the observed mass for the peptides with the theoretical masses for acetaldehyde-modified Hb peptides suggested that the peptides were AcH-modified alpha and beta chain N-termini of Hb. The modified peptides were found in five of six heavy drinker samples. This is the first description of site-specific AcH-Hb adducts occurring in vivo. The routine detection of such adducts has potential for characterizing usual alcohol intake.

Effect of ethanol on lipoprotein secretion in two human hepatoma cell lines, HepG2 and Hep3B

The two human hepatoma cell lines, HepG2 and Hep3B, have been demonstrated to metabolize ethanol efficiently even in the absence of alcohol dehydrogenase. By using specific metabolic inhibitors, it was found that the microsomal ethanol-oxidizing system (MEOS) plays a significant role in ethanol metabolism in these two cell lines. There is a strong positive correlation between the rates of ethanol metabolism and the total cytochrome P-450 levels in the hepatoma cells. The involvement of the cytochrome P-450 system was further supported by the induction of aniline p-hydroxylase activity after ethanol treatment. However, the 3- to 4-fold elevation in aniline p-hydroxylase activity was not accompanied by an increase in cytochrome P450IIE1 mRNA level. Exposure of HepG2 and Hep3B cells to ethanol resulted in an increase of accumulation of apoA-I (15%-45% over control) in a dose-dependent manner (from 5 to 50 mM) of ethanol over a 24-hr period. All other major apolipoproteins which included apo CII, apo CIII and apoE, with the exception of apoB, were not affected by these treatments. At a concentration of ethanol of 25 mM or greater, accumulation of apoB, VLDL and LDL triglyceride were increased by 20% to 25% over the control level. Elevation of HDL cholesterol (40%-70% over control) was observed when the cells were exposed to an ethanol concentration of > or = 10 mM. Metyrapone, which inhibited the MEOS, was capable of blocking the induction of apoAI caused by ethanol treatment.

Effects of acute alcohol intoxication on gluconeogenesis and its hormonal responsiveness in isolated, perfused rat liver

Rats were acutely administered ethanol as a primed constant infusion in order to produce sustained blood ethanol levels of 8-12 or 55-65 mM. At the end of ethanol infusion the livers were either freeze-clamped in vivo or isolated and perfused for metabolic studies. The rate of gluconeogenesis and its responsiveness to phenylephrine (10 microM), prostaglandin F2 alpha (5 microM) and glucagon (10 nM), as well as the redox state of the cytosolic NAD(+)-NADH system were assessed in livers isolated from acutely ethanol-treated rats, and subsequently perfused without ethanol. For liver clamped in vivo, high- but not low-ethanol treatment decreased the ATP content by 31% and slightly increased ADP and AMP content, resulting in a decreased energy charge (11%). Glutamate and aspartate content was also increased in high-dose ethanol-infused rats with no changes in malate and 2-oxoglutarate content. Gluconeogenesis with saturating concentrations of lactate (4 mM)+pyruvate (0.4 mM) was delayed in reaching a plateau in the livers of high-dose ethanol-treated rats and its response to all three stimulators was impaired. Low-dose ethanol treatment only decreased the liver response to phenylephrine. While the perfused livers of low-dose ethanol-treated rats displayed no changes in adenine nucleotide content, the livers of high-dose ethanol-treated rats had a decreased ATP (35%) and an increased AMP (77%) content, paralleled by a fall in the total adenine nucleotides (14%) and energy charge (14%). No differences were observed between the saline- and ethanol-treated rats with respect to malate-aspartate shuttle intermediate concentration in perfused livers. Also, the livers of high-, but not low-dose ethanol-treated rats had a more negative value of NAD(+)-NADH redox state as compared to the livers of control rats. The data suggest that acute ethanol intoxication produces changes in liver metabolism and its responsiveness to hormones/agonists that are demonstrable for at least 2 hr after isolation and perfusion of the liver.

Cardiorespiratory reflex due to pulmonary J receptors stimulation by acetaldehyde in rats

Acetaldehyde (AcH) administered intravenously or into the right ventricle induces reflex bradycardia, hypotension, and apnea in the rat. The efferent pathway for this reflex is vagal and probably secondary to pulmonary J receptors stimulation. Located between the alveoli and the pulmonary capillary, J receptors are accessible through the pulmonary circulation and the airways. For this reason, a method for indirect nebulization (IN) of AcH into the airways, that provides a continuous record of respiration without changes in intrapulmonary pressure, was developed. IN of AcH (n = 14) induced bradycardia (64 +/- 3.1%), hypotension (34 +/- 4.2%), and apnea (79%), which were blocked by vagotomy (n = 9). The latencies (s) for bradycardia (0.34 +/- 0.06), hypotension (0.68 +/- 0.11), and apnea (0.25 +/- 0.11) were significantly shorter than those obtained by the intravenous route. Three rats that did not develop apnea had an equivalent response, where both tidal volume and minute ventilation decreased about 40% and these effects were also blocked by vagotomy. Indirect nebulization of AcH allowed us to demonstrate that pulmonary J receptors are responsible for this reflex response.

Alcohol, liver, and nutrition

Until two decades ago, dietary deficiencies were considered to be the major reason why alcoholics developed liver disease. As the overall nutrition of the population improved, more emphasis was placed on secondary malnutrition. Direct hepatotoxic effects of ethanol were also established, some of which were linked to redox changes produced by reduced nicotinamide adenine dinucleotide (NADH) generated via the alcohol dehydrogenase (ADH) pathway. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving cytochrome P-450: the newly discovered ethanol-inducible cytochrome P-450 (P-450IIE1) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. P-450 induction also explains depletion (and enhanced toxicity) of nutritional factors such as vitamin A. Even at the early fatty-liver stage, alcoholics commonly have a very low hepatic concentration of vitamin A. Ethanol administration in animals was found to depress hepatic levels of vitamin A, even when administered with diets containing large amounts of the vitamin, reflecting, in part, accelerated microsomal degradation through newly discovered microsomal pathways of retinol metabolism, inducible by either ethanol or drug administration. The hepatic depletion of vitamin A was strikingly exacerbated when ethanol and other drugs were given together, mimicking a common clinical occurrence. Hepatic retinoid depletion was found to be associated with lysosomal lesions and decreased detoxification of chemical carcinogens. To alleviate these adverse effects, as well as to correct problems of night blindness and sexual inadequacies, the alcoholic patient should be provided with vitamin A supplementation. Such therapy, however, is complicated by the fact that in excessive amounts vitamin A is hepatotoxic, an effect exacerbated by long-term ethanol consumption. This results in striking morphologic and functional alterations of the mitochondria with leakage of mitochondrial enzymes, hepatic necrosis, and fibrosis. Thus, treatment with vitamin A and other nutritional factors (such as proteins) is beneficial but must take into account a narrowed therapeutic window in alcoholics who have increased needs for such nutrients, but also display an enhanced susceptibility to their adverse effects. Massive doses of choline also exerted some toxic effects and failed to prevent the development of alcoholic cirrhosis. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also enhances pyridoxine and perhaps folate degradation and stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts.(ABSTRACT TRUNCATED AT 400 WORDS)

Formation of a 37 kilodalton liver protein-acetaldehyde adduct in vivo and in liver cell culture during chronic alcohol exposure

With the use of antibodies that can recognize acetaldehyde adducts and the application of various immunological techniques, several protein-AAs have now been shown to form in vivo during chronic alcohol ingestion. These protein-AAs include the 37-kDa liver protein-AA, the CytP450IIE1-AA, hemoglobin-AA, two serum protein-AAs with molecular weights of 50 kDa and 103 kDa, and collagen type I protein-AA in liver. If acetaldehyde is the agent responsible for alcoholic liver injury, acetaldehyde toxicity in chronic alcohol ingestion must be linked to the ability of acetaldehyde to form adducts with proteins and perhaps other macromolecules. This is at least one mechanism of acetaldehyde-mediated liver injury. For proteins that serve critical functions, acetaldehyde adduct formation may alter their functions and thereby produce organ damage. Acetaldehyde adduct formation can also elicit humoral or cytotoxic immune responses and these responses may also lead to organ injury.

The effect of the prostaglandin analogue-misoprostol on rat liver mitochondria after chronic alcohol feeding

Rats fed ethanol (36% of total calories in a nutritionally adequate liquid diet) for 5 weeks develop functional alterations of hepatic mitochondria and steatosis of the liver. At the fatty liver stage, ADP-stimulated respiration of mitochondria was depressed in ethanol fed rats by 30% (p less than 0.001) with glutamate + malate and by 23% (p less than 0.001) with succinate as substrates. A similar decrease was noted in the respiratory control ratio (RCR) (34% and 29%, respectively). The total lipid content of the liver increased 2.6 fold (p less than 0.001). Mitochondrial dysfunction could be prevented, in part, by the treatment with a synthetic derivative of prostaglandin E1, misoprostol, at a mean daily dose of 80 micrograms/kg of body weight. The RCR with glutamate + malate as substrates was improved by 36% (p less than 0.05). We conclude that misoprostol attenuates several functional alterations in liver mitochondria during alcohol feeding.

Mechanism of ethanol induced hepatic injury

Ethanol is hepatotoxic through redox changes produced by the NADH generated in its oxidation via the alcohol dehydrogenase pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins and purines. Ethanol is also oxidized in liver microsomes by an ethanol-inducible cytochrome P-450 (P-450IIE1) which contributes to ethanol metabolism and tolerance, and activates xenobiotics to toxic radicals thereby explaining increased vulnerability of the heavy drinker to industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens and even nutritional factors such as vitamin A. Induction also results in energy wastage and increased production of acetaldehyde. Acetaldehyde, in turn, causes injury through the formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, and alterations in microtubules, plasma membranes and mitochondria with a striking impairment of oxygen utilization. Acetaldehyde also causes glutathione depletion and lipid peroxidation, and stimulates hepatic collagen synthesis, thereby promoting fibrosis.

High levels of acetaldehyde in nonalcoholic liver injury after threonine or ethanol administration

Acetaldehyde, a product of ethanol oxidation which forms adducts with proteins, has been incriminated in the pathogenesis of alcoholic liver injury. High serum antibody titers against acetaldehyde-protein adducts have been found not only in alcoholics but also in patients with nonalcoholic liver disease, suggesting a contribution of acetaldehyde derived from sources other than exogenous ethanol. To investigate the effect of liver injury on the removal and the production of acetaldehyde, we produced fibrosis and cirrhosis (by chronic administration of carbon tetrachloride) and fatty liver (with very small doses of dimethylnitrosamine) in rats. Endogenous blood acetaldehyde levels increased by 38% in rats with severe liver injury (p less than 0.005), but not significantly in rats with fatty liver. However, an i.v. load of threonine (a physiological source of acetaldehyde), in amounts equivalent to the daily intake of this amino acid, increased blood and hepatic acetaldehyde levels in the rats with both types of liver injury more than in controls. Threonine dehydrogenase and dehydratase activities, involved in the major pathways for threonine degradation in mitochondria and cytosol, respectively, were markedly decreased in rats with liver injury with a resulting increase in hepatic threonine concentration. Moreover, the threonine aldolase activity, which splits threonine into glycine and acetaldehyde, remained unaffected or even slightly increased. Liver injury was also associated with impaired mitochondrial functions, including a 10 to 23% decrease in acetaldehyde oxidation (depending upon the severity of the lesions). As a consequence, administration of ethanol (an exogenous source of acetaldehyde) resulted in striking elevations in the levels of acetaldehyde in carbon tetrachloride-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver mitochondrial aldehyde dehydrogenase: in vitro expression, in vitro import, and effect of alcohols on import

An in vitro expression plasmid (pGRAP) that contained the cDNA coding for the rat mitochondrial aldehyde dehydrogenase precursor was constructed, mRNA was synthesized then translated, and the in vitro synthesized precursor of aldehyde dehydrogenase was used in an in vitro import assay. As expected the 19 amino acid signal peptide of the precursor allowed import of the precursor into rat liver mitochondria. This in vitro system was used to examine the effect of alcohols on import. It was found that the alcohols (ethyl, butyl, hexyl, and octyl) tested inhibited the import of the aldehyde dehydrogenase precursor. Pretreatment of the mitochondria with alcohol was responsible for the inhibition. The inhibition appeared to be relatively specific for pre-aldehyde dehydrogenase as the precursor of ornithine transcarbamylase was still imported in the presence of alcohols. Of potential physiological significance was finding that ethanol inhibited import in a dose-response fashion; 50% inhibition occurred at 75 mM, a concentration achievable during the ingestion of alcohol. In addition, the concentrations of alcohols required to produce an inhibitory effect on import decreased as the hydrocarbon chain length of alcohols increased. The inhibitory effect of alcohols appeared to be specific as other solvents examined did not inhibit import. We postulate that alcohols may perturb the mitochondrial membrane and affect the receptor-translocator necessary for the import of the aldehyde dehydrogenase precursor.

Correlations between serum proteins modified by acetaldehyde and biochemical variables in heavy drinkers

A strong and highly significant correlation was observed between serum aspartate transaminase (AST) activity and an index of the cytotoxic activity associated with serum proteins modified by acetaldehyde in a group of 24 heavy drinkers. A weaker but significant correlation (R = 0.564, p = 0.008) was found between total serum creatine kinase activity and this index of serum cytotoxicity. As it is likely that the concentration of circulating modified protein was largely determined by the quantity of free acetaldehyde generated in the liver and that the AST activity was mainly derived from damaged hepatocytes, the data indicate a correlation between hepatic acetaldehyde generation and hepatocyte damage. This correlation may indicate either that increased quantities of acetaldehyde are released by damaged hepatocytes or that acetaldehyde is hepatotoxic in vivo. As only the creatine kinase isoenzyme present in skeletal muscle (CK-MM) was demonstrable in the serum in all but one of our patients, the data also suggest that circulating modified serum proteins may be toxic towards skeletal muscle cells.

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 CO2 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 CO2 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.

Hepatotoxicity of acetaldehyde in rats

The ability of acetaldehyde to initiate hepatotoxicity as evidenced by enzyme leakage, hepatic fat accumulation and histological alterations was studied in rats. Neither oral nor intraperitoneal treatment with acetaldehyde had any hepatotoxic effect, even following aldehyde dehydrogenase inhibition by disulfiram. This is probably due to the inability of exogenously added acetaldehyde to penetrate liver cell membranes. In contrast, acetaldehyde derived metabolically from ethanol was capable of inducing moderate hepatotoxicity when it accumulated upon pretreatment with disulfiram. Acetaldehyde may thus be partly responsible for alcohol-induced liver damage.

Studies on the mechanism of acetaldehyde-mediated inhibition of rat liver transaminases

Incubation of mitochondria-depleted rat liver homogenates with 5 mmol/l acetaldehyde at 37 degrees C for 1 h inhibited both aspartate and alanine aminotransferases by 30%. Inhibition was prevented by decreasing temperature to 4 degrees C or by preincubating homogenates with cyanate but was unaffected by cyanamide and methylpyrazole which block acetaldehyde oxidation and reduction respectively. Cyanate-sensitive acetaldehyde-mediated inhibition of purified porcine heart transaminases was also demonstrated in the presence of rat liver homogenate but not in Tris/sucrose medium. Moreover, porcine transaminases were inhibited by trichloroacetic acid extracts of rat liver homogenates previously incubated with acetaldehyde but not by extracts of homogenates incubated with both acetaldehyde and cyanate. These findings suggest that acetaldehyde-mediated transaminase inhibition requires further non-oxidative metabolism of acetaldehyde. Since transaminase activities were not restored by addition of pyridoxal 5'-phosphate to the assay systems, acetaldehyde-induced transaminase inhibition does not appear to be mediated by displacement or depletion of this B6 coenzyme.

Evidence for the generation of transaminase inhibitor(s) during ethanol metabolism by rat liver homogenates: a potential mechanism for alcohol toxicity

Since ethanol consumption decreases hepatic aminotransferase activities in vivo, mechanisms of ethanol-mediated transaminase inhibition were explored in vitro using mitochondria-depleted rat liver homogenates. When homogenates were incubated at 37 degrees with 50 mM ethanol for 1 hr, alanine aminotransferase decreased by 20%, while aspartate aminotransferase was unchanged. After 2 hr, aspartate aminotransferase decreased by 20% and by 3 hr, alanine and aspartate aminotransferases were decreased by 31 and 23%, respectively. Levels of acetaldehyde generated during ethanol oxidation were 525 +/- 47 microM at 1 hr, 855 +/- 14 microM at 2 hr, and 1293 +/- 140 microM at 3 hr. Although inhibition of alcohol oxidation with methylpyrazole or cyanide markedly decreased ethanol-mediated transaminase inhibition, neither incubation with acetate nor generation of reducing equivalents by oxidation of lactate, malate, xylitol, or sorbitol altered the activity of either enzyme. However, semicarbazide, an aldehyde scavenger, prevented inhibition of both aminotransferases by ethanol. Moreover, incubation with 5 mM acetaldehyde for 1 hr inhibited alanine and aspartate aminotransferases by 36 and 26%, respectively. Cyanamide, an aldehyde dehydrogenase inhibitor, had little effect on ethanol-mediated transaminase inhibition. Thus, metabolism of ethanol by rat liver homogenates produces transaminase inhibition similar to that described in vivo and this effect requires acetaldehyde generation but not acetaldehyde oxidation. Since addition of pyridoxal 5'-phosphate to assay mixes did not reverse ethanol effects, aminotransferase inhibition does not result from displacement of vitamin B6 coenzymes.

Acetaldehyde causes a prolongation of the doubling time and an increase in the modal volume of cells in culture

The effects of culturing four human cell lines--Raji, MOLT-4, WI-L2, and K562--in the presence of 10-360 microM acetaldehyde for 3-18 days have been investigated. Concentrations of 45-360 microM caused a prolongation of the cell doubling time, and those of 90-360 microM caused an increase in the modal cell volume and in the protein content per cell. The results indicate that relatively low concentrations of acetaldehyde cause an impairment of cell proliferation and an abnormality of cell growth in vitro and support the possibility that ethanol-derived acetaldehyde may be responsible for some aspects of tissue damage in chronic alcoholics, including the increase in the mean cell volume of erythrocytes. Three of the four cell lines studied showed a reduction and the fourth showed no change in modal cell volume after culture with 100 mM ethanol, suggesting that the macrocytosis of red cells induced by chronic alcoholism is not caused via some direct effect of ethanol on the erythron.

Biochemical basis of alcoholism: statements and hypotheses of present research

Experimental results and theoretical considerations on the biology of alcoholism are devoted to the following topics: genetically determined differences in metabolic tolerance; participation of the alternative alcohol metabolizing systems in chronic alcohol intake; genetically determined differences in functional tolerance of the CNS to the hypnotic effect of alcohol; cross tolerance between alcohol and centrally active drugs; dissociation of tolerance and cross tolerance from physical dependence; permanent effect of uncontrolled drinking behavior induced by alkaloid metabolites in the CNS; genetically determined alterations in the function of opiate receptors; and genetic predisposition to addiction due to innate endorphin deficiency. For the purpose of introducing the most important research teams and their main work, statements from selected publications of individual groups have been classified as to subject matter and summarized. Although the number for summary-quotations had to be restricted, the criterion for selection was the relevance to the etiology of alcoholism rather than consequences of alcohol drinking.

Lowering of blood acetaldehyde but not ethanol concentrations by pantethine following alcohol ingestion: different effects in flushing and nonflushing subjects

A rise in blood acetaldehyde concentrations following alcohol ingestion was significantly inhibited when healthy nonflushing subjects were administered a clinical dose of pantethine orally. However, similar findings were not observed in flushing (alcohol-sensitive) subjects lacking hepatic low Km aldehyde dehydrogenase (ALDH). The blood ethanol concentrations were not altered by this treatment in either flushing or nonflushing subjects. Acetaldehyde (45 microM) added in vitro to whole blood and plasma obtained 1 hr after pantethine administration disappeared as the incubation continued similarly as with blood and plasma obtained prior to pantethine treatment. Pantethine-related metabolites, such as taurine, pantetheine, coenzyme A, and pantothenate, activated ALDH in vitro. Hepatic acetaldehyde levels following ethanol loading of rats treated with pantethine were much lower than in untreated rats. The pantethine action observed only in nonflushing subjects might be due to an accelerated oxidation of acetaldehyde by the activation of low Km ALDH by pantethine-related metabolites formed in the liver.

Aldehyde dehydrogenase in alcoholic subjects

Hepatic aldehyde dehydrogenase activity is depressed in alcoholic liver disease and may account for the observation that alcoholics develop high blood acetaldehyde concentrations following ethanol. To determine whether this is a specific defect in alcoholics, aldehyde dehydrogenase was studied in liver tissue obtained from three groups of subjects. Group I comprised 30 patients with alcoholic liver disease, Group II consisted of eight subjects with liver disease unrelated to alcohol abuse and Group III was a control group of 10 individuals with no significant liver disease. Mean hepatic aldehyde dehydrogenase activity was significantly lower in Group I than in Groups II or III [4.9 +/- 0.6 (mean +/- S.E.), compared to 10.2 +/- 1.8 and 12.4 +/- 1.1 nmoles of acetaldehyde oxidized per min X mg of protein, respectively]. Aldehyde dehydrogenase activity in Group II was relatively well maintained. Aldehyde dehydrogenase activity was found in cytosolic and mitochondrial fractions of liver homogenates. In alcoholic subjects, cytosolic aldehyde dehydrogenase activity was not more depressed than was mitochondrial aldehyde dehydrogenase. Isoelectric focusing demonstrated a single mitochondrial isoenzyme and a single cytosolic isoenzyme in most cases in Group III. In contrast, multiple cytosolic isoenzymes were consistently found in liver tissue from Group I subjects. These findings suggest that depressed aldehyde dehydrogenase activity in alcoholic subjects is not a consequence of liver disease.

Ethanol feeding can produce secondary alterations in aldehyde dehydrogenase isozymes

Depressed hepatic aldehyde dehydrogenase (ALDH) activity levels have been observed in alcoholics, but whether the deficit is primary or secondary in nature remains controversial. In this study, we examined liver ALDH in rodent (rat) and primate (baboon) animal models pair-fed nutritionally adequate ethanol or isocaloric carbohydrate containing liquid diets. Both species show qualitative changes in ALDH isozymes after ethanol consumption. The changes include alterations in isozyme patterns seen upon electrofocusing and decreased responsiveness to the ALDH inhibitor, disulfiram. The subcellular locus of most of the changes is cytosolic in the baboon and mitochondrial in the rat. Study of partially purified (enriched) baboon cytosolic ALDH confirmed changes seen in the original cytosols and kinetic characterization of the enriched enzyme revealed a 9-fold higher Km for acetaldehyde in ALDH from an ethanol treated animal. We note that qualitative and quantitative changes secondary to ethanol treatment in the primate model closely parallel those described in human alcoholics.

A report of unusually high blood ethanol and acetaldehyde levels in two surviving patients

Two men with unusually high blood acetaldehyde levels of 750 and 2410 micrograms/dl presented only mild symptomatology. Their blood ethanol levels, 730 and 1121 mg/dl, were also extraordinarily high. However, liver function tests demonstrated no abnormalities.

Formation of Schiff base adduct between acetaldehyde and rat liver microsomal phosphatidylethanolamine

Recent studies have established the formation of acetaldehyde adducts of proteins even at low concentrations of acetaldehyde expected to occur in vivo under conditions of ethanol metabolism. Although formation of acetaldehyde adducts with phospholipids has been obtained at high pH values and at high concentrations of acetaldehyde, the occurrence of such adducts under more physiological conditions had yet to be demonstrated. Rat liver microsomes were incubated with 0.2 mM [14C]acetaldehyde at pH 7.4 and 37 degrees C. After treatment with sodium borohydride to reduce any Schiff bases formed, the phospholipids were isolated. The major radioactive component within the phospholipid fraction had chromatographic properties identical to N-ethylphosphatidylethanolamine. In addition, the nitrogenous base derived therefrom by acid hydrolysis was identical to N-ethylethanolamine. These results indicate that a Schiff base adduct between acetaldehyde and microsomal phosphatidylethanolamine had been formed during incubation of low concentrations of acetaldehyde with rat liver microsomes.

Inhibition of the oxidation of acetaldehyde and formaldehyde by hepatocytes and mitochondria by crotonaldehyde

Crotonaldehyde was oxidized by disrupted rat liver mitochondrial fractions or by intact mitochondria at rates that were only 10 to 15% that of acetaldehyde. Although a poor substrate for oxidation, crotonaldehyde is an effective inhibitor of the oxidation of acetaldehyde by mitochondrial aldehyde dehydrogenase, by intact mitochondria, and by isolated hepatocytes. Inhibition by crotonaldehyde was competitive with respect to acetaldehyde, and the Ki for crotonaldehyde was about 5 to 20 microM. Crotonaldehyde had no effect on the oxidation of glutamate or succinate. Very low levels of acetaldehyde were detected during the metabolism of ethanol. Crotonaldehyde increased the accumulation of acetaldehyde more than 10-fold, indicating that crotonaldehyde, besides inhibiting the oxidation of added acetaldehyde, also inhibited the oxidation of acetaldehyde generated by the metabolism of ethanol. Formaldehyde was a substrate for the low-Km mitochondrial aldehyde dehydrogenase, as well as for a cytosolic, glutathione-dependent formaldehyde dehydrogenase. Crotonaldehyde was a potent inhibitor of mitochondrial oxidation of formaldehyde, but had no effect on the activity of formaldehyde dehydrogenase. In hepatocytes, crotonaldehyde produced about 30 to 40% inhibition of formaldehyde oxidation, which was similar to the inhibition produced by cyanamide. This suggested that part of the formaldehyde oxidation occurred via the mitochondrial aldehyde dehydrogenase, and part via formaldehyde dehydrogenase. The fact that inhibition by crotonaldehyde is competitive may be of value since other commonly used inhibitors of aldehyde dehydrogenase are irreversible inhibitors of the enzyme.

The isolation and properties of mitochondria from rat pancreas

A technique for the isolation of functional rat pancreatic mitochondria is described. The resultant mitochondrial preparations contained oligomycin-insensitive Mg2+-ATPase activity and coupled respiration could only be demonstrated in the absence of Mg2+ and in the presence of EDTA.

Effects of chronic ethanol feeding and acetaldehyde metabolism on calcium transport by rat liver mitochondria

The prolonged feeding of ethanol to rats alters in vitro mitochondrial transport of calcium. Hepatic mitochondria isolated from rats fed ethanol for 7 weeks exhibited decreased retention of calcium in the presence of 4mM-Pi. This defect was associated with enhanced efflux of calcium when mitochondria were incubated with EGTA. Acetaldehyde at low, "physiological" concentrations (100 microM) enhanced calcium retention by mitochondria but this response was blunted after chronic ethanol administration. The in vitro actions of acetaldehyde appear to be mediated, in part, by its metabolism in mitochondria since pretreatment of rats with cyanamide (an aldehyde dehydrogenase inhibitor) prevents this effect.

Uninterrupted prolonged ethanol oxidation as a main pathogenetic factor of alcoholic liver damage: evidence from a new liquid diet animal model

Marked fatty infiltration and degenerative or mild inflammatory changes including eosinophilic cytoplasmic degeneration in centrilobular cells and focal inflammatory changes with cell necrosis were observed in livers of rats maintained for 12 weeks on a nutritionally adequate and balanced liquid ethanol diet. The animals continuously oxidized ethanol due to the supplementation of the diet with a low dose of 4-methylpyrazole (4-MP, an alcohol dehydrogenase inhibitor), that decreased ethanol elimination by about 20%. In other, equicalorically pair-fed groups of rats receiving (a) a similar ethanol-containing liquid diet without 4-MP or (b) a diet with 4-MP and 20% less ethanol, only a few minor changes were seen. The liver histology of rats pair-fed a control diet with a 4 times higher doses of 4-MP was completely normal. The results indicate that the prolonged imbalance of hepatic metabolism due to the uninterrupted oxidation of ethanol is a crucial factor in the development of alcoholic liver injury.

Subcellular localization of acetaldehyde dehydrogenase in human liver

The subcellular distribution of aldehyde dehydrogenase activity was determined in human liver biopsies by analytical sucrose density-gradient centrifugation. There was bimodal distribution of activity corresponding to mitochondrial and cytosolic localizations. At pH 9.6 cytosolic aldehyde dehydrogenase had a lower apparent Kappm for NAD (0.03 mmol l-1), than the mitochondrial enzyme (Kappm NAD = 1.1 mmol l-1). Also, the pH optimum for cytosolic aldehyde dehydrogenase activity (pH 7.5) was lower than that for the mitochondrial enzyme activity (pH 9.0), and the cytosolic enzyme activity was more sensitive to inhibition by disulfiram in vitro. Disulfiram (40 mumol l-1) caused a 70% reduction in cytosolic aldehyde dehydrogenase activity, but only a 30% reduction in mitochondrial enzyme activity after 10 min incubation. The liver cytosol may therefore be the major site of acetaldehyde oxidation in vivo in man.

Determinants of blood acetaldehyde level during ethanol oxidation in chronic alcoholics

We analyzed the blood alcohol and acetaldehyde concentrations in nine alcoholics and four healthy nonalcoholic controls during and after an intravenous infusion of a high and a low dose of alcohol. In the alcoholics, the mean rates of plasma ethanol disappearance were significantly higher than in nonalcoholic controls. In the control subjects, the blood acetaldehyde levels were, in general, below the detection limit (less than 0.5 microM), but in sharp contrast to this, an elevated blood acetaldehyde during ethanol infusion was found in 6/9 alcoholics. Peak blood acetaldehyde values were higher after the high than the low dose of alcohol. Fructose infusion significantly enhanced the rate of plasma ethanol disappearance both in controls and in alcoholics, and this was usually associated with a significant elevation of blood acetaldehyde level. The maximal specific activities (expressed as milliunits/mg og protein) of alcohol, lactate, and aldehyde dehydrogenases in liver were significantly lower in alcoholics than in controls. Even more importantly, the peak blood acetaldehyde correlated negatively with the activity of hepatic "low-Km" aldehyde dehydrogenase. Our results suggest that the main reason for blood acetaldehyde elevation seen in these chronic alcoholics is their impaired capacity to metabolize acetaldehyde. This may be further accentuated by the increased rate of ethanol oxidation.

The subcellular distribution and properties of aldehyde dehydrogenase of hepatoma AH-130

Aldehyde dehydrogenase subcellular distribution and activity were studied in the Yoshida hepatoma AH-130 and rat liver. NAD+- and NADP+-dependent dehydrogenase activities were lower in all hepatoma subfractions (except the cytosol) than in liver subfractions. In the presence of 0.025 mM substrate 78-80% of the liver NAD+- or NADP+-dependent aldehyde dehydrogenase was found in the mitochondria. With 10 mM substrate the enzyme activity was primarily in the mitochondria and microsomes. In the hepatoma a sharp increase of the soluble aldehyde dehydrogenase (either NAD+- or NADP+ dependent) was observed at all substrate concentrations. The Km of the different isoenzymes (either identified by their localization or coenzyme dependency) were of the same order for liver and hepatoma. However, a high Km enzyme was present in liver mitochondria outer membranes but not in hepatoma. Hepatoma acetaldehyde dehydrogenase was inhibited, as was the liver enzyme, by diethyldithiocarbamate. The return of activity was slower for the hepatoma and neonatal liver than for the adult liver enzyme.

Low Km ALDH isozyme and alcoholic liver injury

To assess the relationship between the polymorphism of aldehyde dehydrogenase (ALDH) isozyme and alcoholic liver injury, ALDH isozyme was analyzed by isoelectric focusing electrophoresis in hair roots from normal volunteers and alcoholics with chronic liver disease. Liver biopsy specimens from alcoholics and non-alcoholics with chronic liver disease were also analyzed. It was found that (1) the frequency of low Km ALDH isozyme in hair roots from chronic alcoholics with liver injury was 90%, which was significantly higher than those from normal volunteers (44%) and from non-alcoholics with chronic liver disease (56%); (2) the isozyme pattern of liver specimens analyzed coincided with that of hair roots; (3) the low Km ALDH isozyme-positive subjects including alcoholics showed no facial flushing, and negative subjects showed facial flushing after drinking alcohol. It is concluded that a much higher frequency of low Km ALDH isozyme was found in chronic alcoholics with liver injury. There was no apparent difference in hepatic biochemical and histological findings between chronic alcoholics with and without low Km ALDH isozyme, suggesting that acetaldehyde does not play a primary role in the pathogenesis of alcoholic liver injury.

Effect of chronic ethanol feeding on hepatic mitochondria in the monkey

The effect of chronic ethanol feeding on hepatic mitochondrial morphology and histochemically measured succinic dehydrogenase activity was assessed. Five monkeys of the species Macaca radiata received a nutritionally adequate diet containing 50% of the calories as ethanol, while five others were pair-fed the same diet except that ethanol was isocalorically substituted by carbohydrate. Liver morphology was assessed at 12 and 24 months and at sacrifice after 40 to 48 months of ethanol feeding. The ethanol-fed animals developed mild to moderate fatty liver as did some of the controls. No necrosis or fibrosis developed. All ethanol-fed animals developed centrilobolar megamitochondria and centrilobular "shift" in histochemically assayed succinic dehydrogenase activity characteristic of animals fed ethanol for prolonged periods. These mitochondrial changes persisted throughout the 48-month test period without progressive increase in severity or accompanying pathology. It is concluded that the morphologic and histochemically assessed mitochondrial changes do not necessarily represent a progressive destructive effect of ethanol.

Effects of magnesium and calcium on mitochondrial and cytosolic liver aldehyde dehydrogenases

The effects of Mg2+ and Ca2+ ions on the activities of mitochondrial and cytosolic aldehyde dehydrogenases isolated from horse, rat, and beef livers were investigated in 0.1 M sodium phosphate, pH 7.5, at 25 degrees C. As with the Mg2+-enhancement of the horse liver mitochondrial enzyme [17], Mg2+-activation was observed for the mitochondrial enzymes from rat and beef. The cytosolic enzymes from horse, rat, and beef livers were inhibited in the presence of Mg2+ ions. The effects of Ca2+ ions on the activity were essentially the same as those observed in the presence of Mg2+ ions; the mitochondrial isozymes were activated while the cytosolic isozymes were inhibited. The fact that only the activity of mitochondrial forms of mammalian liver aldehyde dehydrogenase was enhanced by Ca2+ or Mg2+ ions may be related to the in vivo regulation of aldehyde metabolism, a presumed mitochondrial event.