1
|
Teschke R. Microsomal Ethanol-Oxidizing System: Success Over 50 Years and an Encouraging Future. Alcohol Clin Exp Res 2019; 43:386-400. [PMID: 30667528 DOI: 10.1111/acer.13961] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 01/13/2019] [Indexed: 01/07/2023]
Abstract
Fifty years ago, in 1968, the pioneering scientists Charles S. Lieber and Leonore M. DeCarli discovered the capacity for liver microsomes to oxidize ethanol (EtOH) and named it the microsomal ethanol-oxidizing system (MEOS), which revolutionized clinical and experimental alcohol research. The last 50 years of MEOS are now reviewed and highlighted. Since its discovery and as outlined in a plethora of studies, significant insight was gained regarding the fascinating nature of MEOS: (i) MEOS is distinct from alcohol dehydrogenase and catalase, representing a multienzyme complex with cytochrome P450 (CYP) and its preferred isoenzyme CYP 2E1, NADPH-cytochrome P450 reductase, and phospholipids; (ii) it plays a significant role in alcohol metabolism at high alcohol concentrations and after induction due to prolonged alcohol use; (iii) hydroxyl radicals and superoxide radicals promote microsomal EtOH oxidation, assisted by phospholipid peroxides; (iv) new aspects focus on microsomal oxidative stress through generation of reactive oxygen species (ROS), with intermediates such as hydroxyethyl radical, ethoxy radical, acetyl radical, singlet radical, hydroxyl radical, alkoxyl radical, and peroxyl radical; (v) triggered by CYP 2E1, ROS are involved in the initiation and perpetuation of alcoholic liver injury, consequently shifting the previous nutrition-based concept to a clear molecular-based disease; (vi) intestinal CYP 2E1 induction and ROS are involved in endotoxemia, leaky gut, and intestinal microbiome modifications, together with hepatic CYP 2E1 and liver injury; (vii) circulating blood CYP 2E1 exosomes may be of diagnostic value; (viii) circadian rhythms provide high MEOS activities associated with significant alcohol metabolism and potential toxicity risks as a largely neglected topic; and (ix) a variety of genetic animal models are useful and have been applied elucidating mechanistic aspects of MEOS. In essence, MEOS along with its CYP 2E1 component currently explains several mechanistic steps leading to alcoholic liver injury and has a promising future in alcohol research.
Collapse
Affiliation(s)
- Rolf Teschke
- Division of Gastroenterology and Hepatology (RT), Department of Internal Medicine II, Klinikum Hanau, Academic Teaching Hospital of the Medical Faculty, Goethe University Frankfurt/Main, Frankfurt/Main, Germany
| |
Collapse
|
2
|
Cinti DL, Grundin R, Orrenius S. The effect of ethanol on drug oxidations in vitro and the significance of ethanol-cytochrome P-450 interaction. Biochem J 2010; 134:367-75. [PMID: 16742795 PMCID: PMC1177821 DOI: 10.1042/bj1340367] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effect of ethanol on N-demethylation of aminopyrine in rat liver slices and in the microsomal fraction and on microsomal hydroxylation of pentobarbital and aniline was studied. With liver slices N-demethylation of aminopyrine was stimulated by 35-40% at low ethanol concentrations (2mm), whereas no stimulation occurred at high concentrations (100mm). With the liver microsomal fraction, an inhibitory effect was observed only at high ethanol concentrations (100mm). This was also observed with the other drugs studied. In agreement with these results, only at a high concentration did ethanol interfere with the binding of drug substrates to cytochrome P-450. Further, as previously reported, ethanol produced a reverse type I spectral change when added to the liver microsomal fraction. Evidence that this spectral change is due to removal of substrate, endogenously bound to cytochrome P-450, is reported. A dual effect of ethanol is assumed to explain the present findings; in liver slices, at a low ethanol concentration, the enhanced rate of drug oxidation is the result of an increased NADH concentration, whereas the inhibitory effect observed with the microsomal fraction at high ethanol concentration is due to the interference by ethanol with the binding of drug substrates to cytochrome P-450.
Collapse
Affiliation(s)
- D L Cinti
- Department of Forensic Medicine, Karolinska Institutet, Stockholm, Sweden
| | | | | |
Collapse
|
3
|
Comporti M, Signorini C, Leoncini S, Gardi C, Ciccoli L, Giardini A, Vecchio D, Arezzini B. Ethanol-induced oxidative stress: basic knowledge. GENES & NUTRITION 2010; 5:101-9. [PMID: 20606811 PMCID: PMC2885167 DOI: 10.1007/s12263-009-0159-9] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 11/09/2009] [Indexed: 12/20/2022]
Abstract
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.
Collapse
Affiliation(s)
- Mario Comporti
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Cinzia Signorini
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Silvia Leoncini
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Concetta Gardi
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Lucia Ciccoli
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Anna Giardini
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Daniela Vecchio
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| | - Beatrice Arezzini
- Department of Pathophysiology, Experimental Medicine and Public Health, University of Siena, via A. Moro, 53100 Siena, Italy
| |
Collapse
|
4
|
|
5
|
|
6
|
Lieber CS. The discovery of the microsomal ethanol oxidizing system and its physiologic and pathologic role. Drug Metab Rev 2005; 36:511-29. [PMID: 15554233 DOI: 10.1081/dmr-200033441] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Oxidation of ethanol via alcohol dehydrogenase (ADH) explains various metabolic effects of ethanol but does not account for the tolerance. This fact, as well as the discovery of the proliferation of the smooth endoplasmic reticulum (SER) after chronic alcohol consumption, suggested the existence of an additional pathway which was then described by Lieber and DeCarli, namely the microsomal ethanol oxidizing system (MEOS), involving cytochrome P450. The existence of this system was initially challenged but the effect of ethanol on liver microsomes was confirmed by Remmer and his group. After chronic ethanol consumption, the activity of the MEOS increases, with an associated rise in cytochrome P450, especially CYP2E1, most conclusively shown in alcohol dehydrogenase negative deer mice. There is also cross-induction of the metabolism of other drugs, resulting in drug tolerance. Furthermore, the conversion of hepatotoxic agents to toxic metabolites increases, which explains the enhanced susceptibility of alcoholics to the adverse effects of various xenobiotics, including industrial solvents. CYP2E1 also activates some commonly used drugs (such as acetaminophen) to their toxic metabolites, and promotes carcinogenesis. In addition, catabolism of retinol is accelerated resulting in its depletion. Contrasting with the stimulating effects of chronic consumption, acute ethanol intake inhibits the metabolism of other drugs. Moreover, metabolism by CYP2E1 results in a significant release of free radicals which, in turn, diminishes reduced glutathione (GSH) and other defense systems against oxidative stress which plays a major pathogenic role in alcoholic liver disease. CYP1A2 and CYP3A4, two other perivenular P450s, also sustain the metabolism of ethanol, thereby contributing to MEOS activity and possibly liver injury. CYP2E1 has also a physiologic role which comprises gluconeogenesis from ketones, oxidation of fatty acids, and detoxification of xenobiotics other than ethanol. Excess of these physiological substrates (such as seen in obesity and diabetes) also leads to CYP2E1 induction and nonalcoholic fatty liver disease (NAFLD), which includes nonalcoholic fatty liver and nonalcoholic steatohepatitis (NASH), with pathological lesions similar to those observed in alcoholic steatohepatitis. Increases of CYP2E1 and its mRNA prevail in the perivenular zone, the area of maximal liver damage. CYP2E1 up-regulation was also demonstrated in obese patients as well as in rat models of obesity and NASH. Furthermore, NASH is increasingly recognized as a precursor to more severe liver disease, sometimes evolving into "cryptogenic" cirrhosis. The prevalence of NAFLD averages 20% and that of NASH 2% to 3% in the general population, making these conditions the most common liver diseases in the United States. Considering the pathogenic role that up-regulation of CYP2E1 also plays in alcoholic liver disease (vide supra), it is apparent that a major therapeutic challenge is now to find a way to control this toxic process. CYP2E1 inhibitors oppose alcohol-induced liver damage, but heretofore available compounds are too toxic for clinical use. Recently, however, polyenylphosphatidylcholine (PPC), an innocuous mixture of polyunsaturated phosphatidylcholines extracted from soybeans (and its active component dilinoleoylphosphatidylcholine), were discovered to decrease CYP2E1 activity. PPC also opposes hepatic oxidative stress and fibrosis. It is now being tested clinically.
Collapse
Affiliation(s)
- Charles S Lieber
- Mount Sinai School of Medicine, Section of Liver Disease and Nutrition and Alcohol Research Center, Bronx Veterans Affairs Medical Center, USA
| |
Collapse
|
7
|
Lieber CS. Alcoholic fatty liver: its pathogenesis and mechanism of progression to inflammation and fibrosis. Alcohol 2004; 34:9-19. [PMID: 15670660 DOI: 10.1016/j.alcohol.2004.07.008] [Citation(s) in RCA: 431] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Revised: 07/16/2004] [Accepted: 07/20/2004] [Indexed: 02/06/2023]
Abstract
Liver disease in the alcoholic is due not only to malnutrition but also to ethanol's hepatotoxicity linked to its metabolism by means of the alcohol dehydrogenase and cytochrome P450 2E1 (CYP2E1) pathways and the resulting production of toxic acetaldehyde. In addition, alcohol dehydrogenase-mediated ethanol metabolism generates the reduced form of nicotinamide adenine dinucleotide (NADH), which promotes steatosis by stimulating the synthesis of fatty acids and opposing their oxidation. Steatosis is also promoted by excess dietary lipids and can be attenuated by their replacement with medium-chain triglycerides. Through reduction of pyruvate, elevated NADH also increases lactate, which stimulates collagen synthesis in myofibroblasts. Furthermore, CYP2E1 activity is inducible by its substrates, not only ethanol but also fatty acids. Their excess and metabolism by means of this pathway generate release of free radicals, which cause oxidative stress, with peroxidation of lipids and membrane damage, including altered enzyme activities. Products of lipid peroxidation such as 4-hydroxynonenal stimulate collagen generation and fibrosis, which are further increased through diminished feedback inhibition of collagen synthesis because acetaldehyde forms adducts with the carboxyl-terminal propeptide of procollagen in hepatic stellate cells. Acetaldehyde is also toxic to the mitochondria, and it aggravates their oxidative stress by binding to reduced glutathione and promoting its leakage. Oxidative stress and associated cellular injury promote inflammation, which is aggravated by increased production of the proinflammatory cytokine tumor necrosis factor-alpha in the Kupffer cells. These are activated by induction of their CYP2E1 as well as by endotoxin. The endotoxin-stimulated tumor necrosis factor-alpha release is decreased by dilinoleoylphosphatidylcholine, the active phosphatidylcholine (PC) species of polyenylphosphatidylcholine (PPC). Moreover, defense mechanisms provided by peroxisome proliferator-activated receptor alpha and omega fatty acid oxidation are readily overwhelmed, particularly in female rats and also in women who have low hepatic induction of fatty acid-binding protein (L-FABPc). Accordingly, the intracellular concentration of free fatty acids may become high enough to injure membranes, thereby contributing to necrosis, inflammation, and progression to fibrosis and cirrhosis. Eventually, hepatic S-adenosylmethionine and PCs become depleted in the alcoholic, with impairment of their multiple cellular functions, which can be restored by PC replenishment. Thus, prevention and therapy opposing the development of steatosis and its progression to more severe injury can be achieved by a multifactorial approach: control of alcohol consumption, avoidance of obesity and of excess dietary long-chain fatty acids, or their replacement with medium-chain fatty acids, and replenishment of S-adenosylmethionine and PCs by using PPC. Progress in the understanding of the pathogenesis of alcoholic fatty liver and its progression to inflammation and fibrosis has resulted in prospects for their better prevention and treatment.
Collapse
|
8
|
Lieber CS. The unexpected outcomes of medical research: serendipity and the microsomal ethanol oxidizing system. J Hepatol 2004; 40:198-202. [PMID: 14739088 DOI: 10.1016/j.jhep.2003.12.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Charles S Lieber
- Section of Liver Disease and Nutrition, Alcohol Research, Bronx Veterans Affairs Medical Center (151-2) and Mt Sinai School of Medicine, 130 West Kingsbridge Road, Bronx, NY 10468-3922, USA.
| |
Collapse
|
9
|
Lieber CS. Microsomal Ethanol-Oxidizing System (MEOS): The First 30 Years (1968-1998)-A Review. Alcohol Clin Exp Res 1999. [DOI: 10.1111/j.1530-0277.1999.tb04217.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
10
|
|
11
|
Cederbaum AI, Qureshi A, Cohen G. Production of formaldehyde and acetone by hydroxyl-radical generating systems during the metabolism of tertiary butyl alcohol. Biochem Pharmacol 1983; 32:3517-24. [PMID: 6316986 DOI: 10.1016/0006-2952(83)90297-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
t-Butyl alcohol is not a substrate for alcohol dehydrogenase or for the peroxidatic activity of catalase and, therefore, it is used frequently as an example of a non-metabolizable alcohol. t-Butyl alcohol is, however, a scavenger of the hydroxyl radical. The current report demonstrates that t-butyl alcohol can be oxidized to formaldehyde plus acetone by hydroxyl radicals generated from four different systems. The systems studied were: (a) two chemical systems, namely, the iron catalyzed oxidation of ascorbic acid and the Fenton reaction between H2O2 and iron; (b) an enzymatic system, the coupled oxidation of xanthine by xanthine oxidase; and (c) a membrane-bound system, NADPH-dependent microsomal electron transfer. The oxidation of t-butyl alcohol appeared to be mediated by hydroxyl radicals, or by a species with the oxidizing power of the hydroxyl radical, because the production of formaldehyde plus acetone was (a) inhibited by competing scavengers of the hydroxyl radical; (b) stimulated by the addition of iron-EDTA; and (c) inhibited by catalase. The last observation suggests that H2O2 served as the precursor of the hydroxyl radical in all three systems. A possible mechanism is hydrogen abstraction to form the alkoxyl radical [CH3)3-C-O.), spontaneous fission of the alkoxyl radical to produce acetone and the methyl radical (CH3.), interaction of the methyl radical with O2 to form the methyl peroxy radical (CH300.), and decomposition of the later to formaldehyde. These results extend the alcohol oxidizing capacity of the microsomal alcohol oxidizing system to a tertiary alcohol. Since t-butyl alcohol is not a substrate for alcohol dehydrogenase or catalase, the ability of microsomes to oxidize t-butyl alcohol lends further support for a role for hydroxyl radicals in the microsomal alcohol oxidation system. In view of the production of formaldehyde, and the reactivity as well as further metabolism of this aldehyde, caution should be used in interpreting experiments in which t-butyl alcohol is used as a presumed "non-metabolizable" alcohol. t-Butyl alcohol may be a valuable probe for the detection of hydroxyl radicals in intact cells and in vivo.
Collapse
|
12
|
Winston GW, Cederbaum AI. NADPH-dependent production of oxy radicals by purified components of the rat liver mixed function oxidase system. II. Role in microsomal oxidation of ethanol. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)33015-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
13
|
Damgaard SE. The D(V/K) isotope effect of the cytochrome P-450-mediated oxidation of ethanol and its biological applications. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 125:593-603. [PMID: 7117257 DOI: 10.1111/j.1432-1033.1982.tb06724.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
14
|
Appel KE, Frank N, Wiessler M. Metabolism of nitrosoacetoxymethylmethylamine in liver microsomes. Biochem Pharmacol 1981; 30:2767-72. [PMID: 7317074 DOI: 10.1016/0006-2952(81)90413-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
15
|
The interaction of hepatic cytochrome P-450 with organic solvents. The effect of organic solvents on apparent spectral binding constants for hydrocarbon substrates. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68950-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
16
|
Hartz TK, Houston MR, Lockwood LB. Substrate Specificity and Kinetic Properties of NADP +—Dependent Alcohol Dehydrogenase of Phycomyces Blakesleeanus. Mycologia 1978. [DOI: 10.1080/00275514.1978.12020262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- T. K. Hartz
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky 42101
| | - M. R. Houston
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky 42101
| | - L. B. Lockwood
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky 42101
| |
Collapse
|
17
|
Miwa GT, Levin W, Thomas PE, Lu AY. The direct oxidation of ethanol by a catalase- and alcohol dehydrogenase-free reconstituted system containing cytochrome P-4501. Arch Biochem Biophys 1978; 187:464-75. [PMID: 27144 DOI: 10.1016/0003-9861(78)90058-9] [Citation(s) in RCA: 83] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
18
|
Reconstitution of the microsomal ethanol-oxidizing system. Qualitative and quantitative changes of cytochrome P-450 after chronic ethanol consumption. J Biol Chem 1977. [DOI: 10.1016/s0021-9258(19)66943-7] [Citation(s) in RCA: 225] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
19
|
Rahimtula AD, O'Brien PJ. The role of cytochrome P-450 in the hydroperoxide-catalyzed oxidation of alcohols by rat-liver microsomes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 77:201-8. [PMID: 20305 DOI: 10.1111/j.1432-1033.1977.tb11658.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The organic hydroperoxide cumene hydroperoxide is capable of oxidizing ethanol to acetaldehyde in the presence of either catalase, purified cytochrome P-450 or rat liver microsomes. Other hemoproteins like horseradish peroxidase, cytochrome c or hemoglobin were ineffective. In addition to ethanol, higher alcohols like 1-propanol, 1-butanol and 1-pentanol are also oxidized to their corresponding aldehydes to a lesser extent. Other organic hydroxyperoxides will replace cumene hydroperoxide in oxidizing ethanol but less effectively. The cumene-hydroperoxide-dependent ethanol oxidation in microsomes was inhibited partially by cytochrome P-450 inhibitors but was unaffected by catalase inhibitors. Phenobarbital pretreatment of rats increased the specific activity of the cumene-hydroperoxide-dependent ethanol oxidation per mg of microsomes about seven-fold. The evidence suggests that cytochrome P-450 rather than catalase is the enzyme responsible for hydroperoxide-dependent ethanol oxidation. However, when H2O2 is used in place of cumene hydroperoxide, the microsomal ethanol oxidation closely resembles the catalase system.
Collapse
|
20
|
Thurman RG, Brentzel HJ. The role of alcohol dehydrogenase in microsomal ethanol oxidation and the adaptive increase in ethanol metabolism due to chronic treatment with ethanol. Alcohol Clin Exp Res 1977; 1:33-8. [PMID: 201176 DOI: 10.1111/j.1530-0277.1977.tb05763.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
21
|
Teschke R, Matsuzaki S, Ohnishi K, DeCarli LM, Lieber CS. Microsomal ethanol oxidizing system (MEOS): current status of its characterization and its role. Alcohol Clin Exp Res 1977; 1:7-15. [PMID: 412430 DOI: 10.1111/j.1530-0277.1977.tb05759.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
|
22
|
Khanna JM, Kalant H. In vivo significance of the microsomal ethanol oxidizing system (MEOS). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1977; 85A:281-302. [PMID: 200118 DOI: 10.1007/978-1-4899-5181-6_19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
23
|
Teschke R, Matsuzaki S, Ohnishi K, Hasumura Y, Lieber CS. Metabolism of alcohol at high concentrations: role and biochemical nature of the hepatic microsomal ethanol oxidizing system. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1977; 85A:257-80. [PMID: 562604 DOI: 10.1007/978-1-4899-5181-6_18] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
At intermediate and higher alcohol concentrations, ethanol metabolism proceeds via alcohol dehydrogenase (ADH) and the microsomal ethanol oxidizing system (MEOS), whereas catalase plays no significant role. Following prolonged ethanol consumption, an enhancement of both MEOS activity as well as the rates of ethanol metabolism occurs; the latter persisted despite inhibition of ADH by pyrazole and catalase by sodium axide, suggesting the involvement of MEOS in the adaptive increase. MEOS exhibits characteristics similar to those of other microsomal drug metabolizing enzymes and can be differentiated and isolated from both ADH and catalase activities. Reconstitution of MEOS activity was achieved with partially purified cytochrome P-450 and NADPH-cytochrome c reductase in the presence of synthetic phospholipid.
Collapse
|
24
|
Vatsis KP, Schulman MP. Pathways of ethanol oxidation in hepatic microsomes of acatalasemic (Csb) mice. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1977; 85A:303-17. [PMID: 21533 DOI: 10.1007/978-1-4899-5181-6_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
25
|
|
26
|
Jonen HG, Kahl R, Kahl GF. Enhancement of microsomal aniline and acetanilide hydroxylation by haemoglobin. Xenobiotica 1976; 6:307-20. [PMID: 820088 DOI: 10.3109/00498257609151642] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
1. Haemogloblin and myoglobin enhance rat liver microsomal p-hydroxylation of aniline and acetanilide. Microsomal N-demethylation of ethylmorphine and aminopyrine is not increased by haemoproteins. 2. The enhancement of microsomal p-hydroxylation is maximal at high substrate concentration and high haeme compound concentration. 3. Detergent-purified NADPH-cytochrome c reductase, free flavins and manganese ions considerably increase the haemoglobin-mediated, tissue-free hydroxylation of aniline. Microsomal aniline hydroxylation is not enhanced by haeme, ferric ion or albumin. 4 Catalase and cyanide ions are powerful inhibitors of haemoglobin-mediated aniline hydroxylation both in the presence and absence of tissue. Carbon monoxide inhibits the hydroxylase activity of the tissue-free system to a smaller extent than that of a system containing microsomes plus haemoglobin whereas p-chloromercuribenzoate inhibits only the flavoprotein-dependent hydroxylation of aniline mediated by haemoglobin. 5. Several possibilities of interactions between substrate, microsomes and haeme compounds are proposed.
Collapse
|
27
|
|
28
|
Rawat AK. Neurochemical consequences of ethanol on the nervous system. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1976; 19:123-72. [PMID: 13042 DOI: 10.1016/s0074-7742(08)60703-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
29
|
Ioannides C, Lake BG, Parke DV. Enhancement of hepatic microsomal drug metabolism in vitro following ethanol administration. Xenobiotica 1975; 5:665-76. [PMID: 1189461 DOI: 10.3109/00498257509056136] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
1. Administration of ethanol intraperitoneally at low dosages (10-25 mg/kg) to rats stimulates hepatic microsomal mixed-function oxidase activity in vitro. 2. Pretreatment with ethanol administered orally has no effect on in vivo drug metabolism as measured by pentobarbitone plasma half-life and has no effect on the excretion of ascorbic acid. Ethanol administration does not enhance its own binding to cytochrome P-450. 3. These observations suggest that the administration of ethanol, at moderate dosage, does not give rise to induction of hepatic cytochrome P-450. 4. Unwashed hepatic microsomes are contaminated with alcohol dehydrogenase, but pretreatment with ethanol does not increase microsomal generation of NADH. 5. Pretreatment with ethanol has no stimulatory effect on NADH-NADP+ transhydrogenation. 6. The stimulation of hepatic drug metabolism in vitro following administration of ethanol is not due to increased cytochrome P-450 nor to increased NADPH, per se, but appears to result from an increase in the activity of NADPH-cytochrome c reductase.
Collapse
|
30
|
Mezey E, Potter JJ, Brandes D. Effects of a choline-deficient diet on the induction of drug- and ethanol-metabolizing enzymes and on the alteration of rates of ethanol degradation by ethanol and phenobarbital. Biochem Pharmacol 1975; 24:1975-81. [PMID: 1212248 DOI: 10.1016/0006-2952(75)90385-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
31
|
Corrall RJ, Yu LC, Rosner BA, Margolis JM, Rodman HM, Kam W, Landau BR. Stereospecificity of the microsomal ethanol-oxidizing system. Biochem Pharmacol 1975; 24:1825-7. [PMID: 9946 DOI: 10.1016/0006-2952(75)90467-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
32
|
|
33
|
Roach MK. Microsomal ethanol oxidation: activity in vitro and in vivo. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1975; 56:33-55. [PMID: 238369 DOI: 10.1007/978-1-4684-7529-6_2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Studies by several investigators have confirmed that the microsomal fraction of mammalian liver oxidizes ethanol to acetaldehyde in a reaction that requires NADPH and oxygen. Efforts to identify the enzymes involved have produced conflicting opinions of the reaction mechanism, however. Initially, the microsomal mixed function oxidase system was assumed to be capable of oxidizing ethanol in a mechanism that did not involve either alcohol dehydrogenase or catalase. Later evidence suggested that the oxidative enzyme was, in fact, catalase, a contaminant of microsomal preparations and that the mixed function oxidase system merely furnished hydrogen peroxide to the reaction. Much current research supports the latter interpretation. Other workers provide evidence that favors a system in which catalase does not participate. Attempts to define the reaction process have involved studies with catalase inhibitors, kinetic studies of the different reaction systems, and physical separation of catalase from the microsomal components. Questions of the mechanism of microsomal ethanol oxidation may prove to be purely academic, however. Efforts to prove that the system has significant in vivo activity generally have not been successful.
Collapse
|
34
|
Thurman RG, McKenna WR. Pathways of ethanol metabolism in perfused rat liver. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1975; 56:57-76. [PMID: 1096557 DOI: 10.1007/978-1-4684-7529-6_3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The primary pathway of hepatic ethanol metabolism involves alcohol dehydrogenase. Hydrogen generated from ethanol metabolism enters the mitochondrial space most likely as malate over a substrate shuttle mechanism, and is subsequently oxidized by the mitochondrial respiratory chain. The rate-limiting step in this overall multicompartmental process is the rate of reduced cofactor (NADH) reoxidation by the respiratory chain. Since the electron flux in the respiratory chain is controlled by the ADP supply, alcohol dehydrogenase-dependent ethanol metabolism can be activated by perturbations which circumvent the rate-limiting step, such as artificial electron acceptors, gluconeogenic precursors, and uncoupling agents. Moreover, an ATP utilizing process is responsible for the stimulation of ethanol metabilism observed following chronic pretreatment with ethanol. In perfused rat liver catalase also participates in ethanol metabolism to a lesser extent than alcohol dehydrogenase. Quantitative assessments indicate that the predominant ethanol oxidase at low ethanol concentrations (less than 20 mM) is a alcohol dehydrogenase; however, at higher ethanol concentrations, a significant portion of total ethanol metabolism (up to 50%) is mediated by catalase-hydrogen peroxide complex. This pathway is limited by the rate of generation of hydrogen peroxide in the hepatocyte, and can be stimulated with substrates for intraperoxisomal hydrogen peroxide generation such as glycolate, urate and D-amino acids. Considerable evidence implicates catalase-hydrogen peroxide complex in the mechanism of NADPH-dependent microsomal ethanol oxidation.
Collapse
|
35
|
Teschke R, Hasumura Y, Lieber CS. Hepatic microsomal ethanol-oxidizing system: solubilization, isolation, and characterization. Arch Biochem Biophys 1974; 163:404-15. [PMID: 4152897 DOI: 10.1016/0003-9861(74)90492-5] [Citation(s) in RCA: 112] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
|
36
|
Mezey E. Alcohol Metabolism during Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1974. [DOI: 10.1007/978-1-4684-3249-7_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
37
|
Grunnet N, Quistorff B, Thieden HI. Rate-limiting factors in ethanol oxidation by isolated rat-liver parenchymal cells. Effect of ethanol concentration, fructose, pyruvate and pyrazole. EUROPEAN JOURNAL OF BIOCHEMISTRY 1973; 40:275-82. [PMID: 4359143 DOI: 10.1111/j.1432-1033.1973.tb03195.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
38
|
|
39
|
Vatsis KP, Schulman MP. Absence of ethanol metabolism in "acatalatic" hepatic microsomes that oxidize drugs. Biochem Biophys Res Commun 1973; 52:588-94. [PMID: 4711173 DOI: 10.1016/0006-291x(73)90753-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
|
40
|
Fellenius E, Nisbeth U, Pilström L, Kiessling KH. Changes in the activity of citrate lyase, malic enzyme and acetyl-CoA synthetase in rat liver after short-term and long-term feeding with ethanol. Br J Nutr 1973; 29:307-16. [PMID: 4693563 DOI: 10.1079/bjn19730105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
1. The effect of short-term and long-term feeding (0–80 d) with a liquid diet containing ethanol on the activity of rat hepatic enzymes related to lipogenesis has been evaluated. Carbohydrates were isoenergetically substituted for ethanol in the control animals.2. The maximum concentration of triglycerides in the livers was reached after about 30 d, when it was almost three times as high as in the control animals. The activity of malic enzyme (EC1·1·1·40) and ATP citrate lyase (EC4·1·3·8) decreased significantly in the ethanol group, compared with the control rats, within 10 d and remained low during the rest of the experiment (80 d). After 20 d, the acetyl-CoA synthetase (EC6·2·1·1) activity increased significantly in the livers of the ethanol-fed rats but fell subsequently to values similar to those in the livers of the control rats. Thus, despite a pronounced increase in the amount of triglyceride in the livers of rats on a liquid diet containing ethanol, there was a dramatic decrease in the activity of the enzymes (malic enzyme and citrate lyase) involved in lipogenesis.3. The almost unchanged activity of acetyl-CoA synthetase shows that the utilization of acetate, produced when ethanol is oxidized, is not stimulated by long-term feeding with ethanol. The involvement of citrate lyase in various postulated shuttles for the transport of reducing equivalents across the mitochondrial membrane and the role of malic enzyme in the microsomal ethanol-oxidizing system are discussed.
Collapse
|
41
|
Oshino N, Oshino R, Chance B. The characteristics of the "peroxidatic" reaction of catalase in ethanol oxidation. Biochem J 1973; 131:555-63. [PMID: 4720713 PMCID: PMC1177502 DOI: 10.1042/bj1310555] [Citation(s) in RCA: 170] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Ethanol oxidation by rat liver catalase (the ;peroxidatic' reaction) was studied quantitatively with respect to the rate of H(2)O(2) generation, catalase haem concentration, ethanol concentration and the steady-state concentration of the catalase-H(2)O(2) intermediate (Compound I). At a low ratio of H(2)O(2)-generation rate to catalase haem concentration, the rate of ethanol oxidation was independent of the catalase haem concentration. The magnitude of the inhibition of ethanol oxidation by cyanide was not paralleled by the formation of the catalase-cyanide complex and was altered greatly by varying either the ethanol concentration or the ratio of the rate of H(2)O(2) generation to catalase haem concentration. The ethanol concentration producing a half-maximal activity was also dependent on the ratio of the H(2)O(2)-generation rate to catalase haem concentration. These phenomena are explained by changes in the proportion of the ;catalatic' and ;peroxidatic' reactions in the overall H(2)O(2)-decomposition reaction. There was a correlation between the proportion of the ;peroxidatic' reaction in the overall catalase reaction and the steady-state concentration of the catalase-H(2)O(2) intermediate. Regardless of the concentration of ethanol and the rate of H(2)O(2) generation, a half-saturation of the steady state of the catalase-H(2)O(2) intermediate indicated that about 45% of the H(2)O(2) was being utilized by the ethanol-oxidation reaction. The results reported show that the experimental results in the study on the ;microsomal ethanol-oxidation system' may be reinterpreted and the catalase ;peroxidatic' reaction provides a quantitative explanation for the activity hitherto attributed to the ;microsomal ethanol-oxidation system'.
Collapse
|
42
|
|
43
|
|
44
|
Feytmans E, Leighton F. Effects of pyrazole and 3-amino-1,2,4-triazole on methanol and ethanol metabolism by the rat. Biochem Pharmacol 1973; 22:349-60. [PMID: 4687132 DOI: 10.1016/0006-2952(73)90416-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
45
|
|
46
|
Ishii H, Lieber J, Lieber CS. Effect of ethanol on the amount and enzyme activities of hepatic rough and smooth microsomal membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1973; 291:411-20. [PMID: 4690860 DOI: 10.1016/0005-2736(73)90493-8] [Citation(s) in RCA: 127] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
47
|
Pieper WA, Skeen MJ. Changes in blood methanol concentrations in chimpanzees during periods of chronic ethanol ingestion. Biochem Pharmacol 1973; 22:163-73. [PMID: 4202808 DOI: 10.1016/0006-2952(73)90270-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
|
48
|
Lieber CS. Possible Role of Microsomal Changes Induced by Ethanol Intake in the Development of Tolerance and Dependence. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1973. [DOI: 10.1007/978-1-4684-3234-3_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
|
49
|
Biochemical Changes in Mitochondria as a Mechanism in Metabolic Tolerance to Ethanol. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1973. [DOI: 10.1007/978-1-4684-3234-3_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
|
50
|
Teschke R, Hasumura Y, Joly JG, Lieber CS. Microsomal ethanol-oxidizing system (MEOS): purification and properties of a rat liver system free of catalase and alcohol dehydrogenase. Biochem Biophys Res Commun 1972; 49:1187-93. [PMID: 4405124 DOI: 10.1016/0006-291x(72)90594-3] [Citation(s) in RCA: 101] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|