Showing papers on "Aldehyde dehydrogenase published in 1992"

Aldehyde Dehydrogenases and Their Role in Carcinogenesis

Abstract: Aldehydes are highly reactive molecules that may have a variety of effects on biological systems. They can be generated from a virtually limitless number of endogenous and exogenous sources. Although some aldehyde-mediated effects such as vision are beneficial, many effects are deleterious, including cytotoxicity, mutagenicity, and carcinogenicity. A variety of enzymes have evolved to metabolize aldehydes to less reactive forms. Among the most effective pathways for aldehyde metabolism is their oxidation to carboxylic acids by aldehyde dehydrogenases (ALDHs). ALDHs are a family of NADP-dependent enzymes with common structural and functional features that catalyze the oxidation of a broad spectrum of aliphatic and aromatic aldehydes. Based on primary sequence analysis, three major classes of mammalian ALDHs--1, 2, and 3--have been identified. Classes 1 and 3 contain both constitutively expressed and inducible cytosolic forms. Class 2 consists of constitutive mitochondrial enzymes. Each class appears to oxidize a variety of substrates that may be derived either from endogenous sources such as amino acid, biogenic amine, or lipid metabolism or from exogenous sources, including aldehydes derived from xenobiotic metabolism. Changes in ALDH activity have been observed during experimental liver and urinary bladder carcinogenesis and in a number of human tumors, including some liver, colon, and mammary cancers. Changes in ALDH define at least one population of preneoplastic cells having a high probability of progressing to overt neoplasms. The most common change is the appearance of class 3 ALDH dehydrogenase activity in tumors arising in tissues that normally do not express this form. The changes in enzyme activity occur early in tumorigenesis and are the result of permanent changes in ALDH gene expression. This review discusses several aspects of ALDH expression during carcinogenesis. A brief introduction examines the variety of sources of aldehydes. This is followed by a discussion of the mammalian ALDHs. Because the ALDHs are a relatively understudied family of enzymes, this section presents what is currently known about the general structural and functional properties of the enzymes and the interrelationships of the various forms. The remainder of the review discusses various aspects of the ALDHs in relation to tumorigenesis. The expression of ALDH during experimental carcinogenesis and what is known about the molecular mechanisms underlying those changes are discussed. This is followed by an extended discussion of the potential roles for ALDH in tumorigenesis. The role of ALDH in the metabolism of cyclophosphamidelike chemotherapeutic agents is described. This work suggests that modulation of ALDH activity may an important determinant of the effectiveness of certain chemotherapeutic agents.(ABSTRACT TRUNCATED AT 400 WORDS)

A review of the pharmacokinetics and pharmacodynamics of disulfiram and its metabolites.

Abstract: After ingestion, disulfiram (DSF) is rapidly converted, probably in the stomach, to its bis (diethyldithiocarbamato) copper complex. Consequently, absorption and distribution via the gastrointestinal mucosa into the blood might involve both the parent drug and its copper complex. In the blood, both compounds are rapidly degraded to form diethyldithiocarbamic acid (DDC), which is unstable and is further degraded to form diethylamine and carbon disulphide. DDC is also a substrate of phase II metabolism, which involves formation of diethyldithiomethylcarbamate (Me-DDC) and the glucuronic acid of DDC. Me-DDC also undergoes oxidative biotransformation to diethylthiomethylcarbamate (Me-DTC), which is further oxidized to its corresponding sulphoxide and sulphone metabolites. Me-DTC may to act as a suicide inhibitor with a preference for the mitochondrial low Km isozyme of aldehyde dehydrogenases (ALDH 1), whereas the two S-oxidized metabolites, especially the sulfone metabolite, are more potent inhibitors not only of ALDH 1, but also of the cytosolic high Km isozyme of ALDH (ALDH 2). The inhibitory reaction between the enzyme and each of the three metabolites is characterized by a covalent adduct formation, probably with the cysteine residue at the active site of the enzymes. The adduct formed is nonreducible at a physiological concentration of glutathione, and inactivation in the presence of this endogenous tripeptide was increased by action in vitro of the sulphoxide and sulphone metabolites. Those findings are all in concordance with the in vivo observations made on DSF. In human volunteers treated with increasing doses of DSF and challenged with ethanol between each of the dosage periods, the mean plasma concentrations of Me-DTC at steady state were proportional to the DSF doses given. There was also a close relationship between increased oxidative metabolic formation of Me-DTC, high oxidative formation of acetaldehyde, and the full complements of a valid disulfiram ethanol reaction (DER). Consequently, Me-DTC in plasma may not only serve as a marker of the oxidative metabolic function of the liver, but also of the therapeutic effectiveness of the treatment in subjects at steady state. Obviously, there is a need for individual dose-titration regimens. In patients with alcohol-related severe hepatocellular damage, the oxidative P 450 catalyzed formation of the Me-DTC and probably also of its sulfoxide and sulphone metabolites is impaired, and thus inactivation of ALDH activity in the liver appears to be delayed or even completely absent. The consequence for the patient may be an insufficient DER.(ABSTRACT TRUNCATED AT 400 WORDS)

Retinal oxidation activity and biological role of human cytosolic aldehyde dehydrogenase.

Abstract: The major cytosolic aldehyde dehydrogenase isozyme (ALDH1) exhibits strong activity for oxidation of retinal to retinoic acid, while the major mitochondrial ALDH2 and the stomach cytosolic ALDH3 have no such activity. The Km of ALDH1 for retinal is about 0.06 mumol/l at pH 7.5, and the catalytic efficiency (Vmax/Km) for retinal is about 600 times higher than that for acetaldehyde. Thus, ALDH1 can efficiently produce retinoic acid from retinal in tissues with low retinal concentrations (< 0.01 mumol/l). The gene for ALDH1 has hormone response elements. These findings suggest that the major physiological substrate of human ALDH1 is retinal, and that its primary biological role is generation of retinoic acid resulting in modulation of cell differentiation including hormone-mediated development.

The pharmacology and toxicology of disulfiram and its metabolites.

Abstract: Disulfiram (Antabuse) is one of several aldehyde dehydrogenase (ALDH) inhibitors that raise the plasma level of acetaldehyde following ethanol ingestion. The usually pleasant reaction to ethanol is thereby changed to an unpleasant one, owing to a number of bodily reactions to acetaldehyde. Populations showing genetic polymorphism with a lack of some isozymes of ALDH have exhibited an intolerance to ethanol similar to that seen with disulfiram. A normal isozyme pattern seems to be a prerequisite for the development of alcoholism, which supports the principle of disulfiram treatment. Disulfiram is an irreversible ALDH inhibitor when administered in vivo. Diethylthiomethylcarbamate (Me-DTC) is formed from disulfiram in three metabolic steps. This compound and two further oxidized metabolites appear to be active metabolites of disulfiram. Measurements of plasma Me-DTC or the reduction of leucocyte ALDH 1 activity may be valuable markers for the proper dose titration of disulfiram and the rational use of this drug. Some toxicological points are discussed.

Molecular genetics of human aldehyde dehydrogenase

Abstract: Four non-allelic genes, which encode four different aldehyde dehydrogenase (ALDH) isozymes, have been cloned and characterized at the present time. The coding nucleotide sequences, and organization of introns and exons of these genes have been elucidated. The ALDH1 gene encodes the major cytosolic A

Taxon-specific recruitment of enzymes as major soluble proteins in the corneal epithelium of three mammals, chicken, and squid.

Abstract: Studies of others have shown that class 3 aldehyde dehydrogenase is a major component of the epithelial cells of the mammalian cornea. Here we demonstrate by peptide sequencing that other major proteins of the corneal epithelium are also identical or related to enzymes in the human, mouse, kangaroo, chicken, and squid. Aldehyde dehydrogenase class 3 was found to be the major protein of human, mouse, and kangaroo corneal epithelial cells. Peptidyl prolyl cis-trans isomerase (cyclophilin) or a homologue thereof is strikingly abundant in the corneal epithelial cells of chicken, but not mammals, and appears to be absent from the cornea of squid. By contrast, enolase or its homologue is relatively abundant in both the mammalian and chicken corneal epithelial cells. In some instances, abundant enzymes are common to cornea and lens in the same species--for example, arginino-succinate lyase/delta 1-crystallin in the chicken and glutathione S-transferase-like protein in the squid; in other cases, the abundant proteins in the cornea have not been found as lens crystallins in any species--for example, aldehyde dehydrogenase class 3 and cyclophilin. These data suggest that enzymes and certain enzyme-crystallins have been recruited as major corneal proteins in a taxon-specific manner and may serve structural rather than, or as well as, enzymatic roles in corneal epithelial cells.

Prodrugs of nitroxyl as inhibitors of aldehyde dehydrogenase.

Abstract: In the preceding paper, analogs of chlorpropamide with an OMe substituent on the sulfonamide nitrogen were shown to inhibit aldehyde dehydrogenase (AlDH), and it was postulated that these compounds were bioactivated by O-demethylation to release nitroxyl (HN = O, nitrosyl hydride), which is an inhibitor of AlDH. Further evidence for the production of nitroxyl from compounds with O-acyl instead of OMe on the sulfonamide nitrogen is now presented. Thus, nitrous oxide (N2O), the end product of nitroxyl dimerization and disproportionation, was found to be generated on alkaline or enzymatic hydrolysis of N,O-diacylated N-hydroxyarylsulfonamides. Since the latter compounds strongly inhibit yeast AlDH in vitro after bioactivation by an esterase intrinsic to this enzyme, nitroxyl generated from these compounds must be the common intermediate that inhibits AlDH.

Regional distribution of low-Km mitochondrial aldehyde dehydrogenase in the rat central nervous system.

Abstract: To clarify the regional capacity of the brain to oxidize biogenic aldehydes and ethanol-derived acetaldehyde, a quantitative immunohistochemical study of the microregional and cellular expression of low Km mitochondrial aldehyde dehydrogenase (mALDH; EC 1.2.1.3) in the rat central nervous system was undertaken, using antiserum raised in rabbit against low-Km aldehyde dehydrogenase purified from rat liver mitochondria. mALDH-specific immunoreactivity (IR) was observed to various extent in the majority of structures in all brain and spinal cord areas. Staining was strong in the extranuclear cytoplasm of neuronal and glial cell bodies but less pronounced in their processes and terminals, the conducting tracts, white matter and neuropile and in blood vessels. Immunostaining density was 2 to 3 times higher in neuronal perikarya as compared with neuropile. mALDH-positive neurons were found in all brain regions, being strongest in the inferior olive and hippocampus stratum pyramidale and weakest in substantia nigra. The percentage of morphologically identifiable ALDH-positive neurons ranged from 40% in the arcuate hypothalamic nucleus to 88% in the cerebellar Purkinje cells. A comparison of the heterogeneous expression of mALDH in various rat CNS regions and cells, as observed in the present study, with the corresponding previously published distributions of the potential acetaldehyde-producing enzymes ADH and cytochrome P450 2E1 indicates major differences, which may help in understanding potential acetaldehyde-mediated CNS effects of ethanol. Knowledge of the regional distribution of high-affinity aldehyde dehydrogenase should also throw light on the neurophysiological role of local regulation of the metabolism of biogenic aldehydes in the brain.

Role of aldehyde dehydrogenase in the protection of hematopoietic progenitor cells from 4-hydroperoxycyclophosphamide by interleukin 1 beta and tumor necrosis factor.

Abstract: Preincubation of human bone marrow cells with interleukin 1β (IL-1) and tumor necrosis factor α (TNF-α) for 20 h can protect early progenitor cells from 4-hydroperoxycyclophosphamide (4-HC) toxicity. In this report, we have studied the mechanism for such protection. We examined the effect of the length of incubation time and found that preincubation for at least 20 h with IL-1 and TNF-α is needed for significant protection. The addition of 2 µg/ml cycloheximide, a protein synthesis inhibitor, during the 20-h preincubation completely abolished the protection observed for all colony-forming cells. In order to study the role of aldehyde dehydrogenase (ALDH), an enzyme which inactivates 4-HC, we used diethylaminobenzaldehyde, an inhibitor of ALDH. Diethylaminobenzaldehyde was added during the last 10 min of the 20-h preincubation with IL-1 and TNF-α. Diethylaminobenzaldehyde prevented the protection of colony-forming cells from 4-HC. Finally, using the same protection assay system, we showed that a 20-h preincubation with IL-1 and TNF-α can also protect early progenitor cells from phenylketophosphamide, an analogue of 4-HC which is resistant to inactivation by ALDH. From these studies, we conclude that preincubation with IL-1 and TNF-α for at least 20 h is required for the protection of early progenitor cells from 4-HC. During that time period, protein synthesis, specifically aldehyde dehydrogenase synthesis, is critical for the protection from 4-HC. Preincubation with IL-1 and TNF-α also protects early progenitors from phenylketophosphamide. Because phenylketophosphamide cannot be metabolized by ALDH, the reason for this protection must be due to other, as yet unidentified, mechanisms.

Genetic polymorphism and activities of human lung alcohol and aldehyde dehydrogenases: implications for ethanol metabolism and cytotoxicity.

Abstract: Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) exhibit genetic polymorphism and tissue specificity. ADH and ALDH isozyme phenotypes from 39 surgical Chinese lung specimens were identified by agarose isoelectric focusing. The identity of the lung β-ADHs was further demonstrated by their characteristic pH-activity profiles for ethanol oxidation,Km values for NAD and ethanol, and inhibition by 4-methylpyrazole or 1,10-phenanthroline. The β2 allele, coding for β2 polypeptide, was found to be predominant in the lung specimens studied. The ADH activities in the lungs with the homozygous phenotype ADH2 2-2 (exhibiting β2β2) and ADH2 1-1 (exhibiting β1β1) and the heterozygous phenotype ADH2 2-1 (exhibiting β2β2, β2β1, and β1β1) were determined to be 999±77, 48±17, and 494±61 nmol/min/g tissue, respectively. Fifty-one percent of the specimens studied lacked the ALDH2 activity band on the isoelectric focusing gels. The activities in the lung tissues with the ALDH2-active phenotype and the inactive phenotype were determined to be 30±3 and 17±1 nmol/min/g tissue, respectively. These findings indicate that human pulmonary ethanol-metabolizing activities differ significantly with respect to genetic polymorphism at both theADH2 and theALDH2 loci. The results suggest that individuals with highVmax β2-ADH and deficient in low-Km mitochondrial ALDH2, accounting for approximately 45% of the Chinese population, may end up with acetaldehyde accumulation during alcohol consumption, rendering them vulnerable to tissue injury caused by this highly reactive and toxic metabolite.

Glutathione and antioxidants protect microsomes against lipid peroxidation and enzyme inactivation.

Abstract: The study investigated the relationship between lipid peroxidation and enzyme inactivation in rat hepatic microsomes and whether prior inactivation of aldehyde dehydrogenase (ALDH) exacerbated inactivation of other enzymes. In microsomes incubated with 2.5 μM iron as ferric sulfate and 50 μM ascorbate, ALDH, glucose-6-phosphate (G6Pase) and cytochrome P450 (Cyt-P450) levels decreased rapidly and concurrently with increased levels of thiobarbituric acid-reactive substances. Microsomal glutathioneS-transferase and nicotinamide adenine dinucleotide phosphate-cytochromec reductase were little affected during 1 hr of incubation. Addition of reduced glutathione partially protected, andN,N′-diphenyl-p-phenylenediamine and butylated hydroxytoluene completely protected microsomes against inactivation of ALDH, G6Pase and Cyt-P450, as well as lipid peroxidation induced by iron and ascorbate. ALDH was more susceptible than G6Pase to inactivation by iron and ascorbate, and was thus an excellent marker for oxidative stress. Inhibition of ALDH by cyanamide injection of rats exacerbated the inactivation of G6Pase in microsomes incubated with 0.1 mM, but not 25 μM 4-hydroxynonenal (4-HN). 4-HN did not stimulate lipid peroxidation. Thus, 4-HN may play a minor role in microsomal enzyme inactivation. In contrast, lipid, peroxyl radicals play an important role in microsomal enzyme inactivation, as evidenced by the prevention of both lipid peroxidation and enzyme inactivation by chain-breaking antioxidants.

Regional distribution of mammalian corneal aldehyde dehydrogenase and alcohol dehydrogenase

Abstract: The regional distribution of mouse aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase activities in mouse ocular tissues was examined using spectrophotometric and agarose-isoelectric focusing techniques. The results established that these enzymes are predominantly localized in the cornea. Bioch

Long-chain alcohol and aldehyde dehydrogenase activities in Acinetobacter calcoaceticus strain HO1-N.

Abstract: Three alcohol dehydrogenases have been identified in Acinetobacter calcoaceticus sp. strain HO1-N: an NAD+-dependent enzyme and two NADP+-dependent enzymes. One of the NADP+-dependent alcohol dehydrogenases was partially purified and was specific for long-chain substrates. With tetradecanol as substrate an apparent K m value of 5.2 μM was calculated. This enzyme has a pI of 4.5 and a molecular mass of 144 kDa. All three alcohol dehydrogenases were constitutively expressed. Three aldehyde dehydrogenases were also identified: an NAD+-dependent enzyme, an NADP+-dependent enzyme and one which was nucleotide independent. The NAD+-dependent enzyme represented only 2% of the total activity and was not studied further. The NADP+-dependent enzyme was strongly induced by growth of cells on alkanes and was associated with hydrocarbon vesicles. With tetradecanal as substrate an apparent K m value of 0.2 μM was calculated. The nucleotide-independent aldehyde dehydrogenase could use either Wurster's Blue or phenazine methosulphate (PMS) as an artificial electron acceptor. This enzyme represents approximately 80% of the total long-chain aldehyde oxidizing activity within the cell when the enzymes were induced by growing the cells on hexadecane. It is particulate but can be solubilized using Triton X-100. The enzyme has an apparent K m of 0.36 mM for decanal.

N1-hydroxylated derivatives of chlorpropamide and its analogs as inhibitors of aldehyde dehydrogenase in vivo.

Abstract: Certain (arylsulfonyl)urea hypoglycemic drugs exemplified by chlorpropamide (CP) are known to interact pharmacologically with alcohol (ethanol) to elicit a chlorpropamide-alcohol flushing (CPAF) reaction that is reminiscent of the disulfiram-ethanol reaction (DER) In the present structure-activity study, designed to elucidate the mechanism of inhibition of aldehyde dehydrogenase (AlDH) by CP, we discovered that the N1-methoxy derivative of CP 2a was a potent inhibitor of AlDH in vivo similar in activity to that of the N1-ethyl derivative 2b Both 2a and 2b can release n-propyl isocyanate, a known inhibitor of AlDH, nonenzymatically However, (arylsulfonyl)carbamates that are structurally analogous to 2a were also active inhibitors of AlDH, whereas the corresponding (arylsulfonyl)carbamate analogs of 2b were uniformly without activity We propose a mechanism of bioactivation of 2a and its analogs that involves initial O-demethylation followed by disproportionation and solvolysis of the intermediate formed to release nitroxyl, the putative inhibitor of AlDH

Development of Aldehyde Dehydrogenase and Alcohol Dehydrogenase in Mouse Eye: Evidence for Light-Induced Changes

Abstract: We have studied the development of ocular aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) activities in C57BL/6J inbred male mice. Eyes were removed from freshly killed mice, enucleated, extracted, and analyzed for enzyme activities for animals of various ages during neonatal development, up to the adult stage. Activity levels were compared between mice maintained from birth in either complete darkness or on a 12-hour light/dark cycle. Ocular ALDH activity increased dramatically ( > 30-fold) during the first 3 weeks of life. Moreover, light-adapted animals showed significantly higher ALDH activities from day 8. Ocular ADH activity also increased during development (> 5-fold) although the profile showed a steady increase to reach adult levels. Light-adapted mice showed no significant differences in ADH activity up to the weaning stage, as compared with mice maintained in darkness. These observations support proposals from earlier studies for major functional roles for both corneal ALDH and ADH in protecting the eye against ultraviolet light-induced damage.

Distribution of Alcohol Dehydrogenase and the Low Km Form of Aldehyde Dehydrogenase in Isolated Perivenous and Periportal Hepatocytes in Rats

Abstract: UNLABELLED Hepatic damage induced by chronic alcohol abuse starts in the perivenous (PV) zone of the hepatic lobule To explain this vulnerability in the PV zone, periportal (PP) and PV hepatocytes were isolated by digitonin-collagenase perfusion and the distributions of class I alcohol dehydrogenase (ADH) and the low-Km mitochondrial aldehyde dehydrogenase (ALDH) were studied ADH was measured by three approaches ie, specific activity, immunoreactive enzyme content and ADH mRNA level ALDH was determined by specific activity and immunoreactive enzyme content When compared with PV hepatocytes, isolated PP cells exhibited higher lactate dehydrogenase (PP/PV = 13-15), higher alanine aminotransferase (PP/PV = 17-19), but lower glutamine synthase (PP/PV less than 001) By prelabeling the PP zone with acridine orange before digitonin-collagenase digestion, flow cytometry indicated that mainly the isolated PP hepatocytes exhibited fluorescence ADH activities and ADH mRNA levels did not differ in PP and PV cells With a polyclonal antibody directed specifically against class I ADH, ADH immunoreactive protein also did not differ in PP vs PV cells By activity assay, the low Km ALDH activities were found to be lower in the PV hepatocytes (PP/PV = 13) This was confirmed by immunotransblot with anti-ALDH IgG (PP/PV = 16) IN CONCLUSION the preferential damage of the PV zone produced by ethanol is not caused by differences of ADH distribution in liver but could be related partly to a decrease in the low-Km ALDH in the PV zone