Assay of human blood aldehyde dehydrogenase activity by high-performance liquid chromatography

Non-enzymatic conversion of primary oxidation products of Docosahexaenoic acid into less toxic acid molecules

Docosahexaenoic acid (DHA) is long chain omega-3 fatty acid with known health benefits and clinical significance. However, 4-hydroxy hexenal (HHE), an enzymatic oxidation product of DHA has recently been reported to have health-damaging effects. This conflict raises major concern on the long-term clinical use of these fatty acids. Even though the enzymatic and non-enzymatic conversion of HHE to nontoxic acid molecules is possible by the aldehyde detoxification systems, it has not yet studied. To address this, primary oxidation products of DHA in lipoxidase system were subjected to non-enzymatic conversion at physiological temperature over a period of 1 week. The reaction was monitored using HPLC, IR spectroscopy and biochemical assays (based on the loss of conjugated dienes, lipid peroxides aldehydes). Short term and long term cytotoxicity of the compounds generated at various time points were analyzed. IR and HPLC spectra revealed that the level of aldehydes in the primary oxidation products reduced over time, generating acids and acid derivatives within a week period. In short term and long term cytotoxicity analysis, initial decomposition products were found more toxic than the 1-week decomposition products. Further, when primary oxidation products were subjected to aldehyde dehydrogenase mediated oxidation, it generated products that are also less toxic. The study suggests the possible non-enzymatic conversion of primary oxidation products of DHA to less cytotoxic acid molecules. Exploration of the physiological roles of these acid molecules may explain the biological potential of omega-3 fatty acids.

Determination of biological markers for alcohol abuse

Alcoholism is one of the most frequent addictions and an important subject in forensic medicine and clinical toxicology. Several laboratory abnormalities are associated with excessive alcohol consumption. They are useful in the diagnosis of alcoholism especially during the follow-up of various treatment programs. The biological markers mostly used for diagnosis of alcoholism are presented. Especially, methods for the determination of the following diagnostic tools are reviewed: congener alcohols, gamma-glutamyltransferase, aspartate and alanine aminotransferase, beta-hexosaminidase, erythrocyte aldehyde dehydrogenase, alpha-amino-n-butyric acid to leucine ratio, macrocytosis, carbohydrate-deficient transferrin, (apo)lipoproteins, fatty acid ethyl esters, blood acetate, acetaldehyde adducts, 5-hydroxytryptophol, dolichol and condensation products. No laboratory test exists that is reliable enough for the exact diagnosis of alcoholism. The combination of physician interview, questionnaire and laboratory markers is necessary for the diagnosis of alcoholism.

Comparison of blood aldehyde dehydrogenase activities in moist snuff users, cigarette smokers and nontobacco users

The aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activity was determined in samples of whole blood and in isolated erythrocytes and leukocytes from users of Swedish moist snuff, cigarette smokers and non-tobacco-using controls. The mean whole blood ALDH activity of the smokers was reduced by 21% (p less than 0.001) when compared to the controls, while that of the snuff users was reduced by only 8% (not significant). Similar but somewhat less pronounced differences were obtained both in the assays with erythrocytes and leukocytes. In the cigarette smokers, the whole blood activity correlated significantly (r = -0.79, p less than 0.001) with the plasma concentration of cotinine, the major metabolite of nicotine, whereas no correlation was observed for the users of moist snuff. Similar plasma nicotine and cotinine levels were found in smokers and snuff users, which indicates that the reduced blood ALDH activity in smokers is not caused by nicotine or any of its metabolites, but more likely, by components formed during combustion of tobacco. Since a reduced blood ALDH activity has previously been suggested as an indicator of excessive alcohol consumption, the present results show that, in future studies on blood ALDH, the smoking habits should also be taken into account.

Use of leukocyte aldehyde dehydrogenase activity to monitor inhibitory effect of disulfiram treatment

Aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activity was determined in leukocytes and erythrocytes from alcoholic patients during different stages of disulfiram (Antabuse) treatment. Assays were performed by incubating intact isolated blood cells in phosphate-buffered saline (pH 7.4, 37 degrees C), using 3,4-dihydroxyphenylacetaldehyde (DOPAL), the biogenic aldehyde derived from dopamine, as substrate. The ALDH activity was assessed from the amount of 3,4-dihydroxyphenylacetic acid (DOPAC) formed, as analysed by high-performance liquid chromatography with electrochemical detection. The leukocyte ALDH, which is similar to the liver "mitochondrial" low-Km ALDH isozyme, was maximally inhibited (about 40-60%) within 2 to 3 days after the initial disulfiram administration (dosage 200 or 400 mg/day orally). The time to reach maximum inhibition (about 95%) of the erythrocyte ALDH, which closely resembles the liver "cytosolic" high-Km isozyme, varied from 3 to more than 6 days. When medication was completed, the leukocyte ALDH activity remained unaltered for the first 2 days, and did not revert to normal levels until about 6 to 7 days after terminating treatment. The erythrocyte ALDH was still inhibited by about 90% 1 week after the last disulfiram administration. These results suggest that the leukocyte ALDH activity might provide an easily accessible marker for monitoring effect and time course of ALDH inhibition during disulfiram treatment.

Inhibition of human erythrocyte and leukocyte aldehyde dehydrogenase activities by diethylthiocarbamic acid methyl ester. An in vivo metabolite of disulfiram

The inhibitory effects of diethylthiocarbamic acid methyl ester (DTC-Me), an in vivo metabolite of disulfiram (Antabuse), on the aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activities in human erythrocytes and leukocytes were studied. ALDH assays were performed by incubating intact isolated blood cells in the presence of different concentrations of DTC-Me, using 3,4-dihydroxy-phenylacetaldehyde, the aldehyde derived from dopamine, as the substrate. DTC-Me was more selective as inhibitor of the leukocyte ALDH activity (which resembles the liver "mitochondrial" low Km ALDH), whereas both disulfiram and diethyldithiocarbamic acid, the reduced monomer of disulfiram, were more selective for the erythrocyte ALDH (which is similar to the "cytosolic" high-Km ALDH). Diethylthiocarbamic acid, the free acid of DTC-Me, was less potent than DTC-Me, and caused similar inactivation of the erythrocyte and leukocyte ALDH activities. The inhibition of ALDH by DTC-Me could not be completely restored by extensive dilution of intact or sonicated blood cell samples, which indicated that ALDH was irreversibly inhibited. Since the inhibition patterns with DTC-Me agrees with the previously reported patterns of inhibition of the high-Km and low-Km isozymes after the administration of disulfiram, the results suggest that DTC-Me might be the active in vivo inhibitory metabolite of disulfiram.

Aldehyde dehydrogenase activity in blood from various vertebrates

1. Aldehyde dehydrogenase activity was determined in whole blood samples from 17 selected vertebrates of 5 classes, using 3,4-dihydroxyphenylacetaldehyde (the aldehyde derived from dopamine) as substrate. 2. Aldehyde dehydrogenase activity in blood was widely but unevenly distributed among the species studied. 3. Mean aldehyde dehydrogenase activities in the range of 40-140 nmol/min.ml blood (measured at 37 degrees C, pH 8.8) were found in blood from man, monkey, rabbit, guinea pig and mouse (C57BL and NMRI strains), with the highest activity in rabbit blood. 4. Much lower aldehyde dehydrogenase activities (0.5-7.5 nmol/min.ml blood) were found in blood from Sprague-Dawley and Wistar rat, dog, cat, horse, pig, chicken, caiman, frog and rainbow trout, whereas the activities in blood from DBA mouse, cow, sheep and crucian carp were close to the detection limit.

Reactions of biogenic aldehydes with hemoglobin

The aldehyde derivatives of dopamine and serotonin, 3,4-dihydroxyphenylacetaldehyde (DOPAL) and 5-hydroxyindole-3-acetaldehyde (5-HIAL), respectively, were incubated with human hemoglobin under physiological conditions. Both DOPAL and 5-HIAL, as well as dopamine, showed a time-dependent disappearance during the incubations, whereas this was not observed with serotonin. The amounts of free aldehydes recovered after incubation with hemoglobin, as analysed by high-performance liquid chromatography with electrochemical detection, corresponded to the amounts of acid metabolites formed in enzymatic assays, when the samples instead were incubated with aldehyde dehydrogenase. Incubations with DOPAL, 5-HIAL, or dopamine, and hemoglobin also resulted in distinct increases in the absorption spectra between 250-350 nm, whereas no similar increase was observed with serotonin. Addition of sodium borohydride to the incubates, which is used to stabilize Schiff base adducts between aldehydes and proteins, resulted in reduction of DOPAL and 5-HIAL to their corresponding alcohol metabolites. However, a rapid initial disappearance of the aldehydes, as analysed from the recoveries of the alcohol metabolites, was observed, followed by a more slow disappearance rate throughout the incubation period.

Effect of acute ethanol administration on human blood aldehyde dehydrogenase activity

The aldehyde dehydrogenase (EC 1.2.1.3) activity in human blood was measured after acute oral administration of two different doses of ethanol to healthy subjects. No changes in aldehyde dehydrogenase activity were observed in either of the two dose groups, as compared to control subjects receiving no ethanol. Likewise, incubation of human whole blood samples with 20 mM ethanol for 2 hr caused no change in aldehyde dehydrogenase activity. The results show that human blood aldehyde dehydrogenase activity is not affected by acute ethanol administration.

Effects of disulfiram, cyanamide and 1-aminocyclopropanol on the aldehyde dehydrogenase activity in human erythrocytes and leukocytes

The effects of the aldehyde dehydrogenase (ALDH; EC 1.2.1.3) inhibitors disulfiram, cyanamide and 1-aminocyclopropanol (ACP) on the ALDH activities in human erythrocytes and leukocytes were studied. Assays were performed by incubating intact or sonicated blood cells in the presence of different concentrations of the inhibitors, using 3,4-dihydroxyphenylacetaldehyde, the aldehyde derived from dopamine oxidation, as the substrate. The amount of acid metabolite formed was measured using high-performance liquid chromatography with electrochemical detection. The erythrocyte ALDH was extremely sensitive to disulfiram, and only about 0.5 microM was needed to cause a 50% inhibition of the activity. The leukocyte activity was less sensitive, and showed a similar degree of inhibition at an 100-fold higher concentration of disulfiram. Cyanamide and ACP were both potent inactivators of the leukocyte ALDH activity, giving a 50% inhibition at concentrations of 10 and 50 microM, respectively, whereas the erythrocyte activity was much less affected. Diethyldithiocarbamate, the reduced metabolite of disulfiram, and coprine, from which ACP is derived, were much less effective inhibitors of the erythrocyte and leukocyte ALDH activities than were disulfiram and ACP.

Effects of ethanol, acetaldehyde and disulfiram on the metabolism of biogenic aldehydes in isolated human blood cells and platelets

The effects of ethanol, acetaldehyde and disulfiram on the metabolism of biogenic aldehydes were measured in different human blood fractions. Intact erythrocytes, leukocytes and platelets were incubated in phosphate-buffered saline with 3,4-dihydroxyphenylacetaldehyde (DOPAL) or 5-hydroxy-indole-3-acetaldehyde (5-HIAL), the aldehydes derived from dopamine and serotonin, respectively. The disappearance of the aldehyde and the formation of acid and alcohol metabolites were analysed in the presence of different concentrations of ethanol, acetaldehyde or disulfiram using high-performance liquid chromatography with electrochemical detection. Ethanol at a concentration of 20 mM did not affect the biogenic aldehyde metabolism. High concentrations of acetaldehyde caused a dose-dependent inhibition of the disappearance rate of the biogenic aldehydes and of the formation rate of acid metabolites. In incubations with leukocytes or platelets, the inhibition of the acid formation was associated with a slight increase in the formation of the alcohol metabolites. Disulfiram at a concentration of 50 microM totally inhibited the metabolism of DOPAL and 5-HIAL in incubations with erythrocytes or platelets, whereas much less inhibition was observed in incubations with leukocytes.