Integration of a physiologically-based pharmacokinetic model with a whole-body, organ-resolved genome-scale model for characterization of ethanol and acetaldehyde metabolism.

Ethanol is one of the most widely used recreational substances in the world and due to its ubiquitous use, ethanol abuse has been the cause of over 3.3 million deaths each year. In addition to its effects, ethanol's primary metabolite, acetaldehyde, is a carcinogen that can cause symptoms of facial flushing, headaches, and nausea. How strongly ethanol or acetaldehyde affects an individual depends highly on the genetic polymorphisms of certain genes. In particular, the genetic polymorphisms of mitochondrial aldehyde dehydrogenase, ALDH2, play a large role in the metabolism of acetaldehyde. Thus, it is important to characterize how genetic variations can lead to different exposures and responses to ethanol and acetaldehyde. While the pharmacokinetics of ethanol metabolism through alcohol dehydrogenase have been thoroughly explored in previous studies, in this paper, we combined a base physiologically-based pharmacokinetic (PBPK) model with a whole-body genome-scale model (WBM) to gain further insight into the effect of other less explored processes and genetic variations on ethanol metabolism. This combined model was fit to clinical data and used to show the effect of alcohol concentrations, organ damage, ALDH2 enzyme polymorphisms, and ALDH2-inhibiting drug disulfiram on ethanol and acetaldehyde exposure. Through estimating the reaction rates of auxiliary processes with dynamic Flux Balance Analysis, The PBPK-WBM was able to navigate around a lack of kinetic constants traditionally associated with PK modelling and demonstrate the compensatory effects of the body in response to decreased liver enzyme expression. Additionally, the model demonstrated that acetaldehyde exposure increased with higher dosages of disulfiram and decreased ALDH2 efficiency, and that moderate consumption rates of ethanol could lead to unexpected accumulations in acetaldehyde. This modelling framework combines the comprehensive steady-state analyses from genome-scale models with the dynamics of traditional PK models to create a highly personalized form of PBPK modelling that can push the boundaries of precision medicine.

Wuzhi capsule regulates chloroacetaldehyde pharmacokinetics behaviour and alleviates high-dose cyclophosphamide-induced nephrotoxicity and neurotoxicity in rats.

High-dose cyclophosphamide (HD-CTX) treatment often leads to severe nephrotoxicity and neurotoxicity, which are mainly caused by one of its metabolites, chloroacetaldehyde (CAA). However, there are no effective antidotes to prevent these side effects. The objective of this study was to evaluate the effect of Wuzhi Capsule (WZC) on the pharmacokinetics of CTX and its metabolites in rats, and the attenuation of CAA induced kidney and brain injuries, which was produced at equimolar with 2-dechloroethylcyclophosphamide. Rats were treated with single- or multiple-dose of WZC when giving HD-CTX, and the plasma concentration of CTX and its metabolites were quantitated by UHPLC-MS/MS Single-dose, not multiple-dose of WZC co-administration (300 mg/kg) significantly reduced Cmax and AUC0→24 h of DC-CTX by 33.10% and 35.51%, respectively. Biochemical assay suggested oxidative stress was involved in kidney and brain injuries by HD-CTX, which were attenuated by single-dose WZC (300 mg/kg) pre-treatment, with increased glutathione, glutathione peroxidase and superoxide dismutase contents/or activities in both tissues and plasma (P < 0.05). Meanwhile, WZC pre-treatment could also significantly decrease the plasma levels of creatinine, blood urea nitrogen and malondialdehyde (P < 0.05). Additionally, WZC treatment improved the morphology and pathology condition of the kidneys and brains in rats. In conclusion, single-dose WZC co-administration decreased CAA production and exerted protective effect on CTX-induced oxidative stress in kidney and brain, whereas repetitive WZC co-administration with CTX was probably not recommended.

Effect of Alcohol Sensitivity in Healthy Young Adults on Breath Pharmacokinetics of Acetaldehyde After Mouth Washing with Alcohol.

BACKGROUND: Acetaldehyde is causally related to head and neck cancer. Individuals with aldehyde dehydrogenase 2 deficiency experience alcohol sensitivity and are referred to as "flushers" because of their skin-flushing response to high blood acetaldehyde levels after alcohol consumption. Acetaldehyde is produced in the oral cavity after local alcohol exposure without alcohol ingestion. However, the relationship between the oral acetaldehyde level after local alcohol exposure and alcohol sensitivity is unclear. Herein, sampling the exhaled breath, we evaluated the effect of alcohol sensitivity on the pharmacokinetics of ethanol (EtOH) and acetaldehyde in breath after mouth washing with alcohol. METHODS: Twenty-eight healthy young adults were divided into flusher and nonflusher groups based on an EtOH patch test. The subjects washed their mouths for 30 seconds with 40 ml of 5% v/v alcohol, and their breath samples were collected 12 times over 20 minutes after mouth washing and rinsing with water. EtOH and acetaldehyde concentrations in all breath samples were measured using sensor gas chromatography. RESULTS: Breath EtOH concentrations exponentially decreased in both groups after mouth washing with alcohol. Breath acetaldehyde concentrations showed an immediate increase, followed by an almost exponential decrease in both groups, but concentrations in the flusher group remained higher than those in the nonflusher group throughout the 20-minute measurement period. This was reflected in a peak concentration (Cmax ) of 808 ± 70 parts-per-billion (ppb) versus 1,715 ± 223 ppb, respectively (p = 0.001), and area under the curve values of 3,528 ± 1,399 ppb minutes versus 8,637 ± 1,293 ppb minutes, respectively (p = 0.002). CONCLUSIONS: This study revealed high concentrations of acetaldehyde in breath after local alcohol exposure in the oral cavity among flushers even without alcohol ingestion. This contributes to an increased risk among flushers of mutagenic DNA lesions in the mucosa of the upper digestive tract and cancer.

Comparison of realistic and idealized breathing patterns in computational models of airflow and vapor dosimetry in the rodent upper respiratory tract.

CONTEXT: Computational fluid dynamics (CFD) simulations of airflows coupled with physiologically based pharmacokinetic (PBPK) modeling of respiratory tissue doses of airborne materials have traditionally used either steady-state inhalation or a sinusoidal approximation of the breathing cycle for airflow simulations despite their differences from normal breathing patterns. OBJECTIVE: Evaluate the impact of realistic breathing patterns, including sniffing, on predicted nasal tissue concentrations of a reactive vapor that targets the nose in rats as a case study. MATERIALS AND METHODS: Whole-body plethysmography measurements from a free-breathing rat were used to produce profiles of normal breathing, sniffing and combinations of both as flow inputs to CFD/PBPK simulations of acetaldehyde exposure. RESULTS: For the normal measured ventilation profile, modest reductions in time- and tissue depth-dependent areas under the curve (AUC) acetaldehyde concentrations were predicted in the wet squamous, respiratory and transitional epithelium along the main airflow path, while corresponding increases were predicted in the olfactory epithelium, especially the most distal regions of the ethmoid turbinates, versus the idealized profile. The higher amplitude/frequency sniffing profile produced greater AUC increases over the idealized profile in the olfactory epithelium, especially in the posterior region. CONCLUSIONS: The differences in tissue AUCs at known lesion-forming regions for acetaldehyde between normal and idealized profiles were minimal, suggesting that sinusoidal profiles may be used for this chemical and exposure concentration. However, depending upon the chemical, exposure system and concentration and the time spent sniffing, the use of realistic breathing profiles, including sniffing, could become an important modulator for local tissue dose predictions.

A novel antifungal is active against Candida albicans biofilms and inhibits mutagenic acetaldehyde production in vitro.

The ability of C. albicans to form biofilms is a major virulence factor and a challenge for management. This is evident in biofilm-associated chronic oral-oesophageal candidosis, which has been shown to be potentially carcinogenic in vivo. We have previously shown that most Candida spp. can produce significant levels of mutagenic acetaldehyde (ACH). ACH is also an important mediator of candidal biofilm formation. We have also reported that D,L-2-hydroxyisocaproic acid (HICA) significantly inhibits planktonic growth of C. albicans. The aim of the present study was to investigate the effect of HICA on C. albicans biofilm formation and ACH production in vitro. Inhibition of biofilm formation by HICA, analogous control compounds or caspofungin was measured using XTT to measure biofilm metabolic activity and PicoGreen as a marker of biomass. Biofilms were visualised by scanning electron microscopy (SEM). ACH levels were measured by gas chromatography. Transcriptional changes in the genes involved in ACH metabolism were measured using RT-qPCR. The mean metabolic activity and biomass of all pre-grown (4, 24, 48 h) biofilms were significantly reduced after exposure to HICA (p<0.05) with the largest reductions seen at acidic pH. Caspofungin was mainly active against biofilms pre-grown for 4 h at neutral pH. Mutagenic levels (>40 µM) of ACH were detected in 24 and 48 h biofilms at both pHs. Interestingly, no ACH production was detected from D-glucose in the presence of HICA at acidic pH (p<0.05). Expression of genes responsible for ACH catabolism was up-regulated by HICA but down-regulated by caspofungin. SEM showed aberrant hyphae and collapsed hyphal structures during incubation with HICA at acidic pH. We conclude that HICA has potential as an antifungal agent with ability to inhibit C. albicans cell growth and biofilm formation. HICA also significantly reduces the mutagenic potential of C. albicans biofilms, which may be important when treating bacterial-fungal biofilm infections.

Permeability and toxicity characteristics of L-cysteine and 2-methyl-thiazolidine-4-carboxylic acid in Caco-2 cells.

Acetaldehyde is a known mutagenic substance and has been classified as a group-one carcinogen by the WHO. It is possible to bind acetaldehyde locally in the gastrointestinal (GI) tract with the semi-essential amino acid l-cysteine, which reacts covalently with acetaldehyde and forms compound 2-methyl-thiozolidine-4-carboxylic acid (MTCA). The Caco-2 cell line was used to determine the permeation of l-cysteine and MTCA, as well as the possible cell toxicity of both substances. Neither of the substances permeated through the Caco-2 cells at the concentrations used in this study, and only the highest concentration of MTCA affected the viability of the cells in the MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) test. These results showed that when l-cysteine is administered in formulations releasing it locally in the lower parts of GI tract, it is not absorbed but can react with acetaldehyde, and that neither l-cysteine nor MTCA is harmful to the cells when present locally in the upper parts of GI tract. This study also shows that MTCA is sensitive at a lower pH of 5.5. Since stable MTCA is desired in different parts of the GI tract, this observation raises concern over the influence of lower pH on l-cysteine-containing product ability to bind and eliminate carcinogenic acetaldehyde.

A lung dosimetry model of vapor uptake and tissue disposition.

Inhaled vapors may be absorbed at the alveolar-capillary membrane and enter arterial blood flow to be carried to other organs of the body. Thus, the biological effects of inhaled vapors depend on vapor uptake in the lung and distribution to the rest of the body. A mechanistic model of vapor uptake in the human lung and surrounding tissues was developed for soluble and reactive vapors during a single breath. Lung uptake and tissue disposition of inhaled formaldehyde, acrolein, and acetaldehyde were simulated for different solubilities and reactivities. Formaldehyde, a highly reactive and soluble vapor, was estimated to be taken up by the tissues in the upper tracheobronchial airways with shallow penetration into the lung. Vapors with moderate solubility such as acrolein and acetaldehyde were estimated to penetrate deeper into the lung, reaching the alveolar region where absorbed vapors had a much higher probability of passing through the thin alveolar-capillary membrane to reach the blood. For all vapors, tissue concentration reached its maximum at the end of inhalation at the air-tissue interface. The depth of peak concentration moved within the tissue layer due to vapor desorption during exhalation. The proposed vapor uptake model offers a mechanistic approach for calculations of lung vapor uptake, air:tissue flux, and tissue concentration profiles within the respiratory tract that can be correlated to local biological response in the lung. In addition, the uptake model provides the necessary input for pharmacokinetic models of inhaled chemicals in the body, thus reducing the need for estimating requisite parameters.

Using a pharmacokinetic model to relate an individual's susceptibility to alcohol dependence to genotypes.

BACKGROUND/AIMS: Population-based studies have successfully identified genes affecting common diseases, but have not provided a molecular mechanism. We describe an approach for alcohol dependence connecting a mechanistic model at the molecular level with disease risk at the population level, and investigate how this model implies statistical gene-gene interactions that affect disease risk. METHODS: We develop a pharmacokinetic model describing how genetic variations in ADH1B, ADH1C, ADH7, ALDH2, and TAS2R38 affect consumption behavior, and alcohol and acetaldehyde levels over time in various tissues of individuals with a particular genotype to predict their susceptibility to alcohol dependence. RESULTS: We show that there is good agreement between the observed genotype/haplotype frequencies and those predicted by the model among cases and controls. Based on this framework, we show that we expect to observe statistical interactions among these genes for a reasonably large sample size when logistic regression models are used to relate genotype effects and disease risk. CONCLUSION: Our model exemplifies mechanistic modeling of how genes interact to influence an individual's susceptibility to alcohol dependence. We anticipate that this general approach could also be applied to study other diseases at the molecular level.

Computational prediction of local drug effect on carcinogenic acetaldehyde in the mouth based on in vitro/in vivo results of freely soluble L-cysteine.

BACKGROUND: The computational models for predicting oral drug absorption in humans using in vitro and in vivo data have been published. However, only a limited number of studies are available on the prediction of local drug efficacy in the mouth using computational models. AIM: The goal of this study was to develop a simulation model for prediction of drug amount and effect on carcinogenic acetaldehyde in the mouth. METHODS: The model was based partly on our previous studies in which we showed in vivo that l-cysteine-containing tablets can eliminate carcinogenic salivary acetaldehyde in the mouth during smoking. To develop as informative a model as possible, we also investigated whether a lower saliva pH (4.7) can affect the freely soluble l-cysteine dissolution rate and cysteine stability profile in the mouth, compared to the normal saliva pH of 7.4. RESULTS: Stability of the active drug is not pH dependent and thus users with normal, healthy saliva pH and those with lower pH can benefit from cysteine-containing products. The simulated saliva profiles of l-cysteine and acetaldehyde corresponded to the in vivo results. CONCLUSIONS: The model developed can be used as an alternative tool to obtain faster and cheaper answers on how freely soluble drugs affect local conditions in the mouth. Because tobacco smoke contains more than 60 carcinogenic compounds, the model developed can offer a new view in eliminating or reducing not only one toxic compound from smoke but also many others compounds using only one formulation containing various active compounds.

Targets of chloroacetaldehyde-induced nephrotoxicity.

Chloroacetaldehyde, one of the main products of hepatic ifosfamide metabolism, contributes to its nephrotoxicity. However, the pathophysiology of this toxicity is not fully understood. The present work examined the time and dose effects of clinically relevant concentrations of chloroacetaldehyde (25-75microM) on precision-cut rat renal cortical slices metabolizing a physiological concentration of lactate. Chloroacetaldehyde toxicity was demonstrated by the decrease in total glutathione and cellular ATP levels. The drop of cellular ATP was linked to the inhibition of oxidative phosphorylation at the level of complex I of the mitochondrial respiratory chain. The large decrease in glucose synthesis from lactate was explained by the inhibition of some gluconeogenic enzymes, mainly glyceraldehyde 3-phosphate dehydrogenase. The decrease in lactate utilization was demonstrated not only by a defect of gluconeogenesis but also by the decrease in [(14)CO(2)] formation from [U-(14)C]-lactate. All the effects of chloroacetaldehyde were concentration and time-dependent. Finally, the chloroacetaldehyde-induced inhibition of glyceraldehyde 3-phosphate dehydrogenase, which is also a glycolytic enzyme, suggests that, under conditions close to those found during ifosfamide therapy, the inhibition of glycolytic pathway by chloroacetaldehyde might be responsible, at least in part, for the therapeutic efficacy of ifosfamide.

Pharmacokinetic and pharmacodynamic basis for overcoming acetaldehyde-induced adverse reaction in Asian alcoholics, heterozygous for the variant ALDH2*2 gene allele.

OBJECTIVES: It has been well documented that although homozygosity of the variant aldehyde dehydrogenese-2 (ALDH2) gene allele, ALDH2*2, in Asians almost fully protects against alcoholism, the heterozygosity only affords a partial protection to varying degrees. The partial protection against alcoholism has been ascribed to the faster elimination of acetaldehyde by residual hepatic ALDH2 activity and the lower accumulation in circulation in nonalcoholic heterozygotes. The physiological basis for overcoming the protection in ALDH2*1/*2 alcoholics, however, remains unclear. METHODS: To address this question, we recruited a total of 27 Han Chinese alcohol-dependent men, matched by age and body mass index, controlled for normal liver and cardiovascular functions, from a population base of 221 alcoholics. The participants were divided into ALDH2*1/*1 homozygotes (n = 13) and ALDH2*1/*2 heterozygotes (n = 14). After a moderate dose of ethanol (0.5 g/kg body weight), blood ethanol/acetaldehyde/acetate concentrations, cardiac and extracranial/intracranial arterial hemodynamic parameters, as well as self-rated subjective sensations, were measured for 130 min. RESULTS: ALDH2*1/*2 alcoholics exhibited significantly higher blood acetaldehyde levels as well as prominent cardiovascular effects and the subjective perceptions, compared with the ALDH2*1/*1 alcoholics. Comparable profiles of blood acetaldehyde were found between heterozygotic alcoholics and the previously reported nonalcoholic heterozygotes intaking the same dose of ethanol. ALDH2*1/*2 alcoholics revealed, however, significantly lower intensities in both physiologic and psychologic responses than did the nonalcoholic heterozygotes. CONCLUSION: These results indicate that acetaldehyde, rather than ethanol or acetate, is primarily responsible for the observed alcohol sensitivity reactions in heterozygotic alcoholics and suggest that physiological tolerance and/or innate low sensitivity may play a crucial role in overcoming the deterring response. A potential pharmacogenetic classification of acetaldehydism and alcoholism for alcoholics carrying the different ALDH2 genotypes is proposed.

Differences in simulated liver concentrations of toxic coumarin metabolites in rats and different human populations evaluated through physiologically based biokinetic (PBBK) modeling.

Coumarin is bioactivated via 3,4-epoxidation resulting in formation of the hepatotoxic o-hydroxyphenylacetaldehyde (oHPA) and detoxified by cytochrome P450 2A6 (CYP2A6) hydroxylation leading to 7-hydroxycoumarin. The present study defines physiologically based biokinetic (PBBK) models to predict liver levels of the toxic oHPA metabolite of coumarin in rats and in human subjects with normal or deficient CYP2A6 catalyzed coumarin 7-hydroxylation. The results reveal that the predicted maximum tissue concentration (C(max)) of oHPA in the liver of wild type human subjects and of subjects deficient in CYP2A6 catalyzed 7-hydroxylation are, respectively, three and one order of magnitude lower than the values predicted for rat liver. Another difference between CYP2A6 deficient and wild type human subjects is a 500-fold difference in the area under the curve 0-24h (AUC(0-24h)) for the time-dependent oHPA liver concentration pointing at a relative higher percentage of the original dose converted in time through this pathway when CYP2A6 is deficient. For wild type human subjects and the subjects with completely deficient coumarin 7-hydroxylation the AUC(0-24h) values for oHPA in the liver are, respectively, three and one order of magnitude lower than that for rat liver. Even when 7-hydroxylation is deficient, the chances on formation of the hepatotoxic oHPA metabolite will be significantly lower in the liver of humans than those expected in the liver of rats when exposed to a similar dose on a body-weight basis. This conclusion should be taken into account when extrapolating data from experimental studies in sensitive animals, i.e., rats, to the general human population.

Ethanol injected into the hypothalamic arcuate nucleus induces behavioral stimulation in rats: an effect prevented by catalase inhibition and naltrexone.

It is suggested that some of the behavioral effects of ethanol, including its psychomotor properties, are mediated by beta-endorphin and opioid receptors. Ethanol-induced increases in the release of hypothalamic beta-endorphin depend on the catalasemic conversion of ethanol to acetaldehyde. Here, we evaluated the locomotor activity in rats microinjected with ethanol directly into the hypothalamic arcuate nucleus (ArcN), the main site of beta-endorphin synthesis in the brain and a region with high levels of catalase expression. Intra-ArcN ethanol-induced changes in motor activity were also investigated in rats pretreated with the opioid receptor antagonist, naltrexone (0-2 mg/kg) or the catalase inhibitor 3-amino-1,2,4-triazole (AT; 0-1 g/kg). We found that ethanol microinjections of 64 or 128, but not 256 microg, produced locomotor stimulation. Intra-ArcN ethanol (128 microg)-induced activation was prevented by naltrexone and AT, whereas these compounds did not affect spontaneous activity. The present results support earlier evidence indicating that the ArcN and the beta-endorphinic neurons of this nucleus are necessary for ethanol to induce stimulation. In addition, our data suggest that brain structures that, as the ArcN, are rich in catalase may support the formation of ethanol-derived pharmacologically relevant concentrations of acetaldehyde and, thus be of particular importance for the behavioral effects of ethanol.

A PBPK model for evaluating the impact of aldehyde dehydrogenase polymorphisms on comparative rat and human nasal tissue acetaldehyde dosimetry.

Acetaldehyde is an important intermediate in the chemical synthesis and normal oxidative metabolism of several industrially important compounds, including ethanol, ethyl acetate, and vinyl acetate. Chronic inhalation of acetaldehyde leads to degeneration of the olfactory and respiratory epithelium in rats at concentrations > 50 ppm (90 day exposure) and respiratory and olfactory nasal tumors at concentrations > or = 750 ppm, the lowest concentration tested in the 2-yr chronic bioassay. Differences in the anatomy and biochemistry of the rodent and human nose, including polymorphisms in human high-affinity acetaldehyde dehydrogenase (ALDH2), are important considerations for interspecies extrapolations in the risk assessment of acetaldehyde. A physiologically based pharmacokinetic model of rat and human nasal tissues was constructed for acetaldehyde to support a dosimetry-based risk assessment for acetaldehyde (Dorman et al., 2008). The rodent model was developed using published metabolic constants and calibrated using upper-respiratory-tract acetaldehyde extraction data. The human nasal model incorporates previously published tissue volumes, blood flows, and acetaldehyde metabolic constants. ALDH2 polymorphisms were represented in the human model as reduced rates of acetaldehyde metabolism. Steady-state dorsal olfactory epithelial tissue acetaldehyde concentrations in the rat were predicted to be 409, 6287, and 12,634 microM at noncytotoxic (50 ppm), and cytotoxic/tumorigenic exposure concentrations (750 and 1500 ppm), respectively. The human equivalent concentration (HEC) of the rat no-observed-adverse-effect level (NOAEL) of 50 ppm, based on steady-state acetaldehyde concentrations from continual exposures, was 67 ppm. Respiratory and olfactory epithelial tissue acetaldehyde and H(+) (pH) concentrations were largely linear functions of exposure in both species. The impact of presumed ALDH2 polymorphisms on human olfactory tissue concentrations was negligible; the high-affinity, low-capacity ALDH2 does not contribute significantly to acetaldehyde metabolism in the nasal tissues. The human equivalent acetaldehyde concentration for homozygous low activity was 66 ppm, 1.5% lower than for the homozygous full activity phenotype. The rat and human acetaldehyde PBPK models developed here can also be used as a bridge between acetaldehyde dose-response and mode-of-action data as well as between similar databases for other acetaldehyde-producing nasal toxicants.

Pharmacokinetic and pharmacodynamic basis for partial protection against alcoholism in Asians, heterozygous for the variant ALDH2*2 gene allele.

OBJECTIVES: It has been well documented that although homozygosity of the variant aldehyde dehydrogenase-2 (ALDH2) gene allele, ALDH2*2, in Asians almost fully protects against alcoholism, the heterozygosity only affords a partial protection to varying degrees. The full protection against alcoholism has been ascribed to the low-amount of alcohol hypersensitivity accompanied by a prolonged and large accumulation of acetaldehyde in blood (Peng et al. Pharmacogenetics 1999; 9:463-476). The physiological basis for the partial protection, however, remains unclear. METHODS: To address this question, we recruited a total of 32 adult Han Chinese men, matched by age, body-mass index, and nutritional state from a population base of 404 men. The subjects were divided into 3 combinatorial genotypic groups of alcohol dehydrogenase (ADH) and ALDH, that is, ALDH2*1/*1-ADH1B*1/*1-ADH1C*1/*1 (n=8), ALDH2*1/*1-ADH1B*2/*2-ADH1C*1/*1 (n=8), and ALDH2*1/*2-ADH1B*2/*2-ADH1C*1/*1 (n=16). Following a moderate dose of ethanol (0.5 g/kg body weight), blood ethanol/acetaldehyde/acetate concentrations, cardiac and extracranial/intracranial arterial hemodynamic parameters, as well as self-rated subjective sensations, were measured for 130 min. RESULTS: Heterozygotic ALDH2*1/*2 subjects were found to be strikingly responsive to the moderate amount of alcohol, as evidenced by the prominent cardiovascular effects as well as subjective perceptions of general discomfort for as long as 2 h following ingestion. The ADH1B polymorphisms did not appear to correlate with the pharmacokinetic and pharmacodynamic effects. CONCLUSIONS: These results indicate that acetaldehyde, rather than ethanol or acetate, is primarily responsible for the observed alcohol sensitivity reactions and suggest that substantially lower accumulation of blood acetaldehyde in the heterozygotes significantly reduces the aversion reaction to low amounts of alcohol that permits other biological as well as environmental factors to facilitate drinking and the according risk for the disease.

Acetaldehyde, polymorphisms and the cardiovascular system.

To date, the only genes that have been consistently replicated across racial and ethnic groups to influence alcoholism vulnerability are polymorphisms in the alcohol-metabolizing enzymes, i.e. cytosolic alcohol dehydrogenase 1B (ADH1B) and mitochondrial aldehyde dehydrogenase 2 (ALDH2). Both the variant ADHIB*2 and ALDH2*2 alleles significantly protect against developing alcoholism. The protection has been thought to result from accumulation of acetaldehyde after drinking. Unlike ALDH2*2, direct correlation between ADHI1B*2 and blood acetaldehyde has not been verified. ALDH2*2/*2 homozygosity appeared to almost completely protect against alcoholism, whereas ALDH2* 1/*2 heterozygosity appeared to reduce risk of the disease only about threefold. Direct correlations of blood ethanol and acetaldehyde concentrations, cardiovascular haemodynamic responses, and the subjective perceptions after challenge with low (0.2g/kg) to moderate (0.5g/kg) alcohol in individuals with different ALDH2 genotypes support the notion that full protection against alcoholism byALDH2*2/*2 may derive from either abstinence or deliberate moderation in alcohol consumption due to strong discomfort from physiological and psychological responses caused by persistently elevated blood acetaldehyde after ingestion of a small amount of alcohol, and that the partial protection by ALDH2*1/*2 can be ascribed to significantly lower acetaldehyde build-up in blood and the according adverse reactions.

Ethanol and acetaldehyde: in vivo quantitation and effects on cholinergic function in rat brain.

First, ethanol (EtOH) and acetaldehyde levels were determined simultaneously in the striatum of free-moving rats after administration of their major oxidative enzyme inhibitors followed by EtOH. The results showed that acetaldehyde was present in the cyanamide (CY) + EtOH, CY + 4-methylpyrazole (4-MP) + EtOH and CY + sodium azide + EtOH groups. The CY + EtOH-induced peak acetaldehyde level was 195.2 +/- 19.4 microM, and this value was significantly higher than those in the other groups. The peak EtOH level was 25.9 +/- 2.3mM in the CY + 4-MP + EtOH group, and this level was considerably higher than the value in EtOH. No significant difference in brain EtOH levels was found in any of the other groups studied. Second, the effects of EtOH and acetaldehyde on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) were investigated in the frontal cortex and hippocampus of high acetaldehyde-producing rats using RT-PCR and Western blot. The results showed that EtOH and acetaldehyde decreased ChAT expression at 40 and 240 min after EtOH dosing in the brain. The acetaldehyde-induced reduction in ChAT expression was significantly higher than that induced by EtOH. No remarkable alteration of AChE expression was observed. The study suggested that catalase made a significant contribution to acetaldehyde formation in the rat brain, and that EtOH and acetaldehyde decreased ChAT expression at 40 and 240 min after EtOH dosing.

Maturation of whisky changes ethanol elimination kinetics and neural effects by increasing nonvolatile congeners.

BACKGROUND: The maturation of distilled spirits is known to change constituent congeners to improve the qualities of smell and taste. However, it has been largely unknown how maturation modifies the pharmacokinetics or neuropharmacological effects of ethanol. We used single malt whiskies to investigate the effects of spirit maturation on ethanol metabolism and drunkenness. METHODS: Mice were injected with 5-year (5-y) or 20-year (20-y) aged single malt whisky with a concentration of 20% (w/v) ethanol at a dose of 3 g/kg. The concentrations of ethanol and its metabolites in the blood and the duration of loss of righting reflex (LORR) were compared between the 2 whisky groups. In addition, the effects of nonvolatile congeners in whisky on the biomedical reactivities of ethanol were investigated by administering a nonvolatile fraction added to a 20% ethanol solution, whose fraction was prepared by evaporating 16-y whisky. Liver alcohol dehydrogenase (ADH) activity was measured with whisky as the substrate or in the presence of nonvolatile congeners with ethanol as the substrate. RESULTS: The rate of ethanol elimination (mmol/kg/h) was smaller in the 20-y whisky group than in the 5-y group (p<0.01 by Fisher's protected least significant difference), which resulted in lower concentrations of blood acetaldehyde and acetate in the former group than in the latter group (p<0.01 by ANOVA). Nonvolatile congeners added to the ethanol solution also depressed the rate of ethanol elimination in mice. In vitro studies demonstrated that liver ADH activity measured with whisky as the substrate was decreased as a function of the age of the whisky, and that the activity measured with ethanol as the substrate was strongly inhibited by nonvolatile congeners. The duration of LORR was longer in the 20-y group than in the 5-y group (p<0.01). Nonvolatile congeners also prolonged the duration of ethanol-induced LORR, when administered together with ethanol. CONCLUSION: Maturation of whisky delayed ethanol metabolism to lower the level of blood acetaldehyde and acetate with increasing inhibition of liver ADH activity by nonvolatile congeners. It also prolonged drunkenness by enhancing the neurodepressive effects of ethanol, due to increases in the amount of nonvolatile congeners. These biomedical effects of whisky maturation may reduce aversive reactions and cytotoxicity due to acetaldehyde, and may also limit overdrinking with the larger neurodepression.

A new method for estimating the retention of selected smoke constituents in the respiratory tract of smokers during cigarette smoking.

This report describes a new method for estimating the retention of selected mainstream smoke constituents in the respiratory tract of adult smokers during cigarette smoking. Both particulate-phase (PP) constituents including nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and N'-nitrosonornicotine (NNN), two tobacco-specific nitrosamines (TSNA), and gas-vapor-phase (GVP) constituents including carbon monoxide (CO), isoprene (IP), acetaldehyde (AA), and ethylene, were studied. To estimate the amounts of smoke constituents delivered during smoking, we used predetermined linear relationships between the measured cigarette filter solanesol content and machine-generated mainstream deliveries of these selected compounds. To determine the amounts of smoke constituents exhaled, the expired breath was directed through a Cambridge filter pad (CFP) attached to an infrared spectrometer. PP compounds were trapped on the CFP for later analysis and GVP compounds were analyzed in near real time. The smokers' respiratory parameters during smoking, such as inhalation/exhalation volume and time, were monitored using LifeShirt(R), a respiratory inductive plethysmography (RIP) device. The retention of each smoke constituent, expressed as a percentage, was then calculated as the difference between the amount delivered (estimated) and the amount exhaled relative to the amount delivered. We studied 16 adult male smokers who smoked cigarettes according to 3 predefined smoking patterns: no inhalation (pattern A), normal inhalation (pattern B), and deep inhalation (pattern C). For the three PP constituents, the mean retentions for pattern A ranged between 10 and 20%; and while the mean retentions of the two TSNAs were significantly higher for pattern C (84% for NNK and 97% for NNN) than those for pattern B (63% for NNK and 84% for NNN), the mean retentions of nicotine were basically the same between patterns B and C, which were both greater than 98%. For the GVP constituents, the retentions were similar between pattern B and pattern C, although different constituents were retained to different degrees (average values of 33%, 52%, 79%, and 99% for ethylene, IP, CO, and AA, respectively). The differences in the retention between different constituents could be interpreted in terms of each constituent's physical properties such as volatility and solubility. In conclusion, the method described is suitable for studying the retention of selected mainstream smoke constituents in the respiratory tract of smokers.

Ifosfamide-induced nephrotoxicity: mechanism and prevention.

The efficacy of ifosfamide (IFO), an antineoplastic drug, is severely limited by a high incidence of nephrotoxicity of unknown etiology. We hypothesized that inhibition of complex I (C-I) by chloroacetaldehyde (CAA), a metabolite of IFO, is the chief cause of nephrotoxicity, and that agmatine (AGM), which we found to augment mitochondrial oxidative phosphorylation and beta-oxidation, would prevent nephrotoxicity. Our model system was isolated mitochondria obtained from the kidney cortex of rats treated with IFO or IFO + AGM. Oxidative phosphorylation was determined with electron donors specific to complexes I, II, III, or IV (C-I, C-II, C-III, or C-IV, respectively). A parallel study was done with (13)C-labeled pyruvate to assess metabolic dysfunction. Ifosfamide treatment significantly inhibited oxidative phosphorylation with only C-I substrates. Inhibition of C-I was associated with a significant elevation of [NADH], depletion of [NAD], and decreased flux through pyruvate dehydrogenase and the TCA cycle. However, administration of AGM with IFO increased [cyclic AMP (cAMP)] and prevented IFO-induced inhibition of C-I. In vitro studies with various metabolites of IFO showed that only CAA inhibited C-I, even with supplementation with 2-mercaptoethane sulfonic acid. Following IFO treatment daily for 5 days with 50 mg/kg, the level of CAA in the renal cortex was approximately 15 micromol/L. Taken together, these observations support the hypothesis that CAA is accumulated in renal cortex and is responsible for nephrotoxicity. AGM may be protective by increasing tissue [cAMP], which phosphorylates NADH:oxidoreductase. The current findings may have an important implication for the prevention of IFO-induced nephrotoxicity and/or mitochondrial diseases secondary to defective C-I.