Alcohol and the mystique of flushing

Moderate ethanol exposure during early ontogeny of the rat alters respiratory plasticity, ultrasonic distress vocalizations, increases brain catalase activity, and acetaldehyde-mediated ethanol intake

Early ontogeny of the rat (late gestation and postnatal first week) is a sensitive period to ethanol’s positive reinforcing effects and its detrimental effects on respiratory plasticity. Recent studies show that acetaldehyde, the first ethanol metabolite, plays a key role in the modulation of ethanol motivational effects. Ethanol brain metabolization into acetaldehyde via the catalase system appears critical in modulating ethanol positive reinforcing consequences. Catalase system activity peak levels occur early in the ontogeny. Yet, the role of ethanol-derived acetaldehyde during the late gestational period on respiration response, ultrasonic vocalizations (USVs), and ethanol intake during the first week of the rat remains poorly explored. In the present study, pregnant rats were given a subcutaneous injection of an acetaldehyde-sequestering agent (D-penicillamine, 50 mg/kg) or saline (0.9% NaCl), 30 min prior to an intragastric administration of ethanol (2.0 g/kg) or water (vehicle) on gestational days 17–20. Respiration rates (breaths/min) and apneic episodes in a whole-body plethysmograph were registered on postnatal days (PDs) 2 and 4, while simultaneously pups received milk or ethanol infusions for 40-min in an artificial lactation test. Each intake test was followed by a 5-min long USVs emission record. On PD 8, immediately after pups completed a 15-min ethanol intake test, brain samples were collected and kept frozen for catalase activity determination. Results indicated that a moderate experience with ethanol during the late gestational period disrupted breathing plasticity, increased ethanol intake, as well brain catalase activity. Animals postnatally exposed to ethanol increased their ethanol intake and exerted differential affective reactions on USVs and apneic episodes depending on whether the experience with ethanol occur prenatal or postnatally. Under the present experimental conditions, we failed to observe, a clear role of acetaldehyde mediating ethanol’s effects on respiratory plasticity or affective states, nevertheless gestational acetaldehyde was of crucial importance in determining subsequent ethanol intake affinity. As a whole, results emphasize the importance of considering the participation of acetaldehyde in fetal programming processes derived from a brief moderate ethanol experience early in development, which in turn, argues against “safe or harmless” ethanol levels of exposure.

The educational potential of alcohol-related flushing among Chinese young people

Aim: This paper describes Chinese university students' understanding of the meaning of the alcohol-related flushing response and how they reacted to their own and someone else's flushing in a group drinking situation. Method: The researcher surveyed 530 Chinese university students about their understanding of flushing and their perception of how people respond to a person who visibly flushes while drinking alcohol. Findings: Most students did not know about the physiological cause of flushing. There were significant gender differences in both reactions to and perception of responses to a person who flushes. There was no direct relationship between flushing and drinking behaviour.

CONCLUSIONS

This description of flushing behaviour and responses to a flushing person is discussed in terms of educational opportunities to change behaviours that could reduce the cancer related risks of this visibly at-risk group.

Acetaldehyde involvement in ethanol's postabsortive effects during early ontogeny

Clinical and biomedical studies sustains the notion that early ontogeny is a vulnerable window to the impact of alcohol. Experiences with the drug during these stages increase latter disposition to prefer, use or abuse ethanol. This period of enhanced sensitivity to ethanol is accompanied by a high rate of activity in the central catalase system, which metabolizes ethanol in the brain. Acetaldehyde (ACD), the first oxidation product of ethanol, has been found to share many neurobehavioral effects with the drug. Cumulative evidence supports this notion in models employing adults. Nevertheless very few studies have been conducted to analyze the role of ACD in ethanol postabsorptive effects, in newborns or infant rats. In this work we review recent experimental literature that syndicates ACD as a mediator agent of reinforcing aspects of ethanol, during early ontogenetic stages. We also show a meta-analytical correlational approach that proposes how differences in the activity of brain catalase across ontogeny, could be modulating patterns of ethanol consumption.

Anxiogenic and stress-inducing effects of peripherally administered acetaldehyde in mice: similarities with the disulfiram-ethanol reaction

Peripheral accumulation of acetaldehyde, the first metabolite of ethanol, produces autonomic responses in humans called "flushing". The aversive characteristics of flushing observed in some populations with an isoform of aldehyde dehydrogenase (ALDH2) less active, are the basis for treating alcoholics with disulfiram, an ALDH inhibitor. Although ethanol and centrally formed acetaldehyde have anxiolytic effects, peripheral accumulation of acetaldehyde may be aversive in part because it is anxiogenic.

OBJECTIVES

We investigated the effect of direct administration of acetaldehyde on behavioral measures of anxiety and on hormonal markers of stress in mice. The impact of disulfiram on the anxiolytic actions of ethanol was evaluated. Acetate (a metabolite of acetaldehyde) was also studied.

METHODS

CD1 male mice received acetaldehyde (0, 25, 50, 75 or 100 mg/kg) at different time intervals and were assessed in the elevated plus maze and in the dark-light box. Corticosterone release after acetaldehyde administration was also assessed. Additional experiments evaluated the impact of disulfiram on the anxiolytic effect of ethanol (0 or 1 mg/kg), and the effect of acetate on the plus maze.

RESULTS

Direct administration of acetaldehyde (100 mg/kg) had an anxiogenic effect at 1, 11 or 26 min after IP administration. Acetaldehyde was ten times more potent than ethanol at inducing corticosterone release. Disulfiram did not affect behavior on its own, but blocked the anxiolytic effect of ethanol at doses of 30 and 60 mg/kg, and had an anxiogenic effect at the highest dose (90 mg/kg) when co-administered with ethanol. Acetate did not affect any of the anxiety parameters.

CONCLUSIONS

Peripheral administration or accumulation of acetaldehyde produces anxiogenic effects and induces endocrine stress responses. This effect is not mediated by its metabolite acetate.

Artisanal alcohol production in Mayan Guatemala: chemical safety evaluation with special regard to acetaldehyde contamination

There is a lack of knowledge regarding the composition, production, distribution, and consumption of artisanal alcohol, particularly in the developing world. In Nahualá, an indigenous Mayan municipality located in highland Guatemala, heavy alcohol consumption appears to have had a significant negative impact on health, a major role in cases of violence and domestic abuse, and a link to street habitation. Cuxa, an artisanally, as well as commercially produced sugarcane alcohol, is widely consumed by heavy drinkers in this community. Cuxa samples from all distribution points in the community were obtained and chemically analyzed for health-relevant constituents and contaminants including methanol, acetaldehyde, higher alcohols, and metals. From those, only acetaldehyde was confirmed to be present in unusually high levels (up to 126 g/hl of pure alcohol), particularly in samples that were produced clandestinely. Acetaldehyde has been evaluated as "possibly carcinogenic" and has also been identified as having significant human exposure in a recent risk assessment. This study explores the reasons for the elevated levels of acetaldehyde, through both sampling and analyses of raw and intermediary products of cuxa production, as well as interviews from producers of the clandestine alcohol. For further insight, we experimentally produced this alcohol in our laboratory, based on the directions provided by the producers, as well as materials from the town itself. Based on these data, the origin of the acetaldehyde contamination appears to be due to chemical changes induced during processing, with the major causative factors consisting of poor hygiene, aerobic working conditions, and inadequate yeast strains, compounded by flawed distillation methodology that neglects separation of the first fractions of the distillate. These results indicate a preventable public health concern for consumers, which can be overcome through education about good manufacturing practices, as well as financial incentives to separate the acetaldehyde-rich fractions during distillation.

Alcohol in Mayan Guatemala: consumption, distribution, production and composition of cuxa

AIMS

To describe the consumption, distribution, production and chemical composition of alcohol, including cuxa (pronounced 'coo sha'), in Nahualá, a highland Mayan municipality in Guatemala. Cuxa is a sugarcane-derived spirit, in part produced clandestinely, that has been distributed in the community for several decades.

METHODS

Key informant interviews with alcohol distributors and consumers, cuxa producers and health professionals, as well as analyses of questionnaires from a sample of 47 spouses who came to the local health centre for problems related to their husband's drinking. Sampling and chemical analysis of cuxa from 12 of 13 identified sales points in the head-town of Nahualá and its nearby settlements (10 km radius). Fieldwork was conducted between November 2007 and March 2008.

RESULTS

Alcohol consumption was found to be integrated culturally in this community. The overall drinking culture was marked by irregular heavy drinking occasions, especially around market days, with substantial inebriation and health problems, especially among street inhabiting drinkers. Cuxa contributed to these problems, and cuxa drinking was socially stigmatized. Cuxa was produced both clandestinely and industrially, and sold legally by taverns and illegally by clandestine distributors. The alcoholic strength of the samples was typically between 17 and 19% vol.; clandestinely produced cuxa samples showed acetaldehyde contamination.

CONCLUSIONS

Measures should be taken to reduce the harm associated with alcohol in this community, including efforts to reduce acetaldehyde levels in cuxa.

Reduction in the anxiolytic effects of ethanol by centrally formed acetaldehyde: the role of catalase inhibitors and acetaldehyde-sequestering agents

RATIONALE

Considerable evidence indicates that brain ethanol metabolism mediated by catalase is involved in modulating some of the behavioral and physiological effects of this drug, which suggests that the first metabolite of ethanol, acetaldehyde, may have central actions. Previous results have shown that acetaldehyde administered into the lateral ventricles produced anxiolysis in a novel open arena in rats.

OBJECTIVES

The present studies investigate the effects of centrally formed acetaldehyde on ethanol-induced anxiolysis.

MATERIALS AND METHODS

The effects of the catalase inhibitor sodium azide (SA; 0 or 10 mg/kg, IP) on ethanol-induced anxiolysis (0.0, 0.5, or 1.0 g/kg, IP) were evaluated in CD1 mice in two anxiety paradigms, the elevated plus maze and the dark/light box. Additional studies assessed the effect of the noncompetitive catalase inhibitor 3-amino-1,2,4-triazole (AT; 0.5 g/kg, IP) and the acetaldehyde inactivation agent D: -penicillamine (50 mg/kg, IP) on the plus maze.

RESULTS

SA reduced the anxiolytic effects of ethanol on several parameters evaluated in the elevated plus maze and in the dark/light box. In the plus maze, AT completely blocked and D-penicillamine significantly reduced the anxiolytic properties of ethanol.

CONCLUSIONS

Thus, when cerebral metabolism of ethanol into acetaldehyde is blocked by catalase inhibitors, or acetaldehyde is inactivated, there is a suppressive effect on the anxiolytic actions of ethanol. These data provide further support for the idea that centrally formed or administered acetaldehyde can contribute to some of the psychopharmacological actions of ethanol, including its anxiolytic properties.

Overview of the role of alcohol dehydrogenase and aldehyde dehydrogenase and their variants in the genesis of alcohol-related pathology

Alcohol dehydrogenase (ADH) and mitochondrial aldehyde dehydrogenase (ALDH2) are responsible for metabolizing the bulk of ethanol consumed as part of the diet and their activities contribute to the rate of ethanol elimination from the blood. They are expressed at highest levels in liver, but at lower levels in many tissues. This pathway probably evolved as a detoxification mechanism for environmental alcohols. However, with the consumption of large amounts of ethanol, the oxidation of ethanol can become a major energy source and, particularly in the liver, interferes with the metabolism of other nutrients. Polymorphic variants of the genes for these enzymes encode enzymes with altered kinetic properties. The pathophysiological effects of these variants may be mediated by accumulation of acetaldehyde; high-activity ADH variants are predicted to increase the rate of acetaldehyde generation, while the low-activity ALDH2 variant is associated with an inability to metabolize this compound. The effects of acetaldehyde may be expressed either in the cells generating it, or by delivery of acetaldehyde to various tissues by the bloodstream or even saliva. Inheritance of the high-activity ADH β2, encoded by theADH2*2gene, and the inactiveALDH2*2gene product have been conclusively associated with reduced risk of alcoholism. This association is influenced by gene–environment interactions, such as religion and national origin. The variants have also been studied for association with alcoholic liver disease, cancer, fetal alcohol syndrome, CVD, gout, asthma and clearance of xenobiotics. The strongest correlations found to date have been those between theALDH2*2allele and cancers of the oro-pharynx and oesophagus. It will be important to replicate other interesting associations between these variants and other cancers and heart disease, and to determine the biochemical mechanisms underlying the associations.

ALDH2 genotype-associated differences in the acute effects of alcohol on P300, psychomotor performance, and subjective response in healthy young Korean men: a double-blind placebo-controlled crossover study

BACKGROUND

This study investigated the acute effects of alcohol on neurophysiological and psychomotor functions and the subjective response in healthy young Korean men according to the mitochondrial aldehyde dehydrogenase (ALDH2) genotype.

METHOD

A total of 24 males, half with ALDH2*1/*1 (active form) and the rest with ALDH2*1/*2 (inactive form), were selected through genotyping. In a double-blind placebo-controlled crossover design, each subject consumed either a 0.5 g/kg dose of alcohol or a placebo on two separate occasions, 1 week apart. The blood alcohol concentrations (BACs), P300 of event-related potential, psychomotor performance, and perceived feelings were assessed.

RESULTS

Although the BACs were similar between the two groups, the effects of alcohol on P300 were greater overall in subjects with ALDH2*1/*2 than in subjects with ALDH2*1/*1. Psychomotor performance was more impaired after alcohol ingestion in subjects with ALDH2*1/*2 than in subjects with ALDH2*1/*1. The subjective response after alcohol ingestion was more negative in subjects with ALDH2*1/*2, compared to subjects with ALDH2*1/*1.

CONCLUSIONS

These results suggest that the ALDH2 polymorphism is an important factor in determining the effects of alcohol on various psychobehavioral functions.

Catalase as a regulator of the propensity to ingest alcohol in genetically determined acatalasemic individuals from Israel

Direct descendants of an individual residing in Israel, who was diagnosed in the 1960s with a genetic deficiency in catalase, were examined for their propensity to consume alcohol.These individuals were found to possess a lower level of catalase activity compared to that of a group of matched controls with the same ethnic background.While no differences were observed in the propensity to drink alcohol between the two groups, the catalase deficient individuals did show a significant positive correlation between catalase activity and alcohol drinking behaviour as measured by Q-value. No such relationship was observed in the matched controls.The findings suggest that the apparent acatalasemia in the experimental subjects may act as a limiting factor for these individuals and that catalase may play an important role in regulating alcohol drinking behaviour. These results are consistent with previous animal and human studies which suggest that catalase, via its ability to produce acetaldehyde through the metabolism of ethanol, may have a regulatory role in the propensity to drink alcohol.

A review of alcohol clearance in humans

The level of blood or brain alcohol is considered to influence alcohol ingestion by causing subjective perceptions or neural activations that are reinforcing or rewarding. Alcohol-dependent people may try to maintain some desired tissue level, drinking to replace the millimolar levels that were cleared from the blood by metabolism. The biomedical literature describes many approaches to understanding the role of blood alcohol levels in human physiology and behavior, and this review examines some of the published results. They include the general kinetics of intake and removal of beverage alcohol as well as the characteristics of many different catalysts that can interact with alcohol. Because ingested alcohol creates blood levels that are a 1000-fold greater than those normally experienced during abstinence, ethanol may impose itself as an alternate substrate for the many oxidoreductases that act physiologically on other endogenous alcohols. Many enzymes that can act on millimolar ethanol have been isolated, and their structural genes are sequenced. Unfortunately, the genetic sequence does not indicate the physiological material upon which the translated gene product may act. In a sense, the set of enzymes with catalytic sites occupied by millimolar ethanol during alcohol drinking might constructively be regarded as "orphan gene products" whose physiological role remains to be clarified. This review is designed to indicate some of what is known, what is not known, and what needs to be known to improve the interpretations regarding adaptations to beverage alcohol and the ability of millimolar levels of alcohol to diminish dysphoria. The dysphoria may be influenced by ethanol, by ethanol metabolites, or by altered metabolism of currently unspecified endogenous substrates. A major challenge is to evaluate the multiple alternative variables within a context that stimulates curiosity and encourages quantitative tests of the relative contribution of each variable to the overall physiology of an individual.

Acute reactions to alcohol

Where the experience of alcohol is unpleasant because of adverse reactions to small amounts, alcohol consumption is likely to be low and alcohol dependence rare. This is shown by many studies of Asian subjects who experience the alcohol flush reaction (AFR) due to inherited aldehyde dehydrogenase (ALDH) deficiency. Alcohol reactions are less common and on average less severe in non-Asian subjects, but they do occur and can affect alcohol consumption. Information about alcohol reactions and their consequences in Europeans is reviewed, and such reactions are compared with those caused by mitochondrial ALDH deficiency in Asians.

Polymorphism of alcohol-metabolizing genes affects drinking behavior and alcoholic liver disease in Japanese men

Alcohol is known to be mainly metabolized in the liver by alcohol dehydrogenase 2 (ADH2) and aldehyde dehydrogenase 2 (ALDH2), and cytochrome P-450IIEI. The purpose of this study was to clarify the role of polymorphism of these ethanol-metabolizing enzymes in drinking behavior and the progression of alcoholic liver disease among Japanese men. Polymorphism of the ADH2, ALDH2, and P-45IIEI genes were determined by polymerase chain reaction, followed by restriction fragment-length polymorphism analysis in 189 normal Japanese men and 26 male patients with alcoholic liver disease. Drinking behavior was estimated by self-assessment according to DSM-III-R criteria. Facial flushing was reported in 91 subjects heterozygous for ALDH2*1/*2 and in two subjects homozygous for ALDH2*2/*2, but was not found in 96 subjects homozygous for ALDH2*1/*1. In contrast, polymorphism of ADH2 and P-450IIEI did not differ between flushers and nonflushers. Although the flushers only drank a small amount of alcohol (< 20 g of ethanol/day), the nonflushers were divided into a group of moderate drinkers (20 to 80 g/day; n = 54) and a group of heavy drinkers (> 80 g/day; n = 42). A high preponderance of heterozygosity for the ADH2*1/*2 genes (20/42; 60%) and a high frequency of the ADH2*1 allele were found in heavy drinkers, compared with moderate drinkers. However, cytochrome P-45IIEI gene polymorphism was similar among the moderate and heavy drinkers. Not only a high frequency of the ALDH2*1 and ADH2*1 alleles, but also a high frequency of the P-450IIEI c2 allele was found in the patients with alcoholic liver disease. From these results, the drinking behavior of Japanese men is strongly influenced by the ALDH2*1 allele, and the level of alcohol intake is affected by the ADH2*1 allele, but not by cytochrome P-45IIEI. However, progression to alcoholic liver disease among heavy drinkers may be affected by the cytochrome P-450IIEI c2 allele.

Catalase and the production of brain acetaldehyde: a possible mediator of the psychopharmacological effects of ethanol

This review represents an attempt to assess the available data on the role of catalase in the mediation of the behavioral actions of ethanol and the regulation of voluntary ethanol consumption. It is argued that acetaldehyde may be formed in brain through the peroxidatic activity of catalase. Furthermore, acetaldehyde formed centrally through the activity of this enzyme, may be responsible, at least in part, for some of the motivational, behavioral and neurotoxic effects of ethanol.

Voice of the victims

Over the past 10 years, I have been privileged to conduct educational forums for audiences containing many recovering alcoholics or otherwise chemically dependent persons. In these forums about the addictive diseases and their treatment and research possibilities, significant interaction with the audience members occurs. During these interactions, certain anecdotal phenomena seem to predominate. The repetitive nature of these reports suggests the need for systematic investigation. As with editorial comments in major medical journals, observed phenomena and unanswered questions from the victims can be valuable in the generation of testable hypotheses. Perhaps the ideas presented herein will be useful in the development of future research on alcohol abuse and alcohol dependence.