Acetaldehyde induces histamine release from purified rat peritoneal mast cells

Aldh2 Attenuates Stem Cell Factor/Kit-Dependent Signaling and Activation in Mast Cells

Mitochondrial aldehyde dehydrogenase (ALDH2) metabolizes endogenous and exogenous aldehydes and protects cells against oxidative injury. Inactivating genetic polymorphisms in humans are common and associate with alcohol flush reactions. However, whether mast cell Aldh2 activity impacts normal mast cell responses is unknown. Using bone marrow-derived mast cells from Aldh2 knockout mice, we found evidence for a role of mast cell Aldh2 in Kit-mediated responses. Aldh2-deficient mast cells showed enhanced Kit tyrosine kinase phosphorylation and activity after stimulation with its ligand (stem cell factor) and augmentation of downstream signaling pathways, including Stat4, MAPKs, and Akt. The activity of the phosphatase Shp-1, which attenuates Kit activity, was reduced in Aldh2^−/− mast cells, along with an increase in reactive oxygen species, known to regulate Shp-1. Reduced Shp-1 activity concomitant with sustained Kit signaling resulted in greater proliferation following Kit engagement, and increased mediator and cytokine release when Aldh2^−/− mast cells were co-stimulated via Kit and FcεRI. However, FcεRI-mediated signaling and responses were unaffected. Therefore, our findings reveal a functional role for mast cell intrinsic Aldh2 in the control of Kit activation and Kit-mediated responses, which may lead to a better understanding of mast cell reactivity in conditions related to ALDH2 polymorphisms.

Thirst sensation and oral dryness following alcohol intake

Substantial acute and chronic intakes of alcohol or ethanol (EtOH) severely influence oral sensations, such as thirst and oral dryness (dry mouth, xerostomia). Thirst sensation and oral dryness are primarily caused by the activation of neurons in brain regions, including the circumventricular organs and hypothalamus, which are referred to as the dipsogenic center, and by a decrease in salivary secretion, respectively. The sensation of thirst experienced after heavy-alcohol drinking is widely regarded as a consequence of EtOH-induced diuresis; however, EtOH in high doses induces anti-diuresis. Recently, it has been proposed that the ethanol metabolite acetaldehyde induces thirst via two distinct processes in the central nervous system from EtOH-induced diuresis, based on the results of animal experiments. The present review describes new insights regarding the induction mechanism of thirst sensation and oral dryness after drinking alcohol.

Update on innate immunity and perspectives on metabolite regulation in acute pancreatitis

PURPOSE OF REVIEW

Acute pancreatitis is a major cause of gastrointestinal morbidity for which specific therapy is greatly needed to prevent progression to and induce resolution of severe disease.

RECENT FINDINGS

Innate immune components and metabolite signaling are recently identified as strong determinants of disease severity and resolution in acute pancreatitis and this work will be discussed herein.

SUMMARY

Targeting innate immune cell populations and metabolite signaling pathways in acute pancreatitis may result in broader and ultimately more efficacious re-direction of the inflammatory programme toward disease resolution and improved clinical outcomes.

Alcohol Intake During Pregnancy and Offspring's Atopic Eczema Risk

BACKGROUND

Although alcohol consumption has been suggested to have an effect on the immune system, it is unknown whether alcohol consumption has a role in developing allergic diseases. We aimed to examine the associations of total alcohol intake during pregnancy with the risks of childhood asthma and atopic eczema in a birth cohort in Japan.

METHODS

Pregnant women were recruited at a maternal clinic from May 2000 to October 2001. The children who were born to these mothers were followed until November 2007. Total alcohol intake, including alcohol as a cooking ingredient, was assessed using 5-day dietary records. Mother reports of physician-diagnosed asthma and atopic eczema were annually obtained from the questionnaires. Asthma assessed by the American Thoracic Society Division of Lung Diseases questionnaire and atopic eczema assessed by International Study of Asthma and Allergies in Childhood questions were also obtained in 2007. A total of 350 children participated in the follow-up survey.

RESULTS

Maternal total alcohol intake during pregnancy was associated with increased risks of atopic eczema before age 3. The positive association with atopic eczema was also observed when it was defined as before age 5. In the high versus the low tertile of maternal total alcohol intake, the estimated hazard ratios (HRs) of child's eczema were 1.90 (95% CI: 0.96 to 3.76) before age 3 and 1.74 (95% CI: 0.93 to 3.24) before age 5, respectively. The estimated HRs of child's asthma before age 3 was 1.61 (95% CI: 0.70 to 3.69) in the high versus the low of maternal total alcohol intake and 2.11 (95% CI: 0.93 to 4.81) among children having drinking mothers versus nondrinking mothers in pregnancy, although maternal alcohol intake during pregnancy was not significantly associated with the risk of asthma before age 5.

CONCLUSIONS

Alcohol consumption during pregnancy might have an effect on developing atopic eczema in offspring.

Serum concentrations of mast cell tryptase are reduced in heavy drinkers

BACKGROUND

Baseline serum tryptase concentrations are commonly used in clinical practice as a marker of the body's mast cell burden. This study aimed to investigate serum tryptase concentrations in heavy drinkers.

METHODS

Serum tryptase concentrations were determined in 126 heavy drinkers (75% males, median age 47 years) who were admitted to the hospital because of alcohol withdrawal syndrome (n = 60), general symptoms with abnormalities on biochemical tests that indicated acute liver disease (n = 19), complications of advanced liver disease (n = 33), and miscellaneous reasons (n = 14). Results were compared with those of 70 healthy controls (66% males, median age 40 years).

RESULTS

Serum tryptase concentrations were lower in heavy drinkers than in healthy controls (median 2.23 μg/l vs. median 3.25 μg/l, p < 0.001). Ten heavy drinkers (7.9%) had undetectable (<1 μg/l) serum tryptase levels versus none of the healthy controls (p = 0.01). The association of low tryptase levels with heavy drinking was independent of age, gender, and smoking status. Among heavy drinkers, the lowest tryptase concentrations were observed in patients with alcohol withdrawal syndrome and patients with general symptoms with abnormalities on biochemical tests that indicated acute liver disease. Furthermore, serum tryptase concentrations were negatively correlated with markers of acute liver damage or alcohol consumption (serum aspartate aminotransferase and gamma-glutamyl transferase). Atopy (skin prick test positivity) was not associated with serum tryptase concentrations in heavy drinkers.

CONCLUSIONS

Serum concentrations of mast cell tryptase are lower in heavy drinkers than in healthy controls.

Regulation of the Cardiovascular System by Histamine

Histamine mediates a wide range of cellular responses, including allergic and inflammatory reactions, gastric acid secretion, and neurotransmission in the central nervous system. Histamine also exerts a series of actions upon the cardiovascular system but may not normally play a significant role in regulating cardiovascular function. During tissue injury, inflammation, and allergic responses, mast cells (or non-mast cells) within the tissues can release large amounts of histamine that leads to noticeable cardiovascular effects. Owing to intensive research during several decades, the distribution, function, and pathophysiological role of cardiovascular H₁- and H₂-receptors has become recognized adequately. Besides the recognized H₁- and H₂-receptor-mediated cardiovascular responses, novel roles of H₃- and H₄-receptors in cardiovascular physiology and pathophysiology have been identified over the last decade. In this review, we describe recent advances in our understanding of cardiovascular function and dysfunction mediated by histamine receptors, including H₃- and H₄-receptors, their potential mechanisms of action, and their pathological significance.

Histamine H4-receptors inhibit mast cell renin release in ischemia/reperfusion via protein kinase C ε-dependent aldehyde dehydrogenase type-2 activation

Renin released by ischemia/reperfusion (I/R) from cardiac mast cells (MCs) activates a local renin-angiotensin system (RAS) causing arrhythmic dysfunction. Ischemic preconditioning (IPC) inhibits MC renin release and consequent activation of this local RAS. We postulated that MC histamine H4-receptors (H4Rs), being Gαi/o-coupled, might activate a protein kinase C isotype-ε (PKCε)-aldehyde dehydrogenase type-2 (ALDH2) cascade, ultimately eliminating MC-degranulating and renin-releasing effects of aldehydes formed in I/R and associated arrhythmias. We tested this hypothesis in ex vivo hearts, human mastocytoma cells, and bone marrow-derived MCs from wild-type and H4R knockout mice. We found that activation of MC H4Rs mimics the cardioprotective anti-RAS effects of IPC and that protection depends on the sequential activation of PKCε and ALDH2 in MCs, reducing aldehyde-induced MC degranulation and renin release and alleviating reperfusion arrhythmias. These cardioprotective effects are mimicked by selective H4R agonists and disappear when H4Rs are pharmacologically blocked or genetically deleted. Our results uncover a novel cardioprotective pathway in I/R, whereby activation of H4Rs on the MC membrane, possibly by MC-derived histamine, leads sequentially to PKCε and ALDH2 activation, reduction of toxic aldehyde-induced MC renin release, prevention of RAS activation, reduction of norepinephrine release, and ultimately to alleviation of reperfusion arrhythmias. This newly discovered protective pathway suggests that MC H4Rs may represent a new pharmacologic and therapeutic target for the direct alleviation of RAS-induced cardiac dysfunctions, including ischemic heart disease and congestive heart failure.

Genetic determinants of both ethanol and acetaldehyde metabolism influence alcohol hypersensitivity and drinking behaviour among Scandinavians

BACKGROUND

Although hypersensitivity reactions following intake of alcoholic drinks are common in Caucasians, the underlying mechanisms and clinical significance are not known. In contrast, in Asians, alcohol-induced asthma and flushing have been shown to be because of a single nucleotide polymorphism (SNP), the acetaldehyde dehydrogenase 2 (ALDH2) 487lys, causing decreased acetaldehyde (the metabolite of ethanol) metabolism and high levels of histamine. However, the ALDH2 487lys is absent in Caucasians.

OBJECTIVES

To investigate the genetic determinants of self-reported alcohol-induced hypersensitivity reactions in Caucasians.

METHODS

The study included two population-based studies of 1216 and 6784 adults living in Copenhagen. Assessment of alcohol consumption and hypersensitivity reactions (in a subgroup) was performed by a questionnaire and was related to common SNPs of genes encoding alcohol dehydrogenases (ADHs) and ALDHs.

RESULTS

In both populations, alcohol drinkers with a genetically determined fast metabolism of ethanol (the A allele of the ADH1b rs1229984) had an increased risk of alcohol-induced hypersensitivity reactions (odds ratio AA/AG vs. GG in combined populations: 1.82, 95% CI 1.04-3.17). In both populations, a common SNP encoding ALDH1b1 (rs2228093) was found to be significantly associated with alcohol-induced hypersensitivity (odds ratio TT vs. CC in combined populations: 2.53, 95% CI 1.31-4.90).

CONCLUSIONS

Our data support that alcohol sensitivity in Caucasians is genetically determined and suggest that a histamine-releasing effect of acetaldehyde represents a plausible biological mechanism. Furthermore, we present the first report of a clinically significant SNP within the acetaldehyde-metabolizing system in a Caucasian population.

Prevalence of self-reported hypersensitivity symptoms following intake of alcoholic drinks

BACKGROUND; Although hypersensitivity symptoms following alcoholic drink consumption are common in asthmatics, the prevalence of such symptoms in the general population is not known.

OBJECTIVE

To assess the prevalence of hypersensitivity symptoms following alcoholic drink consumption in an adult Northern European general population and the association of these symptoms with the prevalence of allergic rhinitis (AR) and asthma.

METHODS

In 2006, a postal questionnaire was sent to a random sample of 18-69-year-olds living in Copenhagen, the capital of Denmark. The response rate was 70.7% (4242/6000).

RESULTS

The prevalence of alcohol-induced symptoms from the upper airways, lower airways, and skin was 7.6% [95% confidence interval (CI): 6.8-8.4%], 3.2% (95% CI: 2.7-3.8%), and 7.2% (95% CI: 6.4-8.9%), respectively. A total of 13.9% (95% CI: 12.9-15.0%) had ever experienced alcohol-induced symptoms from at least one of the three regions (upper airways, lower airways, or skin), and 9.9% (95% CI: 9.0-10.8%) had experienced symptoms in the last 12 months. All types of beverages were commonly reported as triggers of hypersensitivity symptoms, red wine being the most common. Alcohol-induced hypersensitivity symptoms from the upper and lower airways were significantly more prevalent in persons with AR and asthma (odds ratios between 3.0 and 8.1, P-value <0.001 for all associations).

CONCLUSIONS

In this Northern European general population, self-reported hypersensitivity symptoms following the intake of alcoholic drinks are common. These symptoms were markedly more prevalent in persons with AR and asthma. The underlying mechanisms and the clinical significance of these symptoms remain to be elucidated.

Association between alcohol consumption and aeroallergen sensitization in Danish adults

BACKGROUND

It has been proposed that alcohol consumption may be one of the lifestyle factors associated with a westernized, urban, and affluent lifestyle contributing to the rise in atopic disease.

OBJECTIVE

The aim was to investigate the association between alcohol consumption and atopy (aeroallergen sensitization).

METHODS

In 1982, a population-based cross-sectional study of 3608 Danes (79% of the invited), aged 30, 40, 50, and 60 years, was carried out. Information on alcohol consumption was obtained by a questionnaire. Aeroallergen sensitization was defined as a positive test for the detection of specific IgE against a panel of 19 common inhalant allergens in stored serum samples. A total of 3317 subjects with complete information on all variables were included in the analyses.

RESULTS

We found a statistically significant association between alcohol consumption and aeroallergen sensitization (independent of the type of alcoholic drink consumed). This association appeared to relate only to those who consumed more than 8 drinks/week. After adjustment for confounders this association was only statistically significant for those who consumed 15-21 drinks/week (adjusted odds ratio 1.8, 95% confidence interval 1.2-2.8).

CONCLUSION

In this adult general population, self-reported alcohol consumption was positively associated with aeroallergen sensitization.

Impairment of the intestinal barrier by ethanol involves enteric microflora and mast cell activation in rodents

Alcohol hepatic toxicity in heavy drinkers is associated with high endotoxin blood levels and increased intestinal permeability. Because endotoxins can cross damaged mucosa, we investigated the mechanisms through which ethanol impairs the colonic epithelium of rats submitted to acute alcohol intake. Colonic permeability to (51)Cr-ethylenediamintetraacetic acid was increased 24 hours after 3.0 g/kg ethanol intake (3.2 +/- 0.2% versus 2.2 +/- 0.2%) and was associated with significant endotoxemia. Antibiotics and doxantrazole (a mast cell membrane stabilizer) significantly inhibited the effect of ethanol. Two hours after intake, plasma concentrations of ethanol were twofold higher in antibiotic-treated rats than in controls (155.8 +/- 9.3 mg/dl versus 75.7 +/- 7.6 mg/dl, P < 0.001). Lumenal concentrations of acetaldehyde were markedly increased after ethanol intake (132.6 +/- 31.6 micromol/L versus 20.8 +/- 1.4 micromol/L, P < 0.05) and antibiotics diminished this increase (86.2 +/- 10.9 micromol/L). In colonic samples mounted in Ussing chambers, acetaldehyde but not ethanol increased dextran flux across the mucosa by 54%. Doxantrazole inhibited the effect of acetaldehyde. This study demonstrates that an acute and moderate ethanol intake alters the epithelial barrier through ethanol oxidation into acetaldehyde by the colonic microflora and downstream mast cell activation. Such alterations that remain for longer periods could result in excessive endotoxin passage, which could explain the subsequent endotoxemia frequently observed in patients with alcoholic liver disease.

Alcoholism: genes and mechanisms

Alcoholism is a chronic relapsing/remitting disease that is frequently unrecognized and untreated, in part because of the partial efficacy of treatment. Only approximately one-third of patients remain abstinent and one-third have fully relapsed 1 year after withdrawal from alcohol, with treated patients doing substantially better than untreated [1]. The partial effectiveness of strategies for prevention and treatment, and variation in clinical course and side effects, represent a challenge and an opportunity to better understand the neurobiology of addiction. The strong heritability of alcoholism suggests the existence of inherited functional variants of genes that alter the metabolism of alcohol and variants of other genes that alter the neurobiologies of reward, executive cognitive function, anxiety/dysphoria, and neuronal plasticity. Each of these neurobiologies has been identified as a critical domain in the addictions. Functional alleles that alter alcoholism-related intermediate phenotypes include common alcohol dehydrogenase 1B and aldehyde dehydrogenase 2 variants that cause the aversive flushing reaction; catechol-O-methyltransferase (COMT) Val158Met leading to differences in three aspects of neurobiology: executive cognitive function, stress/anxiety response, and opioid function; opioid receptor μ1 (OPRM1) Asn40Asp, which may serve as a gatekeeper molecule in the action of naltrexone, a drug used in alcoholism treatment; and HTTLPR, which alters serotonin transporter function and appears to affect stress response and anxiety/dysphoria, which are factors relevant to initial vulnerability, the process of addiction, and relapse.

Acetaldehyde induces histamine release from human airway mast cells to cause bronchoconstriction

BACKGROUND

Approximately half of the Japanese asthmatics experience exacerbation of asthma after alcohol consumption. We previously reported that this phenomenon is probably caused by histamine release from mast cells by acetaldehyde stimulation. However, no reports have described the effects of acetaldehyde on human airway mast cells. The purpose of the present study was to demonstrate acetaldehyde-induced histamine release from human airway mast cells with subsequent airway smooth muscle contraction and to investigate the ensuing mechanisms.

METHODS

Human tissue samples were prepared from the lungs resected from patients with lung cancer. The effect of acetaldehyde on airway muscle tone and the concentration of chemical mediators released in the organ bath were measured before and after acetaldehyde stimulation. Mast cells were prepared from lung parenchyma by the immunomagnetic method and then stimulated with acetaldehyde to determine the chemical mediators released.

RESULTS

Acetaldehyde (>3 x 10(-4) M) increased airway muscle tone, which was associated with a significant increase in the release of histamine, but not thromboxane B2 or cysteinyl-leukotrienes. A histamine (H1 receptor) antagonist completely inhibited acetaldehyde-induced bronchial smooth muscle contraction. Acetaldehyde also induced a significant histamine release from human lung mast cells and degranulation of mast cells.

CONCLUSIONS

The present results strongly suggest that acetaldehyde stimulates human airway mast cells to release histamine, which may be involved in bronchial smooth muscle contraction following alcohol consumption.

Ethanol causes inflammation in the airways by a neurogenic and TRPV1-dependent mechanism

Ethanol (EtOH) stimulates peptidergic primary sensory neurons via the activation of the transient receptor potential vanilloid-1 (TRPV1). EtOH is also known to trigger attacks of asthma in susceptible individuals. Our aim was to investigate whether EtOH produces airway inflammation via a TRPV1-dependent mechanism and to verify whether this effect is produced via a mechanism distinct from that of acetaldehyde (AcH). EtOH caused a Ca(2+)-dependent release of neuropeptides from guinea pigs airways, an effect that was inhibited by both capsaicin pretreatment and the TRPV1 antagonist capsazepine (CPZ). Furthermore, EtOH contracted isolated guinea pig bronchi, showing efficacy similar to that of carbachol: this effect of EtOH was sensitive to capsaicin pretreatment, tachykinin receptor blockade, and TRPV1 antagonism. The EtOH metabolite AcH also contracted isolated guinea pig bronchi, but this action was not affected by capsaicin pretreatment, tachykinin receptor, or TRPV1 antagonism. EtOH by intravenous or intragastric route of administration caused bronchoconstriction and increased plasma extravasation in the guinea pig airways, effects that were abolished selectively by CPZ. In conclusion, we have demonstrated that EtOH stimulates peptidergic primary sensory neurons in the guinea pig airways by TRPV1 activation. This excitatory effect of EtOH, distinct from that of AcH, results in neurogenic inflammatory responses that may contribute to the mechanism of EtOH-induced asthma.

Relative reactivities of histamine and indoleamines with acetaldehyde

Relative reactivities of histamine and indoleamines such as tryptamine, 5-hydroxytryptamine and 5-methoxytryptamine with acetaldehyde (AA) under physiological conditions were investigated. AA was found to have much higher reactivity towards histamine than towards indoleamines. For example, when a reaction mixture of AA (1 mM) and histamine or tryptamine (5 mM) in 0.1 M phosphate buffer (pH 7.4) was incubated at 37 degrees C for 24 h, AA decreased by 11% in the case of tryptamine, while in the case of histamine, it decreased 88%. In addition, the reaction product of AA with histamine was investigated. Mixtures of a fixed amount of histamine (5 mM) and various amounts of AA (1-20 mM) in phosphate buffer (pH 7.4) were incubated for 5 h at 37 degrees C. In all cases, only one product, 4-methylspinaceamine (4-MSPA), was observed. The yield of 4-MSPA was in approximate agreement with the losses of histamine and AA, indicating that the loss of histamine caused by the reaction of AA was quantatively converted to 4-MSPA. These results show that the reaction of AA with histamine easily takes place to produce 4-MSPA in an aqueous medium close to physiological conditions.

Serum levels of mast cell tryptase, vascular endothelial growth factor and basic fibroblast growth factor in patients with acute pancreatitis

PURPOSE

Mast cell tryptase, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) possibly play a role in the pathogenesis of acute pancreatitis (AP). The aim is to describe their serum levels in relation to severity of AP.

METHODS

Seventy patients with AP were studied. Thirty-one had mild acute pancreatitis and 39 severe AP of whom 21 developed organ dysfunction. Serum concentration of tryptase was determined with fluoroimmunoassay (UniCAP), and VEGF and bFGF with ELISA at admission and on days 1, 2, and 7 post-hospitalization.

RESULTS

The peak tryptase levels and tryptase levels at 2nd day after symptom onset, although mostly within normal range, were significantly higher in patients with organ dysfunction than in patients without organ dysfunction (6.6 microg/l (inter quartile range 4.8 to 12.6) versus 4.0 microg/l (2.7 to 6.2); P = 0.018 and 6.0 microg/l (4.4 to 7.6) versus 3.4 microg/l (2.3 to 4.8); P = 0.006, respectively). Median serum VEGF and bFGF concentrations increased during follow-up, were significantly higher on day 7 than on days 0, 1, and 2, but were not related to development of organ dysfunction.

CONCLUSIONS

Mast cell activation, as defined by serum tryptase levels, may play a role in the development of remote organ dysfunction in patients with AP. However, neither tryptase nor the factors VEGF and bFGF serve as predictors of organ dysfunction in clinical AP.

The relationship of alcohol consumption to total immunoglobulin E and the development of immunoglobulin E sensitization: the Copenhagen Allergy Study

BACKGROUND

Several studies in patient populations have reported a positive association between alcohol consumption and serum total IgE. Furthermore, we have previously reported a positive association between alcohol consumption and the prevalence of skin prick test (SPT positivity) to inhalant allergens in a population-based cross-sectional study.

OBJECTIVE

To investigate the relationship of alcohol consumption to levels of serum total IgE and the development of IgE sensitization to inhalant allergens.

METHODS

In 1990, self-reported consumption of alcohol, serum total IgE, SPT positivity and specific IgE positivity to inhalant allergens were assessed in 1112 subjects, aged 15-69 years, participating in a population-based cross-sectional study in Copenhagen, Denmark. In 1998, they were invited to a follow-up and 734 were re-examined (participation rate 69.0%). Adjustment for potential confounders was performed by using multivariable regression analyses.

RESULTS

In non-atopic (specific IgE negative) subjects there was a positive association between alcohol consumption and the concentration of total IgE (P = 0.001). During the follow-up period, 45 and 33 subjects developed SPT positivity and specific IgE positivity, respectively. There was no significant association between alcohol consumption and the development of SPT positivity or specific IgE positivity. However, the risk of developing SPT positivity tended to increase with increasing consumption of alcohol (P = 0.055).

CONCLUSIONS

This epidemiological study confirms that alcohol consumption has an influence on levels of serum total IgE. A significant association between alcohol consumption and the development of IgE sensitization was not established. However, there seems to be a lack epidemiological data on this issue.

Ethanol as a cause of hypersensitivity reactions to alcoholic beverages

BACKGROUND

Adverse reactions after ingestion of alcoholic beverages are common. Metabolic differences in individuals and also the histamine content in alcoholic beverages have been implicated. By contrast pure ethanol has rarely been reported as a cause of hypersensitivity reactions and its mechanism has not been clarified yet.

OBJECTIVE

To determine whether ethanol itself accounts for alcohol hypersensitivity in patients with anaphylactic reactions after alcohol intake. In search of possible pathomechanisms all patients were analysed by skin prick testing and sulfidoleukotriene production of peripheral leucocytes using ethanol and its metabolites.

METHODS

Double-blind, placebo-controlled food challenges with a cumulated amount of 30 mL ethanol were performed in 12 adult patients with a positive history of adverse reactions after consumption of different alcoholic beverages. Skin prick tests and measurement of sulfidoleukotriene production were performed using different concentrations of ethanol and acetaldehyde from 50 to 1000 mm.

RESULTS

Oral challenges with pure ethanol were positive in six out of eleven patients. All challenge-positive patients, but also four out of five challenge-negative patients, showed an increased sulfidoleukotriene production in-vitro compared with healthy controls. Skin prick tests using alcoholic beverages, ethanol, acetaldehyde and acetic acid were negative in all patients (12/12).

CONCLUSION

Our study shows that ethanol itself is a common causative factor in hypersensitivity reactions to alcoholic beverages. These reactions occur dose-dependent and a non-IgE-mediated pathomechanism is likely, because skin prick tests were negative in all cases. Increased sulfidoleukotriene production was determined in some patients, but is no reliable predictor. Therefore oral provocation tests remain indispensable in making the diagnosis of ethanol hypersensitivity.

Lack of disulfiram-like reaction with metronidazole and ethanol

BACKGROUND

Metronidazole, an effective antianaerobic agent, has been reported to have aversive properties when ingested with ethanol. This is thought to be due to the blocking of hepatic aldehyde dehydrogenase (ALDH) enzyme followed by the accumulation of acetaldehyde in the blood. However, based on animal studies and on only 10 human case reports, the existence of metronidazole-related disulfiram-like reaction has recently been questioned.

OBJECTIVE

To investigate the possible disulfiram-like properties of metronidazole and ethanol in human volunteers.

METHODS

Of 12 healthy male volunteers in this double-blind study, one-half received metronidazole for 5 days and the other half received placebo. All volunteers received ethanol 0.4 g/kg at the beginning of the study. Repeated blood samples were taken every 20 minutes for 4 hours, and blood acetaldehyde and ethanol concentrations were determined. Blood pressure, heart rate, and skin temperature were also measured every 20 minutes for objective signs of a possible disulfiram-like reaction. Volunteers also completed a questionnaire focusing on the subjective signs of disulfiram-like reaction.

RESULTS

Metronidazole did not raise blood acetaldehyde or have any objective or subjective adverse effects when used together with ethanol.

CONCLUSIONS

This study shows that metronidazole does not have an effect on blood acetaldehyde concentrations when ingested with ethanol and does not have any objective or subjective disulfiram-like properties. However, it is possible that disulfiram-like reaction can occur in some subgroups and by other mechanisms than the inhibition of hepatic ALDH.

Metronidazole increases intracolonic but not peripheral blood acetaldehyde in chronic ethanol-treated rats

BACKGROUND

Metronidazole leads to the overgrowth of aerobic flora in the large intestine by reducing the number of anaerobes. According to our previous studies, this shift may increase intracolonic bacterial acetaldehyde formation if ethanol is present. Metronidazole is also reported to cause disulfiram-like effects after alcohol intake, although the mechanism behind this is obscure. Therefore, the aim was to study the effect of long-term metronidazole and alcohol treatment on intracolonic acetaldehyde levels and to explore the possible role of intestinal bacteria in the metronidazole related disulfiram-like reaction.

METHODS

A total of 32 rats were divided into four groups: controls (n = 6), controls receiving metronidazole (n = 6), ethanol group (n = 10), and ethanol and metronidazole group (n = 10). All rats were pair-fed with the liquid diet for 6-weeks, whereafter blood and intracolonic acetaldehyde levels and liver and colonic mucosal alcohol (ADH) and aldehyde dehydrogenase (ALDH) activities were analyzed.

RESULTS

The rats receiving ethanol and metronidazole had five times higher intracolonic acetaldehyde levels than the rats receiving only ethanol (431.4 +/- 163.5 microM vs. 84.7 +/- 14.4 microM,p = 0.0035). In contrast, blood acetaldehyde levels were equal. Cecal cultures showed the increased growth of Enterobacteriaceae in the metronidazole groups. Metronidazole had no inhibitory effect on hepatic or colonic mucosal ADH and ALDH activities.

CONCLUSIONS

The increase in intracolonic acetaldehyde after metronidazole treatment is probably due to the replacement of intestinal anaerobes by ADH-containing aerobes. Unlike disulfiram, metronidazole neither inhibits liver ALDH nor increases blood acetaldehyde. Thus, our findings suggested that the mechanism behind metronidazole related disulfiram-like reaction might be located in the gut flora instead of the liver.