Short-term salivary acetaldehyde increase due to direct exposure to alcoholic beverages as an additional cancer risk factor beyond ethanol metabolism

The role of periodontitis in cancer development, with a focus on oral cancers

Periodontitis is a severe gum infection that begins as gingivitis and can lead to gum recession, bone loss, and tooth loss if left untreated. It is primarily caused by bacterial infection, which triggers inflammation and the formation of periodontal pockets. Notably, periodontitis is associated with systemic health issues and has been linked to heart disease, diabetes, respiratory diseases, adverse pregnancy outcomes, and cancers. Accordingly, the presence of chronic inflammation and immune system dysregulation in individuals with periodontitis significantly contributes to the initiation and progression of various cancers, particularly oral cancers. These processes promote genetic mutations, impair DNA repair mechanisms, and create a tumor-supportive environment. Moreover, the bacteria associated with periodontitis produce harmful byproducts and toxins that directly damage the DNA within oral cells, exacerbating cancer development. In addition, chronic inflammation not only stimulates cell proliferation but also inhibits apoptosis, causes DNA damage, and triggers the release of pro-inflammatory cytokines. Collectively, these factors play a crucial role in the progression of cancer in individuals affected by periodontitis. Further, specific viral and bacterial agents, such as hepatitis B and C viruses, human papillomavirus (HPV), Helicobacter pylori (H. pylori), and Porphyromonas gingivalis, contribute to cancer development through distinct mechanisms. Bacterial infections have systemic implications for cancer development, while viral infections provoke immune and inflammatory responses that can lead to genetic mutations. This review will elucidate the link between periodontitis and cancers, particularly oral cancers, exploring their underlying mechanisms to provide insights for future research and treatment advancements.

Adolescent alcohol use is associated with differences in the diversity and composition of the oral microbiome

BACKGROUND

Adolescence is a sensitive stage of oral microbial development that often coincides with the initiation and escalation of alcohol use. Thus, adolescents may be particularly susceptible to alcohol-induced alterations in the oral microbiome, though minimal research has been done in this area. Understanding the connection between the oral microbiome and alcohol use during adolescence is important to understand fully the biological consequences of alcohol use to mitigate potential adverse outcomes.

METHODS

Saliva samples were collected from adolescents aged 17-19 who used alcohol heavily (n = 21, 52.4% female) and those who did not use alcohol or any other substances (n = 18, 44.4% female). We utilized 16S rRNA sequencing to examine differences in microbial diversity and composition between the groups.

RESULTS

For alpha diversity, evenness was significantly lower in the drinking group than the control group as indicated by Pielou's evenness, Shannon, and Simpson indices. There were no statistically significant findings for beta diversity. Differential abundance analyses revealed higher abundances of Rothia and Corynebacterium in the alcohol-using group using both centered-log-ratio and relative abundance normalization. These genera are known for their high capacity to convert alcohol into acetaldehyde, a toxic metabolite reported to play a role in the neurobiological effects of alcohol. An unclassified Clostridia UCG-014, Streptobacillus, Comamonas, unclassified Lachnospiraceae, and Parvimonas were also identified as significantly different between groups when using only one of the normalization techniques.

CONCLUSIONS

This is the first study designed specifically to compare the oral microbiome of adolescents who use alcohol with that of control participants. Our findings reveal distinct alcohol-related differences in microbial composition and taxon abundance, emphasizing the importance of understanding the impact on the oral microbiome of alcohol use during adolescence. Because the oral microbiome is malleable, this study provides foundational work for future prevention and intervention studies.

Homologous recombination contributes to the repair of acetaldehyde-induced DNA damage

Acetaldehyde, a chemical that can cause DNA damage and contribute to cancer, is prevalently present in our environment, e.g. in alcohol, tobacco, and food. Although aldehyde potentially promotes crosslinking reactions among biological substances including DNA, RNA, and protein, it remains unclear what types of DNA damage are caused by acetaldehyde and how they are repaired. In this study, we explored mechanisms involved in the repair of acetaldehyde-induced DNA damage by examining the cellular sensitivity to acetaldehyde in the collection of human TK6 mutant deficient in each genome maintenance system. Among the mutants, mismatch repair mutants did not show hypersensitivity to acetaldehyde, while mutants deficient in base and nucleotide excision repair pathways or homologous recombination (HR) exhibited higher sensitivity to acetaldehyde than did wild-type cells. We found that acetaldehyde-induced RAD51 foci representing HR intermediates were prolonged in HR-deficient cells. These results indicate a pivotal role of HR in the repair of acetaldehyde-induced DNA damage. These results suggest that acetaldehyde causes complex DNA damages that require various types of repair pathways. Mutants deficient in the removal of protein adducts from DNA ends such as TDP1-/- and TDP2-/- cells exhibited hypersensitivity to acetaldehyde. Strikingly, the double mutant deficient in both TDP1 and RAD54 showed similar sensitivity to each single mutant. This epistatic relationship between TDP1-/- and RAD54-/- suggests that the protein-DNA adducts generated by acetaldehyde need to be removed for efficient repair by HR. Our study would help understand the molecular mechanism of the genotoxic and mutagenic effects of acetaldehyde.

Enhanced Expression of Alcohol Dehydrogenase I in Pichia pastoris Reduces the Content of Acetaldehyde in Wines

Acetaldehyde is an important carbonyl compound commonly detected in wines. A high concentration of acetaldehyde can affect the flavor of wines and result in adverse effects on human health. Alcohol dehydrogenase I (ADH1) in Saccharomyces cerevisiae catalyzes the reduction reaction of acetaldehyde into ethanol in the presence of cofactors, showing the potential to reduce the content of acetaldehyde in wines. In this study, ADH1 was successfully expressed in Pichia pastoris GS115 based on codon optimization. Then, the expression level of ADH1 was enhanced by replacing its promoter with optimized promoters and increasing the copy number of the expression cassette, with ADH1 being purified using nickel column affinity chromatography. The enzymatic activity of purified ADH1 reached 605.44 ± 44.30 U/mg. The results of the effect of ADH1 on the content of acetaldehyde in wine revealed that the acetaldehyde content of wine samples was reduced from 168.05 ± 0.55 to 113.17 ± 6.08 mg/L with the addition of 5 mM NADH and the catalysis of ADH1, and from 135.53 ± 4.08 to 52.89 ± 2.20 mg/L through cofactor regeneration. Our study provides a novel approach to reducing the content of acetaldehyde in wines through enzymatic catalysis.

Acetaldehyde as a Food Flavoring Substance: Aspects of Risk Assessment

The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) has reviewed the currently available data in order to assess the health risks associated with the use of acetaldehyde as a flavoring substance in foods. Acetaldehyde is genotoxic in vitro. Following oral intake of ethanol or inhalation exposure to acetaldehyde, systemic genotoxic effects of acetaldehyde in vivo cannot be ruled out (induction of DNA adducts and micronuclei). At present, the key question of whether acetaldehyde is genotoxic and mutagenic in vivo after oral exposure cannot be answered conclusively. There is also insufficient data on human exposure. Consequently, it is currently not possible to reliably assess the health risk associated with the use of acetaldehyde as a flavoring substance. However, considering the genotoxic potential of acetaldehyde as well as numerous data gaps that need to be filled to allow a comprehensive risk assessment, the SKLM considers that the use of acetaldehyde as a flavoring may pose a safety concern. For reasons of precautionary consumer protection, the SKLM recommends that the scientific base for approval of the intentional addition of acetaldehyde to foods as a flavoring substance should be reassessed.

Alcohol consumption and oral microbiome composition in a sample of healthy young adults

The oral microbiomes of 24 healthy adults (50% female; mean age = 24.3) were examined using 16 s ribosomal RNA sequencing and compared between light and heavy drinkers. Beta diversity was related at the trend level to drinking group, and light drinkers had significantly higher abundances of key oral taxa such as Lactobacillales. These preliminary results may offer insight into early effects of heavy drinking on the composition of the oral microbiome.

The p53 DNA damage response and Fanconi anemia DNA repair pathway protect against acetaldehyde-induced replication stress in esophageal keratinocytes

Alcohol contributes to cellular accumulation of acetaldehyde, a primary metabolite of alcohol and a major human carcinogen. Acetaldehyde can form DNA adducts and induce interstrand crosslinks (ICLs) that are repaired by the Fanconi anemia DNA repair pathway (FA pathway). Individuals with deficiency in acetaldehyde detoxification or in the FA pathway have an increased risk of squamous-cell carcinomas (SCCs) including those of the esophagus. In a recent report, we described the molecular basis of acetaldehyde-induced DNA damage in esophageal keratinocytes [1]. We demonstrated that, at physiologically relevant concentrations, acetaldehyde induces DNA damage at the DNA replication fork. This resulted in replication stress, leading to activation of the ATR-Chk1-dependent cell cycle checkpoints. We also reported that the p53 DNA damage response is elevated in response to acetaldehyde and that the FA pathway limits acetaldehyde-induced genomic instability. Here, we highlight these findings and present additional results to discuss the role of the FA pathway and p53 DNA damage response in the protection against genomic instability and esophageal carcinogenesis.

Stellungnahme zu Acetaldehyd als Aromastoff: Aspekte der Risikobewertung

Opinion on acetaldehyde as a flavouring substance: considerations for risk assessment

Acetaldehyde occurs naturally in many foods and is also used as a flavouring due to its fruity aroma. The International Agency for Research on Cancer (IARC) classified acetaldehyde as possibly carcinogenic to humans and, in combination with oral intake via alcoholic beverages, as carcinogenic to humans. Therefore, the question arises whether the use of acetaldehyde as a flavouring agent is still justifiable. The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) reviewed the scientific basis for health risk assessment of the use of acetaldehyde as a flavouring substance and adopted an opinion. Based on the available data, it is at present not possible to conclude if acetaldehyde is genotoxic and mutagenic in vivo after oral exposure. There is also uncertainty regarding the contribution of acetaldehyde as a flavouring substance to the overall exposure to acetaldehyde. Therefore, a science-based assessment on health risk related to the use of acetaldehyde as a flavouring is not possible at present. Considering the genotoxic potential as well as numerous data gaps that need to be closed for a full risk assessment, the SKLM is concerned about the safety of acetaldehyde as a flavouring substance. For reasons of precautionary consumer protection, the SKLM considers that the use of acetaldehyde as a food additive should be re-evaluated.

FANCD2 limits acetaldehyde-induced genomic instability during DNA replication in esophageal keratinocytes

Individuals with Fanconi anemia (FA), a rare genetic bone marrow failure syndrome, have an increased risk of young-onset head and neck squamous cell carcinomas (SCCs) and esophageal SCC. The FA DNA repair pathway is activated upon DNA damage induced by acetaldehyde, a chief alcohol metabolite and one of the major carcinogens in humans. However, the molecular basis of acetaldehyde-induced genomic instability in SCCs of the head and neck and of the esophagus in FA remains elusive. Here, we report the effects of acetaldehyde on replication stress response in esophageal epithelial cells (keratinocytes). Acetaldehyde-exposed esophageal keratinocytes displayed accumulation of DNA damage foci consisting of 53BP1 and BRCA1. At physiologically relevant concentrations, acetaldehyde activated the ATR-Chk1 pathway, leading to S- and G2/M-phase delay with accumulation of the FA complementation group D2 protein (FANCD2) at the sites of DNA synthesis, suggesting that acetaldehyde impedes replication fork progression. Consistently, depletion of the replication fork protection protein Timeless led to elevated DNA damage upon acetaldehyde exposure. Furthermore, FANCD2 depletion exacerbated replication abnormalities, elevated DNA damage, and led to apoptotic cell death, indicating that FANCD2 prevents acetaldehyde-induced genomic instability in esophageal keratinocytes. These observations contribute to our understanding of the mechanisms that drive genomic instability in FA patients and alcohol-related carcinogenesis, thereby providing a translational implication in the development of more effective therapies for SCCs.

Alcohol Drinking Pattern and Risk of Head and Neck Cancer: A Nationwide Cohort Study

Alcohol consumption is a major risk factor for head and neck cancer (HNC), yet little data exist examining drinking patterns and HNC risk. In this population-based, retrospective cohort study, 11,737,467 subjects were recruited from the Korean National Health Insurance Service database. The risks of overall HNC and HNC subtypes according to average alcohol consumption, drinking frequency, and daily amount were examined using Cox proportional hazard models. Over the median follow-up of 6.4 years, 15,832 HNC cases were identified. HNC risk linearly increased with drinking frequency (p-trend < 0.01; adjusted hazard ratio [aHR] 1.55, 95% confidence interval [CI] 1.45–1.67 in subjects who drank 7 days/week). HNC risk also increased according to daily amount of alcohol consumption (p-trend < 0.01), but plateaued from 5–7 units/occasion (aHR 1.25, 95% CI 1.19–1.31) to >14 units/occasion (aHR 1.26, 95% CI 1.13–1.40). When stratified by average alcohol consumption, drinking frequency, but not daily amount, showed a linear relationship with HNC risk in moderate and heavy drinkers. When comparing the HNC subtypes, similar tendencies were observed in cancers of the oral cavity, pharynx, and larynx, but not in the salivary gland. In conclusion, drinking frequency is a stronger risk factor for HNC, especially for cancer of the oral cavity, pharynx, and larynx, than the daily amount of alcohol consumption.

Free radical-mediated acetaldehyde formation by model reactions of dietary components: effects of meat, wine, cooking oil and coffee

Background

Alcohol consumption and the ingestion of red meat and oxidized cooking oil are risk factors of gastric and colorectal cancers. We reported that acetaldehyde (AcAld) is generated from Heme/Mb/Meat-Linoleate-EtOH model reaction mixtures, and thus could be a new plausible mechanism for the carcinogenesis (Kasai and Kawai, ACS Omega, 2021).

Results

In this study, we investigated the effects of wine and coffee, in addition to meat components, on this reaction. Depending on the conditions, such as pH, reaction time and choice of free hemin, myoglobin (Mb), as well as meat extracts (raw meat, baked meat, salami), wine and coffee enhanced AcAld formation. Polyphenols in red wine and coffee may stimulate AcAld formation by acting as pro-oxidants in the presence of Heme/Mb/Meat. In a model reaction of Mb + EtOH + H₂O₂, we observed time-dependent AcAld formation. In support of these in vitro data, after the consumption of a red meat-rich diet with red wine, the fecal AcAld level significantly increased as compared to the levels associated with a diet of fish + wine, or red meat without alcohol.

Conclusions

These results suggested that AcAld generation from dietary components may be an important mechanism of gastrointestinal tract carcinogenesis.

Bifacial biological effects of ethanol: acetaldehyde production by oral Streptococcus species and the antibacterial effects of ethanol against these bacteria

Background:Many previous studies have focused on the acetaldehyde produced from ethanol by oral bacteria as a risk factor for oral cancer. Most of these studies involved low ethanol concentrations (ca. 10 mM), but oral bacteria are exposed to a wide range of ethanol concentrations (100–10,000 mM) when alcoholic beverages are consumed. In contrast, ethanol is widely used at high concentrations (> 5,000 mM) as an antiseptic/disinfectant, suggesting that ethanol has bifacial biological effects; i.e. it acts as both a metabolic substrate for bacterial acetaldehyde production and an antimicrobial agent.

Materials and methods:We examined the acetaldehyde production from ethanol by oral streptococci and the effects of ethanol exposure on the growth and viability of these bacteria at a wide range of ethanol concentrations (10–10,000 mM).

Results:Acetaldehyde production was the highest at an ethanol concentration of 2,000 mM (2.1–48-fold higher than that seen at an ethanol concentration of 10 mM). Bacterial growth was inhibited by > 1,000 mM of ethanol, and the bacteria did not seem viable in the presence of > 5,000 mM of ethanol, although they still produced acetaldehyde.

Conclusion:Ethanol has bifacial biological effects, and the concentration ranges of these effects overlap.

New Plausible Mechanism for Gastric and Colorectal Carcinogenesis: Free Radical-Mediated Acetaldehyde Generation in a Heme/Myoglobin-Linoleate-Ethanol Mixture

Epidemiological studies have revealed that alcohol, red meat, and cooking oil (or linoleate) are risk factors for both gastric and colon cancers. A survey of the mutation spectra of the p53 tumor suppressor gene in these cancers suggested that the types of mutations and the hot spots are similar to those induced by acetaldehyde (AcAld) in an in vitro p53 mutation analysis system. Accordingly, various combinations of possible factors, components, or model compounds were reacted in an emulsion and tested for the generation of AcAld. Efficient AcAld formation was only observed with combinations of three factors, red meat homogenate (or heme/myoglobin), methyl linoleate, and ethanol, but not by any combination of the two. The generated AcAld levels (ca. 500 μM) far exceeded the minimum mutagenic concentration (40-100 μM) obtained using concentrations of meat homogenate (or heme/Mb), linoleate, and ethanol comparable to those in the stomach after an ordinary meal. A mutagenic level of AcAld (75 μM) was also generated with a physiological concentration of ethanol, heme, and linoleate in the colon. As a mechanism, linoleate hydroperoxide formation and its decomposition in the presence of myoglobin (or heme) to generate the OH radical seem to be involved in the ethanol-to-AcAld conversion.

Interventions to prevent periodontal disease in tobacco-, alcohol-, and drug-dependent individuals

Substance abuse affects more than one sixth of the world's population. More importantly, the nature of the abuse and the type of addictive substances available to individuals is increasing exponentially. All substances with abusive potential impact both the human immuno-inflammatory system and oral microbial communities, and therefore play a critical role in the etiopathogenesis of periodontal diseases. Evidence strongly supports the efficacy of professionally delivered cessation counseling. Dentists, dental therapists, and hygienists are ideally placed to deliver this therapy, and to spearhead efforts to provide behavioral and pharmacologic support for cessation. The purpose of this review is to examine the biologic mechanisms underlying their role in disease causation, to understand the pharmacologic and behavioral basis for their habituation, and to investigate the efficacy of population-based and personalized interventions in prevention of periodontal disease.

The interplay of the oral microbiome and alcohol consumption in oral squamous cell carcinomas

Oral cancer (OC) is among the top twenty occurring cancers in the world, with a mortality rate of 50%. A shift to a functionally inflammatory or a 'disease state' oral microbiome composition has been observed amongst patients with premalignant disorders and OC, with evidence suggesting alcohol could be exacerbating the inflammatory influence of the oral microorganisms. Alcohol dehydrogenase (ADH, EC 1.1.1.1) converts alcohol into a known carcinogenic metabolite, acetaldehyde and while ADH levels in oral mucosa are low, several oral commensal species possess ADH and could produce genotoxic levels of acetaldehyde. With a direct association between oral microbiome status, alcohol and poor oral health status combining to induce chronic inflammation with increased acetaldehyde levels - this leads to a tumour promoting environment. This new disease state increases the production of reactive oxygen species (ROS), while impairing anti-oxidant systems thus activating the redox signalling required for the promotion and survival of tumours. This review aims to highlight the evidence linking these processes in the progression of oral cancer.

Influence of Alcohol Content and Storage Conditions on the Physicochemical Stability of Spirit Drinks

The purpose of this study was to investigate the effects of alcohol by volume (ABV) and storage temperature on changes in the clarity of rye and plum distillates, and their content of volatile compounds. Distillates with initial ABVs of 93.26% v/v (rye distillate) and 82.03% v/v (plum distillate) were diluted with deionized water to 40, 50, and 70% v/v. The samples were stored in darkness at different temperatures (−18 °C, 0 °C, 8 °C, 20 °C) for 8 weeks. The results showed that reducing the alcohol content and storage temperature caused turbidity to increase. The samples prepared from rye distillate were characterized by significantly lower turbidity than those produced from plum distillate. The highest increase in turbidity in comparison to the controls was observed in the samples with 40% v/v alcohol content stored at a temperature of −18 °C. Storage of the rye and plum distillates samples at different temperatures resulted in changes to the concentrations of volatile compounds, i.e., lower levels of acetaldehyde and higher alcohols, and increased content of esters. However, the alcohol content and storage temperature had no statistically significant effect on methanol concentration.

Wine Consumption and Oral Cavity Cancer: Friend or Foe, Two Faces of Janus

The health benefits of moderate wine consumption have been extensively studied during the last few decades. Some studies have demonstrated protective associations between moderate drinking and several diseases including oral cavity cancer (OCC). However, due to the various adverse effects related to ethanol content, the recommendation of moderate wine consumption has been controversial. The polyphenolic components of wine contribute to its beneficial effects with different biological pathways, including antioxidant, lipid regulating and anti-inflammatory effects. On the other hand, in the oral cavity, ethanol is oxidized to form acetaldehyde, a metabolite with genotoxic properties. This review is a critical compilation of both the beneficial and the detrimental effects of wine consumption on OCC.

Periodontitis and oral cancer - current concepts of the etiopathogenesis

Gingival tissues are attacked by oral pathogens which can induce inflammatory reactions. The immune-inflammatory responses play essential roles in the patient susceptibility to periodontal diseases. There is a wealth of evidence indicating a link between chronic inflammation and risk of malignant transformation of the affected oral epithelium. Periodontitis is associated with an increased risk of developing chronic systemic conditions including autoimmune diseases and different types of cancers. Besides, some risk factors such as smoking, alcohol consumption and human papilloma virus have been found to be associated with both periodontitis and oral cancer. This review article aimed to study the current concepts in pathogenesis of chronic periodontitis and oral cancer by reviewing the related articles.

Alcohol-based mouthwash as a risk factor of oral cancer: A systematic review

BACKGROUND

Oral and pharynx cancer represent a serious global problem, reaching an incidence of half a million cases annually. The role of tobacco and alcohol have been studied and proven to be one of its risk factors. We also know that mouthwashes contain a variable percentage of alcohol, so there is a reasonable concern about their role in carcinogenesis.

MATERIALS AND METHODS

To answer the PICOS (Population; Intervention; Comparison; Outcomes; Study) question: Do patients (Population) who use alcohol-based mouthwashes (Intervention) compared to those who do not use them (Comparison) have higher acetaldehyde levels in saliva or higher risk of oral cancer development? (Outcomes) Meta-analyses, systematic reviews, randomized and non-randomized clinical trials, case-control studies, and prospective and retrospective cohort studies were included (Study). Two independent authors conducted literature screening through MEDLINE, Scopus and the Cochrane Library, and they also conducted article and data extraction to undertake quality analyses. The main outcome measures were salivary acetaldehyde levels or the risk of oral cancer development. The most relevant data was extracted and the risk of bias from the studies included was also evaluated.

RESULTS

Out of 497 potentially eligible papers, 8 studies were included in the qualitative analysis which include a total of 43,499 subjects: two meta-analyses, a clinical trial, three case-control studies and two cohort studies. One study (n = 3,926) found a relationship between alcohol mouthwash and oral cancer, two studies (n = 25,033) found this relationship when a high frequency of mouthwash was present, three studies (n = 14,482) failed to find this relationship and 2 studies (n = 58) found a temporary increase of acetaldehyde levels in saliva after alcohol mouthwash.

CONCLUSIONS

It cannot be guaranteed that the use of mouthwash represents an independent risk factor for the development of head and neck cancer. However, the risk does increase when it occurs in association with other carcinogenic risk factors.

Alcohol-Derived Acetaldehyde Exposure in the Oral Cavity

Alcohol is classified by the International Agency for Research on Cancer (IARC) as a human carcinogen and its consumption has been associated to an increased risk of liver, breast, colorectum, and upper aerodigestive tract (UADT) cancers. Its mechanisms of carcinogenicity remain unclear and various hypotheses have been formulated depending on the target organ considered. In the case of UADT cancers, alcohol's major metabolite acetaldehyde seems to play a crucial role. Acetaldehyde reacts with DNA inducing modifications, which, if not repaired, can result in mutations and lead to cancer development. Despite alcohol being mainly metabolized in the liver, several studies performed in humans found higher levels of acetaldehyde in saliva compared to those found in blood immediately after alcohol consumption. These results suggest that alcohol-derived acetaldehyde exposure may occur in the oral cavity independently from liver metabolism. This hypothesis is supported by our recent results showing the presence of acetaldehyde-related DNA modifications in oral cells of monkeys and humans exposed to alcohol, overall suggesting that the alcohol metabolism in the oral cavity is an independent cancer risk factor. This review article will focus on illustrating the factors modulating alcohol-derived acetaldehyde exposure and effects in the oral cavity.

Local Acetaldehyde-An Essential Role in Alcohol-Related Upper Gastrointestinal Tract Carcinogenesis

The resident microbiome plays a key role in exposure of the upper gastrointestinal (GI) tract mucosa to acetaldehyde (ACH), a carcinogenic metabolite of ethanol. Poor oral health is a significant risk factor for oral and esophageal carcinogenesis and is characterized by a dysbiotic microbiome. Dysbiosis leads to increased growth of opportunistic pathogens (such as Candida yeasts) and may cause an up to 100% increase in the local ACH production, which is further modified by organ-specific expression and gene polymorphisms of ethanol-metabolizing and ACH-metabolizing enzymes. A point mutation in the aldehyde dehydrogenase 2 gene has randomized millions of alcohol consumers to markedly increased local ACH exposure via saliva and gastric juice, which is associated with a manifold risk for upper GI tract cancers. This human cancer model proves conclusively the causal relationship between ACH and upper GI tract carcinogenesis and provides novel possibilities for the quantitative assessment of ACH carcinogenicity in the human oropharynx. ACH formed from ethanol present in "non-alcoholic" beverages, fermented food, or added during food preparation forms a significant epidemiologic bias in cancer epidemiology. The same also concerns "free" ACH present in mutagenic concentrations in multiple beverages and foodstuffs. Local exposure to ACH is cumulative and can be reduced markedly both at the population and individual level. At best, a person would never consume tobacco, alcohol, or both. However, even smoking cessation and moderation of alcohol consumption are associated with a marked decrease in local ACH exposure and cancer risk, especially among established risk groups.

Key role of local acetaldehyde in upper GI tract carcinogenesis

Ethanol is neither genotoxic nor mutagenic. Its first metabolite acetaldehyde, however, is a powerful local carcinogen. Point mutation in ALDH2 gene proves the causal relationship between acetaldehyde and upper digestive tract cancer in humans. Salivary acetaldehyde concentration and exposure time are the two major and quantifiable factors regulating the degree of local acetaldehyde exposure in the ideal target organ, oropharynx. Instant microbial acetaldehyde formation from alcohol represents >70% of total ethanol associated acetaldehyde exposure in the mouth. In the oropharynx and achlorhydric stomach acetaldehyde is not metabolized to safe products, instead in the presence of alcohol it accumulates in saliva and gastric juice in mutagenic concentrations. A common denominator in alcohol, tobacco and food associated upper digestive tract carcinogenesis is acetaldehyde. Epidemiological studies on upper GI tract cancer are biased, since they miss information on acetaldehyde exposure derived from alcohol and acetaldehyde present in 'non-alcoholic' beverages and food.

A High Resolution/Accurate Mass (HRAM) Data-Dependent MS3 Neutral Loss Screening, Classification, and Relative Quantitation Methodology for Carbonyl Compounds in Saliva

Reactive carbonyl compounds (RCCs) are ubiquitous in the environment and are generated endogenously as a result of various physiological and pathological processes. These compounds can react with biological molecules inducing deleterious processes believed to be at the basis of their toxic effects. Several of these compounds are implicated in neurotoxic processes, aging disorders, and cancer. Therefore, a method characterizing exposures to these chemicals will provide insights into how they may influence overall health and contribute to disease pathogenesis. Here, we have developed a high resolution accurate mass (HRAM) screening strategy allowing simultaneous identification and relative quantitation of DNPH-derivatized carbonyls in human biological fluids. The screening strategy involves the diagnostic neutral loss of hydroxyl radical triggering MS3 fragmentation, which is only observed in positive ionization mode of DNPH-derivatized carbonyls. Unique fragmentation pathways were used to develop a classification scheme for characterizing known and unanticipated/unknown carbonyl compounds present in saliva. Furthermore, a relative quantitation strategy was implemented to assess variations in the levels of carbonyl compounds before and after exposure using deuterated d 3 -DNPH. This relative quantitation method was tested on human samples before and after exposure to specific amounts of alcohol. The nano-electrospray ionization (nano-ESI) in positive mode afforded excellent sensitivity with detection limits on-column in the high-attomole levels. To the best of our knowledge, this is the first report of a method using HRAM neutral loss screening of carbonyl compounds. In addition, the method allows simultaneous characterization and relative quantitation of DNPH-derivatized compounds using nano-ESI in positive mode. Graphical Abstract ᅟ.

ALDH2-deficiency as genetic epidemiologic and biochemical model for the carcinogenicity of acetaldehyde

Humans are cumulatively exposed to acetaldehyde from various sources including alcoholic beverages, tobacco smoke, foods and beverages. The genetic-epidemiologic and biochemical evidence in ALDH2-deficient humans provides strong evidence for the causal relationship between acetaldehyde-exposure due to alcohol consumption and cancer of the upper digestive tract. The risk assessment has so far relied on thresholds based on animal toxicology with lower one-sided confidence limit of the benchmark dose values (BMDL) typically ranging between 11 and 63 mg/kg bodyweight (bw)/day dependent on species and endpoint. The animal data is problematic for regulatory toxicology for various reasons (lack in study quality, problems in animal models and appropriateness of endpoints - especially cancer - for transfer to humans). In this study, data from genetic epidemiologic and biochemical studies are reviewed. The increase in the daily exposure dose to acetaldehyde in alcohol-consuming ALDH2-deficients vs. ALDH2-actives was about twofold. The acetaldehyde increase due to ALDH2 inactivity was calculated to be 6.7 μg/kg bw/day for heavy drinkers, which is associated with odds ratios of up to 7 for head and neck as well as oesophageal cancer. Previous animal toxicology based risk assessments may have underestimated the risk of acetaldehyde. Risk assessments of acetaldehyde need to be revised using this updated evidence.

Isotopic separation of acetaldehyde and methanol from their deuterated isotopologues on a porous layer open tubular column allows quantification by stable isotope dilution without mass spectrometric detection

An isotopic separation of acetaldehyde and acetaldehyde-2,2,2-d3 was achieved in a temperature programmed run on a porous layer open tubular (PLOT) capillary column coated with particles of divinylbenzene ethylene glycol/dimethylacrylate (Rt^®-U-BOND). This is the prerequisite for the development of quantitative analytical methods based on a stable isotope dilution assay (SIDA) without a mass spectrometric detection (non-MS SIDA). For routine analysis a flame ionization detector (FID) can thus be applied as a robust and low-cost alternative. In a preliminary study, static headspace extraction and gas chromatographic separation (HS-GC-FID) of acetaldehyde in aqueous solutions was shown as an application. Good linearity was obtained in a calibration range from 0.4 to 40mgL^-1, with peak integration benefitting from the inverse isotope effect encountered on the specific porous polymer. Furthermore, separation of methanol and deuterated methanol (d3) could also be achieved under the same chromatographic conditions. The achieved isotopic separation of these important volatile compounds now allows non-MS SIDA-based methods that are still to be developed.

European Code against Cancer 4th Edition: Alcohol drinking and cancer

Alcohol consumption is the third leading risk factor for disease and mortality in Europe. As evaluated by the International Agency for Research on Cancer (IARC) Monographs, a causal relationship is established for consumption of alcoholic beverages and cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colorectum and female breast, even at low and moderate alcohol intakes. The higher the amount of alcohol consumed, the higher the risk of developing cancer. In Europe, an estimated 10% (95% CI: 7%-13%) of all cancer cases in men and 3% (95% CI: 1%-5%) of all cancer cases in women are attributable to alcohol consumption. Several biological mechanisms explain the carcinogenicity of alcohol; among them, ethanol and its genotoxic metabolite, acetaldehyde, play a major role. Taking all this evidence into account, a recommendation of the 4th edition of European Code against Cancer is: "If you drink alcohol of any type, limit your intake. Not drinking alcohol is better for cancer prevention."

The hydrogen-storing microporous silica 'Microcluster' reduces acetaldehyde contained in a distilled spirit

Acetaldehyde is a detrimental substance produced in alcoholic liquor aging. We assessed an ability of hydrogen-storing microporous silica 'Microcluster' (MC+) to reduce acetaldehyde, as compared with autoclave-dehydrogenated MC+ (MC-). Acetaldehyde was quantified spectrophotometrically by an enzymatic method. Authentic acetaldehyde was treated by MC+ for 20min, and decreased from 43.4ppm to 10.9ppm, but maintained at 49.3ppm by MC-. On the other hand, acetaldehyde contained in a distilled spirit was decreased from 29.5ppm to 3.1ppm at 20min by MC+, but not decreased by MC-. Addition of MC+ or MC- to distilled water without acetaldehyde showed no seeming effect on the quantification used. Accordingly acetaldehyde in a distilled spirit is reduced to ethanol by hydrogen contained in MC+, but not by the silica moiety of MC+. Hydrogen gas of 1.2mL was released for 20min from MC+ of 0.59g in water, resulting in dissolved hydrogen of 1.09ppm and an oxidation- reduction potential of -687.0mV indicative of a marked reducing ability. Thus, MC+ has an ability to reduce acetaldehyde in a distilled spirit due to dissolved hydrogen released from MC+.

Alcoholic Beverage Consumption and Chronic Diseases

Epidemiological and experimental studies have consistently linked alcoholic beverage consumption with the development of several chronic disorders, such as cancer, cardiovascular diseases, diabetes mellitus and obesity. The impact of drinking is usually dose-dependent, and light to moderate drinking tends to lower risks of certain diseases, while heavy drinking tends to increase the risks. Besides, other factors such as drinking frequency, genetic susceptibility, smoking, diet, and hormone status can modify the association. The amount of ethanol in alcoholic beverages is the determining factor in most cases, and beverage types could also make an influence. This review summarizes recent studies on alcoholic beverage consumption and several chronic diseases, trying to assess the effects of different drinking patterns, beverage types, interaction with other risk factors, and provide mechanistic explanations.

Increased levels of the acetaldehyde-derived DNA adduct N 2-ethyldeoxyguanosine in oral mucosa DNA from Rhesus monkeys exposed to alcohol

Alcohol is a human carcinogen. A causal link has been established between alcohol drinking and cancers of the upper aerodigestive tract, colon, liver and breast. Despite this established association, the underlying mechanisms of alcohol-induced carcinogenesis remain unclear. Various mechanisms may come into play depending on the type of cancer; however, convincing evidence supports the concept that ethanol's major metabolite acetaldehyde may play a major role. Acetaldehyde can react with DNA forming adducts which can serve as biomarkers of carcinogen exposure and potentially of cancer risk. The major DNA adduct formed from this reaction is N (2)-ethylidenedeoxyguanosine, which can be quantified as its reduced form N (2)-ethyl-dG by LC-ESI-MS/MS. To investigate the potential use of N (2)-ethyl-dG as a biomarker of alcohol-induced DNA damage, we quantified this adduct in DNA from the oral, oesophageal and mammary gland tissues from rhesus monkeys exposed to alcohol drinking over their lifetimes and compared it to controls. N (2)-Ethyl-dG levels were significantly higher in the oral mucosa DNA of the exposed animals. Levels of the DNA adduct measured in the oesophageal mucosa of exposed animals were not significantly different from controls. A correlation between the levels measured in the oral and oesophageal DNA, however, was observed, suggesting a common source of formation of the DNA adducts. N (2) -Ethyl-dG was measured in mammary gland DNA from a small cohort of female animals, but no difference was observed between exposed animals and controls. These results support the hypothesis that acetaldehyde induces DNA damage in the oral mucosa of alcohol-exposed animals and that it may play role in the alcohol-induced carcinogenic process. The decrease of N (2)-ethyl-dG levels in exposed tissues further removed from the mouth also suggests a role of alcohol metabolism in the oral cavity, which may be considered separately from ethanol liver metabolism in the investigation of ethanol-related cancer risk.

European Code against Cancer 4th Edition: Alcohol drinking and cancer

Alcohol consumption is the third leading risk factor for disease and mortality in Europe. The International Agency for Research on Cancer (IARC) Monographs provide strengthened evidence that the consumption of alcoholic beverages is causally associated with cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colorectum and female breast, even for low and moderate alcohol intakes. The risk of cancer increases in a dose-dependent manner, and the higher the amount of alcohol consumed, the higher the risk of developing cancer. Several biological mechanisms explain the carcinogenicity of alcohol; among them, ethanol and its genotoxic metabolite acetaldehyde play a major role. Taking all this evidence into account, a recommendation of the 4th edition of the European Code against Cancer (ECAC) is: "If you drink alcohol of any type, limit your intake. Not drinking alcohol is better for cancer prevention."

Oral cavity and oropharyngeal squamous cell carcinoma--an update

Oral cavity squamous cell carcinoma (OC-SCC) is the most common malignancy of the head and neck (excluding nonmelanoma skin cancer). Recent trends have shown a dramatic rise in the incidence of oropharyngeal squamous cell carcinoma (OP-SCC), with a marked increase in lesions related to human papillomavirus infection. This update presents the latest evidence regarding OC-SCC and OP-SCC. In particular, the authors compare and contrast tumors at these two sites with respect to epidemiology, etiopathogenesis, clinicopathologic presentation, clinical assessment, imaging, management, and prognosis. It is important for clinicians to be aware of differences between OC-SCC and OP-SCC so that appropriate patient education and multidisciplinary care can be provided to optimize outcomes.

Ethanol versus Phytochemicals in Wine: Oral Cancer Risk in a Light Drinking Perspective

This narrative review aims to summarize the current controversy on the balance between ethanol and phytochemicals in wine, focusing on light drinking and oral cancer. Extensive literature search included PUBMED and EMBASE databases to identify in human studies and systematic reviews (up to March 2015), which contributed to elucidate this issue. Independently from the type of beverage, meta-analyses considering light drinking (≤1 drinks/day or ≤12.5 g/day of ethanol) reported relative risks (RR) for oral, oro-pharyngeal, or upper aero-digestive tract cancers, ranging from 1.0 to 1.3. One meta-analysis measured the overall wine-specific RR, which corresponded to 2.1. Although little evidence exists on light wine intake, phytochemicals seem not to affect oral cancer risk, being probably present below the effective dosages and/or due to their low bioavailability. As expected, the risk of oral cancer, even in light drinking conditions, increases when associated with smoking habit and high-risk genotypes of alcohol and aldehyde dehydrogenases.

Acetaldehyde production capacity of salivary microflora in alcoholics during early recovery

This study investigated whether a relationship exists between the acetaldehyde production capacity of salivary microflora (sAPC) in recovering alcoholics, and craving, and/or resumption of drinking within 12 weeks after embarking on an abstinence-based treatment program. Serial sAPC measurements were determined by gas chromatography on spontaneous saliva samples of 30 male alcoholics on days 2, 4, 11, and 18 during a 21-day in-patient treatment program. Craving was measured simultaneously with the Penn Alcohol Craving Scale. Outcome over 12 weeks was assessed by telephone interviews. There was no significant change in sAPC values from day 2 to day 18, while craving scores decreased markedly between day 2 to day 4. Sixteen participants remained abstinent for the full 12 weeks. Statistically significant differences were found between the sAPC values of the group that remained abstinent and the group that resumed drinking within 12 weeks. The highest sAPC value measured on day 2 had a strong predictive value for maintained abstinence at 12 weeks for beer-only drinkers or drinkers consuming less than 320 g of alcohol per week. The study is the first investigation into a potential relationship between the acetaldehyde production capacity of salivary microflora and early resumption of drinking in recovering alcoholics. The findings suggest that such a relationship indeed exists for beer-only drinkers, possibly linked to lower alcohol intake, and that it is unrelated to withdrawal craving. sAPC is proposed as a candidate biomarker with diagnostic and/or prognostic potential.

Implications of acetaldehyde-derived DNA adducts for understanding alcohol-related carcinogenesis

Among various potential mechanisms that could explain alcohol carcinogenicity, the metabolism of ethanol to acetaldehyde represents an obvious possible mechanism, at least in some tissues. The fundamental principle of genotoxic carcinogenesis is the formation of mutagenic DNA adducts in proliferating cells. If not repaired, these adducts can result in mutations during DNA replication, which are passed on to cells during mitosis. Consistent with a genotoxic mechanism, acetaldehyde does react with DNA to form a variety of different types of DNA adducts. In this chapter we will focus more specifically on N2-ethylidene-deoxyguanosine (N2-ethylidene-dG), the major DNA adduct formed from the reaction of acetaldehyde with DNA and specifically highlight recent data on the measurement of this DNA adduct in the human body after alcohol exposure. Because results are of particular biological relevance for alcohol-related cancer of the upper aerodigestive tract (UADT), we will also discuss the histology and cytology of the UADT, with the goal of placing the adduct data in the relevant cellular context for mechanistic interpretation. Furthermore, we will discuss the sources and concentrations of acetaldehyde and ethanol in different cell types during alcohol consumption in humans. Finally, in the last part of the chapter, we will critically evaluate the concept of carcinogenic levels of acetaldehyde, which has been raised in the literature, and discuss how data from acetaldehyde genotoxicity are and can be utilized in physiologically based models to evaluate exposure risk.

Recent evidence on alcohol and cancer epidemiology

This review presents an overview of the impact of alcohol consumption on cancer risk. Results from the 2009 International Agency for Research on Cancer monograph as well as the most recent meta-analyses and epidemiological studies are considered. Alcohol consumption is one of the most important known risk factors for human cancer and potentially one of the most avoidable factors, but it is increasing worldwide. Ethanol in alcoholic beverages is carcinogenic to humans and causes several cancers (oral cavity, pharynx, larynx, esophagus, colorectum, liver and female breast). Cumulative lifetime consumption, frequency and drinking pattern appear to play a role in risk characterization. While the role of heavy drinking has been long recognized, new evidence suggests that light consumption (up to one drink/day) is also associated with adverse effects. In addition, some genetic polymorphisms interact with alcohol metabolism and may modify its impact.

Risk assessment for the Italian population of acetaldehyde in alcoholic and non-alcoholic beverages

Acetaldehyde is a naturally-occurring carcinogenic compound, present in different food items, especially in alcoholic beverages. The aims of this study were to measure acetaldehyde concentration in different beverages consumed in Italy and to estimate the potential cancer risk. The analytical procedure was based on headspace solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), using the isotopic dilution method. The margin of exposure (MOE) approach of the European Food Safety Authority (EFSA) was used for risk characterisation. The highest concentrations (median, min-max) were detected in grappa samples (499, 23.4-1850mg/l), followed by fruit-based liqueurs and spirits (62.0, 5.23-483mg/l) and wine (68.0, 18.1-477mg/l); the lowest were detected in gin (0.91, 0.78-1.90mg/l). The lowest MOE was estimated for high wine consumers (69). These results suggest that regulatory measures and consumer guidance may be necessary for acetaldehyde in beverages.

Determination of acetaldehyde in saliva by gas-diffusion flow injection analysis

The consumption of ethanol is known to increase the likelihood of oral cancer. In addition, there has been a growing concern about possible association between long term use of ethanol-containing mouthwashes and oral cancer. Acetaldehyde, known to be a carcinogen, is the first metabolite of ethanol and it can be produced in the oral cavity after consumption or exposure to ethanol. This paper reports on the development of a gas-diffusion flow injection method for the online determination of salivary acetaldehyde by its colour reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride. Acetaldehyde samples and standards (80 μL) were injected into the donor stream containing NaCl from which acetaldehyde diffused through the hydrophobic Teflon membrane of the gas-diffusion cell into the acceptor stream containing the two reagents mentioned above. The resultant intense green coloured dye was monitored spectrophotometrically at 600 nm. Under the optimum working conditions the method is characterized by a sampling rate of 9h(-1), a linear calibration range of 0.5-15 mg L(-1) (absorbance=5.40×10(-2) [acetaldehyde, mg L(-1)], R(2)=0.998), a relative standard deviation (RSD) of 1.90% (n=10, acetaldehyde concentration of 2.5 mg L(-1)), and a limit of detection (LOD) of 12.3 μg L(-1). The LOD and sampling rate of the proposed method are superior to those of the conventional gas chromatographic (GC) method (LOD=93.0 μg L(-1) and sampling rate=4 h(-1)). The reliability of the proposed method was illustrated by the fact that spiked with acetaldehyde saliva samples yielded excellent recoveries (96.6-101.9%), comparable to those obtained by GC (96.4-102.3%) and there was no statistically significant difference at the 95% confidence level between the two methods when non-spiked saliva samples were analysed.

Alcohol and acetaldehyde in African fermented milk mursik--a possible etiologic factor for high incidence of esophageal cancer in western Kenya

BACKGROUND

Esophageal cancer is unusually frequent in Western Kenya, despite the low prevalence of classical risk factors such as heavy drinking and tobacco smoking. Among Kenyans consumption of fermented milk is an old tradition. Our hypothesis is that alcohol and acetaldehyde are produced during the fermentation process and that their carcinogenic potential contributes to the high incidence of esophageal cancer.

METHODS

Eight samples of mursik milk starter cultures were collected from different Kalenjin families in the Rift Valley province, Western Kenya. A protocol provided by the families was used for milk fermentation. Ethanol and acetaldehyde levels were measured by gas chromatography. The microbial flora in starter cultures was identified by 16S and 18S sequencing.

RESULTS

7/8 starter cultures produced mutagenic (>100 μmol/L) levels of acetaldehyde and 4/8 starter cultures produced more than 1,000 μmol/L of acetaldehyde. The highest alcohol levels (mean 79.4 mmol/L) were detected in the four fermented milks with highest acetaldehyde production. The mean number of microbial species in the starter cultures was 5 (range 2-8). Yeasts were identified in all starter cultures (mean 1.5 species/milk) but their proportion of the total microbial count varied markedly (mean 35%, range 7%-90%). A combination of yeast and lactobacilli, especially Candida krusei with Lactobacillus kefiri, with the exclusion of other species, seemed to correlate with higher acetaldehyde and ethanol levels.

CONCLUSIONS

Significant levels of ethanol and acetaldehyde were produced during mursik fermentation.

IMPACT

When ingested several times daily the repeated exposure to carcinogenic levels of acetaldehyde may contribute to esophageal carcinogenesis.

Detection of acetaldehyde derived N(2)-ethyl-2'-deoxyguanosine in human leukocyte DNA following alcohol consumption

Epidemiological studies have shown an association between alcohol (ethanol) consumption and increased cancer risk. The effect of alcohol consumption on the levels and persistence of N(2)-ethylidene-2'-deoxyguanosine (N(2)-ethylidene-dG) formed by acetaldehyde, the oxidative metabolite of ethanol, in human leukocyte DNA was investigated. DNA was isolated from venous blood samples obtained from 30 male non-smoking individuals before consumption of alcohol (0h) and subsequently at 3-5h following the consumption of 150mL of vodka (containing 42% pure ethanol). Additional samples were collected 24h and 48h post-alcohol consumption. The levels of N(2)-ethyl-2'-deoxyguanosine (N(2)-ethyl-dG) in the DNA were determined following reduction of N(2)-ethylidene-dG with sodium cyanoborohydride using a liquid chromatography-tandem mass spectrometry selected reaction monitoring method. A slight time-dependent trend showing an increase and decrease in the levels of N(2)-ethyl-dG was observed following consumption of alcohol compared to time 0h, however, the differences were not statistically significant. The average levels of N(2)-ethyl-dG observed at 0h, 3-5h, 24h and 48h time points following ingestion of alcohol were 34.6±21.9, 35.1±21.0, 36.8±20.7 and 35.6±21.1 per 10(8) 2'-deoxynucleosides, respectively. In conclusion, alcohol consumption that could be encountered under social drinking conditions, does not significantly alter the levels of the acetaldehyde derived DNA adduct, N(2)-ethyl-dG in human leukocyte DNA from healthy individuals.

Effect of rinsing with ethanol-containing mouthrinses on the production of salivary acetaldehyde

It has been suggested that the use of alcohol-containing mouthrinses could lead to the presence of acetaldehyde in saliva. In this cross-over study, salivary acetaldehyde levels and microbial profiles were determined before and after rinsing with ethanol-containing mouthrinses with essential oils (EO) and cetyl pyridinium chloride (CPC) as the active ingredients, and with 21.6% ethanol and water controls. After rinsing with all ethanol-containing rinses, acetaldehyde was detected in saliva after 30 s but declined to low levels after 5 min. The highest peak levels were seen with the ethanol control (median = 82.9 μM at 2 min) and were significantly higher than those seen at the same time after rinsing with the EO rinse (43.1 μM). There was no correlation between microbial counts or plaque scores and acetaldehyde levels, although dividing the subjects on the basis of a peak acetaldehyde salivary concentration of > 90.8 μM after the ethanol rinse revealed that the high responders were highly significantly more likely to harbour salivary yeasts than were the low responders. Rinsing with ethanol-containing mouthrinses causes a rapid, but transient, increase in salivary acetaldehyde levels.