Ville Salaspuro

Synergistic effect of alcohol drinking and smoking on in vivo acetaldehyde concentration in saliva

Alcohol drinking and smoking are independent risk factors for upper digestive tract cancers. Furthermore, their combined use interacts in a multiplicative way on cancer risk. There is convincing evidence that acetaldehyde, the first metabolite of ethanol and a constituent of tobacco smoke, is a local carcinogen in humans. Therefore, we examined the combined effect of alcohol drinking and tobacco smoking on in vivo acetaldehyde concentration in saliva. Seven smokers and 6 nonsmokers participated in the study. First, to measure the effect of alcohol on salivary acetaldehyde, all volunteers ingested 0.8 g/kg body weight of ethanol and saliva samples were collected every 20 min for 160 min thereafter. After a 3‐day washout period, smokers ingested again the same amount of ethanol and smoked one cigarette every 20 min and saliva samples were collected at 10 min intervals for 160 min. Acetaldehyde and ethanol concentrations were analyzed by headspace gas chromatograph. Firstly, smokers without concomitant smoking during ethanol challenge had 2 times higher in vivo salivary acetaldehyde concentrations than nonsmokers after ethanol ingestion (AUC 114.8 ± 11.5 vs. 54.2 ± 8.7 μM × hr, respectively; p = 0.002). Secondly, smokers with active smoking during ethanol challenge had 7 times higher in vivo salivary acetaldehyde levels than nonsmokers (AUC 369.5 ± 12.2 vs. 54.2 ± 8.7 μM × hr, respectively; p < 0.001). We conclude that this markedly increased exposure of upper digestive tract mucosa to carcinogenic salivary acetaldehyde of smoking and drinking subjects may explain the synergistic and multiplicative risk effect of alcohol drinking and tobacco smoking on upper gastrointestinal tract carcinogenesis.

Removal of acetaldehyde from saliva by a slow-release buccal tablet of L-cysteine

High alcohol intake is an independent risk factor for upper gastrointestinal (GI)‐tract cancers. There is increasing evidence that acetaldehyde, the first metabolite of ethanol, might be responsible for ethanol‐associated carcinogenesis. Especially among Asian heavy drinkers with the ALDH2‐deficiency gene, i.e., a genetic inability to remove acetaldehyde, the risk of digestive tract cancers is markedly increased. Local acetaldehyde production from ethanol either by oral microbes, mucosal cells or salivary glands is a plausible carcinogenic agent in the saliva. The aim of our study was to examine whether is it possible to bind carcinogenic acetaldehyde from saliva with L‐cysteine, which is slowly released from a special buccal tablet. Nine healthy male volunteers took part in our study, and each subject served as his own control. A placebo or L‐cysteine‐containing tablet was fastened under the upper lip. Thereafter the volunteers ingested 0.8 g/kg of body weight of 10% (v/v) ethanol, and saliva samples were collected at 20 min intervals for 320 min. Salivary acetaldehyde and ethanol levels were analysed by headspace gas chromatography. The mean reduction of acetaldehyde concentration of the saliva with the L‐cysteine tablet compared to placebo was 59% (CL95% 43%, 76%). Area under the curve (AUC0–320min) with the L‐cysteine and placebo tablet were 54.3 ± 11 μM × hr and 162 ± 34.2 μM × hr (mean ± SEM), respectively (p = 0.003). After alcohol intake, up to two‐thirds of carcinogenic acetaldehyde can be removed from saliva with a slow‐releasing buccal L‐cysteine drug formulation. Thus, a buccal cysteine tablet could potentially be used to prevent upper GI‐tract cancers, especially among high‐risk individuals.

Eliminating Carcinogenic Acetaldehyde By Cysteine From Saliva During Smoking

Tobacco smoking is one of the strongest risk factors not only for lung cancer but also for cancers of the upper gastrointestinal tract. Acetaldehyde has been shown to dissolve into the saliva during smoking and to be a local carcinogen in the human upper digestive tract. Cysteine can bind to acetaldehyde and eliminate its toxicity. We developed a tablet that releases cysteine into the oral cavity during smoking and could therefore be a potential chemopreventive agent against toxicity of tobacco smoke. In this study, the efficacy of l-cysteine–containing tablets to reduce the carcinogenic acetaldehyde in the saliva during tobacco smoking was examined. Seven volunteers smoked five cigarettes. During every smoking period, each volunteer sucked a blinded tablet containing 0, 1.25, 2.5, 5, or 10 mg of l-cysteine. Acetaldehyde was analyzed from salivary samples gas chromatographically at 0, 5, and 10 minutes from the beginning of the smoking. All tablets containing l-cysteine reduced highly significantly the salivary acetaldehyde; 5 mg of l-cysteine was the minimum concentration to totally eliminate the acetaldehyde from saliva. The mean salivary acetaldehyde concentrations in samples collected immediately after smoking with 0, 1.25, 2.5, 5, or 10 mg of l-cysteine were 228 ± 115 μmol/L, 85 ± 42 μmol/L (P = 0.007), 9 ± 7 μmol/L, 0.09 ± 0.2 μmol/L, 0 ± 0 μmol/L (P < 0.001), respectively. In conclusion, carcinogenic acetaldehyde could be totally inactivated in the saliva during smoking by sucking tablet containing 5 mg of l-cysteine. Even a small reduction of the carcinogenicity of cigarette smoke could gain benefit at the population level. Hence, this finding warrants for further clinical trials for l-cysteine tablet in the prevention of upper digestive tract cancers in smokers. (Cancer Epidemiol Biomarkers Prev 2006;15(1):146–9)

Formulation and in-vivo evaluation of L-cysteine chewing gums for binding carcinogenic acetaldehyde in the saliva during smoking

Cigarette smoke contains toxic amounts of acetaldehyde that dissolves in saliva, posing a significant risk of developing oral, laryngeal and pharyngeal carcinomas. l‐Cysteine, a non‐essential amino acid, can react covalently with carcinogenic acetaldehyde to form a stable, non‐toxic 2‐methylthiazolidine‐4‐carboxylic acid. The main aim of this study was to find out whether it is possible to develop a chewing gum formulation that would contain cysteine in amounts sufficient to bind all the acetaldehyde dissolved in saliva during the smoking of one cigarette. The main variables in the development process were: (1) chemical form of cysteine (l‐cysteine or l‐cysteine hydrochloride), (2) the amount of the active ingredient in a gum and (3) manufacturing procedure (traditional or novel compression method). Saliva samples were taken over 2.5 minutes before smoking and since smoking was started for 2.5 minutes periods for 10 minutes. During a five minutes smoking period with a placebo chewing gum, acetaldehyde levels increased from 0 to 150–185 μm. Once smoking was stopped, the acetaldehyde levels quickly fell to levels clearly below the in‐vitro mutagenic level of 50 μm. All chewing gums containing cysteine could bind almost the whole of the acetaldehyde in the saliva during smoking. However, elimination of saliva acetaldehyde during smoking does not make smoking completely harmless. Cysteine as a free base would be somewhat better than cysteine hydrochloride due to its slower dissolution rate. Both traditional and direct compression methods to prepare chewing gums can be utilized and the dose of l‐cysteine required is very low (5 mg).

Interaction of alcohol and tobacco in upper aerodigestive tract and stomach cancer.

There is increasing epidemiological, biochemical, and genetic evidence supporting the role of the first metabolite of alcohol oxidation - acetaldehyde - as a common denominator in the pathogenesis o