Alcohol abuse is a major cause of liver disease in Western countries. In the United States it has been estimated that there are some 25,000 deaths from cirrhosis yearly, about half of which are related with alcohol [1]. The cirrhosis death rate (irrespective of cause) in the United States is about 12 per 100,000 population, while the 5 and 10-year survival rates for alcoholic cirrhosis are reported at 23% and 7%, respectively, much worse than other types of cirrhosis [1].

Alcohol can cause liver damage in the form of steatosis or fatty liver, hepatitis, fibrosis and liver cirrhosis. In general, the amount and duration of alcohol abuse correlate with the presence and severity of liver damage, at least as regards the initial stage of fatty liver [2]. It is still uncertain, however, why only 20–30% of long-term alcohol abusers develop severe liver disease. For instance, one study estimated that cirrhosis develops in only 14% of alcoholics consuming 160 g of alcohol (12 drinks) per day for 8 years [1]. The relatively low incidence of severe liver damage in alcoholics and the poor correlation between the amount of alcohol and the severity of the disease suggest that in addition to genetic influences, the pathogenesis of alcoholic liver disease involves other important environmental factors [3–5].

One hypothesis is that substances such as polyphenols may be present in the diet, or even in alcoholic beverages, thereby contributing to inhibit alcohol induced damage. Polyphenols possess a variety of biological functions, including antioxidant, anti-inflammatory, and anticancer effects. Resveratrol is a phytoalexin polyphenolic compound found in various plants, including grapes, berries, and peanuts. Multiple lines of compelling evidence indicate its beneficial effects on neurological, hepatic, and cardiovascular systems. Resveratrol has also been reported to have anti-cancer, anti-mycotic, and anti-bacterial properties [6–9].

Among the possible mechanisms responsible for its biological activities are downregulation of the inflammatory response through inhibition of synthesis and release of pro-inflammatory mediators, modification of eicosanoid synthesis, inhibition of Kupffer cells and adhesion molecules, inhibition of activated immune cells, or inhibition of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) via its inhibitory effects on nuclear factor (kappa)B (NF-(kappa)B) or the activator protein-1 (AP-1) [5, 10–12]. Pharmacokinetic studies revealed that the target organs of resveratrol are liver and kidney, where it is concentrated after absorption and is mainly converted to a sulfated form and a glucuronide conjugate [13].

The present study investigates whether resveratrol is able to reduce alcohol-induced mortality and liver damage in mice.

Alcohol is toxic for both humans and animals, and exerts important negative effects upon the liver, brain, heart, skeletal muscle, pancreas, hematological and immune systems, gastrointestinal apparatus and endocrine system [14, 15]. Chronic alcohol abuse induces multiorgan deterioration with an increase in mortality. In humans, for example, alcoholics with severe denutrition suffer a 54% mortality rate after 12 months versus 9% among patients with mild denutrition [16]. The present experimental study found chronic (6 weeks in mice with an average lifespan of two years) and severe alcohol intoxication (40% of all fluid intake in the form of alcohol) to cause increased mortality after the second week. Food and alcohol intake was similar in the alcohol and alcohol plus resveratrol mice groups but a strong difference in mortality was observed between them. The cause of death was not known, though the most likely explanation is multiorgan failure secondary to denutrition, coagulation disorders (hypercoagulability was seen in the alcohol group, thus complicating blood extraction), liver alterations, increased infections and endotoxemia. Oxidative stress and endotoxin (lipopolysaccharide (LPS)) are commonly elevated in the blood of alcoholics and in certain animal models of alcoholic liver disease [17]. It causes the release of a battery of cytokines from macrophages and other cells. Reactive oxygen species are capable of damaging the cell in many ways. They have been shown to react with all major classes of cellular constituents: lipids, proteins and nucleic acids. It is well established that chronic ethanol administration leads to oxidative stress in the liver and other organs [18]. Thus, a high amount of alcohol intake, as observed in this model, has deleterious effects on circulatory, immune and neural systems as well as on blood elements, endocrine glands, pancreas, liver and muscles and bone leading to increased in mortality [19].

Alcoholic patients have a high prevalence of protein-calorie malnutrition and vitamin deficiencies [20, 21]. In our study a significant decrease was observed in food ingestion and body weight among the alcohol-consuming mice. There are many reasons for malnutrition, perhaps the most important of which is decreased intake of nutrients. Calories derived from alcohol, are called "empty calories"., in reference to the fact that alcohol, which has 7.1 kcal/g, is not utilized properly by the body as a nutrient [22]. Thus, its intake is not associated with normal (expected) weight gain. The reasons for decreased intake of foods are many and include alcohol per se, presence of liver disease, impairment of the taste and smell acuity, maldigestion (decrease in bile salts or lipase), malabsorption (changes in gut mucosa and its enzymes, altered permeability, changes in motility and possibly gut edema) [23].

The alcohol plus resveratrol group showed an important decrease in mortality. The mechanisms by which resveratrol reduces alcohol-induced mortality are not clear, though its antioxidant, antiinflammatory and antiinfectious properties may play a role [5–7, 10, 23]. Resveratrol also suppresses the expression of inducible nitric oxide synthase and cyclooxygenase-2, is a potent inhibitor of nuclear factor kB (NF-kB) nuclear translocation by blocking kB kinase activity, and decreases platelet aggregation [24–28]. In our study, one mouse died in the resveratrol group. This death may have been due to aggression between individuals, as this mouse had paw lesions. In another published study involving resveratrol administered orally to mice at doses similar to our own, no increased mortality in the resveratrol group versus the controls was likewise observed [29].

The chronic consumption of high doses of alcohol can cause liver damage and cirrhosis in humans. However, in animals it is very difficult to establish an experimental model of alcoholic liver disease. Very few such models have been developed, and most do not involve only alcohol, i.e., they also include additional elements such as hypercaloric diets, iron, endotoxins or other toxins. The model closest to reality (animals with free access to food and drink) is that described by Tsukamoto et al. [30], though it induces alcoholic liver disease by administering a diet rich in polyunsaturated fats and alcohol through a nasogastric tube. Our own model attempts to reproduce situations as close as possibly to reality, i.e., the mice are able to spontaneously eat (standard diet) and drink as much as they want, without the influence of factors that enhance the liver damaging capacity of alcohol. The alcohol concentration in mouse arterial blood was modest, since alcohol consumption was irregular (i.e., free access). This may possibly be the reason why the blood alcohol concentrations and liver lesions in the mice were modest. The alcoholic intoxication model employed, and probably also the action of genetic factors, yields moderate liver damage without either liver fibrosis or cirrhosis – despite the high alcohol concentrations involved. In unpublished studies we found that liver cirrhosis could not be achieved in mice given lower doses of alcohol for longer periods of time (20% of drinking volume for 6 months).

Although cirrhosis could not be induced, the alcohol group showed a moderate increase in transaminase levels, with a greater rise in ALT, as occurs in alcoholic liver disease [31]. These increased laboratory values are not directly correlated to the histological severity of the disease as in humans [32]. The generation of free radicals as a result of alcohol did not correlate with elevated pathology scores in the liver or high ALT levels and acts as redox signals for cytokine production but does not directly damage the liver [33]. Resveratrol decreased the liver laboratory values and the corresponding liver damage – probably as a result of the diminished release of proinflammatory cytokines such as IL-1 as a result of Kupffer cell activation. In this context, over 75% of all individuals with alcoholic hepatitis have increased plasma IL-1 levels [34, 35]. TNF-alfa serum levels have been related to mortality and the severity of the hepatic lesions observed in humans and produced by alcohol intake [35, 36]. However TNF-alfa levels are poor diagnostic markers for the severity of TNF-dependent liver inflammation [37]. Other studies dealing with plasma levels of TNF-alfa and IL-1 in response (LPS), indicate that the TNF-alfa plasma level rises soon after the injection of LPS and that is the reason why it cannot be observed in our study. Otherwise IL-1 remains elevated for a longer period of time. This can be explained by augmented clearance of TNF-alfa not affecting IL-1, a smaller systemic inflammatory response or to neutralization of TNF-alfa by a soluble receptor resulting in a marked attenuation of the late phase of the alcohol action [38].

Both IL-1 and TNF-alfa are produced after macrophage activation and produce an endothelial activation process leading to an increase of adhesion molecules expression, secretion of other cytokines, growth factors, ecosanoid production, nitric oxide and increased endothelial thrombogenicity. Both cytokines produce fibroblast activation leading to proliferation and augmented extracellular matrix synthesis. IL-1 and TNF-alfa produce stimulation of the acute phase systemic manifestation including somnolence, fever, changes in liver protein synthesis, changes in metabolism (caquexia), PMN migration, ACTH liberation and augmented steroid liberation [39].

Other effects of resveratrol upon on the liver can be the inhibition of nitric oxide production by the Kupffer cells [5] and antioxidant action similar to that of other substances such as S-adenosylmethionine [40].

Resveratrol reduces mortality and liver damage produced by alcohol in mice. If our findings are confirmed by further research, resveratrol could be administered to patients with chronic alcoholism to reduce the mortality and liver damage associated with alcohol abuse. It could even be prophylactically added to alcoholic beverages, in a way similar (10 mg/L of any alcoholic beverage), similar to how chlorine is added to water to prevent infections.