Effect of melatonin and vitamin C on expression of endothelial NOS in heart of chronic alcoholic rats.

The aim of this study was to investigate the effects of melatonin and vitamin C on expression of endothelial nitric oxide synthase (NOS) in heart tissue of chronic alcoholic rats. Twenty-four adult male Wistar rats weighing 200-250 g were used in this study. Rats were divided into four groups. The first group served as control (n = 6). The second group was treated with ethanol (%7.2) for 28 days (n = 6), which was administered in artificial isocaloric diets. The third group was given ethanol and supplemented with 40 mg/kg vitamin C [intraperitoneally (i.p.)] (n = 6). The fourth group was given ethanol and supplemented with 4 mg/kg melatonin (i.p.) (n = 6). At the end of the experiment, rats were sacrificed and heart tissues were processed for immunohistochemistry analysis to endothelial NOS (eNOS). eNOS immunoreactivity showed heterogeneous distribution in control group. eNOS immunoreactivity was (+) in some myocytes and (++) in some others. Expression of eNOS in alcohol group was heterogeneous like control group but also stronger than that. Immunoreactivity was (+++) in myocytes near the epicardial zone and (++) in myocytes near the endocardium border. In melatonin and vitamin C-treated groups, eNOS immunoreactivity was diffuse and the intensity of reaction was (+++) in subepicardial region. However, eNOS immunoreactivity scores were weaker in these groups when compared with the alcohol group. Our results indicate that alleviation of oxidative stress by antioxidant therapy reduces reactive oxygen species-mediated nitric oxide inactivation.

Alcohol metabolism and cancer risk.

Chronic alcohol consumption increases the risk for cancer of the organs and tissues of the respiratory tract and the upper digestive tract (i.e., upper aerodigestive tract), liver, colon, rectum, and breast. Various factors may contribute to the development (i.e., pathogenesis) of alcohol-associated cancer, including the actions of acetaldehyde, the first and most toxic metabolite of alcohol metabolism. The main enzymes involved in alcohol and acetaldehyde metabolism are alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), which are encoded by multiple genes. Because some of these genes exist in several variants (i.e., are polymorphic), and the enzymes encoded by certain variants may result in elevated acetaldehyde levels, the presence of these variants may predispose to certain cancers. Several mechanisms may contribute to alcohol-related cancer development. Acetaldehyde itself is a cancer-causing substance in experimental animals and reacts with DNA to form cancer-promoting compounds. In addition, highly reactive, oxygen-containing molecules that are generated during certain pathways of alcohol metabolism can damage the DNA, thus also inducing tumor development. Together with other factors related to chronic alcohol consumption, these metabolism-related factors may increase tumor risk in chronic heavy drinkers.

Intracellular proteolytic systems in alcohol-induced tissue injury.

The body constantly produces proteins and degrades proteins that are no longer needed or are defective. The process of protein breakdown, called proteolysis, is essential to cell survival. Numerous proteolytic systems exist in mammalian cells, the most important of which are the lysosomes, the ubiquitin-proteasome pathway, and enzymes called calpains. Lysosomes are small cell components that contain specific enzymes (i.e., proteases) which break down proteins. Alcohol interferes with the formation and activity of lysosomes and thus may contribute to protein accumulation in the liver, which can have harmful effects on that organ. In the ubiquitin-proteasome pathway, proteins that are to be degraded are first marked by the addition of ubiquitin molecules and then broken down by large protein complexes called proteasomes. Alcohol impairs this proteolytic system through several mechanisms, possibly leading to inflammation and even cell death. Calpains are proteases that are involved in several physiological processes, including the breakdown of proteins that give cells their shape and stability. In contrast to the lysosomal and ubiquitin-proteasome systems, calpains in brain cells are activated by alcohol, to potentially detrimental effect.

A role for interleukin-10 in alcohol-induced liver sensitization to bacterial lipopolysaccharide.

BACKGROUND: Proinflammatory cytokines play an important role in alcohol-induced liver injury. The role of anti-inflammatory cytokines in the initiation and progression of alcoholic liver disease has received little attention. This study tested the hypothesis that an imbalance exists between pro- and anti-inflammatory cytokines in the liver during chronic exposure to alcohol. Alcohol exposure results in predominantly proinflammatory cytokine secretion and liver injury. METHODS: IL-10 knock-out and their C57BL/6J counterpart wild-type mice were fed alcohol in drinking water for 7 weeks. At the end of alcohol feeding, Gram-negative bacterial lipopolysaccharide (LPS) was administered, and the animals were killed after 3 and 8 hr. Liver histology, plasma alanine aminotransferase and aspartate aminotransferase activity, tumor necrosis factor-alpha, interleukin (IL)-1beta and IL-10 levels, and liver cytokine messenger RNA levels were measured. RESULTS: Alcohol feeding and LPS treatment did not change plasma enzyme activity levels in wild-type mice. In the IL-10 knock-out mice, LPS alone increased aspartate aminotransferase and alanine aminotransferase enzyme activity, and this was potentiated by alcohol. Alcohol induced liver steatosis in both wild-type and knock-out mice. LPS markedly enhanced the histological effects further, especially in the knock-out mice, with the emergence of focal necrosis, polymorphonuclear infiltration, and microabscesses in the liver. Plasma tumor necrosis factor-alpha and IL-1beta levels were not affected by alcohol alone. Proinflammatory cytokine levels were increased by LPS and further enhanced by alcohol treatment, particularly in the IL-10 knock-out mice. IL-10 plasma levels in the wild-type animals were down-regulated by alcohol. Changes in liver cytokine messenger RNA paralleled those seen in plasma cytokine levels. CONCLUSIONS: Alcohol-induced liver sensitization to LPS in wild-type mice may involve down-regulation of IL-10. This anti-inflammatory cytokine, known for its hepatoprotective effects, is secreted simultaneously with proinflammatory cytokines. IL-10 may also limit alcohol-induced liver damage by counteracting the effects of proinflammatory cytokines.