Alcohol-stimulated promotion of tumors in the gastrointestinal tract.

Alcohol is a major risk factor for cancers of the upper gastrointestinal tract but the association with cancers of the large bowel is not as clearly established. In recent studies, we have provided experimental support for the associations in the esophagus and oral cavity. Our studies also indicate that the tumor promotion ability of ethanol is related to its ability to generate oxygen free radicals as measured by an increase in indices of lipid peroxidation. This increase in lipid peroxidation was evident in the liver as well as the tissues targeted by the site-specific carcinogens and promoted by ethanol. Studies in mice showed that the increased lipid peroxidation as well as tumor incidence was inhibited by the administration of vitamin E, the potent antioxidant. Determination of fatty acid profiles showed significant alterations when ethanol was used as a tumor promoter after treatment with the carcinogen. Ethanol as a promoter caused an increase in esophageal polyunsaturated fatty acids (PUFA). Ethanol promotion was also evident in increased arachidonate and an exaggeration in PUFA that are involved in eicosanoid production. Thus, these results suggest that ethanol-related promotion may be the result of excessive cell proliferation induced by disordered lipid and eicosanoid metabolism that may cause a selective outgrowth of the carcinogen-initiated cells. Supporting evidence for ethanol-induced hyper-regeneration is also reviewed.

Ethanol-mediated promotion of oesophageal carcinogenesis: association with lipid peroxidation and changes in phospholipid fatty acid profile of the target tissue.

Ethanol consumption is a high risk factor for oesophageal carcinoma and studies indicate that it acts as a promoter of N-nitrosomethylbenzylamine (NMBzA)-induced oesophageal carcinogenesis. The studies described here indicate that ethanol-induced promotion was related with an increase in indices of lipid peroxidation in the target oesophageal tissue and that such an increase was associated with significant changes in the fatty acid profile of phospholipids. Young Sprague-Dawley rats were treated with NMBzA, 2.5 mg/kg body weight, three times a week for 3 weeks, and a week afterwards fed a 7% ethanolic diet that was continued until their death at 10 months. Cumulative ethane exhaled by rats was measured a week before their death and was found to increase significantly with NMBzA treatment but more so when followed by ethanol consumption. Cholesterol, phospholipids, and some indices of lipid peroxidation were measured in the oesophagus and liver. Whereas the levels of cholesterol and phospholipids were not affected in control-fed rats with or without the NMBzA treatment, ethanol consumption by either the untreated or NMBzA-treated rats caused a significant increase in the targeted oesophagus as well as the liver, the major site of ethanol and carcinogen metabolism. Ethanol consumption also increased all the indices of lipid peroxidation, i.e. malondialdehyde, lipid fluorescence, diene- and triene-conjugates; the largest increases were observed in rats that received both NMBzA and ethanol. A comparison of the fatty acid profile of phospholipids from the oesophagus and liver indicated significant alterations both with the NMBzA treatment and ethanol consumption. However, the fatty acid profile with regard to its peroxidability was significantly modified only with ethanol consumption and only in the oesophagus of the NMBzA-treated or untreated rats. Also, hepatic phospholipids showed a substantial increase in linolenate and no change in arachidonate, but the oesophageal phospholipids exhibited a pronounced increase in the levels of C18:3, C20:2, C20:3, C20:3' and C22:6 with a significant increase in arachidonate when use of ethanol followed the NMBzA treatment, suggesting a disorder in lipid and eicosanoid metabolism. We propose that ethanol may promote carcinogenesis through excessive cell proliferation induced by disordered lipid and eicosanoid metabolism that may cause a selective outgrowth of the initiated cells.

Restenosis following subclavian artery angioplasty for treatment of coronary-subclavian steal syndrome: definitive treatment with Palmaz-stent placement.

We report a case of progressive angina pectoris 4 years post coronary bypass surgery, in which the left internal mammary artery (LIMA) was grafted to the native left anterior descending coronary artery. The coronary-subclavian steal phenomenon was proven angiographically with retrograde reflux through the LIMA graft into the distal subclavian vessel, downstream from a critical stenosis at the origin of the subclavian artery. After initially successful angioplasty of the ostial subclavian lesion, restenosis and return of angina prompted repeat dilatation and placement of a Palmaz 154-M stent. Follow-up catheterization has demonstrated persistent patency at the stented site and absence of coronary steal.

Lipid peroxidation and ethanol-related tumor promotion in Fischer-344 rats treated with tobacco-specific nitrosamines.

Male Fischer-344 rats were treated, by gavage, with a total dose of 40 mmol/kg of N'-nitrosonornicotine (NNN) or 20 mmol/kg of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), three times a week for 4 weeks. One week afterwards the rats were fed an isocaloric liquid diet containing 7% (v/v) ethanol and continued on this diet until killed. Cumulative ethane exhaled by a rat by 180 min was measured at 54 weeks of the start of the study and was found to increase significantly (P < 0.001) with either NNN or NNK treatment but more so when followed by ethanol consumption. Other indices of lipid peroxidation, cholesterol and phospholipids were measured in the lipid extracts from the liver, esophagus and lungs at 55 weeks. Ethanol consumption increased the amount of cholesterol and phospholipids per g of tissue in naïve or NNN- and NNK-treated rats. All peroxidative indices measured, i.e. malondialdehyde (MDA), diene- and triene-conjugates and lipid fluorescence, were significantly increased in the liver, the main metabolic and peroxidative site, with ethanol consumption in rats whether they were treated with NNN or NNK or remained untreated. Overall, the indices of lipid peroxidation also showed an increase in other tissues, but the results differed with different indices. The differences in indices may be due to differences in lipid peroxidation products measured or to differences in their rates of production and degradation or conversion to other products. However, the largest increases in indices were seen with ethanol consumption by either NNN- or NNK-treated rats. Incidence of tumors in the tissues was also assessed and showed about a two-fold increase with ethanol consumption in the tumors of esophagus, oral cavity, lungs and liver induced by either NNN or NNK. Ethanol also caused an increase in the mean frequency and mean size of the tumors induced. The results suggest that ethanol-related promotion of NNN- and NNK-induced tumors may result from increased lipid peroxidation in the target tissue.

Alcohol, immunomodulation, and disease.

Recent research findings point to a spectrum of alcohol-induced immune dysfunctions in animal models and humans. Use of alcohol in vivo causes abnormalities in the function and/or structure of a broad array of cells involved in humoral and cellular immunity, including lymphocytes, Kupffer cells and other macrophages, as well as the endothelium of blood vessels and lymphatics. Regulatory cytokines and neuroendocrine factors can mediate some of these immunomodulatory effects which may be further re-phased, exaggerated or unbalanced by other drugs of misuse. A variety of animal models is available to study acute and chronic alcoholism, non-alcohol drug misuse, AIDS as well as other opportunistic infections, and neoplasias, which hold promise of clarifying the role of alcohol as an immunomodulator.

Alcohol-associated generation of oxygen free radicals and tumor promotion.

We discuss evidence indicating how ethanol could generate oxygen free radicals. Recent use of techniques such as spin trapping and EPR spectroscopy have demonstrably confirmed that both acute and chronic alcohol use by laboratory animals would generate free radical intermediates. These radicals are of biological origin and presumably involve lipids. However, an exact identification of the intermediates produced has not been worked out with the currently available methodologies. Also not known is the mechanism whereby ethanol could initiate free radicals. The relationship between generation of free radicals and cell toxicity or carcinogenesis is also not understood. Using a variety of systems that included different species, strains and gender (male Sprague-Dawley and Fisher-344 rats, female C57BL/6 mice, male Syrian golden hamsters) and carcinogens (NMBZA, NNN, NNK, DMBA and LP-BM5 retrovirus) we have shown an association of lipid peroxidation with ethanol tumor promotionability. However, the process of tumor promotion in general is not very clear and the role played by ethanol in this process is still more unclear. Here we are reviewing evidence that could possibly be involved in such promotion processes.

Ethanol-mediated promotion of oral carcinogenesis in hamsters: association with lipid peroxidation.

Pouches of male Syrian Golden hamsters were painted with 1% 7,12-dimethylbenz[a]anthracene (DMBA) three times for one week. One week after DMBA treatment, hamsters were fed an ethanolic diet and continued on this diet until they were killed 22 and 35 weeks after the start of the experiment. Phospholipids, cholesterol, indexes of lipid peroxidation (malondialdehyde, diene and triene conjugates, lipid fluorescence), and the antioxidants glutathione and vitamin E were determined in the buccal mucosa, as was the incidence of tumors. At 22 weeks, the relative proportion of cholesterol to phospholipids in ethanol-consuming hamsters was significantly increased. At 35 weeks, most of the treatments showed a return of cholesterol vs. phospholipids toward that of untreated mucosa at 22 weeks. Ethanol consumption also increased the indexes of lipid peroxidation at 22 weeks; the largest increases occurred when ethanol use was combined with DMBA treatment. However, at 35 weeks such increases in lipid peroxidation had either returned to intermediate levels or were not different from the untreated controls at 22 weeks. Glutathione decreased in pouches of hamsters fed ethanol diets at 22 weeks, but at 35 weeks there was no appreciable difference. However, vitamin E increased significantly with ethanol consumption at 22 weeks, which increased further when combined with DMBA treatment, but at 35 weeks these values were intermediate. No tumors were seen at 22 weeks. At 35 weeks, DMBA-treated ethanol-fed hamsters had a significantly higher incidence of tumors, more multiple tumors per hamster with tumors, and more of the larger tumors than DMBA-treated control-fed hamsters. The results suggest that an increase in lipid peroxidation occurs with ethanol-related tumor promotion processes, but this lipid peroxidation declines when tumors appear to be preceded by increases in cholesterol relative to phospholipids and increases in vitamin E.

Modulation of cancer growth by vitamin E and alcohol.

Seventy-five percent of esophageal cancers are alcohol related, yet alcohol is not a carcinogen. Ethanol may promote carcinogenesis via increased free radical products during its metabolism, as indicated by data from this and other studies. Ethanol is oxidized to acetaldehyde by alcohol dehydrogenase, catalase and the microsomal ethanol oxidizing system (MEOS). Free radicals (FR) are released during the oxidation of ethanol by the MEOS. An increased formation of FR in tissues would increase their oxidative stress and may increase their susceptibility for developing chemically induced cancers. FR and some FR products can rapidly react with biological materials, i.e. lipids, proteins and nucleic acids, forming toxic products. This study focuses on the effects of FR and/or FR products on cancer promotion during alcohol metabolism. Eight groups of mice were fed nutritionally adequate diets supplemented with vitamin E and/or ethanol. Some groups of mice were also orally gavaged with N-nitrosomethylbenzylamine (NMBzA), an esophageal carcinogen. Following the feeding of the various diets for 22 weeks, livers and esophagi were removed and the FR burden in the liver measured by the presence of lipid peroxide products and the number of tumors in each esophagus determined. These studies indicate that a linear relationship exists between the increasing number of esophageal tumors and increasing levels of lipid peroxide products that are formed during FR activity. These results show that FR and/or FR products are the cancer promoters during ethanol metabolism, since diets supplemented with high levels of vitamin E, which inhibits ethanol-induced FR activity and the formation of FR products, suppress the promotion of cancer by ethanol.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol stimulation of lipid peroxidation and esophageal tumor growth in mice immunocompromised by retrovirus infection.

Tumor appearance can be accelerated in the immunodeficient and immunosuppressed animal. The role of lipid peroxidation and immune dysfunction induced by retrovirus and ethanol treatments on cancer promotion were investigated. Following the initiation of esophageal cancer by methylbenzylnitrosamine, ethanol consumption and retrovirus infection individually and concomitantly increased growth of esophageal tumors. Dietary supplementation with vitamin E reduced the size and frequency of the developed tumors. Tumor growth modifications in the vitamin E supplemented animals may be due to changes in T-cell numbers and functions stimulated by vitamin E. In addition, increased production of free radicals following ethanol treatment and retrovirus infection, and the suppression of these formations lipid peroxide by vitamin E is accompanied by lower incidence and size of tumors. Thus, the mechanisms of tumor enhancement observed in immunocompromised animals may include a combination of immunomodulation and modification of oxidant production by ethanol consumption and retrovirus infection.

Vitamin E protection against nitrosamine-induced esophageal tumor incidence in mice immunocompromised by retroviral infection.

Retrovirally induced immunosuppression may elevate the incidence of chemically induced cancers. A proposed hypothesis to explain this relationship is the increased free radical activity observed during retroviral infection and carcinogen activation. We previously found that vitamin E retarded growth of esophageal tumors accompanied by reductions of free radical products. This study investigated the contribution that retroviral immunosuppression has on esophageal cancer induced by the carcinogen N-nitrosomethylbenzylamine (NMBzA), and the response that increased levels of dietary vitamin E has on this induced carcinogenesis. Female C57BL/6 mice received NMBzA or vehicle (corn oil) i.p. weekly for 3 weeks. Then some of the mice were infected with LP-BM5 murine retrovirus and fed diets containing 30 IU vitamin E or 172 IU vitamin E/kg of diet. As an assessment of free radical activity, exhaled ethane was measured prior to killing the animals at 26 weeks. Esophagi from the various mice groups were assessed for size and frequency of tumors. Livers homogenates were analyzed for vitamins A and E, lipid fluorescence, conjugated dienes and malondialdehyde. Hepatic levels of vitamin A and E were decreased (P < 0.05) and indices of lipid peroxidation were greater (P < 0.05) in NMBzA-treated mice relative to controls. Lipid peroxidation and serum transaminases (ALT and AST) were greatest in mice given NMBzA and infected with the retroviruses. Incidence of esophageal tumors were also greatest in the NMBzA-treated, immunocompromised animals. Mice fed vitamin E-supplemented diets showed increased (P < 0.05) hepatic concentrations of vitamin E and vitamin A, decreased activities of serum transaminases, decreased indices of lipid peroxidation, and decreased size and frequency of esophageal tumors in both the immunocompromised and non-immunocompromised mice. These results suggest that vitamin E plays an antioxidant function that retards the incidence of esophageal cancers in immunocompromised and non-immunocompromised animals.

Vitamin E inhibition of lipid peroxidation and ethanol-mediated promotion of esophageal tumorigenesis.

Promotion of chemically induced esophageal cancer by ethanol may include the generation of highly reactive free radicals and thus may be preventable by the antioxidant vitamin E. In the present study, female C57BL/6 mice received N-nitrosomethylbenzylamine (NMBzA, 0.2 mg/kg ig) three times a week for three weeks. After this esophageal carcinogenic treatment, mice were fed a nutritionally adequate liquid diet with 30% of the calories supplied by ethanol or an isocaloric carbohydrate with or without supplemental alpha-tocopherol (142 mg/kg diet). As a marker of in vivo lipid peroxidation, exhaled ethane was collected and measured 24 hours "before" the mice were killed after 20 weeks of dietary treatment. Hepatic malondialdehyde, lipid fluorescence, and conjugated dienes were determined as markers of products of lipid peroxidation and serum aminotransferases as indexes of liver toxicity. Hepatic liver concentrations of vitamins A and E and the size and frequency of esophageal tumors were also assessed. Ethanol consumption after NMBzA administration significantly increased (p less than 0.05) the size and frequency of esophageal tumors. These ethanol-promoted effects were accompanied by increases in indexes of in vivo and accumulated products of lipid peroxidation. Similarly treated animals that received supplemental dietary vitamin E showed significant reductions (p less than 0.05) in mean tumor size and frequency of tumors as well as a decrease in the indexes of hepatic lipid peroxidation. The results suggest that promotion of NMBzA-induced esophageal tumors by ethanol may in part result from increased lipid peroxidation and that vitamin E reduces carcinogenicity of NMBzA or ethanol promoter effects by inhibiting lipid peroxidation.

Alcohol acts to promote incidence of tumors.

Alcohol is a major cancer risk factor. A variety of roles in carcinogenesis have been assigned to ethanol. Our recent studies indicate that ethanol may act as tumor promoter. Further studies suggest that ethanol may act as tumor promoter through free radicals generated during its metabolism because an increase in tumors was observed under conditions in which ethanol-induced lipid peroxidation could take place and not in which such lipid peroxidation could not occur. Other possibilities include ethanol effect on cell necrosis and cell proliferation and generation of a secondary mutagenic event through a DNA repair deficiency. The immune system, because it is a defense mechanism against carcinogenesis and because ethanol is immunosuppressive, must also play a role. Our current studies are aimed at elucidating some of these mechanisms and pointing out the complexity of the mechanisms that are affected by ethanol and that may be involved in tumor promotion.

Vitamin E reduction of lipid peroxidation products in rats fed cod liver oil and ethanol.

The purpose of this study was to investigate the effects of vitamin E supplementation on ethanol- and cod liver oil-induced lipid peroxidation. Adult male rats received diets containing ethanol, cod liver oil and supplemented with vitamin E for 28 days. Following treatment, hepatic conjugated dienes, lipid fluorescence, and exhalation of ethane were measured as indices of lipid peroxidation. Ethane expiration over a 3-hour period was reduced by 96% in rats fed ethanol supplemented with vitamin E. Exhalation of ethane was increased by CLO feeding but was reduced 89% in the CLO-fed rats supplemented with vitamin E. In addition, ethane production was elevated in rats fed ethanol plus CLO compared to rats fed diets containing CLO supplemented with vitamin E. Supplementation of the CLO diet with vitamin E also significantly decreased hepatic conjugated fatty acid dienes levels. Levels of hepatic conjugated fatty acid dienes from rats fed ethanol plus vitamin E were reduced 91% compared to rats fed ethanol diets. Additionally, hepatic lipid fluorescence expressed as per mg of hepatic phospholipid basis was also significantly increased in rat groups fed vitamin E, ethanol, and cod liver oil diets. Where vitamin E was added to these same diets a significant decrease of hepatic lipid peroxidation products occurred. The observed reduction in lipid peroxidation by vitamin E may be useful to retard lipid peroxides derived materials involved in the development of alcoholic liver diseases.

The effect of vitamin E (alpha-tocopherol) supplementation on hepatic levels of vitamin A and E in ethanol and cod liver oil fed rats.

Eight groups of 5 rats were fed 8 differing liquid diets with and without ethanol, cod liver oil and/or increased levels of vitamin E. Hepatic levels of vitamins A and E were determined following the 28-day feeding time. Ethanol consumption decreased the levels of hepatic vitamin E (p less than 0.05), vitamin A (p less than 0.05) and the ratio of vitamin A/E (p less than 0.05). Hepatic levels of vitamins A and E were unaffected in rats fed cod liver oil. Supplementation of the normal dietary level of 30 IU of vitamin E per kg diet, with an additional 142 IU alpha tocopherol/kg diet, restored hepatic concentrations of vitamin E to normal levels in alcohol-fed rats. The hepatic levels of vitamin A in rats fed ethanol diets supplemented with vitamin E were less than that of control rats but were 4.3 times greater than that of rats on ethanol diets unsupplemented with vitamin E. However, the vitamin A and E ratio was equal to normal in this group of rats. The vitamin A/E ratio was reduced in liver of rats fed non-alcoholic diets supplemented with vitamin E due to increased levels of hepatic vitamin E. Additionally, rats fed cod liver oil diets containing ethanol also indicated decreased hepatic vitamin A and E levels. However, these levels were greater than that of rats fed only alcoholic diets suggesting that these vitamins are replaced by the vitamin A and E content in the cod liver oil.(ABSTRACT TRUNCATED AT 250 WORDS)