Increased vitamin E levels in the lungs of guinea pigs exposed to mainstream or sidestream smoke

Alpha-tocopherol protects against cisplatin-induced toxicity without interfering with antitumor efficacy

Our aim was 2-fold: to investigate the role of alpha-tocopherol supplementation on the antitumor activity of DDP and to evaluate the effect of alpha-tocopherol on the survival and neurotoxicity of DDP-treated mice. Experiments performed on the M14 human melanoma line demonstrated that alpha-tocopherol supplementation did not influence the efficacy of DDP; the inhibition of cell survival and of the in vivo tumor growth after treatment with alpha-tocopherol and DDP combination was similar to that observed after DDP alone. Conversely, alpha-tocopherol was also able to increase survival of mice treated with a high dose of DDP. While DDP alone produced death in about 70% of mice, the combination reduced deaths to about 30%. Analysis of oxidative stress markers and peroxidative damage in organs indicated that the protective effect of alpha-tocopherol was mainly related to its antioxidant activity. A significant increase in the concentration of TBARS and decreased PUFAs and catalase activity were observed after DDP treatment, while with alpha-tocopherol the levels of these markers were comparable to those observed in untreated mice. Histologic analysis performed on peripheral nerve revealed that alpha-tocopherol also protected mice from severe neurologic damage induced by DDP treatment. In conclusion, our results demonstrate that alpha-tocopherol protects against the systemic toxicity and neurotoxicity induced by DDP without interfering with its antitumor activity and suggest that this combination is a promising strategy to improve the therapeutic index of DDP-based chemotherapy.

Cigarette smoke radicals and the role of free radicals in chemical carcinogenicity

This article consists of two parts: a brief overview of the ways in which free radicals can be involved in chemical carcinogenesis, and a review of cigarette smoke chemistry. Carcinogenesis is generally agreed to involve at least three stages: initiation, promotion, and progression. It is suggested that radicals sometimes are involved in the initiation step, either in the oxidative activation of a procarcinogen (such as benzo[a]pyrene) to its carcinogenic form or in the binding of the carcinogenic species to DNA, or both. The fraction of initiation events that involve radicals, as opposed to two-electron steps, is not known, but radicals probably are involved in a substantial number, although probably not a majority, of cancer initiation reactions. Promotion always involves radicals, at least to some extent. Progression probably does not normally involve radicals. The second part of this article reviews the molecular mechanisms involved in cigarette-induced tumors, particularly by aqueous cigarette tar (ACT) extracts and by a model of these solutions, aged solutions of catechol. ACT solutions as well as aged solutions of catechol contain a quinone-hydroquinone-semiquinone system that can reduce oxygen to produce superoxide and hence hydrogen peroxide and the hydroxyl radical. Both the cigarette tar radical and the catechol-derived radical can penetrate viable cells, bind to DNA, and cause nicks.

Adaptation of lung antioxidants to cigarette smoking in humans

We investigated the effect of free radical scavengers, micronutrient antioxidants, on antioxidant enzyme activities in cigarette smokers. We measured the intracellular superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities and vitamin E and beta-carotene levels in the bronchoalveolar cells of 14 smokers before and after 6 weeks of supplementation with vitamins E and C and beta-carotene. Eight nonsmokers served as control subjects. CAT and GPx activities were higher in BAL cells from smokers compared with nonsmokers (20.5 +/- 2.3 vs 9.6 +/- 1.3 U/10(6) cells; p = 0.027; 0.90 +/- 0.10 vs 0.46 +/- 0.12 U/10(6) cells; p = 0.049, respectively), while there was no difference in SOD activity between the two groups. Likewise, vitamin E and beta-carotene concentrations were markedly higher in smokers' lung lavage cells (403.3 +/- 81.0 in smokers vs 16.6 +/- 5.3 ng/10(6) cells in nonsmokers, and 1.23 +/- 0.21 in smokers vs 0.15 +/- 0.04 ng/10(6) cells in nonsmokers, respectively). The serum levels of vitamin E and C and beta-carotene increased by 2.0-, 1.6-, and 8.9-fold in smokers after supplementation, which were similar to nonsmokers. Similarly, BAL cell vitamin E increased from 403.3 +/- 81.0 to 477.4 +/- 97.7 ng/10(6) cells and beta-carotene increased from 1.23 +/- 0.21 to 4.32 +/- 0.45 ng/10(6) cells (p < 0.05). Despite increased concentrations of vitamins in serum as well as beta-carotene levels in BAL cells, there was no significant down regulation in SOD, CAT, or GPx activities in the lung lavage cells. These data suggest that augmentation of micronutrient antioxidants in smokers and nonsmokers does not appear to have an effect on antioxidant enzyme activities, suggesting a differential regulation of these defenses.

Suppression of the hydrazine-induced formation of megamitochondria in the rat liver by coenzyme Q10

The effects of coenzyme Q10 (CoQ10) on the hydrazine-induced changes in the structure of mitochondria and those in antioxidant systems of the liver were investigated using rats as experimental animals. Animals were placed on a powdered diet containing 1.0% hydrazine for 7-8 days in the presence or absence of the combined treatment with CoQ10. Results obtained were as follows: (a) treatment of animals with CoQ10 prevented the hydrazine-induced formation of megamitochondria in the liver; (b) changes observed in the liver of the hydrazine-treated animals in comparison to the control were increases in the contents of alpha-tocopherol and CoQ analogs, increases in the levels of lipid peroxidation, decreases in the level of reduced glutathione with increases in that of oxidized glutathione, and increases in the ratio of unsaturated to saturated fatty acids in phospholipid domains of mitochondrial membranes; and (c) administration of CoQ10 to hydrazine-treated animals suppressed enhanced lipid peroxidation and improved lowered adenosine diphosphate/O ratios of mitochondria. The present data suggest that CoQ10 suppresses the hydrazine-induced formation of megamitochondria by scavenging free radicals generated from hydrazine and its metabolites.

Influences of tobacco smoke and vitamin E depletion on the distal lung of weanling rats

Tobacco smoke is associated with pulmonary emphysema via elastase-antielastase and oxidant-antioxidant imbalance. This study addressed the tobacco smoke-induced changes in the lungs of weanling rats with vitamin E depletion. Three-week-old Wistar rats fed on vitamin E-depleted or normal diet were intermittently exposed to tobacco smoke by Hamburg II machines for 4 weeks. Tobacco smoke significantly suppressed body weight increases, particularly in the vitamin E-depleted group. In the normal diet group, tobacco smoke induced emphysematous changes with significant increases in the mean linear intercept (Lm) and the destructive index (DI), which was supported by an increase in elastase-like activity and a decrease in elastase inhibitory capacity (EIC) in bronchoalveolar lavage (BAL) fluid. Vitamin E depletion alone altered neither Lm nor DI. In tobacco-exposed animals in addition to vitamin E depletion, elastase-like activity, EIC in BAL fluid and DI were comparable to that in tobacco-exposed animals on a normal diet. However, Lm was markedly decreased with thickened epithelium and shrunk alveolar space. These results suggest that vitamin E depletion, when linked to tobacco exposure, might induce impaired lung development in the weanling rats, which is different from the emphysematous changes.

Mainstream and sidestream cigarette smoke exposure increases retinol in guinea pig lungs

We have studied in guinea pigs the effects of cigarette smoke exposure on vitamin A (retinol) levels in plasma, lung, lung lavage, and liver. Smoke was generated from 1R3F cigarettes in a smoke exposure instrument designed by University of Kentucky Tobacco and Health Research Institute. Three-week-old male guinea pigs were exposed to mainstream, sidestream, or sham smoke, generated twice daily from three cigarettes for 6 weeks. In addition, some animals were kept as room controls for some time. After 6 weeks of smoke exposure, some animals were allowed to recover for 6 weeks without smoke. After 6 weeks of smoking, the plasma retinol levels were lower in both smoke exposed groups when compared to the values in the sham group. Furthermore, in comparison to the sham group, the mainstream and sidestream smoke exposed groups showed a 7.6- and 8.3-fold increase in the levels of lung retinol, respectively. After the 6-week recovery period, plasma retinol of both smoke-exposed groups reached the control levels. In contrast, withdrawal of smoking did not show such an effect on the lung retinol level in both mainstream or sidestream groups. Electronmicroscopy of the lungs showed deleterious alterations in the morphology of the lungs in both mainstream and sidestream groups. Although the mechanism(s) involved in the elevation of retinol content of the lung due to smoke exposure remains to be elucidated, it is of interest that elevation of retinol content and alteration of lung morphology occurred not only in the mainstream smoke exposed but also in the sidestream group.

Cigarette smoking and oxidative damage in the lung

Cigarette smoke contains a large variety of compounds, including many oxidants and free radicals that are capable of initiating or promotes oxidative damage. Also, oxidative damage may result from reactive oxygen species generated by the increased and activated phagocytes following cigarette smoking. In vitro studies are generally supportive of the hypothesis that cigarette smoke can initiate or promote oxidative damage. However, information obtained from in vivo studies is inconclusive. Contrary to expectations, the levels of lipid peroxidation products were found to be decreased or unchanged in the lungs of chronically smoked rats. Metabolic adaptation, such as accumulation of vitamin E in the lung, and increased activities of superoxide dismutase in alveolar macrophages and pulmonary tissues of chronically smoked animals may enable smoked subjects to counteract oxidative stress and to resist further damage to smoke exposure. However, it is also possible that the metabolic adaptation may be secondary to inflammatory response and injury repair process following smoking exposure. More studies are needed to better understand the role of oxidative damage in the etiology of smoking-related disorders.

Exposure of rats to low concentration of cigarette smoke increases myocardial sensitivity to ischaemia/reperfusion

It is suggested that passive smoking or smoke-exposure increase the risk of coronary heart disease. The same mechanisms as active smoking might play a role. The aim of this study was to determine whether exposure to smoke aggravated ischaemia/reperfusion injury. As a parameter of cellular function and integrity mitochondrial oxidative function was measured. Low molecular weight iron (LMWI) and alpha-tocopherol levels were determined to assess the possibility of toxic hydroxyl radical involvement in myocardial ischaemia/reperfusion injury of smoke-exposed rats. Rats were exposed to a small concentration of cigarette smoke for 2 months (the carboxyhemoglobin concentration did not increase), whereafter hearts were isolated and subjected to ischaemia and ischaemia followed by reperfusion. Mitochondrial oxidative function, low molecular weight iron and alpha-tocopherol were determined. The impairment in mitochondrial oxidative function, LMWI content elevation and the decrease in alpha-tocopherol concentration during ischaemia/reperfusion were significantly more severe in hearts of smoke-exposed rats than non-smokers. These results suggest that exposure to smoke increased the sensitivity of hearts to ischaemia/reperfusion injury, and that a free radical mechanism might participate.

Vitamin E and oxidative stress

Oxidative stress can result from or be enhanced by a large variety of conditions, including nutritional imbalance, exposure to chemical and physical agents in the environment, strenuous physical activities, injury, and hereditary disorders. While many enzymes and compounds are involved in protecting cells from the adverse effects of oxidative stress, vitamin E occupies an important and unique position in the overall antioxidant defense. The antioxidant function of vitamin E is closely related to the status of many dietary components. Vitamin E-depleted animals are generally more susceptible to the adverse effects of environmental agents than supplemented animals. Also, vitamin E supplementation is beneficial to certain groups of the population. However, supplementing vitamin E in experimental subjects maintained on a nutritionally adequate diet does not always provide additional protection. Differential metabolic responses in various organs and differences in experimental conditions often contribute in the discrepancies in the literature. The lack of clear evidence for the occurrence of lipid peroxidation or antioxidant function of vitamin E in vivo can be attributed partly to the presence of active pathways for metabolizing hydroperoxides, aldehydes, and other oxidation products. Specific and sensitive techniques for measuring lipid peroxidation products in biological systems are essential for understanding the role of free radical-induced lipid peroxidation in tissue damage and antioxidant function of vitamin E in vivo.

Increased vitamin E content in the lung after ozone exposure: a possible mobilization in response to oxidative stress

Vitamin E (vE) is a biological free radical scavenger capable of providing antioxidant protection depending upon its tissue content. In previous studies, we observed that vE increased significantly in rat lungs after oxidant exposure, and we postulated that vE may be mobilized to the lung from other body sites under oxidative stress. To test this hypothesis, we fed Long-Evans rats either a vE-supplemented or a vE-deficient diet, injected them intraperitoneally with 14C-labeled vE, and then exposed half of each group to 0.5 ppm ozone (O3) for 5 days. After exposure, we determined vE content and label retention in lungs, liver, kidney, heart, brain, plasma, and white adipose tissue. Tissue vE content of all tissues generally reflected the dietary level, but labeled vE retention in all tissues was inversely related to tissue content, possibly reflecting a saturation of existing vE receptor sites in supplemented rats. Following O3 exposure, lung vE content increased significantly in supplemented rats and decreased in deficient rats, but the decrease was not statistically significant, and vE content remained unchanged in all other tissues of both dietary groups. Retention of 14C-labeled vE increased in all tissues of O3-exposed rats of both dietary groups, except in vE-deficient adipose tissue and vE-supplemented brain, where it decreased, and plasma, where it did not change. The marked increases in lung vE content and labeled vE retention of O3-exposed vE-supplemented rats support our hypothesis that vE may be mobilized to the lung in response to oxidative stress, providing that the vitamin is sufficiently available in other body sites.