Vitamin E supplementation and respiratory effects of ozone in humans

Tocotrienols: Dietary Supplements for Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. Emphysema and chronic bronchitis are the two major phenotypes of COPD, which have many symptoms, such as dyspnea, chronic cough, and mucus overproduction. Emphysema is characterized by the destruction of the alveolar wall, while chronic bronchitis is characterized by limitations in expiratory airflow. Cigarette smoking is the most significant risk factor for the pathogenesis of COPD in the developed world. Chronic inflammation contributes to the onset and progression of the disease and furthers the risk of comorbidities. Current treatment options and prevention strategies for COPD are very limited. Tocotrienols are a group of vitamin E molecules with antioxidant and anti-inflammatory properties. Individual tocotrienols (α, γ, and δ) have shown their ability to attenuate inflammation specifically via suppressing nuclear factor-κB-mediated cytokine production. The δ- and γ-forms of tocotrienols have been indicated as the most effective in the prevention of macrophage infiltration, production of reactive oxygen species, and cytokine secretion. This review briefly discusses the pathogenesis of COPD and the role of inflammation therein. Furthermore, we summarize the in vitro and in vivo evidence for the anti-inflammatory activity of tocotrienols and their potential application to COPD management. Coupled with the bioavailability and safety profile of tocotrienols, the ability of these compounds to modulate COPD progression by targeting the inflammation pathways renders them potential candidates for novel therapeutic approaches in the treatment of COPD patients.

Supplementation with omega-3 fatty acids potentiates oxidative stress in human airway epithelial cells exposed to ozone

BACKGROUND

Dietary intake of the omega-3 family of polyunsaturated fatty acids (ω-3 FA) is associated with anti-inflammatory effects. However, unsaturated fatty acids are susceptible to oxidation, which produces pro-inflammatory mediators. Ozone (O₃) is a tropospheric pollutant that reacts rapidly with unsaturated fatty acids to produce electrophilic and oxidative mediators of inflammation.

OBJECTIVE

Determine whether supplementation with ω-3 FA alters O₃-induced oxidative stress in human airway epithelial cells (HAEC).

METHODS

16-HBE cells expressing a genetically encoded sensor of the reduced to oxidized glutathione ratio (GSH/GSSG, E_GSH) were supplemented with saturated, monounsaturated, or ω-3 FA prior to exposure to 0, 0.08, 0.1, or 0.3 ppm O₃. Lipid peroxidation was measured in cellular lipid extracts and intact cells following O₃ exposure.

RESULTS

Relative to cells incubated with the saturated or monounsaturated fatty acids, cells supplemented with ω-3 FA containing 5 or 6 double bonds showed a marked increase in E_GSH during exposure to O₃ concentrations as low as 0.08 ppm. Consistent with this finding, the concentration of lipid hydroperoxides produced following O₃ exposure was significantly elevated in ω-3 FA supplemented cells.

DISCUSSION

Supplementation with polyunsaturated ω-3 FA potentiates oxidative responses, as indicated by E_GSH, in HAEC exposed to environmentally relevant concentrations of O₃. This effect is mediated by the increased formation of lipid hydroperoxides produced by the reaction of O₃ with polyunsaturated fatty acids. Given the inflammatory activity of lipid hydroperoxides, these findings have implications for the potential role of ω-3 FA in increasing human susceptibility to the adverse health effects of O₃ exposure.

Dietary and pharmacological intervention to mitigate the cardiopulmonary effects of air pollution toxicity

BACKGROUND

Exposure to air pollution contributes importantly to excess morbidity and mortality. And while regulatory actions under the "Clean Air Act" have saved millions of lives by improving air quality, there are still millions of people in the U.S. who live in areas where particulate air pollution (PM) levels exceed the U.S. Environmental Protection Agency's National Ambient Air Quality Standards. Therefore, apart from such localities working to attain such standards the protection of the health of public and in particular those at high risk might benefit from interventional strategies that would ameliorate air pollution's adverse health effects. Because inflammation and oxidative stress appear to mediate the health effects of air pollution, one interventional approach to consider is the use of dietary supplementation or medication with anti-inflammatory or antioxidant properties to block the biological responses that initiate the pathophysiological process that culminates in adverse health effects.

SCOPE OF REVIEW

This article reviews the capability of dietary supplementation, such as antioxidant vitamins, polyunsaturated fatty acids, and medications as a strategy to mitigate air pollution-induced subclinical cardiopulmonary effects.

MAJOR CONCLUSIONS

Antioxidant vitamins C and E protect the lungs against short-term ozone and PM exposure. Polyunsaturated fatty acids, such as fish oil and olive oil appear to offer protection against short-term air pollution-induced adverse cardiovascular responses.

GENERAL SIGNIFICANCE

Taking dietary supplements or medications with antioxidant or anti-inflammatory properties has the potential to provide at least partial protection against air pollution-induced adverse health effects in those individuals who are known to be most susceptible, namely those with pre-existing respiratory and cardiovascular diseases. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

Improved lung function following dietary antioxidant supplementation in exercise-induced asthmatics

INTRODUCTION

Oxidative stress is a characteristic of exercise-induced asthma (EIA), however antioxidant supplementation may attenuate EIA. The purpose of this study was to determine if ascorbic (AsA) and α-tocopherol supplementation would improve airway function in subjects with EIA.

METHODS

A single-blind randomized crossover design with eight clinically diagnosed EIA subjects (22.0 ± 0.7 year) and five healthy control subjects (28.2 ± 1.4 year) was used. Subjects consumed vitamins (V) (AsA 500 mg; α-tocopherol 300 IU) or placebo (PLA) daily for three weeks, followed by a three week washout period and then three weeks of the alternative treatment. Ten-minute treadmill tests (90% VO2peak) were performed with pulmonary function testing (forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and between 25 and 75% (FEF25-75%), and peak expiratory flow rates (PEFR)) measured pre-exercise and 1, 5, 15, and 30 min post-exercise.

RESULTS

Supplementation led to significant improvements at minute 5 and minute 15 in FVC; FEV1; PERF; FEF25-75% and minute 30 in FEV1 and FEF25-75% post-exercise.

CONCLUSION

AsA and α-tocopherol may aid the recovery of pulmonary function in subjects with EIA.

The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

Modification by antioxidant supplementation of changes in human lung function associated with air pollutant exposure: a systematic review

BACKGROUND

Outdoor air pollution, given its demonstrated negative effects on the respiratory system, is a growing public health concern worldwide, particularly in urban cities. Human exposure to pollutants such as ozone, nitrogen oxides, combustion-related particulate matter and oxides of sulfur is responsible for significant cardiopulmonary morbidity and mortality in both adults and children. Several antioxidants have shown an ability to partially attenuate the negative physiological and functional impacts of air pollutants. This study systematically presents current data on the potential benefits of antioxidant supplementation on lung function outcomes associated with air pollutant exposures in intact humans.

METHODS

Electronic databases (MEDLINE, EMBASE, BIOSIS Previews, Web of Sciences, Environmental Sciences & Pollution Management and TOXNET) were systematically searched for all studies published up to April 2009. Search terms relating to the concepts of respiratory tract diseases, respiratory function tests, air pollution, and antioxidants were used. Data was systematically abstracted from original articles that satisfied selection criteria for inclusion. For inclusion, the studies needed to have evaluated human subjects, given supplemental antioxidants, under conditions of known levels of air pollutants with measured lung function before and after antioxidant administration and/or air pollution exposure. Selected studies were summarized and conclusions presented.

RESULTS

Eight studies investigated the role of antioxidant supplementation on measured lung function outcomes after subject exposure to air pollutants under controlled conditions; 5 of these studies concluded that pollutant-induced airway hyper-responsiveness and diminution in lung function measurements were attenuated by antioxidant supplementation. The remaining five studies took place under ambient (uncontrolled) exposures and unanimously concluded that antioxidant supplementations attenuate the negative effects of urban air pollution on lung function.

CONCLUSIONS

The data evaluating modification of changes in lung function associated with air pollutant exposure by antioxidant supplementation, in intact humans, is limited. Of 13 studies dedicated to this concern, ten demonstrated an attenuation of pollution-associated decrements. There is growing evidence for the benefit of anti-oxidant supplementation in moderating the effects of air pollution on lung function, but more research on human participants is needed to inform this topic.

Dietary antioxidants and ozone-induced bronchial hyperresponsiveness in adults with asthma

Ozone exposure aggravates asthma, as has been demonstrated in both controlled exposures and epidemiologic studies. In the current double-blind crossover study, the authors evaluated the effects of dietary antioxidants (i.e., 400 IU vitamin E/500 mg vitamin C) on ozone-induced bronchial hyperresponsiveness in adult subjects with asthma. Seventeen subjects were exposed to 0.12 ppm of ozone or to air for 45 min during intermittent moderate exercise. Bronchial hyperresponsiveness was assessed with 10-min sulfur dioxide (i.e., 0.10 ppm and 0.25 ppm) inhalation challenges. Subjects who were given dietary antioxidants responded less severely to sulfur dioxide challenge than subjects given a placebo (i.e., forced expiratory volume in the 1st sec: -1.2% vs. 4.4%, respectively; peak flow: +2.2% vs. -3.0%, respectively; and mid-forced expiratory flow: +2.0% vs. -4.3%, respectively). Effects were more pronounced when subjects were grouped by response to sulfur dioxide at the screening visit. The results suggest that dietary supplementation with vitamins E and C benefits asthmatic adults who are exposed to air pollutants.

Dietary influences on chronic obstructive lung disease and asthma: a review of the epidemiological evidence

The epidemiological evidence for a relationship between diet and indicators of asthma and chronic obstructive pulmonary disease (COPD) is evaluated. The review focuses on the intake of Na, n-3 fatty acids, and antioxidant vitamins as well as fruit and vegetables. Experimental studies suggest that a high-Na diet has a small adverse effect on airway reactivity in asthma patients. However, observational studies provide no clear evidence that high Na intake has adverse effects on airway reactivity or asthma symptoms in open populations. n-3 Polyunsaturated fatty acids, which are present in fish oils, are metabolized into less broncho-constricting and inflammatory mediators than n-6 polyunsaturated fatty acids. Studies in the general adult population suggest that a high fish intake has a beneficial effect on lung function, but the relationship with respiratory symptoms and clinically-manifest asthma or COPD is less evident. Also, experimental studies in asthma patients have not demonstrated an improvement in asthma severity after supplementations with fish oil. Several studies showed a beneficial association between fruit and vegetable intake and lung function, but the relationship with respiratory symptoms and the clinically-manifest disease was less convincing. A similar pattern was found for vitamin C in relation to indicators of asthma and COPD, but there are still conflicting results with respect to vitamin E and beta-carotene. In conclusion, the epidemiological evidence for a beneficial effect on indicators of asthma and COPD of eating fish, fruit and vegetables is increasing. However, the effectiveness of dietary supplementation in open-population samples is often not demonstrated. Several unresolved questions are raised, which should be addressed in future studies on the relationship between diet and respiratory disease.

Acute effects of ozone on pulmonary function of cyclists receiving antioxidant supplements

OBJECTIVES

To identify whether acute lung function effects of ozone can be modulated by antioxidant vitamin supplementation.

METHODS

Amateur cyclists (n = 26) were studied in the summer of 1994 in The Netherlands. Repeated lung function measurements were performed with a rolling seal spirometer after training sessions or competitive races on four to 14 occasions. The cyclists were assigned to two study groups. The supplementation group (n = 12) received antioxidant supplements (15 mg beta-carotene, 75 mg vitamin E, and 650 mg vitamin C) once a day for three months. The control group did not receive supplementation. For each subject, lung function after exercise was regressed on the previous eight hour mean ozone concentration. The individual regression coefficients were pooled for each study group and weighted with the inverse of the variance.

RESULTS

The eight hour mean ozone concentration was 101 micrograms/m3 (30 to 205 micrograms/m3). For the supplementation group, there was no effect of ozone on FVC, FEV1, peak expiratory flow (PEF), and maximal mid-expiratory flow (MMEF). For the control group the mean coefficients were negative, except for MMEF. The difference between the groups was 2.08 (95% confidence interval (95% CI) 1.31 to 2.85) ml/microgram/m3 for FVC, 1.66 (95% CI 0.62 to 2.70) for FEV1, 6.83 (95% CI 3.17 to 10.49) for PEF, and 0.42 (95% CI -1.38 to 2.22) for MMEF.

CONCLUSION

The results suggest that antioxidant vitamin supplementation protects against acute effects of ozone on lung function in heavily exercising amateur cyclists.

Inhaled albuterol does not protect against ozone toxicity in nonasthmatic athletes

We evaluated the acute prophylactic efficacy of albuterol aerosol in protecting nonasthmatic athletes from the untoward effects of 0.21 ppm ozone (O3) on symptoms, pulmonary function, exercise performance, and post-exposure histamine bronchoprovocation. Fifteen trained competitive cyclists participated in a randomized crossover study consisting of double-blinded inhalations of albuterol (180 micrograms) and placebo approximately 30 min prior to heavy continuous exercise (minute ventilation, [VE] greater than or equal to 80 L/min) for 60 min, followed by a maximal sprint (peak VE greater than 140 L/min) until exhaustion. Each subject was exposed randomly to either 0.21 ppm O3 or filtered air (FA) during the four single-blinded exposure sessions. Albuterol pretreatment resulted in modest but significant bronchodilation as compared to placebo. However, albuterol did not prevent O3-induced respiratory symptoms, decrements in forced vital capacity (FVC), forced expired volume in one second (FEV1.0), and maximum midexpiratory flow rate (FEF25-75%), and positive histamine challenges as compared to that with placebo/O3. There were no statistically significant differences in the metabolic data or ride times across all drugs and exposures, although the peak VE was significantly lower with O3 than FA (142.3 vs. 150.7 L/min, respectively) regardless of drug. The results indicate that acute pretreatment with inhaled albuterol is unable to prevent or ameliorate O3-induced symptoms and alterations in pulmonary function and exercise performance. The contribution of beta-adrenergic mechanisms in the acute airway responses to O3 appears to be minimal.