Selenium, glutathione peroxidase and asthma

Honey in Bronchial Asthma: From Folk Tales to Scientific Facts

Bronchial asthma is one of the most common chronic inflammatory diseases. Complementary and alternative medicine is increasingly used for treating bronchial asthma. Ten electronic databases were searched to investigate whether honey alone or in combination with other ingredients can be considered as the potential treatment for bronchial asthma. Combinations of honey and Nigella sativa (NS) showed significant improvement in all pulmonary functions, including forced expiratory volume (FEV1) (MD = 0.52, P < .001), forced vital capacity (FVC) (MD = 0.55, P = .002), and peak expiratory flow rate (PEFR) (MD = 80.60, P < .001), in both moderate and severe, uncontrolled persistent asthma compared with baseline. Asthma control test scores also improved significantly (MD = 11.22, P < .001) in patients using combinations of honey and NS compared with baseline. Patients with a less severe grade of asthma showed a significant positive response in clinical parameters upon using honey. One study showed that using celery seeds and honey was associated with clinical improvement of both lung functions, FEV1 (MD = 18.09, P < .001) and FVC (MD = 24.23, P < .001), and respiratory parameters compared with baseline. In conclusion, honey alone has no strong evidence of being effective in controlling asthma. However, when used in combination with other substances, it showed a relatively high efficacy in patients with asthma. This finding may help in asthma control with lower cost alternatives and better outcomes.

Oxidative stress status and plasma trace elements in patients with asthma or allergic rhinitis

INTRODUCTION

This study was conducted to evaluate the oxidant/antioxidant balance (oxidative stress status) and plasma essential trace element levels in patients with bronchial asthma or allergic rhinitis.

METHODS

A total of 94 individuals consisting of 19 allergic asthmatics; 17 non-allergic asthmatics; 22 patients with allergic rhinitis; and 36 healthy control people were enrolled into this study. Superoxide dismutase (CuZnSOD) and glutathione peroxidase (GSH-Px) activity as antioxidant defence mechanism parameters, along with malondialdehyde (MDA) as a marker of lipid peroxidation, were determined in erythrocytes of patient groups and controls. Plasma copper and zinc levels were also determined in all groups.

RESULTS

CuZnSOD activity was significantly lower in all groups of patients (p<0.001 for allergic asthmatics, p=0.008 for allergic rhinitis patients, and p<0.001 for non-allergic asthmatics) when compared to those of controls. Erythrocyte GSH-Px enzyme activity was not different when compared to that of the control group. Similarly, the patient groups had no difference from those of the controls with respect to erythrocyte MDA levels. While plasma Cu levels in all asthmatic patients were not different from those of the controls, allergic rhinitis patients had significantly elevated (p<0.001) Cu levels compared to those of the controls. No statistically significant difference was established between patient groups and controls with respect to plasma zinc levels.

CONCLUSION

While defective CuZnSOD activity observed in all patients groups was expected to cause an increase in lipid peroxidation indicated by high MDA levels in these patients groups, the fact that MDA levels were not different from those of controls in all patient groups indicates that other components of anti-oxidant defence system preserve their functions in these patients. On the other hand, statistically significant difference between all patients groups and controls with respect to trace elements was only observed in allergic rhinitis patients who had higher levels of Cu than those of controls.

Serum vitamin A concentrations in asthmatic children in Japan

BACKGROUND

Vitamin A is an essential micronutrient with important roles in immunity and maintenance of normal epithelial cell differentiation. Little information is available regarding the relationship between vitamin A concentrations and asthma despite the repair of epithelial and other structural changes being of utmost importance for the relief of symptoms and control of the disease. The authors evaluated vitamin A and vitamin E concentrations in well-nourished children with asthma.

METHODS

The serum vitamin A and vitamin E concentrations were measured by high performance liquid chromatography methods. Statistical analysis was performed using the Mann-Whitney U-test and Peason's correlation coefficient test.

RESULTS

According to these methods, the mean serum vitamin A concentrations were significantly lower (19.41+/-7.45 microg/dL, mean+/-SD) in asthmatic children than controls (29.52+/-11.34 microg/dL, P=0.0001). To compare the correlation of C-reactive protein and serum vitamin A concentrations, there was also significant difference between the two groups.

CONCLUSION

The data suggest that there is a correlation between vitamin A deficiency and the mechanism of asthmatic response. These data support that the mechanism of hypovitaminosis A in asthmatic children may involve not only the acute phase response but also the various degrees of chronic epitherial damage of airways.

Dietary intake in patients with asthma: a case control study

OBJECTIVE

This case-controlled study investigated differences in dietary intake between a population with and without asthma.

METHODS

A case-controlled study of the dietary intakes of subjects with asthma (n = 54, average age 23.59 +/- 9.6 y; group 1) and healthy subjects (n = 54, average age 27.07 +/- 7.2 y; group 2) using 3-d dietary intakes was undertaken. Fifty-four patients with asthma and healthy non-asthmatic subjects matched by age and sex were selected. All enrolled subjects (asthmatic and non-asthmatic) received instruction to record their daily dietary intake for 3 d including a weekend day. Pulmonary function tests were performed in asthmatic patients.

RESULTS

Total energy intake and distribution of energy were normal in both groups (39.7% carbohydrates in group 1 and 41% in group 2, 19.4% proteins in group 1 and 22% in group 2, and 40.9% lipids in group 1 and 37% in group 2). A higher intake of vitamin A (642 +/- 399 microg/d) was detected in non-asthmatic than in asthmatic subjects (459 +/- 242 microg/d, P < 0.05). Daily intake of vitamin C was higher in non-asthmatic subjects (124 +/- 70 mg) than in asthmatic subjects (93.1 +/- 63.9 mg, P < 0.05). Vitamin E intake was higher in non-asthmatic subjects (7.3 +/- 1.2 mg) than in asthmatic subjects (5.1 +/- 2.3 mg, P < 0.05). Correlation analysis between daily intake and forced expiratory volume in 1 s (FEV1) in group 1 (asthmatic subjects) showed a positive association between omega-3 fatty acids (g/d) and FEV1 (r = 0.6, P < 0.05). No statistical correlations were detected between omega-6 and omega-9 fatty acid intakes and FEV1. Multivariant analysis with the dependent variable of FEV1 showed that only vitamin C and omega-3 fatty acids remained in the model after adjusting for smoking, age, and sex (F = 14.24, P < 0.001), with an increase of 0.25% (95% confidence interval = 0.1-0.4) in FEV1 with each 1 mug of vitamin C intake and an increase of 99.3% (95% confidence interval = 81.59-137.19) in FEV1 with each 1 g of omega-3 fatty acids.

CONCLUSIONS

Asthmatic patients have a lower intake of vitamins A, C, and E than do non-asthmatic subjects. Intake of omega-3 fatty acids was correlated with FEV1.

Glutathione peroxidase activity and serum selenium concentration in intrinsic asthmatic patients

Serum glutathione peroxidase (GSH-Px) activity and selenium concentration were compared in intrinsic asthmatic patients and non-asthmatic control subjects. Serum GSH-Px activity and selenium concentration were assessed in 46 asthmatic patients and 75 age- and sex-matched non-asthmatic subjects by spectrophotometric assay. Mean serum GSH-Px activity was lower in intrinsic asthmatic subjects (9.4 +/- 2.6 pmol NADPH oxidized/min/g of protein) than in non-asthmatic subjects (16.3 +/- 2.9 pmol NADPH oxidized/min/g of protein). Mean serum selenium was lower in intrinsic asthmatic subjects (1.15 +/- 0.23 microM) than in non-asthmatic subjects (1.98 +/- 0.27 microM). Asthmatic patients have significantly lower concentration of selenium and GSH-Px activity measured in serum.

Respiratory and allergic diseases: from upper respiratory tract infections to asthma

Patients with asthma and allergic rhinitis may benefit from hydration and a diet low in sodium, omega-6 fatty acids, and transfatty acids, but high in omega-3 fatty acids (i.e., fish, almonds, walnuts, pumpkin, and flax seeds), onions, and fruits and vegetables (at least five servings a day). Physicians may need to be more cautious when prescribing antibiotics to children in their first year of life when they are born to families with a history of atopy. More research is needed to establish whether supplementation with probiotics (lactobacillus and bifidobacterium) during the first year of life or after antibiotic use decreases the risk of developing asthma and allergic rhinitis. Despite a theoretic basis for the use of vitamin C supplements in asthmatic patients, the evidence is still equivocal, and long-term studies are needed. The evidence is stronger for exercise-induced asthma, in which the use of vitamin C supplementation at a dosage of 1 to 2 g per day may be helpful. It is also possible that fish oil supplements, administered in a dosage of 1 to 1.2 g of EPA and DHA per day, also may be helpful to some patients with asthma. Long-term studies of fish oil and vitamin C are needed for more definite answers. For the patient interested in incorporating nutritional approaches, vitamin C and fish oils have a safe profile. However, aspirin-sensitive individuals should avoid fish oils, and red blood cell magnesium levels may help in making the decision whether to use additional magnesium supplements. Combination herbal formulas should be used in the treatment of asthma with medical supervision and in collaboration with an experienced herbalist or practitioner of TCM. Safe herbs, such as Boswellia and gingko, may be used singly as adjuncts to a comprehensive plan of care if the patient and practitioner have an interest in trying them while staying alert for drug-herb interactions. No data on the long-term use of these single herbs in asthma exist. For the motivated patient, mind-body interventions such as yoga, hypnosis, and biofeedback-assisted relaxation and breathing exercises are beneficial for stress reduction in general and may be helpful in further controlling asthma. Encouraging parents to learn how to massage their asthmatic children may appeal to some parents and provide benefits for parents and children alike. Acupuncture and chiropractic treatment cannot be recommended at this time, although some patients may derive benefit because of the placebo effect. For patients with allergic rhinitis, there are no good clinical research data on the use of quercetin and vitamin C. Similarly, freeze-dried stinging nettle leaves may be tried, but the applicable research evidence also is poor. Further studies are needed to assess the efficacy of these supplements and herbs. Homeopathic remedies based on extreme dilutions of the allergen may be beneficial in allergic rhinitis but require collaboration with an experienced homeopath. There are no research data on constitutional homeopathic approaches to asthma and allergic rhinitis. Patients with COPD are helped by exercise, pulmonary rehabilitation, and increased caloric protein and fat intake. Vitamin C and n-3 supplements are safe and reasonable; however, studies are needed to establish their efficacy in COPD. On the other hand, there are convincing data in favor of N-acetyl-cysteine supplementation for the patient with COPD at doses ranging between 400 and 1200 mg daily. Red blood cell magnesium levels may guide the use of magnesium replacement. The use of L-carnitine and coenzyme Q10 in patients with COPD needs further study. The addition of essential oils to the dietary regimen of patients with chronic bronchitis is worth exploring. Patients with upper respiratory tract infections can expect a shorter duration of symptoms by taking high doses of vitamin C (2 g) with zinc supplements, preferably the nasal zinc gel, at the onset of their symptoms. Adding an herb such as echinacea or Andrographis shortens the duration of the common cold. The one study on Elderberry's use for the flu was encouraging, and the data on the homeopathic remedy Oscillococcinum interesting, but more studies should be performed. Saline washes may be helpful to patients with allergic rhinitis and chronic sinusitis. Patients also may try the German combination (available in the United States) of elderberry, vervain, gentian, primrose, and sorrel that has been tested in randomized clinical trials. Bromelain is safe to try; the trials of bromelain supplementation were promising but were never repeated. The preceding suggestions need to be grounded in a program based on optimal medical management. Patients need to be well educated in the proper medical management of their disease and skilled at monitoring disease stability and progress. Asthmatic patients need to monitor their bronchodilator usage and peak flow meter measurements to step up their medical treatment in a timely manner, if needed. Patients welcome physician guidance when exploring the breadth of treatments available today. A true patient-physician partnership is always empowering to patients who are serious about regaining their function and health.

The potential role of tocopherol in asthma and allergies: modification of the leukotriene pathway

Metabolism of arachidonic acid via the 5-lipoxygenase (5-LO) pathway leads to the formation of hydroperoxyeicosatetraenoic acids (HPETEs) and leukotriene (LT) A4. This unstable allylic epoxide can be further converted by secondary enzymes into LTB(4) and cysteinyl LTs. LTs represent a family of potent biologically active compounds synthesised by specific cell types and by transcellular biosynthetic mechanisms. Cysteinyl LTs are involved in the pathogenesis of asthma, and recent data indicate that individuals with asthma may have enhanced basal excretion of urinary LTE4 compared with normal individuals. Tocopherol (vitamin E) and tocopherol acetate strongly inhibit potato 5-LO in an irreversible and noncompetitive way, and, by affecting the redox state of cells possessing 5-LO, they may influence the production of biologically active LTs. It has been reported that normal plasma levels of tocopherol may enhance the lipoxygenation of arachidonic acid, whereas higher tocopherol levels exert a suppressive effect that is consistent with its role as a hydroperoxide scavenger. Receptor-mediated activation of neutrophils in individuals with asthma results in the synthesis of LTs. This activation is inhibited by tocopherol in a concentration-dependent manner. Additional controlled studies are needed to assess the effect of tocopherol on leukotriene production in asthmatic individuals. The results of these studies may be useful in developing new therapeutic approaches in asthmatic/allergic patients.

Antioxidant activity levels and oxidative stress as blood markers of allergic response to drugs

Antioxidant enzymes work together in human blood cells against toxic reactive oxygen species. Although their relationship with several pathophysiologic processes has been stated, not much is known about the connection between antioxidant defence and allergy. This study was designed to determine the enzymatic activities and the oxidative indices in the blood and serum proteins in patients suffering from allergy to drugs. We hypothesize that serum and blood reactions may serve as useful clinical marker for the allergic state. We used enzymatic antioxidant activities, thiobarbituric acid reactive substances, and carbonyl contents of proteins as suitable markers. We determined superoxide dismutases, glutathione peroxidase and catalase activities in each cell type. After antihistaminics plus steroids were given as part of a protocol treatment, enzymatic antioxidant activities, thiobarbituric acid reactive substance levels, and carbonyl contents were used as recovering markers for the disease. We found a relationship between antioxidant enzymatic activities, thiobarbituric acid reactive substance levels, and carbonyl contents for allergic reactions belonging to several type I and type IV allergies, as well as cross-reactive intolerance to nonsteroidal anti-inflammatory drugs and an anaphylactoid reaction to a radiocontrast media. A similar pattern also exists for analogous allergic manifestations and disease-like status.Key words: allergy, blood, catalase, glutathione peroxidase, superoxide dismutase.

Diet and asthma

The role of food intolerance in asthma is well recognized, and where food avoidance measures are instituted considerable improvement in asthma symptoms and in reduction in drug therapy and hospital admissions can result. These benefits may have a greater impact in those patients with greater symptoms. However, the promise of such benefits should not result in an approach which ignores inhaled drug therapy, or in a dietary regime which is inappropriate in the face of mild symptoms. Whilst sub-optimal intake of dietary nutrients is also a recently recognized potential risk factor for asthma, available data are insufficient to implicate any as casual. A number of studies have sought to establish the role of the antioxidant vitamins, A, C and E and selenium, yet others of the elements sodium and magnesium. Sub-optimal nutrient intake may enhance asthmatic inflammation, consequently contributing to bronchial hyperreactivity. Prospective studies of supplementation therapy are needed to confirm this.

Chemical and biological activity of free radical 'scavengers' in allergic diseases

Reactive oxygen species (ROS) are generated constantly in vivo. They can lead to lipid peroxidation and oxidation of some enzymes, as well as protein oxidation and degradation. Cells possess several biological systems, defined as 'scavengers', to protect themselves from the radical-mediated damage. Immune cells may discharge their arsenal of toxic agents against host tissues, resulting in oxidative damage and inflammation. Therefore, free radical production and disturbance in redox status can modulate the expression of a variety of immune and inflammatory molecules, leading to inflammatory processes, both exacerbating inflammation and effecting tissue damage. Recently, abnormal immunity has been related to oxidative imbalance, and antioxidant functions are linked to anti-inflammatory and/or immunosuppressive properties. Currently, allergy is one of the most important human diseases. We studied the role of the primary antioxidant defence system, constituted by the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase, protecting cells from toxic oxygen. We analyzed how they are involved in blood cells detoxification, and how the imbalance of reactive oxygen species is related to inflammation in allergic diseases by affecting immune cells. Finally, we discuss the published data that relates anti-free radical therapy to the management of human allergic diseases.

Allergy to drugs: antioxidant enzymic activities, lipid peroxidation and protein oxidative damage in human blood

Reactive oxygen species lead to lipid peroxidation and specific oxidation of some specific enzymes, proteins and other macromolecules, thus affecting many intra- and intercellular systems. Recently, antioxidant functions have been linked to anti-inflammatory properties. Cell defences against toxic oxygen include antioxidant enzymes. We studied the enzymic antioxidant capacity in human blood of both erythrocytes and mononuclear cells from patients suffering from an allergic reaction to different drugs. We determined superoxide dismutases (SODs), glutathione peroxidase (GSHPx) and catalase (CAT) activities in each cell type. We also determined the extent of thiobarbituric acid reactive substances (TBARS) and the oxidative damage to proteins, in order to study the correlation between the cellular enzymic activities, the oxidative status and the allergic reaction. In mononuclear cells from allergic patients, SODs and CAT activities were enhanced compared with controls. Conversely, a decrease in GSHPx activity was found. In erythrocytes, higher values for CAT, GSHPx and SODs activities were found in allergic patients. TBARS were also enhanced in both types of cells, and the carbonyl content of serum was equally increased. The respective enzymic imbalances in mononuclear cells and erythrocytes, namely, GSHPx/SOD and CAT/SOD, and their consequences are discussed. To our knowledge, this is the first global study of antioxidant enzyme determinations, including TBARS level and carbonyl content, in patients suffering from allergies to drugs.

Antioxidant enzymes and human diseases

OBJECTIVES

To describe the importance of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase working together in human cells against toxic reactive oxygen species, their relationship with several pathophysiologic processes and their possible therapeutic implications.

CONCLUSIONS

Reactive oxygen species (ROS) are involved in the cell growth, differentiation, progression, and death. Low concentrations of ROS may be beneficial or even indispensable in processes such as intracellular signaling and defense against micro-organisms. Nevertheless, higher amounts of ROS play a role in the aging process as well as in a number of human disease states, including cancer, ischemia, and failures in immunity and endocrine functions. As a safeguard against the accumulation of ROS, several nonenzymatic and enzymatic antioxidant activities exist. Therefore, when oxidative stress arises as a consequence of a pathologic event, a defense system promotes the regulation and expression of these enzymes.

Asthma, oxidant stress, and diet

It has been suggested that the increased prevalence of atopy and asthma observed in many developed countries over the past 30 y is in part the result of a decrease in the incidence and severity of early childhood infections. The immunologic consequence of this phenomenon has been the expansion of T-lymphocyte populations away from the T-helper 1 (Th1) subset and in the direction of the Th2 subset. This leads to the creation of a cytokine-mediated propensity for the development of an intense inflammatory response in the airways, resulting in oxidative stress, airway tissue injury, and the development of atopy and asthmatic symptomatology. Over this same period, there has been a decreased intake of dietary substances that contribute to antioxidant defense, and this appears to have contributed to the rise of atopy and asthma. Studies evaluating the efficacy of these antioxidant substances in the prevention of asthma and as adjuvants in the treatment of asthma are reviewed, and suggestions are made for the direction of future studies.

Effect of selenium supplementation in asthmatic subjects on the expression of endothelial cell adhesion molecules in culture

Endothelial cells play a major role in immunologic reactions, in which cellular adhesion molecules P-selectin, ICAM-1, VCAM-1, and ELAM-1 are important mediators in the recruitment of leukocytes in pulmonary inflammation. Selenium (Se) is known to modulate immunological mechanisms of asthma. The aim of our investigation was to examine whether Se supplementation in cortico-dependent asthmatic patients may modulate adhesion molecule expression in cultured endothelium. Our findings indicated that P-selectin, VCAM-1, and ELAM-1 expression on human umbilical vein endothelial cells stimulated with peripheral blood mononuclear cells obtained from asthmatics before supplementation with Se was significantly higher than from healthy donors (p < 0.05). The production of ICAM-1 showed only slight augmentation. The levels of VCAM-1 and ELAM-1 expression were significantly decreased after 3 mo of Se supplementation (p < 0.05). After 6 mo of intervention period the intensity of P-selectin and ICAM-1 expression was also significantly reduced (p < 0.05 and p < 0.01, respectively). The inhibitory effect of Se on the adhesion molecule expression was studied in cultured endothelial cells after interferon-gamma stimulation. Our data suggest that Se affects the expression of P-selectin, ICAM-1, VCAM-1, and ELAM-1 in a dose-dependent manner and the half-maximal inhibitory concentrations were 3.4, 0.5, 4, and 3.8 microg/mL, respectively. The maximal inhibitions (greater than 80%) were observed in vitro with 10 microg/mL Se (p < 0.01). Regulation of adhesion molecule expression may be an important mechanism through which the inflammation may be controlled.

Dietary antioxidants and magnesium in type 1 brittle asthma: a case control study

BACKGROUND

Type 1 brittle asthma is a rare form of asthma. Atopy, psychosocial factors and diet may contribute to this condition. As increased dietary magnesium has a beneficial effect on lung function and selenium, vitamins A, C and E have antioxidant properties, a study was undertaken to test the hypothesis that patients with brittle asthma have diets deficient in these nutrients compared with subjects with non-brittle asthma and healthy adults.

METHODS

A case control study of the dietary intakes of 20 subjects with brittle asthma, 20 with non-brittle asthma, and 20 healthy adults was performed using five day weighed dietary records. Intake of magnesium was the primary outcome measure with selenium and vitamins A, C and E as secondary outcomes. Serum levels were measured at the same time as the dietary assessment.

RESULTS

Sixty subjects (27 men) of mean age 49.5 years were recruited and completed the study. Subjects with brittle asthma had statistically lower median dietary intakes of vitamins A and E than the other groups (vitamin A: brittle asthma 522.5 micrograms/day, non-brittle asthma 869.5 micrograms/day, healthy adults 806.5 micrograms/day; vitamin E: brittle asthma 4.3 mg/day, non-brittle asthma 4.6 mg/day, healthy adults 4.5 mg/day). Median dietary intakes for the other nutrients were not significantly different between groups. Serum levels were within normal ranges for each nutrient in all subjects. Intakes less than the reference nutrient intake (RNI) for magnesium and vitamins A and C, and less than the safe intake (SI) for vitamin E were more likely in patients with brittle asthma than in those with non-brittle asthma.

CONCLUSION

Nutrient deficiency and reduced antioxidant activity may contribute to disease activity in type 1 brittle asthma, although a prospective study of replacement therapy will be needed to confirm this hypothesis.

Nebulized glutathione induces bronchoconstriction in patients with mild asthma

To assess the effects on bronchial responsiveness of nebulized glutathione (GSH), one of the most efficient scavengers of oxidant substances in the airways, we studied eight patients with mild asthma (FEV1, 88 +/- 11% predicted [SD]) in a randomized, double-blind, cross-over, placebo-controlled fashion. Bronchial challenge was measured using both FEV1 and total pulmonary resistance (Rrs) by the forced oscillation technique. Patients received nebulized GSH (600 mg with 4 ml of 0.9% sodium chloride) or placebo (identical saline solution) over a period of 25 min, 1 wk apart. Placebo provoked subclinical mild bronchoconstriction (changes from baseline: FEV1, -1%; Rrs, +17%); by contrast, GSH caused major airway narrowing (changes from baseline: FEV1, -19%; Rrs, +61%) and induced cough (four patients) or breathlessness (three patients). Differences between placebo and GSH after challenge were also noticeable in both FEV1 (p = 0.03) and Rrs (p = 0.02). Neither osmolarity (660 mosm.kg-1) nor pH (3.0) of the GSH solution accounted for these effects. Nebulized salbutamol (5.0 mg) given before the GSH challenge blocked GSH-induced bronchoconstriction. Furthermore, GSH-induced FEV1 falls were inversely correlated with metabisulfite bronchoprovocation (provocative dose [PD20], 1.49 +/- 1.83 mumol) but not with methacholine challenge. The detrimental effects of nebulized GSH on the airway bronchial tone in patients with mild asthma strongly suggests bronchoconstriction provoked by sulfite formation.

Asthma and oxidant stress: nutritional, environmental, and genetic risk factors

A considerable body of evidence suggests that oxidant stress results in inflammation and tissue damage in the respiratory system, and later in immune damage, and that individuals with lowered cellular reducing capacity are at increased risk to develop asthma. Reducing capacity in the erythrocyte is generated through the pentose phosphate pathway and this pathway also generates a major portion of the reducing capacity in all cells of the body. Therefore, dietary, environmental, and genetic factors which diminish cellular reducing capacity will increase tissue vulnerability to oxidant stress and are likely to increase asthma risk. Dietary selenium deficiency lowers red cell glutathione peroxidase activity and is associated with an increased risk for asthma, and low dietary intakes of vitamins C and E also appear to increase asthma risk. High body iron stores increase free radical production and may also elevate asthma risk. Environmental lead exposure depresses the activities of a several enzyme systems that influence cellular reducing capacity (glucose-6-phosphate dehydrogenase, NAD synthetase, glutathione peroxidase, superoxide dismutase, catalase) and consequently may increase asthma risk. Genetically-determined low activity of glucose-6-phosphate dehydrogenase lowers cellular reducing capacity and may also heighten asthma risk. Simple dietary and environmental interventions may significantly reduce oxidant stress and prevent or minimize the development of asthmatic symptoms and should prove to be a cost effective approach to asthma management in addition to current pharmacological strategies.

Antioxidant status in asthma

Reduced levels of glutathione peroxidase (GSH-Px) have been observed in adults with asthma. This study examines the antioxidant status in children with asthma compared with a control group in a cross-sectional analysis. Red blood cell GSH-Px, superoxide dismutase (SOD), and plasma concentrations of retinol, vitamin C, alpha tocopherol, and cholesterol were measured in 37 subjects (26 males) with stable controlled asthma. Thirty-five subjects (20 males) without eczema, hayfever, or recurrent respiratory symptoms were used as a control group. Children with asthma had significantly reduced red blood cell GSH-Px activity compared with controls [median (inter-quartile range) for asthma group, 10.25 (9.25-11.91); for control group, 11.75 (10.34-12.26) IU/g Hb; P = 0.006]. There were no significant differences in activity of SOD or vitamin C, retinol, or alpha tocopherol/cholesterol ratio. The reduction in GSH-Px activity may have therapeutic and etiological implications for asthma. The effects of disease activity and treatment on antioxidant status needs for further study.