Antioxidant status in asthma

Oxidative stress in allergic respiratory diseases

There is ample evidence that allergic disorders, such as asthma, rhinitis, and atopic dermatitis, are mediated by oxidative stress. Excessive exposure to reactive oxygen and nitrogen species is the hallmark of oxidative stress and leads to damage of proteins, lipids, and DNA. Oxidative stress occurs not only as a result of inflammation but also from environmental exposure to air pollution and cigarette smoke. The specific localization of antioxidant enzymes in the lung and the rapid reaction of nitric oxide with reactive oxygen species, such as superoxide, suggest that antioxidant enzymes might also function as cell-signaling agents or regulators of cell signaling. Therapeutic interventions that decrease exposure to environmental reactive oxygen species or augment endogenous antioxidant defenses might be beneficial as adjunctive therapies for allergic respiratory disorders.

Vitamin A status in children with asthma

Low vitamin A levels have been found in a number of diseases in children. The aim of this study was to examine the vitamin A status in children with asthma and to correlate the changes with severity of disease. Serum levels of vitamin A, retinol-binding protein (RBP), and albumin were estimated in 35 asthmatic children (24 males) in the age group of 2-12 years (mean 5.89 years) and 29 controls (19 males). Both study and control groups were similar with respect to age, sex, and overall nutritional status. Twenty-four children in the study group (68.6%) had moderate to severe persistent asthma and eight children had mild persistent asthma. Only three patients suffered from mild intermittent asthma. Vitamin A levels in children with asthma (mean +/- SD 22.14 +/- 5.38 microg/dl) were found to be significantly lower than their controls (mean +/- SD 27.54 +/- 4.83 microg/dl) (p = 0.0001). Age, age of onset of asthma, and gender had no correlation with serum vitamin A levels. Low serum vitamin A levels (< 20 microg/dl) were observed four times more commonly in the study group (28.6%) than controls (6.9%). Severity of asthma had a negative correlation with serum vitamin A levels (r = - 0.61, p = 0.0001). Children with severe persistent asthma had markedly low serum vitamin A levels (mean +/- SD 13.42 +/- 5.19 microg/dl) as compared with mild intermittent asthma (mean +/- SD 24.61 +/- 2.32 microg/dl). Therapeutic trials are needed to prove whether low vitamin A levels contribute to asthma severity and the clinical utility of vitamin A supplementation in asthmatic children.

Lipid peroxidation as determined by plasma isoprostanes is related to disease severity in mild asthma

Oxidlative stress is believed to play an important role in the pathophysiology of asthma. Recently discovered F2-isoprostanes, of which 8-iso-PGF2alpha is the most well-known isomer, have emerged as the most reliable marker of in vivo oxidative stress. The aim of this study was to examine 8-iso-PGF2alpha as a biomarker of oxidative stress in mild asthma in relation to endogenous and dietary antioxidant protection. Total (free and esterified) plasma 8-iso-PGF2alpha, plasma dietary antioxidants (vitamins E and C, Beta-carotene, Zn, and Se), and erythrocyte antioxidant enzyme activities (glutathione peroxidase and superoxide dismutase) were measured in 15 mild asthmatics and 15 age-and sex-matched controls. Total plasma 8-iso-PGF2alpha levels [median (quartile 1 - quartile 3)] were significantly increased in the asthmatics [213 pg/mL (122-455) vs. 139 pg/mL (109-174), P= 0.042]. The 8-iso PGF2alpha levels were found to be associated with clinical asthma severity (P = 0.044) and inhaled corticosteroid use (P = 0.027) in asthmatics. No differences were observed in the plasma dietary antioxidant vitamins. The asthmatics had significantly lower plasma levels of Zn (P = 0.027) and Se (P = 0.006). Plasma Se correlated negatively with 8-iso-PGF2alpha (r = -0.725, P= 0.002). No differences between the groups were observed for glutathione peroxidase or superoxide dismutase, however, superoxide dismutase activity was negatively associated with asthma severity (P = 0.042). In conclusion, oxidative stress is increased in mildly asthmatics, as reflected by increased plasma levels of 8-iso-PGF2alpha and a deficiency in plasma Zn and Se. The isoprostane 8-iso-PGF2alpha may provide a useful tool in intervention studies aimed at improving clinical status in asthma.

Consumption of fresh fruit rich in vitamin C and wheezing symptoms in children. SIDRIA Collaborative Group, Italy (Italian Studies on Respiratory Disorders in Children and the Environment)

BACKGROUND

A beneficial effect of fresh fruit consumption on lung function has been observed in several studies. The epidemiological evidence of the effect on respiratory symptoms and asthma is limited. The consumption of fruit rich in vitamin C was examined in relation to wheezing and other respiratory symptoms in cross sectional and follow up studies of Italian children.

METHODS

Standardised respiratory questionnaires were filled in by parents of 18 737 children aged 6-7 years living in eight areas of Northern and Central Italy. The winter intake of citrus fruit and kiwi fruit by the children was categorised as less than once per week, 1-2 per week, 3-4 per week, and 5-7 per week. A subset of 4104 children from two areas was reinvestigated after one year using a second parental questionnaire to record the occurrence of wheezing symptoms over the intervening period.

RESULTS

In the cross sectional analysis, after controlling for several confounders (sex, study area, paternal education, household density, maternal smoking, paternal smoking, dampness or mould in the child's bedroom, parental asthma), intake of citrus fruit or kiwi fruit was a highly significant protective factor for wheeze in the last 12 months (odds ratio (OR) = 0.66, 95% confidence intervals (CI) 0.55 to 0.78, for those eating fruit 5-7 times per week compared with less than once per week), shortness of breath with wheeze (OR = 0.68, 95% CI 0.56 to 0.84), severe wheeze (OR = 0.59, 95% CI 0.40 to 0.85), nocturnal cough (OR = 0.73, 95% CI 0.65 to 0.83), chronic cough (OR = 0.75, 95% CI 0.65 to 0.88), and non-coryzal rhinitis (OR = 0.72, 95% CI 0.63 to 0.83). In the follow up study fruit intake recorded at baseline was a strong and independent predictor of all symptoms investigated except non-coryzal rhinitis. In most cases the protective effect was evident even among children whose intake of fruit was only 1-2 times per week and no clear dose-response relationship was found. The effect was stronger (although not significantly so (p = 0.13)) in subjects with a history of asthma; those eating fresh fruit at least once a week experienced a lower one year occurrence of wheeze (29. 3%) than those eating fruit less than once per week (47.1%) (OR = 0. 46, 95% CI 0.27 to 0.81).

CONCLUSIONS

Although the effect of other dietary components cannot be excluded, it is concluded that the consumption of fruit rich in vitamin C, even at a low level of intake, may reduce wheezing symptoms in childhood, especially among already susceptible individuals.

Treatment of obstructive airway disease with a cysteine donor protein supplement: a case report

Oxidant/antioxidant imbalance can occur in obstructive airways disease as a result of ongoing inflammation. Glutathione (GSH) plays a major role in pulmonary antioxidant protection. As an alternative or complement to anti-inflammatory therapy, augmenting antioxidant protection could diminish the effects of inflammation. We describe a case of a patient who had obstructive lung disease responsive to corticosteroids, and low whole blood GSH levels. After 1 month of supplementation with a whey-based oral supplement designed to provide GSH precursors, whole blood GSH levels and pulmonary function increased significantly and dramatically. The potential for such supplementation in pulmonary inflammatory conditions deserves further study.

Oxidative stress and pulmonary inflammation: pharmacological intervention with antioxidants

Reactive oxygen and nitrogen species are generated by several inflammatory and structural cells of the airways. These oxidant species may have important effects on different lung cells as regulators of signal transduction, activators of key transcription factors, and modulators of gene expression and apoptosis. Thus, an increased oxidative stress accompanied by reduced endogenous antioxidant defences may have a role in the pathogenesis of a number of inflammatory pulmonary diseases including asthma. Although antioxidant drugs could play a useful role in the therapy of inflammatory lung diseases, their clinical impact is relatively modest at present. Rigorous clinical investigation with the existing antioxidants and development of new drugs with improved lung bioavailability are necessary in the future.pc 1999 Academic Press@p$hr