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

The Role of Vitamins in the Pathogenesis of Asthma

Vitamins play a crucial role in the proper functioning of organisms. Disturbances of their levels, seen as deficiency or excess, enhance the development of various diseases, including those of the cardiovascular, immune, or respiratory systems. The present paper aims to summarize the role of vitamins in one of the most common diseases of the respiratory system, asthma. This narrative review describes the influence of vitamins on asthma and its main symptoms such as bronchial hyperreactivity, airway inflammation, oxidative stress, and airway remodeling, as well as the correlation between vitamin intake and levels and the risk of asthma in both pre- and postnatal life.

Anti-allergic effects of vitamin E in allergic diseases: An updated review

Allergic diseases are caused by the immune system's response to innocent antigens called allergens. Recent decades have seen a significant increase in the prevalence of allergic diseases worldwide, which has imposed various socio-economic effects in different countries. Various factors, including genetic factors, industrialization, improved hygiene, and climate change contribute to the development of allergic diseases in many parts of the world. Moreover, changes in lifestyle and diet habits play pivotal roles in the prevalence of allergic diseases. Dietary changes caused by decreased intake of antioxidants such as vitamin E lead to the generation of oxidative stress, which is central to the development of allergic diseases. It has been reported in many articles that oxidative stress diverts immune responses to the cells associated with the pathogenesis of allergic diseases. The aim of this short review was to summarize current knowledge about the anti-allergic properties of vitamin E.

Anti-allergic function of α-Tocopherol is mediated by suppression of PI3K-PKB activity in mast cells in mouse model of allergic rhinitis

BACKGROUND

Alpha-Tocopherol (α-TCP), one major form of vitamin E, has been known as a treatment for airway allergic inflammation. However, the role and mechanism of α-TCP in treating allergic rhinitis remains unclear.

OBJECTIVE

In this study we examined the inhibitory function of α-TCP in a mouse model of allergic rhinitis.

METHODS

Allergic phenotype was examined by hematoxylin and eosin staining. Total IgE, OVA-specific IgE, OVA-specific IgG1 and OVA-specific IgG2a levels were examined by ELISA. mRNA expression was measured by qPCR, protein levels were examined by Western Blot.

RESULTS

Histological analysis of the nasal membranes revealed that there was a significant reduction in inflammatory cells appearance in cross-sections in alpha-TCP treatment of Ovalbumin (OVA)-sensitized mice compared to OVA sensitized animals. In addition, eosinophils were significantly reduced in nasal mucosa of alpha-TCP treatment of OVA-sensitized mice compared to the OVA group. Lower total IgE, OVA-specific IgE, OVA-specific IgG1 and OVA-specific IgG2a levels were found in alpha-TCP treatment of OVA-sensitized mice compared to the OVA group. Furthermore, we found that the subepithelial distribution of tryptase positive mast cells was reduced in the alpha-TCP treatment of OVA-sensitized mice. More importantly, the PI3K-PKB pathway was suppressed by α-TCP in mast cells.

CONCLUSIONS

Our results demonstrated that α-TCP-mediated suppression of PI3K-PKB activity in mast cells is a potential mechanism of anti-allergic function of α-TCP.

A reappraisal of the mucoactive activity and clinical efficacy of bromhexine

Since its introduction to the market in 1963, bromhexine, an over-the-counter drug, has been investigated for its activity in animal models and in humans with diverse respiratory conditions. Bromhexine is a derivate of the Adhatoda vasica plant used in some countries for the treatment of various respiratory diseases. Bromhexine has been found to enhance the secretion of various mucus components by modifying the physicochemical characteristics of mucus. These changes, in turn, increase mucociliary clearance and reduce cough. Principal clinical research studies were primarily developed in an era when stringent methodological approaches and good clinical practices were not developed yet. Clinical studies were conducted mainly in patients with chronic bronchitis and in patients with various respiratory diseases, and demonstrated the efficacy of bromhexine in improving respiratory symptoms. Furthermore, the co-administration of antibiotics with bromhexine amplified the actions of the antibiotic. Although the clinical evidence shows only modest but positive results, bromhexine is indicated for its mucoactive activity. Larger trials with adequate methodology are required to identify when treatment with bromhexine can improve clinical outcomes.

Prostaglandin D2 receptor antagonists in early development as potential therapeutic options for asthma

INTRODUCTION

Asthma is a chronic inflammatory disease characterized by bronchial hyper-reactivity. Although many currently available treatment regimens are effective, poor symptom control and refractory severe disease still represent major unmet needs. In the last years, numerous molecular therapeutic targets that interfere with the innate inflammatory response in asthma have been identified. Promising preliminary results concern the signaling cascade promoted by prostaglandin D2 (PGD2) and its receptor antagonists.

AREAS COVERED

The aim of this review is to provide the most recent clinical and preclinical data on the efficacy and safety of newly developed compounds for the treatment of allergic asthma. The authors will present an overview of the pathogenetic molecular mechanisms sustaining the chronic inflammatory response in asthma; the focus will be then directed on the mediators of the PGD2 pathway, the chemoattractant receptor-homologous molecule expressed on TH2 cells, and their latest antagonists developed.

EXPERT OPINION

Bronchodilators and corticosteroids are not sufficient to achieve a satisfactory management of all asthmatic patients; the development of new specific treatments appears therefore essential. The good results in terms of cellular, functional and clinical outcomes, together with an acceptable safety of the CRTh2 antagonists represent a promising start for a tailored management of allergic asthma.

Oxidative stress and respiratory system: pharmacological and clinical reappraisal of N-acetylcysteine

The large surface area for gas exchange makes the respiratory system particularly susceptible to oxidative stress-mediated injury. Both endogenous and exogenous pro-oxidants (e.g. cigarette smoke) trigger activation of leukocytes and host defenses. These mechanisms interact in a "multilevel cycle" responsible for the control of the oxidant/antioxidant homeostasis. Several studies have demonstrated the presence of increased oxidative stress and decreased antioxidants (e.g. reduced glutathione [GSH]) in subjects with chronic obstructive pulmonary disease (COPD), but the contribution of oxidative stress to the pathophysiology of COPD is generally only minimally discussed. The aim of this review was to provide a comprehensive overview of the role of oxidative stress in the pathogenesis of respiratory diseases, particularly COPD, and to examine the available clinical and experimental evidence on the use of the antioxidant N-acetylcysteine (NAC), a precursor of GSH, as an adjunct to standard therapy for the treatment of COPD. The proposed concept of "multilevel cycle" helps understand the relationship between respiratory diseases and oxidative stress, thus clarifying the rationale for using NAC in COPD. Until recently, antioxidant drugs such as NAC have been regarded only as mucolytic agents. Nevertheless, several clinical trials indicate that NAC may reduce the rate of COPD exacerbations and improve small airways function. The most plausible explanation for the beneficial effects observed in patients with COPD treated with NAC lies in the mucolytic and antioxidant effects of this drug. Modulation of bronchial inflammation by NAC may further account for these favorable clinical results.

Gamma-tocopherol prevents airway eosinophilia and mucous cell hyperplasia in experimentally induced allergic rhinitis and asthma

BACKGROUND

Traditional therapies for asthma and allergic rhinitis (AR) such as corticosteroids and antihistamines are not without limitations and side effects. The use of complementary and alternative approaches to treat allergic airways disease, including the use of herbal and dietary supplements, is increasing but their efficacy and safety are relatively understudied. Previously, we have demonstrated that gamma-tocopherol (gammaT), the primary form of dietary vitamin E, is more effective than alpha-tocopherol, the primary form found in supplements and tissue, in reducing systemic inflammation induced by non-immunogenic stimuli.

OBJECTIVE

We used allergic Brown Norway rats to test the hypothesis that a dietary supplement with gammaT would protect from adverse nasal and pulmonary responses to airway allergen provocation.

METHODS

Ovalbumin (OVA)-sensitized Brown Norway rats were treated orally with gammaT before intranasal provocation with OVA. Twenty-four hours after two challenges, histopathological changes in the nose, sinus and pulmonary airways were compared with gene expression and cytokine production in bronchoalveolar lavage fluid and plasma.

RESULTS

We found that acute dosing for 4 days with gammaT was sufficient to provide broad protection from inflammatory cell recruitment and epithelial cell alterations induced by allergen challenge. Eosinophil infiltration into airspaces and tissues of the lung, nose, sinus and nasolacrimal duct was blocked in allergic rats treated with gammaT. Pulmonary production of soluble mediators PGE(2), LTB(4) and cysteinyl leukotrienes, and nasal expression of IL-4, -5, -13 and IFN-gamma were also inhibited by gammaT. Mucous cell metaplasia, the increase in the number of goblet cells and amounts of intraepithelial mucus storage, was induced by allergen in both pulmonary and nasal airways and decreased by treatment with gammaT.

CONCLUSIONS

Acute treatment with gammaT inhibits important inflammatory pathways that underlie the pathogenesis of both AR and asthma. Supplementation with gammaT may be a novel complementary therapy for allergic airways disease.

Ozone enhancement of lower airway allergic inflammation is prevented by gamma-tocopherol

Ozone is a commonly encountered environmental oxidant which has been linked to asthma exacerbation in epidemiological studies. Ozone induces airway inflammation and enhances response to inhaled allergen. It has been suggested that antioxidant therapy may minimize the adverse effects of ozone in asthma. We have previously shown that the antioxidant gamma-tocopherol (gammaT), an isoform of vitamin E, also has anti-inflammatory effects. We employed a Brown Norway rat model of ozone-enhanced allergic responses to test the therapeutic effects of gammaT on O(3)-induced airway inflammation. Ovalbumin (OVA)-sensitized rats were intranasally challenged with 0 or 0.5% OVA on Days 1 and 2, and exposed to 0 or 1 ppm ozone (8 h/day) on Days 4 and 5. Rats were also given 0 or 100 mg/kg gammaT on Days 2 through 5. Pulmonary tissue and bronchoalveolar lavage fluid (BALF) were collected on Day 6. OVA challenge caused increased total cells (267% increase) and eosinophils (4000%) in BALF that was unaffected by ozone exposure. Morphometric evaluation of lung tissue revealed increases in intraepithelial mucosubstances (IM) (300%) and subepithelial eosinophils (400%) in main axial airways. Ozone exposure of allergic rats enhanced IM increases in proximal axial airways (200%), induced cys-leukotrienes, MCP-1, and IL-6 production in BALF, and upregulated expression of IL-5 and IL-13 mRNA. gammaT treatment had no effect on IM increases by allergen, but blocked enhancement by ozone. gammaT attenuated both OVA- or ozone-stimulated eosinophilic infiltration, and increases of BALF cys-leukotrienes, MCP-1, and IL-6, as well as IL-5 and IL-13 mRNA. These data demonstrate broad anti-inflammatory effects of a gammaT and suggest that it may be an effective therapy of allergic airway inflammation.

Vitamin E and mast cells

Mast cells play an important role in the immune system by interacting with B and T cells and by releasing several mediators involved in activating other cells. Hyperreactivity of mast cells and their uncontrolled accumulation in tissues lead to increased release of inflammatory mediators contributing to the pathogenesis of several diseases such as rheumatoid arthritis, atherosclerosis, multiple sclerosis, and allergic disorders such as asthma and allergic rhinitis. Interference with mast cell proliferation, survival, degranulation, and migration by synthetic or natural compounds may represent a preventive strategy for the management of these diseases. Natural vitamin E covers a group of eight analogues-the alpha-, beta-, gamma-, and delta-tocopherols and the alpha-, beta-, gamma-, and delta-tocotrienols, but only alpha-tocopherol is efficiently retained by the liver and distributed to peripheral tissues. Mast cells preferentially locate in the proximity of tissues that interface with the external environment (the epithelial surface of the skin, the gastrointestinal mucosa, and the respiratory system), what may render them accessible to treatments with inefficiently retained natural vitamin E analogues and synthetic derivatives. In addition to scavenging free radicals, the natural vitamin E analogues differently modulate signal transduction and gene expression in several cell lines; in mast cells, protein kinase C, protein phosphatase 2A, and protein kinase B are affected by vitamin E, leading to the modulation of proliferation, apoptosis, secretion, and migration. In this chapter, the possibility that vitamin E can prevent diseases with mast cells involvement by modulating signal transduction and gene expression is evaluated.

Effects of alpha tocopherol and probucol supplements on allergen-induced airway inflammation and hyperresponsiveness in a mouse model of allergic asthma

OBJECTIVE

We investigated the role of antioxidants in airway hyperresponsiveness to acetylcholine using young asthma model mice, which were sensitized and stimulated with ovalbumin.

METHODS

The mice had been fed either a normal diet, an alpha-tocopherol-supplemented diet or a probucol-supplemented diet 14 days before the first sensitization. They were immunized with antigen at intervals of 12 days and, starting from 10 days after the second immunization, they were exposed to antigen 3 times every 4th day using an ultrasonic nebulizer. Twenty-four hours after the last antigen inhalation, airway responsiveness to acetylcholine was measured and bronchoalveolar lavage fluid (BALF) was collected. A blood and lung tissue study was also carried out.

RESULTS

Twenty-four hours after the last antigen challenge, both IL-4 and IL-5 in the BALF of alpha-tocopherol-supplemented mice were significantly decreased. The IL-5 level in probucol-supplemented mice was also decreased, but there was no difference in IL-4 levels. The serum IgE level was decreased in probucol-supplemented mice. Differential cell rates of the fluid revealed a significant decrease in eosinophils due to antioxidant supplementation. Airway hyperresponsiveness to acetylcholine was also repressed in antioxidant-supplemented mice. In histological sections of lung tissue, inflammatory cells and mucus secretion were markedly reduced in antioxidant-supplemented mice. We investigated the antioxidant effect on our model mice by examining 8-isoprostane in BALF and lung tissue, and acrolein in BALF; however, our experiment gave us no evidence of the antioxidant properties of either alpha-tocopherol or probucol contributing to the reduction of airway inflammation.

CONCLUSION

These findings indicate that alpha-tocopherol and probucol suppress allergic responses in asthma model mice, although these two drugs cause suppression in different ways that are unrelated to antioxidation.

The role of selenium, zinc and antioxidant vitamin supplementation in the treatment of bronchial asthma: adjuvant therapy or not?

In the last few years, nutrition has represented an important conditioning factor of many cardiovascular, gastrointestinal and pulmonary chronic diseases. Many published works have documented specific inflammatory abnormalities in the airways of subjects with mild-to-moderate persistent bronchial asthma in which the inflammation state is often associated with an increased generation of reactive oxygen species and free radical-mediated reactions. This evidence has stimulated many researchers to suppose that the oxidative stress could be an important pathogenetic determining factor in the progression of chronic diseases, and the decrease of oxidant insults to the lung can be modified with antioxidant supplementary therapy. There are many studies regarding dietary interventions that confirm the relationship to oxidative stress, bronchial inflammation, the development of asthmatic symptoms and the lowered cellular reducing capacity. Simple dietary and environmental supplementations significantly reduce the oxidant stress, minimise the development of asthmatic symptoms, and should prove to be an effective new approach to asthma management in addition to current pharmacological strategies. Many randomised controlled trials with antioxidant vitamins and trace element supplements have not confirmed the results shown in other clinical trials. The aim of this review is to focus the attention on published works discussing the relationship between asthma and nutritional supplements (some trace elements and vitamins) and the effectiveness of these supplements in the treatment of bronchial asthma.

Effect of vitamin E supplementation on the regular treatment of seasonal allergic rhinitis

BACKGROUND

Vitamin E supplementation is widely used in clinical practice for the prevention and treatment of different medical conditions. Evidence from basic science studies suggests that vitamin E may reduce immune allergic responses. However, only a few clinical studies of the effect of vitamin E on allergic conditions have been performed in patients with atopic dermatitis and asthma, and none have been performed in patients with allergic rhinitis.

OBJECTIVE

To determine the effect of high-dose vitamin E supplementation in combination with the usual ("real-life") treatment on the symptoms of seasonal allergic rhinitis during the pollen season.

METHODS

In a double-blind, placebo-controlled, randomized study, 112 patients with documented hay fever received either vitamin E (800 mg/d) or placebo in addition to their regular antiallergic treatment during the pollen season. Patients recorded their daily nasal and eye symptoms and their daily need for other medications to control allergic symptoms.

RESULTS

Although no effect was observed on ocular symptoms, nasal symptom scores were lower in patients who received vitamin E supplementation during the hay fever season. However, there was no reduction in the percentage of days with serious symptoms or in the percentage of days that medications were used to control allergic symptoms during the pollen season.

CONCLUSIONS

Vitamin E supplementation may be a valuable addition to the treatment of patients with seasonal allergic rhinitis. However, further clinical and basic science studies are needed to determine its real value.

Serum antioxidant concentrations among U.S. adults with self-reported asthma

Antioxidants may protect the lungs of people with asthma against oxidative stress. Among participants aged > or = 20 years from the Third National Health and Nutrition Examination Survey (1988-1994), we examined serum antioxidant concentrations of 771 persons with current asthma, 352 persons with former asthma, and 15,418 persons without asthma. After adjustment for age, participants with current asthma had similar mean concentrations of vitamin A, retinyl esters, vitamin C, vitamin E, vitamin E/cholesterol ratio, vitamin E/triglyceride ratio, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, lycopene, and selenium as participants without asthma. We repeated these analyses among participants who did not use vitamin or mineral supplements. After age adjustment, participants with current asthma had lower vitamin C and beta-cryptoxanthin concentrations and a lower mean vitamin E/triglyceride ratio than participants without asthma. In multiple linear regression models that included age, sex, race or ethnicity, education, smoking status, nonhigh-density lipoprotein cholesterol concentration, high-density lipoprotein cholesterol concentration, body mass index, physical activity, and alcohol use, asthma status was not significantly associated with any of the antioxidant concentrations. However, lower vitamin C concentrations were observed among people with current or former asthma than among people who never had asthma (p = 0.014). In the United States, people with asthma do not have manifest antioxidant deficiencies.

Serum total antioxidant status in severe exacerbation of asthma: correlation with the severity of the disease

Oxidative processes, mediated by oxygen free radicals are recognized to contribute significantly to the inflammatory pathology of bronchial asthma. An imbalance between oxidants and antioxidants has also been proposed in this disease. This study examines the serum total antioxidant status (TAS) in asthmatic patients with severe exacerbation of their disease and the probable correlation with clinical or laboratory findings. The TAS was measured in 20 patients (10 men and 10 women, with a mean age of 41.95 +/- 20.75 years), using a colorimetric method. On the days of admission and discharge, the forced expiratory volume in 1 sec (FEV1), the partial arterial oxygen pressure (PaO2), and severity criteria were recorded and correlated with TAS at the same time. The TAS was also measured in 10 healthy subjects (8 men and 2 women, mean age of 39 +/- 9 years). A statistically significant decrease of TAS was observed on admission day compared to that on discharge day (0.98 +/- 0.08 vs. 1.12 +/- 0.17 mmol/L, p < 0.001, respectively, paired t-test) suggesting the presence of oxidative stress during an asthma attack. The TAS on admission was also statistically significantly decreased compared to that of normal subjects (0.98 +/- 0.08 vs. 1.19 +/- 0.09 mmo/L, p < 0.001, respectively, paired t-test). A statistically significant correlation was observed between FEV1 change and TAS change, from admission to discharge day (r = 0.58, p = 0.007, Pearson correlation). Finally, a statistically significant correlation was found between FEV1 change and TAS on discharge day (r = 0.65, p = 0.002). Decreased TAS was found during an asthma attack, probably as a consequence of increased oxidative stress. The TAS change was correlated with severity criteria, such as FEV1. Therefore, it seems that measurement of TAS could be a simple and useful tool in the evaluation of an asthma attack. The supplementary administration of antioxidants in future needs further clarification.

Dietary components with demonstrated effectiveness in decreasing the severity of exercise-induced asthma

Exercise-induced asthma (EIA) occurs in up to 90% of individuals with asthma and approximately 10% of the general population without asthma. EIA describes a condition in which vigorous physical activity triggers acute airway narrowing with heightened airway reactivity resulting in reductions in forced expiratory volume in 1 second of greater than 10% compared with pre-exercise values. Treatment of EIA almost exclusively involves the use of pharmacological medications. However, there is accumulating evidence that a dietary excess of salt and omega-6 fatty acids, and a dietary deficiency of antioxidant vitamins and omega-3 fatty acids, can modify the severity of EIA. The modification of these dietary factors has the potential to reduce the incidence and prevalence of this disease. The dietary component most studied to date is dietary salt. Recent studies have supported a role for dietary salt as a modifier of the severity of EIA, suggesting that salt-restrictive diets can reduce the severity of EIA. Since EIA is part of the asthmatic diathesis, it is possible that EIA may serve as a useful model for investigation of potential dietary interventions for reducing airway hyperresponsiveness.