Combination treatment with high-dose vitamin C and alpha-tocopherol does not enhance respiratory-tract lining fluid vitamin C levels in asthmatics

Effect of dietary interventions on markers of type 2 inflammation in asthma: A systematic review

INTRODUCTION

Type 2 (T2) inflammation is a key mechanism in the pathophysiology of asthma. Diet may have immunomodulatory effects, and a role for diet in T2 inflammation has been suggested in the literature. Indeed, diet and food allergies play a role in children with atopic asthma, but less is known about diet in relation to adult asthma, which is often non-atopic.

OBJECTIVE

To review the effect of dietary interventions on markers of T2 inflammation in adults with asthma.

METHODS

The databases PubMed, Embase, Cochrane Library, and CINAHL were searched for eligible studies until December 2022. We included studies of all types of foods, nutrients, diets or supplements, either as an exposure or as an intervention, in adults and adolescents with asthma. Outcomes of interest included the T2 biomarkers FeNO, eosinophils, IL-4, IL-5, IL-13, eosinophil cationic protein and eosinophil peroxidase. The methodological quality of eligible studies was systematically evaluated, and the results were summarised according to dietary clusters.

RESULTS

The systematic search identified studies on the dietary clusters antioxidants (n = 14), fatty acids, (n = 14), Mediterranean-style diets (n = 5), phytotherapy (n = 7), prebiotics & probiotics (n = 8), vitamin D (n = 7), and other dietary factors (n = 5). Studies within the phytotherapy and omega-3 poly-unsaturated fatty acids (PUFA) clusters showed possible improvements in T2 inflammation. Furthermore, we found little evidence for an effect of antioxidants, prebiotics & probiotics, and Mediterranean-style diets on T2 inflammation. However, heterogeneity in study protocols, methodological shortcomings and limited power of almost all studies make it difficult to fully determine the impact of different dietary approaches on T2 inflammation in asthma.

CONCLUSIONS

Overall, the current evidence does not support a specific dietary intervention to improve T2 inflammation in asthma. Interventions involving phytotherapy and omega-3 PUFA currently have the best evidence and warrant further evaluation in well-designed and adequately powered studies, while taking into account T2-high phenotypes of asthma.

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.

Asthma, allergy and vitamin E: Current and future perspectives

Asthma and allergic disease result from interactions of environmental exposures and genetics. Vitamin E is one environmental factor that can modify development of allergy early in life and modify responses to allergen after allergen sensitization. Seemingly varied outcomes from vitamin E are consistent with the differential functions of the isoforms of vitamin E. Mechanistic studies demonstrate that the vitamin E isoforms α-tocopherol and γ-tocopherol have opposite functions in regulation of allergic inflammation and development of allergic disease, with α-tocopherol having anti-inflammatory functions and γ-tocopherol having pro-inflammatory functions in allergy and asthma. Moreover, global differences in prevalence of asthma by country may be a result, at least in part, of differences in consumption of these two isoforms of tocopherols. It is critical in clinical and animal studies that measurements of the isoforms of tocopherols be determined in vehicles for the treatments, and in the plasma and/or tissues before and after intervention. As allergic inflammation is modifiable by tocopherol isoforms, differential regulation by tocopherol isoforms provide a foundation for development of interventions to improve lung function in disease and raise the possibility of early life dietary interventions to limit the development of lung disease.

Amelioration of PM2.5-induced lung toxicity in rats by nutritional supplementation with fish oil and Vitamin E

BACKGROUND

Exposure to fine particulate matter (PM_2.5) has been associated with respiratory morbidity and mortality. Identification of interventional measures that are efficacious against PM_2.5-induced toxicity may provide public health benefits. This study examined the inhibitory effects of nutritional supplementation with fish oil as a source of omega-3 fatty acids and vitamin E (Vit E) on PM_2.5-induced lung toxicity in rats.

METHOD

Sixty four male Sprague Dawley rats were gavaged with phosphate buffered saline (PBS), corn oil (5 ml/kg), fish oil (150 mg/kg), or Vit E (75 mg/kg), respectively, once a day for 21 consecutive days prior to intratracheal instillation of PM_2.5 (10 mg/kg) every other day for a total of 3 times. Serum and bronchoalveolar lavage fluids (BALFs) were collected 24 h after the last instillation of PM_2.5. Levels of total proteins (TP), lactate dehydrogenase (LDH), superoxide dismutase (SOD), 8-epi-prostaglandin F2α (8-epi-PGF2α), interleukin-1β (IL-1β), C-reactive protein (CRP), IL-6, and tumor necrosis factor-ɑ (TNF-ɑ) were analyzed for markers of cell injury and inflammation. Additionally, histological alterations of lung tissues were examined by hematoxylin-eosin staining.

RESULT

Exposure to PM_2.5 resulted in lung toxicity, represented as increased levels of total proteins, LDH, 8-epi-PGF2α, IL-1β and TNF-α, and increased infiltration of inflammatory cells, and decreased SOD in the BALFs, and systemic inflammation, as evinced by increased levels of CRP and IL-6 in serum. Strikingly, supplementation with fish oil but not Vit E significantly ameliorated PM_2.5-induced lung toxicity and systemic inflammation.

CONCLUSION

PM_2.5 exposure induces oxidative stress, lung injury and inflammation, which is ameliorated significantly by fish oil and partially by Vit E.

Probiotic Bifidobacterium lactis, anti-oxidant vitamin E/C and anti-inflammatory dha attenuate lung inflammation due to pm2.5 exposure in mice

The incidence of asthma and allergic diseases of the airways is constantly increasing, both in the industrialised and developing countries, due to harmful and excessive quantities of air pollution. Although some studies have shown an effect of dietary supplementation of specific nutrients (especially with anti-oxidant and anti-inflammatory properties) in reducing airways inflammatory response, the results are not yet conclusive and the science is still at its infancy. Our hypothesis is that combining such nutrients could provide more benefits than using them alone. The aim of the research project proposed here is to investigate whether specific combinations of nutrients (docosahexanoic acid, vitamin C and E, and Bifidobacterium lactis strain BB-12®, included in an engineered diet) can act synergistically to reduce inflammation given by high level of air pollution. Beside the role of docosahexanoic acid, vitamins C and E on airways inflammatory disease, no study examined the effect of the supplementation of this probiotic strain in pathological conditions caused by air pollution so far. Herein we used a well-established in vivo model for the study of pollution effects, which consists in female BALB/c mice receiving by pharyngeal aspiration either a sham or a particulate matter with diameter <2.5 μm (PM 2.5) containing aerosol. Before treatment, mice were fed either a chow or a supplemented diet. By performing histological analyses and gene expression profiles on lung sections and serum measurement of the cytokine interleukin 10, we found that a specific combination of all the aforementioned nutrients rather than nutrients alone had a synergistic protective effect against PM2.5-induced inflammation. In conclusion, our study support that a supplemental nutritional intervention based on a combination of the probiotic B. lactis BB-12, the anti-oxidant vitamin C and E, and the anti-inflammatory docosahexanoic acid represents a rational option for alleviating air pollution-related lung inflammation.

The effect of dietary components on inflammatory lung diseases - a literature review

Anti-inflammatory treatment in chronic inflammatory lung diseases usually involves glucocorticosteroids. With patients suffering from serious side effects or becoming resistant, specific nutrients, that are suggested to positively influence disease progression, can be considered as new treatment options. The dietary inflammatory index is used to calculate effects of dietary components on inflammation and lung function to identify most potent dietary components, based on 162 articles. The positive effects of n-3 PUFAs and vitamin E on lung function can at least partially be explained by their anti-inflammatory effect. Many other dietary components showed only small or no effects on inflammation and/or lung function, although the number of weighted studies was often too small for a reliable assessment. Optimal beneficial dietary elements might reduce the required amounts of anti-inflammatory treatments, thereby decreasing both side effects and development of resistance as to improve quality of life of patients suffering from chronic inflammatory lung diseases.

Reduced Antioxidant and Cytoprotective Capacity in Allergy and Asthma

In asthma, reactive oxygen species induce damage to biomolecules like proteins. This oxidative stress can promote inflammation, but its contribution to asthma pathology is controversial, not in the least because antioxidant interventions have proven rather unsuccessful. Recent studies indicate that the oxidative stress at baseline can be predictive of the fall in FEV1 upon an allergen challenge and of sensitization to an allergen. Interestingly, this baseline oxidative stress correlated with the capacity of antioxidant and cytoprotective responses to deal with reactive oxygen species, but not with inflammatory parameters. These findings have led to several considerations in relation to antioxidant trials that are discussed. Trials should be complemented by in-depth analyses of the failing antioxidant and cytoprotective responses and their consequences for cellular function in asthma.

Cyclic nitroxide radicals attenuate inflammation and Hyper-responsiveness in a mouse model of allergic asthma

The effects of stable cyclic nitroxide radicals have been extensively investigated both in vivo and in vitro demonstrating anti-inflammatory, radioprotective, anti-mutagenic, age-retardant, hypotensive, anti-cancer and anti-teratogenic activities. Yet, these stable radicals have not been evaluated in asthma and other airway inflammatory disorders. The present study investigated the effect of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl (TPL) and 3-carbamoyl-proxyl (3-CP) in a mouse model of ovalbumin (OVA)-induced allergic asthma. Both 3-CP and TPL were non-toxic when administered either orally (1% w/w nitroxide-containing chow) or via intraperitoneal (IP) injection (∼300 mg/kg). Feeding the mice orally demonstrated that 3-CP was more effective than TPL in reducing inflammatory cell recruitment into the airway and in suppressing airway hyper-responsiveness (AHR) in OVA-challenged mice. To characterize the optimal time-window of intervention and mode of drug administration, 3-CP was given orally during allergen sensitization, during allergen challenge or during both sensitization and challenge stages, and via IP injection or intranasal instillation for 3 days during the challenge period. 3-CP given via all modes of delivery markedly inhibited OVA-induced airway inflammation, expression of cytokines, AHR and protein nitration of the lung tissue. Oral administration during the entire experiment was the most efficient delivery of 3-CP and was more effective than dexamethasone a potent corticosteroid used for asthma treatment. Under a similar administration regimen (IP injection before the OVA challenge), the effect of 3-CP was similar to that of dexamethasone and even greater on AHR and protein nitration. The protective effect of the nitroxides, which preferentially react with free radicals, in suppressing the increase of main asthmatic inflammatory markers substantiate the key role played by reactive oxygen and nitrogen species in the molecular mechanism of asthma. The present results demonstrate the therapeutic potential of nitroxides for the treatment of asthma.

Identification of vitamin C transporters in the human airways: a cross-sectional in vivo study

OBJECTIVES

Vitamin C is an important low-molecular weight antioxidant at the air-lung interface. Despite its critical role as a sacrificial antioxidant, little is known about its transport into the respiratory tract lining fluid (RTLF), or the underlying airway epithelial cells. While several vitamin C transporters have been identified, such as sodium-ascorbate cotransporters (SVCT1/2) and glucose transporters (GLUTs), the latter transporting dehydroascorbate, knowledge of their protein distribution within the human lung is limited, in the case of GLUTs or unknown for SVCTs.

SETTING AND PARTICIPANTS

Protein expression of vitamin C transporters (SVCT1/2 and GLUT1-4) was examined by immunohistochemistry in endobronchial biopsies, and by FACS in airway leucocytes from lavage fluid, obtained from 32 volunteers; 16 healthy and 16 mild asthmatic subjects. In addition, antioxidant concentrations were determined in RTLF. The study was performed at one Swedish centre.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was to establish the location of vitamin C transporters in the human airways. As secondary outcome measures, RTLF vitamin C concentration was measured and related to transporter expression, as well as bronchial epithelial inflammatory and goblet cells numbers.

RESULTS

Positive staining was identified for SVCT1 and 2 in the vascular endothelium. SVCT2 and GLUT2 were present in the apical bronchial epithelium, where SVCT2 staining was predominately localised to goblet cells and inversely related to RTLF vitamin C concentrations.

CONCLUSIONS

This experimental study is the first to demonstrate protein expression of GLUT2 and SVCT2 in the human bronchial epithelium. A negative correlation between SVCT2-positive goblet cells and bronchial RTLF vitamin C concentrations suggests a possible role for goblet cells in regulating the extracellular vitamin C pool.

Vitamins C and E for asthma and exercise-induced bronchoconstriction

BACKGROUND

The association between dietary antioxidants and asthma or exercise-induced bronchoconstriction (EIB) is not fully understood. Vitamin C and vitamin E are natural antioxidants that are predominantly present in fruits and vegetables; inadequate vitamin E intake is associated with airway inflammation. It has been postulated that the combination may be more beneficial than either single antioxidant for people with asthma and exercise-induced bronchoconstriction.

OBJECTIVES

To assess the effects of supplementation of vitamins C and E versus placebo (or no vitamin C and E supplementation) on exacerbations and health-related quality of life (HRQL) in adults and children with chronic asthma. To also examine the potential effects of vitamins C and E on exercise-induced bronchoconstriction in people with asthma and in people without a diagnosis of asthma who experience symptoms only on exercise.

SEARCH METHODS

Trials were identified from the Cochrane Airways Review Group Specialised Register and from trial registry websites. Searches were conducted in September 2013.

SELECTION CRITERIA

We included randomised controlled trials of adults and children with a diagnosis of asthma. We separately considered trials in which participants had received a diagnosis of exercise-induced bronchoconstriction (or exercise-induced asthma). Trials comparing vitamin C and E supplementation versus placebo were included. We included trials in which asthma management for treatment and control groups included similar background therapy. Short-term use of vitamins C and E at the time of exacerbation or for cold symptoms in people with asthma is outside the scope of this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of potential studies and subsequently screened full-text study reports for inclusion. We used standard methods as expected by The Cochrane Collaboration.

MAIN RESULTS

It was not possible to aggregate the five included studies (214 participants). Four studies (206 participants) addressed the question of whether differences in outcomes were seen when vitamin C and E supplementation versus placebo was provided for participants with asthma, and only one of those studies (160 children) included a paediatric population; the remaining three studies included a combined total of just 46 adults. An additional study considered the question of whether differences in outcomes were noted when vitamin C and E supplementation was compared with placebo for exercise-induced asthma; this trial included only eight participants. The randomisation process of the trials were unclear leading us to downgrade the quality of the evidence. Four of the studies were double blind while the other study was single blind.None of these studies provided data on our two prespecified primary outcome measures: exacerbations and HRQL. Lung function data obtained from the studies were inconclusive. The only studies that provided any suggestion of an effect, and only with some outcomes, were the paediatric study, especially for children with moderate to severe asthma, and the small study on exercise-induced asthma. Even so, this evidence was judged to be at moderate/low quality. Only one study contributed data on asthma symptoms and adverse events, reporting no evidence of an effect of the intervention for symptoms and that one participant in the treatment group dropped out due to cystitis.

AUTHORS' CONCLUSIONS

It is not possible to draw firm conclusions from this review with respect to the comparison of vitamin C and E supplementation versus placebo in the management of asthma or exercise-induced bronchoconstriction. We found only one study relevant to exercise-induced bronchoconstriction; most included participants came from studies designed to assess the effect of vitamin supplementation on the impact of atmospheric pollutants (such as ozone). Evidence is lacking on the comparison of vitamin C and E supplementation versus placebo for asthma with respect to outcomes such as HRQL and exacerbations, which were not addressed by any of the included studies.When compared with lung function tests alone, HRQL scores and exacerbation frequency are better indicators of the severity of asthma, its impact on daily activities and its response to treatment in a patient population. These end points are well recognised in good quality studies of asthma management. However, clinical studies of vitamins C and E in the management of asthma using these important end points of exacerbations and effects on quality of life are not available, and evidence is insufficient to support robust conclusions on the role of vitamin C and E supplementation in asthma and exercise-induced breathlessness.

Supplementation with γ-tocopherol attenuates endotoxin-induced airway neutrophil and mucous cell responses in rats

Neutrophil-mediated tissue injury is a shared pathogenesis of both chronic pulmonary diseases and acute responses to pathogens, allergens, and airborne pollutants. Interventions to minimize toxic effects of neutrophil-derived oxidants and proteases are usually limited to corticosteroids, which can have adverse side effects. We used a rodent model of endotoxin-induced lung injury to test the hypothesis that the dietary supplement γ-tocopherol (γT), a natural form of vitamin E with antioxidant and novel anti-inflammatory properties, will protect from adverse nasal and pulmonary inflammatory responses induced by endotoxin (lipopolysaccharide; LPS). Male Fisher F344 rats were intranasally (i.n.) instilled with LPS for 2 consecutive days. Beginning 2 days before i.n. LPS, the rats were gavaged daily with 30mg/kg γT. Twenty-four hours after the last i.n. LPS, bronchoalveolar lavage fluid (BALF) was collected, and pulmonary and nasal tissues were analyzed for gene expression and morphometric analyses of neutrophils and intraepithelial mucosubstances (IM). LPS caused increased BALF total cells (70% increase), neutrophils (300%), protein (35%), PGE2 (500%), and secreted mucins (75%). Robust increases in neutrophils and IM were detected in conducting airways. Pulmonary expression of MUC5AC, MIP-2, CINC-1, and MCP-1 was elevated three- to eightfold by LPS. Treatment with γT inhibited LPS-induced increases in BALF total cells, neutrophils, protein, PGE2, and secreted mucins, as well as IM and tissue neutrophil influx. Furthermore γT induced the expression of the regulatory cytokines IL-10 and IFN-γ while decreasing MUC5AC, MIP-2, CINC-1, and MCP-1. These data demonstrate novel therapeutic effects of the dietary vitamin E γT promoting anti-inflammatory pathways to protect from neutrophil-mediated lung injury.

Vitamin E isoforms as modulators of lung inflammation

Asthma and allergic diseases are complex conditions caused by a combination of genetic and environmental factors. Clinical studies suggest a number of protective dietary factors for asthma, including vitamin E. However, studies of vitamin E in allergy commonly result in seemingly conflicting outcomes. Recent work indicates that allergic inflammation is inhibited by supplementation with the purified natural vitamin E isoform α-tocopherol but elevated by the isoform γ-tocopherol when administered at physiological tissue concentrations. In this review, we discuss opposing regulatory effects of α-tocopherol and γ-tocopherol on allergic lung inflammation in clinical trials and in animal studies. A better understanding of the differential regulation of inflammation by isoforms of vitamin E provides a basis towards the design of clinical studies and diets that would effectively modulate inflammatory pathways in lung disease.

Vitamin C for asthma and exercise-induced bronchoconstriction

BACKGROUND

Dietary antioxidants, such as vitamin C, in the epithelial lining and lining fluids of the lung may be beneficial in the reduction of oxidative damage (Arab 2002). They may therefore be of benefit in reducing symptoms of inflammatory airway conditions such as asthma, and may also be beneficial in reducing exercise-induced bronchoconstriction, which is a well-recognised feature of asthma and is considered a marker of airways inflammation. However, the association between dietary antioxidants and asthma severity or exercise-induced bronchoconstriction is not fully understood.

OBJECTIVES

To examine the effects of vitamin C supplementation on exacerbations and health-related quality of life (HRQL) in adults and children with asthma or exercise-induced bronchoconstriction compared to placebo or no vitamin C.

SEARCH METHODS

We identified trials from the Cochrane Airways Group's Specialised Register (CAGR). The Register contains trial reports identified through systematic searches of a number of bibliographic databases, and handsearching of journals and meeting abstracts. We also searched trial registry websites. The searches were conducted in December 2012.

SELECTION CRITERIA

We included randomised controlled trials (RCTs). We included both adults and children with a diagnosis of asthma. In separate analyses we considered trials with a diagnosis of exercise-induced bronchoconstriction (or exercise-induced asthma). We included trials comparing vitamin C supplementation with placebo, or vitamin C supplementation with no supplementation. We included trials where the asthma management of both treatment and control groups provided similar background therapy. The primary focus of the review is on daily vitamin C supplementation to prevent exacerbations and improve HRQL. The short-term use of vitamin C at the time of exacerbations or for cold symptoms in people with asthma are outside the scope of this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of potential studies, and subsequently screened full text study reports for inclusion. We used standard methods expected by The Cochrane Collaboration.

MAIN RESULTS

A total of 11 trials with 419 participants met our inclusion criteria. In 10 studies the participants were adults and only one was in children. Reporting of study design was inadequate to determine risk of bias for most of the studies and poor availability of data for our key outcomes may indicate some selective outcome reporting. Four studies were parallel-group and the remainder were cross-over studies. Eight studies included people with asthma and three studies included 40 participants with exercise-induced asthma. Five studies reported results using single-dose regimes prior to bronchial challenges or exercise tests. There was marked heterogeneity in vitamin C dosage regimes used in the selected studies, compounding the difficulties in carrying out meaningful analyses.One study on 201 adults with asthma reported no significant difference in our primary outcome, health-related quality of life (HRQL), and overall the quality of this evidence was low. There were no data available to evaluate the effects of vitamin C supplementation on our other primary outcome, exacerbations in adults. One small study reported data on asthma exacerbations in children and there were no exacerbations in either the vitamin C or placebo groups (very low quality evidence). In another study conducted in 41 adults, exacerbations were not defined according to our criteria and the data were not available in a format suitable for evaluation by our methods. Lung function and symptoms data were contributed by single studies. We rated the quality of this evidence as moderate, but further research is required to assess any clinical implications that may be related to the changes in these parameters. In each of these outcomes there was no significant difference between vitamin C and placebo. No adverse events at all were reported; again this is very low quality evidence.Studies in exercise-induced bronchoconstriction suggested some improvement in lung function measures with vitamin C supplementation, but theses studies were few and very small, with limited data and we judged the quality of the evidence to be low.

AUTHORS' CONCLUSIONS

Currently, evidence is not available to provide a robust assessment on the use of vitamin C in the management of asthma or exercise-induced bronchoconstriction. Further research is very likely to have an important impact on our confidence in the estimates of effect and is likely to change the estimates. There is no indication currently that vitamin C can be recommended as a therapeutic agent in asthma. There was some indication that vitamin C was helpful in exercise-induced breathlessness in terms of lung function and symptoms; however, as these findings were provided only by small studies they are inconclusive. Most published studies to date are too small and inconsistent to provide guidance. Well-designed trials with good quality clinical endpoints, such as exacerbation rates and health-related quality of life scores, are required.

Effect of selenium and vitamin C on clinical outcomes, trace element status, and antioxidant enzyme activity in horses with acute and chronic lower airway disease. A randomized clinical trial

Excess production of reactive oxygen species is involved in the pathogenesis of airway disorders in horses. Trace element antioxidants have a beneficial role in oxidant/antioxidant balance. The aim of the present study was to evaluate the effect of a combination of sodium selenite and ascorbic acid on clinical outcome, antioxidant enzymes, and trace elements status in horses with lower airway disease. For this purpose, 40 draft horses with lower airway disease were randomly selected (acute, n = 20; chronic, n = 20). Both acute and chronic cases were randomly allocated into two subgroups (ten each). Groups 1 and 2 were the horses with acute disease, while groups 3 and 4 were chronically ill. For all groups, each horse was administered antibiotic, non-steroidal anti-inflammatory, and mucolytic drug. In addition, groups 2 and 4 were injected with 15 mg/kg sodium selenite and 30 mg/kg ascorbic acid every 24 h for successive 4 weeks. Venous blood samples were obtained from diseased horses on three occasions; at first examination, and at 2 and 4 weeks post-treatment. Clinically, antioxidant supplementation improved the clinical signs with significant decrease (p < 0.05) of the clinical index score in both acute and chronic cases. In supplemented groups compared with non-supplemented, there was a significant increase (p < 0.05) in the levels of copper, zinc, selenium, and iron as well as in the activity of glutathione-S-transferase and catalase. Meanwhile, there was a significant decrease (p < 0.05) in the levels of manganese, malondialdehyde, hydrogen peroxide, and low-density lipoprotein and in the activity of glutathione reductase. The results of the present study indicate that administration of sodium selenite and ascorbic acid may have beneficial effect on clinical outcome and antioxidant balance in horses with acute and chronic lower airway disease.

Effects of ex vivo γ-tocopherol on airway macrophage function in healthy and mild allergic asthmatics

Elevated inflammation and altered immune responses are features found in atopic asthmatic airways. Recent studies indicate γ-tocopherol (GT) supplementation can suppress airway inflammation in allergic asthma. We studied the effects of in vitro GT supplementation on receptor-mediated phagocytosis and expression of cell surface molecules associated with innate and adaptive immunity on sputum-derived macrophages. Cells from nonsmoking healthy (n = 6) and mild house dust mite-sensitive allergic asthmatics (n = 6) were treated ex vivo with GT (300 µM) or saline (control). Phagocytosis of opsonized zymosan A bioparticles (Saccharomyces cerevisiae) and expression of surface molecules associated with innate and adaptive immunity were assessed using flow cytometry. GT caused significantly decreased (p < 0.05) internalization of attached zymosan bioparticles and decreased (p < 0.05) macrophage expression of CD206, CD36 and CD86 in allergic asthmatics but not in controls. Overall, GT caused downregulation of both innate and adaptive immune response elements, and atopic status appears to be an important factor.

Isoforms of Vitamin E Differentially Regulate PKC α and Inflammation: A Review

Vitamin E regulation of disease has been extensively studied but most studies focus on the α-tocopherol isoform of vitamin E. These reports indicate contradictory outcomes for anti-inflammatory functions of the α-tocopherol isoform of vitamin E with regards to animal and clinical studies. These seemingly disparate results are consistent with our recent studies demonstrating that purified natural forms of vitamin E have opposing regulatory functions during inflammation. In this review, we discuss that α-tocopherol inhibits whereas γ-tocopherol elevates allergic inflammation, airway hyperresponsiveness, leukocyte transendothelial migration, and endothelial cell adhesion molecule signaling through protein kinase Cα. Moreover, we have demonstrated that α-tocopherol is an antagonist and γ-tocopherol is an agonist of PKCα through direct binding to a regulatory domain of PKCα. In summary, we have determined mechanisms for opposing regulatory functions of α-tocopherol and γ-tocopherol on inflammation. Information from our studies will have significant impact on the design of clinical studies and on vitamin E consumption.

Reduced medication use and improved pulmonary function with supplements containing vegetable and fruit concentrate, fish oil and probiotics in asthmatic school children: a randomised controlled trial

Dietary pattern changes may be one of the key factors associated with increasing asthma prevalence. Observational studies have found negative associations between fruit, vegetable and fish consumption and risk of asthma. Experimental studies have also shown that probiotics can modulate the immune system. However, each dietary component exhibits a modest effect. The objective of the present study was to investigate the joint effect of multiple beneficial dietary components on asthma. We designed a 16-week school-based double-blind placebo-controlled randomised trial. The supplement group received fruit plus vegetable concentrate, fish oil and probiotics (FVFP supplement), while the control group received placebos. A total of 192 asthmatic children aged 10-12 years were recruited from elementary schools in metropolitan Taipei. Pulmonary function, medication usage, Paediatric Asthma Quality of Life Questionnaire (PAQLQ) score and the Childhood Asthma Control Test score were evaluated at baseline, and at weeks 8 and 16. Compared with the placebo group, the supplement group showed significant improvement in pulmonary function parameters (91 v. 178 ml for forced vital capacity (FVC), 40 v. 107 ml for forced expiratory volume in 1 s (FEV1) and 1·6 v. 4·8 % for FEV1:FVC ratio; all P values < 0·01) and had a significantly reduced proportion of those using short-acting inhaled bronchodilators and inhaled corticosteroids. However, the PAQLQ score and the Childhood Asthma Control Test score were not significantly different between the two groups, possibly because the majority of the children were treated routinely. FVFP supplements reduced medication use and improved pulmonary function in asthmatic children. The present study supports an adjuvant intervention with a combination of fruit, vegetable, fish and probiotic foods.

Isoforms of vitamin E differentially regulate inflammation

Vitamin E regulation of disease has been extensively studied in humans, animal models and cell systems. Most of these studies focus on the α-tocopherol isoform of vitamin E. These reports indicate contradictory outcomes for anti-inflammatory functions of the α-tocopherol isoform of vitamin E, especially with regards to clinical studies of asthma and atherosclerosis. These seemingly disparate clinical results are consistent with recently reported unrecognized properties of isoforms of vitamin E. Recently, it has been reported that physiological levels of purified natural forms of vitamin E have opposing regulatory functions during inflammation. These opposing regulatory functions by physiological levels of vitamin E isoforms impact interpretations of previous studies on vitamin E. Moreover, additional recent studies also indicate that the effects of vitamin E isoforms on inflammation are only partially reversible using physiological levels of a vitamin E isoform with opposing immunoregulatory function. Thus, this further influences interpretations of previous studies with vitamin E in which there was inflammation and substantial vitamin E isoforms present before the initiation of the study. In summary, this review will discuss regulation of inflammation by vitamin E, including alternative interpretations of previous studies in the literature with regards to vitamin E isoforms.

Mega-dose vitamin C attenuated lung inflammation in mouse asthma model

Asthma is a Th2-dependent disease mediated by IgE and Th2 cytokines, and asthmatic patients suffer from oxidative stresses from abnormal airway inflammation. Vitamin C is a micro-nutrient functioning as an antioxidant. When administered at a mega-dose, vitamin C has been reported to shift immune responses toward Th1. Thus, we tried to determine whether vitamin C exerted beneficial effects in asthma animal model. Asthma was induced in mice by sensitizing and challenging with ovalbumin. At the time of challenge, 3~5 mg of vitamin C was administered and the effects were evaluated. Vitamin C did not modulate Th1/Th2 balance in asthma model. However, it decreased airway hyperreactivity to methacholine, decreased inflammatory cell numbers in brochoalveolar lavage fluid, and moderate reduction of perivascular and peribronchiolar inflammatory cell infiltration. These results suggest that vitamin C administered at the time of antigen challenge exerted anti-inflammatory effects. Further studies based on chronic asthma model are needed to evaluate a long-term effect of vitamin C in asthma. In conclusion, even though vitamin C did not show any Th1/Th2 shifting effects in this experiment, it still exerted moderate anti-inflammatory effects. Considering other beneficial effects and inexpensiveness of vitamin C, mega-dose usage of vitamin C could be a potential supplementary modality for the management of asthma.

Novel antioxidant approaches to the treatment of upper airway inflammation

PURPOSE OF REVIEW

Current understanding of the role of oxidative stress in airway inflammation suggests that antioxidant therapy may be important to optimize the treatment. This review summarizes recent investigations of novel antioxidant agents for upper airway inflammation, with selected studies focused on lower airway disease as additional candidate therapeutics.

RECENT FINDINGS

Recently investigated antioxidant therapies for airway inflammation may be broadly grouped into three categories: endogenous metabolic agents, vitamins/nutrients, and botanical extracts. Studies examining effects in upper airway inflammation are limited and primarily consist of in-vitro human and in-vivo animal models. More extensive studies have investigated the benefits of antioxidants in lower airway conditions such as allergic asthma. Existing evidence identifies antioxidant agents with potential therapeutic value, although human studies suggest that subpopulations affected by specific genetic, environmental, dietary factors, or all are most likely to benefit from antioxidant therapy.

SUMMARY

Oxidative stress plays a causative role in upper airway inflammation, and novel strategies to mitigate cellular injury with antioxidant therapy may ameliorate disease in target populations. Preclinical studies demonstrate evidence of anti-inflammatory effects for a number of promising antioxidant agents. Well designed interventional human studies of the upper airway, which account for complex gene-environment-diet interactions, will be necessary to adequately examine the potential clinical benefit of antioxidant therapies for rhinosinusitis.