Associations between antioxidant status, markers of oxidative stress and immune responses in allergic adults

Thioredoxin reductase selenoproteins from different organisms as potential drug targets for treatment of human diseases

Human thioredoxin reductase (TrxR) is a selenoprotein with a central role in cellular redox homeostasis, utilizing a highly reactive and solvent-exposed selenocysteine (Sec) residue in its active site. Pharmacological modulation of TrxR can be obtained with several classes of small compounds showing different mechanisms of action, but most often dependent upon interactions with its Sec residue. The clinical implications of TrxR modulation as mediated by small compounds have been studied in diverse diseases, from rheumatoid arthritis and ischemia to cancer and parasitic infections. The possible involvement of TrxR in these diseases was in some cases serendipitously discovered, by finding that existing clinically used drugs are also TrxR inhibitors. Inhibiting isoforms of human TrxR is, however, not the only strategy for human disease treatment, as some pathogenic parasites also depend upon Sec-containing TrxR variants, including S. mansoni, B. malayi or O. volvulus. Inhibiting parasite TrxR has been shown to selectively kill parasites and can thus become a promising treatment strategy, especially in the context of quickly emerging resistance towards other drugs. Here we have summarized the basis for the targeting of selenoprotein TrxR variants with small molecules for therapeutic purposes in different human disease contexts. We discuss how Sec engagement appears to be an indispensable part of treatment efficacy and how some therapeutically promising compounds have been evaluated in preclinical or clinical studies. Several research questions remain before a wider application of selenoprotein TrxR inhibition as a first-line treatment strategy might be developed. These include further mechanistic studies of downstream effects that may mediate treatment efficacy, identification of isoform-specific enzyme inhibition patterns for some given therapeutic compounds, and the further elucidation of cell-specific effects in disease contexts such as in the tumor microenvironment or in host-parasite interactions, and which of these effects may be dependent upon the specific targeting of Sec in distinct TrxR isoforms.

Selenium and selenoproteins in prostanoid metabolism and immunity

Selenium (Se) is an essential trace element that functions in the form of the 21st amino acid, selenocysteine (Sec) in a defined set of proteins. Se deficiency is associated with pathological conditions in humans and animals, where incorporation of Sec into selenoproteins is reduced along with their expression and catalytic activity. Supplementation of Se-deficient population with Se has shown health benefits suggesting the importance of Se in physiology. An interesting paradigm to explain, in part, the health benefits of Se stems from the observations that selenoprotein-dependent modulation of inflammation and efficient resolution of inflammation relies on mechanisms involving a group of bioactive lipid mediators, prostanoids, which orchestrate a concerted action toward maintenance and restoration of homeostatic immune responses. Such an effect involves the interaction of various immune cells with these lipid mediators where cellular redox gatekeeper functions of selenoproteins further aid in not only dampening inflammation, but also initiating an effective and active resolution process. Here we have summarized the current literature on the multifaceted roles of Se/selenoproteins in the regulation of these bioactive lipid mediators and their immunomodulatory effects.

Biomarkers of oxidative stress study VI. Endogenous plasma antioxidants fail as useful biomarkers of endotoxin-induced oxidative stress

This is the newest report in a series of publications aiming to identify a blood-based antioxidant biomarker that could serve as an in vivo indicator of oxidative stress. The goal of the study was to test whether acutely exposing Göttingen mini pigs to the endotoxin lipopolysaccharide (LPS) results in a loss of antioxidants from plasma. We set as a criterion that a significant effect should be measured in plasma and seen at both doses and at more than one time point. Animals were injected with two doses of LPS at 2.5 and 5 µg/kg iv. Control plasma was collected from each animal before the LPS injection. After the LPS injection, plasma samples were collected at 2, 16, 48, and 72 h. Compared with the controls at the same time point, statistically significant losses were not found for either dose at multiple time points in any of the following potential markers: ascorbic acid, tocopherols (α, δ, γ), ratios of GSH/GSSG and cysteine/cystine, mixed disulfides, and total antioxidant capacity. However, uric acid, total GSH, and total Cys were significantly increased, probably because LPS had a harmful effect on the liver. The leakage of substances from damaged cells into the plasma may have increased plasma antioxidant concentrations, making changes difficult to interpret. Although this study used a mini-pig animal model of LPS-induced oxidative stress, it confirmed our previous findings in different rat models that measurement of antioxidants in plasma is not useful for the assessment of oxidative damage in vivo.

Interaction between blood selenium concentration and a levels of oxidative stress and antioxidative capacity in healthy children

The study aimed at defining the relationship between blood selenium concentration (Se-B) and levels of oxidative stress and antioxidative capacity in healthy children. The studies were conducted on 337 children (mean age: 8.53±1.92 years). The groups of individuals with Se-B <1st quartile (group I, Se-B<70μg/L), with Se-B fitting the range of 1st quartile and median (group II, Se-B: 70-76.9μg/L), with Se-B between the median and 3rd quartile (group III, Se-B: 77-83.9μg/L) and those with Se-B above the 3rd quartile (group IV, Se-B≥84μg/L) were distinguished. Level of oxidative stress was defined using determination of urine malonyldialdehyde concentration (MDA) and urine 8-hydroxy-2-deoxyguanosine concentration (8-OHdg). Urine total antioxidant status (TAS) was determined. In group IV TAS was significantly higher than in groups I-III. A positive correlation was detected between Se-B and TAS. In healthy children an appropriately high Se-B seems to ensure higher total antioxidative status.

25-Hydroxyvitamin D3-deficiency enhances oxidative stress and corticosteroid resistance in severe asthma exacerbation

Oxidative stress plays a significant role in exacerbation of asthma. The role of vitamin D in oxidative stress and asthma exacerbation remains unclear. We aimed to determine the relationship between vitamin D status and oxidative stress in asthma exacerbation. Severe asthma exacerbation patients with 25-hydroxyvitamin D3-deficiency (V-D deficiency) or 25-hydroxyvitamin D-sufficiency (V-D sufficiency) were enrolled. Severe asthma exacerbation with V-D-deficiency showed lower forced expiratory volume in one second (FEV1) compared to that with V-D-sufficiency. V-D-deficiency intensified ROS release and DNA damage and increased TNF-α, OGG1 and NFκB expression and NFκB phosphorylation in severe asthma exacerbation. Supplemental vitamin D3 significantly increased the rates of FEV1 change and decreased ROS and DNA damage in V-D-deficiency. Vitamin D3 inhibited LPS-induced ROS and DNA damage and were associated with a decline in TNF-α and NFκB in epithelial cells. H₂O₂ reduces nuclear translocation of glucocorticoid receptors in airway epithelial cell lines. V-D pretreatment enhanced the dexamethasone-induced nuclear translocation of glucocorticoid receptors in airway epithelial cell lines and monocytes from 25-hydroxyvitamin D3-deficiency asthma patients. These findings indicate that V-D deficiency aggravates oxidative stress and DNA damage, suggesting a possible mechanism for corticosteroid resistance in severe asthma exacerbation.

Complex effects of vitamin E and vitamin C supplementation on in vitro neonatal mononuclear cell responses to allergens

Low maternal dietary vitamin E (but not vitamin C) intake during pregnancy has been associated with increased in vitro cord blood mononuclear cell (CBMC) proliferative responses, childhood wheezing and asthma. We investigated whether these associations reflect direct effects of vitamin E by investigating the effects of supplementing CBMC cultures with physiological concentrations of vitamin E. CBMC from seventy neonates were cultured supplemented with either nothing, α-tocopherol or ascorbic acid. Proliferative, IFN-γ, IL-4, IL-10 and TGF-β responses were measured. In general, vitamin E supplementation was associated with a trend for reduced proliferative responses after stimulation with antigens and house dust mite, and with increased proliferation after stimulation with timothy grass allergen. There was a trend for CBMC cultures to exhibit decreased secretion of IFN-γ, IL-10 and IL-4. Supplementation with vitamin C had no effect on CBMC proliferation, but increased IFN-γ and IL-4 production, and decreased IL-10 production. In conclusion, in vitro vitamin E and C supplementation of CBMC modifies neonatal immune function, but not in a manner predicted by observational epidemiological studies. The observed associations between vitamin E and childhood respiratory disease are complex, and the nature and form of nutritional intervention need to be carefully considered before inclusion in trials.

Selenium and asthma

Se is a potent nutritional antioxidant important for various aspects of human health. Because asthma has been demonstrated to involve increased oxidative stress, levels of Se intake have been hypothesized to play an important role in the pathogenesis of asthma. However, significant associations between Se status and prevalence or severity of asthma have not been consistently demonstrated in human studies. This highlights both the complex etiology of human asthma and the inherent problems with correlative nutritional studies. In this review, the different findings in human studies are discussed along with results from limited intervention studies. Mouse models of asthma have provided more definitive results suggesting that the benefits of Se supplementation may depend on an individual's initial Se status. This likely involves T helper cell differentiation and the mechanistic studies that have provided important insight into the effects of Se levels on immune cell function are summarized. Importantly, the benefits and adverse effects of Se supplementation must both be considered in using this nutritional supplement for treating asthma. With this in mind new approaches are discussed that may provide more safe and effective means for using Se supplementation for asthma or other disorders involving inflammation or immunity.

Effect of pre-breathing oxygen at different depth on oxidative status and calcium concentration in lymphocytes of scuba divers

AIM

In-water pre-breathing oxygen at various depths reduces decompression-induced bubble formation and platelet activation, but it could induce side effects such as oxidative stress. The aim of this study was to investigate the effect of in-water pre-breathing oxygen, at different depths, on the oxidative status and intracellular calcium ([Ca(2+) ]i) of peripheral blood lymphocytes isolated from six divers. They participated in a 4-diving protocol. Two week recovery time was allowed between successive dives. Before diving, all divers, for 20 min, breathed normally at sea level (dive 1), 100% oxygen at sea level (dive 2), 100% oxygen at 6 msw (dive 3), 100% oxygen at 12 msw (dive 4). Then they dived to 30 msw for 20 min with air tank.

METHODS

Blood samples were collected before and after each dive. Hydrogen peroxide (H(2) O(2) ) levels, catalase (CAT) activity, mRNA expression of CAT, glutathione peroxidase (GPx) and superoxide dismutase (SOD), and the [Ca(2+) ]i in lymphocytes were measured.

RESULTS

The dives slightly decreased lymphocyte number and significantly reduced lymphocyte H(2) O(2) levels. CAT activity was higher after scuba diving and, dive 3 enhanced mRNA gene expression of CAT, GPx and SOD. The [Ca(2+) ]i was higher after dive 1 and 2 than pre-diving, while was maintained at pre-diving value after dive 3 and 4.

CONCLUSION

Our results suggest that pre-breathing oxygen, in particular at 12 msw, may enhance lymphocyte antioxidant activity and reduce reactive oxygen species levels. Pre-breathing oxygen in water may also preserve calcium homeostasis, suggesting a protective role in the physiological lymphocyte cell functions.

Oxidative stress and antioxidant status in Saudi asthmatic patients

OBJECTIVES

Asthma is a chronic inflammatory airway disorder associated with recruitment of inflammatory cells. This study aims to clarify the role of oxidative stress and antioxidant status in the deterioration accompanied asthma.

DESIGN AND METHODS

Vitamin E, Vitamin C, superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), total antioxidant status together with the concentrations of lipid peroxides, total nitrates and oxidative DNA damage (8-oxodeoxyguanine) were determined in plasma or whole blood of 47 Saudi asthmatic patients and compared to age-matching control samples.

RESULTS

The present study showed that asthmatic patients have significantly decreased levels of GSH, α-tocopherol, GPx, total antioxidant status and higher levels of SOD, lipid peroxides, total nitrate and 8-oxo-dG. Vitamin C recorded more or less similar levels in both groups.

CONCLUSION

Alteration of the selected measured parameters confirms that oxidative stress and defective antioxidant status could represent the primary causative factor in the pathogenesis of asthma.

Protective effects of Mentha haplocalyx ethanol extract (MH) in a mouse model of allergic asthma

Mentha haplocalyx Briq., a commonly used herb in traditional Oriental medicine, has a variety of known pharmacological properties. However, neither the protective effects of Mentha haplocalyx ethanol extract (MH) against inflammation of the airway in an asthmatic model nor the mechanisms involved, have previously been reported. In the present study, an ovalbumin (OVA)-induced mouse model of allergic asthma was used to investigate whether MH was effective against the disease through regulation of airway inflammation. The MH treatment significantly inhibited increases in immunoglobulin (Ig) E and T-helper 2 (Th2)-type cytokines such as IL-4 and IL-5 in bronchoalveolar lavage fluid (BALF) and lung tissue. Inflammatory cell infiltration of the airway in mice treated with MH was effectively alleviated when compared with infiltration seen in the OVA-induced group. These data indicated that decreased cytokine levels are the result of the decreased number of invaded leukocytes. Also, the generation of reactive oxygen species (ROS) in BALF was diminished by MH treatment. Taken together, these findings indicate that the administration of MH may have potential therapeutic value in the treatment of inflammatory disease.

Glutathione peroxidase 1 deficiency attenuates allergen-induced airway inflammation by suppressing Th2 and Th17 cell development

Engagement of T cell receptor (TCR) triggers signaling pathways that mediate activation, proliferation, and differentiation of T lymphocytes. Such signaling events are mediated by reactive oxygen species (ROS), including hydrogen peroxide and lipid peroxides, both of which are reduced by glutathione peroxidase 1 (GPx1). We have now examined the role of GPx1 in the activation, differentiation, and functions of CD4(+) T helper (Th) cells. TCR stimulation increased the intracellular ROS concentration in Th cells in a time-dependent manner, and such TCR-induced ROS generation was found to promote cell proliferation. GPx1-deficient Th cells produced higher levels of intracellular ROS and interleukin-2 than wild-type Th cells and proliferated at a faster rate than did wild-type cells. Moreover, differentiation of GPx1-deficient Th cells was biased toward Th1, and Th17 cell development was also impeded by GPx1 depletion. Consistent with these findings, GPx1-null mice were protected from the development of ovalbumin-induced allergic asthma. Eosinophil infiltration, goblet cell hyperplasia, collagen deposition, and airway hyperresponsiveness were thus all attenuated in the lungs of GPx1-null mice. These data indicate that GPx1-dependent control of intracellular ROS accumulation is important not only for regulation of Th cell proliferation but for modulation of differentiation into Th1, Th2, and Th17 cells.

Antioxidants and allergic disease: a case of too little or too much?

Speculation persists as to the possible role, if any, of dietary antioxidants in allergic disease. While it has been hypothesized that the recent increase in allergic disease is a consequence of declining dietary antioxidant intake, an alternative hypothesis proposes that the increase in allergic disease is due to increasing antioxidant intake. Dietary trends are conflicting; the intake of some antioxidants has declined, for others intakes are likely to have increased. Animal model studies demonstrate that antioxidant supplementation at the time of primary and subsequent allergen exposure attenuates allergic inflammatory responses. The data from human studies are less clear. Observational epidemiological studies of humans are beset by several methodological limitations associated with the assessment of diet and predominantly focus on asthma. Most observational studies report potentially beneficial associations between dietary antioxidants and allergic outcomes, but a small minority report potentially adverse associations. Human intervention studies suggest that single antioxidant supplements confer minimal, if any clinical benefit in adults with asthma, however, there is still scope for studies in children, atopic dermatitis, allergic rhinitis (AR) and of antioxidant combinations. More recently, it has been suggested that dietary antioxidants in the developmental context of fetal and infant development influence the development childhood asthma and atopic sensitization possibly by affecting the first interactions between the neonatal immune system and allergens. While a small number of birth cohort studies have reported potentially beneficial associations between maternal intake of some antioxidants during pregnancy and childhood asthma, there is very limited data suggesting associations between maternal antioxidant intake and childhood atopic dermatitis and AR. The available epidemiological, animal, molecular and immunological data suggest that there are associations between antioxidants and asthma and to a much lesser extent, atopic dermatitis and AR. However, the exact nature of the relationships and the potential for therapeutic intervention remain unclear.

Relationship between oxidative stress-related biomarkers and antioxidant status with asthma and atopy in young adults: a population-based study

BACKGROUND AND AIM

Enhanced oxidative stress has been described in adults who suffer from symptoms of asthma and poor lung function. This study assessed the relation between markers of oxidative stress and antioxidant status and lung function, symptoms of asthma, atopy and bronchial hyperresponsiveness (BHR) in young adults.

METHODS

A sub-sample of 589 individuals aged 22-28 years, selected from a total of 1232 included in a survey assessing early and current risk factors for chronic diseases, participated in the study. Participants were from an agricultural area of Chile, responded to a Spanish version of the European Community Respiratory Health Survey questionnaire, were skin tested to eight allergens, and challenged with methacholine to assess BHR. Five hundred and eighty-five individuals had measures of plasma biomarkers ferric reducing ability of plasma, uric acid, protein carbonyls and 564 had 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) assessed.

RESULTS

All participants had detectable plasma 8-iso-PGF(2alpha) and carbonyl levels. There was no indication for an association between markers of antioxidant status or oxidative stress with any of the outcomes studied.

CONCLUSION

The levels of oxidative stress-related biomarkers and antioxidant status in plasma may not be related to asthma in the general population in the absence of more severe symptoms or exacerbations.

Maternal mood scores in mid-pregnancy are related to aspects of neonatal immune function

BACKGROUND

Although there are recognised associations between psychological and immune function, the effects of maternal depressive symptoms on fetal immune development have not been investigated.

METHODS

This study examined the relationship between maternal depression scores as assessed by the Beck Depression Inventory (BDI) in the second trimester and measure of neonatal immune function measured in cord blood. This study was conducted in a cohort of women (n=83) who had received either fish oil containing 3.7 g/day n-3 polyunsaturated fatty acid (n-3PUFA) or a placebo from 20 weeks gestation as part of a randomised controlled trial.

RESULTS

At 20 weeks gestation, prior to the intervention, 22% of women in the study manifested mild to moderate depressive symptoms (BDI > or =10). Neonates of these women had higher lymphoproliferative responses to a range of stimuli (including egg ovalbumin and cat allergen) compared with neonates of women with normal BDI scores (<10). These neonates also showed higher spontaneous cytokine production including (IL-6 and IL-10) and higher stimulated cytokine responses to both bacterial antigens and allergens. These patterns were evident after allowing for maternal age and education, parity, gestation, infant gender, delivery method and neonatal n-3/n-6 PUFA status.

CONCLUSION

This exploratory study supports the notion that maternal mood in pregnancy may have the potential to influence fetal immune development. Further studies are needed to determine the significance of this.

Nutrient intake and immune function of elderly subjects

OBJECTIVE

Food intake, aging, and immune function share complex influences. Therefore, the purpose of this study was to examine relationships between nutrient intakes from food and dietary supplements and a biomarker of immune function.

DESIGN

Data were collected from participants in a cross-sectional study as well as baseline data from a longitudinal study (n=89). Subjects completed 24-hour food recalls, including supplement intake. Polyclonal mitogen phytohemmagluttin (PHA) was the immune function stimulator used. Height and weight were used to calculate body mass index.

STATISTICAL ANALYSES PERFORMED

Descriptive, bivariate correlation, Spearman's rho for nonparametric data, t tests, and stepwise regression with nutrient intakes as independent variables and T-cell proliferation as dependent variables.

RESULTS

Significant positive correlations (P< or =0.05) were found between PHA-induced proliferation and intake of docosahexaenoic acid (DHA), eicosahexaenoic acid (EPA), sodium, and selenium, although intakes of DHA plus EPA were inadequate when compared to recommended intakes. A significant negative correlation with total vitamin A, with many vitamin A levels being above the upper limit of safety. Regression analyses found these nutrients to be variables significant in explaining the variance in PHA (P=0.005).

CONCLUSIONS

Selenium, sodium, DHA, EPA, and vitamin A intake from diet and supplements were associated with PHA-induced proliferative responses. Clients may be counseled to have adequate selenium, EPA, DHA intake, and vitamin A, but avoid excess vitamin A.

Mutated glutathione-S-transferase reduced airway inflammation by limiting oxidative stress and Th2 response

Oxidative stress is an important factor in the pathogenesis of asthma. Furthermore, antioxidants like GST are reduced in asthma patients. In the present study, the therapeutic effects of exogenous GST and mGST were evaluated in a mice model. GST mutated at residues 21/27 has reduced IgE binding with similar enzyme activity as that of GST. To evaluate the therapeutic effects of GST, BALB/c mice were immunized and challenged with ovalbumin. Mice were given GST, mGST, and alpha-lipoic acid by inhalation and sacrificed on Day 31 to evaluate inflammation and oxidative stress. Mice treated with mGST showed significantly reduced total cell count (P<0.01) and eosinophils (P<0.01) in BALF compared to GST- or PBS-treated groups. The lung inflammation score was lowest for the mGST-treated group along with reduced IL-4 (P<0.01) and OVA-specific IgE than other groups. Oxidative stress as per the lipid peroxidation level in BALF of mGST-treated mice was reduced significantly in comparison to PBS- or GST-treated mice. In conclusion, inhalation of mGST reduced airway inflammation in mice. Mutated GST with reduced allergenicity has better therapeutic potential and can be explored as an adjunct therapy in asthma.

Hepatic chemoprotective enzyme responses to 2-substituted selenazolidine-4(R)-carboxylic acids

In epidemiology and human supplementation studies, as well as many animal models, selenium has shown antitumorigenic activity. The mechanism of action, however, has not been satisfactorily resolved. Selenium supplementation affects many enzymes in addition to those where selenocysteine is an essential component. Such enzymes include cytoprotective detoxifying enzymes, and the regulation of these enzymes by a set of 2-substituted selenazolidine-4(R)-carboxylic acids (SCAs) has been investigated. Following seven consecutive daily doses of these prodrugs of L-selenocysteine, changes in hepatic enzyme activities and/or mRNA levels of glutathione transferase (GST), microsomal epoxide hydrolase (mEH), NAD(P)H-quinone oxidoreductase (NQO), UDP-glucuronosyltransferase (UGT), glutathione peroxidase (GPx), and thioredoxin reductase (TR) have been observed. Among the enzymes examined, UGTs and GPx were found to be the least affected. Among the compounds, 2-oxoSCA produced the most changes and 2-phenylSCA produced the least, none. For no two compounds was the pattern of changes identical, and for a single compound, few changes were reproduced in common by the two routes of administration investigated. In general, more changes were elicited following intraperitoneal (i.p.) administration than with the intragastric (i.g.) route. This dominance was typified by 2-butylSCA and 2-cyclohexylSCA where enzyme activity elevations (TR and mEH with both, NQO with 2-butylSCA) were seen only with the i.p. route. With 2-oxoSCA, however, GST, TR, and NQO activities were found to be elevated independent of route. Only with GST (both routes) and TR (i.p. route), elevations in mRNAs accompanied the 2-oxoSCA elicited elevations of activities at the time of sacrifice. For some enzymes, most notably mEH with compounds administered i.p., elevations in mRNAs were not manifest as increased enzyme activity. Thus, although constituting a closely related series of compounds, each 2-substituted SCA produced its own unique pattern of changes, and for most members, changes were predominant following i.p. administration.