Retinoic acid inhibits interleukin-4-induced eotaxin production in a human bronchial epithelial cell line

Antioxidant Intake and Biomarkers of Asthma in Relation to Smoking Status-A Review

Asthma is considered a chronic inflammatory disorder associated with airway hyperresponsiveness (AHR). Increased oxidative stress (OS) is a clinical feature of asthma, which promotes the inflammatory responses in bronchial/airway epithelial cells. Smokers and nonsmokers with asthma have been shown to have increases in several OS and inflammatory biomarkers. However, studies suggest significant differences in OS and inflammation biomarkers between smokers and nonsmokers. A few studies suggest associations between antioxidant intake from diet/supplements and asthma in patients with different smoking status. Evidence is lacking on the protective role of antioxidant vitamin and/or mineral consumption against asthma by smoking status with respect to inflammation and OS biomarkers. Therefore, the aim of this review is to highlight current knowledge regarding the relations between antioxidant intake, asthma, and its associated biomarkers, according to smoking status. This paper can be used to guide future research directions towards the health consequences of antioxidant intake in smoking and nonsmoking asthmatics.

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.

Retinoid receptors are expressed in mouse and human lungs

Retinoid receptors are members of nuclear receptor superfamily consisting of two distinct families: RARs (retinoic acid receptors) and RXRs (retinoid X receptors). Each family contains three receptor subtypes α, β, and γ. Retinoids transduce their effects through binding to retinoid receptors and inhibit transcription factors such as activator protein-1 and nuclear factor-κB (NF-κB) both of which regulate the transcription of several inflammatory genes. Considering the role of retinoid receptors in lung physiology, we need a precise understanding of their expression in normal and inflamed lungs. We used light and electron microscopic immunohistochemistry and Western blot to determine the expression of retinoid receptors in a murine model of endotoxin-induced (E. coli; 055:B5, 80 μg intranasal) acute lung inflammation and normal human lungs. Western blot showed expression of all six retinoid receptor subtypes in normal and inflamed mouse lungs. Immunohistology localized differential expression of retinoid receptors in airway epithelium, alveolar/septal macrophages, vascular endothelium and alveolar septum in mouse lungs. Intranasal LPS challenge in mice resulted in increased expression of RXRα in airway epithelium compared to control animals. All six retinoid receptor subtypes were expressed in normal human lungs. Immunoelectron microscopy further confirmed the localization of all the receptors in various lung cells including the nucleus of these cells. The basal and altered expression of retinoid receptors in normal and inflamed lungs, respectively, may suggest their roles in lung pathophysiology.

Metabolic Phenotypes in Asthmatic Adults: Relationship with Inflammatory and Clinical Phenotypes and Prognostic Implications

Bronchial asthma is a chronic disease that affects individuals of all ages. It has a high prevalence and is associated with high morbidity and considerable levels of mortality. However, asthma is not a single disease, and multiple subtypes or phenotypes (clinical, inflammatory or combinations thereof) can be detected, namely in aggregated clusters. Most studies have characterised asthma phenotypes and clusters of phenotypes using mainly clinical and inflammatory parameters. These studies are important because they may have clinical and prognostic implications and may also help to tailor personalised treatment approaches. In addition, various metabolomics studies have helped to further define the metabolic features of asthma, using electronic noses or targeted and untargeted approaches. Besides discriminating between asthma and a healthy state, metabolomics can detect the metabolic signatures associated with some asthma subtypes, namely eosinophilic and non-eosinophilic phenotypes or the obese asthma phenotype, and this may prove very useful in point-of-care application. Furthermore, metabolomics also discriminates between asthma and other “phenotypes” of chronic obstructive airway diseases, such as chronic obstructive pulmonary disease (COPD) or Asthma–COPD Overlap (ACO). However, there are still various aspects that need to be more thoroughly investigated in the context of asthma phenotypes in adequately designed, homogeneous, multicentre studies, using adequate tools and integrating metabolomics into a multiple-level approach.

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.

Modulación de la respuesta alérgica por los carotenoides de la dieta

<p>Los carotenoides son pigmentos isoprenoides que están presentes de manera natural y en altas concentraciones en la mayoría de alimentos vegetales —entre ellos, aguacate, papaya, tomate y zanahoria—, pero también encontrados como aditivos y colorantes en diversos productos cárnicos, aceites vegetales, salsas, aderezos, harinas, entre otros. En los últimos años, algunos estudios han descrito que los carotenoides de la dieta participan en varios procesos fisiopatológicos, incluyendo la respuesta inmune de tipo alérgico. Las tasas de prevalencia para este tipo de enfermedades han incrementado de manera alarmante durante las últimas cinco décadas en todo el mundo, a la vez que varios factores e hipótesis se han planteado tratando de explicar este fenómeno: uno de ellos es la hipótesis de la dieta, la cual plantea que la composición de varios micro y macronutrientes de la alimentación, así como los cambios en los patrones dietarios, influirían en tal problemática. Evidencia epidemiológica y básica experimental emergente señala que los carotenoides de la dieta participan en la regulación de la inflamación alérgica, y por ello se postulan como coadyuvantes en la terapia de tales padecimientos. En el presente artículo se revisará el estado del arte en relación a los efectos de los carotenoides de la dieta sobre la patología alérgica.</p>

Essential vitamins for an effective T cell response

Effective adaptive immune responses rely upon appropriate activation of T cells by antigenic peptide-major histocompatibility complex on the surface of antigen presenting cells (APCs). Activation relies on additional signals including co-stimulatory molecules on the surface of the APCs that promote T cell expansion. The immune response is further sculpted by the cytokine environment. However, T cells also respond to other environmental signals including hormones, neurotransmitters, and vitamins. In this review, we summarize the mechanisms through which vitamins A and D impact immune responses, particularly in the context of T cell responses.

Potential role of nuclear receptor ligand all-trans retinoic acids in the treatment of fungal keratitis

Fungal keratitis (FK) is a worldwide visual impairment disease. This infectious fungus initiates the primary innate immune response and, later the adaptive immune response. The inflammatory process is related to a variety of immune cells, including macrophages, helper T cells, neutrophils, dendritic cells, and Treg cells, and is associated with proinflammatory, chemotactic and regulatory cytokines. All-trans retinoic acids (ATRA) have diverse immunomodulatory actions in a number of inflammatory and autoimmune conditions. These retinoids regulate the transcriptional levels of target genes through the activation of nuclear receptors. Retinoic acid receptor α (RAR α), retinoic acid receptor γ (RAR γ), and retinoid X receptor α (RXR α) are expressed in the cornea and immune cells. This paper summarizes new findings regarding ATRA in immune and inflammatory diseases and analyzes the perspective application of ATRA in FK.

The flavone eupatilin inhibits eotaxin expression in an NF-κB-dependent and STAT6-independent manner

The CC chemokine eotaxin contributes to epithelium-induced inflammation in airway diseases such as asthma. Eupatilin (5,7-dihydroxy-3',4',6'-trimethoxyflavone), a bioactive component of Artemisia asiatica Nakai (Asteraceae), is reported to inhibit the adhesion of eosinophils to bronchial epithelial cells. However, little is known about the molecular mechanism of eupatilin-induced attenuation of bronchial epithelium-induced inflammation. In this study, we investigated the effect of eupatilin on expression of eotaxin-1 (CCL11), a potent chemoattractant for eosinophils. Eupatilin significantly inhibited eotaxin expression in bronchial epithelial cells stimulated with TNF-α, while NF-κB and IκBα kinase (IKK) activities declined concurrently. Eupatilin also inhibited mitogen-activated protein kinase (MAPK) activity; however, all of these anti-inflammatory activities were reversed by MAPK overexpression. In contrast, eupatilin did not affect the signal transducer and activator of transcription 6 (STAT6) signalling in bronchial epithelial cells stimulated with IL-4. Furthermore, eupatilin significantly attenuated TNF-α-induced eosinophil migration. These results suggest that the eupatilin inhibits the signalling of MAPK, IKK, NF-κB and eotaxin-1 in bronchial epithelial cells, leading to inhibition of eosinophil migration.

All-trans retinoic acid attenuates airway inflammation by inhibiting Th2 and Th17 response in experimental allergic asthma

Background

Airway inflammation is mainly mediated by T helper 2 cells (Th2) that characteristically produce interleukin (IL)-4, IL-5, and IL-13. Epidemiological studies have revealed an inverse association between the dietary intake of vitamin A and the occurrence of asthma. Serum vitamin A concentrations are significantly lower in asthmatic subjects than in healthy control subjects. It has been reported that all-trans retinoic acid (ATRA), a potent derivative of vitamin A, regulates immune responses. However, its role in Th2-mediated airway inflammation remains unclear. We investigated the effects of ATRA in a mouse model of allergic airway inflammation.

Results

We found that ATRA treatment attenuated airway inflammation and decreased mRNA levels of Th2- and Th17-related transcription factors. The data showed that airway inflammation coincided with levels of Th2- and Th17-related cytokines. We also showed that ATRA inhibited Th17 and promoted inducible regulatory T-cell differentiation, whereas it did not induce an obvious effect on Th2 differentiation in vitro. Our data suggest that ATRA may interfere with the in vivo Th2 responses via T-cell extrinsic mechanisms.

Conclusions

Administration of ATRA dramatically attenuated airway inflammation by inhibiting Th2 and Th17 differentiation and/or functions. ATRA may have potential therapeutic effects for airway inflammation in asthmatic patients.

Adenovirus-mediated RAR-β over-expression enhances ATRA-induced neuronal differentiation of rat mesenchymal stem cells

INTRODUCTION

The retinoic acid (RA) signaling pathway plays important roles in neural development. All-trans retinoic acid (ATRA) activates the RA signal by regulating RAR-β in mesenchymal stem cell (MSC)-derived neuron cells. Here, we try to investigate whether RAR-β over-expression can affect neuronal differentiation of MSCs.

MATERIAL AND METHODS

The RAR-β gene was constructed into adenovirus Ad-RAR-β by using the AdEasy system. The MSCs were infected with Ad-RAR-β. Real time-polymerase chain reaction (RT-PCR), Western blot and immunofluorescence were performed to detect the expression and localization of RAR-β. The MSCs were treated with 1 µmol/l ATRA and modified neuronal induction medium (MNM). Soma size and axon length of induced neurons were measured. Neural specific markers were detected by RT-PCR, western blot and immunofluorescence to evaluate neuronal differentiation.

RESULTS

The 1300 bp fragment of RAR-β gene was confirmed to be correctly cloned in the adenovirus vector. Cloudiness amplification of Ad-RAR-β was observed in HEK293 cells during package. After 48 h of Ad-RAR-β infection, about 70% of MSCs were RFP-positive. RAR-β expression was increased by about 1988-fold and located in the nucleus. RAR-β over-expression did not affect neuronal differentiation efficiency; however, soma size of induced neuron cells enlarged from 716.25 ±95.96 µm(2) to 1160.12 ±352.65 µm(2) and axon length from 64.17 ±11.88 µm to 83.98 ±13.69 µm. Neural markers other than nestin - NSE, MAP-2, Tau, and Tuj1 - were increased by 4- to 11-fold in RAR-β over-expressed neuron cells with ATRA/MNM induction compared with the Ad-null control group.

CONCLUSIONS

Our results have demonstrated that adenovirus-mediated RAR-β over-expression could facilitate neuron cell types of MSCs in vitro, indicating that the RAR-β-activated RA signal might be a vital factor in neuronal differentiation.

Blackcurrant proanthocyanidins augment IFN-gamma-induced suppression of IL-4 stimulated CCL26 secretion in alveolar epithelial cells

Epidemiological studies reveal that fruit consumption reduces the prevalence of airway inflammation and childhood asthma. In particular, blackcurrant polyphenolic extracts have been shown to alleviate lung inflammation. Since IL-4-stimulated eotaxin-3 (CCL26) secretion is a major factor in the continuous eosinophil recruitment observed in atopic asthma, our focus was to evaluate the effectiveness of blackcurrant polyphenolic compounds on CCL26 secretion in human alveolar epithelial cells. Our results indicate that a proanthocyanin-enriched blackcurrant extract (BC-P), but not anthocyanin-enriched blackcurrant extract suppressed both IL-4- and IL-13-stimulated CCL26 secretion in a dose-dependent manner. Furthermore pre-incubation of cells with BC-P caused a time-dependent suppression of IL-4-stimulated CCL26 secretion. Moreover, epigallocatechin (EGC), and to a lesser extent epicatechin, metabolites identified in the proanthocyanidin extract, suppressed IL-4-stimulated CCL26 secretion. EGC was also effective at reducing the cellular phosphorylated STAT-6/STAT-6 ratio. Furthermore, both BC-P and purified EGC potentiated the ability of IFN-gamma to suppress IL-4-stimulated CCL26 secretion. The progression of an allergic immune response is complex, identifying plant compounds that target specific cellular events and complement the body's own immune actions is important for the development of functional foods. Our findings support the potential for blackcurrant polyphenolic compounds to reduce eosinophil recruitment and alleviate eosinophilic-driven airway inflammation.

Vitamin A deficiency and wheezing

BACKGROUND

Vitamin A deficiency may increase the responsiveness of the respiratory tract and increase the risk of respiratory tract infection, resulting in airway obstruction and wheezing. This study aimed to investigate the relation between vitamin A deficiency and infant wheezing.

METHODS

Three ml venous blood samples were collected from 331 hospitalized children who suffered from wheezing to determine the serum vitamin A concentration and the relationship between vitamin A and some causative factors of wheezing.

RESULTS

The severity of vitamin A deficiency was related to the course of wheezing. In the persistent wheezing group, 14 patients (34.1%) were diagnosed as having severe vitamin A deficiency and 16 patients (39%) having moderate vitamin A deficiency; among the acute wheezing group, 18 patients (16.4%) were diagnosed as having severe vitamin A deficiency and 32 patients (29%) having moderate vitamin A deficiency. Comparison of the two groups revealed that there was a significantly higher rate of moderate and severe vitamin A deficiency in the persistent wheezing group than in the acute wheezing group (P<0.01). The severity of vitamin A deficiency was related to the infants' wheezing severity. Severe vitamin A deficiency was found in 24 patients (47%) in the severe wheezing group and 8 (8%) in the mild and moderate wheezing groups. The rate of severe vitamin A deficiency was significantly higher in patients with severe wheezing than in those with mild and moderate wheezing (P<0.01).

CONCLUSIONS

Serum vitamin A deficiency could be commonly found in infants with wheezing. The severity of vitamin A deficiency might be related to the course of wheezing and the infants' wheezing severity.

Serum vitamin A and beta-carotene levels in children with asthma

BACKGROUND

Low serum levels of dietary antioxidants are associated with allergic diseases including asthma. Vitamin A and carotenoids are dietary antioxidants that are likely to play an important role against airway inflammation.

METHODS

This study included 433 asthmatic schoolchildren and 537 healthy control subjects, between 6 and 18 years of age. Serum beta-carotene, vitamin A, cholesterol, and triglycerides levels were studied in all subjects.

RESULTS

Serum vitamin A concentration was significantly lower in asthmatic subjects than in healthy control subjects (19.4 +/- 1.1 mg/dL vs. 28.9 +/- 0.86 mg/dL) (p < 0.001). There were no significant differences in the levels of beta-carotene, cholesterol, and triglycerides between the two groups.

CONCLUSION

Reduction of vitamin A in asthmatic children may have etiological implications for the disease.

Localized Th1-, Th2-, T regulatory cell-, and inflammation-associated hepatic and pulmonary immune responses in Ascaris suum-infected swine are increased by retinoic acid

Pigs infected with Ascaris suum or controls were given 100 microg (low-dose) or 1,000 microg (high-dose) all-trans retinoic acid (ATRA)/kg body weight in corn oil or corn oil alone per os on days after inoculation (DAI) -1, +1, and +3 with infective eggs. Treatment with ATRA increased interleukin 4 (IL4) and IL12p70 in plasma of infected pigs at 7 DAI and augmented bronchoalveolar lavage (BAL) eosinophilia observed at 7 and 14 DAI. To explore potential molecular mechanisms underlying these observations, a quantitative real-time reverse transcription (RT)-PCR array was used to examine mRNA expression in tissue. Ascaris-infected pigs had increased levels of liver mRNA for T-helper-2 (Th2)-associated cytokines, mast cell markers, and T regulatory (Treg) cells, while infected pigs given ATRA had higher IL4, IL13, CCL11, CCL26, CCL17, CCL22, and TPSB1 expression. Gene expression for Th1-associated markers (IFNG, IL12B, and TBX21), the CXCR3 ligand (CXCL9), IL1B, and the putative Treg marker TNFRSF18 was also increased. Expression of IL4, IL13, IL1B, IL6, CCL11, and CCL26 was increased in the lungs of infected pigs treated with ATRA. To determine a putative cellular source of eosinophil chemoattractants, alveolar macrophages were treated with IL4 and/or ATRA in vitro. IL4 induced CCL11, CCL17, CCL22, and CCL26 mRNA, and ATRA increased the basal and IL4-stimulated expression of CCL17 and CCL22. Thus, ATRA augments a diverse Th1-, Th2-, Treg-, and inflammation-associated response in swine infected with A. suum, and the increased BAL eosinophilia may be related to enhanced induction of eosinophil chemokine activity by alveolar macrophages.

Divergent functions for airway epithelial matrix metalloproteinase 7 and retinoic acid in experimental asthma

The innate immune response of airway epithelial cells to aeroallergen initiates the development of T cell responses that are central to allergic inflammation. Although proteinase allergens induce the expression of interleukin 25 we show that epithelial matrix metalloproteinase 7 (MMP7) was expressed in asthma and was required for maximal activity of IL-25 in promoting T helper type 2 cell differentiation. Allergen-challenged Mmp7^−/− mice showed reduced airway hyperreactivity, allergic inflammatory cytokine production and increased expression of retinal dehydrogenase (RALDH)-1. Inhibition of RALDH-1 restored the asthma phenotype in Mmp7^−/− mice and inhibited lung T regulatory cell responses while exogenous administration of retinoic acid attenuated the asthma phenotype. Thus, MMP7 coordinates allergic lung inflammation by activating IL-25 while simultaneously inhibiting retinoid-dependent T regulatory cell development.

Effects of all-trans retinoic acid on Th1- and Th2-related chemokines production in monocytes

Low vitamin C and reduced alpha-carotene intake are associated with increased asthma risk in children. In addition, mean serum vitamin A concentrations are significantly lower in asthmatic children than in controls. All-trans retinoic acid (ATRA) is a derivative of vitamin A. Macrophage-derived chemokine (MDC) is a T helper cell-type 2 (Th2)-related chemokine involved in the recruitment of Th2 cells toward inflammatory sites. On the other hand, Th1-related chemokine, interferon-inducible protein 10 (IP-10)/CXCL10 is also important in allergic inflammation. Both Th1- and Th2-related chemokines play an important role in allergic asthma. To survey whether ATRA and ascorbic acid effect Th1- and Th2-related chemokine expression in monocytes. To test this, THP-1 cells were pre-treated with ATRA or ascorbic acid and stimulated by lipopolysaccharide (LPS) or poly I:C. Supernatants were measured for Th2-related (MDC) and Th1-related (IP-10) chemokine concentrations by ELISA. The effects of ATRA on mitogen-activated protein kinase (MAPK) and NFkb were evaluated with Western blotting. After stimulation, ATRA significantly down-regulated MDC and IP-10 in a dose-dependent manner. Similarly, ascorbic acid reduced the LPS-induced changes in MDC but only with a high dose. However, asorbic acid had no effect on IP-10 changes either induced by LPS or poly I:C. RT-PCR showed ATRA inhibited IP-10 expression through decreasing the level of transcription. Furthermore, ATRA suppressed the expression of LPS-stimulated c-Raf, MKK1/2 and ERK expression of THP-1 cells. In conclusion, ATRA suppressed Th2- and Th1-related chemokines expression in THP-1 cells, at least in part via the c-Raf-MKK1/2-ERK/MAPK pathway.

Retinol concentrations after birth are inversely associated with atopic manifestations in children and young adults

BACKGROUND

Vitamin A has anti-inflammatory and immunomodulatory effects, and its deficiency results in impaired specific and innate immunity. Vitamin A is essential for inducing the gut-homing specificity on T cells.

OBJECTIVE

As an impaired gut immune response in early infancy may contribute to the development of atopic sensitization, we looked for an association of plasma retinol concentrations and the subsequent development of allergic symptoms in healthy infants.

METHODS

A cohort of 200 unselected, full-term newborns were followed up from birth to age 20 years. The plasma retinol concentration was determined in cord blood (n=97), at ages of 2, 4 and 12 months (n=95), and at ages 5 years (n=155) and 11 years (n=151). The subjects were re-examined at the ages of 5, 11 and 20 years with assessment of the occurrence of allergic symptoms during the preceding year, skin prick testing and measurement of serum total IgE.

RESULTS

subjects with allergic symptoms or a positive skin prick test (SPT) in childhood or adolescence had lower retinol concentrations in infancy and childhood than symptom-free subjects. The difference was most pronounced at age 2 months. Retinol concentration at 2 months correlated inversely with positive SPT at ages of 5 and 20 years, and with allergic symptoms at age 20 years.

CONCLUSION

Retinol concentration in young infants is inversely associated with the subsequent development of allergic symptoms. We propose that an inborn regulation of retinol may play a role in atopic sensitization, possibly through regulating the intestinal T cell responses.

Glycyrrhizin derivative inhibits eotaxin 1 production via STAT6 in human lung fibroblasts

We recently demonstrated that glycyrrhizin (GL) and its derivatives down-regulate TNFalpha- and IL-4-induced eotaxin 1 production by the human fetal lung fibroblast line HFL-1 at protein or mRNA levels. In particular, the GL derivative hetero-30-OH-GL (3beta-[(2-O-beta-D-glucopyranuronosyl-beta-D-glucopyranuronosyl)oxy]-olean-11,13(18)-dien-30-ol) showed marked inhibition of eotaxin 1 production with less cytotoxicity than 18beta-GL. To identify the molecular mechanism of this effect, we focused on the inhibition of the transcriptional factors NF-kappaB and signal transducer and activator of transcription 6 (STAT6), which regulate eotaxin 1 gene activation. STAT6 phosphorylation and translocation of phospho-STAT6 from cytosol to nuclei were slightly inhibited by 18beta-GL and significantly inhibited by hetero-30-OH-GL. While IkappaBalpha degradation and translocation of NF-kappaB p65 to nuclei were not significantly affected by either compound, the stability of eotaxin-1 mRNA was decreased with hetero-30-OH-GL. In addition, eotaxin 1 promoter activity was markedly inhibited by hetero-30-OH-GL. Electrophoretic mobility shift assay (EMSA) confirmed these results. Thus, hetero-30-OH-GL significantly inhibited eotaxin 1 expression by the selective inhibition of IL-4 signal transduction as well as by enhanced mRNA degradation.