9-cis retinoic acid modulates the type I allergic immune response

Vitamin A and vitamin D induced nuclear hormone receptor activation and its impact on B cell differentiation and immunoglobulin production

Vitamin A and vitamin D metabolites are ligands to nuclear receptors - namely RAR, RXR and VDR. The activation of these receptors in human B cells impacts B cell maturation and function. In this review, we discuss how 9-cis retinoic acid (9cRA) and 1,25-dihydroxyvitamin D3 (calcitriol) individually or in conjunction, signal through their nuclear receptors and thereby impact B cell differentiation, immunoglobulin class switching to IgA at the expense of IgE, and also B cell migration and homing. Impact of the vitamin metabolites individually on B cell survival factors are well elucidated, be it the regulation of BAFF and APRIL, the induction of TGF-β or suppression of NF-κB. Very little is known about the impact of 9cRA and calcitriol together on B cells. Recently our group revealed that 9cRA and calcitriol together in the context of the B cell differentiation, induces naïve B cell differentiation into IgA+ plasmablasts, the functional and underlying molecular regulations however require further investigation. In conclusion, the conjunctional impact of these nuclear receptor ligands on B cell functionality is important to better understand B cell dependent clinical outcomes in allergy and autoimmunity. Within this review, we hypothesize that a balance between both vitamins is of utmost importance to provide a robust humoral immune response and a better treatment of disorders characterised by dysregulated immune responses such as IgE-dependent allergy or autoimmunity such as lupus erythematosus.

Intestinal factors promoting the development of RORγt+ cells and oral tolerance

The gastrointestinal tract has to harmonize the two seemingly opposite functions of fulfilling nutritional needs and avoiding the entry of pathogens, toxins and agents that can cause physical damage. This balance requires a constant adjustment of absorptive and defending functions by sensing environmental changes or noxious substances and initiating adaptive or protective mechanisms against them through a complex network of receptors integrated with the central nervous system that communicate with cells of the innate and adaptive immune system. Effective homeostatic processes at barrier sites take the responsibility for oral tolerance, which protects from adverse reactions to food that cause allergic diseases. During a very specific time interval in early life, the establishment of a stable microbiota in the large intestine is sufficient to prevent pathological events in adulthood towards a much larger bacterial community and provide tolerance towards diverse food antigens encountered later in life. The beneficial effects of the microbiome are mainly exerted by innate and adaptive cells that express the transcription factor RORγt, in whose generation, mediated by different bacterial metabolites, retinoic acid signalling plays a predominant role. In addition, recent investigations indicate that food antigens also contribute, analogously to microbial-derived signals, to educating innate immune cells and instructing the development and function of RORγt+ cells in the small intestine, complementing and expanding the tolerogenic effect of the microbiome in the colon. This review addresses the mechanisms through which microbiota-produced metabolites and dietary antigens maintain intestinal homeostasis, highlighting the complementarity and redundancy between their functions.

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.

Evaluating Risk: Benefit Ratio of Fat-Soluble Vitamin Supplementation to SARS-CoV-2-Infected Autoimmune and Cancer Patients: Do Vitamin–Drug Interactions Exist?

Simple Summary

This review brings attention to a crucial yet under-investigated subject which is vitamin–drug interactions. Fat-soluble vitamins such as vitamins A, D, E, and K have been proven to possess many beneficial effects in the treatment and prevention of COVID-19. Moreover, it has been reported that deficiencies of fat-soluble vitamins have been directly linked to COVID-19 infection-related morbidity and mortality, especially in high-risk populations such as cancer and autoimmune patients. However, many vitamin–drug interactions exist between most of the newly COVID-19 FDA-approved medications and fat-soluble vitamins. Hence, this mandates personalizing the COVID-19 treatment protocols, especially for patients who have any deficiency in any of these vital vitamins. Weighing the risk-to-benefit ratio of supplementing any of these fat-soluble vitamins with COVID-19 medications is considered crucial to maximize the therapeutic benefit and decrease the side effects of these drugs.

Abstract

COVID-19 is a recent pandemic that mandated the scientific society to provide effective evidence-based therapeutic approaches for the prevention and treatment for such a global threat, especially to those patients who hold a higher risk of infection and complications, such as patients with autoimmune diseases and cancer. Recent research has examined the role of various fat-soluble vitamins (vitamins A, D, E, and K) in reducing the severity of COVID-19 infection. Studies showed that deficiency in fat-soluble vitamins abrogates the immune system, thus rendering individuals more susceptible to COVID-19 infection. Moreover, another line of evidence showed that supplementation of fat-soluble vitamins during the course of infection enhances the viral clearance episode by promoting an adequate immune response. However, more thorough research is needed to define the adequate use of vitamin supplements in cancer and autoimmune patients infected with COVID-19. Moreover, it is crucial to highlight the vitamin–drug interactions of the COVID-19 therapeutic modalities and fat-soluble vitamins. With an emphasis on cancer and autoimmune patients, the current review aims to clarify the role of fat-soluble vitamins in SARS-CoV-2 infection and to estimate the risk-to-benefit ratio of a fat-soluble supplement administered to patients taking FDA-approved COVID-19 medications such as antivirals, anti-inflammatory, receptor blockers, and monoclonal antibodies.

Plasma Levels of Bioactive Vitamin D and A5 Ligands Positively Correlate with Clinical Atopic Dermatitis Markers

BACKGROUND

Over the past decade, several controversial studies described a relationship between vitamin D and atopic diseases. Low plasma vitamin D levels or even vitamin D deficiency was associated with an increased incidence of atopic disease, postulating that a higher dietary intake of vitamin D may be a beneficial strategy against atopic diseases such as atopic dermatitis (AD).

OBJECTIVE

Our aim was to determine the relationship between plasma 25-hydroxyvitamin D3 (25(OH)D3) levels, the levels of the ligand of the vitamin D receptor (VDR) heterodimerization partner as well as the retinoid X receptor (RXR) and the active vitamin A5 derivative 9-cis-13,14-dihydroretinoic acid (9CDHRA) and AD severity.

METHODS/RESULTS

Samples from AD patients (n = 20) and healthy volunteers (n = 20) were assessed. In our study, the frequently measured VDR ligand precursor 25(OH)D3 in addition to the VDR-ligand 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 9CDHRA displayed no different levels when compared with the plasma of AD patients and healthy volunteers. When performing further correlation studies focusing on AD patients, plasma 25(OH)D3 levels showed a negative correlation with eosinophils in blood (EOS) and SCORing Atopic Dermatitis (SCORAD) values, while 1,25(OH)2D3 and 9CDHRA levels correlated positively with plasma IgE, EOS, and SCORAD values.

CONCLUSION

In consequence, the metabolic activation of vitamin D from 25(OH)D3 towards 1,25(OH)2D3 as well as the co-liganding of the RXR by 9CDHRA may be an important signalling mechanism, an important marker for AD development and severity as well as the basis for novel nutritional and pharmaceutical AD treatment options.

Vitamin A controls the allergic response through T follicular helper cell as well as plasmablast differentiation

BACKGROUND

Vitamin A regulates the adaptive immune response and a modulatory impact on type I allergy is discussed. The cellular mechanisms are largely unknown.

OBJECTIVE

To determine the vitamin A-responding specific lymphocyte reaction in vivo.

METHODS

Antigen-specific B and T lymphocytes were analyzed in an adoptive transfer airway inflammation mouse model in response to 9-cis retinoic acid (9cRA) and after lymphocyte-specific genetic targeting of the receptor RARα. Flow cytometry, quantitative PCR, next-generation sequencing, and specific Ig-ELISA were used to characterize the cells functionally.

RESULTS

Systemic 9cRA profoundly enhanced the specific IgA-secreting B-cell frequencies in the lung tissue and serum IgA while reducing serum IgE concentrations. RARα overexpression in antigen-specific B cells promoted differentiation into plasmablasts at the expense of germinal center B cells. In antigen-specific T cells, RARα strongly promoted the differentiation of T follicular helper cells followed by an enhanced germinal center response.

CONCLUSIONS

9cRA signaling via RARα impacts the allergen-specific immunoglobulin response directly by the differentiation of B cells and indirectly by promoting T follicular helper cells.

9-cis Retinoic acid and 1.25-dihydroxyvitamin D3 drive differentiation into IgA+ secreting plasmablasts in human naïve B cells

Calcitriol and 9-cis retinoic acid (9cRA) play a fundamental role in shaping the adaptive immune response by altering the Ig profile and the differentiation of B cells, controlled by their corresponding nuclear receptors, VDR and RAR. Herein, after the establishment of a plasmablast differentiation culture, we investigated how both ligands modulate human naïve B cell differentiation and to which extent VDR/RXR and RAR/RXR signaling interferes. Calcitriol and 9cRA mediated activation of purified naïve B cells resulted in a strong differentiation of CD27⁺ CD38⁺ plasmablasts and antibody secretion. The significant IgA response was preceded by a strong induction of α-germline transcription (GLT). Induction of αGLT and consecutively IgA secretion driven by calcitriol is a novel observation and we show by magnetic chromatin IP that this was mediated by recruitment of the VDR to the TGF-β promoter thus inducing TGF-β expression. Finally, as revealed by transcriptomic profiling calcitriol and 9cRA modulate several signals required for differentiation and isotype switching in a noncompeting but rather additive manner. Calcitriol and 9cRA participate in the control of the IgA response in human activated naïve B cells. The balance between both ligands may be an important factor in channeling humoral immune responses toward a protective direction.

Vitamin A deficiency exacerbates extrinsic atopic dermatitis development by potentiating type 2 helper T cell-type inflammation and mast cell activation

BACKGROUND

Vitamin A deficiency (VAD) has been hypothesized to play a role in the pathophysiology of atopic dermatitis (AD).

OBJECTIVE

We sought to verify whether VAD can exacerbate AD development, and explore the possible pathophysiologic mechanism.

METHODS

We detected serum vitamin A (VA) concentration in different phenotypes of AD infants (intrinsic AD, iAD and extrinsic AD, eAD), and established ovalbumin (OVA) percutaneous sensitized AD model and passive cutaneous anaphylaxis (PCA) model on VAD and vitamin A supplementation (VAS) model in wild-type mice (C57BL/6) and established AD model on both normal VA (VAN) and VAD feeding mast cell deficiency mice (ckit^w-sh/w-sh ).

RESULTS

The average serum VA concentration of eAD was significantly lower than that of iAD, as well as healthy controls. In OVA-induced C57BL/6 mouse AD model, compared with VAN group, VAD mice manifested significantly more mast cells accumulation in the skin lesions, more severe Th2-mediated inflammation, including higher serum IgG1 and IgE levels, more IL-4, IL-13 mRNA expression in OVA-sensitized skin, and lower Th1 immune response, including lower serum IgG2a and IFN-γ mRNA expression in the skin. But there was no significant difference in the expression of IL-17 mRNA between OVA-treated skin of VAN and VAD mice. However, in OVA-induced ckit^w-sh/w-sh mouse AD model, we did not find any significant differences in the above measurements between VAD and VAN group. In PCA model, VAD mice showed remarkable more blue dye leakage than that in VAN mice. Compared with VAD group, the above-mentioned inflammatory measurements in VAS group and VAN group were similar in OVA-induced AD model mice.

CONCLUSIONS AND CLINICAL RELEVANCE

VAD can exacerbate extrinsic AD by augmenting Th2-mediated inflammation and mast cell activation. Therapeutic VAS can rescue VAD-aggravated eAD. It may provide a new strategy for future prevention or treatment of atopic dermatitis.

Retinoids in health and disease: A role for hepatic stellate cells in affecting retinoid levels

Vitamin A (retinol) is important for normal growth, vision and reproduction. It has a role in the immune response and the development of metabolic syndrome. Most of the retinol present in the body is stored as retinyl esters within lipid droplets in hepatic stellate cells (HSCs). In case of liver damage, HSCs release large amounts of stored retinol, which is partially converted to retinoic acid (RA). This surge of RA can mediate the immune response and enhance the regeneration of the liver. If the damage persists activated HSCs change into myofibroblast-like cells producing extracellular matrix, which increases the chance of tumorigenesis to occur. RA has been shown to decrease proliferation and metastasis of hepatocellular carcinoma. The levels of RA and RA signaling are influenced by the possibility to esterify retinol towards retinyl esters. This suggests a complex regulation between different retinoids, with an important regulatory role for HSCs.

The Effect of Melatonin on Locomotor Behavior and Muscle Physiology in the Sea Cucumber Apostichopus japonicus

Melatonin is a highly conserved hormone in evolutionary history. It occurs in numerous organisms and plays a role in the endocrine and immune systems. Locomotor behavior is a basic behavior in animals and is an important indicator of circadian rhythms, which are coordinated by the nervous and endocrine systems. To date, the effect of melatonin on locomotor behavior has been studied in vertebrates, including syrian hamsters, sparrows, rats, zebrafish, goldfish, and flatworms. However, there have been few studies of the effects of melatonin on locomotor behavior in marine invertebrates. The goals of present study were to show the existence of melatonin in the sea cucumber Apostichopus japonicus and to evaluate its effect on locomotor activity. In addition, muscle tissues from control and melatonin-treated sea cucumbers were tested using ultra performance liquid chromatography and quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) to determine the changes of metabolic activity in muscle. Melatonin was present in the coelomic fluid of A. japonicus at a concentration of ∼135.0 ng/L. The total distance traveled and number steps taken over 9 h after melatonin administration decreased with increasing concentration of the melatonin dose. Mean and maximum velocity of movement and stride length and stride frequency also decreased, but their differences were not statistically significant. Overall, these results suggest that melatonin administration had a sedative effect on A. japonicus. The levels of 22 different metabolites were altered in the muscle tissues of melatonin-treated sea cucumbers. Serotonin, 9-cis retinoic acid, all-trans retinoic acid, flavin mononucleotide in muscles were downregulated after melatonin administration. Moreover, a high free fatty acid (FFA) concentration and a decrease in the adenosine 5′-triphosphate (ATP) concentration in the muscle tissues of the melatonin-treated group were detected as well. These results suggest that the sedative effect of melatonin involves some other metabolic pathways, and the reduced locomotor modulator—serotonin, inhibited fatty acid oxidation and disturbed oxidative phosphorylation are potential physiological mechanisms that result in the inhibitory effect of melatonin on locomotion in sea cucumbers.

Role of Vitamin A in the Immune System

Vitamin A (VitA) is a micronutrient that is crucial for maintaining vision, promoting growth and development, and protecting epithelium and mucus integrity in the body. VitA is known as an anti-inflammation vitamin because of its critical role in enhancing immune function. VitA is involved in the development of the immune system and plays regulatory roles in cellular immune responses and humoral immune processes. VitA has demonstrated a therapeutic effect in the treatment of various infectious diseases. To better understand the relationship between nutrition and the immune system, the authors review recent literature about VitA in immunity research and briefly introduce the clinical application of VitA in the treatment of several infectious diseases.

Vitamin A and D in allergy: from experimental animal models and cellular studies to human disease

Introduction

Vitamins A and D are able to modulate innate and adaptive immune responses and may therefore influence the development and the course of allergic diseases.

Materials and methods

This article reviews the current evidence for the experimental effects of vitamins A and D in vivo in animal models and on immune cells in vitro, and discusses their translational implication. A systematic literature search over the last 10 years was performed using MEDLINE and PubMed databases.

Results

Deficiencies of vitamin A or vitamin D in mouse models of allergic asthma seem to exacerbate allergic symptoms along with enhanced lung inflammation and Th2 cytokine production. In contrast, supplementation regimes especially with vitamin D were able to attenuate symptoms in therapeutic mouse models. The active metabolites retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (VD3) induced tolerogenic dendritic cells (DCs) and up-regulated T‑regulatory cells in the allergic sensitization phase, which likely contributes to tolerance induction. Additionally, RA and VD3 maintained the stability of eosinophils and mast cells in the effector phase, thereby reducing allergic mediator release. Thus, both active vitamin metabolites RA and VD3 are able to influence allergic immune responses at several immunological sites.

Conclusion

Animal studies predict that vitamin A and D may also be attractive players in the control of allergy in humans. Whether these experimental observations can be translated to the human situation remains open, as results from clinical trials are controversial.

Control of Innate and Adaptive Lymphocytes by the RAR-Retinoic Acid Axis

Lymphocytes, such as T cells, B cells, and innate lymphoid cells (ILCs), play central roles in regulating immune responses. Retinoic acids (RAs) are vitamin A metabolites, produced and metabolized by certain tissue cells and myeloid cells in a tissue-specific manner. It has been established that RAs induce gut-homing receptors on T cells, B cells, and ILCs. A mounting body of evidence indicates that RAs exert far-reaching effects on functional differentiation and fate of these lymphocytes. For example, RAs promote effector T cell maintenance, generation of induced gut-homing regulatory and effector T cell subsets, antibody production by B cells, and functional maturation of ILCs. Key functions of RAs in regulating major groups of innate and adaptive lymphocytes are highlighted in this article.