Retinoic acid enhances the levels of IL-10 in TLR-stimulated B cells from patients with relapsing-remitting multiple sclerosis

Irradiation Attenuates Systemic Lupus Erythematosus-Like Morbidity in NZBWF1 Mice: Focusing on CD180-Negative Cells

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that can induce systemic inflammation. Ultraviolet-A and X-ray irradiation have been reported to have therapeutic effects in patients with SLE. We previously demonstrated that CD180-negative cells, these are radiosensitive, contribute to the development of SLE-like morbidity in NZBWF1 mice. In this study, the effects of irradiation on SLE-like morbidity manifestations in NZBWF1 mice and on CD180-negative cells were investigated. Whole-body irradiation, excluding the head, attenuated SLE-like morbidity in vivo, as indicated by the prevention of the renal lesion development, inhibition of anti-dsDNA antibody production, reduction of urinary protein levels, and prolongation of the lifespan. Irradiation also reduced the proportion of CD180-negative cells in the spleen. Although other immune cells or molecules may be triggered because of the whole-body irradiation treatment, previous research, and the current results suggest a strong relationship between the radiation-induced decrease in CD180-negative cells and the amelioration of SLE-like morbidities. Clinical trials assessing CD180-negative cells as a therapeutic target for SLE have been hampered by the lack of validated cell markers; nonetheless, the present findings suggest that radiotherapy may be a new therapeutic strategy for managing SLE symptoms.

Cell surface expression of human RP105 depends on N-glycosylation of MD-1

For its cell surface expression, radioprotective 105 (RP105) - an orphan Toll-like receptor - must form a complex with a soluble glycoprotein called myeloid differentiation 1 (MD-1). The number of RP105-negative cells is significantly increased in patients with systemic lupus erythematosus (SLE); however, to elucidate the mechanism underlying this increase, how RP105 is expressed on the cell surface depending on MD-1 should be investigated. We demonstrated that RP105 exhibits two forms depending on MD-1 and its two N-glycosylation sites, N96 and N156. Cell surface expression of RP105 decreased in the presence of mutant MD-1 (N96Q/N156Q). Nonglycosylated MD-1 decreased the de novo cell surface expression of RP105 but not pre-expressed RP105. Thus, the N-glycans of MD-1 may represent targets for SLE therapy.

The Multiple Sclerosis Modulatory Potential of Natural Multi-Targeting Antioxidants

Multiple sclerosis (MS) is a complex neurodegenerative disease. Although its pathogenesis is rather vague in some aspects, it is well known to be an inflammatory process characterized by inflammatory cytokine release and oxidative burden, resulting in demyelination and reduced remyelination and axonal survival together with microglial activation. Antioxidant compounds are gaining interest towards the manipulation of MS, since they offer, in most of the cases, many benefits, due to their pleiotropical activity, that mainly derives from the oxidative stress decrease. This review analyzes research articles, of the last decade, which describe biological in vitro, in vivo and clinical evaluation of various categories of the most therapeutically applied natural antioxidant compounds, and some of their derivatives, with anti-MS activity. It also summarizes some of the main characteristics of MS and the role the reactive oxygen and nitrogen species may have in its progression, as well as their relation with the other mechanistic aspects of the disease, in order for the multi-targeting potential of those antioxidants to be defined and the source of origination of such activity explained. Antioxidant compounds with specific characteristics are expected to affect positively some aspects of the disease, and their potential may render them as effective candidates for neurological impairment reduction in combination with the MS treatment regimen. However, more studies are needed in order such antioxidants to be established as recommended treatment to MS patients.

Therapeutic Potential of Combined Therapy of Vitamin A and Vitamin C in the Experimental Autoimmune Encephalomyelitis (EAE) in Lewis Rats

Demyelination, inflammation, oxidative injury, and glial activation are the main pathological hallmarks of multiple sclerosis (MS). Vitamins, as essential micronutrients, seem to be crucial in the pathogenesis of MS, and particularly vitamins A and C were found to have a protective role in MS development or progression. In this study, the therapeutic potential of combined therapy of vitamins A and C on progression of experimental autoimmune encephalomyelitis (EAE) and myelin repair mechanisms was examined. EAE, an animal model of MS, was induced in female Lewis rats. The rats were treated with daily intraperitoneal injections of vitamins A and C and their combination. We found that co-supplementation of vitamins A and C mitigated neurological severity and EAE disease progression. Histological study confirmed a significant reduction in demyelination size, inflammation and immune cell infiltration as well as microglia and astrocyte activation following co-administration of vitamins A and C. Co-administration of vitamins A and C also decreased the levels of pro-inflammatory cytokines (TNF-α, IL1β) and iNOS and increased gene expressions of IL-10, Nrf-2, HO-1, and MBP. Combination therapy of vitamins A and C also increased the total antioxidant capacity and decreased levels of oxidative stress markers. Finally, we proved that co-administration of vitamins A and C has anti-apoptotic and neuroprotective impacts in EAE via decreasing caspase-3 and increasing BDNF and NeuN expressing cells. The present study suggests that combined therapy of vitamins A and C may be an effective strategy for development of alternative medicine in boosting myelin repair in demyelinating diseases.

Retinoids are not linked to risk of multiple sclerosis: A Danish nationwide cohort study

BACKGROUND AND PURPOSE

Multiple sclerosis (MS) is a chronic immune-mediated disease of the central nervous system with an undetermined etiology. Retinoids may have immunomodulatory effects that favorably influence MS progression. We aimed to explore the yet unknown relationship between exposure to retinoids and the risk of acquiring MS.

METHODS

We performed a nationwide cohort study in the Danish population in the period 1998-2016, comparing MS incidence in three groups: users of systemic retinoids; users of topical retinoids (negative control group); and users of non-retinoid acne drugs (control group). We used data from the Danish Multiple Sclerosis Registry (DMSR), the Danish National Prescription Registry and the Danish National Patient Registry. Linkage was obtained through the personal identification number (CPR number). We addressed confounding by three-way propensity score (PS)-matching weights. Additionally, to evaluate a cumulative dose-response effect for systemic retinoids on MS incidence, we conducted a case-control study, nested within the cohort.

RESULTS

A total of 257,193 users of non-retinoid acne drugs, 130,560 users of topical retinoids, and 75,610 users of systemic retinoids were included. Systemic retinoid use was not associated with a reduced risk of MS compared to non-retinoid acne drug use in crude (hazard ratio [HR] 0.80, 95% confidence interval [CI] 0.61 to 1.05]) and weighted analyses (HR 0.89, 95% CI 0.67 to 1.20). There was no evidence of a cumulative dose-response association between systemic retinoids and MS incidence.

CONCLUSIONS

Use of systemic retinoids was not associated with a reduced incidence of MS compared to use of non-retinoid acne drugs in this study.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Dietary Supplements on Controlling Multiple Sclerosis Symptoms and Relapses: Current Clinical Evidence and Future Perspectives

Background: Multiple sclerosis (MS) constitutes a chronic progressive demyelinating disease which negatively affects the central nervous system. MS symptoms detrimentally affect the quality of life, as well as the life expectancy of MS patients. In this aspect, the present study aims to critically summarize and evaluate the currently available clinical studies focusing on the potential beneficial effects of dietary supplements on controlling MS symptomatology and relapse. Methods: PubMed database was comprehensively searched, using relative keywords to identify clinical trials that investigated the beneficial effects of dietary supplementation against MS symptomatology and progression. 40 clinical trials were found, which were divided into categories. Results: Nutritional status of MS patients, as well as supplementation have been suggested as potential factors affecting progression. Several substantial studies have documented a systematically high prevalence of vitamin A, B12 and D3 deficiency amongst MS patients. At present, clinical data have suggested that most of the dietary supplements under study may exert antioxidant and anti-inflammatory properties, improving depression symptomatology and quality of life overall. However, malnutrition risk in MS patients has not been adequately explored in order for more precise conclusions to be drawn. The supplements that may have a positive effect on MS are vitamins, fatty acids, antioxidants, phytochemicals and melatonin. Conclusions: Several dietary supplements may decrease inflammation and fatigue, also increasing also autoimmunity tolerance in MS patients, and thus improving quality of life and life expectancy. Currently, there is no effective clinical indication for applying dietary supplementation as complementary treatment against MS symptomatology.

Frequency and immunophenotype of IL10-producing regulatory B cells in optic neuritis

Mouse models of multiple sclerosis (MS) have shown the importance of interleukin-10 (IL-10) -producing regulatory B (Breg) cells in dampening disease activity and inhibiting disease initiation and progression. In MS and other autoimmune diseases decreased frequency and functionality of Breg cells correlate with disease activity and the percentage of IL-10-producing Breg cells decreases during relapse and normalizes in remission. Optic neuritis (ON) is a common first clinical manifestation of MS and IL-10-producing Breg cells may be crucial in the transition from ON to MS, we therefore investigate the frequency and function of Breg cells in ON as a clinical model of early demyelinating disease. B cells were purified from 27 patients with ON sampled close to symptom onset (median 23 days, range 7-41 days) and 13 healthy controls. The B cells were stimulated and cultured for 48 hr with CD40 ligand and CpG before measurement of intracellular IL-10 and the surface markers CD19, CD1d, CD5, CD24, CD38 and CD27 by flow cytometry. The frequency of B-cell subsets was analysed in peripheral blood and cerebral spinal fluid (CSF) of patients. Sixty-five per cent of the IL-10-producing Breg cells co-expressed CD24 and CD38, and only 14% were CD24^high  CD27⁺ , suggesting that the naive B cells are the primary source of IL-10 in the B-cell culture, followed by memory cells in both healthy controls and patients. The frequency of naive CD19⁺  CD24⁺  CD38⁺ Breg cells was higher in patients with ON compared with controls. The ability of Breg cells to produce IL-10 was at normal levels in both ON patients with high risk and those with low risk of progression to MS. We found no correlation between Breg cell function and the presence of brain white matter lesions by magnetic resonance imaging or CSF oligoclonal bands indicative of ON patients carrying a higher risk of conversion to MS. The frequencies of IL-10-producing B cells did not correlate with the conversion to MS at 2-year follow up. Interleukin-10 was primarily produced by naive and memory B cells. The frequency of IL-10-secreting B cells did not correlate with risk factors of MS. Breg cell function at clinical onset of ON is not a determining factor for conversion to MS.

Retinoic Acid, Leaky Gut, and Autoimmune Diseases

A leaky gut has been observed in a number of autoimmune diseases including type 1 diabetes, multiple sclerosis, inflammatory bowel disease, and systemic lupus erythematosus. Previous studies from our laboratory have shown that lupus mice also bear a leaky gut and that the intestinal barrier function can be enhanced by gut colonization of probiotics such as Lactobacillus spp. Retinoic acid (RA) can increase the relative abundance of Lactobacillus spp. in the gut. Interestingly, RA has also been shown to strengthen the barrier function of epithelial cells in vitro and in the absence of probiotic bacteria. These reports bring up an interesting question of whether RA exerts protective effects on the intestinal barrier directly or through regulating the microbiota colonization. In this review, we will discuss the roles of RA in immunomodulation, recent literature on the involvement of a leaky gut in different autoimmune diseases, and how RA shapes the outcomes of these diseases.

A review on potential roles of vitamins in incidence, progression, and improvement of multiple sclerosis

Multiple Sclerosis (MS) is an inflammatory and neurodegenerative disease, with unknown etiology. Vitamins, as important micronutrients playing different roles in body, seem to be important in MS pathogenesis. In vitro, in vivo and human studies, supports the protective role of some vitamins in MS occurrence or progression. Current study reviews recent insights and reports about the importance of vitamins in MS incidence or progression. In accordance, the importance of all water and fat-soluble vitamins in MS pathogenesis based on observational studies in human population and their role in the function of immune system as well as possible therapeutic opportunities are discussed in depth throughout this review.

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.

Inhibition of HDAC enhances STAT acetylation, blocks NF-κB, and suppresses the renal inflammation and fibrosis in Npr1 haplotype male mice

Guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) plays a critical role in the regulation of blood pressure and fluid volume homeostasis. Mice lacking functional Npr1 (coding for GC-A/NPRA) exhibit hypertension and congestive heart failure. However, the underlying mechanisms remain largely less clear. The objective of the present study was to determine the physiological efficacy and impact of all-trans-retinoic acid (ATRA) and sodium butyrate (NaBu) in ameliorating the renal fibrosis, inflammation, and hypertension in Npr1 gene-disrupted haplotype (1-copy; +/-) mice (50% expression levels of NPRA). Both ATRA and NaBu, either alone or in combination, decreased the elevated levels of renal proinflammatory and profibrotic cytokines and lowered blood pressure in Npr1+/- mice compared with untreated controls. The treatment with ATRA-NaBu facilitated the dissociation of histone deacetylase (HDAC) 1 and 2 from signal transducer and activator of transcription 1 (STAT1) and enhanced its acetylation in the kidneys of Npr1+/- mice. The acetylated STAT1 formed a complex with nuclear factor-κB (NF-κB) p65, thereby inhibiting its DNA-binding activity and downstream proinflammatory and profibrotic signaling cascades. The present results demonstrate that the treatment of the haplotype Npr1+/- mice with ATRA-NaBu significantly lowered blood pressure and reduced the renal inflammation and fibrosis involving the interactive roles of HDAC, NF-κB (p65), and STAT1. The current findings will help in developing the molecular therapeutic targets and new treatment strategies for hypertension and renal dysfunction in humans.

Retinoic acid receptor agonist Am80 inhibits CXCL2 production from microglial BV-2 cells via attenuation of NF-κB signaling

Accumulating lines of evidence suggest that retinoic acid receptor agonists such as Am80 exerts anti-inflammatory actions in the central nervous system, although detailed mechanisms of the action remain largely unknown. Our previous findings suggest that Am80 provides therapeutic effect on intracerebral hemorrhage in mice via suppression of expression of chemokine (C-X-C motif) ligand 2 (CXCL2). Here we investigated the mechanisms of inhibitory action of Am80 on expression of CXCL2 and other pro-inflammatory factors in microglial BV-2 cells. Pretreatment with Am80 markedly suppressed lipopolysaccharide (LPS)-induced expression of CXCL2 mRNA and release of CXCL2 protein. Am80 had no effect on LPS-induced activation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinase. On the other hand, Am80 prevented LPS-induced nuclear translocation of p65 subunit of NF-κB complex. In addition, total expression levels of p65 and IκBα proteins, as well as of mRNAs encoding p65 and IκBα, were lowered by Am80. Dependence of CXCL2 expression on NF-κB was confirmed by the effect of an NF-κB inhibitor caffeic acid phenethyl ester that abolished LPS-induced CXCL2 expression. Caffeic acid phenethyl ester also abolished LPS-induced expression of inducible nitric oxide synthase, interleukin-1β and tumor necrosis factor α, which may be relevant to the inhibitory effect of Am80 on expression of these pro-inflammatory factors. We additionally found that Am80 attenuated LPS-induced up-regulation of CD14, a co-receptor for Toll-like receptor 4 (TLR4). These results suggest that inhibitory effect on TLR4 signaling mediated by NF-κB pathway underlies the anti-inflammatory action of retinoic acid receptor agonists in microglia.

Synergistic activation of Arg1 gene by retinoic acid and IL-4 involves chromatin remodeling for transcription initiation and elongation coupling

All-trans Retinoic acid (RA) and its derivatives are potent therapeutics for immunological functions including wound repair. However, the molecular mechanism of RA modulation in innate immunity is poorly understood, especially in macrophages. We found that topical application of RA significantly improves wound healing and that RA and IL-4 synergistically activate Arg1, a critical gene for tissue repair, in M2 polarized macrophages. This involves feed forward regulation of Raldh2, a rate-limiting enzyme for RA biosynthesis, and requires Med25 to coordinate RAR, STAT6 and chromatin remodeler, Brg1 to remodel the +1 nucleosome of Arg1 for transcription initiation. By recruiting elongation factor TFIIS, Med25 also facilitates transcriptional initiation-elongation coupling. This study uncovers synergistic activation of Arg1 by RA and IL-4 in M2 macrophages that involves feed forward regulation of RA synthesis and dual functions of Med25 in nucleosome remodeling and transcription initiation-elongation coupling that underlies robust modulatory activity of RA in innate immunity.

Illuminating vitamin D effects on B cells--the multiple sclerosis perspective

Vitamin D is associated with many immune-mediated disorders. In multiple sclerosis (MS) a poor vitamin D status is a major environmental factor associated with disease incidence and severity. The inflammation in MS is primarily T-cell-mediated, but increasing evidence points to an important role for B cells. This has paved the way for investigating vitamin D effects on B cells. In this review we elaborate on vitamin D interactions with antibody production, T-cell-stimulating capacity and regulatory B cells. Although in vitro plasma cell generation and expression of co-stimulatory molecules are inhibited and the function of regulatory B cells is promoted, this is not supported by in vivo data. We speculate that differences might be explained by the B-cell-Epstein-Barr virus interaction in MS, the exquisite role of germinal centres in B-cell biology, and/or in vivo interactions with other hormones and vitamins that interfere with the vitamin D pathways. Further research is warranted to illuminate this tube-versus-body paradox.