Characterization of the multiple sclerosis traits: Nuclear receptors (NR) impaired apoptosis pathway and the role of 1-alpha 25-dihydroxyvitamin D3

Deciphering the shift from benign to active relapsing-remitting multiple sclerosis: Insights into T regulatory cell dysfunction and apoptosis regulation

BACKGROUND

Relapsing-remitting multiple sclerosis (RRMS), a common demyelinating disease among young adults, follows a benign course in 10-15% of cases, where patients experience minimal neurological disability for a decade following disease onset. However, there is potential for these benign cases to transition into a clinically active, relapsing state.

OBJECTIVE

To elucidate the biological mechanisms underlying the transition from benign to active RRMS using gene expression analysis.

METHODS

We employed complementary-DNA microarrays to examine peripheral-blood gene expression patterns in patients with benign MS, defined as having a disease duration exceeding 10 years and an Expanded Disability Status Scale (EDSS) score of ≤3.0. We compared the gene expression pattern between patients who switched to active disease (Switching BMS) with those who maintained a benign state (Permanent-BMS) during an additional 5-year follow-up.

RESULTS

We identified two primary mechanisms linked to the transition from benign MS to clinically active disease. The first involves the suppression of regulatory T cell activity, and the second pertains to the dysfunction of nuclear receptor 4 A family-dependent apoptosis. These mechanisms collectively contribute to an augmented autoimmune response and increased disease activity.

CONCLUSIONS

The intricate gene regulatory networks that operate in switching-BMS are related to suppression of immune tolerance and aberrant apoptosis. These findings may lead to new therapeutic targets to prevent the escalation to active disease.

The Selective Agonist for Sphingosine-1-Phosphate Receptors Siponimod Increases the Expression Level of NR4A Genes in Microglia Cell Line

Fingolimod (FTY720) and siponimod (BAF312) are selective agonists for sphingosine-1-phosphate (S1P) receptors approved for the treatment of relapsing–remitting (RR) and secondary progressive (SP) multiple sclerosis (MS), respectively. BAF312 exerts pro-myelination and neuro-protective functions on CNS resident cells, although the underlying molecular mechanism is not yet fully understood. NR4A2 is an anti-inflammatory gene, belonging to the NR4A family, whose expression is reduced in blood from treatment-naïve patients with RRMS, but is restored in patients treated with FTY720 for more than two years. We performed an in vitro study to investigate the potential involvement of the NR4A genes in the protective and restorative effects of BAF312. We showed that BAF312 enhances the expression of NR4A1 and NR4A2 in the N9 microglial cell line, but has no effect in the peripheral blood mononuclear cells and oligodendrocytes. This study suggests a novel molecular mechanism of action for the selective agonists for S1P receptors within the CNS.

Nuclear receptor Nur77: its role in chronic inflammatory diseases

Nur77 is a nuclear receptor that has been implicated as a regulator of inflammatory disease. The expression of Nur77 increases upon stimulation of immune cells and is differentially expressed in chronically inflamed organs in human and experimental models. Furthermore, in a variety of animal models dedicated to study inflammatory diseases, changes in Nur77 expression alter disease outcome. The available studies comprise a wealth of information on the function of Nur77 in diverse cell types and tissues. Negative cross-talk of Nur77 with the NFκB signaling complex is an example of Nur77 effector function. An alternative mechanism of action has been established, involving Nur77-mediated modulation of metabolism in macrophages as well as in T cells. In this review, we summarize our current knowledge on the role of Nur77 in atherosclerosis, inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, and sepsis. Detailed insight in the control of inflammatory responses will be essential in order to advance Nur77-targeted therapeutic interventions in inflammatory disease.

Progress and Promise of Nur77-based Therapeutics for Central Nervous System Disorders

Nur77 belongs to the NR4A subgroup of the nuclear receptor superfamily. Unlike other nuclear receptors, a natural ligand for Nur77 has not been identified yet. However, a few small molecules can interact with this receptor and induce a conformational change to mediate its activity. The expression and activation of Nur77 can be rapidly increased using various physiological and pathological stimuli. In vivo and in vitro studies have demonstrated its regulatory role in tissues and cells of multiple systems by means of participation in cell differentiation, apoptosis, metabolism, mitochondrial homeostasis, and other processes. Although research on Nur77 in the pathophysiology of the central nervous system (CNS) is currently limited, the present data support the fact that Nur77 is involved in many neurological disorders such as stroke, multiple sclerosis, Parkinson’s disease. This indicates that activation of Nur77 has considerable potential in treating these diseases. This review summarizes the regulatory mechanisms of Nur77 in CNS diseases and presents available evidence for its potential as targeted therapy, especially for cerebrovascular and inflammation-related CNS diseases.

NURR1 Impairment in Multiple Sclerosis

The transcription factor NURR1 is a constitutively active orphan receptor belonging to the steroid hormone receptor class NR4A. Although a genetic association between NURR1 and autoimmune inflammatory diseases has never emerged from genome-wide association studies (GWAS), alterations in the expression of NURR1 have been observed in various autoimmune diseases. Specifically, its role in autoimmune inflammatory diseases is mainly related to its capability to counteract inflammation. In fact, NURR1 exerts anti-inflammatory functions inhibiting the transcription of the molecules involved in proinflammatory pathways, not only in the peripheral blood compartment, but also in the cerebral parenchyma acting in microglial cells and astrocytes. In parallel, NURR1 has been also linked to dopamine-associated brain disorders, such as Parkinson’s disease (PD) and schizophrenia, since it is involved in the development and in the maintenance of midbrain dopaminergic neurons (mDA). Considering its role in neuro- and systemic inflammatory processes, here we review the evidences supporting its contribution to multiple sclerosis (MS), a chronic inflammatory autoimmune disease affecting the central nervous system (CNS). To date, the specific role of NURR1 in MS is still debated and few authors have studied this topic. Here, we plan to clarify this issue analyzing the reported association between NURR1 and MS in human and murine model studies.

Study of the NR4A family gene expression in patients with multiple sclerosis treated with Fingolimod

BACKGROUND AND PURPOSE

Fingolimod is a drug approved for treatment of relapsing-remitting multiple sclerosis (RRMS) that exerts its effects via sequestering lymphocytes within the lymph nodes. The drug, acting on the sphingosine-1-phosphate pathway, is involved in a plethora of processes and, to date, its mechanism of action is not completely understood. Recently, it has been demonstrated that Fingolimod increases the expression of transcription factor NR4A2 in murine brain. NR4A2 belongs to nuclear receptor family 4, group A (NR4A) along with NR4A1 and NR4A3. The role of NR4A2 in the pathogenesis of multiple sclerosis is already known and supported by its down-regulation observed in blood obtained from patients with RRMS compared with healthy controls (HCs). It is notable that NR4A2 impairment is reversed in patients with RRMS during pregnancy, which represents a transitory state of immune tolerance, associated with reduced disease activity. An inverse correlation between NR4A2 gene expression levels and clinical parameters indicates that more aggressive forms of the disease are characterized by lower levels of NR4A2.

METHODS

Gene expression levels of NR4A in blood obtained from HCs, treatment-naive (T0) and Fingolimod-treated patients with RRMS were evaluated to determine their contribution to drug response.

RESULTS

Gene expression levels of NR4A were down-regulated in T0 patients compared with HCs. Patients treated with Fingolimod for >2 years were characterized by higher levels of NR4A2 compared with the T0 group, approaching those of HCs. NR4A1 and NR4A3 levels were not altered.

CONCLUSIONS

Involvement of the NR4A family in the pathogenesis of multiple sclerosis and a role of Fingolimod in the recovery from NR4A2 deficit can be hypothesized based on our data.

Nr4a1 plays a crucial modulatory role in Th1/Th17 cell responses and CNS autoimmunity

Nuclear receptor4 group A1 (Nr4a1), an orphan nuclear receptor, is down-regulated in peripheral blood mononuclear cells (MNCs) of individuals with multiple sclerosis (MS), and Nr4a1 deficiency results in severe experimental autoimmune encephalomyelitis (EAE), an animal model of MS, caused by increased macrophage infiltration into the central nervous system (CNS). However, the role of Nr4a1 in macrophage phenotype and T cell responses remains poorly understood. In the present study we show that macrophages/microglia of Nr4a1^-/- mice, which exhibited earlier onset and more severe clinical EAE, were polarized to an enhanced type 1 (M1) phenotype and produced higher levels of IL-12 and TNF-α than wild type mice. Significantly increased numbers of CD4⁺ T cells and frequency of CD4⁺IFN-γ⁺ and CD4⁺IL-17⁺ T cells were observed in the CNS and spleen of Nr4a1^-/- mice, with decreased percentages of apoptosis in CD4⁺ T cells. The percentages of CD4⁺Foxp3⁺ Treg cells in the CNS of Nr4a1^-/- mice were also reduced. Furthermore, purified CD4⁺ T cells from naïve Nr4a1^-/- mice exhibited enhanced Th1 and Th17 differentiation capacity, and MOG-reactive Th17 cells from Nr4a1^-/- mice adoptively transferred more severe EAE in recipient mice. Our results, for the first time, demonstrate that Nr4a1 not only induces Type 2 macrophages/microglia phenotype, but is also a critical inhibitory molecule for Th1/Th17 cell differentiation. This finding indicates that Nr4a1-related molecule(s) may have therapeutic potential in MS and likely other autoimmune disorders.

Multiple faces of fibroblast growth factor-23

PURPOSE OF REVIEW

This review examines the role of fibroblast growth factor-23 (FGF-23) in mineral metabolism, innate immunity and adverse cardiovascular outcomes.

RECENT FINDINGS

FGF-23, produced by osteocytes in bone, activates FGFR/α-Klotho (α-Kl) complexes in the kidney. The resulting bone-kidney axis coordinates renal phosphate reabsorption with bone mineralization, and creates a counter-regulatory feedback loop to prevent vitamin D toxicity. FGF-23 acts to counter-regulate the effects of vitamin D on innate immunity and cardiovascular responses. FGF-23 is ectopically expressed along with α-Kl in activated macrophages, creating a proinflammatory paracrine signaling pathway that counters the antiinflammatory actions of vitamin D. FGF-23 also inhibits angiotensin-converting enzyme 2 expression and increases sodium reabsorption in the kidney, leading to hypertension and left ventricular hypertrophy. Finally, FGF-23 is purported to cause adverse cardiac and impair neutrophil responses through activation of FGFRs in the absence of α-Kl. Although secreted forms of α-Kl have FGF-23 independent effects, the possibility of α-Kl independent effects of FGF-23 is controversial and requires additional experimental validation.

SUMMARY

FGF-23 participates in a bone-kidney axis regulating mineral homeostasis, proinflammatory paracrine macrophage signaling pathways, and in a bone-cardio-renal axis regulating hemodynamics that counteract the effects of vitamin D.

Transcriptional modulation of regulatory T cell development by novel regulators NR4As

Regulatory T (Treg) cells with high expression of both CD25 and Foxp3 are developed in the thymus and also peripheral tissues. Treg cells suppress the activation and functions of effector T cells raised against specific antigens and are crucial for maintaining immune homeostasis. Treg cell development is associated with the induction of and epigenetic alterations of forkhead transcription factor Foxp3. Foxp3 expression is increased by the activation of several transcription factors including nuclear factor-kappa B (NF-κB), nuclear factor of activated T cells (NFAT), and Smad3 in response to various signals such as TGFβ, retinoic acid, and rapamycin. Recently, the orphan nuclear receptor 4A proteins (NR4As) including NR4A1 (Nur77), NR4A2 (Nurr1), and NR4A3 (Nor1) are reported to regulate Treg cell development through activation of Foxp3 and have therapeutic potentials in treating immune disorders. This review summarizes the function and regulatory mechanisms of Treg cells and also implicates current advances in immunomodulatory functions of NR4As and their therapeutic potentials in inflammation and cancer.

Advances in the immunopathogenesis of multiple sclerosis

PURPOSE OF REVIEW

Recent studies indicate a role for immune dysregulation in the pathogenesis of multiple sclerosis, an inflammatory demyelinating and degenerative disease of the central nervous system. This review addresses the current mechanisms of immune dysregulation in the development of multiple sclerosis, including the impact of environmental risk factors on immunity in both multiple sclerosis and its animal models.

RECENT FINDINGS

CD4 T-helper (Th) cells have long been implicated as the main drivers of pathogenesis of multiple sclerosis. However, current studies indicate that multiple sclerosis is largely a heterogeneous disease process, which involves both innate and adaptive immune-mediated inflammatory mechanisms that ultimately contribute to demyelination and neurodegeneration. Therefore, B cells, CD8 T cells, and microglia/macrophages can also play an important role in the immunopathogenesis of multiple sclerosis apart from proinflammatory CD4 Th1/Th17 cell subsets. Furthermore, increasing evidence indicates that environmental risk factors, such as Vitamin D deficiency, Epstein-Barr virus, smoking, Western diet, and the commensal microbiota, influence the development of multiple sclerosis through interactions with genetic variants of multiple sclerosis, thus leading to the dysregulation of immune responses.

SUMMARY

A better understanding of immune-mediated mechanisms in the pathogenesis of multiple sclerosis and the contribution of environmental risk factors toward the development of multiple sclerosis will help further improve therapeutic approaches to prevent disease progression.

Transcription factor Nr4a1 couples sympathetic and inflammatory cues in CNS-recruited macrophages to limit neuroinflammation

The molecular mechanisms that link the sympathetic stress response and inflammation remain obscure. Here we found that the transcription factor Nr4a1 regulated the production of norepinephrine (NE) in macrophages and thereby limited experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Lack of Nr4a1 in myeloid cells led to enhanced NE production, accelerated infiltration of leukocytes into the central nervous system (CNS) and disease exacerbation in vivo. In contrast, myeloid-specific deletion of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, protected mice against EAE. Furthermore, we found that Nr4a1 repressed autocrine NE production in macrophages by recruiting the corepressor CoREST to the Th promoter. Our data reveal a new role for macrophages in neuroinflammation and identify Nr4a1 as a key regulator of catecholamine production by macrophages.

1, 25(OH)2D3 protects β cell against high glucose-induced apoptosis through mTOR suppressing

Diabetes mellitus is a leading cause of death and disability worldwide, which presents a serious public health crisis in China nowadays. It has been well recognized that excessive β-cell apoptosis is the key pathogenesis of diabetes, of which the mammalian target of rapamycin (mTOR) serves as the critical signaling pathway. Emerging evidence indicates that vitamin D deficiency acts as a potential risk factor for diabetes. The present study aims to test the hypothesis that 1 alpha, 25-dihydroxyvitamin D(3) [1, 25(OH)2D3] can inhibit β-cell apoptosis via the suppression of mTOR signaling pathway. β-cells (INS-1) were cultured in the context of normal glucose or high glucose media with or without 1, 25(OH)2D3 treatment. β-cell apoptosis was evaluated by inverted fluorescence microscope, flow cytometry and electron microscope, respectively. Quantitative RT-PCR and Western blotting were performed to assess the possible perturbations in mTOR signaling pathway. High glucose significantly increased β-cell apoptosis. Of importance, RT-PCR and Western blotting demonstrated that high glucose inhibited DNA-damage-inducible transcript 4 (DDIT4) and TSC1/TSC2, up-regulated Rheb/mTOR/p70S6K and enhanced expression of the apoptosis regulating proteins, such as phospho-Bcl-2, cytochrome C and cleaved caspase. Interestingly, 1, 25(OH)2D3 treatment reversed high glucose induced pathological changes in mTOR signaling pathway, restored expression of DDIT4 and TSC1/TSC2, blocked aberrant up-regulation of Rheb/mTOR/p70S6K and the apoptosis regulating proteins, and effectively inhibited β-cell apoptosis. Therefore, 1, 25(OH)2D3 treatment can effectively protects β cell against high glucose-induced apoptosis mainly via the suppression of mTOR signaling pathway, which may be considered as a potential therapy for patients with diabetes.

Nur77 deficiency leads to systemic inflammation in elderly mice

Background

Nur77, an orphan member of the nuclear receptor superfamily, has been implicated in the regulation of inflammation. However, the in vivo function of Nur77 remains largely unexplored. In the current study, we investigated the role of Nur77 in inflammation and immunity in mice.

Findings

We found that elderly 8-month-old Nur77-deficient mice (Nur77^−/−) developed systemic inflammation. Compared to wild-type (WT) mice (Nur77^+/+), Nur77^−/− mice showed splenomegaly, severe infiltration of inflammatory cells in several organs including liver, lung, spleen and kidney, increased hyperplasia of fibrous tissue in the lung and enlargement of kidney glomeruli. Additionally, Nur77^−/− mice had increased production of pro-inflammatory cytokines and immunoglobulin, and elicited pro-inflammatory M1-like polarization in macrophages as revealed by increased expression of CXCL11 and INDO, and decreased expression of MRC1.

Conclusions

These in vivo observations provide evidence for a pivotal role for Nur77 in the regulation of systemic inflammation and emphasize the pathogenic significance of Nur77 in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-015-0085-0) contains supplementary material, which is available to authorized users.

Optimizing multiple sclerosis diagnosis: gene expression and genomic association

OBJECTIVE

The diagnosis of multiple sclerosis (MS) at disease onset is sometimes masqueraded by other diagnostic options resembling MS clinically or radiologically (NonMS). In the present study we utilized findings of large-scale Genome-Wide Association Studies (GWAS) to develop a blood gene expression-based classification tool to assist in diagnosis during the first demyelinating event.

METHODS

We have merged knowledge of 110 MS susceptibility genes gained from MS GWAS studies together with our experimental results of differential blood gene expression profiling between 80 MS and 31 NonMS patients. Multiple classification algorithms were applied to this cohort to construct a diagnostic classifier that correctly distinguished between MS and NonMS patients. Accuracy of the classifier was tested on an additional independent group of 146 patients including 121 MS and 25 NonMS patients.

RESULTS

We have constructed a 42 gene-transcript expression-based MS diagnostic classifier. The overall accuracy of the classifier, as tested on an independent patient population consisting of diagnostically challenging cases including NonMS patients with positive MRI findings, achieved a correct classification rate of 76.0 ± 3.5%.

INTERPRETATION

The presented diagnostic classification tool complements the existing diagnostic McDonald criteria by assisting in the accurate exclusion of other neurological diseases at presentation of the first demyelinating event suggestive of MS.

Epstein-Barr virus genetic variants are associated with multiple sclerosis

OBJECTIVE

We analyzed the Epstein-Barr nuclear antigen 2 (EBNA2) gene, which contains the most variable region of the viral genome, in persons with multiple sclerosis (MS) and control subjects to verify whether virus genetic variants are involved in disease development.

METHODS

A seminested PCR approach and Sanger sequencing were used to analyze EBNA2 in 53 patients and 38 matched healthy donors (HDs). High-throughput sequencing by Illumina MiSeq was also applied in a subgroup of donors (17 patients and 17 HDs). Patients underwent gadolinium-enhanced MRI and human leucocyte antigen typing.

RESULTS

MS risk significantly correlated with an excess of 1.2 allele (odds ratio [OR] = 5.13; 95% confidence interval [CI] 1.84-14.32; p = 0.016) and underrepresentation of 1.3B allele (OR = 0.23; 95% CI 0.08-0.51; p = 0.0006). We identified new genetic variants, mostly 1.2 allele- and MS-associated (especially amino acid variation at position 245; OR = 9.4; 95% CI 1.19-78.72; p = 0.0123). In all cases, the consensus sequence from deep sequencing confirmed Sanger sequencing (including the cosegregation of newly identified variants with known EBNA2 alleles) and showed that the extent of genotype intraindividual variability was higher than expected: rare EBNA2 variants were detected in all HDs and patients with MS (range 1-17 and 3-19, respectively). EBNA2 variants did not seem to correlate with human leucocyte antigen typing or clinical/MRI features.

CONCLUSIONS

Our study unveils a strong association between Epstein-Barr virus genomic variants and MS, reinforcing the idea that Epstein-Barr virus contributes to disease development.

Effect of Alfacalcidol on multiple sclerosis-related fatigue: A randomized, double-blind placebo-controlled study

Context:

Fatigue is one of the most common and disabling symptoms of multiple sclerosis (MS); however, there is no medication that has been approved specifically to treat MS-related fatigue.

Objective:

We aimed to evaluate the effect of vitamin D analogue, Alfacalcidol, on MS-related fatigue.

Design, settings, participants:

This was a randomized, double-blind, parallel group, placebo-controlled trial in patients with clinically definite MS by McDonald criteria conducted in a single university-affiliated medical center in Israel. Randomly selected patients from the Sheba MS Registry computerized database ( N=600) were assessed using the self-report Fatigue Severity Scale (FSS). Patients with clinically meaningful fatigue ( N=259) were further assessed for trial eligibility, and MS patients with significant fatigue ( N=158; 61%, 118 females, mean age 41.1 ± 9.2 years and mean disease duration of 6.2 ± 5.5 years) were included in the study and randomized to receive treatment or placebo.

Intervention:

Alfacalcidol (1 mcg/d, N=80) or placebo ( N=78) was administered for six consecutive months.

Main outcome measure:

The primary endpoint of the study was the change between Alfacalcidol and placebo-treated patients in the Fatigue Impact Scale (FIS) score; the cut-off point for improvement was defined as 30% decrease. All analyses followed the intention-to-treat principle and were performed for all participants based on the group they were randomly allocated regardless of whether or not they dropped out.

Results:

Alfacalcidol decreased the mean relative FIS score as compared with placebo (–41.6% vs. –27.4%, p=0.007, respectively). This advantage was further emphasized when the modified FIS (MFIS) relative change was calculated. Quality of Life (QoL) improved in Alfacalcidol-treated patients as compared with placebo in the RAYS psychological ( p=0.033) and social ( p=0.043) sub-scales. The Alfacalcidol-treated group had reduced number of relapses ( p=0.006) and higher proportion of relapse-free patients ( p=0.007). Reduction of relapses by Alfacalcidol became significant at 4 months of treatment, was sustained at 6 months and decayed 2 months after drug discontinuation. Alfacalcidol treatment was safe and no serious adverse events were recorded.

Conclusion:

Alfacalcidol is a safe and effective treatment strategy to decrease fatigue and improve QoL in patients with MS.