Characterization of Multiple Sclerosis candidate gene expression kinetics in rat experimental autoimmune encephalomyelitis

Overview of the role and action mechanism of microRNA-128 in viral infections

Recently in vivo and in vitro studies have provided evidence establishing the significance of microRNAs (miRNAs) in both physiological and pathological conditions. In this regard, the role of miRNA-128 (miR-128) in health and diseases has been found, and its critical regulatory role in the context of some viral diseases has been recently identified. For instance, it has been found that miR-128 can serve as an antiviral mediator and significantly limit the replication and dissemination of human immunodeficiency virus type 1 (HIV-1). Besides, it has been noted that poliovirus receptor-related 4 (PVRL4) is post-transcriptionally regulated by miR-128, representing possible miRNA targets that can modulate measles virus infection. Of note, the downregulation of seminal exosomes eca-miR-128 is associated with the long-term persistence of Equine arteritis virus (EAV) in the reproductive tract, and this particular miRNA is a putative regulator of chemokine ligand 16 (C-X-C motif) as determined by target prediction analysis. In this review, the latest information on the role and action mechanism of miR-128 in viral infections will be summarized and discussed in detail.

Effect of Vitamin D on Experimental Autoimmune Neuroinflammation Is Dependent on Haplotypes Comprising Naturally Occurring Allelic Variants of CIITA (Mhc2ta)

An increasing body of evidence associates low vitamin D levels with increased risk of multiple sclerosis (MS), suggesting the possibility of a gene-environment interaction for this environmental factor in MS pathogenesis. Moreover, it has been shown that vitamin D downregulates major histocompatibility complex (MHC) class II expression in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. We here report about the impact of a dietary vitamin D supplementation on EAE in the rat strains having functionally relevant allelic variations in the CIITA (Mhc2ta) gene, a master regulator of MHC class II expression. Full length myelin oligodendrocyte glycoprotein (MOG)-EAE was induced in DA.PVG^av1-Vra4 congenic rats harboring the Vra4 locus from PVG strain in the EAE- susceptible DA background, and compared to the parental strains. The congenic rats fed with either vitamin D supplemented, deprived or regular diet developed an intermediate clinical EAE phenotype, in contrast to DA and PVG strains. Immunopathological studies revealed vitamin D dose-dependent effect on demyelination and inflammatory infiltration of the central nervous system (CNS), expression of MHC class II and CIITA, as well as downregulation of a range of pro-inflammatory genes. Taken together, our findings demonstrate an impact of vitamin D on the target tissue pathology and peripheral immune response during EAE in DA.PVG^av1-Vra4 congenic strain. Thereby, our data provide evidence of a modulatory effect of vitamin D in context of genetic variances in the Vra4 locus/Mhc2ta gene in MS-like neuroinflammation, with potential relevance for the human demyelinating disease.

Featured Article: Modulation of the OGF-OGFr pathway alters cytokine profiles in experimental autoimmune encephalomyelitis and multiple sclerosis

The endogenous neuropeptide opioid growth factor, chemically termed [Met⁵]-enkephalin, has growth inhibitory and immunomodulatory properties. Opioid growth factor is distributed widely throughout most tissues, is autocrine and paracrine produced, and interacts at the nuclear-associated receptor, OGFr. Serum levels of opioid growth factor are decreased in patients with multiple sclerosis and in animals with experimental autoimmune encephalomyelitis suggesting that the OGF-OGFr pathway becomes dysregulated in this disease. This study begins to assess other cytokines that are altered following opioid growth factor or low-dose naltrexone modulation of the OGF-OGFr axis in mice with experimental autoimmune encephalomyelitis using serum samples collected in mice treated for 10 or 20 days and assayed by a multiplex cytokine assay for inflammatory markers. Cytokines of interest were validated in mice at six days following immunization for experimental autoimmune encephalomyelitis. In addition, selected cytokines were validated with serum from MS patients treated with low-dose naltrexone alone or low-dose naltrexone in combination with glatiramer acetate (Copaxone®). Experimental autoimmune encephalomyelitis mice had elevated levels of 7 of 10 cytokines. Treatment with opioid growth factor or low-dose naltrexone resulted in elevated expression levels of the IL-6 cytokine, and significantly reduced IL-10 values, relative to saline-treated experimental autoimmune encephalomyelitis mice. TNF-γ values were increased in experimental autoimmune encephalomyelitis mice relative to normal, but were not altered by opioid growth factor or low-dose naltrexone. IFN-γ levels were reduced in opioid growth factor- or low-dose naltrexone-treated experimental autoimmune encephalomyelitis mice relative to saline-treated mice at 10 days, and elevated relative to normal values at 20 days. Validation studies revealed that within six days of immunization, opioid growth factor or low-dose naltrexone modulated IL-6 and IL-10 cytokine expression. Validation in human serum revealed markedly reduced IL-6 cytokine levels in MS patients taking low-dose naltrexone relative to standard care. In summary, modulation of the OGF-OGFr pathway regulates some inflammatory cytokines, and together with opioid growth factor serum levels, may begin to form a panel of valid biomarkers to monitor progression of multiple sclerosis and response to therapy. Impact statement Modulation of the opioid growth factor (OGF)-OGF receptor (OGFr) alters inflammatory cytokine expression in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). Multiplex cytokine assays demonstrated that mice with chronic EAE and treated with either OGF or low-dose naltrexone (LDN) had decreased expression of interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and the anti-inflammatory cytokine IL-10 within 10 days or treatment, as well as increased serum expression of the pro-inflammatory cytokine IL-6, relative to immunized mice receiving saline. Multiplex data were validated using ELISA kits and serum from MS patients treated with LDN and revealed decreased in IL-6 levels in patients taking LDN relative to standard care alone. These data, along with serum levels of OGF, begin to formulate a selective biomarker profile for MS that is easily measured and effective at monitoring disease progression and response to therapy.

Functional genomics analysis of vitamin D effects on CD4+ T cells in vivo in experimental autoimmune encephalomyelitis ‬

Vitamin D exerts multiple immunomodulatory functions and has been implicated in the etiology and treatment of several autoimmune diseases, including multiple sclerosis (MS). We have previously reported that in juvenile/adolescent rats, vitamin D supplementation protects from experimental autoimmune encephalomyelitis (EAE), a model of MS. Here we demonstrate that this protective effect associates with decreased proliferation of CD4+ T cells and lower frequency of pathogenic T helper (Th) 17 cells. Using transcriptome, methylome, and pathway analyses in CD4+ T cells, we show that vitamin D affects multiple signaling and metabolic pathways critical for T-cell activation and differentiation into Th1 and Th17 subsets in vivo. Namely, Jak/Stat, Erk/Mapk, and Pi3K/Akt/mTor signaling pathway genes were down-regulated upon vitamin D supplementation. The protective effect associated with epigenetic mechanisms, such as (i) changed levels of enzymes involved in establishment and maintenance of epigenetic marks, i.e., DNA methylation and histone modifications; (ii) genome-wide reduction of DNA methylation, and (iii) up-regulation of noncoding RNAs, including microRNAs, with concomitant down-regulation of their protein-coding target RNAs involved in T-cell activation and differentiation. We further demonstrate that treatment of myelin-specific T cells with vitamin D reduces frequency of Th1 and Th17 cells, down-regulates genes in key signaling pathways and epigenetic machinery, and impairs their ability to transfer EAE. Finally, orthologs of nearly 50% of candidate MS risk genes and 40% of signature genes of myelin-reactive T cells in MS changed their expression in vivo in EAE upon supplementation, supporting the hypothesis that vitamin D may modulate risk for developing MS.

Next-generation sequencing identifies microRNAs that associate with pathogenic autoimmune neuroinflammation in rats

MicroRNAs (miRNAs) are known to regulate most biological processes and have been found dysregulated in a variety of diseases, including multiple sclerosis (MS). In this study, we characterized miRNAs that associate with susceptibility to develop experimental autoimmune encephalomyelitis (EAE) in rats, a well-established animal model of MS. Using Illumina next-generation sequencing, we detected 544 miRNAs in the lymph nodes of EAE-susceptible Dark Agouti and EAE-resistant Piebald Virol Glaxo rats during immune activation. Forty-three miRNAs were found differentially expressed between the two strains, with 81% (35 out of 43) showing higher expression in the susceptible strain. Only 33% of tested miRNAs displayed differential expression in naive lymph nodes, suggesting that a majority of regulated miRNAs are EAE dependent. Further investigation of a selected six miRNAs indicates differences in cellular source and kinetics of expression. Several of the miRNAs, including miR-146a, miR-21, miR-181a, miR-223, and let-7, have previously been implicated in immune system regulation. Moreover, 77% (33 out of 43) of the miRNAs were associated with MS and other autoimmune diseases. Target genes likely regulated by the miRNAs were identified using computational predictions combined with whole-genome expression data. Differentially expressed miRNAs and their targets involve functions important for MS and EAE, such as immune cell migration through targeting genes like Cxcr3 and cellular maintenance and signaling by regulation of Prkcd and Stat1. In addition, we demonstrated that these three genes are direct targets of miR-181a. Our study highlights the impact of multiple miRNAs, displaying diverse kinetics and cellular sources, on development of pathogenic autoimmune inflammation.

Interleukin-22 protects rat PC12 pheochromocytoma cells from serum deprivation-induced cell death

Interleukin-22 (IL-22), an IL-10 family cytokine, mediates the crosstalk between leukocytes and epithelial cells. Previous studies reported that IL-22 expresses in mouse brain, and the rat PC12 cells are responsive to IL-22 stimulation. However, the biological roles of IL-22 in neuronal cells remain largely unknown. We show here that IL-22 activates Stat3, p38 mitogen-activated protein kinases (MAPK), and Akt pathways and inhibits Erk/MAPK pathway in naïve PC12 cells. We further demonstrate that IL-22 protects naïve PC12 cells from serum starvation-induced cell death via the Jak1/Stat3 and Akt pathways. We also show that IL-22 has no effects on naïve PC12 cell proliferation and cannot protect naïve PC12 cells from 1-methyl-4-phenylpyridinium (MPP(+))-induced cytotoxicity. However, IL-22 exerts a dose-dependent protective effect on MPP(+)-induced neurodegeneration in nerve growth factor-differentiated PC12 cells. Overall, our data suggest that IL-22 might play a role in neurological processes. To our knowledge, this is the first report showing that IL-22 confers a neuroprotective function, which may provide a new therapeutic option for treatment of neurodegenerative diseases.

Gene expression in the spinal cord in female lewis rats with experimental autoimmune encephalomyelitis induced with myelin basic protein

Background

Experimental autoimmune encephalomyelitis (EAE), the best available model of multiple sclerosis, can be induced in different animal strains using immunization with central nervous system antigens. EAE is associated with inflammation and demyelination of the nervous system. Micro-array can be used to investigate gene expression and biological pathways that are altered during disease. There are few studies of the changes in gene expression in EAE, and these have mostly been done in a chronic mouse EAE model. EAE induced in the Lewis with myelin basic protein (MBP-EAE) is well characterised, making it an ideal candidate for the analysis of gene expression in this disease model.

Methodology/Principal Findings

MBP-EAE was induced in female Lewis rats by inoculation with MBP and adjuvants. Total RNA was extracted from the spinal cords and used for micro-array analysis using AffimetrixGeneChip Rat Exon 1.0 ST Arrays. Gene expression in the spinal cords was compared between healthy female rats and female rats with MBP-EAE. Gene expression in the spinal cord of rats with MBP-EAE differed from that in the spinal cord of normal rats, and there was regulation of pathways involved with immune function and nervous system function. For selected genes the change in expression was confirmed with real-time PCR.

Conclusions/Significance

EAE leads to modulation of gene expression in the spinal cord. We have identified the genes that are most significantly regulated in MBP-EAE in the Lewis rat and produced a profile of gene expression in the spinal cord at the peak of disease.

Expression of Ccl11 associates with immune response modulation and protection against neuroinflammation in rats

Multiple sclerosis (MS) is a polygenic disease characterized by inflammation and demyelination in the central nervous system (CNS), which can be modeled in experimental autoimmune encephalomyelitis (EAE). The Eae18b locus on rat chromosome 10 has previously been linked to regulation of beta-chemokine expression and severity of EAE. Moreover, the homologous chemokine cluster in humans showed evidence of association with susceptibility to MS. We here established a congenic rat strain with Eae18b locus containing a chemokine cluster (Ccl2, Ccl7, Ccl11, Ccl12 and Ccl1) from the EAE- resistant PVG rat strain on the susceptible DA background and utilized myelin oligodendrocyte glycoprotein (MOG)-induced EAE to characterize the mechanisms underlying the genetic regulation. Congenic rats developed a milder disease compared to the susceptible DA strain, and this was reflected in decreased demyelination and in reduced recruitment of inflammatory cells to the brain. The congenic strain also showed significantly increased Ccl11 mRNA expression in draining lymph nodes and spinal cord after EAE induction. In the lymph nodes, macrophages were the main producers of CCL11, whereas macrophages and lymphocytes expressed the main CCL11 receptor, namely CCR3. Accordingly, the congenic strain also showed significantly increased Ccr3 mRNA expression in lymph nodes. In the CNS, the main producers of CCL11 were neurons, whereas CCR3 was detected on neurons and CSF producing ependymal cells. This corresponded to increased levels of CCL11 protein in the cerebrospinal fluid of the congenic rats. Increased intrathecal production of CCL11 in congenic rats was accompanied by a tighter blood brain barrier, reflected by more occludin⁺ blood vessels. In addition, the congenic strain showed a reduced antigen specific response and a predominant anti-inflammatory Th2 phenotype. These results indicate novel mechanisms in the genetic regulation of neuroinflammation.

Interleukin 18 Receptor 1 expression distinguishes patients with multiple sclerosis

Definition of dysregulated immune components in multiple sclerosis may help in the identification of new therapeutic targets. Deviation of the interleukin 18 receptor 1 (IL18R1) is of particular interest since the receptor is critical for experimental neuroinflammation. The objective of this study was to determine whether expression of IL18R1 varies between multiple sclerosis patients and controls, and to test genetic association of IL18R1 with multiple sclerosis. We used quantitative real-time PCR to assess mRNA levels of IL18R1 in cerebrospinal fluid and peripheral blood mononuclear cells of 191 patients with multiple sclerosis, 61 patients with clinically isolated syndrome and 168 controls having other neurological disorders. Association was tested in 2153 patients with multiple sclerosis and 1733 controls using 13 tagging single nucleotide polymorphisms within the IL18R1 gene. We found that patients with multiple sclerosis had increased IL18R1 mRNA expression in both cerebrospinal fluid cells ( p < 0.05) and peripheral blood mononuclear cells ( p < 0.05) compared with controls. Patients with clinically isolated syndrome had elevated levels compared with controls in cerebrospinal fluid cells ( p < 0.001) but not in peripheral blood mononuclear cells. The gene was not associated to multiple sclerosis. We conclude that the increased expression of IL18R1 may contribute pathogenically to disease and is therefore a potential therapeutic target. The absence of a genetic association in the IL18R1 gene itself suggests regulation from other parts of the genome, or as part of the inflammatory cascade in multiple sclerosis without a prime genetic cause.

Interleukin 18 in the CNS

Interleukin (IL)-18 is a cytokine isolated as an important modulator of immune responses and subsequently shown to be pleiotropic. IL-18 and its receptors are expressed in the central nervous system (CNS) where they participate in neuroinflammatory/neurodegenerative processes but also influence homeostasis and behavior. Work on IL-18 null mice, the localization of the IL-18 receptor complex in neurons and the neuronal expression of decoy isoforms of the receptor subunits are beginning to reveal the complexity and the significance of the IL-18 system in the CNS. This review summarizes current knowledge on the central role of IL-18 in health and disease.

Alternative splicing and transcriptome profiling of experimental autoimmune encephalomyelitis using genome-wide exon arrays

Background

Multiple Sclerosis (MS) is a chronic inflammatory disease causing demyelination and nerve loss in the central nervous system. Experimental autoimmune encephalomyelitis (EAE) is an animal model of MS that is widely used to investigate complex pathogenic mechanisms. Transcriptional control through isoform selection and mRNA levels determines pathway activation and ultimately susceptibility to disease.

Methodology/Principal Findings

We have studied the role of alternative splicing and differential expression in lymph node cells from EAE-susceptible Dark Agouti (DA) and EAE-resistant Piebald Virol Glaxo.AV1 (PVG) inbred rat strains using Affymetrix Gene Chip Rat Exon 1.0 ST Arrays. Comparing the two strains, we identified 11 differentially spliced and 206 differentially expressed genes at day 7 post-immunization, as well as 9 differentially spliced and 144 differentially expressed genes upon autoantigen re-stimulation. Functional clustering and pathway analysis implicate genes for glycosylation, lymphocyte activation, potassium channel activity and cellular differentiation in EAE susceptibility.

Conclusions/Significance

Our results demonstrate that alternative splicing occurs during complex disease and may govern EAE susceptibility. Additionally, transcriptome analysis not only identified previously defined EAE pathways regulating the immune system, but also novel mechanisms. Furthermore, several identified genes overlap known quantitative trait loci, providing novel causative candidate targets governing EAE.