Exome sequencing in multiple sclerosis families identifies 12 candidate genes and nominates biological pathways for the genesis of disease.

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system characterized by myelin loss and neuronal dysfunction. Although the majority of patients do not present familial aggregation, Mendelian forms have been described. We performed whole-exome sequencing analysis in 132 patients from 34 multi-incident families, which nominated likely pathogenic variants for MS in 12 genes of the innate immune system that regulate the transcription and activation of inflammatory mediators. Rare missense or nonsense variants were identified in genes of the fibrinolysis and complement pathways (PLAU, MASP1, C2), inflammasome assembly (NLRP12), Wnt signaling (UBR2, CTNNA3, NFATC2, RNF213), nuclear receptor complexes (NCOA3), and cation channels and exchangers (KCNG4, SLC24A6, SLC8B1). These genes suggest a disruption of interconnected immunological and pro-inflammatory pathways as the initial event in the pathophysiology of familial MS, and provide the molecular and biological rationale for the chronic inflammation, demyelination and neurodegeneration observed in MS patients.

Genetic analysis of nucleotide-binding leucine-rich repeat (NLR) receptors in multiple sclerosis.

Genetic and functional analyses of the inflammasome suggest a role for this multiprotein complex in the biological mechanisms leading to the onset and progression of multiple sclerosis (MS). Nucleotide-binding, leucine-rich repeat (NLR) receptors trigger the activation and assembly of specific inflammasomes in response to danger signals. Mining exome sequencing data from 326 MS patients identified 17 rare missense or nonsense variants in NLR family pyrin domain containing 1 (NLRP1), NLRP3, NLRP6, NLRP7 and NLR family CARD domain containing 4 (NLRC4). Genotyping these variants in 2503 MS cases and 1076 healthy controls did not result in statistically significant differences between groups, and segregation analysis within MS families was largely unsupportive of co-segregation of these variants with disease. However, the identification of MS patients harboring rare homozygote variants in NLRP1 (p.Ile601Phe and p.Ser1387Ile), a variant in NLRP3 (p.Leu832Ile) resulting in the substitution of a critical amino acid for the formation of its leucine-rich repeat domain, and several MS patients with NLRC4 variants (p.Arg310Ter and p.Glu600Ter) causing protein truncations suggest that rare protein-altering variants in inflammasome-activating NLR receptors may contribute to MS risk.

Expression of the neuroprotective protein aryl hydrocarbon receptor nuclear translocator 2 correlates with neuronal stress and disability in models of multiple sclerosis.

BACKGROUND: Axonal degeneration and neuronal loss have been described as the major causes of irreversible clinical disability in multiple sclerosis (MS). The aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) protein has been associated with neuroprotection in models of ischemia and neuronal responses to stressors. METHODS: To characterize its potential to influence inflammatory neurodegeneration, we examined ARNT2 expression in the experimental autoimmune encephalomyelitis (EAE) model of MS and characterized mediators that influence ARNT2 expression as well as plausible partners and targets. RESULTS: Arnt2 message and protein levels dropped significantly in EAE spinal cords as disease developed and were lowest at peak disability. ARNT2 expression is prominent in neuronal cell bodies within the gray matter with some staining in glial fibrillary acidic protein (GFAP)+ astrocytes in healthy animals. At peak disease, ARNT2 expression is reduced by 20-50% in gray matter neurons compared to healthy controls. ARNT2 intensity in neurons throughout the EAE spinal cord correlated inversely with the degree of immune cell infiltration (r = - 0.5085, p < 0.01) and axonal damage identified with SMI32 staining (r = - 0.376, p = 0.032). To understand the relationship between ARNT2 expression and neuronal health, we exposed enriched cortical cultures of neurons to hydrogen peroxide (H2O2) to mimic oxidative stress. H2O2 at lower doses rapidly increased ARNT2 protein levels which returned to baseline within 3-4 h. Exposure to higher doses of H2O2) dropped ARNT2 levels below baseline, preceding cytotoxicity measured by morphological changes and lactate dehydrogenase release from cells. Decreases in ARNT2 secondary to staurosporine and H2O2 preceded increases in cleaved caspase 3 and associated apoptosis. We also examined expression of neuronal pas 4 (Npas4), whose heterodimerization with ARNT2 drives expression of the neurotrophic factor brain-derived neurotrophic factor (Bdnf). Like ARNT2, Npas4 levels also decline at the onset of EAE and are linked to decreases in Bdnf. In vitro, H2O2 exposure drives Npas4 expression that is tied to increases in Bdnf. CONCLUSION: Our data support ARNT2 as a neuronal transcription factor whose sustained expression is linked to neuronal and axonal health, protection that may primarily be driven through its partnering with Npas4 to influence BDNF expression.

Modulating inflammation and neuroprotection in multiple sclerosis.

Multiple sclerosis (MS) is a neurological disorder of the central nervous system with a presentation and disease course that is largely unpredictable. MS can cause loss of balance, impaired vision or speech, weakness and paralysis, fatigue, depression, and cognitive impairment. Immunomodulation is a major target given the appearance of focal demyelinating lesions in myelin-rich white matter, yet progression and an increasing appreciation for gray matter involvement, even during the earliest phases of the disease, highlights the need to afford neuroprotection and limit neurodegenerative processes that correlate with disability. This review summarizes key aspects of MS pathophysiology and histopathology with a focus on neuroimmune interactions in MS, which may facilitate neurodegeneration through both direct and indirect mechanisms. There is a focus on processes thought to influence disease progression and the role of oxidative stress and mitochondrial dysfunction in MS. The goals and efficacy of current disease-modifying therapies and those in the pipeline are discussed, highlighting recent advances in our understanding of pathways mediating disease progression to identify and translate both immunomodulatory and neuroprotective therapeutics from the bench to the clinic.

Oral administration of the nitroxide radical TEMPOL exhibits immunomodulatory and therapeutic properties in multiple sclerosis models.

Therapies with both immunomodulatory and neuroprotective properties are thought to have the greatest promise in reducing the severity and progression of multiple sclerosis (MS). Several reactive oxygen (ROS) and reactive nitrogen species (RNS) are implicated in inflammatory-mediated damage to the central nervous system (CNS) in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a stable nitroxide radical with potent antioxidant activity. The goal of our studies was to investigate the immunomodulatory effects and therapeutic potential of orally-delivered TEMPOL in the mouse EAE model. Mice receiving TEMPOL chow ad libitum for 2weeks prior to induction of active EAE showed delayed onset and reduced incidence of disease compared to control-fed animals. Reduced disease severity was associated with limited microglial activation and fewer inflammatory infiltrates. TEMPOL's effects were immunomodulatory, not immunosuppressive: T cells produced less interferon-γ and tumor necrosis factor-α, and TEMPOL-fed mice exhibited a shift towards TH2-type antibody responses. Both myeloid and myeloid-dendritic cells of TEMPOL-fed EAE animals had significantly lower levels of MHC class II expression than controls; CD40 was also significantly reduced. TEMPOL administration was associated with an enrichment of CD8+ T cell populations and CD4+FoxP3+ regulatory populations. TEMPOL reduced the severity of clinical disease when administered after the induction of disease, and also after the onset of clinical symptoms. To exclude effects on T cell priming in vivo, TEMPOL was tested with the passive transfer of encephalitogenic T cells and was found to reduce the incidence and peak severity of disease. Protection was associated with reduced infiltrates and a relative sparing of neurofilaments and axons. The ability of oral TEMPOL to reduce inflammation and axonal damage and loss demonstrate both anti-inflammatory and protective properties, with significant promise for the treatment of MS and related neurological disorders.

SPARC expression by cerebral microvascular endothelial cells in vitro and its influence on blood-brain barrier properties.

BACKGROUND: SPARC (secreted protein acidic and rich in cysteine) is a nonstructural, cell-matrix modulating protein involved in angiogenesis and endothelial barrier function, yet its potential role in cerebrovascular development, inflammation, and repair in the central nervous system (CNS) remains undetermined. METHODS: This study examines SPARC expression in cultured human cerebral microvascular endothelial cells (hCMEC/D3)-an in vitro model of the blood-brain barrier (BBB)-as they transition between proliferative and barrier phenotypes and encounter pro-inflammatory stimuli. SPARC protein levels were quantified by Western blotting and immunocytochemistry and messenger RNA (mRNA) by RT-PCR. RESULTS: Constitutive SPARC expression by proliferating hCMEC/D3s is reduced as cells mature and establish a confluent monolayer. SPARC expression positively correlated with the proliferation marker Ki-67 suggesting a role for SPARC in cerebrovascular development. The pro-inflammatory molecules tumor necrosis factor-α (TNF-α) and endotoxin lipopolysaccharide (LPS) increased SPARC expression in cerebral endothelia. Interferon gamma (IFN-γ) abrogated SPARC induction observed with TNF-α alone. Barrier function assays show recombinant human (rh)-SPARC increased paracellular permeability and decreased transendothelial electrical resistance (TEER). This was paralleled by reduced zonula occludens-1 (ZO-1) and occludin expression in hCMEC/D3s exposed to rh-SPARC (1-10 µg/ml) compared with cells in media containing a physiological dose of SPARC. CONCLUSIONS: Together, these findings define a role for SPARC in influencing cerebral microvascular properties and function during development and inflammation at the BBB such that it may mediate processes of CNS inflammation and repair.

Myelin basic protein-specific TCR/HLA-DRB5*01:01 transgenic mice support the etiologic role of DRB5*01:01 in multiple sclerosis.

Genetic susceptibility to multiple sclerosis (MS) has been linked to the HLA-DR15 haplotype consisting of DRB1*15:01(DR2b) and DRB5*01:01(DR2a) alleles. Given almost complete linkage disequilibrium of the two alleles, recent studies suggested differential roles in susceptibility (DR2b) or protection from MS (DR2a). Our objective was to assess the potential contribution of DR2a to disease etiology in MS using a humanized model of autoimmunity. To assess the potential contribution of DR2a to disease etiology, we created DR2a humanized transgenic (Tg) mice and subsequently crossed them to Tg mice expressing TL3A6, an MS patient-derived myelin basic protein 83-99-specific TCR. In TL3A6/DR2a Tg mice, CD4 Tg T cells escape thymic and peripheral deletion and initiate spontaneous experimental autoimmune encephalomyelitis (EAE) at low rates, depending on the level of DR2a expression. The ability to induce active EAE was also increased in animals expressing higher levels of DR2a. Inflammatory infiltrates and neuronal damage were present throughout the spinal cord, consistent with a classical ascending EAE phenotype with minor involvement of the cerebellum, brainstem, and peripheral nerve roots in spontaneous, as well as actively induced, disease. These studies emphasize the pathologic contribution of the DR2a allele to the development of autoimmunity when expressed as the sole MHC class II molecule, as well as strongly argue for DR2a as a contributor to the CNS autoimmunity in MS.

Identification of endothelin 2 as an inflammatory factor that promotes central nervous system remyelination.

The development of new regenerative therapies for multiple sclerosis is hindered by the lack of potential targets for enhancing remyelination. The study of naturally regenerative processes such as the innate immune response represents a powerful approach for target discovery to solve this problem. By 'mining' these processes using transcriptional profiling we can identify candidate factors that can then be tested individually in clinically-relevant models of demyelination and remyelination. Here, therefore, we have examined a previously described in vivo model of the innate immune response in which zymosan-induced macrophage activation in the retina promotes myelin sheath formation by oligodendrocytes generated from transplanted precursor cells. While this model is not itself clinically relevant, it does provide a logical starting point for this study as factors that promote myelination must be present. Microarray analysis of zymosan-treated retinae identified several cytokines (CXCL13, endothelin 2, CCL20 and CXCL2) to be significantly upregulated. When tested in a cerebellar slice culture model, CXCL13 and endothelin 2 promoted myelination and endothelin 2 also promoted remyelination. In studies to identify the receptor responsible for this regenerative effect of endothelin 2, analysis of both remyelination following experimental demyelination and of different stages of multiple sclerosis lesions in human post-mortem tissue revealed high levels of endothelin receptor type B in oligodendrocyte lineage cells. Confirming a role for this receptor in remyelination, small molecule agonists and antagonists of endothelin receptor type B administered in slice cultures promoted and inhibited remyelination, respectively. Antagonists of endothelin receptor type B also inhibited remyelination of experimentally-generated demyelination in vivo. Our work therefore identifies endothelin 2 and the endothelin receptor type B as a regenerative pathway and suggests that endothelin receptor type B agonists represent a promising therapeutic approach to promote myelin regeneration.

A rapid review of differences in cerebrospinal neurofilament light levels in clinical subtypes of progressive multiple sclerosis.

Background: Multiple sclerosis (MS) is divided into three clinical phenotypes: relapsing-remitting MS (RRMS), secondary progressive MS (SPMS), and primary progressive MS (PPMS). It is unknown to what extent SPMS and PPMS pathophysiology share inflammatory or neurodegenerative pathological processes. Cerebrospinal (CSF) neurofilament light (NfL) has been broadly studied in different MS phenotypes and is a candidate biomarker for comparing MS subtypes. Research question: Are CSF NfL levels different among clinical subtypes of progressive MS? Methods: A search strategy identifying original research investigating fluid neurodegenerative biomarkers in progressive forms of MS between 2010 and 2022 was applied to Medline. Identified articles underwent title and abstract screen and full text review against pre-specified criteria. Data abstraction was limited to studies that measured NfL levels in the CSF. Reported statistical comparisons of NfL levels between clinical phenotypes were abstracted qualitatively. Results: 18 studies that focused on investigating direct comparisons of CSF NfL from people with MS were included in the final report. We found NfL levels were typically reported to be higher in relapsing and progressive MS compared to healthy controls. Notably, higher NfL levels were not clearly associated with progressive MS subtypes when compared to relapsing MS, and there was no observed difference in NfL levels between PPMS and SPMS in articles that separately assessed these phenotypes. Conclusion: CSF NfL levels distinguish individuals with MS from healthy controls but do not differentiate MS subtypes. Broad biological phenotyping is needed to overcome limitations of current clinical phenotyping and improve biomarker translatability to decision-making in the clinic.

Dolutegravir-containing HIV therapy reversibly alters mitochondrial health and morphology in cultured human fibroblasts and peripheral blood mononuclear cells.

OBJECTIVES: Given the success of combination antiretroviral therapy (cART) in treating HIV viremia, drug toxicity remains an area of interest in HIV research. Despite newer integrase strand transfer inhibitors (InSTIs), such as dolutegravir (DTG) and raltegravir (RAL), having excellent clinical tolerance, there is emerging evidence of off-target effects and toxicities. Although limited in number, recent reports have highlighted the vulnerability of mitochondria to these toxicities. The aim of the present study is to quantify changes in cellular and mitochondrial health following exposure to current cART regimens at pharmacological concentrations. A secondary objective is to determine whether any cART-associated toxicities would be modulated by human telomerase reverse transcriptase (hTERT). METHODS: We longitudinally evaluated markers of cellular (cell count, apoptosis), and mitochondrial health [mitochondrial reactive oxygen species (mtROS), membrane potential (MMP) and mass (mtMass)] by flow cytometry in WI-38 human fibroblast with differing hTERT expression/localization and peripheral blood mononuclear cells. This was done after 9 days of exposure to, and 6 days following the removal of, seven current cART regimens, including three that contained DTG. Mitochondrial morphology was assessed by florescence microscopy and quantified using a recently developed deep learning-based pipeline. RESULTS: Exposure to DTG-containing regimens increased apoptosis, mtROS, mtMass, induced fragmented mitochondrial networks compared with non-DTG-containing regimens, including a RAL-based combination. These effects were unmodulated by telomerase expression. All effects were fully reversible following removal of drug pressure. CONCLUSION: Taken together, our observations indicate that DTG-containing regimens negatively impact cellular and mitochondrial health and may be more toxic to mitochondria, even among the generally well tolerated InSTI-based cART.

Serum neurofilament light chain correlates with myelin and axonal magnetic resonance imaging markers in multiple sclerosis.

BACKGROUND: Neurofilaments are cytoskeletal proteins that are detectable in the blood after neuroaxonal injury. Multiple sclerosis (MS) disease progression, greater lesion volume, and brain atrophy are associated with higher levels of serum neurofilament light chain (NfL), but few studies have examined the relationship between NfL and advanced magnetic resonance imaging (MRI) measures related to myelin and axons. We assessed the relationship between serum NfL and brain MRI measures in a diverse group of MS participants. METHODS AND MATERIALS: 103 participants (20 clinically isolated syndrome, 33 relapsing-remitting, 30 secondary progressive, 20 primary progressive) underwent 3T MRI to obtain myelin water fraction (MWF), geometric mean T2 (GMT2), water content, T1; high angular resolution diffusion imaging (HARDI)-derived axial diffusivity (AD), radial diffusivity (RD), fractional anisotropy (FA); diffusion basis spectrum imaging (DBSI)-derived AD, RD, FA; restricted, hindered, water and fiber fractions; and volume measurements of normalized brain, lesion, thalamic, deep gray matter (GM), and cortical thickness. Multiple linear regressions assessed the strength of association between serum NfL (dependent variable) and each MRI measure in whole brain (WB), normal appearing white matter (NAWM) and T2 lesions (independent variables), while controlling for age, expanded disability status scale, and disease duration. RESULTS: Serum NfL levels were significantly associated with metrics of axonal damage (FA: R2WB-HARDI = 0.29, R2NAWM-HARDI = 0.31, R2NAWM-DBSI = 0.30, R2Lesion-DBSI = 0.31; AD: R2WB-HARDI=0.31), myelin damage (MWF: R2WB = 0.29, R2NAWM = 0.30, RD: R2WB-HARDI = 0.32, R2NAWM-HARDI = 0.34, R2Lesion-DBSI = 0.30), edema and inflammation (T1: R2Lesion = 0.32; GMT2: R2WB = 0.31, R2Lesion = 0.31), and cellularity (restricted fraction R2WB = 0.30, R2NAWM = 0.32) across the entire MS cohort. Higher serum NfL levels were associated with significantly higher T2 lesion volume (R2 = 0.35), lower brain structure volumes (thalamus R2 = 0.31; deep GM R2 = 0.33; normalized brain R2 = 0.31), and smaller cortical thickness R2 = 0.31). CONCLUSION: The association between NfL and myelin MRI markers suggest that elevated serum NfL is a useful biomarker that reflects not only acute axonal damage, but also damage to myelin and inflammation, likely due to the known synergistic myelin-axon coupling relationship.

From the prodromal stage of multiple sclerosis to disease prevention.

A prodrome is an early set of signs or symptoms that indicate the onset of a disease before more typical symptoms develop. Prodromal stages are well recognized in some neurological and immune-mediated diseases such as Parkinson disease, schizophrenia, type 1 diabetes mellitus and rheumatoid arthritis. Emerging evidence indicates that a prodromal stage exists in multiple sclerosis (MS), raising the possibility of intervention at this stage to delay or prevent the development of classical MS. However, much remains unclear about the prodromal stage of MS and considerable research is needed to fully characterize the prodrome and develop standardized criteria to reliably identify individuals with prodromal MS who are at high risk of progressing to a diagnosis of MS. In this Roadmap, we draw on work in other diseases to propose a disease framework for MS that incorporates the prodromal stage, and set out key steps and considerations needed in future research to fully characterize the MS prodrome, identify early disease markers and develop standardized criteria that will enable reliable identification of individuals with prodromal MS, thereby facilitating trials of interventions to slow or stop progression beyond the prodrome.

Elevated levels of serum CD5 antigen-like protein distinguish secondary progressive multiple sclerosis from other disease subtypes.

CD5 antigen-like (CD5L) protein is a macrophage-secreted protein with roles in immunomodulation and lipid homeostasis. We compared serum CD5L levels in healthy controls to individuals diagnosed with clinically isolated syndrome, relapsing remitting (RR), secondary progressive (SP), and primary progressive (PP) multiple sclerosis (MS). CD5L was increased in SPMS relative to controls, RRMS, and PPMS. SPMS CD5L was associated with longer disease duration independent of age, sex, or disease severity. The positive relationship between CD5L and disease duration in SPMS suggests a chronic peripheral inflammatory profile compared to other subtypes, particularly PPMS, warranting investigation of functional roles for CD5L in MS.

Unique clinical and pathological features in HLA-DRB1*0401-restricted MBP 111-129-specific humanized TCR transgenic mice.

Amino acid residues 111-129 represent an immunodominant epitope of myelin basic protein (MBP) in humans with human leukocyte antigen (HLA)-DRB1*0401 allele(s). The MBP 111-129-specific T cell clone MS2-3C8 was repeatedly isolated from a patient with multiple sclerosis (MS), suggesting an involvement of MS2-3C8 T cells in the pathogenesis. To address the pathogenic potential of the MS2-3C8 T cell clone, we generated transgenic (Tg) mice expressing its T cell receptor and restriction element, HLA-DRB1*0401, to examine the pathogenic characteristics of MS2-3C8 Tg T cells by adoptive transfer into HLA-DRB1*0401 Tg mice. In addition to the ascending paralysis typical of experimental autoimmune encephalomyelitis, mice displayed dysphagia due to restriction in jaw and tongue movements and abnormal gait. In accordance with the clinical phenotype, infiltrates of MS2-3C8 Tg T cells and inflammatory lesions were predominantly located in the brainstem and the cranial nerve roots in addition to the spinal cord and spinal nerve roots. Together, these data suggest a pathogenic role of MBP-specific T cells in inflammatory demyelination within the brainstem and cranial nerve roots during the progression of MS. This notion may help to explain the clinical and pathological heterogeneity of MS.

Different development of myelin basic protein agonist- and antagonist-specific human TCR transgenic T cells in the thymus and periphery.

Myelin basic protein (MBP)-specific T cells are thought to play a role in the development of multiple sclerosis. MBP residues 111-129 compose an immunodominant epitope cluster restricted by HLA-DRB1*0401. The sequence of residues 111-129 of MBP (MBP(111-129)) differs in humans (MBP122:Arg) and mice (MBP122:Lys) at aa 122. We previously found that approximately 50% of human MBP(111-129) (MBP122:Arg)-specific T cell clones, including MS2-3C8 can proliferate in response to mouse MBP(111-129) (MBP122:Lys). However, the other half of T cell clones, including HD4-1C2, cannot proliferate in response to MBP(111-129) (MBP122:Lys). We found that MBP(111-129) (MBP122:Lys) is an antagonist for HD4-1C2 TCR, therefore, MS2-3C8 and HD4-1C2 TCRs are agonist- and antagonist-specific TCRs in mice, respectively. Therefore, we examined the development of HD4-1C2 TCR and MS2-3C8 TCR transgenic (Tg) T cells in the thymus and periphery. We found that dual TCR expression exclusively facilitates the development of MBP(111-129) TCR Tg T cells in the periphery of HD4-1C2 TCR/HLA-DRB1*0401 Tg mice although it is not required for their development in the thymus. We also found that MS2-3C8 TCR Tg CD8(+) T cells develop along with MS2-3C8 TCR Tg CD4(+) T cells, and that dual TCR expression was crucial for the development of MS2-3C8 TCR Tg CD4(+) and CD8(+) T cells in the thymus and periphery, respectively. These results suggest that thymic and peripheral development of MBP-specific T cells are different; however, dual TCR expression can facilitate their development.

Enhanced expression of complement and microglial-specific genes prior to clinical progression in the MOG-experimental autoimmune encephalomyelitis model of multiple sclerosis.

Understanding the biological changes responsible for failures in repair and the development of progressive MS is paramount for therapeutic intervention. In a well characterized experimental autoimmune encephalomyelitis (EAE) model of MS the clinical phenotype features an acute attack with partial recovery followed by a chronic or progressive disease phase. Neuropathology-focused gene expression profiles were generated from spinal cord, hindbrain and forebrain of mice 25 days after the induction of EAE, the time when recovery plateaus and transitions to a chronic or worsening phase. Differences in gene expression were most pronounced in the spinal cord of EAE mice compared to sham-immunized animals, with a subset of genes also found to be differentially expressed in the hindbrain and the forebrain, albeit with smaller fold-changes in expression. Our data suggests that changes in complement components, chemoattractant cytokines and especially enrichment in microglial cells may be the primary drivers of processes that limit recovery in EAE.

Oligodendrocyte ARNT2 expression is altered in models of MS.

OBJECTIVE: We examined expression of aryl hydrocarbon receptor nuclear translocator 2 (ARNT2), a basic-loop-helix transcription factor implicated in neuronal development and axonal health, in oligodendrocyte (OL) cultures and over the course of chronic experimental autoimmune encephalomyelitis (EAE), the murine model of multiple sclerosis (MS). METHODS: We assessed OL ARNT2 expression in EAE compared with sham-immunized controls and also in OL primary cultures and over the course of dibutyryl cyclic adenosine monophosphate (dbcAMP)-mediated maturation of the immortalized Oli-neu cell line. We also tested the functional role of ARNT2 in influencing OL characteristics using small interfering RNA (siRNA). RESULTS: ARNT2 is localized to Olig2+ cells in healthy spinal cord gray and white matter. Despite a significant expansion of Olig2+ cells in the white matter at peak disease, ARNT2 is reduced by almost half in OLs, along with a reduction in the percentage of ARNT2+/Olig2+ cells. Mature OLs in mixed cortical cultures or OLs matured from embryonic progenitors express negligible ARNT2. Similarly, Oli-neu cells express high levels of ARNT2, which are reduced following dbcAMP maturation. siRNA-mediated knockdown of ARNT2 affected OL viability, which led to an enrichment of myelin-producing OLs. CONCLUSION: The analysis of ARNT2 expression in OLs demonstrates that OL ARNT2 expression is altered in EAE and during OL maturation. Findings point to ARNT2 as an important mediator of OL viability and differentiation and warrant further characterization as a target for intervention in demyelinating disorders such as MS.

Expression of CD1d by astrocytes corresponds with relative activity in multiple sclerosis lesions.

The CD1 protein family present lipid antigens to the immune system. CD1d has been observed in the CNS of MS patients, yet no studies have quantitatively characterized this expression and related it to inflammatory demyelinative activity in MS plaques. In this study, we set out to localize and quantify the presence of CD1d expression by astrocytes in MS brain tissue lesions. Formalin-fixed, paraffin-embedded MS and control brain tissues were examined. Lesions were classified as active, chronic active or chronic silent. Using immunofluorescence, the density of CD1d-positive cells was determined in active lesions, chronic active lesion edges and chronic active lesion centers. The percentage of CD1d-positive cells that were GFAP-positive was also determined in each of these regions. CD1d immunoreactivity was significantly increased in MS compared to control tissue, was significantly more prevalent in areas of active demyelination, and colocalized with GFAP-positive reactive astrocytes. Increases of CD1d immunoreactivity in the CNS of MS patients being greatest in areas of active demyelination and localized to GFAP-positive astrocytes lend support to the hypothesis of a lipid-targeted autoimmune process contributing to the pathogenesis of MS.

Mucosal Administration of E-selectin Limits Disability in Models of Multiple Sclerosis.

E-selectin plays an important role in mediating the rolling of leukocytes along and thus, the subsequent extravasation across activated endothelial cells comprising the microvasculature of the blood brain barrier (BBB). In multiple sclerosis (MS) and other inflammatory disorders of the central nervous system (CNS), the microvasculature is altered and immune cells infiltrate the brain and spinal cord contributing to damage, demyelination and ultimately disability. While mucosal administration is typically used to affect lymphocyte hyporesponsiveness or tolerance to suspect autoantigens, intranasal administration to E-selectin has previously been shown to protect against CNS inflammatory insults. We characterized the potential for mucosal administration of E-selectin to modulate CNS autoimmunity in the experimental autoimmune encephalomyelitis (EAE) model of MS. Intranasally administered E-selectin reduced swelling by as much as 50% in delayed-type hypersensitivity reactions compared to ovalbumin-tolerized controls. Intranasal E-selectin delivery prior to disease induction with myelin oligodendrocyte glycoprotein (MOG)35-55 reduced disease severity and total disease burden by more than 50% compared to PBS-tolerized animals; this protection was not associated with differences in the magnitude of the autoimmune response. Examination after the onset of disease showed that protection was associated with significant reductions in inflammatory infiltrates throughout the spinal cord. Tolerization to E-selectin did not influence encephalitogenic characteristics of autoreactive T cells such as IFN-gamma or IL-17 production. Clinical disease was also significantly reduced when E-selectin was first delivered after the onset of clinical symptoms. Splenic and lymph node (LN) populations from E-selectin-tolerized animals showed E-selectin-specific T cell responses and production of the immunomodulatory cytokine IL-10. Transfer of enriched CD4+ T cells from E-selectin tolerized mice limited disability in the passive SJL model of relapsing remitting MS. These results suggest a role for influencing E-selectin specific responses to limit neuroinflammation that warrants further exploration and characterization to better understand its potential to mitigate neurodegeneration in disorders such as MS.

High production of CXCL13 in blood and brain during persistent infection with the relapsing fever spirochete Borrelia turicatae.

Relapsing fever (RF) is a multisystemic borrelial infection with frequent neurologic involvement referred to as neuroborreliosis. The absence of an effective antibody response results in persistent infection. To study the consequences to the brain of persistent infection with the RF spirochete Borrelia turicatae, we studied B cell (Igh6-/-) and B and T (Rag1-/-) cell-deficient mice inoculated with isogenic serotypes 1 (Bt1) or 2 (Bt2). We found that Bt1 was more tissue tropic than Bt2, not only for brain but also for heart. Igh6-/- mice developed more severe clinical disease than Rag1-/- mice. Bt1-infected brains had widespread microgliosis/brain macrophage activation despite localization of spirochetes in the leptomeninges rather than the brain parenchyma itself. Oligoarray analysis revealed that CXCL13 was the most upregulated gene in the brain of Bt1-infected Igh6-/- mice. CXCL13 was also the most abundant of the chemokines we measured in infected blood. Persistent infection did not result in injury to the brain. Treatment with exogenous interleukin-10 reduced microgliosis in the brain and production of CXCL13 in the blood. We concluded that brain involvement in B cell-deficient mice persistently infected with B. turicatae is characterized by prominent microgliosis and production of CXCL13 without detectable injury.