The critical role of antigen-presentation-induced cytokine crosstalk in the central nervous system in multiple sclerosis and experimental autoimmune encephalomyelitis

Protective effect of microRNA-134-3p on multiple sclerosis through inhibiting PRSS57 and promotion of CD34+ cell proliferation in rats

MicroRNAs (miRs) have been extensively studied for their involvement in multiple sclerosis (MS). We investigated the involvement of miR-134-3p on MS. The MS rat model was established, and positive expression of interleukin-17 (IL-17) was detected using the immunohistochemical method while the expression of miR-134-3p and serine protease 57 (PRSS57) was determined by means of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Second, the miR-134-3p overexpression or short hairpin RNA against PRSS57 was introduced into the CD34⁺ cells to investigate the levels of proliferation and apoptosis-related genes by RT-qPCR and Western blot analysis. In addition, analysis of the targeting relations of miR-134-3p and PRSS57 was conducted using online software and dual-luciferase reporter gene assay. Furthermore, neuronal functions, inflammatory response, proliferation, and apoptosis of CD34⁺ cells were assayed by flow cytometry, enzyme-linked immunosorbent assay, and methyl thiazolyl tetrazolium. IL-17 and PRSS57 expression increased while miR-134-3p expression decreased in the spinal cord from MS rats. miR-134-3p could target PRSS57. miR-134-3p overexpression or PRSS57 silencing enhanced mitochondrial activity of neurons, mitochondrial membrane potential content, CD34⁺ cell proliferation, while decreasing Cyt C content, inflammatory response, and cell apoptosis. Collectively, overexpression of miR-134-3p promotes CD34⁺ cell proliferation via inhibition of PRSS57 in MS, which may serve as a promising target for MS intervention.

Cell Clearing Systems Bridging Neuro-Immunity and Synaptic Plasticity

In recent years, functional interconnections emerged between synaptic transmission, inflammatory/immune mediators, and central nervous system (CNS) (patho)-physiology. Such interconnections rose up to a level that involves synaptic plasticity, both concerning its molecular mechanisms and the clinical outcomes related to its behavioral abnormalities. Within this context, synaptic plasticity, apart from being modulated by classic CNS molecules, is strongly affected by the immune system, and vice versa. This is not surprising, given the common molecular pathways that operate at the cross-road between the CNS and immune system. When searching for a common pathway bridging neuro-immune and synaptic dysregulations, the two major cell-clearing cell clearing systems, namely the ubiquitin proteasome system (UPS) and autophagy, take center stage. In fact, just like is happening for the turnover of key proteins involved in neurotransmitter release, antigen processing within both peripheral and CNS-resident antigen presenting cells is carried out by UPS and autophagy. Recent evidence unravelling the functional cross-talk between the cell-clearing pathways challenged the traditional concept of autophagy and UPS as independent systems. In fact, autophagy and UPS are simultaneously affected in a variety of CNS disorders where synaptic and inflammatory/immune alterations concur. In this review, we discuss the role of autophagy and UPS in bridging synaptic plasticity with neuro-immunity, while posing a special emphasis on their interactions, which may be key to defining the role of immunity in synaptic plasticity in health and disease.

A Sentinel in the Crosstalk Between the Nervous and Immune System: The (Immuno)-Proteasome

The wealth of recent evidence about a bi-directional communication between nerve- and immune- cells revolutionized the traditional concept about the brain as an “immune-privileged” organ while opening novel avenues in the pathophysiology of CNS disorders. In fact, altered communication between the immune and nervous system is emerging as a common hallmark in neuro-developmental, neurodegenerative, and neuro-immunological diseases. At molecular level, the ubiquitin proteasome machinery operates as a sentinel at the crossroad between the immune system and brain. In fact, the standard proteasome and its alternative/inducible counterpart, the immunoproteasome, operate dynamically and coordinately in both nerve- and immune- cells to modulate neurotransmission, oxidative/inflammatory stress response, and immunity. When dysregulations of the proteasome system occur, altered amounts of standard- vs. immune-proteasome subtypes translate into altered communication between neurons, glia, and immune cells. This contributes to neuro-inflammatory pathology in a variety of neurological disorders encompassing Parkinson's, Alzheimer's, and Huntingtin's diseases, brain trauma, epilepsy, and Multiple Sclerosis. In the present review, we analyze those proteasome-dependent molecular interactions which sustain communication between neurons, glia, and brain circulating T-lymphocytes both in baseline and pathological conditions. The evidence here discussed converges in that upregulation of immunoproteasome to the detriment of the standard proteasome, is commonly implicated in the inflammatory- and immune- biology of neurodegeneration. These concepts may foster additional studies investigating the role of immunoproteasome as a potential target in neurodegenerative and neuro-immunological disorders.

Dendritic Cell PD-L1 Limits Autoimmunity and Follicular T Cell Differentiation and Function

The programmed death (PD)-1 coinhibitory receptor regulates the balance between T cell activation and tolerance. Although the PD-1 ligands, PD-L1 and PD-L2, are expressed on a variety of cell types, the cell type-specific functions of PD-1 ligands in inducing signals through PD-1 are unknown. In this study, we use PD-L1 conditional knockout mice to investigate the cell type-specific functions of PD-L1. We demonstrate that PD-L1 expressed on dendritic cells (DCs), and to a lesser extent on B cells, attenuates the progression of experimental autoimmune encephalomyelitis and inhibits naive and effector T cells. PD-1 is highly expressed on effector populations, including T follicular helper (Tfh) cells and T follicular regulatory (Tfr) cells, which reside in germinal centers. We also show that DC PD-L1 is essential for limiting Tfh and Tfr cell differentiation. In addition, we find that PD-1 suppresses Tfh cell differentiation and help for Ig class switching, even in the presence of wild-type Tfr cells. Our work points to critical roles for PD-L1 expressed on DCs in mediating PD-1 functions.

Matrine Treatment Blocks NogoA-Induced Neural Inhibitory Signaling Pathway in Ongoing Experimental Autoimmune Encephalomyelitis

Myelin-associated inhibitors, such as NogoA, myelin-associated glycoprotein (MAG), and oligodendrocyte myelin glycoprotein (OMgp), play a pivotal role in the lack of neuroregeneration in multiple sclerosis, an inflammatory demyelinating disease of the central nervous system (CNS). Matrine (MAT), a monomer that is used in traditional Chinese medicine as an anti-inflammatory agent, has shown beneficial effects in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. However, the underlying mechanisms of MAT-induced EAE amelioration are not fully understood. In the present study, we show that MAT treatment suppressed ongoing EAE, and this effect correlated with an increased expression of growth-associated protein 43, an established marker for axonal regeneration. MAT treatment significantly reduced the levels of NogoA, its receptor complex NgR/p75NTR/LINGO-1, and their downstream RhoA/ROCK signaling pathway in the CNS. In contrast, intracellular cyclic AMP (cAMP) levels and its protein kinase (protein kinase A (PKA)), which can promote axonal regrowth by inactivating the RhoA, were upregulated. Importantly, adding MAT in primary astrocytes in vitro largely induced cAMP/PKA expression, and blockade of cAMP significantly diminished MAT-induced expression of PKA and production of BDNF, a potent neurotrophic factor for neuroregeneration. Taken together, our findings demonstrate that the beneficial effects of MAT on EAE can be attributed not only to its capacity for immunomodulation, but also to its directly promoting regeneration of the injured CNS.

Multiple Sclerosis and Obesity: Possible Roles of Adipokines

Multiple Sclerosis (MS) is an autoimmune disorder of the Central Nervous System that has been associated with several environmental factors, such as diet and obesity. The possible link between MS and obesity has become more interesting in recent years since the discovery of the remarkable properties of adipose tissue. Once MS is initiated, obesity can contribute to increased disease severity by negatively influencing disease progress and treatment response, but, also, obesity in early life is highly relevant as a susceptibility factor and causally related risk for late MS development. The aim of this review was to discuss recent evidence about the link between obesity, as a chronic inflammatory state, and the pathogenesis of MS as a chronic autoimmune and inflammatory disease. First, we describe the main cells involved in MS pathogenesis, both from neural tissue and from the immune system, and including a new participant, the adipocyte, focusing on their roles in MS. Second, we concentrate on the role of several adipokines that are able to participate in the mediation of the immune response in MS and on the possible cross talk between the latter. Finally, we explore recent therapy that involves the transplantation of adipocyte precursor cells for the treatment of MS.

Gut-associated lymphoid tissue, gut microbes and susceptibility to experimental autoimmune encephalomyelitis

Gut microbiota and gut-associated lymphoid tissue have been increasingly appreciated as important players in pathogenesis of various autoimmune diseases, including multiple sclerosis. Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis that can be induced with an injection of spinal cord homogenate emulsified in complete Freund's adjuvant in Dark Agouti (DA) rats, but not in Albino Oxford (AO) rats. In this study, mesenteric lymph nodes (MLN), Peyer's patches (PP) and gut microbiota were analysed in these two rat strains. There was higher proportion of CD4(+) T cells and regulatory T cells in non-immunised DA rats in comparison to AO rats. Also, DA rat MLN and PP cells were higher producers of pro-inflammatory cytokines interferon-γ and interleukin-17. Finally, microbial analyses showed that uncultivated species of Turicibacter and Atopostipes genus were exclusively present in AO rats, in faeces and intestinal tissue, respectively. Thus, it is clear that in comparison of an EAE-susceptible with an EAE-resistant strain of rats, various discrepancies at the level of gut associated lymphoid tissue, as well as at the level of gut microbiota can be observed. Future studies should determine if the differences have functional significance for EAE pathogenesis.

Genetic, Immune-Inflammatory, and Oxidative Stress Biomarkers as Predictors for Disability and Disease Progression in Multiple Sclerosis

The aim of this study was to evaluate the TNFβ NcoI polymorphism (rs909253) and immune-inflammatory, oxidative, and nitrosative stress (IO&NS) biomarkers as predictors of disease progression in multiple sclerosis (MS). We included 212 MS patients (150 female, 62 male, mean (±standard deviation (SD)) age = 42.7 ± 13.8 years) and 249 healthy controls (177 female, 72 male, 36.8 ± 11 years). The disability was measured the Expanded Disability Status Scale (EDSS) in 2006 and 2011. We determined the TNFβ NcoI polymorphism and serum levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, IL-4, IL-10, and IL-17, albumin, ferritin, and plasma levels of lipid hydroperoxides (CL-LOOH), carbonyl protein, advanced oxidation protein products (AOPPs), nitric oxide metabolites (NOx), and total radical-trapping antioxidant parameter (TRAP). The mean EDSS (±SD) in 2006 was 1.62 ± 2.01 and in 2011 3.16 ± 2.29, and disease duration was 7.34 ± 7.0 years. IL-10, TNF-α, IFN-γ, AOPP, and NOx levels were significantly higher and IL-4 lower in MS patients with a higher 2011 EDSS scores (≥3) as compared with those with EDSS < 3. The actual increases in EDSS from 2006 to 2011 were positively associated with TNF-α and IFN-γ. Increased IFN-γ values were associated with higher pyramidal symptoms and increased IL-6 with sensitive symptoms. Increased carbonyl protein and IL-10 but lowered albumin levels predicted cerebellar symptoms. The TNFB1/B2 genotype decreased risk towards progression of pyramidal symptoms. Treatments with IFN-β and glatiramer acetate significantly reduced TNF-α but did not affect the other IO&NS biomarkers or disease progression. Taken together, IO&NS biomarkers and NcoI TNFβ genotypes predict high disability in MS and are associated with different aspects of disease progression. New drugs to treat MS should also target oxidative stress pathways.

Interferon gamma in autoimmunity: A complicated player on a complex stage

Early views of autoimmune disease cast IFNγ as a prototypic pro-inflammatory factor. It is now clear that IFNγ is capable of both pro- and anti-inflammatory activities with the functional outcome dependent on the physiological and pathological setting examined. Here, the major immune modulatory activities of IFNγ are reviewed and current evidence for the impact of IFNγ on pathology and regulation of several autoimmune diseases and disease models is summarized.

Association between multiple sclerosis risk-associated SNPs and relapse and disability--a prospective cohort study

BACKGROUND

The modulating effects of the multiple sclerosis (MS) risk-associated single-nucleotide polymorphisms (SNPs) on MS clinical course are not well established.

OBJECTIVES

The objective of this paper is to investigate whether known MS risk-associated SNPs were associated with clinical course, and whether these SNPs modified the 25(OH)D-relapse association.

METHODS

Using a prospective cohort of 141 participants with relapsing-remitting MS and genotype data followed between 2002 and 2005, genotype-vitamin D interactions and the genetic predictors of relapse were assessed using survival analysis, and genetic predictors of 25(OH)D and disability progression were evaluated by multilevel mixed-effects linear regression.

RESULTS

While no SNP reached statistical significance after multiple testing, five SNPs were associated with relapse, with significant cumulative genotype risk effects and two demonstrated significant allele dose-response. Two SNPs altered the 25(OH)D-relapse association with significant allele dose-response. Five SNPs modified levels of 25(OH)D, with significant cumulative genotype 'risk' effect, and three demonstrated significant allele dose-response. We found no consistent evidence for an association between any SNPs and disability.

CONCLUSIONS

Our study provides evidence for an association between known MS risk-associated SNPs and relapse. Our findings indicate gene-environment interactions may be an important mechanism on MS clinical course, and provide support for the role of vitamin D in MS relapse.

Targeting the shift from M1 to M2 macrophages in experimental autoimmune encephalomyelitis mice treated with fasudil

We observed the therapeutic effect of Fasudil and explored its mechanisms in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Fasudil, a selective Rho kinase (ROCK) inhibitor, was injected intraperitoneally at 40 mg/kg/d in early and late stages of EAE induction. Fasudil ameliorated the clinical severity of EAE at different stages, and decreased the expression of ROCK-II in spleen, accompanied by an improvement in demyelination and inhibition of inflammatory cells. Fasudil mainly inhibited CD4⁺IL-17⁺ T cells in early treatment, but also elevated CD4⁺IL-10⁺ regulatory T cells and IL-10 production in late treatment. The treatment of Fasudil shifted inflammatory M1 to anti-inflammatory M2 macrophages in both early and late treatment, being shown by inhibiting CD16/32, iNOS, IL-12, TLR4 and CD40 and increasing CD206, Arg-1, IL-10 and CD14 in spleen. By using Western blot and immunohistochemistry, iNOS and Arg-1, as two most specific markers for M1 and M2, was inhibited or induced in splenic macrophages and spinal cords of EAE mice treated with Fasudil. In vitro experiments also indicate that Fasudil shifts M1 to M2 phenotype, which does not require the participation or auxiliary of other cells. The polarization of M2 macrophages was associated with the decrease of inflammatory cytokine IL-1β, TNF-α and MCP-1. These results demonstrate that Fasudil has therapeutic potential in EAE possibly through inducing the polarization of M2 macrophages and inhibiting inflammatory responses.

The novel HSP90 inhibitor, PU-H71, suppresses glial cell activation but weakly affects clinical signs of EAE

Ansamycins are very effective HSP90 inhibitors that showed significant beneficial effects in the treatment of EAE. However, their toxicity and poor stability in solution limit their clinical use. In the present study we have characterized the anti-inflammatory properties of a novel HSP90 inhibitor, PU-H71, and tested its effects in EAE. Our findings show that PU-H71 reduced lipopolysaccharide astrocyte activation but failed to reduce the inflammatory cytokine activation. In contrast to ansamycins, PU-H71 weakly affects EAE clinical course. In conclusion, although PU-H71 displayed some anti-inflammatory properties, it appeared in vivo less effective than the more toxic HSP90 inhibitors.

Tract-based spatial statistics analysis of diffusion-tensor imaging data in pediatric- and adult-onset multiple sclerosis

BACKGROUND

White matter (WM) microstructure may vary significantly in pediatric-onset (PO) and adult-onset (AO) patients with multiple sclerosis (MS), a difference that could be explained by the effects of an inherent plasticity in the affected pediatric brains early in the disease, and a phenomenon that does not occur later in life. This hypothesis would support the observation that disease progression is much slower in POMS compared to AOMS patients.

OBJECTIVES

To examine WM microstructure in the brain of adults with POMS and AOMS, using tract based spatial statistics (TBSS) analysis of diffusion-tensor imaging (DTI).

METHODS

Adults with relapsing-remitting (RR) POMS, who were diagnosed before age of 18 years (n = 16), were compared with age-matched (AOA, n = 23) and disease duration-matched (AOD, n = 22) RR patients who developed MS after the age of 18 years. Scans were analyzed using the FSL software package (Oxford, UK) and statistics were performed using TBSS to evaluate WM microstructure between groups based on the mean fractional anisotropy (FA) values obtained from the DTI.

RESULTS

Widespread cortical and deep WM area differences characterized by increased FA values were seen in the AOAMS compared with POMS group (P < 0.05, TFCE corrected). Significantly increased FA values of posterior WM areas were detected in the AODMS compared with POMS group (P < 0.05, TFCE corrected).

CONCLUSION

Increased FA values in WM areas of the AOMS compared with the POMS patients suggest that diffuse WM microstructure changes are more attributable to age of onset than a simple function of disease duration and age.

Temporal changes in innate immune signals in a rat model of alcohol withdrawal in emotional and cardiorespiratory homeostatic nuclei

Background

Chronic alcohol use changes the brain’s inflammatory state. However, there is little work examining the progression of the cytokine response during alcohol withdrawal, a period of profound autonomic and emotional upset. This study examines the inflammatory response in the central nucleus of the amygdala (CeA) and dorsal vagal complex (DVC), brain regions neuroanatomically associated with affective and cardiorespiratory regulation in an in vivo rat model of withdrawal following a single chronic exposure.

Methods

For qRT-PCR studies, we measured the expression of TNF-α, NOS-2, Ccl2 (MCP-1), MHC II invariant chain CD74, and the TNF receptor Tnfrsf1a in CeA and DVC samples from adult male rats exposed to a liquid alcohol diet for thirty-five days and in similarly treated animals at four hours and forty-eight hours following alcohol withdrawal. ANOVA was used to identify statistically significant treatment effects. Immunohistochemistry (IHC) and confocal microscopy were performed in a second set of animals during chronic alcohol exposure and subsequent 48-hour withdrawal.

Results

Following a chronic alcohol exposure, withdrawal resulted in a statistically significant increase in the expression of mRNAs specific for innate immune markers Ccl2, TNF-α, NOS-2, Tnfrsf1a, and CD74. This response was present in both the CeA and DVC and most prominent at 48 hours. Confocal IHC of samples taken 48 hours into withdrawal demonstrate the presence of TNF-α staining surrounding cells expressing the neural marker NeuN and endothelial cells colabeled with ICAM-1 (CD54) and RECA-1, markers associated with an inflammatory response. Again, findings were consistent in both brain regions.

Conclusions

This study demonstrates the rapid induction of Ccl2, TNF-α, NOS-2, Tnfrsf1a and CD74 expression during alcohol withdrawal in both the CeA and DVC. IHC dual labeling showed an increase in TNF-α surrounding neurons and ICAM-1 on vascular endothelial cells 48 hours into withdrawal, confirming the inflammatory response at the protein level. These findings suggest that an abrupt cessation of alcohol intake leads to an acute central nervous system (CNS) inflammatory response in these regions that regulate autonomic and emotional state.

Cytokines in autoimmunity: role in induction, regulation, and treatment

Cytokines play a pivotal role in the pathogenesis of autoimmune diseases. The precise triggers for the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic autoimmune responses remain to be defined for most of the naturally occurring autoimmune diseases. Studies conducted in experimental models of human autoimmune diseases and observations in patients have revealed a general scheme in which proinflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and recovery from acute phase of the disease. This idea is embodied in the T helper (Th) 1/Th2 paradigm, which over the past two decades has had a major influence on our thinking about the role of cytokines in autoimmunity. Interestingly, over the past decade, the interleukin (IL)-17/IL-23 axis has rapidly emerged as the new paradigm that has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. In this 2-volume special issue of the journal, leading experts have presented their research findings and viewpoints on the role of cytokines in the context of specific autoimmune diseases.