LPA1 signaling drives Schwann cell dedifferentiation in experimental autoimmune neuritis.

BACKGROUND: Lysophosphatidic acid (LPA) is a pleiotropic lipid messenger that addresses at least six specific G-protein coupled receptors. Accumulating evidence indicates a significant involvement of LPA in immune cell regulation as well as Schwann cell physiology, with potential relevance for the pathophysiology of peripheral neuroinflammation. However, the role of LPA signaling in inflammatory neuropathies has remained completely undefined. Given the broad expression of LPA receptors on both Schwann cells and cells of the innate and adaptive immune system, we hypothesized that inhibition of LPA signaling may ameliorate the course of disease in experimental autoimmune neuritis (EAN). METHODS: We induced active EAN by inoculation of myelin protein 2 peptide (P255-78) in female Lewis rats. Animals received the orally available LPA receptor antagonist AM095, specifically targeting the LPA1 receptor subtype. AM095 was administered daily via oral gavage in a therapeutic regimen from 10 until 28 days post-immunization (dpi). Analyses were based on clinical testing, hemogram profiles, immunohistochemistry and morphometric assessment of myelination. RESULTS: Lewis rats treated with AM095 displayed a significant improvement in clinical scores, most notably during the remission phase. Cellular infiltration of sciatic nerve was only discretely affected by AM095. Hemogram profiles indicated no impact on circulating leukocytes. However, sciatic nerve immunohistochemistry revealed a reduction in the number of Schwann cells expressing the dedifferentiation marker Sox2 paralleled by a corresponding increase in differentiating Sox10-positive Schwann cells. In line with this, morphometric analysis of sciatic nerve semi-thin sections identified a significant increase in large-caliber myelinated axons at 28 dpi. Myelin thickness was unaffected by AM095. CONCLUSION: Thus, LPA1 signaling may present a novel therapeutic target for the treatment of inflammatory neuropathies, potentially affecting regenerative responses in the peripheral nerve by modulating Schwann cell differentiation.

CX3CR1 But Not CCR2 Expression Is Required for the Development of Autoimmune Peripheral Neuropathy in Mice.

One hallmark of Guillain-Barre syndrome (GBS), a prototypic autoimmune peripheral neuropathy (APN) is infiltration of leukocytes (macrophages and T cells) into peripheral nerves, where chemokines and their receptors play major roles. In this study, we aimed to understand the potential contribution of chemokine receptors CCR2 and CX3CR1 in APN by using a well-established mouse model, B7.2 transgenic (L31) mice, which possesses a predisposed inflammatory background. We crossbred respectively CCR2KO and CX3CR1KO mice with L31 mice. The disease was initiated by partial ligation on one of the sciatic nerves. APN pathology and neurological function were evaluated on the other non-ligated sciatic nerve/limb. Our results revealed that L31/CX3CR1KO but not L31/CCR2KO mice were resistant to APN. CX3CR1 is needed for maintaining circulating monocyte and CD8+ T cell survival. While migration of a significant number of activated CD8+ T cells to peripheral nerves is essential in autoimmune response in nerve, recruitment of monocytes into PNS seems optional. Disease onset is independent of CCR2 mediated blood-derived macrophage recruitment, which can be replaced by compensatory proliferation of resident macrophages in peripheral nerve. CX3CR1 could also contribute to APN via its critical involvement in maintaining nerve macrophage phagocytic ability. We conclude that blockade of CX3CR1 signaling may represent an interesting anti-inflammatory strategy to improve therapeutic management for GBS patients.

Protective Role of Limitrin in Experimental Autoimmune Optic Neuritis.

Purpose: This study investigated the role of limitrin in the pathogenesis of demyelinating optic neuritis using an experimental autoimmune optic neuritis (EAON) model. Methods: EAON was induced in mice via subcutaneous injection with myelin oligodendrocyte glycoprotein peptide. Limitrin protein and mRNA expression were examined in the optic nerve before and after EAON induction. Proinflammatory cytokine expression profiles and degree of glial activation were compared between wild-type (WT) and limitrin knockout mice by real-time PCR and histologic analysis, respectively, after EAON induction. Plasma limitrin levels in patients with optic neuritis and healthy controls were measured by ELISA. Results: Limitrin expression, observed in astrocytes in the optic nerve of WT mice, was lower in EAON-induced than in naïve WT mice. A comparative analysis of WT and limitrin knockout mice revealed that limitrin deficiency induced more severe neuroinflammation and glial hyperactivation in the optic nerve after EAON induction. Limitrin-deficient astrocytes were more chemotactically responsive to neuroinflammatory stimulation than WT astrocytes. Patients with optic neuritis demonstrated higher plasma limitrin levels than healthy controls (P = 0.0001), which was negatively correlated with visual acuity at the nadir of the optic neuritis attack (r = 0.46, P = 0.036). Conclusions: Limitrin deficiency induced severe neuroinflammation and reactive gliosis in the optic nerve after EAON induction. Our results imply that astrocyte-derived limitrin may protect against neuroinflammation by decreasing immune cell infiltration into the optic nerve. The plasma limitrin level may reflect the extent of blood-brain barrier disruption and provide a valuable biomarker reflecting the severity of optic neuritis.

The therapeutic effects of ginkgolides in Guillain-Barré syndrome and experimental autoimmune neuritis.

BACKGROUND: Guillain-Barré syndrome (GBS) is an acquired immune-mediated inflammatory peripheral neuropathy. The immune regulation of ginkgolides have been revealed in recent years. We herein investigate the potential therapeutic effects of ginkgolides both on GBS and its animal model, experimental autoimmune neuritis (EAN). METHODS: EAN in C57BL/6 mice induced by subcutaneous injection with peripheral nerve myelin P0 protein peptide 180-199 (P0 peptide) were treated with ginkgolides at three different doses. GBS patients were randomly divided into two groups, the experimental group and the control group. The experimental group were treated with ginkgolides as soon as diagnosed. RESULTS: Our data indicated that ginkgolides administration daily ameliorated the score of EAN and delayed the peak of disease in EAN mice. Ginkgolides also down-regulated the proportions of T helper (Th) 17 cells in EAN spleens. Furthermore, we also found that administration of ginkgolides significantly decreased the levels of interferon (IFN)-γ and interleukin-12 (IL)-12 in GBS patients. CONCLUSIONS: Our results suggested that ginkgolides ameliorated the clinical score of EAN through down-regulating the proportions of Th 17 cells. Ginkgolides also suppressed inflammation response by decreasing pro-inflammatory cytokines IFN-γ and IL-12, suggesting ginkgolides had potential therapeutic effects on GBS patients and EAN in the future.

The dynamic expression of canonical Wnt/ß-catenin signalling pathway in the pathologic process of experimental autoimmune neuritis.

Background: Guillain-Barré syndrome (GBS), an autoimmune disease and an acute inflammation disorder, is currently the most frequent cause of acute flaccid paralysis worldwide. EAN, an animal model of GBS, is a CD4+ T cell-mediated autoimmune disease of the PNS. Wnt/ß-catenin signals are critically important to several fundamental aspects of peripheral nerve development and play a crucial role in Schwann cell proliferation. Here, we investigate the role of Wnt/ß-catenin signalling cascades in EAN rats.Methods: 28 male Lewis rats weighing 170 ± 10 g were randomly divided into control group (n = 7) and EAN groups (Early group; Peak group and Recovery group. n = 7 per group). EAN rats were immunized with P257-81 peptide; weighed daily, and the neurologic signs of EAN were evaluated every day. The sciatic nerve was taken on the days 10, 17, and 30 p.i. for H&E staining, transmission electron microscopy and immunohistochemical staining; blood samples were collected weekly from caudal vein to detect IFN-γ, IL-4, TGF-ß1; and the sciatic nerve was taken to examinate the dynamics expression of Wnt/ß-catenin pathway molecules.Results: In our study, we chose tail-root injection to better model GBS. Moreover, we observed that IFN-γ levels paralleled clinical EAN, and the levels of TGF-ß1 and IL-4 gradually increased and peaked in the recovery phase. In addition, we have shown that canonical Wnt signalling is upregulated and reached a peak in the late recovery phase.Conclusion: Our findings suggest that Wnt/ß-catenin signalling is associated with the promotion of remyelination in EAN rats.

Effects of APELIN-13 on the expression of IL-6, TNF-α, and IFN-γ in rats with experimental autoimmune neuritis.

The objective of this paper was to study the effects of PYR-ARG-PRO-ARG-LEU-SER-HIS-YSGLY-PRO-MET-PRO-PHE-OH (APELIN-13) on the expression of inflammatory factors interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) in rats with experimental autoimmune neuritis (EAN). A total of 30 rats were divided into a control group, an EAN group, and an APELIN-13 group. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of IL-6, TNF-α, and IFN-γ in rat plasma. Real-time quantitative Polymerase Chain Reaction (PCR) and Western blot were used to detect the protein and mRNA expression of IL-6, TNF-α, and IFN-γ in rat lymph nodes. In the EAN group, the infiltration of various types of inflammatory cells and focal demyelination were observed near the nerve fascicles of sciatic nerves. Compared with the EAN group, the infiltration of inflammatory cells and demyelination in the APELIN-13 group decreased significantly. The levels of plasma IL-6, TNF-α, and IFN-γ in the EAN group were significantly higher than those in the control group (P < 0.05) but significantly lower than those in the APELIN-13 group (P < 0.05). Compared with the control group, the mRNA and protein expression of IL-6, TNF-α, and IFN-γ increased significantly (P < 0.05) in the EAN group but decreased significantly in the APELIN-13 group (P < 0.05). In conclusion, APELIN-13 exerted a protective effect against EAN in rats.

NRG1 type I dependent autoparacrine stimulation of Schwann cells in onion bulbs of peripheral neuropathies.

In contrast to acute peripheral nerve injury, the molecular response of Schwann cells in chronic neuropathies remains poorly understood. Onion bulb structures are a pathological hallmark of demyelinating neuropathies, but the nature of these formations is unknown. Here, we show that Schwann cells induce the expression of Neuregulin-1 type I (NRG1-I), a paracrine growth factor, in various chronic demyelinating diseases. Genetic disruption of Schwann cell-derived NRG1 signalling in a mouse model of Charcot-Marie-Tooth Disease 1A (CMT1A), suppresses hypermyelination and the formation of onion bulbs. Transgenic overexpression of NRG1-I in Schwann cells on a wildtype background is sufficient to mediate an interaction between Schwann cells via an ErbB2 receptor-MEK/ERK signaling axis, which causes onion bulb formations and results in a peripheral neuropathy reminiscent of CMT1A. We suggest that diseased Schwann cells mount a regeneration program that is beneficial in acute nerve injury, but that overstimulation of Schwann cells in chronic neuropathies is detrimental.

Myelin Protein Zero180-199 Peptide Induced Experimental Autoimmune Neuritis in C57BL/6 Mice.

Mouse models of peripheral demyelinating neuropathy play an important role in enabling the study of disease pathogenesis. Further, induction in transgenic mice allows for the precise interrogation of disease mechanisms, as well as the analysis of the efficacy and mechanisms of potential new therapies. Here we describe a method to successfully induce experimental autoimmune neuritis (EAN) using myelin protein zero (P0)180-199 peptide in combination with Freund's complete adjuvant and pertussis toxin in the C57BL/6 mouse strain. We also outline a sensitive paradigm of accurately assessing the extent of functional deficits occurring in murine EAN.

Mitochondrial damage and "plugging" of transport selectively in myelinated, small-diameter axons are major early events in peripheral neuroinflammation.

BACKGROUND: Small-diameter, myelinated axons are selectively susceptible to dysfunction in several inflammatory PNS and CNS diseases, resulting in pain and degeneration, but the mechanism is not known. METHODS: We used in vivo confocal microscopy to compare the effects of inflammation in experimental autoimmune neuritis (EAN), a model of Guillain-Barré syndrome (GBS), on mitochondrial function and transport in large- and small-diameter axons. We have compared mitochondrial function and transport in vivo in (i) healthy axons, (ii) axons affected by experimental autoimmune neuritis, and (iii) axons in which mitochondria were focally damaged by laser induced photo-toxicity. RESULTS: Mitochondria affected by inflammation or laser damage became depolarized, fragmented, and immobile. Importantly, the loss of functional mitochondria was accompanied by an increase in the number of mitochondria transported towards, and into, the damaged area, perhaps compensating for loss of ATP and allowing buffering of the likely excessive Ca2+ concentration. In large-diameter axons, healthy mitochondria were found to move into the damaged area bypassing the dysfunctional mitochondria, re-populating the damaged segment of the axon. However, in small-diameter axons, the depolarized mitochondria appeared to "plug" the axon, obstructing, sometimes completely, the incoming (mainly anterograde) transport of mitochondria. Over time (~ 2 h), the transported, functional mitochondria accumulated at the obstruction, and the distal part of the small-diameter axons became depleted of functional mitochondria. CONCLUSIONS: The data show that neuroinflammation, in common with photo-toxic damage, induces depolarization and fragmentation of axonal mitochondria, which remain immobile at the site of damage. The damaged, immobile mitochondria can "plug" myelinated, small-diameter axons so that successful mitochondrial transport is prevented, depleting the distal axon of functioning mitochondria. Our observations may explain the selective vulnerability of small-diameter axons to dysfunction and degeneration in a number of neurodegenerative and neuroinflammatory disorders.

Enhanced glycolysis contributes to the pathogenesis of experimental autoimmune neuritis.

BACKGROUND: With the recognition of the key roles of cellular metabolism in immunity, targeting metabolic pathway becomes a new strategy for autoimmune disease treatment. Guillain-Barré syndrome (GBS) is an acute immune-mediated inflammatory demyelinating disease of the peripheral nervous system, characterized by inflammatory cell infiltration. These inflammatory cells, including activated macrophages, Th1 cells, and Th17 cells, generally undergo metabolic reprogramming and rely mainly on glycolysis to exert functions. This study aimed to explore whether enhanced glycolysis contributed to the pathogenesis of experimental autoimmune neuritis (EAN), a classic model of GBS. METHODS: Preventive and therapeutic treatments with glycolysis inhibitor, 2-deoxy-D-glucose (2-DG), were applied to EAN rats. The effects of treatments were determined by clinical scoring, weighting, and tissue examination. Flow cytometry and ELISA were used to evaluate T cell differentiation, autoantibody level, and macrophage functions in vivo and in vitro. RESULTS: Glycolysis inhibition with 2-DG not only inhibited the initiation, but also prevented the progression of EAN, evidenced by the improved clinical scores, weight loss, inflammatory cell infiltration, and demyelination of sciatic nerves. 2-DG inhibited the differentiation of Th1, Th17, and Tfh cells but enhanced Treg cell development, accompanied with reduced autoantibody secretion. Further experiments in vitro proved glycolysis inhibition decreased the nitric oxide production and phagocytosis of macrophages and suppressed the maturation of dendritic cells (DC). CONCLUSION: The effects of glycolysis inhibition on both innate and adaptive immune responses and the alleviation of animal clinical symptoms indicated that enhanced glycolysis contributed to the pathogenesis of EAN. Glycolysis inhibition may be a new therapy for GBS.

Inhibition of triggering receptor expressed on myeloid cells-1 ameliorates experimental autoimmune neuritis.

Experimental autoimmune neuritis (EAN) is a cluster of differentiation 4+ T helper 1 cell-mediated inflammatory demyelinating disease of the peripheral nervous system and serves as a useful animal model for Guillain­Barré syndrome. Triggering receptor expressed on myeloid cells­1 (TREM­1) is an important receptor involved in sepsis and the innate inflammatory response. Linear plasmid 17 (LP 17) peptide is a competitive antagonist of TREM­1. To investigate the role of TREM­1 in EAN, 64 male Lewis rats were randomly divided into four groups: Normal saline, complete Freund's adjuvant, EAN and LP 17. The present study assessed the mRNA expression levels of TREM­1, tumor necrosis factor­α and interleukin­1ß in sciatic nerves and peripheral blood mononuclear cells. The results demonstrated that inhibiting TREM-1 by administering LP 17 ameliorated symptoms and reduced inflammation in EAN rats. The present study concluded that TREM­1 may be involved in the pathogenesis of EAN, and that inhibition of TREM-1 may ameliorate EAN.

Toll-Like Receptor 2, Toll-Like Receptor 4, Myeloid Differentiation Response Gene 88, and Toll-IL-1 Receptor Domain-Containing Adaptor-Inducing Interferon-γ (TRIF) Selectively Regulate Susceptibility of P0106-125-Induced Murine Experimental Autoimmune Neuritis.

The functional relevance of the innate immune system has not yet been dissected in P0106-125-induced murine experimental autoimmune neuritis. Therefore, the role of Toll-like receptor (TLR) 2, TLR4, myeloid differentiation response gene 88, and Toll-IL-1 receptor domain-containing adaptor-inducing interferon-γ (TRIF), factors critically involved in the TLR signaling pathway, was studied in experimental autoimmune neuritis. In the absence of TLR2, TLR4, myeloid differentiation response gene 88, or TRIF, the clinical course was significantly attenuated compared to wild-type mice. This could be attributed to impaired NF-κB activation, as shown by the absence of nuclear translocation of RelA with a decreased expression of IL-6, IL-12p40, and IL-17A. Remarkably, P0106-125-immunized TLR20/0 mice exhibited a delayed recovery as compared to TLR40/0 mice, which was because of an impaired T helper cell 2 polarization. Immunized TLR20/0 mice were unable to induce OX40 and OX40L by matrix metalloproteinase-2 on splenic dendritic cells. Subsequently, M2 polarization was impaired and macrophages were unable to sufficiently induce T regulatory cells (Tregs). Thus, in the recovery phase, Tregs were significantly increased in TLR40/0 mice as compared to wild-type mice, whereas Tregs in immunized TLR20/0 mice were only slightly increased. Our data highlight the relevance of innate immunity and, especially, the tight interaction between the innate and the adaptive immune system, which should be considered for therapeutic approaches of autoimmune diseases.

Resolvin D1 Programs Inflammation Resolution by Increasing TGF-ß Expression Induced by Dying Cell Clearance in Experimental Autoimmune Neuritis.

UNLABELLED: Experimental autoimmune neuritis (EAN) is the animal model of human acute inflammatory demyelinating polyradiculoneuropathies (AIDP), an auto-immune inflammatory demyelination disease of the peripheral nervous system (PNS) and the world's leading cause of acute autoimmune neuromuscular paralysis. EAN and AIDP are characterized by self-limitation with spontaneous recovery; however, endogenous pathways that regulate inflammation resolution in EAN and AIDP remain elusive. A pathway of endogenous mediators, especially resolvins and clearance of apoptotic cells, may be involved. Here, we determined that resolvin D1 (RvD1), its synthetic enzyme, and its receptor were greatly increased in PNS during the recovery stage of EAN. Both endogenous and exogenous RvD1 increased regulatory T (Treg) cell and anti-inflammatory macrophage counts in PNS, enhanced inflammation resolution, and promoted disease recovery in EAN rats. Moreover, RvD1 upregulated the transforming growth factor-ß (TGF-ß) level and pharmacologic inhibition of TGF-ß signaling suppressed RvD1-induced Treg cell counts, but not anti-inflammatory macrophage counts, and RvD1-improved inflammation resolution and disease recovery in EAN rats. Mechanistically, the RvD1-enhanced macrophage phagocytosis of apoptotic T cells leading to reduced apoptotic T-cell accumulation in PNS induced TGF-ß production and caused Treg cells to promote inflammation resolution and disease recovery in EAN. Therefore, these data highlight the crucial role of RvD1 as an important pro-resolving molecule in EAN and suggest its potential as a therapeutic target in human neuropathies. SIGNIFICANCE STATEMENT: Experimental autoimmune neuritis (EAN) is the animal model of human acute inflammatory demyelinating polyradiculoneuropathies, an auto-immune inflammatory demyelination disease of the peripheral nervous system (PNS) and the world's leading cause of acute autoimmune neuromuscular paralysis. Here, we demonstrated that resolvin D1 (RvD1) promoted macrophage phagocytosis of apoptotic T cells in PNS, thereby upregulating transforming growth factor-ß by macrophages, increased local Treg cell counts, and finally promoted inflammation resolution and disease recovery in EAN. These data highlight the crucial role of RvD1 as an important pro-resolving molecule in EAN and suggest that it has potential as a therapeutic target in human neuritis.

Dimethyl fumarate attenuates experimental autoimmune neuritis through the nuclear factor erythroid-derived 2-related factor 2/hemoxygenase-1 pathway by altering the balance of M1/M2 macrophages.

BACKGROUND: Guillain-Barré syndrome (GBS) is an acute, post-infectious, immune-mediated, demyelinating disease of peripheral nerves and nerve roots. Dimethyl fumarate (DMF), a fumaric acid ester, exhibits various biological activities, including multiple immunomodulatory and neuroprotective effects. However, the potential mechanism underlying the effect of DMF in GBS animal model experimental autoimmune neuritis (EAN) is unclear. METHODS: Using EAN, an established GBS model, we investigated the effect of DMF by assessing clinical score, histological staining and electrophysiological studies. Then, we further explored the potential mechanism by Western blot analysis, flow cytometry, fluorescence immunohistochemistry, PCR, and ELISA analysis. The Mann-Whitney U test was used to compare differences between control group and treatment groups where appropriate. RESULTS: DMF treatment reduced the neurological deficits by ameliorating inflammatory cell infiltration and demyelination of sciatic nerves. In addition, DMF treatment decreased the level of pro-inflammatory M1 macrophages while increasing the number of anti-inflammatory M2 macrophages in the spleens and sciatic nerves of EAN rats. In RAW 264.7, a shift in macrophage polarization from M1 to M2 phenotype was demonstrated to be depended on DMF application. In sciatic nerves, DMF treatment elevated the level of the antioxidant transcription factor nuclear factor erythroid-derived 2-related factor 2 (Nrf2) and its target gene hemoxygenase-1 (HO-1) which could facilitate macrophage polarization toward M2 type. Moreover, DMF improved the inflammatory milieu in spleens of EAN rats, characterized by downregulation of messenger RNA (mRNA) of IFN-γ, TNF-α, IL-6, and IL-17 and upregulation of mRNA level of IL-4 and IL-10. CONCLUSIONS: Taken together, our data demonstrate that DMF can effectively suppress EAN, and the mechanism involves altering the balance of M1/M2 macrophages and attenuating inflammation.

RAD001 (everolimus) attenuates experimental autoimmune neuritis by inhibiting the mTOR pathway, elevating Akt activity and polarizing M2 macrophages.

Guillain-Barre' syndrome (GBS) is an acute, postinfectious, immune-mediated, demyelinating disease of peripheral nerves and nerve roots. As a classical animal model of GBS, experimental autoimmune neuritis (EAN) has become well-accepted. Additionally, the potent immune modulation exerted by mammalian target of rapamycin (mTOR) inhibitors has been used to treat cancers and showed beneficial effects. Here we demonstrate that the mTOR inhibitor RAD001 (everolimus) protected rats from the symptoms of EAN, as shown by decreased paralysis, diminished inflammatory cell infiltration, reductions in demyelination of peripheral nerves and improved nerve conduction. Furthermore, RAD001 shifted macrophage polarization toward the protective M2 phenotype and modified the inflammatory milieu by downregulating the production of pro-inflammatory cytokines including IFN-γ and IL-17as well as upregulating the release of anti-inflammatory cytokines such as IL-4 and TGF-ß. Amounts of the mTOR downstream targets p-P70S6K and p-4E-BP1 in sciatic nerves decreased, whereas the level of its upstream protein p-Akt was elevated. This demonstrated that RAD001 inhibited the mTOR pathway and encouraged the expression of p-Akt, which led to M2 macrophage polarization, thus improved the outcome of EAN in rats. Consequently, RAD001 exhibits strong potential as a therapeutic strategy for ameliorating peripheral poly-neuropathy.

Activation of the adenosine A2A receptor exacerbates experimental autoimmune neuritis in Lewis rats in association with enhanced humoral immunity.

Accumulated evidence demonstrated that Adenosine A2A receptor (A2AR) is involved in the inflammatory diseases. In the present study, we showed that a selective A2AR agonist, CGS21680, exacerbated experimental autoimmune neuritis in Lewis rats induced with bovine peripheral myelin. The exacerbation was accompanied with reduced CD4(+)Foxp3(+) T cells, increased CD4(+)CXCR5(+) T cells, B cells, dendritic cells and antigen-specific autoantibodies, which is possibly due to the inhibition of IL-2 induced by CGS21680. Combined with previous studies, our data indicate that the effects of A2AR stimulation in vivo are variable in different diseases. Caution should be taken in the use of A2AR agonists.

Lesional accumulation of CD8(+) cells in sciatic nerves of experimental autoimmune neuritis rats.

Experimental autoimmune neuritis (EAN) is a well-known animal model of human demyelinating polyneuropathies. Macrophages are the major immune cells in peripheral nerves and may exert tissue-damage or tissue-protective activity during EAN. While considered to define a subpopulation of T lymphocytes, CD8 expression has been found on certain macrophages that show cytotoxic effects. Here we have studied the spatiotemporal accumulation of CD8(+) cells in sciatic nerves of EAN rats. A robust accumulation of CD8(+) cells was observed in the sciatic nerves of EAN rats, which was positively correlated with the severity of neurological signs in EAN. Moreover, double-labelling experiments showed that the major cellular sources of CD8 were reactive macrophages. Therefore, our data here suggest a pathological role of CD8(+) macrophages in EAN, which makes CD8(+) macrophage a potential therapeutic target for EAN.

Myelin ultrastructure of sciatic nerve in rat experimental autoimmune neuritis model and its correlation with associated protein expression.

To explore the relationship of peripheral nerve ultrastructure and its associated protein expression in experimental autoimmune neuritis (EAN). EAN was established in Lewis rats using an emulsified mixture of P0 peptide 180-199, Mycobacterium tuberculosis, and incomplete Freund's adjuvant. Rats immunized with saline solution were used as a control group. Sciatic nerve ultrastructure and immunofluorescence histopathology were measured at the neuromuscular severity peak on day 18 post-induction. Cell-specific protein markers were used for immunofluorescence histopathology staining to characterize sciatic nerve cells: CD3 (T cell), Iba-1 (microglia), S100 (myelin), and neurofilament 200 (axon). The results showed that swelling of the myelin lamellae, vesicular disorganization, separation of the myelin lamellae, and an attenuation or disappearance of the axon were observed by transmission electron microscopy in the EAN group. CD3 and Iba-1 increased significantly in the structures characterized by separation or swelling of the myelin lamellae, and increased slightly in the structures characterized by vesicular of the myelin lamellae, S100 decreased in the structures characterized by vesicular disorganization or separation of the myelin lamellae. And neurofilament 200 decreased in the structures characterized by separation of the myelin lamellae. Furthermore, we found that Iba1 were positive in the myelin sheath, and overlapped with S100, which significantly indicated that Schwann cells played as macrophage-like cells during the disease progression of ENA. Our findings may be a significant supplement for the knowledge of EAN model, and may offer a novel sight on the treatment of Guillain-Barré syndrome.

MiR-125a targets effector programs to stabilize Treg-mediated immune homeostasis.

Although different autoimmune diseases show discrete clinical features, there are common molecular pathways intimately involved. Here we show that miR-125a is downregulated in peripheral CD4(+) T cells of human autoimmune diseases including systemic lupus erythematosus and Crohn's disease, and relevant autoimmune mouse models. miR-125a stabilizes both the commitment and immunoregulatory capacity of Treg cells. In miR-125a-deficient mice, the balance appears to shift from immune suppression to inflammation, and results in more severe pathogenesis of colitis and experimental autoimmune encephalomyelitis (EAE). The genome-wide target analysis reveals that miR-125a suppresses several effector T-cell factors including Stat3, Ifng and Il13. Using a chemically synthesized miR-125a analogue, we show potential to re-programme the immune homeostasis in EAE models. These findings point to miR-125a as a critical factor that controls autoimmune diseases by stabilizing Treg-mediated immune homeostasis.

Retinoic acid receptor stimulation ameliorates experimental autoimmune optic neuritis.

BACKGROUND: To determine whether all-trans retinoic acid or a synthetic retinoic acid receptor-α/ß-specific agonist, Am80, can reduce the degree of experimental autoimmune optic neuritis in mice with experimental autoimmune encephalomyelitis. METHODS: Optic neuritis was induced in C57BL/6 mice by immunizing them with myelin oligodendrocyte glycoprotein35-55 . All-trans retinoic acid (350 µg/mouse/time point) or Am80 (5 mg/kg/time point) was administered every other day from day 0 to day 20. The degree of experimental autoimmune encephalomyelitis was scored and histopathological analysis of the optic neuritis was performed on day 22 after the immunization. In vivo-primed draining lymph node cells obtained from vehicle-treated or all-trans retinoic acid-treated mice were stimulated with myelin oligodendrocyte glycoprotein35-55 , and the culture supernatant was collected for assays of interferon-γ and interleukin-17. RESULTS: All-trans retinoic acid treatment significantly reduced the clinical score of experimental autoimmune encephalomyelitis and the severity of the optic neuritis by histopathological analysis. The production of interferon-γ and interleukin-17 was significantly reduced in all-trans retinoic acid-treated mice compared with vehicle-treated mice. Am80 treatment also significantly decreased the severity of the optic neuritis in mice with experimental autoimmune encephalomyelitis. CONCLUSIONS: These findings demonstrate that all-trans retinoic acid and Am80 treatment were able to reduce the severity of optic neuritis in mice with experimental autoimmune encephalomyelitis. Activation of retinoic acid receptor-α/ß may be a molecular target for the treatment of autoimmune optic neuritis induced by Th1 or Th17-dominated immune responses.