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.

Parthenolide inhibits the initiation of experimental autoimmune neuritis.

A growing body of evidence suggests the anti-inflammatory and antitumor effects of parthenolide (PAR). Here we show that PAR treatment inhibits the initiation of experimental autoimmune neuritis (EAN), suppresses the production of TNF-α, IFN-γ, IL-1ß and IL-17, and decreases Th1 and Th17 cells at early time point. However, such anti-inflammatory effect vanishes later and PAR impedes the recovery of EAN in late phase, which is accompanied with inhibited apoptosis of inflammatory cells. Our results indicate that PAR plays dual roles in EAN and it is not proper to be applied in autoimmune diseases of nervous system.

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.

Suppression of experimental autoimmune optic neuritis by the novel agent fingolimod.

PURPOSE: Fingolimod is an immunomodulating agent that has been approved for the treatment of multiple sclerosis. Fingolimod-phosphate is an antagonist of sphingosine-1-phosphate receptor and known to act by preventing infiltration of autoreactive lymphocytes into the central nervous system. In this study, we investigated whether fingolimod prevents experimental autoimmune optic neuritis (EAON). METHODS: EAON was induced by immunizing C57BL/6 mice with myelin oligodendrocyte glycoprotein-derived peptide 35-55 (MOG-p). After MOG-p immunization, fingolimod was administered intragastrically from day 1 (entire phase study) or from day 9 (effector phase study) until day 35. Visual acuity of the mice was measured using OptoMotry on days 7, 14, 21, 28, and 35 after immunization. On day 35 after immunization, the mice were killed and eyes and entire length of the optic nerves were submitted for histopathologic evaluation. RESULTS: In the positive control group, visual acuity decreased markedly from approximately day 14 after immunization, reaching a nadir on day 21. In the fingolimod-treated groups in both entire phase and effector phase studies, there was only minimal decline in visual acuity on day 14 after immunization, and mild deterioration on day 21, followed by recovery. Histopathologic study showed that fingolimod given throughout the entire phase or only from the effector phase suppressed murine EAON. Immunohistochemical study for neurofilament demonstrated no irregularity of the linear structure of the optic nerve in the fingolimod-treated mice compared with the positive control group. CONCLUSION: Fingolimod ameliorated EAON even when started after optic neuritis had developed. Further study is warranted to examine whether these findings are applicable to human disease.

Analysis of the pathogenesis of experimental autoimmune optic neuritis.

Optic neuritis associated with multiple sclerosis has a strong association with organ-specific autoimmune disease. The goal of our research is to establish an optimal organ-specific animal model to elucidate the pathogenetic mechanisms of the disease and to develop therapeutic strategies using the model. This paper is divided into five sections: (1) clinical picture of optic neuritis associated with multiple sclerosis, (2) elucidation of pathogenesis using animal models with inflammation in optic nerve and spinal cord, (3) clinical relevance of concurrent encephalomyelitis in optic neuritis model, (4) retinal damage in a concurrent multiple sclerosis and optic neuritis model, and (5) development of novel therapies using mouse optic neuritis model. Advanced therapies using biologicals have succeeded to control intractable optic neuritis in animal models. This may ultimately lead to prevention of vision loss within a short period from acute onset of optic neuritis in human. By conducting research flexibly, ready to switch from the bench to the bedside and from the bedside to the bench as the opportunity arises, this strategy may help to guide the research of optic neuritis in the right direction.

Administration of dehydroepiandrosterone ameliorates experimental autoimmune neuritis in Lewis rats.

Dehydroepiandrosterone (DHEA) is an abundant adrenal steroid in serum of humans, and has been reported to have anti-inflammatory, anti-proliferative, and certain immune-regulating properties. Experimental autoimmune neuritis (EAN) is a Th1 cell-mediated animal model of Guillain-Barré syndrome (GBS) in humans. In the present study, DHEA was administered subcutaneously to Lewis rats immunized with bovine peripheral myelin (BPM) in Freund's complete adjuvant. Rats treated with DHEA displayed significant delay in onset, decreased inflammatory cell infiltration in the PNS. Benefit was associated with significant decreases in numbers of IFN-gamma and TNF-alpha expressing cells in the PNS, BPM-stimulated T cell proliferation and IFN-gamma, TNF-alpha-secretion in the spleen cells. Only 2 mg DHEA-treated EAN rats decreased peak clinical score. No significant difference of supernatant IL-10 was found among the treatment and control groups. These results suggest that DHEA can ameliorate the severity of EAN by suppressing the proliferation of autoreactive T cell and expression of pro-inflammatory cytokines.

A human anti-neuronal autoantibody against GABA B receptor induces experimental autoimmune agrypnia.

In the serum and cerebrospinal fluid of a patient with recurrent acute episodes of respiratory crises, autonomic symptoms and total insomnia (agrypnia), we identified a novel anti-neural complement fixing antibody directed against GABA(B) receptor (GABA(B)R). Patient purified IgG recognized a band of approximately 110 kDa on protein extracts of mouse cerebellum, cortex and brainstem and immunolabelled cultured Chinese hamster ovary (CHO) cells, transfected with human GABA(B)R1 and rat GABA(B)R2 receptors. Western blot analysis of transfected CHO homogenates showed the same band using both patient purified IgG and anti-GABA(B)R1 antibody. In order to verify the pathogenic role of these purified antibodies, we injected patient IgG intrathecally into cisterna magna of C57BL/6 mice pre-implanted with EEG electrodes and we observed severe ataxia followed by breathing depression and total suppression of slow wave sleep, as evidenced by EEG recording, in a dose-dependent manner. Immunohistochemistry on brain sections of mice injected with patient IgG showed the simultaneous presence of bound human IgG and C5b-9 deposits on Purkinje cells and cerebellar granular layer. After incubation with anti-GABA(B)R antibody, a marked reduction of receptor immunostaining was found with relative sparing of neuronal architecture. In conclusion we recognized an anti-neuronal autoantibody directed against GABA(B)R that is associated with autoimmune agrypnia and we showed that our patient purified IgG was able to induce in mice experimental autoimmune agrypnia characterized by a complex neurological syndrome affecting several CNS functions.

Immunolocalization and activation of nuclear factor-kappaB in the sciatic nerves of rats with experimental autoimmune neuritis.

Recent data support an important role played by nuclear factor kappa B (NF-kappaB) in peripheral neuropathies. We investigated expression and activation of NF-kappaB in experimental autoimmune neuritis (EAN) in rat sciatic nerves removed after 7, 14 and 21 days after immunization. Immunoreactivity for the activated form of NF-kappaB was found in the nuclei of T cells and macrophages at days 14 and 21, and also in the nuclei of few Schwann cells and of vascular endothelial cells at all time points, especially during the peak stage. Western blot showed a single band corresponding to 65 kDa in all EAN animals. NF-kappaB DNA-binding activity was revealed by electrophoretic mobility shift assay. Our results support NF-kappaB activation in EAN during the induction stage as well as in the disease remission.

Inhibition of Ras attenuates the course of experimental autoimmune neuritis.

EAN induced in Lewis rats by immunization with peripheral bovine myelin was treated by the Ras inhibitor farnesylthiosalicylate (FTS). Treatment from day 0 with FTS (5 mg/kg intraperitoneally twice daily) attenuated peak clinical scores (mean+/-S.E., 2.5+/-0.5 compared to 4.1+/-0.5 in saline treated controls, p=0.018, t-test) but not recovery. Treatment from day 10 with FTS attenuated peak disability (2.5+/-0.6, p=0.032 compared to saline treated controls) and improved recovery (0.84+/-0.42, untreated controls 2.4+/-0.6, p=0.028 by repeated measures ANOVA). Effects were confirmed by rotarod and nerve conduction studies. An inactive analogue, geranylthiosalicylate, had no clinical effect. Inhibition of Ras is of potential use in the treatment of inflammatory neuropathies.

Heterozygous null mutation of myelin P0 protein enhances susceptibility to autoimmune neuritis targeting P0 peptide.

Mice with a heterozygous null mutation in myelin protein zero (P0(+/-)) develop late-onset clinical paralysis associated with inflammatory pathology in the peripheral nerves. Although the development of this illness is known to require T cells and macrophages, little is understood regarding the immunological defect in the mice. Here we report that young P0(+/-) mice, free from clinical manifestations, have a defect in central tolerance to P0, and are more prone to induction of experimental autoimmune neuritis (EAN) by sensitization against P0(180-199 )peptide. Notably, we found that the P0 gene is transcribed in the thymus of wild-type and the P0(+/-) mice in an amount proportional to the gene dosage. We then replaced the thymus of wild-type mice with that of the P0-deficient mice and vice versa. Immunization of these mice with P0(180-199 )revealed that a lower thymic P0 transcript would be associated with the higher recall T cell response to P0(180-199), thus accounting for the higher susceptibility of the P0(+/-) mice to P0-induced EAN. These results imply that a heterozygous mutation in an autoantigen could cause defective central tolerance to the autoantigen. As such, autoimmune T cells may play some role in "genetic" diseases caused by a heterozygous gene defect.

[Guillain-Barre syndrome: etiology and pathogenesis]. / Síndrome de Guillain-Barré: etiología y patogénesis.

Guillain-Barre syndrome (GBS) is a reactive, self-limited, monophasic disease triggered by a preceding bacterial or viral infection. GBS has also been linked to underlying systemic diseases, certain malignancies, surgery, pregnancy, trauma severe infection, and tissue transplantation (bone marrow and organs). Although its pathogenesis is unclear, it is likely to be a consequence of an immune mediated process. Therefore, we believe that GBS results from an aberrant immune response that somehow mistakenly attacks the nerve tissue of its host, most probably by recognizing a molecular similar epitope mechanism (molecular mimicry). Immune reactions against these epitopes result in acute inflammatory demyelinating neuropathy or acute axonal forms. GBS has a worldwide distribution with an annual incidence of approximately 1.2-8.6 cases per 100,000 people. Both genders are at similar risk (but there is a slight male predominance). All ages are affected, although the distribution is bimodal. The supporting measures are critically important to provide optimal treatment. Immunomodulation with plasma exchange and intravenous immunoglobulin treatments shorten the disease course. Outcome is generally good, with virtually full recovery in 70-80% of the patients. In this review physiopathological aspects and clinical implications of GBS are fully discussed.

Síndrome de Guillain-Barré: etiología y patogénesis / Guillain-Barre syndrome: etiology and pathogenesis

Guillain-Barre syndrome (GBS) is a reactive, self-limited, monophasic disease triggered by a preceding bacterial or viral infection. GBS has also been linked to underlying systemic diseases, certain malignancies, surgery, pregnancy, trauma severe infection, and tissue transplantation (bone marrow and organs). Although its pathogenesis is unclear, it is likely to be a consequence of an immune mediated process. Therefore, we believe that GBS results from an aberrant immune response that somehow mistakenly attacks the nerve tissue of its host, most probably by recognizing a molecular similar epitope mechanism (molecular mimicry). Immune reactions against these epitopes result in acute inflammatory demyelinating neuropathy or acute axonal forms. GBS has a worldwide distribution with an annual incidence of approximately 1.2-8.6 cases per 100,000 people. Both genders are at similar risk (but there is a slight male predominance). All ages are affected, although the distribution is bimodal. The supporting measures are critically important to provide optimal treatment. Immunomodulation with plasma exchange and intravenous immunoglobulin treatments shorten the disease course. Outcome is generally good, with virtually full recovery in 70-80 of the patients. In this review physiopathological aspects and clinical implications of GBS are fully discussed.

Intranasal administration of recombinant mouse interleukin-12 increases inflammation and demyelination in chronic experimental autoimmune neuritis in Lewis rats.

To examine whether interleukin (IL)-12 modulates ongoing chronic experimental autoimmune neuritis (EAN), we evaluated the effects of recombinant mouse IL-12 (rmIL-12) in Lewis rats with chronic EAN, induced by immunization with P0 peptide (180-199) plus complete Freund's adjuvant. Rats were treated intranasally with either 0.1 or 1 microg/rat/day rmIL-12 for 6 days from the onset of clinical chronic EAN, on days 5-10 postimmunization (p.i.). Only high-dose rmIL-12 exacerbated chronic EAN. This clinical effect was associated with higher numbers of inflammatory cells and more severe demyelination in sciatic nerve sections on days 15 and 80 p.i. compared with low-dose rmIL-12-treated rats and phosphate-buffered saline (PBS)-treated control rats. High-dose rmIL-12 increased significantly the lymph node mononuclear cell proliferation in response to P0 peptide 180-199 and IFN-gamma production in the sciatic nerves. These data indicate that intranasally administered IL-12 acts as a proinflammatory cytokine in chronic EAN. Effective inhibition of IL-12 in vivo could be considered for therapeutic use in chronic inflammatory demyelinating polyradiculoneuropathy.

Depletion of Vbeta4 TCR does not induce resistance to EAN--further evidence for diversity of TCR usage.

In EAN, TCR variable (V) gene usage is still controversial. A dominant usage of a TCR Vbeta4-associated idiotype has been reported. To assess the role of TCR Vbeta4 positive T-cells in susceptibility to induction of EAN, we suppressed the selection of this idiotype by neonatal treatment of Lewis rats with anti-TCR Vbeta4 monoclonal antibody (mAb). Anti-Vbeta4 treatment had no effect on development of clinical disease after immunization with the neuritogenic P2-peptide amino acids (aa) 53-78. Furthermore, lymph node cells from anti-Vbeta4 treated animals isolated after immunization with P2-peptide did not exhibit a reduced proliferative response towards whole P2-protein or P2-peptide. Our results indicate that T-cells utilizing other TCR V chains can functionally replace the neuritogenic cell population, which is dominant in stable T-cell lines.

Restimulation of resting autoreactive T cells by Schwann cells in vitro.

This study demonstrates that rat Schwann cells can reactivate resting experimental allergic neuritis generating P(2) and P(2) peptide specific CD4(+) T cell lines. T cell proliferation was significantly greater to P(2) than to P(2) peptide (SP-26) or ovalbumin (OA). Four-level analysis of variance showed that T cell proliferation with endogenous or exogenous P(2) was not significantly different for Schwann cells plus cytokine IFN-gamma (P = 0.5071) unlike P(2) peptide or OA specific T cells (P = 0.0056 and 0.0003, respectively). Untreated Schwann cells were more effective inducers than irradiated or fixed Schwann cells. As stimulated CD4(+) P(2) T cells produce IFN-gamma and TNF-alpha, this could exacerbate blood nerve barrier breakdown that has been increasingly implicated in inflammatory demyelinating neuropathies (IDNs). This would permit entry of antibodies and complement, thereby contributing to the demyelination process. Schwann cell induced reactivation of CD4(+) T cells may therefore play a role in IDNs.

Resistance and susceptibility to experimental autoimmune neuritis in Sprague-Dawley and Lewis rats correlate with different levels of autoreactive T and B cell responses to myelin antigens.

Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various mouse and rat strains show different susceptibilities to EAN that can be induced by immunization with bovine PNS myelin (BPM) + Freund's complete adjuvant (FCA). We examined PNS-induced T and B cell responses and cytokine protein production as well as mRNA expression to study the mechanisms behind susceptibility to EAN in Lewis rats and resistance in Sprague-Dawley (SD) rats. Lewis rats with EAN have elevated PNS myelin-reactive interferon-gamma (IFN-gamma) production, TNF-alpha mRNA expression, and increased B cell responses to PNS myelin antigens, but low PNS myelin-reactive transforming growth factor-beta (TGF-beta) and interleukin (IL)-10 mRNA expression in lymph node mononuclear cells (MNC). In contrast, resistance to EAN in SD rats is associated with reduced BPM and P2 peptide-reactive IFN-gamma production, TNF-alpha mRNA expression, and suppressed B cell responses to PNS myelin antigens as well as up-regulation of TGF-beta and IL-10 mRNA expression. Resistance to EAN is also associated with low-grade inflammation or absence of histological evidence of EAN. These results suggest that differential autoreactive T and B cells responses to PNS myelin antigens are strain specific, and the susceptibility to EAN is related to quantitative rather than qualitative differences in distribution between proinflammatory and anti-inflammatory cytokines.

Thalidomide suppresses T- and B-cell responses to myelin antigen in experimental allergic neuritis.

The effects of thalidomide and, for reference, dexamethasone on T- and B-cell functions were assayed in vitro in Lewis rats with experimental allergic neuritis induced by active immunization with bovine peripheral nerve myelin (BPM) and complete Freund's adjuvant. Thalidomide and dexamethasone at the concentration ranges 10(-5)-10(-7) g/ml and 4 x 10(-5)-4 x 10(-9) g/ml, respectively, both inhibited phytohemagglutinin (PHA)- and BPM-induced T-cell proliferation as well as levels of PHA- and BPM-reactive interferon (IFN)-gamma-secreting cells, reflecting the suppression of Th1-like cells. The effect of dexamethasone was most pronounced on PHA-induced T-cell proliferation and IFN-gamma secretion, whereas the effect of thalidomide was most pronounced on BPM-induced T-cell proliferation and IFN-gamma secretion. Thalidomide reduced the B-cell responses to both BPM and Mycobacterium tuberculosis purified protein derivative, but to a lesser extent than dexamethasone. The in vitro design described could be useful to evaluate compounds with putative immunomodulatory activities. The inhibitory effects of thalidomide on autoantigen-induced Th1-cell functions may warrant the use of this substance in T-cell-mediated autoimmune diseases.

Guillain-Barré as an autoimmune disease.

Guillain-Barré syndrome (GBS) entails a demyelinating process of the peripheral nervous system. The etiopathogenesis of the syndrome is still a matter of debate although considerable progress has been accomplished in the recent years. Abundant evidence has been put forward so as to support the role of the immune system in initiating and perpetuating the ongoing damage culminating in the emergence of the clinically overt syndrome. As such, data on the involvement of the humoral immune pathways add to the information already presented with regard to cell-mediated mechanisms participating in disruption of peripheral nerve. The following review will focus on the current knowledge of these complex mechanisms and the relative significance of each in the pathogenesis of GBS.

Synergy between antibody and P2-reactive T cells in experimental allergic neuritis.

Studies were conducted in experimental allergic neuritis (EAN) to evaluate the possible interaction of cellular and humoral immune mechanisms in the demyelinating process. EAN was induced in Lewis rats by passive transfer of T cells reactive to P2 myelin protein or by active immunisation with whole myelin. Animals were then given systemic antimyelin antibody or control serum and assessed clinically, electrophysiologically and with semiquantitative histological studies. Animals given intraperitoneal (i.p.) P2-reactive T cells and systemic antimyelin antibody developed much more severe disease than those given i.p. T cells alone (P < 0.001). In actively immunised animals, the addition of systemic antimyelin antibody did not significantly alter disease severity. We believe the more severe disease in animals receiving T cells and antimyelin antibody reflects synergy between cellular and humoral immune mechanisms whereby neural antigen-specific T cells breach the blood-nerve barrier, allowing demyelinating antibody access to the endoneurium. In EAN induced by active immunisation with whole myelin it is likely that both B and T cell activation occurs and that the more severe demyelination characteristic of this disease reflects the involvement of both humoral and cellular immunity.