FTY720 attenuates lesional interleukin-17(+) cell accumulation in rat experimental autoimmune neuritis

P2X7 receptor antagonists modulate experimental autoimmune neuritis via regulation of NLRP3 inflammasome activation and Th17 and Th1 cell differentiation

BACKGROUND

Guillain-Barré syndrome (GBS), a post-infectious, immune-mediated, acute demyelinating disease of the peripheral nerves and nerve roots, represents the most prevalent and severe acute paralyzing neuropathy. Purinergic P2X7 receptors (P2X7R) play a crucial role in central nervous system inflammation. However, little is known about their role in the immune-inflammatory response within the peripheral nervous system.

METHODS

Initially, we assessed the expression of purinergic P2X7R in the peripheral blood of patients with GBS using flow cytometry and qRT-PCR. Next, we explored the expression of P2 X7R in CD4+ T cells, CD8+ T cells, and macrophages within the sciatic nerves and spleens of rats using immunofluorescence labeling and flow cytometry. The P2X7R antagonist brilliant blue G (BBG) was employed to examine its therapeutic impact on rats with experimental autoimmune neuritis (EAN) induced by immunization with the P0180 - 199 peptide. We analyzed CD4+ T cell differentiation in splenic mononuclear cells using flow cytometry, assessed Th17 cell differentiation in the sciatic nerve through immunofluorescence staining, and examined the expression of pro-inflammatory cytokine mRNA using RT-PCR. Additionally, we performed protein blotting to assess the expression of P2X7R and NLRP3-related inflammatory proteins within the sciatic nerve. Lastly, we utilized flow cytometry and immunofluorescence labeling to examine the expression of NLRP3 on CD4+ T cells in rats with EAN.

RESULTS

P2X7R expression was elevated not only in the peripheral blood of patients with GBS but also in rats with EAN. In rats with EAN, inhibiting P2X7R with BBG alleviated neurological symptoms, reduced demyelination, decreased inflammatory cell infiltration of the peripheral nerves, and improved nerve conduction. BBG also limited the production of pro-inflammatory molecules, down-regulated the expression of P2X7R and NLRP3, and suppressed the differentiation of Th1 and Th17 cells, thus protecting against EAN. These effects collectively contribute to modifying the inflammatory environment and enhancing outcomes in EAN rats.

CONCLUSIONS

Suppression of P2X7R relieved EAN manifestation by regulating CD4+ T cell differentiation and NLRP3 inflammasome activation. This finding underscores the potential significance of P2X7R as a target for anti-inflammatory treatments, advancing research and management of GBS.

Biological analysis of the potential pathogenic mechanisms of Infectious COVID-19 and Guillain-Barré syndrome

Background

Guillain-Barré syndrome (GBS) is a medical condition characterized by the immune system of the body attacking the peripheral nerves, including those in the spinal nerve roots, peripheral nerves, and cranial nerves. It can cause limb weakness, abnormal sensations, and facial nerve paralysis. Some studies have reported clinical cases associated with the severe coronavirus disease 2019 (COVID-19) and GBS, but how COVID-19 affects GBS is unclear.

Methods

We utilized bioinformatics techniques to explore the potential genetic connection between COVID-19 and GBS. Differential expression of genes (DEGs) related to COVID-19 and GBS was collected from the Gene Expression Omnibus (GEO) database. By taking the intersection, we obtained shared DEGs for COVID-19 and GBS. Subsequently, we utilized bioinformatics analysis tools to analyze common DEGs, conducting functional enrichment analysis and constructing Protein-protein interaction networks (PPI), Transcription factors (TF) -gene networks, and TF-miRNA networks. Finally, we validated our findings by constructing the Receiver Operating Characteristic (ROC) curves.

Results

This study utilizes bioinformatics tools for the first time to investigate the close genetic relationship between COVID-19 and GBS. CAMP, LTF, DEFA1B, SAMD9, GBP1, DDX60, DEFA4, and OAS3 are identified as the most significant interacting genes between COVID-19 and GBS. In addition, the signaling pathway of NOD-like receptors is believed to be essential in the link between COVID-19 and GBS.

Is there a causal nexus between COVID-19 infection, COVID-19 vaccination, and Guillain-Barré syndrome?

Guillain-Barré syndrome (GBS) is an immune-mediated inflammatory polyradiculoneuropathy, which commonly leads to a very high level of neurological disability. Especially, after the global outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the causation between GBS and SARS-CoV-2 infection and the coronavirus disease 2019 (COVID-19) vaccination have aroused widespread concern. In the review, we analyzed the impacts of SARS-CoV-2 infection and COVID-19 vaccination on GBS globally, aiming to further understand the characteristics of GBS associated with COVID-19. Based on the electrophysiological data, patients suffering from GBS related to COVID-19 manifested as an acute inflammatory demyelinating polyneuropathy (AIDP). Moreover, we summarized the current findings, which may evidence GBS linking to SARS-CoV-2 infection and COVID-19 vaccination, and discussed the underlying mechanisms whether and how the SARS-CoV-2 virus and COVID-19 vaccination can induce GBS and its variants.

Siponimod ameliorates experimental autoimmune neuritis

BACKGROUND

Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP) are human autoimmune peripheral neuropathy. Besides humoral immunity, cellular immunity is also believed to contribute to these pathologies, especially CIDP. Sphingosine-1-phosphate receptor 1 (S1PR1) regulates the maturation, migration, and trafficking of lymphocytes. As of date, the therapeutic effect of sphingosine-1-phosphate receptor (S1PR) agonists on patients with GBS or CIDP remains unclear.

METHODS

To evaluate the effect of siponimod, an agonist of S1PR1 and S1PR5, on experimental autoimmune neuritis (EAN), an animal model of autoimmune peripheral neuropathy, was used. Lewis rats were immunized with 125 μg of synthetic peptide from bovine P2 protein. Rats in the siponimod group were orally administered 1.0 mg/kg siponimod and those in the EAN group were administrated the vehicle on days 5-27 post-immunization (p.i.) daily. The symptom severity was recorded daily. The changes in the expression of cytokines and transcription factors in the lymph nodes and cauda equina (CE) which correlate with the pathogenesis of EAN and recovery of injured nerve were measured using reverse transcription quantitative PCR. Histological study of CE was also performed.

RESULTS

Flaccid paralysis developed on day 11 p.i. in both groups. Siponimod relieved the symptom severity and decreased the expression of interferon-gamma and IL-10 mRNAs in lymph nodes and CE compared with that in the EAN group. The expression of Jun proto-oncogene (c-Jun) mRNA increased from the peak to the recovery phase and that of Sonic hedgehog signaling molecule (Shh) and Glial cell line-derived neurotrophic factor (Gdnf) increased prior to increase in c-Jun with no difference observed between the two groups. Histologically, siponimod also reduced demyelinating lesions and inflammatory cell invasion in CE.

CONCLUSIONS

Siponimod has a potential to ameliorate EAN. Shh and Gdnf, as well as C-Jun played a significant role during the recovery of injured nerves.

Repurposing MS immunotherapies for CIDP and other autoimmune neuropathies: unfulfilled promise or efficient strategy?

Despite advances in the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and other common autoimmune neuropathies (AN), still-many patients with these diseases do not respond satisfactorily to the available treatments. Repurposing of disease-modifying therapies (DMTs) from other autoimmune conditions, particularly multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), is a promising strategy that may accelerate the establishment of novel treatment choices for AN. This approach appears attractive due to homologies in the pathogenesis of these diseases and the extensive post-marketing experience that has been gathered from treating MS and NMOSD patients. The idea is also strengthened by a number of studies that explored the efficacy of DMTs in animal models of AN but also in some CIDP patients. We here review the available preclinical and clinical data of approved MS therapeutics in terms of their applicability to AN, especially CIDP. Promising therapeutic approaches appear to be B cell-directed and complement-targeting strategies, such as anti-CD20/anti-CD19 agents, Bruton's tyrosine kinase inhibitors and anti-C5 agents, as they exert their effects in the periphery. This is a major advantage because, in contrast to MS, their action in the periphery is sufficient to exert significant immunomodulation.

Sphingosine-1-phosphate receptor modulators in stroke treatment

Sphingosine-1-phosphate (S1P) is a bioactive lysophospholipid that can influence a broad range of biological processes through its binding to five distinct G protein-coupled receptors. S1P receptor modulators are a new group of immunosuppressive agents currently used in the immunotherapy of multiple sclerosis. Inflammation following stroke may exacerbate injury. Given that S1P signaling is linked to multiple immune processes, therapies targeting the S1P axis may be suitable for treating stroke. In this review, we outline S1P metabolism and S1P receptors, discuss the mechanisms of action of S1P receptor modulators in lymphocyte migration and their direct action on cells of the central nervous system, and provide a concise summary of the efficacy of S1P receptor modulators in animal studies and clinical trials on treatments for stroke.

FTY720 controls disease severity and attenuates sciatic nerve damage in chronic experimental autoimmune neuritis

Background

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an autoimmune-mediated inflammatory disease of the peripheral nervous system characterized by a response directed against certain myelin proteins and for which therapies are limited. Previous studies have suggested a beneficial role of FTY720, a sphingosine 1-phosphate (S1P) receptor agonist, known to deplete lymphocytes from the peripheral blood by sequestering them into lymph nodes, in the treatment of experimental autoimmune neuritis (EAN). Therefore, we investigated whether FTY720 is also beneficial in chronic experimental autoimmune neuritis (c-EAN), a recently developed rat model mimicking human CIDP.

Methods

c-EAN was induced in Lewis rats by immunization with S-palm P0(180–199) peptide. Rats were treated with FTY720 (1 mg/kg) or vehicle intraperitoneally once daily from the onset of clinical signs for 18 days; clinical signs were assessed daily until 60 days post-immunization (dpi). Electrophysiological and histological features were examined at different time points. We also evaluated the serum levels of different pro- and anti-inflammatory cytokines by ELISA or flow cytometry at 18, 40, and 60 dpi.

Results

Our data demonstrate that FTY720 decreased the severity and abolished the chronicity of the disease in c-EAN rats. Therapeutic FTY720 treatment reversed electrophysiological and histological anomalies, suggesting that myelinated fibers were subsequently preserved, it inhibited macrophage and IL-17⁺ cell infiltration in PNS, and it significantly reduced circulating pro-inflammatory cytokines.

Conclusions

FTY720 treatment has beneficial effects on c-EAN, a new animal model mimicking human CIDP. We have shown that FTY720 is an effective immunomodulatory agent, improving the disease course of c-EAN, preserving the myelinated fibers, attenuating the axonal degeneration, and decreasing the number of infiltrated inflammatory cells in peripheral nerves. These data confirm the interest of testing FTY720 or molecules targeting S1P in human peripheral neuropathies.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1441-4) contains supplementary material, which is available to authorized users.

Class I PI3K inhibitor ZSTK474 attenuates experimental autoimmune neuritis by decreasing the frequency of Th1/Th17 cells and reducing the production of proinflammatory cytokines

The Class I phosphatidylinositol 3-kinase inhibitor, 2-(2-difluoromethy lbenzimidazol-1-yl)-4,6-dimorpholino-1,3,5-triazine (ZSTK474), has anti-inflammatory and immunoregulatory properties. However, whether it can be used to treat Guillain-Barré syndrome (GBS)-a neuroinflammatory disorder-is unknown. We induced experimental autoimmune neuritis (EAN) in Lewis rats, an established model of GBS. Orally administered ZSTK474 decreased neurological deficits in the GBS model, as demonstrated by diminished inflammatory cell infiltration, and ameliorated demyelination of sciatic nerves. Additionally, ZSTK474 decreased the number of Th1/Th17 cells and levels of the proinflammatory cytokines interleukin (IL)-1α, IL-1β, IL-17, IL-23, interferon-γ, and tumor necrosis factor-α. We propose that the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin complex 1 (PI3K/AKT/mTORC1) pathway likely contributed to the neuroprotective effect of ZSTK474. ZSTK474 effectively decreases the frequency of Th1/Th17 cells, thereby reducing the production of proinflammatory cytokines and successfully alleviating the symptoms of EAN. Thus, the neuroprotective effect of ZSTK474 indicates its potential utility as anti-inflammatory therapy for GBS.

Fingolimod promotes blood-nerve barrier properties in vitro

OBJECTIVE

The main effect of fingolimod is thought to be functional antagonism of lymphocytic S1P1 receptors and the prevention of lymphocyte egress from lymphoid tissues, thereby reducing lymphocyte infiltration into the nervous system. However, a growing number of reports suggest that fingolimod also has a direct effect on several cell types in the nervous system. Although we previously reported that fingolimod enhances blood-brain barrier (BBB) functions, there have been no investigations regarding the blood-nerve barrier (BNB). In this study, we examine how fingolimod affects the BNB.

METHODS

An immortalized human peripheral nerve microvascular endothelial cell line (HPnMEC) was used to evaluate BNB barrier properties. We examined tight junction proteins and barrier functions of HPnMECs in conditioned medium with or without fingolimod-phosphate and blood sera from patients with typical chronic inflammatory demyelinating polyneuropathy (CIDP).

RESULTS

Incubation with fingolimod-phosphate increased levels of claudin-5 mRNA and protein as well as TEER values in HPnMECs. Conversely, typical CIDP sera decreased claudin-5 mRNA/protein levels and TEER values in HPnMECs; however, pretreatment with fingolimod-phosphate inhibited the effects of the typical CIDP sera.

CONCLUSIONS

Fingolimod-phosphate directly modifies the BNB and enhances barrier properties. This mechanism may be a viable therapeutic target for CIDP, and fingolimod may be useful in patients with typical CIDP who have severe barrier disruption.

Curcumin: A natural modulator of immune cells in systemic lupus erythematosus

Curcumin is a polyphenol natural product isolated from turmeric, interacting with different cellular and molecular targets and, consequently, showing a wide range of pharmacological effects. Recent preclinical and clinical trials have revealed immunomodulatory properties of curcumin that arise from its effects on immune cells and mediators involved in the immune response, such as various T-lymphocyte subsets and dendritic cells, as well as different inflammatory cytokines. Systemic lupus erythematosus (SLE) is an inflammatory, chronic autoimmune-mediated disease characterized by the presence of autoantibodies, deposition of immune complexes in various organs, recruitment of autoreactive and inflammatory T cells, and excessive levels of plasma proinflammatory cytokines. The function and numbers of dendritic cells and T cell subsets, such as T helper 1 (Th1), Th17, and regulatory T cells have been found to be significantly altered in SLE. In the present report, we reviewed the results of in vitro, experimental (pre-clinical), and clinical studies pertaining to the modulatory effects that curcumin produces on the function and numbers of dendritic cells and T cell subsets, as well as relevant cytokines that participate in SLE.

Fingolimod attenuates experimental autoimmune neuritis and contributes to Schwann cell-mediated axonal protection

Background

Fingolimod, a sphingosine-1-phosphate receptor modulator with well-described immunomodulatory properties involving peripheral immune cell trafficking, was the first oral agent approved for the treatment of relapsing remitting multiple sclerosis. Analogous immunomodulatory treatment options for chronic peripheral autoimmune neuropathies are lacking.

Methods

We tested fingolimod in the animal model of experimental autoimmune neuritis in Lewis rat. Six to eight-week-old female rats were immunized with P2 peptide and from this day on treated with fingolimod. Histology of the sciatic nerve was done to analyze T cell and macrophage cell count, intercellular adhesion molecule (ICAM) and amyloid precursor protein (APP) expression, as well as apoptotic Schwann cell counts.

Results

Preventive oral treatment with 0.1 mg/kg up to 3 mg/kg fingolimod once daily dissolved in rapeseed oil completely ameliorated clinical neuritis signs. It reduced circulating peripheral blood T cells and infiltrating T cells and macrophages in the sciatic nerve, whereas at the same time, it preserved blood-nerve barrier impermeability. Most importantly, fingolimod showed beneficial properties on the pathogenic process as indicated by fewer apoptotic Schwann cells and a lower amount of amyloid precursor protein indicative of axonal damage at the peak of disease course.

Conclusions

Taken together, orally administered low-dose fingolimod showed an impressive immunomodulatory effect in the rat model of experimental autoimmune neuritis. Our current observations introduce fingolimod as an attractive treatment option for neuritis patients.

Sphingosine-1-phosphate modulators in inflammatory skin diseases - lining up for clinical translation

The bioactive lysophospholipid sphingosine-1-phosphate (S1P) is best known for its activity as T-cell-active chemoattractant regulating the egress of T cells from the lymph node and, consequently, the availability of T cells for migration into peripheral tissues. This physiological role of S1P is exploited by the drug fingolimod, a first-line therapy for multiple sclerosis, which "detains" T cells in the lymph nodes. In recent year, it has been elucidated that S1P exerts regulatory functions far beyond T-cell egress from the lymph node. Thus, it additionally regulates, among others, homing of several immune cell populations into peripheral tissues under inflammatory conditions. In addition, evidence, mostly derived from mouse models, has accumulated that S1P may be involved in the pathogenesis of several inflammatory skin disorder and that S1P receptor modulators applied topically are effective in treating skin diseases. These recent developments highlight the pharmacological modulation of the S1P/S1P receptor system as a potential new therapeutic strategy for a plethora of inflammatory skin diseases. The impact of S1P receptor modulation on inflammatory skin diseases next requires testing in human patients.

PR-957, a selective inhibitor of immunoproteasome subunit low-MW polypeptide 7, attenuates experimental autoimmune neuritis by suppressing Th17-cell differentiation and regulating cytokine production

Experimental autoimmune neuritis (EAN) is a CD4⁺ T-cell-mediated autoimmune inflammatory demyelinating disease of the peripheral nervous system. It has been replicated in an animal model of human inflammatory demyelinating polyradiculoneuropathy, Guillain-Barré syndrome. In this study, we evaluated the therapeutic efficacy of a selective inhibitor of the immunoproteasome subunit, low-MW polypeptide 7 (PR-957) in rats with EAN. Our results showed that PR-957 significantly delayed onset day, reduced severity and shortened duration of EAN, and alleviated demyelination and inflammatory infiltration in sciatic nerves. In addition to significantly regulating expression of the cytokine profile, PR-957 treatment down-regulated the proportion of proinflammatory T-helper (T_h)17 cells in sciatic nerves and spleens of rats with EAN. Data presented show the role of PR-957 in the signal transducer and activator of transcription 3 (STAT3) pathway. PR-957 not only decreased expression of IL-6 and IL-23 but also led to down-regulation of STAT3 phosphorylation in CD4⁺ T cells. Regulation of the STAT3 pathway led to a reduction in retinoid-related orphan nuclear receptor γ t and IL-17 production. Furthermore, reduction of STAT3 phosphorylation may have directly suppressed T_h17-cell differentiation. Therefore, our study demonstrates that PR-957 could potently alleviate inflammation in rats with EAN and that it may be a likely candidate for treating Guillain-Barré syndrome.-Liu, H., Wan, C., Ding, Y., Han, R., He, Y., Xiao, J., Hao, J. PR-957, a selective inhibitor of immunoproteasome subunit low-MW polypeptide 7, attenuates experimental autoimmune neuritis by suppressing T_h17-cell differentiation and regulating cytokine production.

Sphingosine 1-Phosphate Receptor Modulators and Drug Discovery

Initial discovery on sphingosine 1-phosphate (S1P) as an intracellular second messenger was faced unexpectedly with roles of S1P as a first messenger, which subsequently resulted in cloning of its G protein-coupled receptors, S1P_1–5. The molecular identification of S1P receptors opened up a new avenue for pathophysiological research on this lipid mediator. Cellular and molecular in vitro studies and in vivo studies on gene deficient mice have elucidated cellular signaling pathways and the pathophysiological meanings of S1P receptors. Another unexpected finding that fingolimod (FTY720) modulates S1P receptors accelerated drug discovery in this field. Fingolimod was approved as a first-in-class, orally active drug for relapsing multiple sclerosis in 2010, and its applications in other disease conditions are currently under clinical trials. In addition, more selective S1P receptor modulators with better pharmacokinetic profiles and fewer side effects are under development. Some of them are being clinically tested in the contexts of multiple sclerosis and other autoimmune and inflammatory disorders, such as, psoriasis, Crohn’s disease, ulcerative colitis, polymyositis, dermatomyositis, liver failure, renal failure, acute stroke, and transplant rejection. In this review, the authors discuss the state of the art regarding the status of drug discovery efforts targeting S1P receptors and place emphasis on potential clinical applications.

Programmed Death Ligand 1 Plays a Neuroprotective Role in Experimental Autoimmune Neuritis by Controlling Peripheral Nervous System Inflammation of Rats

Programmed death 1 (PD-1; CD279), a member of the CD28 family, is an inhibitory receptor on T cells and is responsible for T cell dysfunction in infectious diseases and cancers. The ligand for PD-1, programmed death ligand 1 (PD-L1; also known as B7-H1, CD274), is a member of the B7 family. The engagement of PD-1 with programmed death ligand can downregulate autoreactive T cells that participate in multiple autoimmune diseases. Experimental autoimmune neuritis (EAN) is an animal model of Guillain-Barré syndrome, and the pathogenesis of EAN is mediated principally through T cells and macrophages. In this study, we investigated the effects of PD-L1 in EAN rats. For preventative and therapeutic management, we administered PD-L1, which successfully decreased the severity of EAN; it alleviated the neurologic course of EAN, as well as inhibited the infiltration of inflammatory cells and demyelination of sciatic nerves. Our data revealed that PD-L1 treatment inhibited lymphocyte proliferation and altered T cell differentiation by inducing decreases in IFN-γ⁺CD4⁺ Th1 cells and IL-17⁺CD4⁺ Th17 cells and increases in IL-4⁺CD4⁺ Th2 cells and Foxp3⁺CD4⁺ regulatory T cells. The expression levels of p-STAT3 and Foxp3 were significantly different in PD-L1-treated groups compared with the control group. Additionally, PD-L1 regulated the expression of Foxp3 and p-STAT3 in EAN, probably by inhibiting PI3K/AKT/mTOR signaling expression. In summary, PD-L1 is a potentially useful agent for the treatment of EAN because of its anti-inflammatory and neuroprotective effects.

Fingolimod for multiple sclerosis and emerging indications: appropriate patient selection, safety precautions, and special considerations

Fingolimod (FTY720), an immunotherapeutic drug targeting the sphingosine-1-phosphate receptor, is a widely used medication for relapsing-remitting multiple sclerosis (MS). Apart from the pivotal Phase III trials demonstrating efficacy against placebo and interferon-β-1a once weekly, sufficient clinical data are now available to assess its real-world efficacy and safety profile. Approved indications of fingolimod differ between countries. This discrepancy, to some extent, reflects the intermediate position of fingolimod in the expanding lineup of MS medications. With individualization of therapy, appropriate patient selection gets more important. We discuss various scenarios for fingolimod use in relapsing-remitting MS and their pitfalls: as first-line therapy, as escalation therapy after failure of previous immunotherapies, and as de-escalation therapy following highly potent immunotherapies. Potential side effects such as bradycardia, infections, macular edema, teratogenicity, and progressive multifocal leukoencephalopathy as well as appropriate safety precautions are outlined. Disease reactivation has been described upon fingolimod cessation; therefore, patients should be closely monitored for MS activity for several months after stopping fingolimod. Finally, we discuss preclinical and clinical data indicating neuroprotective effects of fingolimod, which might open the way to future indications such as stroke, Alzheimer’s disease, and other neurodegenerative disorders.

New strategies in the management of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an acute and usually monophasic, neurological, demyelinating disease. Although most patients have good outcomes without sequelae after conventional plasma exchange and intravenous immunoglobulin therapy, 20% of patients continue to have severe disease and 5% die of their disease. Therefore, there is an obvious need for more acceptable and efficacious therapies. Experimental autoimmune neuritis (EAN) is the classical animal model for GBS. As there is no specific drug for GBS, several drugs targeting the humoral and cellular components of the immune response have been used to treat EAN in the endeavour to find new treatment alternatives for GBS. This review focused on some new strategies for GBS, which have been reported but have not yet been widely used, and on the main drugs which have been investigated in EAN.

Characterization of a new rat model for chronic inflammatory demyelinating polyneuropathies

Our objective was to develop a chronic model of EAN which could be used as a tool to test treatment strategies for CIDP. Lewis rats injected with S-palmitoylated P0(180-199) peptide developed a chronic, sometimes relapsing-remitting type of disease. Our model fulfills electrophysiological criteria of demyelination with axonal degeneration, confirmed by immunohistopathology. The late phase of the chronic disease was characterized by accumulation of IL-17(+) cells and macrophages in sciatic nerves and by high serum IL-17 levels. In conclusion, we have developed a reliable and reproducible animal model resembling CIDP that can now be used for translational drug studies.

Mitigated Tregs and augmented Th17 cells and cytokines are associated with severity of experimental autoimmune neuritis

Experimental autoimmune neuritis (EAN), an animal model of human Guillain-Barré syndrome, has long been considered as a T helper (Th) 1 cell-mediated autoimmune disorder. However, deficiency of IFN-γ, a signature Th1 cytokine, aggravated EAN, with features of elevated production of IL-17A, despite an alleviated systemic Th1 immune response. We hypothesized that Th17 cells and their cytokines might play a pathogenic role in EAN. To further clarify the roles of these Th and regulatory T cell (Treg) cytokines in the pathogenesis of EAN and their interrelationship, we investigated the expression of Th1/Th2/Th17/Treg cytokines in EAN in this study. We found that the levels of Th17 cells and IL-17A in cauda equina (CE)-infiltrating cells and splenic mononuclear cells (MNCs) as well as in serum paralleled the disease evolution, which increased progressively during the initiation stage and reached higher value at the peak of EAN. The same pattern was also noticed for the expression of IL-22. The diverse expression profiles of FoxP3, IL-17 receptors A and C were seen in CE-infiltrating cells and splenic MNCs in EAN. These findings indicate a major pro-inflammatory role of Th17 cells and IL-17A in the pathogenesis of EAN. Therapeutic interventions may be focused upon inhibiting Th17 cells and their cytokines in the early phase of EAN, so as to delay and suppress clinical signs of the disease, which has relevance for future studies on pathogenesis and treatment of GBS in humans.

FTY720 impairs CD8 T-cell function independently of the sphingosine-1-phosphate pathway

Fingolimod (FTY720) is a multiple sclerosis (MS) therapeutic that upon phosphorylation causes the internalization of sphingosine-1-phosphate receptors (S1PR) and traps CCR7+ T-cells in lymph nodes but relatively spares CCR7-effector T-cells. Nonetheless, FTY720-treated patients are more susceptible to viral infections, indicating a CD8 T-cell defect. Thus, the effects of FTY720 on CD8 T-cells were investigated. To this end, we utilized experimental autoimmune encephalomyelitis (EAE) and a murine influenza model. CD8 T-cell trafficking, IFNγ and Granzyme B (GrB) production were assessed by flow cytometry. CD8 T-cell cytotoxic function was assessed in vitro by an LDH release assay. FTY720 not only ameliorated EAE by sequestering T-cells, but also reduced IFNγ and Granzyme B (GrB) in splenic CD8 T-cells. Murine influenza infection was exacerbated and mortality was increased, as FTY720 inhibited CD8 T-cell GrB production and lung infiltration. Remarkably, only the unphosphorylated compound was able to reduce IFNγ and GrB levels in CD8 T-cells and inhibits their cytotoxic function in vitro. The phosphorylated moiety had no effect in vitro, indicating that CD8 T-cell suppression by FTY720 is independent of S1PR modulation. The addition of arachidonic acid rescued CD8 T-cell function, suggesting that this effect may be mediated via inhibition of cytosolic phospholipase A2. Herein, we demonstrate that FTY720 suppresses CD8 T-cells independently of its trafficking effects and S1PR modulation. This provides a novel explanation not only for the increased rate of viral infections in FTY720-treated patients, but also for its efficacy in MS, as CD8 T-cells have emerged as crucial mediators of MS pathogenesis.

Erythropoietin-derived nonerythropoietic peptide ameliorates experimental autoimmune neuritis by inflammation suppression and tissue protection

Experimental autoimmune neuritis (EAN) is an autoantigen-specific T-cell-mediated disease model for human demyelinating inflammatory disease of the peripheral nervous system. Erythropoietin (EPO) has been known to promote EAN recovery but its haematopoiesis stimulating effects may limit its clinic application. Here we investigated the effects and potential mechanisms of an EPO-derived nonerythropoietic peptide, ARA 290, in EAN. Exogenous ARA 290 intervention greatly improved EAN recovery, improved nerve regeneration and remyelination, and suppressed nerve inflammation. Furthermore, haematopoiesis was not induced by ARA 290 during EAN treatment. ARA 290 intervention suppressed lymphocyte proliferation and altered helper T cell differentiation by inducing increase of Foxp3+/CD4+ regulatory T cells and IL-4+/CD4+ Th2 cells and decrease of IFN-γ+/CD4+ Th1 cells in EAN. In addition, ARA 290 inhibited inflammatory macrophage activation and promoted its phagocytic activity. In vitro, ARA 290 was shown to promote Schwann cell proliferation and inhibit its inflammatory activation. In summary, our data demonstrated that ARA 290 could effectively suppress EAN by attenuating inflammation and exerting direct cell protection, indicating that ARA 290 could be a potent candidate for treatment of autoimmune neuropathies.

Roles of T helper 17 cells and interleukin-17 in neuroautoimmune diseases with emphasis on multiple sclerosis and Guillain-Barré syndrome as well as their animal models

The identification of T helper 17 (Th17) cells challenges the Th1/Th2 paradigm of the immune response and invites intensive exploration of their mechanisms and functions in the field of autoimmune diseases, host defense, allergy, etc. The collective data have shown that transforming growth factor-β (TGF-β), interleukin (IL)-6, IL-1β, IL-21, and IL-23 are involved in the differentiation program of Th17 cells. The transcription factors RORγT, STAT3, RORγ, RORα, and IRF4 exert regulatory effects on the development of Th17 cells. Among the Th17-related effector cytokines, such as IL-17, IL-17F, IL-21, and IL-22, IL-17 is regarded as a key cytokine to induce inflammatory responses. This review outlines the cytokines and transcription factors involved in the differentiation of Th17 cells and their effector functions, with specific focus on the roles of Th17 cells and IL-17 in neuroautoimmune diseases, especially in multiple sclerosis and Guillain-Barré syndrome, as well as in their animal models, experimental autoimmune encephalomyelitis and experimental autoimmune neuritis.

Sphingosine 1-phosphate receptor 5 mediates the immune quiescence of the human brain endothelial barrier

Background

The sphingosine 1-phosphate (S1P) receptor modulator FTY720P (Gilenya®) potently reduces relapse rate and lesion activity in the neuroinflammatory disorder multiple sclerosis. Although most of its efficacy has been shown to be related to immunosuppression through the induction of lymphopenia, it has been suggested that a number of its beneficial effects are related to altered endothelial and blood–brain barrier (BBB) functionality. However, to date it remains unknown whether brain endothelial S1P receptors are involved in the maintenance of the function of the BBB thereby mediating immune quiescence of the brain. Here we demonstrate that the brain endothelial receptor S1P₅ largely contributes to the maintenance of brain endothelial barrier function.

Methods

We analyzed the expression of S1P₅ in human post-mortem tissues using immunohistochemistry. The function of S1P₅ at the BBB was assessed in cultured human brain endothelial cells (ECs) using agonists and lentivirus-mediated knockdown of S1P₅. Subsequent analyses of different aspects of the brain EC barrier included the formation of a tight barrier, the expression of BBB proteins and markers of inflammation and monocyte transmigration.

Results

We show that activation of S1P₅ on cultured human brain ECs by a selective agonist elicits enhanced barrier integrity and reduced transendothelial migration of monocytes in vitro. These results were corroborated by genetically silencing S1P₅ in brain ECs. Interestingly, functional studies with these cells revealed that S1P₅ strongly contributes to brain EC barrier function and underlies the expression of specific BBB endothelial characteristics such as tight junctions and permeability. In addition, S1P₅ maintains the immunoquiescent state of brain ECs with low expression levels of leukocyte adhesion molecules and inflammatory chemokines and cytokines through lowering the activation of the transcription factor NFκB.

Conclusion

Our findings demonstrate that S1P₅ in brain ECs contributes to optimal barrier formation and maintenance of immune quiescence of the barrier endothelium.

Atorvastatin ameliorates experimental autoimmune neuritis by decreased Th1/Th17 cytokines and up-regulated T regulatory cells

Statins have anti-inflammatory and immune-regulating properties. To investigate the effects of atorvastatin on experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome (GBS), atorvastatin was administered to Lewis rats immunized with bovine peripheral myelin in complete Freund's adjuvant. We found that atorvastatin ameliorated the clinical symptoms of EAN, decreased the numbers of inflammatory cells as well as IFN-γ(+) and IL-17(+) cells in sciatic nerves, decreased the CD80 expression and increased the number of CD25(+)Foxp3(+) cells in mononuclear cells (MNC), and decreased the levels of IFN-γ in MNC culture supernatants. These data provide strong evidence that atorvastatin can act as an inhibitor in EAN by inhibiting the immune response of Th1 and Th17, decreasing the expression of co-stimulatory molecule, and up-regulating the number of T regulatory cells. These data demonstrated that statins could be used as a therapeutic strategy in human GBS in future.

S1P is associated with protection in human and experimental cerebral malaria

Cerebral malaria (CM) is associated with excessive inflammatory responses and endothelial activation. Sphingosine 1-phosphate (S1P) is a signaling sphingolipid implicated in regulating vascular integrity, inflammation and T-cell migration. We hypothesized that altered S1P signaling during malaria contributes to endothelial activation and inflammation, and show that plasma S1P levels were decreased in Ugandan children with CM compared with children with uncomplicated malaria. Using the Plasmodium berghei ANKA (PbA) model of experimental CM (ECM), we demonstrate that humanized S1P lyase (hS1PL)(-/-) mice with reduced S1P lyase activity (resulting in increased bio-available S1P) had improved survival compared with wild-type littermates. Prophylactic and therapeutic treatment of infected mice with compounds that modulate the S1P pathway and are in human trials for other conditions (FTY720 or LX2931) significantly improved survival in ECM. FTY720 treatment improved vascular integrity as indicated by reduced levels of soluble intercellular adhesion molecule (sICAM), increased angiopoietin 1 (Ang1) (regulator of endothelial quiescence) levels, and decreased Evans blue dye leakage into brain parenchyma. Furthermore, treatment with FTY720 decreased IFNγ levels in plasma as well as CD4(+) and CD8(+) T-cell infiltration into the brain. Finally, when administered during infection in combination with artesunate, FTY720 treatment resulted in increased survival to ECM. These findings implicate dysregulation of the S1P pathway in the pathogenesis of human and murine CM and suggest a novel therapeutic strategy to improve clinical outcome in severe malaria.

Fingolimod (FTY720): discovery and development of an oral drug to treat multiple sclerosis

The discovery of fingolimod (FTY720/Gilenya; Novartis), an orally active immunomodulatory drug, has opened up new approaches to the treatment of multiple sclerosis, the most common inflammatory disorder of the central nervous system. Elucidation of the effects of fingolimod--mediated by the modulation of sphingosine 1-phosphate (S1P) receptors--has indicated that its therapeutic activity could be due to regulation of the migration of selected lymphocyte subsets into the central nervous system and direct effects on neural cells, particularly astrocytes. An improved understanding of the biology of S1P receptors has also been gained. This article describes the discovery and development of fingolimod, which was approved by the US Food and Drug Administration in September 2010 as a first-line treatment for relapsing forms of multiple sclerosis, thereby becoming the first oral disease-modifying therapy to be approved for multiple sclerosis in the United States.

MS-275, an histone deacetylase inhibitor, reduces the inflammatory reaction in rat experimental autoimmune neuritis

Experimental autoimmune neuritis (EAN) is a T cell-mediated autoimmune inflammatory demyelinating disease of the peripheral nervous system and serves as the animal model of human inflammatory demyelinating polyradiculoneuropathies. MS-275, a potent histone deacetylase inhibitor currently undergoing clinical investigations for various malignancies, has been reported to demonstrate promising anti-inflammatory activities. In our present study, MS-275 administration (3.5 mg/kg i.p.) to EAN rats once daily from the appearance of first neurological signs greatly reduced the severity and duration of EAN and attenuated local accumulation of macrophages, T cells and B cells, and demyelination of sciatic nerves. Further, significant reduction of mRNA levels of pro-inflammatory interleukin-1beta, interferon-gamma, interleukine-17, inducible nitric oxide synthase and matrix metalloproteinase-9 was observed in sciatic nerves of MS-275 treated EAN rats. In lymph nodes, MS-275 depressed pro-inflammatory cytokines as well, but increased expression of anti-inflammatory cytokine interleukine-10 and of foxhead box protein3 (Foxp3), a unique transcription factor of regulatory T cells. In addition, MS-275 treatment increased proportion of infiltrated Foxp3(+) cells and anti-inflammatory M2 macrophages in sciatic nerves of EAN rats. In summary, our data demonstrated that MS-275 could effectively suppress inflammation in EAN, through suppressing inflammatory T cells, macrophages and cytokines, and inducing anti-inflammatory immune cells and molecules, suggesting MS-275 as a potent candidate for treatment of autoimmune neuropathies.

FTY720 (fingolimod) in Multiple Sclerosis: therapeutic effects in the immune and the central nervous system

FTY720 (fingolimod) is a first-in-class sphingosine 1-phosphate (S1P) receptor modulator that was highly effective in Phase II clinical trials for Multiple Sclerosis (MS). FTY720 is phosphorylated in vivo by sphingosine kinase-2 to form the active moiety FTY720-phosphate that binds to four of the five G protein-coupled S1P receptor subtypes. Studies using conditional S1P1 receptor-deficient and sphingosine kinase-deficient mice showed that the egress of lymphocytes from lymph nodes requires signalling of lymphocytic S1P1 receptors by the endogenous ligand S1P. The S1P mimetic FTY720-phosphate causes internalization and degradation of cell membrane-expressed S1P1, thereby antagonizing S1P action at the receptor. In models of human MS and demyelinating polyneuropathies, functional antagonism of lymphocytic S1P1 slows S1P-driven egress of lymphocytes from lymph nodes, thereby reducing the numbers of autoaggressive TH17 cells that recirculate via lymph and blood to the central nervous system and the sciatic/ischiatic nerves. Based on its lipophilic nature, FTY720 crosses the blood-brain barrier, and ongoing experiments suggest that the drug also down-modulates S1P1 in neural cells/astrocytes to reduce astrogliosis, a phenomenon associated with neurodegeneration in MS. This may help restore gap-junctional communication of astrocytes with neurons and cells of the blood-brain barrier. Additional effects may result from (down-) modulation of S1P3 in astrocytes and of S1P1 and S1P5 in oligodendrocytes. In conclusion, FTY720 may act through immune-based and central mechanisms to reduce inflammation and support structural restoration of the central nervous system parenchyma. Beyond the autoimmune indications, very recent studies suggest that short-term, low-dose administration of FTY720 could help treat chronic (viral) infections. Differential effects of the drug on the trafficking of naïve, central memory and effector memory T cell subsets are discussed.

Compound A, a Plant Origin Ligand of Glucocorticoid Receptors, Increases Regulatory T Cells and M2 Macrophages to Attenuate Experimental Autoimmune Neuritis with Reduced Side Effects

Experimental autoimmune neuritis (EAN) is a helper T cell-mediated autoimmune demyelinating inflammatory disease of the peripheral nervous system and serves as the animal model for human inflammatory demyelinating polyneuropathies. Compound A, a plant-derived phenyl aziridine precursor, was reported to activate glucocorticoid receptors to exert transrepression but not transactivation properties. In this study, we investigated the effects of Compound A in EAN rats. Compound A greatly suppressed paraparesis in EAN, even when administrated after the appearance of the first neurological signs. Accumulation of macrophages and lymphocytes, demyelination, and mRNA levels of inflammatory molecules in sciatic nerves of EAN were greatly attenuated by Compound A. In addition, Compound A inhibited progression of neuropathic pain and repressed microglia but not astrocyte activation and IL-1β and TNF-α up-regulation in EAN spinal cords. In EAN sciatic nerves, Compound A treatment increased numbers of anti-inflammatory M2 macrophages. Furthermore, Compound A induced the switch of macrophages from inflammatory M1 type to anti-inflammatory M2 type in vitro. In lymph nodes of EAN rats, Compound A depressed Th1 and Th17 cytokines, but increased Th2 cytokine and Foxp3 expression. An increase of Foxp3+/CD4+ regulatory T cells was seen in peripheral blood of EAN rats following Compound A treatment. In addition, Compound A did not cause a hyperglycemia effect in EAN rats as compared with the immunosuppressive steroid prednisolone. Therefore, our data demonstrated that Compound A could effectively suppress EAN with reduced side effects by attenuating inflammation, suggesting that Compound A could be a potent candidate for treatment of autoimmune neuropathies.