Cutting edge: Alternative signaling of Th17 cell development by sphingosine 1-phosphate

Mechanistic insights into the therapeutic effects on liver fibrosis in Wilson's disease: a transcriptomic and network pharmacology-based approach

Background

The mechanism of the Bushen Huoxue Huazhuo Formula (BSHXHZF) in treating Wilson's disease (WD) liver fibrosis was investigated in this study using transcriptomics, network pharmacology, and molecular docking approaches.

Methods

Differentially expressed long non-coding RNAs (DELncRNAs) and messenger RNAs in the liver tissues of different groups were identified using high-throughput chip sequencing. Furthermore, the target genes of DELncRNAs were identified, followed by GO functional enrichment and KEGG pathway analyses. DELncRNAs were validated using quantitative reverse transcription-polymerase chain reaction. Active compounds of BSHXHZF and their associated pathways relevant to liver fibrosis treatment in WD, with initial validation via molecular docking.

Results

Transcriptomic analysis identified 63 DELncRNAs by comparing the control with the model and treatment groups. Key DELncRNAs included NONMMUT060008.2, NONMMUT096375.1, and ENSMUST00000153523. Target genes such as Pik3cd, Pld1, Oprd1, Ppp2r2b, and Cers5 were implicated in sphingolipid signaling, metabolism, and AMPK pathways. The "BSHXHZF-Component-Target" network highlighted active ingredients, including tanshinone IIA, quercetin, and luteolin, which play key roles in treating liver fibrosis. Main signaling pathways included IL-17, HIF-1, prolactin, and NF-κB.

Conclusion

The therapeutic effects of BSHXHZF in liver fibrosis associated with WD are likely linked to its modulation of sphingolipid and IL-17 signaling pathways.

Sphingosine-1-Phosphate Signalling Inhibition Suppresses Th1-Like Treg Generation by Reversing Mitochondrial Uncoupling

Inflammatory environments induce the generation of dysfunctional IFNγ+T-bet+FOXP3+ Th1-like Tregs, which show defective function and are found in autoimmune conditions including multiple sclerosis (MS). The pathways that control the generation of Th1-like Tregs are not well understood. Sphingosine-1-phosphate (S1P) signalling molecules are upregulated in Th1-like Tregs, and in vivo S1P inhibition with Fingolimod (FTY720) inhibits the expression of genes responsible for Treg plasticity in MS patients. However, the underlying mechanisms are unknown. Here we show that S1P signalling inhibition by FTY720 inhibits the generation of Th1-like Tregs and rescues their suppressive function. These effects are mediated by a decrease in mTORC1 signalling and reversal of the mitochondrial uncoupling that Tregs undergo during their reprogramming into Th1-like Tregs in vitro. Finally, these results are validated in in vivo-generated Th1-like Tregs, as Tregs from MS patients treated with FTY720 display decreased Th1-like Treg frequency, increased suppressive function and mitochondrial metabolism rebalance. These results highlight the involvement of mitochondrial uncoupling in Treg reprogramming and identify S1P signalling inhibition as a target to suppress the generation of dysfunctional Th1-like Tregs.

Blocking the Sphingosine-1-Phosphate Receptor 2 (S1P2) Reduces the Severity of Collagen-Induced Arthritis in DBA-1J Mice

The amount of sphingosine 1-phosphate (S1P) found in the synovial tissue of individuals with rheumatoid arthritis is five times greater than that in those with osteoarthritis. Our study aims to determine whether inhibiting S1P2 can mitigate collagen-induced rheumatoid arthritis (CIA) by using an S1P2 antagonist, JTE-013, alongside DBA-1J S1pr2 wild-type (WT) and knock-out (KO) mice. CIA causes increases in arthritis scores, foot swelling, synovial hyperplasia, pannus formation, proteoglycan depletion, cartilage damage, and bone erosion, but these effects are markedly reduced when JTE-013 is administered to S1pr2 WT mice. CIA also elevates mRNA expression levels of pro-inflammatory Th1/Th17 cytokines in the foot and spleen, which are significantly decreased by JTE-013 in S1pr2 WT mice. Additionally, CIA raises Th1/Th17 and Treg cell counts, while JTE-013 reduces these elevations in the spleens of S1pr2 WT mice. Treatment with JTE-013 or the absence of S1pr2 curtails the differentiation of naïve T cells into Th1 and Th17 cells in a dose-dependent manner. In SW982 human synovial cells, JTE-013 lowers LPS-induced increases in pro-inflammatory cytokine levels. Overall, these findings propose that blocking S1P2 in immune and synovial cells may alleviate rheumatoid arthritis symptoms and offer a potential therapeutic approach.

Fingolimod, a sphingosine-1-phosphate receptor modulator, prevents neonatal bronchopulmonary dysplasia and subsequent airway remodeling in a murine model

Neonatal bronchopulmonary dysplasia (BPD) is associated with alveolar simplification and airway remodeling. Airway remodeling leads to deformation of airways characterized by peribronchial collagen deposition and hypertrophy of airway smooth muscle, which contribute to the narrowing of airways. Poorly developed lungs contribute to reduced lung function that deteriorates with the passage of time. We have earlier shown that sphingosine kinase 1 (SPHK 1)/sphingosine-1-phosphate (S1P)/S1P receptor1 (S1PR1) signaling plays a role in the pathogenesis of BPD. In this study, we investigated the role of fingolimod or FTY720, a known S1PR1 modulator approved for the treatment of multiple sclerosis in the treatment of BPD. Fingolimod promotes the degradation of S1PR1 by preventing its recycling, thus serving as the equivalent of an inhibitor. Exposure of neonatal mice to hyperoxia enhanced the expression of S1PR1 in both airways and alveoli as compared with normoxia. This increased expression of S1PR1 in the airways persisted into adulthood, accompanied by airway remodeling and airway hyperreactivity (AHR) after neonatal hyperoxia. Intranasal fingolimod at a much lower dose compared with the intraperitoneal route of administration during neonatal hyperoxia improved alveolarization in neonates and reduced airway remodeling and AHR in adult mice associated with improved lung function. The intranasal route was not associated with the lymphopenia seen with the intraperitoneal route of administration of the drug. An increase in S1PR1 expression in the airways was associated with an increase in the expression of enzyme lysyl oxidase (LOX) in the airways following hyperoxia, which was suppressed by fingolimod. This association warrants further investigation.NEW & NOTEWORTHY The role of the S1P receptor1 modulator, fingolimod, as an FDA-approved drug in preventing the recurrence of multiple sclerosis is established. Fingolimod prevented bronchopulmonary dysplasia (BPD) and its sequela of airway remodeling in a neonatal murine model. This protection was associated with the downregulation of lysyl oxidase signaling pathway. Fingolimod could be repurposed for the therapy of BPD.

Promising strategies in natural products treatments of psoriasis-update

Psoriasis is a chronic, relapsing, inflammatory skin disease and has been increasing year by year. It is linked to other serious illnesses, such as psoriatic arthritis, cardiometabolic syndrome, and depression, resulting in a notable decrease in the quality of life for patients. Existing therapies merely alleviate symptoms, rather than providing a cure. An in-depth under-standing of the pathogenesis of psoriasis is helpful to discover new therapeutic targets and develop effective novel therapeutic agents, so it has important clinical significance. This article reviews the new progress in the study of pathogenesis and natural products of psoriasis in recent years. These natural products were summarized, mainly classified as terpenoids, polyphenols and alkaloids. However, the translation of experimental results to the clinic takes a long way to go.

Neutrophilia in severe asthma is reduced in Ormdl3 overexpressing mice

Genome-wide association studies have linked the ORM (yeast)-like protein isoform 3 (ORMDL3) to asthma severity. Although ORMDL3 is a member of a family that negatively regulates serine palmitoyltransferase (SPT) and thus biosynthesis of sphingolipids, it is still unclear whether ORMDL3 and altered sphingolipid synthesis are causally related to non-Th2 severe asthma associated with a predominant neutrophil inflammation and high interleukin-17 (IL-17) levels. Here, we examined the effects of ORMDL3 overexpression in a preclinical mouse model of allergic lung inflammation that is predominantly neutrophilic and recapitulates many of the clinical features of severe human asthma. ORMDL3 overexpression reduced lung and circulating levels of dihydrosphingosine, the product of SPT. However, the most prominent effect on sphingolipid levels was reduction of circulating S1P. The LPS/OVA challenge increased markers of Th17 inflammation with a predominant infiltration of neutrophils into the lung. A significant decrease of neutrophil infiltration was observed in the Ormdl3 transgenic mice challenged with LPS/OVA compared to the wild type and concomitant decrease in IL-17, that plays a key role in the pathogenesis of neutrophilic asthma. LPS decreased survival of murine neutrophils, which was prevented by co-treatment with S1P. Moreover, S1P potentiated LPS-induced chemotaxis of neutrophil, suggesting that S1P can regulate neutrophil survival and recruitment following LPS airway inflammation. Our findings reveal a novel connection between ORMDL3 overexpression, circulating levels of S1P, IL-17 and neutrophil recruitment into the lung, and questions the potential involvement of ORMDL3 in the pathology, leading to development of severe neutrophilic asthma.

Sphingosine 1-Phosphate as Essential Signaling Molecule in Inflammatory Skin Diseases

Sphingolipids are crucial molecules of the mammalian epidermis. The formation of skin-specific ceramides contributes to the formation of lipid lamellae, which are important for the protection of the epidermis from excessive water loss and protect the skin from the invasion of pathogens and the penetration of xenobiotics. In addition to being structural constituents of the epidermal layer, sphingolipids are also key signaling molecules that participate in the regulation of epidermal cells and the immune cells of the skin. While the importance of ceramides with regard to the proliferation and differentiation of skin cells has been known for a long time, it has emerged in recent years that the sphingolipid sphingosine 1-phosphate (S1P) is also involved in processes such as the proliferation and differentiation of keratinocytes. In addition, the immunomodulatory role of this sphingolipid species is becoming increasingly apparent. This is significant as S1P mediates a variety of its actions via G-protein coupled receptors. It is, therefore, not surprising that dysregulation in the signaling pathways of S1P is involved in the pathophysiological conditions of skin diseases. In the present review, the importance of S1P in skin cells, as well as the immune cells of the skin, is elaborated. In particular, the role of the molecule in inflammatory skin diseases will be discussed. This is important because interfering with S1P signaling pathways may represent an innovative option for the treatment of inflammatory skin diseases.

Sphingosine 1-phosphate receptor, a new therapeutic direction in different diseases

Sphingosine 1-phosphate receptor (S1PR), as a kind of G protein-coupled receptor, has five subtypes, including S1PR1, S1PR2, S1PR3, S1PR4, and S1PR5. Sphingosine 1-phosphate receptor (S1P) and S1PR regulate the trafficking of neutrophils and some cells, which has great effects on immune systems, lung tissue, and liver tissue. Presently, many related reports have proved that S1PR has a strong effect on the migration of lymphocytes, tumor cells, neutrophils, and many other cells via the regulation of signals, pathways, and enzymes. In this way, S1PR can regulate the relative response of the organism. Thus, S1PR has become a possible target for the treatment of autoimmune diseases, pulmonary disease, liver disease, and cancer. In this review, we mainly focus on the research of the S1PR for the new therapeutic directions of different diseases and is expected to assist support in the clinic and drug use.

Sphingosine 1-phosphate receptor-targeted therapeutics in rheumatic diseases

Sphingosine 1-phosphate (S1P), which acts via G protein-coupled S1P receptors (S1PRs), is a bioactive lipid essential for vascular integrity and lymphocyte trafficking. The S1P-S1PR signalling axis is a key component of the inflammatory response in autoimmune rheumatic diseases. Several drugs that target S1PRs have been approved for the treatment of multiple sclerosis and inflammatory bowel disease and are under clinical testing for patients with systemic lupus erythematosus (SLE). Preclinical studies support the hypothesis that targeting the S1P-S1PR axis would be beneficial to patients with SLE, rheumatoid arthritis (RA) and systemic sclerosis (SSc) by reducing pathological inflammation. Whereas most preclinical research and development efforts are focused on reducing lymphocyte trafficking, protective effects of circulating S1P on endothelial S1PRs, which maintain the vascular barrier and enable blood circulation while dampening leukocyte extravasation, have been largely overlooked. In this Review, we take a holistic view of S1P-S1PR signalling in lymphocyte and vascular pathobiology. We focus on the potential of S1PR modulators for the treatment of SLE, RA and SSc and summarize the rationale, pathobiology and evidence from preclinical models and clinical studies. Improved understanding of S1P pathobiology in autoimmune rheumatic diseases and S1PR therapeutic modulation is anticipated to lead to efficacious and safer management of these diseases.

Pruritus: A Sensory Symptom Generated in Cutaneous Immuno-Neuronal Crosstalk

Pruritus or itch generated in the skin is one of the most widespread symptoms associated with various dermatological and systemic (immunological) conditions. Although many details about the molecular mechanisms of the development of both acute and chronic itch were uncovered in the last 2 decades, our understanding is still incomplete and the clinical management of pruritic conditions is one of the biggest challenges in daily dermatological practice. Recent research revealed molecular interactions between pruriceptive sensory neurons and surrounding cutaneous cell types including keratinocytes, as well as resident and transient cells of innate and adaptive immunity. Especially in inflammatory conditions, these cutaneous cells can produce various mediators, which can contribute to the excitation of pruriceptive sensory fibers resulting in itch sensation. There also exists significant communication in the opposite direction: sensory neurons can release mediators that maintain an inflamed, pruritic tissue-environment. In this review, we summarize the current knowledge about the sensory transduction of pruritus detailing the local intercellular interactions that generate itch. We especially emphasize the role of various pruritic mediators in the bidirectional crosstalk between cutaneous non-neuronal cells and sensory fibers. We also list various dermatoses and immunological conditions associated with itch, and discuss the potential immune-neuronal interactions promoting the development of pruritus in the particular diseases. These data may unveil putative new targets for antipruritic pharmacological interventions.

Plasma S1P (Sphingosine-1-Phosphate) Links to Hypertension and Biomarkers of Inflammation and Cardiovascular Disease: Findings From a Translational Investigation

[Figure: see text].

Comparative Efficacy and Safety of Ozanimod and Dimethyl Fumarate for Relapsing-Remitting Multiple Sclerosis Using Matching-Adjusted Indirect Comparison

BACKGROUND

Patients with multiple sclerosis (MS) experience relapses and sustained disability progression. Since 2004, the number of disease-modifying therapies (DMTs) for MS has grown substantially. As a result, patients, healthcare providers, and insurers are increasingly interested in comparative efficacy and safety evaluations to distinguish between treatment options, but head-to-head studies between DMTs are limited.

OBJECTIVE

The aim of the current study was to compare efficacy and safety outcomes with the DMTs ozanimod and dimethyl fumarate (DMF) using a matching-adjusted indirect comparison (MAIC) to adjust for cross-trial differences in study design and population.

METHODS

A systematic literature review was performed to identify clinical studies evaluating the efficacy and safety of ozanimod compared with DMF. Individual patient-level data (IPD) for ozanimod were obtained from the SUNBEAM and RADIANCE Part B trials, and aggregate-level patient data (APD) for DMF were obtained from CONFIRM and DEFINE. A MAIC is used to weight IPD to APD based on important baseline patient characteristics considered to be effect modifiers or prognostic factors in order to balance the covariate distribution to establish more homogenous trial populations. Once trial populations are determined to be sufficiently homogenous, outcomes of interest are estimated and used to generate treatment effects between the weighted IPD and APD. We used MAIC methodology to compare efficacy and safety outcomes of interest between ozanimod 1.0 mg once daily (OD) and DMF 240 mg twice daily (BID), including confirmed disability progression (CDP) at 3 and 6 months, annualized relapse rate (ARR), proportion of patients relapsed, overall adverse events (AEs), serious AEs (SAEs), and discontinuations due to AEs.

RESULTS

After matching patient data, baseline patient characteristics were balanced between patients receiving ozanimod and those receiving DMF. Compared with DMF, ozanimod demonstrated significantly improved CDP at 3 months (hazard ratio 0.67; 95% confidence interval [CI] 0.53-0.86), ARR (rate ratio [RR] 0.80; 95% CI 0.67-0.97), proportion of patients relapsed (odds ratio [OR] 0.66; 95% CI 0.52-0.83), overall AEs (OR 0.11; 95% CI 0.08-0.16), SAEs (OR 0.27; 95% CI 0.19-0.39), and discontinuations (OR 0.11; 95% CI 0.07-0.17). CDP at 6 months did not differ significantly between the two agents (RR 0.89; 95% CI 0.62-1.26).

CONCLUSIONS

After adjustment of baseline patient characteristics, the MAIC demonstrated that the efficacy and safety of ozanimod 1.0 mg OD was superior to that of DMF 240 mg BID. Although a MAIC is less likely to produce biased estimates than a naïve or a standard indirect treatment comparison via a common comparator, limitations include potential confounding due to unobserved and thus unaccounted for baseline differences.

Blockage of sphingosine-1-phosphate receptor 2 attenuates 2,4-dinitrochlorobenzene-induced atopic dermatitis in mice

Sphingosine-1-phosphate (S1P) and its receptors have been implicated in functions of Langerhans cells and atopic dermatitis. In this study, we investigated the roles of S1P receptor type 2 (S1P₂) in a mouse model of atopic dermatitis, which was induced by topical application of 2,4-dinitrochlorobenzene (DNCB) on ventral skin on D0, followed by repeated DNCB challenge on both ears from D7 to D49. Wild-type mice with atopic dermatitis displayed severe inflammation and mast cell accumulation in ear tissues and elevated IgE levels in serum. Furthermore, the mice showed significantly increased sizes of draining lymph nodes, high levels of inflammatory cytokines (IL-4, IL-13, IL-17, and IFN-γ) in the ears and lymph nodes and high levels of chemokines CCL17 and CCL22 in ears. Administration of JTE-013, a selective antagonist of S1P₂ (3 mg/kg, i.p, from D19 to D49) before DNCB challenge significantly suppressed DNCB-induced atopic responses in ears and lymph nodes. JTE-013 administration also significantly decreased the lymph nodes sizes, the levels of inflammatory cytokines (IL-4, IL-13, IL-17, and IFN-γ) in the ears and lymph nodes, and the levels of chemokines CCL17 and CCL22 in ears. Furthermore, the inflammatory responses of atopic dermatitis were greatly ameliorated in S1pr2 gene-deficient mice. As CCL17 and CCL22 are CCR4 ligands, acting as Th2-attracting chemokines, we investigated CCL17 and CCL22 expression in bone marrow-derived dendritic cells (BMDCs) from wild-type and S1pr2 gene-deficient mice. Addition of IL-4 (10 ng/mL) markedly increased the levels of CCL17 and CCL22, but IL-4-induced CCL17 and CCL22 expression was significantly blunted in BMDCs from S1pr2 gene-deficient mice. Furthermore, pretreatment with JTE-013 (1-30 μM) dose-dependently suppressed this induction in BMDCs from wild-type mice. Our results demonstrate that blockage of S1P₂ ameliorates not only DNCB-induced atopic dermatitis symptoms but also Th2 cell-attracting capacity of dendritic cells, suggesting S1P₂ as a potential therapeutic target for atopic dermatitis.

Th17 cells and their cytokines serve as potential therapeutic target in experimental autoimmune neuritis

BACKGROUND

Accumulating evidence has pointed that T helper 17 cells and their cytokines are pathogenic in Guillain-Barré syndrome (GBS). However, little is known concerning the IL-17 expression change trend during the whole course of disease, and whether drugs specially targeting Th17 cells or their cytokines have potential effects on experimental autoimmune neuritis (EAN) is uncertain.

METHODS

We explored the IL-17 and receptor-related orphan receptor-gamma-t (RORγt) expression change trends in EAN rats to identify the stage of effect of Th17 pathway in EAN, and further, we investigated the effect of RORγt inhibitors by assessing clinical score, histological staining, and IL-17 and RORγt expression change trends in serum and tissues.

RESULTS

The expression level of IL-17 and RORγt in serum and tissues increased with the progression of the disease in the EAN group and decreased after the disease reaching its peak. RORγt-IN-1 treatment strikingly reduced the neurological deficits by ameliorating inflammatory cell infiltration, deceased the serum IL-17 and RORγt levels, and further downregulated the expression of IL-17 and RORγt mRNA in spleen, lymphnodes, and sciatic nerve.

CONCLUSIONS

Th17 cells and their cytokines are closely associated with the onset of GBS and the novel RORγt inhibitors may be prospective strategies in treating GBS.

S1P-S1PR1 Signaling: the "Sphinx" in Osteoimmunology

The fundamental interaction between the immune and skeletal systems, termed as osteoimmunology, has been demonstrated to play indispensable roles in the maintenance of balance between bone resorption and formation. The pleiotropic sphingolipid metabolite, sphingosine 1-phosphate (S1P), together with its cognate receptor, sphingosine-1-phosphate receptor-1 (S1PR1), are known as key players in osteoimmunology due to the regulation on both immune system and bone remodeling. The role of S1P-S1PR1 signaling in bone remodeling can be directly targeting both osteoclastogenesis and osteogenesis. Meanwhile, inflammatory cell function and polarization in both adaptive immune (T cell subsets) and innate immune cells (macrophages) are also regulated by this signaling axis, suggesting that S1P-S1PR1 signaling could aslo indirectly regulate bone remodeling via modulating the immune system. Therefore, it could be likely that S1P-S1PR1 signaling might take part in the maintenance of continuous bone turnover under physiological conditions, while lead to the pathogenesis of bone deformities during inflammation. In this review, we summarized the immunological regulation of S1P-S1PR1 signal axis during bone remodeling with an emphasis on how osteo-immune regulators are affected by inflammation, an issue with relevance to chronical bone disorders such as rheumatoid arthritis, spondyloarthritis and periodontitis.

Myeloid sphingosine-1-phosphate receptor 1 is important for CNS autoimmunity and neuroinflammation

The critical role of sphingosine-1-phosphate (S1P) signaling in lymphocyte trafficking is well recognized, however, the contribution of myeloid cell-S1P signaling in neuroimmunity is less well understood. We previously reported that C57BL/6J mice harboring phosphorylation defective S1P receptor 1 (S1P₁) (with mutated serines in the carboxyl terminus, leading to impaired receptor internalization) [S1P₁(S5A)] developed severe, T_H17-dominant experimental autoimmune encephalomyelitis. In this study, we demonstrate that S1P₁-mediated T_H17 polarization is not an intrinsic T cell effect, but dependent on sustained S1P₁ signaling in myeloid cells. First, utilizing the S1P₁(S5A) mice in the EAE model, we observed that S1P₁ activated and enhanced antigen presentation function in myeloid cells. Second, sequential phosphorylation of STAT3 occurred in dendritic cells, monocytes, and macrophages/microglia during neuroinflammation. Third, we show that pro-inflammatory (CD45^hiCD11b⁺Ly6C^hi) monocytes contribute to T_H17 differentiation and neuroinflammation by regulating IL-6 expression. Finally, results from experiments utilizing myeloid cell-specific S1P₁ overexpression (S1pr1^f/stop/f:LysM^Cre) mice demonstrate that myeloid cell S1P₁ directly contributes to severity of neuroinflammation. These findings reveal the critical contribution of myeloid-S1P₁ signaling in CNS autoimmunity.

Correlation of myomir-206 and proinflammatory cytokines (IL-16 and IL-17) in patients with rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a persistent autoimmune disease in which the activity of proinflammatory cytokines and the imbalance, related to the inflammatory process, between elements of bone tissue remodeling such as osteoclasts and osteoblasts play a key role in development of erosions and bone destruction. MicroRNAs are important regulators of skeletal remodeling and are involved in RA pathogenesis. Myomir-206 (miR-206) is unrivalled among the myomirRs, where it is expressed in skeletal muscle and either absent or minimally expressed in other tissues.

MATERIAL AND METHODS

This study was designed to analyze the miR-206 expression pattern in peripheral blood mononuclear cells (PBMCs) using quantitative real time polymerase chain reaction and its correlation with IL-16/IL-17 proinflammatory cytokines in two groups - 20 healthy individuals and 30 patients with RA.

RESULTS

Elevated expression of miR-206 was observed in RA patients compared with healthy controls (p < 0.001). A significant increase in both IL-17 and IL-16 serum levels was found in the RA group (p < 0.01 and p < 0.05; respectively) compared to the control group. miR-206 expression level and IL-17 production were directly positively correlated (r = 0.491; p < 0.01). ROC analysis of miR-206 showed a cutoff value of 2.7 with 70% sensitivity, 85% specificity, and the area under the curve was 0.802 (p < 0.001) with the 95% confidence interval from 0. 676 to 0.927.

CONCLUSIONS

Taken together, our results indicate the importance of miR-206 expression in patients with RA, as a potential new biomarker that affects bone loss/deformity and its collaborative role with proinflammatory cytokines such as IL-16 and IL-17 in RA bone metabolism. Particular interest should be given to further research to determine the contribution of expression of miR-206 in RA pathogenesis.

Sphingosine Kinases promote IL-17 expression in human T lymphocytes

Sphingosine 1-phosphate (S1P) has a role in many cellular processes. S1P is involved in cell growth and apoptosis, regulation of cell trafficking, production of cytokines and chemokines. The kinases SphK1 and SphK2 (SphKs) phosphorilate Sphingosine (Sph) to S1P and several phosphatases revert S1P to sphingosine, thus assuring a balanced pool that can be depleted by a Sphingosine lyase in hexadecenal compounds and aldehydes. There are evidences that SphK1 and 2 may per se control cellular processes. Here, we report that Sph kinases regulate IL-17 expression in human T cells. SphKs inhibition impairs the production of IL-17, while their overexpression up-regulates expression of the cytokine through acetylation of IL-17 promoter. SphKs were up-regulated also in PBMCs of patients affected by IL-17 related diseases. Thus, S1P/S1P kinases axis is a mechanism likely to promote IL-17 expression in human T cells, representing a possible therapeutic target in human inflammatory diseases.

The emerging alliance of sphingosine-1-phosphate signalling and immune cells: from basic mechanisms to implications in hypertension

The immune system plays a considerable role in hypertension. In particular, T-lymphocytes are recognized as important players in its pathogenesis. Despite substantial experimental efforts, the molecular mechanisms underlying the nature of T-cell activation contributing to an onset of hypertension or disease perpetuation are still elusive. Amongst other cell types, lymphocytes express distinct profiles of GPCRs for sphingosine-1-phosphate (S1P) - a bioactive phospholipid that is involved in many critical cell processes and most importantly majorly regulates T-cell development, lymphocyte recirculation, tissue-homing patterns and chemotactic responses. Recent findings have revealed a key role for S1P chemotaxis and T-cell mobilization for the onset of experimental hypertension, and elevated circulating S1P levels have been linked to several inflammation-associated diseases including hypertension in patients. In this article, we review the recent progress towards understanding how S1P and its receptors regulate immune cell trafficking and function and its potential relevance for the pathophysiology of hypertension. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Reversing HIV latency via sphingosine-1-phosphate receptor 1 signaling

OBJECTIVE

In this study, we looked for a new family of latency reversing agents.

DESIGN

We searched for G-protein-coupled receptors (GPCR) coexpressed with the C-C chemokine receptor type 5 (CCR5) in primary CD4 T cells that activate infected cells and boost HIV production.

METHODS

GPCR coexpression was unveiled by reverse transcriptase-PCR. We used fluorescence resonance energy transfer to analyze the dimerization with CCR5 of the expressed GPCR. Viral entry was measured by flow cytometry, reverse transcription by quantitative PCR, nuclear factor-kappa B translocation by immunofluorescence, long terminal repeat activation using a gene reporter assay and viral production by p24 quantification.

RESULTS

Gαi-coupled sphingosine-1-phophate receptor 1 (S1P1) is highly coexpressed with CCR5 on primary CD4 T cells and dimerizes with it. The presence of S1P1 had major effects neither on viral entry nor on reverse transcription. Yet, S1P1 signaling induced NFκB activation, boosting the expression of the HIV LTR. Consequently, in culture medium containing sphingosine-1-phophate, the presence of S1P1 enhanced the replication of a CCR5-, but also of a CXCR4-using HIV-1 strain. The S1P1 ligand FTY720, a drug used in multiple sclerosis treatment, inhibited HIV-1 productive infection of monocyte-derived dendritic cells and of severe combined immunodeficiency mice engrafted with human peripheral blood mononuclear cells. Conversely, S1P1 agonists were able to force latently infected peripheral blood mononuclear cells and lymph node cells to produce virions in vitro.

CONCLUSION

Altogether these data indicate that the presence of S1P1 facilitates HIV-1 replicative cycle by boosting viral genome transcription, S1P1 antagonists have anti-HIV effects and S1P1 agonists are HIV latency reversing agents.

Single-cell profiling reveals GPCR heterogeneity and functional patterning during neuroinflammation

GPCR expression was intensively studied in bulk cDNA of leukocyte populations, but limited data are available with respect to expression in individual cells. Here, we show a microfluidic-based single-cell GPCR expression analysis in primary T cells, myeloid cells, and endothelial cells under naive conditions and during experimental autoimmune encephalomyelitis, the mouse model of multiple sclerosis. We found that neuroinflammation induces characteristic changes in GPCR heterogeneity and patterning, and we identify various functionally relevant subgroups with specific GPCR profiles among spinal cord-infiltrating CD4 T cells, macrophages, microglia, or endothelial cells. Using GPCRs CXCR4, S1P1, and LPHN2 as examples, we show how this information can be used to develop new strategies for the functional modulation of Th17 cells and activated endothelial cells. Taken together, single-cell GPCR expression analysis identifies functionally relevant subpopulations with specific GPCR repertoires and provides a basis for the development of new therapeutic strategies in immune disorders.

Sphingosine 1-Phosphate Receptor 1 Signaling in Mammalian Cells

The bioactive lipid, sphingosine 1-phosphate (S1P) binds to a family of G protein-coupled receptors, termed S1P₁-S1P₅. These receptors function in, for example, the cardiovascular system to regulate vascular barrier integrity and tone, the nervous system to regulate neuronal differentiation, myelination and oligodendrocyte/glial cell survival and the immune system to regulate T- and B-cell subsets and trafficking. S1P receptors also participate in the pathophysiology of autoimmunity, inflammatory disease, cancer, neurodegeneration and others. In this review, we describe how S1P₁ can form a complex with G-protein and β-arrestin, which function together to regulate effector pathways. We also discuss the role of the S1P₁-Platelet derived growth factor receptor β functional complex (which deploys G-protein/β-arrestin and receptor tyrosine kinase signaling) in regulating cell migration. Possible mechanisms by which different S1P-chaperones, such as Apolipoprotein M-High-Density Lipoprotein induce biological programmes in cells are also described. Finally, the role of S1P₁ in health and disease and as a target for clinical intervention is appraised.

Effect of sphingosine kinase modulators on interleukin-1β release, sphingosine 1-phosphate receptor 1 expression and experimental autoimmune encephalomyelitis

BACKGROUND AND PURPOSE

The sphingosine analogue, FTY720 (GilenyaR ), alleviates clinical disease progression in multiple sclerosis. Here, we variously assessed the effects of an azide analogue of (S)-FTY720 vinylphosphonate (compound 5; a sphingosine kinase 1 activator), (R)-FTY720 methyl ether (ROMe, a sphingosine kinase 2 inhibitor) and RB-020 (a sphingosine kinase 1 inhibitor and sphingosine kinase 2 substrate) on IL-1β formation, sphingosine 1-phosphate levels and expression of S1P1 receptors. We also assessed the effect of compound 5 and ROMe in an experimental autoimmune encephalomyelitis (EAE) model in mice.

EXPERIMENTAL APPROACH

We measured IL-1β formation by macrophages, sphingosine 1-phosphate levels and expression levels of S1P1 receptors in vitro and clinical score in mice with EAE and the extent of inflammatory cell infiltration into the spinal cord in vivo.

KEY RESULTS

Treatment of differentiated U937 macrophages with compound 5, RB-020 or sphingosine (but not ROMe) enhanced IL-1β release. These data suggest that these compounds might be pro-inflammatory in vitro. However, compound 5 or ROMe reduced disease progression and infiltration of inflammatory cells into the spinal cord in EAE, and ROMe induced a reduction in CD4+ and CD8+ T-cell levels in the blood (lymphopenia). Indeed, ROMe induced a marked decrease in expression of cell surface S1P1 receptors in vitro.

CONCLUSION AND IMPLICATIONS

This is the first demonstration that an activator of sphingosine kinase 1 (compound 5) and an inhibitor of sphingosine kinase 2 (ROMe, which also reduces cell surface S1P1 receptor expression) have an anti-inflammatory action in EAE.

NF-κB Pathways in the Pathogenesis of Multiple Sclerosis and the Therapeutic Implications

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathways are involved in cell immune responses, apoptosis and infections. In multiple sclerosis (MS), NF-κB pathways are changed, leading to increased levels of NF-κB activation in cells. This may indicate a key role for NF-κB in MS pathogenesis. NF-κB signaling is complex, with many elements involved in its activation and regulation. Interestingly, current MS treatments are found to be directly or indirectly linked to NF-κB pathways and act to adjust the innate and adaptive immune system in patients. In this review, we will first focus on the intricacies of NF-κB signaling, including the activating pathways and regulatory elements. Next, we will theorize about the role of NF-κB in MS pathogenesis, based on current research findings, and discuss some of the associated therapeutic implications. Lastly, we will review four new MS treatments which interrupt NF-κB pathways—fingolimod, teriflunomide, dimethyl fumarate (DMF) and laquinimod (LAQ)—and explain their mechanisms, and the possible strategy for MS treatments in the future.

Sphingosine 1-phosphate signaling impacts lymphocyte migration, inflammation and infection

Sphingosine 1-phosphate (S1P) is a sphingosine containing lipid intermediate obtained from ceramide. S1P is known to be an important signaling molecule and plays multiple roles in the context of immunity. This lysophospholipid binds and activates G-protein-coupled receptors (GPCRs) known as S1P receptors 1-5 (S1P1-5). Once activated, these GPCRs mediate signaling that can lead to alterations in cell proliferation, survival or migration, and can also have other effects such as promoting angiogenesis. In this review, we will present evidence demonstrating a role for S1P in lymphocyte migration, inflammation and infection, as well as in cancer. The therapeutic potential of targeting S1P receptors, kinases and lyase will also be discussed.

Sphingosine kinase 1/sphingosine-1-phosphate regulates the expression of interleukin-17A in activated microglia in cerebral ischemia/reperfusion

BACKGROUND

Microglial activation is one of the causative factors of neuroinflammation in cerebral ischemia/reperfusion (IR). Sphingosine kinase 1 (Sphk1), a key enzyme responsible for phosphorylating sphingosine into sphingosine-1-phosphate (S1P), plays an important role in the regulation of proinflammatory cytokines in activated microglia. Recent research demonstrated that S1P increased IL-17A-secretion and then worsened CNS (central nervous system) inflammation. Thus, in the present study, we sought to use microglial cells as the object of study to discuss the molecular mechanisms in Sphk1/S1P-regulated IL-17A-secretion in IR.

METHODS

We used immunofluorescence and confocal microscopy to detect whether Sphk1 is expressed in microglia after cerebral IR or oxygen-glucose deprivation (OGDR). Western blot analysis was used to estimate the total Sphk1 protein level at different time points after OGDR. To detect cytokine secretion in microglial supernatants in response to OGDR, we measured the concentration of IL-17A in the culture supernatants using an enzyme-linked immunosorbent assay (ELISA). To evaluate whether microglia subjected to OGDR exhibited neuronal injury, we used a commercially available terminal transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) kit to detect apoptotic neurons.

RESULTS

Sphk1 was expressed in microglia in response to cerebral IR or OGDR at appointed time. Pre-injection with PF-543, an inhibitor of Sphk1, before IR clearly reduced the expression of Sphk1 in microglia relative to brain IR alone. The number of TUNEL-positive neurons was also decreased in the PF-543-pretreated animals before IR compared to the animals with IR alone. When S1P was administered in OGDR microglia, IL-17A expression and neuronal apoptosis were increased compared to OGDR alone and the administration of S1P alone. ELISA further confirmed the above results. Moreover, the inhibition of Sphk1 by siRNA reduced IL-17A production and relieved neuronal apoptosis in OGDR microglia.

CONCLUSION

These results indicated that Sphk1/S1P regulates the expression of IL-17A in activated microglia, inducing neuronal apoptosis in cerebral ischemia/reperfusion. The microglial Sphk1/S1P pathway may thus be a potential therapeutic target to control neuroinflammation in brain IR.

Interleukin 27R regulates CD4+ T cell phenotype and impacts protective immunity during Mycobacterium tuberculosis infection

Loss of IL-27R on T cells results in increased protection from Mycobacterium tuberculosis. Torrado et al. demonstrate that IL-27R^−/− T cells show improved fitness that is associated with decreased expression of cell death molecules, maintenance of IL-2 production, and preferential accumulation in the lung parenchyma and around infected macrophages.

CD4⁺ T cells mediate protection against Mycobacterium tuberculosis (Mtb); however, the phenotype of protective T cells is undefined, thereby confounding vaccination efforts. IL-27 is highly expressed during human tuberculosis (TB), and absence of IL-27R (Il27ra) specifically on T cells results in increased protection. IL-27R deficiency during chronic Mtb infection does not impact antigen-specific CD4⁺ T cell number but maintains programmed death-1 (PD-1), CD69, and CD127 expression while reducing T-bet and killer cell lectin-like receptor G1 (KLRG1) expression. Furthermore, T-bet haploinsufficiency results in failure to generate KLRG1⁺, antigen-specific CD4⁺ T cells, and in improved protection. T cells in Il27ra^−/− mice accumulate preferentially in the lung parenchyma within close proximity to Mtb, and antigen-specific CD4⁺ T cells lacking IL-27R are intrinsically more fit than intact T cells and maintain IL-2 production. Improved fitness of IL-27R–deficient T cells is not associated with increased proliferation but with decreased expression of cell death–associated markers. Therefore, during Mtb infection, IL-27R acts intrinsically on T cells to limit protection and reduce fitness, whereas the IL-27R–deficient environment alters the phenotype and location of T cells. The significant expression of IL-27 in TB and the negative influence of IL-27R on T cell function demonstrate the pathway by which this cytokine/receptor pair is detrimental in TB.

Alzheimer's disease vaccine development: A new strategy focusing on immune modulation

Despite significant advances in the development of Alzheimer's disease (AD) vaccines effective in animal models, these prototypes have been clinically unsuccessful; apparently the result of using immunogens modified to prevent inflammation. Hence, a new paradigm is needed that uses entire AD-associated immunogens, a notion supported by recent successful passive immunotherapy results, with adjuvants that induce Th2-only while inhibiting without abrogating Th1 immunity. Here, we discuss the obstacles to AD vaccine development and Th2-adjuvants that by acting on dendritic and T cells, would elicit regardless of the antigen a safe and effective antibody response, while preventing damaging neuroinflammation and ameliorating immunosenescence.

Regulation of IL-17 in autoimmune diseases by transcriptional factors and microRNAs

In recent years, IL-17A (IL-17), a pro-inflammatory cytokine, has received intense attention of researchers and clinicians alike with documented effects in inflammation and autoimmune diseases. IL-17 mobilizes, recruits and activates different cells to increase inflammation. Although protective in infections, overproduction of IL-17 promotes inflammation in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, psoriasis, among others. Regulating IL-17 levels or action by using IL-17-blocking antibodies or IL-17R antagonist has shown to attenuate experimental autoimmune diseases. It is now known that in addition to IL-17-specific transcription factor, RORγt, several other transcription factors and select microRNAs (miRNA) regulate IL-17. Given that miRNAs are dysregulated in autoimmune diseases, a better understanding of transcriptional factors and miRNA regulation of IL-17 expression and function will be essential for devising potential new therapies. In this review, we will overview IL-17 induction and function in relation to autoimmune diseases. In addition, current findings on transcriptional regulation of IL-17 induction and plausible interplay between IL-17 and miRNA in autoimmune diseases are highlighted.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

Novel therapies for memory cells in autoimmune diseases

Autoimmune diseases are a major cause of morbidity, and their incidence and prevalence continue to rise. Treatments for these diseases are non-specific and result in significant adverse effects. Targeted therapies may help in improving the risk : benefit ratio associated with treatment. Immunological memory is an important feature of the vertebrate immune system that results in the production of cells that are long-lived and able to respond to antigens in a more robust manner. In the setting of autoimmunity this characteristic becomes detrimental due to the ongoing response to a self-antigen(s). These memory cells have been shown to play key roles in various autoimmune diseases such as type 1 diabetes, multiple sclerosis and psoriasis. Memory T cells and B cells can be identified based on various molecules expressed on their surface. Memory T cells can be divided into three main categories - central memory, effector memory and resident memory cells. These subsets have different proliferative potential and cytokine-producing abilities. Utilizing differentially expressed surface molecules or downstream signalling pathway proteins in these cells it is now possible to target memory cells while sparing naive cells. We will discuss the various available options for such a strategy and several potential strategies that may yield successful therapies in the future.

Different correlation of sphingosine-1-phosphate receptor 1 with receptor activator of nuclear factor kappa B ligand and regulatory T cells in rat periapical lesions

INTRODUCTION

Sphingosine-1-phosphate receptor 1 (S1P1) is crucial for regulation of immunity and bone metabolism. This study aimed to investigate the expression of S1P1 in rat periapical lesions and its relationship with receptor activator of nuclear factor kappa B ligand (RANKL) and regulatory T (Treg) cells.

METHODS

Periapical lesions were induced by pulp exposure in the first lower molars of 55 Wistar rats. Thirty rats were killed on days 0, 7, 14, 21, 28, and 35, and their mandibles were harvested for x-ray imaging, micro-computed tomography scanning, histologic observation, immunohistochemistry, enzyme histochemistry, and double immunofluorescence analysis. The remaining 25 rats were killed on days 0, 14, 21, 28, and 35, and mandibles were harvested for flow cytometry.

RESULTS

The volume and area of the periapical lesions increased from day 0 to day 21 and then remained comparably stable after day 28. S1P1-positive cells were observed in the inflammatory periapical regions; the number of S1P1-positive cells peaked at day 14 and then decreased from day 21 to day 35. The distribution of S1P1-positive cells was positively correlated with the dynamics of RANKL-positive cells but was negatively correlated with that of Treg cells.

CONCLUSIONS

S1P1 expression was differentially correlated with RANKL and Treg cell infiltration in the periapical lesions and is therefore a contributing factor to the pathogenesis of such lesions.

Sphingosine-1-phosphate receptor 1 signalling in T cells: trafficking and beyond

Sphingosine-1-phosphate (S1P) is a lipid second messenger that signals via five G protein-coupled receptors (S1P1-5 ). S1P receptor (S1PR) signalling is associated with a wide variety of physiological processes including lymphocyte biology, their recirculation and determination of T-cell phenotypes. The effect of FTY720 (Fingolimod, Gilenya™) to regulate lymphocyte egress and to ameliorate paralysis in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis led to the use of FTY720 as a first-line oral agent for treatment of relapsing-remitting multiple sclerosis. However, a significant body of research suggests that S1P signalling may participate in diverse immune regulatory functions other than lymphocyte trafficking. This review article discusses the current knowledge of S1P signalling in the fate and function of T regulatory, T helper type 17 and memory T cells in health and disease.

Fingolimod attenuates splenocyte-induced demyelination in cerebellar slice cultures

The family of sphingosine-1-phosphate receptors (S1PRs) is G-protein-coupled, comprised of subtypes S1PR1-S1PR5 and activated by the endogenous ligand S1P. The phosphorylated version of Fingolimod (pFTY720), an oral therapy for multiple sclerosis (MS), induces S1PR1 internalisation in T cells, subsequent insensitivity to S1P gradients and sequestering of these cells within lymphoid organs, thus limiting immune response. S1PRs are also expressed in neuronal and glial cells where pFTY720 is suggested to directly protect against lysolecithin-induced deficits in myelination state in organotypic cerebellar slices. Of note, the effect of pFTY720 on immune cells already migrated into the CNS, prior to treatment, has not been well established. We have previously found that organotypic slice cultures do contain immune cells, which, in principle, could also be regulated by pFTY720 to maintain levels of myelin. Here, a mouse organotypic cerebellar slice and splenocyte co-culture model was thus used to investigate the effects of pFTY720 on splenocyte-induced demyelination. Spleen cells isolated from myelin oligodendrocyte glycoprotein immunised mice (MOG-splenocytes) or from 2D2 transgenic mice (2D2-splenocytes) both induced demyelination when co-cultured with mouse organotypic cerebellar slices, to a similar extent as lysolecithin. As expected, in vivo treatment of MOG-immunised mice with FTY720 inhibited demyelination induced by MOG-splenocytes. Importantly, in vitro treatment of MOG- and 2D2-splenocytes with pFTY720 also attenuated demyelination caused by these cells. In addition, while in vitro treatment of 2D2-splenocytes with pFTY720 did not alter cell phenotype, pFTY720 inhibited the release of the pro-inflammatory cytokines such as interferon gamma (IFNγ) and interleukin 6 (IL6) from these cells. This work suggests that treatment of splenocytes by pFTY720 attenuates demyelination and reduces pro-inflammatory cytokine release, which likely contributes to enhanced myelination state induced by pFTY720 in organotypic cerebellar slices.

Is MS an inflammatory or primary degenerative disease?

Multiple sclerosis (MS) is characterized by multiple areas of inflammation, demyelination and neurodegeneration. Multiple molecular and cellular components mediate neuroinflammation in MS. They involve: adhesion molecules, chemokines, cytokines, matalloproteases and the following cells: CD4+ T cells, CD8+ T cells, B cells, microglia and macrophages. Infiltrating Th1 CD4+ T cells secrete proinflammatory cytokines. They stimulate the release of chemokines, expression of adhesion molecules and can be factors that cause damage to the myelin sheath and axons. Chemokines stimulate integrin activation, mediate leukocyte locomotion on endothelial cells and participate in transendothelial migration. CD8+ cells can directly damage axons. B cells are involved in the production of antibodies which can participate in demyelination. B cells can also function as antigen presenting cells and contribute to T cell activation. Neuroinflammation is not only present in relapsing-remitting MS, but also in the secondary and primary progressive forms of the disease. The association between inflammation consisting of T cells, B cells, plasma cells and macrophages and axonal injury exists in MS patients including the progressive forms of the disease. The above association does not exclude the possibility that neurodegeneration can exist independently from inflammation. Very little inflammation is seen in cortical MS plaques. Anti-inflammatory therapies with different mode of action change the course of MS. Anti-inflammatory and immunomodulatory treatments are beneficial in the early relapsing stage of MS, but these treatments are ineffective in secondary progressive and primary progressive MS. In the stage of progressive MS, inflammation becomes trapped behind a closed or repaired blood-brain barrier. In such a situation current immunomodulatory, immunosuppressive or anti-inflammatory treatments might not reach this inflammatory process to exert a beneficial effect.

The role of sphingosine 1-phosphate receptors in the treatment of demyelinating diseases

Sphingosine 1-phosphate receptors (S1PRs) are a family of G-protein coupled receptors composed of subtypes S1PR1–5 and activated by the endogenous ligand sphingosine 1-phosphate. S1PRs are modulated by the recently approved oral therapy for relapsing–remitting multiple sclerosis, called fingolimod (FTY720). The phosphorylated version of FTY720 (pFTY720) is a pan-S1PR agonist, with the exception of S1PR2. This drug promotes the internalization of S1PR1s in T cells and is said to act as a ‘functional antagonist’ making lymphocytes ‘blind’ to sphingosine 1-phosphate gradients and limiting cell egress from lymph nodes. This immunomodulatory effect of pFTY720 is proposed to be the prime mechanism by which this compound is efficacious in the treatment of multiple sclerosis. Importantly, however, S1PRs are also expressed in many other cell types, for example, cells of the cardiovascular system and the CNS. Studies have shown that pFTY720 enters the CNS and that modulation of S1PRs can alter the cellular physiology of neurons, astrocytes, microglia and oligodendrocytes. These works are suggestive of a potential role for S1PRs expressed in brain cells as targets for pFTY720. This article reviews the role of S1PRs in oligodendrocytes. The authors start by first debating whether pFTY720-mediated internalization of S1PRs causes ‘functional antagonism’ and/or ‘pathway-specific continued signaling’. The authors then describe the signaling pathways that are modulated by S1PRs expressed in oligodendrocytes and also outline the role of S1PRs in oligodendrocyte differentiation, process extension, survival and migration. Finally, the authors discuss the in vitro studies that suggest pFTY720 promotes myelination state versus the in vivo studies that suggest pFTY720 may not alter myelination. The authors conclude by suggesting that S1PRs in the CNS may be of potential use as drug targets not only for multiple sclerosis, but possibly for a number of other demyelinating disorders.

Sphingosine-1-phosphate exhibits anti-proliferative and anti-inflammatory effects in mouse models of psoriasis

BACKGROUND

It has been indicated that the sphingolipid sphingosine-1-phosphate (S1P) restrains the ability of dendritic cells to migrate to lymph nodes. Furthermore S1P has been demonstrated to inhibit cell growth in human keratinocytes. However, only little is known about the effect of S1P in hyperproliferative and inflammatory in vivo models.

OBJECTIVE

In this study, locally acting S1P was explored in different experimental mouse models of psoriasis vulgaris.

METHODS

S1P and FTY720 were tested in the imiquimod-induced psoriasis mouse model, the mouse tail assay and a pilot study of the severe combined immunodeficiency mice (SCID).

RESULTS

In the imiquimod model the positive control diflorasone diacetate and S1P, but not FTY720 reduced the imiquimod-induced epidermal hyperproliferation of the ear skin. This effect was confirmed in the SCID model, where S1P treated skin from patients suffering from psoriasis showed a decrease in epidermal thickness compared to vehicle. In the imiquimod model, there was also significant inhibition of ear swelling and a moderate reduction of inflammatory cell influx and oedema formation in ear skin by S1P treatment. The inflammatory response on the back skin was, however, only reduced by diflorasone diacetate. In the mouse tail assay, the influence of S1P and FTY720 in stratum granulosum formation was tested compared to the positive control calcipotriol. Whereas topical administration of calcipotriol led to a low but significant increase of stratum granulosum, S1P and FTY720 lacked such an effect.

CONCLUSION

Taken together, these results imply that topical administration of S1P might be a new option for the treatment of mild to moderate psoriasis lesions.

The ataxia telangiectasia mutated kinase pathway regulates IL-23 expression by human dendritic cells

Little is known of the regulation of IL-23 secretion in dendritic cells (DC) despite its importance for human Th17 responses. In this study, we show for first time, to our knowledge, that the ataxia telangiectasia mutated (ATM) pathway, involved in DNA damage sensing, acts as an IL-23 repressor. Inhibition of ATM with the highly selective antagonist KU55933 markedly increased IL-23 secretion in human monocyte-derived DC and freshly isolated myeloid DC. In contrast, inhibiting the closely related mammalian target of rapamycin had no effect on IL-23. Priming naive CD4(+) T cells with ATM-inhibited DC increased Th17 responses over and above those obtained with mature DC. Although ATM blockade increased the abundance of p19, p35, and p40 mRNA, IL-12p70 secretion was unaffected. To further examine a role for ATM in IL-23 regulation, we exposed DC to low doses of ionizing radiation. Exposure of DC to x-rays resulted in ATM phosphorylation and a corresponding depression of IL-23. Importantly, ATM inhibition with KU55933 prevented radiation-induced ATM phosphorylation and abrogated the capacity of x-rays to suppress IL-23. To explore how ATM repressed IL-23, we examined a role for endoplasmic reticulum stress responses by measuring generation of the spliced form of X-box protein-1, a key endoplasmic reticulum stress transcription factor. Inhibition of ATM increased the abundance of X-box protein-1 mRNA, and this was followed 3 h later by increased peak p19 transcription and IL-23 release. In summary, ATM activation or inhibition, respectively, inhibited or augmented IL-23 release. This novel role of the ATM pathway represents a new therapeutic target in autoimmunity and vaccine development.

Interleukin-27: balancing protective and pathological immunity

It has been more than 15 years since the identification of individual interleukin-27 (IL-27) and IL-27 receptor components. The last decade has seen the description of the signaling pathways engaged by IL-27, and an appreciation has emerged that this cytokine can modulate the intensity and duration of many classes of T cell responses. Here we provide an overview of the immunobiology of IL-27 and review advances in understanding the functions of individual IL-27 and IL-27 receptor subunits and the role of IL-27 in dictating the balance between protective and pathological immunity. Additionally, this cytokine has been proposed as a therapy to modify inflammatory conditions or to promote antitumor responses, and situations where experimental and clinical data sets implicate IL-27 in the outcome of disease are highlighted.

The Shc family protein adaptor, Rai, acts as a negative regulator of Th17 and Th1 cell development

Rai, a Shc adapter family member, acts as a negative regulator of antigen receptor signaling in T and B cells. Rai(-/-) mice develop lupus-like autoimmunity associated to the spontaneous activation of self-reactive lymphocytes. Here, we have addressed the potential role of Rai in the development of the proinflammatory Th1 and Th17 subsets, which are centrally implicated in the pathogenesis of a number of autoimmune diseases, including lupus. We show that Rai(-/-) mice display a spontaneous Th1/Th17 bias. In vitro polarization experiments on naive and effector/memory CD4(+) T cells demonstrate that Rai(-/-) favors the development and expansion of Th17 but not Th1 cells, indicating that Rai modulates TCR signaling to antagonize the pathways driving naive CD4(+) T cell differentiation to the Th17 lineage, while indirectly limiting Th1 cell development in vivo. Th1 and Th17 cell infiltrates were found in the kidneys of Rai(-/-) mice, providing evidence that Rai(-/-) contributes to the development of lupus nephritis, not only by enhancing lymphocyte activation but also by promoting the development and expansion of proinflammatory effector T cells. Interestingly, T cells from SLE patients were found to have a defect in Rai expression, suggesting a role for Rai in disease pathogenesis.