Mass cytometry analysis identifies T cell immune signature of aplastic anemia and predicts the response to cyclosporine

Aplastic anemia (AA) is an auto-activated T cell-mediated bone marrow failure. Cyclosporine is often used to treat non-severe AA, which demonstrates a more heterogeneous condition than severe AA. The response rate to cyclosporine is only around 50% in non-severe AA. To better predict response to cyclosporine and pinpoint who is the appropriate candidate for cyclosporine, we performed phenotypic and functional T cell immune signature at single cell level by mass cytometry from 30 patients with non-severe AA. Unexpectedly, non-significant differences of T cell subsets were observed between AA and healthy control or cyclosporine-responder and non-responders. Interestingly, when screening the expression of co-inhibitory molecules, T cell trafficking mediators, and cytokines, we found an increase of cytotoxic T lymphocyte antigen 4 (CTLA-4) on T cells in response to cyclosporine and a lower level of CTLA-4 on CD8⁺ T cells was correlated to hematologic response. Moreover, a decreased expression of sphingosine-1-phosphate receptor 1 (S1P₁) on naive T cells and a lower level of interleukin-9 (IL-9) on T helpers also predicted a better response to cyclosporine, respectively. Therefore, the T cell immune signature, especially in CTAL-4, S1P₁, and IL-9, has a predictive value for response to cyclosporine. Collectively, our study implies that immune signature analysis of T cell by mass cytometry is a useful tool to make a strategic decision on cyclosporine treatment of AA.

Co-modulation of T cells and B cells enhances the inhibition of inflammation in experimental hypersensitivity pneumonitis

Background

Hypersensitivity pneumonitis (HP) is an interstitial lung disease characterized by antigen-triggered neutrophilic exacerbations. Although CD4⁺ T cells are sufficient for HP pathogenesis, this never translated into efficient T cell-specific therapies. Increasing evidence shows that B cells also play decisive roles in HP. Here, we aimed to further define the respective contributions of B and T cells in subacute experimental HP.

Methods

Mice were subjected to a protocol of subacute exposure to the archaeon Methanosphaera stadmanae to induce experimental HP. Using models of adoptive transfers of B cells and T cells in Rag1-deficient mice and of B cell-specific S1P₁ deletion, we assessed the importance of B cells in the development of HP by evaluating inflammation in bronchoalveolar lavage fluid. We also aimed to determine if injected antibodies targeting B and/or T cells could alleviate HP exacerbations using a therapeutic course of intervention.

Results

Even though B cells are not sufficient to induce HP, they strongly potentiate CD4⁺ T cell-induced HP‑associated neutrophilic inflammation in the airways. However, the reduction of 85% of lung B cells in mice with a CD19-driven S1P₁ deletion does not dampen HP inflammation, suggesting that lung B cells are not necessary in large numbers to sustain local inflammation. Finally, we found that injecting antibodies targeting B cells after experimental HP was induced does not dampen neutrophilic exacerbation. Yet, injection of antibodies directed against B cells and T cells yielded a potent 76% inhibition of neutrophilic accumulation in the lungs. This inhibition occurred despite partial, sometimes mild, depletion of B cells and T cells subsets.

Conclusions

Although B cells are required for maximal inflammation in subacute experimental HP, partial reduction of B cells fails to reduce HP-associated inflammation by itself. However, co-modulation of T cells and B cells yields enhanced inhibition of HP exacerbation caused by an antigenic rechallenge.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02200-9.

Sphingosine Kinase-1 Is Overexpressed and Correlates with Hypoxia in Osteosarcoma: Relationship with Clinicopathological Parameters

The Sphingosine kinase-1/Sphingosine 1-Phosphate (SphK1/S1P) signaling pathway is overexpressed in various cancers, and is instrumental for the adaptation to hypoxia in a number of solid tumor models, but no data are available in osteosarcoma. Here we report that SphK1 and the S1P₁ receptor are involved in HIF-1α accumulation in hypoxic osteosarcoma cells. FTY720 (Fingolimod), which targets SphK1 and S1P_1, prevented HIF-1α accumulation, and also inhibited cell proliferation in both normoxia and hypoxia unlike conventional chemotherapy. In human biopsies, a significant increase of SphK1 activity was observed in cancer compared with normal bones. In all sets of TMA samples (130 cases of osteosarcoma), immunohistochemical analysis showed the hypoxic marker GLUT-1, SphK1 and S1P₁ were expressed in tumors. SphK1 correlated with the GLUT-1 suggesting that SphK1 is overexpressed and correlates with intratumoral hypoxia. No correlation was found between GLUT-1 or SphK1 and response to chemotherapy, but a statistical difference was found with increased S1P₁ expression in patients with poor response in long bone osteosarcomas. Importantly, multivariate analyses showed that GLUT-1 was associated with an increased risk of death in flat bone, whereas SphK1 and S1P₁ were associated with an increased risk of death in long bones.

Deletion of Sphingosine 1-Phosphate receptor 1 in cardiomyocytes during development leads to abnormal ventricular conduction and fibrosis

Sphingosine 1-Phosphate receptor 1 (S1P1 , encoded by S1pr1) is a G protein-coupled receptor that signals in multiple cell types including endothelial cells and cardiomyocytes. Cardiomyocyte-specific deletion of S1pr1 during mouse development leads to ventricular noncompaction, with 44% of mutant mice surviving to adulthood. Adult survivors of embryonic cardiomyocyte S1pr1 deletion showed cardiac hypertrabeculation consistent with ventricular noncompaction. Surprisingly, systolic function in mutant mice was preserved through at least 1 year of age. Cardiac conduction was abnormal in cardiomyocyte S1pr1 mutant mice, with prolonged QRS intervals in mutants as compared with littermate control mice. Immunostaining of hearts from S1pr1 mutant embryos displayed a zone of intermediate Connexin 40 (Cx40) expression in the trabecular myocardium. However, we observed no significant differences in Cx40 and Connexin 43 immunostaining in hearts from adult survivors of embryonic cardiomyocyte S1pr1 deletion, which suggests normalized development of the ventricular conduction system in mutant mice. By contrast, the adult survivors of embryonic cardiomyocyte S1pr1 deletion showed increased cardiac fibrosis as compared with littermate controls. These results demonstrate that ventricular hypertrabeculation caused by embryonic deletion of cardiomyocyte S1pr1 correlates with cardiac fibrosis, which contributes to abnormal ventricular conduction. These results also reveal conduction abnormalities in the setting of hypertrabeculation with normal systolic function, which may be of clinical relevance in humans with ventricular hypertrabeculation.

Protective effect of the sphingosine-1 phosphate receptor agonist siponimod on disrupted blood brain barrier function

Sphingosine 1 phosphate (S1P) is a bioactive sphingolipid that exerts several functions in physiological and pathological conditions. The modulation of one of its receptors, S1P1, plays an important role in the egress of lymphocytes from lymph nodes and is a useful target in multiple sclerosis (MS) treatment. A new drug, siponimod (BAF-312) has been recently approved for the treatment of secondary progressive MS and has affinity for two S1P receptors, S1P1 and S1P5. The two receptors are expressed by endothelial cells that, as components of the blood-brain barrier (BBB), prevent the access of solutes and lymphocytes into the central nervous system, function often compromised in MS. Using an in vitro BBB model exposed to inflammatory cytokines (TNFα and IFNγ, 5 UI and 10 UI respectively), we evaluated the effects of BAF-312 (100 nM) on expression and function of endothelial tight junctional proteins (Zo-1 and claudin-5), regulation of transendothelial electrical resistance (TEER) and permeability to FITC-conjugated dextran. Zo-1 expression, as well as TEER values, were promptly recovered (24 h) when both S1P1 and S1P5 were activated by BAF-312. In contrast, at this time point, activation of S1P5 with the selective agonist UC-42-WP04 (300 nM) or with BAF-312, under blockade of S1P1 with the selective antagonist NIBR-0213 (1 μM), resulted in recovery of expression and localization of claudin-5 and reduction of TNFα/INFγ-induced expression of metalloproteinase 9. Only after a prolonged BAF-312 exposure (48 h), S1P1 was involved through activation of the PI3K/Akt pathway. The PI3K inhibitor LY294002 (10 µM) prevented in fact the effects of BAF-312 on all the parameters examined. In conclusion, BAF-312, by modulating both S1P1 and S1P5, may strengthen BBB properties, thus providing additional effects in the treatment of MS.

Impact of S1P Mimetics on Mesenteric Ischemia/Reperfusion Injury

Mesenteric ischemia/reperfusion (I/R), following the transient deprivation of blood flow to the gut, triggers an acute flogistic process involving the disruption of endothelial and epithelial barriers integrity, the activation of immune cells, and the abundant release of inflammatory mediators. Among them, the lipid mediator sphingosine-1-phosphate (S1P) is involved in maintaining epithelial and endothelial barrier integrity and in governing the migration of immune cells through the interaction with S1P_1–5 receptors. Therefore, the present work aims to investigate the involvement of S1P signaling in intestinal I/R-induced injury by studying the effects of FTY720, the non-selective S1P_1,3–5 agonist, and comparing them with the responses to ozanimod, selective S1P_1,5 agonist, in a murine model of gut I/R. Intestinal edema, gut and lung neutrophil infiltration, and oxidative stress were evaluated through biochemical and morphological assays. The collected results highlight the protective action of FTY720 against the inflammatory cascade elicited by mesenteric I/R injury, mainly through the control of vascular barrier integrity. While these beneficial effects were mimicked by ozanimod and can be therefore attributed largely to the effects exerted by FTY720 on S1P₁, the recruitment of myeloid cells to the injured areas, limited by FTY720 but not by ozanimod, rather suggests the involvement of other receptor subtypes.

A label-free impedance assay in endothelial cells differentiates the activation and desensitization properties of clinical S1P1 agonists

Sphingosine-1 phosphate receptor-1 (S1P1 ) activation maintains endothelial barrier integrity, whereas S1P1 desensitization induces peripheral blood lymphopenia. The latter is exploited in the approval and/or late-stage development of receptor-desensitizing agents targeting the S1P1 receptor in multiple sclerosis, such as siponimod, ozanimod, and ponesimod. SAR247799 is a recently described G protein-biased S1P1 agonist that activates S1P1 without desensitization and thus has endothelial-protective properties in patients without reducing lymphocytes. As SAR247799 demonstrated endothelial-protective effects at sub-lymphocyte-reducing doses, the possibility exists that other S1P1 modulators could also exhibit endothelial-protective properties at lower doses. To explore this possibility, we sought to quantitatively compare the biased properties of SAR247799 with the most advanced clinical molecules targeting S1P1 . In this study, we define the β-arrestin pathway component of the impedance profile following S1P1 activation in a human umbilical vein endothelial cell line (HUVEC) and report quantitative indices of the S1P1 activation-to-desensitization ratio of various clinical molecules. In a label-free impedance assay assessing endothelial barrier integrity and disruption, the mean estimates (95% confidence interval) of the activation-to-desensitization ratios of SAR247799, ponesimod, ozanimod, and siponimod were 114 (91.1-143), 7.66 (3.41-17.2), 6.35 (3.21-12.5), and 0.170 (0.0523-0.555), respectively. Thus, we show that SAR247799 is the most G protein-biased S1P1 agonist currently characterized. This rank order of bias among the most clinically advanced S1P1 modulators provides a new perspective on the relative potential of these clinical molecules for improving endothelial function in patients in relation to their lymphocyte-reducing (desensitization) properties.

Reciprocal Interaction between Vascular Filopodia and Neural Stem Cells Shapes Neurogenesis in the Ventral Telencephalon

Angiogenesis and neurogenesis are tightly coupled during embryonic brain development. However, little is known about how these two processes interact. We show that nascent blood vessels actively contact dividing neural stem cells by endothelial filopodia in the ventricular zone (VZ) of the murine ventral telencephalon; this association is conserved in the human ventral VZ. Using mouse mutants with altered vascular filopodia density, we show that this interaction leads to prolonged cell cycle of apical neural progenitors (ANPs) and favors early neuronal differentiation. Interestingly, pharmacological experiments reveal that ANPs induce vascular filopodia formation by upregulating vascular endothelial growth factor (VEGF)-A in a cell-cycle-dependent manner. This mutual relationship between vascular filopodia and ANPs works as a self-regulatory system that senses ANP proliferation rates and rapidly adjusts neuronal production levels. Our findings indicate a function of vascular filopodia in fine-tuning neural stem cell behavior, which is the basis for proper brain development.

Siponimod (Mayzent) Downregulates RhoA and Cell Surface Expression of the S1P1 and CX3CR1 Receptors in Mouse RAW 264.7 Macrophages

The Siponimod (Mayzent) is a newly developed drug, similar to Fingolimod (FTY720) but with fewer side effects, approved by the Food and Drug Administration for the treatment of multiple sclerosis (MS). The therapeutic effect of siponimod and FTY720 in MS relies on their inhibitory effect on the sphingosine 1-phosphate (S1P) signaling. These drugs bind to the S1P receptors and block the CCL2 chemokine pathway that is responsible for the exit of the immune cells from the lymphoid organs, and circulation, thus preventing immune cell-dependent injury to the nervous system. We recently found that FTY720 beside its effect on the S1P pathway also blocks the RhoA pathway, which is involved in the actin cytoskeleton-related function of macrophages, such as expression/recycling of fractalkine (CX3CL1) receptors (CX3CR1), which direct macrophages to the transplanted organs during the development of the long-term (chronic) rejection. Here we tested the effects of siponimod on the RhoA pathway and the expression of the S1P1 and CX3CR1 receptors in mouse RAW 264.7 macrophages. We found that siponimod downregulates the expression of RhoA protein and decreases the cell surface expression of S1P1 and CX3CR1 receptors. This newly discovered crosstalk between S1P and RhoA/CX3CR1 pathways may help in the development of novel anti-chronic rejection therapies in clinical transplantation.

Central Modulation of Selective Sphingosine-1-Phosphate Receptor 1 Ameliorates Experimental Multiple Sclerosis

Future treatments of multiple sclerosis (MS), a chronic autoimmune neurodegenerative disease of the central nervous system (CNS), aim for simultaneous early targeting of peripheral immune function and neuroinflammation. Sphingosine-1-phosphate (S1P) receptor modulators are among the most promising drugs with both “immunological” and “non-immunological” actions. Selective S1P receptor modulators have been recently approved for MS and shown clinical efficacy in its mouse model, the experimental autoimmune encephalomyelitis (EAE). Here, we investigated the anti-inflammatory/neuroprotective effects of ozanimod (RPC1063), a S1P_1/5 modulator recently approved in the United States for the treatment of MS, by performing ex vivo studies in EAE brain. Electrophysiological experiments, supported by molecular and immunofluorescence analysis, revealed that ozanimod was able to dampen the EAE glutamatergic synaptic alterations, through attenuation of local inflammatory response driven by activated microglia and infiltrating T cells, the main CNS-cellular players of EAE synaptopathy. Electrophysiological studies with selective S1P₁ (AUY954) and S1P₅ (A971432) agonists suggested that S1P₁ modulation is the main driver of the anti-excitotoxic activity mediated by ozanimod. Accordingly, in vivo intra-cerebroventricular treatment of EAE mice with AUY954 ameliorated clinical disability. Altogether these results strengthened the relevance of S1P₁ agonists as immunomodulatory and neuroprotective drugs for MS therapy.

In silico Docking Studies of Fingolimod and S1P1 Agonists

The sphingosine-1-phosphate receptor 1 (S1P₁), originally the endothelial differentiation gene 1 receptor (EDG-1), is one of five G protein–coupled receptors (GPCRs) S1P_1–5 that bind to and are activated by sphingosine-1-phosphate (S1P). The lipid S1P is an intermediate in sphingolipid homeostasis, and S1P₁ is a major medical target for immune system modulation; agonism of the receptor produces a myriad of biological responses, including endothelial cell barrier integrity, chemotaxis, lymphocyte trafficking/targeting, angiogenesis, as well as regulation of the cardiovascular system. Use of in silico docking simulations on the crystal structure of S1P₁ allows for pinpointing the residues within the receptor’s active site that actively contribute to the binding of S1P, and point to how these specific interactions can be exploited to design more effective synthetic analogs to specifically target S1P₁ in the presence of the closely related receptors S1P₂, S1P₃, S1P₄, and S1P₅. We examined the binding properties of the endogenous substrate as well as a selection of synthetic sphingosine-derived S1P₁ modulators of S1P₁ with in silico docking simulations using the software package Molecular Operating Environment^® (MOE^®). The modeling studies reveal the relevance of phosphorylation, i.e., the presence of a phosphate or phosphonate moiety within the substrate for successful binding to occur, and indicate which residues are responsible for S1P₁ binding of the most prominent sphingosine-1-phosphate receptor (S1PR) modulators, including fingolimod and its structural relatives. Furthermore, trends in steric preferences as for the binding of enantiomers to S1P₁ could be observed, facilitating future design of receptor-specific substrates to precisely target the active site of S1P₁.

A novel S1P1 modulator IMMH002 ameliorates psoriasis in multiple animal models

Psoriasis is characterized by abnormal proliferation of keratinocytes, as well as infiltration of immune cells into the dermis and epidermis, causing itchy, scaly and erythematous plaques of skin. The understanding of this chronic inflammatory skin disease remains unclear and all available treatments have their limitations currently. Here, we showed that IMMH002, a novel orally active S1P₁ modulator, desensitized peripheral pathogenic lymphocytes to egress signal from secondary lymphoid organs and thymus. Using different psoriasis animal models, we demonstrated that IMMH002 could significantly relieve skin damage as revealed by PASI score and pathological injure evaluation. Mechanistically, IMMH002 regulated CD3⁺ T lymphocytes re-distribution by inducing lymphocytes’ homing, thus decreased T lymphocytes allocation in the peripheral blood and skin but increased in the thymus. Our results suggest that the novel S1P₁ agonist, IMMH002, exert extraordinary capacity to rapidly modulate T lymphocytes distribution, representing a promising drug candidate for psoriasis treatment.

CCN2 Mediates S1P-Induced Upregulation of COX2 Expression in Human Granulosa-Lutein Cells

CCN1 and CCN2 are members of the CCN family and play essential roles in the regulation of multiple female reproductive functions, including ovulation. Cyclooxygenase-2 (COX2) is a critical mediator of ovulation and can be induced by sphingosine-1-phosphate (S1P) through the S1P_1/3-mediated Yes-associated protein (YAP) signaling. However, it is unclear whether CCN1 or CCN2 can mediate S1P-induced upregulation of COX2 expression and increase in prostaglandin E2 (PGE2) production in human granulosa-lutein (hGL) cells. In the present study, we investigated the effects of S1P on the expressions of CCN1 and CCN2 in hGL cells. Additionally, we used a dual inhibition approach (siRNA-mediated silencing and small molecular inhibitors) to investigate the molecular mechanisms of S1P effects. Our results showed that S1P treatment significantly upregulated the expression of CCN1 and CCN2 in a concentration-dependent manner in hGL cells. Additionally, inhibition or silencing of S1P₁, but not S1P₃, completely abolished the S1P-induced upregulation of CCN2 expression. Furthermore, we demonstrated that S1P-induced nuclear translocation of YAP and inhibition or silencing of YAP completely abolished the S1P-induced upregulation of CCN1 and CCN2 expression. Notably, silencing of CCN2, but not CCN1, completely reversed the S1P-induced upregulation of COX2 expression and the increase in PGE2 production. Thus, CCN2 mediates the S1P-induced upregulation of COX2 expression through the S1P₁-mediated signaling pathway in hGL cells. Our findings expand our understanding of the molecular mechanism underlying the S1P-mediated cellular activities in the human ovary.

First use of cenerimod, a selective S1P1 receptor modulator, for the treatment of SLE: a double-blind, randomised, placebo-controlled, proof-of-concept study

Objective

To investigate the pharmacodynamics, pharmacokinetics and safety of cenerimod—a potent, oral, selective sphingosine 1-phosphate 1 receptor modulator—in patients with SLE.

Methods

This multicentre, double-blind, placebo-controlled study was conducted in two parts. In part A, patients with SLE were randomised 1:1:1:1 to receive oral cenerimod 0.5, 1 or 2 mg, or placebo once daily for 12 weeks. Following an interim safety review of part A, additional patients were randomised 3:1 for part B and received cenerimod 4 mg or placebo once daily for 12 weeks. Endpoints included changes in total lymphocyte count, SLE Disease Activity Index-2000 (SLEDAI-2K) score (modified (mSLEDAI-2K) to exclude leucopenia), biomarker anti-double-stranded DNA (anti-dsDNA) antibodies, pharmacokinetic assessments and treatment-emergent adverse events (TEAEs).

Results

Part A included 49 patients (1:1:1:1 receiving cenerimod 0.5, 1 or 2 mg, or placebo) and part B included 18 patients (13 cenerimod; 5 placebo). Cenerimod caused a statistically significant dose-dependent reduction in total lymphocyte count from baseline to end of treatment (EOT). Compared with placebo at EOT, cenerimod 4 mg had an estimated treatment effect on change from baseline in mSLEDAI-2K score of −2.420 (p=0.0306), and on anti-dsDNA antibodies of −64.55 U/mL (p=0.0082), suggesting clinical and biological improvement in these exploratory efficacy analyses. Trough plasma concentrations were dose proportional and reached steady-state conditions after 4 weeks of once daily dosing. All groups reported similar, non-dose-related frequencies of TEAEs (cenerimod 0.5 mg: 41.7%; 1 mg: 41.7%; 2 mg: 46.2%; 4 mg: 38.5% and placebo: 58.8%). A small, dose-related, non-clinically relevant decrease in heart rate was only observed in the first 6 hours after initiation.

Conclusions

With an acceptable safety profile, the efficacy findings suggest that cenerimod has the potential to treat patients with SLE. Further investigation in larger patient populations with longer treatment duration is warranted.

Sphingosine-1-Phosphate Receptor Subtype 1 (S1P1) Modulator IMMH001 Regulates Adjuvant- and Collagen-Induced Arthritis

Sphingosine-1-phosphate receptor subtype 1 (S1P₁) is essential for lymphocyte egress from lymphoid organs into systemic circulation and provides a well-defined drug target for autoimmune disorders. IMMH001, also called SYL930, is a specific S1P₁/S1P₄/S1P₅ modulator. Here, we investigated the potential therapeutic effect of IMMH001 on rheumatoid arthritis (RA). IMMH001 rendered periphery blood lymphocytes insensitive to the egress signal from secondary lymphoid organs. Importantly, in both rat adjuvant-induced arthritis and collagen-induced arthritis models, IMMH001 treatment significantly inhibited the progression of RA and RA-associated histological changes in the joints of Sprague-Dawley rats, including hind paw swelling and arthritic index, and thus reduced the pathological score. Furthermore, IMMH001 markedly decreased proinflammatory cytokine and chemokine release from the damaged joints. These data demonstrated that IMMH001 is a promising drug candidate for RA treatment.

S1P1 Regulates M1/M2 Polarization toward Brain Injury after Transient Focal Cerebral Ischemia

M1/M2 polarization of immune cells including microglia has been well characterized. It mediates detrimental or beneficial roles in neuroinflammatory disorders including cerebral ischemia. We have previously found that sphingosine 1-phospate receptor subtype 1 (S1P₁) in post-ischemic brain following transient middle cerebral artery occlusion (tMCAO) can trigger microglial activation, leading to brain damage. Although the link between S1P₁ and microglial activation as a pathogenesis in cerebral ischemia had been clearly demonstrated, whether the pathogenic role of S1P₁ is associated with its regulation of M1/M2 polarization remains unclear. Thus, this study aimed to determine whether S1P₁ was associated with regulation of M1/M2 polarization in post-ischemic brain. Suppressing S1P₁ activity with its functional antagonist, AUY954 (5 mg/kg, p.o.), attenuated mRNA upregulation of M1 polarization markers in post-ischemic brain at 1 day and 3 days after tMCAO challenge. Similarly, suppressing S1P₁ activity with AUY954 administration inhibited M1-polarizatioin-relevant NF-κB activation in post-ischemic brain. Particularly, NF-κB activation was observed in activated microglia of post-ischemic brain and markedly attenuated by AUY954, indicating that M1 polarization through S1P₁ in post-ischemic brain mainly occurred in activated microglia. Suppressing S1P₁ activity with AUY954 also increased mRNA expression levels of M2 polarization markers in post-ischemic brain, further indicating that S1P₁ could also influence M2 polarization in post-ischemic brain. Finally, suppressing S1P₁ activity decreased phosphorylation of M1-relevant ERK1/2, p38, and JNK MAPKs, but increased phosphorylation of M2-relevant Akt, all of which were downstream pathways following S1P₁ activation. Overall, these results revealed S1P₁-regulated M1/M2 polarization toward brain damage as a pathogenesis of cerebral ischemia.

Crosstalk between Fas and S1P1 signaling via NF-kB in osteoclasts controls bone destruction in the TMJ due to rheumatoid arthritis

Rheumatoid arthritis (RA) mainly affects various joints of the body, including the temporomandibular joint (TMJ), and it involves an infiltration of autoantibodies and inflammatory leukocytes into articular tissues and the synovium. Initially, the synovial lining tissue becomes engaged with several kinds of infiltrating cells, including osteoclasts, macrophages, lymphocytes, and plasma cells. Eventually, bone degradation occurs. In order to elucidate the best therapy for RA, a comprehensive study of RA pathogenesis needs to be completed. In this article, we discuss a Fas-deficient condition which develops into RA, with an emphasis on the role of sphingosine 1-phosphate (S1P)/S1P receptor 1 signaling which induces the migration of osteoclast precursor cells. We describe that Fas/S1P₁ signaling via NF-κB activation in osteoclasts is a key factor in TMJ-RA severity and we discuss a strategy for blocking nuclear translocation of the p50 NF-κB subunit as a potential therapy for attenuating osteoclastogenesis.

CD69: from activation marker to metabolic gatekeeper

CD69 is a membrane-bound, type II C-lectin receptor. It is a classical early marker of lymphocyte activation due to its rapid appearance on the surface of the plasma membrane after stimulation. CD69 is expressed by several subsets of tissue resident immune cells, including resident memory T (TRM) cells and gamma delta (γδ) T cells, and is therefore considered a marker of tissue retention. Recent evidence has revealed that CD69 regulates some specific functions of selected T-cell subsets, determining the migration-retention ratio as well as the acquisition of effector or regulatory phenotypes. Specifically, CD69 regulates the differentiation of regulatory T (Treg) cells as well as the secretion of IFN-γ, IL-17, and IL-22. The identification of putative CD69 ligands, such as Galectin-1 (Gal-1), suggests that CD69-induced signaling can be regulated not only during cognate contacts between T cells and antigen-presenting cells in lymphoid organs, but also in the periphery, where cytokines and other metabolites control the final outcome of the immune response. Here, we will discuss new aspects of the molecular signaling mediated by CD69 and its involvement in the metabolic reprogramming regulating TH-effector lineages.

Inflammatory responses in Multiple Sclerosis normal-appearing white matter and in non-immune mediated neurological conditions with wallerian axonal degeneration: A comparative study

Inflammatory-like changes in the white matter (WM) are commonly observed in conditions of axonal degeneration by different etiologies. This study is a systematic comparison of the principal features of the inflammatory-like changes in the WM in different pathological conditions characterized by axonal damage/degeneration, focusing in particular on Multiple Sclerosis (MS) normal-appearing white matter (NAWM) compared to non immune-mediated disorders. The study was performed on sections of NAWM from 15 MS cases, 11 cases of non immune-mediated disorders with wallerian axonal degeneration (stroke, trauma, amyotrophic lateral sclerosis), 3 cases of viral encephalitis, 6 control cases. Common features of the inflammatory-like changes observed in all of the conditions of WM pathology were diffuse endothelial expression of VCAM-1, microglial activation with expression of M2 markers, increased expression of sphingosine receptors. Inflammation in MS NAWM was characterized, compared to non immune-mediated conditions, by higher VCAM-1 expression, higher density of perivascular lymphocytes, focal perivascular inflammation with microglial expression of M1 markers, ongoing acute axonal damage correlating with VCAM-1 expression but not with microglia activation. Inflammatory changes in MS NAWM share all the main features observed in the WM in non immune-mediated conditions with wallerian axonal degeneration (with differences to a large extent more quantitative than qualitative), but with superimposition of disease-specific perivascular inflammation and ongoing acute axonal damage.

Identification of Sphingosine 1-Phosphate Receptor Subtype 1 (S1P1) as a Pathogenic Factor in Transient Focal Cerebral Ischemia

Medically relevant roles of receptor-mediated sphingosine 1-phosphate (S1P) signaling have become a successful or promising target for multiple sclerosis or cerebral ischemia. Animal-based proof-of-concept validation for the latter is particularly through the neuroprotective efficacy of FTY720, a non-selective S1P receptor modulator, presumably via activation of S1P₁. In spite of a clear link between S1P signaling and cerebral ischemia, it remains unknown whether the role of S1P₁ is pathogenic or neuroprotective. Here, we investigated the involvement of S1P₁ along with its role in cerebral ischemia using a transient middle cerebral artery occlusion ("tMCAO") model. Brain damage following tMCAO, as assessed by brain infarction, neurological deficit score, and neural cell death, was reduced by oral administration of AUY954, a selective S1P₁ modulator as a functional antagonist, in a therapeutic paradigm, indicating that S1P₁ is a pathogenic mediator rather than a neuroprotective mediator. This pathogenic role of S1P₁ in cerebral ischemia was reaffirmed because tMCAO-induced brain damage was reduced by genetic knockdown with an intracerebroventricular microinjection of S1P₁ shRNA lentivirus into the brain. Genetic knockdown of S1P₁ or AUY954 exposure reduced microglial activation, as assessed by reduction in the number of activated microglia and reversed morphology from amoeboid to ramified, and microglial proliferation in ischemic brain. Its role in microglial activation was recapitulated in lipopolysaccharide-stimulated primary mouse microglia, in which the mRNA expression level of TNF-α and IL-1β, well-known markers for microglial activation, was reduced in microglia transfected with S1P₁ siRNA. These data suggest that the pathogenic role of S1P₁ is associated with microglial activation in ischemic brain. Additionally, the pathogenic role of S1P₁ in cerebral ischemia appears to be associated with the blood-brain barrier disruption and brain-derived neurotrophic factor (BDNF) downregulation. Overall, findings from the current study clearly identify S1P₁ signaling as a pathogenic factor in transient focal cerebral ischemia, further implicating S1P₁ antagonists including functional antagonists as plausible therapeutic agents for human stroke.

Sphingosine 1-phosphate receptor-1 in cardiomyocytes is required for normal cardiac development

Sphingosine 1-phosphate (S1P) is a bioactive lipid that acts via G protein-coupled receptors. The S1P receptor S1P1, encoded by S1pr1, is expressed in developing heart but its roles there remain largely unexplored. Analysis of S1pr1 LacZ knockin embryos revealed β-galactosidase staining in cardiomyocytes in the septum and in the trabecular layer of hearts collected at 12.5 days post coitus (dpc) and weak staining in the inner aspect of the compact layer at 15.5 dpc and later. Nkx2-5-Cre- and Mlc2a-Cre-mediated conditional knockout of S1pr1 led to ventricular noncompaction and ventricular septal defects at 18.5 dpc and to perinatal lethality in the majority of mutants. Further analysis of Mlc2a-Cre conditional mutants revealed no gross phenotype at 12.5 dpc but absence of the normal increase in the number of cardiomyocytes and the thickness of the compact layer at 13.5 dpc and after. Consistent with relative lack of a compact layer, in situ hybridization at 13.5 dpc revealed expression of trabecular markers extending almost to the epicardium in mutants. Mutant hearts also showed decreased myofibril organization in the compact but not trabecular myocardium at 12.5 dpc. These results suggest that S1P signaling via S1P1 in cardiomyocytes plays a previously unknown and necessary role in heart development in mice.

Identification and Preclinical Pharmacology of BMS-986104: A Differentiated S1P1 Receptor Modulator in Clinical Trials

Clinical validation of S1P receptor modulation therapy was achieved with the approval of fingolimod (Gilenya, 1) as the first oral therapy for relapsing remitting multiple sclerosis. However, 1 causes a dose-dependent reduction in the heart rate (bradycardia), which occurs within hours after first dose. We disclose the identification of clinical compound BMS-986104 (3d), a novel S1P1 receptor modulator, which demonstrates ligand-biased signaling and differentiates from 1 in terms of cardiovascular and pulmonary safety based on preclinical pharmacology while showing equivalent efficacy in a T-cell transfer colitis model.

Late-stage optimization of a tercyclic class of S1P3-sparing, S1P1 receptor agonists

Poor solubility and cationic amphiphilic drug-likeness were liabilities identified for a lead series of S1P3-sparing, S1P1 agonists originally developed from a high-throughput screening campaign. This work describes the subsequent optimization of these leads by balancing potency, selectivity, solubility and overall molecular charge. Focused SAR studies revealed favorable structural modifications that, when combined, produced compounds with overall balanced profiles. The low brain exposure observed in rat suggests that these compounds would be best suited for the potential treatment of peripheral autoimmune disorders.

Beta Adrenergic Signaling: A Targetable Regulator of Angiosarcoma and Hemangiosarcoma

Human angiosarcomas and canine hemangiosarcomas are highly aggressive cancers thought to arise from cells of vascular origin. The pathological features, morphological organization, and clinical behavior of canine hemangiosarcomas are virtually indistinct from those of human angiosarcomas. Overall survival with current standard-of-care approaches remains dismal for both humans and dogs, and each is likely to succumb to their disease within a short duration. While angiosarcomas in humans are extremely rare, limiting their study and treatment options, canine hemangiosarcomas occur frequently. Therefore, studies of these sarcomas in dogs can be used to advance treatment approaches for both patient groups. Emerging data suggest that angiosarcomas and hemangiosarcomas utilize beta adrenergic signaling to drive their progression by regulating the tumor cell niche and fine-tuning cellular responses within the tumor microenvironment. These discoveries indicate that inhibition of beta adrenergic signaling could serve as an Achilles heel for these tumors and emphasize the need to design therapeutic strategies that target tumor cell and stromal cell constituents. In this review, we summarize recent discoveries and present new hypotheses regarding the roles of beta adrenergic signaling in angiosarcomas and hemangiosarcomas. Because the use of beta adrenergic receptor antagonists is well established in human and veterinary medicine, beta blockade could provide an immediate adjunct therapy for treatment along with a tangible opportunity to improve upon the outcomes of both humans and dogs with these diseases.

Discovery of APD334: Design of a Clinical Stage Functional Antagonist of the Sphingosine-1-phosphate-1 Receptor

APD334 was discovered as part of our internal effort to identify potent, centrally available, functional antagonists of the S1P1 receptor for use as next generation therapeutics for treating multiple sclerosis (MS) and other autoimmune diseases. APD334 is a potent functional antagonist of S1P1 and has a favorable PK/PD profile, producing robust lymphocyte lowering at relatively low plasma concentrations in several preclinical species. This new agent was efficacious in a mouse experimental autoimmune encephalomyelitis (EAE) model of MS and a rat collagen induced arthritis (CIA) model and was found to have appreciable central exposure.

The anticoagulant activated protein C (aPC) promotes metaplasticity in the hippocampus through an EPCR-PAR1-S1P1 receptors dependent mechanism

Thrombin and other clotting factors regulate long-term potentiation (LTP) in the hippocampus through the activation of the protease activated receptor 1 (PAR1) and consequent potentiation of N-methyl-d-aspartate receptor (NMDAR) functions. We have recently shown that the activation of PAR1 either by thrombin or the anticoagulant factor activated protein C (aPC) has differential effects on LTP. While thrombin activation of PAR1 induces an NMDAR-mediated slow onset LTP, which saturates the ability to induce further LTP in the exposed network, aPC stimulation of PAR1 enhances tetanus induced LTP through a voltage-gated calcium channels mediated mechanism. In this study, we addressed the mechanisms by which aPC enhances LTP in hippocampal slices. Using extracellular recordings, we show that a short tetanic stimulation, which does not induce LTP, is able to enhance plasticity in the presence of aPC through a mechanism that requires the activation of sphingosine-1 phosphate receptor 1 and intracellular Ca(2+) stores. These data identify aPC as a "metaplastic molecule", capable of shifting the threshold of LTP towards further potentiation. Our findings propose novel strategies to enhance plasticity in neurological diseases associated with the breakdown of the blood brain barrier and alterations in synaptic plasticity.

S1P lyase in thymic perivascular spaces promotes egress of mature thymocytes via up-regulation of S1P receptor 1

Sphingosine 1-phosphate (S1P) and S1P receptor 1 (S1P1) play an important role in the egress of mature CD4 or CD8 single-positive (SP) thymocytes from the thymus. Fingolimod hydrochloride (FTY720), an S1P1 functional antagonist, induced significant accumulation of CD62L(high)CD69(low) mature SP thymocytes in the thymic medulla. Immunohistochemical staining using anti-S1P1 antibody revealed that S1P1 is predominantly expressed on thymocytes in the thymic medulla and is strongly down-regulated even at 3h after FTY720 administration. 2-Acetyl-4-tetrahydroxybutylimidazole (THI), an S1P lyase inhibitor, also induced accumulation of mature SP thymocytes in the thymic medulla with an enlargement of the perivascular spaces (PVS). At 6h after THI administration, S1P1-expressing thymocytes reduced partially as if to form clusters and hardly existed in the proximity of CD31-expressing blood vessels in the thymic medulla, suggesting S1P lyase expression in the cells constructing thymic medullary PVS. To determine the cells expressing S1P lyase in the thymus, we newly established a mAb (YK19-2) specific for mouse S1P lyase. Immunohistochemical staining with YK19-2 revealed that S1P lyase is predominantly expressed in non-lymphoid thymic stromal cells in the thymic medulla. In the thymic medullary PVS, S1P lyase was expressed in ER-TR7-positive cells (reticular fibroblasts and pericytes) and CD31-positive vascular endothelial cells. Our findings suggest that S1P lyase expressed in the thymic medullary PVS keeps the tissue S1P concentration low around the vessels and promotes thymic egress via up-regulation of S1P1.

Second generation S1P pathway modulators: research strategies and clinical developments

Multiple Sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system (CNS) through demyelination and neurodegeneration. Until recently, major therapeutic treatments have relied on agents requiring injection delivery. In September 2010, fingolimod/FTY720 (Gilenya, Novartis) was approved as the first oral treatment for relapsing forms of MS. Fingolimod causes down-modulation of S1P1 receptors on lymphocytes which prevents the invasion of autoaggressive T cells into the CNS. In astrocytes, down-modulation of S1P1 by the drug reduces astrogliosis, a hallmark of MS, thereby allowing restoration of productive astrocyte communication with other neural cells and the blood brain barrier. Animal data further suggest that the drug directly supports the recovery of nerve conduction and remyelination. In human MS, such mechanisms may explain the significant decrease in the number of inflammatory markers on brain magnetic resonance imaging in recent clinical trials, and the reduction of brain atrophy by the drug. Fingolimod binds to 4 of the 5 known S1P receptor subtypes, and significant efforts were made over the past 5 years to develop next generation S1P receptor modulators and determine the minimal receptor selectivity needed for maximal therapeutic efficacy in MS patients. Other approaches considered were competitive antagonists of the S1P1 receptor, inhibitors of the S1P lyase to prevent S1P degradation, and anti-S1P antibodies. Below we discuss the current status of the field, and the functional properties of the most advanced compounds. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

Gastric parietal cell atrophy and depletion after administration of a sphingosine-1-phosphate 1 inhibitor

Sphingosine-1-phosphate (S1P) is a major bioactive phospholipid, which binds to and activates a family of five G-protein-coupled receptors designated as S1P 1 (S1P1) through S1P5. The S1P1 receptor subtype, expressed primarily on lymphocytes, is known to play a critical role in the regulation of lymphocyte trafficking. S1P1 inhibitors result in the inhibition of lymphoid cell trafficking and are of interest to treat various inflammatory conditions. In this study, we describe a gastric finding associated with oral gavage administration of a small molecule S1P1 inhibitor to Sprague-Dawley rats. Rats were administered an S1P1 inhibitor once daily for 4 weeks and necropsies were conducted at the end of the dosing phase, and clinical pathology and histopathologic examination were performed. Lymphopenia and changes in lymphoid tissues were noted and were consistent with the pharmacodynamic effects for S1P1 inhibitory action. Histopathologic examination of the stomach revealed atrophy and depletion of gastric parietal cells in the glandular portion of the stomach. There are no literature data to suggest that this gastric effect is related to S1P1 pharmacology. Therefore, the mechanism of the observed gastric lesion is likely chemotype mediated.

A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 control a diverse array of migratory events in adaptive immune function. Most prominently, CCR7 promotes homing of T cells and DCs to T cell areas of lymphoid tissues where T cell priming occurs. However, CCR7 and its ligands also contribute to a multitude of adaptive immune functions including thymocyte development, secondary lymphoid organogenesis, high affinity antibody responses, regulatory and memory T cell function, and lymphocyte egress from tissues. In this survey, we summarise the role of CCR7 in adaptive immunity and describe recent progress in understanding how this axis is regulated. In particular we highlight CCX-CKR, which scavenges both CCR7 ligands, and discuss its emerging significance in the immune system.

Optimization of a Potent, Orally Active S1P1 Agonist Containing a Quinolinone Core

The optimization of a series of S1P1 agonists with limited activity against S1P3 is reported. A polar headgroup was used to improve the physicochemical and pharmacokinetic parameters of lead quinolinone 6. When dosed orally at 1 and 3 mg/kg, the azahydroxymethyl analogue 22 achieved statistically significant lowering of circulating blood lymphocytes 24 h postdose. In rats, a dose-proportional increase in exposure was measured when 22 was dosed orally at 2 and 100 mg/kg.

Discovery of CS-0777: A Potent, Selective, and Orally Active S1P1 Agonist

CS-0777 (3) is phosphorylated in vivo, and the phosphate of CS-0777 (CS-0777-P) (4) acts as a selective S1P receptor-1 (S1P1) modulator. We report herein the synthesis of CS-0777 and CS-0777-P, pharmacological effects such as S1P1 and S1P3 agonist activity in vitro, peripheral blood lymphocyte lowering effects and the suppressive effect on experimental autoimmune encephalomyelitis (EAE), and also the pharmacokinetics in rats. CS-0777-P had ∼320-fold greater agonist activity for human S1P1 (EC50; 1.1 nM) relative to S1P3 (EC50; 350 nM). Following administration of single oral doses of 0.1 and 1 mg/kg of CS-0777 in rats, lymphocyte counts decreased significantly, with a nadir at 12 h postdose and recovery to vehicle control levels by 5 days postdose. In the EAE model compared to the vehicle-treated group, significant decreases in the cumulative EAE scores were observed for the 0.1 and 1 mg/kg CS-0777 groups in rats. CS-0777 is currently in clinical trials for the treatment of multiple sclerosis (MS).

Discovery of a Potent, S1P3-Sparing Benzothiazole Agonist of Sphingosine-1-Phosphate Receptor 1 (S1P1)

Optimization of a benzofuranyl S1P1 agonist lead compound (3) led to the discovery of 1-(3-fluoro-4-(5-(2-fluorobenzyl)benzo[d]thiazol-2-yl)benzyl)azetidine-3-carboxylic acid (14), a potent S1P1 agonist with minimal activity at S1P3. Dosed orally at 0.3 mg/kg, 14 significantly reduced blood lymphocyte counts 24 h postdose and attenuated a delayed type hypersensitivity (DTH) response to antigen challenge.

Discovery of AMG 369, a Thiazolo[5,4-b]pyridine Agonist of S1P1 and S1P5

The optimization of a series of thiazolopyridine S1P1 agonists with limited activity at the S1P3 receptor is reported. These efforts resulted in the discovery of 1-(3-fluoro-4-(5-(1-phenylcyclopropyl)thiazolo-[5,4-b]pyridin-2-yl)benzyl)azetidine-3-carboxylic acid (5d, AMG 369), a potent dual S1P1/S1P5 agonist with limited activity at S1P3 and no activity at S1P2/S1P4. Dosed orally at 0.1 mg/kg, 5d is shown to reduce blood lymphocyte counts 24 h postdose and delay the onset and reduce the severity of experimental autoimmune encephalomyelitis in rat.

Benzofuran Derivatives as Potent, Orally Active S1P1 Receptor Agonists: A Preclinical Lead Molecule for MS

We have discovered novel benzofuran-based S1P1 agonists with excellent in vitro potency and selectivity. 1-((4-(5-Benzylbenzofuran-2-yl)-3-fluorophenyl)methyl) azetidine-3-carboxylic acid (18) is a potent S1P1 agonist with >1000× selectivity over S1P3. It demonstrated a good in vitro ADME profile and excellent oral bioavailability across species. Dosed orally at 0.3 mg/kg, 18 significantly reduced blood lymphocyte counts 24 h postdose and demonstrated efficacy in a mouse EAE model of relapsing MS.