Sphingosine-1-phosphate Receptor Research Articles

The investigation of selective sphingosine-1 phosphate receptor 1&4 modulator to treat alopecia areata mouse model

Abstract Alopecia areata (AA) is a T cell mediated autoimmune disease characterized phenotypically by hair loss. NKG2D +CD8 +T cells is involved in the pathogenesis of AA. Sphingosine-1 phosphate (S1P) is a biologically active metabolite of cell membrane sphingolipids, which is essential for immune cell transport, and is known to be mainly involved in immune and inflammatory reactions. Due to involvement of S1P receptor (S1PR) in the immune system, S1PR modulator is being investigated for application in multiple sclerosis and other conditions. Among the five S1PRs, S1PRs 1&4 modulator (NXC736, Nextgen Bioscience, South Korea) was used to confirm its efficacy in the treatment of AA. AA lesion size measurement, disease-free ratio, immunohistochemistry and flow cytometry were used for analysis method. After oral administration of NXC736 for 84 days to AA mice, it was confirmed that the AA lesion area and disease-free ratio were significantly decreased compared to control group, and the infiltration of CD8 +T cells in the lesion skin was also significantly decreased. In addition, NKG2D level was decreased in effector CD8 +T cells. According to this result, we speculate that S1PR 1&4 modulator can be used as a promising treatment for AA. Supported by Nextgen Bioscience

SPHK1-S1P-S1PR1 signaling pathway is emerging as a potential therapeutic target in improving endothelial barrier function and prevent coronary artery disease.

Abstract Sphingosine kinases (SPHKs) catalyze the formation of sphingosine 1 phosphate (S1P) from sphingosine. S1P, a lipid mediator, was shown to be one such factor promoting endothelial barrier function. S1P binds to S1P receptor-1 (S1PR1) in endothelial cells, leading to activation of heterotrimeric G proteins (Gi), and signals enhancement of endothelial barrier function by the activation of small GTPase Rac1. We hypothesized that SPHK1 via generation of S1P induces reannealing of adherens junctions and thereby prevents thrombin-induced endothelial permeability. To understand the role of SPHK1 pathway, we depleted SPHK1 protein in endothelial cells using SPHK1 specific small interference (si) RNA. Depletion of SPHK1 significantly disrupted the adherens junction, VE-cadherin and increased the gap formation of endothelial cells. Upon depletion of SPHK1 we found decrease cell proliferation and migration, but no change in the expression of Sphingosine 1 Phosphate Receptor 1 (S1PR1) expression in endothelial cells. To determine if in the absence of SPHK1, does S1P has any pharmacological role, we treated the cells with Sphingosine 1 Phosphate (S1P) at the dose of 1μM. We found that S1P re-anneal the adherens junctions and improve cell proliferation and migration in SPHK1 depleted endothelial cells. This indicates that SPHK1 via generation of S1P prevents endothelial permeability through S1PR1 receptor activation. Upon treatment with S1P in SPHK1 depleted endothelia showed completely recovery in barrier function. In conclusion, our study for the first time shows that SPHK1 maintains endothelial barrier function and reanneals adherens junctions, thus hastens the recovery process. CTRE grant to Professor Nadeem Fazal, MD, PhD

Myeloid cells and sphingosine-1-phosphate are required for TCRαβ +intraepithelial lymphocyte recruitment to the colon epithelium

Abstract Intraepithelial lymphocytes (IELs) of the colon are essential for barrier maintenance and repair after injury. As bacterial depletion or global MyD88 deficiency results in a significant reduction of colon IELs and impaired barrier integrity, we aimed to connect the signals of how bacteria recruit colon IELs to the epithelium using conditional knockouts of MyD88 to target T cells (Lck-Cre), IECs (Villin-Cre), and myeloid cells (LysM-Cre). Only in the colons of LysM-Cre +mice were TCRαβ +IELs reduced, at 3.3-fold (p<0.005 compared to Cre −littermate controls) without effect on lamina propria T cells or myeloid cells. TCRγδ +IELs were unaffected in all knockouts, suggesting they are recruited via different mechanisms. We then examined upregulated cell surface gene expression of IELs during recruitment, identifying sphingosine-1-phosphate receptor 1 (S1PR1) as a candidate for further study. Indeed, S1PR1 expression is significantly increased at 3.7-fold in IELs (p<0.05 compared to lamina propria T cells). In accordance with these findings, we demonstrated that TCRαβ+ IEL recruitment is blocked by administration of the S1PR1 receptor agonist FTY720 (p<0.05 compared to vehicle treatment). Furthermore, myeloid cell production of sphingosine-1-phosphate (S1P) was required for colon TCRαβ +IEL recruitment in a MyD88-dependent manner. In the TNF ΔARE/+model of spontaneous colitis, loss of myeloid MyD88 resulted in protection from disease (p<0.05 compared to Cre-littermate controls). Overall, these data demonstrate the requirement for myeloid-produced S1P for TCRαβ+ IEL recruitment to the colon and suggest that TCRαβ +IELs can contribute to intestinal inflammation under a specific genetic predisposition.

Dysregulated sphingolipid metabolism contributes to NASH-HCC disease progression

Background: Nonalcoholic fatty liver disease (NAFLD) is the fastest-rising cause of end-stage liver disease for liver transplantation. The underlying mechanisms of NAFLD disease progression from nonalcoholic steatohepatitis (NASH) to hepatocellular carcinoma (HCC) remain unclear. It has been well-accepted that inflammation and dysregulation of sphingolipid metabolism are two important contributors to NASH progression. Recent advances in gene profiling technologies have significantly improved the current understanding of NASH-HCC pathogenesis. However, the key pathway changes underlying liver fibrosis and dysregulation of sphingolipid metabolism haven’t been fully elucidated and are the focus of this study. Methods: DIMOND NASH mouse model (C57BL/6J and 129S1/SvlmJ mixed background) was used in this study. Male mice (21 to 24-week-old) were fed with WDSW (Western diet, Harlan, TD88137, and a high fructose-glucose solution, 23.1g/L D-fructose plus 18.9g/L D-glucose) or standard chow diet ad libitum for six months or one year. At the end of the study, liver tissues were harvested for total RNA isolation using Trizol. Gene profiles were analyzed using the NanoString nCounter® Gene Expression Fibrosis V2 panel with sphingolipid metabolism pathways. The differentially expressed genes (DEGs) between groups were determined using Rosalind. QIAGEN Ingenuity Pathway Analysis (IPA) was used to analyze the DEGs. Human HCC patient data were downloaded from The Cancer Genome Atlas Program (TCGA). The sphingolipid profiles in the serum and liver were determined using LC-MS/MS. Results: All the mice developed NASH and HCC after feeding with WDSW for 6 months and 1 year, respectively. Bioinformatic analysis identified 191 DEGs in the NASH group and 250 DEGs in HCC group compared to the corresponding controls. The IPA analysis revealed that the major pathways related to inflammation and fibrosis were upregulated in both NASH and HCC mice. The expression levels of key genes related to ceramide synthesis and metabolism [serine palmitoyltransferase long chain base subunit 2 (Sptlc2), ceramide synthase 6 (Cers6), N-acylsphingosine amidohydrolase 2 (Asah2)] and sphingosine-1-phosphate receptor 2 (S1PR2) were significantly upregulated in NASH mice. In HCC group, Cers5, Cers6, sphingomyelin synthase 1 (Sgms1), Asah1, and S1PR3 were significantly increased. The expression levels of sphingosine kinase 2 and S1P lyase 1 were decreased both in NASH and HCC. Analysis of the TCGA data set showed that CERS5, CERS6, SPTLC2, ASAH1 and SGMS1 were highly expressed in HCC compared to healthy controls. The LC-MS/MS data also showed significant changes in sphingolipid profiles in serum and liver NASH and HCC. Conclusion: Our study suggests that dysregulated sphingolipid metabolism is associated with NASH and HCC disease progression. Further validation and research are needed for the potential application of sphingolipid profiles as diagnostic or prognostic markers in the clinic. This study was supported by VA Merit Award I01BX004033; Research Career Scientist Award (IK6BX004477); VA ShEEP grants (1IS1BX005517-01 and 1 IS1 BX004777-01) National Institutes of Health Grant R01 DK104893, R01DK-057543 and R21 AA026629-01. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Albumin protects the ultrastructure of the endothelial glycocalyx of coronary arteries in myocardial ischemia-reperfusion injury in vivo

Myocardial ischemia-reperfusion (I/R) injury induces endothelial glycocalyx (GCX) degradation. Several candidate GCX-protective factors including albumin have been identified, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. Albumin is a carrier protein for sphingosine 1-phosphate (S1P), which has protective effects on the cardiovascular system. However, changes inhibited by albumin in the endothelial GCX structure in I/R in vivo via the S1P receptor has not been reported. In this study, we aimed to determine whether albumin prevents the shedding of endothelial GCX in response to I/R in vivo. Rats were divided into four groups: control (CON), I/R, I/R with albumin preload (I/R + ALB), and I/R + ALB with S1P receptor agonist fingolimod (I/R + ALB + FIN). FIN acts as an initial agonist of S1P receptor 1 and downregulates the receptor in an inhibitory manner. The CON and I/R groups received saline and I/R + ALB and I/R + ALB + FIN groups received albumin solution before left anterior descending coronary artery ligation. Our study used rat albumin. Shedding of endothelial GCX was evaluated in the myocardium by electron microscopy, and the concentration of serum syndecan-1 was measured. Thus, albumin administration maintained the structure of endothelial GCX and prevented shedding of endothelial GCX via the S1P receptor in myocardial I/R, and FIN annihilated the protective effect of albumin against I/R injury.

Lysophospholipid (S1P) receptors in GtoPdb v.2023.1

Sphingosine 1-phosphate (S1P) receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Lysophospholipid receptors [96]) are activated by the endogenous lipid sphingosine 1-phosphate (S1P). Originally cloned as orphan members of the endothelial differentiation gene (edg) family [16, 123], the receptors are currently designated as S1P1R through S1P5R [73, 16, 123]. Their gene nomenclature has been codified as human S1PR1, S1PR2, etc. (HUGO Gene Nomenclature Committee, HGNC) and S1pr1, S1pr2, etc. for mice (Mouse Genome Informatics Database, MGI) to reflect species and receptor function. All S1P receptors (S1PRs) have been knocked-out in mice constitutively and in some cases, conditionally. S1PRs, particularly S1P1, are expressed throughout all mammalian organ systems. Ligand delivery occurs via two known carriers (or "chaperones"): albumin and HDL-bound apolipoprotein M (ApoM), the latter of which elicits biased agonist signaling by S1P1 in multiple cell types [18, 53]. The five S1PRs, two chaperones, and active cellular metabolism have complicated analyses of receptor ligand binding in native systems. Signaling pathways and physiological roles have been characterized through radioligand binding in heterologous expression systems, targeted deletion of the different S1PRs, and most recently, mouse models that report in vivo S1P1R activation [101, 103]. The structures of S1P1 [180, 69, 108, 184], S1P2 [32], S1P3[116, 187], and S1P5 [110, 185] are solved, and confirmed aspects of ligand binding, specificity, and receptor activation, determined previously through biochemical and genetic studies [69, 17]. fingolimod (FTY720), the first FDA-approved drug to target any of the lysophospholipid receptors, binds as a phosphorylated metabolite to four of the five S1PRs, and was the first oral therapy for multiple sclerosis (MS) [35]. Second-generation S1PR modulators siponimod, ozanimod, and ponesimod that target S1P1 and S1P5 are also FDA approved for the treatment of various MS forms [16, 123]. In 2021, ozanimod became the first S1PR modulator to be FDA approved for the treatment of ulcerative colitis [145]. The mechanisms of action of fingolimod and other S1PR-modulating drugs now in development include binding S1PRs in multiple organ systems, e.g., immune and nervous systems, although the precise nature of their receptor interactions requires clarification [141, 37, 63, 64].

Revealing concealed cardioprotection by platelet Mfsd2b-released S1P in human and murine myocardial infarction

Antiplatelet medication is standard of care in acute myocardial infarction (AMI). However, it may have obscured beneficial properties of the activated platelet secretome. We identify platelets as major source of a sphingosine-1-phosphate (S1P) burst during AMI, and find its magnitude to favorably associate with cardiovascular mortality and infarct size in STEMI patients over 12 months. Experimentally, administration of supernatant from activated platelets reduces infarct size in murine AMI, which is blunted in platelets deficient for S1P export (Mfsd2b) or production (Sphk1) and in mice deficient for cardiomyocyte S1P receptor 1 (S1P1). Our study reveals an exploitable therapeutic window in antiplatelet therapy in AMI as the GPIIb/IIIa antagonist tirofiban preserves S1P release and cardioprotection, whereas the P2Y12 antagonist cangrelor does not. Here, we report that platelet-mediated intrinsic cardioprotection is an exciting therapeutic paradigm reaching beyond AMI, the benefits of which may need to be considered in all antiplatelet therapies.

Mocravimod, a S1P receptor modulator, increases T cell counts in bone marrow biopsies from patients undergoing allogeneic hematopoietic stem cell transplantation

Graft-versus-leukemia (GvL) effects are critical to prevent relapses after allogeneic hematopoietic cell transplantation (allo-HCT). However, the success of allo-HCT is limited by graft-versus-host disease (GvHD). Both, CD4+ and CD8+ T cells contribute to GvHD and GvL. The sphingosine-1-phosphate receptor (S1PR) signaling plays a crucial role in lymphocyte trafficking. Mocravimod is an S1PR modulator and its administration leads to blocking lymphocyte egress from lymphoid organs. We hypothesized that this applies to the bone marrow (BM) too, and analyzed BM biopsies from the clinical study with mocravimod (phase I trial in allo-HCT patients; NCT01830010) by immunohistochemical staining for CD3, CD4, CD8, TIA1, FoxP3, PD1, T-Bet, GATA3, and ROR-γt to identify and quantify T cell subsets in situ. Allo-HCT patients without receiving mocravimod were used as controls. BM from 9 patients in the mocravimod group and 10 patients in the control group were examined. CD3+ T cells were found to accumulate in the BM of mocravimod-treated patients compared to controls, both on day 30 and 90 post-transplant. The effect was stronger for CD4+ T cells, than CD8+ T cells, which is in line with data from murine studies showing that CD4+ T cells are more sensitive to mocravimod treatment than CD8+ T cells. Clinically-relevant acute GvHD events (grade II-IV) were slightly lower, but comparable to controls when mocravimod was administered. Taken together, data are supportive of mocravimod’s mode of action and bring additional evidence of fewer relapses for allo-HCT patients treated with S1PR modulators.

Lysophospholipid (LPA) receptors in GtoPdb v.2023.1

Lysophosphatidic acid (LPA) receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Lysophospholipid Receptors [62, 23, 91, 144]) are activated by the endogenous phospholipid LPA. The first receptor, LPA1, was identified as ventricular zone gene-1 (vzg-1) [46], This discovery represented the beginning of the de-orphanisation of members of the endothelial differentiation gene (edg) family, as other LPA and sphingosine 1-phosphate (S1P) receptors were found. Five additional LPA receptors (LPA2,3,4,5,6) have since been identified [91] and their gene nomenclature codified for human LPAR1, LPAR2, etc. (HUGO Gene Nomenclature Committee, HGNC) and Lpar1, Lpar2, etc. for mice (Mouse Genome Informatics Database, MGI) to reflect species and receptor function of their corresponding proteins. The crystal structure of LPA1 [17, 80, 2] and LPA6 [128] are solved and indicate that LPA accesses the extracellular binding pocket, consistent with its proposed delivery via autotaxin [17]. These studies have also implicated cross-talk with endocannabinoids via phosphorylated intermediates that can also activate these receptors. The binding affinities to LPA1 of unlabeled, natural LPA and anandamide phosphate (AEAp) were measured using backscattering interferometry (pKd = 9) [92, 115]. Utilization of this method indicated affinities that were 77-fold lower than when measured using radioactivity-based protocols [143]. Targeted deletion of LPA receptors has clarified signalling pathways and identified physiological and pathophysiological roles. Multiple groups have independently published validation of all six LPA receptors described in these tables, and further validation was achieved using a distinct read-out via a novel TGFα "shedding* assay [54]. LPA has been proposed to be a ligand for GPR35 [103], supported by a study revealing that LPA modulates macrophage function through GPR35 [60]. However chemokine (C-X-C motif) ligand 17 (CXCL17) is reported to be a ligand for GPR35/CXCR8 [85]. Moreover, LPA has also been described as an agonist for the transient receptor potential (Trp) ion channels TRPV1 [96] and TRPA1 [65]. All of these proposed non-GPCR receptor identities require confirmation and are not currently recognized as bona fide LPA receptors.

Relationship Between Infections and Absolute Lymphocyte Count During Phase 3 and Open-label Extension Trials of Ozanimod in Patients With Relapsing Multiple Sclerosis (P7-3.002)

Relationship Between Infections and Absolute Lymphocyte Count During Phase 3 and Open-label Extension Trials of Ozanimod in Patients With Relapsing Multiple Sclerosis (P7-3.002)

Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV), and Cryptococcal Infections Associated With Sphingosine-1-Phosphate Receptor (S1PR) Modulators: A Review (P12-10.005)

<h3>Objective:</h3> To summarize the existing data on the incidence of herpes simplex virus (HSV), varicella-zoster virus (VZV), and Cryptococcus sp. infections with sphingosine-1-phosphate receptor (S1PR) modulators. <h3>Background:</h3> S1PR modulators are a novel class of disease-modifying therapies for multiple sclerosis (MS) that produce immunosuppression and potential lymphopenia. Herpesvirus and cryptococcal diseases were the most common opportunistic infections in clinical trials. Several post-hoc analyses have subsequently been published with revised incidence rates (IRs) for these conditions. <h3>Design/Methods:</h3> A literature review and descriptive analysis of phase-3 trials (n=6), post-marketing studies (n=8), and case reports (n=17) were conducted using PubMed and Google Scholar. Further data was accessed through Novartis AG, Bristol-Myers Squibb, and Janssen Pharmaceuticals. <h3>Results:</h3> <h3>FINGOLIMOD:</h3> Herpesvirus infection rates were similar between placebo (2.8%) and 0.5 mg (2.1%) but increased with 1.25 mg (5.5%) in the TRANSFORMS study. VZV rates were higher with fingolimod 0.5 mg (3.0%; 11 per 1000 patient-years [PY]) than with placebo (1.0%; 6 per 1000 PY), but comparable post-marketing. Cryptococcal infections (n=74) had an IR of 9 per 100,000 PY, and 13 cases were individually reported. <h3>SIPONIMOD:</h3> VZV reactivation occurred more frequently with siponimod (2%) than with placebo (1%); EXPAND extension analyses calculated an IR of 0.9 for HSV and 1.8 for VZV infections. One case of cryptococcal meningitis (from 7236 PY of exposure) was documented. <h3>OZANIMOD:</h3> An integrated safety analysis reported oral herpes at 1.5%, VZV at 1.4%, and HSV at 0.5% from all clinical trials versus 0.7%, 0.6%, and 0.1% from the phase-3 trials. The IR of herpes zoster was 5.3/1000 PY. <h3>PONESIMOD:</h3> The incidence of herpetic infections was equal between both groups (4.8%) in the OPTIMUM trial. Cryptococcal infections have not yet been reported with ozanimod or ponesimod. <h3>Conclusions:</h3> Overall, the incidence of these opportunistic infections associated with S1PR modulators in MS was low, with favorable outcomes and limited fatalities. <b>Disclosure:</b> Dr. Sharma has nothing to disclose. Mr. JHA has nothing to disclose. Dr. Khanal has nothing to disclose. Dr. Sriwastava has nothing to disclose.

Long-term Safety of Ozanimod in Relapsing Multiple Sclerosis and Moderately to Severely Active Ulcerative Colitis (P7-3.007)

Long-term Safety of Ozanimod in Relapsing Multiple Sclerosis and Moderately to Severely Active Ulcerative Colitis (P7-3.007)

Serologic Response and Clinical Outcomes of SARS-CoV-2 Infection and Vaccination in Ozanimod-Treated Participants With Relapsing Multiple Sclerosis (P2-3.018)

Serologic Response and Clinical Outcomes of SARS-CoV-2 Infection and Vaccination in Ozanimod-Treated Participants With Relapsing Multiple Sclerosis (P2-3.018)

Apolipoprotein M supports S1P production and conservation and mediates prolonged Akt activation via S1PR1 and S1PR3.

Sphingosine 1-phosphate (S1P) is one of the lipid mediators involved in diverse physiological functions. S1P circulates in blood and lymph bound to carrier proteins. Three S1P carrier proteins have been reported, albumin, apolipoprotein M (ApoM) and apolipoprotein A4 (ApoA4). The carrier-bound S1P exerts its functions via specific S1P receptors (S1PR1-5) on target cells. Previous studies showed several differences in physiological functions between albumin-bound S1P and ApoM-bound S1P. However, molecular mechanisms underlying the carrier-dependent differences have not been clarified. In addition, ApoA4 is a recently identified S1P carrier protein, and its functional differences from albumin and ApoM have not been addressed. Here, we compared the three carrier proteins in the processes of S1P degradation, release from S1P-producing cells and receptor activation. ApoM retained S1P more stable than albumin and ApoA4 in the cell culture medium when compared in the equimolar amounts. ApoM facilitated theS1P release from endothelial cells most efficiently. Furthermore, ApoM-bound S1P showed a tendency to induce prolonged activation of Akt via S1PR1 and S1PR3. These results suggest that the carrier-dependent functional differences of S1P are partly ascribed to the differences in the S1P stability, S1P-releasing efficiency and signaling duration.

Changing Treatment Trends for MS Patients Recently Initiated on Their First DMT (P12-3.012)

<h3>Objective:</h3> To evaluate if disease-modify therapy (DMT) choice has changed for treatment-naïve multiple sclerosis (MS) patients from 2020–2022. <h3>Background:</h3> Cross-sectional audit of MS patients was conducted annually. Data were reviewed by an independent market intelligence agency which specializes in tracking the neurology market. <h3>Design/Methods:</h3> US neurologists (2020: N=199; 2021: N=205; 2022: N=208) completed a survey and contributed chart reviews for a retrospective, cross-sectional audit on MS patients who started their first DMT within the prior 3 months (2020: N=1,006; 2021: N=1,018; 2022: N=1,095). MS patients were analysed as a whole, as well as by physician-reported MS subtypes for relapsing-remitting MS (RRMS; N=722, N=768, N=827), active secondary progressive MS (aSPMS; N=74, N=50, N=59), and primary progressive MS (PPMS; N=92, N=69, N=72). <h3>Results:</h3> Overall use of glatiramer acetate (GA) (32% in 2020, 16% in 2022) has declined; use of fumarate agents (13%, 21%) and anti-CD20 monoclonal antibody (mAb) DMTs (13%, 21%) expanded. Interferon (13% in 2020 and 2022) and S1P receptor modulator class (12%, 14%) use has remained stable. Use of both brand (18%, 11%) and generics (14%, 6%) of GA declined. For fumarates, use has shifted from branded dimethyl fumarate (DMF; 13%, 8%) to generic DMF (0%, 6%) and diroximel fumarate (0%, 6%). For S1Ps, use has shifted from fingolimod (10%, 6%) to ozanimod (0%, 4%) and ponesimod (0%, 1%). Changes in DMT use are similar for RRMS: GA use declined (31%, 16%); fumarates (17%, 23%) and anti-CD20 mAb DMT (9%, 19%) use expanded. GA use also declined for aSPMS (30%, 7%) and PPMS (30%, 8%); anti-CD20 mAb DMT use grew for aSPMS (19%, 41%). <h3>Conclusions:</h3> DMT prescribing trends are evolving for MS patients recently initiated on their first DMT. Use of GA agents has fallen across MS subtypes, while use of the high-efficacy anti-CD20 mAb DMT class has expanded. <b>Disclosure:</b> Dr. McFadden has nothing to disclose.

Psoriasis: A Primer for General Physicians.

Psoriasis is a multisystem, polygenic, inflammatory condition that typically causes changes in the skin. Although there is a significant genetic component, environmental factors like infections can have a significant impact on triggering the disease. A major part of the pathogenesis of psoriasis is played by the Interleukin (IL) IL23/IL17 axis along with the immune-related cells mainly macrophages and dendritic cells (DCs). Additionally, the role of various cytokines along with the toll-like receptors has also been pointed out in immunopathogenesis. These have been supported by the efficacy of biological therapies including TNF alpha inhibitors and inhibitors of IL17 and IL23. We have summarized the topical as well as systemic therapies for psoriasis including biologics. The article throws light on a few emerging therapeutic options like modulators of sphingosine 1-phosphate receptor 1 and Rho-associated kinase 2 inhibitors.

Research Highlights.

Research Highlights.

Modulating sphingosine 1-phosphate receptor signaling skews intrahepatic leukocytes and attenuates murine nonalcoholic steatohepatitis.

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid associated with nonalcoholic steatohepatitis (NASH). Immune cell-driven inflammation is a key determinant of NASH progression. Macrophages, monocytes, NK cells, T cells, NKT cells, and B cells variably express S1P receptors from a repertoire of 5 receptors termed S1P1 - S1P5. We have previously demonstrated that non-specific S1P receptor antagonism ameliorates NASH and attenuates hepatic macrophage accumulation. However, the effect of S1P receptor antagonism on additional immune cell populations in NASH remains unknown. We hypothesized that S1P receptor specific modulation may ameliorate NASH by altering leukocyte recruitment. A murine NASH model was established by dietary feeding of C57BL/6 male mice with a diet high in fructose, saturated fat, and cholesterol (FFC) for 24 weeks. In the last 4 weeks of dietary feeding, the mice received the S1P1,4,5 modulator Etrasimod or the S1P1 modulator Amiselimod, daily by oral gavage. Liver injury and inflammation were determined by histological and gene expression analyses. Intrahepatic leukocyte populations were analyzed by flow cytometry, immunohistochemistry, and mRNA expression. Alanine aminotransferase, a sensitive circulating marker for liver injury, was reduced in response to Etrasimod and Amiselimod treatment. Liver histology showed a reduction in inflammatory foci in Etrasimod-treated mice. Etrasimod treatment substantially altered the intrahepatic leukocyte populations through a reduction in the frequency of T cells, B cells, and NKT cells and a proportional increase in CD11b+ myeloid cells, polymorphonuclear cells, and double negative T cells in FFC-fed and control standard chow diet (CD)-fed mice. In contrast, FFC-fed Amiselimod-treated mice showed no changes in the frequencies of intrahepatic leukocytes. Consistent with the improvement in liver injury and inflammation, hepatic macrophage accumulation and the gene expression of proinflammatory markers such as Lgals3 and Mcp-1 were decreased in Etrasimod-treated FFC-fed mice. Etrasimod treated mouse livers demonstrated an increase in non-inflammatory (Marco) and lipid associated (Trem2) macrophage markers. Thus, S1P1,4,5 modulation by Etrasimod is more effective than S1P1 antagonism by Amiselimod, at the dose tested, in ameliorating NASH, likely due to the alteration of leukocyte trafficking and recruitment. Etrasimod treatment results in a substantial attenuation of liver injury and inflammation in murine NASH.

Very-long-chain fatty acids induce glial-derived sphingosine-1-phosphate synthesis, secretion, and neuroinflammation

VLCFAs (very-long-chain fatty acids) are the most abundant fatty acids in myelin. Hence, during demyelination or aging, glia are exposed to higher levels of VLCFA than normal. We report that glia convert these VLCFA into sphingosine-1-phosphate (S1P) via a glial-specific S1P pathway. Excess S1P causes neuroinflammation, NF-κB activation, and macrophage infiltration into the CNS. Suppressing the function of S1P in fly glia or neurons, or administration of Fingolimod, an S1P receptor antagonist, strongly attenuates the phenotypes caused by excess VLCFAs. In contrast, elevating the VLCFA levels in glia and immune cells exacerbates these phenotypes. Elevated VLCFA and S1P are also toxic in vertebrates based on a mouse model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). Indeed, reducing VLCFA with bezafibrate ameliorates the phenotypes. Moreover, simultaneous use of bezafibrate and fingolimod synergizes to improve EAE, suggesting that lowering VLCFA and S1P is a treatment avenue for MS.

Potentiation of Sphingolipids and TGF-β in the human corneal stroma reveals intricate signaling pathway crosstalks

Corneal haze brought on by fibrosis due to insult can lead to partial or complete vision loss. Currently, corneal transplantation is the gold standard for treating severe corneal fibrosis, which comes with the risk of rejection and the issue of donor tissue shortages. Sphingolipids (SPLs) are known to be associated with fibrosis in various tissues and organs, including the cornea. We previously reported that SPLs are tightly related to Transforming Growth Factor β (TGF-β) signaling and corneal fibrogenesis. This study aimed to elucidate the interplay of SPLs, specifically sphingosine-1-phosphate (S1P) signaling, and its’ interactions with TGF-β signaling through detailed analyses of the corresponding downstream signaling targets in the context of corneal fibrosis, in vitro. Healthy human corneal fibroblasts (HCFs) were isolated, plated on polycarbonate membranes, and stimulated with a stable Vitamin C derivative. The 3D constructs were treated with either 5 μM sphingosine-1-phosphate (S1P), 5 μM SPHK I2 (I2; inhibitor of sphingosine kinase 1, one of the two enzymes responsible for generating S1P in mammalian cells), 0.1 ng/mL TGF-β1, or 0.1 ng/mL TGF-β3. Cultures with control medium-only served as controls. All 3D constructs were examined for protein expression of fibrotic markers, SPLs, TGF-βs, and relevant downstream signaling pathways. This data revealed no significant changes in any LTBP (latent TGF-β binding proteins) expression when stimulated with S1P or I2. However, LTBP1 was significantly upregulated via stimulation of TGF-β1 and TGF-β3, whereas LTBP2 was significantly upregulated only with TGF-β3 stimulation. Significant downregulation of TGF-β receptor II (TGF-βRII) following S1P stimulation but significant upregulation following I2 stimulation was observed. Following TGF-β1, S1P, and I2 stimulation, phospho-SMAD2 (pSMAD2) was significantly downregulated. Furthermore, I2 stimulation led to significant downregulation of SMAD4. Adhesion/proliferation/transcription regulation targets, SRC, FAK, and pERK 1/2 were all significantly downregulated by exogenous S1P, whereas I2 only significantly downregulated FAK. Exogenous TGF-β3 caused significant upregulation of AKT. Interestingly, both I2 and TGF-β3 caused significant downregulation of JNK expression. Lastly, TGF-β1 led to significant upregulation of sphingosine kinase 1 (SphK1) and sphingosine-1-phosphate receptor 3 (S1PR3), whereas TGF-β3 caused significant upregulation of only SphK1. Together with previously published work from our group and others, S1P inhibition exhibits great potential as an efficacious anti-fibrotic modality in human corneal stromal ECM. The current findings shed further light on a very complex and rather incompletely investigated mechanism, and cement the intricate crosstalk between SPLs and TGF-β in corneal fibrogenesis. Future studies will dictate the potential of utilizing SPLs/TGF-β signaling modulators as novel therapeutics in corneal fibrosis.