Sphingosine 1-phosphate receptors regulate TLR4-induced CXCL5 release from astrocytes and microglia

The sphingosine 1-phosphate analogue, FTY720, modulates the lipidomic signature of the mouse hippocampus

The small-molecule drug, FTY720 (fingolimod), is a synthetic sphingosine 1-phosphate (S1P) analogue currently used to treat relapsing-remitting multiple sclerosis in both adults and children. FTY720 can cross the blood-brain barrier (BBB) and, over time, accumulate in lipid-rich areas of the central nervous system (CNS) by incorporating into phospholipid membranes. FTY720 has been shown to enhance cell membrane fluidity, which can modulate the functions of glial cells and neuronal populations involved in regulating behaviour. Moreover, direct modulation of S1P receptor-mediated lipid signalling by FTY720 can impact homeostatic CNS physiology, including neurotransmitter release probability, the biophysical properties of synaptic membranes, ion channel and transmembrane receptor kinetics, and synaptic plasticity mechanisms. The aim of this study was to investigate how chronic FTY720 treatment alters the lipid composition of CNS tissue in adolescent mice at a key stage of brain maturation. We focused on the hippocampus, a brain region known to be important for learning, memory, and the processing of sensory and emotional stimuli. Using mass spectrometry-based lipidomics, we discovered that FTY720 increases the fatty acid chain length of hydroxy-phosphatidylcholine (PCOH) lipids in the mouse hippocampus. It also decreases PCOH monounsaturated fatty acids (MUFAs) and increases PCOH polyunsaturated fatty acids (PUFAs). A total of 99 lipid species were up-regulated in the mouse hippocampus following 3 weeks of oral FTY720 exposure, whereas only 3 lipid species were down-regulated. FTY720 also modulated anxiety-like behaviours in young mice but did not affect spatial learning or memory formation. Our study presents a comprehensive overview of the lipid classes and lipid species that are altered in the hippocampus following chronic FTY720 exposure and provides novel insight into cellular and molecular mechanisms that may underlie the therapeutic or adverse effects of FTY720 in the central nervous system.

DCPIB Attenuates Ischemia-Reperfusion Injury by Regulating Microglial M1/M2 Polarization and Oxidative Stress

The inflammatory response plays an indispensable role in ischemia-reperfusion injury, the most significant of which is the inflammatory response caused by microglial polarization. Anti-inflammatory therapy is also an important remedial measure after failed vascular reconstruction. Maintaining the internal homeostasis of the brain is a crucial measure for suppressing the inflammatory response. The mechanism underlying the relationship between DCPIB, a selective blocker of volume-regulated anion channels (VRAC), and inflammation induced by cerebral ischemia-reperfusion injury is currently unclear. The purpose of this study was to investigate the relationship between DCPIB and microglial M1/M2 polarization-mediated inflammation after cerebral ischemia-reperfusion injury. C57BL/6 mice were subjected to transient middle cerebral artery occlusion (tMCAO). DCPIB was administered by a lateral ventricular injection within 5 min after reperfusion. Behavioral assessments were conducted at 1, 3, and 7 days after tMCAO/R. Pathological injuries were evaluated using TTC assay, HE and Nissl staining, brain water content measurement, and immunofluorescence staining. The levels of inflammatory cytokines were analyzed using qPCR and ELISA. Additionally, the phenotypic variations of microglia were examined using immunofluorescence staining. In mouse tMCAO/R model, DCPIB administration markably reduced mortality, improved behavioral performance, and alleviated pathological injury. DCPIB treatment significantly inhibited the inflammatory response, promoted the conversion of M1 microglia to M2 microglia via the MAPK signaling pathway, and ultimately protected neurons from the microglia-mediated inflammatory response. In addition, DCPIB inhibited oxidative stress induced by cerebral ischemia-reperfusion injury. In conclusion, DCPIB attenuates cerebral ischemia-reperfusion injury by regulating microglial M1/M2 polarization and oxidative stress.

Mechanical epilation exerts complex biological effects on human hair follicles and perifollicular skin: An ex vivo study approach

OBJECTIVE

Electrical epilation of unwanted hair is a widely used hair removal method, but it is largely unknown how this affects the biology of human hair follicles (HF) and perifollicular skin. Here, we have begun to explore how mechanical epilation changes selected key biological read-out parameters ex vivo within and around the pilosebaceous unit.

METHODS

Human full-thickness scalp skin samples were epilated ex vivo using an electro-mechanical device, organ-cultured for up to 6 days in serum-free, supplemented medium, and assessed at different time points by quantitative (immuno-)histomorphometry for selected relevant read-out parameters in epilated and sham-epilated control samples.

RESULTS

Epilation removed most of the hair shafts, often together with fragments of the outer and inner root sheath and hair matrix. This was associated with persistent focal thinning of the HF basal membrane, decreased melanin content of the residual HF epithelium, and increased HF keratinocyte apoptosis, including in the bulge, yet without affecting the number of cytokeratin 15+ HF epithelial stem cells. Sebocyte apoptosis in the peripheral zone was increased, albeit without visibly altering sebum production. Epilation transiently perturbed HF immune privilege, and increased the expression of ICAM-1 in the bulge and bulb mesenchyme, and the number of perifollicular MHC class II+ cells as well as mast cells around the distal epithelium and promoted mast cell degranulation around the suprabulbar and bulbar area. Moreover, compared to controls, several key players of neurogenic skin inflammation, itch, and/or thermosensation (TRPV1, TRPA1, NGF, and NKR1) were differentially expressed in post-epilation skin.

CONCLUSION

These data generated in denervated, organ-cultured human scalp skin demonstrate that epilation-induced mechanical HF trauma elicits surprisingly complex biological responses. These may contribute to the delayed re-growth of thinner and lighter hair shafts post-epilation and temporary post-epilation discomfort. Our findings also provide pointers regarding the development of topically applicable agents that minimize undesirable sequelae of epilation.

Consistency of mouse models with human intracerebral hemorrhage: core targets and non-coding RNA regulatory axis

Intracerebral hemorrhage (ICH) has a high mortality and disability rate. Numerous basic studies on pathogenesis and therapeutics have been performed in mice. However, the consistency of the experimental mouse model and the human ICH patient remains unclear. This has slowed progress in translational medicine. Furthermore, effective therapeutic targets and reliable regulatory networks for ICH are needed. Therefore, we determined the differentially expressed (DE) messenger RNAs (mRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) before and after murine ICH and analyzed their regulatory relationships. Subsequently, data on mRNAs from human peripheral blood after ICH were obtained from the Gene Expression Omnibus database. The DE mRNAs after human ICH were compared with those of the mouse. Finally, we obtained seven genes with translational medicine research value and verified them in mice. Then the regulatory network of these genes was analyzed in humans. Similarly, species homologies of these regulatory pathways were identified. In conclusion, we found that the mouse ICH model mimics the human disease mainly in terms of chemokines and inflammatory factors. This has important implications for future research into the mechanisms of ICH injury and repair.

Human motor neurons derived from induced pluripotent stem cells are susceptible to SARS-CoV-2 infection

Introduction

COVID-19 typically causes Q7 respiratory disorders, but a high proportion of patients also reports neurological and neuromuscular symptoms during and after SARSCoV-2 infection. Despite a number of studies documenting SARS-CoV-2 infection of various neuronal cell populations, the impact of SARS-CoV-2 exposure on motor neuronal cells specifically has not been investigated so far.

Methods

Thus, by using human iPSC-derived motor neurons (iPSC-MNs) we assessed: (i) the expression of SARS-CoV-2 main receptors; (ii) iPSC-MN infectability by SARS-CoV-2; and (iii) the effect of SARS-CoV-2 exposure on iPSC-MN transcriptome.

Results

Gene expression profiling and immunofluorescence (IF) analysis of the main host cell receptors recognized by SARS-CoV-2 revealed that all of them are expressed in iPSC-MNs, with CD147 and NRP1 being the most represented ones. By analyzing SARS-CoV-2 N1 and N2 gene expression over time, we observed that human iPSC-MNs were productively infected by SARS-CoV-2 in the absence of cytopathic effect. Supernatants collected from SARS-CoV-2-infected iPSC-MNs were able to re-infect VeroE6 cells. Image analyses of SARS-CoV-2 nucleocapsid proteins by IF confirmed iPSC-MN infectability. Furthermore, SARS-CoV-2 infection in iPSCMNs significantly altered the expression of genes (IL-6, ANG, S1PR1, BCL2, BAX, Casp8, HLA-A, ERAP1, CD147, MX1) associated with cell survival and metabolism, as well as antiviral and inflammatory response.

Discussion

These results suggest for the very first time that SARS-CoV-2 can productively infect human iPSC-derived MNs probably by binding CD147 and NRP1 receptors. Such information will be important to unveil the biological bases of neuromuscular disorders characterizing SARS-CoV-2 infection and the so called long-COVID symptoms.

The murine metastatic microenvironment of experimental brain metastases of breast cancer differs by host age in vivo: a proteomic study

Breast cancer in young patients is known to exhibit more aggressive biological behavior and is associated with a less favorable prognosis than the same disease in older patients, owing in part to an increased incidence of brain metastases. The mechanistic explanations behind these findings remain poorly understood. We recently reported that young mice, in comparison to older mice, developed significantly greater brain metastases in four mouse models of triple-negative and luminal B breast cancer. Here we have performed a quantitative mass spectrometry-based proteomic analysis to identify proteins potentially contributing to age-related disparities in the development of breast cancer brain metastases. Using a mouse hematogenous model of brain-tropic triple-negative breast cancer (MDA-MB-231BR), we harvested subpopulations of tumor metastases, the tumor-adjacent metastatic microenvironment, and uninvolved brain tissues via laser microdissection followed by quantitative proteomic analysis using high resolution mass spectrometry to characterize differentially abundant proteins potentially contributing to age-dependent rates of brain metastasis. Pathway analysis revealed significant alterations in signaling pathways, particularly in the metastatic microenvironment, modulating tumorigenesis, metabolic processes, inflammation, and neuronal signaling. Tenascin C (TNC) was significantly elevated in all laser microdissection (LMD) enriched compartments harvested from young mice relative to older hosts, which was validated and confirmed by immunoblot analysis of whole brain lysates. Additional in vitro studies including migration and wound-healing assays demonstrated TNC as a positive regulator of tumor cell migration. These results provide important new insights regarding microenvironmental factors, including TNC, as mechanisms contributing to the increased brain cancer metastatic phenotype observed in young breast cancer patients.

Sphingosine 1-phosphate signaling during infection and immunity

Sphingolipids are essential components of all eukaryotic membranes. The bioactive sphingolipid molecule, Sphingosine 1-Phosphate (S1P), regulates various important biological functions. This review aims to provide a comprehensive overview of the role of S1P signaling pathway in various immune cell functions under different pathophysiological conditions including bacterial and viral infections, autoimmune disorders, inflammation, and cancer. We covered the aspects of S1P pathways in NOD/TLR pathways, bacterial and viral infections, autoimmune disorders, and tumor immunology. This implies that targeting S1P signaling can be used as a strategy to block these pathologies. Our current understanding of targeting various components of S1P signaling for therapeutic purposes and the present status of S1P pathway inhibitors or modulators in disease conditions where the host immune system plays a pivotal role is the primary focus of this review.

Prognostic significance of plasma S1P in acute intracerebral hemorrhage: A prospective cohort study

OBJECTIVE

Sphingosine-1-phosphate (S1P) may regulate neuroinflammatory immunity and blood-brain barrier integrity. This study was designed to assess the prognostic role of plasma S1P in intracerebral hemorrhage (ICH).

METHODS

In this prospective cohort study, plasma S1P levels were measured in 51 controls, at admission in 114 ICH patients and at days 1, 3, 5 and 7 in 51 of all patients. Univariate analysis and multivariate analysis were sequentially used to investigate severity correlation and prognosis association.

RESULTS

Plasma S1P levels were significantly elevated at admission, peaked at day 5, and declined at day 7, which were significantly higher during 7 days than those of controls (all P < 0.001). Areas under receiver operating characteristic curve (AUCs) of plasma S1P levels insignificant differed among all time points (all P > 0.05). Admission plasma S1P levels, in close correlation with National Institutes of Health Stroke Scale (NIHSS) scores [β, 7.661; 95 % confidence interval (CI), 4.893-10.399; P < 0.001] and hematoma volume (β, 1.285; 95 % CI, 0.348-2.230; P < 0.001), independently predicted 3-month poor prognosis (modified Rankin Scale scores of 3-6) (odds ratio, 3.184; 95 % CI, 1.057-9.597; P = 0.040). Admission plasma S1P levels had AUC of 0.799 (95 % CI, 0.713-0.868) for prognosis prediction. The levels > 240.4 ng/ml distinguished risk of poor prognosis with the maximum Youden index of 0.518. Prediction model integrating NIHSS scores, hematoma volume and admission plasma S1P levels had substantially higher prognostic predictive ability than NIHSS scores (P = 0.023), but not than hematoma volume (P = 0.061).

CONCLUSION

There is a significant elevation of plasma S1P levels during early period after ICH, which were independently related to severity and poor prognosis. Thus, plasma S1P may be a potential prognostic biomarker of ICH.

Immune System and Brain/Intestinal Barrier Functions in Psychiatric Diseases: Is Sphingosine-1-Phosphate at the Helm?

Over the past few decades, extensive research has shed light on immune alterations and the significance of dysfunctional biological barriers in psychiatric disorders. The leaky gut phenomenon, intimately linked to the integrity of both brain and intestinal barriers, may play a crucial role in the origin of peripheral and central inflammation in these pathologies. Sphingosine-1-phosphate (S1P) is a bioactive lipid that regulates both the immune response and the permeability of biological barriers. Notably, S1P-based drugs, such as fingolimod and ozanimod, have received approval for treating multiple sclerosis, an autoimmune disease of the central nervous system (CNS), and ulcerative colitis, an inflammatory condition of the colon, respectively. Although the precise mechanisms of action are still under investigation, the effectiveness of S1P-based drugs in treating these pathologies sparks a debate on extending their use in psychiatry. This comprehensive review aims to delve into the molecular mechanisms through which S1P modulates the immune system and brain/intestinal barrier functions. Furthermore, it will specifically focus on psychiatric diseases, with the primary objective of uncovering the potential of innovative therapies based on S1P signaling.

The S1P receptor 1 antagonist Ponesimod reduces TLR4-induced neuroinflammation and increases Aβ clearance in 5XFAD mice

BACKGROUND

Previously, we showed that the sphingosine-1-phosphate (S1P) transporter spinster 2 (Spns2) mediates activation of microglia in response to amyloid β peptide (Aβ). Here, we investigated if Ponesimod, a functional S1P receptor 1 (S1PR1) antagonist, prevents Aβ-induced activation of glial cells and Alzheimer's disease (AD) pathology.

METHODS

We used primary cultures of glial cells and the 5XFAD mouse model to determine the effect of Aβ and Ponesimod on glial activation, Aβ phagocytosis, cytokine levels and pro-inflammatory signaling pathways, AD pathology, and cognitive performance.

FINDINGS

Aβ42 increased the levels of TLR4 and S1PR1, leading to their complex formation. Ponesimod prevented the increase in TLR4 and S1PR1 levels, as well as the formation of their complex. It also reduced the activation of the pro-inflammatory Stat1 and p38 MAPK signaling pathways, while activating the anti-inflammatory Stat6 pathway. This was consistent with increased phagocytosis of Aβ42 in primary cultured microglia. In 5XFAD mice, Ponesimod decreased the levels of TNF-α and CXCL10, which activate TLR4 and Stat1. It also increased the level of IL-33, an anti-inflammatory cytokine that promotes Aβ42 phagocytosis by microglia. As a result of these changes, Ponesimod decreased the number of Iba-1+ microglia and GFAP+ astrocytes, and the size and number of amyloid plaques, while improving spatial memory as measured in a Y-maze test.

INTERPRETATION

Ponesimod targeting S1PR1 is a promising therapeutic approach to reprogram microglia, reduce neuroinflammation, and increase Aβ clearance in AD.

FUNDING

NIHR01AG064234, RF1AG078338, R21AG078601, VAI01BX003643.

Development of MAPT S305 mutation models exhibiting elevated 4R tau expression, resulting in altered neuronal and astrocytic function

Due to the importance of 4R tau in the pathogenicity of primary tauopathies, it has been challenging to model these diseases in iPSC-derived neurons, which express very low levels of 4R tau. To address this problem we have developed a panel of isogenic iPSC lines carrying the MAPT splice-site mutations S305S, S305I or S305N, derived from four different donors. All three mutations significantly increased the proportion of 4R tau expression in iPSC-neurons and astrocytes, with up to 80% 4R transcripts in S305N neurons from as early as 4 weeks of differentiation. Transcriptomic and functional analyses of S305 mutant neurons revealed shared disruption in glutamate signaling and synaptic maturity, but divergent effects on mitochondrial bioenergetics. In iPSC-astrocytes, S305 mutations induced lysosomal disruption and inflammation and exacerbated internalization of exogenous tau that may be a precursor to the glial pathologies observed in many tauopathies. In conclusion, we present a novel panel of human iPSC lines that express unprecedented levels of 4R tau in neurons and astrocytes. These lines recapitulate previously characterized tauopathy-relevant phenotypes, but also highlight functional differences between the wild type 4R and mutant 4R proteins. We also highlight the functional importance of MAPT expression in astrocytes. These lines will be highly beneficial to tauopathy researchers enabling a more complete understanding of the pathogenic mechanisms underlying 4R tauopathies across different cell types.

Astrocytic CXCL5 hinders microglial phagocytosis of myelin debris and aggravates white matter injury in chronic cerebral ischemia

BACKGROUND

Chronic cerebral ischemia induces white matter injury (WMI) contributing to cognitive decline. Both astrocytes and microglia play vital roles in the demyelination and remyelination processes, but the underlying mechanism remains unclear. This study aimed to explore the influence of the chemokine CXCL5 on WMI and cognitive decline in chronic cerebral ischemia and the underlying mechanism.

METHODS

Bilateral carotid artery stenosis (BCAS) model was constructed to mimic chronic cerebral ischemia in 7-10 weeks old male mice. Astrocytic Cxcl5 conditional knockout (cKO) mice were constructed and mice with Cxcl5 overexpressing in astrocytes were generated by stereotactic injection of adeno-associated virus (AAV). WMI was evaluated by magnetic resonance imaging (MRI), electron microscopy, histological staining and western blotting. Cognitive function was examined by a series of neurobehavioral tests. The proliferation and differentiation of oligodendrocyte progenitor cells (OPCs), phagocytosis of microglia were analyzed via immunofluorescence staining, western blotting or flow cytometry.

RESULTS

CXCL5 was significantly elevated in the corpus callosum (CC) and serum in BCAS model, mainly expressed in astrocytes, and Cxcl5 cKO mice displayed improved WMI and cognitive performance. Recombinant CXCL5 (rCXCL5) had no direct effect on the proliferation and differentiation of OPCs in vitro. Astrocytic specific Cxcl5 overexpression aggravated WMI and cognitive decline induced by chronic cerebral ischemia, while microglia depletion counteracted this effect. Recombinant CXCL5 remarkably hindered microglial phagocytosis of myelin debris, which was rescued by inhibition of CXCL5 receptor C-X-C motif chemokine receptor 2 (CXCR2).

CONCLUSION

Our study revealed that astrocyte-derived CXCL5 aggravated WMI and cognitive decline by inhibiting microglial phagocytosis of myelin debris, suggesting a novel astrocyte-microglia circuit mediated by CXCL5-CXCR2 signaling in chronic cerebral ischemia.

The Effects of Antipsychotics in Experimental Models of Krabbe Disease

The role of altered myelin in the onset and development of schizophrenia and changes in myelin due to antipsychotics remains unclear. Antipsychotics are D₂ receptor antagonists, yet D₂ receptor agonists increase oligodendrocyte progenitor numbers and limit oligodendrocyte injury. Conflicting studies suggest these drugs promote the differentiation of neural progenitors to oligodendrocyte lineage, while others report antipsychotics inhibit the proliferation and differentiation of oligodendrocyte precursors. Here, we utilised in-vitro (human astrocytes), ex-vivo (organotypic slice cultures) and in-vivo (twitcher mouse model) experimental study designs of psychosine-induced demyelination, a toxin that accumulates in Krabbe disease (KD), to investigate direct effects of antipsychotics on glial cell dysfunction and demyelination. Typical and atypical antipsychotics, and selective D₂ and 5HT_2A receptor antagonists, attenuated psychosine-induced cell viability, toxicity, and morphological aberrations in human astrocyte cultures. Haloperidol and clozapine reduced psychosine-induced demyelination in mouse organotypic cerebellar slices. These drugs also attenuated the effects of psychosine on astrocytes and microglia and restored non-phosphorylated neurofilament levels, indicating neuroprotective effects. In the demyelinating twitcher mouse model of KD, haloperidol improved mobility and significantly increased the survival of these animals. Overall, this study suggests that antipsychotics directly regulate glial cell dysfunction and exert a protective effect on myelin loss. This work also points toward the potential use of these pharmacological agents in KD.

Astrocyte-Derived Exosomes Differentially Shape T Cells' Immune Response in MS Patients

Astrocytes, the most abundant group of glia cells in the brain, provide support for neurons and indicate multiple various functions in the central nervous system (CNS). Growing data additionally describe their role in the regulation of immune system activity. They exert their function not only by direct contact with other cell types, but also through an indirect method, e.g., by secreting various molecules. One such structure is extracellular vesicles, which are important mediators of crosstalk between cells. In our study, we observed that the impact of exosomes derived from astrocytes with various functional phenotype differently affect the immune response of CD4+ T cells, both from healthy individuals and from patients with multiple sclerosis (MS). Astrocytes, by modulating exosome cargo, impacts the release of IFN-γ, IL-17A and CCL2 in our experimental conditions. Considering the proteins concentration in cell culture supernatants and the cellular percentage of Th phenotypes, it could be stated that human astrocytes, by the release of exosomes, are able to modify the activity of human T cells.

Time- and Sex-Dependent Effects of Fingolimod Treatment in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia. Fingolimod has previously shown beneficial effects in different animal models of AD. However, it has shown contradictory effects when it has been applied at early disease stages. Our objective was to evaluate fingolimod in two different treatment paradigms. To address this aim, we treated male and female APP-transgenic mice for 50 days, starting either before plaque deposition at 50 days of age (early) or at 125 days of age (late). To evaluate the effects, we investigated the neuroinflammatory and glial markers, the Aβ load, and the concentration of the brain-derived neurotrophic factor (BDNF). We found a reduced Aβ load only in male animals in the late treatment paradigm. These animals also showed reduced microglia activation and reduced IL-1β. No other treatment group showed any difference in comparison to the controls. On the other hand, we detected a linear correlation between BDNF and the brain Aβ concentrations. The fingolimod treatment has shown beneficial effects in AD models, but the outcome depends on the neuroinflammatory state at the start of the treatment. Thus, according to our data, a fingolimod treatment would be effective after the onset of the first AD symptoms, mainly affecting the neuroinflammatory reaction to the ongoing Aβ deposition.

Ceramide/Sphingosine 1-Phosphate Axis as a Key Target for Diagnosis and Treatment in Alzheimer’s Disease and Other Neurodegenerative Diseases

Alzheimer’s disease (AD) is considered the most prevalent neurodegenerative disease and the leading cause of dementia worldwide. Sphingolipids, such as ceramide or sphingosine 1-phosphate, are bioactive molecules implicated in structural and signaling functions. Metabolic dysfunction in the highly conserved pathways to produce sphingolipids may lead to or be a consequence of an underlying disease. Recent studies on transcriptomics and sphingolipidomics have observed alterations in sphingolipid metabolism of both enzymes and metabolites involved in their synthesis in several neurodegenerative diseases, including AD. In this review, we highlight the most relevant findings related to ceramide and neurodegeneration, with a special focus on AD.

Extracellular Cardiolipin Modulates Select Immune Functions of Astrocytes in Toll-Like Receptor (TLR) 4-Dependent Manner

Alzheimer's disease (AD) is characterized by chronic neuroinflammation, which is partially mediated by dysregulated functions of glial cells. Cardiolipin (CL) is a phospholipid normally confined to the inner mitochondrial membrane; however, it has been detected in human sera, indicating that it can exist in the extracellular space where it may interact with nearby cells. Although CL has been shown to modulate several functions of microglia in a toll-like receptor (TLR) 4-dependent manner, the effects of extracellular CL on astrocytes are unknown. In addition to their homeostatic functions, astrocytes participate in neuroimmune responses of the brain and express TLR 4. Therefore, we hypothesized that extracellular CL (1) modulates the secretion of cytokines and cytotoxins by astrocytes, as well as their phagocytic activity, and (2) acts by interacting with astrocyte TLR 4. We demonstrate that CL inhibits the lipopolysaccharide- (LPS-) induced secretion of cytotoxins and expression of glial fibrillary acidic protein (GFAP) by human U118 MG astrocytic cells. CL alone upregulates the phagocytic activity of human astrocytic cells and primary murine astrocytes. CL in combination with LPS upregulates secretion of interleukin (IL)-1β by astrocytic cells. Furthermore, CL alone increases the secretion of monocyte chemoattractant protein (MCP)-1 by astrocytic cells, which is blocked by the TLR 4-specific antagonist TAK-242. We demonstrate that CL upregulates MCP-1 secretion in the absence of its natural carrier protein, β2-glycoprotein 1, indicating that CL may be bioactive in the brain where this protein is not present. Lastly, we show that CL downregulates the expression of astrocytic TLR 4, implying that CL engages this receptor, as its activation has been shown to lead to its degradation. Overall, our study extends the list of cell type functions of which CL modulates and provides evidence that CL, or liposomes containing this phospholipid can be used to modulate specific neuroimmune functions of astrocytes.

Botanically-Derived Δ9-Tetrahydrocannabinol and Cannabidiol, and Their 1:1 Combination, Modulate Toll-like Receptor 3 and 4 Signalling in Immune Cells from People with Multiple Sclerosis

The innate immune response to bacterial and viral molecules involves the coordinated production of cytokines, chemokines, and type I interferons (IFNs), which is orchestrated by toll-like receptors (TLRs). TLRs, and their intracellular signalling intermediates, are closely associated with multiple sclerosis (MS) pathogenesis. Recent data from our laboratory reported that the plant-derived cannabinoids, Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), regulate viral and bacterial inflammatory signalling pathways controlled by TLR3 and TLR4 in macrophages. The aim of this study was to assess the impact of THC and CBD, when delivered in isolation and in combination (1:1), on TLR3- and TLR4-dependent signalling in peripheral blood mononuclear cells (PBMCs) from people with MS (pwMS; n = 21) and healthy controls (HCs; n = 26). We employed the use of poly(I:C) and lipopolysaccharide (LPS) to induce viral TLR3 and bacterial TLR4 signalling, and PBMCs were pre-exposed to plant-derived highly purified THC (10 μM), CBD (10 μM), or a combination of both phytocannabinoids (1:1 ratio, 10:10 μM), prior to LPS/poly(I:C) exposure. TLR3 stimulation promoted the protein expression of the chemokine CXCL10 and the type I IFN-β in PBMCs from both cohorts. THC and CBD (delivered in 1:1 combination at 10 μM) attenuated TLR3-induced CXCL10 and IFN-β protein expression in PBMCs from pwMS and HCs, and this effect was not seen consistently when THC and CBD were delivered alone. In terms of LPS, TLR4 activation promoted TNF-α expression in PBMCs from both cohorts, and, interestingly, CBD when delivered alone at 10 μM, and in combination with THC (in 1:1 combination at 10 μM), exacerbated TLR4-induced TNF-α protein expression in PBMCs from pwMS and HCs. THC and CBD displayed no evidence of toxicity in primary PBMCs. No significant alteration in the relative expression of TLR3 and TLR4 mRNA, or components of the endocannabinoid system, including the cannabinoid receptor CB₁ (encoded by CNR1 gene) and CB₂ (encoded by CNR2 gene), and endocannabinoid metabolising enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGLL), was determined in PBMCs from pwMS versus HCs. Given their role in inflammation, TLRs are clinical targets, and data herein identify CBD and THC as TLR3 and TLR4 modulating drugs in primary immune cells in vitro. This offers insight on the cellular target(s) of phytocannabinoids in targeting inflammation in the context of MS.

CD44 deficiency represses neuroinflammation and rescues dopaminergic neurons in a mouse model of Parkinson's disease

CD44 is a transmembrane protein that transduces extracellular stimuli to immune response. Neuroinflammation is a causative factor in neurodegenerative diseases, such as Parkinson's disease (PD). Owing to its role in inflammation, this study investigated whether CD44 is involved in the pathological progression of PD. Our data showed that CD44 deficiency largely abolished proinflammatory cytokine expression in primary microglia and astrocytes. In PD model mice, CD44 knockout improved behavioral defects, prevented TH loss in the SNpc and striatum, and blocked activation of microglia and astrocytes. Moreover, CD44 neutralization by anti-CD44 antibody recapitulated the phenotypes observed in CD44 knockout mice. Mechanistically, CD44 neutralization blocked TLR4 expression and NF-κB p65 nuclear translocation induced by lipopolysaccharide in BV2 cells. Overall, our results indicate that CD44 deficiency has a beneficial role against PD, which is likely due to repression of the TLR4/NF-κB axis, leading to reduced neuroinflammation. Therefore, CD44 might be a therapeutic target for the development of anti-PD agents.

Early Toll-like receptor 4 inhibition improves immune dysfunction in the hippocampus after hypoxic-ischemic brain damage

Background: Toll-like receptor 4 (TLR4) is implicated in neonatal hypoxic-ischemic brain damage (HIBD), but the underlying mechanism is unclear. Hypothesis: We hypothesized that TLR4 mediates brain damage after hypoxic ischemia (HI) by inducing abnormal neuroimmune responses, including activation of immune cells and expression disorder of immune factors, while early inhibition of TLR4 can alleviate the neuroimmune dysfunction. Method: Postnatal day 7 rats were randomized into control, HI, and HI+TAK-242 (TAK-242) groups. The HIBD model was developed using the Rice-Vannucci method (the left side was the ipsilateral side of HI). TAK-242 (0.5 mg/kg) was given to rat pups in the TAK-242 group at 30 min before modeling. Immunofluorescence, immunohistochemistry, and western blotting were used to determine the TLR4 expression; the number of Iba-1+, GFAP+, CD161+, MPO+, and CD3+ cells; ICAM-1 and C3a expression; and interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-10 expression in the hippocampal CA1 region. Result: Significantly increased TLR4 expression was observed in the left hippocampus, and was alleviated by TAK-242. The significant increases in Iba-1+, MPO+, and CD161+ cells at 24 h and 7 days after HI and in GFAP+ and CD3+ T cells at 7 days after HI were also counteracted by TAK-242, but no significant differences were observed among groups at 24 h after HI. ICAM-1 expression increased 24 h after HI, while C3a expression decreased; TAK-242 also alleviated these changes. TNF-α and IL-1β expression increased, while IL-10 expression decreased at 24 h and 7 days after HI; TAK-242 counteracted the increased TNF-α and IL-1β expression at 24 h and the changes in IL-1β and IL-10 at 7 days, but induced no significant differences in IL-10 expression at 24 h and TNF-α expression at 7 days. Conclusion: Early TLR4 inhibition can alleviate hippocampal immune dysfunction after neonatal HIBD.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Signaling through the S1P-S1PR Axis in the Gut, the Immune and the Central Nervous System in Multiple Sclerosis: Implication for Pathogenesis and Treatment

Sphingosine 1-phosphate (S1P) is a signaling molecule with complex biological functions that are exerted through the activation of sphingosine 1-phosphate receptors 1–5 (S1PR1–5). S1PR expression is necessary for cell proliferation, angiogenesis, neurogenesis and, importantly, for the egress of lymphocytes from secondary lymphoid organs. Since the inflammatory process is a key element of immune-mediated diseases, including multiple sclerosis (MS), S1PR modulators are currently used to ameliorate systemic immune responses. The ubiquitous expression of S1PRs by immune, intestinal and neural cells has significant implications for the regulation of the gut–brain axis. The dysfunction of this bidirectional communication system may be a significant factor contributing to MS pathogenesis, since an impaired intestinal barrier could lead to interaction between immune cells and microbiota with a potential to initiate abnormal local and systemic immune responses towards the central nervous system (CNS). It appears that the secondary mechanisms of S1PR modulators affecting the gut immune system, the intestinal barrier and directly the CNS, are coordinated to promote therapeutic effects. The scope of this review is to focus on S1P−S1PR functions in the cells of the CNS, the gut and the immune system with particular emphasis on the immunologic effects of S1PR modulation and its implication in MS.

Hybrid Nanoparticles as a Novel Tool for Regulating Psychosine-Induced Neuroinflammation and Demyelination In Vitro and Ex vivo

Polymeric nanoparticles are being extensively investigated as an approach for brain delivery of drugs, especially for their controlled release and targeting capacity. Nose-to-brain administration of nanoparticles, bypassing the blood brain barrier, offers a promising strategy to deliver drugs to the central nervous system. Here, we investigated the potential of hybrid nanoparticles as a therapeutic approach for demyelinating diseases, more specifically for Krabbe's disease. This rare leukodystrophy is characterized by the lack of enzyme galactosylceramidase, leading to the accumulation of toxic psychosine in glial cells causing neuroinflammation, extensive demyelination and death. We present evidence that lecithin/chitosan nanoparticles prevent damage associated with psychosine by sequestering the neurotoxic sphingolipid via physicochemical hydrophobic interactions. We showed how nanoparticles prevented the cytotoxicity caused by psychosine in cultured human astrocytes in vitro, and how the nanoparticle size and PDI augmented while the electrostatic charges of the surface decreased, suggesting a direct interaction between psychosine and the nanoparticles. Moreover, we studied the effects of nanoparticles ex vivo using mouse cerebellar organotypic cultures, observing that nanoparticles prevented the demyelination and axonal damage caused by psychosine, as well as a moderate prevention of the astrocytic death. Taken together, these results suggest that lecithin-chitosan nanoparticles are a potential novel delivery system for drugs for certain demyelinating conditions such as Krabbe's disease, due to their dual effect: not only are they an efficient platform for drug delivery, but they exert a protective effect themselves in tampering the levels of psychosine accumulation.

[Vascular inflammation underlies the development of atherothrombotic stroke]

Atherothrombotic stroke is the one of the most common subtypes of ischemic cerebral circulatory disorders, the cause of which is atherosclerosis of the major arteries of the brain or their branches. The results of recent studies have shown that the atherosclerotic process is based on an inflammatory process in the vascular wall that leads to the initiation of atherosclerosis, endothelial dysfunction, oxidative stress, and the redistribution of various protein components in the blood-brain barrier. As a result, the progression of the described conditions leads to the manifestation of clinical symptoms and the formation of an acute vascular event. Understanding of the molecular components underlying functional disorders and damages of the cerebral vessels gives the key to modern therapy strategies. It is forming the foundation for the adequate, pathogenetically reasonable drug correction. For such patients, it should be aimed at the normalization of cerebral and central hemodynamics and incorporate the mechanisms of neuroplasticity. The drug 2-ethyl-6-methyl-3-oxypyridine-succinate (mexidol) can be considered as one of the pathogenetically justified agents in complex drug therapy of brain ischemia.

Integrative analysis of potential biomarkers and immune cell infiltration in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease in the elderly population. However, there are no reliable diagnostic biomarkers for PD, and the pathogenesis of PD still needs further study. The aim of the current study was to identify potential biomarkers and explore the pathogenesis of PD.

METHODS

We conducted an integrative analysis of messenger RNA (mRNA), microRNA (miRNA), and long noncoding RNA (lncRNA) expression profiles of PD using data from the Gene Expression Omnibus (GEO). The GSE110720, GSE110719 and GSE133347 data sets were selected and analysed. Gene ontology (GO) enrichment and gene set variation analysis (GSVA) were performed for annotation, visualization, and integrated discovery. Protein-protein interaction (PPI) and competing endogenous RNA (ceRNA) networks were constructed, and hub genes were identified. Meanwhile, the immune infiltration analysis of hub genes was analysed. Moreover, receiver operating characteristic (ROC) curves were generated to verify the diagnostic value of the differentially expressed genes (DEGs). Finally, the genes with high area under the curve (AUC) values were verified by human samples.

RESULTS

We identified 464 DEGs closely related to PD, including 154 mRNAs, 134 miRNAs, and 176 lncRNAs. The GO analyses indicated that changes in PD were mainly enriched in receptor ligand activity and cytokine receptor binding. The KEGG enrichment analysis showed that these DEGs were significantly involved in cytokine-cytokine receptor interactions, signalling pathways regulating the pluripotency of stem cells and Th17 cell differentiation. GSVA suggested that growth factor binding, IL2-stat5 signalling, and IL6-jak-stat3 signalling were crucial in the development of PD. A total of five hub genes (NPBWR2, CXCL10, CXCL5, S1PR5, and GALR1) were selected via the PPI network. A ceRNA network of the CXCL5, CXCL10 and S1PR5 genes was constructed, and target genes of the three genes were screened. The immune infiltration analysis showed that there were significant differences in a variety of immune cells between the hub genes. The expression of DEGs was validated in clinical human samples by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The expression levels of hsa-miR6895-5p, hsa-miR6791-5p, hsa-miR518f-5p, hsa-miR455-3p and TEKT4P2 were decreased, while the levels of TPTE2P6 were increased in human samples. These findings are consistent with the bioinformatics analysis results.

CONCLUSION

We found that the immune inflammatory response and immune cell regulation were involved in the pathogenesis of PD. Five hub genes involved in the immune infiltration biological processes of PD based on bioinformatics. We verified the DEGs with significant differences by qRT-PCR. These findings might provide new insight into the pathogenesis of PD and the development of diagnostic and therapeutic strategies for PD.

Lessons from S1P receptor targeting in multiple sclerosis

Sphingosine 1-phosphate (S1P) is a potent bioactive sphingolipid binding to specific G protein-coupled receptors expressed in several organs. The relevance of S1P-S1P receptor axis in the pathophysiology of immune and nervous systems has encouraged the development of S1P receptor modulators for the treatment of neurological, autoimmune and/or inflammatory disorders. Currently, four S1P receptor modulators are approved drugs for multiple sclerosis (MS), an inflammatory disorder of the central nervous system. As main pharmacologic effect, these treatments induce lymphopenia due to the loss of responsiveness to S1P gradients guiding lymphocyte egress from lymphoid organs into the bloodstream. Recent data point to immunological effects of the S1P modulators beyond the inhibition of lymphocyte trafficking. Further, these drugs may cross the blood-brain barrier and directly target CNS resident cells expressing S1P receptors. Here we review the role of S1P signalling in neuroimmunology at the light of the evidences generated from the study of the mechanism of action of S1P receptor modulators in MS and integrate this information with findings derived from neuroinflammatory animal models and in vitro observations. These insights can direct the application of therapeutic approaches targeting S1P receptors in other disease areas.

Transcriptomic Analysis of Peripheral Monocytes upon Fingolimod Treatment in Relapsing Remitting Multiple Sclerosis Patients

Fingolimod (FTY), a second-line oral drug approved for relapsing remitting Multiple Sclerosis (RRMS) acts in preventing lymphocyte migration outside lymph nodes; moreover, several lines of evidence suggest that it also inhibits myeloid cell activation. In this study, we investigated the transcriptional changes induced by FTY in monocytes in order to better elucidate its mechanism of action. CD14⁺ monocytes were collected from 24 RRMS patients sampled at baseline and after 6 months of treatment and RNA profiles were obtained through next-generation sequencing. We conducted pathway and sub-paths analysis, followed by centrality analysis of cell-specific interactomes on differentially expressed genes (DEGs). We investigated also the predictive role of baseline monocyte transcription profile in influencing the response to FTY therapy. We observed a marked down-regulation effect (60 down-regulated vs. 0 up-regulated genes). Most of the down-regulated DEGs resulted related with monocyte activation and migration like IL7R, CCR7 and the Wnt signaling mediators LEF1 and TCF7. The involvement of Wnt signaling was also confirmed by subpaths analyses. Furthermore, pathway and network analyses showed an involvement of processes related to immune function and cell migration. Baseline transcriptional profile of the HLA class II gene HLA-DQA1 and HLA-DPA1 were associated with evidence of disease activity after 2 years of treatment. Our data support the evidence that FTY induces major transcriptional changes in monocytes, mainly regarding genes involved in cell trafficking and immune cell activation. The baseline transcriptional levels of genes associated with antigen presenting function were associated with disease activity after 2 years of FTY treatment.

The progress of chemokines and chemokine receptors in autism spectrum disorders

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders and the main symptoms of ASD are impairments in social communication and abnormal behavioral patterns. Studies have shown that immune dysfunction and neuroinflammation play a key role in ASD patients and experimental models. Chemokines are groups of small proteins that regulate cell migration and mediate inflammation responses via binding to chemokine receptors. Thus, chemokines/chemokine receptors may be involved in neurodevelopmental disorders and associated with ASD. In this review, we summarize the research progress of chemokine aberrations in ASD and also review the recent progress of clinical treatment of ASD and pharmacological research related to chemokines/chemokine receptors. This review highlights the possible connection between chemokines/chemokine receptors and ASD, and provides novel potential targets for drug discovery of ASD.

Activation of sphingosine-1-phosphate receptor subtype 1 in the central nervous system contributes to morphine-induced hyperalgesia and antinociceptive tolerance in rodents

ABSTRACT

Morphine-induced alterations in sphingolipid metabolism in the spinal cord and increased formation of the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P) have been implicated in the development of morphine-induced hyperalgesia (OIH; increased pain sensitivity) and antinociceptive tolerance. These adverse effects hamper opioid use for treating chronic pain and contribute to dependence and abuse. S1P produces distinct effects through 5 G-protein-coupled receptors (S1PR1-5) and several intracellular targets. How S1P exerts its effects in response to morphine remains unknown. Here, we report that S1P contributes to the development of morphine-induced hyperalgesia and tolerance through S1P receptor subtype 1 (S1PR1) signaling in uninjured male and female rodents, which can be blocked by targeting S1PR1 with S1PR1 antagonists or RNA silencing. In mouse neuropathic pain models, S1PR1 antagonists blocked the development of tolerance to the antiallodynic effects of morphine without altering morphine pharmacokinetics and prevented prolonged morphine-induced neuropathic pain. Targeting S1PR1 reduced morphine-induced neuroinflammatory events in the dorsal horn of the spinal cord: increased glial marker expression, mitogen-activated protein kinase p38 and nuclear factor κB activation, and increased inflammatory cytokine expression, such as interleukin-1β, a cytokine central in the modulation of opioid-induced neural plasticity. Our results identify S1PR1 as a critical path for S1P signaling in response to sustained morphine and reveal downstream neuroinflammatory pathways impacted by S1PR1 activation. Our data support investigating S1PR1 antagonists as a clinical approach to mitigate opioid-induced adverse effects and repurposing the functional S1PR1 antagonist FTY720, which is FDA-approved for multiple sclerosis, as an opioid adjunct.

The p75 neurotrophin receptor as a novel intermediate in L-dopa-induced dyskinesia in experimental Parkinson's disease

In Parkinson's disease (PD), long-term administration of L-dopa often leads to L-dopa-induced dyskinesia (LID), a debilitating motor complication. The p75 neurotrophin receptor (p75NTR) is likely to play a critical role in the regulation of dendritic spine density and morphology and appears to be associated with neuroinflammation, which previously has been identified as a crucial mechanism in LID. While aberrant modifications of p75NTR in neurological diseases have been extensively documented, only a few studies report p75NTR dysfunction in PD, and no data are available in LID. Here, we explored the functional role of p75NTR in LID. In LID rats, we identified that p75NTR was significantly increased in the lesioned striatum. In 6-hydroxydopamine (6-OHDA)-hemilesioned rats, specific knockdown of striatal p75NTR levels achieved by viral vector injection into the striatum prevented the development of LID and increased striatal structural plasticity. By contrast, we found that in 6-OHDA-hemilesioned rats, striatal p75NTR overexpression exacerbated LID and facilitated striatal dendritic spine losses. Moreover, we observed that the immunomodulatory drug fingolimod attenuated LID without lessening the therapeutic efficacy of L-dopa and normalized p75NTR levels. Together, these data demonstrate for the first time that p75NTR plays a pivotal role in the development of LID and that p75NTR may act as a potential novel target for the management of LID.

Astrocytes lure CXCR2-expressing CD4+ T cells to gray matter via TAK1-mediated chemokine production in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is a chronic neurological disease of the central nervous system driven by peripheral immune cell infiltration and glial activation. The pathological hallmark of MS is demyelination, and mounting evidence suggests neuronal damage in gray matter is a major contributor to disease irreversibility. While T cells are found in both gray and white matter of MS tissue, they are typically confined to the white matter of the most commonly used mouse model of MS, experimental autoimmune encephalomyelitis (EAE). Here, we used a modified EAE mouse model (Type-B EAE) that displays severe neuronal damage to investigate the interplay between peripheral immune cells and glial cells in the event of neuronal damage. We show that CD4+ T cells migrate to the spinal cord gray matter, preferentially to ventral horns. Compared to CD4+ T cells in white matter, gray matter-infiltrated CD4+ T cells were mostly immobilized and interacted with neurons, which are behaviors associated with detrimental effects to normal neuronal function. T cell-specific deletion of CXCR2 significantly decreased CD4+ T cell infiltration into gray matter in Type-B EAE mice. Further, astrocyte-targeted deletion of TAK1 inhibited production of CXCR2 ligands such as CXCL1 in gray matter, successfully prevented T cell migration into spinal cord gray matter, and averted neuronal damage and motor dysfunction in Type-B EAE mice. This study identifies astrocyte chemokine production as a requisite for the invasion of CD4+T cell into the gray matter to induce neuronal damage.

Role of the SphK-S1P-S1PRs pathway in invasion of the nervous system by SARS-CoV-2 infection

Global spread of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is still ongoing. Before an effective vaccine is available, the development of potential treatments for resultant coronavirus disease 2019 (COVID‐19) is crucial. One of the disease hallmarks is hyper‐inflammatory responses, which usually leads to a severe lung disease. Patients with COVID‐19 also frequently suffer from neurological symptoms such as acute diffuse encephalomyelitis, brain injury and psychiatric complications. The metabolic pathway of sphingosine‐1‐phosphate (S1P) is a dynamic regulator of various cell types and disease processes, including the nervous system. It has been demonstrated that S1P and its metabolic enzymes, regulating neuroinflammation and neurogenesis, exhibit important functions during viral infection. S1P receptor 1 (S1PR1) analogues including AAL‐R and RP‐002 inhibit pathophysiological responses at the early stage of H1N1 virus infection and then play a protective role. Fingolimod (FTY720) is an S1P receptor modulator and is being tested for treating COVID‐19. Our review provides an overview of SARS‐CoV‐2 infection and critical role of the SphK‐S1P‐SIPR pathway in invasion of SARS‐CoV‐2 infection, particularly in the central nervous system (CNS). This may help design therapeutic strategies based on the S1P‐mediated signal transduction, and the adjuvant therapeutic effects of S1P analogues to limit or prevent the interaction between the host and SARS‐CoV‐2, block the spread of the SARS‐CoV‐2, and consequently treat related complications in the CNS.

The Role of Sphingolipids and Specialized Pro-Resolving Mediators in Alzheimer's Disease

Alzheimer’s disease (AD) is the leading cause of dementia worldwide giving rise to devastating forms of cognitive decline, which impacts patients’ lives and that of their proxies. Pathologically, AD is characterized by extracellular amyloid deposition, neurofibrillary tangles and chronic neuroinflammation. To date, there is no cure that prevents progression of AD. In this review, we elaborate on how bioactive lipids, including sphingolipids (SL) and specialized pro-resolving lipid mediators (SPM), affect ongoing neuroinflammatory processes during AD and how we may exploit them for the development of new biomarker panels and/or therapies. In particular, we here describe how SPM and SL metabolism, ranging from ω-3/6 polyunsaturated fatty acids and their metabolites to ceramides and sphingosine-1-phosphate, initiates pro- and anti-inflammatory signaling cascades in the central nervous system (CNS) and what changes occur therein during AD pathology. Finally, we discuss novel therapeutic approaches to resolve chronic neuroinflammation in AD by modulating the SPM and SL pathways.

FOLFIRINOX regulated tumor immune microenvironment to extend the survival of patients with resectable pancreatic ductal adenocarcinoma

Background

Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly malignant tumors worldwide due to its ineffective diagnosis and poor prognosis. The longest median overall survival (OS) to PDAC patients has been provided by FOLFIRINOX. It is essential to identify the mechanisms of FOLFIRINOX to gain new insights for the treatment of PDAC.

Methods

We compared gene expression levels of PDAC patients who received neoadjuvant FOLFIRINOX prior to surgery with those of patients who received no neoadjuvant chemotherapy. Bioinformatics analysis was applied to screen differentially expressed genes (DEGs). Three microarray data sets were downloaded to analyze gene expression data between PDAC and adjacent non-tumor tissues. Overlapping DEGs were subjected to Kaplan-Meier survival analysis. The genes relating to poor outcomes and would be decreased after FOLFIRINOX were input into the Oncomine, University of Alabama Cancer (UALCAN), and LinkedOmics databases to analyze the gene expression and regulation networks.

Results

A total of 83 differentially expressed genes (DEGs) were screened and subjected to bioinformatics analysis, which indicated FOLFIRINOX influenced the immune microenvironment of PDAC. Seventy-three genes significantly associated with the OS of PDAC patients. A Venn diagram revealed CXCL5 and PLAU were related to poor outcomes and would decrease after FOLFIRINOX chemotherapy of PDAC patients. It turned out that CXCL5 participated in the immune response-regulating signaling pathway in PDAC patients.

Conclusions

FOLFIRINOX regulated tumor immunity by reducing expression of the immunosuppressive gene CXCL5, laying a foundation for further study of combination therapy of FOLFIRINOX and immunotherapy.

Hydrogels for 3D Neural Tissue Models: Understanding Cell-Material Interactions at a Molecular Level

The development of 3D neural tissue analogs is of great interest to a range of biomedical engineering applications including tissue engineering of neural interfaces, treatment of neurodegenerative diseases and in vitro assessment of cell-material interactions. Despite continued efforts to develop synthetic or biosynthetic hydrogels which promote the development of complex neural networks in 3D, successful long-term 3D approaches have been restricted to the use of biologically derived constructs. In this study a poly (vinyl alcohol) biosynthetic hydrogel functionalized with gelatin and sericin (PVA-SG), was used to understand the interplay between cell-cell communication and cell-material interaction. This was used to probe critical short-term interactions that determine the success or failure of neural network growth and ultimately the development of a useful model. Complex primary ventral mesencephalic (VM) neural cells were encapsulated in PVA-SG hydrogels and critical molecular cues that demonstrate mechanosensory interaction were examined. Neuronal presence was constant over the 10 day culture, but the astrocyte population decreased in number. The lack of astrocytic support led to a reduction in neural process outgrowth from 24.0 ± 1.3 μm on Day 7 to 7.0 ± 0.1 μm on Day 10. Subsequently, purified astrocytes were studied in isolation to understand the reasons behind PVA-SG hydrogel inability to support neural network development. It was proposed that the spatially restrictive nature (or tight mesh size) of PVA-SG hydrogels limited the astrocytic actin polymerization together with a cytoplasmic-nuclear translocation of YAP over time, causing an alteration in their cell cycle. This was confirmed by the evaluation of p27^/Kip1 gene that was found to be upregulated by a twofold increase in expression at both Days 7 and 10 compared to Day 3, indicating the quiescent stage of the astrocytes in PVA-SG hydrogel. Cell migration was further studied by the quantification of MMP-2 production that was negligible compared to 2D controls, ranging from 2.7 ± 2.3% on Day 3 to 5.3 ± 2.9% on Day 10. This study demonstrates the importance of understanding astrocyte-material interactions at the molecular level, with the need to address spatial constraints in the 3D hydrogel environment. These findings will inform the design of future hydrogel constructs with greater capacity for remodeling by the cell population to create space for cell migration and neural process extension.

Sphingolipid Metabolism in Glioblastoma and Metastatic Brain Tumors: A Review of Sphingomyelinases and Sphingosine-1-Phosphate

Glioblastoma (GBM) is a primary malignant brain tumor with a dismal prognosis, partially due to our inability to completely remove and kill all GBM cells. Rapid tumor recurrence contributes to a median survival of only 15 months with the current standard of care which includes maximal surgical resection, radiation, and temozolomide (TMZ), a blood-brain barrier (BBB) penetrant chemotherapy. Radiation and TMZ cause sphingomyelinases (SMase) to hydrolyze sphingomyelins to generate ceramides, which induce apoptosis. However, cells can evade apoptosis by converting ceramides to sphingosine-1-phosphate (S1P). S1P has been implicated in a wide range of cancers including GBM. Upregulation of S1P has been linked to the proliferation and invasion of GBM and other cancers that display a propensity for brain metastasis. To mediate their biological effects, SMases and S1P modulate signaling via phospholipase C (PLC) and phospholipase D (PLD). In addition, both SMase and S1P may alter the integrity of the BBB leading to infiltration of tumor-promoting immune populations. SMase activity has been associated with tumor evasion of the immune system, while S1P creates a gradient for trafficking of innate and adaptive immune cells. This review will explore the role of sphingolipid metabolism and pharmacological interventions in GBM and metastatic brain tumors with a focus on SMase and S1P.

SARS-CoV-2 Infection: A Role for S1P/S1P Receptor Signaling in the Nervous System?

The recent coronavirus disease (COVID-19) is still spreading worldwide. The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus responsible for COVID-19, binds to its receptor angiotensin-converting enzyme 2 (ACE2), and replicates within the cells of the nasal cavity, then spreads along the airway tracts, causing mild clinical manifestations, and, in a majority of patients, a persisting loss of smell. In some individuals, SARS-CoV-2 reaches and infects several organs, including the lung, leading to severe pulmonary disease. SARS-CoV-2 induces neurological symptoms, likely contributing to morbidity and mortality through unknown mechanisms. Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid with pleiotropic properties and functions in many tissues, including the nervous system. S1P regulates neurogenesis and inflammation and it is implicated in multiple sclerosis (MS). Notably, Fingolimod (FTY720), a modulator of S1P receptors, has been approved for the treatment of MS and is being tested for COVID-19. Here, we discuss the putative role of S1P on viral infection and in the modulation of inflammation and survival in the stem cell niche of the olfactory epithelium. This could help to design therapeutic strategies based on S1P-mediated signaling to limit or overcome the host-virus interaction, virus propagation and the pathogenesis and complications involving the nervous system.

Dabigatran Suppresses PAR-1/SphK/S1P Activation of Astrocytes in Experimental Autoimmune Encephalomyelitis Model

Multiple sclerosis (MS) is an inflammatory autoimmune disease affecting the central nervous system (CNS) that currently does not have any effective treatment. Experimental autoimmune encephalomyelitis (EAE) is often employed as a model to mimic the clinical manifestations of MS, mainly CNS demyelination. Coagulation is known to participate in crosstalk with inflammation and autoimmunity. We herein explored the correlation between the coagulation cascade and CNS immune diseases in vitro using primary astrocytes isolated from mice and in vivo using a mouse model of EAE. We showed that dabigatran, a clinical oral anti-coagulant drug, suppressed the thrombin-induced activation of astrocytes, and the underlying mechanisms are related to the activity of protease-activated receptor-1 (PAR-1), sphingosine-1-phosphate (S1P), and sphingosine kinases (SphKs). Importantly, dabigatran effectively recovered neurological function, reduced inflammation in the spinal cord, and prevented spinal cord demyelination caused by EAE. We suggest that dabigatran, a specific inhibitor of thrombin, antagonized the effect of thrombin in astrocytes by limiting the activation of PAR-1, in turn downregulating SphK1 and disrupting S1P receptor signaling. These findings reveal critical information about the relationship between coagulation mechanisms and CNS immune diseases and will contribute to the clinical translation and development of therapeutic strategies against MS.

The ceramide-S1P pathway as a druggable target to alleviate peripheral neuropathic pain

Introduction: Neuropathic pain disorders are diverse, and the currently available therapies are ineffective in the majority of cases. Therefore, there is a major need for gaining novel mechanistic insights and developing new treatment strategies for neuropathic pain. Areas covered: We performed an in-depth literature search on the molecular mechanisms and systemic importance of the ceramide-to-S1P rheostat regulating neuron function and neuroimmune interactions in the development of neuropathic pain. Expert opinion: The S1P receptor modulator FTY720 (fingolimod, Gilenya®), LPA receptor antagonists and several mechanistically related compounds in clinical development raise great expectations for treating neuropathic pain disorders. Research on S1P receptors, S1P receptor modulators or SPHK inhibitors with distinct selectivity, pharmacokinetics and safety must provide more mechanistic insight into whether they may qualify as useful treatment options for neuropathic pain disorders. The functional relevance of genetic variations within the ceramide-to-S1P rheostat should be explored for an enhanced understanding of neuropathic pain pathogenesis. The ceramide-to-S1P rheostat is emerging as a critically important regulator hub of neuroimmune interactions along the pain pathway, and improved mechanistic insight is required to develop more precise and effective drug treatment options for patients suffering from neuropathic pain disorders.

Molecular Effects of FDA-Approved Multiple Sclerosis Drugs on Glial Cells and Neurons of the Central Nervous System

Multiple sclerosis (MS) is characterized by peripheral and central inflammatory features, as well as demyelination and neurodegeneration. The available Food and Drug Administration (FDA)-approved drugs for MS have been designed to suppress the peripheral immune system. In addition, however, the effects of these drugs may be partially attributed to their influence on glial cells and neurons of the central nervous system (CNS). We here describe the molecular effects of the traditional and more recent FDA-approved MS drugs Fingolimod, Dimethyl Fumarate, Glatiramer Acetate, Interferon-β, Teriflunomide, Laquinimod, Natalizumab, Alemtuzumab and Ocrelizumab on microglia, astrocytes, neurons and oligodendrocytes. Furthermore, we point to a possible common molecular effect of these drugs, namely a key role for NFκB signaling, causing a switch from pro-inflammatory microglia and astrocytes to anti-inflammatory phenotypes of these CNS cell types that recently emerged as central players in MS pathogenesis. This notion argues for the need to further explore the molecular mechanisms underlying MS drug action.

Fingolimod Rescues Demyelination in a Mouse Model of Krabbe's Disease

Krabbe's disease is an infantile neurodegenerative disease, which is affected by mutations in the lysosomal enzyme galactocerebrosidase, leading to the accumulation of its metabolite psychosine. We have shown previously that the S1P receptor agonist fingolimod (FTY720) attenuates psychosine-induced glial cell death and demyelination both in vitro and ex vivo models.

Krabbe's disease is an infantile neurodegenerative disease, which is affected by mutations in the lysosomal enzyme galactocerebrosidase, leading to the accumulation of its metabolite psychosine. We have shown previously that the S1P receptor agonist fingolimod (FTY720) attenuates psychosine-induced glial cell death and demyelination both in vitro and ex vivo models. These data, together with a lack of therapies for Krabbe's disease, prompted the current preclinical study examining the effects of fingolimod in twitcher mice, a murine model of Krabbe's disease. Twitcher mice, both male and female, carrying a natural mutation in the galc gene were given fingolimod via drinking water (1 mg/kg/d). The direct impact of fingolimod administration was assessed via histochemical and biochemical analysis using markers of myelin, astrocytes, microglia, neurons, globoid cells, and immune cells. The effects of fingolimod on twitching behavior and life span were also demonstrated. Our results show that treatment of twitcher mice with fingolimod significantly rescued myelin levels compared with vehicle-treated animals and also regulated astrocyte and microglial reactivity. Furthermore, nonphosphorylated neurofilament levels were decreased, indicating neuroprotective and neurorestorative processes. These protective effects of fingolimod on twitcher mice brain pathology was reflected by an increased life span of fingolimod-treated twitcher mice. These in vivo findings corroborate initial in vitro studies and highlight the potential use of S1P receptors as drug targets for treatment of Krabbe's disease.

SIGNIFICANCE STATEMENT This study demonstrates that the administration of the therapy known as fingolimod in a mouse model of Krabbe's disease (namely, the twitcher mouse model) significantly rescues myelin levels. Further, the drug fingolimod also regulates the reactivity of glial cells, astrocytes and microglia, in this mouse model. These protective effects of fingolimod result in an increased life span of twitcher mice.

Sphingosine-1-Phosphate Receptors Modulators Decrease Signs of Neuroinflammation and Prevent Parkinson's Disease Symptoms in the 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Mouse Model

Sphingosine-1-phosphate (S1P) is a potent bioactive lipid mediator that acts as a natural ligand upon binding to five different receptors that are located in astrocytes, oligodendrocytes, microglial and neuronal cells. Recently, global activation of these receptors by FTY720 (fingolimod) has been suggested to provide neuroprotection in animal model of Parkinson’s disease (PD). Among S1P receptors, the subtype 1 (S1P1R) has been linked to features of neuroprotection and, using the selective agonist SEW2871, the present investigation assessed potential benefits (and mechanisms) of this receptor subtype in an established animal model of PD. We demonstrated that oral treatments with SEW2871 are able to provide protection to the same levels as FTY720 against loss of dopaminergic neurons and motor deficits in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (30 mg/kg, i.p., 5 days) mouse model of PD. At the molecular level, we observed that the beneficial effects of both S1PR agonists were not associated with alterations in ERK and Akt levels, two markers of molecular adaptations in the striatum neurons. However, these compounds have the capacity to prevent signs of neuroinflammation such as the activation of astrocytes and glial cells, as well as MPTP-induced reduction of BDNF levels in key regions of the brain implicated in motor functions. These findings suggest that selective S1P1R modulation has the ability to provide neuroprotection in response to MPTP neurotoxicity. Targeting S1P1R in PD therapy may represent a prominent candidate for treatment of this neurodegenerative conditions.

Sphingosine 1-phosphate promotes the proliferation of olfactory ensheathing cells through YAP signaling and participates in the formation of olfactory nerve layer

Olfactory ensheathing cells (OECs) are unique glial cells with axonal growth-promoting properties in the olfactory epithelium and olfactory bulb, covering the entire length of the olfactory nerve. The proliferation of OECs is necessary for the formation of the presumptive olfactory nerve layer (ONL) during development and OECs transplantation. However, the molecular mechanism underlying the regulation of OEC proliferation in the ONL still remains unknown. In the present study, we examined the role of sphingosine 1-phosphate (S1P) and S1P receptors (S1PRs) on OEC proliferation. Initially, reverse transcription-PCR (RT-PCR), western blot and immunostaining revealed that S1PRs were highly expressed in the OECs in vitro and in vivo. Furthermore, we found that S1P treatment promoted the proliferation of primary cultured OECs mediated by S1PR1. Mechanistically, yes-associated protein (YAP) was required for S1P-induced OEC proliferation through RhoA signaling. Finally, conditional knockout of YAP in OECs reduced OEC proliferation in ONL, which impaired the axonal projection and growth of olfactory sensory neurons, and olfactory functions. Taken together, these results reveal a previously unrecognized function of S1P/RhoA/YAP pathway in the proliferation of OECs, contributing to the formation of ONL and the projection, growth, and function of olfactory sensory neurons during development.

The roles played by TLR4 in the pathogenesis of multiple sclerosis; A systematic review article

Multiple sclerosis (MS) is a world-wide pro-inflammatory based disease, which is prevalent among young individuals. The etiology of the disease and its related complications are yet to be clarified. It has been hypothesized that environmental factors, including pathogen-associated molecular patterns (PAMPs) and the internal factors such as damage-associated molecular patterns (DAMPs), may be the most important inducers/stimulators of the disorder and its related complications. Previous investigations proved that pathogen recognition receptors (PRRs) are the main sensors for the PAMPs and DAMPs. Therefore, it seems that the PRRs have been considered to be the plausible molecules participating in the etiology of MS. Toll-like receptors (TLRs) have been the widely studied PRRs and their roles have been documented in human-related diseases. TLR4 is the main PRR expressed on the cell surface of several immune cells including macrophages and dendritic cells. Several investigations reported that TLR4 to be the main molecule involved in the pathogenesis of pro-inflammatory based diseases. Thus, it has been hypothesized that TLR4 may be a part of the MS puzzle. This review article discusses the role of TLR4 in the MS pathogenesis using recent in vitro and in vivo investigations.

TAK1 inhibition in mouse astrocyte cultures ameliorates cytokine-induced chemokine production and neutrophil migration

Systemic inflammation can exacerbate symptoms of many neurological diseases. This effect may be facilitated by glial cells of the central nervous system (CNS) that alter their transcriptional responses and up-regulate cytokine and chemokine expression which can, in turn trigger immune surveillance. In this study, we sought to determine the effects of pro-inflammatory cytokine stimulation (TNF, IL-1α, IL-1β) on astrocyte and microglia chemokine secretion. Primary cultures of astrocytes or microglia were stimulated with the recombinant cytokines and the levels of secreted chemokines were semi-quantitatively determined using a chemokine-specific proteome profiler array and densitometry. Pharmacological inhibitors were used to determine the effects of p38 MAPK, JNK, ERK1/2, NFkB, and transforming growth factor beta-associated kinase 1 (TAK1) in controlling chemokine production. Finally, neutrophil migration assays were performed to demonstrate functionality. Our data show that stimulated astrocytes secrete at least eight chemokines as a response to cytokine stimulation. These include those involved in neutrophil chemo-attraction and proved capable of promoting neutrophil migration in vitro. In contrast, microglia up-regulated few chemokines in response to cytokine stimulation and did not promote neutrophil migration. However, microglia readily secreted chemokines following stimulation with the toll-like receptor agonists. Finally, we show that both the production of chemokines and neutrophil migration resulting from cytokine stimulation of astrocytes was dependent on TAK1 signaling. Collectively, this study adds to the understanding of how astrocytes and microglia respond to stimuli and their role in promoting neutrophil migration to the CNS during inflammatory conditions.

Chemokines and their receptors promoting the recruitment of myeloid-derived suppressor cells into the tumor

Myeloid-derived suppressor cells (MDSCs) expand in tumor-bearing host. They suppress anti-tumor immune response and promote tumor growth. Chemokines play a vital role in recruiting MDSCs into tumor tissue. They can also induce the generation of MDSCs in the bone marrow, maintain their suppressive activity, and promote their proliferation and differentiation. Here, we review CCL2/CCL12-CCR2, CCL3/4/5-CCR5, CCL15-CCR1, CX3CL1/CCL26-CX3CR1, CXCL5/2/1-CXCR2, CXCL8-CXCR1/2, CCL21-CCR7, CXCL13-CXCR5 signaling pathways, their role in MDSCs recruitment to tumor tissue, and their correlation with tumor development, metastasis and prognosis. Targeting chemokines and their receptors may serve as a promising strategy in immunotherapy, especially combined with other strategies such as chemotherapy, cyclin-dependent kinase or immune checkpoints inhibitors.

Matrine alleviates astrogliosis through sphingosine 1-phosphate signaling in experimental autoimmune encephalomyelitis

Expression of sphingosine/sphingosine 1-phosphate (SPH/S1P) in resident cells of the central nervous system plays an important role in the pathogenesis of multiple sclerosis (MS). Accumulated evidence has shown the protective effects of S1P receptor modulators on MS and its animal model, experimental autoimmune encephalomyelitis (EAE). However, effective therapies to regulate SPH/S1P molecules themselves have not been well addressed. Our previous studies showed that matrine (MAT), a natural alkaloid component extracted from the Sophora root, has beneficial effects in EAE through immunomodulation. Here we demonstrate that MAT alleviated astrogliosis in the CNS of EAE rats, and downregulated levels of SPH, S1P and S1P1 expression in CNS tissues and astrocytes. Expression of SPH kinases (SPHK) 1 and 2, which splice SPH into S1P, was also inhibited by MAT treatment. In vitro studies showed a direct inhibitory effect of MAT on S1P1 expression of activated astrocytes, suggesting that MAT could function as an S1PRs antagonist. Moreover, MAT upregulated the expression of plasma gelsolin, which combines with S1P to reduce its concentration. These findings indicate that MAT could alleviate astrogliosis in EAE through diminishing the SPH/SPHK/S1P1 pathway.

Impact of fingolimod on CD4+ T cell subset and cytokine profile of relapsing remitting multiple sclerosis patients

Fingolimod inhibits the egress of lymphocytes from lymphatic tissues and also directly affects their functions by modulation of the sphingosine-1-phosphate receptor 1 (S1P1). Our aim was to evaluate the impact of fingolimod on diverse CD4+ T cell subsets, and cytokines. Sixty-six relapsing remitting multiple sclerosis (RRMS) patients were treated with oral fingolimod (0.5 mg) for 6 months, and blood samples were collected at baseline, 3 months, and 6 months. Serum levels of seven cytokines and five chemokines were measured by multiplex immunoassay, and frequencies of peripheral blood mononuclear cell subsets were assessed by flow cytometry, and compared with those of 60 healthy controls. CCL2 (p = 0.039), and CCL5 (p = 0.001) levels were significantly higher in fingolimod-treated patients than healthy controls, whereas end-of-study serum levels of IL-6, IL-8, IL-17A, IL-22, IL-23, TNF-α, CXCL10, and CXCL13 were comparable to the baseline levels. Six months of fingolimod treatment reduced CD3+ T cell (mean ± standard deviation, 72.9% ± 5.5 vs. 60.1% ± 11.1, p < 0.001), CD4+ T cell (62.2% ± 8.5 vs. 24.6% ± 12.9, p < 0.001), CD4+CD25hi regulatory T cell (Treg) (3.4% ± 1.3 vs. 2.0% ± 1.4, p < 0.01), and CD19+ B cell (13.2% ± 5.8 vs. 5.3% ± 2.7, p < 0.001) frequencies, while CD8+ T cells (31.8% ± 7.8 vs. 57.8% ± 13.2, p < 0.001) were increased, and NK and NKT cells remained unchanged. The proportions of intracytoplasmic IL-4, IL-10, IFN-γ, and TNF-α-producing T cells were increased, whereas IL-17-producing cells remained relatively constant as measured by flow cytometry. Fingolimod appears to primarily diminish lymphocyte subsets involved in antigen presentation (CD19+ B and CD4+ T cells) rather than immune cells (CD8+ T, NK, and NKT cells) in charge of host defense against pathogens. In contrast, a relative increase is observed in pro- and anti-inflammatory cytokine-producing T helper subsets (IFN-γ, TNF-α, IL-4, and IL-10-producing CD4+ T cells), suggesting that effector T cells are suppressed to a lesser degree by S1P1 modulation.

Neural sphingosine 1-phosphate accumulation activates microglia and links impaired autophagy and inflammation

Microglia mediated responses to neuronal damage in the form of neuroinflammation is a common thread propagating neuropathology. In this study, we investigated the microglial alterations occurring as a result of sphingosine 1-phosphate (S1P) accumulation in neural cells. We evidenced increased microglial activation in the brains of neural S1P-lyase (SGPL1) ablated mice (SGPL1^fl/fl/Nes ) as shown by an activated and deramified morphology and increased activation markers on microglia. In addition, an increase of pro-inflammatory cytokines in sorted and primary cultured microglia generated from SGPL1 deficient mice was noticed. Further, we assessed autophagy, one of the major mechanisms in the brain that keeps inflammation in check. Indeed, microglial inflammation was accompanied by defective microglial autophagy in SGPL1 ablated mice. Rescuing autophagy by treatment with rapamycin was sufficient to decrease interleukin 6 (IL-6) but not tumor necrosis factor (TNF) secretion in cultured microglia. Rapamycin mediated decrease of IL-6 secretion suggests a particular mechanistic target of rapamycin (mTOR)-IL-6 link and appeared to be microglia specific. Using pharmacological inhibitors of the major receptors of S1P expressed in the microglia, we identified S1P receptor 2 (S1PR2) as the mediator of both impaired autophagy and proinflammatory effects. In line with these results, the addition of exogenous S1P to BV2 microglial cells showed similar effects as those observed in the genetic knock out of SGPL1 in the neural cells. In summary, we show a novel role of the S1P-S1PR2 axis in the microglia of mice with neural-targeted SGPL1 ablation and in BV2 microglial cell line exogenously treated with S1P.