Transcriptional regulation in primary mouse brain microvascular endothelial cells following apical or basolateral pharmacological treatment with S1P or S1P4 agonist in C57B/6J wildtype versus global S1P4 KO mice
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ABSTRACT: The precise regulation of blood-brain-barrier (BBB) permeability for immune cells and blood-borne substances is essential to maintain brain homeostasis. Sphingosine-1-phosphate (S1P), a lipid signaling molecule enriched in plasma, is known to affect BBB permeability. Previous studies focussed on endothelial S1P receptors 1 and 2, reporting a barrier-protective effect of S1P1 and a barrier-disruptive effect of S1P2. Here we present novel data characterizing the expression, localization and function of the hitherto exclusively immunce cell-associated S1P receptor 4 (S1P4) on primary brain microvascular endothelial cells (BMECs). We detected a robust expression of S1P4 in homeostatic BMECs and pinpointed its localization to abluminal endothelial membranes by electron microscopy. Basolateral S1P treatment of BMECs led to increased permeability in vitro associated with S1P4 downregulation. Likewise, downregulation of S1P4 was observed in mouse brain microvessels after stroke, a neurological disease associated with BBB impairment. RNA sequencing analysis of BMECs suggested involvement of S1P4 in endothelial homeostasis, apicobasal polarity and barrier function. Using siRNA, pharmacological agonists and antagonists of S1P4 both in vitro and in vivo, we demonstrate a barrier-protective function of S1P4. We therefore suggest S1P4 as a novel target regulating BBB permeability and propose its therapeutic targeting in CNS diseases associated with BBB dysfunction.
Project description:The brain and spinal cord are endowed with particular vascular systems, known as the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) respectively, which maintain homeostasis between nervous parenchyma and peripheral circulation. Despite these common features, the BSCB presents structural and functional differences resulting in distinct vulnerability to pathological insults when compared to the BBB. Although, the heterogeneity of endothelial cell types underlies their remarkable ability to sub-specialize and provide specific requirements for a given vascular bed, very little is known concerning intrinsic differences between microvascular endothelial cells (MECs) derived from brain (BMECs) and spinal cord (SCMECs), including their response to inflammation. We used Agilent Whole Rattus Genome Microarray 4X44K to compare rat BMECs and SCMECs in both basal and inflammatory conditions; TNF-α-induced, TWEAK-induced and LPS-induced gene expression after 6 hr, 12 hr, 24 hr and 48 hr incubation.
Project description:Brain microvascular endothelial cells (BMECs) are part of the blood-brain barrier (BBB). These cells express Cacnb3 transcripts encoding the Cavβ3 protein, which is a subunit of the voltage-gated Ca2+ (Cav) channels. However, potassium depolarization and electrophysiological recordings in BMECs did not reveal a significant Cav channel function, regardless of the presence or absence of Cavβ3. In vivo, the integrity of the BBB was reduced in the absence of Cavβ3. Following induction of experimental autoimmune encephalomyelitis (EAE), Cavβ3-deficient (Cavβ3-/-) mice showed earlier disease onset with exacerbated clinical disability and increased infiltration of T-cells. In vitro, the trans-endothelial resistance of Cavβ3-/- BMEC monolayers was lower than that of wild-type, permeability to albumin and dextran was increased, and the organization of the junctional protein ZO-1 was impaired in the absence and presence of the pro-inflammatory mediator thrombin. The results suggest that Cavβ3, independent of its function as a subunit of Cav channels, tightly controls cytoplasmic [Ca2+] and Ca2+-dependent MLC phosphorylation and that this role of Cavβ3 in BMECs contributes to the integrity of the BBB and decreases severity of clinical EAE disease.
Project description:The blood-brain barrier (BBB) is a unique set of properties of the brain vasculature which severely restricts its permeability to proteins and small molecules. Classic chick-quail chimera studies showed that these properties are not intrinsic to the brain vasculature but rather are induced by surrounding neural tissue. Here we identify Spock1 as a candidate neuronal signal for regulating BBB permeability in zebrafish and mice. Mosaic genetic analysis shows that neuronally-expressed Spock1 is cell non-autonomously required for a functional BBB. Leakage in spock1 mutants is associated with altered extracellular matrix (ECM), increased endothelial transcytosis, and altered pericyte-endothelial interactions. Furthermore, a single dose of recombinant SPOCK1 into spock1 mutants quenches gelatinase activity, restores vascular expression of BBB genes including mcamb, and partially restores barrier function. These analyses support a model in which neuronally secreted Spock1 induces BBB properties by altering the ECM, thereby regulating pericyte-endothelial interactions and downstream vascular gene expression.
Project description:SARS-CoV-2 is considered to affect the central nervous system (CNS) by interacting with the blood–brain barrier (BBB), which is defined by tight junctions that seal paracellular gaps between brain microvascular endothelial like cells (BMECs). Although SARS-CoV-2 infection of BMECs has been reported, the mechanism has not been fully elucidated. Here, we investigated the mechanism using iPSC derived brain microvascular endothelial like cells (iPSC-BMELCs). We observed that iPSC-BMELCs were infected with SARS-CoV-2, which resulted in inflammatory responses. RNA-seq analysis revealed that SARS-CoV-2 modulated the expression of signal molecules in iPSC-BMELCs. These findings suggest that SARS-CoV-2 infection causes BBB dysfunction in humans.
Project description:The blood-brain barrier (BBB) is lined by brain microvascular endothelial cells (BMECs) which regulate transport into and out of the brain. We used human induced pluripotent stem cell (iPSC)-derived cell types to model BBB function within 2D and 3D in vitro models. We compare gene expression between different iPSC-derived cell types, and specifically profile the response of iPSC-derived BMEC-like cells (iBMECs) to differentiation media volume, microenvironmental cues, and cytokines.
Project description:Induced pluripotent stem cells were differentiated to brain microvascular endothelial cells (BMECs) using previously published protocols with minor changes. RNA was collected from purified BMECs after barrier induction and submitted for sequencing.
Project description:The blood-brain barrier (BBB) consists of specific physical barriers, enzymes and transporters, which together maintain the necessary extracellular environment of the central nervous system (CNS). The main physical barrier is found in the CNS endothelial cell, and depends on continuous complexes of tight junctions combined with reduced vesicular transport. Other possible constituents of the BBB include extracellular matrix, astrocytes and pericytes, but the relative contribution of these different components to the BBB remains largely unknown. Here we demonstrate a direct role of pericytes at the BBB in vivo. Using a set of adult viable pericyte-deficient mouse mutants we show that pericyte deficiency increases the permeability of the BBB to water and a range of low-molecular-mass and high-molecular-mass tracers. The increased permeability occurs by endothelial transcytosis, a process that is rapidly arrested by the drug imatinib. Furthermore, we show that pericytes function at the BBB in at least two ways: by regulating BBB-specific gene expression patterns in endothelial cells, and by inducing polarization of astrocyte end-feet surrounding CNS blood vessels. Our results indicate a novel and critical role for pericytes in the integration of endothelial and astrocyte functions at the neurovascular unit, and in the regulation of the BBB. The brain microvascular fragments were isolated from mice with different genotypes, each represented by 3-4 biological replicates. Genotypes 1-2: Platelet derived growth factor-B (PDGF-B) retention-motif knockout (pdgfbret/ret) represent the pericyte-deficient situation, and the heterozygous mice (pdgfbret/+) are used as controls. Genotypes 3-4: Hypomorphic PDGF-B mutants that rescue pdgfb-/- null mice, in which a one copy of a conditionally silent human PDGF-B transgene targeted to the Rosa 26 locus (R26P) is turned on by endothelial-specific expression of Cre recombinase. In this data set these mice are named as Tie2Cre, R26P+/0, pdgfb-/- (representing the pericyte-deficient situation). Mice wt for pdgfb (pdgfb+/+) and carrying one silent copy of R26P (R26P+/0), are used as controls. Genotype 5: Adult Notch3+/+ wildtype (WT).
Project description:Claudin-5 (CLDN5) is an endothelial tight junction protein essential for blood-brain barrier (BBB) formation. Abnormal CLDN5 expression is common in brain disease, and knockdown of Cldn5 at the BBB has been proposed to facilitate drug delivery to the brain. To study the consequences of CLDN5 loss in the mature brain, we induced mosaic endothelial-specific Cldn5 gene ablation in adult mice (Cldn5iECKO). These mice displayed increased BBB permeability to tracers up to 10 kDa in size from 7 days post induction (dpi) and ensuing lethality from 11 dpi. Single-cell RNA sequencing at 12 dpi revealed profound transcriptomic differences in brain endothelial cells regardless of their Cldn5 status in mosaic mice, suggesting major non-cell-autonomous responses. Reactive microglia and astrocytes suggested rapid cellular responses to BBB leakage. Our study demonstrates a critical role for CLDN5 in the adult BBB and provides molecular insight into the consequences and risks associated with CLDN5 inhibition.
Project description:We describe the construction a 3D blood-brain barrier model comprised of iPSC-derived brain endothelium cultured in channels within gelatin hydrogels. The iPSC-derived brain endothelium displays key features of the blood-brain barrier phenotype, including tight junction formation, efflux transporter activity, low paracellular permeability, and suppressed levels of transcytosis compared to non-blood-brain barrier endothelial controls. Collectively, this work provides the foundation for a fully human, biomimetic neurovascular model to study BBB in health and disease.
Project description:Although type III interferons (IFN), also known as IFN-λ or IL28/IL-29, restrict infection by several viruses, their mechanism of inhibitory action has remained uncertain. We used recombinant IFN-λ and mice lacking the IFN-λ receptor (IFNLR1) to evaluate the effect of IFN-λ on infection with West Nile virus (WNV), an encephalitic flavivirus. Cell culture studies in keratinocytes and dendritic cells showed no direct antiviral effect of exogenous IFN-λ even though ISGs were induced. Correspondingly, we observed no differences in WNV burden between wild-type and Ifnlr1-/- mice in the draining lymph node, spleen, and blood. However, we detected earlier dissemination and increased WNV infection in the brain and spinal cord of Ifnlr1-/- mice, yet this was not associated with a direct antiviral effect on infection of neurons. Instead, an increase in blood-brain barrier (BBB) permeability was observed in Ifnlr1-/- mice. Accordingly, treatment of mice with pegylated IFN-λ2 resulted in decreased BBB permeability, reduced WNV infection in the brain without impacting viremia, and improved survival against lethal virus challenge. An in vitro model of the BBB showed that IFN-λ signaling in brain microvascular endothelial cells increased transendothelial electrical resistance, decreased virus movement across the barrier, and modulated tight junction protein localization in a protein synthesis- and STAT1-independent manner. Our data establish a novel indirect antiviral function of IFN-λ in which non-canonical signaling through IFNLR1 tightens the BBB and restricts viral neuroinvasion and pathogenesis. This finding suggests new clinical applications for IFN-λ in treating viral or autoimmune diseases. Transcriptome profiling of bone-marrow derived Dendritic cells(BMDCs), treated with either Serum Free Media(Mock), interferon beta(IFNb), or interferon lambda(IFNL) for 6 hours.