Choroid Plexus Epithelium Research Articles

Increased cytokine expression in the choroid plexus stroma and epithelium in response to endotoxin-induced systemic inflammation in mice.

Sepsis-associated encephalopathy (SAE) is characterized as diffuse brain dysfunction in patients with excessive systemic inflammatory reaction to an infection. In our previous studies using a mouse model of SAE with intraperitoneal injection of lipopolysaccharide (LPS), tissue concentrations of various cytokines were elevated in the entire brain parenchyma 4 and 24 h following LPS administration. Cytokines elevated at 4 h were produced by the choroid plexus, leptomeninges and vascular endothelium, while those at 24 h were produced by astrocytes. Interleukin (IL)-1β did not increase in the concentration in the brain parenchyma during the period from 1 to 24 h following LPS. In the present study, we hypothesized that the intracranial cells that initially respond to systemic inflammation are situated in the choroid plexus and produce IL-1β to initiate cytokine-mediated reactions. We quantified the transcript levels of related cytokines within the choroid plexus and specified the choroid plexus cells that are involved in the immediate cytokine-mediated responses. Mice received LPS or saline by intraperitoneal injection. Four hours after treatments, the choroid plexuses were isolated and subjected to cytokine gene expression analyses using real-time reverse transcription-polymerase chain reaction. Another group of mice was fixed at 1, 4 and 24 h after treatments and the expression of cytokines and receptors was studied with double immunohistofluorescence staining. The transcript levels of IL-1β, CC-motif ligand (CCL)2, CXC-motif ligand (CXCL)1, CXCL2 and IL-6 in the choroid plexus were significantly increased in mice treated with LPS compared to saline control. The IL-1β expression was remarkable in choroid plexus macrophages at 1 and 4 h but not in the brain parenchyma. Choroid plexus stromal cells expressed IL-1 receptor type 1 (IL-1R1). The IL-1R1-bearing stromal cells produced CCL2, CXCL1, CXCL2 and IL-6 at 4 h. Choroid plexus epithelial cells expressed CXCR2, a common receptor for CXCL1 and CXCL2. Choroid plexus epithelial cells also expressed CCL2, CXCL1 and CXCL2 at 4 h, and IL-1R1-bearing stromal cells expressed CXCR2. Therefore, in response to systemic LPS injection, one of the intracranial reactions was initiated within the choroid plexus using IL-1β derived from macrophages. The choroid plexus stromal cells subsequently had elevated expression of CCL2, CXCL1, CXCL2 and IL-6. The choroid plexus epithelial cells also had elevated expression of CCL2, CXCL1 and CXCL2. The presence of receptors for these cytokines on both epithelial and stromal cells raised the possibility of reciprocal interactions between these cells. The results suggested that the immediate early responses exerted by the choroid plexus are relevant to understanding how SAE is initiated in clinical settings.

Age-related changes of choroid plexus morphology, vascularization and epithelial proliferation

The choroid plexus (ChP) is essential for brain homeostasis by regulating the secretion of the cerebrospinal fluid (CSF). Despite a substantial body of work on the pathologically alterations of the ChP, there is lack of data concerning the naturally occurring morphological changes asso-ciated with ageing. In this study, we investigated 30 human ChP tissue samples that were divided into 3 groups according to age. Morphometric analysis of psammoma bodies (PBs) on hematoxylin and eosin (H&E)-stained samples and immunohistochemical analysis of ChP were performed (using antibodies to transmembrane phosphoglycoprotein protein CD34 and nuclear protein Ki-67). Amyloid deposits were detected using Congo red staining. Middle-aged and older individuals exhibited a significantly higher numerical density (ndPB) mostly as increased immature forms, which led us to question the proposed nomenclature. The proliferation rate of the ChP epithelium did not show significant difference between groups. The vascular area was markedly decreased and accompanied by amyloid deposition in blood vessel walls. While the deposits were limited to middle-sized blood vessels in the middle-aged group, in the older group deposits were also present around small vessels. The identified major morphological alterations of ageing ChP tissue provide further understanding of disfunctions of the blood-cerebrospinal fluid barrier that underlie neurodegenerative disorders.

Choroid plexus epithelial cells as a model to study nongenomic steroid signaling and its effect on ion channel function.

The choroid plexus (CP) is an epithelial tissue primarily responsible for the secretion of the cerebrospinal fluid (CSF). Choroid plexuses are found in each of the four brain ventricles: two laterals, third and fourth. They ensure continuous production of CSF to provide nutrients, remove waste products and provide a mechanical buffer to protect the brain. Tight junctions in the CP epithelium form a barrier between the blood plasma and the CSF, which allow channels and transporters in the CP to establish a highly regulated concentration gradient of ions between the two fluids, thereby controlling the composition of CSF. CP plays an important part in healthy brain homeostasis, as its failure to maintain adequate CSF perfusion is implicated in Alzheimer's disease and traumatic brain injury. And yet, the physiology of CP and the mechanism of its age-related functional decline is one of the most understudied areas of neurobiology. Here, we describe a protocol to isolate and identify individual choroid plexus epithelial cells (CPEC) from murine brain for whole-cell patch-clamp recordings and ion channel identification. Using the recording from the inwardly rectifying potassium channel Kir7.1 and TRPM3 that are abundant in CP, we demonstrate a technique to study the regulators of ion channels in the choroid plexus.

MODL-30. DISSECTING THE ROLE OF MULTI-CILIOGENESIS NETWORK IN CHOROID PLEXUS TUMOR

The choroid plexus (CP) in brain ventricles consists of a fibro-vascular core encapsulated by epithelial cells that possess clusters of primary cilia on cell surface. CP tumors are rare primary brain neoplasms that most commonly occur in young children. Compared to the benign CP papilloma, choroid plexus carcinoma (CPC) is poorly understood and highly lethal with few treatments available. Molecular, cytogenetics and genomics studies uncovered complex alterations in CPC including frequent chromosomal loss and recurrent focal aberrations, whereas abnormal NOTCH signaling is observed in many CP tumors. We showed that activation of both NOTCH and Sonic Hedgehog (SHH) signaling in mice drives the formation of aggressive CP tumor. Molecular and histology analyses demonstrated that these murine CP tumors closely resemble their human counterparts, which also display aberrant SHH and NOTCH signaling, suggesting they may represent potential therapeutic avenues. Indeed, treatment with vismodegib, an FDA-approved SHH pathway inhibitor, suppresses CP tumor growth. Unlike multi-ciliated CP epithelial cells, tumor cells in these animal models are characterized by a solitary primary cilium. Though key genes of the multi-ciliogenesis circuit driven by Geminin coiled-coil domain-containing protein 1 (GEMC1) are expressed in CP epithelium, GEMC1-dependent transcriptional program is suppressed in NOTCH-driven CP tumors. Importantly, CPCs in humans consist of tumor cells with a solitary primary cilium and exhibit profound defects multi-ciliogenesis program. Together, these results indicate that a solitary primary cilium is crucial for CPC development, whereas multi-ciliogenesis circuit possesses tumor suppressive functions and may represent a novel therapeutic target in CPC.

Morphological alterations of the choroid plexus epithelium in Alzheimer’s disease

AbstractBackgroundThe choroid plexus (CP), is a complex structure localized in the ventricles of the brain, which mainly consist of tightly connected choroid plexus epithelial (CPE) cells surrounding fenestrated capillaries. These CPE cells form the blood‐cerebrospinal fluid barrier and play a vital role in the maintenance of brain homeostasis. During Alzheimer’s disease (AD) several CPE related processes are severely affected (Brkic, 2015) and evidence indicates that CP‐derived extracellular vesicles play an important role in AD pathogenesis. In this study morphological alterations of the CPE cells were characterized in two distinct AD mice models (APP/PS1tg/wt and APPNLGF/NLGF). Additionally, we investigated the subcellular localization and performed quantification of multivesicular bodies (MVBs) and intraluminal vesicles (ILVs) using transmission electron microscopy (TEM) and 3D‐scanning electron microscopy (3D‐SEM).MethodCP tissue was isolated from APPwt/wt, APP/PS1tg/wt, APPNLGF/NLGF mice at different timepoints (age 10w, 20w, 30w and 40w). Isolated CP was processed for TEM and 3D‐SEM imaging as previously described in (Balusu, 2016; Kremer, 2015). Visualization of the samples was performed using a TEM (JEOL) and FIB‐SEM (Zeiss) and manual segmentation of 3D‐SEM images was done using Microscopy Image Browser (Belevich, 2016).ResultIn both APP/PS1tg/wt and APPNLGF/NLGF mice morphological alterations of the CP are visible at the age of 20 weeks, the ultrastructure is damaged. The CPE cells lose their typical cuboidal shape, are more point‐shaped, the cytoplasm becomes more translucent, the nuclei are irregularly shaped and the mitochondria are more condensed. These changes become increasingly prominent as the mice age. In APPwt/wt mice, the same morphological alterations of the CP become visible at later age. Early during disease progression (10 w), we observed higher levels of ILVs in the CP of APP/PS1tg/wt compared to age‐matched APPwt/wt mice, while levels normalized at later stages. In APPNLGF/NLGF mice higher MVB and ILV levels are observed early during disease progression.ConclusionUltrastructural changes of the CP epithelium are present in different AD mice models. Furthermore, we observed differences in levels of ILVs in the CP early during disease progression. Further research might give insights into the role of the CP and ILVs in AD pathogenesis.

SARS-CoV-2 Infects the Brain Choroid Plexus and Disrupts the Blood-CSF Barrier in Human Brain Organoids.

SummaryCoronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, leads to respiratory symptoms that can be fatal. However, neurological symptoms have also been observed in some patients. The cause of these complications is currently unknown. Here, we use human-pluripotent-stem-cell-derived brain organoids to examine SARS-CoV-2 neurotropism. We find expression of viral receptor ACE2 in mature choroid plexus cells expressing abundant lipoproteins, but not in neurons or other cell types. We challenge organoids with SARS-CoV-2 spike pseudovirus and live virus to demonstrate viral tropism for choroid plexus epithelial cells but little to no infection of neurons or glia. We find that infected cells are apolipoprotein- and ACE2-expressing cells of the choroid plexus epithelial barrier. Finally, we show that infection with SARS-CoV-2 damages the choroid plexus epithelium, leading to leakage across this important barrier that normally prevents entry of pathogens, immune cells, and cytokines into cerebrospinal fluid and the brain.

A Narrative Review of the Role of Transthyretin in Health and Disease.

Transthyretin (TTR) is a tetrameric transport protein highly conserved through vertebrate evolution and synthesized in the liver, choroid plexus, and retinal pigment epithelium. TTR transports the thyroid hormone thyroxine and the retinol-binding protein (RBP) bound to retinol (vitamin A). Mutations in TTR are associated with inherited transthyretin amyloidosis (ATTRv), a progressive, debilitating disease that is ultimately fatal and is characterized by misfolding of TTR and aggregation as amyloid fibrils, predominantly leading to cardiomyopathy or polyneuropathy depending on the particular TTR mutation. Transthyretin amyloid cardiomyopathy can also occur as an age-related disease caused by misfolding of wild-type TTR. Apart from its transport role, little is known about possible additional physiological functions of TTR. Evidence from animal model systems in which TTR has been disrupted via gene knockout is adding to our cumulative understanding of TTR function. There is growing evidence that TTR may have a role in neuroprotection and promotion of neurite outgrowth in response to injury. Here, we review the literature describing potential roles of TTR in neurobiology and in the pathophysiology of diseases other than ATTR amyloidosis. A greater understanding of these processes may also contribute to further clarification of the pathology of ATTR and the effects of potential therapies for TTR-related conditions.

Glucose, Fructose, and Urate Transporters in the Choroid Plexus Epithelium.

The choroid plexus plays a central role in the regulation of the microenvironment of the central nervous system by secreting the majority of the cerebrospinal fluid and controlling its composition, despite that it only represents approximately 1% of the total brain weight. In addition to a variety of transporter and channel proteins for solutes and water, the choroid plexus epithelial cells are equipped with glucose, fructose, and urate transporters that are used as energy sources or antioxidative neuroprotective substrates. This review focuses on the recent advances in the understanding of the transporters of the SLC2A and SLC5A families (GLUT1, SGLT2, GLUT5, GLUT8, and GLUT9), as well as on the urate-transporting URAT1 and BCRP/ABCG2, which are expressed in choroid plexus epithelial cells. The glucose, fructose, and urate transporters repertoire in the choroid plexus epithelium share similar features with the renal proximal tubular epithelium, although some of these transporters exhibit inversely polarized submembrane localization. Since choroid plexus epithelial cells have high energy demands for proper functioning, a decline in the expression and function of these transporters can contribute to the process of age-associated brain impairment and pathophysiology of neurodegenerative diseases.

Human Pluripotent Stem Cell-Derived Neural Cells and Brain Organoids Reveal SARS-CoV-2 Neurotropism Predominates in Choroid Plexus Epithelium.

Neurological complications are common in patients with COVID-19. Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal pathogen of COVID-19, has been detected in some patient brains, its ability to infect brain cells and impact their function is not well understood. Here, we investigated the susceptibility of human induced pluripotent stem cell (hiPSC)-derived monolayer brain cells and region-specific brain organoids to SARS-CoV-2 infection. We found that neurons and astrocytes were sparsely infected, but choroid plexus epithelial cells underwent robust infection. We optimized a protocol to generate choroid plexus organoids from hiPSCs and showed that productive SARS-CoV-2 infection of these organoids is associated with increased cell death and transcriptional dysregulation indicative of an inflammatory response and cellular function deficits. Together, our findings provide evidence for selective SARS-CoV-2 neurotropism and support the use of hiPSC-derived brain organoids as a platform to investigate SARS-CoV-2 infection susceptibility of brain cells, mechanisms of virus-induced brain dysfunction, and treatment strategies.

Tracking Calcium Dynamics and Immune Surveillance at the Choroid Plexus Blood-Cerebrospinal Fluid Interface

The choroid plexus (ChP) epithelium is a source of secreted signaling factors in cerebrospinal fluid (CSF) and a key barrier between blood and brain. Here, we develop imaging tools to interrogate these functions in adult lateral ventricle ChP in whole-mount explants and in awake mice. By imaging epithelial cells in intact ChP explants, we observed calcium activity and secretory events that increased in frequency following delivery of serotonergic agonists. Using chronic two-photon imaging in awake mice, we observed spontaneous subcellular calcium events as well as strong agonist-evoked calcium activation and cytoplasmic secretion into CSF. Three-dimensional imaging of motility and mobility of multiple types of ChP immune cells at baseline and following immune challenge or focal injury revealed a range of surveillance and defensive behaviors. Together, these tools should help illuminate the diverse functions of this understudied body-brain interface.

Idebenone does not inhibit disability progression in primary progressive MS

BackgroundMultiple sclerosis (MS) is a chronic, immune-mediated neurodegenerative disorder of the central nervous system (CNS). While current MS therapies target the inflammatory processes, no treatment explicitly targets mitochondrial dysfunction and resulting axonal loss. Therefore, the aim of this study was to determine whether idebenone inhibits mitochondrial dysfunction and accumulation of disability in primary progressive MS (PPMS) and to enhance understanding of pathogenic mechanisms of PPMS progression using cerebrospinal fluid (CSF) biomarkers. MethodsThe double-blind, placebo-controlled Phase I/II clinical trial of Idebenone in patients with Primary Progressive MS (IPPoMS; NCT00950248) was an adaptively designed, baseline-versus-treatment, placebo-controlled, CSF-biomarker-supported trial. Based on interim analysis of the 1-year pre-treatment data, change in the area under the curve of Combinatorial Weight-Adjusted Disability Score (CombiWISE) became the primary outcome, with >80% power to detect ≥40% efficacy with 28 patients/arm treated for 2 years in baseline versus treatment paradigm. Changes in traditional disability scales and in brain ventricular volume were secondary outcomes. Exploratory outcomes included CSF biomarkers of mitochondrial dysfunction (Growth/differentiation factor 15 [GDF15] and lactate), axonal damage (neurofilament light chain [NFL]), innate immunity (sCD14), blood brain barrier leakage (albumin quotient) and retinal nerve fiber layer thinning. ResultsIdebenone was well tolerated but did not inhibit disability progression or CNS tissue destruction. Concentrations of GDF15, secreted predominantly by astrocytes and choroid plexus epithelium in vitro, increased after exposure to mitochondrial toxin rotenone, validating the ability of this biomarker to measure intrathecal mitochondrial damage. CSF GDF15 levels correlated strongly with age and MS patients had CSF levels of GDF15 significantly above age-adjusted healthy volunteers, with highest levels measured in PPMS. Idebenone did not change CSF GDF15 levels. ConclusionMitochondrial dysfunction exceeding normal aging reflected by age-adjusted CSF GDF15 is present in the majority of PPMS patients, but it is not inhibited by idebenone.

Endoplasmic Reticulum Calcium Pumps and Tumor Cell Differentiation.

Endoplasmic reticulum (ER) calcium homeostasis plays an essential role in cellular calcium signaling, intra-ER protein chaperoning and maturation, as well as in the interaction of the ER with other organelles. Calcium is accumulated in the ER by sarco/endoplasmic reticulum calcium ATPases (SERCA enzymes) that generate by active, ATP-dependent transport, a several thousand-fold calcium ion concentration gradient between the cytosol (low nanomolar) and the ER lumen (high micromolar). SERCA enzymes are coded by three genes that by alternative splicing give rise to several isoforms, which can display isoform-specific calcium transport characteristics. SERCA expression levels and isoenzyme composition vary according to cell type, and this constitutes a mechanism whereby ER calcium homeostasis is adapted to the signaling and metabolic needs of the cell, depending on its phenotype, its state of activation and differentiation. As reviewed here, in several normal epithelial cell types including bronchial, mammary, gastric, colonic and choroid plexus epithelium, as well as in mature cells of hematopoietic origin such as pumps are simultaneously expressed, whereas in corresponding tumors and leukemias SERCA3 expression is selectively down-regulated. SERCA3 expression is restored during the pharmacologically induced differentiation of various cancer and leukemia cell types. SERCA3 is a useful marker for the study of cell differentiation, and the loss of SERCA3 expression constitutes a previously unrecognized example of the remodeling of calcium homeostasis in tumors.

Three-Dimensional Explant Platform for Studies on Choroid Plexus Epithelium.

The choroid plexus (CP) plays a major role in controlling the entry of substances and immune cells into the brain as it forms the blood-cerebrospinal fluid barrier (BCSFB) in the brain ventricles. Dysregulated immune cell trafficking through the epithelial cell (EC) layer of CP is central for the pathogenesis of infectious diseases in the brain and many neurodegenerative disorders. In vitro studies elucidating the function of the CP have so far been limited to the monolayer culture of CP ECs. To mimic immune cell migration across the CP barrier, a three-dimensional model would be advantageous. Here, we present an in vitro platform for studies of the immune cell trafficking based on CP explants/organoids. The explants were generated from fragments of mouse CPs in Matrigel, where the cells formed luminal spaces and could be maintained in culture for at least 8 weeks. We demonstrate expression of the major CP markers in the explants, including transthyretin and aquaporin 1 as well as ZO1 and ICAM-1, indicating a capacity for secretion of cerebrospinal fluid (CSF) and presence of tight junctions. CP explants displayed CP-like cell polarization and formed an intact EC barrier. We also show that the expression of transthyretin, transferrin, occludin and other genes associated with various functions of CP was maintained in the explants at similar levels as in native CP. By using dendritic cells and neutrophils, we show that the migration activity of immune cells and their interactions with CP epithelium can be monitored by microscopy. Thereby, the three-dimensional CP explant model can be used to study the cellular and molecular mechanisms mediating immune cell migration through CP epithelium and other functions of choroid EC. We propose this platform can potentially be used in the search for therapeutic targets and intervention strategies to improve control of (drug) substances and (immune) cell entry into the central nervous system.

Meningeal Immunity and Its Function in Maintenance of the Central Nervous System in Health and Disease.

Neuroimmunology, albeit a relatively established discipline, has recently sparked numerous exciting findings on microglia, the resident macrophages of the central nervous system (CNS). This review addresses meningeal immunity, a less-studied aspect of neuroimmune interactions. The meninges, a triple layer of membranes-the pia mater, arachnoid mater, and dura mater-surround the CNS, encompassing the cerebrospinal fluid produced by the choroid plexus epithelium. Unlike the adjacent brain parenchyma, the meninges contain a wide repertoire of immune cells. These constitute meningeal immunity, which is primarily concerned with immune surveillance of the CNS, and-according to recent evidence-also participates in postinjury CNS recovery, chronic neurodegenerative conditions, and even higher brain function. Meningeal immunity has recently come under the spotlight owing to the characterization of meningeal lymphatic vessels draining the CNS. Here, we review the current state of our understanding of meningeal immunity and its effects on healthy and diseased brains.

Choroid plexus LAT2 and SNAT3 as partners in CSF amino acid homeostasis maintenance

BackgroundCerebrospinal fluid (CSF) is mainly produced by the choroid plexus (CP) located in brain ventricles. Although derived from blood plasma, it is nearly protein-free (~ 250-fold less) and contains about 2–20-fold less free amino acids, with the exception of glutamine (Gln) which is nearly equal. The aim of this study was to determine which amino acid transporters are expressed in mouse CP epithelium in order to gain understanding about how this barrier maintains the observed amino acid concentration gradient.MethodsExpression of amino acid transporters was assessed in isolated choroid plexuses (CPs) by qRT-PCR followed by localization studies using immunofluorescence with specific antibodies. The impact of LAT2 (Slc7a8) antiporter deletion on CSF amino acids was determined.ResultsThe purity of isolated choroid plexuses was tested on the mRNA level using specific markers, in particular transthyretin (Ttr) that was enriched 330-fold in CP compared to cerebral tissue. In a first experimental round, 14 out of 32 Slc amino acid transporters tested on the mRNA level by qPCR were selected for further investigation. Out of these, five were considered highly expressed, SNAT1 (Slc38a1), SNAT3 (Slc38a3), LAT2 (Slc7a8), ASC1 (Slc7a10) and SIT1 (Slc6a20b). Three of them were visualized by immunofluorescence: SNAT1 (Slc38a1), a neutral amino acid-Na+ symporter, found at the blood side basolateral membrane of CP epithelium, while SNAT3 (Slc38a3), an amino acid-Na+ symporter and H+ antiporter, as well as LAT2 (Slc7a8), a neutral amino acid antiporter, were localized at the CSF-facing luminal membrane. In a LAT2 knock-out mouse model, CSF Gln was unchanged, whereas other amino acids normally 2–20-fold lower than in plasma, were increased, in particular the LAT2 uptake substrates leucine (Leu), valine (Val) and tryptophan (Trp) and some other amino acids such as glutamate (Glu), glycine (Gly) and proline (Pro).ConclusionThese results suggest that Gln is actively transported by SNAT1 from the blood into CP epithelial cells and then released luminally into CSF via SNAT3 and LAT2. Its efflux via LAT2 may drive the reuptake from the CSF of essential amino acid substrates of this antiporter and thereby participates to maintaining the amino acid gradient between plasma and CSF.

Cerebrospinal fluid dynamics modulation by diet and cytokines in rats

BackgroundIdiopathic intracranial hypertension (IIH) is a neurological disorder characterised by raised cerebrospinal fluid (CSF) pressure in the absence of any intracranial pathology. IIH mainly affects women with obesity between the ages of 15 and 45. Two possible mechanisms that could explain the increased CSF pressure in IIH are excessive CSF production by the choroid plexus (CP) epithelium or impaired CSF drainage from the brain. However, the molecular mechanisms controlling these mechanisms in IIH remain to be determined.MethodsIn vivo ventriculo-cisternal perfusion (VCP) and variable rate infusion (VRI) techniques were used to assess changes in rates of CSF secretion and resistance to CSF drainage in female and male Wistar rats fed either a control (C) or high-fat (HF) diet (under anaesthesia with 20 μl/100 g medetomidine, 50 μl/100 g ketamine i.p). In addition, CSF secretion and drainage were assessed in female rats following treatment with inflammatory mediators known to be elevated in the CSF of IIH patients: C–C motif chemokine ligand 2 (CCL2), interleukin (IL)-17 (IL-17), IL-6, IL-1β, tumour necrosis factor-α (TNF-α), as well as glucocorticoid hydrocortisone (HC).ResultsFemale rats fed the HF diet had greater CSF secretion compared to those on control diet (3.18 ± 0.12 μl/min HF, 1.49 ± 0.15 μl/min control). Increased CSF secretion was seen in both groups following HC treatment (by 132% in controls and 114% in HF) but only in control rats following TNF-α treatment (137% increase). The resistance to CSF drainage was not different between control and HF fed female rats (6.13 ± 0.44 mmH2O min/μl controls, and 7.09 ± 0.26 mmH2O min/μl HF). and when treated with CCL2, both groups displayed an increase in resistance to CSF drainage of 141% (controls) and 139% (HF) indicating lower levels of CSF drainage.ConclusionsWeight loss and therapies targeting HC, TNF-α and CCL2, whether separately or in combination, may be beneficial to modulate rates of CSF secretion and/or resistance to CSF drainage pathways, both factors likely contributing to the raised intracranial pressure (ICP) observed in female IIH patients with obesity.

Principles of neuroanatomical architecture supporting brain–immune cell–cell interactions

AbstractThe brain interacts with the immune system under inflammatory and non‐inflammatory conditions. Brain cells have the capacity to produce a variety of cytokines in response to systemic immune activation. Therefore, we hypothesized that brain cells and immune cells move close to each other, so that they can carry out intercellular interactions. In the present article, I review our studies to determine the site for the brain–immune cell–cell interactions. The leptomeninges, choroid plexus stroma and epithelium, attachments of the choroid plexuses, vascular endothelial cells, cells of the perivascular space, and astrocytic end‐feet compose the histological architecture that supports interactions between bone marrow‐derived myeloid cells and brain parenchymal cells under non‐inflammatory conditions. This architecture also functions as the interface at which systemic inflammation‐induced responses can be conveyed to the brain parenchyma under inflammatory conditions. It should be noted that such brain–immune interactions occur in the absence of florid inflammatory cell infiltrates in the brain parenchyma, and with relative preservation of the blood‐brain barrier. Rather, cells comprising the blood‐brain barrier act as the interface linking peripheral immune activation and brain responses. These responses, known as “neuroinflammation”, are unique to the brain. Neuroinflammation differs from the histological inflammation that is accompanied by a florid infiltration of the leptomeninges (meningitis) and/or brain parenchyma (encephalitis) by inflammatory cells. In this review, the relevance of histological studies to unravel the mechanisms linking systemic inflammation, brain–immune interface cells and brain parenchymal cells, with a special emphasis on sepsis‐associated encephalopathy, is discussed.

Genetic disruption of slc4a10 alters the capacity for cellular metabolism and vectorial ion transport in the choroid plexus epithelium

BackgroundGenetic disruption of slc4a10, which encodes the sodium-dependent chloride/bicarbonate exchanger Ncbe, leads to a major decrease in Na+-dependent HCO3− import into choroid plexus epithelial cells in mice and to a marked reduction in brain intraventricular fluid volume. This suggests that Ncbe functionally is a key element in vectorial Na+ transport and thereby for cerebrospinal fluid secretion in the choroid plexus. However, slc4a10 disruption results in severe changes in expression of Na+,K+-ATPase complexes and other major transport proteins, indicating that profound cellular changes accompany the genetic manipulation.MethodsA tandem mass tag labeling strategy was chosen for quantitative mass spectrometry. Alterations in the broader patterns of protein expression in the choroid plexus in response to genetic disruption of Ncbe was validated by semi-quantitative immunoblotting, immunohistochemistry and morphometry.ResultsThe abundance of 601 proteins were found significantly altered in the choroid plexus from Ncbe ko mice relative to Ncbe wt. In addition to a variety of transport proteins, particularly large changes in the abundance of proteins involved in cellular energy metabolism were detected in the Ncbe ko mice. In general, the abundance of rate limiting glycolytic enzymes and several mitochondrial enzymes were reduced following slc4a10 disruption. Surprisingly, this was accompanied by increased ATP levels in choroid plexus cells, indicating that the reduction in capacity for energy metabolism was adaptive to high ATP rather than causal for a decreased capacity for ion and water transport. Ncbe-deficient cells also had a reduced cell area and decreased K+ content.ConclusionOur findings suggest that the lack of effective Na+-entry into the epithelial cells of the choroid plexus leads to a profound change in the cellular phenotype, shifting from a high-rate secretory function towards a more dormant state; similar to what is observed during ageing or Alzheimer’s disease.

Tracking Calcium Dynamics and Immune Surveillance at the Choroid Plexus Blood-Cerebrospinal Fluid Interface

The choroid plexus (ChP) epithelium is a source of secreted signaling factors in cerebrospinal fluid (CSF) and a key barrier between blood and brain. Here, we develop imaging tools to interrogate these functions in adult lateral ventricle ChP in wholemount explants and in awake mice. By imaging epithelial cells in intact ChP explants, we observed calcium activity and secretory events that increased in frequency following delivery of serotonergic agonists. Using chronic two-photon imaging in awake mice, we observed spontaneous subcellular calcium events as well as strong agonist-evoked calcium activation and cytoplasmic secretion into CSF. Three-dimensional imaging of motility and mobility of multiple types of ChP immune cells at baseline and following immune challenge or focal injury revealed a range of surveillance and defensive behaviors. Together, these tools should help illuminate the diverse functions of this understudied body-brain interface.

Neonatal Susceptibility to Meningitis Results from the Immaturity of Epithelial Barriers and Gut Microbiota

Neonates are highly susceptible to bacterial meningitis as compared to children and adults. Group B streptococcus (GBS) is a major cause of neonatal meningitis. Neonatal meningitis can result from GBS intestinal colonization and translocation across the intestinal barrier (IB). Here, we show that the immaturity of the neonatal intestinal microbiota results in low resistance to GBS intestinal colonization and higher permissiveness of the gut vascular barrier. Additionally, the age-dependent but microbiota-independent Wnt activity in intestinal and choroid plexus (CP) epithelia results in a lower degree of cell-cell junctions’ polarization which favors bacterial translocation. This study reveals that neonatal susceptibility to GBS meningitis results from the age-dependent immaturity of the microbiota and developmental pathways associated with neonatal tissue growth, which concur to GBS gut colonization, systemic dissemination and neuroinvasion. Whereas the activation of developmental pathways is intrinsic to neonates, interventions aimed at maturing the microbiota may help prevent neonatal meningitis.