Establishment and characterization of an immortalized Z310 choroidal epithelial cell line from murine choroid plexus

The hypervirulent Group B Streptococcus HvgA adhesin promotes central nervous system invasion through transcellular crossing of the choroid plexus

BACKGROUND

Group B Streptococcus (GBS) is the leading cause of neonatal meningitis responsible for a substantial cause of death and disability worldwide. The vast majority of GBS neonatal meningitis cases are due to the CC17 hypervirulent clone. However, the cellular and molecular pathways involved in brain invasion by GBS CC17 isolates remain largely elusive. Here, we studied the specific interaction of the CC17 clone with the choroid plexus, the main component of the blood-cerebrospinal fluid (CSF) barrier.

METHODS

The interaction of GBS CC17 or non-CC17 strains with choroid plexus cells was studied using an in vivo mouse model of meningitis and in vitro models of primary and transformed rodent choroid plexus epithelial cells (CPEC and Z310). In vivo interaction of GBS with the choroid plexus was assessed by microscopy. Bacterial invasion and cell barrier penetration were examined in vitro, as well as chemokines and cytokines in response to infection.

RESULTS

GBS CC17 was found associated with the choroid plexus of the lateral, 3rd and 4th ventricles. Infection of choroid plexus epithelial cells revealed an efficient internalization of the bacteria into the cells with GBS CC17 displaying a greater ability to invade these cells than a non-CC17 strain. Internalization of the GBS CC17 strain involved the CC17-specific HvgA adhesin and occurred via a clathrin-dependent mechanism leading to transcellular transcytosis across the choroid plexus epithelial monolayer. CPEC infection resulted in the secretion of several chemokines, including CCL2, CCL3, CCL20, CX3CL1, and the matrix metalloproteinase MMP3, as well as immune cell infiltration.

CONCLUSION

Our findings reveal a GBS strain-specific ability to infect the blood-CSF barrier, which appears to be an important site of bacterial entry and an active site of immune cell trafficking in response to infection.

In vitro models of the choroid plexus and the blood-cerebrospinal fluid barrier: advances, applications, and perspectives

The choroid plexus (CP), a highly vascularized endothelial-epithelial convolute, is placed in the ventricular system of the brain and produces a large part of the cerebrospinal fluid (CSF). Additionally, the CP is the location of a blood-CSF barrier (BCSFB) that separates the CSF from the blood stream in the CP endothelium. In vitro models of the CP and the BCSFB are of high importance to investigate the biological functions of the CP and the BCSFB. Since the CP is involved in several serious diseases, these in vitro models promise help in researching the processes contributing to the diseases and during the development of treatment options. In this review, we provide an overview on the available models and the advances that have been made toward more sophisticated and "in vivo near" systems as organoids and microfluidic lab-on-a-chip approaches. We go into the applications and research objectives for which the various modeling systems can be used and discuss the possible future prospects and perspectives.

Lead exposure disturbs ATP7B-mediated copper export from brain barrier cells by inhibiting XIAP-regulated COMMD1 protein degradation

The brain barrier is an important structure for metal ion homeostasis. According to studies, lead (Pb) exposure disrupts the transportation of copper (Cu) through the brain barrier, which may cause impairment of the nervous system; however, the specific mechanism is unknown. The previous studies suggested the X-linked inhibitor of apoptosis (XIAP) is a sensor for cellular Cu level which mediate the degradation of the MURR1 domain-containing 1 (COMMD1) protein. XIAP/COMMD1 axis was thought to be an important regulator in Cu metabolism maintenance. In this study, the role of XIAP-regulated COMMD1 protein degradation in Pb-induced Cu disorders in brain barrier cells was investigated. Pb exposure significantly increased Cu levels in both cell types, according to atomic absorption technology testing. Western blotting and reverse transcription PCR (RT-PCR) showed that COMMD1 protein levels were significantly increased, whereas XIAP, ATP7A, and ATP7B protein levels were significantly decreased. However, there were no significant effects at the messenger RNA (mRNA) level (XIAP, ATP7A, and ATP7B). Pb-induced Cu accumulation and ATP7B expression were reduced when COMMD1 was knocked down by transient small interfering RNA (siRNA) transfection. In addition, transient plasmid transfection of XIAP before Pb exposure reduced Pb-induced Cu accumulation, increased COMMD1 protein levels, and decreased ATP7B levels. In conclusion, Pb exposure can reduce XIAP protein expression, increase COMMD1 protein levels, and specifically decrease ATP7B protein levels, resulting in Cu accumulation in brain barrier cells.

Extracellular vesicles derived from the choroid plexus trigger the differentiation of neural stem cells

The choroid plexus secrets cerebrospinal fluid (CSF) composed of electrolytes, cytokines, growth factors, metabolites and extracellular vesicles (EVs) that flow through the interconnected brain ventricles. On their course, CSF components can act as signals that affect, for example, neural stem cells (NSCs) residing in niches of the ventricular wall. We studied EV-born CSF signals in an in vitro culture system. We purified EVs from the secretome of a choroid plexus cell line (Z310 cells), and from primary choroid plexus cultures and co-cultured those EVs with NSCs isolated from the niche of the lateral and the third ventricle. EVsZ310 and EVsCHP were purified by differential centrifugation. This yielded fractions of EVs of 50-150-nm diameter that induced a complex multicellular network formation and NSC differentiation. Both types of EV converted the round NSCs to cells that extended long processes that contacted nearby, alike-shaped cells. Mass spectrometry showed that the differentiation-inducing EVZ310 were enriched for membrane and membrane-associated proteins involved in cell differentiation, membrane trafficking, and membrane organization. We hypothesize that this type of EV Z310 cargo causes changes of stem cell morphology that leads to multicellular networks in the niches. This cell-shape transition may represent an initial step in NSC differentiation.

Distinct functions of dimeric and monomeric scaffold protein Alix in regulating F-actin assembly and loading of exosomal cargo

Alix is a ubiquitously expressed scaffold protein that participates in numerous cellular processes related to the remodeling/repair of membranes and the actin cytoskeleton. Alix exists in monomeric and dimeric/multimeric configurations, but how dimer formation occurs and what role the dimer has in Alix-mediated processes are still largely elusive. Here, we reveal a mechanism for Alix homodimerization mediated by disulfide bonds under physiological conditions, and demonstrate that the Alix dimer is enriched in exosomes and F-actin cytoskeleton subcellular fractions. Proteomic analysis of exosomes derived from Alix^-/- primary cells underlined the indispensable role of Alix in loading syntenin into exosomes, thereby regulating the cellular levels of this protein. Using a set of deletion mutants, we define the function of Alix Bro1 domain, which is solely required for its exosomal localization, and that of the V domain, which is needed for recruiting syntenin into exosomes. We reveal an essential role for Cys⁸¹⁴ within the disordered proline rich domain (PRD) for Alix dimerization. By mutating this residue, we show that Alix remains exclusively monomeric and, in this configuration, is effective in loading syntenin into exosomes. In contrast, loss of dimerization affects the ability of Alix to associate with F-actin, thereby compromising Alix-mediated cytoskeleton remodeling. We propose that dimeric and monomeric forms of Alix selectively execute two of the protein's main functions: exosomal cargo loading and cytoskeleton remodeling.

In Vitro Models of the Blood–Cerebrospinal Fluid Barrier and Their Applications in the Development and Research of (Neuro)Pharmaceuticals

The pharmaceutical research sector has been facing the challenge of neurotherapeutics development and its inherited high-risk and high-failure-rate nature for decades. This hurdle is partly attributable to the presence of brain barriers, considered both as obstacles and opportunities for the entry of drug substances. The blood–cerebrospinal fluid (CSF) barrier (BCSFB), an under-studied brain barrier site compared to the blood–brain barrier (BBB), can be considered a potential therapeutic target to improve the delivery of CNS therapeutics and provide brain protection measures. Therefore, leveraging robust and authentic in vitro models of the BCSFB can diminish the time and effort spent on unproductive or redundant development activities by a preliminary assessment of the desired physiochemical behavior of an agent toward this barrier. To this end, the current review summarizes the efforts and progresses made to this research area with a notable focus on the attribution of these models and applied techniques to the pharmaceutical sector and the development of neuropharmacological therapeutics and diagnostics. A survey of available in vitro models, with their advantages and limitations and cell lines in hand will be provided, followed by highlighting the potential applications of such models in the (neuro)therapeutics discovery and development pipelines.

Experimental approaches for manipulating choroid plexus epithelial cells

Choroid plexus (ChP) epithelial cells are crucial for the function of the blood-cerebrospinal fluid barrier (BCSFB) in the developing and mature brain. The ChP is considered the primary source and regulator of CSF, secreting many important factors that nourish the brain. It also performs CSF clearance functions including removing Amyloid beta and potassium. As such, the ChP is a promising target for gene and drug therapy for neurodevelopmental and neurological disorders in the central nervous system (CNS). This review describes the current successful and emerging experimental approaches for targeting ChP epithelial cells. We highlight methodological strategies to specifically target these cells for gain or loss of function in vivo. We cover both genetic models and viral gene delivery systems. Additionally, several lines of reporters to access the ChP epithelia are reviewed. Finally, we discuss exciting new approaches, such as chemical activation and transplantation of engineered ChP epithelial cells. We elaborate on fundamental functions of the ChP in secretion and clearance and outline experimental approaches paving the way to clinical applications.

Pb Induces MCP-1 in the Choroid Plexus

Lead (Pb) is an environmental element that has been implicated in the development of dementia and Alzheimer's disease (AD). Additionally, innate immune activation contributes to AD pathophysiology. However, the mechanisms involved remain poorly understood. The choroid plexus (CP) is not only the site of cerebrospinal fluid (CSF) production, but also an important location for communication between the circulation and the CSF. In this study, we investigated the involvement of the CP during Pb exposure by evaluating the expression of the monocyte chemoattractant protein-1 (MCP-1). MCP-1 is highly expressed in the CP compared to other CNS tissues. MCP-1 regulates macrophage infiltration and is upregulated in AD brains. Our study revealed that Pb exposure stimulated MCP-1 expression, along with a significantly increased macrophage infiltration into the CP. By using cultured Z310 rat CP cells, Pb exposure stimulated MCP-1 expression in a dose-related fashion and markedly activated both NF-κB and p38 MAP kinase. Interestingly, both SB 203580, a p38 inhibitor, and BAY 11-7082, an NF-κB p65 inhibitor, significantly blocked Pb-induced MCP-1 expression. However, SB203580 did not directly inhibit NF-κB p65 phosphorylation. In conclusion, Pb exposure stimulates MCP-1 expression via the p38 and NF-κB p65 pathways along with macrophage infiltration into the CP.

TRIP6 functions in brain ciliogenesis

TRIP6, a member of the ZYXIN-family of LIM domain proteins, is a focal adhesion component. Trip6 deletion in the mouse, reported here, reveals a function in the brain: ependymal and choroid plexus epithelial cells are carrying, unexpectedly, fewer and shorter cilia, are poorly differentiated, and the mice develop hydrocephalus. TRIP6 carries numerous protein interaction domains and its functions require homodimerization. Indeed, TRIP6 disruption in vitro (in a choroid plexus epithelial cell line), via RNAi or inhibition of its homodimerization, confirms its function in ciliogenesis. Using super-resolution microscopy, we demonstrate TRIP6 localization at the pericentriolar material and along the ciliary axoneme. The requirement for homodimerization which doubles its interaction sites, its punctate localization along the axoneme, and its co-localization with other cilia components suggest a scaffold/co-transporter function for TRIP6 in cilia. Thus, this work uncovers an essential role of a LIM-domain protein assembly factor in mammalian ciliogenesis.

Oxidized/deamidated-ceruloplasmin dysregulates choroid plexus epithelial cells functionality and barrier properties via RGD-recognizing integrin binding

Choroid plexus epithelial cells (CPEpiCs) determine the composition of cerebrospinal fluid (CSF) and constitute the blood-CSF barrier (BCSFB), functions that are altered in neurodegenerative diseases. In Parkinson's disease (PD) the pathological environment oxidizes and deamidates the ceruloplasmin, a CSF-resident ferroxidase, which undergoes a gain of RGD-recognizing integrin binding property, that may result in signal transduction. We investigated the effects that oxidized/deamidated ceruloplasmin (Cp-ox/de) may exert on CPEpiCs functions. Through RGD-recognizing integrins binding, Cp-ox/de mediates CPEpiCs adhesion and intracellular signaling, resulting in cell proliferation inhibition and alteration of the secretome profile in terms of proteins related to cell-extracellular matrix interaction. Oxidative conditions, comparable to those found in the CSF of PD patients, induced CPEpiCs barrier leakage, allowing Cp-ox/de to cross it, transducing integrins-mediated signal that further worsens BCSFB integrity. This mechanism might contribute to PD pathological processes altering CSF composition and aggravating the already compromised BCSFB function.

The Choroid Plexus Is an Alternative Source of Prolactin to the Rat Brain

Among the more than 300 functions attributed to prolactin (PRL), this hormone has been associated with the induction of neurogenesis and differentiation of olfactory neurons especially during pregnancy, which are essential for maternal behavior. Despite the original hypothesis that PRL enters the central nervous system through a process mediated by PRL receptors (PRLR) at the choroid plexus (CP), recent data suggested that PRL transport into the brain is independent of its receptors. Based on transcriptomic data suggesting that PRL could be expressed in the CP, this work aimed to confirm PRL synthesis and secretion by CP epithelial cells (CPEC). The secretion of PRL and the distribution of PRLR in CPEC were further characterized using an in vitro model of the rat blood-cerebrospinal fluid barrier. RT-PCR analysis of PRL transcripts showed its presence in pregnant rat CP, in CPEC, and in the rat immortalized CP cell line, Z310. These observations were reinforced by immunocytochemistry staining of PRL in CPEC and Z310 cell cytoplasm. A 63-kDa immunoreactive PRL protein was detected by Western blot in CP protein extracts as well as in culture medium incubated with rat pituitary and samples of rat cerebrospinal fluid and serum. Positive immunocytochemistry staining of PRLR was present throughout the CPEC cytoplasm and in the apical and basal membrane of these cells. Altogether, our evidences suggest that CP is an alternative source of PRL to the brain, which might impact neurogenesis of olfactory neurons at the subventricular zone, given its proximity to the CP.

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.

Targeting the Choroid Plexuses for Protein Drug Delivery

Delivery of therapeutic agents to the central nervous system is challenged by the barriers in place to regulate brain homeostasis. This is especially true for protein therapeutics. Targeting the barrier formed by the choroid plexuses at the interfaces of the systemic circulation and ventricular system may be a surrogate brain delivery strategy to circumvent the blood-brain barrier. Heterogenous cell populations located at the choroid plexuses provide diverse functions in regulating the exchange of material within the ventricular space. Receptor-mediated transcytosis may be a promising mechanism to deliver protein therapeutics across the tight junctions formed by choroid plexus epithelial cells. However, cerebrospinal fluid flow and other barriers formed by ependymal cells and perivascular spaces should also be considered for evaluation of protein therapeutic disposition. Various preclinical methods have been applied to delineate protein transport across the choroid plexuses, including imaging strategies, ventriculocisternal perfusions, and primary choroid plexus epithelial cell models. When used in combination with simultaneous measures of cerebrospinal fluid dynamics, they can yield important insight into pharmacokinetic properties within the brain. This review aims to provide an overview of the choroid plexuses and ventricular system to address their function as a barrier to pharmaceutical interventions and relevance for central nervous system drug delivery of protein therapeutics. Protein therapeutics targeting the ventricular system may provide new approaches in treating central nervous system diseases.

An efficient autometallography approach to localize lead at ultra-structural levels of cultured cells

Understanding the precise intracellular localization of lead (Pb) is a key in deciphering processes in Pb-induced toxicology. However, it is a great challenge to trace Pbin vitro, especially in cultured cells. We aimed to find an innovative and efficient approach to investigate distribution of Pb in cells and to validate it through determining the subcellular Pb content. We identified its ultra-structural distribution with autometallography under electron microscopy in a choroidal epithelial Z310 cell line. Electron microscopy in combination with energy-dispersive X-ray spectroscope (EDS) was employed to provide further evidence of Pb location. In addition, Pb content was determined in the cytosol, membrane/organelle, nucleus and cytoskeleton fractions with atomic absorption spectroscopy. Pb was found predominantly inside the nuclear membranes and some was distributed in the cytoplasm under low-concentration exposure. Nuclear existence of Pb was verified by EDS under electron microscopy. Once standardized for protein content, Pb percentage in the nucleus fraction reached the highest level (76%). Our results indicate that Pb is accumulated mainly in the nucleus of choroid plexus. This method is sensitive and precise in providing optimal means to study the ultra-structural localization of Pb forin vitromodels. In addition, it offers the possibility of localization of other metals in cultured cells. Some procedures may also be adopted to detect target proteins via immunoreactions.

The Rhythmicity of Clock Genes is Disrupted in the Choroid Plexus of the APP/PS1 Mouse Model of Alzheimer's Disease

BACKGROUND

The choroid plexus (CP), which constitutes the blood-cerebrospinal fluid barrier, was recently identified as an important component of the circadian clock system.

OBJECTIVE

The fact that circadian rhythm disruption is closely associated to Alzheimer's disease (AD) led us to investigate whether AD pathology can contribute to disturbances of the circadian clock in the CP.

METHODS

For this purpose, we evaluated the expression of core-clock genes at different time points, in 6- and 12-month-old female and male APP/PS1 mouse models of AD. In addition, we also assessed the effect of melatonin pre-treatment in vitro before amyloid-β stimulus in the daily pattern of brain and muscle Arnt-like protein 1 (Bmal1) expression.

RESULTS

Our results showed a dysregulation of circadian rhythmicity of Bmal1 expression in female and male APP/PS1 transgenic 12-month-old mice and of Period 2 (Per2) expression in male mice. In addition, a significant circadian pattern of Bmal1 was measured the intermittent melatonin pre-treatment group, showing that melatonin can reset the CP circadian clock.

CONCLUSION

These results demonstrated a connection between AD and the disruption of circadian rhythm in the CP, representing an attractive target for disease prevention and/or treatment.

ABC Transporters at the Blood-Brain Interfaces, Their Study Models, and Drug Delivery Implications in Gliomas

Drug delivery into the brain is regulated by the blood-brain interfaces. The blood-brain barrier (BBB), the blood-cerebrospinal fluid barrier (BCSFB), and the blood-arachnoid barrier (BAB) regulate the exchange of substances between the blood and brain parenchyma. These selective barriers present a high impermeability to most substances, with the selective transport of nutrients and transporters preventing the entry and accumulation of possibly toxic molecules, comprising many therapeutic drugs. Transporters of the ATP-binding cassette (ABC) superfamily have an important role in drug delivery, because they extrude a broad molecular diversity of xenobiotics, including several anticancer drugs, preventing their entry into the brain. Gliomas are the most common primary tumors diagnosed in adults, which are often characterized by a poor prognosis, notably in the case of high-grade gliomas. Therapeutic treatments frequently fail due to the difficulty of delivering drugs through the brain barriers, adding to diverse mechanisms developed by the cancer, including the overexpression or expression de novo of ABC transporters in tumoral cells and/or in the endothelial cells forming the blood-brain tumor barrier (BBTB). Many models have been developed to study the phenotype, molecular characteristics, and function of the blood-brain interfaces as well as to evaluate drug permeability into the brain. These include in vitro, in vivo, and in silico models, which together can help us to better understand their implication in drug resistance and to develop new therapeutics or delivery strategies to improve the treatment of pathologies of the central nervous system (CNS). In this review, we present the principal characteristics of the blood-brain interfaces; then, we focus on the ABC transporters present on them and their implication in drug delivery; next, we present some of the most important models used for the study of drug transport; finally, we summarize the implication of ABC transporters in glioma and the BBTB in drug resistance and the strategies to improve the delivery of CNS anticancer drugs.

Basal Sodium-Dependent Vitamin C Transporter 2 polarization in choroid plexus explant cells in normal or scorbutic conditions

Vitamin C is incorporated into the cerebrospinal fluid (CSF) through choroid plexus cells. While the transfer of vitamin C from the blood to the brain has been studied functionally, the vitamin C transporter, SVCT2, has not been detected in the basolateral membrane of choroid plexus cells. Furthermore, it is unknown how its expression is induced in the developing brain and modulated in scurvy conditions. We concluded that SVCT2 is intensely expressed in the second half of embryonic brain development and postnatal stages. In postnatal and adult brain, SVCT2 is highly expressed in all choroidal plexus epithelial cells, shown by colocalization with GLUT1 in the basolateral membranes and without MCT1 colocalization, which is expressed in the apical membrane. We confirmed that choroid plexus explant cells (in vitro) form a sealed epithelial structure, which polarized basolaterally, endogenous or overexpressed SVCT2. These results are reproduced in vivo by injecting hSVCT2wt-EYFP lentivirus into the CSF. Overexpressed SVCT2 incorporates AA (intraperitoneally injected) from the blood to the CSF. Finally, we observed in Guinea pig brain under scorbutic condition, that normal distribution of SVCT2 in choroid plexus may be regulated by peripheral concentrations of vitamin C. Additionally, we observed that SVCT2 polarization also depends on the metabolic stage of the choroid plexus cells.

Bitter taste signaling mediated by Tas2r144 is down-regulated by 17β-estradiol and progesterone in the rat choroid plexus

The blood-cerebrospinal fluid barrier is constituted by choroid plexus epithelial cells (CPEC) that regulate molecular trafficking between the blood and the cerebrospinal fluid. We hypothesize that taste receptors expressed in CPEC monitor the composition of these body fluids in a sex hormone dependent way. Thus, we compared the expression of taste related genes in the choroid plexus of sham and ovariectomized female rats, and then studied the effect of 17β-estradiol and progesterone in their expression and function. We found that the bitter receptors Tas2r109, Tas2r144, and the taste-related genes Plcb2 and Trpm5 were down-regulated by ovarian hormones in vivo and ex vivo with functional implications. Knocking-down Tas2r144 with a specific siRNA in a CPEC line (Z310) effectively reduced the Ca²⁺ response to the bitter compound denatonium benzoate, in a similar manner to female sex hormones alone, suggesting that female sex hormones downregulated the responses of CPEC to chemical stimuli by reducing Tas2r144.

Culture Model for Non-human Primate Choroid Plexus

While there are murine and rat choroid plexus epithelial cell cultures, a translationally relevant model for choroid plexus activation and function is still lacking. The rhesus macaque is the gold standard for modeling viral infection and activation of CNS, including HIV-associated neurocognitive disorders. We have developed a rhesus macaque choroid plexus epithelial cell culture model which we believe to be suitable for studies of inflammation associated with viral infection of the CNS. Epithelial morphology and function were assessed using vimentin, phalloidin, the tight junction protein zonula-occludens-1 (ZO-1), and focal adhesion kinase (FAK). Choroid plexus epithelial cell type was confirmed using immunofluorescence with two proteins highly expressed in the choroid plexus: transthyretin and α-klotho. Finally, barrier properties of the model were monitored using pro- and anti-inflammatory mediators (TNF-α, the TLR2 agonist PamCys3K, and dexamethasone). When pro-inflammatory TNF-α was added to the xCelligence wells, there was a decrease in barrier function, which decreased in a step-wise fashion with each additional administration. This barrier function was repaired upon addition of the steroid dexamethasone. The TLR2 agonist PAM3CysK increased barrier functions in TNF-α treated wells. We have presented a model of the blood-CSF barrier that will allow study into pro- and anti-inflammatory conditions in the brain, while simultaneously measuring real time changes to epithelial cells.

A unique androgen excess signature in idiopathic intracranial hypertension is linked to cerebrospinal fluid dynamics

Idiopathic intracranial hypertension (IIH) is a condition of unknown etiology, characterized by elevated intracranial pressure frequently manifesting with chronic headaches and visual loss. Similar to polycystic ovary syndrome (PCOS), IIH predominantly affects obese women of reproductive age. In this study, we comprehensively examined the systemic and cerebrospinal fluid (CSF) androgen metabolome in women with IIH in comparison with sex-, BMI-, and age-matched control groups with either simple obesity or PCOS (i.e., obesity and androgen excess). Women with IIH showed a pattern of androgen excess distinct to that observed in PCOS and simple obesity, with increased serum testosterone and increased CSF testosterone and androstenedione. Human choroid plexus expressed the androgen receptor, alongside the androgen-activating enzyme aldoketoreductase type 1C3. We show that in a rat choroid plexus cell line, testosterone significantly enhanced the activity of Na⁺/K⁺-ATPase, a surrogate of CSF secretion. We demonstrate that IIH patients have a unique signature of androgen excess and provide evidence that androgens can modulate CSF secretion via the choroid plexus. These findings implicate androgen excess as a potential causal driver and therapeutic target in IIH.

Women with idiopathic intracranial hypertension have a unique androgen excess signature that is associated with modulation of cerebrospinal fluid secretion dynamics.

pH-sensitive polymer micelles provide selective and potentiated lytic capacity to venom peptides for effective intracellular delivery

Endocytosed biomacromolecule delivery systems must escape the endosomal trafficking pathway in order for their cargo to exert effects in other cellular compartments. Although endosomal release is well-recognized as one of the greatest barriers to efficacy of biologic drugs with intracellular targets, most drug carriers have relied on cationic materials that passively induce endosomal swelling and membrane rupture with low efficiency. To address the endosome release challenge, our lab has developed a diblock copolymer system for nucleic acid delivery that selectively displays a potent membrane-lytic peptide (melittin) in response to the pH drop during the endosomal maturation. To further optimize this system, we evaluated a panel of peptides with reported lytic activity in comparison to melittin. Nineteen different lytic peptides were synthesized and their membrane-lytic properties at both neutral and acidic pH characterized using a red blood cell hemolysis assay. The top five performing peptides were then conjugated to our pH-sensitive diblock copolymer via disulfide linkers and used to deliver a variety of nucleic acids to cultured mammalian cells as well as in vivo to the mouse brain. We demonstrate that the sharp pH-transition of VIPER compensates for potential advantages from pH-sensitive peptides, such that polymer-peptide conjugates with poorly selective but highly lytic peptides achieve safe and effective transfection both in vitro and in vivo. In addition, peptides that require release from polymer backbones for lysis were less effective in the VIPER system, likely due to limited endosomal reducing power of target cells. Finally, we show that certain peptides are potentiated in lytic ability by polymer conjugation and that these peptide-polymer constructs are most effective in vivo.

Sex Hormones Protect Against Amyloid-β Induced Oxidative Stress in the Choroid Plexus Cell Line Z310

The choroid plexus (CP) epithelium is a unique structure in the brain that forms an interface between the peripheral blood on the basal side and the cerebrospinal fluid (CSF) on the apical side. It is a relevant source of many polypeptides secreted to the CSF with neuroprotective functions and also participates in the elimination and detoxification of brain metabolites, such as β-amyloid (Aβ) removal from the CSF through transporter-mediated influx. The CP is also a target tissue for sex hormones (SHs) that have recognised neuroprotective effects against a variety of insults, including Aβ toxicity and oxidative stress in the central nervous system. The present study aimed to understand how SHs modulate Aβ-induced oxidative stress in a CP cell line (Z310 cell line) by analysing the effects of Aβ1-42 on oxidative stress, mitochondrial function and apoptosis, as well as by assessing how 17β-oestradiol (E2 ) and 5α-dihydrotestosterone (DHT) modulated these effects and the cellular uptake of Aβ1-42 by CP cells. Our findings show that E2 and DHT treatment reduce Aβ1-42 -induced oxidative stress and the internalisation of Aβ1-42 by CP epithelial cells, highlighting the importance of considering the background of SHs and therefore sex-related differences in Aβ metabolism and clearance by CP cells.

Alix-mediated assembly of the actomyosin-tight junction polarity complex preserves epithelial polarity and epithelial barrier

Maintenance of epithelial cell polarity and epithelial barrier relies on the spatial organization of the actin cytoskeleton and proper positioning/assembly of intercellular junctions. However, how these processes are regulated is poorly understood. Here we reveal a key role for the multifunctional protein Alix in both processes. In a knockout mouse model of Alix, we identified overt structural changes in the epithelium of the choroid plexus and in the ependyma, such as asymmetrical cell shape and size, misplacement and abnormal beating of cilia, blebbing of the microvilli. These defects culminate in excessive cell extrusion, enlargement of the lateral ventricles and hydrocephalus. Mechanistically, we find that by interacting with F-actin, the Par complex and ZO-1, Alix ensures the formation and maintenance of the apically restricted actomyosin-tight junction complex. We propose that in this capacity Alix plays a role in the establishment of apical-basal polarity and in the maintenance of the epithelial barrier.

Neuroinvasion and Inflammation in Viral Central Nervous System Infections

Neurotropic viruses can cause devastating central nervous system (CNS) infections, especially in young children and the elderly. The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) have been described as relevant sites of entry for specific viruses as well as for leukocytes, which are recruited during the proinflammatory response in the course of CNS infection. In this review, we illustrate examples of established brain barrier models, in which the specific reaction patterns of different viral families can be analyzed. Furthermore, we highlight the pathogen specific array of cytokines and chemokines involved in immunological responses in viral CNS infections. We discuss in detail the link between specific cytokines and chemokines and leukocyte migration profiles. The thorough understanding of the complex and interrelated inflammatory mechanisms as well as identifying universal mediators promoting CNS inflammation is essential for the development of new diagnostic and treatment strategies.

'Smelling' the cerebrospinal fluid: olfactory signaling molecules are expressed in and mediate chemosensory signaling from the choroid plexus

The olfactory-type signaling machinery has been known to be involved not only in odorant detection but also in other tissues with unsuspected sensory roles. As a barrier, the choroid plexus (CP) is an active participant in the monitoring of the cerebrospinal fluid (CSF), promptly responding to alterations in its composition. We hypothesized that olfactory signaling could be active in CP, contributing to the surveillance of the CSF composition. We determined the mRNA and protein expression of the major components of the olfactory transduction pathway in the rat CP, including odorant receptors, the olfactory G-protein (Gαolf), adenylate cyclase 3 and cyclic nucleotide-gated channel 2. The functionality of the transduction pathway and the intracellular mechanisms involved were analyzed by DC field potential recording electrophysiological analysis, in an ex vivo CP-brain setup, using polyamines as stimuli and blockers of the downstream signaling pathways. Concentration-dependent responses were obtained for the polyamines studied (cadaverine, putrescine, spermine and spermidine), all known to be present in the CSF. Transfection of a CP epithelial cell line with siRNA against Gαolf effectively knocked down protein expression and reduced the CP cells' response to spermine. Thus, the key components of the olfactory chemosensory apparatus are present and are functional in murine CP, and polyamines seem to trigger both the cAMP and the phospholipase C-inositol 1,4,5-trisphosphate pathways. Olfactory-like chemosensory signaling may be an essential component of the CP chemical surveillance apparatus to detect alterations in the CSF composition, and to elicit responses to modulate and maintain brain homeostasis.

Microbubbles and ultrasound increase intraventricular polyplex gene transfer to the brain

Neurons in the brain can be damaged or lost from neurodegenerative disease, stroke, or traumatic injury. Although neurogenesis occurs in mammalian adult brains, the levels of natural neurogenesis are insufficient to restore function in these cases. Gene therapy has been pursued as a promising strategy to induce differentiation of neural progenitor cells into functional neurons. Non-viral vectors are a preferred method of gene transfer due to potential safety and manufacturing benefits but suffer from lower delivery efficiencies compared to viral vectors. Since the neural stem and progenitor cells reside in the subventricular zone of the brain, intraventricular injection has been used as an administration route for gene transfer to these cells. However, the choroid plexus epithelium remains an obstacle to delivery. Recently, transient disruption of the blood-brain barrier by microbubble-enhanced ultrasound has been used to successfully improve drug delivery to the brain after intravenous injection. In this work, we demonstrate that microbubble-enhanced ultrasound can similarly improve gene transfer to the subventricular zone after intraventricular injection. Microbubbles of different surface charges (neutral, slightly cationic, and cationic) were prepared, characterized by acoustic flow cytometry, and evaluated for their ability to increase the permeability of immortalized choroid plexus epithelium monolayers in vitro. Based on these results, slightly cationic microbubbles were evaluated for microbubble and ultrasound-mediated enhancement of non-viral gene transfer in vivo. When coupled with our previously reported gene delivery vehicles, the slightly cationic microbubbles significantly increased ultrasound-mediated transfection of the murine brain when compared to commercially available Definity® microbubbles. Temporary disruption of the choroid plexus by microbubble-enhanced ultrasound is therefore a viable way of enhancing gene delivery to the brain and merits further research.

Modeling immune functions of the mouse blood-cerebrospinal fluid barrier in vitro: primary rather than immortalized mouse choroid plexus epithelial cells are suited to study immune cell migration across this brain barrier

Background

The blood–cerebrospinal fluid barrier (BCSFB) established by the choroid plexus (CP) epithelium has been recognized as a potential entry site of immune cells into the central nervous system during immunosurveillance and neuroinflammation. The location of the choroid plexus impedes in vivo analysis of immune cell trafficking across the BCSFB. Thus, research on cellular and molecular mechanisms of immune cell migration across the BCSFB is largely limited to in vitro models. In addition to forming contact-inhibited epithelial monolayers that express adhesion molecules, the optimal in vitro model must establish a tight permeability barrier as this influences immune cell diapedesis.

Methods

We compared cell line models of the mouse BCSFB derived from the Immortomouse^® and the ECPC4 line to primary mouse choroid plexus epithelial cell (pmCPEC) cultures for their ability to establish differentiated and tight in vitro models of the BCSFB.

Results

We found that inducible cell line models established from the Immortomouse^® or the ECPC4 tumor cell line did not express characteristic epithelial proteins such as cytokeratin and E-cadherin and failed to reproducibly establish contact-inhibited epithelial monolayers that formed a tight permeability barrier. In contrast, cultures of highly-purified pmCPECs expressed cytokeratin and displayed mature BCSFB characteristic junctional complexes as visualized by the junctional localization of E-cadherin, β-catenin and claudins-1, -2, -3 and -11. pmCPECs formed a tight barrier with low permeability and high electrical resistance. When grown in inverted filter cultures, pmCPECs were suitable to study T cell migration from the basolateral to the apical side of the BCSFB, thus correctly modelling in vivo migration of immune cells from the blood to the CSF.

Conclusions

Our study excludes inducible and tumor cell line mouse models as suitable to study immune functions of the BCSFB in vitro. Rather, we introduce here an in vitro inverted filter model of the primary mouse BCSFB suited to study the cellular and molecular mechanisms mediating immune cell migration across the BCSFB during immunosurveillance and neuroinflammation.

From Single Cells to Engineered and Explanted Tissues: New Perspectives in Bacterial Infection Biology

Cell culture techniques are essential for studying host-pathogen interactions. In addition to the broad range of single cell type-based two-dimensional cell culture models, an enormous amount of coculture systems, combining two or more different cell types, has been developed. These systems enable microscopic visualization and molecular analyses of bacterial adherence and internalization mechanisms and also provide a suitable setup for various biochemical, immunological, and pharmacological applications. The implementation of natural or synthetical scaffolds elevated the model complexity to the level of three-dimensional cell culture. Additionally, several transwell-based cell culture techniques are applied to study bacterial interaction with physiological tissue barriers. For keeping highly differentiated phenotype of eukaryotic cells in ex vivo culture conditions, different kinds of microgravity-simulating rotary-wall vessel systems are employed. Furthermore, the implementation of microfluidic pumps enables constant nutrient and gas exchange during cell cultivation and allows the investigation of long-term infection processes. The highest level of cell culture complexity is reached by engineered and explanted tissues which currently pave the way for a more comprehensive view on microbial pathogenicity mechanisms.

Characterization of efflux transport proteins of the human choroid plexus papilloma cell line HIBCPP, a functional in vitro model of the blood-cerebrospinal fluid barrier

PURPOSE

To characterize the human choroid plexus (CP) papilloma cell line HIBCPP with respect to ABC export protein expression and function in order to evaluate its use as an in vitro model to study carrier-mediated transport processes at the CP.

METHODS

Expression profiles of ABC transporters were studied by quantitative real-time PCR and Western Blot analysis. Functionality of transporters was investigated by means of uptake experiments and permeation studies carried out on permeable filter systems. In addition, immunohistochemistry served to study localization of ABCC1 and ABCC4.

RESULTS

Both qPCR and Western Blot revealed that ABC transporters known to be expressed in CP are also expressed in HIBCPP cells. Immunohistochemistry confirmed basolateral expression of ABCC1. Functionality of ABCC1, ABCC4, ABCB1 and ABCG2 could be shown in uptake assays.

CONCLUSIONS

Altogether, the HIBCPP cells promise to be a functional and relevant in vitro tool to investigate transport processes at the blood-cerebrospinal fluid barrier.

Development of the choroid plexus and blood-CSF barrier

Well-known as one of the main sources of cerebrospinal fluid (CSF), the choroid plexuses have been, and still remain, a relatively understudied tissue in neuroscience. The choroid plexus and CSF (along with the blood-brain barrier proper) are recognized to provide a robust protective effort for the brain: a physical barrier to impede entrance of toxic metabolites to the brain; a “biochemical” barrier that facilitates removal of moieties that circumvent this physical barrier; and buoyant physical protection by CSF itself. In addition, the choroid plexus-CSF system has been shown to be integral for normal brain development, central nervous system (CNS) homeostasis, and repair after disease and trauma. It has been suggested to provide a stem-cell like repository for neuronal and astrocyte glial cell progenitors. By far, the most widely recognized choroid plexus role is as the site of the blood-CSF barrier, controller of the internal CNS microenvironment. Mechanisms involved combine structural diffusion restraint from tight junctions between plexus epithelial cells (physical barrier) and specific exchange mechanisms across the interface (enzymatic barrier). The current hypothesis states that early in development this interface is functional and more specific than in the adult, with differences historically termed as “immaturity” actually correctly reflecting developmental specialization. The advanced knowledge of the choroid plexus-CSF system proves itself imperative to understand a range of neurological diseases, from those caused by plexus or CSF drainage dysfunction (e.g., hydrocephalus) to more complicated late-stage diseases (e.g., Alzheimer's) and failure of CNS regeneration. This review will focus on choroid plexus development, outlining how early specializations may be exploited clinically.

Brain disposition of α-Synuclein: roles of brain barrier systems and implications for Parkinson's disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by the accumulation of α-Synuclein (a-Syn) into Lewy body inclusions and the loss of dopaminergic neurons in the substantia nigra (SN). Accumulation of a-Syn can induce a progressive, cyclical pathology that results in the transmission of toxic, aggregated a-Syn species to healthy neurons, leading to further neurodegeneration such as occurs in PD. The blood–brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barriers (BCSFB) are responsible for regulating the access of nutrients and other molecules to the brain, but very little is known about their regulatory roles in maintaining the homeostasis of a-Syn in the CSF and brain parenchyma. This review analyzes the current literature reports on the transport of a-Syn by various brain cell types with a particular focus on the potential transport mechanisms of a-Syn at the BBB and BCSFB. The indication of altered a-Syn transport by brain barriers in PD pathoetiology and the perspectives in this research area are also discussed.

The role of choroid plexus in IVIG-induced beta-amyloid clearance

We have shown that intravenous immunoglobulin (IVIG) contains anti-Aβ autoantibodies and IVIG could induce beta amyloid (Aβ) efflux from cerebrospinal fluid (CSF) to blood in both Multiple Sclerosis (MS) and Alzheimer disease (AD) patients. However, the molecular mechanism underlying IVIG-induced Aβ efflux remains unclear. In this study, we used amyloid precursor protein (AβPP) transgenic mice to investigate if the IVIG could induce efflux of Aβ from the brain and whether low-density lipoprotein receptor-related protein-1 (LRP1), a hypothetic Aβ transporter in blood-CSF barrier (BCB); could mediate this clearance process. We currently provide strong evidence to demonstrate that IVIG could reduce brain Aβ levels by pulling Aβ into the blood system in AβPP transgenic mice. In the mechanistic study, IVIG could induce Aβ efflux through the in vitro BCB membrane formed by cultured BCB epithelial cells. Both receptor-associated protein (RAP; a functional inhibitor of LRP1), and LRP1 siRNA were able to significantly inhibit the Aβ efflux. Should Aβ prove to be the underlying cause of AD, our results strongly suggest that IVIG could be beneficial in the therapy for AD by inducing efflux of Aβ from the brain through the LRP1 in the BCB.

Development of a physiologically-based pharmacokinetic model of the rat central nervous system

Central nervous system (CNS) drug disposition is dictated by a drug's physicochemical properties and its ability to permeate physiological barriers. The blood-brain barrier (BBB), blood-cerebrospinal fluid barrier and centrally located drug transporter proteins influence drug disposition within the central nervous system. Attainment of adequate brain-to-plasma and cerebrospinal fluid-to-plasma partitioning is important in determining the efficacy of centrally acting therapeutics. We have developed a physiologically-based pharmacokinetic model of the rat CNS which incorporates brain interstitial fluid (ISF), choroidal epithelial and total cerebrospinal fluid (CSF) compartments and accurately predicts CNS pharmacokinetics. The model yielded reasonable predictions of unbound brain-to-plasma partition ratio (Kpuu,brain) and CSF:plasma ratio (CSF:Plasmau) using a series of in vitro permeability and unbound fraction parameters. When using in vitro permeability data obtained from L-mdr1a cells to estimate rat in vivo permeability, the model successfully predicted, to within 4-fold, Kpuu,brain and CSF:Plasmau for 81.5% of compounds simulated. The model presented allows for simultaneous simulation and analysis of both brain biophase and CSF to accurately predict CNS pharmacokinetics from preclinical drug parameters routinely available during discovery and development pathways.

Regulation of copper transport crossing brain barrier systems by Cu-ATPases: effect of manganese exposure

Regulation of cellular copper (Cu) homeostasis involves Cu-transporting ATPases (Cu-ATPases), i.e., ATP7A and ATP7B. The question as to how these Cu-ATPases in brain barrier systems transport Cu, i.e., toward brain parenchyma, cerebrospinal fluid (CSF), or blood, remained unanswered. This study was designed to characterize roles of Cu-ATPases in regulating Cu transport at the blood-brain barrier (BBB) and blood-CSF barrier (BCB) and to investigate how exposure to toxic manganese (Mn) altered the function of Cu-ATPases, thereby contributing to the etiology of Mn-induced parkinsonian disorder. Studies by quantitative real-time RT-PCR (qPCR), Western blot, and immunocytochemistry revealed that both Cu-ATPases expressed abundantly in BBB and BCB. Transport kinetic studies by in situ brain infusion and ventriculo-cisternal (VC) perfusion in Sprague Dawley rat suggested that the BBB was a major site for Cu entry into brain, whereas the BCB was a predominant route for Cu efflux from the CSF to blood. Confocal evidence showed that the presence of excess Cu or Mn in the choroid plexus cells led to ATP7A relocating toward the apical microvilli facing the CSF, but ATP7B toward the basolateral membrane facing blood. Mn exposure inhibited the production of both Cu-ATPases. Collectively, these data suggest that Cu is transported by the BBB from the blood to brain, which is mediated by ATP7A in brain capillary. By diffusion, Cu ions move from the interstitial fluid into the CSF, where they are taken up by the BCB. Within the choroidal epithelial cells, Cu ions are transported by ATP7B back to the blood. Mn exposure alters these processes, leading to Cu dyshomeostasis-associated neuronal injury.

Upregulation of zinc transporter 2 in the blood-CSF barrier following lead exposure

Zinc (Zn) is an essential element for normal brain function; an abnormal Zn homeostasis in brain and the cerebrospinal fluid (CSF) has been implied in the etiology of Alzheimer's disease (AD). However, the mechanisms that regulate Zn transport in the blood-brain interface remain unknown. This study was designed to investigate Zn transport by the blood-CSF barrier (BCB) in the choroid plexus, with a particular focus on Zn transporter-2 (ZnT2), and to understand if lead (Pb) accumulation in the choroid plexus disturbed the Zn regulatory function in the BCB. Confocal microscopy, quantitative PCR and western blot demonstrated the presence of ZnT2 in the choroidal epithelia; ZnT2 was primarily in cytosol in freshly isolated plexus tissues but more toward the peripheral membrane in established choroidal Z310 cells. Exposure of rats to Pb (single ip injection of 50 mg Pb acetate/kg) for 24 h increased ZnT2 fluorescent signals in plexus tissues by confocal imaging and protein expression by western blot. Similar results were obtained by in vitro experiments using Z310 cells. Further studies using cultured cells and a two-chamber Transwell device showed that Pb treatment significantly reduced the cellular Zn concentration and led to an increased transport of Zn across the BCB, the effect that may be due to the increased ZnT2 by Pb exposure. Taken together, these results indicate that ZnT2 is present in the BCB; Pb exposure increases the ZnT2 expression in choroidal epithelial cells by a yet unknown mechanism and as a result, more Zn ions may be deposited into the intracellular Zn pool, leading to a relative Zn deficiency state in the cytoplasm at the BCB.

Choroid plexus transcytosis and exosome shuttling deliver folate into brain parenchyma

Loss of folate receptor-α function is associated with cerebral folate transport deficiency and childhood-onset neurodegeneration. To clarify the mechanism of cerebral folate transport at the blood-cerebrospinal fluid barrier, we investigate the transport of 5-methyltetrahydrofolate in polarized cells. Here we identify folate receptor-α-positive intralumenal vesicles within multivesicular bodies and demonstrate the directional cotransport of human folate receptor-α, and labelled folate from the basolateral to the apical membrane in rat choroid plexus cells. Both the apical medium of folate receptor-α-transfected rat choroid plexus cells and human cerebrospinal fluid contain folate receptor-α-positive exosomes. Loss of folate receptor-α-expressing cerebrospinal fluid exosomes correlates with severely reduced 5-methyltetrahydrofolate concentration, corroborating the importance of the folate receptor-α-mediated folate transport in the cerebrospinal fluid. Intraventricular injections of folate receptor-α-positive and -negative exosomes into mouse brains demonstrate folate receptor-α-dependent delivery of exosomes into the brain parenchyma. Our results unravel a new pathway of folate receptor-α-dependent exosome-mediated folate delivery into the brain parenchyma and opens new avenues for cerebral drug targeting.

Involvement of CTR1 and ATP7A in lead (Pb)-induced copper (Cu) accumulation in choroidal epithelial cells

The blood-cerebrospinal fluid barrier (BCB) plays a key role in maintaining copper (Cu) homeostasis in the brain. Cumulative evidences indicate that lead (Pb) exposure alters cerebral Cu homeostasis, which may underlie the development of neurodegenerative diseases. This study investigated the roles of Cu transporter 1 (CTR1) and ATP7A, two Cu transporters, in Pb-induced Cu accumulation in the choroidal epithelial cells. Pb exposure resulted in increased intracellular (64)Cu retention, accompanying with up-regulated CTR1 level. Knockdown of CTR1 using siRNA before Pb exposure diminished the Pb-induced increase of (64)Cu uptake. The expression level of ATP7A was down-regulated following the Pb exposure. ATP7A siRNA knockdown, or PCMB treatment, inhibited the (64)Cu efflux from the cells, while the following additional incubation with Pb failed to further increase the intracellular (64)Cu retention. Cu exposure, or intracellular Cu accumulation following the tetracycline (Tet)-induced overexpression of CTR1, did not result in significant change in ATP7A expression. Taken together, these data indicate that CTR1 and ATP7A play important roles in Cu transport in choroidal epithelial cells, and the Pb-induced intracellular Cu accumulation appears to be mediated, at least in part, via the alteration of CTR1 and ATP7A expression levels following Pb exposure.

Synergistic interactions between cytokines and AVP at the blood-CSF barrier result in increased chemokine production and augmented influx of leukocytes after brain injury

Several lines of evidence indicate that the blood-cerebrospinal fluid barrier (BCSFB), which primarily resides in the choroid plexus (CP), plays a significant pathophysiological role not only in neuroinflammatory diseases, such as multiple sclerosis, but also in traumatic brain injury (TBI). Here we investigated how arginine vasopressin (AVP) regulates function of the BCSFB in the context of post-traumatic neuroinflammation. It has previously been shown that AVP exacerbates various forms of brain injury, but the mechanisms underlying this AVP action are poorly understood. Type 1A AVP receptor is highly expressed on the CP epithelium and the CP synthesizes AVP. Using the controlled cortical impact model of TBI, we demonstrated decreased post-traumatic production of proinflammatory mediators by the CP and reduced influx of inflammatory cells across the BCSFB in AVP-deficient Brattleboro rats when compared with Long-Evans rats, a parental strain for Brattleboro rats. Arginine vasopressin was also found to play an important role in post-traumatic activation of c-Jun N-terminal kinase (JNK) in the CP. In the CP epithelial cell cultures, AVP augmented the tumor necrosis factor-α– and interleukin-1β–dependent increase in synthesis of proinflammatory mediators, including neutrophil chemoattractants, an action largely dependent on the JNK signaling pathway. Under in vivo conditions, a selective JNK inhibitor decreased the post-traumatic production of neutrophil chemoattractants by the CP and reduced the influx of neutrophils across the BCSFB. These results provide evidence for the synergistic interactions between proinflammatory cytokines and AVP, a ligand for G protein-coupled receptors, and support a pathophysiological role of AVP in post-traumatic neuroinflammation.

Ultrahigh accuracy imaging modality for super-localization microscopy

Super-localization microscopy encompasses techniques that depend on the accurate localization of individual molecules from generally low-light images. The obtainable localization accuracies, however, are ultimately limited by the image detector's pixelation and noise. We present the ultrahigh accuracy imaging modality (UAIM), which allows users to obtain accuracies approaching the accuracy that is achievable only in the absence of detector pixelation and noise, and which we found can experimentally provide a >200% accuracy improvement over conventional low-light imaging.

Culture models to study leukocyte trafficking across the choroid plexus

Background

A critical point during the course of central nervous system infection is the influx of leukocytes from the blood into the brain across the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). However, experimental in vitro models to investigate leukocyte transmigration across cultured choroid plexus epithelial cells have been lacking so far.

Methods

We have developed a porcine and human “inverted” culture insert system that enables leukocyte transmigration specifically from the physiologically relevant basolateral side. The models use primary porcine choroid plexus epithelial cells (PCPEC) and human choroid plexus papilloma cells (HIBCPP). As a prerequisite for a functional barrier, we optimized culture conditions in which cells are maintained in serum-containing medium until high barrier function is reached. Leukocyte transmigration through the plexus epithelial cells is analysed by three-dimensional Apotome^®-imaging and electron microscopy, and the route of transmigration through the plexus epithelial cells, i.e. transcellular as well as paracellular, can be determined.

Discussion

As a functionally relevant porcine and human BCSFB model, PCPEC and HIBCPP respectively, offer a wide range of options for analysis of disease-related mechanisms at the choroid plexus epithelium, especially involving human pathogens. Moreover, our in vitro models facilitate the investigation of leukocyte entry into the CNS via the blood-CSF barrier.

Culture of choroid plexus epithelial cells and in vitro model of blood-CSF barrier

Chemical homeostasis in the extracellular fluid of the central nervous system (CNS) is maintained by two brain barrier systems, i.e., the blood-brain barrier (BBB) that separates the blood circulation from brain interstitial fluid and the blood-cerebrospinal fluid barrier (BCB) that separates the blood from the cerebrospinal fluid (CSF). The choroid plexus, where the BCB is located, is a polarized tissue, with the basolateral side of the choroidal epithelium facing the blood and the apical microvilli in direct contact with the CSF. The tissue plays a wide range of roles in brain development, aging, nutrient transport, endocrine regulation, and pathogenesis of certain neurodegenerative disorders. This chapter describes two in vitro cultures that have been well established to allow for study of the BCB structure and function. The primary choroidal epithelial cell culture can be established from rat choroid plexus tissue, and a similar immortalized murine choroidal epithelial cell culture known as Z310 cells has also been established. Both cultures display a dominant polygonal morphology, and immunochemical studies demonstrate the presence of transthyretin, a thyroxine transport protein known to be exclusively produced by the choroidal epithelia in the CNS. These cultures have been adapted for use on freely permeable Transwell(®) membranes sandwiched between two culture chambers, facilitating transport studies of various compounds across this barrier in vitro. These choroidal epithelia cultures with the Transwell system will perceivably assist blood-CSF barrier research.

3D single molecule tracking with multifocal plane microscopy reveals rapid intercellular transferrin transport at epithelial cell barriers

The study of intracellular transport pathways at epithelial cell barriers that line diverse tissue sites is fundamental to understanding tissue homeostasis. A major impediment to investigating such processes at the subcellular level has been the lack of imaging approaches that support fast three-dimensional (3D) tracking of cellular dynamics in thick cellular specimens. Here, we report significant advances in multifocal plane microscopy and demonstrate 3D single molecule tracking of rapid protein dynamics in a 10 micron thick live epithelial cell monolayer. We have investigated the transferrin receptor (TfR) pathway, which is not only essential for iron delivery but is also of importance for targeted drug delivery across cellular barriers at specific body sites, such as the brain that is impermeable to blood-borne substances. Using multifocal plane microscopy, we have discovered a cellular process of intercellular transfer involving rapid exchange of Tf molecules between two adjacent cells in the monolayer. Furthermore, 3D tracking of Tf molecules at the lateral plasma membrane has led to the identification of different modes of endocytosis and exocytosis, which exhibit distinct temporal and intracellular spatial trajectories. These results reveal the complexity of the 3D trafficking pathways in epithelial cell barriers. The methods and approaches reported here can enable the study of fast 3D cellular dynamics in other cell systems and models, and underscore the importance of developing advanced imaging technologies to study such processes.

Loss of TP53 expression in immortalized choroid plexus epithelial cells results in increased resistance to anticancer agents

Choroid plexus carcinomas are malignant brain tumors predominantly arising in young children. Because a prognostic role of p53 alterations has been demonstrated, further research into potential underlying mechanisms is essential. Our objective was, therefore, to investigate the role of p53 in the growth-inhibitory potential of a variety of anticancer agents in the rodent choroid plexus epithelial cell line Z310. Furthermore, association of p53 alterations with proliferative activity (Ki67/MIB1) in choroid plexus carcinoma samples (N = 20) was examined by use of immunohistochemistry. Silencing of TP53 expression did not significantly alter metabolic activity in Z310 cells and p53 protein expression status was not associated with increased proliferative activity in choroid plexus carcinomas. However, the growth-inhibitory activity of vincristine, doxorubicin, carboplatin, etoposide, and temozolomide was significantly impaired by silencing of TP53. In conclusion, these results indicate a potential predictive role of p53 in choroid plexus carcinomas. Alterations of p53 should be taken into account when evaluating the effect of anticancer agents in future clinical trials.

A novel porcine in vitro model of the blood-cerebrospinal fluid barrier with strong barrier function

Epithelial cells of the plexus choroideus form the structural basis of the blood-cerebrospinal fluid barrier (BCSFB). In vitro models of the BCSFB presenting characteristics of a functional barrier are of significant scientific interest as tools for examination of BCSFB function. Due to a lack of suitable cell lines as in vitro models, primary porcine plexus epithelial cells were subjected to a series of selective cultivation steps until a stable continuous subcultivatable epithelial cell line (PCP-R) was established. PCP-R cells grow in a regular polygonal pattern with a doubling time of 28–36 h. At a cell number of 1.5×10⁵ in a 24-well plate confluence is reached in 56–72 h. Cells are cytokeratin positive and chromosomal analysis revealed 56 chromosomes at peak (84th subculture). Employing reverse transcription PCR mRNA expression of several transporters and components of cell junctions could be detected. The latter includes tight junction components like Claudin-1 and -3, ZO-1, and Occludin, and the adherens junction protein E-cadherin. Cellular localization studies of ZO-1, Occludin and Claudin-1 by immunofluorescence and morphological analysis by electron microscopy demonstrated formation of a dense tight junction structure. Importantly, when grown on cell culture inserts PCP-R developed typical characteristics of a functional BCSFB including high transepithelial electrical resistance above 600 Ω×cm² as well as low permeability for macromolecules. In summary, our data suggest the PCP-R cell line as a suitable in vitro model of the porcine BCSFB.

Protective effects of isothiocyanates on blood-CSF barrier disruption induced by oxidative stress

The choroid plexuses (CPs) form the blood-cerebrospinal fluid (CSF) barrier (BCSFB) and play an important role in maintaining brain normal function and the brain response to injury. Many neurological disorders are associated with oxidative stress that can impact CP function. This study examined the effects of isothiocyanates, an abundant component in cruciferous vegetables, on H(2)O(2)-induced BCSFB disruption and CP cell death in vitro. It further examined the potential role of a transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), in isothiocyanate-induced protection. Sulforaphane (SF) significantly reduced H(2)O(2)-induced BCSFB disruption as assessed by transepithelial electrical resistance (29 ± 7% reduction vs. 92 ± 2% decrease in controls) and [(3)H]mannitol permeability. Allyl-isothiocyanate (AITC) had a similar protective effect. H(2)O(2)-induced epithelial cell death was also reduced by these isothiocyanates. In primary CP cells, SF and AITC reduced cell death by 42 ± 3% and 53 ± 10%, respectively. Similar protection was found in a CP cell line Z310. Protection was only found with pretreatment for 12-48 h and not with acute exposure (1 h). The protective effects of SF and AITC were associated with Nrf2 nuclear translocation and upregulated expression of antioxidative systems regulated by Nrf2, including heme oxygenase-1, NAD(P)H quinine oxidoreductase, and cysteine/glutamate exchange transporter. Thus isothiocyanates, as diet or medicine, may be a method for protecting BCSFB in neurological disorders.

Mechanism of copper transport at the blood-cerebrospinal fluid barrier: influence of iron deficiency in an in vitro model

Copper (Cu) is an essential trace element that requires tight homeostatic regulation to ensure appropriate supply while not causing cytotoxicity due to its strong redox potential. Our previous in vivo study has shown that iron deficiency (FeD) increases Cu levels in brain tissues, particularly in the choroid plexus, where the blood-cerebrospinal fluid (CSF) barrier resides. This study was designed to elucidate the mechanism by which FeD results in excess Cu accumulation at the blood-CSF barrier. The effect of FeD on cellular Cu retention and transporters Cu transporter-1 (Ctr1), divalent metal transporter 1 (DMT1), antioxidant protein-1 (ATOX1) and ATP7A was examined in choroidal epithelial Z310 cells. The results revealed that deferoximine treatment (FeD) resulted in 70% increase in cellular Cu retention (P < 0.05). A significant increase in the mRNA levels of DMT1, but not Ctr1, was also observed after FeD treatment, suggesting a critical role of DMT1 in cellular Cu regulation during FeD. Knocking down Ctr1 or DMT1 resulted in significantly lower Cu uptake by Z310 cells, whereas the knocking down of ATOX1 or ATP7A led to substantial increases of cellular retention of Cu. Taken together, these results suggest that Ctr1, DMT1, ATOX1 and ATP7A contribute to Cu transport at the blood-CSF barrier, and that the accumulation of intracellular Cu found in the Z310 cells during FeD appears to be mediated, at least in part, via the upregulation of DMT1 after FeD treatment.

Relative contribution of CTR1 and DMT1 in copper transport by the blood-CSF barrier: implication in manganese-induced neurotoxicity

The homeostasis of copper (Cu) in the cerebrospinal fluid (CSF) is partially regulated by the Cu transporter-1 (CTR1) and divalent metal transporter-1 (DMT1) at the blood-CSF barrier (BCB) in the choroid plexus. Data from human and animal studies suggest an increased Cu concentration in blood, CSF, and brains following in vivo manganese (Mn) exposure. This study was designed to investigate the relative role of CTR1 and DMT1 in Cu transport under normal or Mn-exposed conditions using an immortalized choroidal Z310 cell line. Mn exposure in vitro resulted in an increased cellular 64Cu uptake and the up-regulation of both CTR1 and DMT1. Knocking down CTR1 by siRNA counteracted the Mn-induced increase of 64Cu uptake, while knocking down DMT1 siRNA resulted in an increased cellular 64Cu uptake in Mn-exposed cells. To distinguish the roles of CTR1 and DMT1 in Cu transport, the Z310 cell-based tetracycline (Tet)-inducible CTR1 and DMT1 expression cell lines were developed, namely iZCTR1 and iZDMT1 cells, respectively. In iZCTR1 cells, Tet induction led to a robust increase (25 fold) of 64Cu uptake with the time course corresponding to the increased CTR1. Induction of DMT1 by Tet in iZDMT1 cells, however, resulted in only a slight increase of 64Cu uptake in contrast to a substantial increase in DMT1 mRNA and protein expression. These data indicate that CTR1, but not DMT1, plays an essential role in transporting Cu by the BCB in the choroid plexus. Mn-induced cellular overload of Cu at the BCB is due, primarily, to Mn-induced over-expression of CTR1.