Pentosan polysulfate protects brain endothelial cells against bacterial lipopolysaccharide-induced damages

Taraxacum coreanum (Korean Dandelion) Extract Protects Against Lipopolysaccharide-Induced Blood-Brain Barrier Destruction via Regulation of Tight Junctions and Inflammatory Responses in bEnd.3 Cells

Dysfunction of the blood-brain barrier (BBB) is closely related to neuroinflammation-mediated neurodegenerative disorders. Lipopolysaccharide (LPS), an endotoxin, can cause inflammation by impairing the brain endothelial barrier function and increasing the BBB permeability. Although Taraxacum coreanum NAKAI extract (TC), a traditional medicine widely used in Korea, has antioxidant and anti-inflammatory properties, the protective effects on neuroinflammation and BBB dysfunction are not fully understood. In the present study, bEnd.3 cerebral vascular endothelial cells were treated with TC followed by LPS exposure, and the effects on transendothelial electrical resistance (TEER) values, pro-inflammatory cytokine production, and expression of proteins related to inflammatory responses and tight junction integrity were assessed. The TC-treated group exhibited elevated TEER values in bEnd.3 monolayer compared to LPS-only treated group. In addition, TC treatment increased the expression of proteins involved in the tight junctions, such as ZO-1, claudin-5, and occludin. Furthermore, the TC-treated group suppressed the proteins expression-related to nuclear factor-κB (NF-κB) pathway. Taken together, TC attenuates LPS-induced neuroinflammatory responses by regulating NF-κB activation, which may contribute to protecting against BBB disruption. These findings suggest that TC may have the potential to be used as a material for functional foods to prevent neuroinflammation-related brain diseases.

Activation of glial cells induces proinflammatory properties in brain capillary endothelial cells in vitro

Neurodegenerative diseases are often accompanied by neuroinflammation and impairment of the blood-brain barrier (BBB) mediated by activated glial cells through their release of proinflammatory molecules. To study the effects of glial cells on mouse brain endothelial cells (mBECs), we developed an in vitro BBB model with inflammation by preactivating mixed glial cells (MGCs) with lipopolysaccharide (LPS) before co-culturing with mBECs to study the influence of molecules released by activated MGCs. The response of the mBECs to activated MGCs was compared to direct stimulation with LPS. The cytokine profile of activated MGCs was analyzed together with their effects on the mBEC's integrity, expression of tight junction proteins, adhesion molecules, and BBB-specific transport proteins. Stimulation of MGCs significantly upregulated mRNA expression and secretion of several pro-inflammatory cytokines. Co-culturing mBECs with pre-stimulated MGCs significantly affected the barrier integrity of mBECs similar to direct stimulation with LPS. The gene expression levels of tight junction proteins were unaltered, but tight junction proteins revealed rearrangements with respect to subcellular distribution. Compared to direct stimulation with LPS, the expression of cell-adhesion molecules was significantly increased when mBECs were co-cultured with prestimulated MGCs and thus pre-activating MGCs transforms mBECs into a proinflammatory phenotype.

Impaired instructive and protective barrier functions of the endothelial cell glycocalyx pericellular matrix is impacted in COVID-19 disease

The aim of this study was to review the roles of endothelial cells in normal tissue function and to show how COVID-19 disease impacts on endothelial cell properties that lead to much of its associated symptomatology. This places the endothelial cell as a prominent cell type to target therapeutically in the treatment of this disorder. Advances in glycosaminoglycan analytical techniques and functional glycomics have improved glycosaminoglycan mimetics development, providing agents that can more appropriately target various aspects of the behaviour of the endothelial cell in-situ and have also provided polymers with potential to prevent viral infection. Thus, promising approaches are being developed to combat COVID-19 disease and the plethora of symptoms this disease produces. Glycosaminoglycan mimetics that improve endothelial glycocalyx boundary functions have promising properties in the prevention of viral infection, improve endothelial cell function and have disease-modifying potential. Endothelial cell integrity, forming tight junctions in cerebral cell populations in the blood-brain barrier, prevents the exposure of the central nervous system to circulating toxins and harmful chemicals, which may contribute to the troublesome brain fogging phenomena reported in cognitive processing in long COVID disease.

Metabolic Endotoxemia: From the Gut to Neurodegeneration

Metabolic endotoxemia is a severe health problem for residents in developed countries who follow a Western diet, disrupting intestinal microbiota and the whole organism's homeostasis. Although the effect of endotoxin on the human immune system is well known, its long-term impact on the human body, lasting many months or even years, is unknown. This is due to the difficulty of conducting in vitro and in vivo studies on the prolonged effect of endotoxin on the central nervous system. In this article, based on the available literature, we traced the path of endotoxin from the intestines to the blood through the intestinal epithelium and factors promoting the development of metabolic endotoxemia. The presence of endotoxin in the bloodstream and the inflammation it induces may contribute to lowering the blood-brain barrier, potentially allowing its penetration into the central nervous system; although, the theory is still controversial. Microglia, guarding the central nervous system, are the first line of defense and respond to endotoxin with activation, which may contribute to the development of neurodegenerative diseases. We traced the pro-inflammatory role of endotoxin in neurodegenerative diseases and its impact on the epigenetic regulation of microglial phenotypes.

Effect of esketamine pretreatment on acute sepsis-associated encephalopathy

PURPOSE

Esketamine, the S(+) enantiomer of ketamine, exhibits good anesthetic efficacy and controllability; however, its potential clinical applications, particularly in sepsis-associated encephalopathy (SAE), remain underexplored. SAE involves the development of diffuse brain dysfunction after sepsis, leading to markedly increased sepsis-related disability and mortality. In this study, we investigated the effects of esketamine pretreatment on acute SAE.

METHODS

Mice were randomly divided into four groups: control (C, n = 22), acute SAE (L, n = 22), esketamine pretreatment + acute SAE (EL, n = 22), and nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor (ML385) + esketamine pretreatment + acute SAE (N + EL, n = 22). Acute SAE was established using intraperitoneal (i.p.) injection of lipopolysaccharide (LPS; 10 mg/kg), while controls received equal amounts of saline. The EL group received daily i.p. injections of esketamine (10 mg/kg) for 5 consecutive days, followed by LPS on day 6. The N + EL group received i.p. injections of ML385 (30 mg/kg) 1 h before esketamine pretreatment. The remainder of treatment followed the same protocol as the EL group. Behavioral tests were performed 24 h post-LPS injection, and whole blood and brain tissues were collected for further analysis.

RESULTS

Esketamine improved sepsis symptoms, 7-day survival, and spatial cognitive impairment, without altering locomotor activity. Moreover, esketamine reversed the LPS-induced increase in serum S100 calcium-binding protein β and neuron-specific enolase levels and reduced hippocampal neuroinflammation, oxidative stress, and neuronal apoptosis in the EL group. However, these neuroprotective effects of esketamine were reversed by ML385.

CONCLUSION

The results of our study suggest that esketamine pretreatment mitigates acute SAE, highlighting the involvement of the Nrf2/heme oxygenase-1 pathway in mediating its neuroprotective effects.

Pentosan Polysulfate Affords Pleotropic Protection to Multiple Cells and Tissues

Pentosan polysulfate (PPS), a small semi-synthetic highly sulfated heparan sulfate (HS)-like molecule, shares many of the interactive properties of HS. The aim of this review was to outline the potential of PPS as an interventional therapeutic protective agent in physiological processes affecting pathological tissues. PPS is a multifunctional molecule with diverse therapeutic actions against many disease processes. PPS has been used for decades in the treatment of interstitial cystitis and painful bowel disease, it has tissue-protective properties as a protease inhibitor in cartilage, tendon and IVD, and it has been used as a cell-directive component in bioscaffolds in tissue engineering applications. PPS regulates complement activation, coagulation, fibrinolysis and thrombocytopenia, and it promotes the synthesis of hyaluronan. Nerve growth factor production in osteocytes is inhibited by PPS, reducing bone pain in osteoarthritis and rheumatoid arthritis (OA/RA). PPS also removes fatty compounds from lipid-engorged subchondral blood vessels in OA/RA cartilage, reducing joint pain. PPS regulates cytokine and inflammatory mediator production and is also an anti-tumor agent that promotes the proliferation and differentiation of mesenchymal stem cells and the development of progenitor cell lineages that have proven to be useful in strategies designed to effect repair of the degenerate intervertebral disc (IVD) and OA cartilage. PPS stimulates proteoglycan synthesis by chondrocytes in the presence or absence of interleukin (IL)-1, and stimulates hyaluronan production by synoviocytes. PPS is thus a multifunctional tissue-protective molecule of potential therapeutic application for a diverse range of disease processes.

Role of interleukin-6 and interleukin-10 in morphological and functional changes of the blood-brain barrier in hypertriglyceridemia

BACKGROUND

Hypertriglyceridemia is closely linked to atherosclerosis related inflammatory processes and blood-brain barrier (BBB) dysfunction. Using apolipoprotein B-100 (APOB-100) transgenic mice, an animal model of chronic hypertriglyceridemia, we analyzed BBB function and morphology in vitro and ex vivo. Our objective was to determine which BBB characteristics are produced mainly by interleukin (IL)-6, an atherosclerosis promoting cytokine, and whether these actions can be antagonized by IL-10, an anti-inflammatory cytokine.

METHODS

Brain endothelial and glial cell cultures and brain microvessels were isolated from wild type (WT) and APOB-100 transgenic mice and were treated with IL-6, IL-10 and their combination. First, IL-6 and IL-10 production was measured in WT and APOB-100 microvessels using qPCR. Then functional parameters of endothelial cell cultures were analyzed and immunocytochemistry for key BBB proteins was performed.

RESULTS

IL-6 mRNA levels were higher in brain microvessels than in brain parenchyma of APOB-100 transgenic mice. Transendothelial electric resistance and P-glycoprotein activity were lower, and paracellular permeability was higher in cultured APOB-100 brain endothelial cells. These features were sensitive to both IL-6 and IL-10 treatments. A decreased P-glycoprotein immunostaining was measured in transgenic endothelial cells under control conditions and in WT cells after treating them with IL-6. This effect was antagonized by IL-10. Changes in immunostaining for tight junction proteins were observed after IL-6 exposure, which were in part antagonized by IL-10. In glial cell cultures an increase in aquaporin-4 immunolabeling in the transgenic group and an increase in microglia cell density in WT glia cultures was detected after IL-6 treatment, which was antagonized by IL-10. In isolated brain microvessels a decrease in P-glycoprotein immunolabeled area fraction was measured in APOB-100 microvessels under control conditions and in WT microvessels after every cytokine treatment. ZO-1 immunolabeling showed characteristics similar to that of P-glycoprotein. No change was seen in claudin-5 and occludin immunoreactive area fractions in microvessels. A decrease in aquaporin-4 immunoreactivity was measured in WT microvessels treated by IL-6, which was antagonized by IL-10.

CONCLUSION

IL-6 produced in microvessels contributes to BBB impairment observed in the APOB-100 mice. We showed that IL-10 partly antagonizes the effects of IL-6 at the BBB.

In Vitro Study of the Blood-Brain Barrier Transport of Natural Compounds Recovered from Agrifood By-Products and Microalgae

Agrifood by-products and microalgae represent a low-cost and valuable source of bioactive compounds with neuroprotective properties. However, the neuroprotective effectiveness of therapeutic molecules can be limited by their capacity to cross the blood-brain barrier (BBB) and reach the brain. In this research, various green extracts from Robinia pseudoacacia (ASFE), Cyphomandra betacea (T33), Coffea arabica (PPC1), Olea europaea L., (OL-SS), Citrus sinensis (PLE100) by-products and from the microalgae Dunaliella salina (DS) that have demonstrated in vitro neuroprotective potential were submitted to an in vitro BBB permeability and transport assay based on an immortalized human brain microvascular endothelial cells (HBMEC) model. Toxicity and BBB integrity tests were performed, and the transport of target bioactive molecules across the BBB were evaluated after 2 and 4 h of incubation using gas and liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (GC/LC-Q-TOF-MS). The HBMEC-BBB transport assay revealed a high permeability of representative neuroprotective compounds, such as mono- and sesquiterpenoids, phytosterols and some phenolic compounds. The obtained results from the proposed in vitro BBB cellular model provide further evidence of the neuroprotective potential of the target natural extracts, which represent a promising source of functional ingredients to be transferred into food supplements, food additives, or nutraceuticals with scientifically supported neuroprotective claims.

Cytoskeleton Elements Contribute to Prion Peptide-Induced Endothelial Barrier Breakdown in a Blood–Brain Barrier In Vitro System

The mechanisms involved in the interaction of PrP 106-126, a peptide corresponding to the prion protein amyloidogenic region, with the blood–brain barrier (BBB) were studied. PrP 106-126 treatment that was previously shown to impair BBB function, reduced cAMP levels in cultured brain endothelial cells, increased nitric oxide (NO) levels, and changed the activation mode of the small GTPases Rac1 (inactivation) and RhoA (activation). The latter are well established regulators of endothelial barrier properties that act via cytoskeletal elements. Indeed, liquid chromatography-mass spectrometry (LC-MS)-based proteomic profiling study revealed extensive changes in expression of cytoskeleton-related proteins. These results shed light on the nature of the interaction between the prion peptide PrP 106-126 and the BBB and emphasize the importance of the cytoskeleton in endothelium response to prion- induced stress.

Blood-Brain Barrier Disruption by Lipopolysaccharide and Sepsis-Associated Encephalopathy

As a complex multicellular structure of the vascular system at the central nervous system (CNS), the blood-brain barrier (BBB) separates the CNS from the system circulation and regulates the influx and efflux of substances to maintain the steady-state environment of the CNS. Lipopolysaccharide (LPS), the cell wall component of Gram-negative bacteria, can damage the barrier function of BBB and further promote the occurrence and development of sepsis-associated encephalopathy (SAE). Here, we conduct a literature review of the direct and indirect damage mechanisms of LPS to BBB and the relationship between these processes and SAE. We believe that after LPS destroys BBB, a large number of inflammatory factors and neurotoxins will enter and damage the brain tissue, which will activate brain immune cells to mediate inflammatory response and in turn further destroys BBB. This vicious circle will ultimately lead to the progression of SAE. Finally, we present a succinct overview of the treatment of SAE by restoring the BBB barrier function and summarize novel opportunities in controlling the progression of SAE by targeting the BBB.

Astrocytic VEGFA: An essential mediator in blood-brain-barrier disruption in Parkinson's disease

The integrity of blood-brain-barrier (BBB) is essential for normal brain functions, synaptic remodeling, and angiogenesis. BBB disruption is a common pathology during Parkinson's disease (PD), and has been hypothesized to contribute to the progression of PD. However, the molecular mechanism of BBB disruption in PD needs further investigation. Here, A53T PD mouse and a 3-cell type in vitro BBB model were used to study the roles of α-synuclein (α-syn) in BBB disruption with the key results confirmed in the brains of PD patients obtained at autopsy. The A53T PD mouse studies showed that the expression of tight junction-related proteins decreased, along with increased vascular permeability and accumulation of oligomeric α-syn in activated astrocytes in the brain. The in vitro BBB model studies demonstrated that treatment with oligomeric α-syn, but not monomeric or fibrillar α-syn, resulted in significant disruption of BBB integrity. This process involved the expression and release of vascular endothelial growth factor A (VEGFA) and nitric oxide (NO) from oligomeric α-syn treated astrocytes. Increased levels of VEGFA and iNOS were also observed in the brain of PD patients. Blocking the VEGFA signaling pathway in the in vitro BBB model effectively protected the barrier against the harmful effects of oligomeric α-syn. Finally, the protective effects on BBB integrity associated with inhibition of VEGFA signaling pathway was also confirmed in PD mice. Taken together, our study concluded that oligomeric α-syn is critically involved in PD-associated BBB disruption, in a process that is mediated by astrocyte-derived VEGFA.

Surface charge, glycocalyx, and blood-brain barrier function

The negative surface charge of brain microvessel endothelial cells is derived from the special composition of their membrane lipids and the thick endothelial surface glycocalyx. They are important elements of the unique defense systems of the blood-brain barrier. The tissue-specific properties, components, function and charge of the brain endothelial glycocalyx have only been studied in detail in the past 15 years. This review highlights the importance of the negative surface charge in the permeability of macromolecules and nanoparticles as well as in drug interactions. We discuss surface charge and glycoxalyx changes in pathologies related to the brain microvasculature and protective measures against glycocalyx shedding and damage. We present biophysical techniques, including a microfluidic chip device, to measure surface charge of living brain endothelial cells and imaging methods for visualization of surface charge and glycocalyx.

Design and Validation of Liposomal ApoE2 Gene Delivery System to Evade Blood-Brain Barrier for Effective Treatment of Alzheimer's Disease

Targeting gene-based therapeutics to the brain is a strategy actively sought to treat Alzheimer's disease (AD). Recent findings discovered the role of apolipoprotein E (ApoE) isoforms in the clearance of toxic amyloid beta proteins from the brain. ApoE2 isoform is beneficial for preventing AD development, whereas ApoE4 is a major contributing factor to the disease. In this paper, we demonstrated efficient brain-targeted delivery of ApoE2 encoding plasmid DNA (pApoE2) using glucose transporter-1 (glut-1) targeted liposomes. Liposomes were surface-functionalized with a glut-1 targeting ligand mannose (MAN) and a cell-penetrating peptide (CPP) to enhance brain-targeting and cellular internalization, respectively. Among various CPPs, rabies virus glycoprotein peptide (RVG) or penetratin (Pen) was selected as a cell-penetration enhancer. Dual (RVGMAN and PenMAN)-functionalized liposomes were cytocompatible at 100 nM phospholipid concentration and demonstrated significantly higher expression of ApoE2 in bEnd.3 cells, primary neurons, and astrocytes compared to monofunctionalized and unmodified (plain) liposomes. Dual-modified liposomes also showed ∼2 times higher protein expression than other formulation controls in neurons cultured below the in vitro BBB model. These results translated well to in vivo efficacy study with significantly higher transfection of pApoE2 in the C57BL/6 mice brain following single tail vein administration of RVGMAN and PenMAN functionalized liposomes without any noticeable signs of toxicity. These results illustrate the potential of surface-modified liposomes for safe and brain-targeted delivery of the pApoE2 gene for effective AD therapy.

Diammonium glycyrrhizinate lipid ligand ameliorates lipopolysaccharide-induced acute lung injury by modulating vascular endothelial barrier function

The aim of the present study was to investigate the effects of diammonium glycyrrhizinate lipid ligand (DGLL) treatment on acute lung injury (ALI) and pulmonary edema induced by lipopolysaccharide (LPS) in Sprague-Dawley rats. Rats orally received 30, 60 and 120 mg/kg DGLL. After 1 h, the rat ALI model was established by LPS (10 mg/kg) intraperitoneal injection. After 6 h, lung injury was evaluated using hematoxylin and eosin staining techniques. Pulmonary edema was evaluated using lung wet-dry weight ratio, protein concentrations in the bronchoalveolar lavage fluid (BALF) and Evans blue (EB) extravasation in lung tissue. The expression levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in lung tissues were measured using ELISA. Myeloperoxidase (MPO) expression levels were detected by immunohistochemical staining. Western blotting was used to measure the expression level changes of intercellular adhesion molecule (ICAM)-1, as well as adherent and tight junction proteins, including vascular endothelial (VE)-cadherin, zonula occludens (ZO)-1, occludin and junctional adhesion molecule (JAM)-1 that were associated with pulmonary inflammation and microvascular permeability. DGLL treatment significantly alleviated ALI induced by LPS, which was demonstrated by reduction of MPO-positive cells and expression levels of TNF-α, IL-1β and ICAM-1 in rat lung tissues. In addition, DGLL abrogated LPS-induced pulmonary edema, decreased the protein concentration in BALF and reduced EB extravasation. DGLL also reversed the reduced expression of VE-cadherin and tight junction proteins, including ZO-1, occludin and JAM-1 in the lung tissues caused by LPS. In conclusion, DGLL exhibits a protective effect on LPS-induced rat ALI, which is associated with the inhibition of inflammatory cell infiltration and microvascular barrier disruption. The present results provide a theoretical basis for the application of DGLL for the potential clinical treatment of ALI.

Drug-Resistant Temporal Lobe Epilepsy Alters the Expression and Functional Coupling to Gαi/o Proteins of CB1 and CB2 Receptors in the Microvasculature of the Human Brain

Cannabinoid receptors 1 and 2 (CB1 and CB2, respectively) play an important role in maintaining the integrity of the blood–brain barrier (BBB). On the other hand, BBB dysfunction is a common feature in drug-resistant epilepsy. The focus of the present study was to characterize protein expression levels and Gαi/o protein-induced activation by CB1 and CB2 receptors in the microvascular endothelial cells (MECs) isolated from the brain of patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). MECs were isolated from the hippocampus and temporal neocortex of 12 patients with DR-MTLE and 12 non-epileptic autopsies. Immunofluorescence experiments were carried out to determine the localization of CB1 and CB2 receptors in the different cell elements of MECs. Protein expression levels of CB1 and CB2 receptors were determined by Western blot experiments. [³⁵S]-GTPγS binding assay was used to evaluate the Gαi/o protein activation induced by specific agonists. Immunofluorescent double-labeling showed that CB1 and CB2 receptors colocalize with tight junction proteins (claudin-5, occludin, and zonula occludens-1), glial fibrillary acidic protein and platelet-derived growth factor receptor-β. These results support that CB1 and CB2 receptors are expressed in the human isolated microvessels fragments consisting of MECs, astrocyte end feet, and pericytes. The hippocampal microvasculature of patients with DR-MTLE presented lower protein expression of CB1 and CB2 receptors (66 and 43%, respectively; p < 0.001). However, its Gαi/o protein activation was with high efficiency (CB1, 251%, p < 0.0008; CB2, 255%, p < 0.0001). Microvasculature of temporal neocortex presented protein overexpression of CB1 and CB2 receptors (35 and 41%, respectively; p < 0.01). Their coupled Gαi/o protein activation was with higher efficiency for CB1 receptors (103%, p < 0.006), but lower potency (p < 0.004) for CB2 receptors. The present study revealed opposite changes in the protein expression of CB1 and CB2 receptors when hippocampus (diminished expression of CB1 and CB2) and temporal neocortex (increased expression of CB1 and CB2) were compared. However, the exposure to specific CB1 and CB2 agonists results in high efficiency for activation of coupled Gαi/o proteins in the brain microvasculature of patients with DR-MTLE. CB1 and CB2 receptors with high efficiency could represent a therapeutic target to maintain the integrity of the BBB in patients with DR-MTLE.

Serum amyloid A-induced blood-brain barrier dysfunction associated with decreased claudin-5 expression in rat brain endothelial cells and its inhibition by high-density lipoprotein in vitro

The blood-brain barrier (BBB) is the multicellular interface located between the peripheral circulation and the brain parenchyma. BBB dysfunction is reported in many CNS diseases, such cognitive impairment, depression, Alzheimer's disease (AD), and multiple sclerosis (MS). Emerging evidence indicates that liver-derived inflammatory mediators are upregulated in neurological diseases with BBB dysfunction. Serum amyloid A (SAA), an acute phase protein secreted by hepatocytes, could be a candidate inflammatory signaling molecule transmitted from the liver to the brain; however, its contribution to BBB dysfunction is poorly understood. The present study aimed to elucidate the involvement of SAA in BBB impairment in an in vitro BBB model using rat brain microvascular endothelial cells (RBECs). We demonstrated that Apo-SAA significantly decreased transendothelial electrical resistance (TEER) and increased sodium fluorescein (Na-F) permeability in RBEC monolayers. Apo-SAA also decreased claudin-5 expression levels in RBECs. Furthermore, the Apo-SAA-mediated impairment of the BBB with decreased claudin-5 expression was inhibited by the addition of a high-density lipoprotein (HDL) related to SAA in plasma. These findings suggest that HDL counteracts the effects of SAA on BBB function. Therefore, the functional imbalance between SAA and HDL may induce BBB impairment, thereby triggering development of neuroinflammation. SAA could be a significant endogenous mediator in the liver-to-brain inflammation axis.

Expression of VEGF- and tight junction-related proteins in the neocortical microvasculature of patients with drug-resistant temporal lobe epilepsy

The blood-brain barrier (BBB) maintains the optimal microenvironment for brain function. Tight junctions (TJs) allow endothelial cells to adhere to each other, leading to the formation of a barrier that prevents the penetration of most molecules via transcellular routes. Evidence has indicated that seizure-induced vascular endothelial growth factor (VEGF) type 2 receptor (VEGFR-2) pathway activation weakens TJs, inducing vasodilatation and increasing vascular permeability and subsequent brain injury. The present study focused on investigating the expression levels of VEGF-related (VEGF-A and VEGFR-2) and TJ-related proteins (claudin-5, occludin and ZO-1) in the neocortical microvasculature of patients with drug-resistant temporal lobe epilepsy (TLE). The results obtained from hippocampal sclerosis TLE (HS-TLE) patients were compared with those obtained from patients with TLE secondary to lesions (lesion-TLE) and autopsy samples. The Western blotting and immunofluorescence results showed that VEGF-A and VEGFR-2 protein expression levels were increased in HS-TLE and lesion-TLE patients compared to autopsy group. On the other hand, claudin-5 expression was higher in HS-TLE patients and lesion-TLE patients than autopsies. The expression level of occludin and ZO-1 was decreased in HS-TLE patients. Our study described modifications to the integrity of the BBB that may contribute to the pathogenesis of TLE, in which the VEGF system may play an important role. We demonstrated that the same modifications were present in both HS-TLE and lesion-TLE patients, which suggests that seizures modify these systems and that they are not associated with the establishment of epilepsy.

In vitro modeling of blood-brain barrier and interface functions in neuroimmune communication

Neuroimmune communication contributes to both baseline and adaptive physiological functions, as well as disease states. The vascular blood-brain barrier (BBB) and associated cells of the neurovascular unit (NVU) serve as an important interface for immune communication between the brain and periphery through the blood. Immune functions and interactions of the BBB and NVU in this context can be categorized into at least five neuroimmune axes, which include (1) immune modulation of BBB impermeability, (2) immune regulation of BBB transporters, secretions, and other functions, (3) BBB uptake and transport of immunoactive substances, (4) immune cell trafficking, and (5) BBB secretions of immunoactive substances. These axes may act separately or in concert to mediate various aspects of immune signaling at the BBB. Much of what we understand about immune axes has been from work conducted using in vitro BBB models, and recent advances in BBB and NVU modeling highlight the potential of these newer models for improving our understanding of how the brain and immune system communicate. In this review, we discuss how conventional in vitro models of the BBB have improved our understanding of the 5 neuroimmune axes. We further evaluate the existing literature on neuroimmune functions of novel in vitro BBB models, such as those derived from human induced pluripotent stem cells (iPSCs) and discuss their utility in evaluating aspects of neuroimmune communication.

Platelet regulates neuroinflammation and restores blood-brain barrier integrity in a mouse model of traumatic brain injury

Neuroinflammation accompanied by microglial activation triggers multiple cell death after traumatic brain injury (TBI). The secondary injury caused by inflammation may persist for a long time. Recently, platelet C-type lectin-like 2 receptor (CLEC-2) has been shown to regulate inflammation in certain diseases. However, its possible effects on TBI remain poorly understood. Here, we aimed to investigate the role of platelet CLEC-2 in the pathological process of neuroinflammation after TBI. In this study, mice were subjected to sham or controlled cortical impact injury, and arbitrarily received recombinant platelet CLEC-2. In parallel, BV2 cells were treated with lipopolysaccharide (LPS) to mimic microglial activation after TBI. Primary endothelial cells were also subjected to LPS in order to replicate the inflammatory damage caused by TBI. We used western blot analysis, reverse transcription polymerase chain reaction (RT-PCR), and immunostaining to evaluate the role of platelet CLEC-2 in TBI. In conditional knock out platelet CLEC-2 mice, trauma worsened the integrity of the blood-brain barrier and amplified the release of inflammatory cytokines. In wild type mice subjected to controlled cortical impact injury, recombinant platelet CLEC-2 administration altered the secretion of inflammatory cytokines, reduced brain edema, and improved neurological function. In vitro, the polarization phenotype of microglia induced by LPS was transformed by recombinant platelet CLEC-2, and this conversion depended on the mammalian target of rapamycin (mTOR) pathway. Endothelial cell injury by LPS was ameliorated when microglia expressed mostly M2 phenotype markers. In conclusion, platelet CLEC-2 regulates trauma-induced neuroinflammation and restores blood-brain barrier integrity.

PAMAM dendrimers: blood-brain barrier transport and neuronal uptake after focal brain ischemia

Drug delivery to the central nervous system is restricted by the blood-brain barrier (BBB). However, with the onset of stroke, the BBB becomes leaky, providing a window of opportunity to passively target the brain. Here, cationic poly(amido amine) (PAMAM) dendrimers of different generations were functionalized with poly(ethylene glycol) (PEG) to reduce cytotoxicity and prolong blood circulation half-life, aiming for a safe in vivo drug delivery system in a stroke scenario. Rhodamine B isothiocyanate (RITC) was covalently tethered to the dendrimer backbone and used as a small surrogate drug as well as for tracking purposes. The biocompatibility of PAMAM was markedly increased by PEGylation as a function of dendrimer generation and degree of functionalization. The PEGylated RITC-modified dendrimers did not affect the integrity of an in vitro BBB model. Additionally, the functionalized dendrimers remained safe when in contact with the bEnd.3 cells and rat primary astrocytes composing the in vitro BBB model after hypoxia induced by oxygen-glucose deprivation. Modification with PEG also decreased the interaction and uptake by endothelial cells of PAMAM, indicating that the transport across a leaky BBB due to focal brain ischemia would be facilitated. Next, the functionalized dendrimers were tested in contact with red blood cells showing no haemolysis for the PEGylated PAMAM, in contrast to the unmodified dendrimer. Interestingly, the PEG-modified dendrimers reduced blood clotting, which may be an added beneficial function in the context of stroke. The optimized PAMAM formulation was intravenously administered in mice after inducing permanent focal brain ischemia. Twenty-four hours after administration, dendrimers could be detected in the brain, including in neurons of the ischemic cortex. Our results suggest that the proposed formulation has the potential for becoming a successful delivery vector for therapeutic application to the injured brain after stroke reaching the ischemic neurons.

Cerebrovascular Pathology in Hypertriglyceridemic APOB-100 Transgenic Mice

Hypertriglyceridemia is not only a serious risk factor in the development of cardiovascular diseases, but it is linked to neurodegeneration, too. Previously, we generated transgenic mice overexpressing the human APOB-100 protein, a mouse model of human atherosclerosis. In this model we observed high plasma levels of triglycerides, oxidative stress, tau hyperphosphorylation, synaptic dysfunction, cognitive impairment, increased neural apoptosis and neurodegeneration. Neurovascular dysfunction is recognized as a key factor in the development of neurodegenerative diseases, but the cellular and molecular events linking cerebrovascular pathology and neurodegeneration are not fully understood. Our aim was to study cerebrovascular changes in APOB-100 transgenic mice. We described the kinetics of the development of chronic hypertriglyceridemia in the transgenic animals. Increased blood-brain barrier permeability was found in the hippocampus of APOB-100 transgenic mice which was accompanied by structural changes. Using transmission electron microscopy, we detected changes in the brain capillary endothelial tight junction structure and edematous swelling of astrocyte endfeet. In brain microvessels isolated from APOB-100 transgenic animals increased Lox-1, Aqp4, and decreased Meox-2, Mfsd2a, Abcb1a, Lrp2, Glut-1, Nos2, Nos3, Vim, and in transgenic brains reduced Cdh2 and Gfap-σ gene expressions were measured using quantitative real-time PCR. We confirmed the decreased P-glycoprotein (ABCB1) and vimentin expression related to the neurovascular unit by immunostaining in transgenic brain sections using confocal microscopy. We conclude that in chronic hypertriglyceridemic APOB-100 transgenic mice both functional and morphological cerebrovascular pathology can be observed, and this animal model could be a useful tool to study the link between cerebrovascular pathology and neurodegeneration.

Niosomes decorated with dual ligands targeting brain endothelial transporters increase cargo penetration across the blood-brain barrier

Nanoparticles targeting transporters of the blood-brain barrier (BBB) are promising candidates to increase the brain penetration of biopharmacons. Solute carriers (SLC) are expressed at high levels in brain endothelial cells and show a specific pattern at the BBB. The aim of our study was to test glutathione and ligands of SLC transporters as single or dual BBB targeting molecules for nanovesicles. High mRNA expression levels for hexose and neutral amino acid transporting SLCs were found in isolated rat brain microvessels and our rat primary cell based co-culture BBB model. Niosomes were derivatized with glutathione and SLC ligands glucopyranose and alanine. Serum albumin complexed with Evans blue (67 kDa), which has a very low BBB penetration, was selected as a cargo. The presence of targeting ligands on niosomes, especially dual labeling, increased the uptake of the cargo molecule in cultured brain endothelial cells. This cellular uptake was temperature dependent and could be decreased with a metabolic inhibitor and endocytosis blockers filipin and cytochalasin D. Making the negative surface charge of brain endothelial cells more positive with a cationic lipid or digesting the glycocalyx with neuraminidase elevated the uptake of the cargo after treatment with targeted nanocarriers. Treatment with niosomes increased plasma membrane fluidity, suggesting the fusion of nanovesicles with endothelial cell membranes. Targeting ligands elevated the permeability of the cargo across the BBB in the culture model and in mice, and dual-ligand decoration of niosomes was more effective than single ligand labeling. Our data indicate that dual labeling with ligands of multiple SLC transporters can potentially be exploited for BBB targeting of nanoparticles.

Neurovascular unit crosstalk: Pericytes and astrocytes modify cytokine secretion patterns of brain endothelial cells

Crosstalk among brain endothelial cells (BECs), pericytes, and astrocytes occurs by way of soluble factors, including cytokines. Here, we studied cytokine secretion from both mouse BEC monocultures and tri-cultured with pericytes and astrocytes. Four cytokines were constitutively secreted by BEC monolayers, 12 by LPS-stimulated BECs, 10 by tri-cultures, and 14 by LPS-stimulated tri-cultures. Cytokine levels were generally higher with either LPS stimulation or tri-culture when compared to monocultures and highest in tri-cultures stimulated by LPS. LPS-stimulated secretions fell into eight patterns as categorized by the polarization of cytokine secretions. To determine the cellular origin of cytokine increases in tri-cultures, we cultured mouse BECs with human pericytes and astrocytes and measured cytokines in species-specific assays. Thus, cytokines detected in the human immunoassay were from pericytes/astrocytes and those detected in the mouse immunoassay were from BECs. Several unique patterns were thus found. For example, TNF-alpha was only of pericyte/astrocyte origin; granulocyte colony-stimulating factor was only of BEC origin; IL-6, MCP-1, and GM-CSF of astrocyte/pericyte origin were found in both the luminal and abluminal chambers, suggesting the presence of brain-to-blood transporters. We conclude that crosstalk influences cytokine secretion under constitutive and stimulated conditions from both BECs and pericytes/astrocytes.

Protection of cultured brain endothelial cells from cytokine-induced damage by α-melanocyte stimulating hormone

The blood–brain barrier (BBB), an interface between the systemic circulation and the nervous system, can be a target of cytokines in inflammatory conditions. Pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) induce damage in brain endothelial cells and BBB dysfunction which contribute to neuronal injury. The neuroprotective effects of α-melanocyte stimulating hormone (α-MSH) were investigated in experimental models, but there are no data related to the BBB. Based on our recent study, in which α-MSH reduced barrier dysfunction in human intestinal epithelial cells induced by TNF-α and IL-1β, we hypothesized a protective effect of α-MSH on brain endothelial cells. We examined the effect of these two pro-inflammatory cytokines, and the neuropeptide α-MSH on a culture model of the BBB, primary rat brain endothelial cells co-cultured with rat brain pericytes and glial cells. We demonstrated the expression of melanocortin-1 receptor in isolated rat brain microvessels and cultured brain endothelial cells by RT-PCR and immunohistochemistry. TNF-α and IL-1β induced cell damage, measured by impedance and MTT assay, which was attenuated by α-MSH (1 and 10 pM). The peptide inhibited the cytokine-induced increase in brain endothelial permeability, and restored the morphological changes in cellular junctions visualized by immunostaining for claudin-5 and β-catenin. Elevated production of reactive oxygen species and the nuclear translocation of NF-κB were also reduced by α-MSH in brain endothelial cells stimulated by cytokines. We demonstrated for the first time the direct beneficial effect of α-MSH on cultured brain endothelial cells, indicating that this neurohormone may be protective at the BBB.

P120 regulates beta-catenin nuclear translocation through E-cadherin endocytosis in ventilator-induced lung injury

Mechanical stretch induces epithelial barrier dysfunction by altering the location and degradation of cellular junction proteins. p120-catenin (p120) is a cell-cell junction protein known to protect against ventilator-induced lung injury (VILI) that results from improper ventilation of patients. In this study, we sought to determine the role of p120 in VILI and its relationship with the cellular response to mechanical stretch. Mouse lung epithelial cells (MLE-12) transfected with p120 siRNA, p120 cDNA, or E-cadherin siRNA were subjected to 20% cyclic stretch for 2 or 4 hours. Wild-type male C57BL/6 mice were transfected with p120 siRNA-liposome complex to delete p120 in vivo and then subjected to mechanical ventilation. Cyclic stretch induced p120 degradation and the endocytosis of E-cadherin, which induced β-catenin translocation into the nucleus, a key event in lung injury progress and repair. These findings reveal that by reducing β-catenin nuclear translocation through inhibition of E-cadherin endocytosis, p120 protects against ventilator-induced lung injury.

Cellular Pharmacological Effects of the Traditional Japanese Kampo Medicine Yokukansan on Brain Cells

Yokukansan (YKS) is a traditional Japanese Kampo medicine currently used for the treatment of the behavioral psychological symptoms associated with dementia (BPSD), which is frequently problematic in neurodegenerative disorders such as Alzheimer’s disease. Regarding the pharmacological mechanisms underlying its efficacy, we recently reviewed the multiple effects of YKS on the neurotransmitter systems (e.g., glutamatergic, serotonergic, dopaminergic, cholinergic, GABAergic, and adrenergic neurotransmission) in various brain regions that are related to the psychological, emotional, cognitive, or memory functions. These multiple effects are thought to be caused by multiple components included in YKS. In addition, YKS exhibits various effects on brain cells (i.e., neurons, glial cells including astrocytes, oligodendrocytes, and microglial cells, and endothelial cells). In this review, we summarize recent evidence demonstrating the cellular pharmacological effects of YKS on these brain cells, and discuss the current understanding of its efficacy and mechanism. In particular, YKS maintains the neuronal survival and function by multiple beneficial effects, including anti-apoptosis, anti-oxidation, anti-endoplasmic reticulum stress, and neurogenesis. YKS also acts on glial cells by: facilitating the transport of glutamate into astrocytes; promoting the proliferation and differentiation of oligodendrocytes; and enhancing the anti-inflammatory properties of microglial cells. These glial effects are thought to support neuronal functioning within the brain. Various ingredients involved in these effects have been identified, some of which can pass through the artificial blood–brain barrier without disrupting the endothelial tight junctions. This multitude of interactive effects displayed by YKS on neuronal and glial cells is suggested to be involved in the multitude of neuropsychopharmacological actions of YKS, which are related to the improvement of BPSD.

Role of pattern recognition receptors of the neurovascular unit in inflamm-aging

Aging is associated with chronic inflammation partly mediated by increased levels of damage-associated molecular patterns, which activate pattern recognition receptors (PRRs) of the innate immune system. Furthermore, many aging-related disorders are associated with inflammation. PRRs, such as Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain-like receptors (NLRs), are expressed not only in cells of the innate immune system but also in other cells, including cells of the neurovascular unit and cerebral vasculature forming the blood-brain barrier. In this review, we summarize our present knowledge about the relationship between activation of PRRs expressed by cells of the neurovascular unit-blood-brain barrier, chronic inflammation, and aging-related pathologies of the brain. The most important damage-associated molecular pattern-sensing PRRs in the brain are TLR2, TLR4, and NLR family pyrin domain-containing protein-1 and pyrin domain-containing protein-3, which are activated during physiological and pathological aging in microglia, neurons, astrocytes, and possibly endothelial cells and pericytes.

High-throughput proteomics and the fight against pathogens

Pathogens pose a major threat to human and animal welfare. Understanding the interspecies host-pathogen protein-protein interactions could lead to the development of novel strategies to combat infectious diseases through the rapid development of new therapeutics. The first step in understanding the host-pathogen crosstalk is to identify interacting proteins in order to define crucial hot-spots in the host-pathogen interactome, such as the proposed pharmaceutical targets by means of high-throughput proteomic methodologies. In order to obtain holistic insight into the inter- and intra-species bimolecular interactions, apart from the proteomic approach, sophisticated in silico modeling is used to correlate the obtained large data sets with other omics data and clinical outcomes. Since the main focus in this area has been directed towards human medicine, it is time to extrapolate the existing expertise to a new emerging field: the 'systems veterinary medicine'. Therefore, this review addresses high-throughput mass spectrometry-based technology for monitoring protein-protein interactions in vitro and in vivo and discusses pathogen cultivation, model host cells and available bioinformatic tools employed in vaccine development.

Luteolin Inhibits Fibrillary β-Amyloid1-40-Induced Inflammation in a Human Blood-Brain Barrier Model by Suppressing the p38 MAPK-Mediated NF-κB Signaling Pathways

Amyloid-β peptides (Aβ) exist in several forms and are known as key modulators of Alzheimer's disease (AD). Fibrillary Aβ (fAβ) has been found to disrupt the blood-brain barrier (BBB) by triggering and promoting inflammation. In this study, luteolin, a naturally occurring flavonoid that has shown beneficial properties in the central nervous system, was evaluated as a potential agent to preserve barrier function and inhibit inflammatory responses at the BBB that was injured by fAβ_1-40. We established an in vitro BBB model by co-culturing human brain microvascular endothelial cells (hBMECs) and human astrocytes (hAs) under fAβ_1-40-damaged conditions and investigated the effect of luteolin by analyzing cellular toxicity, barrier function, cytokine production and inflammation-related intracellular signaling pathways. Our results demonstrated that, in cells injured by fAβ_1-40, luteolin increased cell viability of hBMECs and hAs. The cytoprotection of the co-culture against the damage induced by fAβ_1-40 was also increased at both the apical and basolateral sides. Luteolin protected the barrier function by preserving transendothelial electrical resistance and relieving aggravated permeability in the human BBB model after being exposed to fAβ_1-40. Moreover, in both the apical and basolateral sides of the co-culture, luteolin reduced fAβ_1-40-induced inflammatory mediator and cytokine production, including cyclooxygenase-2 (COX-2), tumor necrosis factor α (TNF-α), interleukin 1 β (IL-1β), interleukin 6 (IL-6), and interleukin 8 (IL-8), however it did not show sufficient effects on scavenging intracellular reactive oxygen species (ROS) in hBMECs and hAs. The mechanism of BBB protection against fAβ_1-40-induced injury may be related to the regulation of inflammatory signal transduction, which involves inhibition of p38 mitogen-activated protein kinase (MAPK) activation, downregulation of phosphorylated inhibitory κB kinase (phosphor-IKK) levels, relief of inhibitory κB α (IκBα) degradation, blockage of nuclear factor κB (NF-κB) p65 nuclear translocation, and reduction of the release of inflammatory cytokines. Moreover, the employment of p38 MAPK and NF-κB inhibitors reversed luteolin-mediated barrier function and cytokine release. Taken together, luteolin may serve as a potential therapeutic agent for BBB protection by inhibiting inflammation following fAβ_1-40-induced injury.

Sodium Pentosan Polysulfate Reduced Renal Ischemia-Reperfusion-Induced Oxidative Stress and Inflammatory Responses in an Experimental Animal Model

Acute kidney injury (AKI) remains an independent risk factor for mortality and morbidity after vascular surgery (affecting the renal arteries) or aortic surgery (requiring suprarenal aortic clamping). These types of vascular surgery produce renal ischemia/reperfusion (I/R) injury, a common cause of AKI. The present studies aimed at monitoring the course of renal I/R injury at the cellular level and investigating the efficacy of long-term preoperative and single-shot intraoperative administration of sodium pentosan polysulfate (PPS) to protect renal tissue from acute I/R injury both in native and diabetic kidneys in rats. Western blot analyses of the proapoptotic (bax) and antiapoptotic (bcl-2) signaling pathways, as well as the extent of DNA damage (phospho-p53), were performed. Oxidative stress followed upon the termination of malondialdehyde, reduced glutathione, thiol group, and superoxide dismutase plasma levels. Inflammatory changes were measured by the determination of serum tumor necrosis factor-α and interleukin-1 levels. Morphological changes were detected by histological examinations. Our results showed that the long-term administration of PPS has an advantage in reducing I/R kidney injury in diabetic rats, while high-dose, single-shot parenteral administration of PPS prior to revascularization might be useful in nondiabetic rats.

LDL-Cholesterol Increases the Transcytosis of Molecules through Endothelial Monolayers

Cholesterol has been identified as a causative factor in numerous pathologies including atherosclerosis and cancer. One of the frequent effects of elevated cholesterol levels in humans is the compromise of endothelial function due to activation of pro-inflammatory signalling pathways. While the mechanisms involved in endothelial activation by cholesterol during an inflammatory response are well established, less is known about the mechanisms by which cholesterol may affect endothelial barrier function, which were the subject of the present study. Here we show that low density lipoprotein (LDL) increases the permeability of endothelial monolayers to high molecular weight dextrans in an LDL receptor and cholesterol-dependent manner. The increased permeability seen upon LDL treatment was not caused by disruption of cell-to-cell junctions as determined by a normal localization of VE-Cadherin and ZO-1 proteins, and no major alterations in transendothelial electrical resistance or permeability to fluorescein. We show instead that LDL increases the level of high molecular weight transcytosis and that this occurs in an LDL receptor, cholesterol and caveolae-dependent way. Our findings contribute to our understanding of the systemic pathological effects of elevated cholesterol and the transport of cargo through endothelial monolayers.

Potential for brain accessibility and analysis of stability of selected flavonoids in relation to neuroprotection in vitro

Natural food sources constitute a promising source of new compounds with neuroprotective properties, once they have the ability to reach the brain. Our aim was to evaluate the brain accessibility of quercetin, epigallocatechin gallate (EGCG) and cyanidin-3-glucoside (C3G) in relation to their neuroprotective capability. Primary cortical neuron cultures were exposed to oxidative insult in the absence and presence of the selected compounds, and neuroprotection was assessed through evaluation of apoptotic-like and necrotic-like cell death. The brain accessibility of selected compounds was assessed using an optimised human blood-brain barrier model. The blood-brain barrier model was crossed rapidly by EGCG and more slowly by C3G, but not by quercetin. EGCG protected against oxidation-induced neuronal necrotic-like cell death by ~40%, and apoptosis by ~30%. Both quercetin and C3G were less effective, since only the lowest quercetin concentration was protective, and C3G only prevented necrosis by ~37%. Quercetin, EGCG and C3G effectively inhibited α-synuclein fibrillation over the relevant timescale applied here. Overall, EGCG seems to be the most promising neuroprotective compound. Thus, inclusion of this polyphenol in the diet might provide an affordable means to reduce the impact of neurodegenerative diseases.

Distinct Contributions of Astrocytes and Pericytes to Neuroinflammation Identified in a 3D Human Blood-Brain Barrier on a Chip

Neurovascular inflammation is a major contributor to many neurological disorders, but modeling these processes in vitro has proven to be difficult. Here, we microengineered a three-dimensional (3D) model of the human blood-brain barrier (BBB) within a microfluidic chip by creating a cylindrical collagen gel containing a central hollow lumen inside a microchannel, culturing primary human brain microvascular endothelial cells on the gel’s inner surface, and flowing medium through the lumen. Studies were carried out with the engineered microvessel containing endothelium in the presence or absence of either primary human brain pericytes beneath the endothelium or primary human brain astrocytes within the surrounding collagen gel to explore the ability of this simplified model to identify distinct contributions of these supporting cells to the neuroinflammatory response. This human 3D BBB-on-a-chip exhibited barrier permeability similar to that observed in other in vitro BBB models created with non-human cells, and when stimulated with the inflammatory trigger, tumor necrosis factor-alpha (TNF-α), different secretion profiles for granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) were observed depending on the presence of astrocytes or pericytes. Importantly, the levels of these responses detected in the 3D BBB chip were significantly greater than when the same cells were co-cultured in static Transwell plates. Thus, as G-CSF and IL-6 have been reported to play important roles in neuroprotection and neuroactivation in vivo, this 3D BBB chip potentially offers a new method to study human neurovascular function and inflammation in vitro, and to identify physiological contributions of individual cell types.

Lyophilized Powder of Catalpol and Puerarin Protects Neurovascular Unit from Stroke

Hunting for an effective medicine for brain stroke has been a medical task in neuroscience for decades. The present research showed that the lyophilized Powder of Catalpol and Puerarin (C-P) in all the tested doses (65.4 mg/kg, 32.7 mg/kg, 16.4 mg/kg) significantly reduced the neurological deficiency, infarct volume and apoptotic cells in ischemic/reperfusion (I/R) rats. It also promoted astrocyte processes and prolonged neuron axons in infarct area. Further, it decreased MDA, NO, NF-κB/p65, TNF-α, IL-1β and IL-6 and enhanced the EPOR and GAF-43. 65.4 mg/kg and 32.7 mg/kg C-P could up-regulated EPO and VEGF significantly. In vitro, 49 μg/mL and 24.5 μg/mL C-P decreased the leakage of sodium fluorescein and increased the activity of γ-GTP. Additionally, it increased SOD and decreased MDA, NO, and LDH and decreased NF-κB/p65, TNF-α, IL-1β and IL-6 and unregulated EPO, EPOR, VEGF, and GAP-43. Only the dose of 49 μg/mL increased TEER and Claudin-5 and turned the typically damaged morphologies of neurons, astrocytes and endothelium into a favorable trend. These data imply that C-P improved the recovery of neurological deficiency in motor, sense, balance and reflex, and protected the whole NVU by anti-oxidative stress, anti-inflammation and up-regulating some protective factors. This research provides a candidate medicine for brain stroke and, at the same time, a pattern for drug study targeting NVU in vitro.

LPS Induces Occludin Dysregulation in Cerebral Microvascular Endothelial Cells via MAPK Signaling and Augmenting MMP-2 Levels

Disrupted blood-brain barrier (BBB) integrity contributes to cerebral edema during central nervous system infection. The current study explored the mechanism of lipopolysaccharide- (LPS-) induced dysregulation of tight junction (TJ) proteins. Human cerebral microvascular endothelial cells (hCMEC/D3) were exposed to LPS, SB203580 (p38MAPK inhibitor), or SP600125 (JNK inhibitor), and cell vitality was determined by MTT assay. The proteins expressions of p38MAPK, JNK, and TJs (occludin and zonula occludens- (ZO-) 1) were determined by western blot. The mRNA levels of TJ components and MMP-2 were measured with quantitative real-time polymerase chain reaction (qRT-PCR), and MMP-2 protein levels were determined by enzyme-linked immunosorbent assay (ELISA). LPS, SB203580, and SP600125 under respective concentrations of 10, 7.69, or 0.22 µg/mL had no effects on cell vitality. Treatment with LPS decreased mRNA and protein levels of occludin and ZO-1 and enhanced p38MAPK and JNK phosphorylation and MMP-2 expression. These effects were attenuated by pretreatment with SB203580 or SP600125, but not in ZO-1 expression. Both doxycycline hyclate (a total MMP inhibitor) and SB-3CT (a specific MMP-2 inhibitor) partially attenuated the LPS-induced downregulation of occludin. These data suggest that MMP-2 overexpression and p38MAPK/JNK pathways are involved in the LPS-mediated alterations of occludin in hCMEC/D3; however, ZO-1 levels are not influenced by p38MAPK/JNK.

Pretreatment with andrographolide pills(®) attenuates lipopolysaccharide-induced pulmonary microcirculatory disturbance and acute lung injury in rats

OBJECTIVE

The purpose of this study was to explore the protective effect of AP on LPS-induced PMD and ALI.

METHODS

Male SD rats were continuously infused with LPS (5 mg/kg/h) for one hour to induce PMD and ALI. AP was administrated orally one hour before LPS exposure. Arterial blood pressure and HR were monitored. Blood gas analysis, histological observation, cytokines in plasma, leukocyte recruitment, pulmonary oxidative stress, microvessel permeability, edema, and related proteins were evaluated six hours after LPS challenge.

RESULTS

Rats receiving LPS exhibited significant alterations, including hypotension, tachycardia, increase in cytokines, neutrophil adhesion and infiltration, oxidative stress, and microvessel hyperpermeability, resulting in pulmonary injury and dysfunction. AP (0.18 g/kg or 1.8 g/kg) improved rat survival rate, and significantly attenuated all aforementioned insults, and inhibited LPS-induced increase in adhesion molecules, up-regulation of Cav-1 and Src kinase and NADPH oxidase subunits (p47(phox) and p67(phox) ) membrane translocation in lung tissue, and preserved JAM-1 and claudin-5.

CONCLUSIONS

The results demonstrated the protective effect of AP on LPS-induced PMD and ALI, suggesting the potential of AP as a prophylactic strategy for LPS-induced ALI.

Hydrophilic bile acids protect human blood-brain barrier endothelial cells from disruption by unconjugated bilirubin: an in vitro study

Ursodeoxycholic acid and its main conjugate glycoursodeoxycholic acid are bile acids with neuroprotective properties. Our previous studies demonstrated their anti-apoptotic, anti-inflammatory, and antioxidant properties in neural cells exposed to elevated levels of unconjugated bilirubin (UCB) as in severe jaundice. In a simplified model of the blood-brain barrier, formed by confluent monolayers of a cell line of human brain microvascular endothelial cells, UCB has shown to induce caspase-3 activation and cell death, as well as interleukin-6 release and a loss of blood-brain barrier integrity. Here, we tested the preventive and restorative effects of these bile acids regarding the disruption of blood-brain barrier properties by UCB in in vitro conditions mimicking severe neonatal hyperbilirubinemia and using the same experimental blood-brain barrier model. Both bile acids reduced the apoptotic cell death induced by UCB, but only glycoursodeoxycholic acid significantly counteracted caspase-3 activation. Bile acids also prevented the upregulation of interleukin-6 mRNA, whereas only ursodeoxycholic acid abrogated cytokine release. Regarding barrier integrity, only ursodeoxycholic acid abrogated UCB-induced barrier permeability. Better protective effects were obtained by bile acid pre-treatment, but a strong efficacy was still observed by their addition after UCB treatment. Finally, both bile acids showed ability to cross confluent monolayers of human brain microvascular endothelial cells in a time-dependent manner. Collectively, data disclose a therapeutic time-window for preventive and restorative effects of ursodeoxycholic acid and glycoursodeoxycholic acid against UCB-induced blood-brain barrier disruption and damage to human brain microvascular endothelial cells.

Quercetin protects human brain microvascular endothelial cells from fibrillar β-amyloid1-40-induced toxicity

Amyloid beta-peptides (Aβ) are known to undergo active transport across the blood-brain barrier, and cerebral amyloid angiopathy has been shown to be a prominent feature in the majority of Alzheimer׳s disease. Quercetin is a natural flavonoid molecule and has been demonstrated to have potent neuroprotective effects, but its protective effect on endothelial cells under Aβ-damaged condition is unclear. In the present study, the protective effects of quercetin on brain microvascular endothelial cells injured by fibrillar Aβ_1–40 (fAβ_1–40) were observed. The results show that fAβ_1–40-induced cytotoxicity in human brain microvascular endothelial cells (hBMECs) can be relieved by quercetin treatment. Quercetin increases cell viability, reduces the release of lactate dehydrogenase, and relieves nuclear condensation. Quercetin also alleviates intracellular reactive oxygen species generation and increases superoxide dismutase activity. Moreover, it strengthens the barrier integrity through the preservation of the transendothelial electrical resistance value, the relief of aggravated permeability, and the increase of characteristic enzyme levels after being exposed to fAβ_1–40. In conclusion, quercetin protects hBMECs from fAβ_1–40-induced toxicity.

Low dose cranial irradiation-induced cerebrovascular damage is reversible in mice

Background

High-dose radiation-induced blood-brain barrier breakdown contributes to acute radiation toxicity syndrome and delayed brain injury, but there are few data on the effects of low dose cranial irradiation. Our goal was to measure blood-brain barrier changes after low (0.1 Gy), moderate (2 Gy) and high (10 Gy) dose irradiation under in vivo and in vitro conditions.

Methodology

Cranial irradiation was performed on 10-day-old and 10-week-old mice. Blood-brain barrier permeability for Evans blue, body weight and number of peripheral mononuclear and circulating endothelial progenitor cells were evaluated 1, 4 and 26 weeks postirradiation. Barrier properties of primary mouse brain endothelial cells co-cultured with glial cells were determined by measurement of resistance and permeability for marker molecules and staining for interendothelial junctions. Endothelial senescence was determined by senescence associated β-galactosidase staining.

Principle Findings

Extravasation of Evans blue increased in cerebrum and cerebellum in adult mice 1 week and in infant mice 4 weeks postirradiation at all treatment doses. Head irradiation with 10 Gy decreased body weight. The number of circulating endothelial progenitor cells in blood was decreased 1 day after irradiation with 0.1 and 2 Gy. Increase in the permeability of cultured brain endothelial monolayers for fluorescein and albumin was time- and radiation dose dependent and accompanied by changes in junctional immunostaining for claudin-5, ZO-1 and β-catenin. The number of cultured brain endothelial and glial cells decreased from third day of postirradiation and senescence in endothelial cells increased at 2 and 10 Gy.

Conclusion

Not only high but low and moderate doses of cranial irradiation increase permeability of cerebral vessels in mice, but this effect is reversible by 6 months. In-vitro experiments suggest that irradiation changes junctional morphology, decreases cell number and causes senescence in brain endothelial cells.

Acute effects of short-chain alkylglycerols on blood-brain barrier properties of cultured brain endothelial cells

BACKGROUND AND PURPOSE

The blood-brain barrier (BBB) restricts drug penetration to the brain preventing effective treatment of patients suffering from brain tumours. Intra-arterial injection of short-chain alkylglycerols (AGs) opens the BBB and increases delivery of molecules to rodent brain parenchyma in vivo. The mechanism underlying AG-mediated modification of BBB permeability is still unknown. Here, we have tested the effects of AGs on barrier properties of cultured brain microvascular endothelial cells.

EXPERIMENTAL APPROACH

The effects of two AGs, 1-O-pentylglycerol and 2-O-hexyldiglycerol were examined using an in vitro BBB model consisting of primary cultures of rat brain endothelial cells, co-cultured with rat cerebral glial cells. Integrity of the paracellular, tight junction-based, permeation route was analysed by functional assays, immunostaining for junctional proteins, freeze-fracture electron microscopy, and analysis of claudin-claudin trans-interactions.

KEY RESULTS

AG treatment (5 min) reversibly reduced transendothelial electrical resistance and increased BBB permeability for fluorescein accompanied by changes in cell morphology and immunostaining for claudin-5 and β-catenin. These short-term changes were not accompanied by alterations of inter-endothelial tight junction strand complexity or the trans-interaction of claudin-5.

CONCLUSION AND IMPLICATIONS

AG-mediated increase in brain endothelial paracellular permeability was short, reversible and did not affect tight junction strand complexity. Redistribution of junctional proteins and alterations in the cell shape indicate the involvement of the cytoskeleton in the action of AGs. These data confirm the results from in vivo studies in rodents characterizing AGs as adjuvants that transiently open the BBB.

Blood-brain barrier dysfunction in mice induced by lipopolysaccharide is attenuated by dapsone

Blood-brain barrier (BBB) dysfunction is a key event in the development of many central nervous system (CNS) diseases, such as septic encephalopathy and stroke. 4,4'-Diaminodiphenylsulfone (DDS, Dapsone) has displayed neuroprotective effect, but whether DDS has protective role on BBB integrity is not clear. This study was designed to examine the effect of DDS on lipopolysaccharide (LPS)-induced BBB disruption and oxidative stress in brain vessels. Using in vivo multiphoton imaging, we found that DDS administration significantly restored BBB integrity compromised by LPS. DDS also increased the expression of tight junction proteins occludin, zona occludens-1 (ZO-1) and claudin-5 in brain vessels. Level of reactive oxygen species (ROS) was reduced by DDS treatment, which may due to decreased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and NOX2 expression. Our results showed that LPS-induced BBB dysfunction could be attenuated by DDS, indicated that DDS has a therapeutic potential for treating CNS infection and other BBB related diseases.

P-glycoprotein mediated efflux limits the transport of the novel anti-Parkinson's disease candidate drug FLZ across the physiological and PD pathological in vitro BBB models

FLZ, a novel anti-Parkinson's disease (PD) candidate drug, has shown poor blood-brain barrier (BBB) penetration based on the pharmacokinetic study using rat brain. P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are two important transporters obstructing substrates entry into the CNS as well as in relation to PD neuropathology. However, it is unclear whether P-gp and BCRP are involved in low BBB permeability of FLZ and what the differences of FLZ brain penetration are between normal and Parkinson's conditions. For this purpose, in vitro BBB models mimicking physiological and PD pathological-related BBB properties were constructed by C6 astroglial cells co-cultured with primary normal or PD rat cerebral microvessel endothelial cells (rCMECs) and in vitro permeability experiments of FLZ were carried out. High transepithelial electrical resistance (TEER) and low permeability for sodium fluorescein (NaF) confirmed the BBB functionality of the two models. Significantly greater expressions of P-gp and BCRP were detected in PD rCMECs associated with the lower in vitro BBB permeability of FLZ in pathological BBB model compared with physiological model. In transport studies only P-gp blocker effectively inhibited the efflux of FLZ, which was consistent with the in vivo permeability data. This result was also confirmed by ATPase assays, suggesting FLZ is a substrate for P-gp but not BCRP. The present study first established in vitro BBB models reproducing PD-related changes of BBB functions in vivo and demonstrated that poor brain penetration of FLZ and low BBB permeability were due to the P-gp transport.

Development and validation of a LC-MS/MS method for assessment of an anti-inflammatory indolinone derivative by in vitro blood-brain barrier models

The compound (E,Z)-3-(4-hydroxy-3,5-dimethoxybenzylidene)indolin-2-one (indolinone) was identified from lipophilic woad extracts (Isatis tinctoria L., Brassicaceae) as a compound possessing potent histamine release inhibitory and anti-inflammatory properties [1]. To further evaluate the potential of indolinone in terms of crossing the blood-brain barrier (BBB), we screened the compound in several in vitro cell-based human and animal BBB models. Therefore, we developed a quantitative LC-MS/MS method for the compound in modified Ringer HEPES buffer (RHB) and validated it according to FDA and EMA guidelines [2,3]. The calibration curve of indolinone in the range between 30.0 and 3000ng/ml was quadratic, and the limit of quantification was 30.0ng/ml. Dilution of samples up to 100-fold did not affect precision and accuracy. The carry-over was within acceptance criteria. Indolinone proved to be stable in RHB for 3h at room temperature (RT), and for three successive freeze/thaw cycles. The processed samples could be stored in the autosampler at 10°C for at least 28h. Moreover, indolinone was stable for at least 16 days in RHB when stored below -65°C. This validation study demonstrates that our method is specific, selective, precise, accurate, and capable to produce reliable results. In the immortalized human BBB mono-culture model, the apparent permeability coefficient from apical to basolateral (PappA→B), and the Papp from basolateral to apical (PappB→A) were 19.2±0.485×10(-6)cm/s and 21.7±0.326×10(-6)cm/s, respectively. For the primary rat/bovine BBB co-culture model a PappA→B of 27.1±1.67×10(-6)cm/s was determined. In the primary rat BBB triple co-culture model, the PappA→B and the PappB→A were 56.2±3.63×10(-6)cm/s and 34.6±1.41×10(-6)cm/s, respectively. The data obtained with the different models showed good correlation and were indicative of a high BBB permeation potential of indolinone confirmed by in silico prediction calculations. P-glycoprotein (P-gp) interaction for indolinone was studied with the aid of a calcein-AM uptake assay, and by calculation of the efflux ratio (ER) from the bidirectional permeability assays. For both bidirectional BBB models an ER below 2 was calculated, indicating that no active mediated transport mechanism is involved for indolinone. In porcine brain capillary endothelial cells (PBCECs), the calcein-AM uptake assay demonstrated that indolinone is neither a P-gp substrate nor a P-gp inhibitor and is accumulated into cells at high extent.

Efflux transport of serum amyloid P component at the blood-brain barrier

Serum amyloid P component (SAP), a member of the innate immune system, does not penetrate the brain in physiological conditions; however, SAP is a stabilizing component of the amyloid plaques in neurodegenerative diseases. We investigated the cerebrovascular transport of human SAP in animal experiments and in culture blood-brain barrier (BBB) models. After intravenous injection, no SAP could be detected by immunohistochemistry or ELISA in healthy rat brains. Salmonella typhimurium lipopolysaccharide injection increased BBB permeability for SAP and the number of cerebral vessels labeled with fluorescein isothiocyanate (FITC)-SAP in mice. Furthermore, when SAP was injected to the rat hippocampus, a time-dependent decrease in brain concentration was seen demonstrating a rapid SAP efflux transport in vivo. A temperature-dependent bidirectional transport of FITC-SAP was observed in rat brain endothelial monolayers. The permeability coefficient for FITC-SAP was significantly higher in abluminal to luminal (brain to blood) than in the opposite direction. The luminal release of FITC-SAP from loaded endothelial cells was also significantly higher than the abluminal one. Our data indicate the presence of BBB efflux transport mechanisms protecting the brain from SAP penetration. Damaged BBB integrity due to pathological insults may increase brain SAP concentration contributing to development of neurodegenerative diseases.

Species-Dependent Blood-Brain Barrier Disruption of Lipopolysaccharide: Amelioration by Colistin In Vitro and In Vivo

The aim of this study was to use in vitro and in vivo models to assess the impact of lipopolysaccharide (LPS) from two different bacterial species on blood-brain barrier (BBB) integrity and brain uptake of colistin. Following repeated administration of LPS from Pseudomonas aeruginosa, the brain-to-plasma ratio of [¹⁴C]sucrose in Swiss outbred mice was not significantly increased. Furthermore, while the brain uptake of colistin in mice increased 3-fold following administration of LPS from Salmonella enterica, LPS from P. aeruginosa had no significant effect on colistin brain uptake. This apparent species-dependent effect did not appear to correlate with differences in plasma cytokine levels, as the concentrations of tumor necrosis factor alpha and interleukin-6 following administration of each LPS were not different (P > 0.05). To clarify whether this species-specific effect of LPS was due to direct effects on the BBB, human brain capillary endothelial (hCMEC/D3) cells were treated with LPS from P. aeruginosa or S. enterica and claudin-5 expression was measured by Western blotting. S. enterica LPS significantly (P < 0.05) reduced claudin-5 expression at a concentration of 7.5 μg/ml. In contrast, P. aeruginosa LPS decreased (P < 0.05) claudin-5 expression only at the highest concentration tested (i.e., 30 μg/ml). Coadministration of therapeutic concentrations of colistin ameliorated the S. enterica LPS-induced reduction in claudin-5 expression in hCMEC/D3 cells and the perturbation in BBB function in mice. This study demonstrates that BBB disruption induced by LPS is species dependent, at least between P. aeruginosa and S. enterica, and can be ameliorated by colistin.