Cerebral Endothelial Cells Research Articles

The Contribution of Hyperhomocysteinemia to Aβ‐Induced Endothelial Cell Apoptosis, Blood Brain Barrier Dysfunction, and Angiogenic Deficits

AbstractBackgroundCerebrovascular dysfunction has been implicated as a major contributor to Alzheimer’s Disease (AD) pathology, with particularly endothelial cell (EC) stress promoting the focal ischemia, cerebral blood flow impairments, and blood brain barrier (BBB) permeability that are pathologically characteristic in AD. Recent evidence has emerged suggesting a link between cardiovascular (CV) diseases and AD pathology, particularly showing that CV/cerebrovascular risk factors, including hyperhomocysteinemia (Hhcy), contribute to AD pathology and risk. Despite this, the underlying molecular mechanisms for this interaction remain unclear. Previously, our lab has demonstrated that amyloid beta (Aβ), particularly Aβ40‐Q22 (the vasculotropic Dutch mutant), promotes TRAIL death receptor (DR)‐mediated apoptosis, barrier permeability, and angiogenic impairment within human cerebral ECs. We tested the hypothesis that Hhcy exacerbates Aβ‐induced cerebral EC TRAIL DR‐mediated apoptosis, barrier dysfunction, and angiogenesis defects.MethodHuman cerebral microvascular ECs (HCMECs) were challenged with AβQ22 and/or homocysteine (Hcy). Apoptotic mediator expression, caspase activation, cytochrome c release, and DNA fragmentation were measured to assess apoptosis. Junction protein expression, trans‐endothelial‐electrical‐resistance (TEER), and inflammatory mediators were measured to assess EC barrier integrity. Angiogenesis inhibition and activation (cytokine expression, pVEGFR2Y1175 expression/localization, VEGF‐A ELISA) assays were utilized to measure EC angiogenic capability and wound healing and actin polymerization assays were utilized to measure EC wound healing ability.ResultCombined challenge of ECs with AβQ22 and Hcy potentiated increases in TRAIL DR‐related apoptotic mediators' expression, caspase activity, cytochrome c release, and DNA fragmentation and potentiated decreases in anti‐apoptotic mediators’ expression at differential timepoints. Treatment of ECs with AβQ22 and Hcy additively decreased TEER and, at certain timepoints, potentiated decreased junction protein expression, increased inflammatory mediator expression, and phosphorylated BBB protein expression. Combined treatment of ECs with AβQ22 and Hcy additively decreased angiogenesis progression, angiogenesis‐stimulating cytokine expression, wound healing capability, and actin polymerization levels. Additionally, Hcy decreased HCMEC soluble VEGF‐A levels.ConclusionThe presence of high Hcy exacerbates Aβ induced‐EC apoptosis, barrier dysfunction, and angiogenic impairment. This study revealed several of the specific molecular mechanism through which amyloidosis and CV risk factors may additively act to produce EC dysfunction and death in AD.

Inhibition of mitochondrial carbonic anhydrases prevents Amyloid β‐induced cell death and blood brain barrier permeability in cerebrovascular endothelial cells

AbstractBackgroundThe Neurovascular Unit (NVU) is an important multicellular structure of the central nervous system (CNS) which has been observed to become dysfunctional in Alzheimer Disease (AD) and cerebral amyloid angiopathy (CAA). Amyloidosis disrupts the function of cerebrovascular endothelial cells (ECs) through the activation of the intrinsic apoptotic pathway, and the induction of blood brain barrier (BBB) permeability. Previous findings in our lab demonstrate that Acetazolamide (ATZ) and methazolamide (MTZ), pan‐Carbonic Anhydrase (CA) inhibitors, prevent mitochondria mediated apoptosis in cerebrovascular ECs through the reduction of Aβ induced cytochrome C release from the mitochondria, caspase‐9 activation, and mitochondrial H2O2 production. Due to the reduction of mitochondria mediated cell death via pan‐CA inhibitors we hypothesize that the mitochondrial isoforms, CA‐VA/B, are involved in cell death and other deleterious mechanisms induced by Aβ. Thus, we anticipate using selective CA‐V inhibitors will reduce cerebrovascular EC apoptosis and prevent the loss of BBB resistance.MethodHuman cerebral microvascular ECs (hCMECs) were treated with Aβ40‐Q22 Dutch mutant alone and in combination with a CA‐V inhibitor. We measured outcomes of mitochondria mediated apoptosis and BBB integrity. Apoptosis was evaluated by measuring the changes in the protein expression of caspase‐9, BAX, and BCL‐2 with western blot. We used live‐cell imaging to measure active caspase‐3. The release of cytochrome C and the mitochondrial membrane potential was detected using immunocytochemistry (ICC). Mitochondria H2O2 production was measured by isolating mitochondria and using a commercially available kit, Amplex Red (Invitrogen). We assessed the permeability of hCMECs using the ECIS ZΘ technology. The changes in protein expression of EC activation markers, VCAM‐1 and ICAM‐1, were determined with western blot.ResultInhibition of CA‐VA/B prevented Aβ40‐Q22 induced DNA fragmentation, caspase‐9 and ‐3 activation, cytochrome C release from the mitochondria, loss of mitochondria membrane potential, and mitochondrial H2O2 production in human cerebrovascular ECs. The inhibition of CA‐VA/B also reduced Aβ40‐Q22 induced BBB permeability and increase in vascular adhesion protein VCAM‐1 in hCMECs.ConclusionThe inhibition of CA‐V is protective to cerebrovascular ECs in models of amyloidosis, through the prevention of mitochondria‐mediated cell death and loss of cerebral EC barrier function.

Fibrillar tau induces blood brain barrier permeability, endothelial cell activation and bioenergetic alterations

AbstractBackgroundAlzheimer’s Disease, the most common form of dementia, is characterized by the accumulation of amyloid‐beta plaques and neurofibrillary tangles formed by hyperphosphorylated tau in the brain, leading to neuronal loss and cognitive decline. The neurovascular unit, a complex system of several cell types surrounding brain vessels, is extremely important for blood flow regulation, amyloid and tau clearance, and proper brain function. Tau aggregates produced by neurons and glial cells reach endothelial cells (EC) at vessel walls by tau spreading. Currently, the mechanisms responsible for the effects of tau on ECs remain to be understood. We hypothesize that aggregated tau fibrils mediate alterations in bioenergetics in these cells, associated to pro‐inflammatory EC activation, BBB permeability and eventually EC death.MethodImmortalized human brain microvascular endothelial cells (D3) and primary human cerebral endothelial cells (hCECs) were challenged with aggregated 1N4R tau fibrils (5nM‐25nM) for 3‐72h. Trans‐endothelial electrical resistance (TEER) was measured by the ECIS Zθ system as an in vitro model of the BBB. Cytokine production and release was assessed using a V‐Plex Neuroinflammatory Panel 1 (MSD). We performed immunocytochemical analysis of junction protein expression and western blotting for EC activation markers. EC bioenergetics were measured by Seahorse Extracellular Flux Analyzer and EC death was determined by Cell Death Elisa and LDH Release (Roche).ResultTEER was reduced following incubation with fibrillar 1N4R tau. VCAM‐1 expression significantly increased with 25nM tau (24h) and 5nM (48h), and ICAM‐1 followed similar trends. Junction protein (ZO‐1, VE‐Cadherin) expression was decreased. Aggregated tau (25nM) caused an increase in glycolysis at 24‐hours, which reverted at further timepoints, whereas mitochondrial ATP production increased (48h) and then decreased (72h). After 72h treatment, 25nM tau induced a significant increase in apoptotic cell death and LDH release, yet no significant changes in cell death were observed at previous timepoints.ConclusionOur results suggest that tau fibrils mediate a stress response with a metabolic shift in ECs, in association with pro‐inflammatory EC activation. These molecular changes can contribute to BBB permeability and eventually cell death, further exacerbating cerebrovascular dysfunction.

Interfering TRIB3 protects the blood brain barrier through PI3K/Akt pathway to alleviate cerebral ischemia-reperfusion injury in diabetes mellitus mice

This study aimed to treat diabetic cerebral ischemia-reperfusion injury (CI/RI) by affecting blood brain barrier (BBB) permeability and integrity. The CI/RI model in DM mice and a high glucose (HG) treated oxygen and glucose deprivation/reoxygenation (OGD/R) brain endothelial cell model were established for the study. Evans blue (EB) staining was used to evaluate the permeability of BBB in vivo. TTC staining was used to analyze cerebral infarction. The location and expression of tribbles homolog 3 (TRIB3) in endothelial cells were detected by immunofluorescence. Western blotting was used to detect the protein expressions of TRIB3, tight junction molecules, adhesion molecules, phosphorylated protein kinase B (p-AKT) and AKT. The levels of pro-inflammatory cytokines were detected by qRT-PCR. Trans-epithelial electrical resistance (TEER) and fluorescein isothiocyanate (FITC)-dextran were used to measure vascular permeability in vitro. TRIB3 ubiquitination and acetylation levels were detected. Acetyltransferase bound to TRIB3 were identified by immunoprecipitation. TRIB3 was localized in cerebral endothelial cells and was highly expressed in diabetic CI/R mice. The BBB permeability in diabetic CI/R mice and HG-treated OGD/R cells was increased, while the junction integrity was decreased. Interference with TRIB3 in vitro reduces BBB permeability and increases junction integrity. In vivo interfering with TRIB3 reduced cerebral infarction volume, BBB permeability and inflammation levels, and upregulated p-AKT levels. The phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin reversed the effects of TRIB3-interfering plasmid. In vitro HG treatment induced TRIB3 acetylation through acetyltransferase p300, which in turn reduced ubiquitination and stabilized TRIB3. Interfering TRIB3 protects BBB by activating PI3K/AKT pathway and alleviates brain injury, which provides a new target for diabetic CI/RI.

Knockdown of Smox protects the integrity of the blood-brain barrier through antioxidant effect and Nrf2 pathway activation in stroke

Once an ischemic stroke occurs, reactive oxygen species (ROS) and oxidative stress degrade the tight connections between cerebral endothelial cells resulting in their damage. The expression of antioxidant genes may be enhanced, and ROS formation may be reduced following Nrf2 activation, which is associated with protection against ischemic stroke. Overexpression of spermine oxidase (Smox) in the neocortex led to increased H2O2 production. However, how Smox impacts the regulation of the blood–brain barrier (BBB) through antioxidants has not been examined yet. We conducted experiments both in the cell level and in the transient middle cerebral artery occlusion (tMCAO) model to evaluate the effect of Smox siRNA lentivirus (si-Smox) knockdown on BBB protection against ischemic stroke. Mice treated with si-Smox showed remarkably decreased BBB breakdown and reduced endothelial inflammation following stroke. The treatment with si-Smox significantly elevated the Bcl-2 to Bax ratio and decreased the production of cleaved caspase-3 in the tMCAO model. Further investigation revealed that the neuroprotective effect was the result of the antioxidant properties of si-Smox, which reduced oxidative stress and enhanced CD31+ cells in the peri-infarct cortical areas. Of significance, si-Smox activated Nrf2 in both bEnd.3 cells and tMCAO animals, and blocking Nrf2 with brusatol diminished the protective effects of si-Smox. The study findings suggest that si-Smox exerts neuroprotective effects and promotes angiogenesis by activating the Nrf2 pathway, thus decreasing oxidative stress and apoptosis caused by tMCAO. As a result, si-Smox may hold potential as a therapeutic candidate for preserving BBB integrity while treating ischemic stroke.

Brain Endothelial Cells Activate Neuroinflammatory Pathways in Response to Early Cerebral Small Vessel Disease (CSVD) Patients' Plasma.

The pathogenesis of cerebral small vessel disease (CSVD) is largely unknown. Endothelial disfunction has been suggested as the turning point in CSVD development. In this study, we tested the effect of plasma from CSVD patients on human cerebral microvascular endothelial cells with the aim of describing the pattern of endothelial activation. Plasma samples from three groups of young subjects have been tested: PTs (subjects affected by early stage CSVD); CTRLs (control subjects without abnormalities at MRI scanning); BDs (blood donors). Human Brain Endothelial Cells 5i (HBEC5i) were treated with plasma and total RNA was extracted. RNAs were pooled to reduce gene expression-based variability and NGS analysis was performed. Differentially expressed genes were highlighted comparing PTs, CTRLs and BDs with HBEC5i untreated cells. No significantly altered pathway was evaluated in BD-related treatment. Regulation of p38 MAPK cascade (GO:1900744) was the only pathway altered in CTRL-related treatment. Indeed, 36 different biological processes turned out to be deregulated after PT treatment of HBEC5i, i.e., the cytokine-mediated signaling pathway (GO:0019221). Endothelial cells activate inflammatory pathways in response to stimuli from CSVD patients' plasma, suggesting the pathogenetic role of neuroinflammation from the early asymptomatic phases of cerebrovascular disease.

Interaction of amisulpride with GLUT1 at the blood-brain barrier. Relevance to Alzheimer's disease.

Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies indicate that antipsychotics interact with facilitated glucose transporters (GLUT), including GLUT1, and that GLUT1 BBB expression decreases in AD. We tested the hypotheses that amisulpride (charge: +1) interacts with GLUT1, and that BBB transport of amisulpride is compromised in AD. GLUT1 substrates, GLUT1 inhibitors and GLUT-interacting antipsychotics were identified by literature review and their physicochemical characteristics summarised. Interactions between amisulpride and GLUT1 were studied using in silico approaches and the human cerebral endothelial cell line, hCMEC/D3. Brain distribution of [3H]amisulpride was determined using in situ perfusion in wild type (WT) and 5xFamilial AD (5xFAD) mice. With transmission electron microscopy (TEM) we investigated brain capillary degeneration in WT mice, 5xFAD mice and human samples. Western blots determined BBB transporter expression in mouse and human. Literature review revealed that, although D-glucose has no charge, charged molecules can interact with GLUT1. GLUT1 substrates are smaller (184.95±6.45g/mol) than inhibitors (325.50±14.40g/mol) and GLUT-interacting antipsychotics (369.38±16.04). Molecular docking showed beta-D-glucose (free energy binding: -15.39kcal/mol) and amisulpride (-29.04kcal/mol) interact with GLUT1. Amisulpride did not affect [14C]D-glucose hCMEC/D3 accumulation. [3H]amisulpride uptake into the brain (except supernatant) of 5xFAD mice compared to WT remained unchanged. TEM revealed brain capillary degeneration in human AD. There was no difference in GLUT1 or P-glycoprotein BBB expression between WT and 5xFAD mice. In contrast, caudate P-glycoprotein, but not GLUT1, expression was decreased in human AD capillaries versus controls. This study provides new details about the BBB transport of amisulpride, evidence that amisulpride interacts with GLUT1 and that BBB transporter expression is altered in AD. This suggests that antipsychotics could potentially exacerbate the cerebral hypometabolism in AD. Further research into the mechanism of amisulpride transport by GLUT1 is important for improving antipsychotics safety.

Estrogenic regulation of claudin 5 and tight junction protein 1 gene expression in zebrafish: A role on blood-brain barrier?

The blood-brain barrier (BBB) is a physical interface between the blood and the brain parenchyma, playing key roles in brain homeostasis. In mammals, the BBB is established thanks to tight junctions between cerebral endothelial cells, involving claudin, occludin, and zonula occludens proteins. Estrogens have been documented to modulate BBB permeability. Interestingly, in the brain of zebrafish, the estrogen-synthesizing activity is strong due to the high expression of Aromatase B protein, encoded by the cyp19a1b gene, in radial glial cells (neural stem cells). Given the roles of estrogens in BBB function, we investigated their impact on the expression of genes involved in BBB tight junctions. We treated zebrafish embryos and adult males with 17β-estradiol and observed an increased cerebral expression of tight junction and claudin 5 genes in adult males only. In females, treatment with the nuclear estrogen receptor antagonist (ICI182,780 ) had no impact. Interestingly, telencephalic injuries performed in males decreased tight junction gene expression that was partially reversed with 17β-estradiol. This was further confirmed by extravasation experiments of Evans blue showing that estrogenic treatment limits BBB leakage. We also highlighted the intimate links between endothelial cells and neural stem cells, suggesting that cholesterol and peripheral steroids could be taken up by endothelial cells and used as precursors for estrogen synthesis by neural stem cells. Together, our results show that zebrafish provides an alternative model to further investigate the role of steroids on the expression of genes involved in BBB integrity, both in constitutive and regenerative physiological conditions. The link we described between capillaries endothelial cells and steroidogenic neural cells encourages the use of this model in understanding the mechanisms by which peripheral steroids get into neural tissue and modulate neurogenic activity.

Shedding Light on Lysosomal Malondialdehyde Affecting Vitamin B12 Transport during Cerebral Ischemia/Reperfusion Injury.

Cerebral ischemia-reperfusion injury (CIRI) is often accompanied by upregulation of homocysteine (Hcy). Excessive Hcy damages cerebral vascular endothelial cells and neurons, inducing neurotoxicity and even neurodegeneration. Normally, supplementation of vitamin B12 is an ideal intervention to reduce Hcy. However, vitamin B12 therapy is clinically inefficacious for CIRI. Considering oxidative stress is closely related to CIRI, the lysosome is the pivotal site for vitamin B12 transport. Lysosomal oxidative stress might hinder the transport of vitamin B12. Whether lysosomal malondialdehyde (lysosomal MDA), as the authoritative biomarker of lysosomal oxidative stress, interferes with the transport of vitamin B12 has not been elucidated. This is ascribed to the absence of effective methods for real-time and in situ measurement of lysosomal MDA within living brains. Herein, a fluorescence imaging agent, Lyso-MCBH, was constructed to specifically monitor lysosomal MDA by entering the brain and targeting the lysosome. Erupting the lysosomal MDA level in living brains of mice under CIRI was first observed using Lyso-MCBH. Excessive lysosomal MDA was found to affect the efficacy of vitamin B12 by blocking the transport of vitamin B12 from the lysosome to the cytoplasm. More importantly, the expression and function of the vitamin B12 transporter LMBD1 were proved to be associated with excessive lysosomal MDA. Altogether, the revealing of the lysosomal MDA-LMBD1 axis provides a cogent interpretation of the inefficacy of vitamin B12 in CIRI, which could be a prospective therapeutic target.

CERCAM is a prognostic biomarker associated with immune infiltration of macrophage M2 polarization in head and neck squamous carcinoma

PurposeThis study aimed to investigate the relevance of cerebral endothelial cell adhesion molecule (CERCAM) expression to head and neck squamous cell carcinoma (HNSCC) prognosis and immune infiltration by macrophage M2 polarization.MethodsTimer, UALCAN and HPA databases was used to analyze the differences in mRNA and protein levels of CERCAM expression in HNSCC. The Timer database was also applied to analyze the correlation between CERCAM in HNSCC and immune infiltration. TCGA-HNSCC database was applied to analyze the correlation between CERCAM expression levels and clinicopathological features, and its diagnostic and prognostic value in HNSCC was also assessed. The cBioPortal and MethSurv databases were then applied to analyze the genetic variation and methylation status of CERCAM. In vitro cellular assays were performed to provide evidence that CERCAM promotes malignant biological behavior of tumors and promotes macrophage M2 polarization in tumors. Finally, underlying pathophysiological mechanisms of CERCAM involvement in the development of HNSCC were predicted using a bioinformatics approach.ResultsCERCAM is significantly overexpressed in HNSCC and correlates with poor prognostic levels and has good performance in predicting survival status in HNSCC patients. Cox regression analysis indicates that CERCAM expression levels are independent risk factors for predicting OS, DSS, and PFI. CERCAM promotes tumor malignant biological behavior and promotes macrophage M2 polarization immune infiltration in HNSCC. In addition, CERCAM promotes tumor cell adhesion in head and neck squamous carcinoma and promotes tumor progression through several oncogenic signaling pathways.ConclusionCERCAM may serve as a new diagnostic and prognostic biomarker in HNSCC and is a promising therapeutic target for HNSCC.

Integrated transcriptomic and proteomic profiling reveals the key molecular signatures of brain endothelial reperfusion injury.

Reperfusion therapy after ischemic stroke often causes brain microvascular injury. However, the underlying mechanisms are unclear. Transcriptomic and proteomic analyses were performed on human cerebral microvascular endothelial cells following oxygen-glucose deprivation (OGD) or OGD plus recovery (OGD/R) to identify molecules and signaling pathways dysregulated by reperfusion. Major findings were further validated in a mouse model of cerebral ischemia and reperfusion. Transcriptomic analysis identified 390 differentially expressed genes (DEGs) between the OGD/R and OGD group. Pathway analysis indicated that these genes were mostly associated with inflammation, including the TNF signaling pathway, TGF-β signaling pathway, cytokine-cytokine receptor interaction, NOD-like receptor signaling pathway, and NF-κB signaling pathway. Proteomic analysis identified 201 differentially expressed proteins (DEPs), which were primarily associated with extracellular matrix destruction and remodeling, impairment of endothelial transport function, and inflammatory responses. Six genes (DUSP1, JUNB, NFKBIA, NR4A1, SERPINE1, and THBS1) were upregulated by OGD/R at both the mRNA and protein levels. In mice with cerebral ischemia and reperfusion, brain TNF signaling pathway was activated by reperfusion, and inhibiting TNF-α with adalimumab significantly attenuated reperfusion-induced brain endothelial inflammation. In addition, the protein level of THBS1 was substantially upregulated upon reperfusion in brain endothelial cells and the peri-endothelial area in mice receiving cerebral ischemia. Our study reveals the key molecular signatures of brain endothelial reperfusion injury and provides potential therapeutic targets for the treatment of brain microvascular injury after reperfusion therapy in ischemic stroke.

Molecular weight of hyaluronic acid crosslinked into biomaterial scaffolds affects angiogenic potential.

While hyaluronic acid (HA)-based hydrogels have been used clinically for decades, the mechanisms by which HA exerts molecular weight-dependent bioactivity and how chemical modification and crosslinking may affect molecular weight-dependent bioactivity remain poorly understood. This knowledge gap presents a significant barrier to designing HA hydrogels with predictable bioactivities. As HA has been widely reported to have molecular weight-dependent effects on endothelial cells (ECs), we investigated how the molecular weight of HA in either soluble or crosslinked forms affects angiogenesis and interrogated CD44 clustering on the surface of endothelial cells as a candidate mechanism for these affects. Using soluble HA, our results show high molecular weight (HMW) HA, but not low molecular weight (LMW) HA, increased viability and tube formation in cultured human cerebral microvascular ECs (HCMVECs). No size of HA affected proliferation. When HCMVECs were cultured with crosslinked HA of varying molecular weights in the form of HA-based microporous annealed particle scaffold (HMAPS), the cell response was comparable to when cultured with soluble HA. Similarly, when implanted subcutaneously, HMAPS with HMW HA were more vascularized than those with LMW HA. We also show that antibody-mediated CD44 clustering resulted in HCMVECs with increased viability and tube-like structure formation in a manner comparable to exposure to HMW HA, suggesting that HMW acts through CD44 clustering. STATEMENT OF SIGNIFICANCE: Biomaterials based on hyaluronic acid (HA), a bioactive extracellular matrix polysaccharide, have been used in clinical products for several years. Despite the knowledge that HA molecular weight heavily influences its bioactivity, molecular weight has been largely ignored in the development of HA-based biomaterials. Given the high viscosity of high molecular weight HA typically found in native tissues, lower molecular weight polysaccharides have been used most commonly for biomaterial fabrication. By comparing the ability of injectable, microporous annealed particle scaffolds (MAPS) fabricated from variably sized HA to promote angiogenesis, this study demonstrates that MAPS with high molecular weight HA better support vascularization, likely through an unique ability to induce clustering of CD44 receptors on endothelial cells.

Thyrotropin receptor autoantibody (TRAb) enhance the expression of thyrotropin receptor on mouse brain vascular endothelial cells: in vivo and in vitro.

The possibility that thyrotropin receptor (TSHR) expression in non-thyroid tissue is well-documented. However, there is insufficient data on the expression of TSHR in medulla oblongata regions, particularly when focusing on the background of encephalopathy associated with hyperthyroidism. In this study, we explored the expression of the functional TSHR in Graves' disease (GD) mouse cerebral vascular endothelial cells and the effects of thyrotropin receptor autoantibody (TRAb) on its expression. A mouse model of GD was constructed with an adenovirus overexpressing TSHR289. The location and expression of the TSHR gene and protein in vivo were determined via RT-qPCR, Western blot, and immunofluorescence techniques. The effect of TRAb on the expression of functional TSHR in vitro was investigated using bEnd.3 cells. Our results show that medulla oblongata vascular endothelial cells from GD mice expressed higher levels of TSHR compared to control mice. In an in vitro experiment, novel results demonstrated that after treatment with a monoclonal TSHR-specific agonistic antibody (M22), the expression of TSHR on the bEnd.3 cells increased at both the protein and mRNA levels. Furthermore, compared with bEnd.3 cells were treated with IBMX only, those treated with M22 showed increased cAMP production. This study suggested that TSHR is expressed and functionally active in the mouse medulla oblongata and in vitro-cultured bEnd.3 cells and TRAb (M22) increased the expression of TSHR on bEnd.3 cells.

Cerebral endothelial cell-derived extracellular vesicles regulate microglial polarization and promote autophagy via delivery of miR-672-5p

The interaction between cerebral endothelial cells (CEC) and brain parenchymal cells is critical to maintain neurovascular homeostasis, whereas extracellular vesicles (EVs) are essential to mediate the cell–cell communication. Previous researches demonstrated that CEC-derived EVs (CEC-EVs) confer neuroprotective actions. However, the molecular mechanisms remain unknown. In this study, we isolated EVs from CEC and assessed their immune-regulatory actions in microglial cells and mice following lipopolysaccharide (LPS) exposure. We found that CEC-EVs treatment significantly ameliorated LPS-induced inflammatory activation, shifting microglial polarization from pro-inflammatory phenotype to anti-inflammatory phenotype. Meanwhile, microglial cells can effectively internalize CEC-EVs and this process was further enhanced by immune activation. Next, the miRNA microarray analysis revealed that CEC-EVs increased expression of miR-672-5p, which was demonstrated to be the cargo of CEC-EVs. TGFβ-activated kinase 1 (TAK1)-binding proteins 2 (TAB2) was identified to be the target of miR-672-5p. Through inhibiting TAB2, miR-672-5p derived from CEC-EVs suppressed TAK1-TAB signaling and thereby mitigating the downstream NF-κB activation. Furthermore, we found that by delivering miR-672-5p, CEC-EVs promoted autophagy and hence stimulating autophagic degradation of NLRP3 inflammasome. Our work firstly revealed the neuroimmune-modulating actions of CEC-EVs and further demonstrated that miR-672-5p secreted from CEC-EVs inhibits microglial pro-inflammatory polarization and facilitates autophagic process via targeting TAB2.

Iron overload induces cerebral endothelial senescence in aged mice and in primary culture in a sex-dependent manner.

Iron imbalance in the brain negatively affects brain function. With aging, iron levels increase in the brain and contribute to brain damage and neurological disorders. Changes in the cerebral vasculature with aging may enhance iron entry into the brain parenchyma, leading to iron overload and its deleterious consequences. Endothelial senescence has emerged as an important contributor to age-related changes in the cerebral vasculature. Evidence indicates that iron overload may induce senescence in cultured cell lines. Importantly, cells derived from female human and mice generally show enhanced senescence-associated phenotype, compared with males. Thus, we hypothesize that cerebral endothelial cells (CEC) derived from aged female mice are more susceptible to iron-induced senescence, compared with CEC from aged males. We found that aged female mice, but not males, showed cognitive deficits when chronically treated with ferric citrate (FC), and their brains and the brain vasculature showed senescence-associated phenotype. We also found that primary culture of CEC derived from aged female mice, but not male-derived CEC, exhibited senescence-associated phenotype when treated with FC. We identified that the transmembrane receptor Robo4 was downregulated in the brain vasculature and in cultured primary CEC derived from aged female mice, compared with those from male mice. We discovered that Robo4 downregulation contributed to enhanced vulnerability to FC-induced senescence. Thus, our study identifies Robo4 downregulation as a driver of senescence induced by iron overload in primary culture of CEC and a potential risk factor of brain vasculature impairment and brain dysfunction.

The anti-amoebic potential of carboxamide derivatives containing sulfonyl or sulfamoyl moieties against brain-eating Naegleria fowleri.

Naegleria fowleri is a free-living thermophilic flagellate amoeba that causes a rare but life-threatening infection called primary amoebic meningoencephalitis (PAM), with a very high fatality rate. Herein, the anti-amoebic potential of carboxamide derivatives possessing sulfonyl or sulfamoyl moiety was assessed against pathogenic N. fowleri using amoebicidal, cytotoxicity and cytopathogenicity assays. The results from amoebicidal experiments showed that derivatives dramatically reduced N. fowleri viability. Selected derivatives demonstrated IC50 values at lower concentrations; 1j showed IC50 at 24.65 μM, while 1k inhibited 50% amoebae growth at 23.31 μM. Compounds with significant amoebicidal effects demonstrated limited cytotoxicity against human cerebral microvascular endothelial cells. Finally, some derivatives mitigated N. fowleri-instigated host cell death. Ultimately, this study demonstrated that 1j and 1k exhibited potent anti-amoebic activity and ought to be looked at in future studies for the development of therapeutic anti-amoebic pharmaceuticals. Further investigation is required to determine the clinical relevance of our findings.

Curcumin in vitro Neuroprotective Effects Are Mediated by p62/keap-1/Nrf2 and PI3K/AKT Signaling Pathway and Autophagy Inhibition.

Oxidative stress and autophagy are potential mechanisms associated with cerebral ischemia/reperfusion injury (IRI) and is usually linked to inflammatory responses and apoptosis. Curcumin has recently been demonstrated to exhibit anti-inflammatory, anti-oxidant, anti-apoptotic and autophagy regulation properties. However, mechanism of curcumin on IRI-induced oxidative stress and autophagy remains not well understood. We evaluated the protective effects and potential mechanisms of curcumin on cerebral microvascular endothelial cells (bEnd.3) and neuronal cells (HT22) against oxygen glucose deprivation/reoxygenation (OGD/R) in vitro models that mimic in vivo cerebral IRI. The cell counting kit-8 (CCK-8) and lactate dehydrogenase (LDH) activity assays revealed that curcumin attenuated the OGD/R-induced injury in a dose-specific manner. OGD/R induced elevated levels of inflammatory cytokines TNF-alpha, IL-6 as well as IL-1beta, and these effects were notably reduced by curcumin. OGD/R-mediated apoptosis was suppressed by curcumin via upregulating B-cell lymphoma-2 (Bcl-2) and downregulating Bcl-associated X (Bax), cleaved-caspase3 and TUNEL apoptosis marker. Additionally, curcumin increased superoxide dismutase (SOD) and glutathione (GSH), but suppressed malondialdehyde (MDA) and reactive oxygen species (ROS) content. Curcumin inhibited the levels of autophagic biomarkers such as LC3 II/LC3 I and Beclin1. Particularly, curcumin induced p62 accumulation and its interactions with keap1 and promoted NF-E2-related factor 2 (Nrf2) translocation to nucleus, accompanied by increased NADPH quinone dehydrogenase (Nqo1) and heme oxygenase 1 (HO-1). Treatment of curcumin increased phosphorylation-phosphatidylinositol 3 kinase (p-PI3K) and p-protein kinase B (p-AKT). The autophagy inhibitor 3-methyladenine (3-MA) activated the keap-1/Nrf2 and PI3K/AKT pathways. This study highlights the neuroprotective effects of curcumin on cerebral IRI.

Claudin-10 in the Blood Brain Barrier Function of Cerebral Endothelial Cells and Transendothelial Invasion of Breast Cancer Cells.

Claudin-10 (CLDN10) is a membrane integral protein. It is one of the widely expressed tight junctional claudins with functions not well defined. In the present study, the expression profile and its role in cerebral endothelial cells and in the interaction between breast cancer and endothelial cells were investigated. CLDN10 expression was examined in a wide range of cell types. Brain endothelial cell models with or without CLDN10 expression were generated using the hCMEC/D3 cell line and used to test the barrier and permeability functions. Transendothelial drug delivery and invasion were also evaluated. hCMEC/D3 cells express high levels of CLDN10, compared with peripheral endothelial cells, mesothelial cells, fibroblasts, and breast cancer cells, which were either negative or expressed low levels of CLDN10. Knockdown of CLDN10 in hCMEC/D3 cells resulted in impaired tight junctions as seen by reduced transendothelial electric resistance and paracellular permeability. It also accelerated invasion of breast cancer cells through the endothelial cell layer. CLDN10 knockdown in hCMEC/D3 cells led to an increase in transendothelial chemodrug delivery. Furthermore, the SRC kinase inhibitor (AZM475271) was able to decrease the impedance and increase the paracellular permeability in cerebral endothelial cells. Cerebral endothelial cells express high levels of CLDN10, a protein regulating barrier function and thereby drug permeability and cancer invasiveness in brain endothelial cells, suggesting that it is a novel therapeutic target for the treatment of brain metastasis-related diseases.

Age-Associated Changes in Endothelial Transcriptome and Epigenetic Landscapes Correlate With Elevated Risk of Cerebral Microbleeds.

Background Stroke is a leading global cause of human death and disability, with advanced aging associated with elevated incidences of stroke. Despite high mortality and morbidity of stroke, the mechanisms leading to blood-brain barrier dysfunction and development of stroke with age are poorly understood. In the vasculature of brain, endothelial cells (ECs) constitute the core component of the blood-brain barrier and provide a physical barrier composed of tight junctions, adherens junctions, and basement membrane. Methods and Results We show, in mice, the incidents of intracerebral bleeding increases with age. After isolating an enriched population of cerebral ECs from murine brains at 2, 6, 12, 18, and 24 months, we studied age-associated changes in gene expression. The study reveals age-dependent dysregulation of 1388 genes, including many involved in the maintenance of the blood-brain barrier and vascular integrity. We also investigated age-dependent changes on the levels of CpG methylationand accessible chromatin in cerebral ECs. Our study reveals correlations between age-dependent changes in chromatin structure and gene expression, whereas the dynamics of DNA methylation changes are different. Conclusions We find significant age-dependent downregulation of the Aplnr gene along with age-dependent reduction in chromatin accessibility of promoter region of the Aplnr gene in cerebral ECs. Aplnr is associated with positive regulation of vasodilation and is implicated in vascular health. Altogether, our data suggest a potential role of the apelinergic axis involving the ligand apelin and its receptor to be critical in maintenance of the blood-brain barrier and vascular integrity.

Application of In vitro transcytosis models to brain targeted biologics.

The blood brain barrier (BBB) efficiently limits the penetration of biologics drugs from blood to brain. Establishment of an in vitro BBB model can facilitate screening of central nervous system (CNS) drug candidates and accelerate CNS drug development. Despite many established in vitro models, their application to biologics drug selection has been limited. Here, we report the evaluation of in vitro transcytosis of anti-human transferrin receptor (TfR) antibodies across human, cynomolgus and mouse species. We first evaluated human models including human cerebral microvascular endothelial cell line hCMEC/D3 and human colon epithelial cell line Caco-2 models. hCMEC/D3 model displayed low trans-epithelial electrical resistance (TEER), strong paracellular transport, and similar transcytosis of anti-TfR and control antibodies. In contrast, the Caco-2 model displayed high TEER value and low paracellular transport. Anti-hTfR antibodies demonstrated up to 70-fold better transcytosis compared to control IgG. Transcytosis of anti-hTfR.B1 antibody in Caco-2 model was dose-dependent and saturated at 3 μg/mL. Enhanced transcytosis of anti-hTfR.B1 was also observed in a monkey brain endothelial cell based (MBT) model. Importantly, anti-hTfR.B1 showed relatively high brain radioactivity concentration in a non-human primate positron emission tomography study indicating that the in vitro transcytosis from both Caco-2 and MBT models aligns with in vivo brain exposure. Typically, brain exposure of CNS targeted biologics is evaluated in mice. However, antibodies, such as the anti-human TfR antibodies, do not cross-react with the mouse target. Therefore, validation of a mouse in vitro transcytosis model is needed to better understand the in vitro in vivo correlation. Here, we performed transcytosis of anti-mouse TfR antibodies in mouse brain endothelial cell-based models, bEnd3 and the murine intestinal epithelial cell line mIEC. There is a good correlation between in vitro transcytosis of anti-mTfR antibodies and bispecifics in mIEC model and their mouse brain uptake. These data strengthen our confidence in the predictive power of the in vitro transcytosis models. Both mouse and human in vitro models will serve as important screening assays for brain targeted biologics selection in CNS drug development.