Modulation of the blood–brain barrier permeability by plasma glycoprotein orosomucoid

Mechanisms of triple-negative breast cancer extravasation: Impact of the physical environment and endothelial glycocalyx

Cancer metastasis is the leading cause of death for those afflicted with cancer. In cancer metastasis, the cancer cells break off from the primary tumor, penetrate nearby blood vessels, and attach and extravasate out of the vessels to form secondary tumors at distant organs. This makes extravasation a critical step of the metastatic cascade. Herein, with a focus on triple-negative breast cancer, the role that the prospective secondary tumor microenvironment's mechanical properties play in circulating tumor cells' extravasation is reviewed. Specifically, the effects of the physically regulated vascular endothelial glycocalyx barrier element, vascular flow factors, and subendothelial extracellular matrix mechanical properties on cancer cell extravasation are examined. The ultimate goal of this review is to clarify the physical mechanisms that drive triple-negative breast cancer extravasation, as these mechanisms may be potential new targets for anti-metastasis therapy.

Heparan Sulfate Modulation Affects Breast Cancer Cell Adhesion and Transmigration across In Vitro Blood-Brain Barrier

The disruption of endothelial heparan sulfate (HS) is an early event in tumor cell metastasis across vascular barriers, and the reinforcement of endothelial HS reduces tumor cell adhesion to endothelium. Our recent study showed that while vascular endothelial growth factor (VEGF) greatly reduces HS at an in vitro blood-brain barrier (BBB) formed by human cerebral microvascular endothelial cells (hCMECs), it significantly enhances HS on a breast cancer cell, MDA-MB-231 (MB231). Here, we tested that this differential effect of VEGF on the HS favors MB231 adhesion and transmigration. We also tested if agents that enhance endothelial HS may affect the HS of MB231 and reduce its adhesion and transmigration. To test these hypotheses, we generated an in vitro BBB by culturing hCMECs on either a glass-bottom dish or a Transwell filter. We first quantified the HS of the BBB and MB231 after treatment with VEGF and endothelial HS-enhancing agents and then quantified the adhesion and transmigration of MB231 across the BBB after pretreatment with these agents. Our results demonstrated that the reduced/enhanced BBB HS and enhanced/reduced MB231 HS increase/decrease MB231 adhesion to and transmigration across the BBB. Our findings suggest a therapeutic intervention by targeting the HS-mediated breast cancer brain metastasis.

Orosomucoid-1 Arises as a Shared Altered Protein in Two Models of Multiple Sclerosis

Multiple sclerosis (MS) is a complex autoimmune and neurodegenerative disorder that affects the central nervous system (CNS). It is characterized by a heterogeneous disease course involving demyelination and inflammation. In this study, we utilized two distinct animal models, cuprizone (CPZ)-induced demyelination and experimental autoimmune encephalomyelitis (EAE), to replicate various aspects of the disease. We aimed to investigate the differential CNS responses by examining the proteomic profiles of EAE mice during the peak disease (15 days post-induction) and cuprizone-fed mice during the acute phase (38 days). Specifically, we focused on two different regions of the CNS: the dorsal cortex (Cx) and the entire spinal cord (SC). Our findings revealed varied glial, synaptic, dendritic, mitochondrial, and inflammatory responses within these regions for each model. Notably, we identified a single protein, Orosomucoid-1 (Orm1), also known as Alpha-1-acid glycoprotein 1 (AGP1), that consistently exhibited alterations in both models and regions. This study provides insights into the similarities and differences in the responses of these regions in two distinct demyelinating models.

Acute Phase Protein Orosomucoid (Alpha-1-Acid Glycoprotein) Predicts Delayed Cerebral Ischemia and 3-Month Unfavorable Outcome after Aneurysmal Subarachnoid Hemorrhage

The pathophysiology and consequences of early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (aSAH) remain incompletely understood. This study aims to investigate the role of orosomucoid (ORM) in aSAH, its potential as a marker for assessing the extent of EBI-induced damage, and its correlation with delayed cerebral ischemia (DCI) and functional recovery over a 3-month period. We collected serum specimens 72 h post-aSAH to measure ORM levels. The study included 151 aSAH patients and 105 healthy subjects. The serum ORM levels within the patient cohort significantly exceeded those in the control group (p < 0.001). The ORM value showed significant correlation with the admission WFNS (p < 0.0001) and mFS scores (p < 0.05). Substantially elevated serum ORM levels at 72 h post-aSAH were detected among patients experiencing DCI, as well as those with poor functional outcomes after 3 months (p = 0.009 and p < 0.001). Binary logistic regression analyses revealed that serum ORM at 72 h post-SAH was independently associated with DCI and 3-month functional outcome after adjusting for confounders. The early stage events of aSAH influence the level of ORM. ORM serves as a marker for assessing the extent of damage during EBI and is linked to the occurrence of DCI as well as unfavorable long-term functional outcomes.

Molecular Mechanisms of Acute Organophosphate Nephrotoxicity

Organophosphates (OPs) are toxic chemicals produced by an esterification process and some other routes. They are the main components of herbicides, pesticides, and insecticides and are also widely used in the production of plastics and solvents. Acute or chronic exposure to OPs can manifest in various levels of toxicity to humans, animals, plants, and insects. OPs containing insecticides were widely used in many countries during the 20th century, and some of them continue to be used today. In particular, 36 OPs have been registered in the USA, and all of them have the potential to cause acute and sub-acute toxicity. Renal damage and impairment of kidney function after exposure to OPs, accompanied by the development of clinical manifestations of poisoning back in the early 1990s of the last century, was considered a rare manifestation of their toxicity. However, since the beginning of the 21st century, nephrotoxicity of OPs as a manifestation of delayed toxicity is the subject of greater attention of researchers. In this article, we present a modern view on the molecular pathophysiological mechanisms of acute nephrotoxicity of organophosphate compounds.

Human Galectin-7 Gene LGALS7 Promoter Sequence Polymorphisms and Risk of Spontaneous Intracerebral Hemorrhage: A Prospective Study

Background and purpose

Despite evidence for the role of genetic factors in stroke, only a small proportion of strokes have been clearly attributed to monogenic factors, due to phenotypic heterogeneity. The goal of this study was to determine whether a significant relationship exists between human galectin-7 gene LGALS7 promoter region polymorphisms and the risk of stroke due to non-traumatic intracerebral hemorrhage (ICH).

Methods

This two-stage genetic association study included an initial exploratory stage followed by a discovery stage. During the exploratory stage, transgenic galectin-7 mice or transgenic mice with the scrambled sequence of the hairpin structure –silenced down gene LGALS7—were generated and then expressed differentially expressed proteins and galectin-7-interacting proteins were identified through proteomic analysis. During the discovery stage, a single-nucleotide polymorphism (SNP) genotyping approach was used to determine associations between 2 LGALS7 SNPs and ICH stroke risk for a cohort of 24 patients with stroke of the Chinese Han population and 70 controls.

Results

During the exploratory phase, LGALS7 expression was found to be decreased in TGLGALS–DOWN mice as compared to its expression in TGLGALS mice. During the discovery phase, analysis of LGALS7 sequences of 24 non-traumatic ICH cases and 70 controls led to the identification of 2 ICH susceptibility loci: a genomic region on 19q13.2 containing two LGALS7 SNPs, rs567785577 and rs138945880, whereby the A allele of rs567785577 and the T allele of rs138945880 were associated with greater risk of contracting ICH [for T and A vs. C and G, unadjusted odds ratio (OR) = 13.5; 95% CI = 2.249–146.5; p = 0.002]. This is the first study to genotype the galectin-7 promoter in patients with hemorrhagic stroke. Genotype and allele association tests and preliminary analysis of patients with stroke revealed that a single locus may be a genetic risk factor for hemorrhagic stroke.

Conclusion

A and T alleles of two novel SNP loci of 19q13.2, rs567785577 and rs138945880, respectively, were evaluated for associations with susceptibility to ICH. Further studies with expanded case numbers that include subjects of other ethnic populations are needed to elucidate mechanisms underlying associations between these SNPs and ICH risk.

The Glomerular Endothelium Restricts Albumin Filtration

Inflammatory activation and/or dysfunction of the glomerular endothelium triggers proteinuria in many systemic and localized vascular disorders. Among them are the thrombotic microangiopathies, many forms of glomerulonephritis, and acute inflammatory episodes like sepsis and COVID-19 illness. Another example is the chronic endothelial dysfunction that develops in cardiovascular disease and in metabolic disorders like diabetes. While the glomerular endothelium is a porous sieve that filters prodigious amounts of water and small solutes, it also bars the bulk of albumin and large plasma proteins from passing into the glomerular filtrate. This endothelial barrier function is ascribed predominantly to the endothelial glycocalyx with its endothelial surface layer, that together form a relatively thick, mucinous coat composed of glycosaminoglycans, proteoglycans, glycolipids, sialomucins and other glycoproteins, as well as secreted and circulating proteins. The glycocalyx/endothelial surface layer not only covers the glomerular endothelium; it extends into the endothelial fenestrae. Some glycocalyx components span or are attached to the apical endothelial cell plasma membrane and form the formal glycocalyx. Other components, including small proteoglycans and circulating proteins like albumin and orosomucoid, form the endothelial surface layer and are bound to the glycocalyx due to weak intermolecular interactions. Indeed, bound plasma albumin is a major constituent of the endothelial surface layer and contributes to its barrier function. A role for glomerular endothelial cells in the barrier of the glomerular capillary wall to protein filtration has been demonstrated by many elegant studies. However, it can only be fully understood in the context of other components, including the glomerular basement membrane, the podocytes and reabsorption of proteins by tubule epithelial cells. Discovery of the precise mechanisms that lead to glycocalyx/endothelial surface layer disruption within glomerular capillaries will hopefully lead to pharmacological interventions that specifically target this important structure.

The blood-brain barrier in systemic infection and inflammation

The vascular blood-brain barrier is a highly regulated interface between the blood and brain. Its primary function is to protect central neurons while signaling the presence of systemic inflammation and infection to the brain to enable a protective sickness behavior response. With increasing degrees and duration of systemic inflammation, the vascular blood-brain barrier becomes more permeable to solutes, undergoes an increase in lymphocyte trafficking, and is infiltrated by innate immune cells; endothelial cell damage may occasionally occur. Perturbation of neuronal function results in the clinical features of encephalopathy. Here, the molecular and cellular anatomy of the vascular blood-brain barrier is reviewed, first in a healthy context and second in a systemic inflammatory context. Distinct from the molecular and cellular mediators of the blood-brain barrier's response to inflammation, several moderators influence the direction and magnitude at genetic, system, cellular and molecular levels. These include sex, genetic background, age, pre-existing brain pathology, systemic comorbidity, and gut dysbiosis. Further progress is required to define and measure mediators and moderators of the blood-brain barrier's response to systemic inflammation in order to explain the heterogeneity observed in animal and human studies.

Direct Current Stimulation Disrupts Endothelial Glycocalyx and Tight Junctions of the Blood-Brain Barrier in vitro

Transcranial direct current stimulation (tDCS) is a non-invasive physical therapy to treat many psychiatric disorders and to enhance memory and cognition in healthy individuals. Our recent studies showed that tDCS with the proper dosage and duration can transiently enhance the permeability (P) of the blood-brain barrier (BBB) in rat brain to various sized solutes. Based on the in vivo permeability data, a transport model for the paracellular pathway of the BBB also predicted that tDCS can transiently disrupt the endothelial glycocalyx (EG) and the tight junction between endothelial cells. To confirm these predictions and to investigate the structural mechanisms by which tDCS modulates P of the BBB, we directly quantified the EG and tight junctions of in vitro BBB models after DCS treatment. Human cerebral microvascular endothelial cells (hCMECs) and mouse brain microvascular endothelial cells (bEnd3) were cultured on the Transwell filter with 3 μm pores to generate in vitro BBBs. After confluence, 0.1–1 mA/cm² DCS was applied for 5 and 10 min. TEER and P to dextran-70k of the in vitro BBB were measured, HS (heparan sulfate) and hyaluronic acid (HA) of EG was immuno-stained and quantified, as well as the tight junction ZO-1. We found disrupted EG and ZO-1 when P to dextran-70k was increased and TEER was decreased by the DCS. To further investigate the cellular signaling mechanism of DCS on the BBB permeability, we pretreated the in vitro BBB with a nitric oxide synthase (NOS) inhibitor, L-NMMA. L-NMMA diminished the effect of DCS on the BBB permeability by protecting the EG and reinforcing tight junctions. These in vitro results conform to the in vivo observations and confirm the model prediction that DCS can disrupt the EG and tight junction of the BBB. Nevertheless, the in vivo effects of DCS are transient which backup its safety in the clinical application. In conclusion, our current study directly elucidates the structural and signaling mechanisms by which DCS modulates the BBB permeability.

Bioinformatic analysis identifies potential key genes of epilepsy

Background

Epilepsy is one of the most common brain disorders worldwide. It is usually hard to be identified properly, and a third of patients are drug-resistant. Genes related to the progression and prognosis of epilepsy are particularly needed to be identified.

Methods

In our study, we downloaded the Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE143272. Differentially expressed genes (DEGs) with a fold change (FC) >1.2 and a P-value <0.05 were identified by GEO2R and grouped in male, female and overlapping DEGs. Functional enrichment analysis and Protein-Protein Interaction (PPI) network analysis were performed.

Results

In total, 183 DEGs overlapped (77 ups and 106 downs), 302 DEGs (185 ups and 117 downs) in the male dataset, and 750 DEGs (464 ups and 286 downs) in the female dataset were obtained from the GSE143272 dataset. These DEGs were markedly enriched under various Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) terms. 16 following hub genes were identified based on PPI network analysis: ADCY7, C3AR1, DEGS1, CXCL1 in male-specific DEGs, TOLLIP, ORM1, ELANE, QPCT in female-specific DEGs and FCAR, CD3G, CLEC12A, MOSPD2, CD3D, ALDH3B1, GPR97, PLAUR in overlapping DEGs.

Conclusion

This discovery-driven study may be useful to provide a novel insight into the diagnosis and treatment of epilepsy. However, more experiments are needed in the future to study the functional roles of these genes in epilepsy.

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.

Orosomucoid can predict baseline peritoneal transport characteristics in peritoneal dialysis patients and reduce peritoneal proteins loss

Peritoneal dialysis (PD) is a replacement therapy for end-stage renal disease patients. In the first 4-8 weeks of PD, the patients were given an empirical dialysis prescription due to unknown peritoneal transport characteristics. Proteomic analysis could be used to identify serum biomarkers. In a discovery set, patients were divided into three groups according to the peritoneal equilibration test (PET) results: high (H), high average (HA), low average and low (LA&L) groups. A total of 1051 identified proteins were screened by Nano HPLC-MS/MS. The top two proteins among different peritoneal transport characteristics were Orosomucoid 2 (ORM2) and C-reactive protein (CRP). In a validation set, CRP was significantly elevated in H group than LA&L group, consistent with proteomic analysis. Serum ORM2 was enhanced in LA&L group compared with H and HA group. The expression of ORM2 in peritoneum was also enriched in LA&L group. At last, supplying exogenous ORM could reduce peritoneal proteins loss, without causing a pro-inflammatory response in mice. ORM2 and CRP could be used as biomarkers to predict the baseline peritoneal transport characteristics, and guide the early PD treatment. ORM may serve as a novel therapeutic target for decreasing peritoneal proteins loss in PD patients. SIGNIFICANCE: Peritoneal dialysis (PD) is associated with the functional alterations of the peritoneum. PD patients were often given an empirical dialysis prescription due to the unknown peritoneal transport characteristics in the first 4-8 weeks since PD started. Therefore, it is urgently needed to find biomarkers to predict the baseline peritoneal transport characteristics. In this study, we employed a proteomic analysis to identify serum biomarkers in a training set and verified the screened biomarkers in a validation set. We also found that Orosomucoid (ORM) has the potential to decrease peritoneal proteins loss in PD therapy.

Endothelial glycocalyx as an important factor in composition of blood-brain barrier

The blood‐brain barrier is a dynamic and complex neurovascular unit that protects neurons from somatic circulatory factors as well as regulates the internal environmental stability of the central nervous system. Endothelial glycocalyx is a critical component of an extended neurovascular unit that influences the structure of the blood‐brain barrier and plays various physiological functions, including an important role in maintaining normal neuronal homeostasis. Specifically, glycocalyx acts in physical and charge barriers, mechanical transduction, regulation of vascular permeability, modulation of inflammatory response, and anticoagulation. Since intact glycocalyx is necessary to maintain the stability and integrity of the internal environment of the blood‐brain barrier, damage to glycocalyx can lead to the dysfunction of the blood‐brain barrier. This review discusses the role of glycocalyx in the context of the substantial literature regarding the blood‐brain barrier research, in order to provide a theoretical basis for the diagnosis and treatment of neurological diseases as well as point to new breakthroughs and innovations in glycocalyx‐dependent blood‐brain barrier function.

Transcellular Model for Neutral and Charged Nanoparticles Across an In Vitro Blood-Brain Barrier

Purpose

The therapeutic drug-loaded nanoparticles (NPs, 20–100 nm) have been widely used to treat brain disorders. To improve systemic brain delivery efficacy of these NPs, it is necessary to quantify their transport parameters across the blood–brain barrier (BBB) and understand the underlying transport mechanism.

Methods

Permeability of an in vitro BBB, bEnd3 (mouse brain microvascular endothelial cells) monolayer, to three neutral NPs with the representative diameters was measured using an automated fluorometer system. To elucidate the transport mechanism of the neutral NPs across the in vitro BBB, and that of positively charged NPs whose BBB permeability was measured in a previous study, we developed a novel transcellular model, which incorporates the charge of the in vitro BBB, the mechanical property of the cell membrane, the ion concentrations of the surrounding salt solution and the size and charge of the NPs.

Results

Our model indicates that the negative charge of the surface glycocalyx and basement membrane of the BBB plays a pivotal role in the transcelluar transport of NPs with diameter 20-100 nm across the BBB. The electrostatic force between the negative charge at the in vitro BBB and the positive charge at NPs greatly enhances NP permeability. The predictions from our transcellular model fit very well with the measured BBB permeability for both neutral and charged NPs.

Conclusion

Our model can be used to predict the optimal size and charge of the NPs and the optimal charge of the BBB for an optimal systemic drug delivery strategy to the brain.

Multimodal analysis of the effects of dexamethasone on high-altitude cerebral oedema: protocol for a pilot study

Background

Acute mountain sickness (AMS) is a cluster of symptoms that commonly occur in those ascending to high altitudes. Symptoms can include headaches, nausea, insomnia and fatigue. Exposure to high altitude can also lead to high-altitude cerebral oedema (HACE), which is a potential cause of death whilst mountaineering. Generally, AMS precedes the development of HACE. Historical studies have demonstrated the effectiveness of regular dexamethasone administration in reducing the symptoms of AMS. However, the mechanism by which dexamethasone works to reduce symptoms AMS remains poorly understood. Further studies, simulating altitude using hypoxic tents, have characterised the effect of prolonged exposure to normobaric hypoxia on cerebral oedema and blood flow using MRI. This randomised trial assesses the effect of dexamethasone on hypoxia-induced cerebral oedema in healthy adult volunteers.

Methods/design

D4H is a double-blind placebo-controlled randomised trial assessing the effect of dexamethasone on hypoxia-induced cerebral oedema. In total, 20 volunteers were randomised in pairs to receive either 8.25 mg dexamethasone or normal saline placebo intravenously after 8 h of hypoxia with an FiO₂ of 12%. Serial MRI images of the brain and spinal cord were obtained at hours 0, 7, 11, 22 and 26 of the study along with serum and urinary markers to correlate with the severity of cerebral oedema and the effect of the intervention.

Discussion

MRI has been used to identify changes in cerebral vasculature in the development of AMS and HACE. Dexamethasone is effective at reducing the symptoms of AMS; however, the mechanism of this effect is unknown. If this study demonstrates a clear objective benefit of dexamethasone in this setting, future studies may be able to demonstrate that dexamethasone is an effective therapy for oedema associated with brain and spinal cord ischaemia beyond AMS.

Trial registration

Clinicaltrials.gov, NCT03341676. Registered on 14 November 2017.

Glycocalyx degradation leads to blood-brain barrier dysfunction and brain edema after asphyxia cardiac arrest in rats

The role of glycocalyx in blood-brain barrier (BBB) integrity and brain damage is poorly understood. Our study aimed to investigate the impacts of endothelial glycocalyx on BBB function in a rat model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Male Sprague-Dawley rats subjected to 8-min asphyxia CA/CPR. Compared to controls, glycocalyx was mildly injured by CA, severely disrupted by hyaluronidase (HAase) with CA, and mitigated by hydrocortisone (HC) with CA. More importantly, the disruption of glycocalyx caused by HAase treatment was associated with higher BBB permeability and aggravated brain edema at 24 h after return of spontaneous circulation, as well as lower survival rate and poorer neurologic outcome at seventh day. Reversely, less degradation of glycocalyx by HC treatment was accompanied by higher seven-day survival rate and better neurologic outcome. Mechanistically, HAase treatment further increased CA/CPR-induced activation of glia cells and expression of inflammatory factors, whereas HC decreased them in the brain cortex and hippocampus. Glycocalyx degradation results in BBB leakage, brain edema, and deteriorates neurologic outcome after asphyxia CA/CPR in rats. Preservation of glycocalyx by HC could improve neurologic outcome and reduce BBB permeability, apparently through reduced gene transcription-protein synthesis and inflammation.

Novel effect of α-lactalbumin on the yohimbine-induced hot flush increase of the tail skin temperature in ovariectomized rats

5-Hydroxytryptamine (5-HT) and noradrenaline have been thought to play important roles in the mechanism of hot flush. Then, to clarify the relation between serotonergic and adrenergic nervous systems on the mechanism of hot flush, the effect of paroxetine, 5-HT reuptake inhibitor (SSRI) was evaluated on the yohimbine-induced hot flush increase of tail skin temperature in ovariectomized female rats. Yohimbine (adrenaline α₂ antagonist) significantly increased the tail skin temperature in course of time. Clonidine (adrenaline α₂ agonist) significantly attenuated this effect. Paroxetine also significantly inhibited the increase of tail skin temperature by yohimbine. α-Lactalbumin having SSRI activity in vitro study also significantly inhibited the increase of tail skin temperature, but not significantly decreased the initial temperature. This difference may explain the different mechanism between paroxetine (SSRI) and α-lactalbumin, suggesting new mechanism of hot flush.

Transport Across the Blood-Brain Barrier

The blood-brain barrier (BBB) is a dynamic barrier essential for maintaining the microenvironment of the brain. Although the special anatomical features of the BBB determine its protective role for the central nervous system (CNS) from blood-borne neurotoxins, however, the BBB extremely limits the therapeutic efficacy of drugs into the CNS, which greatly hinders the treatment of major brain diseases. This chapter summarized the unique structures of the BBB; described a variety of in vivo and in vitro experimental methods for determining the transport properties of the BBB and the permeability of the BBB to water, ions, and solutes including nutrients, therapeutic agents, and drug carriers; and presented recently developed mathematical models which quantitatively correlate the anatomical structures of the BBB with its barrier functions. Recent findings for modulation of the BBB permeability by chemical and physical stimuli were described. Finally, drug delivery strategies through specific trans-BBB routes were discussed.

Elevated levels of protein AMBP in cerebrospinal fluid of women with preeclampsia compared to normotensive pregnant women

PURPOSE

To investigate the cerebrospinal fluid (CSF) proteome of patients with preeclampsia (PE) and normotensive pregnant women, in order to provide a better understanding of brain involvement in PE.

EXPERIMENTAL DESIGN

Ninety-eight CSF samples (43 women with PE and 55 normotensive controls) were analyzed by LC-MS/MS proteome profiling. CSF was obtained during the spinal puncture before caesarean delivery.

RESULTS

Eight proteins were higher abundant and 17 proteins were lower abundant in patients with PE. The most significantly differentially abundant protein was protein AMBP (alpha-1-microglobulin/bikunin precursor). This finding was validated by performing an ELISA experiment (p = 0.002).

CONCLUSIONS AND CLINICAL RELEVANCE

The current study showed a clear difference between the protein profiles of CSF from patients with PE and normotensive pregnant women. Protein AMBP is a precursor of a heme-binding protein that counteracts the damaging effects of free hemoglobin, which may be related to the presence of free hemoglobin in CSF. Protein levels showed correlations with clinical symptoms during pregnancy and postpartum. To our knowledge, this is the first LC-MS/MS proteome profiling study on a unique set of CSF samples from (severe) preeclamptic patients and normotensive pregnant women.

Microperfusion Technique to Investigate Regulation of Microvessel Permeability in Rat Mesentery

Experiments to measure the permeability properties of individually perfused microvessels provide a bridge between investigation of molecular and cellular mechanisms regulating vascular permeability in cultured endothelial cell monolayers and the functional exchange properties of whole microvascular beds. A method to cannulate and perfuse venular microvessels of rat mesentery and measure the hydraulic conductivity of the microvessel wall is described. The main equipment needed includes an intravital microscope with a large modified stage that supports micromanipulators to position three different microtools: (1) a beveled glass micropipette to cannulate and perfuse the microvessel; (2) a glass micro-occluder to transiently block perfusion and enable measurement of transvascular water flow movement at a measured hydrostatic pressure, and (3) a blunt glass rod to stabilize the mesenteric tissue at the site of cannulation. The modified Landis micro-occlusion technique uses red cells suspended in the artificial perfusate as markers of transvascular fluid movement, and also enables repeated measurements of these flows as experimental conditions are changed and hydrostatic and colloid osmotic pressure difference across the microvessels are carefully controlled. Measurements of hydraulic conductivity first using a control perfusate, then after re-cannulation of the same microvessel with the test perfusates enable paired comparisons of the microvessel response under these well-controlled conditions. Attempts to extend the method to microvessels in the mesentery of mice with genetic modifications expected to modify vascular permeability were severely limited because of the absence of long straight and unbranched microvessels in the mouse mesentery, but the recent availability of the rats with similar genetic modifications using the CRISPR/Cas9 technology is expected to open new areas of investigation where the methods described herein can be applied.

Orosomucoid1: Involved in vascular endothelial growth factor-induced blood-brain barrier leakage after ischemic stroke in mouse

Vascular endothelial growth factor (VEGF) is a promising candidate for the treatment of ischemic stroke. However, accumulating evidence demonstrated that VEGF could exacerbate blood-brain barrier (BBB) disruption after ischemic stroke. This study was designed to investigate the underlying mechanisms. In the present study, a transient (90 min) middle cerebral artery occlusion (MCAO) model was performed to induce ischemic stroke in mice. VEGF was administered intracerebroventricularly 3h after reperfusion. A gene expression microarray was utilized to investigate the differentially expressed genes among the sham, MCAO, and VEGF groups. A total of 3381 mRNAs were significantly altered by cerebral ischemia when compared with the sham group, and 15 of them were changed in the VEGF group when compared with the MCAO group. Among the 15 genes, orosomucoid (Orm) 1 was most sharply changed, and this gene has previously been reported to maintain the permeability of microvessels and integrity of the BBB. Results of the microarray showed that the expression of Orm1 increased after cerebral ischemia, whereas it decreased in response to VEGF, which was confirmed by real-time quantitative PCR, western blotting, immunohistochemistry, and immunofluorescence. The bioinformatics analysis indicated two NF-κB binding sites on the Orm1 promoter, and a super-shift assay verified that NF-κB could bind the Orm1 promoter. Results of the electrophoretic mobility shift assay (EMSA) revealed that VEGF inhibited the DNA-binding activity of NF-κB/p65. Furthermore, the elevated expression and activation of key members in the canonical NF-κB pathway induced by cerebral ischemia were also inhibited by VEGF treatment. In conclusion, this study demonstrated that decreasing the Orm1 expression via inhibition of the NF-κB pathway could be a possible mechanism involved in the aggravation of BBB disruption after stroke by VEGF.

Adhesion of malignant mammary tumor cells MDA-MB-231 to microvessel wall increases microvascular permeability via degradation of endothelial surface glycocalyx

To investigate the effect of tumor cell adhesion on microvascular permeability (P) in intact microvessels, we measured the adhesion rate of human mammary carcinoma MDA-MB-231, the hydraulic conductivity (L(p)), the P, and reflection coefficient (σ) to albumin of the microvessels at the initial tumor cell adhesion and after ∼45 min cell perfusion in the postcapillary venules of rat mesentery in vivo. Rats (Sprague-Dawley, 250-300 g) were anesthetized with pentobarbital sodium given subcutaneously. A midline incision was made in the abdominal wall, and the mesentery was gently taken out and arranged on the surface of a glass coverslip for the measurement. An individual postcapillary venule was perfused with cells at a rate of ∼1 mm/s, which is the mean blood flow velocity in this type of microvessels. At the initial tumor cell adhesion, which was defined as one adherent cell in ∼100- to 145-μm vessel segment, L(p) was 1.5-fold and P was 2.3-fold of their controls, and σ decreased from 0.92 to 0.64; after ∼45-min perfusion, the adhesion increased to ∼5 adherent cells in ∼100- to 145-μm vessel segment, while L(p) increased to 2.8-fold, P to 5.7-fold of their controls, and σ decreased from 0.92 to 0.42. Combining these measured data with the predictions from a mathematical model for the interendothelial transport suggests that tumor cell adhesion to the microvessel wall degrades the endothelial surface glycocalyx (ESG) layer. This suggestion was confirmed by immunostaining of heparan sulfate of the ESG on the microvessel wall. Preserving of the ESG by a plasma glycoprotein orosomucoid decreased the P to albumin and reduced the tumor cell adhesion.

α1-Acid glycoprotein induced effects in rat brain microvessel endothelial cells

α1-Acid glycoprotein (AGP) is a positive acute phase protein which is elevated 1-10 times during inflammation. Whereas AGP has been reported to have immunomodulatory properties, other biological functions of this protein such as its effects on the blood-brain barrier (BBB) endothelium are unknown. Tight junction (TJ) proteins (ZO-1 and occludin) are crucial in maintaining BBB integrity and brain homeostasis. As inflammatory cytokines have been shown to alter BBB integrity and TJ protein expression, we hypothesized that AGP changes BBB function by stimulating inflammatory cytokines and/or directly modulating TJ protein expression. We used primary rat brain microvessel endothelial cells (RBMECs) as an in vitro BBB model to study the direct effects of AGP on the brain microvasculature. No change in cytokine levels was detected in supernatant from AGP-treated RBMECs, despite increased mRNA expression by the cells. Paracellular permeability was decreased up to 20%, across RBMEC monolayers following treatment with AGP, suggesting its role in enhancing BBB integrity. RBMECs showed a biphasic response of increased occludin protein expression following AGP treatment while ZO-1 expression changed in a dose- and time-dependent manner. These changes in TJ proteins suggest that AGP induced changes in occludin related to enhanced barrier properties while the change in ZO-1 may play a secondary role in BBB integrity and/or as an intracellular signaling molecule. AGP significantly changed transcription factor activator protein 1 (AP-1) DNA-binding activity which provides evidence of the potential cell signaling pathways that contribute to the effect of AGP in RBMECs. Together, this supports our hypothesis that AGP has a direct effect in brain microvasculature and may play an important role in altering BBB integrity in inflammatory-related diseases.

Microvascular transport and tumor cell adhesion in the microcirculation

One critical step in tumor metastasis is tumor cell adhesion to the endothelium forming the microvessel wall. Understanding this step may lead to new therapeutic concepts for tumor metastasis. Vascular endothelium forming the microvessel wall and the glycocalyx layer at its surface are the principal barriers to, and regulators of the material exchange between circulating blood and body tissues. The cleft between adjacent ECs (interendothelial cleft) is the principal pathway for water and solutes transport through the microvessel wall in health. It is also suggested to be the pathway for high molecular weight plasma proteins, leukocytes and tumor cells across microvessel walls in disease. Thus the first part of the review introduced the mathematical models for water and solutes transport through the interendothelial cleft. These models, combined with the experimental results from in vivo animal studies and electron microscopic observations, are used to evaluate the role of the endothelial surface glycocalyx, the junction strand geometry in the interendothelial cleft, and the surrounding extracellular matrix and tissue cells, as the determinants of microvascular transport. The second part of the review demonstrated how the microvascular permeability, hydrodynamic factors, microvascular geometry and cell adhesion molecules affect tumor cell adhesion in the microcirculation.

An electrodiffusion model for the blood-brain barrier permeability to charged molecules

The endothelial surface glycocalyx layer (SGL) and the basement membrane (BM) are two important components of the blood-brain barrier (BBB). They provide large resistance to solute transport across the BBB in addition to the tight junctions in the cleft between adjacent endothelial cells. Due to their glycosaminoglycan compositions, they carry negative charge under physiological conditions. To investigate the charge effect of the SGL and BM on the BBB permeability to charged solutes, we developed an electrodiffusion model for the transport of charged molecules across the BBB. In this model, constant charge densities were assumed in the SGL and in the BM. Both electrostatic and steric interaction and exclusion to charged molecules were considered within the SGL and the BM and at their interfaces with noncharged regions of the BBB. On the basis of permeability data for the positively charged ribonuclease (+4,radius=2.01 nm) and negatively charged α-lactalbumin (-10,radius=2.08 nm) measured in intact rat mesenteric and pial microvessels, our model predicted that the charge density in both SGL and BM would be ∼30 mEq/L, which is comparable to that in the SGL of mesenteric microvessels. Interestingly, our model also revealed that due to the largest concentration drop in the BM, there is a region with a higher concentration of negatively charged α-lactalbumin in the uncharged inter-endothelial cleft, although the concentration of α-lactalbumin is always lower than that of positively charged ribonuclease and that of a neutral solute in the charged SGL and BM.

ApoE isoform-specific regulation of regeneration in the peripheral nervous system

Apolipoprotein E (apoE) is a 34 kDa glycoprotein with three distinct isoforms in the human population (apoE2, apoE3 and apoE4) known to play a major role in differentially influencing risk to, as well as outcome from, disease and injury in the central nervous system. In general, the apoE4 allele is associated with poorer outcomes after disease or injury, whereas apoE3 is associated with better responses. The extent to which different apoE isoforms influence degenerative and regenerative events in the peripheral nervous system (PNS) is still to be established, and the mechanisms through which apoE exerts its isoform-specific effects remain unclear. Here, we have investigated isoform-specific effects of human apoE on the mouse PNS. Experiments in mice ubiquitously expressing human apoE3 or human apoE4 on a null mouse apoE background revealed that apoE4 expression significantly disrupted peripheral nerve regeneration and subsequent neuromuscular junction re-innervation following nerve injury compared with apoE3, with no observable effects on normal development, maturation or Wallerian degeneration. Proteomic isobaric tag for relative and absolute quantitation (iTRAQ) screens comparing healthy and regenerating peripheral nerves from mice expressing apoE3 or apoE4 revealed significant differences in networks of proteins regulating cellular outgrowth and regeneration (myosin/actin proteins), as well as differences in expression levels of proteins involved in regulating the blood-nerve barrier (including orosomucoid 1). Taken together, these findings have identified isoform-specific roles for apoE in determining the protein composition of peripheral nerve as well as regulating nerve regeneration pathways in vivo.

Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes

Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value.