Regulation Of Blood-brain Barrier Function Research Articles

Role of microRNAs in the regulation of blood-brain barrier function in ischemic stroke and under hypoxic conditions in vitro

The blood-brain barrier (BBB) is a highly specialized structure that separates the brain from the blood and allows the exchange of molecules between these two compartments through selective channels. The breakdown of the BBB is implicated in the development of severe neurological diseases, especially stroke and traumatic brain injury. Oxygen-glucose deprivation is used to mimic stroke and traumatic brain injury in vitro. Pathways that trigger BBB dysfunction include an imbalance of oxidative stress, excitotoxicity, iron metabolism, cytokine release, cell injury, and cell death. MicroRNAs are small non-coding RNA molecules that regulate gene expression and are emerging as biomarkers for the diagnosis of central nervous system (CNS) injuries. In this review, the regulatory role of potential microRNA biomarkers and related therapeutic targets on the BBB is discussed. A thorough understanding of the potential role of various cellular and linker proteins, among others, in the BBB will open further therapeutic options for the treatment of neurological diseases.

Anti-Amnesic Effect of Walnut via the Regulation of BBB Function and Neuro-Inflammation in Aβ1-42-Induced Mice.

This study was conducted to assess the protective effect of walnut (Juglans regia L.) extract on amyloid beta (Aβ)1-42-induced institute of cancer research (ICR) mice. By conducting a Y-maze, passive avoidance, and Morris water maze tests with amyloidogenic mice, it was found that walnut extract ameliorated behavioral dysfunction and memory deficit. The walnut extract showed a protective effect on the antioxidant system and cholinergic system by regulating malondialdehyde (MDA) levels, superoxide dismutase (SOD) contents, reduced glutathione (GSH) contents, acetylcholine (ACh) levels, acetylcholinesterase (AChE) activity, and protein expression of AChE and choline acetyltransferase (ChAT). Furthermore, the walnut extract suppressed Aβ-induced abnormality of mitochondrial function by ameliorating reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP contents. Finally, the walnut extract regulated the expression of zonula occludens-1 (ZO-1) and occludin concerned with blood–brain barrier (BBB) function, expression of tumor necrosis factor-alpha (TNF-α), tumor necrosis factor receptor 1 (TNFR1), phosphorylated c-Jun N-terminal kinase (p-JNK), phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (p-IκB), cyclooxygenase-2 (COX-2), and interleukin 1 beta (IL-1β), related to neuroinflammation and the expression of phosphorylated protein kinase B (p-Akt), caspase-3, hyperphosphorylation of tau (p-tau), and heme oxygenase-1 (HO-1), associated with the Aβ-related Akt pathway.

Blood Serum Cytokines Induce Changes in Blood‐Brain Barrier Permeability and Gene Expression in an In Vitro Blood‐Brain Barrier Model

The blood‐brain barrier (BBB), a semi‐permeable interface between the brain and the blood, is a key player in the of development and progression of brain‐related illnesses such as traumatic brain injury (TBI), Alzheimer’s disease (AD), multiple sclerosis (MS), and schizophrenia (SCZ). With these disorders, pathologic BBB leakiness is caused by changes in the cellular milieu on the brain‐side as well as on the blood‐side of the BBB. On the brain‐side, injury to neurons, astrocytes, microglia, and pericytes can lead to increased BBB leakiness, while on the blood‐side, pathophysiologic levels of circulating factors such as hormones, inflammatory cytokines, and immune cells can significantly alter BBB leakiness.The objective of this study was to discover novel biomarkers of BBB leakiness using the in vitro three‐dimensional Neurovascular Unit (3D NVU; Research Triangle Institute International, Durham, NC) to examine the impact of human blood serum on transcriptional regulation and function of the BBB. The 3D NVU integrates endothelial, neuronal, astrocytic, and microglial cells into a three‐dimensional platform, and allows for the assessment of BBB permeability (transendothelial electrical resistance (TEER, Ω cm2)). Blood serum of secondary progressive MS patients (two men, two women) and four healthy individuals (two men, two women) were purchased from PrecisionMed, Inc. (Solana Beach, CA), and diluted to 40% with cell culture media for testing. TEER of the 3D NVU was recorded immediately prior to serum exposure (baseline), and again at 24 hours after serum treatment. At the end of the experiment, cells of the 3D NVU were collected, and expression of 84 MS‐related genes were measured by quantitative RT‐PCR. BBB permeability was calculated as TEERSerum – TEERBaseline. The protein levels of 100 serum cytokines were measured in undiluted serum samples by membrane‐based sandwich immunoassay. Multiple regression analysis was used to determine the relationship among TEER, serum cytokine levels, and BBB gene expression.We found that no single serum cytokine was a strong predictor of BBB permeability, however, serum‐induced changes in expression of chemokine ligand 12 (Ccl12/Mcp‐5), chemokine ligand 7 (Ccl7), hexosaminidase subunit beta (Hexb), interleukin 13 (Il13), interleukin 1 beta (Il1b), protein tyrosine phosphatase non‐receptor type 11 (Ptpn11), and vascular adhesion molecule 1 (Vcam1) were strong and significant predictors of BBB permeability (R2’s ≥ 0.76, P’s ≤ 0.004). Some of these genes (Il1b, Hexb and Vcam1) have been shown previously to play a role in regulation of BBB function, however, genes such as Ptpn11 have not yet been implicated in BBB permeability. This preliminary study demonstrates that the 3D NVU can be used to elucidate novel, physiologically relevant biomarkers of BBB‐related neurological and psychological disorders. In the future, we plan to perform RNA‐sequencing to examine a broader range of differential gene expression in our study.Support or Funding InformationFunded by TATRC AMEDD Advanced Medical Technology Initiative grant. The views expressed in this abstract are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.

Dual Roles of Astrocyte-Derived Factors in Regulation of Blood-Brain Barrier Function after Brain Damage.

The blood-brain barrier (BBB) is a major functional barrier in the central nervous system (CNS), and inhibits the extravasation of intravascular contents and transports various essential nutrients between the blood and the brain. After brain damage by traumatic brain injury, cerebral ischemia and several other CNS disorders, the functions of the BBB are disrupted, resulting in severe secondary damage including brain edema and inflammatory injury. Therefore, BBB protection and recovery are considered novel therapeutic strategies for reducing brain damage. Emerging evidence suggests key roles of astrocyte-derived factors in BBB disruption and recovery after brain damage. The astrocyte-derived vascular permeability factors include vascular endothelial growth factors, matrix metalloproteinases, nitric oxide, glutamate and endothelin-1, which enhance BBB permeability leading to BBB disruption. By contrast, the astrocyte-derived protective factors include angiopoietin-1, sonic hedgehog, glial-derived neurotrophic factor, retinoic acid and insulin-like growth factor-1 and apolipoprotein E which attenuate BBB permeability resulting in recovery of BBB function. In this review, the roles of these astrocyte-derived factors in BBB function are summarized, and their significance as therapeutic targets for BBB protection and recovery after brain damage are discussed.

Regulation of brain endothelial barrier function by microRNAs in health and neuroinflammation.

Brain endothelial cells constitute the major cellular element of the highly specialized blood-brain barrier (BBB) and thereby contribute to CNS homeostasis by restricting entry of circulating leukocytes and blood-borne molecules into the CNS. Therefore, compromised function of brain endothelial cells has serious consequences for BBB integrity. This has been associated with early events in the pathogenesis of several disorders that affect the CNS, such as multiple sclerosis, HIV-associated neurologic disorder, and stroke. Recent studies demonstrate that brain endothelial microRNAs play critical roles in the regulation of BBB function under normal and neuroinflammatory conditions. This review will focus on emerging evidence that indicates that brain endothelial microRNAs regulate barrier function and orchestrate various phases of the neuroinflammatory response, including endothelial activation in response to cytokines as well as restoration of inflamed endothelium into a quiescent state. In particular, we discuss novel microRNA regulatory mechanisms and their contribution to cellular interactions at the neurovascular unit that influence the overall function of the BBB in health and during neuroinflammation.-Lopez-Ramirez, M. A., Reijerkerk, A., de Vries, H. E., Romero, I. A. Regulation of brain endothelial barrier function by microRNAs in health and neuroinflammation.

Pregnane X Receptor (PXR) Regulates P-Glycoprotein at the Blood-Brain Barrier: Functional Similarities between Pig and Human PXR

Pharmacotherapy of central nervous system (CNS) disorders is impaired by the drug efflux transporter, P-glycoprotein, which limits drug penetration across the blood-brain barrier into the CNS. One strategy to increase brain drug levels is to modulate P-glycoprotein regulation. This approach requires understanding of the mechanisms that control transporter expression and function. One mechanism through which P-glycoprotein is regulated is the nuclear receptor, pregnane X receptor (PXR). Xenobiotics including drugs activate PXR and induce P-glycoprotein, which potentially affects pharmacokinetics/pharmacodynamics of coadministered drugs. Because rodent models are not suitable to predict xenobiotic interactions with human PXR, in a porcine model, we studied functional similarities between pig and human PXR. We used brain capillary endothelial cells from pig to study the effect of PXR activation on P-glycoprotein. To activate PXR, we used the PXR ligands, rifampicin, hyperforin, and pregnenolone-16alpha-carbonitrile (PCN), and measured abcb1 mRNA with quantitative polymerase chain reaction, P-glycoprotein expression with Western blotting, and P-glycoprotein transport activity with a calcein assay. We provide first proof of principle that the human PXR ligands, rifampicin and hyperforin, but not the rodent PXR ligand, PCN, activate pig PXR at the blood-brain barrier and induce mRNA, protein expression, and transport activity of P-glycoprotein. Our data indicate functional similarities between human and pig PXR that suggest the pig model could be useful for predicting xenobiotic-PXR interactions in humans. Because PXR is crucial in controlling drug efflux transporters, our findings will contribute to a better understanding of the regulation of blood-brain barrier function, which could potentially have important clinical implications for the treatment of CNS disorders.

Regulation of blood-brain barrier endothelial cells by nitric oxide.

Nitric oxide (NO) synthesized by vascular endothelial cells is a potent vasodilator substance. The actions of NO extend well beyond its vasodilatory properties, and increasingly, NO has been recognized as an important signal for intercellular and intracellular communication. Recently, NO has been implicated in the regulation of vascular and blood-brain barrier permeability. NO has also been shown to modulate ion channels in excitable cells, thus affecting neuronal firing. We report the results of patch-clamp experiments that show a modulatory action of NO as well as cGMP and cAMP on a hyperpolarization-activated current (Iha) carried by both Na+ and K+ ions in blood-brain barrier endothelial cells. Iha was recorded in cells dialyzed with 0.2 mmol/L GTP-gamma-S to inhibit a large inwardly rectifying potassium current. This ionic current and its modulation by NO may play a role in the regulation of the transport of ions, nutrients, and other molecules to the brain and serve as an integral part of the blood-brain barrier. The modulation of Iha by a cyclic guanosine nucleotide may also explain previous reports suggesting a role for NO in the regulation of blood-brain barrier function.

Locus coeruleus: Regulation of blood-brain barrier function in normal and emotionally stressed rats

Locus coeruleus: Regulation of blood-brain barrier function in normal and emotionally stressed rats