Tight junction in blood-brain barrier: an overview of structure, regulation, and regulator substances

The Role of Brain Barriers in Maintaining Brain Vitamin Levels

It is increasingly recognized that tissue-specific nutrient deficiencies can exist in the absence of whole-body deficiency and that these deficiencies may result from disease or disease-related physiological processes. Brain and central nervous system tissues require adequate nutrient levels to function. Many nutrients are concentrated in the cerebrospinal fluid relative to the serum in healthy individuals, and other nutrients resist depletion in the presence of whole-body nutrient depletion. The endothelial, epithelial, and arachnoid brain barriers work in concert to selectively transport, concentrate, and maintain levels of the specific nutrients required by the brain while also blocking the passage of blood-borne toxins and pathogens to brain and central nervous system tissues. These barriers preserve nutrient levels within the brain and actively concentrate nutrients within the cerebrospinal fluid and brain. The roles of physical and energetic barriers, including the blood–brain and blood–nerve barriers, in maintaining brain nutrient levels in health and disease are discussed.

Propofol attenuated TNF-α-modulated occludin expression by inhibiting Hif-1α/ VEGF/ VEGFR-2/ ERK signaling pathway in hCMEC/D3 cells

Background

The levels of tight junction proteins (TJs), especially occludin, correlate with blood-brain barrier (BBB) disruption caused by inflammation in central nervous system (CNS). It has been reported that propofol, the most commonly used anesthetic, could inhibit inflammation response in CNS. In this study, we investigated the effects of tumor necrosis factor-α (TNF-α) and propofol on occludin expression in human cerebral microvascular endothelial cell line, D3 clone (hCMEC/D3 cells), and explored the underlying mechanisms.

Methods

The hCMEC/D3 cells were treated with propofol, followed by TNF-α. The expression and phosphorylation of Hif-1α, VEGF, VEGFR-2, ERK, p38MAPK and occludin were measured by Western blot analysis. The cell viability of hCMEC/D3 cells was measured by cell counting kit-8.

Results

TNF-α (10 ng/ml, 4 h) significantly decreased the expression of occludin, which was attenuated by propofol (25 μM). TNF-α induced Hif-1α/VEGF/VEGFR-2/ERK signaling pathway, while propofol could inhibit it. TNF-α induced the phosphorylation of p38MAPK, while propofol had no effect on it. In addition, the inhibitors of Hif-1α, VEGFR-2, and ERK could reduce the effect of TNF-α on occludin expression.

Conclusion

TNF-α could decrease the expression of occludin via activating Hif-1α/ VEGF/ VEGFR-2/ ERK signaling pathway, which was attenuated by propofol.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0788-5) contains supplementary material, which is available to authorized users.

Approaches to CNS Drug Delivery with a Focus on Transporter-Mediated Transcytosis

Drug delivery to the central nervous system (CNS) conferred by brain barriers is a major obstacle in the development of effective neurotherapeutics. In this review, a classification of current approaches of clinical or investigational importance for the delivery of therapeutics to the CNS is presented. This classification includes the use of formulations administered systemically that can elicit transcytosis-mediated transport by interacting with transporters expressed by transvascular endothelial cells. Neurotherapeutics can also be delivered to the CNS by means of surgical intervention using specialized catheters or implantable reservoirs. Strategies for delivering drugs to the CNS have evolved tremendously during the last two decades, yet, some factors can affect the quality of data generated in preclinical investigation, which can hamper the extension of the applications of these strategies into clinically useful tools. Here, we disclose some of these factors and propose some solutions that may prove valuable at bridging the gap between preclinical findings and clinical trials.

Fibronectin inhibitor pUR4 attenuates tumor necrosis factor α-induced endothelial hyperpermeability by modulating β1 integrin activation

BACKGROUND

The blood-spinal cord barrier (BSCB) is composed of a monolayer of endothelium linked with tight junctions and extracellular matrix (ECM)-rich basement membranes and is surrounded by astrocyte foot processes. Endothelial permeability is regulated by interaction between endothelial cells and ECM proteins. Fibronectin (FN) is a principal ECM component of microvessels. Excessive FN deposition disrupts cell-cell adhesion in fibroblasts through β1 integrin ligation. To determine whether excessive FN deposition contributes to the disruption of endothelial integrity, we used an in vitro model of the endothelial monolayer to investigate whether the FN inhibitor pUR4 prevents FN deposition into the subendothelial matrix and attenuates endothelial leakage.

METHODS

To correlate the effects of excessive FN accumulation in microvessels on BSCB disruption, spinal nerve ligation-which induces BSCB leakage-was applied, and FN expression in the spinal cord was evaluated through immunohistochemistry and immunoblotting. To elucidate the effects by which pUR4 modulates endothelial permeability, brain-derived endothelial (bEND.3) cells treated with tumor necrosis factor (TNF)-α were used to mimic a leaky BSCB. A bEND.3 monolayer was preincubated with pUR4 before TNF-α treatment. The transendothelial electrical resistance (TEER) measurement and transendothelial permeability assay were applied to assess the endothelial integrity of the bEND.3 monolayer. Immunofluorescence analysis and immunoblotting were performed to evaluate the inhibitory effects of pUR4 on TNF-α-induced FN deposition. To determine the mechanisms underlying pUR4-mediated endothelial permeability, cell morphology, stress fiber formation, myosin light chain (MLC) phosphorylation, and β1 integrin-mediated signaling were evaluated through immunofluorescence analysis and immunoblotting.

RESULTS

Excessive FN was accumulated in the microvessels of the spinal cord after spinal nerve ligation; moreover, pUR4 inhibited TNF-α-induced FN deposition in the bEND.3 monolayer and maintained intact TEER and endothelial permeability. Furthermore, pUR4 reduced cell morphology alteration, actin stress fiber formation, and MLC phosphorylation, thereby attenuating paracellular gap formation. Moreover, pUR4 reduced β1 integrin activation and downstream signaling.

CONCLUSIONS

pUR4 reduces TNF-α-induced β1 integrin activation by depleting ECM FN, leading to a decrease in endothelial hyperpermeability and maintenance of monolayer integrity. These findings suggest therapeutic benefits of pUR4 in pathological vascular leakage treatment.

Recombinant FGF21 Protects Against Blood-Brain Barrier Leakage Through Nrf2 Upregulation in Type 2 Diabetes Mice

Blood-brain barrier (BBB) damage is a characteristic feature of diabetes mellitus pathology and plays significant roles in diabetes-associated neurological disorders. However, effective treatments for diabetes targeting BBB damage are yet to be developed. Fibroblast growth factor 21 (FGF21) is a potent regulator of lipid and glucose metabolism. In this study, we tested the hypothesis that recombinant FGF21 (rFGF21) administration may reduce type 2 diabetes (T2D)-induced BBB disruption via NF-E2-related factor-2 (Nrf2) upregulation. Our experimental results show that rFGF21 treatment significantly ameliorated BBB permeability and preserved junction protein expression in db/db mice in vivo. This protective effect was further confirmed by ameliorated transendothelial permeability and junction protein loss by rFGF21 under hyperglycemia and IL1β (HG-IL1β) condition in cultured human brain microvascular endothelial cells (HBMEC) in vitro. We further reveal that rFGF21 can activate FGF receptor 1 (FGFR1) that increases its binding with Kelch ECH-associating protein 1 (Keap1), a repressor of Nrf2, thereby reducing Keap1-Nrf2 interaction leading to Nrf2 release. These data suggest that rFGF21 administration may decrease T2D-induced BBB permeability, at least in part via FGFR1-Keap1-Nrf2 activation pathway. This study may provide an impetus for development of therapeutics targeting BBB damage in diabetes.

Stimulation of S1PR5 with A-971432, a selective agonist, preserves blood-brain barrier integrity and exerts therapeutic effect in an animal model of Huntington's disease

Huntington's disease (HD) is the most common neurodegenerative disorder for which no effective cure is yet available. Although several agents have been identified to provide benefits so far, the number of therapeutic options remains limited with only symptomatic treatment available. Over the past few years, we have demonstrated that sphingolipid-based approaches may open the door to new and more targeted treatments for the disease. In this study, we investigated the therapeutic potential of stimulating sphingosine-1-phosphate (S1P) receptor 5 by the new selective agonist A-971432 (provided by AbbVie) in R6/2 mice, a widely used HD animal model. Chronic administration of low-dose (0.1 mg/kg) A-971432 slowed down the progression of the disease and significantly prolonged lifespan in symptomatic R6/2 mice. Such beneficial effects were associated with activation of pro-survival pathways (BDNF, AKT and ERK) and with reduction of mutant huntingtin aggregation. A-971432 also protected blood-brain barrier (BBB) homeostasis in the same mice. Interestingly, when administered early in the disease, before any overt symptoms, A-971432 completely protected HD mice from the classic progressive motor deficit and preserved BBB integrity. Beside representing a promising strategy to take into consideration for the development of alternative therapeutic options for HD, selective stimulation of S1P receptor 5 may be also seen as an effective approach to target brain vasculature defects in the disease.

Myosin IIA Regulated Tight Junction in Oxygen Glucose-Deprived Brain Endothelial Cells Via Activation of TLR4/PI3K/Akt/JNK1/2/14-3-3ε/NF-κB/MMP9 Signal Transduction Pathway

Non-muscle myosin heavy chain IIA (NMMHC IIA), a member of Myosin II family, plays a critical role in various cellular physiological processes. Our previous research had suggested that NMMHC IIA could participate in regulating tight junction morphological changes induced by ischemia stroke. Thus, in the current study, we attempted to uncover the regulation pattern of NMMHC IIA on tight junction dysfunction in oxygen glucose-deprived (OGD) mouse brain bEND.3 endothelial cells. The regulation of NMMHC IIA on tight junction in OGD-stimulated bEND.3 cells was evaluated by western blotting assay. Morphologic change of occludin, claudin-5, and ZO-1 tight junction proteins was compared with pretreatment with NMMHC II inhibitor blebbistatin via immunohistochemical staining. Detection of activation of NMMHC IIA on OGD-mediated tight junction transduction pathway was investigated via Koch's postulate using corresponding protein inhibitor. Our results showed that NMMHC IIA was activated in OGD-stimulated bEND.3 endothelial cells. The inhibition of NMMHC IIA could attenuate the morphologic change of occludin, claudin-5, and ZO-1 tight junction proteins. NMMHC IIA participated in regulating downstream transduction pathway TLR4, phosphatidylinositol 3-kinase (PI3K), Akt, JNK1/2, 14-3-3ε, nuclear factor kappa B (NF-кB) and matrix metalloprotein 9 (MMP9). Blocking of these pathways using indicated inhibitors demonstrated that NMMHC IIA destroyed the connection of tight junction via the activation of TLR4/PI3K/Akt/JNK1/2/14-3-3ε/NF-κB/MMP9 pathway. Our study described the key role of NMMHC IIA in OGD-stimulated mouse brain bEND.3 endothelial cells, while also exhibited the molecule effect on tight junction dysfunction via TLR4/PI3K/Akt/JNK1/2/14-3-3ε/NF-κB/MMP9 signal transduction pathway.

Restraint Stress Induced Hyperpermeability and Damage of the Blood-Brain Barrier in the Amygdala of Adult Rats

Intense or prolonged exposure to stress can damage various brain structures, including the amygdala and hippocampus, which are associated with emotional-cognitive functions. Furthermore, this deterioration has been linked to a myriad of neurodegenerative and psychiatric disorders, in particular through disruption of the blood-brain barrier (BBB). However, insights remain scarce concerning the effects and mechanisms associated with stress on the BBB in the amygdala. This study explored the effects of restraint stress on the permeability and integrity of the BBB in the amygdala of male adult SD rats. Serum levels of corticosterone (CORT) and S100B were determined through ELISA. The permeability of the BBB was assessed by measuring Evans Blue (EB) leakage in tissue samples from the rats’ amygdala. These samples were immunostained for markers of tight junctions (Claudin-5, Occludin, ZO-1) and adherens junctions (VE-cadherin), as well as GLUT-1 and AQP-4. Staining was evaluated through confocal microscopy, and the level of expression of these proteins was quantified using the Western Blot (WB) technique. The ultrastructure of brain microvascular endothelial cells was assessed with transmission electron microscopy. Moreover, interleukin-1 beta (IL-1β) content in serum and amygdalar tissues were determined by employing ELISA. Exposure to restraint stress was associated with higher serum levels of S100B and EB leakage in amygdala tissues, especially in days 14 and 21 of the experiment, indicating increased permeability of the BBB. After restraint stress, significant decreases in protein expression were detected for tight junctions, adherens junctions and GLUT-1, while a significant increase was observed for AQP-4. The variation trends of fluorescence intensity generally paralleled these results. Following restraint stress, transmission electron microscopy ascertained enlarged gaps in tight junctions and thickened basal membranes in amygdalar capillaries. In addition, increased IL-1β contents in serum and amygdalar tissues were observed in the restraint-stressed groups. These findings suggest that restraint stress mediates time-dependent alterations in the permeability of the BBB, with modifications in the expression of proteins from tight junctions and adherens junctions, as well as ultrastructural changes in brain microvascular endothelial cells. And it was associated with the inflammation. These alterations may be associated with behavioral and cognitive dysfunctions and neurodegenerative disorders.

EphB2-dependent signaling promotes neuronal excitotoxicity and inflammation in the acute phase of ischemic stroke

Local cerebral hypoperfusion causes ischemic stroke while driving multiple cell-specific responses including inflammation, glutamate-induced neurotoxicity mediated via NMDAR, edema formation and angiogenesis. Despite the relevance of these pathophysiological mechanisms for disease progression and outcome, molecular determinants controlling the onset of these processes are only partially understood. In this context, our study intended to investigate the functional role of EphB2, a receptor tyrosine kinase that is crucial for synapse function and binds to membrane-associated ephrin-B ligands.

Cerebral ischemia was induced in Ephb2^−/− mice by transient middle cerebral artery occlusion followed by different times (6, 12, 24 and 48 h) of reperfusion. Histological, neurofunctional and transcriptome analyses indicated an increase in EphB2 phosphorylation under these conditions and attenuated progression of stroke in Ephb2^−/− mice. Moreover, while infiltration of microglia/macrophages and astrocytes into the peri-infarct region was not altered, expression of the pro-inflammatory mediators MCP-1 and IL-6 was decreased in these mice. In vitro analyses indicated that binding of EphB2 to astrocytic ephrin-B ligands stimulates NF-κB-mediated cytokine expression via the MAPK pathway. Further magnetic resonance imaging of the Ephb2^−/− ischemic brain revealed a lower level of cytotoxic edema formation within 6 h upon onset of reperfusion. On the mechanistic level, absence of neuronal EphB2 decreased the mitochondrial Ca²⁺ load upon specific activation of NMDAR but not during synaptic activity. Furthermore, neuron-specific loss of ephrin-B2 reduced the extent of cerebral tissue damage in the acute phase of ischemic stroke.

Collectively, EphB2 may promote the immediate response to an ischemia-reperfusion event in the central nervous system by (i) pro-inflammatory activation of astrocytes via ephrin-B-dependent signaling and (ii) amplification of NMDA-evoked neuronal excitotoxicity.

The use of bacterial cellulose as a basement membrane improves the plausibility of the static in vitro blood-brain barrier model

There are several blood-brain barrier (BBB) models available for pharmaceutical research, but none of those are able to properly imitate the permeability of this special barrier. In this study, it is aimed to produce different BBB models with different cellular combinations and different basement membrane polymers, such as polyethylene terephthalate (PET) and bacterial cellulose (BC), which has not been used for BBB models before, to compare their barrier properties. Primary human brain microvascular endothelial cells were seeded on the luminal side and primary human astrocytes and/or primary human brain microvascular pericytes were seeded on the abluminal side of the membranes. Immunofluorescence (IF) staining results indicate that the expression of tight and adherence junction proteins increases on the 5th day of the cultivation. In accordance with Live-Dead staining results, IF images show that cells in the model lose their viability before the 10th day. Transendothelial electrical resistance (TEER) measurements indicate that BC membrane leads to statistically higher (p < 0.05) TEER values than the standard Transwell PET insert membrane. Sucrose and caffeine permeability values of all models are close to in vivo values. BC shows potential to be used as a more reliable basement membrane for BBB models for pharmaceutical research.

Involvement of CYP2E1 in the Course of Brain Edema Induced by Subacute Poisoning With 1,2-Dichloroethane in Mice

This study was designed to explore the role of cytochrome P4502E1 (CYP2E1) expression in the course of brain edema induced by subacute poisoning with 1,2-dichloroethane (1,2-DCE). Mice were randomly divided into five groups: the control group, the 1,2-DCE poisoned group, and the low-, medium- and high-dose diallyl sulfide (DAS) intervention groups. The present study found that CYP2E1 expression levels in the brains of the 1,2-DCE-poisoned group were upregulated transcriptionally; in contrast, the levels were suppressed by DAS pretreatment in the intervention groups. In addition, the expression levels of both Nrf2 and HO-1 were also upregulated transcriptionally in the brains of the 1,2-DCE-poisoned group, while they were suppressed dose-dependently in the intervention groups. Moreover, compared with the control group, MDA levels and water contents in the brains of the 1,2-DCE-poisoned group increased, whereas NPSH levels and tight junction (TJ) protein levels decreased significantly. Conversely, compared with the 1,2-DCE- poisoned group, MDA levels and water contents in the brains of the intervention groups decreased, and NPSH levels and TJ protein levels increased significantly. Furthermore, pathological changes of brain edema observed in the 1,2-DCE-poisoned group were markedly improved in the intervention groups. Collectively, our results suggested that CYP2E1 expression could be transcriptionally upregulated in 1,2-DCE-poisoned mice, which might enhance 1,2-DCE metabolism in vivo, and induce oxidative damage and TJ disruption in the brain, ultimately leading to brain edema.

Nanodelivery systems for overcoming limited transportation of therapeutic molecules through the blood-brain barrier

Due to the impermeable structure and barrier function of the blood-brain barrier (BBB), the delivery of therapeutic molecules into the CNS is extremely limited. Nanodelivery systems are regarded as the most effective and versatile carriers for the CNS, as they can transport cargo molecules across the BBB via various mechanisms. This review emphasizes the multi-functionalization strategies of nanodelivery systems and combinatorial approaches for the delivery of therapeutic drugs and genes into the CNS. The characteristics and functions of the BBB and underlying mechanisms of molecular translocation across the BBB are also described.

rhIGF-1 reduces the permeability of the blood-brain barrier following intracerebral hemorrhage in mice

Disruption of the blood-brain barrier results in the formation of edema and contributes to the loss of neurological function following intracerebral hemorrhage (ICH). This study examined insulin-like growth factor-1 (IGF-1) as a treatment and its mechanism of action for protecting the blood-brain barrier after ICH in mice. 171 Male CD-1 mice were subjected to ICH via collagenase or autologous blood. A dose study for recombinant human IGF-1 (rhIGF-1) was performed. Brain water content and behavioral deficits were evaluated at 24 and 72 h after the surgery, and Evans blue extravasation and hemoglobin assay were conducted at 24 h. Western blotting was performed for the mechanism study and interventions were used targeting the IGF-1R/GSK3β/MEKK1 pathway. rhIGF-1 reduced edema and blood-brain barrier permeability, and improved neurobehavior outcomes. Western blots showed that rhIGF-1 reduced p-GSK3β and MEKK1 expression, thereby increasing occludin and claudin-5 expression. Inhibition and knockdown of IGF-1R reversed the therapeutic benefits of rhIGF-1. The findings within suggest that stimulation of the IGF-1R is a therapeutic target for ICH which may lead to improved neurofunctional and blood-brain barrier protection.

LncRNA SNHG1 alleviates OGD induced injury in BMEC via miR-338/HIF-1α axis

BACKGROUND

Brain microvascular endothelial cell (BMEC) is an important therapeutic target for the inhibition of brain vascular dysfunction in ischemic stroke. Expression of long non-coding RNA SNHG1 is reportedly upregulated in BMEC after OGD. The present study aims to investigate the potential roles of SNHG1 in OGD-induced injury in BMEC.

METHODS

Mice primary brain microvascular endothelial cells (BMEC) were cultured under "normal" or "oxygen/glucose-deprived" (OGD) conditions. The expression of SNHG1 and miR-338 after OGD were examined by qPCR. shRNA against SNHG1 was used to knockdown SNHG1 in BMEC. MiR-338-3p mimic and inhibitor were used to change the expression of miR-338 in BMEC. The relationship between SNHG1 and miR-338, and the relationship between miR-338 and HIF-1α were clarified using RNA pull-down and luciferase reporter gene assays, respectively.

RESULTS

SNHG1 and miR-338 were upregulated in OGD induced BMEC. SNHG1 silence aggravated OGD-induced cell apoptosis by down-regulating Bcl-2, HIF-1α and VEGF-A, and upregulating caspase 3 activity and Bax. MiR-338 was upregulated in SNHG1-silenced BMEC. RNA pull-down assays showed that SNHG1 could be directly bound by miR-338. In addition, miR-338 overexpression reduced cell viability in OGD while miR-338 inhibition protected BMEC against OGD-induced injury. Furthermore, luciferase reporter assay showed that HIF-1α was a direct target of miR-338.

CONCLUSIONS

SNHG1 exerted protective effects against OGD induced injury via sponging miR-338, thus upregulating HIF-1α/VEGF-A in BMEC.

The peripheral immune response after stroke-A double edge sword for blood-brain barrier integrity

The blood‐brain barrier (BBB) is a highly regulated interface that separates the peripheral circulation and the brain. It plays a vital role in regulating the trafficking of solutes, fluid, and cells at the blood‐brain interface and maintaining the homeostasis of brain microenvironment for normal neuronal activity. Growing evidence has led to the realization that ischemic stroke elicits profound immune responses in the circulation and the activation of multiple subsets of immune cells, which in turn affect both the early disruption and the later repair of the BBB after stroke. Distinct phenotypes or subsets of peripheral immune cells along with diverse intracellular mechanisms contribute to the dynamic changes of BBB integrity after stroke. This review focuses on the interaction between the peripheral immune cells and the BBB after ischemic stroke. Understanding their reciprocal interaction may generate new directions for stroke research and may also drive the innovation of easy accessible immune modulatory treatment strategies targeting BBB in the pursuit of better stroke recovery.

The effect of hypoxia on ZEB1 expression in a mimetic system of the blood-brain barrier

The blood-brain barrier consists of a tightly sealed monolayer of endothelial cells being vital in maintaining a stable intracerebral microenvironment. The barrier is receptive to leakage upon exposure to environmental factors, like hypoxia, and its disruption has been suggested as a constituent in the pathophysiology of both neurological and psychiatric disorders. The schizophrenia associated ZEB1 gene encodes a transcription factor susceptible to transcriptional control by a hypoxia induced factor, HIF1A, known to be implicated in blood-brain barrier dysfunction. However, whether ZEB1 is also implicated in maintaining blood-brain barrier integrity upon hypoxia is unknown. Here we assessed Hif1a, Zo1 and Zeb1 mRNA expression and ZO1 protein abundancy in a mimetic system of the in vivo blood-brain barrier comprising mouse brain endothelial cells subjected to the norm- and proven hypoxic conditions. Despite that, Hif1a mRNA expression was significantly increased, clearly indicating that the oxygen-deprived environment introduced a hypoxia response in the cells, we found no hypoxia-induced changes in neither ZO1 abundancy nor in the expression of Zo1 and Zeb1 mRNA. However, independent of hypoxia status, we found that Zeb1 and Zo1 mRNA expression is highly correlated. Further studies are warranted that investigate the implication of the ZEB1/ZO1 axis in blood-brain barrier maintenance under different physiological conditions.

Drug Delivery Nanosystems for the Localized Treatment of Glioblastoma Multiforme

Glioblastoma multiforme is one of the most prevalent and malignant forms of central nervous system tumors. The treatment of glioblastoma remains a great challenge due to its location in the intracranial space and the presence of the blood⁻brain tumor barrier. There is an urgent need to develop novel therapy approaches for this tumor, to improve the clinical outcomes, and to reduce the rate of recurrence and adverse effects associated with present options. The formulation of therapeutic agents in nanostructures is one of the most promising approaches to treat glioblastoma due to the increased availability at the target site, and the possibility to co-deliver a range of drugs and diagnostic agents. Moreover, the local administration of nanostructures presents significant additional advantages, since it overcomes blood⁻brain barrier penetration issues to reach higher concentrations of therapeutic agents in the tumor area with minimal side effects. In this paper, we aim to review the attempts to develop nanostructures as local drug delivery systems able to deliver multiple agents for both therapeutic and diagnostic functions for the management of glioblastoma.

Postpartum increases in cerebral edema and inflammation in response to placental ischemia during pregnancy

Reduced placental blood flow results in placental ischemia, an initiating event in the pathophysiology of preeclampsia, a hypertensive pregnancy disorder. While studies show increased mortality risk from Alzheimer's disease, stroke, and cerebrovascular complications in women with a history of preeclampsia, the underlying mechanisms are unknown. During pregnancy, placental ischemia, induced by reducing uterine perfusion pressure (RUPP), leads to cerebral edema and increased blood-brain barrier (BBB) permeability; however whether these complications persist after delivery is not known. Therefore, we tested the hypothesis that placental ischemia contributes to postpartum cerebral edema and neuroinflammation. On gestational day 14, time-pregnant Sprague Dawley rats underwent Sham (n = 10) or RUPP (n = 9) surgery and brain tissue collected 2 months post-delivery. Water content increased in posterior cortex but not hippocampus, striatum, or anterior cerebrum following RUPP. Using a rat cytokine multi-plex kit, posterior cortical IL-17, IL-1α, IL-1β, Leptin, and MIP2 increased while hippocampal IL-4, IL-12(p70) and RANTES increased and IL-18 decreased following RUPP. Western blot analysis showed no changes in astrocyte marker, Glial Fibrillary Acidic Protein (GFAP); however, the microglia marker, ionized calcium binding adaptor molecule (Iba1) tended to increase in hippocampus of RUPP-exposed rats. Immunofluorescence staining revealed reduced number of posterior cortical microglia but increased activated (Type 4) microglia in RUPP. Astrocyte number increased in both regions but area covered by astrocytes increased only in posterior cortex following RUPP. BBB-associated proteins, Claudin-1, Aquaporin-4, and zonular occludens-1 expression were unaltered; however, posterior cortical occludin decreased. These results suggest that 2 months postpartum, neuroinflammation, along with decreased occludin expression, may partly explain posterior cortical edema in rats with history of placental ischemia.

The pericyte-glia interface at the blood-brain barrier

The cerebrovasculature is a multicellular structure with varying rheological and permeability properties. The outer wall of the brain capillary endothelium is enclosed by pericytes and astrocyte end feet, anatomically assembled to guarantee barrier functions. We, here, focus on the pericyte modifications occurring in disease conditions, reviewing evidence supporting the interplay amongst pericytes, the endothelium, and glial cells in health and pathology. Deconstruction and reactivity of pericytes and glial cells around the capillary endothelium occur in response to traumatic brain injury, epilepsy, and neurodegenerative disorders, impacting vascular permeability and participating in neuroinflammation. As this represents a growing field of research, addressing the multicellular reorganization occurring at the outer wall of the blood-brain barrier (BBB) in response to an acute insult or a chronic disease could disclose novel disease mechanisms and therapeutic targets.

A novel IL-1RA-PEP fusion protein alleviates blood-brain barrier disruption after ischemia-reperfusion in male rats

BACKGROUND

Current options to treat clinical relapse in inflammatory central nervous system (CNS) conditions such as cerebral ischemia-reperfusion injury are limited, and agents that are more effective are required. Disruption of the blood-brain barrier is an early feature of lesion formation that correlates with clinical exacerbation and facilitates the entry of inflammatory medium and inflammatory cells. Interleukin-1 receptor antagonist (IL-1RA) is a naturally occurring anti-inflammatory antagonist of the interleukin-1 (IL-1) family. The broad-spectrum anti-inflammatory effects of IL-1RA have been investigated against various forms of neuroinflammation. However, the effect of IL-1RA on blood-brain barrier disruption following ischemia-reperfusion has not been reported.

METHODS

In this study, we investigated the effects of IL-1RA and a novel protein (IL-1RA-PEP) that was fused to IL-1RA with a cell penetrating peptide, on blood-brain barrier integrity, in male rats subjected to transient middle cerebral artery occlusion.

RESULTS

After intravenous administration, IL-1RA-PEP (50 mg/kg) penetrated cerebral tissues more effectively than IL-1RA. Moreover, it preserved blood-brain barrier integrity, attenuated changes in expression and localization of tight junction proteins and matrix metalloproteinases, and enhanced angiogenesis in ischemic brain tissue. Further study suggested that the effects of IL-1RA-PEP on preserving blood-brain barrier integrity might be closely correlated with the p65/NF-κB pathway, as evidenced by the effects of the inhibitor JSH-23.

CONCLUSIONS

Collectively, our results demonstrated that IL-1RA-PEP could effectively penetrate the brain of rats with middle cerebral artery occlusion and ameliorate blood-brain barrier disruption. This finding might represent its novel therapeutic potential in the treatment of the cerebral ischemia-reperfusion injury.

Nanoparticle-Based Therapeutics for Brain Injury

Brain injuries affect a large patient population with major physical and emotional suffering for patients and their relatives; at a significant cost to the society. Effective diagnostic and therapeutic options available for brain injuries are limited by the complex brain injury pathology involving blood-brain barrier (BBB). Brain injuries, including ischemic stroke and brain trauma, initiate BBB opening for a short period of time, which is followed by a second reopening for an extended time. The leaky BBB and/or the alterations in the receptor expression on BBB may provide opportunities for therapeutic delivery via nanoparticles (NPs). The approaches for therapeutic interventions via NP delivery are aimed at salvaging the pericontusional/penumbra area for possible neuroprotection and neurovascular unit preservation. The focus of this progress report is to provide a survey of NP strategies employed in cerebral ischemia and brain trauma and finally provide insights for improved NP-based diagnostic/treatment approaches.

Wip1 regulates blood-brain barrier function and neuro-inflammation induced by lipopolysaccharide via the sonic hedgehog signaling signaling pathway

The blood brain barrier (BBB) is a diffusion barrier that maintains the brain environment. Wip1 is a nuclear phosphatase induced by many factors and involved in various stresses, tumorigenesis, organismal aging, and neurogenesis. Wip1's role in BBB integrity has not been thoroughly investigated. The purpose of the present study was to investigate the effect and mechanism of Wip1 on lipopolysaccharide (LPS)-induced BBB dysfunction and inflammation in an in vitro BBB model. The in vitro BBB model was established by co-culturing human brain-microvascular endothelial cells and human astrocytes and then exposing them to 1μg/ml LPS for 6, 12, 18, 24, and 48h. Wip1 expression was significantly elevated by LPS treatment. Knockdown of Wip1 aggravated the increased permeability and decreased transepithelial electrical resistance, protein expression of ZO-1, and occludin induced by LPS. Wip1 silencing augmented the elevated inflammatory cytokines TNF-α, IL-1β, IL-12, and IL-6 of the BBB induced by LPS, whereas overexpression of Wip1 showed a contrary effect. Sonic hedgehog signaling (SHH) was activated by Wip1 overexpression and inhibited by Wip1 silencing. Additionally, activating or inhibiting the SHH pathway by purmorphamine or cyclopamine, respectively, abolished the Wip1-induced changes in transepithelial electrical resistance and permeability and inflammatory responses in the LPS-injured BBB model. Our results demonstrate that Wip1 may protect the BBB against LPS-induced integrity disruption and inflammatory response through the SHH signaling pathway.

Mechanisms of the Testis Toxicity Induced by Chronic Exposure to Mequindox

Mequindox (MEQ) is a synthetic antimicrobial agent widely used in China since the 1980s. Although the toxicity of MEQ is well recognized, its testis toxicity has not been adequately investigated. In the present study, we provide evidence that MEQ triggers oxidative stress, mitochondrion dysfunction and spermatogenesis deficiency in mice after exposure to MEQ (0, 25, 55, and 110 mg/kg in the diet) for up to 18 months. The genotoxicity and adrenal toxicity may contribute to sperm abnormalities caused by MEQ. Moreover, using LC/MS-IT-TOF analysis, two metabolites, 3-methyl-2-(1-hydroxyethyl) quinoxaline-N4-monoxide (M4) and 3-methyl-2-(1-hydroxyethyl) quinoxaline-N1-monoxide (M8), were detected in the serum of mice, which directly confirms the relationship between the N→O group reduction metabolism of MEQ and oxidative stress. Interestingly, only M4 was detected in the testes, suggesting that the higher reproductive toxicity of M4 than M8 might be due to the increased stability of M4-radical (M4-R) compared to M8-radical (M8-R). Furthermore, the expression of the blood-testis barrier (BTB)-associated junctions such as tight junctions, gap junctions and basal ectoplasmic specializations were also examined. The present study demonstrated for the first time the role of the M4 in testis toxicity, and illustrated that the oxidative stress, mitochondrion dysfunction and interference in spermatogenesis, as well as the altered expression of BTB related junctions, were involved in the reproductive toxicity mediated by MEQ in vivo.

Toxic metabolites, Sertoli cells and Y chromosome related genes are potentially linked to the reproductive toxicity induced by mequindox

Mequindox (MEQ) is a relatively new synthetic antibacterial agent widely applied in China since the 1980s. However, its reproductive toxicity has not been adequately performed. In the present study, four groups of male Kunming mice (10 mice/group) were fed diets containing MEQ (0, 25, 55 and 110 mg/kg in the diet) for up to 18 months. The results show that M4 could pass through the blood-testis barrier (BTB), and demonstrate that Sertoli cells (SCs) are the main toxic target for MEQ to induce spermatogenesis deficiency. Furthermore, adrenal toxicity, adverse effects on the hypothalamic-pituitary-testicular axis (HPTA) and Leydig cells, as well as the expression of genes related to steroid biosynthesis and cholesterol transport, were responsible for the alterations in sex hormones in the serum of male mice after exposure to MEQ. Additionally, the changed levels of Y chromosome microdeletion related genes, such as DDX3Y, HSF2, Sly and Ssty2 in the testis might be a mechanism for the inhibition of spermatogenesis induced by MEQ. The present study illustrates for the first time the toxic metabolites of MEQ in testis of mice, and suggests that SCs, sex hormones and Y chromosome microdeletion genes are involved in reproductive toxicity mediated by MEQ in vivo.

EAE Induction by Passive Transfer of MOG-specific CD4+ T Cells

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS), which is a chronic inflammatory disease of the central nervous system (CNS). It is characterized by focal demyelination and inflammatory responses mediated by myelin-specific autoreactive CD4⁺ T cells. Using a passive transfer model of EAE in mice, we have demonstrated that regional specific neural signals by sensory-sympathetic communications create gateways for immune cells at specific blood vessels of the CNS, a phenomenon known as the gateway reflex ( Arima et al., 2012 ; Tracey, 2012; Arima et al., 2013 ; Sabharwal et al., 2014 ; Arima et al., 2015b ). Here we describe protocols for passive transfer model of EAE using freshly isolated (MOG)-specific CD4⁺ T cells or periodically restimulated MOG-specific CD4⁺ T cell lines, which are suitable for tracking pathogenic CD4⁺ T cells in vivo, particularly in the CNS ( Ogura et al., 2008 ; Arima et al., 2012 and 2015b).

Sac-1004, a vascular leakage blocker, reduces cerebral ischemia-reperfusion injury by suppressing blood-brain barrier disruption and inflammation

Background

Blood–brain barrier (BBB) breakdown and inflammation are critical events in ischemic stroke, contributing to aggravated brain damage. The BBB mainly consists of microvascular endothelial cells sealed by tight junctions to protect the brain from blood-borne substances. Thus, the maintenance of BBB integrity may be a potential target for neuroprotection. Sac-1004, a pseudo-sugar derivative of cholesterol, enhances the endothelial barrier by the stabilization of the cortical actin ring.

Results

Here, we report on the protective effects of Sac-1004 on cerebral ischemia-reperfusion (I/R) injury. Treatment with Sac-1004 significantly blocked the interleukin-1β-induced monolayer hyperpermeability of human brain microvascular endothelial cells (HBMECs), loss of tight junctions, and formation of actin stress fiber. Sac-1004 suppressed the expression of adhesion molecules, adhesion of U937 cells, and activation of nuclear factor-κB in HBMECs. Using a rat model of transient focal cerebral ischemia, it was shown that Sac-1004 effectively ameliorated neurological deficits and ischemic damage. In addition, Sac-1004 decreased BBB leakage and rescued tight junction-related proteins. Moreover, the staining of CD11b and glial fibrillary acidic protein showed that Sac-1004 inhibited glial activation.

Conclusions

Taken together, these results demonstrate that Sac-1004 has neuroprotective activities through maintaining BBB integrity, suggesting that it is a great therapeutic candidate for stroke.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0897-3) contains supplementary material, which is available to authorized users.

miR-Let7A Controls the Cell Death and Tight Junction Density of Brain Endothelial Cells under High Glucose Condition

Hyperglycemia-induced stress in the brain of patients with diabetes triggers the disruption of blood-brain barrier (BBB), leading to diverse neurological diseases including stroke and dementia. Recently, the role of microRNA becomes an interest in the research for deciphering the mechanism of brain endothelial cell damage under hyperglycemia. Therefore, we investigated whether mircoRNA Let7A (miR-Let7A) controls the damage of brain endothelial (bEnd.3) cells against high glucose condition. Cell viability, cell death marker expressions (p-53, Bax, and cleaved poly ADP-ribose polymerase), the loss of tight junction proteins (ZO-1 and claudin-5), proinflammatory response (interleukin-6, tumor necrosis factor-α), inducible nitric oxide synthase, and nitrite production were confirmed using MTT, reverse transcription-PCR, quantitative-PCR, Western blotting, immunofluorescence, and Griess reagent assay. miR-Let7A overexpression significantly prevented cell death and loss of tight junction proteins and attenuated proinflammatory response and nitrite production in the bEnd.3 cells under high glucose condition. Taken together, we suggest that miR-Let7A may attenuate brain endothelial cell damage by controlling cell death signaling, loss of tight junction proteins, and proinflammatory response against high glucose stress. In the future, the manipulation of miR-Let7A may be a novel solution in controlling BBB disruption which leads to the central nervous system diseases.

Physical insights into the blood-brain barrier translocation mechanisms

The number of individuals suffering from diseases of the central nervous system (CNS) is growing with an aging population. While candidate drugs for many of these diseases are available, most of these pharmaceutical agents cannot reach the brain rendering most of the drug therapies that target the CNS inefficient. The reason is the blood-brain barrier (BBB), a complex and dynamic interface that controls the influx and efflux of substances through a number of different translocation mechanisms. Here, we present these mechanisms providing, also, the necessary background related to the morphology and various characteristics of the BBB. Moreover, we discuss various numerical and simulation approaches used to study the BBB, and possible future directions based on multi-scale methods. We anticipate that this review will motivate multi-disciplinary research on the BBB aiming at the design of effective drug therapies.

Treatment of Movement Disorders With Focused Ultrasound

Although the use of ultrasound as a potential therapeutic modality in the brain has been under study for several decades, relatively few neuroscientists or neurologists are familiar with this technology. Stereotactic brain lesioning had been widely used as a treatment for medically refractory patients with essential tremor (ET), Parkinson disease (PD), and dystonia but has been largely replaced by deep brain stimulation (DBS) surgery, with advantages both in safety and efficacy. However, DBS is associated with complications including intracerebral hemorrhage, infection, and hardware malfunction. The occurrence of these complications has spurred interest in less invasive stereotactic brain lesioning methods including magnetic resonance imaging–guided high intensity–focused ultrasound (FUS) surgery. Engineering advances now allow sound waves to be targeted noninvasively through the skull to a brain target. High intensities of sonic energy can create a coagulation lesion similar to that of older radiofrequency stereotactic methods, but without opening the skull, recent Food and Drug Administration approval of unilateral thalamotomy for treatment of ET. Clinical studies of stereotactic FUS for aspects of PD are underway. Moderate intensity, pulsed FUS has also demonstrated the potential to safely open the blood-brain barrier for localized delivery of therapeutics including proteins, genes, and cell-based therapy for PD and related disorders. The goal of this review is to provide basic and clinical neuroscientists with a level of understanding to interact with medical physicists, biomedical engineers, and radiologists to accelerate the application of this powerful technology to brain disease

Berberine alleviates dextran sodium sulfate-induced colitis by improving intestinal barrier function and reducing inflammation and oxidative stress

Berberine has demonstrated efficacy in alleviating experimental colitis in vivo and in vitro. However, the anti-colitis mechanisms of berberine that enable it to promote intestinal barrier function in vivo remain unclear. The present study aimed to evaluate the effect of berberine on intestinal epithelial barrier function, expression of tight junction proteins and the levels of inflammatory and oxidative stress factors in the intestinal mucosa of dextran sulfate sodium (DSS)-induced colitis mice. Berberine (100 mg/kg) was administered for five days to mice with established colitis, induced by administration of DSS (3% w/v) for six days. Intestinal barrier function and the presence of proinflammatory factors, oxidative stress and active signaling pathways in the colon were determined principally by western blotting and reverse transcription-quantitative polymerase chain reaction. It was observed that berberine reduced weight loss, shortening of the colon and colon damage in DSS-colitis mice. In addition, berberine significantly inhibited the increase of fluorescein isothiocyanate-dextran in serum and the decrease of zonula occluden-1 (also known as tight junction protein-1), occludin and epithelial cadherin expression in colonic tissue, relative to a DSS-treated control group. Berberine also significantly inhibited the expression of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α mRNA and phosphorylation of signal transducer and activator of transcription 3. Furthermore, berberine reduced the levels of myeloperoxidase and increased the levels of superoxide dismutase and catalase in colon and serum samples relative to the control group. The expression of cluster of differentiation 68 in the colon of colitis mice was also reduced by berberine. Collectively, these data suggest that berberine alleviates colitis principally by improving intestinal barrier function and promoting anti-inflammatory and antioxidative stress responses. In turn these effects inhibit macrophage infiltration into the colon and thus may be central to the anti-colitis activity of berberine.

Mild hypothermia alleviates brain oedema and blood-brain barrier disruption by attenuating tight junction and adherens junction breakdown in a swine model of cardiopulmonary resuscitation

Mild hypothermia improves survival and neurological recovery after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). However, the mechanism underlying this phenomenon is not fully elucidated. The aim of this study was to determine whether mild hypothermia alleviates early blood-brain barrier (BBB) disruption. We investigated the effects of mild hypothermia on neurologic outcome, survival rate, brain water content, BBB permeability and changes in tight junctions (TJs) and adherens junctions (AJs) after CA and CPR. Pigs were subjected to 8 min of untreated ventricular fibrillation followed by CPR. Mild hypothermia (33°C) was intravascularly induced and maintained at this temperature for 12 h, followed by active rewarming. Mild hypothermia significantly reduced cortical water content, decreased BBB permeability and attenuated TJ ultrastructural and basement membrane breakdown in brain cortical microvessels. Mild hypothermia also attenuated the CPR-induced decreases in TJ (occludin, claudin-5, ZO-1) and AJ (VE-cadherin) protein and mRNA expression. Furthermore, mild hypothermia decreased the CA- and CPR-induced increases in matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression and increased angiogenin-1 (Ang-1) expression. Our findings suggest that mild hypothermia attenuates the CA- and resuscitation-induced early brain oedema and BBB disruption, and this improvement might be at least partially associated with attenuation of the breakdown of TJ and AJ, suppression of MMP-9 and VEGF expression, and upregulation of Ang-1 expression.

Folate nutrition and blood-brain barrier dysfunction

Mammals require essential nutrients from dietary sources to support normal metabolic, physiological and neuronal functions, to prevent diseases of nutritional deficiency as well as to prevent chronic disease. Disease and/or its treatment can modify fundamental biological processes including cellular nutrient accretion, stability and function in cells. These effects can be isolated to a specific diseased organ in the absence of whole-body alterations in nutrient status or biochemistry. Loss of blood-brain barrier function, which occurs in in-born errors of metabolism and in chronic disease, can cause brain-specific folate deficiency and contribute to disease co-morbidity. The role of brain folate deficiency in neuropsychiatric disorders is reviewed, as well as emerging diagnostic and nutritional strategies to identify and address brain folate deficiency in blood-brain barrier dysfunction.

Nanobiomaterials' applications in neurodegenerative diseases

The blood-brain barrier is the interface between the blood and brain, impeding the passage of most circulating cells and molecules, protecting the latter from foreign substances, and maintaining central nervous system homeostasis. However, its restrictive nature constitutes an obstacle, preventing therapeutic drugs from entering the brain. Usually, a large systemic dose is required to achieve pharmacological therapeutic levels in the brain, leading to adverse effects in the body. As a consequence, various strategies are being developed to enhance the amount and concentration of therapeutic compounds in the brain. One such tool is nanotechnology, in which nanostructures that are 1-100 nm are designed to deliver drugs to the brain. In this review, we examine many nanotechnology-based approaches to the treatment of neurodegenerative diseases. The review begins with a brief history of nanotechnology, followed by a discussion of its definition, the properties of most reported nanomaterials, their biocompatibility, the mechanisms of cell-material interactions, and the current status of nanotechnology in treating Alzheimer's, Parkinson's diseases, and amyotrophic lateral sclerosis. Of all strategies to deliver drug to the brain that are used in nanotechnology, drug release systems are the most frequently reported.

Macrophage Ontogeny Underlies Differences in Tumor-Specific Education in Brain Malignancies

Extensive transcriptional and ontogenetic diversity exists among normal tissue-resident macrophages, with unique transcriptional profiles endowing the cells with tissue-specific functions. However, it is unknown whether the origins of different macrophage populations affect their roles in malignancy. Given potential artifacts associated with irradiation-based lineage tracing, it remains unclear if bone-marrow-derived macrophages (BMDMs) are present in tumors of the brain, a tissue with no homeostatic involvement of BMDMs. Here, we employed multiple models of murine brain malignancy and genetic lineage tracing to demonstrate that BMDMs are abundant in primary and metastatic brain tumors. Our data indicate that distinct transcriptional networks in brain-resident microglia and recruited BMDMs are associated with tumor-mediated education yet are also influenced by chromatin landscapes established before tumor initiation. Furthermore, we demonstrate that microglia specifically repress Itga4 (CD49D), enabling its utility as a discriminatory marker between microglia and BMDMs in primary and metastatic disease in mouse and human.

Evidence of Hepatitis E virus breaking through the blood-brain barrier and replicating in the central nervous system

Neurologic dysfunctions such as Guillain-Barre' syndrome, encephalitis, meningitis and transverse myelitis occur frequently in patients with hepatitis E virus (HEV) infection, and this study was conducted to better characterize the role of HEV in the pathogenesis of neurologic disorders. Genotype 4 strain of swine HEV was used to inoculate Mongolian gerbils. Reverse transcription-nested polymerase chain reaction (RT-nPCR), ELISA, histopathology, ultrastructural pathology and enzyme immunohistochemistry method were conducted to investigate the replication and localization of HEV in the central nervous system (CNS) and the consequent pathological changes. Both positive- and negative-strand HEV RNA was detectable in brain and spinal cord from 7 to 28 dpi (days postinoculation) via RT-nPCR. Various pathological changes such as perineural invasion, neuron necrosis, microglia nodule, lymphocyte infiltration, perivascular cuff and myelin degeneration were observed in HEV-positive brains and spinal cords. Immunohistochemical (IHC) staining targeting on HEV ORF2 protein revealed positive signals concentrated mainly in the cytoplasm of neuron, ependymal epithelium and choroid plexus area. Positive area density of ZO-1 (zonula occludens-1) in brain of HEV-positive gerbils decreased, while the GFAP (glial fibrillary acidic protein) expression was upregulated compared with control groups. These results provide strong evidence that HEV is able to damage the blood-brain barrier (BBB), replicate in brain and spinal cord, and hammer the causative role of HEV in the pathogenesis of neurologic disorders.

Inhibitory effect of melatonin on cerebral endothelial cells dysfunction induced by methamphetamine via NADPH oxidase-2

Melatonin is a hormone that mostly produced from the pineal gland, and it performs as a strong neuroprotectant to both neuron and glial cells against methamphetamine (METH)-induced neurotoxicity. Recently, it has been found that METH also damages the blood brain barrier (BBB) structure and function. However, the protective mechanism of melatonin on the BBB impairment caused by METH has not been investigated. In this study, the primary rat brain microvascular endothelium cells (BMVECs) isolated from neonatal rats was used to investigate the protective effect of melatonin on METH-induced BBB impairment and the underlying mechanism. The results demonstrated that melatonin decreased the level of reactive oxygen species (ROS), reactive nitrogen species (RNS), and apoptosis induced by METH via NADPH oxidase (NOX)-2 since apocynin, a NOX-2 inhibitor abolished those changes. In addition, melatonin was found to improve cell integrity by increasing the transendothelial electric resistance (TEER) values, and up-regulate the tight junction proteins ZO-1, occludin, and claudin-5, thereby decreasing the paracellular permeability caused by METH mediated by NOX-2. Our data suggest that METH induces BBB impairment by mediating NOX-2 activity, and then induces oxidative and nitrative stress, as well as apoptosis, which causes the impairment of cell integrity, and that melatonin reduces these negative effects of METH by mediating via MT1/2 receptors.

The molecular constituents of the blood-brain barrier

The blood-brain barrier (BBB) maintains the optimal microenvironment in the central nervous system (CNS) for proper brain function. The BBB comprises specialized CNS endothelial cells with fundamental molecular properties essential for the function and integrity of the BBB. The restrictive nature of the BBB hinders the delivery of therapeutics for many neurological disorders. In addition, recent evidence shows that BBB dysfunction can precede or hasten the progression of several neurological diseases. Despite the physiological significance of the BBB in health and disease, major discoveries of the molecular regulators of BBB formation and function have occurred only recently. This review highlights recent findings describing the molecular determinants and core cellular pathways that confer BBB properties on CNS endothelial cells.