Blood Occludin Level as a Potential Biomarker for Early Blood Brain Barrier Damage Following Ischemic Stroke

Circulating Blood-Brain Barrier Proteins for Differentiating Ischaemic Stroke Patients from Stroke Mimics

BACKGROUND

Stroke is one of the leading causes of death and disability worldwide. The diagnosis of stroke remains largely clinical, yet widely used stroke scoring systems and brain imaging do not satisfactorily allow the distinction of ischaemic stroke (IS) patients from stroke mimics (SMs). Blood biomarkers are promising tools that could facilitate clinical triage.

METHODS

This study recruited 66 patients with IS and 24 SMs. The levels of Glial fibrillary acidic protein (GFAP), Neuron-specific enolase (NSE), Neurofilament light chain (NfL) and blood-brain barrier (BBB) proteins [Occludin (OCLN), Zonula occludens 1 (ZO-1), Claudin-5] in blood serum were measured by enzyme-linked immunosorbent assay technique. Biomarker levels in IS patients and SMs were compared using the Mann-Whitney U test. Multivariable logistic regression analysis was used to evaluate the diagnostic performance of biomarkers in combination with the National Institutes of Health Stroke Scale (NIHSS) score.

RESULTS

More significant differences in circulating GFAP, NfL, OCLN, ZO-1, and Claudin-5 but not NSE were found in IS patients compared to SMs. A combination of circulating ZO-1, Claudin-5, and OCLN with NIHSS score gives the highest diagnostic accuracy, sensitivity, and specificity.

CONCLUSIONS

A prediction model with circulating BBB proteins in combination with NIHSS score differentiates between IS patients and SMs.

Biochemical, biomechanical and imaging biomarkers of ischemic stroke: Time for integrative thinking

Stroke is one of the leading causes of adult disability affecting millions of people worldwide. Post-stroke cognitive and motor impairments diminish quality of life and functional independence. There is an increased risk of having a second stroke and developing secondary conditions with long-term social and economic impacts. With increasing number of stroke incidents, shortage of medical professionals and limited budgets, health services are struggling to provide a care that can break the vicious cycle of stroke. Effective post-stroke recovery hinges on holistic, integrative and personalized care starting from improved diagnosis and treatment in clinics to continuous rehabilitation and support in the community. To improve stroke care pathways, there have been growing efforts in discovering biomarkers that can provide valuable insights into the neural, physiological and biomechanical consequences of stroke and how patients respond to new interventions. In this review paper, we aim to summarize recent biomarker discovery research focusing on three modalities (brain imaging, blood sampling and gait assessments), look at some established and forthcoming biomarkers, and discuss their usefulness and complementarity within the context of comprehensive stroke care. We also emphasize the importance of biomarker guided personalized interventions to enhance stroke treatment and post-stroke recovery.

Treatment of Ischemic Stroke by Atorvastatin-Loaded PEGylated Liposome

There is insufficient evidence on the effect of nanoparticles, particularly liposomes loaded with a statin, on acute ischemic stroke. We investigated the impact of atorvastatin-loaded PEG (polyethylene glycol) conjugated liposomes (LipoStatin) on the outcomes in rats with cerebral ischemia-reperfusion. PEGylated liposome loaded with atorvastatin was developed as a nanoparticle to specifically accumulate in an ischemic region and release the drug to ameliorate the harmful effects of the stroke. LipoStatin was administered to rats with transient middle cerebral artery occlusion through the tail vein immediately after reperfusion (LipoStatin group). LipoStatin efficiently accumulated at the cerebral ischemic injury site of the rat. The LipoStatin group showed a significantly reduced infarct volume (p < 0.01) in brain micro-MR imaging and improved neurological function recovery compared to the control group (p < 0.05). In addition, markedly improved brain metabolism using fluorine-18 fluorodeoxyglucose micro-PET/CT imaging was demonstrated in the LipoStatin group compared with the control group (p < 0.01). Mechanistically, as a result of evaluation through IL-1 beta, TNF-alpha, ICAM-1, and Iba-1 mRNA expression levels at 5 days after cerebral ischemia, LipoStatin showed significant anti-inflammatory effects. Protein expression of occludin, JAM-A, Caveolin-1, and eNOS by western blot at 3 days and fluorescent images at 7 days showed considerable recovery of blood-brain barrier breakdown and endothelial dysfunction. PEGylated LipoStatin can be more effectively delivered to the ischemic brain and may have significant neuroprotective effects. Thus, PEGylated LipoStatin can be further developed as a promising targeted therapy for ischemic stroke and other major vascular diseases.

Contribution of zinc accumulation to ischemic brain injury and its mechanisms about oxidative stress, inflammation, and autophagy: an update

Ischemic stroke is a leading cause of death and disability worldwide, and presently, there is no effective neuroprotective therapy. Zinc is an essential trace element that plays important physiological roles in the central nervous system. Free zinc concentration is tightly regulated by zinc-related proteins in the brain under normal conditions. Disruption of zinc homeostasis, however, has been found to play an important role in the mechanism of brain injury following ischemic stroke. A large of free zinc releases from storage sites after cerebral ischemia, which affects the functions and survival of nerve cells, including neurons, astrocytes, and microglia, resulting in cell death. Ischemia-triggered intracellular zinc accumulation also disrupts the function of blood-brain barrier via increasing its permeability, impairing endothelial cell function, and altering tight junction levels. Oxidative stress and neuroinflammation have been reported to be as major pathological mechanisms in cerebral ischemia/reperfusion injury. Studies have showed that the accumulation of intracellular free zinc could impair mitochondrial function to result in oxidative stress, and form a positive feedback loop between zinc accumulation and reactive oxygen species production, which leads to a series of harmful reactions. Meanwhile, elevated intracellular zinc leads to neuroinflammation. Recent studies also showed that autophagy is one of the important mechanisms of zinc toxicity after ischemic injury. Interrupting the accumulation of zinc will reduce cerebral ischemia injury and improve neurological outcomes. This review summarizes the role of zinc toxicity in cellular and tissue damage following cerebral ischemia, focusing on the mechanisms about oxidative stress, inflammation, and autophagy.

Association of serum occludin levels and perihematomal edema volumes in intracranial hemorrhage patients

BACKGROUND AND PURPOSE

Perihematomal edema (PHE) is one of the severe secondary damages following intracranial hemorrhage (ICH). Studies showed that blood-brain barrier (BBB) injury contributes to the development of PHE. Previous studies showed that occludin protein is a potential biomarker of BBB injury. In the present study, we investigated whether the levels of serum occludin on admission are associated with PHE volumes in ICH patients.

METHODS

This cross-sectional study included 90ICH patients and 32 healthy controls.The volumes of hematoma and PHE were assessed using non-contrast cranial CT within 30 min of admission. Blood samples were drawn on admission, and the levels of baseline serum occludin were detected using enzyme-linked immunosorbent assay. Partial correlation analysis and multiple linear regression analysis were performed to evaluate the association between serum occludin levels and PHE volumes in ICH patients.

RESULTS

The serum occludin levels in ICH patients were much higher than health controls (median 0.27 vs. 0.13 ng/mL, p < 0.001). At admission, 34 ICH patients (37.78%) had experienced a severe PHE (≥30 mL), and their serum occludin levels were higher compared to those with mild PHE (<30 mL) (0.78 vs. 0.21 ng/mL, p < 0.001). The area under the receiver operating characteristics curve (ROC) of serum occludin level in predicting severe PHE was 0.747 (95% confidence interval CI 0.644-0.832, p < 0.001). There was a significant positive correlation between serum occludin levels and PHE volumes (partial correlation r = 0.675, p < 0.001). Multiple linear regression analysis showed that serum occludin levels remained independently associated with the PHE volumes after adjusting other confounding factors.

CONCLUSION

The present study showed that serum occludin levels at admission were independently correlated with PHE volumes in ICH patients, which may provide a biomarker indicating PHE volume change.

High-resolution omics of vascular ageing and inflammatory pathways in neurodegeneration

High-resolution omics, particularly single-cell and spatial transcriptomic profiling, are rapidly enhancing our comprehension of the normal molecular diversity of gliovascular cells, as well as their age-related changes that contribute to neurodegeneration. With more omic profiling studies being conducted, it is becoming increasingly essential to synthesise valuable information from the rapidly accumulating findings. In this review, we present an overview of the molecular features of neurovascular and glial cells that have been recently discovered through omic profiling, with a focus on those that have potentially significant functional implications and/or show cross-species differences between human and mouse, and that are linked to vascular deficits and inflammatory pathways in ageing and neurodegenerative disorders. Additionally, we highlight the translational applications of omic profiling, and discuss omic-based strategies to accelerate biomarker discovery and facilitate disease course-modifying therapeutics development for neurodegenerative conditions.

A novel human iPSC model of COL4A1/A2 small vessel disease unveils a key pathogenic role of matrix metalloproteinases

Cerebral small vessel disease (SVD) affects the small vessels in the brain and is a leading cause of stroke and dementia. Emerging evidence supports a role of the extracellular matrix (ECM), at the interface between blood and brain, in the progression of SVD pathology, but this remains poorly characterized. To address ECM role in SVD, we developed a co-culture model of mural and endothelial cells using human induced pluripotent stem cells from patients with COL4A1/A2 SVD-related mutations. This model revealed that these mutations induce apoptosis, migration defects, ECM remodeling, and transcriptome changes in mural cells. Importantly, these mural cell defects exert a detrimental effect on endothelial cell tight junctions through paracrine actions. COL4A1/A2 models also express high levels of matrix metalloproteinases (MMPs), and inhibiting MMP activity partially rescues the ECM abnormalities and mural cell phenotypic changes. These data provide a basis for targeting MMP as a therapeutic opportunity in SVD.

Drugs with a negative impact on cognitive function (Part 1): chronic kidney disease as a risk factor

People living with chronic kidney disease (CKD) frequently suffer from mild cognitive impairment and/or other neurocognitive disorders. This review in two parts will focus on adverse drug reactions resulting in cognitive impairment as a potentially modifiable risk factor in CKD patients. Many patients with CKD have a substantial burden of comorbidities leading to polypharmacy. A recent study found that patients seen by nephrologists were the most complex to treat because of their high number of comorbidities and medications. Due to polypharmacy, these patients may experience a wide range of adverse drug reactions. Along with CKD progression, the accumulation of uremic toxins may lead to blood-brain barrier (BBB) disruption and pharmacokinetic alterations, increasing the risk of adverse reactions affecting the central nervous system (CNS). In patients on dialysis, the excretion of drugs that depend on kidney function is severely reduced such that adverse and toxic levels of a drug or its metabolites may be reached at relatively low doses, unless dosing is adjusted. This first review will discuss how CKD represents a risk factor for adverse drug reactions affecting the CNS via (i) BBB disruption associated with CKD and (ii) the impact of reduced kidney function and dialysis itself on drug pharmacokinetics.

Stroke-induced damage on the blood-brain barrier

The blood-brain barrier (BBB) is a functional phenotype exhibited by the neurovascular unit (NVU). It is maintained and regulated by the interaction between cellular and non-cellular matrix components of the NVU. The BBB plays a vital role in maintaining the dynamic stability of the intracerebral microenvironment as a barrier layer at the critical interface between the blood and neural tissues. The large contact area (approximately 20 m2/1.3 kg brain) and short diffusion distance between neurons and capillaries allow endothelial cells to dominate the regulatory role. The NVU is a structural component of the BBB. Individual cells and components of the NVU work together to maintain BBB stability. One of the hallmarks of acute ischemic stroke is the disruption of the BBB, including impaired function of the tight junction and other molecules, as well as increased BBB permeability, leading to brain edema and a range of clinical symptoms. This review summarizes the cellular composition of the BBB and describes the protein composition of the barrier functional junction complex and the mechanisms regulating acute ischemic stroke-induced BBB disruption.

The tight junction protein occludin modulates blood-brain barrier integrity and neurological function after ischemic stroke in mice

Blood-brain barrier (BBB) disruption contributes to brain injury and neurological impairment. Tight junctions (TJs) and cell-cell adhesion complexes develop between endothelial cells in the brain to establish and maintain the BBB. Occludin, the first transmembrane protein identified in TJs, has received intense research interest because numerous in vitro studies have suggested its importance in maintaining BBB integrity. However, its role in maintaining BBB integrity after ischemic stroke is less clear owing to the lack of in vivo evidence. This study aimed to investigate the dynamics and function of occludin across the acute and chronic phases after stroke using occludin-deficient mice. By photochemically induced thrombosis model, the expression of occludin was decreased in brain endothelial cells from ischemic lesions. The neurological function of occludin-deficient mice was continuously impaired compared to that of wild-type mice. BBB integrity evaluated by Evans blue and 0.5-kDa fluorescein in the acute phase and by 10-kDa fluorescein isothiocyanate-labeled dextran in the chronic phase was decreased to a greater extent after stroke in occludin-deficient mice. Furthermore, occludin-deficient mice showed decreased claudin-5 and neovascularization after stroke. Our study reveals that occludin plays an important role from the acute to the chronic phase after ischemic stroke in vivo.

Wharton's jelly mesenchymal stem cells attenuate global hypoxia-induced learning and memory impairment via preventing blood-brain barrier breakdown

Objectives

Intracerebroventricular (ICV) injections of mesenchymal stem cells (MSCs) may improve the function and structure of blood-brain barrier (BBB), possibly by preserving the BBB integrity. This study examined the impact of Wharton's jelly (WJ)-MSCs on cognitive dysfunction and BBB disruption following a protracted hypoxic state.

Materials and Methods

Twenty-four male Wistar rats were randomly studied in four groups: Control (Co): Healthy animals, Sham (Sh): Rats were placed in the cage without hypoxia induction and with ICV injection of vehicle, Hypoxic (Hx)+vehicle: Hypoxic rats with ICV injection of vehicle (5 μl of PBS), and Hx+MSCs: Hypoxic rats with ICV injection of MSCs. Spatial learning and memory were evaluated one week after WJ-MSCs injection, and then animals were sacrificed for molecular research.

Results

Hypoxia increased latency and lowered the time and distance required reaching the target quarter, according to the findings. Furthermore, hypoxic rats had lower gene expression and protein levels of hippocampus vascular endothelial (VE)-cadherin, claudin 5, and tricellulin gene expression than Co and Sh animals (P<0.05). Finally, administering WJ-MSCs after long-term hypoxia effectively reversed the cognitive deficits and prevented the BBB breakdown via the upregulation of VE-cadherin, claudin 5, and tricellulin genes (P<0.05).

Conclusion

These findings suggest that prolonged hypoxia induces spatial learning and memory dysfunction and increases BBB disruption, the potential mechanism of which might be via reducing VE-cadherin, claudin 5, and tricellulin genes. Hence, appropriate treatment with WJ-MSCs could reverse ischemia adverse effects and protect the BBB integrity following prolonged hypoxia.

Blood-Brain Barrier Disintegration in Growth-Restricted Fetuses with Brain Sparing Effect

The endothelial cells of the blood-brain barrier adhere closely, which is provided by tight junctions (TJs). The aim of the study was to assess the damage to the endothelial TJs in pregnancy, complicated by fetal growth restriction (FGR) and circulatory centralization (brain-sparing effect, BS). The serum concentrations of NR1 subunit of the N-methyl-D-aspartate receptor (NR1), nucleoside diphosphate kinase A (NME1), S100 calcium-binding protein B (S100B), occludin (OCLN), claudin-5 (CLN5), and zonula occludens protein – 1 (zo-1), and the placental expressions of OCLN, claudin-4 (CLN4), CLN5, and zo-1 were assessed with ELISA. The significantly higher serum NME1 concentrations and the serum CLN5/zo-1 index were observed in FGR pregnancy with BS, as compared to the FGR group without BS. The FGR newborns with BS were about 20 times more likely to develop an intraventricular hemorrhage (IVH) than the FGR infants without BS. The cerebroplacental ratio (CPR) allowed to predict the IVH in growth-restricted fetuses. The significantly lower placental CLN4 expression was observed in the FGR group with BS and who postnatally developed an IVH, as compared to the growth-restricted infants with BS without IVH signs. Pregnancy complicated by FGR and BS is associated with the destabilization of the fetal blood-brain barrier. The IVH in newborns is reflected in the inhibition of the placental CLN4 expression, which may be a useful marker in the prediction of an IVH among growth-restricted fetuses.

Evaluation of Changes in Peripheric Biomarkers Related to Blood Brain Barrier Damage in Patients with Schizophrenia and Their Correlation with Symptoms

OBJECTIVE

The aim of the study was to evaluate the levels of peripheric biomarkers that have been associated with blood brain barrier (BBB) damage in healthy controls and two groups of patients with schizophrenia, those who received typical-atypical antipsychotics and those who received only atypical antipsychotics. Additionally, we sought relationships between these biomarkers and schizophrenia symptoms.

METHODS

This study was conducted with the inclusion of 41 healthy volunteers and 75 patients with schizophrenia. The biomarkers measured to evaluate BBB injury were as follows: spectrin breakdown product 145 (SBDP145), spectrin breakdown product 150 (SBDP150), ubiquitin carboxy terminal hydrolase L1 (UCHL1), ubiquitin ligase cullin-3 (cullin), occludin and claudin, which were measured via ELISA. Symptoms of patients with schizophrenia were evaluated with the Scale for the Assessment of Positive Symptoms (SAPS), Scale for the Assessment of Negative Symptoms, the Clinical Global Impression Scale (CGI), and the general assessment of functionality (GAF).

RESULTS

Compared to controls, SBDP145 (p = 0.022) and cullin (p = 0.046) levels were significantly higher in patients with schizophrenia receiving atypical antipsychotic treatment. SBDP150 levels were lower in the combination treatment group compared to the control group (p = 0.022). Claudin (p = 0.804), occludin (p = 0.058) and UCHL1 (p = 0.715) levels were similar among groups. In recipients of combination treatment, SBDP145 levels were found to be positively correlated with SAPS-total (r = 0.440, p = 0.036) and SAPS-delusions (r = 0.494, p = 0.017) scores.

CONCLUSION

The relationships demonstrated in this study indicate that more comprehensive research is needed to understand whether BBB defects contribute to clinical characteristics in patients with schizophrenia.

Edaravone Dexborneol Downregulates Neutrophil Extracellular Trap Expression and Ameliorates Blood-Brain Barrier Permeability in Acute Ischemic Stroke

Background

Our previous work has shown that inflammatory processes play a detrimental role in the pathophysiology of acute ischemic stroke (AIS). Neutrophil extracellular traps (NETs) have been recognized as a key contributor to the proinflammatory response in AIS and could aggravate blood-brain barrier (BBB) damage. Recently, experimental and clinical researches showed that Edaravone Dexborneol (Eda.B), which is comprised of two active ingredients, Edaravone and (+)-Borneol, was effective in treatment of AIS. However, it is not clear whether the effects of Eda.B against AIS are related to NETs and BBB permeability.

Methods

Experiment 1 was to detect the effects of Eda.B in AIS patients. Serum samples of volunteers and AIS patients were collected before and 3 days after Edaravone Dexborneol treatment. Markers of NETs and occludin were detected by ELISA kit. Experiment 2 was to explore the effects of Eda.B on experimental stroke mice. Male C57BL/6 mice were subjected to distal middle cerebral artery occlusion (MCAO) and treated with vehicle, Eda.B, or DeoxyribonueleaseI (DNase I). After stroke, the neurobehavioral tests, infarct volume, and cerebral blood flow evaluation were determined. Leakage of Evans blue was to assess the integrity of BBB. Western blot, real-time quantitative polymerase chain reaction (RT-qPCR), and immunofluorescence were used to examine the expression of NETs and tight junction- (TJ-) associated proteins.

Results

Eda.B significantly improved neurological function and cerebral blood flow but reduced infarct volume after experimental stroke. Eda.B downregulated level of NETs in serum samples of AIS patients and tissue samples of MCAO mouse cortex. Eda.B and DNase I alleviated BBB permeability by upregulating TJ-associated proteins.

Conclusion

NETs are related to the early stage of AIS. Eda.B exerted neuroprotective effects and ameliorated BBB permeability after AIS.

Higher serum occludin after successful reperfusion Is associated with early neurological deterioration

Aims

Early neurological deterioration (END) is an important factor that affects prognosis in patients with acute ischemic stroke. We explored the relationship between serum occludin levels after successful reperfusion and END in patients treated with endovascular thrombectomy (EVT).

Methods

We prospectively enrolled 120 stroke patients who underwent EVT with successful reperfusion. Enzyme‐linked immunosorbent assay was used to detect the serum occludin levels on admission and within 1 h after successful reperfusion. Receiver operating characteristic curves (ROC) and regression analysis were used to compare the relationship between serum occludin and END after thrombectomy.

Results

Among the 120 patients, 36 (30%) experienced END. The END group had higher serum occludin levels than the non‐END group after successful reperfusion [4.31 (3.71–5.38) vs 6.32 (5.88–6.99), p < 0.001]. The ROC curve showed that postoperative serum occludin levels had a significant prediction value for END (AUC: 0.86, p < 0.001). Regression analysis showed that serum occludin was an independent risk factor for END in EVT patients (adjusted odds ratio: 4.46, 95% confidence interval: 1.92–10.32; p < 0.001).

Conclusions

The higher serum occludin levels were strongly related to END after successful reperfusion. Serum occludin may be an independent risk factor for END in EVT patients.

Blood-brain barrier and gut barrier dysfunction in chronic kidney disease with a focus on circulating biomarkers and tight junction proteins

Kidney failure and associated uraemia have implications for the cardiovascular system, brain, and blood–brain barrier (BBB). We aim to examine BBB disruption, by assessing brain-derived neurotropic factor (BDNF), neuron-specific enolase (NSE) levels, and gut-blood barrier (GBB) disruption by trimethylamine N-oxide (TMAO), in chronic kidney disease (CKD) patients. Additionally, endothelial tight-junction protein expressions and modulation via TMAO were assessed. Serum from chronic kidney disease (CKD) female and male haemodialysis (HD) patients, and controls, were used to measure BDNF and NSE by enzyme-linked immunosorbent assays, and TMAO by mass spectrometry. Immunofluorescent staining of subcutaneous fat biopsies from kidney transplant recipients, and controls, were used to measure microvascular expression of tight-junction proteins (claudin-5, occludin, JAM-1), and control microvasculature for TMAO effects. HD patients versus controls, had significantly lower and higher serum levels of BDNF and NSE, respectively. In CKD biopsies versus controls, reduced expression of claudin-5, occludin, and JAM-1 were observed. Incubation with TMAO significantly decreased expression of all tight-junction proteins in the microvasculature. Uraemia affects BBB and GBB resulting in altered levels of circulating NSE, BDNF and TMAO, respectively, and it also reduces expression of tight-junction proteins that confer BBB maintenance. TMAO serves as a potential candidate to alter BBB integrity in CKD.

Modeling the blood-brain barrier for treatment of central nervous system (CNS) diseases

The blood-brain barrier (BBB) is the most specialized biological barrier in the body. This configuration of specialized cells protects the brain from invasion of molecules and particles through formation of tight junctions. To learn more about transport to the brain, in vitro modeling of the BBB is continuously advanced. The types of models and cells selected vary with the goal of each individual study, but the same validation methods, quantification of tight junctions, and permeability assays are often used. With Transwells and microfluidic devices, more information regarding formation of the BBB has been observed. Disease models have been developed to examine the effects on BBB integrity. The goal of modeling is not only to understand normal BBB physiology, but also to create treatments for diseases. This review will highlight several recent studies to show the diversity in model selection and the many applications of BBB models in in vitro research.

Increased Expression of Tight Junction Proteins and Blood-Brain Barrier Integrity in MCAO Rats Following Injection of miR-149-5p

Cerebral ischemia is a common neurodegenerative disease in which damage to the blood-brain barrier (BBB) is the main consequence. In cerebral ischemia, the level of miR-149-5p and tight junction proteins are decreased, while the level of Calpine is increased, finally leading to increased BBB permeability. This study investigated the effect of miR-149-5p mimic on the expression of Calpain, Occludin, and ZO-1 and the consequences of cerebral ischemia. Cerebral ischemia model was performed via middle cerebral artery occlusion (MCAO) method on female Wistar rats. Four groups of Wistar rats were studied: Sham, cerebral ischemia without treatment, Scramble miR, and miR-149-5p mimic treatment. Then, neurological defects and BBB permeability (via Evans blue staining), cerebral edema (cerebrospinal fluid percentage), and ZO-1, Occludin, and Calapin expression (by quantitative real time- PCR) were investigated. qRT-PCR results showed miR-149-5p expression decreases after cerebral ischemia induction. In addition, Occludin and ZO-1 expression significantly increased in miR-149-5p group. In contrast, Calapin expression, BBB permeability, brain water content and neurological defects were significantly decreased. It seems that the increased level of miR-149-5p exerts its protective effect on cerebral ischemia due to increasing of tight junction proteins.

Tocotrienols reach the brain and play roles in the attenuation of body weight gain and improvement of cognitive function in high-fat diet-treated mice

Obesity induces severe disorders such as type 2 diabetes and cardiovascular events, and the number of people with obesity is increasing all over the world. Furthermore, it is possible that obesity increases the risk of cognitive dysfunction via the acceleration of oxidative damage. Tocotrienols, which are part of the vitamin E family, have antioxidant and anti-obesity effects. However, the effects of tocotrienols on high-fat diet-treated mice have not been completely elucidated. In this study, we assessed changes in body weight, spatial reference memory acquisition, liver lipid droplet size, blood brain barrier-related protein expressions and antioxidative defense systems in high-fat diet-treated mice in the presence or absence of tocotrienols. The results showed that tocotrienols significantly inhibited body weight gain and lipid droplet synthesis. Although the amount was very small, it was confirmed that tocotrienols surely reached the brain in the perfused brain. Treatment with tocotrienols was tended to improve cognitive function in the control mice. However, tocotrienols did not modulate blood brain barrier-related protein expressions or antioxidative defense systems. These results indicate that treatment with tocotrienols could be effective for the prevention of obesity and cognitive dysfunction. Further extended research is needed to elucidate the relationship between anti-obesity and antioxidant effects of tocotrienols, especially in the brain.

MicroRNA let-7f alleviates vascular endothelial cell dysfunction via targeting HMGA2 under oxygen-glucose deprivation and reoxygenation

Stroke is a fatal disease with high disability and mortality and there is no credible treatment for stroke at present. Studies on stroke are extensively developed to explore the underlying mechanisms of ischemic and reperfusion injuries. Herein, we investigated the functions of microRNA let-7f (also termed let-7f-5p) in vascular endothelial cell dysfunction. The bEnd.3 cells were stimulated with oxygen-glucose deprivation and reoxygenation (OGD/R) to mimic cell injury in vitro. CCK-8 assays, flow cytometry and western blot analyses were conducted to examine the viability and apoptosis of bEnd.3 cells. Reverse transcription quantitative polymerase chain reaction analyses were employed to measure RNA expression. Endothelial cell permeability in vitro assay was employed to assess endothelial permeability of bEnd.3 cells, and expression levels of proteins associated with cell apoptosis or blood-brain barrier (BBB) were detected by western blot analyses. Luciferase reporter assay was conducted to explore the combination between let-7f and HMGA2. We found that OGD/R induced injuries on endothelial cells (bEnd.3) by decreasing cell viability and promoting cell apoptosis. Let-7f exhibited low expression in bEnd.3 cells under OGD/R. Let-7f overexpression increased the viability of bEnd.3 cells and inhibited cell apoptosis. In addition, the endothelial permeability of bEnd.3 cells was increased by OGD/R and reversed by let-7f overexpression. The levels of tight junction proteins (ZO-1 and occludin) were downregulated by OGD/R and then reversed by let-7f overexpression. Mechanistically, HMGA2 is a target gene of let-7f and its expression was negatively regulated by let-7f. Rescue assays revealed that HMGA2 overexpression reversed the effects of let-7f overexpression on cell viability, cell apoptosis, endothelial permeability, and BBB function. In conclusion, let-7f alleviates vascular endothelial cell dysfunction by downregulating HMGA2 expression under OGD/R.

Blood-Brain Barrier Dysfunction in CNS Disorders and Putative Therapeutic Targets: An Overview

The blood-brain barrier (BBB) is a fundamental component of the central nervous system (CNS). Its functional and structural integrity is vital to maintain the homeostasis of the brain microenvironment by controlling the passage of substances and regulating the trafficking of immune cells between the blood and the brain. The BBB is primarily composed of highly specialized microvascular endothelial cells. These cells’ special features and physiological properties are acquired and maintained through the concerted effort of hemodynamic and cellular cues from the surrounding environment. This complex multicellular system, comprising endothelial cells, astrocytes, pericytes, and neurons, is known as the neurovascular unit (NVU). The BBB strictly controls the transport of nutrients and metabolites into brain parenchyma through a tightly regulated transport system while limiting the access of potentially harmful substances via efflux transcytosis and metabolic mechanisms. Not surprisingly, a disruption of the BBB has been associated with the onset and/or progression of major neurological disorders. Although the association between disease and BBB disruption is clear, its nature is not always evident, specifically with regard to whether an impaired BBB function results from the pathological condition or whether the BBB damage is the primary pathogenic factor prodromal to the onset of the disease. In either case, repairing the barrier could be a viable option for treating and/or reducing the effects of CNS disorders. In this review, we describe the fundamental structure and function of the BBB in both healthy and altered/diseased conditions. Additionally, we provide an overview of the potential therapeutic targets that could be leveraged to restore the integrity of the BBB concomitant to the treatment of these brain disorders.

Isobaric Tags for Relative and Absolute Quantitation-Based Quantitative Serum Proteomics Analysis in Ischemic Stroke Patients With Hemorrhagic Transformation

Hemorrhagic transformation (HT), which occurs with or without reperfusion treatments (thrombolysis and/or thrombectomy), deteriorates the outcomes of ischemic stroke patients. It is essential to find clinically reliable biomarkers that can predict HT. In this study, we screened for potential serum biomarkers from an existing blood bank and database with 243 suspected acute ischemic stroke (AIS) patients. A total of 37 patients were enrolled, who were diagnosed as AIS without receiving reperfusion treatment. They were divided into two groups based on whether they were accompanied with HT or not (five HT and 32 non-HT). Serum samples were labeled by isobaric tags for relative and absolute quantitation (iTRAQ) and analyzed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and compared under NCBInr database. A total of 647 proteins in sera samples were captured, and the levels of 17 proteins (12 upregulated and five downregulated) were significantly different. These differentially expressed proteins were further categorized with Gene Ontology functional classification annotation and Kyoto Encyclopedia of Genes and Genomes metabolic pathway analysis into biological processes. Further protein–protein interaction analysis using String database discovered that, among the differentially expressed proteins, 10 pairs of proteins were found to have crosstalk connections, which may have direct (physical) and indirect (functional) interactions for the development of HT. Our findings suggest that these differentially expressed proteins could serve as potential biomarkers for predicting HT after ischemic stroke.

Serum Occludin Level Combined With NIHSS Score Predicts Hemorrhage Transformation in Ischemic Stroke Patients With Reperfusion

Hemorrhagic transformation (HT) is a severe complication following acute ischemic stroke, particularly with reperfusion interventions, leading to poor prognosis. Serum occludin level is related with blood brain barrier disruption, and the National Institute of Health stroke scale (NIHSS) score reflects stroke severity. We investigated whether the two covariates are independently associated with HT and their combination can improve the accuracy of HT prediction in ischemic stroke patients with reperfusion therapy. Seventy-six patients were screened from the established database of acute ischemic stroke in our previous study, which contains all clinical information, including serum occludin levels, baseline NIHSS score, and hemorrhagic events. Multivariate logistic regression analysis showed that serum occludin level (OR = 4.969, 95% CI: 2.069-11.935, p < 0.001) and baseline NIHSS score (OR = 1.293, 95% CI 1.079-1.550, p = 0.005) were independent risk factors of HT after adjusting for potential confounders. Compared with non-HT patients, HT patients had higher baseline NIHSS score [12 (10.5-18.0) versus 6 (4-12), p = 0.003] and serum occludin level (5.47 ± 1.25 versus 3.81 ± 1.19, p < 0.001). Moreover, receiver operating characteristic curve based on leave-one-out cross-validation showed that the combination of serum occludin level and NIHSS score significantly improved the accuracy of predicting HT (0.919, 95% CI 0.857-0.982, p < 0.001). These findings suggest that the combination of two methods may provide a better tool for HT prediction in acute ischemic stroke patients with reperfusion therapy.

Hypoxia Inducible Factors as Central Players in the Pathogenesis and Pathophysiology of Cardiovascular Diseases

Cardiovascular (CV) diseases are the major cause of death in industrialized countries. The main function of the CV system is to deliver nutrients and oxygen to all tissues. During most CV pathologies, oxygen and nutrient delivery is decreased or completely halted. Several mechanisms, including increased oxygen transport and delivery, as well as increased blood flow are triggered to compensate for the hypoxic state. If the compensatory mechanisms fail to sufficiently correct the hypoxia, irreversible damage can occur. Thus, hypoxia plays a central role in the pathogenesis and pathophysiology of CV diseases. Hypoxia inducible factors (HIFs) orchestrate the gene transcription for hundreds of proteins involved in erythropoiesis, glucose transport, angiogenesis, glycolytic metabolism, reactive oxygen species (ROS) handling, cell proliferation and survival, among others. The overall regulation of the expression of HIF-dependent genes depends on the severity, duration, and location of hypoxia. In the present review, common CV diseases were selected to illustrate that HIFs, and proteins derived directly or indirectly from their stabilization and activation, are related to the development and perpetuation of hypoxia in these pathologies. We further classify CV diseases into acute and chronic hypoxic states to better understand the temporal relevance of HIFs in the pathogenesis, disease progression and clinical outcomes of these diseases. We conclude that HIFs and their derived factors are fundamental in the genesis and progression of CV diseases. Understanding these mechanisms will lead to more effective treatment strategies leading to reduced morbidity and mortality.

Function and Biomarkers of the Blood-Brain Barrier in a Neonatal Germinal Matrix Haemorrhage Model

Germinal matrix haemorrhage (GMH), caused by rupturing blood vessels in the germinal matrix, is a prevalent driver of preterm brain injuries and death. Our group recently developed a model simulating GMH using intrastriatal injections of collagenase in 5-day-old rats, which corresponds to the brain development of human preterm infants. This study aimed to define changes to the blood-brain barrier (BBB) and to evaluate BBB proteins as biomarkers in this GMH model. Regional BBB functions were investigated using blood to brain ¹⁴C-sucrose uptake as well as using biotinylated BBB tracers. Blood plasma and cerebrospinal fluids were collected at various times after GMH and analysed with ELISA for OCLN and CLDN5. The immunoreactivity of BBB proteins was assessed in brain sections. Tracer experiments showed that GMH produced a defined region surrounding the hematoma where many vessels lost their integrity. This region expanded for at least 6 h following GMH, thereafter resolution of both hematoma and re-establishment of BBB function occurred. The sucrose experiment indicated that regions somewhat more distant to the hematoma also exhibited BBB dysfunction; however, BBB function was normalised within 5 days of GMH. This shows that GMH leads to a temporal dysfunction in the BBB that may be important in pathological processes as well as in connection to therapeutic interventions. We detected an increase of tight-junction proteins in both CSF and plasma after GMH making them potential biomarkers for GMH.

Targeting the Cerebrovascular System: Next-Generation Biomarkers and Treatment for Mild Traumatic Brain Injury

The diagnosis, prognosis, and treatment of mild traumatic brain injuries (mTBIs), such as concussions, are significant unmet medical issues. The kinetic forces that occur in mTBI adversely affect the cerebral vasculature, making cerebrovascular injury (CVI) a pathophysiological hallmark of mTBI. Given the importance of a healthy cerebrovascular system in overall brain function, CVI is likely to contribute to neurological dysfunction after mTBI. As such, CVI and related pathomechanisms may provide objective biomarkers and therapeutic targets to improve the clinical management and outcomes of mTBI. Despite this potential, until recently, few studies have focused on the cerebral vasculature in this context. This article will begin by providing a brief overview of the cerebrovascular system followed by a review of the literature regarding how mTBI can affect the integrity and function of the cerebrovascular system, and how this may ultimately contribute to neurological dysfunction and neurodegenerative conditions. We then discuss promising avenues of research related to mTBI biomarkers and interventions that target CVI, and conclude that a clinical approach that takes CVI into account could result in substantial improvements in the care and outcomes of patients with mTBI.

Circulating tight-junction proteins are potential biomarkers for blood-brain barrier function in a model of neonatal hypoxic/ischemic brain injury

Background

Neonatal encephalopathy often leads to lifelong disabilities with limited treatments currently available. The brain vasculature is an important factor in many neonatal neurological disorders but there is a lack of diagnostic tools to evaluate the brain vascular dysfunction of neonates in the clinical setting. Measurement of blood–brain barrier tight-junction (TJ) proteins have shown promise as biomarkers for brain injury in the adult. Here we tested the biomarker potential of tight-junctions in the context of neonatal brain injury.

Methods

The levels of TJ-proteins (occluding, claudin-5, and zonula occludens protein 1) in both blood plasma and cerebrospinal fluid (CSF) as well as blood–brain barrier function via ¹⁴C-sucrose (342 Da) and Evans blue extravasation were measured in a hypoxia/ischemia brain-injury model in neonatal rats.

Results

Time-dependent changes of occludin and claudin-5 levels could be measured in blood and CSF after hypoxia/ischemia with males generally having higher levels than females. The levels of claudin-5 in CSF correlated with the severity of the brain injury at 24 h post- hypoxia/ischemia. Simultaneously, we detected early increase in blood–brain barrier-permeability at 6 and 24 h after hypoxia/ischemia.

Conclusions

Levels of circulating claudin-5 and occludin are increased after hypoxic/ischemic brain injuries and blood–brain barrier-impairment and have promise as early biomarkers for cerebral vascular dysfunction and as a tool for risk assessment of neonatal brain injuries.

Serum Occludin as a Biomarker to Predict the Severity of Acute Ischemic Stroke, Hemorrhagic Transformation, and Patient Prognosis

Blood-brain barrier (BBB) damage plays an important role in overall brain injury following acute ischemic stroke (AIS). We investigated the potential utility of serum occludin, a BBB damage biomarker, in predicting the severity of AIS, hemorrhagic transformation (HT) and patient prognosis. A total of 243 patients, suspected of suffering an AIS and admitted to the emergency room at Xuanwu Hospital between November 2018 to March 2019, were enrolled in this study. Serum occludin levels were measured by enzyme linked immunosorbent assay and clinical data were collected from each patient. Receiver operating characteristic curves (ROC) were used to analyze the relationship between serum occludin and AIS. Multiple logistic regression analysis was used to analyze the relationship between serum occludin and stroke prognosis. Serum occludin levels were significantly elevated in acute stroke cases compared with those with stroke-like symptoms (P<0.001). In the moderate and severe cerebral infarction (CI) groups, serum occludin levels were significantly higher than those in the mild CI group (P<0.001). Patients with HT had higher occludin levels than non-HT patients (P<0.05). In addition, serum occludin level of patients with poor prognosis was significantly higher than that of the patients with good prognosis for non-reperfusion therapy. The ROC curve showed that serum occludin could reasonably predict HT and poor prognosis. Moreover, serum occludin were independently associated with 90-day poor prognosis. These findings suggest that the serum occludin levels could be used to identify early acute stroke cases and may predict the severity of AIS and HT as well as the prognosis at 90 days.

Plasma Levels of Occludin and Claudin-5 in Acute Stroke Are Correlated with the Type and Location of Stroke but Not with the Neurological State of Patients-Preliminary Data

The blood–brain barrier is the structure (BBB), which isolates the central nervous system from the external environmental. During a stroke, the BBB gets damaged, which is accompanied by changes in the concentrations and distributions of claudin-5, occludin, ZO-1, and other building blocks of the BBB. The aim of this study was to assess the concentrations of selected components of the BBB—occludin, claudin-5, and zonulin (ZO-1)—and to define a potential relationship between the concentrations of these three substances and the type of stroke, the location and extent of the infarct focus, the neurological/functional status in the acute phase of the disease, and the patient’s clinical profile. Methods: In this prospective study, we qualified patients with first-in-life stroke. All patients were analyzed according to: the presence of comorbidities, type of stroke (OCSP), treatment type in the first day of hospitalization, hemorrhagic transformation of infarct focus (ECASS), neurological status on the first day of stroke (NIHSS), functional status (mRS) on the ninth day of disease. In all patients, the plasma concentrations of claudin-5, occludin, and ZO-1 on the first day of stroke were examined and next, the mean concentrations were analyzed and compared between subgroups created on the basis of demographical and clinical features. Results: The mean concentration of occludin was significantly higher in patients with partial anterior cerebral infarct (PACI) compared to patients with posterior cerebral infarct (POCI; 1.03 vs. 0.66 ng/mL; p = 0.009) and in patients with location of ischemic stroke in the carotid artery supply compared with in the vertebrobasilar supply (respectively: 1.036 vs. 0.660 ng/mL; p = 0.009). The mean concentration of claudin 5 was significantly higher in patients with PACI compared to patients with POCI (0.37 vs. 0.21 ng/mL; p = 0.011) and in patients with location of ischemic stroke in the carotid artery supply in comparison with vertebrobasilar supply (respectively: 0.373 vs. 0.249 ng/mL; p = 0.011). The differences in mean occludin and claudin 5 concentrations between female and male were statistically not significant, similarly between patients < 65 years and older. A significantly higher mean concentration of zonulin was observed in patients > 65 years of age compared to younger patients (0.59 vs. 0.48 ng/mL; p = 0.010) and in patients with arterial hypertension compared to patients without the disease (0.63 ng/mL vs. 0.26 ng/mL; p = 0.026). There were no statistically significant relationships between the concentration of occludin, claudin 5, and zonulin and the neurological status according to the NIHSS on the first day of stroke. Conclusions: The location of stroke in the anterior part of the brain’s blood supply is associated with high blood levels of occludin and claudin 5 in the acute phase of stroke. The blood concentration of occludin is significantly lower in lacunar stroke comparing to this in non-lacunar stroke. Old age and arterial hypertension correlate positively with the concentration of zonulin 1 in acute stroke. There is no relationship between the blood levels of occludin, claudin 5, and zonulin 1 on the first day of stroke and the neurological and functional status in the acute phase of the disease.

Occludin regulation of blood-brain barrier and potential therapeutic target in ischemic stroke

Occludin is a key structural component of the blood–brain barrier (BBB) that has recently become an important focus of research in BBB damages. Many studies have demonstrated that occludin could regulate the integrity and permeability of the BBB. The function of BBB depends on the level of occludin protein expression in brain endothelial cells. Moreover, occludin may serve as a potential biomarker for hemorrhage transformation after acute ischemic stroke. In this review, we summarize the role of occludin in BBB integrity and the regulatory mechanisms of occludin in the permeability of BBB after ischemic stroke. Multiple factors have been found to regulate occludin protein functions in maintaining BBB permeability, such as Matrix metalloproteinas-mediated cleavage, phosphorylation, ubiquitination, and related inflammatory factors. In addition, various signaling pathways participate in regulating the occludin expression, including nuclear factor-kappa B, mitogen-activated protein kinase, protein kinase c, RhoK, and ERK1/2. Emerging therapeutic interventions for ischemic stroke targeting occludin are described, including normobaric hyperoxia, Chinese medicine, chemical drugs, genes, steroid hormones, small molecular peptides, and other therapies. Since occludin has been shown to play a critical role in regulating BBB integrity, further preclinical studies will help evaluate and validate occludin as a viable therapeutic target for ischemic stroke.

Central nervous system diseases associated with blood brain barrier breakdown - A Comprehensive update of existing literatures

Blood vessels that supply and feed the central nervous system (CNS) possess unique and exclusive properties, named as blood–brain barrier (BBB). It is responsible for tight regulation of the movement of ions, molecules, and cells between the blood and the brain thereby maintaining controlled chemical composition of the neuronal milieu required for appropriate functioning. It also protects the neural tissue from toxic plasma components, blood cells and pathogens from entering the brain. In this review the importance of BBB and its disruption causing brain pathology and progression to different neurological diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD) etc. will be discussed.

Peripheral Blood Occludin Level as a Biomarker for Perioperative Cerebral Edema in Patients with Brain Tumors

Objective

Cerebral edema is a common complication of brain tumors in the perioperative period. However, there is currently no reliable and convenient method to evaluate the extent of brain edema. The objective is to explore the effectiveness of serum occludin on predicting the extent of perioperative brain edema and outcome in patients with brain tumors.

Methods

This prospective study enrolled 55 patients with brain tumors and 24 healthy controls in Sanbo Brain Hospital from June 2019 through November 2019. Serum occludin levels were measured preoperatively and on postoperative day 1. Peritumoral edema was assessed preoperatively using MRI. Pericavity brain edema on postoperative day 1 was evaluated using CT.

Results

Compared with healthy controls, the serum occludin level was higher in patients with brain tumors both preoperatively and postoperatively (P < 0.001). The serum occludin level correlated positively with the degree of brain edema preoperatively (r = 0.78, P < 0.001) and postoperatively (r = 0.59, P < 0.001). At an optimal cutoff of 3.015 ng/mL, the preoperative serum occludin level discriminated between mild and severe preoperative brain edema with a sensitivity of 90.48% and specificity of 84.62%. At an optimal cutoff value of 3.033 ng/mL, the postoperative serum occludin level distinguished between mild and severe postoperative brain edema with a sensitivity of 97.30% and specificity of 55.56%.

Conclusions

The serum occludin level is associated with cerebral edema and could potentially be used as a biomarker for perioperative cerebral edema. This trial is registered with ChiCTR1900023742.

Occludin degradation makes brain microvascular endothelial cells more vulnerable to reperfusion injury in vitro

Intracerebral hemorrhage is the most dangerous complication in tPA thrombolytic therapy for ischemic stroke, which occurs as a consequence of endothelial cell death at the blood-brain barrier (BBB) during thrombolytic reperfusion. We have previously shown that cerebral ischemia-induced rapid occludin degradation and BBB disruption. Here we demonstrated an important role of occludin degradation in facilitating the evolution of ischemic endothelial cells toward death. Cultured brain microvascular endothelial cells (bEnd.3 cells) were exposed to oxygen-glucose deprivation (OGD) or incubated with occludin siRNA or occludin AAV to achieve an occludin deficiency or over-expression status before exposing to reoxygenation (R) or TNF-α treatment. Cell death was assessed by measuring lactate dehydrogenase release, TUNEL staining, and flow cytometry analysis. Inhibition of OGD-induced occludin degradation with SB-3CT or over-expression of occludin with occludin AAV both significantly attenuated OGD/R-induced apoptosis and pyroptosis in bEnd.3 cells. Consistently, knockdown of occludin with siRNA potentiated TNF-α-induced apoptosis, supporting an important role of occludin integrity in endothelial cell survival. Similar results were observed for pyroptosis, in which occludin knockdown with siRNA led to a significant augmentation of cytokines secretion, inflammasome activation, and pyroptosis occurrence in TNF-α-treated bEnd.3 cells. Lastly, up-regulation of c-Yes, PI3K/AKT, and ERK concurrently occurred with occludin degradation after OGD/R or TNF-α treatment, and the level of these proteins were further increased when inhibition of occludin degradation or over-expression of occludin. These data indicate that occludin degradation inflicted during ischemia makes BBB endothelial cells more vulnerable to reperfusion-associated stress stimuli.

Brain tight junction protein expression in sepsis in an autopsy series

Background

Neuroinflammation often develops in sepsis along with increasing permeability of the blood-brain barrier (BBB), which leads to septic encephalopathy. The barrier is formed by tight junction structures between the cerebral endothelial cells. We investigated the expression of tight junction proteins related to endothelial permeability in brain autopsy specimens in critically ill patients deceased with sepsis and analyzed the relationship of BBB damage with measures of systemic inflammation and systemic organ dysfunction.

Methods

The case series included all (385) adult patients deceased due to sepsis in the years 2007–2015 with available brain specimens taken at autopsy. Specimens were categorized according to anatomical location (cerebrum, cerebellum). The immunohistochemical stainings were performed for occludin, ZO-1, and claudin. Patients were categorized as having BBB damage if there was no expression of occludin in the endothelium of cerebral microvessels.

Results

Brain tissue samples were available in 47 autopsies, of which 38% (18/47) had no expression of occludin in the endothelium of cerebral microvessels, 34% (16/47) developed multiple organ failure before death, and 74.5% (35/47) had septic shock.

The deceased with BBB damage had higher maximum SOFA scores (16 vs. 14, p = 0.04) and more often had procalcitonin levels above 10 μg/L (56% vs. 28%, p = 0.045) during their ICU stay. BBB damage in the cerebellum was more common in cases with C-reactive protein (CRP) above 100 mg/L as compared with CRP less than 100 (69% vs. 25%, p = 0.025).

Conclusions

In fatal sepsis, damaged BBB defined as a loss of cerebral endothelial expression of occludin is related with severe organ dysfunction and systemic inflammation.

Multicellular 3D Neurovascular Unit Model for Assessing Hypoxia and Neuroinflammation Induced Blood-Brain Barrier Dysfunction

The blood-brain barrier (BBB) is a dynamic component of the brain-vascular interface that maintains brain homeostasis and regulates solute permeability into brain tissue. The expression of tight junction proteins between adjacent endothelial cells and the presence of efflux proteins prevents entry of foreign substances into the brain parenchyma. BBB dysfunction, however, is evident in many neurological disorders including ischemic stroke, trauma, and chronic neurodegenerative diseases. Currently, major contributors to BBB dysfunction are not well understood. Here, we employed a multicellular 3D neurovascular unit organoid containing human brain microvascular endothelial cells, pericytes, astrocytes, microglia, oligodendrocytes and neurons to model the effects of hypoxia and neuroinflammation on BBB function. Organoids were cultured in hypoxic chamber with 0.1% O2 for 24 hours. Organoids cultured under this hypoxic condition showed increased permeability, pro-inflammatory cytokine production, and increased oxidative stress. The anti-inflammatory agents, secoisolariciresinol diglucoside and 2-arachidonoyl glycerol, demonstrated protection by reducing inflammatory cytokine levels in the organoids under hypoxic conditions. Through the assessment of a free radical scavenger and an anti-inflammatory endocannabinoid, we hereby report the utility of the model in drug development for drug candidates that may reduce the effects of ROS and inflammation under disease conditions. This 3D organoid model recapitulates characteristics of BBB dysfunction under hypoxic physiological conditions and when exposed to exogenous neuroinflammatory mediators and hence may have potential in disease modeling and therapeutic development.

The functional role of hemojuvelin in acute ischemic stroke

Our study aimed to establish the role of hemojuvelin (HJV) in acute ischemic stroke (AIS). We performed immunohistochemistry for HJV expression in human brain tissues from 10 AIS and 2 non-stroke autopsy subjects. Plasma HJV was measured in 112 AIS patients within 48 h after stroke. The results showed significantly increased HJV expression in brain tissues from AIS patients compare to non-stroke subjects. After adjusting for clinical variables, plasma levels of HJV within 48 h after stroke were an independent predictor of poor functional outcome three months post-stroke (OR:1.78, 95% CI: 1.03-3.07; P = 0.038). In basic part, Western blotting showed that HJV expression in mice brains was apparent at 3 h after middle cerebral artery occlusion (MCAO), and increased significantly at 72 h. In cultured cortical neurons, expression of HJV protein increased remarkably 24 h after oxygen glucose deprivation (OGD), and small interfering RNAs (siHJV) transfected OGD neurons had a lower apoptotic rate. Importantly, 72 h post-MCAO, HJV knockout mice had significantly smaller infarcts and less expression of cleaved caspase-3 protein compared with wild-type mice. In summary, HJV participates in the mechanisms of post-stroke neuronal injury, and that plasma HJV levels can be a potential early outcome indicator for AIS patients.

Mechanisms of Blood-Brain Barrier Dysfunction in Traumatic Brain Injury

Traumatic brain injuries (TBIs) account for the majority of injury-related deaths in the United States with roughly two million TBIs occurring annually. Due to the spectrum of severity and heterogeneity in TBIs, investigation into the secondary injury is necessary in order to formulate an effective treatment. A mechanical consequence of trauma involves dysregulation of the blood–brain barrier (BBB) which contributes to secondary injury and exposure of peripheral components to the brain parenchyma. Recent studies have shed light on the mechanisms of BBB breakdown in TBI including novel intracellular signaling and cell–cell interactions within the BBB niche. The current review provides an overview of the BBB, novel detection methods for disruption, and the cellular and molecular mechanisms implicated in regulating its stability following TBI.

Management of Traumatic Brain Injury: From Present to Future

TBI (traumatic brain injury) is a major cause of death among youth in industrialized societies. Brain damage following traumatic injury is a result of direct and indirect mechanisms; indirect or secondary injury involves the initiation of an acute inflammatory response, including the breakdown of the blood–brain barrier (BBB), brain edema, infiltration of peripheral blood cells, and activation of resident immunocompetent cells, as well as the release of numerous immune mediators such as interleukins and chemotactic factors. TBI can cause changes in molecular signaling and cellular functions and structures, in addition to tissue damage, such as hemorrhage, diffuse axonal damages, and contusions. TBI typically disturbs brain functions such as executive actions, cognitive grade, attention, memory data processing, and language abilities. Animal models have been developed to reproduce the different features of human TBI, better understand its pathophysiology, and discover potential new treatments. For many years, the first approach to manage TBI has been treatment of the injured tissue with interventions designed to reduce the complex secondary-injury cascade. Several studies in the literature have stressed the importance of more closely examining injuries, including endothelial, microglia, astroglia, oligodendroglia, and precursor cells. Significant effort has been invested in developing neuroprotective agents. The aim of this work is to review TBI pathophysiology and existing and potential new therapeutic strategies in the management of inflammatory events and behavioral deficits associated with TBI.

Transcriptional Response and Morphological Features of the Neurovascular Unit and Associated Extracellular Matrix After Experimental Stroke in Mice

Experimental stroke studies yielded insights into single reactions of the neurovascular unit (NVU) and associated extracellular matrix (ECM). However, the extent of simultaneous processes caused by ischemia and their underlying transcriptional changes are still poorly understood. Strictly following the NVU and ECM concept, this study explored transcriptional responses of cellular and non-cellular components as well as their morphological characteristics following ischemia. Mice were subjected to 4 or 24 h of unilateral middle cerebral artery occlusion. In the neocortex and the striatum, cytoskeletal and glial elements as well as blood-brain barrier and ECM components were analyzed using real-time PCR. Western blot analyses allowed characterization of protein levels and multiple immunofluorescence labeling enabled morphological assessment. Out of 37 genes analyzed, the majority exhibited decreased mRNA levels in ischemic areas, while changes occurred as early as 4 h after ischemia. Down-regulated mRNA levels were predominantly localized in the neocortex, such as the structural elements α-catenin 2, N-cadherin, β-catenin 1, and βIII-tubulin, consistently decreasing 4 and 24 h after ischemia. However, a few genes, e.g., claudin-5 and Pcam1, exhibited increased mRNA levels after ischemia. For several components such as βIII-tubulin, N-cadherin, and β-catenin 1, matching transcriptional and immunofluorescence signals were obtained, whereas a few markers including neurofilaments exhibited opposite directions. In conclusion, the variety in gene regulation emphasizes the complexity of interactions within the ischemia-affected NVU and ECM. These data might help to focus future research on a set of highly sensitive elements, which might prospectively facilitate neuroprotective strategies beyond the traditional single target perspective.

C3a Receptor Inhibition Protects Brain Endothelial Cells Against Oxygen-glucose Deprivation/Reperfusion

The complement cascade is a central component of innate immunity which plays a critical role in brain inflammation. Complement C3a receptor (C3aR) is a key mediator of post-ischemic cerebral injury, and pharmacological antagonism of the C3a receptor is neuroprotective in stroke. Cerebral ischemia injures brain endothelial cells, causing blood brain barrier (BBB) disruption which further exacerbates ischemic neuronal injury. In this study, we used an in vitro model of ischemia (oxygen glucose deprivation; OGD) to investigate the protective effect of a C3aR antagonist (C3aRA, SB290157) on brain endothelial cells (bEnd.3). Following 24 hours of reperfusion, OGD-induced cell death was assessed by TUNEL and Caspase-3 staining. Western blot and immunocytochemistry were utilized to demonstrate that OGD upregulates inflammatory, oxidative stress and antioxidant markers (ICAM-1, Cox-2, Nox-2 and MnSOD) in endothelial cells and that C3aRA treatment significantly attenuate these markers. We also found that C3aRA administration restored the expression level of the tight junction protein occludin in endothelial cells following OGD. Interestingly, OGD/reperfusion injury increased the phosphorylation of ERK1/2 and C3aR inhibition significantly reduced the activation of ERK suggesting that endothelial C3aR may act via ERK signaling. Furthermore, exogenous C3a administration stimulates these same inflammatory mechanisms both with and without OGD, and C3aRA suppresses these C3a-mediated responses, supporting an antagonist role for C3aRA. Based on these results, we conclude that C3aRA administration attenuates inflammation, oxidative stress, ERK activation, and protects brain endothelial cells following experimental brain ischemia.

Astrocyte dysfunction and neurovascular impairment in neurological disorders: Correlation or causation?

The neurovascular unit, consisting of neurons, astrocytes, and vascular cells, has become the focus of much discussion in the last two decades and emerging literature now suggests an association between neurovascular dysfunction and neurological disorders. In this review, we synthesize the known and suspected contributions of astrocytes to neurovascular dysfunction in disease. Throughout the brain, astrocytes are centrally positioned to dynamically mediate interactions between neurons and the cerebral vasculature, and play key roles in blood-brain barrier maintenance and neurovascular coupling. It is increasingly apparent that the changes in astrocytes in response to a variety of insults to brain tissue -collectively referred to as "reactive astrogliosis" - are not just an epiphenomenon restricted to morphological alterations, but comprise functional changes in astrocytes that contribute to the phenotype of neurological diseases with both beneficial and detrimental effects. In the context of the neurovascular unit, astrocyte dysfunction accompanies, and may contribute to, blood-brain barrier impairment and neurovascular dysregulation, highlighting the need to determine the exact nature of the relationship between astrocyte dysfunction and neurovascular impairments. Targeting astrocytes may represent a new strategy in combinatorial therapeutics for preventing the mismatch of energy supply and demand that often accompanies neurological disorders.

Current progress in searching for clinically useful biomarkers of blood-brain barrier damage following cerebral ischemia

Ischemic stroke is a leading cause of death and disability. Fear of intracranial hemorrhage (ICH) has been the primary reason for withholding tissue plasminogen activator (tPA) and thrombectomy, the only two widely accepted treatments for ischemic stroke. Thrombolysis treatment is only allowed in a very narrow time window (within 4.5–6 h). However, so far, other than the time window guideline, there is no reliable indicator available in the clinic to predict ICH before thrombolysis treatment. Recently, extensive research efforts have been devoted to the development of reliable indicators to predict ICH and safely guide the thrombolysis treatment. Accumulating evidence suggests that ischemic brain regions with a compromised blood–brain barrier (BBB) before tPA treatment develop ICH at the later time during thrombolytic reperfusion. Assessing BBB damage before thrombolysis could potentially help predict the risk of ICH after thrombolysis. This article reviews the literature reports on BBB damage biomarkers that have been developed in recent years, including biochemical markers such as BBB structural proteins, circulating brain microvascular endothelial cells, plasma albumin, and brain parenchyma proteins, as well as image markers such as magnetic resonance imaging assessment for BBB damage.

Roles of blood-brain barrier integrins and extracellular matrix in stroke

Ischemicstroke is a leading cause of death and disability in the United States, but recent advances in treatments [i.e., endovascular thrombectomy and tissue plasminogen activator (t-PA)] that target the stroke-causing blood clot, while improving overall stroke mortality rates, have had much less of an impact on overall stroke morbidity. This may in part be attributed to the lack of therapeutics targeting reperfusion-induced injury after the blood clot has been removed, which, if left unchecked, can expand injury from its core into the surrounding at risk tissue (penumbra). This occurs in two phases of increased permeability of the blood-brain barrier, a physical barrier that under physiologic conditions regulates brain influx and efflux of substances and consists of tight junction forming endothelial cells (and transporter proteins), astrocytes, pericytes, extracellular matrix, and their integrin cellular receptors. During, embryonic development, maturity, and following stroke reperfusion, cerebral vasculature undergoes significant changes including changes in expression of integrins and degradation of surrounding extracellular matrix. Integrins, heterodimers with α and β subunits, and their extracellular matrix ligands, a collection of proteoglycans, glycoproteins, and collagens, have been modestly studied in the context of stroke compared with other diseases (e.g., cancer). In this review, we describe the effect that various integrins and extracellular matrix components have in embryonic brain development, and how this changes in both maturity and in the poststroke environment. Particular focus will be on how these changes in integrins and the extracellular matrix affect blood-brain barrier components and their potential as diagnostic and therapeutic targets for ischemic stroke.

Dysregulated Bile Transporters and Impaired Tight Junctions During Chronic Liver Injury in Mice

BACKGROUND & AIMS

Liver fibrosis, hepatocellular necrosis, inflammation, and proliferation of liver progenitor cells are features of chronic liver injury. Mouse models have been used to study the end-stage pathophysiology of chronic liver injury. However, little is known about differences in the mechanisms of liver injury among different mouse models because of our inability to visualize the progression of liver injury in vivo in mice. We developed a method to visualize bile transport and blood-bile barrier (BBlB) integrity in live mice.

METHODS

C57BL/6 mice were fed a choline-deficient, ethionine-supplemented (CDE) diet or a diet containing 0.1% 3,5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC) for up to 4 weeks to induce chronic liver injury. We used quantitative liver intravital microscopy (qLIM) for real-time assessment of bile transport and BBlB integrity in the intact livers of the live mice fed the CDE, DDC, or chow (control) diets. Liver tissues were collected from mice and analyzed by histology, immunohistochemistry, real-time polymerase chain reaction, and immunoblots.

RESULTS

Mice with liver injury induced by a CDE or a DDC diet had breaches in the BBlB and impaired bile secretion, observed by qLIM compared with control mice. Impaired bile secretion was associated with reduced expression of several tight-junction proteins (claudins 3, 5, and 7) and bile transporters (NTCP, OATP1, BSEP, ABCG5, and ABCG8). A prolonged (2-week) CDE, but not DDC, diet led to re-expression of tight junction proteins and bile transporters, concomitant with the reestablishment of BBlB integrity and bile secretion.

CONCLUSIONS

We used qLIM to study chronic liver injury, induced by a choline-deficient or DDC diet, in mice. Progression of chronic liver injury was accompanied by loss of bile transporters and tight junction proteins.

MicroRNA-130a regulates cerebral ischemia-induced blood-brain barrier permeability by targeting Homeobox A5

Blood-brain barrier (BBB) disruption plays a critical role in brain injury induced by cerebral ischemia, and preserving BBB integrity during ischemia could alleviate cerebral injury. We examined the role of miR-130a in ischemic BBB disruption by using models of rat middle cerebral artery occlusion and cell oxygen-glucose deprivation. We found that ischemia significantly increased microRNA-130a (miR-130a) level and that miR-130a was predominantly from brain microvascular endothelial cells. Antagomir-130a, an antagonist of miR-130a, could attenuate brain edema, lower BBB permeability, reduce infarct volume, and improve neurologic function. MiR-130a overexpression induced by miR-130a mimic increased monolayer permeability, and intercellular inhibition of miR-130a by a miR-130a inhibitor suppressed oxygen-glucose deprivation-induced increase in monolayer permeability. Moreover, dual luciferase reporter system showed that Homeobox A5 was the direct target of miR-130a. MiR-130a, by inhibiting Homeobox A5 expression, could down-regulate occludin, thereby increasing BBB permeability. Our results suggested that miR-130a might be implicated in ischemia-induced BBB dysfunction and serve as a target for the treatment of ischemic stroke.-Wang, Y., Wang, M.-D., Xia, Y.-P., Gao, Y., Zhu, Y.-Y., Chen, S.-C., Mao, L., He, Q.-W., Yue, Z.-Y., Hu, B. MicroRNA-130a regulates cerebral ischemia-induced blood-brain barrier permeability by targeting Homeobox A5.

Normobaric Hyperoxia Reduces Blood Occludin Fragments in Rats and Patients With Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Damage of the blood-brain barrier (BBB) increases the incidence of neurovascular complications, especially for cerebral hemorrhage after tPA (tissue-type plasminogen activator) therapy. Currently, there is no effective method to evaluate the extent of BBB damage to guide tPA use. Herein, we investigated whether blood levels of tight junction proteins could serve as biomarker of BBB damages in acute ischemic stroke (AIS) in both rats and patients. We examined whether this biomarker could reflect the extent of BBB permeability during cerebral ischemia/reperfusion and the effects of normobaric hyperoxia (NBO) on BBB damage.

METHODS

Rats were exposed to NBO (100% O₂) or normoxia (21% O₂) during middle cerebral artery occlusion. BBB permeability was determined. Occludin and claudin-5 in blood and cerebromicrovessels were measured. Patients with AIS were assigned to oxygen therapy or room air for 4 hours, and blood occludin and claudin-5 were measured at different time points after stroke.

RESULTS

Cerebral ischemia/reperfusion resulted in the degradation of occludin and claudin-5 in microvessels, leading to increased BBB permeability in rats. In blood samples, occludin increased with 4-hour ischemia and remained elevated during reperfusion, correlating well with its loss from ischemic cerebral microvessels. NBO treatment both prevented occludin degradation in microvessels and reduced occludin levels in blood, leading to improved neurological functions in rats. In patients with AIS receiving intravenous tPA thrombolysis, the blood occludin was already elevated when patients arrived at hospital (within 4.5 hours since symptoms appeared) and remained at a high level for 72 hours. NBO significantly lowered the level of blood occludin and improved neurological functions in patients with AIS.

CONCLUSIONS

Blood occludin may be a clinically viable biomarker for evaluating BBB damage during ischemia/reperfusion. NBO therapy has the potential to reduce blood occludin, protect BBB, and improve outcome in AIS patients with intravenous tPA thrombolysis.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02974283.