Increased Blood-brain Barrier Permeability Research Articles

Cognitive Impairments, Neuroinflammation and Blood-Brain Barrier Permeability in Mice Exposed to Chronic Sleep Fragmentation during the Daylight Period.

Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH) and sleep fragmentation (SF). In murine models, chronic SF can impair endothelial function and induce cognitive declines. These deficits are likely mediated, at least in part, by alterations in Blood-brain barrier (BBB) integrity. Male C57Bl/6J mice were randomly assigned to SF or sleep control (SC) conditions for 4 or 9 weeks and in a subset 2 or 6 weeks of normal sleep recovery. The presence of inflammation and microglia activation were evaluated. Explicit memory function was assessed with the novel object recognition (NOR) test, while BBB permeability was determined by systemic dextran-4kDA-FITC injection and Claudin 5 expression. SF exposures resulted in decreased NOR performance and in increased inflammatory markers and microglial activation, as well as enhanced BBB permeability. Explicit memory and BBB permeability were significantly associated. BBB permeability remained elevated after 2 weeks of sleep recovery (p < 0.01) and returned to baseline values only after 6 weeks. Chronic SF exposures mimicking the fragmentation of sleep that characterizes patients with OSA elicits evidence of inflammation in brain regions and explicit memory impairments in mice. Similarly, SF is also associated with increased BBB permeability, the magnitude of which is closely associated with cognitive functional losses. Despite the normalization of sleep patterns, BBB functional recovery is a protracted process that merits further investigation.

Sex-dependent Cerebrovascular Aging and Vulnerability to Traumatic Brain Injury in a Transgenic Mouse Model of a Fibrillin-1 Associated Connective Tissue Disorder

Marfan syndrome (MFS) is a connective tissue disorder (CTD) associated with mutations in fibrillin-1 (Fbn1), leading to systemic increases in transforming growth factor-β (TGF-β) availability and signaling that induces an accelerated vascular aging phenotype with known peripheral vascular dysfunction by 6-months (6M) of age in Fbn1 C1041G/+ (MFS) mice. TGF-β has been implicated in cerebrovascular dysfunction, loss of blood-brain barrier (BBB) integrity, age-related neuroinflammation and neurological deficits. Improvements in MFS treatment and life expectancy have uncovered a risk for cerebrovascular complications such as stroke, and cerebral aneurysm, predominantly in the posterior cerebral artery (PCA). CTDs have shown unmasking events via mild traumatic brain injury (mTBI), where patients display increased severity and recovery times. Cerebrovascular dysfunction and neuropathology have been minimally investigated in MFS. We hypothesized that abnormal Fbn1 protein expression is associated with a sex-dependent accelerated aging phenotype in the aorta, cerebrovasculature, BBB permeability, neuroinflammation, behavior, and glutamate homeostasis, leaving the brain more vulnerable to mTBI. Male and female 6M MFS, 6M C57BL/6 (WT) control, and middle-aged 12M WT mice were utilized. In vivo ultrasound imaging demonstrated increased aortic root diameters and stiffness in MFS mice compared to 6M WT mice, like 12M WT, where MFS males were affected more than females. Aortic results were associated with decreased PCA blood flow velocity in MFS males, where MFS females were similar to 6 and 12M WT female mice. In 6M MFS mice, Evans blue extravasation and Immunoglobulin G staining demonstrated increased BBB permeability in the hippocampus to large and small molecules, respectively, as compared to WT and like 12M WT. In adjacent sections, iba-1 stained cells had morphologies indicative of reactive microglia. Acute glial activation and BBB permeability can disrupt glutamate homeostasis, where in vivo electrochemical recordings in the hippocampus showed slower glutamate clearance and elevated baseline glutamate concentrations in MFS and 12M WT mice. Higher neurobehavioral severity scale (NSS) scores in 6M MFS mice suggested neurobehavioral alterations that were more like 12M WT. Midline fluid percussion was used to induce mTBI, where 6M MFS male mice and both female groups required a 15% lower pressure to induce mTBI righting reflex times (5-10 minutes) compared to 6M WT male mice. Mice were evaluated at 1-day post injury, where BBB permeability to large and small molecules and microglia activation were increased, glutamate clearance was slowed, and NSS scores were increased compared to 6M WT and were similar to 6M MFS and 12M WT mice. These novel findings signify MFS as a disease of accelerated cerebrovascular aging phenotype and demonstrate potential vulnerability to injury, where chronic TGF-β dysregulation may be a critical regulator of age-related pathology. Valley_Research_Partnership-P1A-5012, NIH-R15HL145646, NIH-R01NS100793, Midwestern Graduate Funds This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Programmed cell death 10 increased blood-brain barrier permeability through HMGB1/TLR4 mediated downregulation of endothelial ZO-1 in glioblastoma

Dysfunction of blood brain barrier (BBB) contributes to the development of peritumoral edema (PTE) and GBM progression. Programmed cell death 10 (PDCD10) exerts various influence on cancers, especially in glioblastoma (GBM). We previously found that PDCD10 expression was positively correlated with PTE extent in GBM. Thus, the present study aims to investigate the emerging role of PDCD10 in regulating BBB permeability in GBM. Here we found that in vitro indirect co-culture of endothelial cells (ECs) with Pdcd10-overexpressed GL261 cells resulted in a significant increase of FITC-Dextran (MW, 4000) leakage by reducing endothelial zonula occluden-1 (ZO-1) and Claudin-5 expression in ECs respectively. Overexpression of Pdcd10 in GBM cells (GL261) triggered an increase of soluble high mobility group box 1 (HMGB1) release, which in turn activated endothelial toll like receptor 4 (TLR4) and downstream NF-κB, Erk1/2 and Akt signaling in ECs through a paracrine manner. Moreover, Pdcd10-overexpressed GL261 cells facilitated a formation of abnormal vasculature and increased the BBB permeability in vivo. Our present study demonstrates that upregulation of PDCD10 in GBM triggered HMGB1/TLR4 signaling in ECs and significantly decreased endothelial ZO-1 expression, which in turn dominantly increased BBB permeability and contributed to tumor progression in GBM.

Persistent Peri-Ablation Blood-Brain Barrier Opening After Laser Interstitial Thermal Therapy for Brain Tumors.

Purpose Laser interstitial thermal therapy (LITT) is a minimally invasive, image-guided, cytoreductive procedure to treat recurrent glioblastoma. This study implemented dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) methods and employed a model selection paradigm to localize and quantify post-LITT blood-brain barrier (BBB) permeability in the ablation vicinity. Serum levels of neuron-specific enolase (NSE), a peripheral marker of increased BBB permeability, were measured. Methods Seventeen patients were enrolled in the study. Using an enzyme-linked immunosorbent assay, serum NSE was measured preoperatively, 24 hours postoperatively, and at two, eight, 12, and 16 weeks postoperatively, depending on postoperative adjuvant treatment. Of the 17 patients, four had longitudinal DCE-MRI data available, from which blood-to-brain forward volumetric transfer constant (Ktrans) data were assessed. Imaging was performed preoperatively, 24 hours postoperatively, and between two and eight weeks postoperatively. Results Serum NSE increased at 24 hours following ablation (p=0.04), peaked at two weeks, and returned to baseline by eight weeks postoperatively. Ktrans was found to be elevated in the peri-ablation periphery 24 hours after the procedure. This increase persisted for two weeks. Conclusion Following the LITT procedure, serum NSE levels and peri-ablation Ktrans estimated from DCE-MRI demonstrated increases during the first two weeks after ablation, suggesting transiently increased BBB permeability.

New Insights into Alzheimer's Disease: Novel Pathogenesis, Drug Target and Delivery.

Alzheimer's disease (AD), the most common type of dementia, is characterized by senile plaques composed of amyloid β protein (Aβ) and neurofilament tangles derived from the hyperphosphorylation of tau protein. However, the developed medicines targeting Aβ and tau have not obtained ideal clinical efficacy, which raises a challenge to the hypothesis that AD is Aβ cascade-induced. A critical problem of AD pathogenesis is which endogenous factor induces Aβ aggregation and tau phosphorylation. Recently, age-associated endogenous formaldehyde has been suggested to be a direct trigger for Aβ- and tau-related pathology. Another key issue is whether or not AD drugs are successfully delivered to the damaged neurons. Both the blood-brain barrier (BBB) and extracellular space (ECS) are the barriers for drug delivery. Unexpectedly, Aβ-related SP deposition in ECS slows down or stops interstitial fluid drainage in AD, which is the direct reason for drug delivery failure. Here, we propose a new pathogenesis and perspectives on the direction of AD drug development and drug delivery: (1) aging-related formaldehyde is a direct trigger for Aβ assembly and tau hyperphosphorylation, and the new target for AD therapy is formaldehyde; (2) nano-packaging and physical therapy may be the promising strategy for increasing BBB permeability and accelerating interstitial fluid drainage.

Safety Assessments of Electroacupuncture-Mediated Blood–Brain Barrier Opening: An Animal Study

The presence of the Blood–Brain barrier (BBB) makes it difficult for therapeutic agents to reach the brain to treat brain diseases. As an emerging treatment, electroacupuncture (EA)-mediated BBB opening can temporarily increase the permeability of the brain blood vessels to increase the concentration of the therapeutic agent in the brain parenchyma, which offers great clinical benefits. Recent studies have suggested that BBB opening with excessive exposure levels may cause tissue/cell damage and short-term behavioral changes. Here, we investigated whether the EA-mediated BBB opening cause serious adverse events in the normal rat brain tissue and motor behavior, such as brain tissue damage, histopathologic alteration, or aggravated behavioral changes. EA was performed on the accupoint GV26 and GV20. Evans Blue Assay (EBA) and fluorescein isothiocyanate (FITC)–dextran Assay were performed to assess the BBB permeability. Immunofluorescence of GFAP-positive cells was marked and Hematoxylin-eosin (HE) Staining was carried out for assessing brain cortex damage. Tunel Assay was conducted to assess cell apoptosis. ELISA was used to measure the contents of TNF-α and IL-1β in brain tissue to explore the inflammatory response. The open field test, balance beam test and Y-Maze test were carried out to assess and neural behaviour. EA can induce an increase in BBB permeability on rats, allowing the macromolecular tracer Evans blue (EB) and Fluorescein Isothiocyanate (FITC)–Dextran to enter the brain. Histological analysis indicated that there was no obvious red blood cell leakage and a cellular apoptotic response in the brain tissue of rats with EA treatment. In addition, EA stimulation at specific parameters did not impair the rats’ motor ability, balance and coordination, and short-term spatial learning and memory. Our results suggest that EA can safely and effectively open the BBB in rats without causing brain damage and behavioral memory impairment.

The evolution of blood brain barrier permeability changes after stroke, and its implications on clinical outcome: a systematic review and meta-analysis.

Blood-brain barrier permeability (BBBp) is key process involved in ischemic stroke pathophysiology. However, there is a lack of consensus on how BBBp evolves after the ischaemic injury, and its clinical relevance at different time points post stroke. To assess BBBp evolution through stroke phases, and its implications on patient outcomes. We screened PubMed/MEDLINE, EMBASE, Web of Science, Scopus and Cochrane Central Register of Controlled Trials up to December 31, 2021. We included research quantitatively using neuroimaging to assess BBBp in stroke patients. BBBp in the different phases was evaluated by a random effect model based on the standardized mean difference (SMD) between the ipsilateral and contralateral sides of the brain. We performed subgroup analysis on clinical outcome, reperfusion treatment, haemorrhagic transformation and imaging method. We identified 3761 studies of which 22 (1592 patients, 1787 evaluations) were included in our study. Overall, 17 studies reported BBBp for the hyperacute phase, eight for the acute, five for the subacute and two for the chronic phase. All phases were associated with increased BBBp : 0.74 (0.48-0.99), 1.68 (0.94-2.42), 1.98 (0.96-3.00) and 1.00 (0.45-1.55) respectively. An increase in BBBp was associated with hemorrhagic transformation in the hyperacute phase, and with improved functional outcomes in the late subacute phase. BBBp is persistently increased after stroke, peaking in the acute and subacute phases. The degree of BBBp influences patient outcomes depending on stroke phase. Our findings support the clinical relevance of BBBp dynamics in stroke care.

552 Quantifying the Blood-Brain Barrier in Acute Ischemic Stroke Using Novel MR Imaging

INTRODUCTION: Acute ischemic stroke causes endothelial cell and tight junction damage, resulting in blood-brain barrier (BBB) disruption. BBB disruption is a significant risk factor for hemorrhagic conversion, which is seen in up to 20-40% of patients, increasing mortality by 7.9-fold. A number of processes, such as reperfusion injury, neuroinflammation, and neoangiogenesis impact the BBB permeability, which can fluctuate for several weeks after stroke. Despite its significance, BBB permeability is not taken into consideration in the management of this patient population. METHODS: We used two MRI sequences, diffusion-prepared pseudocontinuous arterial spin labeling (DP-pCASL) and Neurite Orientation Dispersion and Density Imaging (NODDI) to scan patients greater than 18 years old who presented with acute ischemic stroke. DP-pCASL generates cerebral blood flow, arterial transit time (ATT), and BBB permeability. NODDI generates neurite dispersion index (NDI), orientation dispersion index (ODI), and free water index (ISO) maps. Normalized BBB permeability above the 75th percentile of the vascular territories was defined as high permeability. RESULTS: Ten patients were enrolled with a mean age of 66.8 ± 13.9 and NIHSS of 15.8 ± 8.0. Patients were scanned at a mean 83.4 ± 78.8 hours from symptom onset. Two patients had received alteplase and 6 patients underwent mechanical thrombectomy. Multivariable logistic regression showed that increasing ATT (p &lt;0.001), decreasing ODI signal (p = 0.001), increasing relative monocyte count (p = 0.001) were significant predictors of increased BBB permeability. Intubation/general anesthesia decreased the odds of high BBB permeability (OR 0.072, p &lt; 0.001). CONCLUSIONS: Higher ATT, higher monocyte count, lower ODI, and lack of anesthesia were significant predictors of high BBB permeability in stroke patients. We provide a detailed account of our addition of DP-pCASL and NODDI into the stroke imaging protocol.

Alteration of the blood-brain barrier by COVID-19 and its implication in the permeation of drugs into the brain.

Diverse neurological symptoms have been reported in patients with SARS-CoV-2 disease (COVID-19), including stroke, ataxia, meningitis, encephalitis, and cognitive impairment. These alterations can cause serious sequelae or death and are associated with the entry of SARS-CoV-2 into the Central Nervous System (CNS). This mini-review discusses the main proposed mechanisms by which SARS-CoV-2 interacts with the blood-brain barrier (BBB) and its involvement in the passage of drugs into the CNS. We performed a search in PubMed with the terms "COVID-19" or "SARS-CoV-2" and "blood-brain barrier injury" or "brain injury" from the year 2019 to 2022. We found proposed evidence that SARS-CoV-2 infects neurovascular cells and increases BBB permeability by increasing the expression of matrix metalloproteinase-9 that degrades type IV collagen in the basement membrane and through activating RhoA, which induces restructuring of the cytoskeleton and alters the integrity of the barrier. The breakdown of the BBB triggers a severe inflammatory response, causing the cytokine storm (release of IL-1β, IL-6, TNF-α, etc.) characteristic of the severe phase of COVID-19, which includes the recruitment of macrophages and lymphocytes and the activation of astrocytes and microglia. We conclude that the increased permeability of the BBB would allow the passage of drugs that would not reach the brain in a normal physiological state, thus enhancing certain drugs' beneficial or adverse effects. We hope this article will encourage research on the impact of drugs on patients with COVID-19 and recovered patients with sequelae, focusing mainly on possible dose adjustments and changes in pharmacokinetic parameters.

Antiretroviral drugs efavirenz, dolutegravir and bictegravir dysregulate blood-brain barrier integrity and function.

The implementation of combined antiretroviral therapy (cART) significantly reduces the mortality associated with human immunodeficiency virus (HIV) infection. However, complications such as HIV-associated neurocognitive disorders (HAND) remain a major health concern. We hypothesized that the toxicity of antiretroviral drugs (ARVs) may contribute to the pathogenesis of HAND in addition to cerebral viral infection. To address this question, we evaluated the impact of HIV integrase strand transfer inhibitors (dolutegravir and bictegravir), and a non-nucleoside reverse transcriptase inhibitor (efavirenz) on the integrity and permeability of various human and mouse blood-brain barrier (BBB) models, in vitro, ex vivo and in vivo. We observed a significant downregulation of tight junction proteins (TJP1/Tjp1, OCLN/Ocln and CLDN5/Cldn5), upregulation of proinflammatory cytokines (IL6/Il6, IL8/Il8, IL1β/Il1β) and NOS2/Nos2, and alteration of membrane-associated transporters (ABCB1/Abcb1a, ABCG2/Abcg2 and SLC2A1/Slc2a1) mRNA expression, in vitro, in human (hCMEC/D3) and primary cultures of mouse microvascular endothelial cells, and ex vivo in isolated mouse brain capillaries treated with efavirenz, dolutegravir, and/or bictegravir. We also observed a significant increase in BBB permeability in vivo following treatment with the selected ARVs in mice applying NaF permeability assay. Taken together, these results suggest that clinically recommended integrase strand transfer inhibitors such as dolutegravir may exacerbate HIV-associated cerebrovascular pathology, which may contribute to the associated short-term neuropsychiatric side effects and the high incidence of mild forms of HAND reported in the clinical setting.

Exosomal miR-370-3p increases the permeability of blood-brain barrier in ischemia/reperfusion stroke of brain by targeting MPK1.

Ischemia/reperfusion (I/R) damage induced by stroke poses a serious hazard to human life, while mechanism of blood-brain barrier (BBB) dysfunction is still unknown. To imitate stroke induced ischemia conditions in vivo, the rat model of cerebral I/R damage was created by middle cerebral artery occlusion (MCAO). In vitro, the rat microvascular endothelial cell line bEND.3 was subjected to oxygen-glucose deprivation/reperfusion (OGD/R). Evans blue was used to evaluate the permeability of the blood-brain barrier (BBB). To evaluate gene expression at the mRNA and protein levels, researchers used real-time PCR and western blotting. Infarct volume and BBB permeability were considerably higher in cerebral (I/R) animals than in the Sham group. Exosomal miR-370-3p expression was shown to be higher in the brains of I/R injured rats and OGD/R treatment bEND.3. The BBB permeability was considerably increased when miR-370-3p was downregulated in OGD/R pretreated bEND.3. miR-370-3p regulates MAPK1 expression by targeting it. In bEND.3, OGD/R therapy increased BBB permeability substantially. OGD/R was inhibited by miR-370-3p mimic transfection, while miR-370-3p mimic was abolished by co-transfection with MAPK1 overexpression lentivirus. In cerebral I/R damage, exosomal miR-370-3p targets MAPK1 and aggregates BBB permeability.

Changes in serum blood-brain barrier markers after bilateral tonic-clonic seizures

ObjectiveSeizures have been shown to increase blood-brain barrier (BBB) permeability, yet the role of this phenomenon is not fully understood. Additionally, dysfunction of the BBB leads to initiation and propagation of seizures in animal models. To demonstrate the increased permeability of the BBB in time, we investigated changes of the serum levels of BBB markers in patients with epilepsy after bilateral tonic-clonic seizures. We chose markers that might reflect endothelial activation (ICAM-1, selectins), BBB leakage (MMP-9, S100B) and mechanisms of BBB restoration (TIMP-1, thrombomodulin -TM). MethodsWe enrolled 50 consecutive patients hospitalised after bilateral tonic-clonic seizures who agreed to take part in the study and 50 participants with no history of epilepsy. Serum levels of selected markers were measured by ELISA at 1-3, 24, and 72 hours after seizures and one time in the control group. ResultsWe found increased levels of S100B, ICAM-1, MMP-9 and P-selectin at 1-3 and 24 hours after seizures and TIMP-1 and TM at 24 and 72 hours after seizures as compared to the control group. The level of E-selectin was decreased at 72 hours after seizures. ConclusionsOur findings suggest early activation of endothelium and increased BBB permeability after seizures. While we are aware of the limitations due to the non-specificity of the tested proteins, our results might indicate the presence of prolonged BBB impairment due to seizure activity.

Brain regional pharmacokinetics of hydroxytyrosol and its molecular mechanism against depression assessed by multi-omics approaches

BackgroundHydroxytyrosol (HT), as the main compound in olive leaves with its potential ability to cross blood-brain barrier (BBB), has exhibited the advantaged antidepressant effect. However, no information is available regarding the brain regional uptake of HT, as well the underlying antidepressant mechanism remains unclear. PurposeTo comprehensively reveal the brain uptake of HT and its specific mechanism on the accompanying antidepressant activity. Study design and methodsThe BBB penetration and brain regional distribution of HT in the normal and chronic unpredictable mild stress (CUMS)–induced depressive mice in consideration with the BBB integrality were analyzed. Then, the hippocampal region–specific responses of biomolecules and concurrent alterations in the therapeutic effect of HT on depression were explored using untargeted metabolomics, spatial–resolved metabolomics and tissue proteomics, which were confirmed by LPS–induced BV–2 microglia and CUMS mice. ResultsBBB permeability analysis in normal and CUMS mice confirmed that increased BBB permeability of CUMS mice was induced by the deficiency of tight junction-related proteins. Consistently, according to the established LC–MS/MS method, it was found that HT could not be largely detected in the cerebrospinal fluids and brains of normal mice after oral administration, while it could excessively penetrate the BBB (200–fold higher), and mostly distributed in the hippocampus of CUMS mice. Meanwhile, multi–omics analysis combined with targeted analysis discovered that HT could mainly improve fatty acid biosynthesis and metabolism in the hippocampus with region–specific responses and accompanying inhibition of C3–CD11b pathway in CUMS mice. Besides, in vitro experiments further confirmed the anti–complement ability of HT, which could inhibit C3–CD11b pathway for alleviating the LPS–induced BV–2 microglia activation. ConclusionHT can excessively penetrate the BBB and be mostly distributed in the hippocampus of depressive mice, which contribute to improve fatty acid biosynthesis and metabolism in the hippocampus with region–specific responses and accompanying inhibition of C3–CD11b pathway for microglia activation. These findings give the clearer understanding of brain regional pharmacokinetics of HT and its accompanying molecular mechanism against depression.

Blood-Brain Barrier Integrity Damage in Bacterial Meningitis: The Underlying Link, Mechanisms, and Therapeutic Targets.

Despite advances in supportive care and antimicrobial treatment, bacterial meningitis remains the most serious infection of the central nervous system (CNS) that poses a serious risk to life. This clinical dilemma is largely due to our insufficient knowledge of the pathology behind this disease. By controlling the entry of molecules into the CNS microenvironment, the blood-brain barrier (BBB), a highly selective cellular monolayer that is specific to the CNS's microvasculature, regulates communication between the CNS and the rest of the body. A defining feature of the pathogenesis of bacterial meningitis is the increase in BBB permeability. So far, several contributing factors for BBB disruption have been reported, including direct cellular damage brought on by bacterial virulence factors, as well as host-specific proteins or inflammatory pathways being activated. Recent studies have demonstrated that targeting pathological factors contributing to enhanced BBB permeability is an effective therapeutic complement to antimicrobial therapy for treating bacterial meningitis. Hence, understanding how these meningitis-causing pathogens affect the BBB permeability will provide novel perspectives for investigating bacterial meningitis's pathogenesis, prevention, and therapies. Here, we summarized the recent research progress on meningitis-causing pathogens disrupting the barrier function of BBB. This review provides handy information on BBB disruption by meningitis-causing pathogens, and helps design future research as well as develop potential combination therapies.

Abstract TP228: Differential Effect Of Serum From Intracerebral Hemorrhage And Small Vessel Disease Patients On Nonischemic Cerebral Arteries

Introduction: There is evidence that circulating factors disrupt vessel function in the contralateral hemisphere after stroke. However, how different stroke subtypes, that have more severe vascular disruption, affect nonischemic vessels is unknown. Here, we compared circulating factors from human patients with distinct stroke subtypes of cardioembolic (CE), small vessel disease (SVD), and intracerebral hemorrhage (ICH). We hypothesized that serum from ICH patients would cause greater vascular dysfunction of nonischemic arteries than CE, and that serum from SVD patients would have an intermediate effect. Methods: Serum was obtained 24 hours poststroke from patients with SVD (n=3), ICH (n=4), and CE (n=7) and pooled. All patients had a medical history of hypertension. Only SVD and CE patients received tPA. Pooled serum 20% v/v was perfused into the lumen of 3 rd order posterior cerebral arteries (PCA, CE &amp; ICH n=5, SVD n=6) that were mounted on glass cannulas and pressurized in an arteriograph chamber. Blood brain barrier (BBB) permeability and vascular reactivity was studied to investigate effects on myogenic tone and endothelial function. Data are presented as mean±SEM. Results: All vessels reacted myogenically at pressures ≥40 mmHg. However, serum from ICH patients caused a significant increase in tone at 20 mmHg vs. CE and SVD groups: 37.5±1.6 vs. 9.0±1.9% and 13.0±4.8% p&lt;0.05. There was no difference in dilation to NS309; however, constriction to nitric oxide synthase (NOS) inhibition with L-NAME was impaired with SVD and ICH serum compared to CE: 14.0±2.3% vs. 4.6±0.8% (p&lt;0.05) and 5.8±2.1% (p=0.09). However, reactivity to sodium nitroprusside, an NO donor, was not different between groups. Serum caused an increase in BBB permeability over time that was not different with the different serums. Conclusions: Circulating factors from ICH, SVD and CE patients had differing vascular effects on nonischemic cerebral arteries. Serum from ICH patients was vasoconstrictive, potentially due to hemostatic factors, whereas serum from both SVD and ICH patients had impaired NO reactivity demonstrating endothelial dysfunction. These effects of ischemic stroke could affect the contralateral hemisphere and contribute to outcome and therapeutic responses.

Brain targeted borneol-baicalin liposome improves blood-brain barrier integrity after cerebral ischemia-reperfusion injury via inhibiting HIF-1α/VEGF/eNOS/NO signal pathway

Baicalin (BA) is widely used in the treatment of cerebral ischemia-reperfusion injury (CIRI). The key to treating encephalopathy is to increase the amounts of drugs entering the brain. Borneol-baicalin liposome (BO-BA-LP) was prepared in previous research based on the characteristics of borneol (BO) in promoting drug brain entry. In this study, the effect of BO-BA-LP on improving blood-brain barrier (BBB) integrity was researched. Results showed BO-BA-LP may increase ability of BA to penetrate the cell membrane in vitro. Pharmacokinetic results showed the BO-BA-LP could increase concentrations of BA in plasma and brain tissues of normal and CIRI mice. Pharmacological results revealed BO-BA-LP could improve the neurological function, brain edema, and histopathology of CIRI mice. Besides, BO-BA-LP could protect BBB by regulating hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF)/endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) pathway. The research showed that BO in BO-BA-LP could increase the absorption of BA by increasing BBB permeability, leading to a better therapeutic effect of BO-BA-LP on CIRI mice.

Effect of ventilator-induced lung injury on blood-brain barrier permeability in rats

To observe the effect of ventilator-induced lung injury (VILI) on blood-brain barrier permeability in rats. Forty-eight healthy clean male Sprague-Dawley (SD) rats were randomly divided into sham operation (Sham) group, low tidal volume (LVT) mechanical ventilation group (LVT group), normal tidal volume (NVT) mechanical ventilation group (NVT group) and high tidal volume (HVT) mechanical ventilation group (HVT group) with 12 rats in each group. After anesthesia, rats in the Sham group were intubated and kept spontaneous breathing. The rats in different tidal volume (VT) groups were mechanically ventilated by endotracheal intubation with VT of 6 mL/kg (LVT group), 10 mL/kg (NVT group), and 20 mL/kg (HVT group), respectively. The inspiration-expiration ratio of the three groups was 1:1, the ventilation frequency was 40 times/min, and the ventilation time was 3 hours. At the end of the experiment, the bronchoalveolar lavage fluid (BALF) of rats was collected, and the levels of pro-inflammatory factors [tumor necrosis factor-α (TNF-α), interleukins (IL-1β and IL-6)] in BALF were detected by enzyme-linked immunosorbent assay (ELISA). The lung tissues of rats were collected, and the lung wet/dry weight (W/D) ratio was calculated. The pathological changes of lung tissues were observed under light microscopy after hematoxylin-eosin (HE) staining, and lung injury scores were performed. The brain tissue of rats was taken to measure the brain water content, and the Evans blue (EB) content of brain tissue was measured to reflect the permeability of the blood-brain barrier. The tight junction proteins in the brain tissues were detected by Western blotting. After 3 hours of mechanical ventilation, with the increase of VT, the degree of lung injury in VILI rats gradually increased. When VT reached 20 mL/kg, lung tissue structure was significantly injured, alveolar wall edema, alveolar congestion, lung interstitial thickening, a large number of inflammatory cells infiltrated, and the lung injury score, lung W/D ratio, and the levels of TNF-α, IL-1β and IL-6 in BALF were significantly higher than those in the Sham group [lung injury score: 10.6±1.1 vs. 1.4±1.0, lung W/D ratio: 6.6±0.8 vs. 3.7±0.6, TNF-α (ng/L): 832.9±97.9 vs. 103.8±23.3, IL-1β (ng/L): 68.9±14.1 vs. 15.7±2.6, IL-6 (ng/L): 70.8±16.4 vs. 20.3±5.4, all P < 0.05]. Lung injury in rats was accompanied by aggravating brain injury. When VT reached 20 mL/kg, brain water content and EB content in brain tissue were significantly higher than those in the Sham group [brain water content: (85.4±3.6)% vs. (68.7±2.7)%, EB content in brain tissue (μg/g): 887±78 vs. 97±14, both P < 0.05], and the protein expressions of claudin-5, occluding and zonula occluden-1 (ZO-1) in the brain tissue were significantly lower than those in the Sham group [claudin-5 protein (claudin-5/β-actin): 0.67±0.12 vs. 1.45±0.19, occludin protein (occludin/β-actin): 0.48±0.11 vs. 0.99±0.21, ZO-1 protein (ZO-1/β-actin): 0.13±0.03 vs. 0.63±0.12, all P < 0.05]. VILI can induce brain edema and increase blood-brain barrier permeability in rats, which may be related to the down-regulation of tight junction protein expression in the brain tissue.

Mechanobiological modulation of blood-brain barrier permeability by laser stimulation of endothelial-targeted nanoparticles.

The blood-brain barrier (BBB) maintains an optimal environment for brain homeostasis but excludes most therapeutics from entering the brain. Strategies that reversibly increase BBB permeability are essential for treating brain diseases and are the focus of significant preclinical and translational interest. Picosecond laser excitation of tight junction-targeted gold nanoparticles (AuNPs) generates a nanoscale mechanical perturbation and induces a graded and reversible increase in BBB permeability (OptoBBB). Here we advanced this technique by showing that targeting endothelial glycoproteins leads to >10-fold higher targeting efficiency than targeting tight junctions both in vitro and in vivo. With both tight-junction and glycoprotein targeting, we demonstrate that OptoBBB is associated with a transient elevation and propagation of Ca2+, actin polymerization, and phosphorylation of ERK1/2 (extracellular signal-regulated protein kinase). These collectively activate the cytoskeleton resulting in increased paracellular permeability. The Ca2+ response involves internal Ca2+ depletion and Ca2+ influx with contributions from mechanosensitive ion channels (TRPV4, Piezo1). We provide insight into how the excitation of tight junction protein (JAM-A)-targeted and endothelial (glycocalyx)-targeted AuNPs leads to similar mechanobiological modulation of BBB permeability while targeting the glycocalyx significantly improves the nanoparticle accumulation in the brain. The results will be critical for guiding the future development of this technology for brain disease treatment.

Nitric oxide availability in cerebral microangiopathy

To develop a test of individual nitric oxide (NO) availability based on changes in erythrocyte rheological properties after incubation with a NO donor and to evaluate the role of these disorders in brain damage and development of cognitive impairment (CI) in cerebral small vessel disease (cSVD). In 73 cSVD patients (48 (65.8%) women, mean age 60.1±6.5), the rheological properties of erythrocytes before and after incubation with 10 μmol/L L-arginine-NO donor were evaluated using a laser-optical rotating cell analyzer, and the blood-brain barrier (BBB) permeability by MRI-T1 dynamic contrast. Among the studied parameters of erythrocyte rheological properties, the best characteristic by ROC analysis was the rate of erythrocyte disaggregation (y-dis) after incubation with L-arginine (area under the curve 0.733 (0.609-0.856), sensitivity 67%, specificity 79%). Patients with a y-dis threshold >113 sec-1 had more severe CI, arterial hypertension, white matter lesions, and increased BBB permeability in gray matter and normal-appearing white matter. The prolonged rate of erythrocyte disaggregation in cSVD patients after incubation with L-arginine indicates the risk for disease progression due to decreased NO bioavailability/disruption of the functional L-arginine-eNOS-NO system. This test can be used to assess individual NO bioavailability and potentially identify indications for modifying therapy with NO donors such as L-arginine. Clinical trials are needed to standardize and evaluate the efficacy of NO donor therapy in patients with cSVD and CI.

Enhanced brain delivery of hypoxia-sensitive liposomes by hydroxyurea for rescue therapy of hyperacute ischemic stroke.

Ischemic stroke is characterized by high morbidity, disability, and mortality. Unfortunately, the only FDA-approved pharmacological thrombolytic, alteplase, has a narrow therapeutic window of only 4.5 h. Other drugs like neuroprotective agents have not been clinically used because of their low efficacy. To improve the efficacy of neuroprotective agents and the effectiveness of rescue therapies for hyperacute ischemic stroke, we investigated and verified the variation trends of the blood-brain barrier (BBB) permeability and regional cerebral blood flow over 24 h in rats that had ischemic strokes. Hypoperfusion and the biphasic increase of BBB permeability are still the main limiting factors for lesion-specific drug distribution and drugbrain penetration. Herein, the nitric oxide donor hydroxyurea (HYD) was reported to downregulate the expression of tight junction proteins and upregulate intracellular nitric oxide content in the brain microvascular endothelial cells subjected to oxygen-glucose deprivation, which was shown to facilitate the transport of liposomes across brain endothelialmonolayer in an in vitro model. HYD also increased the BBB permeability and promoted microcirculation in the hyperacute phase of stroke. The neutrophil-like cell-membrane-fusogenic hypoxia-sensitive liposomes exhibited excellent performance in targeting the inflamed brain microvascular endothelial cells, enhancing cell association, and promoting rapid hypoxic-responsive release in the hypoxic microenvironment. Overall, the combined HYD and hypoxia-sensitive liposome dosing regimen effectively decreased the cerebral infarction volume and relieved neurological dysfunction in rats that had ischemic strokes; these therapies were involved in the anti-oxidative stress effect and the neurotrophic effect mediated by macrophage migration inhibitory factor.