Changes In Blood-brain Barrier Permeability Research Articles

Apolipoprotein C3-rich low-density lipoprotein (AC3RL) exacerbates cerebral ischaemic stroke injury by increasing BBB leakage via LOX-1

Abstract Background Ischaemic stroke causes the abrupt reduction or cessation of blood flow to the brain results in a cascade of events that can compromise blood-brain barrier (BBB) integrity. We revealed that an increase in apolipoprotein C3 (ApoC3)-rich low-density lipoprotein (AC3RL) is associated with endothelial cell apoptosis and inflammatory responses, indicating that AC3RL is one of the risk factors for cardiovascular events. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) triggers a cascade of events within endothelial cells that leads to endothelial dysfunction. Purpose We aimed to investigate whether AC3RL affects BBB permeability via the LOX-1, and thus increases brain damage. Methods We collected the whole blood from normal and patients with ischaemic events and separated them by centrifugation. AC3RL were collected using FPLC. We performed middle cerebral artery occlusion (MCAO) surgery to induce ischaemic stroke using B6 (C57BL/6) and LOX-1-/- mice injected with AC3RL. Triphenyl tetrazolium chloride (TTC) and Evans blue stains were accessed to confirm brain injury and BBB permeability. Results FPLC results showed that patients with ischaemic events presented higher levels of AC3RL compared to normal people. TTC stain showed the increased area of ischaemic penumbra damage in B6 mice with AC3RL injection, and LOX-1-/- mice with AC3RL injection were significantly protected. Evans blue dye leakage was observed in the brain tissues of B6 mice with AC3RL injection. LOX-1-/- mice with AC3RL injection revealed a decrease in BBB permeability. The modified neurological severity score (mNSS) method revealed a significant rise in B6 mice with AC3RL injection, which suggested a decline in motor and nervous function. LOX-1-/- mice with AC3RL injection significantly improved in motor and neurological functioning. Conclusions We demonstrate that AC3RL, through its effects on LOX-1, is associated with an increased risk of BBB damage after stroke. Therefore, pharmacological inhibition of AC3RL-LOX-1 interaction will be the main strategy to reduce severe brain damage. Figure 1: (A) AC3RL percentage (%) in individuals. Normal: healthy people, Ischemic event: patients who have experienced an ischemic event. **p < 0.001 vs. Normal group. (B, C) TTC stain of brain tissue after euthanasia to pinpoint the site of brain damage. The white portion of the mice brains indicated the site of the injury. (D, E) Evans blue dye leakage study in mice brains exhibited BBB permeability changes. (F) Assessment of mice's motor and neurological performance using the mNSS. Data are expressed as the mean ± SEM. **p < 0.001, ****p < 0.0001 vs. sham group, ##p < 0.001 vs. B6 I.V. AC3RL group.Graphical abstractFigure 1.

The molecular mechanisms by which the NLRP3 inflammasome regulates blood-brain barrier permeability following cryptococcal meningitis

ObjectiveTo investigate the mechanism underlying the regulation of blood-brain barrier permeability changes during cryptococcal meningitis by NLRP3 and Vimentin. MethodsSprague-Dawley rats were treated with WT Cryptococcus neoformans (Cn) or CPS1-/- Cn. Neuronal apoptosis was assessed using TUNEL staining, and pathological changes were observed using electron microscopy and HE staining. The expressions of NLRP3, Vimentin, and NF-κB in the cerebral cortex and human brain microvascular endothelial cells (HBMECs) were examined through Western blot and qRT-PCR. siNLRP3 and siVimentin were separately transfected into HBMECs, the expressions of specific factors were assessed. NF-κB and Vimentin levels were detected through immunofluorescence, apoptosis was measured using flow cytometry, and changes in the optical density (OD) of HRP were determined using ELISA. ResultsThe expressions of NLRP3, Vimentin, and NF-κB were upregulated following intervention with WT Cn in vivo and in vitro. Electron microscopy revealed loose nuclear membranes in neurons and increased apoptosis in the cerebral cortex and hippocampus induced by WT Cn, accompanied by a reduction in the OD of HRP in vitro. siNLRP3 decreased the expressions of Vimentin, nuclear NF-κB, and β-Tubulin in HBMECs, while siVimentin downregulated total NLRP3 and nuclear NF-κB levels. Both siNLRP3 and siVimentin reduced cell apoptosis after WT Cn infection. HBMECs displayed a reduced monolayer permeability to HRP and improved cell structure arrangement. ConclusionVimentin and the NLRP3 inflammasome are both implicated in the pathological process of cryptococcal meningitis. An interaction between Vimentin and the NLRP3 inflammasome is evident, likely mediated through the NF-κB signaling pathway.

Measurement of blood-brain barrier water exchange rate using diffusion-prepared and multi-echo arterial spin labelling: Comparison of quantitative values and age dependence.

Water exchange rate (Kw) across the blood-brain barrier (BBB) is an important physiological parameter that may provide new insight into ageing and neurodegenerative disease. Recently, two non-invasive arterial spin labelling (ASL) MRI methods have been developed to measure Kw, but results from the different methods have not been directly compared. Furthermore, the association of Kw with age for each method has not been investigated in a single cohort. Thirty participants (70% female, 63.8 ± 10.4years) were scanned at 3T with Diffusion-Prepared ASL (DP-ASL) and Multi-Echo ASL (ME-ASL) using previously implemented acquisition and analysis protocols. Grey matter Kw, cerebral blood flow (CBF) and arterial transit time (ATT) were extracted. CBF values were consistent; approximately 50 ml/min/100 g for both methods, and a strong positive correlation in CBF from both methods across participants (r = 0.82, p < 0.001). ATT was significantly different between methods (on average 147.7ms lower when measured with DP-ASL compared to ME-ASL) but was positively correlated across participants (r = 0.39, p < 0.05). Significantly different Kw values of 106.6±19.7min-1 and 306.8±71.7min-1 were measured using DP-ASL and ME-ASL, respectively, and DP-ASL Kw and ME-ASL Kw were negatively correlated across participants (r = -0.46, p < 0.01). Kw measured using ME-ASL had a significant linear relationship with age (p < 0.05). In conclusion, DP-ASL and ME-ASL provided estimates of Kw with significantly different quantitative values and inconsistent dependence with age. We propose future standardisation of modelling and fitting methods for DP-ASL and ME-ASL, to evaluate the effect on Kw quantification. Also, sensitivity and bias analyses should be performed for both approaches, to assess the effect of varying acquisition and fitting parameters. Lastly, comparison with independent measures of BBB water transport, and with physiological and clinical biomarkers known to be associated with changes in BBB permeability, are essential to validate the ASL methods, and to demonstrate their clinical utility.

Adrenocorticotropic hormone therapy alters Q-albumin ratios in patients with infantile epileptic spasms syndrome of unknown etiology

PurposeInfantile epileptic spasms syndrome (IESS) with epileptic spasms as the main seizure type, is treated with adrenocorticotropic hormone (ACTH). This study, for the first time, examines the effects of epileptic spasms and ACTH on blood-brain barrier (BBB) permeability in patients with IESS of unknown etiology. MethodsWe prospectively evaluated the changes in BBB permeability in patients with IESS of unknown etiology at the Saitama Children's Medical Center between February 2012 and February 2024. We compared the levels of serum-albumin, cerebrospinal fluid (CSF)-albumin, Q-albumin, and CSF-neuron-specific enolase (NSE) before and after ACTH therapy. We also assessed the correlation between the frequency of epileptic spasms and these markers. ResultsOverall, 16 patients with IESS (8 males) were included in the study. The median age at IESS onset was 5 (range, 2–9) months. The median duration between the epileptic spasms onset and the serum and CSF sample examination before ACTH therapy was 26 (range, 1–154) days. After ACTH therapy, CSF-albumin and Q-albumin levels significantly decreased (CSF-albumin: 13.5 (9.0–32.0) mg/dL vs 11.0 (7.0–19.0) mg/dL, p = 0.001. Q-albumin: 3.7× 10−3 (2.2 × 10−3-7.3 × 10−3) vs 2.8× 10−3 (1.9 × 10−3-4.5 × 10−3), p = 0.003). No correlation was observed between the epileptic spasms frequency and levels of serum-albumin, CSF-albumin, Q-albumin, and CSF-NSE (Spearman's coefficient: r = 0.291, r = 0.141, r = 0.094, and r = −0.471, respectively). ConclusionACTH therapy is one of the factors that play a role in restoring BBB permeability in patients with IESS of unknown etiology. Our findings may be useful in elucidating the mechanism of ACTH action and IESS pathophysiology.

MR Assessment of Acute Changes of Cerebral Perfusion, Metabolism, and Blood-Brain Barrier Permeability in Response to Aerobic Exercise.

It remains unclear how a single bout of exercise affects brain perfusion, oxygen metabolism, and blood-brain barrier (BBB) permeability. Addressing this unresolved issue is essential to understand the acute changes in cerebral physiology induced by aerobic exercise. To dynamically monitor the acute changes in cerebral physiology subsequent to a single aerobic exercise training session using noninvasive MRI measurements. Prospective. Twenty-three healthy participants (18-35 years, 10 females/13 males) were enrolled and divided into 10-minute exercising (N = 10) and 20-minute exercising (N = 13) groups. 3.0 T/Phase Contrast (PC) MRI (gradient echo), T2-Relaxation-Under-Spin-Tagging (TRUST) MRI (gradient echo EPI), Water-Extraction-with-Phase-Contrast-Arterial-Spin-Tagging (WEPCAST) MRI (gradient echo EPI) and T1-weighted magnetization-prepared-rapid-acquisition-of-gradient-echo (MPRAGE) (gradient echo). A baseline MR measurement plus four repeated MR measurements immediately after 10 or 20 minutes moderate running exercise. MR measurements included cerebral blood flow (CBF) as measured by PC MRI, venous oxygenation (Yv) and cerebral metabolic rate of oxygen (CMRO2) as assessed by TRUST MRI, water extraction fraction (E), and BBB permeability-surface-area product (PS) as determined by WEPCAST MRI. The time dependence of the physiological parameters was studied with a linear mixed-effect model. Additionally, pairwise t-tests comparison of the physiological parameters at each time point was conducted. A P-value of <0.05 was considered statistically significant. There was an initial drop (8.22 ± 2.60%) followed by a recovery in CBF after exercise, while Yv revealed a significant decrease (6.37 ± 0.92%), i.e., an increased oxygen extraction, and returned to baseline at later time points. CMRO2 showed a trend of increase (5.68 ± 3.04%) and a significant interaction between time and group. In addition, E increased significantly (3.86% ± 0.89) and returned to baseline level at later time points, while PS remained elevated (13.33 ± 4.79%). A single bout of moderate aerobic exercise can induce acute alterations in cerebral perfusion, metabolism, and BBB permeability. 2 TECHNICAL EFFICACY: Stage 2.

The role of CCN1 in kidney-brain crosstalk

Cognitive impairment and dementia are major global health problems of the aging human population. It is estimated that about 55 million people were living with dementia in 2019 and this number is expected to triple by 2050. Dementia can result from abnormal structure and function of brain blood vessels that may develop in a variety of conditions including chronic kidney disease (CKD). Recent studies from our laboratory suggest that in addition to controlling blood volume and blood pressure (renin), and blood cell count (erythropoietin), the kidney produces novel systemic angiogenic hormones to maintain blood vessels, such as the matricellular protein Cellular Communication Network factor 1 (CCN1). These hormones are then released to the blood and may act as new molecular mechanisms of kidney-brain crosstalk. We hypothesized that kidney-derived CCN1 helps to preserve the normal structure and function of blood vessels throughout the body, including a healthy blood-brain barrier (BBB). We further hypothesized that reduced plasma CCN1 caused by diminished renal production of CCN1 due to kidney disease plays a major role in the development of brain vascular dysfunction, and therefore in the pathogenesis and progression of dementia and cognitive impairment. Intravital multiphoton (MPM) imaging of the intact mouse brain in control or after 5/6 nephrectomy (5/6 Nx), a well-established mouse model of chronic kidney disease (CKD) was used to measure changes in BBB permeability with or without chronic CCN1 treatment. Kidney and BBB structure/function phenotyping was performed using CCN1 ELISA assay, the Medibeacon transdermal GFR measurement system, tissue harvest, and immunohistochemistry. Compared to control, 5/6 Nx mice had reduced plasma CCN1 levels, reduced GFR, but no difference in systolic blood pressure. MPM imaging showed increased fluorescence intensity of mid-size plasma proteins (A680 conjugated Albumin 70 kDa) compared to high molecular weight markers (A488 conjugated Dextran 500 kDa) in brain interstitium in 5/6 Nx compared to control. In addition, the density of cell-to-cell junctions in brain endothelial cells were 20% reduced in CKD compared to control healthy mice. In brain endothelial cells cultured in vitro, CCN1 treatment had protective effects on cell proliferation, motility and angiogenesis as confirmed by scratch and tube formation assays. In summary, this study identified new mechanisms of kidney-brain crosstalk, and helped to improve our mechanistic understanding of cerebrovascular pathology in CKD. DK123564, DK064324, DK135290. This is the full abstract presented at the American Physiology Summit 2024 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.

Feasibility of measuring blood-brain barrier permeability using ultra-short echo time radial magnetic resonance imaging.

The purpose of this study is to evaluate the feasibility of using 3-dimensional (3D) ultra-short echo time (UTE) radial imaging method for measurement of the permeability of the blood-brain barrier (BBB) to gadolinium-based contrast agent. In this study, we propose to use the golden-angle radial sparse parallel (GRASP) method with 3D center-out trajectories for UTE, hence named as 3D UTE-GRASP. We first examined the feasibility of using 3D UTE-GRASP dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) for differentiating subtle BBB disruptions induced by focused ultrasound (FUS). Then, we examined the BBB permeability changes in Alzheimer's disease (AD) pathology using Alzheimer's disease transgenic mice (5xFAD) at different ages. For FUS experiments, we used four Sprague Dawley rats at similar ages where we compared BBB permeability of each rat receiving the FUS sonication with different acoustic power (0.4-1.0MPa). For AD transgenic mice experiments, we included three 5xFAD mice (6, 12, and 16 months old) and three wild-type mice (4, 8, and 12 months old). The result from FUS experiments showed a progressive increase in BBB permeability with increase of acoustic power (p <.05), demonstrating the sensitivity of DCE-MRI method for detecting subtle changes in BBB disruption. Our AD transgenic mice experiments suggest an early BBB disruption in 5xFAD mice, which is further impaired with aging. The results in this study substantiate the feasibility of using the proposed 3D UTE-GRASP method for detecting subtle BBB permeability changes expected in neurodegenerative diseases, such as AD.

Optimal timing for drug delivery into the hippocampus by focused ultrasound: A comparison of hydrophilic and lipophilic compounds

AimsPrevious studies have reported that focused ultrasound (FUS) helps modulate the blood-brain barrier (BBB). These studies have generally used the paracellular pathway owing to tight junction proteins (TJPs) regulation. However, BBB transport pathways also include diffusion and transcytosis. Few studies have examined transcellular transport across endothelial cells. We supposed that increased BBB permeability caused by FUS may affect transcytosis. We investigated drug delivery through transcytosis and paracellular transport to the brain after BBB modulation using FUS. Main methodsFUS and microbubbles were applied to the hippocampus of rats, and were euthanized at 1, 4, 24, and 48 h after sonication. To investigate paracellular transport, we analyzed TJPs, including zona occludens-1 (ZO-1) and occludin. We also investigated caveola-mediated transcytosis by analyzing caveola formation and major facilitator superfamily domain-containing 2a (Mfsd2a) levels, which inhibit caveola vesicle formation. Key findingsOne hour after FUS, ZO-1 and occludin expression was the lowest and gradually increased over time, returning to baseline 24 h after FUS treatment. Compared with that of TJPs, caveola formation started to increase 1 h after FUS treatment and peaked at 4 h after FUS treatment before returning to baseline by 48 h after FUS treatment. Decreased Mfsd2a levels were observed at 1 h and 4 h after FUS treatment, indicating increased caveola formation. SignificanceFUS induces BBB permeability changes and regulates both paracellular transport and caveola-mediated transcytosis. However, a time difference was observed between these two mechanisms. Hence, when delivering drugs into the brain after FUS, the optimal drug administration timing should be determined by the mechanism by which each drug passes through the BBB.

Restraint stress induces blood-brain barrier injury in rat amygdala by activating the Rho/ROCK signaling pathway

To investigate the role of Rho/ROCK signaling pathway in mediating restraint stress-induced blood-brain barrier (BBB) injury in the amygdala of rats. Sixty male SD rats were randomized equally into control group (with food and water deprivation for 6 h per day), restraint stress group (with restraint for 6 h per day), stress + fasudil treatment (administered by intraperitoneal injection at 1 mg/100 g 30 min before the 6-h restraint) group, and fasudil treatment alone group. The elevated plus-maze test was used to detect behavioral changes of the rats, serum corticosterone and S100B levels were determined with ELISA, and Evans Blue leakage in the brain tissue was examined to evaluate the changes in BBB permeability. The changes in expression levels of tight junction proteins in the amygdala were detected using immunofluorescence assay and Western blotting, and Rho/ROCK pathway activation was detected by Pull-down test and Western blotting. Ultrastructural changes of the cerebral microvascular endothelial cells were observed using transmission electron microscopy. Compared with those in the control group, the rats in restrain stress group and stress+fasudil group showed obvious anxiety-like behavior with significantly increased serum corticosterone level (P<0.001). Compared with those in the control group and stress+fasudil group, the rat models of restrain stress showed more obvious Evans Blue leakage and higher S100B expression (P<0.01) but lower expressions of tight junction proteins in the amygdala. Pull-down test and Western blotting confirmed that the expression levels of RhoA-GTP, ROCK2 and P-MLC 2 were significantly higher in stress group than in the control group and stress + fasudil group (P<0.05). Transmission electron microscopy revealed obvious ultrastructural changes in the cerebral microvascular endothelial cells in the rat models of restrain stress. Restraint stress induces BBB injury in the amygdala of rats by activating the Rho/ROCK signaling pathway.

Andrographolide Improves ApoE4-Mediated Blood-Brain Barrier Injury by Alleviating Inflammation.

The pathological and physiological studies of Alzheimer's disease (AD) have been in-depth, and apolipoprotein E4 (ApoE4) has been proven to be highly correlated with AD, and clinical and experimental data show that ApoE4 can cause blood-brain barrier (BBB) injury, and the change of BBB permeability is an important factor affecting the development of AD. Andrographolide (Andro), as the active component of the natural plant Andrographis paniculata, has been proven to have anti-inflammatory and antioxidant effects, which have potential neuroprotective effects. To verify the protective effect of Andro on BBB in a short term, our research group used atorvastatin (Atorva)-mediated zebrafish brain injury model and the ApoE4-mediated cell co-culture model of BBB injury to explore the protective effects and mechanisms of Andro on BBB injury. Studies have shown that Andro can inhibit the activation of CypA/NF-κB/MMP-9 signaling pathway and has achieved the effect of antagonizing the inhibition of ApoE4 on intercellular tight junction proteins (occludin, claudin-5, and ZO-1). At the same time, Andro can inhibit the secretion of cell adhesion molecules (VCAM-1 and ICAM-1) in cells, thereby delaying the occurrence and progression of neuroinflammation and playing a protective role in BBB. In conclusion, Andro is a potent natural product which can protect the blood-brain barrier.

Imaging quantitative changes in blood-brain barrier permeability using [18F]2-fluoro-2-deoxy-sorbitol ([18F]FDS) PET in relation to glial cell recruitment in a mouse model of endotoxemia

The quantitative relationship between the disruption of the blood-brain barrier (BBB) and the recruitment of glial cells was explored in a mouse model of endotoxemia. [18F]2-Fluoro-2-deoxy-sorbitol ([18F]FDS) PET imaging was used as a paracellular marker for quantitative monitoring of BBB permeability after i.v injection of increasing doses of lipopolysaccharide (LPS) or vehicle (saline, n = 5). The brain distribution of [18F]FDS (VT, mL.cm−3) was estimated using kinetic modeling. LPS dose-dependently increased the brain VT of [18F]FDS after injection of LPS 4 mg/kg (5.2 ± 2.4-fold, n = 4, p < 0.01) or 5 mg/kg (9.0 ± 9.1-fold, n = 4, p < 0.01) but not 3 mg/kg (p > 0.05, n = 7). In 12 individuals belonging to the different groups, changes in BBB permeability were compared with expression of markers of astrocyte (GFAP) and microglial cell (CD11b) using ex vivo immunohistochemistry. Increased expression of CD11b and GFAP expression was observed in mice injected with 3 mg/kg of LPS, which did not increase with higher LPS doses. Quantitative [18F]FDS PET imaging can capture different levels of BBB permeability in vivo. A biphasic effect was observed with the lowest dose of LPS that triggered neuroinflammation without disruptive changes in BBB permeability, and higher LPS doses that increased BBB permeability without additional recruitment of glial cells.

Dynamic Contrast-enhanced MRI Quantification of Altered Vascular Permeability in Autoimmune Encephalitis.

Background Blood-brain barrier (BBB) permeability change is a possible pathologic mechanism of autoimmune encephalitis. Purpose To evaluate the change in BBB permeability in patients with autoimmune encephalitis as compared with healthy controls by using dynamic contrast-enhanced (DCE) MRI and to explore its predictive value for treatment response in patients. Materials and Methods This single-center retrospective study included consecutive patients with probable or possible autoimmune encephalitis and healthy controls who underwent DCE MRI between April 2020 and May 2021. Automatic volumetric segmentation was performed on three-dimensional T1-weighted images, and volume transfer constant (Ktrans) values were calculated at encephalitis-associated brain regions. Ktrans values were compared between the patients and controls, with adjustment for age and sex with use of a nonparametric approach. The Wilcoxon rank sum test was performed to compare Ktrans values of the good (improvement in modified Rankin Scale [mRS] score of at least two points or achievement of an mRS score of ≤2) and poor (improvement in mRS score of less than two points and achievement of an mRS score >2) treatment response groups among the patients. Results Thirty-eight patients with autoimmune encephalitis (median age, 38 years [IQR, 29-59 years]; 20 [53%] female) and 17 controls (median age, 71 years [IQR, 63-77 years]; 12 [71%] female) were included. All brain regions showed higher Ktrans values in patients as compared with controls (P < .001). The median difference in Ktrans between the patients and controls was largest in the right parahippocampal gyrus (25.1 × 10-4 min-1 [95% CI: 17.6, 43.4]). Among patients, the poor treatment response group had higher baseline Ktrans values in both cerebellar cortices (P = .03), the left cerebellar cortex (P = .02), right cerebellar cortex (P = .045), left cerebral cortex (P = .045), and left postcentral gyrus (P = .03) than the good treatment response group. Conclusion DCE MRI demonstrated that BBB permeability was increased in all brain regions in patients with autoimmune encephalitis as compared with controls, and baseline Ktrans values were higher in patients with poor treatment response in the cerebellar cortex, left cerebral cortex, and left postcentral gyrus as compared with the good response group. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Filippi and Rocca in this issue.

Angiotensin II, blood-brain barrier permeability, and microglia interplay during the transition from pre-to hypertensive phase in spontaneously hypertensive rats.

Hypertension is characterized by upregulation of the renin-angiotensin system, increased blood-brain barrier (BBB) permeability, microglia activation within autonomic nuclei, and an intense sympathoexcitation. There is no information on the interplay of these events during the development of neurogenic hypertension. We sought to identify the interaction and time-course changes of Ang II availability, barrier dysfunction, microglia activation, and autonomic imbalance within autonomic areas during the development of neurogenic hypertension. Sequential changes of hemodynamic/autonomic parameters, BBB permeability, microglia structure/density (IBA-1), and angiotensin II (Ang II) immunofluorescence were evaluated within the paraventricular hypothalamic nucleus, nucleus of the solitary tract, and rostral ventrolateral medulla of Wistar and spontaneously hypertensive rats (SHRs) aged 4 weeks, 5 weeks, 6 weeks, 8 weeks, and 12weeks. The somatosensory cortex and hypoglossal nucleus were also analyzed as non-autonomic control areas. Increased brain Ang II availability (4th-5thweek) was the first observed change, followed by the incipient BBB leakage and increased microglia density (6thweek). From the 5th-6thweeks on, BBB leakage, Ang II, and IBA-1 densities increased continuously, allowing a parallel increase in both Ang II-microglia colocalization and the transition of microglial cells from highly ramified in the basal surveillant condition (4th-5thweek) to shorter process arbors, fewer endpoints, and enlarged soma in the disease-associate condition (6th week to the 12th week). Simultaneously with increased Ang II-microglia colocalization and microglia morphologic phenotypic changes, sympathetic activity and pressure variability increased, autonomic control deteriorated, and blood pressure increased. These responses were not specific for autonomic nuclei but also occurred at a lower magnitude in the somatosensory cortex and hypoglossal nucleus, indicating the predominance of hypertension-induced effects on autonomic areas. No changes were observed in age-matched controls where Ang II density did not change. Brain Ang II density is the initial stimulus to drive coordinated changes in BBB permeability and microglial reactivity. Increased BBB dysfunction allows access of plasma Ang II and increases its local availability and the colocalization and activation of microglial cells. It is a potent stimulus to augments vasomotor sympathetic activity, autonomic imbalance, and pressure elevation during the establishment of hypertension.

The Effects of Transcranial Direct Current Stimulation and Exercise on Salivary S100B Protein Indicated Blood-Brain Barrier Permeability: A Pilot Study

ObjectiveThis study aimed to assess the effect of transcranial direct current stimulation (tDCS) and exercise on blood-brain barrier (BBB) permeability in humans as assessed through the quantification of the salivary protein biomarker S100B. It was hypothesized that active tDCS would induce a significant increase in salivary S100B concentration when compared with sham stimulation and no stimulation. It also was hypothesized that the increase in salivary S100B concentration would be greater after active tDCS and exercise than after tDCS or exercise alone. Materials and MethodsA total of 13 healthy adults (five male, eight female), ranging in age from 21 to 32 years, underwent three experimental conditions (active tDCS, sham tDCS, inactive control). To assess exercise- and tDCS-induced changes in BBB permeability, S100B in saliva was measured. Saliva samples were taken before tDCS, after tDCS, and immediately after a ramped cycling time-to-exhaustion (TTE) task. Active tDCS involved the application of anodal stimulation over the primary motor cortex for 20 minutes at 2 mA. ResultsS100B concentrations in the control condition did not differ significantly from the active condition (estimate = 0.10, SE = 0.36, t = 0.27, p = 0.79) or the sham condition (estimate = 0.33, SE = 0.36, t = 0.89, p = 0.38). Similarly, S100B concentrations at baseline did not differ significantly from post-intervention (estimate = −0.35, SE = 0.34, t = −1.03, p = 0.31) or post-TTE (estimate = 0.66, SE = 0.34, t = 1.93, p = 0.06). ConclusionsThis research provides novel insight into the effect of tDCS and exercise on S100B-indicated BBB permeability in humans. Although the effects of tDCS were not significant, increases in salivary S100B after a fatiguing cycling task may indicate exercise-induced changes in BBB permeability.

SURG-22. MECHANISMS OF BBB PERMEABILITY CHANGES TRIGGERED BY LASER THERAPY

Abstract The blood-brain barrier (BBB) severely limits access of systemically delivered drugs to the brain and brain tumors. Laser interstitial thermal therapy (LITT) has previously been shown to increase BBB permeability in both patients and in mice. The exact mechanisms of LITT-induced BBB permeability changes and their temporal features have yet to be elucidated. To answer this question, we used an established mouse model of LITT to evaluate changes in endothelial cell tight junction integrity and transcytosis over time in normal brain and demonstrate changes in transcytosis in human GBM tumor samples. Mean vesicular density (MVD) was calculated using electron microscopy to evaluate transcytosis. Immunohistochemistry (IHC) was used to assess tight junction integrity (Claudin 5 area/CD31 area) and Mfsd2a levels (Mfsd2a area/CD31 area) along endothelial cells in the laser penumbra. Tight junction integrity decreased 2.5 fold 3 days after LITT, with continued decrease 14 days post-LITT. Mean vesicular density (MVD) in endothelial cells within the laser penumbra increased 3-4 fold compared to sham treated mice, with a peak increase 14 days after LITT before returning to baseline levels 21 days after treatment. These changes in transcytosis correlated with a significant decrease in the intensity of Mfsd2a IHC in the laser penumbra at day 14. Finally, we found similar low levels of transcytosis in non-enhancing and enhancing human GBM tumor samples, confirming that transcytosis is potentially targetable to manipulate BBB permeability. CONCLUSION: Disruptions in tight junction integrity continue up to 14 days after LITT, while LITT-induced increases in transcytosis occur in a delayed fashion, peaking 14 days after laser treatment. Increased transcytosis is inversely correlated with decreased Mfsd2a expression, suggesting a role for Mfsd2a in regulation of LITT-induced BBB changes. Importantly, baseline levels of transcytosis in human GBM appear to be low, such that transcytosis could be targeted to increase BBB permeability.

Apolipoprotein C3-rich low-density lipoprotein (AC3RL) increases BBB permeability and deteriorates cerebral ischemic stroke injury

Abstract Background Ischaemic stroke causes disability due to brain damage resulting from blood supply obstruction or increased permeability of the blood-brain barrier (BBB) that exposes the blood to toxic substances during reperfusion. Apolipoprotein C3 is a crucial triglyceride transport modulator, and its overexpression raises the risk of dyslipidemia and cardiovascular disease. Clinically, we observed that stroke patients have higher levels of apolipoprotein C3-rich low-density lipoprotein (AC3RL) expression than healthy individuals, and they also have worse prognoses. Simultaneously, we found that an increase in AC3RL is involved in endothelial cell apoptosis and inflammatory response, which may be linked to the occurrence of brain injury after stroke. Purpose This study aimed to explore whether the high expression of AC3RL would increase the permeability of the blood-brain barrier, and aggravate brain damage. Methods The intraluminal monofilament model of middle cerebral artery occlusion (MCAO) experiment was carried out using C57BL/6 and apolipoprotein E gene knockout mice (ApoE-/-). WT receive an IV injection of AC3RL, which was separate from stroke patients' plasma. APOE-/- was fed a high-fat diet to promote AC3RL higher expression. We performed 60-minute ischaemic and 7-day reperfusion. The modified neurological severity score (mNSS) method was used to assess motor and neurological scores. Evans blue dye was injected through the tail vein one hour before euth (A) AC3RL, which was separated from stroke patients' plasma. (B) AC3RL concentration in individuals. (C) The white portion of the mice brains TTC stain indicates the site of the injury. (D) Evans blue dye leakage study in mice brains exhibited BBB permeability changes. (E) Assessment of mice's motor and neurological performance using the mNSS. anasia to assess BBB permeability. TTC staining of brain tissue after euthanasia to pinpoint the site of brain damage. Results Evans blue dye leakage was observed in the brain tissues of the group with high AC3RL expression, indicating that the BBB permeability has expanded. The mNSS method revealed a significant rise in mice with high levels of AC3RL expression, which suggested a decline in motor and nervous function. Conclusions Whether endogenous or exogenous, increased expression of AC3RL leads to more severe cerebral ischemic injury and motor dysfunction, which we believe may be due to increased BBB permeability caused by AC3RL. Therefore, AC3RL can be used as a disease predictor in the future, reducing AC3RL will be the main indicator for reducing severe brain injury.Figure 1.Figure 2.

Intracarotid Infusion of Redox-Active Manganese Porphyrin, MnTnBuOE-2-PyP5+, following Reperfusion Improves Long-Term, 28-Day Post-Stroke Outcomes in Rats.

Endovascular mechanical thrombectomy, combined with a tissue plasminogen activator (t-PA), is efficacious as a standard care for qualifying ischemic stroke patients. However, > 50% of thrombectomy patients still have poor outcomes. Manganese porphyrins, commonly known as mimics of superoxide dismutases, are potent redox-active catalytic compounds that decrease oxidative/nitrosative stress and in turn decrease inflammatory responses, mitigating therefore the secondary injury of the ischemic brain. This study investigates the effect of intracarotid MnTnBuOE-2-PyP5+ (BMX-001) administration on long-term, 28-day post-stroke recovery in a clinically relevant setting. The 90 min of transient middle cerebral artery occlusion was performed in young, aged, male, female, and spontaneous hypertension rats. All physiological parameters, including blood pressure, blood gas, glucose, and temperature, were well controlled during ischemia. Either BMX-001 or a vehicle solution was infused through the carotid artery immediately after the removal of filament, mimicking endovascular thrombectomy, and was followed by 7 days of subcutaneous injection. Neurologic deficits and infarct volume were assessed at 28 days in a blinded manner. The effects of BMX-001 on the carotid arterial wall and blood-brain barrier permeability and its interaction with t-PA were assessed in normal rats. There were no intra-group differences in physiological variables. BMX-001-treated stroke rats regained body weight earlier, performed better in behavioral tests, and had smaller brain infarct size compared to the vehicle-treated group. No vascular wall damage and blood-brain barrier permeability changes were detected after the BMX-001 infusion. There was no drug interaction between BMX-001 and t-PA. Intracarotid BMX-001 infusion was safe, and it significantly improved stroke outcomes in rats. These findings indicate that BMX-001 is a candidate drug as an adjunct treatment for thrombectomy procedure to further improve the neurologic outcomes of thrombectomy patients. This study warrants further clinical investigation of BMX-001 as a new stroke therapy.

Determination of Blood-Brain Barrier Hyperpermeability Using Intravital Microscopy.

The blood vessels that vascularize the central nervous system (CNS) exhibit unique properties, termed the blood-brain barrier (BBB). The BBB allows these blood vessels to tightly regulate the movement of ions, molecules, and cells between the blood and the brain. The BBB is held together by tight junctions of the neighboring endothelial cells of the barrier, more specifically by tight junction proteins (TJPs) which can take the form of either integral transmembrane proteins or accessory cytoplasmic membrane proteins. BBB permeability can furthermore be affected by various factors, including but not limited to TJP expression, size, shape, charge, and type of extravascular molecules, as well as the nature of the vascular beds. The BBB is essential for the proper maintenance of CNS function, and its structural integrity has been implicated in several disorders and conditions. For instance, it has been shown that in the cases of traumatic brain injury (TBI), TBI-associated edema, and increased intracranial pressure are primarily caused by cases of hyperpermeability seen because of BBB dysfunction. Intravital microscopy is one of the most reliable methods for measuring BBB hyperpermeability in rodent models of BBB dysfunction in vivo. Here, we describe the surgical and imaging methods to determine the changes in BBB permeability at the level of the pial microvasculature in a mouse model of TBI using intravital microscopy.

Improving measurement of blood-brain barrier permeability with reduced scan time using deep-learning-derived capillary input function

PurposeIn Dynamic contrast-enhanced MRI (DCE-MRI), Arterial Input Function (AIF) has been shown to be a significant contributor to uncertainty in the estimation of kinetic parameters. This study is to assess the feasibility of using a deep learning network to estimate local Capillary Input Function (CIF) to estimate blood-brain barrier (BBB) permeability, while reducing the required scan time. Materials and MethodA total of 13 healthy subjects (younger (<40 y/o): 8, older (> 67 y/o): 5) were recruited and underwent 25-min DCE-MRI scans. The 25 min data were retrospectively truncated to 10 min to simulate a reduced scan time of 10 min. A deep learning network was trained to predict the CIF using simulated tissue contrast dynamics with two vascular transport models. The BBB permeability (PS) was measured using 3 methods: (i) Ca-25min, using DCE-MRI data of 25 min with individually sampled AIF (Ca); (ii) Ca-10min, using truncated 10min data with AIF (Ca); and (iii) Cp-10min, using truncated 10 min data with CIF (Cp). The PS estimates from the Ca-25min method were used as reference standard values to assess the accuracy of the Ca-10min and Cp-10min methods in estimating the PS values. ResultsWhen compared to the reference method(Ca-25min), the Ca-10min and Cp-10min methods resulted in an overestimation of PS by 217 ± 241 % and 48.0 ± 30.2 %, respectively. The Bland Altman analysis showed that the mean difference from the reference was 8.85 ± 1.78 (x10−4 min−1) with the Ca-10min, while it was reduced to 1.63 ± 2.25 (x10−4 min−1) with the Cp-10min, resulting in an average reduction of 81%. The limits of agreement also reduced by up to 39.2% with the Cp-10min. We found a 75% increase of BBB permeability in the gray matter and a 35% increase in the white matter, when comparing the older group to the younger group. ConclusionsWe demonstrated the feasibility of estimating the capillary-level input functions using a deep learning network. We also showed that this method can be used to estimate subtle age-related changes in BBB permeability with reduced scan time, without compromising accuracy. Moreover, the trained deep learning network can automatically select CIF, reducing the potential uncertainty resulting from manual user-intervention.

Zika virus E protein modulates functions of human brain microvascular endothelial cells and astrocytes: implications on blood-brain barrier properties.

Neurotropic viruses can cross the otherwise dynamically regulated blood-brain barrier (BBB) and affect the brain cells. Zika virus (ZIKV) is an enveloped neurotropic Flavivirus known to cause severe neurological complications, such as encephalitis and fetal microcephaly. In the present study, we employed human brain microvascular endothelial cells (hBMECs) and astrocytes derived from human progenitors to establish a physiologically relevant BBB model. We used this model to investigate the effects of ZIKV envelope (E) protein on properties of cells comprising the BBB. E protein is the principal viral protein involved in interaction with host cell surface receptors, facilitating the viral entry. Our findings show that the presence of ZIKV E protein leads to activation of both hBMECs and astrocytes. In hBMECs, we observed a decrease in the expression of crucial endothelial junction proteins such as ZO-1, Occludin and VE-Cadherin, which are vital in establishment and maintenance of the BBB. Consequently, the ZIKV E protein induced changes in BBB integrity and permeability. We also found upregulation of genes involved in leukocyte recruitment along with increased proinflammatory chemokines and cytokines upon exposure to E protein. Additionally, the E protein also led to astrogliosis, evident from the elevated expression of GFAP and Vimentin. Both cell types comprising the BBB exhibited inflammatory response upon exposure to E protein which may influence viral access into the central nervous system (CNS) and subsequent infection of other CNS cells. Overall, our study provides valuable insights into the transient changes that occur at the site of BBB upon ZIKV infection.