Degree Of Blood-brain Barrier Disruption Research Articles

Abstract TP17: Increased Interstitial Free Water Is Detected In Regions Of Increased Blood-brain Barrier Disruption In The White Matter Of Patients With Cerebral Small Vessel Disease.

Background: Diffusion tensor imaging (DTI) can be used to detect the accumulation of interstitial free water (FW) in the white matter of patients with cerebral small vessel disease (cSVD). Dynamic susceptibility contrast (DSC) imaging can be used to measure disruption of the blood-brain barrier (BBB). We hypothesized that regions of increased BBB disruption detected with DSC would show increased free water detected with DTI. Methods: A subset of patients enrolled in an ongoing study investigating the pathogenesis of cSVD were included. All patients had evidence of cSVD and a history of stroke >3 months prior to imaging. MRIs were performed with both DTI and DSC. White matter was segmented out from gray matter and CSF. FW was calculated from the DTI, and BBB permeability was calculated from aligned DSC. Regions of BBB disruption were grouped into 0.05% intervals ranging from 0-5%. For each echelon of BBB disruption, the average free water in that region was calculated for each patient. Mixed effects linear regression was used to test whether the degree of BBB disruption was associated with colocalized mean FW across all subjects while covarying for age and sex. Results: There were 11 subjects included in the analysis with a median age of 70, 45% were female. Increasing BBB disruption was associated with increased colocalized FW (beta = 0.13 [0.008 - 0.018], p < 0.0001). The figure shows a scatter of all data points with slopes fitted for each individual patient. Within subject linear regression of FW with BBB was significant for all patients and for the 9 patients with p<0.001, the R2 values ranged from 0.83 to 0.97 with a mean value of 0.91, suggesting that in most cases the FW increase is attributable largely to the disruption of the BBB. Conclusions: Disruption of the BBB leads to increased FW in the white matter of patients with cSVD. This proof of principle study demonstrates how these two biomarkers may be informative in when studying the pathogenesis of cSVD.

Influence of Acoustic Parameters and Sonication Schemes on Transcranial Blood–Brain Barrier Disruption Induced by Pulsed Weakly Focused Ultrasound

Pulsed ultrasound combined with microbubbles use can disrupt the blood–brain barrier (BBB) temporarily; this technique opens a temporal window to deliver large therapeutic molecules into brain tissue. There are published studies to discuss the efficacy and safety of the different ultrasound parameters, microbubble dosages and sizes, and sonication schemes on BBB disruption, but optimal the paradigm is still under investigation. Our study is aimed to investigate how different sonication parameters, time, and microbubble dose can affect BBB disruption, the dynamics of BBB disruption, and the efficacy of different sonication schemes on BBB disruption. Method: We used pulsed weakly focused ultrasound to open the BBB of C57/B6 mice. Evans blue dye (EBD) was used to determine the degree of BBB disruption. With a given acoustic pressure of 0.56 MPa and pulse repetitive frequency of 1 Hz, burst lengths of 10 ms to 50 ms, microbubbles of 100 μL/kg to 300 μL/kg, and sonication times of 60 s to 150 s were used to open the BBB for parameter study. Brain EBD accumulation was measured at 1, 4, and 24 h after sonication for the time–response relationship study; EBD of 100 mg/kg to 200 mg/kg was administered for the dose–response relationship study; EBD injection 0 to 6 h after sonication was performed for the BBB disruption dynamic study; brain EBD accumulation induced by one sonication and two sonications was investigated to study the effectiveness on BBB disruption; and a histology study was performed for brain tissue damage evaluation. Results: Pulsed weakly focused ultrasound opens the BBB extensively. Longer burst lengths and a larger microbubble dose result in a higher degree of BBB disruption; a sonication time longer than 60 s did not increase BBB disruption; brain EBD accumulation peaks 1 h after sonication and remains 81% of the peak level 24 h after sonication; the EBD dose administered correlates with brain EBD accumulation; BBB disruption decreases as time goes on after sonication and lasts for 6 h at least; and brain EBD accumulation induced by two sonication increases 74.8% of that induced by one sonication. There was limited adverse effects associated with sonication, including petechial hemorrhages and mild neuronal degeneration. Conclusions: BBB can be opened extensively and reversibly by pulsed weakly focused ultrasound with limited brain tissue damage. Since EBD combines with albumin in plasma to form a conjugate of 83 kDa, these results may simulate ultrasound-induced brain delivery of therapeutic molecules of this size scale. The result of our study may contribute to finding the optimal paradigm of focused ultrasound-induced BBB disruption.

The Association Between Neurological Prognosis and the Degree of Blood-Brain Barrier Disruption in Cardiac Arrest Survivors Who Underwent Target Temperature Management.

This study aimed to compare day-specific associations of blood-brain barrier (BBB) disruption with neurological outcome in survivors of out-of-hospital cardiac arrest (OHCA) treated with target temperature management (TTM) and lumbar drainage. This retrospective single-center study included 68 survivors of OHCA who underwent TTM between April 2018 and December 2019. The albumin quotient (QA) was calculated as QA = albumincerebrospinal fluid/albuminserum immediately (day 1) and 24 (day 2), 48 (day 3), and 72h (day 4) after the return of spontaneous circulation. The degree of BBB disruption was weighted using the following scoring system: QA value of 0.007 or less (normal), QA value greater than 0.007-0.01 (mild), QA value greater than 0.01-0.02 (moderate), and QA value greater than 0.02 (severe). Points were assigned as follows: 0 (normal), 1 (mild), 4 (moderate), and 9 (severe). Neurological outcome was determined at 6months after the return of spontaneous circulation, as well as cerebral performance category (CPC), dichotomized as good (CPC score 1-2) and poor (CPC score 3-5) outcome. We enrolled 68 patients (48 men, 71%); 37 (54%) patients had a poor neurological outcome. The distributions of poor versus good outcomes at 6months in patients with moderate and severe BBB disruption were 19 of 22 (80%) vs. 18 of 46 (50%) on day 1, 31 of 37 (79%) vs. 6 of 31 (32%) on day 2, 32 of 37 (81%) vs. 5 of 31 (30%) on day 3, and 32 of 39 (85%) vs. 5 of 29 (30%) on day 4 (P < 0.001), respectively. Using receiver operating characteristic analyses, optimal cutoff values (sensitivity, specificity) of QA levels for the prediction of neurological outcome were as follows: day 1, greater than 0.009 (56.8%, 87.1%); day 2, greater than 0.012 (81.1%, 87.1%); day 3, greater than 0.013 (83.8%, 87.1%); day 4, greater than 0.013 (86.5%, 87.1%); the sum of all time points, greater than 0.039 (89.5%, 79.4%); and scoring system, greater than 9 (91.9%, 87.1%). In this proof of concept study, QA was associated with poor neurological outcome in survivors of OHCA treated with TTM with no contraindication to lumbar drainage. A large multicenter prospective study is needed to validate the utility of BBB disruption as a prognosticator of neurological outcome.

Abstract PO013: Blood-brain barrier dysfunction leads to neuronal loss in glioma pathology

Abstract The blood-brain barrier (BBB) defines the physiological function of the brain. Its disruption is common in multiple neuropathological diseases. Accumulating evidence suggest that BBB alterations occur in early stages of neurodegenerative diseases, being associated with neuronal loss processes. The vascular abnormalities and BBB leakage characterize the progression of gliomas, however it is unclear their correlation with the neurodegeneration observed in such tumors. Methods: To establish the different gene signatures we have performed an in-silico analysis using glioma data sets and we have validated the results in a cohort of 26 gliomas (high and low grade) and 7 controls from non-tumor donors. We have also used patient-derived xenografts (PDXs) to correlate the degree of BBB disruption (measured by IgG extravasation immunofluorescence staining) with the neuronal loss (evaluated by NeuN immunofluorescence staining) and with the motor impairment (assessed by a rotarod test). Results: We measured the expression of a series of signatures associated with different biological processes, relevant for glioma development. The “Synapse” and the “BBB dysfunction” signatures were inversely correlated during glioma development. Thus, the most aggressive tumors were associated with BBB breakdown and neuronal dysfunction. These phenotypes correlate with the mesenchymal subtype of gliomas and with a shorter survival. The vascular normalization induced by the isocitrate dehydrogenase 1 (IDH1) mutations rescued the neuronal loss, reducing the motor impairment and increasing the overall survival of PDX-bearing mice. Conclusions: Our data demonstrate that vascular normalization can revert the neuronal loss and the aggressiveness in those tumors, which is linked to the appearance of motor dysfunction symptoms. Overall, we propose that disruption of the BBB is associated with neurodegeneration in glioma patients. These results could help us to understand the progression of this pathology as well as other neurodegenerative diseases and therefore to improve their therapeutic approaches. Citation Format: Pablo Mata-Martínez, Berta Segura-Collar, Maria Garranzo-Asensio, Juan M. Sepúlveda-Sánchez, Aurelio Hernández-Lain, Pilar Sánchez-Gómez, Ricardo Gargini. Blood-brain barrier dysfunction leads to neuronal loss in glioma pathology [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PO013.

Effect of Adipose-Derived Mesenchymal Stem Cell Administration and Mild Hypothermia Induction on Delayed Neuronal Death After Transient Global Cerebral Ischemia

Global cerebral ischemia is a cause of poor prognosis after resuscitation from cardiac arrest. Various attempts have been made to minimize global cerebral ischemia but none been more effective than mild hypothermia induction. A few studies have shown the effect of mesenchymal stem cells on global cerebral ischemia, but no studies have compared this effect with mild hypothermia or assessed any possible interaction. We aimed to show the effect of mesenchymal stem cells on delayed neuronal death after global cerebral ischemia and to compare this effect with mild hypothermia. Experimental study. Animal research laboratory. Adult male Sprague-Dawley rats weighing 250-300 g. Rats were subjected to 7 minutes of transient global cerebral ischemia and randomized into four groups: control, mild hypothermia, injection of human adipose-derived mesenchymal stem cells, and combined application of mild hypothermia and mesenchymal stem cells, along with four sham groups treated identically. Rats were euthanized 7 days after global cerebral ischemia. Degree of neuronal death in hippocampus was significantly higher in control than in other groups. The number of activated microglia was higher in control group than in other groups and was higher in mild hypothermia than shams, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells. Degree of blood-brain barrier disruption and the count of infiltrated neutrophils were significantly higher in control than in other groups. Degree of oxidative injury was significantly higher in control than other groups. It was higher in mild hypothermia than sham groups, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells and was higher in mesenchymal stem cells group than sham groups. Significantly, worse functional results were found in control than in other groups. Administration of mesenchymal stem cells after transient global cerebral ischemia has a prominent protective effect on delayed neuron death, even compared with mild hypothermia.

Fluorescein Isothiocyanate (FITC)-Dextran Extravasation as a Measure of Blood-Brain Barrier Permeability.

The blood-brain barrier (BBB) is formed in part by vascular endothelial cells that constitute the capillaries and microvessels of the brain. The function of this barrier is to maintain homeostasis within the brain microenvironment and buffer the brain from changes in the periphery. A dysfunction of the BBB would permit circulating molecules and pathogens typically restricted to the periphery to enter the brain and interfere with normal brain function. As increased permeability of the BBB is associated with several neuropathologies, it is important to have a reliable and sensitive method that determines BBB permeability and the degree of BBB disruption. A detailed protocol is presented for assessing the integrity of the BBB by transcardial perfusion of a 10,000 Da FITC-labeled dextran molecule and its visualization to determine the degree of extravasation from brain microvessels. © 2017 by John Wiley & Sons, Inc.

Safety Validation of Repeated Blood–Brain Barrier Disruption Using Focused Ultrasound

The purpose of this study was to investigate the effects on the brain of multiple sessions of blood–brain barrier (BBB) disruption using focused ultrasound (FUS) in combination with micro-bubbles over a range of acoustic exposure levels. Six weekly sessions of FUS, using acoustical pressures between 0.66 and 0.80 MPa, were performed under magnetic resonance guidance. The success and degree of BBB disruption was estimated by signal enhancement of post-contrast T1-weighted imaging of the treated area. Histopathological analysis was performed after the last treatment. The consequences of repeated BBB disruption varied from no indications of vascular damage to signs of micro-hemorrhages, macrophage infiltration, micro-scar formations and cystic cavities. The signal enhancement on the contrast-enhanced T1-weighted imaging had limited value for predicting small-vessel damage. T2-weighted imaging corresponded well with the effects on histopathology and could be used to study treatment effects over time. This study demonstrates that repeated BBB disruption by FUS can be performed with no or limited damage to the brain tissue.

Cationic surface charge enhances early regional deposition of liposomes after intracarotid injection.

Rapid first pass uptake of drugs is necessary to increase tissue deposition after intraarterial (IA) injection. Here we tested whether brain tissue deposition of a nanoparticulate liposomal carrier could be enhanced by coordinated manipulation of liposome surface charge and physiological parameters, such as IA injection during transient cerebral hypoperfusion (TCH). Different degrees of blood-brain barrier disruption were induced by focused ultrasound in three sets of Sprague-Dawley rats. Brain tissue retention was then compared for anionic, cationic, and charge-neutral liposomes after IA injection combined with TCH. The liposomes contained a non-exchangeable carbocyanine membrane optical label that could be quantified using diffuse reflectance spectroscopy (DRS) or visualized by multispectral imaging. Real-time concentration-time curves in brain were obtained after each liposomal injection. Having observed greater tissue retention of cationic liposomes compared to other liposomes in all three groups, we tested uptake of cationic liposomes in C6 tumor bearing rats. DRS and multispectral imaging of postmortem sections revealed increased liposomal uptake by the C6 brain tumor as compared to non-tumor contralateral hemisphere. We conclude that regional deposition of liposomes can be enhanced without BBB disruption using IA injection of cationic liposomal formulations in healthy and C6 tumor bearing rats.

Effect of Ultrasound Treatment on Brain Edema in a Traumatic Brain Injury Model with the Weight Drop Method

Background: For the treatment of traumatic brain edema, an efficient modality has not yet emerged. There have been many studies to date which have reported the employment of low-frequency ultrasound for blood-brain barrier disruption (BBBD). However, the authors have observed that low-intensity ultrasound increases water permeability without cellular damage in cartilage cells. We have therefore attempted to observe the effects of applying this low-intensity ultrasound to an experimental animal model. Methods: A traumatic brain injury rat model was established according to the weight drop method developing the traumatic brain edema. The degree of BBBD was measured by the changes in the water content and spectrophotometric absorbance of Evans blue dye in the cerebrum after low-frequency ultrasound. Results: The cerebral water content levels showed that the BBBD gradually increased after impact and thereafter decreased after 6 h. After low-frequency ultrasound exposure, the values of water content and spectrophotometric absorbance of Evans blue dye were the lowest at 0 h, and were increased at 2 and 5 h of ultrasonic exposure (after impact). Conclusion: We suggest that traumatic brain edema in the rat model may be alleviated by low-frequency ultrasound, and low-frequency ultrasound might be proposed as a novel treatment modality for brain edema.

CXCL13 and CXCL12 in Central Nervous System Lymphoma Patients

Homing of malignant lymphocytes to the central nervous system (CNS) may play a role in the pathogenesis of CNS lymphoma. In this study, we evaluated the chemokines CXCL12 and CXCL13 in the cerebrospinal fluid (CSF) and serum of patients with CNS lymphoma. Samples from 30 patients with CNS lymphoma (23 with primary and 7 with secondary CNS lymphoma; all B-cell lymphoma) and 40 controls (10 patients with other CNS malignancies and 30 without a malignant CNS disease) were examined. CXCL12 and CXCL13 concentrations were measured using enzyme-linked immunosorbent assays. The grade of blood-brain barrier disruption was estimated by the CSF/serum albumin ratio. CNS lymphoma patients and controls did not differ in CXCL12 serum and CSF levels. Serum levels of CXCL13 were generally low. CXCL13 CSF levels, however, were significantly higher in CNS lymphoma patients as compared with controls (P < 0.0001). Chemokine levels in CSF and serum did not correlate. In CNS lymphoma, CXCL13 concentration in CSF correlated with the degree of blood-brain barrier disruption (R = 0.66; P = 0.003). Elevated CSF levels of CXCL12 and CXCL13 measured in seven CNS lymphoma patients during therapy decreased in five patients who responded to chemotherapy and increased in two with lymphoma progression. Our results suggest a production of CXCL13 within the CNS of CNS lymphoma patients, which decreases with response to therapy. Thus, CXCL13 may represent a marker for further diagnostic and prognostic studies.

Effects of VEGF on the Blood-Brain Barrier Disruption Caused by Hyperosmolarity

This study was performed to test whether disruption of the blood-brain barrier (BBB) caused by hyperosmolarity could be related to vascular endothelial growth factor (VEGF), using anti-VEGF antibody and ciclopirox olamine (CPX), an inducer of VEGF. CPX 50 mg/kg or normal saline was given intraperitoneally to male Wistar rats 18 h before BBB disruption. Two craniotomies were made on the ipsilateral cortex (IC-1 and IC-2) where the BBB would be disrupted, and a third hole was made on the contralateral cortex (CC) to expose the cortices. We applied normal saline (to IC-1 and the CC) or anti-VEGF antibody (to IC-2) for 90 min before BBB disruption with intracarotid injection of 25% mannitol. The degree of BBB disruption was determined by measuring the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid and the volume of ³H-dextran distribution. The protein levels of VEGF were determined with Western blot analysis. In the control animals, hyperosmolar mannitol significantly increased (415%) the K_i in IC-1. The K_i was attenuated with anti-VEGF antibody application (–28%, p < 0.05). Even though the protein levels of VEGF were strongly increased with CPX pretreatment, this upregulation did not alter the hyperosmolar BBB disruption in the saline- or in the antibody-treated cortex. The data on the volume of dextran distribution followed the same pattern as that of the K_i but without a statistically significant difference between IC-1 and IC-2 in either group. Our data demonstrated that hyperosmolar BBB disruption could be attenuated with anti-VEGF antibody. However, upregulation of VEGF with CPX did not alter the degree of hyperosmolar BBB disruption with or without anti-VEGF antibody treatment. This study suggests that the contribution of VEGF in hyperosmolar BBB disruption is limited.

Effects of Deferoxamine on Blood-Brain Barrier Disruption and VEGF in Focal Cerebral Ischemia

Abstract Objective: Deferoxamine, an iron chelator, is reported to induce hypoxia-inducible factor 1 (HIF-1) that leads to transcriptional activation of numerous genes including vascular endothelial growth factor (VEGF) that is known to increase blood–brain barrier (BBB) permeability. This study was performed to test whether deferoxamine would disrupt BBB further in focal cerebral ischemia by altering the level of VEGF. Methods: Rats were injected intraperitoneally with normal saline (control group), 300 mg/kg deferoxamine mesylate 18 (deferoxamine 18 group) or 48 (deferoxamine 48 group) hours before middle cerebral artery (MCA) occlusion. The transfer coefficient (Ki) of 14C-α-aminoisobutyric acid (14C-AIB) and the volume of 3H-dextran distribution were determined to measure the degree of BBB disruption 1 hour after MCA occlusion. Immunohistochemistry using a monoclonal VEGF antibody was performed to determine the protein level of VEGF. Results: In all groups of animals, the Ki of the ischemic cortex (IC...

Effects of 17β-Estradiol on Blood-Brain Barrier Disruption during Focal Cerebral Ischemia in Younger and Older Rats

This study was performed to compare the effects of 17beta-estradiol on blood-brain barrier disruption in focal cerebral ischemia between younger and older rats. Younger (three-month-old) and older (24-month-old) ovariectomized female Fischer 344 rats were studied. In one half of each age group, a 500 microg 17beta-estradiol 21-day release pellet and in another half, a vehicle pellet was implanted 21 days before the experiments. One hour after middle cerebral artery occlusion, the transfer coefficient (Ki) of 14C-alpha-aminoisobutyric acid and the volume of 3H-dextran distribution were determined to examine the degree of blood-brain barrier disruption. In all four groups, the Ki in the ischemic cortex was higher than in the corresponding contralateral cortex. There was no significant difference in the Ki in both cortices among the groups. The volume of dextran distribution of the ischemic cortex was only greater than in the corresponding contralateral cortex in the older 17beta-estradiol-treated group, and the volume of that group was greater than the younger 17beta-estradiol-treated group (4.00 +/- 1.29 VS. 2.13 +/- 0.88 ml/100 g). After analyzing the difference in Ki between the ischemic cortex and the contralateral cortex in each animal, the difference was significantly greater in the older 17beta-estradiol-treated rats than the older vehicle-treated rats (3.40 +/- 2.10 VS. 1.26 +/- 1.44 microl/g/min). In the younger rats, however, 17beta-estradiol did not significantly affect the difference. Our data showed that 17beta-estradiol treatment failed to attenuate the BBB disruption in the cerebral ischemic cortex in the older or younger Fischer 344 rats. However, our data also suggest the possibility that 17beta-estradiol could aggravate the BBB disruption in older rats.

Uptake of 18F-fluorocholine, 18F-fluoro-ethyl-L-tyrosine and 18F-fluoro-2-deoxyglucose in F98 gliomas in the rat

The positron emission tomography (PET) tracers (18)F-fluoro-ethyl-L: -tyrosine (FET), (18)F-fluorocholine (N,N-dimethyl-N-[(18)F]fluoromethyl-2-hydroxyethylammonium (FCH]) and (18)F-fluoro-2-deoxyglucose (FDG) are used in the diagnosis of brain tumours. The aim of this study was threefold: (a) to assess the uptake of the different tracers in the F98 rat glioma, (b) to evaluate the impact of blood-brain barrier (BBB) disruption and microvessel density (MVD) on tracer uptake and (c) to compare the uptake in the tumours to that in the radiation injuries (induced by proton irradiation of healthy rats) of our previous study. F98 gliomas were induced in 26 rats. The uptake of FET, FCH and FDG was measured using autoradiography and correlated with histology, disruption of the BBB and MVD. The mean FET, FCH and FDG standardised uptake values (SUVs) in the tumour and the contralateral normal cortex (in parentheses) were 4.19+/-0.86 (1.32+/-0.26), 2.98+/-0.58 (0.51+/-0.11) and 11.02+/-3.84 (4.76+/-1.77) respectively. MVD was significantly correlated only with FCH uptake. There was a trend towards a negative correlation between the degree of BBB disruption and FCH uptake and a trend towards a positive correlation with FET uptake. The ratio of the uptake in tumours to that in the radiation injuries was 1.97 (FCH), 2.71 (FET) and 2.37 (FDG). MVD displayed a significant effect only on FCH uptake. The degree of BBB disruption seems to affect the accumulation of FET and FCH, but not FDG. Mean tumour uptake for all tracers was significantly higher than the accumulation in radiation injuries.

Effects of VEGF and nitric oxide synthase inhibition on blood–brain barrier disruption in the ischemic and non-ischemic cerebral cortex

Objectives: This study was performed to compare the effects of exogenous vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) inhibition on blood–brain barrier (BBB) disruption in the ischemic cortex (IC) and non-ischemic contralateral cortex (CC) during the early stage of focal cerebral ischemia in rats.Methods: A middle cerebral artery (MCA) was occluded after a craniotomy in each rat under isoflurane anesthesia. Two more craniotomies were performed over the contralateral non-ischemic hemisphere to expose cerebral cortex. For the control rats, the normal saline patches were applied to all three craniotomy holes (control group). To inhibit NOS, NG-nitro-L-arginine-methyl ester (L-NAME) (10 mg/kg) was administered i.v. 20 minutes after MCA occlusion (L-NAME group). In another group, VEGF (10−10 M) was topically applied 30 minutes after MCA occlusion on the IC as well as one of the holes of the contralateral cortex (VEGF group). To investigate the effects of the combination of VEGF and L-NAME, both L-NAME and VEGF were administered as described above (L-NAME+ VEGF group). The transfer coefficient (Ki) of 14C-α-aminoisobutyric acid and the volume of 3H-dextran (70000 Da) distribution were determined to measure the degree of BBB disruption at 1 hour after MCA occlusion.Results: In the control group, Ki of the IC was significantly higher than the contralateral cortex (CC) (p<0.005). VEGF application increased the Ki of the IC further when compared with the control group (+51%, p<0.05%). L-NAME administration produced no significant decrease in the Ki of the IC when compared with the control group. With L-NAME+ VEGF administration, the Ki of the IC became significantly lower than that of the VEGF alone (−38%, p<0.005). Thus, L-NAME produced a much greater decrease in the Ki of the IC in the VEGF treated than the control animals (p<0.05). In the non-IC, VEGF, L-NAME, or their combination did not affect BBB disruption. The volume of dextran distribution followed a similar pattern to Ki.Discussion: Our data suggest that even in the early stage of focal cerebral ischemia, the degree of BBB disruption in response to the exogenous VEGF is much greater in the ischemic than in the non-IC and that the mechanism of the increase of BBB disruption by VEGF in the IC involves the NOS pathway.

Effects of 17beta-estradiol on blood-brain barrier disruption during focal ischemia in rats.

This study was performed to test whether 17beta-estradiol could attenuate the blood-brain barrier disruption caused by middle cerebral artery occlusion in the ovariectomized rats. Rats aged twelve to fourteen weeks were used in this study. Their ovaries were removed one week prior to the implantation of the pellets. For the 17beta-estradiol group, a 500 microg 17beta-estradiol 21 day-release pellet was implanted and for the control group, a vehicle pellet was implanted 21 days before the experiments. One hour after middle cerebral artery occlusion under isoflurane anesthesia, the transfer coefficient of 14C-alpha-aminoisobutyric acid (104 Daltons) and the volume of 3H-dextran (70,000 Daltons) distribution were determined to represent the degree of blood-brain barrier disruption. Blood pressures and blood gases were similar between controls and 17beta-estradiol-treated rats. In both groups, the transfer coefficient of the ischemic cortex was higher than that of the corresponding contralateral cortex (control: Ischemic Cortex 12.5 +/- 5.9 microl/g/min, Contralateral Cortex 3.0 +/- 1.6, p < 0.001; 17beta-estradiol: Ischemic Cortex 6.7 +/- 3.3 micro l/g/min, Contralateral Cortex 2.2 +/- 0.9, p < 0.01). There was no significant difference in the transfer coefficient of the contralateral cortex between these two groups. However, the transfer coefficient of the Ischemic Cortex of the 17beta-estradiol-treated animals was 46 % lower than that of the control, vehicle-treated rats (p < 0.05). The increase of the volume of 3H-dextran distribution with middle cerebral artery occlusion was significant in the vehicle-treated rats (Ischemic Cortex: 6.4 +/- 2.7 ml/100 g, Contralateral Cortex: 3.8 +/- 0.8, p < 0.01) but not in the 17beta-estradiol-treated animals. Our data suggest that chronic 17beta-estradiol treatment was effective in reducing blood-brain barrier disruption during focal ischemia in the ovariectomized rats.

Quantitative Analysis of Papaverine-Mediated Blood–Brain Barrier Disruption in Rats

The blood–brain barrier (BBB) is a permeability barrier of interconnected brain capillary endothelial cells. Intraarterial infusion of papaverine relieves cerebral vasospasms by inhibiting smooth muscle contractions and it may simultaneously lead to a disruption of BBB permeability. To date, the mechanism underlying this phenomenon and the quantification of BBB disruption remains elusive. We first examined the changes in cerebrovascular permeability after an intracarotid infusion of papaverine (0.20%) in rats by an in situ brain perfusion technique. We then demonstrated that changes in cerebrovascular permeability depend on the concentration of papaverine. This is the first study in which the degree of BBB disruption was accurately quantified in terms of [14C]sucrose and it was demonstrated that papaverine has a prolonged effect on cerebrovascular permeability. This result suggests the importance of in vivo experiments for a precise evaluation of permeability for many other agents, particularly for the central nervous system.

In vivo assessment of the window of barrier opening after osmotic blood-brain barrier disruption in humans.

Osmotic blood-brain barrier (BBB) disruption induced by intraarterial infusion of mannitol is used in conjunction with chemotherapy to treat human brain tumors. The time course to barrier closure, or the so-called therapeutic window, has been examined in animals but little information is available in humans. The authors, therefore assessed the time course to barrier closure after osmotic BBB disruption in humans. Disruption of the BBB was demonstrated using 99mTc-glucoheptonate (TcGH) single-photon emission computerized tomography (SPECT) scanning in 12 patients who were treated monthly with combination chemotherapy in conjunction with BBB disruption. The primary diagnosis was primary central nervous system lymphoma in seven patients and primitive neuroectodermal tumors in five. The TcGH (20 mCi) was injected at 1- to 480-minute intervals after osmotic BBB disruption, and patients underwent SPECT scanning after 4 hours. A total of 38 studies was performed. Good-to-excellent BBB disruption was obtained in 29 procedures and poor-to-moderate disruption was seen in the other nine studies. The TcGH indices correlated with the degree of BBB disruption as measured postprocedure on contrast-enhanced CT scans (r = 0.852). Mean baseline TcGH indices were 1.02+/-0.07. For the group of patients with good-to-excellent disruptions the mean indices at 1 minute postdisruption measured 2.19+/-0.18. After 40 minutes no significant change was noted (mean index 2.13+/-0.2). Then the indices declined more steeply and at 120 minutes after the disruption the index was 1.36+/-0.02. A very slow decline was noted between 120 and 240 minutes after mannitol infusion. At 240 minutes the barrier was still open for all good-to-excellent disruptions (index 1.33+/-0.08) but at 480 minutes the mean indices had returned to the baseline level. Results of these in vivo human studies indicate that the time course to closure of the disrupted BBB for low-molecular-weight complexes is longer than previously estimated. The barrier is widely open during the first 40 minutes after osmotic BBB disruption and returns to baseline levels only after 6 to 8 hours following the induction of good or excellent disruption. These findings have important clinical implications for the design of therapeutic protocols.

Blood-brain barrier damage in patients with bacterial meningitis: association with tumor necrosis factor-alpha but not interleukin-1 beta.

Brain damage after meningeal infection could result from impairment of cerebral endothelial cell functions and disruption of blood-brain barriers. Tumor necrosis factor-alpha (TNF alpha) and interleukin-1 beta (IL-1 beta) produce many of their effects by acting on endothelial cells. This study correlates levels of TNF alpha and IL-1 beta in paired cerebrospinal fluid (CSF) and serum samples with the degree of blood-brain barrier damage, as manifested by CSF to serum albumin quotient, in 48 patients with bacterial meningitis and 66 controls. CSF levels of TNF alpha and IL-1 beta in bacterial meningitis were significantly higher than in controls. Intrathecal levels of TNF alpha, but not IL-1 beta, correlated with albumin quotient (P less than .001), with degree of blood-brain barrier disruption (P less than .001), and with disease severity and indices of meningeal inflammation. Sequential CSF samples demonstrated that IL-1 beta and TNF alpha disappear from the CSF within 24 h of antibiotic treatment. Data presented here suggest that TNF alpha is related to blood-brain barrier damage in bacterial meningitis and that its effect could be dissociated from that of IL-1 beta.

Radionuclide assessment of blood-brain barrier disruption performed for chemotherapy of high grade malignant brain gliomas

Compared to the conventional mode of chemotherapy of malignant brain gliomas following surgery and radiation therapy, chemotherapy after transient disruption of the blood-brain barrier coupled with intraarterial administration of methotrexate improved median survival from 12–14 to 22 months in our experience. Technetium-99m-DTPA brain scintigraphy played a unique and important role in the documentation of optimum blood-brain barrier disruption. Patients with excellent clinical outcome had significantly ( P < 0.0005) better blood-brain barrier disruption than patients with poor outcome. The results indicate that the clinical outcome is related to the degree of blood-brain barrier disruption.