Application of Delayed Contrast Extravasation Magnetic Resonance Imaging for Depicting Subtle Blood-Brain Barrier Disruption in a Traumatic Brain Injury Model.

The blood-brain barrier (BBB) is composed of brain microvasculature that provides selective transport of solutes from the systemic circulation into the central nervous system to protect the brain and spinal microenvironment. Damage to the BBB in the acute phase after traumatic brain injury (TBI) is recognized as a major underlying mechanism leading to secondary long-term damage. Because of the lack of technological ability to detect subtle BBB disruption (BBBd) in the chronic phase, however, the presence of chronic BBBd is disputable. Thus, the dynamics and course of long-term BBBd post-TBI remains elusive. Thirty C57BL/6 male mice subjected to TBI using our weight drop closed head injury model and 19 naïve controls were scanned by magnetic resonance imaging (MRI) up to 540 days after injury. The BBB maps were calculated from delayed contrast extravasation MRI (DCM) with high spatial resolution and high sensitivity to subtle BBBd, enabling depiction and quantification of BBB permeability. At each time point, 2-6 animals were sacrificed and their brains were extracted, sectioned, and stained for BBB biomarkers including: blood microvessel coverage by astrocyte using GFAP, AQP4, ZO-1 gaps, and IgG leakage. We found that DCM provided depiction of subtle yet significant BBBd up to 1.5 years after TBI, with significantly higher sensitivity than standard contrast-enhanced T1-weighted and T2-weighted MRI (BBBd volumes main effect DCM/T1/T2 p < 0.0001 F(2,70) = 107.3, time point p < 0.0001 F(2,133, 18.66) = 23.53). In 33% of the cases, both in the acute and chronic stages, there was no detectable enhancement on standard T1-MRI, nor detectable hyperintensities on T2-MRI, whereas DCM showed significant BBBd volumes. The BBBd values of TBI mice at the chronic stage were found significantly higher compared with age matched naïve animals at 30, 60, and 540 days. The calculated BBB maps were histologically validated by determining significant correlation between the calculated levels of disruption and a diverse set of histopathological parameters obtained from different brain regions, presenting different components of the BBB. Cumulative evidence from recent years points to BBBd as a central component of the pathophysiology of TBI. Therefore, it is expected that routine use of highly sensitive non-invasive techniques to measure BBBd, such as DCM with advanced analysis methods, may enhance our understanding of the changes in BBB function after TBI. Application of the DCM technology to other CNS disorders, as well as to normal aging, may shed light on the involvement of chronic subtle BBBd in these conditions.

BBB opening by low pulsed electric fields, depicted by delayed-contrast MRI, enables efficient delivery of therapeutic doxorubicin doses into mice brains.

BACKGROUND: Pharmacological treatment of CNS diseases is limited due to the presence of the blood-brain barrier (BBB). Recent years showed significant advancement in the field of CNS drug delivery enablers, with technologies such as MR-guided focused ultrasound reaching clinical trials. This have inspired researchers in the field to invent novel brain barriers opening (BBo) technologies that are required to be simple, fast, safe and efficient. One such technology, recently developed by us, is BDF (Barrier Disrupting Fields), based on low pulsed electric fields (L-PEFs) for opening the BBB in a controlled, safe, reversible and non-invasive manner. Here, we conducted an in vivo study to show that BDF is a feasible technology for delivering Doxorubicin (Doxo) into mice brain. Means for depicting BBBo levels were developed and applied for monitoring the treatment and predicting response. Overall, the goals of the presented study were to demonstrate the feasibility for delivering therapeutic Doxo doses into naïve and tumor-bearing mice brains and applying delayed-contrast MRI (DCM) for monitoring the levels of BBBo. METHODS: L-PEFs were applied using plate electrodes placed on the intact skull of naïve mice. L-PEFs/Sham mice were scanned immediately after the procedure by DCM ("MRI experiment"), or injected with Doxo and Trypan blue followed by delayed (4 h) perfusion and brain extraction ("Doxo experiment"). Doxo concentrations were measured in brain samples using confocal microscopy and compared to IC50 of Doxo in glioma cell lines in vitro. In order to map BBBo extent throughout the brain, pixel by pixel MR image analysis was performed using the DCM data. Finally, the efficacy of L-PEFs in combination with Doxo was tested in nude mice bearing intracranial human glioma tumors. RESULTS: Significant amount of Doxo was found in cortical regions of all L-PEFs-treated mice brains (0.50 ± 0.06 µg Doxo/gr brain) while in Sham brains, Doxo concentrations were below or on the verge of detection limit (0.03 ± 0.02 µg Doxo/gr brain). This concentration was x97 higher than IC50 of Doxo calculated in gl261 mouse glioma cells and x8 higher than IC50 of Doxo calculated in U87 human glioma cells. DCM analysis revealed significant BBBo levels in the cortical regions of L-PEFs-treated mice; the average volume of BBBo in the L-PEFs-treated mice was x29 higher than in the Sham group. The calculated BBBo levels dropped exponentially as a function of BBBo threshold, similarly to the electric fields distribution in the brain. Finally, combining non-invasive L-PEFs with Doxo significantly decreased brain tumors growth rates in nude mice. CONCLUSIONS: Our results demonstrate significant BBBo levels induced by extra-cranial L-PEFs, enabling efficient delivery of therapeutic Doxo doses into the brain and reducing tumor growth. As BBBo was undetectable by standard contrast-enhanced MRI, DCM was applied to generate maps depicting the BBBo levels throughout the brain. These findings suggest that BDF is a promising technology for efficient drug delivery into the brain with important implications for future treatment of brain cancer and additional CNS diseases.

Definition of the contribution of an Osteopontin-producing CD11c+ microglial subset to Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of incurable dementia and represents a critical public health issue as the world's population ages. Although microglial dysregulation is a cardinal feature of AD, the extensive heterogeneity of these immunological cells in the brain has impeded our understanding of their contribution to this disease. Here, we identify a pathogenic microglial subset which expresses the CD11c surface marker as the sole producer of Osteopontin (OPN) in the 5XFAD mouse model of AD. OPN production divides Disease-Associated Microglia (DAM) into two functionally distinct subsets, i.e., a protective CD11c+OPN- subset that robustly ingests amyloid ß (Aß) in a noninflammatory fashion and a pathogenic CD11c+OPN+ subset that produces proinflammatory cytokines and fails to ingest significant amounts of Aß. Genetic ablation of OPN or administration of monoclonal anti-OPN antibody to 5XFAD mice reduces proinflammatory microglia, plaque formation, and numbers of dystrophic neurites and results in improved cognitive function. Analysis of brain tissue from AD patients indicates that levels of OPN-producing CD11c+ microglia correlate strongly with the degree of cognitive deficit and AD neuropathology. These findings define an OPN-dependent pathway to disease driven by a distinct microglial subset, and identify OPN as a novel therapeutic target for potentially effective immunotherapy to treat AD.

Albumin-EDTA-Vanadium Is a Powerful Anti-Proliferative Agent, Following Entrance into Glioma Cells via Caveolae-Mediated Endocytosis.

Human serum albumin (HSA) is efficiently taken up by cancer cells as a source of carbon and energy. In this study, we prepared a monomodified derivative of HSA covalently linked to an EDTA derivative and investigated its efficacy to shuttle weakly anti-proliferative EDTA associating ligands such as vanadium, into a cancer cell line. HSA-S-MAL-(CH2)2-NH-CO-EDTA was found to associate both with the vanadium anion (+5) and the vanadium cation (+4) with more than thrice the associating affinity of those ligands toward EDTA. Both conjugates internalized into glioma tumor cell line via caveolae-mediated endocytosis pathway and showed potent anti-proliferative capacities. IC50 values were in the range of 0.2 to 0.3 µM, potentiating the anti-proliferative efficacies of vanadium (+4) and vanadium (+5) twenty to thirty fold, respectively. HSA-EDTA-VO++ in particular is a cancer permeable prodrug conjugate. The associated vanadium (+4) is not released, nor is it active anti-proliferatively prior to its engagement with the cancerous cells. The bound vanadium (+4) dissociates from the conjugate under acidic conditions with half maximal value at pH 5.8. In conclusion, the anti-proliferative activity feature of vanadium can be amplified and directed toward a cancer cell line. This is accomplished using a specially designed HSA-EDTA-shuttling vehicle, enabling vanadium to be anti-proliferatively active at the low micromolar range of concentration.

Potential neurotoxicity of titanium implants: Prospective, in-vivo and in-vitro study.

Titanium dioxide (TiO2) is a frequently used biomaterial, particularly in orthopedic and dental implants, and it is considered an inert and benign compound. This has resulted in toxicological scrutiny for TiO2 in the past decade, with numerus studies showing potential pathologic downstream effects. Herein we describe case report of a 77-year-old male with subacute CNS dysfunction, secondary to breakdown of a titanium-based carotid stent and leading to blood levels 1000 times higher (3 ppm) than the reported normal. We prospectively collected tissues adjacent to orthopedic implants and found a positive correlation between titanium concentration and time of implant in the body (r = 0.67, p < 0.02). Rats bearing titanium implants or intravascularly treated with TiO2 nanoparticles (TiNP) exhibited memory impairments. A human blood-brain barrier (BBB) in-vitro model exposed to TiNP showed paracellular leakiness, which was corroborated in-vivo with the decrease of key BBB transcripts in isolated blood vessels from hippocampi harvested from TiNP-treated mice. Titanium particles rapidly internalized into brain-like endothelial cells via caveolae-mediated endocytosis and macropinocytosis and induced pro-inflammatory reaction with increased expression of pro-inflammatory genes and proteins. Immune reaction was mediated partially by IL-1R and IL-6. In summary, we show that high levels of titanium accumulate in humans adjacent to orthopedic implants, and our in-vivo and in-vitro studies suggest it may be neurotoxic.

Endothelial Iron Homeostasis Regulates Blood-Brain Barrier Integrity via the HIF2α-Ve-Cadherin Pathway.

The objective of this study was to investigate the molecular response to damage at the blood brain barrier (BBB) and to elucidate critical pathways that might lead to effective treatment in central nervous system (CNS) pathologies in which the BBB is compromised. We have used a human, stem-cell derived in-vitro BBB injury model to gain a better understanding of the mechanisms controlling BBB integrity. Chemical injury induced by exposure to an organophosphate resulted in rapid lipid peroxidation, initiating a ferroptosis-like process. Additionally, mitochondrial ROS formation (MRF) and increase in mitochondrial membrane permeability were induced, leading to apoptotic cell death. Yet, these processes did not directly result in damage to barrier functionality, since blocking them did not reverse the increased permeability. We found that the iron chelator, Desferal© significantly decreased MRF and apoptosis subsequent to barrier insult, while also rescuing barrier integrity by inhibiting the labile iron pool increase, inducing HIF2α expression and preventing the degradation of Ve-cadherin specifically on the endothelial cell surface. Moreover, the novel nitroxide JP4-039 significantly rescued both injury-induced endothelium cell toxicity and barrier functionality. Elucidating a regulatory pathway that maintains BBB integrity illuminates a potential therapeutic approach to protect the BBB degradation that is evident in many neurological diseases.

Dietary alpha linolenic acid in pregnant mice and during weaning increases brain docosahexaenoic acid and improves recognition memory in the offspring.

Docosahexaenoic acid (DHA) is critical for normal brain development and function. DHA is in danger of being significantly reduced in the human food supply, and the question of whether its metabolic precursor, the essential n-3 alpha linolenic acid (ALA) during pregnancy, can support fetal brain DHA levels for optimal neurodevelopment, is fundamental. Female mice were fed either ALA-enriched or Control diet during pregnancy and lactation. The direct effect of maternal dietary ALA on lipids was analyzed in liver, red blood cells, brain and brain vasculature, together with genes of fatty acid metabolism and transport in three-week-old offspring. The long-term effect of maternal dietary ALA on brain fatty acids and memory was studied in 19-week-old offspring. Three-week-old ALA offspring showed higher levels of n-3 fatty acids in liver, red blood cell, blood-brain barrier (BBB) vasculature and brain parenchyma, DHA enrichment in brain phospholipids and higher gene and protein expression of the DHA transporter, major facilitator superfamily domain containing 2a, compared to Controls. 19-week-old ALA offspring showed higher brain DHA levels and better memory performance than Controls. The increased brain DHA levels induced by maternal dietary ALA during pregnancy-lactation, together with the up-regulated levels of major facilitator superfamily domain containing 2a, may indicate a mode for greater DHA uptake with long-term impact on better memory in ALA offspring.

miR-504 modulates the stemness and mesenchymal transition of glioma stem cells and their interaction with microglia via delivery by extracellular vesicles.

Glioblastoma (GBM) is a highly aggressive tumor with poor prognosis. A small subpopulation of glioma stem cells (GSCs) has been implicated in radiation resistance and tumor recurrence. In this study we analyzed the expression of miRNAs associated with the functions of GSCs using miRNA microarray analysis of these cells compared with human neural stem cells. These analyses identified gene clusters associated with glioma cell invasiveness, axonal guidance, and TGF-ß signaling. miR-504 was significantly downregulated in GSCs compared with NSCs, its expression was lower in GBM compared with normal brain specimens and further decreased in the mesenchymal glioma subtype. Overexpression of miR-504 in GSCs inhibited their self-renewal, migration and the expression of mesenchymal markers. The inhibitory effect of miR-504 was mediated by targeting Grb10 expression which acts as an oncogene in GSCs and GBM. Overexpression of exogenous miR-504 resulted also in its delivery to cocultured microglia by GSC-secreted extracellular vesicles (EVs) and in the abrogation of the GSC-induced polarization of microglia to M2 subtype. Finally, miR-504 overexpression prolonged the survival of mice harboring GSC-derived xenografts and decreased tumor growth. In summary, we identified miRNAs and potential target networks that play a role in the stemness and mesenchymal transition of GSCs and the miR-504/Grb10 pathway as an important regulator of this process. Overexpression of miR-504 exerted antitumor effects in GSCs as well as bystander effects on the polarization of microglia via delivery by EVs.

Caspase-1 has a critical role in blood-brain barrier injury and its inhibition contributes to multifaceted repair.

BACKGROUND: Excessive inflammation might activate and injure the blood-brain barrier (BBB), a common feature of many central nervous system (CNS) disorders. We previously developed an in vitro BBB injury model in which the organophosphate paraoxon (PX) affects the BBB endothelium by attenuating junctional protein expression leading to weakened barrier integrity. The objective of this study was to investigate the inflammatory cellular response at the BBB to elucidate critical pathways that might lead to effective treatment in CNS pathologies in which the BBB is compromised. We hypothesized that caspase-1, a core component of the inflammasome complex, might have important role in BBB function since accumulating evidence indicates its involvement in brain inflammation and pathophysiology. METHODS: An in vitro human BBB model was employed to investigate BBB functions related to inflammation, primarily adhesion and transmigration of peripheral blood mononuclear cells (PBMCs). Caspase-1 pathway was studied by measurements of its activation state and its role in PBMCs adhesion, transmigration, and BBB permeability were investigated using the specific caspase-1 inhibitor, VX-765. Expression level of adhesion and junctional molecules and the secretion of pro-inflammatory cytokines were measured in vitro and in vivo at the BBB endothelium after exposure to PX. The potential repair effect of blocking caspase-1 and downstream molecules was evaluated by immunocytochemistry, ELISA, and Nanostring technology. RESULTS: PX affected the BBB in vitro by elevating the expression of the adhesion molecules E-selectin and ICAM-1 leading to increased adhesion of PBMCs to endothelial monolayer, followed by elevated transendothelial-migration which was ICAM-1 and LFA-1 dependent. Blocking caspase-8 and 9 rescued the viability of the endothelial cells but not the elevated transmigration of PBMCs. Inhibition of caspase-1, on the other hand, robustly restored all of barrier insults tested including PBMCs adhesion and transmigration, permeability, and VE-cadherin protein levels. The in vitro inflammatory response induced by PX and the role of caspase-1 in BBB injury were corroborated in vivo in isolated blood vessels from hippocampi of mice exposed to PX and treated with VX-765. CONCLUSIONS: These results shed light on the important role of caspase-1 in BBB insult in general and specifically in the inflamed endothelium, and suggest therapeutic potential for various CNS disorders, by targeting caspase-1 in the injured BBB.

Naphthoquinone-Dopamine Hybrids Inhibit α-Synuclein Aggregation, Disrupt Preformed Fibrils, and Attenuate Aggregate-Induced Toxicity.

Accumulation and aggregation of the intrinsically disordered protein α-synuclein (α-Syn) into amyloid fibrils are hallmarks of a series of heterogeneous neurodegenerative disorders, known as synucleinopathies and most notably Parkinson's disease (PD). The crucial role of α-Syn aggregation in PD makes it an attractive target for the development of disease-modifying therapeutics that would inhibit α-Syn aggregation or disrupt its preformed fibrillar assemblies. To this end, we have designed and synthesized two naphthoquinone-dopamine-based hybrid small molecules, NQDA and Cl-NQDA, and demonstrated their ability to inhibit in vitro amyloid formation by α-Syn using ThT assay, CD, TEM, and Congo red birefringence. Moreover, these hybrid molecules efficiently disassembled preformed fibrils of α-Syn into nontoxic species, as evident from LUV leakage assay. NQDA and Cl-NQDA were found to have low cytotoxicity and they attenuated the toxicity induced by α-Syn towards SH-SY5Y neuroblastoma cells. NQDA was found to efficiently cross an in vitro human blood-brain barrier model. These naphthoquinone-dopamine based derivatives can be an attractive scaffold for therapeutic design towards PD.