By The Blood-brain Barrier Integrity Research Articles

Abstract 3461: Focused ultrasound induced blood-tumor barrier permeability of combinatorial chemotherapy

Abstract Background: Incidence of patients having brain metastasis of breast cancer has increased due to enhanced treatment for peripheral disease. Breast cancer brain metastasis is often fatal and occurs in 15-20% of patients diagnosed with stage IV breast cancer. Traditional chemotherapy delivery to the brain is limited by the blood-brain barrier (BBB) and blood-tumor barrier (BTB). Low intensity focused ultrasound (LIFU) is a unique technique recently investigated to non-invasively disrupt these barriers and aid neuro-modulation. Herein, we demonstrate the use of a clinical LIFU device to modulate blood-tumor permeability and deliver combined chemotherapy in a novel preclinical model of brain metastases of breast cancer. Methods: Brain colonizing MDA-MB-231Br cells transfected with luciferase were injected into athymic Nu/Nu female mice by intracardiac injection into the left ventricle (per mouse 175,000 cells). Brain metastasis was allowed to develop, and tumor burden was monitored by bioluminescent imaging IVIS Spectrum CT (Perkin Elmer). Mice were randomized into sham or single treatment or combined treatment groups on Day 21 (Doxil nanoparticles 5.6 mg/kg or Paclitaxel 10mg/kg). Mice receiving LIFU were placed on a specially designed animal restraint with the skull partially immersed in degassed water. T1 weighted MRI was used to identify and localize sonication spots within the cortex, and mice were sonicated using 0.4uL/kg Definity© at 0.3 cavitation dose for 60sec. Treatment with LIFU was continued once weekly for three consecutive weeks. Survival and tumor burden was recorded until mice developed neurological symptoms. LIFU induced blood-brain barrier breakdown in healthy mice was also analyzed by in-situ brain perfusion with 14CSucrose, 3HGlucose, and 3HIvermectin to monitor BBB integrity and transporter function. Results: Mice receiving LIFU+paclitaxel+Doxil-NP showed significantly lower tumor burden (peak area 635.9) and higher median survival of 60 days as compared to vehicle (29d) and LIFU+vehicle (32d) groups. Analysis of BBB permeability in healthy mice demonstrated significantly higher passive permeability marker accumulation than non-sonicated contralateral hemisphere. Conclusion: Timing the combined chemotherapy with LIFU induced windows of maximal BBB opening resulted in slower tumor progression and increased survival in a preclinical model of breast cancer brain metastasis. Future directions aim to combine these results and evaluate underlying mechanisms of enhanced permeability post-LIFU. Citation Format: Tasneem A. Arsiwala, Kathryn E. Blethen, Samuel A. Sprowls, Ross A. Fladeland, Brooke Keilkowski, Morgan Glass, Trenton Pritt, Peng Wang, Ali Rezai, Paul R. Lockman. Focused ultrasound induced blood-tumor barrier permeability of combinatorial chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3461.

DDRE-49. TRANSIENT OPENING OF THE BLOOD-BRAIN BARRIER BY VASOACTIVE PEPTIDES TO INCREASE CNS DRUG DELIVERY: REALITY VERSUS WISHFUL THINKING?

Abstract BACKGROUND Drug delivery to treat neurologic disease and cancers of the central nervous system (CNS) is severely limited by the blood-brain barrier (BBB). Vasoactive peptides (VAPs) such as regadenoson, adenosine, and labradimil have been shown in animal studies to transiently open the BBB, and regadenoson is currently under investigation in humans to determine if it might improve CNS drug delivery. There is currently limited information regarding the potential for other VAPs to open the BBB transiently. METHODS We performed a review of the literature evaluating the physiologic effects of vasoactive peptides on the vasculature of the brain and systemic organs. To assess the likelihood that a vasoactive peptide might transiently disrupt the BBB, we devised a four-tier classification system to organize data available in the literature which factors in alterations in BBB integrity and effects on normal brain vasculature and systemic blood vessels. This data was further sorted based on whether it comes from humans, animals, or in vitro systems. RESULTS We identified 38 VAPs with potential BBB permeability-altering properties. To date, none of these has been shown to open the BBB in humans. Thirteen VAPs increased BBB permeability in rodents. The remaining 25 had favorable physiologic effects on blood vessels but lack specific information on permeability changes to the BBB. We ranked VAPs in a four-tier ranking system related to their known physiologic actions. CONCLUSION Rodent studies document that analogs of bradykinin and adenosine transiently disrupt the BBB leading to higher chemotherapy concentrations in the CNS. VAPs remain an understudied class of drugs with the potential to increase drug delivery to the CNS. Dozens of VAPs have yet to be formally evaluated for this important clinical effect. This retrospective review summarizes the available data on VAPs highlighting agents that deserve further in vitro and in vivo investigations.

Angiogenesis and Blood-Brain Barrier Permeability in Vascular Remodeling after Stroke.

Angiogenesis, the growth of new blood vessels, is a natural defense mechanism helping to restore oxygen and nutrient supply to the affected brain tissue following an ischemic stroke. By stimulating vessel growth, angiogenesis may stabilize brain perfusion, thereby promoting neuronal survival, brain plasticity, and neurologic recovery. However, therapeutic angiogenesis after stroke faces challenges: new angiogenesis-induced vessels have a higher than normal permeability, and treatment to promote angiogenesis may exacerbate outcomes in stroke patients. The development of therapies requires elucidation of the precise cellular and molecular basis of the disease. Microenvironment homeostasis of the central nervous system is essential for its normal function and is maintained by the blood-brain barrier (BBB). Tight junction proteins (TJP) form the tight junction (TJ) between vascular endothelial cells (ECs) and play a key role in regulating the BBB permeability. We demonstrated that after stroke, new angiogenesis-induced vessels in peri-infarct areas have abnormally high BBB permeability due to a lack of major TJPs in ECs. Therefore, promoting TJ formation and BBB integrity in the new vessels coupled with speedy angiogenesis will provide a promising and safer treatment strategy for improving recovery from stroke. Pericyte is a central neurovascular unite component in vascular barriergenesis and are vital to BBB integrity. We found that pericytes also play a key role in stroke-induced angiogenesis and TJ formation in the newly formed vessels. Based on these findings, in this article, we focus on regulation aspects of the BBB functions and describe cellular and molecular special features of TJ formation with an emphasis on role of pericytes in BBB integrity during angiogenesis after stroke.

Understanding the Uptake of Nanomedicines at Different Stages of Brain Cancer Using a Modular Nanocarrier Platform and Precision Bispecific Antibodies.

Increasing accumulation and retention of nanomedicines within tumor tissue is a significant challenge, particularly in the case of brain tumors where access to the tumor through the vasculature is restricted by the blood–brain barrier (BBB). This makes the application of nanomedicines in neuro-oncology often considered unfeasible, with efficacy limited to regions of significant disease progression and compromised BBB. However, little is understood about how the evolving tumor–brain physiology during disease progression affects the permeability and retention of designer nanomedicines. We report here the development of a modular nanomedicine platform that, when used in conjunction with a unique model of how tumorigenesis affects BBB integrity, allows investigation of how nanomaterial properties affect uptake and retention in brain tissue. By combining different in vivo longitudinal imaging techniques (including positron emission tomography and magnetic resonance imaging), we have evaluated the retention of nanomedicines with predefined physicochemical properties (size and surface functionality) and established a relationship between structure and tissue accumulation as a function of a new parameter that measures BBB leakiness; this offers significant advancements in our ability to relate tumor accumulation of nanomedicines to more physiologically relevant parameters. Our data show that accumulation of nanomedicines in brain tumor tissue is better correlated with the leakiness of the BBB than actual tumor volume. This was evaluated by establishing brain tumors using a spontaneous and endogenously derived glioblastoma model providing a unique opportunity to assess these parameters individually and compare the results across multiple mice. We also quantitatively demonstrate that smaller nanomedicines (20 nm) can indeed cross the BBB and accumulate in tumors at earlier stages of the disease than larger analogues, therefore opening the possibility of developing patient-specific nanoparticle treatment interventions in earlier stages of the disease. Importantly, these results provide a more predictive approach for designing efficacious personalized nanomedicines based on a particular patient’s condition.

GDNF-expressing macrophages mitigate loss of dopamine neurons and improve Parkinsonian symptoms in MitoPark mice

Glial cell line-derived neurotrophic factor (GDNF) is the most potent neuroprotective agent tested in cellular and animal models of Parkinson’s disease (PD). However, CNS delivery of GDNF is restricted by the blood-brain barrier (BBB). Using total body irradiation as transplant preconditioning, we previously reported that hematopoietic stem cell (HSC) transplantation (HSCT)-based macrophage-mediated gene therapy could deliver GDNF to the brain to prevent degeneration of nigrostriatal dopamine (DA) neurons in an acute murine neurotoxicity model. Here, we validate this therapeutic approach in a chronic progressive PD model – the MitoPark mouse, with head shielding to avoid inducing neuroinflammation and compromising BBB integrity. Bone marrow HSCs were transduced ex vivo with a lentiviral vector expressing macrophage promoter-driven GDNF and transplanted into MitoPark mice exhibiting well developed PD-like impairments. Transgene-expressing macrophages infiltrated the midbrains of MitoPark mice, but not normal littermates, and delivered GDNF locally. Macrophage GDNF delivery markedly improved both motor and non-motor symptoms, and dramatically mitigated the loss of both DA neurons in the substantia nigra and tyrosine hydroxylase-positive axonal terminals in the striatum. Our data support further development of this HSCT-based macrophage-mediated GDNF delivery approach in order to address the unmet need for a disease-modifying therapy for PD.

Alzheimer Disease and Cellular Mechanisms of Memory Storage

Most ongoing efforts to combat Alzheimer disease (AD) are focused on treating its clinical symptoms, but the neuropathologic changes underlying AD appear decades earlier and become essentially irreversible by the time the disease reaches its clinical stages. This necessitates treating AD at preclinical stages, which requires a better understanding of the primary mechanisms leading to AD pathology. Here I argue that such an understanding calls for addressing perhaps the most puzzling question in AD-why the underlying pathology selectively impairs neurons that are involved in memory formation and storage. Memory formation is associated with epigenetic chromatin modifications and may, therefore, be accompanied by the synthesis of proteins unique to neurons involved in memory. These proteins could be recognized by the immune system as "nonself" antigens. This does not happen in the healthy brain because of its isolation from the immune system by the blood-brain barrier (BBB). All risk factors for AD impair the BBB, which may allow the immune system to attack memory-involved neurons and make them vulnerable to AD-associated pathology. This hypothesis is testable and, if confirmed, could redirect therapeutic efforts toward maintaining BBB integrity people belonging to AD risk groups rather than treating them when it is too late.