Abstract

Abstract BACKGROUND The blood-brain-barrier (BBB) is predominantly regulated by brain endothelial cells held together by junctional proteins. The BBB poses a significant hinderance to CNS drug entry of effective chemotherapy agents. Previous BBB studies have shown that disruption of tricellular and/or bicellular tight junctional proteins transiently increased CNS drug permeability. OBJECTIVE To evaluate the effect of drug proteins angubindin-1, C-CPE, and C-CPEmt on tight junction proteins angulin-1, claudin-3, and claudin 5, respectively, aimed at transiently enhancing BBB permeability and decreasing glioma growth. METHODS We evaluated junctional disruption with drug proteins, angubindin-1 (600µg/mL), C-CPE (200µg/mL), and C-CPEmt (200µg/mL) on rat brain endothelium. Endothelial junctional integrity studies were assessed by immunoblotting and cell-cell electrical impedance assays. Treatment effects on rat malignant glioma (S635) was measured via migration and rat glioma models. RESULTS Overall, we observed a time-dependent effect of drug proteins on junctional expression and function. Immunoblotting demonstrated a significant decrease (p< 0.05) in angulin-1 expression 5-hours after angubindin-1 treatment, while claudin-3 and claudin-5 expression barely decreased between 2 and 24-hours after C-CPE and C-CPEmt treatment, respectively. Cell-cell integrity was disrupted by 73%, 52%, and 69% compared with control, 3-hours after angubindin-1, C-CPE, and C-CPEmt treatment, respectively. Studies assessing qualitative junctional expression changes after drug proteins are ongoing. Gliomas cells expressed high angulin-1, and interestingly, migration was 50% decreased with angubindin-1 treatment, yet no migration changes were evident with C-CPE or C-CPEmt treatment. Rat glioma model studies evaluating liposomal doxorubicin combined with angubindin-1 are currently being explored to display effects on CNS drug concentrations, cytotoxicity, junctional expression, and survival. DISCUSSION Transient disruption of BBB tricellular junctions was seen with angubindin-1 treatment. Additionally, cell migration was hindered in angulin-1 overexpressing gliomas. These findings are promising and demonstrate the need for more combinational therapies aimed at increasing BBB permeability while also impairing glioma progression.

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