Targeted Nanoparticles to Mitigate Radiation-Induced Blood-Brain Barrier Disruption and Cognitive Impairment

Karima Ait-Aissa; Madelyn Klemmensen; Nathanial Lindsey; Isabella Grumbach

doi:10.1152/physiol.2024.39.S1.2162

Abstract only Background: Damage to neurovascular endothelium contributes to cognitive decline through increased blood-brain barrier (BBB) permeability. In our studies of mice and endothelial cells (ECs) subject to irradiation, we detect increases in mitochondrial reactive oxygen species ( mt ROS), mitochondrial DNA ( mt DNA) damage, and cell-free release of mt DNA. Cell-free mt DNA acts as a damage associated molecular pattern (DAMP), and similarly to bacterial DNA, binds Toll-like receptor 9, triggering a pro-inflammatory and pro-oxidative response. However, these irradiation-induced effects are attenuated with TLR9 inhibition or mt ROS scavenging. Our preliminary data implicate TLR9’s critical role in propagating a feedforward mechanism of sustained oxidative endothelial damage and dysfunction following radiation therapy. We hypothesize that specific inhibition of TLR9 in neurovascular ECs during radiation will prevent BBB permeability and cognitive decline. Thus, the purpose of the study is to use a novel nanoparticle (NP)-based tool to examine the sequela of cranial irradiation and provide proof-of-concept for its use as a mitigator. Methods: To target TLR9 in irradiated ECs, poly (lactic-co-glycolic acid)-based NP coated with cyclic Arg-Gly-Asp (cRGD)-peptide were designed and loaded with TLR9 antagonist (aTLR9, ODN-2088, 2.23ug/mg particle). cRGD-peptide is a ligand for integrin αvβ3, which is highly expressed in ECs post-irradiation (IR). C57Bl6 mice were administered NP-ODN-2088 (aTLR9-NP) or empty-NP (3mg injection) and subjected to unilateral cranial Xray IR (dose of 12Gy). 30d post-IR, memory and learning ability were assessed with the Novel Object Recognition (NOR) and Y-maze tests. The functionality of the NPs was assessed in vivo via BBB permeability, neuronal density, mt DNA damage, and serum levels of mt DNA and in vitro via mtROS production levels and inflammatory markers measurement in human brain microvascular endothelial cells (HBMECs) 5 days post-IR (IR dose of 4Gy). Results: In cultured HBMECs, treatment with aTLR9-NP prevented mt ROS production 120hours post-IR. This correlated with attenuated inflammatory intermediates (p65, TNFa, IL6, and IL8), as compared to treatment with vehicle. In mice, aTLR9-NP treatment preserved integrity of mt DNA isolated from brain tissue and decreased blood levels of circulating cell-free mt DNA. aTLR9-NP treatment showed protective effects on BBB permeability and neuronal dropout, and these findings corresponded with preserved cognition in both, NOR and Y-maze tests. NP treatment caused no changes in alkaline phosphatase, alanine transaminase, aspartate aminotransferase, or bilirubin levels, indicating no liver injury. Conclusion: Inhibition of TLR9 in ECs was observed to prevent radiation-induced BBB permeability, neuronal dropout, and cognitive decline. Our findings support a pathway through which TLR9 links oxidative endothelial injury to neurological pathology. Currently there are no pharmacological options for treating radiation-induced normal tissue injury and targeting TLR9 poses a promising strategy. American Heart Association 2021CDA 853499. NIH R01 EY 031544-02 Veterans Affairs I01 BX000163-12. 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.

Targeted Nanoparticles to Mitigate Radiation-Induced Blood-Brain Barrier Disruption and Cognitive Impairment

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