The Bradykinin B2 Receptor Agonist (NG291) Causes Rapid Onset of Transient Blood-Brain Barrier Disruption Without Evidence of Early Brain Injury

Sergio R Rodríguez-Massó; Michelle A Erickson; William A Banks; Henning Ulrich; Antonio Henrique Martins

doi:10.3389/fnins.2021.791709

The Bradykinin B2 Receptor Agonist (NG291) Causes Rapid Onset of Transient Blood-Brain Barrier Disruption Without Evidence of Early Brain Injury

Front Neurosci. 2021 Dec 15:15:791709. doi: 10.3389/fnins.2021.791709. eCollection 2021.

Authors

Sergio R Rodríguez-Massó¹, Michelle A Erickson^{2

3}, William A Banks^{2

3}, Henning Ulrich⁴, Antonio Henrique Martins¹

Affiliations

¹ Department of Pharmacology and Toxicology, University of Puerto Rico Medical Sciences Campus, San Juan, PR, United States.
² Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA, United States.
³ Division of Gerontology and Geriatric Medicine, Department of Medicine, School of Medicine, University of Washington, Seattle, WA, United States.
⁴ Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil.

Abstract

Background: The blood-brain barrier (BBB) describes the brain's highly specialized capillaries, which form a dynamic interface that maintains central nervous system (CNS) homeostasis. The BBB supports the CNS, in part, by preventing the entry of potentially harmful circulating molecules into the brain. However, this specialized function is challenging for the development of CNS therapeutics. Several strategies to facilitate drug delivery into the brain parenchyma via disruption of the BBB have been proposed. Bradykinin has proven effective in disrupting mechanisms across the blood-tumor barrier. Unfortunately, bradykinin has limited therapeutic value because of its short half-life and the undesirable biological activity elicited by its active metabolites. Objective: To evaluate NG291, a stable bradykinin analog, with selective agonist activity on the bradykinin-B2 receptor and its ability to disrupt the BBB transiently. Methods: Sprague Dawley rats and CD-1 mice were subjected to NG291 treatment (either 50 or 100 μg/kg, intravenously). Time and dose-dependent BBB disruption were evaluated by histological analysis of Evans blue (EB) extravasation. Transcellular and paracellular BBB leakage were assessed by infiltration of ^99mTc-albumin (66.5 KDa) and ¹⁴C-sucrose (340 Da) radiolabeled probes into the brains of CD-1 mice treated with NG291. NG291 influence on P-glycoprotein (P-gp) efflux pump activity was evaluated by quantifying the brain accumulation of ³H-verapamil, a known P-gp substrate, in CD-1 mice. Results: NG291-mediated BBB disruption was localized, dose-dependent, and reversible as measured by EB extravasation. ^99mTc-albumin leakage was significantly increased by 50 μg/kg of NG291, whereas 100 μg/kg of NG291 significantly augmented both ¹⁴C-sucrose and ^99mTc-albumin leakage. NG291 enhanced P-gp efflux transporter activity and was unable to increase brain uptake of the P-gp substrate pralidoxime. NG291 did not evoke significant short-term neurotoxicity, as it did not increase brain water content, the number of Fluoro-Jade C positive cells, or astrocyte activation. Conclusion: Our findings strongly suggest that NG291 increases BBB permeability by two different mechanisms in a dose-dependent manner and increases P-gp efflux transport. This increased permeability may facilitate the penetration into the brain of therapeutic candidates that are not P-gp substrates.

Keywords: blood–brain barrier; bradykinin; bradykinin B2 receptor; drug delivery; peptide.