Abstract Body: Intro: The exact effects of extracellular vesicles (EVs) on renal hemodynamics and blood pressure remain to be determined. In this study, we examined the effect of EVs from hypertensive mice and humans on Angiotensin II (ANG II)-induced vascular response in an ex vivo model of isolated and perfused renal afferent arterioles (Af-Arts) and also assessed their effect on renal blood flow (RBF) and systolic blood pressure (SBP) in normotensive mice in vivo.
Method: Circulating EVs were collected from mice with ANG II-induced hypertension (n=5) and hypertensive humans (n=2). Differential centrifugation (DCF) (5000G x 30min, followed by 17.000G for 30 minutes) was applied to generate an EV pellet (p20) which was subsequently run through size exclusion chromatography (SEC). EV size and concentration was determined by nanoparticle tracking analysis and spectral flow cytometry. Basic EV characterization was performed with cryo electron microscopy and western blotting of EV and non EV proteins.
Following a 30-minute perfusion with EVs (p20 EV pellet (10¹⁰/ml) or fraction 1-3 or 4-6 of SEC (doses 1-9^7/ml)), dose-response curves to ANG II (10^-12 to 10^-6 mol/l) were measured in Af-Arts of C57BL/6 mice. Similar doses of EVs were infused into the penile vein of C57BL/6 mice and RBF and SBP were measured. As EVs might deliver AT1R we explored the final common pathway in vasoconstriction in vessels treated with EVs from hypertensive animals vs controls by performing immunoblotting of myosin light chain II S19 phosphorylation.
Results: EVs deriving from ANG II-treated mice and hypertensive humans, but not those from normotensive control mice and humans, significantly enhanced the vasoconstrictor response to ANG II in Af-Arts of C57BL/6 mice. The same vasoconstrictor response was observed when Af-Arts were perfused with combined EV preps from DCF and SEC (fraction 1-3 vs fraction 1-6) from hypertensive animals. In vivo injection of EVs from ANG II-treated hypertensive mice reduced RBF and increased SBP in C57BL/6 mice compared to EVs from normotensive control mice. Immunoblotting of myosin light chain II S19 phosphorylation was inconclusive.
Conclusion: These data suggest that EVs from hypertensive animals and humans directly affect ANG II response, renal hemodynamic and blood pressure regulation. Further work is needed to identify the EV effector candidate for enhanced ANG II response and possible effect on ART1 activation.