Abstract 185: Utilization of Nanoformulated Copper/Zinc Superoxide Dismutase (CuZnSOD) to Attenuate the Central Angiotensin II-Induced Pressor Response

Abstract

Elevated levels of superoxide (O 2 .- ) in the brain and dysregulation of angiotensin II (AngII)-dependent neural mechanisms are associated with cardiovascular diseases, such as hypertension. For improved brain delivery of CuZnSOD protein, a O 2 .- -specific scavenging enzyme, we developed SOD nano, a polyion complex with a polyethylene glycol corona and polyethyleneimine core that electrostatically binds CuZnSOD protein. Our previous studies in cultured neurons indicate that SOD nano enters neurons through active endocytosis and localizes to various organelles where it scavenges O 2 .- and effectively inhibits AngII intra-neuronal signaling. Here, we hypothesized that centrally administered SOD nano ameliorates AngII-dependent neurogenic hypertension by delivering functional CuZnSOD protein to AngII sensitive brain regions. For these studies, C57Bl/6 male mice were instrumented with carotid catheter radiotelemeters to record mean arterial pressure (MAP). Intracerebroventricular (ICV) cannulae were implanted for the administration of SOD nano and daily injections of AngII (350 ng) before and after SOD nano treatment. The average AngII-induced increase in MAP for 3 days prior to treatment was 9.2 + 0.7 mmHg. ICV-administered SOD nano (113 U SOD activity) significantly inhibited the acute, central AngII pressor response for at least 3 days (ΔMAP D1= 1.3 + 1.4 mmHg; D2 = -2.7 + 3.7 mmHg; D3 = 3.4 + 4.1; n=3, p< 0.05 vs. AngII response 3 days prior). In contrast, ICV-administered saline did not alter the AngII-induced pressor response (ΔMAP D1 = 8.0 + 2.8 mmHg, D2 = 9.6 + 1.5, D3 = 7.3 + 1.2, n=4). Additionally, free CuZnSOD protein (ICV, 113 U SOD activity) did not attenuate the central AngII pressor response (ΔMAP D1 = 6.6 + 0.4 mmHg, D2 = 10.7 + 2.3, D3 = 16.3 + 8.4, n=2); thus, suggesting enhanced stability and/or cellular uptake of the SOD nano compared to free protein. Notably, the distribution of fluorescently labeled SOD nanozyme administered ICV was detected throughout the ventricular system, primarily in ependymal cells lining the brain ventricles and in the choroid plexus. These data suggest that this nanotechnology approach is effective in delivery CuZnSOD protein in vivo to AngII sensitive brain regions where it inhibits brain angiotensinergic signaling.