β-Arrestin2 Deficiency in the Subfornical Organ Alters Fluid Intake and Blood Pressure Regulation

Abstract

The activation of the angiotensin type 1 receptor (AT1R) in the brain through canonical Gαq-mediated signaling results in dipsogenic and pressor responses to angiotensin II (ANG). Non-canonical or β-arrestin-mediated signaling of AT1R activation is hypothesized to counterbalance maladaptive G protein signaling during disease. Recently, we found that global genetic deletion of β-arrestin2 ( Arrb2) resulted in higher 0.15 M saline intake at baseline and an exacerbated increase in blood pressure (BP) in response to deoxycorticosterone acetate-salt treatment, suggesting a protective role for ARRB2 during hypertension. We hypothesized that ARRB2 activation specifically within the subfornical organ (SFO) contributes to fluid intake and BP regulation. Male and female Arrb2FLOX mice received intracerebroventricular (ICV) injection of adeno-associated virus (AAV)-CRE to induce deletion of Arrb2 from the SFO. Infection with ICV AAV-CRE primarily targeted the SFO with few off-targets. Mice receiving ICV-AAV-Cre-GFP are denoted Arrb2SFO-KO, and littermate controls receiving ICV-AAV-GFP are denoted Arrb2WT. First, fluid intake was evaluated using the two-bottle choice paradigm, where mice were presented with two bottles, one containing water and one containing 0.15M NaCl. At baseline, Arrb2SFO-KO mice exhibited a significant increase in saline intake compared to controls ( Arrb2WT=1.7±0.9 and Arrb2SFO-KO 3.0±1.4 mL/day p<0.05; n=13 and 18, respectively). This resulted in a saline preference, meaning mice preferred saline over water by more than 50% by volume. Second, we challenged the animals to water- and sodium-depleted conditions to elevate levels of endogenous ANG. After 18h of water and sodium depletion, mice were subjected to the same two-bottle choice paradigm and fluid intake was recorded for 4 hours. Preliminarily, we found Arrb2SFO-KO mice to exhibit higher 0.15M saline intake in both water replete and depleted conditions ( Arrb2WT=0.39±0.13 vs. Arrb2SFO-KO=0.82±0.80 mL/day; n=7-17 p=0.15 and Arrb2WT=1.66±0.95 vs. Arrb2SFO-KO=1.93±1.07 mL/day; n=9-12 p=0.55). BP was evaluated in response to ICV-ANG infusion (1 μg in 5 min) in awake animals. Arrb2SFO-KO mice had higher BP within the first 15 minutes in response to ICV-ANG infusion ( Arrb2WT=1566±85 vs. Arrb2SFO-KO=1726±61 mmHg*min; n=11 p<0.05). Collectively, selective Arrb2 deletion in the SFO increased saline intake and exacerbated the pressor response to ICV-ANG. Overall, these data indicate that ARRB2 in the SFO is protective against sodium ingestion and increases in BP. Stimulation of the AT1R/β-arrestin axis in the brain may represent a novel strategy to treat hypertension. AHA to NMM, NIH to CDS and JLG. 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.