Neuronal (Pro)renin Receptor Regulates Angiotensin II Type 1 Receptors‐Mediated Calcium Activity in the Paraventricular Nucleus of the Hypothalamus in Hypertension

The (Pro)renin (PRR) receptor is a new player of the brain renin‐angiotensin system. We recently reported that adeno‐associated virus (AAV2) mediated PRR knockdown in the paraventricular nucleus of the hypothalamus (PVN) attenuated BP (119 ± 3 vs. 139 ± 7 mmHg), and the cardiac sympathetic tone (ΔHR to propranolol: −123 ± 46 vs. −181 ± 16 bpm) and vasomotor sympathetic tone (ΔBP to chlorisondamine: −47 ± 9 vs. −69 ± 5 mmHg) in DOCA‐salt hypertension. PVN is composed of parvocellular and magnocellular neurons expressing angiotensin receptors and vasopressin (AVP), which are key regulators for salt‐sensitive hypertension. Accordingly, we hypothesized that AAV2 mediated PVN‐PRR knockdown attenuates salt‐sensitive hypertension by regulating angiotensin receptors, and the vasopressin synthesis. To test our hypothesis, the PRR‐LoxP mice were injected with either AAV2‐eGPF (GFP) or AAV2‐Cre‐eGFP (Cre) bilaterally into the PVN (1.8×10 8 Vg). Three days post viral injection, mice received either DOCA‐salt (50mg DOCA pellet + 0.9%NaCl drinking solution) or sham (sham pellet + tap water) treatment 14 days. Angiotensin II type 1a (AT 1a R), type 2 (AT 2 R), Mas1 receptors (Mas1R), and vasopressin mRNA levels (Fold change vs. sham) were measured by real time PCR. To identify the cellular distribution of the AAV2 and PRR in the PVN, we used a combination of cholera toxin subunit B (CTB)‐medicated RVLM‐PVN retrograde tracing, immunofluorescent labeling of AVP to identify the RVLM‐PVN Pre‐sympathetic neurons and AVP positive neurons. We found that the PRR was broadly expressed in 95% of the RVLM‐PVN Pre‐sympathetic neurons and AVP positive neurons. AAV2‐eGFP was found to target neurons including the RVLM‐PVN Pre‐sympathetic neurons and AVP positive neurons, but not the astrocytes and microglia evaluated by double immunofluorescent labeling with neural cell specific markers (NeuN, GFAP, Iba1). DOCA‐salt treatment increased the AT 1a R (2.5 ± 0.2), AT 2 R (1.6 ± 0.1), and AVP (6.4 ± 0.2), but decreased the Mas1R (0.06 ± 0.01) mRNA levels compared to the sham (1.0 ± 0.1) treatment. Importantly, Cre injection into the PVN attenuated ( p < 0.01) the elevation of the AT 1a R (1.6 ± 0.1), AT 2 R (0.8 ± 0.1), and AVP (3.7 ± 0.3), without affecting ( p > 0.05) the Mas1R (0.07 ± 0.01) mRNA levels compared with the GFP following DOCA‐salt treatment. To functional determine AT 1a R activity, Ang II‐induced calcium activity in the PVN was evaluated using GCaMP6 calcium biosensor on brain slices. The amplitude (11.8 ± 0.8 vs. 4.8 ± 5.9, % of Maximal Response) and activation sites (13 ± 2 vs. 4 ± 3, Sites/Field of View) of calcium events were significantly elevated in PVN from mice received 2 weeks of DOCA‐salt compared to sham. More importantly, Cre significantly reduced the amplitude (6.5 ± 3.8, % of Maximal Response) and number of activation sites (5 ± 2, Sites/Field of View) of the calcium events compared with the GFP following DOCA‐salt treatment. In summary, PVN‐targeted PRR deletion attenuates DOCA‐salt hypertension, AT 1a R activation and AVP expression in the PVN, and is associated with reduction in sympathetic tone in mice indicating an important role of PVN PRR in BP regulation. Support or Funding Information NIH/NHLBI (R01HL122770) and Innovative Research Grant (17IRG33370128) to Feng This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .