Deletion of Secreted Form of Prorenin in the Subfornical Organ Attenuates the Development of DOCA‐salt Induced Hypertension

We and others have previously reported that the (pro)renin receptor plays an important role in the development of hypertension, possibly by non‐proteolytic activation of prorenin in the central nervous system. In the brain, there are two alternate transcripts encoding prorenin; the secreted form of prorenin (sProrenin) encoded by renin‐a, and an intracellular form of prorenin (icProrenin) encoded by renin‐b. The importance of brain sProrenin in the development of hypertension is not yet fully understood. We found that sProrenin is expressed in the subfornical organ (SFO) of the brain, a key brain circumventricular organ involved in BP regulation and body fluid homeostasis. Here, we hypothesize that sProrenin in the SFO regulates BP and body fluid homeostasis, and contributes to the development of hypertension. To test this hypothesis, C57Bl/6J mice were treated with either deoxycorticosterone acetate (DOCA)‐salt (2.5mg/g of DOCA pellet, 0.9% NaCl in drinking water) or Sham (Sham pellet, with tap drinking water) for 2 weeks. SFO tissues were fixed for immuno‐labeling (n=3) of mouse prorenin. We found that prorenin immuno‐reactivity in the SFO was higher in the DOCA‐salt (0.29 ± 0.03 RFU) compared with the Sham (0.10 ± 0.04 RFU, P =0.01) treated mice, suggesting an elevation of prorenin protein level in the SFO. To further examine the functional importance of sProrenin in the SFO, we used Cre‐LoxP recombination to knockdown sProrenin, but not icProrenin, in the Renin‐a Flox mice by micro‐injecting either control adeno‐associated virus (AAV2‐eGFP, n=4) or AAV2‐Cre‐eGFP (n=5) directly to the SFO. Two weeks prior to injection, telemetric transmitters were implanted into the carotid artery and mice were allowed to recover for BP recording in a conscious free moving state. One week following AAV2 injection, mice were given DOCA‐salt (2.5mg/g DOCA, 0.9% NaCl in drinking water) for 2 weeks. The baseline BP (mmHg) was similar between mice that received AAV2‐eGFP (104.2 ± 2.3) compared to AAV2‐Cre‐eGFP (98.1 ± 2.50; p>0.05). DOCA‐salt significantly increased BP in mice that received either AAV2‐eGFP (147.8 ± 5.7) or AAV2‐Cre‐eGFP (130.4 ±1.7) compared with their respective baseline (p<0.0001). However, mice received AAV2‐Cre‐eGFP had significantly lower BP compared with mice received AAV2‐eGFP (p<0.01). Surprisingly, fluid intake was similar between the mice that received AAV2‐Cre‐eGFP (13 ± 1 ml/day) compared to the AAV2‐eGFP treated mice (20 ± 4 ml/day, P =0.15). In sum, the prorenin protein level in the SFO is elevated in DOCA‐salt‐induced hypertensive mice. Selective deletion of sProrenin in the SFO attenuates hypertension without affecting fluid intake following DOCA‐salt treatment. We conclude that sProrenin produced locally within the SFO is involved in regulation of blood pressure and contributes to the pathophysiology of neurogenic hypertension. Support or Funding Information NIH/NHLBI (1R01HL122770) TO YUMEI FENG