Prorenin Induces Intracellular Signaling And Reactive Oxygen Species In The Brainstem.

The activation of the brain renin angiotensin system (RAS) is required for the blood pressure (BP) elevation in models of neurogenic hypertension (HT). However, it remains unclear whether the expression of prorenin and its binding to prorenin receptor (PRR) in particular brain regions is required for the activation of the brain RAS. Compelling new evidence indicates that renin is expressed in the proximity of the rostral ventrolateral medulla (RVLM) and the nucleus ambiguous within the brainstem where RAS genes including PRR, angiotensinogen, and angiotensin receptors were also detected. Thus, we hypothesized that prorenin acts within the brainstem to induce extracellular signal-regulated kinases (ERK1/2) phosphorylation and generation of reactive oxygen species (ROS) resulting in BP elevation through a PRR-dependent mechanism. Neonatal brainstem neurons obtained from mice at postnatal day 1-3 were cultured and subsequently incubated in presence of recombinant prorenin (rProrenin; 100 nM) or vehicle. rProrenin increased the ratio of phosphorylated-to-total ERK1/2 from 0.7±0.1 A.U. at baseline to 1.0±0.1 A.U. at 30 min (54% increase; p=0.004; n=7) and 1.3±0.1 A.U. at 60 min (102% increase; p<0.0001; n=7). Both PRO20, a PRR blocker, and Ro-31, a protein kinase C inhibitor, abrogated prorenin-induced ERK1/2 phosphorylation, suggesting a PRR-dependent component to this response. Treatment with rProrenin increased NADPH oxidase activity by 47.2±9.5 % compared to vehicle control (p<0.05, n=5). RVLM-targeted stereotactic microinjection of glutamate, rProrenin, or Ang II, but not vehicle, induced an acute BP elevation in isoflurane-anesthetized C57BL/6J mice. Moreover, preliminary data indicate that RVLM-targeted ablation of PRR in PRR-flox mice attenuates the pressor response to deoxycorticosterone (DOCA)-salt in females (WT=132±3 vs KO=120±3 mmHg; p<0.05; n=3-4), but not males (n=5-8), during the first week on DOCA-salt treatment. There was no difference in BP during the 2 nd and 3 rd week of DOCA-salt. We conclude that prorenin induces PRR-mediated downstream signaling involving ERK1/2 phosphorylation and generation of ROS in brainstem neurons, which might contribute to BP elevation in neurogenic HT in sex-dependent manner.