Involvement of the Brain (Pro)renin Receptor in Cardiovascular Homeostasis

Abstract

Despite overwhelming evidence of the importance of brain renin-angiotensin system (RAS), the very existence of intrinsic brain RAS remains controversial. To investigate the hypothesis that the brain (pro)renin receptor (PRR) is physiologically important in the brain RAS regulation and cardiovascular functions. PRR is broadly distributed within neurons of cardiovascular-relevant brain regions. The physiological functions of PRR were studied in the supraoptic nucleus (SON) because this brain region showed greater levels of PRR mRNA in the spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto (WKY) rats. Adeno-associated virus (AAV)-mediated overexpression of human PRR in the SON of normal rats resulted in increases in plasma and urine vasopressin, and decreases in H(2)O intake and urine output without any effects on mean arterial pressure and heart rate. Knockdown of endogenous PRR by AAV-short hairpin RNA in the SON of SHRs attenuated age-dependent increases in mean arterial pressure and caused a decrease in heart rate and plasma vasopressin. Incubation of neuronal cells in culture with human prorenin and angiotensinogen resulted in increased generation of angiotensin I and II. Furthermore, renin treatment increased phosphorylation of extracellular signal-regulated kinase ½ in neurons from both WKY rats and SHRs; however, the stimulation was 50% greater in the SHR. The study demonstrates that brain PRR is functional and plays a role in the neural control of cardiovascular functions. This may help resolve a long-held controversy concerning the existence of intrinsic and functional brain RAS.