(Pro)renin receptor knockdown in the paraventricular nucleus of the hypothalamus attenuates hypertension development and AT₁ receptor-mediated calcium events

Abstract

Activation of the brain renin-angiotensin system (RAS) is a pivotal step in the pathogenesis of hypertension. The paraventricular nucleus (PVN) of the hypothalamus is a critical part of the angiotensinergic sympatho-excitatory neuronal network involved in neural control of blood pressure and hypertension. However, the importance of the PVN (pro)renin receptor (PVN-PRR)—a key component of the brain RAS—in hypertension development has not been examined. In this study, we investigated the involvement and mechanisms of the PVN-PRR in DOCA-salt-induced hypertension, a mouse model of hypertension. Using nanoinjection of adeno-associated virus-mediated Cre recombinase expression to knock down the PRR specifically in the PVN, we report here that PVN-PRR knockdown attenuated the enhanced blood pressure and sympathetic tone associated with hypertension. Mechanistically, we found that PVN-PRR knockdown was associated with reduced activation of ERK (extracellular signal-regulated kinase)-1/2 in the PVN and rostral ventrolateral medulla during hypertension. In addition, using the genetically encoded Ca2+ biosensor GCaMP6 to monitor Ca2+-signaling events in the neurons of PVN brain slices, we identified a reduction in angiotensin II type 1 receptor-mediated Ca2+ activity as part of the mechanism by which PVN-PRR knockdown attenuates hypertension. Our study demonstrates an essential role of the PRR in PVN neurons in hypertension through regulation of ERK1/2 activation and angiotensin II type 1 receptor-mediated Ca2+ activity. NEW & NOTEWORTHY PRR knockdown in PVN neurons attenuates the development of DOCA-salt hypertension and autonomic dysfunction through a decrease in ERK1/2 activation in the PVN and RVLM during hypertension. In addition, PRR knockdown reduced AT1aR expression and AT1R-mediated calcium activity during hypertension. Furthermore, we characterized the neuronal targeting specificity of AAV serotype 2 in the mouse PVN and validated the advantages of the genetically encoded calcium biosensor GCaMP6 in visualizing neuronal calcium activity in the PVN.

Increased (Pro)renin Receptor Expression in the Hypertensive Human Brain

“…In addition, we found that the PRR in the PVN and RVLM is predominantly expressed in neurons, and not astrocytes, a finding in accord with those of our previous study on the human SFO (Cooper et al, 2018). In vivo studies in rodents have similarly found that the PRR is expressed in neurons but not in astrocytes (Shan et al, 2008;Huber et al, 2015;Souza et al, 2019). This cell-type expression pattern extends to in vitro cell culture studies, which have also shown that the PRR is expressed in neurons but not astrocytes (Shan et al, 2010;Peng et al, 2013;Shi et al, 2014).…”

“…This cell-type expression pattern extends to in vitro cell culture studies, which have also shown that the PRR is expressed in neurons but not astrocytes (Shan et al, 2010;Peng et al, 2013;Shi et al, 2014). Although these in vitro studies reported PRR expression in microglia, studies in mice provide no evidence for PRR localization in microglia in PVN tissue (Souza et al, 2019). On the other hand, a small number of microglia in human SFO tissue are reported to be positive for PRR immunoreactivity (Cooper et al, 2018).…”

“…Although previous studies reported that Ang II can access the PVN and RVLM in hypertension due to blood brain barrier breakdown (Biancardi et al, 2014;Biancardi and Stern, 2016), more recent studies have shown that the PRR represents the main source of local Ang II production in the brain (Li et al, 2014(Li et al, , 2015b. Accumulating evidence from experimental animal models points to a pivotal role for the brain PRR in hypertension development (Shan et al, 2010;Li et al, 2012Li et al, , 2014Souza et al, 2019). To understand the clinical significance of the brain PRR in human hypertension, we investigated PRR expression and cellular localization in the PVN and RVLM of human subjects.…”

“…PVN is a part of Ang II-sensitive neural circuits (Chen and Toney, 2003;Cato and Toney, 2005;Knight et al, 2013) that receive excitatory projections from circumventricular organs in the forebrain; excitatory neurons in this brain nucleus projects to the RVLM, activating sympathetic premotor C1 neurons and increasing sympathetic activity and BP (Tagawa and Dampney, 1999;Li et al, 2003). Previous studies have demonstrated expression of the PRR in the PVN and established its role in the regulation of sympathetic activity and vasopressin secretion in NTN and HTN animals (Huber et al, 2015;Pitra et al, 2016Pitra et al, , 2019Souza et al, 2019). PRR expression is also upregulated in the hypothalamus of HTN mice (Li et al, 2015a).…”

“…A recent study reported that neuronal PRR activation is a novel mechanism for cardiovascular and metabolic regulation in obesity and diabetes (Worker et al, 2020). Despite evidence from preclinical studies suggesting a pivotal role for the PRR in cardiovascular diseases (Shan et al, 2010;Li et al, 2012;Huber et al, 2015;Souza et al, 2019), the clinical importance of the PRR in the PVN and RVLM has yet to be defined.…”