Abstract 4366496: Muscarinic Acetylcholine Receptor 3 Knockout is Associated with Salt Sensitive Hypertension

Abstract

Introduction: Hypertension ( HTN ) is characterized by reduced vascular contractility and nitric oxide ( NO ) bioavailability. Cilia dysfunctions present various symptoms including HTN. We showed previously that the inability of primary endothelial cilia to sense fluid shear stress can lead to NO deficiency in vitro ; however, the molecular mechanism linking cilia with HTN pathogenesis is incompletely understood, limiting our ability to prevent the initiation and progression of HTN. Hypothesis: Our project seeks to fill this gap in knowledge by exploring the role of muscarinic acetylcholine receptor 3 ( M3R ), which we discovered to be localized to primary cilia, in HTN pathogenesis. M3R activation by acetylcholine ( ACh ) contributes to arterial dilatation via activation of downstream effector phosphatidylinositol 4,5-bisphosphate ( PIP2 ), leading to an increase in calcium and NO release. This finding led us to propose that M3R activation could function as a molecular switch to enhance NO generation and promote vasodilation. Furthermore, recent reports revealed the crucial role of M3R in salt sensitivity and the development of HTN. This incited us to hypothesize that the M3R pathway is involved in the pathogenesis of HTN and that targeting this pathway may hold utility for HTN treatment. Methods: To examine the role of vascular or kidney M3R in blood pressure ( BP ) in vivo , endothelial- and epithelial-specific M3R knockout ( KO ) mouse models were created, and their BP was examined by tail cuff in the presence or absence of salt diet (4% NaCl). Results: Endothelial KO of M3R was associated with increased BP in male and female mice in the presence or absence of salt diet ( P<0.0001 for systolic, P<0.0001 for diastolic, and P<0.0001 for MAP). Notably, salt diet was associated with increased BP in M3R KOs, suggesting possible involvement of M3R pathway in salt-sensitive HTN. Surprisingly, kidney-specific KO of M3R was also associated with increased BP ( P<0.0001 for systolic, P<0.0001 for diastolic, and P<0.0001 for MAP); however, this increase in BP was not exacerbated by salt diet ( P>0.05 ). Conclusion: Our data suggests that impairment of M3R pathway in the vasculature could lead to diminished ACh-mediated vascular relaxation and HTN, while its impairment in the kidney could be involved in the pathogenesis of salt-sensitive HTN. This study offers new insight to utilize M3R as molecular target for therapeutic interventions designed to prevent detrimental effects of HTN.