Abstract Body (Do not enter title and authors here): Introduction: Hypertension (HTN) is a major health burden, emphasizing the need for novel drugs. The particulate guanylyl cyclase receptor A (GC-A) has vasodilating, natriuretic, antioxidant and antifibrotic effects when activated by atrial or b-type natriuretic peptide (ANP and BNP) and generating cGMP. Previously we reported the discovery of a small molecule, MCUF-651, that enhances the ANP/BNP/GC-A/cGMP pathway via positive allosteric modulation. However, the cardioprotective and antihypertensive actions of MCUF-651 unknown. Here, we hypothesized that MCUF-651 have antioxidant and antifibrotic actions in human cardiomyocytes (HCMs) and cardiac fibroblasts (HCFs) and blood pressure (BP) lowering and renal enhancing actions in a rat model of HTN.
Methods: Oxidative stress in HCMs was induced with hydrogen peroxide (H₂O₂) and treated with DMSO (control), ANP (10^-6M) or ANP+MCUF-651 (1, 5 or 10 µM). Intracellular reactive oxygen species (ROS) was determined using DHE staining. Fibrotic gene expression (a-SMA and COL1A1) was induced by TGFβ-1 in HCFs and then treated together with DMSO, ANP (10^-6M) or ANP+MCUF-651 (1, 5 or 10 µM). A single IV bolus of MCUF-651(10 or 25 mg/kg; n=8/dose) or vehicle (V; n=7) was injected into spontaneous hypertensive rats (SHRs). Plasma and urinary cGMP (PcGMP and UcGMP; measure of GC-A target engagement), systolic BP (SBP), urinary volume (UV) and sodium (UNa) excretion were assessed at baseline (BL) and over 60-mins post-bolus.
Results: H₂O₂ increased DHE staining in HCMs, indicating elevated ROS, which was reduce with ANP treatment. Notably, ANP+MCUF-651 decreased DHE levels in HCMs further than ANP alone. Treatment with ANP+MCUF-651 inhibited a -SMA and COL1A1 mRNA expression levels induced by TGFβ-1 in HCFs more than ANP alone. In SHRs, PcGMP and UcGMP significantly increased, dose-dependently, with MCUF-651 compared to vehicle. These cGMP elevations with MCUF-651 were associated with significant SBP reductions at 15-mins post bolus compared to vehicle (ΔSBP 10 mg/kg: -35±17; 25 mg/kg: -44±15; V: -17±14 mmHg; P=0.03), which was sustained over 60 mins. Also, MCUF-651 significantly, and dose-dependently, increased UV and UNa excretion from BL.
Conclusions: We reported for the first time, MCUF-651, a novel GC-A small molecule, has antioxidant and antifibrotic actions in HCMs and HCFs, and in SHRs, elevated cGMP, reduced SBP and enhanced UV and UNa. Our data supports the development of MCUF-651 as a potential new HTN therapy.