Cardiac Grafts Engineered from Human iPSC Ventricular-Pure or Heterogeneous Cardiomyocytes Display Synchronous and Spontaneous Contraction and Reduced Ventricular Tachycardia in Rats with Chronic Heart Failure

Abstract

Introduction: Aldosterone (Aldo) is synthesized and secreted by the adrenal cortex zona glomerulosa (ZG) cells. In heart failure (HF) patients Aldo is increased and plays a critical role in inducing and maintaining sodium and water retention as well as mediating myocardial remodeling and fibrosis. MANP is a novel Mayo Clinic designer natriuretic peptide (NP) which was demonstrated to inhibit circulating Aldo levels in vivo canines and in human subjects. Importantly, 3′, 5′ cyclic guanosine monophosphate (cGMP) generated by NPs activates protein kinase G (PKG) and also binds to phosphodiesterases (PDEs). Both PKG and PDEs have been suggested to play a role in the actions of NPs. To date no study has defined the direct cellular inhibitory effects of MANP on Aldo in human adrenal cells. Our goals were therefore to define the mechanisms of the inhibitory actions of MANP on Aldo in ZG cells with a special focus on cGMP and PDE's. Hypothesis: We hypothesized that MANP directly inhibits Aldo in adrenal cortex ZG cells and the inhibitory effect is mediated partially through PDEs. Methods: The ZG cell line H295R cells were cultured in 24-well plates for 24 hrs and starved overnight with serum free medium before stimulation/treatment. MANP (10 −8 , 10 −7 or 10 −6 M) was added to cells after starvation. Angiotensin II (ANG II, 10 −8 , 10 −7 or 10 −6 M) was employed to stimulate Aldo release. Supernatants were collected after 24 hrs for Aldo quantification with commercial ELISA kits. The PDE inhibitor IBMX (500 uM) and protein kinase G (PKG) specific cGMP analog 8-CPT-cGMP (100 uM) were used. Data are presented as Mean ± SEM, *P < .05 between two groups by unpaired t-test. Results: Angiotensin II stimulated Aldo secretion in a dose-dependent manner. MANP inhibited ANG II stimulated Aldo in a dose dependent manner (10 −8