Abstract
Renal nerves play a critical role in cardiorenal interactions. Renal denervation (RDN) improved survival in some experimental heart failure (HF) models. It is not known whether these favorable effects are indirect, explainable by a decrease in vascular afterload, or diminished neurohumoral response in the kidneys, or whether RDN procedure per se has direct myocardial effects in the failing heart. To elucidate mechanisms how RDN affects failing heart, we studied load-independent indexes of ventricular function, gene markers of myocardial remodeling, and cardiac sympathetic signaling in HF, induced by chronic volume overload (aorto-caval fistula, ACF) of Ren2 transgenic rats. Volume overload by ACF led to left ventricular (LV) hypertrophy and dysfunction, myocardial remodeling (upregulated Nppa, MYH 7/6 genes), increased renal and circulating norepinephrine (NE), reduced myocardial NE content, increased monoaminoxidase A (MAO-A), ROS production and decreased tyrosine hydroxylase (+) nerve staining. RDN in HF animals decreased congestion in the lungs and the liver, improved load-independent cardiac function (Ees, PRSW, Ees/Ea ratio), without affecting arterial elastance or LV pressure, reduced adverse myocardial remodeling (Myh 7/6, collagen I/III ratio), decreased myocardial MAO-A and inhibited renal neprilysin activity. RDN increased myocardial expression of acetylcholinesterase (Ache) and muscarinic receptors (Chrm2), decreased circulating and renal NE, but increased myocardial NE content, restoring so autonomic control of the heart. These changes likely explain improvements in survival after RDN in this model. The results suggest that RDN has remote, load-independent and favorable intrinsic myocardial effects in the failing heart. RDN therefore could be a useful therapeutic strategy in HF.