Calcimimetic R568 improved cardiac remodeling by classic and novel renin-angiotensin system in spontaneously hypertensive rats

One major cause of cardiac mortality is heart disease caused by hypertension. The formation of cyclic adenosine monophosphate (cAMP) is inhibited by calcium-sensitive receptor (CaSR) activation which increases intracellular Ca2+ concentrations and suppresses renin release. As we know, renin-angiotensin system (RAS) is closely related to development of essential hypertension (EH). Therefore, we focused on exploring the roles of NPSR568 (R568)-activated CaSR in cardiac remodeling of spontaneously hypertensive rats (SHRs), as well as the activity of classic and novel RAS. Wistar-Kyoto rats (WKYs) and SHRs were treated by R568 for four and eight weeks, respectively, and their blood pressure (BP), echocardiographic values, heart-to-body weight ratio (HW/BW%), and left ventricle-to-body weight ratio (LVW/BW%) were evaluated. Then Masson's trichrome staining and hematoxylin and eosin staining as well as RT-qPCR analysis of beta-isoform of myosin heavy chain and brain natriuretic peptide mRNA expression were performed. A Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay and analysis of apoptosis marker proteins were used to assess the extent of myocardial apoptosis. The CaSR expression and the activity of classic and novel RAS were examined by immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay. The present study revealed that the development of hypertension was accompanied by increased BP, apoptosis, hypertrophy, and fibrosis, along with decreased expression of CaSR, decreased novel RAS, and increased classic RAS in myocardial tissues. R568 administration for four and eight weeks reduced BP and myocardial remodeling and reversed the low expression of CaSR; moreover, classic RAS was suppressed and novel RAS was activated in the myocardium. Taken together, these data indicate that R568 may effectively inhibit EH myocardial remodeling by inhibiting classic RAS and activating novel RAS in SHRs.