Cardiomyocytes
Cardiomyocyte MR plays a role in regulating cardiac function, electrical conduction and fibrosis, through direct signal mediation and through paracrine MR-dependent activity. In neonatal rat cardiomyocytes, aldosterone induces expression of angiotensin-converting enzyme via MR, creating a vicious circular cascade involving the renin-angiotensin-aldosterone-system (Harada et al., 2001). Long-time aldosterone exposure induces cardiomyocyte hypertrophy, this effect being suppressed by eplerenone (Yamamuro et al., 2006). Moreover, MR activation by aldosterone led to an increase in the hypertrophic and pro-inflammatory cytokine cardiotrophin-1 (CT-1) in adult HL-1 cardiomyocytes, suggesting CT-1 as a possible mediator of cardiomyocyte growth (López-Andrés et al., 2008). Finally, CD14, a ligand of TLR4 (toll-like receptor-4), has been proposed as a mediator of the chronotropic effects of the aldosterone/MR pathway activation in cardiomyocytes (Mannic et al., 2015). Thus, MR activation plays a central role in cardiomyocyte hypertrophy.