Submitted on April 23, 2008
Revised on September 26, 2008
Accepted on October 1, 2008
Regulation of ACE2 in Cardiac Myocytes and Fibroblasts
Patricia E. Gallagher1, Carlos M Ferrario1, and E. Ann Tallant1*
1 Wake Forest University School of Medicine
* To whom correspondence should be addressed. E-mail: atallant{at}wfubmc.edu.
Angiotensin converting enzyme 2 (ACE2) preferentially forms angiotensin-(1-7) [Ang-(1-7)] from angiotensin II (Ang II). We showed that cardiac ACE2 is elevated following treatment of coronary artery ligated rats with AT1 receptor blockers (ARBs). Cardiac myocytes and fibroblasts were isolated from neonatal rats, to determine the molecular mechanisms for the ACE2 up-regulation by ARB treatment. Ang II significantly reduced ACE2 activity and down-regulated ACE2 mRNA in cardiac myocytes, effects blocked by the ARB losartan, indicating that Ang II regulates ACE2. Ang II also reduced ACE2 mRNA in cardiac fibroblasts; however, no enzyme activity was detected, reflecting the limited expression of ACE2 in these cells. Endothelin-1 (Et-1) also significantly reduced myocyte ACE2 mRNA. The reduction in ACE2 mRNA by Ang II or Et-1 was blocked by inhibitors of mitogen-activated protein (MAP) kinase kinase 1, MEK1, suggesting that Ang II or Et-1 activate ERK1/ERK2 to reduce ACE2. While ACE2 mRNA was not affected by Ang-(1-7), both the Ang II- and Et-1-mediated reductions in ACE2 mRNA were blocked by the heptapeptide. The Ang-(1-7) modulatory effect was prevented by the Ang-(1-7) receptor antagonist [D-Ala7]-Ang-(1-7), indicating that the Ang-(1-7) response was mediated by a specific AT(1-7) receptor. Myocyte treatment with atrial natriuretic peptide (ANP) also reversed the ACE2 mRNA down-regulation by Ang II or Et-1, while treatment with ANP alone was ineffective. These results indicate that multiple hypertrophic and anti-hypertropic peptides regulate ACE2 production in myocytes, suggesting that ACE2 expression in the heart is dependent upon the compliment and concentration of regulatory molecules.
