Loss of Angiotensin-Converting Enzyme 2 Exacerbates Myocardial Injury via Activation of the CTGF-Fractalkine Signaling Pathway

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) has been implicated in human heart failure, but the mechanism remains elusive. We hypothesized that ACE2 deficiency would exacerbate angiotensin (Ang) II-mediated myocardial injury. METHODS AND RESULTS: 10-week-old ACE2 knockout (ACE2KO) and wild-type mice received by mini-osmotic pump either AngII (1.5 mg·kg(-1)·day(-1)) or saline for 2 weeks. ACE2 deficiency triggered greater increases in the expression of connective tissue growth factor (CTGF), fractalkine (FKN) and phosphorylated ERK1/2 in AngII-treated ACE2KO hearts. These changes were associated with greater activation of matrix metalloproteinase (MMP) 2, MMP9 and MT1-MMP and exacerbation of myocardial injury and dysfunction. In cultured cardiofibroblasts, exposure to AngII (100 nmol/L) for 30 min resulted in marked increases in superoxide production and expression of CTGF, FKN and phosphorylated ERK1/2, which were strikingly prevented by recombinant human ACE2 (rhACE2; 1mg/ml) and the CTGF-neutralizing antibody (5 μg/ml), but were aggravated by ACE2 inhibitor DX600 (0.5 μmol/L). These protective effects of rhACE2 were eradicated by the Ang-(1-7) antagonist A779 (1 μmol/L). More intriguingly, rhACE2 treatment significantly abolished AngII-mediated increases in MMP2, MMP9 and MT1-MMP in cardiofibroblasts. CONCLUSIONS: Loss of ACE2 exacerbates AngII-mediated inflammation, myocardial injury and dysfunction in ACE2-deficient hearts via activation of the CTGF-FKN-ERK and MMP signaling. ACE2 gene may represent a potential candidate to prevent and treat myocardial injury and heart diseases.