Background Activation of the renin-angiotensin system and the subsequent generation of angiotensin（Ang）Ⅱis an important mediator of myocardial fibrosis,pathological hypertrophy and heart failure.Angiotensin-convert...Background Activation of the renin-angiotensin system and the subsequent generation of angiotensin（Ang）Ⅱis an important mediator of myocardial fibrosis,pathological hypertrophy and heart failure.Angiotensin-converting enzyme 2（ACE2） has recently been identified as AngⅡ-degrading enzyme capable of generating Ang（1 -7） and as a negative regulator of the renin-angiotensin system.We assessed the hypothesis that ACE2 mediates its anti-fibrotic and anti-hyper-trophic effects through the modulation of AngⅡsignaling. Methods We implanted mini-osmotic pumps with AngⅡ(1.5 mg·kg<sup>-1</sup>·d<sup>-1</sup>) for 14 days in male wildtype（WT） mice which were then treated with recombinant human ACE2(rhACE2;2 mg·kg<sup>-1</sup>,d i.p.) or placebo.Systolic blood pressure of mouse was measured using the tail cuff method with the IITC Blood Pressure Monitoring Systems.Results Chronic AngⅡinfusion resulted in a predicted pressor response（peak SBP:163±7 mm Hg,n=8,P【0.01）,treatment with rhACE2 reduced the pressor response（139±4 mm Hg;n=6,P【0.05）and reduced the hypertrophic response based on left ventricular mass and expressions of atrial natriuretic factor,brain natriuretic peptide andα-skeletal actin（P【0.05,respectively）.Interestingly,echocardiographic assessment including tissue Doppler measurement revealed attenuated ventricular hypertrophy and improvement in diastolic dysfunction in AngⅡ-treated mice injected with rhACE2.Trichrome and picrosirius red staining showed a marked increase in myocardial fibrosis in response to AngⅡwhich was suppressed by rhACE2（collagen volume fraction; 7.3%±1.3%vs.4.1%±1.1%;n=6～7,P【0.05） with reduced expression of collagenⅠandⅢ,fibronectin and transforming growth factor-P in response to rhACE2.In male ACE2 knockout mice（Ace2-/y）,AngⅡinfusion resulted in greater pressor response（186±8 mm Hg;re=8,P【0.01） and worsening diastolic dysfunction compared to WT mice infused with AngⅡ.Conclusions In the setting of elevated AngⅡ,loss of ACE2 increases AngⅡ-induced hypertension and diastolic dysfunction. In contrast,recombinant human ACE2 prevents AngⅡ-mediated hypertension,myocardial hypertrophy and fibrosis.We conclude that ACE2 plays a pivotal role in the prevention of hypertension,myocardial hypertrophy and fibrosis acting as a protective mechanism in the heart to limit the pathological effects of an activated systemic and/or local RAS and ACE2 represents a novel therapeutic strategy for cardiovascular disorders.展开更多
文摘Background Activation of the renin-angiotensin system and the subsequent generation of angiotensin（Ang）Ⅱis an important mediator of myocardial fibrosis,pathological hypertrophy and heart failure.Angiotensin-converting enzyme 2（ACE2） has recently been identified as AngⅡ-degrading enzyme capable of generating Ang（1 -7） and as a negative regulator of the renin-angiotensin system.We assessed the hypothesis that ACE2 mediates its anti-fibrotic and anti-hyper-trophic effects through the modulation of AngⅡsignaling. Methods We implanted mini-osmotic pumps with AngⅡ(1.5 mg·kg<sup>-1</sup>·d<sup>-1</sup>) for 14 days in male wildtype（WT） mice which were then treated with recombinant human ACE2(rhACE2;2 mg·kg<sup>-1</sup>,d i.p.) or placebo.Systolic blood pressure of mouse was measured using the tail cuff method with the IITC Blood Pressure Monitoring Systems.Results Chronic AngⅡinfusion resulted in a predicted pressor response（peak SBP:163±7 mm Hg,n=8,P【0.01）,treatment with rhACE2 reduced the pressor response（139±4 mm Hg;n=6,P【0.05）and reduced the hypertrophic response based on left ventricular mass and expressions of atrial natriuretic factor,brain natriuretic peptide andα-skeletal actin（P【0.05,respectively）.Interestingly,echocardiographic assessment including tissue Doppler measurement revealed attenuated ventricular hypertrophy and improvement in diastolic dysfunction in AngⅡ-treated mice injected with rhACE2.Trichrome and picrosirius red staining showed a marked increase in myocardial fibrosis in response to AngⅡwhich was suppressed by rhACE2（collagen volume fraction; 7.3%±1.3%vs.4.1%±1.1%;n=6～7,P【0.05） with reduced expression of collagenⅠandⅢ,fibronectin and transforming growth factor-P in response to rhACE2.In male ACE2 knockout mice（Ace2-/y）,AngⅡinfusion resulted in greater pressor response（186±8 mm Hg;re=8,P【0.01） and worsening diastolic dysfunction compared to WT mice infused with AngⅡ.Conclusions In the setting of elevated AngⅡ,loss of ACE2 increases AngⅡ-induced hypertension and diastolic dysfunction. In contrast,recombinant human ACE2 prevents AngⅡ-mediated hypertension,myocardial hypertrophy and fibrosis.We conclude that ACE2 plays a pivotal role in the prevention of hypertension,myocardial hypertrophy and fibrosis acting as a protective mechanism in the heart to limit the pathological effects of an activated systemic and/or local RAS and ACE2 represents a novel therapeutic strategy for cardiovascular disorders.
