Effects of angiotensin (1-7) upon right ventricular function in experimental rat pulmonary embolism

Captopril improves postresuscitation hemodynamics protective against pulmonary embolism by activating the ACE2/Ang-(1-7)/Mas axis

Acute pulmonary embolism (APE) has a very high mortality rate, especially at cardiac arrest and even after the return of spontaneous circulation (ROSC). This study investigated the protective effect of the angiotensin-converting enzyme (ACE) inhibitor captopril on postresuscitation hemodynamics, in a porcine model of cardiac arrest established by APE. Twenty-nine Beijing Landrace pigs were infused with an autologous thrombus leading to cardiac arrest and subjected to standard cardiopulmonary resuscitation and thrombolysis. Ten resuscitated pigs were randomly and equally apportioned to receive either captopril (22.22 mg/kg) infusion or the same volume saline, 30 min after ROSC. Hemodynamic changes and ACE-Ang II-angiotensin II type 1 receptor (AT1R) and ACE2/Ang-(1-7)/Mas receptor axis levels were determined. APE was associated with a decline in mean arterial pressure and a dramatic increase in pulmonary artery pressure and mean right ventricular pressure. After ROSC, captopril infusion was associated with significantly lower mean right ventricular pressure and systemic and pulmonary vascular resistance, faster heart rate, and higher Ang-(1-7) levels, ACE2/ACE, and Ang-(1-7)/Ang II, compared with the saline infusion. The ACE2/Ang-(1-7)/Mas pathway correlated negatively with external vascular lung water and pulmonary vascular permeability and positively with the right cardiac index. In conclusion, in a pig model of APE leading to cardiac arrest, captopril infusion was associated with less mean right ventricular pressure overload after resuscitation, compared with saline infusion. The reduction in systemic and pulmonary vascular resistance associated with captopril may be by inhibiting the ACE-Ang II-AT1R axis and activating the ACE2/Ang-(1-7)/Mas axis.

Effect of a stable Angiotensin-(1-7) analogue on progenitor cell recruitment and cardiovascular function post myocardial infarction

Background

Angiotensin‐(1–7) improves cardiac function and remodeling after myocardial infarction (MI). This may involve recruitment of hematopoietic progenitor cells that support angiogenesis. However, angiotensin‐(1–7) is rapidly metabolized in plasma and tissue. The authors investigated in mice the effect of a metabolically stable angiotensin‐(1–7) analogue, cyclic angiotensin‐(1–7), on progenitor cell recruitment and on the heart post MI, when given in the angiogenesis phase of remodeling.

Methods and Results

Angiogenic progenitor cell recruitment was measured by using flow cytometry 24 and 72 hours after a daily bolus injection of cyclic angiotensin‐(1–7) in healthy C57BL/6 mice. Further, mice underwent MI or sham surgery and subsequently received saline or 2 different doses of cyclic angiotensin‐(1–7) for 3 or 9 weeks. Cyclic angiotensin‐(1–7) increased circulating hematopoietic progenitor cells at 24 hours but not 72 hours. Post MI, cyclic angiotensin‐(1–7) diminished cardiomyocyte hypertrophy and reduced myogenic tone, without altering cardiovascular function or cardiac histology at 9 weeks. Importantly, cyclic angiotensin‐(1–7)–treated mice had reduced cardiac capillary density at 3 weeks after MI but not after 9 weeks. Finally, cyclic angiotensin‐(1–7) decreased tube formation by cultured human umbilical vein endothelial cells.

Conclusions

Our results suggest that cyclic angiotensin‐(1–7), when given early after MI, recruits progenitor cells but does not lead to improved angiogenesis, most likely because it simultaneously exerts antiangiogenic effect in adult endothelial cells. Apparently, optimal treatment with cyclic angiotensin‐(1–7) depends on the time point of onset of application after MI.