Increasing angiotensin-converting enzyme (ACE) 2/ACE axes ratio alleviates early pulmonary vascular remodeling in a porcine model of acute pulmonary embolism with cardiac arrest

Abstract

Background: Acute pulmonary embolism (APE) with cardiac arrest (CA) is characterized by high mortality in emergency due to pulmonary arterial hypertension (PAH). This study aims to determine whether early pulmonary artery remodeling occurs in PAH caused by massive APE with CA and the protective effects of increasing angiotensin-converting enzyme (ACE) 2-angiotensin (Ang) (1-7)-Mas receptor axis and ACE-Ang II-Ang II type 1 receptor (AT1) axis (ACE2/ACE axes) ratio on pulmonary artery lesion after return of spontaneous circulation (ROSC).

Methods: To establish a porcine massive APE with CA model, autologous thrombus was injected into the external jugular vein until mean arterial pressure dropped below 30 mmHg (1 mmHg=0.133 kPa). Cardiopulmonary resuscitation and thrombolysis were delivered to regain spontaneous circulation. Pigs were divided into four groups of five pigs each: control group, APE-CA group, ROSC-saline group, and ROSC-captopril group, to examine the endothelial pathological changes and expression of ACE2/ACE axes in pulmonary artery with or without captopril.

Results: Histological analysis of samples from the APE-CA and ROSC-saline groups showed that pulmonary arterioles were almost completely occluded by accumulated endothelial cells. Western blotting analysis revealed a decrease in the pulmonary arterial ACE2/ACE axes ratio and increases in angiopoietin-2/angiopoietin-1 ratio and expression of vascular endothelial growth factor (VEGF) in the APE-CA group compared with the control group. Captopril significantly suppressed the activation of angiopoietin-2/angiopoietin-1 and VEGF in plexiform lesions formed by proliferative endothelial cells after ROSC. Captopril also alleviated endothelial cell apoptosis by increasing the B-cell lymphoma-2 (Bcl-2)/Bcl-2-associated X (Bax) ratio and decreasing cleaved caspase-3 expression.

Conclusion: Increasing the ACE2/ACE axes ratio may ameliorate pulmonary arterial remodeling by inhibiting the apoptosis and proliferation of endothelial cells after ROSC induced by APE.

Keywords: Acute pulmonary embolism; Angiotensin-converting enzyme; Cardiac arrest; Early pulmonary vascular remodeling.

Figure 1

Morphological and ultrastructure evaluation of pulmonary artery in APE. A: morphological evaluation of pulmonary artery in APE. Pulmonary arteries were occluded in the APE-CA and ROSC-saline groups (black arrow, ×100); fewer pulmonary arteries were occluded in the ROSC-captopril group (×100); plexiform lesions in the ROSC-saline group (enlargement, black arrows, ×400) and concentric lesions in ROSC-captopril group (enlargement, black arrows, ×400) were found. B: ultrastructure of endothelial cells in APE. Normal endothelial cell structure in the control group (black arrows, ×7,000), endothelial cell migration into vascular lumen in the APE-CA group (black arrows, ×10,000), and endothelial cell apoptosis in the APE-CA group (black arrows, ×10,000 and ×30,000). APE: acute pulmonary embolism; ROSC: return of spontaneous circulation; CA: cardiac arrest.

Figure 2

Protein expression of RAS in the pulmonary artery and effects of captopril on APE. A: protein expression and quantitative analysis of RAS in the pulmonary artery and effects of captopril on APE, as revealed by Western blotting analysis; B: immunohistochemistry analysis of protein expression of ACE2 in the pulmonary artery in the control, APE-CA (black arrow pointing to expression of ACE2 in vascular endothelial cells), ROSC-saline (black arrow showing expression of ACE2 in vascular endothelial cells), and ROSC-captopril groups (red arrow showing expression of ACE2 in proliferative endotheliocytes); protein expression of Mas receptor in the pulmonary artery in the control, APE-CA (red arrow showing expression of Mas in proliferative endotheliocytes), ROSC-saline, and ROSC-captopril groups (black arrow showing expression of Mas receptor in vascular endothelial cells; red arrow showing expression of Mas receptor in proliferative endotheliocytes). Compared with the control group, ^*P<0.05, ^**P<0.01, ^***P<0.001; compared with the APE-CA group, ^##P<0.01, ^###P<0.001; compared with the ROSC-saline group, ^{^}P<0.05. Scale bar in B: 100 μm. RAS: renin angiotensin system; APE: acute pulmonary embolism; ACE2: angiotensin-converting enzyme 2; CA: cardiac arrest; ROSC: return of spontaneous circulation.