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.

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.

ECMO attenuates inflammation response and increases ATPase activity in brain of swine model with cardiac arrest compared with CCPR.

Extracorporeal membrane oxygenation (ECMO) could increase survival rate and neurological outcomes of cardiac arrest (CA) patients compared with conventional cardiopulmonary resuscitation (CCPR). Currently, the underlying mechanisms how ECMO improves neurological outcomes of CA patients compared with CCPR have not been revealed. A pig model of CA was established by ventricular fibrillation induction and then underwent CCPR or ECMO. Survival and hemodynamics during the 6 h after return of spontaneous circulation (ROSC) were compared. The levels of inflammatory cytokines and Ca2+-ATPase and NA+-K+-ATPase activities were detected. Brain tissues histology and ultra-microstructure in CCPR and ECMO groups were also examined. Results suggested that ECMO significantly improved the survival of pigs compared with CCPR. Heart rate (HR) decreased while cardiac output (CO) increased along with the time after ROSC in both ECMO and CCPR groups. At each time point, HR in ECMO groups was lower than that in CCPR group while CO and mean arterial pressure in ECMO group was higher than CCPR group. In ECMO group, lower levels of IL-1, IL-1ß, IL-6, TNFα, and TGFß, especially IL-1, IL-6, TNFα, and TGFß, were found compared that in CCPR group while no difference of IL-10 between the two groups was observed. Similar with the results from enzyme-linked immunosorbent assay, decreased expressions of IL-6 and TGFß were also identified by Western blotting. And Ca2+-ATPase and NA+-K+-ATPase activities were increased by ECMO compared with CCPR. Hematoxylin and eosin staining and ultra-microstructure examination also revealed an improved inflammation situation in ECMO group compared with CCPR group.

Imbalance of angiotensin-converting enzymes affects myocardial apoptosis during cardiac arrest induced by acute pulmonary embolism in a porcine model.

Acute pulmonary embolism (APE) with cardiac arrest (CA) is associated with a high mortality rate. Even upon return of the spontaneous circulation (ROSC), APE­CA survivors are prone to myocardial cell apoptosis, a key cellular mechanism that induces heart failure. A recent study by our group discovered a post­resuscitation imbalance in the serum angiotensin­converting enzyme (ACE)2/ACE axis of the renin­angiotensin system (RAS), as well as regressive cardiac function in a porcine model of APE­CA. However, it has remained elusive how this imbalance in the ACE2/ACE axis affects myocardial cell apoptosis. In the present study, western blot and immunohistochemical analyses demonstrated that the RAS was only activated in the left myocardium, as evidenced by a decreased ACE2/ACE ratio following APE­CA and ROSC, but not the right myocardium. Ultrastructural analysis confirmed myocardial apoptosis in the left and right myocardium. Furthermore, B­cell lymphoma 2 (Bcl­2)­associated X protein (Bax) and caspase­3 levels were elevated and Bcl­2 levels were decreased in the left myocardium following APE­CA and ROSC. Treatment with the ACE inhibitor captopril for 30 min after initiation of ROSC prevented the increase in Bax and the decrease in Bcl­2 in the left myocardium compared with that in saline­treated pigs. Captopril also inhibited the activation of extracellular signal­regulated kinase (ERK)1/2 in the left myocardium. The results of the present study suggest that an imbalance in the ACE2/ACE axis has an important role in myocardial apoptosis following APE­CA, which may be attributed to decreased ERK1/2 activation. In addition, it was indicated that captopril prevents apoptosis in the left myocardium after ROSC.

Association between ACE2/ACE balance and pneumocyte apoptosis in a porcine model of acute pulmonary thromboembolism with cardiac arrest.

Acute pulmonary embolism (APE) is frequently reported in patients with cardiac arrest (CA) in emergency care. Pneumocyte apoptosis is commonly observed in the lungs following an APE. An important pathological mechanism evoking apoptosis during a lipopolysaccharide­induced acute lung injury is the angiotensin­converting enzyme 2 (ACE2)/ACE imbalance. The present study uses a porcine model to examine the anti­apoptotic effects of captopril on APE­CA and the return of spontaneous circulation (ROSC). Pigs were randomly assigned into four groups: Control, APE­CA, ROSC­saline, and ROSC­captopril. Surviving pigs were euthanized at 6 h and lungs were isolated for analysis using several biochemical assays. Compared with the control group, the ACE2/ACE ratio was lower in the APE­CA and ROSC pigs. In addition, APE­CA pigs had higher Bcl­2­associated X protein (Bax) and cleaved caspase­3 levels, and lower B­cell lymphoma­2 (Bcl­2) level compared to control pigs. Captopril treatment reduced lung apoptosis, as demonstrated by lower TUNEL­positive cells, higher Bcl­2, and lower cleaved caspase­3 protein levels in the lung. Notably, the ACE2/ACE ratio was positively correlated with Bcl­2 protein levels and Bcl­2/Bax ratio. In conclusion, captopril has a protective effect against lung apoptosis following ROSC and that maintaining the balance of the ACE2/ACE axis is important for inhibiting pulmonary apoptosis during APE.

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.