The Effects Of ACE2on Monocrotaline-induced Pulmonary Arterial Hypertension In Rats

Objectives：Pulmonary arterial hypertension (PAH) is associated with endothelialdysfunction, inflammation,vasoconstriction, vascular smooth muscle cell proliferation,fibrosis and remodeling of the pulmonary vessels, eventually leading to right heartfailure and death.With poor diagnosis and limited therapeutic options,the fatality rateof PAH is high.In2000,a new member of the RAS, angiotensin converting enzyme2(ACE2), was discovered.Many studies have shown that the ACE2-Ang-(1-7)-Masaxis which ACE2is involved in is a negative regulator of the classic ACE-AngⅡ-AT1axis and plays an important roles in vasodilation, anti-proliferation, anti-inflammatory, anti-fibrosis and anti-plateletaggregation. In our study, we focused onthe effects of ACE2on monocrotaline-induced PAH in rats, to investigate whetherACE2activator resorcinolnaphthalein (Rec) can prevent monocrotaline (MCT)induced pulmonary arterial hypertension in rats, and what related cell signaltransduction pathway might play a role in it.Methods：1. Male Sprague-Dawley rats (12wk old) were randomly divided into4groups:control group,MCT group,Rec group and Rec+A779（Mas receptorantagonist）group.First day,control rats received vehicle subcutaneous,whereas othersreceived a single injection of MCT subcutaneous.Second day,osmotic minipumpscontaining vehicle were implanted subcutaneously in control rats,at the sametime,osmotic minipumps containing vehicle,Rec or Rec+A779were implantedrespectively in MCT rats,Rec rats and Rec+A779rats.2. Used rat tail noninvasive blood pressure measurement to measure the rats’blood pressure after14days of pumps’ implant,once a week,3times every time,theaverage of three data as the final measure blood pressure values. 3.Used the right cardiac catheterization measurement to measure the rats’ meanpulmonary artery pressure after14days of pumps’ implant, and to calculate the rightheart index; HE staining analyze of film thickness of the pulmonary artery andpulmonary small artery obstruction as well.4. Detected ACE2, Mas, P-Akt and P-eNOS expression level in lung tissue byWestern-blot.5. Detected Ang-(1-7) level in lung tissue by ELISA.6. Measured NO concentration in lung tissue.Results：1. The effects of ACE2on mean pulmonary artery pressure and bloodpressure in rats. There was no difference between Rec group and the control groupin mean pulmonary artery pressure; Elevated mean pulmonary artery pressure isobserved in the MCT group and Rec+A779group has resulted in;There was nodifference among the four groups in rats blood pressure.2. The effects of ACE2on pulmonary artery in rats. We observed increasedpulmonary vessel wall thickness in MCT group and Rec+A779group, whereas noobviously thickened pulmonary vessel wall in Rec group and the control group.3. The effects of ACE2on right ventricle hypertrophy index in rats. MCTgroup and Rec+A779group has resulted in right ventricular hypertrophy,whereas Recgroup had no difference with the control group.4. The effects of ACE2on each component in the lung tissue of rats.Compared with MCT group and Rec+A779group,the level of ACE2, Mas, P-akt,P-eNOS and the concentration of NO have elevated in Rec group.Conclusion：1. ACE2can prevent monocrotaline induced pulmonary arterial hypertension,increased pulmonary vessel wall thickness and right ventricular hypertrophy in rats.2. ACE2had no obvious effect on systemic blood pressure of rats.3. Rec can activate the ACE2in vivo.4. ACE2play roles through ACE2-Ang-(1-7)-Mas axis. 5. By Akt/eNOS downstream signaling pathway, ACE2can activate eNOS togenerate NO to lower mean pulmonary artery pressure in rats.