Angiotensin-Converting Enzyme 2 Inhibits Apoptosis of Pulmonary Endothelial Cells During Acute Lung Injury Through Suppressing SMAD2 Phosphorylation

Abstract

Background/Aims: Angiotensin converting enzyme 2 (ACE2) has an established role in suppressing the severity of acute lung injury (ALI), especially when it was applied together with transplantation of human umbilical cord mesenchymal stem cells (uMSCs). Although the effects of ACE2 in ALI are believed to mainly result from its role in hydrolyzing angiotensin II (AngII), which subsequently reduces the vascular tension and subsequent pulmonary accumulation of inflammatory cells, we and others have recently reported a possible role of ACE2 in suppressing the ALI-induced apoptosis of pulmonary endothelial cells. However, the underlying mechanisms remain undetermined. Methods: Here, we analyzed the alteration in lung injury severity in ALI after ACE2, by histology and inflammatory cytokine levels. We analyzed apoptosis-associated proteins in lung after ALI, as well as in cultured endothelial cells treated with nitric oxide (NO). We overexpressed SMAD7 to inhibit SMAD2 signaling in cultured endothelial cells and examined its effects on NO-induced cell apoptosis. Results: ACE2 alleviated severity of lung injury after ALI. ACE2 significantly decreased the ALI-induced apoptosis of pulmonary cells in vivo, and ACE2 protected endothelial cells against NO-induced apoptosis in vitro. NO induced phosphorylation of a key factor of transforming growth factor β (TGF β) receptor signaling, SMAD2, which could be dose-dependently inhibited by ACE2. Inhibition of SMAD2 phosphorylation through expression of its inhibitor SMAD7 significantly inhibited NO-induced cell apoptosis, without need for ACE2. Conclusion: Our data suggest that ACE2-mediated AngII degradation may inhibit AngII-mediated SMAD2-phophorylation, possibly through a TGFβ-independent manner, which subsequently suppresses the ALI-induced cell death. Our results thus reveal a novel molecular pathway that controls the pathogenesis of ALI.

Angiotensin-Converting Enzyme 2 Inhibits Apoptosis of Pulmonary Endothelial Cells During Acute Lung Injury Through Suppressing MiR-4262

“…After acclimatization for 1 week, a group of mice were used as the no-injury group and received no treatments (NT). The lung injury model was induced in another groups of mice, by intraperitoneal administration of the bleomycin solution (10mg/mL, Sigma-Aldrich, St Louis, MO, USA) at 20 mg/kg body weight, as has been applied and described before [6][7][8][9][10]14]. This ALI model is stable and easy to be built.…”

“…Human embryonic kidney 293 cell line (HEK293) and Human lung epithelial cell line HULEC-5a (HULEC) were purchased from ATCC (American Type Culture Collection, Manassas, VA, USA), and has been described before [9]. HULEC-5a is an immortalized human microvascular endothelial cell Line [15], and were maintained in MCDB131 media (without L-Glutamine, ATCC) supplemented with 10ng/ml Epidermal Growth Factor (EGF, Sigma-Aldrich), 1µg/ml Hydrocortisone (Sigma-Aldrich), 10mmol/l Glutamine (Invitrogen, Carlsbad, CA, USA) and 10% fetal bovine serum (FBS, Invitrogen).…”

“…In the case of defective apoptosis, it may contribute to etiological aspects of autoimmune diseases [11][12][13]. We have previously found that ACE2 induced upregulation of Bcl-2 protein in the mouse lung after ALI [9], whereas the mechanisms remain to be determined.…”

“…ACE2 is the homolog of ACE but counterbalances the ACE activity through induction of degradation of Ang II [5]. Recently, we and others have shown that ACE2 has therapeutic effects on ALI, at least partially through suppression of apoptosis of PECs [6][7][8][9][10]. However, the molecular mechanisms underlying the inhibitory effects of ACE2 on cell apoptosis are not completely understood.…”

miR-4262 regulates chondrocyte viability, apoptosis, autophagy by targeting SIRT1 and activating PI3K/AKT/mTOR signaling pathway in rats with osteoarthritis

“…Previous study has suggested that miR-4262 participates in the development of acute lung injury through regulating the apoptosis of pulmonary endothelial cells (13). Zhang et al (14) and Lu et al (15) have demonstrated that miR-4262 exerts pro-proliferation effect in human cutaneous malignant melanoma cells and hepatocellular carcinoma cells.…”