ACE2 Attenuates Epithelial-Mesenchymal Transition in MLE-12 Cells Induced by Silica

Drug Des Devel Ther. 2020 Apr 21:14:1547-1559. doi: 10.2147/DDDT.S252351. eCollection 2020.

Abstract

Purpose: The role of angiotensin-converting enzyme 2 (ACE2) in silicosis remains unknown, although previous studies have suggested that ACE2 may be beneficial. We, therefore, investigated the effect of ACE2 on silicosis, particularly with regard to its role in regulating the epithelial-mesenchymal transition (EMT) induced by silica, with the aim to uncover a new potential target for the treatment of pulmonary fibrosis.

Materials and methods: We employed wild-type mice treated with diminazene aceturate (DIZE, an ACE2 activator, 15 mg/kg/day for 4 weeks), hACE2-transgenic mice (overexpress the ACE2 gene), and the mouse lung type II epithelial cell line treated with DIZE (10-7 M for 48 h) or angiotensin-(1-7) [Ang-(1-7)] (10-4 M for 48 h), following induced fibrotic responses to determine the protective potential of ACE2. Silicosis models were established by orotracheal instillation of SiO2 (2.5 mg/mouse). Immunostaining was used to determine α-smooth muscle actin (α-SMA) expression. The activities of angiotensin-converting enzyme (ACE) and ACE2 and the levels of angiotensin II (Ang II) and Ang-(1-7) were detected by enzyme-linked immunosorbent assay. The mRNA expression of ACE and ACE2, and protein expression of the renin-angiotensin system (RAS) components and EMT indicators were studied by qRT-PCR and Western blot, respectively.

Results: DIZE treatment and overexpression of ACE2 markedly inhibited the formation of silica-induced lung fibrosis and increased the level of E-cadherin, with concomitant downregulation of pro-collagen, vimentin, and α-SMA via RAS signaling. Furthermore, DIZE and Ang-(1-7) attenuated the EMT and collagen deposition induced by silica in MLE-12 cells. Moreover, these effects were abrogated by MLN-4760 (a specific ACE2 inhibitor) and A779 (a specific Mas receptor blocker).

Conclusion: The overexpression of ACE2 and treatment with DIZE can ameliorate EMT in silicotic mice via activation of the ACE2-Ang-(1-7)-Mas receptor axis, and these changes are accompanied by suppression of the ACE-Ang II-AT1 receptor axis.

Keywords: angiotensin-converting enzyme; angiotensin-converting enzyme 2; diminazene aceturate; renin–angiotensin system; silicosis fibrosis; transgenic mice.

MeSH terms

  • Angiotensin-Converting Enzyme 2 / genetics
  • Angiotensin-Converting Enzyme 2 / metabolism*
  • Animals
  • Cell Line
  • Dose-Response Relationship, Drug
  • Epithelial-Mesenchymal Transition / drug effects*
  • Male
  • Mice
  • Mice, Inbred ICR
  • Silicon Dioxide / pharmacology*
  • Silicosis / metabolism*
  • Structure-Activity Relationship

Substances

  • Silicon Dioxide
  • Ace2 protein, mouse
  • Angiotensin-Converting Enzyme 2

Grants and funding

This study was supported by the National Natural Science Foundation of China (grant no. 81972988); National Natural Science Foundation of China (grant no. 81472953); Natural Science Foundation of Hebei Province (grant no. H2016209170); Postgraduate Innovation Funding Program of Hebei Province (No. CXZZBS2017127); Postgraduate Student Innovation Fund of North China University of Science and Technology (grant no. 2017B10).