Prior hypoxia prevents downregulation of ACE-2 by hyperoxia in fetal human lung fibroblasts.
Purpose/Aim of Study: The renin angiotensin system is involved in experimentally induced lung fibrosis. Angiotensin (ANG)-II is profibrotic. Angiotensin converting enzyme-2 (ACE-2) cleaves ANG-II and is thus protective. ACE-2 has recently been reported to be significantly decreased under hyperoxic conditions. Hyperoxia is linked to Bronchopulmonary Dysplasia and lung fibrosis. Fetal lung cells normally do not undergo fibrotic changes with physiologic hypoxemia. We hypothesized that hypoxia prior to hyperoxic exposure in fetal lung fibroblasts (IMR-90 cell line) might be protective by preventing ACE-2 downregulation.


METHODS
IMR-90 cells were exposed to hypoxia (1%O2/99%N2) followed by hyperoxia (95%O2/5%CO2) or normoxia (21%O2) in vitro. Cells and culture media were recovered separately for assays of ACE-2, TNF-α-converting enzyme (TACE), αSmooth muscle actin (αSMA)-myofibroblast marker-, N-cadherin, and β-catenin immunoreactive protein.


RESULTS
ACE-2 significantly increased when IMR-90 were hypoxic prior to hyperoxic exposure with no recovery. In contrast to hyperoxia alone, ACE-2 did not decrease when IMR-90 were hypoxic prior to hyperoxic exposure with recovery. TACE/ADAM17 protein and mRNA were significantly decreased under these conditions. αSMA N-cadherin, and β-catenin proteins were significantly decreased with or without normoxic recovery.


CONCLUSIONS
Hypoxia prior to hyperoxic exposure of fetal lung fibroblasts prevented ACE-2 downregulation and decreased ADAM17/TACE protein and mRNA. αSMA, N-cadherin, and β-catenin were also significantly decreased under these conditions.
a Department of Pediatrics and Human Development , Division of Neonatology , Michigan State University , East Lansing , Michigan , USA.
Tarek L
TL
Mohamed
b Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan , USA.
Hang T
HT
Nguyen
a Department of Pediatrics and Human Development , Division of Neonatology , Michigan State University , East Lansing , Michigan , USA.
Amal
A
Abdul-Hafez
c Department of Physiology , Michigan State University , East Lansing , Michigan , USA.
Vinh X
VX
Dang
d Department of Microbiology and Molecular Genetics , Michigan State University , East Lansing , Michigan , USA.
MyTrang T
MT
Dang
a Department of Pediatrics and Human Development , Division of Neonatology , Michigan State University , East Lansing , Michigan , USA.
Ira H
IH
Gewolb
c Department of Physiology , Michigan State University , East Lansing , Michigan , USA.
Bruce D
BD
Uhal
D000199:Actins / Q000378:metabolism; D000804:Angiotensin II / Q000378:metabolism; D000085962:Angiotensin-Converting Enzyme 2; D015820:Cadherins / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism / Q000503:physiopathology*; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D008168:Lung / Q000378:metabolism / Q000502:physiology*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D011658:Pulmonary Fibrosis / Q000378:metabolism / Q000503:physiopathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
D000199:Actins; D015820:Cadherins; D014409:Tumor Necrosis Factor-alpha; D051176:beta Catenin; D000804:Angiotensin II; D007703:Peptidyl-Dipeptidase A; C000705307:ACE2 protein, human; D000085962:Angiotensin-Converting Enzyme 2
bronchopulmonary dysplasia; chronic lung disease; fetal lung fibroblasts; hyperoxia; hypoxia