Hyperoxia downregulates angiotensin-converting enzyme-2 in human fetal lung fibroblasts.

Chinyere I Oarhe, Vinh Dang, MyTrang Dang, Hang Nguyen, Indiwari Gopallawa, Ira H Gewolb, Bruce D Uhal

Index: Pediatr. Res. 77(5) , 656-62, (2015)

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Abstract

Angiotensin (ANG) II is involved in experimental hyperoxia-induced lung fibrosis. Angiotensin-converting enzyme-2 (ACE-2) degrades ANG II and is thus protective, but is downregulated in adult human and experimental lung fibrosis. Hyperoxia is a known cause of chronic fibrotic lung disease in neonates, but the role of ACE-2 in neonatal lung fibrosis is unknown. We hypothesized that ACE-2 in human fetal lung cells might be downregulated by hyperoxic gas.Fetal human lung fibroblast IMR90 cells were exposed to hyperoxic (95% O2/5% CO2) or normoxic (21% O2/5% CO2) gas in vitro. Cells and culture media were recovered separately for assays of ACE-2 enzymatic activity, mRNA, and immunoreactive protein.Hyperoxia decreased ACE-2 immunoreactive protein and enzyme activity in IMR90 cells (both P < 0.01), but did not change ACE-2 mRNA. ACE-2 protein was increased in the cell supernatant, suggesting protease-mediated ectodomain shedding. TAPI-2, an inhibitor of TNF-α-converting enzyme (TACE/ADAM17), prevented both the decrease in cellular ACE-2 and the increase in soluble ACE-2 (both P < 0.05).These data show that ACE-2 is expressed in fetal human lung fibroblasts but is significantly decreased by hyperoxic gas. They also suggest that hyperoxia decreases ACE-2 through a shedding mechanism mediated by ADAM17/TACE.