O₂-evoked regulation of HIF-1α and NF-κB in perinatal lung epithelium requires glutathione biosynthesis

Abstract

To test the genetic capacity of the perinatal lung to respond to O(2) shifts that coincide with the first respiratory movements, rat fetal alveolar type II (fATII) epithelial cells were cultured at fetal distal lung PO(2) (23 Torr) and then exposed to postnatal (23 --> 76 Torr; mild hyperoxic shift), moderate (23 --> 152 Torr; moderate hyperoxic shift), or severe (23 --> 722 Torr; severe hyperoxic shift) oxygenation. Nuclear abundance and consensus binding characteristics of hypoxia-inducible factor (HIF)-1alpha and nuclear factor (NF)-kappaB (Rel A/p65) plus glutathione biosynthetic capacity were determined. Maximal HIF-1alpha activation at 23 Torr was sustained over the postnatal shift in (Delta) PO(2) and was elevated in vivo throughout late gestation. NF-kappaB was activated by the acute postnatal DeltaPO(2) in fATII cells, becoming maximal with moderate and severe oxygenation in vitro and within 6 h of birth in vivo, declining thereafter. fATII cell and whole lung glutathione and GSH-to-GSSG ratio increased fourfold with a postnatal DeltaPO(2) and were matched by threefold activity increases in gamma-glutamylcysteine synthetase and glutathione synthase. GSH concentration depletion by L-buthionine-(S, R)-sulfoximine abrogated both HIF-1alpha and NF-kappaB activation, with HIF-1alpha showing a heightened sensitivity to GSH concentration. We conclude that O(2)-linked genetic regulation in perinatal lung epithelium is responsive to developmental changes in glutathione biosynthetic capacity.