Hyperoxia-Induced Lung Injury in Gamma-Glutamyl Transferase Deficiency Is Associated with Alterations in Nitrosative and Nitrative Stress

Abstract

␥-Glutamyl transferase (GGT) regulates glutathione metabolism and cysteine supply. GGT inactivation in GGT enu1 mice limits cysteine availability causing cellular glutathione deficiency. In lung, the resultant oxidant burden is associated with increased nitric oxide (NO) production, yet GGT enu1 mice still exhibit higher mortality in hyperoxia. We hypothesized that NO metabolism is altered under severe oxidant stress and contributes to lung cellular injury and death. We compared lung injury, NO synthase (NOS) expression, nitrate/nitrite production, nitroso product formation, peroxynitrite accumulation, and cell death in wild-type and GGT enu1 mice in normoxia and hyperoxia. The role of NOS activity in cell death was determined by NOS inhibition. Exposure of wild-type mice to hyperoxia caused increased lung injury, altered NO metabolism, and induction of cell death compared with normoxia, which was attenuated by NOS inhibition. Each of these lung injury indices were magnified in hyperoxia-exposed GGT enu1 mice except nitrosation , which showed a diminished decrease compared with wild-type mice. NOS inhibition attenuated cell death only slightly , likely due to further exacerbation of oxidant stress. Taken together , these data suggest that apoptosis in hyperoxia is partially NO-dependent and reiterate the importance of cellular glutathione in lung antioxidant defense. Therefore, reduced denitrosylation of proteins, possibly resulting in impaired cellular repair, and excessive apoptotic cell death likely contribute to increased lung injury and mortality of GGT enu1 mice in hyperoxia.

Transcription Factor Klf4, Induced in the Lung by Oxygen at Birth, Regulates Perinatal Fibroblast and Myofibroblast Differentiation

“…Cellular apoptosis was assessed by immunohistochemistry using antibodies against activate phosphorylated p53 (sc-18078-R, mSer20), p21 cip1/Waf1 (C-19 sc-397) and caspase-3 (H-277, sc-7148) [27]. All antibodies were from Santa Cruz Biotechnology (Santa Cruz, CA).…”

Increased Hyperoxia-Induced Lung Injury in Nitric Oxide Synthase 2 Null Mice Is Mediated via Angiopoietin 2

“…Most data suggest that hyperoxia exposure up-regulates inducible NOS (NOS2) and endothelial NOS (NOS3) expression in adult (8)(9)(10)(11)(12)(13)(14)(15)(16) and neonatal (7,(16)(17)(18)(19) lungs. In ALI and cell death, the endogenous production of NO is said to be mostly contributed by up-regulation of NOS2 in the lung (20)(21)(22).…”

Novel Peptide for Attenuation of Hyperoxia-induced Disruption of Lung Endothelial Barrier and Pulmonary Edema via Modulating Peroxynitrite Formation

“…The superoxide radicals react with NO generated by eNOS and form more potent oxidizing reactive nitrogen species such as peroxynitrite. eNOS plays an important role in peroxynitrite formation and protein tyrosine nitration in endothelial cells during hyperoxia (4,9,21). L-Arginine, a substrate for NOS, enhances injury in the isolated rabbit lung during hyperoxia (22).…”

“…Effective therapy is lacking because the molecular mechanism of hyperoxia-induced vascular leakage is not completely understood. The hyperoxia-induced damages to lung cells have been attributed to the generation of reactive oxygen species and subsequent formation of more potent oxidants such as peroxynitrite (3)(4)(5). Reactive oxygen species generated during hyperoxia have been shown to increase lung vascular leakage due to endothelial injuries in oxygen toxicity (6 -8).…”