Effect of Glutathione on Lung Activator Protein-1 Activation and Heme Oxygenase-1 Induction in the Immature Rat

Abstract

Differences in lung heme oxygenase-1 (HO-1) regulation have been demonstrated in newborn (Ͻ12 h old) and adult (Ͼ2 month old) rats after exposure to hyperoxia. Contrary to adults, neonates do not demonstrate increased lung HO-1 induction nor transcription factor activator protein-1 (AP-1) binding in hyperoxia. Because AP-1 activation can be posttranslationally modified by oxidants or reductants, we investigated whether differences in lung glutathione (GSH) content account for the maturational differences in AP-1 activation and subsequent HO-1 gene regulation after hyperoxia. Neonatal rats were injected with either 1-buthionine-[S,R] sulfoximine (BSO), diamide, or selenite during the 72-h hyperoxic exposure. Lung GSH content, glutathione disulfide (GSSG) content, AP-1 binding, and HO-1 mRNA were evaluated. The ratios of GSSG to GSH were used to reflect the GSH redox state in the lungs. Changes in lung GSSG/GSH ratio did not alter AP-1 binding but did increase HO-1 mRNA in neonates. These data suggest that the neonatal lung is relatively resistant to AP-1 activation and HO-1 induction by GSH perturbation. HO-1, the rate-limiting enzyme in the degradation of heme to bilirubin, is a stress response protein with antioxidant properties. This enzyme is differentially expressed in the lungs of neonatal and adult rats after exposure to hyperoxia. Contrary to adult rats, neonates did not demonstrate increased HO-1 induction (1) nor lung transcription factor AP-1 binding (2) in hyperoxia. Nonetheless, the neonates were able to compensate for the lack of HO-1 mRNA induction by elevating lung HO-1 protein and total HO activity, perhaps through posttranscriptional mechanisms. It is not clear what events mediate the lack of HO-1 mRNA induction and the lack of change in AP-1 binding in the neonatal lungs after hyperoxia.The transcription factor AP-1 is a known stress response complex that functions in signal transduction by inducing the expression of specific downstream genes. The AP-1 complex consists of various heterodimers of fos/jun proteins or homodimers of jun/jun proteins. Several mechanisms are believed to be involved in regulating AP-1 transcriptional activity, including differential gene expression of fos or jun, conformational alterations, posttranslational modification, and altered DNA-binding specificities of the heterodimers (3). In vitro studies demonstrate that AP-1 DNA-binding activity can be modulated by oxidants or reductants via a conserved cysteine residue on the DNA binding domains of either jun or fos protein (4). Alterations of AP-1 binding activity are also observed in many in vivo situations where the cellular GSH content is changed, such as in oxidative stress.GSH coexists with its disulfide, GSSG. Either increased GSSG content or an increased GSSG/GSH ratio can reflect cellular oxidative stress. Many studies have shown that antioxidant agents (5, 6) or antioxidant enzyme systems such as the thioredoxin/thioredoxin reductase complex (7-9) decrease the ratio of GSSG/GSH and enhance AP-1 binding activit...

Molecular mechanisms of hyperoxia-induced acute lung injury

“…Changes in lung GSSG/GSH ratio did not alter AP-1 binding but did increase HO-1 mRNA in neonates. These data suggest that the neonatal lung is relatively resistant to AP-1 activation and HO-1 induction by GSH perturbation (113).…”

“…Differences in lung heme oxygenase-1 (HO-1) regulation have been demonstrated in NB rats after exposure to hyperoxia. Contrary to adults, neonates do not demonstrate increased lung HO-1 induction nor AP-1 binding in hyperoxia (113). As AP-1 activation can be post-translationally modified by oxidants or reductants, Yang et al investigated whether differences in lung glutathione (GSH) content could account for the maturational differences in AP-1 activation and subsequent HO-1 gene regulation after hyperoxia.…”

Cigarette smoke-induced expression of heme oxygenase-1 in human lung fibroblasts is regulated by intracellular glutathione

“…Induction of HO-1 in response to GSH depletion has been shown in the mouse (58) and rat (49) liver; this GSH-related increase in HO-1 is proposed to have antiapoptotic and/or antioxidant properties (57,60,64,72) that would serve to counteract the loss of intracellular GSH. We hypothesized that cigarette smoke would induce HO-1 in lung fibroblasts because of alterations in intracellular GSH levels.The molecular mechanisms involved in the induction of HO-1 are diverse and include transcription factors such as nuclear factor-B (NF-B), mitogen-activated protein kinases (MAPKs), activator protein-1 (AP-1) and nuclear factor, erythroid-derived 2, like 2 (Nrf2) (4,33,38,39,74). These transcription factors are sensitive to conditions of oxidative stress, particularly Nrf2.…”

“…The molecular mechanisms involved in the induction of HO-1 are diverse and include transcription factors such as nuclear factor-B (NF-B), mitogen-activated protein kinases (MAPKs), activator protein-1 (AP-1) and nuclear factor, erythroid-derived 2, like 2 (Nrf2) (4,33,38,39,74). These transcription factors are sensitive to conditions of oxidative stress, particularly Nrf2.…”

Interleukin-10 Inhibits Proinflammatory Chemokine Release by Neutrophils of the Newborn without Suppression of Nuclear Factor-κB

“…Studies from our laboratory have demonstrated that there are developmental differences in IL-8 production (PMNs from newborns releasing IL-8 to a greater degree than PMNs from adults) and associated NF-B activity (3,9). In addition, recent studies have shown maturational differences in the regulation of another transcription factor, activating protein-1 (23,24), as well as in the expression of cell-surface receptors (25)(26)(27).…”