title: Chronic lung injury in the neonatal rat: up-regulation of TGFβ1 and nitration of IGF-R1 by peroxynitrite as likely contributors to impaired alveologenesis.
abstract: Postnatal alveolarization is regulated by a number of growth factors, including insulin-like growth factor-I (IGF-I) acting through the insulin-like growth factor receptor-1 (IGF-R1). Exposure of the neonatal rat lung to 60% O2 for 14 days results in impairments of lung cell proliferation, secondary crest formation, and alveologenesis. This lung injury is mediated by peroxynitrite and is prevented by treatment with a peroxynitrite decomposition catalyst. We hypothesized that one of the mechanisms by which peroxynitrite induces lung injury in 60% O2 is through nitration and inactivation of critical growth factors or their receptors. Increased nitration of both IGF-I and IGF-R1 was evident in 60% O2-exposed lungs, which was reversible by concurrent treatment with a peroxynitrite decomposition catalyst. Increased nitration of the IGF-R1 was associated with its reduced activation, as assessed by IGF-R1 phosphotyrosine content. IGF-I displacement binding plots were conducted in vitro using rat fetal lung distal epithelial cells which respond to IGF-I by an increase in DNA synthesis. When IGF-I was nitrated to a degree similar to that observed in vivo there was minimal, if any, effect on IGF-I displacement binding. In contrast, nitrating cell IGF-R1 to a similar degree to that observed in vivo completely prevented specific binding of IGF-I to the IGF-R1, and attenuated an IGF-I-mediated increase in DNA synthesis. Additionally, we hypothesized that peroxynitrite also impairs alveologenesis by being an upstream regulator of the growth inhibitor, TGFβ1. That 60% O2-induced impairment of alveologenesis was mediated in part by TGFβ1 was confirmed by demonstrating an improvement in secondary crest formation when 60% O2-exposed pups received concurrent treatment with the TGFß1 activin receptor-like kinase, SB 431542. That the increased TGFβ1 content in lungs of pups exposed to 60% O2 was regulated by peroxynitrite was confirmed by its attenuation by concurrent treatment with a peroxynitrite decomposition catalyst. We conclude that peroxynitrite contributes to the impaired alveologenesis observed following the exposure of neonatal rats to 60% O2 both by preventing binding of IGF-I to the IGF-R1, secondary to nitration of the IGF-R1, and by causing an up-regulation of the growth inhibitor, TGFβ1.
authors.affiliation: Lung Biology Programme, Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 1X8.
authors.forename: Rosetta
authors.initials: R
authors.lastname: Belcastro
authors.affiliation: Lung Biology Programme, Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 1X8.
authors.forename: Lianet
authors.initials: L
authors.lastname: Lopez
authors.affiliation: Lung Biology Programme, Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 1X8.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Lung Biology Programme, Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 1X8; Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8.
authors.forename: Azhar
authors.initials: A
authors.lastname: Masood
authors.affiliation: Lung Biology Programme, Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 1X8; Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8; Department of Paediatrics, University of Toronto, Toronto, Ontario M5G 1X8. Electronic address: keith.tanswell@sickkids.ca.
authors.forename: A Keith
authors.initials: AK
authors.lastname: Tanswell
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001549:Benzamides / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004149:Dioxoles / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D018496:Hyperoxia / Q000150:complications / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D055370:Lung Injury / Q000188:drug therapy / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008665:Metalloporphyrins / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors / Q000378:metabolism; D061251:Primary Cell Culture; D011485:Protein Binding; D011650:Pulmonary Alveoli / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017451:Receptors, Somatomedin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism
chemical_list: C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; C466420:5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron(III) chloride; D001549:Benzamides; D004149:Dioxoles; D008665:Metalloporphyrins; D009566:Nitrates; D017451:Receptors, Somatomedin; D053773:Transforming Growth Factor beta1; C548904:insulin-like growth factor-1, rat; D030421:Peroxynitrous Acid; D007334:Insulin-Like Growth Factor I; D004247:DNA
keywords: Alveolar formation; Bronchopulmonary Dysplasia; Growth factors; Oxygen toxicity; Peroxynitrite; Protein Nitration; TGFβ1