The angiogenic factor midkine is regulated by dexamethasone and retinoic acid during alveolarization and in alveolar epithelial cells

Zhang Huayan, Garber, Cui Zheng, Foley, Mohan, Jobanputra Minesh, Kaplan Feige, Sweezey, Gonzales, Savani

Description

A precise balance exists between the actions of endogenous glucocorticoids (GC) and retinoids to promote normal lung development, in particular during alveolarization. The mechanisms controlling this balance are largely unknown, but recent evidence suggests that midkine (MK), a retinoic acid-regulated, pro-angiogenic growth factor, may function as a critical regulator. The purpose of this study was to examine regulation of MK by GC and RA during postnatal alveolar formation in rats. Methods Newborn rats were treated with dexamethasone (DEX) and/or all-trans-retinoic acid (RA) during the first two weeks of life. Lung morphology was assessed by light microscopy and radial alveolar counts. MK mRNA and protein expression in response to different treatment were determined by Northern and Western blots. In addition, MK protein expression in cultured human alveolar type 2-like cells treated with DEX and RA was also determined. Results Lung histology confirmed that DEX treatment inhibited and RA treatment stimulated alveolar formation, whereas concurrent administration of RA with DEX prevented the DEX effects. During normal development, MK expression was maximal during the period of alveolarization from postnatal day 5 (PN5) to PN15. DEX treatment of rat pups decreased, and RA treatment increased lung MK expression, whereas concurrent DEX+RA treatment prevented the DEX-induced decrease in MK expression. Using human alveolar type 2 (AT2)-like cells differentiated in culture, we confirmed that DEX and cAMP decreased, and RA increased MK expression. Conclusion We conclude that MK is expressed by AT2 cells, and is differentially regulated by corticosteroid and retinoid treatment in a manner consistent with hormonal effects on alveolarization during postnatal lung development.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2009
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Respiratory Research

BioMedCentral

Open Access Research The angiogenic factor midkine is regulated by dexamethasone and retinoic acid during alveolarization and in alveolar epithelial cells 1 1 1 1 Huayan Zhang , Samuel J Garber , Zheng Cui , Joseph P Foley , 1 1 2 3 Gopi S Mohan , Minesh Jobanputra , Feige Kaplan , Neil B Sweezey , 1 1,4 Linda W Gonzales and Rashmin C Savani*

1 Address: Division of Neonatology, Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, 2 3 Philadelphia, PA, USA, Departments of Human Genetics and Pediatrics, McGill University, Montreal, Canada, Division of Respiratory Medicine, 4 Departments of Pediatrics and Physiology, The Hospital for Sick Children, University of Toronto, Toronto, Canada and Divisions of Pulmonary & Vascular Biology and NeonatalPerinatal Medicine, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA

Email: Huayan Zhang  [e-mail]; Samuel J Garber  [e-mail]; Zheng Cui  [e-mail]; Joseph P Foley  [e-mail]; Gopi S Mohan  [e-mail]; Minesh Jobanputra  [e-mail]; Feige Kaplan  [e-mail]; Neil B Sweezey  [e-mail]; Linda W Gonzales  [e-mail]; Rashmin C Savani*  [e-mail] * Corresponding author

Published: 21 August 2009 Received: 11 January 2009 Accepted: 21 August 2009 Respiratory Research2009,10:77 doi:10.1186/146599211077 This article is available from: http://respiratoryresearch.com/content/10/1/77 © 2009 Zhang et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Background:A precise balance exists between the actions of endogenous glucocorticoids (GC) and retinoids to promote normal lung development, in particular during alveolarization. The mechanisms controlling this balance are largely unknown, but recent evidence suggests that midkine (MK), a retinoic acidregulated, proangiogenic growth factor, may function as a critical regulator. The purpose of this study was to examine regulat ion of MK by GC and RA during postnatal alveolar formation in rats.

Methods:Newborn rats were treated with dexamethasone (DEX) and/or alltransretinoic acid (RA) during the first two weeks of life. Lung morphology was assessed by light microscopy and radial alveolar counts. MK mRNA and protein expression in response to different treatment were determined by Northern and Western blots. In addition, MK protein expression in cultured human alveolar type 2like cells treated with DEX and RA was also determined.

Results:Lung histology confirmed that DEX treatment inhibited and RA treatment stimulated alveolar formation, whereas concurrent administration of RA with DEX prevented the DEX effects. During normal development, MK expression was maximal during the period of alveolarization from postnatal day 5 (PN5) to PN15. DEX treatment of rat pups decreased, and RA treatment increased lung MK expression, whereas concurrent DEX+RA treatment prevented the DEXinduced decrease in MK expression. Using human alveolar type 2 (AT2)like cells differentiated in culture, we confirmed that DEX and cAMP decreased, and RA increased MK expression.

Conclusion:We conclude that MK is expressed by AT2 cells, and is differentially regulated by corticosteroid and retinoid treatment in a manner consistent with hormonal effects on alveolarization during postnatal lung development.

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