title: Altered regulation of retinoic acid synthesis in nitrofen-induced hypoplastic lung.
abstract: Retinoids are a group of molecules derived from vitamin A, which play an important role in lung development. Within the cell, retinol can either be oxidized to retinal or esterified to retinyl esters by lecithin : retinol acyltransferase (LRAT) for storage. Retinal is then oxidized to an active metabolite of vitamin A, retinoic acid (RA) by retinal dehydrogenase (RALDH). RA is the active metabolite of vitamin A. Cyp26 (a1,b1, and c1), which is a member of the cytochrome P450 family, acts by reducing the activity of RA. Cyp26 type b1 is the predominant subtype expressed in the murine lung. Several studies have suggested that nitrofen may interfere with the retinoid pathway resulting in congenital diaphragmatic hernia (CDH) and pulmonary hypoplasia. Recently, it was reported that nitrofen may act by inhibiting RALDH2. The aim of this study was to examine the pulmonary expression of Cyp26b1, LRAT, and RALDH2, the key enzymes involved in the synthesis of RA, in order to understand the mechanisms underlying pulmonary hypoplasia in the nitrofen CDH model. Pregnant rats were exposed to either olive oil or 100 mg of nitrofen on day 9 of gestation (D9). Fetal lungs were harvested at D15, D17, D19, and D21. D17, D19, and D21 lungs were divided into three groups: control, nitrofen without CDH and nitrofen with CDH, whereas D15 lungs were divided into only two groups; control and nitrofen as the diaphragm is not fully formed yet at this stage. Real- time PCR was performed to evaluate the relative level of Cyp26b1, LRAT, and RALDH2 expression in the lung. Relative levels of Cyp26b1 mRNA were significantly decreased in the lungs of nitrofen with CDH (D17;0.19 +/- 0.09, D19;0.70 +/- 0.20, D21;0.40 +/- 0.36) and nitrofen without CDH (D17;0.14 +/- 0.06, D19;0.54 +/- 0.42, D21;0.51 +/- 0.56) compared to controls (D17;0.35 +/- 0.16, D19;1.15 +/- 0.48, D21;1.28 +/- 0.78) (P < 0.05). LRAT expression was also significantly decreased in nitrofen with CDH (D17; 19.3 +/- 7.8, D19; 4.3 +/- 1.1, D21; 3.3 +/- 1.6) and nitrofen without CDH (D17; 21.2 +/- 11.1, D19; 4.5 +/- 3.6, D21; 4.1 +/- 1.6) compared to controls (D17; 153.7 +/- 29.8, D19; 26.8 +/- 16.8 D21; 10.1 +/- 3.8) (P < 0.05). There was no significant difference in the relative levels of Cyp26b1 and LRAT between nitrofen with CDH and nitrofen without CDH. There were no significant differences in RALDH2 expression among the groups at any stages. Down-regulation of Cryp26b1 and LRAT demonstrates that RA content is decreased in nitrofen induced hypoplastic lungs compared to controls. The finding that RALDH2 expression in the hypoplastic lung is not altered suggests that nitrofen may act by interfering with the retinoid metabolism during the early stage of the retinoid signaling pathway.
authors.affiliation: The Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin 12, Ireland.
authors.forename: Nana
authors.initials: N
authors.lastname: Nakazawa
authors.forename: Hajime
authors.initials: H
authors.lastname: Takayasu
authors.forename: Sandra
authors.initials: S
authors.lastname: Montedonico
authors.forename: Prem
authors.initials: P
authors.lastname: Puri
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D006540:Herbicides / Q000008:administration & dosage / Q000633:toxicity*; D006548:Hernia, Diaphragmatic / Q000139:chemically induced* / Q000201:enzymology; D065630:Hernias, Diaphragmatic, Congenital; D008168:Lung / Q000002:abnormalities* / Q000187:drug effects / Q000201:enzymology; D008171:Lung Diseases / Q000139:chemically induced* / Q000201:enzymology / Q000503:physiopathology; D000069463:Olive Oil; D010647:Phenyl Ethers / Q000008:administration & dosage / Q000633:toxicity*; D010938:Plant Oils / Q000008:administration & dosage; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D050697:Retinal Dehydrogenase / Q000378:metabolism; D000072516:Retinoic Acid 4-Hydroxylase; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D006540:Herbicides; D000069463:Olive Oil; D010647:Phenyl Ethers; D010938:Plant Oils; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D000072516:Retinoic Acid 4-Hydroxylase; C521403:Aldh1a2 protein, rat; D050697:Retinal Dehydrogenase; D000217:Acyltransferases; C056942:lecithin-retinol acyltransferase; C007350:nitrofen