Prenatal administration of all-trans retinoic acid upregulates leptin signaling in hypoplastic rat lungs with experimental congenital diaphragmatic hernia.

Abstract

PURPOSE:

Pulmonary hypoplasia (PH), characterized by alveolar immaturity, is one of the leading causes of respiratory insufficiency in newborns with congenital diaphragmatic hernia (CDH). Leptin (Lep) and its receptor (Lep-R) play an important role in fetal lung growth by stimulating alveolar differentiation and maturation. Lep and Lep-R are strongly expressed by alveolar cells during the saccular stage of fetal lung development. Lep-deficient mice exhibit decreased alveolarization with reduced pulmonary surfactant phospholipid synthesis, similar to human and nitrofen-induced PH. Prenatal administration of all-trans retinoic acid (ATRA) has been shown to stimulate alveolarization in nitrofen-induced PH. Recent studies have demonstrated that Lep and Lep-R expression in developing lungs is regulated by ATRA. We hypothesized that prenatal treatment with ATRA increases pulmonary Lep and Lep-R expression in the nitrofen model of CDH-associated PH.

METHODS:

Time-mated rats received either 100 mg nitrofen or vehicle via oral-gastric lavage on embryonic day 9.5 (E9.5). Control and nitrofen-exposed dams were randomly assigned to either intraperitoneal ATRA (5 mg/kg/d) or placebo administration on E18.5, E19.5 and E20.5. Fetal lungs were harvested on E21.5, and divided into Control+Placebo, Control+ATRA, Nitrofen+Placebo and Nitrofen+ATRA. Alveolarization was assessed using stereo- and morphometric analysis techniques. Surfactant phospholipid synthesis was analyzed by labeling for surfactant protein B (SP-B). Pulmonary gene expression levels of Lep and Lep-R were determined using quantitative real-time polymerase chain reaction. Immunohistochemical staining for Lep and Lep-R was performed to evaluate alveolar protein expression and localization.

RESULTS:

In vivo administration of ATRA resulted in significantly increased lung-to-body weight ratio with enhanced radial alveolar count and decreased mean linear intercept compared to placebo treatment. Immunofluorescence analysis demonstrated markedly increased pulmonary SP-B expression in Nitrofen+ATRA compared to Nitrofen+Placebo. Relative mRNA expression of Lep and Lep-R was significantly increased in Nitrofen+ATRA compared to Nitrofen+Placebo. Lep and Lep-R immunoreactivity was markedly increased in interstitial and alveolar epithelial cells of Nitrofen+ATRA compared to Nitrofen+Placebo.

CONCLUSION:

Increased Lep and Lep-R expression after prenatal administration of ATRA in nitrofen-induced PH suggests that ATRA may have therapeutic potential in attenuating CDH-associated PH by stimulating alveolarization and de novo surfactant production.

• Authors: Florian Friedmacher, Alejandro Daniel Hofmann, Toshiaki Takahashi, Hiromizu Takahashi, Balazs Kutasy, Prem Puri
• Journal: Pediatric surgery international (Pediatr Surg Int) Vol. 30 Issue 12 Pg. 1183-90 (Dec 2014) ISSN: 1437-9813 [Electronic] Germany
• PMID: 25330951 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Leptin
• RNA, Messenger
• Tretinoin

Topics

• Animals
• Disease Models, Animal
• Female
• Hernias, Diaphragmatic, Congenital (drug therapy, genetics, metabolism)
• Immunohistochemistry
• Leptin (biosynthesis, genetics)
• Lung (embryology, metabolism)
• Organogenesis (drug effects)
• Pregnancy
• Pregnancy, Animal
• RNA, Messenger (genetics)
• Rats
• Rats, Sprague-Dawley
• Real-Time Polymerase Chain Reaction
• Signal Transduction
• Tretinoin (pharmacology)
• Up-Regulation (drug effects)