Antenatal endotoxin disrupts lung vitamin D receptor and 25-hydroxyvitamin D 1α-hydroxylase expression in the developing rat.
Vitamin D [vit D; 1,25-(OH)2D] treatment improves survival and lung alveolar and vascular growth in an experimental model of bronchopulmonary dysplasia (BPD) after antenatal exposure to endotoxin (ETX). However, little is known about lung-specific 1,25-(OH)2D3 regulation during development, especially regarding maturational changes in lung-specific expression of the vitamin D receptor (VDR), 1α-hydroxylase (1α-OHase), and CYP24A1 during late gestation and the effects of antenatal ETX exposure on 1,25-(OH)2D3 metabolism in the lung. We hypothesized that vit D regulatory proteins undergo maturation regulation in the late fetal and early neonatal lung and that prenatal exposure to ETX impairs lung growth partly through abnormal endogenous vit D metabolism. Normal fetal rat lungs were harvested between embryonic day 15 and postnatal day 14. Lung homogenates were assayed for VDR, 1α-OHase, and CYP24A1 protein contents by Western blot analysis. Fetal rats were injected on embryonic day 20 with intra-amniotic ETX, ETX + 1,25-(OH)2D3, or saline and delivered 2 days later. Pulmonary artery endothelial cells (PAECs) from fetal sheep were assessed for VDR, 1α-OHase, and CYP24A1 expression after treatment with 25-(OH)D3, 1,25-(OH)2D3, ETX, ETX + 25-(OH)D3, or ETX + 1,25-(OH)2D3. We found that lung VDR, 1α-OHase, and CYP2741 protein expression dramatically increase immediately before birth (P < 0.01 vs. early fetal values). Antenatal ETX increases CYP24A1 expression (P < 0.05) and decreases VDR and 1α-OHase expression at birth (P < 0.001), but these changes are prevented with concurrent vit D treatment (P < 0.001). ETX-induced reduction of fetal PAEC growth and tube formation and lung 1α-OHase expression are prevented by vit D treatment (P < 0.001). We conclude that lung VDR, 1α-OHase, and CYP24A1 protein content markedly increase before birth and that antenatal ETX disrupts lung vit D metabolism through downregulation of VDR and increased vit D catabolic enzyme expression, including changes in developing endothelium. We speculate that endogenous vitamin D metabolism modulates normal fetal lung development and that prenatal disruption of vit D signaling may contribute to impaired postnatal lung growth at least partly through altered angiogenic signaling.
Pediatric Heart Lung Center, University of Colorado Denver School of Medicine, Aurora, Colorado; Section of Neonatology, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado; erica.mandell@childrenscolorado.org.
Erica
E
Mandell
Pediatric Heart Lung Center, University of Colorado Denver School of Medicine, Aurora, Colorado; Section of Pulmonary Medicine, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado; and.
Gregory J
GJ
Seedorf
Pediatric Heart Lung Center, University of Colorado Denver School of Medicine, Aurora, Colorado; Section of Neonatology, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado;
Sharon
S
Ryan
Pediatric Heart Lung Center, University of Colorado Denver School of Medicine, Aurora, Colorado; Section of Neonatology, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado;
Jason
J
Gien
Department of Parmacology, University of Colorado Denver School of Medicine, Aurora, Colorado.
Scott D
SD
Cramer
Pediatric Heart Lung Center, University of Colorado Denver School of Medicine, Aurora, Colorado; Section of Pulmonary Medicine, Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado; and.
Steven H
SH
Abman
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000096:biosynthesis*; D000818:Animals; D001997:Bronchopulmonary Dysplasia / Q000139:chemically induced / Q000196:embryology / Q000473:pathology; D002112:Calcifediol / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D004731:Endotoxins / Q000633:toxicity*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D008168:Lung / Q000196:embryology* / Q000473:pathology; D011651:Pulmonary Artery / Q000196:embryology / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018167:Receptors, Calcitriol / Q000096:biosynthesis*; D012756:Sheep; D065668:Vitamin D3 24-Hydroxylase / Q000096:biosynthesis
D004731:Endotoxins; D018167:Receptors, Calcitriol; C585551:Cyp24a1 protein, rat; D065668:Vitamin D3 24-Hydroxylase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002112:Calcifediol
BPD; angiogenesis; chorioamnionitis; lung development; vitamin D