The calcitriol analogue EB1089 impairs alveolarization and induces localized regions of increased fibroblast density in neonatal rat lung.
The active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3, or calcitriol), is a potent mitogen for fibroblasts cultured from rat lungs at postnatal day 4 (P4), during the peak of septation (P3 to P7). In light of the key role of fibroblasts in alveolar septation, the authors conducted studies to measure the extent to which 1,25-(OH)2D3 affects lung maturation in vivo, as well as its ability to influence the stimulatory activity of all-trans retinoic acid (RA). To identify a calcitriol analogue with maximal mitogenic activity and low systemic toxicity, two compounds with reduced calcemic activity (EB1089 and CB1093) and a superagonist (MC1288) were evaluated in neonatal rat lung fibroblast cultures. All 3 analogues were more potent mitogens than 1,25-(OH)(2)D3 itself (MC1288 approximately CB1093 > EB1089 > 1,25-(OH)2D3). In addition, each was more effective than 1,25-(OH)2D3(EB1089 > CB1093 > MC1288 > 1,25-(OH)2D3) in the activation of a vitamin D response element from the platelet-derived growth factor (PDGF)-A gene, whose expression is essential for normal alveolarization. Daily administration of EB1089 to rats 4 to 12 days of age caused an increase in mean alveolar chord length (P < .0001), and also elicited prominent regions of fibroblast hypercellularity, as defined in terms of a vimentin-positive, factor VIII-negative phenotype. EB1089 and RA each induced the expression of 2 important lung structural proteins, collagen and elastin. Regions of fibroblast hypercellularity induced by EB1089 were strongly positive for expression of the alveolarization-relevant growth factors, PDGF-AA and vascular endothelial growth factor (VEGF). These studies demonstrate that 1,25-(OH)2D3 disrupts the overall alveolarization process in the neonatal lung, although it stimulates expression of some proteins associated with lung morphogenesis.
Ormerod
Angela K
AK
Department of Molecular and Biomedical Pharmacology, College of Medicine, 800 Rose Street, University of Kentucky, Lexington, Kentucky 40536-0298, USA.
Xing
Zhenlan
Z
Pedigo
Nancy G
NG
Mishra
Anjali
A
Kaetzel
David M
DM
D000818:Animals; D000831:Animals, Newborn; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology; D048708:Cell Growth Processes / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis; D004357:Drug Synergism; D004549:Elastin / Q000096:biosynthesis; D005169:Factor VIII / Q000096:biosynthesis; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008934:Mitogens / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis / Q000235:genetics; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014212:Tretinoin / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis; D014746:Vimentin / Q000096:biosynthesis; D030181:Vitamin D Response Element / Q000187:drug effects / Q000235:genetics
D008934:Mitogens; D010982:Platelet-Derived Growth Factor; D042461:Vascular Endothelial Growth Factor A; D014746:Vimentin; C075278:platelet-derived growth factor A; D014212:Tretinoin; D005169:Factor VIII; D003094:Collagen; D004549:Elastin; D002117:Calcitriol; C078903:seocalcitol