1alpha,25(OH)2D3 and its 3-epimer promote rat lung alveolar epithelial-mesenchymal interactions and inhibit lipofibroblast apoptosis.
Although alveolar wall thinning has been attributed to apoptosis of interstitial lung lipofibroblasts (LFs), the underlying molecular mechanism(s) remains unknown. Although the physiological vitamin D steroid hormone 1alpha,25(OH)(2)D(3) (1,25D) has been suggested as a local paracrine/autocrine effector of fetal lung maturation and is known to affect fibroblast apoptosis, its effects on LF apoptosis are unknown. We determined the role of 1,25D and its metabolite, C-3-epimer (3-epi-1,25D), on LF and alveolar type II (ATII) cell differentiation, proliferation, and apoptosis. Embryonic day 19 Sprague-Dawley fetal rat lung LFs and ATII cells were treated with 1,25D or 3-epi-1,25D (1 x 10(-10) to 1 x 10(-8) M) for 24 h, and cell proliferation, apoptosis, and differentiation were assessed. Both 1,25D and 3-epi-1,25D exhibited dose-dependent increases in expression of the key homeostatic epithelial-mesenchymal differentiation markers, increased LF and ATII cell proliferation, and decreased apoptosis. Furthermore, rat pups administered 1,25D from postnatal days 0 to 14 showed increased expressions of key LF and ATII cell differentiation markers, increased Bcl-2-to-Bax ratio as an index of decreased spontaneous alveolar LF and ATII cell apoptosis, increased alveolar count, and a paradoxical increase in septal thickness. We conclude that spatial- and temporal-specific actions of vitamin D play a critical role in perinatal lung maturation by stimulating key alveolar epithelial-mesenchymal interactions and by modulating LF proliferation/apoptosis. These data not only provide the biological rationale for the presence of an alveolar vitamin D paracrine system, but also provide the first integrated molecular mechanism for increased surfactant synthesis and alveolar septal thinning during perinatal lung maturation.
Sakurai
R
R
Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA 90502, USA.
Shin
E
E
Fonseca
S
S
Sakurai
T
T
Litonjua
A A
AA
Weiss
S T
ST
Torday
J S
JS
Rehan
V K
VK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers / Q000378:metabolism; D002117:Calcitriol / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D002450:Cell Communication / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects; D005260:Female; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects; D008648:Mesoderm / Q000166:cytology* / Q000187:drug effects; D008954:Models, Biological; D019899:Paracrine Communication / Q000187:drug effects; D011650:Pulmonary Alveoli / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism
D015415:Biomarkers; D002117:Calcitriol