Characterization of vitamin D production by human ocular barrier cells

Vitamin D3 is a secosteroid mainly synthesized from the conversion of the skin precursor 7-dehydrocholesterol (7DHC) to vitamin D3 by ultraviolet (UV) B sunlight. Extrarenal synthesis of vitamin D3 has been reported in many tissues and cells, including barrier sites. This study characterizes the exp...

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Bibliographic Details
Published in:	Investigative ophthalmology & visual science 2014-04, Vol.55 (4), p.2140-2147
Main Authors:	Alsalem, Jawaher A, Patel, Deepali, Susarla, Radhika, Coca-Prados, Miguel, Bland, Rosemary, Walker, Elizabeth A, Rauz, Saaeha, Wallace, Graham R
Format:	Article
Language:	eng
Subjects:	25-Hydroxyvitamin D3 1-alpha-Hydroxylase - biosynthesis 25-Hydroxyvitamin D3 1-alpha-Hydroxylase - genetics Cell Line Cholecalciferol - biosynthesis Endothelium, Corneal - cytology Endothelium, Corneal - metabolism Gene Expression Regulation Humans Immunoenzyme Techniques Immunohistochemistry Retinal Pigment Epithelium - cytology Retinal Pigment Epithelium - metabolism Reverse Transcriptase Polymerase Chain Reaction RNA, Messenger - genetics Sclera - cytology Sclera - metabolism
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Summary:	Vitamin D3 is a secosteroid mainly synthesized from the conversion of the skin precursor 7-dehydrocholesterol (7DHC) to vitamin D3 by ultraviolet (UV) B sunlight. Extrarenal synthesis of vitamin D3 has been reported in many tissues and cells, including barrier sites. This study characterizes the expression of components of vitamin D3 signaling in human ocular barrier cells. Primary human scleral fibroblasts (HSF), human corneal endothelial (HCEC-12), nonpigmented ciliary body epithelial (ODM-2), and adult retinal pigment epithelial (ARPE-19) cell lines were analyzed for the expression of vitamin D receptor (VDR), the vitamin D3 activating enzymes 1α-hydroxylase (CYP27B1), 25-hydroxylases (CYP27A1 and CYP2R1), the vitamin D3 inactivating enzyme 24-hydroxylase (CYP24A1), and the endocytic receptors cubilin and megalin using a combination of RT-PCR, immunocytochemistry, and enzyme immunoassay (EIA). The HSF, HCEC-12, ODM-2, and ARPE-19 express mRNA and protein for all vitamin D3 synthesizing and metabolizing components. The cell types tested, except HSF, are able to convert inactive 25-hydroxyvitamin D3 (25[OH]D3) into active 1,25-hydroxyvitamin D3 (1,25[OH]2D3). This novel study demonstrated that ocular barrier epithelial cells express the machinery for vitamin D3 and can produce 1,25(OH)2D3. We suggest that vitamin D3 might have a role in immune regulation and barrier function in ocular barrier epithelial cells.
ISSN:	1552-5783 1552-5783