TY - JOUR
T1 - Vitamin D receptor and metabolite effects on corneal epithelial cell gap junction proteins
AU - Lu, Xiaowen
AU - Chen, Zhong
AU - Vick, Sarah
AU - Watsky, Mitchell A.
N1 - Funding Information:
We are grateful to Dr. Amy Estes (Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA) and The Eye Guys, Eye Physicians and Surgeons of Augusta, GA for providing donor corneal rims. This work was supported by NIH Grant EY021747-06.
Funding Information:
We are grateful to Dr. Amy Estes (Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA) and The Eye Guys, Eye Physicians and Surgeons of Augusta, GA for providing donor corneal rims. This work was supported by NIH Grant EY021747-06 .
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/10
Y1 - 2019/10
N2 - Vitamin D is a fat-soluble prohormone that can be activated both systemically and within individual tissues. Our lab has previously demonstrated that the corneal epithelium can activate vitamin D and that the vitamin D metabolites 1,25(OH)2D3 and 24R,25(OH)2D3 can affect corneal epithelial migration, proliferation, and tight and gap junction function. These vitamin D-derived metabolites signal through the vitamin D receptor (VDR). The purpose of this study was to specifically determine the effects of 1,25(OH)2D3 and 24R,25(OH)2D3 on corneal epithelial cell gap junction proteins. Connexin (Cx) 26, 30 and 43 protein expression was detected in a human corneal epithelial cell line (HCEC), wild type and vitamin D receptor knockout (VDR-/-) mouse corneas, and cultured mouse primary epithelial cells (MPCEC). In vitro gap junction function was assessed using the scrape loading/dye transfer assay. HCEC and MPCEC were treated with 1,25(OH)2D3 or 24R,25(OH)2D3. Western blotting was used to detect gap junction proteins. Vitamin D3 effects on epithelial intracellular Ca++ (Ca++ i) were determined using the dye Cal-520. Cx26 and Cx43 protein levels were significantly increased in HCEC and MPCEC treated with both 1,25(OH)2D3 and 24R,25(OH)2D3. Cx30 and Cx43 protein levels were also significantly increased in VDR-/- MPCEC. In vitro gap junction connectivity was significanlty enhanced in HCEC and MPCEC cultured with 24R,25(OH)2D3 and 1,25(OH)2D3. Ca++ i was not affected by 1,25(OH)2D3 or 24R,25(OH)2D3 in HCEC or MPCEC. We conclude that both 1,25(OH)2D3 and 24R,25(OH)2D3 are positive regulators of connexin proteins and gap junction communication in the corneal epithelium. These vitamin D metabolites appear to signal through both VDR-dependent and -independent pathways. The effects of vitamin D on corneal epithelial gap junctions do not seem to be dependent on Ca++ i.
AB - Vitamin D is a fat-soluble prohormone that can be activated both systemically and within individual tissues. Our lab has previously demonstrated that the corneal epithelium can activate vitamin D and that the vitamin D metabolites 1,25(OH)2D3 and 24R,25(OH)2D3 can affect corneal epithelial migration, proliferation, and tight and gap junction function. These vitamin D-derived metabolites signal through the vitamin D receptor (VDR). The purpose of this study was to specifically determine the effects of 1,25(OH)2D3 and 24R,25(OH)2D3 on corneal epithelial cell gap junction proteins. Connexin (Cx) 26, 30 and 43 protein expression was detected in a human corneal epithelial cell line (HCEC), wild type and vitamin D receptor knockout (VDR-/-) mouse corneas, and cultured mouse primary epithelial cells (MPCEC). In vitro gap junction function was assessed using the scrape loading/dye transfer assay. HCEC and MPCEC were treated with 1,25(OH)2D3 or 24R,25(OH)2D3. Western blotting was used to detect gap junction proteins. Vitamin D3 effects on epithelial intracellular Ca++ (Ca++ i) were determined using the dye Cal-520. Cx26 and Cx43 protein levels were significantly increased in HCEC and MPCEC treated with both 1,25(OH)2D3 and 24R,25(OH)2D3. Cx30 and Cx43 protein levels were also significantly increased in VDR-/- MPCEC. In vitro gap junction connectivity was significanlty enhanced in HCEC and MPCEC cultured with 24R,25(OH)2D3 and 1,25(OH)2D3. Ca++ i was not affected by 1,25(OH)2D3 or 24R,25(OH)2D3 in HCEC or MPCEC. We conclude that both 1,25(OH)2D3 and 24R,25(OH)2D3 are positive regulators of connexin proteins and gap junction communication in the corneal epithelium. These vitamin D metabolites appear to signal through both VDR-dependent and -independent pathways. The effects of vitamin D on corneal epithelial gap junctions do not seem to be dependent on Ca++ i.
KW - Connexins
KW - Corneal epithelium
KW - Gap junction
KW - Vitamin D
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U2 - 10.1016/j.exer.2019.107776
DO - 10.1016/j.exer.2019.107776
M3 - Article
C2 - 31465769
AN - SCOPUS:85071597572
SN - 0014-4835
VL - 187
JO - Experimental eye research
JF - Experimental eye research
M1 - 107776
ER -