氰钴胺
视网膜
维生素B12
化学
荧光
血-视网膜屏障
维生素
受体
内分泌学
生物化学
医学
光学
物理
糖尿病
糖尿病性视网膜病变
作者
Yoshimasa Kinoshita,Kagayaki Nogami,Ryuta Jomura,Shin‐ichi Akanuma,Hajime Abe,Masahiko Inoûye,Yoshiyuki Kubo,Ken‐ichi Hosoya
标识
DOI:10.1021/acs.molpharmaceut.8b00617
摘要
The blood-to-retina supply of cyanocobalamin (vitamin B12) across the blood–retinal barrier (BRB) was investigated by synthesizing a fluorescence-labeled cyanocobalamin (Cy5-cyanocobalamin). In the in vivo analysis following internal jugular injection of Cy5-cyanocobalamin, confocal microscopy showed the distribution of Cy5-cyanocobalamin in the inner plexiform layer (IPL), the outer plexiform layer (OPL), and the retinal pigment epithelium (RPE). In the in vitro analysis with TR-iBRB2 cells, an in vitro model cell line of the inner BRB, Cy5-cyanocobalamin uptake by TR-iBRB2 cells exhibited a time-dependent increase after preincubation with transcobalamin II (TCII) protein, during its residual uptake without preincubation with TCII protein. The Cy5-cyanocobalamin uptake by TR-iBRB2 cells was significantly reduced in the presence of unlabeled cyanocobalamin, chlorpromazine, and chloroquine and was also significantly reduced under Ca2+-free conditions. Confocal microscopy of the TR-iBRB2 cells showed fluorescence signals of Cy5-cyanocobalamin and GFP-TCII protein, and these signals merged with each other. The RT-PCR, Western blot, and immunohistochemistry clearly suggested the expression of TCII receptor (TCII-R) in the inner and outer BRB. These results suggested the involvement of receptor-mediated endocytosis in the blood-to-retina transport of cyanocobalamin at the inner BRB with implying its possible involvement at the outer BRB.
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