Duncan K G, Hosseini K, Bailey K R, Yang H, Lowe R J, Matthes M T, Kane J P, LaVail M M, Schwartz D M, Duncan J L
Department of Ophthalmology, University of California, San Francisco, California 94143, USA.
Br J Ophthalmol. 2009 Aug;93(8):1116-20. doi: 10.1136/bjo.2008.144006. Epub 2009 Mar 19.
Excessive lipid accumulation in Bruch's membrane (BrM) is a hallmark of ageing, the major risk factor for age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells may utilise reverse cholesterol transport (RCT) activity to move lipid into BrM, mediated through ATP-binding cassette A1 (ABCA1) and scavenger receptor BI (SR-BI).
ABCA1 expression was assessed by reverse transcription polymerase chain reaction (RT-PCR) and western blotting of human RPE cell extracts. Lipid transport assays were performed using radiolabelled photoreceptor outer segments (POS). ABCA1 and SR-BI expression was examined in normal mouse eyes by immunofluorescence staining. BrMs of ABCA1 and SR-BI heterozygous mice were examined microscopically.
Human RPE cells expressed ABCA1 mRNA and protein. The ABCA1 and SR-BI inhibitor glyburide (also known as glibenclamide) abolished basal transport of POS-derived lipids in RPE cells in the presence of high-density lipoprotein. Mouse retina and RPE expressed ABCA1 and SR-BI. SR-BI was highly expressed in RPE. BrMs were significantly thickened in SR-BI heterozygous mice, but not in ABCA1 heterozygous mice.
RPE cells express ABCA1 and SR-BI. This implies a significant role for SR-BI and ABCA1 in lipid transport and RCT in the retina and RPE.
布鲁赫膜（BrM）中脂质过度积累是衰老的标志，也是年龄相关性黄斑变性（AMD）的主要危险因素。视网膜色素上皮（RPE）细胞可能利用逆向胆固醇转运（RCT）活性，通过ATP结合盒A1（ABCA1）和清道夫受体BI（SR-BI）介导将脂质转运至BrM。
通过逆转录聚合酶链反应（RT-PCR）和对人RPE细胞提取物进行蛋白质印迹法评估ABCA1表达。使用放射性标记的光感受器外段（POS）进行脂质转运测定。通过免疫荧光染色检测正常小鼠眼中ABCA1和SR-BI的表达。对ABCA1和SR-BI杂合小鼠的BrM进行显微镜检查。
人RPE细胞表达ABCA1 mRNA和蛋白质。在存在高密度脂蛋白的情况下，ABCA1和SR-BI抑制剂格列本脲（也称为优降糖）消除了RPE细胞中POS衍生脂质的基础转运。小鼠视网膜和RPE表达ABCA1和SR-BI。SR-BI在RPE中高表达。SR-BI杂合小鼠的BrM明显增厚，但ABCA1杂合小鼠的BrM未增厚。
RPE细胞表达ABCA1和SR-BI。这意味着SR-BI和ABCA1在视网膜和RPE的脂质转运和RCT中起重要作用。
