Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, United States.
Arch Biochem Biophys. 2012 Feb 15;518(2):119-26. doi: 10.1016/j.abb.2011.12.016. Epub 2011 Dec 29.
The retina is the sensory organ in the back of the eye which absorbs and converts light to electrochemical impulses transferred to the brain. Herein, we studied how retinal environment affects enzyme-mediated cholesterol removal. We focused on two mitochondrial cytochrome P450 enzymes, CYPs 27A1 and 11A1, which catalyze the first steps in metabolism of cholesterol in the retina and other tissues. Phospholipids (PL) from mitochondria of bovine neural retina, retinal pigment epithelium, liver and adrenal cortex were isolated and compared for the effect on kinetic properties of purified recombinant CYPs in the reconstituted system in vitro. The four studied tissues were also evaluated for the mitochondrial PL and cholesterol content and levels of CYPs 27A1, 11A1 and their redox partners. The data obtained were used for modeling the retinal environment in the in vitro enzyme assays in which we detected the P450 metabolites, 22R-hydroxycholesterol and 5-cholestenoic acid, unexpectedly found by us in the retina in our previous studies. The effect of the by-product of the visual cycle pyridinium bis-retinoid A2E on kinetics of CYP27A1-mediated cholesterol metabolism was also investigated. The results provide insight into the retina's regulation of the enzyme-mediated cholesterol removal.
视网膜是眼睛后部的感觉器官，它吸收光线并将其转化为电化学脉冲，然后将这些脉冲传输到大脑。在此，我们研究了视网膜环境如何影响酶介导的胆固醇清除。我们专注于两种线粒体细胞色素 P450 酶，CYP27A1 和 11A1，它们催化胆固醇在视网膜和其他组织中的代谢的第一步。从牛神经视网膜、视网膜色素上皮、肝脏和肾上腺皮质的线粒体中分离出磷脂（PL），并在体外重组体系中比较它们对纯化重组 CYP 的动力学特性的影响。还评估了这四种研究组织的线粒体 PL 和胆固醇含量，以及 CYP27A1、11A1 及其氧化还原伴侣的水平。所得数据用于模拟体外酶测定中的视网膜环境，我们在之前的研究中在视网膜中意外地检测到了 P450 代谢物 22R-羟基胆固醇和 5-胆甾烯酸。还研究了视觉循环副产物吡啶二聚视黄醛 A2E 对 CYP27A1 介导的胆固醇代谢动力学的影响。研究结果深入了解了视网膜对酶介导的胆固醇清除的调节。
