Girão H, Mota M C, Ramalho J, Pereira P
Department of Ophthalmology and Visual Sciences, Biomedical Institute for Research in Light and Image, Coimbra University Hospitals, Portugal.
Exp Eye Res. 1998 May;66(5):645-52. doi: 10.1006/exer.1998.0465.
Human lens membranes contain the highest cholesterol content of any known biological membrane. Although cholesterol is prone to oxidation, the presence of its oxidation products in human cataract has not been shown before. This study was designed to investigate the presence of cholesterol oxides in human cataractous lenses. Human clear lenses (n = 48) were obtained from Coimbra University Hospital Eye Bank. Human cataracts (n = 54) were obtained by routine extracapsular surgery. Cholesterol oxides were isolated by solid-phase extraction on a C18 cartridge and quantified as TMS-ether derivatives by gas chromatography. The extraction procedure allows for an efficient recovery of the major cholesterol oxides, while retaining virtually all cholesterol. Exposure of membranes isolated from transparent human lenses to the free radical generator 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH) produced 7 alpha-hydroxycholesterol (6%), 7 beta-hydroxycholesterol (19%), 5 alpha, 6 alpha-epoxycholestanol (1%) and 7-ketocholesterol (74%) as major oxidation products. Cataractous lenses contained quantifiable amounts of 7 beta-hydroxycholesterol (7.3 +/- 0.74 mmol mol-1 cholesterol), 7-ketocholesterol (4.2 +/- 0.32 mmol mol-1 cholesterol), 5 alpha, 6 alpha-epoxycholestanol (0.9 +/- 0.16 mmol mol-1 cholesterol), 20 alpha-hydroxycholesterol (0.6 +/- 0.13 mmol mol-1 cholesterol) and 25-hydroxycholesterol (0.1 +/- 0.02 mmol mol-1 cholesterol), whereas clear lenses contained no detectable amounts of cholesterol oxides. We have shown, for the first time, that oxysterols accumulate in human cataracts. Although the total amount of oxidized cholesterol in cataracts is not likely to be high it may account for much of the membrane damage associated with cataract formation.
人晶状体膜的胆固醇含量是所有已知生物膜中最高的。尽管胆固醇易于氧化，但此前尚未证实其氧化产物在人类白内障中的存在。本研究旨在调查人白内障晶状体中氧化胆固醇的存在情况。人透明晶状体（n = 48）取自科英布拉大学医院眼库。人白内障（n = 54）通过常规囊外手术获取。通过在C18柱上进行固相萃取分离氧化胆固醇，并通过气相色谱将其定量为TMS - 醚衍生物。该萃取程序可有效回收主要的氧化胆固醇，同时几乎保留所有胆固醇。将从透明人晶状体分离的膜暴露于自由基发生器2,2'-偶氮二异丁脒二盐酸盐（AAPH），产生的主要氧化产物为7α - 羟基胆固醇（6%）、7β - 羟基胆固醇（19%）、5α,6α - 环氧胆甾烷醇（1%）和7 - 酮胆固醇（74%）。白内障晶状体含有可定量的7β - 羟基胆固醇（7.3±0.74 mmol/mol胆固醇）、7 - 酮胆固醇（4.2±0.32 mmol/mol胆固醇）、5α,6α - 环氧胆甾烷醇（0.9±0.16 mmol/mol胆固醇）、20α - 羟基胆固醇（0.6±0.13 mmol/mol胆固醇）和25 - 羟基胆固醇（0.1±0.02 mmol/mol胆固醇），而透明晶状体未检测到氧化胆固醇。我们首次表明，氧化甾醇在人类白内障中积累。尽管白内障中氧化胆固醇的总量可能不高，但它可能是与白内障形成相关的许多膜损伤的原因。
