Garner B, Davies M J, Truscott R J
Australian Cataract Research Foundation, Department of Chemistry, University of Wollongong, Wollongong, NSW, 2522, Australia.
Exp Eye Res. 2000 Jan;70(1):81-8. doi: 10.1006/exer.1999.0754.
Recent studies have identified specific hydroxylated amino acid oxidation products which strongly suggest the presence of hydroxyl radical (HO.)-damaged proteins in human cataractous lenses. In the present study, the ability of early stage (type II) and advanced (type IV) nuclear cataractous lens homogenates to catalyse HO. production in the presence of H(2)O(2)was investigated using electron paramagnetic resonance (EPR) spectroscopy with the free radical trap, 5,5-dimethyl-1-pyrroline- N -oxide (DMPO). Cataractous lens homogenates incubated with 1 m m H(2)O(2)generated a distinct HO. signal, which was significantly more intense in the nuclear region of the type IV compared to the type II lenses. The ability of individual lens nuclei and cortices to stimulate HO. production was positively correlated. The DMPO-HO. signal was competitively inhibited by ethanol, confirming that the DMPO-HO. signal was due to HO. formation and not DMPO-OOH degradation. The metal ion chelator, diethylenetriaminepentaacetic acid, also inhibited HO. formation, indicating that lenticular metal ions play a key role in HO. formation. Cataractous lens homogenates also stimulated ascorbyl radical production, further suggesting the presence of redox-active metal ions in the tissue. Analysis of lenses for total Fe and Cu (using atomic absorption spectrometry) showed that the more advanced type IV lenses tended to have higher Fe, but similar Cu, levels compared to the type II lenses. The levels of both metals were lower in non-cataractous lenses. These data support the hypothesis that transition metal-mediated HO. production may play a role in the aetiology of age-related nuclear cataract.
最近的研究已经鉴定出特定的羟基化氨基酸氧化产物，这强烈表明在人类白内障晶状体中存在羟基自由基（HO·）损伤的蛋白质。在本研究中，使用带有自由基捕获剂5,5-二甲基-1-吡咯啉-N-氧化物（DMPO）的电子顺磁共振（EPR）光谱，研究了早期（II型）和晚期（IV型）核性白内障晶状体匀浆在H₂O₂存在下催化HO·产生的能力。用1 mM H₂O₂孵育的白内障晶状体匀浆产生了明显的HO·信号，与II型晶状体相比，IV型晶状体核区域的该信号明显更强。单个晶状体核和皮质刺激HO·产生的能力呈正相关。DMPO-HO·信号受到乙醇的竞争性抑制，证实DMPO-HO·信号是由于HO·的形成而非DMPO-OOH的降解。金属离子螯合剂二乙烯三胺五乙酸也抑制HO·的形成，表明晶状体金属离子在HO·形成中起关键作用。白内障晶状体匀浆还刺激了抗坏血酸自由基的产生，进一步表明组织中存在氧化还原活性金属离子。对晶状体总铁和铜的分析（使用原子吸收光谱法）表明，与II型晶状体相比，更晚期的IV型晶状体往往具有更高的铁含量，但铜含量相似。非白内障晶状体中这两种金属的含量较低。这些数据支持了过渡金属介导的HO·产生可能在年龄相关性核性白内障的病因中起作用这一假说。
