Reddan J, Sevilla M, Giblin F, Padgaonkar V, Dziedzic D, Leverenz V
Department of Biological Sciences, Oakland University, Rochester, Michigan 48309-4401.
Lens Eye Toxic Res. 1992;9(3-4):385-93.
In order to investigate the mechanism by which H2O2 damages the epithelium, 8 x 10(5) rabbit lens epithelial cells were treated with TEMPOL or deferoxamine and exposed to a single sublethal dose of 0.5 mM H2O2. TEMPOL is a SOD mimic, has a characteristic EPR spectrum and is metal independent. EPR spectra indicated that TEMPOL was not destroyed by H2O2, catalyzed the destruction of the superoxide anion, and penetrated the cells. Cells treated with H2O2 showed membrane blebbing, growth inhibition, an increase in GSSG, a dose-dependent decrease in GSH, ATP, NAD+, and in the activity of G3PDH, and in lactate production. H2O2 stimulated the hexose mono-phosphate shunt and induced single strand breaks in DNA. Treatment with TEMPOL or deferoxamine prevented or curtailed H2O2-induced inhibition of growth, the decrease in NAD+, the induction of single strand breaks in DNA, and membrane blebbing, but not the other biochemical parameters investigated. Both TEMPOL and deferoxamine prevent Fe+2-mediated generation of the damaging hydroxyl radical. TEMPOL reacts with superoxide and thus prevents it from recycling Fe+3 to Fe+2. It also oxidizes DNA-Fe+2 to DNA-Fe+3. Deferoxamine chelates intracellular Fe+3 and prevents its reduction to Fe+2. These compounds which limit the availability of Fe+2 by different means indicate that transition metals (including those bound to DNA) mediate certain of the damaging effects of H2O2.
为了研究过氧化氢损伤上皮细胞的机制，将8×10⁵个兔晶状体上皮细胞用TEMPOL或去铁胺处理，然后暴露于0.5 mM的单次亚致死剂量过氧化氢中。TEMPOL是一种超氧化物歧化酶模拟物，具有特征性的电子顺磁共振光谱且不依赖金属。电子顺磁共振光谱表明TEMPOL不会被过氧化氢破坏，能催化超氧阴离子的破坏，并能穿透细胞。用过氧化氢处理的细胞出现膜泡化、生长抑制、谷胱甘肽二硫化物增加、谷胱甘肽、三磷酸腺苷、烟酰胺腺嘌呤二核苷酸以及甘油醛-3-磷酸脱氢酶活性和乳酸生成呈剂量依赖性降低。过氧化氢刺激磷酸戊糖途径并诱导DNA单链断裂。用TEMPOL或去铁胺处理可预防或减少过氧化氢诱导的生长抑制、烟酰胺腺嘌呤二核苷酸降低、DNA单链断裂诱导以及膜泡化，但不能预防或减少所研究的其他生化参数变化。TEMPOL和去铁胺均可预防亚铁介导的损伤性羟基自由基的生成。TEMPOL与超氧阴离子反应，从而防止其将铁离子从三价还原为二价。它还将DNA-亚铁氧化为DNA-铁离子。去铁胺螯合细胞内的铁离子并防止其还原为亚铁离子。这些通过不同方式限制亚铁可用性的化合物表明，过渡金属（包括与DNA结合的那些）介导了过氧化氢的某些损伤作用。
