North J A, Spector A A, Buettner G R
Department of Biochemistry, College of Medicine, University of Iowa, Iowa City 52242.
Am J Physiol. 1994 Jul;267(1 Pt 1):C177-88. doi: 10.1152/ajpcell.1994.267.1.C177.
Lipid-derived free radicals generated from intact human U937 monocytes exposed to iron-induced oxidative stress were detected by electron paramagnetic resonance (EPR) with the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Lipid radical formation was enhanced when the cells were enriched with n-3 or n-6 polyunsaturated fatty acids. Computer simulation indicated that at least two POBN spin adducts were formed, having spectral characteristics consistent with carbon-centered radicals (aN = 15.9 G and aH = 2.6 G; aN = 15.1 G and aH = 2.8 G). These alkyl radicals are probably formed by beta-scission of alkoxyl radicals. POBN spin adduct formation correlated with ethane generation. Addition of ascorbate to the assay medium greatly increased the radical signal intensity. Although radical generation was cell dependent and POBN spin adducts were observed in cell homogenates, the adducts formed by the intact cells were detected only in the extracellular medium. These findings indicate that the extent of lipid radical formation in response to oxidative stress can be influenced by changes in the polyunsaturated fatty acid composition of the cell lipids and suggest the possibility that carbon-centered lipi radicals may interact with extracellular structures.
通过电子顺磁共振（EPR）结合自旋捕捉剂α-（4-吡啶-1-氧化物）-N-叔丁基硝酮（POBN），检测暴露于铁诱导氧化应激下的完整人U937单核细胞产生的脂质衍生自由基。当细胞富含n-3或n-6多不饱和脂肪酸时，脂质自由基的形成会增强。计算机模拟表明，至少形成了两种POBN自旋加合物，其光谱特征与碳中心自由基一致（aN = 15.9 G，aH = 2.6 G；aN = 15.1 G，aH = 2.8 G）。这些烷基自由基可能是由烷氧基自由基的β-断裂形成的。POBN自旋加合物的形成与乙烷生成相关。向测定培养基中添加抗坏血酸会大大增加自由基信号强度。尽管自由基的产生依赖于细胞，并且在细胞匀浆中观察到了POBN自旋加合物，但完整细胞形成的加合物仅在细胞外培养基中被检测到。这些发现表明，氧化应激反应中脂质自由基的形成程度可能受细胞脂质中多不饱和脂肪酸组成变化的影响，并提示碳中心脂质自由基可能与细胞外结构相互作用的可能性。
