Although the physiological role of uncoupling proteins (UCPs) 2 and 3 is uncertain, their activation by superoxide and by lipid peroxidation products suggest that UCPs are central to the mitochondrial response to reactive oxygen species. We examined whether superoxide and lipid peroxidation products such as 4-hydroxy-2-trans-nonenal act independently to activate UCPs, or if they share a common pathway, perhaps by superoxide exposure leading to the formation of lipid peroxidation products. This possibility can be tested by blocking the putative reactive oxygen species cascade with selective antioxidants and then reactivating UCPs with distal cascade components. We synthesized a mitochondria-targeted derivative of the spin trap alpha-phenyl-N-tert-butylnitrone, which reacts rapidly with carbon-centered radicals but is unreactive with superoxide and lipid peroxidation products. [4-[4-[[(1,1-Dimethylethyl)-oxidoimino]methyl]phenoxy]butyl]triphenylphosphonium bromide (MitoPBN) prevented the activation of UCPs by superoxide but did not block activation by hydroxynonenal. This was not due to MitoPBN reacting with superoxide or the hydroxyl radical or by acting as a chain-breaking antioxidant. MitoPBN did react with carbon-centered radicals and also prevented lipid peroxidation by the carbon-centered radical generator 2,2'-azobis(2-methyl propionamidine) dihydrochloride (AAPH). Furthermore, AAPH activated UCPs, and this was blocked by MitoPBN. These data suggest that superoxide and lipid peroxidation products share a common pathway for the activation of UCPs. Superoxide releases iron from iron-sulfur center proteins, which then generates carbon-centered radicals that initiate lipid peroxidation, yielding breakdown products that activate UCPs.

中文翻译：

---

超氧化物通过产生以碳为中心的自由基并引发脂质过氧化作用来激活解偶联蛋白：使用源自α-苯基-N-叔丁基硝基的线粒体靶向自旋阱的研究。

尽管解偶联蛋白（UCPs）2和3的生理作用尚不确定，但它们通过超氧化物和脂质过氧化产物的激活表明UCP对线粒体对活性氧的反应至关重要。我们检查过氧化物和脂质过氧化产物（例如4-羟基-2-反式壬烯醛）是否独立发挥作用来激活UCP，或者它们是否共享一条共同的途径，也许是通过超氧化物暴露导致脂质过氧化产物的形成。可以通过以下方法测试这种可能性：用选择性抗氧化剂阻断推定的活性氧物种级联，然后用远端级联组分重新激活UCP。我们合成了自旋阱α-苯基-N-叔丁基硝酮的线粒体靶向衍生物，它与以碳为中心的自由基快速反应，但与超氧化物和脂质过氧化产物不反应。[4- [4-[[（（1,1-二甲基乙基）-氧代氨基]甲基]苯氧基]丁基]三苯基溴化（（MitoPBN）阻止了过氧化物激活UCP，但没有阻止羟基壬烯的激活。这不是由于MitoPBN与超氧化物或羟基自由基发生反应，或者不是作为链断裂抗氧化剂。MitoPBN确实与以碳为中心的自由基发生反应，并且还通过以碳为中心的自由基产生剂2,2'-偶氮双（2-甲基丙ion）二盐酸盐（AAPH）阻止了脂质过氧化。此外，AAPH激活了UCP，并且被MitoPBN阻止了。这些数据表明，超氧化物和脂质过氧化产物具有激活UCP的共同途径。