Patel Samir P, Sullivan Patrick G, Pandya Jignesh D, Rabchevsky Alexander G
Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington.
Department of Physiology, University of Kentucky, Lexington.
J Neurosci Res. 2009 Jan;87(1):130-140. doi: 10.1002/jnr.21814.
We recently documented the progressive nature of mitochondrial dysfunction over 24 hr after contusion spinal cord injury (SCI), but the underlying mechanism has not been elucidated. We investigated the effects of targeting two distinct possible mechanisms of mitochondrial dysfunction by using the mitochondrial uncoupler 2,4-dinitrophenol (2,4-DNP) or the nitroxide antioxidant Tempol after contusion SCI in rats. A novel aspect of this study was that all assessments were made in both synaptosomal (neuronal)- and nonsynaptosomal (glial and neuronal soma)-derived mitochondria 24 hr after injury. Mitochondrial uncouplers target Ca(2+) cycling and subsequent reactive oxygen species production in mitochondria after injury. When 2,4-DNP was injected 15 and 30 min after injury, mitochondrial function was preserved in both populations compared with vehicle-treated rats, whereas 1 hr postinjury treatment was ineffective. Conversely, targeting peroxynitrite with Tempol failed to maintain normal bioenergetics in synaptic mitochondria, but was effective in nonsynaptic mitochondria when administered 15 min after injury. When administered at 15 and 30 min after injury, increased hydroxynonenal, 3-NT, and protein carbonyl levels were significantly reduced by 2,4-DNP, whereas Tempol only reduced 3-NT and protein carbonyls after SCI. Despite such antioxidant effects, only 2,4-DNP was effective in preventing mitochondrial dysfunction, indicating that mitochondrial Ca(2+) overload may be the key mechanism involved in acute mitochondrial damage after SCI. Collectively, our observations demonstrate the significant role that mitochondrial dysfunction plays in SCI neuropathology. Moreover, they indicate that combinatorial therapeutic approaches targeting different populations of mitochondria holds great potential in fostering neuroprotection after acute SCI.
我们最近记录了脊髓挫伤性损伤（SCI）后24小时内线粒体功能障碍的进展性质，但潜在机制尚未阐明。我们研究了在大鼠脊髓挫伤性损伤后，通过使用线粒体解偶联剂2,4-二硝基苯酚（2,4-DNP）或氮氧化物抗氧化剂Tempol，针对线粒体功能障碍的两种不同可能机制所产生的影响。本研究的一个新特点是，所有评估均在损伤后24小时取自突触体（神经元）和非突触体（神经胶质和神经元胞体）的线粒体中进行。线粒体解偶联剂靶向损伤后线粒体中的Ca(2+)循环及随后的活性氧生成。损伤后15分钟和30分钟注射2,4-DNP时，与给予赋形剂处理的大鼠相比，这两种类型的线粒体功能均得以保留，而损伤后1小时给药则无效。相反，用Tempol靶向过氧亚硝酸盐未能维持突触线粒体中的正常生物能量学，但在损伤后15分钟给药时对非突触线粒体有效。在损伤后15分钟和30分钟给药时，2,4-DNP可显著降低羟基壬烯醛、3-硝基酪氨酸和蛋白质羰基水平的升高，而Tempol仅在脊髓损伤后降低3-硝基酪氨酸和蛋白质羰基水平。尽管有这种抗氧化作用，但只有2,4-DNP能有效预防线粒体功能障碍，这表明线粒体Ca(2+)超载可能是脊髓损伤后急性线粒体损伤的关键机制。总体而言，我们的观察结果表明线粒体功能障碍在脊髓损伤神经病理学中发挥着重要作用。此外，它们表明针对不同线粒体群体的联合治疗方法在促进急性脊髓损伤后的神经保护方面具有巨大潜力。
