Clark Robert S B, Nathaniel Paula D, Zhang Xiaopeng, Dixon C Edward, Alber Sean M, Watkins Simon C, Melick John A, Kochanek Patrick M, Graham Steven H
Department of Critical Care Medicine, The Safar Center for Resuscitation Research and the Brain Trauma Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
J Cereb Blood Flow Metab. 2007 Feb;27(2):316-26. doi: 10.1038/sj.jcbfm.9600338. Epub 2006 May 17.
The pathobiology of traumatic brain injury (TBI) includes activation of multiple caspases followed by cell death with a spectrum of apoptotic phenotypes. There are initiator (e.g. caspase-2, -8, and -9) and effector (e.g. caspase-3 and -7) caspases. Recently, caspase-2 and -8 have been shown to regulate cell death via provoking cytochrome c release from the mitochondria upstream of caspase-9. Here, we show that an intracerebral injection of the pan-caspase inhibitor boc-Aspartyl(OMe)-fluoromethylketone (BAF; 1 micromol) 1 min after TBI in rats reduces caspase-3-like activity, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and tissue damage, and cytochrome c release in ipsilateral cortex at 24 h versus vehicle. To investigate whether either caspase-2 and/or caspase-8 activation may contribute to cytochrome release, the effect of BAF treatment on caspase-2 and caspase-8 proteolysis was also examined. boc-aspartyl(OMe)-fluoromethylketone treatment inhibited proteolysis of caspase-2 but not caspase-8 24 h after TBI in rats versus vehicle. However, BAF with or without nerve growth factor (12.5 ng/h x 14 days intracerebrally via osmotic pump) did not result in differences in motor function, Morris water maze performance, hippocampal neuron survival, nor contusion volume at 14 days. These data suggest that BAF treatment reduces acute cell death after TBI by inhibiting mitochondrial release of cytochrome c, possibly via a mechanism involving initiator caspases; however, BAF appears to delay cell death, rather than result in permanent protection.
创伤性脑损伤（TBI）的病理生物学过程包括多种半胱天冬酶的激活，随后细胞死亡并呈现出一系列凋亡表型。存在起始半胱天冬酶（如半胱天冬酶-2、-8和-9）和效应半胱天冬酶（如半胱天冬酶-3和-7）。最近的研究表明，半胱天冬酶-2和-8可通过促使细胞色素c从位于半胱天冬酶-9上游的线粒体中释放来调节细胞死亡。在此，我们发现，在大鼠创伤性脑损伤后1分钟脑室内注射泛半胱天冬酶抑制剂boc-天冬氨酸（OMe）-氟甲基酮（BAF；1微摩尔），与注射赋形剂相比，可在24小时时降低同侧皮质中半胱天冬酶-3样活性、末端脱氧核苷酸转移酶介导的dUTP缺口末端标记（TUNEL）以及组织损伤，并减少细胞色素c的释放。为了研究半胱天冬酶-2和/或半胱天冬酶-8的激活是否可能导致细胞色素释放，我们还检测了BAF处理对大鼠创伤性脑损伤后24小时半胱天冬酶-2和半胱天冬酶-8蛋白水解的影响。与注射赋形剂相比，boc-天冬氨酸（OMe）-氟甲基酮处理可抑制大鼠创伤性脑损伤后24小时半胱天冬酶-2的蛋白水解，但对半胱天冬酶-8无抑制作用。然而，无论是否联合神经生长因子（通过渗透泵脑室内注射12.5纳克/小时×14天），BAF在14天时均未导致运动功能、莫里斯水迷宫表现、海马神经元存活以及挫伤体积出现差异。这些数据表明，BAF处理可能通过抑制细胞色素c从线粒体的释放来减少创伤性脑损伤后的急性细胞死亡，其机制可能涉及起始半胱天冬酶；然而，BAF似乎只是延迟了细胞死亡，而非带来永久性保护。
