Rapid upregulation of caspase-3 in rat spinal cord after injury: mRNA, protein, and cellular localization correlates with apoptotic cell death

Although the precise mechanisms explaining loss of, and failure to regain, function after spinal cord injury are unknown, there is increasing interest in the role of "secondary cell death." One prevalent theme in cell loss in other regions of the CNS involves apoptosis executed by the intracellular caspase proteases. A recent study demonstrated that spinal cord injury rapi dly increased the activation of caspase-3. Our previous studies demonstrate d peak apoptosis in three of four cellular compartments 3 days after contro lled contusion in the rat. We have extended these analyses to include enzym e and substrate studies of caspase subfamilies both in rostral and in cauda l adjacent segments compared to the lesion site. Although presumed activati on of programmed proenzyme is considered the mechanism for enhanced caspase s, our novel analyses were designed to detect upregulation of gene expressi on. We surveyed traumatically injured spinal cord for caspase family messag es with a modified differential mRNA display approach and found that the ca spase-3 (CASP3) message was present and upregulated severalfold after injur y. Our results clearly demonstrate that cell death in the spinal cord occur s after posttranslational activation of caspases that follow, at least for caspase-3, initial upregulation of CASP3 mRNA levels. (C) 2000 Academic Pre ss.