Activation of Caspases in Spinal Cord Injury

Caspases, a family of aspartate-specific cysteine proteases, are essential in the initiation and execution of apoptosis (Creagh et al., 2003 Cohen, 1997). They are expressed as inactive proenzymes (zymogens) that become active during apoptosis. Out of 14 caspase enzymes, caspase-3 appears to be the major effector of neuronal apoptosis induced by a variety of stimuli as well as traumatic injuries (Fig. 4.4). A role for caspase-3 in injury-induced neuronal cell death has been established using semispecific peptide caspase inhibitors. Caspases not only cleave other downstream caspases but also a variety of enzymes, cytokines, cytoskeletal, nuclear, and cell cycle regulatory proteins (Cohen, 1997). Their activities in brain and spinal cord tissues are regulated by the occurrence in zymogens form, by members of Bcl-2 family, and certain cellular inhibitor of apoptosis proteins (cIAPs). 

Caspases are closely associated with apoptotic cell death in experimental SCI (Yakovlev et al., 2005). Thus, SCI is accompanied by a rapid upregulation of 

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