Targeted Gene Inactivation of Calpain-1 Suppresses Cortical Degeneration Due to Traumatic Brain Injury and Neuronal Apoptosis Induced by Oxidative Stress*

Background: Calpains play an important role in the regulation of cell death. Results: Calpain-1 inhibition decreases cortical neurodegeneration following TBI by regulating calcium influx and apoptosis of neurons under oxidative stress. Conclusion: Genetic inhibition of calpain-1 reduces neurodegeneration and suppresses neuronal apoptosis. Significance: Targeted inhibition of calpain-1 offers a promising therapeutic approach against TBI and other neurodegenerative diseases. Calpains are calcium-regulated cysteine proteases that have been implicated in the regulation of cell death pathways. Here, we used our calpain-1 null mouse model to evaluate the function of calpain-1 in neural degeneration following a rodent model of traumatic brain injury. In vivo, calpain-1 null mice show significantly less neural degeneration and apoptosis and a smaller contusion 3 days post-injury than wild type littermates. Protection from traumatic brain injury corroborated with the resistance of calpain-1 neurons to apoptosis induced by oxidative stress. Biochemical analysis revealed that caspase-3 activation, extracellular calcium entry, mitochondrial membrane permeability, and release of apoptosis-inducing factor from mitochondria are partially blocked in the calpain-1 null neurons. These findings suggest that the calpain-1 knock-out mice may serve as a useful model system for neuronal protection and apoptosis in traumatic brain injury and other neurodegenerative disorders in which oxidative stress plays a role.