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"Expression of Pro-apoptotic Bcl-2 family proteins following Traumatic Brain Injury (TBI) in the Immature Rat Brain"

Julie Chu
Mentor: Dr. Pamela Mertz
St. Mary's College of Maryland, 2006-2007

    The Bcl-2 and caspase families are important regulators of programmed cell death (PCD) in experimental models of traumatic brain injury (TBI). The Bcl-2 family members such as anti-apoptotic Bcl-2 and Bcl-XL suppress PCD, whereas pro-apoptotic proteins including Bad, Bax, Bak, and Bim promote PCD. Cysteine proteases, called caspases, are synthesized as inactive forms, which can be activated by proteolytic cleavage. Activated caspases participating in mammalian cell death can be divided into two major categories involving initiators such as caspases-8 and -9 and effectors such as caspases-3 and -4. The Bcl-2 family proteins and caspases are closely related in the apoptotic pathways. For example, activated caspase-8 cleaves and activates pro-apoptotic Bid. The activated form of truncated Bid translocates to mitochondria to trigger Bax to form pore-like complexes, which release inner mitochondrial apoptotic components such as cytochrome c. Levels of various apoptotic proteins were compared between TBI brain samples of Sprague Dawley rat models treated with controlled cortical impact and sham brain samples, which were used as a control. From the results obtained during last summer's internship, the pro-apoptotic protein Bad level in the brain mitochondria left hemisphere of TBI samples obtained four hours after injury was higher than the level of Bad in the brain mitochondria right hemisphere samples. The results form my St. Mary's Project indicated that the Bad and caspase-3 levels in the brain homogenate TBI samples collected four hours after injury were not significantly higher than brain homogenate sham samples.