DNase I disinhibition is predominantly associated with actin hyperpolymerization after traumatic brain injury.
To elucidate a role for the cytoskeletal protein actin in post-traumatic apoptotic cell death, the ability of actin-containing tissue extracts to inhibit exogenous DNase I was evaluated. In addition, cortical, hippocampal and thalamic extracts were examined for caspase-mediated actin cleavage and changes in actin polymerization state. Rats were anesthetized, subjected to lateral fluid percussion brain injury of moderate severity, and euthanized at 1 h, 6 h, 24 h, 1 week or 3 weeks post-injury (n = 3 per time-point). Tissue extracts from all brain regions of sham (uninjured) animals inhibited exogenous DNase I activity to a significant extent. However, inhibition of DNase I was significantly reduced at 1 h and 6 h in the injured hippocampus, and at 1 h, 6 h and 3 weeks in the thalamus. DNase I in cortical extracts of all injured animals was inhibited to a similar extent as that in uninjured animals. Actin fragments consistent with caspase-mediated proteolysis were observed in immunoblots of the injured hippocampus and thalamus at 1 h and 24 h, respectively, and were present up to 3 weeks post-injury. Transient actin hyperpolymerization was observed at 1 and 6 h post-injury in the thalamus and hippocampus, while actin depolymerization was observed at 1 and 3 weeks in the cortex and thalamus. Collectively our data suggest that DNase I disinhibition following brain trauma is associated predominantly with actin hyperpolymerization but also with actin depolymerization and concomitant caspase-mediated actin proteolysis.
Department of Neurosurgery, University of Pennsylvania, Philadelphia, USA.
F M
FM
Bareyre
R
R
Raghupathi
K E
KE
Saatman
T K
TK
McIntosh
D000199:Actins / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D001930:Brain Injuries / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004195:Disease Models, Animal; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D015151:Immunoblotting; D008297:Male; D010296:Parietal Lobe / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013702:Temporal Lobe / Q000378:metabolism / Q000473:pathology; D013788:Thalamus / Q000378:metabolism / Q000473:pathology; D014020:Tissue Extracts / Q000494:pharmacology; D014949:Wounds, Nonpenetrating
D000199:Actins; D014020:Tissue Extracts; D003850:Deoxyribonuclease I; D020169:Caspases