• Aiguo Wu, Zhe Ying, and Fernando Gomez-Pinilla.
• Department of Physiological Science, University of California at Los Angeles (UCLA), Los Angeles, California 90095, USA.
• J. Neurotrauma. 2007 Oct 1;24(10):1587-95.

AbstractTraumatic brain injury (TBI) produces a state of vulnerability that reduces the brain capacity to cope with secondary insults. The silent information regulator 2 (Sir2) has been implicated with maintaining genomic stability and cellular homeostasis under challenging situation. Here we explore the possibility that the action of Sir2alpha (mammalian Sir2) in the brain can extend to serve neuronal plasticity. We provide novel evidence showing that mild TBI reduces the expression of Sir2alpha in the hippocampus, in proportion to increased levels of protein oxidation. In addition, we show that dietary supplementation of omega-3 fatty acids that ameliorates protein oxidation was effective to reverse the reduction of Sir2alpha level in injured rats. Given that oxidative stress is a subproduct of dysfunctional energy homeostasis, we measured AMP-activated protein kinase (AMPK) and phosphorylated-AMPK (p-AMPK) to have an indication of the energy status of cells. Hippocampal levels of total and phosphorylated AMPK were reduced after TBI and levels were normalized by omega-3 fatty acts supplements. Further, we found that TBI reduced ubiquitous mitochondrial creatine kinase (uMtCK), an enzyme implicated in the energetic regulation of Ca2+-pumps and in the maintenance of Ca2+-homeostasis. Omega-3 fatty acids supplements normalized the levels of uMtCK after lesion. Furthermore, we found that the correlation between Sir2alpha and AMPK or p-AMPK was disrupted by TBI, but restored by omega-3 fatty acids supplements. Our results suggest that TBI may compromise neuronal protective mechanisms by involving the action of Sir2alpha. In addition, results show the capacity of omega-3 fatty acids to counteract some of the effects of TBI by normalizing levels of molecular systems associated with energy homeostasis.

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