Mitochondrial damage: a target for new therapeutic horizons.

Traumatic brain injury (TBI) represents a leading cause of death and morbidity, as well as a considerable social and economical burden in western countries, and has thus emerged as a formidable therapeutic challenge. Yet despite tremendous efforts enlightening the mechanisms of neuronal death, hopes for the "magic bullet" have been repeatedly deceived, and TBI management has remained focused on the control of increased intracranial pressure. Indeed, impairment of cerebral metabolism is traditionally attributed to impaired oxygen delivery mediated by reduced cerebral perfusion in the swollen cerebral parenchyma. Although intuitively appealing, this hypothesis is not entirely supported by physiological facts and does not take into consideration mitochondrial dysfunction that has been repeatedly reported in both human and animal TBI. Although the nature and origin of the events leading to mitochondrial damage may be different, most share a permeabilization of mitochondrial membrane, which therefore may represent a logical target for new therapeutic strategies. Therefore, the proteins mediating these events may represent promising targets for new TBI therapies. Furthermore, mimicking anti-apoptotic proteins, such as Bcl-2 or XIAP, or inhibiting mitochondrial pro-apoptotic proteins, such as Smac/DIABLO, Omi/HTRA2, and ARTS (septin 4 isoform 2) may represent useful novel therapeutic strategies. This review focuses on mechanisms of the mitochondrial membrane permeabilization and its consequences and discusses the current and possible future therapeutic implications of this key event of neuronal death.