Progesterone as a neuroprotective factor in traumatic and ischemic brain injury.

The search for a "magic bullet" drug targeting a single receptor for the treatment of stroke or traumatic brain injury (TBI) has failed thus far for a variety of reasons. The pathophysiology of ischemic brain injury and TBI involves a number of mechanisms leading to neuronal injury, including excitotoxicity, free radical damage, inflammation, necrosis, and apoptosis. Brain injury also triggers auto-protective mechanisms, including the up-regulation of anti-inflammatory cytokines and endogenous antioxidants. In these conditions an agent with pleiotropic consequences is more likely to provide effective neuroprotection and repair than one operating primarily on a single, or a small number of, injury mechanisms. There is growing evidence, including recently published clinical trials, that progesterone and perhaps its metabolite allopregnanolone exert neuroprotective effects on the injured central nervous system (CNS). Laboratories around the world have shown that progesterone and allopregnanolone act through numerous metabolic and physiological pathways that can affect the injury response in many different tissues and organ systems. Furthermore, progesterone is a natural hormone, synthesized in both males and females, that can act as a pro-drug for other metabolites with their own distinct mode of action in CNS repair. These properties make progesterone a unique and compelling natural agent to consider for testing in clinical trial for CNS injuries including TBI and stroke.