Antioxidant effects in brain and spinal cord injury

Oxygen radical-mediated lipid peroxidation appears to be a critical factor in posttraumatic neuronal degeneration. Thus, numerous studies have evaluated the neuroprotective efficacy of pharmacologic agents with lipid antioxidant activity in models of spinal cord and brain injury. Intensive pretreatment of animals with the endogenous lipid peroxyl radical scavenger alpha tocopherol (i.e., vitamin E) has been shown to decrease posttraumatic spinal cord ischemia and to enhance chronic neurologic recovery. However, the slow CNS tissue uptake of vitamin E requires chronic dosing, making it an impractical agent for the treatment of acute neural injury. The glucocorticoid steroid methylprednisolone has been shown to possess significant antioxidant efficacy and, when administered to animals or humans in antioxidant dosages, improves chronic neurologic recovery after spinal cord injury. This activity of methylprednisolone is independent of the steroid's glucocorticoid receptor- mediated actions. Novel antioxidant 21-aminosteroids have been developed that are devoid of glucocorticoid activity but have greater antioxidant efficacy than methylprednisolone. One of these, U74006F or tirilazad mesylate, has been shown to be effective in animal models of brain and spinal cord injury and is currently undergoing phase II clinical trials. Compounds that combine the amino functionality of the 21-aminosteroids with the peroxyl radical scavenging chromanol portion of vitamin E (i.e., 2-methylaminochromans) have also recently shown promise as neuroprotective agents. The consistent benefit afforded by antioxidant compounds adds further support to the concept that lipid peroxidation is an important therapeutic target for acute pharmacologic neuroprotection.