INTERRELATIONSHIPS BETWEEN ASTROCYTE FUNCTION, OXIDATIVE STRESS AND ANTIOXIDANT STATUS WITHIN THE CENTRAL-NERVOUS-SYSTEM

Astrocytes have, until recently, been thought of as the passive suppor ting elements of the central nervous system. However, recent developme nts suggest that these cells actually play a crucial and vital role in the overall physiology of the brain. Astrocytes selectively express a host of cell membrane and nuclear receptors that are responsive to va rious neuroactive compounds. In addition, the cell membrane has a numb er of important transporters for these compounds. Direct evidence for the selective co-expression of neurotransmitters, transporters on both neurons and astrocytes, provides additional evidence for metabolic co mpartmentation within the central nervous system. Oxidative stress as defined by the excessive production of free radicals can alter dramati cally the function of the cell. The free radical nitric oxide has attr acted a considerable amount of attention recently, due to its role as a physiological second messenger but also because of its neurotoxic po tential when produced in excess. We provide, therefore, an in-depth di scussion on how this free radical and its metabolites affect the intra and intercellular physiology of the astrocyte(s) and surrounding neur ons. Finally, we look at the ways in which astrocytes can counteract t he production of free radicals in general by using their antioxidant p athways. The glutathione antioxidant system will be the focus of atten tion, since astrocytes have an enormous capacity for, and efficiency b uilt into this particular system. (C) 1997 Elsevier Science Ltd. All r ights reserved.