Release of trophic factors and immune molecules from astrocytes

Abstract

It is now quite clear that as part of their support role, astrocytes produce and release multiple proteins that impact survival, migration, differentiation, and function of proximate neurons. This astrocyte role is particularly evident during development, remains in play in the normal adult brain, and is enhanced after injury. The molecules produced include those known traditionally as cytokines, chemokines, and trophic factors. Importantly, these proteins can serve as trophic or toxic agents and may be differentially regulated by the signals impacting on astrocytes at various stages of brain development and maturity (Fig. 13.1). The story of proteins produced by astrocytes, then, is a complex one. Multiple trophic or toxic molecules may be produced. The molecular mix may change from the developing animal to the adult, and after a lesion. Moreover, there is regional heterogeneity in the astrocytederived molecules, suggesting that those produced by region-specific astrocytes may be adapted to interact specifically with proximate neurons. To present evidence supporting this view, the present chapter is organized (Fig. 13.1) to discuss (1) the roles of astrocyte-derived cytokines, chemokines, and trophic factors on neurons, (2) regional differences in astrocyte function, (3) differences in astrocyte function with aging and after injury, and (4) molecules that regulate the role of astrocytes as trophic or immune molecule producers.