Glial mediation of hormonal actions on the Drosophila brain

Insect glial cells function both as a barrier that insulates the central nervous system (CNS) from circulation and as a bridge that mediates hormonal effects on CNS neurons and other cell types. In this review, we summarize recent studies on how glial cells mediate hormonal actions on the CNS of the fruit fly Drosophila melanogaster. Drosophila glia receive multiple classes of circulating hormones, including insulin-like peptides, fat body-derived signals, gut-derived cytokines, and the steroid hormone ecdysone. These hormones convey physiological information, including nutritional state, pathological conditions, and developmental timing, to neurons and other cells within the CNS. Acting as gatekeepers, glial cells restrict hormone access to the CNS, while also serving as interpreters that translate systemic hormonal cues into context-dependent local signals. Understanding how Drosophila glial cells mediate hormonal actions on the CNS may help elucidate conserved principles of neuroendocrine communication across species.