Astrocytes cultured in vitro produce estradiol-17 beta and express aromatase cytochrome P-450 (P-450 AROM) mRNA

Aromatase cytochrome P-450 (P-450(AROM)) is an enzyme that catalyzes the conversion of androgen to estrogen. Estrogen plays an important role in the neuronal function by promoting the formation of dendrites and may be involved in protecting the neurons in the cerebral cortex against specific pathological conditions such as Alzheimer's disease. However, the cellular origin of estrogen in the brain is not known. The present study demonstrated for the first time the production of estradiol-17 beta and expression of P-450(AROM) mRNA in astrocytes isolated from the cerebral cortex of neonatal rats. Immunocytochemical studies using a monospecific antibody against rat P-450(AROM) has shown that this enzyme was localized in the cytoplasm of astrocytes. Interleukin-l (IL-1) has been shown to stimulate the proliferation and differentiation of astrocytes and to affect the aromatase activity in non-neuronal cells such as Sertoli, Leydig, and placental cells. Treatment of astrocytes with IL-1 beta induced a dose-dependent inhibition of estradiol production. This inhibitory action of IL-1 beta can be reversed by the addition of anti-IL-1 beta antibody. Since astrocytes are involved in the synaptic reorganization in the brain by removing cellular debris and by providing the necessary biological factors for neuronal growth, the ability of astrocytes to produce estradiol-17 beta and express P-450(AROM) mRNA in vitro suggests a new role for these cells in protecting and supporting neurons.