Elsevier

Neuroscience

Volume 89, Issue 2, March 1999, Pages 567-578
Neuroscience

Aromatase expression by astrocytes after brain injury: implications for local estrogen formation in brain repair

https://doi.org/10.1016/S0306-4522(98)00340-6Get rights and content

Abstract

Recent evidence indicates that 17(3-estradiol may have neuroprotective and neuroregenerative properties. Estradiol is formed locally in neural tissue from precursor androgens. The expression of aromatase, the enzyme that catalyses the conversion of androgens to estrogens, is restricted, under normal circumstances, to specific neuronal populations. These neurons are located in brain areas in which local estrogen formation may be involved in neuroendocrine control and in the modulation of reproductive or sex dimorphic behaviours. In this study the distribution of aromatase immunoreactivity has been assessed in the brain of mice and rats after a neurotoxic lesion induced by the systemic administration of kainic acid. This treatment resulted in the induction of aromatase expression by reactive glia in the hippocampus and in other brain areas that are affected by kainic acid. The reactive glia were identified as astrocytes by co-localization of aromatase with glial fibrillary acidic protein and by ultrastructural analysis. No immunoreactive astrocytes were detected in control animals. The same result, thede novo induction of aromatase expression in reactive astrocytes on the hippocampus, was observed after a penetrating brain injury. Furthermore, using a3H20 assay, aromatase activity was found to increase significantly in the injured hippocampus.

These findings indicate that although astrocytes do not normally express aromatase, the enzyme expression is induced in these glial cells by different forms of brain injury. The results suggest a role for local astroglial estrogen formation in brain repair.

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