Estrogen Effects on Neurite Outgrowth and Cytoskeletal Gene Expression in ERα-Transfected PC12 Cell Lines

The potential of gonadal steroids like estrogen (E) to promote neurite sprouting is of interest in development and aging, as well as after neural trauma. The specific roles of the two main estrogen receptors, ERα and ERβ, in neuronal sprouting are not yet well understood. We examined the hypothesis that E can enhance nerve growth factor (NGF)-stimulated neurite sprouting in an ERα-dependent manner. PC12 cells that were stably transfected with the full-length rat ERα gene (PCER) and a control line of cells transfected with vector DNA alone (PCCON) were compared. Both cell lines vigorously differentiate neurites when treated with NGF. We determined that both lines show basal expression of ERβ mRNA, but only the PCER cells express ERα mRNA. Estrogen treatment markedly enhanced NGF-stimulated neurite outgrowth from PCER but not from PCCON cells. Significantly larger proportions of PCER cells (34 and 53% at 24 and 48 h, respectively) had neurites than did the PCCON cells (17 and 26% at 24 and 48 h) after E plus NGF treatment. We also examined the effects of E and NGF treatment of PCER and PCCON cells on peripherin, α-tubulin, and tau mRNA expression. In undifferentiated PCER cells, E treatment increased peripherin, reduced α-tubulin, and did not alter tau mRNA levels. No changes in these mRNAs were observed in the controls (undifferentiated PCCON cells) after E treatment. NGF treatment markedly stimulated expression of peripherin, α-tubulin, and tau mRNAs in both PCER and PCCON cells. From these observations we conclude that E synergizes with NGF and stimulates neurite sprouting and also modulates expression of several cytoskeletal mRNAs through ERα.