Estrogen effects on neurite outgrowth and cytoskeletal gene expression in ER alpha-transfected PC12 cell lines

The potential of gonadal steroids like estrogen (E) to promote neurite spro uting is of interest in development and aging, as well as after neural trau ma. The specific roles of the two main estrogen receptors, Ella and ER beta , in neuronal sprouting are not yet well understood. We examined the hypoth esis that E can enhance nerve growth factor (NGF)-stimulated neurite sprout ing in an ER alpha -dependent manner. PC12 cells that were stably transfect ed with the full-length rat ER alpha gene (PCER) and a control line of cell s 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 ERP mRNA, but only the PCER cells expr ess Ella mRNA. Estrogen treatment markedly enhanced NGF-stimulated neurite outgrowth from PCER but not from PCCON cells. Significantly larger proporti ons of PCER cells (34 and 53% at 24 and 48 h, respectively) had neurites th an did the PCCON cells (17 and 26% at 24 and 48 h) after E plus NGF treatme nt. We also examined the effects of E and NGF treatment of PCER and PCCON c ells on peripherin, alpha -tubulin, and tau mRNA expression. In undifferent iated PCER cells, E treatment increased peripherin, reduced alpha -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 trea tment markedly stimulated expression of peripherin, alpha -tubulin, and tau mRNAs in both PCER and PCCON cells. From these observations we conclude th at E synergizes with NGF and stimulates neurite sprouting and also modulate s expression of several cytoskeletal mRNAs through ER alpha. (C) 2001 Acade mic Press.