Axogenic effect of estradiol in hypothalamic neurons involve MAPK signaling

S.V. GOROSITO; H.F. CARRER; M.J. CAMBIASSO

Villa Giardino, Córdoba, Argentina

Taller; VII Taller Argentino de Neurociencia; 2005

We have shown that 17-b-estradiol induces a selective enhancement of the growth of axons in male derived hypothalamic neurons in vitro. We also demonstrated that this effect was not exerted through the classical intracellular estrogen receptor but depends on a membrane mechanism in which the tyrosine-kinase receptor B participated. The purpose of the present work was to investigate if the activation of mitogen-activated protein kinase (MAP kinase) pathway is required for estrogen-induced axon growth. Dissociated hypothalamic neurons taken from male fetuses at gestational day 16 were grown in astroglia-conditioned medium and 17-b-estradiol (E2) 10nM for 48 h. After 3h washout, cultures were pulsed with E2, E2 conjugated to bovine serum albumin [17-b-estradiol-6-(O-carboximetil) oxima; E2-BSA] or BDNF and harvested for Western blotting. E2 rapidly induced tyrosine phosphorylation of both extracellular signal regulated kinases 1 and 2 (ERK1 and ERK2). Analysis of the temporal course of MAPK activation showed increased levels of phosphorylated ERK up to 60 min after E2 exposure, with a maximal response at 5-15 min. UO126 (specific inhibitor of MEK 1/2, 25 mM) blocked E2 induced axonal elongation and ERK phosphorylation, confirming the involvement of ERK in the neuritogenic effect of E2. The membrane impermeable construct E2-BSA proved as effective as free E2 to induce ERK phosphorylation and axon elongation, suggesting that E2 exerted its effect through a membrane-associated receptor.