Effect of estrogen and FGF-2 interaction on lactotroph cell proliferation mediated by membrane-initiated signaling

SOSA L.; GUTIÉRREZ S.; PETITI J.P.; VACA A.; DE PAUL A.L.; TORRES A.I.

Florencia

Congreso; 15th International Congress of Endocrinology & European Congress of Endocrinology, ICE-ECE 2012; 2012

Estradiol (E2) may directly ienteract with groeth factors stimulating cell proliferation and differentiation. Previously, we have demonstrated that E2 through membrane estrogen receptor alpha (mREalpha) modulates the lactotroph cell population which exhibit noticeable changes in the pituitary gland. The aim of this study was to analyze the mREalpha contribution on lactotroph cell proliferation in response to E2 and FGF2 interaction evaluating the pathway involved in this effect. Pituitary cell cultures from Wistar female rats were treated with 10 nM of E2. E2 membrane-impermeable conjugated (E2-BSA), PPT (ERalpha agonist), DPN (ERbeta antagonist) alone or combined with FGF2(0.6 nM) for 30 min or 4 h. The lactotroph cell number was quantified by BRdU/PRL and PKC alpha and epsilon, phosphorilated (p) and total Akt or ERK1/2, and beta-actin protein expression by western blot. In addition, MEK(PD98059) and ER (ICI182780) inhibitors were used. The subcellular translocation of PKC alpha and epsilon was visualized by confocal microscopy. FGF receptors were identified by inmuno-electron microscopy. Statistical analysis: ANOVA-Tukey. In serum free condition, E2, E2-BSA, PPT, DPN or FGF2 alone did not modify the lactotroph cell number, whereas Es/FGF2, E2-BSA/FGF2 or PPT/FGF2 co-incubation significantly increased the mitogenic activity of these cells after 30 min or 4 h, being this effect blocked by ICI 182780 or PD98059 pre-treatment. The subcellular distribution of PKC alpha and p-Akt did not exhibit any significant variation after treatments. However, the stimulation for 30 min with the combinated treatments described above induced a remarkable increase of pERK1/2 and PKC epsilon translocation to lactotroph plasma membrane that was accompanied with a significant increase of PKC epsilon expression after 4 h. These findings show a cooperative effect of E2 and FGF2 on lactotroph proliferation triggered by signaling initiated at the plasma membrane with the contribution of mRE alpha and the activation of PKCepsilon/ERK1/2. This regulatory effect could participate in the homeostasis of pituitary cell populations.