Contribution of Akt/ERK1/2-NF-kB signalling pathway in the lactotroph cell proliferation induced by lipopolysaccharide

RODRIGO-FANTON E; GUTIÉRREZ, S; SOSA, LV; PALMERI, C. M.; PETITI, J. P.; MUKDSI, J. H.; TORRES, A I; DE PAUL, A L

Congreso; III iberoamerican Congress of Neuroimmunomodulation; 2009

We previously demonstrated that lipopolysaccharide (LPS) induced lactotroph proliferation from hyperplastic pituitaries. We evaluated the intracellular mechanism involved in PRL-cells proliferation analyzing the TLR4/CD14, Akt/ERK1/2 signalling pathway and NF-kB in response to LPS. Male rats were estrogenized with estradiol-benzoate (E2, 10mg) for 60 days. Pituitaries were cultured and treated with: LPS (100ng/ml; 60min), E2 (100nM; 10min), Interaction: LPS+E2 (Inter; 60min), and Sensitization: pre-incubation with E2 (10min) followed by LPS (100ng/ml; 60min; Sens). TLR4, CD14, pAkt, pERK1/2 and NF-kB, were determined by western blot from cytosolic (CE) and nuclear extracts (NE) and by immuno-electron-microscopy. In CE, TLR4 and CD14 levels increased in presence of LPS and they were detected in the cytoplasm of pituitary cells. Activation of Akt and ERK1/2 was detected in all LPS treatments but these levels were attenuated by pre-incubation with E2 (Sens). In LPS and Inter, NF-kB showed a higher expression in NE compared to CE (ANOVA-Fisher p<0.05), indicating its nuclear translocation. In both compartments, E2 exhibited no changes in NF-kB expression whereas in Sens high levels of NF-kB were detected in CE compared to NE indicating its cytosolic retention induced by E2. Lactotrophs respond to LPS through TLR4/CD14 activating Akt/ERK1/2/NF-kB signalling pathway to elicit lactotroph proliferation.