title: Functional Toll-like receptor 4 expressed in lactotrophs mediates LPS-induced proliferation in experimental pituitary hyperplasia.
abstract: Toll like receptor 4 (TLR4) has been characterized for its ability to recognize bacterial endotoxin lipopolysaccharide (LPS). Considering that infections or inflammatory processes might contribute to the progression of pituitary tumors, we analyzed the TLR4 functional role by evaluating the LPS effect on lactotroph proliferation in primary cultures from experimental pituitary tumors, and examined the involvement of PI3K-Akt and NF-κB activation in this effect. In addition, the role of 17β-estradiol as a possible modulator of LPS-induced PRL cell proliferation was further investigated. In estrogen-induced hyperplasic pituitaries, LPS triggered lactotroph cell proliferation. However, endotoxin failed to increase the number of lactotrophs taking up BrdU in normal pituitaries. Moreover, incubation with anti-TLR4 antibody significantly reduced LPS-induced lactotroph proliferation, suggesting a functional role of this receptor. As a sign of TLR4 activation, an LPS challenge increased IL-6 release in normal and tumoral cells. By flow cytometry, TLR4 baseline expression was revealed at the plasma membrane of tumoral lactotrophs, without changes noted in the percentage of double PRL/TLR4 positive cells after LPS stimulus. Increases in TLR4 intracellular expression were detected as well as rises in CD14, p-Akt and NF-κB after an LPS challenge, as assessed by western blotting. The TLR4/PRL and PRL/NF-κB co-localization was also corroborated by immunofluorescence and the involvement of PI3K/Akt signaling in lactotroph proliferation and IL-6 release was revealed through the PI3K inhibitor Ly-294002. In addition, 17β-estradiol attenuated the LPS-evoked increase in tumoral lactotroph proliferation and IL-6 release. Collectively these results demonstrate the presence of functional TLR4 in lactotrophs from estrogen-induced hyperplasic pituitaries, which responded to the proliferative stimulation and IL-6 release induced by LPS through TLR4/CD14, with a contribution of the PI3K-Akt and NF-κB signaling pathways.
authors: Centro de Microscopía Electrónica, Instituto de Investigaciones en Ciencias de la Salud (INICSA-CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Av. Enrique Barros y Enfermera Gordillo, Ciudad Universitaria, CP 5000, Córdoba, Argentina.
authors: María Eugenia
authors: ME
authors: Sabatino
authors: Liliana Del Valle
authors: Ldel V
authors: Sosa
authors: Juan Pablo
authors: JP
authors: Petiti
authors: Jorge Humberto
authors: JH
authors: Mukdsi
authors: Iván Darío
authors: ID
authors: Mascanfroni
authors: Claudia Gabriela
authors: CG
authors: Pellizas
authors: Silvina
authors: S
authors: Gutiérrez
authors: Alicia Inés
authors: AI
authors: Torres
authors: Ana Lucía
authors: AL
authors: De Paul
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D006965:Hyperplasia / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism* / Q000648:ultrastructure; D010911:Pituitary Neoplasms / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D015850:Interleukin-6; D008070:Lipopolysaccharides; D016328:NF-kappa B; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: 17β-estradiol; IL-6; Lactotroph cells; Lipopolysaccharide; NF-κB; PI3K; Toll-like receptor 4