Functional Toll-like receptor 4 expressed in lactotrophs mediates LPS-induced proliferation in experimental pituitary hyperplasia

SABATINO M; SOSA L; PETITI J; MUKDSI J; MASCANFRONI ID; PELLIZAS CG; GUTIERREZ S; TORRES AI; DE PAUL AL

EXPERIMENTAL CELL RESEARCH

ELSEVIER INC

Lugar: Amsterdam ; Año: 2013 vol. 319 p. 3020 - 3024

0014-4827

Tolllikereceptor4(TLR4)hasbeencharacterizedforitsabilitytorecognizebacterialendotoxin lipopolysaccharide(LPS).Consideringthatinfectionsorinflammatory processesmightcontribute totheprogressionofpituitarytumors,weanalyzedtheTLR4functionalrolebyevaluatingtheLPS effect onlactotrophproliferationinprimaryculturesfromexperimentalpituitarytumors,and examinedtheinvolvementofPI3K-AktandNF-κB activationinthiseffect.Inaddition,theroleof 17β-estradiolasapossiblemodulatorofLPS-inducedPRLcellproliferationwasfurther investigated.Inestrogen-inducedhyperplasicpituitaries,LPStriggeredlactotrophcellprolifera- tion. However,endotoxinfailedtoincreasethenumberoflactotrophstakingupBrdUinnormal pituitaries. Moreover,incubationwithanti-TLR4antibodysignificantly reducedLPS-induced lactotrophproliferation,suggestingafunctionalroleofthisreceptor.AsasignofTLR4activation, an LPSchallengeincreasedIL-6releaseinnormalandtumoralcells.By flow cytometry,TLR4 baseline expressionwasrevealedattheplasmamembraneoftumorallactotrophs,without changes notedinthepercentageofdoublePRL/TLR4positivecellsafterLPSstimulus.Increasesin TLR4 intracellularexpressionweredetectedaswellasrisesinCD14,p-AktandNF-κB afteranLPS challenge, asassessedbywesternblotting.TheTLR4/PRLandPRL/NF-κB co-localizationwasalso corroboratedbyimmunofluorescence andtheinvolvementofPI3K/Aktsignalinginlactotroph proliferationandIL-6releasewasrevealedthroughthePI3KinhibitorLy-294002.Inaddition, 17β-estradiolattenuatedtheLPS-evokedincreaseintumorallactotrophproliferationandIL-6 release. CollectivelytheseresultsdemonstratethepresenceoffunctionalTLR4inlactotrophs fromestrogen-inducedhyperplasicpituitaries,whichrespondedtotheproliferativestimulation and IL-6releaseinducedbyLPSthroughTLR4/CD14,withacontributionofthePI3K-Aktand NF-κB signalingpathways.