S100B IS A DAMAGE ASSOCIATED MOLECULAR PATTERN PROTEIN (DAMP) THAT PROMOTES REACTIVE GLIOSIS IN A RAGE DEPENDENT MANNER

RAMOS AJ; ALEJANDRO VILLARREAL, ROCIO SEOANE, AGUSTINA GONZÁLEZ TORRES, MARIA FLORENCIA ANGELO, ROLANDO X. AVILES REYES, ALICIA ROSSI AND PHILIP A. BARKER

Cancun/Merida

Congreso; ISN-ASN Meeting /Glia Satellite Meeting in the context of the ISN-ASN Cancun; 2013

International Society for Neurochemistry

Background: After brain injury, S100B extracellular level dramatically increases due to active release from astrocytes and passive release from dying glia behaving as a DAMP protein. Extracellular S100B induces astroglial secretion of pro-inflammatory mediators and actives microglia. S100B binds to the Receptor for Advanced Glycation End products (RAGE). RAGE downstream signaling induces NF-ĸB activity. Objective: To analyze if S100B can induce astroglial changes towards a reactive phenotype in vitro and in vivo. Methods: Primary cortical astrocytes were transfected with different plasmids encoding RAGE, DN-RAGE, or RhoGTPases, and exposed to S100B to perform gain-loss of function studies. Astroglial morphology was studied by immunocytochemistry and phalloidin staining. In vivo S100B was injected intracortically to anaesthetized male Wistar rats and brain sections were evaluated by vimentin and GFAP immunostaining. Results: S100B nanomolar or micromolar levels induced RAGE-dependent astroglial hypertrophy, increased cell division showed by BrdU as well as the induction of a migratory phenotype in astrocytes subjected to artificial injury by scratch wound healing assays. Hypertrophy and migratory facilitation induced by S100B were blocked by transfecting dominant negative forms of small RhoGTPases Rac-1 and Cdc-42 or DN-RAGE. In addition, S100B exposure facilitates astrocytic survival to oxidative stress induced by H2O2, an effect abolished by Erk, Akt but not by NF-kB blockage. S100B also activates NF-ĸB transcriptional activity and RAGE promoter in a dose-dependent manner in reporter studies. S100B augmented endogenous RAGE expression, an effect partially prevented by NF-ĸB blockage or the expression of a dominant negative Sp1. In vivo, intracerebral infusion of S100B is enough to induce an astroglial reactive phenotype with increased vimentin and GFAP expression in normal brains. Conclusions: These findings demonstrate that S100B/RAGE induces phenotypic changes in astrocytes similar to those observed during reactive gliosis in vitro. In agreement with its role as a DAMP, extracellular S100B activates different RAGEdependent signaling cascades that may support a feed-forward autocrine loop that promotes inflammation in the injured brain. Supported by: UBACYT, PIP CONICET 1728, PICT 2008-1590