Autocrine S100B signalling in astrocytes is mediated by RAGE receptor and NFKB activation

VILLARREAL A; GONZALEZ TORRES MA; ANGELO MF; AVILES REYES RX; DAIGENEAULT K; BARKER PA; RAMOS AJ

Mar del Plata, Argentina

Congreso; LIV Reunión Aual de la Sociedad Argentina de Investigación Clínica y LVII Reunión Científica Anual de la Sociedad Argentina de Inmunología; 2009

Sociedad Argentina de Investigación Clínica y Sociedad Argentina de Inmunología

S100B is secreted by astrocytes after traumatic or ischemic brain injury. Once released to the extracelular space, S100B has autocrine effects on astrocytes. In vitro, S100B induces cell division and secretion of pro-inflammatory molecules from astrocytes. RAGE expression is induced by hypoxia or cellular stress and has been shown to mediate S100B effects in different cell types. RAGE downstream signaling involves NFKB activation. The aim of this study was to analyze if the S100B effects on astroglial are mediated by RAGE and NFKB.   Primary astrocytic cultures were exposed to different doses of S100B. S100B induced an increase in RAGE expression and activation of NFKB in a time and dose-dependent manner. NFKB activation was analyzed by p65 subunit nuclear localization and by a NFKB reporter plasmid. Using another set of reporter plasmids containing conserved sequences of RAGE promoter, we demonstrated that the proximal promoter was activated by S100B and that NFKB –but not Sp1- blockage abrogated that induction thus showing the NFKB role in the control of RAGE expression. Astroglial projections (number and complexity) were increased by S100B exposure and this effect was efficiently blocked by a NFKB inhibitor or partially inhibited by blocking anti-RAGE antibodies. Blocking RAGE signaling had a deleterious effect on cell morphology and cell survival.  Our results demonstrate that S100B effects on astrocytes are mediated by RAGE and NFKB activation. Since S100B increases the expression of its own receptor RAGE, S100B has a efficient feed-forward mechanism to expand its effects from the site of release to the surrounding area.