S100B modifies astroglial cell morphology, promotes migration and activates NF-kB in a dose- dependent manner

VILLARREAL A; SEAONE R; ANGELO F; AVILES REYES R X; RAMOS AJ

Congreso; Society for Neuroscience; 2011

S100B is a major constituent of astrocytes cytoplasm and its secretion is increased under cell stress conditions such as those produced by brain ischemia, hypoxia or traumatic brain injury. Extracellular S100B has autocrine effects on astrocytes inducing cell proliferation and secretion of pro-inflammatory mediators. Most of the S100B effects are mediated by the Receptor for Advanced Glycated End Products RAGE) which showed to induce NF-κB transcriptional activity in cell lines and primary neurons. By using rat primary astrocytes exposed to increasing S100B levels, we show here that astroglial morphology is profoundly altered by S100B exposure which increases the complexity of cell projections in filamentous astrocytes in the nanomolar range of concentration (up to 500 nM). This effect is prevented by RAGE-neutralizing antibodies. Scratch wound healing assays demonstrated that S100B stimulated astrocytes to extend membrane protrusions and to migrate into the wounded areas, in a RAGE-dependent manner. S100B also promoted NF-κB nuclear localization in primary astrocytes and significantly activated a GFP-NF-κB reporter construct in a dose-dependent manner. Further, chemical NF-κB blockage with suphazalazine reduced the absolute number and complexity of glial cell projections, an effect prevented by 1 μM, but not 10nM, S100B which restored the cell morphology. Astrocytes exposed for 16h to nanomolar S100B also improved their survival to oxidative stress conditions induced by a subsequent 2 μM exposure to hydrogen peroxide 200 μM. Together, these findings suggest that astrocytes respond to extracellular S100B in a RAGE-dependent manner with morphological changes, alterations of their migratory capacity and activation of NF-κB dependent transcription, all features that resemble reactive gliosis in vivo. These results support the hypothesis that S100B may behave as a Damage-Associated Molecular Pattern (DAMP) protein that promotes the initial phases of neuroinflammation by stimulating reactive gliosis.