Expression of C/EBPalpha and C/EBPbeta in glial cells in vitro after inducing glial activation by different stimuli.

We studied the involvement of two members of the CCAAT/enhancer binding proteins (C/EBPs) family of transcription factors, C/EBPalpha and C/EBPbeta, in glial activation induced by different stimuli in rat cerebellar neuronal-glial cultures. Glial activation was induced by two types of neuronal death--excitotoxic and apoptotic. We had previously reported that these two induction mechanisms resulted in different patterns of glial activation (K. Pérez-Capote, J. Serratosa, C. Solà, Excitotoxic and apoptotic neuronal death induce different patterns of glial activation in vitro, J. Neurochem. 94 (2005) 226-237), only the former involving an inflammatory response. Glial activation was also induced by lipopolysaccharide (LPS) from E. coli, an inflammatory agent with a known direct effect on glial cells. Using immunocytochemical techniques, here we examined whether changes in C/EBPalpha and C/EBPbeta expression are selectively associated with a determinate pattern of glial activation. Excitotoxic neuronal death increased glial C/EBPbeta expression in the absence of alterations in C/EBPalpha expression, while no effect was observed following neuronal apoptosis. LPS treatment decreased C/EBPalpha and increased C/EBPbeta expression in glial cells. These results implicate C/EBPs in glial activation, although these two factors appear to have different roles. C/EBPalpha expression decreases only in response to LPS, while C/EBPbeta expression is increased by both LPS and excitotoxic neuronal death, although not by neuronal apoptosis. These results show that C/EBPbeta plays an active role in glial activation, but only when this involves an inflammatory reaction, suggesting a role for C/EBPbeta in neuroinflammation.