IL-1β induces GFAP expression in vitro and in vivo and protects neurons from traumatic injury-associated apoptosis in rat brain striatum via NFκB/Ca²⁺-calmodulin/ERK mitogen-activated protein kinase signaling pathway.

Reactive astrogliosis, a feature of neuro-inflammation is induced by a number of endogenous mediators including cytokines. Despite interleukin-1 beta (IL-1β) stands out as the major inducer of this process, the underlying mechanism and its role on neuronal viability remain elusive. We investigated in human astrocytoma cells and the rat brain striatum, the role of the nuclear factor-kB (NF-kB) intracellular Ca(2+) concentration ([Ca(2+)]i) calmodulin (CaM) and extracellular regulated mitogen-activated protein kinases (ERK1/2) in IL-1β-induced expression of glial fibrillary acidic protein (GFAP) and neuronal apoptosis associated to a brain trauma. Cell data showed that IL-1β (1 ng/ml) increased NF-kB, pERK1/2 and GFAP expression. Nevertheless, further increase in IL-1β levels reversed progressively these responses. Preventing ERK1/2 activation with 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthiol]-butadiene antagonized IL-1β-induced GFAP expression while inhibiting selectively nuclear translocation of NF-kB with caffeic-acid phenethyl-ester down-regulated both ERK1/2 and GFAP expression induced by IL-1β. The GFAP response was also prevented by antagonizing selectively increase in [Ca(2+)]i, CaM activity or inducible nitric oxide synthase expression with respectively ryanodine plus 2-aminoethoxydiphenyl-borate, N-(6-aminohexyl)-5-chloro-1-naphthalensulfonamide hydrochloride and N-[(3-(aminomethyl)-phenyl]methyl]-ethanimidamide dihydrochloride. Data in vivo supported these findings and showed that GFAP expression induced by IL-1β (50 ng/ml) correlated with attenuated glial scar formation and reduced neuronal apoptosis. Our data identified the NF-kB/Ca(2+)-CaM/ERK signaling pathway as a novel in vivo key regulator of IL-1β-induced astrogliosis which may represent a potential target in neurodegeneration.