Ouabain activates NFκB through an NMDA signaling pathway in cultured cerebellar cells

Na,K-ATPase, an ion pump, has been shown to interact with other proteins in signaling complexes in cardiac myocytes, renal and glial cells, and several other cell types. Our previous in vivo studies indicated that intrahippocampal administration of ouabain (OUA), an inhibitor of Na,K-ATPase, induces NFκB activation, leading to an increase in mRNA levels of target genes of this transcription factor in the rat hippocampus. The present work investigated whether OUA can regulate NF-κB in primary cultured rat cerebellar cells. Cells were treated with different concentrations of OUA (1, 10 or 100 μM) for different periods of time (1, 2 and 4 h). OUA induced a time- and concentration-dependent activation of NFκB (peak of activation: 10 μM, 2 h), involving both p50/p65 and p50/p50 NFκB dimers. OUA (10 μM, 2 h) induced upregulation of tumor necrosis factor α (Tnf-α), interleukin-1β (Il-1β), and brain derived neurotrophic factor (Bdnf) mRNA levels. Both NFκB activation and gene expression activation induced by OUA (10 μM) were abolished when cells were pre-treated for 20 min with MK-801 (N-Methyl-D-Aspartate (NMDA) receptor antagonist), manumycin A (farnesyltransferase inhibitor), PP-1(Src-family tyrosine kinase inhibitor) and PD98059 (mitogen-activated protein kinase (MAPK) inhibitor). OUA (10 μM) alone or in the presence of MK-801, PP-1, PD98059 did not cause cell death or DNA fragmentation. These findings suggest that OUA activates NFκB by NMDA-Src-Ras-like protein through MAPK pathways in cultured cerebellar cells. This pathway may mediate an adaptive response in the central nervous system.