Distinct signaling pathways for induction of type IINOS by IFN-γ and LPS in BV-2 microglial cells

Nitric oxide,(NO) release upon microglial cell activation has been implicated in the tissue injury and cell death in many neurodegenerative diseases Recent studies have indicated the ability of interferon-gamma (IFN gamma) and lipopolysaccharides (LPS) to independently induce type 11 nitric oxide synthase (iNOS) expression and NO production in BV-2 microglial cells. However, a detailed comparison between the signaling pathways activating iNOS by these two agents has not been accomplished. Analysis of PKC isoforms revealed mainly the presence of PKC delta, L and X in BV-2 cells. Although both IFN gamma and LPS could specifically enhance the tyrosine phosphorylation of PKC delta, treatment with IFN gamma induced a steady increase of phospho-PKC delta for up to 1 h, whereas treatment with LPS elevated phospho-PKC delta levels only transiently, with peak activity at 5 min. Rottlerin, a specific inhibitor for PKC delta, dose-dependently inhibited IFN gamma- and LPS-induced NO production. Despite the common involvement of PKC delta, IFN gamma- but not LPS-induced NO production involved extracellular signal-regulated kinases (ERK1/2) cascade and IFN gamma-induced phosphorylation of ERK1/2 was mediated through PKC. On the other hand, LPS- but not IFN gamma-induced NO production was through stimulation of NF-kappa B activation and nuclear translocation to interact with DNA. These results demonstrated distinct signaling pathways for induction of iNOS by IFN gamma and LPS in BV-2 microglial cells. (c) 2005 Elsevier Ltd. All rights reserved.