The Stimulation of Inducible Nitric-oxide Synthase by the Prion Protein Fragment 106-126 in Human Microglia is Tumor Necrosis Factor-α-dependent and Involves p38 Mitogen-activated Protein Kinase

Abstract

A synthetic peptide consisting of amino acid residues 106-126 of the human prion protein (PrP-(106-126)) has been previously demonstrated to be neurotoxic and to induce microglial activation. The present study investigated the expression of the inducible form of the nitricoxide synthase (NOS-II) in human microglial cells treated with PrP-(106-126). Using reverse transcriptasepolymerase chain reaction, we found that PrP-(106-126) induces NOS-II gene expression after 24 h of treatment and that this effect is accompanied by a peak of nuclear factor kappa B (NF-κB) binding at 30 min as evaluated by electrophoretic mobility shift assay. Since our previous data demonstrated tumor necrosis factor-α (TNF-α) to be a potent inducer of NOS-II in these cells, we analyzed the expression of this cytokine in PrP-(106-126)-treated microglia. PrP-(106-126) caused the release of TNF-α as detected by enzyme-linked immunosorbent assay, and a blocking antibody, anti-TNF-α, abolished NOS-II induction elicited by this peptide. Moreover, PrP-(106-126) activates p38 mitogen-activated protein kinase, and the inhibition of this pathway determines the ablation of NF-κB binding induced by this fragment peptide.