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  • Title: AUF-1 mediates inhibition by nitric oxide of lipopolysaccharide-induced matrix metalloproteinase-9 expression in cultured astrocytes.
    Author: Liu W, Rosenberg GA, Liu KJ.
    Journal: J Neurosci Res; 2006 Aug 01; 84(2):360-9. PubMed ID: 16683234.
    Abstract:
    Neuroinflammatory diseases are associated with increased production of matrix metalloproteinase-9 (MMP-9) and excessive generation of nitric oxide (NO). NO has been reported to have variable effects on MMP-9 gene expression and activation in various cell types. In the present study, we investigated the effect of NOon MMP-9 expression in primary cortical astrocytes. Zymography and real-time PCR showed that lipopolysaccharide (LPS) dramatically increased latent MMP-9 gelatinolytic activity and MMP-9 mRNA expression. By using the NO donor DETA NONOate, we observed a dose-dependent inhibition of MMP-9 induction by LPS. Active forms of MMP-9 were not found by zymography after NO treatment. The MEK1/2 inhibitor U0126 completely inhibited LPS-induced MMP-9, which was partially inhibited by the p38 MAPK inhibitor SB203580. NO had no effect on LPS-stimulated ERK1/2 and p38 MAPK activation, suggesting that the inhibitory action of NO occurs downstream of MAPK cascades. Real-time PCR analysis showed that NO accelerated the degradation of MMP-9 mRNA after LPS induction. Western blotting and pull-down assay demonstrated that NO increased AUF-1 expression as well as its specific binding to the MMP-9 gene 3'-untranslated region. Knockdown of AUF-1 with siRNA partially reversed the inhibitory action of NO on LPS-stimulated MMP-9 induction. We conclude that NO does not activate MMP-9 in astrocyte cultures but reduces LPS-induced MMP-9 expression via accelerating MMP-9 mRNA degradation, which is partially mediated by AUF-1. Our results suggest that elevated NO concentrations may suppress MMP-9 and restrict the inflammatory response in neurodegenerative diseases.
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