AUF-1 mediates inhibition by nitric oxide of lipopolysaccharide-induced matrix metalloproteinase-9 expression in cultured astrocytes

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.

Expression Profile of Six RNA-Binding Proteins in Pulmonary Sarcoidosis

“…In the context of sub-cellular localisation, another RBP called NCL (alias nucleolin) has an unique property as it is additionally present on the cellular surface of macrophages where it mediates phagocytosis of apoptotic cells[18]. Of these RBPs, NCL, HuR and AUF1 have all been reported to affect MMP-9 expression[19–21]…”

“…A lot of potential targets of the RBPs, including MMP-9, have already been reported to be dysregulated in sarcoidosis [1, 2, 4, 5, 10, 19–22]. To our knowledge, no clinical study has yet addressed the in vivo expression of RBPs in pulmonary sarcoidosis or other non-malignant pulmonary pathologies.…”

Inhibition of Matrix Metalloproteinases-2/-9 Transiently Reduces Pre-Oligodendrocyte Loss during Lipopolysaccharide- but Not Tumour Necrosis Factor-alpha-Induced Inflammation in Fetal Ovine Glial Culture

“…The current study presents findings from cultures in which all glial cell types were present. Several in vitro studies have shown that mixed astrocyte and microglia cultures produce both gelatinases following LPS exposure, but the expression of active MMP-9 is dependent on the presence of microglia [28,29,30] and that TNF-α stimulates MMP-2 in cultured astrocytes [31,32]. In vivo, this may result in degradation of the neurovascular matrix given the association of MMP-9 with blood-brain barrier rupture.…”

mRNA stability control: a clandestine force in normal and malignant hematopoiesis

“…114 Knockdown experiments targeting all four AUF1 isoforms have confirmed the destabilizing effects of AUF1 against multiple ARE-containing transcripts. 43,108,[120][121][122] Although many reports demonstrate a destabilizing effect of AUF1 on mRNA transcripts, some studies indicated that it can also have a stabilizing effect. Overexpression of each of the four AUF1 isoforms stabilized a b-globin construct containing a GM-CSF or c-fos ARE.…”