Induction of matrix metalloproteinase-1 gene transcription by tumour necrosis factor α via the p50/p50 homodimer of nuclear factor-κ B in activated human hepatic stellate cells

Background/Aims: Liver injury results in the activation of hepatic stellate cells (HSCs), which in turn produce matrix metalloproteinase (MMP) in response to pro-inflammatory cytokines for tissue remodelling. This study explored the transcriptional induction of the MMP-1 gene by tumour necrosis factor-α (TNF-α) in HSCs. Methods: The LI90 human HSC line was used in the present study. Gelatin zymography, enzyme-linked immunosorbent assay, Northern blotting and gene promoter-reporter assays were used to analyse the induction of MMP-1 protein, mRNA expression and gene transcription respectively. Deletional or site-directed mutations were introduced into the promoter region and transiently transfected into LI90 cells to determine the cis-acting elements necessary for TNF-α inducibility. Gel shift mobility assays were used to determine the transcriptional factors involved in the TNF-α responsiveness. Results: TNF-α upregulated MMP-1 protein and mRNA expression in a dose-dependent manner. A time-course experiment revealed a rapid induction of MMP-1 mRNA expression after TNF-α treatment. Mutation in a putative nuclear factor (NF)-κB-binding site at -2541bp almost completely abolished the TNF-α response to MMP-1 gene-promoter activity, suggesting transcriptional regulation of MMP-1 expression by TNF-α via this site. Electrophoretic mobility shift assay and supershift assays indicated that this transcriptional regulation was regulated via the p50/p50 homodimer of NF-κB. Conclusions: MMP-1 gene expression might be induced by TNF-α via the p50/p50 homodimer of NF-κB in activated human HSCs.