Background/aims: Collagen accumulation in liver fibrosis is due in part to decreased expression of matrix metalloproteinase (MMP)-1 relative to TIMP-1. LX-2 hepatic stellate cells produce increased amounts of collagen and tissue inhibitor of metalloproteinase (TIMP)-1 in response to leptin. The effect of leptin on MMP-1 production has not been reported.
Methods: LX-2 cells were treated with leptin with or without inhibitors. We determined: phosphorylation of Janus kinase (JAK) 1 and -2, signal transducer and activator of transcription (STAT)3 and -5, extracellular signal-regulated kinase (ERK)1/2 and p38 by Western blot; H2O2 concentration by a colorimetric method; MMP-1 mRNA levels and stability by Northern blot; MMP-1 promoter activity as well as pro-MMP-1 by ELISA; and active MMP-1 by fluorescence.
Results: LX-2 cells constitutively expressed the MMP-1 gene and leptin repressed the basal level of MMP-1 mRNA and its promoter activity. The repression was mediated by JAK/STAT pathway in synergism with JAK-mediated H2O2-dependent ERK1/2 and p38 pathways. ERK1/2 inhibited MMP-1 promoter activity, whereas p38 decreased the message stability, contributing to mRNA down-regulation. Inhibition of MMP-1 gene diminished secreted pro-MMP-1 and active MMP-1.
Conclusions: Leptin represses MMP-1 gene expression via the synergistic actions of the JAK/STAT pathway and JAK-mediated H2O2-dependent ERK1/2 and p38 pathways.