Transforming growth factor-β1 (TGF-β1), the main cytokine involved in liver fibrogenesis, induces expression of the type I collagen genes in hepatic stellate cells by a transcriptional mechanism, which is hydrogen peroxide and de novo protein synthesis dependent. Our recent studies have revealed that expression of type I collagen and matrix metalloproteinase-13 (MMP-13) mRNAs in hepatic stellate cells is reciprocally modulated. Because TGF-β1 induces a transient elevation of α1(I) collagen mRNA, we investigated whether this cytokine was able to induce the expression of MMP-13 mRNA during the downfall of the α1(I) collagen mRNA. In the present study, we report that TGF-β1 induces a rapid decline in steady-state levels of MMP-13 mRNA at the time that it induces the expression of α1(I) collagen mRNA. This change in MMP-13 mRNA expression occurs within the first 6 h postcytokine administration and is accompanied by a twofold increase in gene transcription and a fivefold decrease in mRNA half-life. This is followed by increased expression of MMP-13 mRNA, which reaches maximal values by 48 h. Our results also show that this TGF-β1-mediated effect is de novo protein synthesis-dependent and requires the activity of p38MAPK, phosphatidylinositol 3-kinase, AKT, and p70S6k. Altogether, our data suggest that regulation of MMP-13 by TGF-β1 is a complex process involving transcriptional and posttranscriptional mechanisms.
A Recombinant Collagen-mRNA Platform for Controllable Protein Synthesis