UDCA-treatment upregulates the expression of TIMP-1 and alters MMP9 activity. HepG2 cells were either left untreated (control) or pretreated with 200 μmol/l UDCA (UDCA) for 2 hours. Cells were then either stimulated with 10 nmol/l PMA (PMA) for an additional 24 hours or left non-stimulated. (A,B) The relative expression levels of TIMP-1 and TIMP-3 were assayed by qRT-PCR. Expression was normalized to GAPDH and expressed as fold change of control sample. Mean values ± SEM are shown (n = 3). ***p < 0.001. (C) Conditioned media from treated and control cells were analyzed for the expression and activity of MMP9 and MMP2 using zymography. Equal amounts of proteins were loaded in each lane. (D) Band intensities of MMP9 proform (pro-MMP9) were densitometrically determined in three independent experiments (including the one shown) and compared to the active MMP9 form (92 kDa); the diagram shows pro-MMP9/MMP9 ratio. Mean values ± SEM are shown (n = 3). *p < 0.05.