Connective tissue growth factor reacts as an IL-6/STAT3-regulated hepatic negative acute phase protein

Figure 2 Interleukin-6 acts as an inhibitor of transforming growth factor β1 induced CYR61/CTGF/NOV 2/connective tissue growth factor protein expression in cultured rat hepatocytes. A: Western blottings of CYR61/CTGF/NOV (CCN) 2/connective tissue growth factor (CTGF) of rat hepatocytes (PC) cultured under serum-free conditions with or without addition of rr interleukin (rrIL)-6 at indicated concentrations 30 min prior addition of rhTGFβ1 (1 μg/L). The cell culture only with IL-6 at indicated concentrations served as internal control. Cells were harvested after another 24 h. β-actin served as loading control. Representative blots are shown. Blots were quantified relative to β-actin using the Lumi Imager System. Quantifications represent the mean ± SD of 3 independent cultures. ^aP < 0.05, ^bP < 0.0001 vs untreated control; B: Western blottings of CCN2/CTGF of rat PC cultured as stated in (A) under serum-free conditions with or without addition of rrIL-6 (10 μg/L) 30 min prior addition of rhTGFβ1 (1 μg/L) where indicated. The cells were harvested after 1, 2, 4 and 24 h. β-actin served as loading control. A representative blot of 3 independent experiments is shown; C: Western blottings of phosphorylated and total Smad2 and Smad3, the latter antibody cross-reacting with Smad1. Rat PC were cultured for 24 h under serum-free conditions with or without addition of rh transforming growth factor (TGF) β1 (1 μg/L) and indicated concentrations of rrIL-6. Representative blots are shown.