Figure 7
Retinoic acid sequestration is important for the anti-fibrotic activity of R-III. (A) Schematic drawing of the mechanism of action of R-III in hepatic stellate cells (HSCs). R-III enters HSCs via a retinol-binding protein (RBP) receptor STRA6 and sequesters retinoic acid (RA), which not only ① inhibits the retinoic acid receptor (RAR)-mediated pathway but also ② blocks the nuclear translocation of Smad3 via IL-1β signaling. (B, C) Total RNA was extracted from the livers of control mice, CCl4-treated mice (CCl4 administered three times per week over a period of 7 weeks), and CCl4/R-III-treated mice (R-III injected daily during the last 2 weeks of CCl4 treatment), and the expression levels of the collagen type I alpha 1 (col1a1), α-SMA, PAI-1 (B), and IL-1β (C) were analyzed by real-time PCR. P-value, two-sample t-test (n = 10). (D) Hepatic stellate cells after passage 1 were treated with R-III (0.1 μM) or R-IIIA/IB (0.1 μM) for 20 h, and the α-SMA and collagen type I expression levels were then analyzed by real-time PCR. **P < 0.01, paired t-test (n = 3) (compared with untreated HSCs-P1).
