Figure 4. IL-6 decreases D1-catalyzed T4-to-T3 conversion in HepG2 cells.
IL-6 inhibition of D1-catalyzed T3 production in intact cells was dose-dependent (A) and already observed after 2 hours of incubation (B). The effect of IL-6 was not altered by low FT4 levels (2 pM; C) and was abolished by the addition of 2 mM NAC to culture media (D). In contrast, IL-6 stimulated D1 activity in the DTT-stimulated assay in HepG2 cell sonicate (E). DIO1 mRNA levels in HepG2 cells were induced by IL-6, and this effect was blocked by U0126 or SB203580, but not by 2 mM NAC (F). DIO1 mRNA levels of control cells were set as 1. Data are mean ± SD of at least 3 independent experiments. *P < 0.001 versus control.