Silibinin but not SIL inhibits innate inflammatory and antiviral signaling.

A, B, effect of silibinin and SIL on NF-κB dependent transcription. Huh7 cells were transfected with an NF-κB responsive reporter plasmid (pRDII-luc) and twenty-four hours later, cells were pretreated with the indicated doses of silibinin (A) or SIL (B). Cells were then treated with 10 ng/ml TNF-α and luciferase activity measured by Britelite assay 3.5 hours later. C, D, effect of silibinin and SIL on IRF-3 driven transcription from the IFN-B promoter. Huh7.5.1 cells were co-transfected with a luciferase reporter plasmid under control of the IFN-B promoter and IRF-35D, a constitutively active mutant of IRF-3 [28]. Twenty-four hours later, cells were pretreated with the indicated doses of silibinin (C) or SIL (D). Luciferase activity measured by Britelite assay 24 hours later. Fluorescence is reported as relative light units (RLU). Error bars represent standard deviation from triplicate cultures.