FIG 3.

Quercetin dose dependently inhibits VP24 IFN-inhibitory function. (A) HEK293T cells were cotransfected with pISRE-luc, RL-TK, and VP24 plasmid. Twenty-four hours after transfection, cells were stimulated with IFN-α and quercetin was added to VP24-cotransfected cells. After 8 h, cells were lysed and luciferase was measured. Results are shown as percent VP24 inhibitory activity on ISRE expression using as a positive control of inhibition (100%) cells not treated with quercetin. Firefly luciferase activity was normalized to the Renilla luciferase internal control. (B) HEK293T cells were treated with quercetin and cytotoxicity was measured. Results are shown as percentage of cells treated with quercetin over untreated cells. (C) HEK293T cells transfected with pcDNA3.1 or VP24 plasmid. After 24 h, cells were stimulated with IFN-α and treated or not with quercetin (30 μM). After 24 h, total RNA was extracted, and RT-qPCR was performed. Results are shown as percent ISG15 mRNA expression in VP24-cotransfected cells (treated or not with quercetin) over empty vector control. Data represent the means ± SDs from three independent experiments. **, P < 0.01, two-tailed unpaired Student’s t test (n = 3).