Figure 1
Garcinol reduces the constitutively active form of STAT3. (A) The chemical structure of garcinol. (B) Garcinol causes inhibition of translocation of STAT3 to the nucleus in C3A cells. (C) Garcinol suppresses phospho-STAT3 (Tyr 705) levels in a dose dependent manner. C3A cells (2×106/ml) were treated with the indicated concentrations of garcinol for 6 h, and the whole cell extract was subjected to western blotting analysis using phospho-STAT3 antibody. (D) Garcinol suppresses phospho-STAT3 levels in a time-dependent manner. C3A cells (2×106/ml) were treated with the 50 μM garcinol for the indicated times, after which western blotting was performed as described for panel C. The same blots were stripped and reprobed with STAT3 antibody to verify equal protein loading. (E) C3A cells (2×106/ml) were treated with the 50 μM garcinol for the indicated times, after which western blotting was performed against phospho-JAK2 antibody. The same blots were stripped and reprobed with JAK2 antibody to verify equal protein loading. (F) IL-6 induces phosphorylation of STAT3 in a dose dependent manner. HUH-7 cells (2×106/ml) were treated with indicated concentrations of IL-6 (10 ng/ml) for 15 min and the whole-cell extracts were subjected to western blotting analysis. (G) Garcinol downregulates IL-6–induced phospho-STAT3 in HUH-7 cells. HUH-7 cells (2×106/ml) were treated with 50 μM garcinol for the indicated durations and then stimulated with IL-6 (10 ng/ml) for 15 min and the whole-cell extracts were subjected to western blotting analysis. (H) Garcinol did not affect phospho-STAT3 (Ser727) levels in C3A cells. C3A cells (2×106/ml) were treated with the indicated concentrations of garcinol for 6 h, and the whole cell extract was subjected to immune-blotting analysis using phospho-STAT3 (Ser727) antibody. The same blots were stripped and reprobed with STAT3 antibody to verify equal protein loading.