Glycyrrhetinic Acid Suppressed NF-κB Activation in TNF-α-Induced Hepatocytes

Tumor necrosis factor-alpha (TNF-alpha) is a crucial inflammatory cytokine when hepatocytes are damaged. Glycyrrhiza uralensis Fisch. (Chinese licorice) has been widely used in Chinese herbal prescriptions for the treatment of liver diseases and as a food additive. Nuclear factor-kappa B (NF-kappa B) reporter gene assay in TNF-alpha-induced HepG2 was used as a screening platform. I kappa B alpha phosphorylation and p6S translocation were measured by Western blotting, and nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) gene expression were further confirmed in rat primary hepatocytes. Results showed that TNF-a enhanced NF-kappa B activity was significantly attenuated by glycyrrhetinic acid in a concentration-dependent manner in the NF-kappa B reporter gene assay. Glycyrrhetinic acid decreased the gene expression of iNOS through inhibited I kappa B alpha phosphorylation and p65 translocation in protein level. Furthermore, NO production and iNOS expression were reduced by glycyrrhetinic acid in TNF-alpha-induced rat primary hepatocytes. These results suggest that glycyrrhetinic acid may provide hepatoprotection against chronic liver inflammation through attenuating NF-kappa B activation to alleviate the inflammation.