Glycyrrhizin inhibits interleukin-8 production and nuclear factor-kappaB activity in lung epithelial cells, but not through glucocorticoid receptors.

This study was designed to examine the glucocorticoid-like inhibitory effect of glycyrrhizin (GL) on interleukin (IL)-8 production in A549 lung epithelial cells. GL, as well as dexamethasone (DEX) inhibited both tumor necrosis factor (TNF)-alpha- and IL-1beta-induced IL-8 production, mRNA expression, and promoter activity in A549 cells. Both GL and DEX inhibited transactivation of nuclear factor (NF)-kappaB, without inhibiting translocation of the NF-kappaB p65 subunit to the nucleus. However, the effect of GL was insensitive to RU486, a GR antagonist, and to GR knockdown by siRNA. Furthermore, only GL inhibited DNA binding of p65 to the IL-8 promoter region. These findings indicated that GL had a glucocorticoid-like inhibitory effect on IL-8 production via a mechanism that differs from that of glucocorticoids.