Effects of 18β-glycyrrhetinic acid on pro-inflammatory cytokines and neuronal apoptosis in the hippocampus of lipopolysaccharide-treated mice

Objectives : <TEX>18β</TEX>-Glycyrrhetinic acid (18betaGA) is an metabolite of glycyrrhizin in Glycyrrhiza (licorice). The present study investigated anti-inflammatory and anti-apoptosis effect of 18betaGA on the brain tissue of lipopolysaccharide (LPS)-treated C57BL/6 mice. Methods : 18betaGA was administered orally with low (30 mg/kg) and high (100 mg/kg) doses for 3 days prior to LPS (3 mg/kg) injection. Pro-inflammatory cytokines mRNA including tumor necrosis factor-<TEX>α</TEX> (TNF-<TEX>α</TEX>), interleukin (IL)-<TEX>1β</TEX>, IL-6, and inflammatory enzyme cyclooxygenase-2 (COX-2) mRNA were measured in the cerebral cortex, hippocampus, and hypothalamus tissue using real-time polymerase chain reaction at 24 h after the LPS injection. Histological changes of Cornu ammonis area 1 (CA1) neurons, Bax, Bcl-2, and caspase-3 expression in the hippocampus was also evaluated by immunohistochemistry and Western blotting method. Results : 18betaGA significantly attenuated the up-regulation of TNF-<TEX>α</TEX>, IL-<TEX>1β</TEX>, IL-6 mRNA, and COX-2 mRNA expression in the brain tissues induced by the LPS injection. 18betaGA also significantly attenuated the reductions of the thickness of CA1 and the number of CA1 neurons. The up-regulation of Bax protein expression in the hippocampal tissue by the LPS injection was significantly attenuated, while the ratio of Bcl-2/Bax expression was increased by 18betaGA treatment. 18betaGA also significantly attenuated the up-regulation of Bax and caspase-3 expression in the CA1 of the hippocampus. Conclusion : This results indicate that 18betaGA has anti-inflammatory and anti-apoptosis effect under neuroinflammation induced by the LPS injection and suggest that 18betaGA may be a beneficial drug for various brain diseases accompanied with the brain tissue inflammation.