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Although the cholinesterase inhibitor tacrine has been successfully used for the treatment of Alzheimer's disease, it is known to have hepatotoxic effects. Liquiritigenin (LQ), an active flavonoid in Glycyrrhizae radix, exerts protective effects against liver damage. This study investigated the toxic effect of tacrine on hepatocytes and the beneficial effect of LQ on tacrine intoxication in vivo and in vitro, and the underlying mechanism involved. In hepatocyte cell lines, tacrine induced cell death and oxidative stress, as indicated by decreases in cell viability and glutathione (GSH) contents, which were blocked by pretreatment with LQ. Fluorescent activated cell sorter (FACS) analysis revealed that LQ inhibited cellular H 2 O 2 production and mitochondrial dysfunction induced by tacrine in HepG2 cells. Furthermore, LQ promoted inhibitory phosphorylation of glycogen synthase kinase-3β (GSK3β) and prevented decreases in GSK3β phosphorylation induced by tacrine. In rats treatment with tacrine at 30 mg/kg increased hepatic damage as assessed by blood biochemistry and histopathology. Administration of LQ (10 or 30 mg/kg/d, per os (p.o.)) or the hepatoprotective drug sylimarin (100 mg/kg/d) for 3 d inhibited elevations in alanine aminotransferase, aspartate aminotransferase, and histological changes induced by tacrine. These results show that LQ efficaciously protects the rat liver against tacrine-induced liver damage, and suggest that LQ is a therapeutic candidate for ameliorating the hepatotoxic effects of tacrine.Key words tacrine; liquiritigenin; glycogen synthase kinase-3β; liver; oxidative stress; mitochondria Tacrine (9-amino-1,2,3,4-tetrahydroacridine hydrochloride) is recommended as the first-line treatment for Alzheimer's disease by the US Food and Drug Administration. It is an active cholinesterase inhibitor that blocks the degradation of cholinergic nerves in the cerebral cortex and hippocampus to increase cholinergic transmission. 1) However, although tacrine has positive therapeutic effects, it has been demonstrated to increased serum alanine aminotransferase (ALT) levels in about 30% of patients, and this seriously limits its clinical use.2) A number of authors have reported that tacrine-induced hepatotoxicity is related to cytochrome P450 1A2 in human liver microsomes and is associated with mitochondrial dysfunction.3-5) Studies also have showed that the hepatotoxic effect of tacrine is associated with oxidative stress, as demonstrated by increased reactive oxygen species (ROS) production and decreased intracellular glutathione (GSH).6-8) However, mechanism responsible for tacrine-induced hepatotoxicity has not yet been elucidated. Nevertheless many studies have shown that anthraquinones, chromone glycosides, phenolic amide, and an herbal medicine protect hepatocytes from the toxic effects of tacrine. [9][10][11][12] Oxidative stress is state in which the balance between ROS production and antioxidants is shifted in favor of ROS, and is associated with severity of liver damage.13) ROS normally work ...

Background and objective: Methamphetamine (Meth) is a widely abused psychostimulant that produces hyperlocomotion in rodents. Radix of Glycyrrhizae uralensis comprises a variety of bioactive components that have neuroprotective effects. In a previous study, we have demonstrated methanol extracts from radix of Glycyrrhizae uralensis (MEGR) suppress acute cocaine-induced extracellular dopamine release in the nucleus accumbens. In the present study, we investigated the effect of MEGR on acute Meth-induced hyperlocomotion.Methods: Male Sprague-Dawley rats were orally administered with MEGR (60 mg/kg and 180 mg/kg) 60 min prior to an intraperitoneal injection of Meth (1.0 mg/kg).Results: Behavioral analysis showed acute Meth greatly increased locomotor activities, while pretreatment