Effect of Dihydroartemisinin on Oxidative Damage and Energy Metabolism of HepG2 Cells and Its Synergistic Effect with Sorafenib / 中国实验方剂学杂志

Objective:To explore the inhibitory effect of dihydroartemisinin （DHA） on the proliferation of HepG2 cells， elucidate the mechanism from the perspectives of oxidative damage and energy metabolism， and discuss the possibility of combined use of DHA with sorafenib （Sora）. Method:Cell counting kit-8 （CCK-8） assay was used to obtain the 50% inhibitory concentration （IC₅₀） of DHA and Sora on HepG2 and SW480 cells and Chou-Talalay method was used to obtain the combination index （CI） of DHA and Sora. HepG2 cells were classified into the control group， DHA group （10 µmol·L^-1）， Sora group （5 µmol·L^-1）， and DHA + Sora group （DHA 10 µmol·L^-1， Sora 5 µmol·L^-1） and then incubated with corresponding drugs for 8-12 h. Seahorse XF glycolytic rate assay kit and cell mito stress test kit were employed to respectively detect the glycolysis function of cells and oxidative phosphorylation function of mitochondria. DCFH-DA and lipid peroxidation MDA assay kit were separately used to analyze the intracellular levels of reactive oxygen species （ROS） and malondialdehyde （MDA）. Western blot was applied to determine the intracellular levels of heme oxygenase-1 （HO-1） and glutamate-cysteine ligase catalytic subunit （GCLC）. Result:Compared with the control group， DHA alone inhibited the ATP synthesis in mitochondrial oxidative phosphorylation and glycolysis （<italic>P</italic><0.01）， increased the levels of intracellular ROS and MDA （<italic>P<</italic>0.05）， and decreased the levels of HO-1 and GCLC （<italic>P<</italic>0.05） in HepG2 cells. DHA and Sora had synergistic inhibitory effect on proliferation of HepG2 and SW480 cells， with CI < 0.90. The DHA + Sora group showed stronger suppression of ATP synthesis in mitochondrial oxidative phosphorylation and glycolysis （<italic>P</italic><0.01）， higher levels of intracellular ROS and MDA （<italic>P<</italic>0.01）， and lower levels of intracellular antioxidation-related proteins HO-1 and GCLC in HepG2 cells （<italic>P<</italic>0.01） than the DHA group. Conclusion:DHA may increase the level of MDA by reducing HO-1 and GCLC and increasing ROS in HepG2 cells， which results in mitochondria oxidative damage， restricts cell glycolysis and mitochondrial oxidative phosphorylation， and thus finally inhibits the proliferation of HepG2 cells. DHA and Sora have synergistic inhibitory effect on the proliferation of HepG2 and SW480 cells， and the mechanism may be related to the synergistic oxidative damage that affects the mitochondrial electron transport chain and suppresses cell energy metabolism.

Galangin Activates the ERK/AKT-Driven Nrf2 Signaling Pathway to Increase the Level of Reduced Glutathione in Human Keratinocytes

Previously, we demonstrated that galangin (3,5,7-trihydroxyflavone) protects human keratinocytes against ultraviolet B (UVB)-induced oxidative damage. In this study, we investigated the effect of galangin on induction of antioxidant enzymes involved in synthesis of reduced glutathione (GSH), and investigated the associated upstream signaling cascades. By activating nuclear factor-erythroid 2-related factor (Nrf2), galangin treatment significantly increased expression of glutamate-cysteine ligase catalytic subunit (GCLC) and glutathione synthetase (GSS). This activation of Nrf2 depended on extracellular signal-regulated kinases (ERKs) and protein kinase B (AKT) signaling. Inhibition of GSH in galangin-treated cells attenuated the protective effect of galangin against the deleterious effects of UVB. Our results reveal that galangin protects human keratinocytes by activating ERK/AKT-Nrf2, leading to elevated expression of GSH-synthesizing enzymes.