Objective: To explore the eff ect of galangin on DNA topoisomerases in lung cancer cells A549 and H46 as well on cell growth.
Methods: The inhibitory effect of galangin on the growth of A549 and H46 cells was analyzed by MTT method. The effect of galangin on Topo I activity was detected by the agarose gel electrophoresis method. Furthermore, the interaction between galangin and Topo I was evaluated by fluorescence spectroscopy. Finally, the eff ect of galangin on the Topo I structure was discussed.
Results: Galangin could induce the apoptosis of A549 and H46 cells (IC50 was 0.221 mmol/L and 0.173 mmol/L, respectively). Agarose gel electrophoresis showed that galangin exerted significant inhibitory effect on Topo I activity. Fluorescence spectrum analysis showed that galangin was able to quench Topo I fluorescence, and hydrophobic interaction was the main driving force. Circular dichroism analysis showed that galangin induced Topo I conformation change and increased the content of α-helix, which prevented the formation of active center and in turn led to the decrease in Topo I activity. Molecular simulation results showed that galangin could bind to the active center of Topo I to form hydrogen bonds with the catalytic site at Arg364 and Asn352.
Conclusion: Galangin is able to inhibit Topo I activity and to reduce the unwinding rate of single stranded DNNA in tumor cells, which plays an important role in induction of A549 and H46 cell apoptosis.