Enhancing tetrandrine cytotoxicity in human lung carcinoma A549 cells by suppressing mitochondrial ATP production
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ATP depletion induced by inhibiting glycolysis or mitochondrial ATP production has been demonstrated to cause cancer cell death. Whether ATP depletion can enhance the efficacy and potency of anti-cancer effects of herbal compounds is so far unknown. We examined the enhancing effect of ATP depletion on anti-cancer actions of tetrandrine (TET) in human lung carcinoma A549 cells. A 24-h incubation of A549 cells with tetrandrine caused a concentration-dependent cytotoxic effect (LC50 = 66.1 μM). Co-incubation with 20 mM 2-deoxyglucose (2-DG, glycolysis inhibitor) caused only a very slight enhancement of tetrandrine cytotoxicity. By contrast, inhibiting mitochondrial ATP production with oligomycin (10 μM, ATP synthase inhibitor) and FCCP (30 μM, uncoupling agent) (thus, oligo-FCCP) on its own caused only slight cell cytotoxicity but strongly potentiated tetrandrine cytotoxicity (tetrandrine LC50 = 15.6 μM). The stronger enhancing effect of oligo-FCCP than 2-DG on TET toxicity did not result from more severe overall ATP depletion, since both treatments caused a similar ATP level suppression. Neither oligo-FCCP nor 2-DG synergized with tetrandrine in decreasing mitochondrial membrane potential. TET on its own triggered reactive oxygen species (ROS) production, and oligo-FCCP, but not 2-DG, potentiated TET in causing ROS production. Taken together, our results suggest that inhibiting ATP production from mitochondria, but not from glycolysis, appears to be a very effective means in augmenting TET-triggered ROS production and hence toxicity in A549 cells.
KeywordsTetrandrine Mitochondria ATP depletion A549 Glycolysis
LRS conducted the experiments. LWCC, KSC, FL, and CWC participated in research design and data analysis. LWCC, YML, and KLW wrote the paper. All the authors read and approved the manuscript.
Macau Science and Technology Development Fund (FUNDO PARA O DESENVOLVIMENTO DAS CIÊNCIAS E DA TECNOLOGIA) for support (Grant number 002/2015/A1) (LWCC). China Medical University, Taiwan, and the Ministry of Science and Technology of Taiwan for providing funding (103-2320-B-039-015-; 104-2320-B-039-030-; 104-2320-B-039-013-; 105-2320-B-039-028-; DMR-106-086; DMR-106-089; DMR-107-083; DMR-108-083) (Y.M.L., K.L.W, and K.S.C.).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
No humans or animals were used in this study; only cell lines were used in this work and therefore ethical approval is not required.
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