2. Academic Validation
  3. Rapanone, a naturally occurring benzoquinone, inhibits mitochondrial respiration and induces HepG2 cell death

Rapanone, a naturally occurring benzoquinone, inhibits mitochondrial respiration and induces HepG2 cell death

  • Toxicol In Vitro. 2020 Mar;63:104737. doi: 10.1016/j.tiv.2019.104737.
Gilberto L Pardo Andreu 1,  Felipe Zuccolotto Dos Reis 2,  Michael González-Durruthy 3,  René Delgado Hernández 4,  Richard F D'Vries 5,  Wim Vanden Berghe 6,  Luciane C Alberici 2
Affiliations

Affiliations

  • 1 Center for Research and Biological Evaluations, Institute of Pharmaceutical and Foods Sciences, University of Havana (UH), Av. 23 # 2317 b/ 214 and 222, La Coronela, La Lisa, PO 13600 Havana, Cuba. Electronic address: [email protected].
  • 2 Department of Physics and Chemistry, Faculty of Pharmaceutical Sciences of Ribeirao Preto, University of Sao Paulo (USP), Brazil.
  • 3 LAQV-REQUIMTE of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal; Soft Matter and Molecular Biophysics Group, Department of Applied Physics, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
  • 4 Center for Research and Biological Evaluations, Institute of Pharmaceutical and Foods Sciences, University of Havana (UH), Av. 23 # 2317 b/ 214 and 222, La Coronela, La Lisa, PO 13600 Havana, Cuba.
  • 5 Facultad de Ciencias Básicas, Universidad Santiago de Cali, Calle 5 # 62-00, Cali, Valle del Cauca, Colombia.
  • 6 Laboratory of Protein Chemistry, Proteomics and Epigenetic Signaling (PPES), Department of Biomedical Sciences, University of Antwerp (UA), Belgium.
PMID: 31756542 DOI: 10.1016/j.tiv.2019.104737
Abstract

Rapanone is a natural occurring benzoquinone with several biological effects including unclear cytotoxic mechanisms. Here we addressed if mitochondria are involved in the cytotoxicity of rapanone towards Cancer cells by employing hepatic carcinoma (HepG2) cells and isolated rat liver mitochondria. In the HepG2, rapanone (20-40 μM) induced a concentration-dependent mitochondrial membrane potential dissipation, ATP depletion, hydrogen peroxide generation and, phosphatidyl serine externalization; the latter being indicative of Apoptosis induction. Rapanone toxicity towards primary rats hepatocytes (IC50 = 35.58 ± 1.50 μM) was lower than that found for HepG2 cells (IC50 = 27.89 ± 0.75 μM). Loading of isolated mitochondria with rapanone (5-20 μM) caused a concentration-dependent inhibition of phosphorylating and uncoupled respirations supported by complex I (glutamate and malate) or the complex II (succinate) substrates, being the latter eliminated by complex IV substrate (TMPD/ascorbate). Rapanone also dissipated mitochondrial membrane potential, depleted ATP content, released Ca2+ from Ca2+-loaded mitochondria, increased ROS generation, cytochrome c release and membrane fluidity. Further analysis demonstrated that rapanone prevented the cytochrome c reduction in the presence of decylbenzilquinol, identifying complex III as the site of its inhibitory action. Computational docking results of rapanone to cytochrome bc1 (Cyt bc1) complex from the human sources found spontaneous thermodynamic processes for the quinone-Qo and Qi binding interactions, supporting the experimental in vitro assays. Collectively, these observations suggest that rapanone impairs mitochondrial respiration by inhibiting electron transport chain at Complex III and promotes mitochondrial dysfunction. This property is potentially involved in rapanone toxicity on Cancer cells.

Keywords

Anticancer; Complex III; Cytotoxicity; HepG2; Mitochondria; Rapanone.

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