Taxifolin synergizes Andrographolide-induced cell death by attenuation of autophagy and augmentation of caspase dependent and independent cell death in HeLa cells

PLoS One. 2017 Feb 9;12(2):e0171325. doi: 10.1371/journal.pone.0171325. eCollection 2017.

Abstract

Andrographolide (Andro) has emerged recently as a potential and effective anticancer agent with induction of apoptosis in some cancer cell lines while induction of G2/M arrest with weak apoptosis in others. Few studies have proved that Andro is also effective in combination therapy. The flavonoid Taxifolin (Taxi) has showed anti-oxidant and antiproliferative effects against different cancer cells. Therefore, the present study investigated the cytotoxic effects of Andro alone or in combination with Taxi on HeLa cells. The combination of Andro with Taxi was synergistic at all tested concentrations and combination ratios. Andro alone induced caspase-dependent apoptosis which was enhanced by the combination with Taxi and attenuated partly by using Z-Vad-Fmk. Andro induced a protective reactive oxygen species (ROS)-dependent autophagy which was attenuated by Taxi. The activation of p53 was involved in Andro-induced autophagy where the use of Taxi or pifithrin-α (PFT-α) decreased it while the activation of JNK was involved in the cell death of HeLa cells but not in the induction of autophagy. The mitochondrial outer-membrane permeabilization (MOMP) plays an important role in Andro-induced cell death in HeLa cells. Andro alone increased the MOMP which was further increased in the case of combination. This led to the increase in AIF and cytochrome c release from mitochondria which consequently increased caspase-dependent and independent cell death. In conclusion, Andro induced a protective autophagy in HeLa cells which was reduced by Taxi and the cell death was increased by increasing the MOMP and subsequently the caspase-dependent and independent cell death.

MeSH terms

  • Apoptosis / drug effects*
  • Autophagy / drug effects*
  • Caspases / metabolism*
  • Cell Death / drug effects
  • Cell Proliferation / drug effects
  • Diterpenes / pharmacology*
  • Drug Synergism
  • HeLa Cells
  • Humans
  • Quercetin / analogs & derivatives*
  • Quercetin / pharmacology
  • Signal Transduction / drug effects

Substances

  • Diterpenes
  • andrographolide
  • Quercetin
  • taxifolin
  • Caspases

Grants and funding

This work was supported by the City University of Hong Kong Strategic Research Grant (#7002109) to HYC; http://www.cityu.edu.hk/ and the Department of Health, Hong Kong SAR Government HKCMMS project (HKCMMS Phase VIII Grants #9211046, 9211047, 9211048 and 9211051) http://www.cmd.gov.hk/html/eng/hkcmms/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.