Apoptosis

, Volume 18, Issue 5, pp 605–617

Tiron and trolox potentiate the autophagic cell death induced by magnolol analog Ery5 by activation of Bax in HL-60 cells

  • Suresh Kumar
  • Ajay Kumar
  • Anup Singh Pathania
  • Santosh Kumar Guru
  • Srinivas Jada
  • Parduman Raj Sharma
  • Shashi Bhushan
  • Ajit Kumar Saxena
  • H. M. Sampath Kumar
  • Fayaz Malik
Original Paper

DOI: 10.1007/s10495-013-0805-y

Cite this article as:
Kumar, S., Kumar, A., Pathania, A.S. et al. Apoptosis (2013) 18: 605. doi:10.1007/s10495-013-0805-y

Abstract

This study describes the mechanism of trolox and tiron induced potentiation of cytotoxicity caused by Ery5, an analog of magnolol, in human myeloid leukemia HL-60 cells. Ery5 induced cytotoxicity in HL-60 cells by involving activation of bax and cleavage of caspase 3, which contributed towards activation of both apoptotic and autophagic pathways. Trolox and tiron, even at non-toxic concentrations, contributed to the cytotoxicity of Ery5 by activation of autophagic proteins like ATG7, ATG12 and LC3-II. Z-VAD-fmk mediated reduction in the cytotoxicity and expression of autophagic proteins, further suggested that autophagy induced by Ery5 is largely dependent upon caspases. Interestingly, Ery5 induced autophagy was accompanied by the downregulation of PI3K/AKT pathway whereas, trolox and tiron strongly enhanced this effect. In addition to that treatment of cells with Ery5, trolox and tiron individually, displayed a marked upregulation of Bax. The involvement of Bax in trolox and tiron induced enhancement of the cytotoxicity of Ery5 was confirmed, when siRNA induced silencing of Bax led to increased viability of the cells and exerted a strong inhibitory effect on LC3-II accumulation and p62 degradation in case of cells treated by the combination of Ery5 with trolox or tiron. Additionally, an important role of PARP in Ery5 mediated cell death has been suggested by PARP silencing experiments, however, potentiation of autophagic cytotoxicity by trolox and tiron did not seem to be dependent on PARP-1. Therefore, Bax seems to play a vital role in trolox and tiron mediated potentiation of autophagic cell death by Ery5 in HL-60 cells.

Keywords

AutophagyApoptosisBaxEry5PARP-1TroloxTiron

Abbreviations

AO

Acridine orange

ATG

Autophagy-related gene

BH3

Bcl2 homology 3

LC3

Microtubule-associated protein light chain 3

MTT

3-(4,5-Dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide

PARP-1

Poly(ADP-ribose) polymerase-1

PI

Propidium iodide

Rh-123

Rhodamine-123

ROS

Reactive oxygen species

siRNA

Small interfering RNA

Tiron

4,5-Dihydroxy-1,3-benzene disulfonic acid-disodium salt

Trolox

6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid

zVAD (zVAD fmk)

Benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone

SEM

Scanning electron microscopy

Supplementary material

10495_2013_805_MOESM1_ESM.pdf (649 kb)
Supplementary material 1 (PDF 648 kb)

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Suresh Kumar
    • 1
  • Ajay Kumar
    • 1
  • Anup Singh Pathania
    • 1
  • Santosh Kumar Guru
    • 1
  • Srinivas Jada
    • 2
  • Parduman Raj Sharma
    • 1
  • Shashi Bhushan
    • 1
  • Ajit Kumar Saxena
    • 1
  • H. M. Sampath Kumar
    • 2
  • Fayaz Malik
    • 1
  1. 1.Department of Cancer PharmacologyIndian Institute of Integrative Medicine (CSIR)JammuIndia
  2. 2.Organic Division-IIndian Institute of Chemical TechnologyHyderabadIndia