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Reactive oxygen species mediate thymoquinone-induced apoptosis and activate ERK and JNK signaling

Nahed El-Najjar1, Manal Chatila, Hiba Moukadem

  • 1Department of Biology, American University of Beirut, Beirut, Lebanon.

Apoptosis : an International Journal on Programmed Cell Death
|November 3, 2009
PubMed

Insights

Thymoquinone (TQ) from black seed oil inhibits colon cancer cell growth by inducing apoptosis through reactive oxygen species (ROS). Mitogen-activated protein kinases (MAPK) play a protective role in this process.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • Thymoquinone (TQ), found in black seed essential oil, is recognized for its potential to induce apoptosis and oxidative stress.
  • The precise role of oxidants in TQ-mediated cell death remains unclear.

Purpose of the Study:

  • To investigate the mechanism of TQ-induced colon cancer cell death.
  • To determine the involvement of reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPK) in TQ's anti-cancer effects.

Main Methods:

  • TQ's effect on various human colon cancer cell lines (Caco-2, HCT-116, LoVo, DLD-1, HT-29) and normal intestinal cells (FHs74Int) was assessed.
  • Apoptosis was analyzed using flow cytometry, M30 cytodeath assay, and caspase-3/7 activation.
  • The role of ROS was examined by pre-incubating cells with N-acetyl cysteine (NAC).
  • MAPK (JNK, ERK, p38) phosphorylation was measured, and specific inhibitors (PD98059, SP600125) were used to study their function.

Main Results:

  • TQ inhibited proliferation in colon cancer cells but not in normal intestinal cells.
  • Apoptotic cell death, confirmed by caspase activation, was the primary mechanism of TQ-induced growth inhibition in DLD-1 cells.
  • TQ-induced apoptosis was dependent on ROS generation, as it was blocked by NAC.
  • TQ increased JNK and ERK phosphorylation, which was abolished by NAC, indicating ROS-dependent MAPK activation.
  • ERK and JNK were found to have pro-survival roles, as inhibiting them enhanced TQ-induced cell death.

Conclusions:

  • TQ exhibits selective anti-proliferative effects on colon cancer cells.
  • The pro-oxidant activity of TQ is directly linked to its ability to induce apoptosis in colon cancer cells.
  • MAPK signaling pathways (JNK and ERK) play a protective role against TQ-induced apoptosis, suggesting a complex interplay between ROS and MAPK in TQ's mechanism of action.

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