Reactive oxygen species and PI3K/Akt signaling play key roles in the induction of Nrf2-driven heme oxygenase-1 expression in sulforaphane-treated human mesothelioma MSTO-211H cells

Our plain-English summary of Reactive oxygen species and PI3K/Akt signaling play key roles in the induction of Nrf2-driven heme oxygenase-1 expression in sulforaphane-treated human mesothelioma MSTO-211H cells, by Y.J. Lee, H.Y. Jeong, Y.B. Kim, et al (Food and Chemical Toxicology, 2012).

The study

• Authors: Y.J. Lee, H.Y. Jeong, Y.B. Kim, Y.J. Lee, S.Y. Won, J.H. Shim, M.K. Cho, H.S. Nam, S.H. Lee
• Journal: Food and Chemical Toxicology
• Published: 2012;50(2):116-23
• Cited by: 92 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The nuclear factor erythroid-derived 2 related factor 2 (Nrf2)/heme oxygenase (HO)-1 induction plays cytoprotective roles against oxidative injury, apoptosis, and anticancer therapy; however, little is known about its regulation in human mesothelioma MSTO-211H cells. In this study, we investigated Nrf2/HO-1 induction in response to sulforaphane and determined the signaling pathways involved in this process. Sulforaphane treatment decreased cell viability and triggered a rapid and transient increase in the intracellular ROS levels. Pretreatment with N-acetylcysteine (NAC) prevented sulforaphane-induced cytotoxicity. Erk1/2 was activated within 1h of sulforaphane addition, whereas Akt phosphorylation was suppressed until the first 8h, and was then maintained at an elevated level until 72h, displaying a biphasic regulatory feature. Nrf2 protein levels in both nuclear and whole cell lysates were increased after sulforaphane treatment and were decreased by pretreatment with NAC, actinomycin D and cycloheximide. Activation of the Nrf2/HO-1 system after sulforaphane treatment was suppressed by pretreatment with NAC or Ly294002, a PI3K inhibitor. Knockdown of Nrf2 with siRNA decreased cell viability and attenuated sulforaphane-induced HO-1 up-regulation. Overall, our results indicate that ROS generation and/or activation of PI3K/Akt signaling regulate cell survival and Nrf2-driven HO-1 expression in sulforaphane-treated MSTO-211H cells.

Copyright © 2011 Elsevier Ltd. All rights reserved.

In plain English

This was a laboratory study of a human malignant mesothelioma cell line, MSTO-211H, grown in dishes. It did not study people or asbestos exposure. The authors treated the cells with sulforaphane, a compound found in broccoli and cabbage, at 0 to 40 micromolar. After 72 hours, cell viability was about 95.3%, 76.2% and 35.0% of untreated cells at 10, 20 and 40 micromolar. Sulforaphane caused a rapid rise in reactive oxygen species, a form of chemical stress inside cells, which peaked at 3 hours. Pretreating the cells with the antioxidant N-acetylcysteine kept viability close to that of untreated cells. Sulforaphane raised levels of the protein Nrf2 and of the enzyme heme oxygenase-1 (HO-1). N-acetylcysteine and the PI3K blocker Ly294002 suppressed this response. Silencing Nrf2 lowered HO-1 and reduced living cells to 81.1% of control at 72 hours. The authors concluded that PI3K/Akt signaling is required for this Nrf2-driven HO-1 expression. They stated that further studies on the role of Akt activation are needed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiment on a cultured human cancer cell line
• Who was studied: The human malignant mesothelioma cell line MSTO-211H, obtained from the American Type Culture Collection. No human subjects or animals were studied.
• Exposure: Sulforaphane, a compound from broccoli and related vegetables, at 0 to 40 micromolar for up to 72 hours. Some cells were also pretreated with N-acetylcysteine (an antioxidant), Ly294002 (a PI3K blocker), PD98059 (a MEK blocker), actinomycin D, cycloheximide or MG132. Asbestos was not used in the experiments.
• Main results:
  • At 72 hours, viability of sulforaphane-treated cells was approximately 95.3%, 76.2% and 35.0% of control cells at 10, 20 and 40 micromolar, respectively.
  • Reactive oxygen species (ROS) production in treated cells began within 10 minutes, peaked at 3 hours and declined until 24 hours.
  • In cells pretreated with N-acetylcysteine, viability stayed in almost the same range as untreated controls. The authors took this to suggest that ROS play a critical role in the cell-killing effect of sulforaphane.
  • Sulforaphane activated Erk1/2 within 1 hour. Akt phosphorylation was suppressed early and later stayed slightly above control levels through 72 hours.
  • Pretreatment with Ly294002 and PD98059 did not significantly reduce the cell-killing effect of sulforaphane.
  • Sulforaphane rapidly increased Nrf2 in the nuclear fractions of the cells.
  • HO-1 induction by sulforaphane was seen as early as 2 hours and lasted at least 72 hours.
  • Activation of the Nrf2/HO-1 system by sulforaphane was suppressed by pretreatment with N-acetylcysteine or Ly294002.
  • Silencing Nrf2 with siRNA inhibited cell proliferation and HO-1 expression. Living cells fell from about 91.5% of control at 24 hours to 81.1% at 72 hours.
• The authors' conclusion: The authors concluded that PI3K/Akt signaling is required for the Nrf2-driven HO-1 expression caused by sulforaphane in MSTO-211H cells. They also concluded that the effects of sulforaphane were related to reactive oxygen species.
• Limitations the authors state:
  • The authors stated it is not clear that PI3K/Akt signaling protects the cells against sulforaphane's cell-killing effect, because blocking PI3K significantly increased that effect only at 20 micromolar.
  • The authors stated that further studies are needed on the consequences of Akt activation.
  • The authors stated that the precise nature of Erk1/2 phosphorylation had not been determined.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Reactive Oxygen Species (ROS), Mesothelioma, Apoptosis, Biphasic Mesothelioma.

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