Peroxiredoxin 3 levels regulate a mitochondrial redox setpoint in malignant mesothelioma cells

Our plain-English summary of Peroxiredoxin 3 levels regulate a mitochondrial redox setpoint in malignant mesothelioma cells, by B. Cunniff, A.N. Wozniak, P. Sweeney, et al (Redox Biology, 2014).

The study

• Authors: B. Cunniff, A.N. Wozniak, P. Sweeney, K. DeCosta, N.H. Heintz
• Journal: Redox Biology
• Published: 2014;3:79-87
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Peroxiredoxin 3 (PRX3), a typical 2-Cys peroxiredoxin located exclusively in the mitochondrial matrix, is the principal peroxidase responsible for metabolizing mitochondrial hydrogen peroxide, a byproduct of cellular respiration originating from the mitochondrial electron transport chain. Mitochondrial oxidants are produced in excess in cancer cells due to oncogenic transformation and metabolic reorganization, and signals through FOXM1 and other redox-responsive factors to support a hyper-proliferative state. Over-expression of PRX3 in cancer cells has been shown to counteract oncogene-induced senescence and support tumor cell growth and survival making PRX3 a credible therapeutic target. Using malignant mesothelioma (MM) cells stably expressing shRNAs to PRX3 we show that decreased expression of PRX3 alters mitochondrial structure, function and cell cycle kinetics. As compared to control cells, knockdown of PRX3 expression increased mitochondrial membrane potential, basal ATP production, oxygen consumption and extracellular acidification rates. shPRX3 MM cells failed to progress through the cell cycle compared to wild type controls, with increased numbers of cells in G2/M phase. Diminished PRX3 expression also induced mitochondrial hyperfusion similar to the DRP1 inhibitor mdivi-1. Cell cycle progression and changes in mitochondrial networking were rescued by transient expression of either catalase or mitochondrial-targeted catalase, indicating high levels of hydrogen peroxide contribute to perturbations in mitochondrial structure and function in shPRX3 MM cells. Our results indicate that PRX3 levels establish a redox set point that permits MM cells to thrive in response to increased levels of mROS, and that perturbing the redox status governed by PRX3 impairs proliferation by altering cell cycle-dependent dynamics between mitochondrial networking and energy metabolism.

Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

In plain English

This laboratory study used human malignant mesothelioma cells grown in culture. It did not study asbestos or patients. The authors lowered the cells' levels of peroxiredoxin 3 (PRX3), a mitochondrial enzyme that breaks down hydrogen peroxide, and compared these cells with control mesothelioma cells. In the PRX3-reduced cells, the PRX3 signal was about 6-fold lower and staining for mitochondrial oxidants rose 30%. These cells had higher ATP levels, mitochondrial membrane potential, oxygen consumption and extracellular acidification rates. Their mitochondria formed longer, more branched networks, as also seen in control cells given the fission inhibitor mdivi-1, and more of them were in the G2/M phase of the cell cycle. Transfecting the PRX3-reduced cells with expression vectors so that they produced catalase or mitochondria-targeted catalase lowered oxidants to levels comparable to control cells, made the networks more fragmented again and reversed the G2/M block. The authors concluded that their data support the hypothesis that PRX3 establishes a redox set point required for proper mitochondrial structure and cell cycle progression. They noted they could not directly measure the change in mitochondrial metabolism.

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 (cell culture) experiment comparing mesothelioma cells with reduced PRX3 against control cells
• Who was studied: Human malignant mesothelioma cells (HM) grown in culture, with stable PRX3-knockdown (HMshPRX3) and control lines. No patients or workers were studied, and the article does not describe the cells' origin beyond a citation.
• Exposure: No asbestos or fiber exposure was studied. The experimental manipulation was reduction of PRX3 by short hairpin RNA. Some cells were also treated with the DRP1 inhibitor mdivi-1, or were transiently transfected with expression vectors so that they produced catalase or mitochondria-targeted catalase.
• Main results:
  • In HMshPRX3 cells, the anti-PRX3 fluorescence signal was approximately 6-fold lower than in HM control cells.
  • HMshPRX3 cells showed a 30% increase in MitoSOX Red fluorescence, a marker of mitochondrial oxidants, compared with HM cells.
  • HMshPRX3 cells had increased mitochondrial membrane potential and significantly higher ATP levels than HM cells.
  • Basal oxygen consumption rates and extracellular acidification rates were higher in HMshPRX3 cells than in HM cells.
  • HMshPRX3 cells had significantly longer and more branched mitochondrial networks. This was reproduced in HM cells treated with mdivi-1.
  • HMshPRX3 cells showed decreased phosphorylation of DRP1 at serine 616.
  • HMshPRX3 cells had significantly more cells in the G2/M phase of the cell cycle than HM cells.
  • When HMshPRX3 cells were made to express catalase or mitochondria-targeted catalase, mitochondrial oxidants fell to levels comparable to HM cells.
  • HMshPRX3 cells expressing catalase or mitochondria-targeted catalase had a more fragmented mitochondrial network than HMshPRX3 cells given a control vector.
  • Expression of catalase or mitochondria-targeted catalase reversed the G2/M cell cycle block in HMshPRX3 cells.
• The authors' conclusion: The authors concluded that their data support the hypothesis that PRX3 establishes a redox set point required for proper mitochondrial structure and cell cycle progression in these cells.
• Limitations the authors state:
  • The authors could not directly measure the suggested increase in mitochondrial metabolism, because HMshPRX3 cells did not respond to electron transport chain inhibitors in the Seahorse assay.
  • The authors did not investigate the activity or oxidation state of the fusion protein MFN2.
  • The authors noted that results on mitochondrial oxidative stress are difficult to compare across cell lines.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma.

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