AMP converted from intracellularly transported adenosine upregulates p53 expression to induce malignant pleural mesothelioma cell apoptosis

Our plain-English summary of AMP converted from intracellularly transported adenosine upregulates p53 expression to induce malignant pleural mesothelioma cell apoptosis, by Y. Nogi, T. Kanno, T. Nakano, et al (Cellular Physiology and Biochemistry, 2012).

The study

• Authors: Y. Nogi, T. Kanno, T. Nakano, Y. Fujita, C. Tabata, K. Fukuoka, A. Gotoh, T. Nishizaki
• Journal: Cellular Physiology and Biochemistry
• Published: 2012;30(1):61-74
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background/aims: The present study investigated adenosine-induced apoptosis in human malignant pleural mesothelioma cells.

Methods: MTT assay, TUNEL staining, flow cytometry using propidium iodide and annexin V-FITC, real-time RT-PCR, Western blotting, and assay of caspase-3, -8, and -9 activities were carried out using malignant pleural mesothelioma cell lines such as NCI-H28, NCI-H2052, NCI-H2452, and MSTO-211H cells, and p53 or A(3) adenosine receptor was knocked-down by transfecting each siRNA into cells.

Results: Adenosine induced apoptosis in all the malignant pleural mesothelioma cells used here, independently of caspase activation. The adenosine effect was prevented by the adenosine transporter inhibitor dipyridamole, the adenosine kinase inhibitor ABT-702, or the A(3) adenosine receptor inhibitor MRS1191. Adenosine upregulated expression of the p53 mRNA and protein, that is abolished by ABT-702, but not by knocking-down A(3) adenosine receptor. Adenosine-induced apoptosis in NCI-H28 cells was significantly inhibited by knocking-down p53 and in part by knocking-down A(3) adenosine receptor.

Conclusion: The results of the present study show that AMP converted from intracellularly transported adenosine upregulates p53 expression to induce caspase-independent apoptosis in malignant pleural mesothelioma cells and that A(3) adenosine receptor also participates partially in the apoptosis by the different mechanism.

Copyright © 2012 S. Karger AG, Basel.

In plain English

This was a laboratory study of four purchased human malignant pleural mesothelioma cell lines (NCI-H28, NCI-H2052, NCI-H2452 and MSTO-211H), not of patients. Asbestos was not studied and appears only in the background. The authors treated the cells with adenosine at 0.01 to 10 mM for 24 to 72 hours. Adenosine reduced cell survival in all four lines, most in NCI-H2452 and least in NCI-H2052. Further tests showed the cells were dying by apoptosis (programmed cell death). The effect was almost reversed by drugs that stop adenosine entering cells (dipyridamole) or turning into AMP (ABT-702). It was significantly reduced by an A3 adenosine receptor blocker (MRS1191). Detailed experiments, mainly in NCI-H28 cells, found that the cell death was largely independent of caspase enzymes. In those cells adenosine raised levels of p53 (a tumor-suppressor protein) and its mRNA, and ABT-702 strongly reduced the rise in p53 mRNA. Silencing p53 reduced the cell death, and silencing the A3 receptor reduced it less. The authors concluded that AMP made from adenosine inside the cells raises p53 to cause apoptosis, with the A3 receptor playing a partial, separate role.

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 experiment on human mesothelioma cell lines grown in culture
• Who was studied: Four human malignant pleural mesothelioma cell lines (NCI-H28, NCI-H2052, NCI-H2452, MSTO-211H) purchased from the American Type Culture Collection. Mechanism experiments were done mainly in NCI-H28 cells. Most experiments were repeated as 4 independent experiments.
• Exposure: Adenosine at 0.01 to 10 mM for 24 to 72 hours, with 3 mM for 24 hours in most experiments. It was tested with and without drugs that block adenosine uptake, adenosine kinase, adenosine receptors, AMPK, adenosine deaminase or caspases. It was also tested with p53, GATA-2 or the A3 receptor silenced by siRNA. No asbestos exposure was studied.
• Main results:
  • Adenosine reduced cell viability in all four cell lines, depending on concentration and treatment time. The strength of the effect ran NCI-H2452 > NCI-H28 > MSTO-211H > NCI-H2052.
  • In all four lines, adenosine (3 mM, 24 h) significantly increased the number of TUNEL-positive (apoptotic) cells compared with before treatment. Flow cytometry also showed more cells in early and late apoptosis.
  • Adenosine-induced apoptosis was almost reversed by the adenosine transporter inhibitor dipyridamole or the adenosine kinase inhibitor ABT-702. It was significantly inhibited by the A3 receptor inhibitor MRS1191. It was not affected by blockers of other adenosine receptors (8-CPT, DMPX, MRS1706), the AMPK inhibitor Compound C, or the adenosine deaminase inhibitor EHNA.
  • In NCI-H28 cells, the pan-caspase inhibitor Z-VAD-fmk did little to stop adenosine-induced cell death, and no apparent activation of caspase-3, -8 or -9 was seen. The authors described the apoptosis as largely caspase-independent.
  • In NCI-H28 cells, adenosine raised AIF and AMID mRNA. It did not change AIF or AMID protein levels or move these proteins into the nucleus.
  • In NCI-H28 cells, adenosine increased p53 mRNA (over 1 to 12 h) and p53 protein (over 1 to 6 h).
  • Silencing p53 significantly prevented adenosine-induced cell death in NCI-H28 cells. It also significantly suppressed the rise in TUNEL-positive cells.
  • In NCI-H28 cells, ABT-702 strongly inhibited the adenosine-induced rise in p53 mRNA. Silencing GATA-2 or the A3 receptor did not affect it.
  • Silencing the A3 adenosine receptor also reduced adenosine-induced cell death and TUNEL-positive cells in NCI-H28 cells, but less than silencing p53 did.
• The authors' conclusion: The authors concluded that adenosine taken into the cells and converted to AMP raises p53 expression, inducing caspase-independent apoptosis in malignant pleural mesothelioma cells. They concluded that the A3 adenosine receptor takes part in the apoptosis as a branch pathway.

Topics

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

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