mTOR signaling pathway is inhibited downstream of the cyclophilin D-mediated mitochondrial permeability transition in honokiol-triggered regulated necrosis

  • Authors:
    • Wei Tian
    • Jieni Xiong
    • Saisa Zhu
    • Dong Xu
    • Hong Shen
    • Yongchuan Deng
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  • Published online on: February 10, 2016     https://doi.org/10.3892/mmr.2016.4885
  • Pages: 3227-3235
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Abstract

Honokiol (HNK) is a pharmacologically active small molecule that is isolated from the traditional Chinese medicinal herb, houpu. It may induce diversified types of regulated cell death, which are dependent on different cell types and varying concentrations of therapeutic agent. We previously reported that HNK triggers a cyclophilin D (CypD)-mediated regulated necrosis in various cell lines at certain concentrations (two‑fold higher than its half maximal inhibitory concentration). Subsequent study revealed that HNK induced cell death transition from early apoptosis to regulated necrosis in parallel with the increase of HNK dose. In the current study, a lower concentration of HNK (30 µg/ml) than previously reported also induced simplex CypD‑mediated mitochondrial permeability transition (MPT)‑associated regulated necrosis in the HEK‑293 human embryonic kidney cell line. HNK, at concentration of 30 µg/ml, induced necrotic cell death in HEK‑293 cells, which was demonstrated by positive staining for propidium iodide. No DNA ladder patterns or apoptotic bodies were detected in cells that underwent this type of necrotic cell death. Caspase‑8 and ‑3 were not activated during the process of HNK‑induced necrosis. In addition, pan‑caspase inhibitor, z‑VAD‑fmk and receptor‑interacting protein 1 inhibitor, necrostatin‑1 did not inhibit HNK‑induced necrosis. However, CypD inhibitor, cyclosporin A (CsA), blocked HNK‑induced necrosis. These findings indicate that 30 µg/ml HNK induced simplex CypD-mediated MPT‑associated regulated necrosis in HEK‑293 cells. Furthermore, the findings demonstrated that during HNK-triggered regulated necrosis the mammalian target of rapamycin (mTOR) signaling pathway is also inhibited. Pretreatment with CsA, therefore, inhibits HNK‑triggered regulated necrosis and reverses dephosphorylation of Akt, eIF4E‑binding protein 1 and S6 kinase. This indicated that the mTOR signaling pathway is effective downstream of the CypD‑mediated MPT and before the onset of plasma membrane breakdown during the regulated necrosis process. Therefore, it has been demonstrated for the first time, to the best of our knowledge, that the mTOR signaling pathway was inhibited downstream of the CypD-mediated MPT in the process of HNK-induced regulated necrosis.
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April-2016
Volume 13 Issue 4

Print ISSN: 1791-2997
Online ISSN:1791-3004

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Spandidos Publications style
Tian W, Xiong J, Zhu S, Xu D, Shen H and Deng Y: mTOR signaling pathway is inhibited downstream of the cyclophilin D-mediated mitochondrial permeability transition in honokiol-triggered regulated necrosis. Mol Med Rep 13: 3227-3235, 2016
APA
Tian, W., Xiong, J., Zhu, S., Xu, D., Shen, H., & Deng, Y. (2016). mTOR signaling pathway is inhibited downstream of the cyclophilin D-mediated mitochondrial permeability transition in honokiol-triggered regulated necrosis. Molecular Medicine Reports, 13, 3227-3235. https://doi.org/10.3892/mmr.2016.4885
MLA
Tian, W., Xiong, J., Zhu, S., Xu, D., Shen, H., Deng, Y."mTOR signaling pathway is inhibited downstream of the cyclophilin D-mediated mitochondrial permeability transition in honokiol-triggered regulated necrosis". Molecular Medicine Reports 13.4 (2016): 3227-3235.
Chicago
Tian, W., Xiong, J., Zhu, S., Xu, D., Shen, H., Deng, Y."mTOR signaling pathway is inhibited downstream of the cyclophilin D-mediated mitochondrial permeability transition in honokiol-triggered regulated necrosis". Molecular Medicine Reports 13, no. 4 (2016): 3227-3235. https://doi.org/10.3892/mmr.2016.4885