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TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy

The hypoxic microenvironment which is present following irradiation has been proven to promote radiation-induced injury to normal tissues. Previous studies have demonstrated that telomerase reverse transcriptase (TERT) is regulated by hypoxia, and that it plays a protective role in the process of wo...

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Autores principales: Liu, Qi, Sun, Yong, Lv, Yuefeng, Le, Ziyu, Xin, Yuhu, Zhang, Ping, Liu, Yong
Formato: Online Artículo Texto
Lenguaje:English
Publicado: D.A. Spandidos 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4990283/
https://www.ncbi.nlm.nih.gov/pubmed/27431814
http://dx.doi.org/10.3892/ijmm.2016.2673
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author Liu, Qi
Sun, Yong
Lv, Yuefeng
Le, Ziyu
Xin, Yuhu
Zhang, Ping
Liu, Yong
author_facet Liu, Qi
Sun, Yong
Lv, Yuefeng
Le, Ziyu
Xin, Yuhu
Zhang, Ping
Liu, Yong
author_sort Liu, Qi
collection PubMed
description The hypoxic microenvironment which is present following irradiation has been proven to promote radiation-induced injury to normal tissues. Previous studies have demonstrated that telomerase reverse transcriptase (TERT) is regulated by hypoxia, and that it plays a protective role in the process of wound repair. However, its effects on radiation-induced injury remain unclear. In this study, we examined the effects of human TERT on irradiation-induced late rectal injury in fibroblasts under hypoxic conditions. We also performed in vivo experiments. The rectums of 5-week-old female C57BL/6N mice were irradiated locally with a single dose of 25 Gy. We then examined the fibrotic changes using hematoxylin and eosin staining, and Masson's staining. The expression of hypoxia inducible factor-1α (HIF-1α) and TERT was analyzed by immunohistochemistry. In in vitro experiments, apoptosis, reactive oxygen species (ROS) production and the autophagy level induced by exposure to hypoxia were assayed in fibroblasts. The association between TERT, nuclear factor-κB (NF-κB) and the autophagy level was examined by western blot analysis. The antioxidant effects of TERT were examined on the basis of the ratio of glutathione to glutathione disulfide (GSH/GSSG) and mitochondrial membrane potential. Rectal fibrosis was induced significantly at 12 weeks following irradiation. The HIF-1α and TERT expression levels increased in the fibrotic region. The TERT-overexpressing fibroblasts (transfected with an hTERT-expressing lentiviral vector) exhibited reduced apoptosis, reduced ROS production, a higher autophagy level, a higher GSH/GSSG ratio and stable mitochondrial membrane potential compared with the fibroblasts in which TERT had been silenced by siRNA. NF-κB was activated by TERT, and the inhibition of TERT reduced the autophagy level in the fibroblasts. These results demonstrate that TERT decreases cellular ROS production, while maintaining mitochondrial function and protecting the cells from hypoxia-induced apoptosis, which may thus attenuate the effects of irradiation-induced hypoxia on rectal injury following irradiation.
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spelling pubmed-49902832016-08-26 TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy Liu, Qi Sun, Yong Lv, Yuefeng Le, Ziyu Xin, Yuhu Zhang, Ping Liu, Yong Int J Mol Med Articles The hypoxic microenvironment which is present following irradiation has been proven to promote radiation-induced injury to normal tissues. Previous studies have demonstrated that telomerase reverse transcriptase (TERT) is regulated by hypoxia, and that it plays a protective role in the process of wound repair. However, its effects on radiation-induced injury remain unclear. In this study, we examined the effects of human TERT on irradiation-induced late rectal injury in fibroblasts under hypoxic conditions. We also performed in vivo experiments. The rectums of 5-week-old female C57BL/6N mice were irradiated locally with a single dose of 25 Gy. We then examined the fibrotic changes using hematoxylin and eosin staining, and Masson's staining. The expression of hypoxia inducible factor-1α (HIF-1α) and TERT was analyzed by immunohistochemistry. In in vitro experiments, apoptosis, reactive oxygen species (ROS) production and the autophagy level induced by exposure to hypoxia were assayed in fibroblasts. The association between TERT, nuclear factor-κB (NF-κB) and the autophagy level was examined by western blot analysis. The antioxidant effects of TERT were examined on the basis of the ratio of glutathione to glutathione disulfide (GSH/GSSG) and mitochondrial membrane potential. Rectal fibrosis was induced significantly at 12 weeks following irradiation. The HIF-1α and TERT expression levels increased in the fibrotic region. The TERT-overexpressing fibroblasts (transfected with an hTERT-expressing lentiviral vector) exhibited reduced apoptosis, reduced ROS production, a higher autophagy level, a higher GSH/GSSG ratio and stable mitochondrial membrane potential compared with the fibroblasts in which TERT had been silenced by siRNA. NF-κB was activated by TERT, and the inhibition of TERT reduced the autophagy level in the fibroblasts. These results demonstrate that TERT decreases cellular ROS production, while maintaining mitochondrial function and protecting the cells from hypoxia-induced apoptosis, which may thus attenuate the effects of irradiation-induced hypoxia on rectal injury following irradiation. D.A. Spandidos 2016-09 2016-07-11 /pmc/articles/PMC4990283/ /pubmed/27431814 http://dx.doi.org/10.3892/ijmm.2016.2673 Text en Copyright: © Liu et al. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License (https://creativecommons.org/licenses/by-nc-nd/4.0/) , which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
spellingShingle Articles
Liu, Qi
Sun, Yong
Lv, Yuefeng
Le, Ziyu
Xin, Yuhu
Zhang, Ping
Liu, Yong
TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy
title TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy
title_full TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy
title_fullStr TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy
title_full_unstemmed TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy
title_short TERT alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ROS levels through the activation of NF-κB and autophagy
title_sort tert alleviates irradiation-induced late rectal injury by reducing hypoxia-induced ros levels through the activation of nf-κb and autophagy
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4990283/
https://www.ncbi.nlm.nih.gov/pubmed/27431814
http://dx.doi.org/10.3892/ijmm.2016.2673
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