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Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator

BACKGROUND: Gut ischemia and hypoxia post severe burn leads to breakdown of intestinal epithelial barrier and enteric bacterial translocation (EBT), resulting in serious complications, such as systemic inflammatory response syndrome, sepsis and multiple organ failure. Cystic fibrosis transmembrane c...

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Autores principales: Liu, Xinzhu, Chen, Yu, You, Bo, Peng, Yuan, Chen, Yajie, Yang, Zichen, Zhang, Yixin, Chen, Jing
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7809362/
https://www.ncbi.nlm.nih.gov/pubmed/33501367
http://dx.doi.org/10.1093/burnst/tkaa042
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author Liu, Xinzhu
Chen, Yu
You, Bo
Peng, Yuan
Chen, Yajie
Yang, Zichen
Zhang, Yixin
Chen, Jing
author_facet Liu, Xinzhu
Chen, Yu
You, Bo
Peng, Yuan
Chen, Yajie
Yang, Zichen
Zhang, Yixin
Chen, Jing
author_sort Liu, Xinzhu
collection PubMed
description BACKGROUND: Gut ischemia and hypoxia post severe burn leads to breakdown of intestinal epithelial barrier and enteric bacterial translocation (EBT), resulting in serious complications, such as systemic inflammatory response syndrome, sepsis and multiple organ failure. Cystic fibrosis transmembrane conductance regulator (CFTR) is known to be downregulated by hypoxia and modulate junctional complexes, which are crucial structures maintaining the intestinal barrier. This study aimed to investigate whether CFTR plays a role in both regulating the intestinal barrier and mediating EBT post severe burn, as well as the signaling pathways involved in these processes. METHODS: An in vitro Caco-2 cell model subjected to hypoxic injury and an in vivo mouse model with a 30% total body surface area full-thickness dermal burn were established. DF 508 mice (mice with F508del CFTR gene mutation) were used as an in vivo model to further demonstrate the role of CFTR in maintaining normal intestinal barrier function. QRT-PCR, western blot, ELISA, TER assay and immunofluorescence staining were used to detect the expression and localization of CFTR and tight junction proteins, as well as the function of tight junctions. RESULTS: Our data indicated that, in Caco-2 cells, the hypoxia condition significantly reduced CFTR expression; activated extracellular signal-regulated kinase and nuclear factor-κB signaling; elevated secretion of inflammatory factors (tumor necrosis factor-α, interleukin-1β and interleukin-8); downregulated zonula occludens-1, occludin and E-cadherin expression; decreased transepithelial electrical resistance values; and led to a cellular mislocation of ZO-1. More importantly, knockdown of CFTR caused similar alterations. The upregulation of inflammatory factors and downregulation of tight junction proteins (ZO-1 and occludin) induced by knockdown of CFTR could be reversed by specific extracellular signal-regulated kinase or nuclear factor-κB inhibition. In support of the in vitro data, exuberant secretion of pro-inflammatory mediators and EBT was observed in the intestine of severely burnt mice in vivo. EBT occurred in DF508 mice (mice with the F508del CFTR gene mutation), accompanied by augmented tumor necrosis factor-α, interleukin-1β and interleukin-8 levels in the ileum compared to wildtype mice. In addition, vitamin D3 was shown to protect the intestinal epithelial barrier from hypoxic injury. CONCLUSIONS: Collectively, the present study illustrated that CFTR and downstream signaling were critical in modulating the intestinal epithelial junction and EBT post severe burn.
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spelling pubmed-78093622021-01-25 Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator Liu, Xinzhu Chen, Yu You, Bo Peng, Yuan Chen, Yajie Yang, Zichen Zhang, Yixin Chen, Jing Burns Trauma Research Article BACKGROUND: Gut ischemia and hypoxia post severe burn leads to breakdown of intestinal epithelial barrier and enteric bacterial translocation (EBT), resulting in serious complications, such as systemic inflammatory response syndrome, sepsis and multiple organ failure. Cystic fibrosis transmembrane conductance regulator (CFTR) is known to be downregulated by hypoxia and modulate junctional complexes, which are crucial structures maintaining the intestinal barrier. This study aimed to investigate whether CFTR plays a role in both regulating the intestinal barrier and mediating EBT post severe burn, as well as the signaling pathways involved in these processes. METHODS: An in vitro Caco-2 cell model subjected to hypoxic injury and an in vivo mouse model with a 30% total body surface area full-thickness dermal burn were established. DF 508 mice (mice with F508del CFTR gene mutation) were used as an in vivo model to further demonstrate the role of CFTR in maintaining normal intestinal barrier function. QRT-PCR, western blot, ELISA, TER assay and immunofluorescence staining were used to detect the expression and localization of CFTR and tight junction proteins, as well as the function of tight junctions. RESULTS: Our data indicated that, in Caco-2 cells, the hypoxia condition significantly reduced CFTR expression; activated extracellular signal-regulated kinase and nuclear factor-κB signaling; elevated secretion of inflammatory factors (tumor necrosis factor-α, interleukin-1β and interleukin-8); downregulated zonula occludens-1, occludin and E-cadherin expression; decreased transepithelial electrical resistance values; and led to a cellular mislocation of ZO-1. More importantly, knockdown of CFTR caused similar alterations. The upregulation of inflammatory factors and downregulation of tight junction proteins (ZO-1 and occludin) induced by knockdown of CFTR could be reversed by specific extracellular signal-regulated kinase or nuclear factor-κB inhibition. In support of the in vitro data, exuberant secretion of pro-inflammatory mediators and EBT was observed in the intestine of severely burnt mice in vivo. EBT occurred in DF508 mice (mice with the F508del CFTR gene mutation), accompanied by augmented tumor necrosis factor-α, interleukin-1β and interleukin-8 levels in the ileum compared to wildtype mice. In addition, vitamin D3 was shown to protect the intestinal epithelial barrier from hypoxic injury. CONCLUSIONS: Collectively, the present study illustrated that CFTR and downstream signaling were critical in modulating the intestinal epithelial junction and EBT post severe burn. Oxford University Press 2021-01-15 /pmc/articles/PMC7809362/ /pubmed/33501367 http://dx.doi.org/10.1093/burnst/tkaa042 Text en © The Author(s) 2021. Published by Oxford University Press. https://creativecommons.org/licenses/by/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) ), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Liu, Xinzhu
Chen, Yu
You, Bo
Peng, Yuan
Chen, Yajie
Yang, Zichen
Zhang, Yixin
Chen, Jing
Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
title Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
title_full Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
title_fullStr Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
title_full_unstemmed Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
title_short Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
title_sort molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7809362/
https://www.ncbi.nlm.nih.gov/pubmed/33501367
http://dx.doi.org/10.1093/burnst/tkaa042
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