Juquan Song1, Jana de Libero2, Steven E Wolf2. 1. Division of Burn/Trauma/Critical Care, Department of Surgery, University of Texas Southwestern Medical Center, Dallas, Texas. Electronic address: juquan.song@utsouthwestern.edu. 2. Division of Burn/Trauma/Critical Care, Department of Surgery, University of Texas Southwestern Medical Center, Dallas, Texas.
Abstract
BACKGROUND: Previous studies showed that liver dysfunction develops soon after severe burn, and this is associated with activation of endoplasmic reticulum (ER) stress. Autophagy is a catabolic process to maintain cellular organelle balance; ER stress is associated with autophagy signaling cascades. We thus sought to determine whether autophagy signals were associated with damage in the liver after burn, and further whether burn-associated ER stress activates autophagy signals in hepatocytes. METHODS: C57BL/6 male mice received a 25% total body surface area full-thickness scald burn, and liver was harvested at 24 h after burn. HepG2 cells were stimulated with an ER stress inducer thapsigargin (TG) for 24 h to mimic ER stress in vitro. Terminal deoxyuridine nick-end labeling staining was performed on histologic sections of liver. Autophagy was assessed by immunoblotting. Statistical analysis was performed using the Student t-test and significance was accepted at P < 0.05. RESULTS: Terminal deoxyuridine nick-end labeling positive-stained hepatocytes increased in burned animals with a significant elevation of caspase 3 activity (P < 0.05). Hepatic autophagy-related (ATG) protein 3, ATG5 and light chain (LC) 3B elevated significantly in burn animals as well (P < 0.05). Expression of Beclin-1, LC3A, and LC3B increased in HepG2 cells in response to TG, similar to the response seen in vivo. Cytosolic adenosine triphosphate dropped significantly, and adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) were phosphorylated as well in response to TG (P < 0.05). CONCLUSIONS: ER stress, which occurs in hepatocytes after severe injury, is associated with autophagy and liver damage after severe burn. In response to ER stress, activated autophagy is associated with adenosine monophosphate-activated protein kinase and mammalian target target of rapamycin pathway.
BACKGROUND: Previous studies showed that liver dysfunction develops soon after severe burn, and this is associated with activation of endoplasmic reticulum (ER) stress. Autophagy is a catabolic process to maintain cellular organelle balance; ER stress is associated with autophagy signaling cascades. We thus sought to determine whether autophagy signals were associated with damage in the liver after burn, and further whether burn-associated ER stress activates autophagy signals in hepatocytes. METHODS: C57BL/6 male mice received a 25% total body surface area full-thickness scald burn, and liver was harvested at 24 h after burn. HepG2 cells were stimulated with an ER stress inducer thapsigargin (TG) for 24 h to mimic ER stress in vitro. Terminal deoxyuridine nick-end labeling staining was performed on histologic sections of liver. Autophagy was assessed by immunoblotting. Statistical analysis was performed using the Student t-test and significance was accepted at P < 0.05. RESULTS: Terminal deoxyuridine nick-end labeling positive-stained hepatocytes increased in burned animals with a significant elevation of caspase 3 activity (P < 0.05). Hepatic autophagy-related (ATG) protein 3, ATG5 and light chain (LC) 3B elevated significantly in burn animals as well (P < 0.05). Expression of Beclin-1, LC3A, and LC3B increased in HepG2 cells in response to TG, similar to the response seen in vivo. Cytosolic adenosine triphosphate dropped significantly, and adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) were phosphorylated as well in response to TG (P < 0.05). CONCLUSIONS: ER stress, which occurs in hepatocytes after severe injury, is associated with autophagy and liver damage after severe burn. In response to ER stress, activated autophagy is associated with adenosine monophosphate-activated protein kinase and mammalian target target of rapamycin pathway.
Authors: Zachary M Earley; Suhail Akhtar; Stefan J Green; Ankur Naqib; Omair Khan; Abigail R Cannon; Adam M Hammer; Niya L Morris; Xiaoling Li; Joshua M Eberhardt; Richard L Gamelli; Richard H Kennedy; Mashkoor A Choudhry Journal: PLoS One Date: 2015-07-08 Impact factor: 3.240