CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP) Deficiency Attenuates Heatstroke-Induced Intestinal Injury

Yanfang Pei,Zhengtao Gu,Xiehong Liu,Lei Su,Zhongwei Zhang,Jie Huang,Yu Jiang,Fangfang Yuan,Weiwei Xiao,Xiaotong Han,Maiying Fan,Yan Cao,Fang Chen

doi:10.1007/s10753-021-01577-x

Abstract

The intestine is one of the main target organs involved in the pathological process of heatstroke. CCAAT/enhancer-binding protein homologous protein (CHOP) is involved in endoplasmic reticulum (ER) stress-induced apoptosis. This study aimed to explore the role of CHOP in heatstroke-induced intestinal injury and potential therapy. An in vitro heat stress (HS) model using Caco-2 cells was employed. We observed the role of CHOP in apoptosis-mediated intestinal epithelial cell injury secondary to HS by evaluating cell viability, lactate dehydrogenase release, apoptosis levels, and GRP78, PERK, ATF4, CHOP, Bcl-2, and BAX mRNA and protein expression. To further study the role of CHOP in HS-induced intestinal barrier dysfunction, we assessed transepithelial electrical resistance, paracellular tracer flux, ultrastructure of tight junctions, and protein expression of ZO-1 and occludin. Male wild-type mice and CHOP knockout mice were used for in vivo experiments. We evaluated serum d-lactate and diamine oxidase levels, histopathological changes, intestinal ultrastructure, and ZO-1 and occludin protein expression. HS activated the PERK-CHOP pathway and promoted apoptosis by upregulating BAX and downregulating Bcl-2; these effects were prevented by CHOP silencing. Intestinal epithelial barrier function was disrupted by HS in vitro and in vivo. CHOP silencing prevented intestinal barrier dysfunction in Caco-2 cells, whereas CHOP knockout mice exhibited decreased intestinal mucosal injury. The ER stress inhibitor 4-phenylbutyrate (4-PBA) prevented HS-induced intestinal injury in vitro and in vivo. This study indicated that CHOP deficiency attenuates heatstroke-induced intestinal injury and may contribute to the identification of a novel therapy against heatstroke associated with the ER stress pathway.

Highlights

With global warming, the morbidity and mortality of heatstroke have increased in recent years [1, 2]
Our results indicate that CCAAT/enhancer-binding protein homologous protein (CHOP) mediates intestinal epithelial apoptosis and barrier dysfunction induced by heatstroke. 4-PBA prevents apoptosis and improves the integrity of the intestinal barrier, underscoring its utility as a potential treatment for heatstroke
Apoptosis is a type of programmed cell death that is implicated in intestinal epithelial cell death [22]

Summary

Introduction

The morbidity and mortality of heatstroke have increased in recent years [1, 2]. Heatstroke is characterized by extreme hyperthermia (core temperature ≥ 40 °C), central nervous system dysfunction, and multiple organ failure. The intestine is one of the primary target organs involved in the pathophysiological process of heatstroke. The intestine is considered to be the largest reservoir of bacteria and toxins in the body. 300–500 different types of bacteria are present in the human intestine [3]. Endotoxins and pathogens can enter the circulatory system of the body through an impaired intestinal barrier, inducing endotoxemia and multiple organ dysfunction syndrome (MODS) [4]. The underlying mechanisms of intestinal injury in heatstroke remain poorly understood

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