Effects of Acute Heat Stress on a Newly Established Chicken Hepatocyte-Nonparenchymal Cell Co-Culture Model.

Máté Mackei,Szabolcs Nagy,Gábor Mátis,Péter Gálfi,Ferenc Husvéth,Zsuzsanna Neogrády,Károly Dublecz,Csaba Kővágó,Andor Molnár,László Pál

doi:10.3390/ani10030409

Abstract

Simple SummaryAmong many environmental stress factors, heat stress can intensely deteriorate animal health, welfare, and productivity in poultry farming. In the present study, a novel cell culture comprised of different liver cell types from chickens was established to serve as a model for studying the effects of acute heat stress. Short, 1 h heat exposure strongly affected liver cells by increasing metabolism, triggering oxidative stress, and decreasing the generation of certain mediatory molecules of the cellular stress response. However, these alterations were normalized after 2 h of heat stress, suggesting a fast adaptation of liver cells. The results of this study underline the impact of short-term heat stress as a potential harmful factor affecting liver function in chickens.Heat stress is one of the most important issues in broiler flocks impairing animal health and productivity. On a cellular level, excess heat exposure can trigger heat shock response acting for the restoration of cell homeostasis by several mechanisms, such as affecting heat shock protein synthesis, redox homeostasis and pro-inflammatory cytokine production. The major aim of this study was to establish a novel avian hepatocyte—nonparenchymal cell co-culture as a model for investigating the cellular effects of heat stress and its interaction with inflammation in chicken liver. Cell fractions were isolated by differential centrifugation from a freshly perfused chicken liver, and hepatocyte mono-cultures as well as hepatocyte–nonparenchymal cell co-cultures (with cell ratio 6:1, hepatocytes to nonparenchymal cells, mimicking a milder hepatic inflammation) were prepared. Isolated and cultured cells were characterized by flow cytometry and immunocytochemistry applying hepatocyte- and macrophage-specific antibodies. Confluent cell cultures were exposed to 43 °C temperature for 1 or 2 h, while controls were cultured at 38.5 °C. The metabolic activity, LDH enzyme activity, reactive oxygen species (H2O2) production, extracellular concentration of heat shock protein 70 (HSP70), and that of the pro-inflammatory cytokines interleukin (IL-)6 and IL-8 were assessed. Shorter heat stress applied for 1 h could strongly influence liver cell function by significantly increasing catabolic metabolism and extracellular H2O2 release, and by significantly decreasing HSP70, IL-6, and IL-8 production on both cell culture models. However, all these alterations were restored after 2 h heat exposure, indicating a fast recovery of liver cells. Hepatocyte mono-cultures and hepatocyte—nonparenchymal cell co-cultures responded to heat stress in a similar manner, but the higher metabolic rate of co-cultured cells may have contributed to a better capability of inflamed liver cells for accommodation to stress conditions. In conclusion, the established new primary cell culture models provide suitable tools for studying the hepatic inflammatory and stress response. The results of this study highlight the impact of short-term heat stress on the liver in chickens, underline the mediatory role of oxidative stress in acute stress response, and suggest a fast cellular adaptation potential in liver cells.

Highlights

Environmental stressors have highly relevant negative impacts on the health condition and productivity of the chickens in broiler farming
For the characterization of cell fractions gained by the established method and to study the cellular effect of heat stress, liver cells had to be isolated from the same single chicken in order to ensure the homogeneity of the prepared primary cell cultures
Culture models are indicated with asterisks on the clamps

Summary

Introduction

Environmental stressors have highly relevant negative impacts on the health condition and productivity of the chickens in broiler farming. Heat stress is an important issue in intensive poultry production, with increasing significance due to the climate change. Especially when combined with higher air humidity, can cause suffering and remarkably deteriorates the health, welfare, and growth performance of broilers [1]. A specific stress response pathway, called heat shock response (HSR) is initiated by heat stress acting for the restoration of cell homeostasis by complex alterations of several signaling and metabolic pathways [2]. Heat shock proteins (HSPs) are primarily involved in the successful cellular adaptation to stress conditions, while the synthesis of most other proteins gets discontinued during HSR [3]. HSR is usually linked to enhanced oxidative stress, reflected by elevated levels of pro-oxidants (such as reactive oxygen species, ROS) and inadequate level of antioxidants [1]

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