TDK conference 2020

Heat stress is a serious concern in broiler production as global temperatures are increasing as a result of climate change as well as because of increasing production intensity of broilers. Acute heat stress has implications for both animal welfare and production economy. An increase of only a few degrees can lead to acute heat stress in broiler chickens as well as long term production losses. On the level of the organism it can lead to acute cardiac death and increased permeability of the enteric mucosa contributing to increased susceptibility to infection by bacteria inhabiting the gut. Liver, as the key organ of metabolic processes can be also highly affected by elevated environmental temperatures. On cellular level heat causes misfolding of proteins leading to loss of their function. Heat can also provoke increased production of reactive oxygen species and other radicals resulting in oxidative stress.

The aim of the present study was to establish a novel chicken hepatocyte – non-parenchymal cell co-culture model in order to investigate the cellular effects of heat stress on the liver during conditions of mild inflammation.

Hepatocyte – non-parenchymal cell co-cultures as well as hepatocyte monocultures were established from Ross-308 chickens and characterized by classical staining and immunocytochemistry as well as flow cytometry. The cultures were heat treated at 43oC for one and two hours to mimic acute heat stress versus controls maintained at a physiological chicken temperature of 38.5oC. Following the treatment, metabolic activity, extracellular lactate dehydrogenase (LDH) enzyme activity and concentration of H2O2, Heat Shock Protein 70 (HSP70), Interleukin-6 and -8 were measured in the culture medium with various assays.

The results showed significant increases in metabolic activity of both mono and co-cultures compared to controls. Reactive oxygen species production was only significantly increased after one-hour treatments of both cultures and significantly higher in monocultures compared to co-cultures. HSP70 concentration was significantly decreased in both cultures after one hour and values were increased back to baseline after two hours. Both interleukin-6 and -8 were significantly lowered after one hour in both cultures and were returned to the level of the baseline after two hours.

The results show that the establishment of the mentioned novel chicken hepatic co-culture was successful, and the data obtained seems to be in accordance with earlier heat experiments on different animal species, furthermore, suggesting a successful hepatic adaptation to heat stress after longer heat exposure. In future experiments it would be also of high importance to develop the cell culture using more complex, multiple tissue derived models and to carry out different in vivo experiments to see how extrapolable the results are to the level of the living organism.