TDK conference 2017

Heat stress triggered by the elevated environmental temperature is one of the main stress factors in intensive poultry farming, contributing to animal welfare and production issues. Cellular prooxidant (mainly H2O2) production is commonly increased by heat stress, while the enhanced heat shock protein production effectively facilitates the metabolic adaptation to the altered environmental conditions. As the liver plays central role in the heat stress response, in which the specific role of different cell types is not fully elucidated, the main goal of the present study was to investigate the hepatic cellular response to heat stress in broilers.

In vitro experiments were carried out on a hepatocyte – Kupffer cell co-culture of chicken origin. Hepatocytes and Kupffer cells were isolated from the liver of 20-day-old Ross 308 broilers by multi-step perfusion, enzymatic digestion with collagenase and differential centrifugation. To study the specific role of different cell types, hepatocyte mono-cultures and co-cultures with cell ratio of 6:1 (hepatocyte to Kupffer cells) were prepared with freshly isolated cells. After 24 h of culturing, confluent cell cultures were incubated at 44°C for 1 or 2 h, while control cells were cultured at 37°C during the entire trial. Viability of cells was assessed directly following heat exposure and after 20 h recovery time by MTS and CCK-8 assays; the concentration of H2O2 in culture media was measured by the Amplex red method.

Cell viability was significantly decreased by heat stress on both cell culture models directly after heat exposure. A prolonged deterioration in cell viability was observed following 20 h recovery time only in case of cells exposed to heat stress for the longer, 2 h incubation time. In this case, cellular H2O2 production was significantly increased on both cell cultures, but with a remarkably higher extent on co-cultures than on hepatocyte mono-cultures.

It can be concluded based on our results that heat stress can highly diminish viability of liver cells in chicken. The heat stress-evoked elevation in H2O2 production of cultured cells suggests that the hepatic release of prooxidants may play central role in the oxidative stress related to stress response. Further, the key function of Kupffer cells in the stress-induced prooxidant production was also proven in the present study.