Abstract
Background: As global temperatures rise, heat stress has become one of the major environmental stressors in the poultry industry. The purpose of the study was to investigate the effects of heat stress on immune function and oxidative stress, and further reveal the possible mechanisms of oxidative stress induced by heat stress for thymus and spleen of broilers. Methods: At the age of 28 days, thirty broilers were randomly divided into the control group (25 ± 2°C; 24 h/day) and the heat stress group (36 ± 2°C; 8 h/day); the experience was lasted for 1 week. At the end of the experience, the broilers per group were respectively euthanized and collected some samples, then to be analyzed. Results: The results showed that the levels of heat shock proteins 70 (HSP70,P＜ 0.01), corticosterone (CORT,P＜ 0.01), the contents of malondialdehyde (MDA, P＜ 0.05), interleukin-6 (IL-6, P＜ 0.01) and tumor necrosis factor-alpha (TNF-α, P＜ 0.01) in serum were significantly higher in heat stress group than that in the control group; The activities of total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and contents of glutathione (GSH) in heat stress group significantly reduced (P＜ 0.05) in serum. Compared with the control group, the birds subjected to heat stress reduced the weight (P＜ 0.01) and the indices of thymus (P＜ 0.01), the activities of T-AOC (P＜ 0.01) and SOD (P＜ 0.05) of spleen, and levels of IL-10 (P＜ 0.05) and the GSH-PX (P＜ 0.05) in thymus and spleen, and increased the IL-6 content of thymus (P＜ 0.05), the MDA content (P＜ 0.01), and the reactive oxygen species (ROS) levels (P＜ 0.01) in thymus and spleen. Moreover, the expression of immunoglobulin G (IgG) gene in thymus and spleen of heat stressed broiler significantly increased by reverse transcription-polymerase chain reaction (RT-PCR) and real time RT-PCR (qRT-PCR; P＜ 0.05); However, the expression of immunoglobulin M (IgM) gene in spleen significantly increased (P＜ 0.05), and had no significant difference (P＞ 0.05) in thymus of heat-stressed broiler. Furthermore, the relative expression of ATP binding cassette subfamily G member 2 (ABCG2) in thymus and spleen (P＜ 0.05), sodium dependent vitamin C transporter-2 (SVCT-2, P＜ 0.01) and mitochondria calcium uniporter (MCU, P＜ 0.01) mRNA in thymus of heat stressed broilers significantly increased; and the expression of ABCG2 (P＜ 0.05), SVCT-2 (P＜ 0.01) and MCU (P＜ 0.01) protein of thymus and spleen in the heat-stressed broiler increased significantly compared with the control group. Conclusions: In summary, the study confirmed that heat stress caused oxidative stress to immune organs of broilers, further reduced immune function. Moreover, the potential mechanisms of heat stress-induced oxidative stress for thymus and spleen was further reveal in broilers.
Hyperthermia Affects Immune and Oxidative Stress Indices of Immune Organs of Broilers by Changing the Expressions of ABCG2, SVCT-2 and MCU