Research Note: Heat stress affects immune and oxidative stress indices of the immune organs of broilers by changing the expressions of adenosine triphosphate-binding cassette subfamily G member 2, sodium-dependent vitamin C transporter-2, and mitochondrial calcium uniporter

This study aimed to determine the mechanisms of heat-induced oxidative stress in the thymus and spleen of broilers. After 28 d, 30 broilers were randomly divided into the control (25°C ± 2°C; 24 h/d) and heat-stressed (36°C ± 2°C; 8 h/d) groups; the experiment lasted for 1 wk. The broilers in each group were euthanized, and some samples were collected and analyzed at 35 d. The results showed that 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 the IgG gene in the thymus and spleen of heat-stressed broilers was increased (P < 0.05); however, the expression of the IgM gene in the spleen was increased (P < 0.05), with no difference (P > 0.05) in the thymus of heat-stressed broilers compared with the control. Furthermore, the relative expression of adenosine triphosphate-binding cassette subfamily G member 2 (ABCG2) in the thymus and spleen both increased (P < 0.05). The sodium-dependent vitamin C transporter-2 (SVCT-2) (P < 0.01) and mitochondrial calcium uniporter (MCU) (P < 0.01) mRNA levels in the thymus of heat-stressed broilers increased, and the expression of ABCG2 (P < 0.05), SVCT-2 (P < 0.01), and MCU (P < 0.01) proteins in the thymus and spleen of heat-stressed broilers increased compared with the control group. This study confirmed that heat stress-induced oxidative stress in the immune organs of broilers, further reducing immune function.