PI3K/AKT pathway modulation and cold acclimation alleviation concerning apoptosis and necroptosis in broiler thymus

Moderate cold stimulation regulates the thymus's growth and function and facilitates cold acclimatization in broilers. However, the underlying mechanism remains unknown. To explore the possible mechanism of the thymus in cold-acclimated broilers against cold stress, 240 1-day-old Arbor Acres (AA) broilers were assigned to two groups randomly. The control group (C) was housed at conventional temperatures. The temperature during the first week was 33-34°C. Between the ages of 8 and 32 days, the temperature was lowered by 1°C every two days, i.e., gradually from 32°C to 20°C, and then maintained at 20°C until 42 days of age. The cold-acclimated group (C-3) was housed at the same temperature as C from 1-7 days after birth. Between 8 and 42 days, the temperature of C-3 was 3°C colder than C. After 24 h exposure to acute cold stress (ACS) at 42 days, C and C-3 were named as S and S-3. The results showed that ACS was able to induce oxidation stress, modulate PI3K/AKT signal, and cause necroptosis and apoptosis in broiler thymus. By contrast, cold acclimation could alleviate apoptosis and necroptosis induced by cold stress via alleviating oxidative stress, efficiently activating the PI3K/AKT signal, as well as decreasing apoptotic and necrotic genes’ levels. This study offers a novel theoretical basis for cold acclimation to improve the body's cold tolerance.