Intermittent and mild cold stimulation enhances immune function of broilers via co-regulation of CIRP and TRPM8 on NF-κB and MAPK signaling pathways

Improving immune function is an important indicator for establishing cold adaptation in broilers. In the study, to explore the effects and molecular mechanisms of intermittent and mild cold stimulation (IMCS) on the immune function of broilers, CIRP and TRPM8, induced by cold stimulation, as well as the NF-κB and MAPK pathways which play an important role in immune response, were selected to investigate. A total of 192 one-day-old broilers (Ross 308) were selected and randomly divided into the control group (CC) and the cold stimulation group (CS). The broilers in CC were raised at normal feeding temperature from day 1 to 43, while the broilers in CS were subjected to cold stimulation from day 15 to 35, with a temperature 3 °C below that of the CC group for 5 h, at one day intervals. The results showed that IMCS had little effect on the broiler hearts, and the myocardial structure was not damaged. On day 22, IMCS significantly increased the mRNA levels of CIRP, TRPM8, P65, P38, COX-2, TNF-α, IFN- γ, IL-6, IL-10, and the protein levels of CIRP, P65, P38, IL-1β and iNOS in the hearts, and the levels of CIRP and all cytokines in the serum (P ≤ 0.05). The mRNA and protein levels of IκB-α were significantly reduced (P ≤ 0.05). On day 36, the mRNA levels of TRPM8, P65, ERK and IL-10 in the hearts and the content of COX-2 in the serum in CS were increased significantly (P ≤ 0.05), while the mRNA levels of IκB-α, P38 and IL-1β were decreased significantly (P ≤ 0.05). On day 43, IMCS significantly upregulated the mRNA levels of TRPM8, IFN- γ, IL-4, IL-6, IL-10, and the protein levels of IκB-α, P38, and the levels of iNOS, TNF-α, IL6 and IL10 in the serum (P ≤ 0.05); whereas it significantly downregulated CIRP, JNK, P38, iNOS, TNF-α mRNA levels, and CIRP, P65, ERK, JNK, IL1β and iNOS protein levels (P ≤ 0.05). Therefore, IMCS can enhance broiler immune function through co-regulation of CIRP and TRPM8 on the NF-κB and MAPK pathways, which facilitate the cold adaptation in broilers.