Effect of Akt activation on apoptosis-related gene expression in the crop tissues of male and female pigeons (Columba livia)

Abstract

The current study investigated whether the expression of apoptosis genes in the pigeon crops was affected by the Akt signaling pathway during crop milk formation. First, 78 pairs of adult White King pigeons were randomly assigned to 7 groups, and the expression of apoptosis-related genes and Akt signaling pathway-related proteins in the crop tissues during different breeding stages were examined. The results showed that the mRNA levels of Bak, caspase-3, caspase-6, and caspase-9 in female crops all increased and reached their highest levels at d 17 of incubation ( I17 ). In male crops, the levels of caspase-3 and caspase-9 gene expression peaked at d 1 of chick rearing ( R1 ). The lowest level of Bcl-2 gene expression in females was observed at I17. The expression ratios of p-Akt (Ser473)/Akt and p-Akt (Thr308)/Akt in male crops decreased to their minimum at R1, while it was observed at d 7 of chick rearing ( R7 ) in females. Second, 36 pairs of adult pigeons were divided into 3 groups and were subjected to SC79 injections with dosages of 0, 0.02, or 0.04 mg/kg bodyweight. The SC79 injections resulted in a considerable decrease in growth performance of pigeon squabs. In male crops, the expression ratios of p-Akt (Ser473)/Akt and p-Akt (Thr308)/Akt were significantly elevated in the 0.02 mg/kg SC79 group, while in female crops, they were higher in the 0.04 mg/kg SC79 group ( P < 0.05). The SC79 injection inhibited the gene expression of Bak in female crops, but enhanced the gene expression of Bcl-2 in both male and female crops. In the 0.04 mg/kg SC79 group, a 50.7 to 75.7% decrease was observed in the expression of caspase-3, caspase-6, and caspase-9 in male and female pigeon crops. Expression of the caspase-8 gene and total Akt protein in pigeon crops was not changed in different breeding stages or after SC79 injection. In conclusion, the expression of genes related to mitochondria-dependent apoptosis can be regulated by the Akt signaling pathway, which may play a potential role in pigeon milk formation.

Lipid accumulation and oxidative stress in the crop tissues of male and female pigeons during incubation and chick-rearing periods

“…The membrane permeability of mitochondria is regulated by Bcl-2 family members, and the activation of initiator caspases and effector caspases is triggered sequentially. Caspase-3 and caspase-9 gene expression levels peaked at d 1 of chick rearing ( Xie et al, 2021 ). The mitochondria-dependent process possibly contributed to the desquamation to form pigeon milk.…”

“…The gene expression levels of various transporters and key synthetases of amino acids and fatty acids were commonly upregulated from the terminal phase of incubation to the early phase of chick rearing ( Xie et al, 2017 , 2020 ). Cell keratinization and mitochondria-dependent apoptosis seem to be indispensable factors that induce the degeneration of crop cells, and these nutritive epithelial cells are finally sloughed off into the cavity to form ‘milk’ ( Gillespie et al, 2013 ; Xie et al, 2021 ).…”

“…Apoptosis through ROS-mediated mitochondrial pathway has been reported in various types of cells ( Rehman et al, 2014 ; Wen et al, 2020 ; Feng et al, 2022 ). Our previous study shows that cell apoptosis may play a potential role in the desquamation of crop epithelial cell ( Xie et al, 2021 ). A cycle of production and turnover of cornified epithelium takes nearly four hours, which ensured the continuous supply of crop milk ( Gillespie et al, 2013 ).…”

Differential expression of glucose metabolism‐related genes and AMP‐activated protein kinases in crop tissue of male and female pigeons (Columba livia domestica) during the incubation and chick‐rearing periods

“…In pigeons, lipids accumulation in crop tissue was enhanced during the process of milk formation. In addition, a previous study showed that the phosphorylation level of protein kinase B (Akt) was inhibited at the peak of lactation (Xie et al, 2021). INSR/PI3K (phosphatidylin‐ositol‐3‐kinase)/Akt is one of the classical pathways in response to insulin.…”

Chemical composition of pigeon crop milk and factors affecting its production: a review

“…Studies have indicated that insulin can bind to insulin receptors, and that phosphorylated insulin receptor substrate 1 ( IRS1 ) regulates protein synthesis in skeletal muscle satellite cells and in the breast tissue of dairy cows by activating signaling pathways such as protein kinase B-target of rapamycin complex 1 ( Akt-TORC1 ; Bolster et al, 2004 ; Yang et al, 2015 ; Xie et al, 2021 ; Ye et al, 2022 ). Our previous study showed that the serum prolactin and insulin contents in lactating pigeons were significantly higher than those in nonbreeding pigeons, and the phosphorylated protein levels of IRS1, Akt, TOR, ribosomal protein S6 kinase 1 ( S6K1 ), ribosomal protein S6 ( S6 ), eukaryotic initiation factor 4E binding protein 1 ( 4EBP1 ), and eukaryotic initiation factor 4E ( eIF4E ) were all upregulated during lactation ( Hu et al, 2016 ).…”