Yang Yang, Han Wanwan, Zhang Aijia, Zhao Mindie, Cong Wei, Jia Yimin, Wang Deyun, Zhao Ruqian
MOE Joint International Research Laboratory of Animal Health & Food Safety, Institute of Immunology, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
J Anim Sci Biotechnol. 2022 Mar 8;13(1):29. doi: 10.1186/s40104-022-00677-4.
Corticotropin-releasing hormone (CRH), the major secretagogue of the hypothalamic-pituitary-adrenal (HPA) axis, is intricately intertwined with the clock genes to regulate the circadian rhythm of various body functions. N6-methyladenosine (mA) RNA methylation is involved in the regulation of circadian rhythm, yet it remains unknown whether CRH expression and mA modification oscillate with the clock genes in chicken hypothalamus and how the circadian rhythms change under chronic stress.
Chronic exposure to corticosterone (CORT) eliminated the diurnal patterns of plasma CORT and melatonin levels in the chicken. The circadian rhythms of clock genes in hippocampus, hypothalamus and pituitary are all disturbed to different extent in CORT-treated chickens. The most striking changes occur in hypothalamus in which the diurnal fluctuation of CRH mRNA is flattened, together with mRNA of other feeding-related neuropeptides. Interestingly, hypothalamic mA level oscillates in an opposite pattern to CRH mRNA, with lowest mA level after midnight (ZT18) corresponding to the peak of CRH mRNA before dawn (ZT22). CORT diminished the circadian rhythm of mA methylation with significantly increased level at night. Further site-specific mA analysis on 3'UTR of CRH mRNA indicates that higher mA on 3'UTR of CRH mRNA coincides with lower CRH mRNA at night (ZT18 and ZT22).
Our results indicate that chronic stress disrupts the circadian rhythms of CRH expression in hypothalamus, leading to dysfunction of HPA axis in the chicken. RNA mA modification is involved in the regulation of circadian rhythms in chicken hypothalamus under both basal and chronic stress conditions.
促肾上腺皮质激素释放激素（CRH）是下丘脑-垂体-肾上腺（HPA）轴的主要促分泌素，与生物钟基因紧密相连，以调节身体各种功能的昼夜节律。N6-甲基腺苷（m⁶A）RNA甲基化参与昼夜节律的调节，但CRH表达和m⁶A修饰是否与鸡下丘脑的生物钟基因同步振荡，以及慢性应激下昼夜节律如何变化尚不清楚。
长期暴露于皮质酮（CORT）消除了鸡血浆中CORT和褪黑素水平的昼夜模式。在接受CORT处理的鸡中，海马、下丘脑和垂体中生物钟基因的昼夜节律均受到不同程度的干扰。最显著的变化发生在下丘脑，其中CRH mRNA的昼夜波动变平，其他与进食相关的神经肽的mRNA也如此。有趣的是，下丘脑m⁶A水平与CRH mRNA呈相反的振荡模式，午夜后（ZT18）最低的m⁶A水平对应黎明前（ZT22）CRH mRNA的峰值。CORT减弱了m⁶A甲基化的昼夜节律，夜间水平显著升高。对CRH mRNA的3'UTR进行进一步的位点特异性m⁶A分析表明，夜间（ZT18和ZT22）CRH mRNA的3'UTR上较高的m⁶A与较低的CRH mRNA一致。
我们的结果表明，慢性应激扰乱了下丘脑CRH表达的昼夜节律，导致鸡的HPA轴功能障碍。RNA m⁶A修饰在基础和慢性应激条件下均参与鸡下丘脑昼夜节律的调节。
