神经肽W（NPW）对家鸡应激轴的抑制效应研究

In vertebrates, corticotropin (ACTH), released by pituitary, is a critical part of stress axis (also called HPA axis) and essential for stress response. In general, biosynthesis and secretion of ACTH is controlled by both hypothalamic stimulatory factor and inhibitory factor (CRIF), but the identity of this CRIF remains an open question at present. Recently, using chicken as model, we found that neuropeptide W (NPW) and its receptor (NPBWR2) expressed abundantly respectively in chicken hypothalamus and pituitary. Meanwhile, NPW was proved to be a potential factor in inhibiting chicken pituitary ACTH release. These preliminary results suggest a possibility that NPW may be a potential CRIF in chickens, which could inhibit stress axis and might be regulated by glucocorticoid (GC) in a feedback manner. To test this hypothesis, using chicken as model, this study aims to examine: 1) the spatio-temporal expression of NPW-NPBWR2 in chicken hypothalamus-pituitary axis; 2) the locations of NPW in chicken hypothalamus and NPBWR2 in chicken pituitary; 3) effects of cNPW in inhibiting pituitary ACTH secretion/synthesis and stress axis; 4) effects of GC in regulating NPW-NPBWR2 expression in chicken hypothalamus-pituitary axis. The results from our study could not only contribute to clarify the regulating mechanism of chicken stress axis, but also lay the theoretical foundation for breeding and improving the production performance in chickens.

促肾上腺皮质激素（ACTH）作为脊椎动物垂体分泌的应激轴中间介质，对机体响应伤害刺激至关重要，其释放/生成受下丘脑分泌的刺激因子和抑制因子（CRIF）调控，但生理性CRIF仍未获鉴定。以家鸡为模型，申请人发现神经肽W（NPW）及其受体（NPBWR2）分别在下丘脑和垂体中高表达，且NPW具有高效抑制ACTH分泌的潜能，提示：NPW可能是家鸡下丘脑分泌的生理性CRIF，可以抑制应激轴活性并受糖皮质激素（GC）反馈调节。为验证该假说，本申请项目拟采用现代生物学手段探究：（1）家鸡下丘脑-垂体轴上NPW-NPBWR2的发育时序表达；（2）NPW在家鸡下丘脑、NPBWR2在家鸡垂体中的定位；（3）NPW对家鸡垂体ACTH分泌/合成及应激轴活性的影响；（4）GC对家鸡下丘脑NPW和垂体NPBWR2的反馈调节效应。本研究不仅有望阐明家鸡应激轴的调控机制，也将为家鸡生产性能的提升和品种选育奠定理论基础。

在脊椎动物中，“下丘脑-垂体-肾上腺”轴上的一系列激素和受体对调控应激反应至关重要，故被称为应激轴。一般而言，应激轴被下丘脑分泌的刺激因子（如CRH）激活，受肾上腺分泌的糖皮质激素（GC）负反馈抑制，进而维持动态平衡。目前，普遍认为下丘脑还可以分泌一种生理性的垂体促肾上腺皮质激素（ACTH）释放抑制因子（CRIF），但该因子为何种物质尚不清楚。在家鸡（c-）中，申请人发现神经肽W（NPW）在下丘脑高表达、其受体（NPBWR2）在垂体中高表达，而NPW还具有高效抑制ACTH分泌的潜能，提示：NPW可能是家鸡下丘脑分泌的生理性CRIF，可以抑制应激轴活性并受GC反馈调节。本研究拟围绕“NPW对家鸡应激轴的抑制效应及其反馈调节”开展研究，采用多种现代生物学手段开展研究，结果显示：（1）NPW-NPBWR2在不同发育阶段家鸡下丘脑-垂体轴中表达的动态变化规律与垂体POMC表达趋势基本维持一致；（2）在家鸡垂体中，NPBWR2和阿黑皮素原（POMC，编码ACTH及其相关肽的基因）均主要表达于头部区域，且NPBWR2大量表达于分泌ACTH的细胞中；（3）在体外培养的家鸡垂体原代细胞中，NPW可以抑制ACTH分泌，且该效应与cAMP/PKA信号通路有关，但未发现其影响ACTH生成的效应；（4）皮下注射实验和原代垂体细胞培养实验均显示糖皮质激素可以反馈调节家鸡下丘脑-垂体轴中的NPW-NPBWR2，使其表达量上调，进而下调应激轴活性。以上研究充分说明NPW极可能是家鸡体内的生理性CRIF，通过激活NPBWR2抑制ACTH分泌，进而减弱应激轴活性，下丘脑-垂体轴上的NPW-NPBWR2也受到GC的反馈调节。以上研究成果为阐明家鸡应激轴的调控机制提供线索，也为家鸡生产性能的提升和品种选育奠定理论基础。