A study of the impact of a natural gain-of-function substitution in the porcine glucocorticoid receptor on HPA axis regulation, glucocorticoid receptor signaling, and responsiveness to stress

下丘脑-垂体-肾上腺(HPA)轴通过协调行为、内分泌和免疫反应，在应激适应中起着关键作用。HPA轴对应激反应的有效激活和及时终止，特别是主要效应激素糖皮质激素(GC)的释放，促进了适应性应对，降低了应激的生物成本，有利于动物的健康和生产。在此之前，我们在猪糖皮质激素受体(GRAla61Val)中发现了一个独特的自然功能获得突变Ala610Val。糖皮质激素受体(GR)是一种配体激活的转录因子，是GC生理作用的主要转导因子，在HPA轴的反馈调节中起着核心作用。我们发现GRAla61Val替代显著下调了整个HPA轴的活性。GRAla61Val替换引起的神经内分泌变化如何影响应激恢复能力，从而影响在具有挑战性的条件下的生产和福利相关性状，这一点还有待阐明。特别是，尽管GR信号在病理生理条件下也有很高的相关性，但关于GRAla610Val和GR超敏反应对免疫应激源的反应以及基于GC的药物在这方面的疗效的信息尚不清楚。因此，在拟议的项目中，我们旨在探索GRAla610Val对作为急性细菌感染和炎症模型的内毒素(LPS)攻击的免疫、神经内分泌、行为和代谢反应的时间动态的影响。此外，我们的目标是利用这一免疫挑战，在体内检测GRAla610Val诱导的GR超敏反应是否导致携带者对外源性糖皮质激素的敏感性增加。最后，为了更好地了解观察到的GRAla610Val的表型结果，并获得对HPA轴调节和GR信号通路的新见解，将通过整体转录组分析来探索GRAla610Val在HPA轴的中央分支和相关的糖皮质激素靶标组织(外周血单核细胞，肝脏)中引起的基因表达变化。除了扩大目前对猪HPA轴生物学和GR超敏反应的现有知识外，该项目的结果将对猪的育种具有直接意义，从而提高猪的韧性，也将对基于GC的炎症性疾病治疗的改进具有直接意义。

The hypothalamus-pituitary-adrenal (HPA) axis plays a pivotal role in the adaptation to stress, by coordinating the behavioral, endocrine, and immune responses. Efficient activation and timely termination of HPA axis response to stress, particularly release of the main effector hormones glucocorticoids (GC), promotes adaptive coping, and reduces the biological costs of stress which is beneficial for animal health and performance.Previously, we identified a unique, natural gain-of-function mutation Ala610Val in the porcine glucocorticoid receptor (GRAla61Val). Glucocorticoid receptor (GR), a ligand activated transcription factor, is the main transducer of physiological action of GC, and plays a central role in feedback regulation of the HPA axis. We discovered that the GRAla61Val substitution significantly downregulates activity of the entire HPA axis. It remains to be elucidated, how the neuroendocrine changes caused by the GRAla61Val substitution influence stress resilience and consequently production- and welfare-related traits under challenging conditions. In particular, in spite of the high relevance of GR signaling also in pathophysiological conditions, there is no information on the impact of GRAla610Val, and of GR hypersensitivity in general, on responses to immunological stressors, and on therapeutic efficacy of GC-based drugs in this context. Therefore, in the proposed project we aim to explore the impact of GRAla610Val on the temporal dynamics of the immune, neuroendocrine, behavioral and metabolic responses to endotoxin (LPS) challenge serving as a model of acute bacterial infection and inflammation. Furthermore, we aim to exploit this immune challenge to examine, whether GR hypersensitivity induced by GRAla610Val leads to higher sensitivity of the carriers to exogenous glucocorticoids in vivo. Finally, to better understand the observed phenotypic consequences of GRAla610Val and to gain novel insights into HPA axis regulation and GR signaling pathway, gene expression changes caused by GRAla610Val in the central branch of the HPA axis and in relevant glucocorticoid-target tissues (peripheral blood mononuclear cells, liver) will be explored by holistic transcriptome analyses.Besides expanding the current knowledge on HPA axis biology in pigs and on GR hypersensitivity in general, the project results will have direct implications for pig breeding towards higher resilience and also for the improvement of GC-based therapy of inflammatory diseases.