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。 高效激活和及时终止HPA轴对应激的反应，特别是释放主要效应激素糖皮质激素（GC），促进适应性应对，并降低应激的生物学成本，这对动物的健康和性能有利。糖皮质激素受体（GR）是一种配体激活的转录因子，是GC生理作用的主要传导体，在HPA轴的反馈调节中起着核心作用。我们发现GRAla 61 Val取代显著下调整个HPA轴的活性。GRAla 61 Val取代引起的神经内分泌变化如何影响应激恢复力，从而影响具有挑战性的条件下的生产和福利相关性状，仍有待阐明。特别地，尽管GR信号传导在病理生理学状况中也具有高度相关性，但是在这种情况下，没有关于GRAla 610 Val和一般GR超敏性对免疫应激物的应答的影响以及对基于GC的药物的治疗功效的信息。因此，在所提出的项目中，我们的目标是探索GRAla 610 Val对作为急性细菌感染和炎症模型的内毒素（LPS）激发的免疫、神经内分泌、行为和代谢反应的时间动力学的影响。此外，我们的目标是利用这种免疫挑战来检查，是否GR超敏反应诱导的GRAla 610 Val导致更高的敏感性的载体外源性糖皮质激素在体内。最后，为了更好地理解所观察到的GRAla 610 Val的表型结果，并获得对HPA轴调节和GR信号通路的新见解，GRAla 610 Val在HPA轴的中央分支和相关糖皮质激素靶组织中引起的基因表达变化（外周血单核细胞，肝脏）将通过整体转录组分析进行探索。除了扩展目前对猪HPA轴生物学和一般GR超敏反应的认识外，该项目的结果将直接影响到猪的育种，使其具有更高的适应能力，并改善基于GC的炎症性疾病治疗。

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.