褪黑激素介导单色光影响鸡垂体Pit-1活性的作用机制

Our previous study have found that monochromatic green light increases the plasma growth hormone (GH) level, promotes the proliferation of skeletal muscle satellite cells and enhances the productive performance in chicks. However, the mechanism of how the color light information affects the secretion of GH is not clear. The latest study found that Pit-1 is a pituitary specific transcription factor and plays an important role in growth and development via regulating the expression of GH gene in the anterior pituitary. We found in the previous research that melatonin mediates the effect of monochromatic lights on the growth and development in chicks. Therefore, the project will investigate the role and pathways (melatonin – pituitary GH and/or melatonin – hypothalamus – pituitary GH) of melatonin mediates the monochromatic lights affect the expression of Pit-1 in chick pituitary after blocking the secretion of melatonin; and study the membrane receptor pathways and mechanism of intracellular signaling transduction of melatonin mediates the monochromatic lights affect the activity of Pit-1 and regulate the synthesis and release of GH by using RNA interference and inhibitors of intracellular signaling pathways in chick pituitary cells in vitro. The results will be critical for our understanding the regulatory mechanisms of GH synthesis and release from the molecular level, reveal the internal regular pattern between the environmental changes and the functional expression of gene, and to be effective use of color light information to provide a new theoretical guidance in improving the productive performance in poultry.

本课题组前期研究发现单色绿光能显著提高鸡血浆GH水平，促进骨骼肌卫星细胞增殖和提高生产性能，但对于光色信息如何影响GH分泌的作用机制尚不完全清楚。新近在垂体前叶发现的Pit-1是一种具有调控GH基因表达，参与调节机体生长发育的重要转录因子。我们前一课题研究发现褪黑激素介导了单色光对鸡生长发育的影响。本项目拟在此基础上利用松果体和眼球摘除以阻断褪黑激素分泌，研究褪黑激素在单色光影响垂体Pit-1表达的作用和作用途径（褪黑激素-垂体GH 和/或 褪黑激素-下丘脑-垂体GH）；同时利用siRNA及信号分子抑制剂体外研究褪黑激素在单色光影响垂体Pit-1活性进而调控GH合成与释放的膜受体途径和胞内信号转导通路。该研究结果对于从分子水平上认识GH合成与释放的调控网络机制、揭示环境变化与基因功能表达的内在联系具有重要的理论意义，也为合理利用光色信息提高家禽生产性能提供新的理论指导。

本课题组前期研究发现单色绿光能显著提高鸡血浆GH水平，促进骨骼肌卫星细胞增殖和提高生产性能，但对于光色信息如何影响GH分泌的作用机制尚不完全清楚。为此，本项目利用形态学、分子生物学、细胞培养和环境生理学等方法研究了褪黑激素在单色光影响鸡垂体Pit-1活性的作用机制。结果发现，AC/PKA、PLC以及胞内/外Ca2+信号通路均参与调节了褪黑激素膜受体Mel1b和Mel1c介导的单色光影响鸡腺垂体细胞Pit-1表达和GH的合成与分泌，其中，褪黑激素发挥作用的途径包括直接途径（褪黑激素→腺垂体GH）和间接途径（褪黑激素→下丘脑GHRH/SST→垂体GH，和/或 褪黑激素→垂体SST→垂体SSTR2→垂体GH）。该结果阐明了褪黑激素在单色光影响鸡垂体Pit-1表达的作用、作用途径及胞内信号转导机制，揭示了环境变化与基因功能表达的内在联系，为合理利用光色信息提高家禽生产性能提供新的理论指导。