条件增敏和敲除糖皮质激素受体活性导致Leydig细胞睾酮降低的机制

Glucocorticoid (GC) has profound effect on male reproductive system. Either GC deficiency (such as Addison's disease or GC resistance due to its receptor GR mutation) or GC excess (such as Cushing's syndrome) causes the disturbance of male reproductive function. However, how GC affects male reproductive function is still unclear. Leydig cell is the major cell type to produce testosterone, which maintains male reproductive function. Many factors regulate Leydig cell development, among which GC may be one of these factors. Excess GC also suppresses testosterone production, and this suppression may be different from its initial stimulation during earlier Leydig cell development. Therefore, we use Cre-loxP system to knockout GR in Leydig cells using Leydig cell specific gene Cyp17a1 promoter. We also found that GR mutation by replacing one base at position 610 to cause the change of methionine to leucine thus activating GR by 10 fold. We then use Cre-loxP system to knockin GR (GR610L) in Leydig cells to increase GR action using Cyp17a1 promoter. Therefore, this application will explore the mechanism of GC at normal or abnormal levels to regulate Leydig cell development, thus providing with the theoretical and clinical bases for GC application and avoiding the side effects of GC in male reproductive system.

糖皮质激素（GC）对于男性生殖内分泌有重要作用。GC平衡的紊乱如GC低下（Addison病）、GC抵抗（糖皮质激素受体GR变异）还是GC过多（Cushing综合征）都会引起男性生殖内分泌障碍。睾丸间质（Leydig）细胞是男性生殖内分泌细胞的重要组成之一，它分泌睾酮而维持男性性功能。许多因子控制Leydig细胞发育，GC可能是其中一种调节因子。根据我们前期的研究结果，我们认为GC促进Leydig干细胞进入Leydig谱系，而过多GC又抑制Leydig细胞分泌睾酮，两者的机制不同，我们应用条件基因打靶技术敲除小鼠Leydig细胞GC受体以及应用基因突变技术增加GC受体的敏感性来研究GC对Leydig细胞分泌睾酮的影响及其机制并验证这一假说。本研究将提供GC对Leydig细胞发育和功能影响的分子机制，为临床诊治GC相关的男性生殖内分泌障碍提供理论基础。

糖皮质激素在许多生理学功能中发挥重要作用，然而过量的糖皮质激素（例如应激条件下）可对机体产生有害作用。在睾丸中，Leydig细胞表达糖皮质激素受体并且糖皮质激素在Leydig细胞系中通过糖皮质激素受体抑制雄激素合成。在药理学上，虽然糖皮质激素抑制了Leydig细胞的功能，但其在Leydig细胞发育过程中的作用尚不明确。在本课题中，我们研究了人工合成的糖皮质激素-地塞米松对大鼠Leydig干细胞增殖和分化的影响。我们从Leydig细胞清除后的大鼠睾丸中获得曲细精管并借助体外曲细精管培养系统，发现地塞米松通过下调类固醇合成酶基因Cyp17a1和Scarb1降低了Leydig干细胞的分化活性，由于拮抗剂RU38486逆转了地塞米松介导的抑制作用，我们推测地塞米松抑制Leydig干细胞分化的作用可能是糖皮质激素受体介导的。此外，我们发现地塞米松对Leydig干细胞的增殖率没有影响。由此我们得出结论：在药理学上，地塞米松会阻滞Leydig干细胞的分化。本研究提供了地塞米松对Leydig 干细胞发育和功能影响的分子机制，为临床诊治糖皮质激素相关的男性生殖内分泌障碍提供理论基础。