熊胆粉调节FXR/糖皮质激素水平抗抑郁作用及机制研究

Depression is one of the high-prevalence diseases in modern society. Its pathogenesis is complicated and the treatment strategy is limited due to the limitation of available drugs. Hyperthyroidism of HPA axis induced by excessive glucocorticoids (GC) secreted by adrenal gland is one of the causes. Researches show that adrenal farnesoid X receptor (FXR) can regulate the level of GC. FXR is a bile acid receptor and is also regulated by bile acids (BAs) negative feedback loop. Our previous study found that the bile acid level of FXR knockout mice was robustly elevated and FXR knockout mice showed anti-depressive like behavior. In clinical depression patients, our preliminary experiments displayed that serum tauroursodeoxycholic acid (TUDCA) and taurochenodeoxycholic acid (TCDCA) levels were reduced significantly. Moreover, the serum levels of many taurocholic acids in variety of depression model mice were found to decrease remarkably, which was accompanied with the decrease of FXR expression in adrenal gland. Bear gall powder has been used as traditional Chinese medicine for thousands years. It is rich in variety of bile acids, especially TUDCA and TCDCA. Our preliminary data showed that bear gall powder had the efficacy of antidepression. Based on the aforementioned facts, we hypothesized "bear gall powder exerts antidepressant effect through upregulation bile acids levels, thus negatively regulating FXR expression leading to the decrease of the secretion of GC from adrenal gland". This study intends to elucidate the mechanism from multiple aspects, including animals, tissues, cells and molecular levels, to provide a theory basis for its clinical application in the treatment of depression.

抑郁症为当前社会高发病，发病原因复杂，现有药物治疗效果有限。肾上腺分泌的糖皮质激素（GC）过多造成的HPA轴功能亢进是病机之一。研究表明，肾上腺法尼醇X受体（FXR）可调节GC水平。FXR是一种胆汁酸（BAs）受体，同时也受BAs负反馈调控。我们前期研究发现，FXR基因敲除小鼠不仅多种BAs大幅升高，且出现抗抑郁样作用；我们初步实验发现在抑郁患者中牛磺熊去氧胆酸（TUDCA）和牛磺鹅去氧胆酸（TCDCA）发生显著下调，在多种抑郁小鼠模型中多种牛磺类BAs也出现了显著下调，同时肾上腺FXR表达上升。熊胆粉为传统常用中药，富含多种BAs，尤其是TUDCA和TCDCA，我们发现熊胆粉具有抗抑郁作用。据此，我们提出“熊胆粉通过上调BAs调控FXR表达继而调节GC水平发挥抗抑郁作用”假说。本研究拟在动物、组织、细胞、分子等层面阐明此机制，为其临床应用于抑郁症的治疗提供理论基础。

抑郁症为当前社会高发病，发病原因复杂，现有药物治疗效果有限。肾上腺分泌的糖皮质激素（GC）过多造成的HPA轴功能亢进是病机之一。研究表明，肾上腺法尼醇X受体（FXR）可调节GC水平。FXR是一种胆汁酸（BAs）受体，同时也受BAs负反馈调控。我们前期研究发现，FXR基因敲除小鼠不仅多种BAs大幅升高，且出现抗抑郁样作用；我们初步实验发现在抑郁患者中牛磺熊去氧胆酸（TUDCA）和牛磺鹅去氧胆酸（TCDCA）发生显著下调，在多种抑郁小鼠模型中多种牛磺类BAs也出现了显著下调，同时肾上腺FXR表达上升。熊胆粉为传统常用中药，富含多种BAs，尤其是TUDCA和TCDCA，我们发现熊胆粉具有抗抑郁作用。据此，我们提出“熊胆粉通过上调BAs调控FXR表达继而调节GC水平发挥抗抑郁作用”假说。通过项目的实施，产生的主要结果如下：a.在对抑郁模型年龄的筛选后发现，青年鼠最适合建立抑郁模型，故选取青年鼠进入下一步实验；b.在对三种不同类型的、不同造模时长抑郁小鼠模型筛选后发现，造模五周的慢性应激模型是最接近临床且最稳定的模型；c.发现三种抑郁小鼠模型和临床首发抑郁患者血液样本中BAs均发生了显著性变化，其中熊胆粉的主要成分TUDCA和TCDCA在抑郁临床样本中出现了显著下降；d.熊胆粉具有抗抑郁的作用，可以改善慢性应激小鼠的抑郁样行为学表现以及神经递质的变化，逆转血清中BAs的水平；e.熊胆粉可以调节慢性应激抑郁小鼠血清皮质酮水平，调节肾上腺皮质细胞H295R分泌的皮质醇以及皮质醇合成关键酶3β-羟类固醇脱氢酶2（3β-HSD2）基因表达水平；f.熊胆粉可以调控慢性应激小鼠肾上腺FXR表达水平，在给予毛猴素刺激、过表达FXR和给予FXR激动剂GW4064的H295R中亦发现熊胆粉通过调控FXR继而抑制3β-HSD2降低肾上腺分泌GC的作用机制。. 以上结果阐明了抑郁状态下BAs水平的变化，为调节BAs水平抗抑郁提供了理论依据；为开发以熊胆粉为代表的一类上调BAs调控FXR继而调节GC水平的抗抑郁新药奠定了基础；有望提高复方中药的国际声誉、推动中药研究的现代化发展。