维生素D/VDR通过调控胆管上皮细胞凋亡参与PBC胆管损伤和自身免疫应答的作用及机制研究

Biliary epithelial cells (BECs) are the central of development and progression of primary biliary cholangitis (PBC). The apoptosis of BECs directly induce ductopenic and may subsequently promote autoimmune response. Vitamin D receptor (VDR) is a potential nuclear receptor target of PBC. It is mainly expressed in non-parenchymal cells such as biliary epithelial cells in the liver, and may be involved in the regulation of pathological and physiological processes related to biliary epithelial cells, that is warranted to investigate in further researches. We found that the incidence of PBC is closely related to vitamin D. Patients with vitamin D deficiency had more severe bile duct destruction, and were more frequently failure to achieve response to UDCA, and subsequently had a worse long-term prognosis. Mice feed with vitamin D-free diet developed more severe cholestasis after bile duct ligation. Knockdown of VDR in biliary epithelial cells in vitro could aggravate apoptosis caused by toxic bile acids. Based on the results, our hypothesis is that vitamin D/VDR is involved in the development and progression of PBC, and its regulation of apoptosis of biliary epithelial cells plays an important role. Based on clinical specimens, animal models, and in vitro functional experiments, we will investigate the influences and mechanisms of vitamin D-VDR signal in the regulation BECs apoptosis, and the subsequent effects on bile duct injury and autoimmune response in PBC. This study will provide theoretical and experimental evidences for new therapies development in PBC.

胆管上皮细胞是PBC发生发展的中心，其凋亡破坏直接导致胆管进行性消失，并可促进自身免疫应答。维生素D受体VDR是PBC潜在的核受体靶点，在肝脏主要表达于胆管上皮细胞等非实质细胞，可能在胆管上皮细胞相关病理生理过程中发挥重要作用。我们发现PBC的发病与维生素D联系紧密；伴维生素D缺乏的患者胆管破坏更严重，且UDCA应答率更低、远期预后较差；无维生素D饮食小鼠胆管结扎后，胆汁淤积表现更重；体外敲除胆管上皮细胞中的VDR，可加重胆汁酸导致的细胞凋亡，而维生素D干预有抑制作用。我们推测：维生素D/VDR参与了PBC的发生、发展，其对胆管上皮细胞凋亡的调控在其中发挥重要作用，而维生素干预可抑制这一过程。本课题拟以胆管上皮细胞凋亡为切入点，从临床标本、动物模型、体外功能等多层面，深入探讨维生素D调控胆管上皮细胞凋亡参与PBC自身免疫应答和胆管炎症的作用及机制，为新治疗策略提供理论依据和试验基础。

PBC患者常伴脂溶性维生素D缺乏症，既往研究主要关注其与肝性骨病的联系，近年研究提示维生素D-VDR在胆汁酸代谢和炎症免疫等过程中可能发挥重要作用，本课题旨在通过临床队列、患者组织样本和维生素相关干预的体内外实验，探索维生素D缺乏这一PBC中常见脂溶性维生素缺乏症对疾病发生、发展的影响及可能机制。我们发现：（1）维生素D/VDR作为重要的遗传和环境因素与PBC的发病风险存在紧密联系，VDR限制性内切酶Taq I (rs731236)的基因多态性、户外活动时间相关的维生素D缺乏是PBC发病的危险因素；（2）血清维生素D水平与PBC的胆管损伤程度密切相关，补充后的血清维生素D水平早期变化与VDR基因多态性可联合用于预测PBC患者UDCA治疗应答，基于治疗后1月生化指标改变可作为UDCA的早期生化应答标准，其对2年和5年内的无事件生存预测优于既往标准；（3）维生素D缺乏饮食可加重PBC模型鼠(dnTGFβRⅡ)胆管损伤和汇管区淋巴细胞浸润，肝脏Th1、Th17等炎性细胞显著增多；（4）敲减胆管上皮细胞中的VDR可促进GCDC诱导的细胞凋亡，而外源性加入活性维生素D抑制毒性胆汁酸导致的细胞凋亡；（5）PBC中1型固有淋巴细胞（ILC1）比例下降，且与维生素D缺乏和UDCA治疗存在显著相关。本课题为以维生素D/VDR作为PBC新的干预策略提供试验依据，课题支持下发表SCI论文4篇，均行课题编号标注，参与培养博士研究生1名，硕士研究生2名，副主编专著2部，并参与编写PBC、PSC等相关临床诊疗指南2部，作为主要完成人获陕西省科学技术进步奖一等奖1项。