生物钟调控溶质转运体和内外源物处置的作用机制研究

Drug transporters affect the concentration within tissues and removal efficiency of endogenous and exogenous substances, and play an important role in the detoxification of these substances. The rhythmic expression of transporters is the main cause of the diurnal differences in pharmacokinetics and toxicity of many endogenous and exogenous substances. However, as a large family of transporter, the rhythmicity of SLCs and interactions with circadian clock are still unclear. In the previous study, many SLCs were found to be expressed in a circadian manner. Among them, glutamine transporter Slc38a3 and uric acid transporter Slc2a9 showed very significant rhythmicity. In addition, knockout of the clock gene E4bp4 up-regulates the expression of Slc38a3 and Slc2a9, and blunts their rhythmicity. Therefore, it is reasonable to speculate that the circadian clock is very likely to regulate the rhythmic SLCs (e.g., Slc2a9 and Slc38a3) and disposition of their exogenous and exogenous substrates. On the basis of the previous stage, this project will clarify the regulatory mechanism of circadian clock on rhythmic SLCs, and further explore the regulatory effects of circadian clock on chronopharmacokinetics, chronotoxicity and related diseases of SLCs substrates. The implementation of this project will provide a scientific basis for the safe and rational use of drugs (optimization of drugging time) and provide a novel circadian clock-targeting drug target for the treatment of SLCs-related diseases.

药物转运体影响组织中内外源物质的浓度和清除效率，在内外源物解毒中发挥重要作用。转运体的节律是许多内外源物质药代和毒性产生昼夜差异的根源。然而，溶质转运体（SLCs）作为转运体中的大家族，其节律性及其与生物钟的关联目前仍不明确。前期研究发现SLCs家族中许多成员呈节律性表达，其中谷氨酰胺转运体Slc38a3和尿酸转运体Slc2a9的节律性尤为显著。时钟因子E4bp4敲除上调Slc38a3和Slc2a9的表达，并削弱两者节律性。因此，有理由推测生物钟很有可能调控节律SLCs（如Slc38a3和Slc2a9）及其内外源底物的处置。本项目拟在前期基础上，将阐明生物钟对节律SLCs的调控作用机制，并探讨生物钟对节律SLCs底物的时辰药代动力学、时辰毒性和相关疾病的调控效应。此项目的实施将为药物的安全合理使用（用药时间优化）提供科学依据，并为SLCs相关疾病治疗提供生物钟靶向型药物新靶标。

本项目围绕时钟因子E4BP4对药物转运体SLC的调控作用展开详细深入的研究。研究发现，E4BP4可负向调控肝SLC2A9 的表达和转运活性，影响肝脏对SLC2A9内源性底物尿酸的吸收和血液中的尿酸水平。基于野生型小鼠和E4BP4敲除小鼠建立高尿酸血症模型，发现E4BP4敲除小鼠更不容易患高尿酸血症。机制研究表明，E4BP4 通过与SLC2A9 P2 启动子中的 D-box 直接结合来抑制 Slc2a9 的转录和表达。因此，E4BP4可作为 SLC2A9 和尿酸稳态的新型调节剂，本研究有潜力为高尿酸血症相关疾病的治疗提供降尿酸的新方法。研究中还发现节律性核受体PPAR-γ可调节SLC1A5介导的谷氨酰胺/甲硫氨酸转运。根据这些研究成果，共发表了3篇SCI论文，并均已加以标注（含中科院一区论文1篇，二区1篇，三区1篇）。作为编委发表英文专著1部。此项目有助于明确 SLCs 节律性，为相关药物时辰毒性的产生原因指明方向，并为用药时间的优化提供科学指导。生物钟对节律 SLCs 的调控网络及机制解析，使预测相关药物的时辰毒性和高尿酸血症的患病易感性有据可循。