藏药佐太中硫化汞胃肠形态转化和跨膜吸收关键机制研究

Zuotai (gTso thal) is one of the most precious drugs in traditional Tibetan medicine, which is synthesized from mercury, sulfur, eight metals, eight minerals and other adjuvants by traditional Tibetan physician using mysterious and special processing methods. Meanwhile, Zuotai is also the representative drug of traditional Tibetan medicine containing heavy metals. Although Zuotai compound preparations are wildly used in Tibetan areas, and having no significant adverse effects to patents in long-term clinical practice, the safety of Zuotai is still suspected by modern people because of lacking modern scientific corroborations. Recently, Our group has found that the major component in Zuotai is mercuric sulfide (HgS), and certified that the mercury of Zuotai can be absorbed through gastrointestine by the fact mercury was accumulated in organs after animals were treated with Zuotai. Therefore, it is crucial to reveal the mechanisms on species conversion and transmembrane absorption of mercuric sulfide of Zuotai in gastrointestine for the solution to the heavy metals safety problem of traditional Tibetan medicine. On the basis of our preliminary findings and the lasted research progresses on conversion-absorption mechanisms of cinnabar and inorganic mercury, we will detect the converted species of mercuric sulfide of Zuotai in gastrointestine and blood by modern spectroscopy technology. Then, we plan to screen and verify the roles of amino-acid/peptide transporters, divalent metals transporters, organic anion transporters and multi-drug resistance-associated proteins in the transmembrane absorption of converted species of mercuric sulfide in Zuotai by the molecular biology, bilayer membrane models, cell monolayer models and animals experiments, and reveal the roles of hydrophobic diffusion of plasma membrane and intestinal villous capillary wall holes in the process of transporting converted components of mercury onto blood using bilayer membrane models and cell monolayer models.In conclusion, we will elucidate the mechanism of conversion and absorption of Zuotai in vivo, and provide new research ideas and strategies for solving the safety problem of traditional Tibetan medicine containing heavy metals by this research.

佐太是含重金属藏药的最典型代表，由藏医对水银经特殊炮制而成。含有佐太的藏药复方制剂在临床使用极为普遍，且长期临床实践未见毒性，但缺乏科学确证，其安全性备受现代社会质疑。我们前期研究发现佐太主含硫化汞，口服后可在体内产生汞蓄积。而胃肠转化吸收是口服药物进入机体的关键起始阶段，因而揭示佐太中硫化汞在胃肠中形态转化和跨膜吸收机制是解决藏药重金属安全性问题的重要突破口。基于前期研究基础及朱砂和无机汞转化吸收最新研究进展，我们拟采用现代波谱技术测定佐太中硫化汞在胃肠中的转化形态和入血后的存在状态。从分子、磷脂双层膜、细胞单层和整体动物4个层次上筛选和验证肠上皮细胞中氨基酸/多肽转运载体、二价金属离子转运载体、有机阴离子转运载体、多耐药相关蛋白在佐太中硫化汞转化形态跨膜转运中的作用，探明疏水性质膜扩散和肠绒毛毛细血管壁孔在佐太中汞转运入血中的作用机制，为解决藏药重金属安全性问题提供新的研究思路和策略。

针对佐太中汞在胃肠中如何进行形态转化和吸收的科学问题，本项目采用X射线能谱、X射线荧光、X射线衍射、扫描电镜、原子力显微镜、同步辐射X射线吸收精细结构谱、同步辐射微区X射线荧光等技术，对佐太及其在离体胃肠组织中汞的转化形态和微区吸收分布进行了研究。研究结果发现：1）佐太是一种具有微纳米尺度的传统药物，其微粒多为200～700 nm，最低可达100 nm以下，并常聚集成几～20 μm无定型的松散堆聚态颗粒；2）佐太中主要元素为汞（Hg）和硫（S），以及少量的其他元素；3）佐太含有立方晶系HgS、斜方晶系S8、六方晶系C、立方晶系Cu1.8S、六方晶系Cu6S6、六方晶系Fe1.05S0.95等，其中汞主要是以立方晶系HgS形式存在；4）在胃肠道中，佐太中汞依然主要为立方晶系HgS，仅有少量转化为HgCys2；5）佐太中汞在肠壁组织主要以立方晶系HgS和HgCys2形式存在；6）佐太中汞主要分布在胃黏膜表层，而粘膜下层、肌层、浆膜层的汞信号极低或无信号；7）佐太汞在肠道中主要分布在肠腔、粘膜表层，而粘膜层、粘膜下层等分布极少。本研究建立了包括同步辐射微区X射线荧光分析技术和X射线吸收精细结构谱技术在内的藏药重金属在体转化研究的同步辐射技术，为研究佐太中重金属进入机体后的形态结构与功能关系开启一扇大门。