吡咯里西啶生物碱(PAs)是国际公认的植物性肝毒成分。研究表明：PAs需经肝CYP酶催化生成活性代谢物而致肝毒性。CYP酶存在于肝细胞内，故肝细胞对PAs的摄取及转运对其毒性至关重要，然而该机制尚未阐明。肝细胞基底侧表达OCT1转运体，胆管侧表达MATE1，两者分别介导有机阳离子由血液入肝细胞，及由肝细胞外排至胆汁。我们已发现，OCT1介导肝细胞对PAs代表化合物野百合碱、倒千里光碱的摄取，OCT1抑制剂可显著减少其摄取并减弱其毒性，推测OCT1/MATE1可能介导PAs的肝脏摄取和转运。本项目拟应用稳定表达人OCT1、MATE1及CYP酶的单转、双转及三重转染的转基因细胞模型、人原代肝细胞、基因敲除小鼠，阐明PAs的肝脏摄取和转运机制，揭示OCT1/MATE1在PAs致肝毒中的重要性；为PAs的肝毒防治提供新思路；获得PAs结构-体外肝毒关系，为预测PAs体内肝毒性提供依据。

Pyrrolizidine alkaloids(PAs) are well known hepatic toxin widely distributed in many plant species. It has been demonstrated that the PAs have minimal toxicity in their original form, and will be metabolized by cytochrome CYP in liver (especially by CYP3A4), to form reactive metabolites which react with nucleophiles (such as SH, OH, NH groups on nucleotides, proteins, glutathione) to form adducts, finally lead to the acute and chronic liver diseases. Since CYP located in hepatocyte, the uptake and transport of PAs is one of the key factor on hepatic toxicity, however this mechanism has not been clarified yet. The basolateral localization of organic cation transporter 1(OCT1) and the apical localization of multidrug and toxin extrusion protein 1 (MATE1) will mediate the uptake of organic cation from blood into hepatocyte and excretion to bile, respectively. Our previous results revealed that OCT1 mediated hepatocyte uptake of monocrotaline and retrorsine (typical PAs), the OCT1 inhibitors reduced the uptake of monocrotaline and attenuate the hepatocyte toxicity, which can be deduced that OCT1(MATE1) mediated monocrotaline and retrorsine uptake and transport in liver. The present study will establish and employ a few of cell models stable expression of human OCT1(hOCT1), human MATE1(hMATE1) and human CYP(especially CYP3A4), the primary cultured human hepatocytes, and OCT1 transporter knockout mice, to elucidate the effect of OCT1 and MATE1 in the uptake and extrusion of PAs in liver, to study the effect of OCT1 inhibitors on accumulation of PAs in liver and toxicity induced by PAs, and to explore the structure-toxicity relationship. The results will be helpful for discovering of a new strategy to reduce the liver toxicity caused by PAs and predicting the liver toxicity of PAs in vivo.