title: Organic cation transporter 1 mediates the uptake of monocrotaline and plays an important role in its hepatotoxicity.
abstract: Monocrotaline (MCT) is a kind of toxic retronecine-type pyrrolizidine alkaloids (PAs) from plants of Crotalaria, which can be bio-activated by cytochrome P450 (CYP) enzymes in liver and then induce hepatotoxicity. Since CYPs are localized in the endoplasmic reticulum, the influx of MCT to the liver is the key step for its hepatotoxicity. The objective of the present study was to investigate the role of organic cation transporter 1 (OCT1), a transporter mainly expressed in liver, in the uptake of MCT and in hepatotoxicity induced by MCT. The results revealed that MCT markedly inhibited the uptake of 1-methyl-4-phenylpyridinium (MPP(+)), an OCT1 substrate, in Madin-Darby canine kidney (MDCK) cells stably expressing human OCT1 (MDCK-hOCT1) with the IC50 of 5.52±0.56μM. The uptake of MCT was significantly higher in MDCK-hOCT1 cells than in MDCK-mock cells, and MCT uptake in MDCK-hOCT1 cells followed Michaelis-Menten kinetics with the Km and Vmax values of 25.0±6.7μM and 266±64pmol/mg protein/min, respectively. Moreover, the OCT1 inhibitors, such as quinidine, d-tetrahydropalmatine (d-THP), obviously inhibited the uptake of MCT in MDCK-hOCT1 cells and isolated rat primary hepatocytes, and attenuated the viability reduction and LDH release of the primary cultured rat hepatocytes caused by MCT. In conclusion, OCT1 mediates the hepatic uptake of MCT and may play an important role in MCT induced-hepatotoxicity.
authors.affiliation: Department of Pharmaceutical Analysis and Drug Metabolism, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, PR China.
authors.forename: Meijuan
authors.initials: M
authors.lastname: Tu
authors.forename: Siyuan
authors.initials: S
authors.lastname: Sun
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Xueying
authors.initials: X
authors.lastname: Peng
authors.forename: Ruihan
authors.initials: R
authors.lastname: Wang
authors.forename: Liping
authors.initials: L
authors.lastname: Li
authors.forename: Su
authors.initials: S
authors.lastname: Zeng
authors.forename: Hui
authors.initials: H
authors.lastname: Zhou
authors.forename: Huidi
authors.initials: H
authors.lastname: Jiang
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004285:Dogs; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D008297:Male; D016686:Monocrotaline / Q000494:pharmacology*; D027702:Organic Cation Transporter 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D027702:Organic Cation Transporter 1; D016686:Monocrotaline; D007770:L-Lactate Dehydrogenase; D015655:1-Methyl-4-phenylpyridinium
keywords: 1-methyl-4-phenylpyridinium; 2-(N-Morpholino)ethanesulfonic acid; 4-(4-(dimethylamino)styryl)-N-methylpyridinium; ASP(+); CYP; DHM; DMSO; HBSS; Hank's balanced salt solution; Hepatotoxicity; Liver; MCT; MDCK; MES; MPP+; Madin–Darby canine kidney; Monocrotaline; OCT1; PAs; SDS; TEA; Uptake; cytochrome P450; d-THP; d-tetrahydropalmatine; dehydromonocrotaline; dimethyl sulfoxide; monocrotaline; organic cation transporter 1; pyrrolizidine alkaloids; sodium dodecyl sulfonate; tetraethylammonium