Cui Yue J, Aleksunes Lauren M, Tanaka Yuji, Goedken Michael J, Klaassen Curtis D
Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Toxicol Sci. 2009 Jul;110(1):47-60. doi: 10.1093/toxsci/kfp094. Epub 2009 Apr 30.
Alpha-naphthyl isothiocyanate (ANIT) is a hepatotoxicant that produces acute intrahepatic cholestasis in rodents. Farnesoid X receptor (FXR) and pregnane X receptor (PXR) are two major bile acid sensors in liver. The purpose of this study was to characterize the regulation of hepatic transporters by FXR and PXR during ANIT-induced liver injury. Wild-type, FXR-null, and PXR-null mice were administered ANIT (75 mg/kg, po) and evaluated 48 h later for hepatotoxicity and messenger RNA (mRNA) expression of basolateral uptake (sodium taurocholate-cotransporting polypeptide, organic anion transporting polypeptide [Oatp] 1a1, Oatp1a4, Oatp1b2) and efflux transporters (organic solute transporter [Ost] alpha, Ostbeta, multidrug resistance-associated protein [Mrp] 3, Mrp4), as well as canalicular transporters (bile salt export pump [Bsep], Mrp2, multidrug resistance protein 2 [Mdr2], ATPase, class I, type 8B, member 1 [Atp8b1]). Livers from wild-type and PXR-null mice had comparable multifocal necrosis 48 h after ANIT. However, ANIT-treated FXR-null mice have fewer and smaller necrotic foci than wild-type mice but had scattered single-cell hepatocyte necrosis throughout the liver. Serum alanine transaminase, alkaline phosphatase (ALP), and direct bilirubin were increased in all genotypes, with higher ALP levels in FXR-null mice. Serum and liver unconjugated bile acids were higher in ANIT-treated FXR-null mice than the other two genotypes. ANIT induced mRNA expression of Mdr2, Bsep, and Atp8b1 in wild-type and PXR-null mice but failed to upregulate these genes in FXR-null mice. mRNA expression of uptake transporters declined in livers of all genotypes following ANIT treatment. ANIT increased Ostbeta and Mrp3 mRNA in livers of wild-type and PXR-null mice but did not alter Ostbeta mRNA in FXR-null mice. In conclusion, FXR deficiency enhances susceptibility of mice to ANIT-induced liver injury, likely a result of impaired induction of hepatobiliary efflux transporters and subsequent hepatic accumulation of unconjugated bile acids.
α-萘基异硫氰酸酯（ANIT）是一种肝毒性物质，可在啮齿动物中引起急性肝内胆汁淤积。法尼酯X受体（FXR）和孕烷X受体（PXR）是肝脏中的两种主要胆汁酸传感器。本研究的目的是表征在ANIT诱导的肝损伤过程中FXR和PXR对肝脏转运蛋白的调节作用。给野生型、FXR基因敲除和PXR基因敲除小鼠口服ANIT（75 mg/kg），48小时后评估肝毒性以及基底外侧摄取转运蛋白（牛磺胆酸钠共转运多肽、有机阴离子转运多肽[Oatp]1a1、Oatp1a4、Oatp1b2）和外排转运蛋白（有机溶质转运蛋白[Ost]α、Ostβ、多药耐药相关蛋白[Mrp]3、Mrp4）以及胆小管转运蛋白（胆盐输出泵[Bsep]、Mrp2、多药耐药蛋白2[Mdr2]、ATP酶，I类，8B型，成员1[Atp8b1]）的信使核糖核酸（mRNA）表达。ANIT处理48小时后，野生型和PXR基因敲除小鼠的肝脏出现类似的多灶性坏死。然而，ANIT处理的FXR基因敲除小鼠的坏死灶比野生型小鼠更少、更小，但在整个肝脏中存在散在的单细胞肝细胞坏死。所有基因型的血清丙氨酸转氨酶、碱性磷酸酶（ALP）和直接胆红素均升高，FXR基因敲除小鼠的ALP水平更高。ANIT处理的FXR基因敲除小鼠的血清和肝脏非结合胆汁酸高于其他两种基因型。ANIT在野生型和PXR基因敲除小鼠中诱导Mdr2、Bsep和Atp8b1的mRNA表达，但在FXR基因敲除小鼠中未能上调这些基因。ANIT处理后，所有基因型小鼠肝脏中摄取转运蛋白的mRNA表达均下降。ANIT增加了野生型和PXR基因敲除小鼠肝脏中Ostβ和Mrp3的mRNA表达，但未改变FXR基因敲除小鼠中Ostβ的mRNA表达。总之，FXR缺乏增强了小鼠对ANIT诱导的肝损伤的易感性，这可能是肝胆外排转运蛋白诱导受损以及随后肝脏中非结合胆汁酸蓄积的结果。
