Aleksunes Lauren M, Scheffer George L, Jakowski Amy B, Pruimboom-Brees Ingrid M, Manautou José E
Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269, USA.
Toxicol Sci. 2006 Feb;89(2):370-9. doi: 10.1093/toxsci/kfi332. Epub 2005 Sep 21.
Following acute chemical injury, hepatocytes are generally more resistant to toxicant re-exposure. Alterations in expression of hepatobiliary transport systems may contribute to this resistance by preventing accumulation of potentially toxic chemicals. Previous data demonstrate the concomitant reduction of uptake transporter and induction of efflux transporter mRNA during chemical liver injury. The present study further characterizes the expression of multidrug resistance-associated proteins 1-4 (Mrp1-4), breast cancer resistance protein (Bcrp) and sodium-taurocholate co-transporting polypeptide (Ntcp) in mouse liver following administration of the hepatotoxicants acetaminophen (APAP) and carbon tetrachloride (CCl4). Mice received hepatotoxic doses of APAP (400 mg/kg), CCl4 (10 or 25 microl/kg), or vehicle, ip. Livers were collected at 6, 24, and 48 h for Western blot quantification and immunofluorescence analysis. Protein expression of Bcrp was unchanged with treatment. Ntcp levels were preserved in APAP-exposed livers and reduced to 30-50% of control after CCl4. Conversely, Mrp1-4 expression was differentially up-regulated. CCl4 increased Mrp1 (3.5-fold), Mrp2 (1.4-fold), and Mrp4 (26-fold) while reducing Mrp3 levels to 20% of control. Administration of APAP enhanced expression of Mrp2 (1.6-fold), Mrp3 (3.5-fold), and Mrp4 (16-fold). Immunostaining of liver sections obtained 48 h after hepatotoxicant treatment confirmed expression patterns of a subset of transporters (Bcrp, Ntcp, Mrp3, and Mrp4). Double immunofluorescence imaging demonstrated the simultaneous down-regulation of Ntcp and up-regulation of Mrp4 in hepatocytes adjacent to the central vein after CCl4. Altered expression of transporters may reduce the overall chemical burden of an injured liver during recovery and contribute to the resistance of hepatocytes to subsequent toxicant exposure.
急性化学损伤后，肝细胞通常对再次接触毒物更具抵抗力。肝胆转运系统表达的改变可能通过阻止潜在有毒化学物质的蓄积而导致这种抵抗力。先前的数据表明，在化学性肝损伤期间，摄取转运体的表达会同时降低，而外排转运体的mRNA会被诱导。本研究进一步表征了在给予肝毒性药物对乙酰氨基酚（APAP）和四氯化碳（CCl4）后，小鼠肝脏中多药耐药相关蛋白1-4（Mrp1-4）、乳腺癌耐药蛋白（Bcrp）和牛磺胆酸钠共转运多肽（Ntcp）的表达。小鼠腹腔注射给予肝毒性剂量的APAP（400 mg/kg）、CCl4（10或25 μl/kg）或赋形剂。在6、24和48小时收集肝脏用于蛋白质印迹定量和免疫荧光分析。Bcrp的蛋白表达在治疗后未发生变化。Ntcp水平在暴露于APAP的肝脏中得以保留，而在CCl4作用后降至对照的30%-50%。相反，Mrp1-4的表达有差异地上调。CCl4使Mrp1增加3.5倍、Mrp2增加1.4倍、Mrp4增加26倍，同时使Mrp3水平降至对照的20%。给予APAP增强了Mrp2（1.6倍）、Mrp3（3.5倍）和Mrp4（16倍）的表达。肝毒性药物治疗48小时后获得的肝脏切片免疫染色证实了一部分转运体（Bcrp、Ntcp、Mrp3和Mrp4）的表达模式。双重免疫荧光成像显示，CCl4作用后，中央静脉附近的肝细胞中Ntcp同时下调，Mrp4上调。转运体表达的改变可能会在恢复过程中减轻受损肝脏的整体化学负担，并有助于肝细胞对后续毒物暴露产生抵抗力。
