The UDP-Glucuronosyltransferase (UGT) 1A Polymorphism c.2042C>G (rs8330) Is Associated with Increased Human Liver Acetaminophen Glucuronidation, Increased UGT1A Exon 5a/5b Splice Variant mRNA Ratio, and Decreased Risk of Unintentional Acetaminophen-Induced Acute Liver Failure
The UDP-Glucuronosyltransferase (UGT) 1A Polymorphism c.2042C>G (rs8330) Is Associated with Increased Human Liver Acetaminophen Glucuronidation, Increased UGT1A Exon 5a/5b Splice Variant mRNA Ratio, and Decreased Risk of Unintentional Acetaminophen-Induced Acute Liver Failure
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DOI：
10.1124/jpet.112.202010
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发表时间：
2013-05-01
影响因子：
3.5
通讯作者：
Lee, William M.
中科院分区：
文献类型：
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作者：
Court, Michael H.;Freytsis, Marina;Lee, William M.
对乙酰氨基酚主要通过肝脏葡萄糖醛酸化清除。编码对乙酰氨基酚UDP-葡萄糖醛酸转移酶（UGT）的基因多态性可以解释对乙酰氨基酚葡萄糖醛酸化的个体间差异和对乙酰氨基酚过量后肝损伤的可变风险。在本研究中，对人肝库样本进行了对乙酰氨基酚葡萄糖醛酸化活性表型分析和主要对乙酰氨基酚葡萄糖醛酸化酶（UGT 1A 1、1A 6、1A 9和2B 15）基因型分析。其中，只有位于共享UGT 1A-39 UTR区域的三个连锁单核苷酸多态性（SNP）（rs 10929303、rs 1042640、rs 8330）与对乙酰氨基酚葡萄糖醛酸化活性相关，在所有检测的对乙酰氨基酚浓度下，rs 8330始终显示出较高的对乙酰氨基酚葡萄糖醛酸化。使用酶-UGT 1A-3 'UTR报告基因的机制研究表明，这些SNP不会改变mRNA的稳定性或翻译效率。然而，有证据表明，在具有rs 8330变异等位基因的肝脏中，外显子5a与外显子5 b的量存在等位基因失衡，且基因剂量成比例增加，外显子5a与外显子5 b含有UGT 1A mRNA剪接转录物。共转染研究表明，含有外显子5 b的cDNA对含有外显子5a的UGT 1A 1和UGT 1A 6 cDNA的对乙酰氨基酚葡萄糖醛酸化具有抑制作用。计算机模拟分析预测，rs 8330产生了一个外显子剪接增强子位点，在剪接过程中可能有利于外显子5a（超过外显子5 b）的利用。最后，与其他原因引起的急性肝衰竭患者或人种或种族匹配的人群相比，无意中对乙酰氨基酚过量引起的急性肝衰竭患者中rs 8330的患病率显著较低（P = 0.027，卡方检验）。总之，这些发现表明rs 8330是对乙酰氨基酚葡萄糖醛酸化的一个重要决定因素，并可能影响个体对乙酰氨基酚诱导的肝损伤的风险。
Acetaminophen is cleared primarily by hepatic glucuronidation. Polymorphisms in genes encoding the acetaminophen UDP-glucuronosyltransferase (UGT) enzymes could explain interindividual variability in acetaminophen glucuronidation and variable risk for liver injury after acetaminophen overdose. In this study, human liver bank samples were phenotyped for acetaminophen glucuronidation activity and genotyped for the major acetaminophen-glucuronidating enzymes (UGTs 1A1, 1A6, 1A9, and 2B15). Of these, only three linked single nucleotide polymorphisms (SNPs) located in the shared UGT1A-39UTR region (rs10929303, rs1042640, rs8330) were associated with acetaminophen glucuronidation activity, with rs8330 consistently showing higher acetaminophen glucuronidation at all the tested concentrations of acetaminophen. Mechanistic studies using luciferase-UGT1A-3'UTR reporters indicated that these SNPs do not alter mRNA stability or translation efficiency. However, there was evidence for allelic imbalance and a gene-dose proportional increase in the amount of exon 5a versus exon 5b containing UGT1A mRNA spliced transcripts in livers with the rs8330 variant allele. Cotransfection studies demonstrated an inhibitory effect of exon 5b containing cDNAs on acetaminophen glucuronidation by UGT1A1 and UGT1A6 cDNAs containing exon 5a. In silico analysis predicted that rs8330 creates an exon splice enhancer site that could favor exon 5a (over exon 5b) utilization during splicing. Finally, the prevalence of rs8330 was significantly lower (P = 0.027, chi(2) test) in patients who had acute liver failure from unintentional acetaminophen overdose compared with patients with acute liver failure from other causes or a race- or ethnicity-matched population. Together, these findings suggest that rs8330 is an important determinant of acetaminophen glucuronidation and could affect an individual's risk for acetaminophen-induced liver injury.