Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
Toxicol Appl Pharmacol. 2014 Feb 1;274(3):417-24. doi: 10.1016/j.taap.2013.12.003. Epub 2013 Dec 15.
Acetaminophen (APAP) overdose causes severe and occasionally fatal liver injury. Numerous drugs that attenuate APAP toxicity have been described. However these compounds frequently protect by cytochrome P450 inhibition, thereby preventing the initiating step of toxicity. We have previously shown that pretreatment with allopurinol can effectively protect against APAP toxicity, but the mechanism remains unclear. In the current study, C3HeB/FeJ mice were administered allopurinol 18h or 1h prior to an APAP overdose. Administration of allopurinol 18h prior to APAP overdose resulted in an 88% reduction in liver injury (serum ALT) 6h after APAP; however, 1h pretreatment offered no protection. APAP-cysteine adducts and glutathione depletion kinetics were similar with or without allopurinol pretreatment. The phosphorylation and mitochondrial translocation of c-jun-N-terminal-kinase (JNK) have been implicated in the progression of APAP toxicity. In our study we showed equivalent early JNK activation (2h) however late JNK activation (6h) was attenuated in allopurinol treated mice, which suggests that later JNK activation is more critical for the toxicity. Additional mice were administered oxypurinol (primary metabolite of allopurinol) 18h or 1h pre-APAP, but neither treatment protected. This finding implicated an aldehyde oxidase (AO)-mediated metabolism of allopurinol, so mice were treated with hydralazine to inhibit AO prior to allopurinol/APAP administration, which eliminated the protective effects of allopurinol. We evaluated potential targets of AO-mediated preconditioning and found increased hepatic metallothionein 18h post-allopurinol. These data show metabolism of allopurinol occurring independent of P450 isoenzymes preconditions the liver and renders the animal less susceptible to an APAP overdose.
对乙酰氨基酚（APAP）过量会导致严重且偶尔致命的肝损伤。已经描述了许多可以减轻 APAP 毒性的药物。然而，这些化合物通常通过细胞色素 P450 抑制来保护，从而阻止毒性的起始步骤。我们之前已经表明，预先用别嘌醇治疗可以有效地预防 APAP 毒性，但其机制尚不清楚。在当前的研究中，C3HeB/FeJ 小鼠在 APAP 过量前 18 小时或 1 小时给予别嘌醇。APAP 过量前 18 小时给予别嘌醇可使 APAP 后 6 小时的肝损伤（血清 ALT）减少 88%；然而，1 小时预处理没有提供保护。有无别嘌醇预处理，APAP-半胱氨酸加合物和谷胱甘肽耗竭动力学均相似。c-jun-N-末端激酶（JNK）的磷酸化和线粒体易位已被牵连到 APAP 毒性的进展中。在我们的研究中，我们显示了早期 JNK 激活（2 小时）的等效性，但是在别嘌醇处理的小鼠中晚期 JNK 激活（6 小时）被减弱，这表明晚期 JNK 激活对毒性更为关键。另外的小鼠给予氧嘌呤醇（别嘌醇的主要代谢物）18 小时或 1 小时前 APAP，但两种治疗均未提供保护。这一发现暗示了别嘌醇的醛氧化酶（AO）介导的代谢，因此在给予别嘌醇/APAP 之前，用肼屈嗪处理小鼠以抑制 AO，从而消除了别嘌醇的保护作用。我们评估了 AO 介导的预处理的潜在靶点，并发现别嘌醇后 18 小时肝内金属硫蛋白增加。这些数据表明，别嘌醇的代谢发生在细胞色素 P450 同工酶之外，使肝脏预先适应，并使动物对 APAP 过量更不易受影响。
