Protection against acetaminophen-induced liver injury by allopurinol is dependent on aldehyde oxidase-mediated liver preconditioning

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 18 h or 1 h prior to an APAP overdose. Administration of allopurinol 18 h prior to APAP overdose resulted in an 88% reduction in liver injury (serum ALT) 6 h after APAP; however, 1 h 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 (2 h) however late JNK activation (6 h) 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) 18 h or 1 h 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 18 h 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.     

Lithocholic acid feeding results in direct hepato-toxicity independent of neutrophil function in mice

Lithocholic acid (LCA) supplementation in the diet results in intrahepatic cholestasis and bile infarcts. Previously we showed that an innate immune response is critical for cholestatic liver injury in the bile duct ligated mice. Thus, the purpose of this study was to investigate the role of neutrophils in the mechanism of liver injury caused by feeding mice a diet containing LCA. C57BL/6 mice were given control or 1% LCA containing diet for 24–96 h and then examined for parameters of hepatotoxicity. Plasma ALT levels were significantly increased by 48 h after LCA feeding, which correlated with both neutrophil recruitment to the liver and upregulation of numerous pro-inflammatory genes. The injury was confirmed by histology. Deficiency in intercellular adhesion molecule-1 (ICAM-1) expression or inhibition of neutrophil function failed to protect against the injury. Bile acid levels were quantified in plasma and bile of LCA-fed mice after 48 and 96 h. Only the observed biliary levels of taurochenodeoxycholic acid and potentially tauro-LCA caused direct cytotoxicity in mouse hepatocytes. These data support the conclusion that neutrophil recruitment occurs after the onset of bile acid-induced necrosis in LCA-fed animals, and is not a primary mechanism of cell death when cholestasis occurs through accumulation of hydrophobic bile acids.     

CYP2C19基因多态性与抗结核药物性肝损害的关系研究Δ

目的:探讨肝药酶细胞色素P4502C19(CYP2C19)基因多态性与抗结核药物性肝损害(ATDIH)易感性的关系。方法:采用回顾性病例对照研究方法,采用聚合酶链式反应-限制性片段长度多态性(PCR-RFLP)方法对ATDIH病例组106例与抗结核治疗无肝损害的对照组103例的CYP2C19*2和CYP2C19*3位点进行基因型分型,分析基因多态性与ATDIH的相关性。结果:病例组与对照组CYP2C19*2和CYP2C19*3基因表型频率差异无统计学意义(P>0.05)。根据CYP2C19*2和CYP2C19*3双基因表型的代谢速度分为快代谢型、中间代谢型和慢代谢型。Logistic回归分析表明,慢代谢型患者出现肝损害的危险性是快代谢型的2.657倍(95%CI=1.089⁶.482)。结论:汉族人群CYP2C19*2和CYP2C19*3基因多态性可能与ATDIH的发生有关,慢代谢型患者较快代谢型患者更易出现肝损害。     

抗结核药物性肝炎相关危险因素探讨

目的：探讨抗结核药物性肝炎的相关危险因素。方法回顾分析2011年12月-2012年12月658例（男296例,女362例）结核病患者的临床资料。结果抗结核药物性肝炎发生率24.9%,男性少于女性,HBV感染组高于非HBV感染组;随年龄增长发生率升高;大约90%的患者发生在用药后3个月内。结论年龄、HBV感染是抗结核药物性肝炎的主要危险因素,女性患者及HBV-DNA阳性患者更易出现药物性肝炎,对于此类患者需密切监测肝功能。     

Misoprostol protection against acetaminophen-induced hepatotoxicity in the rat

The hepatoprotective effects of misoprostol on acetaminophen (APAP)-induced toxicity were studied in the rat. Liver injury was evaluated at 36 hr after APAP administration by measuring serum ornithine carbamoyltransferase (OCT) and alanine aminotransferase (ALT) levels, by using tetranitroblue tetrazolium (TNBT) staining and by histological analysis. After APAP administration, peak serum levels of the drug were detected at 15 min. Liver GSH was depleted from control levels of 448±48 µg/g to 82±2 µg/g (P<0.01) within 3 hr. Serum ALT levels increased significantly after 16 hr and H&E staining revealed significant hepatic necrosis after 12 hr. Rats treated with misoprostol before and after APAP administration showed reduced OCT and ALT levels at 36 hr of overdose (454±446 IU/liter and 2571±2944 IU/liter, respectively) compared to those without misoprostol treatment (1348±480 IU/liter and 6077±3025 IU/liter, respectively,P<0.01). TNBT staining showed a reduced area of damage from 28.6±22.3% to 7.3±8.9% (P<0.01), and H&E staining also showed less extensive hepatic necrosis in rats treated with misoprostol before and after the overdose. In a time sequence study, misoprostol treatment starting within 10 hr of overdose showed the same protective effect as when it was given before and after APAP ingestion. No protection was detected when the treatment was started during the development of hepatic injury. However, misoprostol given when injury was established seemed to be protective. Our results show that misoprostol protects the liver against APAP-induced injury if given within 10 hr of overdose. Late administration of misoprostol may also be beneficial and thus may be considered in treating patients with APAP toxicity.This study is supported by the Australian National Health and Medical Research Council Grant 91/0662.     

Hepatoprotective Properties of Aqueous Leaf Extract of Persea Americana,Mill (Lauraceae) ‘Avocado’ Against CCL4-Induced Damage in Rats

Background

Natural products from plants have received considerable attention in recent years due to their diverse pharmacological properties, including antioxidants and hepatoprotective activities. The protective effects of aqueous extract of Persea americana (AEPA) against carbon tetrachloride (CCl₄)-induced hepatotoxicity in male albino rats was investigated.

Materials and Methods

Liver damage was induced in rats by administering a 1:1 (v/v) mixture of CCl₄ and olive oil [3 ml/kg, subcutaneously (sc)] after pre-treatment for 7 days with AEPA. Hepatoprotective effects of AEPA was evaluated by estimating the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and levels of total bilirubin (TBL). The effects of AEPA on biomarkers of oxidative damage (lipid peroxidation) and antioxidant enzymes namely, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S-transferase (GST) were measured in liver post mitochondrial fraction.

Results

AEPA and Reducdyn® showed significant (p<0.05) hepatoprotective activity by decreasing the activities of ALT, AST, ALP and reducing the levels of TBL. The activities of antioxidant enzymes, levels of malondialdehyde and protein carbonyls were also decreased dose-dependently in the AEPA-treated rats. Pre-treatment with AEPA also decreased the serum levels of glutathione significantly.

Conclusion

These data revealed that AEPA possesses significant hepatoprotective effects against CCl₄-induced toxicity attributable to its constituent phytochemicals. The mechanism of hepatoprotection seems to be through modulation of antioxidant enzyme system.