Cover Cathleen, Fickert Peter, Knight Tamara R, Fuchsbichler Andrea, Farhood Anwar, Trauner Michael, Jaeschke Hartmut
Liver Research Institute, University of Arizona, Tucson, Arizona 85737, USA.
Toxicol Sci. 2005 Mar;84(1):201-8. doi: 10.1093/toxsci/kfi065. Epub 2004 Dec 15.
DNA fragmentation in hepatocytes occurs early after acetaminophen (AAP) overdose in mice. DNA strandbreaks can induce excessive activation of poly(ADP-ribose) polymerases (PARP), which may lead to oncotic necrosis. Based on controversial findings with chemical PARP inhibitors, the role of PARP-1 activation in AAP hepatotoxicity remains unclear. To investigate PARP-1 activation and evaluate a pathophysiological role of PARP-1, we used both PARP inhibitors (3-aminobenzamide; 5-aminoisoquinolinone) and PARP gene knockout mice (PARP-/-). Treatment of C3Heb/FeJ mice with 300 mg/kg AAP resulted in DNA fragmentation and alanine aminotransferase (ALT) release as early as 3 h, with further increase of these parameters up to 12 h. Few nuclei of hepatocytes stained positive for poly-ADP-ribosylated nuclear proteins (PAR) as indicator for PARP-1 activation at 4.5 h. However, the number of PAR-positive cells and staining intensity increased substantially at 6 and 12 h. Pretreatment with 500 mg/kg 3-aminobenzamide before AAP attenuated hepatic glutathione depletion and completely eliminated DNA fragmentation and liver injury. Delayed treatment several hours after AAP was still partially protective. On the other hand, liver injury was not attenuated in PARP-/- mice compared to wild-type animals. Similarly, the specific PARP-1 inhibitor 5-aminoisoquinolinone (5 mg/kg) was not protective. However, 3-aminobenzamide attenuated liver injury in WT and PARP-/- mice. In summary, PARP-1 activation is a consequence of DNA fragmentation after AAP overdose. However, PARP-1 activation is not a relevant event for AAP-induced oncotic necrosis. The protection of 3-aminobenzamide against AAP-induced liver injury was due to reduced metabolic activation and potentially its antioxidant effect but independent of PARP-1 inhibition.
对乙酰氨基酚（AAP）过量摄入后，小鼠肝细胞中的DNA片段化会在早期发生。DNA链断裂可诱导聚（ADP - 核糖）聚合酶（PARP）过度激活，这可能导致细胞肿胀性坏死。基于化学PARP抑制剂存在争议的研究结果，PARP - 1激活在AAP肝毒性中的作用仍不清楚。为了研究PARP - 1激活并评估PARP - 1的病理生理作用，我们使用了PARP抑制剂（3 - 氨基苯甲酰胺；5 - 氨基异喹啉酮）和PARP基因敲除小鼠（PARP - / -）。用300 mg/kg AAP处理C3Heb/FeJ小鼠，早在3小时就导致DNA片段化和丙氨酸转氨酶（ALT）释放，这些参数在12小时内进一步增加。在4.5小时时，很少有肝细胞核对聚 - ADP - 核糖基化核蛋白（PAR）染色呈阳性，作为PARP - 1激活的指标。然而，PAR阳性细胞数量和染色强度在6小时和12小时时大幅增加。在AAP给药前用500 mg/kg 3 - 氨基苯甲酰胺预处理可减轻肝脏谷胱甘肽耗竭，并完全消除DNA片段化和肝损伤。在AAP给药数小时后延迟治疗仍具有部分保护作用。另一方面，与野生型动物相比，PARP - / -小鼠的肝损伤并未减轻。同样，特异性PARP - 1抑制剂5 - 氨基异喹啉酮（5 mg/kg）也没有保护作用。然而，3 - 氨基苯甲酰胺减轻了野生型和PARP - / -小鼠的肝损伤。总之，PARP - 1激活是AAP过量摄入后DNA片段化的结果。然而，PARP - 1激活与AAP诱导的细胞肿胀性坏死无关。3 - 氨基苯甲酰胺对AAP诱导的肝损伤的保护作用是由于代谢激活减少和潜在的抗氧化作用，但与PARP - 1抑制无关。
