Roberts R A, Soames A R, James N H, Gill J H, Wheeldon E B
Zeneca Central Toxicology Laboratory, Alderley Park, Macclesfield, United Kingdom.
Toxicol Appl Pharmacol. 1995 Dec;135(2):192-9. doi: 10.1006/taap.1995.1223.
It has been proposed that several nongenotoxic compounds act as hepatocarcinogens by suppressing the apoptosis that would normally act to remove damaged or potentially initiated cells from the liver. During our investigations of this hypothesis using a widely applied protocol, we have found that the stress induced by the process of gavage dosing can induce massive apoptosis in livers uniquely primed by withdrawal of the hepatomitogen cyproterone acetate from the hyperplastic rat liver. This effect of gavage dosing was not seen in livers of naive animals. Apoptosis was measured by both in situ end labeling (ISEL) of the DNA damage associated with programmed cell death and conventional hematoxylin and eosin (H&E) staining of apoptotic morphology. Apoptotic rates measured by H&E increased significantly from 0.005 +/- 0.010% on Day 11 to 0.657 +/- 0.315% of hepatocytes on Day 15, 4 days after cessation of 10 days dosing with CPA (120 mg/kg). The readministration of CPA suppressed > 89% of this Day 15 apoptosis. However, the readministration of vehicle alone (corn oil) caused a 390% increase in apoptosis to 2.56 +/- 1.31% of hepatocytes. Similar results were obtained using ISEL. Measurements of liver to body weight ratios and total DNA per liver reflected these changes in cell loss by apoptosis. In a second experiment, CPA was administered for 10 days as before then animals were subjected to readministration of CPA in corn oil, CPA in saline, corn oil, saline, or sham dosed. Again, apoptosis was dramatically suppressed by the readministration of CPA in either vehicle but was dramatically increased to around 2% of hepatocytes in all other groups, including the sham dosed group. Data on food consumption provided no evidence for a reduction in food intake as a causative agent but rather pointed to a less efficient usage of food in the stressed animals. The ability of stress to induce liver apoptosis should be borne in mind in the design and interpretation of future toxicological studies aimed at understanding the putative suppression of apoptosis by liver nongenotoxic carcinogens and other toxicants.
有人提出，几种非遗传毒性化合物通过抑制细胞凋亡而成为肝癌致癌物，而细胞凋亡通常会清除肝脏中受损或可能已启动的细胞。在我们使用广泛应用的方案对这一假设进行研究的过程中，我们发现，灌胃给药过程所诱导的应激能够在由增生性大鼠肝脏中撤去肝有丝分裂原醋酸环丙孕酮而独特致敏的肝脏中诱导大量细胞凋亡。这种灌胃给药的效应在未接触过实验的动物肝脏中未观察到。通过与程序性细胞死亡相关的DNA损伤的原位末端标记（ISEL）以及凋亡形态的传统苏木精和伊红（H&E）染色来检测细胞凋亡。用H&E检测的凋亡率从第11天的0.005±0.010%显著增加到第15天的0.657±0.315%的肝细胞凋亡率，这是在以120mg/kg的剂量连续给药10天停止4天后。再次给予醋酸环丙孕酮可抑制第15天细胞凋亡的89%以上。然而，仅再次给予赋形剂（玉米油）可使细胞凋亡增加390%，达到肝细胞的2.56±1.31%。使用ISEL也获得了类似的结果。肝脏与体重比以及每肝脏总DNA的测量反映了这些因细胞凋亡导致的细胞损失变化。在第二个实验中，如之前一样给予醋酸环丙孕酮10天，然后对动物再次给予玉米油中的醋酸环丙孕酮、盐水中的醋酸环丙孕酮、玉米油、盐水或假给药。同样，再次给予任何一种赋形剂中的醋酸环丙孕酮都能显著抑制细胞凋亡，但在所有其他组，包括假给药组，细胞凋亡都显著增加至约2%的肝细胞凋亡率。食物消耗数据没有提供证据表明食物摄入量减少是一个致病因素，而是表明应激动物对食物的利用效率较低。在旨在理解肝脏非遗传毒性致癌物和其他毒物对细胞凋亡的假定抑制作用的未来毒理学研究的设计和解释中，应牢记应激诱导肝脏细胞凋亡的能力。
