Department of Gastroenterology and Hepatology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Department of Pathology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Mod Pathol. 2019 Jul;32(7):997-1007. doi: 10.1038/s41379-019-0218-8. Epub 2019 Feb 26.
Nonalcoholic fatty liver disease is a major liver disease that leads to cirrhosis and/or hepatocellular carcinoma in a subset of patients. The mechanism underlying disease progression is largely unknown. p53-binding protein 1 (53BP1) is a DNA damage response protein that rapidly localizes at the site of DNA double-strand breaks. In this study, we investigated nuclear 53BP1-positive foci formation as an indicator of DNA double-strand breaks in human nonalcoholic fatty liver disease liver tissues by immunofluorescence microscopy. A total of 52 liver tissue samples, including 43 nonalcoholic fatty liver disease samples and 9 controls, were studied. Our results show that the number of abnormal 53BP1-positive foci in hepatocytes (defined as three or more discrete nuclear foci and/or large foci greater than 1 μM) was significantly increased in nonalcoholic fatty liver disease patients compared to that in controls, both in nonalcoholic fatty liver (p < 0.01) and nonalcoholic steatohepatitis patients (p < 0.01). The number of large foci was significantly increased in the nonalcoholic steatohepatitis cases compared to that in the nonalcoholic fatty liver cases (p < 0.05) and correlated with increased stage of fibrosis. The number of large-foci-expressing hepatocytes was positively correlated with increased age (p < 0.01) and negatively correlated with serum platelet count (p < 0.05). In addition, we performed an in vitro assay using rat hepatocytes treated with the saturated free fatty acid palmitate. Treatment appeared to augment the number of abnormal foci, indicating an induction of double-strand breaks in the hepatocytes through free fatty acid treatment in a caspase-dependent manner. This study demonstrates that 53BP1-positive nuclear foci formation is associated with disease progression in nonalcoholic fatty liver disease patients. Analysis of 53BP1 expression might be a feasible technique to estimate genomic instability in nonalcoholic fatty liver disease.
非酒精性脂肪性肝病是一种主要的肝脏疾病，在一部分患者中可导致肝硬化和/或肝细胞癌。疾病进展的机制在很大程度上尚不清楚。p53 结合蛋白 1（53BP1）是一种 DNA 损伤反应蛋白，可迅速定位于 DNA 双链断裂部位。在这项研究中，我们通过免疫荧光显微镜研究了核 53BP1 阳性焦点形成作为人非酒精性脂肪性肝病肝组织中 DNA 双链断裂的指标。共研究了 52 个肝组织样本，包括 43 个非酒精性脂肪性肝病样本和 9 个对照。我们的结果表明，与对照组相比，非酒精性脂肪性肝病患者的肝细胞中异常 53BP1 阳性焦点（定义为三个或更多离散核焦点和/或大于 1μm 的大焦点）数量显著增加，在非酒精性脂肪性肝病（p<0.01）和非酒精性脂肪性肝炎患者中（p<0.01）。与非酒精性脂肪性肝病病例相比，非酒精性脂肪性肝炎病例中大焦点的数量显著增加（p<0.05），且与纤维化分期增加相关。大焦点表达的肝细胞数量与年龄增加呈正相关（p<0.01），与血清血小板计数呈负相关（p<0.05）。此外，我们使用用饱和游离脂肪酸棕榈酸处理的大鼠肝细胞进行了体外测定。结果表明，处理似乎通过半胱天冬酶依赖性方式增加了异常焦点的数量，表明游离脂肪酸处理诱导了肝细胞中的双链断裂。这项研究表明，53BP1 阳性核焦点形成与非酒精性脂肪性肝病患者的疾病进展相关。53BP1 表达分析可能是一种可行的技术，可用于估计非酒精性脂肪性肝病中的基因组不稳定性。
