Zhao Q, Guo Z, Deng W, Fu S, Zhang C, Chen M, Ju W, Wang D, He X
Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
Biotherapy Department, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
Cell Death Dis. 2016 Apr 14;7(4):e2186. doi: 10.1038/cddis.2016.66.
Hepatic steatosis is associated with significant morbidity and mortality after liver resection and transplantation. This study focuses on the role of autophagy in regulating sensitivity of fatty livers to ischemia and reperfusion (I/R) injury. Quantitative immunohistochemistry conducted on human liver allograft biopsies showed that, the reduction of autophagy markers LC3 and Beclin-1 at 1 h after reperfusion, was correlated with hepatic steatosis and poor survival of liver transplant recipients. In animal studies, western blotting and confocal imaging analysis associated the increase in sensitivity to I/R injury with low autophagy activity in fatty livers. Screening of autophagy-related proteins showed that Atg3 and Atg7 expression levels were marked decreased, whereas calpain 2 expression was upregulated during I/R in fatty livers. Calpain 2 inhibition or knockdown enhanced autophagy and suppressed cell death. Further point mutation experiments revealed that calpain 2 cleaved Atg3 and Atg7 at Atg3Δ92-97 and Atg7Δ344-349, respectively. In vivo and in vitro overexpression of Atg3 or Atg7 enhanced autophagy and suppressed cell death after I/R in fatty livers. Collectively, calpain 2-mediated degradation of Atg3 and Atg7 in fatty livers increases their sensitivity to I/R injury. Increasing autophagy may ameliorate fatty liver damage and represent a valuable method to expand the liver donor pool.
肝脂肪变性与肝切除和肝移植后的高发病率和死亡率相关。本研究聚焦于自噬在调节脂肪肝对缺血再灌注（I/R）损伤敏感性中的作用。对人肝移植活检组织进行的定量免疫组化显示，再灌注1小时后自噬标志物LC3和Beclin-1的减少与肝脂肪变性及肝移植受者的低生存率相关。在动物研究中，蛋白质免疫印迹法和共聚焦成像分析表明，脂肪肝对I/R损伤的敏感性增加与自噬活性降低有关。自噬相关蛋白筛查显示，脂肪肝在I/R期间Atg3和Atg7表达水平显著降低，而钙蛋白酶2表达上调。抑制或敲低钙蛋白酶2可增强自噬并抑制细胞死亡。进一步的点突变实验表明，钙蛋白酶2分别在Atg3Δ92 - 97和Atg7Δ344 - 349处切割Atg3和Atg7。在体内和体外过表达Atg3或Atg7可增强脂肪肝I/R后的自噬并抑制细胞死亡。总体而言，钙蛋白酶2介导的脂肪肝中Atg3和Atg7的降解增加了其对I/R损伤的敏感性。增加自噬可能改善脂肪肝损伤，并代表一种扩大肝供体库的有价值方法。
