Center for Liver Transplantation, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China.
J Clin Invest. 2024 May 14;134(13):e180451. doi: 10.1172/JCI180451.
Steatotic donor livers are becoming more and more common in liver transplantation. However, the current use of steatotic grafts is less acceptable than normal grafts due to their higher susceptibility to ischemia/reperfusion (I/R) injury. To investigate the mechanism underlying the susceptibility of steatotic liver to I/R injury, we detected cell death markers and inflammation in clinical donor livers and animal models. We found that caspase-8-mediated hepatic apoptosis is activated in steatotic liver I/R injury. However, ablation of caspase-8 only slightly mitigated steatotic liver I/R injury without affecting inflammation. We further demonstrated that RIPK1 kinase induces both caspase-8-mediated apoptosis and cell death-independent inflammation. Inhibition of RIPK1 kinase significantly protects against steatotic liver I/R injury by alleviating both hepatic apoptosis and inflammation. Additionally, we found that RIPK1 activation is induced by Z-DNA binding protein 1 (ZBP1) but not the canonical TNF-α pathway during steatotic liver I/R injury. Deletion of ZBP1 substantially decreases the steatotic liver I/R injury. Mechanistically, ZBP1 is amplified by palmitic acid-activated JNK pathway in steatotic livers. Upon I/R injury, excessive reactive oxygen species trigger ZBP1 activation by inducing its aggregation independent of the Z-nucleic acids sensing action in steatotic livers, leading to the kinase activation of RIPK1 and the subsequent aggravation of liver injury. Thus, ZBP1-mediated RIPK1-driven apoptosis and inflammation exacerbate steatotic liver I/R injury, which could be targeted to protect steatotic donor livers during transplantation.
在肝移植中,越来越多的供体肝脏出现脂肪变性。然而,由于其更容易发生缺血/再灌注(I/R)损伤,目前脂肪变性供体移植物的使用不如正常供体移植物可接受。为了研究脂肪变性肝脏对 I/R 损伤易感性的机制,我们检测了临床供体肝脏和动物模型中的细胞死亡标志物和炎症。我们发现,caspase-8 介导的肝凋亡在脂肪变性肝 I/R 损伤中被激活。然而,caspase-8 的消融仅略微减轻了脂肪变性肝 I/R 损伤,而不影响炎症。我们进一步证明,RIPK1 激酶诱导 caspase-8 介导的凋亡和细胞死亡非依赖性炎症。RIPK1 激酶的抑制显著通过减轻肝凋亡和炎症来保护脂肪变性肝免受 I/R 损伤。此外,我们发现 RIPK1 的激活是由 Z-DNA 结合蛋白 1(ZBP1)而非经典的 TNF-α 途径在脂肪变性肝 I/R 损伤期间诱导的。ZBP1 的缺失大大降低了脂肪变性肝 I/R 损伤。在机制上,ZBP1 被脂肪酸激活的 JNK 途径在脂肪变性肝脏中放大。在 I/R 损伤时,过多的活性氧通过诱导其聚集而独立于 Z-核酸感应作用触发 ZBP1 的激活,导致 RIPK1 的激酶激活和随后的肝损伤加重。因此,ZBP1 介导的 RIPK1 驱动的凋亡和炎症加剧了脂肪变性肝 I/R 损伤,这可以作为保护移植期间脂肪变性供体肝脏的靶点。
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