Dumont-UCLA Transplantation Center, Department of Surgery, Division of Liver and Pancreas Transplantation, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095, USA.
Division of Hepato-Biliary-Pancreatic Surgery and Transplantation, Department of Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Cell Death Dis. 2023 Nov 23;14(11):762. doi: 10.1038/s41419-023-06221-0.
Sirtuin 1 (SIRT1) is a histone/protein deacetylase in the cellular response to inflammatory, metabolic, and oxidative stressors. We previously reported that myeloid SIRT1 regulates the inflamed liver's canonical pyroptosis cell death pathway. However, whether/how hepatocyte SIRT1 is engaged in programmed cell death in the cold-stressed liver remains uncertain. Here, we undertook translational studies in human and mouse orthotopic liver transplantation (OLT) to interrogate the significance of hepatocyte-specific SIRT1 in cold-stored donor livers and liver grafts after reperfusion. In the clinical arm of sixty human OLT patients, hepatic SIRT1 levels in cold-preserved donor livers correlated with the anti-apoptotic Bcl-2 expression. After reperfusion, improved OLT function was accompanied by hepatic SIRT1 levels negatively associated with cleaved caspase-3 expression. In the experimental arm, we compared FLOX-control with hepatocyte-specific SIRT1-KO livers after orthotopic transplantation into WT mouse recipients, parallel with primary murine hepatocyte cultures subjected to cold activation with/without knockdown of SIRT1, GSDME, and IL18Rβ. Indeed, hepatocyte SIRT1 deficiency upregulated apoptosis and GSDME-mediated programmed cell death, deteriorating hepatocellular function and shortening OLT survival. Augmented GSDME processing, accompanied by increased secretion of IL18 by stressed hepatocytes, was prominent in SIRT1-deficient, cold-stored livers. Hepatocyte SIRT1 expression regulated anti-apoptotic Bcl-2/XIAP proteins, suppressed cold stress-triggered apoptosis, and mitigated GSDME licensing to release IL18. Notably, consistent with the ability of IL18 to depress hepatocyte SIRT1 and Bcl-2/XIAP in vitro, IL18 neutralization in vivo prevented hepatocellular damage and restored the anti-apoptotic phenotype in otherwise injury-prone SIRT1-deficient OLTs. In conclusion, this translational study identifies a novel hepatocyte SIRT1-IL18 molecular circuit as a therapeutic target in the mechanism underpinning hepatocyte death pathways in human and mouse liver transplantation.
Sirtuin 1（SIRT1）是细胞对炎症、代谢和氧化应激反应的组蛋白/蛋白去乙酰化酶。我们之前报道过，髓系 SIRT1 调节炎症肝脏的经典细胞焦亡细胞死亡途径。然而，肝细胞 SIRT1 是否以及如何参与冷应激肝脏中的程序性细胞死亡仍不确定。在这里，我们在人源和小鼠原位肝移植（OLT）中进行了转化研究，以研究肝细胞特异性 SIRT1 在冷保存供体肝脏中的意义以及再灌注后肝移植物中的程序性细胞死亡。在 60 名接受 OLT 的人类患者的临床研究中，冷保存供体肝脏中的肝 SIRT1 水平与抗凋亡 Bcl-2 表达相关。再灌注后，OLT 功能改善与肝 SIRT1 水平呈负相关，与 cleaved caspase-3 表达呈负相关。在实验部分，我们比较了 FLOX 对照与经肝特异性 SIRT1-KO 处理的肝脏，这些肝脏被移植到 WT 小鼠受体中，同时平行进行了原发性小鼠肝细胞培养，这些细胞在冷激活时使用/不使用 SIRT1、GSDME 和 IL18Rβ 的敲低。事实上，肝细胞 SIRT1 缺乏会增加细胞凋亡和 GSDME 介导的程序性细胞死亡，从而恶化肝细胞功能并缩短 OLT 存活时间。在 SIRT1 缺陷、冷储存的肝脏中，GSDME 加工增强，同时应激肝细胞中 IL18 的分泌增加。肝细胞 SIRT1 表达调节抗凋亡 Bcl-2/XIAP 蛋白，抑制冷应激触发的细胞凋亡，并减轻 GSDME 许可以释放 IL18。值得注意的是，与 IL18 在体外降低肝细胞 SIRT1 和 Bcl-2/XIAP 的能力一致，体内的 IL18 中和防止了肝细胞损伤，并恢复了原本易受损的 SIRT1 缺陷型 OLT 中的抗凋亡表型。总之，这项转化研究确定了一种新的肝细胞 SIRT1-IL18 分子回路，作为人类和小鼠肝移植中肝细胞死亡途径的潜在治疗靶点。
