Department of Hepatobiliary Surgery, The First Affiliated Hospital of Anhui Medical University & Department of Hepatobiliary Surgery, Nanjing Drum Tower Hospital, Clinical College of Nanjing Medical University, Nanjing 210008, Jiangsu Province, China.
Department of Hepatobiliary Surgery, Nanjing Drum Tower Hospital, Nanjing University Medical School, Nanjing 210008, Jiangsu Province, China.
J Hepatol. 2023 Aug;79(2):403-416. doi: 10.1016/j.jhep.2023.03.039. Epub 2023 Apr 9.
BACKGROUND & AIMS: Non-alcoholic steatohepatitis (NASH) is a chronic inflammatory disease that can further progress to cirrhosis and hepatocellular carcinoma. However, the key molecular mechanisms behind this process have not been clarified.
We analyzed human NASH and normal liver tissue samples by RNA-sequencing and liquid chromatography-mass spectrometry, identifying hepatocyte cytosolic protein Myc-interacting zinc-finger protein 1 (Miz1) as a potential target in NASH progression. We established a Western diet+fructose-induced NASH model in hepatocyte-specific Miz1 knockout and adeno-associated virus type 8-overexpressing mice. Human NASH liver organoids were used to confirm the mechanism, and immunoprecipitation and mass spectrometry were used to detect proteins that could interact with Miz1.
We demonstrate that Miz1 is reduced in hepatocytes in human NASH. Miz1 is shown to bind to peroxiredoxin 6 (PRDX6), retaining it in the cytosol, blocking its interaction with mitochondrial Parkin at Cys431, and inhibiting Parkin-mediated mitophagy. In NASH livers, loss of hepatocyte Miz1 results in PRDX6-mediated inhibition of mitophagy, increased dysfunctional mitochondria in hepatocytes, and production of proinflammatory cytokines, including TNFα, by hepatic macrophages. Crucially, the increased production of TNFα results in a further reduction in hepatocyte Miz1 by E3-ubiquitination. This produces a positive feedback loop of TNFα-mediated hepatocyte Miz1 degradation, resulting in PRDX6-mediated inhibition of hepatocyte mitophagy, with the accumulation of dysfunctional mitochondria in hepatocytes and increased macrophage TNFα production.
Our study identified hepatocyte Miz1 as a suppressor of NASH progression via its role in mitophagy; we also identified a positive feedback loop by which TNFα production induces degradation of cytosolic Miz1, which inhibits mitophagy and thus leads to increased macrophage TNFα production. Interruption of this positive feedback loop could be a strategy to inhibit the progression of NASH.
Non-alcoholic steatohepatitis (NASH) is a chronic inflammatory disease that can further develop into cirrhosis and hepatocellular carcinoma. However, the key molecular mechanism of this process has not been fully clarified. Herein, we identified a positive feedback loop of macrophage TNFα-mediated hepatocyte Miz1 degradation, resulting in PRDX6-mediated inhibition of hepatocyte mitophagy, aggravation of mitochondrial damage and increased macrophage TNFα production. Our findings not only provide mechanistic insight into NASH progression but also provide potential therapeutic targets for patients with NASH. Our human NASH liver organoid culture is therefore a useful platform for exploring treatment strategies for NASH development.
非酒精性脂肪性肝炎（NASH）是一种慢性炎症性疾病，可进一步发展为肝硬化和肝细胞癌。然而，这一过程背后的关键分子机制尚不清楚。
我们通过 RNA 测序和液相色谱-质谱分析了人类 NASH 和正常肝组织样本，确定了肝细胞溶质蛋白 Myc 相互作用锌指蛋白 1（Miz1）是 NASH 进展中的一个潜在靶点。我们在肝特异性 Miz1 敲除和腺相关病毒 8 过表达小鼠中建立了西方饮食+果糖诱导的 NASH 模型。使用人类 NASH 肝类器官来验证机制，并进行免疫沉淀和质谱检测以检测可以与 Miz1 相互作用的蛋白质。
我们证明 Miz1 在人类 NASH 中在肝细胞中减少。Miz1 被证明与过氧化物还原酶 6（PRDX6）结合，将其保留在细胞质中，阻止其与线粒体 Parkin 在 Cys431 处相互作用，并抑制 Parkin 介导的线粒体自噬。在 NASH 肝脏中，肝细胞 Miz1 的缺失导致 PRDX6 介导的线粒体自噬抑制、肝细胞中功能失调的线粒体增加以及肝脏巨噬细胞产生促炎细胞因子，包括 TNFα。至关重要的是，TNFα 的增加导致 E3 泛素化进一步降低肝细胞 Miz1。这产生了 TNFα 介导的肝细胞 Miz1 降解的正反馈环，导致 PRDX6 介导的肝细胞线粒体自噬抑制，肝细胞中功能失调的线粒体积累增加，巨噬细胞 TNFα 产生增加。
我们的研究通过其在线粒体自噬中的作用确定了肝细胞 Miz1 是 NASH 进展的抑制剂；我们还发现了一个正反馈环，其中 TNFα 的产生诱导胞质 Miz1 的降解，从而抑制线粒体自噬，进而导致巨噬细胞 TNFα 产生增加。阻断这个正反馈环可能是抑制 NASH 进展的一种策略。
非酒精性脂肪性肝炎（NASH）是一种慢性炎症性疾病，可进一步发展为肝硬化和肝癌。然而，这一过程的关键分子机制尚未完全阐明。在此，我们发现了一个巨噬细胞 TNFα 介导的肝细胞 Miz1 降解的正反馈环，导致 PRDX6 介导的肝细胞线粒体自噬抑制、线粒体损伤加重和巨噬细胞 TNFα 产生增加。我们的研究结果不仅为 NASH 进展提供了机制上的见解，也为 NASH 患者提供了潜在的治疗靶点。因此，我们的人类 NASH 肝类器官培养是探索 NASH 发展治疗策略的有用平台。
