Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, China.
Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
Br J Pharmacol. 2023 Oct;180(19):2577-2598. doi: 10.1111/bph.16156. Epub 2023 Jun 26.
Senescence in hepatic stellate cells (HSCs) limits liver fibrosis. Glutaminolysis promotes HSC activation. Here, we investigated how emodin affected HSC senescence involving glutaminolysis.
Senescence, glutaminolysis metabolites, Nur77 nuclear translocation, glutaminase 1 (GLS1) promoter methylation and related signalling pathways were examined in human HSC-LX2 cells using multiple cellular and molecular approaches. Fibrotic mice with shRNA-mediated knockdown of Nur77 were treated with emodin-vitamin A liposome for investigating the mechanisms in vivo. Human fibrotic liver samples were examined to verify the clinical relevance.
Emodin upregulated several key markers of senescence and inhibited glutaminolysis cascade in HSCs. Emodin promoted Nur77 nuclear translocation, and knockdown of Nur77 abolished emodin blockade of glutaminolysis and induction of HSC senescence. Mechanistically, emodin facilitated Nur77/DNMT3b interaction and increased GLS1 promoter methylation, leading to inhibited GLS1 expression and blockade of glutaminolysis. Moreover, the glutaminolysis intermediate α-ketoglutarate promoted extracellular signal-regulated kinase (ERK) phosphorylation, which in turn phosphorylated Nur77 and reduced its interaction with DNMT3b. This led to decreased GLS1 promoter methylation and increased GLS1 expression, forming an ERK/Nur77/glutaminolysis positive feedback loop. However, emodin repressed ERK phosphorylation and interrupted the feedback cascade, stimulating senescence in HSCs. Studies in mice showed that emodin-vitamin A liposome inhibited glutaminolysis and induced senescence in HSCs, and consequently alleviated liver fibrosis; but knockdown of Nur77 abrogated these beneficial effects. Similar alterations were validated in human fibrotic liver tissues.
Emodin stimulated HSC senescence through interruption of glutaminolysis. HSC-targeted delivery of emodin represented a therapeutic option for liver fibrosis.
肝星状细胞（HSCs）衰老可限制肝纤维化。谷氨酰胺分解代谢可促进 HSC 活化。在此，我们研究了大黄素如何通过谷氨酰胺分解代谢影响 HSC 衰老。
采用多种细胞和分子方法，在人 HSC-LX2 细胞中检测衰老、谷氨酰胺分解代谢产物、Nur77 核易位、谷氨酰胺酶 1（GLS1）启动子甲基化及相关信号通路。利用 shRNA 介导的 Nur77 敲低的肝纤维化小鼠用大黄素-维生素 A 脂质体治疗，以在体内研究其机制。检测人纤维性肝组织样本以验证其临床相关性。
大黄素上调了 HSCs 衰老的几个关键标志物，并抑制了谷氨酰胺分解代谢级联反应。大黄素促进 Nur77 核易位，而 Nur77 敲低则消除了大黄素对谷氨酰胺分解代谢和 HSC 衰老的抑制作用。在机制上，大黄素促进了 Nur77/DNMT3b 相互作用，增加了 GLS1 启动子甲基化，导致 GLS1 表达受抑制和谷氨酰胺分解代谢受阻。此外，谷氨酰胺分解代谢中间产物α-酮戊二酸促进细胞外信号调节激酶（ERK）磷酸化，进而磷酸化 Nur77 并减少其与 DNMT3b 的相互作用。这导致 GLS1 启动子甲基化减少和 GLS1 表达增加，形成了一个 ERK/Nur77/谷氨酰胺分解代谢正反馈回路。然而，大黄素抑制了 ERK 磷酸化并打断了该反馈级联，刺激了 HSCs 衰老。在小鼠中的研究表明，大黄素-维生素 A 脂质体抑制了 HSCs 的谷氨酰胺分解代谢并诱导其衰老，从而减轻了肝纤维化；但 Nur77 敲低则消除了这些有益作用。在人纤维性肝组织中也验证了类似的改变。
大黄素通过打断谷氨酰胺分解代谢刺激了 HSC 衰老。大黄素靶向 HSC 治疗可能为肝纤维化提供一种治疗选择。
