Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada.
Int J Mol Sci. 2024 Jul 24;25(15):8046. doi: 10.3390/ijms25158046.
Progression of metabolic dysfunction-associated steatites liver disease (MASLD) to steatohepatitis (MASH) is driven by stress-inducing lipids that promote liver inflammation and fibrosis, and MASH can lead to cirrhosis and hepatocellular carcinoma. Previously, we showed coordinated defenses regulated by transcription factors, nuclear factor erythroid 2-related factor-1 (Nrf1) and -2 (Nrf2), protect against hepatic lipid stress. Here, we investigated protective effects of hepatocyte Nrf1 and Nrf2 against MASH-linked liver fibrosis and tumorigenesis. Male and female mice with flox alleles for genes encoding Nrf1 (), Nrf2 (), or both were fed a MASH-inducing diet enriched with high fat, fructose, and cholesterol (HFFC) or a control diet for 24-52 weeks. During this period, hepatocyte Nrf1, Nrf2, or combined deficiency for ~7 days, ~7 weeks, and ~35 weeks was induced by administering mice hepatocyte-targeting adeno-associated virus (AAV) expressing Cre recombinase. The effects on MASH, markers of liver fibrosis and proliferation, and liver tumorigenesis were compared to control mice receiving AAV-expressing green fluorescent protein. Also, to assess the impact of Nrf1 and Nrf2 induction on liver fibrosis, HFFC diet-fed C57bl/6J mice received weekly injections of carbon tetrachloride, and from week 16 to 24, mice were treated with the Nrf2-activating drug bardoxolone, hepatocyte overexpression of human NRF1 (hNRF1), or both, and these groups were compared to control. Compared to the control diet, 24-week feeding with the HFFC diet increased bodyweight as well as liver weight, steatosis, and inflammation. It also increased hepatocyte proliferation and a marker of liver damage, p62. Hepatocyte Nrf1 and combined deficiency increased liver steatosis in control diet-fed but not HFFC diet-fed mice, and increased liver inflammation under both diet conditions. Hepatocyte Nrf1 deficiency also increased hepatocyte proliferation, whereas combined deficiency did not, and this also occurred for p62 level in control diet-fed conditions. In 52-week HFFC diet-fed mice, 35 weeks of hepatocyte Nrf1 deficiency, but not combined deficiency, resulted in more liver tumors in male mice, but not in female mice. In contrast, hepatocyte Nrf2 deficiency had no effect on any of these parameters. However, in the 15-week CCL4-exposed and 24-week HFFC diet-fed mice, Nrf2 induction with bardoxolone reduced liver steatosis, inflammation, fibrosis, and proliferation. Induction of hepatic Nrf1 activity with hNRF1 enhanced the effect of bardoxolone on steatosis and may have stimulated liver progenitor cells. Physiologic Nrf1 delays MASLD progression, Nrf2 induction alleviates MASH, and combined enhancement synergistically protects against steatosis and may facilitate liver repair.
代谢相关脂肪性肝病（MAFLD）向脂肪性肝炎（MASH）的进展是由应激诱导的脂质驱动的，这些脂质促进肝脏炎症和纤维化，而 MASH 可导致肝硬化和肝细胞癌。此前，我们发现受转录因子（核因子红细胞 2 相关因子 1（Nrf1）和 Nrf2）调控的协调防御可抵抗肝脂质应激。在这里，我们研究了肝细胞 Nrf1 和 Nrf2 对 MASH 相关肝纤维化和肿瘤发生的保护作用。雄性和雌性 Nrf1（）、Nrf2（）或两者的基因编码 flox 等位基因的小鼠用富含高脂肪、果糖和胆固醇的 MASH 诱导饮食（HFFC）或对照饮食喂养 24-52 周。在此期间，通过给予小鼠肝靶向腺相关病毒（AAV）表达 Cre 重组酶，诱导约 7 天、约 7 周和约 35 周的肝细胞 Nrf1、Nrf2 或两者的缺失。将这些效果与接受 AAV 表达绿色荧光蛋白的对照小鼠进行比较。此外，为了评估 Nrf1 和 Nrf2 诱导对肝纤维化的影响，HFFC 饮食喂养的 C57bl/6J 小鼠接受每周一次的四氯化碳注射，从第 16 周到第 24 周，用 Nrf2 激活药物 bardoxolone、肝细胞过表达人 NRF1（hNRF1）或两者治疗，并与对照组进行比较。与对照饮食相比，24 周的 HFFC 饮食喂养增加了体重、肝重、脂肪变性和炎症。它还增加了肝细胞增殖和肝损伤标志物 p62。肝细胞 Nrf1 缺失增加了对照饮食喂养但不增加 HFFC 饮食喂养小鼠的肝脂肪变性，并在两种饮食条件下增加了肝炎症。肝细胞 Nrf1 缺失还增加了肝细胞增殖，而联合缺失则没有，这也发生在对照饮食喂养条件下的 p62 水平。在 52 周的 HFFC 饮食喂养的小鼠中，35 周的肝细胞 Nrf1 缺失，但不是联合缺失，导致雄性小鼠的肝脏肿瘤更多，但在雌性小鼠中没有。相比之下，肝细胞 Nrf2 缺失对这些参数没有影响。然而，在 15 周的 CCL4 暴露和 24 周的 HFFC 饮食喂养的小鼠中，用 bardoxolone 诱导 Nrf2 可减少肝脂肪变性、炎症、纤维化和增殖。用 hNRF1 诱导肝 Nrf1 活性增强了 bardoxolone 对脂肪变性的作用，并且可能刺激了肝祖细胞。生理 Nrf1 可延缓 MASLD 进展，Nrf2 诱导可减轻 MASH，联合增强可协同抵抗脂肪变性并可能促进肝修复。
