Proinflammatory hepatic macrophage activation plays a key role in the development of nonalcoholic steatohepatitis (NASH). This involves increased embryonic hepatic Kupffer cell (KC) death, facilitating the replacement of KCs with bone marrow–derived recruited hepatic macrophages (RHMs) that highly express proinflammatory genes. Moreover, phago/efferocytic activity of KCs is diminished in NASH, enhancing liver inflammation. However, the molecular mechanisms underlying these changes in KCs are not known. Here, we show that hypoxia-inducible factor 2α (HIF-2α) mediates NASH-associated decreased KC growth and efferocytosis by enhancing lysosomal stress. At the molecular level, HIF-2α stimulated mammalian target of rapamycin (mTOR)– and extracellular signal–regulated kinase-dependent inhibitory transcription factor EB (TFEB) phosphorylation, leading to decreased lysosomal and phagocytic gene expression. With increased metabolic stress and phago/efferocytic burden in NASH, these changes were sufficient to increase lysosomal stress, causing decreased efferocytosis and lysosomal cell death. Of interest, HIF-2α–dependent TFEB regulation only occurred in KCs but not RHMs. Instead, in RHMs, HIF-2α promoted mitochondrial reactive oxygen species production and proinflammatory activation by increasing ANT2 expression and mitochondrial permeability transition. Consequently, myeloid lineage–specific or KC-specific HIF-2α depletion or the inhibition of mTOR-dependent TFEB inhibition using antisense oligonucleotide treatment protected against the development of NASH in mice. Moreover, treatment with an HIF-2α–specific inhibitor reduced inflammatory and fibrogenic gene expression in human liver spheroids cultured under a NASH-like condition. Together, our results suggest that macrophage subtype–specific effects of HIF-2α collectively contribute to the proinflammatory activation of liver macrophages, leading to the development of NASH.

中文翻译：

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HIF-2α 驱动非酒精性脂肪性肝炎中肝脏 Kupffer 细胞死亡和促炎募集的巨噬细胞活化


促炎性肝巨噬细胞活化在非酒精性脂肪性肝炎 （NASH） 的发生中起关键作用。这涉及胚胎肝库普弗细胞 （KC） 死亡的增加，促进用骨髓来源的募集的肝巨噬细胞 （RHM） 取代 KC，这些巨噬细胞高度表达促炎基因。此外，在 NASH 中，KCs 的吞噬/泡生细胞活性降低，从而增强肝脏炎症。然而，KCs 中这些变化背后的分子机制尚不清楚。在这里，我们表明缺氧诱导因子 2α （HIF-2α） 通过增强溶酶体应激介导 NASH 相关的 KC 生长和胞吐作用减少。在分子水平上，HIF-2α 刺激哺乳动物雷帕霉素靶标 （mTOR） 和细胞外信号调节的激酶依赖性抑制转录因子 EB （TFEB） 磷酸化，导致溶酶体和吞噬细胞基因表达降低。随着 NASH 中代谢应激和吞噬/泡泡细胞负荷的增加，这些变化足以增加溶酶体应激，导致泡泡细胞增多减少和溶酶体细胞死亡。有趣的是，HIF-2α 依赖性 TFEB 调节仅发生在 KCs 中，而不发生在 RHM 中。相反，在 RHM 中，HIF-2α 通过增加 ANT2 表达和线粒体通透性转换来促进线粒体活性氧的产生和促炎激活。因此，髓系特异性或 KC 特异性 HIF-2α 耗竭或使用反义寡核苷酸处理抑制 mTOR 依赖性 TFEB 抑制可防止小鼠发生 NASH。此外，用 HIF-2α 特异性抑制剂处理降低了在 NASH 样条件下培养的人肝球体中的炎症和纤维化基因表达。 总之，我们的结果表明，HIF-2α 的巨噬细胞亚型特异性作用共同促进肝脏巨噬细胞的促炎激活，导致 NASH 的发展。