Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada.
J Immunol. 2023 Nov 15;211(10):1561-1577. doi: 10.4049/jimmunol.2300293.
Lipid accumulation in macrophages (Mφs) is a hallmark of atherosclerosis, yet how lipid accumulation affects inflammatory responses through rewiring of Mφ metabolism is poorly understood. We modeled lipid accumulation in cultured wild-type mouse thioglycolate-elicited peritoneal Mφs and bone marrow-derived Mφs with conditional (Lyz2-Cre) or complete genetic deficiency of Vhl, Hif1a, Nos2, and Nfe2l2. Transfection studies employed RAW264.7 cells. Mφs were cultured for 24 h with oxidized low-density lipoprotein (oxLDL) or cholesterol and then were stimulated with LPS. Transcriptomics revealed that oxLDL accumulation in Mφs downregulated inflammatory, hypoxia, and cholesterol metabolism pathways, whereas the antioxidant pathway, fatty acid oxidation, and ABC family proteins were upregulated. Metabolomics and extracellular metabolic flux assays showed that oxLDL accumulation suppressed LPS-induced glycolysis. Intracellular lipid accumulation in Mφs impaired LPS-induced inflammation by reducing both hypoxia-inducible factor 1-α (HIF-1α) stability and transactivation capacity; thus, the phenotype was not rescued in Vhl-/- Mφs. Intracellular lipid accumulation in Mφs also enhanced LPS-induced NF erythroid 2-related factor 2 (Nrf2)-mediated antioxidative defense that destabilizes HIF-1α, and Nrf2-deficient Mφs resisted the inhibitory effects of lipid accumulation on glycolysis and inflammatory gene expression. Furthermore, oxLDL shifted NADPH consumption from HIF-1α- to Nrf2-regulated apoenzymes. Thus, we postulate that repurposing NADPH consumption from HIF-1α to Nrf2 transcriptional pathways is critical in modulating inflammatory responses in Mφs with accumulated intracellular lipid. The relevance of our in vitro models was established by comparative transcriptomic analyses, which revealed that Mφs cultured with oxLDL and stimulated with LPS shared similar inflammatory and metabolic profiles with foamy Mφs derived from the atherosclerotic mouse and human aorta.
巨噬细胞(Mφs)中的脂质积累是动脉粥样硬化的一个标志,但脂质积累如何通过重排 Mφ 代谢来影响炎症反应,人们对此知之甚少。我们在培养的野生型小鼠巯基乙酸酯诱导的腹腔 Mφs 和骨髓来源的 Mφs 中模拟了脂质积累,这些 Mφs 存在条件性(Lyz2-Cre)或完全缺失 Vhl、Hif1a、Nos2 和 Nfe2l2 的基因。转染研究采用 RAW264.7 细胞。用氧化低密度脂蛋白(oxLDL)或胆固醇培养 Mφs 24 小时,然后用 LPS 刺激。转录组学研究表明,oxLDL 在 Mφs 中的积累下调了炎症、缺氧和胆固醇代谢途径,而上调了抗氧化途径、脂肪酸氧化和 ABC 家族蛋白。代谢组学和细胞外代谢通量测定显示,oxLDL 积累抑制了 LPS 诱导的糖酵解。Mφs 内的细胞内脂质积累通过降低缺氧诱导因子 1-α(HIF-1α)的稳定性和转录激活能力来抑制 LPS 诱导的炎症,因此在 Vhl-/- Mφs 中该表型无法得到挽救。Mφs 内的细胞内脂质积累也增强了 LPS 诱导的 NF 红细胞 2 相关因子 2(Nrf2)介导的抗氧化防御,使 HIF-1α 不稳定,而 Nrf2 缺陷型 Mφs 抵抗脂质积累对糖酵解和炎症基因表达的抑制作用。此外,oxLDL 将 NADPH 的消耗从 HIF-1α 转移到 Nrf2 调节的脱辅基酶。因此,我们假设,将 NADPH 的消耗从 HIF-1α 重定向到 Nrf2 转录途径,对于调节富含细胞内脂质的 Mφs 中的炎症反应至关重要。我们的体外模型的相关性通过比较转录组分析得到了确立,该分析表明,用 oxLDL 培养并用 LPS 刺激的 Mφs 与从动脉粥样硬化小鼠和人类主动脉衍生的泡沫 Mφs 具有相似的炎症和代谢特征。
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