Department of Biochemistry and Molecular Biology, Michigan State University, Lansing, MI, United States.
Institute for Integrative Toxicology, Michigan State University, Lansing, MI, United States.
Front Immunol. 2022 Nov 3;13:993614. doi: 10.3389/fimmu.2022.993614. eCollection 2022.
Preclinical and clinical studies suggest that consumption of long chain omega-3 polyunsaturated fatty acids (PUFAs) reduces severity of chronic inflammatory and autoimmune diseases. While these ameliorative effects are conventionally associated with downregulated expression of proinflammatory cytokine and chemokine genes, our laboratory has recently identified Type 1 interferon (IFN1)-regulated gene expression to be another key target of omega-3 PUFAs. Here we used single cell RNA sequencing (scRNAseq) to gain new mechanistic perspectives on how the omega-3 PUFA docosahexaenoic acid (DHA) influences TLR4-driven proinflammatory and IFN1-regulated gene expression in a novel self-renewing murine fetal liver-derived macrophage (FLM) model. FLMs were cultured with 25 µM DHA or vehicle for 24 h, treated with modest concentration of LPS (20 ng/ml) for 1 and 4 h, and then subjected to scRNAseq using the 10X Chromium System. At 0 h (i.e., in the absence of LPS), DHA increased expression of genes associated with the NRF2 antioxidant response (e.g. , ) and metal homeostasis (e.g., ), both of which are consistent with DHA-induced polarization of FLMs to a more anti-inflammatory phenotype. At 1 h post-LPS treatment, DHA inhibited LPS-induced cholesterol synthesis genes (e.g. , , and which potentially could contribute to interference with TLR4-mediated inflammatory signaling. At 4 h post-LPS treatment, LPS-treated FLMs reflected a more robust inflammatory response including upregulation of proinflammatory cytokine (e.g. ) and chemokine (e.g.) genes as well as IFN1-regulated genes (e.g. ), many of which were suppressed by DHA. Using single-cell regulatory network inference and clustering (SCENIC) to identify gene expression networks, we found DHA modestly downregulated LPS-induced expression of NF-κB-target genes. Importantly, LPS induced a subset of FLMs simultaneously expressing NF-κB- and IRF7/STAT1/STAT2-target genes that were conspicuously absent in DHA-pretreated FLMs. Thus, DHA potently targeted both the NF-κB and the IFN1 responses. Altogether, scRNAseq generated a valuable dataset that provides new insights into multiple overlapping mechanisms by which DHA may transcriptionally or post-transcriptionally regulate LPS-induced proinflammatory and IFN1-driven responses in macrophages.
临床前和临床研究表明,长链 ω-3 多不饱和脂肪酸(PUFA)的消耗可降低慢性炎症和自身免疫性疾病的严重程度。虽然这些改善作用通常与促炎细胞因子和趋化因子基因的下调表达有关,但我们实验室最近发现,I 型干扰素(IFN1)调节的基因表达是 ω-3 PUFAs 的另一个关键靶点。在这里,我们使用单细胞 RNA 测序(scRNAseq)在新型自我更新的胎肝来源巨噬细胞(FLM)模型中获得了关于 ω-3 PUFADHA 如何影响 TLR4 驱动的促炎和 IFN1 调节基因表达的新机制观点。将 FLM 用 25 µM DHA 或载体培养 24 小时,用适度浓度的 LPS(20 ng/ml)处理 1 和 4 小时,然后使用 10X Chromium 系统进行 scRNAseq。在 0 小时(即没有 LPS 的情况下),DHA 增加了与 NRF2 抗氧化反应相关的基因的表达(例如,和 )和金属稳态(例如,),这两者都与 DHA 诱导的 FLM 向更抗炎表型的极化一致。在 LPS 处理后 1 小时,DHA 抑制了 LPS 诱导的胆固醇合成基因(例如,和 ),这可能有助于干扰 TLR4 介导的炎症信号。在 LPS 处理后 4 小时,LPS 处理的 FLM 反映了更强烈的炎症反应,包括促炎细胞因子(例如)和趋化因子(例如)以及 IFN1 调节基因(例如)的上调,其中许多基因被 DHA 抑制。使用单细胞调控网络推断和聚类(SCENIC)来识别基因表达网络,我们发现 DHA 适度地下调了 LPS 诱导的 NF-κB 靶基因的表达。重要的是,LPS 诱导了一小部分 FLM 同时表达 NF-κB 和 IRF7/STAT1/STAT2 靶基因,而在 DHA 预处理的 FLM 中则明显不存在。因此,DHA 强烈靶向 NF-κB 和 IFN1 反应。总的来说,scRNAseq 生成了一个有价值的数据集,提供了新的见解,即 DHA 可能通过转录或转录后调节巨噬细胞中 LPS 诱导的促炎和 IFN1 驱动的反应的多种重叠机制。
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