Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma, USA.
J Biol Chem. 2024 Jan;300(1):105566. doi: 10.1016/j.jbc.2023.105566. Epub 2023 Dec 14.
Macrophages play critical roles in inflammation and tissue homeostasis, and their functions are regulated by various autocrine, paracrine, and endocrine factors. We have previously shown that CTRP6, a secreted protein of the C1q family, targets both adipocytes and macrophages to promote obesity-linked inflammation. However, the gene programs and signaling pathways directly regulated by CTRP6 in macrophages remain unknown. Here, we combine transcriptomic and phosphoproteomic analyses to show that CTRP6 activates inflammatory gene programs and signaling pathways in mouse bone marrow-derived macrophages (BMDMs). Treatment of BMDMs with CTRP6 upregulated proinflammatory, and suppressed the antiinflammatory, gene expression. We also showed that CTRP6 activates p44/42-MAPK, p38-MAPK, and NF-κB signaling pathways to promote inflammatory cytokine secretion from BMDMs, and that pharmacologic inhibition of these signaling pathways markedly attenuated the effects of CTRP6. Pretreatment of BMDMs with CTRP6 also sensitized and potentiated the BMDMs response to lipopolysaccharide (LPS)-induced inflammatory signaling and cytokine secretion. Consistent with the metabolic phenotype of proinflammatory macrophages, CTRP6 treatment induced a shift toward aerobic glycolysis and lactate production, reduced oxidative metabolism, and elevated mitochondrial reactive oxygen species production in BMDMs. Importantly, in accordance with our in vitro findings, BMDMs from CTRP6-deficient mice were less inflammatory at baseline and showed a marked suppression of LPS-induced inflammatory gene expression and cytokine secretion. Finally, loss of CTRP6 in mice also dampened LPS-induced inflammation and hypothermia. Collectively, our findings suggest that CTRP6 regulates and primes the macrophage response to inflammatory stimuli and thus may have a role in modulating tissue inflammatory tone in different physiological and disease contexts.
巨噬细胞在炎症和组织稳态中发挥关键作用，其功能受各种自分泌、旁分泌和内分泌因子的调节。我们之前已经表明，C1q 家族的分泌蛋白 CTRP6 靶向脂肪细胞和巨噬细胞，以促进与肥胖相关的炎症。然而，CTRP6 在巨噬细胞中直接调控的基因程序和信号通路仍不清楚。在这里，我们结合转录组学和磷酸化蛋白质组学分析，表明 CTRP6 激活了小鼠骨髓来源的巨噬细胞（BMDM）中的炎症基因程序和信号通路。CTRP6 处理 BMDM 上调促炎基因表达，抑制抗炎基因表达。我们还表明，CTRP6 激活 p44/42-MAPK、p38-MAPK 和 NF-κB 信号通路，促进 BMDM 中炎症细胞因子的分泌，而这些信号通路的药理学抑制显著减弱了 CTRP6 的作用。CTRP6 预处理 BMDM 也使 BMDM 对脂多糖（LPS）诱导的炎症信号和细胞因子分泌的反应变得敏感和增强。与促炎巨噬细胞的代谢表型一致，CTRP6 处理诱导 BMDM 向有氧糖酵解和乳酸产生转移，减少氧化代谢，并增加线粒体活性氧产生。重要的是，与我们的体外发现一致，CTRP6 缺陷型小鼠的 BMDM 在基础水平上炎症反应较低，并且 LPS 诱导的炎症基因表达和细胞因子分泌受到明显抑制。最后，CTRP6 在小鼠中的缺失也抑制了 LPS 诱导的炎症和体温过低。总之，我们的研究结果表明，CTRP6 调节并启动了巨噬细胞对炎症刺激的反应，因此可能在不同的生理和疾病背景下调节组织炎症反应。
