Tumor-secreted factors induce IL-1β maturation via the glucose-mediated synergistic axis of mTOR and NF-κB pathways in mouse macrophages

Macrophages are one of the major cell types that produce IL-1β. IL-1β maturation occurs via inflammasome activation, and mature IL-1β is then released from the cell. Secreted IL-1β mediates inflammatory reactions in various pathological environments, such as those in infectious, autoimmune, and cancerous diseases. Although the mechanism of IL-1β production has been discovered in infectious and autoimmune diseases, its production mechanism in the tumor microenvironment is unclear. Therefore, the mechanism of IL-1β production in macrophages in the tumor microenvironment was investigated in this study. First, bone marrow-derived macrophages obtained from C57BL/6 mice were treated with B16F10 tumor-conditioned media (TCM) in vitro. TCM increased the levels of IL-1β via glucose-mediated activation of the inflammasome. Moreover, TCM enhanced the activation of both NF-κB and mTOR pathways in a glucose-dependent manner. In particular, the expression levels of mTORC1 component proteins were dependent on the TCM-induced activation of NF-κB signaling. In addition, TCM affected ASC-ASC interactions through increasing intracellular reactive oxygen species levels. Finally, glucose inhibition by inoculation with 2-deoxy-D-glucose in vivo decreased the IL-1β levels in both the blood and tumor region of B16F10-bearing C57BL/6 mice relative to those in PBS-injected tumor-bearing mice. These results suggest that glucose supplied from blood vessels might be important for IL-1β production in tumor-associated macrophages via the integrated signals of the NF-κB and mTOR pathways in the tumor microenvironment.

巨噬细胞（Macrophages）是产生白细胞介素1β（IL-1β）的主要细胞类型之一。IL-1β的成熟过程依赖于炎性体（inflammasome）的激活，成熟后的IL-1β随后被释放至细胞外。分泌型IL-1β可在感染、自身免疫及肿瘤等多种病理环境中介导炎症反应。尽管IL-1β的产生机制在感染性与自身免疫性疾病中已被阐明，但其在肿瘤微环境（tumor microenvironment）中的调控机制仍不明确。因此，本研究针对肿瘤微环境中巨噬细胞内IL-1β的产生机制展开了探究。首先，本研究体外采用B16F10肿瘤条件培养基（TCM）处理源自C57BL/6小鼠的骨髓来源巨噬细胞（bone marrow-derived macrophages）。实验结果显示，TCM可通过葡萄糖介导的炎性体激活通路提升IL-1β的表达水平。此外，TCM可通过葡萄糖依赖的方式，同时增强核因子κB（NF-κB）与雷帕霉素靶蛋白（mTOR）两条信号通路的激活活性。具体而言，雷帕霉素靶蛋白复合物1（mTORC1）的组分蛋白表达水平，依赖于TCM诱导激活的NF-κB信号通路。此外，TCM可通过提高细胞内活性氧（reactive oxygen species）水平影响ASC-ASC的相互作用。最后，体内通过接种2-脱氧-D-葡萄糖（2-deoxy-D-glucose）抑制葡萄糖代谢后，与注射磷酸盐缓冲液（PBS）的荷瘤小鼠相比，携带B16F10肿瘤的C57BL/6小鼠的血液及肿瘤区域内的IL-1β水平均出现下降。上述研究结果表明，在肿瘤微环境中，血管供应的葡萄糖可能通过整合NF-κB与mTOR通路的信号，在肿瘤相关巨噬细胞（tumor-associated macrophages）的IL-1β产生过程中发挥重要作用。