放射治疗是头颈鳞状细胞癌（HNSCC）的重要补充治疗，但它并不一定能导致肿瘤完全消退。免疫抑制性巨噬细胞的浸润被认为介导了放射治疗抵抗，但其机制在很大程度上仍未被探索。本研究旨在阐明免疫抑制巨噬细胞在放疗过程中的作用及其相关机制。荷有同基因SCC-VII肿瘤的雄性C3H小鼠接受放射治疗（2×8Gy）。评估了辐射对肿瘤浸润巨噬细胞的影响。在经过辐照的肿瘤培养基（irCM）和辐照的肿瘤源性细胞外囊泡（irTEV）处理后，评估了骨髓源性巨噬细胞的分化、增殖、迁移和炎症细胞因子。使用液相色谱-质谱法对 irTEV 进行了全面的代谢组学分析，同时研究了关键代谢物在体外和体内巨噬细胞中的机制。SCC-VII 同基因移植肿瘤的放射治疗增加了肿瘤微环境中 M1 和 M2 巨噬细胞的极化并驱使浸润的巨噬细胞产生免疫抑制表型。辐射诱导的巨噬细胞极化和免疫抑制依赖于 irTEV，irTEV 向巨噬细胞递送更多量的烟酰胺 (NAM)。 NAM直接与NF-κB转录活性调节因子USP7结合，通过NAM减少NF-κB进入细胞核的易位，从而减少细胞因子IL6和IL8的释放。烟酰胺磷酸核糖转移酶 (NAMPT) 是 NAD 代谢的限速酶，其酶活性增加，导致受辐射的 HNSCC 和 irTEV 中辐射诱导的 NAM 积累水平。抑制 NAMPT 可以降低 irTEV 中的 NAM 水平，并通过减轻巨噬细胞的免疫抑制功能来提高放疗敏感性。放疗可以诱导 HNSCC 细胞的 NAD 代谢重编程，从而调节巨噬细胞向免疫抑制表型发展。药理学靶向 NAD 代谢可能是 HNSCC 放疗增敏的一种有前景的策略。版权所有 © 2024 Elsevier Ltd. 保留所有权利。

radiotherapy stands as an important complementary treatment for head and neck squamous cell carcinoma (HNSCC), yet it does not invariably result in complete tumor regression. The infiltration of immunosuppressive macrophages is believed to mediate the radiotherapy resistance, which mechanism remains largely unexplored. This study aimed to elucidate the role of immunosuppressive macrophages during radiotherapy and the associated underlying mechanisms.Male C3H mice bearing syngeneic SCC-VII tumor were received irradiation (2 × 8Gy). The impact of irradiation on tumor-infiltrating macrophages were assessed. Bone marrow derived macrophages were evaluated in differentiation, proliferation, migration, and inflammatory cytokines after treatment of irradiated tumor culture medium (irCM) and irradiated tumor derived extracellular vesicles (irTEVs). A comprehensive metabolomics profiling of the irTEVs was conducted using liquid chromatography-mass spectrometry, while key metabolites were investigated the mechanism in macrophage in vitro and in vivo.Radiotherapy on SCC-VII syngeneic graft tumors increased polarization of both M1 and M2 macrophages in tumor microenvironment and drove infiltrated macrophages towards an immunosuppressive phenotype. Irradiation-induced polarization and immunosuppression of macrophages were dependent on irTEVs which delivered an increased amount of nicotinamide (NAM) to macrophages. NAM directly bound to the NF-κB transcriptional activity regulator USP7, through which NAM reduced translocation of NF-κB into the nucleus, thereby decreasing the release of cytokines IL6 and IL8. Increased enzyme activity of nicotinamide phosphoribosyl transferase (NAMPT) which is the rate-limiting enzyme of NAD+ metabolism, contributed to the irradiation-induced accumulation levels of NAM in irradiated HNSCC and irTEVs. Inhibition of NAMPT decreased NAM levels in irTEVs and increased radiotherapy sensitivity through alleviating immunosuppressive function of macrophages.Radiotherapy could induce NAD+ metabolic reprogramming of HNSCC cells, which regulate macrophage towards an immunosuppressive phenotype. Pharmacological targeting NAD+ metabolism might be a promising strategy for radiotherapy sensitization of HNSCC.Copyright © 2024 Elsevier Ltd. All rights reserved.