O6-Methylguanine DNA Methyltransferase Regulates Beta-glucan Trained Immunity of Macrophages

Trained immunity is the heightened state of innate immune memory that enhances immune response resulting in nonspecific protection. Epigenetic changes and metabolic reprogramming are critical steps that regulate trained immunity. In this study, we reported the involvement of O6-methylguanine DNA methyltransferase (MGMT), a DNA repair enzyme of lesion induced by alkylating agents, in regulation the trained immunity induced by ß-glucan (BG). Pharmacological inhibition or silencing of MGMT expression altered LPS stimulated pro-inflammatory cytokine productions in BG-trained bone marrow derived macrophages (BMMs). Targeted deletion of Mgmt in BMMs resulted in reduction of the trained responses both in vitro and in vivo models. The transcriptomic analysis revealed that the dampening trained immunity in MGMT KO BMMs is partially mediated by ATM/FXR/AMPK axis affecting the MAPK/mTOR/HIF1a pathways and the reduction in glycolysis function. Taken together, a failure to resolve a DNA damage may have consequences for innate immune memory. Overall design: Transcriptomic profile of unstimulated, BG-primed (BG24), BG-primed with LPS stimulation WT and MGMT KO macrophages.

训练免疫（trained immunity）是固有免疫记忆的增强状态，可强化免疫应答并提供非特异性保护。表观遗传改变与代谢重编程是调控训练免疫的关键步骤。本研究报道了O6-甲基鸟嘌呤DNA甲基转移酶（O6-methylguanine DNA methyltransferase，MGMT）——一种修复烷化剂诱导DNA损伤的DNA修复酶——在β-葡聚糖（β-glucan，BG）诱导的训练免疫调控中的参与作用。对MGMT进行药物抑制或表达沉默，可改变β-葡聚糖预刺激的骨髓来源巨噬细胞（bone marrow derived macrophages，BMMs）中脂多糖（LPS）诱导的促炎细胞因子产生水平。在骨髓来源巨噬细胞中靶向敲除Mgmt基因，可在体外与体内模型中削弱训练免疫应答。转录组学分析显示，MGMT敲除（MGMT KO）骨髓来源巨噬细胞的训练免疫减弱现象，部分通过ATM/FXR/AMPK信号轴介导，该轴可调控MAPK/mTOR/HIF1α通路并降低糖酵解功能。综上，DNA损伤修复缺陷可能对固有免疫记忆产生影响。本实验整体设计为：对野生型（wild type，WT）与MGMT敲除（MGMT KO）巨噬细胞的三类样本进行转录组谱分析，分别为未刺激组、β-葡聚糖预刺激组（BG24）、β-葡聚糖预刺激后联合脂多糖刺激组。