Trained immunity, induced by β-glucan in monocytes, is mediated by activating metabolic pathways that result in epigenetic rewiring of cellular functional programs; however, molecular mechanisms underlying these changes remain unclear. Here, we report a key immunometabolic and epigenetic pathway mediated by the miR–9-5p -isocitrate dehydrogenase 3α (IDH3α) axis in trained immunity. We found that β-glucan–trained miR–9-5p –/– monocytes showed decreased IL-1β, IL-6, and TNF-α production after LPS stimulation. Trained miR–9-5p –/– mice produced decreased levels of proinflammatory cytokines upon rechallenge in vivo and had worse protection against Candida albicans infection. miR–9-5p targeted IDH3α and reduced α-ketoglutarate (α-KG) levels to stabilize HIF-1α, which promoted glycolysis. Accumulating succinate and fumarate via miR–9-5p action integrated immunometabolic circuits to induce histone modifications by inhibiting KDM5 demethylases. β-Glucan–trained monocytes exhibited low IDH3α levels, and IDH3α overexpression blocked the induction of trained immunity by monocytes. Monocytes with IDH3α variants from autosomal recessive retinitis pigmentosa patients showed a trained immunity phenotype at immunometabolic and epigenetic levels. These findings suggest that miR–9-5p and IDH3α act as critical metabolic and epigenetic switches in trained immunity.
Trained monocytes and macrophages produce reactive oxygen species (ROS), which trigger antioxidative glutathione (GSH) response to buffer the rising ROS. However, whether and how the trained immunity is shaped by GSH synthesis remains unknown. Here, we report that β-glucan-trained macrophages from mice harboring a myeloid-specific deletion of the catalytic subunit of glutamate-cysteine ligase ( Gclc) showed impaired GSH synthesis and decreased proinflammatory cytokine production in response to lipopolysaccharide challenge. Gclc deficiency compromised the activation of mammalian target of rapamycin-1 (mTOR) and expression of c-Myc transcription factors, abrogating the energy utilization and the metabolic reprogramming that allows β-glucan-trained macrophages to switch to glycolysis and glutaminolysis. Furthermore, Gclc deletion repressed effective H3K27me3 demethylation in the promoters of immunometabolic genes, such as Gls , Hk2, and Glut1, in β-glucan-trained macrophages by promoting the methyltransferase enhancer of zeste homolog 2 (EZH2). In vivo , myeloid-specific ablation of Gclc decreased the secretion of proinflammatory cytokines upon rechallenge with Candida albicans and these animals were less protected against the infection, compared with control littermates. Moreover, pharmacological inhibition of EZH2 enhanced the trained immunity response against Candida infection in Gclc-deficient mouse and human peripheral blood mononuclear cells treated with GCLC inhibitor buthionine sulfoximine (BSO). Thus, antioxidative GSH synthesis supports an environment conducive to β-glucan-induced metabolic and epigenetic reprogramming in trained immunity, allowing exploration of its functional consequences in autoimmune or inflammatory disease.
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The effectiveness of the commonly used therapy is low for treating triple-negative breast cancer (TNBC). Macrophages, accounting for up to 50% of the TNBC tumor mass, are involved in innate and adaptive immunity, which can serve as an effective weapon against TNBC via combined immunotherapy. Here, we engineered mannose and glycocholic acid-modified trimethyl chitosan (MTG) nanoparticles (NPs) encapsulating signal regulatory protein α (SIRPα) siRNA (siSIRPα, a macrophage checkpoint inhibitor) and mucin 1 (MUC1) pDNA (pMUC1, a therapeutic pDNA vaccine) (MTG/siSIRPα/pMUC1 NPs) for in situ educating macrophages via an oral route to exert the cooperative antitumor effects of siSIRPα and pMUC1. Orally delivered MTG-based NPs accumulated in the macrophages in lymph nodes and tumor tissues via the intestinal lymphatic transport pathway, leading to strong cellular immunity responses. Following the transfection of orally administered MTG/siSIRPα/pMUC1 NPs within the same macrophages, siSIRPα strengthened the pMUC1 vaccine-induced systemic cellular immunity, while pMUC1 enhanced siSIRPα-mediated macrophage phagocytosis, M1-phenotype polarization, and tumor microenvironment (TME) remodeling at the tumor sites, thereby inhibiting the growth and metastasis of TNBC. The simultaneous achievements of the mutual promotion of innate and adaptive immunity in the local TME and in the whole body suggested that MTG/siSIRPα/pMUC1 NPs would provide a promising paradigm for the combined immunotherapy of TNBC via oral delivery of genes.
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