Gut Microbiota-Derived Butyrate Induces Trained Immunity in Intestinal Macrophages to Potentiate Antitumor Immunity

Abstract

The gut microbiota metabolite butyrate plays an important role in maintaining intestinal immune homeostasis, but it’s still unclear whether it can induce trained immunity in intestinal macrophages and thus affect anti-tumor immune responses. This study aimed to investigate the ability of butyrate to induce trained immunity in intestinal macrophages and its function and mechanism in anti-tumor immunity. We used an MC38 colorectal cancer mouse model, combined with strategies such as broad-spectrum antibiotics to clear gut microbiota, butyrate supplementation, colonization with butyrate-producing bacteria, macrophage depletion, and adoptive transfer. In vitro, we pretreated bone marrow-derived macrophages and intestinal lamina propria macrophages with butyrate, allowed them to rest, then gave a secondary stimulus to assess cytokine secretion, phagocytic function, metabolic reprogramming, and epigenetic modifications. RNA-seq, ATAC-seq, and CUT&Tag were used to analyze the molecular mechanisms. Butyrate pretreatment induced trained immunity in macrophages, showing significantly enhanced TNF-α, IL-6, and IL-1β secretion after a second stimulus, increased glycolysis, and enriched H3K4me3 modifications at key inflammatory gene promoters. Mechanistically, butyrate drives epigenetic reprogramming and metabolic remodeling in macrophages by inhibiting histone deacetylase activity and activating the GPR43-mTOR-HIF-1α signaling axis. In tumor-bearing mice, butyrate supplementation or colonization with butyrate-producing bacteria significantly enhanced the anti-tumor phenotype of intestinal macrophages, promoted CD8⁺ T cell infiltration and activation in tumors, and suppressed tumor growth; this effect was markedly weakened in mice with macrophage-specific trained immunity deficiency. Gut microbiota-derived butyrate induces trained immunity in intestinal macrophages, reshapes the tumor immune microenvironment, and enhances anti-tumor immune responses, offering new ideas for tumor immunotherapy targeting the microbiota metabolite-macrophage trained immunity axis.