TGM2-deficient macrophages exhibited a significant upregulation of pro-inflammatory signatures.
Macrophages are essential for tissue homeostasis, orchestrating the initiation and resolution of both innate and adaptive immunity with profound impacts on protective immunity and immune-mediated pathological damage. Macrophages are heterogeneous subsets. During the inflammatory response, they include both pro-inflammatory subsets and subsets that promote inflammation resolution, and different macrophage subsets play distinct roles in the dynamic processes at different time points. In the current study, we found that a subset of TGM2+ macrophages with inflammation-resolving properties gradually increases during the inflammation resolution phase in the LPS-induced endotoxin shock model. The peak expression of the TGM2 gene occurs mainly during the inflammation resolution phase. Additionally, transcriptome analysis revealed that compared with wild-type (WT) macrophages, TGM2-deficient macrophages exhibited a significant upregulation of pro-inflammatory signatures and a marked downregulation of lipid metabolic synthesis processes. In lipid rescue experiments, we found that the elevated inflammation phenotype of TGM2-deficient macrophages could be restored. Moreover, a significant anti-inflammatory function of this macrophage subset was observed in mouse models of severe disease, enterocolitis, and endotoxin shock. We uncover an inflammatory remodeling of the neuro-metabolic landscape in macrophages, whereby serotonin induces TGM2-mediated serotonylation of in AKT1. Overall design: Bone marrow cells were isolated from 6-8 week-old male wild-type (WT) and TGM2KO mice and then bone marrow-derived macrophages (BMDMs) were obtained and cultured with the stimulation of M-CSF (25ng/ml) for 7 days. BMDMs from WT and TGM2KO mice were either left unstimulated or polarized to a proinflammatory state by treatment with LPS (10ng/ml) for 6 hours. Total RNA was extracted from each sample (containing 1.0 × 106 macrophages) using TRIzol reagent, following the manufacturer's instructions and cDNA library preparation for RNA-sequencing analysis. cDNA library preparation and sequencing were both performed by Annoroad Gene Technology (Beijing) Co., Ltd.