Tet2 modulates M2 macrophage polarization via mRNA 5-methylcytosine in allergic rhinitis

Allergic rhinitis (AR) represents a hallmark of obvious hypersensitivity with an imbalance of immune responses, including abnormal macrophage activity in local tissues. It has been reported that alternatively activated macrophages (M2) may contribute to allergic pathogenesis. Ten-eleven translocation (Tet) enzymes can oxidize 5-methylcytosine (m5C) in mRNA, implying the epigenetic regulation of post-transcriptional RNA modification. Our previous study suggested that decreased Tet2 impairs the function of regulatory T cells, failing to exert a protective role in AR. However, the mechanism of Tet2 in macrophage polarization has been little discussed. In this paper, we investigate the regulatory role of Tet2 in macrophage polarization under allergic inflammation.

Macrophage immunofluorescence and eosinophil counts were used to confirm the inflammatory and polarized state in the nasal mucosa of AR patients. Additionally, we used Raw264.7 cells to explore the relationships among mRNA methylation, Tet2 expression, and the macrophage polarization process. Furthermore an Ovalbumin (OVA)-mediated AR mouse model was established with wild-type (WT) and Tet2 gene knockout (Tet2^-/-) mice to verify the role of Tet2 in AR severity and macrophage polarization. The final stage comprised RNA sequencing, methylated RNA immunoprecipitation with qPCR (MeRIP-qPCR) using bone marrow-derived macrophages (BMDMs) from WT and Tet2^-/- mice to explore the effect of Tet2 deficiency on the mRNA methylation level of M2-related genes under OVA treatment. A two-tailed Student's t-test was used to compare two groups, and Spearman correlation analysis was applied for relationship analysis.

M2-macrophages were confirmed as the dominant subtype associated with eosinophil levels in AR nasal tissues. In vitro analyses demonstrated that mRNA methylation and Tet2 are linked to M2 macrophages. Additionally, we found that Tet2 influences local allergic severity and macrophage polarization. Specifically, Tet2 deficiency decreased the mRNA m5C demethylation levels of Klf4 and Rock1, contributing to M2 polarization in an allergic state.

The findings of this study demonstrate that Tet2 may play a protective role in AR by negatively regulating M2-related factors through mRNA m5C demethylation. These findings provide new insights into AR therapy, suggesting that intervening in macrophage polarization at the post-transcriptional level could be a novel therapeutic strategy.