PLA2G7-Mediated Pro-Inflammatory Activation of Lipid-Associated Macrophages Drives Pulpitis.

AIM: Pulpitis is a common and painful disease characterised by complex and dynamic immune responses and may lead to irreversible tissue damage or tooth loss. Macrophages act as key sentinels that exhibit differential metabolic reprogramming, tightly orchestrating the immune microenvironment. However, the specific metabolic mechanisms governing macrophage-driven inflammatory activation in pulpitis remain unclear. Here, we reveal a specific lipid metabolism-driven immune pathway within macrophages in pulpitis.

METHODOLOGY: An integrative analysis of single-cell RNA sequencing (scRNA-seq), lipidomics and bulk RNA sequencing (RNA-seq) was employed to characterise macrophage subpopulations and metabolic alterations in pulpitis. Western blot and immunofluorescence staining were performed to validate the expression of phospholipase A2 group VII (PLA2G7) in human pulp tissues. In vitro, an inflammatory THP-1 macrophage model was established to investigate the effects of PLA2G7 inhibition and lysophosphatidylcholine (LPC) supplementation, and macrophage inflammatory activation was assessed by RT-qPCR, Western blot, ELISA and immunofluorescence staining. Bioinformatic analyses and fluorescence recovery after photobleaching (FRAP) experiments were conducted to identify the upstream transcriptional regulator of PLA2G7 and explore its regulatory mechanism. A murine pulpitis model treated with the PLA2G7 inhibitor darapladib was used to evaluate the anti-inflammatory effects by ELISA, immunohistochemical and immunofluorescence staining.

RESULTS: ScRNA-seq, lipidomics and RNA-seq analyses identified a distinct lipid-associated macrophage subset with high PLA2G7 expression in pulpitis. The abundance of this subset increased with inflammatory severity. Immunofluorescence and Western blot validated increased PLA2G7 expression in lipid-associated macrophages in pulpitis tissues. In vitro, inhibition of PLA2G7 significantly suppressed inflammatory responses, whereas supplementation with LPC attenuated this anti-inflammatory effect. In vivo, darapladib-mediated inhibition of PLA2G7 significantly attenuated pulpitis progression and reduced macrophage activation in mice. Mechanistically, integrative bioinformatic analysis identified JunD proto-oncogene (JUND) as a transcriptional regulator of PLA2G7, potentially via liquid-liquid phase separation (LLPS)-mediated transcriptional condensates.

CONCLUSIONS: These findings identify PLA2G7 as a potential biomarker for pulpitis and reveal a JUND-PLA2G7-LPC signalling axis linking lipid metabolism to macrophage-mediated inflammatory responses, providing a novel perspective for preserving dental pulp vitality.