MT2A-Mediated Regulation of Cuproptosis in Human Dental Pulp Cells Modulates Macrophage M1 Polarization in Pulpitis

Background: The progression of pulpitis is strongly affected by the fate of dental pulp cells, with their modes of cell death determining whether inflammation resolves or leads to irreversible necrosis. Cuproptosis, a copper-dependent form of regulated cell death, has been implicated in inflammatory and metabolic disorders. Given the high metabolic activity of pulp cells and dynamic copper fluctuations during inflammation, cuproptosis may play a role in pulpitis, though this remains unexplored. Methods: Copper deposition was examined in inflamed dental pulp using copper staining, and cuproptosis activation was assessed by lipoylated Dihydrolipoamide S-acetyltransferase (lip-DLAT) expression through Western blot (WB) and immunofluorescence (IF). Key cuproptosis-related genes, including Metallothionein 2A (MT2A), were identified from Gene Expression Omnibus (GEO) datasets and validated. A mouse pulpitis model with MTII (MT2A ortholog in mouse) knockdown was used to evaluate pulp tissue changes via Hematoxylin and Eosin staining and IF staining, and immune infiltration analyses were performed to identify MT2A-related immune cells. Finally, an inflammatory human dental pulp cells (hDPCs) model was used to assess its effects on macrophages by flow cytometry. Results: Inflamed human pulp tissues exhibited marked copper accumulation and significantly elevated lip-DLAT expression, indicating activation of cuproptosis. Bioinformatic analysis of GEO datasets identified 6 hub cuproptosis-related genes, which were validated by reverse transcription quantitative polymerase chain reaction. In hDPCs, the cuproptosis inhibitor tetrathiomolybdate reduced copper overload, cell death, and lip-DLAT expression. Conversely, MT2A knockdown enhanced cuproptosis, as evidenced by increased copper accumulation, lip-DLAT levels, and IL-6 expression. Moreover, MT2A knockdown in the inflammatory hDPCs model promoted M1 macrophage polarization. Conclusion: Cuproptosis is activated in inflamed dental pulp and contributes to the pathogenesis of pulpitis. MT2A functions as a protective regulator, mitigating cuproptosis and modulating macrophage-mediated inflammatory responses. Targeting cuproptosis and MT2A may represent a novel therapeutic strategy for preserving pulp vitality.