BACKGROUND

Although it has been established that protein kinase D (PKD) plays a crucial role in various diseases, its precise role in myocarditis remains elusive.

METHODS

To investigate PKD's involvement in myocarditis, we established a mouse model of myocarditis using doxorubicin (DOX) to assess cardiac function, observe pathological changes, and quantify inflammatory cytokine levels in heart tissues. Additionally, macrophages were isolated from heart tissues of both control and DOX-treated groups to assess PKD expression and inflammatory cytokines in these macrophages. We explored the molecular mechanism of Neurogenic Differentiation 2 (NeuroD2) in myocarditis by utilizing NeuroD2 overexpression plasmids and NeuroD2 small interfering RNA (siRNA). Furthermore, we conducted dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays to investigate the interaction between NeuroD2 and PKD.

RESULTS

We observed significant upregulation of PKD in macrophages and heart tissues induced by DOX. The administration of a PKD inhibitor reduced inflammatory cytokine levels, improved cardiac function, and mitigated pathological changes in myocarditis-afflicted mice. Mechanistically, we found upregulated expression of NeuroD2 in both macrophages and heart tissues exposed to DOX. NeuroD2 could directly target PKD, enhancing the NLRP3/NF-κB signaling pathway and exacerbating macrophage inflammation.

CONCLUSIONS

Our study demonstrates that NeuroD2 can directly bind to the PKD promoter, potentially promoting inflammatory activation of macrophages in DOX-induced myocarditis via the NLRP3/NF-κB pathway. This suggests that the NeuroD2/PKD axis may hold promise as a potential therapeutic approach for treating DOX-induced myocarditis.