MCC950 attenuates plasma cell mastitis in an MDSC-dependent manner

Plasma cell mastitis (PCM) is a sterile inflammatory condition primarily characterized by periductal inflammation and ductal ectasia. Currently, there is a lack of non-invasive or minimally invasive treatment option other than surgical intervention. The NLRP3 inflammasome has been implicated in the pathogenesis and progression of various inflammatory diseases, however, its involvement in PCM has not yet been reported. In this study, we initially observed the pronounced upregulation of NLRP3 in both human and mouse PCM tissue and elucidated the mechanism underlying the attenuation of PCM through inhibition of NLRP3. We established the PCM murine model and collected samples on day 14, when inflammation reached its peak, for subsequent research purposes. MCC950, an NLRP3 inhibitor, was utilized to effectively ameliorate PCM by significantly reducing plasma cell infiltration in mammary tissue, as well as attenuate the expression of pro-inflammatory cytokines including IL-1β, TNF-α, IL-2, and IL-6. Mechanistically, we observed that MCC950 augmented the function of myeloid-derived suppressor cells (MDSCs), which in turn inhibited the infiltration of plasma cells. Furthermore, it was noted that depleting MDSCs greatly compromised the therapeutic efficacy of MCC950. Collectively, our findings suggest that the administration of MCC950 has the potential to impede the progression of PCM by augmenting MDSCs both numerically and functionally, ultimately treating PCM effectively. This study provides valuable insights into the utilization of pharmacological agents for PCM treatment.