Selenium alleviates Staphylococcus aureus-induced mastitis by modulating mitochondrial dynamics and inhibiting the...

The pathogenesis of bovine mastitis involves inflammation and cell death, with pyroptosis being a key factor in its development. Currently, antibiotics remain the primary therapeutic option for bovine mastitis, however, the increasing prevalence of antibiotic resistance constitutes a major public health threat. Selenium (Se) has been reported to alleviate inflammation primarily through its antioxidant properties, but the mechanism by which Se regulates pyroptosis in bovine mastitis remains unclear.

In this study, an in vitro mastitis model was established by infecting MAC-T cells with inactivated Staphylococcus aureus (S. aureus) (MOI = 10, 12 h). The results revealed that the mitochondrial membrane potential of the MAC-T cells in the infection group decreased significantly. Moreover, the accumulation of Reactive oxygen species (ROS) was accompanied by the activation of NOD-like receptor family containing pyrin domain 3 (NLRP3), the expression of the pyroptosis-related genes gasdermin D amino terminal fragment (GSDMD-N), and cysteine ​​aspartate specific protease 1 (cleaved-caspase 1). Pretreatment with Se, the NLRP3 inhibitor MCC950 and the antioxidant N-acetylcysteine ​​(NAC) attenuated mitochondrial damage, ROS accumulation, and the inhibition of pyroptosis. An in vivo mastitis model was established in mice fed a high-selenium diet (containing 1.5 mg/kg Se) and intramammarily injected with inactivated S. aureus (1 × 10⁸ CFU/mL). Histological analysis revealed intact alveolar structure and reduced inflammatory cell infiltration in mice fed the high-selenium diet. The expression of the inflammasome NLRP3 downregulated, and the expression of GSDMD-N, a direct executor of pyroptosis, upregulated.

Our in vitro and in vivo results confirmed that Se alleviate mitochondrial damage and pyroptosis by inhibiting the NLRP3 pathway, ultimately alleviating mastitis.