Streptococcus equi subsp. zooepidemicus triggered NETs formation in neutrophils depending on GSDMD activation

Abstract Streptococcus equi subsp. zooepidemicus (SEZ) is an opportunistic pathogen that poses a significant threat to a diverse array of species. Neutrophils can release neutrophil extracellular traps (NETs) to eliminate bacteria. However, the role of NETs in SEZ infection remains poorly understood. This study aims to investigate the impact of gasdermin D (GSDMD) on NETs formation during SEZ infection. Our results reveal that SEZ infection induces murine lethality, accompanied by extensive neutrophil infiltration in the spleen, as corroborated by peritoneal lavage and hematological analyses. Mechanistically, ex vivo infection of bone marrow-derived neutrophils triggered robust NETosis, indicating that this process constitutes a critical anti-SEZ defense. Intriguingly, although SEZ infection upregulated GSDMD expression, genetic ablation of GSDMD paradoxically enhanced neutrophil recruitment to infection sites. Surprisingly, this amplified recruitment failed to augment NETs production, suggesting that GSDMD is essential for NETs release, which was evidenced by disulfiram treatment, a specific inhibitor of GSDMD pore formation. Consequently, GSDMD-deficient mice exhibited heightened lethality upon SEZ challenge, confirming the non-redundant function of GSDMD in orchestrating protective responses to infection. These results underscore the importance of neutrophils in the immune response against SEZ infection and reinforce the crucial role of GSDMD in NETs formation.