Disruption of host E3 ubiquitin ligase Smurf1 promotes resistance to Salmonella by enhancing bacterial clearance and limiting inflammatory tissue damage

Background Smurf1 is an E3 ubiquitin ligase that negatively regulates innate immune signaling and plays roles in host resistance to mycobacterial and viral infections. Its function during Salmonella infection remains unknown. Objective To investigate the impact of Smurf1 on innate immunity against Salmonella enterica serovar Typhimurium ( S. Typhimurium) using in vitro and in vivo models. Methods Bone marrow-derived macrophages (BMDMs) from wild-type and Smurf1 -/- mice were infected with S. Typhimurium to assess bacterial replication, p38 MAPK activation, cytokine production, and cell viability. Wild-type and Smurf1 -/- mice were infected intraperitoneally or orally, and bacterial burden, cytokine levels, histopathology, and survival were evaluated. The effect of pharmacological Smurf1 inhibition with compound A01 was assessed in macrophages and mice. Results Smurf1 -/- macrophages showed enhanced p38 MAPK activation and higher Tnf and Il10 mRNA at early stages of infection when bacterial burdens were equivalent, consistent with Smurf1 acting as a negative regulator of signaling induced by microbial ligands. At later time points, Smurf1 -/- macrophages exhibited significantly reduced intracellular S. Typhimurium replication, without differences in bacterial uptake or cell viability, accompanied by lower secretion of TNF, IL-6, IL-1β, IL-12, CXCL1, and IL-10. Smurf1 -/- mice showed lower bacterial loads in liver and spleen, reduced hepatic cytokine levels, attenuated tissue damage, and improved survival compared to wild-type controls. A01-mediated Smurf1 inhibition reduced bacterial burden and cytokine production in macrophages and mice. Conclusion Smurf1 promotes S. Typhimurium replication and amplifies infection-induced immunopathology, acting as a host susceptibility factor during salmonellosis. These findings suggest Smurf1 as a potential therapeutic target to enhance bacterial clearance and limit tissue damage.