TRAF1 Inhibits Macrophage Killing of Sporothrix schenckii by Enhancing NOS2 Expression and Activity

Abstract Background Sporotrichosis is a chronic, deep fungal infection of skin caused by S.schenckii. Macrophages are predominant in S.schenckii infected skin and able to phagocytize and kill the fungus. Local hyperthermia is effective to treat sporotrichosis, however, its mechanism of action remains not fully understood. Methods Using single-cell RNA sequencing of sporotrichosis lesions, coupled with in vitro and in vivo sporotrichosis models, we investigated the role of TRAF1 and NOS2. Mechanistic studies included co-immunoprecipitation, ubiquitination assays, and site-directed mutagenesis. Therapeutic mechanism of hyperthermia were evaluated in vivo and in vitro. Results We demonstrated for the first time that TRAF1 could delay the healing of sporotrichosis by inhibiting phagocytosis and killing of macrophages to S.schenckii. This effect of TRAF1 is caused by binding NOS2 to regulate its expression and enzymatic activity, through inhibition of NOS2 ubiquitination and subsequent proteasome-induced degradation. Our team's previous research has demonstrated the efficacy of hyperthermia in treating sporotrichosis. Our experiments indicate that hyperthermia can downregulate the expression of TRAF1 and NOS2 in macrophages. Conclusions We identify TRAF1-mediated stabilization of NOS2 as a key immune evasion mechanism in S. schenckii infection. Local hyperthermia represents a targeted therapy against this pathway, offering a novel strategy for enhancing the therapeutic effect of hyperthermia.