Hemin Inhibits the Activation of STING in Macrophages by Inducing HO-1, Promoting Endometriosis Development

Introduction: Endometriosis (EMS) is an estrogen-dependent inflammatory disorder characterized by immune dysregulation. This condition profoundly affects the quality of life and reproductive health of nearly 200 million women of reproductive age worldwide and poses significant clinical challenges due to lack of diagnosis tools and effective treatment. Peritoneal macrophages play a central role in promoting the initiation and progression of EMS. Bioinformatics studies have indicated that the STimulator of INterferon Gene (STING) was downregulated in the macrophages in EMS, and this influenced their polarization and functional. However, the specific contribution of STING pathway alterations to EMS pathogenesis remains unclear. Methods: We integrated scRNA-seq data from EMS patients and healthy controls－including lesions, eutopic endometrium, non-lesional tissue, and peritoneal fluid from EMS patients and healthy controls(n = 19,291 total samples)－to analyze macrophage STING expression and function. Mouse EMS model was generated by injecting uterus fragments into WT or STING-/- mice. Peritoneal fluid was collected and macrophage proportions and subtypes were assessed via flow cytometry. Macrophages were depleted in STING-/- mice prior to EMS induction to evaluate their role in disease progression. In vitro, hemin was used to treat macrophages to investigate how heme oxygenase-1 (HO-1) modulates the STING pathway, assessed through immunoblotting, co-immunoprecipitation, ELISA, and multiplex immunofluorescence. Results: Bioinformatic analysis revealed that macrophages within the EMS lesions are primarily derived from peritoneal macrophages and exhibit decreased STING expression, which correlated negatively with HO-1. STING-/- mice developed more numerous and larger EMS lesions, accompanied by a decreased proportion of large peritoneal macrophages and an increase in small peritoneal macrophages. A marked elevation in M2-type macrophages within the lesions was detected in STING-/- mice. In vitro, hemin-induced HO-1 suppressed STING pathway activation in macrophages. Mechanistically, HO-1 inhibited the translocation of STING from the endoplasmic reticulum to the Golgi, thereby suppressing STING signaling and facilitating EMS. Conclusion: Macrophages are essential for lesion formation in STING-/- mice. In vitro, hemin promotes EMS progression via HO-1－mediated suppression of the STING pathway. Our findings identify the heme-HO-1-STING axis as a key immunomodulatory pathway in EMS and suggest its potential as a therapeutic target.