Mechanism of Bushen Wenyang Huayu Formula against oxidative damage by Let-7b-Bach1 in the treatment of endometriosis

ETHNOPHARMACOLOGICAL RELEVANCE: Endometriosis (EMs) is a prevalent and challenging gynecological disease and current therapeutic outcomes are suboptimal. Traditional Chinese medicine (TCM) has numerous advantages in treating EMs. Bushen Wenyang Huayu Formula (BWHF), a TCM prescription, has exhibited significant clinical efficacy in treating endometriosis (EMs). However, its exact molecular mechanism remains unclear. AIM OF THE STUDY: MicroRNA (miRNA) and oxidative stress (OS) are crucial for the occurrence and development of EMs. This study aims to explore the epigenetic mechanism underlying the efficacy of BWHF in affecting OS by altering miRNAs in EMs. MATERIALS AND METHODS: Fifty female SD rats were randomly divided into sham, model, low-dose BWHF (BWHF-L), high-dose BWHF (BWHF-H), and gestrinone groups, each consisting of 10 rats. The EMs rat model was established by autologous transplantation. Sham and model group were given with distilled water, and treatment group was given with BWHF or gestrinone. The therapeutic effects of BWHF on EMs were evaluated using ectopic lesion volume and morphology, inflammatory cytokine levels, and ROS levels. The expression of Let-7b was detected by CISH. Human endometrial stromal cells (hESCs) were treated with H2O2 to establish an OS cell model, followed by intervention with BWHF. hESCs migration and invasion were detected using wound healing and invasion assays. The expression of Bach1, Nrf2, and HO-1 in vivo and vitro were detected by immunohistochemistry staining, immunofluorescence staining, Western blot analysis, and qRT-PCR. The direct interaction of let-7b with the 3'-UTR of Bach1 mRNA was assessed using a dual-luciferase reporter assay. RESULTS: BWHF treatment inhibited the formation of ectopic lesions in EMs rats. Mechanistically, BWHF up-regulated let-7b, leading to decreased Bach1 expression and the subsequent relief of Bach1-mediated repression on the HO-1 promoter. Furthermore, BWHF elevated Nrf2 levels and facilitated its nuclear translocation. The translocated Nrf2 then bound to the HO-1 promoter to activate transcription, thereby counteracting oxidative stress and mitigating EMs. CONCLUSIONS: BWHF alleviates EMs by upregulating let-7b, which suppresses its target Bach1, thereby relieving Bach1-mediated repression of the HO-1 promoter and allowing for enhanced activation by Nrf2. This study reveals an epigenetic mechanism underlying the therapeutic effect of BWHF against EMs, providing valuable insights for advancing its clinical application.