Methyl ester sulfonate suppresses leydig cell steroidogenesis by targeting the GATA2/TGF-β1/SMAD signaling axis.

Exposure to environmental pollutants during development has been implicated in causing reproductive dysfunction in adult male mice, yet the specific molecular mechanisms by which certain pollutants induce such damage remain poorly understood. Methyl ester sulfonate (MES), a widely used anionic surfactant marketed as a "green" alternative, lacks a comprehensive assessment of its reproductive toxicity. To address this knowledge gap, we established a mouse model of developmental exposure, administering MES (0.06, 0.6, and 6 mg/L) via drinking water from gestational day (GD) 8.5 to postnatal day (PND) 56. Our results showed that developmental MES exposure induced significant histopathological alterations in adult male testes, including impaired blood-testis barrier (BTB) integrity, disorganized spermatocyte alignment, seminiferous tubule vacuolation, and testicular fibrosis. These structural defects were accompanied by significantly reduced serum testosterone and impaired spermatogenesis. Mechanistically, we combined RNA sequencing, molecular docking, and cell thermal shift assay-Western blotting (CETSA-WB) to uncover a novel pathway in Leydig cells (LCs). We demonstrated that MES directly bound to and stabilized the transcription factor GATA binding protein 2 (GATA2), which in turn activated the transforming growth factor-β1 (TGF-β1)/SMAD signaling pathway. This cascade suppressed luteinizing hormone receptor (LHR) expression, ultimately impairing testosterone synthesis. This study provides the first mechanistic evidence of MES induced reproductive toxicity in mammals, challenging its safety profile and highlighting a novel GATA2/TGF-β1/LHR axis that governs steroidogenesis. Our findings underscore the urgent need for a thorough environmental risk assessment of MES.