Capsaicin Inhibits Ferroptosis through Facilitating SYVN1-Mediated Ubiquitination and Degradation of ACSL4.

As the primary active component of chili peppers, capsaicin (CAP) remains controversial regarding its potential carcinogenic effects. This study aimed to elucidate the role of capsaicin in tumor progression and its underlying molecular mechanisms. Cellular proliferation was assessed using MTT assay and soft-agar colony formation assay. Mitochondrial morphology was observed via transmission electron microscopy (TEM), while untargeted metabolomics and proteomics were combined to identify key targets. Molecular docking, cellular thermal shift assay (CETSA), and ACSL4 point mutant plasmid validation were employed to investigate mechanistic interactions. Results demonstrated that capsaicin inhibits ferroptosis by promoting ubiquitination of long-chain acyl-CoA synthetase 4 (ACSL4). Molecular docking and coimmunoprecipitation-mass spectrometry (Co-IP/MS) revealed that capsaicin and the E3 ubiquitin ligase SYVN1 synergistically target ACSL4. Key site mutation experiments confirmed that capsaicin directly binds to the Asp362 residue of ACSL4, enhancing its interaction with SYVN1. This promotes SYVN1-mediated polyubiquitination of ACSL4 at Lys367, ultimately suppressing ferroptosis and accelerating tumor progression. This study is the first to elucidate capsaicin's novel mechanism of antagonizing ferroptosis by regulating ACSL4 degradation via the ubiquitin-proteasome system. These findings provide a theoretical foundation for dietary interventions for colorectal cancer (CRC) patients.