Berberine from Tibetan Medicine Dracocephalum tanguticum Maxim Suppresses Colorectal Tumor Growth and Inhibits CD8⁺ T Cells Ferroptosis via the NRF2–SLC7A11–GPX4 Axis

Objective: This study aimed to identify berberine as the candidate active constituent of Dracocephalum tanguticum Maxim ( D. tanguticum ) and to investigate whether it suppresses colorectal tumor growth by inhibiting ferroptosis in cytotoxic T lymphocytes via the NRF2–SLC7A11–GPX4 axis. Methods: The antitumor activity of D. tanguticum ethanol extract (DME) was evaluated in CT-26 murine colorectal cancer cells using CCK-8, wound healing, and colony formation assays. Flow cytometry was used to determine the proportion of CD8+ T cells in tumor-bearing mice and to assess exhaustion markers on tumor-infiltrating CD8+ T cells. Transcriptomic sequencing and molecular docking were performed to identify the interaction between berberine (BBR), tentatively identified as a candidate active constituent of DME, and GPX4, and the effect of BBR on erastin-induced ferroptosis in CD8⁺ T cells was subsequently validated. Results: BBR, a putatively annotated candidate metabolite putatively annotated from DME, attenuated ferroptosis in tumor-infiltrating CD8⁺ T cells, as confirmed by rescue assays using ferroptosis inducers. Accordingly, BBR treatment increased the proportion of functional CD8⁺ T cells while reducing exhausted T-cell populations in both in vitro and in vivo models. Mechanistically, BBR activated the NRF2–SLC7A11–GPX4 axis, leading to GPX4 upregulation and ferroptosis suppression in CD8⁺ T cells. Conclusion: Berberine, a candidate metabolite derived from D. tanguticum , enhances CD8+T cells function and suppresses ferroptosis via the NRF2–SLC7A11–GPX4 pathway, supporting its further development as a novel immunotherapeutic agent for colorectal cancer.