Shikonin improves intestinal barrier function through modulation of GPX4 expression in intestinal epithelial cells

Shikonin has been reported to regulate caudal-type homeobox 2 (CDX2)-mediated intestinal epithelial cell (IEC) differentiation, and ferroptosis has been identified a critical event during this process. However, the exact role of ferroptosis in shikonin-induced IEC differentiation remains unclear. Accordingly, the aim of this study was to elucidate the involvement of ferroptosis in CDX2-mediated IEC differentiation induced by shikonin. Real-time polymerase chain reaction, western blotting, luciferase assay, immunoprecipitation, and chromatin immunoprecipitation were used to reveal the mechanism underlying shikonin-modulated ferroptosis-dependent IEC differentiation in HT-29 and Caco-2 cells. Shikonin treatment reduced ferroptosis in IECs, as evidenced by the increased expression of glutathione peroxidase 4 (GPX4) and solute carrier family 7 (cationic amino acid transporter) member 11, which enhanced CDX2 expression and improved IEC barrier function. Mechanistically, shikonin activated the protein kinase A (PKA)/cAMP-responsive element-binding protein (CREB) signaling cascade, promoting CREB binding to the GPX4 promoter and initiating GPX4 transactivation. GPX4 inhibition reversed the effects of shikonin on CDX2 expression. Endogenous pyruvate kinase isozyme M2 interacted with phosphodiesterase 4; this interaction was disrupted by shikonin, leading to the activation of PKA/CREB signaling. The findings of this study indicate that a low dose of shikonin improves IEC barrier function through GPX4-mediated inhibition of ferroptosis, highlighting its potential as a therapeutic agent for intestinal mucosal injury.