Quercetin and lupeol accelerate keratinocyte wound healing by dual modulation of GLP-1 receptor activity and stability.

AIMS: While primarily known for its critical role in glucose metabolism, the glucagon-like peptide-1 receptor (GLP-1R) is increasingly recognized for its significant involvement in tissue repair and regeneration. This study comprehensively investigates how the natural compounds, quercetin and lupeol, regulate GLP-1R expression, protein stability, and subsequent downstream signaling pathways in keratinocytes. MATERIALS AND METHODS: Cells were treated with quercetin or lupeol. GLP-1R expression was analyzed at both mRNA and protein levels. Promoter regulation was evaluated by luciferase assays, site-directed mutagenesis, and chromatin immunoprecipitation. Molecular docking, molecular dynamics (MD) simulations, and cycloheximide chase assays evaluated GLP-1R interactions and stability. Downstream signaling and wound-healing markers were examined by Western blotting. KEY FINDINGS: Quercetin and lupeol significantly increased GLP-1R expression and protein stability through complementary mechanisms. Quercetin enhanced GLP-1R transcription via GATA6-dependent promoter activation, leading to ERK-mediated β-catenin phosphorylation and increased expression of COL1A1, COL4A1, and MMP9, indicating enhanced extracellular matrix remodeling. In contrast, lupeol predominantly promoted a proliferative response by markedly increasing Cyclin D1 together with COL4A1 expression. Molecular docking and MD simulation predicted quercetin binding to GLP-1R residues Ser31 and Leu32 and lupeol binding to Leu32, consistent with cycloheximide chase assays demonstrating delayed GLP-1R degradation. SIGNIFICANCE: These findings identify quercetin and lupeol as natural modulators of GLP-1R that enhance receptor availability through distinct transcriptional and post-translational mechanisms. By activating ERK-dependent regenerative signaling, quercetin primarily promotes matrix remodeling, whereas lupeol supports cellular proliferation, highlighting their therapeutic potential for modulating GLP-1R-mediated tissue repair.