Quercetin Suppresses LCN2 and Restores Autophagy via the MAPK/ERK–mTOR Pathway in Bovine Endometrial Epithelial Cells and Attenuates Fibrotic Remodeling in LPS-Induced Mouse Endometritis

Bovine endometritis frequently progresses to endometrial fibrosis, a leading cause of implantation failure and infertility in dairy cows, yet the upstream events that disrupt endometrial autophagy during uterine inflammation remain poorly defined, and the anti-fibrotic target of quercetin (Que) in the bovine endometrium is unknown. We therefore combined data-independent acquisition (DIA) proteomics of healthy and fibrotic bovine endometria (n = 4 per group) with network pharmacology, molecular docking and a cellular thermal shift assay (CETSA), gain- and loss-of-function studies in TGF-β1-stimulated primary bovine endometrial epithelial cells (BEECs), and a 48 h LPS-induced mouse endometritis model in female C57BL/6 mice. LCN2 was markedly upregulated in fibrotic endometria and was prioritized among five candidate targets; docking predicted binding within the LCN2 pocket, and CETSA showed increased thermal stability of LCN2, consistent with target engagement. In BEECs, LCN2 overexpression activated MAPK/ERK–mTOR signaling, suppressed autophagic flux and promoted epithelial–mesenchymal transition (EMT), whereas LCN2 silencing reversed these phenotypes. Quercetin dose-dependently reduced LCN2 abundance and MAPK/ERK–mTOR phosphorylation, restored autophagic flux and reversed TGF-β1-induced EMT, and ERK inhibition abolished the LCN2-driven phenotype. In LPS-challenged mice, oral quercetin lowered uterine LCN2, recovered autophagy markers and reduced collagen deposition and endometrial damage. These preclinical findings associate LCN2 with impaired endometrial autophagy and EMT and suggest that quercetin may attenuate this cascade; binding affinity, LCN2 dependency and efficacy in cattle were not established and require validation in larger cohorts, purified-protein binding assays and chronic bovine models.