Uncovering a Glaucoma-Linked Lysophosphatidic Acid–MAPK/AP-1 Fibrosis Axis in Human Trabecular Meshwork Cells and Its Modulation by Diospyros kaki Leaf Extract

Dysregulated extracellular matrix (ECM) deposition and epithelial-mesenchymal transition (EMT) in the trabecular meshwork (TM) contribute to glaucoma-associated fibrotic remodeling, and lysophosphatidic acid (LPA) potently induces these profibrotic responses in human trabecular meshwork (HTM) cells. We investigated whether an ethanolic extract of <i>Diospyros kaki</i> leaves (EEDK) attenuates LPA-induced fibrosis and explored the underlying mechanisms. HTM cells were stimulated with LPA and treated with ethanol-based EEDK extracts. Expression of ECM/fibrosis-related genes (<i>FN1</i>, <i>ACTA2</i>, <i>COL1A1</i>, <i>COL3A1</i>, <i>COL4A1</i>, <i>COL6A2</i>, <i>CCN2</i>) and EMT markers (<i>CDH2</i>, <i>VIM</i>, <i>SNAI1</i>) was assessed, along with cell migration using a wound-healing assay. Upstream regulatory pathways were examined via transcription factor prediction, AP-1 reporter assays, and analyses of MAPK/AP-1 signaling. Among the extracts tested, the 70% ethanol EEDK extract showed the strongest antifibrotic activity, significantly reducing LPA-induced ECM gene/protein expression and inhibiting HTM cell migration in a dose-dependent manner, whereas the 90% ethanol extract showed minimal effects. LPA robustly activated MAPK-dependent AP-1 signaling, and either pharmacologic inhibition of MAPK pathways or treatment with 70% ethanol EEDK comparably suppressed AP-1 activity and decreased downstream ECM/EMT gene expression. Thus, 70% ethanol EEDK mitigates LPA-induced TM fibrosis by inhibiting MAPK/AP-1-mediated transcription, supporting its potential as an antifibrotic strategy for glaucoma.