Lysophosphatidic acid-mediated NF-κB activation promotes FOXC2 expression essential for lymphatic valve development.

The lymphatic system maintains tissue fluid balance, and FOXC2 mutations cause lymphoedema-distichiasis syndrome, which is characterized by lymphatic valve defects. Although oscillatory shear stress regulates FOXC2 expression, other extracellular regulators remain unclear. In this study, we identified LPA4 and LPA6, two Gα12/Gα13-coupled receptors for the bioactive lipid lysophosphatidic acid (LPA), as key regulators of FOXC2 expression and lymphatic valve development. Lymphatic endothelial cell-specific (LEC-specific) Lpa4 Lpa6-deficient mice exhibited impaired lymphatic valve formation and maintenance, which resembled phenotypes of LEC-specific Foxc2-deficient mice, including abnormal lymphatic vessel patterning. Mechanistically, lymphatic endothelial Lpa4/Lpa6 ablation reduced FOXC2 expression in vitro and in vivo. NF-κB was found to be essential for LPA-induced FOXC2 expression through the LPA4/LPA6-Gα12/Gα13-Rho kinase signaling axis. Accordingly, pharmacological inhibition of NF-κB and Rho kinase impaired lymphatic valve maintenance in mice. These results suggested that lymphatic endothelial LPA4 and LPA6 synergistically regulate FOXC2 expression through NF-κB activation and play an important role in lymphatic valve formation and maintenance. Our findings provide a molecular basis for lymphatic vessel development with a therapeutic potential for targeting lymphatic system-associated diseases.