AP-1 Is an Initial Convergent Transcriptional Response in Lymphatic Endothelium to VEGF-C or TNFα

The lymphatic vasculature plays a central role in resolving inflammation by draining interstitial fluid, immune cells, and inflammatory mediators. While vascular endothelial growth factor C (VEGF-C) is a well-established driver of lymphangiogenesis, the effects of chronic pro-inflammatory cytokines on lymphatic remodeling remain incompletely defined.

Here, we investigated how tumor necrosis factor alpha (TNFα) compares with VEGF-C in regulating lymphatic endothelial structure and function using human dermal lymphatic endothelial cells (HDLECs).

In tube formation and spheroid sprouting assays, both VEGF-C and TNFα supported early lymphangiogenic events, promoting robust sprouting and network development within 24 h. However, when pre-formed microvascular networks were challenged, prolonged TNFα exposure triggered progressive destabilization, characterized by tube fragmentation, reduced proliferation, and impaired metabolic activity, whereas VEGF-C preserved network stability. Mechanistically, both VEGF-C and TNFα induced rapid phosphorylation of p38 MAPK and upregulation of Activator Protein-1 (AP-1) transcription factor subunits within 30 min, suggesting a convergent early transcriptional response. Bulk RNA-sequencing confirmed shared induction of AP-1 family genes (FOS, JUN, ATF), highlighting AP-1 as a candidate regulator of the transition between adaptive and maladaptive outcomes. We propose that transient AP-1 activation promotes pro-lymphangiogenic programs, while sustained TNFα signaling redirects AP-1 activity toward stress, growth arrest, and apoptosis, leading to lymphatic regression.

These findings identify TNFα as a temporally bifunctional regulator of lymphatic endothelial fate.