Vascular endothelial growth factor promotes macrophage apoptosis through stimulation of tumor necrosis factor superfamily member 14 (TNFSF14/LIGHT)

Resolution of inflammation is critical for normal wound healing. Inflammation is prolonged and fails to resolve properly in chronic wounds. We used in vivo and in vitro approaches to show that vascular endothelial growth factor (VEGF) induces macrophage apoptosis and to delineate mechanisms involved in this process. VEGF inhibition during wound healing leads to an increased number of macrophages remaining in wounds, suggesting the involvement of VEGF in removal of these cells from the wound. If this effect has physiological relevance, it likely occurs via apoptosis. We show that VEGF increases apoptosis of macrophages in vitro using Annexin V-FITC staining and caspase activation. Microarray analysis, reverse transcription-polymerase chain reaction, and immunoblotting showed that VEGF increases the expression of tumor necrosis factor superfamily member 14 (TNFSF14/LIGHT) in macrophages. We also show that in macrophages LIGHT promotes apoptosis through the lymphotoxin beta receptor. Moreover, inhibition of LIGHT prevents VEGF-induced death, suggesting that LIGHT mediates VEGF-induced macrophage apoptosis. Taken together, our results identify a novel role for VEGF and for LIGHT in macrophage apoptosis during wound healing, an event critical in the resolution of inflammation. This finding may lead to the development of new strategies to improve resolution of inflammation in problematic wounds.