Leukotriene B4 antagonism ameliorates experimental lymphedema

Acquired lymphedema is a cancer sequela and a global health problem currently lacking pharmacologic therapy. We have previously demonstrated that ketoprofen, an anti-inflammatory agent with dual 5-lipoxygenase and cyclooxygenase inhibitory properties, effectively reverses histopathology in experimental lymphedema. We show that the therapeutic benefit of ketoprofen is specifically attributable to its inhibition of the 5-lipoxygenase metabolite leukotriene B 4 (LTB 4 ). LTB 4 antagonism reversed edema, improved lymphatic function, and restored lymphatic architecture in the murine tail model of lymphedema. In vitro, LTB 4 was functionally bimodal: Lower LTB 4 concentrations promoted human lymphatic endothelial cell sprouting and growth, but higher concentrations inhibited lymphangiogenesis and induced apoptosis. During lymphedema progression, lymphatic fluid LTB 4 concentrations rose from initial prolymphangiogenic concentrations into an antilymphangiogenic range. LTB 4 biosynthesis was similarly elevated in lymphedema patients. Low concentrations of LTB 4 stimulated, whereas high concentrations of LTB 4 inhibited, vascular endothelial growth factor receptor 3 and Notch pathways in cultured human lymphatic endothelial cells. Lymphatic-specific Notch1 −/− mice were refractory to the beneficial effects of LTB 4 antagonism, suggesting that LTB 4 suppression of Notch signaling is an important mechanism in disease maintenance. In summary, we found that LTB 4 was harmful to lymphatic repair at the concentrations observed in established disease. Our findings suggest that LTB 4 is a promising drug target for the treatment of acquired lymphedema.