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Published on: December 23, 2010
Leukotriene B4 antagonism ameliorates experimental lymphedema
Wen Tian1,2, Stanley G Rockson3, Xinguo Jiang1,2
1VA Palo Alto Health Care System, Palo Alto, CA 94304, USA.
Abstract:
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 B4 (LTB4). LTB4 antagonism reversed edema, improved lymphatic function, and restored lymphatic architecture in the murine tail model of lymphedema. In vitro, LTB4 was functionally bimodal: Lower LTB4 concentrations promoted human lymphatic endothelial cell sprouting and growth, but higher concentrations inhibited lymphangiogenesis and induced apoptosis. During lymphedema progression, lymphatic fluid LTB4 concentrations rose from initial prolymphangiogenic concentrations into an antilymphangiogenic range. LTB4 biosynthesis was similarly elevated in lymphedema patients. Low concentrations of LTB4 stimulated, whereas high concentrations of LTB4 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 LTB4 antagonism, suggesting that LTB4 suppression of Notch signaling is an important mechanism in disease maintenance. In summary, we found that LTB4 was harmful to lymphatic repair at the concentrations observed in established disease. Our findings suggest that LTB4 is a promising drug target for the treatment of acquired lymphedema.
Insights
Leukotriene B4 (LTB4) plays a dual role in lymphedema, promoting repair at low levels but hindering it at high concentrations. Targeting LTB4 offers a potential therapeutic strategy for acquired lymphedema.
Area of Science:
- Biomedical Science
- Molecular Biology
- Pathology
Background:
- Acquired lymphedema is a significant global health issue with limited pharmacological treatments.
- Ketoprofen, an anti-inflammatory drug, has shown promise in reversing lymphedema pathology.
- The specific mechanism behind ketoprofen's efficacy was previously unclear.
Purpose of the Study:
- To investigate the precise role of leukotriene B4 (LTB4) in acquired lymphedema.
- To determine if LTB4 antagonism could serve as a therapeutic strategy for lymphedema.
- To elucidate the molecular pathways affected by LTB4 in lymphatic endothelial cells.
Main Methods:
- Utilized a murine tail model to study lymphedema progression and treatment.
- Administered ketoprofen and assessed its effects on edema, lymphatic function, and architecture.
- Investigated the in vitro effects of varying LTB4 concentrations on human lymphatic endothelial cells.
- Analyzed LTB4 levels in lymphatic fluid and patient samples.
- Examined the impact of LTB4 on vascular endothelial growth factor receptor 3 and Notch pathways.
- Used lymphatic-specific Notch1-deficient mice to assess the role of Notch signaling.
Main Results:
- Ketoprofen's therapeutic benefit was specifically linked to the inhibition of LTB4.
- LTB4 antagonism reversed edema, improved lymphatic function, and restored lymphatic architecture in mice.
- In vitro studies revealed a bimodal effect of LTB4: promoting cell growth at low concentrations and inhibiting it at high concentrations.
- LTB4 concentrations increased during lymphedema progression, shifting from a pro-lymphangiogenic to an anti-lymphangiogenic range.
- Elevated LTB4 biosynthesis was observed in lymphedema patients.
- High LTB4 concentrations inhibited key pathways (VEGFR3, Notch) in lymphatic endothelial cells.
- Notch1-deficient mice showed refractoriness to LTB4 antagonism, highlighting LTB4's role in disease maintenance via Notch signaling suppression.
Conclusions:
- LTB4 is detrimental to lymphatic repair at the concentrations found in established lymphedema.
- LTB4 acts as an anti-lymphangiogenic factor at elevated levels, contributing to disease progression.
- Targeting LTB4 represents a promising therapeutic avenue for acquired lymphedema treatment.
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