Abnormal Lymphatic Sphingosine-1-Phosphate Signaling Aggravates Lymphatic Dysfunction and Tissue Inflammation

Area of Science:

• Immunology
• Vascular Biology
• Cell Signaling

Background:

• Lymphedema is a global health issue lacking effective drug treatments.
• Dysregulated lymphatic endothelial cell (LEC) signaling and T-cell immunity are key therapeutic targets.
• Sphingosine-1-phosphate (S1P) signaling is crucial for LEC function and T-cell regulation.

Purpose of the Study:

• To investigate the role of S1P signaling in lymphatic endothelial cells (LECs) in lymphedema.
• To determine the impact of altered S1P signaling on T-cell activation and differentiation.
• To evaluate P-selectin as a therapeutic target for lymphedema.

Main Methods:

• Assessed S1P signaling in human and mouse lymphedema tissues.
• Generated LEC-specific S1pr1-deficient mice (S1pr1^LECKO) to study lymphedema progression.
• Co-cultured LECs with CD4 T cells to analyze T-cell activation and differentiation.
• Tested P-selectin blockade efficacy in vivo and in vitro.

Main Results:

• Decreased S1P signaling via S1PR1 in lymphedematous LECs correlated with disease severity.
• S1pr1 deficiency in LECs exacerbated lymphedema and increased CD4 T-cell infiltration.
• Inhibition of S1PR1 in LECs promoted T-helper cell differentiation and enhanced P-selectin expression.
• P-selectin blockade reduced lymphedema and Th1/Th2 immune responses in mice.

Conclusions:

• Reduced LEC S1P signaling aggravates lymphedema by increasing LEC adhesion and pathogenic T-cell responses.
• P-selectin inhibitors represent a potential therapeutic strategy for lymphedema treatment.