Sphingosine-1-phosphate receptor 3 promotes leukocyte rolling by mobilizing endothelial P-selectin

Area of Science:

• Immunology
• Cell Biology
• Vascular Biology

Background:

• Sphingosine-1-phosphate (S1P) is implicated in inflammatory processes.
• The precise role of S1P in leukocyte rolling remains incompletely understood.

Purpose of the Study:

• To elucidate the role of S1P in leukocyte rolling during inflammation.
• To identify the specific S1P receptors and signaling pathways involved.

Main Methods:

• Intravital microscopy in inflamed mouse cremaster muscle venules.
• Experiments using human endothelial cells.
• Genetic manipulation (S1P3 deficiency, endothelial-specific S1P1 knockout) and pharmacological inhibition.

Main Results:

• S1P administration enhances P-selectin-dependent leukocyte rolling.
• Endothelial S1P receptor 3 (S1P3) and downstream signaling (Gαq, PLCβ, Ca2+) are critical for S1P-mediated rolling.
• Mast cell-released S1P mobilizes P-selectin via S1P3.
• Histamine and epinephrine stimulate sphingosine kinase 1 (Sphk1) to promote rolling, requiring S1P3.
• S1P receptor 1 (S1P1) inhibits Sphk1 and blocks rolling, acting counter-regulatory to S1P3.

Conclusions:

• S1P is a significant direct and indirect mediator of leukocyte rolling in inflammation.
• The study characterizes the pro-rolling function of S1P3 and the counter-regulatory role of S1P1.
• These findings highlight S1P receptors as potential therapeutic targets for inflammatory conditions.