Tumor necrosis factor-alpha induces adhesion molecule expression through the sphingosine kinase pathway

Area of Science:

• Cellular Biology
• Immunology
• Biochemistry

Background:

• Signaling pathways linking tumor necrosis factor-alpha (TNFalpha) receptors to inflammatory responses are not fully understood.
• Endothelial cell activation is a key process in inflammation and immune responses.

Purpose of the Study:

• To elucidate the signaling pathway mediating TNFalpha-induced endothelial cell activation.
• To investigate the role of sphingosine kinase (SKase) and its product sphingosine 1-phosphate (S1P) in TNFalpha signaling.

Main Methods:

• Treatment of human umbilical vein endothelial cells with TNFalpha.
• Measurement of SKase activation, S1P generation, and adhesion protein expression (E-selectin, vascular adhesion molecule-1).
• Assessment of extracellular signal-regulated kinases (ERK) and NF-kappaB activation.
• Inhibition of SKase using N,N-dimethylsphingosine.

Main Results:

• TNFalpha rapidly activated SKase and increased S1P generation in endothelial cells.
• S1P, but not ceramide or sphingosine, dose-dependently stimulated adhesion protein expression.
• S1P mimicked TNFalpha's effects on ERK and NF-kappaB activation.
• SKase inhibition blocked TNFalpha-induced endothelial cell activation markers.

Conclusions:

• The SKase pathway, via S1P generation, is crucial for TNFalpha-induced endothelial cell activation.
• This pathway mediates inflammatory responses by activating ERK and NF-kappaB signaling.
• Findings reveal a key mechanism in TNFalpha-driven inflammation.