Enzymatically hydrolyzed low-density lipoprotein modulates inflammatory responses in endothelial cells

Area of Science:

• Biochemistry
• Cell Biology
• Immunology

Background:

• Modified low-density lipoprotein (E-LDL) selectively induces interleukin-8 (IL-8) in endothelial cells.
• Nuclear factor-kappaB (NF-kappaB) is a key regulator of IL-8 transcription.

Purpose of the Study:

• To investigate the effect of E-LDL on NF-kappaB activation in endothelial cells.
• To elucidate the molecular mechanisms underlying E-LDL's influence on IL-8 production.

Main Methods:

• Electrophoretic mobility shift assays and immunofluorescence to assess NF-kappaB activation.
• Analysis of inhibitor of NF-kappaB (IkappaB) phosphorylation and activator protein-1 (AP-1) activation.
• Chromatin immunoprecipitation to determine transcription factor binding to the IL-8 promoter.

Main Results:

• E-LDL inhibited NF-kappaB activation by tumor necrosis factor-alpha (TNF-alpha) in EA.hy926 cells.
• Inhibition occurred upstream of NF-kappaB translocation, with suppressed IkappaB phosphorylation.
• E-LDL activated AP-1, and removal of free fatty acids abolished both AP-1 activation and NF-kappaB inhibition.

Conclusions:

• E-LDL modulates endothelial IL-8 production through differential regulation of NF-kappaB and AP-1.
• Phosphorylated c-jun, not NF-kappaBp65, bound to the IL-8 promoter.
• These findings suggest a protective role for E-LDL-induced IL-8 in vessel wall homeostasis and lipoprotein clearance.