CD40-40L signaling in vascular inflammation

Area of Science:

• Cardiovascular Biology
• Molecular Signaling
• Immunology

Background:

• CD40 ligation in the vasculature can promote inflammation, plaque instability, and thrombosis.
• The precise redox-sensitive signaling mechanisms linking CD40-CD40L interactions to inflammatory mediator release remain incompletely understood.
• Previous work indicated CD40-CD40L interactions modulate reactive oxygen species (ROS) release.

Purpose of the Study:

• To elucidate the signaling pathway by which CD40L binding to CD40 mediates inflammatory secretion in endothelial cells.
• To investigate the role of redox sensitivity in CD40L-induced inflammatory responses.
• To identify key kinases and transcription factors involved in CD40L-mediated endothelial cell activation.

Main Methods:

• Endothelial cells were treated with recombinant CD40L or adenoviral vectors.
• Pharmacological inhibitors of phosphatidylinositol 3-kinase (PI3K) and p38 mitogen-activated protein kinase (MAPK) were used.
• Adenovirus-mediated gene transfer was employed to inactivate Akt and p38 MAPK.
• Confocal microscopy assessed nuclear translocation of NF-kappaB.
• Intracellular CD40L and MCP1 levels were quantified.

Main Results:

• CD40L dose-dependently induced intracellular CD40L and MCP1 release in endothelial cells in a redox-sensitive manner.
• Inhibition of PI3K and p38 MAPK, or inactivation of Akt and p38 MAPK, blocked CD40L effects.
• Akt mediated CD40L-induced CD40L synthesis and MCP1 release via NF-kappaB activation in a redox-sensitive pathway.
• CD40L stimulation promoted NF-kappaB nuclear translocation, an effect augmented by Akt and inhibited by Akt inactivation.

Conclusions:

• Redox-sensitive CD40-CD40L interactions activate Akt and p38 MAPK, leading to NF-kappaB stimulation.
• This pathway enhances the synthesis of CD40L and MCP1 in endothelial cells.
• Elevated CD40L and MCP1 may contribute to atherothrombosis by increasing the adherence of CD40-positive cells like monocytes and platelets to the vessel wall.