Tumor necrosis factor decreases thrombin receptor expression in endothelial cells

Area of Science:

• Endothelial Cell Biology
• Inflammation Research
• Molecular Signaling

Background:

• The proteolytically activated thrombin receptor (PATR) plays a crucial role in endothelial cell function.
• Tumor necrosis factor-alpha (TNF alpha) is a key proinflammatory cytokine involved in various cellular processes.

Purpose of the Study:

• To investigate the impact of TNF alpha on PATR expression in human umbilical vein endothelial cells (HUVEC).
• To determine how TNF alpha-induced changes in PATR affect endothelial cell responsiveness to thrombin.

Main Methods:

• HUVEC were treated with TNF alpha, and PATR mRNA and protein levels were assessed using Northern analysis and immunoblotting.
• Nuclear run-on assays were performed to evaluate transcription rates.
• Thrombin-induced changes in intracellular calcium ([Ca2+]i) and endothelial cell shape (electrical impedance) were measured.

Main Results:

• TNF alpha treatment significantly decreased PATR mRNA and protein expression in a time- and dose-dependent manner.
• The reduction in PATR mRNA was attributed to decreased transcription rates.
• Endothelial cells pretreated with TNF alpha exhibited a blunted calcium response and reduced shape change upon thrombin stimulation, while histamine response remained unaffected.

Conclusions:

• TNF alpha downregulates both PATR mRNA and protein expression in HUVEC.
• The observed decrease in PATR expression explains the impaired thrombin signaling in TNF alpha-exposed endothelial cells.
• This finding highlights a mechanism by which inflammation can modulate endothelial cell responses to coagulation factors.