Photochemically modulated endothelial cell thrombogenicity via the thrombomodulin-tissue factor pathways

Area of Science:

• Vascular biology
• Photochemistry
• Coagulation science

Background:

• Photodynamic therapy (PDT) utilizes photosensitizers and light to generate reactive oxygen species for biological effects.
• While PDT has applications involving thrombosis, preventing thrombosis is crucial in vascular treatments.
• Endothelial cells regulate coagulation via thrombomodulin (TM) and tissue factor (TF).

Purpose of the Study:

• To investigate the impact of PDT on thrombomodulin (TM) and tissue factor (TF) expression and activity in endothelial cells.
• To determine if PDT alters the procoagulant or anticoagulant balance of endothelial cells.
• To assess the potential implications for PDT's use in vascular settings.

Main Methods:

• Human umbilical vein endothelial cells were exposed to PDT using chloro-aluminum-sulfonated phthalocyanine and specific light wavelengths.
• TM and TF levels were quantified using fluorescence spectroscopy.
• Microparticle (MP) release and TF functionality were analyzed via flow cytometry and Factor Xa generation assays.

Main Results:

• PDT significantly decreased TM expression and increased functional TF expression in a light-energy dose-dependent manner.
• PDT-treated cells released substantial numbers of TF-containing microparticles.
• TF was predominantly found intracellularly and within microparticles, indicating altered cellular localization.

Conclusions:

• PDT disrupts the anticoagulant balance of endothelial cells, promoting a prothrombotic state.
• The observed changes in TM and TF may explain PDT-induced thrombosis.
• These findings raise concerns about PDT's suitability as an adjuvant therapy for vascular restenosis if the prothrombotic effects are not managed.