# NF-κB-Mediated Upregulation of Tissue Factor Contributes to the Procoagulant Phenotype of Smooth Muscle Cells from Abdominal Aorta Aneurysm in Human

## TL;DR

This study shows that smooth muscle cells from abdominal aortic aneurysms have a procoagulant trait due to increased tissue factor expression, driven by the NF-κB pathway.

## Contribution

The paper identifies the NF-κB-mediated upregulation of tissue factor as a novel mechanism for the procoagulant phenotype in abdominal aortic aneurysms.

## Key findings

- Smooth muscle cells from AAA show increased thrombin generation and phosphatidylserine exposure compared to TAA and healthy aorta.
- NF-κB p65 nuclear translocation and PAR-2 overexpression in AAA SMCs lead to higher TF gene expression.
- Pharmacological inhibition of IκK and PAR-2 reduces TF expression in AAA SMCs.

## Abstract

Aneurysms of the thoracic (TAA) and abdominal aorta (AAA) have different pathophysiological mechanisms. AAA has an intraluminal thrombus, while TAA does not. This suggests a prothrombotic phenotype in AAA, probably at the level of vascular smooth muscle cells (SMCs) known to express tissue factor (TF).

To explore the TF-dependent thrombin generation in SMCs in AAA compared with TAA and healthy aorta (HA) and the underlying mechanisms contributing to a procoagulant phenotype.

Human HA, AAA, or TAA tissues and corresponding SMC primary cultures were used to analyze SMC-supported thrombin generation and TF expression.

In the absence of added TF, thrombin generation was increased at the surface of SMCs from AAA compared with TAA and HA, indicating a cellular procoagulant phenotype, which is transmitted through mitosis. Phosphatidylserine exposure was increased at the surface of SMCs from AAA. As expected, reactive oxygen species generation and the proinflammatory cytokine TNF-α were increased in SMCs from AAA. Overexpression of protease-activated receptor 2 and nuclear translocation of NF-κB p65 in SMCs and tissue from AAA triggered increased TF gene expression. Higher active basal TF expression was also observed in SMCs from AAA, which was inhibited by BAY 11–7082 (pharmacological inhibitor of IκK) and GB83 (pharmacological inhibitor of PAR-2).

We demonstrated a PAR-2-mediated activation of the canonical NF-κB pathway, which triggers TF transcription in AAA. This procoagulant profile is transmitted from tissue to primary SMC cultures and through numerous passages, which can maintain thrombus formation.