Assessing the role of endothelium-protective drugs: Functional and molecular insights into chronic thromboembolic pulmonary hypertension derived endothelial cells.

Introduction: Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by the presence of organized clots obstructing the pulmonary arteries. Pulmonary endarterectomy (PEA) is the standard treatment, but in cases of inoperability, Riociguat, a soluble guanylate cyclase (sGC) stimulator, is the only approved pharmacological option. Endothelial dysfunction (ED) plays a central role, with the NO/sGC/cGMP pathway being critically involved. The aim of this study is to identify the molecular pathways contributing to ED and assess the therapeutic potential of Riociguat, BAY 60-2770, and Sildenafil in reinstating vascular homeostasis.

Materials And Methods: Endothelial cells (ECs) were isolated from PEA specimens of individuals diagnosed with CTEPH (CTEPH-EC). ECs derived from healthy pulmonary arteries (HPAECs) were used as controls. Cells were treated with different concentrations of Riociguat, BAY-60-2770 and Sildenafil, followed by functional assays, transcriptomic, and molecular analyses.

Results: The drugs used induced significant effects on endothelial cell dynamics, including decreased proliferation, increased apoptosis, and enhanced angiogenesis both in vitro and in vivo. Transcriptomic analysis followed by validation studies identified significant alterations in genes related to angiogenesis, with marked changes observed following BAY 60-2770 treatment. Dysregulation in the ERK/eNOS/PKG signaling pathway was demonstrated in CTEPH-EC compared to HPAEC at both the gene and protein level. Treatment with Riociguat and Sildenafil restored ERK/eNOS, but not PKG signaling.

Conclusion: Therapeutic approaches targeting endothelial dysfunction and the NO/sGC pathway in CTEPH partially restore endothelial function, highlighting the dual action of Riociguat and Sildenafil, stimulating sGC while exerting upstream effects by enhancing eNOS signaling. These findings underscore the importance of targeted pharmacological approaches to improve patient outcomes.