Activated factor X inhibition ameliorates NF-κB-IL-6-mediated perivascular inflammation and pulmonary hypertension

Activated factor X (FXa) induces inflammatory response and cell proliferation in various cell types via activation of proteinase-activated receptor-1 (PAR₁) and/or PAR₂. We thus aimed to investigate the impact of FXa on the development of pulmonary arterial hypertension (PAH) and the mechanisms involved. The effects of edoxaban, a selective FXa inhibitor, on hemodynamic, right ventricular (RV) hypertrophy, and vascular remodeling were evaluated in a monocrotaline (MCT)-exposed pulmonary hypertension (PH) rat model. At 21 days after a single subcutaneous injection of MCT of 60 mg/kg, right ventricular systolic pressure (RVSP) and total pulmonary vascular resistance index (TPRI) were elevated concomitant with the increased plasma FXa and lung interleukin-6 (<i>IL-6</i>) mRNA. Daily administration of edoxaban (10 mg/kg/day, by gavage) starting from the day of MCT injection for 21 days ameliorated RVSP, TPRI, RV hypertrophy, pulmonary vascular remodeling, and macrophage accumulation. Edoxaban reduced nuclear factor-kappa B (NF-κB) activity and <i>IL-6</i> mRNA level in the lungs of MCT-exposed rats. mRNA levels of <i>FXa</i>, <i>PAR₁,</i> and <i>PAR₂</i> in cultured pulmonary arterial smooth muscle cells (PASMCs) isolated from patients with PAH were higher than those seen in normal PASMCs. FXa stimulation increased cell proliferation and mRNA level of <i>IL-6</i> in normal PASMCs, both of which were blunted by edoxaban and PAR₁ antagonist. Moreover, FXa stimulation activated extracellularly regulated kinases 1/2 in a PAR₁-dependent manner. Inhibition of FXa ameliorates NF-κB-IL-6-mediated perivascular inflammation, pulmonary vascular remodeling, and the development of PH in MCT-exposed rats, suggesting that FXa may be a potential target for the treatment of PAH.<b>NEW & NOTEWORTHY</b> This study demonstrated that chronic treatment with activated factor X (FXa) inhibitor ameliorated NF-κB-IL-6-mediated perivascular inflammation in a rat model with pulmonary arterial hypertension, which is associated with elevated FXa activity. FXa may act on pulmonary arterial smooth muscle cells, inducing cell proliferation and inflammatory response via upregulated PAR₁, thereby contributing to pulmonary vascular remodeling. Understanding the patient-specific pathophysiology is a prerequisite for applying FXa-targeted therapy to the treatment of pulmonary arterial hypertension.