The effects of siRNA-mediated knockdown of AP-1 on pulmonary arterial and right ventricular dysfunction associated with cardiac and pulmonary fibrosis in cardiopulmonary disease

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Romania’s National Recovery and Resilience Plan, PNRR-III-C9-2022-I8, CF 93/15.11.2022, Financing Contract no. 760063/23.05.2023, and by the Romanian Academy Pulmonary hypertension (PH) is a complex multifactorial vascular pathology characterized by an increased pulmonary arterial pressure, vasoconstriction, remodelling of the pulmonary vasculature, thrombosis in situ and inflammation associated with right-side heart failure. Herein, we explored the potential beneficial effects of treatment with siRNA AP-1 on pulmonary arterial and right ventricular dysfunction and perivascular and interstitial fibrosis in pulmonary artery (PA), right ventricle (RV) and lung in an experimental animal model of monocrotaline (MCT)-induced pulmonary arterial hypertension. Golden Syrian hamsters were divided into: (1) C group; (2) MCT group obtained by a single subcutaneous injection of 60 mg/kg MCT at the beginning of the experiment; (3) MCT- siRNA AP-1 group received a one-time subcutaneous dose of MCT and subcutaneous injections containing 100nM siRNA AP-1, every two weeks. All animal groups received water and standard chow ad libitum for 3 months. In comparison with the MCT group, siRNA AP-1 treatment had significant beneficial effects contributing to: (1) a reduction in TGF-β1/ET-1/IL-1β plasma concentrations; (2) a reduced level of cytosolic ROS production in PA, RV and lung, and ultrastructural improvements of these tissues; (3) a decrease of inflammatory and fibrotic marker expressions in PA (COL1A, Fibronectin, Vimentin, α-SMA, CTGF, Calponin, MMP-9), RV (COL1A, CTGF, Fibronectin, α-SMA, F-actin, OB-cadherin) and lung (COL1A, CTGF, Fibronectin, α-SMA, OB-cadherin), and an increase of endothelial marker expressions (CD31/VE-cadherin) in PA; (4) structural and functional recoveries of PA (reduced VTI/Vel, restored vascular response) and RV (enlarged internal cavity diameter in diastole, increased TAPSE/PRVOFs) associated with a decrease in systolic/diastolic blood pressure, and heart rate; (5) a reduced protein expression profile of AP-1S3/ pFAK/FAK/pERK/ERK and a significant decrease in the expression levels of miRNA-145, miRNA-210, miRNA-21, and miRNA-214 along with an increase of miRNA-124 and miRNA-204. The siRNA AP-1-based therapy led to an improvement of pulmonary arterial and right ventricular function accompanied by a regression of perivascular and interstitial fibrosis in PA, RV and lung and a down-regulation of key inflammatory and fibrotic markers in MCT-treated hamsters.