The modulatory effects of Nrf2 activators in a pulmonary arterial hypertension model

Background: Pulmonary arterial hypertension (PAH) is characterized by proliferation of vascular wall cells, including smooth muscle cells and increased lung microvasculature resistance. Oxidative stress is implicated in the pathogenesis of PAH mediating both vasoconstrictor and arterial remodelling. Targeting nuclear factor erythroid-derived 2-like 2 (Nrf2) has shown promising clinical results due to antioxidant, anti-inflammatory and anti-fibrotic effects. Our aim was to test the effect of Nrf2 activators on primary airway smooth muscle cells (PASMC) under oxidative stress. Methods: PASMC from n=3 healthy donors were cultured with Nrf2 activators CDDO, C4X_6665 and GSK Compound 7 (0.3-1000nM) or MMF and Sulforafane (1-10μM) for 48h under both normoxic (20% O2) and hypoxic (2% O2) conditions. Quantitative PCR for the Nrf2 target gene NQO1, monocyte chemoattractant protein-1 (MCP-1), thrombospondin (THBS) 1 and 4, endothelin-1 (EDN1) and type I collagen (COL1A1) and cell proliferation assays were performed. Results: All Nrf2 activator compounds induced a dose-dependent increase in NQO1 and decrease in EDN1 (vasoconstrictor) and THBS1 (regulator of angiogenesis and fibrosis) under both normoxic and hypoxic conditions. The non-selective Nrf2 activators CDDO and Sulforafane also reduced MCP-1 in both normoxic and hypoxic conditions. There were no effects on cell proliferation by any compounds apart from the top concentration of CDDO (100 nM) and Sulforafane (10 μM) which both reduced proliferation. Conclusion: Our data in PASMC cells demonstrate that Nrf2 activating compounds antagonise PAH pathways, even in the presence of hypoxic conditions.