KEAP1 and pulmonary arterial hypertension: In addition, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4)-derived reactive oxygen species (ROS) have been shown to promote the activation of a number of growth factors and promote a change in endothelial cell phenotype to mesenchymal via the TGF-β pathway and have also been implicated in the proliferation of PAH PASMCs [23], which may have been associated with dysregulation of the Kelch-like ECH-associated protein 1 (Keap-1)/Nrf2 pathway [15].