The pathogenesis of PAH involves multiple processes, interconnected at the molecular, cellular, and tissue levels, such as endothelial dysfunction [36,37], excessive vasoconstriction [38,39,40,41], vascular remodeling [3,42,43], oxidative stress, inflammation and immune dysregulation [40,44,45], metabolic dysregulation [46,47], and thrombosis [39,48], i.e., processes driven by iNOS overexpression (Figure 1). This evidence concerns the gene NOS2 and pulmonary arterial hypertension.