PTGS1 and pulmonary arterial hypertension: For example, we have previously shown that COX-1–derived prostanoids regulate airway function63 and others have shown roles for endogenous prostacyclin in lung fibrosis after bleomycin-induced lung injury64 and in regulating intravascular thrombosis in pulmonary hypertension.65 All these responses may be associated, partly or wholly, with prostacyclin derived from nonendothelial sources, which should now be considered.