PTGS2 and chronic obstructive pulmonary disease: Although in vitro studies have reported COX-2 upregulation by CSE in non-pulmonary artery cell types, such as human small airway epithelial cells [25], in endothelial cells, such as human umbilical vein endothelial cells [26] and human pulmonary microvascular endothelial cells [27], and in vivo studies have demonstrated COX-2 induction in the lung tissue of both patients with COPD and smokers without COPD compared with non-smokers without COPD [26], our study is the first to show that CSE induces COX-2 expression in PASMCs and PAECs, the two cell main types of pulmonary artery vasculature.