Background <p>Pulmonary arterial hypertension (PAH) is a hemodynamic disorder that can progress to right heart failure and result in death.</p> Objective <p>This study investigated the molecular mechanisms underlying the onset and progression of PAH to identify potential therapeutic targets.</p> Methods <p>Peripheral blood samples from PAH patients were analyzed to assess serum levels of DKK1 and CKAP4, as well as NF-κB pathway activation. Supernatants from hypoxia-treated pulmonary artery endothelial cells (PAECs), plasmid-transfected cells, and SC75741-treated cells were used to modulate pulmonary artery smooth muscle cells (PASMCs). RT-qPCR, Western blot, and ELISA were employed to quantify DKK1 and CKAP4 expression and evaluate NF-κB pathway activation in PASMCs. EdU staining and CCK-8 viability assay were performed to assess cell proliferation, while DCFH-DA staining and ELISA were used to measure ROS, SOD, and MDA levels. </p> Results <p>DKK1 and CKAP4 expression were positively correlated, and both were upregulated with increasing pulmonary artery systolic pressure (PASP) in PAH patients. The supernatant from hypoxia-exposed PAECs induced NF-κB pathway activation, cell proliferation, and oxidative stress in PASMCs, effects that were inhibited by siDKK1, siCKAP4, and SC75741.</p> Conclusions <p>Hypoxia stimulated PAECs to secrete DKK1, which in turn upregulated CKAP4 expression and activated the NF-κB pathway in PASMCs, promoting cell proliferation and oxidative stress.</p> Graphical abstract <p></p>