Furthermore, PAH is closely associated with the changes of the intracellular oxidant state, many antioxidant factors maintain the vascular homeostasis, such as the nuclear factor E2 related factor 2 (NFE2L2), heme oxygenase 1 (HMOX-1), quinone oxidoreductase 1 (NQO1) and superoxide dismutase (SOD), whose expressions or enzyme activities may partially reflect the oxidant state of the organism 7, 8. Here, HMOX1 is linked to pulmonary arterial hypertension.