HMOX1 and pulmonary arterial hypertension: After 24 h of exposure, cytokine expression (IL1B, IL6, CXCL8, TNF) as well as PAH biomarkers previously identified for chemical metabolism (CYP1A1, CYP1B1), oxidative stress (ALDH3A1, HMOX1, NQO1), and barrier integrity (TJP2) were evaluated.