HMOX1 and pneumothorax: In vitro experiments in a human monocyte/macrophage cell line, THP-1, cultured under conditions mimicking the condition of lung macrophages during the pneumothorax condition and treatment in smokers (CS exposure with short hypoxia then reoxygenation) showed that HIF-1α was responsible for inducing HO-1, BVR and H-ferritin expression.