ALOX5 and pulmonary arterial hypertension: Recent evidence demonstrates that leukotrienes (LTs), important eicosanoid products of leukocytes, including macrophages, play an essential role in the inflammatory mechanism in PAH (Bittleman and Casale, 1995): in patients with PAH, it was highlighted that the level of 5-lipoxygenase (5-LO) expression is increased in pulmonary macrophages and small pulmonary artery endothelial cells (PAECs) (Wright et al., 1998).