In preclinical models of pulmonary fibrosis and pulmonary artery hypertension (PAH), genetic deletion of Sphk1 or inhibition of SPHK1 (but not SPHK2) activity with PF543, a small molecule inhibitor of SPHK1, reduced bleomycin-induced development of lung fibrosis or hypoxia-induced PAH in mice. The gene discussed is SPHK2; the disease is pulmonary arterial hypertension.