Endotoxin causes increased activity of IL-6 and acid sphingomyelinase (aSMase) in HPASMCs, promotes pulmonary vasoconstriction, induces endothelial dysfunction and enhances the contractile response to serotonin, ultimately leading to PH in patients with acute respiratory distress syndrome (ARDS) (170). The gene discussed is SMPD1; the disease is endothelial dysfunction.