Quantitative Lipidomics in Pulmonary Alveolar Proteinosis

Rationale: Pulmonary alveolar proteinosis (PAP) is characterized by filling of the alveolar spaces by lipoprotein-rich material of ill-defined composition, and is caused by molecularly different and often rare diseases that occur from birth to old age.Objectives: To perform a quantitative lipidomic analysis of lipids and the surfactant proteins A, B, and C in lavage fluids from patients with proteinosis of different causes in comparison with healthy control subjects.Methods: During the last two decades, we have collected BAL samples from patients with PAP due to autoantibodies against granulocyte-macrophage colony-stimulating factor; genetic mutations in CSF2RA (colony-stimulating factor 2 receptor α-subunit), MARS (methionyl aminoacyl-tRNA synthetase), FARSB (phenylalanine-tRNA synthetase, β-subunit), and NPC2 (Niemann-Pick disease type C2); and secondary to myeloid leukemia. Their lipid composition was quantified.Measurements and Main Results: Free cholesterol was largely increased by 60-fold and cholesteryl esters were increased by 24-fold. There was an excessive, more than 130-fold increase in ceramide and other sphingolipids. In particular, the long-chain ceramides d18:1/20:0 and d18:1/24:0 were elevated and likely contributed to the proapoptotic environment observed in PAP. Cellular debris lipids such as phosphatidylethanolamine and phosphatidylserine were only moderately increased, by four- to sevenfold. The surfactant lipid class phosphatidylcholine expanded 17-fold, lysophosphatidylcholine expanded 54-fold, and the surfactant proteins A, B, and C expanded 144-, 4-, and 17-fold, respectively. These changes did not differ among the various diseases that cause PAP.Conclusions: This insight into the alveolar lipidome may provide monitoring tools and lead to new therapeutic strategies for PAP.