Characterizations of Pneumocystis carinii and rat lung lipids: glyceryl ethers and fatty alcohols.

Pneumocystis carinii carinii and rat lung phospholipids contained 3-6% 1-alkyl-2-acyl glycerols composed of the glyceryl ether species, 1-O-octadecyl glycerol (batyl alcohol), 1-O-octadec-9-enyl glycerol (selachyl alcohol), 1-O-hexadecyl glycerol (chimyl alcohol), and 1-O-hexadec-9-enyl glycerol. Of the major phospholipid classes, phosphatidylinositol (PI) and phosphatidylserine contained the highest percentage of alkyl acyl glycerols. Methylprednisolone treatment caused an increase in alkyl acyl PI of rat lung lipids from 12% to 45%. As the PI concentration in lung phospholipids increases in rats treated with methylprednisolone, the increase in alkyl acyl PI was substantial; the proportions of alkyl acyl phosphatidylethanolamine and alkyl acyl lyso phosphatidylcholine (PC) also increased. Pneumocystis phospholipids contained higher proportions of alkyl acyl PC than the phospholipids of the lungs from normal and immunosuppressed uninfected rats. The glyceryl ether compositions of P. carinii carinii PC and lyso PC were similar, which suggests that lyso PC in the organism is derived by phospholipase A2 action on PC. This was not the case for PC and lyso PC of the lung controls. Analysis of the free fatty alcohols, precursors of glyceryl ethers identified only saturated species in P. carinii carinii and rat lung controls. Thus, the introduction of a double bond in the alcohol moiety of glyceryl ethers occurs after formation of the ether linkage between fatty alcohol and the glyceryl backbone.

Characterizations of neutral lipid fatty acids and cis-9,10-epoxy octadecanoic acid in Pneumocystis carinii carinii.

Pneumocystis carinii causes pneumonitis in immunodeficient individuals and is a prevalent opportunistic infection of patients with AIDS. This pathogen resides extracellularly in the hypophase lining the alveolar epithelium, which is highly enriched in lung surfactant lipids. Procedures yielding highly pure organism preparations that enable reliable biochemical analyses of organisms isolated from the lungs of infected laboratory animals have been developed. The results of the present study revealed that the fatty acid profiles of total lipids, the neutral lipid traction, and individual neutral lipid classes of lungs from normal and immunosuppressed rats as well as P. carinii were grossly similar, although some quantitative differences were detected. One qualitative exception found was the detection in P. carinii of the rare fatty acid cis-9,10-epoxy stearic acid, which was not detected in the lipids of rat lungs. The detection of this fatty acid in P. carinii may also have important taxonomic implications. Unlike phospholipids, many of the fatty acids of nonmembrane neutral lipids may be utilized by P. carinii for other cellular functions, such as stored reserves for energy production and precursors for organism-specific membrane lipids. The present study represents the first report of detailed fatty acid analyses of individual neutral lipid classes of this important opportunistic pathogen.

Detailed analyses of individual neutral lipid classes of Pneumocystis.

Individual neutral lipid classes of Pneumocystis carinii carinii were isolated and purified by thin-layer chromatography. The fatty acids in steryl esters, triglycerides, free fatty acids, diglycerides, and monoglycerides were quantified by gas-liquid chromatography. The fatty acid compositions of these lipids were similar to those of the neutral lipid classes in whole rat lung controls, unlike comparable studies of phospholipid classes. The free fatty alcohols of rat lung controls and P. carinii were also identified and quantified; only saturated fatty alcohols were detected.