Mass spectrometric analysis of ceramide composition in mono-, di-, tri-, and tetraglycosylceramides from mouse kidney: an experimental model for uropathogenic Escherichia coli.

Many bacteria have been shown to bind to the carbohydrate part of glycosphingolipids, but also the lipid moieties of receptor-active glycolipids are of importance. To investigate the chemistry of the ceramides of kidney glycolipids to which the uropathogenic Escherichia coli bind, different mass spectrometric techniques were utilized. First, a mixture of glycolipids isolated from man and mice kidney was separated by thin-layer chromatography (TLC) and scanned by direct desorption from the plate by fast atom bombardment mass spectrometry (TLC/FAB-MS). Second, the glycolipids were purified by preparative TLC and analyzed by negative-ion FAB-MS. After methylation, further analyses were made with positive-ion FAB-MS, positive-ion electron ionization (EI)-MS, high-temperature capillary gas chromatography (GC/EI-MS) and positive-ion matrix-assisted laser desorption/ionization (MALDI)-MS. The ceramide compositions of the four glycolipids were determined using all these MS techniques and the reliability of the different methods for this type of analyses is discussed. Comparison of the mouse kidney glycolipids with the corresponding glycolipids from human kidney showed the same degree of hydroxylation of ceramides among mono- and disaccharide glycolipids, but a significantly higher degree of hydroxylation among mouse kidney glycolipids with three and four sugar residues. This result might be of relevance for the binding of P-fimbriated E. coli to the urinary tract tissues.