Hypoxia remodels the composition of the constituent ceramide species of HexCer and Hex2Cer with phytosphingosine and hydroxy fatty acids in human colon cancer LS174T cells.

ABSTRACT

Oxygen-requiring enzymes, such as Δ4-desaturase (dihydroceramide desaturase), sphingolipid Δ4-desaturase/C-4-hydroxylase, and fatty acid 2-hydroxylase are involved in ceramide synthesis. We prepared free ceramides, sphingomyelins and glycosphingolipids (GSLs) from cancer cells cultivated under conditions of normoxia and hypoxia, and analyzed these compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Human colon cancer LS174T cells were employed because these cells highly express hydroxyl fatty acids and phytosphingosine (t180) which are expected to be greatly influenced by changes in oxygen levels. As expected, the populations of dihydro-species of free ceramide and sphingomyelin with C160 non-hydroxy fatty acid were elevated, and the populations of HexCers and Hex2Cers, composed of C160 or C160 hydroxy fatty acid (C160h), and sphingosine (d181) or t180, were decreased under hypoxia. However, appreciable populations of HexCer and Hex2Cer species of C240 or C240h and t180 remained. These results suggest that the individual species of GSLs with fatty acids possessing different alkyl chain lengths, either non-hydroxy fatty acids or hydroxyl fatty acids, may be metabolized individually.