Synthesis, NMR characterization and divergent biological actions of 2′-hydroxy-ceramide/dihydroceramide stereoisomers in MCF7 cells

A straightforward method for the simultaneous preparation of (2S, 3R, 2'R)-and (2S, 3R, 2'S)-2'-hydroxyceramides (2'-OHCer) from (2S, 3R)-sphingosine acetonide precursors and racemic mixtures of 2-hydroxy fatty acids (2-OHFAs) is described. The obtained 2'-OH-C4-, -C6-, -C12-, -C16-Cer and 2'-OH-C6-dhCer pairs of diastereoisomers were characterized thoroughly by TLC, MS, NMR, and optical rotation. Dynamic and multidimensional NMR studies provided evidence that polar interfaces of 20-OHCers are extended and more rigid than observed for the corresponding non-hydroxylated analogs. Stereospecific profile on growth suppression of MCF7 cells was observed for (2'R)-and (2'S)-2'-OH-C6-Cers and their dihydro analogs. The (2'R)-isomers were more active than the (2'S)-isomers (IC50 similar to 3 mu M/8 mu M and IC50 similar to 8 mu M/ 12 mu M, respectively), surpassing activity of the ordinary C6-Cer (IC50 similar to 12 mu M) and C6-dhCer (IC50 similar to 38 mu M). Neither isomer of 2'-OH-C6-Cers and 2'-OH-C6-dhCers was metabolized to their cellular long chain 2'-OH-homologs. Surprisingly, the most active (2'R)-isomers did not influence the levels of the cellular Cers nor dhCers. Contrary to this, the (2'S)-isomers generated cellular Cers and dhCers efficiently. In comparison, the ordinary C6-Cer and C6-dhCer also significantly increased the levels of their cellular long chain homologs. These peculiar anabolic responses and SAR data suggest that (2'R)-2'-OHCers/dhCers may interact with some distinct cellular regulatory targets in a specific and more effective manner than their non-hydroxylated analogs. Thus, stereoisomers of 2'-OHCers can be potentially utilized as novel molecular tools to study lipid-protein interactions, cell signaling phenomena and to understand the role of hydroxylated sphingolipids in cancer biology, pathogenesis and therapy. Published by Elsevier Ltd.