2-hexadecenal and sphingosine-1-phosphate

Sphingosine 1-phosphate, a bioactive signaling molecule with diverse cellular functions, is irreversibly degraded by the endoplasmic reticulum enzyme sphingosine 1-phosphate lyase, generating trans-2-hexadecenal and phosphoethanolamine. We recently demonstrated that trans-2-hexadecenal causes cytoskeletal reorganization, detachment, and apoptosis in multiple cell types via a JNK-dependent pathway. These findings and the known chemistry of related α,β-unsaturated aldehydes raise the possibility that trans-2-hexadecenal may interact with additional cellular components. In this study, we show that it reacts readily with deoxyguanosine and DNA to produce the diastereomeric cyclic 1,N(2)-deoxyguanosine adducts 3-(2-deoxy-β-d-erythro-pentofuranosyl)-5,6,7,8-tetrahydro-8R-hydroxy-6R-tridecylpyrimido[1,2-a]purine-10(3H)one and 3-(2-deoxy-β-d-erythro-pentofuranosyl)-5,6,7,8-tetrahydro-8S-hydroxy-6S-tridecylpyrimido[1,2-a]purine-10(3H)one. Thus, our findings suggest that trans-2-hexadecenal produced endogenously by sphingosine 1-phosphate lyase can react directly with DNA forming aldehyde-derived DNA adducts with potentially mutagenic consequences.

Topics: Aldehyde-Lyases; Aldehydes; Deoxyguanosine; DNA Adducts; Lysophospholipids; Mutagenesis; Sphingolipids; Sphingosine

Sphingosine-1-phosphate (S1P) is a sphingolipid signaling molecule crucial for cell survival and proliferation. S1P-mediated signaling is largely controlled through its biosynthesis and degradation, and S1P lyase (S1PL) is the only known enzyme that irreversibly degrades sphingoid base-1-phosphates to phosphoethanolamine and the corresponding fatty aldehydes. S1PL-mediated degradation of S1P results in the formation of (2E)-hexadecenal, whereas hexadecanal is the product of dihydrosphingosine-1-phosphate (DHS1P) degradation. Fatty aldehydes can undergo biotransformation to fatty acids and/or alcohols, making them elusive and rendering the task of fatty aldehyde quantitation challenging. We have developed a simple, highly sensitive, and high-throughput protocol for (2E)-hexadecenal quantitation as a semicarbazone derivative by liquid chromatography-electrospray ionization-tandem mass spectrometry. The approach was applied to determining S1PL activity in vitro with the ability to use as low as 0.25μg of microsomal protein per assay. The method is also applicable to the use of total tissue homogenate as the source of S1PL. A correction for (2E)-hexadecenal disappearance due to its biotransformation during enzymatic reaction is required, especially at higher protein concentrations. The method was applied to confirm FTY720 as the inhibitor of S1PL with an IC₅₀ value of 52.4μM.

Topics: Aldehyde-Lyases; Aldehydes; Animals; Chromatography, High Pressure Liquid; Fingolimod Hydrochloride; Hydrogenation; Kinetics; Lysophospholipids; Mice; Microsomes, Liver; Propylene Glycols; Rats; Semicarbazones; Spectrometry, Mass, Electrospray Ionization; Sphingosine; Stereoisomerism; Tandem Mass Spectrometry

Lysosphingolipids are important lipid signaling molecules that are associated predominantly with high density lipoproteins (HDL) in human plasma. Further, HDL has been shown to be a target for the reactive chlorinating species (RCS) produced by myeloperoxidase (MPO). Accordingly, RCS attack of lysosphingolipids was characterized in these studies. It was shown that RCS attack of sphingosylphosphorylcholine results in the formation of 2-hexadecenal and 1-cyano methano phosphocholine. The structures were identified and confirmed predominantly using mass spectrometric analyses. Further, it was demonstrated that RCS attack of another bioactive lysosphingolipid sphingosine 1-phosphate also results in the formation of 2-hexadecenal from its sphingosine base. Using a synthetically prepared, deuterated 2-hexadecenal internal standard, it was determined that 2-hexadecenal quickly accumulated in HDL treated with MPO/RCS generating system. Thus, the present studies characterize the formation of a novel group of lipid products generated following RCS attack of lysosphingolipids.

Topics: Aldehydes; Chlorine; Chromatography, High Pressure Liquid; Gas Chromatography-Mass Spectrometry; Lipoproteins, HDL; Lysophospholipids; Peroxidase; Phosphorylcholine; Sphingosine