quantitative-qualitative-method-for-sphingomyelin-lc-ms-using-two

Quantitative and Qualitative Method for Sphingomyelin by LC-MS Using Two Stable Isotopically Labeled Sphingomyelin Species

We present a method of analyzing sphingomyelin (SM) qualitatively and quantitatively by liquid chromatography-electrospray Ionization-tandem mass ...

Teikyo University

Sphingomyelin (ceramide-phosphocholine, CerPCho) is a common sphingolipid in mammalian cells and is composed of phosphorylcholine and ceramide as polar and hydrophobic components, respectively. In this study, a qualitative liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS/MS) analysis is proposed in which CerPCho structures were assigned based on product ion spectra corresponding to sphingosylphosphorylcholine and N-acyl moieties. From MS/MS/MS analysis of CerPCho, we observed product ion spectra of the N-acyl fatty acids as [RCO] ions as well as sphingosylphosphorylcholine. A calibration curve for CerPCho was constructed using two stable isotopically labeled CerPCho species and then used to quantify the CerPCho species in HeLa cells as a proof-of-principle study. The present study proposes an accurate method for quantifying and assigning structures to each CerPCho species in crude biologic samples by LC-ESI-MS/MS/MS analysis.

Comprehensive Quantitation Using Two Stable Isotopically Labeled Species and Direct Detection of N-Acyl Moiety of Sphingomyelin.

Macrophage foam cells play critical roles in the initiation and development of atherosclerosis by synthesizing and accumulating cholesteryl ester (CE) in lipid droplets. However, in analyzing lipid metabolism in foam cell formation, studies have focused on the sterol group, and little research has been done on the acyl chains. Therefore, we adapted a model system using liposomes containing particular acyl chains and examined the effect of various acyl chains on foam cell formation. Of the phosphatidylserine (PS) liposomes tested containing PS, phosphatidylcholine, and cholesterol, we found that unsaturated (C18:1), but not saturated (C16:0 and C18:0), PS liposomes induced lipid droplet formation, indicating that foam cell formation depends on the nature of the acyl chain of the PS liposomes. Experiments on the uptake and accumulation of cholesterol from liposomes by adding [C]cholesterol suggested that foam cell formation could be induced only when cholesterol was converted to CE in the case of C18:1 PS liposomes. Both microscopic observations and metabolic analysis suggest that cholesterol incorporated into either C16:0 or C18:0 PS liposomes may stay intact after being taken in by endosomes. The [C]C18:1 fatty acyl chain in the C18:1 PS liposome was used to synthesize CE and triacylglycerol (TG). Interestingly, the [C]C16:0 in the C18:1 PS liposome was metabolized to sphingomyelin rather than being incorporated into either CE or TG, which could be because of enzymatic acyl chain selectivity. In conclusion, our results indicate that the acyl chain preference of macrophages could have some impact on their progression to foam cells.

Acyl Chain Preference in Foam Cell Formation from Mouse Peritoneal Macrophages.

ABCD1 is a gene responsible for X-linked adrenoleukodystrophy (X-ALD), and is critical for the transport of very long-chain fatty acids (VLCFA) into peroxisomes and subsequent β-oxidation. VLCFA-containing lipids accumulate in X-ALD patients, although the effect of ABCD1-deficiency on each lipid species in the central nervous system has not been fully characterized. In this study, each phospholipid and lysophospholipid species in Abcd1-deficient mice brains were profiled by liquid chromatography-mass spectrometry. Among the phospholipid and lysophospholipid species that are significantly more enriched in Abcd1-deficient mice brains, VLCFA were present in 75, 15, 5, 4, and 1 species of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, lysophosphatidylcholine, and lysophosphatidylethanolamine, respectively. Most VLCFA were incorporated at the sn-1 position of phosphatidylcholine and phosphatidylethanolamine. Among the phospholipid species that are significantly less enriched in Abcd1-deficient mice brains, odd-numbered saturated or mono-unsaturated fatty acyl moieties are contained in all phosphatidylcholine species. In addition, a number of phosphatidylglycerol, phosphatidylinositol, and phosphatidylserine species contained highly unsaturated fatty acyl moieties. Intriguingly, 44:1 phosphatidylcholine with VLCFA was mainly distributed in the gray matter, such as the cortex, but not in the white matter in the cerebrum and cerebellum. These results show that ABCD1-deficiency causes metabolic alternation of long-chain fatty acids and VLCFA. Moreover, our results imply a molecular mechanism for the incorporation of saturated or monounsaturated VLCFA into the sn-1 position of phospholipids, and also indicate that the distribution of phospholipids with VLCFA may correlate with the development of X-ALD.

Yuko Fujiwara

Faculty of Pharmaceutical Sciences

Teikyo University

Quantitative and Qualitative Method for Sphingomyelin by LC-MS Using Two Stable Isotopically Labeled Sphingomyelin Species

Yuko Fujiwara

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Faculty of Pharmaceutical Sciences

Teikyo University

Quantitative and Qualitative Method for Sphingomyelin by LC-MS Using Two Stable Isotopically Labeled Sphingomyelin Species

Faculty of Pharmaceutical Sciences