Serine palmitoyltransferase inhibitor myriocin induces the regression of atherosclerotic plaques in hyperlipidemic ApoE-deficient mice.

Myriocin, a potent inhibitor of serine palmitoyltransferase (SPT), has been shown to reduce plasma sphingolipids, cholesterol and triglycerides in hyperlipidemic apolipoprotein E knockout (apoE KO) mice. We hypothesized that the inhibition of sphingolipid biosynthesis modulates the composition of atherosclerotic plaque via its lipid-lowering effects. To test this hypothesis, the effect of myriocin on plasma lipids, sphingolipids and atherosclerosis progression, regression and lesion composition was investigated in apoE KO mice. Myriocin was administered to 24-week-old male apoE KO mice for 12 weeks. Myriocin-treated apoE KO mice had significant reductions in plasma total cholesterol, triglycerides, VLDL-cholesterol, ceramide, sphinganine and sphingomyelin (SM) compared to 24- and 36-week-old control mice. The ratio of SM to phosphatidylcholine (SM/PC), an independent risk factor for coronary artery disease, was also reduced by myriocin. Compared to 24- and 36-week controls, atherosclerotic lesion area and macrophage content in the aortic root and brachiocephalic arteries of myriocin-treated ApoE KO mice were reduced but there was only a slight increase in smooth muscle content. However, the content of collagen within aortic root lesions was increased in myriocin-treated apoE KO mice. In summary, the inhibition of SPT lowers plasma sphingolipids and atherogenic plasma lipids leading to the regression of pre-existing atherosclerotic lesions and to the formation of a stable plaque phenotype.

Inhibition of sphingomyelin synthesis reduces atherogenesis in apolipoprotein E-knockout mice.

BACKGROUND: In clinical studies, sphingomyelin (SM) plasma levels correlated with the occurrence of coronary heart disease independently of plasma cholesterol levels. We hypothesized that inhibition of SM synthesis would have antiatherogenic effects. To test this hypothesis, apolipoprotein E (apoE)-knockout (KO) mice were treated with myriocin, a potent inhibitor of serine palmitoyltransferase, the rate-limiting enzyme in SM biosynthesis. METHODS AND RESULTS: Diet-admix treatment of apoE-KO mice with myriocin in Western diet for 12 weeks lowered SM and sphinganine plasma levels. Decreases in sphinganine and SM concentrations were also observed in the liver and aorta of myriocin-treated animals compared with controls. Inhibition of de novo sphingolipid biosynthesis reduced total cholesterol and triglyceride plasma levels. Cholesterol distribution in lipoproteins demonstrated a decrease in beta-VLDL and LDL cholesterol and an increase in HDL cholesterol. Oil red O staining of total aortas demonstrated reduction of atherosclerotic lesion coverage in the myriocin-treated group. Atherosclerotic plaque area was also reduced in the aortic root and brachiocephalic artery. CONCLUSIONS: Inhibition of de novo SM biosynthesis in apoE-KO mice lowers plasma cholesterol and triglyceride levels, raises HDL cholesterol, and prevents development of atherosclerotic lesions.

Quantitative bioanalysis of enantiomeric drugs using capillary electrophoresis and electrospray mass spectrometry.

A novel assay method for an enantiomeric pair of drugs has been developed using a combination of capillary electrophoresis and electrospray tandem mass spectrometry connected with a homemade interface. Accurate quantification was demonstrated in plasma from 0.25 to 50 microg/ml. A liquid-liquid sample preparation technique allowed improvement in the quantitation limit to 10 ng/ml. Variables for the enantiomeric separation, including chiral selective reagent, organic solvents, buffer and acid concentration as well as injection technique, were optimized. This assay proved adequate for analysis of neat, spiked plasma, and plasma from a pharmacological study of the drug enantiomers.