Establishment of a Measurement System for Sphingolipids in the Cerebrospinal Fluid Based on Liquid Chromatography-Tandem Mass Spectrometry, and Its Application in the Diagnosis of Carcinomatous Meningitis.

Sphingolipids have been demonstrated to be involved in many human diseases. However, measurement of sphingolipids, especially of sphingosine 1-phosphate (S1P) and dihydro-sphingosine 1-phosphate (dhS1P), in blood samples requires strict sampling, since blood cells easily secrete these substances during sampling and storage, making it difficult to introduce measurement of sphingolipids in clinical laboratory medicine. On the other hand, cerebrospinal fluid (CSF) contains few blood cells. Therefore, we attempted to establish a system based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the measurement of sphingolipids in the CSF, and applied it for the diagnosis of carcinomatous meningitis. We developed and validated a LC-MS/MS-based measurement system for S1P and dhS1P and for ceramides and sphingosines, used this system to measure the levels of these sphingolipids in the CSF collected from the subjects with cancerous meningitis, and compared the levels with those in normal routine CSF samples. Both the measurement systems for S1P/dhS1P and for ceramides/sphingosines provided precision with the coefficient of variation below 20% for sphingolipids in the CSF samples. We also confirmed that the levels of S1P, as well as ceramides/sphingosines, in the CSF samples did not increase after the sampling. In the CSF samples collected from patients with cancerous meningitis, we observed that the ratio of S1P to ceramides/sphingosine and that of dhS1P to dihydro-sphingosine were higher than those in control samples. We established and validated a measurement system for sphingolipids in the CSF. The system offers promise for being introduced into clinical laboratory testing.