Sphingolipidomic Profiling of Rat Serum by UPLC-Q-TOF-MS: Application to Rheumatoid Arthritis Study

Sphingolipids (SPLs) are biologically important molecules, but the structural diversity and complexity of SPLs brings significant analytical challenges for their study. In this paper, we have developed an UPLC-Q-TOF-MS-based sphingolipidomic approach for the comprehensive identification and quantification of SPLs in rat serum. A total of 120 SPLs covering seven subcategories were identified for the first time. Method validations including linearity, sensitivity, reproducibility, and recovery were also evaluated. This method was exemplarily applied to characterize the SPL alterations in rheumatoid arthritis (RA) rats and the intervention effects of indomethacin (IDM). Partial least squares-discriminant analysis (PLS-DA) showed that the model group was well separated from the control group, whereas the IDM-treated group exhibited a trend to recover the controls. Twenty-six significantly changed SPL markers were explored, and the levels of ceramides (Cers) and their metabolites were found to be reversed by IDM treatment. These results indicate that IDM exerts anti-arthritic effects through the suppression of Cer-mediated COX-2 activation and resulting PEG₂ liberation. The present study demonstrates a promising potential of this method for the understanding of RA and the anti-arthritic mechanisms of relevant drugs.