The phosphatidylcholine/lysophosphatidylcholine ratio in human plasma is an indicator of the severity of rheumatoid arthritis: Investigations by 31P NMR and MALDI-TOF MS

Objectives: Lipid second messengers, e.g. lysophosphatidylcholines (LPC) are involved in the pathogenesis of inflammatory diseases, for instance, rheumatoid arthritis (RA). Unfortunately, the analysis of LPC in complex mixtures as present in body fluids is still challenging. Design and methods: Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) was applied for phospholipid (PL) analysis of organic extracts of synovial fluids from patients with RA as well as the corresponding plasma. These data were compared with results obtained by high resolution 31P NMR spectroscopy. Results: Synovial fluids may be replaced by plasma since the analysis of both body fluids gives very similar results. Patients undergoing treatment with TNF-α inhibitors (ADALIMUMAB (HUMIRA®)) were examined in order to investigate whether the clinically-significant attenuation of disease activity is accompanied by changes of the PL composition of plasma. It will be shown that especially the PC/LPC ratios of plasma represent a reliable measure of inflammation and increase upon therapy. Conclusions: Since plasma samples are readily available, our approach might be useful to draw conclusions before puncture of the affected joints is necessary and the PC/LPC ratio detected in plasma may serve as an indicator of RA in early stages.