Platelet activating factor is elevated in cerebral spinal fluid and plasma of patients with relapsing-remitting multiple sclerosis

Platelet-activating factor (PAF) is a phospholipid mediator of inflammation with a wide range of biological activities, including the alteration of barrier function of endothelium. A biological assay combined with high pressure liquid chromatography-tandem mass spectrometry showed that plasma and cerebral spinal fluid (CSF) PAF levels in 20 patients with relapsing/remitting or secondary progressive multiple sclerosis (MS) studied by magnetic resonance imaging (MRI) were significantly higher than in healthy controls (plasma: 3.29 ± 4.52 vs. 0.48 ± 0.36 ng/ml, p <0.002; CSF: 4.95 ± 6.22 ng/ml vs. 0.01 ± 0.04 ng/ml, p <0.0001). Values were also significantly higher in relapsing/remitting than in secondary progressive (plasma: 5.10 ± 4.97 vs. 0.52 ± 0.85 ng/ml, p <0.005; CSF: 8.59 ± 6.39 vs. 0.55 ± 0.68 ng/ml, p <0.002). It was also found that both plasma (R ²: 0.65) and CSF (R ²: 0.72) levels were correlated with the MRI number of gadolinium enhancing lesions, which are markers of blood-brain barrier (BBB) injury, whereas their peaks were not correlated with the MRI number of white matter lesions, nor with the expanded disability status score (EDSS) according to Kurtze [Kurtze, J.F., 1983. Rating neurological impairment in multiple sclerosis: an expanded disability scale (EDSS). Neurology 33, 1444- 1452]. Both plasma and CSF in patients with relapsing/remitting MS and marked gadolinium enhancement contained the two major molecular species of PAF: 1- 0-hexadecyl- (C16:O) and 1-0-octadecyl-sn-glycero-3-phosphocholine (C18:O). The ratio of the two molecular species was different in the two biological fluids, being PAF C18:0 more abundant in CSF and PAF C16:0 in plasma, indicating a different cellular origin of PAF or different enzymatic processing. These findings suggest that PAF is a significant mediator of BBB injury in the early stages of MS, rather than a marker of its progression and severity.