Red Blood Cell Membrane Fluidity in the Etiology of Multiple Sclerosis

Abstract

Organisms adjust the order, or fluidity, of their cellular membranes in response to changes in their physio- chemical environment by adjusting the lipid composition of their membranes. We investigated membrane fluidity using the phospholipid, fatty acid and cholesterol content of red blood cells (RBCs) from multiple sclerosis (MS) patients and correlated this with C-reactive protein (CRP) as well as with the severity of neurological outcome as measured by the Kurtzke Expanded Disability Status Scale (EDSS) and its Functional System Scores. The study group consisted of 31 patients with MS and 30 healthy control subjects. Phos- pholipids were determined using a colorimetric assay, fatty acids by gas chromatography, cholesterol by an enzymatic assay and CRP by a Beckman nephelometer. Cell membrane fluidity was calculated according to previously established formulae. RBC membrane fluidity as measured by the sat- urated to polyunsaturated fatty acid ratio was higher in patients than in controls (P = 0.04). The phosphatidyleth- anolamine saturated to polyunsaturated fatty acid ratio showed highly significant positive correlations with the EDSS and CRP \ 5 lg/ml. CRP showed significant inverse correlations with the saturated nature but positive correla- tions with the ordered-crystalline-phase to liquid-crystal- line-phase lipid ratio. In this study we show that membrane fluidity as measured by the relationship between membrane fatty acids, phospholipids and cholesterol is closely inter- related with inflammation and disease outcome in patients with MS. In conclusion, our findings suggest that the membrane lipid composition of patients with MS and, con- sequently, membrane fluidity are altered, which seems to be influenced by the inflammatory status.