Lipids of erythrocyte membranes of COPD patients: a quantitative and qualitative study

Chronic obstructive pulmonary disease (COPD) is characterized by inflammation of lung parenchyma and pulmonary hypoxemia with a proven systemic component. Tobacco smoke is the most important risk factor and plasma membrane plays a major role in the disease pathology and progression. The properties of biological membranes are a function of their lipid composition. Any change in its composition may lead to the pathophysiology. In COPD research, erythrocytes are emerging as a new therapeutic venture, as their shape and properties change in the disease. Therefore we studied the lipid composition of the erythrocyte membranes of COPD patients. The study included 30 patients having COPD, 10 healthy smokers and 10 non-smokers. Erythrocytes were separated from peripheral blood and their membranes prepared, followed by estimation of proteins, cholesterol and phospholipids. Individual phospholipids were identified and separated by TLC and fatty acid composition determined by gas chromatography. The data were analyzed statistically and P < 0.05 was considered significant. Our results demonstrate that in very severe COPD, proteins decrease, whereas phospholipids and cholesterol contents increase significantly, which showed a consistent negative correlation with FEV1%. The fatty acid analysis showed preponderance towards saturated fatty acids mainly arachidic and behenic acid, suggesting a decrease in membrane fluidity or a closer packing of lipid rafts. We are the first to report about preponderance of saturated fatty acids in plasma membrane of erythrocytes of COPD patients which may decrease the membrane fluidity and possibly impair the functions of the plasma membrane in the disease.