Chromatographic Analysis of Phospholipids during Monocyte Maturation

Abstract

Whether ether phospholipids are intrinsic to cell membranes or are acquired concomitantly with capacity for motion is unknown. Plasmalogen content was assessed in the human monocyte-macrophage-like cell line U937 that can be induced with dimethylsulfoxide (1.3%) to synchronously differentiate from poorly motile immature leukocytic cells to briskly motile mature cells. The phosphatidylethanolamine (PE) content of immature cells was 180 ± 10 μg/10⁸ cells for U937 cells. Alkaline hydrolysis of PE resulted in 50% lyso-PE and 50% free fatty acid. Treatment of lyso-PE with acid and phospholipase A₂ demonstrated that PE is 1-(0-1'-aklenyl), 2-acyl PE. This was confirmed by infrared and proton nuclear magnetic resonance ('H-NMR) spectroscopy. The phosphatidylcholine (PC) content of immature cells was 235 ± 5 μg/10⁸ cells. In contrast to PE< 100% of PC was diacyl homologues. Following differentiation to mature motile cells, the plasmalogen content of PE and PE significantly increased. The content of PC and PE in normal motile human peripheral blood monocytes was similar. The increase of plasmalogen in the PE component and its appearance in the PC component of mature motile U937 cells may indicate that plasmalogen correlates with the acquisition of motile function.