Alterations of red cell membrane properties in neuroacanthocytosis.

Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington's disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an "acanthocytic state" of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration.

Vesicles generated during storage of red blood cells enhance the generation of radical oxygen species in activated neutrophils.

Erythrocytes are known to shed vesicles in vivo, under various conditions in vitro, and, with impact for transfusion medicine, during storage of red blood cell concentrates (Vsto vesicles). Vsto vesicles of blood transfusions have been shown to deliver glycosylphosphatidylinositol-linked proteins to recipient erythrocytes, to display prothrombotic activity, and to have an inhibitory effect on macrophages. The interaction of Vsto vesicles with and their effect on neutrophilic granulocytes has not yet been studied in detail. Fluorescently labeled Vsto and calcium-induced vesicles were prepared in order to study the uptake of labeled vesicular components by neutrophils as compared to the process of phagocytosis of zymosan using flow cytometry and confocal microscopy. The activating effect of Vsto vesicles on neutrophils was addressed by a luminometric assay for stimulated radical oxygen species (ROS) generation.Coincubation of vesicles and neutrophils results in a transfer of vesicular components to the cells. This uptake is different from a phagocytotic process and is enhanced upon interference with the cellular actin cytoskeleton. Preincubation of neutrophils with Vsto vesicles results in an enhanced ROS generation by neutrophils,which is further increased upon fMLP stimulation and during zymosan phagocytosis. The activating effect of Vsto vesicles on neutrophils might be due to the specific accumulation of lysophospholipids in Vsto vesicles and should be considered as a possible contributor to the pathogenesis of transfusion-related acute lung injury.