The formation of neurotoxic beta-amyloid fibrils in Alzheimer's disease (AD) is suggested to involve membrane rafts and to be promoted, in vitro, by enriched concentrations of gangliosides, particularly GM1, and the cholesterol therein. In our study, the presence of rafts and their content of the major membrane lipids and gangliosides in the temporal cortex, reflecting late stages of AD pathology, and the frontal cortex, presenting earlier stages, has been investigated. Whole tissue and isolated detergent-resistant membrane fractions (DRMs) were analysed from 10 AD and 10 age-matched control autopsy brains. DRMs from the frontal cortex of AD brains contained a significantly higher concentration (lmol/lmol glycerophospholipids), of ganglioside GM1 (22.3 ± 4.6 compared to 10.3 ± 6.4, p < 0.001) and GM2 (2.5 ± 1.0 compared to 0.55 ± 0.3, p < 0.001). Similar increases of these gangliosides were also seen in DRMs from the temporal cortex of AD brains, which, in addition, comprised significantly lower proportions of DRMs. Moreover, these remaining rafts were depleted in cholesterol (from 1.5 ± 0.2 to 0.6 ± 0.3 lmol/lmol glycerophospholipids, p < 0.001). In summary, we found an increased proportion of GM1 and GM2 in DRMs, and accelerating plaque formation at an early stage, which may gradually lead to membrane raft disruptions and thereby affect cellular functions associated with the presence of such membrane domains.

Sulfatide is a myelin component of the central (CNS) and peripheral nervous system (PNS) and is used extensively to identify oligodendrocyte progenitor cells. We have explored sulfatide expression in CNS gray matter (cerebellum, cerebral cortex, and hippocampus) and the PNS in adult rats using an anti-sulfatide antibody (Sulph I) and confocal microscopy. Biochemical analyses revealed two Sulph I antigens, sulfatide and seminolipid; sulfatide was present at about five times higher concentration, and the affinity of Sulph I for sulfatide was 2.5 times higher than that for seminolipid. Thus sulfatide was considered the dominant antigen. We found Sulph I immunostaining, in addition to that in myelinated areas in subpopulations of astrocytes and neurons. Astrocyte Sulph I staining was localized to the cell bodies and in some cases also to the processes. In the cerebellum, some Sulph I-positive astrocytes corresponded to Golgi epithelial cell bodies. We also found Sulph I staining in neuronal cell bodies, which in some neurons was clearly localized to the cytoplasm and in others to the nuclear membrane. Sulph I immunostaining in the PNS was located in the myelin sheath and paranodal end segments. These results demonstrate the expression of sulfatide in cell types other than oligodendrocytes and Schwann cells, showing that sulfatide is not a selective marker for adult oligodendrocyte progenitor cells. Moreover, these findings show that sulfatide is localized also to intracellular compartments and indicate that other roles of sulfatide in astrocytes and neurons, compared to myelin, might be considered.

Arylsulfatase A (ASA) degrades sulfatide, seminolipid and lactosylceramide sulfate, glycolipids recognized by the Sulph I antibody although sulfatide is considered the main antigen. Sulfatide is myelin associated but studies have shown a minor distribution also in non-myelin forming cells. The aim of this work was to further study sulfatide in neurons and astrocytes by immunohistochemistry, facilitated by investigation of tissue from adult ASA deficient (ASA − /− ) mice. Cells with a low presence of sulfatide might be detected due to lack of ASA activity and accumulation of Sulph I antigens. Sulfatide positive astrocytes and neurons were more numerous and intensely stained in ASA − /− mice, demonstrating a sulfatide accumulation compared to controls. Sulph I staining was especially increased in the molecular layer of cerebellum, in which Purkinje cell dendrites displayed an altered morphology, and in layer IV-VI of cerebral cortex. In hippocampus, immunostaining was found in neuronal cytoplasm in ASA − /− but in nuclear membranes of control mice. We observed a gray matter astrogliosis, which appeared to be associated to sulfatide accumulation. In addition, the developmental change (<20 months) of Sulph I antigens, galactosylceramide, phospholipids and cholesterol were followed by lipid analyses which verified sulfatide and seminolipid accumulation in adult ASA − /− mice, although no lactosylceramide sulfate could be detected. In addition to demonstrating sulfatide in neurons and astrocytes, this study supports the value of ASA − /− mice as a model for metachromatic leukodystrophy and suggests that accumulation of sulfatide beyond myelin might contribute to the pathology of this disease. 0300-4864 C 2004 Kluwer Academic Publishers

Arylsulfatase A (ASA) degrades sulfatide, seminolipid and lactosylceramide sulfate, glycolipids recognized by the Sulph I antibody although sulfatide is considered the main antigen. Sulfatide is myelin associated but studies have shown a minor distribution also in non-myelin forming cells. The aim of this work was to further study sulfatide in neurons and astrocytes by immunohistochemistry, facilitated by investigation of tissue from adult ASA deficient (ASA -/-) mice. Cells with a low presence of sulfatide might be detected due to lack of ASA activity and accumulation of Sulph I antigens. Sulfatide positive astrocytes and neurons were more numerous and intensely stained in ASA -/- mice, demonstrating a sulfatide accumulation compared to controls. Sulph I staining was especially increased in the molecular layer of cerebellum, in which Purkinje cell dendrites displayed an altered morphology, and in layer IV-VI of cerebral cortex. In hippocampus, immunostaining was found in neuronal cytoplasm in ASA -/- but in nuclear membranes of control mice. We observed a gray matter astrogliosis, which appeared to be associated to sulfatide accumulation. In addition, the developmental change (<20 months) of Sulph I antigens, galactosylceramide, phospholipids and cholesterol were followed by lipid analyses which verified sulfatide and seminolipid accumulation in adult ASA -/- mice, although no lactosylceramide sulfate could be detected. In addition to demonstrating sulfatide in neurons and astrocytes, this study supports the value of ASA -/- mice as a model for metachromatic leukodystrophy and suggests that accumulation of sulfatide beyond myelin might contribute to the pathology of this disease.