Impaired Sphingolipid Hydrolase Activities in Dementia with Lewy Bodies and Multiple System Atrophy.

The synucleinopathies are a group of neurodegenerative diseases characterized by the oligomerization of alpha-synuclein protein in neurons or glial cells. Recent studies provide data that ceramide metabolism impairment may play a role in the pathogenesis of synucleinopathies due to its influence on alpha-synuclein accumulation. The aim of the current study was to assess changes in activities of enzymes involved in ceramide metabolism in patients with different synucleinopathies (Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA)). The study enrolled 163 PD, 44 DLB, and 30 MSA patients as well as 159 controls. Glucocerebrosidase, alpha-galactosidase, acid sphingomyelinase enzyme activities, and concentrations of the corresponding substrates (hexosylsphingosine, globotriaosylsphingosine, lysosphingomyelin) were measured by liquid chromatography tandem-mass spectrometry in blood. Expression levels of GBA, GLA, and SMPD1 genes encoding glucoceresobridase, alpha-galactosidase, and acid sphingomyelinase enzymes, correspondently, were analyzed by real-time PCR with TaqMan assay in CD45 + blood cells. Increased hexosylsphingosine concentration was observed in DLB and MSA patients in comparison to PD and controls (p < 0.001) and it was associated with earlier age at onset (AAO) of DLB (p = 0.0008). SMPD1 expression was decreased in MSA compared to controls (p = 0.015). Acid sphingomyelinase activity was decreased in DLB, MSA patients compared to PD patients (p < 0.0001, p < 0.0001, respectively), and in MSA compared to controls (p < 0.0001). Lower acid sphingomyelinase activity was associated with earlier AAO of PD (p = 0.012). Our data support the role of lysosomal dysfunction in the pathogenesis of synucleinopathies, namely, the pronounced alterations of lysosomal activities involved in ceramide metabolism in patients with MSA and DLB.

[Plasma Exosomes in Inherited Forms of Parkinson's Disease].

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Alpha-synuclein misfolding and aggregation resulting in neurototoxicity is a hallmark of PD. The prion properties of alpha-synuclein are still under discussion. Exosomes (extrcellular vesicles 40-100 nm in size) can play a key role in the transport of pathogenic forms of alpha-synuclein. The most frequent inherited forms of the disease are PD associated with mutation in the leucine-rich repeat kinase 2 (LRRK2-PD) and glucocerebrosidase (GBA-PD) genes. The aim of our work is to evaluate the concentration and size of exosomes derived from blood plasma of patients with GBA-PD, asymptomatic GBA mutation carriers, and the effect of GBA and LRRK2 mutations on alpha-synuclein level in exosomes derived from peripheral blood plasma. Plasma extracellular vesicles were isolated via chemical precipitation and sequential ultracentrifugation and characterized by transmission electron microscopy, nanoparticle tracking analysis (NTA), and flow cytometry. Total alpha-synuclein level in plasma exosomes was estimated by enzyme-linked immunosorbent assay. Patients with sporadic PD, PD with dementia, patients with inherited PD (GBA-PD, LRRK2-PD), and GBA mutation carriers were included in the study. The concentration on plasma exosomes was higher in GBA-PD patients that in sporadic PD patients, asymptomatic carriers of mutations on GBA gene, and control (p = 0.004, 0.019 and 0.0001 respectively). The size of plasma exosomes was higher in GBA-PD patients compared to asymptomatic carriers of GBA mutations and control (p = 0.009 and 0.0001, respectively). No significant difference was found for exosomal alpha-synuclein levels in the studied groups. Our results allowed us to suggest that a decrease in GBA activity may affect the pool of plasma exosomes, and mutations in the LRRK2 and GBA genes do not influence the level of plasma exosomal alpha-synuclein.

Genetics variants and expression of the SCARB2 gene in the pathogenesis of Parkinson's disease in Russia.

Lysosomal integral membrane protein-2 (LIMP-2), encoded by the SCARB2 gene, is the specific lysosomal receptor for glucocerebrosidase enzyme. Association between rs6812193 and rs68250047 of SCARB2 with PD has been shown in genetic studies, including large genome-wide association studies. The aim of the current study was to determine whether rs6812193 and rs8475 are associated with PD in Russia. rs6812193 and rs8475 were genotyped in a total of 604 PD patients (65 PD patients with positive (fPD) and 539 PD patients with negative family history (sPD)) and 413 controls and also in 17 patients with PD associated with GBA mutations (PD-GBA) and 18 asymptomatic GBA mutation carriers (GBA-Carriers). SCARB2 expression was measured by real-time PCR in CD45+ blood cells in part of individuals in the studied groups. No linkage disequilibrium was shown between rs6812193 and rs8475 in Russian population. Increased PD risk for TT variant of rs8475 (OR = 2.02; p < 0.001) was found in sPD patients but not in fPD. rs6812193 and rs8475 were not associated with age at onset (AAO) of PD. SCARB2 expression level was decreased in GBA-PD patients and GBA-Carriers compared to PD patients (padjusted = 0.02, padjusted = 0.003, respectively) and GBA-Carriers compared to controls (padjusted = 0.013) with no significant difference in PD patients and controls. SCARB2 expression was not modified with rs6812193 and rs8475. In conclusion, rs8475 was associated with PD status. rs6812193 and rs8475 are not genetic modifier of AAO of PD and do not influence on SCARB2 mRNA level in CD45+ blood cells in studied groups. SCARB2 expression could be modified with GBA mutations and is independent of PD status.

[The use of Akatinol Memantine in the treatment of gait disturbances in Parkinson's disease]. / Vliyanie Akatinola Memantina na narusheniya khod'by na razvernutykh stadiyakh bolezni Parkinsona.

OBJECTIVE: To assess the efficacy of memantine hydrochloride in the treatment of GD in PD patients. MATERIALS AND METHODS: Patients of the main group (n=30) received memantine hydrochloride (akatinol memantine) in a dose of 20 mg/day for 3 months in addition to antiparkinsonian therapy. Patients of the comparison group (n=25) received only antiparkinsonian drugs. Cognitive rating scales and computerized gait assessment protocol were performed in both groups twice in 3 months interval in order to examine cognitive deficit and gait parameters. RESULTS: The increase in MMSE scores, improvement in gait cycle phases ratio and increase of cadence according to computerized gait analysis were observed in the main group compared to the comparison group. CONCLUSION: The improvement in gait achieved during the study confirms that the treatment of cortical gait disturbances in patients with PD using memantine hydrochloride is a promising area of therapy.

Plasma cytokine profile in synucleinophaties with dementia.

Immune response may play a pivotal role in the pathogenesis of the common synucleinopathy as Parkinson's disease (PD) and could be mediated with the accumulation of neurotoxic alpha-synuclein. There is limited evidence for immune response in another synucleinopathy as dementia with Lewy bodies (DLB). Recent data suggest that immune response may contribute to cognitive impairment. We aimed to estimate plasma cytokine profile in patients with synucleinopathies with dementia (PD dementia (PDD), DLB). Plasma cytokine levels (interferon-gamma (IFN-gamma), interleukin (IL)-4 (IL-4), IL-6, IL-10, tumor necrosis factor alpha (TNF-alpha), monocyte chemoattractant protein-1 (MCP-1)). were estimated in 16 patients with DLB, 19 patients with PDD, 28 patients with PD without dementia (PD) and 19 individuals without neurological disorders (controls) using Luminex array system. Cognitive status was assessed with the Mini-Mental State Examination (MMSE). TNF-alpha and IL-6 plasma levels were elevated in patients with synucleinopathies with dementia (DLB, PDD) compared to controls and IL-10 plasma level was increased in PDD compared to controls (p < 0.05). IFN-gamma levels were decreased in PD and PDD patients compared to controls (p < 0.001, p = 0.026, respectively) and in PD patients than in DLB patients (p = 0.032). Patients with PD, PDD, and DLB were characterized by increased plasma levels of MCP-1 compared to controls (p < 0.001). At the same time, no differences in TNF-alpha, IL-10, IL-6 plasma levels in PD patients compared to controls were found. Our study demonstrated more pronounced immune response in synucleinopathies associated with dementia compared to PD without demetia.

[Modern views on gait impairment in Parkinson`s disease and its correction]. / Sovremennye predstavleniia o narusheniiakh khod'by pri bolezni Parkinsona i metodakh ikh korrektsii.

The article reviews the causes of gait impairment in patients with Parkinson's disease (PD). The emphasis is made on modern ideas, according to which gait impairment in PD is caused by a multisystem lesion and non-dopaminergic dependent mechanisms play the leading role. It is highlighted that gait impairment in PD is associated with the disruption of frontal/subcortical neural pathways which requires a special approach to pharmacological and non-pharmacological therapy. Based on pathogenetic mechanisms, much attention is paid to anti-dementia medications. Attention is drawn to the fact that the use of memantine hydrochloride (akatinol memantine) is a promising direction for gait impairment correction in the advanced and late stages of PD due to the improvement of glutamatergic transfer from the striatum to the specific areas of the cerebral cortex involved in gait control. The results of the latest clinical trials are analyzed.

[The clinical features of Parkinson's disease in patients with mutations and polymorphic variants of GBA gene]. / Klinicheskie osobennosti bolezni Parkinsona u patsientov s mutatsiiami i polimorfnymi variantami gena GBA.

BACKGROUND: Mutations in the glucocerebrosidase gene (GBA) increase the risk of Parkinson's disease (PD) by 6-10 times in all populations and are associated with the early-onset of PD, development of cognitive impairment and presence of psychotic disorders. At the same time, polymorphic variants associated with the twofold increase in the risk of PD were also described in the GBA gene. AIM: To estimate the clinical features of PD in patients with mutations and polymorphic variants of the GBA gene. MATERIAL AND METHODS: Evaluation of motor, cognitive, emotional, psychotic and autonomic dysfunctions in patients with mutations (N370S, L444P) and polymorphic variants (E326K, T369M) in the GBA gene was performed using clinical scales. RESULTS: Patients with mutations (mGBA-PD), and with polymorphic variants (pGBA-PD) in the GBA gene were compared with the group of patients with sporadic PD (sPD). Compared to sPD, affective disorders (depression and anxiety) were more expressed in the mGBA-PD group (p=0.001) and the general GBA-PD group (p=0.001) assessed with Sheehan anxiety rating scale, in the pGBA-PD group (p=0.012) and the general GBA-PD group (p=0.05) assessed with the NPI, in the mGBA-PD (p=0.003), pGBA-PD (p=0.022), and general GBA-PD groups (p=0.001) assessed with the Hospital Anxiety and Depression scale (HADS 'A'), and in the pGBA-PD group (p=0.005) assessed with the HADS 'D'. Non-motor symptoms assessed with the PD-NMS were more expressed in the pGBA-PD patients (p=0.007) and in the total group with GBA-PD (p=0,014) compared to sPD. Cognitive impairment measured with MMSE was more marked in mGBA-PD patients (p=0.022). Differences in motor and non-motor clinical symptoms between pGBA-PD and mGBA-PD groups were not found. CONCLUSION: Thus, clinical features of non-motor symptoms were described both in carriers of GBA mutations and polymorphisms. Identification of the specific clinical phenotype of PD in carriers of GBA polymorphic variants is important due to their relatively high prevalence in PD patients.

[Characteristics of the regulation of neurotrophic mechanisms in ischemic stroke].

AIM: To explore the endogenous and pharmacological activation of neurotrophic mechanisms in a model of brain ischemic lesion in rats. MATERIAL AND METHODS: The study was performed on 170 male albino rats (195-205 g). The model of ischemic stroke was accomplished by the electrocoagulation of the proximal segment of the left middle cerebral artery and simultaneous permanent ligation of the left common carotid artery. RESULTS AND CONCLUSION: The evaluation of NSE, NO, VEGF, NGF levels in the brain cytoplasmic lysate and plasma showed the delayed activation of neurotrophic mechanisms in astrocytes accompanied by a decrease in delayed alteration of neurons. The use of cytoflavin in the treatment of stroke was accompanied by the earlier and more intense activation of neurotrophic mechanisms in astrocytes, delayed activation of neurotrophic mechanisms in endothelial cells, which promoted neuroprotection in acute ischemic stroke.

A cytofluorometric study of membrane rafts in human monocyte subsets in atherosclerosis.

The peripheral blood monocytes of atherosclerotic patients are pre-activated and have some of the features of tissue macrophages. Their adhesion to the endothelium is 1.5 times higher than that of monocytes from healthy subjects, and they express a number of receptors and antigens typical of tissue macrophages. Additionally, earlier we showed that the biosynthesis of gangliosides, whose main function is the formation of membrane rafts, is significantly activated in blood monocytes from atherosclerotic patients, as well as during the in vitro differentiation of normal monocytes into macrophages. In this study, we investigated the expression of membrane rafts on various monocyte subsets from healthy subjects and atherosclerotic patients. Based on flow cytometry results, the monocytes in the examined atherosclerotic patients were found to differ from those in healthy subjects by a twofold increase in the proportion of the intermediate subset (CD14(++)/CD16(+)) and by enhancement in the expression of the fractalkine receptor CX3CR1 on the intermediate and non-classical subsets (CD14(++)/CD16(+) and CD14(+)/CD16(++)) (2.3 and 1.8 times, respectively). This suggests a pre-activated state of monocytes in atherosclerotic patients. At the same time, the expression of the membrane raft marker on the monocyte subsets was similar in both studied groups. However, a study of the in vitro differentiation of monocytes into macrophages showed that the membrane raft expression increased 2 times as early as on the 1st day of culturing and 3 times on the 7th day compared to that in freshly isolated monocytes. Therefore, it is suggested that monocytes in atherosclerosis accumulate gangliosides that are used to form membrane rafts during the macrophage differentiation after the migration of monocytes into the arterial intima.

[Activation of ganglioside GM3 biosynthesis in human blood mononuclear cells in atherosclerosis].

Using blood monocytes and lymphocytes from atherosclerotic patients and healthy subjects we have investigated activity of GM3 synthase, cellular levels of ganglioside GM3 and its role in monocyte adhesion to cultured human umbilical vein endothelial cells (HUVEC). The results showed that activity of GM3 synthase and cellular levels of ganglioside GM3 in blood mononuclear cells from atherosclerotic patients were several-fold higher than those from healthy subjects. In monocytes the activity of GM3 synthase was one an order of magnitude higher than in lymphocytes from both groups studied; this suggests the major contribution of monocytes to enhanced biosynthesis and levels of GM3 in mononuclear cells in atherosclerosis. Enrichment of monocytes from healthy subjects with ganglioside GM3 by incubation in medium containing this ganglioside increased adherence of these monocytes to HUVEC up to the values typical for monocytes from atherosclerotic patients. In addition, an increase in CD1 1b integrin expression was observed that was comparable to that seen in lipopolysaccharide-activated monocytes. It is suggested that in atherosclerosis the enhanced cellular levels of GM3 in monocytes and lymphocytes may be an important element of cell activation that facilitates their adhesion to endothelial cells and penetration into intima.

[Aseptic meningitis season caused by enteroviruses in 2007: molecular-epidemiological aspects].

AIM: Analysis of manifestation of epidemic process of aseptic meningitis and causes of its activation using molecular genetic methods. MATERIALS AND METHODS: Samples of feces and CSF, nasopharyngeal swabs from 296 patients with aseptic meningitis (AM), as well as 240 samples of drinking water and 6 samples of lake water were studied. Epidemiologic analysis, isolation of enteroviruses in Hep-2 and RD cell cultures, RT-PCR, partial sequencing of 5'NTR and genome region coding VP1 were performed. RESULTS: Marked rise of AM caused by enteroviruses in Nizhny Novgorod during 2001 - 2007 was demonstrated. From August to October 2007, enteroviruses were detected in 93.8% of patients with AM (22.5 per thousand). Seasonal rise of incidence was determined by 9 serotypes of enteroviruses: E30 - 26 cases (53.1%), E7 - 7 (14.3%), E18 - 5 (10.3%), E13 - 3 (6.1%), E9 - 2 (4.0%), CB5 - 3 (6.1%),CA1 - 1 (2.0%), CA9 - 1 (2.0%), CA13 - 1 (2.0%). Serotype E30, represented by two subtypes, dominated. Dominating subtype E30-N1 was closely related with E30 strains isolated in 1994 - 2001 in Europe. Subtype E30-N2 was genetically related with Asian strains isolated in 2000 - 2006. RNA of E7, E9, E13, E18, CB5 viruses and dominating subtype E30-N1 were detected in nasopharyngeal swabs from patients with AM, which can explain rapid and wide spread of these viruses in susceptible population by aspiration route of transmission. CONCLUSION: Increased incidence of AM in Nizhny Novgorod in 2007 was caused by variant of E30 virus, which was genetically related with strains isolated in European countries in 1997.

Ganglioside GM3 and its biological functions.

Metabolism, topology, and possible mechanisms for regulation of the ganglioside GM3 content in the cell are reviewed. Under consideration are biological functions of GM3, such as involvement in cell differentiation, proliferation, oncogenesis, and apoptosis.

Lipid second messengers and cell signaling in vascular wall.

Agonists of cellular receptors, such as receptor tyrosine kinases, G protein-coupled receptors, cytokine receptors, etc., activate phospholipases (C(gamma), C(beta), A(2), D), sphingomyelinase, and phosphatidylinositol-3-kinase. This produces active lipid metabolites, some of which are second messengers: inositol trisphosphate, diacylglycerides, ceramide, and phosphatidylinositol 3,4,5-trisphosphate. These universal mechanisms are involved in signal transduction to maintain blood vessel functions: regulation of vasodilation and vasoconstriction, mechanical stress resistance, and anticoagulant properties of the vessel lumen surface. Different signaling pathways realized through lipid second messengers interact to one another and modulate intracellular events. In early stages of atherogenesis, namely, accumulation of low density lipoproteins in the vascular wall, cascades of pro-atherogenic signal transduction are triggered through lipid second messengers. This leads to atherosclerosis, the general immuno-inflammatory disease of the vascular system.

Activation of ganglioside GM3 biosynthesis in human monocyte/macrophages during culturing in vitro.

We found that GM3 levels in human peripheral blood monocytes and cultured monocyte-derived macrophages were 0.37 and 2.7 microg per million cells, respectively. GM3 synthase of monocytes and to a greater extent of monocyte-derived macrophages was shown to be able to sialylate endogenous substrate, lactosylceramide (LacCer), to form GM3. With exogenously added LacCer, GM3 synthase activity was 57.1 and 563 pmol/h per mg protein in monocytes and monocyte-derived macrophages, respectively. The revealed changes in ganglioside GM3 biosynthesis are specific as the activity of some other sialyltransferases under these conditions was not altered. Human anti-GM3 synthase antibody detected in monocytes a main protein with molecular weight of 60 kD and minor proteins with molecular masses of 52 and 64 kD. In monocyte-derived macrophages the amounts of 60 kD protein and especially 64 kD protein sharply rose. Thus, the increase in ganglioside GM3 levels, GM3 synthase activity, and the enzyme amounts during culturing of monocyte/macrophages may be one of the mechanisms of in vivo increased ganglioside GM3 levels in arterial atherosclerotic lesions.

[Optimization of RT-PCR for the identification of VP4 gene of group A rotaviruses and evaluation of its diagnostic efficiency].

A method is suggested for the detection of the human rotavirus VP4 gene by RT-PCR. The method is universal for all [P] types of group A rotavirus in clinical samples. As against RNA electrophoresis and ELISA, it provides for a more accurate detection of rotaviruses by 18.8 and 26.5%, respectively. It was established by RT-PCR in February, 2002, in Nizhny Novgorod, that rotaviruses were responsible for 67% of acute gastroenteritis in hospitalized children.

Development of antibody to human GM3 synthase and immunodetection of the enzyme in human tissues.

Polyclonal antibody was raised to a cloned fragment of human GM3 synthase. Affinity purified R27C1 antibody to the tagged recombinant protein inhibited GM3 synthase activity in human liver and HL-60 cells in a dose-dependent manner. However, the R27C1 antibody did not affect liver sialyltransferase activity towards asialofetuin. We are the first to measure GM3 synthase activity in human liver (194 +/- 60 pmol NeuAc/h per mg protein), which was about 10-fold lower than in phorbol myristate acetate-stimulated HL-60 cells (1353 +/- 573 pmol NeuAc/h per mg protein). On immunoblotting the R27C1 antibody recognized a common protein band in a number of human tissues (liver, brain, atherosclerotic aortic intima, HL-60 cells) with molecular mass of about 60 kD, which is similar to that of the purified GM3 synthase from rat liver. In human liver and aortic intima, the 60-kD band was almost a single band, which makes possible the use of the R27C1 antibody for immunohistochemical studies in these tissues.

[Disturbed cooperation of hepatocytes in the rhythm of protein synthesis by chelating agent of cytoplasmic calcium BAPTA-AM]. / Narushenie kooperatsii gepatotsitov v ritme sinteza belka khelatorom tsitoplasmaticheskogo kal'tsiia BAPTA-AM.

Previously we demonstrated synchronized oscillations of protein synthesis rate in the hepatocyte cultures upon accumulation of monosialognaglioside GM1 in the medium or after introduction of exogenous GM1 to the medium. The synchronized oscillations of the protein synthesis rate in dense hepatocyte cultures were blocked 30 min after their treatment with 10-20 microM BAPTA-AM--a chelating agent of cytoplasmic calcium. Enzyme immunoassay for GM1 demonstrated similar amounts of GM1 in the medium conditioned for 3 h by dense hepatocyte cultures pretreated with 20 microns]M BAPTA-AM for 1 h and in the medium of normal dense cultures--0.0060 +/- 0.0005 and 0.0055 +/- 0.0005 pmol/1000 cells, respectively. The content of GM1 was also similar in the normal and BAPTA-AM-pretreated hepatocytes--0.158 +/- 0.013 and 0.183 +/- 0.014 pmol/1000 cells, respectively. The synchronized rhythm of protein synthesis has been confirmed in the diluted cultures in the medium conditioned by the normal dense cultures. However, the medium conditioned by the dense cultures pretreated with BAPTA-AM induces no synchronization of the diluted cultures. Since GM1 concentration was normal in this medium, we propose the effect of physicochemical form of the gangliosides accumulated in the medium on their ability to synchronize the rhythm of protein synthesis.

Sialidase activity in normal and atherosclerotic human aortic intima.

Sialidase activity has been determined in homogenates of human aortic intima by measuring the amount of GM1 formed during the incubation of ganglioside GD1a with the tissue homogenates. Areas with atherosclerotic lesions as well as adjacent areas without histological evidence of atherosclerosis were taken for comparison. The rate of GM1 formation from GD1a in the presence of homogenates of the atherosclerotic intima was 20 pmol/h per mg protein. Homogenates of the unaffected intima did not desialylate GD1a. Sialidase activity of the atherosclerotic intima was linear for 1.5 h at GD1a content up to 1.5 nmol and at homogenate protein up to 1 micro g. NH4Cl and NeuAc2en, inhibitors of lysosomal function and plasma membrane-bound sialidase, respectively, reduced sialidase activity of homogenates of the atherosclerotic intima by 94%. The results indicate that atherosclerotic lesions and unaffected intima differ in their activity and specificity of sialidases that cleave gangliosides.

Sialyltransferase activity in normal and atherosclerotic human aorta intima.

Sialyltransferase activity has been determined in Golgi membrane fractions isolated from atherosclerotic and normal intima of human aorta by measuring the transfer of N-acetylneuraminic acid (NeuAc) from CMP-NeuAc to asialofetuin. The asialofetuin-sialyltransferase activity was found to be twofold higher in the atherosclerotic intima than in the normal intima. The mean value of the apparent Michaelis constant (Km) for the sialylating enzyme in both tissues did not differ and was 57 microM. In contrast, the maximal velocity (Vmax) was 2-fold higher for the atherosclerotic intima than for the normal intima. These results suggest that expression of asialofetuin-sialyltransferases of the aortal intima may be increased in atherosclerosis.

Phenotype determination of anti-GM3 positive cells in atherosclerotic lesions of the human aorta. Hypothetical role of ganglioside GM3 in foam cell formation.

Earlier we reported that atherosclerotic plaques contain cells which were specifically and very intensively stained with anti-GM3 antibodies although no GM3 positive cells were detected in the normal non-diseased arterial intima. Because of their lipid inclusions, GM3 positive cells in atherosclerotic lesions seemed to be foam cells but their origin needed clarification. Using an immunohistochemical technique in the present work, we showed that some of these foam cells contained CD68 antigen. However, the most intense accumulation of GM3 occurred in the areas composed of foam cells which did not stain with any cell type-specific antibodies, including antibodies to macrophages (anti-CD68) and smooth muscle cells (anti-smooth muscle alpha-actin), perhaps, because the cell type-specific antigens were lost during the transformation of intimal cells into foam cells. Ultrastructural analysis of the areas where foam cells overexpressed GM3 demonstrated that some foam cells lacked both a basal membrane and myofilaments but contained a large number of secondary lysosomes and phagolysosomes, morphological features which might indicate their macrophage origin. Other foam cells contained a few myofilaments and fragments of basal membrane around their plasmalemmal membrane, suggesting a smooth muscle cell origin. These observations indicate that accumulation of excessive amounts of GM3 occurs in different cell types transforming into foam cells. We suggest that up-regulation of GM3 synthesis in intimal cells might be an essential event in foam cell formation. Shedding of a large number of membrane-bound microvesicles from the cell surface of foam cells was observed in areas of atherosclerotic lesions corresponding to extracellular GM3 accumulation. We speculate that extracellularly localised GM3 might affect the differentiation and modification of intimal cells in atherosclerotic lesions.