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Enzyme replacement therapy (ERT) is a treatment option for lysosomal storage disorders (LSDs) caused by deficiencies of soluble lysosomal enzymes. ERT depends on receptor-mediated transport of intravenously injected recombinant enzyme to lysosomes of patient cells. The blood-brain barrier (BBB) prevents efficient transfer of therapeutic polypeptides from the blood to the brain parenchyma and thus hinders effective treatment of LSDs with CNS involvement. We compared the potential of five brain-targeting peptides to promote brain delivery of the lysosomal enzyme arylsulfatase A (ASA). Fusion proteins between ASA and the protein transduction domain of the human immunodeficiency virus TAT protein (Tat), an Angiopep peptide (Ang-2), and the receptor-binding domains of human apolipoprotein B (ApoB) and ApoE (two versions, ApoE-I and ApoE-II) were generated. All ASA fusion proteins were enzymatically active and targeted to lysosomes when added to cultured cells. In contrast to wild-type ASA, which is taken up by mannose-6-phosphate receptors, all chimeric proteins were additionally endocytosed via mannose-6-phosphate-independent routes. For ASA-Ang-2, ASA-ApoE-I, and ASA-ApoE-II, uptake was partially due to the low-density lipoprotein receptor-related protein 1. Transendothelial transfer in a BBB cell culture model was elevated for ASA-ApoB, ASA-ApoE-I, and ASA-ApoE-II. Brain delivery was, however, increased only for ASA-ApoE-II. ApoE-II was also superior to wild-type ASA in reducing lysosomal storage in the CNS of ASA-knock-out mice treated by ERT. Therefore, the ApoE-derived peptide appears useful to treat metachromatic leukodystrophy and possibly other neurological disorders more efficiently.

Metachromatic leukodystrophy (MLD) is a recessive autosomal disease which is characterized by an accumulation of sulfatides in the central and peripheral nervous system. It is due to the enzyme deficiency of the sulfatide sulfatase i.e. arylsulfatase A (ASA). we studied 5/200 cases of MLD and clearly distinguished three clinical forms. One of them presented the juvenile form; two presented the late infantile form; and two other presented the adult form. The Magnetic Resonance Imaging (MRI) of these patients showed a diffuse, bilateral and symmetrical demyelination. The biochemical diagnosis of MLD patients evidencing the low activity of ASA and sulfatide accumulation., Patients and Methods: We studied 5/200 MLD patients addressed to us for behavioral abnormalities and progressive mental deterioration. All of them were diagnosed at first by brain MRI evidencing a bilateral demyelination, then the measurement of ASA activity using P-nitrocathecol sulfate as substrate, finally the sulfatiduria was performed using thin-layer chromatography using alpha-naphtol reagent., Results: In this study, from 200 patients presenting behavioral abnormalities and a progressive mental deterioration, we reported just 2 patients were diagnosed as late-infantile form of MLD. Only1 case presented as the juvenile form; and 2 patients with the adult-type of MLD. The brain magnetic resonance imaging (MRI) of all patients showed characteristic lesions of MLD with extensive demyelination. Biochemical investigations of these patients detected a low level of ASA activity at 0°C and 37°C; the excess of sulfatide in sulfatiduria., Conclusion: MRI is required to orient the diagnosis of MLD patients; the latter must be confirmed by the biochemical investigations which is based on the measurement of ASA activity and the excess of sulfatide showed in the sulfatiduria., Virtual Slides: The virtual slide(s) for this article can be found here:http://www.diagnosticpathology.diagnomx.eu/vs/1791578262610232.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by deficiency in arylsulfatase A (ASA). Concentrations of cholesterol and its metabolites were determined in ASA deficient [ASA(-/-)] mice which serve as an animal model of MLD. We observed a significant reduction in cholesterol content in the brain of adult ASA(-/-) mice when compared to wild-type controls. This was not due to loss of myelin, because ASA(-/-) mice do not demyelinate. Other cholesterol metabolites were not changed significantly in ASA(-/-) mice, except for an increase in lathosterol. Moreover, reduced cholesterol levels were also found in tissue samples from two juvenile MLD cases. Since high cholesterol levels are important for myelination, and various cellular processes, like vesicular trafficking and signal transduction, reduced cholesterol levels might be an important factor in the molecular pathology of MLD.

Inherited deficiency for the lysosomal enzyme arylsulfatase A (ASA) leads to lysosomal storage of sulfatides and to dramatic demyelination in the CNS of humans (metachromatic leukodystrophy, MLD). As an animal model, ASA(-/-) mice have previously been generated by disruption of the ASA gene and are known to develop lysosomal sulfatide storage similar to that in human MLD, and, moreover, to become deaf because of degeneration of the primary neurons of the auditory pathway. The present study deals with the cellular and topographic distribution of sulfatide storage throughout the CNS of ASA(-/-) mice between a few days and 24 months of age. Sulfatide accumulation was detected on the ultrastructural level and by histochemical staining with alcian blue. Sulfatide storage was found in oligodendroglia and neurons in young mice, and in activated microglia (phagocytes) in adult mice. Neuronal sulfatide storage was most prominent in many nuclei of the medulla oblongata and pons, and in several nuclei of midbrain and forebrain. Sulfatide-storing phagocytes were most frequent in the white matter tracts of aged ASA(-/-) mice, whereas no widespread demyelination was obvious. Loss of neurons was found in two nuclei of the auditory pathway of aged ASA(-/-) mice (ventral cochlear nucleus and nucleus of trapezoid body). The distributional pattern of sulfatide storage throughout the CNS of ASA(-/-) mice largely corresponds to data reported for human MLD. An important difference, however, which remains unexplained at present, is the absence of obvious demyelination from the CNS of ASA(-/-) mice up to the age of 2 years.

Metachromatic leukodystrophy (MLD) is an autosomal recessive neurodegenerative disorder due to deficiency of the enzyme arylsulfatase A that leads to progressive, diffuse demyelination. The syndrome of nonverbal learning disability has been attributed to white matter abnormality and has been reported in children with this disorder and in some healthy family member carriers of gene. We examined the neuropsychologic profiles and MRIs of eight members of the family of a 7-year-old girl with this disease, all of whom were heterozygous carriers of the mutation and five of whom were also carriers of the MLD pseudodeficiency gene. All had low normal levels of arylsulfatase A, and seven of the eight had average or better profiles across all assessed neuropsychological domains. The patient's younger sister had a profile with features of the syndrome of nonverbal learning disability despite a normal MRI, whereas two members with minor white matter findings did not. This family does not provide evidence for the syndrome of nonverbal learning disability in heterozygous carriers of the gene for MLD, even when associated with the MLD pseudodeficiency gene.

Objectives: We describe 2 patients with epilepsy as an early manifestation of late onset metachromatic leukodystrophy (MLD)., Methods and Results: The first patient presented with epileptic seizures at the age of 34 years while neurological and cognitive abnormalities appeared later. MRI findings were compatible with leukodystrophy and low levels of arylsulphatase-A activity confirmed MLD. The second patient developed epileptic seizures and behavioral disturbances at the age of 19 years. She remained stable and seizure free for 8 years. Afterwards she developed uncontrolled epileptic seizures and status epilepticus as well as neurological and cognitive impairment. Leukodystrophy was diagnosed by MRI findings and low levels of arylsulphatase-A activity were compatible with MLD., Conclusion: Our 2 cases postulate that epileptic seizures may be an early and prominent manifestation of late onset MLD.

Background: The leukodystrophies constitute a wide spectrum of cerebral disorders of varying etiology. The imaging appearances on CT and MRI are recognizable as abnormalities of white matter; however, it may be impossible to arrive at the correct diagnosis based on imaging studies alone., Patients and Methods: Three patients of varying age and clinical symptomatology diagnosed with metachromatic leukodystrophy (MLD) had remarkably similar MRI appearances. A "tigroid" or "leopard-skin" appearance was demonstrated within deep white matter in each case., Results: All of the patients had biochemical confirmation of MLD., Conclusion: Although the "tigroid" pattern previously was considered to be pathognomonic of Pelizaeus-Merzbacher disease, the diagnosis of MLD must now be considered when these MRI appearances are encountered.

The carrier rates of a genetic marker for arylsulphatase A pseudodeficiency (ASA-PD) were determined in three series of patients with vascular dementia (VaD) or Alzheimer's disease (AD). In the first community-based sample, the 1524 + 95A-->G mutation, which is known to be associated with ASA-PD, was present in 35% of VaD cases and none of the AD cases. In a second sample of cases drawn from a Dementia Register, the mutation rates were 18% (VaD) and 16% (AD). Brain DNA from a post-mortem sample revealed the ASA-PD mutation in 60% of VaD cases and 34% of AD cases. These rates are higher than previous studies of culturally similar populations and suggest that ASA-PD may be a risk factor for dementia.

A 4-year old boy died of diffuse disseminated sclerosis (DDS) of the brain and was found to have also pseudoarylsulfatase A deficiency (PASAD) with about 20% residual arylsulfatase A (ASA) and cerebroside sulfatase (CS) activity. The reexamination of lipids did not show any sulfatide accumulation in the patient's organ extracts. Although the residual CS activity in the patient's extracts was clearly demonstrable only after partial purification, it was concluded that this activity protects organ tissues from sulfatide accumulation in PASAD, since in sulfatide lipidosis (metachromatic leukodystrophy, MLD) no residual CS activity was detectable. The study of residual ASA activity in the patient's fibroblasts by gel electrofocusing resulted in an almost normal enzyme microheterogeneity. However, the detailed study of the brain galactolipids in the patient revealed an elevated ratio of sulfatide/galactocerebroside content, despite the decrease of both lipids. In tissues of other patients with severe demyelinating diseases different from DDS and MLD, this galactolipid ratio was also found to be increased, especially in three patients with adrenoleukodystrophy. A general mechanism of this anomaly in severe demyelination is considered.