Gaucher Disease: Our primary interest is to understand the pathogenesis of the neurological involvement in this disease and to test novel therapeutic approaches. Over the past year, we have further delineated the pathologic and clinical abnormalities of the variant of Gaucher disease with parkinsonism. Using a neuronal model system that we developed, we found that mutated glucocerebrosidase provides additional cellular toxicity when the proteosomal degradation pathway is stressed by the addition of an inhibitor of this pathway. A chemical chaperone partially reversed this susceptibility. This finding may explain the association of parkinsonism in individuals carrying mutations of the glucocerebrosidase gene. We found that in patients with Gaucher disease and parkinsonism there is colocalization of alpha-synuclein and glucocerebrosidase in cultured cells and in Lewy bodies found in the brain of those patients. These observations indicate that mutant glucocerebrosidase, even in heterozygotes, may be toxic and are a risk factor for parkinsonism. This work is likely to provide insights into the genetics, pathogenesis and treatment of Parkinson disease as well as Gaucher disease. We therefore plan to initiate experiments using small molecules that are active site chemical chaperones in order to enhance enzyme activity of patients with Gaucher disease, particularly in the brain. These compounds promote normal folding of the mutated enzyme and are likely to decrease its toxicity. Therefore, if successful, this approach may also be useful to slow the progression of parkinsonian encephalopathies that associated with mutations of the glucocerebrosidase gene. We are conducting a randomized controlled trial of OGT 918 (N-butyldeoxynojirimycin, Zaveska) as a substrate reduction approach for the treatment of patients with neuronopathic Gaucher disease. We are evaluating primarily the neurological abnormalities, and in particular the slow eye movements of these patients. Thus far, this medication is well tolerated. Results of the 1st year will be available in FY 2006. Fabry Disease: Patients with this second most common lysosomal disorder have a severely painful peripheral neuropathy, premature strokes and myocardial infarctions, and kidney insufficiency. We have been exploring enzyme replacement therapy (ERT) for Fabry disease. Patients on long-term therapy had significant reduction in pain, improvement in sensing cold and warm and in their sweat function. However, ERT did not reduce the incidence of stroke. We therefore performed extensive studies on the pathogenesis of stroke in Fabry disease. Our ongoing hypothesis regarding strokes this disorder is that reactive oxygen species play an important role. We found increased staining for 3-nitrotyrosine in dermal and cerebral blood vessels and elevated nitrotyrosine and myeloperoxidase levels in blood of patients. Myeloperoxidase elevation may be related to our observation of premature atherosclerosis in patients with Fabry disease, a finding confirmed by another group in a mouse model for this disorder. We found that the likelihood of occurrence of cerebral lesions seen on MRI in patients with Fabry disease seems to be modified by alterations of other genetic risk factors for stroke such as interleukin-6, factor V Leiden, protein Z and endothelial nitric oxide synthase. These observations should contribute to the general understanding of Fabry disease and vasculopathies of the general population. Because of the partial effect of ERT in adult patients, we hypothesized that better results may be obtained when it is initiated in childhood. We therefore completed a 6 month study on ERT in children 7-17 years of age with Fabry disease. Preliminary results demonstrate that ERT was safe and led to a marked reduction in neuropathic pain and gastrointestinal dysfunction as well as overall improvement in quality of life. This study is continuing in order to determine the long-term effect of ERT in this patient population. Using genomic techniques, we identified a gene that is over-expressed in children with Fabry disease. This finding should help understand the pathogenesis of this disease and serve as a potential marker to monitor response to specific therapies. We also initiated a program of active-site chaperone therapy in patients with Fabry disease who have with enhanceable alpha-galactosidase A activity. Initial work in our laboratory confirmed marked in vitro enhanceability of the deficient enzyme in peripheral blood white cells of some patients by the chemical chaperone. A treatment trial with such an agent is planned for the near future. The extensive delivery throughout the body of chemical chaperones should have a significant advantage over ERT where the infused enzyme enters into vascular endothelial cells for the most part. This therapeutic approach should be applicable to other disorders where the mutated enzyme is enhanceable. Mucolipidosis IV: We continued our investigation of 35 patients with this autosomal recessive neurogenetic disorder with particular emphasis on their progressive retinal degeneration. The latter is thought to be caused by death of neurons in the retina. Using electroretinography and visual evoked potential we quantified the decline of retinal function in MLIV. This study will be useful to identify the optimal stage for therapeutic intervention to prevent progression of the retinal dystrophy in MLIV. The neurological aspect of this disorder is developmental in nature with little decline over the years. It is therefore evident that mucolipidosis IV is both a developmental and a degenerative disorder. The presentation as a cerebral palsy-like encephalopathy often delays the correct diagnosis of this condition. Leukodystrophies: We collaborated on the identification of novel functional and chemical means to identify and characterize patients with the leukodystrophy CACH (childhood ataxia with CNS hypomyelination), a leukodystrophy that was first identified by DMNB in 1992. Patients with CACH develop a progressive neurological deterioration in childhood or adolescence and sometimes in adulthood. It is caused by a deficiency of eukaryotic initiation factor 2B (eIF2B). The clinical decline is often initiated or worsens after stress such as a mild head trauma or an intercurrent febrile illness. eIF2B is a protein complex that is essential for the regulation of protein synthesis, particularly in response to stress. Over the past year we collaborated on a finding that patients with eIF2B mutations have marked decrease of asialo-transferrin in the cerebrospinal fluid. The reduction of asialo-transferrin likely reflects disturbance in the function of oligodendrocytes and astrocytes. If this finding is confirmed, it will be useful as a diagnostic tool and possibly as a marker for therapeutic trials. We also identified an increase in ATF4, a transcription factor controlled by eIF2B, in cells that undergo stress in the endoplasmic reticulum. These eIF2B abnormalities suggest enhanced translation of specific mRNA of proteins in response to stress and may serve to screen for both diagnosis and identification of potential therapeutic agents. Finally, we investigated a new leukodystrophy syndrome we recently identified that combines a dysmyelination and selective pituitary gland hypogonadotrphic hypogonadism. We found a unique disorganization of the myelin sheath, abnormal myelin periodicity and deposits of proteinaceous material in peripheral nerves. It is likely that these investigations will lead to a better understanding of myelination and maintenance of the myelin sheath.
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