[Biogenesis, the Function of Peroxisomes, and Their Role in Genetic Disease: With a Focus on the ABC Transporter].

Peroxisomes are organelles that are present in almost all eukaryotic cells. These organelles were first described in 1954, in the cytoplasm of the proximal tubule cells in the mouse kidney, using electron microscopy by Rhodin and referred to as "microbodies". Then, de Duve and Baudhuin isolated microbodies from rat liver using density gradient centrifugation, defined the microbodies as membrane-bound organelles containing several H2O2-producing oxidases and H2O2-degrading catalase, and named them peroxisomes. At present, the biogenesis of peroxisomes in mammals involves three different processes: the formation of pre-peroxisomes from the endoplasmic reticulum, the import of peroxisomal membrane and matrix proteins to the pre-peroxisomes, and the growth and division of the peroxisomes. These organelles are involved in a variety of metabolic processes, including the ß-oxidation of very long chain fatty acids, and the synthesis of ether phospholipids and bile acids in mammals. These metabolic pathways require the transport of metabolites in and out of peroxisomes. The transport of such metabolites is facilitated in part by the ATP-binding cassette (ABC) transporter. Impairment of the biogenesis and function of peroxisomes causes severe peroxisomal disorders. Since I began peroxisome research at Professor de Duve's laboratory in 1985, I have studied the biogenesis and function of peroxisomes and peroxisome diseases for more than 30 years, with a focus on ABC transporters. Here, I review the biogenesis of peroxisomes, the targeting of ABC transporters to the peroxisome, and the function of ABC transporters in physiological and pathological processes, including X-linked adrenoleukodystrophy, a neurodegenerative disease.

Spastic paraparesis caused by X-linked adrenoleukodystrophy mimicking vacuolar myelopathy in a human immunodeficiency virus patient: A case report.

RATIONALE: Vacuolar myelopathy is one of most common cause of spastic paresis in patients with human immunodeficiency virus (HIV) infection. However, X-linked adrenoleukodystrophy (X-ALD), which is a metabolic disorder caused by impairment of peroxisomal beta-oxidation of very-long-chain fatty acids (VLCFA), also manifests as various neurological deteriorations including adult onset spastic paraparesis. To the best of our knowledge, there has been no report of newly developed spastic paresis due to X-ALD in a patient with HIV infection. PATIENT CONCERNS: A 30-year-old male had presented with progressive spastic paraparesis for 1 year. DIAGNOSIS: X-ALD. INTERVENTION: Brain and spine magnetic resonance imaging (MRI), VLCFA, and genetic test. OUTCOMES: His spinal MRI mimicked vacuolar myelopathy, but he was finally diagnosed with X-ALD using the VLCFA and genetic test. LESSONS: Although rare, isolated spastic paraparesis can occur in HIV patients; additional tests such as VLCFA can be useful for the differential diagnosis. More data are needed to understand the pathological mechanisms underlying the two diseases.

Etiology and treatment of adrenoleukodystrophy: new insights from Drosophila.

Adrenoleukodystrophy (ALD) is a fatal progressive neurodegenerative disorder affecting brain white matter. The most common form of ALD is X-linked (X-ALD) and results from mutation of the ABCD1-encoded very-long-chain fatty acid (VLCFA) transporter. X-ALD is clinically heterogeneous, with the cerebral form being the most severe. Diagnosed in boys usually between the ages of 4 and 8 years, cerebral X-ALD symptoms progress rapidly (in as little as 2 years) through declines in cognition, learning and behavior, to paralysis and ultimately to a vegetative state and death. Currently, there are no good treatments for X-ALD. Here, we exploit the Drosophila bubblegum (bgm) double bubble (dbb) model of neurometabolic disease to expand diagnostic power and therapeutic potential for ALD. We show that loss of the Drosophila long-/very-long-chain acyl-CoA synthetase genes bgm and/or dbb is indistinguishable from loss of the Drosophila ABC transporter gene ABCD Shared loss-of-function phenotypes for synthetase and transporter mutants point to a lipid metabolic pathway association with ALD-like neurodegenerative disease in Drosophila; a pathway association that has yet to be established in humans. We also show that manipulation of environment increases the severity of neurodegeneration in bgm and dbb mutant flies, adding even further to a suite of new candidate ALD disease-causing genes and pathways in humans. Finally, we show that it is a lack of lipid metabolic pathway product and not (as commonly thought) an accumulation of pathway precursor that is causative of neurometabolic disease: addition of medium-chain fatty acids to the diet of bgm or dbb mutant flies prevents the onset of neurodegeneration. Taken together, our data provide new foundations both for diagnosing ALD and for designing effective, mechanism-based treatment protocols.This article has an associated First Person interview with the first author of the paper.

Clinically distinct presentations of copper deficiency myeloneuropathy and cytopenias in a patient using excessive zinc-containing denture adhesive.

OBJECTIVES: While copper deficiency has long been known to cause cytopenias, copper deficiency myeloneuropathy is a more recently described entity. Here, we present the case of two clinically distinct presentations of acquired copper deficiency syndromes secondary to excessive use of zinc-containing denture adhesive over five years: myeloneuropathy and severe macrocytic anemia and neutropenia. METHODS: Extensive laboratory testing and histologic evaluation of the liver and bone marrow, were necessary to rule out other disease processes and establish the diagnosis of copper deficiency. RESULTS: The initial presentation consisted of a myelopathy involving the posterior columns. Serum and urine copper were significantly decreased, and serum zinc was elevated. On second presentation (five years later), multiple hematological abnormalities were detected. Serum copper was again decreased, while serum zinc was elevated. CONCLUSIONS: Zinc overload is a preventable cause of copper deficiency syndromes. This rare entity presented herein highlights the importance of patient, as well as provider, education.

A de-novo large deletion of 2.8 kb produced in the ABCD1 gene causing adrenoleukodystrophy disease.

X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disorder caused by mutations in the ABCD1 gene, which encodes an ATP-binding cassette transporter protein, ALDP. The disease is characterized by increased concentrations of very long chain fatty acids (VLCFAs) in plasma, adrenal, testicular, and nerve tissues. For this study, our objective was to conduct clinical, molecular, and genetic studies of a Tunisian patient with X-ALD. The diagnosis was based on clinical indications, biochemical analyses, typical brain-scan patterns, and molecular biology; the molecular analyses were based on PCR, long-range PCR, and sequencing. The molecular analysis by long-range PCR and direct sequencing of the ABCD1 gene showed the presence of a de-novo 2794 bp deletion covering the whole of exon 2. Using bioinformatics tools, we demonstrate that the large deletion is located in a region rich with Alu sequences. Furthermore, we suggest that the AluJb sequence could be the cause of the large deletion of intron 1, exon 2, and intron 2, and the creation of a premature stop codon within exon 3. This report is the first report in which we demonstrate the breakpoints and the size of a large deletion in a Tunisian with X-ALD.

X-linked adrenoleukodystrophy: pathogenesis and treatment.

X-linked adrenoleukodystrophy (X-ALD) is a puzzling inborn error of metabolism with a strikingly heterogeneous clinical spectrum. All patients have mutations in the ABCD1 gene and accumulate very long chain fatty acids in all tissues. Virtually all male X-ALD patients develop adrenocortical insufficiency in childhood and progressive myelopathy and peripheral neuropathy in adulthood. A subset of male patients, however, develops a fatal cerebral demyelinating disease, cerebral adrenoleukodystrophy. Female patients also develop progressive myelopathy and peripheral neuropathy, but generally at a later age than males. They only very rarely develop adrenocortical insufficiency or cerebral adrenoleukodystrophy. This review proposes to simplify the classification of the clinical spectrum of X-ALD and reviews the largely unresolved pathophysiological mechanisms and the current treatment options.

[Anesthetic management of a patient with adrenoleukodystrophy].

Adrenoleukodystrophy (ALD) is a genetic disorder with demyelination of the central nervous system and adrenal insufficiency. A 24-year-old man with ALD was scheduled for dental treatment under general anesthesia. He was diagnosted as having ALD at the age of 5. Past medical history included recurrent cervical cellulitis, adrenal insufficiency, mental retardation, muscle weakness and seizure disorder. General anesthesia was induced using betamethasone as a steroid cover, sevoflurane and nitrous oxide-oxygen and maintained with sevoflurane and nitrous oxide-oxygen. Nasal intubation was performed without using a muscle relaxant. Patients with ALD cannot metabolize very long chain fatty acid, so we did not use propofol containing long chain fatty acid. Operation and anesthesia were uneventful. There were no complications during and after anesthesia.

Spastic paraparesis and sensorineural hearing loss in a patient with neurobrucellosis.

OBJECTIVE: Brucellosis is a zoonotic disease and still a major public health problem in many geographic areas including Mediterranean basin and Middle East. Brucellosis causes multisystemic involvement and although rare central nervous system involvement causes serious manifestations. Neurobrucellosis occurs less than 5% of patients and presents with meningitis,encephalitis, myelitis, myelopathy, stroke, paraplegia, radiculoneuritis, intracerebral abscess, epidural abscess, demyelination and cranial nerve involvement or any combination of these manifestations. Spastic paraparesis and the sensorineural involvement are rarely reported in the literature. METHODS: Herein we present a 28 years-old man with spastic paraparesis and sensorineural hearing loss due to neurobrucellosis. RESULTS: The patient was treated with antibiotics combination for 6 months and underwent rehabilitation program. CONCLUSIONS: Neurobrucellosis should be ruled out in patients with unexplained neurological symptoms and/or sensorineuralhearing loss particularly in those living in endemic areas.

[Peroxisomal ABC transporters and X-linked adrenoleukodystrophy]. / Transporteurs ABC peroxysomaux et adrénoleucodystrophie liée au chromosome X.

X-linked adrenoleukodystrophy (X-ALD) is a complex neurodegenerative disease associated with mutations in the ABCD1 gene, which encodes for a peroxisomal ABC transporter. Thanks to the efforts of the ELA foundation and to the recent successes of gene therapy published in Science in 2009, X-ALD is better known but still remains poorly understood. The exact role of ABCD1 and its homologs, as well as the exact link between the biochemical and metabolic peroxisomal defects and the clinical symptoms of the disease remain to be elucidated. This review summarizes the knowledge concerning the subfamily D of the ABC transporter family and concerning X-ALD, the most frequent peroxisomal disorder.

Adrenoleukodystrophy.

X-linked adrenoleukodystrophy (ALD) is caused by mutations in the ABCD1 gene that encodes a protein of the peroxisomal membrane named ALDP. Mutations in ALDP result in elevated levels of very long chain fatty acids (VLCFA) and reduced VLCFA oxidation in peroxisomes. Three main phenotypes are seen in affected males. The childhood cerebral form manifests usually between ages 4 and 8 years. It initially resembles attention deficit disorder or hyperactivity. Progressive central demyelination with impairment of cognition, behavior, vision, hearing, and motor function follow the initial symptoms and often lead to total disability within 2 years. The second phenotype, adrenomyeloneuropathy, manifests most commonly in the late twenties as progressive paraparesis, sphincter disturbances, sexual dysfunction, and often, impaired adrenocortical function; all symptoms are progressive over decades. The third phenotype, 'Addison disease only', presents with primary adrenocortical insufficiency between age 2 years and adulthood and most commonly by age 7.5 years, without evidence of neurologic abnormality. Approximately 50% of females who are carriers develop neurologic manifestations that resemble adrenomyeloneuropathy but have a later onset (age ≥35 years) and a milder disease. In this review, we will give an overview of the present understanding of ALD, and the implications of new diagnostics and treatment.

Pathomechanisms underlying X-adrenoleukodystrophy: a three-hit hypothesis.

X-adrenoleukodystrophy (X-ALD) is a complex disease where inactivation of ABCD1 gene results in clinically diverse phenotypes, the fatal disorder of cerebral ALD (cALD) or a milder disorder of adrenomyeloneuropathy (AMN). Loss of ABCD1 function results in defective beta oxidation of very long chain fatty acids (VLCFA) resulting in excessive accumulation of VLCFA, the biochemical "hall mark" of X-ALD. At present, the ABCD1-mediated mechanisms that determine the different phenotype of X-ALD are not well understood. The studies reviewed here suggest for a "three-hit hypothesis" for neuropathology of cALD. An improved understanding of the molecular mechanisms associated with these three phases of cALD disease should facilitate the development of effective pharmacological therapeutics for X-ALD.

Head trauma can initiate the onset of adreno-leukodystrophy.

X-linked adreno-leukodystrophy and its adult variant, adrenomyeloneuropathy, are caused by mutations in ABCD1 that encodes a peroxisomal membrane protein of unknown physiological significance. In spite of identical mutations, they can have markedly divergent neurological and neuropathologic characteristics. Adreno-leukodystrophy classically presents in normal boys with mild neuropsychiatric features, which progress to frank neurological signs, the vegetative state and death in approximately three years. Adrenomyeloneuropathy typically affects young men with spastic paraparesis and sensory ataxia that can progress over decades. The neuropathologic correlate for adreno-leukodystrophy is severe inflammatory demyelination of posterior cerebral white matter, while a chronic distal axonopathy of spinal cord and peripheral nerve occurs in adrenomyeloneuropathy. Consequently, both modifier genes and environmental factors have been implicated in their pathogeneses. We report five cases of adreno-leukodystrophy whose onsets were initiated by moderate to severe head trauma, two of whom were conversions from adrenomyeloneuropathy. Their clinical courses were rapidly incapacitating, short (i.e., weeks to a few years) and fatal due to marked cerebral inflammatory demyelination. These cases, in concert with several previous reports, indicate that head trauma is one environmental factor that can have a profoundly deleterious effect on those genetically at risk for, or with milder clinical phenotypes of, this disease. Avoidance of potential head trauma and a rapid response to episodes of moderate to severe head trauma in this patient population seem prudent.

Leukoencephalopathies associated with inborn errors of metabolism in adults.

The discovery of a leukoencephalopathy is a frequent situation in neurological practice and the diagnostic approach is often difficult given the numerous possible aetiologies, which include multiple acquired causes and genetic diseases including inborn errors of metabolism (IEMs). It is now clear that IEMs can have their clinical onset from early infancy until late adulthood. These diseases are particularly important to recognize because specific treatments often exist. In this review, illustrated by personal observations, we give an overview of late-onset leukoencephalopathies caused by IEMs.

Live cell FRET microscopy: homo- and heterodimerization of two human peroxisomal ABC transporters, the adrenoleukodystrophy protein (ALDP, ABCD1) and PMP70 (ABCD3).

The adrenoleukodystrophy protein (ALDP) and the 70-kDa peroxisomal membrane protein (PMP70) are half-ATP-binding cassette (ABC) transporters in the mammalian peroxisome membrane. Mutations in the gene encoding ALDP result in a devastating neurodegenerative disorder, X-linked adrenoleukodystrophy (X-ALD) that is associated with elevated levels of very long chain fatty acids because of impaired peroxisomal beta-oxidation. The interactions of peroxisomal ABC transporters, their role in the peroxisomal membrane, and their functions in disease pathogenesis are poorly understood. Studies on ABC transporters revealed that half-transporters have to dimerize to gain functionality. So far, conflicting observations are described for ALDP. By the use of in vitro methods (yeast two-hybrid and immunoprecipitation assays) on the one hand, it was shown that ALDP can form homodimers as well as heterodimers with PMP70 and ALDR, while on the other hand, it was demonstrated that ALDP and PMP70 exclusively homodimerize. To circumvent the problems of artificial interactions due to biochemical sample preparation in vitro, we investigated protein-protein interaction of ALDP in its physiological environment by FRET microscopy in intact living cells. The statistical relevance of FRET data was determined in two different ways using probability distribution shift analysis and Kolmogorov-Smirnov statistics. We demonstrate in vivo that ALDP and PMP70 form homodimers as well as ALDP/PMP70 heterodimers where ALDP homodimers predominate. Using C-terminal deletion constructs of ALDP, we demonstrate that the last 87 C-terminal amino acids harbor the most important protein domain mediating these interactions, and that the N-terminal transmembrane region of ALDP has an additional stabilization effect on ALDP homodimers. Loss of ALDP homo- or heterodimerization is highly relevant for understanding the disease mechanisms of X-ALD.

Adreno-leukodystrophy: oxidative stress of mice and men.

X-linked adreno-leukodystrophy is a progressive, systemic peroxisomal disorder that affects primarily nervous system myelin and axons as well as the adrenal cortex. Several divergent clinical phenotypes can occur in the same family; thus, there is no correlation between the clinical phenotype and the mutation in the ABCD1 gene in this disease. The most urgent and unresolved clinical issue is the fulminant inflammatory (immune) demyelination of the central nervous system in which a variety of cellular participants, cytokines, and chemokines are noted. A knockout mouse model exhibits mitochondrial deficits and axonal degeneration, but not inflammatory demyelination. To determine whether oxidative stress and damage might play a pathogenic role, we assessed standard biochemical and immunohistochemical markers of such activity both in our knockout mouse model and patients. We find that oxidative stress, as judged by increased immunoreactivity for the mitochondrial manganese-superoxide dismutase, is present in the knockout mouse liver, adrenal cortex, and renal cortex, tissues that normally express high levels of ABCD1 but no evidence of oxidative damage. The brain does not exhibit either oxidative stress or damage. On the other hand, both the human adrenal cortex and brain show evidence of oxidative stress (e.g. hemoxygenase-1 and manganese-superoxide dismutase) and oxidative damage, particularly from lipid peroxidation (4-hydroxynonenal and malondialdehyde). The presence of nitrotyrosylated proteins is strong circumstantial evidence for the participation of the highly toxic peroxynitrite molecule, whereas the demonstration of interferon gamma and interleukin-12 is indicative of a TH1 response in the inflammatory demyelinative lesions of the cerebral phenotype. These differences between the adreno-leukodystrophy mouse and human patients are intriguing and may provide a clue to the phenotypic divergence in this disease.

X-linked adrenoleukodystrophy: therapeutic approaches to distinct phenotypes.

X-linked adrenoleukodystrophy (X-ALD) in males can present with eight distinct phenotypes, which vary greatly in respect to phenotypic expression, age of onset and rate of progression and therapy. The plasma very long chain fatty acid assay permits precise diagnosis and is already abnormal at birth. The clinical features, molecular biology, pathogenesis, and therapeutic approaches, including the indications for Hematopoietic Stem Cell Transplants (HCT) and dietary therapy are discussed, with emphasis on the asymptomatic, childhood cerebral, and adrenomyeloneuropathy phenotypes. The rationale for neonatal screening and the profound effect that such screening would have on the therapy of X-ALD, including the role of HCT, are discussed.