Identification of the inflammatory cells in the central nervous system of patients with adrenoleukodystrophy

Immune response of BV-2 microglial cells is impacted by peroxisomal beta-oxidation

Microglia are crucial for brain homeostasis, and dysfunction of these cells is a key driver in most neurodegenerative diseases, including peroxisomal leukodystrophies. In X-linked adrenoleukodystrophy (X-ALD), a neuroinflammatory disorder, very long-chain fatty acid (VLCFA) accumulation due to impaired degradation within peroxisomes results in microglial defects, but the underlying mechanisms remain unclear. Using CRISPR/Cas9 gene editing of key genes in peroxisomal VLCFA breakdown (Abcd1, Abcd2, and Acox1), we recently established easily accessible microglial BV-2 cell models to study the impact of dysfunctional peroxisomal β-oxidation and revealed a disease-associated microglial-like signature in these cell lines. Transcriptomic analysis suggested consequences on the immune response. To clarify how impaired lipid degradation impacts the immune function of microglia, we here used RNA-sequencing and functional assays related to the immune response to compare wild-type and mutant BV-2 cell lines under basal conditions and upon pro-inflammatory lipopolysaccharide (LPS) activation. A majority of genes encoding proinflammatory cytokines, as well as genes involved in phagocytosis, antigen presentation, and co-stimulation of T lymphocytes, were found differentially overexpressed. The transcriptomic alterations were reflected by altered phagocytic capacity, inflammasome activation, increased release of inflammatory cytokines, including TNF, and upregulated response of T lymphocytes primed by mutant BV-2 cells presenting peptides. Together, the present study shows that peroxisomal β-oxidation defects resulting in lipid alterations, including VLCFA accumulation, directly reprogram the main cellular functions of microglia. The elucidation of this link between lipid metabolism and the immune response of microglia will help to better understand the pathogenesis of peroxisomal leukodystrophies.

Peroxisomal ABC Transporters: An Update

ATP-binding cassette (ABC) transporters constitute one of the largest superfamilies of conserved proteins from bacteria to mammals. In humans, three members of this family are expressed in the peroxisomal membrane and belong to the subfamily D: ABCD1 (ALDP), ABCD2 (ALDRP), and ABCD3 (PMP70). These half-transporters must dimerize to form a functional transporter, but they are thought to exist primarily as tetramers. They possess overlapping but specific substrate specificity, allowing the transport of various lipids into the peroxisomal matrix. The defects of ABCD1 and ABCD3 are responsible for two genetic disorders called X-linked adrenoleukodystrophy and congenital bile acid synthesis defect 5, respectively. In addition to their role in peroxisome metabolism, it has recently been proposed that peroxisomal ABC transporters participate in cell signaling and cell control, particularly in cancer. This review presents an overview of the knowledge on the structure, function, and mechanisms involving these proteins and their link to pathologies. We summarize the different in vitro and in vivo models existing across the species to study peroxisomal ABC transporters and the consequences of their defects. Finally, an overview of the known and possible interactome involving these proteins, which reveal putative and unexpected new functions, is shown and discussed.

Fulminating Autoimmune Demyelination with Optic Neuropathy in a Case of Pediatric Cerebral Adrenoleukodystrophy: Case Report and Review of the Literature

X-linked adrenoleukodystrophy (ALD) is a leukodystrophy characterized not only by progressive loss of myelin in the central nervous system due to dysmyelination, but also by acute, subacute, or chronic inflammatory demyelination. This results in the phenotypic variability of cerebral ALD (cerALD), which is independent of the genotype. In this article, we reported a fulminant presentation with fluctuating encephalopathy and visual loss in a patient with childhood onset cerALD. Brain MRI showed symmetric confluent occipito-temporal demyelination with severe disruption of the blood–brain barrier and prechiasmal optic neuropathy. The patient's cerebral spinal fluid (CSF) demonstrated an elevated IgG index, myelin basic proteins, and oligoclonal bands. Within 48 hours of receiving immunomodulating therapy, the patient's symptoms of psychomotor slowing, visual impairment, and areflexia partially resolved. High plasma C26:0 levels and high ratios of C24/22 and C26/22 were diagnostic of ALD. It has been shown that environmental factors play an important role in the inflammatory demyelination responsible for the severe phenotypes of cerALD.

Peroxisomes in Immune Response and Inflammation

The immune response is essential to protect organisms from infection and an altered self. An organism’s overall metabolic status is now recognized as an important and long-overlooked mediator of immunity and has spurred new explorations of immune-related metabolic abnormalities. Peroxisomes are essential metabolic organelles with a central role in the synthesis and turnover of complex lipids and reactive species. Peroxisomes have recently been identified as pivotal regulators of immune functions and inflammation in the development and during infection, defining a new branch of immunometabolism. This review summarizes the current evidence that has helped to identify peroxisomes as central regulators of immunity and highlights the peroxisomal proteins and metabolites that have acquired relevance in human pathologies for their link to the development of inflammation, neuropathies, aging and cancer. This review then describes how peroxisomes govern immune signaling strategies such as phagocytosis and cytokine production and their relevance in fighting bacterial and viral infections. The mechanisms by which peroxisomes either control the activation of the immune response or trigger cellular metabolic changes that activate and resolve immune responses are also described.

The genetically modified polysialylated form of neural cell adhesion molecule-positive cells for potential treatment of X-linked adrenoleukodystrophy

PURPOSE

Cell transplantation of myelin-producing exogenous cells is being extensively explored as a means of remyelinating axons in X-linked adrenoleukodystrophy. We determined whether 3,3',5-Triiodo-L-thyronine (T3) overexpresses the ABCD2 gene in the polysialylated (PSA) form of neural cell adhesion molecule (NCAM)-positive cells and promotes cell proliferation and favors oligodendrocyte lineage differentiation.

MATERIALS AND METHODS

PSA-NCAM+ cells from newborn Sprague-Dawley rats were grown for five days on uncoated dishes in defined medium with or without supplementation of basic fibroblast growth factor (bFGF) and/or T3. Then, PSA-NCAM+ spheres were prepared in single cells and transferred to polyornithine/fibronectin-coated glass coverslips for five days to determine the fate of the cells according to the supplementation of these molecules. T3 responsiveness of ABCD2 was analyzed using real-time quantitative polymerase chain reaction, the growth and fate of cells were determined using 5-bromo-2-deoxyuridine incorporation and immunocytochemistry, respectively.

RESULTS

Results demonstrated that T3 induces overexpression of the ABCD2 gene in PSA-NCAM+ cells, and can enhance PSA-NCAM+ cell growth in the presence of bFGF, favoring an oligodendrocyte fate.

CONCLUSION

These results may provide new insights into investigation of PSA-NCAM+ cells for therapeutic application to X-linked adrenoleukodystrophy.

General aspects and neuropathology of X-linked adrenoleukodystrophy

X-adrenoleukodystrophy (X-ALD) is a metabolic, peroxisomal disease affecting the nervous system, adrenal cortex and testis resulting from inactivating mutations in ABCD1 gene which encodes a peroxisomal membrane half-adenosine triphosphate (ATP)-binding cassette transporter, ABCD1 (or ALDP), whose defect is associated with impaired peroxisomal beta-oxidation and accumulation of saturated very long-chain fatty acids (VLCFA) in tissues and body fluids. Several phenotypes are recognized in male patients including cerebral ALD in childhood, adolescence or adulthood, adrenomyeloneuropathy (AMN), Addison's disease and, eventually, gonadal insufficiency. Female carriers might present with mild to severe myeloneuropathy that resembles AMN. There is a lack of phenotype-genotype correlations, as the same ABCD1 gene mutation may be associated with different phenotypes in the same family, suggesting that genetic, epigenetic, environmental and stochastic factors are probably contributory to the development and course of the disease. Degenerative changes, like those seen in pure AMN without cerebral demyelination, are characterized by loss of axons and secondary myelin in the long tracts of the spinal cord, possibly related to the impaired lipid metabolism of VLCFAs and the associated alterations (ie, oxidative damage). Similar lesions are encountered following inactivation of ABCD1 in mice (ABCD1(-)). A different and more aggressive phenotype is secondary to cerebral demyelination, very often accompanied by inflammatory changes in the white matter of the brain and associated with activation of T lymphocytes, CD1 presentation and increased levels of cytokines, gamma-interferon, interleukin (IL)-1alpha, IL-2 and IL-6, Granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-alpha, chemokines and chemokine receptors.

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.

Pharmacokinetics of clofarabine in patients with high-risk inherited metabolic disorders undergoing brain-sparing hematopoietic cell transplantation

Clofarabine, a newer purine analog with reduced central nervous system toxicity, may prove advantageous in hematopoietic cell transplantation in patients for whom neurotoxicity is a natural part of disease progression. This study evaluated clofarabine pharmacokinetics in adult and pediatric patients undergoing hematopoietic cell transplantation for the treatment of high-risk, inherited metabolic disorders. Clofarabine (40 mg/m(2)/d) was administered intravenously on days -7 to -3. Kinetic sampling occurred with doses 1 and 5, along with a single level collected on day of transplant (day(0)). Sixteen patients were studied with a median (range) age and body surface area (BSA) of 7.5 years (0.5-43) and 0.94 m(2) (0.31-2.3), respectively. Clofarabine area under the concentration-time curve from time 0 to infinity was 931 ng·h/mL (685-1876), maximum concentration was 226 ng/mL (162-600), and minimum concentration was 3.2 ng/mL (1.7-5.6). Clofarabine clearance was 1.6 L/h/kg (0.7-2.4) and weakly correlated with weight (r(2) = 0.33) and BSA (r(2) = 0.26). No difference in plasma concentrations was found between dose 1 and dose 5 (all P > .05). All concentrations were below the limit of quantification (1 ng/mL) on day(0) in patients with normal renal function. Variability in clofarabine clearance was approximately 3-fold and was not adequately explained by covariates describing renal function and body size. In patients with adequate renal function, no drug accumulation occurs with consecutive daily dosing.

Polyunsaturated fatty acids, neuroinflammation and well being

The innate immune system of the brain is principally composed of microglial cells and astrocytes, which, once activated, protect neurons against insults (infectious agents, lesions, etc.). Activated glial cells produce inflammatory cytokines that act specifically through receptors expressed by the brain. The functional consequences of brain cytokine action (also called neuroinflammation) are alterations in cognition, mood and behaviour, a hallmark of altered well-being. In addition, proinflammatory cytokines play a key role in depression and neurodegenerative diseases linked to aging. Polyunsaturated fatty acids (PUFA) are essential nutrients and essential components of neuronal and glial cell membranes. PUFA from the diet regulate both prostaglandin and proinflammatory cytokine production. n-3 fatty acids are anti-inflammatory while n-6 fatty acids are precursors of prostaglandins. Inappropriate amounts of dietary n-6 and n-3 fatty acids could lead to neuroinflammation because of their abundance in the brain and reduced well-being. Depending on which PUFA are present in the diet, neuroinflammation will, therefore, be kept at a minimum or exacerbated. This could explain the protective role of n-3 fatty acids in neurodegenerative diseases linked to aging.

Is microglial apoptosis an early pathogenic change in cerebral X-linked adrenoleukodystrophy?

OBJECTIVE

Mutations in the X-linked adrenoleukodystrophy (X-ALD) protein cause accumulation of unbranched saturated very-long-chain fatty acids, particularly in brain and adrenal cortex. In humans, the genetic defect causes progressive inflammatory demyelination in the brain, where very-long-chain fatty acids accumulate within phospholipid fractions such as lysophosphatidylcholine.

METHODS

To address mechanisms of inflammation, we studied microglial activation in human ALD (10 autopsies) and lysophosphatidylcholine (C24:0) injection into the parietal cortex of mice.

RESULTS

Unexpectedly, we found a zone lacking microglia within perilesional white matter, immediately beyond the actively demyelinating lesion edge. Surrounding this zone we observed clusters of activated and apoptotic microglia within subcortical white matter. Lysophosphatidylcholine (C24:0) injection in mice led to widespread microglial activation and apoptosis.

INTERPRETATION

Our data suggest that the distinct mononuclear phagocytic cell response seen in cerebral X-ALD results, at least in part, from aberrant signaling to cognate receptors on microglia. Our findings support a hypothesis that microglial apoptosis in perilesional white matter represents an early stage in lesion evolution and may be an appropriate target for intervention in X-ALD patients with evidence of cerebral demyelination.

Immune response in leukodystrophies

Although the genetics and biochemistry of leukodystrophies have been extensively explored, the immune response in these disorders has received relatively little attention. Both the disease course and its response to treatment may be highly dependent on the immune system. In this review, we compare three common leukodystrophies, each with a different immune response: (1) X-linked adrenoleukodystrophy, which demonstrates a severe, lymphocytic inflammatory response; (2) metachromatic leukodystrophy, which yields a histiocytic response; and (3) vanishing white-matter disease, in which no inflammation is typically seen. We highlight the biochemical, pathologic, and clinical differences, while focusing on the immune response in each disease. We also review the response of leukodystrophies to immunomodulatory therapies and interventions such as hematopoietic stem-cell transplantation. Future studies may delineate specific inflammatory markers as possible candidates for therapeutic intervention.

Experimental models of spontaneous autoimmune disease in the central nervous system

Animal models have become essential tools for studying the human autoimmune disease. They are of vital importance in explorations of disease aspects, where, for diverse reasons, human material is unavailable. This is especially true for disease processes preceding clinical diagnosis and for tissues, which are inaccessible to routine biopsy. Early developing multiple sclerosis (MS) makes an excellent point in case for these limitations. Useful disease models should be developing spontaneously, without a need of artificial, adjuvant-supported induction protocols, and they should reflect credibly at least some of the complex features of human disease. The aim of this review is to compile models that exhibit spontaneous organ-specific autoimmunity and explore their use for studying MS. We first evaluate a few naturally occurring models of organ-specific autoimmune diseases and then screen autoimmunity in animals with compromised immune regulation (neonatal thymectomy, transgenesis, etc.). While most of these models affect organs other than the nervous tissues, central nervous system (CNS)-specific autoimmune disease is readily noted either after transgenic overexpression of cytokines or chemokines within the CNS or by introducing CNS-specific immune receptors into the lymphocyte repertoire. Most recently, spontaneous autoimmunity resembling MS was obtained by transgenic expression of self-reactive T cell receptors and B cell receptors. These transgenic models are not only of promise for studying directly disease processes during the entire course of the disease but may also be helpful in drug discovery.

Immunopathogenesis of adrenoleukodystrophy: current understanding

Adrenoleukodystrophy is a neurometabolic disease with a decreased ability to degrade very long chain fatty acids (VLCFA) and significant phenotypic variation. Unlike most neurometabolic diseases, the success of hematopoietic stem cell transplantation (HSCT) is based on acquiring a new immune system rather than enzyme replacement. VLCFA accumulation appears necessary but not sufficient for pathogenesis. Evidence for the involvement of different components of the immune system in the pathogenesis of the cerebral lesions (cellular, cytokines, humoral, and complement) is reviewed, along with both HSCT and non-HSCT immunologic approaches to treatment and future directions.

The brain as a target of inflammation: common pathways link inflammatory and neurodegenerative diseases

Classical knowledge distinguishes between inflammatory and non-inflammatory diseases of the brain. Either the immune system acts on the CNS and initiates a damage cascade, as in autoimmune (e.g. multiple sclerosis) and infectious conditions, or the primary insult is not inflammation but ischemia or degeneration, as in stroke and Alzheimer's disease, respectively. However, as we review here, recent advances have blurred this distinction. On the one hand, the classical inflammatory diseases of the brain also exhibit profound and early neurodegenerative features - remarkably, it has been known for more than a century that neuronal damage is a key feature of multiple sclerosis pathology, yet this was neglected until very recently. On the other hand, immune mechanisms might set the pace of progressive CNS damage in primary neurodegeneration. Despite differing initial events, increasing evidence indicates that even in clinically heterogeneous diseases, there might be common immunological pathways that result in neurotoxicity and reveal targets for more efficient therapies.

T-cell receptor Vβ gene usage in CSF lymphocytes in X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a peroxisomal disorder with impaired very-long-chain fatty acid (VLCFA) metabolism that produces a neurological disease with significant variability of clinical phenotypes even within kindred. The two most common forms are the cerebral form (CALD) with an important inflammatory reaction at the active edge of demyelinating lesions, resembling some aspects of multiple sclerosis pathology, and adrenomyeloneuropathy (AMN), which involves the spinal cord and in which the inflammatory reaction is mild or absent. One hypothesis is that the phenotypic variability is related to T cell-mediated immune mechanisms playing a primary role in the demyelinating pathogenic process of CALD. The present study aims to test the hypothesis that CSF of patients with the CALD form contains highly restricted T cell populations. The variable regions of the T cell receptor beta chains (TCR Vbeta) were studied in CSF from 29 ALD patients with different phenotypes. RNA was extracted and cDNA synthesized from CSF lymphocytes; TCR Vbeta gene segments were amplified from the cDNA by polymerase chain reaction (PCR) using 20 family-specific primers. PCR products were analyzed by Southern blot. Some amplified Vbeta products were sequenced. The majority of ALD patients (21/29), whatever their phenotype, exhibited oligoclonal T cell expansion. However the overexpression of some TCR Vbeta families was heterogeneous among the different patients without any preponderance of specific Vbeta families or any clustering according to clinical phenotype. In particular a dominant TCR Vbeta utilization was not found in patients with CALD.

Free radical release in C6 glial cells enriched in hexacosanoic acid: implication for X-linked adrenoleukodystrophy pathogenesis

Free radicals have been implicated in the etiopathology of some neurological and demyelinating diseases. To evaluate their involvement in the cerebral form of X-linked adrenoleukodystrophy (cerALD) disorder, characterised by very long chain fatty acid (VLCFA) accumulation, we utilised an in vitro model using rat C6 glial cells, enriched in hexacosenoic acid (C26:0, HA). Modified cells were incubated in presence of oxidative stressors, such as bacterial endotoxin lipopolisaccharides (LPS) and human oxidised low-density lipoprotein (ox-LDL), and the production of proinflammatory cytokines, nitrite, nitrate and superoxide was determined in the supernatants. The results show that modified cells produce higher amounts of nitric oxide (NO) products and superoxide compared to native C6 cells, supporting the role of free radicals as important pathophysiological modulator of the neuroinflammatory response in ALD. This hypothesis suggests that the cerebral damage in ALD could be due to intracellular signalling activated by interaction of exogenous factors with the particular membrane fatty acid composition.

Control of glial immune function by neurons

The immune status of the central nervous system (CNS) is strictly regulated. In the healthy brain, immune responses are kept to a minimum. In contrast, in a variety of inflammatory and neurodegenerative diseases, including multiple sclerosis, infections, trauma, stroke, neoplasia, and Alzheimer's disease, glial cells such as microglia gain antigen-presenting capacity through the expression of major histocompatibility complex (MHC) molecules. Further, proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF), interleukin-1beta (IL-1beta), and interferon-gamma (IFN-gamma), as well as chemokines, are synthesized by resident brain cells and T lymphocytes invade the affected brain tissue. The proinflammatory cytokines stimulate microglial MHC expression in the lesioned CNS areas only. However, the induction of brain immunity is strongly counterregulated in intact CNS areas. For instance, recent work demonstrated that microglia are kept in a quiescent state in the intact CNS by local interactions between the microglia receptor CD200 and its ligand, which is expressed on neurons. Work done in our laboratory showed that neurons suppressed MHC expression in surrounding glial cells, in particular microglia and astrocytes. This control of MHC expression by neurons was dependent on their electrical activity. In brain tissue with intact neurons, the MHC class II inducibility of microglia and astrocytes by the proinflammatory cytokine IFN-gamma was reduced. Paralysis of neuronal electric activity by neurotoxins restored the induction of MHC molecules on microglia and astrocytes. Loss of neurons or their physiological activity would render the impaired CNS areas recognizable by invading T lymphocytes. Thus, immunity in the CNS is inhibited by the local microenvironment, in particular by physiologically active neurons, to prevent unwanted immune mediated damage of neurons.

Potential environmental and host participants in the early white matter lesion of adreno-leukodystrophy: morphologic evidence for CD8 cytotoxic T cells, cytolysis of oligodendrocytes, and CD1-mediated lipid antigen presentation

The 2 most common forms of X-linked adreno-leukodystrophy (ALD) are the juvenile or childhood cerebral form with inflammatory demyelination and the adult adrenomyeloneuropathy (AMN) involving spinal cord tracts without significant inflammation. Modifier genes or environmental factors may contribute to the phenotypic variability. We performed immunohistochemical, an in situ polymerase chain reaction, and TUNEL analyses to identify several viruses, lymphocyte subpopulations, apoptotic cells, and effector molecules, focusing on morphologically normal white matter, dysmyelinative and acute demyelinative lesions. No distinguishing viral antigens were detected. Most lymphocytes were CD8 cytotoxic T cells (CTLs) with the alpha/beta TCR, and they infiltrated morphologically unaffected white matter. Only a few oligodendrocytes were immunoreactive for caspase-3. MHC class II- and TGF-beta-positive microglia were present. CD44, which can mediate MHC-unrestricted target cell death, was seen on many lymphocytes and white matter elements. CD1 molecules, which play major roles in MHC-unrestricted lipid antigen presentation, were noted. Our data indicate that unconventional CD8 CTLs are operative in the early stages of dysmyelination/demyelination and that cytolysis of oligodendrocytes, rather than apoptosis, appears to be the major mode of oligodendrocytic death. The presentation of lipid antigens may be a key pathogenetic element in ALD and AMN-ALD.

Serum autoantibody responses to myelin oligodendrocyte glycoprotein and myelin basic protein in X-linked adrenoleukodystrophy and multiple sclerosis

We analyzed the sera of 51 patients with various phenotypes of X-linked adrenoleukodystrophy (X-ALD), 20 patients with multiple sclerosis (MS) and 22 healthy volunteers for the presence of autoantibodies specific for the recombinant extracellular immunoglobulin-like domain of human myelin oligodendrocyte glycoprotein (rhMOG(Igd)) and myelin basic protein (MBP). Anti-rhMOG(Igd) autoantibodies were significantly more frequent in X-ALD and MS patients as opposed to healthy individuals (p<0.05). Anti-MBP autoantibodies were present in about one-fourth of X-ALD and MS patients but in less than 10% of healthy individuals. Anti-rhMOG(Igd) autoantibody responses were not accompanied by increased T cell reactivity against rhMOG(Igd). These findings may have important implications for the understanding of humoral anti-myelin immunoreactivity in demyelinating diseases of the central nervous system such as X-ALD and MS.

Increased frequency of activated lymphocytes in the cerebrospinal fluid of patients with acute schizophrenia

We compared the cerebrospinal fluid (CSF) cytology of 30 acutely psychotic patients at the initial phase of their hospital treatment with that of 46 control individuals with no psychiatric disorder or central nervous system (CNS) disease. The cytological profile of May-Grünwald-Giemsa stained CSF cell slides of the patients was significantly different from that of the control population. The most striking finding was a significantly increased frequency of lymphoid cells showing morphological features of activation/stimulation and a decreased proportion of normal small lymphocytes. Many of the cells with aberrant morphology displayed structural details similar to those of the 'P cells' previously described in the blood of schizophrenic patients. The patients' CSF also contained elevated proportions of monocytes/macrophages, some of which were found in 'rosettes' with activated lymphocytes indicating an increased intercellular adhesion. Possible pathogenic mechanisms behind lymphocyte activation and macrophage dominance in the CSF of acutely ill psychotic patients are discussed.

Lovastatin therapy for X-linked adrenoleukodystrophy: clinical and biochemical observations on 12 patients

X-linked adrenoleukodystrophy (X-ALD) is a progressive demyelinating disorder whose neurological signs and symptoms can manifest in childhood as cerebral ALD or in adulthood in the form of a progressive myelopathy (AMN). The consistent metabolic abnormality in all forms of X-ALD is an inherited defect in the peroxisomal beta-oxidation of very long chain (VLC) fatty acids (>C(22:0)) which may in turn lead to a neuroinflammatory process associated with demyelination of the cerebral white matter. The current treatment for X-ALD with Lorenzo's oil aims to lower the excessive quantities of VLC fatty acids that accumulate in the patients' plasma and tissues, but does not directly address the inflammatory process in X-ALD. We have previously demonstrated that lovastatin and other 3-HMG-CoA reductase inhibitors are capable of normalizing VLC fatty acid levels in primary skin fibroblasts derived from X-ALD patients. Lovastatin can block the induction of inducible nitric oxide synthase and proinflammatory cytokines in astrocytes, microglia, and macrophages in vitro. In a preliminary report, we demonstrated that lovastatin therapy can normalize VLC fatty acids in the plasma of patients with X-ALD. Here we report our clinical and biochemical observations on 12 patients with X-ALD who were treated with lovastatin for up to 12 months. Our results show that the high plasma levels of hexacosanoic acid (C(26:0)) showed a decline from pretreatment values within 1 to 3 months of starting therapy with 40 mg of lovastatin per day and stabilized at various levels during a period of observation up to 12 months. The percentage decline from pretreatment values varied and did not correlate with the type of ALD gene mutation (point mutation versus gene deletion). In 6 patients, in whom red cell membrane fatty acid composition was studied, a mean correction of 50% of the excess C(26:0) was observed after 6 months of therapy suggesting sustained benefit. In a few patients who discontinued lovastatin therapy plasma C(26:0) levels reverted to pretreatment values suggesting a cause and effect relationship between these events. Two patients dropped out of the study claiming no clinical benefit, 1 was withdrawn due to adverse effects, and an adult patient with cerebral involvement died during the study. A 10-year-old boy with severe cerebral involvement showed worsening of his neurological status. All patients with AMN remained neurologically stable or showed modest subjective improvement. All patients who did not have Addison's disease at the time of enrollment maintained normal adrenal function throughout the study. The implications of our findings for developing an effective therapy for X-ALD are discussed.

X-linked adrenoleukodystrophy: first report of the Italian Study Group

In this paper we report Italian data on X-linked adrenoleukodystrophy (ALD) collected from 1985 to 1997. This disease appears to be the most common of the peroxisomal disorders and is associated with a functional defect of the peroxisomal very long chain fatty acid (VLCFA) oxidation. In Italy 117 cases have been recognized, but many cases may be unrecognized due to the heterogeneous clinical manifestations that vary from mild to very severe forms. To control the devastating course of this disease two therapeutic approaches are under evaluation: bone marrow transplantation (BMT) and dietary treatment based on a mixture of glyceroyl trioleate (GTO) and glyceroyl trierucate (GTE). Our experience of 68 subjects submitted to dietary treatment shows that almost all patients with signs of cerebral involvement at the beginning of treatment worsened or died, patients with the milder form, adrenomyeloneuropathy (AMN), remained stable, while 4 of the 15 presymptomatic subjects developed neurological signs of the disease. In recent years a more accurate selection of patients and donors for BMT has given favourable results, but some strict criteria should be respected.

Antiglycosphingolipid immune responses in neurology. The Vienna experience with isotypes, subclasses, and disease

IgM, IgG, IgA, and IgG subclass anti-GM1, anti-GQ1b, and anti-asialo-GM1 (anti-GA1) antibodies, respectively, were investigated by ELISA in serum from neurological and other patients. Increased anti-GM1 occurred mostly in approximately 15-35% of the cases without statistical differences; high percentages were found in Guillain-Barré syndrome (GBS) preceded by gastrointestinal infection and multifocal motor neuropathy. Roughly, IgM anti-GM1 was most frequent; however, distinct IgG and IgA reactions were found i.a. in GBS. A particular IgM anti-mono- and disialoganglioside pattern occurred in a patient with sensorimotor neuropathy and paraproteinemia. Anti-GQ1b was elevated in all Miller-Fisher patients, with some prevalence of IgG2 among IgG subclasses. Cross-reactivity of anti-GQ1b was demonstrated with Campylobacter jejuni lipopolysaccharides. Increased anti-GM1 and/or anti-GA1 was more frequent in systemic lupus erythematosus with central nervous system involvement than without. Incidence of anti-GM1 and anti-GA1 in X-adrenoleukodystrophy was relatively high. Although anti-GSL antibodies seem to have limited diagnostic value, studies of isotypes, subclass patterns, and cross-reactivities may lead to further insight into the origin of (auto) immune responses and their immunepathogenetic role in disease.

Immunoablation does not delay the neurologic progression of X-linked adrenoleukodystrophy

We report the results of a near total myeloablation in preparation for bone marrow transplantation in a boy with minimal symptoms of X-linked adrenoleukodystrophy. Severe cerebral X-linked adrenoleukodystrophy developed in the patient after failure of bone marrow transplantation. This experience suggests that immunotherapy alone is not responsible for the improvement observed in some patients with X-ALD after BMT.

A mouse model for X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with impaired beta-oxidation of very long chain fatty acids (VLCFAs) and reduced function of peroxisomal very long chain fatty acyl-CoA synthetase (VLCS) that leads to severe and progressive neurological disability. The X-ALD gene, identified by positional cloning, encodes a peroxisomal membrane protein (adrenoleukodystrophy protein; ALDP) that belongs to the ATP binding cassette transporter protein superfamily. Mutational analyses and functional studies of the X-ALD gene confirm that it and not VLCS is the gene responsible for X-ALD. Its role in the beta-oxidation of VLCFAs and its effect on the function of VLCS are unclear. The complex pathology of X-ALD and the extreme variability of its clinical phenotypes are also unexplained. To facilitate understanding of X-ALD pathophysiology, we developed an X-ALD mouse model by gene targeting. The X-ALD mouse exhibits reduced beta-oxidation of VLCFAs, resulting in significantly elevated levels of saturated VLCFAs in total lipids from all tissues measured and in cholesterol esters from adrenal glands. Lipid cleft inclusions were observed in adrenocortical cells of X-ALD mice under the electron microscope. No neurological involvement has been detected in X-ALD mice up to 6 months. We conclude that X-ALD mice exhibit biochemical defects equivalent to those found in human X-ALD and thus provide an experimental system for testing therapeutic intervention.

Intrathecal IgA synthesis in X-linked cerebral adrenoleukodystrophy

Cerebrospinal fluid data on 25 patients suffering from various phenotypes of X-linked adrenoleukodystrophy have been evaluated neurochemically including cerebrospinal fluid/serum quotient diagrams. Intrathecal IgA production in 13 of 14 patients with cerebral adrenoleukodystrophy was the most sensitive parameter in cerebrospinal fluid and was not seen in any of the neurologically asymptomatic patients or in the patients with adrenomyeloneuropathy. A blood-cerebrospinal fluid barrier dysfunction was found in 9 of these 14 patients. Additional intrathecal IgG or IgM synthesis was observed in 3 patients each. In 1 patient with lumbar punctures before and after onset of neurologic symptoms intrathecal IgA synthesis was seen only after the appearance of neurologic symptoms. Repetition of lumbar punctures in 5 neurologically symptomatic patients with cerebral adrenoleukodystrophy revealed a similar pattern of intrathecal IgA synthesis with a tendency of decreasing IgA concentration. The pathophysiologic aspects of intrathecal IgA synthesis are discussed in relation to other demyelinating and inflammatory neurologic diseases.

X linked adrenoleukodystrophy: clinical presentation, diagnosis, and therapy

X linked adrenoleukodystrophy (X-ALD) is an inherited disorder of peroxisomal metabolism, biochemically characterised by accumulation of saturated very long chain fatty acids. Accumulation of these fatty acids is associated with cerebral demyelination, peripheral nerve abnormalities, and adrenocortical and testicular insufficiency. The lowest estimated birth incidence is one per 100,000. At least six phenotypes can be distinguished, of which the two most frequent are childhood cerebral ALD and adrenomyeloneuropathy. The X-ALD gene has been identified, but thus far no relation between genotype and phenotype has been found. Diagnosis is relatively easy and can be confirmed reliably, and prenatal testing is possible in affected families. Several therapeutic options, some with promising perspectives, are available. Neurologists and other physicians seem not to be familiar with the many facets of X-ALD. In this review, the clinical presentation, the relative frequencies of the different phenotypes, and the diagnostic and therapeutic options are presented.

Human leukocyte antigens and cytokine expression in cerebral inflammatory demyelinative lesions of X-linked adrenoleukodystrophy and multiple sclerosis

The two most common forms of X-linked adrenoleukodystrophy (X-ALD) are the cerebral forms (CER) with an inflammatory demyelinating reaction that resembles multiple sclerosis, and adrenomyeloneuropathy (AMN) which involves primarily the spinal cord and in which the inflammatory reaction is mild or absent. We found no significant association between the childhood cerebral form (CCER) or AMN and the human leukocyte (HLA) class I and Class II antigens including the class II DR2 haplotypes associated with multiple sclerosis. Inflammatory cytokine (tumor necrosis factor-alpha, interleukin-1 beta, interleukin-4, interleukin-6 and interferon-gamma) gene expression was increased in multiple sclerosis brain lesions, as has been reported previously, but much less so in CER brain lesions. These findings suggest that the pathogenesis of the inflammatory response in X-ALD differs from that in multiple sclerosis.

Effects of exogenous hexacosanoic acid on biochemical myelin composition in weaning and post-weaning rats

X-linked Adrenoleukodistrophy (ALD) is characterized by an increase of very long chain fatty acids (VLCFA) in particular of hexacosanoic acid (HA), in tissues and fluids. The biochemical abnormality is due to the dysfunction of peroxisomal degradation of VLCFA. To-date it is unclear if the demyelination which characterizes this disease is the direct consequence of HA accumulation. In order to investigate whether the large amounts of exogenous HA could affect myelin synthesis, 500 micrograms of this fatty acid dissolved in peanut oil were administered daily and by gavage to newborn rats. Since myelin is actively synthesized during early neonatal life and it can be altered by environmental factors including diet, we analyzed lipid and protein composition of myelin after 20, 30 and 60 days of HA administration. Our results show that exogenous HA is incorporated in myelin where it determines biochemical alterations in normal rats having a functioning peroxisomal system. Even though the differences between controls and treated rats are slight, we observed in test rats, a decrease of 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity and of myelin basic protein (MBP) content at any time studied. The decrease of glycolipids (GL) was present only after 20 days of treatment. Since these parameters are related to myelin development, our data lead us to think that the myelin of the treated animals is less mature than that of controls.

Immunohistochemical investigation of human leukocyte antigen (HLA)-DR-positive astrocytes in adrenoleukodystrophy brain

We investigated immunohistochemically the expression of human leukocyte antigen (HLA)-DR in postmortem brain tissue of two adult patients with adrenoleukodystrophy (ALD). In addition to microglia and macrophages, a significant number of star-like cells were stained positively for HLA-DR in demyelinating lesions of both patients. Such cells congregated in the peripheral zone of the lesions. A mirror image analysis as well as double immunostaining for HLA-DR and glial fibrillary acidic protein established that these cells were a subset of reactive astrocytes. Together with other reports demonstrating that astrocytes express HLA-DR only under very limited conditions, the results of this study suggest the involvement of immune and inflammatory responses in the pathological processes of ALD.

Animal models of demyelination

Demyelination is a pathological feature that is characteristic of many diseases of the central nervous system (CNS) including multiple sclerosis (MS), sub-acute sclerosing panencephalomyelitis (SSPE), metachromatic leukodystrophy and Pelizaeus-Merzbacher disease. While demyelination is a pathological end-point that is common to all of these diseases, the cellular and molecular mechanisms responsible for this pathology are very different . These range from genetic defects that affect lipid metabolism in the leukodystrophies, cytopathic effects of viral infection in SSPE to the action of immunological effector mechanisms in MS and the viral encephalopathies. Irrespective of the initial cause of myelin degradation, many of these disorders are associated with some degree of CNS inflammation, as indicated by the local activation of microglia, recruitment of macrophages or the intrathecal synthesis of immunoglobulin. Many of these phenomena are now being duplicated in animal models, providing not only new insights into the pathogenesis of human demyelinating diseases , but also unexpected interrelationships between the immune response in the CNS and the pathogenesis of diseases such as Alzheimers disease and HIV encephalopathy. Autoimmune mediated models of inflammatory demyelinating CNS disease have proved particularly valuable in this respect as they allow the effects of defined immune effector mechanisms to be studied in the absence of CNS infection.

Temporary improvement of neurological symptoms with gammaglobulin therapy in a boy with adrenoleukodystrophy

A 10-year-old boy with adrenoleukodystrophy was treated with gammaglobulin in conjunction with a mixture of glyceryl trioleate and glyceryl trierucate. With a high dose of gammaglobulin, clinical improvement, including the reduction of visual field defects, was noted. On magnetic resonance imaging, attenuation of the enhancement of the rim with gadolinium was observed, suggesting repair of the blood-brain barrier. When auditory agnosia developed later, a temporary improvement was again obtained with gammaglobulin. Although the progress of the disease could not be arrested permanently, gammaglobulin therapy seemed to have been associated with temporary improvement of the clinical symptoms in this patient with adrenoleukodystrophy.

Interactions of a very long chain fatty acid with model membranes and serum albumin. Implications for the pathogenesis of adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an inherited disorder of fatty acid metabolism marked by accumulation of very long chain saturated fatty acids (VLCFA), especially the 26-carbon acid, hexacosanoic acid (HA), in membranes and tissues. We have studied interactions of 13C-enriched HA with model membranes (phospholipid bilayer vesicles) and bovine serum albumin (BSA) by 13C NMR spectroscopy to compare properties of HA with those of typical dietary fatty acids. In phospholipid bilayers the carboxyl group of HA is localized in the aqueous interface, with an apparent pKa (7.4) similar to other fatty acids; the acyl chain must then penetrate very deeply into the membrane. Desorption of HA from vesicles (t1+2 = 3 h) is orders of magnitude slower than shorter chain fatty acids. In mixtures of vesicles and BSA, HA partitions much more favorably to phospholipid bilayers than typical fatty acids. BSA binds a maximum of only 1 mole of HA at one binding site. Calorimetric experiments show strong perturbations of acyl chains of phospholipids by HA. We predict that disruptive effects of VLCFA on cell membrane structure and function may explain the neurological manifestations of ALD patients. These effects will be further amplified by slow desorption of VLCFA from membranes and by the ineffective binding to serum albumin.

Tumor necrosis factor-alpha and X-linked adrenoleukodystrophy

The two most common forms of X-linked adrenoleukodystrophy (X-ALD), the childhood cerebral form (CCER) and the adult form, adrenomyeloneuropathy (AMN), arise from the same mutations in the X-ALD gene at Xq28. These two forms are distinguished by the degree of cerebral inflammation. Segregation analysis suggests that an autosomal modifying gene may be a major determinant of phenotype in X-ALD. Thus, a modifying gene could be involved in initiating or promoting the inflammatory response. In this study we detected a difference in tumor necrosis factor-alpha (TNF-alpha) bioactivity, but not TNF-alpha protein levels, in serum from some advanced CCER patients. Early-stage CCER patients and AMN patients were in the normal range. Allelic differences in TNF-alpha or levels of soluble TNF receptor did not account for bioactivity differences or phenotypic heterogeneity in X-ALD.

Adrenoleukodystrophy: molecular genetics, pathology, and Lorenzo's oil

Knowledge about adrenoleukodystrophy (ALD), a disorder which was described first in 1923, has increased greatly during recent years. The principal biochemical abnormality, the presumed enzyme defect, and the gene defect, have been defined. A dietary therapy has been proposed and attracted world-wide attention through a motion picture. Nevertheless, many questions remain and cannot be answered without a more fundamental understanding of pathology and pathogenesis. This article will provide a review of the history, clinical features, pathology, biochemistry, and the gene defect, and then appraise current efforts to clarify pathogenesis and develop therapeutic approaches.

Very long chain fatty acids in higher animals--a review

Fatty acids with greater than 22 carbon atoms (very long chain fatty acids, VLCFA) are present in small amounts in most animal tissues. Saturated and monoenoic VLCFA are major components of brain, while the polyenoic VLCFA occur in significant amounts in certain specialized animal tissues such as retina and spermatozoa. Biosynthesis of VLCFA occurs by carbon chain elongation of shorter chain fatty acid precursors while beta-oxidation takes place almost exclusively in peroxisomes. Mitochondria are unable to oxidize VLCFA because they lack a specific VLCFA coenzyme A synthetase, the first enzyme in the beta-oxidation pathway. VLCFA accumulate in the tissues of patients with inherited abnormalities in peroxisomal assembly, and also in individuals with defects in enzymes catalyzing individual reactions along the beta-oxidation pathway. It is believed that the accumulation of VLCFA in patient tissues contributes to the severe pathological changes which are a feature of these conditions. However, little is known of the role of VLCFA in normal cellular processes, and of the molecular basis for their contribution to the disease process. The present review provides an outline of the current knowledge of VLCFA including their biosynthesis, degradation, possible function and involvement in human disease.

Komrower Lecture. Adrenoleukodystrophy: natural history, treatment and outcome

Our laboratory has identified nearly 2000 patients with X-linked adrenoleukodystrophy (ALD) and conducted therapeutic trials in groups of patients who represent the major phenotypes. We report recent results of dietary therapy with a mixture of glyceryl trioleate and glyceryl trierucate oil, also referred to as Lorenzo's Oil, in the asymptomatic and childhood cerebral phenotypes. Fifty-three patients started this therapy at a mean age of 7.5 years at a time when they were free of neurological symptoms. Although analysis of data is hampered by the lack of a concurrent control group, follow-up studies after 39 months of therapy suggest that subsequent neurological involvement was less frequent and less severe than anticipated from historical controls. Retrospective analysis of the effect of the oil in patients with the severe childhood cerebral phenotype indicates that there was a slight but statistically significant slowing of clinical progression and delay of death.

Multislice proton magnetic resonance spectroscopic imaging in X-linked adrenoleukodystrophy

Multislice proton magnetic resonance spectroscopic imaging permits metabolic analysis of brain tissue in vivo by data acquisition in four oblique axial slices, each 15-mm thick and divided into 0.8-ml single-volume elements. We applied this technique to the systematic study of 25 patients with adrenoleukodystrophy: 3 with the severe childhood or adult cerebral form of the disease, 5 with adrenomyeloneuropathy, 12 with no demonstrable neurological involvement, and 5 women heterozygous for adrenoleukodystrophy who had some degree of neurological disability. Abnormalities on magnetic resonance spectroscopic imaging included a reduction in N-acetyl aspartate, an increase in choline-containing compounds, and at times, an increase in lactate. Five patients showed abnormalities in the presence of normal-appearing magnetic resonance images, and in 8 other patients the alterations on spectroscopic images were more severe than those demonstrable by magnetic resonance imaging. Correlation with clinical course suggests that an increase in the choline-containing compounds is associated with an active demyelinative process, whereas such compounds are not elevated in lesions that are stable. We conclude that magnetic resonance spectroscopic imaging is a more sensitive indicator of early neurological involvement than is magnetic resonance imaging, and that the character of abnormalities detected by the former technique may serve as a gauge of the degree of activity of the demyelinating process and as a guide to the selection and evaluation of therapeutic approaches.

CSF findings in adrenoleukodystrophy: correlation between measures of cytokines, IgG production, and disease severity

The childhood-onset cerebral form of adrenoleukodystrophy has a devastating neurologic prognosis. Unfortunately, there is no early method of distinguishing it from the more benign forms of adrenoleukodystrophy, such as adrenomyeloneuropathy. To evaluate the manner in which this disease entity may be reflected in the cerebrospinal fluid, we studied a consecutive series of 19 patients, all with biochemically proved adrenoleukodystrophy. total protein, immunoglobulin production, cytokine levels, and cerebrospinal fluid pressure were measured. In this single sample of cerebrospinal fluid, a significant correlation existed between clinical stage of the illness and cerebrospinal fluid myelin basic protein. No correlation existed with total protein, cytokines, or measures of immunoglobulin production.

Lipid and fatty acid composition of brain tissue from adrenoleukodystrophy patients

White matter and active plaque tissue from adrenoleukodystrophy (ALD) patients were analysed for lipid class and fatty acid compositions and the results compared with white matter from normal brain. ALD white matter was characterised by increased levels of cholesteryl esters and decreased levels of phosphatidylethanolamine, including phosphatidylethanolamine plasmalogen, in comparison with normal brain white matter. In addition to even higher levels of cholesteryl esters, ALD plaque tissue had reduced levels of cerebrosides as well as phosphatidylethanolamines. The loss of phosphatidylethanolamine plasmalogen is indicative of early demyelination. Total lipid from ALD white matter and ALD plaque tissue contained nearly five times and seven times, respectively, more 26:0 than total lipid from normal brain white matter. The 26:0 in ALD white matter was elevated in all lipid classes except phosphatidylinositol, but was located mainly in cerebrosides, phosphatidylcholine, sphingomyelin, and sulfatides. Most of the 26:0 in ALD plaque tissue was present in cholesteryl esters, followed by phosphatidylcholine and sphingomyelin, with reduced amounts in cerebrosides as compared with ALD white matter. The results are consistent with an initial accumulation of very-long-chain fatty acids in ALD white matter, primarily in sphingolipids and phosphatidylcholine, and subsequent accumulation of very-long-chain fatty acids in cholesteryl esters during demyelination. In addition, it was notable that the sphingolipids, especially sphingomyelin in ALD brain, had decreased levels of 24:1 and increased levels of 18:0, as well as increased levels of very-long-chain fatty acids. The extent to which the data shed light on mechanisms of demyelination in ALD is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotypes of mononuclear cell infiltrates in human central nervous system

Using a panel of monoclonal antibodies applicable for identification of cell types in paraffin sections, the prevalence of mononuclear cell infiltrates with different phenotypes was estimated in large areas taken from 11 cases of acute and chronic inflammatory diseases in the human central nervous system. The present study clearly demonstrated a diversity of inflammatory mononuclear cell infiltrates, and the dominance of cell types in individual lesions appeared to be determined by both the nature of the diseases and the age of the lesions. The possible pathognomonic significance of a relatively high prevalence of CD4+CD45RO+ lymphocytes in acute rabies and in a convalescent stage of Japanese encephalitis and subacute sclerosing panencephalitis is discussed.