Cerebral folate deficiency and CNS inflammatory markers in Alpers disease

We describe a 3.5-year-old female with Alpers disease with a POLG genotype of p.A467T/p.G848S and with a lethal outcome. Laboratory investigation revealed elevated CSF neopterin, IL-6, IL-8, IFN-gamma, reduced CSF 5-methyltetrahydrofolate (5MTHF), and increased serum as well as CSF folate receptor blocking autoantibodies. Treatment with oral Leucovorine (5-formyl-tetrahydrofolate) was initiated at 0.25mg/kg bid, and later increased to 4mg/kg bid. Under treatment CSF levels of 5MTHF, seizure frequency and communicative abilities improved. Over a time span of 17months, CSF levels of IL-6 and IFN-gamma decreased, levels of folate receptor blocking autoantibodies continued to raise, whereas CSF IL-8 remained elevated 1500-fold above normal. The child died without apparent stress at the age of 5.5years. Alpers disease, a neurodegenerative disease usually presents in the first years of life as a progressive encephalopathy with multifocal myoclonic seizures, developmental regression, cortical blindness and early death. The underlying genetic defect has been attributed to mutations of the catalytic subunit of the mitochondrial DNA polymerase-gamma leading to an organ-specific mitochondrial DNA depletion syndrome with reduced activity of respiratory chain enzyme complexes in the brain and the liver. A curative therapy is not available. This case report of Alpers disease provides new insights into the pathophysiology of Alpers disease, where mitochondrial dysfunction in conjunction with inflammatory cytokines and blocking folate receptor autoantibodies may lead to a secondary cerebral folate deficiency syndrome. The treatment of the latter provides relief to the patient without stopping the underlying disease.

POLG1Mutations Associated With Progressive Encephalopathy in Childhood

We have identified compound heterozygous missense mutations in POLG1, encoding the mitochondrial DNA polymerase gamma (Pol gamma), in 7 children with progressive encephalopathy from 5 unrelated families. The clinical features in 6 of the children included psychomotor regression, refractory seizures, stroke-like episodes, hepatopathy, and ataxia compatible with Alpers-Huttenlocher syndrome. Three families harbored a previously reported A467T substitution, which was found in compound with the earlier described G848S or the W748S substitution or a novel R574W substitution. Two families harbored the W748S change in compound with either of 2 novel mutations predicted to give an R232H or M1163R substitution. Muscle morphology showed mitochondrial myopathy with cytochrome c oxidase (COX)-deficient fibers in 4 patients. mtDNA analyses in muscle tissue revealed mtDNA depletion in 3 of the children and mtDNA deletions in the 2 sibling pairs. Neuropathologic investigation in 3 children revealed widespread cortical degeneration with gliosis and subcortical neuronal loss, especially in the thalamus, whereas there were only subcortical neurodegenerative findings in another child. The results support the concept that deletions as well as depletion of mtDNA are involved in the pathogenesis of Alpers-Huttenlocher syndrome and add 3 new POLG1 mutations associated with an early-onset neurodegenerative disease.

Tissue preconditioning may explain concentric lesions in Baló's type of multiple sclerosis

Lesions of Baló's concentric sclerosis are characterized by alternating layers of myelinated and demyelinated tissue. The reason for concentric demyelination in this variant of multiple sclerosis is unclear. In the present study we investigated the immunopathology in autopsy tissue of 14 patients with acute multiple sclerosis or fulminant exacerbations of chronic multiple sclerosis with Baló-type lesions in the CNS, focusing on the patterns of tissue injury in actively demyelinating lesions. We found that all active concentric lesions followed a pattern of demyelination that bears resemblances to hypoxia-like tissue injury. This was associated with high expression of inducible nitric oxide synthase in macrophages and microglia. At the edge of active lesions and, less consistently, in the outermost layer of preserved myelin, proteins involved in tissue preconditioning, such as hypoxia-inducible factor 1alpha and heat-shock protein 70, were expressed mainly in oligodendrocytes and to a lesser degree also in astrocytes and macrophages. Due to their neuroprotective effects, the rim of periplaque tissue, where these proteins are expressed, may be resistant to further damage in an expanding lesion and may therefore remain as a layer of preserved myelinated tissue.

Mitochondrial DNA depletion in Alpers syndrome

Mitochondrial dysfunction of the energy generating system was suggested in two infants with progressive infantile poliodystrophy characterised by hypotonia, refractory epilepsy, visual impairment, psychomotor retardation, profound brain atrophy, hepatopathy, and increased levels of lactate in blood and cerebrospinal fluid. Histochemical and electron microscopic analyses of liver biopsies revealed cytochrome c oxidase deficiency, microvesicular steatosis, and enormous multiplication of mitochondria of various sizes. In the first patient, the quantitative Southern blot analyses in tissues obtained at autopsy demonstrated reduced content of mtDNA in the liver, brain, and fibroblasts (11 %, 15 %, and 25 % of the mean values in controls) while a normal content of mtDNA was found in muscle and heart. In the second patient, a reduced content of mtDNA was found in the muscle, liver, and brain (15 %, 10 %, and 30 %, respectively, of the mean values in controls). Biochemical studies in the first patient revealed decreased activities of all respiratory chain complexes except complex II in isolated liver mitochondria and decreased amounts of respiratory chain complexes I, III, IV and ATP synthase in liver and frontal cortex, but not in muscle, heart, and fibroblasts. In conclusions, mtDNA depletion associated with Alpers syndrome may be tissue specific.

A mutation in mitochondrial DNA-encoded cytochrome c oxidase II gene in a child with Alpers-Huttenlocher-like disease

OBJECTIVE

Cytochrome c oxidase (COX) deficiency has been demonstrated in some patients with Alpers-Huttenlocher disease, but no genetic background has been identified. Our objective was to determine the molecular defect underlying the mitochondrial respiratory chain deficiency in a child with Alpers-Huttenlocher-like progressive cerebrohepatic disease.

METHODS

The entire coding region of mitochondrial DNA was analyzed by conformation-sensitive gel electrophoresis and sequencing. Biochemical and morphologic investigations were performed on tissue biopsy material, including oximetric and spectrophotometric analyses of oxidative phosphorylation, histochemistry, and electron microscopy.

RESULTS

Postmortem histologic examination revealed a marked loss of neurons in the olivary nuclei and a spongy change in the calcarine cortex, fatty infiltration and micronodular cirrhosis of the liver, and atrophic ovaries. A novel heteroplasmic 7706G>A mutation was found in the COX II gene. The median degree of the mutant heteroplasmy was 90% in 5 tissues examined but was lower in the blood of asymptomatic maternal relatives. The distribution of the mutant heteroplasmy was skewed to the left in single muscle fibers of the proband and her mother. The 7706G>A mutation converts a hydrophobic alanine in a conserved transmembrane segment to hydrophilic threonine.

CONCLUSIONS

The 7706G>A mutation is pathogenic and may lead to impaired dioxygen transfer to the active site of COX. The clinical phenotype of this patient resembled that in Alpers-Huttenlocher disease, suggesting that analysis of mitochondrial DNA is worthwhile in patients with a progressive cerebrohepatic disease.

Diagnostic criteria for respiratory chain disorders in adults and children

BACKGROUND

Respiratory chain (RC) disorders are clinically, biochemically, and molecularly heterogeneous. The lack of standardized diagnostic criteria poses difficulties in evaluating diagnostic methodologies.

OBJECTIVE

To assess proposed adult RC diagnostic criteria that classify patients into "definite," "probable," or "possible" categories.

METHODS

The authors applied the adult RC diagnostic criteria retrospectively to 146 consecutive children referred for investigation of a suspected RC disorder. Data were collected from hospital, genetics, and laboratory records, and the diagnoses predicted by the adult criteria were compared with the previously assigned assessments.

RESULTS

The authors identified three major difficulties in applying the adult criteria:lack of pediatric-specific criteria; difficulty in segregating continuous data into circumscribed major and minor criteria; and lack of additivity of clinical features or enzyme tests. They therefore modified the adult criteria to allow for pediatric clinical and histologic features and for more sensitive coding of RC enzyme and functional studies. Reanalysis of the patients' data resulted in congruence between the diagnostic certainty previously assigned by the authors' center and that defined by the new general RC diagnostic criteria in 99% of patients.

CONCLUSIONS

These general diagnostic criteria appear to improve the sensitivity of the adult criteria. They need further assessment in prospective clinical and epidemiologic studies.

MR spectroscopic findings in a case of Alpers-Huttenlocher syndrome

Alpers-Huttenlocher syndrome, considered a mitochondrial disease, combines encephalopathy and liver failure. An 11-year-old boy with Alpers-Huttenlocher syndrome underwent conventional MR imaging, diffusion-weighted imaging, and proton MR spectroscopy. Diffusion-weighted imaging showed cytotoxic edema interpreted as acute-phase encephalopathy. MR spectroscopy revealed a lactate peak in the cortex that appeared abnormal on diffusion-weighted images, possibly representing respiratory deficiency with anaerobic metabolism. MR spectroscopy proved to be more sensitive regarding lactate detection than did neurometabolic examination of serum and CSF. A reduced N-acetylaspartate-creatine ratio was detected in both the cortex that appeared abnormal and the cortex that appeared normal on the diffusion-weighted images, indicating neuronal damage that was widespread, even beyond the boundaries of conventional MR imaging changes.

Inducible nitric oxide synthase and nitrotyrosine are found in monocytes/macrophages and/or astrocytes in acute, but not in chronic, multiple sclerosis

We have examined the localization of inducible nitric oxide synthase (iNOS) and nitrotyrosine (the product of nitration of tyrosine by peroxynitrite, a highly reactive derivative of nitric oxide [NO]) in demyelinating lesions from (i) two young adult patients with acute multiple sclerosis (MS), (ii) a child with MS (consistent with diffuse sclerosis), and (iii) five adult patients with chronic MS. Previous reports have suggested a possible correlation between iNOS, peroxynitrite, related nitrogen-derived oxidants, and the demyelinating processes in MS. We have demonstrated iNOS-immunoreactive cells in both acute-MS and diffuse-sclerosis-type lesions. In acute-MS lesions, iNOS was localized in both monocytes/macrophages and reactive astrocytes. However, foamy (myelin-laden) macrophages and the majority of reactive astrocytes were iNOS negative. In specimens from the childhood MS patient, iNOS protein was present only in a subpopulation of reactive or hypertrophic astrocytes. In contrast, no iNOS staining was detected in chronic-MS lesions. Immunohistochemical staining of acute-MS lesions with an antibody to nitrotyrosine revealed codistribution of iNOS- and nitrotyrosine-positive cells, although nitrotyrosine staining was more widespread in cells of the monocyte/macrophage lineage. In diffuse-sclerosis-type lesions, nitrotyrosine staining was present in hypertrophic astrocytes, whereas it was absent in chronic-MS lesions. These results suggest that NO and nitrogen-derived oxidants may play a role in the initiation of demyelination in acute-MS lesions but not in the later phase of the disease.

Overexpression of DM20 messenger RNA in two brothers with Pelizaeus-Merzbacher disease

Pelizaeus-Merzbacher disease is a rare, sex-linked recessive, dysmyelinating disease of the central nervous system that has been associated with mutations in the myelin proteolipid protein (PLP) gene. Only 25% of patients studied with Pelizaeus-Merzbacher disease have exonic mutations in this gene, the underlying cause of the disease in the remaining patients is unknown. The PLP gene encodes two major alternatively spliced transcripts called PLP and DM20. PLP messenger RNA is specifically expressed in central nervous system tissue, whereas DM20 messenger RNA is found in central nervous system, cardiac, and other tissues. We studied cultured skin fibroblasts from 2 brothers with Pelizaeus-Merzbacher disease who exhibited no detectable exonic mutation of the PLP gene. Examination of RNA from these cells showed that the level of DM20 messenger RNA is elevated sixfold relative to male control skin fibroblasts. An unrelated female carrier, also with no detectable exonic mutation, showed a threefold increase in DM20 messenger RNA in cultured skin fibroblasts. Our findings suggest that in some patients, Pelizaeus-Merzbacher disease is caused by overexpression of PLP gene transcripts, and that in these families a 50% increase of DM20 messenger RNA in females, relative to the increase in affected males, can identify a female carrier.

The neonatal progeroid syndrome (Wiedemann-Rautenstrauch) and its relationship to Pelizaeus-Merzbacher's disease

The neuropathology of a clinically well-documented case of the neonatal progeroid syndrome Wiedemann-Rautenstrauch is described. The most striking feature was a nearly complete absence of mature myelin in the brain. When immunohistochemistry for myelin basic protein was applied, some subcortical nerve fibres were accompanied by immature myelin sheaths. The neuropathology corresponds exactly to that of Pelizaeus-Merzbacher disease (Seitelberger type). Furthermore, this morphology, with the presence of myelin basic protein in the absence of mature myelin sheaths is reminiscent of the early stages of myelination in the newborn. From a brief review of the literature on Wiedemann-Rautenstrauch syndrome, we conclude, that the neuropathology of the syndrome is heterogeneous, and that there is relationship between the progeroid aspect and pathological myelination.

A case of Pelizaeus-Merzbacher disease showing increased dosage of the proteolipid protein gene

Clinical, neuropathological and molecular genetic studies in a 9 month old boy with Pelizaeus-Merzbacher disease are described. The principal clinical features were developmental delay, nystagmus, stridor and seizures. Both brain and spinal cord showed almost complete absence of stainable central myelin, while cranial and spinal root myelin was preserved. Probes for cDNA in the boy and his asymptomatic mother indicated an increase in the dosage of proteolipid protein gene (of at least twofold) compared with controls.

Biochemical diagnosis of Canavan disease

Canavan disease (CD) is a rare autosomal recessive disorder characterized by macrocephaly and progressive leukodystrophy. Up to now biopsy or necropsy were required to define the diagnosis. Recently the disease has been related to N-acetylaspartic aciduria and deficiency of aspartoacylase, an enzyme possibly involved in the myelin synthesis. These biochemical findings have provided a diagnostic marker for the disease. We report a new case of infantile CD in which the demonstration of N-acetylaspartic aciduria and a marked deficiency of aspartoacylase activity confirmed the diagnosis.

Accumulation of alpha B-crystallin in brains of patients with Alexander's disease is not due to an abnormality of the 5'-flanking and coding sequence of the genomic DNA

alpha B-Crystallin is a major protein component of Rosenthal fibers, which massively accumulate in the brains of patients suffering from Alexander's disease. To examine whether or not accumulation of alpha B-crystallin is due to any abnormality of the gene structures, we determined the sequence of the alpha B-crystallin gene in two cases of pathologically confirmed Alexander's disease. Direct sequencing of the promoter and coding regions of the alpha B-crystallin gene in patients revealed them to have a normal sequence. Northern blotting showed a single alpha B-crystallin mRNA species expressed in the Alexander's disease brain.

Phosphorylation of alpha-crystallin B in Alexander's disease brain

The phosphorylation of alpha-crystallin B was studied in homogenates of autopsy samples of brain tissue from patients with Alexander's disease, a condition characterized by over-expression of this protein. After incubation in the presence of [gamma-32P]ATP and cAMP the homogenates were analyzed by two-dimensional electrophoresis, (isoelectric focusing followed by SDS-PAGE). Three major polypeptides having the same molecular weight as bovine lens alpha-crystallin B and pIs 7.1, 6.9 and 6.7 were detected in the Coomassie blue stained gels. These three polypeptides were recognized by an alpha-crystallin B-specific antiserum in Western blots. The polypeptides with pIs 7.1 and 6.7 co-migrated in isoelectric focusing gels with bovine lens alpha B and its phosphorylated form alpha Bp, respectively. Radioautography of the two-dimensional gels demonstrated the presence of 32P in the most acidic polypeptide. The results demonstrate the occurrence of alpha B phosphorylation in Alexander's disease brain tissue.

[Demyelinating elements of demyelinated encephalopathy]

The myelin basic protein (MBPi) accounts for the main encephalitogenic antigen of the demyelinating encephalopathy, but other myelin elements also be noted by some articles. We tried to determine the relationship between W1 protein and the demyelinating encephalopathies. The 2',3'-cyclic nucleotide 3'-phospho-diesterase(CNPase, a gift from Dr. Yasuzo Tuskada) monoclonal antibody was used as a probe to study the W1 protein level in 5 different demyelinating encephalopathies and 2 normal adult brains with immunocytochemical technique. Two different demyelinating types of W1 protein level were found out. Type 1 showed the W1 protein level parallel with demyelinated feature in general pathology whereas the type 2 showed demyelinated in the general pathology but the W1 protein level was normal in the immunocytochemical study. Multiple system degeneration, Binswanger's disease and postvaccinal encephalopathy of type B encephalitis belong to type 1 and multiple sclerosis and Balo's concentric sclerosis belong to type 2. These results might indicate the different pathogenesis of demyelinating encephalopathies.

Liver involvement in Alpers disease

Alpers disease consists of diffuse cerebral degeneration manifested as developmental delay, seizures, vomiting, and progressive neuromuscular deterioration, with liver disease and death. We report the clinical course of the liver disease, histologic progression of the hepatic lesions, and etiologic investigations in five patients (four girls, three kinships). All had grown and developed normally until seen at 6 to 36 months of age (mean 20 months), with vomiting (n = 5), progressive hypotonia (n = 3), or seizures (n = 2). All had been given anticonvulsants, including valproic acid in three. Liver disease was noted at a mean age of 35 months (range 9 to 67 months), with hepatomegaly (two patients), abnormal hepatic synthetic function (three) or transaminase values (three), and cirrhosis in one. Patients survived for a mean of 4.6 weeks (range 1 to 8 weeks) after the identification of liver disease; all died of hepatic failure. Results of evaluation for infectious and metabolic causes of liver disease and causes of degenerative neuromuscular disease were negative in all patients. Premortem liver biopsy specimens (n = 3) demonstrated an early lesion consisting of lobular disarray, microvesicular steatosis, periportal acute and chronic inflammation, and individual hepatocyte necrosis. Autopsy findings (n = 5) consisted of macrovesicular steatosis, massive hepatocyte dropout, and proliferation of bile ductular elements, with almost complete replacement of hepatocytes by proliferating bile ductular elements in two patients. Brain showed characteristic neuronal degeneration. We conclude that Alpers disease can be a cause of rapidly progressive liver failure in early childhood. Although the cause of this autosomal recessive disease is not known, it does not appear to be related to peroxisomal dysfunction.

Metabolism of saturated and polyunsaturated very-long-chain fatty acids in fibroblasts from patients with defects in peroxisomal beta-oxidation

The metabolism of [1-14C]lignoceric acid (C24:0) and [1-14C]tetracosatetraenoic acid (C24:4, n-6) was studied in normal skin fibroblast cultures and in cultures from patients with defects in peroxisomal beta-oxidation (but normal peroxisomal numbers). Cells from X-linked adrenoleukodystrophy (ALD) patients with a presumed defect in a peroxisomal acyl-CoA synthetase, specific for fatty acids of carbon chain lengths greater than 22 (very-long-chain fatty acids; VLCFA), showed a relatively normal production of radiolabelled CO2 and water-soluble metabolites from [1-14C]C24:0. However, the products of synthesis from acetate de novo (released by beta-oxidation), i.e. C16 and C18 fatty acids, were decreased, and carbon chain elongation of the fatty acid was increased. In contrast, cell lines from two patients with an unidentified lesion in peroxisomal beta-oxidation (peroxisomal disease, PD) showed a marked deficiency in CO2 and water-soluble metabolite production, a decreased synthesis of C16 and C18 fatty acids and an increase in carbon chain elongation. The relatively normal beta-oxidation activity of ALD cells appears to be related to low uptake of substrate, as a defect in beta-oxidation is apparent when measurements are performed on cell suspensions under high uptake conditions. Oxidation of [1-14C]C24:4 was relatively normal in ALD cells and in the cells from one PD patient but abnormal in those from the other. Our data suggest that, despite the deficiency in VLCFA CoA synthetase, ALD cells retain a near normal ability to oxidize both saturated and polyunsaturated VLCFA under some culture conditions. However, acetate released by beta-oxidation of the saturated VLCFA and, to a much lesser degree, the polyunsaturated VLCFA, appears to be used preferentially for the production of CO2 and water-soluble products, and acetate availability for fatty acid synthesis in other subcellular compartments is markedly decreased. It is likely that the increased carbon chain elongation of the saturated VLCFA which is also observed reflects the increased availability of substrate (C24:0) and/or an increase in microsomal elongation activity in ALD cells.

Cellular oxidation of lignoceric acid is regulated by the subcellular localization of lignoceroyl-CoA ligases

The acyl-CoA ligases convert free fatty acids to acyl-CoA derivatives, and these enzymes have been shown to be present in mitochondria, peroxisomes, and endoplasmic reticulum. Because their activity is obligatory for fatty acid metabolism, it is important to identify their substrate specificities and subcellular distributions to further understand the cellular regulation of these pathways. To define the role of the enzymes and organelles involved in the metabolism of very long chain (VLC) fatty acids, we studied human genetic cell mutants impaired for the metabolism of these molecules. Fibroblast cell lines were derived from patients with X-linked adrenoleukodystrophy (X-ALD) and Zellweger's cerebro-hepato-renal syndrome (CHRS). While peroxisomes are present and morphologically normal in X-ALD, they are either greatly reduced in number or absent in CHRS. Palmitoyl-CoA ligase is known to be present in mitochondria, peroxisomes, and endoplasmic reticulum (microsomes). We found enzyme-dependent formation of lignoceroyl-CoA in these same organelles (specific activities were 0.32 +/- 0.12, 0.86 +/- 0.12, and 0.78 +/- 0.07 nmol/h per mg protein, respectively). However, lignoceroyl-CoA synthesis was inhibited by an antibody to palmitoyl-CoA ligase in isolated mitochondria while it was not inhibited in peroxisomes or endoplasmic reticulum (ER). This suggests that palmitoyl-CoA ligase and lignoceroyl-CoA are different enzymes and that mitochondria lack lignoceroyl-CoA ligase. This conclusion is further supported by data showing that oxidation of lignoceric acid was found almost exclusively in peroxisomes (0.17 nmol/h per mg protein) but was largely absent from mitochondria and the finding that monolayers of CHRS fibroblasts lacking peroxisomes showed a pronounced deficiency in lignoceric acid oxidation in situ (1.8% of control). In spite of the observation that lignoceroyl-CoA ligase activity is present on the cytoplasmic surface of ER, our data indicate that lignoceroyl-CoA synthesized by ER is not available for oxidation in mitochondria. This organelle plays no physiological role in the beta-oxidation of VLC fatty acids. Furthermore, the normal peroxisomal oxidation of lignoceroyl-CoA but deficient oxidation of lignoceric acid in X-ALD cells indicates that cellular VLC fatty acid oxidation is dependent on peroxisomal lignoceroyl-CoA ligase. These studies allow us to propose a model for the subcellular localization of various acyl-CoA ligases and to describe how these enzymes control cellular fatty acid metabolism.

[X-linked adrenoleukodystrophy and other peroxisomal diseases caused by a failing peroxisomal beta-oxidation system: clinical expression, diagnosis and treatment]

X-linked adrenoleukodystrophy (ALD) is a sex-linked, neurodegenerative disorder which in its most stereotypic form manifests itself in a boy who progresses normally for the first years of life and then presents with CNS signs and symptoms such as behavioural abnormalities, visual and auditory disturbances and an abnormal gait. The course of the disease is progressive, culminating within a few years in dementia, blindness, quadriplegia and death. Recently it has become clear that ALD is caused by an impairment in the peroxisomal beta-oxidation system leading to the accumulation of very-long-chain fatty acids. Accumulation occurs not only in plasma but also in brain giving rise to increasing myelin instability and subsequent demyelination. Apart from X-linked ALD there are a number of other disorders all characterized by a deficient peroxisomal beta-oxidation activity. It is remarkable that the clinical presentation of these different inborn errors of peroxisomal beta-oxidation differs markedly. In this paper the inborn errors of peroxisomal beta-oxidation known at present will be discussed with particular emphasis on ALD.