Peroxisomal disorders in children: immunohistochemistry and neuropathology

Characterization of Severity in Zellweger Spectrum Disorder by Clinical Findings: A Scoping Review, Meta-Analysis and Medical Chart Review

Zellweger spectrum disorder (ZSD) is a rare, debilitating genetic disorder of peroxisome biogenesis that affects multiple organ systems and presents with broad clinical heterogeneity. Although severe, intermediate, and mild forms of ZSD have been described, these designations are often arbitrary, presenting difficulty in understanding individual prognosis and treatment effectiveness. The purpose of this study is to conduct a scoping review and meta-analysis of existing literature and a medical chart review to determine if characterization of clinical findings can predict severity in ZSD. Our PubMed search for articles describing severity, clinical findings, and survival in ZSD resulted in 107 studies (representing 307 patients) that were included in the review and meta-analysis. We also collected and analyzed these same parameters from medical records of 136 ZSD individuals from our natural history study. Common clinical findings that were significantly different across severity categories included seizures, hypotonia, reduced mobility, feeding difficulties, renal cysts, adrenal insufficiency, hearing and vision loss, and a shortened lifespan. Our primary data analysis also revealed significant differences across severity categories in failure to thrive, gastroesophageal reflux, bone fractures, global developmental delay, verbal communication difficulties, and cardiac abnormalities. Univariable multinomial logistic modeling analysis of clinical findings and very long chain fatty acid (VLCFA) hexacosanoic acid (C26:0) levels showed that the number of clinical findings present among seizures, abnormal EEG, renal cysts, and cardiac abnormalities, as well as plasma C26:0 fatty acid levels could differentiate severity categories. We report the largest characterization of clinical findings in relation to overall disease severity in ZSD. This information will be useful in determining appropriate outcomes for specific subjects in clinical trials for ZSD.

The impact of cold acclimation and hibernation on antioxidant defenses in the ground squirrel (Spermophilus citellus): an update

Any alteration in oxidative metabolism is coupled with a corresponding response by an antioxidant defense (AD) in appropriate subcellular compartments. Seasonal hibernators pass through circannual metabolic adaptations that allow them to either maintain euthermy (cold acclimation) or enter winter torpor with body temperature falling to low values. The present study aimed to investigate the corresponding pattern of AD enzyme protein expressions associated with these strategies in the main tissues involved in whole animal energy homeostasis: brown and white adipose tissues (BAT and WAT, respectively), liver, and skeletal muscle. European ground squirrels (Spermophilus citellus) were exposed to low temperature (4 ± 1 °C) and then divided into two groups: (1) animals fell into torpor (hibernating group) and (2) animals stayed active and euthermic for 1, 3, 7, 12, or 21 days (cold-exposed group). We examined the effects of cold acclimation and hibernation on the tissue-dependent protein expression of four enzymes which catalyze the two-step detoxification of superoxide to water: superoxide dismutase 1 and 2 (SOD 1 and 2), catalase (CAT), and glutathione peroxidase (GSH-Px). The results showed that hibernation induced an increase of AD enzyme protein expressions in BAT and skeletal muscle. However, AD enzyme contents in liver were largely unaffected during torpor. Under these conditions, different WAT depots responded by elevating the amounts of specific enzymes, as follows: SOD 1 in retroperitoneal WAT, GSH-Px in gonadal WAT, and CAT in subcutaneous WAT. Similar perturbations of AD enzymes contents were seen in all tissues during cold acclimation, often in a time-dependent manner. It can be concluded that BAT and muscle AD capacity undergo the most dramatic changes during both cold acclimation and hibernation, while liver is relatively unaffected by either condition. Additionally, this study provides a basis for further metabolic study that will illuminate the causes of these tissue-specific AD responses, particularly the novel finding of distinct responses by different WAT depots in hibernators.

A developmental and genetic classification for malformations of cortical development: update 2012

Malformations of cerebral cortical development include a wide range of developmental disorders that are common causes of neurodevelopmental delay and epilepsy. In addition, study of these disorders contributes greatly to the understanding of normal brain development and its perturbations. The rapid recent evolution of molecular biology, genetics and imaging has resulted in an explosive increase in our knowledge of cerebral cortex development and in the number and types of malformations of cortical development that have been reported. These advances continue to modify our perception of these malformations. This review addresses recent changes in our perception of these disorders and proposes a modified classification based upon updates in our knowledge of cerebral cortical development.

Very-long-chain fatty acids activate lysosomal hydrolases in neonatal human skin tissue

OBJECTIVE

The aim of this study was to examine the in vitro effect of peroxisomal dysfunction on lysosomal enzymes, the autophagic machinery in the cell, in order to understand the mechanisms of pathogenesis of peroxisomal disorders.

MATERIALS AND METHODS

Foreskin samples were obtained immediately after circumcision of 1- to 2-day-old infants at the Maternity Hospital, Kuwait. Skin tissues were cleaned, cut into slices of 1-2 mm2 in size and treated with lignoceric acid (1-20 microg/ml), a very-long-chain fatty acid (VLCFA), in the presence or absence of 1-5 mM aminotriazole (ATZ). A battery of lysosomal enzymes were assayed following treatment of dermal tissue with VLCFA or ATZ.

RESULTS

Treatment of skin slices with lignoceric acid significantly increased (p < 0.001) the enzymic activities of acid lipase, acid phosphatase, alpha-glucosidase, alpha-galactosidase, N-acetyl-alpha-D-glucosaminidase (NAGA) and N-acetyl-alpha-D-galactosaminidase (NAGTA). ATZ (1-5 mM), an inhibitor of key peroxi somal enzyme catalase, also markedly increased the enzymic activities of acid phosphatase, alpha-glucosidase (23%) and alpha-galactosidase (18%) without any significant effect on NAGA or NAGTA. Western blot analysis further revealed that both VLCFA and ATZ significantly increased the protein expression of lysosomal enzymes, beta-galactosidase and beta-glucuronidase.

CONCLUSION

Experimen tal dysfunction of peroxisomes mimicked by elevated VLCFA or ATZ-mediated catalase inhibition significantly increased the activities of lysosomal hydrolases in human dermal tissue, suggesting that activation of the lysosomal system could be one of the factors responsible for cellular damage during pathogenesis of peroxisomal diseases.

Cellular and subcellular localization of catalase in the heart of transgenic mice

Previous studies have described a cardiac-specific, catalase-overexpressing transgenic mouse model that was used to study myocardial oxidative injury. This study was undertaken to demonstrate cellular and subcellular localization of catalase in the hearts of transgenic mice. By the light microscopic immunoperoxidase method, we found that the overexpressed catalase was exclusively localized in cardiomyocytes. The ratios of immunoreactive cardiomyocytes in the heart were quite different among three transgenic lines examined but agreed with the elevated levels of catalase activity. In the cardiac blood vessels, positive cells were found in the walls of pulmonary veins and the vena cava, which consist of cardiomyocytes, but not in the pulmonary arteries, aorta, or cardiac valves. The electron microscopic immunogold method revealed that the elevated catalase was in sarcoplasm, nucleus, and peroxisomes, but not in mitochondria. In contrast to these distributions, catalase in the non-transgenic cardiomyocytes was in peroxisomes only. In addition, the number and size of peroxisomes in the transgenic cardiomyocytes were markedly increased, but no other ultrastructural changes were observed in comparison with those of non-transgenic mice. These results demonstrated that the elevated catalase in transgenic mouse heart is localized in cardiomyocytes and is distributed to peroxisomal and extraperoxisomal, but not mitochondrial, compartments.

Developmental and pathological expression of peroxisomal enzymes: their relationship of D-bifunctional protein deficiency and Zellweger syndrome

We present the developmental changes of peroxisomal enzymes, catalase, L-bifunctional protein (L-BF) and D-bifunctional protein (D-BF), in the normal brains, and patients with D-BF deficiency, a new peroxisomal disease. D-BF immunoreactivity was observed in controls as early as 13 gestational weeks (GW) and increased with maturation. The adult pattern with fine granule staining of somata and dendrites became apparent in adolescence. L-BF appeared at 20 GW in the cerebral cortex and Purkinje cells and positive glia appeared early in the white matter at 17 GW, and then increased with age. Catalase-positive neurons were identified in the same manner as L-BF, D-BF deficiency in both fetus and infant showed markedly diminished enzyme immunoreactivity. Patients demonstrate reduced D-BF expression. Zellweger syndrome shows decreased expression for the three proteins. This study shows that the peroxisomal enzymes may be closely related to neuronal maturation and gliogenesis in human brain and to disturbance of neuronal migration as seen in Zellweger syndrome significant. D-BF deficiency may exhibit a range of symptoms during the neonatal and early infantile periods some of which may be similar to Zellweger syndrome.

Peroxisomal bifunctional enzyme deficiency: serial neurophysiological examinations of a case

We report on a case of 21-month-old girl with peroxisomal bifunctional enzyme deficiency, which was diagnosed by means of complementation analysis. Serial neurophysiological examinations were also carried out. The motor and sensory nerve conduction velocities of the median nerve showed lower borderline values at 3 months of age and were within range at 11 months of age. Later, those velocities gradually decreased. The electrically elicited blink reflex at 3 months of age showed the prolongation of latencies of R1, R2 and R2' and the interpeak latencies of R1-R2 and R1-R2'. Furthermore, R1, R2 and R2' showed prolonged latencies at 11 months of age and were absent at 15 months of age. The auditory brainstem response (ABR) showed, bilaterally, normal latency of wave I, prolonged interpeak latencies of waves I-V. At 11 months of age, waves III and IV-V of ABR were detected, but their amplitude was very low. At the age of 15 months ABR was absent. These results and the following report are valuable for understanding the pathogenesis of neurological symptoms.

Developmental immunohistochemistry of the 22 kDa peroxisomal membrane protein in the human brain

We studied immunohistochemically the 22 kDa peroxisomal membrane protein (PMP 22). In the control brain, the immunopositive neurons for PMP 22 appeared 2-3 weeks earlier than those for peroxisomal enzymes. PMP 22-immunopositive glial cells appeared at 26-27 gestational weeks, increased with gestational age, and were rarely recognized after 1 year of age. In the patients with Zellweger syndrome, PMP 22-immunoreactivity was recognized in neurons, glias, liver and kidney cells.

Immunohistochemistry for a bifunctional protein in patients with peroxisomal disorders

Immunohistochemical studies using antisera against bifunctional protein, a beta-oxidation enzyme, were performed on liver, kidney, and brain tissue specimens from patients with peroxisomal disorders and from controls to investigate the distribution and development of peroxisomes. Bifunctional protein-positive granules were not found in patients with Zellweger syndrome or neonatal adrenoleukodystrophy, whereas positive immunoreactivity was observed from 8 and 6 weeks gestation in the liver and kidney, respectively, and in the brain, from 23-25 weeks in the brainstem neurons and from 12-14 weeks in the white matter glia, in controls. Bifunctional protein immunoreactivity then increased with gestation in the brain. These results suggest that bifunctional protein immunohistochemistry is useful for the detection of peroxisomes, which are closely related to neuronal maturation and gliogenesis in premyelination in human brain development.

The importance of tissue fixation for light microscopic immunohistochemical localization of peroxisomal proteins: the superiority of Carnoy's fixative over Baker's formalin and Bouin's solution

We have compared the effects of fixation with three commonly used fixatives upon preservation of the antigenicity of six peroxisomal proteins in rat liver using both immunohistochemical staining and Western blotting of fixed tissue extracts. The immunoreactivity of all six peroxisomal proteins was well preserved and peroxisomes were clearly identified in material fixed in Carnoy's fixative. Moreover, the corresponding proteins stained well in Western blots prepared from extracts of Carnoy-fixed material. The intensity of the immunohistochemical staining was reduced at different rates for individual peroxisomal proteins after fixation in Baker's formalin, but peroxisomes were still well visualized with antibodies to catalase and some beta-oxidation enzymes. No evidence of immunohistochemical staining for any peroxisomal antigens was obtained after fixation in Bouin's fluid. For detection of the antibody binding sites in Carnoy's fixed material, the avidin-biotin-peroxidase complex (ABC) with aminoethyl carbazole as chromogen was found to be superior to the methods of peroxidase-antiperoxidase/diaminobenzidine and protein A-gold with silver intensification. Using Carnoy-fixative and the ABC-method, we demonstrate light microscopic immunohistochemical localization of peroxisomal antigens in several rat tissues as well as in human post-mortem liver.

Neuropathology of peroxisomal diseases

This paper gives a description of the essential neuropathological techniques applied to the study of metabolic disorders affecting the nervous system. Subsequently, the neuropathological features of a series of peroxisomal disorders are described with special attention being paid to adrenoleukodystrophy.

Secondary alterations of human hepatocellular peroxisomes

The morphological and morphometric characteristics of peroxisomes in normal human liver and the peroxisomal alterations in the liver of patients with acquired or congenital non-peroxisomal diseases are reviewed. Secondary peroxisomal changes are observed in steatosis, hepatitis and cirrhosis induced by various agents (viruses, alcohol, drugs, etc.), in cholestasis, in hepatomas, in extra-hepatic cancer with or without liver metastasis, in extrahepatic inflammatory processes, in metabolic disorders affecting metabolism of carbohydrates, lipids and lipoproteins, glycoproteins, amino acids, bilirubin or copper, and in altered thyroid hormone levels. They are recognized as a proliferation of peroxisomes (increased in number and to a lesser extent in surface density and volume density) often accompanied by a minor reduction in size (at most to 68% of the mean diameter in control livers) but very rarely by an increase in mean peroxisomal diameter, and as proliferation-related changes in shape (tails, gastruloid cisternae, funnel-like constrictions, elongation, protrusions) in at least a few of the peroxisomes. These secondary alterations of the peroxisomes are clearly distinguishable from the primary changes in peroxisomes observed in the liver of patients with congenital peroxisomal disorders.

Developmental immunohistochemistry of bifunctional protein in human brain

Immunohistochemical studies of a peroxisomal enzyme, bifunctional protein, were performed on human brains (occipital cortex, cerebellum, pons) from fetus to young adult. Bifunctional protein-positive neurons appeared at 23-25 weeks of gestation in the facial nuclei of pons, at 27-28 weeks in the occipital cortex and Purkinje cells of vermis, and at 36-38 weeks in the Purkinje cells of the cerebellar hemisphere and pontine nuclei. They then increased in number with gestational age. However, bifunctional protein-positive glia appeared early in the occipital deep white matter at 17-20 weeks of gestation, their appearance shifting from the deep to the superficial white matter with increasing age. These results suggest that bifunctional protein is closely related to neuronal maturation and gliogenesis of premyelination in the human brain during development as other peroxisomal enzymes.