Hereditary ceruloplasmin deficiency with hemosiderosis: a clinicopathological study of a Japanese family

Identification of mineral deposits in the brain on radiological images: a systematic review

OBJECTIVES

MRI has allowed the study of mineral deposition in the brain throughout life and in disease. However, studies differ in their reporting of minerals on MRI for reasons that are unclear.

METHODS

We conducted a systematic review from 1985 to July 2011 to determine the appearance of iron, calcium, copper and manganese on MRI and CT and their reliability. We assessed which imaging investigations provided the most consistent results compared with histology.

RESULTS

Of 325 papers on minerals imaging, we included 46 studies that confirmed findings either directly or indirectly using a non-imaging method such as histology. Within this group, there was inconsistency in the identification of iron probably because of changes in its paramagnetic properties during its degradation. Iron appeared consistently hypointense only on T2*-weighted MRI, and along with calcified areas, hyperattenuated on CT. Appearance of copper, calcium and manganese, although consistently reported as hyperintense on T1-weighted MRI, was confirmed histologically in few studies. On T2-weighted imaging, calcified areas were always reported as hypointense, while the appearance of iron depended on the concentration, location and degradation stage.

CONCLUSIONS

More work is required to improve the reliability of imaging methods to detect and differentiate brain mineral deposition accurately.

KEY POINTS

There is inconsistency in reporting the appearance of minerals on radiological images. • Only 46 studies confirmed mineral appearance using a non-imaging method. • Iron is the mineral more widely studied, consistently hypointense on T2*-weighted MRI. • T1-weighted MRI consistently reported copper, calcium and manganese hyperintense. • Calcium is consistently reported hypointense on T2-weighted MRI and hyperattenuating on CT.

Review article: the iron overload syndromes

BACKGROUND

Iron overload syndromes encompass a wide range of hereditary and acquired conditions. Major developments in the field of genetics and the discovery of hepcidin as a central regulator of iron homeostasis have greatly increased our understanding of the pathophysiology of iron overload syndromes.

AIM

To review advances in iron regulation and iron overload syndrome with special emphasis on hereditary haemochromatosis, the prototype iron overload syndrome.

METHODS

A PubMed search using words such as 'iron overload', 'hemochromatosis', 'HFE', 'Non-HFE', 'secondary iron overload' was undertaken.

RESULTS

Iron overload is associated with significant morbidity and mortality. Sensitive diagnostic tests and effective therapy are widely available and can prevent complications associated with iron accumulation in end- organs. Therapeutic phlebotomy remains the cornerstone of therapy for removal of excess body iron, but novel therapeutic agents including oral iron chelators have been developed for iron overload associated with anaemia.

CONCLUSIONS

Iron overload disorders are common. Inexpensive screening tests as well as confirmatory diagnostic tests are widely available. Increased awareness of the causes and importance of early diagnosis and knowledge of the appropriate use of genetic testing are encouraged. The availability of novel treatments should increase therapeutic options for patients with iron overload disorders.

Aceruloplasminemia: retinal histopathologic manifestations and iron-mediated melanosome degradation

OBJECTIVE

To examine the retinal histopathologic manifestation of aceruloplasminemia, an autosomal recessive disease caused by mutation of the ferroxidase ceruloplasmin, resulting in tissue iron overload.

METHODS

The morphologic features of the human aceruloplasminemic retina were studied with light and electron microscopy. Retinal iron accumulation was assessed with Perls Prussian blue staining, immunohistochemistry, and secondary ion mass spectrometry.

RESULTS

Light and electron microscopic analysis revealed several ocular pathologic findings that resembled age-related macular degeneration, including retinal pigment epithelium (RPE) depigmentation, atrophy and hypertrophy, nodular and diffuse drusen, and lipofuscin and melanolipofuscin granules. Complement deposition was detected in drusen. The RPE cells and neural retina had increased levels of iron. Two major types of RPE cells were observed: melanosome rich and melanosome poor. Melanosome-rich cells had increased levels of iron and melanolipofuscin. The melanolipofuscin granules were observed in large aggregates, where some of the melanosomes were degrading. Melanosome-poor cells lacked melanosomes, melanolipofuscin, and lipofuscin but contained electron-dense aggregates high in iron, phosphorus, and sulfur.

CONCLUSIONS

The findings in the aceruloplasminemic retina resemble some of those found in age-related macular degeneration. Also, they suggest that melanosomes in the RPE can be degraded via iron-mediated reactive oxygen species production.

CLINICAL RELEVANCE

Mechanisms underlying the pathologic mechanisms found in aceruloplasminemia also may be important in age-related macular degeneration.

Extensive brain pathology in a patient with aceruloplasminemia with a prolonged duration of illness

We report the sixth autopsy case of a patient with aceruloplasminemia. He was the younger brother of the first reported autopsy case of this disease. Among autopsy cases with aceruloplasminemia reported to date, he had the longest duration of neurologic disorders. The neuropathologic findings showed that the basal ganglia and dentate nuclei were most severely affected. The most striking finding in the present case was that marked iron deposition was evident in the cerebral cortex. Many enlarged or deformed astrocytes and globular structures, both of which were heavily iron loaded, were found in the cerebral cortex as well as in the basal ganglia. Pyramidal neurons in his cerebral cortex were fewer in number than observed in the previous reported cases. There was a negative correlation between the number of cortical pyramidal neurons and globular structures. The present case clearly indicates that the neuropathologic process in aceruloplasminemia extends beyond the basal ganglia to the cerebral cortex with time.

MRI findings in neuroferritinopathy

Neuroferritinopathy is a neurodegenerative disease which demonstrates brain iron accumulation caused by the mutations in the ferritin light chain gene. On brain MRI in neuroferritinopathy, iron deposits are observed as low-intensity areas on T2WI and as signal loss on T2∗WI. On T2WI, hyperintense abnormalities reflecting tissue edema and gliosis are also seen. Another characteristic finding is the presence of symmetrical cystic changes in the basal ganglia, which are seen in the advanced stages of this disorder. Atrophy is sometimes noted in the cerebellar and cerebral cortices. The variety in the MRI findings is specific to neuroferritinopathy. Based on observations of an excessive iron content in patients with chronic neurologic disorders, such as Parkinson disease and Alzheimer disease, the presence of excess iron is therefore recognized as a major risk factor for neurodegenerative diseases. The future development of multimodal and advanced MRI techniques is thus expected to play an important role in accurately measuring the brain iron content and thereby further elucidating the neurodegenerative process.

Wilson's disease

In the almost 100 years since Wilson's description of the illness that now bears his name, tremendous advances have been made in our understanding of this disorder. The genetic basis for Wilson's disease - mutation within the ATP7B gene - has been identified. The pathophysiologic basis for the damage resulting from the inability to excrete copper via the biliary system with its consequent gradual accumulation, first in the liver and ultimately in the brain and other organs and tissues, is now known. This has led to the development of effective diagnostic and treatment modalities that, although they may not eliminate the disorder, do provide the means for efficient diagnosis and effective amelioration if carried out in a dedicated and persistent fashion. Nevertheless, Wilson's disease remains both a diagnostic and treatment challenge for physician and patient. Its protean clinical manifestations make diagnosis difficult. Appropriate diagnostic evaluations to confirm the diagnosis and institute treatment can be confusing. In this chapter, the clinical manifestations, diagnostic evaluation, and treatment approaches for Wilson's disease are discussed.

Ceruloplasmin protects against rotenone-induced oxidative stress and neurotoxicity

To clarify the neuroprotective property of ceruloplasmin and the pathogenesis of aceruloplasminemia, we generated ceruloplasmin-deficient (CP⁻/⁻) mice on the C57BL/10 genetic background and further treated them with a mitochondrial complex I inhibitor, rotenone. There was no iron accumulation in the brains of CP⁻/⁻ mice at least up to 60 weeks of age. Without rotenone treatment, CP⁻/⁻ mice showed slight motor dysfunction compared with CP⁺/⁺ mice, but there were no detectable differences in the levels of oxidative stress markers between these two groups. A low dose of rotenone did not affect the mitochondrial complex I activity in our mice, however, it caused a significant change in motor behavior, neuropathology, or the levels of oxidative stress markers in CP⁻/⁻ mice, but not in CP⁺/⁺ mice. Our data support that ceruloplasmin protects against rotenone-induced oxidative stress and neurotoxicity, probably through its antioxidant properties independently of its function of iron metabolism.

Impact of copper limitation on expression and function of multicopper oxidases (ferroxidases)

Copper is an essential trace element whose recommended intake is met by most North American diets. However, incidence of new cases of secondary copper deficiency is rising due to complications of gastric bypass surgery and high zinc exposure. Patients frequently are ataxic and anemic. Anemia of copper deficiency was first described in the 19th century, but the underlying biochemistry remains unknown. Approximately one dozen cuproenzymes have been characterized in mammals. Four of these are referred to as multicopper oxidases (MCO) due to their copper binding geometries. They have iron oxidase activity (ferroxidase). These include the hepatic secreted protein ceruloplasmin representing ∼90% of plasma copper, a splice-variant of ceruloplasmin originally characterized in brain linked by glycosylphosphatidylinositol (GPI) to membranes, an intestinal enriched MCO named hephaestin, and newly described MCO in placenta called zyklopen. Limitation in available copper appears to limit function of the MCO group exhibited as impaired iron flux due to the copper requirement of MCO for their ferroxidase activity. Dietary copper deficiency is associated with lower levels of ceruloplasmin, GPI-ceruloplasmin, and hephaestin. Limitation of copper does not appear to limit synthesis of MCO but rather their stability and turnover. However, there appears to be a disconnect between limitation in MCO function and anemia, because humans and mice missing ceruloplasmin are not anemic despite hepatic iron overload and hypoferremia. Furthermore, anemic copper-deficient mammals are not improved by iron replacement. This suggests that the anemia of copper deficiency is not caused by iron limitation but rather impairment in iron utilization.

Decreased serum ceruloplasmin levels characteristically aggravate nigral iron deposition in Parkinson's disease

In vivo and post-mortem studies have demonstrated that increased nigral iron content in patients with Parkinson's disease is a prominent pathophysiological feature. However, the mechanism and risk factors associated with nigral iron deposition in patients with Parkinson's disease have not been identified and represent a key challenge in understanding its pathogenesis and for its diagnosis. In this study, we assessed iron levels in patients with Parkinson's disease and in age- and gender-matched control subjects by measuring phase values using magnetic resonance based susceptibility-weighted phase imaging in a 3T magnetic resonance system. Phase values were measured from brain regions including bilateral substantia nigra, globus pallidus, putamen, caudate, thalamus, red nucleus and frontal white matter of 45 patients with Parkinson's disease with decreased or normal serum ceruloplasmin levels, together with age- and gender-matched control subjects. Correlative analyses between phase values, serum ceruloplasmin levels and disease severity showed that the nigral bilateral average phase values in patients with Parkinson's disease were significantly lower than in control subjects and correlated with disease severity according to the Hoehn and Yahr Scale. The Unified Parkinson's Disease Rating Scale motor scores from the clinically most affected side were significantly correlated with the phase values of the contralateral substantia nigra. Furthermore, nigral bilateral average phase values correlated highly with the level of serum ceruloplasmin. Specifically, in the subset of patients with Parkinson's disease exhibiting reduced levels of serum ceruloplasmin, we found lowered nigral bilateral average phase values, suggesting increased nigral iron content, while those patients with normal levels of serum ceruloplasmin exhibited no changes as compared with control subjects. These findings suggest that decreased levels of serum ceruloplasmin may specifically exacerbate nigral iron deposition in patients with Parkinson's disease. Combining susceptibility-weighted phase imaging with serum ceruloplasmin determination is likely to be useful for the diagnosis and assessment of a subset of patients with Parkinson's disease.

Molecular basis of iron-loading disorders

Iron-loading disorders (haemochromatosis) represent an important class of human diseases. Primary iron loading results from inherited disturbances in the mechanisms regulating intestinal iron absorption, such that excess iron is taken up from the diet. Body iron load can also be increased by repeated blood transfusions (secondary iron loading), usually as part of the treatment for various haematological disorders. In these syndromes, an element of enhanced iron absorption is also often involved. The central regulator of body iron trafficking is the liver-derived peptide hepcidin. Hepcidin limits iron entry into the plasma from macrophages, intestinal enterocytes and other cells by binding to the sole iron-export protein ferroportin, and facilitating its removal from the plasma membrane. Mutations in hepcidin or its upstream regulators (HFE, TFR2, HFE2 and BMP6) lead to reduced or absent hepcidin expression and a concomitant increase in iron absorption. Mutations in ferroportin that prevent hepcidin binding produce a similar result. Increased ineffective erythropoiesis, which often characterises erythrocyte disorders, also leads to reduced hepcidin expression and increased absorption. Recent advances in our understanding of hepcidin and body iron homeostasis provide the potential for a range of new diagnostic and therapeutic tools for haemochromatosis and related conditions.

Central diabetes insipidus and hypothalamic hypothyroidism associated with aceruloplasminemia

Aceruloplasminemia is a rare autosomal recessive disease first reported by Miyajima et al. (Neurology 37: 761-767, 1987); it is clinically characterized by diabetes mellitus, retinal degeneration and neurological abnormalities, such as cerebellar ataxia, extrapyramidal signs and dementia. Aceruloplasminemia is caused by mutations in the ceruloplasmin gene, which results in the absence of serum ceruloplasmin and iron overload in the brain, liver, pancreas and other organ tissues. However, little is known about endocrine diseases associated with aceruloplasminemia. We report herein a case of aceruloplasminemia accompanied by central diabetes insipidus and hypothalamic hypothyroidism.

Brain and retinal ferroportin 1 dysregulation in polycythaemia mice

Disruption of iron homeostasis within the central nervous system (CNS) can lead to profound abnormalities during both development and aging in mammals. The radiation-induced polycythaemia (Pcm) mutation, a 58-bp microdeletion in the promoter region of ferroportin 1 (Fpn1), disrupts transcriptional and post-transcriptional regulation of this pivotal iron transporter. This regulatory mutation induces dynamic alterations in peripheral iron homeostasis such that newborn homozygous Pcm mice exhibit iron deficiency anemia with increased duodenal Fpn1 expression while adult homozygotes display decreased Fpn1 expression and anemia despite organismal iron overload. Herein we report the impact of the Pcm microdeletion on iron homeostasis in two compartments of the central nervous system: brain and retina. At birth, Pcm homozygotes show a marked decrease in brain iron content and reduced levels of Fpn1 expression. Upregulation of transferrin receptor 1 (TfR1) in brain microvasculature appears to mediate the compensatory iron uptake during postnatal development and iron content in Pcm brain is restored to wild-type levels by 7 weeks of age. Similarly, changes in expression are transient and expression of Fpn1 and TfR1 is indistinguishable between Pcm homozygotes and wild-type by 12 weeks of age. Strikingly, the adult Pcm brain is effectively protected from the peripheral iron overload and maintains normal iron content. In contrast to Fpn1 downregulation in perinatal brain, the retina of Pcm homozygotes reveals increased levels of Fpn1 expression. While retinal morphology appears normal at birth and during early postnatal development, adult Pcm mice demonstrate a marked, age-dependent loss of photoreceptors. This phenotype demonstrates the importance of iron homeostasis in retinal health.

Iron supplementation by intraperitoneal injection eliminates the accumulation of hepatic copper induced by excess calcium in rats

Excess calcium is well known to induce iron deficiency. Furthermore, excess calcium increases hepatic copper concentration and decreases renal copper concentration. We investigated the effect of iron supplementation on the tissue distribution of copper in rats given a high-calcium diet. Male rats (5 weeks old) were divided into four groups; a control group, and three groups given a diet containing 5-fold higher calcium than its requirement and an intraperitoneal iron supplementation of 0, 1 or 2 mg/week as iron dextran. The animals were fed their respective experimental diets with or without iron supplementation for 4 weeks. Although the high-calcium diet had no effect on calcium concentrations in the liver, kidney, testis, spleen and plasma, it reduced haematocrit and iron concentrations in the liver, kidney and testis and the rats had a moderate iron deficiency. The iron supplementation restored to normal these signs of iron deficiency. The high-calcium diet increased hepatic copper concentration but decreased plasma copper concentration and ceruloplasmin activity, which was restored by the iron supplementation. The copper concentration in bile was neither affected by the high-calcium diet nor the iron supplementation. The high-calcium diet decreased the copper concentration in the kidney, which was not restored by the iron supplementation. These results suggest that secondary iron deficiency stimulates hepatic accumulation of copper in rats given excess calcium by suppressing copper efflux into the circulation. The reduced renal copper concentration by excess calcium is independent of the iron deficiency.

Age-dependent expression of hephaestin in the brain of ceruloplasmin-deficient mice

Aceruloplasminemia is an autosomal recessive disorder caused by mutations in the ceruloplasmin (CP) gene. It is characterized by iron accumulation in the brain and in visceral organs. However, little is known about the mechanism of iron transport in these regions. Adult CP null (CP(-/-)) mice show increased iron deposition in several regions of brain, such as the cerebellum and brainstem. In this study, we investigated the expression of the ceruloplasmin homolog hephaestin (Heph) in the brain of CP(-/-) mice as a function of age. In the cerebral cortex and caudate putamen of 80-week-old CP(-/-) mice, the expression of Heph increased significantly whilst iron levels remain normal [Patel BN, Dunn RJ, Jeong SY, Zhu Q, Julien JP, David S. Ceruloplasmin regulates iron levels in the CNS and prevents free radical injury. J Neurosci 2002;22(15):6578-6], indicating that Heph might compensate for the loss of CP. In contrast, the substantia nigra and cerebellum of 80-week-old CP(-/-) mice accumulate iron but do not express high levels or significant decrease of Heph, suggesting that Heph does not replace CP in these regions. These data suggest that Heph may compensate for the loss of CP in a region-specific manner.

Aceruloplasminemia: a novel mutation in a family with marked phenotypic variability

Hereditary aceruloplasminemia (HA) is a rare inherited disease characterized by anemia, iron overload, diabetes, and neurodegeneration. HA is caused by the homozygous mutation of the ceruloplasmin (CP) gene. We report two siblings with markedly different phenotypes carrying a novel mutation: a homozygous deletion of two nucleotides (1257-1258 TT del) causing the premature stop of the Cp protein translation (Y401X). An early diagnosis of iron overload was made in the female sibling who was subsequently treated with deferoxamine. At the age of 54, her neurologic symptoms were limited to mild akinetic signs and a history of seizures; moreover, her fasting blood glucose level never exceeded 120 mg/dL. The male sibling, who had not received any specific treatment for HA, developed severe diabetes at the age of 32 and at 48 manifested a progressively disabling neurologic disease. Possible physiopathological bases of these intrafamilial phenotypic variations are discussed.

Microglia and astroglia prevent oxidative stress-induced neuronal cell death: implications for aceruloplasminemia

We partially characterized the transferrin-independent iron uptake (Tf-IU) of neuronal and glial cells in the previous report. In the present study, we further examined a mechanism of which glial cells protect neuronal cells against iron stress using neuron-microglia (N-MG) and neuron-astrocyte (N-AS) co-cultures. When each solely purified cell was treated with iron citrate, cell death occurred in N and MG. However, AS proliferated under the same condition. Both N-MG and N-AS co-cultures were effective in resistance to excessive iron. The total and specific Tf-IU activities of N-MG co-cultures similar to those of N did not increase in a density-dependent manner. Contrarily, the total activity of AS was extremely high and the specific activity was extremely low as a result of proliferation. Regarding of effect of co-cultures on H(2)O(2)-induced cell death, N-MG co-cultures were less effective, but N-AS co-cultures were more effective in protecting N from the oxidative stress. These results suggest that N-MG co-cultures suppress the Tf-IU and N-AS co-cultures stimulate AS proliferation to protect neuronal cells. Brain cells from aceruloplasminemia with mutations in the ceruloplasmin gene take up iron by Tf-IU. Therefore, the different mechanisms of neuronal cell protection by MG and AS may explain the pathophysiological observations in the brains of patient with aceruloplasminemia.

Copper and iron disorders of the brain

Copper and iron are transition elements essential for life. These metals are required to maintain the brain's biochemistry such that deficiency or excess of either copper or iron results in central nervous system disease. This review focuses on the inherited disorders in humans that directly affect copper or iron homeostasis in the brain. Elucidation of the molecular genetic basis of these rare disorders has provided insight into the mechanisms of copper and iron acquisition, trafficking, storage, and excretion in the brain. This knowledge permits a greater understanding of copper and iron roles in neurobiology and neurologic disease and may allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

N-tert-butyl hydroxylamine, a mitochondrial antioxidant, protects human retinal pigment epithelial cells from iron overload: relevance to macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe visual impairment in the elderly in developed countries. AMD patients have elevated levels of iron within the retinal pigment epithelia (RPE), which may lead to oxidative damage to mitochondria, disruption of retinal metabolism, and vision impairment or loss. As a possible model for iron-induced AMD, we investigated the effects of excess iron in cultured human fetal RPE cells on oxidant levels and mitochondrial cytochrome c oxidase (complex IV) function and tested for protection by N-tert-butyl hydroxylamine (NtBHA), a known mitochondrial antioxidant. RPE exposure to ferric ammonium citrate resulted in a time- and dose-dependent increase in intracellular iron, which increased oxidant production and decreased glutathione (GSH) levels and mitochondrial complex IV activity. NtBHA addition to iron-overloaded RPE cells led to a reduction of intracellular iron content, oxidative stress, and partial restoration of complex IV activity and GSH content. NtBHA might be useful in AMD due to its potential to reduce oxidative stress, mitochondrial damage, and age-related iron accumulation, which may damage normal RPE function and lead to loss of vision.

Decreased T2 signal in the thalami may be a sign of lysosomal storage disease

INTRODUCTION

Lysosomal disorders are rare and are caused by genetically transmitted lysosomal enzyme deficiencies. A decreased T2 signal in the thalamus has occasionally been reported.

AIMS

Because the finding of bilateral abnormal signal intensity of the thalamus on T2-weighted images has not been systematically reviewed, and its value as a diagnostic tool critically evaluated, we carried out a systematic review of the literature.

METHODS

Articles in English with 30 trios of keywords were collected from PubMed. Exclusion criteria were lack of conventional T2-weighted images in the protocol and not being a human study. Finally, 111 articles were included. The thalamus was considered affected only if mentioned in the text or in the figure legends.

RESULTS

Some 117 patients with various lysosomal diseases and five patients with ceruloplasmin deficiency were reported to have a bilateral decrease in T2 signal intensity. At least one article reported a bilateral decrease in signal intensity of the thalami on T2-weighted images in association with GM1 and GM2 gangliosidosis and with Krabbe's disease, aspartylglucosaminuria, mannosidosis, fucosidosis, and mucolipidosis IV. Furthermore, thalamic alteration was a consistent finding in several types of neuronal ceroid lipofuscinosis (NCL) including CLN1 (infantile NCL), CLN2 (classic late infantile NCL), CLN3 (juvenile NCL), CLN5 (Finnish variant late infantile NCL), and CLN7 (Turkish variant late infantile NCL).

CONCLUSION

A decrease in T2 signal intensity in the thalami seems to be a sign of lysosomal disease.

Schizophrenia-like psychosis and aceruloplasminemia

Schizophrenia-like illnesses occur in a variety of medical and neurological conditions but to date have not been described in association with aceruloplasminemia. Aceruloplasminemia is an autosomal recessive disorder of iron metabolism which leads to iron deposition in the basal ganglia, thalamus, cerebellum and hippocampus and which usually presents in middle age with extrapyramidal symptoms and dementia. We describe a 21-year-old woman on treatment for aceruloplasminemia who presented with schizophrenia-like psychosis and declining function in the absence of neurological signs. Neuropsychological testing showed significant dominant hemisphere deficits. Magnetic resonance imaging showed bilateral iron deposition in the cerebellar dentate nuclei and thalami, frontal atrophy, and periventricular white matter hyperintensities. Functional imaging suggested global hypoperfusion. The clinical, cognitive and imaging findings were not typical for either aceruloplasminemia or schizophrenia alone and the possible relationship between the two disorders is discussed with particular reference to implications for our understanding of schizophrenia.

Age-related changes in iron homeostasis and cell death in the cerebellum of ceruloplasmin-deficient mice

Iron is essential for a variety of cellular functions, but its levels and bioavailability must be tightly regulated because of its toxic redox activity. A number of transporters, binding proteins, reductases, and ferroxidases help maintain iron homeostasis to prevent cell damage. The multi-copper ferroxidase ceruloplasmin (Cp) converts toxic ferrous iron to its nontoxic ferric form and is required for iron efflux from cells. Absence of this enzyme in humans leads to iron accumulation and neurodegeneration in the CNS. Here we report on the changes that occur in the cerebellum of Cp null (Cp-/-) mice with aging. We show that iron accumulation, which is reflected in increased ferritin expression, occurs mainly in astrocytes by 24 months in Cp-/- mice and is accompanied by a significant loss of these cells. In contrast, Purkinje neurons and the large neurons in the deep nuclei of Cp-/- mice do not accumulate iron but express high levels of the iron importer divalent metal transporter 1, suggesting that these cells may be iron deprived. This is also accompanied by a significant reduction in the number of Purkinje neurons. These data suggest that astrocytes play a central role in the acquisition of iron from the circulation and that two different mechanisms underlie the loss of astrocytes and neurons in Cp-/- mice. These findings provide a better understanding of the degenerative changes seen in humans with aceruloplasminemia and have implications for normal aging and neurodegenerative diseases in which iron accumulation occurs.

Early onset insulin-dependent diabetes mellitus as an initial manifestation of aceruloplasminaemia

BACKGROUND

Aceruloplasminaemia is an autosomal recessive disorder caused by specific mutations in the ceruloplasmin gene. Aceruloplasminaemia is clinically characterized by diabetes mellitus, pigment degeneration of the retina, and neurological abnormalities, such as cerebellar ataxia, extrapyramidal signs, and dementia. We present a patient with aceruloplasminaemia who, until progressive neurological abnormalities were noticed, had been treated for more than 30 years as having Type 1 diabetes mellitus requiring multiple insulin injection therapy.

CASE REPORT

The patient was a 58-year-old man. At the age of 23 years, he developed diabetes that required multiple insulin injection therapy. At the age of 39 years, he was commenced on continuous subcutaneous insulin infusion (CSII) therapy. Despite CSII therapy, the patient's blood glucose levels were poorly controlled (HbA(1c), approximately 9.5%). He was diagnosed as having aceruloplasminaemia at 58 years of age when he presented with progressive cerebellar ataxia, extrapyramidal signs of recent onset and pigment degeneration of the retina.

CONCLUSIONS

It is possible that some diabetic patients with aceruloplasminaemia are mistakenly diagnosed as having Type 1 diabetes mellitus, as they have reduced insulin secretion and develop diabetes at a younger age, before neurological abnormalities associated with aceruloplasminaemia are apparent. Therefore, aceruloplasminaemia should be considered in patients with insulin-dependent diabetes mellitus who develop progressive neurological abnormalities of unknown aetiology along with a microcytic hypochromic anaemia and retinal degeneration.

Mitochondrial involvement in genetically determined transition metal toxicity

Iron that is not specifically chaperoned through its essential functional pathways is damaging to biological systems, in major part by catalyzing the production of reactive oxygen species. Iron serves in several essential roles in the mitochondrion, as an essential cofactor for certain enzymes of electron transport, and through its involvement in the assembly of iron-sulfur clusters and iron-porphyrin (heme) complexes, both processes occurring in the mitochondrion. Therefore, there are mechanisms that deliver iron specifically to mitochondria, although these are not well understood. Under normal circumstances the mitochondrion has levels of stored iron that are higher than other organelles, though lower than in cytosol, while in some disorders of iron metabolism, mitochondrial iron levels exceed those in the cytosol. Under these circumstances of excess iron, protective mechanisms are overwhelmed and mitochondrial damage ensues. This may take the form of acute oxidative stress with structural damage and functional impairment, but also may result in long-term damage to the mitochondrial genome. This review discusses the evidence that mitochondria do indeed accumulate iron in several genetic disorders, and are a direct target for iron toxicity when it is present in excess. We then consider two classes of genetic disorders involving iron and the mitochondrion. The first include defects in genes directly regulating mitochondrial iron metabolism that lead to Friedreich's ataxia and the various sideroblastic anemias, with excessive mitochondrial iron accumulation. Under the second class, we discuss various primary hemochromatoses that lead to direct mitochondrial damage, with reference to mutations in genes encoding HFE, hepcidin, hemojuvelin, transferrin receptor-2, ferroportin, transferrin, and ceruloplasmin.

Iron overload and antioxidative role of perivascular astrocytes in aceruloplasminemia

Aceruloplasminemia (ACP) is an inherited disorder of iron metabolism caused by the lack of ceruloplasmin activity; the neuropathological hallmarks are excessive iron deposition, neuronal loss, bizarrely deformed astrocytes, and numerous 'grumose or foamy spheroid bodies (GFSBs)'. We histopathologically examined two autopsied ACP brains, and observed for the first time that GFSBs form in clusters at the ends of perivascular astrocytic foot processes. Both the deformed astrocytes and the GFSBs contained ferric iron and were intensely immunolabelled with antibodies against the antioxidant proteins ferritin and manganese superoxide dismutase (Mn SOD). Ceruloplasmin is largely produced by perivascular astrocytes in the central nervous system and exhibits a ferroxidase activity that inhibits iron-associated lipid peroxidation and hydroxyl radical formation; therefore, the lack of ceruloplasmin causes direct oxidative stress on astrocytes. The intense immunolabelling of ferritin and Mn SOD most likely reflects a defensive response to iron-mediated oxidative stress. This study suggests that astrocytes play key roles in iron trafficking and the detoxification of iron-mediated free radicals at the blood-brain barrier and in the parenchyma in ACP brain. The antioxidative ability of astrocytes is one of their essential neuroprotective effects, and the decompensation of this ability may lead to secondary neuronal cell death in ACP.

Ceruloplasmin in neurodegenerative diseases

For decades, abnormalities in ceruloplasmin (Cp) synthesis have been associated with neurodegenerative disease. From the early observation that low circulating serum ceruloplasmin levels served as a marker for Wilson's disease to the recent characterization of a neurodegenerative disorder associated with a complete lack of serum ceruloplasmin, the link between Cp and neuropathology has strengthened. The mechanisms associated with these different central nervous system abnormalities are very distinct. In Wilson's disease, a defect in the P-type ATPase results in abnormal hepatic copper accumulation that eventually leaks into the circulation and is abnormally deposited in the brain. In this case, copper deposition results in the neurodegenerative phenotype observed. Patients with autosomal recessive condition, aceruloplasminemia, lack the ferroxidase activity inherent to the multi-copper oxidase ceruloplasmin and develop abnormal iron accumulation within the central nervous system. In the following review ceruloplasmin gene expression, structure and function will be presented and the role of ceruloplasmin in iron metabolism will be discussed. The molecular events underlying the different forms of neurodegeneration observed will be presented. Understanding the role of ceruloplasmin within the central nervous system is fundamental to further our understanding of the pathology observed. Is the ferroxidase function more essential than the antioxidant role? Does Cp help maintain nitrosothiol stores or does it oxidize critical brain substrates? The answers to these questions hold the promise for the treatment of devastating neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. It is essential to further elucidate the mechanism of the neuronal injury associated with these disorders.

Aceruloplasminemia in an asymptomatic patient with a new mutation. Diagnosis and family genetic analysis

A 39-year-old asymptomatic man showed elevated serum ferritin levels, mild hypertransaminasemia and serum ceruloplasmin almost undetectable. There was histological iron accumulation within the hepatocytes and also in the central nervous system (MRI). A genetic analysis revealed a new missense mutation in the ceruloplasmin gene. Two of the other four siblings were also affected by this mutation.

Hereditary ferritinopathy: a novel mutation, its cellular pathology, and pathogenetic insights

We report a family of French Canadian and Dutch ancestry with hereditary ferritinopathy (neuroferritinopathy) and a novel mutation (C insertion at nt646-647 in exon 4) in the ferritin light chain gene, resulting in a longer than normal protein. Our failure to immunostain most of the abnormal ferritin deposits in the proband with a conformation-dependent monoclonal antibody to ferritin light chain supported a previously postulated conformational change of ferritin light chain in this disease. The posterior putamen and cerebellum were the primary pathologic loci in our proband, but asymptomatic hepatocytic intranuclear accumulations of iron and ferritin also were present. Both neurons and glia displayed highly distinctive, if not pathognomonic, swollen to vacuolated nuclei containing ferritin and iron. Hyaline deposits, again staining for both ferritin and iron, were additional morphologic features that may be unique to the ferritinopathies. The iron, at least in putamen where there was a nearly 40-fold increase, appeared to be both in the ferrous (Fe2+) and ferric (Fe3+) form; it was the most likely cause of the observed neuronal and glial apoptosis. We found morphologic evidence of both lipid peroxidation and abnormal nitration of proteins in putaminal neurons and glia, confirming the expected oxidative stress due to this excessive iron. Biochemical and immunohistochemical abnormalities in mitochondria also were demonstrated, probably due to an imbalance in iron homeostasis that had a deleterious effect on the respiratory chain.

Vermal atrophy of alcoholics correlate with serum thiamine levels but not with dentate iron concentrations as estimated by MRI

Chronic alcohol consumption is frequently accompanied by cerebellar degeneration. The exact aetiology of alcoholic cerebellar degeneration is still a matter of debate. The aim of the present study was to investigate whether patients with chronic alcohol consumption exhibit a decrease in dentate nuclei intensity as measured by MRI, and if so, whether this decrease correlates with cerebellar atrophy as revealed by MR imaging or with clinical signs of cerebellar ataxia. A decrease in dentate nuclei intensity would indirectly indicate that iron accumulation, and therefore, oxidative stress may play a role in alcoholic cerebellar degeneration. MRI of 45 alcoholics and 44 age and sex-matched healthy control subjects was performed using a 3D-T1-weighted fast low angle shot (FLASH) echo sequence. Signal intensities of the dentate nuclei and cerebellar white matter were bilaterally measured. Planimetric measurements of cerebellar size were performed using a 3D-T1-weighted magnetization prepared rapid acquisition gradient echo (MPRAGE) sequence. Results demonstrated that dentate nuclei intensity was not significantly decreased in patients with chronic alcohol consumption (mean +/- SD signal intensity 65.36 +/- 13.0) if compared with control subjects (mean +/- SD signal intensity 68.95 +/- 9.4) (p = 0.15). Dentate nuclei intensity did not correlate with cerebellar size neither in control subjects nor in alcoholics. In contrast, vitamin B1 level correlated with cerebellar size in alcoholics even if the vitamin B1 concentration was within normal values (r = 0.344, p = 0.028). These results support the view that thiamine deficiency rather than direct neurotoxic effects of alcohol is the main causative factor for the development of alcoholic cerebellar degeneration.

Monoamine transporter inhibitors and norepinephrine reduce dopamine-dependent iron toxicity in cells derived from the substantia nigra

The role of dopamine in iron uptake into catecholaminergic neurons, and dopamine oxidation to aminochrome and its one-electron reduction in iron-mediated neurotoxicity, was studied in RCSN-3 cells, which express both tyrosine hydroxylase and monoamine transporters. The mean +/- SD uptake of 100 microm 59FeCl3 in RCSN-3 cells was 25 +/- 4 pmol per min per mg, which increased to 28 +/- 8 pmol per min per mg when complexed with dopamine (Fe(III)-dopamine). This uptake was inhibited by 2 microm nomifensine (43%p < 0.05), 100 microm imipramine (62%p < 0.01), 30 microm reboxetine (71%p < 0.01) and 2 mm dopamine (84%p < 0.01). The uptake of 59Fe-dopamine complex was Na+, Cl- and temperature dependent. No toxic effects in RCSN-3 cells were observed when the cells were incubated with 100 microm FeCl3 alone or complexed with dopamine. However, 100 microm Fe(III)-dopamine in the presence of 100 microm dicoumarol, an inhibitor of DT-diaphorase, induced toxicity (44% cell death; p < 0.001), which was inhibited by 2 microm nomifensine, 30 microm reboxetine and 2 mm norepinephrine. The neuroprotective action of norepinephrine can be explained by (1) its ability to form complexes with Fe3+, (2) the uptake of Fe-norepinephrine complex via the norepinephrine transporter and (3) lack of toxicity of the Fe-norepinephrine complex even when DT-diaphorase is inhibited. These results support the proposed neuroprotective role of DT-diaphorase and norepinephrine.

Anemia and impaired stress-induced erythropoiesis in aceruloplasminemic mice

Ceruloplasmin (Cp) is an abundant, copper-containing plasma protein with an important role in iron homeostasis. Patients with hereditary Cp deficiency have iron deposits in liver and other organs, consistent with impaired iron flux. The mild anemia reported in some patients suggests a possible role for Cp in iron delivery to red cell precursors during erythropoiesis. To investigate this function of Cp, we determined the hematologic parameters in Cp-deficient mice under normal conditions and after erythropoiesis-inducing stress. Cp(-/-) mice have below normal hematocrit, red cell hemoglobin and volume, and serum iron. Red cell number and turnover and reticulocyte counts were identical in Cp(-/-) and Cp(+/+) mice. Thus, Cp(-/-) have mild microcytic, hypochromic anemia consistent with normal red cell formation but defective iron availability. Cp(-/-) and Cp(+/+) mice subjected to phenylhydrazine-induced hemolytic anemia exhibited identical decreases in hematologic parameters, but Cp(-/-) mice showed diminished recovery after removal of the stress. Administration of purified human Cp or iron-saturated transferrin to Cp(-/-) mice partially restored hemoglobin formation in reticulocytes. The mild anemia in Cp(-/-) mice and the diminished response to stress may reflect inefficient recycling of iron between the reticuloendothelial and erythropoietic systems. Our findings suggest a role for Cp in erythropoiesis by providing sufficient iron to the erythroid tissue and that the requirement for Cp is raised after erythropoietic stress.

Disruption of ceruloplasmin and hephaestin in mice causes retinal iron overload and retinal degeneration with features of age-related macular degeneration

Mechanisms of brain and retinal iron homeostasis have become subjects of increased interest after the discovery of elevated iron levels in brains of patients with Alzheimer's disease and retinas of patients with age-related macular degeneration. To determine whether the ferroxidase ceruloplasmin (Cp) and its homolog hephaestin (Heph) are important for retinal iron homeostasis, we studied retinas from mice deficient in Cp and/or Heph. In normal mice, Cp and Heph localize to Müller glia and retinal pigment epithelium, a blood-brain barrier. Mice deficient in both Cp and Heph, but not each individually, had a striking, age-dependent increase in retinal pigment epithelium and retinal iron. The iron storage protein ferritin was also increased in Cp-/-Heph-/Y retinas. After retinal iron levels had increased, Cp-/-Heph-/Y mice had age-dependent retinal pigment epithelium hypertrophy, hyperplasia and death, photoreceptor degeneration, and subretinal neovascularization, providing a model of some features of the human retinal diseases aceruloplasminemia and age-related macular degeneration. This pathology indicates that Cp and Heph are critical for CNS iron homeostasis and that loss of Cp and Heph in the mouse leads to age-dependent retinal neurodegeneration, providing a model that can be used to test the therapeutic efficacy of iron chelators and antiangiogenic agents.

Aceruloplasminemia, an iron metabolic disorder

Aceruloplasminemia is an inherited disorder of iron metabolism caused by the complete lack of ceruloplasmin ferroxidase activity caused by mutations in the ceruloplasmin gene. It is characterized by iron accumulation in the brain as well as visceral organs. Clinically, the disease consists of the triad of adult-onset neurologic disease, retinal degeneration and diabetes mellitus. The neurological symptoms, which include involuntary movements, ataxia, and dementia, reflect the sites of iron deposition. Severe iron overload and extensive neuronal loss were observed in the basal ganglia, while iron deposition and neuronal cell loss were trivial in the frontal cortices. The cerebellar cortex showed marked loss of Purkinje cells. Iron deposition was more prominent in the astrocytes than in the neurons. Excess iron functions as a potent catalyst of biologic oxidation. Astrocytic deformity and globular structures are characteristic features in aceruloplasminemia brains. The globular structures in the astrocytes were seen in proportion to the degree of iron deposition and reacted positively to anti-4-hydroxynonenal, one of the indicators of lipid peroxidation, and anti-ubiquitin antibodies, but not to anti-alpha-synuclein antibody. The lack of ceruloplasmin may primarily damage astrocytes in the aceruloplasminemia brains through lipid peroxidation. Ceruloplasmin may play an essential role in neuronal survival in the central nervous system.

Genetic defects in copper metabolism

Genetic defects in copper metabolism highlight the delicate balance mammalian systems have developed to maintain normal copper homeostasis. Menkes disease, the mottled mouse, the Atox-1-deficient mouse and the ctr1 knockout mouse reveal the importance of adequate copper intake during embryogenesis and early development, especially in the central nervous system. The toxicity associated with excess copper as manifest in Wilson disease, the toxic milk mouse, the LEC rat and copper toxicosis in the Bedlington terrier demonstrate the profound cellular susceptibility to copper overload, in particular, in the brain and liver. Ceruloplasmin (Cp) contains 95% of the copper found in human serum, and inherited loss of this protein results in diabetes, retinal degeneration and neurodegeneration. Despite normal copper metabolism, aceruloplasminemic patients and the Cp knockout mouse have disturbed iron homeostasis and mild hepatic copper retention. These genetic disorders of copper metabolism provide valuable insight into the mechanisms regulating copper homeostasis and models to further dissect the role of this essential metal in health and disease.

Expression of a membrane-bound form of the ferroxidase ceruloplasmin by leptomeningeal cells

Ceruloplasmin is a key enzyme involved in detoxifying ferrous iron, which can generate free radicals. The secreted form of ceruloplasmin is produced by the liver and is abundant in serum. We have previously identified a membrane-bound glycosylphosphatidylinositol (GPI)-anchored form of ceruloplasmin (GPI-Cp) that is expressed by astrocytes in the central nervous system (CNS) (Patel and David. 1997. J Biol Chem 272:20185-20190). We now provide direct evidence that rat leptomeningeal cells, which cover the surface of the brain, also express GPI-Cp. The expression of GPI-Cp on the surface of these cells increases with postnatal development and is regulated in vitro by cell density, time in culture, and various extracellular matrix molecules. The expression of GPI-Cp also appears to be regulated differently in astrocytes and leptomeningeal cells in vitro. The abundant expression of GPI-Cp on the surface of leptomeningeal cells suggests that these cells play a role in antioxidant defense along the surface of the postnatal CNS possibly by detoxifying the cerebrospinal fluid.

Quantitative evaluation of expression of iron-metabolism genes in ceruloplasmin-deficient mice

Aceruloplasminemia is an autosomal recessive disorder caused by mutations in the ceruloplasmin (CP) gene, and is characterized by a unique combination of neurovisceral iron overload and iron deficiency anemia. We generated CP-deficient (CP(-/-)) mice to investigate the functional involvement of CP in iron metabolism. The mice showed a marked iron overload in the liver and mild iron deficiency anemia. We examined the expression of iron-metabolism genes in the duodenum and liver using TaqMan RT-PCR. The divalent metal transporter 1 (DMT1), ferroportin 1 (FPN1), and hephaestin (HEPH) genes were not up-regulated in the duodenum from CP(-/-) mice. These data suggest that the mechanism of hepatic iron overload in aceruloplasminemia is quite different from that in hemochromatoses and atransferrinemia. In the liver, CP(-/-) mice showed no increase of gene expression for DMT1 and transferrin receptors (TFR and TFR2), indicating that none of the known pathways of iron uptake is activated in hepatocytes of CP(-/-) mice. This result supports the hypothesis that CP mainly acts to release iron from cells in the liver.

Astrocytic deformity and globular structures are characteristic of the brains of patients with aceruloplasminemia

Aceruloplasminemia is an interesting disease, the study of which helps elucidate how iron-induced oxidative stress is involved in neuronal cell death. In order to study the neuropathological characteristics associated with oxidative stress, we scrutinized the brains of 5 patients with aceruloplasminemia histopathologically and immunohistochemically. The pathological findings were essentially similar in all patients. In the frontal cortices, iron deposition and neuronal cell loss were trivial, but in the basal ganglia (especially in the caudate nucleus and putamen), severe iron overload and extensive neuronal loss were noted. Iron deposition was more prominent in the astrocytes than in the neurons in both regions. 4-hydroxynonenal (HNE), one of the most physiologically active lipid peroxides, was strongly detected on neurons and astrocytes by immunostaining. Markedly deformed astrocytes were observed in the striatum. These astrocytes were similar to Alzheimer type 1 astrocytes. Globular structures were seen in proportion to the degree of iron deposition. They clearly reacted with anti-glial fibrillary acidic protein (GFAP) and anti-S-100 antibodies and contained glial fibril-like filaments, but showed no or only faint immunoreactivity to antibodies for neuronal marker proteins, such as neurofilament and synaptophysin. Therefore, the globular structures presumably originated from astrocytes. The structures also reacted positively to anti-HNE and anti-ubiquitin antibodies. We conclude that astrocytic deformities and globular structures are characteristic neuropathological features of aceruloplasminemia and are closely linked to iron overload and subsequent oxidative stress.

Ceruloplasmin metabolism and function

Ceruloplasmin is a serum ferroxidase that contains greater than 95% of the copper found in plasma. This protein is a member of the multicopper oxidase family, an evolutionarily conserved group of proteins that utilize copper to couple substrate oxidation with the four-electron reduction of oxygen to water. Despite the need for copper in ceruloplasmin function, this protein plays no essential role in the transport or metabolism of this metal. Aceruloplasminemia is a neurodegenerative disease resulting from inherited loss-of-function mutations in the ceruloplasmin gene. Characterization of this disorder revealed a critical physiological role for ceruloplasmin in determining the rate of iron efflux from cells with mobilizable iron stores and has provided new insights into human iron metabolism and nutrition.

Iron in neurodegenerative disorders

Increasing evidence implicates a role of iron in the pathogenesis of numerous neurodegenerative diseases due to its capacity to enhance production of toxic reactive radicals and to induce protein aggregation. The underlying mechanism of iron accumulation in areas of the brain specific for the respective disease, however, is still unknown. Recent molecular and biochemical studies provide new insights into the consequences of impairment of brain iron metabolism. This review summarizes our understanding of the regulation of iron in the brain and defines the current knowledge on the involvement of iron metabolism in neurodegenerative diseases with genetically determined iron accumulation in the brain.