Amyotrophic lateral sclerosis of Guam: the nature of the neuropathological findings

Endemic parkinsonism: clusters, biology and clinical features

The term 'endemic parkinsonism' refers to diseases that manifest with a dominant parkinsonian syndrome, which can be typical or atypical, and are present only in a particular geographically defined location or population. Ten phenotypes of endemic parkinsonism are currently known: three in the Western Pacific region; two in the Asian-Oceanic region; one in the Caribbean islands of Guadeloupe and Martinique; and four in Europe. Some of these disease entities seem to be disappearing over time and therefore are probably triggered by unique environmental factors. By contrast, other types persist because they are exclusively genetically determined. Given the geographical clustering and potential overlap in biological and clinical features of these exceptionally interesting diseases, this Review provides a historical reference text and offers current perspectives on each of the 10 phenotypes of endemic parkinsonism. Knowledge obtained from the study of these disease entities supports the hypothesis that both genetic and environmental factors contribute to the development of neurodegenerative diseases, not only in endemic parkinsonism but also in general. At the same time, this understanding suggests useful directions for further research in this area.

Is Exposure to BMAA a Risk Factor for Neurodegenerative Diseases? A Response to a Critical Review of the BMAA Hypothesis

In a literature survey, Chernoff et al. (2017) dismissed the hypothesis that chronic exposure to β-N-methylamino-L-alanine (BMAA) may be a risk factor for progressive neurodegenerative disease. They question the growing scientific literature that suggests the following: (1) BMAA exposure causes ALS/PDC among the indigenous Chamorro people of Guam; (2) Guamanian ALS/PDC shares clinical and neuropathological features with Alzheimer's disease, Parkinson's disease, and ALS; (3) one possible mechanism for protein misfolds is misincorporation of BMAA into proteins as a substitute for L-serine; and (4) chronic exposure to BMAA through diet or environmental exposures to cyanobacterial blooms can cause neurodegenerative disease. We here identify multiple errors in their critique including the following: (1) their review selectively cites the published literature; (2) the authors reported favorably on HILIC methods of BMAA detection while the literature shows significant matrix effects and peak coelution in HILIC that may prevent detection and quantification of BMAA in cyanobacteria; (3) the authors build alternative arguments to the BMAA hypothesis, rather than explain the published literature which, to date, has been unable to refute the BMAA hypothesis; and (4) the authors erroneously attribute methods to incorrect studies, indicative of a failure to carefully consider all relevant publications. The lack of attention to BMAA research begins with the review's title which incorrectly refers to BMAA as a "non-essential" amino acid. Research regarding chronic exposure to BMAA as a cause of human neurodegenerative diseases is emerging and requires additional resources, validation, and research. Here, we propose strategies for improvement in the execution and reporting of analytical methods and the need for additional and well-executed inter-lab comparisons for BMAA quantitation. We emphasize the need for optimization and validation of analytical methods to ensure that they are fit-for-purpose. Although there remain gaps in the literature, an increasingly large body of data from multiple independent labs using orthogonal methods provides increasing evidence that chronic exposure to BMAA may be a risk factor for neurological illness.

l-Serine Reduces Spinal Cord Pathology in a Vervet Model of Preclinical ALS/MND

The early neuropathological features of amyotrophic lateral sclerosis/motor neuron disease (ALS/MND) are protein aggregates in motor neurons and microglial activation. Similar pathology characterizes Guamanian ALS/Parkinsonism dementia complex, which may be triggered by the cyanotoxin β-N-methylamino-l-alanine (BMAA). We report here the occurrence of ALS/MND-type pathological changes in vervets (Chlorocebus sabaeus; n = 8) fed oral doses of a dry powder of BMAA HCl salt (210 mg/kg/day) for 140 days. Spinal cords and brains from toxin-exposed vervets were compared to controls fed rice flour (210 mg/kg/day) and to vervets coadministered equal amounts of BMAA and l-serine (210 mg/kg/day). Immunohistochemistry and quantitative image analysis were used to examine markers of ALS/MND and glial activation. UHPLC-MS/MS was used to confirm BMAA exposures in dosed vervets. Motor neuron degeneration was demonstrated in BMAA-dosed vervets by TDP-43⁺ proteinopathy in anterior horn cells, by reactive astrogliosis, by activated microglia, and by damage to myelinated axons in the lateral corticospinal tracts. Vervets dosed with BMAA + l-serine displayed reduced neuropathological changes. This study demonstrates that chronic dietary exposure to BMAA causes ALS/MND-type pathological changes in the vervet and coadministration of l-serine reduces the amount of reactive gliosis and the number of protein inclusions in motor neurons.

Dysfunction of Protein Quality Control in Parkinsonism-Dementia Complex of Guam

Guam parkinsonism–dementia complex (G-PDC) is an enigmatic neurodegenerative disease that is endemic to the Pacific island of Guam. G-PDC patients are clinically characterized by progressive cognitive impairment and parkinsonism. Neuropathologically, G-PDC is characterized by abundant neurofibrillary tangles, which are composed of hyperphosphorylated tau, marked deposition of 43-kDa TAR DNA-binding protein, and neuronal loss. Although both genetic and environmental factors have been implicated, the etiology and pathogenesis of G-PDC remain unknown. Recent neuropathological studies have provided new clues about the pathomechanisms involved in G-PDC. For example, deposition of abnormal components of the protein quality control system in brains of G-PDC patients indicates a role for proteostasis imbalance in the disease. This opens up promising avenues for new research on G-PDC and could have important implications for the study of other neurodegenerative disorders.

Amyotrophic lateral sclerosis and parkinsonism-dementia complex of the Hohara focus of the Kii Peninsula: A multiple proteinopathy?

The high incidence of amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia complex (PDC) has been previously known in the Kii Peninsula of Japan and in Guam. Recently, the accumulation of various proteins, such as tau, trans-activation response DNA binding protein 43 kDa (TDP-43), and alpha-synuclein (αSyn), was reported in the brains of patients with ALS/PDC in Guam. To confirm whether similar findings are present in Kii ALS/PDC, we neuropathologically examined the brains and spinal cords of 18 patients with ALS/PDC (clinical diagnoses: eight ALS and 10 PDC) in Hohara Village, which is the eastern focus of Kii ALS. The average age at death was 71.6 years, and 16 patients (88.9%) had a family history of ALS/PDC. Autopsy specimens were immunohistochemically examined with antibodies against four major proteins. Neurofibrillary tangles, including ghost tangles, and tau-positive astrocytes were distributed widely in all of the brains examined, and TDP-43-positive neuronal cytoplasmic inclusions were observed mainly in the limbic system. Synuclein pathology was present in 14 patients (77.8%). These patients were classified into three pathological subtypes according to the most prominent proteinopathy: the tauopathy-dominant type, the TDP-43 proteinopathy-dominant type, and the synucleinopathy-dominant type. Five patients with severe tau deposition showed clinical features of atypical parkinsonism and dementia with or without motor neuron disease. Eight patients were predominated by phosphorylated TDP-43 inclusions and clinically showed ALS, and five patients were predominated by synuclein pathology and clinically showed signs of PDC. Based on the common characteristic tau pathology, three subtypes seemed to be pathologically continuous on a spectrum of a single disease. Thus, we conclude that ALS/PDC in the Hohara focus of the Kii Peninsula is a single disease characterized neuropathologically by a multiple proteinopathy, even though the clinical manifestations of the three subtypes differed from each other. It remains unclear whether the coexistence of the three proteinopathies was incidental or pathogenetically related.

A critical review of the postulated role of the non-essential amino acid, β-N-methylamino-L-alanine, in neurodegenerative disease in humans

The compound BMAA (β-N-methylamino-L-alanine) has been postulated to play a significant role in four serious neurological human diseases: Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) found on Guam, and ALS, Parkinsonism, and dementia that occur globally. ALS/PDC with symptoms of all three diseases first came to the attention of the scientific community during and after World War II. It was initially associated with cycad flour used for food because BMAA is a product of symbiotic cycad root-dwelling cyanobacteria. Human consumption of flying foxes that fed on cycad seeds was later suggested as a source of BMAA on Guam and a cause of ALS/PDC. Subsequently, the hypothesis was expanded to include a causative role for BMAA in other neurodegenerative diseases including Alzheimer's disease (AD) through exposures attributed to proximity to freshwaters and/or consumption of seafood due to its purported production by most species of cyanobacteria. The hypothesis that BMAA is the critical factor in the genesis of these neurodegenerative diseases received considerable attention in the medical, scientific, and public arenas. This review examines the history of ALS/PDC and the BMAA-human disease hypotheses; similarities and differences between ALS/PDC and the other diseases with similar symptomologies; the relationship of ALS/PDC to other similar diseases, studies of BMAA-mediated effects in lab animals, inconsistencies and data gaps in the hypothesis; and other compounds and agents that were suggested as the cause of ALS/PDC on Guam. The review concludes that the hypothesis of a causal BMAA neurodegenerative disease relationship is not supported by existing data.

Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain

Neurofibrillary tangles (NFT) and β-amyloid plaques are the neurological hallmarks of both Alzheimer's disease and an unusual paralytic illness suffered by Chamorro villagers on the Pacific island of Guam. Many Chamorros with the disease suffer dementia, and in some villages one-quarter of the adults perished from the disease. Like Alzheimer's, the causal factors of Guamanian amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC) are poorly understood. In replicated experiments, we found that chronic dietary exposure to a cyanobacterial toxin present in the traditional Chamorro diet, β-N-methylamino-l-alanine (BMAA), triggers the formation of both NFT and β-amyloid deposits similar in structure and density to those found in brain tissues of Chamorros who died with ALS/PDC. Vervets (Chlorocebus sabaeus) fed for 140 days with BMAA-dosed fruit developed NFT and sparse β-amyloid deposits in the brain. Co-administration of the dietary amino acid l-serine with l-BMAA significantly reduced the density of NFT. These findings indicate that while chronic exposure to the environmental toxin BMAA can trigger neurodegeneration in vulnerable individuals, increasing the amount of l-serine in the diet can reduce the risk.

Neurodegeneration and sport

The recent interest in concussion in sport has resulted in significant media focus about chronic traumatic encephalopathy (CTE), although a direct causative link(s) between concussion and CTE is not established. Typically, sport-related CTE occurs in a retired athlete with or without a history of concussion(s) who presents with a constellation of cognitive, mood, and/or behavioral symptoms and who has postmortem findings of tau deposition within the brain. There are many confounding variables, however, that can account for brain tau deposition, including genetic mutations, drugs, normal aging, environmental factors, postmortem brain processing, and toxins. To understand the roles of such factors in neurodegenerative diseases that may occur in athletes, this article reviews some neurodegenerative diseases that may present with similar findings in nonathletes. The article also reviews pathological changes identified with normal aging, and reviews the pathological findings of CTE in light of all these factors. While many of these athletes have a history of exposure to head impacts as a part of contact sport, there is insufficient evidence to establish causation between sports concussion and CTE. It is likely that many of the cases with neuropathological findings represent the normal aging process, the effects of opiate abuse, or a variant of frontotemporal lobar degeneration. Whether particular genetic causes may place athletes at greater risk of neurodegenerative disease is yet to be determined.

Hippocampal sclerosis in the parkinsonism-dementia complex of Guam: quantitative examination of neurons, neurofibrillary tangles, and TDP-43 immunoreactivity in CA1

The cornu ammonis 1 (CA1) area in the hippocampus of the parkinsonism-dementia complex (PDC) of Guam was examined quantitatively with special references to the number of neurons, intraneuronal (i) and extracellular (e) neurofibirillary tangles (NFTs), and TDP-43 (43-kDa trans-activation-responsive region DNA-binding protein)-immunopositive structures, in 24 Chamorro patients with PDC of Guam and seven control Chamorro Guamanians (both groups having no ischemic or anoxic complications). The results were that: (i) in the patients with mildly involved PDC, total numbers of neurons, iNFTs and eNFTs were almost the same as those of neurons of controls; (ii) in patients severely involved, total numbers of neurons, iNFTs and eNFTs decreased markedly; (iii) the decrease of the number of pyramidal neurons in CA1 with positive nuclear TDP-43 was intimately correlated with the decrease in total neuron numbers; (iv) whereas the numbers of neurons and TDP-43-immunopositive intracytoplasmic aggregation in the CA1 area were inversely correlated; and (v) depression of nuclear TDP-43 immuonostainability was not affected by the presence or absence of NFTs. In conclusion, hippocampal sclerosis exists in PDC; there is a possibility of elimination of eNFTs which appeared in the CA1 in patients with PDC and loss of the neurons correlates with disappearance of nuclear TDP-43, but not with appearance of intraneurocytoplasmic TDP-43 aggregation or iNFTs.

Alzheimer disease and amyotrophic lateral sclerosis: an etiopathogenic connection

The etiopathogenesis of neither the sporadic form of Alzheimer disease (AD) nor of amyotrophic lateral sclerosis (ALS) is well understood. The activity of protein phosphatase-2A (PP2A), which regulates the phosphorylation of tau and neurofilaments, is negatively regulated by the myeloid leukemia-associated protein SET, also known as inhibitor-2 of PP2A, I2(PP2A). In AD brain, PP2A activity is compromised, probably because I2(PP2A) is overexpressed and is selectively cleaved at asparagine 175 into an N-terminal fragment, I2NTF, and a C-terminal fragment, I2CTF, and both fragments inhibit PP2A. Here, we analyzed the spinal cords from ALS and control cases for I2(PP2A) cleavage and PP2A activity. As observed in AD brain, we found a selective increase in the cleavage of I2(PP2A) into I2NTF and I2CTF and inhibition of the activity and not the expression of PP2A in the spinal cords of ALS cases. To test the hypothesis that both AD and ALS could be triggered by I2CTF, a cleavage product of I2(PP2A), we transduced by intracerebroventricular injections newborn rats with adeno-associated virus serotype 1 (AAV1) containing human I2CTF. AAV1-I2CTF produced reference memory impairment and tau pathology, and intraneuronal accumulation of Aβ by 5-8 months, and motor deficit and hyperphosphorylation and proliferation of neurofilaments, tau and TDP-43 pathologies, degeneration and loss of motor neurons and axons in the spinal cord by 10-14 months in rats. These findings suggest a previously undiscovered etiopathogenic relationship between sporadic forms of AD and ALS that is linked to I2(PP2A) and the potential of I2(PP2A)-based therapeutics for these diseases.

Guam dementia syndrome revisited in 2011

PURPOSE OF REVIEW

This review covers the amyotrophic lateral sclerosis (ALS)/parkinsonism dementia complex (PDC) of Guam. Clinical and epidemiological characteristics, genetic possible and environmental causes, and neuropathological features of the disease are discussed.

RECENT FINDINGS

Recent studies of clinical syndromes and neuropathological studies are compared with previous descriptions of the disease. The latest genetic and environmental studies are also reviewed.

SUMMARY

In recent years, understanding of the molecular pathogenesis of neurodegenerative diseases has evolved. ALS/PDC shares neuropathological features found in many neurodegenerative diseases such as Alzheimer's disease, Lewy body disease, and frontotemporal lobar degeneration. Thus, examining ALS/PDC may provide further explanations on how various proteins seen in neurodegenerative disorders may be interrelated.

Immunohistochemical expression of IGF-I and GSK in the spinal cord of Kii and Guamanian ALS patients

Insulin-like growth factor-I (IGF-I) is a potent survival factor for motor neurons in animals, and glycogen synthase kinase-3beta (GSK-3beta) is suspected to play roles in apoptosis and tau phosphorylation. Here we report the immunological expression of IGF-I, GSK-3beta, phosphorylated-GSK-3alpha/beta (p-GSK-3alpha/beta) and phosphorylated-tau in the spinal cord and hippocampus of Kii and Guam amyotrophic lateral sclerosis (ALS) patients. Sixteen ALS patients (10 Japanese sporadic, 3 Kii and 3 Guam ALS) and 14 neurological controls (10 Japanese and 4 Guamanian) were examined. The immunoreactivity for each antibody was rated by the percentages of positive neurons to total anterior horn neurons in each patient and was analyzed statistically. Many normal-looking neurons from Japanese sporadic ALS, Kii ALS and Guam ALS patients, as well as from Japanese and Guam controls, were positive for anti-IGF-I antibody. A positive correlation between IR scores for anti-IGF-I antibody and clinical durations of Japanese sporadic ALS patients was found in this study (P < 0.0001). This suggested that IGF-I might have a protective effect against ALS degeneration. In Japanese sporadic ALS patients, abnormal as well as normal-looking neurons showed significant high IR scores for anti-GSK-3beta antibody than those of controls. Anterior horn neurons from Guam and Kii ALS patients characteristically showed weak staining for anti-GSK-3beta antibody but were markedly positive for anti-pGSK-3alpha/beta antibody compared to those from both Japanese controls and Japanese sporadic ALS patients, and showed the co-localization of IGF-I and p-GSK-3alpha/beta. This suggested that the IGF-I signaling pathway in Guam and Kii ALS patients might function to phosphorylate GSK-3beta to protect neurons from ALS degeneration. Neurofibrillary tangles (NFTs) in the hippocampus and spinal cord from Kii and Guam ALS patients showed the co-localization of PHF-tau and p-GSK-3alpha/beta by a confocal laser scanning technique. The predominant expression of p-GSK-3alpha/beta compared to GSK-3beta in spinal motor neurons and the co-localization of p-GSK-3alpha/beta and PHF-tau in NFT-laden neurons in the hippocampus and spinal cord were characteristic findings of Kii and Guam ALS patients.

Enduring involvement of tau, beta-amyloid, alpha-synuclein, ubiquitin and TDP-43 pathology in the amyotrophic lateral sclerosis/parkinsonism-dementia complex of Guam (ALS/PDC)

Guam ALS/PDC is a severe tangle forming disorder endemic to Guam with features overlapping such neurodegenerative disorders as Alzheimer disease (AD), Parkinson disease (PD), progressive supranuclear palsy (PSP), ALS, corticobasal degeneration (CBD) and pallido-ponto-nigral degeneration (PPND). Since the prevalence is declining, we examined brain tissue from 35 clinically diagnosed Chamorro patients with ALS/PDC and two Chamorro controls autopsied between 1946 and 2006, to determine if distinct variations in the pathology could be identified up to this time. Although the age at autopsy increased by 4.5-5 years per decade, we identified no qualitative differences in pathological deposits with antibodies against tau, ubiquitin, A beta, alpha-synuclein and TDP-43, indicating that these more recently identified proteins have been involved in the neuropathogenesis over the past 6 decades. Tau and TDP-43 positive neuronal, oligodendroglial and astrocytic inclusions involving multiple nerve fiber tracts occurred in both the ALS and PDC types, reinforcing the concept that these forms are part of the same disorder. The results obtained may help to define the commonality of the Guam disease with other tangle forming disorders and may help in monitoring the epidemiological changes that are taking place.

Update on recent molecular and genetic advances in frontotemporal lobar degeneration

Great strides have been made in the last 2 years in the field of frontotemporal lobar degeneration (FTLD), particularly with respect to the genetics and molecular biology of FTLD with ubiquitinated inclusions. It is now clear that most cases of familial FTLD with ubiquitinated inclusions have mutations in the progranulin gene, located on chromosome 17. It is also clear that most ubiquitinated inclusions in FTLD with ubiquitinated inclusions are composed primarily of TAR DNA-binding protein-43. Thus, FTLDs can be separated into 2 major groups (i.e. tauopathies and ubiquitinopathies), and most of the ubiquitinopathies can now be defined as TAR DNA-binding protein-43 proteinopathies. Many of the familial FTLDs are linked to chromosome 17, including both the familial tauopathies and the familial TAR DNA-binding protein-43 proteinopathies with progranulin mutations. This review highlights the neuropathologic features and the most important discoveries of the last 2 years and places these findings into the historical context of FTLD.

Pathological TDP-43 in parkinsonism-dementia complex and amyotrophic lateral sclerosis of Guam

Pathological TDP-43 is the major disease protein in frontotemporal lobar degeneration characterized by ubiquitin inclusions (FTLD-U) with/without motor neuron disease (MND) and in amyotrophic lateral sclerosis (ALS). As Guamanian parkinsonism-dementia complex (PDC) or Guamanian ALS (G-PDC or G-ALS) of the Chamorro population may present clinically similar to FTLD-U and ALS, TDP-43 pathology may be present in the G-PDC and G-ALS. Thus, we examined cortical or spinal cord samples from 54 Guamanian subjects for evidence of TDP-43 pathology. In addition to cortical neurofibrillary and glial tau pathology, G-PDC was associated with cortical TDP-43 positive dystrophic neurites and neuronal and glial inclusions in gray and/or white matter. Biochemical analyses showed the presence of FTLD-U-like insoluble TDP-43 in G-PDC, but not in Guam controls (G-C). Spinal cord pathology of G-PDC or G-ALS was characterized by tau positive tangles as well as TDP-43 positive inclusions in lower motor neurons and glial cells. G-C had variable tau and negligible TDP-43 pathology. These results indicate that G-PDC and G-ALS are associated with pathological TDP-43 similar to FTLD-U with/without MND as well as ALS, and that neocortical or hippocampal TDP-43 pathology distinguishes controls from disease subjects better than tau pathology. Finally, we conclude that the spectrum of TDP-43 proteinopathies should be expanded to include neurodegenerative cognitive and motor diseases, affecting the Chamorro population of Guam.

Amyotrophic lateral sclerosis with dementia: an autopsy case showing many Bunina bodies, tau-positive neuronal and astrocytic plaque-like pathologies, and pallido-nigral degeneration

We report the case of a 54-year-old woman with mental retardation who developed frontotemporal dementia and amyotrophic lateral sclerosis (ALS) in the presenium. She presented with dementia at age 48, and motor neuron signs developed at age 53. She had no family history of dementia or ALS. Postmortem examination disclosed histopathological features of ALS, including pyramidal tract degeneration, mild loss of motor neurons, and many Bunina bodies immunoreactive for cystatin C, but not ubiquitin-positive inclusions. Unusual features of this case included severe neuronal loss in the substantia nigra and medial globus pallidus. The subthalamic nucleus, limbic system, and cerebral cortex were well preserved. In addition, neurofibrillary tangles (NFTs) were found in the frontal, temporal, insular, and cingulate cortices, nucleus basalis of Meynert, and locus coeruleus, and to a lesser degree, in the dentate nucleus, cerebellum, hippocampus, and amygdala. No ballooned neurons, tufted astrocytes, or astrocytic plaques were found. Tau immunostaining demonstrated many pretangles rather than NFTs and glial lesions resembling astrocytic plaques in the frontal and temporal cortices. This glial tau pathology predominantly developed in the middle to deep layers in the primary motor cortex, and was frequently associated with the walls of blood vessels. NFTs were immunolabeled with 3-repeat and 4-repeat specific antibodies against tau, respectively. Although the pathophysiological relationship between tau pathology and the selective involvement of motor neurons, substantia nigra, and globus pallidus was unclear, we considered that it might be more than coincidental.

Tau-Positive Fine Granules in the Cerebral White Matter: A Novel Finding Among the Tauopathies Exclusive to Parkinsonism-Dementia Complex of Guam

We examined the autopsied brains of cases of 6 types of tauopathy: parkinsonism-dementia complex of Guam (PDC), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), Pick disease, Alzheimer disease (AD), and myotonic dystrophy together with Guamanian controls. Light microscopy sections of these brains were examined using anti-tau antibodies. Tau-positive fine granules (TFGs) were globe-shaped, and 3 to 6 mum in diameter, were observed predominantly in the frontal white matter in 30 of the 35 patients with PDC. However, no TFGs were found in association with PSP, myotonic dystrophy, Pick disease, AD, or CBD. Western blot analysis of frozen brain tissue taken from the PDC cases revealed that the frontal cortex was hyperphosphorylated and contained 6 tau isoforms (3R+4R tau). However, in the present study, it was revealed that the novel TFGs in the white matter of patients with PDC was composed of 4R tau. Western blot analysis of sarkosyl-insoluble tau from the white matter of the PDC cases showed 2 major bands of 60 and 64 kDa and one minor band of 67 kDa. After dephosphorylation, these bands resolved into one major band of 4-repeat (4R) tau isoform and 3 minor bands of 3-repeat (3R) and 4R tau isoforms. Moreover, the TFGs observed in cases in which the number of neurofibrillary tangles (NFTs) was higher than the threshold level were not correlated with the presence of cortical NFTs. In conclusion, these novel TFGs were found almost exclusively in PDC brains and could therefore be considered as a characteristic neuropathologic marker of this particular tauopathy. The TFGs were hyperphosphorylated tau-positive structures that may be formed by a different mechanism from that used to produce cortical NFTs.

Neurofibrillary tangles in ALS and Parkinsonism-dementia complex focus in Kii, Japan

Brains of 41 residents without neurodegenerative diseases in the high-incidence area of ALS/parkinsonism-dementia complex (ALS/PDC) of the Kii Peninsula of Japan were neuropathologically examined. Neurofibrillary tangles (NFTs) in the hippocampal area were present in 11 of the 41 cases, but the frequency of NFT-positive cases in each age group was similar to that of the normal Japanese population and far less than that of Guamanians without ALS/PDC.

The nature of the parkinsonism-dementia complex and amyotrophic lateral sclerosis of Guam and magnesium deficiency

The parkinsonism-dementia complex (PDC) and amyotrophic lateral sclerosis (ALS) were the fatal neurological diseases, showing very high incidence during 1950-1970 and dramatic decrease after 1970 on Guam. Through the research, the present author insisted that; (1) NFTs in Guam ALS patients are merely a background feature widely dispersed in the population, (2) Guam ALS and PDC are basically different diseases, and (3) Guam ALS occurs initially as classic ALS. As pathogeneses of the diseases, intake of low calcium (Ca) and magnesium (Mg) and high aluminum water and of some plant excitatory neurotoxin has been speculated. To elucidate the pathogenesis, the author performed an experiment exposing rats to low Ca and/or Mg intake for two generations, so as to follow the actual way of human living on the island, since several generations live continuously in the same environment. The study indicates that continuous low Mg intake for two generations induces exclusive loss of dopaminergic neurons in in rats, and may support the Mg hypothesis in the pathogenesis of PDC of Guam.

The basic aspects of therapeutics in amyotrophic lateral sclerosis

Once thought to be a single pathological disease state, amyotrophic lateral sclerosis (ALS) is now recognized to be the limited phenotypic expression of a complex, heterogeneous group of biological processes, resulting in an unrelenting loss of motor neurons. On average, individuals affected with the disease live <5 years. In this article, the complex nature of the pathogenesis of ALS, including features of age dependency, environmental associations, and genetics, is reviewed. Once held to be uncommon, it is now clear that ALS is associated with a frontotemporal dementia and that this process may reflect disturbances in the microtubule-associated tau protein metabolism. The motor neuron ultimately succumbs in a state where significant disruptions in neurofilament metabolism, mitochondrial function, and management of oxidative stress exist. The microenvironment of the neuron becomes a complex milieu in which high levels of glutamate provide a source of chronic excitatory neurotoxicity, and the contributions of activated microglial cells lead to further cascades of motor neuron death, perhaps serving to propagate the disease once established. The final process of motor neuron death encompasses many features of apoptosis, but it is clear that this alone cannot account for all features of motor neuron loss and that aspects of a necrosis-apoptosis continuum are at play. Designing pharmacological strategies to mitigate against this process thus becomes an increasingly complex issue, which is reviewed in this article.

Spinal cord neurofibrillary pathology in Alzheimer disease and Guam Parkinsonism-dementia complex

We examined spinal cords of neurodegenerative disease patients and controls living on the Island of Guam and in the continental United States. These patients had pathologically confirmed parkinsonism dementia-complex (PDC) with or without amyotrophic lateral sclerosis (ALS), or Alzheimer disease (AD), respectively. Nearly all of the spinal cords examined from both groups of patients contained neurofibrillary tangles (NFT). The immunohistochemical profile of these NFTs indicates that they are composed of hyperphosphorylated tau protein like their counterparts in the brains of these patients. Western blot analysis confirmed this by revealing that sarcosyl insoluble tau in spinal cord extracts from patients with NFTs exhibited the presence of all 6 tau isoforms similar to that from AD and ALS/PDC cortical gray matter.

Substantia nigra in progressive supranuclear palsy, corticobasal degeneration, and parkinsonism-dementia complex of Guam: specific pathological features

Disease-specific findings in the substantia nigra were examined in cases of progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and parkinsonism-dementia complex of Guam (PDC); diseases in which the patients exhibit dementia and parkinsonism, with neurofibrillary tangles (NFTs) and glial tangles composed of hyperphosphorylated tau. Loss of pigmented neurons was extremely severe in these 3 diseases, and decrease of the nonpigmented neurons was severe in PSP and CBD. On the other hand, in PDC the decrease of the nonpigmented neurons was different in each patient. Topographically, in PSP the nonpigmented neurons were particularly depleted in the ventral part and relative preservation of the pigmented neurons was observed in the medial part at the level examined. Many NFTs were observed in PDC. Although the number of NFTs was small, many pretangles were seen in the neurons in CBD. Granular and hazy astrocytic inclusions were identified exclusively in PDC. Numerous argyrophilic neuropile threads were identified in CBD and PSP, but these were few in PDC. Many foamy spheroid bodies as well as coiled bodies were observed in PSP and CBD, but only a few were observed in PDC. In conclusion, PDC is a disease that is distinctly different from PSP and CBD. It is possible to differentiate between PSP and CBD by the occurrence of many pretangles in CBD, but some similarities between these 2 diseases indicate the existence of common pathological mechanisms.

Tau protein isoforms, phosphorylation and role in neurodegenerative disorders

Tau proteins belong to the family of microtubule-associated proteins. They are mainly expressed in neurons where they play an important role in the assembly of tubulin monomers into microtubules to constitute the neuronal microtubules network. Microtubules are involved in maintaining the cell shape and serve as tracks for axonal transport. Tau proteins also establish some links between microtubules and other cytoskeletal elements or proteins. Tau proteins are translated from a single gene located on chromosome 17. Their expression is developmentally regulated by an alternative splicing mechanism and six different isoforms exist in the human adult brain. Tau proteins are the major constituents of intraneuronal and glial fibrillar lesions described in Alzheimer's disease and numerous neurodegenerative disorders referred to as 'tauopathies'. Molecular analysis has revealed that an abnormal phosphorylation might be one of the important events in the process leading to their aggregation. Moreover, a specific set of pathological tau proteins exhibiting a typical biochemical pattern, and a different regional and laminar distribution could characterize each of these disorders. Finally, a direct correlation has been established between the progressive involvement of the neocortical areas and the increasing severity of dementia, suggesting that pathological tau proteins are reliable marker of the neurodegenerative process. The recent discovery of tau gene mutations in frontotemporal dementia with parkinsonism linked to chromosome 17 has reinforced the predominant role attributed to tau proteins in the pathogenesis of neurodegenerative disorders, and underlined the fact that distinct sets of tau isoforms expressed in different neuronal populations could lead to different pathologies.

Alpha-synuclein inclusions in amygdala in the brains of patients with the parkinsonism-dementia complex of Guam

We investigated by immunohistochemistry the deposition of alpha-synuclein in the brains of deceased patients with the parkinsonism-dementia complex (PDC) of Guam. Five of 13 PDC brains showed numerous alpha-synuclein positive neuronal inclusions and abnormal neurites, chiefly in the amygdala. Similar alpha-synuclein positive lesions were observed, although to a lesser extent, in the entorhinal cortex and the dorsal vagal nucleus. No alpha-synuclein positive inclusions were observed in motor cortex or locus coeruleus, and only a small number of positive inclusions were found in the Sommer's sector, temporal cortex, or substantia nigra. Some of the alpha-synuclein positive inclusions were reminiscent of cortical Lewy bodies (LB), but many of those in the amygdala coexisted with tau-positive pretangles and/or neurofibrillary tangles (NFT) within the same neurons. In these neurons, tau-positive shells encapsulated alpha-synuclein positive central cores or irregularly shaped alpha-synuclein-positive deposition intermingled with pretangles/NFT. Thus, the present study suggests that a common mechanism may govern aggregation of alpha-synuclein and tau in the amygdala, and that aggregation of alpha-synuclein may play some role in the neurodegenerative process of a tauopathy (i.e. PDC) in which Abeta deposition is virtually absent.

Neuropathology of parkinsonism-dementia complex and amyotrophic lateral sclerosis of Guam: an update

A comparative study was performed to investigate the differences and similarities of the neuropathological findings in the parkinsonism-dementia complex (PDC) and amyotrophic lateral sclerosis (ALS) of Guam, progressive supranuclear palsy and classic ALS. Based on the findings, it is proposed that (a) PDC is a discrete disease entity, (b) NFTs in Chamorro ALS are merely a background feature widely distributed in this population, (c) Chamorro ALS is a disease combined with classic ALS and neurofibrillary degeneration, (d) thus a subtype of "Guam ALS" is not present, and (e) PDC and ALS of Guam are different diseases.

Possible relation of atypical parkinsonism in the French West Indies with consumption of tropical plants: a case-control study. Caribbean Parkinsonism Study Group

BACKGROUND

In Europe and North America, Parkinson's disease is the major form of parkinsonism; less than 4% of cases are progressive supranuclear palsy (PSP) and about 20% are atypical parkinsonism. The distribution of these subgroups is different in the French West Indies. We aimed to define the clinical and demographic specificity of these disorders in Guadeloupe and to investigate a postulated link with consumption of herbal tea and fruits from the Annonaceae family (Annona muricata and Annona squamosa), which contain neurotoxic benzyltetrahydroisoquinoline alkaloids.

METHODS

Between September, 1996, and August, 1998, 87 consecutive patients with parkinsonism were referred to the single neurological department in Guadeloupe. After detailed clinical, neurophysiological, cognitive, and neuroradiological assessment, they were classified by generally accepted criteria as having Parkinson's disease, PSP, or atypical parkinsonism. We compared the amount of tropical fruits and herbal tea consumed by the various parkinsonian subgroups and by frequency-matched controls (patients with benign symptoms and no neurodegenerative disease).

FINDINGS

Of the 87 patients, 22 had Parkinson's disease, 31 had PSP, 30 had atypical parkinsonism, and four had atypical parkinsonism associated with motor neuron disease, 44 of the patients with PSP or atypical parkinsonism were male. The patients with atypical parkinsonism had symmetrical rigidity and bradykinesia, and no levodopa peak-dose dyskinesias. Patients with PSP differed from those with atypical parkinsonism because they had supranuclear vertical down-gaze palsy, severe gait and balance problems, and frontal-lobe syndrome. 29 patients with PSP reported regular consumption of pawpaw fruit, and 26 drank herbal tea. 30 patients with atypical parkinsonism reported regular consumption of pawpaw fruit, and 24 drank herbal tea. Both of these groups consumed significantly more fruit and herbal tea than patients with Parkinson's disease (fruit: odds ratio 23.6; herbal tea: 28.2); and controls (fruit: 20.7; herbal tea: 6.48).

INTERPRETATION

Our study confirms the over-representation of atypical parkinsonism and PSP in patients with parkinsonism in the French West Indies. Chronic exposure to neurotoxic alkaloids could be an important aetiological factor because these compounds induce parkinsonism in animals. A larger epidemiological study, to clarify the link between these fruits with atypical parkinsonism and PSP, is proposed.

Autosomal dominant dementia with widespread neurofibrillary tangles

Several familial dementing conditions with atypical features have been characterized, but only rarely is the neuropathology dominated solely by neurofibrillary lesions. We present a Midwestern American pedigree spanning four generations in which 15 individuals were affected by early-onset dementia with long disease duration, with an autosomal dominant inheritance pattern, and with tau-rich neurofibrillary pathology found in the brain post mortem. The average age at presentation was 55 years with gradual onset and progression of memory loss and personality change. After 30 years' disease duration, the proband's neuropathologic examination demonstrated abundant intraneuronal neurofibrillary tangles (NFTs) involving the hippocampus, pallidum, subthalamic nucleus, substantia nigra, pons, and medulla. Only sparse neocortical tangles were present and amyloid plaques were absent. The tangles were recognized by antibodies specific for phosphorylation-independent (Tau-2, T46, 133, and Alz-50) and phosphorylation-dependent epitopes (AT8, T3P, PHF-1, 12E8, AT6, AT18, AT30) in tau proteins. Electron microscopy of NFTs in the dentate gyrus and midbrain demonstrated paired helical filaments. Although the clinical phenotype resembles Alzheimer's disease, and the neuropathologic phenotype resembles progressive supranuclear palsy, an alternative consideration is that this familial disorder may be a new or distinct disease entity.

Guamanian neurodegenerative disease: ultrastructural studies of skin

It is evident that Guamanian amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia complex (PDC) are clinical variants of a single disease entity and that Guamanian ALS is clinically indistinguishable from sporadic ALS. We studied by electron microscopy the skin tissues from 11 patients with Guamanian neurodegenerative disease (PDC and ALS), 11 Chamorro control subjects, 10 Japanese patients with sporadic ALS and 11 Japanese control patients. Among patients with sporadic ALS, there was an inverse relationship of collagen fiber diameter and the duration of disease and a marked increase of amorphous material in the ground substance. These findings were not observed in the Guamanian patients or controls. Therefore, the skin studies reinforce the view of a different disease mechanism in Guamanian ALS and PDC compared to sporadic ALS.

Neurodegenerative disorders with extensive tau pathology: a comparative study and review

Many neurodegenerative disorders with onset in mid to late adult life present diagnostic challenges to clinicians and pathologists alike. A distinguishing neuropathological feature has traditionally been the presence or absence of neurofibrillary tangles. Recent biochemical and molecular biological studies have identified the microtubule-binding protein tau as the predominant component of these and related inclusions, and have provided powerful new reagents for the study of neurodegenerative diseases. Several diseases previously considered distinct pathophysiological entities contain similar tau-immunoreactive lesions, but qualitative and regional anatomical differences in vulnerability can differentiate the disorders. Comparison of tau-immunoreactive lesions in three relatively uncommon neurodegenerative diseases-progressive supranuclear palsy, Pick's disease, and corticobasal degeneration-illustrates the types of analyses that demonstrate unexpected pathological similarities, but also fundamental differences between these disorders. These results have important implications for the differential diagnosis of disorders containing tau-immunoreactive lesions, including Alzheimer's disease.