Amyotrophic lateral sclerosis, Parkinson's disease, and the amyotrophic lateral sclerosis-Parkinsonism-dementia complex on Guam: a review and summary of attempts to demonstrate infection as the aetiology

Linking Environmental Genotoxins to Neurodegenerative Diseases Through Transcriptional Mutagenesis

Numerous lines of evidence suggest that DNA damage contributes to the initiation, progression, and severity of neurodegenerative diseases. However, the molecular mechanisms responsible for this relationship remain unclear. This review integrates historical data with contemporary findings to propose that DNA damage exacerbates neurodegenerative diseases by inducing transcription errors. First, we describe the scientific rationale and basic biological concepts that underpin this hypothesis. Then, we provide epidemiological, cellular, and molecular data to support this idea, and we describe new and recently published observations that suggest that the former high incidence of neurodegenerative disease in Guam may have been driven by DNA damage-induced transcription errors. Finally, we explore the long-term implications of these findings on our understanding of the impact of genotoxic stress on human aging and disease.

Retroviral Elements in Pathophysiology and as Therapeutic Targets for Amyotrophic Lateral Sclerosis

The study of the role of retroviruses in amyotrophic lateral sclerosis (ALS) dates back to the 1960s shortly after transposable elements themselves were first discovered. It was quickly realized that in wild mice both horizontal and vertical transmissions of retroviral elements were key to the development of an ALS-like syndrome leading to the postulate that endogenous retroviruses (ERVs) contribute significantly to the pathogenicity of this disease. Subsequent studies identified retroviral reverse transcriptase activity in brains of individuals with ALS from Guam. However, except for a single study from the former Soviet Union, ALS could not be transmitted to rhesus macaques. The discovery of an ALS-like syndrome in human immunodeficiency virus (HIV) and human T cell leukemia virus infected individuals led to renewed interest in the field and reverse transcriptase activity was found in the blood and cerebrospinal fluid of individuals with sporadic ALS. However, exogenous retroviruses could not be found in individuals with ALS which further reinforced the possibility of involvement of a human ERV (HERV). The first demonstration of the involvement of a HERV was the discovery of the activation of human endogenous retrovirus-K subtype HML-2 in the brains of individuals with ALS. The envelope protein of HML-2 is neurotoxic and transgenic animals expressing the envelope protein develop an ALS-like syndrome. Activation of HML-2 occurs in the context of generalized transposable element activation and is not specific for ALS. Individuals with HIV-associated ALS show a remarkable response to antiretroviral therapy; however, antiretroviral trials in ALS down-regulate HML-2 without ameliorating the disease. This highlights the need for specific drugs to be developed against HML-2 as a novel therapeutic target for ALS. Other approaches might include antisense oligonucleotides, shRNA targeted against the envelope gene or antibodies that can target the extracellular envelope protein. Future clinical trials in ALS should consider combination therapies to control these ERVs.

Historical vignette: Leonard T. Kurland, FACE (1921-2001), the rise of neuroepidemiology, and the Rochester Epidemiology Project

The creation of the field of neuroepidemiology was one of the two principal professional achievements of the American College of Epidemiology Fellow Leonard T. Kurland (1921-2001), the other being the establishment of the Rochester Project. In the former, Kurland established the role of the neuroepidemiologists in the development of the corpus of knowledge needed to control and prevent the occurrence of neurological conditions. Two examples of his endeavors in this regard were his work on the Guamanian focus of neurodegenerative diseases and his seminal investigations into the epidemiology of multiple sclerosis. He was also instrumental in the development of the Rochester, Minnesota community as a population laboratory within which epidemiologic investigations could be mounted. This pioneering achievement created a resource used by many generations of epidemiologists and clinicians to examine health and disease in the population.

Prion-like propagation of α-synuclein in neurodegenerative diseases

Prions are defined as proteinaceous infectious particles that do not contain nucleic acids. Neuropathological investigations of post-mortem brains and recent studies of experimental transmission have suggested that amyloid-like abnormal protein aggregates, which are the defining feature of many neurodegenerative diseases, behave like prions and propagate throughout the brain. This prion-like propagation may be the underlying mechanism of onset and progression of neurodegenerative diseases, although the precise molecular mechanisms involved remain unclear. However, in vitro and in vivo experimental models of prion-like propagation using pathogenic protein seeds are well established and are extremely valuable for the exploration and evaluation of novel drugs and therapies for neurodegenerative diseases for which there is no effective treatment. In this chapter, we introduce the experimental models of prion-like propagation of α-synuclein, which is accumulated in Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, and we describe their applications for the development of new diagnostic and therapeutic modalities. We also introduce the concept of "α-syn strains," which may underlie the pathological and clinical diversity of α-synucleinopathies.

Defining neurodegeneration on Guam by targeted genomic sequencing

OBJECTIVE

Amyotrophic lateral sclerosis/parkinsonism-dementia complex has been described in Guam, Western Papua, and the Kii Peninsula of Japan. The etiology and pathogenesis of this complex neurodegenerative disease remains enigmatic.

METHODS

In this study, we have used targeted genomic sequencing to evaluate the contribution of genetic variability in the pathogenesis of amyotrophic lateral sclerosis, parkinsonism, and dementia in Guamanian Chamorros.

RESULTS

Genes previously linked to or associated with amyotrophic lateral sclerosis, parkinsonism, dementia, and related neurodegenerative syndromes were sequenced in Chamorro subjects living in the Mariana Islands. Homozygous PINK1 p.L347P, heterozygous DCTN1 p.T54I, FUS p.P431L, and HTT (42 CAG repeats) were identified as pathogenic mutations.

INTERPRETATION

The findings explain the clinical, pathologic, and genetic heterogeneity observed in some multi-incident families and contribute to the excess incidence of neurodegeneration previously reported on Guam.

Transmission of multiple system atrophy prions to transgenic mice

Prions are proteins that adopt alternative conformations, which become self-propagating. Increasing evidence argues that prions feature in the synucleinopathies that include Parkinson's disease, Lewy body dementia, and multiple system atrophy (MSA). Although TgM83(+/+) mice homozygous for a mutant A53T α-synuclein transgene begin developing CNS dysfunction spontaneously at ∼10 mo of age, uninoculated TgM83(+/-) mice (hemizygous for the transgene) remain healthy. To determine whether MSA brains contain α-synuclein prions, we inoculated the TgM83(+/-) mice with brain homogenates from two pathologically confirmed MSA cases. Inoculated TgM83(+/-) mice developed progressive signs of neurologic disease with an incubation period of ∼100 d, whereas the same mice inoculated with brain homogenates from spontaneously ill TgM83(+/+) mice developed neurologic dysfunction in ∼210 d. Brains of MSA-inoculated mice exhibited prominent astrocytic gliosis and microglial activation as well as widespread deposits of phosphorylated α-synuclein that were proteinase K sensitive, detergent insoluble, and formic acid extractable. Our results provide compelling evidence that α-synuclein aggregates formed in the brains of MSA patients are transmissible and, as such, are prions. The MSA prion represents a unique human pathogen that is lethal upon transmission to Tg mice and as such, is reminiscent of the prion causing kuru, which was transmitted to chimpanzees nearly 5 decades ago.

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.

Urgent opportunistic observations: the study of changing, transient and disappearing phenomena of medical interest in disrupted primitive human communities

Two newly identified foci of usually rare disease occurring in high incidence in isolated primitive populations of West New Guinea are discussed as examples of medical problems that demand immediate intensive investigation because the unique naturally occurring experiments they represent are soon likely to be altered. These are: (1) amyotrophic lateral sclerosis, Parkinsonism, and dementia syndromes in a small population of Auyu and Jakai peoples in the Lowlands, and (2) an epidemic of burns from cysticercosis epilepsy from newly introduced Taenia solium in pigs in the Ekari people of the Wissel Lakes in the Highlands. A third new example is a focus of male pseudohermaphroditism among the Simbari Anga in the Highlands of Papua New Guinea. These are presented along with a series of eleven further examples of the kind of problems that require urgent opportunistic observation because of the extreme changes that investigation and therapeutic and preventive efforts themselves, as well as the inevitable effects of acculturation, will evoke from the moment an investigator or other outsider from a technologically advanced culture enters the previously isolated community.

The tau H2 haplotype is almost exclusively Caucasian in origin

We have assessed the distribution of the tau H1/H2 haplotype in the publicly available reference series of samples with representatives of most racial groups. This analysis shows that the H2 haplotype is probably exclusively Caucasian in origin and its marginal occurrence in other racial groups is likely to reflect admixture. We discuss this observation in terms of the origin of the H2 haplotype and the epidemiology of the tauopathies.

Progressive supranuclear palsy and its relation to pacific foci of the parkinsonism-dementia complex and Guadeloupean parkinsonism

Steele, Richardson and Olszweski in 1964 described a distinctive clinical and pathological entity they called progressive supranuclear palsy (PSP). Now on Guadeloupe in the Carribbean French West Indies, Caparros-Lefebvre is identifying many patients with similar clinical and histological features. Others have a clinical syndrome of atypical parkinsonism that resembles the parkinsonism-dementia complex (PDC) of Guam and the Kii peninsula of Japan (PDC). But in those Pacific foci the histology is different and the abnormal tau is of Alzheimer's type rather than the PSP type of Guadeloupe. In both locales, neurotoxins of local foods are implicated in etiology. Future studies will confirm if Guadeloupean parkinsonism is truly a geographic focus of PSP, and if dietary factors account for both.

Induction of beta (A4)-amyloid in primates by injection of Alzheimer's disease brain homogenate. Comparison with transmission of spongiform encephalopathy

Amyloid plaques, associated with argyrophilic dystrophic neurites, and cerebral amyloid angiopathy (CAA), but no neurofibrillary tangles, were found in the brains of three middle-aged marmoset monkeys that had been injected intracerebrally (ic) 6-7 yr earlier with brain tissue from a patient with early-onset Alzheimer's disease. Such changes were not found in the brains of three age-matched control marmosets. Immunochemically the amyloid plaques and CAA stained with antibody to beta (A4)-protein. The plaques and CAA displayed dichroic birefringence when stained with Congo red and viewed under polarized light. beta (A4)-amyloid plaques and CAA were also found in the brain of one of two marmosets injected ic 6 yr previously with brain tissue from a patient with prion disease with concomitant beta (A4)-amyloid plaques and CAA. An occasional beta (A4)-amyloid plaque was found in the brains of two of four marmosets injected ic > 4.5 yr previously with brain tissue from three elderly patients, two of whom had suspected (but untransmitted) CJD. No beta (A4)-amyloid plaques or CAA were found in six marmosets who were older than the injected animals, in four marmosets that had not developed spongiform encephalopathy (SE) having been injected several years previously with human brain tissue from three younger patients with suspected or atypical prion disease, or in 10 younger marmosets who had undergone various neurosurgical procedures. Seventeen marmosets injected in the same way with brain tissue from patients or animals with SE developed SE 17-49 mo after injection. These results suggest that beta (A4)-amyloidosis is a transmissible process comparable to the transmissibility of SE.

Parkinson's disease and exposure to rural environmental factors: a population based case-control study

To determine whether a history of exposure to rural environmental factors leads to an increased likelihood of developing idiopathic Parkinson's disease, we conducted a case-control study of 130 cases and 260 randomly selected community controls (matched with the cases by sex and age +/- 2.5 years at a ratio of 2 controls: 1 case) in the city of Calgary. The data were collected by personal interviews and were analyzed using conditional logistic regression for matched sets. The ages of the cases ranged from 36.5 to 90.7 years (mean = 68.5 +/- 11.3 years). The mean age at diagnosis was 61.1 +/- 12.4 years. The mean duration of disease was 7.8 +/- 0.6 years. Eleven (9.1%) cases were diagnosed before age 40. In this sample from the Province of Alberta, Canada, no significant increase in risk for Parkinson's disease was associated with a history of rural living, farm living, or well water drinking in early childhood or at any time during the first 45 years of life.

Similarities of guamanian ALS/PD to post-encephalitic parkinsonism/ALS: possible viral cause

Guamanian amyotrophic lateral sclerosis with parkinsonism-dementia (ALS/PD) has been the subject of intensive study since its discovery in 1947 because of its extraordinarily high incidence in a small ethnic group (Chamorros) whose dietary lack and customs have suggested possible causes. As yet, these and other suspected causes have eluded proof. Because of marked similarities between Guamanian ALS/PD and late onset post-encephalitic (encephalitis lethargica) parkinsonism and ALS it is suggested that they have a common cause. The parkinsonism and ALS in the two disorders are clinically very similar and neuropathological studies have shown a very similar distribution of neurofibrillary tangles in neurons. Some clinical differences, such as ocular features in the post-encephalitic cases and dementia in Guamanian ALS/PD, can be explained by differences in the severity of infection and the interval between the encephalitis and onset of sequelae. Although unproven, influenza A (HswilN1 strain) has long been suspected as the cause of encephalitis lethargica because of simultaneous pandemics of the two diseases in the 1920s. Because influenza A can persistently infect cells and has a marked propensity to mutate it is an optimal candidate among other RNA viruses for delayed nervous system infection as a possible cause of ALS/PD.

Transmissible and non-transmissible neurodegenerative disease: similarities in age of onset and genetics in relation to aetiology

In only a few cases is transmissible dementia known to have been acquired by infection from a source outside the individual; the remaining cases can be classified as sporadic, loosely familial, or autosomal dominant. Each group has a characteristic mean age of onset. A range of neurodegenerative diseases (including Alzheimer-type dementia and amyotrophic lateral sclerosis) can also be classified in this way, with similar characteristic mean ages of onset. The emergence of these diseases in later middle age, and the interdependence of age of onset and the type of familial occurrence suggest that these pathological processes are related to those genetic mechanisms which determine senescence. It is argued that the majority of cases of transmissible dementia arise, not from infection, but from the expression of endogenous virogene sequences as part of the aging processes.

Amyotrophic lateral sclerosis: Part 2. Etiopathogenesis

The pathogenesis of the motor neuronal degeneration in amyotrophic lateral sclerosis (ALS) is unclear, though several possible etiological factors are currently being investigated. A unifying hypothesis will have to explain the diverse geographical occurrence, clinical features, and selective vulnerability and relative resistance of different neuronal populations in the disease. It is possible that different biochemical defects underlie this diversity, or alternatively that the many factors incriminated in the etiology may act upon an underlying genetic-biochemical abnormality to trigger premature neuronal death. Viruses, metals, endogenous toxins, immune dysfunction, endocrine abnormalities, impaired DNA repair, altered axonal transport, and trauma have all been etiologically linked with ALS, but convincing research evidence of a causative role for any of these factors is yet to be demonstrated.

Coexistence of idiopathic Parkinson's disease and Creutzfeldt-Jakob disease

The association of idiopathic Parkinson's disease and Creutzfeldt-Jakob disease has not been reported previously. We describe the clinical findings in a patient with both disorders, confirmed at autopsy. The differential diagnosis of parkinsonism with cognitive and psychiatric disturbances is reviewed with emphasis on conditions which may complicate the course of idiopathic Parkinson's disease. The etiological implications of this combination are considered.

Epidemiology of motor neuron disease in northern Sweden

All cases of motor neuron disease (MND), encompassing amyotrophic lateral sclerosis (ALS), progressive bulbar paralysis (PBP) and progressive spinal muscular atrophy (PSMA), in northern Sweden, diagnosed between 1969-1980 have been analysed. 128 cases were found, corresponding to an average annual incidence rate of 1.67 per 100,000. The prevalence on December 31, 1980 was 4.8 per 100,000. Age-specific incidence rates were higher in the high age groups with a maximum at 60-64 years for males, at 70-74 years for females and at 65-69 years for the sexes combined. The median age at onset was 61 years. Clustering was not found in mining districts and overrepresentation of miners and stone treaters was not observed. Minor differences in incidence rates, as measured by the standardized morbidity ratio, SMR, were found between the inland, coastal and mountain areas. The median survival time after onset of disease was 32 months for ALS, 30 months for PBP and 70 months for PSMA. The combined survival rate for all MND cases was 28% after 5 years and 15% after 10 years. The male to female ratio was 1.1:1, and 4.7% were familial cases.

Nerve cell protein metabolism and degenerative disease

The mechanisms and organelles through which control of protein synthesis within healthy nerve cells is governed are discussed, and the ways in which expression of these biochemical pathways can be related to cell morphology are described. The volumes of the nucleus and nucleolus, and the amount of RNA within the cell body, are all interrelated and seem to be set at genetically predetermined levels which normally match the neurones basal needs for replacement proteins in respect of the size of its' projection field. However, in situations of (induced) hyperactivity or cell damage, or in others where disease may lower nerve cell activity, the protein requirements change, and it is noted that these morphological features also alter in a direction appropriate to the need for greater or lesser amounts of protein. How these alterations in protein synthesis can provide information as to both the basic pathology, or even the pathogenesis, of degenerative disease of the nervous system is illustrated by reference to Alzheimer's disease and motor neurone disease.

[Virologic studies in patients with amyotrophic lateral sclerosis]

The effects of intracerebral inoculation of cerebrospinal fluid in mice from 9 patients with amyotrophic lateral sclerosis are reported. There were 704 animals inoculated. The results were considered positive when the animals presented difficulties in walking and equilibrating. Cases 1, 2, 6, 7 and 9 were positives in the first passage. In case 1, the positivity was reached from first to fourth passage and in case 6, to third passage. At sight of this results, the possibility of that disease to be caused by slow-virus is discussed.

Epidemiology of Parkinson's disease--an overview

Among the white races, the prevalence rates of Parkinson's disease range from 66 to 187 per 100,000 population, through without any obvious geographical pattern. A similar variation is found in the annual incidence rates with estimates from 5 to 24 per 100,000 population. The black races may be partially protected against the disease. Both sexes are probably equally affected by the disease. Parkinson's disease usually begins after the age of 50 years, and the risk of the disease steeply rises with advancing age. Parkinson's disease is often omitted in death certificates; mortality rates with Parkinson's disease as an underlying cause of death vary from 0.5 to 3.8 per 100,000. Levodopa treatment, by reducing the excess mortality accompanying the natural course of Parkinson's disease, may increase the number of patients living with this disease in the near future. Postencephalitic Parkinson's disease, developing as a sequel to lethargic encephalitis and accounting for some two thirds of parkinsonian cases shortly after the epidemic, has probably been a transient phase in the epidemiology of Parkinson's disease and is now disappearing. Data from epidemiological investigations have advanced our understanding of the cause of Parkinson's disease only to a small extent. No other characteristic than race has been found to influence the susceptibility to the disease. The environmental risks for Parkinson's disease have not been unequivocally demonstrated. Highly conflicting information is available as to the contribution of hereditary to the pathogenesis of Parkinson's disease. Seroepidemiological investigations have shown an increased antibody response against herpes simplex virus in parkinsonian patients, but attempts to detect herpes virus specific products or DNA sequences in the brain material have been unsuccessful.

Amyotrophic lateral sclerosis among Chamorro migrants from Guam

Amyotrophic lateral sclerosis (ALS), which occurs in unusually high incidence among the Chamorro people on the island of Guam, has developed in 28 Chamorro migrants--24 of whom had onset in the United States, Japan, Germany, or Korea--after periods of absence from Guam of 1 to 34 years. Thus, the latency period for the disease, if caused by environmental factors on Guam, may be over three decades. Four further patients developed ALS within 1 to 14 years of their return to Guam after long-term residence in the continental United States. The minimum exposure time to environmental variables on Guam, based on age at migration, was 18 years, and all patients had spent their childhood and adolescence on Guam. Estimates of crude mortality rates for ALS from these data are considerably higher than for the United States population, and lower than the ALS mortality rates for nonmigrant Chamorros on Guam.

Cellular immunity in Guamanians with amyotrophic lateral sclerosis and Parkinsonism-dementia

To test the hypothesis that host resistance factors may be abnormal in Guamanians in whom amyotrophic lateral sclerosis and Parkinsonism-dementia develop, cellular immunity was evaluated in both diseases and compared to that of Guamanians with other nervous-system diseases, normal adult Guamanians and non-Guamanians with amyotrophic lateral sclerosis and Parkinsonism. Diminished responses to skin-test antigens, lymphopenia, diminished per cent and total T cells and, less frequently, decreased mitogen responses were seen in Guamanian patients with amytorophic lateral sclerosis and Parkinsonism-dementia but not in the other patient or normal groups. Guamanian patients with amyotrophic lateral sclerosis and diminished cellular immunity had an increased frequency of HLA-Bw35 (P less than 0.005) and shorter mean duration of disease (P less than 0.05) than those with normal cellular immunity. In Parkinsonism dementia diminished cellular immunity was less strongly associated with HLA-BW35 (P less than 0.05) and was not associated with differences in duration of disease. Normal Guamanians and those with other nervous-system diseases showed no association of diminished cellular immunity with HLA-Bw35. The association appeared disease-related, with onset concomitant with the neurologic expression of Guamanian amyotrophic lateral sclerosis and Parkinsonism-dementia.

Slow Infections of the Central Nervous System

This review describes the recent advances in slow infections of the nervous system emphasizing the pathogenetic aspects of these diseases. A theoretical model for the pathogenesis of subacute sclerosing panencephalitis (SSPE) is proposed, illustrating the factors that may affect host response to the measles virus and allow it to persist and produce the panencephalitis. The isolation of an oncogenic virus from progressive multifocal leukoencephalopathy (PML) has implications in the consideration of a viral etiology for some brain tumors. The agent responsible for the transmissibility of kuru and Creutzfeldt-Jakob disease (CJD) remains uncharacterized despite recent interest in viroids and abnormalities in replication of cell membranes. The epidemiological data on multiple sclerosis suggests an exposure to an infectious agent at an early age of life modified by the host response. No specific agent has been consistently associated with multiple sclerosis. Amyotrophic lateral sclerosis (ALS), Parkinson’s disease, Mollare’s meningitis and Behcet’s disease are other examples where a virus is suspect but unproven. The ability of viruses to persist in the host for months to years has linked many chronic neurologic diseases to an infectious agent, enlarging the spectrum of disease caused by viruses.