Early-onset, conjugal, twin-discordant, and clusters of sporadic ALS: Pathway to discovery of etiology via lifetime exposome research

An introduction to environmental neurotoxicology: Lessons from a clinical perspective

In 1992, the Committee on Neurotoxicology and Models for Assessing Risk of the National Academy of Sciences in Washington DC focused with a scientific perspective on the identification of substances with neurotoxic potential, studies of exposed populations, risk assessment, and biologic markers of disease. This Committee recommended: "all physicians should be trained to take a thorough occupational-exposure history and to be aware of other possible sources of toxic exposure". Although convened after several outbreaks of neurotoxic syndromes, clinical neurological considerations were lacking. After defining keys words, namely Environment, Neurotoxicology and Neurotoxicants, we present some demonstrative cases; e.g., the Epidemic Neuropathy in Cuba, Minamata disease, ALS/PDC on Guam, and the ALS hot spot in the French Alps. Always with a clinical and practical approach, we will then review the milieux that contain and convey potential neurotoxicants, the different exposure routes and the clinical presentations. Drawing lessons from clinical cases, we offer some thoughts concerning the future of Environmental Neurotoxicology (ENT). Pointing notably to the diffuse chemical contamination of ecosystems and living beings, including Homo sapiens, we question the real impact of agents with neurotoxic potential on the human brain, considering the effects, for example, of air pollution, endocrine disruptors and nanoparticles. Concern is expressed over the lack of knowledge of the non-monotonic kinetics of many of these chemicals, the major concern being related to mixtures and low-dose exposures, as well as the delayed appearance in clinical expression of prevalent neurodegenerative diseases.

Introducing the Role of Genotoxicity in Neurodegenerative Diseases and Neuropsychiatric Disorders

Decades of research have identified genetic and environmental factors involved in age-related neurodegenerative diseases and, to a lesser extent, neuropsychiatric disorders. Genomic instability, i.e., the loss of genome integrity, is a common feature among both neurodegenerative (mayo-trophic lateral sclerosis, Parkinson's disease, Alzheimer's disease) and psychiatric (schizophrenia, autism, bipolar depression) disorders. Genomic instability is associated with the accumulation of persistent DNA damage and the activation of DNA damage response (DDR) pathways, as well as pathologic neuronal cell loss or senescence. Typically, DDR signaling ensures that genomic and proteomic homeostasis are maintained in both dividing cells, including neural progenitors, and post-mitotic neurons. However, dysregulation of these protective responses, in part due to aging or environmental insults, contributes to the progressive development of neurodegenerative and/or psychiatric disorders. In this Special Issue, we introduce and highlight the overlap between neurodegenerative diseases and neuropsychiatric disorders, as well as the emerging clinical, genomic, and molecular evidence for the contributions of DNA damage and aberrant DNA repair. Our goal is to illuminate the importance of this subject to uncover possible treatment and prevention strategies for relevant devastating brain diseases.

Corrected speciation and gyromitrin content of false morels linked to ALS patients with mostly slow-acetylator phenotypes

A case-control study of sporadic amyotrophic lateral sclerosis (ALS) in a mountainous village in the French Alps discovered an association of cases with a history of eating wild fungi (false morels) collected locally and initially identified and erroneously reported as Gyromitra gigas. Specialist re-examination of dried specimens of the ALS-associated fungi demonstrated they were members of the G. esculenta group, namely G. venenata and G. esculenta, species that have been reported to contain substantially higher concentrations of gyromitrin than present in G. gigas. Gyromitrin is metabolized to monomethylhydrazine, which is responsible not only for the acute oral toxic and neurotoxic properties of false morels but also has genotoxic potential with proposed mechanistic relevance to the etiology of neurodegenerative disease. Most ALS patients had a slow- or intermediate-acetylator phenotype predicted by N-acetyltransferase-2 (NAT2) genotyping, which would increase the risk for neurotoxic and genotoxic effects of gyromitrin metabolites.

Avocational exposure associations with ALS risk, survival, and phenotype: A Michigan-based case-control study

INTRODUCTION

Environmental exposures strongly influence ALS risk and identification is needed to reduce ALS burden. Participation in hobbies and exercise may alter ALS risk and phenotype, warranting an assessment to understand their contribution to the ALS exposome.

METHODS

Participants with ALS and healthy controls were recruited from University of Michigan and self-completed a survey to ascertain hobbies, exercise, and avocational exposures. Exposure variables were associated with ALS risk, survival, onset segment, and onset age.

RESULTS

ALS (n = 400) and control (n = 287) participants self-reported avocational activities. Cases were slightly older (median age 63.0 vs. 61.1 years, p = 0.019) and had a lower educational attainment (p < 0.001) compared to controls; otherwise, demographics were well balanced. Risks associating with ALS after multiple comparison correction included golfing (odds ratio (OR) 3.48, padjusted = 0.004), recreational dancing (OR 2.00, padjusted = 0.040), performing gardening or yard work (OR 1.71, padjusted = 0.040) five years prior to ALS and personal (OR 1.76, padjusted = 0.047) or family (OR 2.21, padjusted = 0.040) participation in woodworking, and personal participation in hunting and shooting (OR 1.89, padjusted = 0.040). No exposures associated with ALS survival and onset. Those reporting swimming (3.86 years, padjusted = 0.016) and weightlifting (3.83 years, padjusted = 0.020) exercise 5 years prior to ALS onset had an earlier onset age.

DISCUSSION

The identified exposures in this study may represent important modifiable ALS factors that influence ALS phenotype. Thus, exposures related to hobbies and exercise should be captured in studies examining the ALS exposome.

Environmental neurology: Concepts and short history of an interdisciplinary approach to etiology, treatment and prevention

Environmental Neurology (EN), a sub-discipline of Neurology and Neurological Sciences, favors an interdisciplinary collaboration allowing a holistic approach to understanding the impact of environmental factors on the nervous system and their relationship with neurological diseases. Several examples of diseases and conditions show the large scope of subjects addressed by EN. The EN sub-discipline focuses on both individual and population issues thus joining patient care and public health, respectively. Neuropathogenesis is addressed by several major questions: How do the environment and nervous system interact? Which exogenous factors can trigger neurological disease? When, where and how do they act? What are the therapeutic implications, and how can these disorders be controlled or prevented. To answer such questions, we address the incentive for, philosophy of and methods developed by EN, which seeks to safeguard Brain Health and, thus, the quality of life.

Presymptomatic geographical distribution of ALS patients suggests the involvement of environmental factors in the disease pathogenesis

BACKGROUND

Given that the pathogenetic process of ALS begins many years prior to its clinical onset, examining patients' residential histories may offer insights on the disease risk factors. Here, we analyzed the spatial distribution of a large ALS cohort in the 50 years preceding the disease onset.

METHODS

Data from the PARALS register were used. A spatial cluster analysis was performed at the time of disease onset and at 1-year intervals up to 50 years prior to that.

RESULTS

A total of 1124 patients were included. The analysis revealed a higher-incidence cluster in a large area (435,000 inhabitants) west of Turin. From 9 to 2 years before their onset, 105 cases were expected and 150 were observed, resulting in a relative risk of 1.49 (P = 0.04). We also found a surprising high number of patients pairs (51) and trios (3) who lived in the same dwelling while not being related. Noticeably, these occurrences were not observed in large dwellings as we would have expected. The probability of this occurring in smaller buildings only by chance was very low (P = 0.01 and P = 0.04 for pairs and trios, respectively).

CONCLUSIONS

We identified a higher-incidence ALS cluster in the years preceding the disease onset. The cluster area being densely populated, many exposures could have contributed to the high incidence ALS cluster, while we could not find a shared exposure among the dwellings where multiple patients had lived. However, these findings support that exogenous factors are likely involved in the ALS pathogenesis.