Cigarettes and amyotrophic lateral sclerosis: only smoke or also fire?

From use of omics to systems biology: Identifying therapeutic targets for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a heterogeneous progressive neurodegenerative disorder with available treatments such as riluzole and edaravone extending survival by an average of 3-6 months. The lack of highly effective, widely available therapies reflects the complexity of ALS. Omics technologies, including genomics, transcriptomic and proteomics have contributed to the identification of biological pathways dysregulated and targeted by therapeutic strategies in preclinical and clinical trials. Integrating clinical, environmental and neuroimaging information with omics data and applying a systems biology approach can further improve our understanding of the disease with the potential to stratify patients and provide more personalised medicine. This chapter will review the omics technologies that contribute to a systems biology approach and how these components have assisted in identifying therapeutic targets. Current strategies, including the use of genetic screening and biosampling in clinical trials, as well as the future application of additional technological advances, will also be discussed.

Unraveling the complex interplay between genes, environment, and climate in ALS

Various genetic and environmental risk factors have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). Despite this, the cause of most ALS cases remains obscure. In this review, we describe the current evidence implicating genetic and environmental factors in motor neuron degeneration. While the risk exerted by many environmental factors may appear small, their effect could be magnified by the presence of a genetic predisposition. We postulate that gene-environment interactions account for at least a portion of the unknown etiology in ALS. Climate underlies multiple environmental factors, some of which have been implied in ALS etiology, and the impact of global temperature increase on the gene-environment interactions should be carefully monitored. We describe the main concepts underlying such interactions. Although a lack of large cohorts with detailed genetic and environmental information hampers the search for gene-environment interactions, newer algorithms and machine learning approaches offer an opportunity to break this stalemate. Understanding how genetic and environmental factors interact to cause ALS may ultimately pave the way towards precision medicine becoming an integral part of ALS care.

Influence of cigarette smoking on ALS outcome: a population-based study

OBJECTIVE

To assess the prognostic influence of premorbid smoking habits and vascular risk profile on amyotrophic lateral sclerosis (ALS) phenotype and outcome in a population-based cohort of Italian patients.

METHODS

A total of 650 patients with ALS from the Piemonte/Valle d'Aosta Register for ALS, incident in the 2007-2011 period, were recruited. Information about premorbid cigarette smoking habits and chronic obstructive pulmonary disease (COPD) were collected at the time of diagnosis.

RESULTS

Current smokers had a significantly shorter median survival (1.9 years, IQR 1.2-3.4) compared with former (2.3 years, IQR 1.5-4.2) and never smokers (2.7 years, IQR 1.8-4.6) (p=0.001). Also COPD adversely influenced patients' prognosis. Both smoking habits and CODP were retained in Cox multivariable model.

CONCLUSIONS

This study has demonstrated in a large population-based cohort of patients with ALS that cigarette smoking is an independent negative prognostic factor for survival, with a dose-response gradient. Its effect is not related to the presence of COPD or to respiratory status at time of diagnosis. The understanding of the mechanisms, either genetic or epigenetic, through which exogenous factors influence disease phenotype is of major importance towards a more focused approach to cure ALS.

Environmental risk factors and amyotrophic lateral sclerosis (ALS): a case-control study of ALS in Michigan

An interim report of a case-control study was conducted to explore the role of environmental factors in the development of amyotrophic lateral sclerosis (ALS). Sixty-six cases and 66 age- and gender-matched controls were recruited. Detailed information regarding residence history, occupational history, smoking, physical activity, and other factors was obtained using questionnaires. The association of ALS with potential risk factors, including smoking, physical activity and chemical exposure, was investigated using conditional logistic regression models. As compared to controls, a greater number of our randomly selected ALS patients reported exposure to fertilizers to treat private yards and gardens and occupational exposure to pesticides in the last 30 years than our randomly selected control cases. Smoking, occupational exposures to metals, dust/fibers/fumes/gas and radiation, and physical activity were not associated with ALS when comparing the randomly selected ALS patients to the control subjects. To further explore and confirm results, exposures over several time frames, including 0-10 and 10-30 years earlier, were considered, and analyses were stratified by age and gender. Pesticide and fertilizer exposure were both significantly associated with ALS in the randomly selected ALS patients. While study results need to be interpreted cautiously given the small sample size and the lack of direct exposure measures, these results suggest that environmental and particularly residential exposure factors warrant close attention in studies examining risk factors of ALS.

Amyotrophic Lateral Sclerosis: An update for 2013 Clinical Features, Pathophysiology, Management and Therapeutic Trials

Amyotrophic lateral sclerosis (ALS), first described by Jean-Martin Charcot in the 1870s, is an age-related disorder that leads to degeneration of motor neurons. The disease begins focally in the central nervous system and then spreads relentlessly. The clinical diagnosis, defined by progressive signs and symptoms of upper and lower motor neuron dysfunction, is confirmed by electromyography. Additional testing excludes other conditions. The disease is heterogeneous, but most patients die of respiratory muscle weakness less than 3 years from symptom-onset. Like other age-related neurodegenerative diseases, ALS has genetic and environmental triggers. Of the five to 10% of cases that are inherited, mutations have been discovered for a high proportion. In addition to genetic factors, age, tobacco use, and athleticism may contribute to sporadic ALS, but important etiologies are unidentified for most patients. Complex pathophysiological processes, including mitochondrial dysfunction, aggregation of misfolded protein, oxidative stress, excitotoxicity, inflammation and apoptosis, involve both motor neurons and surrounding glial cells. There is clinical and pathological overlap with other neurodegenerative diseases, particularly frontotemporal dementia. The mechanisms leading to disease propagation in the brain are a current focus of research. To date, one medication, riluzole, licensed in 1996, has been proved to prolong survival in ALS. Numerous clinical trials have so far been unable to identify another neuroprotective agent. Researchers now aim to slow disease progression by targeting known pathophysiological pathways or genetic defects. Current approaches are directed at muscle proteins such as Nogo, energetic balance, cell replacement, and abnormal gene products resulting from mutations. Until better understanding of the causes and mechanisms underlying progression lead to more robust neuroprotective agents, symptomatic therapies can extend life and improve quality of life. Palliative care programs such as hospice give emotional and physical support to patients and families throughout much of the disease course.

Nutrition management of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurological disease with high risk of malnutrition. Symptoms of dysphagia, depression, cognitive impairment, difficulty with self-feeding and meal preparation, hypermetabolism, anxiety, respiratory insufficiency, and fatigue with meals increase the risk of malnutrition. Malnutrition negatively affects prognosis and quality of life, making early and frequent nutrition assessment and intervention essential. Implementation of an adequate calorie diet, dietary texture modification, use of adaptive eating utensils, and placement of a feeding tube aid in preventing malnutrition. When nutrition status is compromised by dysphagia and weight loss (5%-10% of usual body weight) or body mass index <20 kg/m(2) without weight loss and when forced vital capacity is >50%, a percutaneous endoscopic gastrostomy placement is indicated. When forced vital capacity is <50%, a radiologically inserted gastrostomy is the preferred means of enteral placement due to lessened aspiration and respiratory risk. Parenteral nutrition (PN) is indicated only when enteral nutrition (EN) is contraindicated or impossible. This article reviews the background of ALS, nutrition implications and risk of malnutrition, treatment strategies to prevent malnutrition, the role of EN and PN, and feeding tube placement methods according to disease stage.

Regulation of FMO and PON detoxication systems in ALS human tissues

Amyotrophic lateral sclerosis (ALS) is an adult-onset, progressive, and fatal neurodegenerative disease with unknown etiology. Recent evidence suggests an association between the exposure to toxic environmental factors and sporadic ALS. The flavin-containing monooxygenases (FMOs) and paraoxonase (PONs) genes encode enzymes involved in xenobiotic detoxication and are associated with ALS. FMO and PON gene expression has been examined in the human central nervous system including human brain subregions defined as the spinal cord, medulla, and cerebral cortex and in the peripheral tissues (lymphocytes, fibroblasts) in ALS patients and normal control subjects. FMO expression was generally higher in tissues from ALS subjects than in control tissues, with the largest increases in FMO expression detected in the spinal cord. In peripheral tissues, the FMO mRNA level was found to be lower compared with FMO expression in brain tissue, and no differences were detected between ALS patients and the control tissue. FMO and PON gene expression was low in peripheral tissues. In contrast to FMO5 expression, the PON2 gene was down-regulated in ALS patients compared to the controls. Because FMO and PON are involved in the detoxication processes and their functional activity to bioactivate chemicals to toxins has been documented, the data herein suggest that environmental toxin exposure may play a role in a subset of individuals who contract ALS by altering FMO and PON gene expression. Although the precise pathogenic link is presently unknown, these findings suggest a role at FMO and PON genes in the development of ALS.

Spatial clustering of amyotrophic lateral sclerosis and the potential role of BMAA

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative syndrome which has no known cause, except for a small proportion of cases which are genetically inherited. The development of ALS likely involves both genetic and environmental risk factors. Environmental risk factors implicated in ALS have included heavy metals, trauma, pesticides, electrical injuries, electromagnetic radiation and the cyanobacterial-derived neurotoxin beta-N-methylamino-L-alanine (BMAA). To investigate possible environmental risks, a number of epidemiological studies of ALS have been conducted. Some of these studies employ spatial analysis techniques that examine for spatial clusters of ALS and can help guide further research into identifying environmental exposures. Despite identifying geographical disparities in the distribution of ALS cases, these studies have not provided any clear associations with environmental factors. We review the literature on important studies of spatial clustering of ALS and explore the hypothesized link between the neurotoxin BMAA and ALS.

Pesticide exposure and amyotrophic lateral sclerosis

Our objectives were to summarize literature on the association of amyotrophic lateral sclerosis (ALS) with pesticides as a group and to evaluate associations of ALS with specific pesticides. We conducted a meta-analysis of published studies of ALS and pesticides as a group and investigated the association of ALS with specific pesticides, using data from the Agricultural Health Study (AHS), a cohort including 84,739 private pesticide applicators and spouses. AHS participants provided information on pesticide use at enrollment in 1993-1997. In mortality data collected through February 2010, ALS was recorded on death certificates of 41 individuals whom we compared to the remaining cohort (controls), using unconditional logistic regression adjusted for age and gender to calculate odds ratios (ORs) and 95% confidence intervals. In the meta-analysis, ALS was associated with use of pesticides as a group (1.9, 1.1-3.1). In the AHS, ALS was not associated with pesticides as a group, but was associated with use of organochlorine insecticides (OCs) (1.6, 0.8-3.5), pyrethroids (1.4, 0.6-3.4), herbicides (1.6, 0.7-3.7), and fumigants (1.8, 0.8-3.9). ORs were elevated forever use of the specific OCs aldrin (2.1, 0.8-5.1), dieldrin (2.6, 0.9-7.3), DDT (2.1, 0.9-5.0), and toxaphene (2.0, 0.8-4.9). None of these associations was statistically significant. Similar results were observed in an analysis restricted to men. In conclusion, the meta-analysis suggests that ALS risk is associated with use of pesticides as a group, and our analysis of AHS data points to OC use in particular. The latter results are novel but based on a small number of cases and require replication in other populations.

Amyotrophic lateral sclerosis: pathophysiology, diagnosis and management

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease associated with a life expectancy of approximately 3 years after symptom onset, but the range of survival extends from a few months for some to decades for approximately 5% of patients. There is no clear cause in the majority of cases and just one medication, riluzole, has been shown to modestly prolong survival. Research has identified some of the cellular processes that occur after disease onset, including mitochondrial dysfunction, protein aggregation, generation of free radicals, excitotoxicity, inflammation and apoptosis, but for most patients the underlying cause is unknown. While ALS is considered to be a complex genetic disorder in which multiple genes in combination with environmental exposures combine to render a person susceptible, few genetic or environmental risks have been discovered to date. The diagnosis is based on the history and examination showing progressive upper and lower motor neuron findings. The electromyogram can help confirm the diagnosis, and additional tests are used to exclude other conditions. Published practice parameters guide the care of patients with ALS. Until the elucidation of aetiologies leads to the development of more robust neuroprotective agents, both pharmacological and nonpharmacological treatments are directed at maintaining quality of life and prolonging life to the greatest extent possible. Riluzole, ventilatory support for those with respiratory insufficiency, gastrostomy for those with dysphagia and multidisciplinary care may help extend life. The off-label use of many symptomatic agents can have a meaningful impact for those with the illness. Palliative care ensures dignity toward the end stages of the disease. Clinical trials currently aim to slow disease progression by testing drugs that impact one or more of the processes that are initiated after disease onset. Novel therapies currently in trials include potential neuroprotective agents with differing mechanisms of action, vaccine therapies, stem cell injections and diaphragmatic pacing.

The cyanobacteria derived toxin Beta-N-methylamino-L-alanine and amyotrophic lateral sclerosis

There is mounting evidence to suggest that environmental factors play a major role in the development of neurodegenerative diseases like ALS (Amyotrophic Lateral Sclerosis). The non-protein amino acid beta-N-methylamino-L-alanine (BMAA) was first associated with the high incidence of Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) in Guam, and has been implicated as a potential environmental factor in ALS, Alzheimer’s disease, and other neurodegenerative diseases. BMAA has a number of toxic effects on motor neurons including direct agonist action on NMDA and AMPA receptors, induction of oxidative stress, and depletion of glutathione. As a non-protein amino acid, there is also the strong possibility that BMAA could cause intraneuronal protein misfolding, the hallmark of neurodegeneration. While an animal model for BMAA-induced ALS is lacking, there is substantial evidence to support a link between this toxin and ALS. The ramifications of discovering an environmental trigger for ALS are enormous. In this article, we discuss the history, ecology, pharmacology and clinical ramifications of this ubiquitous, cyanobacteria-derived toxin.

Flavin-containing monooxygenase mRNA levels are up-regulated in als brain areas in SOD1-mutant mice

Flavin-containing monooxygenases (FMOs) are a family of microsomal enzymes involved in the oxygenation of a variety of nucleophilic heteroatom-containing xenobiotics. Recent results have pointed to a relation between Amyotrophic Lateral Sclerosis (ALS) and FMO genes. ALS is an adult-onset, progressive, and fatal neurodegenerative disease. We have compared FMO mRNA expression in the control mouse strain C57BL/6J and in a SOD1-mutated (G93A) ALS mouse model. Fmo expression was examined in total brain, and in subregions including cerebellum, cerebral hemisphere, brainstem, and spinal cord of control and SOD1-mutated mice. We have also considered expression in male and female mice because FMO regulation is gender-related. Real-Time TaqMan PCR was used for FMO expression analysis. Normalization was done using hypoxanthine-guanine phosphoribosyl transferase (Hprt) as a control housekeeping gene. Fmo genes, except Fmo3, were detectably expressed in the central nervous system of both control and ALS model mice. FMO expression was generally greater in the ALS mouse model than in control mice, with the highest increase in Fmo1 expression in spinal cord and brainstem. In addition, we showed greater Fmo expression in males than in female mice in the ALS model. The expression of Fmo1 mRNA correlated with Sod1 mRNA expression in pathologic brain areas. We hypothesize that alteration of FMO gene expression is a consequence of the pathological environment linked to oxidative stress related to mutated SOD1.

Association of smoking with amyotrophic lateral sclerosis risk and survival in men and women: a prospective study

Background

Previous epidemiologic studies have examined the association of smoking with amyotrophic lateral sclerosis (ALS) incidence, but their results have been inconsistent. Moreover, limited information exists on the association between smoking and survival in ALS patients. We evaluated the association of smoking with ALS incidence and survival in a population-based cohort.

Methods

We conducted a case-control study nested in the General Practice Research Database, a computerized clinical database in the United Kingdom. Cases were 1143 individuals with a diagnosis of ALS; 11,371 matched controls were selected among GPRD participants free of ALS. Predictors of survival were determined in the ALS cases. Smoking information was obtained from the computer database.

Results

Smoking was not associated with the risk of ALS in this population. The rate ratio (RR) of ALS comparing ever versus never smokers was 1.04, 95% confidence interval (CI) 0.80-1.34. In analysis stratified by gender, however, ever smoking was associated with ALS in women (RR 1.53, 95% CI 1.04-2.23) but not in men (RR 0.75, 95% CI 0.53-1.06). Mortality was 71% after 2.1 average years of follow-up. Old age and female sex were associated with lower survival. Smoking was a predictor of mortality only in women. Comparing ever versus never smokers, RR (95% CI) of death was 1.31 (1.04-1.65) in women, and 0.90 (0.72-1.11) in men.

Conclusion

In this large population-based study, smoking was associated with ALS risk and worse survival in women but not in men.