A chemogenomic approach is required for effective treatment of amyotrophic lateral sclerosis

ALS is a fatal untreatable disease involving degeneration of motor neurons. Μultiple causative genes encoding proteins with versatile functions have been identified indicating that diverse biological pathways lead to ALS. Chemical entities still represent a promising choice to delay ALS progression, attenuate symptoms and/or increase life expectancy, but also gene-based and stem cell-based therapies are in the process of development, and some are tested in clinical trials. Various compounds proved effective in transgenic models overexpressing distinct ALS causative genes unfortunately though, they showed no efficacy in clinical trials. Notably, while animal models provide a uniform genetic background for preclinical testing, ALS patients are not stratified, and the distinct genetic forms of ALS are treated as one group, which could explain the observed discrepancies between treating genetically homogeneous mice and quite heterogeneous patient cohorts. We suggest that chemical entity-genotype correlation should be exploited to guide patient stratification for pharmacotherapy, that is administered drugs should be selected based on the ALS genetic background.

Cycad exposure and risk of dementia, MCI, and PDC in the Chamorro population of Guam

OBJECTIVE

To study cycad-derived products as possible risk factors for dementia, mild cognitive impairment (MCI), and parkinsonism-dementia complex (PDC) on Guam.

METHODS

Complete risk factor data from in-person interviews of 166 cases of Guam dementia, 50 cases of amnestic MCI, and 21 cases of PDC were compared with 1,581 controls in the base population regarding exposure to cycad-derived products from a traditional food (fadang), consumption of fruit bats, and use of cycad-derived topical medicine.

RESULTS

Adjusted odds ratios (ORs) and 95% CIs for picking, processing, and eating fadang in young adulthood ranged from 1.42 (1.05 to 1.91) to 2.87 (1.48 to 5.56) and were consistently elevated and significant across all three diagnostic outcomes. Associations independent of exposure in young adulthood were for picking (OR 0.78, 95% CI 0.64 to 0.96) and processing (OR 0.77, 95% CI 0.63 to 0.94) fadang in childhood with Guam dementia. Men showed stronger and more consistent relations across exposure groups in young adulthood compared with women. No associations were found for consumption of fruit bats or exposure to cycad used as a topical medicine for any of the outcomes. Estimated adjusted population attributable risks suggest that exposure to eating fadang in young adulthood incurred the highest attributable risk percent.

CONCLUSIONS

Environmental lifestyle and diet may contribute to the etiology of neurodegenerative diseases in the native population of Guam.

Cycad toxins, Helicobacter pylori and parkinsonism: cholesterol glucosides as the common denomenator

Understanding sporadic cases of age-dependent neurodegenerative diseases such as parkinsonism requires the evaluation of potential environmental factors. Amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC), a neurological disorder in which features of parkinsonism are present and for which no consistent genetic explanation has been found, has been linked to the consumption of cycad (Cycas micronesica). Similarly, epidemiological evidence suggests an association between parkinsonism and gastric ulcer caused by Helicobacter pylori infection. While common immunological and inflammatory changes have been proposed to account for the link between parkinsonism and H. pylori infection, we propose an alternate explanation based on our work on the "cycad theory" of ALS-PDC. Recent experiments in our laboratory have identified several sterol glucosides in cycad that have neurotoxic properties in vitro and that appear to be linked to the development of neurodegenerative disease in vivo. Specifically, mice fed cycad display behavioural symptoms of parkinsonism such as reduced gait length, as well as neuropathological signs such as a loss of striatal dopaminergic (DAergic) terminals and an upregulation of the dopamine D2 receptor. These cycad-derived sterol glucosides are structurally similar to cholesterol glucosides that account for a significant part pf the lipid profile of H. pylori. We hypothesize that cholesterol glucosides arising from H. pylori infection may act as neurotoxins, promoting the degeneration of the DAergic neurons affected in parkinsonism, in a similar reaction to that which is thought to link cycad consumption and ALS-PDC. This hypothesis will be tested in future studies that will include exposing mice to purified sterol or cholestorol glucosides derived from cycad and comparing these mice behaviourally and neuropathologically to ones chronically infected with H. pylori.

Examining the interaction of apo E and neurotoxicity on a murine model of ALS-PDC

Epidemiological studies have shown a positive relationship between cycad flour consumption and the development of the neurodegenerative disorder, amyotrophic lateral sclerosis – parkinsonism – dementia complex (ALS-PDC). Apolipoprotein E (apo E) allele variations have been associated with genetic susceptibility in neurodegenerative diseases, including ALS-PDC. We have studied cycad toxicity in a mouse model of ALS-PDC with a particular interest in its impact on the central nervous system (CNS) in both apo E knock-out (KO) mice and their wild-type (WT) counterparts. Behavioral motor tests, motor neuron counts, and immunohistochemical staining in brain and spinal cord, as well as routine histological examinations on internal organs, were performed to evaluate cycad toxicity. Plasma cholesterol levels were also measured before and during the study. Cycad treatment was associated with higher levels of plasma cholesterol only in apo E KO mice; increased levels of plasma cholesterol did not result in increased athero genesis. Cycad-fed wild-type mice developed progressive behavioral deficits including ALS-PDC-like pathological outcomes, while cycad-fed apo E KO mice were not significantly affected. Cycad-fed wild-type mice had shorter gait length measurements along with higher active caspase-3 levels in the striatum, substantia nigra, primary motor cortex, and spinal cord as compared with corresponding controls. These changes were associated with decreased labeling for glutamate transporter 1B and tyrosine hydroxylase activity levels. No evidence of cycad toxicity was observed in internal organs of either wild-type or apo E KO mice. Our data demonstrate that apo E KO mice are less susceptible to cycad toxicity, suggesting a role for apo E as a possible genetic susceptibility factor for some forms of toxin-induced neurodegeneration.Key words: apolipoprotein E, amyotrophic lateral sclerosis (ALS), ALS-parkinsonism dementia complex (ALS-PDC), parkinsonism, dementia, neurodegeneration, glutamate transporter, sterol, sterol glucoside.

Cycad neurotoxins, consumption of flying foxes, and ALS-PDC disease in Guam

The Chamorro people of Guam have been afflicted with a complex of neurodegenerative diseases (now known as ALS-PDC) with similarities to ALS, AD, and PD at a far higher rate than other populations throughout the world. Chamorro consumption of flying foxes may have generated sufficiently high cumulative doses of plant neurotoxins to result in ALS-PDC neuropathologies, since the flying foxes forage on neurotoxic cycad seeds.