Researchers use worms to study Parkinson’s neurodegeneration
Study links tire components, higher temperatures and age to neurodegeneration
Components from tire wear, higher temperatures and age accelerate the degeneration of dopaminergic neurons in Parkinson’s disease, a new study done in nematode worms suggests.
The study, “Tire components, age and temperature accelerate neurodegeneration in C. elegans models of Alzheimer’s and Parkinson’s disease,” was published in the journal Environmental Pollution.
This study emphasizes the use of nematode worms as a model to understand the connections between neurodegeneration, age, and the impact of ambient temperature when exposed to specific elements of non-exhaust emissions or urban aerosols.
The incidence and prevalence of neurodegenerative diseases is increasing rapidly. The global burden of Parkinson’s disease has risen from 2.5 million affected people in 1990 to 6.1 million in 2016.
Besides genetic factors and aging, air pollution also is an identified risk factor for Parkinson’s and other neurodegenerative diseases. Air pollution has been found to correlate with the accumulation of alpha-synuclein in the brain, resulting in the death of dopamine-producing (dopaminergic) neurons, or nerve cells. This results in the depletion of dopamine and Parkinson’s symptoms emerge.
Urban air close to roads with heavy traffic represents a mixture of pollutants, and it was shown that solid nanoparticles also are a component of aerosols.
Tire wear generated by road simulators contained aggregates of nanoparticles that resemble engineered silica nanomaterials. Additionally, material analysis attributed a part of the nano silica in products to car tires and pavements.
Previous studies have identified nano silica as a cause of Parkinson’s neurodegeneration, and other such diseases, in cell cultures in the lab and in the nematode worm model Caenorhabditis elegans (C. elegans).
Widely used in aging research
C. elegans is widely used in aging research, considering it is an organism with a short life cycle and a mean lifespan of 15-20 days. Its genome is fully sequenced and more than 60% of its genes have the same structure and function as human genes.
Moreover, several age-associated features are conserved between C. elegans and humans, including progressive degeneration of different tissues, decline in physiological functions and stress resistance, and increased probability of death with age.
These conserved features can be analyzed under the microscope to study the effects of genetic or environmental factors on the aging and disease processes, with implications for human health.
Based on this knowledge, researchers at Leibniz Research Institute for Environmental Medicine in Düsseldorf, Germany, studied the influence of nano silica, as an example of a tire wear component, and age on a C. elegans model of Parkinson’s disease. Additionally, different ambient temperatures were tested, having in mind the effects of global warming.
Nano silica from different sources, including genuine tire components, accelerated the neurodegeneration of dopaminergic neurons in the Parkinson’s worm model. This effect was accelerated with increased age and exposure to higher temperatures.
Dendritic beading
Neurodegeneration was analyzed based on dendritic beading, a general indicator of the degeneration of single neurons, which represents an early step of a cascade that leads to neuronal death.
Moreover, middle-aged worms were found to be the most vulnerable age group, with the percentage of neurodegeneration increasing with age from young (6 days) to middle-aged (10 days) worms, and with a higher ambient temperature of 25 degrees Celsius (77 degrees Fahrenheit).
Specifically, in middle-aged worms, exposure to nano silica induced 85% dendritic beading at 15 C (59 F), 75% at 20 C (68 F), and 90% at 25 C (77 F).
Moreover, young animals exposed to nano silica particles showed signs of neurodegeneration earlier.
“Taken together, the discovery of … silica-induced neurodegeneration in the nematode [C. elegans] strengthens the environmental relevance of our results and previous modelling of nano silica as component of tire wear that distributes in the environment,” the researchers wrote.
Similar results were observed in a C. elegans model of Alzheimer’s disease, which revealed worms were particularly sensitive to the effects of tire wear, age, and temperature, observed by a reduction in nerve function measured by neuromuscular (swimming) fitness of the worms.
“This is the first time that we have studied the effect of temperature on the degeneration of neurons, and the results are really exciting,” Anna von Mikecz, the senior author of the study, said in a press release. She added  that “the studies in C. elegans Alzheimer’s and Parkinson’s models show that cold ambient temperature prolongs their health span.”
However, nano silica is only one component of tire wear, and future studies should include more constituents as well as environmental samples in neurodegeneration experiments.
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