Both environment and genes play vital roles in increasing a person's risk to neurological disorders. However, only genes are often considered to be the main culprit for the disability, and environmental factors are usually overlooked. Recently, scientists from Brigham and Women's Hospital have evaluated the effects of hundreds of environmental factors on the development of neurological disorders.
The findings published in the journal Cell claims that environmental factors heighten neurological inflammation including a herbicide that is banned in Europe and currently in use in the US.
"When we study inflammation and neurodegeneration, we learn that the environment may play just as important of a role as genetics," said corresponding author Francisco Quintana, PhD, a principal investigator in the Ann Romney Center for Neurologic Diseases at the Brigham. "We created a platform to systematically investigate the understudied effects of environmental exposures. As an example, we followed up on one of our top hits, an herbicide currently banned in Europe. The goal of our work is to return results that can guide future epidemiological studies and identify actionable targets."
Using a novel zebrafish model of multiple sclerosis, the team added each compound to the water and evaluated the effects of each one on CNS inflammation. They narrowed in on five compounds that increased the activity of nos2a, a gene associated with inflammation. The researchers tested the compounds in mouse astrocytes--star-shaped cells that reside in the brain and spinal cord. They found that linuron, an herbicide, and methyl carbamate, a compound used by the textile, polymer and pharmaceutical industries, boosted inflammation in the astrocytes.
Linuron is an herbicide used in agriculture to kill grass and weeds. Although currently available in the U.S. and elsewhere, linuron was recently banned in Europe because of its potential risk to mammals. Using bioinformatic analysis, lab-based studies of cells from mice and patients with multiple sclerosis, gene editing, and computational modeling, Quintana and colleagues put together a molecular pathway through which linuron may drive inflammatory responses in astrocytes. Their findings highlight the role of Sigmar1, a membrane receptor that has been linked to the development of neurological disorders such as amyotrophic lateral sclerosis (ALS), a disease that has long been thought to have environmental contributors.
The researchers note that their findings are limited to the 976 compounds tested but that their approach could be scaled up if a larger library of chemicals is available for testing. These studies aim to identify candidate environmental exposures that affect central nervous system inflammation. However, the authors caution that follow-up epidemiological studies will be needed to further evaluate these findings and their implications in humans.
In addition to the current study, Quintana and colleagues are collaborating with the EPA on a parallel study of gut inflammation and the role of ToxCast chemicals in contributing to diseases such as irritable bowel syndrome (IBS). The team is also studying the implications of astrocyte inflammation in brain tumors and are interested in how the newly uncovered pathway may influence the immune response in glioblastoma.
"Our findings support the need for systematic investigation of the effects of the 'exposome'--all of the environmental exposures people experience in their lifetime--on neurologic diseases and other conditions," said Quintana. "Studies of the exposome have the potential to identify unknown origins of inflammation and key environmental factors that may contribute to risk."