Congressional briefing on neurological diseases and the environment (Environmental Factor, April 2018)

Congressional staffers representing House and Senate offices, along with public health policy professionals, attended a March 8 briefing on Capitol Hill to learn more about connections between neurological diseases and the environment. NIEHS and National Toxicology Program Director Linda Birnbaum, Ph.D., was one of three experts who made presentations.

She was joined by Avraham Reichenberg, Ph.D., from the Icahn School of Medicine at Mount Sinai, and Caroline M. Tanner, M.D., Ph.D., from the University of California at San Francisco and the San Francisco Veterans Affairs Health Care System. The three shared scientific findings regarding neurological diseases across the lifespan.

Reichenberg, Tanner, Birnbaum, Meyer, and Thompson

From right, Reichenberg, Tanner, and Birnbaum were joined by MJFF representatives Brittany Meyer, J.D., associate director for public policy, and Ted Thompson, J.D., senior vice president for public policy. (Photo courtesy of Jed Bullock)

The event was co-sponsored by four groups.

The Friends of the National Institute of Environmental Health Sciences (FNIEHS).
The Michael J. Fox Foundation (MJFF).
The Congressional Caucus on Parkinson’s Disease.
The Congressional Neuroscience Caucus.

Attendees, numbering more than 60, asked questions of all three scientists. Interests covered a wide range of topics, including the mechanisms involved in environmental influences on health, the need for clinicians to ask patients about environmental exposures, exposures children may face when outside the home in school or daycare settings, and drinking water sources contaminated by arsenic.

Exposures, genes, and neurological disease

Birnbaum highlighted neurological diseases known to have an environmental component.

Alzheimer’s disease.
Amyotrophic lateral sclerosis (ALS).
Autism spectrum disorder (ASD).
Depression.
Multiple system atrophy.
Parkinson’s disease (PD).
Progressive supranuclear palsy.
Schizophrenia.

NIEHS-funded research has uncovered environmental connections with these conditions, according to Birnbaum, including a finding that prenatal vitamins reduce the risk of autism, and organophosphate (OP) pesticide exposure can speed progression of PD.

The scientists spoke to a packed room. Birnbaum emphasized that our brains are especially vulnerable to exposures during developmental periods, such as early life and puberty. (Photo courtesy of Jed Bullock)

Genetic variations may make a person more susceptible to exposures, she explained. “PD patients with lower expression of the PON1 gene, which is important for OP metabolism, showed faster progression of motor and depressive symptoms,” Birnbaum told the audience.

One attendee asked about environmental risk factors for ALS. Birnbaum described growing evidence that exposure to air pollution, especially near-roadway pollution, is associated with increased risk of ALS. The American Academy of Neurology announced results of a preliminary study, partially funded by NIEHS, that found links between increased exposure to diesel exhaust and higher risk of ALS in Denmark.

Schizophrenia, Parkinson’s

Scientists know that genetics and our environment contribute to neurological disorders, but more research is needed to understand this complex biological relationship. (Photo courtesy of NIEHS)

Reichenberg, an NIEHS grantee who also receives funding from the Eunice Kennedy Shriver National Institute on Child Health and Human Development, presented studies on environmental factors involved in schizophrenia and ASD. He said that more than 100 risk factors have been found for autism, and 170 have been found for schizophrenia. Genes play an important role, according to Reichenberg, but to focus only on heritability is to oversimplify the causes.

According to Tanner, whose research has been funded by NIEHS and the National Institute of Neurological Disorders and Stroke (NINDS), the global burden of PD is expected to rise with increasing life expectancy worldwide. “Current evidence suggest only 10 percent of all parkinsonism is caused by a single genetic defect,” she said, citing twin studies. “The environment is an important contributor to the cause of PD.”

The theme of gene-environment interaction is important in Tanner’s work as well. Using data from the Agricultural Health Study, which is funded by NIEHS, the National Cancer Institute, and others, Tanner examined links between PD and exposure to the pesticide, paraquat. She reported that the risk of PD was associated with the combination of paraquat exposure and having a particular variant of a gene known as GSTT1.

Prevention is possible

Tanner presented the promising findings of further research that showed that increased risk of PD was not observed in farmers using gloves during pesticide application. She recommended further research into links between PD and preventable exposures, as well as preventative therapies.

Birnbaum emphasized the promise of prevention. “Environmental factors are more readily identified and modified than genetic factors, and therefore present tremendous opportunity to prevent noncommunicable disease,” she said.

Citations:
Schmidt RJ, Hansen RL, Hartiala J, Allayee H, Schmidt LC, Tancredi DJ, Tassone F, Hertz-Picciotto I. 2011. Prenatal vitamins, one-carbon metabolism gene variants, and risk for autism. Epidemiology 22(4):476–485.

Paul KC, Sinsheimer JS, Cockburn M, Bronstein JM, Bordelon Y, Ritz B. 2017. Organophosphate pesticides and PON1 L55M in Parkinson's disease progression. Environ Int 107:75–81.

Modabbernia A, Velthorst E, Reichenberg A. 2017. Environmental risk factors for autism: an evidence-based review of systematic reviews and meta-analyses. Mol Autism 8:13.

Radua J, Ramella-Cravaro V, Ioannidis JPA, Reichenberg A, Phiphopthatsanee N, Amir T, Yenn Thoo H, Oliver D, Davies C, Morgan C, McGuire P, Murray RM, Fusar-Poli P. 2018. What causes psychosis? An umbrella review of risk and protective factors. World Psychiatry 17(1):49–66.

Tanner CM, Ottman R, Goldman SM, Ellenberg J, Chan P, Mayeux R, Langston JW. 1999. Parkinson disease in twins: an etiologic study. JAMA 281(4):341–346.

Goldman SM, Kamel F, Ross GW, Bhudhikanok GS, Hoppin JA, Korell M, Marras C, Meng C, Umbach DM, Kasten M, Chade AR, Comyns K, Richards MB, Sandler DP, Blair A, Langston JW, Tanner CM. 2012. Genetic modification of the association of paraquat and Parkinson's disease. Mov Discord 27(13):1652–1658.

Furlong M, Tanner CM, Goldman SM, Bhudhikanok GS, Blair A, Chade A, Comyns K, Hoppin JA, Kasten M, Korell M, Langston JW, Marras C, Meng C, Richards M, Ross GW, Umbach DM, Sandler DP, Kamel F. 2015. Protective glove use and hygiene habits modify the associations of specific pesticides with Parkinson's disease. Environ Int 75:144–150.