A new study indicates that tiny particles of polystyrene can promote the clumping of a protein involved in Parkinson’s.

Plastic waste is a growing problem, and as plastics break down the pieces can be problematic. A new study in Science Advances suggests that tiny plastic particles may be the latest environmental contributor to Parkinson’s disease (PD).

Microplastics are defined as particles smaller than 5 millimeters in diameter — for comparison, a grain of rice is 6 millimeters— and can also include nanoplastics (less than 1 micrometer). According to past research, it is common for blood samples to contain polystyrene nanoparticles, which come from pieces of foam packing materials, cups and cutlery. Research has also shown that unlike other kinds of plastic, polystyrene nanoparticles can enter the brain.

Parkinson’s disease is diagnosed when a protein, called alpha-synuclein, begins to clump in vulnerable neurons in the brain. The clumping ultimately affects dopamine, the neurotransmitter that gets progressively lost in PD, leading to early signs of the disease. This new study shows that polystyrene nanoparticles can interact with alpha-synuclein and promote its clumping in test tubes, in brain cells grown in a petri dish, and in mice.

About the Study & Results

Nanoplastic contaminants promote alpha-synuclein clumping.

Researchers mixed alpha-synuclein “seeds” with nanoplastics in test tubes to see if the presence of nanoplastics triggered the clumping of alpha-synuclein. After three days, they observed that, when combined with alpha-synuclein seeds, the nanoplastics promoted the acceleration of alpha-synuclein clumping formations.

Nanoplastic contaminants interact with alpha-synuclein at very specific regions of the protein.

Using computer modeling, the research team predicted a strong interaction between polystyrene nanoparticles and a region of alpha-synuclein. To validate this prediction, the team created a shortened version of alpha-synuclein that lacked the region the nanoparticles were predicted to interact with. Without that part of alpha-synuclein, the nanoparticles did not stick to the protein in lab experiments, indicating that the computer model was accurate.

Nanoplastic contaminants accelerate alpha synuclein clumping in neurons.

In mouse neurons grown in a petri dish, the researchers observed that nanoplastics were internalized into a specific compartment within the cell, called the lysosome, where alpha-synuclein tends to clump. They found that the nanoplastics accelerated the accumulation of pathogenic alpha-synuclein in these cells.

Nanoplastic contaminants accelerate alpha synuclein clumping in the mouse brain.

The researchers injected alpha-synuclein seeds and nanoplastics into the brains of live mice and found that about 20% of dopaminergic neurons — those thought to be crucial in the development of Parkinson’s — internalized both. Injecting the combination into mice led to an increase in alpha-synuclein clumps in dopaminergic neurons and an increase in alpha-synuclein pathology (as measured by molecular markers) compared to injecting the seeds alone. In 3 of 10 mice injected, nanoplastics alone led to alpha-synuclein pathology.

Traces of polystyrene can be found in human brain tissues. Finally, in brain tissue samples obtained from people with Lewy body dementia, a condition characterized by the presence of alpha-synuclein aggregates, the research team identified traces of polystyrene. This discovery suggests the potential presence of plastic nanoparticles in the human brain.

Highlights

•  Alpha-synuclein clumping was triggered and/or accelerated by nanoplastics in three different models — test tubes, brain cells grown in a petri dish and in mice brains.
• The interaction between polystyrene nanoparticles and alpha-synuclein occurs at a specific region in the alpha-synuclein protein.
• In brain tissue samples from people with Lewy body dementia, traces of polystyrene can be detected, suggesting that plastic nanoparticles may be present in human brains.

What does this mean?

Plastic waste may be contributing to Parkinson’s as an environmental factor. However, we do not yet know how such interactions might be happening in humans and whether the type of plastic might play a role.

What do these findings mean to the people with PD right now?

People are exposed to and consume microplastics every day, through breathing, eating foods and drinking liquids — whether they are packaged in plastic or not. Studies like this one are integral to disentangling how the effects of environmental toxicants contribute to the development of PD — we now know that polystyrene nanoparticles can make their way into the brain. Explore the environmental risk factors connected to Parkinson’s.

People who are concerned that they may be experiencing Parkinson’s symptoms should talk to a healthcare provider.

Learn More

The Parkinson’s Foundation believes in empowering the Parkinson’s community through education. Learn more about PD and the topics in this article through our below resources, or by calling our free Helpline at 1-800-4PD-INFO (1-800-473-4636) for answers to your Parkinson’s questions.

• Environmental Factors
• PD & Pollution: Something in the Air
• Top Parkinson’s Science News Articles of 2023

“I study the brain’s immune cells, called microglia,” said Lindsay Mitchell De Biase, PhD, from the University of California, Los Angeles. “Any population of neurons, including dopamine neurons, are intimately surrounded by and permeated by these cells. Whenever there is a challenge to the central nervous system, whether that is an injury or an infection, these cells change the way they function and interact with neurons.”

Through her 2021 Parkinson’s Foundation Stanley Fahn Junior Faculty Award, Dr. De Biase is studying how microglia influence vulnerability of dopamine neurons to Parkinson’s disease (PD). She and her research team hope to find ways to harness the transformative nature of microglia to preserve dopamine neurons and slow PD progression.

Microglial cells regulate central nervous system inflammation and the signaling connections between neurons. Emerging research suggests that mitochondria, organelles which generate the energy necessary to power cells, play an important role in regulating how microglia function. Understanding this interaction between mitochondria and microglial function, particularly the ability of these cells to influence the health of dopamine neurons, is where Dr. De Biase’s research comes into play.

“Many gene mutations that increase the risk for Parkinson’s are mutations in genes related to mitochondrial function,” said Dr. De Biase. “We think that some of these mutations are increasing disease risk, not only by affecting energy production within neurons, but by pushing microglial cells into a damaging, inflammatory state.”

Dr. De Biase is using novel technology to study the role of microglial mitochondria in a mouse model of PD. The intervention strategy she developed could be used in people who are at high risk for developing Parkinson’s, to delay disease development or prevent it. In people with PD, the strategy could create a more neuroprotective environment and preserve remaining dopamine neurons to delay PD progression.

Dr. De Biase’s research involves manipulating the function of microglia to see if it can protect midbrain dopamine neurons, which regulate movement, and play an important role in PD progression. Microglia play a key role in promoting neuronal health by mitigating overactivity and assisting in the formation of new connections between neurons. Dr. De Biase is working to harness these beneficial actions, seeking to “program” microglia to protect dopamine neurons and slow PD progression.

“Microglia are dynamic, malleable cells and could represent therapeutic targets that are highly distinct from others that have been explored thus far,” said Dr. De Biase.

“My greatest hope from our work comes from the fact that microglial cells are so dynamic,” she said. “These cells really can change their properties in many different contexts, and I think that makes them one of the most targetable cell populations in the brain. So, my hope is that what we are learning will reveal strategies that are really feasible for harnessing the neuroprotective abilities of these cells.”

Meet more Parkinson’s researchers! Explore our My PD Stories featuring PD researchers.

People with Parkinson’s disease (PD) are at a higher risk of hospitalization and face many challenges while in the hospital.

Hospital staff may not be familiar enough with PD to understand symptoms or realize they can worsen if you do not receive Parkinson’s medications on time. Careful preparation and clear communication can help minimize complications and recovery time.

People with Parkinson’s and their care partner can use the Five Parkinson’s Care Needs from our Hospital Safety Guide, listed below, to communicate PD needs during a hospital visit, whether planned or unplanned.

1.  I need my hospital chart to include my exact medications and match my at-home schedule.

Why it’s important: Hospitals often follow standardized medication schedules to ensure timely administration for most patients, but this doesn’t prioritize the complex medication routines that people with Parkinson’s follow.

What to look out for: Make sure the hospital records your exact medication times rather than the number of times per day you take them. Otherwise, the hospital will

follow their schedule instead of yours.

What to ask for: Ask to verbally review your hospital medication list and schedule with the hospital care team, confirming that they ordered medications according to the correct specific times. You can also request a printout to review and compare to your Medication Form.

2.  I need to take my Parkinson’s medications within 15 minutes of my usual schedule.

Why it’s important: Delayed or missed doses can lead to falls, difficulty participating in rehabilitation and being less prepared to go home after leaving the hospital.

What to look out for: Many hospitals allow nurses to give medications up to an hour before or after the scheduled time.

What to ask for: Remind nurses when it is almost time for your medications. Ask nurses to help you take your medications according to your home schedule. Describe your symptoms and how they are affected when you do not receive medication on time, every time.

3.  I need to avoid medications that make my Parkinson’s worse. These medications include those that block dopamine, sedatives and certain pain medications.

Why it’s important: Lack of dopamine in the brain is the primary cause of Parkinson’s movement symptoms. When dopamine-blocking medications are given to someone with Parkinson’s, they can worsen the symptoms they are given to treat and cause harmful side effects.

What to look out for: Your care team may prescribe new medications to treat nausea, confusion and psychosis (hallucinations and delusions) without realizing they can worsen Parkinson’s symptoms.

What to ask for: Share the list of harmful medications on the Parkinson’s Care Summary and ask for a safe alternative.

4.  I need to move my body as safely and regularly as possible, ideally three times a day.

Why it’s important: For people with PD, regular movement — often coupled with physical and occupational therapy — is important for controlling PD symptoms, preventing falls and minimizing complications.

What to look out for: In the hospital, your care team may limit your movement to keep you safe, especially if you are weak after surgery, have low blood pressure or have other issues that put you at risk of falling.

What to ask for: Ask for rehabilitation therapy (physical and occupational therapy) if you need help moving safely. If it is safe, continue daily activities, such as dressing, walking to the bathroom, sitting in a chair for meals and taking short walks

5.  I need to be screened for swallowing changes to safely maintain my medication routine and minimize my risk of aspiration pneumonia and weight loss.

Why it’s important: Difficulty swallowing, called dysphagia, is common for people with Parkinson’s. Minor swallowing issues can worsen and create severe complications during a hospital stay.

What to look out for: Staff may order “NPO” (nothing by mouth) with the goal of preventing severe swallowing-related complications, stopping Parkinson’s medications, along with all other food, liquid, and medications. This can make swallowing issues worse!  

What to ask for: Instead of stopping Parkinson’s medications, you want to avoid medication pauses. Ask the nurse about ways to continue Parkinson’s medications safely.

In addition to providing useful information and tools to help you advocate for your best care, and explain the Five Parkinson’s Care Needs to hospital staff, the Hospital Safety Guide provides:

• Forms for you to fill out with personal care details and medication schedules.
• Tips for care partners.
• Parkinson’s care information to share with the hospital care team.

Order and download the free Hospital Safety Guide right now.