How tiny plastic particles disrupt the gut-brain axis and aggravate Parkinson’s disease
WHO emphasises that while the risks are concerning, the exact effects and safe exposure levels are still unclear, highlighting the urgent need for further research.
Recent research suggests that consuming nanoplastics—tiny plastic particles smaller than 100 nanometres—may worsen Parkinson's disease (PD), a neurological disorder affecting movement and coordination, because certain dopamine-producing nerve cells begin to die.
The study focused on how polystyrene nanoplastics impact the body. These minuscule plastics can infiltrate tissues, interfere with normal cell functions, and accumulate in organs.
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In mice, ingestion of nanoplastics damaged the gut lining, altered the balance of gut bacteria, disrupted intestinal metabolites, and caused liver inflammation.
These findings suggest that environmental nanoplastics may exacerbate Parkinson's disease by disturbing the gut-liver-brain connection, demonstrating that gut health directly influences brain function.
Parkinson's disease affects both motor and non-motor functions. Common motor symptoms include tremors, slowed movements, muscle stiffness, poor balance, and changes in walking. Non-motor symptoms can include sleep disturbances, cognitive difficulties, mood disorders, digestive issues, fatigue, and loss of smell. The disease progressively destroys dopamine-producing neurons, increasing dependence on caregivers, raising the risk of falls and injuries, and, in advanced stages, causing cognitive decline and dementia.
Progressive condition
According to the World Health Organisation, Parkinson's is a serious, progressive condition that significantly contributes to disability worldwide, and access to effective treatment remains limited in many countries.
Globally, PD affects millions and could reach 25 million by 2050. In Kenya, over 8,000 people are estimated to have Parkinson's, but diagnosis and treatment are constrained by limited resources.
Metabolism and the gut
Scientists increasingly believe Parkinson's is not just a brain disorder but also involves metabolism and the gut, meaning changes in the digestive system can affect brain health.
In the study, mice that consumed small amounts of polystyrene nanoplastics over roughly three months experienced significant gut damage. About a third of their mucus-producing goblet cells were lost, and more gut cells died than usual, weakening the gut barrier and making it easier for harmful substances and bacteria to affect other organs.
The gut bacteria also changed dramatically. Although bacterial diversity increased, some changes were harmful. The bacterium Desulfovibrio grew excessively, linked to inflammation and the buildup of α-synuclein, a protein central to Parkinson's disease. The balance between major bacterial groups shifted, further disrupting gut health.
Nanoplastics also altered hundreds of chemicals in the gut, affecting metabolism and key pathways related to inflammation, liver function, detoxification, and energy regulation. The livers of exposed mice showed signs of inflammation, indicating that the effects of nanoplastics are systemic, not confined to the gut.
Disrupt gut-liver-brain axis
The study highlights that nanoplastics can disrupt the gut-liver-brain axis, a critical pathway for overall metabolic and brain health. This disruption may worsen Parkinson's by promoting inflammation, metabolic imbalances, and conditions that favour brain cell damage. The research underscores that environmental exposure to tiny plastic particles could be an overlooked factor in Parkinson's progression, emphasising the importance of gut protection and reduced plastic pollution.
According to the WHO, nanoplastics enter the human body mainly through ingestion and inhalation. People may ingest them via contaminated food or water, allowing particles to pass into the digestive system. Nanoplastics can also be inhaled when airborne particles originate from dust, synthetic textiles, or polluted air, eventually reaching the lungs.
Another study, published in Nature Communications and titled "Anionic Nanoplastic Contaminants Promote Parkinson's Disease‑Associated α‑Synuclein Aggregation," examined how negatively charged polystyrene nanoplastics affect Parkinson's disease. Researchers studied interactions with α-synuclein, a brain protein that normally supports neuron function. In Parkinson's, α-synuclein clumps into toxic aggregates, damaging dopamine-producing neurons in the substantia nigra.
The study found that nanoplastics bind strongly to α-synuclein and accelerate the formation of harmful clumps. Even very small amounts sped up protein aggregation. In lab experiments, nanoplastics entered neurons and disrupted lysosomes, the cells’ waste disposal system, making it harder for neurons to break down toxic protein aggregates.
In mice, exposure to both α-synuclein fibrils and nanoplastics caused clumps to spread widely throughout the brain, particularly affecting dopamine-producing neurons. Surprisingly, nanoplastics alone, over time, could trigger α-synuclein aggregation in neurons.
Environmental exposure
The study suggests that environmental exposure to nanoplastics may worsen or even trigger Parkinson's disease. By promoting α-synuclein aggregation and impairing neurons’ cleanup systems, nanoplastics increase vulnerability to brain damage, contributing to symptoms such as tremors, stiffness, and movement difficulties.
Nanoplastics can also trigger inflammation and immune reactions, leading to chronic tissue inflammation in the gut, lungs, or liver, increasing the risk of other diseases. They produce reactive oxygen species, causing oxidative stress that damages cells, DNA, and proteins, potentially contributing to cell death, cancer, or organ dysfunction. In the digestive system, ingested nanoplastics may disrupt the gut lining, alter gut bacteria, and interfere with nutrient absorption, affecting metabolism and overall digestive health.
Research indicates nanoplastics may affect metabolism, including lipid and glucose regulation, potentially raising the risk of obesity, diabetes, or liver disorders. Animal studies suggest nanoplastics can cross the blood-brain barrier, impacting neuron function, promoting protein aggregation, and influencing behaviour, with possible implications for neurodegenerative diseases like Parkinson's.
Chemical additives in some plastics, such as BPA or phthalates, can leach from nanoplastics and interfere with hormone function, affecting growth, reproduction, or thyroid health. Inhaled nanoplastics may accumulate in the lungs, causing inflammation or impaired function.
WHO emphasises that while these risks are concerning, the exact effects and safe exposure levels are still unclear, highlighting the urgent need for further research.
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