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The Hidden Links of Parkinson’s Disease

Discover how gut health influences Parkinson's disease and overall brain function.

Sriparna Mukherjee, Vladimir Grouza, Alex Tchung, Amandine Even, Moein Yaqubi, Marius Tuznik, Tyler Canon, Sherilyn Junelle Recinto, Christina Gavino, Marie-Josée Bourque, Heidi McBride, Michel Desjardins, Samantha Gruenheid, Jo Anne Stratton, David A. Rudko, Louis-Eric Trudeau

― 7 min read


Gut Health and Gut Health and Parkinson’s Disease Parkinson's development. Exploring gut bacteria's role in
Table of Contents

Parkinson’s disease (PD) is a common neurological disorder that affects millions of people around the world. It's not just about shaky hands and slow movements; it’s a condition that gets more complicated the more we learn about it. Scientists are starting to figure out that PD doesn’t just happen in the brain-it can also involve other parts of the body, particularly the gut.

What is Parkinson’s Disease?

Parkinson’s disease is a progressive disorder that mainly affects movement. It happens when nerve cells in the brain, particularly those that produce dopamine (a chemical that helps control movement), start to break down and die. This leads to symptoms like tremors, stiffness, and difficulty with balance.

But here’s the twist: PD is not just a brain issue. Recent studies point out that the disease could begin in other parts of the body, like the gut. Yes, that’s right! The belly could be where it all begins. It turns out that there’s a connection between our gut health and our brain health-who knew our stomachs had so much say in how we move?

The Growing Knowledge of PD

For many years, PD was thought to be a disease that only affected brain cells. However, researchers now understand that it's more complicated. People with Parkinson’s not only lose these dopamine-producing neurons but also experience issues in other systems of the body. This includes damage to the gut, changes in the immune system, and even problems with energy production in cells.

Researchers have also found that a protein called alpha-synuclein plays a significant role in the disease. This protein, which tends to bunch up in the brains of people with PD, can also be found in the gut, skin, and heart. Imagine having a party crasher that shows up at all your favorite spots!

A Hungry Bacteria and Its Role

One interesting thing that researchers are looking into is the impact of gut bacteria on PD. Studies have shown that people with PD have different types of bacteria in their GUTS compared to healthy people. Some bacteria seem to be less present, while others are more abundant. Think of it as a bacterial party where some guests are missing!

For instance, researchers have noted a drop in the group of bacteria called Prevotellaceae and an increase in Enterobacteriaceae among PD patients. So, it’s possible that an upset gut environment might contribute to the downhill slide of our nervous system.

But wait, there’s more! It appears that certain bacterial infections could even increase the risk of developing Parkinson’s disease. One particular troublemaker, Helicobacter pylori, is known to invade the stomach and has been linked to a higher risk of PD. The plot thickens!

The Gut-Brain Connection

The idea that what happens in our gut can affect our brain has birthed the phrase “the gut-brain axis.” This connection suggests that not only does our gut have a say in our digestion, but it might also influence our mood, our movement, and even the progression of diseases like Parkinson’s.

When bad bacteria take over, it can mess with the gut lining, leading to what’s called "leaky gut." This condition allows bad stuff to get into the bloodstream and potentially trigger Inflammation in the body, including the brain. It’s like having an uninvited guest sneaking into your house through a back door-one that might start throwing a wild party!

The Role of Inflammation

Inflammation-a fancy word for the body’s response to injury or irritation-seems to be a hot topic in the study of PD. When infections or harmful substances show up, the immune system kicks in. However, if the body stays inflamed for too long, it can do more harm than good.

Studies have indicated that bacterial infections could alert the immune system, which then potentially leads to chronic inflammation. This could contribute to the brain’s problems over time, making it relate to the development of Parkinson’s. It's like keeping a fire burning when you really only wanted a cozy campfire!

Animal Studies Bring New Insights

To gain a better understanding of how these processes work, scientists often study animals, such as mice. In recent experiments, researchers infected mice with a bacteria called Citrobacter rodentium. This particular bacteria is a model of what happens in gut infections and allows scientists to explore the effects of gut health on brain function.

When they looked at the mice infected with Citrobacter, they noticed significant changes in their guts and brains over time. Infected mice showed increased inflammation and changes in their gut bacteria, which led scientists to question if these infections could also impact the brain’s health.

Interestingly, the way the immune system responded to the infection and the resulting changes in gut health could influence brain inflammation and overall health. This gives us some clues about how PD might be connected to gut health.

Immune Responses and Their Impact

In their quest for answers, researchers found that after a gut infection, the immune system in the mice responded robustly. This reaction included an increase in certain immune cells and molecules that promote inflammation. In simple terms, the mice’s Immune Systems were on high alert, much like a fire alarm screaming for attention.

What researchers found particularly intriguing was that in mice lacking a specific protein called Pink1, known for its role in energy production and protection against cellular stress, the immune response was heightened. This suggests that Pink1 might help regulate how the immune system reacts to infections and could play a role in PD, considering that some genetic forms of PD involve mutations in this protein.

The Search for the Missing Links

So, what does this all mean for those of us trying to get a handle on Parkinson’s? It means there may be more than one path leading to the disease. Researchers are piecing together the puzzle-figuring out how genetic factors interact with environmental ones. They’re looking at everything from gut bacteria to immune responses to see how they all play a part in the development of PD.

The results thus far suggest that there’s a complicated web connecting the gut health of individuals with the risk of developing Parkinson’s disease. While it may not be a straightforward route, it certainly gives us a lot to think about.

Implications for Prevention and Treatment

As we uncover more about the connections between gut health and PD, it opens up potential avenues for prevention and treatment. This could mean finding new ways to support gut health or even developing treatments that could help protect against or slow the progression of Parkinson’s disease.

Imagine a future where taking care of your gut could be as important as exercise and diet for keeping your brain healthy. It’s hopeful and, let’s be honest-a little funny to think that eating right could help keep your brain fit!

Conclusion

While Parkinson's Disease is a complex and challenging condition, research continues to shed light on various factors that contribute to its development. The relationships between gut bacteria, inflammation, and immune responses provide fascinating insights into a disorder that affects so many lives.

In the end, it’s all about the interconnectedness of our bodies. Just as we should watch what we put in our stomachs, we might also need to pay attention to how it all affects our brains. So, the next time you think about what to eat, remember: you could be making a choice for both your gut and your noggin!

Original Source

Title: A single Citrobacter rodentium infection in Pink1 knockout and wild type mice leads to regional blood-brain-barrier perturbation and glial activation without dopamine neuron axon terminal loss

Abstract: A growing body of research supports the hypothesis of links between immune system activation and the development of Parkinsons disease (PD). A recent study revealed that repeated gastrointestinal infection with Citrobacter rodentium can lead to PD-like motor dysfunction in Pink1 knockout (KO) mice and immune cell entry in the brain. With the objective of better understanding the mechanisms leading to immune attack of the brain in this model, we evaluated the hypothesis that such mild infections are sufficient to increase blood brain barrier (BBB) permeability and cause brain inflammation. Pink1 wild-type (WT) and KO mice were infected with Citrobacter rodentium and at day 13 and 26 post infection, we conducted gadolinium-enhanced magnetic resonance imaging (MRI) to identify signs of BBB permeability changes. Quantification of MRI results provided evidence of increased blood-brain barrier permeability in both WT and Pink1 KO mice at 26 days after the infection in the striatum, dentate gyrus, somatosensory cortex, and thalamus. This was not accompanied by any change in global expression of tight-junction proteins or in markers of the integrity of the dopamine (DA) system in the striatum at both time points. However, chronic microglial activation was detected at day 26 post infection, accompanied by an elevation of the inflammatory mediators eotaxin, IFN{gamma}, CXCL9, IL-17 and MIP-2 in the striatum, accompanied by an elevation of IL-17 and CXCL1 in the serum of Pink1 KO mice. Neutrophil infiltration in the brain of infected mice was also noted at day 26 post infection, as revealed by immune cell profiling by flow cytometry. Finally, a bulk RNA-seq transcriptome analysis revealed that gene sets related to synaptic function were particularly influenced by the infection and that inflammation-related genes were upregulated by the infection in the Pink1 KO mice. Our results support the hypothesis that even after mild gastro-intestinal infection, increased BBB permeability could contribute to perturbations of brain homeostasis including altered expression of synaptic genes, increased microglial activation and the establishment of a chronic state of brain inflammation. Such perturbations could potentially act as a first hit for subsequent induction of PD pathology in the context of aging in genetically susceptible individuals. Author summaryWe hypothesize that immune system activation is linked to the development of Parkinsons disease (PD). Previously work revealed that repeated gastrointestinal infections with Citrobacter rodentium causes PD-like symptoms and immune cell invasion in the brain of Pink1 knockout (KO) mice. In the current study, we tested whether a single mild gut infection alters blood-brain barrier (BBB) permeability and causes brain inflammation. We infected Pink1 WT and KO mice with Citrobacter rodentium and used gadolinium-enhanced MRI to detect BBB permeability changes at 13- and 26-days post-infection. Results showed increased BBB permeability in specific brain regions at 26 days. While tight-junction and dopamine (DA)-related proteins remained unchanged, we observed altered expression of synaptic genes, chronic microglial activation, elevated inflammatory markers, and neutrophil infiltration in the brain. Our findings suggest that even mild gastrointestinal infections can increase BBB permeability, which could be permissive for immune cell entry into the brain and potentially interact with other mechanisms triggering PD pathophysiology, particularly in genetically susceptible individuals.

Authors: Sriparna Mukherjee, Vladimir Grouza, Alex Tchung, Amandine Even, Moein Yaqubi, Marius Tuznik, Tyler Canon, Sherilyn Junelle Recinto, Christina Gavino, Marie-Josée Bourque, Heidi McBride, Michel Desjardins, Samantha Gruenheid, Jo Anne Stratton, David A. Rudko, Louis-Eric Trudeau

Last Update: Dec 24, 2024

Language: English

Source URL: https://www.biorxiv.org/content/10.1101/2024.12.24.630165

Source PDF: https://www.biorxiv.org/content/10.1101/2024.12.24.630165.full.pdf

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to biorxiv for use of its open access interoperability.

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