Mice developed Parkinson's disease after being injected with a mild stomach injury – a finding that provides even more evidence of the connection between the gut and the brain.
In recent years, a series of studies have shown that gut bacteria seem to play an important role in triggering neurodegenerative diseases.
And this new study by neuroscientists in Canada adds weight to that emerging field of research.
After injecting mice with a mild intestinal bacterium, they watched as they sent their immune system to overdrive, reducing the release of dopamine from the brain – a substance that controls movement – and ultimately leads to a form of Parkinson's.
The team believes the findings will translate to people and can lead to the development of a drug that targets the gut to prevent devastating brain disease.
The team believes that the findings will translate to humans, and can lead to the development of a drug that targets the gut to prevent devastating brain disease (file image)
It suggests that some forms are an autoimmune system – where the immune system accidentally attacks the body – and an & # 39; time window & # 39; offers to stop Parkinson's.
These cases probably start in the gut years before patients notice any symptoms of shaking or stiffness.
Dr. co-prime author Diana Matheoud, a neuroscientist at the University of Montreal in Canada, said it contributes to a & # 39; growing number of evidence & # 39; that implies the gut in Parkinson's.
She said: & # 39; This also provides a model to characterize the onset and to develop therapeutic approaches. & # 39;
The study, published in the journal Nature, sheds new light on the degenerative nerve disease that affects one million Americans and 127,000 British.
It prolongs recent work from the same group that has identified a link between Parkinson's and the immune system.
The disease is now & # 39; the world's fastest growing neurological disease – before dementia.
High-ranking victims include actor Michael J Fox, who was diagnosed at the age of 29, and late boxing legend Muhammad Ali. Other patients are Billy Connolly and Sweet Caroline singer Neil Diamond. And this week, the founder of ESPN has revealed that he has also been diagnosed.
Parkinson's is now & # 39; the world's fastest growing neurological disease – before dementia.
There are now around 6.9 million patients worldwide – the number is expected to grow to 14.2 million in 2040. This would qualify as a pandemic.
About one in 10 cases is due to mutations in genes known as PINK1 and Parkin that are responsible for healthy mitochondria – the power stations of cells.
They trigger Parkinson's at a much younger age. But in lab mice they do not cause any symptoms of disease – and the reason may lie in their intestines.
These animals are normally kept in germ-free facilities – conditions that are not representative of those people who are constantly exposed to insects.
In Parkinson's neurons that produce dopamine are destroyed – leading to the much-known tremors. The causes remain unknown.
Dr. co-author Louis-Eric Trudeau, based in the same laboratory, said: “Most of Parkinson's current models are based on the belief neurons that die as a result of toxic elements that accumulate therein.
& # 39; However, this does not explain the fact that Parkinson's disease is initiated in patients a few years before the onset of motor impairment and any noticeable loss of neurons. & # 39;
The Canadian team thinks they have discovered the reason. They infected young mice without the PINK1 gene with a bacterium called Citrobacter rodent.
It mimics the common food poisoning bug E. coli in humans – and causes intestinal inflammation.
The animals developed Parkinson's-style symptoms as they grew older – despite being free from the PINK1 mutation that kills brain cells.
In addition, these were temporarily reversed by injecting them with a drug called L-DOPA – which is used to treat patients.
In normal mice, the immune system reacted correctly to the intestinal infection. But for those without PINK1 it reacted excessively. This caused & # 39; autoimmunity & # 39; – a process that causes the immune system to attack healthy cells.
Rather than dying from the accumulation of toxins, killing dopamine-producing neurons is accompanied by immune cells, the researchers say.
In the infected genetically engineered mice, autoreactive toxic immune cells, called T lymphocytes, were found to be present in the brain.
In laboratory tests on healthy neurons grown in culture dishes they could attack them, the researchers said.
Co-author Dr. Samantha Gru Unit, a microbiologist at McGill University in Montreal, is convinced of the link between Parkinson's and infection.
It will stimulate further research – allowing researchers to develop and test new therapies, she said.
Neuroscientists Dr. Mary Herrick, of Emory University, and Dr. Malu Tansey, of the University of Florida, who were not involved in the study, said it & # 39; compelling reasons & # 39; offers to re-examine the roles of PINK1 and parkin after inherited Parkinson's.
They said the findings suggest that all forms may be more similar than previously thought – and probably relate to dysfunction of both the innate and adaptive branches of the immune system, whose roles in Parkinson's have yet to be fully investigated.
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