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Pathogens lurk in the cat's intestine: toxoplasmosis parasites change our synapses in the brain

Pathogens lurk in the cat's intestine: toxoplasmosis parasites change our synapses in the brain


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Many people infected: How the toxoplasmosis parasite transforms the synapses in the brain

Pets are good for most people. But some of the four-legged friends can transmit diseases. For example, toxoplasmosis, an infectious disease, the causative agent of which can often be found in cat feces. Researchers have now shown in a study how the toxoplasmosis parasite transforms the synapses in the brain.

One of the most common infectious diseases

A few years ago, American scientists reported that some cat owners were more likely to experience aggression and sudden anger. Those who had been infected by Toxoplasma gondii. The worldwide unicellular parasite causes one of the most common infectious diseases, toxoplasmosis.

Unicellular parasite affects birds and mammals

The single-celled parasite Toxoplasma gondii affects birds and mammals - including humans. However, its end hosts are cats.

Researchers from the Institute of Inflammation and Neurodegeneration at the Otto von Guericke University Magdeburg (OVGU) and the Leibniz Institute for Neurobiology (LIN) investigated how the parasite influences the metabolism in the brain of its hosts and demonstrated that it there the molecular composition of synapses changed.

The results of the scientists were published in the specialist journal "Journal of Neuroinflammation".

The disease usually goes unnoticed

According to a communication published by the Science Information Service (idw), around 30 to 50 percent of all people have been infected with toxoplasmas in their lifetime. In the over 50-year-olds, it is even assumed that around 50 percent.

Toxoplasmosis usually goes unnoticed and the infected have no idea that they are infected.

"In healthy people, the infection triggers short-term cold symptoms such as chills, fever and body aches," explains Prof. Dr. Ildiko Rita Dunay, head of the Institute for Inflammation and Neurodegeneration at the OVGU.

“However, such an infection can be dangerous for pregnant women or people with a weakened immune system. There is still no therapy to get rid of the parasite if it affects the brain. Anyone who is infected once will remain so for a lifetime, ”says the expert.

Another problem is that toxoplasmosis often remains undetected in newborns, as experts from the Robert Koch Institute (RKI) reported in the scientific journal "Scientific Reports".

Parasite is absorbed by humans through digestion

The parasite nests in the muscle tissue of infected animals, but not only:

"Toxoplasma gondii is absorbed by humans through the digestive system, gets into the bloodstream and also migrates into the brain, where it can nestle in nerve cells for life" Karl-Heinz Smalla from the Special Laboratory Molecular Biological Techniques at the LIN.

Previous studies by other German researchers have shown that toxoplasmosis can cause serious long-term consequences in the brain.

Scientists from Magdeburg had also found in earlier experiments with mice that animals with Toxoplasma gondii infected showed astonishing changes in behavior:

“The mice, which are prey to cats, had lost their natural fear of cats after the infection. If you presented the smell of cat urine to the rodents, they even seemed to have developed a preference for cats, ”said the researchers.

To explain these changes in behavior, they therefore examined changes in the mouse brains - in particular the molecular composition of synapses, since these are the essential structures for signal processing in the brain.

In cooperation with the Helmholtz Center for Infection Research in Braunschweig, they were able to demonstrate that the amounts in the brain had changed after a toxoplasmosis infection with a total of 300 synaptic proteins.

Proteins on glutamate-releasing excitatory synapses were particularly reduced. On the other hand, increased amounts of proteins involved in immune responses have been found.

Increased immune response

Sulfadiazine is often used to treat toxoplasmosis infections, which in some cases hinders the proliferation of toxoplasmas.

The psychiatrist and neuroscientist Dr. Björn Schott explains: "We now wanted to find out how sulfadiazine treatment affects the molecular changes in the brain caused by infection."

The result: the protein composition in the mouse brains after treatment was comparable to that of non-infected members of the same species.

“All the proteins examined, which are responsible for glutamatergic signal transmission, were back in the normal range. And the inflammatory activity also decreased measurably. "

The infection apparently leads to an increased immune response, which reduces the proteins involved in glutamate-mediated synaptic excitation, while sulfadiazine reduces the toxoplasmas, thereby normalizing the immune response and thus causing synaptic proteins to recover.

Findings could also be relevant for people

These findings could also be medically relevant for humans.

"They support the assumption that Toxoplasma gondii is a risk factor for neuropsychological diseases," said the neuroimmunologist Dunay.

“Malfunction of glutamatergic synapses has been linked to the causes of depression, schizophrenia and autism. Components of the immune response also show references to these diseases, ”explains the expert.

"This suggests that immune responses may cause changes in the synapse that can lead to neuropsychiatric disorders." (Ad)

Author and source information


Video: Brain Parasite Makes Mice Fearless - by Scientific American (July 2022).


Comments:

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