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Many people are infected: how the toxoplasmosis parasite transforms brain synapses
Pets do a great job for most people. But some four-legged friends can transmit diseases. For example, toxoplasmosis, an infectious disease whose pathogen is often found in cat feces. Researchers have now shown in a study how the toxoplasmosis parasite reconstructs 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 be badaulted and irascible. For those who have been infected with Toxoplasma gondii. The unicellular parasite worldwide is one of the most common infectious diseases, toxoplasmosis.
A unicellular parasite infests birds and mammals
Toxoplasma gondii, a unicellular parasite, infests birds and mammals, including humans. His last hosts, however, are cats.
Researchers from the Institute for Inflammation and Neurodegeneration of the Otto von Guericke University of Magdeburg (OVGU) and the Institute of Neurobiology of Leibniz (LIN) have studied in the from a study how the parasite affects the metabolism of the brain of its hosts it changes the molecular composition of synapses.
The results of the scientists were published in the journal "Journal of Neuroinflammation".
The disease usually goes unnoticed
According to a report published by Informationsdienst Wissenschaft (idw), around 30 to 50% of all people have been infected with toxoplasma in their lifetime. For those over 50, they even count for around 50%.
Most toxoplasmosis go unnoticed and infected people do not suspect that they are infected.
"In healthy people, the infection causes short-term cold symptoms such as chills, fever and body aches," Dr. med. Ildiko Rita Dunay, director of the Institute for Inflammation and Neurodegeneration at OVGU.
"Such an infection can be dangerous for pregnant women or people whose immune system is weakened.There is no therapy to get rid of the parasite when it attacks the brain.So, once infected, it will last a lifetime "says the expert.
Another problem is that toxoplasmosis in newborns often remains undetected, as reported by experts at the Robert Koch Institute (RKI) in the journal "Scientific Reports".
The parasite is absorbed by the man by digestion
The parasite nests in the muscle tissue of infected animals, but not only:
"Toxoplasma gondii is absorbed by humans by digestion, enters the bloodstream and also migrates to the brain, where it stays in nerve cells for a long time," Dr. med. Karl-Heinz Smalla of the Special Laboratory Molecular Biology Techniques at LIN.
Previous studies conducted by other German researchers have shown that toxoplasmosis can have serious long-term consequences on the brain.
Even scientists from Magdeburg had already discovered in previous experiments with mice that in animals infected with Toxoplasma gondii it exhibited astonishing behavioral changes:
"The mice, which are prey to cats, lost their natural fear of cats after infection.If rodents had a smell of cat urine, they even seemed to have developed a preference for cats," said researchers.
Therefore, in order to explain these behavioral changes, they studied changes in the mouse brain, particularly the molecular composition of synapses, these structures being essential for signal processing in the brain.
In cooperation with the Helmholtz Center for Infection Research in Braunschweig, they were able to prove that out of a total of 300 synaptic proteins, levels in the brain had changed after infection with toxoplasmosis.
In particular, the proteins were particularly reduced at excitatory synapses releasing glutamate. On the other hand, increased levels of proteins involved in immune responses have been found.
Improved immune response
For the treatment of toxoplasmosis infections, Sulfadiazin is often used, which partially inhibits the proliferation of Toxoplasmen.
Psychiatrist and neuroscientist Björn Schott explains: "We now wanted to know how sulfadiazine treatment affects the molecular changes in the brain caused by the infection."
As a result, the protein composition in the mouse brain after treatment was comparable to uninfected congeners.
"All the proteins examined, which are responsible for transmitting the glutamaterge signal, were again in the normal range, and also the inflammatory activity decreased measurably."
The infection appears to lead to an increased immune response that reduces the proteins involved in glutamate-mediated synaptic excitation, while sulfadiazine reduces toxoplasms and thus normalizes the immune response, thereby resulting in recovery of synaptic proteins.
The results could also be relevant for humans
These findings could also be medically relevant to humans.
"They support the suggestion that Toxoplasma gondii is a risk factor for neuropsychiatric disorders," said neuroimmunologist Dunay.
"The dysfunction of glutamatergic synapses has been implicated in the causes of depression, schizophrenia and autism.The components of the immune response also show references to these diseases," says the expert.
"This suggests that immune responses can cause synapse changes that can lead to neuropsychiatric disorders." (Ad)
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