Many people are infected: how the toxoplasmosis parasite converts synapses in the brain
Pets do extraordinary work for most people. But some four-legged friends can transmit the disease. For example, toxoplasmosis, an infectious disease whose pathogen is often found in cat feces. Researchers have now shown in a study how toxoplasmosis parasites rebuild synapses in the brain.
One of the most common infectious diseases
Several years ago, US scientists reported that some cat owners have the possibility of increased aggression and irritation. For those who have been infected by Toxoplasma Gondii. Single-celled parasites worldwide cause one of the most common infectious diseases, toxoplasmosis.
Unicellular parasites attack birds and mammals
Single-celled parasite Toxoplasma gondii attacks birds and mammals – including humans. His last host, however, is a cat.
Researchers from the Institute for Inflammation and Neurodegeneration of Otto von Guericke University Magdeburg (OVGU) and the Leibniz Institute of Neurobiology (LIN) have investigated the study of how parasites affect metabolism in the brain from their hosts and show that there are changes in the composition of synaptic molecules.
The results of the scientists are published in the journal "Journal of Neuroinflammation".
Disease is usually not noticed
According to a report published by Informationsdienst Wissenschaft (idw), around 30 to 50 percent of all people have been infected with toxoplasma during their lifetime. For those over 50 years, they even rely on around 50 percent.
Most toxoplasmosis is not detected and the infected do not expect that they are infected.
"In healthy people, infections trigger short-term cold symptoms such as chills, fever and aches," explained Prof. Dr. med. Ildiko Rita Dunay, Director of the Institute for Inflammation and Neurodegeneration at OVGU.
"Such infections can be dangerous for pregnant women or people with weakened immune systems. There is no therapy to get rid of parasites when attacking the brain. So after you get infected, it will last a lifetime," said the expert.
Another problem is that toxoplasmosis in neonates often remains undetected, as experts from the Robert Koch Institute (RKI) report in the journal "Scientific Reports".
Parasites are absorbed by humans through digestion
Parasitic nests in the muscle tissue of infected animals, but not only:
"Toxoplasma gondii is absorbed by humans through digestion, enters the bloodstream and also migrates to the brain, where it survives in nerve cells," explained Dr. med. Karl-Heinz Smalla from the Special Lab for Molecular Biology Engineering at LIN.
Previous research by other German researchers shows that toxoplasmosis can cause severe long-term consequences in the brain.
Even Magdeburg scientists have found previous experiments with mice that came to animals infected with Toxoplasma gondii for amazing behavior changes:
"Mice, which are prey to cats, lose the natural fear of cats after infection. If the mice are presented with the smell of cat urine, they even seem to have developed a preference for cats," the researchers said.
Therefore, to explain this behavior change, they investigated changes in the mouse brain – specifically the composition of the synaptic molecules, because this is an important structure for signal processing in the brain.
In collaboration with the Helmholtz Infection Research Center in Braunschweig, they were able to prove that in a total of 300 synaptic proteins, the level in the brain has changed after toxoplasmosis infection.
In particular, proteins are mainly reduced at glutamate-stimulating synapses which release. On the other hand, increased levels of proteins involved in the immune response have been found.
Increased immune response
For the treatment of toxoplasmosis Sulfadiazine infections are often used, which partially inhibits the proliferation of Toxoplasmen.
Psychiatrist and neurologist Björn Schott explains: "We now want to find out how sulfadiazine treatment affects molecular changes in the brain caused by infection."
The result: The composition of proteins in the brains of mice after treatment is comparable to those of non-infected individuals.
"All the proteins examined, which are responsible for the transmission of glutamaterge signals, return within the normal range. And also the activity of inflammation decreases measurably."
Infection seems to produce an increased immune response that reduces the protein involved in glutamate-mediated synaptic stimulation, while sulfadiazine reduces toxoplasm and thereby normalizes the immune response, thereby causing the recovery of synaptic proteins.
Findings can also be relevant to humans
This finding is also medically relevant for humans.
"They support the suggestion that Toxoplasma gondii is a risk factor for neuropsychiatric disorders," said neuroimmunologist Dunay.
"Damage to glutamatergic synapses has been implicated in the causes of depression, schizophrenia, and autism. Also components of the immune response show references to this disease," the expert explained.
"This shows that the immune response can cause synapse changes that can cause neuropsychiatric disorders." (Ad)