Brazilian research shows damage caused by Covid-19 to the brain.

By Gabriela Cupani, from Agência Einstein - It is already known that Covid-19 can cause cognitive decline and symptoms such as memory lapses even in mild cases of the disease. Now, new Brazilian research, published in the journal Cell Reports, shows how the virus acts on the patient's brain. The results may help in developing strategies to prevent these effects.

To investigate this mechanism, scientists from the Federal University of Rio de Janeiro (UFRJ) and the Federal University of the State of Rio de Janeiro (Unirio) injected the Spike protein, the part of the virus responsible for infecting our cells, into the brains of mice. 

Then, the test subjects underwent tests that assessed their spatial memory capacity in the first seven days and over the course of a month. Those that had received the protein had difficulty with this task. But, as often happens with human infection, the effects only appeared later, after about 20 or 30 days. 

When evaluating the rodents' brains, the researchers found that the virus protein activates a receptor involved in the local inflammatory response. This causes cells called microglia to spring into action. They are part of the central nervous system's defense system and eliminate synaptic endings, affecting the connection between neurons. 

“This late neuroinflammation is responsible for the cognitive symptoms of the disease,” explains neuroscientist Claudia Pinto Figueiredo, a professor at UFRJ and one of those responsible for the study. In the hippocampus, a region of the brain related to memory, this causes the well-known lapses that Covid-19 victims report after infection. 

To prove this hypothesis, the team repeated the test with animals that had this receptor blocked by genetic modification. These animals did not experience memory impairment. The finding may pave the way for the use of medications that have this action and could help in prevention even in the acute phase of the disease.

Reversible effect

The research also demonstrated that it is not necessary to have an active infection to suffer from these effects – remnants of the virus in circulation can also reach the central nervous system and cause damage. The good news is that the effect can be reversible. “It is known that the brain is capable of inducing the formation of new neurons, and some habits can help, such as physical activity and good quality sleep,” says the specialist. “But we still don't know the impact on someone with a susceptibility to neurological diseases, and this should be investigated in future research.”