It is already known that Covid-19 is a viral infection that primarily affects the respiratory tract. It was also quickly discovered that the brain was one of several organs affected by disease, observed the loss of smell and taste as the main symptoms. This impact of the coronavirus on the brain, however, has not been completely unraveled by science. At a recent online event, researchers discuss the issue.
According to Revista Veja, scientists from Brazil and Germany will gather in the coming months for an event called “FAPESP Covid-19 Research Webinars”. It is a series of webinars to discuss the impact of the coronavirus on the human brain.
O congress digital, which has the support of the Global Research Council (GRC), started in June, but has dates already scheduled until December 2021. The event's purpose is to bring more and better knowledge about the still obscure effects of Covid -19.
“It is very important to encourage the exchange of knowledge and experiences among researchers from all over the world”, said Luiz Eugênio Mello, FAPESP's scientific director, during the webinar opening on June 7th.
Investigations into the consequences of the coronavirus in the brain have been carried out since March 2020, days after the World Health Organization (WHO) decreed the new pandemic. In April of the same year, the first study on the neurological impact of the disease was published, carried out with hundreds of people in Italy who reported a loss of smell and taste.
Since then, new research has been developed, with approaches ranging from the effects observed in the acute phase to possible neurological sequelae - reported by about 30% of patients who recover.
The congress can be accessed at full by anyone interested.
Brain Coronavirus Analysis
One of the studies presented at the webinar, conducted at Charité Medicine University Berlin, Germany, demonstrated that the new coronavirus uses nasal mucosa as a gateway to the brain.
A search analyzed the presence of olfactory mucosa samples in four brain regions of 33 patients who had the severe form of the disease and died. The team of scientists also followed another 180 patients from the acute phase to a few months after recovery.
Helena Radbruch, one of those responsible for the experiment, stated that the presence of the virus in the nerve cells of the olfactory mucosa seems to explain neurological symptoms, such as loss of smell and taste.
According to her, this is due to the anatomical proximity between mucosal cells, blood vessels and neurotransmitters. Once installed in the mucosa of the nose, the virus it uses neuroanatomical connections to get to the brain and stays there.
The good news, especially for those who have had Covid-19, is that the virus doesn't stay in the brain for long. “We found that only in some patients does Sars-CoV-2 reach this organ and, three weeks after the acute phase, it is no longer there,” said Radbruch.
Another research, carried out at the Federal University of Rio de Janeiro (UFRJ), concluded that, in addition to the olfactory mucosa, there are different ways for the virus to reach the brain. One of them would occur as the disease progresses to different organs and systemic inflammation makes it even more severe.
However, unlike the German experiment reported earlier, the Brazilian survey brought negative news. They proved, through an autopsy, that the new coronavirus was able to break the blood-brain barrier and infiltrate regions of the brain.
“The infection by Sars-CoV-2 caused pneumonia, meningitis and damage to multiple organs due to thrombosis, including: kidneys, lungs, heart, pancreas and brain”, indicated Marilia Zaluar Guimarães, researcher at UFRJ and Instituto D'Or .
According to research, although the virus is usually cleared from the brain a few weeks after the end of the acute phase of the disease, there is an increase in cytokines (inflammation-inducing molecules) at the site. This explains the many post-covid-19 neurological problems.
The positive point found by the Brazilian experiment is that, although Sars-CoV-2 causes brain impacts, which can lead to death, it cannot replicate in the brain.
“We found that the infection causes the reduction of neuroprogenitor cells, but it does not affect the ability of these cells to proliferate. What is curious”, concluded Marilia Zaluar Guimarães.
Another study presented at the FAPESP event was conducted by scientists from the State University of Campinas (Unicamp) and the University of São Paulo (USP). The researchers evaluated samples of brain tissue from patients with Covid-19 and found changes that suggest that damage to the central nervous system has occurred.
According to the research, more than 50 days after diagnosis, the volunteers still had alterations in the structure of the cerebral cortex associated with regions of the olfactory tract. Among those surveyed, about 30% developed some mental suffering such as anxiety, depression, loss of memory and/or cognitive functions.
“We already knew about neurological symptoms, such as loss of smell and taste. With our studies, we were able to show, for the first time, that the virus infects and replicates in astrocytes – the most numerous cells in the central nervous system and essential for the maintenance of neurons”, said Marcelo Mori, researcher at Unicamp and co-author of the study .
“It is not by chance that these signaling pathways are related to neurological diseases, such as Huntington, amyotrophic lateral sclerosis and long-term depression”, completed Jean Pierre Peron, a researcher at the University of São Paulo, who is also a co-author of the research.
In short, it can be said that metabolic changes in infected glial cells (astrocytes and other cell types that act in the support and nutrition of neurons) are related not only to the impact on the brain in the acute phase of the disease, but also in the prolonged neurological sequelae reported by some patients.