Loss of memory, smell, taste, fatigue and fatigue are just symptoms
New article in the journal Nature summarizes what is known about how COVID-19 affects the brain. I will retell it to you, simplifying it a little.
With covid disease, we run the risk of memory loss, strokes and other head problems. There is study, according to which neurological symptoms are manifested in 80 percent of those hospitalized with coronavirus.
The coronavirus attack on our head can be multi-vector:
1. the virus can directly attack certain brain cells,
2. decrease blood flow to brain tissue
3. trigger production immune moleculesthat can harm brain cells.
How covid attacks astrocytes
IN preprint (that is, a "preliminary" article that has not yet undergone rigorous peer review) of a brain study conducted in the UK compares images of the brain before and after illness.
And after the illness is revealed loss of gray matter in several areas of the cerebral cortex associated with the olfactory and gustatory system. Moreover, these losses, it seems, are also among those who were sick easily and who had to be hospitalized. I.e loss of taste and smell - it's all for a reason, the cerebral cortex becomes thinner as a result of the disease.
At the very beginning of the pandemic, there was speculation that the virus could somehow get into the brain and infect neurons - cells responsible for the transmission and processing of information. But research showed that it is difficult for the virus to overcome the protective system of the brain - the blood-brain barrier.
Difficult, but he gets there. Most likely through the nasal mucosa, which borders the brain. The last research show that SARS-CoV-2 can infect astrocytes, the stellate cells of the central nervous system that are responsible, among other things, for providing neurons with nutrients.
Scientists from the University of Campinas in Brazil reportthat analyzed brain samples from 26 people who died from COVID-19. One in four they found signs of brain damage, and 66% of the affected cells were astrocytes.
Thus, infected astrocytes may explain some of the neurological symptoms of covid - fatigue, depression, brain fog, confusion and forgetfulness.
Astrocytes can be vulnerable even if they are not infected with the virus. IN research compared the brains of eight deceased people with COVID-19 to the brains of 14 people from a control group. Researchers found no traces of SARS-CoV-2 in the brains of infected people, however, gene expression was disrupted in some astrocytes and they did not work properly.
Decreased blood flow to the brain
Also accumulated proof of that SARS-CoV-2 can decrease blood flow to the brain, disrupting the function of neurons and ultimately killing them. It does this with the help of infected pericytes - cells that are contained in the walls of capillaries - small blood vessels.
Scientists at University College London have published preprint with evidence that SARS-CoV-2 causes capillary constriction, and as a result, impairment of blood flow.
This was found in hamster brain slices, but we have a similar sequence for ACE2 (angiotensin converting enzyme 2) - the receptor and entry point into the coronavirus cell.
Scientists suggest that in this case, drugs to treat high blood pressure may help. Now there are 2 clinical trials of losartan for the treatment of this disease.
Immune response
The third line of attack of the coronavirus is an overreaction of the body's own immune system after exposure to the coronavirus.
In response to infection, some people's immune systems inadvertently produce "autoantibodies" that attack their own tissues. This can cause long-term illnesses such as optic neuromyelitis, which results in loss of vision and weakness in the limbs.
Autoantibodies can cross the blood-brain barrier, causing disorders ranging from memory impairment to psychosis.
Now the most important question is: what should we do to avoid these sad consequences? We hope scientists will find the answer to this question.
Your Doctor Pavlova
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