If you find yourself extra irritable or sad after recovering from Covid, there may be a biological reason.
Scientists have discovered that the virus can infect brain cells responsible for moodstress and exercise, which prevent them from functioning properly.
Laboratory experiments on human cells showed that Covid damages dopamine production, causing cells to deteriorate to the point where they can no longer grow and divide.
Dopamine – also called the happiness hormone – is also responsible for sleep, concentration, motor learning and memory, so the finding could explain why Covid causes symptoms such as brain fog and blues.
Damage to dopamine neurons can cause fatigue, lack of concentration, moodiness and anxiety, depression, loss of interest and pleasure in experiences, and sleep problems.
A team of… Weill Cornell Medicine, Columbia University and Memorial Sloan Kettering Cancer Centre used human stem cells to generate multiple types of cells found in the human body, to see how the Covid virus affected them all.
Researchers used the lab-grown cells and confirmed their findings with autopsy samples from people infected with Covid.
The study found that only dopamine neurons became infected with SARS-CoV-2, causing them to stop working and send out chemical signals that caused inflammation.
Researchers said the results of their study were unexpected because they initially wanted to discover how Covid affects multiple cells, but only found this impact on dopamine neurons.
Senior author Dr. Shuibing Chen of Weill Cornell Medicine said: ‘This project started to investigate how different types of cells in different organs respond to a SARS-CoV-2 infection. We tested lung cells, heart cells and pancreatic beta cells, but the senescence pathway is only activated in dopamine neurons.
‘This was a completely unexpected result.’
Senescence, or biological aging, is the gradual deterioration of the function of living organisms.
It results in the inability of healthy cells to grow and divide.
Wrinkles, deterioration of vision and hearing loss as people age are all examples of normal aging.
The process also leads to stem cell damage and chronic inflammation.
Dr. Chen added: “The infection rate of dopamine neurons is not as high as that of lung cells, the main target of the virus, but even a small population of infected cells can potentially have a serious effect.”
The researchers suggest that these findings could shed light on the neurological symptoms of people suffering from a long Covid experience.
The study found that about five percent of dopamine neurons can be infected by the Covid virus, which can lead to aging and inflammation.
However, the team also found that three drugs – riluzole, metformin and imatinib – could potentially protect against the Covid virus from infecting dopamine neurons.
Riluzole is a medicine used to treat Lou Gehrig’s disease. Metformin can be used to treat diabetes and imatinub is used to treat leukemia and other cancers.
The scientists said further research into these drugs, all of which have been approved by the Food and Drug Administration, could lead to a way to prevent Covid’s attack on the brain.
Researchers highlighted that while most people may be exposed to Covid, not all are susceptible to damage to dopamine neurons.
There are a number of factors involved in neurological risk, including genetics and the severity of the disease.
They recommend larger human population studies to further investigate this issue.
In addition, because senescence of dopamine neurons is a hallmark of Parkinson’s disease, the researchers recommend that people suffering from long-term Covid-19 be monitored for an increased risk of developing Parkinson’s-related symptoms.
The study was published in Cell Stem Cell.