Study on mice shows Covid virus leads to brain neuron death, higher anxiety, reduced cognition

Bengaluru: A new study has revealed that in mice whose brains were exposed to the spike protein of the SARS-CoV-2 virus, which causes Covid-19, anxiety increased and cognition reduced. This was also accompanied by the protein causing poisoning of neurons in the brain, leading to neuronal death.

The behavioral study, whose findings were published last week in the journal Scientific Reports, was conducted on mice brains using the part of the spike protein called the S1 subunit. Researchers injected the protein into mice brains and observed their behaviour through tests. They noted that the protein did not directly cause cell death; instead, it induced toxicity into the supporting cells around a neuron, called glial cells.

The findings explain some of the mechanisms behind the phenomenon of long Covid, where patients who have recovered from the viral infection tend to feel a range of neurological symptoms — such as reduced cognition, concentration impairment, mood disorders, fatigue, breathlessness, anxiety — for several weeks to months after infection. Studies have increasingly pointed to the effect of the virus on the brain as the explanation, as more findings of long Covid, which affects nearly a third of those infected, come to light.

Such studies on molecular mechanisms through which different parts of the virus affect our cells show the varied pathogenic or disease-causing mechanisms that are at play during a Covid infection.

The fallout of long Covid

Since the early days of the pandemic, many patients had reported lingering symptoms several weeks to months after they recovered. The symptoms that were primarily reported were fatigue, shortness of breath, and brain fog.

Today, we know that anywhere from a third to over half of the Covid patients experience extended symptoms for up to six months. These symptoms tend to be mostly neurological, triggered by the virus’ effect on the brain and the spinal cord, and thus the central nervous system.

Common long Covid symptoms now include fatigue, breathlessness, and brain fog, but also impairment of memory, reduced cognition, increased anxiety and depression, mood disorder, insomnia, shrinking of the brain, continued hair loss, erectile dysfunction or impotence, diminished sense of smell, the onset of diabetes and heart disease, lung dysfunction, tinnitus or buzzing in the ears, and more. Furthermore, such symptoms can be triggered by a mild or non-hospitalised Covid infection as well. Over a third of people who suffer extended symptoms experience them for over a year.

Recently, there has been a surge of research into long Covid, owing to now widely available data. Studies have found many factors that trigger it, including type-2 diabetes, but what causes it and how it can be prevented is still a mystery.