According to a study on mice, the Covid virus causes brain neuron death, anxiety and reduced cognition
The researchers experimented by injecting a protein into mice brains and observing their behaviour. The protein did not directly kill cells but caused toxicity within the cells that support neuronal growth.
Researchers in Bengaluru have discovered an increase in anxiety and a decrease in cognition in mice exposed to the spike protein of the SARS-CoV-2 virus, which causes Covid-19. In addition, neurons in the brain were poisoned by the protein, resulting in degeneration.
Researchers used a subunit of the spike protein called the S1 to conduct the behavioural study in mice brains, whose findings were published in Scientific Reports last week. Tests were performed on mice after the protein was injected into their brains. The scientists found that the protein did not directly cause cell death; instead, it caused toxicity in the glial cells surrounding a neuron.
These findings explain the long Covid, where patients who have recovered from a viral infection may experience neurological symptoms for several weeks to months following illness, such as reduced cognition, difficulty concentrating, mood disorders, fatigue, and anxiety. In recent studies, longer Covid, which affects nearly a third of those infected, has increasingly been attributed to the virus’ effect on the brain.
A covid infection presents a variety of pathogenic or disease-causing mechanisms triggered by its various molecular components.
Several weeks and months after recovering from the pandemic, many patients experienced lingering symptoms. Shortness of breath, fatigue and brain fog was the most commonly reported symptoms.
Covid patients can experience extended symptoms for up to six months, according to our current knowledge. Neurological symptoms are mostly expected, as the virus affects the brain and spinal cord, causing the central nervous system to malfunction.
The common symptoms of long-term COVID include fatigue, breathlessness, brain fog, impaired memory, reduced cognition, anxiety, depression, sleep disorders, shrinking of the brain, hair loss, diabetes, heart disease, lung failure and tinnitus. Also, non-hospitalised or mild Covid infections can cause such symptoms. In more than one-third of cases, prolonged symptoms last more than 12 months.
The recent availability of widely available data has led to an increase in research into long Covid. Many elements have been identified as triggers, including type-2 diabetes, but it is still unknown what causes it and how it may be prevented.
The study’s main results
The researchers employed mice and directly inserted S1 proteins into areas of the brain that handle emotion and cognition to see if the brain-infiltrating S1 protein subunit is implicated in neurological issues. The mice were then put through a battery of behavioural tests to see how their brain function and thinking had changed.
Mice models are thought to be a fair approximation for human models since they share 99 per cent of our genes and have physiological systems comparable to ours. Genetic information and genetic illnesses are handed down in the same way as they are in humans, and their genome is also easily modified.
They may be used to learning about chronic illnesses and ageing because they only live for two years. They’re also tiny, simple to care for, multiply fast, and are cost-effective to keep. Their metabolic and physiological processes have been researched for over a century; thus, they are well-understood and recorded.
The researchers discovered that, while the mice’s ability to walk and locomote remained the same, their capacity to recognise novel things was severely impaired compared to normal mice employed as controls. The protein-injected animals showed anxiety in maze and chamber tests, spending more time in tight locations away from other mice.
The researchers also discovered a substantial drop in the cell density of neurons in the brain areas where the S1 protein was injected, reducing up to 35% in scans and chemical analyses. Glial cells, which surround neurons, were studied by the researchers.
Glial cells are found inside the nervous system and help neurons with their physical and metabolic needs.
Insulation and protection, communication, nutrition, and waste conveyance are all included. When these cells are ‘activated,’ their immune system responds by producing many inflammatory cytokines or proteins. This subsequently causes toxicity in neurons, resulting in various symptoms such as tiredness, sleeplessness, and depression.
The scientists looked at these cells in the test animals since prior research had shown glial cell activation in individuals who died of Covid. The mice discovered that over 60% of glial cell activation was recorded in the mice brains.
They conclude that the virus’s spike protein promotes neuronal cell death via glial cell stimulation and increases anxiety and impaired cognition.