COVID virus attacks brain blood vessels
One of the worrying things about Covid-19 is that in many cases it seems to cause neurological problems such as long term changes to our sense of taste and smell, and so-called “brain fog”. This suggests that the virus is somehow affecting the brain, although we haven’t understood how. Now a new study has shown that the SARS-CoV-2 virus - which causes Covid-19 - can kill the cells - called endothelial cells - that line the small blood vessels that provide the brain with its oxygen supply. Sally Le Page asked the University of Lubeck’s Markus Schwaninger what he thinks is going on...
Markus - They are tiny tubes. They have a diameter of five micrometres so five thousandths of a millimetre in diameter and the wall consists of endothelial cells. These are the cells that form the wall, but outside of the endothelial cell, there is what is called a basement membrane that attaches the endothelial cells with environment.
Sally - So it's a bit like all of these cells are building blocks in the wall and they're all stuck together onto some layer of cement.
Markus - Yes, exactly. What we found is that endothelial cells are lost in SARS-CoV-2 infected patients and only the basement cement as you called it was left over.
Sally - So what happens when the COVID virus infects these cells that are making up the walls of the blood vessels?
Markus - The cell is compromised because the virus production requires energy from the cell. One strategy of the host is that cells that are infected are committing suicide so to speak, to support the survival of the whole organism.
Sally - So if all of the cells that are making up the blood vessels die, what happens to the blood vessel?
Markus - Then there would be no blood flow any longer. That would be lethal, there's no doubt. It's only part of the blood vessels that are dying. In the end, the endothelial cell is gone and only the basement membrane would provide some indication that the blood vessel has been there before. So it's like a ghost vessel that's left over.
Sally - What brains are you looking at when you're looking for this damage?
Markus - We looked at the cortex, the outer part of the brain of patients who died from the disease.
Sally - Now surely it can't be very good for the brain when all of the vessels supplying blood to it get destroyed. What does it mean for the brain as a whole and for the person?
Markus - The blood flow is essential for providing energy and removing waste from the brain tissue. So the effect could lead to stroke-like symptoms for example. If the whole brain is affected it could also lead to confusion, memory loss or delirium in difficult cases.
Sally - Things like confusion and memory loss, they're many of the neurological symptoms people get with long COVID and severe COVID infections. Do you think that it's the virus infecting the blood vessels that is causing these symptoms that we see in COVID patients?
Markus - That's a suggestion that we can make. It could be a cause but we have to do more investigations to prove this concept because so far we just detected these vascular changes. The next thing to investigate would be to link it to the clinical symptoms.
Sally - Obviously you can't investigate the brains of people with long COVID because they still need their brains. Now we know that the virus is damaging the brain, is there anything that we can do to prevent that damage or treat that damage once it's occurred?
Markus - Preventing would be possible if there are small molecule drugs that could inhibit this regulated cell death. However at a later stage, when the damage has occurred, I would assume that it's too late to do anything.
Sally - Have you found drugs that are helpful in preventing this damage?
Markus - Yes, we have tested one drug that prevented the vascular damage in a mouse, but this compound would have to be tested in another species, perhaps also hamsters and then more data is required to see whether the clinical safety is good at all.
Sally - Is it likely that other viruses also damage the brain vessels in a similar way?
Markus - Yes, that's a good suggestion. I mean at least in other coronavirus infections like SARS or MERS, it is very likely that neurological symptoms occurred through a similar mechanism.
Sally - So we might not have this drug in time for the current pandemic but it might be useful in future pandemics.
Markus - Yes, exactly.