Amy Proal - Interview with Dr. Resia Pretorius: LongCovid microclots and Hypercoagulation

[dplaut]

inflammation + gut dysbiosis => (auto)immune response + vascular damage/dysfunction => poor oxygenation, and so on?

This is an interesting hypothesis. I don't know of much evidence supporting it, but it's interesting.

This was my (admittedly poor) attempt to capture at least one way in which oxidative stress might lead to vascular damage/dysfunction (in addition to causing direct endothelial damage; Incalza et al., 2018, Vasc. Pharm.). It's based on the ideas of VanElzakker and Proal: peripheral pro-inflammatory cytokines cause an exaggerated "mirror" production of brainstem cytokines (neuroinflammation) which produce chronic low-level sympathetic activation (promoting vasoconstriction) and activate the immune system (which, in some people, exaggerates vasoconstriction due to anti- adronergic/muscarinic receptor antibodies, according to Scheibenbogen's group). (Regarding neuroinflammation, VanElzakker et al., 2018, Fr. Neurol., explains how difficult it is to measure brainstem neuroinflammation, which might explain the Dutch group's recent failure to replicate Nakatomi's early results.)

Of course, oxygen delivery/extraction might be compromised by many factors beyond exaggerated vasoconstriction, including increased vascular stiffness (Bond et al., 2021, JERPH), reduced RBC deformability (Saha et al., 2019, Cl. Hem. Micro.) and even hypercoagulation (to bring it back to the thread topic).

 

[Consul]

This is the vicious cycle proposed in the Komaroff, Snyder 2021 paper.

That said when it comes to PEM there is the 2019 McGregor (and Chris Armstrong) paper where they seem to dig really deep into it and find it to be a hypoacetylation state. I guess its still unclear what causes that state to emerge but still seems like a very solid attempt at describing what PEM in itself is.

 

[GlassCannonLife]

This was my (admittedly poor) attempt to capture at least one way in which oxidative stress might lead to vascular damage/dysfunction (in addition to causing direct endothelial damage; Incalza et al., 2018, Vasc. Pharm.). It's based on the ideas of VanElzakker and Proal: peripheral pro-inflammatory cytokines cause an exaggerated "mirror" production of brainstem cytokines (neuroinflammation) which produce chronic low-level sympathetic activation (promoting vasoconstriction) and activate the immune system (which, in some people, exaggerates vasoconstriction due to anti- adronergic/muscarinic receptor antibodies, according to Scheibenbogen's group). (Regarding neuroinflammation, VanElzakker et al., 2018, Fr. Neurol., explains how difficult it is to measure brainstem neuroinflammation, which might explain the Dutch group's recent failure to replicate Nakatomi's early results.)

Of course, oxygen delivery/extraction might be compromised by many factors beyond exaggerated vasoconstriction, including increased vascular stiffness (Bond et al., 2021, JERPH), reduced RBC deformability (Saha et al., 2019, Cl. Hem. Micro.) and even hypercoagulation (to bring it back to the thread topic).

That's interesting, but isn't POTS in ME often a consequence of impaired vasoconstriction due to some alpha adrenergic problems? Can't remember if it's receptor or ligand being at fault..

 

[dplaut]

That's interesting, but isn't POTS in ME often a consequence of impaired vasoconstriction due to some alpha adrenergic problems? Can't remember if it's receptor or ligand being at fault..

So maybe a better way to put it is that what is compromised is vascular control. Perhaps chronic sympathetic activation leaves the vasculature less sensitive to the rapid changes in vasoconstriction signaling needed to respond to standing (which would be one form of vascular "stiffness").

 

[Pyrrhus]

I hope we're not getting off-topic here...

isn't POTS in ME often a consequence of impaired vasoconstriction due to some alpha adrenergic problems? Can't remember if it's receptor or ligand being at fault..

Or a third possibility: the nerve cell that is supposed to release the ligand (norepinephrine) to the adrenergic receptor on the muscle cell controlling the blood vessel is failing to release the norepinephrine in the first place, for some reason.

Perhaps chronic sympathetic activation leaves the vasculature less sensitive to the rapid changes in vasoconstriction signaling needed to respond to standing

In this case, the chronic activation of the sympathetic nerve cell would lead to down-regulation of the post-synaptic adrenergic receptors on the muscle cell controlling the blood vessel, leading to a less sensitive neuromuscular connection.

However, David Systrom has described the opposite scenario in ME:
The chronic lack of activation of the sympathetic nerve cell would lead to up-regulation of the post-synaptic adrenergic receptors on the muscle cell controlling the blood vessel, leading to a more sensitive neuromuscular connection.

He backs up this idea with two experimental observations:

1. If you inject a POTS patient with norepinephrine, they exhibit excessive vasoconstriction, with profound circulatory effects. This is also seen in ME patients when they go to the dentist and are injected with a local anesthetic that contains epinephrine - the ME patients exhibit profound, scary circulatory symptoms. (which is why ME patients are advised to specifically ask for a non-epinephrine anesthetic when they visit the dentist)
2. If you stimulate the sympathetic nervous system in POTS patients, only a low level of norepinephrine is released, suggesting that the sympathetic nerve cells are not releasing their neurotransmitters appropriately.

From: Insights from Invasive Cardiopulmonary Exercise Testing of Patients with ME/CFS (Joseph et al., 2021)
https://forums.phoenixrising.me/thr...patients-with-me-cfs-joseph-et-al-2021.82907/

Immunohistochemical studies show that small fibers regulate microvascular tone, primarily by sympathetic and parasympathetic cholinergic synapses on perivascular myocytes. [...] Abnormal venous pooling in the legs on standing is demonstrated in POTS, and the excess peripheral venoconstriction to experimentally infused norepinephrine or phenylephrine documented is consistent with classic post-denervation adrenergic receptor upregulation. This is further supported by low norepinephrine release after sympathetic nervous system stimulation in POTS patients.

 

[Nuno]

Any ideas on what mechanism could inhibit the sympathetic nerve cells from releasing their neurotransmissors?

@Pyrrhus

 

[Pyrrhus]

Any ideas on what mechanism could inhibit the sympathetic nerve cells from releasing their neurotransmissors?

Great question.
There are a lot of potential mechanisms, but they would all fit under the general categories of "neuropathy" and "dysautonomia".

 

[GlassCannonLife]

I hope we're not getting off-topic here...



Or a third possibility: the nerve cell that is supposed to release the receptor (norepinephrine) to the ligand (receptor) on the muscle cell controlling the blood vessel is failing to release the receptor in the first place, for some reason.



In this case, the chronic activation of the sympathetic nerve cell would lead to down-regulation of the post-synaptic adrenergic receptors on the muscle cell controlling the blood vessel, leading to a less sensitive neuromuscular connection.

However, David Systrom has described the opposite scenario in ME:
The chronic lack of activation of the sympathetic nerve cell would lead to up-regulation of the post-synaptic adrenergic receptors on the muscle cell controlling the blood vessel, leading to a more sensitive neuromuscular connection.

He backs up this idea with two experimental observations:

1. If you inject a POTS patient with norepinephrine, they exhibit excessive vasoconstriction, with profound circulatory effects. This is also seen in ME patients when they go to the dentist and are injected with a local anesthetic that contains epinephrine - the ME patients exhibit profound, scary circulatory symptoms. (which is why ME patients are advised to specifically ask for a non-epinephrine anesthetic when they visit the dentist)
2. If you stimulate the sympathetic nervous system in POTS patients, only a low level of norepinephrine is released, suggesting that the sympathetic nerve cells are not releasing their neurotransmitters appropriately.

From: Insights from Invasive Cardiopulmonary Exercise Testing of Patients with ME/CFS (Joseph et al., 2021)
https://forums.phoenixrising.me/thr...patients-with-me-cfs-joseph-et-al-2021.82907/

Very interesting. Sorry for taking it more off-topic..

Just wanted to clarify that the neurotransmitters are the ligands (ie they bind to receptors), and the receptors (eg adrenoreceptors, g protein-coupled receptors, etc) are, well, receptors. Norepinephrine is a neurotransmitter that acts as a ligand for specific adrenergic receptors.

 

[Pyrrhus]

Just wanted to clarify that the neurotransmitters are the ligands (ie they bind to receptors), and the receptors (eg adrenoreceptors, g protein-coupled receptors, etc) are, well, receptors.

D'oh!
Brain fog moment - now fixed!

 

[Shanti1]

Beside the 1999 study, I haven't heard of any research regarding coagulopathies in ME. Have you?

The only other study I’m aware of is this one, which is in the same vein (pun intended) as Berg’s theory that ME/CFS has a relationship with the antiphospholipid antibodies and clotting.

Anticardiolipin antibodies in the sera of patients with diagnosed chronic fatigue syndrome (Hokama 2009)

I have not seen any studies or clinical observations that people with ME have increased thrombosis. There are anecdotal reports from patients and various doctors about improvement with heparin, and some of our forum members seem to have active clotting pathology.

To be complete, there is also this small study showing that pwME do not have increased platelet activation. There is not a lot to go on, but I am open to the possibility that hypercoagulation could be a contributing factor in some pwME and more so in Long-COVID. Thankfully, there is a lot of interest in research in this area, so hopefully, we will have more answers soon.

 

[Consul]

[...]

However, David Systrom has described the opposite scenario in ME:
The chronic lack of activation of the sympathetic nerve cell would lead to up-regulation of the post-synaptic adrenergic receptors on the muscle cell controlling the blood vessel, leading to a more sensitive neuromuscular connection.

He backs up this idea with two experimental observations:

1. If you inject a POTS patient with norepinephrine, they exhibit excessive vasoconstriction, with profound circulatory effects. This is also seen in ME patients when they go to the dentist and are injected with a local anesthetic that contains epinephrine - the ME patients exhibit profound, scary circulatory symptoms. (which is why ME patients are advised to specifically ask for a non-epinephrine anesthetic when they visit the dentist)
2. If you stimulate the sympathetic nervous system in POTS patients, only a low level of norepinephrine is released, suggesting that the sympathetic nerve cells are not releasing their neurotransmitters appropriately.

[...]

Could be because of the calcium ion channel problems found in me/cfs? If they dont replenish properly or are of low quality you might not get the proper action potential to make the signal go through the whole desired distance.

 

[Shanti1]

How do you figure? Apart from the known poor oxygenation due to orthostatic intolerance (and aerobic exercise intolerance), I don't see how poor oxygenation can be a significant factor in most of the main symptoms of ME.

According to the International Consensus Criteria, here are the main symptoms of ME:
https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2796.2011.02428.x

Thanks for your reply, and your insights. Looking at how hypoxia might play into the symptoms outlined in the Consensus Criteria is a great way to think about this.

I think many have a tendency to bias their theories of the pathology of ME according to how they perceive it playing out in their own body. Admittedly, since direct use of oxygen and improving blood flow, blood pressure, and blood volume has improved my own function, including my PEM threshold, I have been viewing many ME/CFS symptoms through a hypoxia lens. Of course, the challenge with ME/CFS is that there are multiple plausible models to explain both the onset and the symptoms.

My perception of PEM is that it happens after something that demands higher ATP production. The most obvious is physical exertion, but mental exertion and emotional stress also increase energy demands. While muscle cells are adept at using anaerobic metabolism for short bursts when needed, other cells, especially brain cells are preferentially aerobic. Since oxygen and blood flow are needed for higher energy demands, and there seem to be multiple mechanisms in ME/CFS that point to limited O2 utilization and altered blood flow, I’ve been considering hypoxia as a potential cause for PEM.

Evidence and mechanisms for hypoxia abound in ME/CFS research. We have altered blood flow from dysautonomia, low blood volume, orthostatic hypotension, low oxygen extraction, b-adrenergic / muscarinic cholinergic receptor antibodies, endothelial dysfunction, confirmed poor cerebral perfusion, low RBC deformability/hyperviscosity, and possible clotting pathology.

Exercise intolerance, brain fog, and fibromyalgia type pain dont seem hard to link to hypoxia. I guess the question is, can it be linked to PEM. I can entertain a hypothesis where oxygen starved cells, pushed to their metabolic limits, force the body to rest by inducing PEM. Also involved in the process would be oxidative stress, lactic acid build up, and perhaps even a “cell-danger” response of some sort. Of course this is only hypothesis, but increased energy demand and decreased oxygen utilization seem like they could work hand in hand to lead to PEM symptoms.

If hypoxia is a player in PEM, it does seem like a secondary effect from an initial trigger (infection, CCI, immune dysregulation, vagus inflammation etc). I also agree that many of ME/CFS symptoms in the Consensus Criteria do not seem linked to hypoxia.

 

[SNT Gatchaman]

I think many have a tendency to bias their theories of the pathology of ME according to how they perceive it playing out in their own body.

Very true

I know I have micro-clots, so am very engaged in this theoretical explanation. However, to be fair to myself I was a big fan long* before I knew I had them. I am also very biased toward impaired RBC deformability as a mechanism for PEM. I don't think my bias is just due to the NZ link with Len Simpson's haemorrheology studies of the 1990s. I think his and others' related observations have not been adequately pursued.

I can envisage interactions between inflamed/dysfunctional endothelium and intravascular content (platelets, micro-clots, RBCs) contributing to tissue oxygen restriction over varying timescales.

For example in my situation:

I perceive "unrefreshing sleep" as a form of mini-PEM, which for me at the moment clears within 30-60 minutes once I start (gently) moving around the house. I have observed feeling more refreshed paradoxically after a poor and more disturbed night's sleep. Knowing that RBC deformability is reduced in the morning makes me wonder if RBC deformability could be at play in both low-demand and high-demand situations. (See this thread for some earlier exploration of that idea.)

Diurnal variation in normal people is possibly hormone-related, but in ME could have an additive contribution from vascular and intravascular pathologies. I do wonder though if an inflamed endothelium (+/- micro-clots) might have more opportunity to injure RBCs that are slowly transiting capillaries in the rest situation. (Also at the other end, being injured by high throughput and increased shear forces).

*For me "long" is about two months in this rapidly developing area of research.

 

[SlamDancin]

@SNT Gatchaman Did you see Martin say that researchers did not find micro clots but found elevated lipids? They seemed to find it noteworthy as he has a more classical ME/CFS from what I know. Did you have any thoughts about that related to the micro clot pathology?

 

[Shanti1]

I know I have micro-clots, so am very engaged in this theoretical explanation. However, to be fair to myself I was a big fan long* before I knew I had them. I am also very biased toward impaired RBC deformability as a mechanism for PEM. I don't think my bias is just due to the NZ link with Len Simpson's haemorrheology studies of the 1990s. I think his and others' related observations have not been adequately pursued.

And I have no clotting pathology, so I am not so focused on it, lol. Hard to be completely objective in science.
Here is a more recent study on RBC deformability in ME/CFS:

Red blood cell deformability is diminished in patients with Chronic Fatigue Syndrome (Saha 2019)
We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls. Our observations suggest that RBC transport through microcapillaries may explain, at least in part, the ME/CFS phenotype, and promises to be a novel first-pass diagnostic test.

I perceive "unrefreshing sleep" as a form of mini-PEM, which for me at the moment clears within 30-60 minutes once I start (gently) moving around the house. I have observed feeling more refreshed paradoxically after a poor and more disturbed night's sleep. Knowing that RBC deformability is reduced in the morning makes me wonder if RBC deformability could be at play in both low-demand and high-demand situations. (See this thread for some earlier exploration of that idea.)

Interesting finding on the diurnal variation in RBC deformability. I am also worse in the morning with brain fog improving after a couple of hours. It is worse if I "fall off the wagon" with my strict low carb diet, so I used to think my brain was succoming at night to some metabolite produced by my microflora. However, it has improved a great deal since I started desmopressin, leading me to think that low cerebral blood profusion at night is also a major contributing factor in my case.

 

[Akasha]

I think many have a tendency to bias their theories of the pathology of ME according to how they perceive it playing out in their own body.

That's so true. I'm very interested in this theory since hypoxia and small vessel thrombosis would explain every one of my symptoms. I don't expect to find microclots in every one of us, but a similar process might explain many cases. Who knows?
These years have taught me not to hope high, but at least I find it fascinating.

I know I have micro-clots

Did you see them with a microscope? I will try to look at my PPP with a very rudimentary process later this week.

 

[Pyrrhus]

The only other study I’m aware of is this one, which is in the same vein (pun intended) as Berg’s theory that ME/CFS has a relationship with the antiphospholipid antibodies and clotting.

Anticardiolipin antibodies in the sera of patients with diagnosed chronic fatigue syndrome (Hokama 2009)

To be complete, there is also this small study showing that pwME do not have increased platelet activation. There is not a lot to go on, but I am open to the possibility that hypercoagulation could be a contributing factor in some pwME and more so in Long-COVID. Thankfully, there is a lot of interest in research in this area, so hopefully, we will have more answers soon.

That's a great collection of coagulation studies. Someone could start a thread "Coagulation Studies" to collect them all together, and to provide a home for any new studies coming out.

Could be because of the calcium ion channel problems found in me/cfs? If they dont replenish properly or are of low quality you might not get the proper action potential to make the signal go through the whole desired distance.

I'm not sure exactly which ion channel problems you are referring to, but yes - if a nerve cell has a disturbance in its ion levels, ion locations, or ion channels, it certainly could prevent the nerve cell from functioning properly, could prevent the nerve cell from firing when it should, or could prevent the action potential from reaching the synapse.

Specifically, a number of viruses that typically infect neurons produce viral proteins called viroporins, which poke holes in the endoplasmic reticulum, releasing large amounts of Ca2+ ions into the cytosol, and poke holes in the plasma membrane, resulting in membrane depolarization and reduction of action potentials.

Admittedly, since direct use of oxygen and improving blood flow, blood pressure, and blood volume has improved my own function, including my PEM threshold, I have been viewing many ME/CFS symptoms through a hypoxia lens.

Makes sense. I also take daily measures to increase my blood volume and improve my blood flow, as they have quite noticeable effects on my symptoms. (But I stopped using my oxygen concentrator years ago.)

Specifically, I drink two high-quality electrolyte solutions a day to increase my blood volume and I take two hot baths a day to improve my blood flow. But this is simply in order to compensate for the daily accumulated effects of my orthostatic intolerance.

My perception of PEM is that it happens after something that demands higher ATP production. The most obvious is physical exertion, but mental exertion and emotional stress also increase energy demands. While muscle cells are adept at using anaerobic metabolism for short bursts when needed, other cells, especially brain cells are preferentially aerobic. Since oxygen and blood flow are needed for higher energy demands, and there seem to be multiple mechanisms in ME/CFS that point to limited O2 utilization and altered blood flow, I’ve been considering hypoxia as a potential cause for PEM.

I see. Thanks so much for sharing!

We have altered blood flow from dysautonomia, low blood volume, orthostatic hypotension, low oxygen extraction, [...], endothelial dysfunction, confirmed poor cerebral perfusion,

I can certainly see how that might sound like a long list, but the standard model of orthostatic intolerance includes them all:
Dysautonomia of the nerves controlling vasoconstriction (which some see as a form of endothelial dysfunction) leads to orthostatic hypotension, low oxygen extraction, and poor cerebral perfusion. Any low blood volume will only worsen this dysautonomia.

I am also worse in the morning with brain fog improving after a couple of hours.

Yes, that seems to be common with ME. It is often attributed to blunted morning cortisol levels. You may find the following discussion interesting:

Is your worst fatigue in the morning too?
https://forums.phoenixrising.me/threads/is-your-worst-fatigue-in-the-morning-too.81272/

 

[SNT Gatchaman]

Did you see Martin say that researchers did not find micro clots but found elevated lipids? They seemed to find it noteworthy as he has a more classical ME/CFS from what I know. Did you have any thoughts about that related to the micro clot pathology?

Yes - it's a fascinating datapoint and will be important to know the numbers for ME. I'd like to think there are only one or two initiating mechanisms — there can't be too many or surely we would have found one of them in the last 30-40 years... The team at Stellenbosch are going to evaluate long-term ME patients for micro-clots, starting in January. Given this is South Africa, I expect many of the patients will have had Covid too, so they might have multiple subgroups to look at.

I don't know very much at all about lipid metabolism so will leave that to others. I do wonder if it's possible to have a similar effect on microvascular endothelial function and oxygen transfer from lipids in the blood as with micro-clots.

Otherwise I was considering whether micro-clots or an equivalent are one of a few initial pathways in to ME, but that metabolic compensations (including abnormal lipid handling) then progress and hold the symptoms, even though the initial cause (e.g. micro-clots, virus or something else) has later resolved.

In this way theories such as the metabolic trap could be important for many patients. We've often talked about ME being "not one disease". It could be that it's essentially one disease but that patients are on a different part of the spectrum of descent to severity and resistance to reversibility.

If that were true, then early work could initially benefit the more mildly or more recently affected and we might learn how to prevent a descent to the more severe; but much more and different work might be required to repair damage and recover ground for those already long-term or more severe. In that case of course you would presumably only need to revert what is currently damaged and not have to climb the entire disease ladder back to physiologically normal.

Very hard to crystal ball here, but I do think that these newer micro-clot, auto-antibody, neuroinflammation, vagus, gut etc etc findings will bring in new minds and new ideas for the benefit of all.

Did you see them with a microscope? I will try to look at my PPP with a very rudimentary process later this week.

Good luck with the attempt! I'm not quite clear on the accuracy of the light microscopy technique. I presume it is cruder and much more prone to artifact. Perhaps it can be used as a screening test before fluorescence microscopy? Ultimately though, given the huge numbers of people newly with LC (and ME waiting too) they are going to need some sort of high-capacity system for clinical use.

I was fortunate enough to have them demonstrated precisely per the Pretorius protocol by an expert. They look like the Professor's published images. (She also saw my images and they received a "thumbs-up").

 

[Consul]

I'm not sure exactly which ion channel problems you are referring to, but yes - if a nerve cell has a disturbance in its ion levels, ion locations, or ion channels, it certainly could prevent the nerve cell from functioning properly, could prevent the nerve cell from firing when it should, or could prevent the action potential from reaching the synapse.

Specifically, a number of viruses that typically infect neurons produce viral proteins called viroporins, which poke holes in the endoplasmic reticulum, releasing large amounts of Ca2+ ions into the cytosol, and poke holes in the plasma membrane, resulting in membrane depolarization and reduction of action potentials.

The australian researchers Sonya Marshall Gradisnik and Donald Staines have been looking at the TRPM3 ion channels, they think dysfunction here is whats causing me/cfs. These receptors are found through out the body and govern calcium transport to many cells but also to e.g mitochondria. Calcium transport needs to happen exactly at the time needed by the cell, not slightly later, so dysfunction here has potential to cause big problems even if we have perfectly fine calcium levels in our blood.

https://pubmed.ncbi.nlm.nih.gov/31014226/
https://www.frontiersin.org/articles/10.3389/fimmu.2019.02545/full

Interresting info on the viral proteins btw!

 

[Consul]

@SNT Gatchaman Did you see Martin say that researchers did not find micro clots but found elevated lipids? They seemed to find it noteworthy as he has a more classical ME/CFS from what I know. Did you have any thoughts about that related to the micro clot pathology?

Pyrrhus just mentioned viroporins that poke holes in the endoplasmic reticulum causing the content to leak out into the cell. From what i see one of the two sections of the ER is serving as a storage of lipids. Maybe Martins elevated lipids are caused by viroporins causing lipids to leak out of the ER.