Imaging robust microglial activation after lipopolysaccharide administration in humans with PET.

[ljimbo423]

Abstract
Neuroinflammation is associated with a broad spectrum of neurodegenerative and psychiatric diseases. The core process in neuroinflammation is activation of microglia, the innate immune cells of the brain.

We measured the neuroinflammatory response produced by a systemic administration of the Escherichia coli lipopolysaccharide (LPS; also called endotoxin) in humans with the positron emission tomography (PET) radiotracer [11C]PBR28, which binds to translocator protein, a molecular marker that is up-regulated by microglial activation.

In addition, inflammatory cytokines in serum and sickness behavior profiles were measured before and after LPS administration to relate brain microglial activation with systemic inflammation and behavior. Eight healthy male subjects each had two 120-min [11C]PBR28 PET scans in 1 d, before and after an LPS challenge. LPS (1.0 ng/kg, i.v.) was administered 180 min before the second [11C]PBR28 scan.

LPS administration significantly increased [11C]PBR28 binding 30-60%, demonstrating microglial activation throughout the brain. This increase was accompanied by an increase in blood levels of inflammatory cytokines, vital sign changes, and sickness symptoms, well-established consequences of LPS administration.

To our knowledge, this is the first demonstration in humans that a systemic LPS challenge induces robust increases in microglial activation in the brain. This imaging paradigm to measure brain microglial activation with [11C]PBR28 PET provides an approach to test new medications in humans for their putative antiinflammatory effects.

LINK

The subjects were given 1.0 ng/kg LPS. To put that in perspective, it takes 1 million ngs to equal 1 milligram!! LPS are extremely toxic!

Couple the above finding with this one from a different study in which Susan Levine and Maureen Hanson were part of and it makes an interesting connection-

ME/CFS patients had significantly higher plasma LPS levels than healthy individuals (median ME/CFS—119.43 pg/mL vs. controls—74.74 pg/mL, P < 0.0005, Fig. 1b and Table 2).

LINK

 

[Hip]

ME/CFS patients had significantly higher plasma LPS levels than healthy individuals (median ME/CFS—119.43 pg/mL vs. controls—74.74 pg/mL, P < 0.0005, Fig. 1b and Table 2).

If you look at Fig 1b (shown below), you see that a lot of ME/CFS patients actually have lower blood levels of LPS than the median LPS level in healthy people.

So blood levels of LPS does not correlate that much with ME/CFS status. If it were possible to measure LPS levels in the brain (which would relate to how much LPS is able to cross the blood-brain barrier), maybe that might show a stronger correlation.

 

[pattismith]

If you look at Fig 1b (shown below), you see that a lot of ME/CFS patients actually have lower levels of LPS than the median LPS level in healthy people.

View attachment 32641

it looks like there is two subgroups in ME/CFS, one with low LPS, and one with high LPS level.
Interesting!

 

[ljimbo423]

If you look at Fig 1b (shown below), you see that a lot of ME/CFS patients actually have lower blood levels of LPS than the median LPS level in healthy people.

I think LPS levels very in ME/CFS significantly, especially in regards to physical activity. Also consider what Jarred Younger is suggesting about sensitized microglia.

EDIT- It could be that viral infections like EBV, etc. can trigger the microglial sensitization that Jarred Younger thinks might be happening in CFS and the LPS consistently re-trigger the sensitized microglia.

If the microglia are sensitized in ME/CFS it might not take much of a rise in LPS levels to cause symptoms, if any and just a slight increase in some people to cause PEM.

Also, some of the "healthy" controls could have high levels of LPS from dysbiosis themselves. I would be very surprised if they didn't given how common dysbiosis is.

Without sensitized microglia though, healthy people would have very mild if any symptoms. Another study showed that exercise increased LPS levels in ME/CFS and they remained high for 72 hours-

Stool sample microbiomes differed between ME/CFS patients and healthy controls in the abundance of several major bacterial phyla.

Following maximal exercise challenge, there was an increase in relative abundance of 6 of the 9 major bacterial phyla/genera in ME/CFS patients from baseline to 72 hours post-exercise compared to only 2 of the 9 phyla/genera in controls (p = 0.005).

There was also a significant difference in clearance of specific bacterial phyla from blood following exercise with high levels of bacterial sequences maintained at 72 hours post-exercise in ME/CFS patients versus clearance in the controls.

These results provide evidence for a systemic effect of an altered gut microbiome in ME/CFS patients compared to controls. Upon exercise challenge, there were significant changes in the abundance of major bacterial phyla in the gut in ME/CFS patients not observed in healthy controls.

In addition, compared to controls clearance of bacteria from the blood was delayed in ME/CFS patients following exercise.

These findings suggest a role for an altered gut microbiome and increased bacterial translocation following exercise in ME/CFS patients that may account for the profound post-exertional malaise experienced by ME/CFS patients.

LINK

 

[Rufous McKinney]

Curious if this phenomenon involves: exosomes...are they escorting these bacteria out of the bloodstream? Or byproducts?
Quote From above:
"There was also a significant difference in clearance of specific bacterial phyla from blood following exercise with high levels of bacterial sequences maintained at 72 hours post-exercise in ME/CFS patients versus clearance in the controls."

 

[ljimbo423]

Curious if this phenomenon involves: exosomes...are they escorting these bacteria out of the bloodstream? Or byproducts?

It's possible that exosomes are involved but I haven't seen any research that shows that (yet!).

 

[ljimbo423]

If it were possible to measure LPS levels in the brain (which would relate to how much LPS is able to cross the blood-brain barrier), maybe that might show a stronger correlation.

It's my understanding that LPS don't have to cross the blood brain barrier to cause microglia activation, brain inflammation and a sickness response.

As the first study I posted shows, LPS activated the microglia in healthy people causing a sickness response and systemic inflammation.

 

[Hip]

It's my understanding that LPS don't have to cross the blood brain barrier to cause microglia activation, brain inflammation and a sickness response.

Yes I think you are right: looking at an old post of mine about how brain inflammation and sickness behavior is activated by peripheral infection or inflammation, LPS in the blood does not need to cross the blood-brain barrier, but can cause brain inflammation via route number 4 detailed in that post (route 4 is where LPS activates macrophages on the circumventricular organs of the brain — the circumventricular organs lack a blood–brain barrier).



But the problem with trying to explain the symptoms of ME/CFS in terms of LPS is simply that ME/CFS patients do not have a substantially higher blood level of LPS compared to healthy controls. The average patient LPS level is not even double that of the controls.

As you say, if the microglia of ME/CFS patients are sensitized, then they may respond even to the low amounts of LPS present in the blood. But if that were the case, then would not be the LPS that is the cause of ME/CFS (as the LPS is also present in healthy people), but the fact that microglia are sensitized.



Also, one thing that confuses me is the first study, where they injected 1 ng of LPS per kg body weight. This is a very small amount of LPS, much lower than the basal level of LPS in the blood of healthy people.

By my calculation, that 1 ng/kg LPS injection will increase the blood LPS concentration by just 5 pg/ml (this is based on the fact that extracellular fluid comprises 20% of body weight).

5 pg/ml is negligible given that basal LPS levels are on average 74.74 pg/ml (from your second study).

Yet the first study found that this tiny increase of 5 pg/ml caused measurable increases in brain inflammation, as well as in sickness behavior symptoms.

That just does not make sense at all.

Something is not right here.

 

[percyval577]

If you look at Fig 1b (shown below), you see that a lot of ME/CFS patients actually have lower blood levels of LPS than the median LPS level in healthy people.

I think LPS levels very in ME/CFS significantly, especially in regards to physical activity. Also consider what Jarred Younger is suggesting about sensitized microglia.

EDIT- It could be that viral infections like EBV, etc. can trigger the microglial sensitization that Jarred Younger thinks might be happening in CFS and the LPS consistently re-trigger the sensitized microglia.

Here another possible component of microglia activation
- rather a microglia sensitization -:

Manganese Potentiates In Vitro Production of Proinflammatory Cytokies and Nitric Oxide Synhases by Microglia Through a Nuclear Factor kappaB-Dependent Mechanism Filipov et al 2005

from the abstract

At all LPS doses, however, proinflammatory cytokine production was dose dependently increased by Mn. Similirarly, LPS-induced NO-production and iNOS expression were substantially enhanced by Mn.

Also:
Manganese modulates pro-inflammatory gene expression in activated glia Chen et al 2006

from the abstract

The potentiated degradation of inhibitory molekule IkB-alpha was one of underlying mechanisms for the increased activation of NF-kB by manganese,

More generel (innate immunesystem):

Manganese Increases the Sensitivity of the cGAS-STING Pathway for Douple Strained DNA and is Required for the Host Defense againt DNA Viruses Wang et al 2018

esp. discussion, interesting is also . p. 676, second column


A preview on this article:

Innate Immune Cells Speak Manganese Haase 2018

 

[percyval577]

The imaging technique @ljimbo423 ´s article (Sandiego et al 2015) tells about is related the one done by the japanese PET study Nakatomi et al 2014 on our disease ("Neuroinflammation in Patients with Chronic Fatique Syndrome ...").

The studies target the 18kDa translocator protein (TSPO).

The protein is invovled in steroidgeneses, apoptosis, inflammation, neurological diseas-related processes and cancer. The precise function remains after 30 years of research still unclear. - After Li et al 2015.

They did another review on TSPO Li et al 2016. They propose that TSPO is an old bacterial protein that has developed additional functions in the outer membrane of mitochondria (abstract). Later they say, the common theme of TSPO in plants, animals and bacteria would seem to be a stress response, eg, a switch between oxygen consumption and photosynthesis in a bacterium.

(Also another review on TSPO Liu et al 2014 suggests that "inflammation" would be said too much.)

 

[nanonug]

it looks like there is two subgroups in ME/CFS, one with low LPS, and one with high LPS level.
Interesting!

Yup, the distribution appears to be bimodal. Given the crappy way (pun intended) my GI system works, I wouldn't be surprised if that is the source of my CFS. It was also the clinical experience of the doctor that diagnosed me, that "CFS begins in the gut."

 

[Hip]

Does anyone share my perplexity at how in the 1st study in the first post, a mere 1 ng/kg = 1000 pg/kg dose of LPS caused the appearance of sickness behavior and brain inflammation?

Injected substances will distribute to all the extracellular fluids of the body. Extracellular fluids account for 20% of body weight. So each kilo of body will contain 200 ml of extracellular fluid.

Thus when you inject 1000 pg of LPS per kilo, in each kilo that LPS gets distributed 200 ml, so in the extracellular fluid (which includes the blood) you get a concentration of 1000 / 200 = 5 pg/ml of LPS.


5 pg/ml is a really low concentration compared to the normal levels of LPS present in the blood, which are on average 74.74 pg/ml.

 

[ljimbo423]

As you say, if the microglia of ME/CFS patients are sensitized, then they may respond even to the low amounts of LPS present in the blood. But if that were the case, then would not be the LPS that is the cause of ME/CFS (as the LPS is also present in healthy people), but the fact that microglia are sensitized.

It seems this is what Jarred Younger is saying. That it's the sensitization of the microglia causing brain inflammation and CFS symptoms. That they are over-reacting to something. Although he hasn't made a connection to LPS yet.

Yet the first study found that this tiny increase of 5 pg/ml caused measurable increases in brain inflammation, as well as in sickness behavior symptoms.

That just does not make sense at all.

Something is not right here.

I have 2-3 more studies that show higher levels of LPS in ME/CFS. It doesn't make sense to me that these are all bad studies.

Especially given that one of the studies I posted above had Susan Levine and Maureen Hanson as part of the studies. Both well respected ME/CFS researchers and I think Susan Levine either use to treat ME/CFS patients or still does.

Here is a quote from a third study that also shows higher levels of LPS in ME/CFS than controls-

Conclusions: This panel differentiates CFS/ME cases from controls with high sensitivity and specificity and therefore represents a potential tool in selecting CFS/ME subjects for clinical studies. Each of these four biological markers relate strongly to the disorder. PGE2 activates dendritic cells and suppresses their ability to attract T cells.

It also suppresses the function of macrophages and neutrophils as well as Th1, CTL-, NK-cell mediated type 1 immunity (e.g. CD3- / CD57+ lymphocytes). PGE2 additionally promotes Th2, Th17 and Tregs and also modulates chemokine production (e.g. IL-8).


When taken together, these data suggest that lipopolysaccharide (LPS), likely from gut bacteria, plays an important role in the pathophysiology of CFS/ME.

LINK

 

[ljimbo423]

Yup, the distribution appears to be bimodal. Given the crappy way (pun intended) my GI system works, I wouldn't be surprised if that is the source of my CFS. It was also the clinical experience of the doctor that diagnosed me, that "CFS begins in the gut."

I think my gut is the root of my CFS. It's not easy to fix it though, in my experience.

The studies I've posted here make a connection to ME/CFS researcher Chris Armstrong's theory that a "slow sepsis" is the cause of ME/CFS and Jarred Younger's theory that sensitized microglia, causing low grade brain inflammation, is the main cause of symptoms.

Is this true? Only time will tell for sure. Rate now it's the best theory I can come up with!

 

[Hip]

I have 2-3 more studies that show higher levels of LPS in ME/CFS. It doesn't make sense to me that these are all bad studies.

It's not even the ME/CFS patients that are the issue here; it's the healthy controls. According to your 2nd study study, heathy people with no symptoms have on average around 75 pg/ml of LPS in their blood.

Then in the 1st study you inject healthy people with 1000 pg of LPS per kilo, which by my above calculation will increase their blood LPS levels by just 5 pg/ml, and all of a sudden these healthy people start experiencing sickness behavior symptoms.

It does not make sense that they can be symptom-free at 75 pg/ml, but then develop symptoms at 80 pg/ml.

 

[ljimbo423]

It's not even the ME/CFS patients that are the issue here; it's the healthy controls. According to your 2nd study study, heathy people with no symptoms have on average around 75 pg/ml of LPS in their blood.

Then in the 1st study you inject healthy people with 1000 pg of LPS per kilo, which by my above calculation will increase their blood LPS levels by just 5 pg/ml, and all of a sudden these healthy people start experiencing sickness behavior symptoms.

It does not make sense that they can be symptom-free at 75 pg/ml, but then develop symptoms at 80 pg/ml.

I don't know but your calculations could possibly be flawed?

The larger point I'm making is that higher levels of LPS have been found in several studies In ME/CFS and LPS can cause microglial activation, brain inflammation and a sickness response. Which is what Jarred Younger thinks is causing ME/CFS symptoms.

 

[unicorn7]

The result for LPS is pretty good, there is a pretty big difference between healthy people and me/cfs people. It doesn’t separate the groups perfectly, but it’s a very significant outcome nonetheless

 

[Hip]

I don't know but your calculations could possibly be flawed?

Could be, and that's why I would like others to look at it. Perhaps @nandixon might be able to throw some light on this issue (as I detailed in this post).

The larger point I'm making is that higher levels of LPS have been found in several studies In ME/CFS and LPS can cause microglial activation, brain inflammation and a sickness response. Which is what Jarred Younger thinks is causing ME/CFS symptoms.

But again a similar issue applies: Average LPS levels in healthy people are 75 pg/ml, whereas in ME/CFS they are 119 pg/ml, which is not even twice the healthy control level.

It makes no sense that you could be perfectly healthy at 75 pg/ml, but then at 119 pg/ml the LPS suddenly causes all the sickness behavior symptoms found ME/CFS.

If ME/CFS patients had for example LPS levels that were 10 or 20 times higher than healthy people, then it might make sense that this greatly elevated level of LPS could be causing these sickness behavior symptoms of ME/CFS.

But when the level in ME/CFS patients is not even 2 times the level of healthy people, it does not look like the LPS can be the cause of the ME/CFS sickness behavior symptoms.

 

[percyval577]

It does not make sense that they can be symptom-free at 75 pg/ml, but then develop symptoms at 80 pg/ml.

Cleaning the teeth helps me (so, since I am improving). You may calculate what that has an effect on cytokines and LPS. Probably not too much.
Once I ate a fish which had obviously quite some fungi. While holding the piece of fish in my mouth and thinking if I should eat it or better not, I felt worse. I guess that hardly any normal person would have detected anything here.

I am not skilled enough to make a mathmatical function out of say two parameters, LPS itself and interpretation of LPS (by say microglia). To some degree it might be a relativism.


For generality, a relativism also appears in other circumstances (hope this comparison makes sense): Ducks or other birds which are prone to get eaten by say eagles, develope a reflex to flee, reasonably. It has been shown that it´s the frequency of the appearance of the shape in the sky, which makes the imprint, not the shape itself. So, it would also be possible that ducks flee geese.

 

[ljimbo423]

But again a similar issue applies: Average LPS levels in healthy people are 75 pg/ml, whereas in ME/CFS they are 119 pg/ml, which is not even twice the healthy control level.

It makes no sense that you could be perfectly healthy at 75 pg/ml, but then at 119 pg/ml the LPS suddenly causes all the sickness behavior symptoms found ME/CFS.

If ME/CFS patients had for example LPS levels that were 10 or 20 times higher than healthy people, then it might make sense that this greatly elevated level of LPS could be causing these sickness behavior symptoms of ME/CFS.

But when the level in ME/CFS patients is not even 2 times the level of healthy people, it does not look like the LPS can be the cause of the ME/CFS sickness behavior symptoms.

I think that might be where Jarred Younger's theory of microglial sensitization comes in.

He mentioned in one of his videos that with sensitized microglia the changes in body chemistry from someone with ME/CFS going for a walk could be enough to trigger the sensitized microglia and symptoms.

If that is taken into consideration with LPS, it might take very small changes in blood levels of LPS to trigger the sensitized microglia and cause symptoms. The other thing Jarred has talked about is a possible compromised blood brain barrier(BBB).

If the BBB is compromised in ME/CFS, again, it might take only very small increases in blood levels of LPS to trigger the microglia and symptoms.