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Archive for the ‘SARS -Cov2’ Category

covid-19 stuff: NAC, glutathione, RT-PCR testing, re-positives

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So, more struggles with biochemistry. Update 70 talks again about N-acetylcysteine (NAC), but goes on to talk about glutathione, and whether glutathione itself might be a type of medication. So let’s get clear, or try to.

Glutathione is a naturally occurring and abundant thiol polypeptide in animal cells. A thiol has an SH (sulfanyl) group attached to a hydrocarbon chain, essentially. As we know, it’s an antioxidant which can be reduced by NAC, and they have structural relations. As Dr Seheult describes glutathione, it’s a combination of three amino acids, with cysteine at the centre. The other two are glycine and glutamate, and the cysteine and the glycine together effectively make up N-acetylcysteine – so NAC is described as a by-product or precursor of glutathione. A case report (regarded as the weakest level of scientific evidence) describes efficacious treatment of two patients with Covid-19-type symptoms using IV and oral glutathione. This and other studies and analyses seem to be begging for full-scale clinical trials to be carried out, but nothing as of mid-May. The treatments could be effective for hypoxemia in particular, due to the action on the disulphide bonds in VWF which are leading to platelet-rich thrombosis.

In his update 71 Seheult broaches the controversial topic of hydroxychloroquine, along with azithromycin and zinc. He suggests there’s evidence that hydroxychloroquine can act as a ‘zinc ionophore’, inducing zinc uptake into cells. Zinc inhibits the RNA-dependent RNA polymerase which SARS-CoV-2 utilises to reproduce. There has been a retrospective study suggesting that treatment with this combination may ‘result in a statistically significant reduction of mortality’, though maybe this hasn’t borne more careful analysis considering the cold water being poured on chloroquine as a treatment in recent months. It may be because it just doesn’t raise zinc levels sufficiently. The findings of the study do suggest the treatment has a statistically significant effect on reducing symptoms in hospitalised patients who are not in ICU – that is, they have relatively mild symptoms. No significant effect for ICU patients.

I should add here that now in August health authorities are warning against any unprescribed use of hydroxychloroquine as a prophylactic due to ineffectiveness and side-effects.

Update 72 began by looking at the sensitivity and specificity of antibody tests available, presumably in the USA. A study examined ‘four new commercially available serological assays [i.e blood serum tests]’, from three German and one US company, and it was found that they all ‘have a sufficient sensitivity and specificity for identifying individuals with past SARS-CoV2 infection’. Of course, the principal issue with the testing is the time it takes to receive results, but maybe that’ll be addressed anon.

Apparently (news to me in very safe – so far – South Australia where hardly anyone I know has had to be tested) there’s a difference between sensitivity and specificity, illustrated by the ‘spin’ and ‘snout’ mnemonic. For a highly specific test if you test positive you’re very sure to be in trouble, and for a highly sensitive test if you test negative you’re sure to be out of danger.

Dr Seheult next describes a retrospective study which looks at glycosylated haemoglobin (HbA1c) as a Covid-19 risk factor. A person’s HbA1c levels (how much glucose is attached to their haemoglobin) are a measure of diabetes. A1c (blood sugar level) is measured in percentages, with 5-6% being normal. The study found that ‘high HbA1c levels is associated with inflammation, hypercoagulability and low SaO2 [oxygen saturation] in Covid-19 patients, and the mortality rate (27.7%) is higher in patients with diabetes’. So HbA1c levels need to be looked at as a priority.

The update next looks at dentistry during the pandemic, for which there’s been little guidance, at least from the CDC. Apparently, during the AIDS crisis, dentists were viewed as modes of transmission, partly due to a NYT article on the subject. In any case, fewer people are now seeing their dentists for obvious reasons, which could lead to an oral health crisis. A number of diseases, including coronary disease, are linked to periodontal problems, so this can exacerbate the pandemic – and dental health, in Australia as in the USA, is not treated with the same gravitas as other forms of health.

Update 73 starts with a look at testing, particularly the reverse transcriptase polymerase chain reaction (RT-PCR) test. So the coronavirus has these spike proteins protruding from a bilipid membrane, with the RNA wrapped inside bound together by disulphide bonds and the like, I think. The protein shell around the virus is called the nucleocapsid. Of course the RNA’s code is specific to SARS-CoV2, so a test needs to look at a segment of the viral RNA and identify it with sufficient – essentially total – specificity. RNA is made up of the four base pairs adenine (A), uracil (U), guanine (G) and cytosine (C), with A pairing always with U and G with C. With that I’m going to switch to Scientific American for more detail.

A test starts with a sterile swab from the back of the nasal passage, aka a sample. Sample collection needs to be done properly, or it could lead to a false-negative result. If there’s viral RNA present, it’s extracted and used to produce a complementary strand of DNA – that’s where the reverse transcriptase enzyme comes in, reversing the usual transcription process from DNA to RNA. This material is then amplified – thousands of copies are made – to ensure a measurable result. The different available test kits generally vary in the segment of genetic material chosen.

I’m hearing that there are serious delays, in the USA at least, in delivering test results. This is extraordinary as, according to the Scientific American article, which is dated late March,

the FDA recently began granting emergency use authorization (EUA) to rapid diagnostic PCR tests that manufacturers say can deliver results in less than an hour. The authorization allows medical devices that have not yet been approved by the agency to be used during public health emergencies. 

What’s happening? According to very recent article from Quartz magazine, the problem is that there are too many kinds of tests. The EUA system was utilised, partly because of the urgency, partly because of the disastrous problem caused by the use of faulty reagents by the CDC back in February. Now there are about 150 tests that have been given EUA approval. Testing delays at first resulted mainly from lack of general lab equipment and PPR for the testers, but increasingly there are problems due to different types of tests, the variability of the tests, knowing which test to use, having the right equipment for each test, the prioritising of certain groups, such as front-line health workers, over others, confirmation of test results by other labs, and of course the overload in demand. We’re talking about the USA here, of course, and it just seems another case of lack of centralised control and uniformity in a state with a failed federal government.

Returning to update 73, Seheult describes a situation in which a SARS-Cov2-infected individual’s immune system has broken down the virus into ineffectual strands of RNA, proteins and other particles. It’s possible that a RT-PCR test could pick up on an RNA fragment, and produce a positive test result in these apparently recovered patients, and in fact this has often occurred. This is called a re-positive. The update describes a study by the South Korean CDC which provides valuable evidence on these re-positive cases. Some 280 re-positive subjects were studied, and about half of them displayed Covid-19 symptoms (on average 14 days after ‘recovery’). Presumably this re-positive finding was after they’d tested negative, i.e they’d first tested positive, then negative, then later positive again, though this isn’t clear. In any case, they checked a percentage of the subjects for antibodies and the result was almost entirely positive. They checked a larger sample for viral particles and found ‘not a single whole viral particle’, according to Dr Seheult, by which I presume he means anything that was replicable or active. They also looked at close contacts of the subjects, in large numbers, and all of them tested negative. So the finding was that these re-positives were, it seemed, the results of ultra-sensitive testing that was picking up viral RNA fragments that were in effect innocuous. This would seem to be a lesson for developing the right types of test. Hopefully a lesson learned.

References

Coronavirus Pandemic Update 70: Glutathione Deficiency, Oxidative Stress, and COVID 19

Coronavirus Pandemic Update 71: New Data on Adding Zinc to Hydroxychloroquine + Azithromycin

Coronavirus Pandemic Update 72: Dentists; Diabetes; Sensitivity of COVID-19 Antibody Tests

Coronavirus Pandemic Update 73: Relapse, Reinfections, & Re-Positives – The Likely Explanation

https://www.scientificamerican.com/article/heres-how-coronavirus-tests-work-and-who-offers-them/

https://qz.com/1886940/why-covid-19-test-results-take-so-long/

Written by stewart henderson

August 5, 2020 at 2:34 pm

more Covid-19 gleanings from MedCram updates 67-69

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polymorphonuclear leukocytes (white blood cells)

I’m continuing my self-education re everything Covid-19 thanks to Dr Seheult’s updates and other useful sites. Update 67 carries on from where we left off, summarising again how SARS-CoV2 induces endothelial dysfunction, before focusing on thrombosis. So we repeat again that a key molecule in normal endothelial function and in the working of AT-1,7 is nitric oxide (NO). Endothelial function (and, to be clear, the endothelium lines the vasculature, which means the body’s blood vessels) is also dependent on the various other enzymes mentioned in the last post, e.g. superoxide dismutase (SOD), and glutathione peroxidase (GPx).

So how does Covid-19 bring about oxidative stress and how does this effect thrombosis? Seheult discusses an article from April this year which addresses this. It describes a previously healthy elderly male admitted to hospital with fever and respiratory symptoms. After rapid deterioration he was sent to ICU, having developed ARDS, acute renal insufficiency and other health problems. Among various measures noted was a ‘massive elevation of von Willebrand factor (VWF), as well as ‘factor VIII of the coagulation cascade’. To quote from the article:

The increased VWF points toward massive endothelial stimulation and damage with release of VWF from Weibel-Palade bodies. Interestingly, endothelial cells express ACE-2, the receptor for SARS-CoV2, thus possibly mediating endothelial activation.

To explain some of these terms: Weibel-Palade bodies are found only in epithelial cells, and they contain VWF, which are released when required for haemostasis and coagulation. VWF is a stringy material of amino acid proteins which combine with platelets (aka thrombocytes) to coagulate the blood. When endothelial cells suffer serious damage, Weibel-Palade bodies inject large amounts of VWF into the bloodstream. Dr Seheult presents the abstract from a 2017 article on the topic:

The main function of VWF is to initiate platelet adhesion upon vascular injury. The hallmark of acute and chronic inflammation is the widespread activation of endothelial cells which provokes excessive VWF secretion from the endothelial cell storage pool. The level of VWF in blood not only reflects the state of endothelial activation early on in the pathogenesis, but also predicts disease outcome. Elevation in the blood level of VWF occurs either by pathologic increase in the rate of basal VWF secretion or by increased evoked VWF release from dysfunctional/activated endothelial cells. The increase in plasma VWF is predictive of prothrombotic complications and multi-organ system failure associated with reduced survival in the context of severe inflammatory response syndrome, type 2 diabetes mellitus, stroke and other inflammatory cardiovascular disease states.

The article points out that an over-production of VWF in highly elongated form is an indication of pathology. This is apparently being seen in serious Covid-19 patients. On the molecular level, the VWF is able to remodel itself from its usual globular conformation when it senses shear forces – note this definition from Science Direct: Shear stress is defined as the frictional force generated by blood flow in the endothelium, that is, the force that the blood flow exerts on the vessel wall, expressed in force-area unit (typically dynes/cm2). The VWF, under this stress, ‘turns into an extended chain format that forms ultra-large strings to which platelets bind to initiate clot formation at sites of vascular damage’. When the shear stress reaches a certain level, factor VIII is released. All of this can be essential for haemostasis, but too much of the multimeric, elongated form of VWF will lead to thrombosis, as appeared to be occurring in the patient described above.

So, as Seheult summarises, SARS-CoV2 binds to ACE-2 receptors and reduces ACE-2 production. This reduction has the effect of increasing AT-2 production and reducing AT-1,7. This results in an increase in superoxide production, oxidative stress and endothelial dysfunction. This in turns leads to an increase in VWF activity in the bloodstream, and local thrombosis. There is evidence from autopsies that thrombosis is a feature of Covid-19 mortality.

In his update 68 Dr Seheult looks at the predisposition of some ethnic groups (in the USA) to the more severe symptoms associated with Covid-19. He discussed a May CDC MMWR (morbidity and mortality weekly report) on 580 hospitalised Covid-19 patients which found that 45% were white, as far as they could ascertain, compared to 55% in that region’s community. 33% were black, compared to 18% in the community, and 8% were Hispanic compared to 14% in the community. A smallish sample, but suggestive. The CDC also reported on New York figures showing that Covid-19 death rates among black/African Americans and Hispanic/Latino persons were substantially higher than in the white population. Many possible reasons – work and living conditions, lower access to care – all generally related to relative poverty. There may also be other, purely physiological grounds for the disparity. A 16-year-old research article published in Circulation describes the results of placing nanosensors in isolated human umbilical vein endothelial cells (HUVECS) from blacks and whites (pardon the over-simplification, I’m only the messenger), as an attempt to measure endothelial oxidative stress. I can’t follow the details of the research, but what they found was that blacks expressed much more NADPH oxidase than whites (that’s bad). Nitric oxide, a reducer of oxidative stress, was produced in greater quantities in whites than in blacks, and the bad superoxides were produced in greater quantities in blacks. I won’t go further into the complex biochemistry, but I must say I find these apparent racial differences very surprising.

Update 68 also looks at increasing hospitalisations (at least in May) of young children due to Kawasaki disease, or something similar. The disease is characterised by inflammation of blood vessels. Symptoms include fever, high heart rate and possibly sepsis. There are a number of similarities to Covid-19, including ‘systemic vascular lesions’. Kawasaki disease is normally rare, and believed to be viral, or a response to a virus. A ten-year-old research paper on the disease hypothesises that the infection enters through the respiratory or gastro-intestinal systems, and so unsurprisingly there are similarities to the reaction to SARS-CoV2. Whether there’s a connection between Covid-19 and an uptick in Kawasaki disease has yet to be confirmed (but I’m behind the times on the research on this).

I’m moving now to update 69, and I’m going to follow Dr Seheult through the whole oxidative stress process again. It’s about reduction of oxygen – the adding of electrons. Adding an electron to oxygen, mediated by NADPH oxidase, produces superoxide. Add another electron and you get hydrogen peroxide. Another electron produces hydroxyl, and yet another produces water, moving from most oxidised to most reduced, and adding electrons also brings on protons. So at both ends of this chain you have neutral or positive molecules, but in between you have, I think ROS, reactive oxygen species, which are a problem. The body’s defence against these include the enzyme superoxide dismutase (SOD), which converts superoxide into hydrogen peroxide and also back into oxygen, and catalase which converts hydrogen peroxide into water and oxygen. Another important enzyme which protects against oxidative damage is glutathione peroxidase (GPx). It takes reduced glutathione (2GS-H, called a sulph-hydryl group) and uses it to reduce hydrogen peroxide into water, in the process oxidising the glutathione into a form of disulphide G-S-S-G. This oxidised form is in turn ‘regenerated back’ by taking the reduced form of NADP+ (NADPH) and converting it via glutathione reductase to NADP+.

So the point is that the accumulation of superoxide in people with diabetes, hypertension, coronory disease etc will be exacerbated by Covid-19. And going through that once more, Covid-19 blocks the ACE-2 receptor, causing an accumulation of AT-2 which stimulates superoxide production, and also a deficiency of AT-1,7, which, mediated by nitric oxide, inhibits superoxide production. The SARS-CoV2 virus also attracts PMNs (polymorphonuclear leukocytes – immune cells including neutrophils), which boost superoxide production, with attendant endothelial damage.

I’ll be continuing this series, and no doubt getting further behind, over the next few weeks.

References

Coronavirus pandemic update 67, presented by Dr Roger Seheult, as with all other updates

Coronavirus pandemic update 68

Coronavirus pandemic update 69 (first 5 minutes or so)

https://www.verywellhealth.com/polymorphonuclear-leukocyte-2252099

Written by stewart henderson

July 29, 2020 at 11:11 am

more on oxidative stress and covid-19

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So, much of this piece will rely on Dr Seheult’s coronavirus update 65. We have this constant set of reactions in the body that reduce oxygen – adding electrons – until we get to water molecules, producing reactive oxygen species (ROS) along the way. This is often described as the oxygen metabolism process. Reactive oxygen species come essentially in three types, superoxides, hydroxy radicals and hydrogen peroxide. The three forms of the enzyme SOD, superoxide dismutase, convert superoxide into oxygen and hydrogen peroxide (H2O2), and then the H2O2 is reduced to H2O by means of glutathione peroxidase (GPx). The GPx, which is broken down in the process is recharged by the enzyme glutathione reductase (GR), which is in turn recharged by other antioxidant products. Also the enzyme catalase, which requires iron, can break H2O2 down into O2 and H2O.

People with diabetes, hypertension and overweight issues, among other things, may have compromised antioxidant systems (too many ROS), linked to angiotensin-converting enzyme 2 (ACE-2) and angiotensin-2. In creating ROS, oxygen is reduced to superoxide by means of the enzyme NADPH oxidase. So, as part of the renin-angiotensin system, angiotensin-2 (AT-2) is converted to angiotensin 1,7 (AT-1,7) by means of angiotensin-converting enzyme 2 (ACE-2). This is important because AT-1,7 effectively blocks superoxide production, while AT-2 promotes it. The virus SARS-CoV2 binds with, and so inactivates, ACE-2, preventing the production of AT-1,7. This action also means that there will be more AT-2 available, and so more superoxides. SARS-CoV2 also, according to Seheult, causes inflammation by recruiting polymorphonuclear neutrophils (PMNs), which stimulate production of superoxides by means of NADPH oxidase. So this, in essence, is why Covid-19 is bringing about oxidative stress.

Seheult next goes on to look at the research evidence for the preceding. A review article from 2005 points out that evidence from animal studies and cell culture studies shows that NADPH oxidase-derived oxidative stress is increased in vascular cells by AT-2, among other ‘agonists’ (chemicals that bind to receptors, thereby producing a response). Another article from 2012 describes several enzyme systems that act to form ROS, including ‘mitochondrial electron leakage from the electron transport chain’ as described in my previous post on the subject, and in Seheult’s update 63. It points out that ROS levels can rise dramatically in older people suffering from oxidative stress due to heart issues such as ischemia-reperfusion (referring to problems with oxygenated blood supply to the heart or other organs). It also points out that it has been shown experimentally that AT-2 stimulates an increase in ROS. A more recent article pertaining to SARS-CoV2 looked at patients in Wuhan and found a substantial increase in neutrophils in the most severe cases. Neutrophils cause ROS to be generated by NADPH oxidase. So Dr Seheult is carefully building up evidence for the case. The last point to deal with is AT-1,7 effects. Seheult has found a 2008 article entitled ‘Angiotensin converting enzyme 2 confers endothelial protection and attenuates atherosclerosis’. Seheult quotes the last line from the abstract:

These data indicate that ACE-2, in an AT-1,7-dependent fashion, functions to improve endothelial homeostasis via a mechanism that may involve attenuation of NADPHox-induced reactive oxygen species production. ACE-2-based treatment approaches may be a novel approach to limit aberrant vascular responses and atherothrombosis.

Atherothrombosis involves disruption of atherosclerotic plaques, which can be an immediate cause of heart attacks. Another article from 2015 essentially confirms the findings, as indicated by its title, ‘ACE-2 and AT-1,7 protect endothelial cell function and prevent early atherosclerosis by inhibiting inflammatory response’. A more recent article, from January 2020, describes how AT-1,7 administration improves endothelial function in women who have suffered from preeclampsia (vasoconstriction, high blood pressure and organ damage due to pregnancy). To give more detail, women in the last stages of pregnancy often suffer vasoconstriction and high protein levels, which is believed to be related to AT-2 levels. Researchers administered local AT-1,7, which is ‘an endogenous inhibitor of... AT-2′, to see if this reduced vasodilation and other symptoms of preeclampsia. What they found was that ‘AT-1,7 increased endothelium-dependent vasodilation via nitric oxide synthase-mediated pathways and attenuated AT-2-mediated constriction in women who have had preeclampsia, suggesting that AT-1,7 may be a viable therapeutic target for improve d microvascular function in women who have had a preeclamptic pregnancy’.

All of this is interesting in itself, of course, and is a little crash course in how research is helping us to tweak our immune systems, but in relation to Covid-19 these finding are of importance due to the comorbidities and general characteristics of patients being hospitalised with Covid-19. Dr Seheult, in his update 65 video, shows that, contrary to what was initially thought, i.e that Covid-19 is primarily a virus affecting the lungs and respiratory system, it may be much more of a problem for those with hypertension, cardiovascular issues and obesity – all of which are related to oxidative stress, as are diabetes and many forms of cancer. They contribute to endothelial dysfunction, which inevitably leads to oxidative stress, and may lead to thrombosis. Seheult here refers to a lengthy 2018 review article, ‘nutrients and oxidative stress: friend or foe?’, which among other things makes useful dietary suggestions for the combatting of oxidative stress – whole grains, nuts, fruit and vegetables, fish and legumes.

It’s been known for some time that endothelial cell dysfunction (ECD) can lead to thrombosis, as it is a major function of these cells to prevent thrombosis. The abstract from a 2002 study finds that ECD ‘is associated with decreased synthesis and oxidative inactivation of nitric oxide (NO)’ and it lists four types of antioxidant enzymes ‘essential for eliminating ROS that can inactivate NO’. It seems that the promotion of these enzymes can be associated with diet as above and with the reduction of risk factors such as hypertension, hypercholesterolaemia (high blood cholesterol), hyperhomocysteinaemia (homocysteine is an amino acid which can contribute to arterial damage and blood clots, and the condition is often associated with lack of vitamin B-12 or folate), cigarette smoking and diabetes mellitus. NO is the key molecule in maintaining endothelial function through these enzymes.

Now I’m having a look at Dr Seheult’s update 66 on blood pressure medications known as ACE inhibitors or ARBs. He cites an editorial article for the New England Journal of Medicine, on ‘inhibitors of the renin-angiotensin-aldosterone system and Covid-19’. This is a triple hormone system responsible for blood pressure regulation and fluid balance. Now, to return to what was outlined before, angiotensin-2 (AT-2) is converted to AT-1,7 by an angiotensin-converting enzyme (ACE-2). The SARS-CoV2 virus binds to the ACE-2 receptor and inhibits the enzyme’s production. This is problematic because AT-2 stimulates superoxide production (that’s bad), while the antioxidant AT-1,7 blocks it, so reducing oxidative stress. SARS-CoV2 also stimulates the production of PMNs, as above, which activates oxidative stress. Another part of this picture is that AT-1 is converted to AT-2 by ACE. There are blood pressure lowering medications, such as benazepril and lisinopril, aka ACE inhibitors, which reduce the production of AT-2. There are also angiotensin receptor blockers (ARBs), which may up-regulate ACE-2 (it isn’t clear, apparently). ACE inhibitors may do the same. The question being asked is, assuming these medications produce more ACE-2, will this lead to more infections because SARS-CoV2 has more ACE-2 to work with? Clearly it would be important to know whether to maintain these medications or not, that’s to say, whether these medications are a risk factor for contracting the virus or recovering from it. The above-mentioned article discusses three studies from different parts of the world, each involving thousands of participants. They all found no risks associating ACE inhibitors and ARBs with a higher risk of infection, severity of illness or death from Covid-19. One of the studies found that ACE inhibitors and statins were associated with a decreased risk of mortality, but these are observational studies and further research would need to be done.

So the above is a rather technical piece, highly reliant on the experts. I write to inform myself, and I’ve certainly been informed by writing this one. Apologies for its laboriousness, but I’ll be continuing… Please consult the references yourself if there’s anything you don’t understand.

References

Coronavirus Pandemic Update 65: COVID-19 and Oxidative Stress (Prevention & Risk Factors)

Coronavirus Pandemic Update 66: ACE-Inhibitors and ARBs – Hypertension Medications with COVID-1

https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/ace-inhibitors/art-20047480

https://www.healthline.com/health/homocysteine-levels

https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/ace-inhibitors/art-20047480

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5831951/

Written by stewart henderson

July 16, 2020 at 4:21 pm

SARS-Cov2 and oxidative stress

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Dr Roger Seheult, just doing his job, workaholically

So I feel it’s time for me to get back to the epidemiology and immunology stuff that I know so little about, especially as it pertains to SARS-Cov2. Watching Dr Seheult’s Medcram updates again after a long hiatus, and catching up with them from the end of April, I note that he’s arguing – and I presume this is a mainstream view, as he clearly keeps an eye on the latest research – that the virus mostly does its damage in attacking the body’s endothelium, and that this in turn causes oxidative stress. The endothelium is a thin layer of cells, or a layer of thin cells, that form the inner lining of the blood and lymph vessels (one day I’ll find out what lymph actually is and does).

Oxidative stress is associated with an imbalance in the level of oxidants such as super-oxide anion and hydrogen peroxide, reduced forms of oxygen (with extra electrons). I don’t really understand this, so I’ll start from scratch. But just preliminary to that, the effects of oxidative stress are manifold. Here’s a summary from news-medical.net:

Oxidative stress leads to many pathophysiological conditions in the body. Some of these include neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease, gene mutations and cancers, chronic fatigue syndrome, fragile X syndrome, heart and blood vessel disorders, atherosclerosis, heart failure, heart attack and inflammatory diseases.

It’s known that SARS-Cov2 enters via the lungs, and does damage there, but it’s now thought that most of the damage is done in the endothelium. To understand this, Dr Seheult is going to teach me some ‘basic’ stuff about metabolism, oxidation, energy production and such. So, we start with mitochondria, the energy-producing organelles inside our cells, which have their own DNA passed down the female line. Looking into a mitochondrion, we have the matrix inside, and around it, between the inner and outer membranes, is the inter-membrane space (IMS). Our food, broken down into its essential components, carbs, fats and proteins, is absorbed into the matrix, and somehow turned into ‘two-carbon units’ called acetyl coenzyme A. This is metabolism, apparently. These molecules go through a famous process called the Krebs cycle, of which I know nothing except that it’s about more metabolism… Although now I know that it produces electrons, tied up in two important molecules, NADH and FADH2. These electrons ‘love to be given up’, a way of saying they ‘want’ to be reduced. The molecule that gives up electrons is said to be oxidised, the receiving molecule is reduced. So think of a molecule being reduced as the opposite of losing, rather counter-intuitively. The oxidised molecule is the one that loses electrons. All this is about energy production within the matrix, and the aim is to end up with a molecule I’ve heard and forgotten much about, adenosine triphosphate (ATP). This molecule is the energy molecule, apparently, and the energy is produced by ‘knocking off’ one of the phosphates, according to Dr Seheult, leaving, apparently, adenosine diphosphate (ADP) plus ‘energy’ (clearly, this part needs a little more detail). So going from the diphosphate form to the triphosphate requires energy, going the other way releases energy – none of which really explains why ATP is the body’s energy source. Anyway…

Returning to the carbs, fats and proteins, they go through these mitochondrial processes to produce electrons which want to reduce stuff. So NADH goes to the membrane which separates the IMS from the matrix of the mitochondrion, where proteins can be found that are willing to accept electrons, i.e. to be reduced. The electrons are brought in ‘at the very top of the scale’ (?) and lose some of their reducing ability, so they go down to a lower state of reduction, and protons are pumped into the IMS. (I’m sure this is all true but making sense of it is another matter. It certainly makes me think of proton pump inhibitors, drugs that reduce gastric reflux, but that would be the subject of another set of posts). Then ‘it goes to another species’ by which I think Seheult means another protein, judging from the video, but what he means by ‘it’ I’ve no idea. The NADH? The wave/body of electrons? Anyway, things keep going down to a lower level, becoming more oxidised, and more and more protons are pumped out. So there comes to be a very high concentration of protons (H+) in the IMS, creating a very low PH (high acidity). Meanwhile, the electron transport chain has gone down so many levels that it can only reduce oxygen itself, which by accepting electrons turns finally into water. It’s apparently essential to have sufficient oxygen to keep this cycle going, and to keep the protons pumping, because the protons in the IMS want to move to a place of lower concentration, in the matrix. In doing this, they pass through a channel, which involves, somehow, a coupling of ADP to ATP. Without enough oxygen, this process is stymied, ATP can’t be supplied, leading to insufficient energy and cell death.

So, I think I understand this, as far as it goes. Now, if you over-eat, with lots of high-calorie fats and carbs entering the cells, you’ll likely end up with a surplus of electrons, tied up in NADH and FADH2, which can cause problems. This is where super-oxides come in.

Oxygen is the final electron acceptor in the electron transport chain, and when you add an electron to this final acceptor you get a super-oxide, an oxygen molecule with an additional electron, aka a radical. These are very reactive and dangerous. They can cause DNA damage and serious inflammation, and the body uses them to kill bacteria. If you add another electron, you get H2O2, hydrogen peroxide, and another one again produces a hydroxy radical, OH. Another electron gives water, so it’s these intermediate molecules that are called ‘dangerous species’. Cells such as neutrophils (a type of white blood cell) make these, via an enzyme called NADPH oxidase, as part of their defence against antigens, but an accumulation of these radicals is problematic and needs to be dealt with.

from Dr Seheult’s presentation, showing the production of reactive oxygen species (ROS) – super-oxide, hydrogen peroxide and hydroxy radicals

One enzyme the body uses to bring down these accumulating radicals is super-oxide dismutase (SOD), which takes two super-oxides and converts them into O2 and H2O2. SOD comes in three types, related to where they reside – in the mitochondria, the cytosol and the extracellular matrix. These enzymes are powered by zinc, copper and, in the mitochondria, manganese. So what happens to the extra hydrogen peroxide created? An enzyme called glutathione peroxidase (GPx) reduces H2O2 to water by giving it two electrons. Where do these electrons come from? According to Seheult, and this is presumably ‘basic’ microbiology, the antioxidant glutathione has two forms, oxidised and reduced. The reduced form is 2GS-H, with a hydrogen bonded to the sulphur group. The oxidised form is G-S-S-G, a disulphide bond replacing the hydrogen. With the reduced form, GPx donates its extra two electrons to H2O2, reducing it to water. The glutathione system is recharged by reducing it back with NADPH, which has two electrons which are converted to NADP+ (?) Glutathione reductase is the key enzyme in that process. It might take me a few lifetimes to get my head around just this much.

Meanwhile there’s another system… Catalase, an iron-boosted enzyme, can convert two molecules of H2O2 into O2 and H2O. This occurs in organelles called peroxisomes. The major point to remember in all this is that super-oxides are harmful species that can cause oxidative stress, and the major solutions come in the form of SOD and GPx. In fact the general name for these harmful molecules – super-oxides, hydrogen peroxide, and hydroxy radicals – is reactive oxygen species (ROS).

So we have to relate all this to the effects of SARS-Cov2, which enters the body through the ACE-2 (angiotensin-converting enzyme-2) receptor. According to a 2008 research paper, ACE-2, the receptor for which is blocked by SARS-Cov2, ‘confers endothelial protection and attenuates atherosclerosis’. Quoting from the paper, we find a section called ‘ACE-2 modulates ANG II(angiotensin 2)-induced ROS production in endothelial cells’. The researchers’ essential finding was that ‘ACE-2 functions to improve endothelial homeostasis’, and it seems this function is being disrupted by SARS-Cov2. As Dr Seheult puts it, SARS-Cov2 inhibits the inhibitor, that is it inhibits ACE-2, which normally acts to regulate angiotensin 1,7 (not explained in this particular video), thus allowing NADPH oxidase to keep producing super-oxides, with the resultant oxidative stress. As Seheult concludes here, subjects with compromised systems caused by diabetes, cardiovascular disease or obesity, affecting the production or effectiveness of SOD and GPx, might be relying on ACE-2 and angiotensin 1,7 to maintain some semblance of health. Are these the subjects that are succumbing most to the virus? That’s to be explored in future videos, and future posts here.

Reference

Coronavirus Pandemic Update 63: Is COVID-19 a Disease of the Endothelium (Blood Vessels and Clots)? (video by Dr Roger Seheult – clearly a hero in this time)


Written by stewart henderson

July 5, 2020 at 11:46 pm