Posts Tagged ‘Dr Roger Seheult’
covid19: monoclonal antibodies, symptomatic v asymptomatic, corticosteroids, comorbidities
keeping it simple, for now
Jacinta: Let’s look at monoclonal antibodies briefly before we continue with those medcram updates. Francis Collins, the somewhat controversial but scientifically reliable directer of the NIH in the USA, recently described ‘monoclonals derived from people who’ve survived covid19’ as the best hope for treatment in the absence of a vaccine. So what are these monoclonals? There are lots of useful videos on youtube that provide detail. I’m picking one from the JAMA network. The technology for producing these types of antibodies was developed in the mid-seventies. It was called ‘murine hybridoma’ technology, murine meaning ‘mice’. I remember first reading about monoclonal antibodies in a Scientific American article in the early eighties. It went straight over my head of course, but now it’s time to get a grip on them. So mice were injected with an antigen, which in general terms is a pathogen that induces an immune response. In more specific terms an antigen is a molecule or structure, part of a larger pathogenic molecule, that can be bound to by an ‘antigen-specific antibody’ or B cell receptor. B cells are lymphocytes that secrete antibodies. So the researchers induced this response, then isolated B cells from the spleen of the mice, which they fused with myelomas (cancerous plasma cells). Cancer cells are notoriously long-lived – see ‘the Immortal Life of Henrietta Lacks’ – so these fused cells, called ‘hybridomas’, act like B cells in producing antibodies, and like tumour cells in their ability to replicate. So these hybridomas can be grown in culture and each one can produce a single antibody type, which targets a single antigen type. Hence monoclonal. They can clone themselves for a specific antigen. So, once you know your antigen, you can create a ‘monoclonal’ specifically for it, or two or three to choose from. And now, with covid19 and with technological development, we can isolate monoclonal antibodies not from mice but from recovered covid19 patients. So that’s a somewhat over-simplified account – for more detailed info on monoclonal antibodies, this zero to finals video is excellent, and there are doubtless others. The target for this work is generally the S-protein of the SARS-CoV2 virus, with various particular sites being looked at, and a number of teams working on the research. Some are pretty well ready to go, with specific antibodies or sets of antibodies. The argument is that they could be used for high-risk groups such as ICU workers and nursing home clients, as a kind of temporary vaccine.
Canto: Okay, something else to keep track of. So update 93 discusses an article published in Nature Medicine – all the authors appear to be Chinese – which looks at 37 asymptomatic covid19-infected subjects and their antibodies, compared to those of 37 symptomatic subjects.
Jacinta: So they looked at their immunoglubulin G (IgG) levels. These are the most common types of antibody, created and released by plasma B cells. They graphed the IgG during the acute and convalescent phases, and they defined the acute phase as that in which the viral RNA was detectable in a respiratory specimen, and the convalescent phase as from eight weeks post-release from hospital. What the graph shows is that the IgG levels decreased from acute to convalescent in both symptomatic and asymptomatic cases, but more in the symptomatic cases. They also looked at ‘neutralisation rates’, which presumably refers to the effect of antibody activity. A positive effect means more neutralising antibodies are produced. These seemed about the same between the phases for both groups, but another graphic shows that in the convalescent phase, the symptomatic group have substantially more neutralising antibodies. It seems from this admittedly small study that asymptomatic subjects are at risk of reinfection, after a period of time.
Canto: And even symptomatic subjects after recovery, as we have obviously no longitudinal studies on anti-viral IgG levels, as the study points out.
Jacinta: Well that takes us to the next study, from Spain, which managed to round up almost 52000 participants. The study tells us between late April and mid-May the estimated seroprevalence (the percentage of inhabitants that had the virus) for the whole country was around 5%, depending on different test types and results, and with great variation between regions. Findings were that prevalence increased with increasing age. Looking at different jobs, those working in healthcare were clearly more at risk, and to a lesser but still significant degree, those working in nursing homes…
Canto: Which is still largely healthcare, but less trained, and often less prepared for this onslaught…
Jacinta: Point taken. And those living in the larger municipalities were more often infected than those in less densely populated regions. Interestingly, they found that the rapid (and cheap) fingerpoint test, which provides results within ten minutes, was pretty close to being as effective as an immunological assay, which is important as the delay in test results has been a major issue.
Canto: Amazing. Why aren’t they using this all the time? Everywhere?
Jacinta: That’s another issue – maybe later. Anyway, much of this study confirms the many smaller studies that have been conducted. They found that healthcare workers comprised 24% of all confirmed cases. This may be partly because they had more access to testing. There is so much to glean from this study, I can only skim. But here are some very interesting remarks in their conclusion:
One in three infections seems to be asymptomatic, while a substantial number of symptomatic cases remained untested. Despite the high impact of covid19 in Spain, prevalence estimates remain low, and are clearly insufficient to provide herd immunity. This cannot be achieved without accepting the collateral damage of many deaths in the susceptible population and overburdening of health systems. In this situation, social distance methods and efforts to identify and isolate new cases are imperative for future epidemic control.
Canto: So there are no easy solutions, and even a vaccine is not necessarily going to be the magic bullet everyone’s hoping for. The proof of the pudding will be in the eating, and we haven’t eaten any vaccines yet. They won’t be on the menu for a while, and it’ll be a lot longer before we can gauge their nutritional value.
Jacinta: Yes, what you’re saying is, we don’t know how long antibodies to this virus will last. We’re still in unexplored terrain with respect to this very unusual and deadly virus. An article published on the Jama Network quite a while ago is still relevant now in its conclusions, as nothing we’ve so far found disconfirms it:
… the immune response to covid19 is not yet fully understood and definitive data on post-infection immunity are lacking. Amidst the uncertainty of this public health crisis, thoughtful and rigorous science will be essential to inform public health policy, planning and practice.
Canto: Frustrating to many. So with update 94 we’re getting towards mid-July and they’re noting that things are hotting up, as the weather is cooling down, in Australia, though of course it bears no comparison to the US tragedy. They were talking about things getting worse in their autumn, but summer hasn’t given them any sort of break.
Jacinta: So update 94 first looks at inhaled corticosteroids, one of many medications being considered and perhaps used by health professionals, others being ivermectin (a broad-spectrum anti-parasitic drug) and nitric oxide, all without solid RCT-type evidence. Even so, case reports and other low-level studies show promise, and these are arguably desperate times. A study presented by Dr Seheult suggested that some corticosteroids showed positive immunological effects in case reports and in vitro. Interestingly, asthmatics have been prescribed corticosteroids quite regularly…
Canto: As have I, from time to time. At least I think it was corticosteroid…
Jacinta: Well, that’s interesting, I know you’re not asthmatic but with bronchiectasis you have asthma-like symptoms at times. And the good news for you, and generally interesting news for us all, is that ‘asthma patients with covid19 do not appear to have a higher rate of hospitalisation or mortality compared with other covid19 patients’. Indeed it may be the opposite, as data from Wuhan indicates that less than 1% of their hospitalised patients had asthma, compared to 5% in the general population. In New York, too, asthma wasn’t even in the top ten comorbidities, which is pretty striking for a virus that hits the lungs first. Similarly, COPD, which your ailment is surely associated with, comes in below diabetes, renal disease and a whole range of cardiovascular issues as a comorbidity factor. A possible reason for this is that the kind of chronic inflammation produced by asthma and COPD is associated with reduced ACE2 expression, meaning fewer receptors for the virus. So these conditions could actually be protective. And they might also be on corticosteroid inhalers, which may also be protective.
Canto: That sounds great. Let’s leave it there before I hear any bad news…
References
Coronavirus Pandemic Update 93: Antibodies, Immunity, & Prevalence of COVID-19 – New Data from Spain
Coronavirus Pandemic Update 94: Inhaled Steroids COVID-19 Treatment; New Pneumonia in Kazakhstan?
How do monoclonal antibodies work? Rituximab, infliximab, adalimumab and others
Coronavirus Treatment and Prevention with Monoclonal Antibodies
more covid 19: vitamin D, helper T cells, testing
I’m continuing with my gleanings from the Medcram Covid-19 updates presented by Dr Roger Seheult, though I’m not up to date with them, because they’re quite comprehensive and nuanced, and I want that detail more than anything. I’m also reading the book Outbreaks and epidemics: battling infection from measles to coronavirus, by Meera Senthilingam, which among other things, highlights the importance of preparedness, co-ordination and resourcing to deal with new and unexpected pathogens but also upsurges and cross-border spread of diseases we haven’t sufficiently dealt with in the past. As we hurtle at an unprecedented rate towards a number of vaccines against SARS-CoV2, for example, we may have to deal firmly, on a governmental level, with the anti-vaccination movement and its disinformation campaigns, but we also have to deal with grossly uneven levels of healthcare within and across nations. This current pandemic has been revelatory, for all but those on the front lines, of the variable impact such outbreaks have on the different levels of empowerment within societies. To take a stark example, Boris Johnson, the British Prime Minister, very likely owes his life to the fact that he is the British Prime Minister. Had he been a fifty-something person of colour living in Dagenham (or most anywhere outside of a UK city), his Covid-19 case would surely have turned out quite differently.
Update 74 is quite brief and mainly touches on vitamin D, the ‘sunlight’ vitamin, also obtained from foods such as fish, especially salmon and tuna, and egg yolks, and mushrooms raised using UV light – but mostly from the sun’s UV. Vitamin D enhances bone and muscle strength and function. A Lancet article is discussed, which correlates ‘vitamin D status’, presumably meaning bodily levels, with Covid-19 mortality. Some surprises in the data – vitamin D deficiency was common in ‘sunny’ Italy and Spain, but less of a problem in Nordic countries, perhaps due to a high vitamin D diet. Deficiencies were greater in poorer regions and in black communities, as of course were higher Covid-19 mortalities. in fact, ‘black people in England and Wales are 4 times more likely to die from Covid-19 than white people’ according to the UK’s Office for National Statistics.
The Lancet article referred to points out two aspects of vitamin D’s possible protection against Covid-19. First, it ‘supports production of antimicrobial peptides in the respiratory epithelium’, which sounds positive, and second it may help to reduce the inflammatory response to the virus because it’s known to interact with and promote the ACE-2 protein, which the virus suppresses. Other articles emphasise the benefits, with no attendant harm, of vitamin D supplements, particularly for the elderly. There have been no systemised, detailed trials as yet relating vitamin D levels to Covid-19 outcomes, but it seems like a no-brainer.
Update 75 continues the argument about SARS-Cov2 attacking the lining of the blood vessels, i.e. the endothelium, with the resultant effect on von Willibrand factor. This happens in the lungs as well as the vascular system, creating clots as well as the growth of new blood vessels as a type of immune response. This essentially marks it out from any kind of influenza. The New England Journal of Medicine has an article, published late May, looking exactly at these differences in the autopsies of Covid-19 victims – endothelialitis (inflammation of the endothelium) and angiogenesis (the formation of new blood vessels). They compared Covid-19 lungs with the lungs of ARDS (acute respiratory distress syndrome) victims, associated with influenza A (H1N1), and with uninfected lungs. They found ‘alveolar capillary microthrombi’ – often difficult to detect with scans – in the Covid-19 lungs at nine times the level of the influenza lungs, and new vessel growth at almost three times that of the influenza lungs. Clearly the new vessel growth is caused by the blockages, and the need to circulate around them. Microscopic analysis shows lymphocytes infiltrating the lungs, adding to inflammation, stiffness and tissue damage. The clotting prevents oxygen being picked up from the alveolar space, leading to low oxygen saturation of the blood. Scanning electron micrographs of the lung endothelium revealed viral particles in the extracellular space, suggesting strongly that the virus itself, and not simply the immune response to it (perivascular inflammation) is causing damage. Dr Seheult brings up NAC again here, as a possible disruptor of the cascade of events, especially in the suppression of superoxide and in the cleaving of disulphide bonds in VWF.
An article in Science, which refers to the adaptive immune system, is next discussed. The adaptive immune system, as opposed to the innate immune system, is a system that creates a memory of a pathogen in order to develop an enhanced response, a system exploited by vaccines. This system includes T cells, of which there are three types, memory, cytotoxic and helper. These cells are apparently involved in lifelong immunity. Vaccine researchers are concerned to create antibodies as protection against the virus, but T cells are also important in this regard, and researchers have found that many infected patients, and non-infected people, do have T cells that attack the virus, probably because they have been infected with other coronaviruses that share proteins, such as the spike protein, with SARS-CoV2. Researchers in fact found that Covid-19 patients all harboured helper T cells that recognised the SARS-CoV2 spike protein, and other SARS-CoV2 proteins, again suggesting the possibility/probability of lifelong immunity. Many others harboured the same helper T cells, which may be protecting them against the worst Covid-19 symptoms, before the fact. This is possibly a very important, and highly explanatory finding. Or maybe not. T cells are long-lasting, so these findings are certainly positive.
Update 76 starts with antibodies, and it’s a bit difficult to follow. It looks at the CDC’s ‘interim guidelines for Covid-19 antibody testing’, and a CNN health article summerizes it thus:
The CDC explains why testing can be wrong so often. A lot has to do with how common the virus is in the population being tested. For example, in a population where the prevalence is 5%, a test with 90% sensitivity and 95% specificity will yield a positive predictive value of 49%. In other words, less than half of those testing positive will truly have antibodies’, the CDC said.
This is hard to follow, but 5% prevalence is fairly standard for this virus, at least at the outset. And so false positives are a problem. To be clear about testing – a person either has the disease or not. If you have it and you test positive, fine, that’s a true positive. If you have it and test negative, that’s a false-negative. If you don’t have it and you test positive, that’s a false-positive. If you don’t have it and test negative, that’s a true negative.
So we can look at percentages and maths, and I’m following Seheult strictly here. So imagine we’ve tested 2100 people in a particular region – that’s everyone in the region. At this stage the disease has a prevalence of 5%, so about 100 out of 2100 have the disease (strictly speaking that’s 4.76%). The test has a sensitivity of 90% and specificity of 95% as above. 90% sensitivity means that the number of true positives from the test will be 90% of the number of those who actually have been infected by the virus. That means 90 people. 95% specificity is about those not infected. So you divide the true negatives by those uninfected to arrive at the 95%. The true negatives will amount to 1900. So 10 people will be false positive and 100 false negatives. When specificity rises, false positives decrease. When sensitivity increases, false negatives decrease. So with high sensitivity a negative result is more conclusive, and with high specificity, a positive result is more conclusive.
Imagine then that the prevalence of the infection has risen to 52% in the same population of 2100. That gives us 1094 with the disease, 1006 without. With the same values for sensitivity and specificity of testing, you’ll have 985 true positives and 50 false positives, and 956 true negatives and 109 false negatives. What you need to know with these results is how things stand for patient x, the person you’re dealing with. This means you need to know the predictive values, positive (PPV) or negative (NPV). This requires some simple maths. Given a positive test result, what chance is there of x having the disease? Or vice versa for a negative result. This means that for the PPV you divide the true positives by the total number of positives, and the same process applies for NPV. Going back to the situation where the prevalence was 5% we get a PPV of 47% and a NPV of 99%. What this means is that when the prevalence is low, the negative predictive value is much higher than the positive predictive value. The implication is important. It’s just not clear at this stage whether you have antibodies against the virus. So you need to raise the specificity of the test, especially if the virus or pathogen has a low prevalence. But looking at the 52% prevalence case, and using the same simple maths we find that the PPV is up at 95% and the NPV goes down to 90%. Prevalence, then, is the main determinant of predictive values.
For testing, this means, just as the disease is becoming prevalent, that’s to say, as it’s just being detected, you need a test with a very high specificity (admittedly a big ask) and/or you need to test those with a high probability, based on current knowledge, of being infected, and those in contact with them.
References
Coronavirus Pandemic Update 74: Vitamin D & COVID 19; Academic Censorship
Coronavirus Pandemic Update 75: COVID-19 Lung Autopsies – New Data
Coronavirus Pandemic Update 76: Antibody Testing False Positives in COVID-19
update 69: NAC, glutathione, oxidative stress, thrombosis
So we start with a closer look at glutathione, and its backbone amino acid chain, including the amino acid cysteine. Cysteine has the formula HO2CCH(NH2)CH2SH. The thiol sub-chain (SH) is important because it can bind to another form of the molecule, with S binding to S (oxidised form) rather than binding to H (reduced form) as here. So, as Dr Seheult explains, if you have two glutathiones, in this reduced form (2GSH), oxidised via hydrogen peroxide (H2O2), you will create a bond (GS-SG) between the two oxidised glutathiones, together with water. This happens in the oxidisation processes in our cells.
Seheult next mentions ADAMTS13, which is also known as von Willibrand factor-cleaving protease, so it’s a zinc-containing enzyme. VWF polymerises via disulphide bonds, and ADAMTS13 can help in disrupting that process, I think. Seheult diverts us by mentioning the disulphide bonds that connect the spiral strands of keratin in hair. A ‘perm’ reduces the molecular structure, breaking the disulphide bonds, so that the individual strands can be straightened, or made more curly, after which ‘you neutralise the perm agent’?? via H2O2, allowing disulphide bonds to re-form keeping the new hair structure in place. That was almost interesting.
So what can we do to assist these glutathione-based processes in relieving oxidative stress? This is apparently where N-Acetylcysteine (NAC) comes in. This molecule, which is ‘the N-acetyl derivative of the natural amino acid L-cysteine’, is ‘an antioxidant and disulphide breaking agent’, according to a 2018 review article in the Journal of Free Radical Research (not a political journal). So NAC is a reducing agent, which, like cysteine, has an SH bond. It breaks disulphide bonds and adds hydrogen, reducing viscosity. NAC has been used as a mucolytic inhalant, and as an agent against tylenol (paracetamol) overdose. How this last effect works is complex and I’ll try to comprehend it.
As Seheult explains it, NAC would act on the metabolite of paracetamol in situations of overdose. In such cases the liver metabolises paracetamol via an alternative pathway, by means of the toxic metabolite NAPQI, which depletes the liver’s glutathione. NAC replenishes the glutathione, but I won’t try to analyse the mechanism here. The main point is that NAC’s glutathione-boosting effects may have potential in dealing with Covid-19 symptoms. According to the above-mentioned review article, glutathione depletion is related to oxidative stress associated with a wide range of illnesses and pathologies, as well as in general ageing. So, a 1997 study in Italy looked at H1N1 flu and NAC treatment in a randomised, double-blind trial of 262 individuals of both sexes, most of them suffering from non-respiratory chronic degenerative diseases. They were divided into a placebo group and a NAC tablet group for a period of six months. No difference was found in both groups contracting the virus, but the majority of the placebo group (79%) came down with symptomatic forms, compared to only 25% of the treatment group, a significant difference. The study concluded that NAC treatment ‘appears to provide a significant attenuation of influenza and influenza-like episodes, especially in elderly high-risk individuals.’
So, recognising that this update is 2-3 months old now, I went online to see if NAC treatment is being used, or more comprehensive trials are being undertaken, as I note that, though case-rates are still disturbingly high, especially in the USA, death-rates are somewhat reduced.
An article from NCBI (the National Center for Biotechnology Information), which post-dates update 69 by a couple of weeks, presents only a hypothesis:
that NAC could act as a potential therapeutic agent in the treatment of COVID-19 through a variety of potential mechanisms, including increasing glutathione, improving T cell response, and modulating inflammation.
However, it didn’t seem as if any effective clinical trials focusing specifically on Covid-19 had been completed at the time of the article. A much more recent article (July 14) in Future Medicine (not such a promising name, given the urgency), presents more biochemical detail of NAC’s action, along with the anticoagulant heparin, and mentions ongoing clinical trials, but not specific results. It also mentions NAC treatment as a preventive for frontline ICU workers and general healthcare workers. It may be that such treatment is already being applied.
So, returning to update 69, Seheult cites another article from 2010 in Biochemical Pharmacology which showed that NAC inhibited viral replication (here the virus was H5N1) and reduced inflammatory cytokines, and again they suggested it as a potential treatment in the case of future influenza pandemics. Another small trial suggested some limited efficacy for NAC in the treatment of acute respiratory distress syndrome (ARDS).
So on it goes. A 2018 article found that ‘[NAC] improves oxidative stress and inflammatory response in patients with community acquired pneumonia [CAP]’. This oxidative stress reduction may be more important for Covid-19 cases because of the possibility of thrombosis due to the effect on VWF. A 2013 study found a significant decrease in a number of coagulation factors with NAC treatment. Of course, with this blood-thinning facility, NAC should not be used for patients with increased bleeding risk during or resulting from surgery. In any case I note that NAC is on the WHO list of most safe drugs or treatments.
And there are more studies. Another 2018 study found that NAC could reverse cerebral injury from strokes exacerbated by diabetes. The study concludes that ‘the diabetic blood and brain become more susceptible to platelet activation and thrombosis’, and that NAC appears to offer protection against the risk of stroke. The study’s explanation of the process here gives me an opportunity for further revision:
[NAC protects against stroke] by altering both systemic and vascular prothrombotic responses via enhancing platelet GSH, and GSH-dependent MG elimination, as well as correcting levels of antioxidants such as SOD1 and GPx-1.
So that’s platelet glutathione, and glutathione-dependent methylglyoxal, and the antioxidants mentioned are superoxide dismutase 1 and glutathione peroxidase 1. The ScienceDirect website does an amazing job of informing us about every known aspect of molecular biochemistry, just saying. Its material on glutathione and its catalysis is exhaustive and exhausting. And it looks as though the silver lining to the tragedy of Covid-19 may be a spike in further research into this and other essential elements of the molecular basis of immune systems.
Dr Seheult goes on to cite one more study, which found that ‘NAC administration promotes lysis of arterial thrombi that are resistant to conventional approaches…’, principally by acting on VWF, and that it is even more effective in combination with ‘a nonpeptidic GpIIa/IIIb (glycoprotein) inhibitor’, with no observed worsening of symptoms or outcome vis-a-vis normal haemostasis.
So I’ll end this piece wondering how things are going with NAC and other applications to reduce both respiratory and thrombotic symptoms in regions where the virus continues to be spread through a mixture of government, business and personal irresponsibility and stupidity. The battle to keep people alive and relatively healthy will, I think, ultimately win over the stupidity of some, but at a terrible and tragic cost. Vaccines are in the offing, but fear, indifference and ignorance will probably have the most adverse influence on their effectiveness.
References
Coronavirus Pandemic Update 69: “NAC” Supplementation and COVID-19 (N-Acetylcysteine)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7261085/
https://www.futuremedicine.com/doi/10.2217/fmb-2020-0074
https://www.sciencedirect.com/science/article/pii/S0304416512002735
https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/methylglyoxal
SARS-Cov2 and oxidative stress
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.
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)