COVID-19 Snip and Shut - TRPM6 Ion Channel, Phospholipid, Phospholipase --> Hypomagnesemia

In my first blog post, Cracking COVID19: the PLA2 clues, I highlighted Phospholipase A2, and its importance to how SARS-CoV-2 replicates.

In my second post, Magnesemia key to Hypokalemia, COVID-19 damage?, I explore why regular reports of Hypokalemia (potassium deficiency) in COVID-19 patients may be due to an underlying, undiagnosed Hypomagnesemia (magnesium deficiency.)

In this post, I discuss the role of ion channel TRPM6 in Magnesium homeostasis, and I speculate how my first post (Phospholipase A2) and my second post (Hypomagnesemia) interlock.

The pandemic virus, SARS-CoV-2, needs raw materials from which to manufacture copies of itself.  It has to take those resources from our bodies.

Among the tools that the virus uses to extract resources from our bodies:  
   a pair of scissors (phospholipase) to cut up our phospholipids, and 
   a pair of scissors (exoribonuclease) to cut up our RNA.

We'll look at phospholipase first, but it will lead us right to exoribonuclease.

I have not yet found research indicating how the virus boosts levels of phospholipase, but levels of phospholipase do rise when the virus attacks, and the virus gets supplies when phospholipase cuts our phospholipids. 

One of our phospholipids (phosphatidylinositol 4,5-bisphosphate) keeps our TRPM6 ion channels open to magnesium.  As the paper says it, "Phosphatidylinositol 4,5-bisphosphate Controls Magnesium Gatekeeper TRPM6 Activity."
Furthermore, the paper finishes with "Our data indicate that PIP2 is required for TRPM6 channel function; hydrolysis of PIP2 by PLC-coupled hormones/agonists may constitute an important pathway for TRPM6 gating, and perhaps Mg2+ homeostasis."  Those researchers build upon previous findings re TRPM6 and Mg, including
"that TRPM6 comprises all or part of the apical Mg2+ channel of Mg2+-absorbing epithelia."

Therefore when the virus is replicating rapidly, 
and phospholipase is rapidly cutting up phospholipids,
it snips a fatty acid chain off phosphatidylinositol 4,5-bisphosphate (thankfully also known as PIP2), and 
TRPM6 ion channel is no longer open to Magnesium.  

My analogy is that PIP2 is like a strap keeping open the door (TRPM6 ion channel) so that magnesium can get through.  The virus boosts the number of phospholipid scissors, but some of those scissors cut the door strap, the door closes, and magnesium levels drop. 

How does that drop in Mg supply matter to the virus?  The virus is getting other materials by using that other pair of scissors--exoribonuclease, which cuts off parts of our RNA.  Activation of the virus's exonuclease "scissors" requires magnesium. After our TRPM6 door shuts, the magnesium supply drops, and I infer that the exonuclease scissors quit cutting our RNA.  I speculate that, at that point, the virus is not getting enough materials to replicate, so within the body the infection rate slows or halts.

If indeed this is how it works, it is a cool little protective trick!  It's as if Little Red Riding Hood ties her front door open with a strip of bacon.  She enjoys the breeze, but if a hungry wolf happens along, it will snack on the bacon before it proceeds into the house for the main course. Gnaw entrée --> no entry.  The door has a spring to pull it closed, so the wolf severs the bacon and the door closes. No more airflow until the wolf goes away.  Except that instead of airflow, what we're really talking about is the flow of magnesium. 

Unfortunately our bodies need magnesium for many of our most critical processes.  It is clear that by starving an infection of magnesium, our biology is severely impacted.

   Example 1: Mg 2+-Dependent DNA Synthesis and RNA Degradation

   Example 2: Short-term Magnesium Deficiency Downregulates Telomerase, Upregulates Neutral Sphingomyelinase and Induces Oxidative DNA Damage in Cardiovascular Tissues


   Example 3: Aging and Magnesium 
         (which mentions "Ca/Mg high ratio prompts blood coagulation.")

That third example would be triggered by low Mg, which sounds relevant, because hypercoagulation has been reported in COVID-19 patients, and separately, COVID-19 patients regularly are hypokalemic, and hypokalemia can be caused by a magnesium deficiency.

Additionally per hypercoagulation, on April 12, I noted research pointing to adrenaline and 5HT as contributors to platelet thrombi growth.  Though not reported in that paper, magnesium is relevant because adrenaline release is attenuated by magnesium.
That last link is worth a read--it is full of relevance, some of which I'll repeat here for your convenient reading:

A Mg deficiency occurs often in ICU patients, in alcoholics and during use of diuretics. Simultaneous administration of Mg is often required for treatment of potassium deficiency. Mg has an anti-arrhythmic effect towards digoxin-mediated dysrhythmias and torsades de pointes, and can be efficient in other arrhythmias. Systematic use of Mg seems to decrease mortality of acute myocardial infarction and is justified during cardiac surgery, often associated with hypomagnesemia, because of vasodilation of coronary arteries and in order to prevent occurrence of arrhythmias. Mg, because of its calcium channel blocking properties and as it lowers the release of epinephrine, is indicated for surgery of pheochromocytoma.

In that passage, you see medical problems that likewise are reported from the ICU for COVID-19 patients.  That gives me additional confidence in asserting that magnesium depletion or deficiency is key to the damage done by COVID-19.

Can magnesium availability explain why the virus does not affect children and women as severely as men? That begs for additional research into how 
   estrogen and estrogen receptors (and repressors), and 
   growth factors and their receptors 
affect TRPM6 expression and function. 

Regulation of the Epithelial Mg2+ Channel TRPM6 by Estrogen.

Epithelial Mg2+ Channel TRPM6: Insight Into the Molecular Regulation.

From this latter paper,

" stimulation of the EGF receptor (EGFR) leads to an intracellular cascade involving Rac1 that promotes trafficking of TRPM6 to the plasma membrane. Furthermore, long-term EGF treatment upregulates the expression of TRPM6. 

"Estrogen has also been shown to stimulate TRPM6 activity upon short-term treatment, next to its long-term regulatory effect on TRPM6 transcription. "


It is important to consider that TRPM6 is not expressed in all parts of the body in the same way.  Relationship Between Low Magnesium Status and TRPM6 Expression in the Kidney and Large Intestine.  

I searched for but did not find a thorough discussion of TRPM6 in the lungs. I wonder if a virus that cleaves PIP2 in the throat lining and airways would shut not only TRPM6 in the throat and airways, but also signal the magnesium-regulating TRPM6 channels in the kidneys, GI tract, and elsewhere.  I have long thought of the lungs as our early warning system, alerting the rest of the body when a pathogen arrives on a breath and trips a detector in the airway lining.  I would bet a Dr. Pepper that when the lung TRPM6 channels stop conducting magnesium, TRPM6 and TRPM7 elsewhere in the body detect that change in status and likewise adjust the flow of magnesium to prevent a runaway infection.  

Sepsis and hypomagnesemia certainly are related..

While we are exploring relevant mechanisms in the lungs, I predict there will be some welcome breakthroughs in cystic fibrosis research if scientists find a coordination between TRPM6 channels in the lungs and TRPM6 in other parts of the body.  In PubMed, 
   Hypomagnesemia fibrosis  returns 62 results

but for
   TRPM6 fibrosis I see only 10 results
If they are finding relationships between TRPM6 and hypomagnesemia,
and they are finding relationships between hypomagnesemia and fibrosis,
then presumably there are discoveries to be made studying TRPM6 and cystic fibrosis.
Today my search inPubMed
Found 1 result for           trpm6 "cystic fibrosis"
and it was because this paper 

    Role of Ion Channels in Gastrointestinal Cancer

contained these separate mentions

   "Various members of the TRP superfamily, including 

   TRPM8, TRPM7, TRPM6 and TRPM2, have been implicated in GI cancers"

   "CFTR is a tumor suppressor in several GI cancers. 

   Cystic fibrosis patients are at a significant risk for CRC"

On this day, April 23, 2020, there was none but this one result.  I predict that will change.

For the conclusion of this post, I had intended to finish with a final look at the relationships between 
   Phosphatidylinositol 4,5-bisphosphate (the phospholipid strap holding TRPM6 open), and
   Phospholipase a2 (the scissors that cut phospholipids).
or, more succinctly, PIP2 and PLA2.

I searched for those terms and Endothelin-1, because I had come across the papers 

Activation of Phospholipase A2 by endothelin-1 in Human Endometrium, and

Sputum and Plasma endothelin-1 Levels in Exacerbations of Chronic Obstructive Pulmonary Disease.

There is much more yet to be read, e.g.

   Protective Effects of Heat Shock Protein 70 Against Hypoxic Pulmonary Hypertension in Neonatal Rats

I see that PIP2, PLA2, and Endothelin-1 are worthy of an entire article.

For tonight, though, I am through.

In what I have already written, I examined the role of ion channel TRPM6 in Magnesium homeostasis, and I discussed aspects of COVID19 disease, including
   Phospholipase A2 and 
   Hypomagnesemia.

Hopefully, this assembled information sheds more light on COVID-19.  If we expect to end this pandemic, we will have to understand the causes of the disease.  To the best of my ability, I have tried to contribute to this understanding.

All the best,

John

Magnesemia key to Hypokalemia, COVID-19 damage?

Magnesemia is the name for magnesium deficiency.
Magnesemia  can cause hypokalemia (potassium deficiency.)
Hypokalemia is reported in nearly all COVID-19 patients.
Could Magnesium be the key to understanding the disease in a way to improve patient outcomes?

In early 2015, I wrote an article about fluorescence and medicine, in which I discussed porphyrins, calcium, and magnesium.  
In early 2019, I further explored the possible medical relevance of Vitamin D to regulation of magnesium.
This prepared me to think about how magnesium plays a role in the current COVID-19 pandemic.

In January 2020, I noted that "Another coronavirus, SARS, has an exoribonuclease that requires Mg2+ as a cofactor. So if I am correct that Vitamin D3 regulates Mg availability, then D3 affects SARS-CoV."
What is an exoribonuclease?  It's another pair of scissors.  In my last post, I talked about how phospholipase is like a pair of scissors powered by a phosphorus and specialized to cut phospholipids.  In this post, we'll consider that exoribonuclease is a pair of scissors activated by Magnesium and specialized to cleave off parts of RNA.

Per Wikipedia, 
   "Exoribonucleases are involved in the degradation of many different RNA species, including messenger RNA, transfer RNA, ribosomal RNA and miRNA."
When I searched PubMed for 
   exoribonuclease pulmonary
I happened across a 2015 discovery that an exoribonuclease PARN is associated with unexplained cases of pulmonary fibrosis. 
That exoribonuclease problem in the lungs sounds suspiciously like the lung problems in COVID-19, the disease which is caused by the virus SARS, which is closely-related to the virus SARS-CoV-2, which is causing the current pandemic and which requires Magnesium as a cofactor for its pair of scissors (its exoribonuclease.)  What type of RNA is SARS-CoV-2 cutting up, and why?  
For the virus, is this how it gets some of the supplies it needs to manufacture new copies of itself?  
For the body, does that RNA degradation prevent a message from getting through? Does it mean some biological process never receives a "stop" or a "go" signal?  Or is DNA replication disrupted or distorted?
Those questions are worthy pursuits for a researcher.  If I were a researcher, I would take that PARN discovery and look specifically at telomeres and RNA primers.

I cannot explain how and why SARS scissors cleave RNA, but I can speculate that by controlling the availability of Magnesium, the immune system can control the activity of the virus.  Vitamin D helps regulate Calcium, and as previously mentioned, I have provided experimental evidence that Vitamin D also helps regulate Magnesium.

Our bodies need Magnesium to function.  Magnesium is stored in our bones, tissues, and fluids.  But the virus also needs Magnesium--to activate its scissors to chop up our RNA.  Is it plausible that the body temporarily decreases the available Magnesium in order to deprive the SARS-CoV-2 virus of the ability to cut our RNA?  In that case, a patient's body would not be deficient of magnesium, per se, but merely it would cut down the supply available to the virus.  I infer this would result in hypomagnesemia, a shortage of magnesium in blood. If so, then the kidneys are the organ regulating magnesium in serum.

If it is detected, hypomagnesemia can be treated.

But if we are low on Magnesium, it can cause potassium deficiency--hypokalemia, and hypokalemia is more likely to be noticed and treated.

Hypokalemia is reported in nearly all COVID-19 patients.

The common-sense treatment for hypokalemia is to give potassium fluids to the patient, but if the underlying cause is hypomagnesemia, then the patient may not get the benefit of the potassium administered.

Even worse, if the patient is hypokalemic because of hypomagnesemia, then I speculate that any treatments also having a negative effect upon magnesium could worsen the problem.  Consider reading the National Institutes of Health fact sheet on Magnesium.

The most relevant part is right here:

Interactions with Medications

Several types of medications have the potential to interact with magnesium supplements or affect magnesium status. A few examples are provided below. People taking these and other medications on a regular basis should discuss their magnesium intakes with their healthcare providers.

Bisphosphonates

Magnesium-rich supplements or medications can decrease the absorption of oral bisphosphonates, such as alendronate (Fosamax®), used to treat osteoporosis [62]. Use of magnesium-rich supplements or medications and oral bisphosphonates should be separated by at least 2 hours [58].

Antibiotics

Magnesium can form insoluble complexes with tetracyclines, such as demeclocycline (Declomycin®) and doxycycline (Vibramycin®), as well as quinolone antibiotics, such as ciprofloxacin (Cipro®) and levofloxacin (Levaquin®). These antibiotics should be taken at least 2 hours before or 4–6 hours after a magnesium-containing supplement [58,63].

Diuretics

Chronic treatment with loop diuretics, such as furosemide (Lasix®) and bumetanide (Bumex®), and thiazide diuretics, such as hydrochlorothiazide (Aquazide H®) and ethacrynic acid (Edecrin®), can increase the loss of magnesium in urine and lead to magnesium depletion [64]. In contrast, potassium-sparing diuretics, such as amiloride (Midamor®) and spironolactone (Aldactone®), reduce magnesium excretion [64].

Proton pump inhibitors

Prescription proton pump inhibitor (PPI) drugs, such as esomeprazole magnesium (Nexium®) and lansoprazole (Prevacid®), when taken for prolonged periods (typically more than a year) can cause hypomagnesemia [65]. In cases that FDA reviewed, magnesium supplements often raised the low serum magnesium levels caused by PPIs. However, in 25% of the cases, supplements did not raise magnesium levels and the patients had to discontinue the PPI. FDA advises healthcare professionals to consider measuring patients’ serum magnesium levels prior to initiating long-term PPI treatment and to check magnesium levels in these patients periodically [65].

I reiterate my previous Twitter threads saying that experts need to do an end-to-end assessment of interdependencies of drugs that are used in treating COVID-19 patients.  I specifically zeroed in on how medications affect Magnesium and affect Tryptophan, but other analytes and pathways should be considered, e.g. Effects upon IFN-gamma? IDO? XO & UA?  Choice of antibiotic, anaesthesia, anti-nausea, and other medicines should be evaluated in light of this novel virus, how it attacks the body, and how the body reacts.

Also, relevance of patient medicines should be considered carefully, for example proton pump inhibitors as mentioned on the NIH page and in other research.

For additional reading on hypomagnesemia, see this excellent article, which mentions a tie-in with another interesting topic, Transient Receptor Potential channels (TRPM6 and TRPM7).  It also provides further details on serum magnesium (e.g. 1/3 of serum Mg is in protein, bound mostly to albumin.)  Furthermore, it mentions the diuretic amiloride as magnesium-sparing (decreases magnesium excretion.) 

To my eye, the structure of Amiloride looks somewhat related to a drug that has been in the news regarding COVID-19: chloroquine.  For that reason, and for the relationship between Phospholipase A2 and chloroquine which I explored in my previous post, I looked up on PubMed
   Amiloride PLA2
Fascinating.  12 results, with titles referring to topics I have discussed: Vitamin D, viruses (parvovirus), arachidonic acid (see my last post re PLA2), DNA synthesis (which we mentioned in this post when discussing telomeres), and angiotensin II (related to the ACE2 receptor by which SARS-CoV-2 invades our cells), 

For COVID-19, we have much to learn about how the virus attacks, and much to learn quickly about which drugs can thwart that attack, and how those drugs do so.  Previous research may already have uncovered clues and answers that will help us end the pandemic.

Cracking COVID19: the PLA2 clues

What are the keys to cracking COVID-19 and stopping this pandemic?

I provide evidence that the solution will involve Phospholipase A2 (PLA2), and I describe the panoramic jigsaw puzzle for which PLA2 is a critical centerpiece.

The COVID-19  numbers are grim: as I write this sentence, 79,506 people are reported to have lost their lives due to the virus, and the actual loss of life worldwide is presumed to be far higher than officially reported.  The same source shows that just under 1.4 million people are infected.  Behind every "1" added to make those large numbers, there is a face, a mind, and a life story, and the numbers continue to grow.  Everyone alive is affected by this pandemic, and a great many people are thinking about how to defeat the virus.

I believe that scientists and medical professionals will unlock the mysteries of COVID-19.  Maybe there are several valid strategies for stopping the SARS-CoV-2 virus.  Possibly everything we need to know is already available in databases of scientific research, but we have to pick out the right pieces and snap them together in just the right way.  I am skilled at pattern-matching.  I have read a great deal of scientific and medical research.  I propose that PLA2 is key.

Phospholipase is like a pair of scissors that cuts only molecules that fit a certain pattern--phospholipids.  I picture the targeted phospholipid molecule as an atomic squid with a phosphorus atom in the squid's head, and two long lipid arms that are chains of carbon and hydrogen atoms.  Those lipid arms are stuck onto the squid's head with a couple of oxygen atoms.  Drop a bunch of these squids in water, and they form a lipid bilayer, meaning that squids line up side by side to form two sheets, phosphorus-heads facing the water and lipid arms facing away from the water.  Because of the way their lipid arms are repelled by water, what results is two sheets of these squids sandwiched at the feet.  Your cell membranes are largely these bilayers of atomic squids.

Phospholipase A2 "scissors" cut off one arm of the squid at a very specific atomic bond where the arm connects to the squid, releasing a molecule named "lysolecithin" that acts as a detergent and can dissolve the membrane of a red blood cell.

For later discussion, it helps to know that the PLA2 scissors are power scissors.  Wikipedia sums up the chemistry nicely as follows:

"PLA2 is regulated by phosphorylation and calcium concentrations. PLA2 is phosphorylated by a MAPK at Serine-505. When phosphorylation is coupled with an influx of calcium ions, PLA2 becomes stimulated and can translocate to the membrane to begin catalysis."

An excellent, longer version is fascinating.

How do I picture it? To operate, the PLA2 scissors require a phosphorus battery, and to phosphorylate the scissors, you need one of those special tiny screwdrivers to jam the phosphorus into the battery compartment and close it up, and the screwdriver is a Calcium atom minus a couple of electrons.  Ca++.

So far we have power scissors that cut off a squid's arm, and the severed arm goes around wrecking red blood cells and causing other destruction.  We know the scissors need power to activate.  Where do the scissors get their phosphorus battery?

I am about to take you on a shortcut.  I found the logic shortcut because I took a long, slow, and circuitous route that gave me the answers in a very non-linear and inefficient way, and only after I assembled the right pieces did I recognize the shortcut when I saw it right there on Wikipedia.

"Phosphorylation of PLA2 may be a result of ligand binding to receptors including:"

   5-HT2 receptors

   mGLUR1

   IFN-gamma receptor

I speculate that these receptors are important to answering questions such as 

• Why does SARS-CoV-2 affect older people more often and more severely than younger people?
• Why do certain drugs/molecules inhibit SARS-CoV-2? (e.g. hydroxychloroquine)
• Why do people ache (head, muscles, etc.) when they get COVID-19?
• Why do people experience mood changes due to the virus and/or due to treatments aimed at the virus?

That first one--what is different between old and young people?  For influenza, we are relentlessly told that children are more vulnerable because "their immune systems are relatively naive."  If that is the case, then you would think COVID-19 would afflict children as often and as severe as influenza, but COVID-19 injures children far less often than it does adults.  If a "naive immune system" is not to blame for severity of viral infection, then what's going on?

In a tweet October 2019 regarding influenza, I asked, "What if age-related serotonin receptor changes are key?"

I also referred to this 1992 research (that does not mention virus,) that reports 5HT2 expression is highest in kids and declines with age, with some differences between sexes:

"Among the ages sampled, the highest levels of 5HT2 receptor binding were found in 6-year-olds. A sharp decline in receptor binding occured during adolescence, with levels reduced by half between ages 13 and 17. This pattern is similar to the one we have observed in brain 5HT2 receptors postmortem. There were no significant sex differences in 5HT2 receptors on platelets in newborn and young children. A trend towards higher binding in girls appears around the onset of menstruation in teenage girls (age 14 and up). These results demonstrate that platelet 5HT2 receptors can serve as a model for age dependent changes in 5HT2 receptors in the brain."

I may be oversimplifying things, but perhaps this insight could inspire a diagnostic that can predict a person's risk from catching SARS-CoV-2.  Is there a difference in 5HT2 receptor binding on platelets in people who get sickest versus people who show no symptoms of COVID-19 infection?  Kids do get sick and die from COVID-19; is there something different about their expression of 5HT2?  Likewise, many older adults are asymptomatic after SARS-CoV-2 exposure.  For their age group, do they have a higher-than-average expression of 5HT2 receptors in some type of cell that might reveal more about how the disease attacks?

Two of the other questions I posed earlier relate to serotonin receptors such as 5HT2.  

• Why do people ache (head, muscles, etc.) when they get COVID-19?
• Why do people experience mood changes due to the virus and/or due to treatments aimed at the virus?

Serotonin is extensively involved in our biology, including cognition, behavior and mood, pain perception (nociception,) immune system function, inflammation, blood clotting, cardiopulmonary function, taste, and smell.  If any of you are allergic to nuts, here's a nut to crack: serotonin production in drying seeds, which I found thanks to Wikipedia.  I wonder what enzymes and molecules remain after the nut baking process?

All serotonergic topics are worth exploring more fully.  For now I will stop with serotonin and zero in on our sense of smell, and I will tie that back to Phospholipase PLA2 (the squid scissors,) and to COVID-19.

I first started thinking about PLA2 and coronavirus on January 23rd when I searched for "phospholipase" and "coronavirus" and found the article 

   "A phospholipase linkage to SARS susceptibility".  

That excellent article led to a 2015 research paper ("Critical role of phospholipase A2 group IID in age-related susceptibility to severe acute respiratory syndrome–CoV infection") 

and via that, other papers worth a read, e.g. the 2018 "Inhibition of Cytosolic Phospholipase A 2 α Impairs an Early Step of Coronavirus Replication in Cell Culture":

"evidence to show that a cellular phospholipase, cPLA2α, which releases fatty acid from the sn-2 position of membrane-associated glycerophospholipids, is critically involved in coronavirus replication, most likely by producing lysophospholipids that are required to form the specialized membrane compartments in which viral RNA synthesis takes place. The importance of this enzyme in coronavirus replication and DMV formation is supported by several lines of evidence, including confocal and electron microscopy, viral replication, and lipidomics studies of coronavirus-infected cells treated with a highly specific cPLA2α inhibitor."

PLA2 kept coming up.

On February 19th I tweeted about a WSJ article mentioning chloroquine as a drug being tried against COVID-19.  I looked up chloroquine and saw that it inhibited PLA2.

Then in response to a March 3rd tweet mentioning chloroquine, I continued to search and think about PLA2.

March 20th the ENT UK and British Rhinological Society tweeted that COVID-19 patients were reporting loss of smell as a symptom of the sickness.

When I looked up anosmia, I saw that snake venom also can cause anosmia, and I knew already that venoms (snake, scorpion,) contain PLA2 enzymes.

I tweeted about how the virus biological effects had something in common with effects of snake bite, i.e. both the virus and a snakebite involve PLA2. 

I am convinced that PLA2 is a center piece of the COVID-19 puzzle.

This article presents a selection of information upon which I base that conclusion.

I look forward to writing more about 

• Phospholipase PLA2, and about how PLA2-inhibiting malaria drugs such as chloroquine and HCQ may help against COVID-19.  [Note: for safety's sake, use only under doctor supervision.]
• Mycobacteria (e.g. Tuberculosis, Chlamydia) treatments in the battle against this pandemic. 
• Molecular structures of promising drugs, metabolic pathways affected, and genetic and other reasons why people's outcomes may vary.

Thank you for reading, 

John C. Beach