Anti-Inflammatory Diet

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Friday, February 26, 2010

ABO Oligosaccharides, RBCs, VWF, Endothelial Cells, Megakaryocytes

Blood Group Antigens Are Synthesized in the Golgi by Glycosyl Transferases A or B

This is another rant about poor teaching and false text book information.  I have been trying to summarize some of the key points of genetics and cell biology that I think should shape the minds of young biologists.  To make my point, I want to outline where the common ABO blood group antigens are made and displayed.

ABO Antigens Are Oligosaccharides, Not Proteins

Red blood cells that are type A will clump together with antibodies that bind to A antigens.  At this point many instructors leap ahead and say that the expression of the A gene results in the production of the A protein, that is displayed on the surface of RBCs.  Wrong.  The antigens are carbohydrates, short chains of sugars called oligosaccharides, attached to a lipid embedded in the RBC membrane.

Glycosyl Transferases - Enzymes that Assemble ABO Oligosaccharides

Oligosaccharides are synthesized by adding one sugar at a time onto a growing chain.  Information-rich oligosaccharides, such as the ABO antigens, are made of several different sugars and are linked in a variety of ways to other sugars, so each sugar is added by a different enzyme.  The sugar-adding-enzymes are called glycosyl transferases.  Similar to other macromolecular polymerizations, e.g. protein and nucleic acid synthesis, the monomer sugars are first activated by bonding to a nucleotide phosphate (typically UDP) and the sugar is transferred from this activated intermediate to the growing sugar chain, in this case the H antigen. 

The glycosyl transferase coded by A allele transfers an N-acetylgalactosamine to the end of the H antigen oligosaccharide, whereas the glycosyl transferase coded by the B allele transfers a galactose residue.

Dominance Means Functional Enzyme, Recessive Means Dysfunctional

The ABO blood group system provides a simple molecular interpretation of genetic dominance.  An allele is dominant if it produces a functional enzyme that gives the phenotype, in this case a particular glycolipid attached to an RBC.  A or B alleles that have mutated to yield dysfunctional proteins that no longer function as glycosyl transferases are recessive.  Recessive alleles don’t impact phenotype.  O antigen is nothing more than the original unmodified H oligossacharide.

ABO Is Bizarre because A and B Code for Two Alternative Functional Enzymes - Codominance

Multiple mutations converted an allele that coded for a glycosyl transferse into a second allele that transferred a different sugar.  A and B alleles code for two different glycosyl transferases that transfer two different sugars.  The result is codominance.  AB individual have both enzymes and produce both A and B antigens on their RBCs.  This is very unusual and inconsistent with Mendelian genetics.

AB Glycosyl Transferases Are in the Golgi to Produce Oligosaccharides for Export

Part of the peculiarity of the ABO system derives from the action of the A and B glycosyl transferases in the Golgi.  Proteins destined for secretion have a hydrophobic group of amino acids, the signal peptide, that is synthesized first as a messenger RNA is translated into protein on a ribosome.  The signal peptide orchestrates binding of the ribosome to the endoplasmic reticulum (ER) and the growing polypeptide is extruded into the ER.  A series of vesicle budding and fusing events transfers proteins to the lamina of the Golgi apparatus and a final fusion event with the cytoplasmic membrane results in secretion.

Specific enzymes retained in the ER and the Golgi recognize particular amino acid sequences and attach sugars to exposed hydroxyl of amino groups (O or N glycosylations).  The ABO antigens are a little unusual in that the oligosaccharide is attached to a lipid anchor, so that the A and B glycosyl transferases localized in the Golgi attach terminal sugars and the glycolipid remains bound to the cytoplasmic membrane and is displayed on the surface of the RBC.

RBCs Don’t Have Nuclei, ER or Golgi, but Normoblasts Do

Mammalian RBC’s don’t have nuclei, because the nuclei were expelled during RBC development.  Since the ER is an extension of the outer membrane of the nucleus and the Golgi is derived from the ER, it follows that RBCs don’t have any of these structures.  RBCs are just collapsed bags of ribosomes, hemoglobin mRNA, cytoplasmic enzymes, a few mitochondria, lots of hemoglobin and stiffened membranes displaying ABO oligosaccharide antigens.  The ABO antigens were assembled and displayed on the membrane before the loss of the nucleus.

ABO Antigens Are Also on von Willebrand Factor of Endothelial Cells and Platelets

I have never heard a good explanation of why a transfusion from a universal, type O donor to recipients with type A, B or AB blood doesn’t cause clumping of RBCs.  The galactose and galactosamine sugars that decorate B and A RBCs also commonly decorate the surfaces of bacteria.  The immune system is prevented from making antibodies against its own antigens and so it only produces antibodies against A or B antigens found in bacteria, if they are not own self RBCs.  Type O individuals lack A and B antigens of their own, so they produce anti-A and Anti-B against bacterial oligosaccharides.  So why don’t the anti-A and anti-B antibodies in type O blood serum clump type A or type B blood?

The answer is that a serum protein, von Willebrand Factor (vWF) is also decorated with the ABO oligosaccharides.  A type A person has type A vWF and a type B person has type A vWF.  Thus, the antibodies against A and B oligosaccharide antigens that are present in type O blood will be inactivated by binding to the A or B oligosaccharides of the recipients vWF.

vWF is synthesized by endothelial cells that line veins and arteries.  It is present in the secretory Weibel-Palade bodies of endothelial cells.  It is also present for secretion by platelets.

So, the ABO blood group antigens are very strange examples that are not protein, not Mendelian and are not even predominantly found on RBCs.  The AB oligosaccharides do provide good examples of the use of activated intermediates in macromolecular synthesis, the origin of organelles, secretion, erythropoiesis and immunology.


Dennis said...

I work in blood banking and I'm here to help. :)

I believe your explanation about why a transfusion from group O to A or B does not agglutinate the RBCs of the recipient to be either mistaken or incomplete. For your explanation to work, the vWF would have to react with all of the antibodies from the O donor with none left over for the RBCs, which may work but I can't say I've heard of that.

The fact is that the antibodies most certainly can react with the recipient's RBCs, but in blood banking these days, plasma is separated from RBCs, and the appropriate product, whether RBCs or plasma, is given for the appropriate indication. Whole blood is, AFAIK, indicated for little if anything. Therefore, that blood product from an O donor has very little plasma in it.

The other reason is dilution. Even were whole blood to be given, in most cases the amount is small compared to the patient's own plasma volume, and even if antibody attachment occurs, it isn't much and presumably causes little harm.

The presence of high ABO antibody titers has been something of a mystery to me, but maybe you've explained it. The presence of such titers means that people are continually exposed to the corresponding antigen, and if those antigens were on gut bacteria, that would seem to explain it.

Dr. Art Ayers said...

Thanks for your informed input.

Alas, my hyperbole has been exposed. I was trying to highlight the fact that vWF carries more ABO antigen than RBCs and to show the difference between glycolipids on RBCs and glycoprotein in the case of vWF.

I don't know if healthcare workers are aware that there are ABO antigens on vWF. I just enjoyed the implication that the A and B glycosyl transferases are active in the Golgi of endothelial cells.

ABO antibody titers may also reflect leaky gut, inflammation and other chronic diseases related to bacterial LPS. I was also trying to emphasize the ubiquity of the ABO oligosaccharide structures.

I enjoy hearing from people with hands on experience. It spices up my speculation and keeps me grounded.

Thanks for your helpful comments.

lightcan said...

Hello Dr. Art,

Sorry to bother you with an unrelated question. I was surprised to see recently that there was some inflammation on two of my intermediate phalanges. They're swollen and sensitive. I have started a couple of weeks ago to take 5000 units vit. D and I'm taking fish oil too, I don't know what can cause it. I have no wheat, and no sugar. Can it be some kind of injury? Do you think I should increase my omega 3 dose from 2.5 ml/d just to help with the healing or stop taking it to allow the inflammation to take its course. (As it is advised in the case of a cold)
Thank you.

Dr. Art Ayers said...

I wouldn't cut back on anti-inflammatory dietary approaches because of an inflammation of hand or feet digits. I would suspect some kind of trauma, in which case system-wide inflammation is still not a good idea.

I would suggest application of castor oil to your whole hand or foot. That should cause a decrease in finger/toe inflammation.

By the way, I just read in Newsweek that the Gold Medal Alpine Skier Lindsay Vonn uses castor oil for her myriad injuries. She credited her Norwegian mother's common sense for that efficacious remedy.

Thanks for the comments.

lightcan said...

Thank you. I tried what I had in the house: a deep heat gel based on menthol and eucalyptus oil as you suggested elsewhere and piroxicam. Still the same, but good to know that I should continue with the CLO. I really appreciate the fact that you replied. There is a plethora of information on internet, it would take days to sift through it, to get to a possible cause.

TanyaMc said...

I am posting on this article because it at least mentions blood clotting..sort of!

Today is my last day of Plavix and full dose aspirin. Tomorrow I go to just a baby aspirin a day. In light of its effects on leaky gut, I looked into nattokinnase again. I found that perhaps it may not be good to take with aspirin (bleeding incident reported), which since I want to stop taking the aspirin is not a problem.

However, since the implanting of the septal occluder in my heart, I am concerned about the scar tissue issue. Natto affects fibrin and scar tissue (so I've read). So if I take it will it disrupt the scarring over of the occluder/plugging of the hole in my heart? Or will it help my heart grow healthy tissue instead of scar tissue?

I am going to ask my doctor about it, of course, but since I am unsure of his 'slant' for supplements, I wanted to explore the issue here if possible.


Dr. Art Ayers said...

Hi Tanya,
Natto or nattokinase, the protease produced by some strains of Bacillus subtilis, activates a fibrinolytic enzyme and is therefore said to be a clot buster. But these are in vitro enzyme assays. There is a big difference between eating a protein, such as nattokinase, and having the enzyme appear in the blood.

I would not expect detectable amounts of nattokinase that is eaten, to end up in the blood, unless the gut is leaky. Of course aspirin makes the gut leaky and taking aspirin with nattokinase, may cause problems with clotting.

So, I wouldn't expect natto to have any impact on clotting or scar formation unless aspirin or some other gut compromise is occurring. I doubt that natto will do anything unless it is a topical application or is altering gut flora.

Good luck with your hole plugging.

TanyaMc said...

How about tomato extract?

TanyaMc said...

If I read the citing/abstracts correctly (quick scan) it works in dogs and rats? Not trying to argue, just reconcile the information. (I don't want to take aspirin and I don't want anotehr stroke/dementia etc!)

Then there is the age old question...just because it is 'natural' is it safe? What about aspirin makes the gut leaky that isn't in other things that thin the blood/make it less sticky. Thanks.

Dr. Art Ayers said...

I don't think that you are having problems with unusual clotting, but rather clots derived from your atrial leak. That might suggest that your treatment would also lessen your stroke risk. Am I wrong?

The pectin suggestion can be satisfied with eating any meal that has tomatoes or apples added. I don't make a special effort, although I frequently eat stewed tomatoes with an egg for breakfast.

Thanks for your comment.

TanyaMc said...

The clot that caused my stroke most likely originated somewhere in my body and passed through the atrial hole into artery and lodged in my brain. The clot was 'large', like the diameter of my little blocked the vertebral artery distal to the PICA branch.

The Plavix and aspirin were to prevent clots during recovery, I think. I am now on one baby aspirin a day for life and wanting to replace it with something safer that can do the same thing. (My dad developed tinnitus from aspirin he thinks.)

I am not sure how much thick/ sticky blood contributed to my symptoms prior to the stroke, but since I was doing anti inflam to the max and still having troubles, from what I've read about symptoms, it makes sense on some levels. And, once in our comments back and forth here you suggested natto (before my stroke) and I am thinking you may have been on to something in hindsight because of the stroke. The doc said there may be an underlying clotting disorder they can't test for (I tested negative for all the known ones including the ones that Mayo developed that only their labs do).

I also had trouble with my first two hip surgeries...non-union of the bone, and then a hematoma after repairing the non-union. I was on lovenox after the first one. I had none the second/third time. Don't know how those all play in or if they are even connected. Stroke was 2 months after third surgery, 5 months after new onset head/neck/shoulder pain that lasted til stroke and bothers some now and then (headed to PT eventually for that).

The optic neuritis vs TIA question also plagues me. The neurologist mentioned NMO antibodies as something to test for next time I see him. Since that is auto-immune again I say why if I am/was eating well...what am I missing? I believe my aura migraines and psuedo MS (I don't have it) were TIAs from the PFO and expect them to go away. I am still experiencing some minor vertigo (seems to be related to sugar intake and getting too tired) which I hope will go away with time.

Also, any clots moving now will be pulmonary, which is not a great alternative, so wish to keep them to a minimum. My mother/family has bad vericose veins, and I am getting some spider veins.My dad...triple bypass @ 58, normal cholesterol. All men in his generation had same surgery also in late 50s. So, guess I am concerned about my vascular health, at the vessel level, not the blood itself so much but sticky blood = clots/plaque that isn't stable????

I had blood work done today, so we'll see where my D levels, Omega 3, and other misc tests (it was a health fair) are at in a week or so. I'm an apple (granny smith with cheese) a day girl, have been off and on all my life. Tomatoe sauces are common in our menu (fresh, home-canned).

Sorry so long. Thanks for your input.

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