See my Science: Laminin:LARGE glycan structure reveals the molecular basis of muscular dystrophy.

August 15, 2016

Laminins are interesting proteins, which is just as well, because they are what I am working on at the moment.

Laminins are large heterotrimeric1 proteins that reside in the extracellular matrix (ECM – the stuff outside cells). If you were to google Laminin, you’d find some stuff about the protein, and a whole mess of stuff about it looking like a crucifix, and how Laminin somehow therefore proves the existence of god and/or intelligent design. It is hopefully clear to you, dear reader, that this is utter nonsense, for 2 reasons:

  1. The diagrams of laminin are exactly that – DIAGRAMS. Cartoons drawn by scientists to make describing these large complex molecules easier. Cartoons of Bugs Bunny are not proof of walking, talking, wise-cracking rabbits;
  2. The pictures (mostly rotary shadowed electron micrographs) of intact laminin are 2 dimensional representations of flexible 3-dimensional molecules, (see fig 1). They don’t look like crucifixes, because they have 3 dimensions – they probably look more like palm trees.
LAMININ, YO.

Fig 1. A Laminin electron micrograph.

This is first protein I’ve worked on that has its own page at Snopes.com, which is quite an achievement.
Right, now I’ve got this curious case of molecular pareidolia off my chest, let’s crack on with why Laminin is pretty damn interesting all by itself.

What Laminins do.

Laminin is a principal component in extracellular structures called ‘basement membranes’ (not the same as lipid/plasma membranes, which you might have heard about in high school biology). Basement membranes are important structures that incorporate Laminins, collagens and other ECM proteins to form protein barriers that separate different tissues layers.

Each Laminin molecule is actually 3 different protein chains attached to each other. Because scientists are exceptionally inventive and imaginative, these three proteins are called Laminin alpha, beta and gamma chains respectively.

They fit together a bit like this (fig 2):

LOOK! IT'S A CRUCIFIX!

Fig 2: Schematic of a Laminin molecule.
Taken from Hohenester & Yurchenco, 2013 http://www.ncbi.nlm.nih.gov/pubmed/23076216

One end of each of the three proteins (the palm tree fronds / the animo-terminus) has an LN-domain (marked LN), and this is involved in forming the basement membrane itself. An LN domain from 3 different Laminin molecules come together to form a sheet like network as shown in fig 3.

Fig 3: How Laminins form a sheet like structure… Taken from Hohenester & Yurchenco, 2013 http://www.ncbi.nlm.nih.gov/pubmed/23076216

This sheet needs to be anchored to the surface of cells. Happily, at the other end of the Laminin, (the base of the palm tree – marked LG1-3/LG4-5 in Fig 2, and marked with a double arrow in Fig 1) there are two functional units that anchor to the surface of cells in two different ways:

    1. By binding to proteins on the surface of the cell called integrins. This happens through the LG1-3 region.
    2. By binding to a specific sugar which is attached to a protein called Dystroglycan. This happens through the LG4-5 region.
      THIS IS WHAT THIS BLOG POST IS ALL ABOUT

Dystroglycan

Dystroglycan is an integral membrane protein – it sits within the plasma membrane (not basement membrane) and has bits that protrude into both the extracellular and intracellular spaces. It links the basement membrane (outside the cell) to the cytoskeleton (a protein framework inside the cell) – see Fig 4.

Dystrophin complex From Baresi & Campbell. http://jcs.biologists.org/content/119/2/199

Fig 4: Dystrophin complex links intracellular (bott0m) and extracellular (top) structures. From Baresi & Campbell. http://jcs.biologists.org/content/119/2/199

 

The extracellular side of Dystroglycan has a unique sugar polymer covalently attached to it. This sugar (called the ‘LARGE glycan’ or ‘Matriglycan’) has so far only been found attached to Dystroglycan until last week had only been detected on one protein – alpha-dystrogylcan. A recent paper by our collaborators – as demonstrated that this sugar can also be found on other proteins, attached via the same sites known to be occupied by other sugar modifications of proteins (such as the glycosaminoglycans, Chrondroitin Sulphate and Heparan Sulphate). The synthesis of the LARGE glycan is also complex, and the whole linkage region has only recently been mapped. Figure 5 shows a summary of what we know so far about the structure of the LARGE glycan and lists the enzymes that are involved in synthesising it.

dystroglycan-synth

Fig 5: How to make LARGE glycan. By the author, information from various papers.

The business end of the LARGE glycan is the -[Glucuronic acid – β1,3 – Xylose α1,3 ] disaccharide polymer – the repeating orange stars and blue/white diamonds on the right of Fig 5. So what the hell is that then?

It is a long chain of alternating Glucuronic acid (a sugar acid similar to Glucose) and Xylose (a sugar that was first isolated from wood, hence Xylose, derived from the greek for wood) units (see Fig 6). The β1,3 & α1,3 refer to how they are connected.  We don’t know quite how long it is yet, or how many modifications there are on each dystroglycan molecule (either 1 or 2). More research required!

Matriglycan repeating unit.

Fig 6: The LARGE glycan repeating unit. By the author, created using chemdraw 14.0

So why do we care about this?

In a nutshell, muscular dystrophy.

If you cannot make:

  • Laminins
  • Dystroglycan
  • Any of the enzymes involved in LARGE glycan synthesis

you get muscular dystrophy. Loss of the genes that encode LARGE glycan synthesis (i.e. the genes shown in Fig 5) lead to a subset of extremely severe muscular dystrophies called “dystroglycanopathies“. They are congenital (inherited) diseases that prevent correct formation of basement membranes. This means that tissues do not form properly, and gives rise to developmental disorders. If we can understand this system, maybe we can fix it?

Our recent work

So, we know what the LARGE glycan is made up of, and we know that it binds to the Laminin G-type (LG) domain 4 of Laminin alpha 2.

What we want to know is how they interact with each other at an atomic level – happily the best tool for this sort of study is X-ray crystallography, which is what I do for a living!

So I expressed, purified2 and crystallised (Fig 7) a fragment of Laminin alpha 2 which contained the LG4 and LG5 domains. I then soaked a tiny (and I mean tiny) amount of the LARGE glycan that our collaborators had synthesised for us into my crystals. Given that when I did this, we had no idea of tightly Laminin alpha 2 bound to the LARGE glycan, this was a bit of a long shot. I setup around 20 different experiments, with different soaking times and concentrations to try and get some ligand into the protein.

Crystals!

Fig 7: Crystals!

 

I cryocooled the crystals in liquid nitrogen and sent them off to Diamond Light source, where we collect our diffraction data. My remote access data collection shift started at 4am. Oh joy. An early start, plenty of coffee and a taxi to work and I was good to go. However – a drawback of the ligand soaking approach I had to take was that I would have no idea whether or not my crystals had the ligand in until I had processed all the data. I didn’t have the time to process the data as I went along, so the data collection was done using ‘the American method’ – Shoot first, ask questions later.

After my 5-hour shift was up, I grabbed breakfast and more coffee and started to process all my data.

About 5 datasets into my haul of data, I hit the jackpot.

Fig 7

Fig 8a : What the Calcium binding site in LG4 looks like.

 

Fig 7: Difference density map of SOMETHING.

Fig 8b: Difference density map of SOMETHING.

Above the calcium binding site in LG4, right where it was predicted to be, was a big green blob in my electron density difference map. If you look at Fig 8a, you can see what the empty binding site looks like – this is a very much simplified representation as there is an awful lot going on. The cyan sphere is a calcium ion. The red/green/blue sticks around the calcium show the orientation of the amino acids in the protein that bind to the calcium. The loops and whirls represent other bits of the protein.

I generated an electron density map that highlights the differences between an empty crystal and a soaked crystals (fig 8b). To generate this map, I simply subtract data from an empty crystal (apo form) from data of a soaked crystals (bound form) – the difference between the two datasets should equal the ligand. Happily, it does! After a bit of building and refining, we end up with the final refined structure of the Laminin:LARGE glycan complex.

Fig 9

Fig 9: THAR SHE BLOWS!

Figure 9 shows this final structure of the ligand with the same density shown in Fig 8, just made transparent.

 

Fig 10

Fig 10: A schematic of important interactions in-between Laminin (red) and the LARGE glycan (black).

When we dive into the binding site and take a look around (Fig 10), we see that all the interactions are between a single glucuronic acid – xylose repeat, even though there are 3 repeats in the sample of LARGE glycan we used. The link between the two sugar rings straddles the calcium ion, forming a sort of chelating or clathrate-type interaction. Oxygen atoms (carrying a net negative charge) interact strongly with the positively charged calcium ion . The carboxylic acid group in the glucuronic acid ring (The O=C=O bit) also pokes into a little positively charged pocket formed by two backbone amino groups (NH). All these interactions combine to form quite a strong interaction for (~0.2µM KD, if anyone is interested) for an interaction with a relatively small interaction surface.

So what have we learned?

We now know exactly how Laminins bind to the LARGE glycan. Let’s be clear – this is not a drug target – we definitely do not want to inhibit this interaction! But this shows us a crucial link in the chain between the cytoskeleton (the internal skeleton of a cell) and the outside world.

We have also seen a really interesting and novel mode of protein-carbohydrate interaction. The Laminin does not recognise individual sugars – it recognises the unique linkage found in the LARGE glycan. Given that there are over 100 proteins in the human genome that contain LG domains, and some of those are also known to bind to the LARGE glycan, our structure provides a paradigm for LG domain – LARGE glycan interactions.

We know that a single disaccharide is sufficient for Laminin to engage (although longer stretches of sugar bind more tightly) and we show that the sugar forms a pseudo-clathrate cage over the calcium in the protein. This is probably why the Laminin-LARGE interaction is ~10x tighter than interactions between proteins and other similar sugars.

Anyway – the paper should be out NOW in Nature Chemical Biology.

A PDF is available here.

The pdb files are here

binding_cartoon_gradient

IMAG0194 copy

The author’s right forearm.

 

 

 


  1. Hetero – different, trimer – three. Made up of 3 different proteins.
  2. Made in mammalian cells – we give mammalian cells DNA that encodes our protein.

Multi-contoured electron Density maps

December 4, 2015

When wandering around the department, I am struck by how few crystallographers use multiple contoured electron density maps* whilst building. I really don’t understand this: YOU’RE THROWING AWAY INFORMATION PEOPLE!

Even at moderate resolution, the information gained can be invaluable:

  1. Precisely locating a heavy atom in a big blob of electron density. The Atom will sit at the highest point of the map. IF you are using multiple contours, this will be obvious! (figure 1)
  2. Resolving His/Asn/Gln sidechain flips. A bit more prone to noise here – but in terms of electrons, O > N > C. You can easily decide which way around Asn and Gln side chains should point, and often get some help with His side chains as well. (figure 2)
Screenshot 2015-12-04 13.05.44

Figure 1a: THAR SHE BLOWS!

This calcium ion sits RIGHT on the peak in the electron density map. No ambiguity where it lies. A single map contoured at 1 sigma is not helpful.

Screenshot 2015-12-04 13.07.38

Figure 1b: Nope. Not helpful.

 

Screenshot 2015-12-04 12.54.32

Figure 2: Gln sidechain flips, made easy…

The increased electron density  on the right hand side here indicate that this Gln residue is the correct way around. Again, a single map contoured at 1 sigma is no use here.

I realise that there are other ways to achieve what I have described, but when you are building your models, saving time and making things easier is hugely helpful. I find using multi-contouring incredibly helpful.

* multi-contours shown here are made using the “Multi-chicken” command in COOT (extensions>maps>multi-chicken). Multi-chicken creates 10 maps contoured at 1,1.5,2, 2.5, etc sigma. I find the default setting is a tad dark so I use “brighten maps” (extensions>maps>brighten maps) a couple of times to sort that out. I then contour the original map at 0.7sigma (depending upon noise) and make it really deep purple.

All screenshots made with COOT.

 


BUG SPLATS!

February 28, 2014

A quick technical note/tip for folks doing recombinant protein expression in E.coli


When doing large-ish scale expression of proteins in E.coli, it is common to freeze the cell pellet post-harvesting and prior to cell lysis and protein purification. Typically this is achieved by re-suspending the cell pellet in a small about of Luria Broth or PBS and then re-pelleting the cells in a 50ml falcon tube, and freezing them at -80ºC.

Whilst this is convenient, the down side of this is that it introduces another centrifugation step into your harvesting protocol, and a solid lump of cell paste can take a while to thaw out fully, and can be difficult to get completely homogenous and lump-free prior to whatever lysis technique you choose to use.

A colleague of mine who recently joined the lab from AstraZeneca (after they closed much of the Alderley Park research facility) has brought with him an ingenious way of speeding both harvesting and thawing out considerably: BUG SPLATS.

Poo in a bag?

Revolutionary bacteria pellet freezing protocol!

Rather than re-suspend your pellet in LB/PBS and re-pellet it, just scoop it out with a spatula (or similar) and place the bug pellet into a small (~10x20cm) press-lock bag.

Collect all the pellet into the bottom of the bag and then smooth it out so that your bug splat is nice and thin (<5mm is ideal), and stick it in the freezer.

The thin bug splat will freeze faster than a pellet in the bottom of a falcon tube.

It will also thaw out much faster. For thawing – snap the brittle, frozen bug splat into small chunks, and empty them into a suitable container (50ml falcon or similar), and add the required amount of lysis/sonication buffer. It should thaw out rapidly, and it should be easier to obtain a smooth, homogenous solution before lysis than a large ~25ml lump of frozen paste in the bottom of a falcon tube.

As the pellet is brittle, you can also snap smaller piece off if you don’t want to thaw the whole thing out.

So there you go – a ludicrously simple way of saving time in the lab, and making the freeze/thaw process faster, which is (anecdotally) better for your protein.


[PODCAST] – Me on Dessert Lionel Discs

March 21, 2013
Damn good coffee, and hot!

Damn good coffee, and hot! (Photo credit: photojenni)

Self promotion, dead ahead!


I have been fortunate enough to have been interviewed by @Astrondrew of  Sound of Science for episode 5 of the Dessert Lionel Discs podcast 😀

In it I talk about how I got into science, who inspired me to do science, and what exactly I do as part of my day job. I also talk Pink Floyd, Crystals, Twin Peaks and damn fine coffee.

Please listen, and I hope you enjoy!


I have been sat in front of this beast for 4 of the last 6 weeks. #SeeMyScience

October 4, 2012

image

This is our venerable BiaCore 3000, an instrument used to figure out if and how tightly molecules interact with each other (using the suitably sci-fi sounding “surface plasmon resonance” technique). Molecular interactions are of supreme importance to the life sciences as interactions between molecules determines pretty much everything. I’ve spent a lot of time recently discovering and characterising novel interactions of my current protein of choice. Details coming to a journal near you…

EDIT: I added some links to the original post in case anyone wanted to dig a little deeper. In addition, I recommend sprpages.nl for more detailed descriptions, and information about binding kinetics, etc.

 


As relevant in 1677 as it is today….

June 12, 2012

…there is no greater folly than to be very inquisitive and laborious to find out the causes of such a phenomenon as never had an existence, and therefore men ought to be cautious and to be fully assured of the truth of the effect before they venture to explicate the cause

The displaying of supposed witchcraft by John Webster, 1677.

Relevant to real scientists, and to those quacks and charlatans seeking a mechanism of action for medicines that do not yet have a proven effect.


So here’s an idea…

February 22, 2010

A rational/skeptic sidewiki project?


I recently discovered Sidewiki, an offering from Google which allows you to read and write wiki-like contributions that can be made to pretty much any webpage out there. It works by adding a toolbar to Internet explorer or Firefox.

Everytime you visit a webpage with a sidewiki entry a little blue “»” appears on the left hand side of your browser and you can drag it out and and read what people have written, or contribute your own entry to a webpage.

Such as this:

From XtalDave

Now – if every skeptic was to take a couple of minutes to very simply address every quack claim on the internet, maybe with a nice link to a relevant peer reviewed pubication, or at least a blog post with references within, we’d have a nice record of objections to particular claims, so when others come accross a link to them in the future, the effort to determine potential flaws in a webpage/study would be reduced.

*SIMPLES*

Let me know what you think about this (comments below) – if people are generally supportive, some sort of web hub to organise efforts might be useful.

 


Antibiotics: take the full course!

February 14, 2010

Good science, for a change. Not woo.


In this season of ear, throat and chest infections, there is a good chance that you, or someone you know, will have been prescribed antibiotics recently.

When given antibiotics, your doctor, and your pharamcist will/should remind you to take the full course of antibiotics.

This paper just out in Molecular Cell explains why.

If you fail to take the full dose of antibioitics, or you miss a dose, you are potentially exposing the bacteria to a sub-lethal dose of antibiotic.

According to this work from Boston & Harvard Universities, sub-lethal doses of a variety of antibiotics (including Ampicilin, a popular choice for GPs to prescribe), rather than killing the bacteria, cause a stress response in the bacteria, which in turns leads to prodution of reactive oxygen species (ROS). Kohanski et al showed that this increase in ROS production can cause up to an 8-fold increase in the mutation rate in E.coli. They confirmed that ROS was the cause by treating the bacterial simultaneously with sub-lethal doses of antibiotics, and thiourea (which limits ROS production). The thiourea returned mutation rate nearly to control levels.

ROS can directly cause random damage to the bacterial genome, leading to an accumulation of mutations. ROS can also lead to the activation of SOS genes, which repair DNA – however, in doing so, they can also introduce mutations.

Taken from here. No permision given, but fair use claimed.

Some of these mutations may confer antibiotic resistance upon a bacteria. Which means your bugs may now survive the course of antibiotics.

The upshot of which is you need more antibiotics, and you may have created your very own drug resistant form of a pathogenic strain of bacteria (think MRSA).

WooHoo! Go YOU!

 

 


Mis-quoting. Quote mining. Quotology. Quotography. LYING.

February 11, 2010

A little piece about mis-quotage, and how it irks me so.


In the space of about 12 hours this week, I read two articles concerning the gross perversion of peer-reviewed scientific literature, and people selectively quoting from said peer-reviewed publications to push forward their own agendas.

The first was Martin Robbins excellent demolition of the BHA’s evidence to parliament. This comes in two parts – the Guardian Article, and his response to the BHA response.

I have touched upon homeopaths doing this before, so it should come as no surprise really.

A particularly insidious example (taken from Martin’s blog at layscience.net) was:

BHA

Cucherat 2000: “There is some evidence that homeopathic treatments are more effective than placebo.”

The full, unabridged quote

There is some evidence that homeopathic treatments are more effective than placebo; however, the strength of this evidence is low because of the low methodological quality of the trials. Studies of high methodological quality were more likely to be negative than the lower quality studies.

Lets us be crystal clear about what is going on here – this is not a mistake. This is not a simple error or omission. Nor is it stupidity or incompetence.

This is lying. Deliberate misdirection. Fabrication. Falsification. Bearing false witness. Mendacity. Fraud. You get the idea.

In the case of the BHA, they misrepresented evidence in front of the UK parliament science and technology committee.

The report is due out on the 22/02/10. I’ll wait and see how far their mendacity gets them.

The second instance of quote-mining lying was discussed in the Guardian piece on how climate change skeptics has mis-quoted the e-mails (so not peer-reviewed) leaked in “climate gate”. Now I’m not a climate scientist, (If you want more info, go to Andy Russell’s excellent blog. He is a climate scientist) but it strikes me that this is probably more important, in that it potentially effects the whole world, and not just the UK. “Climategate” was touted in the international press, and by climate change “skeptics” including Sarah Palin., as example of how global warming is not real, and it is just an artefact created by climatologists… for what reason I have yet to fathom.

(Note: As a general rule –  If Sarah Palin agrees with you then there is a very good chance you are wrong.)

The most prominent example of quote-mining in this case was saying that “tricks” were used to alter/obscure data when they were in fact referring to a visual trick to display data.

The trouble facing people at the wrong end of these mis-quotes, is that the initial mis-quote is often seized upon by the press, and then hurtles around the world faster than you can say “Intergovernmental Panel on Climate Change”. The following “erm, actually, I think you’ll find” article rarely gets any coverage, and thus, the general public only see the lies. In such cases the ball lies firmly in the court of the media – “erm, actually, I think you’ll find” articles are not big and sexy – but they are an incredibly important part of maintaining journalistic integrity, and ensuring that the general public is kept well informed. After all, we cannot expect a democracy to make informed choices when the voting public do not have the necessary information.

The point I am trying to get around to making (probably quite badly,) is that the nature of peer-review keeps scientists honest. This is important, as it tends to have the effect of removing personal bias, hyperbole and egos from the science discussed. It may not be perfect – but it is the best system we have for ensuring that good science is published, and bad science is weeded out.

Perversion of peer-reviewed articles and of scientific discourse in general is the domain of the quack and the charlatan – the fact that the BHA and climate change skeptics have resorted to such underhand tactics speaks volumes about their integrity.


Clutching at homeopathic straws?

January 29, 2010

“Oooh! A new and exciting area of science – does it have big, important-sounding words? EXCELLENT – could it in anyway concievably be applied to homeopathy? F**k it! That’ll do!”


One of the many claims that Homeopathy makes is that of the “Similia Principle” or “like cures like”. It is this principle by which a homepath selects a remedy: Patient presents with symptom X. Compound Y causes symptom X. Give patient an ultramolecular dilution of compound Y to treat symptom X.

In the recent edition of Homeopathy “Special Issue: Biological models of homeopathy Part 2” a paper entitled “The similia principle: Results obtained in a cellular model system” concludes that

“results support the similia principle at the cellular level and add to understanding of how low dose stress conditions influence the regulatory processes underlying self-recovery”

They then document some experiments in which cells that are exposed to a high dose of “stress” (heat shock, or toxic compounds such as Arsenic or Cadmium) cope better with and react more intensly to a subsequent low dose of stress. Why this is surprising, I do not know. Adaptive responses and/or preconditioning of cells (both prokaryotic and eukaryotic) is well researched. A pubmed search for adaptive response generates over 17000 hits, for preconditioning over 8000. (correct as of Jan 29th 2010).

On a cellular/molecular level, this can be explained by more rapid production/activation of certain stress response proteins, such as heat shock proteins and protein folding chaperones – proteins which attempt to either prevent or reverse that damage caused by whatever stress factor is currently blighting the cell’s ability to proliferate and survive. The more rapid response to the second exposure to stress might be as a result of residual levels of certain transcription factors or activators within the cells. This is not explored in the paper. Another possibility is that the cells that survived the initial high dose of stress are intrinsically better able to adapt to the stress, either as a result of mutation or cellular niche or various other arm-wavey possibilities. The first assult with the stress causing compound has naturally selected for those cells with a better chance of survival – this is the basis of something called “Evolution.” Google it. I’m told It’s quite popular.

At the level of an organism, this is basically describes an immune system. An organism is confronted with a “stress”. The organism develops a response (e.g antibodies) to the stress. Next time the stress is encountered, response molecules are quickly produced in massive quantities to prevent damage from stress. Surely everyone saw this graph in GCSE/’A’-level biology?

Source

It’s the basis by which all vaccines work, and how multicellular life responds to any sort of antigen. Very basic stuff. Hence It was taught at GCSE level (at least when I sat GCSE Biology in the early 90s).

This paper, however, does things differently – high dose first, then low dose – and seems to find some extra significance in this. Why? The relative sizes of the doses are immaterial, as long as cells/organism survive, it is now primed to respond to a second insult. IMHO, a more interesting study ( at least on a cellular/molecular level) would be how long does this “priming of the system” last? Does that time correlate in any way with known half lives for mRNA, transcription factors, phosphorylation of various proteins? Is this persistence of this effect related to the size of the initial insult? This is not commented on.

Figure 1 is a nice little diagram of their experimental design.

Fig 1 from here – used without permission, but fair use claimed.

There are two incredibly obvious ommissions in this experimental design…

Low dose, high dose, evaluate.

Low dose, no treatment, evalute.

I imagine that this has been done before – and if I was feeling mean I might suggest that the results maybe very similar to the “high dose/low dose” regimen, and have been ommited –  but irrespsective of this –  one needs to replicate this in your experimental design as a control. Ooops.

But that’s really nitpicking – important nitpicking, IMHO, but nitpicking nevertheless.

They then go on to use these observations to support the basic tenets of homeopathy.

<Screeeeeeech> <double take> Woah there! Did I miss something?
  1. All these experiments are done with actual measurable amounts of compounds present (10uM, 0.3uM – handy, easy to understand concentrations like that). Unlike homeopathic remedies.
  2. When treating someone with a homeopathic remedy, the patient will persumably be taking the *cough* low dose1 *cough* at the same time as he/she is suffering with the effects of the high dose (note – Homeopathy treats symptoms, not causes – so it is easy to see how they might overlook this). So even if the concept of hormesis is real and valid in this context (and there is some controversy about that) what is the biological mechanism by which this occurs? After all a very big number plus a very small number is still a very big number – how does the body determine which compound is for what purpose?
This support of homeopathy is realised though some arm-waving about “postconditioning hormesis” – sadly not ultra-diluted molecules administered after the onset of the symptom travelling back in time to pre-condtion the body before the onset of the symptom and confer partial-immunity, thus helping the patient get better back in the future.
We have a reference to postconditioning in the context of myocardial infarctions – and a reference to a paper which seems to do a decent job of describing postconditioning and then going on to have a stab at getting some clues about the mechanism by which the postconditioning limited the damage caused by the previous myocardial infarction. So postconditioning – fine – plenty of evidence for that in certain contexts.
And then there is reference to hormesis – where giving a small dose of something gives opposite effect of large dose – ok – fine – some examples of that in the literature, (e.g. in context of aging,) but with a caveat that whilst it is an interesting hypothesis, predictions made on the basis of hormesis are not suitably accurate for directing health care choices, policy etc.
Stitch the two together and “POSTCONDITIONING HORMESIS” is born. Orginally toted in this paper – postconditioning hormesis is a strange and intriguing effect – but you can imagine how it might work – low levels of non-damaging stress shortly after major damaging-stress prolong the synthesis/activation of response factors that aid recovery and limit damage – i.e. it is explainable by current scientific thinking – as long as one believes in such vagaries as “avagardos constant” and what have you.
Given that it involves a beneficial small dose been given after stress caused by a toxic high dose, it is perhaps not surprising that Homeopathy has lept upon postconditioning hormesis as a potential mechanism through which it might work. A google search of “postconditioning hormesis” reveals that 6 of the 10 hits on the first page also mention homeopathy. Peter Fisher, the UKs homeopath-in-chief, even mentions it in his lectures now.
However in jumping on the postconditioning hormesis band wagon, Homepathy has seemingly bypassed other, more thorny issues like the mechanism of succussion, lack of evidence for the “memory of water” and the subsequent “memory of sugar” and the molecular mechanism by which this memory is realised in the context of binding to receptor molecules, not-to-mention the ever present “lack of efficacy beyond placebo effect” issue that it suffers from.
For the homeopaths to jump on this phenomenon before it is fully understood and claim it as potential proof for the Similia principle looks awfully like another attempt to dupe the public with important sounding pseudo-scientific waffle…
A bit like this:
It’s clutching at straws.
—-
1 By “low dose”, I of course mean “no dose” – a ultra-dilute potentized solution containing zero active molecues – other than the water and the impurities within. With the memory of the original high dose molecule… transfered to a sugar pill. Got that?