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Showing posts with label parasite. Show all posts
Showing posts with label parasite. Show all posts

Saturday 24 June 2017

Modulating Wnt Signaling in Autism and Cancer








In earlier posts I have covered various signaling pathways such as Wnt, mTOR and the unusually sounding Hedgehog.
You can go into huge detail if you want to understand these pathways, or just take a more superficial view. In most cases, things only start to go wrong if you are hypo/hyper (too little/too much) in these pathways.
We saw with mTOR that most people with autism are likely to have too much activity and so might benefit from mTOR inhibition, but a minority will have the opposite status and stand to benefit from more mTOR activity.
When it comes to Wnt signaling the research suggests the same situation. Wnt signaling is likely to be aberrant, but both extremes exist.

Given the large volume of genetic data, analyzing each gene on its own is not a feasible approach and will take years to complete, let alone attempt to use the information to develop novel therapeutics. To make sense of independent genomic data, one approach is to determine whether multiple risk genes function in common signaling pathways that identify signaling “hubs” where risk genes converge. This approach has led to multiple pathways being implicated, such as synaptic signaling, chromatin remodeling, alternative splicing, and protein translation, among many others. In this review, we analyze recent and historical evidence indicating that multiple risk genes, including genes denoted as high-confidence and likely causal, are part of the Wingless (Wnt signaling) pathway. In the brain, Wnt signaling is an evolutionarily conserved pathway that plays an instrumental role in developing neural circuits and adult brain function.
While the human genetic data is an important supporting factor, it is not the only one. There are a number of mouse genetic knockout (KO) models targeting Wnt signaling molecules, describing molecular, cellular, electrophysiological, and behavioral deficits that are consistent with ASD and ID. Furthermore, the genes involved in Wnt signaling are of significant clinical interest because there are a variety of approved drugs that either inhibit or stimulate this pathway.
There are many drugs developed and tested as modulators of Wnt signaling in the cancer field that could potentially be repurposed for developmental cognitive disorders. In cases where a reduction in Wnt signaling is thought to underlie the pathology of the disorder, usage of compounds that elevated canonical Wnt signaling could be applied. An example of this is GSK-3β inhibitors that have failed in cancer trials but may be effective for ASDs and ID (e.g., Tideglusig, ClinicalTrials.gov identifier: NCT02586935). In cases where elevated Wnt signaling is thought to contribute to disease pathology, there are many potential options to inhibit canonical Wnt signaling using chemicals (Fig. 1) that inhibit the interaction between β-catenin and its targets (e.g., inhibiting β-catenin interaction with the TCF factors), disheveled inhibitors (through targeting of the PDZ domain which generally inhibit the Frizzled–PDZ interaction), and tankyrase inhibitors (e.g., XAV939, which induces the stabilization of axin by inhibiting the poly (ADP)-ribosylating enzymes tankyrase 1 and tankyrase 2)

In recent years, strong autism ties have cropped up for one group of genes in particular: those that make up a well-known signaling pathway called WNT, which also has strong links to cancer. This pathway is especially compelling because some people with autism carry mutations in various members of it, including one of its central players: beta-catenin1. What’s more, studies from the past year indicate that several of the strongest autism candidate genes, including CHD8 and PTEN, interact with this pathway.
“There might be a particular subgroup of genes associated with autism that could all be feeding into or be regulating this pathway,” says Albert Basson, reader in developmental and stem cell biology at King’s College London, who studies CHD8 and WNT. “That clearly has emerged as a relatively major theme over the last few years.”

The connection between cancer and some autism is over-activated pro-growth signaling pathways. Many signaling pathways have growth at one extreme and cell death at the other. In cancer you actually want cell death to suppress tumor growth; in much autism there is also too much growth.  
Many cancers are associated with elevated signaling of mTOR, Wnt and indeed Hedgehog.  These are targets for cancer drug therapy and so there is already a great deal known.
A complication is that in a developmental neurological condition, like autism, it also matters when these signaling pathways were/are disturbed. For example Wnt signaling is known to play a role in dendritic spines and synaptic pruning, some of this is an ongoing process but other parts are competed at an early age, so it would matter when you intervene to modulate these pathways.
Historically cancer therapies involve potent drugs, often with potent side effects, however in recent years there has been growing awareness that some safe existing drugs can have equally potent anti-cancer effects. Many of these drugs are anti-parasite drugs, but even the very widely used diabetes drug Metformin has been shown to have significant anti-cancer effects, not to forget Simvastatin.
Many autism pathways/genes play a role in cancer (RAS, PTEN) and the upstream targets considered in cancer research are also autism targets.  For example many human cancers are RAS dependent and in theory could be treated by a RAS inhibitor, but after decades of looking nobody has found one. So instead scientists go upstream to find another target that will indirectly reduce RAS. This led to the development of PAK1 inhibitors that will reduce RAS.
RAS plays a role in some types of intellectual disability and indeed autism. The collective term is RASopathy.  Logically, drugs that modulate RAS to treat cancer might be helpful in modulating RAS for some autism.
Most types of cancers are complex and so there are multiple potential targets to attack them, but also the same target can have multiple possible approaches. RAS dependent cancers can be targeted via Wnt and even Hedgehog signaling.
This may sound all very complicated but does it have any relevance to autism?
It apparently does because almost all these pathways are known to be disturbed hypo/hyper in autism.  This means that clever insights developed for cancer can be repurposed for autism.


Anti-parasite drugs and Cancer
It is indeed remarkable how many anti-parasite drugs have an anticancer effect and indeed there is a much maligned theory to justify this.



Quite possibly it is just a coincidence.
There are many ways to kill parasites, one of which involves starving them of ATP. ATP is the fuel that is produced in your mitochondria.
Cancer cells and many parasites use a very inefficient way to produce ATP that does not require oxygen. In normal human cells the process followed is known as OXPHOS, by which glucose and oxygen from the blood is converted into ATP (energy) is very efficient. Only when you run low on oxygen, like a marathon runner at the end of the race, can you run into trouble because there is not enough oxygen for OXPHOS.  What happens next is anaerobic respiration, when a different process takes over to make ATP. It is much less efficient and causes lactic acidosis which makes marathon runners' muscles hurt.
A cheap anti-parasite drug Pyrvinium targets anaerobic respiration and starves the parasite of ATP and thus kills it. Another common children’s anti-parasite drug albendazole also works by starving the parasite of ATP.
Other anti-parasite drugs work in different ways.
We already know from the autism trials of Suramin, another anti-parasite drug,  that it works via P2X and P2Y purinergic channels.
Ivermectin  binds to glutamate-gated chloride channels (GluCls) in the membranes of invertebrate nerve and muscle cells, causing increased permeability to chloride ions, resulting in cellular hyper-polarization, followed by paralysis and death.  Fortunately in mammals ivermectin does not cross the BBB.
Ivermectin is also a PAK1 inhibitor and a positive allosteric modulator of P2X7.
Both PAK1 and P2X7 are relevant to many cancers and so not surprisingly research shows that Ivermectin has an anti-cancer effect.
Ivermectin appears to have a positive effect in some autism, but strangely it does not cross the BBB.
Mebendazole is another extremely cheap children’s anti-parasite drug which has remarkable potential anti-cancer properties. It inhibits hedgehog signaling and, via the inhibition of TNIK, it is a Wnt inhibitor.
Unfortunately in the US the private sector has also noticed the anticancer effects of Mebendazole and albendazole and they have recently become astronomically expensive. Mebendazole (MBZ), which costs almost nothing in many countries, now costs hundreds of dollar per dose in the US under the name Emverm. Outside of the US, Mebendazole is OTC in many developed countries. In poor countries it is donated free by big pharma.
In the cancer research they consider taking advantage of the fact that cimetidine (a cheap H2 antihistamine) interacts with Mebendazole to increase its bioavailability. Cimetidine is by chance another generic drug also being considered to be repurposed for cancer.
While some anti-parasite drugs like Suramin have side effects or cannot be taken regularly like Ivermectin, others are seen as safe for continued use even at high doses (e.g. Mebendazole and albendazole).  

Anti-parasite drugs and Autism
Just as many anti-parasite drugs seem to have a positive effect on some cancers it looks likely that the same may be true for autism.  This does not mean that parasites cause either cancer or autism.
We know from Professor Naviaux that some people respond to Suramin.
Two people who comment on this blog have found their child responds to PAK1 inhibitors, one of which is the drug Ivermectin.
There are groups of people on the internet who think parasites cause autism and you will find some of them if you google “autism mebendazole”, but there are some very valid reasons why some people’s autism may respond to mebendazole, but nothing to do with little worms.

Potency of Anticancer drugs
Failed anticancer drugs are already considered as possible drugs to treat neurological conditions.
The same pathways do seem to be involved in some cancer and some neurological conditions, but the severity by which that pathway is affected may be very different, so a new drug may lack potency to treat a type of cancer but be potent enough to benefit others.
In the case of the anti-parasite drugs Ivermectin and indeed mebendazole the dosage being used in current cancer studies are very much higher than normally used.
Very little mebendazole makes its way out of your intestines and so researchers counter this by using a dose 15 times higher and even taking advantage of the interaction with the H2 antagonist cimetidine to boost bioavailability.
The standard human dose of Ivermectin is 3mg, but in the cancer trials (IVINCA trial - IVermectin IN CAncer) in Switzerland and Spain the trial dose is 12, 30 and 60 mg.
So when it comes to autism and the possible repurposing of these drugs, the cancer studies will give valuable safety information, but the likely dose required to fine-tune these signaling pathways will likely be a tiny fraction of the cancer dose.
The newly developed cancer drugs that fail in clinical trials, may have potential in autism but it is unlikely that anyone will develop them, test them and bring them to the market.
The clever thing for autism seems to be to keep an eye on the existing generic drugs considered to benefit the overlapping cancer pathways.

Conclusion
Aberrant Wnt signaling has been identified by researchers as playing a key role in autism; the Simons Foundation is among those now funding further research.

In practical terms you can be either hypo or hyper, but hyper seems more likely. It may be a case of shutting the stable door after the horse has bolted, because the ideal time to modulate Wnt signaling is probably as a baby, or before. Nonetheless some older people may indeed benefit from modulating Wnt; the Simons Foundation must also believe so.
In the case of people with hyperactive Wnt signaling, there is a case to make for the potential use of the cheap anti-parasite drug Mebendazole.
The drug Mebendazole (MBZ) can found in three states/polymorphs called Polymorph A, B or C. This is relevant because they do not cross the blood brain barrier to the same extent.


To treat brain tumors, or indeed potentially some autism, you need MBZ-B or MBZ-C, it looks like MBZ-A does not cross the blood brain barrier.
Fortunately, MBZ-C is  the polymorph found most commonly in generic mebendazole tablets.  
Ivermectin is known not to cross the blood brain barrier but yet has been shown to show anti-tumor activity in brain cancer. The anti-cancer effect is thought to be as a PAK1 inhibitor, but this effect must be occurring outside the brain. Some people do use Ivermectin for autism.
The people using Ivermectin for autism are told they cannot use it continuously. Perhaps as the high dose cancer trials evolve the safety advice may change.





Wednesday 18 March 2015

The Role of Microglia in the Puzzle of Neuro-inflammation in Autism





Regular readers of this and similar blogs will have noticed that the human body functions in quite irrational ways.  We know why this is; we are the product of a very slow evolutionary process, rather than being a clean-sheet design like your smart phone or iPad.

As a result, nothing is ever quite as simple as it seems and at times the cleverer you are, the less likely you are to find a medical therapy effective in humans.

Such is the case with autism, inflammation and microglia.

It might seem that you can track back inflammation in autism to its “root cause”, which could appear to be those immune cells in the brain, called microglia.  We know they are “activated” in autism and we know that autism is typified by an “over-activated” immune response.

Working with the assumption that autism is a brain dysfunction, you would assume that the effective therapy should be inside the so-called blood brain barrier (BBB).

You would then just look for a potent drug that could “stabilize” the microglia/immune cells in the brain, to calm things down.  Having achieved this, you would sit back and marvel at the behavioral change and improvement in cognitive function.

This was exactly the thought process a few years ago when the US  National Institute of Mental Health (NIMH) got together with the Johns Hopkins researchers to follow up on their findings of chronic inflammation in the brains of people with autism.  Subsequent, third party, research has also confirmed that the microglial cells are “activated” in autism


Trial Description


There is a subgroup of children with autism that appear to develop typically for a period of time, and then lose skills, or regress. A recent study by Vargas and co-workers at Johns Hopkins has demonstrated that the regressive subtype of autism is associated with chronic brain neuroinflammation as exemplified by activation of microglia and astroglia and the abnormal production of inflammatory cytokines and growth factors assayed in both tissue samples (brain banks) and CS. The authors remarked that these responses were similar to those seen in some neurodegenerative disorders such as amyotrophic lateral sclerosis, and that chronic microglia activation appears to be responsible for a sustained neuroinflammatory response that facilitates the production of multiple neurotoxic mediators. Chronic neuroglial activation could be the result of an abnormal persistence of a fetal development pattern. In this scenario neuroglial activation could play a role in initiating and in maintaining the pathology. Alternatively, neuroglial activation may only be a secondary response to the initiating causal factor(s) and not a direct effector of injury. Since neuroglial activation requires the nuclear translocation of the pro-inflammatory transcription factor NF-kappa B, and since inhibitors of NF-kappa-B with good CNS penetrance are available, the role of neuroinflammation in initiating and sustaining the autistic condition can be probed.
The antibiotic minocycline is a powerful inhibitor of microglial activation, apparently through blockade of NF-kappa-B nuclear translocation. Minocycline is neuroprotective in mouse models of amyotrophic lateral sclerosis (ALS) and Huntington's disease and has been recently shown to stabilize the course of Huntington's disease in humans over a 2-year period.
To evaluate the possibility of benefit in autistic children, we propose to conduct an open-label trial of the anti-inflammatory antibiotic minocycline, an agent that reduces inflammation by blocking the nuclear translocation of the proinflammatory transcription factor NF-kappa-B. Minocycline is Food and Drug Administration (FDA)-approved for treatment of a variety of infections and has been widely used for the treatment of adolescent acne. Minocycline is currently in phase III trials for the treatment of Huntington's disease and amyotrophic lateral sclerosis.
This proposal is for an initial 6-month, single-arm, off label, open-label study (with a 3 month extension phase offered to responders) that will evaluate dose safety and efficacy of minocycline in 10 children, ages 3 to 12 years, with a primary diagnosis of autism and a history of developmental regression. The subjects will be evaluated by a diagnostic/behavioral assessment, and the extent of neuroinflammation judged by CSF cytokine/chemokine profiles before and after the 6-month treatment. Subjects will also be given 0.6 mg/kg vitamin B6 twice a day as a prophylactic for possible minocycline induced nausea and vomiting. If the results of this feasibility study are encouraging, we expect to conduct a double-blind, placebo-controlled trial of minocycline therapy.


Nothing happens fast in the world of autism and so this six month study of 10 people (who completed the actual trial) was conceived in 2006, was actually concluded in 2013.  Here is the resulting paper:-
  


Conclusions
Changes in the pre- and post-treatment profiles of BDNF in CSF and blood, HGF in CSF and CXCL8 (IL-8) in serum, suggest that minocycline may have effects in the CNS by modulating the production of neurotrophic growth factors. However, in this small group of children, no clinical improvements were observed during or after the six months of minocycline administration.

Unfortunately, this study showed that a treatment, known to effectively stabilize microglial cells, had no positive effect on autism and actually seemed in some cases to make it worse.

We can conclude from this that stabilizing the microglia will not be the “holy grail” for treating autism.  Rather, the activated microglia is just one part of a complex, and only partially understood process.


Microglia as the Immunostat 

In a recent post we saw how Rodney Johnson referred to the microglia as the “immunostat” of the body.  Like the thermostat on the wall in your home central heating system.



This is indeed an interesting analogy and might explain some of what is going on.

We saw in Johnson’s paper all the ways that the immune system outside the blood brain barrier (BBB) was able to communicate with the microglia.  We should assume that this communication works both ways; something that is usually overlooked.

In a perfectly functioning body, as in a perfectly functioning house, the immunostat/thermostat gives a good indication of the actual state/temperature, as well as the one you intended.  So if you set your room thermostat to 72 Fahrenheit / 22 Celsius  you expect the actual temperature to be 72 Fahrenheit / 22 Celsius.

However, in the real world things do not work like this.

We live in a house with very large south facing windows, a big fireplace, underfloor heating in some places and European-style hot water radiators (in the US they do have them).  So we have at least four sources of heat.  In spite of having clever German electronics to control our heating system, the thermostat in the centre of the house, by itself, is not adequate.

Something similar is happening in body and brain of people with autism, just replace temperature with inflammation.

Just as my house has multiple systems resulting in heating, the human body has numerous processes leading to “inflammation”.  Some of these inflammatory processes are interconnected and some are not.  The net result at any one time can be measured by looking at various cytokine levels, gene expression, microglial activation and numerous other things; there is no single measurable thing called “inflammation”.

There will never be a single wonder anti-inflammatory treatment.

The activated state of the microglia rather than being the ultimate target for intervention may just be a reflection of inflammation elsewhere in the body, or alternatively it may be just the result of oxidative stress in the brain.

Just like after a few years you may need to replace your wall thermostat, because it is giving false data, the clever immunostat, that may be the microglia, could have been disrupted by all that oxidative stress in the brain.  It might even be sending its proinflammatory signal in reverse, back across the BBB, to the rest of the body. Not such a crazy idea?


The future of anti-inflammatory interventions

The NIMH and Johns Hopkins would naturally be disappointed by the results of their study; but it was a study well worth doing.  Hopefully they will pursue other avenues of thought.

We already know that there are numerous ways to achieve a degree of immuno-modulatory change and that in some types of autism there can be a profound behavioral impact.

These range from simple Ibuprofen, to steroids like Prednisone; not to mention those Kv1.3 blockers and ShK-peptides.  These will likely all affect the microglia, but it is not their main mode of action.


Insights

As is often the case, there are useful insights that you can learn from a “failed” trial.

I would imagine that an autistic person with ulcerative colitis would also have activated microglia. Treating that person with minocycline should have some stabilizing influence on the microglia, but without resolving the ulcerative colitis, the pro-inflammatory signals continue to be sent around the body.

Turning down the thermostat in my house, when I have a big log fire blazing, has no effect on the temperature. 

The microglia in the brain of people with autism probably should not be activated; we really need to know why they are activated.

If you can work on the numerous processes/pathways leading to “inflammation” you would most likely also achieve some deactivation of the microglia.

Therefore we should look at things like PPAR gamma which are directly relevant to the pathology of autism, and agonists of PPAR gamma also happen to be “anti-inflammatory” and indeed, in the test tube, some can stabilize microglia.

One, far away, day they will bring those ShK-peptides to the market. 

In the meantime, my current targets are Tangeretin and Nobiletin, flavonoids found in tangerines.


For the scientists among you:-

In addition to being a PPAR gamma agonist, Tangeretin is also a known P2Y2 receptor antagonist.  Both properties are potentially useful.

PPAR gamma has been covered in this blog already.  P2 receptors are a class of Purinergic receptor.  Within the field of purinergic signalling, these receptors have been implicated in learning and memory, locomotor and feeding behavior, and sleep. 

Suramin is used in research as a broad-spectrum antagonist of P2 receptors.

It is Suramin that Robert Naviaux, at UC San Diego, has been researching as a potent autism therapy.  He has shown it effective in mouse models, but the problem is that it is not safe for long term use in humans.  Regular readers should note that, yet again, an anti-parasite drug has been found to have an effect in autism.  Parasites do not cause autism, but understanding them better would be a potential advantage.

Why Suramin, a Century-Old, Anti-Parasitic Drug May Hold the Key to Understanding Autism


Dr. Robert Naviaux's recent finding suggests reversible metabolic syndrome could be at core of autism



The full paper is below:-




In particular, P2Y11 is a regulator of immune response.  There are big gaps in the science and I have no idea if tangeretin affects P2Y11.