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Showing posts with label calcium. Show all posts
Showing posts with label calcium. Show all posts

Tuesday 13 June 2017

Eosinophilic Esophagitis – another Granulocyte Disorder Associated with Autism  


There are many comorbidities associated with autism.  I have long held the view that these comorbidities hold the key to understanding each particular case of autism.  In many cases this may be far more useful than genetic testing, which only seems to help in a minority of cases.

“Ringed esophagus” aka “Corrugated esophagus”


This then allows you to put people into sub-groups that may well respond to the same therapy.  This may all sound like common sense, but apparently is not.

Eosinophilic esophagitis (EoE) is a relatively new diagnosis and it is applies to a certain type of reflux/GERD/GORD that might be associated with a difficulty in swallowing and may not respond well to the standard stomach acid lowering therapies.

It is likely that most people with Eosinophilic esophagitis have never been correctly diagnosed. Many people have taken several years to get the correct diagnosis.

It is known that Eosinophilic esophagitis is much more common in autism than the general population. One study showed that EoE is four time more likely to be diagnosed in someone with autism. I suspect many people with autism never have their GI problems fully diagnosed.

We now have to add some new science to this blog


Granulocytes

There is a great deal already in this blog about mast cells.  Many readers have children who have allergies, mast cell activation, or even mastocytosis.  Mast cells are the ones (but not the only ones) that release histamine.

Mast cells are just one type of a class of cells called Granulocytes, that are produced in your bone marrow.

Granulocytes are a category of white blood cells characterized by the presence of granules, which release their contents when they degranulate.

The four types of granulocytes are:- 


·        mast cells

These have been well covered in the past. These are what cause problems for people with pollen allergy.


·        eosinophils

Eosinophils play a crucial part in the killing of parasites because their granules contain a unique, toxic basic protein and cationic protein. Eosinophils regulate other immune cell functions (e.g., CD4+ T cells, dendritic cells, B cells, mast cells, neutrophils, and basophils), they are involved in the destruction of tumor cells, and they promote the repair of damaged tissue. Interleukin-5 interacts with eosinophils and causes them to grow and differentiate; IL-5 is produced by basophils.

Note that some people with autism find that the TSO helminth parasites modify their immune system and improve their autism. This may relate to what is contained in the granules of eosinophils.  


·        basophils 

Basophils are similar to mast cells, in that they contain prestored histamine within their granules. Unlike mast cells they circulate in your blood . Basophils are the least common of the granulocytes, representing about 0.5 to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammatory reactions during immune response, as well as in the formation of acute and chronic allergic diseases, including anaphylaxis, asthma, atopic dermatitis and hay fever. They can produce histamine and serotonin that induce inflammation, and heparin that prevents blood clotting.

There is research underway to try to develop basophil stabilizers.


·        neutrophils

Neutrophils are normally found in the bloodstream. During the beginning phase of inflammation, particularly as a result of bacterial infection, environmental exposure, and some cancers, neutrophils are one of the first-responders of inflammatory cells to migrate towards the site of inflammation.

Neutrophils are recruited to the site of injury within minutes following trauma, and are the hallmark of acute inflammation; however, due to some pathogens being indigestible, they can be unable to resolve certain infections without the assistance of other types of immune cells.

Neutrophils also release an assortment of proteins in three types of granules by a process called degranulation. The contents of these granules have antimicrobial properties, and help combat infection.


An obvious question would be, if you know you have a problem with mast cells are you likely to have an issue with the other types of granulocytes?

One role of eosinophils is to regulate other immune cell functions (e.g., CD4+ T cells, dendritic cells, B cells, mast cells, neutrophils, and basophils).

The subject is highly complex and again not fully understood, but it is clear that granulocytes are all interrelated and so a problem with one may well be associated with a problem with others.

In the case of Eosinophilic esophagitis (EoE), both eosinophils and mast cell are directly involved.

Basophils, like mast cells, release histamine among other things when they degranulate.

Mast cells usually do not circulate in the blood stream, but instead are located in connective tissue.  Circulating granulocytes, like basophils can be recruited out of the blood into a tissue when needed.

So in addition to mast cell stabilizers perhaps, we might benefit from basophil and eosinophil stabilizers.

Surprisingly, the antihistamine cetirizine has Eosinophil-stabilizing properties, as does the asthma drug Montelukast. Both drugs are widely used in children.

Another substance, curine, also inhibits eosinophil influx and activation and is seen as a potential new treatment for asthma.  Interestingly the drug curine, is an alkaloid, that blocks L-type Ca²⁺ channels.

Regular readers may recall that I proposed the L-type calcium channel blocker Verapamil to control my son’s mast cell degranulation. Mast cells degranulate in a very complex fashion that involves the flow of Ca²⁺.

This may or may not be a coincidence. 

Fullerene nanomaterials are being developed as both mast cell and peripheral blood basophil stabilizers.



L-type calcium channels and GI disorders in Autism

There are many types of GI disorder in autism, however I suggest that a large group can be categorized as being broadly Granulocyte Disorders, which may well all respond to L-type calcium channel blockers, to some extent.

Indeed this may be a better solution than the widely used cromolyn sodium.

Perhaps people with autism, and their family members have certain calcium channels that are either overexpressed, or do not close fast enough, leading to a higher level of intracellular calcium.  This of course ties back in with Professor Gargus and his theories about IP3R and the calcium store inside the endoplasmic reticulum”.

This all gets extremely complex.

My rather simple suggestion would be that if you have autism and any GI problem from the esophagus downwards, a three day trial of verapamil just might change your life.  As is almost always the case, there are some people who do not tolerate verapamil.



Interleukin 5

Interleukin 5 (IL-5) is an inflammatory cytokine produced by type-2 T helper cells  (Th2), mast cells, basophils and eosinophils.

IL-5 interacts with eosinophils and causes them to grow and differentiate.

IL-5 has long been associated with the cause of several allergic diseases including allergic rhinitis and asthma, where a large increase in the number of circulating, airway tissue, and induced sputum eosinophils have been observed.

You might expect high levels of IL-5 in people with Eosinophilic esophagitis (EoE)



Anti–IL-5 therapy is associated with marked decreases in peripheral blood and esophageal eosinophilia (including the number of CCR3+ blood cells) in patients with EE and improved clinical outcomes.


Not surprisingly the same anti-IL-5 therapy has been approved to treat severe asthma.


Patients are given mepolizumab by injection every four weeks. It costs £840 per dose.



Mepolizumab for autism?

It is very expensive, so I doubt many people will think of Mepolizumab for autism.  If you have EoE, or severe asthma, you may be able to access this IL-5 therapy, my guess is that it would also reduce the severity of any comorbid autism.


Back to Eosinophilic Esophagitis

I was writing a while ago about food allergy in my book and came across the opinion that food allergy is no more common in autism than in typical people, but what is more common is Eosinophilic Esophagitis.

Eosinophilic esophagitis is a chronic immune system disease. It has been identified only in the past two decades, but is now considered a major cause of digestive system (gastrointestinal) illness.  In many cases it likely remains undiagnosed. If it continues, after a few years swallowing becomes difficult, in part because a “ringed esophagus” develops that impedes the passage of food.

As seems to be often the case there are plenty of contradictions in the diagnosis and treatment, as you will find as you read on.

The symptoms are broadly what would normally be diagnosed as reflux/GERD/GORD. This is very often found in people with autism and I expect in their relatives.

It is relevant to autism because it will be yet another comorbidity that when treated should improve autism, but it is also another marker of a particular sub-group of autism.

There are numerous other GI conditions comorbid with autism - colitis, IBD, IBS etc.  In the end I imagine that the molecular basis of some of these diagnoses is actually the same, so you will find the same therapies may be effective.

It looks like that one common factor is the mast cell and, just as in pollen allergy and asthma, stabilizing mast cells yields great benefit. Stabilizing mast cells is complex but involves the flow of calcium ions, Ca2+.  By modifying the flow of Ca2+ you can prevent mast cells degranulating.  This was one of my earlier discoveries, but there is now research showing the L type calcium channels “open” mast cells.  Keeping these channels closed is actually quite simple.

It would seem logical that the same approach could be therapeutic to other conditions that are, at least in part, mediated by mast cells.

According to the Mayo Clinic these are symptoms of eosinophilic-esophagitis


Adults:

·         Difficulty swallowing (dysphagia)

·         Food impaction

·         Chest pain that is often centrally located and does not respond to antacids

·         Persistent heartburn

·         Upper abdominal pain

·         No response to gastroesophageal reflux disease (GERD) medication

·         Backflow of undigested food (regurgitation)


Children:

·         Difficulty feeding

·         Vomiting

·         Abdominal pain

·         Difficulty swallowing (dysphagia)

·         Food impaction

·         No response to GERD medication

·         Failure to thrive (poor growth, malnutrition and weight loss)


The diagnosis of EoE is typically made on the combination of symptoms and findings of diagnostic testing.


Prior to the development of the EE Diagnostic Panel, EoE could only be diagnosed if gastroesophageal reflux did not respond to a six-week trial of twice-a-day high-dose proton-pump inhibitors (PPIs) or if a negative ambulatory pH study ruled out gastroesophageal reflux disease (GERD).

Treatment strategies include dietary modification to exclude food allergens, medical therapy, and mechanical dilatation of the esophagus.

The current recommendation for first line treatment is PPI in lieu of diet as a significant portion of EOE cases respond to this, and it is a low risk, low cost treatment.

The second and third line therapies are an elimination diet of either the 6 or 4 most common triggers, or topical corticosteroids, including both fluticasone, and topical viscous budesonide.

Elimination diets would be followed by re-introduction of foods under supervision if the first diet is successful. Allergy evaluation has not been found to be an effective means to determine what foods to eliminate.

  


MAST CELL STABILIZERS

In a small case series, Cromolyn sodium failed to show any clinical or histologic improvement in EoE patients

LEUKOTRIENE INHIBITORS

Montelukast is an eosinophil stabilizing agent. It improved clinical symptoms in EoE but there was no histological improvement

PROGNOSIS

As mentioned earlier, EoE is a chronic inflammatory disease of the esophagus. The inflammation leads to remodeling, fibrosis and stricture. Fortunately, no case of esophageal malignancy has been reported in EoE. Patients are generally diagnosed after several years of their symptoms. Although symptomatic improvement occurs after treatment, recurrence is common after discontinuation of treatment. So maintenance therapy is needed to prevent recurrences. At the present time there is no head to head study to suggest the best maintenance treatment. Continuation of swallowed corticosteroid and/or dietary therapy should be done in all EoE patients particularly in those with history of food impaction, dysphagia, esophageal stricture, and in those with rapid symptomatic and histologic relapse following initial treatment



Eosinophilic esophagitis and Mast Cells

Eosinophilic esophagitis is called Eosinophilic because it is mediated by Eosinophils, however it has been established that mast cells also play a role. 



Whereas prior studies have primarily focused on the role of eosinophils in disease diagnosis and pathogenesis, this study investigates the involvement of mast cells.

Herein we have identified local mastocytosis and mast cell degranulation in the esophagus of EE patients; identified an esophageal mast cell associated transcriptome that is significantly divergent from the eosinophil-associated transcriptome with CPA3 mRNA levels serving as the best mast cell surrogate marker; and provide evidence for the involvement of KIT ligand in the pathogenesis of EE.


One possible explanation for eosinophilic esophagitis:















A potential immunological mechanism involved in the pathogenesis of EoE. An uncontrolled TH2 immune response initiated by an allergic insult results in the transition of the esophagus from a normal (NL) to EoE phenotype through enhanced IL-13 production that induces highly elevated CCL26 (eotaxin-3) expression by esophageal epithelium. Dysregulated TH2 immune response and enhanced CCL26 secretion together promote the infiltration of CD4+TH2 cells, eosinophils, and mast cells, and potentially, type-2 innate lymphoid cells (ILC2) and CD4+TH9 cells; into the esophagus. TGF-β and IL-4 produced by the activated mast cells and CD4+TH2 cells may induce eosinophils, ILC2, and/or CD4+TH9 cells to produce IL-9, which in turn, promotes esophageal mastocytosis that contributes to the development of EoE pathophysiology.



Possible Eosinophil stabilizers


CONCLUSIONS Eosinophil-stabilizing properties and favorable safety profile make cetirizine an attractive add-on therapy for NMO. Thus far it has been well-tolerated in our patient population, with incoming data about efficacy expected over the coming months




·        Curine is a bisbenzylisoquinoline alkaloid from Chondrodendron platyphyllum.

·        Curine inhibits eosinophil influx and activation and airway hyper-responsiveness.

·        Curine mechanisms involve inhibition of Ca2+ influx, and IL-13 and eotaxin secretion.

·        No significant toxicity was observed in mice orally treated with curine for 7 days.

·         Curine has the potential for the development of anti-asthmatic drugs.

  

Conclusion

Non conventional therapies for eosinophilic esophagitis might include:-


·        Cetirizine

·        Verapamil

·        Montelukast

·        Curine

The very expensive therapy is Mepolizumab.

If you have one type granulocyte causing a disorder, is seems almost inevitable that the other types of granulocyte are also involved.

Treating granulocyte disorders should improve autism and left untreated they may mask the effect of otherwise useful autism therapies. 

One reader did previously suggest a bone marrow transplant for autism. A rather radical solution, but if someone with autism was given donor bone marrow as part of another therapy, you might well see their autism improve.










Friday 21 April 2017

The Excitatory/Inhibitory Imbalance – GABAA stabilization via IP3R


This blog aims to synthesize the relevant parts of the research and make connections that point towards some potential therapeutic avenues.  Most researchers work in splendid isolation and concentrate on one extremely narrow area of interest.

The GABAA reset, not functional in some autism

On the one hand things are very simple, if the GABAA receptors function correctly and are inhibitory and the glutamate receptors (particularly NMDA and mGluRx) function correctly, there is harmony and a  perfect excitatory/inhibitory balance.

Unfortunately numerous different things can go wrong and you could write a book about each one.

As you dig deeper you see that the sub-unit make-up of GABAA receptors is not only critical but changes.  The plus side is that you can influence this.

Today we see that the receptors themselves are physically movable and sometimes get stuck in the “wrong place”. When the receptors cluster close together they produce a strong inhibitory effect, but continual activation of NMDA receptors by the neurotransmitter glutamate - as occurs naturally during learning and memory, or in epilepsy - leads to an excess of incoming calcium, which ultimately causes the receptors to become more spread out, reducing how much the neuron can be inhibited by GABA. There needs to be a mechanism to move the GABAA receptors back into their original clusters.

Very clever Japanese researchers have figured out the mechanism and to my surprise it involves one of those hubs, where strange things in autism seem to connect to, this time IP3R.





I guess the Japanese answer to my question above is simple. YES,


A very recent science-light article by Gargus on IP3:-






Now to the Japanese.






I wonder if Gargus has read the Japanese research, because both the cause and cure for the GABAA receptors dispersing and clustering is an increase in calcium and both mediated by glutamate.  

The excitatory neurotransmitter glutamate binds to the mGluR receptor and activates IP3 receptor-dependent calcium release and protein kinase C to promote clustering of GABAA receptors at the postsynaptic membrane - the place on a neuron that receives incoming neurotransmitters from connecting neurons.

If Professor Gargus is correct, and IPR3 does not work properly in autism, the GABAA receptors are likely not sitting there in nice neat clusters. As a result their inhibitory effect is reduced and neurons fire when they should not.

Gargus has found that in the types of autism he has investigated IP3 receptor open as they should, but close too fast and so do not release enough calcium from the cell’s internal calcium store (the endoplasmic reticulum).

In particular the Japanese researchers found that:-

“Stabilization of GABA synapses by mGluR-dependent Ca2+ release from IP3R via PKC”
If the IP3 receptor does not stay open as long as it should, not enough Ca2+ will be released and GABA synapses will not be stabilized. Then GABAA receptors will be diffused rather than being in neat clusters.

The science-light version of the Japanese study:-




Just as a thermostat is used to maintain a balanced temperature in a home, different biological processes maintain the balance of almost everything in our bodies, from temperature and oxygen to hormone and blood sugar levels. In our brains, maintaining the balance -- or homeostasis -- between excitation and inhibition within neural circuits is important throughout our lives, and now, researchers at the RIKEN Brain Science Institute and Nagoya University in Japan, and École Normale Supérieure in France have discovered how disturbed inhibitory connections are restored. Published in Cell Reports, the work shows how inhibitory synapses are stabilized when the neurotransmitter glutamate triggers stored calcium to be released from the endoplasmic reticulum in neurons.

"Imbalances in excitation and inhibition in the brain has been linked to several disorders," explains lead author Hiroko Bannai. "In particular, forms of epilepsy and even autism appear to be related to dysfunction in inhibitory connections."

One of the key molecules that regulates excitation/inhibition balance in the brain is the inhibitory neurotransmitter GABA. When GABA binds to GABAA receptors on the outside of a neuron, it prevents that neuron from sending signals to other neurons. The strength of the inhibition can change depending on how these receptors are spaced in the neuron's membrane.

While GABAA receptors are normally clustered together, continual neural activation of NMDA receptors by the neurotransmitter glutamate -- as occurs naturally during learning and memory, or in epilepsy -- leads to an excess of incoming calcium, which ultimately causes the receptors to become more spread out, reducing how much the neuron can be inhibited by GABA.

To combat this effect, the receptors are somehow continually re-clustered, which maintains the proper excitatory/inhibitory balance in the brain. To understand how this is accomplished, the team focused on another signaling pathway that also begins with glutamate, and is known to be important for brain development and the control of neuronal growth.

In this pathway glutamate binds to the mGluR receptor and leads to the release of calcium from internal storage into the neuron's internal environment. Using quantum dot-single particle tracking, the team was able to show that after release, this calcium interacts with protein kinase C to promote clustering of GABAA receptors at the postsynaptic membrane--the place on a neuron that receives incoming neurotransmitters from connecting neurons.

These findings show that glutamate activates distinct receptors and patterns of calcium signaling for opposing control of inhibitory GABA synapses.

Notes Bannai, "it was surprising that the same neurotransmitter that triggers GABAA receptor dispersion from the synapse, also plays a completely opposite role in stabilizing GABAA receptors, and that the processes use different calcium signaling pathways. This shows how complex our bodies are, achieving multiple functions by maximizing a limited number of biological molecules.

Pre-activation of the cluster-forming pathway completely prevented the dispersion of GABAA receptors that normally results from massive excitatory input, as occurs in status epilepticus -- a condition in which epileptic seizures follow one another without recover of consciousness. Bannai explains, "further study of the molecular mechanisms underlying the process we have uncovered could help develop treatments or preventative medication for pathological excitation-inhibition imbalances in the brain.

"The next step in understanding how balance is maintained in the brain is to investigate what controls which pathway is activated by glutamate. Most types of cells use calcium signals to achieve biological functions. On a more basic level, we believe that decoding these signals will help us understand a fundamental biological question: why and how are calcium signals involved in such a variety of biological phenomena?"


The full Japanese study:-





·        Bidirectional synaptic control system by glutamate and Ca2+ signaling

·        Stabilization of GABA synapses by mGluR-dependent Ca2+ release from IP3R via PKC

·        Synaptic GABAAR clusters stabilized through regulation of GABAAR lateral diffusion

·        Competition with an NMDAR-dependent Ca2+ pathway driving synaptic destabilization

GABAergic synaptic transmission regulates brain function by establishing the appropriate excitation-inhibition (E/I) balance in neural circuits. The structure and function of GABAergic synapses are sensitive to destabilization by impinging neurotransmitters. However, signaling mechanisms that promote the restorative homeostatic stabilization of GABAergic synapses remain unknown. Here, by quantum dot single-particle tracking, we characterize a signaling pathway that promotes the stability of GABAA receptor (GABAAR) postsynaptic organization. Slow metabotropic glutamate receptor signaling activates IP3 receptor-dependent calcium release and protein kinase C to promote GABAAR clustering and GABAergic transmission. This GABAAR stabilization pathway counteracts the rapid cluster dispersion caused by glutamate-driven NMDA receptor-dependent calcium influx and calcineurin dephosphorylation, including in conditions of pathological glutamate toxicity. These findings show that glutamate activates distinct receptors and spatiotemporal patterns of calcium signaling for opposing control of GABAergic synapses.



In this study, we demonstrate that the mGluR/IICR/PKC pathway stabilizes GABAergic synapses by constraining lateral diffusion and increasing clustering of GABAARs, without affecting the total number of GABAAR on the cell surface. This pathway defines a unique form of homeostatic regulation of GABAergic transmission under conditions of basal synaptic activity and during recovery from E/I imbalances. The study also highlights the ability of neurons to convert a single neurotransmitter (glutamate) into an asymmetric control system for synaptic efficacy using different calcium-signaling pathways.

The most striking conceptual finding in this study is that two distinct intracellular signaling pathways, NMDAR-driven Ca2+ influx and mGluR-driven Ca2+ release from the ER, effectively driven by the same neurotransmitter, glutamate, have an opposing impact on the stability and function of GABAergic synapses. Sustained Ca2+ influx through ionotropic glutamate receptor-dependent calcium signaling increases GABAAR lateral diffusion, thereby causing the dispersal of synaptic GABAAR, while tonic mGluR-mediated IICR restrains the diffusion of GABAAR, thus increasing its synaptic density. How can Ca2+ influx and IICR exert opposing effects on GABA synaptic structure? Our research indicates that each Ca2+ source activates a different Ca2+-dependent phosphatase/kinase: NMDAR-dependent Ca2+ influx activates calcineurin, while ER Ca2+ release activates PKC.


Taken together, these results lead us to propose the following model for bidirectional competitive regulation of GABAergic synapses by glutamate signaling. Phasic Ca2+ influx through NMDARs following sustained neuronal excitation or injury leads to the activation of calcineurin, overcoming PKC activity and relieving GABAAR diffusion constraints. In contrast, during the maintenance of GABAergic synaptic structures or the recovery from GABAAR dispersal, the ambient tonic mGluR/IICR pathway constrains GABAAR diffusion by PKC activity, overcoming basal calcineurin activity. One possible mechanism of dual regulation of GABAAR by Ca2+ is that each Ca2+-dependent enzyme has a unique sensitivity to the frequency and number of external glutamate release events and can act to decode neuronal inputs (Fujii et al., 2013xNonlinear decoding and asymmetric representation of neuronal input information by CaMKIIα and calcineurin. Fujii, H., Inoue, M., Okuno, H., Sano, Y., Takemoto-Kimura, S., Kitamura, K., Kano, M., and Bito, H. Cell Rep. 2013; 3: 978–987

Abstract | Full Text | Full Text PDF | PubMed | Scopus (24)See all References, Li et al., 2012xCalcium input frequency, duration and amplitude differentially modulate the relative activation of calcineurin and CaMKII. Li, L., Stefan, M.I., and Le Novère, N. PLoS ONE. 2012; 7: e43810

Crossref | PubMed | Scopus (29)See all References, Stefan et al., 2008xAn allosteric model of calmodulin explains differential activation of PP2B and CaMKII. Stefan, M.I., Edelstein, S.J., and Le Novère, N. Proc. Natl. Acad. Sci. USA. 2008; 105: 10768–10773

Crossref | PubMed | Scopus (44)See all References) in inhibitory synapses.

Tight control of E/I balance, the loss of which results in epilepsy and other brain and nervous system diseases/disorders, is dependent on GABAergic synaptic transmission (Mann and Paulsen, 2007xRole of GABAergic inhibition in hippocampal network oscillations. Mann, E.O. and Paulsen, O. Trends Neurosci. 2007; 30: 343–349

Abstract | Full Text | Full Text PDF | PubMed | Scopus (194)See all ReferencesMann and Paulsen, 2007). A recent study showed that the excitation-induced acceleration of GABAAR diffusion and subsequent dispersal of GABAARs from synapses is the cause of generalized epilepsy febrile seizure plus (GEFS+) syndrome (Bouthour et al., 2012xA human mutation in Gabrg2 associated with generalized epilepsy alters the membrane dynamics of GABAA receptors. Bouthour, W., Leroy, F., Emmanuelli, C., Carnaud, M., Dahan, M., Poncer, J.C., and Lévi, S. Cereb. Cortex. 2012; 22: 1542–1553

Crossref | PubMed | Scopus (14)See all ReferencesBouthour et al., 2012). Our results indicate that pre-activation of the mGluR/IICR pathway by DHPG could completely prevent the dispersion of synaptic GABAARs induced by massive excitatory input similar to status epilepticus. Thus, further study of the molecular mechanisms underlying the mGluR/IICR-dependent stabilization of GABAergic synapses via regulation of GABAAR lateral diffusion and synaptic transmission could be helpful in the prevention or treatment of pathological E/I imbalances, for example, in the recovery of GABAergic synapses from epileptic states


DHPG = group I mGluR agonist dihydroxyphenylglycine.

On a practical level you want to inhibit GABAA  dispersion and promote GABAA stabilization. How you might do this would depend on exactly what was the underlying problem.

If the problem is IP3R not releasing enough calcium, you might activate PKC in a different way or just increase the signal from Group 1 mGluR. If the problem is too much calcium influx through NMDA receptors due to excess glutamate, you could increase the re-uptake of glutamate, via GLT-1, using Riluzole.  You could block the flow of Ca2+ through NMDA receptors using an antagonist.

The Japanese used dihydroxyphenylglycine (DHPG) as their Group 1 mGluR agonist.  DHPG is an agonist of mGluR1 and mGluR5.  We have come across mGluR5 many times before in this blog.  Mavoglurant is an experimental drug candidate for the treatment of fragile X syndrome.  It is an antagonist of mGluR5.

We have seen many times before that there is both hypo and hyper function possible and indeed that fragile X is not necessarily a good model for autism.

The selective mGluR5 agonist CHPG protects against traumatic brain injury, which would indeed make sense. Although, that research suggests an entirely different mechanism.



The calcium released by IP3 works in complex way together with DAG (diacylglycerol ) to activate PKC (protein kinase C).





Ideally you would have enough calcium released from IP3, but you could also increase DAG. It depends which part of the process is rate-limiting.

Diacylglycerol (DAG) has been investigated extensively as a fat substitute due to its ability to suppress the accumulation of body fat.  Diglycerides, generally in a mix with monoglycerides are common food additives largely used as emulsifiers. In Europe, when used in food the mix is called E471.


Conclusion

On the one hand things are getting very complicated, but on the other we keep coming back to the same variables (IP3R, mGlur5, GABAA etc.).

It is pretty clear that some very personalized therapy will be needed.  Is it an mGlur5 agonist or antagonist? Or quite possibly neither, because in different parts of the brain it will have a good/bad effect.

It does look like Riluzole should work well in some people.

A safe IP3R agonist looks a possibility. As shown in the diagram earlier in this post,IP3 is usually made in situ, but agonists exist.

In effect autism could be the opposite of Huntington’s disease. In Huntington’s,  type 1 IP3 receptors are  more sensitive to IP3, which leads to the release of too much Ca2+ from the ER. The release of Ca2+ from the ER causes an increase in concentrations of Ca2+inside cells and in mitochondria.

According to Gargus we should have reduced concentrations of Ca2+inside cells in autism.

I suspect it is much more complicated in reality, because it is not just the absolute  level of Ca2+ but rather the flow of Ca2+; so it matters where it is coming from. I think we likely have impaired calcium channel activity of multiple types in autism and the actual level of intracellular calcium will not tell you much at all.

As the Japanese commented, it is surprising that glutamate is the neurotransmitter that controls the clustering, or not, of GABAA receptors.  This suggests that you cannot ignore glutamate and just “fix” GABA.