Treated ID and CBS/DYRK1A in Autism and Down Syndrome

One of the most interesting concepts I have come across writing this blog is the idea of treating people with mental retardation (MR) / intellectual disability (ID). I do keep using the term MR, because 90% of the world has no idea what ID means. MR is a very precise description, which is increasingly rare these days.

I still recall several years ago going to a French-speaking neighbour’s barbecue. The French are generally very family-oriented, but quite traditional when it comes to parenting, (hence their low rates of ADHD diagnosis). At that time, Monty aged around 8, could act strangely and was rather obsessed with fire, matches and cigarette lighters. Our neighbour introduced us to his French friends and explained Monty with a brief use of the word “retardé”, which did not prompt any comments or requests for clarification. In the English language this might have been regarded as a big faux-pas; it did not bother me.  It seemed to work very well to forewarn people not to over-react to any unexpected behaviours. 

In the English language, autism has become a nice word and seems the new ADHD, with people even wanting to be diagnosed with it.  MR/ID is still something reserved for other people; it is not something most people want to be associated with. I do use the term cognitive dysfunction, which is just as explicit as MR but does not seem to upset people.

Cognitive dysfunction (MR/ID) is an inevitable consequence of more severe autism and it is just a question of degree. It is not a comorbidity, it is all part of the same package.

In Down Syndrome (DS) IQ is usually between 45 and 71 and worsens with age. MR/ID is defined as an IQ less than 70 and accounts for 2.3% of the general population. An IQ of 100 would put you in the middle of the IQ bell curve. People with DS tend to be very happy and contented, without the problematic behaviors that can occur in autism. 

The good news is that cognitive dysfunction (MR/ID) is likely to be treatable, as some readers of this blog have discovered. You just need to figure out how, which in itself is more about your perseverance than your IQ. You do not need to be an Einstein (IQ > 160), rather a marathon runner.

I just had the uncanny experience at school during the parent-teacher meetings, to be told that other class members could learn from my younger son Monty, aged 14 with autism; that he has the neatest handwriting in class, his essay had the best structure and that when his geography teacher told his assistant to skip the final question in the test (using longitude and latitude) because it was hard, the assistant said just let him try it; he was the only one to get it right. 

So from aged 8 to 14 he has gone from “retardé” to being something quite different.  The teachers do love his assistants, who are great; but he has had an assistant from the age of 4 and back then things moved forward extremely slowly. He learnt to read and write the very hard way, with a vast amount of 1:1 instruction and the school was amazed when his then assistant taught him to read; I don’t think they expected it ever to happen. By treating cognitive dysfunction pharmacologically for five years normal learning became possible and remains a big surprise to everyone.  His new English teacher knows him from back in the darker old days and seemed more shocked than surprised, after a month of teaching him. "Is this the same boy?"

For the first time at school I am being told to be proud of my younger son’s academic achievements, rather than how talented my older son is. Big brother certainly did not expect such a day and his response was along the lines of “well the others in his class must be really thick then” (like it or not, this is a typical teenage male comment). Little brother still has autism, but it is much less disabling. Big brother is currently teaching him to fence (sword fighting), which he would not have bothered to try doing until recently, because it would not have ended well. Years ago Monty did learn to ski, play basketball and soccer, but that all took a lot of effort with very patient (mostly female) instruction; he initially had no idea what to do if a ball was rolled towards him.  Last week he happily sat through the new Blade Runner film, which is nearly three hours long with the trailers. 

Perhaps there is no need for further “breakthroughs” with my Polypill therapy.  It may be good enough already.

It just seems a pity that more people with cognitive dysfunctions are not treated. There are some extremely intelligent parents with children who have severe autism, indeed an ironic twist of genetics. Some even write autism research, or indeed fund it. Even these people are not treating it.   Their fear of quackery blinds them. There certainly are quacks and there are also those who straddle the line, some of what they say is nonsense, but other ideas may not be.

Imagine having a conversation with Bill Gates, who is using his billions to use vaccines to save millions of lives in poor countries, about the possibility that in some people vaccines might trigger mitochondrial disease and autism.  Any organization talking about autism in relation to vaccines, chelation, aluminium, heavy metals etc and anyone who associates with them are in effect blacklisted.

Why does the global head of neuroscience at Novartis not attend the Autism One or TACA conferences? He does have a son with severe autism. It would be very difficult for him to apply any therapy promoted by anyone who attends these events.

Why does a Professor of Medicine from the US Ivy League apply ideas from this blog to his son, but never leave a comment? It is very clear to me why.

As our reader Roger has commented, why do some leading autism researchers still go on about vaccines? It does their interests much more harm than good. 

I think Roger could teach Dr Naviaux a thing or two about getting his Suramin research funded.  

Enhancing Cognition

The first area I came across where serious research is underway to treat MR/ID concerns RASopathies, a group of disorders that share disturbed levels of a protein called RAS. It was actually French research.

In Down Syndrome (DS) I highlighted research that aims to increase cognitive function by targeting the alpha 5 subunit of the GABA_A receptor. We also saw that the same abnormal level of chloride within in cells that exists in much autism also occurs in Down Syndrome (DS); this is why the Frenchman Ben Ari has patented Bumetanide as a therapy for DS. 

In schizophrenia and bipolar there is also reduced cognitive function, but only in schizophrenia has there been much research and clinical trials to improve it. Histamine receptors were one target of this research. 

Too much or too little CBS (Cystathionine-β-synthase )

One known cause of cognitive dysfunction that has not been mentioned in my posts is CBS and since it was raised in a comment I thought it should be included.

All you need to know if you want to rule out a CBS problem is your level of homocysteine. If it is normal you do not have a problem with CBS. If homocysteine is high you have a case of Hyper-homocystinuria, which may be caused by too little CBS, or for a different reason. If you have very low levels of homocysteine (Hypo-homocystinuria) that may be caused by too much CBS and if you have Down Syndrome elevated CBS is inevitable.

Normalizing CBS is very likely to help cognition.

Cystathionine-β-synthase, also known as CBS, is an enzyme that in humans is encoded by the CBS gene. It catalyzes the first step of the transsulfuration pathway, from homocysteine to cystathionine:

L-serine + L-homocysteine    <------>     L-cystathionine + H₂O

Down syndrome is a medical condition characterized by an overexpression of cystathionine beta synthase (CBS) and so a low level of homocysteine in the blood. It has been speculated that cystathionine beta synthase overexpression could be the major culprit in this disease (along with dysfunctioning of GABA_A and Dyrk1a). The phenotype of down syndrome is the opposite of Hyperhomocysteinemia (described below). Pharmacological inhibitors of CBS have been patented by the Jerome Lejeune Foundation and trials are planned.

Cystathionine beta-synthase is enriched in the brains of Down's patients.

Down's syndrome (DS) or trisomy 21 is the most common genetic cause of mental retardation, and adults with DS develop Alzheimer type of disease (AD). Cystathionine beta-synthase (CBS) is encoded on chromosome 21 and deficiency in its activity causes homocystinuria, the most common inborn error of sulfur amino acid metabolism and characterized by mental retardation and vascular disease. Here, we show that the levels of CBS in DS brains are approximately three times greater than those in the normal individuals. CBS is localized to astrocytes and those surrounding senile plaques in the brains of DS patients with AD. The over-expression of CBS may cause the developmental abnormality in cognition in DS children and that may lead to AD in DS

It is a French foundation that is funding research is develop CBS inhibitors to improve cognition in Down Syndrome.

NovAliX To Collaborate With The Fondation Jérôme Lejeune On Down Syndrome (Trisomy 21)

NovAliX will use its expertise and capabilities in medicinal chemistry and structural biology to develop small molecule lead candidates targeting the cystathionine-beta-synthase (CBS). Indeed inhibition of CBS over-expression has been associated with restoration of cognitive impairment in animal models afflicted with trisomy. 

People with DS have a low incidence of coronary atherosclerotic disease (CAD), which would seem to be linked to their low level of homocysteine (high CBS), but their high level of DYRK1A (see later) may be the cause of their early onset Alzheimer’s. 

Some background on homocystinuria, courtesy of Wikipedia:- 

Classical homocystinuria, also known as cystathionine beta synthase deficiency or CBS deficiency, is an inherited disorder of the metabolism of the amino acid methionine, often involving cystathionine beta synthase.

Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of the amino acid homocysteine in the serum and an increased excretion of homocysteine in the urine.

Signs and symptoms of homocystinuria that may be seen include the following:

• A family history of homocystinuria
• Flush across the cheeks
• Musculoskeletal
• Tall, thin build resembling Marfanoid habitus
• Long limbs (dolichostenomelia)
• High-arched feet (pes cavus)
• Knock knees (genu valgum)
• Pectus excavatum and Pectus carinatum
• Intellectual disability
• Seizures
• Psychiatric disease

The term homocystinuria describes an increased excretion of homocysteine in urine (and incidentally, also an increased concentration in plasma). The source of this increase may be one of many metabolic factors, only one of which is CBS deficiency. Others include the re-methylation defects (cobalamin defects, methionine sythase deficiency, MTHFR) and vitamin deficiencies (cobalamin (vitamin B12) deficiency, folate (vitamin B9) deficiency, riboflavin deficiency (vitamin B2), pyridoxal phosphate deficiency (vitamin B6)). In light of this information, a combined approach to laboratory diagnosis is required to reach a differential diagnosis.  

DYRK1A

You may have noticed that DYRK1A was mentioned as another cause of cognitive loss in Down Syndrome.  DYRK1A is yet another autism gene; it encodes an enzyme that is important in how the brain develops. Too much DYRK1A also leads to reduced levels of homocysteine. 

An OTC DYRK1A inhibitor exists today, epigallocatechin gallate (EGCG).

Targeting trisomic treatments: optimizing Dyrk1a inhibition to improve Down syndrome deficits

A chemical with proven clinical safety rescues Down-syndrome-related phenotypes in through DYRK1A inhibition.

DYRK1A is important in neuronal development and function, and its excessive activity is considered a significant pathogenic factor in Down syndrome and Alzheimer's disease. Thus, inhibition of DYRK1A has been suggested to be a new strategy to modify the disease. Very few compounds, however, have been reported to act as inhibitors, and their potential clinical uses require further evaluation. Here, we newly identify CX-4945, the safety of which has been already proven in the clinical setting, as a potent inhibitor of DYRK1A that acts in an ATP-competitive manner. The inhibitory potency of CX-4945 on DYRK1A (IC50=6.8 nM) in vitro was higher than that of harmine, INDY or proINDY, which are well-known potent inhibitors of DYRK1A. CX-4945 effectively reverses the aberrant phosphorylation of Tau, amyloid precursor protein (APP) and presenilin 1 (PS1) in mammalian cells. To our surprise, feeding with CX-4945 significantly restored the neurological and phenotypic defects induced by the overexpression of minibrain, an ortholog of human DYRK1A, in the Drosophila model. Moreover, oral administration of CX-4945 acutely suppressed Tau hyperphosphorylation in the hippocampus of DYRK1A-overexpressing mice. Our research results demonstrate that CX-4945 is a potent DYRK1A inhibitor and also suggest that it has therapeutic potential for DYRK1A-associated diseases

Epigallocatechin gallate: A useful therapy for cognitive disability in Down syndrome?

Neurodevelopmental alterations and cognitive disability are constant features of Down syndrome (DS), a genetic condition due to triplication of chromosome 21. DYRK1A is one of the triplicated genes that is thought to be strongly involved in brain alterations. Treatment of Dyrk1A transgenic mice with epigallocatechin gallate (EGCG), an inhibitor of DYRK1A, improves cognitive performance, suggesting that EGCG may represent a suitable treatment of DS. Evidence in the Ts65Dn mouse model of DS shows that EGCG restores hippocampal development, although this effect is ephemeral. Other studies, however, show no effects of treatment on hippocampus-dependent memory. On the other hand, a pilot study in young adults with DS shows that EGCG transiently improves some aspects of memory. Interestingly, EGCG plus cognitive training engenders effects that are more prolonged. Studies in various rodent models show a positive impact of EGCG on brain and behavior, but other studies show no effect. In spite of these discrepancies, possibly due to heterogeneity of protocols/timing/species, EGCG seems to exert some beneficial effects on the brain. It is possible that protocols of periodic EGCG administration to individuals with DS (alone or in conjunction with other treatments) may prevent the disappearance of its effects.

Conclusion

Understanding emerging therapies that treat various types of MR/ID, and also the various types of dementia, should unlock interesting avenues to raise cognitive function in many types of autism.

Homocysteine levels are very easy to measure. 

Because the gene miss-expression in Down Syndrome (DS) is fully understood, it makes sense that treatment is more advanced than in autism, which is so heterogenous. There are a lot of people in the world with DS and so there is a big market for drug makers.

The potential drug therapies to improve cognition in Down Syndrome (DS) appear to be:- 

·        Basmisanil, a negative allosteric modulator of α₅ subunit-containing GABA_A receptors. It appears that sodium benzoate may have a similar effect.

·        Bumetanide, an NKCC1 inhibitor

·        Potassium bromide, Br^- displaces Cl^- to lower intracellular Cl^-

·        CBS inhibitor

·        DYRK1A inhibitor, like Epigallocatechin gallate (EGCG), but a more potent inhibitor like CX-4945 (Silmitasertib) might be better.

There is mouse model research to show that a single dose just after birth of a drug that stimulates the sonic hedgehog signaling pathway results in a "normal" adult brain.

The risk of Down Syndrome (DS), caused by a third copy of chromosome 21 (trisomy 21), rises rapidly with increasing maternal age, nonetheless the number of births is stable to falling in most developed countries, due to increased prenatal testing and termination of pregnancy for fetal anomaly (TOPFA). TOPFA is not practiced in countries like Poland and Ireland. In Denmark screening has long been free and TOPFA has risen to 98%. In the UK two thirds of mothers opt for their free DS screening and 90% of those who test positive, opt for their free TOPFA. The one third letting nature take its course are probably mainly younger mothers.

In Catholic countries you have both extremes - in Cork, Ireland DS is present 30 times per 10,000 births, but in Zagreb Croatia it is just 6 per 10,000. In the US the CDC say it 14, while in the UK it is 10.  In South Africa 20 cases of DS occur per 10,000 births; mothers are younger than in Ireland.

In developed countries, the natural prevalence of DS looks to be 0.3%, which is the same as the incidence of strictly defined autism (SDA), which I estimated in an earlier post to be 0.3%. It is just that in developed countries most people with DS are never born. 

I would have thought CX-4945 should be trialed by some clever Alzheimer's researcher and indeed for any Tauopathy. In the meantime perhaps Grandad should drink a lot of green tea to get his dose of EGCG.

Cardiazol, a failed Schizophrenia treatment from the 1930s, repurposed at low doses as a Cognitive Enhancer in Down Syndrome and likely some Autism

Italy has many attractions, one being Lake Como (Villa Clooney). 

It is also the only western country still using Cardiazol, where it is used in a cough medicine

Varanasi and the Ganges, not a place you could forget, particularly the smell.

India is the only other country using Cardiazol

Today’s post draws on clever things going on in Down Syndrome research to improve cognitive function, but puts them in the perspective of the faulty GABA switch. 

In the United States it is estimated that 250,000 families are affected by Down Syndrome.  It is caused by a third copy of chromosome 21, resulting in up-regulation of around 300 genes.  A key feature is low IQ, this is partly caused by a physically smaller cerebellum and it appears partly by the GABA switch.  Research has shown that the cerebellum growth could be normalized, but this post is all about the GABA switch. 

In an earlier very science heavy post we saw how a faulty GABA switch would degrade cognitive function in many people with autism, schizophrenia or Down Syndrome. Basmisanil is a drug in Roche’s development pipeline.

The GABA Switch, Altered GABAa Receptor subunit expression in Autism and Basmisanil

   

More evidence to show the GABA switch affects schizophrenia was provided by our reader Natasa.

Gain-of-function missense variant in SLC12A2, encoding thebumetanide-sensitive NKCC1 cotransporter, identified in human schizophrenia

Perturbations of γ-aminobutyric acid (GABA) neurotransmission in the human prefrontal cortex have been implicated in the pathogenesis of schizophrenia (SCZ), but the mechanisms are unclear. NKCC1 (SLC12A2) is a Cl^--importing cation-Cl^- cotransporter that contributes to the maintenance of depolarizing GABA activity in immature neurons, and variation in SLC12A2 has been shown to increase the risk for schizophrenia via alterations of NKCC1 mRNA expression. However, no disease-causing mutations or functional variants in NKCC1 have been identified in human patients with SCZ. Here, by sequencing three large French-Canadian (FC) patient cohorts of SCZ, autism spectrum disorders (ASD), and intellectual disability (ID), we identified a novel heterozygous NKCC1 missense variant (p.Y199C) in SCZ. This variant is located in an evolutionarily conserved residue in the critical N-terminal regulatory domain and exhibits high predicted pathogenicity. No NKCC1 variants were detected in ASD or ID, and no KCC3 variants were identified in any of the three neurodevelopmental disorder cohorts. Functional experiments show Y199C is a gain-of-function variant, increasing Cl^--dependent and bumetanide-sensitive NKCC1 activity even in conditions in which the transporter is normally functionally silent (hypotonicity). These data are the first to describe a functional missense variant in SLC12A2 in human SCZ, and suggest that genetically encoded dysregulation of NKCC1 may be a risk factor for, or contribute to the pathogenesis of, human SCZ.

This study showed that some with schizophrenia will likely benefit from Bumetanide, but that the underlying reason for excessive NKCC1 activity in schizophrenia is not the same as in ASD.  Different cause but the same end result and the same likely therapy, repurposing an old existing drug.

α3 and α5 sub-units of GABA_A

The science is rather patchy, but it seems that the α3 sub-unit of GABA_A receptors is under-expressed in some autism and there is a fair chance that the α5 sub-unit is correspondingly over-expressed.

We know that over-expression of α5 is associated with cognitive impairment.

Down regulating α5 is currently a hot topic in Down Syndrome and at least two drugs are in development.

Reading the Down Syndrome research suggests that those involved have not really understood what is going on.  They do seek to modify GABA signaling, but have not realized that likely problem is the miss-expression of GABA_A subunits in the first place, exactly as in autism.  As in autism, this faulty “GABA switch” has more than one dimension.  An incremental benefit can be expected from correcting each one.


Further support for the use of low dose Clonazepam in some Autism

In previous posts we saw how Professor Catterall's idea to use low dose clonazepam to treat some autism does translate from mice to humans.  This was based on up-regulating the α3 sub-unit of GABA_A receptors.

There is some new research on this subject and Japanese research is very often of the highest quality.

In the paper below, highlighted by our reader Tyler, they use low dose clonazepam to reduce autistic behavior in a rare condition called Jacobsen syndrome.  While Professor Catterall and several readers of this blog are using low dose clonazepam to upregulate the α3 sub unit of GABA_A receptors, the Japanese attribute the benefit to the γ2 subunit.

Whichever way you look at it, another reason to support trial of low dose clonazepam in autism.  When I say low, I mean a dose 100 to 1,000 times lower than the standard doses.

PX-RICS-deficient mice mimic autism spectrum disorder in Jacobsen syndrome through impaired GABAA receptor trafficking 

Jacobsen syndrome (JBS) is a rare congenital disorder caused by a terminal deletion of the long arm of chromosome 11. A subset of patients exhibit social behavioural problems that meet the diagnostic criteria for autism spectrum disorder (ASD); however, the underlying molecular pathogenesis remains poorly understood.

ASD-like behavioural abnormalities in PX-RICS-deficient mice are ameliorated by enhancing inhibitory synaptic transmission with a GABA_AR agonist (Clonazepam)

   

A curative effect of clonazepam on autistic-like behaviour

 These results demonstrate that ASD-like behaviour in PX-RICS^−/− mice is caused by impaired postsynaptic GABA signalling and that GABA_AR agonists have the potential to treat ASD-like behaviour in JBS patients and possibly non-syndromic ASD individuals.

“Correcting GABA” in Down Syndrome

I expect there may be four different methods, all relating to GABA_A, to improve cognition in Down Syndrome just as there appear to be in autism:-

·        Reduce intracellular Cl- by blocking NKCC1 with bumetanide

 ·        Down regulate α5 sub-units of GABA_A

 ·        Damp down GABAA receptors with an antagonist

 ·        Upregulate α3 sub-units of GABA_A

Two of the above are being pursued in Down Syndrome research, but two do not seem to be.

Enhancing Cognitive Function in Down Syndrome

These are the sort of headlines that appeal to me:-

IQ-Boosting Drugs Aim to Help Down Syndrome Kids Learn

Cognitive-enhancing drugs may have a significant impact, doctors say. An IQ boost of just 10 to 15 points could greatly increase the chance that someone with the syndrome would be able to live independently as an adult, said Brian Skotko, co-director of the Down syndrome program at Massachusetts General Hospital in Boston, who has a sister with the condition.

In 2004, Stanford University neurobiologist Craig Garner and a student of his at the time, Fabian Fernandez, realized scientists might be able to counteract the Down Syndrome with drugs…

Researchers did a test in mice using an old GABA-blocking drug called PTZ. After 17 days, the treatment normalized the rodents’ performance on mazes and certain object recognition and memory tasks for as long as two months, according to results published in 2007 in Nature Neuroscience….

“It was bloody amazing,” Garner said by telephone. “It was shocking how well it worked.”

  

Inhibiting Inhibition to Treat Down Syndrome Symptoms

In their work, Hernandez, who is at Roche AG, and colleagues both at Roche and in academia chronically treated mice that have an animal version of Down syndrome with RO4938581, a drug that targets GABA receptors containing an alpha5 subunit. GABA is the major inhibitory transmitter in the brain, and in Down syndrome, there appears to be too much inhibitory signaling in the hippocampus – where, it so happens, GABA receptors with the alpha5 subunit are concentrated.

Treatment with RO4938581 improved the animals' memory abilities in a maze, decreased hyperactivity and reversed their long-term potentiation deficit. In the hippocampus, which is an important brain structure for memory and cognition, it also increased the birth rate of neurons back to the levels seen in normal animals, and led to a decrease in the number of inhibitory connections between cells.

  

In short there are two methods being developed, both potentially applicable to some autism:-

METHOD 1.   Dampen GABA_A receptors with an antagonist

METHOD 2.   Dampen GABA with an inverse agonist of α5 sub-unit  

Initially it was thought method 1 could not be used because of the risk of seizure/epilepsy.

“these drugs (GABA_A antagonists) are convulsant at high doses, precluding their use as cognition enhancers in humans, particularly considering that DS patients are more prone to convulsions”

From:-

Specific targeting of the GABA-A receptor α5 subtype by a selective inverse agonist restores cognitive deficits in Down syndrome mice

  

However this seems to have been overly conservative.

In the 2007 Stanford study they make a big point of their dosing being far lower than that used to induce seizures.

While you may need for a decade to get hold of Basmisanil (method 2), Cardiazol/PZT (method 1) is available in some pharmacies today.  The only complication is that it is in a cough medicine that also contains Dihydrocodeine.

In some countries Dihydrocodeine is used in OTC painkillers along with paracetamol or ibuprofen, while in other countries it is a banned substance.

In Italy and India Cardiazol, with Dihydrocodeine, is given to toddlers as a cough medicine.

  

METHOD 1.   Dampen GABA_A receptors with an antagonist

  

As seems to be the case quite often, you can sometimes repurpose an old drug rather than spend decades developing a new one.  This is the case with Cardiazol/ Pentylenetetrazol that was used in the Stanford trial.

Confusing Medical Jargon, (again)

Cardiazol, the name an elderly psychiatrist would recognize, is also called:-

·        Pentylenetetrazol
·        Pentylenetetrazole
·        Metrazol
·        Pentetrazol
·        Pentamethylenetetrazol
·        PTZ
·        BTD-001 

·        DS-102

Other than to confuse us, why do they need so many names for the same drug?

Cardiazol/ Pentylenetetrazol is a drug that was widely used in the 1930s in Mental Hospitals to trigger seizures that were supposed to treat people with Schizophrenia.  At much lower doses, it found a new purpose decades ago as an ingredient in cough medicine.

Electroconvulsive therapy later took the place of Cardiazol, as psychiatrists sought to treat people by terrifying them.  It was later concluded that the only benefit in giving people Cardiazol was the fear associated with it. Electroconvulsive therapy is still used today in autism.

  

For a background into Cardiazol as a schizophrenia therapy, the following is not very pleasant reading:-

  

‘A violent thunderstorm’: Cardiazol treatment in British mental hospitals

  

The 2007 Stanford trial of Cardiazol (there called PTZ) also trialed another GABA_A antagonist called picrotoxin (PTX).  Picrotoxin is, not surprisingly, a toxin, it is therefore a research drug but it has been given to horses to make them run faster.

Pharmacotherapy for Cognitive Impairment in a Mouse Model of Down Syndrome

  

Recent neuroanatomical and electrophysiological findings from a

mouse model of Down syndrome (DS), Ts65Dn, suggest that there is

excessive inhibition in the dentate gyrus, a brain region important for

learning and memory. This circuit abnormality is predicted to compromise normal mechanisms of synaptic plasticity, and perhaps mnemonic processing. Here, we show that chronic systemic administration of noncompetitive GABAA antagonists, at non – epileptic doses, leads to a persistent, post drug, recovery of cognition in Ts65Dn mice, as well as recovery of deficits in long – term potentiation (LTP). These data suggest that excessive GABAergic inhibition of specific brain circuits is a potential cause of mental retardation in DS, and that GABAA antagonists may be useful therapeutic tools to facilitate functional changes that can ameliorate cognitive impairment in children and young adults with the disorder.

One important things is that this cognitive enhancing effect persisted for a couple of months.

As you will see in the human clinical trial at the end of this post, they are comparing single doses with daily doses to understand the pharmokinetics.

The lead author, Craig Garner went on to start his own company because nobody seemed interested in his findings.

http://balance-therapeutics.com/

“Balance is now testing a GABA-blocking drug, BTD-001, on 90 adolescents and adults with Down syndrome in Australia, with results expected by early next year, said Lien, chief executive officer of the company.”

GABA_A agonists and antagonists

The jargon does get confusing, if you want to stimulate GABA_A receptors, you would use an agonist like GABA itself, or something that mimics it.

If you want to damp down the effect of GABA_A receptors you would need an antagonist.

So if GABA_A receptors are “malfunctioning”, you could either fix the malfunction or turn them down to reduce their effect.

If you cannot entirely repair the malfunction you could always do both.  The overall effect might be better, or might not be, and it might well vary from person to person depending on the degree and nature of malfunction.

We saw in a previous post the idea of using drugs like bumetanide, diamox, and potassium bromide to restore E/I balance and then give GABA a little boost with a GABA agonist like Picamillon.  This is very easy to test.  In our case that little boost, did not help.

In those people who do not respond well, we can take the idea developed by Stanford for Down Syndrome and do the opposite, use a tiny amount of an antagonist, to see if that fine tuning has any beneficial effect.  We now see this is both simple and safe.

METHOD 2.   Inverse agonists of α5 sub-unit GABA_A

I do like method 2, but would prefer not to wait another decade.

Method 2 sets out to improve cognitive function by dampening the activity of α5 sub-unit GABA_A.

The Downs Syndrome researchers at Roche are developing Basmisanil/RG-1662 for this purpose.  It will be a long while till it appears on the shelf of your local pharmacy.

I did look to see if there any clever ways to down regulate the α5 sub-unit of GABA_A , other than those drugs being developed for Down Syndrome. 

Inverse agonists of of α5 sub-unit GABA_A

• α₅IA
• Basmisanil (RG-1662, RO5186582): derivative of Ro4938581, negative allosteric modulator at GABA_A α₅, in human trials for treating cognitive deficit in Down syndrome.^[3]
• L-655,708
• MRK-016
• PWZ-029: moderate inverse agonist^[4]
• Pyridazines^[5]
• Ro4938581^[6]
• TB-21007^[7][8]

The only option today would be the Pyridazines, which include cefozopran (a 4^th generation antibiotic), cadralazine (reduces blood pressure), minaprine (withdrawn antidepressant), pipofezine (a Russian a tricyclic antidepressant), hydralazine (reduces blood pressure, but has problems), and cilazapril (ACE inhibitor).

Pipofezine looks interesting.

Now we can compare Pipofezine with Mirtazapine.   They are both this tricyclic antidepressants, so both closely related to H1 antihistamine drugs.  We saw in earlier posts that Mirtazapine helps some people with autism in quite unexpected ways.

  

To be classed as a Pyridazines there has to be the benzene ring with two adjacent nitrogen atoms

So mirtazapine is not quite a Pyridazine, so may not directly affect the α5 sub-unit; but it does have potent effects elsewhere on the same receptor.  It is will increase the concentration of neuroactive steroids that act as positive allosteric modulators via the steroid binding site on GABA_A receptors.

  

We saw this in earlier posts that changes in progesterone levels affect not only the function of GABA_A but even the subunit composition and hence indirectly possibly α5 sub-unit expression.

I previously suggested both progesterone and pregnenalone as potential autism therapies.  Pregnenalone has since been trialed at Stanford.

The problem with these substances is that they are also female hormones and giving them in high doses to young boys is not a good idea.  Stanford used adults in their trial.

However, affecting the metabolites of progesterone rather than increasing the amount of progesterone itself may give the good, without the bad.  Also, perhaps there is a reason, oxidative stress perhaps, why progesterone metabolism might be disturbed in autism?

Anyway, it is yet another plausible reason why mirtazapine helps some people with autism.

Influence of mirtazapine on plasma concentrations of neuroactive steroids in major depression and on 3-hydroxysteroid dehydrogenase activity

Certain 3-reduced metabolites of progesterone such as 3,5-tetrahydroprogesterone (3,5-THP, 5-pregnan-3-ol-20-one, allopregnanolone) and 3,5-tetrahydroprogesterone (3,5-THP, 5-pregnan-3-ol-20-one, pregnanolone) are potent positive allosteric modulators of the -aminobutyric acid_A (GABA_A) receptor complex.^1, 2, 3

 Mirtazapine affects neuroactive steroid composition similarly as do SSRIs. The inhibition of the oxidative pathway catalyzed by the microsomal 3-HSD is compatible with an enhanced formation of 3-reduced neuroactive steroids. However, the changes in neuroactive steroid concentrations more likely reflect direct pharmacological effects of this antidepressant rather than clinical improvement in general.

So there may indeed be an effect on α5 sub-unit GABA_A, but there is also an effect on another α5 subunit, this time the nicotinic acetylcholine receptors (nAChR).  Those I looked at in earlier posts.  This is getting rather off-topic.

The gene that encode the α5 sub-unit of nAChR is called CHRNA5.  It is associated with nicotine dependence (and hence lung cancer), but is also linked to anxiety.  GABA sub-units expression also plays a key role in anxiety.  So a reason Mirtazapine should help reduce anxiety.

  

Progesterone modulation ofα5 nAChR subunits influences anxiety-related behavior during estrus cycle 

 It has already been shown that GABA_A receptor subunit expression and composition is modulated by progesterone both in vitro and in vivo(Biggio et al. 2001; Griffiths & Lovick 2005; Lovick 2006; Pierson et al. 2005; Weiland & Orchinik 1995) but this is the first report showing an effect of physiological concentrations of progesterone on nAChR subunit expression levels.

Pharmokinetics of Cardiazol

Since mouse experiments indicated an effect that continues after stopping using the drug, the clinical trials are particularly looking at the so called pharmokinetics.  What is best a small daily dose or occasional larger doses?

You would hope they will be keeping a watchful eye on seizures.

I do not know what doses was used in those mental hospitals in the 1930s, but it must be well documented somewhere.

Safety and Efficacy Study of Orally Administered DS102 in Healthy Subjects

Experimental doses in adults vary widely from a “one off” 100mg to a daily dose of 2000mg. Look how they treat the 7 cohorts in the trial.

The cough medicine has 100mg of Cardiazol per 1ml

The usual dose is one drop per year of age, so a 12 year old would have a 0.6ml  dose containing 60mg of Cardiazol.  That is dosage is give 2 to 4 times a day, so up to 240mg a day

This dose is well up there with the dosage used in the above clinical trial, which starts at a one off dose of just 100mg or daily doses of 500mg in adults.

The above trial has been completed but the results have not been published.

If the trial is positive at the lower dose range, the cough medicine is a very cheap alternative.

Conclusion

I wish a safe inverse agonist of the α5 sub-unit of GABA_A existed for use today.

I do not know anyone with Down Syndrome and this blog does not have many readers from Italy.  The standard pediatric dose of Cardiazol Paracodina  cough medicine might be well worth a try for both those with Down Syndrome and some autism with cognitive dysfunction. 

We actual have quite a few readers from India and that is the only other country using this drug.  In India the producer is Nicholas Piramal and the brand name is Cardiazol Dicodid, it cost 30 US cents for 10ml.  So for less than $1, or 70 rupees, you might have a few months of cognitive enhancement, that is less than some people pay for 1 minute of ABA therapy.

If a few drops of this children’s cough medicine improves cognition please lets us all know.