Variable Expression of GABRA5 and Activation of α5 - a Modifier of Cognitive Function in Autism?

Today’s post sounds complicated. We actually already know that the gene GABRA5, and hence the alpha 5 sub-unit of GABA_A receptors, can affect cognition, but we do not know for sure in whom it is relevant.

Most readers of this blog are lay people, as such we tend to be predisposed to the idea that autism is somehow “hardwired”, something that just happened and cannot be reversed. Some of autism is indeed “hardwired”, you cannot take an adult with autism and “re-prune” his synapses, to produce a more elegant robust network in his brain. But much can be done, because many things in the brain are changing all the time, they are not fixed at all. Today’s post is good example.

GABA is the most important inhibitory neurotransmitter in the brain. There are two types of GABA receptor, A and B. These receptors are made up of sub-units. There are many different possible combinations of sub-units to make GABA_A receptors. These combinations are not fixed, or “hard-wired”; they vary all the time.

The composition of the GABA_A receptor changes its effect. It can change how you feel (anxiety) and it can change you think/learn.

You can actually measure GABRA5 expression in different regions of the brain in a test subject using a PET-CT (Positron Emission Tomography–Computed Tomography) scan and it has been done in some adults with high functioning autism. This machine looks like a big front-leading washing machine, just a bit cleverer. 

The brain GABA-benzodiazepine receptor alpha-5 subtype in autism spectrum disorder: A pilot [11C]Ro15-4513 positron emission tomography study

our primary hypothesis was that, compared to controls, individuals with ASD have a significant reduction in α5 GABA receptor availability in these areas.

Due to the small sample size, we could not examine possible correlations between GABA_A binding and particular symptoms of ASD, age, IQ, or symptoms of comorbidities frequently associated with ASD, such as anxiety disorders, OCD and depression. We were also unable to address the effects of possible neuroanatomical differences between people with ASD and controls, which might lead to partial volume effects in PET studies. However, the modest magnitude of the volumetric differences seen in most studies of high-functioning ASD suggests that it is unlikely that these could fully explain the present findings.

These preliminary results suggest that potentiation of GABA_A signaling, especially at GABA_A α5-subunit containing receptors, might potentially be a novel therapeutic target for ASD. Unselective GABA_A agonists and positive allosteric modulators, such as benzodiazepines, have undesirable features such as abuse potential and tolerance, but more selective modulators might avoid such limitations. Further research should extend this work in a larger sample of ASD individuals. It would also be interesting to use PET with the ligand [¹¹C]Ro15-4513 to measure GABA_A in disorders of known etiology characterised by ASD symptoms, such as Fragile X and 15q11-13 duplication

In summary, we present preliminary evidence of reduced GABA_A α5 expression in adult males with ASD, consistent with the hypothesis that ASD is characterised by a defect in GABA signaling. 

α5GABAA receptor deficiency causes autism-like behaviors

The prevalence of autism spectrum disorders (ASDs), which affect over 1% of the population, has increased twofold in recent years. Reduced expression of GABA_A receptors has been observed in postmortem brain tissue and neuroimaging of individuals with ASDs. We found that deletion of the gene for the α5 subunit of the GABA_A receptor caused robust autism-like behaviors in mice, including reduced social contacts and vocalizations. Screening of human exome sequencing data from 396 ASD subjects revealed potential missense mutations in GABRA5 and in RDX, the gene for the α5GABA_A receptor-anchoring protein radixin, further supporting a α5GABA_A receptor deficiency in ASDs.

The results from the current study suggest that drugs that act as positive allosteric modulators of α5GABA_A receptors may ameliorate autism-like behaviors 

  

Too many or too few the α5GABA_A receptors or too much/little activity?

Regular readers will know that autism is all about extremes hypo/hyper, macro/micro etc. The same is true with α5GABA_A, too few can cause autistic behaviors, but too many can impede learning. You need just the right amount.

The next variable is how well your α5GABA_A are behaving, because even if you have an appropriate number of these receptors, you may not have optimal activity from them. Over activity from α5GABA_A is likely to have the same effect as having too many of them.

Here it becomes very relevant to many with autism and inflammatory comorbidities, because systemic inflammation has been shown to activate α5GABA_A. It has been shown that increased α5GABA_A receptor activity contributes to inflammation-induced memory deficits and, by my extension, to inflammation-induced cognitive decline.

α5GABAA Receptors Regulate Inflammation-Induced Impairment of Long-Term Potentiation

Systemic inflammation causes learning and memory deficits through mechanisms that remain poorly understood. Here, we studied the pathogenesis of memory loss associated with inflammation and found that we could reverse memory deficits by pharmacologically inhibiting α5-subunit-containing γ-aminobutyric acid type A (α5GABA_A) receptors and deleting the gene associated with the α5 subunit. Acute inflammation reduces long-term potentiation, a synaptic correlate of memory, in hippocampal slices from wild-type mice, and this reduction was reversed by inhibition of α5GABA_A receptor function. A tonic inhibitory current generated by α5GABA_A receptors in hippocampal neurons was increased by the key proinflammatory cytokine interleukin-1β through a p38 mitogen-activated protein kinase signaling pathway. Interleukin-1β also increased the surface expression of α5GABA_A receptors in the hippocampus. Collectively, these results show that α5GABA_A receptor activity increases during inflammation and that this increase is critical for inflammation-induced memory deficits.

We saw in an earlier post that overexpression of GABRA5 is found in slow learners and we know that this is a key target of Down Syndrome research, aimed at raising cognitive function.

What can be modified?

It appears that you can modify the expression of GABRA5, which means you can increase/decrease the number of GABA_A receptors that contain an α5 subunit.

You can also tune the response of those α5 subunits. You can increase it or decrease it.

Activation of the α₅ subunit is thought to be the reason why benzodiazepine drugs  have cognitive (reducing) side effects. By extension, inverse agonists of α₅ are seen as likely to be nootropic.

One such drug is LS-193,268  is a nootropic drug invented in 2004 by a team working for Merck, Sharp and Dohme.

A complication is that you do not want to affect the α₂ subunit, or you will cause anxiety. So you need a highly selective inverse agonist.

The new Down Syndrome drug, Basmisanil, is just such a selective inverse agonist of α₅.

“Basmisanil (developmental code names RG-1662, RO5186582) is a highly selective inverse agonist/negative allosteric modulator of α₅ subunit-containing GABA_A receptors which is under development by Roche for the treatment of cognitive impairment associated with Down syndrome.  As of August 2015, it is in phase II clinical trials for this indication.^“

A contradiction

As is often the case, there is an apparent contradiction, because on the one hand a negative allosteric modulator should be nootropic in NT people and appears to raise cognition in models of Down Syndrome; but on the other hand results from a recent study suggests that drugs that act as positive allosteric modulators of α5GABA_A receptors may ameliorate autism-like behaviors.

So which is it?

Quite likely both are right.

It is exactly as we saw a long while back with NMDAR activity, some people have too much and some have too little. Some respond to an agonist, some to an antagonist and some to neither.

What we can say is that fine-tuning α5GABA_A in man and mouse seems a viable option to enhance cognition in those with learning difficulties.

The clever option is probably the positive/negative allosteric modulator route, the one being pursued by big Pharma for Down Syndrome.

I like Dr Pahan’s strategy from this previous post, for poor learners and those with early dementia

https://epiphanyasd.blogspot.com/2017/10/sodium-benzoate-and-gabra5.html

to use cinnamon/NaB to reduce GABRA5 expression, which has got to consequently reduce α5GABA_A activity.

All of these strategies are crude, because what matters is α5GABA_A activity in each part of the brain. This is why changing GABRA5 expression will inevitably have good effects in one area and negative effects in another area. What matter is the net effect, is it good, bad or negligible?

The fact that systemic inflammation increases α5GABA_A activity may contribute to the cognitive decline some people with autism experience.

We previously saw how inflammation changes KCC2 expression and hence potentially increases intra cellular chloride, shifting GABA towards excitatory.

Ideally you would avoid systemic inflammation, but in fact all you can do is treat it.

Increasing α5GABA_A activity I would see as possible strategy for people with high IQ, but some autistic features.

I think those with learning problems are likely to be the ones wanting less α5GABA_A activity.

The people for whom “bumetanide has stopped working” or “NAC has stopped working” are perhaps the ones who have developed systemic inflammation for some reason.  You might only have to measure C-reactive protein (CRP) to prove this.

More reading for those interested:-

The α-5 subunit-containing GABA-A receptor: a target for the treatment of cognitive defects

The role of α5 GABAA receptor agonists in the treatment of cognitive deficits in schizophrenia

Sodium Benzoate and GABRA5 - Raising Cognitive Function in Autism

I am still looking for additional cognitive enhancing autism therapies. It seems the best way to find them may actually be to reread my own blog.

A long time ago I suggested that Cinnamon could well be therapeutic in autism, most likely (but not entirely) due to the sodium benzoate (NaB) it produces in your body.

https://epiphanyasd.blogspot.com/search/label/Cinnamon 

Sodium benzoate (NaB) is both a drug used to reduce ammonia in your blood and a common food additive that acts as a preservative.

NaB has many biological effects.  One effect relates to a protein called DJ-1, which is produced by a Parkinson’s gene (PARK7). I had noticed that when the body tries to turn on its anti-oxidant genes after the switch Nrf2 is activated, the process cannot proceed without enough DJ-1.  This is why Peter Barnes, from my Dean’s list, suggested that patients with COPD might benefit from more DJ-1.  COPD is a kind of severe asthma which occurs with severe oxidative stress, the oxidative stress stops the standard asthma drugs from working, which is why so many people die from COPD. Oxidative stress is a key feature of most autism.

To make more DJ-1 you can use sodium benzoate (NaB) which is produced gradually in the body if you eat cinnamon. So in theory cinnamon is like sustained release NaB, it is also extremely cheap.

Independently of all this NaB has been trialled in schizophrenia and a further larger trial is in progress.  Autism is not schizophrenia, but the hundreds of genes miss-expressed in autism do overlap with the hundreds of genes miss-expressed in schizophrenia, so I call schizophrenia autism’s big brother. 

GABA_A α5 subunit

The scientist readers of this blog may recall that there are two sub-units of the GABA_A receptor that I am seeking to modify, to improve cognition.  One is the α3 subunit and the other is the α5 subunit. Low dose clonazepam works for α3.

The α5 subunit is the target of a new drug to improve cognition in people with Down Syndrome (DS).

Very recent research links the same sub-unit to autism, so it is not just me looking at this.

Reduced expression of α5GABAA receptors elicits autism-like alterations in EEG patterns and sleep-wake behavior                                                                                                              

As is often the case, it looks like some people might need to “turn up the volume” from α5GABA_A receptors and others might need to turn it down.

I had yet to find a practical way to affect α5GABA_A. Now I have realized that I have already stumbled upon such a way to do it.

Pahan, a researcher in Chicago, has shown that he can improve cognition in mice using cinnamon. He noted that in poor learners GABRA5 was elevated, but that after one month of cinnamon GABRA5 was normalized. 

Cognitive loss in autism, schizophrenia and Down Syndrome

Most people might associate MR/ID with autism and indeed Down Syndrome; you likely do not really consider people with schizophrenia to have MR/ID. In reality, cognitive loss is a common feature/problem in schizophrenia and indeed bipolar, just not enough to be called MR/ID.

Those researching schizophrenia seem to focus on NMDA receptors, whereas my blog only goes into the great depths of science when it comes to GABA_A . To the schizophrenia researchers NaB is interesting because it is a d-amino acid oxidase inhibitor, which means that it will enhance NMDA function.  So if you are one of those people with too little NDMA activity (NMDAR hypofunction) then sodium benzoate should make you feel better.

The schizophrenia researchers think NaB is helpful because of its effect on NMDA, for me it is GABRA5 that is of great interest. The same should be true for parents of kids with Down Syndrome (DS). We have seen that bumetanide should, and indeed does, help DS.  It looks to me that NaB/Cinnamon should further help them and no need to wait for Roche to commercialize their GABRA5 drug. 

NaB and Cinnamon

I am yet to determine how much NaB is produced by say 3g of cinnamon.

The clinical trials of NaB use 1g per day in adults. People using cinnamon, like Dr Pahan, for cognition or just lowing blood pressure and blood sugar use around 3g.

It is quite difficult to give a teaspoonful of cinnamon to a child, whereas NaB dissolves in water and does not taste so bad. 

NaB and Cinnamon Trials

I did trial cinnamon by putting it in in large gelatin capsules and at the time I did think it had an effect, but I doubt I got close to Dr Pahan’s dosage.

A prudent dose of NaB would seem to be 6mg/Kg twice a day. This is similar to what is now being trialed in schizophrenia.

A small number of people do not tolerate NaB and logically also cinnamon.  They are DAAO inhibitors, just like Risperidone. People who are histamine intolerant need to avoid DAAO inhibitors. If you have allergies it does not mean you are histamine intolerant.

I did try NaB on myself and I did not notice any effect.

Conclusion

I had already obtained some NaB to follow up on my earlier trial of cinnamon.  Having read about the effect of NaB on GABRA5 expression, I am even more curious to see if it helps.

Any positive effect might be due to DJ-1 boosting the effect of Nrf-2, it might be boosting NMDA or it might be reducing GABRA5 expression. In some people all three would be useful.

Press release:- 

Cinnamon may be fragrant medicine for the brain 

Pahan a researcher at Rush University and the Jesse Brown VA Medical Center in Chicago, has found that cinnamon turns poor learners into good ones—among mice, that is. He hopes the same will hold true for people.

His group published their latest findings online June 24, 2016, in the Journal of Neuroimmune Pharmacology.

"The increase in learning in poor-learning mice after cinnamon treatment was significant," says Pahan. "For example, poor-learning mice took about 150 seconds to find the right hole in the Barnes maze test. On the other hand, after one month of cinnamon treatment, poor-learning mice were finding the right hole within 60 seconds."

Pahan's research shows that the effect appears to be due mainly to sodium benzoate—a chemical produced as cinnamon is broken down in the body.

In their study, Pahan's group first tested mice in mazes to separate the good and poor learners. Good learners made fewer wrong turns and took less time to find food. 

In analyzing baseline disparities between the good and poor learners, Pahan's team found differences in two brain proteins. The gap was all but erased when cinnamon was given. 

"Little is known about the changes that occur in the brains of poor learners," says Pahan. "We saw increases in GABRA5 and a decrease in CREB in the hippocampus of poor learners. Interestingly, these particular changes were reversed by one month of cinnamon treatment." 

The researchers also examined brain cells taken from the mice. They found that sodium benzoate enhanced the structural integrity of the cells—namely in the dendrites, the tree-like extensions of neurons that enable them to communicate with other brain cells. 

As for himself, Pahan isn't waiting for clinical trials. He takes about a teaspoonful—about 3.5 grams—of cinnamon powder mixed with honey as a supplement every night.  

Should the research on cinnamon continue to move forward, he envisions a similar remedy being adopted by struggling students worldwide. 

The paper itself:- 

Cinnamon Converts Poor Learning Mice to Good Learners: Implications for Memory Improvement. 

This study underlines the importance of cinnamon, a commonly used natural spice and flavoring material, and its metabolite sodium benzoate (NaB) in converting poor learning mice to good learning ones. NaB, but not sodium formate, was found to upregulate plasticity-related molecules, stimulate NMDA- and AMPA-sensitive calcium influx and increase of spine density in cultured hippocampal neurons. NaB induced the activation of CREB in hippocampal neurons via protein kinase A (PKA), which was responsible for the upregulation of plasticity-related molecules. Finally, spatial memory consolidation-induced activation of CREB and expression of different plasticity-related molecules were less in the hippocampus of poor learning mice as compared to good learning ones. However, oral treatment of cinnamon and NaB increased spatial memory consolidation-induced activation of CREB and expression of plasticity-related molecules in the hippocampus of poor-learning mice and converted poor learners into good learners. These results describe a novel property of cinnamon in switching poor learners to good learners via stimulating hippocampal plasticity. 

We have seen that cinnamon and NaB modify T cells and protect mice from experimental allergic encephalomyelitis, an animal model of multiple sclerosis. Cinnamon and NaB also upregulate neuroprotective molecules (Parkin and DJ-1) and protect dopaminergic neurons in MPTP mouse model of Parkinson’s disease.  Recently, we have seen that cinnamon and NaB attenuate the activation of p21ras, reduce the formation of reactive oxygen species and protect memory and learning in 5XFAD model of AD. Here we delineate that NaB is also capable of improving plasticity in cultured hippocampal neurons. Our conclusion is based on the following: First, NaB upregulated the expression of a number of plasticity-associated molecules (NR2A, GluR1, Arc, and PSD95) in hippocampal neurons. Second, Gabra5 is known to support long-term depression. It is interesting to see that NaB did not stimulate the expression of Gabra5 in hippocampal neurons. Third, NaB increased the number, size and maturation of dendritic spines in cultured hippocampal neurons, suggesting a beneficial role of NaB in regulating the synaptic efficacy of neurons. Fourth, we observed that NaB did not alter the calcium dependent excitability of hippocampal neurons, but rather stimulated inbound calcium currents in these neurons through ionotropic glutamate receptor. Together, these results clearly demonstrate that NaB is capable of increasing neuronal plasticity.

These results suggest that NaB and cinnamon should not cause health problems and that these compounds may have prospects in boosting plasticity in poor learners and in dementia patients. In summary, we have demonstrated that cinnamon metabolite NaB upregulates plasticity-associated molecules and calcium influx in cultured hippocampal neurons via activation of CREB. While spatial memory consolidation-induced activation of CREB and expression of plasticity-related molecules were less in the hippocampus of poor learning mice as compared to good learning ones, oral administration of cinnamon and NaB increased memory consolidation-induced activation of CREB and expression of plasticity-related molecules in vivo in the hippocampus of poor learning mice and improved their memory and learning almost to the level that observed in untreated good learning ones. These results highlight a novel plasticity-boosting property of cinnamon and its metabolite NaB and suggest that this widely-used spice and/or NaB may be explored for stimulating synaptic plasticity and performance in poor learners.

The schizophrenia trials:-

The efficacy ofsodium benzoate as an adjunctive treatment in early psychosis - CADENCE-BZ: study protocol for a randomized controlled trial

Add-on Treatmentof Benzoate for Schizophrenia A Randomized, Double-blind,Placebo-Controlled Trial of d-Amino Acid Oxidase Inhibitor

Plenty of people with schizophrenia now self-treat with NaB; just look on google.

P.S.

There is now is a small trial in autism:-

A Pilot Trial of Sodium Benzoate, a D-Amino Acid Oxidase Inhibitor, Added on Augmentative and Alternative Communication Intervention for Non-Communicative Children with Autism Spectrum Disorders

https://www.omicsonline.org/open-access/a-pilot-trial-of-sodium-benzoate-a-damino-acid-oxidase-inhibitor-added-on-augmentative-and-alternative-communication-intervention-2161-1025-1000192.php?aid=83472&view=mobile


Results: We noted improvement of communication in half of the children on benzoate. An activation effect was reported by caregivers in three of the six children, and was corroborated by clinician’s observation. Conclusion: Though the data are too preliminary to draw any definite conclusions about efficacy, they do suggest this therapy to be safe, and worthy of a double-blind placebo-controlled study with more children participated for clarification of its efficacy.

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.