Propranolol, Autism and Sodium Ion Channels Nav1.1, Nav1.2, Nav1.3 and Nav1.5

When writing this blog I frequently wonder what happened to all the very clever people; why are these full-time paid researchers often missing the obvious?

Boy with severe headache and ASD, awaiting Propranolol

The answer is, with a few notable exceptions (Catterall, Ben-Ari etc), the clever ones do not study autism, they study things that are much better defined, rare things like Angelman Syndrome and, recently, Pitt-Hopkins Syndrome.  These researchers seem much more rigorous.  For example:-

David Sweatt (Pitt Hopkins)

Pitt–Hopkins Syndrome: intellectual disability due to loss of TCF4-regulated gene transcription

Edwin Weeber (Angelman syndrome)

http://weeberlab.com/as.html

So autism is left to what might be termed the Baron Cohen brigade.

Propranolol

Propranolol is a medication of the beta blocker type.  It is used to treat high blood pressure, a number of types of irregular heart rate, thyrotoxicosis, performance anxiety, and essential tremors. It is used to prevent migraine headaches, and to prevent further heart problems in those with angina or previous heart attacks.

It is a nonselective beta blocker which works by blocking β-adrenergic receptors.

While once a first-line treatment for hypertension, they do not perform as well as other drugs, particularly in the elderly, and evidence is increasing that the most frequently used beta blockers at usual doses carry an unacceptable risk of provoking type 2 diabetes.

Beta blockers block the action of endogenous catecholamines epinephrine (adrenaline) and norepinephrine(noradrenaline) on adrenergic beta receptors, of the sympathetic nervous system, which mediates the fight-or-flight response. Some block all activation of β-adrenergic receptors and others are selective.

It is occasionally used to treat performance anxiety.   Given the effect (above) on the fight or flight response this is logical.

The sympathetic nervous system's primary process is to stimulate the body's fight-or-flight response. It is, however, constantly active at a basic level to maintain homeostasis.

Evidence to support the use in other anxiety disorders is poor.

But what the ever useful Wikipedia almost glosses over is the part I find more interesting:-

Propranolol blocks cardiac and neuronal voltage-gated sodium channels

  

Now we have to hope that cardiologists prescribing Propranolol are fully aware of the role of Nav1.5 in the heart and its role in heart rate.  This has nothing to do with it being a beta blocker.

Hopefully neurologists prescribing it for certain severe headaches understand the role of Nav1.1 in the brain.

It would not surprise me if they did not.

Propranolol earlier in this Blog

Earlier in this blog there are comments regarding the use of low doses of Propranolol to treat anxiety in autism.

Some people report it works wonders, while for others it did nothing.

  

Propranolol in Autism Research

A study was published recently and a reader drew my attention to it, but there have also been a few others.

Blood pressure medicine may improve conversational skills of individuals with autism

An hour after administration, the researchers had a structured conversation with the participants, scoring their performance on six social skills necessary to maintain a conversation: staying on topic, sharing information, reciprocity or shared conversation, transitions or interruptions, nonverbal communication and maintaining eye contact. The researchers found the total communication scores were significantly greater when the individual took propranolol compared to the placebo.

"Though more research is needed to study its effects after more than one dose, these preliminary results show a potential benefit of propranolol to improve the conversational and nonverbal skills of individuals with autism," said Beversdorf

  

Effect of propranolol on verbal problem solving in autism spectrum disorder

Effect of Propranolol on Functional Connectivity in Autism Spectrum Disorder—A Pilot Study

Back to Channelopathies

There are 24,000 human genes, but a much more manageable number of ion channels.  For each ion channel or transporter, there is a gene that expresses it.

When ion channels malfunction, it is called a channelopathy.  Channelopathies are quite well researched and very common in autism.  Early on in this blog I simplified idiopathic classic autism with the following chart.

I suspect that people with channelopathies (Nav1.1, Nav1,2, Nav1.3) caused by dysfunctions in the genes SCN1A, SCN2A, SCN3A are the ones that will most benefit from Propranolol.

I suspect those people will already suffer terrible headaches and/or seizures.

These three channelopathies have been known to be associated with autism for ten years.

Nav1.1 / SCN1A

http://ghr.nlm.nih.gov/gene/SCN1A

Migraine, other headaches

Epilepsy

Dravet syndrome

Regular readers will know that Professor Catterall is the expert on sodium channels and here he is again below

NaV1.1 channels and epilepsy

Nav1.2 / SCN2A

http://ghr.nlm.nih.gov/gene/SCN2A

Epileptic encephalopathy, early infantile, 11 (EIEE11): An autosomal dominant seizure disorder characterized by neonatal or infantile onset of refractory seizures with resultant delayed neurologic development and persistent neurologic abnormalities. Patients may progress to West syndrome, which is characterized by tonic spasms with clustering, arrest of psychomotor development, and hypsarrhythmia on EEG

Nav1.3 / SCN3A

neuronal hyperexcitability and epilepsy 

         Novel SCN3A variants associated with focal epilepsy in             children.

Nav1.5 / SCN5A

http://ghr.nlm.nih.gov/gene/SCN5A

Mainly heart conditions, since this ion channel is expressed mainly in the heart.

Brugada syndrome  Romano-Ward syndrome  etc

Autism and Nav1.1, Nav1.2, Nav1.3

For many years it has been known that the hundreds of variations in the genes SCN1A, SCN2A and SCN3A are associated with autism.  So we can consider them pretty well established autism genes.

Clearly any drug affecting expression of those genes, or affecting the ion channels they express, should be a target autism drug.

Sodium channels SCN1A,SCN2A and SCN3A in familial autism

Conclusion

Some people with autism and severe headaches, or epilepsy, have an underlying sodium channelopathy.  Sodium channel blockers are not as well understood/ developed as calcium channel blockers.

In some cases, but maybe not all, this should be detectable by genetic testing of the genes SCN1A, SCN2A and SCN3A.

If you live in a country that does not bother with genetic testing, you might want to fall back on trial and error and discuss Propranolol with your doctor.

Did all the people with Asperger’s, in the recent study, who became more conversational after a single dose of Propranolol, have problems with Nav1.1, Nav1.2 or Nav1.3 ?  I doubt it.  The other commonly known effects of Propranolol should also play a role.

But for a sub-set of people with Strictly Defined Autism, Propranolol might be hugely beneficial.  Perhaps Professor Catterall should investigate?

“More GABA” for Autism and Epilepsy? Not so Simple

Today’s post was prompted by Tyler highlighting a very recent paper from MIT and Harvard, with some interesting research on GABA in autism.  It also provides the occasion to include an interesting epilepsy therapy, which I encountered a while back.  This fits with my suggestion that the onset of much epilepsy in autism could be prevented.

In the MIT/Harvard study, they were looking into the excitatory/ inhibitory (E/I) imbalance found in ASD and schizophrenia. They used a non-invasive optical method to measure E/I imbalance and this did get some media coverage.  However, I am not sure this could be a diagnostic tool in very young children with classic autism, as was suggested; most such children would not cooperate.  It is not just a problem of being non-verbal, as was suggested in the media.

Indeed, due to the nature of the experiment, the researchers involved older subjects, with milder autism and none had MR/ID (IQ<70).  Being a trial done in the US, of the 20 autistic subjects, 11  were being treated with psychiatric medications: antidepressants (n = 8), antipsychotics (n = 2), antiepileptics (n = 4), and anxiolytics (n = 2).

The easy to read version is from the MIT website:-

Study finds altered brain chemistry in people with autism

The full version is here:-

Reduced GABAergic action in the Autistic Brain

They used something called Binocular Rivalry  as a proxy for  E/I imbalance.

During binocular rivalry, two images, one presented to each eye, vie for perceptual dominance as neuronal populations that are selective for each eye’s input suppress each other in alternation [16, 17]. The strength of perceptual suppression during rivalry is thought to depend on the balance of inhibitory and excitatory cortical dynamics [12–15] and may serve as a non-invasive perceptual marker of the putative perturbation in inhibitory signaling thought to characterize the autistic brain.

We therefore measured the dynamics of binocular rivalry in individuals with and without a diagnosis of autism (41 individuals, 20 with autism). As predicted, individuals with autism demonstrated a slower rate of binocular rivalry (switches per trial: controls = 8.68, autism = 4.19; F(1,37) = 16.52, hp 2 = 0.311, p = 0.001; Figure 1A), which was marked by reduced periods of perceptual suppression (proportion of each trial spent viewing a dominant percept, (dominant percept durations)/(dominant + mixed percept durations): controls = 0.69; autism = 0.55; F(1,36) = 7.27, hp 2 = 0.172, p = 0.011; Figure 1B). The strength of perceptual suppression inversely predicted clinical measures of autistic symptomatology (Autism Diagnostic Observation Schedule [ADOS]: Rs = 0.39, p = 0.027; Figure 1) and showed high test-retest reliability in a control experiment (R = 0.94, p < 0.001; see Supplemental Experimental Procedures and also [18]). These results replicate our previous findings in an independent sample of autistic individuals [11] and confirm rivalry disruptions as a robust behavioral marker of autism.

To test whether altered binocular rivalry dynamics in autism are linked to the reduced action of inhibitory (g-aminobutyric acid [GABA]) or excitatory (glutamate [Glx]) neurotransmitters in the brain, we measured the concentration of these neurotransmitters in visual cortex using magnetic resonance spectroscopy (MRS).

GABA and glutamate are predicted to contribute to different aspects of binocular rivalry dynamics: mutual inhibition between (GABA) and recurrent excitation within (glutamate) populations of neurons coding for the two oscillating percepts [14].

. Critically, reducing either mutual inhibition or recurrent excitation is predicted to reduce the strength of perceptual suppression during rivalry in one implementation of this model [14], mirroring the dynamics we observed in autism. We therefore considered each neurotransmitter separately to test whether inhibitory or excitatory signaling was selectively disrupted in the autistic brain.

As predicted by models of binocular rivalry, GABA concentrations in visual cortex strongly predicted rivalry dynamics in controls, where more GABA corresponded to longer periods of perceptual suppression (Rs = 0.62, p = 0.002; Figure 2B). However, this relationship was strikingly absent in individuals with autism (Rs = 0.02, p = 0.473; Figure 2B). The difference between the two correlations was significant (hp 2 = 0.167, p = 0.013; Figure 2C), indicating a reduced impact of GABA on perceptual suppression in the autistic brain.

GABA was working backwards

Importantly, this finding was specific to GABA: glutamate strongly predicted the dynamics of binocular rivalry in autism (Rs = 0.60, p = 0.004; Figure 2B), to the same degree as that found in controls.

Glumate is working just fine.

These findings suggest that alterations in the GABAergic signaling pathway may characterize autistic neurobiology. Consistent with prior evidence from animal and post-mortem studies, such dysfunction may arise from perturbations in key components of the GABAergic pathway beyond GABA levels, such as receptors [3–9] and inhibitory neuronal density

Together with the pivotal roles of GABA in canonical cortical computations [39] and neurodevelopment [40], these findings point to the GABAergic signaling pathway as a prime suspect in the neurobiology of this pervasive developmental disorder [41]

This study reconfirms what regular readers of this blog already knew.

Epilepsy

I thought it was positive that the MIT researchers suggested that the high level of epilepsy in autism and this E/I imbalance really must be connected.

I have been suggesting for some time that by correcting this E/I imbalance in children with autism, it is likely that the onset of epilepsy could be avoided (in some cases).

I did suggest this to one well known researcher who thought the idea of preventing the onset of epilepsy was not something that the medical community would accept as a concept.

I also raised the novel epilepsy therapy, below, to the same researcher who thought it also would never be considered.

The therapy was to use both bumetanide and potassium bromide to switch GABA back to inhibitory and then give a little boost using a GABA agonist.   

There are many types of epilepsy and some do not respond well to current treatments.  It would seem plausible that the autism-associated type of epilepsy might constitute a specific sub-type.

Combined effect of bumetanide, bromide, and GABAergic agonists: An alternative treatment for intractable seizures

Potassium Bromide was the original epilepsy therapy over a hundred years ago.  It is still used in Germany as a therapy.  Reports from a century ago suggest it has the same effect in autism as Bumetanide. (we saw this in my post on autism history). 

As you can see on Wikipedia there is a wide range of GABA agonists, but the only ones that would help in epilepsy and autism would be the ones that can cross the blood brain barrier.

GABA_A receptor Agonists

·         Bamaluzole

·         GABA

·         Gabamide

·         GABOB

·         Gaboxadol

·         Ibotenic acid

·         Isoguvacine

·         Isonipecotic acid

·         Muscimol

·         Phenibut

·         Picamilon

·         Progabide

·         Quisqualamine

·         SL 75102

·         Thiomuscimol

In an earlier post, we looked at the possible use of small doses of AEDs (anti-epileptic drugs).  One reader found that tiny dose of Valproate (known to raise GABA) had a positive effect when combines with Bumetanide.

In a recent comment one reader showed the same result by combing picamilon with bumetanide.

Both Picamilon and Valproate are having the effect proposed by the epilepsy researchers.

Potassium Bromide does have known side effects, but the idea of further boosting the effect of Bumetanide is interesting.  I have suggested before that this should also be possible using Diamox (Acetazolamide).  Diamox does not affect NKCC1 or E_GABA,  it affects the  Cl-/HCO3-exchanger AE3  to further affect Cl- levels.  

I did suggest this a long time ago in my posts on the GABAa receptor.  I am not the only one to realize this.

NKCC1 and AE3 Appear to Accumulate Chloride in Embryonic Motoneurons

   

Picamilon is well researched Russian drug, sold in other countries as a supplement.  It is a modified version of GABA that includes niacin; together it can cross the blood brain barrier (BBB).

So I think a better version of what the epilepsy researchers suggest might be:-

                           Bumetanide  +  Diamox  +  a touch of Picamilon

What would be the effect in autism?

A New School Year – Still keeping up

Before I return to the science-heavy posts, this is another post to encourage people not just to read about autism, but to treat it.  No pseudoscience or great expense is required.

After close to three years of using biology, rather than just behavioral therapy, where have we got to?

Acquiring new skills is effortless for clever typical kids; we have also got one of those.  For kids with classic autism, even the most basic skills need to be taught and taught again, until eventually, they might sink in.  I do not think this has anything to do with permanent MR/ID (mental retardation/intellectual disability), although I can see why it often gets diagnosed as such; it turns out to be treatable.

In the race to keep up with the typical kids, or at least keep them in sight, we started with ABA and about 1,800 hours a year of 1:1 time with an assistant.  After a few years the typical kids had pulled far ahead.

At age 9, I started to correct the underlying dysfunctions, first with Bumetanide, using very recent findings in the scientific literature.  This coincided with the decision to change his (neurotypical) peer group at school to those 2-3 years his junior.  Time was reset.

We still had the 1,800 hours a year of 1:1 time with an assistant, half at school and half at home.

At age 12, the original peer group is now far out of sight, but after three years we are still keeping up academically with the new “friends at school”.

Monty, now aged 12 with ASD, is in the same small mainstream international school he has attended for eight years.  Three years ago I held him back two years, since he was becoming completely “un-includable”.  So we went Year 1, Year 2, Year 3 then back to Year 2, then Year 3, Year 4 and now Year 5. 

Since most readers are American, where school starts one year later, to convert UK school year to US grade, just subtract one.  UK Year 5 = US 4^th grade.  In the US you finish in 12^th Grade whereas in the UK system you finish in Year 13, both typically in your 18^th year. (so in the US system, he went K, 1^st, 2^nd, then 1^st, 2^nd 3^rd and now 4^th)

Many kids with autism are now “included” in mainstream education, but in reality some are just having a private 1:1 lesson with their assistant at the back of the class. This is not a good idea; for the last three years Monty has been able to follow the teacher.  If you cannot follow the teacher, you really should not be in that class.

We have a new class teacher, an American, he has been teaching for 15 years, but has never had a special needs kid before; that in itself tells you something.  Now he has Monty, aged 12 with “treated” classic autism, something he probably will never see again.

After a couple of weeks, his conclusion is “he can read nicely and do the exercises”.  This makes it sound rather a non-event.  A few short years ago, his school teachers were rather stunned that his 1:1 assistant got him to read very simple words.  Now he can read aloud from “chapter books” to the rest of the class.   

When they had a spelling test (words like graduate, icicles, sausages) he got 18/20 and one of the new girls in class told her mother how clever Monty is.  When told he has “special needs” and an assistant, she replied “special needs … no special needs”.  That was nice, but Monty does still have plenty of special needs, but for three years he has been able to move forward academically at a similar rate to his classmates, albeit that they are all 2 years his junior.  That progression is quite extraordinary, if you know about outcomes in classic autism. 

Having been using ABA for five years prior to starting with the biology/pharmacology, and seen steady but slow progress and so falling ever further behind his peers, I never expected to be here in 2015 with Monty being able to subtract 7,794 from 9,621, or add up 8,756 + 4,326 + 7,832, interpret data from graphs and use x,y coordinates.  Until five years ago he did not even attend numeracy/math classes at school, because we had to focus on basic speech, basic reading and things like standing in line and changing shoes.

I have no idea how far he can go. I was expecting by now to again have to repeat a school year, but it has not been necessary.


Behavioral problems (SIB, anxiety, aggression etc.) were generally rooted in biology and have been more than 90% treatable.

With neither behavioral, nor pharmacological intervention, it would not now be a pretty sight.

It is sad that almost nobody treats Classic Autism pharmacologically; there are so many unnecessary, unhappy, consequences, lives sometimes lost to what can be a treatable condition.

It also appears likely that by treating the dysfunctions in Classic Autism, you may avoid the possible later progression to epilepsy/seizures and all the problems that may cause (even SUDEP, drowning etc).  This was something we had been warned might develop, but now looks much less likely.  For some people, seizures are a bigger issue than their autism. Some data, for those interested:-

Clinical Characteristics of Children with Autism Spectrum Disorder and Co-Occurring Epilepsy

This is among the largest studies to date of children with ASD and co-occurring epilepsy. Our sample includes 5,815 participants with ASD, 289 of whom had co-morbid epilepsy. Using statistical modeling in this well-powered sample of patients we have made several important observations about a contemporary group of individuals with ASD and epilepsy. We identified several correlates of epilepsy in children with ASD including older age, lower cognitive and adaptive functioning, poorer language skills, a history of developmental regression, and more severe ASD symptoms. Through multivariate logistic regression we found that only age and cognitive ability were independent predictors of epilepsy.

The average prevalence of epilepsy among children aged 2 to 17 years in our population-based sample, the NSCH, was 12.5%. This estimate is comparable to a recent report of a 15.5% rate of epilepsy in another population-based sample of children with ASD. While the prevalence was 10% or lower in children under 13 years of age, by adolescence it reached 26.2%. Therefore, the best estimate of the cumulative prevalence of epilepsy in ASD through 17 years of age is 26%. Our study replicates findings from prior studies that have followed children with ASD into adolescence/early adulthood and reported epilepsy prevalence rates from 22% to 38%

Note that Classic Autism accounts for about 30% of ASD; it is not hard to guess where you would find most of the 26% with ASD who later develop epilepsy.  

Odd epileptiform activity (seen on an EEG), falling short of epilepsy, is common in young children with autism and I think might be considered as pre-epilepsy.  Just as someone who has prediabetes has the chance to do something about it, before it progresses to type II diabetes, unusual EEG activity should prompt consideration of a treatable excitatory/inhibitory imbalance. 


Conclusion

At least I have treated the only autism case I am responsible for. I encourage others to do the same; it is never too late, even in adulthood.  We have one reader, Roger, who got his core biological autism dysfunction diagnosed and treated in adulthood.

If you prefer to wait for 100% FDA-guaranteed solutions, you will wait forever.  

Diamox & Bumetanide, Ion Channels Nav1.4 and Cav1.1, HypoPP, Autism and Seizures

So you’re going to spend some time at high altitude, climbing mountains or trekking, don’t forgetto pack your Diamox before you leave home, it can save your life.  She is right.

Today’s post links together subjects that have been covered previously.

It does suggest that there are multiple therapies that may be effective in the large sub-group of autism that is characterized by the neurotransmitter GABA being excitatory (E) rather than inhibitory (I).  The science was covered in the earlier very complicated post:-

GABA A Receptors in Autism – How and Why to Modulate Them

The growing list of potential therapies is:-

·        Bumetanide (awaiting funding for Stage 3 clinical trials in humans)

·        Micro-dose Clonazepam (trials in mouse models of autism)

·        Diamox (off-label use in autism)

·        Potassium Bromide  - to be covered in a later post (in use for 150 years)

Not surprisingly, all of these drugs also have an effect on certain types of seizure.

The optimal therapy in people with this E/I imbalance will likely be a combination of some of the above.

Periodic paralysis

Periodic paralysis (Hypokalemic periodic paralysis or HypoPP) is a rare condition that causes temporary paralysis that can be reversed by taking potassium.  A similar condition is hypokalemic sensory overload, when someone becomes overwhelmed by lights or sounds, but after taking potassium all goes back to normal. Autistic sensory overload, experienced by most people with autism, can also be reduced by potassium.

Though rare, we know that HypoPP is caused by dysfunction in the ion channels Na_v1.4 and/or Ca_v1.1.

For decades one of the treatments for HypoPP has been a diuretic called Diamox/Acetazolamide.

Other treatments include raising potassium levels using supplements or potassium sparing diuretics.

Bumetanide is a diuretic, but rather than raising potassium levels, it does the opposite.  So I always thought it was odd that bumetanide would have a positive effect on HypoPP.  But the research showed a benefit.

Autism and Channelopathies

We know that autism and epilepsy are associated with various ion channel and transporter dysfunctions (channelopathies).  In a recent post I was talking about Cav1.1 to Cav1.4.

Today we are talking about Cav1.1 and Nav1.4.

We know that Nav1.1 is associated with epilepsy and some autism (Dravet syndrome).

Nav1.4 is expressed at high levels in adult skeletal muscle, at low levels in neonatal skeletal muscle, and not at all in brain

Nav1.1 expression increases during the third postnatal week and peaks at the end of the first postnatal month, after which levels decrease by about 50% in the adult.

We saw with calcium channels that a dysfunction in one of Cav1.1 to Cav1.4 can cause a dysfunction in another dysfunction in another one of Cav1.1 to Cav1.4.

We also so that in autism the change in expression of NKCC1 and KCC2 as the brain matures failed to occur and so in effect they remain immature and therefore malfunction.

So it is plausible that sodium channels may also malfunction in a similar way. 

  

Acetazolamide efficacy in hypokalemic periodic paralysis and the predictive role of genotype

Hypokalemic periodic paralysis (hypoPP) is an autosomal dominant neuromuscular disorder characterized by episodes of flaccid skeletal muscle paralysis accompanied by reduced serum potassium levels. It is caused by mutations in one of two sarcolemmal ion channel genes, CACNA1S and SCN4A1-3 that lead to dysfunction of the dihydropyridine receptor or the alpha sub-unit of the skeletal muscle voltage gated sodium channel Nav1.4. Seventy to eighty percent of cases are caused by mutations of CACNA1S and ten percent by mutations of SCN4A4. 

There are no consensus guidelines for the treatment of hypoPP. Current pharmacological agents commonly used include potassium supplements, potassium sparing diuretics and carbonic anhydrase inhibitors (acetazolamide and dichlorphenamide). Dichlorphenamide is the only therapy for hypoPP to have undergone a randomized double blind placebo controlled cross over trial. This trial showed a significant efficacy of dichlorphenamide in reducing attack frequency but the inclusion criteria were based on clinical diagnosis of hypoPP and not genetic confirmation.

  

Ca_v1.1

Ca_v1.1 also known as the calcium channel, voltage-dependent, L type, alpha 1S subunit, (CACNA1S), is a protein which in humans is encoded by the CACNA1S gene

Na_v1.4

Sodium channel protein type 4 subunit alpha is a protein that in humans is encoded by the SCN4A gene.

The Na_v1.4 voltage-gated sodium channel is encoded by the SCN4A gene. Mutations in the gene are associated with hypokalemic periodic paralysis, hyperkalemic periodic paralysis, paramyotonia congenita, and potassium-aggravated myotonia.

Ranolazine

Ranolazine is an antianginal and anti-ischemic drug that is used in patients with chronic angina. Ranzoline blocks Na+ currents of Nav1.4. Both muscle and neuronal Na+ channels are as sensitive to ranolazine block as their cardiac counterparts. At its therapeutic plasma concentrations, ranolazine interacts predominantly with the open but not resting or inactivated Na+ channels. Ranolazine block of open Na+ channels is via the conserved local anesthetic receptor albeit with a relatively slow on-rate.

Muscle channelopathies:does the predicted channel gating pore offer new treatment insights for hypokalaemic periodic paralysis?

Beneficial effects of bumetanide in a CaV1.1-R528H mouse model of hypokalaemic periodic paralysis

Transient attacks of weakness in hypokalaemic periodic paralysis are caused by reduced fibre excitability from paradoxical depolarization of the resting potential in low potassium. Mutations of calcium channel and sodium channel genes have been identified as the underlying molecular defects that cause instability of the resting potential. Despite these scientific advances, therapeutic options remain limited. In a mouse model of hypokalaemic periodic paralysis from a sodium channel mutation (NaV1.4-R669H), we recently showed that inhibition of chloride influx with bumetanide reduced the susceptibility to attacks of weakness, in vitro. The R528H mutation in the calcium channel gene (CACNA1S encoding CaV1.1) is the most common cause of hypokalaemic periodic paralysis. We developed a CaV1.1-R528H knock-in mouse model of hypokalaemic periodic paralysis and show herein that bumetanide protects against both muscle weakness from low K⁺ challenge in vitro and loss of muscle excitability in vivo from a glucose plus insulin infusion. This work demonstrates the critical role of the chloride gradient in modulating the susceptibility to ictal weakness and establishes bumetanide as a potential therapy for hypokalaemic periodic paralysis arising from either NaV1.4 or CaV1.1 mutations.

Mode of action

The research does state that nobody knows why Diamox is effective in many cases of hypoPP.

My reading of the research has already taken me in a different direction.  While researching the GABA_A receptor that is dysfunctional in some autism, it occurred to me that in addition to targeting the NKCC1 receptor with bumetanide, another way of lowering chloride levels within the cells might well exist.

I suggested in an earlier post that Diamox could be used to target the AE3 exchanger.

What Diamox (acetazolamide) does is lower the pH of the blood in the following way.

Acetazolamide is a carbonic anhydrase inhibitor, hence causing the accumulation of carbonic acid Carbonic anhydrase is an enzyme found in red blood cells that catalyses the following reaction:

hence lowering blood pH, by means of the following reaction that carbonic acid undergoes

In doing so there will be an effect on both AE3 and NDAE, below.  This will change the intracellular concentration of Cl-, and hence give a similar result to bumetanide.

This would also explain the phenomenon cited below that pH affects the excitability of the brain.

Over excitability of the brain is the cause of some of the effects seen as autism and clearly Over excitability of the brain will be the cause of some people’s seizures/epilepsy.

Not surprisingly, then one of the uses of Diamox is to avoid seizures.

Acetazolamide in the treatment of seizures.

  

Anion exchanger 3 (AE3) in autism

Anion exchange protein 3 is a membrane transport protein that in humans is encoded by the SLC4A3 gene. It exchanges chloride for bicarbonate ions.  It increases chloride concentration within the cell.  AE3 is an anion exchanger that is primarily expressed in the brain and heart

Its activity is sensitive to pH. AE3 mutations have been linked to seizures

Characterization of an Epilepsy-associated variant of the AE3 Cl-/HCO3-exchanger

Bicarbonate (HCO₃^-) transport mechanisms are the principal regulators of pH in animal cells. Such transport also plays a vital role in acid-base movements in the stomach, pancreas, intestine, kidney, reproductive organs and the central nervous system.

Two types of chloride transporters are required for GABA_A receptor-mediated inhibition in C. elegans

Abstract

Chloride influx through GABA-gated Cl⁻ channels, the principal mechanism for inhibiting neural activity in the brain, requires a Cl⁻ gradient established in part by K⁺–Cl⁻ cotransporters (KCCs). We screened for Caenorhabditis elegans mutants defective for inhibitory neurotransmission and identified mutations in ABTS-1, a Na⁺-driven Cl⁻–HCO₃⁻ exchanger that extrudes chloride from cells, like KCC-2, but also alkalinizes them. While animals lacking ABTS-1 or the K⁺–Cl⁻ cotransporter KCC-2 display only mild behavioural defects, animals lacking both Cl⁻ extruders are paralyzed. This is apparently due to severe disruption of the cellular Cl⁻ gradient such that Cl⁻ flow through GABA-gated channels is reversed and excites rather than inhibits cells. Neuronal expression of both transporters is upregulated during synapse development, and ABTS-1 expression further increases in KCC-2 mutants, suggesting regulation of these transporters is coordinated to control the cellular Cl⁻ gradient. Our results show that Na⁺-driven Cl⁻–HCO₃⁻ exchangers function with KCCs in generating the cellular chloride gradient and suggest a mechanism for the close tie between pH and excitability in the brain.

NKCC1 and AE3 Appear to Accumulate Chloride in Embryonic Motoneurons

Abstract

During early development, γ-aminobutyric acid (GABA) depolarizes and excites neurons, contrary to its typical function in the mature nervous system. As a result, developing networks are hyperexcitable and experience a spontaneous network activity that is important for several aspects of development. GABA is depolarizing because chloride is accumulated beyond its passive distribution in these developing cells. Identifying all of the transporters that accumulate chloride in immature neurons has been elusive and it is unknown whether chloride levels are different at synaptic and extrasynaptic locations. We have therefore assessed intracellular chloride levels specifically at synaptic locations in embryonic motoneurons by measuring the GABAergic reversal potential (E_GABA) for GABA_A miniature postsynaptic currents. When whole cell patch solutions contained 17–52 mM chloride, we found that synaptic E_GABA was around −30 mV. Because of the low HCO₃⁻ permeability of the GABA_A receptor, this value of E_GABA corresponds to approximately 50 mM intracellular chloride. It is likely that synaptic chloride is maintained at levels higher than the patch solution by chloride accumulators. We show that the Na⁺-K⁺-2Cl⁻ cotransporter, NKCC1, is clearly involved in the accumulation of chloride in motoneurons because blocking this transporter hyperpolarized E_GABA and reduced nerve potentials evoked by local application of a GABA_A agonist. However, chloride accumulation following NKCC1 block was still clearly present. We find physiological evidence of chloride accumulation that is dependent on HCO₃⁻ and sensitive to an anion exchanger blocker. These results suggest that the anion exchanger, AE3, is also likely to contribute to chloride accumulation in embryonic motoneurons.

 

Conclusion

So the science does confirm that “chloride accumulation following NKCC1 block was still clearly present”.  This means that bumetanide is likely only a partial solution.

We also see that “anion exchanger, AE3, is also likely to contribute to chloride accumulation in embryonic motoneurons” and “that chloride accumulation that is dependent on HCO₃⁻”.

This is a subject of some research, but it is still early days.

Bicarbonate homeostasis in excitable tissues: role of AE3 Cl−/HCO3−exchanger and carbonic anhydrase XIV interaction

  

I suggest that Diamox, via its effect on HCO₃⁻, may affect anion exchanger AE3 and further reduce chloride accumulation within cells.  This may have a further cumulative effect on GABA.

As we saw earlier, bumetanide does indeed shift GABA from excitatory to inhibitory in people who neurons remain in an immature state (like those of a typical two week old baby).  To my surprise, the use of micro-dose Clonazepam, as proposed by Professor Catterall, but in addition to Bumetanide, has a further effect on GABA’s excitatory/inhibitory imbalance.

Taken together this would highlight the possible further benefit of Diamox.

Normal blood pH is tightly regulated between 7.35 and 7.45.  I do wonder if perhaps in some people with autism, the pH of their blood is slightly elevated (alkaline), this would contribute to excitability of the brain.

Since Diamox increases the oxygen carrying capacity of the blood, I further wonder if this additional oxygen may also be beneficial in some cases.  Since some people are adamant that hypobaric oxygen therapy has beneficial (although not sustained) effects in autism, surely a better treatment would be Diamox?

Since the body is controlled via so-called feedback loops, perhaps in a small subset of people with autism who respond to extra O₂, they actually have blood pH that is higher than 7.45.  In which case measuring blood pH would be a biomarker of who would respond to hypobaric oxygen therapy.  Not surprisingly then, trials of hypobaric oxygen therapy in autism fail, because most of the trial subjects do not have elevated blood pH.

  

So there are many reasons that Diamox should be trialed in autism.  I did find one (DAN) doctor currently using it, but they do not really explain why.

Biomedical Treatment of the Young Adult with ASD