Methylene Blue - used for over a century in Psychiatry, also handy for your fish tank

According to the packaging:-

Effective against a range of fungal and bacterial infections

•          Increases the oxygen-carrying capacity of fish

•          Can be used as an antiseptic directly onto wounds

•          For use in tropical and cold water aquariums

 

Our reader Dragos recently let us all know about his success with very low doses of Methylene Blue (MB).  I think this came as a surprise to many, but actually there is nothing new about using this old pigment as a therapy in psychiatry.  Much is known about its modes of action.

 

What is Methylene Blue?

In 1876, German chemist Heinrich Caro synthesized methylene blue (MB) for the first time in history.  It was used as a dye for textiles. Around the same time, it was found that MB is capable of staining cells by binding to their structures, in addition, sometimes inactivating bacteria. This discovery prepared the way for biological or medical studies related to MB. Numerous scientists applied it to a variety of animal and bacterial studies, importantly Paul Ehrlich introduced it to humans in 1891 as an anti-malarial agent.

I was interested to see why it is used in aquariums, in particular the reference to increases the oxygen-carrying capacity of fish.

Methemoglobinemia (MetHb) is a rare blood disorder that affects how red blood cells deliver oxygen throughout your body.

A common way to treat  MetHb  in humans is to reduce methemoglobin levels using  Methylene blue (MB). Another common treatment, not surprisingly, is to give oxygen.

If you want to increase oxygen levels in the fish in your aquarium you put MB in the water.

More oxygen in your blood would improve exercise endurance meaning you would delay the point at which your mitochondria become unable to keep producing ATP efficiently.

I did some investigation and there is indeed a trend towards people using methyl blue to improve their sporting performance. It is mocked in some newspapers because it makes your tongue turn blue. It makes for good pictures on Instagram.     

The effect will be similar to those long distance cyclists who take beetroot juice, but the mechanism is different.

Be aware that just like beetroot may dye what comes out of your body bright red, MB may give you a hint of blue.

  

Improved Mitochondrial Function

One of the known effects of Methylene Blue (MB) is on the mitochondria.

In numerous papers it has been discussed how MB improves brain mitochondrial respiration.

In neurological disorders such as Alzheimer’s disease, traumatic brain injury, depression, stroke, Parkinson’s disease and some autism, mitochondria contribute to the disorder through decreased energy production and excessive production of reactive oxygen species (ROS).

This subject does get rather complex but in short methylene blue is able to perform alternative electron transport, bypassing parts of the electron transport chain.

In autism terms this means that some people diagnosed with a lack of Complex 1, 2, 3 or 4 in their mitochondria, might want to pay particular attention to how Methylene Blue might be helpful.

Improved mitochondrial function is another reason why sportsmen might want to use MB to enhance their performance.

As we have seen with other enhancing drugs like the Russian Meldonium, the US Diamox and the new US super ketone products, the military do end up using these products.  If you see a picture of a navy seal with a blue tongue you will know where it came from!

 

Methylene Blue inhibits Monoamine Oxidase (MAO)

MAOIs act by inhibiting the activity of monoamine oxidase, thus preventing the breakdown of monoamine neurotransmitters and thereby increasing their availability. There are two types of monoamine oxidase, MAO-A and MAO-B. MAO-A preferentially deaminates serotonin, melatonin, epinephrine, and norepinephrine. MAO-B preferentially deaminates phenethylamine and certain other trace amines; in contrast, MAO-A preferentially deaminates other trace amines, like tyramine, whereas dopamine is equally deaminated by both types.

Methyl blue is a reversible selective MAO-A inhibitor and so has antidepressant properties (it gives you more feel good serotonin). This interesting drug has several other pharmacological actions, including inhibition of nitric oxidase synthase (NOS), and guanylate cyclase and so its antidepressant properties should not be solely ascribed to inhibition of MAO-A. 

Inhibition of neuronal nitric oxide synthase and soluble guanylate cyclase prevents depression-like behaviour in rats exposed to chronic unpredictable mild stress

Beyond treating depression MAOIs (Monoamine oxidase inhibitors) have been found to be effective in the treatment of panic disorder, social phobia, mixed anxiety disorder and depression, bulimia, and post-traumatic stress disorder, as well as borderline personality disorder, and Obsessive Compulsive Disorder (OCD).

MAOIs appear to be particularly effective in the management of bipolar depression.

Methylene blue treatment for residual symptoms of bipolar disorder: randomised crossover study

Background: Residual symptoms and cognitive impairment are among important sources of disability in patients with bipolar disorder. Methylene blue could improve such symptoms because of its potential neuroprotective effects.

Aims: We conducted a double-blind crossover study of a low dose (15 mg, 'placebo') and an active dose (195 mg) of methylene blue in patients with bipolar disorder treated with lamotrigine.

Method: Thirty-seven participants were enrolled in a 6-month trial (trial registration: NCT00214877). The outcome measures included severity of depression, mania and anxiety, and cognitive functioning.

Results: The active dose of methylene blue significantly improved symptoms of depression both on the Montgomery-Åsberg Depression Rating Scale and Hamilton Rating Scale for Depression (P = 0.02 and 0.05 in last-observation-carried-forward analysis). It also reduced the symptoms of anxiety measured by the Hamilton Rating Scale for Anxiety (P = 0.02). The symptoms of mania remained low and stable throughout the study. The effects of methylene blue on cognitive symptoms were not significant. The medication was well tolerated with transient and mild side-effects.

Conclusions: Methylene blue used as an adjunctive medication improved residual symptoms of depression and anxiety in patients with bipolar disorder.

 

Methylene Blue activates oxidative stress response genes via Nrf2

One of the antioxidant effects of MB is activation of the redox switch Nrf2.  In the paper below it is also mentioned that MB has a beneficial against tau proteins. Amyloid and tau proteins clog up the brain in Alzheimer’s and as a result MB has been proposed as a therapy for dementia. 

Methylene blue upregulates Nrf2/ARE genes and prevents tau-related neurotoxicity

Methylene blue (MB, methylthioninium chloride) is a phenothiazine that crosses the blood brain barrier and acts as a redox cycler. Among its beneficial properties are its abilities to act as an antioxidant, to reduce tau protein aggregation and to improve energy metabolism. These actions are of particular interest for the treatment of neurodegenerative diseases with tau protein aggregates known as tauopathies. The present study examined the effects of MB in the P301S mouse model of tauopathy. Both 4 mg/kg MB (low dose) and 40 mg/kg MB (high dose) were administered in the diet ad libitum from 1 to 10 months of age. We assessed behavior, tau pathology, oxidative damage, inflammation and numbers of mitochondria. MB improved the behavioral abnormalities and reduced tau pathology, inflammation and oxidative damage in the P301S mice. These beneficial effects were associated with increased expression of genes regulated by NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE), which play an important role in antioxidant defenses, preventing protein aggregation, and reducing inflammation. The activation of Nrf2/ARE genes is neuroprotective in other transgenic mouse models of neurodegenerative diseases and it appears to be an important mediator of the neuroprotective effects of MB in P301S mice. Moreover, we used Nrf2 knock out fibroblasts to show that the upregulation of Nrf2/ARE genes by MB is Nrf2 dependent and not due to secondary effects of the compound. These findings provide further evidence that MB has important neuroprotective effects that may be beneficial in the treatment of human neurodegenerative diseases with tau pathology.

 

MB to treat inflammation and pain via sodium ion channels and iNOS

MB abates inflammation by suppressing nitric oxide production, and ultimately relieves pain in arthritis and colitis.  

MB suppresses the iNOS/NO-mediated inflammatory signaling by directly downregulating inducible NO synthase (iNOS).

Nitric oxide (NO) is a free radical which, in reactions with various molecules causes multiple biological effects, some good and some harmful.

It is produced by a reaction involving one of three enzymes iNOS, eNOS and nNOS.  i = inducible, n = neuronal and e = endothelial

iNOS is a major downstream mediator of inflammation.

eNOS is very helpful because it can widen blood vessels and so reduce blood pressure and increase blood flow.

nNOS is found in the brain and the peripheral nerve system where it has several important functions.  

MB may impede pain transmission by dampening neuronal excitability elicited by voltage-gated sodium channels (VGSCs).  You would then think that in people with seizures due to malfunctioning sodium channels, MB might be beneficial; for example Nav1.1 in Dravet syndrome. 

Methylene Blue Application to Lessen Pain: Its Analgesic Effect and Mechanism

Methylene blue (MB) is a cationic thiazine dye, widely used as a biological stain and chemical indicator. Growing evidence have revealed that MB functions to restore abnormal vasodilation and notably it is implicated even in pain relief. Physicians began to inject MB into degenerated disks to relieve pain in patients with chronic discogenic low back pain (CDLBP), and some of them achieved remarkable outcomes. For osteoarthritis and colitis, MB abates inflammation by suppressing nitric oxide production, and ultimately relieves pain. However, despite this clinical efficacy, MB has not attracted much public attention in terms of pain relief. Accordingly, this review focuses on how MB lessens pain, noting three major actions of this dye: anti-inflammation, sodium current reduction, and denervation. Moreover, we showed controversies over the efficacy of MB on CDLBP and raised also toxicity issues to look into the limitation of MB application. This analysis is the first attempt to illustrate its analgesic effects, which may offer a novel insight into MB as a pain-relief dye. 

Nicotinic acetylcholine receptors

The modulation of nicotinic acetylcholine receptors (nAChRs) has been suggested to play a role in the pathogenesis of various neurodegenerative diseases. 

MB acts as a non-competitive antagonist on α7 nAChRs.

Well known drugs that act in a similar way include the Alzheimer’s drug Memantine and Ketamine. Recall that intranasal Ketamine has been used in autism. 

Substances  with the opposite effect include nicotine, choline and of course

Amyloid beta, the marker of Alzheimer's disease.

Note that some people need to block α7 nAChRs and some people need to activate them. 

Methylene blue inhibits the function of α7-nicotinic acetylcholine receptors

FDA Drug Safety Communication: Serious CNS reactions possible when methylene blue is given to patients taking certain psychiatric medications

A list of the serotonergic psychiatric medications that can interact with methylene blue can be found here. 

• Methylene blue can interact with serotonergic psychiatric medications and cause serious CNS toxicity.
• In emergency situations requiring life-threatening or urgent treatment with methylene blue (as described above), the availability of alternative interventions should be considered and the benefit of methylene blue treatment should be weighed against the risk of serotonin toxicity. If methylene blue must be administered to a patient receiving a serotonergic drug, the serotonergic drug must be immediately stopped, and the patient should be closely monitored for emergent symptoms of CNS toxicity for two weeks (five weeks if fluoxetine [Prozac] was taken), or until 24 hours after the last dose of methylene blue, whichever comes first.
• In non-emergency situations when non-urgent treatment with methylene blue is contemplated and planned, the serotonergic psychiatric medication should be stopped to allow its activity in the brain to dissipate. Most serotonergic psychiatric drugs should be stopped at least 2 weeks in advance of methylene blue treatment. Fluoxetine (Prozac), which has a longer half-life compared to similar drugs, should be stopped at least 5 weeks in advance.
• Treatment with the serotonergic psychiatric medication may be resumed 24 hours after the last dose of methylene blue.
• Serotonergic psychiatric medications should not be started in a patient receiving methylene blue. Wait until 24 hours after the last dose of methylene blue before starting the antidepressant.
• Educate your patients to recognize the symptoms of serotonin toxicity or CNS toxicity and advise them to contact a healthcare professional immediately if they experience any symptoms while taking serotonergic psychiatric medications or methylene blue.

Conclusion 

Rather surprisingly, this therapy from the fish tank may have wide ranging effects on the autistic brain and in those with dementia, bipolar etc.

Possible benefits might include:

·        Improved production of ATP (energy) in the brain

·        Reduced oxidative stress in the brain

·        Reduced nitrosative stress

·        Reduced inflammation

·        Improved mood (due to increased serotonin)

·        Improved memory and cognitive function

·        Reduction in obsessive behaviors

In one of the papers, they comment that “methylene blue modulates functional connectivity in the human brain”.

It seems to work for Dragos.  You can also see that people on Reddit use it for issues like ADHD. 

 

Note the FDA warning:

Do not combine Methylene Blue with serotonergic psychiatric medications, because of the risk of serotonin syndrome (i.e., serotonin toxicity).

Different Types of Excitatory/Inhibitory Imbalance in Autism, Fragile-X & Schizophrenia

There is much written in the complex scientific literature about the Excitatory/Inhibitory (E/I) imbalance between neurotransmitters in autism. 

Many clinical trials have already been carried out, particularly in Fragile-X.  These trials were generally ruled as failures, in spite of a significant minority who responded quite well in some of these trials.

As we saw in the recent post on the stage II trial of bumetanide in severe autism, there is so much “background noise” in the results from these trials and it is easy to ignore a small group who are responders.  I think if you have less than 40%, or so, of positive responders they likely will get lost in the data. 

You inevitably get a significant minority who appear to respond to the placebo, because people with autism usually have good and bad days and testing is very subjective.

There are numerous positive anecdotes from people who participated in these “failed” trials.  If you have a child who only ever speaks single words, but while on the trial drug starts speaking full sentences and then reverts to single words after the trial, you do have to take note. I doubt this is a coincidence.

Here are some of the trialed drugs, just in Fragile-X, that were supposed to target the E/I imbalance:-

Metabotropic glutamate receptor 5 (mGluR5) antagonist

·        Mavoglurant

·        Lithium

mGluR5 negative allosteric modulator

·        Fenobam

N-methyl-D-aspartic acid (NMDA) antagonist

·        Memantine

Glutamate re-uptake promoter

·        Riluzole

Suggested to have effects on NMDA & mGluR5 & GABA_A

·        Acamprosate

GABA_B agonist

·        Arbaclofen

Positive allosteric modulator (PAM) of GABA_A receptor

·        Ganaxolone

Best not to be too clever

Some things you might use to modify the E/I imbalance can appear to have the opposite effect, as was highlighted in the comments in the post below:-

NMDAR hypo-function causing E/I imbalance in Autism and Schizophrenia – Baclofen, Sodium benzoate and Cinnamon (again)

So whilst it is always a good idea to try and figure things out, you may end up getting things the wrong way around, mixing up hypo and hyper.

The MIT people who work on Fragile-X are really clever and they have not figured it all out.

Fragile-X and Idiopathic Autism

Fragile-X gets a great deal of attention, because its biological basis is understood.  It results in a failure to express the fragile X mental retardation protein (FMRP), which is required for normal neural development.

We saw in the recent post about eIF4E, that this could lead to an E/I imbalance and then autism.

eIF4E inhibitors for Autism – Why not Ribavirin?

Our reader AJ started looking at elF4E and moved on to EIF4E- binding protein number 1.

In the green and orange boxes below you can find elF4E and elF4E-BP2.

This has likely sent some readers to sleep, but for those whose child has Fragile-X, I suggest they read on, because it is exactly here that the lack of fragile X mental retardation protein (FMRP) causes a big problem.  The interaction between FMRP on the binding proteins of elF4E, cause the problem with neuroligins (NLGNs), which causes the E/I imbalance.  Look at the red oval shape labeled FMRP and green egg-shaped NLGNs.

In which case, while AJ might naturally think Ribavirin is a bit risky for idiopathic autism, it might indeed be very effective in some Fragile-X.  You would hope some researcher would investigate this.

Can you have more than one type of E/I imbalance?

Readers whose child responds well to bumetanide probably wonder if they have solved their E/I imbalance.

I think they have most likely improved just one dysfunction that fits under the umbrella term E/I imbalance.  There are likely other dysfunctions that if treated could further improve cognition and behavior.

On the side of GABA, it looks like turning up the volume on α3 sub-unit and turning down the volume on α5 may help. We await the (expensive) Down syndrome drug Basmisanil for the latter, given that the cheap 80 year old drug Cardiazol is no longer widely available. Turning up the volume on α3 sub-unit can be achieved extremely cheaply, and safely, using a tiny dose of Clonazepam.

It does appear that targeting glutamate is going to be rewarding for at least some of those who respond to bumetanide.

One agonist of NMDA receptors is aspartic acid. Our reader Tyler is a fan of L-Aspartic Acid, that is sold as a supplement that may boost athletic performance.  

Others include D-Cycloserine, already used in autism trials; also D-Serine and L-Serine.

D-Serine is synthesized in the brain from L-serine, its enantiomer, it serves as a neuromodulator by co-activating NMDA receptors, making them able to open if they then also bind glutamate. D-serine is a potent agonist at the glycine site of NMDA receptors. For the receptor to open, glutamate and either glycine or D-serine must bind to it; in addition a pore blocker must not be bound (e.g. Mg2+ or Pb2+).

D-Serine is being studied as a potential treatment for schizophrenia and L-serine is in FDA-approved human clinical trials as a possible treatment for ALS/Motor neuron disease.  

You may be thinking, my kid has autism, what has this got to do with ALS/Motor neuron disease (from the ice bucket challenge)? Well one of the Fragile-X trial drugs at the beginning of this post is Riluzole, a drug developed for specially for ALS.  Although it does not help that much in ALS, it does something potentially very useful for some autism, ADHD and schizophrenia; it clears away excess glutamate.

Fragile-X is likely quite different to many other types of autism

I suspect that within Fragile-X there are many variations in the downstream biological dysfunctions and so that even within this definable group, there may be no universal therapies.  So for some people an mGluR5 antagonist may be appropriate, but not for others.

Even within this discrete group, we come back to the need for personalized medicine.

I do not think Fragile-X is a good model for broader autism.

Glutamate Therapies

There are not so many glutamate therapies, so while the guys at MIT might disapprove, it would not be hard to apply some thoughtful trial and error.

You have:

mGluR5

     ·        mGluR5 agonists (only research compounds)

·        mGluR5 positive allosteric modulators (only research compounds)

·        mGluR5 antagonists (Mavoglurant, Lithium)

·        mGluR5 negative allosteric modulators (Fenobam, Pu-erh tea decreases mGluR5 expression )

Today you can only really treat too much mGluR5 activity.  It there is too little activity, the required drugs are not yet available.  I wonder how many people with Fragile-X are drinking Pu-erh tea, it is widely available.

NMDA agonists

D-Cycloserine an antibiotic with similar structure to D-Alanine (D-Cycloserine was trialed in autism and schizophrenia)

ɑ-amino acids:

·         Aspartic acid (trialed and used  by Tyler, suggested for schizophrenia)

·         D-Serine (trialed in schizophrenia)

•    L-Serine

• D-Alanine (trialed in schizophrenia)

• L-Alanine

NMDA antagonists

·        Memantine (widely used off-label in autism, but failed in clinical trials)

·        Ketamine (trialed intra-nasal in autism)

Glutamate re-uptake promoters via GLT-1

·        Riluzole

·        Bromocriptine

·        Beta-lactam antibiotics

Altered Homeostasis in Autism: Cl-, K+, Ca2+, and quite possibly Zn2+

Today’s post will highlight how, perhaps, in 50 years’ time, autism might be understood by the non-scientist.  Sometimes it helps to oversimplify a complex problem in order not to get lost in all the complexities and see what underlying mechanisms may exist.

Homeostasis

Homeostasis is a fancy word for balance or equilibrium.  It is the property of a system in which variables are regulated so that internal conditions remain stable and relatively constant.

All living organisms depend on maintaining a complex set of interacting metabolic chemical reactions. From the simplest unicellular organisms to the most complex plants and animals, internal processes operate to keep the conditions within tight limits to allow these reactions to proceed. Homeostatic processes act at the level of the cell, the tissue, and the organ, as well as for the organism as a whole.

Many diseases involve a disturbance of homeostasis.

Autism is clearly a condition of altered homeostasis, but not severe enough as to become degenerative.

First Chloride Cl^-, Calcium Ca²⁺ , then Potassium K⁺ and now perhaps Zinc Zn²⁺

We have already seen that three very simple ions, chloride Cl^- , calcium Ca²⁺, potassium K⁺ are in the “wrong place” or in the “wrong concentration” in autism.  This in effect tells us that there is altered homeostasis.

Would it then come as a surprise that a fourth ion, zinc Zn²⁺ also appears to be in the “wrong place”, in at least some autism?

Perhaps there is a common mechanism behind this dysfunctional homeostasis? It might be related to cell adhesion molecules like neuroligins (see below), which will be looked at in another post.

Source: By Sarahlobescheese (Created on Paintbrush and Microsoft Word) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Supplementation and Homeostasis

When the lay person hears that something simple is involved in the pathology of autism, the immediate reaction seems to be that you either need more, or less, of it.  So more calcium, more zinc, more magnesium etc.

The problem is more complex; there is enough calcium (and your bones are full of it) but it is not all quite in the right place, so it needs moving around a bit.

When I came across the recent research from Taiwan about the effect of zinc on the NMDA receptors in the brain, I did a quick check and found lots of people supplementing zinc. Some people because the level in their child’s hair was high and some because it was low; the therapy remained the same, more zinc.

Just as Ben-Ari really has figured out many aspects of the excitatory/inhibitory imbalance in GABA in autism and chosen a therapy that indirectly corrects it, the Taiwanese have also gone into their receptor, the NMDA, in detail.  They put forward a well thought out case for modulating it.

Just as Ben Ari choose to move chloride to outside the cells with his drug (Bumetanide), Yi-Ping Hsueh, the Taiwanese researcher, uses an existing  drug called Clioquinol to move zinc from a presynaptic terminal to postsynaptic sites in the brain.  Again, like Ben Ari, she also showed it to be effective in two different mouse models of autism.

Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation

“Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation”

Clioquinolmay help people with autism: study

Scientists compared the interactions of test mice by placing the subjects in a box, mice that had been unchanged, mice with their Tbr1 and Shank2 proteins “knocked off” and another “stranger” mouse.

They found that unchanged mice engaged in high-level interaction with the “stranger” mouse, while mice with Tbr1 and Shank2 deficiencies interacted very little.

Hsueh’s team had previously determined that Tbr1 is a contributing factor of autism, while a team led by South Korean scientist and project coleader Eunjoon Kim discovered that Shank2 is also implicated in the condition.

Both deficiencies hamper the transmission of zinc ions to the NMDAR (N-methyl-D-aspartate) receptor, impairing function.

About 30 percent of children with autism suffer from zinc deficiency.

Hsueh said that previous projects had determined that autism is linked to zinc deficiency, but the research undertaken by Academia Sinica and the South Korean researchers is the first to provide a scientific explanation for the phenomenon by establishing that the social inhibitions caused by autism can be changed by revitalizing the NMDAR receptor.

Hsueh said the results from the experiment conducted on mice can be extrapolated to humans, with a higher than 90 percent relevance between the two species.

She said that as clioquinol is a prescription drug permitted in Taiwan, her team hopes psychiatrists will prescribe the drug to suitable patients.

Zinc Deficiency or Zinc Transmission Deficiency?

A quick review of the research does show very odd levels of zinc in people with autism.  It also transpires that different ways of measuring zinc levels (hair, blood etc) can produce the opposite result.  So it is hard to ascertain that somebody really does have a zinc deficiency.

The key point is the transmission of that Zinc to the NMDA receptors in the brain.  Note the Zn²⁺ modulatory site in the diagram below.

Clioquinol

Clioquinol, has a very tainted past in Japan. The drug was widely used for various conditions in the 1960s, at doses higher than in other countries.  Its use was tied to the emergence of a new condition called Subacute myelo-optico-neuropathy (SMON) , which only seems to have occurred in Japan.

Clioquinol is banned in some countries, but widely available in other countries, like Taiwan,

Clioquinol is showing promise in research into Alzheimer’s.

Some argue that Clioquinol is totally safe and argue for a combined therapy of Clioquinol and zinc.

Treatment with a Copper-Zinc Chelator Markedly and Rapidly Inhibits β-Amyloid Accumulation in Alzheimer's Disease Transgenic Mice

Clioquinol Synergistically Augments Rescue by Zinc Supplementation in a Mouse Model of Acrodermatitis Enteropathica

Conclusions

These studies suggest that oral CQ (or other 8-hydroxyquinolines) coupled with zinc supplementation could provide a facile approach toward treating zinc deficiency in humans by stimulating stem cell proliferation and differentiation of intestinal epithelial cells.

  

SMON: toxicity of clioquinol and the status quo

Subacute myelo-optico-neuropathy (SMON) is a disease characterized by subacute onset of sensory and motor disorders in the lower half of the body and visual impairment preceded by abdominal symptoms. A large number of SMON were observed throughout Japan, and the total number of cases reached nearly 10,000 by 1970. Despite clinical features mimicking infection or multiple sclerosis, SMON was confirmed as being caused by ingestion of clioquinol, an intestinal antibacterial drug, based on extensive epidemiological studies. After the governmental ban on the use of clioquinol in September 1970, there was a dramatic disappearance of new case of SMON. In the 1970s, patients with SMON initiated legal actions against the Government and pharmaceutical companies, and the court ruled that the settlements would be made as health management allowances and lasting medical check-ups. The physical condition of patients with SMON remains severe owing to SMON as well as gerontological complications. The pathological findings in patients with SMON included symmetrical demyelination in the lateral and posterior funiculi of the spinal cord and severe demyelination of the optic nerve in patients with blindness. Although clioquinol may show activity against Alzheimer's disease or malignancy, its toxic effects cause severe irreversible neurological sequelae. Thus, caution must be exercised in the clinical use of clioquinol

Zinc Effects on NMDA Receptor Gating Kinetics

Zinc is an essential micronutrient that accumulates in brain and is required for normal development and function. Both deficiency and excess of zinc alter behavior and can cause brain abnormalities and neuropathies, of which epilepsy, ischemia, and Alzheimer’s degeneration have been the most studied. Aside from catalytic and structural functions in many proteins, ionic zinc (Zn2+) may play important roles in neurotransmission. Free Zn2+ accumulates in the synaptic vesicles of a specific subset of glutamatergic neurons and is coreleased with glutamate in an activity-dependent manner. Upon release, free Zn2+ may modulate neurotransmitter receptors and transporters, activate zinc-sensing metabotropic receptors, and/or gain cellular access through Ca2+-permeable channels. At certain glutamatergic synapses, a primary role for vesicular zinc is to reduce N-methyl-D-aspartate (NMDA) receptor currents . A wide range of extracellular Zn2+ concentrations directly and specifically inhibit NMDA receptor responses, and in the hippocampus, a region highly enriched in vesicular zinc, zinc-positive glutamatergic synapses are also enriched in NMDA receptors. The inhibitory effects of Zn2+ on NMDA receptors have received considerable attention due in part to the pivotal role played by these receptors in synaptic transmission and plasticity. Still, the mechanism by which the inhibition occurs is incompletely understood.

Other ways of modifying NDMA receptors

As the excellent recent paper below from Korea points out, “correcting NMDAR dysfunction has therapeutic potential for ASDs”.  The problem is that in some autism there is too much NMDAR function, and in others there is too little.

So we should not expect much success from any “one size fits all” therapy.

NMDA receptor dysfunction in autism spectrum disorders.

Abnormalities and imbalances in neuronal excitatory and inhibitory synapses have been implicated in diverse neuropsychiatric disorders including autism spectrum disorders (ASDs). Increasing evidence indicates that dysfunction of NMDA receptors (NMDARs) at excitatory synapses is associated with ASDs. In support of this, human ASD-associated genetic variations are found in genes encoding NMDAR subunits. Pharmacological enhancement or suppression of NMDAR function ameliorates ASD symptoms in humans. Animal models of ASD display bidirectional NMDAR dysfunction, and correcting this deficit rescues ASD-like behaviors. These findings suggest that deviation of NMDAR function in either direction contributes to the development of ASDs, and that correcting NMDAR dysfunction has therapeutic potential for ASDs.

Pharmacological modulation of NMDAR function can improve ASD symptoms. D-cycloserine (DCS), an NMDAR agonist, significantly ameliorates social withdrawal  and repetitive behavior  in individuals with ASD.

These results suggest that reduced NMDAR function may contribute to the development of ASDs in humans. Elevated NMDAR function is also implicated in ASDs. Memantine, an NMDAR antagonist, and its analogue amantadine improve ASD-related symptoms including social deficits, inappropriate language, stereotypy, cognitive impairments, lethargy, irritability, inattention, and these results, together with the DCS results, highlight the importance of a normal range of NMDAR function, and suggest that deviation of NMDAR function in either direction leads to ASD.  This concept is in line with the emerging view that synaptic function within a normal range is important and its deviation causes ASDs and intellectual disability

Mice lacking neuroligin-1, an excitatory postsynaptic adhesion molecule, show reduced NMDAR function in the hippocampus and striatum, as evidenced by a decrease in NMDA/AMPA ratio and long-term potentiation (LTP) Neuroligin-1 is thought to enhance synaptic NMDAR function, by

directly interacting with and promoting synaptic localization of NMDARs.

CDPPB, a positive allosteric modulator of mGluR5 that potentiates similarly normalizes NMDAR Dysfunction and behavioral deficits, consistent with the idea that indirectly modulating NMDARs through mGluR5 is a viable approach for treating ASDs.

ASDs involve diverse core and comorbid symptoms. Consistent with this, a single autism-related mutation, neuroligin-3 R451C, causes diverse synaptic phenotypes in different brain regions and circuits. Therefore, synaptic changes should be analyzed in greater detail, ideally using brain region-specific and cell type-specific conditional gene ablation, as recently reported.

Modulators of mGluR5, in addition to NMDARs and AMPARs, have been considered to be a new means of regulating glutamatergic transmission. Therefore, pharmacological rescue of animal models of ASD should ideally involve modulation of both NMDARs and mGluR5, or even other NMDA-modulatory approaches, to better facilitate translation to clinical therapy.

Lastly, because our hypothesis associates bidirectional NMDAR dysfunction with ASDs, there may be clinical cases, such as where individuals with reduced NMDAR function are treated with NMDAR antagonists, which might aggravate the situation and affect the interpretation.

None of the existing autism therapies that modify NDMA receptors have been uniform knockout successes, but are effective in some cases.

These include:-

·        Memantine an NMDAR antagonist

·        D-Cycloserine an NMDAR agonist (the opposite of Memantine)

·        Ketamine, an NMDAR antagonist

Intranasal Ketamine Treatment in an Adult With Autism Spectrum Disorder

So if you respond to Memantine, the chances are you would benefit from intranasal ketamine;  but D-Cycloserine would make you worse.

They recently terminated early the large Memantine autism trial.  In a rational world they would try D-Cycloserine on all those kids who failed to respond to Memantine.  We do not live in a rational world.

Conclusion

I have a feeling that several dysfunctions in autism, including the E/I imbalance of GABA, will ultimately be traced back to neuroligins.

This is an area of science in its infancy and so for today we have to treat the consequences individually. 

Fortunately, the Simons Foundation is funding the right people and so, in the end, we will get to the bottom of it all.

Function and dysfunction of neuroligins

I hope the Taiwanese test Clioquinol on some humans with ASD and let us know the results.  

As the clever Korean researcher above has highlighted, Clioquinol will only benefit those with reduced NMDAR function.  So if I have got things the right way round, Clioquinol will help the same group that respond to D-Cycloserine.  The others would need Memantine/Ketamine, or even better, they have perfect NMDAR function and need nothing at all.