Dyeing to prevent dying? Methylene blue beneficial in Huntington's disease mice

One of the hallmarks of Huntington’s disease is the formation of protein clumps in brain cells. It’s not clear whether these protein bunches cause disease, but treatment with a blue dye that disrupts the clumps has now been shown to delay symptom onset in an HD mouse model. So what’s next for this drug that turns patients’ eyes and urine blue?

Something old, something blue

Methylene blue is a dye that has many uses. In medicine, it has been used for over 100 years to treat conditions ranging from malaria to urinary tract infections.

One reason it’s used to treat so many things might be that it has many biological effects. Methylene blue can act as an anti-oxidant, protecting cells from oxidative damage, and there’s some evidence it can help cells clear out old proteins they no longer need. It can also keep proteins from sticking to one another.

According to new research in cells, fruit flies and mice, methylene blue may also have the potential to help prevent damage in Huntington’s disease. This study suggests that methylene blue’s ability to block protein clumping is important here.

A sticky situation

In order to understand the problem with sticky proteins, let’s go back to the basics.

Where do proteins come from? From a nice, juicy steak, right? It’s true we get protein from our diet, but our bodies then break the proteins down into tiny building blocks, ready to be assembled into the exact proteins we need.

To decide how to put the building blocks back together to form all the chemical machines they need to function, our cells consult their genes. Genes, which are made up of DNA, act as recipes or sets of instructions.

The gene that causes Huntington’s disease is a recipe for a protein called huntingtin. Patients carrying an expanded, or mutated, form of the HD gene produce an expanded, or mutant, huntingtin proteinhuntingtin protein The protein produced by the HD gene..

We’re not fully sure exactly how the expanded huntingtin proteinhuntingtin protein The protein produced by the HD gene. causes harm, but one of its trademark features is that it sticks together, forming clumps of protein in the brain cells of patients. Scientists call the clumps ‘aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases’ because it sounds more impressive.

Aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases of various proteins are found in patients with other diseases like Alzheimer’s and Parkinson’s. So if mutant huntingtin forms aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases, and the aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases are found in neurodegenerativeneurodegenerative A disease caused by progressive malfunctioning and death of brain cells (neurons) diseases, then the aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases must cause the disease, right?

Well, if someone told you that fire trucks are always found at fires, you’d be mistaken to conclude that fire trucks cause fires. The truth is that scientists still don’t understand whether the aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases cause the trouble, or whether they are simply generated by dying brain cells.

To complicate matters, there are different types of aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases. Some are easy to dissolve, while others are hard to dissolve. Evidence is mounting to suggest that it’s the unpaired proteins and the smaller, easy-to-dissolve aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases that really cause the trouble in HD. Those are called soluble aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases, while the hard-to-dissolve ones are called insoluble aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases.

Enter methylene blue – a blue dye that can block the formation of both kinds of aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases.

Divided they fall?

Researchers in California, led by Prof Leslie Thompson, first looked at mutant huntingtin proteinhuntingtin protein The protein produced by the HD gene. isolated in a test tube, tends to form soluble and insoluble aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases. They found that methylene blue not only blocked the formation of aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases, but also disrupted already-formed clumps.

This breaking-down of existing aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases, on top of preventing new aggregateaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases formation, may be good news for patients who already have protein aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases in their brains.

Proteins in a test tube are one thing, but what about brain cells? The next thing the team did was feed methylene blue to neuronsneuron Brain cells that store and transmit information grown in a dish, that had a mutant copy of the HD gene. Methylene blue blocked mutant huntingtin from clumping inside the neuronsneuron Brain cells that store and transmit information. The cells also survived better with methylene blue treatment, a good sign.

Moving up a notch, the team asked what would happen if they fed methylene blue to some fruit flies engineered to carry the HD gene. They found that neurodegenerationneurodegenerative A disease caused by progressive malfunctioning and death of brain cells (neurons) in the flies wasn’t as bad if they fed them methylene blue at an early stage. However, it had no real effect if they introduced it after they reached adulthood.

Next stop, Huntington’s disease model mice. The researchers used R6/2R6/2 a mouse model of Huntington's disease. R6/2 mice have been genetically altered with an abnormal gene that makes them produce a harmful fragment of the mutant huntingtin protein mice, which get sick very quickly. Methylene blue once again stopped the aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases from forming and delayed the onset of movement problems.

It didn’t prevent the symptoms entirely, but follow-up studies in a more slowly-progressive mouse model, that resembles human HD more closely, might give a clearer picture.

At the very least, a drug that disrupts mutant huntingtin aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases can tell us a lot about the role they play in disease.

What about humans?

The idea to look at methylene blue as a treatment for Huntington’s disease didn’t come out of the blue. In fact, this curious dye has a… colorful history in the field of neurodegeration and dementia research.

Methylene blue also affects the formation of aggregatesaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases in Alzheimer’s disease, and a clinical trialclinical trial Very carefully planned experiments designed to answer specific questions about how a drug affects human beings held in 2008 took the Alzheimer’s research community by surprise when huge improvements were reported in patients who took the drug.

That excitement faded somewhat, since no new data came out after the initial study.

Recently, TauRx Therapeuticstherapeutics treatments Inc. – the company behind the original methylene blue trial – announced the initiation of two global clinical trials with Alzheimer’s patients using an ‘improved’ version of methylene blue. The new version is called LMTXTM. It’s touted to have improved ability to reach the brain and fewer side effects. What’s less clear is why the company didn’t press on with a trial of that drug, when the original trial appeared so successful.

The ‘improved’ drug is a step in the right direction, since it’s unclear whether methylene blue can reach the brain in humans when taken orally.

Methylene blue also has a curious property that makes it uniquely tough to test by clinical trialclinical trial Very carefully planned experiments designed to answer specific questions about how a drug affects human beings.

One important aspect of clinical trials is that both researchers and patients should not be biased when recording and reporting symptoms. To avoid bias, trials are double-blinded, which means that neither the researcher nor the subject knows who is taking the actual drug and who is taking the control, or placeboplacebo A placebo is a dummy medicine containing no active ingredients. The placebo effect is a psychological effect that causes people to feel better even if they’re taking a pill that doesn’t work..

But subjects have to take methylene blue until they are blue in the face-literally! Since it’s a dye, methylene blue turns the urine and the whites of the eye blue, making it impossible to run a blinded study. In the Alzheimer’s trial, blue pee was a sure sign that a patient was taking the real drug. Knowing that they’re taking the active treatment can make patients feel better, often quite substantially – the so-called placeboplacebo A placebo is a dummy medicine containing no active ingredients. The placebo effect is a psychological effect that causes people to feel better even if they’re taking a pill that doesn’t work. effect. Could that have biased the outcome of the trial?

Clearly, there are challenges to face before we can say that methylene blue will help treat Huntington’s disease. This drug has been used safely in humans for a long time, but for human trials in HD to be worthwhile, we’ll need to see data proving that the drug gets into the human brain and reaches a level we’d expect to have an effect on aggregateaggregate Lumps of protein that form inside cells in Huntington’s disease and some other degenerative diseases formation.

These preliminary results reported by the Californian research group surely suggest it’s a drug worth pursuing to study aggregation and as a possible treatment approach, and the results of the Alzheimer’s trial will be of much interest to Huntington’s disease patients and families alike.

Learn more

• Article by Sontag and colleagues in the Journal of Neuroscience (full article requires payment or subscription)