Recently I discussed my ‘Plan B’ idea, which involves providing a cheap alternative to expensive drugs for folks living in the developing world with Parkinson’s (Click here for that post).
While doing some research for that particular post, I came across another really interesting bit of science that is being funded by Parkinson’s UK.
It involves Beetroot.
In today’s post we will look at how scientists are attempting turn this red root vegetable into a white root vegetable in an effort to solve Parkinson’s in the developing world.
Pompeii and Mount Vesuvius. Source: NationalGeo
During visits to the ancient Roman city of Pompeii (in Italy), tourists are often drawn by their innocent curiosity to the ‘red light’ district of the city. And while they are there, they are usually amused by the ‘descriptive’ murals that still line the walls of the buildings in that quarter.
So amused in fact that they often miss the beetroots.
I’m not suggesting that anyone spends a great deal of time making a close inspection of the walls, but if you look very carefully, you will often see renditions of beetroots.
They are everywhere. For example:
Two beetroots hanging from the ceiling.
The Romans considered beetroot to be quite the aphrodisiac, believing that the juice ‘promoted amorous feelings’. They also ate the red roots for medicinal purposes, consuming it as a laxative or to cure fever.
And this medicinal angle lets me segway nicely into the actual topic of today’s post. You see, in the modern era researcher are hoping to use beetroot for medicinal purposes again. But this time, the beetroot will be used to solve an issue close to my heart: treating people with Parkinson’s in the developing world.
Using beetroot to treat Parkinson’s?
The protein Alpha Synuclein has long been considered the bad-boy of Parkinson’s disease research. Possibly one of the main villains in the whole scheme of things.
New research suggests that it may be interfering with a neuroprotective pathway, leaving the affected cell more vulnerable to stress/toxins. But that same research has highlighted a novel beneficial feature of an old class of drugs: MAO-B inhibitors.
In today’s post we will outline the new research, discuss the results, and look at whether this new Trk warrants a re-think of MAO-B inhibitors.
The great Harry Houdini. Source: Wikipedia
I’m not sure about you, but I enjoy a good magic trick.
That exhilarating moment when you are left wondering just one thing: How do they do that?
(Seriously, at 4:40 a baguette comes out of thin air – how did he do that?)
Widely believed to have been one of the greatest magicians of all time (Source), Harry Houdini is still to this day revered among those who practise the ‘dark arts’.
Born Erik Weisz in Budapest (in 1874), Houdini arrived in the US in 1878. Fascinated with magic, in 1894, he launched his career as a professional magician and drew attention for his daring feats of escape. He renamed himself “Harry Houdini” – the first name being derived from his childhood nickname, “Ehrie,” and the last name paying homage to the great French magician Jean Eugène Robert-Houdin. In 1899, Houdini’s act caught the eye of Martin Beck, an entertainment manager, and from there the rest is history. Constantly upping the ante, his feats became bolder and more death defying.
And the crowds loved him.
From stage, he moved on to film – ultimately starting his own production company, Houdini Picture Corporation. In addition, he was a passionate debunker of psychics and mediums, his training in magic helping him to expose frauds (which turned him against his former friend Sir Arthur Conan Doyle, who believed deeply in spiritualism).
This is all very interesting, but what does any of it have to do with Parkinson’s?
The motor features of Parkinson’s disease can be managed with treatments that replace the chemical dopamine in the brain.
While there are many medically approved dopamine replacement drugs available for people affected by Parkinson’s disease, there also are more natural sources.
In today’s post we will look at the science and discuss the research supporting one of the most potent natural source for dopamine replacement treatment: Mucuna pruriens
When asked by colleagues and friends what is my ‘plan B’ (that is, if the career in academia does not play out – which is highly probable I might add – Click here to read more about the disastrous state of biomedical research careers), I answer that I have often considered throwing it all in and setting up a not-for-profit, non-governmental organisation to grow plantations of a tropical legume in strategic places around the world, which would provide the third-world with a cheap source of levodopa – the main treatment in the fight against Parkinson’s disease.
Plan B: A legume plantation. Source: Tropicalforages
The response to my answer is generally one of silent wonder – that is: me silently wondering if they think I’m crazy, and them silently wondering what on earth I’m talking about.
As romantic as the concept sounds, there is an element of truth to my Plan B idea.
I have read many news stories and journal articles about the lack of treatment options for those people with Parkinson’s disease living in the developing world.
Hospital facilities in the rural Africa. Source: ParkinsonsLife
Some of the research articles on this topic provide a terribly stark image of the contrast between people suffering from Parkinson’s disease in the developing world versus the modernised world. A fantastic example of this research is the work being done by the dedicated researchers at the Parkinson Institute in Milan (Italy), who have been conducting the “Parkinson’s disease in Africa collaboration project”.
The researchers at the Parkinson Institute in Milan. Source: Parkinson Institute
The project is an assessment of the socio-demographic, epidemiological, clinical features and genetic causes of Parkinson’s disease in people attending the neurology out-patients clinic of the Korle Bu Teaching and Comboni hospitals. Their work has resulted in several really interesting research reports, such as this one:
Title: The modern pre-levodopa era of Parkinson’s disease: insights into motor complications from sub-Saharan Africa.
Authors: Cilia R, Akpalu A, Sarfo FS, Cham M, Amboni M, Cereda E, Fabbri M, Adjei P, Akassi J, Bonetti A, Pezzoli G.
Journal: Brain. 2014 Oct;137(Pt 10):2731-42.
PMID: 25034897 (This article is OPEN ACCESS if you would like to read it)
In this study, the researchers collected data in Ghana between December 2008 and November 2012, and each subject was followed-up for at least 6 months after the initiation of Levodopa therapy. In total, 91 Ghanaians were diagnosed with Parkinson’s disease (58 males, average age at onset 60 ± 11 years), and they were compared to 2282 Italian people with Parkinson’s disease who were recruited during the same period. In long-term follow up, 32 Ghanaians with Parkinson’s disease were assessed (with an average follow period of 2.6 years).
There are some interesting details in the results of the study, such as:
- Although Levodopa therapy was generally delayed – due to availability and affordability – in Ghana (average disease duration before Levodopa treatment was 4.2 years in Ghana versus just 2.4 years in Italy), the actual disease duration – as determined by the occurrence of motor fluctuations and the onset of dyskinesias – was similar in the two populations.
- The motor fluctuations were similar in the two populations, with a slightly lower risk of dyskinesias in Ghanaians.
- Levodopa daily doses were higher in Italians, but this difference was no longer significant after adjusting for body weight.
- Ghanaian Parkinson’s sufferers who developed dyskinesias were younger at onset than those who did not.
Reading these sorts of research reports, I am often left baffled by the modern business world’s approach to medicine. I am also left wondering how an individual’s experience of Parkinson’s disease in some of these developing nations would be improved if a cheap alternative to the dopamine replacement therapies was available.
Are any cheap alternatives available?
This week a group of scientists have published an article which indicates differences between mice and human beings, calling into question the use of these mice in Parkinson’s disease research.
The results could explain way mice do not get Parkinson’s disease, and they may also partly explain why humans do.
In today’s post we will outline the new research, discuss the results, and look at whether Levodopa treatment may (or may not) be a problem.
The humble lab mouse. Source: PBS
Much of our understanding of modern biology is derived from the “lower organisms”.
From yeast to snails (there is a post coming shortly on a snail model of Parkinson’s disease – I kid you not) and from flies to mice, a great deal of what we know about basic biology comes from experimentation on these creatures. So much in fact that many of our current ideas about neurodegenerative diseases result from modelling those conditions in these creatures.
Now say what you like about the ethics and morality of this approach, these organisms have been useful until now. And I say ‘until now’ because an interesting research report was released this week which may call into question much of the knowledge we have from the modelling of Parkinson’s disease is these creatures.
You see, here’s the thing: Flies don’t naturally develop Parkinson’s disease.
Nor do mice. Or snails.
Or yeast for that matter.
So we are forcing a very un-natural state upon the biology of these creatures and then studying the response/effect. Which could be giving us strange results that don’t necessarily apply to human beings. And this may explain our long history of failed clinical trials.
We work with the best tools we have, but it those tools are flawed…
What did the new research report find?
This is the study:
Title: Dopamine oxidation mediates mitochondrial and lysosomal dysfunction in Parkinson’s disease
Authors: Burbulla LF, Song P, Mazzulli JR, Zampese E, Wong YC, Jeon S, Santos DP, Blanz J, Obermaier CD, Strojny C, Savas JN, Kiskinis E, Zhuang X, Krüger R, Surmeier DJ, Krainc D
Journal: Science, 07 Sept 2017 – Early online publication
The researchers who conducted this study began by growing dopamine neurons – a type of cell badly affected by Parkinson’s disease – from induced pluripotent stem (IPS) cells.
What are induced pluripotent stem cells?
BE WARNED: THIS POST MIGHT UPSET SOME READERS
A recently published research report has caused a bit of a fuss in the media, and I have been contacted by a lot of concerned readers regarding this particular study.
It deals with some chemicals – which can be found in everyday products – that may be having a negative effect on biological processes that are related to Parkinson’s disease – specifically, the normal functioning of the mitochondria (the power stations of each cell).
In today’s post we will discuss the new research, what the chemicals do, and whether the Parkinson’s community should be concerned.
It is something that most of us take completely for granted in the modern world. A product that sits in our bathroom, by the sink or on a shelf, and 2-3 times per day we stick some of it in our mouth and brush it around a bit. Given the well ingrained habit of repetitively ingesting of the stuff, we have little trouble with the idea of switching brands or trying new variations (“Oooh look, this one will make your teeth whiter. Let’s try it”).
I mean, come on – it’s just toothpaste. It’s safe, right?
It probably won’t surprise many of you to learn that the composition of toothpaste has changed quite a bit over the years, but what might amaze you is just how many years are involved with that statement:
Egyptian toothbrush. Source: Nathanpaarth
The Egyptians recognised the importance of looking after one’s teeth at a very early stage. Apparently they had a lot of trouble with their teeth because their bread had grit in it which wore away their enamel. As far back as 5000BC, they had a form of toothpaste that they used to clean their teeth. It was a mix of powdered ashes of ox hooves, myrrh, powdered and burnt eggshells, and pumice (Source: Wikipedia). The Greeks, followed by the Romans, improved on the recipes (by adding abrasive ingredients such as crushed bones and oyster shells – delightful, huh?), but it wasn’t until after World War I that the modern day pre-mixed toothpastes became popular.
The cavity fighting chemical, Fluoride, was first added to toothpastes in the 1890s, and in 1908 Newell Sill Jenkins (an American dentist) invented the first toothpaste that contained disinfectants. It was called Kolynos (from the Greek words Kolyo nosos (κωλύω νόσος), meaning “disease prevention”).
Following the advent of Kolynos, most toothpaste companies added antiseptic and disinfectant agents to improve the quality and effectiveness of their product. Being offered a tooth cleaning product with magical antibiotic properties seemed to reassure consumers that they were buying something that might actually work. And this led to more and more chemicals being added to toothpaste. Such additions included chemical like triclosan, cetylpyridinium chloride and benzalkonium chloride.
These chemicals are safe though…right?
This week a biotech company called Voyager Therapeutics announced the results of their ongoing phase Ib clinical trial. The trial is investigating a gene therapy approach for people with severe Parkinson’s disease.
Gene therapy is a technique that involves inserting new DNA into a cell using a virus. The DNA can help the cell to produce beneficial proteins that go on help to alleviate the motor features of Parkinson’s disease.
In today’s post we will discuss gene therapy, review the new results and consider what they mean for the Parkinson’s community.
On 25th August 2012, the Voyager 1 space craft became the first human-made object to exit our solar system.
After 35 years and 11 billion miles of travel, this explorer has finally left the heliosphere (which encompasses our solar system) and it has crossed into the a region of space called the heliosheath – the boundary area that separates our solar system from interstellar space. Next stop on the journey of Voyager 1 will be the Oort cloud, which it will reach in approximately 300 years and it will take the tiny craft about 30,000 years to pass through it.
Where is Voyager 1? Source: Tampabay
Where is Voyager actually going? Well, eventually it will pass within 1 light year of a star called AC +79 3888 (also known as Gliese 445), which lies 17.6 light-years from Earth. It will achieve this goal on a Tuesday afternoon in 40,000 years time.
Gliese 445 (circled). Source: Wikipedia
Remarkably, the Gliese 445 star itself is actually coming towards us. Rather rapidly as well. It is approaching with a current velocity of 119 km/sec – nearly 7 times as fast as Voyager 1 is travelling towards it (the current speed of the craft is 38,000 mph (61,000 km/h).
Interesting, but what does any of that have to do with Parkinson’s disease?
Well closer to home, another ‘Voyager’ is also ‘going boldly where no man has gone before’ (sort of).
Dopamine agonist treatments are associated with approximately 90% of hyper-sexuality and compulsive gambling cases that occur in people with Parkinson’s disease.
This issue does not affect everyone being treated with this class of drugs, but it is a problem that keeps popping up, with extremely damaging consequences for the affected people who gamble away their life’s saving or ruin their marriages/family life.
The U.S. Food and Drug Administration (FDA) is yet to issue proper warning for this well recognised side-effect of dopamine agonists, and yet last week they gave clearance for the clinical testing of a new implantable device that will offer continuous delivery of dopamine agonist medication.
In today’s post, we will discuss what dopamine agonists are, the research regarding the impulsive behaviour associated with them, and why the healthcare regulators should acknowledge that there is a problem.
Dopamine. Source: Wikimedia
Before we start talking about dopamine agonists, let’s start at the very beginning:
What is dopamine?
By the time a person is sitting in front of a neurologist and being told that they ‘have Parkinson’s disease’, they will have lost half the dopamine producing cells in an area of the brain called the midbrain.
Dopamine is a chemical is the brain that plays a role in many basic functions of the brain, such as motor co-ordination, reward, and memory. It works as a signalling molecule (or a neurotransmitter) – a way for brain cells to communicate with each other. Dopamine is released from brain cells that produce this chemical (not all brain cells do this), and it binds to target cells, initiating biological processes within those cells.
Dopamine being released by one cell and binding to receptors on another. Source: Truelibido
Dopamine binds to target cells via five different receptors – that is to say, dopamine is released from one cell and can bind to one of five different receptors on the target cell (depending on which receptor is present). The receptor is analogous to a lock and dopamine is the key. When dopamine binds to a particular receptor it will allow something to happen in that cell. And this is how information from a dopamine neuron is passed or transmitted on to another cell.
Dopamine acts like a key. Source: JourneywithParkinsons
In this post we discuss several recently published research reports suggesting that Parkinson’s disease may be an autoimmune condition. “Autoimmunity” occurs when the defence system of the body starts attacks the body itself.
This new research does not explain what causes of Parkinson’s disease, but it could explain why certain brain cells are being lost in some people with Parkinson’s disease. And such information could point us towards novel therapeutic strategies.
The first issue of Nature. Source: SimpleWikipedia
The journal Nature was first published on 4th November 1869, by Alexander MacMillan. It hoped to “provide cultivated readers with an accessible forum for reading about advances in scientific knowledge.” It has subsequently become one of the most prestigious scientific journals in the world, with an online readership of approximately 3 million unique readers per month (almost as much as we have here at the SoPD).
Each Wednesday afternoon, researchers around the world await the weekly outpouring of new research from Nature. And this week a research report was published in Nature that could be big for the world of Parkinson’s disease. Really big!
On the 21st June, this report was published:
Title: T cells from patients with Parkinson’s disease recognize α-synuclein peptides
Authors: Sulzer D, Alcalay RN, Garretti F, Cote L, Kanter E, Agin-Liebes J, Liong C, McMurtrey C, Hildebrand WH, Mao X, Dawson VL, Dawson TM, Oseroff C, Pham J, Sidney J, Dillon MB, Carpenter C, Weiskopf D, Phillips E, Mallal S, Peters B, Frazier A, Lindestam Arlehamn CS, Sette A
Journal: Nature. 2017 Jun 21. doi: 10.1038/nature22815.
In their study, the investigators collected blood samples from 67 people with Parkinson’s disease and from 36 healthy patients (which were used as control samples). They then exposed the blood samples to fragments of proteins found in brain cells, including fragments of alpha synuclein – this is the protein that is so closely associated with Parkinson’s disease (it makes regular appearances on this blog).
What happened next was rather startling: the blood from the Parkinson’s patients had a strong reaction to two specific fragments of alpha synuclein, while the blood from the control subjects hardly reacted at all to these fragments.
In the image below, you will see the fragments listed along the bottom of the graph (protein fragments are labelled with combinations of alphabetical letters). The grey band on the plot indicates the two fragments that elicited a strong reaction from the blood cells – note the number of black dots (indicating PD samples) within the band, compared to the number of white dots (control samples). The numbers on the left side of the graph indicate the number of reacting cells per 100,000 blood cells.
The investigators concluded from this experiment that these alpha synuclein fragments may be acting as antigenic epitopes, which would drive immune responses in people with Parkinson’s disease and they decided to investigate this further.
Researchers are using a powerful new tool to determine which parts of the brain are involved in movement.
The technology involves shining light on brain cells…and well, a bit of biological magic.
Today we will review some newly published research highlighting how this approach and discuss what it means for Parkinson’s disease.
The Vienna city hall. Source: EUtourists
Personal story: I was at the Dopamine 2016 conference in September last year in lovely Vienna (Austria). Wonderful city, beautiful weather, and an amazing collection of brilliant researchers focused on all things dopamine-related. The conference really highlighted all the new research being done on this chemical.
There was – of course – a lots of research being presented on Parkinson’s disease, given that dopamine plays such an important role in the condition.
And it was all really interesting.
Anyways, I was sitting in one of the lecture presentation session, listening to all these new results being discussed.
And then, a lady from Carnegie Mellon University stood up and (without exaggeration) completely – blew – my – mind!
Her name is Aryn H. Gittis:
She is an Assistant Professor in the Department of Biological Sciences at Carnegie Mellon University, where her group investigates the neural circuits underlying the regulation of movement, learning, motivation, and reward.
And the ‘mind blowing‘ research that she presented in Vienna has recently been published in the journal Nature Neuroscience:
Title: Cell-specific pallidal intervention induces long-lasting motor recovery in dopamine-depleted mice
Authors: Mastro KJ, Zitelli KT, Willard AM, Leblanc KH, Kravitz AV & Gittis AH
Journal: Nature Neuroscience (2017) doi:10.1038/nn.4559
In this report, Dr Gittis and her colleagues demonstrated that elevating the activity of one type of cell in an area of the brain called the globus pallidus, could provide long lasting relief from Parkinson’s-like motor features.
Hang on a second. What is the globus pallidus?
The globus pallidus is a structure deep in the brain and before Dr Gittis and her colleagues published their research, we already knew it played an important role in our ability to move.
Movement is largely controlled by the activity in a specific group of brain regions, collectively known as the ‘Basal ganglia‘.
The basal ganglia structures (blue) in the human brain. Source: iKnowledge
But while the basal ganglia controls movement, it is not the starting point for the movement process.
The prefrontal cortex is where we do most of our ‘thinking’. It is the part of the brain that makes decisions with regards to many of our actions, particularly voluntary movement. It is involved in what we call ‘executive functions’. It is the green area in the image below.
Areas of the cortex. Source: Rasmussenanders
Now the prefrontal cortex might come up with an idea: ‘the left hand should start to play the piano’. The prefrontal cortex will communicate this idea with the premotor cortex and together they will send a very excited signal down into the basal ganglia for it to be considered. Now in this scenario it might help to think of the cortex as hyperactive, completely out of control toddlers, and the basal ganglia as the parental figure. All of the toddlers are making demands/proposals and sending mixed messages, and it is for the inhibiting basal ganglia to gain control and decide which is the best.
So the basal ganglia receives signals from the cortex, processes that information before sending a signal on to another important participant in the regulation of movement: the thalamus.
A brain scan illustrating the location of the thalamus in the human brain. Source: Wikipedia
The thalamus is a structure deep inside the brain that acts like the central control unit of the brain. Everything coming into the brain from the spinal cord, passes through the thalamus. And everything leaving the brain, passes through the thalamus. It is aware of most everything that is going on and it plays an important role in the regulation of movement. If the cortex is the toddler and the basal ganglia is the parent, then the thalamus is the ultimate policeman.
Now to complicate things for you, the processing of movement in the basal ganglia involves a direct pathway and an indirect pathway. In the simplest terms, the direct pathway encourages movement, while the indirect pathway does the opposite: inhibits it.
The thalamus will receive signals from the two pathways and then decide – based on those signals – whether to send an excitatory or inhibitory message to the primary motor cortex, telling it what to do (‘tell the muscles to play the piano’ or ‘don’t start playing the piano’, respectively). The primary motor cortex is the red stripe in the image below.
The primary motor cortex then sends this structured order down the spinal cord (via the corticospinal pathway) and all going well the muscles will do as instructed.
Source: adapted from Pinterest
Now, in Parkinson’s disease, the motor features (slowness of movement and resting tremor) are associated with a breakdown in the processing of those direct and an indirect pathways. This breakdown results in a stronger signal coming from the indirect pathway – thus inhibiting/slowing movement. This situation results from the loss of dopamine in the brain.
Excitatory signals (green) and inhibitory signals (red) in the basal ganglia, in both a normal brain and one with Parkinson’s disease. Source: Animal Physiology 3rd Edition
Under normal circumstances, dopamine neurons release dopamine in the basal ganglia that helps to mediate the local environment. It acts as a kind of lubricant for movement, the oil in the machine if you like. It helps to reduce the inhibitory bias of the basal ganglia.
Thus, with the loss of dopamine neurons in Parkinson’s disease, there is an increased amount of activity coming out of the indirect pathway.
And as a result, the thalamus is kept in an overly inhibited state. With the thalamus subdued, the signal to the motor cortex is unable to work properly. And this is the reason why people with Parkinson’s disease have trouble initiating movement.
Now, as you can see from the basic schematic above, the globus pallidus is one of the main conduits of information into the thalamus. Given this pivotal position in the regulation of movement, the globus pallidus has been a region of major research focus for a long time.
It is also one of the sites targeted in ‘deep brain stimulation’ therapy for Parkinson’s disease (the thalamus being another target). Deep brain stimulation (or DBS) involves placing electrodes deep into the brain to help regulate activity.
DBS in the globus pallidus. Source: APS
By regulating the level of activity in the globus pallidus, DBS can control the signal being sent to the thalamus, reducing the level of inhibition, and thus alleviating the motor related features of the Parkinson’s disease.
The dramatic effects (and benefits) of deep brain stimulation can be seen in this video (kindly provided by fellow kiwi Andrew Johnson):
Deep brain stimulation is not perfect, however.
The placing of the electrodes can sometimes be off target, resulting in limited beneficial effects. Plus the tuning of the device can be a bit fiddly in some cases.
A more precise method of controlling the globus pallidus would be ideal.
Ok, so the globus Pallidus region of the brain is important for movement. What did Dr Gittis and her colleagues find in their research?
They used an amazing piece of technology called ‘optogenetics‘ to specifically determine which group of cells in the globus pallidus are involved in the inhibitory signals going to the thalamus.
And their results are VERY interesting.
But what is optogenetics?
The short answer: ‘Magic’
The long answer: In 1979, Nobel laureate Francis Crick suggested that one of the major challenge facing the study of the brain was the need to control one type of cell in the brain while leaving others unaltered.
The DNA duo: Francis Crick (left) and James Watson. Source: CNN
Electrical stimulation cannot address this challenge because electrodes stimulate everything in the immediate vicinity without distinction. In addition the signals from electrodes lack precision; they cannot turn on/off neurons as dynamically as we require. The same problems (and more) apply to the use of drugs.
Crick later speculated that the answer might be light.
How on earth would you do that?
Well, in 1971 – eight years before Crick considered the problem – two researchers, Walther Stoeckenius and Dieter Oesterhelt, discovered a protein, bacteriorhodopsin, which acts as an ion pump on the surface of a cell membrane. Amazingly, this protein can briefly become activated by green light.
A rather remarkable property.
Later, other groups found similar proteins. One such protein, called ‘Channelrhodopsin’, was discovered in green algae (click here to read more on this). When stimulated by particular frequencies of light, these channels open up on the cell surface and allow ions to pass through. If enough channels open, this process can stimulate particular activity in the cell.
Channelrhodopsin. Source: Openoptogenetics
Interesting, but how do you get this into the brain?
This is Karl Diesseroff:
Looks like the mad scientist type, right? Well, remember his name, because this guy is fast heading for a Nobel prize.
He is the D. H. Chen Professor of Bioengineering and of Psychiatry and Behavioral Sciences at Stanford University. And he is one of the leading researchers in a field that he basically started.
Back in 2005, he and his collaborators published this research report:
Title: Millisecond-timescale, genetically targeted optical control of neural activity
Authors: Boyden ES, Zhang F, Bamberg E, Nagel G, Deisseroth K.
Journal: Nat Neurosci. 2005 Sep;8(9):1263-8. Epub 2005 Aug 14.
In this research report, Deisseroth and his colleagues (particularly Ed Boyden, lead author and now a professor of Biological Engineering at the McGovern Institute for Brain Research at MIT) took the short section of DNA that provides the instructions for making Channelrhodopsin from green algae and they put that piece of DNA into neurons.
And when they then shined blue light on the neurons, guess what happened? Yes, the neurons became activated – that is to say, they produced an ‘action potential’, which is one of the way information is passed from one neuron to another.
Like I said ‘Magic’!
And the best part of this biological manipulation was that Deisseroth and his colleagues could activate the neurons with absolutely amazing precision! By pulsing light on the cells for just millisecond periods, they could elicit instant action potentials:
Precise control of the firing of a neuron. Source: Frontiers
And of course any surrounding cells that do not have the Channelrhodopsin DNA were not affected by the light, but were activated by the signal coming from the Channelrhodopsin+ cells.
This original research report lead to a gold rush-like search for other proteins that are light activated, and we now have an ever increasing toolbox of new proteins with curious properties. For example, we can now not only turn on neurons, but we also have proteins that can shut their activity down, blocking any action potentials (with proteins called ‘Halorhodopsin’ – click here for more on this). And many of these proteins are activated by different frequencies of light. It is really remarkable biology.
Two years after the first report of optogenetics, the first research demonstrating the use of this technology in the brain of a live animal was published (Click here and here to read more on this). And these fantastic tools are not just being used in the brain, they are being applied to tissues all over the body (for example, optogenetics can be used to make heart cells beat – click here to read more on this).
This TED talk video of Ed Boyden’s description of optogenetics is worth watching if you want to better understand the technique and to learn more about it:
Ok, so Dr Gittis and her colleagues used optogenetics in their research. What did they find?
Well, from previous research they knew that there were two types of neurons in the globus pallidus that regulate a lot of the activity in this region. The two types were identifiable by two different proteins: Lim homeobox 6 (Lhx6) and Parvalbumin (PV).
The Lhx6 neurons, which do not have any PV protein, are generally concentrated in the medial portion of the globus pallidus (closer to the centre of the brain). These Lhx6 neurons also have strong connections with the striatum and substantia nigra parts of the brain. The PV neurons, on the other hand, are more concentrated in the lateral portions of the globus pallidus (closer to the side of the brain), and they have strong connections with the thalamus (Click here to read this previous research).
In their new research report, Dr Gittis and her colleagues have used optogenetics to determine the functions of these two types of cells in the globus pallidus.
Initially, they stimulated both Lhx6 and PV neurons at the same time to see if they could restore movement in mice that had been treated with a neurotoxin (6-OHDA) that killed all the dopamine neurons. Unfortunately, they saw no rescue of the motor abilities of the mice.
They next shifted their attention to activating the two groups of cells separately to see if one of them was inhibiting the other. And when they stimulated the PV neurons alone, something amazing happened: the mice basically got up and started moving.
But the really mind blowing part: even after they turned off the stimulating light – after the pulse of light stopped – the mice were still able to keep moving around.
And this effect lasted for several hours! (note that the red line – indicating a decrease in immobility – in the image below remains stable after the stimulation of light pulses – blue lines – has stopped. Even between light pulses the mouse doesn’t return to immobility).
Stimulation of the PV neurons. Source: Nature
The investigators then tested the reverse experiment: inhibiting the Lhx6 neurons.
And guess what?
They found that by inhibiting the Lhx6 neurons with pulses of light, they could restore movement in the dopamine-depleted mice (and again for hours beyond stimulation – note the blue line in the image below remains even after the light pulses – green lines – have stopped).
Inhibiting of the Lhx6 neurons. Source: Nature
This result blew my mind at the conference in Vienna. And even now as I write this, I am still….well, flabbergasted! (there’s a good word).
In addition to being a very elegant experiment and use of this new optogenetic technology, this study opens new doors for us in the Parkinson’s disease research field regarding our understanding of how movement works and how we can now potentially treat PD.
Is optogentics being tested in the clinic?
The incredible answer to this question is: Yes.
A company in Ann Arbor (Michigan) called RetroSense Therapeutics announced in March of 2016 that they had treated their first subject in a Phase I/IIa, open-label, dose-escalation clinical study of the safety and tolerability of their lead product, RST-001 in patients with retinitis pigmentosa (Click here for the press release).
Retinitis pigmentosa is an inherited eye disease that causes severe vision impairment due to the progressive degeneration of the rod photoreceptor cells in the retina. The condition starts with patients experiencing progressive “tunnel vision” and eventual leads to blindness.
RetroSense’s lead product, RST-001 is basically a virus that infects cells with the photosensitivity gene, channelrhodopsin-2, that we discussed above. Several studies have demonstrated the ability of this approach to restore the perception of light and even vision in experimental models of blindness (Click here to read more about this).
The therapy involves injecting RST-001 into the retinas of patients who are blind. The infected cells will then fire when stimulated with blue light coming into the eye, and this information will hopefully be passed on to the brain. All going well, RetroSense plans to enroll 15 blind subjects in its trial, and they will follow them for two years. They hope to release some preliminary data, however, later this year. And a lot of people will be watching this trial and waiting for the results.
So, yes, optogenetics is being tested in humans.
Obviously, however, these are the first tentative steps in this new field. And it may be sometime before the medical regulatory bodies allow researchers to start conducting optogentic trials in the brain, let alone on people with Parkinson’s disease.
What does it all mean?
It is always rather wondrous where new discoveries take us.
A little over 10 years ago, some scientists discovered that by inserting a photosensitivity gene into brain cells they could control the firing of those cells with rapid pulses of light. And now other researchers are using that technology not only to better understand the works of our brains and how we move, but also to help make blind people see again.
Whether this technology will be able to replace therapies like deep brain stimulation with a more precise method of controlling the firing of the globus pallidus, is yet yo be seen. But this amazing new technique in our research toolbox will most certainly help to enhance our understanding of Parkinson’s disease. Taking us one step closer to ridding ourselves of it entirely.
The banner for today’s post was sourced from Scientifica
Last week scientists in Sweden published research demonstrating a method by which the supportive cells of the brain (called astrocytes) can be re-programmed into dopamine neurons… in the brain of a live animal!
It was a really impressive trick and it could have major implications for Parkinson’s disease.
In today’s post is a long read, but in it we will review the research leading up to the study, explain the science behind the impressive feat, and discuss where things go from here.
Different types of cells in the body. Source: Dreamstime
In your body at this present moment in time, there is approximately 40 trillion cells (Source).
The vast majority of those cells have developed into mature types of cell and they are undertaking very specific functions. Muscle cells, heart cells, brain cells – all working together in order to keep you vertical and ticking.
Now, once upon a time we believed that the maturation (or the more technical term: differentiation) of a cell was a one-way street. That is to say, once a cell became what it was destined to become, there was no going back. This was biological dogma.
Then a guy in Japan did something rather amazing.
Who is he and what did he do?
This is Prof Shinya Yamanaka:
Prof Shinya Yamanaka. Source: Glastone Institute
He’s a rockstar in the scientific research community.
Prof Yamanaka is the director of Center for induced Pluripotent Stem Cell Research and Application (CiRA); and a professor at the Institute for Frontier Medical Sciences at Kyoto University.
But more importantly, in 2006 he published a research report demonstrating how someone could take a skin cell and re-program it so that was now a stem cell – capable of becoming any kind of cell in the body.
Here’s the study:
Title: Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.
Authors: Takahashi K, Yamanaka S.
Journal: Cell. 2006 Aug 25;126(4):663-76.
PMID: 16904174 (This article is OPEN ACCESS if you would like to read it)
Shinya Yamanaka‘s team started with the hypothesis that genes which are important to the maintenance of embryonic stem cells (the cells that give rise to all cells in the body) might also be able to cause an embryonic state in mature adult cells. They selected twenty-four genes that had been previously identified as important in embryonic stem cells to test this idea. They used re-engineered retroviruses to deliver these genes to mouse skin cells. The retroviruses were emptied of all their disease causing properties, and could thus function as very efficient biological delivery systems.
The skin cells were engineered so that only cells in which reactivation of the embryonic stem cells-associated gene, Fbx15, would survive the testing process. If Fbx15 was not turned on in the cells, they would die. When the researchers infected the cells with all twenty-four embryonic stem cells genes, remarkably some of the cells survived and began to divide like stem cells.
In order to identify the genes necessary for the reprogramming, the researchers began removing one gene at a time from the pool of twenty-four. Through this process, they were able to narrow down the most effective genes to just four: Oct4, Sox2, cMyc, and Klf4, which became known as the Yamanaka factors.
This new type of cell is called an induced pluripotent stem (IPS) cell – ‘pluripotent’ meaning capable of any fate.
The discovery of IPS cells turned biological dogma on it’s head.
And in acknowledgement of this amazing bit of research, in 2012 Prof Yamanaka and Prof John Gurdon (University of Cambridge) were awarded the Nobel prize for Physiology and Medicine for the discovery that mature cells can be converted back to stem cells.
Prof Yamanaka and Prof Gurdon. Source: UCSF
Prof Gurdon achieved the feat in 1962 when he removed the nucleus of a fertilised frog egg cell and replaced it with the nucleus of a cell taken from a tadpole’s intestine. The modified egg cell then grew into an adult frog! This fascinating research proved that the mature cell still contained the genetic information needed to form all types of cells.
EDITOR’S NOTE: We do not want to be accused of taking anything away from Prof Gurdon’s contribution to this field (which was great!) by not mentioning his efforts here. For the sake of saving time and space, we are focusing on Prof Yamanaka’s research as it is more directly related to today’s post.
Making IPS cells. Source: learn.genetics
This amazing discovery has opened new doors for biological research and provided us with incredible opportunities for therapeutic treatments. For example, we can now take skins cells from a person with Parkinson’s disease and turn those cells into dopamine neurons which can then be tested with various drugs to see which treatment is most effective for that particular person (personalised medicine in it’s purest form).
Some of the option available to Parkinson’s disease. Source: Nature
Imagination is literally the only limiting factor with regards to the possible uses of IPS cell technology.
Shortly after Yamanaka’s research was published in 2006, however, the question was asked ‘rather than going back to a primitive state, can we simply change the fate of a mature cell directly?’ For example, turn a skin cell into a neuron.
This question was raised mainly to address the issue of ‘age’ in the modelling disease using IPS cells. Researchers questioned whether an aged mature cell reprogrammed into an immature IPS cell still carried the characteristics of an aged cell (and can be used to model diseases of the aged), or would we have to wait for the new cell to age before we can run experiments on it. Skin biopsies taken from aged people with neurodegenerative conditions may lose the ‘age’ element of the cell and thus an important part of the personalised medicine concept would be lost.
So researchers began trying to ‘re-program’ mature cells. Taking a skin cell and turning it directly into a heart cell or a brain cell.
And this is probably the craziest part of this whole post because they actually did it!
Different methods of inducing skin cells to become something else. Source: Neuron
In 2010, scientists from Stanford University published this report:
Title: Direct conversion of fibroblasts to functional neurons by defined factors
Authors: Vierbuchen T, Ostermeier A, Pang ZP, Kokubu Y, Südhof TC, Wernig M.
Journal: Nature. 2010 Feb 25;463(7284):1035-41.
In this study, the researchers demonstrated that the activation of three genes (Ascl1, Brn2 and Myt1l) was sufficient to rapidly and efficiently convert skin cells into functional neurons in cell culture. They called them ‘iN’ cells’ or induced neuron cells. The ‘re-programmed’ skin cells made neurons that produced many neuron-specific proteins, generated action potentials (the electrical signal that transmits a signal across a neuron), and formed functional connection (or synapses) with neighbouring cells. It was a pretty impressive achievement, which they beat one year later by converting mature liver cells into neurons – Click here to read more on this – Wow!
The next step – with regards to our Parkinson’s-related interests – was to convert skin cells directly into dopamine neurons (the cells most severely affected in the condition).
And guess what:
Title: Direct conversion of human fibroblasts to dopaminergic neurons.
Authors: Pfisterer U, Kirkeby A, Torper O, Wood J, Nelander J, Dufour A, Björklund A, Lindvall O, Jakobsson J, Parmar M
Journal: Proc Natl Acad Sci U S A (2011) 108:10343-10348.
PMID: 21646515 (This article is OPEN ACCESS if you would like to read it)
In this study, Swedish researchers confirmed that activation of Ascl1, Brn2, and Myt1l re-programmed human skin cells directly into functional neurons. But then if they added the activation of two additional genes, Lmx1a andFoxA2 (which are both involved in dopamine neuron generation), they could convert skin cells directly into dopamine neurons. And those dopamine neurons displayed all of the correct features of normal dopamine neurons.
With the publication of this research, it suddenly seemed like anything was possible and people began make all kinds of cell types out of skin cells. For a good review on making neurons out of skin cells – Click here.
Given that all of this was possible in a cell culture dish, some researchers started wondering if direct reprogramming was possible in the body. So they tried.
And again, guess what:
Title: In vivo reprogramming of adult pancreatic exocrine cells to beta-cells.
Authors: Zhou Q, Brown J, Kanarek A, Rajagopal J, Melton DA.
Journal: Nature. 2008 Oct 2;455(7213):627-32.
Using the activation of three genes (Ngn3, Pdx1 and Mafa), the investigators behind this study re-programmed differentiated pancreatic exocrine cells in adult mice into cells that closely resemble b-cells. And all of this occurred inside the animals, while the animals were wandering around & doing their thing!
Now naturally, researchers in the Parkinson’s disease community began wondering if this could also be achieved in the brain, with dopamine neurons being produced from re-programmed cells.
And (yet again) guess what:
Title: Generation of induced neurons via direct conversion in vivo
Authors: Torper O, Pfisterer U, Wolf DA, Pereira M, Lau S, Jakobsson J, Björklund A, Grealish S, Parmar M.
Journal: Proc Natl Acad Sci U S A. 2013 Apr 23;110(17):7038-43.
PMID: 23530235 (This article is OPEN ACCESS if you would like to read it)
In this study, the Swedish scientists (behind the previous direct re-programming of skin cells into dopamine neurons) wanted to determine if they could re-program cells inside the brain. Firstly, they engineered skin cells with the three genes (Ascl1, Brn2a, & Myt1l) under the control of a special chemical – only in the presence of the chemical, the genes would be activated. They next transplanted these skin cells into the brains of mice and began adding the chemical to the drinking water of the mice. At 1 & 3 months after transplantation, the investigators found re-programmed cells inside the brains of the mice.
Next, the researchers improved on their recipe for producing dopamine neurons by adding the activation of two further genes: Otx2 and Lmx1b (also important in the development of dopamine neurons). So they were now activating a lot of genes: Ascl1, Brn2a, Myt1l, Lmx1a, FoxA2, Otx2 and Lmx1b. Unfortunately, when these reprogrammed cells were transplanted into the brain, few of them survived to become mature dopamine neurons.
The investigators then ask themselves ‘do we really need to transplant cells? Can’t we just reprogram cells inside the brain?’ And this is exactly what they did! They injected the viruses that allow for reprogramming directly into the brains of mice. The experiment was designed so that the cargo of the viruses would only become active in the astrocyte cells, not neurons. And when the researchers looked in the brains of these mice 6 weeks later, they found numerous re-programmed neurons, indicating that direct reprogramming is possible in the intact brain.
So what was so special about the research published last week about? Why the media hype?
The research published last week, by another Swedish group, took this whole process one step further: Not only did they re-program astrocytes in the brain to become dopamine neurons, but they also did this on a large enough scale to correct the motor issues in a mouse model of Parkinson’s disease.
Title: Induction of functional dopamine neurons from human astrocytes in vitro and mouse astrocytes in a Parkinson’s disease model
Authors: di Val Cervo PR, Romanov RA, Spigolon G, Masini D, Martín-Montañez E, Toledo EM, La Manno G, Feyder M, Pifl C, Ng YH, Sánchez SP, Linnarsson S, Wernig M, Harkany T, Fisone G, Arenas E.
Journal: Nature Biotechnology (2017) doi:10.1038/nbt.3835
These researchers began this project 6 years ago with a new cocktail of genes for reprogramming cells to become dopamine neurons. They used the activation of NEUROD1, ASCL1 and LMX1A, and a microRNA miR218 (microRNAs are genes that produce RNA, but not protein – click here for more on this). These genes improved the reprogramming efficiency of human astrocytes to 16% (that is the percentage of astrocytes that were infected with the viruses and went on to became dopamine neurons). The researchers then added some chemicals to the reprogramming process that helps dopamine neurons to develop in normal conditions, and they observed an increase in the level of reprogramming to approx. 30%. And these reprogrammed cells display many of the correct properties of dopamine neurons.
Next the investigators decided to try this conversion inside the brains of mice that had Parkinson’s disease modelled in them (using a neurotoxin). The delivery of the viruses into the brains of these mice resulted in reprogrammed dopamine neurons beginning to appear, and 13 weeks after the viruses were delivered, the researchers observed improvements in the Parkinson’s disease related motor symptoms of the mice. The scientists concluded that with further optimisation, this reprogramming approach may enable clinical therapies for Parkinson’s disease, by the delivery of genes rather than transplanted cells.
How does this reprogramming work?
As we have indicated above, the re-programming utilises re-engineered viruses. They have been emptied of their disease causing elements, allowing us to use them as very efficient biological delivery systems. Importantly, retroviruses infect dividing cells and integrate their ‘cargo’ into the host cell’s DNA.
Retroviral infection and intergration into DNA. Source: Evolution-Biology
The ‘cargo’ in the case of IPS cells, is a copy of the genes that allow reprogramming (such as the Yamanaka genes), which the cell will then start to activate, resulting in the production of protein for those genes. These proteins subsequently go on to activate a variety of genes required for the maintenance of embryonic stem cells (and re-programming of mature cells).
And viruses were also used for the re-programming work in the brain as well.
There is the possibility that one day we will be able to do this without viruses – in 2013, researchers made IPS cells using a specific combination of chemicals (Click here to read more about this) – but at the moment, viruses are the most efficient biological targeting tool we have.
So what does it all mean?
Last week researchers is Sweden published research explaining how they reprogrammed some of the helper cells in the brains of Parkinsonian mice so that they turned into dopamine neurons and helped to alleviate the symptoms the mice were feeling.
This result and the trail of additional results outlined above may one day be looked back upon as the starting point for a whole new way of treating disease and injury to particular organs in the body. Suddenly we have the possibility of re-programming cells in our body to under take a new functions to help combat many of the conditions we suffer.
It is important to appreciate, however, that the application of this technology is still a long way from entering the clinic (a great deal of optimisation is required). But the fact that it is possible and that we can do it, raises hope of more powerful medical therapies for future generations.
As the researchers themselves admit, this technology is still a long way from the clinic. Improving the efficiency of the technique (both the infection of the cells and the reprogramming) will be required as we move down this new road. In addition, we will need to evaluate the long-term consequences of removing support cells (astrocytes) from the carefully balanced system that is the brain. Future innovations, however, may allow us to re-program stronger, more disease-resistant dopamine neurons which could correct the motor symptoms of Parkinson’s disease without being affected by the disease itself (as may be the case in transplanted cells – click here to read more about this).
Watch for a lot more research coming from this topic.
The banner for today’s post was sourced from Greg Dunn (we love his work!)