Genetic mutations (or ‘variants’) in the Leucine-rich repeat kinase 2 (or LRRK2; also known as Dardarin) gene are associated with increased risk of Parkinson’s. As a result this gene has become the focus of a lot of genetic research.
But what about LRRK2’s less well-known, rather neglected sibling LRRK1?
In today’s post, we will look at new research that suggests the LRRK siblings could both be involved with Parkinson’s disease.
I recommend to the reader that today’s post should be read with the following music playing in the background:
Inspired by a poem of the same title, English composer Ralph Vaughan Williams wrote ‘The Lark Ascending’ in 1914. It is still to this day, a tune that remains a firm favourite with BBC listeners here in the UK (Source).
On to business:
While the music and the poem are about a songbird, today’s SoPD post deals with a different kind of Lark.
Or should I say LRRK.
This is Sergey Brin.
He was one of the founders of a small company you may have heard of – it’s called “Google”.
Having changed the way the world searches the internet, he is now turning his attention to other projects.
One of those other projects is close to our hearts: Parkinson’s disease.
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?
Mitochondrial division inhibitor-1 (mdivi-1) is a small molecule drug that is demonstrating very impressive effects in preclinical models of Parkinson’s disease. With further research it could represent a potential future therapy for people with Parkinson’s disease, particularly those with genetic mutations affecting the mitochondria in their cells.
What are mitochondria?
In this post, we will explain what mitochondria are, how they may be involved in Parkinson’s disease, and we will discuss what the results of new research mean for future therapeutic strategies.
Mitochondria are fascinating.
Utterly. Utterly. Fascinating.
On the most basic level, Mitochondria (mitochondrion, singular; from the Greek words mitos (thread) and chondros (granule)) are just tiny little bean-shaped structures within the cells in our body, and their primary function is to act as the power stations. They supply the bulk of energy that cells require to keep the lights on. This chemical form of energy produced by the mitochondria is called adenosine triphosphate (or ATP). Lots of mitochondria are required in each cell to help keep the cell alive (as is shown in the image below, which is showing just the mitochondria (red) and the nucleus (blue) of several cells).
Lots of mitochondria (red) inside cells (nucleus in blue). Source: Clonetech
That’s the basic stuff – the general definition you will find in most text books on biology.
But let me ask you this:
How on earth did mitochondria come to be inside each cell and playing such a fundamental role?
I don’t know. Are you going to tell me?
Because we simply don’t know.
But understand this: Mitochondria are intruders.
In October 2015, researchers from Georgetown University announced the results of a small clinical trial that got the Parkinson’s community very excited. The study involved a cancer drug called Nilotinib, and the results were rather spectacular.
What happened next, however, was a bizarre sequence of disagreements over exactly what should happen next and who should be taking the drug forward. This caused delays to subsequent clinical trials and confusion for the entire Parkinson’s community who were so keenly awaiting fresh news about the drug.
Earlier this year, Georgetown University announced their own follow up phase II clinical trial and this week a second phase II clinical trial funded by a group led by the Michael J Fox foundation was initiated.
In todays post we will look at what Nilotinib is, how it apparently works for Parkinson’s disease, what is planned with the new trial, and how it differs from the ongoing Georgetown Phase II trial.
The FDA. Source: Vaporb2b
This week the U.S. Food and Drug Administration (FDA) has given approval for a multi-centre, double-blind, randomised, placebo-controlled Phase IIa clinical trial to be conducted, testing the safety and tolerability of Nilotinib (Tasigna) in Parkinson’s disease.
This is exciting and welcomed news.
What is Nilotinib?
Nilotinib (pronounced ‘nil-ot-in-ib’ and also known by its brand name Tasigna) is a small-molecule tyrosine kinase inhibitor, that has been approved for the treatment of imatinib-resistant chronic myelogenous leukemia (CML).
What does any that mean?
Basically, it is the drug that is used to treat a type of blood cancer (leukemia) when the other drugs have failed. It was approved for treating this cancer by the FDA in 2007.
Last week at the SoPD, we received an interesting email from reader Gabriel “from Tiana (near Barcelona) (Spain)”. The email brought our attention to an interesting new article that was published in a recent issue of the Journal of Neuroscience.
The research report involves prolyl oligopeptidase (PREP) inhibitors and some pre-clinical data involving a model of Parkinson’s disease.
In today’s post we will review the article and what we know about PREP-inhibitors.
Yes, I know. The obvious first question is:
What is prolil oligoopep..tid… whatever?
It’s really very simple. Prolyl oligopeptidase is a serine protease, that cleaves short peptides containing proline-residue.
Prolyl oligopeptidase (or PREP) is an enzyme that is involved in the making and destruction of certain types of hormones and neuropeptides (Neuropeptides are a group of small molecules used by brain cells to communicate with each other). PREP is required for cutting certain bonds on some of these small molecules, allowing them to function normally or be broken down and recycled.
PREP can be found in cells from most of species – from bacteria to human – suggesting that it has important functions across evolution. In addition, PREP has been associated with amnesia, depression and blood pressure control.
What is has PREP got to do with Parkinson’s disease?
Interestingly, PREP activity changes during the ageing process. It also changes during neurodegenerative conditions, such as Alzheimer’s and Parkinson’s diseases.
Given this situation, several PREP inhibitors were developed during the 1990s, and they were found to have a positive effect on memory and learning in animal models of Alzheimer’s disease (Click here for more on this).
So what is known about PREP in Parkinson’s disease?
Back in 1987, a group of researchers noticed something interesting in the cerebrospinal fluid (the liquid surrounding the brain) of people with Parkinson’s disease:
Title: Post-proline cleaving enzyme in human cerebrospinal fluid from control patients and parkinsonian patients.
Authors: Hagihara M, Nagatsu T.
Journal: Biochem Med Metab Biol. 1987 Dec;38(3):387-91.
When the researchers compared normal healthy subjects with people who have Parkinson’s disease, they found that people with Parkinson’s disease exhibited a marked decrease in the activity of PREP in the cerebrospinal fluid. Interestingly, this decrease was not evident in the blood, suggesting that something was happening in the brain.
This observation was later followed up by other findings, including this journal report:
Title: Prolyl oligopeptidase colocalizes with α-synuclein, β-amyloid, tau protein and astroglia in the post-mortem brain samples with Parkinson’s and Alzheimer’s diseases.
Authors: Hannula MJ, Myöhänen TT, Tenorio-Laranga J, Männistö PT, Garcia-Horsman JA.
Journal: Neuroscience. 2013 Jul 9;242:140-50.
The researchers in this study were investigating where PREP was actually located in the postmortem brain. In people with Parkinson’s disease, they found that a very strong presence of PREP in the substantia nigra (the region which loses dopamine neurons in this condition).
Interestingly, they also noted that PREP was co-localized with the Parkinson’s associated protein alpha synuclein (meaning where they found PREP, they also saw alpha synuclein). It is also interesting to note that they did not see this pattern in the brains of normal healthy controls or people with Alzheimer’s disease.
In 2008, another group found that PREP not only co-localised with alpha synuclein, but it was also doing something quite unexpected:
Title: Prolyl oligopeptidase stimulates the aggregation of alpha-synuclein.
Authors: Brandt I, Gérard M, Sergeant K, Devreese B, Baekelandt V, Augustyns K, Scharpé S, Engelborghs Y, Lambeir AM.
Journal: Peptides. 2008 Sep;29(9):1472-8.
Since alpha synuclein and PREP were in the same locations in the Parkinsonian brain, the researchers in this paper were interested to see if the two protein actually functioned together and required each other to do their respective jobs. What they found, however, when they put the proteins together in cell culture was a surprise: an acceleration in the accumulation (or aggregation) of alpha synuclein.
Aggregation of alpha synuclein is a key feature of the Parkinsonian brain. It is believed to be responsible for the presence of Lewy bodies (the dense circular clusters in cells in the brains of people with Parkinson’s disease) and may be involved in the cell death associated with the condition.
A lewy body (brown with a black arrow) inside a cell. Source: Cure Dementia
With the discovery that PREP is involved with the aggregation of alpha synuclein, the researchers suddenly had a new disease-related target to investigate further. And this is what the new Journal of Neuroscience paper has been explored.
So what was published in the recent Journal of Neuroscience report?
This is Timo.
Dr Timo Myöhänen. Source: University of Helsinki
He’s a dude.
He is also an adjunct professor at the University of Helsinki where he has a research group focused on neurodegenerative disorders. They have a particular interest in PREP and they are the people behind the Journal of Neuroscience research report:
Title: Inhibition of Prolyl Oligopeptidase Restores Spontaneous Motor Behavior in the α-Synuclein Virus Vector-Based Parkinson’s Disease Mouse Model by Decreasing α-Synuclein Oligomeric Species in Mouse Brain.
Authors: Svarcbahs R, Julku UH, Myöhänen TT.
Journal: J Neurosci. 2016 Dec 7;36(49):12485-12497.
Previously Timo and co. have demonstrated that PREP inhibitors can reduce the levels of alpha synuclein in a genetically engineered mouse that produces very higher levels of alpha synuclein (click here to read that report).
In the current study, they modelled Parkinson’s disease in mice using viruses that cause the production of high levels of alpha synuclein in the dopamine neurons (that are affected by Parkinson’s disease). This over-production of alpha synuclein causes problems for the dopamine neurons and some of those cells die off, in effect modelling what is happening in the brains of people with Parkinson’s disease.
Using a PREP inhibitor (KYP-2047, which is crosses the blood–brain barrier), the researchers were able to rescue the behavioural impairment caused by the viral over-production of alpha synuclein. In addition, the administration of the PREP inhibitor reduced the levels of certain types of alpha synuclein in the brain.
The researchers also saw a mild neuroprotective effect with less dopamine neurons dying (perhaps if the study had continued for longer they might have seen a larger difference) and less dopamine dysfunction in the animals that received the PREP inhibitor, suggesting that treatment with the PREP inhibitor protected the dopamine neurons and restored their normal functions.
The critical aspect of this study was that the PREP inhibitor treatment was only given to the animals after the behavioural problems started, and it was still able to provide positive benefits to them. The researchers concluded that these results suggest that PREP inhibitors should be further investigated for Parkinson’s disease.
What does it all mean?
We have had a spate of promising therapies for Parkinson’s disease fail over the last 10-20 years:
- Tocopherol (Parkinson Study Group, 1993)
- Immunophilin (Gold & Nut, 2002)
- Omigapil (TCH346; Olanow et al. 2006)
- CEP1347 (Parkinson Study Group PRECEPT Investigators, 2007)
- Pramipexole (Schapira et al, 2013)
- coenzyme Q10 (Parkinson Study Group QE3 Investigators et al, 2014)
- Cogane (Phytopharm)
- AAV-Neurturin (Ceregene)
Just to name a few…
We desperately need some new and novel targets to help attack this disease, and PREP inhibitors represent a completely new approach. Yes, they are going after alpha synuclein (and the jury is still out as to whether alpha synuclein is a causal agent in the disease), but they are certainly taking a different route.
While the alpha synuclein vaccines and antibodies currently being tested in clinic trials are removing free floating alpha synuclein, PREP inhibitors are stopping alpha synclein from actually aggregating. This is exactly the kind of new approach we are looking for.
Whether PREP inhibitors reducing alpha synuclein aggregation is functionally a good thing for Parkinson’s disease requires further testing. For example, if alpha synuclein is playing an antimicrobial function by aggregating around bacteria/viruses, inhibiting that aggregation might not be a good thing – it might leave us more vulnerable to illness.
But the good news here is that PREP inhibitors represent a new direction for us to explore in the treatment of Parkinson’s disease, and if blocking alpha synuclein aggregation does slow/halt the disease then PREP will definitely be worthy of further investigation.
EDITORIAL NOTE: Full disclosure here, the author of this blog is neither collaborating nor familiar with Dr Timo Myohanen. We just think his research is pretty cool and look forward to seeing where this line of investigation will ultimately lead.
And yes, we’re writing nice things about him in the hope that he won’t mind us borrowing some of the schematics and images from his lab website to better explain what PREP is.