Ursodeoxycholic acid (UDCA) has been proposed as a drug that could be repurposed for Parkinson’s. As a medication, it is called ‘Ursodiol‘ and it is used to treat gallstones.
But there are absorption issues with UDCA: The passage of UDCA through the wall of the small intestine is slow and incomplete (Source).
There may be a solution, however, called Tauroursodeoxycholic acid (TUDCA). Think of it as UDCA-2.0. It is more easily absorbed by the gut. And there is also good evidence to suggest that it has the same beneficial neuroprotective properties as UDCA.
In today’s post we will discuss what exactly UDCA and TUDCA are, review the Parkinson’s research for both, and discuss why one of these drugs should be tested in the clinic for PD.
Gallstones – ouch! Source: Healthline
Let me introduce you to your gallbladder:
It is one of the less appreciated organs; a pear-shaped, hollow organ located just under your liver and on the right side of your body. Its primary function is to store and concentrate your bile. Bile is a yellow-brown digestive enzyme – made and released by the liver – which helps with the digestion of fats in your small intestine (the duodenum).
Now, let me introduce you to your gallstones:
Gallstones are hardened deposits that can form in your gallbladder. About 80% of gallstones are made of cholesterol. The remaining 20% of gallstones are made of calcium salts and bilirubin. Bilirubin is the yellow pigment in bile. When the body produces too much Bilirubin or cholesterol, gallstones can develop.
About 10-20% of the population have gallstones (Source), but the vast majority experience no symptoms and need no treatment.
Interesting intro, but what does any of this have to do with Parkinson’s?
One of the treatments for gallstones is called UDCA. And this compound is being considered for “repurposing” as a treatment for Parkinson’s.
What is UDCA?
Today’s (experimental) post provides something new – an overview of some of the major bits of Parkinson’s-related research that were made available in January 2018.
In January of 2018, the world was rocked by news that New Zealand had become the 11th country in the world to put a rocket into orbit (no really, I’m serious. Not kidding here – Click here to read more). Firmly cementing their place in the rankings of world superpowers. In addition, they became only the second country to have a prime minister get pregnant during their term in office (in this case just 3 months into her term in office – Click here to read more about this).
In major research news, NASA and NOAA announced that 2017 was the hottest year on record globally (without an El Niño), and among the top three hottest years overall (Click here for more on this), and scientists in China reported in the journal Cell that they had created the first monkey clones, named Zhong Zhong and Hua Hua (Click here for that news)
Zhong Zhong the cute little clone. Source: BBC
At the end of each year, it is a useful practise to review the triumphs (and failures) of the past 12 months. It is an exercise of putting everything into perspective.
2017 has been an incredible year for Parkinson’s research.
And while I appreciate that statements like that will not bring much comfort to those living with the condition, it is still important to consider and appreciate what has been achieved over the last 12 months.
In this post, we will try to provide a summary of the Parkinson’s-related research that has taken place in 2017 (Be warned: this is a VERY long post!)
The number of research reports and clinical trial studies per year since 1817
As everyone in the Parkinson’s community is aware, in 2017 we were observing the 200th anniversary of the first description of the condition by James Parkinson (1817). But what a lot of people fail to appreciate is how little research was actually done on the condition during the first 180 years of that period.
The graphs above highlight the number of Parkinson’s-related research reports published (top graph) and the number of clinical study reports published (bottom graph) during each of the last 200 years (according to the online research search engine Pubmed – as determined by searching for the term “Parkinson’s“).
PLEASE NOTE, however, that of the approximately 97,000 “Parkinson’s“-related research reports published during the last 200 years, just under 74,000 of them have been published in the last 20 years.
That means that 3/4 of all the published research on Parkinson’s has been conducted in just the last 2 decades.
And a huge chunk of that (almost 10% – 7321 publications) has been done in 2017 only.
So what happened in 2017? Continue reading
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.
Audrey Hepburn was taking about the city when she uttered the words that title this post, but today we will be talking about the protein that bears the same name: PARIS.
Last week new research was published which demonstrated that in the absence of Parkin and Pink1 protein, the protein PARIS builds up and becomes toxic for cells.
Today’s post will review that research and we’ll discuss what it all means for Parkinson’s disease.
No label required. A magnificent city. Source: HathawaysofHaworth
Today’s post has nothing to do with the city of Paris, but it is always nice to have photos of this European capital gracing the page.
We have recently discussed the Parkinson’s associated proteins Pink1 and Parkin (click here for that post). Today we will be revisiting these proteins as we discuss another protein that they interact with: PARIS (specifically PARIS1).
What is PARIS?
PARIS (aka TBC1D2 or TBC1 Domain Family Member 2) is a GTPase-activating protein.
What does that mean?
Getting a signal from outside of a cell into the interior is a complicated affair. There are numerous ways to do it, but one of the most common involves ‘G-proteins‘. These are involved with transmitting a signal from the outside of a cell into the interior, and when inside the cell G-proteins act as molecular switches.
G-proteins are located inside the cell membrane and are activated by G-protein-coupled receptors. When a signaling molecule binds to the G-protein-coupled receptor on the outside of the cell membrane, the portion of the receptor inside the cell activates the G-protein which then starts of a chain of events resulting in the signal being passed on.
The role of GTPase-Activating Proteins in this process is to turn the G protein’s activity off. In step 4 of the image above, a GTPase-Activating Protein (which is not shown) binds to the G-protein and terminate the activity of the signalling event – returning it to an inactive state.
Thus, GTPase-Activating Proteins – like PARIS – are important regulators of signalling inside the cell.
What do we know about PARIS1 in Parkinson’s disease?
So a few years ago, a group of researchers led by Prof Ted Dawson at John Hopkins School of Medicine published this study:
Title: PARIS (ZNF746) repression of PGC-1α contributes to neurodegeneration in Parkinson’s disease.
Authors: Shin JH, Ko HS, Kang H, Lee Y, Lee YI, Pletinkova O, Troconso JC, Dawson VL, Dawson TM.
Journal: Cell. 2011 Mar 4;144(5):689-702.
PMID: 21376232 (This article is OPEN ACCESS if you would like to read it)
In this study, the researchers noticed that the protein PARIS was accumulating in cells that did not have the Parkinson’s associated protein, Parkin. In those cells, the Parkin gene was mutated so that the Parkin protein was not produced properly. The researchers discovered that Parkin was important for labelling old PARIS protein for disposal. Thus in the absence of Parkin, PARIS protein would not be disposed of and simply piled up.
This build up of PARIS resulted in the loss of dopamine neurons in mice that did not produce Parkin. When the researchers re-introduced normal Parkin protein, the researchers were able to rescue the cell loss. Interestingly, the researchers also found that over production of PARIS in normal mice resulted in cell loss which could be rescued by a similar over production of Parkin.
When they looked in postmortem human brains, the researchers found that levels of PARIS protein were more than two times higher in regions affected by Parkinson’s disease (the striatum and the substantia nigra) of people with sporadic Parkinson’s disease when compared to healthy controls. Interestingly, this increase was only seen with PARIS protein, and not PARIS RNA (where the scientists saw no different with control samples), suggesting a build up of PARIS protein in the Parkinsonian brain.
The investigators concluded that this meant PARIS was could be playing a role in the cell loss associated with Parkinson’s disease.
They followed up this research a few years later with this publication:
Title: Parkin loss leads to PARIS-dependent declines in mitochondrial mass and respiration.
Authors: Stevens DA, Lee Y, Kang HC, Lee BD, Lee YI, Bower A, Jiang H, Kang SU, Andrabi SA, Dawson VL, Shin JH, Dawson TM.
Journal: Proc Natl Acad Sci U S A. 2015 Sep 15;112(37):11696-701.
PMID: 26324925 (This article is OPEN ACCESS if you would like to read it)
In this study, the same researchers found that when they remove the Parkin protein from the brains of adult mice there would be a decrease in the size and number of mitochondria. We have previous discussed mitochondria – the power stations of the cell – and their loss is bad news for a cell (click here to read more on mitochondria).
The researchers next demonstrated that this loss of mitochondria could reversed by removing PARIS protein from the Parkin mutant mice, and this prevented the loss of dopamine neurons. They also showed that the loss of mitochondria (and loss of dopamine neurons) could be caused by over production of PARIS in normal mice.
These results pointed towards an important role for both Parkin and PARIS in the maintenance of healthy mitochondria.
So what new research has been published about PARIS1?
This study was published last week:
Title: PINK1 Primes Parkin-Mediated Ubiquitination of PARIS in Dopaminergic Neuronal Survival.
Authors: Lee Y, Stevens DA, Kang SU, Jiang H, Lee YI, Ko HS, Scarffe LA, Umanah GE, Kang H, Ham S, Kam TI, Allen K, Brahmachari S, Kim JW, Neifert S, Yun SP, Fiesel FC, Springer W, Dawson VL, Shin JH, Dawson TM.
Journal: Cell Rep. 2017 Jan 24;18(4):918-932.
PMID: 28122242 (This article is OPEN ACCESS if you would like to read it)
In their study the researchers found that Parkin is not the only Parkinson’s associated protein in the PARIS story.
We have previously talked about the protein Pink1 (click here to read more on) – and yes, you would be forgiven if you start to think that all Parkinson’s related proteins start with the latter ‘P’. Pink1 grabs Parkin and causes it to bind to dysfunctional mitochondria. Parkin then signals to the rest of the cell for that particular mitochondria to be disposed of. In this study, the researchers found that Pink1 also grabs PARIS and signals for Parkin to dispose of it. In the absence of Pink1, normal Parkin protein does not label old PARIS protein for disposal and PARIS starts to pile up.
The researchers then began manipulating the levels of Pink in the brains of mice and they observed PARIS-dependent cell loss – that is to say, in the absence of Pink1, cells died only when PARIS was present.
These findings suggest that therapies targeting PARIS could be used in people with Parkinson’s disease who are carrying either a Parkin or a Pink1 mutation (both very common in early onset Parkinson’s disease).
What does it all mean?
People with early onset Parkinson’s disease quite often have a genetic mutation in one of a small number of genes – Pink1 and Parkin being prominent amongst these genes. The researchers who conducted the study that we have reviewed today have identified a common mechanism by which both of these proteins could be acting in their roles in Parkinson’s disease: a protein called PARIS.
Currently there is no treatment (that we are aware of) that targets the PARIS protein – nothing in the clinic nor being experimentally tested. Obviously, however, PARIS represents a VERY interesting protein for further investigations. The Dawson lab has several patents on PARIS (Click here and here for more on these), so evidently people will be working on drug candidates that inhibit PARIS.
There is a naturally occurring inhibitor, a micro RNA cluster miR-17-92 (also known as oncomir-1), which reduces the production of PARIS protein by blocking PARIS RNA (Click here for more on this). Using this micro RNA to target PARIS will be very difficult (both activating/delivering the micro RNA and unknown off target effects).
We are assuming that Prof Dawson and colleagues are rapidly screening compounds to determine which can block or inhibit PARIS activity and we will eagerly wait to see the results of that work.
Watch this space.
The banner for today’s post was sourced from Wallpapercave
EDITORIAL NOTE: Yay, 100 posts!