We are going to talk about a snail model of Parkinson’s disease. I kid you not.
Love them or hate them, recent research on snails is helping us to better understand a potential therapeutic target for Parkinson’s disease, called Pituitary adenylate cyclase-activating polypeptide (or PACAP).
In today’s post we will look at what PACAP is, outline the new snail research, and discuss what they mean for people living with Parkinson’s disease.
The humble snail. Source: Warrenphotographic
In a recent post, I talked about a class of drugs called Dipeptidyl peptidase-4 (or DPP-4) inhibitors (Click here to read that post). DPP-4 is a ubiquitous enzyme (it is present on most cells in your body) that breaks down certain proteins.
In that post, I listed some of the proteins that DPP-4 targets – they include:
- Gastrin-releasing peptide (GRP)
- Glucagon-like peptide-1 (GLP-1)
- Glucagon-like peptide-2 (GLP-2)
- Granulocyte-macrophage colony-stimulating factor (GM-CSF)
- GHRH and IGF-1
- High-mobility group box 1 (HMGB1)
- Macrophage-derived chemokine (MDC)
- Macrophage inflammatory protein-1 α (MIP-1 α), chemokine (C-C motif) ligand 3-like 1 (CCL3L1), or LD78β
- Pituitary adenylate cyclase-activating polypeptide (PACAP)
- Neuropeptide Y (NPY)
- Regulated on activation, normal T cell expressed and secreted (Rantes)
- Stromal cell-derived factor-1 (SDF-1)
- Substance P (SP)
Lots of interesting proteins with regards to Parkinson’s disease on this list, including GLP-1 which has been turned in the drug Exenatide (which has demonstrated positive effects in recent clinical trials for Parkinson’s disease – click here and here to read more about this). Another interesting protein on the list is ‘Granulocyte-macrophage colony-stimulating factor‘ (GM-CSF) which we have also discussed in a previous post (Click here to read that post). A synthetic version of GM-CSF (called Sargramostim) has recently been tested in a clinical trial of Parkinson’s disease in Nebraska, and the results of that Phase I trial have been very encouraging.
By treating people with DPP-4 inhibitors (also known as ‘gliptins’), one would be blocking the breaking down of these potentially beneficial proteins – increasing the general amount of GLP-1 and GMCSF that is floating around in the body.
EDITOR’S NOTE: DPP-4 inhibitors have not yet been clinically tested in Parkinson’s disease, and thus we have no idea if they are safe in people with this condition. They are being mentioned here purely as part of an academic discussion.
One protein on the list of DPP-4 targets above that we have not yet discussed is Pituitary adenylate cyclase-activating polypeptide (or PACAP).
And today we are going to have a look at it.
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.