It all began with a 51 year old woman named Auguste Deter.
Auguste Deter. Source: Wikipedia
She was admitted by her husband to the Institution for the Mentally Ill and for Epileptics in Frankfurt, Germany on the 25th November, 1901. Her husband complained that she suffering memory loss and having delusions.
The attending doctor was Dr Alois Alzheimer.
Over the next year, Alois continued to examine Auguste – and what he began calling the “Disease of Forgetfulness” – until he left the institute to take up a position in Munich. He made regular visits back to Frankfurt, however, to follow up on Auguste.
Auguste dies on the 8th April, 1906. She had become completely demented and had existed in a vegatative state. When he examined the brain, Alois found the hall marks of what we today call ‘Alzheimer’s disease’ (namely neurofibrillary tangles and plaques).
Now, almost 110 years later, Alzheimer’s disease is the most common neurodegenerative condition – Parkinson’s disease is the second most common. Alzheimer’s affects 850,000 people in the UK alone (Source: Alzheimer’s Society). Huge efforts have been made in researching this condition and last week some interesting new data was published about the disease that may also have implications for Parkinson’s disease.
Title: Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy.
Authors: Jaunmuktane Z, Mead S, Ellis M, Wadsworth JD, Nicoll AJ, Kenny J, Launchbury F, Linehan J, Richard-Loendt A, Walker AS, Rudge P, Collinge J, Brandner S.
Journal: Nature. 2015 Sep 10;525(7568):247-50.
Published in the prestigious science journal, Nature, the article found signs of Alzheimer’s disease in the autopsied brains of people who had died from Creutzfeldt-Jakob disease (CJD) – the prion induced neurodegenerative condition.
What’s a prion?
Good question! A prion is a small infectious particle – usually composed of an abnormally-folded version of a normal bodily protein – that causes progressive neurodegenerative conditions. The first prion discovered in mammals was Prion protein (PRP): this is the prion that causes CJD.
PrP is considered the only known prion in mammals, but recently other proteins have exhibited prion-like behaviour. One such protein is Amyloid-β protein – the protein that is found clustered in clumps in the brains of people with Alzheimer’s disease.
The brains that were analysed in the study from the journal Nature were collected at death from people who had received human growth-hormone earlier in their lives. The growth-hormone had been extracted from human cadavers and it was injected into people with growth problems (this was a common practise during the 1950s to mid 1980s). Unfortunately, some of the growth-hormone appears to have been contaminated with PrP (possibly one of the cadavers used had undiagnosed CJD) and numerous people were injected with it (65 cases in Britain alone). Many of these individuals have been followed and we have learned a great deal from them regarding CJD. Some of these individuals have also donated their brains to science and it was some of these brains that were analysed in the study being discussed here.
What the authors of the study were expecting to see when they analysed these brains was lots of clusters of PrP. What the authors were not expecting to see was the clustering of Amyloid-β protein in these brains.
Amyloid-β protein (brown) in a section of brain tissue. Source: Nature
Of the eight brains (from people who received PrP infected growth-hormone) the authors analysed, six of them had clustering of Amyloid-β protein present in the brain (in four of those cases it was wide-spread). These brains came from people aged between aged 36–51 years – in such cases it is very rare to see large accumulations of Amyloid-β protein. The researchers also analysed the DNA of the individuals involved in the study and found that none of them were genetically susceptible to Alzheimer’s disease.
The researchers then compared these six brain with the brains of people who died from CJD caused by other means – 119 brains in total and none of them had Amyloid-β protein present in the brain. From these and other experiments, the authors suggested that this was the first human evidence of transmission of Alzheimer’s related pathology.
It is very important to note several details in the study:
1. None of the people whose brains were used in the study exhibited the clinical signs of Alzheimer’s.
2. None of the brains with Amyloid-β pathology had what is called ‘hyperphosphorylated tau neurofibrillary tangles’ – SImilar clumps of Amyloid-β protein, tau neurofibrillary tangles are another characteristic feature of Alzheimer’s disease brains. Their absence is curious.
3. The authors can not dismiss the possibility that the Amyloid-β was not present in the growth-hormone solution. In this case, the Amyloid-β accumulation in the brains could have been caused by some other unknown agent that was present in the injected solution.
A rare editorial note here: The Science of PD is disappointed with the way that this study has been handled by the wider media. While the results are interesting and the authors can be congratulated on their work, a correct interpretation of the results requires further study. This study has simply demonstrated was that Amyloid-β protein may be transmissible in a similar fashion to PrP.
So why are we discussing this Alzheimer’s research here at the Science of Parkinson’s Disease?
Well, for a long time now Parkinson’s researchers have suspected that similar mechanisms may underlying what is happening in PD. That is to say, a prion-like protein may be transmitted between cells in the body (possibly from the gut to the brain – see previous posts) allowing the disease to progress. One protein in particular, Alpha Synuclein, which is present in Lewy bodies – the neurological features associated with Parkinson’s disease, has been implicated in this regards. Recent evidence from lab-based studies suggest that this is possible in cell cultures and in rodents, but whether it is possible in humans is yet to be determined.
NOTE: Since publishing this post, we contacted the authors of the study regarding the presence of Alpha Synuclein and they told us that they were currently conducted a large study investigating what other proteins are also present. Thus far they have not seen any Alpha Synuclein accumulation. Interesting….