Discovery may lead to a treatment to slow Parkinson’s disease
Laura A. Volpicelli-DaleyUsing a robust model for Parkinson’s disease, University of Alabama at Birmingham researchers and colleagues have discovered an interaction in neurons that contributes to Parkinson’s disease, and they have shown that drugs now under development may block the process.
The research team has shown that the most common genetic cause of Parkinson’s disease — a mutant LRRK2 kinase enzyme — contributes to the formation of inclusions in neurons, resembling one of the hallmark pathologies seen in Parkinson’s disease. These inclusions are made up of aggregated alpha synuclein protein, which — the research also shows — can be prevented from forming by using two LRRK2 kinase inhibitor drugs now being developed for clinical use.
The interaction between mutant LRRK2 kinase and alpha-synuclein “may uncover new mechanisms and targets for neuroprotection,” the researchers write in a recent Journal of Neuroscience paper. “These results demonstrate that alpha-synuclein inclusion formation in neurons can be blocked and that novel therapeutic compounds targeting this process by inhibiting LRRK2 kinase activity may slow progression of Parkinson’s disease-associated pathology.”
The potential clinical applications for novel neuroprotection strategies in LRRK2-linked Parkinson’s need to be tested in other preclinical models of Parkinson’s disease, say the researchers, led by corresponding author Laura A. Volpicelli-Daley, Ph.D., and senior author Andrew B. West, Ph.D., Center for Neurodegeneration and Experimental Therapeutics, UAB Department of Neurology.
“These data give us hope for the clinical potential of LRRK2 kinase inhibitors as effective therapies for Parkinson’s disease,” Volpicelli-Daley said. “The LRRK2 kinase inhibitors may inhibit the spread of pathologic alpha-synuclein, not only in patients with LRRK2 mutations, but in all Parkinson’s disease patients. Future studies to validate the safety and efficacy of the LRRK2 inhibitors will be necessary before testing the inhibitors in human clinical trials.”
Besides Parkinson’s disease, alpha-synuclein also plays a central role in development of dementia with Lewy bodies and multiple system atrophy, and it is associated with Alzheimer’s disease and other neurodegenerative disorders.
Primary hippocampal neurons from mice expressing G2019S-LRRK2. The neurons were treated with alpha-synuclein fibrils, and 18 days later immunofluorescence was performed. The magenta shows phospho-alpha-synuclein inclusions in the cell bodies and throughout the axons, which are visualized as green.Research detailsThe Parkinson’s disease model developed by Volpicelli-Daley applies very low concentrations of pre-formed fibrils of alpha-synuclein to in vitro or in vivo neurons. This causes formation of modified alpha-synuclein inclusions that share morphology with those found in the Parkinson’s disease brain after death.
They used this model to test the effects of neuron expression of the mutant LRRK2 (“lark two”) kinase, G2019S-LRRK2, on the formation of the inclusion pathology.
They found that:
- G2019S-LRRK2 enhanced alpha-synuclein inclusions in primary hippocampal neurons from the hippocampus region of the brain, 18 days after fibril exposure, as compared with neurons that over-expressed normal LRRK2.
- The effects of G2019S-LRRK2 expression in the fibril-exposed neurons were lessened by very low concentrations of potent and selective preclinical drugs that inhibit LRRK2 kinase. This suggested that the kinase activity of G2019S-LRRK2, which adds a phosphate onto target proteins, underlies the faster formation of pathologic alpha-synuclein inclusions.
- G2019S-LRRK2 expression enhanced alpha-synuclein inclusion formation in dopamine neurons from the region of the brain called the substantia nigra pars compacta. The substantia nigra pars compacta is the area of the brain that dies in Parkinson’s disease, so this experiment further supports a link between the G2019S-LRRK2 mutation and Parkinson’s pathogenesis.
Andrew B. WestIn fluorescence-recovery-after-photobleaching experiments, they found there was a larger pool of mobile alpha-synuclein, as opposed to membrane-bound alpha-synuclein, in neurons that expressed G2019S-LRRK2. Recent work by others has shown that mobile alpha-synuclein is prone to misfolding and aggregation, so the researchers hypothesize that the G2019S-LRRK2 mutation may contribute to Parkinson’s susceptibility by boosting the amounts of mobile alpha-synuclein in neurons.
Besides Volpicelli-Daley and West, co-authors of the paper “G2019S-LRRK2 expression augments alpha-synuclein sequestration into inclusions in neurons” are Hisham Abdelmotilib, Zhiyong Liu, Lindsay Stoyka, João Paulo Lima Daher and Kyle Fraser, all of the Center for Neurodegeneration and Experimental Therapeutics, UAB Department of Neurology; Austen J. Milnerwood, Centre for Applied Neurogenetics, University of British Columbia; Vivek K. Unni, Jungers Center for Neurosciences Research and Parkinson Center of Oregon, Oregon Health & Science University; Warren D. Hirst, Pfizer Neuroscience and Pain Research Unit, Cambridge, Massachusetts; Zhenyu Yue, Departments of Neurology and Neuroscience, Icahn School of Medicine at Mount Sinai; Hien T. Zhao, Ionis Pharmaceuticals, Carlsbad, California; and Richard E. Kennedy, Comprehensive Center for Healthy Aging and Division of Gerontology, Geriatrics, and Palliative Care, UAB Department of Medicine.
Grants to fund this work came from the American Parkinson’s Disease Association, the Michael J. Fox Foundation LEAPS Award and the National Institutes of Health NS064934.
Volpicelli-Daley is an assistant professor in the Department of Neurology.
West is co-director of the Center for Neurodegeneration and Experimental Therapeutics, and the John A. and Ruth R. Jurenko Professor of Neurology at UAB.
Brain scans offer insights into loss of money skills
Recent studies used magnetic resonance imaging (MRI) to identify brain areas that might be associated with a reduced ability to handle financial affairs. The findings offer researchers new insights into changes in the aging brain that may be tied to faulty—and even risky—financial decisions.
“It’s the $18.1 trillion problem,” said Daniel Marson, J.D., Ph.D., professor of neurology at the University of Alabama at Birmingham, citing an estimate of household wealth (PDF, 6.8M) held by U.S. adults age 65 and older. “That money is at risk in part because of the cognitive disorders of aging.”
Older adults lose at least $2.9 billion per year to scams, fraud, theft, and other misdeeds, according to a 2011 MetLife study (PDF, 855K). A 2016 survey by Investor Protection Trust (PDF, 382K), a nonprofit devoted to investor education, shows that 17 percent of people age 65 or older have been taken advantage of financially.
To better understand how age- and Alzheimer’s-related changes in brain structure and function may influence behavior, learning, and decision making, including financial decisions, NIA-supported scientists are using brain imaging.
“Novel neuroimaging studies, along with studies involving cognitive measures, are providing intriguing data on why older adults—even those who were previously quite savvy about finances—may lose their money-managing abilities,” said Nina Silverberg, Ph.D., program director of the Alzheimer’s Disease Centers at NIA’s Division of Neuroscience.
She added, “These new insights add to our growing understanding of the basic biological changes involved in dementia onset and progression and inform our efforts to find effective interventions. These types of studies also help us learn more about the general cognitive changes associated with aging.”
Assessing financial capacityFinancial capacity is necessary for living independently. It encompasses relatively simple tasks, such as counting change and paying bills, and more complex activities, such as balancing a checkbook and making investment decisions. These tasks require cognitive functions that include math skills, memory, attention, executive function, and judgment.
Not surprisingly, people with Alzheimer’s disease and related dementias have poor financial capacity and may not be able to manage money on their own. In fact, trouble managing money is often an early sign of the disease. Like other functional skills, financial capacity is not lost all at once, but declines gradually as Alzheimer’s progresses and cognition—the ability to think, learn, and remember—erodes.
Scientists in recent years have studied older adults without dementia to identify and measure the brain’s role in various aspects of financial ability—and possibly to predict who may be on the path to reduced capacity. Results suggest that even cognitively normal older adults may be at risk for poor financial decision-making in some circumstances.
Researchers commonly use laboratory tasks, such as those that assess reward processing and risk taking, or neuropsychological measures such as the Financial Capacity Instrument (FCI) to assess decision-making abilities in older adults. The FCI tests abilities such as reading a bank statement, paying bills, and using financial judgment. Now researchers are using structural MRIs to look for brain areas that may be involved in diminished financial capacity, how these develop over time, and how they differ in older adults across the cognitive spectrum.
“Imaging is increasing the depth of our scientific understanding of the brain,” Dr. Marson said. “MRI helps us understand how changes in brain structure and connectivity drive downstream functional changes” in everyday life. For example, when a person has trouble reading a bank statement, an MRI may reveal aspects of brain structure associated with that specific trouble.
“Just as neuroimaging is used as a biomarker for early Alzheimer’s disease, one could imagine researchers using MRIs to develop biomarkers for impaired financial decision making,” said Duke Han, Ph.D., an associate professor of family medicine, neurology, and psychology at the University of Southern California, Los Angeles. “Ideally, scientists could find ways to strengthen the brain to keep seniors functioning better so they are less likely to become victims of financial abuse.”
Linking MRI results to financial capacityResearchers have used different types of MRI to see if brain structure, function, and connectivity relate to financial capacity. So far, no one brain region or activity stands out.
In one early study, Dr. Marson and colleagues found that older adults with mild cognitive impairment (MCI) performed worse than controls on cognitive tests and the FCI. Their performance was moderately associated with the volume of the angular gyrus, a brain structure involved in number processing, calculation, and other processes. Volume changes in the angular gyrus may predict financial-skill deficits in people with memory-related MCI, they concluded (Griffith et al., 2010).
In a follow-up study, Dr. Marson and his team found that reduced volume of the medial frontal cortex, a region of the brain involved in attention and cognitively demanding tasks, was associated with diminished FCI performance in people with mild Alzheimer's disease (Stoeckel et al., 2013).
Building on these studies, a team at Rush University Medical Center, Chicago, found that greater financial literacy—conceptual knowledge and numeracy abilities that may support financial capacity—was associated with greater functional connectivity between the posterior cingulate cortex and three other brain regions in older adults without dementia (Han et al., 2014). They used resting-state functional MRI, which shows functional connectivity between brain regions. The researchers could not discern whether better financial literacy strengthened these brain connections, or whether subjects with strong brain connections were somehow more financially literate than those with weaker connections.
In other research, the same team found that seniors without dementia who were susceptible to financial scams—as determined by a short questionnaire, not actual scams—had lower total gray-matter volume and less gray matter in the frontal and temporal lobes (Han et al., 2016). “Further research is needed to determine whether gray-matter reductions in these regions may be a biomarker for susceptibility to scams in old age,” the authors wrote.
What’s ahead?Use of neuroimaging to better understand brain changes related to decline in financial capacity is a promising area of research. It is too soon to know whether and how such measures may be applied in a clinical setting, but researchers are eager to explore their potential.
“Can we develop a neuroscience of financial capacity? What are the brain regions and networks that support different kinds of financial skills?” asked Dr. Marson.
Dr. Han said he hopes new knowledge will help in efforts to better maintain and improve financial capacity with age and cognitive challenges, not just predict decline. Ultimately, interventions to strengthen or protect certain brain regions might provide much-needed support for functional skills such as financial decision making.
Griffith HR, et al. Magnetic resonance imaging volume of the angular gyri predicts financial skill deficits in people with amnestic cognitive impairment. Journal of the American Geriatrics Society 2010;58:265-274.
Han SD, et al. Financial literacy is associated with medial brain region functional connectivity in old age. Archives of Gerontology and Geriatrics 2014;59(2):429-438.
Han SD, et al. Grey matter correlates of susceptibility to scams in community-dwelling older adults. Brain Imaging and Behavior 2016;10(2):524-532.
Stoeckel LE, et al. MRI volume of the medial frontal cortex predicts financial capacity in patients with mild Alzheimer's disease. Brain Imaging and Behavior 2013;7(3):282-292.
Page last updated: July 14, 2016
Parkinson’s disease biomarker found in patient urine samples
Andrew WestFor more than five years, urine and cerebral-spinal fluid samples from patients with Parkinson’s disease have been locked in freezers in the NINDS National Repository, stored with the expectation they might someday help unravel the still-hidden course of this slow-acting neurodegenerative disease.
Now, research by Andrew West, Ph.D., and colleagues at the University of Alabama at Birmingham has revealed that the tubes hold a brand-new type of biomarker — a phosphorylated protein that correlates with the presence and severity of Parkinson’s disease. West and colleagues, with support from the National Institutes of Health, the Michael J. Fox Foundation for Parkinson’s Disease Research and the Parkinson’s Disease Foundation, are digging deeper into these biobanked samples, to validate the biomarker as a possible guide for future clinical treatments and a monitor of the efficacy of potential new Parkinson’s drugs in real time during treatment.
“Nobody thought we’d be able to measure the activity of this huge protein called LRRK2 (pronounced lark two) in biofluids since it is usually found inside neurons in the brain,” said West, co-director of the Center for Neurodegeneration and Experimental Therapeutics, and the John A. and Ruth R. Jurenko Professor of Neurology at UAB. “New biochemical markers like the one we’ve discovered together with new neuroimaging approaches are going to be the key to successfully stopping Parkinson’s disease in its tracks. I think the days of blindly testing new therapies for complex diseases like Parkinson’s without having active feedback both for ‘on-target’ drug effects and for effectiveness in patients are thankfully coming to an end.”
A biomarker helps physicians predict, diagnose or monitor disease, because the biomarker corresponds to the presence or risk of disease, and its levels may change as the disease progresses. Validated biomarkers can aid both preclinical trial work in the laboratory and future clinical trials of drugs to treat Parkinson’s. West and others are paving the way for an inhibitor drug that prevented neuroinflammation and neurodegeneration in an animal model of the disease, as reported last year by West and colleagues.
The new biomarker findings were published in Neurology in March and Movement Disorders in June. The biomarker, LRRK2, has been shown to play a role in hereditary Parkinson’s, and the most common of these mutations — called G2019S — causes the LRRK2 kinase to add too many phosphates to itself and other proteins. Why this leads to Parkinson’s disease is not yet clear.
The key to West’s biomarker approach was the recognition that LRRK2 can be purified from a new type of vesicle called exosomes found in all human biofluids, like urine and saliva. Cells in the body continually release exosomes that contain a mixture of proteins, RNA and DNA derived from different kinds of cells. West and colleagues were able to purify exosomes from 3- or 4-ounce urine samples donated by patients, and then measure phosphorylated LRRK2 in those exosomes.
The findingsIn the Neurology study, they found that elevated phosphorylated LRRK2 predicted the risk for onset of Parkinson’s disease for people carrying a mutation in LRRK2, which is about 2-3 percent of all Parkinson’s disease patients. These findings were first tested with a preliminary, 14-person cohort of urine samples from the Columbia University Movement Disorders Center. That was followed by a larger replication study of 72 biobanked urine samples from the Michael J. Fox Foundation LRRK2 Cohort Consortium. All samples were provided to UAB in a blinded fashion to ensure the approach was rigorous.
|“New biochemical markers like the one we’ve discovered together with new neuroimaging approaches are going to be the key to successfully stopping Parkinson’s disease in its tracks.”
Next stepsQuestions remain for this evidence of biochemical changes in LRRK2 in idiopathic Parkinson’s disease. One is finding out where the urinary exosomes come from. Given a suspected role for inflammation in Parkinson’s disease, it is interesting that LRRK2 is highly expressed in cells of the innate immune system. A possible explanation for the phosphorylated LRRK2 in patients with more severe disease may be an increased inflammation in those patients who have aggressive progression of disease.
In May, West was awarded a new U01 collaborative grant from the National Institute of Neurological Disorders and Stroke to further explore urinary exosomes and extend the observations to cerebral-spinal fluid as a marker for disease prediction and prognosis.
Besides West, authors of the Neurology paper, “Urinary LRRK2 phosphorylation predicts parkinsonian phenotypes in G2019S LRRK2 carriers,” are Kyle B. Fraser and Mark S. Moehle, of the Center for Neurodegeneration and Experimental Therapeutics and Department of Neurology, UAB School of Medicine; and Roy N. Alcalay, M.D., Columbia University Department of Neurology.
Besides West, authors of the Movement Disorders paper, “Ser(P)-1292 LRRK2 in urinary exosomes is elevated in idiopathic Parkinson’s disease,” are Fraser, Ashlee B. Rawlins, Rachel G. Clark and David G. Standaert, M.D., Ph.D., of the UAB Center for Neurodegeneration and Experimental Therapeutics and Department of Neurology; Alcalay; and Nianjun Liu, Ph.D., Department of Biostatistics, UAB School of Public Health.
Standaert is the John N. Whitaker Professor and chair of the Department of Neurology at UAB.
The MJFF LRRK2 Cohort Consortium provided samples and is coordinated and funded in part by the Michael J. Fox Foundation for Parkinson’s Disease Research. The Parkinson’s Disease Foundation supported the collection of samples from Columbia University. Financial support for the study was provided by National Institutes of Health grants U18 NS082132, R01 NS064934, F31 NS081963, K02 NS0915 and T32 GM008111.