News Article | April 25, 2016
Frontotemporal dementia (FTD), the second most common cause of dementia in people under 65, may be triggered by a defect in immune cells called microglia that causes them to consume the brain’s synaptic connections, according to new research led by UCSF scientists. The new study – published April 21, 2016 in the journal Cell — adds to growing evidence that the brain’s immune system is a driving force behind many neurodegenerative diseases, and suggests new approaches to diagnosing and treating patients with FTD, which currently affects as many as 22 out of 100,000 adults, with typical onset between the ages of 45 and 65. Microglia normally act as the brain’s garbage collectors, disposing of foreign particles such as viruses or bacteria as well as sick and dying brain cells. In the developing brain, microglia also help refine the brain’s circuitry by pruning back unneeded neural connections, which are marked for destruction with immune molecules called “complement proteins.” Recent studies by Harvard neurobiologist Beth Stevens, Ph.D., and others have suggested that this process may go awry during adolescence in patients with schizophrenia, and as a side effect of aging in patients with Alzheimer’s disease: in both cases an overabundance of complement protein appears to cause too many synapses to be tagged for destruction by the microglia. “The brain’s innate immune system is emerging as a common pathway behind many neurodegenerative disorders,” said senior author Eric Huang, M.D., Ph.D., a professor of pathology at UCSF and pathologist at the UCSF-affiliated San Francisco VA Medical Center. “This idea has been controversial, however, because in human patients, neurodegeneration is typically accompanied by some degree of inflammation, with lots of activated microglia, but it’s hard to tell whether that is a driver of the degeneration or a consequence. You need careful experiments using animals models to dissect the cause-effect relationship.” Working with colleagues at UCSF’s Memory and Aging Center and departments of Neurology and Neurological Surgery, as well as the UCSF-affiliated Gladstone Institutes, Stanford University, and others, Huang and his team compared brain tissue from human FTD patients with familial mutations in the progranulin gene to the brains of mice with this gene deleted. In the mice, the defect caused age-related neurodegeneration and excessive grooming akin to the obsessive-compulsive disorder (OCD) symptoms seen in human FTD patients. The researchers found that as the mice aged, the mutation caused a gradual breakdown of microglial cells’ waste disposal systems, which led to excessive activation of these cells’ aggressive immune functions, heightened production of complement proteins, and excessive synaptic pruning in the thalamus, a part of the brain that is highly relevant to human FTD. Additional experiments on isolated microglia made it clear to the researchers that progranulin normally acts as a brake to prevent excessive microglia activation. Without it, it appeared that an unknown aspect of the normal aging process allowed microglia to spiral out of control. However, the researchers showed that they could short-circuit this death spiral by deleting the gene for one of the major complement proteins produced by microglia, called C1qa. Mice with both the progranulin and the C1qa genes turned off lived considerably longer than those with intact C1qa, and didn’t develop OCD-like behaviors. Their brains also showed a drastic reduction in the number of activated microglia and much better protection from synapse loss. “We worked for more than two years to get to that result,” Huang said, “But when we did, it was a really surreal experience. It was immediately clear that blocking complement protein might be a good therapeutic target for FTD patients with progranulin mutations.” Research points to new approaches for dementia patients Huang and his team are now collaborating with a biotech company called Annexon to test therapies that block C1qa. However, these treatments are likely still a long way off. For one thing, treatments for neurodegeneration likely need to be taken early, before the brain damage is done, and there’s still no way to reliably detect the disease before it’s far too late. That’s why the researchers also investigated whether the elevated complement protein levels that would be predicted by their study show up in patients’ cerebrospinal fluid (CSF) — the fluid collected by a spinal tap. If so, they could potentially serve as a biomarker to allow early detection of the disease. Initially they were disappointed by the results: “We looked at CSF from normal and diseased brains side by side, and they looked about the same,” Huang said. “But then we tried separating the FTD patients based on how severe their dementia had been when the CSF samples were taken, and the result was really spectacular. Clearly, as patients’ mental status declined, the level of complement protein in their CSF increased.” Huang said he hopes future research will allow physicians to use this signal to enable earlier diagnosis and to test the effectiveness of potential treatments. If doctors give an anti-complement drug and the levels of complement protein in the CSF go down, he said, that would be a good sign that the immediate danger to the brain has been relieved.
Kerchner G.A.,Stanford University |
Kerchner G.A.,Memory and Aging Center |
Hess C.P.,University of California at San Francisco |
Hammond-Rosenbluth K.E.,University of California at San Francisco |
And 7 more authors.
Neurology | Year: 2010
Objectives:: In Alzheimer disease (AD), mounting evidence points to a greater role for synaptic loss than neuronal loss. Supporting this notion, multiple postmortem studies have demonstrated that the hippocampal CA1 apical neuropil is one of the earliest sites of pathology, exhibiting tau aggregates and then atrophy before there is substantial loss of the CA1 pyramidal neurons themselves. In this cross-sectional study, we tested whether tissue loss in the CA1 apical neuropil layer can be observed in vivo in patients with mild Ad. Methods:: We performed ultra-high-field 7-T MRI on subjects with mild AD (n = 14) and age-matched normal controls (n = 16). With a 2-dimensional T2*-weighted gradient-recalled echo sequence that was easily tolerated by subjects, we obtained cross-sectional slices of the hippocampus at an in-plane resolution of 195 μm. Results:: On images revealing the anatomic landmarks of hippocampal subfields and strata, we observed thinning of the CA1 apical neuropil in subjects with mild AD compared to controls. By contrast, the 2 groups exhibited no difference in the thickness of the CA1 cell body layer or of the entire CA1 subfield. Hippocampal volume, measured on a conventional T1-weighted sequence obtained at 3T, also did not differentiate these patients with mild AD from controls. Conclusions:: CA1 apical neuropil atrophy is apparent in patients with mild AD. With its superior spatial resolution, 7-T MRI permits in vivo analysis of a very focal, early site of AD pathology. Copyright © 2010 by AAN Enterprises, Inc. Source
Hoftberger R.,University of Barcelona |
Hoftberger R.,Medical University of Vienna |
Van Sonderen A.,Erasmus Medical Center |
Leypoldt F.,University Medical Center Schleswig |
And 11 more authors.
Neurology | Year: 2015
Objective: We report the clinical features, comorbidities, and outcome of 22 newly identified patients with antibodies to the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). Methods: This was a retrospective review of patients diagnosed between May 2009 and March 2014. Immunologic techniques have been reported previously. Results: Patients' median age was 62 years (range 23-81; 14 female). Four syndromes were identified: 12 (55%) patients presented with distinctive limbic encephalitis (LE), 8 (36%) with limbic dysfunction along with multifocal/diffuse encephalopathy, one with LE preceded by motor deficits, and one with psychosis with bipolar features. Fourteen patients (64%) had a tumor demonstrated pathologically (5 lung, 4 thymoma, 2 breast, 2 ovarian teratoma) or radiologically (1 lung). Additional antibodies occurred in 7 patients (3 onconeuronal, 1 tumor-related, 2 cell surface, and 1 tumor-related and cell surface), all with neurologic symptoms or tumor reflecting the concurrent autoimmunity. Treatment and outcome were available from 21 patients (median follow-up 72 weeks, range 5-266): 5 had good response to immunotherapy and tumor therapy, 10 partial response, and 6 did not improve. Eventually 5 patients died; all had a tumor or additional paraneoplastic symptoms related to onconeuronal antibodies. Coexistence of onconeuronal antibodies predicted a poor outcome (p = 0.009). Conclusion: Anti-AMPAR encephalitis usually manifests as LE, can present with other symptoms or psychosis, and is paraneoplastic in 64% of cases. Complete and impressive neurologic improvement can occur, but most patients have partial recovery. Screening for a tumor and onconeuronal antibodies is important because their detection influences outcome. © 2015 American Academy of Neurology. Source
Rosen H.J.,University of California at San Francisco |
Rosen H.J.,Memory and Aging Center |
Alcantar O.,University of California at San Francisco |
Alcantar O.,Memory and Aging Center |
And 6 more authors.
Neuropsychology | Year: 2014
Objective: Impaired self-awareness is characteristic of nearly all dementias, including Alzheimer's disease (AD), but the deficit is most severe in the behavioral variant of frontotemporal dementia (bvFTD). The prominence of frontal pathology in bvFTD suggests that failure of online monitoring, the process by which individuals monitor their own cognitive processing in real time, is an important contributor. Metacognitive research offers several approaches to measure self-assessment, some more and others less sensitive to online monitoring. The goal of this study was to assess metacognition in bvFTD using several approaches, and to compare the results with those in AD. Method: We examined metacognition in 12 patients with bvFTD, 14 with AD, and 35 healthy controls using feeling of knowing (FOK), ease of learning (EOL), judgment of learning (JOL), and retrospective confidence rating (CR) tasks, as well as response to feedback about performance. Results: BvFTD and AD were both impaired at FOK compared with controls, although AD showed some sparing. Both groups were similarly impaired at CR and neither group was impaired at JOL after accounting for memory performance. Most striking, bvFTD patients failed to appropriately adjust their predictions about future memory performance even after receiving explicit feedback that they had performed worse than they expected. Conclusions: Both bvFTD and AD show deficits in online monitoring, although the deficit appears more severe in bvFTD. The insensitivity of bvFTD patients to overt feedback may point to unique mechanisms, possibly frontally mediated, that add to their severe lack of self-awareness. © 2013 American Psychological Association. Source
Schlesinger D.,University of Sao Paulo |
Schlesinger D.,Instituto Israelita Of Ensino E Pesquisa Albert Einstein |
Grinberg L.T.,University of Sao Paulo |
Grinberg L.T.,Memory and Aging Center |
And 15 more authors.
Molecular Psychiatry | Year: 2013
Previous studies in dementia epidemiology have reported higher Alzheimer's disease rates in African-Americans when compared with White Americans. To determine whether genetically determined African ancestry is associated with neuropathological changes commonly associated with dementia, we analyzed a population-based brain bank in the highly admixed city of São Paulo, Brazil. African ancestry was estimated through the use of previously described ancestry-informative markers. Risk of presence of neuritic plaques, neurofibrillary tangles, small vessel disease, brain infarcts and Lewy bodies in subjects with significant African ancestry versus those without was determined. Results were adjusted for multiple environmental risk factors, demographic variables and apolipoprotein E genotype. African ancestry was inversely correlated with neuritic plaques (P0.03). Subjects with significant African ancestry (n112, 55.4%) showed lower prevalence of neuritic plaques in the univariate analysis (odds ratio (OR) 0.72, 95% confidence interval (CI) 0.55-0.95, P0.01) and when adjusted for age, sex, APOE genotype and environmental risk factors (OR 0.43, 95% CI 0.21-0.89, P0.02). There were no significant differences for the presence of other neuropathological alterations. We show for the first time, using genetically determined ancestry, that African ancestry may be highly protective of Alzheimer's disease neuropathology, functioning through either genetic variants or unknown environmental factors. Epidemiological studies correlating African-American race/ethnicity with increased Alzheimer's disease rates should not be interpreted as surrogates of genetic ancestry or considered to represent African-derived populations from the developing nations such as Brazil. © 2013 Macmillan Publishers Limited. Source