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1.  Preclinical Assessment of Young Blood Plasma for Alzheimer Disease 
JAMA neurology  2016;73(11):1325-1333.
Alzheimer disease (AD) pathology starts long before clinical symptoms manifest, and there is no therapy to treat, delay, or prevent the disease. A shared blood circulation between 2 mice (aka parabiosis) or repeated injections of young blood plasma (plasma from 2- to 3-month-old mice) into old mice has revealed benefits of young plasma on synaptic function and behavior. However, to our knowledge, the potential benefit of young blood has not been tested in preclinical models of neurodegeneration or AD.
To determine whether young blood plasma ameliorates pathology and cognition in a mouse model for AD and could be a possible future treatment for the disease.
In this preclinical study, mice that harbor a human mutant APP gene, which causes familial AD, were aged to develop AD-like disease including accumulation of amyloid plaques, loss of synaptic and neuronal proteins, and behavioral deficits. The initial parabiosis studies were done in 2010, and the final studies were conducted in 2014. Alzheimer disease model mice were then treated either by surgically connecting them with a young healthy mouse, thus providing a shared blood circulation through parabiosis, or through repeated injections of plasma from young mice.
Neuropathological parameters and changes in hippocampal gene expression in response to the treatment were assessed. In addition, cognition was tested in AD model mice intravenously injected with young blood plasma.
Aged mutant amyloid precursor protein mice with established disease showed a near complete restoration in levels of synaptic and neuronal proteins after exposure to young blood in parabiosis (synaptophysin P = .02; calbindin P = .02) or following intravenous plasma administration (synaptophysin P < .001; calbindin P = .14). Amyloid plaques were not affected, but the beneficial effects in neurons in the hippocampus were accompanied by a reversal of abnormal extracellular receptor kinase signaling (P = .05), a kinase implicated in AD. Moreover, young plasma administration was associated with improved working memory (P = .01) and associative memory (P = .02) in amyloid precursor protein mice.
Factors in young blood have the potential to ameliorate disease in a model of AD.
PMCID: PMC5172595  PMID: 27598869
2.  Ageing, neurodegeneration and brain rejuvenation 
Nature  2016;539(7628):180-186.
Although systemic diseases take the biggest toll on human health and well-being, increasingly, a failing brain is the arbiter of a death preceded by a gradual loss of the essence of being. Ageing, which is fundamental to neurodegeneration and dementia, affects every organ in the body and seems to be encoded partly in a blood-based signature. Indeed, factors in the circulation have been shown to modulate ageing and to rejuvenate numerous organs, including the brain. The discovery of such factors, the identification of their origins and a deeper understanding of their functions is ushering in a new era in ageing and dementia research.
PMCID: PMC5172605  PMID: 27830812
3.  In vivo assessment of behavioral recovery and circulatory exchange in the peritoneal parabiosis model 
Scientific Reports  2016;6:29015.
The sharing of circulation between two animals using a surgical procedure known as parabiosis has created a wealth of information towards our understanding of physiology, most recently in the neuroscience arena. The systemic milieu is a complex reservoir of tissues, immune cells, and circulating molecules that is surprisingly not well understood in terms of its communication across organ systems. While the model has been used to probe complex physiological questions for many years, critical parameters of recovery and exchange kinetics remain incompletely characterized, limiting the ability to design experiments and interpret results for complex questions. Here we provide evidence that mice joined by parabiosis gradually recover much physiology relevant to the study of brain function. Specifically, we describe the timecourse for a variety of recovery parameters, including those for general health and metabolism, motor coordination, activity, and sleep behavior. Finally, we describe the kinetics of chimerism for several lymphocyte populations as well as the uptake of small molecules into the brains of mice following parabiosis. Our characterization provides an important resource to those attempting to understand the complex interplay between the immune system and the brain as well as other organ systems.
PMCID: PMC4929497  PMID: 27364522
4.  CalFluors: A Universal Motif for Fluorogenic Azide Probes across the Visible Spectrum 
Fluorescent bioorthogonal smart probes across the visible spectrum will enable sensitive visualization of metabolically labeled molecules in biological systems. Here we present a unified design, based on the principle of photoinduced electron transfer, to access a panel of highly fluorogenic azide probes that are activated by conversion to the corresponding triazoles via click chemistry. Termed the CalFluors, these probes possess emission maxima that range from green to far red wavelengths, and enable sensitive biomolecule detection under no-wash conditions. We used the CalFluor probes to image various alkyne-labeled biomolecules (glycans, DNA, RNA, and proteins) in cells, developing zebrafish, and mouse brain tissue slices.
Graphical abstract
PMCID: PMC4487548  PMID: 25902190
5.  Nuclear pore complex remodeling by p75NTR cleavage controls TGF-β signaling and astrocyte functions 
Nature neuroscience  2015;18(8):1077-1080.
Astrocytes play critical roles in neuronal activity and inhibition of regeneration. Here we show that the cleaved p75 neurotrophin receptor (p75NTR) is a component of the nuclear pore complex (NPC) required for glial scar formation and reduced gamma oscillations in mice via regulation of TGF-β signaling. The cleaved p75NTR interacts with nucleoporins to promote Smad2 nucleocytoplasmic shuttling. Thus, NPC remodeling by regulated intramembrane cleavage of p75NTR controls astrocyte-neuronal communication in response to profibrotic factors.
PMCID: PMC4878404  PMID: 26120963
7.  Aging. Aging-induced type I interferon signaling at the choroid plexus negatively affects brain function 
Science (New York, N.Y.)  2014;346(6205):89-93.
Age-associated cognitive decline is affected by factors produced inside and outside the brain. We found in aged mice and humans, that the choroid plexus (CP), an epithelial interface between the brain and the circulation, shows a type I interferon (IFN-I)-dependent expression profile, often associated with anti-viral responses. This signature was induced by brain-derived signals present in the cerebrospinal fluid of aged mice. Blocking IFN-I signaling within the brain of cognitively-impaired aged mice, using IFN-I receptor neutralizing antibody, led to partial restoration of cognitive function and hippocampal neurogenesis, and reestablished IFN-II-dependent CP activity, lost in aging. Our data identify an aging-induced IFN-I signature at the CP, and demonstrate its negative influence on brain function, thereby suggesting a potential target for therapeutic intervention for age-related cognitive decline.
PMCID: PMC4869326  PMID: 25147279
8.  Go with your gut: microbiota meet microglia 
Nature neuroscience  2015;18(7):930-931.
Discovering the environmental factors that control microglia is key to understanding and managing brain health. A new study finds that microbiota in the gut are essential for regulating microglia maturation and activation.
PMCID: PMC4867548  PMID: 26108718
9.  Blood-borne revitalization of the aged brain 
JAMA neurology  2015;72(10):1191-1194.
In the modern medical era, more diverse and effective treatment options have translated into increased life expectancy. With this increased lifespan comes increased age-associated disease and the dire need to understand the underlying causes so that therapies can be designed to mitigate the burden to health and the economy. Aging exacts a seemingly inevitable, multi-system deterioration of function that acts as a risk factor for a variety of age-related disorders, including those that devastate organs of limited regenerative potential such as the brain. Rather than studying the brain and mechanisms that govern its aging in isolation from other organ systems, an emerging approach is to understand the relatively unappreciated communication existing between the brain and the systemic environment. Revisiting classical methods of experimental physiology in animal models has uncovered surprising regenerative activity within young blood with translational implications for aging liver, muscle, brain and other organs. Surprisingly, soluble factors present in young or aged blood are sufficient to improve or impair cognitive function, respectively, suggesting an aging continuum of brain-relevant systemic factors. The age-associated plasma chemokine CCL11 has been shown to impair young brain function while GDF11 has been reported to increase the generation of neurons in aged mice. However, the identities of specific factors mediating memory-enhancing effects of young blood and their mechanisms of action remain enigmatic. Here we review recent brain rejuvenation studies in the broader context of systemic rejuvenation research. We discuss putative mechanisms for blood-borne brain rejuvenation while suggesting promising avenues for future research and development of therapies.
PMCID: PMC4867550  PMID: 26237737
10.  PET Imaging of Translocator Protein (18 kDa) in a Mouse Model of Alzheimer's Disease Using N-(2,5-Dimethoxybenzyl)-2-18F-Fluoro-N-(2-Phenoxyphenyl)Acetamide 
Herein we aimed to evaluate the utility of N-(2,5-dimethoxybenzyl)-2-18F-fluoro-N-(2-phenoxyphenyl)acetamide (18F-PBR06) for detecting alterations in translocator protein (TSPO) (18 kDa), a biomarker of microglial activation, in a mouse model of Alzheimer's disease (AD).
Wild-type (wt) and AD mice (i.e., APPL/S) underwent 18F-PBR06 PET imaging at predetermined time points between the ages of 5–6 and 15–16 mo. MR images were fused with PET/CT data to quantify 18F-PBR06 uptake in the hippocampus and cortex. Ex vivo autoradiography and TSPO/CD68 immunostaining were also performed using brain tissue from these mice.
PET images showed significantly higher accumulation of 18F-PBR06 in the cortex and hippocampus of 15- to 16-mo-old APPL/S mice than age-matched wts (cortex/muscle: 2.43 ± 0.19 vs. 1.55 ± 0.15, P < 0.005; hippocampus/muscle: 2.41 ± 0.13 vs. 1.55 ± 0.12, P < 0.005). And although no significant difference was found between wt and APPL/S mice aged 9–10 mo or less using PET (P = 0.64), we were able to visualize and quantify a significant difference in 18F-PBR06 uptake in these mice using autoradiography (cortex/striatum: 1.13 ± 0.04 vs. 0.96 ± 0.01, P < 0.05; hippocampus/striatum: 1.266 ± 0.003 vs. 1.096 ± 0.017, P < 0.001). PET results for 15- to 16-mo-old mice correlated well with autoradiography and immunostaining (i.e., increased 18F-PBR06 uptake in brain regions containing elevated CD68 and TSPO staining in APPL/S mice, compared with wts).
18F-PBR06 shows great potential as a tool for visualizing TSPO/microglia in the progression and treatment of AD.
PMCID: PMC4866832  PMID: 25613536
microglial activation; Alzheimer's disease; translocator protein 18 kDa; PET
11.  Aging: a common driver of chronic diseases and a target for novel interventions 
Cell  2014;159(4):709-713.
Mammalian aging can be delayed with genetic, dietary and pharmacologic approaches. Given that the elderly population is dramatically increasing and that aging is the greatest risk factor for a majority of chronic diseases driving both morbidity and mortality, it is critical to expand Geroscience research directed at extending human healthspan.
PMCID: PMC4852871  PMID: 25417146
12.  Network-driven plasma proteomics expose molecular changes in the Alzheimer’s brain 
Biological pathways that significantly contribute to sporadic Alzheimer’s disease are largely unknown and cannot be observed directly. Cognitive symptoms appear only decades after the molecular disease onset, further complicating analyses. As a consequence, molecular research is often restricted to late-stage post-mortem studies of brain tissue. However, the disease process is expected to trigger numerous cellular signaling pathways and modulate the local and systemic environment, and resulting changes in secreted signaling molecules carry information about otherwise inaccessible pathological processes.
To access this information we probed relative levels of close to 600 secreted signaling proteins from patients’ blood samples using antibody microarrays and mapped disease-specific molecular networks. Using these networks as seeds we then employed independent genome and transcriptome data sets to corroborate potential pathogenic pathways.
We identified Growth-Differentiation Factor (GDF) signaling as a novel Alzheimer’s disease-relevant pathway supported by in vivo and in vitro follow-up experiments, demonstrating the existence of a highly informative link between cellular pathology and changes in circulatory signaling proteins.
Electronic supplementary material
The online version of this article (doi:10.1186/s13024-016-0095-2) contains supplementary material, which is available to authorized users.
PMCID: PMC4845325  PMID: 27112350
13.  Impact of peripheral myeloid cells on amyloid-β pathology in Alzheimer’s disease–like mice 
The Journal of Experimental Medicine  2015;212(11):1811-1818.
Prokop et al. demonstrate that conditional ablation of resident microglia in a mouse model of Alzheimer’s disease (AD) results in no significant change in amyloid-β burden, despite nearly complete replacement with peripheral myeloid cells. The findings suggest that additional triggers appear to be required to exploit the full potential of myeloid cell–based therapies for AD.
Although central nervous system–resident microglia are believed to be ineffective at phagocytosing and clearing amyloid-β (Aβ), a major pathological hallmark of Alzheimer’s disease (AD), it has been suggested that peripheral myeloid cells constitute a heterogeneous cell population with greater Aβ-clearing capabilities. Here, we demonstrate that the conditional ablation of resident microglia in CD11b-HSVTK (TK) mice is followed by a rapid repopulation of the brain by peripherally derived myeloid cells. We used this system to directly assess the ability of peripheral macrophages to reduce Aβ plaque pathology and therefore depleted and replaced the pool of resident microglia with peripherally derived myeloid cells in Aβ-carrying APPPS1 mice crossed to TK mice (APPPS1;TK). Despite a nearly complete exchange of resident microglia with peripheral myeloid cells, there was no significant change in Aβ burden or APP processing in APPPS1;TK mice. Importantly, however, newly recruited peripheral myeloid cells failed to cluster around Aβ deposits. Even additional anti-Aβ antibody treatment aimed at engaging myeloid cells with amyloid plaques neither directed peripherally derived myeloid cells to amyloid plaques nor altered Aβ burden. These data demonstrate that mere recruitment of peripheral myeloid cells to the brain is insufficient in substantially clearing Aβ burden and suggest that specific additional triggers appear to be required to exploit the full potential of myeloid cell–based therapies for AD.
PMCID: PMC4612091  PMID: 26458768
15.  Effects of the Absence of Apolipoprotein E on Lipoproteins, Neurocognitive Function, and Retinal Function 
JAMA neurology  2014;71(10):1228-1236.
The identification of a patient with a rare form of severe dysbetalipoproteinemia allowed the study of the consequences of total absence of apolipoprotein E (apoE).
To discover the molecular basis of this rare disorder and to determine the effects of complete absence of apoE on neurocognitive and visual function and on lipoprotein metabolism.
Whole-exome sequencing was performed on the patient’s DNA. He underwent detailed neurological and visual function testing and lipoprotein analysis. Lipoprotein analysis was also performed in the Cardiovascular Research Institute, University of California, San Francisco, on blood samples from the proband’s mother, wife, 2 daughters, and normolipidemic control participants.
Whole-exome sequencing, lipoprotein analysis, and neurocognitive function.
The patient was homozygous for an ablative APOE frameshift mutation (c.291del, p.E97fs). No other mutations likely to contribute to the phenotype were discovered, with the possible exception of two, in ABCC2 (p.I670T) and LIPC (p.G137R). Despite complete absence of apoE, he had normal vision, exhibited normal cognitive, neurological, and retinal function, had normal findings on brain magnetic resonance imaging, and had normal cerebrospinal fluid levels of β-amyloid and tau proteins. He had no significant symptoms of cardiovascular disease except a suggestion of myocardial ischemia on treadmill testing and mild atherosclerosis noted on carotid ultrasonography. He had exceptionally high cholesterol content (760 mg/dL; to convert to millimoles per liter, multiply by 0.0259) and a high cholesterol to triglycerides ratio (1.52) in very low-density lipoproteins with elevated levels of small-diameter high-density lipoproteins, including high levels of prebeta-1 high-density lipoprotein. Intermediate-density lipoproteins, low-density lipoproteins, and very low-density lipoproteins contained elevated apoA-I and apoA-IV levels. The patient’s apoC-III and apoC-IV levels were decreased in very low-density lipoproteins. Electron microscopy revealed large lamellar particles having electron-opaque cores attached to electron-lucent zones in intermediate-density and low-density lipoproteins. Low-density lipoprotein particle diameters were distributed bimodally.
Despite a profound effect on lipoprotein metabolism, detailed neurocognitive and retinal studies failed to demonstrate any defects. This suggests that functions of apoE in the brain and eye are not essential or that redundant mechanisms exist whereby its role can be fulfilled. Targeted knockdown of apoE in the central nervous system might be a therapeutic modality in neurodegenerative disorders.
PMCID: PMC4714860  PMID: 25111166
16.  Beclin 1 regulates neuronal transforming growth factor-β signaling by mediating recycling of the type I receptor ALK5 
Beclin 1 is a key regulator of multiple trafficking pathways, including autophagy and receptor recycling in yeast and microglia. Decreased beclin 1 levels in the CNS result in neurodegeneration, an effect attributed to impaired autophagy. However, neurons also rely heavily on trophic factors, and signaling through these pathways requires the proper trafficking of trophic factor receptors.
We discovered that beclin 1 regulates signaling through the neuroprotective TGF-β pathway. Beclin 1 is required for recycling of the type I TGF-β receptor ALK5. We show that beclin 1 recruits the retromer to ALK5 and facilitates its localization to Rab11+ endosomes. Decreased levels of beclin 1, or its binding partners VPS34 and UVRAG, impair TGF-β signaling.
These findings identify beclin 1 as a positive regulator of a trophic signaling pathway via receptor recycling, and suggest that neuronal death induced by decreased beclin 1 levels may also be due to impaired trophic factor signaling.
Electronic supplementary material
The online version of this article (doi:10.1186/s13024-015-0065-0) contains supplementary material, which is available to authorized users.
PMCID: PMC4687091  PMID: 26692002
Beclin 1; VPS34; Retromer; TGF-β; ALK5; Protein sorting; Receptor recycling; Neurodegeneration
17.  Autoimmunity contributes to nociceptive sensitization in a mouse model of complex regional pain syndrome 
Pain  2014;155(11):2377-2389.
Complex regional pain syndrome (CRPS) is a painful, disabling, chronic condition whose etiology remains poorly understood. The recent suggestion that immunological mechanisms may underlie CRPS provides an entirely novel framework in which to study the condition and consider new approaches to treatment. Using a murine fracture/cast model of CRPS, we studied the effects of B-cell depletion using anti-CD20 antibodies or by performing experiments in genetically B-cell-deficient (µMT) mice. We observed that mice treated with anti-CD20 developed attenuated vascular and nociceptive CRPS-like changes after tibial fracture and 3 weeks of cast immobilization. In mice with established CRPS-like changes, the depletion of CD-20+ cells slowly reversed nociceptive sensitization. Correspondingly, µMT mice, deficient in producing immunoglobulin M (IgM), failed to fully develop CRPS-like changes after fracture and casting. Depletion of CD20+ cells had no detectable effects on nociceptive sensitization in a model of postoperative incisional pain, however. Immunohistochemical experiments showed that CD20+ cells accumulate near the healing fracture but few such cells collect in skin or sciatic nerves. On the other hand, IgM-containing immune complexes were deposited in skin and sciatic nerve after fracture in wild-type, but not in µMT fracture/cast, mice. Additional experiments demonstrated that complement system activation and deposition of membrane attack complexes were partially blocked by anti-CD20+ treatment. Collectively, our results suggest that CD20-positive B cells produce antibodies that ultimately support the CRPS-like changes in the murine fracture/cast model. Therapies directed at reducing B-cell activity may be of use in treating patients with CRPS.
PMCID: PMC4252476  PMID: 25218828
Autoimmunity; B cell; Complex regional pain syndrome; Pain; Fracture
18.  Stem Cells as Vehicles for Youthful Regeneration of Aged Tissues 
Stem cells hold great promise for regenerative therapies for a wide spectrum of diseases and disorders of aging by virtue of their ability to regenerate tissues and contribute to their homeostasis. Aging is associated with a marked decline in these functionalities of adult stem cells. As such, regeneration of aged tissues is both less efficient and less effective than that of young tissues. Recent studies have revealed the remarkably dynamic responses of stem cells to systemic signals, including the ability of “youthful” factors in the blood of young animals to enhance the functionality of aged stem cells. Thus, there is much hope that even aged stem cells retain a remarkable regenerative potential if provided with the correct cues and environment to engage in tissue repair. The overall focus of the presentations of this session is to address the determinants of changes in stem cell functionality with age, the key characteristics of stem cells in aged tissues, the extent to which those characteristics are capable of being rejuvenated and by what signals, and the potential for stem cell therapeutics for chronic diseases and acute injuries in aged individuals.
PMCID: PMC4022127  PMID: 24833585
Aging; Stem cells; Tissue regeneration; Genome stability; Rejuvenation; Epigenetics.
19.  Sorting Through the Roles of Beclin 1 in Microglia and Neurodegeneration 
Beclin 1 has a well-established role in regulating autophagy, a cellular degradation pathway. Although the yeast ortholog of beclin 1 (Atg6/Vps30) was discovered to also regulate vacuolar protein sorting nearly 30 years ago, the varied functions of beclin 1 in mammalian cells are only beginning to be sorted out. We recently described a role for beclin 1 in regulating recycling of phagocytic receptors in microglia, a function analogous to that of its yeast ortholog. Microglia lacking beclin 1 have a reduced phagocytic capacity, which impairs clearance of amyloid β (Aβ) in a mouse model of Alzheimer’s Disease (AD). Here we summarize these findings and discuss the implications for beclin 1-regulated receptor recycling in neurodegenerative disease.
PMCID: PMC4019692  PMID: 24385262
Beclin 1; phosphatidylinositol 3-phosphate; PI3P; phosphatidylinositol 3-kinase; PI3K; VPS35; retromer; receptor recycling; phagocytosis; Alzheimer’s Disease; neurodegeneration
20.  Microglial Dysfunction in Brain Aging and Alzheimer’s Disease 
Biochemical pharmacology  2014;88(4):594-604.
Microglia, the immune cells of the central nervous system, have long been a subject of study in the Alzheimer’s disease (AD) field due to their dramatic responses to the pathophysiology of the disease. With several large-scale genetic studies in the past year implicating microglial molecules in AD, the potential significance of these cells has become more prominent than ever before. As a disease that is tightly linked to aging, it is perhaps not entirely surprising that microglia of the AD brain share some phenotypes with aging microglia. Yet the relative impacts of both conditions on microglia are less frequently considered in concert. Furthermore, microglial “activation” and “neuroinflammation” are commonly analyzed in studies of neurodegeneration but are somewhat ill-defined concepts that in fact encompass multiple cellular processes. In this review, we have enumerated six distinct functions of microglia and discuss the specific effects of both aging and AD. By calling attention to the commonalities of these two states, we hope to inspire new approaches for dissecting microglial mechanisms.
PMCID: PMC3972294  PMID: 24445162
microglia; aging; Alzheimer’s disease; neuroinflammation; neurodegeneration
21.  APOE ε4 worsens hippocampal CA1 apical neuropil atrophy and episodic memory 
Neurology  2014;82(8):691-697.
Using high-resolution structural MRI, we endeavored to study the relationships among APOE ε4, hippocampal subfield and stratal anatomy, and episodic memory.
Using a cross-sectional design, we studied 11 patients with Alzheimer disease dementia, 14 patients with amnestic mild cognitive impairment, and 14 age-matched healthy controls with no group differences in APOE ε4 carrier status. Each subject underwent ultra-high-field 7.0-tesla MRI targeted to the hippocampus and neuropsychological assessment.
We found a selective, dose-dependent association of APOE ε4 with greater thinning of the CA1 apical neuropil, or stratum radiatum/stratum lacunosum-moleculare (CA1-SRLM), a hippocampal subregion known to exhibit early vulnerability to neurofibrillary pathology in Alzheimer disease. The relationship between the ε4 allele and CA1-SRLM thinning persisted after controlling for dementia severity, and the size of other hippocampal subfields and the entorhinal cortex did not differ by APOE ε4 carrier status. Carriers also exhibited worse episodic memory function but similar performance in other cognitive domains compared with noncarriers. In a statistical mediation analysis, we found support for the hypothesis that CA1-SRLM thinning may link the APOE ε4 allele to its phenotypic effects on memory.
The APOE ε4 allele segregated dose-dependently and selectively with CA1-SRLM thinning and worse episodic memory performance in a pool of older subjects across a cognitive spectrum. These findings highlight a possible role for this gene in influencing a critical hippocampal subregion and an associated symptomatic manifestation.
PMCID: PMC3945665  PMID: 24453080
22.  ALK5-dependent TGF-β signaling is a major determinant of late stage adult neurogenesis 
Nature neuroscience  2014;17(7):943-952.
The transforming growth factor-β (TGF-β) signaling pathway serves critical functions in central nervous system (CNS) development, but apart from its proposed neuroprotective actions, its physiological role in the adult brain is unclear. We observed a prominent activation of TGF-β signaling in the adult dentate gyrus and expression of downstream Smad proteins in this neurogenic zone. Consistent with a function of TGF-β signaling in adult neurogenesis, genetic deletion of the TGF-β receptor ALK5 reduced the number, migration, and dendritic arborization of newborn neurons. Conversely, constitutive activation of neuronal ALK5 in forebrain caused a striking increase in these aspects of neurogenesis and was associated with higher expression of c-fos in newborn neurons and with stronger memory function. Our findings describe a new and unexpected role for ALK5-dependent TGF-β signaling as a regulator of the late stages of adult hippocampal neurogenesis which may have implications for changes in neurogenesis during aging and disease.
PMCID: PMC4096284  PMID: 24859199
23.  The future of blood-based biomarkers for Alzheimer’s disease 
Treatment of Alzheimer’s disease (AD) is significantly hampered by the lack of easily accessible biomarkers that can detect disease presence and predict disease risk reliably. Fluid biomarkers of AD currently provide indications of disease stage; however, they are not robust predictors of disease progression or treatment response, and most are measured in cerebrospinal fluid, which limits their applicability. With these aspects in mind, the aim of this article is to underscore the concerted efforts of the Blood-Based Biomarker Interest Group, an international working group of experts in the field. The points addressed include: (1) the major challenges in the development of blood-based biomarkers of AD, including patient heterogeneity, inclusion of the “right” control population, and the blood– brain barrier; (2) the need for a clear definition of the purpose of the individual markers (e.g., prognostic, diagnostic, or monitoring therapeutic efficacy); (3) a critical evaluation of the ongoing biomarker approaches; and (4) highlighting the need for standardization of preanalytical variables and analytical methodologies used by the field.
PMCID: PMC4128378  PMID: 23850333
24.  Small Molecule p75NTR Ligands Reduce Pathological Phosphorylation and Misfolding of Tau, Inflammatory Changes, Cholinergic Degeneration, and Cognitive Deficits in AβPPL/S Transgenic Mice 
The p75 neurotrophin receptor (p75NTR ) is involved in degenerative mechanisms related to Alzheimer’s disease (AD). In addition, p75NTR levels are increased in AD and the receptor is expressed by neurons that are particularly vulnerable in the disease. Therefore, modulating p75NTR function may be a significant disease-modifying treatment approach. Prior studies indicated that the non-peptide, small molecule p75NTR ligands LM11A-31, and chemically unrelated LM11A-24, could block amyloid-β-induced deleterious signaling and neurodegeneration in vitro, and LM11A-31 was found to mitigate neuritic degeneration and behavioral deficits in a mouse model of AD. In this study, we determined whether these in vivo findings represent class effects of p75NTR ligands by examining LM11A-24 effects. In addition, the range of compound effects was further examined by evaluating tau pathology and neuroinflammation. Following oral administration, both ligands reached brain concentrations known to provide neuroprotection in vitro. Compound induction of p75NTR cleavage provided evidence for CNS target engagement. LM11A-31 and LM11A-24 reduced excessive phosphorylation of tau, and LM11A-31 also inhibited its aberrant folding. Both ligands decreased activation of microglia, while LM11A-31 attenuated reactive astrocytes. Along with decreased inflammatory responses, both ligands reduced cholinergic neurite degeneration. In addition to the amelioration of neuropathology in AD model mice, LM11A-31, but not LM11A-24, prevented impairments in water maze performance, while both ligands prevented deficits in fear conditioning. These findings support a role for p75NTR ligands in preventing fundamental tau-related pathologic mechanisms in AD, and further validate the development of these small molecules as a new class of therapeutic compounds.
PMCID: PMC4278429  PMID: 24898660
Alzheimer’s disease; LM11A-31; LM11A-24; p75 neurotrophin receptor
25.  Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice 
Nature medicine  2014;20(6):659-663.
As human lifespan increases, a greater fraction of the population is suffering from age-related cognitive impairments, making it important to elucidate a means to combat the effects of aging1,2. Here we report that exposure of an aged animal to young blood can counteract and reverse pre-existing effects of brain aging at the molecular, structural, functional and cognitive level. Genome-wide microarray analysis of heterochronic parabionts—in which circulatory systems of young and aged animals are connected—identified synaptic plasticity–related transcriptional changes in the hippocampus of aged mice. Dendritic spine density of mature neurons increased and synaptic plasticity improved in the hippocampus of aged heterochronic parabionts. At the cognitive level, systemic administration of young blood plasma into aged mice improved age-related cognitive impairments in both contextual fear conditioning and spatial learning and memory. Structural and cognitive enhancements elicited by exposure to young blood are mediated, in part, by activation of the cyclic AMP response element binding protein (Creb) in the aged hippocampus. Our data indicate that exposure of aged mice to young blood late in life is capable of rejuvenating synaptic plasticity and improving cognitive function.
PMCID: PMC4224436  PMID: 24793238

Results 1-25 (57)