Faculty Bibliography

Basal forebrain cholinergic neurons play a key role in cognition. This neuronal system is highly dependent on NGF for its synaptic integrity and the phenotypic maintenance of its cell bodies. Basal forebrain cholinergic neurons progressively degenerate in Alzheimer's disease and Down's syndrome, and their atrophy contributes to the manifestation of dementia. Paradoxically, in Alzheimer's disease brains, the synthesis of NGF is not affected and there is abundance of the NGF precursor, proNGF. We have shown that this phenomenon is the result of a deficit in NGF's extracellular metabolism that compromises proNGF maturation and exacerbates its subsequent degradation. We hypothesized that a similar imbalance should be present in Down's syndrome. Using a combination of quantitative reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting and zymography, we investigated signs of NGF metabolic dysfunction in post-mortem brains from the temporal (n = 14), frontal (n = 34) and parietal (n = 20) cortex obtained from subjects with Down's syndrome and age-matched controls (age range 31-68 years). We further examined primary cultures of human foetal Down's syndrome cortex (17-21 gestational age weeks) and brains from Ts65Dn mice (12-22 months), a widely used animal model of Down's syndrome. We report a significant increase in proNGF levels in human and mouse Down's syndrome brains, with a concomitant reduction in the levels of plasminogen and tissue plasminogen activator messenger RNA as well as an increment in neuroserpin expression; enzymes that partake in proNGF maturation. Human Down's syndrome brains also exhibited elevated zymogenic activity of MMP9, the major NGF-degrading protease. Our results indicate a failure in NGF precursor maturation in Down's syndrome brains and a likely enhanced proteolytic degradation of NGF, changes which can compromise the trophic support of basal forebrain cholinergic neurons. The alterations in proNGF and MMP9 were also present in cultures of Down's syndrome foetal cortex; suggesting that this trophic compromise may be amenable to rescue, before frank dementia onset. Our study thus provides a novel paradigm for cholinergic neuroprotection in Alzheimer's disease and Down's syndrome.

Inheritance of the apolipoprotein E4 (apoE4) genotype has been identified as the major genetic risk factor for late-onset Alzheimer's disease (AD). Studies have shown that the binding between apoE and amyloid-beta (Abeta) peptides occurs at residues 244-272 of apoE and residues 12-28 of Abeta. ApoE4 has been implicated in promoting Abeta deposition and impairing clearance of Abeta. We hypothesized that blocking the apoE/Abeta interaction would serve as an effective new approach to AD therapy. We have previously shown that treatment with Abeta12-28P can reduce amyloid plaques in APP/PS1 transgenic (Tg) mice and vascular amyloid in TgSwDI mice with congophilic amyloid angiopathy (CAA). In the present study, we investigated whether the Abeta12-28P elicits a therapeutic effect on tau-related pathology in addition to amyloid pathology using old triple transgenic Alzheimer's disease mice (3xTg, with PS1M146V , APPS we and tauP30 IL transgenes) with established pathology from the ages of 21 to 26 months. We show that treatment with Abeta12-28P substantially reduces tau pathology both immunohistochemically and biochemically, as well as reducing the amyloid burden and suppressing the activation of astrocytes and microglia. These affects correlate with a behavioral amelioration in the treated Tg mice

The accumulation of aggregated, hyperphosphorylated tau as neurofibrillary tangles and neuropil threads are cardinal features of Alzheimer's disease (AD). The other lesions found in AD include amyloid plaques and congophilic amyloid angiopathy, both associated with the extracellular accumulation of the amyloid-beta (Abeta) peptide. AD is the most common cause of dementia globally. Currently, there are no effective means to treat AD or even to slow it down. The dominant theory for the causation of AD is the amyloid cascade hypothesis, which suggests that the aggregation of Abeta as oligomers and amyloid plaques is central to the pathogenesis of AD. Numerous therapies have been developed directed to Abeta-related pathology, in particular various immunotherapeutic approaches. So far all of these have failed in clinical trials. Recently, there has been more focus on therapy directed to tau-related pathology, which correlates better with the cognitive status of patients, compared to the amyloid burden. Immunotherapeutic targeting of tau pathology has shown great potential in treating tau pathologies in mouse models of AD. A number of studies have shown the efficacy of both passive and active immunization. This review summarizes recent advances in therapy targeting pathological tau protein, in particular focusing on immunotherapeutic approaches which are showing great promise. (c) 2014 S. Karger AG, Basel.

Alzheimer's disease (AD), the most prevalent form of dementia worldwide, can be deemed as the next global health epidemic. The biochemistry underlying deposition of amyloid beta (A beta) and hyperphosphorylated tau aggregates in AD has been extensively studied. The oligomeric forms of A beta that are derived from the normal soluble A beta peptides are believed to be the most toxic. However, it is the fibrillar Abeta form that aggregates as amyloid plaques and cerebral amyloid angiopathy, which serve as pathological hallmarks of AD. Moreover, deposits of abnormally phosphorylated tau that form soluble toxic oligomers and then accumulate as neurofibrillary tangles are an essential part of AD pathology. Currently, many strategies are being tested that either inhibit, eradicate or prevent the development of plaques in AD. An exciting new approach on the horizon is the immunization approach. Dramatic results from AD animal models have shown promise for active and passive immune therapies targeting A beta. However, there is very limited data in humans that suggests a clear benefit. Some hurdles faced with these studies arise from complications noted with therapy. Encephalitis has been reported in trials of active immunization and vasogenic edema or amyloid - related imaging abnormalities (ARIA) has been reported with passive immunization in a minority of patients. As yet, therapies targeting only tau are still limited to mouse models with few studies targeting both pathologies. As the majority of approaches tried so far are based on targeting a self - protein, though in an abnormal conformation, benefits of therapy need to be balanced against the possible risks of stimulating excessive toxic inflammation. For better efficacy, future strategies will need to focus on the toxic oligomers and targeting all aspects of AD pathology.

OBJECTIVE: Few data are available on the prevalence of cognitive impairment no dementia (CIND) in rural China. The aim of this study was to estimate the prevalence of CIND in individuals aged 60 years and older in a large rural community, and to analyze the associated risk factors. METHODS: A two-phase, door-to-door epidemiological study was used for residents aged 60 years and older in Ji County, a rural county near Tianjin in Northern China. In phase 1 of the study, the Mini-Mental State Examination and Clinical Dementia Rating were administered for screening purposes. In phase 2, the subjects who screened positive were further examined by neurologists. A total of 5,744 individuals underwent the home visit interview, where demographic variables and comorbidities were recorded; 5,550 individuals completed the two phases. CIND was diagnosed by the Aging, Demographics and Memory Study on CIND criteria. The odds ratio (OR) for each risk factor was calculated by logistic regression analysis. RESULTS: The prevalence of CIND among those aged 60 years and older was 23.3%. The prevalence of CIND was lower among those with a higher level of education or social involvement. CIND was more prevalent in females, older individuals, those with a past history of stroke, and those living without a partner. Significant risk factors were found by multivariate analyses: past history of stroke (OR = 1.889; 95% CI: 1.437-2.483); being female (OR = 1.546; 95% CI: 1.305-1.832); and having no partner (divorced, widowed or single; OR = 1.250; 95% CI: 1.042-1.499). In turn, level of education (OR = 0.560; 95% CI: 0.460-0.681) and engagement in social activities (OR = 0.339; 95% CI: 0.258-0.404) were protective factors. CONCLUSIONS: This is the first large-scale community-based epidemiological study assessing the prevalence of cognitive loss in the rural Chinese population. The total prevalence of CIND observed was 23.3%, which was higher than in other studies in Western and Asian countries. Living without a partner, female gender and previous stroke increased the risk of CIND, whereas a higher level of education and engagement in social activities reduced the risk of CIND.

BACKGROUND: Central to the pathogenesis of Alzheimer's disease (AD) and many other neurodegenerative diseases is the conformational change of a normal self-protein into toxic oligomeric species and amyloid deposits. None of these disorders have an effective therapy, but immunization approaches hold great promise. We have previously shown that active immunization with a novel peptide when polymerized into a stable oligomeric conformation, pBri, induced a humoral immune response to toxic Abeta species in an AD model, APP/PS1 transgenic (Tg) mice, reducing plaque deposits. pBri is a glutaraldehyde polymerized form of the carboxyl fragment of an amyloidogenic protein, which is deposited in the brains of patients with a rare autosomal dominant disease due to a missense mutation in a stop codon, resulting in the translation of an intronic sequence, with no known sequence homology to any mammalian protein. METHODS: In the current study we tested whether pBri-peptide-based immunomodulation is effective at reducing both vascular amyloid deposits and tau-related pathology using TgSwDI mice with extensive congophilic angiopathy and 3xTg mice with tau pathology. RESULTS: Our results indicate that this immunomodulation approach, which produces a humoral response to proteins in a pathological conformation, is effective at reducing both Abeta and tau-related pathologies. CONCLUSIONS: This immunomodulatory approach has the advantage of using a non-self-immunogen that is less likely to be associated with autoimmune toxicity. Furthermore we found that it is able to target all the cardinal features of AD concurrently.

HIV-ITP patients have a unique antibody (Ab) against platelet GPIIIa49-66 which induces oxidative platelet fragmentation in the absence of complement (Cell 106: 551, 2001; JCI 113: 973, 2004). The search for a physiologic ligand that could induce this reaction was undertaken by panning the GPIIIa49-66 peptide with a phage surface display 7-mer peptide library. From 20 positive clones, 1 had 70% identity with a C-terminal region of ADAMTS-18 (a disintegrin and metalloproteinase with thrombospondin (TSR)-like motif 18), which is secreted by endothelial cell (EC). The recombinant C-terminal fragment of ADAMTS-18 can completely dissolve platelet aggregates formed in vitro. Moreover, this fragment lyses thrombi formed in the cerebral artery of mice and reduces infarction and neurologic impairment in murine ischemic stroke model (Blood 113: 6051, 2009). However, whether ADAMTS-18 represents the dominant physiologic mechanism controlling thrombus dissolution in vivo remains to be clarified. Here, we used ADAMTS-18-deficient (ADAMTS-18^-/-) mice to study the contributions of ADAMTS-18 to thrombus formation in vivo. To investigate possible functional differences between WT and ADAMTS-18^-/- platelets, we tested WT and ADAMTS-18^-/- platelets in a model of pulmonary thromboembolism induced by infusion of a mixture of platelet agonist collagen (25 mug per mouse) and epinephrine (1 mug per mouse). In lung tissue Hematoxylin and eosin-stained (HE) slides, the mean number of thrombi per lung was same in the ADAMTS-18^-/- group compared with WT group (163.7 +/-14.38 vs 174.9 +/-11.73, n=30/group, P=0.5480). In vitro, there is no difference between WT and ADAMTS-18^-/- platelet aggregation trace and activation initiated by various platelet agonists ADP (10 muM) or collagen (2 mug/mL). No difference was noted on WT and ADAMTS-18^-/- platelet adhesion on immobilized ligand (fibrinogen). These results indicated ADAMTS-18 had no effect on platelet functio!

Soluble amyloid-beta oligomers (Abetao) trigger Alzheimer's disease (AD) pathophysiology and bind with high affinity to cellular prion protein (PrP(C)). At the postsynaptic density (PSD), extracellular Abetao bound to lipid-anchored PrP(C) activates intracellular Fyn kinase to disrupt synapses. Here, we screened transmembrane PSD proteins heterologously for the ability to couple Abetao-PrP(C) with Fyn. Only coexpression of the metabotropic glutamate receptor, mGluR5, allowed PrP(C)-bound Abetao to activate Fyn. PrP(C) and mGluR5 interact physically, and cytoplasmic Fyn forms a complex with mGluR5. Abetao-PrP(C) generates mGluR5-mediated increases of intracellular calcium in Xenopus oocytes and in neurons, and the latter is also driven by human AD brain extracts. In addition, signaling by Abetao-PrP(C)-mGluR5 complexes mediates eEF2 phosphorylation and dendritic spine loss. For mice expressing familial AD transgenes, mGluR5 antagonism reverses deficits in learning, memory, and synapse density. Thus, Abetao-PrP(C) complexes at the neuronal surface activate mGluR5 to disrupt neuronal function.

Background: We have shown that active immunization with a novel nonself amyloidogenic peptide (pABri) induced a humoral immune response, largely IgM, to both PHF and toxic Abeta species inAD model, APP/PS1 transgenic (Tg) mice. Histology revealed a lower amyloid burden in both the cortex and hippocampus, along with improved cognitive testing scores compared to controls. pABri immunization resulted in lower levels of soluble and insoluble Abeta42 and Abeta40 in Tg mice. Plasma from these mice was used to immunostain human AD temporal cortex brain tissue. Staining of cytoplasm and dendrites of neurons, paired helical filaments, and Abeta plaques was documented. Methods: The novel peptide, pABri, is a carboxyl fragment of an amyloidogenic protein which is deposited in the brain of patients with a rare autosomal dominant disease due to a missense mutation in a stop codon, resulting in the translation of an intronic sequence, with no known sequence homology to any mammalian protein. Hence, this immunomodulatory therapeutic is unlikely to produce autoimmune toxicity since it utilizes a non-self peptide. This current study utilizes the pABri peptide as an immunogen for active immunization in two other mouse AD Tg models: 3xTg, with tau and amyloid pathology, and TgSwDI, with extensive congophilic angiopathy. Toxicity, neuropathology, humoral immune responses, and cognitive behavior were assessed. Results: The antibodies produced are against both the primary sequence of the immunogen as well as to the pathology associated b-sheet structure that is shared by both NFTs and amyloid plaques. These conformationally specific antibodies, reacting to Abeta peptide and tau oligomers, are against a b-sheet conformation since the immunogen, pAbri, is predominantly in such a conformation. Treatment led to cognitive rescue with pABri matching cognition of WT mice. Brain homogenates revealed lower Abeta40 and Abeta42 levels in pABri treated 3xTg mice compared to controls. pABri treatment groups show lower amyloid bu!