<Emphasis Type="Italic">Tau</Emphasis> gene mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17)

Received: October 8, 1999 / Accepted: November 29, 1999 / Published online: February 8, 2000     

Transient reduction of spontaneous neuronal network activity by sublethal amyloid β (1–42) peptide concentrations

Soluble amyloid β_1–42 (Aβ_1–42) peptide has recently been assigned a key role in early Alzheimer’s disease (AD) pathophysiology accounting for synaptic dysfunction before amyloid plaque formation and neurodegeneration can occur. Following sublethal Aβ_1–42 administration, we observed an acute but transient reduction of the spike and burst rate of spontaneously active cortical networks cultured on microelectrode arrays. This simple experimental system appears suitable for future long-term pharmacological and genetic studies of Aβ_1–42 signaling, thus providing a valuable new tool in AD research.     

Parkin Attenuates Wild-Type τ Modification in the Presence of β-Amyloid and α-Synuclein

Changes in tau (τ) metabolism comprise important pathological landmarks in the tauopathies with parkinsonism as well as Parkinson’s disease and Alzheimer’s disease. Mutations in the parkin gene are associated with Parkinson’s disease. Deposits of amyloid proteins, including Aβ and α-synuclein coexist in the brains of patients with dementia with Lewy bodies; however, it is not known how either of them interacts with τ to provoke neurofibrillary tangle formation across the tauopathies. Here, we show a role for parkin against τ pathology in the presence of intracellular Aβ or α-synuclein. Parkin attenuates four-repeat human τ, but not mutant P301L, hyperphosphorylation in the presence of intracellular Aβ_1–42, or α-synuclein and decreases GSK-3β activity in amyloid-stressed M17 human neuroblastoma cells. These data suggest that parkin may counteract the alteration of τ metabolism in certain neurodegenerative diseases with τ cytopathy and parkinsonism. An erratum to this article can be found at     

Cholinotoxic effects of β-amyloid(1–42) peptide on cortical projections of the rat nucleus basalis magnocellularis

β-Amyloid_(1–42) peptide (βAP) was injected into the right nucleus basalis magnocellularis (nbm) of rats. After a 14-day survival time, the acetylcholinesterase and choline acetyltransferase activities and the number of muscarinic receptors were found biochemically to be significantly reduced in the ipsilateral frontal cortices. Confirmation of these data with silver staining also revealed degeneration of the projective fibers of the nbm to the frontal cortex. These results demonstrate the cholinotoxicity of βAP in an in vivo animal model.     

Frontotemporal dementia: clinical, neuroimaging, and molecular biological findings in 6 patients

Establishing the diagnosis in patients with clinical signs and symptoms suggesting primary degenerative disease with marked frontal lobe involvement is difficult. Neuroimaging methods, in particular positron emission tomography (PET) with the tracer ¹⁸fluoro-2-deoxyglucose (FDG) and cerebrospinal fluid (CSF) examination of β-amyloid and tau-protein levels may give additional information. We report five patients with clinical and radiological features of degenerative dementia with predominantly frontal involvement and one patient with primary progressive aphasia Diagnostic work-up included computed tomography (CT), magnetic resonance imaging (MRI), PET and tau-protein and β-amyloid level determination in CSF. While neuropsychological performance varied among patients, CT and MRI demonstrated persistently frontal lobe involvement. PET revealed corresponding changes with frontal hypometabolism, but in addition, four patients (among them two with no corresponding temporal changes in CT or MRI) showed a decreased glucose uptake in the temporal cortices. CSF samples from five patients revealed elevated β-amyloid 1–42 and tau levels in three and two patients, respectively. Reduced β-amyloid 1–40 was found in two patients. We conclude that occurrence of clinical symptoms of frontotemporal dementia is accompanied by frontal hypometabolism regardless of additional clinical findings. The value of determination of β-amyloid and tau protein levels remains to be determined. Received: 26 March 2001 / Accepted: 28 August 2001     

Bace 1

Adrenomedullin (AM) has two specific receptors formed by the calcitonin-receptor-like receptor (CL) and receptor activity-modifying protein (RAMP) 2 or 3. These are known as AM₁ and AM₂ receptors, respectively. In addition, AM has appreciable affinity for the CGRP₁ receptor, composed of CL and RAMP1. The AM₁ receptor has a high degree of selectivity for AM over CGRP and other peptides, and AM_22–52 is an effective antagonist at this receptor. By contrast, the AM₂ receptor shows less specificity for AM, having appreciable affinity for βCGRP. Here, CGRP_8–37 is either equipotent or more effective as an antagonist than AM_22–52, depending on the species from which the receptor components are derived. Thus, under the appropriate circumstances it seems that βCGRP might be able to activate both CGRP₁ and AM₂ receptors and AM could activate both AM₁ and AM₂ receptors as well as CGRP₁ receptors. Current peptide antagonists are not sufficiently selective to discriminate between these three receptors. The CGRP-selectivity of RAMP1 and RAMP3 may be conferred by a putative disulfide bond from the N-terminus to the middle of the extracellular domain of these molecules. This is not present in RAMP2.     

Clinical phenotypic heterogeneity of Alzheimer's disease associated with mutations of the presenilin–1 gene

It is now 10 years since the first report of mutations in the presenilin genes that were deterministic for familial autosomal dominant Alzheimer's disease. The most common of these mutations occurs in the presenilin–1 gene (PSEN1) located on chromosome 14. In the ensuing decade, more than 100 PSEN1 mutations have been described. The emphasis of these reports has largely been on the novelty of the mutations and their potential pathogenic consequences rather than detailed clinical, neuropsychological, neuroimaging and neuropathological accounts of patients with the mutation. This article reviews the clinical phenotypes of reported PSEN1 mutations, emphasizing their heterogeneity, and suggesting that other factors, both genetic and epigenetic,must contribute to disease phenotype.     

Microtubule-associated protein tau, heparan sulphate and α-synuclein in several neurodegenerative diseases with dementia

Microtubule-associated protein tau forms neurofibrillary lesions in Alzheimer’s disease and several other neurodegenerative disorders, such as Niemann-Pick disease type C, subacute sclerosing panencephalitis, argyrophilic grain disease, myotonic dystrophy and motor neuron disease with neurofibrillary tangles. In this study we have compared the characteristics of tau pathology in these diseases using immunohistochemistry and phosphorylation-dependent and phosphorylation-independent anti-tau antibodies. The pattern of staining for heparan sulphate and α-synuclein was also investigated. We show that in all of these diseases tau deposits were stained by all anti-tau antibodies used, with the exception of argyrophilic grains which do not stain with antibody 12E8, confirming our previous findings. Heparan sulphate staining was present to a variable extent in all of these diseases, with the exception of subacute sclerosing panencephalitis, in which no staining was observed. Heparan sulphate staining coexisted with tau staining. In some cases it was more extensive than the tau staining. α-Synuclein staining was present in presynaptic terminals with the exception of one case of Alzheimer’s disease, in which α-synuclein-positive Lewy bodies were observed in the hippocampal formation. These findings indicate that tau deposits are antigenically similar in several neurodegenerative diseases and that tau staining is often associated with heparan sulphate staining, supporting the concept that heparan sulphate may be involved in the assembly of tau protein into filaments. Received: 14 August 1998 / Revised, accepted: 12 November 1998     

Role of vitamin B12, folate, and thyroid stimulating hormone in dementia: A hospital-based study in north Indian population

Background:

Vitamin B₁₂ and folate represent modifiable risk factors for dementia. They may increase the risk of Alzheimer′s dementia (AD) and vascular dementia (VaD) as their deficiency can increase the homocysteine level due to slowed methylation reaction. Homocysteine has a neurotoxic effect that could lead to neurologic disturbances. Hence, it is important to explore the status of serum B₁₂ and folate in AD and VaD to evolve the treatment strategies for the same.

Objectives:

A retrospective study was conducted to assess the levels of vitamin B₁₂, folate, and thyroid stimulating hormone (TSH) in serum and the relationship of these factors, including age and sex to cognitive decline in VaD, AD, and dementia due to other causes (DOC).

Materials and Methods:

Serum vitamin B₁₂, folate, TSH, and total cholesterol were studied in 32 AD patients (mean age: 65 years), 12 VaD patients (mean age: 61 years), 83 DOC (mean age: 65 years), and 127 control subjects (mean age: 49 years). Results: In AD, VaD, and DOC, the levels of vitamin B₁₂ and folate were significantly lower (P < 0.002; 0.026; 0.002 for vitamin B₁₂ and P < 0.000 in all the 3 groups for folate) as compared with the controls. Similarly, TSH levels were significantly lower in AD and DOC (P < 0.008; 0.038) as compared with the controls.

Conclusion:

Vitamin B₁₂ and folate were significantly low in both AD and VaD patients. Hence, B vitamin supplementation should be considered as possible targets for the therapeutic intervention in dementia.     

Expression of α<Subscript>2</Subscript>-macroglobulin,neutrophil elastase,and interleukin-1α differs in early-stage and late-stage atherosclerotic lesions in the arteries of the circle of Willis

Different types of atherosclerotic (AS) lesions can be distinguished histologically and represent different stages of AS plaque development. Late-stage lesions more frequently develop complications such as plaque rupture and thrombosis with vessel occlusion than early AS lesions. To clarify whether protective, destructive, and inflammatory proteins are differentially expressed in early-stage and late-stage AS plaques we examined the proteinase inhibitor α₂-macroglobulin (A2M), the neutrophil elastase (NE)—an enzyme degrading elastin and collagen fibers—and the proinflammatory protein interleukin-1α (IL-1α) in all types of AS plaques in the arteries of the circle of Willis from 78 human autopsy cases of both genders (61–91 years of age). Paraffin sections of AS plaques were immunostained with antibodies directed against A2M, NE and IL-1α. In initial AS lesions A2M was found, whereas NE and IL-1α were absent. NE and IL-1α became detectable as soon as a significant number of macrophages occurred within AS lesions. With increasing histopathological type of AS lesions, a marked increase of the area of the plaque exhibiting NE and IL-1α was observed. The area which exhibits A2M in AS plaques, on the other hand, did not vary significantly between the different stages. Thus, our results indicate a disproportionately high increase of the destructive enzyme NE and the proinflammatory protein IL-1α in relation to A2M with the progression of the grade of AS lesions pointing to the transgression of the protective capacity of A2M by NE and IL-1α in late-stage plaques. Therefore, our findings support the hypothesis that NE-induced tissue damage in late-stage AS plaques contributes to the development of plaque rupture and subsequent thrombosis.     

Increased NPY activity in the PVN contributes to food-restriction induced reductions in blood pressure in aortic coarctation hypertensive rats

We hypothesized that hypothalamic NPYergic mechanisms mediate the blood pressure lowering effect of caloric restriction in hypertensive rats. Aortic coarctation-induced (AC) hypertensive rats (n=25) were assigned to either an ad libitum fed control group (AL) or food restricted group (FR; 60% of AL consumption) for 3 weeks. Rats were instrumented chronically with vascular catheters and bilateral guide cannulae directed at the paraventricular hypothalamic nuclei (PVN). Blood pressure (BP) and heart rate (HR) responses to bilateral PVN microinjection of saline (200 nl) or the putative NPY receptor antagonists [D-Trp32]NPY(1-36) (3.3 micrograms/200 nl) and [D-Tyr27,36 Thr32]NPY(27-36) (D-NPY(27-36); 3.3 micrograms/200 nl) were determined. The FR rats were then refed and cardiovascular responses to PVN injections of NPY receptor antagonists were again determined. FR rats had significantly reduced resting BP (159+/-4 vs. 129+/-4 mmHg) and HR (360+/-11 vs. 326+/-9 bpm) compared to AL controls. Refeeding restored BP and HR of FR rats to levels similar to AL (BP=153+/-4 mmHg, HR=359+/-11 bpm). PVN administration of [D-Trp32]NPY produced foraging behavior and concurrent increases in BP and HR in FR, AL and Re-fed rats. The behavioral activation suggests that [D-Trp32]NPY(1-36) produced activation of NPY receptors. In contrast, D-NPY (27-36) did not produce any behavioral response or affect BP or HR in AL or Re-fed rats. In FR rats, D-NPY (27-36) produced significant increases in BP (peak=15+/-3 mmHg) which partially reversed the effect of FR on BP. Thus, in FR rats with reduced BP, PVN administration of an NPY receptor antagonist increases BP. NPY blockade in the PVN accounted for about 50% of the BP effect of food restriction, thus other mechanisms are likely to be involved. These findings are consistent with the hypothesis that NPYergic mechanisms may contribute to the reduction of BP produced by food restriction.     

Treatment of endothelium with the chemotherapy agent vincristine affects activated protein C generation to a greater degree in newborn plasma than in adult plasma

INTRODUCTION: Activated protein C (APC) is well-established as a physiologically important anticoagulant. During development, plasma concentrations of protein C and alpha(2)macroglobulin, factors involved in APC generation, differ from adult levels. Chemotherapy drugs can perturb endothelial expression of PC-activating receptors. This study examines the effect of chemotherapy treatment of endothelium on APC generation in newborn and adult plasma. MATERIALS AND METHODS: APC generations were initiated on endothelial cells treated with vincristine or media by recalcifying defibrinated plasma with buffer containing thromboplastin. APC generation was terminated by mixing timed subsamples into FFRCMK-EDTA or heparin, followed by EDTA. APC-PCI and APC-alpha(1)AT were assayed by ELISA. APC-alpha(2)M was measured chromogenically. Since heparin converts free APC to APC-PCI, the difference between APC-PCI detected in heparin subsamples and APC-PCI detected in FFRCMK-EDTA subsamples gave the free APC. Cellular expression of EPCR and TM were measured by flow cytometry and Western blot. RESULTS: Vincristine-treated endothelium decreased free APC generation in newborn plasma to a greater degree than in adult plasma. APC-PCI levels in both adult and newborn plasma were unaffected by chemotherapy. Vincristine treatment reduced levels of APC-alpha(1) AT and APC-alpha(2) M to a greater degree in newborn plasma versus adult plasma. Expression of EPCR was reduced in cells treated with vincristine. Conversely, TM was reduced on the cell surface, but increased in whole cell lysates. CONCLUSIONS: The differential response of newborn and adult plasma PC components to chemotherapy-mediated changes in cell surface components may be a factor in the increased risk of thrombosis in children receiving chemotherapy.     

Orphanin FQ-induced outward current in rat hippocampus

Orphanin FQ (OFQ) is a heptadecapeptide that structurally resembles opioid peptides. It has been demonstrated that the moderate density of binding sites of OFQ were localized in the hippocampus and that the expression of OFQ receptor in the hippocampus have an important role in learning and memory. This study was designed to investigate whether activation of the OFQ receptor could induced hyperpolarization in the cultured hippocampus neurons in rats. In the current clamp mode, the application of OFQ (10(-8)-10(-5) M) hyperpolarized the membranes in cultured hippocampus neurons in a concentration-dependent manner. Moreover, in the voltage clamp mode, application of OFQ (10(-6) M) induced outward current in hippocampus CA3 pyramidal neurons. In the presence of TTX (3x10(-7) M), the average maximal amplitude of the outward current deflection induced by OFQ (10(-6) M) at -60 mV of a holding potential was 24.7+/-0.54 pA. The OFQ-induced current reversed at -99.06+/-3.80 mV (3 mM), which was quite close to the K(+) equilibrium potential as calculated by the Nernst equation (E(k)=-96.08 mV, 3 mM) for K(+) in our standard solution. This suggests that OFQ-induced current was mediated by K(+) ion. It has been demonstrated that [Phe(1)psi(CH(2)-NH)Gly(2)]Nociceptin(1-13)NH(2)) (a pseudopeptide analog of nociceptin), and nocistatin are selective antagonists of OFQ. OFQ (10(-6) M)-induced outward current was antagonized by application of [Phe(1)psi(CH(2)-NH)Gly(2)]Nociceptin(1-13)NH(2) (10(-5) M). In contrast, OFQ-induced outward current was not antagonized by application of nocistatin (10(-5) M). These results indicates that there is the physiological functioning receptor of OFQ in the hippocampus.     

Neuroprotective effect of melatonin on soluble Aβ1–42-induced cortical neurodegeneration via Reelin–Dab1 signaling pathway

Objective: Soluble Aβ_1–42 oligomers play a vital role in the development and pathogenesis of Alzheimer’s disease (AD). Melatonin could delay the progress of AD through multiple mechanisms. Reelin–Dab1 signaling plays an important role in AD, including neuronal function and synaptic plasticity. However, whether melatonin could exert its neuroprotective function against soluble Aβ_1–42-induced neurotoxicity during AD development through regulating Reelin–Dab1 signaling remains poorly understood.

Methods: AD rat model was established by soluble Aβ_1–42 repeated intracerebroventricular injection. Using immunohistochemistry and Western blot analyses, the effect of melatonin on synaptic plasticity, neuritic degeneration, and astrocyte activation was investigated in cerebral cortex. Meanwhile, the expression of Reelin and Dab1 was also examined in cerebral cortex. In our in vitro study, Reelin–Dab1 signaling was inhibited by Reelin antibody, and neuroprotective effect of melatonin against Aβ_1–42 was further determined.

Results: Melatonin ameliorated the neurotoxiciy and astrocyte activation induced by Aβ_1–42 in the cerebral cortex. Melatonin also blocked the reduction in Reelin and Dab1 expression induced by Aβ_1–42. Using in vitro study, Reelin inactivation completely abolished the protective effect of melatonin against Aβ_1–42-induced neurotoxicity.

Discussion: Melatonin might play its neuroprotective role against Aβ_1–42 through mediating Reelin–Dab1 signaling pathway. Melatonin could be a safe and remarkable therapeutic candidate for AD and other aged-associated neurodegenerative diseases.     

Receptor-mediated inositide hydrolysis is a neuronal response: comparison of primary neuronal and glial cultures

Cholinergic and adrenergic receptor-stimulated inositide hydrolysis was studied in neuronal and glial cells cultured from brains of 1-day-old Wistar-Kyoto rats. Incubation of the cells with [3H]inositol led to the incorporation of radioactivity specifically into inositol phospholipids. Labeling of the membrane lipids reached a maximum in 2-3 days. Receptor-stimulated breakdown of inositides was determined by following the accumulation of inositol phosphates after incubation of the labeled cells for 60 min with carbachol or norepinephrine in the presence of 10 mM lithium. Carbachol (1 mM) stimulated inositol phosphate production in neurons 30 times higher than that seen in glia. The response stimulated by norepinephrine (75 microM) was 6 times higher in neurons than glia. The response to carbachol was blocked by atropine, and the norepinephrine-induced response was inhibited by prazosin suggesting that the receptors mediating the responses were muscarinic and alpha 1-adrenergic, respectively. These results suggest that muscarinic cholinergic and alpha 1-adrenergic stimulated inositide hydrolysis is primarily a neuronal response and that this biochemical event may be important for transmembrane signaling which occurs during neurotransmission.     

Nociceptin/orphanin FQ and [Pheψ(CH2-NH)Gly]nociceptin(1–13)NH2 modulates the activity of hypothalamic paraventricular nucleus neurons in vitro

Nociceptin, also known as orphanin FQ (N/OFQ), an endogenous ligand for the orphan opioid receptor-like₁ (ORL₁) receptor, is moderately expressed in the hypothalamic paraventricular nucleus (PVN) involved in the integrative control of the function of the endocrine and autonomic nervous systems. Our previous study demonstrated that intracerebroventricular administration of N/OFQ elicits an inhibitory action on the function of the cardiovascular and sympathetic nervous systems in conscious rats. However, the effects of N/OFQ on PVN neurons have not been examined. We investigated the effects of N/OFQ on PVN neurons using a whole-cell patch-clamp recording technique in rat brain slices. N/OFQ (30–1000 nM) hyperpolarized membrane potentials in type 1 and type 2 neurons of the PVN classified by the electrophysiological property. [Phe¹ψ(CH₂-NH)Gly²]nociceptin(1-13)NH₂ (Pheψ) (1–9 μM), a presumed competitive antagonist of the ORL₁ receptor, also hyperpolarized membrane potential in both types of neurons. In voltage clamp studies, N/OFQ (3–3000 nM) activated a K⁺ current concentration-dependently in 69.7% of PVN neurons with an EC₅₀ of 72.4±12 nM. Pheψ (100–9000 nM) also activated a K⁺ current with an EC₅₀ of 818±162 nM in PVN neurons, and significantly reduced the amplitude of the N/OFQ-stimulated current. The N/OFQ-induced current was not antagonized by the classical opioid receptor antagonist naloxone and putative antagonist nocistatin. These findings suggest that N/OFQ may have a functional role in the PVN.     

Serum macroglobulin induces prion protein transition

The accumulation of the protease-resistant (PrPRes) abnormal form of the cellular prion protein (PrPC) plays a central role in Transmissible Spongiform Encephalopathies. In this report we describe a blood serum protein, which is precipitated by 9% PEG-6000, migrates in a sucrose gradient with a density of 1.21–1.17 g/ml, has a molecular mass of approximately 720 kDa and amino acid sequence as α₂-Macroglobulin (α₂-M). This protein can potentiate the conversion of the human recombinant prion protein (23–231 AA) as well as PrPC from the brain of mouse, hamster or cow from the sensitive to the resistant form. Under physiological conditions (pH 7.5; 0.15 M NaCl; 37°C for 30 min; a nanomolar concentration range of PrP) the small, highly structured RNA (shs RNA) may activate the conversion process. We describe the design of an assay for screening for the biomolecules that prevent the PrP transition. Based on our experimental data we discuss the role of the α-helix to β-sheet conformational change in the PrPSen to PrPRes conversion as well as the role of the α₂-M during the initial stage of amyloidogenesis as well as the shs RNAs involvement in the formation of amyloid aggregates in neurodegenerative diseases. The text was submitted by the authors in English.     

Modification of acetylcholine release by nociceptin in conscious rat striatum

Nociceptin (NOC), an endogenous ligand for the orphan opioid receptor ORL1 (ORL1), has recently been recognized as a neuropeptide. We used brain microdialysis and on-line high performance liquid chromatography (HPLC) to examine the effect of NOC on the basal outflow of acetylcholine (ACh) in the freely moving rat striatum in vivo. ACh release was reduced by nociceptin at a concentration of 10(-5) M to 79% of control release. This effect of NOC was attenuated by [Phe1Psi(CH2-NH)Gly2]nociceptin-(1-13)-NH2 (PhePsi), suggesting that NOC activates the ORL1 receptor and (PhePsi) acts as an antagonist on ORL1 in rat striatum in vivo. These findings indicate that NOC may act as a neuropeptide which inhibits ACh release in the striatum via ORL1.     

Characterization of the expression of key adenoviral receptors CAR and integrin β3/β5 subunits on the membrane of human NT2 neurons

Expression of therapeutic gene products in differentiated human NT2 neurons (NT2/Ns) is being explored for ex vivo gene therapy of human neurological diseases. In this study we determined the efficiency of adenovirus (Ad)-mediated gene delivery into NT2/Ns and characterized the expression of several key receptors known to be required for efficient Ad-mediated gene delivery. Undifferentiated NT2 cells and NT2/Ns were infected by Ad expressing green fluorescent protein at an efficiency of 33% and 17%, respectively—percentages much lower than the 92% infectivity obtained from a human non-neuronal cell line A549 cells. This relatively low infectivity of NT2/Ns might be caused by the extremely low expression of integrin subunit β₃ and the reduced expression of β₅ during differentiation. The expression of coxsackie-Ad receptor (CAR) was relatively high and remained constant during differentiation. Blocking CAR receptor using an antibody specific against CAR reduced Ad infectivity in a dose-dependent manner. These observations suggest that modulating the expression of integrin subunits β_3/5 or the functional heterodimer α_vβ_3/5 in human NT2/Ns may enhance adenoviral infectivity of NT2/Ns.