Plasma amyloid concentration in Alzheimer's disease: performance of a high-throughput amyloid assay in distinguishing Alzheimer's disease cases from controls

BACKGROUND: Collection of cerebrospinal fluid (CSF) for measurement of amyloid-β (Aβ) species is a gold standard in Alzheimer's disease (AD) diagnosis, but has risks. Thus, establishing a low-risk blood Aβ test with high AD sensitivity and specificity is of outmost interest. OBJECTIVE: We evaluated the ability of a commercially available plasma Aβ assay to distinguish AD patients from biomarker-healthy controls. METHOD: In a case-control design, we examined plasma samples from 44 AD patients (A + N+) and 49 controls (A-N-) from a memory clinic. AD was diagnosed using a combination of neuropsychological examination, CSF biomarker analysis and brain imaging. Total Aβ40 and total Aβ42 in plasma were measured through enzyme-linked immunosorbent assay (ELISA) technology using ABtest40 and ABtest42 test kits (Araclon Biotech Ltd.). Receiver operating characteristic (ROC) analyses with outcome AD were performed, and sensitivity and specificity were calculated. RESULTS: Plasma Aβ42/40 was weakly positively correlated with CSF Aβ42/40 (Spearman's rho 0.22; p = 0.037). Plasma Aβ42/40 alone was not able to statistically significantly distinguish between AD patients and controls (AUC 0.58; 95% CI 0.46, 0.70). At a cut-point of 0.076 maximizing sensitivity and specificity, plasma Aβ42/40 had a sensitivity of 61.2% and a specificity of 63.6%. CONCLUSION: In this sample, the high-throughput blood Aβ assay was not able to distinguish well between AD patients and controls. Whether or not the assay may be useful in large-scale epidemiological settings remains to be seen

Effect of irradiation/bone marrow transplantation on alveolar epithelial type II cells is aggravated in surfactant protein D deficient mice.

Irradiation followed by bone marrow transplantation (BM-Tx) is a frequent therapeutic intervention causing pathology to the lung. Although alveolar epithelial type II (AE2) cells are essential for lung function and are damaged by irradiation, the long-term consequences of irradiation and BM-Tx are not well characterized. In addition, it is unknown whether surfactant protein D (SP-D) influences the response of AE2 cells to the injurious events. Therefore, wildtype (WT) and SP-D(-/-) mice were subjected to a myeloablative whole body irradiation dose of 8 Gy and subsequent BM-Tx and compared with age- and sex-matched untreated controls. AE2 cell changes were investigated quantitatively by design-based stereology. Compared with WT, untreated SP-D(-/-) mice showed a higher number of larger sized AE2 cells and a greater amount of surfactant-storing lamellar bodies. Irradiation and BM-Tx induced hyperplasia and hypertrophy in WT and SP-D(-/-) mice as well as the formation of giant lamellar bodies. The experimentally induced alterations were more severe in the SP-D(-/-) than in the WT mice, particularly with respect to the surfactant-storing lamellar bodies which were sometimes extremely enlarged in SP-D(-/-) mice. In conclusion, irradiation and BM-Tx have profound long-term effects on AE2 cells and their lamellar bodies. These data may explain some of the clinical pulmonary consequences of this procedure. The data should also be taken into account when BM-Tx is used as an experimental procedure to investigate the impact of bone marrow-derived cells for the phenotype of a specific genotype in the mouse

Dietary spermidine for lowering high blood pressure

Loss of cardiac macroautophagy/autophagy impairs heart function, and evidence accumulates that an increased autophagic flux may protect against cardiovascular disease. We therefore tested the protective capacity of the natural autophagy inducer spermidine in animal models of aging and hypertension, which both represent major risk factors for the development of cardiovascular disease. Dietary spermidine elicits cardioprotective effects in aged mice through enhancing cardiac autophagy and mitophagy. In salt-sensitive rats, spermidine supplementation also delays the development of hypertensive heart disease, coinciding with reduced arterial blood pressure. The high blood pressure-lowering effect likely results from improved global arginine bioavailability and protection from hypertension-associated renal damage. The polyamine spermidine is naturally present in human diets, though to a varying amount depending on food type and preparation. In humans, high dietary spermidine intake correlates with reduced blood pressure and decreased risk of cardiovascular disease and related death. Altogether, spermidine represents a cardio- and vascular- protective autophagy inducer that can be readily integrated in common diets

Worry is associated with robust reductions in heart rate variability: a transdiagnostic study of anxiety psychopathology

Background Individuals with anxiety disorders display reduced resting-state heart rate variability (HRV), although findings have been contradictory and the role of specific symptoms has been less clear. It is possible that HRV reductions may transcend diagnostic categories, consistent with dimensional-trait models of psychopathology. Here we investigated whether anxiety disorders or symptoms of anxiety, stress, worry and depression are more strongly associated with resting-state HRV. Methods Resting-state HRV was calculated in participants with clinical anxiety (n = 25) and healthy controls (n = 58). Symptom severity measures of worry, anxiety, stress, and depression were also collected from participants, regardless of diagnosis. Results Participants who fulfilled DSM-IV criteria for an anxiety disorder displayed diminished HRV, a difference at trend level significance (p = .1, Hedges’ g = -.37, BF10 = .84). High worriers (Total n = 41; n = 22 diagnosed with an anxiety disorder and n = 19 not meeting criteria for any psychopathology) displayed a robust reduction in resting state HRV relative to low worriers (p = .001, Hedges’ g = -.75, BF10 = 28.16). Conclusions The specific symptom of worry – not the diagnosis of an anxiety disorder – was associated with the most robust reductions in HRV, indicating that HRV may provide a transdiagnostic biomarker of worry. These results enhance understanding of the relationship between the cardiac autonomic nervous system and anxiety psychopathology, providing support for dimensional-trait models consistent with the Research Domain Criteria framework

Florbetaben PET imaging to detect amyloid beta plaques in Alzheimer's disease: Phase 3 study

AbstractBackgroundEvaluation of brain β-amyloid by positron emission tomography (PET) imaging can assist in the diagnosis of Alzheimer disease (AD) and other dementias.MethodsOpen-label, nonrandomized, multicenter, phase 3 study to validate the 18F-labeled β-amyloid tracer florbetaben by comparing in vivo PET imaging with post-mortem histopathology.ResultsBrain images and tissue from 74 deceased subjects (of 216 trial participants) were analyzed. Forty-six of 47 neuritic β-amyloid-positive cases were read as PET positive, and 24 of 27 neuritic β-amyloid plaque-negative cases were read as PET negative (sensitivity 97.9% [95% confidence interval or CI 93.8–100%], specificity 88.9% [95% CI 77.0–100%]). In a subgroup, a regional tissue-scan matched analysis was performed. In areas known to strongly accumulate β-amyloid plaques, sensitivity and specificity were 82% to 90%, and 86% to 95%, respectively.ConclusionsFlorbetaben PET shows high sensitivity and specificity for the detection of histopathology-confirmed neuritic β-amyloid plaques and may thus be a valuable adjunct to clinical diagnosis, particularly for the exclusion of AD.Trial registrationClinicalTrials.gov NCT01020838

Cortical Layer 1 and Layer 2/3 Astrocytes Exhibit Distinct Calcium Dynamics In Vivo

Cumulative evidence supports bidirectional interactions between astrocytes and neurons, suggesting glial involvement of neuronal information processing in the brain. Cytosolic calcium (Ca2+) concentration is important for astrocytes as Ca2+ surges co-occur with gliotransmission and neurotransmitter reception. Cerebral cortex is organized in layers which are characterized by distinct cytoarchitecture. We asked if astrocyte-dominant layer 1 (L1) of the somatosensory cortex was different from layer 2/3 (L2/3) in spontaneous astrocytic Ca2+ activity and if it was influenced by background neural activity. Using a two-photon laser scanning microscope, we compared spontaneous Ca2+ activity of astrocytic somata and processes in L1 and L2/3 of anesthetized mature rat somatosensory cortex. We also assessed the contribution of background neural activity to the spontaneous astrocytic Ca2+ dynamics by investigating two distinct EEG states (“synchronized” vs. “de-synchronized” states). We found that astrocytes in L1 had nearly twice higher Ca2+ activity than L2/3. Furthermore, Ca2+ fluctuations of processes within an astrocyte were independent in L1 while those in L2/3 were synchronous. Pharmacological blockades of metabotropic receptors for glutamate, ATP, and acetylcholine, as well as suppression of action potentials did not have a significant effect on the spontaneous somatic Ca2+ activity. These results suggest that spontaneous astrocytic Ca2+ surges occurred in large part intrinsically, rather than neural activity-driven. Our findings propose a new functional segregation of layer 1 and 2/3 that is defined by autonomous astrocytic activity

Nonlinear gap junctions enable long-distance propagation of pulsating calcium waves in astrocyte networks

A new paradigm has recently emerged in brain science whereby communications between glial cells and neuron-glia interactions should be considered together with neurons and their networks to understand higher brain functions. In particular, astrocytes, the main type of glial cells in the cortex, have been shown to communicate with neurons and with each other. They are thought to form a gap-junction-coupled syncytium supporting cell-cell communication via propagating Ca2+ waves. An identified mode of propagation is based on cytoplasm-to-cytoplasm transport of inositol trisphosphate (IP3) through gap junctions that locally trigger Ca2+ pulses via IP3-dependent Ca2+-induced Ca2+ release. It is, however, currently unknown whether this intracellular route is able to support the propagation of long-distance regenerative Ca2+ waves or is restricted to short-distance signaling. Furthermore, the influence of the intracellular signaling dynamics on intercellular propagation remains to be understood. In this work, we propose a model of the gap-junctional route for intercellular Ca2+ wave propagation in astrocytes showing that: (1) long-distance regenerative signaling requires nonlinear coupling in the gap junctions, and (2) even with nonlinear gap junctions, long-distance regenerative signaling is favored when the internal Ca2+ dynamics implements frequency modulation-encoding oscillations with pulsating dynamics, while amplitude modulation-encoding dynamics tends to restrict the propagation range. As a result, spatially heterogeneous molecular properties and/or weak couplings are shown to give rise to rich spatiotemporal dynamics that support complex propagation behaviors. These results shed new light on the mechanisms implicated in the propagation of Ca2+ waves across astrocytes and precise the conditions under which glial cells may participate in information processing in the brain.Comment: Article: 30 pages, 7 figures. Supplementary Material: 11 pages, 6 figure

COX-2, CB2 and P2X7-immunoreactivities are increased in activated microglial cells/macrophages of multiple sclerosis and amyotrophic lateral sclerosis spinal cord

BACKGROUND: While multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) are primarily inflammatory and degenerative disorders respectively, there is increasing evidence for shared cellular mechanisms that may affect disease progression, particularly glial responses. Cyclooxygenase 2 (COX-2) inhibition prolongs survival and cannabinoids ameliorate progression of clinical disease in animal models of ALS and MS respectively, but the mechanism is uncertain. Therefore, three key molecules known to be expressed in activated microglial cells/macrophages, COX-2, CB2 and P2X7, which plays a role in inflammatory cascades, were studied in MS and ALS post-mortem human spinal cord. METHODS: Frozen human post mortem spinal cord specimens, controls (n = 12), ALS (n = 9) and MS (n = 19), were available for study by immunocytochemistry and Western blotting, using specific antibodies to COX-2, CB2 and P2X7, and markers of microglial cells/macrophages (CD 68, ferritin). In addition, autoradiography for peripheral benzodiazepine binding sites was performed on some spinal cord sections using [3H] (R)-PK11195, a marker of activated microglial cells/macrophages. Results of immunostaining and Western blotting were quantified by computerized image and optical density analysis respectively. RESULTS: In control spinal cord, few small microglial cells/macrophages-like COX-2-immunoreactive cells, mostly bipolar with short processes, were scattered throughout the tissue, whilst MS and ALS specimens had significantly greater density of such cells with longer processes in affected regions, by image analysis. Inflammatory cell marker CD68-immunoreactivity, [3H] (R)-PK11195 autoradiography, and double-staining against ferritin confirmed increased production of COX-2 by activated microglial cells/macrophages. An expected 70-kDa band was seen by Western blotting which was significantly increased in MS spinal cord. There was good correlation between the COX-2 immunostaining and optical density of the COX-2 70-kDa band in the MS group (r = 0.89, P = 0.0011, n = 10). MS and ALS specimens also had significantly greater density of P2X7 and CB2-immunoreactive microglial cells/macrophages in affected regions. CONCLUSION: It is hypothesized that the known increase of lesion-associated extracellular ATP contributes via P2X7 activation to release IL-1 beta which in turn induces COX-2 and downstream pathogenic mediators. Selective CNS-penetrant COX-2 and P2X7 inhibitors and CB2 specific agonists deserve evaluation in the progression of MS and ALS

Neuroglial ATP release through innexin channels controls microglial cell movement to a nerve injury

Microglia, the immune cells of the central nervous system, are attracted to sites of injury. The injury releases adenosine triphosphate (ATP) into the extracellular space, activating the microglia, but the full mechanism of release is not known. In glial cells, a family of physiologically regulated unpaired gap junction channels called innexons (invertebrates) or pannexons (vertebrates) located in the cell membrane is permeable to ATP. Innexons, but not pannexons, also pair to make gap junctions. Glial calcium waves, triggered by injury or mechanical stimulation, open pannexon/innexon channels and cause the release of ATP. It has been hypothesized that a glial calcium wave that triggers the release of ATP causes rapid microglial migration to distant lesions. In the present study in the leech, in which a single giant glial cell ensheathes each connective, hydrolysis of ATP with 10 U/ml apyrase or block of innexons with 10 µM carbenoxolone (CBX), which decreased injury-induced ATP release, reduced both movement of microglia and their accumulation at lesions. Directed movement and accumulation were restored in CBX by adding ATP, consistent with separate actions of ATP and nitric oxide, which is required for directed movement but does not activate glia. Injection of glia with innexin2 (Hminx2) RNAi inhibited release of carboxyfluorescein dye and microglial migration, whereas injection of innexin1 (Hminx1) RNAi did not when measured 2 days after injection, indicating that glial cells’ ATP release through innexons was required for microglial migration after nerve injury. Focal stimulation either mechanically or with ATP generated a calcium wave in the glial cell; injury caused a large, persistent intracellular calcium response. Neither the calcium wave nor the persistent response required ATP or its release. Thus, in the leech, innexin membrane channels releasing ATP from glia are required for migration and accumulation of microglia after nerve injury