Clioquinol promotes the degradation of metal-dependent amyloid-β (Aβ) oligomers to restore endocytosis and ameliorate Aβ toxicity

Alzheimer’s disease (AD) is a common, progressive neurodegenerative disorder without effective disease-modifying therapies. The accumulation of amyloid-β peptide (Aβ) is associated with AD. However, identifying new compounds that antagonize the underlying cellular pathologies caused by Aβ has been hindered by a lack of cellular models amenable to high-throughput chemical screening. To address this gap, we use a robust and scalable yeast model of Aβ toxicity where the Aβ peptide transits through the secretory and endocytic compartments as it does in neurons. The pathogenic Aβ 1–42 peptide forms more oligomers and is more toxic than Aβ 1–40 and genome-wide genetic screens identified genes that are known risk factors for AD. Here, we report an unbiased screen of ∼140,000 compounds for rescue of Aβ toxicity. Of ∼30 hits, several were 8-hydroxyquinolines (8-OHQs). Clioquinol (CQ), an 8-OHQ previously reported to reduce Aβ burden, restore metal homeostasis, and improve cognition in mouse AD models, was also effective and rescued the toxicity of Aβ secreted from glutamatergic neurons in Caenorhabditis elegans. In yeast, CQ dramatically reduced Aβ peptide levels in a copper-dependent manner by increasing degradation, ultimately restoring endocytic function. This mirrored its effects on copper-dependent oligomer formation in vitro, which was also reversed by CQ. This unbiased screen indicates that copper-dependent Aβ oligomer formation contributes to Aβ toxicity within the secretory/endosomal pathways where it can be targeted with selective metal binding compounds. Establishing the ability of the Aβ yeast model to identify disease-relevant compounds supports its further exploitation as a validated early discovery platform.Alzheimer’s disease (AD) is a common and devastating neurodegenerative disorder that is projected to increase in frequency as our population ages. The lack of disease-modifying therapies requires new approaches to address the underlying mechanisms of cellular dysfunction and identify potential therapeutics.The amyloid-β peptide (Aβ) plays a major role in AD and ultimately leads to neuronal death and cognitive impairment (1). Aβ peptides of ∼40 aa are generated by the successive cleavage of the amyloid precursor protein (APP) by β- and γ-secretases. Mutations in APP or γ-secretase cause familial AD and bias APP cleavage toward a 42-aa Aβ peptide that predominates in Aβ plaques, is more aggregation prone, and is toxic to neurons (2, 3). Although Aβ plaques are a common, conspicuous feature of pathology in diseased brains, increasing evidence suggests that small oligomers of Aβ are the most toxic species (4, 5).The conservation of protein homeostasis mechanisms—such as protein trafficking and chaperone networks—among all eukaryotes makes yeast a powerful discovery platform for modeling the cellular toxicities caused by neurodegenerative disease proteins (6). In neurons, the cleavage of APP to generate the Aβ peptide occurs within the secretory and endosomal pathways (7). APP is trafficked through the secretory pathway to the plasma membrane and subsequently internalized and recycled through endosomal vesicles and the trans-Golgi network back to the plasma membrane (7). During this recycling, the Aβ peptide is liberated from APP by β/γ-secretases, thus enabling the peptide to interact with multiple membranous compartments within the cell.We have taken advantage of the great conservation of the secretory and endocytic pathways between yeast and neurons to study Aβ in a simple, highly tractable model organism—budding yeast. By expressing Aβ as a fusion to an endoplasmic reticulum (ER) targeting signal, we have mimicked in yeast the multicompartmental distribution of Aβ (8). This approach bypasses the need to recapitulate the entire APP processing pathway and generates an Aβ peptide with exactly the same sequence as is found in the human brain. The ER targeting signal directs cotranslational transport of the primary translation product into the ER, where the signal sequence is removed by signal peptidase. The peptide then transits through the secretory pathway and is secreted from the cell. In yeast, the cell wall prevents secreted Αβ from diffusing away, allowing it to interact with the plasma membrane and undergo endocytosis. As in the human nervous system (2), the aggregation-prone 42-aa peptide is more prone to forming oligomeric species than the 40-aa peptide (9) and is more toxic (8).This model allowed us to take advantage of yeast genetics to perform a completely unbiased screen of the yeast genome for suppressers or enhancers of Aβ toxicity. Of the ∼6,000 genes we tested, we recovered only a handful of modifiers. There are ∼25,000 genes in the human genome and less than 20 (10) have been shown to confer risk for AD. However, several of the yeast genes that alter Aβ toxicity are either direct homologs or interacting partners of human risk factors (8, 10). For example, YAP1802, is the yeast homolog of PICALM, one the most highly validated risk factors for AD (10, 11); INP52, is homologous to SYNJ1, which interacts with the risk factor BIN1 (12, 13); and SLA1 is homologous to SH3KBP1, which interacts with the risk factor CD2AP (14–16). All of these proteins are involved in clathrin-mediated endocytosis in yeast and humans. In addition to ameliorating the toxicity of Aβ in yeast, these proteins reduced Aβ toxicity in both Caenorhabditis elegans and rat cortical neuronal models (8). The recovery of genes that promote clathrin-mediated endocytosis in unbiased genome-wide screens suggested that Aβ poisons this process (8). Indeed, the peptide compromised endocytosis of a transmembrane receptor (Ste3), an activity crucial for neuronal function. Importantly, the mechanism of action of these risk factors had not previously been linked to Aβ. Thus, the yeast model has already provided key insights on the nature of Aβ’s cellular toxicity in the human brain.In this study, we used our yeast Aβ model to identify small molecules that ameliorate toxicity. In an extremely stringent and unbiased screen of 140,000 compounds, we identified a small number of cytoprotective compounds, including 8-hydroxyquinolines (8-OHQs). Members of this family bind metals and are among the few compounds that have been shown to alleviate Aβ toxicity in mouse models of AD (17, 18), and to show early potential as an AD therapeutic (19). Here, we investigate the mechanism of action for the most efficacious member of this family, clioquinol (CQ).     

Unusual intraosseous transmigration of impacted tooth

Transmigration of an impacted tooth through the symphyseal suture is a rare and special developmental anomaly of unknown etiology that is unique to the mandibular canine. Maxillary canine transmigration is even rarer. Transmigrated canines are particularly significant due to the aesthetic and functional importance. A maxillary lateral incisor crossing the mid-palatal suture has never been reported in the literature. The aim of this report is to present the first case of simultaneous transmigration of a lateral incisor and canine in the maxilla. The paper also reports four unusual cases of unilateral canine transmigration in the maxilla and mandible and successful eruption of one of the transmigrated mandibular canines following orthodontic traction. Etiology of transmigration and its clinical considerations are also discussed.     

Assessment and Functional Impact of Allocentric Neglect: A Reminder from a Case Study

SR suffered a right hemispheric stroke more than 3 years ago, and now lives with left-sided hemiparesis and chronic spatial neglect due to damaged white matter pathways connecting the frontal, temporal and parietal regions. We report here that SR suffers from both viewer-centered (i.e., egocentric) and object-centered (i.e., allocentric) spatial neglect. Notably, unlike most neuropsychological and functional assessments that focus on egocentric deficits, a specialized neuropsychological figurative discrimination test (the Apples test) revealed SR’s allocentric neglect. Further, using assessments sensitive to detect functional deficits related to allocentric neglect, we observed SR’s difficulty in reading and using clocks, reflecting his object-centered errors in these everyday activities. SR’s case suggests that allocentric-specific assessments, both neuropsychological and functional, are valuable in standard neglect examinations, particularly to predict daily function after stroke. We recommend that neglect-related functional disability be distinguished further with respect to allocentric spatial deficits, and functional assessments for allocentric neglect should be validated in future large sample studies. Identifying allocentric neglect early, and learning about its influence on daily function, may enhance care quality and facilitate effective rehabilitation planning for stroke recovery.     

Comparison of three newer generation freely available intraocular lens power calculation formulae across all axial lengths

Purpose:The aim of this study is to evaluate the accuracy of three newer generation formulae (Barrett Universal II, EVO, Hill-RBF 2.0) for calculation of power of two standard IOLs—the Acrysof IQ and Tecnis ZCB00 across all axial lengths.Methods:In this retrospective series, 206 eyes of 206 patients, operated for cataract surgery with above two IOLs over the last 6 months, were included in the study. Preoperative biometry measurements were obtained from LenstarLS900. By using recommended lens constants, the mean error for each formula was calculated and compared. Then, the optimized IOL constants were calculated to reduce the mean error to zero. Mean and median absolute errors were calculated for all eyes and separately for short (AL<22.5 mm), medium (22.5–24.5 mm), and long eyes (>24.5 mm). Absolute errors and percentages of eyes within prediction errors of ±0.25 D, ±0.50 D, ±0.75 D, and ±1.00 D were compared.Results:Prediction error with using recommended lens constants was significantly lower in the Barrett Universal II formula as compared to the other two formulae. However, after optimizing lens constants, there were no significant differences in the absolute errors between the three formulae. The formulae ranked by mean absolute error were as follows: Barrett Universal II (0.304 D), EVO (0.317 D), and Hill-RBF (0.322) D. There were no significant differences between absolute errors in the three formulae in each of the short-, medium-, and long-eye subgroups.Conclusion:With proper lens constant optimization, the Barrett Universal II, EVO, and Hill-RBF 2.0 formulae were equally accurate in predicting IOL power across the entire range of axial lengths.     

Serum cartilage oligomeric matrix protein (COMP) in knee osteoarthritis: A novel diagnostic and prognostic biomarker

A case–control study was conducted to estimate the association of cartilage oligomeric matrix protein (COMP) with knee osteoarthritis (OA) and to examine the potential utility of COMP as a diagnostic and prognostic biomarker in early knee OA. The COMP levels were estimated in the blood sera of 150 subjects belonging to study group (n = 100) and control one (n = 50). Patients with confirmed clinical isolated knee OA diagnosed through American College of Rheumatology criteria were included and were without any other cause of knee pain. ELISA was used to determine the levels of COMP, interleukin‐1β (IL‐1β) and tumor necrosis factor‐α (TNF‐α). The median (range) serum COMP levels were observed to be 1117.21 ng/ml (125.03–4209.75 ng/ml) in OA patients and 338.62 ng/ml (118–589 ng/ml) in control subjects with p < 0.001. The COMP levels of study group were negatively correlated (correlation factor ?0.88) with disease duration and positively correlated with age, BMI, pain score and IL‐1β with correlation factors 0.86, 0.63, 0.76, and 0.79, respectively with p < 0.001. Gender differentiation was found in study group with 52% higher COMP level in males as compared to that of females. There was no significant correlation of COMP levels with radiological grading, erythrocyte sedimentation rate (ESR), hemoglobin (Hb), and TNF‐α. The serum COMP levels may be used as a diagnostic OA marker along with prognostic value in determining the patients at risk of rapidly progressing this debilitating joint disease. The serum COMP level remains significantly high in first 3 years of disease duration. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:999–1006, 2013

     

Eulophia Nuda: A Review of Its Traditional Uses,Phytochemistry and Pharmacology

Pharmaceutical Chemistry Journal - Eulophia nuda Lindl. (Orchidaceae) is a small perennial terrestrial herb found in central and Southeast Asian regions usually known for its ethnomedicinal uses by...     

Synthesis,biological activities,and pharmacokinetics studies of a mutual prodrug of aceclofenac and paracetamol

An ester-based mutual prodrug (aceclofenac–paracetamol; AC-PR) was synthesized (one-pot method) with an aim of improving the therapeutic index through prevention of gastrointestinal irritation and bleeding that is associated with aceclofenac. The release of aceclofenac and paracetamol from the ester prodrug (AC-PR) was studied by reverse phase HPLC in hydrochloric acid buffer (pH 1.2), phosphate buffer (pH 7.4), 80 % v/v human plasma, 10 % w/v rat intestinal homogenate and 10 % w/v rat liver homogenate (pH 7.4). The prodrug showed negligible hydrolysis at pH 1.2 as compared to pH 7.4, suggesting that very less of the prodrug would hydrolyze in stomach, but would release the parent drugs at pH 7.4 in adequate amounts. The prodrug showed enhanced anti-inflammatory activity and significant protection against acetic acid-induced writhings (analgesic activity) as compared to that of aceclofenac. Further, the prodrug produced reduced number of ulcers as compared to that of the parent drug. These results suggest that the synthesized mutual prodrug (AC-PR) is better in terms of activity and GIT toxicity than the parent drug.