The cytoplasmic zinc finger protein ZPR1 accumulates in the nucleolus of proliferating cells

The zinc finger protein ZPR1 translocates from the cytoplasm to the nucleus after treatment of cells with mitogens. The function of nuclear ZPR1 has not been defined. Here we demonstrate that ZPR1 accumulates in the nucleolus of proliferating cells. The role of ZPR1 was examined using a gene disruption strategy. Cells lacking ZPR1 are not viable. Biochemical analysis demonstrated that the loss of ZPR1 caused disruption of nucleolar function, including preribosomal RNA expression. These data establish ZPR1 as an essential protein that is required for normal nucleolar function in proliferating cells

A review of quantitative structure-activity relationship modelling approaches to predict the toxicity of mixtures

Exposure to chemicals generally occurs in the form of mixtures. However, the great majority of the toxicity data, upon which chemical safety decisions are based, relate only to single compounds. It is currently unfeasible to test a fully representative proportion of mixtures for potential harmful effects and, as such, in silico modelling provides a practical solution to inform safety assessment. Traditional methodologies for deriving estimations of mixture effects, exemplified by principles such as concentration addition (CA) and independent action (IA), are limited as regards the scope of chemical combinations to which they can reliably be applied. Development of appropriate quantitative structure-activity relationships (QSARs) has been put forward as a solution to the shortcomings present within these techniques – allowing for the potential formulation of versatile predictive tools capable of capturing the activities of a full contingent of possible mixtures. This review addresses the current state-of-the-art as regards application of QSAR towards mixture toxicity, discussing the challenges inherent in the task, whilst considering the strengths and limitations of existing approaches. Forty studies are examined within – through reference to several characteristic elements including the nature of the chemicals and endpoints modelled, the form of descriptors adopted, and the principles behind the statistical techniques employed. Recommendations are in turn provided for practices which may assist in further advancing the field, most notably with regards to ensuring confidence in the acquired predictions.publishedVersio

A Critical Review of Adverse Effects to the Kidney: Mechanisms, Data Sources and In Silico Tools to Assist Prediction

Introduction: The kidney is a major target for toxicity elicited by pharmaceuticals and environmental pollutants. Standard testing which often does not investigate underlying mechanisms has proven not to be an adequate hazard assessment approach. As such, there is an opportunity for the application of computational approaches that utilise multi-scale data based on the Adverse Outcome Pathway (AOP) paradigm, coupled with an understanding of the chemistry underpinning the molecular initiating event (MIE) to provide a deep understanding of how structural fragments of molecules relate to specific mechanisms of nephrotoxicity. Aims covered: The aim of this investigation was to review the current scientific landscape related to computational methods, including mechanistic data, AOPs, publicly available knowledge bases and current in silico models, for the assessment of pharmaceuticals and other chemicals with regard to their potential to elicit nephrotoxicity. A list of over 250 nephrotoxicants enriched with, where possible, mechanistic and AOP-derived understanding was compiled. Expert opinion: Whilst little mechanistic evidence has been translated into AOPs, this review identified a number of data sources of in vitro, in vivo and human data that may assist in the development of in silico models which in turn may shed light on the inter-relationships between nephrotoxicity mechanisms

An Adverse Outcome Pathway for Sensitization of the Respiratory Tract by Low-Molecular-Weight Chemicals: Building Evidence to Support the Utility of In Vitro and In Silico Methods in a Regulatory Context

Sensitization of the respiratory tract is an important occupational health challenge, and understanding the mechanistic basis of this effect is necessary to support the development of toxicological tools to detect chemicals that may cause it. Here we use the adverse outcome pathway (AOP) framework to organize information that may better inform our understanding of sensitization of the respiratory tract, building on a previously published skin sensitization AOP, relying on literature evidence linked to low-molecular-weight organic chemicals and excluding other known respiratory sensitizers acting via different molecular initiating events. The established key events (KEs) are as follows: (1) covalent binding of chemicals to proteins, (2) activation of cellular danger signals (inflammatory cytokines and chemokines and cytoprotective gene pathways), (3) dendritic cell activation and migration, (4) activation, proliferation, and polarization of T cells, and (5) sensitization of the respiratory tract. These events mirror the skin sensitization AOP but with specific differences. For example, there is some evidence that respiratory sensitizers bind preferentially to lysine moieties, whereas skin sensitizers bind to both cysteine and lysine. Furthermore, exposure to respiratory sensitizers seems to result in cell behavior for KEs 2 and 3, as well as the effector T cell response, in general skewing toward cytokine secretions predominantly associated with T helper 2 (Th2) response. Knowledge gaps include the lack of understanding of which KE(s) drive the Th2 polarization. The construction of this AOP may provide insight into predictive tests that would in combination support the discrimination of respiratory-sensitizing from non- and skin-sensitizing chemicals, a clear regulatory need

Specific Inhibition of Phosphodiesterase-4B Results in Anxiolysis and Facilitates Memory Acquisition

Cognitive dysfunction is a core feature of dementia and a prominent feature in psychiatric disease. As non-redundant regulators of intracellular cAMP gradients, phosphodiesterases (PDE) mediate fundamental aspects of brain function relevant to learning, memory, and higher cognitive functions. Phosphodiesterase-4B (PDE4B) is an important phosphodiesterase in the hippocampal formation, is a major Disrupted in Schizophrenia 1 (DISC1) binding partner and is itself a risk gene for psychiatric illness. To define the effects of specific inhibition of the PDE4B subtype, we generated mice with a catalytic domain mutant form of PDE4B (Y358C) that has decreased ability to hydrolyze cAMP. Structural modelling predictions of decreased function and impaired binding with DISC1 were confirmed in cell assays. Phenotypic characterization of the PDE4BY358C mice revealed facilitated phosphorylation of CREB, decreased binding to DISC1, and upregulation of DISC1 and β-Arrestin in hippocampus and amygdala. In behavioural assays, PDE4BY358C mice displayed decreased anxiety and increased exploration, as well as cognitive enhancement across several tests of learning and memory, consistent with synaptic changes including enhanced long-term potentiation and impaired depotentiation ex vivo. PDE4BY358C mice also demonstrated enhanced neurogenesis. Contextual fear memory, though intact at 24 hours, was decreased at 7 days in PDE4BY358C mice, an effect replicated pharmacologically with a non-selective PDE4 inhibitor, implicating cAMP signalling by PDE4B in a very late phase of consolidation. No effect of the PDE4BY358C mutation was observed in the pre-pulse inhibition and forced swim tests. Our data establish specific inhibition of PDE4B as a promising therapeutic approach for disorders of cognition and anxiety, and a putative target for pathological fear memory

Combined point of care nucleic acid and antibody testing for SARS-CoV-2 following emergence of D614G Spike Variant

Rapid COVID-19 diagnosis in hospital is essential, though complicated by 30-50% of nose/throat swabs being negative by SARS-CoV-2 nucleic acid amplification testing (NAAT). Furthermore, the D614G spike mutant now dominates the pandemic and it is unclear how serological tests designed to detect anti-Spike antibodies perform against this variant. We assess the diagnostic accuracy of combined rapid antibody point of care (POC) and nucleic acid assays for suspected COVID-19 disease due to either wild type or the D614G spike mutant SARS-CoV-2. The overall detection rate for COVID-19 is 79.2% (95CI 57.8-92.9%) by rapid NAAT alone. Combined point of care antibody test and rapid NAAT is not impacted by D614G and results in very high sensitivity for COVID-19 diagnosis with very high specificity

Development and Analysis of an Adverse Outcome Pathway Network for Human Neurotoxicity

An adverse outcome pathway (AOP) network is an attempt to represent the complexity of systems toxicology. This study illustrates how an AOP network can be derived and analysed in terms of its topological features to guide research and support chemical risk assessment. A four-step workflow describing general design principles and applied design principles were established and implemented. An AOP network linking nine linear AOPs was mapped and made available in AOPXplorer. The resultant AOP network was modelled and analysed in terms of its topological features, including level of degree, eccentricity and betweenness centrality. Several well connected KEs were identified, and cell injury/death was established as the most hyperlinked KE across the network. The derived network expands the utility of linear AOPs to better understand signalling pathways involved in developmental and adult/aging neurotoxicity. The results provide a solid basis to guide the development of in vitro test method batteries, as well as further quantitative modelling of key events (KEs) and key event relationships (KERs) in the AOP network, with an eventual aim to support hazard characterisation and chemical risk assessment

A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa.

The progression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in Africa has so far been heterogeneous, and the full impact is not yet well understood. In this study, we describe the genomic epidemiology using a dataset of 8746 genomes from 33 African countries and two overseas territories. We show that the epidemics in most countries were initiated by importations predominantly from Europe, which diminished after the early introduction of international travel restrictions. As the pandemic progressed, ongoing transmission in many countries and increasing mobility led to the emergence and spread within the continent of many variants of concern and interest, such as B.1.351, B.1.525, A.23.1, and C.1.1. Although distorted by low sampling numbers and blind spots, the findings highlight that Africa must not be left behind in the global pandemic response, otherwise it could become a source for new variants