Impaired Chromatin Remodelling at STAT1-Regulated Promoters Leads to Global Unresponsiveness of Toxoplasma gondii-Infected Macrophages to IFN-γ

Intracellular pathogens including the apicomplexan and opportunistic parasite Toxoplasma gondii profoundly modify their host cells in order to establish infection. We have shown previously that intracellular T. gondii inhibit up-regulation of regulatory and effector functions in murine macrophages (MΦ) stimulated with interferon (IFN)-γ, which is the cytokine crucial for controlling the parasites' replication. Using genome-wide transcriptome analysis we show herein that infection with T. gondii leads to global unresponsiveness of murine macrophages to IFN-γ. More than 61% and 89% of the transcripts, which were induced or repressed by IFN-γ in non-infected MΦ, respectively, were not altered after stimulation of T. gondii-infected cells with IFN-γ. These genes are involved in a variety of biological processes, which are mostly but not exclusively related to immune responses. Analyses of the underlying mechanisms revealed that IFN-γ-triggered nuclear translocation of STAT1 still occurred in Toxoplasma-infected MΦ. However, STAT1 bound aberrantly to oligonucleotides containing the IFN-γ-responsive gamma-activated site (GAS) consensus sequence. Conversely, IFN-γ did not induce formation of active GAS-STAT1 complexes in nuclear extracts from infected MΦ. Mass spectrometry of protein complexes bound to GAS oligonucleotides showed that T. gondii-infected MΦ are unable to recruit non-muscle actin to IFN-γ-responsive DNA sequences, which appeared to be independent of stimulation with IFN-γ and of STAT1 binding. IFN-γ-induced recruitment of BRG-1 and acetylation of core histones at the IFN-γ-regulated CIITA promoter IV, but not β-actin was diminished by >90% in Toxoplasma-infected MΦ as compared to non-infected control cells. Remarkably, treatment with histone deacetylase inhibitors restored the ability of infected macrophages to express the IFN-γ regulated genes H2-A/E and CIITA. Taken together, these results indicate that Toxoplasma-infected MΦ are unable to respond to IFN-γ due to disturbed chromatin remodelling, but can be rescued using histone deacetylase inhibitors

NMDAR1 autoantibodies amplify behavioral phenotypes of genetic white matter inflammation: a mild encephalitis model with neuropsychiatric relevance

Encephalitis has an estimated prevalence of ≤0.01%. Even with extensive diagnostic work-up, an infectious etiology is identified or suspected in <50% of cases, suggesting a role for etiologically unclear, noninfectious processes. Mild encephalitis runs frequently unnoticed, despite slight neuroinflammation detectable postmortem in many neuropsychiatric illnesses. A widely unexplored field in humans, though clearly documented in rodents, is genetic brain inflammation, particularly that associated with myelin abnormalities, inducing primary white matter encephalitis. We hypothesized that “autoimmune encephalitides” may result from any brain inflammation concurring with the presence of brain antigen-directed autoantibodies, e.g., against N-methyl-D-aspartate-receptor NR1 (NMDAR1-AB), which are not causal of, but may considerably shape the encephalitis phenotype. We therefore immunized young female Cnp−/− mice lacking the structural myelin protein 2′-3′-cyclic nucleotide 3′-phosphodiesterase (Cnp) with a “cocktail” of NMDAR1 peptides. Cnp−/− mice exhibit early low-grade inflammation of white matter tracts and blood–brain barrier disruption. Our novel mental-time-travel test disclosed that Cnp−/− mice are compromised in what–where–when orientation, but this episodic memory readout was not further deteriorated by NMDAR1-AB. In contrast, comparing wild-type and Cnp−/− mice without/with NMDAR1-AB regarding hippocampal learning/memory and motor balance/coordination revealed distinct stair patterns of behavioral pathology. To elucidate a potential contribution of oligodendroglial NMDAR downregulation to NMDAR1-AB effects, we generated conditional NR1 knockout mice. These mice displayed normal Morris water maze and mental-time-travel, but beam balance performance was similar to immunized Cnp−/−. Immunohistochemistry confirmed neuroinflammation/neurodegeneration in Cnp−/− mice, yet without add-on effect of NMDAR1-AB. To conclude, genetic brain inflammation may explain an encephalitic component underlying autoimmune conditions

Does Regulatory Environment affect Earnings Management in Transitional Economies? An Empirical Examination of the Financial Reporting Quality of Cross-Listed Firms of China and Hong Kong

This chapter provides evidence on the impact of regulatory environment on financial reporting quality of transitional economies. This study compares the financial reporting quality of Hong Kong firms which are cross-listed in mainland China with those of Hong Kong firms cross-listed in China using specific earnings management metrics (earnings smoothing, timely loss recognition, value relevance and managing towards earnings targets) under pre- and post-IFRS regimes. The financial reporting quality of Chinese A-share companies and Hong Kong listed companies are examined using earnings management measures. Using 2007 as base year, the study used a cumulative of −5 and +5 years of convergence experience which provide a total of 3,000 firm-year observations. In addition to regression analyses, we used the difference-in-difference analysis to check for the impact of regulatory environments on earnings management. Through the lens of contingency theory, our results indicate that the adoption of the new substantially IFRS-convergent accounting standards in China results in better financial reporting quality evidenced by less earning management. The empirical results further shows that accounting data are more value relevant for Hong Kong listed firms, and that firms listed in China are more likely to engage in accrual-based earnings management than in real earnings management activities. We established that different earnings management practices that are seemingly tolerable in one country may not be tolerable in another due to level of differences in the regulatory environments. The findings show that Hong Kong listed companies’ exhibit higher level of financial reporting quality than Chinese listed companies, which implies that the financial reporting quality under IFRS can be significantly different in regions with different institutional, economic and regulatory environments. The results imply that contingent factors such as country’s institutional structures, its extent of regulation and the strength of its investor protection environments impact on financial reporting quality particularly in transitional and emerging economies. As such, these factors need to be given appropriate considerations by financial reporting regulators and policy-makers interested in controlling earnings management practices among their corporations. This study is a high impact study considering that China plays a significant role in today’s globalised economy. This study is unique as it the first, that we are aware of, to compare real earnings activities against accrual-based earnings management in pre- and post-IFRS adoption periods within the Chinese and Hong Kong financial reporting environments, distinguishing between cross-listed and non-cross-listed firms.N/

Toxoplasma gondii Clonal Strains All Inhibit STAT1 Transcriptional Activity but Polymorphic Effectors Differentially Modulate IFN gamma Induced Gene Expression and STAT1 Phosphorylation

Host defense against the parasite Toxoplasma gondii requires the cytokine interferon-gamma (IFNγ). However, Toxoplasma inhibits the host cell transcriptional response to IFNγ, which is thought to allow the parasite to establish a chronic infection. It is not known whether all strains of Toxoplasma block IFNγ-responsive transcription equally and whether this inhibition occurs solely through the modulation of STAT1 activity or whether other transcription factors are involved. We find that strains from three North American/European clonal lineages of Toxoplasma, types I, II, and III, can differentially modulate specific aspects of IFNγ signaling through the polymorphic effector proteins ROP16 and GRA15. STAT1 tyrosine phosphorylation is activated in the absence of IFNγ by the Toxoplasma kinase ROP16, but this ROP16-activated STAT1 is not transcriptionally active. Many genes induced by STAT1 can also be controlled by other transcription factors and therefore using these genes as specific readouts to determine Toxoplasma inhibition of STAT1 activity might be inappropriate. Indeed, GRA15 and ROP16 modulate the expression of subsets of IFNγ responsive genes through activation of the NF-κB/IRF1 and STAT3/6 transcription factors, respectively. However, using a stable STAT1-specific reporter cell line we show that strains from the type I, II, and III clonal lineages equally inhibit STAT1 transcriptional activity. Furthermore, all three of the clonal lineages significantly inhibit global IFNγ induced gene expression

Conductive Hybrid Cu-HHTP-TCNQ Metal–Organic Frameworks for Chemiresistive Sensing

Electrically conductive metal–organic frameworks (MOFs) and MOF-like coordination polymers are an emerging class of materials that combine good electrical charge transport with unique properties such as nanoporosity. The combination of different metal nodes and organic linkers allows tailoring MOFs to specific properties and applications in electronics, like selective chemiresistive sensing. The intrinsic crystallinity of MOFs, which usually promotes efficient charge transport, makes them also difficult to integrate into flexible systems, as crystalline MOFs are often brittle. The present study reports on a fast and reliable interfacial synthesis of conductive MOF films composed of two different organic ligands, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), lacking long-range periodic order while preserving good electrical conductivity of 0.033 S cm−1 at room temperature and chemiresistive response toward ambient changes. The hybrid nature of the discontinuous film is investigated multiparametrically by electron and atomic force microscopy as well as by Raman spectroscopy. This study demonstrates that including different types of MOFs is a good compromise between structural order and conductivity, thus making hybrid framework architectures to a promising active material for chemiresistive sensors without the need for high crystallinity

Optimal error estimation for H(curl)-conforming p-interpolation in two dimensions

In this paper we prove an optimal error estimate for the H(curl)-conforming projection based p-interpolation operator introduced in [L. Demkowicz and I. Babuska, p interpolation error estimates for edge finite elements of variable order in two dimensions, SIAM J. Numer. Anal., 41 (2003), pp. 1195-1208]. This result is proved on the reference element (either triangle or square) K for regular vector fields in H^r(curl,K) with arbitrary r>0. The formulation of the result in the H(div)-conforming setting, which is relevant for the analysis of high-order boundary element approximations for Maxwell's equations, is provided as well

Toxoplasma gondii Actively Inhibits Neuronal Function in Chronically Infected Mice

Upon infection with the obligate intracellular parasite Toxoplasma gondii, fast replicating tachyzoites infect a broad spectrum of host cells including neurons. Under the pressure of the immune response, tachyzoites convert into slow-replicating bradyzoites, which persist as cysts in neurons. Currently, it is unclear whether T. gondii alters the functional activity of neurons, which may contribute to altered behaviour of T. gondii–infected mice and men. In the present study we demonstrate that upon oral infection with T. gondii cysts, chronically infected BALB/c mice lost over time their natural fear against cat urine which was paralleled by the persistence of the parasite in brain regions affecting behaviour and odor perception. Detailed immunohistochemistry showed that in infected neurons not only parasitic cysts but also the host cell cytoplasm and some axons stained positive for Toxoplasma antigen suggesting that parasitic proteins might directly interfere with neuronal function. In fact, in vitro live cell calcium (Ca2+) imaging studies revealed that tachyzoites actively manipulated Ca2+ signalling upon glutamate stimulation leading either to hyper- or hypo-responsive neurons. Experiments with the endoplasmatic reticulum Ca2+ uptake inhibitor thapsigargin indicate that tachyzoites deplete Ca2+ stores in the endoplasmatic reticulum. Furthermore in vivo studies revealed that the activity-dependent uptake of the potassium analogue thallium was reduced in cyst harbouring neurons indicating their functional impairment. The percentage of non-functional neurons increased over time In conclusion, both bradyzoites and tachyzoites functionally silence infected neurons, which may significantly contribute to the altered behaviour of the host

Cyclin-Dependent Kinase Activity Controls the Onset of the HCMV Lytic Cycle

The onset of human cytomegalovirus (HCMV) lytic infection is strictly synchronized with the host cell cycle. Infected G0/G1 cells support viral immediate early (IE) gene expression and proceed to the G1/S boundary where they finally arrest. In contrast, S/G2 cells can be infected but effectively block IE gene expression and this inhibition is not relieved until host cells have divided and reentered G1. During latent infection IE gene expression is also inhibited, and for reactivation to occur this block to IE gene expression must be overcome. It is only poorly understood which viral and/or cellular activities maintain the block to cell cycle or latency-associated viral IE gene repression and whether the two mechanisms may be linked. Here, we show that the block to IE gene expression during S and G2 phase can be overcome by both genotoxic stress and chemical inhibitors of cellular DNA replication, pointing to the involvement of checkpoint-dependent signaling pathways in controlling IE gene repression. Checkpoint-dependent rescue of IE expression strictly requires p53 and in the absence of checkpoint activation is mimicked by proteasomal inhibition in a p53 dependent manner. Requirement for the cyclin dependent kinase (CDK) inhibitor p21 downstream of p53 suggests a pivotal role for CDKs in controlling IE gene repression in S/G2 and treatment of S/G2 cells with the CDK inhibitor roscovitine alleviates IE repression independently of p53. Importantly, CDK inhibiton also overcomes the block to IE expression during quiescent infection of NTera2 (NT2) cells. Thus, a timely block to CDK activity not only secures phase specificity of the cell cycle dependent HCMV IE gene expression program, but in addition plays a hitherto unrecognized role in preventing the establishment of a latent-like state