FANCD2-dependent mitotic DNA synthesis relies on PCNA K164 ubiquitination

Ubiquitination of proliferating cell nuclear antigen (PCNA) at lysine 164 (K164) activates DNA damage tolerance pathways. Currently, we lack a comprehensive understanding of how PCNA K164 ubiquitination promotes genome stability. To evaluate this, we generated stable cell lines expressing PCNAK164R from the endogenous PCNA locus. Our data reveal that the inability to ubiquitinate K164 causes perturbations in global DNA replication. Persistent replication stress generates under-replicated regions and is exacerbated by the DNA polymerase inhibitor aphidicolin. We show that these phenotypes are due, in part, to impaired Fanconi anemia group D2 protein (FANCD2)-dependent mitotic DNA synthesis (MiDAS) in PCNAK164R cells. FANCD2 mono-ubiquitination is significantly reduced in PCNAK164R mutants, leading to reduced chromatin association and foci formation, both prerequisites for FANCD2-dependent MiDAS. Furthermore, K164 ubiquitination coordinates direct PCNA/FANCD2 colocalization in mitotic nuclei. Here, we show that PCNA K164 ubiquitination maintains human genome stability by promoting FANCD2-dependent MiDAS to prevent the accumulation of under-replicated DNA.

ATR inhibition induces synthetic lethality in mismatch repair-deficient cells and augments immunotherapy

The mismatch repair (MMR) deficiency of cancer cells drives mutagenesis and offers a useful biomarker for immunotherapy. However, many MMR-deficient (MMR-d) tumors do not respond to immunotherapy, highlighting the need for alternative approaches to target MMR-d cancer cells. Here, we show that inhibition of the ATR kinase preferentially kills MMR-d cancer cells. Mechanistically, ATR inhibitor (ATRi) imposes synthetic lethality on MMR-d cells by inducing DNA damage in a replication- and MUS81 nuclease-dependent manner. The DNA damage induced by ATRi is colocalized with both MSH2 and PCNA, suggesting that it arises from DNA structures recognized by MMR proteins during replication. In syngeneic mouse models, ATRi effectively reduces the growth of MMR-d tumors. Interestingly, the antitumor effects of ATRi are partially due to CD8+ T cells. In MMR-d cells, ATRi stimulates the accumulation of nascent DNA fragments in the cytoplasm, activating the cGAS-mediated interferon response. The combination of ATRi and anti-PD-1 antibody reduces the growth of MMR-d tumors more efficiently than ATRi or anti-PD-1 alone, showing the ability of ATRi to augment the immunotherapy of MMR-d tumors. Thus, ATRi selectively targets MMR-d tumor cells by inducing synthetic lethality and enhancing antitumor immunity, providing a promising strategy to complement and augment MMR deficiency-guided immunotherapy.

ATR protects ongoing and newly assembled DNA replication forks through distinct mechanisms

The ATR kinase safeguards genomic integrity during S phase, but how ATR protects DNA replication forks remains incompletely understood. Here, we combine four distinct assays to analyze ATR functions at ongoing and newly assembled replication forks upon replication inhibition by hydroxyurea. At ongoing forks, ATR inhibitor (ATRi) increases MRE11- and EXO1-mediated nascent DNA degradation from PrimPol-generated, single-stranded DNA (ssDNA) gaps. ATRi also exposes template ssDNA through fork uncoupling and nascent DNA degradation. Electron microscopy reveals that ATRi reduces reversed forks by increasing gap-dependent nascent DNA degradation. At new forks, ATRi triggers MRE11- and CtIP-initiated template DNA degradation by EXO1, exposing nascent ssDNA. Upon PARP inhibition, ATRi preferentially exacerbates gap-dependent nascent DNA degradation at ongoing forks in BRCA1/2-deficient cells and disrupts the restored gap protection in BRCA1-deficient, PARP-inhibitor-resistant cells. Thus, ATR protects ongoing and new forks through distinct mechanisms, providing an extended view of ATR's functions in stabilizing replication forks.

TERRA and RAD51AP1 promote alternative lengthening of telomeres through an R- to D-loop switch

Alternative lengthening of telomeres (ALT), a telomerase-independent process maintaining telomeres, is mediated by break-induced replication (BIR). RAD52 promotes ALT by facilitating D-loop formation, but ALT also occurs through a RAD52-independent BIR pathway. Here, we show that the telomere non-coding RNA TERRA forms dynamic telomeric R-loops and contributes to ALT activity in RAD52 knockout cells. TERRA forms R-loops in vitro and at telomeres in a RAD51AP1-dependent manner. The formation of R-loops by TERRA increases G-quadruplexes (G4s) at telomeres. G4 stabilization enhances ALT even when TERRA is depleted, suggesting that G4s act downstream of R-loops to promote BIR. In vitro, the telomeric R-loops assembled by TERRA and RAD51AP1 generate G4s, which persist after R-loop resolution and allow formation of telomeric D-loops without RAD52. Thus, the dynamic telomeric R-loops formed by TERRA and RAD51AP1 enable the RAD52-independent ALT pathway, and G4s orchestrate an R- to D-loop switch at telomeres to stimulate BIR.

Bi-allelic MCM10 variants associated with immune dysfunction and cardiomyopathy cause telomere shortening

Minichromosome maintenance protein 10 (MCM10) is essential for eukaryotic DNA replication. Here, we describe compound heterozygous MCM10 variants in patients with distinctive, but overlapping, clinical phenotypes: natural killer (NK) cell deficiency (NKD) and restrictive cardiomyopathy (RCM) with hypoplasia of the spleen and thymus. To understand the mechanism of MCM10-associated disease, we modeled these variants in human cell lines. MCM10 deficiency causes chronic replication stress that reduces cell viability due to increased genomic instability and telomere erosion. Our data suggest that loss of MCM10 function constrains telomerase activity by accumulating abnormal replication fork structures enriched with single-stranded DNA. Terminally-arrested replication forks in MCM10-deficient cells require endonucleolytic processing by MUS81, as MCM10:MUS81 double mutants display decreased viability and accelerated telomere shortening. We propose that these bi-allelic variants in MCM10 predispose specific cardiac and immune cell lineages to prematurely arrest during differentiation, causing the clinical phenotypes observed in both NKD and RCM patients.

Evaluation of a personal protective equipment support programme for staff during the COVID-19 pandemic in London

BACKGROUND

The coronavirus disease 2019 pandemic has presented an enormous challenge to healthcare providers worldwide. The appropriate use of personal protective equipment (PPE) has been essential to ensure staff and patient safety. The 'PPE Helper Programme' was developed at a large London hospital group to counteract suboptimal PPE practice. Based on a behaviour change model of capability, opportunity and motivation (COM-B), the programme provided PPE support, advice and education to ward staff.

AIM

Evaluation of the PPE Helper Programme.

METHODS

Clinical and non-clinical ward staff completed a questionnaire informed by the Theoretical Domains Framework and COM-B model. The questionnaire was available in paper and electronic versions. Quantitative responses were analysed using descriptive and non-parametric statistics, and free-text responses were analysed thematically.

FINDINGS

Over a 6-week period, PPE helpers made 268 ward visits. Overall, 261 questionnaires were available for analysis. Across the Trust, 68% of respondents reported having had contact with a PPE helper. Staff who had encountered a PPE helper responded significantly more positively to a range of statements about using PPE than staff who had not encountered a PPE helper. Black and minority ethnic staff were significantly more anxious regarding the adequacy of PPE. Non-clinical and redeployed staff (e.g. domestic staff) were most positive about the impact of PPE helpers. Free-text comments showed that staff found the PPE Helper Programme supportive and would have liked it earlier in the pandemic.

CONCLUSION

The PPE Helper Programme is a feasible and beneficial intervention for providing support, advice and education to ward staff during infectious disease outbreaks.

Development and Delivery of a Real-time Hospital-onset COVID-19 Surveillance System Using Network Analysis

Background

Understanding nosocomial acquisition, outbreaks, and transmission chains in real time will be fundamental to ensuring infection-prevention measures are effective in controlling coronavirus disease 2019 (COVID-19) in healthcare. We report the design and implementation of a hospital-onset COVID-19 infection (HOCI) surveillance system for an acute healthcare setting to target prevention interventions.

Methods

The study took place in a large teaching hospital group in London, United Kingdom. All patients tested for SARS-CoV-2 between 4 March and 14 April 2020 were included. Utilizing data routinely collected through electronic healthcare systems we developed a novel surveillance system for determining and reporting HOCI incidence and providing real-time network analysis. We provided daily reports on incidence and trends over time to support HOCI investigation and generated geotemporal reports using network analysis to interrogate admission pathways for common epidemiological links to infer transmission chains. By working with stakeholders the reports were co-designed for end users.

Results

Real-time surveillance reports revealed changing rates of HOCI throughout the course of the COVID-19 epidemic, key wards fueling probable transmission events, HOCIs overrepresented in particular specialties managing high-risk patients, the importance of integrating analysis of individual prior pathways, and the value of co-design in producing data visualization. Our surveillance system can effectively support national surveillance.

Conclusions

Through early analysis of the novel surveillance system we have provided a description of HOCI rates and trends over time using real-time shifting denominator data. We demonstrate the importance of including the analysis of patient pathways and networks in characterizing risk of transmission and targeting infection-control interventions.

Comparison of uniaxial and triaxial accelerometer outputs among individuals with and without Down syndrome

BACKGROUND

Using uniaxial accelerometry approach in measuring physical activity levels of individuals with Down syndrome (DS) might underestimate their energy expenditure due to the unique mediolateral walking pattern. Therefore, the purpose of this study was to examine and compare the relationship between two types of accelerometer outputs, uniaxial and triaxial, and energy expenditure in individuals with and without DS.

METHODS

Eighteen participants with DS and 19 participants without DS wore a GT3X+ accelerometer and a portable metabolic system in three different walking conditions.

RESULTS

Correlations between V̇O2 and each of the two accelerometer outputs (uniaxial: r = 0.75, triaxial: r = 0.75) were not significantly different among individuals without DS (z = 0.14, P = 0.89); however, significant differences in the relationship between V̇O2 and accelerometer outputs (uniaxial: r = 0.53, triaxial: r = 0.64) were observed among individuals with DS (z = -1.72, P < 0.046).

CONCLUSIONS

The findings suggest that when using accelerometers to measure physical activity levels for individuals with DS, triaxial outputs may better predict physical activity levels.

Ubiquitinated-PCNA protects replication forks from DNA2-mediated degradation by regulating Okazaki fragment maturation and chromatin assembly

Upon genotoxic stress, PCNA ubiquitination allows for replication of damaged DNA by recruiting lesion-bypass DNA polymerases. However, PCNA is also ubiquitinated during normal S-phase progression. By employing 293T and RPE1 cells deficient in PCNA ubiquitination, generated through CRISPR/Cas9 gene editing, here, we show that this modification promotes cellular proliferation and suppression of genomic instability under normal growth conditions. Loss of PCNA-ubiquitination results in DNA2-dependent but MRE11-independent nucleolytic degradation of nascent DNA at stalled replication forks. This degradation is linked to defective gap-filling in the wake of the replication fork and incomplete Okazaki fragment maturation, which interferes with efficient PCNA unloading by ATAD5 and subsequent nucleosome deposition by CAF-1. Moreover, concomitant loss of PCNA-ubiquitination and the BRCA pathway results in increased nascent DNA degradation and PARP inhibitor sensitivity. In conclusion, we show that by ensuring efficient Okazaki fragment maturation, PCNA-ubiquitination protects fork integrity and promotes the resistance of BRCA-deficient cells to PARP-inhibitors.

Flap endonuclease overexpression drives genome instability and DNA damage hypersensitivity in a PCNA-dependent manner

Overexpression of the flap endonuclease FEN1 has been observed in a variety of cancer types and is a marker for poor prognosis. To better understand the cellular consequences of FEN1 overexpression we utilized a model of its Saccharomyces cerevisiae homolog, RAD27. In this system, we discovered that flap endonuclease overexpression impedes replication fork progression and leads to an accumulation of cells in mid-S phase. This was accompanied by increased phosphorylation of the checkpoint kinase Rad53 and histone H2A-S129. RAD27 overexpressing cells were hypersensitive to treatment with DNA damaging agents, and defective in ubiquitinating the replication clamp proliferating cell nuclear antigen (PCNA) at lysine 164. These effects were reversed when the interaction between overexpressed Rad27 and PCNA was ablated, suggesting that the observed phenotypes were linked to problems in DNA replication. RAD27 overexpressing cells also exhibited an unexpected dependence on the SUMO ligases SIZ1 and MMS21 for viability. Importantly, we found that overexpression of FEN1 in human cells also led to phosphorylation of CHK1, CHK2, RPA32 and histone H2AX, all markers of genome instability. Our data indicate that flap endonuclease overexpression is a driver of genome instability in yeast and human cells that impairs DNA replication in a manner dependent on its interaction with PCNA.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Mechanisms of DNA Damage Tolerance: Post-Translational Regulation of PCNA

DNA damage is a constant source of stress challenging genomic integrity. To ensure faithful duplication of our genomes, mechanisms have evolved to deal with damage encountered during replication. One such mechanism is referred to as DNA damage tolerance (DDT). DDT allows for replication to continue in the presence of a DNA lesion by promoting damage bypass. Two major DDT pathways exist: error-prone translesion synthesis (TLS) and error-free template switching (TS). TLS recruits low-fidelity DNA polymerases to directly replicate across the damaged template, whereas TS uses the nascent sister chromatid as a template for bypass. Both pathways must be tightly controlled to prevent the accumulation of mutations that can occur from the dysregulation of DDT proteins. A key regulator of error-prone versus error-free DDT is the replication clamp, proliferating cell nuclear antigen (PCNA). Post-translational modifications (PTMs) of PCNA, mainly by ubiquitin and SUMO (small ubiquitin-like modifier), play a critical role in DDT. In this review, we will discuss the different types of PTMs of PCNA and how they regulate DDT in response to replication stress. We will also cover the roles of PCNA PTMs in lagging strand synthesis, meiotic recombination, as well as somatic hypermutation and class switch recombination.

Not just for coding: a new role for histone tails in replication enzyme activation

The processing of Okazaki fragments when they are assembled into nucleosomes has received little attention. In this issue of The FEBS Journal, Seo and colleagues show that binding to histone tails stimulates the enzymatic activity of flap endonuclease 1 (Rad27). Histone tails are structurally similar to the C terminus of Rad27 and can thus mimic its autostimulatory function. This study highlights an active regulatory role for nucleosomes on DNA metabolism.

Effects of Controlled Cortical Impact on the Mouse Brain Vasculome

Perturbations in blood vessels play a critical role in the pathophysiology of brain injury and neurodegeneration. Here, we use a systematic genome-wide transcriptome screening approach to investigate the vasculome after brain trauma in mice. Mice were subjected to controlled cortical impact and brains were extracted for analysis at 24 h post-injury. The core of the traumatic lesion was removed and then cortical microvesels were isolated from nondirectly damaged ipsilateral cortex. Compared to contralateral cortex and normal cortex from sham-operated mice, we identified a wide spectrum of responses in the vasculome after trauma. Up-regulated pathways included those involved in regulation of inflammation and extracellular matrix processes. Decreased pathways included those involved in regulation of metabolism, mitochondrial function, and transport systems. These findings suggest that microvascular perturbations can be widespread and not necessarily localized to core areas of direct injury per se and may further provide a broader gene network context for existing knowledge regarding inflammation, metabolism, and blood-brain barrier alterations after brain trauma. Further efforts are warranted to map the vasculome with higher spatial and temporal resolution from acute to delayed phase post-trauma. Investigating the widespread network responses in the vasculome may reveal potential mechanisms, therapeutic targets, and biomarkers for traumatic brain injury.

Risk factors for hemorrhagic cystitis in pediatric allogeneic hematopoietic stem cell transplant recipients

BACKGROUND

Hemorrhagic cystitis (HC) results in significant morbidity among hematopoietic stem cell transplant (HSCT) recipients. Several potential causes for HC have been postulated, including viral infection, but definitive evidence is lacking, particularly in pediatric HSCT patients.

METHODS

Ninety pediatric HSCT recipients were prospectively tested on a weekly basis for adenovirus (ADV) and BK virus (BKV) by quantitative real-time polymerase chain reaction in blood and urine samples. Results were correlated with the occurrence of grade II-IV HC. The odds ratio (OR) of HC (95% confidence interval) for BKV ≥1 × 10(9) copies/mL of urine was 7.39 (1.52, 35.99), with a P-value of 0.013. Those with acute graft-versus-host disease (aGVHD) also had higher odds of developing HC, with an OR of 5.34. Given a 20% prevalence rate of HC, positive and negative predictive values of 29% and 95% were seen with a cutoff of 10(9) copies/mL.

RESULTS

BK viremia did not reach significance as a risk factor for development of HC (P = 0.06). Only 8 patients showed ADV viruria and 7 showed ADV viremia; all had low viral loads and 4 had no evidence of HC.

CONCLUSION

HC in pediatric HSCT is correlated most strongly to elevated urinary viral load of BKV and to aGVHD, but less strongly to BK viremia.

Advances in clinical NK cell studies: Donor selection, manufacturing and quality control

Natural killer (NK) cells are increasingly used in clinical studies in order to treat patients with various malignancies. The following review summarizes platform lectures and 2013–2015 consortium meetings on manufacturing and clinical use of NK cells in Europe and United States. A broad overview of recent pre-clinical and clinical results in NK cell therapies is provided based on unstimulated, cytokine-activated, as well as genetically engineered NK cells using chimeric antigen receptors (CAR). Differences in donor selection, manufacturing and quality control of NK cells for cancer immunotherapies are described and basic recommendations are outlined for harmonization in future NK cell studies.

Neuregulin1-β decreases interleukin-1β-induced RhoA activation, myosin light chain phosphorylation, and endothelial hyperpermeability

Neuregulin-1 (NRG1) is an endogenous growth factor with multiple functions in the embryonic and postnatal brain. The NRG1 gene is large and complex, transcribing more than twenty transmembrane proteins and generating a large number of isoforms in tissue and cell type-specific patterns. Within the brain, NRG1 functions have been studied most extensively in neurons and glia, as well as in the peripheral vasculature. Recently, NRG1 signaling has been found to be important in the function of brain microvascular endothelial cells, decreasing IL-1β-induced increases in endothelial permeability. In the current experiments, we have investigated the pathways through which the NRG1-β isoform acts on IL-1β-induced endothelial permeability. Our data show that NRG1-β increases barrier function, measured by transendothelial electrical resistance, and decreases IL-1β-induced hyperpermeability, measured by dextran-40 extravasation through a monolayer of brain microvascular endothelial cells plated on transwells. An investigation of key signaling proteins suggests that the effect of NRG1-β on endothelial permeability is mediated through RhoA activation and myosin light chain phosphorylation, events which affect filamentous actin morphology. In addition, AG825, an inhibitor of the erbB2-associated tyrosine kinase, reduces the effect of NRG1-β on IL-1β-induced RhoA activation and myosin light chain phosphorylation. These data add to the evidence that NRG1-β signaling affects changes in the brain microvasculature in the setting of neuroinflammation. We propose the following events for neuregulin-1-mediated effects on Interleukin-1 β (IL-1β)-induced endothelial hyperpermeability: IL-1β leads to RhoA activation, resulting in an increase in phosphorylation of myosin light chain (MLC). Phosphorylation of MLC is known to result in actin contraction and alterations in the f-actin cytoskeletal structure. These changes are associated with increased endothelial permeability. Neuregulin-1β acts through its transmembrane receptors to activate intracellular signaling pathways which inhibit IL-1β-induced RhoA activation and MLC phosphorylation, thereby preserving the f-actin cytoskeletal structure and endothelial barrier function.

Activated and expanded natural killer cells target osteosarcoma tumor initiating cells in an NKG2D-NKG2DL dependent manner

Current therapies fail to cure most metastatic or recurrent bone cancer. We explored the efficacy and the pathways involved in natural killer (NK) cells' elimination of osteosarcoma (OS) cells, including tumor initiating cells (TICs), which are responsible for chemotherapy resistance, recurrence, and metastasis. The expression of ligands for NK cell receptors was studied in primary OS cell lines by flow cytometry. In vitro cytotoxicity of activated and expanded NK (NKAE) cells against OS was tested, and the pathways involved explored by using specific antibody blockade. NKAE cells' ability to target OS TICs was analyzed by flow cytometry and sphere formation assays. Spironolactone (SPIR) was tested for its ability to increase OS cells' susceptibility to NK cell lysis in vitro and in vivo. We found OS cells were susceptible to NKAE cells' lysis both in vivo and in vitro, and this cytolytic activity relied on interaction between NKG2D receptor and NKG2D ligands (NKG2DL). SPIR increased OS cells' susceptibility to lysis by NKAE cells, and could shrink the OS TICs. Our results show NKAE cells target OS cells including the TICs compartment, supporting the use of NK-cell based immunotherapies for OS.

Profound parental bias associated with chromosome 14 acquired uniparental disomy indicates targeting of an imprinted locus

Acquired uniparental disomy (aUPD) is a common finding in myeloid malignancies and typically acts to convert a somatically acquired heterozygous mutation to homozygosity. We sought to identify the target of chromosome 14 aUPD (aUPD14), a recurrent abnormality in myeloid neoplasms and population cohorts of elderly individuals. We identified 29 cases with aUPD14q that defined a minimal affected region (MAR) of 11.2 Mb running from 14q32.12 to the telomere. Exome sequencing (n=7) did not identify recurrently mutated genes, but methylation-specific PCR at the imprinted MEG3-DLK1 locus located within the MAR demonstrated loss of maternal chromosome 14 and gain of paternal chromosome 14 (P<0.0001), with the degree of methylation imbalance correlating with the level of aUPD (r=0.76; P=0.0001). The absence of driver gene mutations in the exomes of three individuals with aUPD14q but no known haematological disorder suggests that aUPD14q may be sufficient to drive clonal haemopoiesis. Analysis of cases with both aUPD14q and JAK2 V617F (n=11) indicated that aUPD14q may be an early event in some cases but a late event in others. We conclude that aUPD14q is a recurrent abnormality that targets an imprinted locus and may promote clonal haemopoiesis either as an initiating event or as a secondary change.

Neuronal production of lipocalin-2 as a help-me signal for glial activation

BACKGROUND AND PURPOSE

We explored the hypothesis that injured neurons release lipocalin-2 as a help me signal.

METHODS

In vivo lipocalin-2 responses were assessed in rat focal cerebral ischemia and human stroke brain samples using a combination of ELISA and immunostaining. In vitro, microglia and astrocytes were exposed to lipocalin-2, and various markers and assays of glial activation were quantified. Functional relevance of neuron-to-glia lipocalin-2 signaling was examined by transferring conditioned media from lipocalin-2-activated microglia and astrocytes onto neurons to see whether activated glia could protect neurons against oxygen-glucose deprivation and promote neuroplasticity.

RESULTS

In human stroke samples and rat cerebral ischemia, neuronal expression of lipocalin-2 was significantly increased. In primary cell cultures, exposing microglia and astrocytes to lipocalin-2 resulted in glial activation. In microglia, lipocalin-2 converted resting ramified shapes into a long-rod morphology with reduced branching, increased interleukin-10 release, and enhanced phagocytosis. In astrocytes, lipocalin-2 upregulated glial fibrillary acid protein, brain-derived neurotropic factor, and thrombospondin-1. Conditioned media from lipocalin-2-treated astrocytes upregulated synaptotagmin, and conditioned media from lipocalin-2-treated microglia upregulated synaptophysin and post-synaptic density 95 (PSD95) and protected neurons against oxygen-glucose deprivation.

CONCLUSIONS

These findings provide proof of concept that lipocalin-2 is released by injured neurons as a help me distress signal that activates microglia and astrocytes into potentially prorecovery phenotypes.

Neuregulin1-β decreases IL-1β-induced neutrophil adhesion to human brain microvascular endothelial cells

Neuroinflammation contributes to the pathophysiology of diverse diseases including stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, and multiple sclerosis, resulting in neurodegeneration and loss of neurological function. The response of the microvascular endothelium often contributes to neuroinflammation. One such response is the upregulation of endothelial adhesion molecules which facilitate neutrophil adhesion to the endothelium and their migration from blood to tissue. Neuregulin-1 (NRG1) is an endogenous growth factor which has been reported to have anti-inflammatory effects in experimental stroke models. We hypothesized that NRG1 would decrease the endothelial response to inflammation and result in a decrease in neutrophil adhesion to endothelial cells. We tested this hypothesis in an in vitro model of cytokine-induced endothelial injury, in which human brain microvascular endothelial cells (BMECs) were treated with IL-1β, along with co-incubation with vehicle or NRG1-β. Outcome measures included protein levels of endothelial ICAM-1, VCAM-1, and E-selectin, as well as the number of neutrophils that adhere to the endothelial monolayer. Our data show that NRG1-β decreased the levels of VCAM-1, E-selectin, and neutrophil adhesion to brain microvascular endothelial cells activated by IL1-β. These findings open new possibilities for investigating NRG1 in neuroprotective strategies in brain injury.

Translational insights into traumatic brain injury occurring during dabigatran or warfarin anticoagulation

To date, only limited data are available on the effects of pretreatment with novel oral anticoagulants in the event of traumatic brain injury (TBI). We determined intracerebral hemorrhage volume and functional outcome in a standardized TBI model in mice treated with warfarin or dabigatran. Additionally, we investigated whether excess concentrations of dabigatran could increase bleeding and whether this was preventable by using prothrombin complex concentrate (PCC). C57 mice were treated orally with warfarin or dabigatran; sham-treated mice served as controls. Effective anticoagulation was verified by measurement of international normalized ratio and diluted thrombin time, and TBI was induced by controlled cortical impact (CCI). Twenty-four hours after CCI, intracerebral hemorrhage volume was larger in warfarin-pretreated mice than in controls (10.1 ± 4.9 vs 4.1 ± 1.7 μL; analysis of variance post hoc P=0.001), but no difference was found between controls and dabigatran-pretreated mice (5.3 ± 1.5 μL). PCC applied 30 minutes after CCI did not reliably reduce intracerebral hemorrhage induced by excess dabigatran concentration compared with saline (10.4 ± 11.2 vs 8.7 ± 7.1 μL). Our data suggest pathophysiological differences in TBI occurring during warfarin and dabigatran anticoagulation. The reduced hemorrhage formation under dabigatran therapy could present a safety advantage compared with warfarin. An excess dabigatran concentration, however, can increase hemorrhage.

Assays to examine endothelial cell migration, tube formation, and gene expression profiles

Common methods for studying angiogenesis in vitro include the tube formation assay, the migration assay, and the study of the endothelial genome. The formation of capillary-like tubes in vitro on basement membrane matrix mimics many steps of the angiogenesis process in vivo and is used widely as a screening test for angiogenic or antiangiogenic factors. Other assays related to the study of angiogenesis include the cell migration assay, the study of gene expression changes during the process of angiogenesis, and the study of endothelial-derived microparticles. Protocols for these procedures will be described here.

Early infections after autologous hematopoietic stem cell transplantation in children and adolescents: the St. Jude experience

INTRODUCTION

Advances in autologous hematopoietic stem cell transplantation (HSCT) over the past 20 years may have had an impact on the morbidity and mortality associated with infections post transplant.

PATIENTS AND METHODS

We sought to retrospectively analyze the epidemiology of the first episode of bacterial, fungal, viral, or parasitic infections 0-30 days post transplant in a cohort of 320 children and adolescents who underwent autologous HSCT in a single institution, between 1990 and 2009 for solid tumors or lymphoma, and in 65 children transplanted for acute leukemia during the same period.

RESULTS

Infections occurred in 66 (21%) patients with solid tumors or lymphoma. Bacterial infections occurred in 33 (10%) including bacteremia in 23 (7%), and viral infections in 34 (11%) patients. Gram-positive bacterial infections were more prevalent than gram-negative bacterial infections (P = 0.03). Infections caused by fungal or parasitic pathogens were uncommon. The decade when transplant was performed (1990-1999 vs. 2000-2009) had no impact on the incidence of bacterial (P = 0.41) or viral (P = 0.47) infection. Between 1990 and 1999, a total of 60 (92%) children were transplanted for leukemia, and 5 (8%) in the 2000-2009 period (P < 0.0001). Infections occurred in 32 (49%) patients. Bacterial (P = 0.004), candidal (P = 0.003), and herpes simplex viral (P = 0.03) infections were more common in patients transplanted for leukemia. In patients transplanted for leukemia, 3 deaths occurred attributed to infection, all before 2000.

CONCLUSION

Changes in epidemiology of infection are likely a result of decline in autologous transplantation for childhood leukemia in the recent era. Autologous transplantation for solid tumors or lymphoma was not associated with mortality from early infections at our institution.

Frequent mutations in SH2D1A (XLP) in males presenting with high-grade mature B-cell neoplasms

X-linked lymphoproliferative syndrome (XLP) is caused by mutations in SH2D1A, and is associated with overwhelming infectious mononucleosis, aplastic anemia, hypogammaglobulinemia, and B-cell lymphomas. However, the frequency of SH2D1A mutations in males who present with B NHL is unknown. Five cases of XLP were diagnosed among 158 males presenting with B NHL (approximately 3.2%). Four of the patients had two episodes of B NHL and one had a single episode of B NHL followed by aggressive infectious mononucleosis. Prospective screening for XLP in males with B-cell lymphoma at the time of initial diagnosis should be considered.

Imaging of contrast medium extravasation in anticoagulation-associated intracerebral hemorrhage with dual-energy computed tomography

BACKGROUND AND PURPOSE

Contrast medium extravasation (CE) in intracerebral hemorrhage (ICH) is a marker of ongoing bleeding and a predictor of hematoma expansion. The aims of the study were to establish an ICH model in which CE can be quantified, characterized in ICH during warfarin and dabigatran anticoagulation, and to evaluate effects of prothrombin complex concentrates on CE in warfarin-associated ICH.

METHODS

CD1-mice were pretreated orally with warfarin, dabigatran, or vehicle. Prothrombin complex concentrates were administered in a subgroup of warfarin-treated mice. ICH was induced by stereotactic injection of collagenase VIIs into the right striatum. Contrast agent (350 μL Isovue 370 mg/mL) was injected intravenously after ICH induction (2-3.5 hours). Thirty minutes later, mice were euthanized, and CE was measured by quantifying the iodine content in the hematoma using dual-energy computed tomography.

RESULTS

The optimal time point for contrast injection was found to be 3 hours after ICH induction, allowing detection of both an increase and a decrease of CE using dual-energy computed tomography. CE was higher in the warfarin group compared with the controls (P=0.002). There was no significant difference in CE between dabigatran-treated mice and controls. CE was higher in the sham-treated warfarin group than in the prothrombin complex concentrates-treated warfarin group (P<0.001).

CONCLUSIONS

Dual-energy computed tomography allows quantifying CE, as a marker of ongoing bleeding, in a model of anticoagulation-associated ICH. Dabigatran induces less CE in ICH than warfarin and consequently reduces risks of hematoma expansion. This constitutes a potential safety advantage of dabigatran over warfarin. Nevertheless, in case of warfarin anticoagulation, prothrombin complex concentrates reduce this side effect.

Cerebrovascular degradation of TRKB by MMP9 in the diabetic brain

Diabetes elevates the risk for neurological diseases, but little is known about the underlying mechanisms. Brain-derived neurotrophic factor (BDNF) is secreted by microvascular endothelial cells (ECs) in the brain, functioning as a neuroprotectant through the activation of the neurotrophic tyrosine kinase receptor TRKB. In a rat model of streptozotocin-induced hyperglycemia, we found that endothelial activation of MMP9 altered TRKB-dependent trophic pathways by degrading TRKB in neurons. Treatment of brain microvascular ECs with advanced glycation endproducts (AGE), a metabolite commonly elevated in diabetic patients, increased MMP9 activation, similar to in vivo findings. Recombinant human MMP9 degraded the TRKB ectodomain in primary neuronal cultures, suggesting that TRKB could be a substrate for MMP9 proteolysis. Consequently, AGE-conditioned endothelial media with elevated MMP9 activity degraded the TRKB ectodomain and simultaneously disrupted the ability of endothelium to protect neurons against hypoxic injury. Our findings demonstrate that neuronal TRKB trophic function is ablated by MMP9-mediated degradation in the diabetic brain, disrupting cerebrovascular trophic coupling and leaving the brain vulnerable to injury.

Pro-angiogenic effects of resveratrol in brain endothelial cells: nitric oxide-mediated regulation of vascular endothelial growth factor and metalloproteinases

Resveratrol may be a powerful way of protecting the brain against a wide variety of stress and injury. Recently, it has been proposed that resveratrol not only reduces brain injury but also promotes recovery after stroke. But the underlying mechanisms are unclear. Here, we tested the hypothesis that resveratrol promotes angiogenesis in cerebral endothelial cells and dissected the signaling pathways involved. Treatment of cerebral endothelial cells with resveratrol promoted proliferation, migration, and tube formation in Matrigel assays. Consistent with these pro-angiogenic responses, resveratrol altered endothelial morphology resulting in cytoskeletal rearrangements of β-catenin and VE-cadherin. These effects of resveratrol were accompanied by activation of phosphoinositide 3 kinase (PI3-K)/Akt and Mitogen-Activated Protein Kinase (MAPK)/ERK signaling pathways that led to endothelial nitric oxide synthase upregulation and increased nitric oxide (NO) levels. Subsequently, elevated NO signaling increased vascular endothelial growth factor and matrix metalloproteinase levels. Sequential blockade of these signaling steps prevented resveratrol-induced angiogenesis in cerebral endothelial cells. These findings provide a mechanistic basis for the potential use of resveratrol as a candidate therapy to promote angiogenesis and neurovascular recovery after stroke.

Neuregulin-1 effects on endothelial and blood-brain-barrier permeability after experimental injury

Blood-brain-barrier disruption occurs with a high incidence after traumatic brain injury, and is an important contributor to many pathological processes, including brain edema, inflammation, and neuronal cell death. Therefore, blood-brain-barrier integrity is an important potential therapeutic target in the treatment of the acute phase of brain trauma. In this short communication, we report our data showing that neuregulin-1 (NRG1), a growth factor with diverse functions in the CNS, ameliorates pathological increases in endothelial permeability and in BBB permeability in experimental models of injury. For in-vitro studies, rat brain endothelial cells were incubated with the inflammatory cytokine IL-1β, which caused an increase in permeability of the cell layer. Co-incubation with NRG1 ameliorated this permeability increase. For in-vivo studies, C57Bl mice were subjected to controlled cortical impact (CCI) under anesthesia, and BBB permeability was assessed by measuring the amount of Evans blue dye extravasation at 2h. NRG1 administered by tail-vein injection 10 minutes after CCI resulted in a decrease in Evans blue dye extravasation by 35%. Since Evans blue extravasation may result from an increase in BBB permeability or from bleeding due to trauma, hemoglobin ELISA was also performed at the same time point. There was a trend towards lower levels of hemoglobin extravasation in the NRG1 group, but the results did not reach statistical significance. MMP-9 activity was not different between groups at 2h. These data suggest that NRG1 has beneficial effects on endothelial permeability and BBB permeability following experimental trauma, and may have neuroprotective potential during CNS injury.

A phase I/II study of CY and topotecan in patients with high-risk malignancies undergoing autologous hematopoietic cell transplantation: the St Jude long-term follow-up

Fifty-eight consecutive children with high-risk malignancies were treated with CY, and targeted topotecan followed by autologous hematopoietic cell transplantation (AHCT) in a phase I/II Institutional Review Board-approved study. Twelve participants enrolled in phase I; 5 received dose level 1 of topotecan 3 mg/m(2) per day, with subsequent doses targeted to total systemic exposure of 100±20 ng h/mL and CY 750 mg/m(2) per day. Seven participants received dose level 2. CY dose escalation to 1 g/m(2) per day was considered excessively toxic; one died from irreversible veno-occlusive disease and two experienced reversible hepatotoxicity. These adverse events halted further dose escalation. A total of 46 participants were enrolled in phase II; results are on the 51 participants who received therapy at dose level 1, the maximum tolerated dose. Diagnoses included neuroblastoma (26), sarcoma (9), lymphoma (8), brain tumors (5), Wilms (2) and retinoblastoma (1). Twenty participants (39.3%) were in CR1 at enrollment; median age was 5.1 years. Most common non-hematological grade III-IV toxicity was gastrointestinal (n=37). Neutrophil and platelet engraftment occurred at a median of 15 and 24 days, respectively. Twenty-six (51%) participants remain alive at a median of 6.4 years after AHCT. CY 3.75 g/m(2), and targeted topotecan followed by AHCT are feasible and produce acceptable toxicity in children with high-risk malignancies.

ETV6-RUNX1-positive childhood acute lymphoblastic leukemia: improved outcome with contemporary therapy

ETV6-RUNX1 fusion is the most common genetic aberration in childhood acute lymphoblastic leukemia (ALL). To evaluate whether outcomes for this drug-sensitive leukemia are improved by contemporary risk-directed therapy, we studied clinical features, response and adverse events of 168 children with newly diagnosed ETV6-RUNX1-positive ALL on St Jude Total Therapy studies XIIIA (N=36), XIIIB (N=38) and XV (N=94). Results were compared with 494 ETV6-RUNX1-negative B-precursor ALL patients. ETV6-RUNX1 was associated with age 1-9 years, pre-treatment classification as low risk and lower levels of minimal residual disease (MRD) on day 19 of therapy (P<0.001). Event-free survival (EFS) or overall survival (OS) did not differ between patients with or without ETV6-RUNX1 in Total XIIIA or XIIIB. By contrast, in Total XV, patients with ETV6-RUNX1 had significantly better EFS (P=0.04; 5-year estimate, 96.8±2.4% versus 88.3±2.5%) and OS (P=0.04; 98.9±1.4% versus 93.7±1.8%) than those without ETV6-RUNX1. Within the ETV6-RUNX1 group, the only significant prognostic factor associated with higher OS was the treatment protocol Total XV (versus XIIIA or XIIIB) (P=0.01). Thus, the MRD-guided treatment schema including intensive asparaginase and high-dose methotrexate in the Total XV study produced significantly better outcomes than previous regimens and demonstrated that nearly all children with ETV6-RUNX1 ALL can be cured.

Characterisation of complementary and alternative medicine use and its impact on medication adherence in inflammatory bowel disease

BACKGROUND

Complementary and alternative medicine (CAM) use among inflammatory bowel disease (IBD) patients is common. We characterised CAM utilisation and assessed its impact on medical adherence in the IBD population.

AIM

To characterise CAM utilisation and assess its impact on medical adherence in the IBD population.

METHODS

Inflammatory bowel disease patients recruited from an out-patient clinic at a tertiary centre were asked to complete a questionnaire on CAM utilisation, conventional IBD therapy, demographics and communication with their gastroenterologist. Adherence was measured using the self-reported Morisky scale. Demographics, clinical characteristics and self-reported adherence among CAM and non-CAM users were compared.

RESULTS

We recruited prospectively 380 IBD subjects (57% Crohn's disease; 35% ulcerative colitis, and 8% indeterminate colitis). The prevalence of CAM use was 56% and did not significantly vary by type of IBD. The most common reason cited for using CAM was ineffectiveness of conventional IBD therapy (40%). The most popular form of CAM was probiotics (53%). CAM users were younger than non-CAM users at diagnosis (21.2 vs. 26.2, P < 0.0001) and more likely than non-CAM users to have a University-level education or higher (75% vs. 62% P = 0.006). There was no overall difference in adherence between CAM and non-CAM users (Morisky score: 1.0 vs. 0.9, P = 0.26).

CONCLUSIONS

The use of complementary and alternative medicine is widely prevalent among IBD patients, and is more frequent among those with experience of adverse effects of conventional medications. From this cross-sectional analysis, complementary and alternative medicine use does not appear to be associated with reduced overall adherence to medical therapy.

γ-glutamylcysteine ethyl ester protects cerebral endothelial cells during injury and decreases blood-brain barrier permeability after experimental brain trauma

Oxidative stress is a pathway of injury that is common to almost all neurological conditions. Hence, methods to scavenge radicals have been extensively tested for neuroprotection. However, saving neurons alone may not be sufficient in treating CNS disease. In this study, we tested the cytoprotective actions of the glutathione precursor gamma-glutamylcysteine ethyl ester (GCEE) in brain endothelium. First, oxidative stress was induced in a human brain microvascular endothelial cell line by exposure to H(2)O(2). Addition of GCEE significantly reduced formation of reactive oxygen species, restored glutathione levels which were reduced in the presence of H(2)O(2), and decreased cell death during H(2)O(2)-mediated injury. Next, we asked whether GCEE can also protect brain endothelial cells against oxygen-glucose deprivation (OGD). As expected, OGD disrupted mitochondrial membrane potentials. GCEE was able to ameliorate these mitochondrial effects. Concomitantly, GCEE significantly decreased endothelial cell death after OGD. Lastly, our in vivo experiments using a mouse model of brain trauma show that post-trauma (10 min after controlled cortical impact) administration of GCEE by intraperitoneal injection results in a decrease in acute blood-brain barrier permeability. These data suggest that the beneficial effects of GCEE on brain endothelial cells and microvessels may contribute to its potential efficacy as a neuroprotective agent in traumatic brain injury.

Intracranial hemorrhage: mechanisms of secondary brain injury

ICH is a disease with high rates of mortality and morbidity, with a substantial public health impact. Spontaneous ICH (sICH) has been extensively studied, and a large body of data has been accumulated on its pathophysiology. However, the literature on traumatic ICH (tICH) is limited, and further investigations of this important topic are needed. This review will highlight some of the cellular pathways in ICH with an emphasis on the mechanisms of secondary injury due to heme toxicity and to events in the coagulation process that are common to both sICH and tICH.

Pilot study of haploidentical natural killer cell transplantation in childhood acute myeloid leukemia

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Background: In the setting of hematopoietic stem cell transplantation (HSCT), donor natural killer (NK) cells exhibit potent anti-leukemic effects without causing graft-versus-host disease. We hypothesized that the transplantation of purified haploidentical NK cells may be a safe and effective form of consolidation therapy that will reduce the risk of relapse among children with acute myeloid leukemia (AML) who are not treated with HSCT. In this pilot study, we assessed the safety, feasibility, and engraftment of NK cell infusions in 10 patients with AML in first remission.Methods: Patients received cyclophosphamide, 60 mg/kg on day -7; fludarabine, 25 mg/m2/day on days -6 through -2; and IL-2, 1 million units/m2, every other day for 6 doses starting on day -1. On day -1, the donor underwent apheresis and the product was purified for CD56+ cells by a two-step procedure. The entire purified product was infused on day 0.Results: The 10 patients had a median age of 2.5 years (range, 8 months to 21 years) and a median leukocyte count of 62 x 109/L (range, 4 to 487) at diagnosis. Leukemic cell genetic abnormalities included CBFβ-MYH11in 4 cases, RBM15-MKL1in 2 cases, MLL-ENL and MLL-AF9 in 1 case each; 2 cases had no detectable abnormalities. Patients received a median of 29 × 106/kg NK cells (range, 5 to 81 × 106/kg). All patients had detectable donor NK cells at one or more time points: donor NK cell chimerism ranged from 0% to 30% during the first 4 weeks after the infusions and was greater than 1% in 9 cases at week 1, 4 cases at week 2, 5 cases at week 3, and 3 cases at week 4. One patient had prolonged NK engraftment (189 days), but no non-hematological toxicity. Grade 3–4 non-hematological toxicity was limited to one respiratory viral infection and one episode of febrile neutropenia. Median length of hospitalization was 2 days (range, 0–3) and median time to neutrophil recovery was 12 days (range, 9–56). With a median follow-up time of 637 days, all patients remain in remission. Conclusions: Haploidentical NK cells can be safely administered to AML patients who are in remission. All patients demonstrated temporary engraftment, which may have antileukemic effects. We have recently opened a new trial to evaluate the efficacy of NK cell therapy in children in first remission of AML.

No significant financial relationships to disclose.

Effects of activating NK cell receptor expression and NK cell reconstitution on the outcomes of unrelated donor hematopoietic cell transplantation for hematologic malignancies

Inhibitory NK cell receptors are recognized as important determinants of NK cell activity in hematopoietic cell transplantation (HCT). The role of activating receptors and their acquisition after HCT is less certain. Therefore, we comprehensively evaluated both inhibitory and activating receptors in 59 patients receiving unrelated donor HCT. NK cell numbers normalized quickly relative to B and T cells; however, the expression of both inhibitory and activating isoforms of killer immunoglobulin-like receptors (KIRs) was delayed. Most NK cells expressed an immature phenotype during the first 6 months post-HCT; however, we found high expression of activating NKp46 and NKp44 natural cytotoxicity receptors (NCRs), and cytotoxicity was preserved. Early reconstituting NK cells from unmanipulated grafts showed lower cytotoxicity than those from T-cell-depleted grafts. Differences in NK cell reconstitution had significant effects on clinical outcomes. Patients whose NK cells reconstituted earlier had better survival and lower relapse rates. The best survival group was recipients who possessed HLA-C2 but their donor lacked the cognate-activating KIR2DS1. Collectively, our data underscore the clinical relevance of reconstituting NK cells and their activating KIRs and NCRs. In addition to NK cell quantification and genotyping, comprehensive assessment of NK cell functions and phenotypes, including activating receptors, is essential.