Exploring and Exploiting Acceptor Preferences of the Human Polysialyltransferases as a Basis for an Inhibitor Screen.

α2,8-Linked polysialic acid (polySia) is an oncofoetal antigen with high abundance during embryonic development. It reappears in malignant tumours of neuroendocrine origin. Two polysialyltransferases (polySTs) ST8SiaII and IV are responsible for polySia biosynthesis. During development, both enzymes are essential to control polySia expression. However, in tumours ST8SiaII is the prevalent enzyme. Consequently, ST8SiaII is an attractive target for novel cancer therapeutics. A major challenge is the high structural and functional conservation of ST8SiaII and -IV. An assay system that enables differential testing of ST8SiaII and -IV would be of high value to search for specific inhibitors. Here we exploited the different modes of acceptor recognition and elongation for this purpose. With DMB-DP3 and DMB-DP12 (fluorescently labelled sialic acid oligomers with a degree of polymerisation of 3 and 12, respectively) we identified stark differences between the two enzymes. The new acceptors enabled the simple comparative testing of the polyST initial transfer rate for a series of CMP-activated and N-substituted sialic acid derivatives. Of these derivatives, the non-transferable CMP-Neu5Cyclo was found to be a new, competitive ST8SiaII inhibitor.

[Frequency and Type of Traumatic Events in Children and Adolescents with a Posttraumatic Stress Disorder]. / Häufigkeit und Art traumatischer Ereignisse bei Kindern und Jugendlichen mit Posttraumatischer Belastungsstörung.

The risk for children and adolescents to be exposed to a potentially traumatic event (PTE) is high. The present study examines the frequency of PTEs in children and adolescents with Posttraumatic Stress Disorder (PTSD), the type of index trauma, and its relation to PTSD symptom severity and gender. A clinical sample of 159 children and adolescents between 7-16 years was assessed using the Clinician-Administered PTSD Scale for Children and Adolescents (CAPS-CA). All reported PTEs from the checklist were analyzed according to frequency. The index events were categorized according to the following categories: cause (random vs. intentional), relation to offender (intrafamilial vs. extrafamilial), patient's role (victim, witness or vicarious traumatization), and type of PTE (physical or sexual violence). Relation between categories and PTSD symptom severity and sex were analyzed with inferential statistics. On average participants reported five PTEs, most frequently physical violence without weapons (57.9%), loss of loved person through death (45.9%), and sexual abuse/assaults (44%). The most frequent index traumata were intentional (76.7%). Regarding trauma type, there was a significant difference concerning higher symptom severity in children and adolescents who experienced sexual abuse/assault compared to physical violence (t=-1.913(109), p=0.05). A significantly higher symptom severity was found for girls compared to boys for the trauma categories extrafamilial offender (z=-2,27, p=0.02), victim (z=-2,11, p=0,04), and sexual abuse/assault (z=-2,43, p=0,01). Clinical and diagnostic implications are discussed in relation to the amendments of PTSD diagnostic criteria in DSM-5.

The anticonvulsant response to valproate in kindled rats is correlated with its effect on neuronal firing in the substantia nigra pars reticulata: a new mechanism of pharmacoresistance.

Resistance to antiepileptic drugs (AEDs) is a major problem in epilepsy treatment. However, mechanisms of resistance are only incompletely understood. We have recently shown that repeated administration of the AED phenytoin allows selecting resistant and responsive rats from the amygdala kindling model of epilepsy, providing a tool to study mechanisms of AED resistance. We now tested whether individual amygdala-kindled rats also differ in their anticonvulsant response to the major AED valproate (VPA) and which mechanism may underlie the different response to VPA. VPA has been proposed to act, at least in part, by reducing spontaneous activity in the substantia nigra pars reticulata (SNr), a main basal ganglia output structure involved in seizure propagation, seizure control, and epilepsy-induced neuroplasticity. Thus, we evaluated whether poor anticonvulsant response to VPA is correlated with low efficacy of VPA on SNr firing rate and pattern in kindled rats. We found (1) that good and poor VPA responders can be selected in kindled rats by repeatedly determining the effect of VPA on the electrographic seizure threshold, and (2) a significant correlation between the anticonvulsant response to VPA in kindled rats and its effect on SNr firing rate and pattern. The less VPA was able to raise seizure threshold, the lower was the VPA-induced reduction of SNr firing rate and the VPA-induced regularity of SNr firing. The data demonstrate for the first time an involvement of the SNr in pharmacoresistant experimental epilepsy and emphasize the relevance of the basal ganglia as target structures for new treatment options.

Chemical synthesis and enzymatic testing of CMP-sialic acid derivatives.

The cycloSal approach has been used in the past for the synthesis of a range of phosphorylated bioconjugates. In those reports, cycloSal nucleotides were allowed to react with different phosphate nucleophiles. With glycopyranosyl phosphates as nucleophiles, diphosphate-linked sugar nucleotides were formed. Here, cycloSal-nucleotides were used to prepare monophosphate-linked sugar nucleotides successfully in high anomeric purity and high chemical yield. The method was successfully used for the synthesis of three nucleotide glycopyranoses as model compounds. The method was then applied to the syntheses of CMP-N-acetyl-neuraminic acids (CMP-Neu5NAc) and of four derivatives with different modifications at their amino functions (N-propanoyl, N-butanoyl, N-pentanoyl and N-cyclopropylcarbonyl). The compounds were used for initial enzymatic studies with a bacterial polysialyltransferase (polyST). Surprisingly, the enzyme showed marked differences in terms of utilisation of the four derivatives. The N-propanoyl, N-butanoyl, and N-pentanoyl derivatives were efficiently used in a first transfer with a fluorescently labelled trisialo-acceptor. However, elongation of the resulting tetrasialo-acceptors worsened progressively with the size of the N-acyl chain. The N-pentanoyl derivative allowed a single transfer, leading to a capped tetramer. The N-cyclopropylcarbonyl derivative was not transferred.

Reliable synthesis of various nucleoside diphosphate glycopyranoses.

A reliable and high yielding synthetic pathway for the synthesis of the biologically highly important class of nucleoside diphosphate sugars (NDP-sugars) was developed by using various cycloSal-nucleotides 1 and 9 as active ester building blocks. The reaction with anomerically pure pyranosyl-1-phosphates 2 led to the target NDP-sugars 20-45 in a nucleophilic displacement reaction, which cleaves the cycloSal moiety in anomerically pure forms. As nucleosides cytidine, uridine, thymidine, adenosine, 2'-deoxy-guanosine and 2',3'-dideoxy-2',3'-didehydrothymidine were used while the phosphates of D-glucose, D-galactose, D-mannose, D-NAc-glucosamine, D-NAc-galactosamine, D-fucose, L-fucose as well as 6-deoxy-D-gulose were introduced.

Evidence on User-Led Innovation in Diabetes Technology (The OPEN Project): Protocol for a Mixed Methods Study.

BACKGROUND: Digital innovations in health care have traditionally followed a top-down pathway, with manufacturers leading the design and production of technology-enabled solutions and those living with chronic conditions involved only as passive recipients of the end product. However, user-driven open-source initiatives in health care are becoming increasingly popular. An example is the growing movement of people with diabetes, who create their own "Do-It-Yourself Artificial Pancreas Systems" (DIYAPS). OBJECTIVE: The overall aim of this study is to establish the empirical evidence base for the clinical effectiveness and quality-of-life benefits of DIYAPS and identify the challenges and possible solutions to enable their wider diffusion. METHODS: A research program comprising 5 work packages will examine the outcomes and potential for scaling up DIYAPS solutions. Quantitative and qualitative methodologies will be used to examine clinical and self-reported outcome measures of DIYAPS users. The majority of members of the research team live with type 1 diabetes and are active DIYAPS users, making Outcomes of Patients' Evidence With Novel, Do-It-Yourself Artificial Pancreas Technology (OPEN) a unique, user-driven research project. RESULTS: This project has received funding from the European Commission's Horizon 2020 Research and Innovation Program, under the Marie Sklodowska-Curie Action Research and Innovation Staff Exchange. Researchers with both academic and nonacademic backgrounds have been recruited to formulate research questions, drive the research process, and disseminate ongoing findings back to the DIYAPS community and other stakeholders. CONCLUSIONS: The OPEN project is unique in that it is a truly patient- and user-led research project, which brings together an international, interdisciplinary, and intersectoral research group, comprising health care professionals, technical developers, biomedical and social scientists, the majority of whom are also living with diabetes. Thus, it directly addresses the core research and user needs of the DIYAPS movement. As a new model of cooperation, it will highlight how researchers in academia, industry, and the patient community can create patient-centric innovation and reduce disease burden together. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/15368.

Azacitidine combined with the selective FLT3 kinase inhibitor crenolanib disrupts stromal protection and inhibits expansion of residual leukemia-initiating cells in FLT3-ITD AML with concurrent epigenetic mutations.

Effectively targeting leukemia-initiating cells (LIC) in FLT3-ITD-mutated acute myeloid leukemia (AML) is crucial for cure. Tyrosine kinase inhibitors (TKI) have limited impact as single agents, failing to eradicate LIC in the bone marrow. Using primary AML samples and a patient-derived xenograft model, we investigated whether combining the FLT3-selective TKI crenolanib with the hypomethylating agent azacitidine (AZA) eliminates FLT3-ITD LIC and whether efficacy of this combination depends on co-existing mutations. Using multiparameter flow cytometry, we show FLT3-ITD occurs within the most primitive Lin-/CD33(+)/CD45dim/CD34+CD38- LIC compartment. Crenolanib alone could not target FLT3-ITD LIC in contact with niche cells while addition of AZA overcame stromal protection resulting in dramatically reduced clonogenic capacity of LIC in vitro and severely impaired engraftment in NSG mice. Strikingly, FLT3-mutated samples harboring TET2 mutations were completely resistant to crenolanib whereas neither NPM1 nor DNMT3A mutations influenced response. Conversely, primary AML LIC harboring either TET2, DNMT3A or NPM1 mutations did not show increased sensitivity to AZA. In summary, resistance of FLT3-ITD LIC to TKI depends on co-existing epigenetic mutations. However, AZA + crenolanib effectively abrogates stromal protection and inhibits survival of FLT3-ITD LIC irrespective of mutations, providing evidence for this combination as a means to suppress residual LIC.

A convenient synthesis of nucleoside diphosphate glycopyranoses and other polyphosphorylated bioconjugates.

In this review, we summarize results obtained using a conceptionally new chemical synthesis of NDP-sugars based on cycloSaligenyl (cycloSal) nucleotides as starting material (cycloSal technique). The cycloSal technique not only leads to stereoisomerically defined NDP-sugars in high yield, but the same principle provides very efficient routes towards nucleoside di- and -triphosphates. Moreover, sugar-nucleotides such as CMP-Neu5Ac and dinucleoside polyphosphates are available. Thus, the method offers a nearly universal chemical access towards a large number of highly interesting bioconjugates and biomolecules.

New efficient synthesis of nucleoside diphosphate glycopyranoses.

A new access for the synthesis of nucleoside diphosphate glycopyranoses has been developed based on the cycloSal-concept. Using this approach, excellent chemical yields were obtained within short reaction times. In comparison to other methods the cycloSal-concept allows a fast and efficient preparation of anomerically defined nucleoside diphosphate glycopyranoses.