Axonal Lysosomal Assays for Characterizing the Effects of LRRK2 G2019S

The degeneration of axon terminals before the soma, referred to as "dying back", is a feature of Parkinson's disease (PD). Axonal assays are needed to model early PD pathogenesis as well as identify protective therapeutics. We hypothesized that defects in axon lysosomal trafficking as well as injury repair might be important contributing factors to "dying back" pathology in PD. Since primary human PD neurons are inaccessible, we developed assays to quantify axonal trafficking and injury repair using induced pluripotent stem cell (iPSC)-derived neurons with LRRK2 G2019S, which is one of the most common known PD mutations, and isogenic controls. We observed a subtle axonal trafficking phenotype that was partially rescued by a LRRK2 inhibitor. Mutant LRRK2 neurons showed increased phosphorylated Rab10-positive lysosomes, and lysosomal membrane damage increased LRRK2-dependent Rab10 phosphorylation. Neurons with mutant LRRK2 showed a transient increase in lysosomes at axotomy injury sites. This was a pilot study that used two patient-derived lines to develop its methodology; we observed subtle phenotypes that might correlate with heterogeneity in LRRK2-PD patients. Further analysis using additional iPSC lines is needed. Therefore, our axonal lysosomal assays can potentially be used to characterize early PD pathogenesis and test possible therapeutics.

The gut microbiota modulates brain network connectivity under physiological conditions and after acute brain ischemia

The gut microbiome has been implicated as a key regulator of brain function in health and disease. But the impact of gut microbiota on functional brain connectivity is unknown. We used resting-state functional magnetic resonance imaging in germ-free and normally colonized mice under naive conditions and after ischemic stroke. We observed a strong, brain-wide increase of functional connectivity in germ-free animals. Graph theoretical analysis revealed significant higher values in germ-free animals, indicating a stronger and denser global network but with less structural organization. Breakdown of network function after stroke equally affected germ-free and colonized mice. Results from histological analyses showed changes in dendritic spine densities, as well as an immature microglial phenotype, indicating impaired microglia-neuron interaction in germ-free mice as potential cause of this phenomenon. These results demonstrate the substantial impact of bacterial colonization on brain-wide function and extend our so far mainly (sub) cellular understanding of the gut-brain axis.

Autocrine prostaglandin feedback determines the kinetics of bacterial type I interferon induction by restricting endosomal TLR4/TRIF complex assembly

TLR4 is unique in its capacity to initiate two qualitatively distinct transcriptional programs from two cellular locations. Cell surface TLR4/MyD88 complexes drive pro-inflammatory cytokine transcription through NF-κB, while endosomal TLR4/TRIF complexes activate IRF3 and a type I interferon response. Feedback circuits to limit signals from both locations are necessary to balance the inflammatory response to Gram negative bacteria, yet how endosomal TLR4/TRIF signals are terminated has remained an open question. We find that activation of TLR4 triggers rapid prostaglandin PGE2 production, necessary to limit the kinetics of endosomal TRIF, but not MyD88, signaling. Mechanistically, autocrine PGE2 activates the specific EP4 receptor to inhibit small GTPase mediated TLR4 trafficking to endosomes and to accelerate autophagic degradation of active TLR4/TRIF complexes. Inhibition of EP4 receptor function does not impair cell surface MyD88 signals, but leads to hyper TRIF dependent type I interferon production in response to bacterial LPS or to macrophage infection by live Gram negative pathogens.

Therapeutic targeting of intracellular Toll-like and interleukin-1/18 receptor (TIR) resistance domain containing proteins for protection against infection, inflammation and disease

TIR domain containing proteins are important immune associated proteins shared among Toll-like and interleukin-1/18 receptor family members. In a recent discovery select bacterial, plant and human TIR proteins exhibit enzymatic activity in binding and processing nicotinamide adenine dinucleotide (NAD+). Based on their abilities to facilitate signaling across biology, we hypothesize that TIR proteins represent unique therapeutic targets for modulating infection, inflammation and disease. Our previous structural studies of bacterial-host TIR proteins B. melitensis (TcpB) and uropathogenic E. coli CFT073 (TcpC) with human host TIRAP and MyD88 characterized peptides that negatively regulate signaling and infection. From these studies we identified interactions that are at or near reported biological TIR protein interfaces. In particular, we identified a functionally important motif found conserved on the C helix of most bacterial, human host and NAD+ consuming TIR proteins. As proof of concept for select targeting of TIR proteins and this region in particular we have used the TLR4 antagonist, TAK-242, which selectively binds within this motif. Treatment with TAK-242 or TLR4-C747S blocks LPS signaling. Additionally, TAK-242 protected mice from lethal influenza challenge similar to an extracellular TLR4 antagonist, Eritoran. Bioinformatic analysis of the region targeted by TAK242 show that it is located within the WxxxE structural motif identified to be important for protecting against microtubule destabilization and includes a catalytically essential glutamic acid (E) residue conserved among nearly all NAD+ consuming TIR proteins. These studies provide a framework for future studies targeting TIR protein function.

Human Neural Stem Cell Induced Functional Network Stabilization After Cortical Stroke: A Longitudinal Resting-State fMRI Study in Mice

Most stroke studies dealing with functional deficits and assessing stem cell therapy produce extensive hemispheric damage and can be seen as a model for severe clinical strokes. However, mild strokes have a better prospect for functional recovery. Recently, anatomic and behavioral changes have been reported for distal occlusion of the middle cerebral artery (MCA), generating a well-circumscribed and small cortical lesion, which can thus be proposed as mild to moderate cortical stroke. Using this cortical stroke model of moderate severity in the nude mouse, we have studied the functional networks with resting-state functional magnetic resonance imaging (fMRI) for 12 weeks following stroke induction. Further, human neural stem cells (hNSCs) were implanted adjacent to the ischemic lesion, and the stable graft vitality was monitored with bioluminescence imaging (BLI). Differentiation of the grafted neural stem cells was analyzed by immunohistochemistry and by patch-clamp electrophysiology. Following stroke induction, we found a pronounced and continuously rising hypersynchronicity of the sensorimotor networks including both hemispheres, in contrast to the severe stroke filament model where profound reduction of the functional connectivity had been reported by us earlier. The vitality of grafted neural stem cells remained stable throughout the whole 12 weeks observation period. In the stem cell treated animals, functional connectivity did not show hypersynchronicity but was globally slightly reduced below baseline at 2 weeks post-stroke, normalizing thereafter completely. Our resting-state fMRI (rsfMRI) studies on cortical stroke reveal for the first time a hypersynchronicity of the functional brain networks. This hypersynchronicity appears as a hallmark of mild cortical strokes, in contrast to severe strokes with striatal involvement where exclusively hyposynchronicity has been reported. The effect of the stem cell graft was an early and persistent normalization of the functional sensorimotor networks across the whole brain. These novel functional results may help interpret future outcome investigations after stroke and demonstrate the highly promising potential of stem cell treatment for functional outcome improvement after stroke.

[Acute idiopathic scrotal edema-an underestimated differential diagnosis of acute scrotum]

Considering that Quist et al. first described the acute idiopathic scrotal edema (AISE) already in 1956, there are not many studies published in literature concerning the etiology, the development, and the progress of the disease since then. According to the literature the incidence of AISE is about 20%. Although it is an important differential diagnosis for acute scrotum, it remains extensively unknown. Therefore, AISE should be kept in mind by urologists, pediatric surgeons and pediatricians to avoid needless surgery or antibiotic therapy.

Vacuum-UV induced DNA strand breaks - influence of the radiosensitizers 5-bromouracil and 8-bromoadenine

Radiation therapy is a basic part of cancer treatment. To increase the DNA damage in carcinogenic cells and preserve healthy tissue at the same time, radiosensitizing molecules such as halogenated nucleobase analogs can be incorporated into the DNA during the cell reproduction cycle. In the present study 8.44 eV photon irradiation induced single strand breaks (SSB) in DNA sequences modified with the radiosensitizer 5-bromouracil (5BrU) and 8-bromoadenine (8BrA) are investigated. 5BrU was incorporated in the 13mer oligonucleotide flanked by different nucleobases. It was demonstrated that the highest SSB cross sections were reached, when cytosine and thymine were adjacent to 5BrU, whereas guanine as a neighboring nucleobase decreases the activity of 5BrU indicating that competing reaction mechanisms are active. This was further investigated with respect to the distance of guanine to 5BrU separated by an increasing number of adenine nucleotides. It was observed that the SSB cross sections were decreasing with an increasing number of adenine spacers between guanine and 5BrU until the SSB cross sections almost reached the level of a non-modified DNA sequence, which demonstrates the high sequence dependence of the sensitizing effect of 5BrU. 8BrA was incorporated in a 13mer oligonucleotide as well and the strand breaks were quantified upon 8.44 eV photon irradiation in direct comparison to a non-modified DNA sequence of the same composition. No clear enhancement of the SSB yield of the modified in comparison to the non-modified DNA sequence could be observed. Additionally, secondary electrons with a maximum energy of 3.6 eV were generated when using Si as a substrate giving rise to further DNA damage. A clear enhancement in the SSB yield can be ascertained, but to the same degree for both the non-modified DNA sequence and the DNA sequence modified with 8BrA.

Persistent Quantitative Vitality of Stem Cell Graft Is Necessary for Stabilization of Functional Brain Networks After Stroke

Stem cell treatment after stroke has demonstrated substantial outcome improvement. However, monitoring of stem cell fate in vivo is still challenging and not routinely performed, yet important to quantify the role of the implanted stem cells on lesion improvement; in several studies even mortality of the graft has been reported. Resting state functional magnetic resonance imaging (rs-fMRI) is a highly sensitive imaging modality to monitor the brain-wide functional network alterations of many brain diseases in vivo. We monitor for 3 months the functional connectivity changes after intracortical stem cell engraftment in large, cortico-striatal (n = 9), and in small, striatal (n = 6) ischemic lesions in the mouse brain with non-invasive rs-fMRI on a 9.4T preclinical MRi scanner with GE-EPI sequence. Graft vitality is continuously recorded by bioluminescence imaging (BLI) roughly every 2 weeks after implantation of 300 k neural stem cells. In cortico-striatal lesions, the lesion extension induces graft vitality loss, in consequence leading to a parallel decrease of functional connectivity strength after a few weeks. In small, striatal lesions, the graft vitality is preserved for the whole observation period and the functional connectivity is stabilized at values as in the pre-stroke situation. But even here, at the end of the observation period of 3 months, the functional connectivity strength is found to decrease despite preserved graft vitality. We conclude that quantitative graft viability is a necessary but not sufficient criterion for functional neuronal network stabilization after stroke. Future studies with even longer time periods after stroke induction will need to identify additional players which have negative influence on the functional brain networks.

Quantitative in vivo dual-color bioluminescence imaging in the mouse brain

Bioluminescence imaging (BLI) is an optical imaging method that can be translated from the cell culture dish in vitro to cell tracking in small animal models in vivo. In contrast to the more widely used fluorescence imaging, which requires light excitation, in BLI the light is exclusively generated by the enzyme luciferase. The luciferase gene can be engineered to target and monitor almost every cell and biological process quantitatively in vitro and even from deep tissue in vivo. While initially used for tumor imaging, bioluminescence was recently optimized for mouse brain imaging of neural cells and monitoring of viability or differentiation of grafted stem cells. Here, we describe the use of bright color-shifted firefly luciferases (Flucs) based on the thermostable x5 Fluc that emit red and green for effective and quantitative unmixing of two human cell populations in vitro and after transplantation into the mouse brain in vivo. Spectral unmixing predicts the ratio of luciferases in vitro and a mixture of cells precisely for cortical grafts, however, with less accuracy for striatal grafts. This dual-color approach enables the simultaneous visualization and quantification of two cell populations on the whole brain scale, with particular relevance for translational studies of neurological disorders providing information on stem cell survival and differentiation in one imaging session in vivo.

Functional networks are impaired by elevated tau-protein but reversible in a regulatable Alzheimer's disease mouse model

Background

Aggregation of tau proteins is a distinct hallmark of tauopathies and has been a focus of research and clinical trials for Alzheimer’s Disease. Recent reports have pointed towards a toxic effect of soluble or oligomeric tau in the spreading of tau pathology in Alzheimer’s disease. Here we investigated the effects of expressing human tau repeat domain (tauRD) with pro- or anti-aggregant mutations in regulatable transgenic mouse models of Alzheimer’s Disease on the functional neuronal networks and the structural connectivity strength.

Methods

Pro-aggregant and anti-aggregant mice were studied when their mutant tauRD was switched on for 12 months to reach the stage where pro-aggregant mice show cognitive impairment, whereas anti-aggregant mice remained cognitively normal. Then, mutant tauRD was switched off by doxycycline treatment for 8 weeks so that soluble transgenic tau disappeared and cognition recovered in the pro-aggregant mice, although some aggregates remained. At these two time points, at baseline after 12 months of mutant tau expression and after 8 weeks of doxycycline treatment, resting state fMRI and diffusion MRI were used to determine functional neuronal networks and fiber connectivities. Results of the transgenic mice were compared with wildtype littermates.

Results

Functional connectivity was strongly reduced in transgenic animals during mutant tauRD expression, in relation to WT mice. Interestingly, transgenic mice with the non-aggregant tau mutant showed identical functional deficits as the pro-aggregant mice, even though in this case there was no cognitive decline by behavioral testing. Upon 8 weeks doxycycline treatment and transgene switch-off, functional connectivity in both transgenic groups presented complete normalization of functional connectivity strength, equivalent to the situation in WT littermates. Structural connectivity was found only marginally sensitive to mutant tau expression (both pro- and anti-aggregant tauRD) and by doxycycline treatment.

Conclusions

Our in vivo investigations unravel for the first time a strong reduction of functional neuronal networks by the presence of increased soluble rather than fibrillary tau, independent of its intrinsic propensity of aggregation, which is reversible by switching tau off. Our functional MRI study thus is an unexpected in vivo validation of a novel property of tau, while previous results pointed to a role of aggregation propensity for a pathological state by histopathology and cognitive decline. Our results present further evidence for early tauopathy biomarkers or a potential early stage drug target by functional networks analysis.

Electronic supplementary material

The online version of this article (10.1186/s13024-019-0316-6) contains supplementary material, which is available to authorized users.

Vacuum-UV and Low-Energy Electron-Induced DNA Strand Breaks - Influence of the DNA Sequence and Substrate

DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF₂ as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7-2.3×10^-16  cm² . The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies <3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold.

The Physico-Chemical Basis of DNA Radiosensitization: Implications for Cancer Radiation Therapy

High-energy radiation is used in combination with radiosensitizing therapeutics to treat cancer. The most common radiosensitizers are halogenated nucleosides and cisplatin derivatives, and recently also metal nanoparticles have been suggested as potential radiosensitizing agents. The radiosensitizing action of these compounds can at least partly be ascribed to an enhanced reactivity towards secondary low-energy electrons generated along the radiation track of the high-energy primary radiation, or to an additional emission of secondary reactive electrons close to the tumor tissue. This is referred to as physico-chemical radiosensitization. In this Concept article we present current experimental methods used to study fundamental processes of physico-chemical radiosensitization and discuss the most relevant classes of radiosensitizers. Open questions in the current discussions are identified and future directions outlined, which can lead to optimized treatment protocols or even novel therapeutic concepts.

Programmable fusion of liposomes mediated by lipidated PNA

We recently reported a DNA-programmed fusion cascade enabling the use of liposomes as nanoreactors for compartmentalized chemical reactions. This communication reports an alternative and robust strategy based on lipidated peptide nucleic acids (LiPs). LiPs enabled fusion of liposomes with remarkable 31% efficiency at 50 °C with low leakage (5%).

Bottom-Up Assembly of Silica and Bioactive Glass Supraparticles with Tunable Hierarchical Porosity

We investigate the formation of spherical supraparticles with controlled and tunable porosity on the nanometer and micrometer scales using the self-organization of a binary mixture of small (nanometer scale) oxidic particles with large (micrometer scale) polystyrene particles in the confinement of an emulsion droplet. The external confinement determines the final, spherical structure of the hybrid assembly, while the small particles form the matrix material. The large particles act as templating porogens to create micropores after combustion at elevated temperatures. We control the pore sizes on the micrometer scale by varying the size of the coassembled polystyrene microspheres and produce supraparticles from both silica- and calcium-containing CaO/SiO₂ particles. Although porous supraparticles are obtained in both cases, we found that the presence of calcium ions substantially complicated the fabrication process since the increased ionic strength of the dispersion compromises the colloidal stability during the assembly process. We minimized these stability issues via the addition of a steric stabilizing agent and by mixing bioactive and silica colloidal particles. We investigated the interaction of the porous particles with bone marrow stromal cells and found an increase in cell attachment with increasing pore size of the self-assembled supraparticles.

Computer-assisted Diagnosis for Early Stage Pleural Mesothelioma

Objectives: Pleural thickenings as biomarker of exposure to asbestos may evolve into malignant pleural mesothelioma. Foritsearly stage, pleurectomy with perioperative treatment can reduce morbidity and mortality. The diagnosis is based on a visual investigation of CT images, which is a time-consuming and subjective procedure. Our aim is to develop an automatic image processing approach to detect and quantitatively assess pleural thickenings.

Methods: We first segment the lung areas, and identify the pleural contours. A convexity model is then used together with a Hounsfield unit threshold to detect pleural thickenings. The assessment of the detected pleural thickenings is based on a spline-based model of the healthy pleura.

Results: Tests were carried out on 14 data sets from three patients. In all cases, pleural contours were reliably identified, and pleural thickenings detected. PC-based Computation times were 85 min for a data set of 716 slices, 35 min for 401 slices, and 4 min for 75 slices, resulting in an average computation time of about 5.2 s per slice. Visualizations of pleurae and detected thickeningswere provided.

Conclusion: Results obtained so far indicate that our approach is able to assist physicians in the tedious task of finding and quantifying pleural thickenings in CT data. In the next step, our system will undergo an evaluation in a clinical test setting using routine CT data to quantifyits performance.

Radiative Rotational Lifetimes and State-Resolved Relative Detachment Cross Sections from Photodetachment Thermometry of Molecular Anions in a Cryogenic Storage Ring

Photodetachment thermometry on a beam of OH^{-} in a cryogenic storage ring cooled to below 10 K is carried out using two-dimensional frequency- and time-dependent photodetachment spectroscopy over 20 min of ion storage. In equilibrium with the low-level blackbody field, we find an effective radiative temperature near 15 K with about 90% of all ions in the rotational ground state. We measure the J=1 natural lifetime (about 193 s) and determine the OH^{-} rotational transition dipole moment with 1.5% uncertainty. We also measure rotationally dependent relative near-threshold photodetachment cross sections for photodetachment thermometry.

Electron holography on HfO2/HfO2-x bilayer structures with multilevel resistive switching properties

Unveiling the physical nature of the oxygen-deficient conductive filaments (CFs) that are responsible for the resistive switching of the HfO₂-based resistive random access memory (RRAM) devices represents a challenging task due to the oxygen vacancy related defect nature and nanometer size of the CFs. As a first important step to this goal, we demonstrate in this work direct visualization and a study of physico-chemical properties of oxygen-deficient amorphous HfO_2-x by carrying out transmission electron microscopy electron holography as well as energy dispersive x-ray spectroscopy on HfO₂/HfO_2-x bilayer heterostructures, which are realized by reactive molecular beam epitaxy. Furthermore, compared to single layer devices, Pt/HfO₂/HfO_2-x /TiN bilayer devices show enhanced resistive switching characteristics with multilevel behavior, indicating their potential as electronic synapses in future neuromorphic computing applications.

FIB based fabrication of an operative Pt/HfO2/TiN device for resistive switching inside a transmission electron microscope

Recent advances in microelectromechanical systems (MEMS) based chips for in situ transmission electron microscopy are opening exciting new avenues in nanoscale research. The capability to perform current-voltage measurements while simultaneously analyzing the corresponding structural, chemical or even electronic structure changes during device operation would be a major breakthrough in the field of nanoelectronics. In this work we demonstrate for the first time how to electrically contact and operate a lamella cut from a resistive random access memory (RRAM) device based on a Pt/HfO₂/TiN metal-insulator-metal (MIM) structure. The device was fabricated using a focused ion beam (FIB) instrument and an in situ lift-out system. The electrical switching characteristics of the electron-transparent lamella were comparable to a conventional reference device. The lamella structure was initially found to be in a low resistance state and could be reset progressively to higher resistance states by increasing the positive bias applied to the Pt anode. This could be followed up with unipolar set/reset operations where the current compliance during set was limited to 400 µA. FIB structures allowing to operate and at the same time characterize electronic devices will be an important tool to improve RRAM device performance based on a microstructural understanding of the switching mechanism.

Perspectives of In Vivo Bioluminescence Imaging: Application to Basic and Translational Neuroscience

BACKGROUND

In vivo bioluminescence imaging has been used extensively for screening assays and for qualitative determination of localization of cells, in particular in cancer studies.

OBJECTIVE

In this review we show the potential of this noninvasive molecular imaging modality to investigate gene activity, dynamic processes, and translational disease processes, all under true in vivo conditions with the specific focus on brain.

RESULTS

We demonstrate a range of applications of bioluminescence imaging in basic and translational neuroscience. Here, emphasis is on the contribution of bioluminescence imaging of the brain to the elucidation of cellular and genetic mechanisms, understanding of dynamic processes, and to the discussion of disease characterization and therapeutic strategies.

Signal integration in lipopolysaccharide (LPS)-stimulated murine macrophages

Using a panel of LPS-inducible genes, selected for the capacity of their products to contribute to endotoxicity, normal macrophages were compared to macrophages deficient in CD14, CD11b/CD18, or TLR4 to elicit gene expression in response to Escherichia coli LPS or the LPS mimetic, Taxol. All genes were TLR4-dependent. At low doses of LPS or Taxol, all genes were also CD14-dependent; however, IP-10 and ICSBP remained poorly inducible even at much higher concentrations. A distinct subset of genes (COX-2, IL-12 p40, and IL-12 p35) was CD11b/CD18-dependent. NF-κB translocation and MAPK phosphorylation were dysregulated in receptor-deficient macrophages. In contrast to E. coli LPS, a Porphyromonas gingivalis LPS preparation was found to be TLR2-, rather than TLR4-dependent, and resulted in differential expression of genes within the panel. These data suggest that: (i) TLR4 is necessary, but not sufficient, to induce the full repertoire of genes examined; (ii) CD14 and CD11b/CD18 facilitate signaling for induction of select subsets of genes that are also TLR4-dependent; and (iii) signaling through TLR2 versus TLR4 differs quantitatively/qualitatively. These data support an LPS signaling complex on murine macrophages that minimally includes CD14, CD11b/CD18, and TLR4 to respond to E. coli LPS to elicit the full spectrum of gene expression.

The cryogenic storage ring CSR

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm(-3) is derived, equivalent to a room-temperature pressure below 10(-14) mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

Molecular interactions of small molecule inhibitors targeting cytoplasmic TIR domains

Regulation of Toll-like receptor (TLR) signaling using small molecule agonists and antagonists have been widely sought after for controlling inflmation and disease. Most studies have focused on therapeutic targeting of TLR extracellular ligand binding domains. Recently, Computer-aided drug design (CADD) screens specifically targeting intracellular Toll-Interleukin-1 receptor resistance domains have identified and functionally characterized several small molecule and peptide inhibitors which protect against lethality in animal models of infection, inflammation and disease. We have sought to structurally characterize the molecular interactions of CADD derived small molecule inhibitors with respective TLR-TIR domains by determining the X-ray co-crystal structures of TLR2 –TIR domain in the presence of C29 and its substructure O-vanillin. Positive electron density is observed near the BB loop and residue Ile 685 of native TLR2-TIR in the presence of the small molecule inhibitor (C29) exhibit compared with the native apo form of this structure. However, the presence of (S-(DIMETHYLARSENIC) CYSTEINE) in this crystallization condition complicate analysis. To rule out the effects of DMSO and (S-(DIMETHYLARSENIC) CYSTEINE) we sought to examine small molecule inhibitor C29L substructure (o-Vanillin) in a second crystal form of TLR2 and which contains a more simplified crystallization condition grown in the presence of 1mM of C29L. This co-crystal exhibits positive electron density located in an around the BB loop compared with apo forms of this structure. Additionally, in this recent structure form we observe additional DD loop density previously not defined in the originally reported crystal form.

Photodissociation of an Internally Cold Beam of CH^{+} Ions in a Cryogenic Storage Ring

We have studied the photodissociation of CH^{+} in the Cryogenic Storage Ring at ambient temperatures below 10 K. Owing to the extremely high vacuum of the cryogenic environment, we were able to store CH^{+} beams with a kinetic energy of ∼60  keV for several minutes. Using a pulsed laser, we observed Feshbach-type near-threshold photodissociation resonances for the rotational levels J=0-2 of CH^{+}, exclusively. In comparison to updated, state-of-the-art calculations, we find excellent agreement in the relative intensities of the resonances for a given J, and we can extract time-dependent level populations. Thus, we can monitor the spontaneous relaxation of CH^{+} to its lowest rotational states and demonstrate the preparation of an internally cold beam of molecular ions.

Using DNA origami nanostructures to determine absolute cross sections for UV photon-induced DNA strand breakage

We have characterized ultraviolet (UV) photon-induced DNA strand break processes by determination of absolute cross sections for photoabsorption and for sequence-specific DNA single strand breakage induced by photons in an energy range from 6.50 to 8.94 eV. These represent the lowest-energy photons able to induce DNA strand breaks. Oligonucleotide targets are immobilized on a UV transparent substrate in controlled quantities through attachment to DNA origami templates. Photon-induced dissociation of single DNA strands is visualized and quantified using atomic force microscopy. The obtained quantum yields for strand breakage vary between 0.06 and 0.5, indicating highly efficient DNA strand breakage by UV photons, which is clearly dependent on the photon energy. Above the ionization threshold strand breakage becomes clearly the dominant form of DNA radiation damage, which is then also dependent on the nucleotide sequence.

Necrotic cell-derived high mobility group box 1 attracts antigen-presenting cells but inhibits hepatocyte growth factor-mediated tropism of mesenchymal stem cells for apoptotic cell death

Tissue damage due to apoptotic or necrotic cell death typically initiates distinct cellular responses, leading either directly to tissue repair and regeneration or to immunological processes first, to clear the site, for example, of potentially damage-inducing agents. Mesenchymal stem cells (MSC) as well as immature dendritic cells (iDC) and monocytes migrate to injured tissues. MSC have regenerative capacity, whereas monocytes and iDC have a critical role in inflammation and induction of immune responses, including autoimmunity after tissue damage. Here, we investigated the influence of apoptotic and necrotic cell death on recruitment of MSC, monocytes and iDC, and identified hepatocyte growth factor (HGF) and the alarmin high mobility group box 1 (HMGB1) as key factors differentially regulating these migratory responses. MSC, but not monocytes or iDC, were attracted by apoptotic cardiomyocytic and neuronal cells, whereas necrosis induced migration of monocytes and iDC, but not of MSC. Only apoptotic cell death resulted in HGF production and HGF-mediated migration of MSC towards the apoptotic targets. In contrast, HMGB1 was predominantly released by the necrotic cells and mediated recruitment of monocytes and iDC via the receptor of advanced glycation end products. Moreover, necrotic cardiomyocytic and neuronal cells caused an HMGB1/toll-like receptor-4-dependent inhibition of MSC migration towards apoptosis or HGF, while recruitment of monocytes and iDC by necrosis or HMGB1 was not affected by apoptotic cells or HGF. Thus, the type of cell death differentially regulates recruitment of either MSC or monocytes and iDC through HGF and HMGB1, respectively, with a dominant, HMGB1-mediated role of necrosis in determining tropism after tissue injury.

The mitochondrial protein TCAIM regulates activation of T cells and thereby promotes tolerance induction of allogeneic transplants

Primary T cell activation and effector cell differentiation is required for rejection of allogeneic grafts in naïve recipients. It has become evident, that mitochondria play an important role for T cell activation. Expression of several mitochondrial proteins such as TCAIM (T cell activation inhibitor, mitochondrial) is down-regulated upon T cell receptor triggering. Here we report that TCAIM inhibited spontaneous development of memory and effector T cells. CD4(+) T cells from Tcaim knock-in (KI) mice showed reduced activation, cytokine secretion and proliferation in vitro. Tcaim KI T cells tolerated allogeneic skin grafts upon transfer into Rag-1 KO mice. CD4(+) and CD8(+) T cells from these mice did not infiltrate skin grafts and kept a naïve or central memory phenotype, respectively. They were unable to acquire effector phenotype and functions. TCAIM altered T cell activation-induced mitochondrial distribution and reduced mitochondrial reactive oxygen species (mROS) production. Thus, TCAIM controls T cell activation and promotes tolerance induction probably by regulating TCR-mediated mitochondrial distribution and mROS production.

Specific Rate Constants of Hydroxyl Radical and Hydrated Electron Reactions Determined by the RCL Method

Relative rate constants of OH radical and eaq - reactions have been determined by comparing, under steady x-irradiation, the effect of various solutes upon the radiationinduced chemiluminescence (RCL) of aqueous dye (DH) solutions, [DH + ·OH] + eaq - → DH* + OH-. The results abundantly confirm other published data. RCL changes upon addition of phosphates indicate prototropic reactions with the oxidized dye, D·+ H2PO4 - ⇌ DH·+ + HPO4 2-, promoting or inhibiting the formation of semioxidized dye (DH·+) as the most efficient RCL precursor. The RCL enhancement commonly observed upon addition of halides and pseudo halides is discussed at some length on the base of previous and present results in order to focus attention to the possible correlation between such RCL enhancement and the effect of halogen-sensitization in radiobiology. RCL results suggest that the halide transients formed from OH radicals, X- + ·OH → X· + OH-, are very powerful oxidizing agents reacting with aromatics by electron-abstraction rather than by addition or H-abstraction. The common application of I- and SCN- as competitors for the estimation of OH radical reactivities is being commented in the context

Inhibition of TLR2 signaling by small molecule inhibitors targeting a novel putative pocket within the TLR2 TIR domain (INM9P.448)

Overexuberant TLR2 signaling has been implicated in numerous diseases. Visual analysis of the TLR2 TIR domain crystal structure suggested the presence of a “pocket” adjacent to the highly conserved and functionally important proline and glycine residues of the BB loop. Given the importance of the BB loop in mediating TLR signal transduction, we hypothesized that Computer-Aided Drug Design (CADD) could be used to identify a small molecule inhibitor(s) that would fit within this “pocket” and blunt TLR2 signaling. Using CADD, ~150 small compounds were identified based on their predicted ability to bind in this pocket. Based on inhibition of IL-8 mRNA induced by TLR2 agonists, compound “C29” was found to inhibit TLR2/1 and TLR2/6 signaling in human HEK-TLR2 and THP-1 cells, but only TLR2/1 signaling in murine macrophages. C29 blocks heat-killed and live bacterial TLR2 agonist-induced proinflammatory cytokine mRNA. C29 prevents the early activation of TLR2-mediated signaling, including NF-κB and MAPKs, as well as MyD88 recruitment to TLR2 in THP-1 cells. C29 is cleavable and the byproduct, o-vanillin, reproduces comparable TLR2 inhibitory activity. O-vanillin covalently interacts with recombinant human TLR2 TIR domain dose-dependently. Mutagenesis of “pocket” residues revealed an indispensable role for TLR2/1, but not TLR2/6, signaling, suggesting divergent roles. Collectively, these results provide proof-of-principle for using CADD to identify inhibitors of TLR2 signaling.

AMPK regulates innate immune signaling and viral control through ULK-1 dependent decrease of STING expression (INM7P.430)

The host protein STING has been shown to be essential for recognition of both viral and intracellular bacterial pathogens, but its regulation remains unclear. Previously, we have described how mitochondrial membrane potential regulates STING-dependent IFN-β induction. The kinase activity of AMPK is controlled by cellular metabolism and intracellular calcium concentration. The goal of our study was to examine whether STING-dependent signaling is regulated by AMPK. Addition of an intracellular calcium chelator or an AMPK inhibitor suppressed IFN-β induction in mouse macrophages stimulated with the STING-dependent ligand DMXAA. Similarly, mouse embryonic fibroblasts (MEFS) lacking AMPK alpha failed to up-regulate IFN-β after DMXAA treatment. Additionally, these AMPK-/- MEFS failed to activate the IRF3-kinase TBK-1 and phosphorylate the transcription factor IRF3 after DMXAA treatment, confirming that STING-dependent signaling is AMPK-dependent. Loss of AMPK led to constitutive activation of the known STING negative regulator ULK-1 and a decrease in the basal level of STING protein. As a result, AMPK-/- MEFS exhibit impaired control of Vesicular Stomatitis Virus, a virus sensed by STING. ULK-1 has been shown to phosphorylate and degrade STING in the presence of dsDNA through the sensor protein cGAS. But in WT MEFS, STING was degraded in response to DMXAA in a cGAS- and ULK-1- independent manner, illustrating a novel regulatory pathway for this crucial signaling protein.

Novel vaccination strategy: Francisella tularensis vaccines based on functionalized catanionic vesicles (VAC7P.963)

Francisella tularensis (Ft) is a Gram-negative, immune-evasive coccobacillus that causes tularemia for which there is no FDA-approved vaccine. We have utilized a novel vaccine approach using synthetic nanoparticles made from catanionic surfactant vesicles (V), functionalized by incorporation of either Ft type B Live Vaccine Strain (Ft LVS) or Ft type A Schu S4 strain (Ft Schu S4) components (i.e., LVS-V and Schu S4-V, respectively). Immunization of C57BL/6 mice with bare V partially protected against Ft LVS, presumably through activation of an innate immune response, yet failed to protect against Ft Schu S4. In contrast, immunization with LVS-V fully protected mice against intraperitoneal (i.p.) Ft LVS challenge, while immunization of mice with either LVS-V or Schu S4-V partially protected C57BL/6 mice against an intranasal (i.n.) Ft Schu S4 challenge. LVS-V-immunization, but not immunization with V, elicited high levels of IgG against non-LPS epitopes and these antisera conferred passive protection against challenge with Ft LVS. Our recently published and ongoing studies aim to identify the protein targets of mouse antisera, study the mechanism of non-specific protection gained by immunization with this nanoparticle vaccine platform (adjuvant effect) in Ft LVS challenge, and enhance protection in Ft Schu S4 challenge. Our data extend the utility of functionalized catanionic surfactant vesicles as a vaccine platform for pathogens.

Implications of glycoprotein VI for theranostics

Glycoprotein VI (GPVI), a membrane glycoprotein solely expressed in platelets and megakaryocytes, plays a critical role in thrombus formation due to collagen/GPVI-mediated platelet activation and adhesion. Recent studies have shown that surface expression of GPVI on circulating platelets is enhanced in acute cardiovascular diseases such as myocardial infarction and ischaemic stroke. Increased GPVI levels are associated with poor clinical outcome and are an early indicator for imminent myocardial infarction in patients with chest pain. The soluble form of the dimeric GPVI fusion protein (sGPVI-Fc) binds with high affinity to collagen and atherosclerotic plaque tissue. Non-invasive imaging studies with radiolabelled sGPVI-Fc show specific binding activity to vascular lesions in vivo. Further, sGPVI-Fc has been developed as a new therapeutic platelet-based strategy for lesion-directed antithrombotic therapy. This review summarises the potential of GPVI for diagnostic and therapeutic options based on novel non-invasive molecular imaging modalities to ameliorate care of patients with cardiovascular diseases.