Second messenger-mediated adjustment of bacterial swimming velocity.

Bacteria swim by means of rotating flagella that are powered by ion influx through membrane-spanning motor complexes. Escherichia coli and related species harness a chemosensory and signal transduction machinery that governs the direction of flagellar rotation and allows them to navigate in chemical gradients. Here, we show that Escherichia coli can also fine-tune its swimming speed with the help of a molecular brake (YcgR) that, upon binding of the nucleotide second messenger cyclic di-GMP, interacts with the motor protein MotA to curb flagellar motor output. Swimming velocity is controlled by the synergistic action of at least five signaling proteins that adjust the cellular concentration of cyclic di-GMP. Activation of this network and the resulting deceleration coincide with nutrient depletion and might represent an adaptation to starvation. These experiments demonstrate that bacteria can modulate flagellar motor output and thus swimming velocity in response to environmental cues.

Imaging Tumor-Targeting Bacteria Using 18F-Fluorodeoxysorbitol Positron Emission Tomography.

BACKGROUND: Microbial-based cancer treatments are an emerging field, with multiple bacterial species evaluated in animal models and some advancing to clinical trials. Noninvasive bacteria-specific imaging approaches can potentially support the development and clinical translation of bacteria-based cancer treatments by assessing the tumor and off-target bacterial colonization. METHODS: 18F-Fluorodeoxysorbitol (18F-FDS) positron emission tomography (PET), a bacteria-specific imaging approach, was used to visualize an attenuated strain of Yersinia enterocolitica, currently in clinical trials as a microbial-based cancer treatment, in murine models of breast cancer. RESULTS: Y. enterocolitica demonstrated excellent 18F-FDS uptake in in vitro assays. Whole-body 18F-FDS PET demonstrated a significantly higher PET signal in tumors with Y. enterocolitica colonization compared to those not colonized, in murine models utilizing direct intratumor or intravenous administration of bacteria, which were confirmed using ex vivo gamma counting. Conversely, 18F-fluorodeoxyglucose (18F-FDG) PET signal was not different in Y. enterocolitica colonized versus uncolonized tumors. CONCLUSIONS: Given that PET is widely used for the management of cancer patients, 18F-FDS PET could be utilized as a complementary approach supporting the development and clinical translation of Y. enterocolitica-based tumor-targeting bacterial therapeutics.

ALPK1 controls TIFA/TRAF6-dependent innate immunity against heptose-1,7-bisphosphate of gram-negative bacteria.

During infection by invasive bacteria, epithelial cells contribute to innate immunity via the local secretion of inflammatory cytokines. These are directly produced by infected cells or by uninfected bystanders via connexin-dependent cell-cell communication. However, the cellular pathways underlying this process remain largely unknown. Here we perform a genome-wide RNA interference screen and identify TIFA and TRAF6 as central players of Shigella flexneri and Salmonella typhimurium-induced interleukin-8 expression. We show that threonine 9 and the forkhead-associated domain of TIFA are necessary for the oligomerization of TIFA in both infected and bystander cells. Subsequently, this process triggers TRAF6 oligomerization and NF-κB activation. We demonstrate that TIFA/TRAF6-dependent cytokine expression is induced by the bacterial metabolite heptose-1,7-bisphosphate (HBP). In addition, we identify alpha-kinase 1 (ALPK1) as the critical kinase responsible for TIFA oligomerization and IL-8 expression in response to infection with S. flexneri and S. typhimurium but also to Neisseria meningitidis. Altogether, these results clearly show that ALPK1 is a master regulator of innate immunity against both invasive and extracellular gram-negative bacteria.

Cell-cell propagation of NF-κB transcription factor and MAP kinase activation amplifies innate immunity against bacterial infection.

The enteroinvasive bacterium Shigella flexneri uses multiple secreted effector proteins to downregulate interleukin-8 (IL-8) expression in infected epithelial cells. Yet, massive IL-8 secretion is observed in Shigellosis. Here we report a host mechanism of cell-cell communication that circumvents the effector proteins and strongly amplifies IL-8 expression during bacterial infection. By monitoring proinflammatory signals at the single-cell level, we found that the activation of the transcription factor NF-κB and the MAP kinases JNK, ERK, and p38 rapidly propagated from infected to uninfected adjacent cells, leading to IL-8 production by uninfected bystander cells. Bystander IL-8 production was also observed during Listeria monocytogenes and Salmonella typhimurium infection. This response could be triggered by recognition of peptidoglycan and is mediated by gap junctions. Thus, we have identified a mechanism of cell-cell communication that amplifies innate immunity against bacterial infection by rapidly spreading proinflammatory signals via gap junctions to yet uninfected cells.

Systems-level overview of host protein phosphorylation during Shigella flexneri infection revealed by phosphoproteomics.

The enteroinvasive bacterium Shigella flexneri invades the intestinal epithelium of humans. During infection, several injected effector proteins promote bacterial internalization, and interfere with multiple host cell responses. To obtain a systems-level overview of host signaling during infection, we analyzed the global dynamics of protein phosphorylation by liquid chromatography-tandem MS and identified several hundred of proteins undergoing a phosphorylation change during the first hours of infection. Functional bioinformatic analysis revealed that they were mostly related to the cytoskeleton, transcription, signal transduction, and cell cycle. Fuzzy c-means clustering identified six temporal profiles of phosphorylation and a functional module composed of ATM-phosphorylated proteins related to genotoxic stress. Pathway enrichment analysis defined mTOR as the most overrepresented pathway. We showed that mTOR complex 1 and 2 were required for S6 kinase and AKT activation, respectively. Comparison with a published phosphoproteome of Salmonella typhimurium-infected cells revealed a large subset of coregulated phosphoproteins. Finally, we showed that S. flexneri effector OspF affected the phosphorylation of several hundred proteins, thereby demonstrating the wide-reaching impact of a single bacterial effector on the host signaling network.

Simultaneous analysis of large-scale RNAi screens for pathogen entry.

BACKGROUND: Large-scale RNAi screening has become an important technology for identifying genes involved in biological processes of interest. However, the quality of large-scale RNAi screening is often deteriorated by off-targets effects. In order to find statistically significant effector genes for pathogen entry, we systematically analyzed entry pathways in human host cells for eight pathogens using image-based kinome-wide siRNA screens with siRNAs from three vendors. We propose a Parallel Mixed Model (PMM) approach that simultaneously analyzes several non-identical screens performed with the same RNAi libraries. RESULTS: We show that PMM gains statistical power for hit detection due to parallel screening. PMM allows incorporating siRNA weights that can be assigned according to available information on RNAi quality. Moreover, PMM is able to estimate a sharedness score that can be used to focus follow-up efforts on generic or specific gene regulators. By fitting a PMM model to our data, we found several novel hit genes for most of the pathogens studied. CONCLUSIONS: Our results show parallel RNAi screening can improve the results of individual screens. This is currently particularly interesting when large-scale parallel datasets are becoming more and more publicly available. Our comprehensive siRNA dataset provides a public, freely available resource for further statistical and biological analyses in the high-content, high-throughput siRNA screening field.

Tailored Modulation of Cellular Pro-inflammatory Responses With Disaccharide Lipid A Mimetics.

Pro-inflammatory signaling mediated by Toll-like receptor 4 (TLR4)/myeloid differentiation-2 (MD-2) complex plays a crucial role in the instantaneous protection against infectious challenge and largely contributes to recovery from Gram-negative infection. Activation of TLR4 also boosts the adaptive immunity which is implemented in the development of vaccine adjuvants by application of minimally toxic TLR4 activating ligands. The modulation of pro-inflammatory responses via the TLR4 signaling pathway was found beneficial for management of acute and chronic inflammatory disorders including asthma, allergy, arthritis, Alzheimer disease pathology, sepsis, and cancer. The TLR4/MD-2 complex can recognize the terminal motif of Gram-negative bacterial lipopolysaccharide (LPS)-a glycophospholipid lipid A. Although immense progress in understanding the molecular basis of LPS-induced TLR4-mediated signaling has been achieved, gradual, and predictable TLR4 activation by structurally defined ligands has not yet been attained. We report on controllable modulation of cellular pro-inflammatory responses by application of novel synthetic glycolipids-disaccharide-based lipid A mimetics (DLAMs) having picomolar affinity for TLR4/MD-2. Using crystal structure inspired design we have developed endotoxin mimetics where the inherently flexible ß(1 → 6)-linked diglucosamine backbone of lipid A is replaced by a conformationally restricted α,α-(1↔1)-linked disaccharide scaffold. The tertiary structure of the disaccharide skeleton of DLAMs mirrors the 3-dimensional shape of TLR4/MD-2 bound E. coli lipid A. Due to exceptional conformational rigidity of the sugar scaffold, the specific 3D organization of DLAM must be preserved upon interaction with proteins. These structural factors along with specific acylation and phosphorylation pattern can ensure picomolar affinity for TLR4 and permit efficient dimerization of TLR4/MD-2/DLAM complexes. Since the binding pose of lipid A in the binding pocket of MD-2 (±180°) is crucial for the expression of biological activity, the chemical structure of DLAMs was designed to permit a predefined binding orientation in the binding groove of MD-2, which ensured tailored and species-independent (human and mice) TLR4 activation. Manipulating phosphorylation and acylation pattern at the sugar moiety facing the secondary dimerization interface allowed for adjustable modulation of the TLR4-mediated signaling. Tailored modulation of cellular pro-inflammatory responses by distinct modifications of the molecular structure of DLAMs was attained in primary human and mouse immune cells, lung epithelial cells and TLR4 transfected HEK293 cells.

Chemotherapy-induced nausea and vomiting: current and new standards in the antiemetic prophylaxis and treatment.

Nausea and vomiting are considered as two of the most distressing side-effects of chemotherapy. Chemotherapy-induced nausea and vomiting have been classified into acute, delayed and anticipatory based on the time of onset. The frequency of nausea and vomiting depends primarily on the emetogenic potential of the chemotherapeutic agents used. With the introduction of the 5-HT3 receptor-antagonists in combination with dexamethasone in the early 1990s approximately 70% of patients receiving highly emetogenic chemotherapy were protected from acute emesis. However, 40% of patients have symptoms in the delayed phase. Another group of antiemetics, the neurokinin-1-receptor-antagonists, have recently been introduced. The addition of neurokinin receptor (NK1 receptor)-antagonists to standard therapy significantly improves emesis protection in the acute and in particular in the delayed phase by approximately 20%. Due to these new developments, revised antiemetic guidelines have been set. Here, the most recent developments in antiemetic therapy, including these guidelines, are reviewed.

Autologous intracoronary mononuclear bone marrow cell transplantation in chronic ischemic cardiomyopathy in humans.

BACKGROUND: Recent data suggest that transplantation of autologous bone marrow cells (BMC) may contribute to myocardial repair after acute myocardial infarction. We hypothesized that patients with chronic ischemic cardiomyopathy could also benefit from autologous BMC transplantation in addition to established heart failure therapy. METHODS AND RESULTS: Five patients with chronic ischemic cardiomyopathy caused by anterior myocardial infarction, 1.3+/-0.5 years ago and open infarct artery, received autologous mononuclear BMC transplantation via balloon catheter in the target vessel at the site of previous occlusion. Patients were followed up at 3 months (left heart catheterisation, 2D-echocardiography, dobutamine stress echocardiography, cardiopulmonary exercise testing) and at 12 months (2D-echocardiography, cardiopulmonary exercise testing). Follow-up examination showed no significant improvement neither in global, regional, and microvascular function, nor in physical performance. CONCLUSIONS: In this pilot trial intracoronary transplantation of autologous, mononuclear BMC did not lead to any significant improvement in myocardial function and physical performance of patients with chronic ischemic heart disease.

Quantitative analysis of transferrin cycling by automated fluorescence microscopy.

Surface receptors are transported between the plasma membrane and intracellular compartments by various endocytic mechanisms and by recycling via different pathways from sorting or recycling endosomes. The analysis of cellular components involved in mediating or regulating these transport steps is of high current interest and requires quantitative methods to determine rates of endocytosis and/or recycling. Various biochemical procedures to measure uptake of labeled ligand molecules or internalization and reappearance of surface-labeled receptors have been developed. Here, we describe a quantitative method based on fluorescence microscopy of adherent cells taking advantage of the transferrin (Tf) receptor as the prototype of cycling transport receptors. Tf is endocytosed with bound Fe(3+) and, upon release of the iron ion in endosomes, recycled as apo-Tf together with the receptor. To follow the ligand-receptor complex, fluorescently labeled Tf is used and detected microscopically with or without releasing Tf from cell surface receptors by acid stripping. To go beyond the observation of a few individual cells, automated fluorescence microscopy is employed to image thousands of cells at different time points and in parallel with different treatments (such as chemical inhibitors, siRNA silencing, or transfection of candidate genes) in a 96-well format. Computer-assisted image analysis allows unbiased quantitation of Tf content of each cell and to distinguish between different cell populations.

A bacterial type III secretion-based protein delivery tool for broad applications in cell biology.

Methods enabling the delivery of proteins into eukaryotic cells are essential to address protein functions. Here we propose broad applications to cell biology for a protein delivery tool based on bacterial type III secretion (T3S). We show that bacterial, viral, and human proteins, fused to the N-terminal fragment of the Yersinia enterocolitica T3S substrate YopE, are effectively delivered into target cells in a fast and controllable manner via the injectisome of extracellular bacteria. This method enables functional interaction studies by the simultaneous injection of multiple proteins and allows the targeting of proteins to different subcellular locations by use of nanobody-fusion proteins. After delivery, proteins can be freed from the YopE fragment by a T3S-translocated viral protease or fusion to ubiquitin and cleavage by endogenous ubiquitin proteases. Finally, we show that this delivery tool is suitable to inject proteins in living animals and combine it with phosphoproteomics to characterize the systems-level impact of proapoptotic human truncated BID on the cellular network.

Interferon alpha (IFN) treatment of bone marrow stroma inhibits haematopoesis.

Prolonged pre-transplant IFN administration in patients with chronic myeloid leukaemia has been associated with an increased risk of fatal transplant-related complications and an inferior outcome after allogeneic bone marrow transplantation. Using a two-stage long-term bone marrow culture as an in vitro model we were able to show a negative effect of higher doses of IFN pre-treatment of bone marrow stroma on haematopoesis. This correlated with a decline in the number of monocytes-macrophages. While monocytes-macrophages itself produce cytokines, a vicious circle may lead to an ineffective function of the microenvironment resulting in ineffective haematopoieses and increased transplant-related complications.

Increase of interleukin-18 serum levels after engraftment correlates with acute graft-versus-host disease in allogeneic peripheral blood stem cell transplantation.

PURPOSE: Acute graft-versus-host disease (GvHD) is a constant and severe complication after allogeneic stem cell transplantation regularly involving skin, liver, gut, and lungs. The cytokine interleukin-18 (IL-18) has been shown to increase in patients who develop acute GvHD after bone marrow tranplantation (BMT). MATERIALS AND METHODS: Here, we measured IL-18 serum levels after peripheral blood stem cell transplantation (PBSCT) at several characteristic time points in 24 patients (median age 46 years). Patients received a median of 7.3 x 10(6)/kg bodyweight CD34-positive blood stem cells from HLA-matched family donors (n = 5), matched unrelated donors (n = 18), and one mismatched unrelated donor. GvHD prophylaxis consisted of cyclosporin A alone or combined with methotrexate and/or mycophenolate mofetil. RESULTS: In 14 patients we observed no GvHD or only GvHD grade I whereas ten patients developed GvHD grade II-IV post transplant. Low, intermediate, and high levels of serum IL-18 were found in patients after allogeneic PBSCT independently of GvHD after transplantation. In contrast to GvHD arising after BMT, there was no clear correlation between absolute IL-18 serum levels and GvHD grade after PBSCT. However, the individual time course of IL-18 serum level after engraftment correlates with acute GvHD after PBSCT. In detail, an increase of serum IL-18 of at least 1.6-fold after engraftment is associated with acute GvHD II or higher with a sensitivity of three out of four. Using the 1.6 "cut-off" for IL-18 increase after engraftment, a specificity of up to 100% can be achieved. CONCLUSION: The time course of IL-18 serum levels might be used for GvHD prediction after PBSCT comparable to absolute serum levels after BMT.

Double high-dose chemotherapy with adriamycin, paclitaxel, cyclophosphamide, and thiotepa followed by autologous peripheral blood stem cell transplantation in women with metastatic breast cancer.

To determine the feasibility, time to progression, and event-free survival, twenty-two women with metastatic breast cancer received two cycles of high-dose chemotherapy (HDCT) followed by peripheral blood stem cell transplantation (PBSCT) early after first-line induction chemotherapy. The median age of the ten (45.5%) pre- and 12 (54.5%) postmenopausal women was 48 (range: 33-60) years. Sixteen patients (72.7%) had at least two or more metastatic sites involved. Protocol induction and mobilization chemotherapy including granulocyte-colony stimulating-factor (G-CSF) consisted of two cycles with adriamycin (60 mg/m(2)) i.v. and paclitaxel (200 mg/m(2)) i.v. After collection of at least 4 x 10(6)/kg bodyweight peripheral blood stem cells, the first HDCT-course of adriamycin (60 mg/m(2)), paclitaxel (200 mg/m(2)) cyclophosphamide (4 g/m(2)), and thiotepa (800 mg/m(2)) (ATCT) was given to at least stable disease (SD) patients. Six to eight weeks later, the second HDCT-ATCT was administered. Each HDCT-cycle was followed by PBSCT with a median of 3.81 x 10(6)/kg bodyweight CD-34 positive cells (range: 1.85-10.38). All women showed median leukocyte engraftment (>1,000 x 10(9)/l) on day +9.4 (range: 7-13) and median platelet engraftment (>20,000 x 10(9)/l) on day +12.3 (range: 8-15). There were no apparent differences in the clinical course and non-hematologic toxicity between the two HDCT-cycles. Of the 21 patients evaluable for response, eight (38.1%) patients achieved complete remission (CR), ten (47.6%) patients showed a partial remission (PR), two patients (9.5%) no change, and one patient (4.8%) progressive disease. After a median observation time of 36 (range 28-55) months, six (28.6%) women are alive, four (19.0%) of them in continuous CR, including two women with stable bone lesions, respectively, and 15 (71.4%) died due to progressive disease. Median time to progression (TTP) was 8 (range 4-19) months. A high initial response rate of early HDCT, including the most active drugs adriamycin and paclitaxel, can be achieved with tolerable toxicity in metastatic breast cancer. New approaches for maintaining primary tumor response achieved with efficacious high-dose chemotherapy are warranted.

Lack of regeneration of myocardium by autologous intracoronary mononuclear bone marrow cell transplantation in humans with large anterior myocardial infarctions.

BACKGROUND: Experimental and preliminary clinical data suggest that transplantation of autologous bone marrow cells (BMC) may contribute to regeneration of the myocardium after acute myocardial infarction. This approach should be tested in patients with large infarctions in whom a positive effect would be most beneficial. METHODS AND RESULTS: After successful recanalization within 5.9 +/- 2.5 h and stent implantation in five patients with a large acute anterior myocardial infarction (AMI), the patients received autologous mononuclear BMCs via a balloon catheter placed into the left anterior descending artery 6.3 +/- 0.4 days after revascularization. At 3-month follow-up, no improvement was observed for left ventricular ejection fraction, regional wall motion in the infarcted zone, contractility index measured via dobutamine stress echocardiography, coronary blood flow reserve and maximal oxygen uptake, respectively. After further follow-up of 12 months, again no change of the left ventricular ejection fraction could be detected. CONCLUSIONS: Intracoronary transplantation of autologous mononuclear BMCs did not improve cardiac function in our patients with large anterior myocardial infarctions after 3 and 12 months.

Shigella flexneri type III secreted effector OspF reveals new crosstalks of proinflammatory signaling pathways during bacterial infection.

Shigella flexneri type III secreted effector OspF harbors a phosphothreonine lyase activity that irreversibly dephosphorylates MAP kinases (MAPKs) p38 and ERK in infected epithelial cells and thereby, dampens innate immunity. Whereas this activity has been well characterized, the impact of OspF on other host signaling pathways that control inflammation was unknown. Here we report that OspF potentiates the activation of the MAPK JNK and the transcription factor NF-κB during S. flexneri infection. This unexpected effect of OspF was dependent on the phosphothreonine lyase activity of OspF on p38, and resulted from the disruption of a negative feedback loop regulation between p38 and TGF-beta activated kinase 1 (TAK1), mediated via the phosphorylation of TAK1-binding protein 1. Interestingly, potentiated JNK activation was not associated with enhanced c-Jun signaling as OspF also inhibits c-Jun expression at the transcriptional level. Altogether, our data reveal the impact of OspF on the activation of NF-κB, JNK and c-Jun, and demonstrate the existence of a negative feedback loop regulation between p38 and TAK1 during S. flexneri infection. Furthermore, this study validates the use of bacterial effectors as molecular tools to identify the crosstalks that connect important host signaling pathways induced upon bacterial infection.

IKKα contributes to canonical NF-κB activation downstream of Nod1-mediated peptidoglycan recognition.

BACKGROUND: During pathogen infection, innate immunity is initiated via the recognition of microbial products by pattern recognition receptors and the subsequent activation of transcription factors that upregulate proinflammatory genes. By controlling the expression of cytokines, chemokines, anti-bacterial peptides and adhesion molecules, the transcription factor nuclear factor-kappa B (NF-κB) has a central function in this process. In a typical model of NF-κB activation, the recognition of pathogen associated molecules triggers the canonical NF-κB pathway that depends on the phosphorylation of Inhibitor of NF-κB (IκB) by the catalytic subunit IκB kinase ß (IKKß), its degradation and the nuclear translocation of NF-κB dimers. METHODOLOGY: Here, we performed an RNA interference (RNAi) screen on Shigella flexneri-induced NF-κB activation to identify new factors involved in the regulation of NF-κB following infection of epithelial cells by invasive bacteria. By targeting a subset of the human signaling proteome, we found that the catalytic subunit IKKα is also required for complete NF-κB activation during infection. Depletion of IKKα by RNAi strongly reduces the nuclear translocation of NF-κB p65 during S. flexneri infection as well as the expression of the proinflammatory chemokine interleukin-8. Similar to IKKß, IKKα contributes to the phosphorylation of IκBα on serines 32 and 36, and to its degradation. Experiments performed with the synthetic Nod1 ligand L-Ala-D-γ-Glu-meso-diaminopimelic acid confirmed that IKKα is involved in NF-κB activation triggered downstream of Nod1-mediated peptidoglycan recognition. CONCLUSIONS: Taken together, these results demonstrate the unexpected role of IKKα in the canonical NF-κB pathway triggered by peptidoglycan recognition during bacterial infection. In addition, they suggest that IKKα may be an important drug target for the development of treatments that aim at limiting inflammation in bacterial infection.

Gemcitabine, vinorelbine and prednisone for refractory or relapsed aggressive lymphoma, results of a phase II single center study.

The optimum therapy for patients with relapsed or refractory aggressive non-Hodgkin's lymphomas (NHL) not qualifying for platinum-based and/or high-dose chemotherapy is not known. We conducted a prospective phase II study evaluating a regimen consisting of gemcitabine (1 g/m2, days 1 and 8), vinorelbine (30 mg/m2, days 1 and 8) and prednisone (100 mg/day, days 1-8) (GVP) given every 21 days. Fifteen patients with a median age of 68 years and a median of three previous therapies were enrolled. Diagnoses included B lymphoblastic (n=1), diffuse large B cell (n=10), anaplastic large T cell (n=2) and peripheral T-cell NHL (n=2). The median international prognostic index score was 3 (six patients with a score of 4 or 5). Five patients achieved a complete remission and three patients a partial remission. The median overall survival was 13.8 months, and the median time to next treatment was 4.4 months. Haematological toxicities of World Health Organisation grades 3/4 were leucopenia in 58%, thrombocytopenia in 33% and anaemia in 17% of all courses. Three patients had grade 3 infections. There was no treatment-related mortality. GVP shows substantial activity in poor prognosis relapsed or refractory aggressive lymphomas and is generally well tolerated, but haematological toxicity is dose limiting.