Impact of thermogenesis induced by chronic β3-adrenergic receptor agonist treatment on inflammatory and infectious response during bacteremia in mice

White adipocytes store energy differently than brown and brite adipocytes which dissipate energy under the form of heat. Studies have shown that adipocytes are able to respond to bacteria thanks to the presence of Toll-like receptors at their surface. Despite this, little is known about the involvement of each class of adipocytes in the infectious response. We treated mice for one week with a β3-adrenergic receptor agonist to induce activation of brown adipose tissue and brite adipocytes within white adipose tissue. Mice were then injected intraperitoneally with E. coli to generate acute infection. The metabolic, infectious and inflammatory parameters of the mice were analysed during 48 hours after infection. Our results shown that in response to bacteria, thermogenic activity promoted a discrete and local anti-inflammatory environment in white adipose tissue characterized by the increase of the IL-1RA secretion. More generally, activation of brown and brite adipocytes did not modify the host response to infection including no additive effect with fever and an equivalent bacteria clearance and inflammatory response. In conclusion, these results suggest an IL-1RA-mediated immunomodulatory activity of thermogenic adipocytes in response to acute bacterial infection and open a way to characterize their effect along more chronic infection as septicaemia.

Escherichia coli Rho GTPase-activating toxin CNF1 mediates NLRP3 inflammasome activation via p21-activated kinases-1/2 during bacteraemia in mice

Inflammasomes are signalling platforms that are assembled in response to infection or sterile inflammation by cytosolic pattern recognition receptors. The consequent inflammasome-triggered caspase-1 activation is critical for the host defence against pathogens. During infection, NLRP3, which is a pattern recognition receptor that is also known as cryopyrin, triggers the assembly of the inflammasome-activating caspase-1 through the recruitment of ASC and Nek7. The activation of the NLRP3 inflammasome is tightly controlled both transcriptionally and post-translationally. Despite the importance of the NLRP3 inflammasome regulation in autoinflammatory and infectious diseases, little is known about the mechanism controlling the activation of NLRP3 and the upstream signalling that regulates the NLRP3 inflammasome assembly. We have previously shown that the Rho-GTPase-activating toxin from Escherichia coli cytotoxic necrotizing factor-1 (CNF1) activates caspase-1, but the upstream mechanism is unclear. Here, we provide evidence of the role of the NLRP3 inflammasome in sensing the activity of bacterial toxins and virulence factors that activate host Rho GTPases. We demonstrate that this activation relies on the monitoring of the toxin's activity on the Rho GTPase Rac2. We also show that the NLRP3 inflammasome is activated by a signalling cascade that involves the p21-activated kinases 1 and 2 (Pak1/2) and the Pak1-mediated phosphorylation of Thr 659 of NLRP3, which is necessary for the NLRP3-Nek7 interaction, inflammasome activation and IL-1β cytokine maturation. Furthermore, inhibition of the Pak-NLRP3 axis decreases the bacterial clearance of CNF1-expressing UTI89 E. coli during bacteraemia in mice. Taken together, our results establish that Pak1 and Pak2 are critical regulators of the NLRP3 inflammasome and reveal the role of the Pak-NLRP3 signalling axis in vivo during bacteraemia in mice.

Modulation of the inflammatory response to LPS by the recruitment and activation of brown and brite adipocytes in mice

Numerous studies have shown that the recruitment and activation of thermogenic adipocytes, which are brown and beige/brite, reduce the mass of adipose tissue and normalize abnormal glycemia and lipidemia. However, the impact of these adipocytes on the inflammatory state of adipose tissue is still not well understood, especially in response to endotoxemia, which is a major aspect of obesity and metabolic diseases. First, we analyzed the phenotype and metabolic function of white and brite primary adipocytes in response to lipopolysaccharide (LPS) treatment in vitro. Then, 8-wk-old male BALB/c mice were treated for 1 wk with a β3-adrenergic receptor agonist (CL316,243, 1 mg/kg/day) to induce recruitment and activation of brown and brite adipocytes and were subsequently injected with LPS (Escherichia coli lipopolysaccharide, 100 μg/mouse ip) to generate acute endotoxemia. The metabolic and inflammatory parameters of the mice were analyzed 6 h later. Our results showed that in response to LPS, thermogenic activity promoted a local anti-inflammatory environment with high secretion of IL-1 receptor antagonist (IL-1RA) without affecting other anti- or proinflammatory cytokines. Interestingly, activation of brite adipocytes reduced the LPS-induced secretion of leptin. However, thermogenic activity and adipocyte function were not altered by LPS treatment in vitro or by acute endotoxemia in vivo. In conclusion, these results suggest an IL-1RA-mediated immunomodulatory activity of thermogenic adipocytes specifically in response to endotoxemia. This encourages potential therapy involving brown and brite adipocytes for the treatment of obesity and associated metabolic diseases.NEW & NOTEWORTHY Recruitment and activation of brown and brite adipocytes in the adipose tissue of mice lead to a local low-grade anti-inflammatory phenotype in response to acute endotoxemia without alteration of adipocyte phenotype and function.

Diet Supplementation in ω3 Polyunsaturated Fatty Acid Favors an Anti-Inflammatory Basal Environment in Mouse Adipose Tissue

Oxylipins are metabolized from dietary ω3 and ω6 polyunsaturated fatty acids and are involved in an inflammatory response. Adipose tissue inflammatory background is a key factor of metabolic disorders and it is accepted that dietary fatty acids, in terms of quality and quantity, modulate oxylipin synthesis in this tissue. Moreover, it has been reported that diet supplementation in ω3 polyunsaturated fatty acids resolves some inflammatory situations. Thus, it is crucial to assess the influence of dietary polyunsaturated fatty acids on oxylipin synthesis and their impact on adipose tissue inflammation. To this end, mice fed an ω6- or ω3-enriched standard diet (ω6/ω3 ratio of 30 and 3.75, respectively) were analyzed for inflammatory phenotype and adipose tissue oxylipin content. Diet enrichment with an ω3 polyunsaturated fatty acid induced an increase in the oxylipins derived from ω6 linoleic acid, ω3 eicosapentaenoic, and ω3 docosahexaenoic acids in brown and white adipose tissues. Among these, the level of pro-resolving mediator intermediates, as well as anti-inflammatory metabolites, were augmented. Concomitantly, expressions of M2 macrophage markers were increased without affecting inflammatory cytokine contents. In vitro, these metabolites did not activate macrophages but participated in macrophage polarization by inflammatory stimuli. In conclusion, we demonstrated that an ω3-enriched diet, in non-obesogenic non-inflammatory conditions, induced synthesis of oxylipins which were involved in an anti-inflammatory response as well as enhancement of the M2 macrophage molecular signature, without affecting inflammatory cytokine secretion.

Immunoadjuvant Properties of the Rho Activating Factor CNF1 in Prophylactic and Curative Vaccination against Leishmania infantum

There is a need to develop new effective immunoadjuvants for prophylactic or therapeutic vaccines against intracellular pathogens. The activation of Rho GTPases by bacterial cytotoxic necrotizing factor 1 (CNF1) elicits humoral protective responses against protein antigens. Here, we set out to investigate whether CNF1 activity initiates humoral immunity against co-administered parasite antigens and anti-microbial immune signaling. We report that co-administration of wild-type (WT) CNF1 with Leishmania (L.) promastigote antigens at the nasal mucosa triggered prophylactic and curative vaccine responses against this parasite. Vaccination of the mucosa with promastigote lysate antigens combined with WT CNF1 conferred protection against high inoculum L. infantum infection, which reached 82% in the spleen. Immune parameter analysis by antigen recall indicated robust T-helper (Th)1 polarization of immune memory cells, with high IL-2 and IFN-γ production combined with decreased IL-4 production. Additionally, we explored the curative effect of WT CNF1 on previously infected animals. We observed that PL combined with WT CNF1, but not the inactive C866S mutant CNF1 (mCNF1), induced a 58% decrease in the parasite burden in the spleen.

The Saccharomyces boulardii CNCM I-745 strain shows protective effects against the B. anthracis LT toxin

The probiotic yeast Saccharomyces boulardii (S. boulardii) has been prescribed for the prophylaxis and treatment of several infectious diarrheal diseases. Gastrointestinal anthrax causes fatal systemic disease. In the present study, we investigated the protective effects conferred by Saccharomyces boulardii CNCM I-745 strain on polarized T84 columnar epithelial cells intoxicated by the lethal toxin (LT) of Bacillus anthracis. Exposure of polarized T84 cells to LT affected cell monolayer integrity, modified the morphology of tight junctions and induced the formation of actin stress fibers. Overnight treatment of cells with S. boulardii before incubation with LT maintained the integrity of the monolayers, prevented morphological modification of tight junctions, restricted the effects of LT on actin remodeling and delayed LT-induced MEK-2 cleavage. Mechanistically, we demonstrated that in the presence of S. boulardii, the medium is depleted of both LF and PA sub-units of LT and the appearance of a cleaved form of PA. Our study highlights the potential of the S. boulardii CNCM I-745 strain as a prophylactic agent against the gastrointestinal form of anthrax.

Escherichia coli α-hemolysin counteracts the anti-virulence innate immune response triggered by the Rho GTPase activating toxin CNF1 during bacteremia

The detection of the activities of pathogen-encoded virulence factors by the innate immune system has emerged as a new paradigm of pathogen recognition. Much remains to be determined with regard to the molecular and cellular components contributing to this defense mechanism in mammals and importance during infection. Here, we reveal the central role of the IL-1β signaling axis and Gr1+ cells in controlling the Escherichia coli burden in the blood in response to the sensing of the Rho GTPase-activating toxin CNF1. Consistently, this innate immune response is abrogated in caspase-1/11-impaired mice or following the treatment of infected mice with an IL-1β antagonist. In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway. Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells. Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.

The pathogenic potentials of most microbes depend on a repertoire of virulence factors. Despite major progress in the understanding of the molecular mechanisms underlying the activities of bacterial effectors, little is known about how they cooperate during infection to overcome host immune defenses and promote microbial persistence. Here, we investigated the roles of two uropathogenic Escherichia coli (UPEC) effectors that are co-ordinately expressed, α-hemolysin (HlyA) and cytotoxic necrotizing factor 1 (CNF1). We demonstrated that the HlyA toxin is critical for bacterial stability in the blood and showed that one important role of HlyA is to inhibit the CNF1-induced host response. Collectively, these findings reveal why the coordinated activities of HlyA and CNF1 are necessary for the full virulence of UPEC. Moreover, they unravel a HlyA-driven counter-defense mechanism used by bacteria to facilitate their survival.

Cherubism allele heterozygosity amplifies microbe-induced inflammatory responses in murine macrophages

Cherubism is a rare autoinflammatory bone disorder that is associated with point mutations in the SH3-domain binding protein 2 (SH3BP2) gene, which encodes the adapter protein 3BP2. Individuals with cherubism present with symmetrical fibro-osseous lesions of the jaw, which are attributed to exacerbated osteoclast activation and defective osteoblast differentiation. Although it is a dominant trait in humans, cherubism appears to be recessively transmitted in mice, suggesting the existence of additional factors in the pathogenesis of cherubism. Here, we report that macrophages from 3BP2-deficient mice exhibited dramatically reduced inflammatory responses to microbial challenge and reduced phagocytosis. 3BP2 was necessary for LPS-induced activation of signaling pathways involved in macrophage function, including SRC, VAV1, p38MAPK, IKKα/β, RAC, and actin polymerization pathways. Conversely, we demonstrated that the presence of a single Sh3bp2 cherubic allele and pathogen-associated molecular pattern (PAMP) stimulation had a strong cooperative effect on macrophage activation and inflammatory responses in mice. Together, the results from our study in murine genetic models support the notion that infection may represent a driver event in the etiology of cherubism in humans and suggest limiting inflammation in affected individuals may reduce manifestation of cherubic lesions.

Saccharomyces boulardii modifies Salmonella typhimurium traffic and host immune responses along the intestinal tract

Salmonella enterica serovar Typhimurium (ST) is an enteropathogenic Gram-negative bacterium that causes infection following oral ingestion. ST spreads rapidly along the gastrointestinal tract (GIT) and invades the intestinal epithelium to ultimately reach internal body organs. The probiotic yeast Saccharomyces boulardii BIOCODEX (S.b-B) is prescribed for prophylaxis of diarrheal infectious diseases. We previously showed that S.b-B prevents weight loss in ST-infected mice and significantly decreases bacterial translocation to the spleen and liver. This study was designed to investigate the effect of S.b-B on ST migration along the GIT and the impact of the yeast on the host's early innate immune responses. Bioluminescent imaging (BLI) was used to evaluate the effect of S.b-B on the progression of luminescent Salmonella Typhimurium (ST-lux) in the GIT of mice pretreated with streptomycin. Photonic emission (PE) was measured in GIT extracts (stomach, small intestine, cecum and colon) at various time periods post-infection (PI). PE analysis revealed that, 45 min PI, ST-lux had migrated slightly faster in the mice treated with S.b-B than in the untreated infected animals. At 90 min PI, ST-lux had reached the cecum in both groups of mice. Adhesion of ST to S.b-B was visualized in the intestines of the mice and probably accounts for (1) the faster elimination of ST-lux in the feces, and (2) reduced translocation of ST to the spleen and liver. In the early phase of infection, S.b-B also modifies the host's immune responses by (1) increasing IFN-γ gene expression and decreasing IL-10 gene expression in the small intestine, and (2) elevating both IFN-γ, and IL-10 mRNA levels in the cecum. BLI revealed that S.b-B modifies ST migration and the host immune response along the GIT. Study findings shed new light on the protective mechanisms of S.b-B during the early phase of Salmonella pathogenesis.

SU-E-J-39: Minimizing IGRT Imaging Exposures: KV Radiograph Vs. KV-CBCT Vs. MV Portal Images

PURPOSE

To compare the IGRT doses from MV, kV and CBCT images.

METHODS

kV imaging systems integrated into Varian Trilogy and TrueBeam accelerators were modeled using BEAMnrc/DOSXYZnrc Monte Carlo codes and the dose to calibration phantoms for a variety of kV beams(kVp, bow-tie filters, etc.) were calculated. The doses to the same phantoms and kV beams were then measured experimentally using calibrated ion-chambers.The "calibrated" Monte Carlo kV beams were used to calculate dose to CT images of patients. Organ doses were analyzed using DVHs.

RESULTS

The doses to the prostate are 0.015 and 2.2cGy using AP kV and MV images; are 0.06 and 2.3cGy using lateral kV and MV images; and, are 1.7 cGy using CBCT images. For head and neck images, the doses to the eye are 0.08 and 0.001 cGy using AP and PA kV images; are 2.3 and 1.8cGy using AP and PA MV images; are 0.001 and 2.4cGy for lateral kV and MV images; and, are 0.2 cGy for CBCT images. For kV radiographs, organ doses can be further reduced, by over 30%, by using bow-tie filters. CBCT doses to the prostate are 1.6 and 0.9cGy for OBI and TrueBeam pelvis scans; a >40% dose reduction for the same image quality. For OBI CBCT head scans the doses to the eye and brain stem are 0.2 and 2.8cGy, respectively.

CONCLUSIONS

Due to the low penetration of kV beams,selecting beam angles so that the sensitive organs are near the beam exit, and/or using bow-tie filters, can substantially reduce organ doses when using kV radiographs. For daily positioning of pediatric brain patient with a set of orthogonal kV images, a CBCT scan, or a set of orthogonal MV images, the doses to the eyes are 0.1, 0.2, and 4.7 cGy, respectively.

cAMP signaling by anthrax edema toxin induces transendothelial cell tunnels, which are resealed by MIM via Arp2/3-driven actin polymerization

RhoA-inhibitory bacterial toxins, such as Staphylococcus aureus EDIN toxin, induce large transendothelial cell macroaperture (TEM) tunnels that rupture the host endothelium barrier and promote bacterial dissemination. Host cells repair these tunnels by extending actin-rich membrane waves from the TEM edges. We reveal that cyclic-AMP signaling produced by Bacillus anthracis edema toxin (ET) also induces TEM formation, which correlates with increased vascular permeability. We show that ET-induced TEM formation resembles liquid dewetting, a physical process of nucleation and growth of holes within a thin liquid film. We also identify the cellular mechanisms of tunnel closure and reveal that the I-BAR domain protein Missing in Metastasis (MIM) senses de novo membrane curvature generated by the TEM, accumulates at the TEM edge, and triggers Arp2/3-dependent actin polymerization, which induces actin-rich membrane waves that close the TEM. Thus, the balance between ET-induced TEM formation and resealing likely determines the integrity of the host endothelium barrier.

Modification of Salmonella Typhimurium motility by the probiotic yeast strain Saccharomyces boulardii

Background

Motility is an important component of Salmonella enterica serovar Typhimurium (ST) pathogenesis allowing the bacteria to move into appropriate niches, across the mucus layer and invade the intestinal epithelium. In vitro, flagellum-associated motility is closely related to the invasive properties of ST. The probiotic yeast Saccharomyces boulardii BIOCODEX (S.b-B) is widely prescribed for the prophylaxis and treatment of diarrheal diseases caused by bacteria or antibiotics. In case of Salmonella infection, S.b-B has been shown to decrease ST invasion of T84 colon cell line. The present study was designed to investigate the impact of S.b-B on ST motility.

Methodology/Principal Findings

Experiments were performed on human colonic T84 cells infected by the Salmonella strain 1344 alone or in the presence of S.b-B. The motility of Salmonella was recorded by time-lapse video microscopy. Next, a manual tracking was performed to analyze bacteria dynamics (MTrackJ plugin, NIH image J software). This revealed that the speed of bacterial movement was modified in the presence of S.b-B. The median curvilinear velocity (CLV) of Salmonella incubated alone with T84 decreased from 43.3 µm/sec to 31.2 µm/sec in the presence of S.b-B. Measurement of track linearity (TL) showed similar trends: S.b-B decreased by 15% the number of bacteria with linear tract (LT) and increased by 22% the number of bacteria with rotator tract (RT). Correlation between ST motility and invasion was further established by studying a non-motile flagella-deficient ST strain. Indeed this strain that moved with a CLV of 0.5 µm/sec, presented a majority of RT and a significant decrease in invasion properties. Importantly, we show that S.b-B modified the motility of the pathogenic strain SL1344 and significantly decreased invasion of T84 cells by this strain.

Conclusions

This study reveals that S.b-B modifies Salmonella's motility and trajectory which may account for the modification of Salmonella's invasion.

Luciferase-expressing Leishmania infantum allows the monitoring of amastigote population size, in vivo, ex vivo and in vitro

Here we engineered transgenic Leishmania infantum that express luciferase, the objectives being to more easily monitor in real time their establishment either in BALB/c mice—the liver and spleen being mainly studied—or in vitro. Whatever stationary phase L. infantum promastigotes population—wild type or engineered to express luciferase—the parasite burden was similar in the liver and the spleen at day 30 post the intravenous inoculation of BALB/c mice. Imaging of L. infantum hosting BALB/C mice provided sensitivity in the range of 20,000 to 40,000 amastigotes/mg tissue, two tissues—liver and spleen—being monitored. Once sampled and processed ex vivo for their luciferin-dependent bioluminescence the threshold sensitivity was shown to range from 1,000 to 6,000 amastigotes/mg tissue. This model further proved to be valuable for in vivo measurement of the efficiency of drugs such as miltefosine and may, therefore, additionally be used to evaluate vaccine-induced protection.

Leishmania infantum/L. chagasi parasites are inoculated in the skin of mammals by sand flies. Though most often these L. infantum-mammal interactions are asymptomatic, they can proceed, in some individuals, to a systemic disease known as visceral leishmaniasis. If left untreated this disease is fatal. The lack of protective or curative vaccines and the limited number of parasite-targeting drugs were incentive to set up experimental conditions that could allow easy monitoring of the fluctuation of the population size of parasites in living laboratory animals. Thus, in the present report, we depict two distinct readout assays that rely on a population of L. infantum we genetically engineered for stably expressing the firefly luciferase gene. These transgenic parasites were either inoculated to BALB/c mice or added to a culture of monocytic cells. Post intravenous inoculation, BALB/c mice were imaged over time, with special attention being given to the liver and the spleen. The sensitivity of this technique ranged from 20,000 to 40,000 parasites/mg of tissue and from 1,000 to 6,000 parasites/mg tissue, for in vivo and ex vivo measurements, respectively. Though preliminary, the data, relying on monocytic cells, are promising for further in vitro screening of small compound libraries.

High prevalence of edin-C encoding RhoA-targeting toxin in clinical isolates of Staphylococcus aureus

Staphylococcus aureus, a major causative agent of human infection, produces a large array of virulence factors, including various toxins. Among them, the host RhoA GTPase ADP-ribosylating EDIN toxins are considered as potential virulence factors. Using the polymerase chain reaction (PCR) assay, we analyzed the virulence profile of 256 S. aureus isolates from various clinical sites of infections. We developed specific primers to detect the three isoforms of edin-encoding genes. We found a prevalence of 14% (36 bacteria) of edin-encoding genes among these clinical isolates. Strikingly, we found that 90% of all edin-bearing S. aureus isolates carried the type-C allele. Both the spa types and the profile of virulence factors of these edin-positive isolates are highly variable. Notably, we show for the first time that edin-C-positive isolates were more frequently recovered from deep-seated infections than other types of infections. Our present work, thus, strongly suggests that the presence of edin-C is a risk factor of S. aureus dissemination in tissues and, thus, represents a predictive marker for a pejorative evolution of staphylococcal infections.

Short term improvement in exercise capacity and symptoms following exercise training in interstitial lung disease

Background:

Interstitial lung disease (ILD) is characterised by exertional dyspnoea, exercise limitation and reduced quality of life. The role of exercise training in this diverse patient group is unclear. The aims of this study were to establish the safety of exercise training in ILD; its effects on exercise capacity, dyspnoea and quality of life; and whether patients with idiopathic pulmonary fibrosis (IPF) had similar responses to those with other types of ILD.

Methods:

57 subjects with ILD (34 IPF) were randomised to receive 8 weeks of supervised exercise training or weekly telephone support. The 6 min walk distance (6MWD), incremental exercise test, modified Medical Research Council (MRC) dyspnoea score and Chronic Respiratory Disease Questionnaire (CRDQ) were performed at baseline, following intervention and at 6 months.

Results:

80% of subjects completed the exercise programme and no adverse events were recorded. The 6MWD increased following training (mean difference to control 35 m, 95% CI 6 to 64 m). A significant reduction in MRC score was observed (0.7 points, 95% CI 0.1 to 1.3) along with improvements in dyspnoea (p = 0.04) and fatigue (p<0.01) on the CRDQ. There was no change in peak oxygen uptake; however, exercise training reduced heart rate at maximum isoworkload (p = 0.01). There were no significant differences in response between those with and without IPF. After 6 months there were no differences between the training and control group for any outcome variable.

Conclusions:

Exercise training improves exercise capacity and symptoms in patients with ILD, but these benefits are not sustained 6 months following intervention.

Trial registration number:

NCT00168285

Specificity of immunomodulator secretion in urinary samples in response to infection by alpha-hemolysin and CNF1 bearing uropathogenic Escherichia coli

Escherichia coli are the most common etiological agents of urinary tract infections (UTIs). Uropathogenic E. coli (UPECs) produce specific toxins including the cytotoxic necrotizing factor-1 (CNF1) and the alpha-hemolysin (alpha-Hly). CNF1 triggers, through Rho protein activation, a specific gene response of host cells, which results in the production for instance of interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and the macrophage inflammatory protein-3alpha (MIP-3alpha). The alpha hemolysin alpha-Hly also triggers the production of inflammatory mediators. Cnf1 is always associated with alpha-hly in a pathogenicity island conserved among UPECs. Using two complementary approaches we have investigated whether alpha-hly and cnf1 bearing UPECs are associated with a specific type of UTI both in term of pathology and host response. Here we report that UPECs bearing alpha-hly/cnf1 have a prevalence of 50% in UPECs isolated from hemorrhagic UTIs, as compared to 30% in the overall UPEC population. In addition, we observed that MCP-1, and IL-8 to a lower extent, is produced in urine at higher concentrations in UTIs caused by UPECs carrying alpha-hly/cnf1.

Bacteria and the ubiquitin pathway

Ubiquitylation participates in a repertoire of reversible post-translational modifications that modulate the function, localization and half-life of proteins by regulating their association with various ubiquitin-binding proteins. In response to pathogen infection, bacterial effectors impact ubiquitin and ubiquitin-like modifications of key proteins in immune and anti-apoptotic signaling cascades. Certain bacteria corrupt the ubiquitylation machinery in order to regulate their virulence factors spatially and temporally or to trigger internalization of bacteria into host cells. Several new examples of how bacterial factors target ubiquitin and ubiquitin-like regulation emphasize the importance of modulating ubiquitin signaling to establish either long-lasting or devastating relationships of bacteria with their hosts.

Induction of transient macroapertures in endothelial cells through RhoA inhibition by Staphylococcus aureus factors

The GTPase RhoA is a major regulator of the assembly of actin stress fibers and the contractility of the actomyosin cytoskeleton. The epidermal cell differentiation inhibitor (EDIN) and EDIN-like ADP-ribosyltransferases of Staphylococcus aureus catalyze the inactivation of RhoA, producing actin cable disruption. We report that purified recombinant EDIN and EDIN-producing S. aureus provoke large transcellular tunnels in endothelial cells that we have named macroapertures (MAs). These structures open transiently, followed by the appearance of actin-containing membrane waves extending over the aperture. Disruption of actin cables, either directly or indirectly, through rhoA RNAi knockdown also triggers the formation of MAs. Intoxication of endothelial monolayers by EDIN produces a loss of barrier function and provides direct access of the endothelium basement membrane to S. aureus.

Bacterial toxins activating Rho GTPases

The CNF1 toxin is produced by some uropathogenic (UPECs) andmeningitis-causing Escherichia coli strains. It belongs to a large family of bacterial virulence factors and toxins modifying cellular regulators of the actin cytoskeleton, namely the Rho GTPases. CNF1 autonomously enters the host cell cytosol, where it catalyzes the constitutive activation of Rho GTPases by deamidation. This activation is, however, attenuated because of activated Rho protein ubiquitin-mediated proteasomal degradation. Both Rho protein activation and deactivation confer phagocytic properties on epithelial and endothelial cells, as well as epithelial cell motility and cell-cell junction dynamics. Transcriptome analysis using DNA microarray revealed that endothelial cells respond to high doses of CNF1 by launching a genetic program of host alarm. This host cell reaction to CNF1 intoxication also indicates that degradation of activated Rho proteins by the proteasome may lead to a lowering of the threshold of the intoxicated cell inflammatory response. These results are consistent with growing evidence that Rho proteins control the cell inflammatory responses. It is tempting to assume that Rho deregulation may participate in various immunological disorders also involved in cancer.

The Rho GTPase activators CNF1 and DNT bacterial toxins have mucosal adjuvant properties

Cytotoxic necrotizing factor 1 (CNF1) from uropathogenic Escherichia coli belongs to a family of factors activating Rho GTPases. We report the in vivo effects of CNF1 in mice co-fed toxin and the soluble protein antigen ovalbumin (OVA). Similar to cholera toxin, CNF1 elicits adjuvanticity anti-OVA responses, both systemic and mucosal. In contrast, the catalytic inactive mutant CNF1-C866S demonstrated no effects. Using dermonecrotic toxin (DNT), a closely related Rho activating toxin from Bordetella, we discovered that the adjuvant property is within the DNT catalytic domain. Manipulation of Rho proteins thus provides a possible new approach for the development of effective mucosal immunoadjuvants.

Emulsion strategies in the microencapsulation of cells: Pathways to thin coherent membranes

Microencapsulation of cell spheroids in an immunoselective, highly biocompatible, biomembrane offers a way to create viable implantation options in the treatment of insulin-dependent diabetes mellitus (IDDM). Traditionally the encapsulation process has been achieved through the injection/extrusion of alginate/cell mixtures into a calcium chloride solution to produce calcium alginate capsules around the cells. A novel alternative is explored here through a procedure using an emulsion process to produce thin adherent calcium alginate membranes around cell spheroids. In this study, a thorough investigation has been used to establish the emulsion process parameters that are critical to the formation of a coherent alginate coat both on a model spheroid system and subsequently on cell spheroids. Optical and fluorescence microscopy are used to assess the morphology and coherence of the calcium alginate/poly-L-ornithine/alginate (APA) capsules produced.

Activation and Proteasomal Degradation of Rho GTPases by Cytotoxic Necrotizing Factor-1 Elicit a Controlled Inflammatory Response

The CNF1 toxin is produced by uropathogenic and meningitis-causing Escherichia coli. CNF1 penetrates autonomously into cells and confers phagocytic properties to epithelial and endothelial cells. CNF1 acts at the molecular level by constitutively activating Rho GTPases attenuated by their cellular ubiquitin-mediated proteasomal degradation. Here we report the relationship between the ubiquitin-mediated proteasomal degradation of activated Rho and the endothelial cell response to the toxin. The type of cellular response to CNF1 intoxication, first screened by DNA microarray analysis, revealed the launching of a program oriented toward an inflammatory response. Parallel to Rho protein activation by CNF1, we also established the kinetics of production of monocyte chemotactic protein-1 (MCP-1), interleukin-8 (IL-8), IL-6, monocyte inflammatory protein-3alpha (MIP-3alpha) and E-selectin. Both the mutation of the catalytic domain of the toxin (CNF1-C866S) and the inhibition of Rho proteins abrogate the CNF1-induced production of the immunomodulators MIP-3alpha, MCP-1, and IL-8. These immunomodulators are also produced upon activation of Cdc42 and Rac preferentially. Our results indicate that, in addition to pathogen molecular pattern recognition by host-receptors, a direct activation of Rho proteins by the CNF1 virulence factor efficiently triggers a cellular reaction of host alert. Consistently, we assume that the CNF1-induced ubiquitin-mediated proteasomal degradation of activated Rho proteins may limit the amplitude of the host cell immune responses.

The use of Gauss-Laguerre vector beams in STED microscopy

This paper examines the use of Gauss-Laguerre beams in STED microscopy. These types of beams are shown to have beneficial properties that can be utilised to generate stable, high quality STED beams resulting in an aberration-resilient generation volume. In this paper we obtain general expressions for Gauss-Laguerre beams being focused through a stratified medium and describe their optimization for STED microscopy purposes. Our results show that the circularly polarised, lowest order "dark" beam is the most beneficial for STED purposes.

Cylindrical vector beam focusing through a dielectric interface: comment

Errors in the results and conclusions presented in the paper "Cylindrical vector beam focusing through a dielectric interface" by Biss and Brown (Opt. Express 9, 490-497 (2001)) are discussed.

Monte Carlo simulation of the image formation process in portal imaging

We have written Monte Carlo programs to simulate the formation of radiological images. Our code is used to propagate a simulated x-ray fluence through each component of an existing video-based portal imaging system. This simulated fluence consists of a 512 x 512 pixel image containing both contrast-detail patterns as well as checker patterns to assess spatial resolution of the simulated portal imager. All of the components of the portal imaging system were modeled as a cascade of eight linear stages. Using this code, one can assess the visual impact of changing components in the imaging chain by changing the appropriate probability density function. Virtual experiments were performed to assess the visual impact of replacing the lens and TV camera by an amorphous silicon array, and the effect of scattered radiation on portal images.