Inflammasome activation by Pseudomonas aeruginosa's ExlA pore-forming toxin is detrimental for the host.

During acute Pseudomonas aeruginosa infection, the inflammatory response is essential for bacterial clearance. Neutrophil recruitment can be initiated following the assembly of an inflammasome within sentinel macrophages, leading to activation of caspase-1, which in turn triggers macrophage pyroptosis and IL-1ß/IL-18 maturation. Inflammasome formation can be induced by a number of bacterial determinants, including Type III secretion systems (T3SSs) or pore-forming toxins, or, alternatively, by lipopolysaccharide (LPS) via caspase-11 activation. Surprisingly, previous studies indicated that a T3SS-induced inflammasome increased pathogenicity in mouse models of P. aeruginosa infection. Here, we investigated the immune reaction of mice infected with a T3SS-negative P. aeruginosa strain (IHMA879472). Virulence of this strain relies on ExlA, a secreted pore-forming toxin. IHMA879472 promoted massive neutrophil infiltration in infected lungs, owing to efficient priming of toll-like receptors, and thus enhanced the expression of inflammatory proteins including pro-IL-1ß and TNF-α. However, mature-IL-1ß and IL-18 were undetectable in wild-type mice, suggesting that ExlA failed to effectively activate caspase-1. Nevertheless, caspase-1/11 deficiency improved survival following infection with IHMA879472, as previously described for T3SS+ bacteria. We conclude that the detrimental effect associated with the ExlA-induced inflammasome is probably not due to hyperinflammation, rather it stems from another inflammasome-dependent process.

The introduction of a standardised national licensing exam as a driver of change in medical education: A qualitative study from Switzerland.

INTRODUCTION: Only a few studies have described the impacts, strengths and needs for further development of national licensing exams (NLE). To gain such insights regarding the Swiss NLE, which includes a multiple-choice and a standardised clinical skills exam, we explored the perceptions of involved experts and stakeholders. METHODS: We explored participants' perceptions in four focus group discussions. The interviews were recorded, transcribed verbatim and qualitatively analysed using a thematic analysis approach. RESULTS: The analysis resulted in five perceived impacts, two strengths and two needs for further developments of the NLE. Perceived impacts were (1) steering students' learning behaviour, (2) supporting teachers and assessors to align teaching to competencies, (3) elevating the importance of the Swiss Catalogue of Learning Objectives, (4) setting incentives for the further development of curricula, and (5) fostering the collaboration between the faculties of medicine. Perceived strengths were the blend of assessment formats, including their competency-based orientation, and the collaborative development approach. Perceived needs lay in the NLE's further development to sustain its fit for purpose and in incentives for people involved. CONCLUSION: According to our study, this NLE had, and has, notable impacts on medical education in Switzerland. Our insights can be useful for others planning a similar undertaking.

[Issues and challenges related to COVID-19 in acute geriatric care: lessons learned from the Geneva experience]. / Enjeux et défis du Covid-19 en gériatrie aiguë: leçons tirées de l'expérience genevoise.

The older patients have been the most affected by the SARS-CoV-2 pandemic. In addition, this infection has been responsible for high mortality rate in this population. In this article we wanted to describe the clinical findings we encountered in older people with COVID-19 and share some of the issues and challenges we faced during the COVID-19 pandemic.

Les personnes âgées ont été les plus touchées par la pandémie de SARS-CoV-2. De plus, cette infection a été responsable d'une mortalité élevée au sein de cette population. Dans cet article, nous avons souhaité décrire les particularités cliniques du Covid-19 que nous avons constatées chez les patients âgés et faire part de plusieurs enjeux et défis auxquels nous avons été confrontés au cours de la pandémie de Covid-19.

Pseudomonas aeruginosa ExlA and Serratia marcescens ShlA trigger cadherin cleavage by promoting calcium influx and ADAM10 activation.

Pore-forming toxins are potent virulence factors secreted by a large array of bacteria. Here, we deciphered the action of ExlA from Pseudomonas aeruginosa and ShlA from Serratia marcescens on host cell-cell junctions. ExlA and ShlA are two members of a unique family of pore-forming toxins secreted by a two-component secretion system. Bacteria secreting either toxin induced an ExlA- or ShlA-dependent rapid cleavage of E-cadherin and VE-cadherin in epithelial and endothelial cells, respectively. Cadherin proteolysis was executed by ADAM10, a host cell transmembrane metalloprotease. ADAM10 activation is controlled in the host cell by cytosolic Ca2+ concentration. We show that Ca2+ influx, induced by ExlA or ShlA pore formation in the plasma membrane, triggered ADAM10 activation, thereby leading to cadherin cleavage. Our data suggest that ADAM10 is not a cellular receptor for ExlA and ShlA, further confirming that ADAM10 activation occurred via Ca2+ signalling. In conclusion, ExlA- and ShlA-secreting bacteria subvert a regulation mechanism of ADAM10 to activate cadherin shedding, inducing intercellular junction rupture, cell rounding and loss of tissue barrier integrity.

Neuromuscular dysfunction, independent of gait dysfunction, modulates trabecular bone homeostasis in mice.

OBJECTIVES: To clarify the effects of neuromuscular dysfunction on hindlimb loading, muscle atrophy, and bone homeostasis. METHODS: We quantified changes to hindlimb loading, muscle atrophy, and bone morphology following either Botulinum toxin A (BTxA) induced muscle paralysis or peripheral nerve injury (PNI) in mice; two in vivo models that we anticipated would differently alter gait and mechanical loading patterns due to their distinct effects on neuromuscular signaling. To confirm the expected behavioral effects of PNI, we assessed mechanical allodynia of the ipsilateral hindlimb using von Frey testing and activity (distance traveled and speed) was monitored in both groups using open field testing. Peak vertical ground reaction forces (GRF) and ankle and knee kinematics during normal locomotion were quantified and used to estimate peak mid-diaphyseal normal strains. Muscle atrophy and trabecular and cortical bone morphology were assessed via high-resolution microCT imaging. RESULTS: BTxA-induced calf paralysis caused severe muscle atrophy and altered gait kinetics and kinematics and reduced gait-induced normal strains. PNI increased mechanical allodynia but did not alter gait, nor did it cause muscle atrophy. We observed that muscle paralysis and PNI both led to severe trabecular bone loss but only BTxA-induced paralysis increased cortical bone resorption. CONCLUSIONS: While mechanical stimuli clearly have essential functions in bone development and adaptation, these data emphasize that neuromuscular signaling, independent of load-induced mechanical strains, may modulate trabecular bone homeostasis in normal and disease states.

Pseudomonas aeruginosa Transmigrates at Epithelial Cell-Cell Junctions, Exploiting Sites of Cell Division and Senescent Cell Extrusion.

To achieve systemic infection, bacterial pathogens must overcome the critical and challenging step of transmigration across epithelial barriers. This is particularly true for opportunistic pathogens such as Pseudomonas aeruginosa, an agent which causes nosocomial infections. Despite extensive study, details on the mechanisms used by this bacterium to transmigrate across epithelial tissues, as well as the entry sites it uses, remain speculative. Here, using real-time microscopy and a model epithelial barrier, we show that P. aeruginosa employs a paracellular transmigration route, taking advantage of altered cell-cell junctions at sites of cell division or when senescent cells are expelled from the cell layer. Once a bacterium transmigrates, it is followed by a cohort of bacteria using the same entry point. The basal compartment is then invaded radially from the initial penetration site. Effective transmigration and propagation require type 4 pili, the type 3 secretion system (T3SS) and a flagellum, although flagellum-deficient bacteria can occasionally invade the basal compartment from wounded areas. In the basal compartment, the bacteria inject the T3SS toxins into host cells, disrupting the cytoskeleton and focal contacts to allow their progression under the cells. Thus, P. aeruginosa exploits intrinsic host cell processes to breach the epithelium and invade the subcellular compartment.

Phenotype and toxicity of the recently discovered exlA-positive Pseudomonas aeruginosa strains collected worldwide.

We recently identified a hypervirulent strain of Pseudomonas aeruginosa, differing significantly from the classical strains in that it lacks the type 3 secretion system (T3SS), a major determinant of P. aeruginosa virulence. This new strain secretes a novel toxin, called ExlA, which induces plasma membrane rupture in host cells. For this study, we collected 18 other exlA-positive T3SS-negative strains, analyzed their main virulence factors and tested their toxicity in various models. Phylogenetic analysis revealed two groups. The strains were isolated on five continents from patients with various pathologies or in the environment. Their proteolytic activity and their motion abilities were highly different, as well as their capacity to infect epithelial, endothelial, fibroblastic and immune cells, which correlated directly with ExlA secretion levels. In contrast, their toxicity towards human erythrocytes was limited. Some strains were hypervirulent in a mouse pneumonia model and others on chicory leaves. We conclude that (i) exlA-positive strains can colonize different habitats and may induce various infection types, (ii) the strains secreting significant amounts of ExlA are cytotoxic for most cell types but are poorly hemolytic, (iii) toxicity in planta does not correlate with ExlA secretion.

VE-cadherin cleavage by LasB protease from Pseudomonas aeruginosa facilitates type III secretion system toxicity in endothelial cells.

Infection of the vascular system by Pseudomonas aeruginosa (Pa) occurs during bacterial dissemination in the body or in blood-borne infections. Type 3 secretion system (T3SS) toxins from Pa induce a massive retraction when injected into endothelial cells. Here, we addressed the role of type 2 secretion system (T2SS) effectors in this process. Mutants with an inactive T2SS were much less effective than wild-type strains at inducing cell retraction. Furthermore, secretomes from wild-types were sufficient to trigger cell-cell junction opening when applied to cells, while T2SS-inactivated mutants had minimal activity. Intoxication was associated with decreased levels of vascular endothelial (VE)-cadherin, a homophilic adhesive protein located at endothelial cell-cell junctions. During the process, the protein was cleaved in the middle of its extracellular domain (positions 335 and 349). VE-cadherin attrition was T3SS-independent but T2SS-dependent. Interestingly, the epithelial (E)-cadherin was unaffected by T2SS effectors, indicating that this mechanism is specific to endothelial cells. We showed that one of the T2SS effectors, the protease LasB, directly affected VE-cadherin proteolysis, hence promoting cell-cell junction disruption. Furthermore, mouse infection with Pa to induce acute pneumonia lead to significant decreases in lung VE-cadherin levels, whereas the decrease was minimal with T2SS-inactivated or LasB-deleted mutant strains. We conclude that the T2SS plays a pivotal role during Pa infection of the vascular system by breaching the endothelial barrier, and propose a model in which the T2SS and the T3SS cooperate to intoxicate endothelial cells.

The end of medical confidentiality? Patients, physicians and the state in history.

Medical confidentiality has come under attack in the public sphere. In recent disasters both journalists and politicians have questioned medical confidentiality and claimed that in specific contexts physicians should be compelled to communicate data on their patients' health. The murders of innocent individuals by a suicidal pilot and a Swiss convicted criminal have generated polemical debates on the topic. In this article, historical data on medical confidentiality is used to show that medical practices of secrecy were regularly attacked in the past, and that the nature of medical confidentiality evolved through time depending on physicians' values and judgements. Our demonstration is based on three moments in history. First, at the end of the 16th century, lay authorities put pressure on physicians to disclose the names of patients suffering from syphilis. Second, in the 18th century, physicians faced constant demands for information about patients' health from relatives and friends. Third, employers and insurance companies in the 20th century requested medical data on sick employees. In these three different situations, history reveals that the concept of medical confidentiality was plastic, modelled in the first instance to defend well-to-do patients, in the second instance it was adapted to accommodate the physician's social role and, finally, to defend universal values and public health. Medical secrecy was, and is today, a medical and societal norm that is shaped collectively. Any change in its definition and enforcement was and should be the result of negotiations with all social actors concerned.

Pharmacological activation of Rap1 antagonizes the endothelial barrier disruption induced by exotoxins ExoS and ExoT of Pseudomonas aeruginosa.

Most clinical strains of Pseudomonas aeruginosa, a leading agent of nosocomial infections, are multiresistant to antibiotherapy. Because of the paucity of new available antibiotics, the investigation of strategies aimed at limiting the action of its major virulence factors has gained much interest. The type 3 secretion system of P. aeruginosa and its effectors are known to be major determinants of toxicity and are required for bacterial dissemination in the host. Bacterial transmigration across the vascular wall is considered to be an important step in the infectious process. Using human endothelial primary cells, we demonstrate that forskolin (FSK), a drug inducing cyclic AMP (cAMP) elevation in eukaryotic cells, strikingly reduced the cell retraction provoked by two type 3 toxins, ExoS and ExoT, found in the majority of clinical strains. Conversely, cytotoxicity of a strain carrying the type 3 effector ExoU was unaffected by FSK. In addition, FSK altered the capacity of two ExoS/ExoT strains to transmigrate across cell monolayers. In agreement with these findings, other drugs and a cytokine inducing the increase of cAMP intracellular levels have also protected cells from retraction. cAMP is an activator of both protein kinase A and EPAC, a GTPase exchange factor of Rap1. Using activators or inhibitors of either pathway, we show that the beneficial effect of FSK is exerted by the activation of the EPAC/Rap1 axis, suggesting that its protective effect is mediated by reinforcing cell-cell and cell-substrate adhesion.

ExsB is required for correct assembly of the Pseudomonas aeruginosa type III secretion apparatus in the bacterial membrane and full virulence in vivo.

Pseudomonas aeruginosa is responsible for high-morbidity infections of cystic fibrosis patients and is a major agent of nosocomial infections. One of its most potent virulence factors is a type III secretion system (T3SS) that injects toxins directly into the host cell cytoplasm. ExsB, a lipoprotein localized in the bacterial outer membrane, is one of the components of this machinery, of which the function remained elusive until now. The localization of the exsB gene within the exsCEBA regulatory gene operon suggested an implication in the T3SS regulation, while its similarity with yscW from Yersinia spp. argued in favor of a role in machinery assembly. The present work shows that ExsB is necessary for full in vivo virulence of P. aeruginosa. Furthermore, the requirement of ExsB for optimal T3SS assembly and activity is demonstrated using eukaryotic cell infection and in vitro assays. In particular, ExsB promotes the assembly of the T3SS secretin in the bacterial outer membrane, highlighting the molecular role of ExsB as a pilotin. This involvement in the regulation of the T3S apparatus assembly may explain the localization of the ExsB-encoding gene within the regulatory gene operon.

Dynamic phosphorylation of VE-cadherin Y685 throughout mouse estrous cycle in ovary and uterus.

We previously reported that vascular endothelial growth factor induced vascular endothelial (VE)-cadherin tyrosine phosphorylation at Y685 in a Src-dependent manner in vitro. Here, we studied the occurrence of Y685 phosphorylation in vivo in the female reproductive tract because it is a unique model of physiological vascular remodeling dependent on vascular endothelial growth factor. We first developed and characterized an anti-phospho-specific antibody against the site Y685 of VE-cadherin to monitor VE-cadherin phosphorylation along the four phases of mouse estrous cycle, termed proestrus, estrus, metestrus, and diestrus. A dynamic profile of tyrosine phosphorylated proteins was observed in both uterus and ovary throughout mouse estrous cycle, including kinase Src, which was found highly active at the estrus phase. The extent of tyrosine phosphorylated VE-cadherin was low at proestrus but strongly increased at estrus and returned to baseline at metestrus and diestrus, suggesting a potent hormonal regulation of this specific process. Indeed, C57Bl/6 female mice treatment with pregnant mare serum gonadotropin and human chorionic gonadotropin confirmed a significant increase in phosphoY685-VE-cadherin compared with that in untreated mice. These results demonstrate that VE-cadherin tyrosine phosphorylation at Y685 is a physiological and hormonally regulated process in female reproductive organs. In addition, this process was concomitant with the early steps of vascular remodeling taking place at estrus stage, suggesting that phosphoY685-VE-cadherin is a biomarker of endothelial cell activation in vivo.

VE-cadherin Y685F knock-in mouse is sensitive to vascular permeability in recurrent angiogenic organs.

Covalent modifications such as tyrosine phosphorylation are associated with the breakdown of endothelial cell junctions and increased vascular permeability. We previously showed that vascular endothelial (VE)-cadherin was tyrosine phosphorylated in vivo in the mouse reproductive tract and that Y685 was a target site for Src in response to vascular endothelial growth factor in vitro. In the present study, we aimed to understand the implication of VE-cadherin phosphorylation at site Y685 in cyclic angiogenic organs. To achieve this aim, we generated a knock-in mouse carrying a tyrosine-to-phenylalanine point mutation of VE-cadherin Y685 (VE-Y685F). Although homozygous VE-Y685F mice were viable and fertile, the nulliparous knock-in female mice exhibited enlarged uteri with edema. This phenotype was observed in 30% of females between 4 to 14 mo old. Histological examination of longitudinal sections of the VE-Y685F uterus showed an extensive disorganization of myometrium and endometrium with highly edematous uterine glands, numerous areas with sparse cells, and increased accumulation of collagen fibers around blood vessels, indicating a fibrotic state. Analysis of cross section of ovaries showed the appearance of spontaneous cysts, which suggested increased vascular hyperpermeability. Electron microscopy analysis of capillaries in the ovary showed a slight but significant increase in the gap size between two adjacent endothelial cell membranes in the junctions of VE-Y685F mice (wild-type, 11.5 ± 0.3, n = 78; and VE-Y685F, 12.48 ± 0.3, n = 65; P = 0.045), as well as collagen fiber accumulation around capillaries. Miles assay revealed that either basal or vascular endothelial growth factor-stimulated permeability in the skin was increased in VE-Y685F mice. Since edema and fibrotic appearance have been identified as hallmarks of initial increased vascular permeability, we conclude that the site Y685 in VE-cadherin is involved in the physiological regulation of capillary permeability. Furthermore, this knock-in mouse model is of potential interest for further studies of diseases that are associated with abnormal vascular permeability.

Structural basis of cytotoxicity mediated by the type III secretion toxin ExoU from Pseudomonas aeruginosa.

The type III secretion system (T3SS) is a complex macromolecular machinery employed by a number of Gram-negative pathogens to inject effectors directly into the cytoplasm of eukaryotic cells. ExoU from the opportunistic pathogen Pseudomonas aeruginosa is one of the most aggressive toxins injected by a T3SS, leading to rapid cell necrosis. Here we report the crystal structure of ExoU in complex with its chaperone, SpcU. ExoU folds into membrane-binding, bridging, and phospholipase domains. SpcU maintains the N-terminus of ExoU in an unfolded state, required for secretion. The phospholipase domain carries an embedded catalytic site whose position within ExoU does not permit direct interaction with the bilayer, which suggests that ExoU must undergo a conformational rearrangement in order to access lipids within the target membrane. The bridging domain connects catalytic domain and membrane-binding domains, the latter of which displays specificity to PI(4,5)P2. Both transfection experiments and infection of eukaryotic cells with ExoU-secreting bacteria show that ExoU ubiquitination results in its co-localization with endosomal markers. This could reflect an attempt of the infected cell to target ExoU for degradation in order to protect itself from its aggressive cytotoxic action.

Epithelial protein lost in neoplasm (EPLIN) interacts with α-catenin and actin filaments in endothelial cells and stabilizes vascular capillary network in vitro.

Adherens junctions are required for vascular endothelium integrity. These structures are formed by the clustering of the homophilic adhesive protein VE-cadherin, which recruits intracellular partners, such as ß- and α-catenins, vinculin, and actin filaments. The dogma according to which α-catenin bridges cadherin·ß-catenin complexes to the actin cytoskeleton has been challenged during the past few years, and the link between the VE-cadherin·catenin complex and the actin cytoskeleton remains unclear. Recently, epithelial protein lost in neoplasm (EPLIN) has been proposed as a possible bond between the E-cadherin·catenin complex and actin in epithelial cells. Herein, we show that EPLIN is expressed at similar levels in endothelial and epithelial cells and is located at interendothelial junctions in confluent cells. Co-immunoprecipitation and GST pulldown experiments provided evidence that EPLIN interacts directly with α-catenin and tethers the VE-cadherin·catenin complex to the actin cytoskeleton. In the absence of EPLIN, vinculin was delocalized from the junctions. Furthermore, suppression of actomyosin tension using blebbistatin triggered a similar vinculin delocalization from the junctions. In a Matrigel assay, EPLIN-depleted endothelial cells exhibited a reduced capacity to form pseudocapillary networks because of numerous breakage events. In conclusion, we propose a model in which EPLIN establishes a link between the cadherin·catenin complex and actin that is independent of actomyosin tension. This link acts as a mechanotransmitter, allowing vinculin binding to α-catenin and formation of a secondary molecular bond between the adherens complex and the cytoskeleton through vinculin. In addition, we provide evidence that the EPLIN clutch is necessary for stabilization of capillary structures in an angiogenesis model.

A microCT-based platform to quantify drug targeting.

BACKGROUND: Heterotopic ossification (HO) is a frequent and debilitating complication of traumatic musculoskeletal injuries and orthopedic procedures. Prophylactic dosing of botulinum toxin type A (BTxA) holds potential as a novel treatment option if accurately distributed throughout soft-tissue volumes where protection is clinically desired. We developed a high-resolution, microcomputed tomography (microCT)-based imaging strategy to assess drug distribution and validated this platform by quantifying distribution achieved via a prototype delivery system versus a single-bolus injection. METHODS: We injected an iodine-containing contrast agent (iodixanol 320 mg I/mL) into dissected rabbit musculature followed by microCT imaging and analysis. To contrast the performance of distributed versus bolus injections, a three-dimensional (3D) 64-cm3-printed soft-tissue holder was developed. A centered 2-cm3 volume of interest (VOI) was targeted with a single-bolus injection or an equal volume distributed injection delivered via a 3D-printed prototype. VOI drug coverage was quantified as a percentage of the VOI volume that was < 1.0 mm from the injected fluid. RESULTS: The microCT-based approach enabled high-resolution quantification of injection distribution within soft tissue. The distributed dosing prototype provided significantly greater tissue coverage of the targeted VOI (72 ± 3%, mean ± standard deviation) when compared to an equal volume bolus dose (43 ± 5%, p = 0.031) while also enhancing the precision of injection targeting. CONCLUSIONS: A microCT-based imaging technique precisely quantifies drug distribution within a soft-tissue VOI, providing a path to overcome a barrier for clinical translation of prophylactic inhibition of HO by BTxA. RELEVANCE STATEMENT: This platform will facilitate rapid optimization of injection parameters for clinical devices used to effectively and safely inhibit the formation of heterotopic ossification. KEY POINTS: • MicroCT provides high-resolution quantification of soft-tissue drug distribution. • Distributed dosing is required to maximize soft-tissue drug coverage. • Imaging platform will enable rapid screening of 3D-printed drug distribution prototypes.

Protocadherin-12 cleavage is a regulated process mediated by ADAM10 protein: evidence of shedding up-regulation in pre-eclampsia.

Protocadherins are a group of transmembrane proteins with homophilic binding activity, members of the cadherin superfamily. Apart from their role in adhesion, the cellular functions of protocadherins are essentially unknown. Protocadherin (PCDH)12 was previously identified in invasive trophoblasts and endothelial and mesangial cells in the mouse. Invalidation studies revealed that the protein was required for optimal placental development. In this article, we show that its human homolog is abundantly expressed in various trophoblast subtypes of the human placenta and at lower levels in endothelial cells. We demonstrate that PCDH12 is shed at high rates in vitro. The shedding mechanism depends on ADAM10 and results in reduced cellular adhesion in a cell migration assay. PCDH12 is subsequently cleaved by the γ-secretase complex, and its cytoplasmic domain is rapidly degraded by the proteasome. PCDH12 shedding is regulated by interlinked intracellular pathways, including those involving protein kinase C, PI3K, and cAMP, that either increase or inhibit cleavage. In endothelial cells, VEGF, prostaglandin E(2), or histamine regulates PCDH12 shedding. The extracellular domain of PCDH12 was also detected in human serum and urine, thus providing evidence of PCDH12 shedding in vivo. Importantly, we observed an increase in circulating PCDH12 in pregnant women who later developed a pre-eclampsia, a frequent pregnancy syndrome and a major cause of maternal and fetal morbidity and mortality. In conclusion, we speculate that, like in mice, PCDH12 may play an important role in human placental development and that proteolytic cleavage in response to external factors, such as cytokines and pathological settings, regulates its activity.

Fibrillin-1 genetic deficiency leads to pathological ageing of arteries in mice.

Fibrillin-1, the major component of extracellular microfibrils that associate with insoluble elastin in elastic fibres, is mainly synthesized during development and postnatal growth and is believed to guide elastogenesis. Mutations in the fibrillin-1 gene cause Marfan syndrome, a multisystem disorder characterized by aortic aneurysms and dissections. The recent finding that early deficiency of elastin modifies vascular ageing has raised the possibility that fibrillin-1 deficiency could also contribute to late-onset pathology of vascular remodelling. To address this question, we examined cardiovascular function in 3-week-old, 6-month-old, and 24-month-old mice that are heterozygous for a hypomorphic structural mutation of fibrillin-1 (Fbn1{+/mgΔ} mice). Our results indicate that Fbn1{+/mgΔ} mice, particularly those that are 24 months old, are slightly more hypotensive than wild-type littermates. Additionally, aneurysm and aortic insufficiency were more frequently observed in ageing Fbn1{+/mgΔ}$ mice than in the wild-type counterparts. We also noted substantial fragmentation and decreased number of elastic lamellae in the aortic wall of Fbn1{+/mgΔ} mice, which were correlated with an increase in aortic stiffness, a decrease in vasoreactivity, altered expression of elastic fibre-related genes, including fibrillin-1 and elastin, and a decrease in the relative ratio between tissue elastin and collagen. Collectively, our findings suggest that the heterozygous mgΔ mutation accelerates some aspects of vascular ageing and eventually leads to aortic manifestations resembling those of Marfan syndrome. Importantly, our data also indicate that vascular abnormalities in Fbn1{+/mgΔ} mice are opposite to those induced by elastin haploinsufficiency during ageing that affect blood pressure, vascular dimensions, and number of elastic lamellae.

[Teaching skills of functional assessment to medical students: why not playing games?]. / Apprentissage de l'evaluation fonctionnelle par les etudiants en médecine: et si on simulait?

Today, physicians take care of an aging population suffering from multiple chronic diseases and disabilities. Therefore, a good knowledge of functional assessment is required, and this topic should be addressed in the undergraduate medical curriculum. This article reports our experience with a seminar on functional assessment using an "aging game" as a pedagogic vector. This seminar is organized by geriatricians, occupational therapists and physical therapists. Medical students are exposed to situations where they experiment disabilities and try to elaborate compensatory strategies. Then, they reflect on a complex discharge project by analyzing a written clinical case. Finally, they are introduced to the use of validated functional assessment instruments. Evaluation indicated that this pedagogic approach is highly valued by students and fosters the acquisition of knowledge in functional assessment.

ExlA: A New Contributor to Pseudomonas aeruginosa Virulence.

ExlA (also called exolysin) is a recently discovered virulence factor secreted by a subset of Pseudomonas aeruginosa strains in which a type 3 secretion system is lacking. exlA-positive strains were identified worldwide in the clinic, causing several types of infectious diseases, and were detected in various locations in the environment. ExlA possesses pore-forming activity and is cytolytic for most human cell types. It belongs to a class of poorly characterized bacterial toxins, sharing a similar protein domain organization and a common secretion pathway. This review summarizes the recent findings regarding ExlA synthesis, its secretion pathway, and its toxic behavior for host cells.