Littérature scientifique sur le sujet « Lungs Pathophysiology »

Respiratory distress in newborn and young infants often develops as a result of acute lung injury, in which disruption of the normal barrier function of the pulmonary endothelium and epithelium causes protein-rich interstitial and alveolar edema. Several conditions may initiate acute lung injury, including aspiration of meconium or gastric contents, bacterial or viral infection, overzealous resuscitation, and birth associated with incomplete lung development that requires ventilatory support with positivepressure mechanical ventilation and high concentrations of inspired oxygen. The latter condition usually occurs after premature birth, but it also may occur as a consequence of impaired fetal lung growth secondary to diaphragmatic hernia or chest compression from lack of liquid in the amniotic cavity. Acute lung injury sometimes progresses to a chronic form of lung disease, which is characterized by edema, fibrosis, airway distortion, and nonuniform inflation of the lungs.

Disrupted daily or circadian rhythms of lung function and inflammatory responses are common features of chronic airway diseases. At the molecular level these circadian rhythms depend on the activity of an autoregulatory feedback loop oscillator of clock gene transcription factors, including the BMAL1:CLOCK activator complex and the repressors PERIOD and CRYPTOCHROME. The key nuclear receptors and transcription factors REV-ERBα and RORα regulate Bmal1 expression and provide stability to the oscillator. Circadian clock dysfunction is implicated in both immune and inflammatory responses to environmental, inflammatory, and infectious agents. Molecular clock function is altered by exposomes, tobacco smoke, lipopolysaccharide, hyperoxia, allergens, bleomycin, as well as bacterial and viral infections. The deacetylase Sirtuin 1 (SIRT1) regulates the timing of the clock through acetylation of BMAL1 and PER2 and controls the clock-dependent functions, which can also be affected by environmental stressors. Environmental agents and redox modulation may alter the levels of REV-ERBα and RORα in lung tissue in association with a heightened DNA damage response, cellular senescence, and inflammation. A reciprocal relationship exists between the molecular clock and immune/inflammatory responses in the lungs. Molecular clock function in lung cells may be used as a biomarker of disease severity and exacerbations or for assessing the efficacy of chronotherapy for disease management. Here, we provide a comprehensive overview of clock-controlled cellular and molecular functions in the lungs and highlight the repercussions of clock disruption on the pathophysiology of chronic airway diseases and their exacerbations. Furthermore, we highlight the potential for the molecular clock as a novel chronopharmacological target for the management of lung pathophysiology.

The process of brain death (BD) detrimentally affects donor lung quality. Ex vivo lung perfusion (EVLP) is a technique originally designed to evaluate marginal donor lungs. Nowadays, its potential as a treatment platform to repair damaged donor lungs is increasingly studied in experimental models. Rat models for EVLP have been described in literature before, yet the pathophysiology of BD was not included in these protocols and prolonged perfusion over 3 hours without anti-inflammatory additives was not achieved. We aimed to establish a model for prolonged EVLP of rat lungs from brain-dead donors, to provide a reliable platform for future experimental studies. Rat lungs were randomly assigned to one of four experimental groups (n = 7/group): 1) healthy, directly procured lungs, 2) lungs procured from rats subjected to 3 hours of BD and 1 hour cold storage (CS), 3) healthy, directly procured lungs subjected to 6 hours EVLP and 4), lungs procured from rats subjected to 3 hours of BD, 1 hour CS and 6 hours EVLP. Lungs from brain-dead rats showed deteriorated ventilation parameters and augmented lung damage when compared to healthy controls, in accordance with the pathophysiology of BD. Subsequent ex vivo perfusion for 6 hours was achieved, both for lungs of healthy donor rats as for pre-injured donor lungs from brain-dead rats. The worsened quality of lungs from brain-dead donors was evident during EVLP as well, as corroborated by deteriorated ventilation performance, increased lactate production and augmented inflammatory status during EVLP. In conclusion, we established a stable model for prolonged EVLP of pre-injured lungs from brain-dead donor rats. In this report we describe tips and pitfalls in the establishment of the rat EVLP model, to enhance reproducibility by other researchers.

AbstractLung transplantation (LTx) has traditionally been limited by a lack of suitable donor lungs. With the recognition that lungs are more robust than initially thought, the size of the donor pool of available lungs has increased dramatically in the past decade. Donation after brain death (DBD) and donation after circulatory death (DCD) lungs, both ideal and extended are now routinely utilized. DBD lungs can be damaged. There are important differences in the public's understanding, legal and consent processes, intensive care unit strategies, lung pathophysiology, logistics, and potential-to-actual donor conversion rates between DBD and DCD. Notwithstanding, the short- and long-term outcomes of LTx from any of these DBD versus DCD donor scenarios are now similar, robust, and continue to improve. Large audits suggest there remains a large untapped pool of DCD (but not DBD) lungs that may yet further dramatically increase lung transplant numbers. Donor scoring systems that might predict the donor conversion rates and lung quality, the role of ex vivo lung perfusion as an assessment and lung resuscitation tool, as well as the potential of donor lung quality biomarkers all have immense promise for the clinical field.

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory disorder which has been first reported in 2001 by Hamano and colleagues in a patient with autoimmune sclerosing pancreatitis. Almost every organ in the human body can be affected by IgG4-RD from infiltration with IgG4-positive plasma cells. Involvement of lungs with IgG4 is reported previously, but still, there is no clear picture of the pathophysiology behind lung involvement. Here, we are presenting a patient who has IgG4-RD presenting as pseudotumor of the lungs.

Tobacco smoking has been established to contribute to the pathogenesis of various respiratory diseases including chronic obstructive pulmonary disease (COPD), lung cancer, and asthma. However, major hurdles in mechanistic studies on the role of smoking in human lungs remain in part due to the lack of ex vivo experimental models and ambiguous data from animal models that can best recapitulate the architecture and pathophysiology of the human lung. Recent development of the lung organoid culture system has opened new avenues for respiratory disease research as organoids are proving to be a sophisticated ex vivo model that functionally and structurally mimics the human lungs better than other traditionally used models. This review will discuss how recent advances in lung organoid systems may help us better determine the injurious and immunological effect of smoking on human lungs and will provide some suggestions for future research directions.

Pulmonary arterial (PA) wall modifications are key pathological features of pulmonary hypertension (PH). Although such abnormalities correlate with heightened phosphorylation of c-Jun N-terminal kinases 1/2 (JNK1/2) in a rat model of PH, the contribution of specific JNK isoforms to the pathophysiology of PH is unknown. Hence, we hypothesized that activation of either one, or both JNK isoforms regulates PA remodeling in PH. We detected increased JNK1/2 phosphorylation in the thickened vessels of PH patients’ lungs compared to that in lungs of healthy individuals. JNK1/2 phosphorylation paralleled a marked reduction in MAP kinase phosphatase 1 (JNK dephosphorylator) expression in patients’ lungs. Association of JNK1/2 activation with vascular modification was confirmed in the calf model of severe hypoxia-induced PH. To ascertain the role of each JNK isoform in pathophysiology of PH, wild-type (WT), JNK1 null (JNK1-/-), and JNK2 null (JNK2-/-) mice were exposed to chronic hypoxia (10% O2 for six weeks) to develop PH. In hypoxic WT lungs, an increase in JNK1/2 phosphorylation was associated with PH-like pathology. Hallmarks of PH pathophysiology, i.e. excessive accumulation of extracellular matrix and vessel muscularization with medial wall thickening, was also detected in hypoxic JNK1-/- lungs, but not in hypoxia-exposed JNK2-/- lungs. However, hypoxia-induced increases in right ventricular systolic pressure (RVSP) and in right ventricular hypertrophy (RVH) were similar in all three genotypes. Our findings suggest that JNK2 participates in PA remodeling (but likely not in vasoconstriction) in murine hypoxic PH and that modulating JNK2 actions might quell vascular abnormalities and limit the course of PH.

Background: Respiratory Syncytial Virus (RSV) is the major cause of severe acute respiratory tract illness in young children worldwide and a main pathogen for the elderly and immune-compromised people. In the absence of vaccines or effective treatments, a better characterization of the pathogenesis of RSV infection is required. To date, the pathophysiology of the disease and its diagnosis has mostly relied on chest X-ray and genome detection in nasopharyngeal swabs. The development of new imaging approaches is instrumental to further the description of RSV spread, virus–host interactions and related acute respiratory disease, at the level of the entire lung. Methods: By combining tissue clearing, 3D microscopy and image processing, we developed a novel visualization tool of RSV infection in undissected mouse lungs. Results: Whole tissue analysis allowed the identification of infected cell subtypes, based on both morphological traits and position within the cellular network. Furthermore, 3D imaging was also valuable to detect the cytoplasmic viral factories, also called inclusion bodies, a hallmark of RSV infection. Conclusions: Whole lung clearing and 3D deep imaging represents an unprecedented visualization method of infected lungs to allow insight into RSV pathophysiology and improve the 2D histology analyses.

Efforts to decipher chronic lung disease and to reconstitute functional lung tissue through regenerative medicine have been hampered by an incomplete understanding of cell-cell interactions governing tissue homeostasis. Because the structure of mammalian lungs is highly conserved at the histologic level, we hypothesized that there are evolutionarily conserved homeostatic mechanisms that keep the fine architecture of the lung in balance. We have leveraged single-cell RNA sequencing techniques to identify conserved patterns of cell-cell cross-talk in adult mammalian lungs, analyzing mouse, rat, pig, and human pulmonary tissues. Specific stereotyped functional roles for each cell type in the distal lung are observed, with alveolar type I cells having a major role in the regulation of tissue homeostasis. This paper provides a systems-level portrait of signaling between alveolar cell populations. These methods may be applicable to other organs, providing a roadmap for identifying key pathways governing pathophysiology and informing regenerative efforts.

OBJECTIVES/GOALS: Asymmetries in lung pathophysiology can result in a maldistribution of gas between regions of the lungs which may generate dangerous pressures that are not observable by clinicians. Our study aims to demonstrate and quantify this through use of high-fidelity simulators to represent a range of commonly encountered clinical pathologies. METHODS/STUDY POPULATION: A benchtop study was performed with two high-fidelity breathing simulators, each representing one lung. This system allows for real-time monitoring of pressure and lung dynamics in a two-lung asymmetric injury model. One simulator was set to a fixed compliance and a resistance. A second simulator had a range of compliance and resistance values. Data were collected for 15 different test cases across a distribution of asymmetries. Each test case is run for 30 cycles. At the end of each ventilatory cycle, a short expiratory hold is performed, allowing pressure in the lung simulator, tubing, and ventilator circuit to equilibrate between cycles. RESULTS/ANTICIPATED RESULTS: Maldistribution of tidal volume was demonstrated when the compliance ratio between lung models (CL1/CL2) was 0.2 and the resistance ratio (RL1/RL2) was 10 with 23.9% (99% CI: 23.9-24.0%) of the gas volume distributed to lung 1 (103 mL L1 vs 327 mL in L2). Additionally, the injured lung when compared with the normal lung experienced higher peak pressures (12.8 cm H2O vs. 6.9 cm H2O, L1 and L2 respectively) and higher compartmentalized plateau pressures (11.5 cm H2O vs. 6.8 cm H2O, L1 and L2 respectively). DISCUSSION/SIGNIFICANCE: We demonstrate significant maldistribution of volume and pressures between two lungs in an asymmetric injury model. This study suggests significant impact of asymmetry in current lung-protective mechanical ventilation strategies and calls for better understanding of case-specific pathophysiologic changes affecting each of the two lungs.

Bibliography: leaves 168-184. The work in this study encompasses oxygen free radical related inflammation in the peripheral lung and in lung cells. Animal and human studies have been used. Methods include cell culture with function studies, protein chemistry, animal and human physiology, and cell and lung structure through histopathology, and various forms of electron microscopy. The work resulting from this thesis has formed an important basis for understanding acute and chronic lung injury.

The cardiopulmonary effects of endotoxin administration (1 microgram/kg) were evaluated in 8-10 week old SPF-derived Yorkshire pigs, both because endotoxemia is a common and important swine problem, and because the pig is a good model for human adult respiratory distress syndrome. Physiological changes included sustained increases in mean pulmonary artery pressure, pulmonary vascular resistance, pulmonary arterial wedge pressure, heart rate, hematocrit, and the arterial partial pressure of carbon dioxide. Transient increases were also observed in central venous pressure and airway pressure. Transient increases, followed by decreases, were observed in mean systemic arterial pressures and systemic vascular resistance. Decreases were seen in cardiac output, cardiac index, arterial partial pressure of oxygen and oxygen saturation. The number of circulating leukocytes, lymphocytes and segmented neutrophils decreased with endotoxin infusion. To investigate the role of airway smooth muscle, bronchial rings were isolated and exposed to contractile agents in tissue baths. A hyperresponsiveness of the third generation bronchi to substance P, carbachol, bradykinin and electric field stimulation was observed. However the increase in response to bradykinin and electric field stimulation were not statistically significant. Histopathology of the lungs demonstrated congestion, hemorrhage and neutrophilic infiltration.
Master of Science

Le travail présenté ici porte sur l’étude de la production et du transport du monoxyde d’azote (NO) dans le poumon humain. Le NO est une molécule dont l’implication dans des processus physiologiques n’a été mis en évidence qu’en 1987. Depuis, il a été démontré que le NO joue de nombreux rôles dans le corps humain. Le NO est un gaz labile (instable) dans les conditions physiologiques, il diffuse très facilement au travers des parois et il a une grande affinité pour l’hémoglobine. La production du NO est liée à 3 isoformes différentes de la protéine appelées synthases du NO ou NO synthases.

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Doctorat en sciences, Spécialisation physique
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Chemoattractant agents play a crucial role in the initiation of immune responses, by regulating the traffic and function of leucocyte populations. Their receptors are therefore considered as potential targets for the development of new therapies in the fields of cancer and inflammatory diseases. ChemR23, a previously orphan receptor discovered in the laboratory, is structurally related to receptors for chemoattractant agents. It is expressed on immature myeloid and plasmacytoid dendritic cells (mDCs and pDCs respectively), as well as on adipocytes, macrophages, NK and endothelial cells. Chemerin, the endogenous ligand of ChemR23, is abundant in various human samples originating from inflammatory diseases, including pleural effusions. Chemerin is secreted as an inactive precursor, prochemerin, and is activated by the removal of six or seven amino-acids from its carboxy-terminus by serine proteases, such as as cathepsin G and elastase. Chemerin acts as a chemoattractant agent of low nanomolar potency for macrophages, immature mDCs and pDCs. It is however more active on pDCs, in line with the higher expression of ChemR23 on these cells. pDCs possess important immunoregulatory properties in lung diseases, and their ability to secrete large amounts of type I interferon (IFN) upon viral infection makes them crucial players in anti-viral immunity.

According to these elements, and to the role of neutrophils in the physiopathology of many inflammatory lung diseases and in the generation of active chemerin, we began in 2007 to study the role of chemerin and its receptor ChemR23 in inflammatory lung diseases. We first characterized the mouse chemerin/ChemR23 system, and described that this system was very similar to the human one, in terms of distribution, pharmacology and functional properties. We then used wild type mice (WT) and mice invalidated for the receptor (ChemR23-/-) in various models of inflammatory lung diseases, including asthma, lung fibrosis, viral pneumonia, and acute lung injury.

Whereas the asthma and lung fibrosis models did not allow to demonstrate a significant role of the chemerin/ChemR23 system (possibly as a result of the lack of production of active chemerin in these models), infection by either the Pneumonia Virus of Mice (PVM), the mouse counterpart of human RSV, or by a murinized H1N1 influenza strain resulted in a significantly higher mortality rate in ChemR23-/- mice as compared to their WT counterparts. Using the PVM-induced pneumonia model, we observed that the excessive mortality of knock-out mice is caused by an inadequate and excessive innate immune response characterized by a massive recruitment of neutrophils to the lungs, associated with a delayed viral clearance and lower type I IFN synthesis. This latter observation suggested an impairment of pDC recruitment, according to the important contribution of pDCs to the production of type I IFNs in viral diseases, and the role of chemerin in the recruitment of these cells. We indeed confirmed a lower recruitment of pDCs in the lung of infected ChemR23-/- mice, as compared to WT mice. However, experiments of adoptive transfert and depletion of pDCs failed to proof a link between impaired pDC recruitment and the excessive morbidity and mortality observed in ChemR23-invalidated mice.

In parallel, we studied the role of the chemerin/ChemR23 system in the control of innate immune responses, by using a model of acute lung injury caused by the intra-tracheal instillation of bacterial lipopolysaccharide (LPS). In this model, administration of recombinant chemerin together with LPS in WT mice resulted in a significant (about 50%) reduction of neutrophil recruitment to both lung parenchyma and airways. Assessment of pro-inflammatory cytokines and chemokines in broncho-alveolar lavage fluids confirmed this anti-inflammatory effect of chemerin, which was ChemR23-dependent, as the inflammatory response of ChemR23-/- mice was unaffected by chemerin. In our hands, chemerin does not modulate macrophage functions, in contrast to data recently published by other groups, attributing anti-inflammatory effects of chemerin or chemerin-derived peptide to the modulation of macrophage activation and phagocytosis. Other hypotheses that could take our observations into account are presently investigated, including an immunomodulatory role of chemerin on lung epithelial or endothelial cells, and/or the ChemR23-dependent recruitment of subtypes of macrophages or other myeloid cells endowed with immunosuppressive properties.

In conclusion, our studies characterized the mouse chemerin/ChemR23 system and highlighted the role of this system in the physiopathology of some inflammatory lung diseases. Our results suggest that the chemerin/ChemR23 system might be considered as a potential therapeutic target for the development of future anti-infectious and anti-inflammatory therapies, particularly for viral pneumonia, which represent a major public health problem, as well as for acute respiratory distress syndrome (ARDS) following severe acute lung injuries.

Les agents chimioattractants jouent un rôle fondamental dans l’initiation des réponses immunes en régulant le trafic et la fonction des populations leucocytaires. Leurs récepteurs constituent dès lors des cibles d’intérêt pour le développement de traitements contre les maladies inflammatoires et le cancer. Le laboratoire d’accueil a identifié le récepteur ChemR23, exprimé à la surface des cellules dendritiques myéloïdes (mDCs) et plasmacytoïdes (pDCs) immatures, des macrophages, des cellules NK, des adipocytes, et des cellules endothéliales. Le ligand endogène du récepteur ChemR23, la chémérine, est présent en abondance dans divers échantillons pathologiques d’origine inflammatoire. La chémérine est produite sous la forme d'un précurseur inactif, la prochémérine, qui nécessite pour devenir active le clivage protéolytique de six ou sept acides aminés à son extrémité carboxy-terminale. La chémérine induit le chimiotactisme des macrophages et des DCs immatures, et en particulier des pDCs immatures en accord avec l’expression plus importante de ChemR23 par les pDCs. Les pDCs jouent un rôle immunorégulateur important en pathologie pulmonaire, en particulier dans la physiopathologie des pneumonies virales, par leur capacité à produire d’importantes quantités d’interféron (IFN) de type I.

Compte tenu de ces éléments et du rôle des polynucléaires neutrophiles dans de nombreuses pathologies pulmonaires, ainsi que dans la génération de chémérine active à partir de son précurseur, nous avons débuté en octobre 2007, l’étude du rôle de la chémérine et de son récepteur ChemR23 dans le contrôle des pathologies pulmonaires inflammatoires. Nous avons tout d’abord caractérisé le système chémérine/ChemR23 chez la souris et avons montré que ce système présentait des caractéristiques similaires à celles décrites chez l’homme, en termes de distribution, de pharmacologie et de propriétés fonctionnelles.

Ensuite, nous avons comparé des souris sauvages et invalidées pour le récepteur ChemR23 (ChemR23-/-) dans divers modèles de pathologies pulmonaires. Les modèles d’asthme et de fibrose pulmonaire induite par instillation de bléomycine ou de silice n’ont pas permis de mettre en évidence un rôle important du couple chémérine/ChemR23, peut-être en raison de l’absence de génération de forme active de chémérine dans ces modèles. En revanche, l’administration de deux agents viraux différents, le PVM (Pneumonia Virus of Mice), l’équivalent murin du RSV humain, et un virus de l’influenza H1N1 murinisé, a résulté en un taux de mortalité 40% plus élevé pour les souris ChemR23-/- par rapport à leurs homologues sauvages. En utilisant le modèle de pneumonie induite par le PVM, nous avons montré que cette différence de mortalité est causée par une réponse immune inappropriée et excessive, associée à une réduction de l’élimination du virus, ainsi qu’à un déficit de synthèse d’IFN de type I. Les pDCs, dans un contexte d’infection virale, sont capables de synthétiser d’importantes quantités d’IFN de type I, et nous avons mis en évidence un déficit relatif de recrutement en pDCs chez les souris ChemR23-/- infectées. Néanmoins, les expériences de transfert adoptif et de déplétion de pDCs n’ont pas permis de lier ce défaut de recrutement à l’excès de morbidité et de mortalité observé chez les souris ChemR23-/- infectées.

En parallèle, le rôle de ce couple ligand-récepteur dans le contrôle des réponses immunitaires innées a été étudié dans un modèle de pneumopathie aiguë induite par instillation intra-trachéale de lipopolysaccharide (LPS). Dans ce modèle, l’administration simultanée de chémérine recombinante avec le LPS entraîne chez les souris sauvages une diminution significative (environ 50%) du nombre de polynucléaires neutrophiles recrutés dans les voies aériennes et dans le parenchyme pulmonaire, ainsi qu’une importante diminution de synthèse de cytokines pro-inflammatoires. Cet effet anti-inflammatoire de la chémérine est dépendant de ChemR23, et ne semble pas être secondaire à un effet de la chémérine sur l’activation des macrophages, contrairement à certaines données publiées récemment par d’autres groupes. D’autres hypothèses permettraient cependant de prendre en compte ces observations, notamment un effet de la chémérine sur les cellules épithéliales et/ou endothéliales pulmonaires, ainsi que sur le recrutement de sous-populations de macrophages ou d’autres cellules myéloïdes possédant des propriétés immunosuppressives. Des expériences complémentaires ont été initiées afin de tester ces hypothèses.

En conclusion, après avoir caractérisé le système chémérine/ChemR23 chez la souris, nos études ont permis de mettre en évidence le rôle de ce couple ligand/récepteur dans la physiopathologie de certaines pneumopathies inflammatoires, ouvrant ainsi de nouvelles perspectives thérapeutiques, en particulier pour le traitement des pneumopathies virales, qui constituent un problème de santé publique majeur, ainsi que des syndromes de détresse respiratoire aiguë (ARDS).
Doctorat en Sciences médicales
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Amongst respiratory diseases, inflammatory lung diseases constitute a major part of public

health problem. As a consequence, investigating the immune mechanisms that contribute to

the pathogenesis of these diseases is essential to identify candidate targets for the

development of new therapeutic drugs. Furthermore, over the past 20 years, the growing awareness

that purinergic signalling events shape the immune and inflammatory responses to infection and

allergic reactions warranted the development of animal models to assess their importance in vivo in

acute lung injury and chronic airway diseases. The field of purinergic inflammation formulated the

unifying concept that ATP is released as a «danger signal» to induce inflammatory responses upon

binding purinergic receptors.

According to these elements, we began in 2007 to evaluate lung inflammation in mice deficient for

the P2Y2 purinergic receptor in TH2 and TH1 models. The most convincing evidence that the P2Y2

receptor is engaged during alarm situations comes from studies related to cystic fibrosis and asthma.

Indeed, chronic respiratory diseases are commonly associated with elevated airway ATP

concentrations, as reported in cystic fibrosis, but also in idiopathic pulmonary fibrosis and chronic

obstructive pulmonary disease (COPD) patients, and they are raised by allergens in asthmatic

patients.

First, we demonstrated a significant role of the P2Y2R in a TH2-ovalbumin(OVA)-induced asthma

model. We observed that eosinophil accumulation, a distinctive feature of lung allergic inflammation,

was defective in OVA-treated P2Y2-deficient mice compared with OVA-treated wild type animals.

Interestingly, the upregulation of VCAM-1 was lower on lung endothelial cells of OVA-treated P2Y2

knockout mice compared with OVA-treated wild type animals. Adhesion assays demonstrated that

the action of UTP on leukocyte adhesion through the regulation of endothelial VCAM-1 was

abolished in P2Y2-deficient lung endothelial cells. Additionally, the level of soluble VCAM-1, reported

as an inducer of eosinophil chemotaxis, was strongly reduced in the bronchoalveolar lavage fluid of

P2Y2-deficient mice.

Secondly, we studied the consequences of P2Y2R loss in lung inflammation initiated after pneumonia

virus of mice (PVM) infection in collaboration with the group of Pr. Daniel Desmecht (ULg). We

demonstrated here that P2Y2

-/-

mice display a severe increase in morbidity and mortality rate in

response to PVM. Lower survival of P2Y2

-/-

mice was not correlated with excessive inflammation

despite the higher level of neutrophil recruiters in their broncho-alveolar fluids. Interestingly, we

observed lower numbers of dendritic cells, CD4

+

T cells and CD8

+

T cells in P2Y2

-/-

mice compared to

P2Y2

+/+

infected lungs. Lower level of IL-12 and higher level of IL-6 in broncho-alveolar fluid support

an inhibition of Th1 response in P2Y2

-/-

mice. Quantification of DC recruiter expression revealed

comparable IP-10 and MIP-3&
Doctorat en Sciences biomédicales et pharmaceutiques
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La pneumopathie interstitielle (PI) est devenue la principale cause de décès de la sclérodermie systémique (ScS). Au cours de PI, l’activation immunitaire déclenche une forte production du monoxyde d’azote (NO) et l’augmentation de la concentration de NO dans l’air expiré des patients atteints de ScS avec PI suggère que cette méthode pourrait détecter précocement l’alvéolite, afin de traiter à temps la PI pour éviter son évolution vers la fibrose pulmonaire. En utilisant le modèle à deux compartiments séparant le NO alvéolaire (CANO) du NO bronchique, nous avons montré que la CANO est : (1) augmentée chez les patients atteints de ScS comparativement aux volontaires sains; (2) associée à l’alvéolite et (3) corrélée à la sévérité de la PI. De plus, une valeur de CANO = 10,8 ppb permettait d’affirmer la présence de la PI et une valeur = 3,8 ppb, d’écarter l’existence d’une PI avec une valeur prédictive= 95%. Le modèle bi-compartimenté néglige la distribution arborisée des voies aériennes et la diffusion axiale du NO, que prend en compte le nouveau « modèle de la trompette ». Les résultats de CANO des 2 méthodes sont comparables (rho=0,98, p<0.001). Enfin, La capacité des sérums à induire la prolifération des fibroblastes pulmonaires et sa conversion en myofibroblaste est augmentée chez les patients atteints de ScS avec une CANO > 5ppb par rapport à celle des patients atteints de ScS qui ont une CANO = 5 ppb et à celle des volontaires sains. Nos résultats suggèrent une relation possible entre l’inflammation alvéolaire et la fibrose pulmonaire au cours de la ScS
Interstitial lung disease (ILD) has become the main cause of death in systemic sclerosis (SSc). In ILD, immune activation leads to strong nitric oxide (NO) output by inducible NO synthase. Increased the whole fractional rate of NO in exhaled air has been reported in SSc patients with ILD and suggested that exhaled NO can be an accurate none-invasive marker of early alveolar inflammation in order to initiate in time treatment. The two compartment-model method partitioned exhaled NO into alveolar concentration (CANO) and conducting airway flux, We hypothesized that overproduction of NO in the lung eventually leads to ILD in SSc. We have found that CANO is significantly increased in SSc patients as compared with healthy controls. We have also demonstrated that high levels of CANO were related to alveolitis and the severity of ILD in SSc. Moreover, we have found that ILD could be ruled in (positive predictive value > 95%) when CANO = 10.8 ppb, and ruled out when CANO values = 3.8 ppb (negative predictive value > 95%). The two-compartment model neglected the trumpet shape of airway tree and the axial diffusion of NO that the advanced “trumpet model” takes account. We have found that CANO levels assessed by the two models were comparable (rho=0,98, p<0.001). Finally, we have found that the serum ability to induce lung fibroblast proliferation and myofibroblast transition was increased in SSc patients with high levels of CANO (>5ppb) as compared to SSc patients with low levels of CANO (=5ppb) and healthy controls. Our findings suggest a possible link between alveolar inflammation, and lung fibrosis in SSc. 1624 caractères avec espace

Mechanical circulatory support devices have gained significant importance in recent years as a viable therapeutic option to support paediatric population and children with single functional ventricle. The Fontan operation helps to reroute the deoxygenated blood to the lungs by bypassing the dysfunctional right ventricle. Total Cavopulmonary Connection (TCPC) is usually a method opted by the clinicians to connect the superior vena cava (SVC) and inferior vena cava (IVC) to the left and right pulmonary artery (LPA and RPA). However, the non-physiologic flow patterns created by the Fontan procedure leads to an increase in chances of platelet deposition and pressure loss which calls for heart transplantation to prevent early and late stage pathophysiology. This had led to modification of TCPC geometry to reduce the pressure and energy loss and thereby unload the single functional ventricle to ensure longer survival period. A study on mechanical circulatory device in conjunction with the modified TCPC geometry has seen little exposure and has opened new gates to develop a variety of state-of-art cavopulmonary assist devices. This study is focused on the selection of optimal TCPC to reduce energy loss and the effect of stent inside the modified TCPC on hemodynamics and flow structures. Four TCPC connections, developed for a particular age group of children, were studied for the velocity field, overall pressure and energy loss. In addition, the four TCPC connection geometries were also studied for distribution of hepatic blood from the IVC to both pulmonary arteries, and hence the lungs, to prevent development of any arteriovenous malformations. The entire stent assembly mounted inside the two best performing TCPC connections was examined for the hemodynamic effects using a series of 3D-CFD simulations. The curved-type connection for the TCPC proved to provide minimum pressure and energy loss along with reduced traces of vortex and recirculation. However, it was not efficient in terms of hepatic blood distribution. The flared geometry performed second best in terms of both minimum power loss and even hepatic blood distribution. There was a slight difference in power loss between the flared and the curved TCPC configuration with stent but the flared geometry had better hepatic blood distribution. This study demonstrated that a stent in conjunction with a TCPC leads to development of a helical flow pattern which provides better mixing of blood and even distribution to both the pulmonary arteries. The design of a stent with the best performing flared TCPC configuration can be optimized to reduce the amount of power loss and vortex generation and can be used to design similar scaled models for paediatric population of various age groups.

Pulmonary arterial hypertension (PAH) is a group of chronic, progressive and fatal diseases, characterized by the dysfunction of the small arteries and microvasculature in the pulmonary circulation. Due to high blood pressure and high resistance in the pulmonary arteries, PAH causes detrimental damage on the lung and right heart ventricle. If left untreated, PAH quickly becomes life threatening. Although the exact pathophysiology remains unknown, there is increasing evidence suggesting that inflammation likely plays an important role in inducing and perpetuating the PAH progress. Although anti-inflammatory therapy has been shown effective in certain connective-tissue-disease-associated PAH, this approach has not been tested in other PAH conditions. The potential benefit of anti-inflammatory therapy to treat various PAH conditions could be of importance and require further study on the possible pathological mechanisms underlying the therapeutic effects.

The pathophysiology of the acute pulmonary damage that may occur in association with sepsis, hemorrhagic shock and microembolism seems to involve the activity of cyclooxygenase derived arachidonate metabolites. In the rat, pulmonary microembolism due to infusion of thrombin together with inhibition of fibrinolysis has been found to induce pulmonary insufficiency with similarities to the clinical adult respiratory distress syndrome. The infusion of thrombin results in systemic hypotension, pulmonary hypertension and platelet aggregation, and subsequently, with a certain dealy in time, to increased pulmonary vascular permeability.The main purposes of this investigation were to study the release of TxA2 and PGI2 following thrcmbin-induced pulmonary microembolizaticn in the rat and to examine the effects of a thromboxane synthetase inhibitor (DazoxibenR) on pulmonary arterial and systemic mean arterial pressure and vascular permeability.During infusion of thrcmbin in rats pulmonary arterial pressure rose from 15 ± 2 to 35 ± 3 rmHg and mean arterial pressure fell from 120 ± 6 to 49 ± 27 mmHg. Plasma thromboxane B2 (TxB2) increased from 0.3 ± 0.004 to 3.6 ± 0.5 ng/ml. Ninety minutes later the lung weight and albunin concentration in the lung were increased (2.21 ± 0.13 g and 22.7 ± 4.7 mg/g) compared with controls (1.12 ± 0.14 g and 8.5 ± 0.9 mg/g). Dazoxiben reduced the elevated pulmonary arterial pressure and the elevated plasma TxB2 concentration following infusion of thrombin. Ninety minutes after infusion of thrcmbin, the in vitro synthesis of TxB2 in lung tissue was increased. Dazoxiben and a specific rabbit anti-rat neutrophil serun reduced this synthesis of TxB in vitro. The lung weight (2.18 ± 0.20 g) and lung albumin concentration (21.4 ± 3.4 mg/g) was not affected by Dazoxiben. The results indicate that TxA2 in an important mediator of the pressure changes in the early phase after infusion of thrombin and that neutrophils are associated with thromboxane formation in the lung tissue. Rats pretreated with the antineutrophil serum had less pulmonary weight (1.69 ± 0.28 g) and the albumin concentration in the edema fluid was decreased (17.3 ± 3.6 mg/g), suggesting that polymorphonuclear leukocytes contributed to the pulmonary dysfunction. Dazoxiben when incubated with thrcmbin in a chromogenic substrate system had a linear, dose-related anti-thrombin effect. At a Dazoxiben concentration of 2.4 mM only a few percent of the thrombin activity remained.