Métabolisme des glucocorticoïdes dans le poumon murin en développement : la voie surrénalienne

Lorsqu’une femme est à risque d’accoucher prématurément, des glucocorticoïdes lui seront administrés afin d’accélérer la maturation pulmonaire du bébé. Après la naissance, différents protocoles peuvent être mis en place pour aider l’enfant à respirer dont l’administration du surfactant et la ventilation. Les glucocorticoïdes ont un effet positif sur la maturation pulmonaire. Par contre, ils nuisent au processus de la septation après la naissance. Les glucocorticoïdes retrouvés dans le poumon en développement peuvent provenir de deux sources, soit de la voie classique de la synthèse des glucocorticoïdes par les surrénales, soit des gènes exprimés dans le poumon. Les sites d’expression des gènes codant pour les enzymes de la synthèse des glucocorticoïdes dans le poumon sont inconnus ainsi que le gène de la 20α-hydroxystéroïde déshydrogénase (20α-HSD). Cette dernière inactive le substrat et le produit de la 21-hydroxylase. Des poumons de fœtus de souris au jour de gestation 15,5, 17,5 et 19,5 ainsi que de souriceaux âgés de 0, 5 et 15 jours ont été utilisés pour des hybridations in situ. Cette étude a montré qu’avant la naissance, l’ARNm de la 21-hydroxylase est situé au niveau des cellules épithéliales distales alors que l’ARNm de la 20α-HSD se retrouve plutôt au niveau des capillaires. Les gènes de la 21-hydroxylase et de la 20α-HSD sont exprimés dans les cellules épithéliales proximales ainsi que dans les cellules endothéliales de veines dans la période entourant la naissance. À la fin du stade sacculaire et pendant le stade alvéolaire, le gène de la 21-hydroxylase est exprimé seulement dans les septa et les parois minces tout comme le gène de la 20α-HSD sauf dans le stade alvéolaire où il n’y avait pas de signal significatif. Ainsi, ces résultats suggèrent que la 20α-HSD pourrait participer au contrôle du niveau d’activité de la 21-hydroxylase en modulant la disponibilité de son substrat.

Potential role of bioactive lipids in the development of non-antibody mediated transfusion-related acute lung injury (TRALI)

Transfusion-related acute lung injury (TRALI) has been the leading cause of transfusion-related morbidity and mortality in the UK and the USA in recent years. A threshold mechanism of TRALI has been proposed in which both patient factors (type and/or severity of clinical insult) and blood product factors (strength and/or concentration of antibodies or biological response modifiers) interact to surpass a threshold for TRALI development (Bux et al. Br J Haematol; 2007; 136: 788-99). The risk of developing antibody-mediated TRALI has been minimised by the introduction of risk-reduction strategies such as limiting the use of plasma from female donors. In contrast, there are no strategies currently in place to mitigate the development of non-antibody mediated TRALI as the mechanisms remain largely undefined. Previous studies have implicated non-polar lipids such as arachidonic acid and various species of hydroxyeicosatetranoic acid (HETE) in the development of non-antibody mediated TRALI (Silliman et al. Transfusion; 2011; 51: 2549-54), however the contribution of these lipids to the development of an inflammatory response in TRALI is poorly understood.

Role of nucleotides on lung epithelial cells : mechanism of release and development of a side-view microscopic chamber to study nucleotide-dependent airway surface liquid height

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Influence of age on the development of immunological lung response in intrauterine undernourishment

Objective: We investigated the effect of intrauterine undernourishment on some features of asthma using a model of allergic lung inflammation in rats. The effects of age at which the rats were challenged (5 and 9 wk) were also evaluated. Methods: Intrauterine undernourished offspring were obtained from dams that were fed 50% of the nourished diet of counterparts and were immunized at 5 and 9 wk of age. They were tested for immunoglobulin E anti-ova titers (by passive cutaneous anaphylaxis), cell count in the bronchoal-veolar fluid, leukotriene concentration, airway reactivity, mucus production, and blood corticosterone and leptin concentrations 21 d, after immunologic challenge. Results: Intrauterine undernourishment significantly reduced the antigen-specific immunoglobulin E production, inflammatory cell infiltration into airways, mucus secretion, and production of leukotrienes B-4/C-4 in the lungs in both age groups compared with respective nourished rats. The increased reactivity to methacholine that follows antigen challenge was not affected by intrauterine undernourishment. Corticosterone levels increased with age in the undernourished rats` offspring, but not in the nourished rats` offspring. Undernourished offspring already presented high levels of corticosterone before inflammatory stimulus and were not modified by antigen challenge. Leptin levels increased with challenge in the nourished rats but not in the undernourished rats and could not be related to corticosterone levels in the. undernourished rats. Conclusion: Intrauterine undernourishment has a striking and age-dependent effect on the off spring, reducing lung allergic inflammation. (C) 2008 Elsevier Inc. All rights reserved.

Interactions between genetic predisposition and environmental toxicants for development of lung cancer

Significant interindividual variations in health outcome may be caused by the inheritance of variant polymorphic genes, such as CYP2D6 and CYP2E1 for activation, and GSTM1 and GSTT1 for detoxification of chemicals. However. mechanistic studies linking the inheritance of predisposing genes with genotoxic effects towards cancer have yet to be systematically conducted. We have studied 54 lung cancer patients and 50 matched normal controls, who have been cigarette smokers, to elucidate the role of polymorphic genes in cancer. Our data indicates that the inheritance of unfavorable CYP2D6, CYP2E1, and GSTT1 genes is strongly correlated with the smoking-related lung cancer. For heavy cigarette smokers (> 30 pack-years), the smoking habit is the strongest predictor of lung cancer risk irrespective of the inheritance of unfavorable metabolizing genes. For moderate to light smokers (< 30 pack-years), the genetic predisposition plays on important role For the risk (odds ratio = 3.46; 95% CL = 0.46-40.2). Using a subgroup of the study population, we observed that cigarette smokers having the defective GST genes have significantly more chromosome aberrations as determined by the fluorescence-in-situ-hybridization (FISH) technique than smokers with the normal GST genes (P < 0.001). In conclusion, our study provides data to indicate that individuals who have inherited unfavorable metabolizing genes have increased body burden of toxicants to cause increased genetic damage and to have increased risk for cancer. Studies like ours can be used to understand the basis for interindividual variations in cancer outcome, to identify high risk individuals and to assess health risk. (C) 1997 Wiley Liss, Inc.

Cardiopulmonary bypass: development of John Gibbon's heart-lung machine

To provide a brief review of the development of cardiopulmonary bypass. A review of the literature on the development of extracorporeal circulation techniques, their essential role in cardiovascular surgery, and the complications associated with their use, including hemolysis and inflammation. The advancement of extracorporeal circulation techniques has played an essential role in minimizing the complications of cardiopulmonary bypass, which can range from various degrees of tissue injury to multiple organ dysfunction syndrome. Investigators have long researched the ways in which cardiopulmonary bypass may insult the human body. Potential solutions arose and laid the groundwork for development of safer postoperative care strategies. Steady progress has been made in cardiopulmonary bypass in the decades since it was first conceived of by Gibbon. Despite the constant evolution of cardiopulmonary bypass techniques and attempts to minimize their complications, it is still essential that clinicians respect the particularities of each patient's physiological function.

Role for ephrinB2 in postnatal lung alveolar development and elastic matrix integrity

Alveoli are formed in the lung by the insertion of secondary tissue folds, termed septa, which are subsequently remodeled to form the mature alveolar wall. Secondary septation requires interplay between three cell types: endothelial cells forming capillaries, contractile interstitial myofibroblasts, and epithelial cells. Here, we report that postnatal lung alveolization critically requires ephrinB2, a ligand for Eph receptor tyrosine kinases expressed by the microvasculature. Mice homozygous for the hypomorphic knockin allele ephrinB2DeltaV/DeltaV, encoding mutant ephrinB2 with a disrupted C-terminal PDZ interaction motif, show severe postnatal lung defects including an almost complete absence of lung alveoli and abnormal and disorganized elastic matrix. Lung alveolar formation is not sensitive to loss of ephrinB2 cytoplasmic tyrosine phosphorylation sites. Postnatal day 1 mutant lungs show extracellular matrix alterations without differences in proportions of major distal cell populations. We conclude that lung alveolar formation relies on endothelial ephrinB2 function.

Influence of natural killer cells and perforin-mediated cytolysis on the development of chemically induced lung cancer in A/J mice

One alternative approach for the treatment of lung cancer might be the activation of the immune system using vaccination strategies. However, most of clinical vaccination trials for lung cancer did not reach their primary end points, suggesting that lung cancer is of low immunogenicity. To provide additional experimental information about this important issue, we investigated which type of immune cells contributes to the protection from lung cancer development. Therefore, A/J mice induced for lung adenomas/adenocarcinomas by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were depleted of CD4(+) or CD8(+) T cells, CD11b(+) macrophages, Gr-1(+) neutrophils and asialo GM1(+) natural killer (NK) cells. Subsequent analysis of tumour growth showed an increase in tumour number only in mice depleted of NK cells. Further asking by which mechanism NK cells suppressed tumour development, we neutralized several death ligands of the tumour necrosis factor (TNF) family known to be involved in NK cell-mediated cytotoxicity. However, neither depletion of TNF-α, TNF-related apoptosis-inducing ligand, TNF-like weak inducer of apoptosis or FasL alone nor in combination induced an augmentation of tumour burden. To show whether an alternative cell death pathway is involved, we next generated A/J mice deficient for perforin. After challenging with NNK, mice deficient for perforin showed an increase in tumour number and volume compared to wild-type A/J mice. In summary, our data suggest that NK cells and perforin-mediated cytolysis are critically involved in the protection from lung cancer giving promise for further immunotherapeutic strategies for this disease.

Development of an epithelium-specific expression cassette with human DNA regulatory elements for transgene expression in lung airways

The efficient expression of therapeutic genes in target cells or tissues is an important component of efficient and safe gene therapy. Utilizing regulatory elements from the human cytokeratin 18 (K18) gene, including 5′ genomic sequences and one of its introns, we have developed a novel expression cassette that can efficiently express reporter genes, as well as the human cystic fibrosis transmembrane conductance regulator (CFTR) gene, in cultured lung epithelial cells. CFTR transcripts expressed from the native K18 enhancer/promoter include two alternative splicing products, due to the activation of two cryptic splice sites in the CFTR coding region. Modification of the K18 intron and CFTR cDNA sequences eliminated the cryptic splice sites without changing the CFTR amino acid sequence, and led to enhanced CFTR mRNA and protein expression as well as biological function. Transgenic expression analysis in mice showed that the modified expression cassette can direct efficient and epithelium-specific expression of the Escherichia coli LacZ gene in the airways of fetal lungs, with no detectable expression in lung fibroblasts or endothelial cells. This is the first expression cassette which selectively directs lung transgene expression for CFTR gene therapy to airway epithelia.

Development and Testing of An Automatic Lung IMRT Planning Algorithm

Knowledge-based radiation treatment is an emerging concept in radiotherapy. It

mainly refers to the technique that can guide or automate treatment planning in

clinic by learning from prior knowledge. Dierent models are developed to realize

it, one of which is proposed by Yuan et al. at Duke for lung IMRT planning. This

model can automatically determine both beam conguration and optimization ob-

jectives with non-coplanar beams based on patient-specic anatomical information.

Although plans automatically generated by this model demonstrate equivalent or

better dosimetric quality compared to clinical approved plans, its validity and gener-

ality are limited due to the empirical assignment to a coecient called angle spread

constraint dened in the beam eciency index used for beam ranking. To eliminate

these limitations, a systematic study on this coecient is needed to acquire evidences

for its optimal value.

To achieve this purpose, eleven lung cancer patients with complex tumor shape

with non-coplanar beams adopted in clinical approved plans were retrospectively

studied in the frame of the automatic lung IMRT treatment algorithm. The primary

and boost plans used in three patients were treated as dierent cases due to the

dierent target size and shape. A total of 14 lung cases, thus, were re-planned using

the knowledge-based automatic lung IMRT planning algorithm by varying angle

spread constraint from 0 to 1 with increment of 0.2. A modied beam angle eciency

index used for navigate the beam selection was adopted. Great eorts were made to assure the quality of plans associated to every angle spread constraint as good

as possible. Important dosimetric parameters for PTV and OARs, quantitatively

re

ecting the plan quality, were extracted from the DVHs and analyzed as a function

of angle spread constraint for each case. Comparisons of these parameters between

clinical plans and model-based plans were evaluated by two-sampled Students t-tests,

and regression analysis on a composite index built on the percentage errors between

dosimetric parameters in the model-based plans and those in the clinical plans as a

function of angle spread constraint was performed.

Results show that model-based plans generally have equivalent or better quality

than clinical approved plans, qualitatively and quantitatively. All dosimetric param-

eters except those for lungs in the automatically generated plans are statistically

better or comparable to those in the clinical plans. On average, more than 15% re-

duction on conformity index and homogeneity index for PTV and V40, V60 for heart

while an 8% and 3% increase on V5, V20 for lungs, respectively, are observed. The

intra-plan comparison among model-based plans demonstrates that plan quality does

not change much with angle spread constraint larger than 0.4. Further examination

on the variation curve of the composite index as a function of angle spread constraint

shows that 0.6 is the optimal value that can result in statistically the best achievable

plans.

Age of blood and recipient factors determine the severity of transfusion-related acute lung injury (TRALI)

Introduction Critical care patients frequently receive blood transfusions. Some reports show an association between aged or stored blood and increased morbidity and mortality, including the development of transfusion-related acute lung injury (TRALI). However, the existence of conflicting data endorses the need for research to either reject this association, or to confirm it and elucidate the underlying mechanisms. Methods Twenty-eight sheep were randomised into two groups, receiving saline or lipopolysaccharide (LPS). Sheep were further randomised to also receive transfusion of pooled and heat-inactivated supernatant from fresh (Day 1) or stored (Day 42) non-leucoreduced human packed red blood cells (PRBC) or an infusion of saline. TRALI was defined by hypoxaemia during or within two hours of transfusion and histological evidence of pulmonary oedema. Regression modelling compared physiology between groups, and to a previous study, using stored platelet concentrates (PLT). Samples of the transfused blood products also underwent cytokine array and biochemical analyses, and their neutrophil priming ability was measured in vitro. Results TRALI did not develop in sheep that first received saline-infusion. In contrast, 80% of sheep that first received LPS-infusion developed TRALI following transfusion with "stored PRBC." The decreased mean arterial pressure and cardiac output as well as increased central venous pressure and body temperature were more severe for TRALI induced by "stored PRBC" than by "stored PLT." Storage-related accumulation of several factors was demonstrated in both "stored PRBC" and "stored PLT", and was associated with increased in vitro neutrophil priming. Concentrations of several factors were higher in the "stored PRBC" than in the "stored PLT," however, there was no difference to neutrophil priming in vitro. Conclusions In this in vivo ovine model, both recipient and blood product factors contributed to the development of TRALI. Sick (LPS infused) sheep rather than healthy (saline infused) sheep predominantly developed TRALI when transfused with supernatant from stored but not fresh PRBC. "Stored PRBC" induced a more severe injury than "stored PLT" and had a different storage lesion profile, suggesting that these outcomes may be associated with storage lesion factors unique to each blood product type. Therefore, the transfusion of fresh rather than stored PRBC may minimise the risk of TRALI.