Hypoxie-bedingte Hemmung der alveolären Flüssigkeitsresorption im Modell der isolierten, ventilierten und perfundierten Kaninchenlunge

Eine intakte alveolar-epitheliale Barriere ist für eine ungestörte Gasaustauschfunktion der Lunge von maßgeblicher Bedeutung. Beeinträchtigungen sowohl der passiven wie auch aktiven Barrierefunktion können hier zu einem folgenschweren Organversagen führen. Der Einfluss alveolärer Hypoxie auf aktive Resorptionsmechanismen des alveolären Epithels wurde bisher unzureichend unter physiologischen Bedingungen untersucht. Im vorliegenden ex-vivo Modell der isolierten, perfundierten und ventilierten Kaninchenlunge wurde der Einfluss von Hypoxie und/oder alveolärer Flüssigkeitsbeladung auf die Funktion des alveolären Epithels untersucht. Der das Epithel auskleidende Flüssigkeitsfilm (epithelial lining fluid (ELF)) wird über aktiven und passiven transmembranösen Flüssigkeitstransport (alveolar fluid clearence (AFC)) reguliert. In dem hier verwendeten Modell konnten wir zeigen, dass der alveoläre Natriumtransport die treibende Kraft des AFC darstellt. Der aktive, durch apikale Amilorid-sensitive Natriumkänale (ENaC) und basolateral lokalisierte Na,KATPase von alveolär nach interstitiell/intravasal gerichtete Natriumgradient führt zu einem konsekutiven Nachströmen von Wasser entlang des Ionengradienten. Die Deposition eines Flüssigkeitsbolus von 2,5 ml per Aerosolierung (engl. excess fluid load) führte im verwendeten Modell zu keiner relevanten Funktionsbeeinträchtigung des isolierten Organs. Es zeigte sich überraschenderweise sogar eine Stimulation des aktiven Natrium- und somit auch Flüssigkeitstransportes, im Sinne einer gesteigerten Ödemresorption. Demgegenüber führte eine alveoläre Hypoxie (zwei Stunden Ventilation mit 3,0 % Sauerstoff) zu einem signifikanten Abfall des AFC und konsekutiver Ödembildung. Ursache hierfür war eine um ca. 60 % reduzierte aktive Natriumresorption mit entsprechender Senkung des Flüssigkeitstransportes. Wir konnten somit erstmals in einem intakten isolierten Lungenmodell (unter Beibehaltung der Ventilation) zeigen, dass alveoläre Hypoxie, nicht jedoch eine iatrogene Flüssigkeitsbeladung des Alveolarraumes zu einer Störung der Ödemresorption der Lunge führt. Diese Beobachtung hat Implikationen für das Verständnis von Krankheitsbildern wie dem akuten Lungenversagen, dem Höhenlungenödem und dem Beinahe-Ertrinken.Alveolar-capillary barrier function is essential to maintain alveolar fluid balance and adequate gas exchange in the lung. Malfunction of either passive and/or active barrier could resolve in a detrimental organ failure So far the influence of alveolar hypoxia on active barrier function and its underlying machinery has been only inadequately described in a physiological environment. Using the ex-vivo model of the isolated, perfused and ventilated rabbit lung, this experimental study evaluated the influence of hypoxia and/or excess fluid load on alveolar epithelium. The epithelial lining fluid (ELF) is balanced via active and passive transmembrane alveolar fluid clearance (AFC). In the present study using the isolated, perfused and ventilated rabbit lung alveolar sodium transport (AST) was evidenced to be the driving force of the AFC. Sodium is actively pumped out of the alveolar epithelial cells into the interstitium by Na,K-ATPase, located on the basolateral membrane of the epithelium, which in turn drives the sodium uptake by amiloride-sensitive sodium channels (ENaCs), located on the apical membrane of the epithelium. This generates an osmotic gradient that drives water out of the alveolar space. The deposition of 2,5 ml excess fluid load resulted in no relevant barrier dysfunction in our isolated organ model. Surprisingly, we found the active sodium- and therefore fluid transport stimulated, ascribed by enhanced edema resorption. In contrast, alveolar hypoxia (2 hours of ventilation with 3,0 % Oxygen) led to a significant decrease of AFC and consecutive alveolar edema formation. Etiologic was the reduction of active AST by about 60 %, correspondingly resulting in a decreased AFC. Taken together, the deleterious effect of alveolar hypoxia, but not experimental alveolar deposition of excess fluid load, on the edema clearence in the distal lung was proofed for the first time in an intact isolated lung model under perpetuated ventilation. Our results establish ramifications for the disease pattern of acute lung injury (ALI), adult respiratory distress syndrome (ARDS), high altitude pulmonary edema (HAPE) and near-drowning syndrome

An integrated approach for the systematic identification and characterization of heart-enriched genes with unknown functions

<p>Abstract</p> <p>Background</p> <p>High throughput techniques have generated a huge set of biological data, which are deposited in various databases. Efficient exploitation of these databases is often hampered by a lack of appropriate tools, which allow easy and reliable identification of genes that miss functional characterization but are correlated with specific biological conditions (e.g. organotypic expression).</p> <p>Results</p> <p>We have developed a simple algorithm (DGSA = Database-dependent Gene Selection and Analysis) to identify genes with unknown functions involved in organ development concentrating on the heart. Using our approach, we identified a large number of yet uncharacterized genes, which are expressed during heart development. An initial functional characterization of genes by loss-of-function analysis employing morpholino injections into zebrafish embryos disclosed severe developmental defects indicating a decisive function of selected genes for developmental processes.</p> <p>Conclusion</p> <p>We conclude that DGSA is a versatile tool for database mining allowing efficient selection of uncharacterized genes for functional analysis.</p

Early onset lung cancer, cigarette smoking and the SNP309 of the murine double minute-2 (MDM2) gene

The polymorphism SNP309 (rs2279744) in the promoter region of the MDM2 gene has been shown to alter protein expression and may play a role in the susceptibility to lung cancer. The MDM2 protein is a key inhibitor of p53 and several mechanisms of MDM2/p53 interactions are presently known: modulating DNA-repair, cell-cycle control, cell growth and apoptosis

Do genetic factors protect for early onset lung cancer? A case control study before the age of 50 years

<p>Abstract</p> <p>Background</p> <p>Early onset lung cancer shows some familial aggregation, pointing to a genetic predisposition. This study was set up to investigate the role of candidate genes in the susceptibility to lung cancer patients younger than 51 years at diagnosis.</p> <p>Methods</p> <p>246 patients with a primary, histologically or cytologically confirmed neoplasm, recruited from 2000 to 2003 in major lung clinics across Germany, were matched to 223 unrelated healthy controls. 11 single nucleotide polymorphisms of genes with reported associations to lung cancer have been genotyped.</p> <p>Results</p> <p>Genetic associations or gene-smoking interactions was found for <it>GPX1(Pro200Leu) </it>and <it>EPHX1(His113Tyr)</it>. Carriers of the Leu-allele of <it>GPX1(Pro200Leu) </it>showed a significant risk reduction of OR = 0.6 (95% CI: 0.4–0.8, p = 0.002) in general and of OR = 0.3 (95% CI:0.1–0.8, p = 0.012) within heavy smokers. We could also find a risk decreasing genetic effect for His-carriers of <it>EPHX1(His113Tyr) </it>for moderate smokers (OR = 0.2, 95% CI:0.1–0.7, p = 0.012). Considered both variants together, a monotone decrease of the OR was found for smokers (OR of 0.20; 95% CI: 0.07–0.60) for each protective allele.</p> <p>Conclusion</p> <p>Smoking is the most important risk factor for young lung cancer patients. However, this study provides some support for the T-Allel of <it>GPX1(Pro200Leu) </it>and the C-Allele of <it>EPHX1(His113Tyr) </it>to play a protective role in early onset lung cancer susceptibility.</p