Search

Bleomycin (BLM)-induced lung injury in mice is a valuable model for investigating the molecular mechanisms that drive inflammation and fibrosis and for evaluating potential therapeutic approaches to treat the disease. Given high variability in the BLM model, it is critical to accurately phenotype the animals in the course of an experiment. In the present study, we aimed to demonstrate the utility of microscopic computed tomography (µCT) imaging combined with an artificial intelligence (AI)-convolutional neural network (CNN)-powered lung segmentation for rapid phenotyping of BLM mice. µCT was performed in freely breathing C57BL/6J mice under isoflurane anesthesia on days 7 and 21 after BLM administration. Terminal invasive lung function measurement and histological assessment of the left lung collagen content were conducted as well. µCT image analysis demonstrated gradual and time-dependent development of lung injury as evident by alterations in the lung density, air-to-tissue volume ratio, and lung aeration in mice treated with BLM. The right and left lung were unequally affected. µCT-derived parameters such as lung density, air-to-tissue volume ratio, and nonaerated lung volume correlated well with the invasive lung function measurement and left lung collagen content. Our study demonstrates the utility of AI-CNN-powered µCT image analysis for rapid and accurate phenotyping of BLM mice in the course of disease development and progression. NEW & NOTEWORTHY: Microscopic computed tomography (µCT) imaging combined with an artificial intelligence (AI)-convolutional neural network (CNN)-powered lung segmentation is a rapid and powerful tool for noninvasive phenotyping of bleomycin mice over the course of the disease. This, in turn, allows earlier and more reliable identification of therapeutic effects of new drug candidates, ultimately leading to the reduction of unnecessary procedures in animals in pharmacological research. [ABSTRACT FROM AUTHOR]

Acute respiratory disorders and permissive hypercapnic strategy may lead to alveolar hypoxia and hypercapnic acidosis. However, the effects of hypercapnia with or without acidosis on hypoxic pulmonary vasoconstriction (HPV) and oxygen diffusion capacity of the lung are controversial. We investigated the effects of hypercapnic acidosis and hypercapnia with normal pH (pH corrected with sodium bicarbonate) on HPV, capillary permeability, gas exchange, and ventilation-perfusion matching in the isolated ventilated-perfused rabbit lung. No alteration in vascular tone was noted during normoxic hypercapnia with or without acidosis compared with normoxic normocapnia. Hypercapnia with normal pH resulted in a transient increase in HPV during the course of consecutive ventilation maneuvers, whereas hypercapnic acidosis increased HPV over time. Hypercapnic acidosis decreased exhaled NO during hypoxia more than hypercapnia with normal pH and normocapnia, whereas intravascular NO release was unchanged. However, inhibition of NO synthesis by nitro-L-arginine (L-NNA) resulted in a loss of the increased HPV caused by hypercapnic acidosis but not that caused by hypercapnia with normal pH. Furthermore, capillary permeability increased during hypoxic hypercapnia with normal pH but not hypoxic hypercapnic acidosis. This effect was NO-dependent because it disappeared during L-NNA administration. Ventilation-perfusion matching and arterial Po2 were improved according to the strength of HPV in hypercapnia compared with normocapnia during Tween nebulization-induced lung injury. In conclusion, the increased HPV during hypercapnic acidosis is beneficial to lung gas exchange by improving ventilation-perfusion matching and preserving the capillary barrier function. These effects seem to be linked to NO-mediated pathways. hypoxia; hypercapnic acidosis; pH; capillary permeability doi: 10.1152/ajplung.00074.2009.

Severe pulmonary hypertension (PH) is a disabling disease with high mortality, characterized by pulmonary vascular remodeling and right heart hypertrophy. In mice with PH induced by chronic hypoxia, we examined the acute and chronic effects of the soluble guanylate cyclase (sGC) activator HMR1766 on hemodynamics and pulmonary vascular remodeling. In isolated perfused mouse lungs from control animals, HMR1766 dose-dependently inhibited the pressor response of acute hypoxia. This dose-response curve was shifted leftward when the effects of HMR1766 were investigated in isolated lungs from chronic hypoxic animals for 21 days at 10% oxygen. Mice exposed for 21 or 35 days to chronic hypoxia developed PH, right heart hypertrophy, and pulmonary vascular remodeling. Treatment with HMR1766 (10 mg x [kg.sup.-1] x [day.sup.-1]), after full establishment of PH from day 21 to day 35, significantly reduced PH, as measured continuously by telemetry. In addition, right ventricular (RV) hypertrophy and structural remodeling of the lung vasculature were reduced. Pharmacological activation of oxidized sGC partially reverses hemodynamic and structural changes in chronic hypoxia-induced experimental PH. vascular remodeling; telemetry doi: 10.1152/ajplung.00189.2009

Compared with the Toll-like receptor 4 (TLR4) ligand LPS restricted to Gram-negative bacteria, few studies have addressed induction of lung inflammation and concomitant leukocyte recruitment in response to TLR2 ligands. This study is the first report showing that selective TLR2 stimulation by its ligand [Pam.sub.3]-Cys-SerLys-Lys-Lys-Lys-OH ([Pam.sub.3][CSK.sub.4]) within the alveolar compartment promoted lung inflammation in mice and induced the migration of circulatory immune cells including mononuclear phagocytes into the inflamed alveolar space. By using the transgenic [CX.sub.3][CR1.sup.+/GYP] mouse strain for high-purity sorting of circulating and alveolar recruited mononuclear phagocytes together with SMART preamplification and whole genome oligonucleotide microarray techniques, we found that alveolar trafficking of mononuclear phagocytes was associated with profound changes of their gene expression profiles (-900 differentially regulated genes postrecruitment). In particular, alveolar recruited mononuclear phagocytes showed upregulated transcripts of genes encoding cytokines/chemokines and pattern recognition receptor (PRR)-associated molecules. Notably, we observed a dynamic change of the genetic program of recruited mononuclear phagocytes obtained from bronchoalveolar lavage fluid at different time points (24 vs. 48 h) post-[Pam.sub.3][CSK.sub.4] challenge. In early alveolar recruited mononuclear phagocytes, mRNA levels of both proinflammatory (e.g., TNF-[alpha], CCL2, and IL-6) and cenval anti-inflammatory/proresolution [e.g., IL- l-receptor antagonist (IL-1RN), CD200 receptor (CD200R), IL-1 receptor-associated kinase (IRAK-M), IL-10, and Bcl-2-associated X protein (Bax)] mediators were found to be highly upregulated simultaneously. In corresponding cells recruited until later time points, transcript levels of anti-inflammatory/proresolution molecules persisted at the same level, whereas mRNA levels of proinflammatory mediators were found to decline. Collectively, our in vivo study identifies genetic programs by which alveolar recruited mononuclear phagocytes may contribute to the development and termination of pneumonia caused by Gram-positive bacteria. Toll-like receptor doi: 10.1152/ajplung.90433.2008.

The protective effects of nitric oxide (NO), a physiological activator of soluble guanylyl cyclase (sGC), have been reported in ischemia-reperfusion (I/R) syndrome of the lung. Therefore, we studied the effects of BAY 41-2272, a novel sGC stimulator, on I/R injury of the lung in an isolated intact organ model. Lung injury was assessed by measuring weight gain and microvascular permeability (capillary filtration coefficient, [K.sub.fc]). Release of reactive oxygen species (ROS) into the perfusate was measured during early reperfusion by electron spin resonance (ESR) spectroscopy. Rabbit lungs were treated with BAY 41-2272, [N.sup.G]-monomethyl-L-arginine (L-NMMA), or NO to evaluate the effects on I/R-induced lung injury. In untreated lungs, a dramatic rise in [K.sub.fc] values and weight gain during reperfusion were observed, and these results were associated with increased ROS production. Both, BAY 41-2272 and L-NMMA significantly attenuated vascular leakage and suppressed ROS release. Additional experiments showed that BAY 41-2272 diminished PMA-induced ROS production by NADPH oxidase. A pharmacological inhibition of the enzyme with consequent reduction in ROS levels decreased I/R injury. NO had only marginal effect on I/R injury. Thus BAY 41-2272 protects against I/R-induced lung injury by interfering with the activation of NADPH oxidases. acute lung injury; nitric oxide; oxidative stress; reactive oxygen species; guanosine 3',5'-cyclic monophosphate

Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine involved in acute lung injury and other processes such as wound repair and tumor growth. MIF exerts pro-proliferative effects on a variety of cell types including monocytes/macrophages, B cells, and gastric epithelial cell lines through binding to the major histocompatibility complex type II-associated invariant chain, CD74. In acute lung injury, inflammatory damage of the alveolar epithelium leads to loss of type I alveolar epithelial cells (AEC-I), which are replaced by proliferation and differentiation of type II alveolar epithelial cells (AEC-II). In this study we have investigated the potential of MIF to contribute to alveolar repair by stimulating alveolar epithelial cell proliferation. We show that routine AEC-II, but not AEC-I, express high surface levels of CD74 in vivo. Culture of AEC-II in vitro resulted in decreased mRNA levels for CD74 and loss of surface CD74 expression, which correlated with a transition of AEC-II to an AEC-I-like phenotype. MIF stimulation of AEC-II induced rapid and prolonged phosphorylation of ERK1/2 and Akt, increased expression of cyclins D1 and E, as well as AEC-II proliferation. Corresponding MIF signaling and enhanced thymidine incorporation was observed after MIF stimulation of MLE-12 cells transfected to overexpress CD74. In contrast, MIF did not induce MAPK activation, gene transcription, or increased proliferation in differentiated AEC-I-like cells that lack CD74. These data suggest a previously unidentified role of MIF-CD74 interaction by inducing proliferation of AEC-II, which may contribute to alveolar repair. lung; epithelial proliferation; resolution of inflammation; macrophage migration inhibitory factor

Lung fibrosis is characterized by increased deposition of ECM, especially collagens, and enhanced proliferation of fibroblasts. L-arginine is a key precursor of nitric oxide, asymmetric dimethylarginine, and proline, an amino acid enriched in collagen. We hypothesized that L-arginine metabolism is altered in pulmonary fibrosis, ultimately affecting collagen synthesis. Expression analysis of key enzymes in the arginine pathway, protein arginine methyltransferases (Prmt), arginine transporters, and arginases by quantitative (q) RT-PCR and Western blot revealed significant upregulation of arginase-1 and -2, but not Prmt or arginine transporters, during bleomycin-induced pulmonary fibrosis in mice. HPLC revealed a concomitant, time-dependent decrease in pulmonary L-arginine levels. Arginase-1 and -2 mRNA and protein expression was increased in primary fibroblasts isolated from bleomycin-treated mice, compared with controls, and assessed by qRT-PCR and Western blot analysis. TGF-[beta]1, a key profibrotic mediator, induced arginase-1 and -2 mRNA expression in primary and NIH/3T3 fibroblasts. Treatment of fibroblasts with the arginase inhibitor, [N.sup.G]-hydroxy-L-arginine, attenuated TGF-[beta]1-stimulated collagen deposition, but not collagen mRNA expression or Smad signaling, in fibroblasts. In human lungs derived from patients with idiopathic pulmonary fibrosis, arginase activity was unchanged, but arginase-1 expression significantly decreased when compared with donor lungs. Our results thus demonstrate that arginase-1 is expressed and functionally important for collagen deposition in lung fibroblasts. TGF-[beta]1-induced upregulation of arginase-1 suggests an interplay between profibrotic agents and L-arginine metabolism during the course of lung fibrosis in the mouse, whereas species-specific regulatory mechanisms may account for the differences observed in mouse and human. lung fibrosis; fibroblasts; collagen

Prematurely born infants who require oxygen therapy often develop bronchopulmonary dysplasia (BPD), a debilitating disorder characterized by pronounced alveolar hypoplasia. Hyperoxic injury is believed to disrupt critical signaling pathways that direct lung development, causing BPD. We investigated the effects of normobaric hyperoxia on transforming growth factor (TGF)-[beta] and bone morphogenetic protein (BMP) signaling in neonatal C57BL/6J mice exposed to 21% or 85% [O.sub.2] between postnatal days P1 and P28. Growth and respiratory compliance were significantly impaired in pups exposed to 85% [O.sub.2], and these pups also exhibited a pronounced arrest of alveolarization, accompanied by dysregulated expression and localization of both receptor (ALK-1, ALK-3, ALK-6, and the TGF-[beta] type II receptor) and Smad (Smads 1, 3, and 4) proteins. TGF-[beta] signaling was potentiated, whereas BMP signaling was impaired both in the lungs of pups exposed to 85% [O.sub.2] as well as in MLE-12 mouse lung epithelial cells and NIH/3T3 and primary lung fibroblasts cultured in 85% [O.sub.2]. After exposure to 85% [O.sub.2], primary alveolar type II cells were more susceptible to TGF-[beta]-induced apoptosis, whereas primary pulmonary artery smooth muscle cells were unaffected. Exposure of primary lung fibroblasts to 85% [O.sub.2] significantly enhanced the TGF-[beta]-stimulated production of the [[alpha].sub.i] subunit of type I collagen (I[[alpha].sub.1]), tissue inhibitor of metalloproteinase- 1, tropoelastin, and tenascin-C. These data demonstrated that hyperoxia significantly affects TGF-[beta]/BMP signaling in the lung, including processes central to septation and, hence, alveolarization. The amenability of these pathways to genetic and pharmacological manipulation may provide alternative avenues for the management of BPD. lung development; transforming growth factor-[beta]; bone morphogenetic protein; neonatal chronic lung disease; alveolarization

The CC chemokine ligand-2 (CCL2) and its receptor CCR2 are essential for monocyte trafficking under inflammatory conditions. However, the mechanisms that determine the intensity and duration of alveolar monocyte accumulation in response to CCL2 gradients in inflamed lungs have not been resolved. To determine the potential role of CCR2-expressing monocytes in regulating alveolar CCL2 levels, we compared leukocyte recruitment kinetics and alveolar CCL2 levels in wild-type and CCR2-deficient mice in response to intratracheal LPS challenge. In wild-type mice, LPS elicited a dose- and time-dependent alveolar monocyte accumulation accompanied by low CCL2 levels in bronchoalveolar lavage fluid (BALF). In contrast, LPS-treated CCR2-deficient mice lacked alveolar monocyte accumulation, which was accompanied by relatively high CCL2 levels in BALF. Similarly, wild-type mice that were treated systemically with the blocking anti-CCR2 antibody MC21 completely lacked LPS-induced alveolar monocyte trafficking that was associated with high CCL2 levels in BALF. Intratracheal application of anti-CCR2 antibody MC21 to locally block CCR2 on both resident and recruited cells did not affect LPS-induced alveolar monocyte trafficking but led to significantly increased BALF CCL2 levels. Reciprocally bone marrow-transplanted, LPS-treated wild-type and CCR2-deficient mice showed a strict inverse relationship between alveolar monocyte recruitment and BALF CCL2 levels. In addition, freshly isolated human and mouse monocytes were capable of integrating CCL2 in vitro. LPS-induced alveolar monocyte accumulation is accompanied by monocytic CCR2-dependent consumption of CCL2 levels in the lung. This feedback loop may limit the intensity of monocyte recruitment to inflamed lungs and play a role in the maintenance of homeostasis. macrophage: neutrophil; chemokine regulation; leukocyte traffic

Hypoxic pulmonary vasoconstriction (HPV) matches lung perfusion to ventilation for optimizing pulmonary gas exchange. Chronic alveolar hypoxia results in vascular remodeling and pulmonary hypertension. Previous studies have reported conflicting results of the effect of chronic alveolar hypoxia on pulmonary vasoreactivity and the contribution of nitric oxide (NO), which may be related to species and strain differences as well as to the duration of chronic hypoxia. Therefore, we investigated the impact of chronic hypoxia on HPV in rabbits, with a focus on lung NO synthesis. After exposure of the animals to normobaric hypoxia (10% [O.sub.2]) for 1 day to 10 wk, vascular reactivity was investigated in ex vivo perfused normoxic ventilated lungs. Chronic hypoxia induced right heart hypertrophy and increased normoxic vascular tone within weeks. The vasoconstrictor response to an acute hypoxic challenge was strongly downregulated within 5 days, whereas the vasoconstrictor response to the thromboxane mimetic U-46619 was maintained. The rapid downregulation of HPV was apparently not linked to changes in the lung vascular NO system, detectable in the exhaled gas and by pharmacological blockage of NO synthesis. Treatment of the animals with long-term inhaled NO reduced right heart hypertrophy and partially maintained the reactivity to acute hypoxia, without any impact on the endogenous NO system being noted. We conclude that chronic hypoxia causes rapid downregulation of acute HPV as a specific event, preceding the development of major pulmonary hypertension and being independent of the lung vascular NO system. Long-term NO inhalation partially maintains the strength of the hypoxic vasoconstrictor response. isolated lung; pulmonary hypertension; right heart failure; inhaled nitric oxide

Incorporation of pulmonary surfactant into fibrin inhibits its plasmic degradation. In the present study we investigated the influence of surfactant proteins (SP)-A, SP-B, and SP-C on the fibrinolysis-inhibitory capacity of surfactant phospholipids. Plasmin-induced fibrinolysis was quantifed by means of a [sup.125]I-fibrin plate assay, and surfactant incorporation into polymerizing fibrin was analyzed by measuring the incorporation of [sup.3]H-labeled L-[alpha]-dipalmitoylphosphatidylcholine into the insoluble clot material. Incorporation of a calf lung surfactant extract (Alveofact) and an organic extract of natural rabbit large surfactant aggregates (LSA) into a fibrin clot revealed a stronger inhibitory effect on plasmic cleavage of this clot than a synthetic phospholipid mixture (PLX) and unprocessed LSA. Reconstitution of PLX with SP-B and SP-C increased, whereas reconstitution with SP-A decreased, the fibrinolysis-inhibitory capacity of the phospholipids. The SP-B effect was paralleled by an increased incorporation of phospholipids into fibrin. We conclude that the inhibitory effect of surfactant incorporation into polymerizing fibrin on its susceptibility to plasmic cleavage is enhanced by SP-B and SP-C but reduced by SP-A. In the case of SP-B, increased phospholipid incorporation may underlie this finding. hyaline membrane; coagulation; pulmonary surfactant; surfactant protein; acute respiratory distress syndrome; fibrosis

Monocyte-endothelium interaction is a fundamental process in many acute and chronic inflammatory diseases. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are fish oil-derived alternative ([omega]-3) precursor fatty acids implicated in the suppression of inflammatory events. We investigated their influence on rolling and adhesion of monocytes to human umbilical vein endothelial cells (HUVEC) under laminar flow conditions in vitro. Exposure of HUVEC to tumor necrosis factor (TNF-[alpha]) strongly increased 1) surface expression of intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), and E-selectin, 2) platelet-activating factor (PAF) synthesis as assessed by thrombin challenge, and 3) rate of rolling and adhesion of monocytes. Preincubation of HUVEC with EPA or DHA markedly suppressed PAF synthesis, monocyte rolling, and adherence, whereas expression of endothelial adhesion molecules was unchanged. Also, PAF receptor antagonists markedly suppressed the adhesion rate of monocytes, and EPA or DHA revealed no additional inhibitory capacity. In contrast, arachidonic acid partially reversed the effect of the antagonist. We conclude that [omega]-3 fatty acids suppress rolling and adherence of monocytes on activated endothelial cells in vitro by affecting endothelial PAF generation. eicosapentaenoic acid; arachidonic acid; adhesion molecules; leukocytes; platelet-activating factor

Intratracheal instillation of the monocyte chemoattractant JE/monocyte chemoattractant protein (MCP)-1 in mice was recently shown to cause increased alveolar monocyte accumulation in the absence of lung inflammation, whereas combined JE/MCP-1/lipopolysaccharide (LPS) challenge provoked acute lung inflammation with early alveolar neutrophil and delayed alveolar monocyte influx. We evaluated the role of resident alveolar macrophages (rAM) in these leukocyte recruitment events and related phenomena of lung inflammation. Depletion of rAM by pretreatment of mice with liposomal clodronate did not affect the JE/MCP-1-driven alveolar monocyte accumulation, despite the observation that rAM constitutively expressed the JE/ MCP-1 receptor CCR2, as analyzed by flow cytometry and immunohistochemistry. In contrast, depletion of rAM largely suppressed alveolar cytokine release as well as neutrophil and monocyte recruitment profiles upon combined JE/MCP-1/LPS treatment. Despite this strongly attenuated alveolar inflammatory response, increased lung permeability was still observed in rAM-depleted mice undergoing JE/MCP-1/LPS challenge. Lung leakage was abrogated by codepletion of circulating neutrophils or administration of anti-CD18. Collectively, rAM are not involved in JE/MCP-1-driven alveolar monocyte recruitment in noninflamed lungs but largely contribute to the alveolar cytokine response and enhanced early neutrophil and delayed monocyte influx under inflammatory conditions (JE/MCP-1/LPS deposition). Loss of lung barrier function observed under these conditions is rAM independent but involves circulating neutrophils via [[beta].sub.2]-integrin engagement. monocyte; neutrophil; vascular permeability; lung; inflammation; depletion

The role of polymorphonuclear neutrophils (PMN) in septic myocardial dysfunction is presently unknown. Staphylococcus aureus infections are frequently associated with septic sequelae. Therefore, we perfused isolated rat hearts with low doses of [alpha]-toxin, the major staphylococcal exotoxin, followed by application of human PMN, N-formyl-methionyl-leucyl-phenylalanine, and arachidonic acid. In contrast to shamperfused hearts (no [alpha]-toxin), a rise in coronary perfusion pressure (CPP) and a reduction of contractile function were noted, and cardiac expression of intercellular adhesion molecule (ICAM)-1 was detected by immunohistochemical methods and real-time PCR. Histological analysis and myeloperoxidase activity indicated cardiac PMN accumulation in [alpha]-toxin-challenged hearts. Major quantities of cysteinyl (cys)-leukotrienes (LT), [LTB.sub.4], and 5-hydroxyeicosatetraenoic acid (5-HETE) were found in the perfusate of [alpha]-toxin-exposed hearts. With an anti-ICAM-1 antibody, neutrophil accumulation, leukotriene (LT) synthesis, coronary vasoconstriction, and the accompanying cardiodepression were suppressed. Similarly, the lipoxygenase inhibitor MK-886 blocked LT synthesis and maintained cardiac function. We conclude that low-dose [alpha]-toxin provokes coronary endothelial ICAM-1 expression and neutrophil accumulation, with subsequent synthesis of cys-LTs, [LTB.sub.4], and 5-HETE under conditions of appropriate stimulation. This response is linked with coronary vasoconstriction and contractile dysfunction, with cys-LT synthesis and maldistribution of perfusion offered as likely underlying mechanisms. bacterial exotoxins; septic heart dysfunction; neutrophil mediators

Mediator generation and signaling events in alveolar epithelial cells attacked by S. aureus [alpha]-toxin. Am J Physiol Lung Cell Mol Physiol 282: L207-L214, 2002; 10.1152/ajplung.00156.2001.--Staphylococcus aureus [alpha]-toxin is a pore-forming bacterial exotoxin that has been implicated as a significant virulence factor in human staphylococcal diseases. In primary cultures of rat pneumocyte type II cells and the human A549 alveolar epithelial cell line, purified [alpha]-toxin provoked rapid-onset phosphatidylinositol (PtdIns) hydrolysis as well as liberation of nitric oxide and the prostanoids PG[E.sub.2], PG[I.sub.2], and thromboxane [A.sub.2]. In addition, sustained upregulation of proinflammatory interleukin (IL)-8 mRNA expression and protein secretion occurred. 'Priming' with low-dose IL-[1.sub.[beta]] markedly enhanced the IL-8 response to [alpha]-toxin, which was then accompanied by IL-6 appearance. The cytokine response was blocked by the intracellular [Ca.sup.2+]-chelating reagent 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, the protein kinase C inhibitor bis-indolyl maleimide I, as well as two independent inhibitors of nuclear factor-[kappa]B activation, pyrrolidine dithiocarbamate and caffeic acid phenethyl ester. We conclude that alveolar epithelial cells are highly reactive target cells of staphylococcal [alpha]-toxin. [alpha]-Toxin pore-associated transmembrane [Ca.sup.2+] flux and PtdIns hydrolysis-related signaling with downstream activation of protein kinase C and nuclear translocation of nuclear factor-[kappa]B are suggested to represent important underlying mechanisms. Such reactivity of the alveolar epithelial cells may be relevant for pathogenic sequelae in staphylococcal lung disease. Staphylococcus aureus; sepsis; inflammation

Schermuly, Ralph Theo, Axel Roehl, Norbert Weissman, Hossein Ardeschir Ghofrani, Hanno Leuchte, Friedrich Grimminger, Werner Seeger, and Dieter Walmrath. Combination of nonspecific PDE inhibitors with inhaled prostacyclin in experimental pulmonary hypertension. Am J Physiol Lung Cell Mol Physiol281: L1361-L1368, 2001.--Inhalation of aerosolized prostacyclin (PG[I.sub.2]) exerts selective pulmonary vasodilation, but its effect is rapidly lost after termination of nebulization. Amplification of the vasodilatory response to inhaled PG[I.sub.2] might be achieved by phosphodiesterase (PDE) inhibitors to stabilize its second messenger, cAMP. We established stable pulmonary hypertension in perfused rabbit lungs by continuous infusion of U-46619. Short-term (10-min) aerosolization maneuvers of PG[I.sub.2] effected a rapid, moderate decrease in pulmonary arterial pressure, with post-PGI2 vasorelaxation being lost within 10-15 min, accompanied by a marginal reduction in shunt flow. Preceding administration of subthreshold doses of the PDE inhibitors theophylline, dipyridamole, and pentoxifylline via the intravascular or inhalational route, which per se did not influence pulmonary hemodynamics, caused more than doubling of the immediate pulmonary arterial pressure drop in response to PG[.I.sub.2] and marked prolongation of the post-PGI2 vasorelaxation to >60 min (all PDE inhibitors tors via both routes of application). This was accompanied by a reduction in shunt flow in the case of aerosolized theophylline (27.5%), pentoxifylline (30.5%), and dipyridamole (33.4%). Coaerosolization of PG[I.sub.2] and PDE inhibitors may be considered as a therapeutic strategy in pulmonary hypertension. gas exchange; multiple inert gas elimination technique; diphridamole; pentoxifylline; theophylline; shunt flow; U-46619; ventilation-perfusion ratio; ventilation-perfusion mismatch Received 23 March 2000; accepted in final form 1 August 2001

A study was conducted to analyze the function of protein kinase C in hypoxic vasoconstriction in rabbit lungs. The lungs were lavaged with 50-ml ashes with endotoxin-free saline. The lavage fluid was then centrifuged at 200 g for 10 min at room temperature. Results indicated that the activation of protein kinase C is involved in the transduction pathway directing pulmonary vasoconstriction based on alveolar hypoxia.

Sex-dependent differences in immunity and coagulation play an active role in the outcome of community-acquired pneumonia (CAP). Contact phase proteins act at the crossroads between inflammation and coagulation thus representing a point of convergence in host defense against infection. Here, we measured the levels of factor XII (FXII), FXIIa-C1 esterase inhibitor (C1INH) complexes, and high-molecular-weight kininogen (HK) in plasma of patients with CAP and correlated them to clinical disease severity. Levels of FXIIa-C1INH/albumin ratio were elevated, irrespective of sex, in plasma of patients with CAP (n = 139) as compared with age-matched donors (n = 58). No simultaneous decrease in FXII levels, indicating its consumption, was observed. Stratification by sex revealed augmented FXII levels in plasma of women with CAP as compared with sex-matched donors yet no apparent differences in men. This sex-specific effect was, however, attributable to lower FXII levels in female donors relative to men donors. Plasma estradiol levels mirrored those for FXII. Levels of HK/albumin ratio were decreased in CAP plasma as compared with donors, however, after stratification by sex, this difference was only observed in women and was related to higher HK/albumin values in female donors as opposed to male donors. Finally, strong negative correlation between plasma levels of HK/albumin ratio and CAP severity, as assessed by CRB65 score, in males and females was observed. Our study identifies sex-dependent differences in plasma levels of the contact phase proteins in elderly subjects that may contribute to specific clinical outcomes in CAP between men and women. [ABSTRACT FROM AUTHOR]

Research was conducted to examine the hypothesis that nitro blue tetrazolium inhibits but does not mimic hypoxic vasoconstriction (HPV) in isolated rabbit lungs. The influence of three superoxide scavengers, superoxide dismutase, 4,5-dihydroxy-1,3-benzene disulfonic acid and nitroblue tetrazolium, and a catalase inhibitor was analyzed. The study supports an important role for superoxide in the basic mechanism of HPV. However, it questions the idea that loss of tonic vasorelaxation through this pathway is the underlying event in rabbit lungs.

A flow cytometric technique for the purification of alveolar macrophages (AM) was developed by utilizing bronchoalveolar lavage (BAL) of patients with acute lung inflammation. The flow cytometric technique involved the separation of AM according BAL samples based on their scatter and autofluorescence characteristics. Furthermore, the isolated AMs retained their ability for tumor necrosis factor-alpha gene expression.

Endotoxin induces the liberation of tumor necrosis factor-alpha (TNF-alpha) in the intravascular and alveolar compartments of rabbit lungs. The introduction of endotoxin into the alveolar compartments produces an increase in alveolar TNF-alpha but hardly any in the vascular space. The release of TNF-alpha is compartmentalized till the physiological barrier properties are retained. The response increases many times with small amounts of serum. Vascular pressures and lung vascular permeability are, however, unaffected.

Administration of the two- and three-series prostanoid precursor, arachidonic acid (AA), and Escherichia coli hemolysin (HlyA) to buffer-perfused rabbit lung models increases pulmonary arterial pressure (PAP) and the release of thromboxane (Tx) B2. The prostanoid precursor, eicosapentaenoic acid (EPA), with HlyA also increases PAP but the increase is less than that caused by AA-HlyA. EPA also stimulates the release of similar amounts of TxB2 and TxB3 and the conversion of EPA to TxA3 is slower than that of AA to TxA2. The vasoconstriction effects of AA and EPA, which cause Tx-mediated pulmonary hypertension are inhibited by the antagonist of the Tx receptor. AA is a two-magnitude greater potent provoker of Tx-mediated pulmonary hypertension than EPA.

A flow cytometric method based on the use of the red fluorescent dye carboxy-SNARF 2-AM for labeling yeast facilitates analysis of phagocytosis of viable Candida albicans by human and rabbit alveolar macrophages. The technique yields a relative index of the mean cellular intake of yeast and allows differentiation of subsets of nonphagocytosing and phagocytosing macrophages.

Computer-assisted morphometric analysis of the washout kinetics of various pulmonary intracapillary leukocytes pools in ex vivo-perfused rabbit lungs shows that half of the leukocyte types reside in the lung microvasculature even after high extracorporeal buffer perfusion. Cells with large pool size influence the basic characteristics of isolated-perfused and transplanted lungs.

Fibrinogen (fbg) leaks into the alveolar space under the influence of various mechanisms when the surroundings are inflammatory. Contamination is prevented by using different synthetic phospholipid mixtures which are based on apoproteins. Contamination may be caused by fibrinolytic activators or preventors. These surfactants prevent the cleavage of the plasma by a distinct dependence on the dose, according to the concentration of the apoproteins in them. The intermediate and terminal cleavage products are seen serially when the plasmin is influenced by Fbg during incubation.

Mayer, Konstantin, Martina Merfels, Marion Muhly Reinholz, Stephanie Gokorsch, Simone Rosseau, Jiirgen Lohmeyer, Nicole Schwarzer, Matthias Kriill, Norbert Suttorp, Friedrich Grimminger, and Werner Seeger.[omega] -3 Fatty acids suppress monocyte adhesion to human endothelial cells: role of endothelial PAF generation. Am J Physiol Heart Circ Physiol 283: H811-818, 2003; 10.1152/ ajpheart.00235.2002.-Monocyte-endothelium interaction is a fundamental process in many acute and chronic inflammatory diseases. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are fish oil-derived alternative ([omega]-3) precursor fatty acids implicated in the suppression of inflammatory events. We investigated their influence on rolling and adhesion of monocytes to human umbilical vein endothelial cells (HUVEC) under laminar flow conditions in vitro. Exposure of HUVEC to tumor necrosis factor (TNF-[alpha]) strongly increased 1) surface expression of intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), and E-selectin, 2) platelet-activating factor (PAF) synthesis as assessed by thrombin challenge, and 3) rate of rolling and adhesion of monocytes. Preincubation of HUVEC with EPA or DHA markedly suppressed PAF synthesis, monocyte rolling, and adherence, whereas expression of endothehal adhesion molecules was unchanged. Also, PAF receptor antagonists markedly suppressed the adhesion rate of monocytes, and EPA or DHA revealed no additional inhibitory capacity. In contrast, arachidonic acid partially reversed the effect of the antagonist. We conclude that [omega]-3 fatty acids suppress rolling and adherence of monocytes on activated endothelial cells in vitro by affecting endothelial PAF generation.

The severity of coronavirus disease 2019 (COVID-19) is linked to an increasing number of risk factors, including exogenous (environmental) stimuli such as air pollution, nicotine, and cigarette smoke. These three factors increase the expression of angiotensin I converting enzyme 2 (ACE2), a key receptor involved in the entry of severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2)--the etiological agent of COVID-19--into respiratory tract epithelial cells. Patients with severe COVID-19 are managed with oxygen support, as are at-risk individuals with chronic lung disease. To date, no study has examined whether an increased fraction of inspired oxygen (FiO2) may affect the expression of SARS-CoV-2 entry receptors and co-receptors, including ACE2 and the transmembrane serine proteases TMPRSS1, TMPRSS2, and TMPRSS11D. To address this, steady-state mRNA levels for genes encoding these SARS-CoV-2 receptors were assessed in the lungs of mouse pups chronically exposed to elevated FiO2, and in the lungs of preterm-born human infants chronically managed with an elevated FiO2. These two scenarios served as models of chronic elevated FiO2 exposure. Additionally, SARS-CoV-2 receptor expression was assessed in primary human nasal, tracheal, esophageal, bronchial, and alveolar epithelial cells, as well as primary mouse alveolar type II cells exposed to elevated oxygen concentrations. While gene expression of ACE2 was unaffected, gene and protein expression of TMPRSS11D was consistently upregulated by exposure to an elevated FiO2. These data highlight the need for further studies that examine the relative contribution of the various viral co-receptors on the infection cycle, and point to oxygen supplementation as a potential risk factor for COVID-19. [ABSTRACT FROM AUTHOR]

Alveolar epithelial barrier functions in ventilated perfused rabbit lungs. Am J Physiol Lung Cell Mol Physiol 280: L896-L904, 2001.--We employed ultrasonic nebulization for homogeneous alveolar tracer deposition into ventilated perfused rabbit lungs. [sup.22]Na and [sup.125]I-albumin transit kinetics were monitored on-line with gamma detectors placed around the lung and the perfusate reservoir. [[sup.3]H]mannitol was measured by repetitive counting of perfusion fluid samples. Volume of the alveolar epithelial lining fluid was estimated with bronchoalveolar lavage with sodium-free isosmolar mannitol solutions. Sodium clearance rate was -2.2 [+ or -] 0.3%/min. This rate was significantly reduced by preadministration of ouabain/amiloride and enhanced by pretreatment with aerosolized terbutaline. The [sup.125]I-albumin clearance rate was -0.40 [+ or -] 0.05%/min. The appearance of [[sup.3]H]mannitol in the perfusate was not influenced by ouabain/amiloride or terbutaline but was markedly enhanced by pretreatment with aerosolized protamine. An epithelial lining fluid volume of 1.22 [+ or -] 0.21 ml was calculated in control lungs. Fluid absorption rate was 1.23 [micro]l [multiplied by] g lung [weight.sup.-1] [multiplied by] [min.sup.-1], which was blunted after pretreatment with ouabain/amiloride. We conclude that alveolar tracer loading by aerosolization is a feasible technique to assess alveolar epithelial barrier properties in aerated lungs. Data on active and passive sodium flux, paracellular solute transit, and net fluid absorption correspond well to those in previous studies in fluid-filled lungs; however, albumin clearance rates were markedly higher in the currently investigated aerated lungs. amiloride; epithelial lining fluid; ion channel; ouabain; protamine; protein clearance

Schermuly, Ralph Theo, Andreas Gunther, Monika Ermert, Leander Ermert, Hossein Ardeschir Ghofrani, Norbert Weissmann, Friedrich Grimminger, Werner Seeger, and Dieter Walmrath. Conebulization of surfactant and urokinase restores gas exchange in perfused lungs with alveolar fibrin formation. Am J Physiol Lung Cell Mol Physiol 280: L792-L800, 2001.--Alveolar fibrin generation has been suggested to possess strong surfactant-inhibitory potency. In perfused rabbit lungs, fibrin formation in the alveolar space was induced by sequential ultrasonic aerosolization of fibrinogen and thrombin, and the efficacy of rescue administration of surfactant and urokinase was investigated. Ventilation-perfusion (VA/Q) distribution was assessed by the multiple inert gas elimination technique. Aerosolization of fibrinogen (~20 mg/kg body wt) increased shunt flow to ~7%. Sequential nebulization of fibrinogen and thrombin (1.3 U/kg body wt) caused alveolar fibrin deposition, documented immunohistologically, and provoked marked shunt flow, progressing to ~22% at the end of the experiments. The hemodynamics were virtually unchanged. Rescue aerosolization of natural bovine surfactant (15 mg/kg body wt) or urokinase-type plasminogen activator (4,500 U/kg body wt), undertaken after fibrin formation, improved gas exchange but progressive shunt flow still occurred (efficacy, surfactant [is greater than] urokinase). In contrast, conebulization of surfactant and urokinase reversed shunt flow to ~7%, with an increased appearance of normal VA/Q matching. We conclude that alveolar fibrin formation is a potent surfactant-inhibitory mechanism in intact lungs, provoking severe VA/Q mismatch with a predominance of shunt flow, and that rescue aerosolization of surfactant plus urokinase may offer restoration of gas exchange under these conditions. urokinase-type plasminogen activator; thrombin; fibrinogen; shunt flow; aerosolization; ventilation-perfusion ratio

Weissmann, Norbert, Stefan Winterhalder, Matthias Nollen, Robert Voswinckel, Karin Quanz, Hossein Ardeschir Ghofrani, Ralph Theo Schermuly, Werner Seeger, and Friedrich Grimminger. NO and reactive oxygen species are involved in biphasic hypoxic vasoconstriction of isolated rabbit lungs. Am J Physiol Lung Cell Mol Physiol 280: L638-L645, 2001.--Hypoxic pulmonary vasoconstriction (HPV) matches lung perfusion with ventilation but may also result in chronic pulmonary hypertension. It has not been clarified whether acute HPV and the response to prolonged alveolar hypoxia are triggered by identical mechanisms. We characterized the vascular response to sustained hypoxic ventilation (3% [O.sub.2] for 120-180 min) in isolated rabbit lungs. Hypoxia provoked a biphasic increase in pulmonary arterial pressure (PAP). Persistent PAP elevation was observed after termination of hypoxia. Total blockage of lung nitric oxide (NO) formation by [N.sup.G]-monomethyl-L-arginine caused a two- to threefold amplification of acute HPV, the sustained pressor response, and the loss of posthypoxic relaxation. This amplification was only moderate when NO formation was partially blocked by the inducible NO synthase inhibitor S-methylisothiourea. The superoxide scavenger nitro blue tetrazolium and the superoxide dismutase inhibitor triethylenetetramine reduced the initial vasoconstrictor response, the prolonged PAP increase, and the loss of posthypoxic vasorelaxation to a similar extent. The NAD(P)H oxidase inhibitor diphenyleneiodonium nearly fully blocked the late vascular responses to hypoxia in a dose that effected a decrease to half of the acute HPV. In conclusion, as similarly suggested for acute HPV, lung NO synthesis and the superoxide-hydrogen peroxide axis appear to be implicated in the prolonged pressor response and the posthypoxic loss of vasorelaxation in perfused rabbit lungs undergoing 2-3 h of hypoxic ventilation. hypoxic pulmonary vasoconstriction; pulmonary hypertension; nitric oxide

Monocytes recruited into the alveolar air space of mice show a monocytic phenotype but upregulate CD14. Am J Physiol Lung Cell Mol Physiol 280: L58-L68, 2001.--The evaluation of monocytes recruited into the alveolar space under both physiological and inflammatory conditions is hampered by difficulties in discriminating these cells from resident alveolar macrophages (rAMs). Using the intravenous injected fluorescent dye PKH26, which accumulated in rAMs without labeling blood leukocytes, we developed a technique that permits the identification, isolation, and functional analysis of monocytes recruited into lung alveoli of mice. Alveolar deposition of murine JE, the homologue of human monocyte chemoattractant protein (MCP)-1 (JE/MCP-1), in mice provoked an alveolar influx of monocytes that were recovered by bronchoalveolar lavage and separated from PKH26-stained rAMs by flow cytometry. Alveolar recruited monocytes showed a blood monocytic phenotype as assessed by cell surface expression of F4/80, CD11a, CD11b, CD18, CD49d, and CD62L. In contrast, CD14 was markedly upregulated on alveolar recruited monocytes together with increased tumor necrosis factor-[Alpha] message, discriminating this monocyte population from peripheral blood monocytes and rAMs. Thus monocytes recruited into the alveolar air space of mice in response to JE/MCP-1 keep phenotypic features of blood monocytes but upregulate CD14 and are 'primed' for enhanced responsiveness to endotoxin with increased cytokine expression. monocyte chemoattractant protein-1; alveolar macrophage; fluorescent dye; flow cytometry

Weissmann, Norbert, Andre Tadic, Jorg Hanze, Frank Rose, Stefan Winterhalder, Matthias Nollen, Ralph Theo Schermuly, Hossein Ardeschir Ghofrani, Werner Seeger, and Friedrich Grimminger. Hypoxic vasoconstriction in intact lungs: a role for NADPH oxidase-derived [H.sub.2][O.sub.2]? Am J Physiol Lung Cell Mol Physiol 279: L683-L690, 2000.--Hypoxic pulmonary vasoconstriction (HPV) matches lung perfusion with ventilation. Controversy exists whether decreased or increased reactive oxygen species may elicit HPV and from which source such oxygen metabolites are derived. In rabbit lungs, we detected transcripts of a nonphagocytic NADPH oxidase subunit homologous to mitogenic oxidase-1 (Mox1) or NADPH oxidase homolog 1 (NOH-1L). In perfused rabbit lungs, we employed 1) a new NADPH oxidase inhibitor [4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF; 100-600 [micro]M)] and 2) the superoxide dismutase (SOD) inhibitors diethyldithiocarbamic acid (DETC; 100 [micro]M to 10 mM) and triethylenetetramine (TETA; 1-25 mM). Specificity of these agents for HPV was investigated by comparison with U-46619-induced vasoconstrictions. AEBSF induced a transient increase in pulmonary arterial pressure with increased strength of HPV. Subsequent to this initial response, normoxic pulmonary arterial pressure was not affected and HPV was specifically suppressed. Whereas DETC turned out to act in a nonspecific fashion, TETA suppressed HPV specifically. These findings provide evidence of a role for a nonphagocytic NAD(P)H oxidase with superoxide and SOD-related hydrogen peroxide formation in HPV. Because HPV was inhibited but not mimicked by the inhibitors, increased rather than decreased superoxide and/or hydrogen peroxide formation is suggested as the hypoxia-provoked signaling event. hypoxic pulmonary vasoconstriction; isolated lung; 4-(2-aminoethyl)benzenesulfonyl fluoride; reduced nicotinamide adenine dinucleotide phosphate oxidase; superoxide dismutase; hydrogen peroxide

The PDE inhibitor zaprinast enhances NO-mediated protection against vascular leakage in reperfused lungs. Am J Physiol Lung Cell Mol Physiol 279: L496-L502, 2000.--Disruption of endothelial barrier properties with development of noncardiogenic pulmonary edema is a major threat in lung ischemiareperfusion (I/R) injury that occurs under conditions of lung transplantation. Inhaled nitric oxide (NO) reduced vascular leakage in lung I/R models, but the efficacy of this agent may be limited. We coadministered NO and zaprinast, a cGMP-specific phosphodiesterase inhibitor, to further augment the NO-cGMP axis. Isolated, buffer-perfused rabbit lungs were exposed to 4.5 h of warm ischemia. Reperfusion provoked a transient elevation in pulmonary arterial pressure and a negligible rise in microvascular pressure followed by a massive increase in the capillary filtration coefficient and severe lung edema formation. Inhalation of 10 parts/million of NO or intravascular application of 100 [micro]M zaprinast on reperfusion both reduced pressor response and moderately attenuated vascular leakage. Combined administration of both agents induced no additional vasodilation at constant microvascular pressures, but additively protected against capillary leakage paralleled by a severalfold increase in perfusate cGMP levels. In conclusion, combining low-dose NO inhalation and phosphodiesterase inhibition may be suitable for the maintenance of graft function in lung transplantation by amplifying the beneficial effect of the NO-cGMP axis and avoiding toxic effects of high NO doses. phosphodiesterase; nitric oxide; lung transplantation; cyclic nucleotides; microvascular permeability

Phenotypic characterization of alveolar monocyte recruitment in acute respiratory distress syndrome. Am J Physiol Lung Cell Mol Physiol 279: L25-L35, 2000.--In 49 acute respiratory distress syndrome (ARDS) patients, the phenotype of alveolar macrophages (AMs) was analyzed by flow cytometry. Bronchoalveolar lavage (BAL) was performed within 24 h after intubation and on days 3-5, 9-12, and 18-21 of mechanical ventilation. The [27E10.sup.high]/[CD11b.sup.high]/ [CD71.sup.low]/[25F9.sup.low]/[HLA DR.sup.low]/[RM3/1.sup.low] AM population in the first BAL indicated extensive monocyte influx into the alveolar compartment. There was no evidence of increased local AM proliferation as assessed by nuclear Ki67 staining. Sequential BAL revealed two distinct patient groups. In one, a decrease in 27E10 and CDllb and an increase in CD71, 25F9, HLA DR, and RM3/1 suggested a reduction in monocyte influx and maturation of recruited cells into AMs, whereas the second group displayed sustained monocyte recruitment. In the first BAL from all patients, monocyte chemoattractant protein (MCP)-1 was increased, and AMs displayed elevated MCP-1 gene expression. In sequential BALs, a decrease in MCP-1 coincided with the disappearance of monocyte-like AMs, whereas persistent upregulation of MCP-1 paralleled ongoing monocyte influx. A highly significant correlation between BAL fluid MCP-1 concentration, the predominance of monocyte-like AMs, and the severity of respiratory failure was noted. alveolar macrophages; monocyte chemoattractant protein-1; fluorescence-activated cell sorting; cell surface molecules

Grimminger, Friedrich, Konstantin Mayer, Ladislau Kiss, Dieter Walmrath, and Werner Seeger. PAF-induced synthesis of tetraenoic and pentaenoic leukotrienes in the isolated rabbit lung. Am. J. Physiol. Lung Cell. Mol. Physiol. 278: L268-L275, 2000.--In an isolated rabbit lung model, we tested the hypothesis that platelet-activating factor (PAF)-induced leukotriene (LT) synthesis is critically dependent on the free precursor fatty acid supply and the possible substitution of arachidonic acid (AA) by eicosapentaenoic acid (EPA). To augment the intravascular polymorphonuclear neutrophils (PMNs) in the isolated lung, human PMNs were infused into the pulmonary artery. LTs and hydroxyeicosatetra(penta)enoic acids were quantified with HPLC techniques. Application of PAF (5 [micro]M) or AA(10 [micro]M) provoked the generation of limited quantities of 4-series LTs and 5-hydroxyeicosatetraenoic acid (total sum of 5-lipoxygenase products [approximately equals] 7 and [approximately equals] 27 pmol/ml in lungs both with and without infused PMNs, respectively). Combined administration amplified 5-lipoxygenase product formation, with a predominance of cysteinyl-LT synthesis in lungs both without (total sum [approximately equals] 67 pmol/ml) and, much more strikingly, with (total sum [approximately equals] 308 pmol/ml) an infusion of neutrophils. EPA (10 [micro]M) elicited exclusive generation of 5-series LTs and 5-hydroxyeicosapentaenoic acid (total sum [approximately equals] 82 pmol/ml). Dual stimulation with PAF and EPA provoked amplification of EPA-derived 5-lipoxygenase product formation, again with predominance of cysteinyl-LTs in lungs without (total sum [approximately equals] 224 pmol/ml) and, in particular, with (total sum [approximately equals] 545 pmol/ml) preceding microvascular PMN entrapment. Combined application of PAF, AA, and EPA resulted in the synthesis of LTs derived from both fatty acids, with a predominance of 5-series products. We conclude that the PAF-evoked 5-lipoxygenase product formation in the neutrophil-harboring lung capillary bed is critically dependent on intravascular precursor fatty acid supply, with EPA representing the preferred substrate compared with AA. PMN-related transcellular eicosanoid synthesis is suggested to underlie the predominant generation of cysteinyl-LTs. The supply of n-3 versus n-6 precursor fatty acid may thus hay e a major impact on inflammatory mediator generation. neutrophils; inflammation; lipid mediators; platelet-activating factor

Postnatal lung maturation generates a large number of small alveoli, with concomitant thinning of alveolar septal walls, generating a large gas exchange surface area but minimizing the distance traversed by the gases. This demand for a large and thin gas exchange surface area is not met in disorders of lung development, such as bronchopulmonary dysplasia (BPD) histopathologically characterized by fewer, larger alveoli and thickened alveolar septal walls. Diseases such as BPD are often modeled in the laboratory mouse to better understand disease pathogenesis or to develop new interventional approaches. To date, there have been no stereology-based longitudinal studies on postnatal mouse lung development that report dynamic changes in alveoli number or alveolar septal wall thickness during lung maturation. To this end, changes in lung structure were quantified over the first 22 mo of postnatal life of C57BL/6J mice. Alveolar density peaked at postnatal day (P)39 and remained unchanged at 9 mo (P274) but was reduced by 22 mo (P669). Alveoli continued to be generated, initially at an accelerated rate between P5 and P14, and at a slower rate thereafter. Between P274 and P669, loss of alveoli was noted, without any reduction in lung volume. A progressive thinning of the alveolar septal wall was noted between P5 and P28. Pronounced sex differences were observed in alveoli number in adult (but not juvenile) mice, when comparing male and female mouse lungs. This sex difference was attributed exclusively to the larger volume of male mouse lungs. [ABSTRACT FROM AUTHOR]