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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 alveolar epithelium plays a critical role in resolving pulmonary edema. We thus hypothesized that its function might be upregulated in rats with heart failure, a condition that severely challenges the lung's ability to maintain fluid balance. Heart failure was induced by left coronary artery ligation. Echocardiographic and cardiovascular hemodynamics confirmed its development at 16 wk postligation. At that time, alveolar fluid clearance was measured by an increase in protein concentration over 1 h of a 5% albumin solution instilled into the lungs. Baseline alveolar fluid clearance was similar in heart failure and age-matched control rats. Terbutaline was added to the instillate to determine whether heart failure rats responded to [beta]-adrenoceptor stimulation. Alveolar fluid clearance in heart failure rats was increased by 194% after terbutaline stimulation compared with a 153% increase by terbutaline in control rats. To determine the mechanisms responsible for this accelerated alveolar fluid clearance, we measured ion transporter expression (ENaC, Na-KATPase, CFTR). No significant upregulation was observed for these ion transporters in the heart failure rats. Lung morphology showed significant alveolar epithelial type II cell hyperplasia in heart failure rats. Thus, alveolar epithelial type II cell hyperplasia is the likely explanation for the increased terbutaline-stimulated alveolar fluid clearance in heart failure rats. These data provide evidence for previously unrecognized mechanisms that can protect against or hasten resolution of alveolar edema in heart failure. albumin; terbutaline

Although alveolar wall thinning has been attributed to apoptosis of interstitial lung lipofibroblasts (LFs), the underlying molecular mechanism(s) remains unknown. Although the physiological vitamin D steroid hormone l[alpha],25(OH)2D3 (1,25D) has been suggested as a local paracrine/ autocrine effector of fetal lung maturation and is known to affect fibroblast apoptosis, its effects on LF apoptosis are unknown. We determined the role of 1,25D and its metabolite, C-3-epimer (3-epi-1,25D), on LF and alveolar type H (ATII) cell differentiation, proliferation, and apoptosis. Embryonic day 19 Sprague-Dawley fetal rat lung LFs and ATII cells were treated with 1,25D or 3-epi-1,25D (1 x [10.sup.-10] to 1 x [10.sup.-8] M) for 24 h, and cell proliferation, apoptosis, and differentiation were assessed. Both 1,25D and 3-epi-1,25D exhibited dose-dependent increases in expression of the key homeostatic epithelial-mesenchymal differentiation markers, increased LF and ATII cell proliferation, and decreased apoptosis. Furthermore, rat pups administered 1,25D from postnatal days 0 to 14 showed increased expressions of key LF and ATII cell differentiation markers, increased Bcl-2-to-Bax ratio as an index of decreased spontaneous alveolar LF and ATII cell apoptosis, increased alveolar count, and a paradoxical increase in septal thickness. We conclude that spatial- and temporal-specific actions of vitamin D play a critical role in perinatal lung maturation by stimulating key alveolar epithelial-mesenchymal interactions and by modulating LF proliferation/ apoptosis. These data not only provide the biological rationale for the presence of an alveolar vitamin D paracrine system, but also provide the first integrated molecular mechanism for increased surfactant synthesis and alveolar septal thinning during perinatal lung maturation. lung development

The adenosine [A.sub.2B] receptor ([A.sub.2B]R) has a wide tissue distribution that includes fibroblasts and endothelial and epithelial cells. The recent generation of an [A.sub.2B][R.sup.-/-] mouse constructed with a [beta]-galactosidase ([beta]-gal) reporter gene under control of the endogenous promoter has provided a valuable tool to quantify [A.sub.2B]R promoter activity (29). To determine the sites of expression of the [A.sub.2B] receptor in the mouse lung, histological and flow cytometric analysis of [beta]-gal reporter gene expression in various lung cell populations was performed. The major site of [A.sub.2B]R promoter activity was found to be the type II alveolar epithelial cells (AECs), identified by coexpression of prosurfactant protein C, with relatively less expression in alveolar macrophages, bronchial epithelial cells, and cells of the vasculature. Highly purified type II AECs were prepared by fluorescence-activated sorting of enhanced green fluorescent protein (eGFP)-positive cells from transgenic mice expressing eGFP under control of the surfactant protein C promoter (21). The type II cells expressed 89-fold higher [A.sub.2B]R mRNA than pulmonary leukocytes, and the [A.sub.2B]R was shown to be functional, as treatment of purified type II AECs with the nonspecific adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) induced an increase in intracellular cAMP greater that the [beta]-adrenergic agonist isoproterenol that was inhibited completely following treatment by ATL-802, a novel, highly potent ([K.sub.i] = 8.6 nM), and selective (>900 fold over other adenosine receptor subtypes) antagonist of the mouse [A.sub.2B]R. lung; [beta]-galactosidase; G protein-coupled receptor; cAMP

UTP is known to regulate alveolar fluid clearance. However, the relative contribution of alveolar type I cells and type II cells to this process is unknown. In this study, we investigated the effects of UTP on ion transport in type I-like cell (AEC I) and type II-like cell (AEC II) monolayers. Luminal treatment of cell monolayers with UTP increased short-circuit current ([I.sub.sc]) of AEC II but decreased [I.sub.sc] of AEC I. The CI channel blockers NPPB and DIDS inhibited the UTP-induced changes in [I.sub.sc] ([DELTA]Isc) in both types of cells. Amiloride, an inhibitor of epithelial [Na.sup.+] channels (ENaC), abolished the UTP-induced [DELTA][I.sub.sc]. in AEC I, but not in AEC II. The general blocker of [K.sup.+] channels, Ba[Cl.sub.2], eliminated the UTP-induced [DELTA][I.sub.sc] in AEC II, but not in AEC I. The intermediate conductance ([IK.sub.Ca]) blocker, clofilium, also blocked the UTP effect in AEC II. The signal transduction pathways mediated by UTP were the same in AEC I and AEC II. Furthermore, UTP increased CI- secretion in AEC II and [Cl.sup.-] absorption in AEC I. Our results suggest that UTP induces opposite changes in [I.sub.sc] in AEC I and AEC II, likely due to the reversed [Cl.sup.-] flux and different contributions of ENaC and [IK.sub.Ca]. Our results further imply a new concept that type II cells contribute to UTP-induced fluid secretion and type I cells contribute to UTP-induced fluid absorption in alveoli. short-circuit current; fluid transport

Normal alveolarization has been studied in rodents using detailed morphometric techniques and loss of function approaches for growth factors and their receptors. However, it remains unclear how these growth factors direct the formation of secondary septae. We have previously developed a transgenic mouse model in which expression of a soluble dominant-negative FGF receptor (dnFGFR) in the prenatal period results in reduced alveolar septae formation and subsequent alveolar simplification. Retinoic acid (RA), a biologically active derivative of vitamin A, can induce regeneration of alveoli in adult rodents. In this study, we demonstrate that RA induces alveolar reseptation in this transgenic mouse model and that realveolarization in adult mice is FGF dependent. Proliferation in the lung parenchyma, an essential prerequisite for lung regrowth was enhanced after 14 days of RA treatment and was not influenced by dnFGFR expression. During normal lung development, formation of secondary septae is associated with the transient presence of [alpha]-smooth muscle actin ([alpha]SMA)-positive interstitial myofibroblasts. One week after completion of RA treatment, [alpha]SMA expression was detected in interstitial fibroblasts, supporting the concept that RA-initiated realveolarization recapitulates aspects of septation that occur during normal lung development. Expression of dnFGFR blocked realveolarizafion with increased PDGF receptor-[alpha] (PDGFR[alpha])-positive cells and decreased aSMA-positive cells. Taken together, our data demonstrate that FGF signaling is required for the induction of aSMA in the PDGFR[alpha]-positive myofibroblast progenitor and the progression of alveolar regeneration. transgenic mouse model; interstitial myofibroblast; emphysema; platelet derived growth factor receptor

Several respiratory diseases are associated with extensive damage of lung epithelia, and the regulatory mechanisms involved in their regeneration are not clearly defined. Growth factors released by epithelial cells or fibroblasts from injured lungs are important regulators of alveolar repair by stimulating cell motility, proliferation, and differentiation. In addition, [K.sup.+] channels regulate cell proliferation/migration and are coupled with growth factor signaling in several tissues. We decided to explore the hypothesis, never investigated before, that [K.sup.+] could play a prominent role in alveolar repair. We employed a model of mechanical wounding of rat alveolar type II epithelia, in primary culture, to study their response to injury. Wound healing was suppressed by one-half upon epidermal growth factor (EGF) titration with EGF-antibody (Ab) or erbB1/erbB2 tyrosine-kinase inhibition with AG-1478/AG-825. The addition of exogenous EGF slightly stimulated the alveolar wound healing and enhanced, by up to five times, alveolar cell migration measured in a Boyden-type chamber. Conditioned medium collected from injured alveolar monolayers also stimulated cell migration; this effect was abolished in the presence of EGF-Ab. The impact of [K.sup.+] channel modulators was examined in basal and EGF-stimulated conditions. Wound healing was stimulated by pinacidil, an ATP-dependent [K.sup.+] channel ([K.sub.ATP]) activator, which also increased cell migration, by twofold, in basal conditions and potentiated the stimulatory effect of EGF. [K.sub.ATP] or KvLQT1 inhibitors (glibenclamide, clofilium) reduced EGF-stimulated wound healing, cell migration, and proliferation. Finally, EGF stimulated [K.sub.ATP] and KvLQT 1 currents and channel expression. In summary, stimulation of [K.sup.+] channels through autocrine activation of EGF receptors could play a crucial role in lung epithelia repair processes. lung; adenosine 5'-triphosphate-stimulated potassium channel; KvLQT1 [K.sup.+] channels; epidermal growth factor; alveolar cell repair; migration; proliferation

Byline: S. Sondergaard (1), S. Karason (2), J. Wiklund (3), S. Lundin (1), O. Stenqvist (1) Keywords: Respiratory mechanics Alveolar pressure Dynostatic algorithm Abstract: Objectives. We evaluated an algorithm for continuous on-line monitoring of alveolar pressure over time in a lung model with lower and upper inflection points and variable resistance ratios and in patients with acute lung injury. The algorithm is based on 'static' pressure/volume curves obtained from tracheal pressure measurements under dynamic conditions. Design and setting. Experimental and clinical evaluation of algorithm in a university hospital laboratory and intensive care unit. Patients. Ten patients undergoing postoperative respiratory therapy (feasibility of tracheal measurement) and ten patients with acute lung injury undergoing ventilator treatment (evaluation of algorithm). Measurements and results. Direct tracheal pressure measurements with a catheter inserted through the endotracheal tube. Comparison of measured alveolar and the dynostatic alveolar pressure vs. time in a lung model with changes in five ventilatory parameters. Examples of clinical monitoring are reported. In the model there was excellent agreement between alveolar pressures obtained by the algorithm, the dynostatic alveolar pressure, and measured alveolar pressure at all ventilator settings. For inspiratory/expiratory resistance ratios between 1:2.1--2.1:1, the dynostatic alveolar pressure was within +-1.5 cm [H.sub.2]O of measured alveolar pressure. In patients the technique for direct tracheal pressure measurement using a catheter inserted through the endotracheal tube functioned satisfactorily with intermittent air flushes for cleansing. Conclusions. Using a thin tracheal pressure catheter inserted through the endotracheal tube alveolar pressure allows continuous bedside monitoring with ease and precision using the dynostatic algorithm. The method is unaffected by tube and connector geometry or by secretions. Author Affiliation: (1) Department of Anaesthesia and Intensive Care, Sahlgrenska University Hospital, Gothenburg, Sweden (2) Department of Anaesthesia and Intensive Care, Landspitali University Hospital, Reykjavik, Iceland (3) Department of Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden Article History: Received Date: 05/02/2002 Accepted Date: 24/02/2003 Article note: Electronic Publication

Byline: Guillermo Bugedo (1), Alejandro Bruhn (1), Glenn Hernandez (1), Gonzalo Rojas (1), Cristian Varela (1), Juan Carlos Tapia (1), Luis Castillo (1) Keywords: Alveolar recruitment Computed tomography (CT) Lung morphology Mechanical ventilation Acute lung injury (ALI) Acute respiratory distress syndrome (ARDS) Abstract: Objective. To assess the acute effect of a lung recruitment maneuver (LRM) on lung morphology in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Patients. Ten patients with ALI/ARDS on mechanical ventilation. Design. Prospective clinical study. Setting. Computed tomography (CT) scan facility in a teaching hospital. Interventions. An LRM performed by stepwise increases in positive end-expiratory pressure (PEEP) of up to 30--40 cm[H.sub.2]O. Lung basal CT sections were taken at end-expiration (patients 1 to 5), and at end-expiration and end-inspiration (patients 6 to10). Arterial blood gases and static compliance (C.sub.st) were measured before, during and after the LRM. Measurements and main results. Poorly aerated and non-aerated tissue at PEEP 10 cm[H.sub.2]O accounted for 60.0+-29.1% of lung parenchyma, while only 1.1+-1.8% was hyperinflated. Increasing PEEP to 20 and 30 cm[H.sub.2]O, compared to PEEP 10 cm[H.sub.2]O, decreased poorly aerated and non-aerated tissue by 16.2+-28.0% and 33.4+-13.8%, respectively (p Conclusions. Lung recruitment maneuvers improve oxygenation by expanding collapsed alveoli without inducing too much hyperinflation in ALI/ARDS patients. An LRM during the CT scan gives morphologic and functional information that could be useful in setting ventilatory parameters. Author Affiliation: (1) Programa de Medicina Intensiva, Departamentos de Anestesiologia y Radiologia, Pontificia Universidad Catolica de Chile , Santiago, Chile (2) , PO Box 114-D, Santiago, Chile Article History: Received Date: 18/01/2002 Accepted Date: 21/11/2002 Article note: Electronic Publication