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Biomedical subjects

Werner Seeger

Publications and source records attributed to Werner Seeger.

At least 19 recordsLinked to original sources
PubMed2007

Immunomodulation by n-3- versus n-6-rich lipid emulsions in murine acute lung injury--role of platelet-activating factor receptor.

OBJECTIVE: Cytokines, platelet-activating factor (PAF), and eicosanoids control local and systemic inflammation. Conventional soybean oil-based lipid emulsions used for parenteral nutrition may aggravate the leukocyte inflammatory response or adhesion to the vessel wall. Fish oil-based lipid emulsions, in contrast, may exert an anti-inflammatory effect. DESIGN: We investigated the impact of lipid emulsions on leukocyte invasion, protein leakage, and cytokines in two murine models of acute inflammation. SETTING: Research laboratory of a university hospital. SUBJECTS: Wild-type mice and PAF-receptor knockout mice. INTERVENTIONS: Mice received an infusion of normal saline, fish oil- or soybean oil-based lipid emulsions before lipopolysaccharide challenge. MEASUREMENTS AND MAIN RESULTS: Preinfusion with soybean oil resulted in increased leukocyte invasion, myeloperoxidase activity, and protein leakage and exaggerated release of tumor necrosis factor (TNF)-alpha as well as macrophage inflammatory protein (MIP)-2 into the alveolar space after intratracheal lipopolysaccharide challenge. In contrast, preinfusion with fish oil reduced leukocyte invasion, myeloperoxidase activity, protein leakage, and TNF-alpha as well as MIP-2 generation. Corresponding profiles were found in plasma following intraperitoneal lipopolysaccharide application: Soybean oil increased but fish oil decreased the TNF-alpha and MIP-2 formation. When PAF-receptor-deficient mice were challenged with lipopolysaccharide, leukocyte invasion, lung tissue myeloperoxidase, cytokine generation, and alveolar protein leakage corresponded to those observed in wild-type animals. Fish oil and soybean oil lost their diverging effects on leukocyte transmigration, myeloperoxidase activity, leakage response, and cytokine generation in these knockout mice. Similarly, the differential impact of both lipid emulsions on these lipopolysaccharide-provoked changes was suppressed after pretreating animals with a PAF-receptor antagonist. CONCLUSIONS: Fish oil- vs. soybean oil-based lipid infusions exert anti- vs. proinflammatory effects in murine models of acute inflammation. The PAF/PAF-receptor-linked signaling appears to be a prerequisite for this differential profile.

Animals↗
PubMed2006

Iloprost-containing liposomes for aerosol application in pulmonary arterial hypertension: formulation aspects and stability.

PURPOSE: Pulmonary arterial hypertension (PAH) is a severe and progressive disease. The prostacyclin analogue iloprost is effective against PAH, but requires six to nine inhalations per day. The feasibility of liposomes to provide a sustained release formulation to reduce inhalation frequency is evaluated from a technological point of view. METHODS: Liposomal formulations consisting of di-palmitoyl-phosphatidyl-choline (DPPC), cholesterol (CH) and polyethyleneglycol-di-palmitoyl-phosphatidyl-ethanolamine (DPPE-PEG) were prepared. Their physico-chemical properties were investigated using dynamic light scattering, atomic force microscopy and differential scanning calorimetry. Stability of liposomes during aerosolization using three different nebulizers (air-jet, ultrasonic and vibrating mesh) was investigated with respect to drug loading and liposome size, pre- and post-nebulization. RESULTS: The phospholipid composition affected the diameters of liposomes only slightly in the range of 200-400 nm. The highest iloprost loading (12 microg/ml) and sufficient liposome stability (70% drug encapsulation post-nebulization) was observed for the DPPC/CH (70:30 molar ratio) liposomes. The formulation's stability was confirmed by the relatively high phase transition temperature (53 degrees C) and unchanged particle sizes. The incorporation of DPPE-PEG in the liposomes (DPPC/CH/DPPE-PEG, 50:45:5 molar ratio) resulted in decreased stability (20-50% drug encapsulation post-nebulization) and a phase transition temperature of 35 degrees C. The vibrating mesh nebulizer offered a number of significant advantages over the other nebulizers, including the production of small aerosol droplets, high output, and the lowest deleterious physical influence upon all investigated liposomes. CONCLUSION: Iloprost-loaded liposomes containing DPPC and CH components yield formulations which are well suited to aerosolization by the vibrating mesh nebulizer. The investigation of sustained release effects for the treatment of PAH in ex vivo and in vivo models is under way.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Classical transient receptor potential channel 6 (TRPC6) is essential for hypoxic pulmonary vasoconstriction and alveolar gas exchange.

Regional alveolar hypoxia causes local vasoconstriction in the lung, shifting blood flow from hypoxic to normoxic areas, thereby maintaining gas exchange. This mechanism is known as hypoxic pulmonary vasoconstriction (HPV). Disturbances in HPV can cause life-threatening hypoxemia whereas chronic hypoxia triggers lung vascular remodeling and pulmonary hypertension. The signaling cascade of this vitally important mechanism is still unresolved. Using transient receptor potential channel 6 (TRPC6)-deficient mice, we show that this channel is a key regulator of acute HPV as this regulatory mechanism was absent in TRPC6(-/-) mice whereas the pulmonary vasoconstrictor response to the thromboxane mimetic U46619 was unchanged. Accordingly, induction of regional hypoventilation resulted in severe arterial hypoxemia in TRPC6(-/-) but not in WT mice. This effect was mirrored by a lack of hypoxia-induced cation influx and currents in smooth-muscle cells from precapillary pulmonary arteries (PASMC) of TRPC6(-/-) mice. In both WT and TRPC6(-/-) PASMC hypoxia caused diacylglycerol (DAG) accumulation. DAG seems to exert its action via TRPC6, as DAG kinase inhibition provoked a cation influx only in WT but not in TRPC6(-/-) PASMC. Notably, chronic hypoxia-induced pulmonary hypertension was independent of TRPC6 activity. We conclude that TRPC6 plays a unique and indispensable role in acute hypoxic pulmonary vasoconstriction. Manipulation of TRPC6 function may thus offer a therapeutic strategy for the control of pulmonary hemodynamics and gas exchange.

Acute Disease↗
PubMed2006

Hyperoxia modulates TGF-beta/BMP signaling in a mouse model of bronchopulmonary dysplasia.

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(2) between postnatal days P1 and P28. Growth and respiratory compliance were significantly impaired in pups exposed to 85% O(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(2) as well as in MLE-12 mouse lung epithelial cells and NIH/3T3 and primary lung fibroblasts cultured in 85% O(2). After exposure to 85% O(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(2) significantly enhanced the TGF-beta-stimulated production of the alpha(1) subunit of type I collagen (Ialpha(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.

Animals↗
PubMed2006

Constitutive homo- and hetero-oligomerization of TbetaRII-B, an alternatively spliced variant of the mouse TGF-beta type II receptor.

Transforming growth factor (TGF)-beta ligands signal through transmembrane type I and type II serine/threonine kinase receptors, which form heteromeric signalling complexes upon ligand binding. Type II TGF-beta receptors (TbetaRII) are reported to exist as homodimers at the cell surface, but the oligomerization pattern and dynamics of TbetaRII splice variants in live cells has not been demonstrated thus far. Using co-immunoprecipitation and bioluminescence resonance energy transfer (BRET), we demonstrate that the mouse TbetaRII receptor splice variant TbetaRII-B is capable of forming ligand-independent homodimers and heterodimers with TbetaRII. The homomeric interaction of mouse (m)TbetaRII-B isoforms, however, is less robust than the heteromeric interactions of mTbetaRII-B with wild-type TbetaRII, which indicates that these receptors may be more likely to heterodimerize when both receptors are expressed. Moreover, we demonstrate that mTbetaRII-B is a signalling receptor with ubiquitous tissue expression. Our study thus demonstrates previously unappreciated complex formation of TGF-beta type II receptors, and suggests that mTbetaRII-B can direct TGF-beta-induced signalling in vitro and in vivo.

Amino Acid Sequence↗
PubMed2006

Favorable effects of inhaled treprostinil in severe pulmonary hypertension: results from randomized controlled pilot studies.

OBJECTIVES: This study sought to investigate the effects of inhaled treprostinil on pulmonary hemodynamics and gas exchange in severe pulmonary hypertension. BACKGROUND: Inhaled iloprost therapy has a proven clinical efficacy in pulmonary arterial hypertension, but this therapy necessitates 6 to 9 inhalation sessions per day. Treprostinil has a longer plasma half-life and might provide favorable properties when applied by inhalation. METHODS: Three different studies were conducted on a total of 123 patients by means of right heart catheterization: 1) a randomized crossover-design study (44 patients), 2) a dose escalation study (31 patients), and 3) a study of reduction of inhalation time while keeping the dose fixed (48 patients). The primary end point was the change in pulmonary vascular resistance (PVR). RESULTS: The mean pulmonary arterial pressure of the enrolled patients was approximately 50 mm Hg in all studies. In study 1, both treprostinil and iloprost at an inhaled dose of 7.5 mug displayed a comparable PVR decrease, with a significantly different time course (p < 0.001), treprostinil showing a more sustained effect on PVR (p < 0.0001) and fewer systemic side effects. In study 2, effects of inhalation were observed for 3 h. A near-maximal acute PVR decrease was observed at 30 mug treprostinil. In study 3, treprostinil was inhaled at increasing concentrations with a pulsed ultrasonic nebulizer, mimicking a metered dose inhaler. A dose of 15 mug treprostinil was inhaled with 18, 9, 3, 2 pulses, or 1 pulse, each mode achieving comparable, sustained pulmonary vasodilation without significant side effects. CONCLUSIONS: Inhaled treprostinil exerts sustained pulmonary vasodilation with excellent tolerability at relatively low doses and may be inhaled in a few breaths.

Administration, Inhalation↗
PubMed2006

Safety and efficacy of inhaled treprostinil as add-on therapy to bosentan in pulmonary arterial hypertension.

OBJECTIVES: This study evaluated the safety and efficacy of inhaled treprostinil as add-on therapy to oral bosentan in patients with pulmonary arterial hypertension (PAH). BACKGROUND: The addition of a long-acting prostacyclin analogue via the inhaled route might be a safe and effective strategy to optimize therapy in PAH patients on bosentan. METHODS: Twelve patients with symptomatic PAH despite bosentan received either 30 microg of inhaled treprostinil 4 times daily (n = 6) or 45 microg 4 times daily (n = 6), via an ultrasonic nebulizer. Six-min walk distance (6MWD), functional class, and hemodynamics were assessed at baseline and 12 weeks. RESULTS: One patient was excluded from analysis due to the subsequent finding of pulmonary capillary hemangiomatosis. In the remaining 11 patients, inhaled treprostinil was safe and well tolerated. Inhaled treprostinil was associated with an increase in 6MWD at 12 weeks (baseline 339 +/- 86, 12 week, 1 h post-inhalation 406 +/- 121 m, 67-m change, p = 0.01). An improvement in 6MWD of 49 m from baseline was noted during the trough period, just before inhalation of treprostinil (p = 0.009). The 6MWD improvement of at least 10% was noted in 1 of 6 patients receiving 30 microg versus 5 of 6 receiving 45 microg. Over 12 weeks, significant decreases were noted in mean pulmonary arterial pressure (-10%) and in pulmonary vascular resistance (-26%). Functional class improved from III to II in 9 of 11 patients. CONCLUSIONS: This trial suggests that inhaled treprostinil is safe, well tolerated, and associated with significant improvements in exercise capacity, functional class, and pulmonary hemodynamics in symptomatic patients with PAH on bosentan.

Administration, Inhalation↗
PubMed2006

Oxygen sensors in hypoxic pulmonary vasoconstriction.

Hypoxic pulmonary vasoconstriction (HPV) is an essential mechanism adapting lung perfusion to regional ventilation. Perturbations to HPV, such as those occurring in pneumonia, acute respiratory distress syndrome and liver failure, can result in arterial hypoxemia. Under conditions of general hypoxia, HPV increases pulmonary vascular resistance and thus causes acute pulmonary hypertension. Despite intensive research, the underlying mechanisms of HPV have not been fully elucidated. Deciphering signalling pathways that result in HPV could suggest novel approaches to address a failure of HPV, as well as for the treatment of pulmonary hypertension associated with HPV. Within this context, this review focuses on current concepts in the oxygen sensing mechanisms that underlie HPV.

Adenosine Triphosphate↗
PubMed2006

Liver carboxylesterase cleaves surfactant protein (SP-) B and promotes surfactant subtype conversion.

Conversion of the biophysically active large surfactant aggregate subtype of alveolar surfactant into the less surface active small surfactant aggregates occurs in vitro and in vivo, possibly in dependency of a carboxylesterase, entitled surfactant convertase. The substrate has yet not been safely identified. Utilizing the in vitro cycling assay we investigated conversion of an organic rabbit lavage extract reconstituted with SP-A. Porcine liver carboxylesterase, which is closely related to surfactant convertase, induced subtype conversion to a similar degree as compared with native lavage fluid containing endogenous convertase. In addition, we asked for cleavage products of SP-B and identified a approximately 12 kDa band upon cycling with liver carboxylesterase, having the same N-terminus as mature SP-B. A band of same molecular weight was found in native lavage fluid after in vitro conversion mediated by the endogenous convertase. We conclude that SP-B plays a pivotal role during subtype conversion and represents the substrate for surfactant convertase.

Amino Acid Sequence↗
PubMed2006

Hypoxia- and non-hypoxia-related pulmonary hypertension - established and new therapies.

Pulmonary hypertension can occur as an isolated disease affecting the lung vessels only, in association with underlying hypoxic lung disorders, or due to chronic thromboembolic disease. Pulmonary hypertension caused by pulmonary venous congestion will not be focused on in this review. Regardless of the underlying disease, chronic cor pulmonale is associated with progressive clinical deterioration and a poor prognosis in most cases. The aim of specific therapies for pulmonary hypertension is to reduce pulmonary vascular resistance and thereby improve right ventricular function. Currently, three classes of drugs (prostanoids, endothelin receptor antagonists, and phosphodiesterase-5 inhibitors) are approved for the treatment of pulmonary arterial hypertension (PAH) in a defined patient population (group I according to the recent WHO classification). However, these medications may also lower pulmonary vascular resistance in patients with associated lung diseases (e.g. chronic obstructive pulmonary disease or lung fibrosis) and significant pulmonary hypertension, for whom these drugs are not yet approved. As non-selective vasodilators may induce gas-exchange disturbances, which preclude their long term use in these patients, such substances should be avoided in the hypoxemic patient. In this article we provide an update of the current understanding of hypoxia- and non-hypoxia-related pulmonary hypertension, addressing both the pathophysiological understanding of different disease aetiologies as well as the therapeutic options currently available.

Animals↗
PubMed2006

Alveolar epithelial cells direct monocyte transepithelial migration upon influenza virus infection: impact of chemokines and adhesion molecules.

Influenza A virus pneumonia is characterized by severe lung injury and high mortality. Early infection elicits a strong recruitment of monocytes from the peripheral blood across the endo-/epithelial barrier into the alveolar air space. However, it is currently unclear which of the infected resident lung cell populations, alveolar epithelial cells or alveolar macrophages, elicit monocyte recruitment during influenza A virus infection. In the current study, we investigated whether influenza A virus infection of primary alveolar epithelial cells and resident alveolar macrophages would elicit a basal-to-apical monocyte transepithelial migration in vitro. We found that infection of alveolar epithelial cells with the mouse-adapted influenza A virus strain PR/8 strongly induced the release of monocyte chemoattractants CCL2 and CCL5 followed by a strong monocyte transepithelial migration, and this monocytic response was strictly dependent on monocyte CCR2 but not CCR5 chemokine receptor expression. Analysis of the adhesion molecule pathways demonstrated a role of ICAM-1, VCAM-1, integrin-associated protein (CD47), and junctional adhesion molecule-c on the epithelial cell surface interacting with monocyte beta(1) and beta(2) integrins and integrin-associated protein in the monocyte transmigration process. Importantly, addition of influenza A virus-infected alveolar macrophages further enhanced monocyte transmigration across virus-infected epithelium in a TNF-alpha-dependent manner. Collectively, the data show an active role for virus-infected alveolar epithelium in the regulation of CCL2/CCR2-dependent monocyte transepithelial migration during influenza infection that is essentially dependent on both classical beta(1) and beta(2) integrins but also junctional adhesion molecule pathways.

Animals↗
PubMed2006

Systematic comparison of the T7-IVT and SMART-based RNA preamplification techniques for DNA microarray experiments.

BACKGROUND: Small biological samples obtained from biopsies or laser microdissection often do not yield sufficient RNA for successful microarray hybridization; therefore, RNA amplification is performed before microarray experiments. We compared 2 commonly used techniques for RNA amplification. METHODS: We compared 2 commercially available methods, Arcturus RiboAmp for in vitro transcription (IVT) and Clontech BD SMART for PCR, to preamplify 50 ng of total RNA isolated from mouse livers and kidneys. Amplification factors of 3 sequences were determined by real-time PCR. Differential expression profiles were compared within and between techniques as well as with unamplified samples with 10K 50mer oligomer-spotted microarrays (MWG Biotech). The microarray results were validated on the transcript and protein levels by comparison with public expression databases. RESULTS: Amplification factors for specific sequences were lower after 2 rounds of IVT than after 12 cycles of SMART. Furthermore, IVT showed a clear decrease in amplification with increasing distance of the amplified sequences from the polyA tail, indicating generation of smaller products. In the microarray experiments, reproducibility of the duplicates was highest after SMART. In addition, SMART-processed samples showed higher correlation when compared with unamplified samples as well as with expression databases. CONCLUSIONS: Whenever 1 round of T7-IVT does not yield sufficient product for microarray hybridization, which is usually the case when <200 ng of total RNA is used as starting material, we suggest the use of SMART PCR for preamplification.

3' Untranslated Regions↗
PubMed2006

[Pulmonary fibrosis--a therapeutic dilemma?].

The idiopathic interstitial pneumonias, especially the idiopathic pulmonary fibrosis (IPF), are life-threatening lung disorders, for which no effective treatment option exists. In view of IPF, the American Thoracic Society (ATS)/European Respiratory Society (ERS) consensus statement recommends a combined therapy with corticosteroids and azathioprine or cyclophosphamide, although data from conclusive clinical trials are yet missing and the recurrent clinical experience is that these drugs do not really help in IPF. Up to now, lung transplantation represents the last and only therapeutic option for IPF subjects. Based on new pathophysiological concepts of IPF, there are meanwhile a couple of different agents under preclinical and clinical assessment, and the increasing number of clinical trials ongoing in IPF raise the hope that an effective treatment comes into reach. The agents investigated and their targets are: acetylcysteine (reactive oxygen species [ROS] scavenging), interferon-gamma 1b (modulation of Th1/Th2 balance, direct antifibrotic effects), pirfenidone and GC 1008 (blockade of transforming growth factor-beta), FG 3019 (blockade of connective tissue growth factor), imatinib mesylate (blockade of platelet-derived growth factor), bosentan (blockade of endothelin), zileutin (blockade of leukotrienes), etanercept (blockade of tumor necrosis factor-alpha), heparin (alveolar anticoagulation). Hopefully, these new therapeutic strategies may help to improve prognosis of IPF in the future.

Acetylcysteine↗
PubMed2006

[Obstructive sleep apnea-related cardiovascular disease].

The clinical spectrum of obstructive sleep apnea-(OSA-)related cardiovascular disease (CVD) comprises systemic arterial hypertension (prevalence: 40-60%), pulmonary hypertension (20-30%), coronary artery disease (20-30%), congestive heart failure (5-10%), and stroke (5-10%). During sleep, heart rhythm disorders such as atrioventricular blocks, sinus arrests and atrial fibrillation can be induced by OSA. OSA-related CVD mainly affects those patients with an apnea-hypopnea index > 30/h and, if left untreated, is linked to increased mortality. Epidemiologic data have clearly shown that cardiovascular risk is increased in OSA independent of confounding factors such as obesity and concomitant metabolic disease. In recent years, the pathophysiology of OSA-related CVD has been further elucidated showing that apart from the well-known sympathetic activation, increased oxidative stress and pro-inflammatory changes seem to play major roles. Furthermore, studies using high resolution ultrasonography have demonstrated endothelial dysfunction and enhanced atherosclerosis in these patients. Finally, animal models of OSA have delineated that daytime arterial hypertension is the consequence of the OSA-associated chronic intermittent hypoxia. Therapy of OSA by continuous positive airway pressure (CPAP) ventilation exerts cardioprotective effects. It has been shown to rectify the vascular micromilieu, restore endothelium-dependent vasodilation, lower 24-h blood pressure, eliminate nocturnal heart rhythm disorders, and improve left ventricular function. Furthermore, long-term CPAP therapy leads to a reduction in important clinical endpoints such as the rates of myocardial infarction and stroke.

Animals↗
PubMed2006

Impact of TASK-1 in human pulmonary artery smooth muscle cells.

The excitability of pulmonary artery smooth muscle cells (PASMC) is regulated by potassium (K+) conductances. Although studies suggest that background K+ currents carried by 2-pore domain K+ channels are important regulators of resting membrane potential in PASMC, their role in human PASMC is unknown. Our study tested the hypothesis that TASK-1 leak K+ channels contribute to the K+ current and resting membrane potential in human PASMC. We used the whole-cell patch-clamp technique and TASK-1 small interfering RNA (siRNA). Noninactivating K+ current performed by TASK-1 K+ channels were identified by current characteristics and inhibition by anandamide and acidosis (pH 6.3), each resulting in significant membrane depolarization. Moreover, we showed that TASK-1 is blocked by moderate hypoxia and activated by treprostinil at clinically relevant concentrations. This is mediated via protein kinase A (PKA)-dependent phosphorylation of TASK-1. To further confirm the role of TASK-1 channels in regulation of resting membrane potential, we knocked down TASK-1 expression using TASK-1 siRNA. The knockdown of TASK-1 was reflected by a significant depolarization of resting membrane potential. Treatment of human PASMC with TASK-1 siRNA resulted in loss of sensitivity to anandamide, acidosis, alkalosis, hypoxia, and treprostinil. These results suggest that (1) TASK-1 is expressed in human PASMC; (2) TASK-1 is hypoxia-sensitive and controls the resting membrane potential, thus implicating an important role for TASK-1 K+ channels in the regulation of pulmonary vascular tone; and (3) treprostinil activates TASK-1 at clinically relevant concentrations via PKA, which might represent an important mechanism underlying the vasorelaxing properties of prostanoids and their beneficial effect in vivo.

Cells, Cultured↗
PubMed2006

Resident alveolar macrophages are replaced by recruited monocytes in response to endotoxin-induced lung inflammation.

In the acute respiratory distress syndrome, recruitment of peripheral blood monocytes results in expansion of the total pool of resident alveolar macrophages. The fate of resident macrophages, or whether recruited monocytes are selectively eliminated from the alveolar airspace or differentiate into resident alveolar macrophages during the resolving phase of inflammation, has not been determined. Here, we analyzed the kinetics of resident and recruited macrophage turnover within the alveolar airspace of untreated and LPS-challenged mice. Using bone marrow chimeric CD45.2 mice that were generated by lethal irradiation of CD45.2 alloantigen-expressing recipient mice and bone marrow transplantation from CD45.1 alloantigen-expressing donor mice, we employed a flow cytometric approach to distinguish recipient from donor-type macrophages in bronchoalveolar lavage fluids. Our data show that resident alveolar macrophages of untreated chimeric CD45.2 mice are very slowly replaced by constitutively immigrating CD45.1 positive monocytes, resulting in a replacement rate of approximately 40% by 1 yr. In contrast, more than 85% of the resident CD45.2 positive alveolar and lung homogenate macrophages were exchanged by donor CD45.1-expressing macrophages within 2 mo after treatment with Escherichia coli endotoxin (LPS). Importantly, fluorescence-activated cell sorter analysis of increased annexin V binding to both recipient and donor-type macrophages revealed increased apoptotic events to underlie this endotoxin-driven inflammatory macrophage turnover. Collectively, the data show that under baseline conditions the alveolar macrophage turnover exhibits very slow kinetics, whereas acute lung inflammation in response to treatment with LPS triggers a brisk acceleration of recruitment of monocytes that replace the resident alveolar macrophage population.

Animals↗
PubMed2006

Endotoxin induced peritonitis elicits monocyte immigration into the lung: implications on alveolar space inflammatory responsiveness.

BACKGROUND: Acute peritonitis developing in response to gram-negative bacterial infection is known to act as a trigger for the development of acute lung injury which is often complicated by the development of nosocomial pneumonia. We hypothesized that endotoxin-induced peritonitis provokes recruitment of monocytes into the lungs, which amplifies lung inflammatory responses to a second hit intra-alveolar challenge with endotoxin. METHODS: Serum and lavage cytokines as well as bronchoalveolar lavage fluid cells were analyzed at different time points after intraperitoneal or intratracheal application of LPS. RESULTS: We observed that mice challenged with intraperitoneal endotoxin developed rapidly increasing serum and bronchoalveolar lavage fluid (BALF) cytokine and chemokine levels (TNFalpha, MIP-2, CCL2) and a nearly two-fold expansion of the alveolar macrophage population by 96 h, but this was not associated with the development of neutrophilic alveolitis. In contrast, expansion of the alveolar macrophage pool was not observed in CCR2-deficient mice and in wild-type mice systemically pretreated with the anti-CD18 antibody GAME-46. An intentional two-fold expansion of alveolar macrophage numbers by intratracheal CCL2 following intraperitoneal endotoxin did not exacerbate the development of acute lung inflammation in response to intratracheal endotoxin compared to mice challenged only with intratracheal endotoxin. CONCLUSION: These data, taken together, show that intraperitoneal endotoxin triggers a CCR2-dependent de novo recruitment of monocytes into the lungs of mice but this does not result in an accentuation of neutrophilic lung inflammation. This finding represents a previously unrecognized novel inflammatory component of lung inflammation that results from endotoxin-induced peritonitis.

Animals↗