Jürgen Lohmeyer

Bronchoalveolar and systemic cytokine profiles in patients with ARDS, severe pneumonia and cardiogenic pulmonary oedema

The aim of this study was to investigate whether bronchoalveolar lavage (BAL) and serum levels of proinflammatory cytokines discriminate between different entities of patients with acute respiratory failure. BAL and circulating concentrations of interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-alpha (TNF-alpha) were measured in 74 mechanically-ventilated patients and 17 healthy controls. Patients were classified as cardiogenic pulmonary oedema (CPO), acute respiratory distress syndrome (ARDS), primary severe pneumonia (PN) and a combined group (PN+ARDS). In all patients with ARDS and/or PN, markedly elevated BAL levels of IL-6 and IL-8 were detected, which were significantly greater than levels in CPO and healthy controls. Absolute quantities and time-course of these cytokines did not differentiate between the absence and presence of lung infection, or different categories of PN. Similarly, circulating IL-6 levels were comparably elevated in patients with ARDS and/or PN, whereas circulating IL-8 concentrations were inconsistently increased. TNF-alpha was rarely detected in BAL samples, but increased serum concentrations were measured in ARDS and/or PN patients. Bronchoalveolar lavage levels of interleukin-6 and interleukin-8, but not tumour necrosis factor-alpha, and serum concentrations of interleukin-6 are consistently elevated in acute respiratory distress syndrome and/or severe pneumonia, discriminating these entities from cardiogenic pulmonary oedema. Alveolar and systemic cytokine profiles do not differentiate between acute respiratory distress syndrome in the absence of lung infection and states of severe primary or secondary pneumonia, which evidently present with comparable local and systemic inflammatory sequelae.

Short-Time Infusion of Fish Oil-Based Lipid Emulsions, Approved for Parenteral Nutrition, Reduces Monocyte Proinflammatory Cytokine Generation and Adhesive Interaction with Endothelium in Humans

Potential impact of ω-3 fatty acids, as contained in fish oil, on immunological function has been suggested because observations of reduced inflammatory diseases in Greenland Inuit were published. A fish oil-based lipid emulsion has recently been approved for parenteral nutrition in many countries. We investigated the influence of a short infusion course of fish oil-based (ω-3) vs conventional (ω-6) lipid emulsion on monocyte function. In a randomized design, twelve healthy volunteers received ω-3 or ω-6 lipid infusion for 48 h, with cross-over repetition of the infusion course after 3 mo. Fatty acid profiles, monocyte cytokine release and adhesive monocyte-endothelium interaction were investigated. Resultant ω-6 lipid emulsion increased plasma-free fatty acids including arachidonic acid, whereas the ω-3/ω-6 fatty acid ratio in monocyte membranes remained largely unchanged. It also caused a tendency toward enhanced monocyte proinflammatory cytokine release and adhesive monocyte-endothelium interaction. In contrast, ω-3 lipid emulsion significantly increased the ω-3/ω-6 fatty acid ratio in the plasma-free fatty acid fraction and in monocyte membrane lipid pool, markedly suppressing monocyte generation of TNF-α, IL-1, IL-6, and IL-8 in response to endotoxin. In addition, it also significantly inhibited both monocyte-endothelium adhesion and transendothelial monocyte migration, although monocyte surface expression of relevant adhesive molecules (CD11b, CD18, CD49 days, CCR2) was unchanged. Although isocaloric, ω-3 and ω-6 lipid emulsions exert differential impact on immunological processes in humans. In addition to its nutritional value, fish oil-based ω-3 lipid emulsion significantly suppresses monocyte proinflammatory cytokine generation and features of monocyte recruitment.

Monocytes are potent facilitators of alveolar neutrophil emigration during lung inflammation: role of the CCL2-CCR2 axis.

Coordinated neutrophil and monocyte recruitment is a characteristic feature of acute lung inflammatory responses. We investigated the role of monocyte chemotactic protein-1 (CCL2, JE) and the chemokine receptor CCR2 in regulating alveolar leukocyte traffic. Groups of wild-type (WT) mice, CCR2-deficient mice, lethally irradiated CCR2-deficient and WT mice that were reciprocally bone marrow transplanted (chimeric CCR2 deficient and WT, respectively), chimeric CCR2-deficient mice with an enriched CCR2+ alveolar macrophage population, and CCR2-deficient mice transfused with CCR2+ mononuclear cells were treated with intratracheal CCL2 and/or Escherichia coli endotoxin. Our data show that alveolar monocyte recruitment is strictly dependent on CCR2. LPS-induced neutrophil migration to the lungs is CCR2 independent. However, when CCR2-bearing blood monocytes are present, alveolar neutrophil accumulation is accelerated and drastically amplified. We suggest that this hitherto unrecognized cooperativity between monocytes and neutrophils contributes to the strong, coordinated leukocyte efflux in lung inflammation.

Monocyte Migration Through the Alveolar Epithelial Barrier: Adhesion Molecule Mechanisms and Impact of Chemokines

Alveolar monocyte influx requires adherence and transmigration through the vascular endothelium, extracellular matrix, and alveolar epithelium. For investigating the monocyte migratory process across the epithelial barrier, we employed both the A549 cell line and isolated human alveolar epithelial cells. Under baseline conditions, spontaneous bidirectional transepithelial monocyte migration was noted, which was dose-dependently increased in the presence of the monocyte chemoattractant protein-1. TNF-α stimulation of the alveolar epithelium provoked the polarized apical secretion of monocyte chemoattractant protein-1 and RANTES and up-regulation of ICAM-1 and VCAM-1 expression, accompanied by markedly enhanced transepithelial monocyte traffic in the basal-to-apical direction. Multiple adhesive interactions were noted to contribute to the enhanced monocyte traffic across the TNF-α-stimulated alveolar epithelium: these included the β2 integrins CD11a, CD11b, CD11c/CD18, the β1 integrins very late Ag (VLA)-4, -5, and -6, and the integrin-associated protein CD47 on monocytes, as well as ICAM-1, VCAM-1, CD47, and matrix components on the epithelial side. In contrast, spontaneous monocyte migration through unstimulated epithelium depended predominantly on CD11b/CD18 and CD47, with some additional contribution of VLA-4, -5, and -6. In summary, unlike transendothelial monocyte traffic, for which β1 and β2 integrins are alternative mechanisms, monocyte migration across the alveolar epithelium largely depends on CD11b/CD18 and CD47 but required the additional engagement of the β1 integrins for optimal migration. In response to inflammatory challenge, the alveolar epithelium orchestrates enhanced monocyte traffic to the apical side by polarized chemokine secretion and up-regulation of ICAM-1 and VCAM-1.

Pneumolysin-Induced Lung Injury Is Independent of Leukocyte Trafficking into the Alveolar Space

Pneumolysin (PLY) is a major virulence factor released by Streptococcus pneumoniae and has been implicated in the pathogenesis of pneumococcal pneumonia. In this study, we evaluated the contribution of newly recruited neutrophils and monocytes and resident alveolar macrophages to the pathogenesis of PLY-induced lung injury. Mice received either adhesion-blocking Abs to inhibit alveolar leukocyte trafficking or liposomal clodronate to deplete alveolar macrophages before intratracheal application of native PLY or its noncytotoxic derivative PdB. We found that treatment with PLY but not PdB resulted in increased lung vascular permeability. In addition, PLY also induced a decrease in the resident alveolar macrophage population, and the recruitment of peripheral blood neutrophils and monocytes into the alveolar space. Blockade of PLY-induced alveolar leukocyte trafficking by pretreatment of mice with anti-CD18 plus anti-CD49d Abs or depletion of circulating neutrophils did not attenuate the increase in lung permeability observed in response to intratracheal PLY. In addition, depletion of resident alveolar macrophages with clodronated liposomes did not reduce alveolar injury developing in response to PLY. PLY-induced lung injury was associated with only a small increase in bronchoalveolar lavage concentrations of cytokines. These data indicate that PLY-induced lung injury results from direct pneumotoxic effects on the alveolar-capillary barrier and is independent of both resident and recruited phagocytic cells.

The Inflammatory versus Constitutive Trafficking of Mononuclear Phagocytes into the Alveolar Space of Mice Is Associated with Drastic Changes in Their Gene Expression Profiles

Mononuclear phagocytes enter the lungs both constitutively to maintain alveolar macrophage and dendritic cell homeostasis, as well as during lung inflammation, where the role of these cells is less well defined. We used a transgenic mouse strain (CX3CR1+/GFP) that harbors a GFP label in circulating monocytes to identify and sort these cells from the vascular and alveolar compartments under both constitutive and acute lung inflammatory conditions. Using nylon arrays combined with real-time RT-PCR for gene expression profiling, we found that flow-sorted, highly purified mononuclear phagocytes recruited to acutely inflamed mouse lungs showed strongly up-regulated mRNA levels of the neutrophil chemoattractants KC, MIP-2, and IP-10, which contrasted with alveolar mononuclear phagocytes that immigrated in steady state. Similar observations were made for the lysosomal cathepsins B, L, and K being strongly up-regulated in mononuclear phagocytes upon recruitment to inflamed lungs but not during constitutive alveolar immigration. Inflammatory elicited mononuclear phagocytes also demonstrated significantly increased mRNA levels of the cytokine TNF-α and the PRR-associated molecules CD14, TLR4, and syndecan-4. Together, inflammatory elicited mononuclear phagocytes exhibit strongly increased neutrophil chemoattractants, lysosomal proteases, and LPS signaling mRNA transcripts, suggesting that these cells may play a major role in acute lung inflammatory processes.

Inhibition of influenza virus-induced NF-kappaB and Raf/MEK/ERK activation can reduce both virus titers and cytokine expression simultaneously in vitro and in vivo

Influenza virus (IV) infection can cause severe pneumonia and death. Therapeutic actions are limited to vaccines and a few anti-viral drugs. These target viral functions thereby selecting resistant variants. During replication IV activates the Raf/MEK/ERK-cascade and the transcription factor NF-kappaB. Both result in virus supportive and anti-viral effects by promoting viral genome transport for virus assembly and by inducing expression of pro-inflammatory host factors. Apart from tissue damage caused by the virus lytic replication, an imbalanced overproduction of anti-viral cytokines can cause severe lung damage as observed in human H5-type IV infections. Recently we showed that inhibition of NF-kappaB activity reduces the virus titer in vitro and in vivo. We have now analyzed whether inhibition of these pathways, allows simultaneous reduction of virus titers and virus-induced cytokines. The results show that inhibition of either pathway indeed leads to decreased virus titers and cytokine expression. This was not only true for infected permanent cells or primary mouse alveolar epithelial cells, but also in infected mice. Hereby we demonstrate for the first time in vitro and in vivo that virus titers and pro-inflammatory cytokine expression can be modulated simultaneously. This could provide a new rationale of future therapeutic strategies to treat IV pneumonia.

Streptococcus pneumoniae Stimulates a STING- and IFN Regulatory Factor 3-Dependent Type I IFN Production in Macrophages, which Regulates RANTES Production in Macrophages, Cocultured Alveolar Epithelial Cells, and Mouse Lungs

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. In this study, we examine an innate immune recognition pathway that senses pneumococcal infection, triggers type I IFN production, and regulates RANTES production. We found that human and murine alveolar macrophages as well as murine bone marrow macrophages, but not alveolar epithelial cells, produced type I IFNs upon infection with S. pneumoniae. This response was dependent on the pore-forming toxin pneumolysin and appeared to be mediated by a cytosolic DNA-sensing pathway involving the adapter molecule STING and the transcription factor IFN regulatory factor 3. Indeed, DNA was present in the cytosol during pneumococcal infection as indicated by the activation of the AIM2 inflammasome, which is known to sense microbial DNA. Type I IFNs produced by S. pneumoniae-infected macrophages positively regulated gene expression and RANTES production in macrophages and cocultured alveolar epithelial cells in vitro. Moreover, type I IFNs controlled RANTES production during pneumococcal pneumonia in vivo. In conclusion, we identified an immune sensing pathway detecting S. pneumoniae that triggers a type I IFN response and positively regulates RANTES production.

Inhaled iloprost is a potent acute pulmonary vasodilator in HIV-related severe pulmonary hypertension

As antiretroviral therapy has improved life expectancy in human immunodeficiency virus (HIV) infection, the life-limiting complication of HIV‐related pulmonary hypertension has come into focus. Inhalation of the stable prostacyclin analogue iloprost is an effective treatment for various forms of precapillary pulmonary hypertension. The main objective of the present study was to evaluate the safety and efficacy of inhaled iloprost in HIV‐related pulmonary hypertension. In eight patients with severe pulmonary hypertension related to HIV infection, right heart and femoral artery catheterisation were performed. The acute effect of oxygen, inhaled nitric oxide and aerosolised iloprost was investigated. Four patients underwent long-term treatment with inhaled iloprost. The rank order of pulmonary vasodilatory potency was iloprost>NO>O2, with a maximum reduction (mean±sem) in pulmonary vascular resistance of 30.6±3.1% (p<0.001), 5.9±3.9% and −0.6±3.9%, respectively. Concomitantly, inhaled iloprost significantly increased the cardiac index and central venous oxygen saturation. Chronic treatment with inhaled iloprost tended to improve the 6 min walking distance and decreased pulmonary vascular resistance in all patients (although not significantly). No serious adverse events and no major interactions with the ongoing antiretroviral therapy were noted. In conclusion, inhaled iloprost is a potent pulmonary vasodilator in human immune deficiency virus-related pulmonary hypertension. Future studies are warranted to confirm the encouraging long-term beneficial results observed in the present limited number of patients.

Dysregulation of the IL-13 receptor system: a novel pathomechanism in pulmonary arterial hypertension.

RATIONALE Idiopathic pulmonary arterial hypertension (IPAH) is characterized by medial hypertrophy due to pulmonary artery smooth muscle cell (paSMC) hyperplasia. Inflammation is proposed to play a role in vessel remodeling associated with IPAH. IL-13 is emerging as a regulator of tissue remodeling; however, the contribution of the IL-13 system to IPAH has not been assessed. OBJECTIVES The objective of this study was to assess the possible contribution of the IL-13 system to IPAH. METHODS Expression and localization of IL-13, and IL-13 receptors IL-4R, IL-13Rα1, and IL-13Rα2 were assessed by real-time reverse transcription-polymerase chain reaction, immunohistochemistry, and flow cytometry in lung tissue, paSMC, and microdissected vascular lesions from patients with IPAH, and in lung tissue from rodents with hypoxia- or monocrotaline-induced pulmonary hypertension. A whole-genome microarray analysis was used to study IL-13-regulated genes in paSMC. MEASUREMENTS AND MAIN RESULTS Pulmonary expression of the IL-13 decoy receptor IL-13Rα2 was up-regulated relative to that of the IL-13 signaling receptors IL-4R and IL-13Rα1 in patients with IPAH and in two animal models of IPAH. IL-13, signaling via STAT3 and STAT6, suppressed proliferation of paSMC by promoting G(0)/G(1) arrest. Whole-genome microarrays revealed that IL-13 suppressed endothelin-1 production by paSMC, suggesting that IL-13 controlled paSMC growth by regulating endothelin production. Ectopic expression of the il13ra2 gene resulted in partial loss of paSMC growth control by IL-13 and blunted IL-13 suppression of endothelin-1 production by paSMC, whereas small-interfering RNA knockdown of il13ra2 gene expression had the opposite effects. CONCLUSIONS The IL-13 system is a novel regulator of paSMC growth. Dysregulation of IL-13 receptor expression in IPAH may partially underlie smooth muscle hypertrophy associated with pathological vascular remodeling in IPAH.