Subpopulation of hyperresponsive polymorphonuclear neutrophils in patients with adult respiratory distress syndrome. Role of cytokine production

TREM-1 is required for enhanced OpZ-induced superoxide generation following priming

Inflammatory agents, microbial products, or stromal factors pre-activate or prime neutrophils to respond to activating stimuli in a rapid and aggressive manner. Primed neutrophils exhibit enhanced chemotaxis, phagocytosis, and respiratory burst when stimulated by secondary activating stimuli. We previously reported that Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) mediates neutrophil effector functions such as increased superoxide generation, transepithelial migration, and chemotaxis. However, it is unclear whether TREM-1 is required for the process of priming itself or for primed responses to subsequent stimulation. To investigate this, we utilized in vitro and in vivo differentiated neutrophils that were primed with TNF-α and then stimulated with the particulate agonist, opsonized zymosan (OpZ). Bone marrow progenitors isolated from WT and Trem-1-/- mice were transduced with estrogen regulated Homeobox8 (ER-Hoxb8) fusion transcription factor and differentiated in vitro into neutrophils following estrogen depletion. The resulting neutrophils expressed high levels of TREM-1 and resembled mature in vivo differentiated neutrophils. The effects of priming on phagocytosis and oxidative burst were determined. Phagocytosis did not require TREM-1 and was not altered by priming. In contrast, priming significantly enhanced OpZ-induced oxygen consumption and superoxide production in WT but not Trem-1-/- neutrophils indicating that TREM-1 is required for primed oxidative burst. TREM-1-dependent effects were not mediated during the process of priming itself as priming enhanced degranulation, ICAM-1 shedding, and IL-1ß release to the same extent in WT and Trem-1-/- neutrophils. Thus, TREM-1 plays a critical role in primed phagocytic respiratory burst and mediates its effects following priming.

Novel neutrophil phenotypic signature in pediatric patients with type 1 diabetes and diabetic ketoacidosis

Type 1 diabetes (T1D) is a chronic inflammatory condition sometimes complicated by acute diabetic ketoacidosis (DKA). A subset of patients with T1D develop DKA independent of known risk factors. This study tested the hypothesis that circulating polymorphonuclear leukocytes (PMN) from children with T1D and DKA would exhibit a primed phenotype and that the signature would be unique in patients predisposed to have DKA. Using a prospective cohort study design, neutrophil phenotype was assessed in 30 patients with T1D seen in endocrinology clinic for routine care, 30 patients with acute DKA, and 36 healthy donors. Circulating PMN from patients with DKA display a primed phenotype with increased basal cell-surface CD11b, L-selectin shedding, and enhanced fMLF-elicited reactive oxygen species (ROS) production. Moreover, PMN from T1D patients both with and without DKA lack the capacity to be further primed by incubation with TNF-α, a classic priming stimulus. Primed PMN phenotypic signatures demonstrated are independent of hemoglobin A1c, the premier biological marker for DKA risk, and are consistent with a hyperinflammatory state. A single nucleotide polymorphism in TLR-1 (1805G>T), known to be associated with a hyperinflammatory PMN phenotype, correlated with DKA. This study elucidated a novel phenotypic signature in circulating PMN from children with T1D with and without DKA, and suggests the possibility of a previously unrecognized PMN phenotype with potential clinical implications. Immunophenotype and genotype may be applicable as biomarkers for DKA risk stratification in patients with T1D.

Circulating BMP9 Protects the Pulmonary Endothelium during Inflammation-induced Lung Injury in Mice

Rationale: Pulmonary endothelial permeability contributes to the high-permeability pulmonary edema that characterizes acute respiratory distress syndrome. Circulating BMP9 (bone morphogenetic protein 9) is emerging as an important regulator of pulmonary vascular homeostasis. Objectives:To determine whether endogenous BMP9 plays a role in preserving pulmonary endothelial integrity and whether loss of endogenous BMP9 occurs during LPS challenge. Methods: A BMP9-neutralizing antibody was administrated to healthy adult mice, and lung vasculature was examined. Potential mechanisms were delineated by transcript analysis in human lung endothelial cells. The impact of BMP9 administration was evaluated in a murine acute lung injury model induced by inhaled LPS. Levels of BMP9 were measured in plasma from patients with sepsis and from endotoxemic mice. Measurements and Main Results: Subacute neutralization of endogenous BMP9 in mice (N = 12) resulted in increased lung vascular permeability (P = 0.022), interstitial edema (P = 0.0047), and neutrophil extravasation (P = 0.029) compared with IgG control treatment (N = 6). In pulmonary endothelial cells, BMP9 regulated transcriptome pathways implicated in vascular permeability and cell-membrane integrity. Augmentation of BMP9 signaling in mice (N = 8) prevented inhaled LPS-induced lung injury (P = 0.0027) and edema (P < 0.0001). In endotoxemic mice (N = 12), endogenous circulating BMP9 concentrations were markedly reduced, the causes of which include a transient reduction in hepatic BMP9 mRNA expression and increased elastase activity in plasma. In human patients with sepsis (N = 10), circulating concentratons of BMP9 were also markedly reduced (P < 0.0001). Conclusions: Endogenous circulating BMP9 is a pulmonary endothelial-protective factor, downregulated during inflammation. Exogenous BMP9 offers a potential therapy to prevent increased pulmonary endothelial permeability in lung injury.

Distinct Histopathologic Features of Complicated Sinusitis

BACKGROUND

Sinusitis complicated by intracranial or orbital extension can be life-threatening and require emergent intervention. Histologic features of complicated sinusitis have yet to be determined and may have significant implications for understanding pathophysiology.

METHODS

A structured histopathology report was utilized to analyze sinus tissue extracted during functional endoscopic sinus surgery (FESS). A total of 13 histopathology variables were compared between patients with complicated sinusitis (CS), CRS without nasal polyps (CRSsNP), and CRS with nasal polyps (CRSwNP).

RESULTS

About 24 CS, 149 uncomplicated CRSsNP, and 191 uncomplicated CRSwNP patients were analyzed. Nasal tissue from CS and CRSwNP patients demonstrated similar levels of overall inflammation (66.7% vs. 69.6% with moderate/severe inflammation, P = .466). Relative to CRSsNP, CS patients showed significantly greater overall inflammation (66.7% vs. 41.6%, P = .019). CS patients demonstrated significantly fewer eosinophils per high power field (eos/HPF) and eosinophil aggregates compared to CRSwNP patients (20.8% vs. 70.7% with 5+eos/HPF, P < .0001; 4.2% vs. 33.5%, P < .0001). Relative to CRSsNP patients, CS patients demonstrated enhanced neutrophil infiltration (45.8% vs. 28.0%, P = .011). About 91.7% of CS patients demonstrated a lymphoplasmacytic predominant inflammatory infiltrate, compared to 69.8% of CRSsNP and 62.8% of CRSwNP patients (P < .0001).

CONCLUSION

Significant histopathological differences were evident in patients with CS, CRSsNP, and CRSwNP. CS patients did not perfectly fit either a CRSsNP or CRSwNP profile, underscoring the importance of delineating the histopathological features of CS. This study offers insight into the histologic aspects of CS, providing initial evidence that it is an aggressive neutrophilic inflammatory process.

Macrophage migration inhibitory factor (MIF) enhances hypochlorous acid production in phagocytic neutrophils

BACKGROUND

Macrophage migration inhibitory factor (MIF) is an important immuno-regulatory cytokine and is elevated in inflammatory conditions. Neutrophils are the first immune cells to migrate to sites of infection and inflammation, where they generate, among other mediators, the potent oxidant hypochlorous acid (HOCl). Here, we investigated the impact of MIF on HOCl production in neutrophils in response to phagocytic stimuli.

METHODS

Production of HOCl during phagocytosis of zymosan was determined using the specific fluorescent probe R19-S in combination with flow cytometry and live cell microscopy. The rate of phagocytosis was monitored using fluorescently-labeled zymosan. Alternatively, HOCl production was assessed during phagocytosis of Pseudomonas aeruginosa by measuring the oxidation of bacterial glutathione to the HOCl-specific product glutathione sulfonamide. Formation of neutrophil extracellular traps (NETs), an oxidant-dependent process, was quantified using a SYTOX Green plate assay.

RESULTS

Exposure of human neutrophils to MIF doubled the proportion of neutrophils producing HOCl during early stages of zymosan phagocytosis, and the concentration of HOCl produced was greater. During phagocytosis of P. aeruginosa, a greater fraction of bacterial glutathione was oxidized to glutathione sulfonamide in MIF-treated compared to control neutrophils. The ability of MIF to increase neutrophil HOCl production was independent of the rate of phagocytosis and could be blocked by the MIF inhibitor 4-IPP. Neutrophils pre-treated with MIF produced more NETs than control cells in response to PMA.

CONCLUSION

Our results suggest a role for MIF in potentiating HOCl production in neutrophils in response to phagocytic stimuli. We propose that this newly discovered activity of MIF contributes to its role in mediating the inflammatory response and enhances host defence.

The Neutrophil’s Role During Health and Disease

Neutrophils have always been considered as uncomplicated front-line troopers of the innate immune system equipped with limited proinflammatory duties. Yet recently, the role of the neutrophil has been undergoing a rejuvenation of sorts. Neutrophils are now considered complex cells capable of a significant array of specialized functions, and as an effector of the innate immune response, they are able to regulate many processes such as acute injury and repair, cancer, autoimmunity, and chronic inflammatory processes. Furthermore, evidence exists to indicate that neutrophils also contribute to adaptive immunity by aiding the development of specific adaptive immune responses or guiding the subsequent adaptive immune response. With this revived interest in neutrophils and their many novel functions, it is prudent to review what is currently known about neutrophils and, even more importantly, understand what information is lacking. We discuss the essential features of the neutrophil, from its origins, lifespan, subsets, margination and sequestration of the neutrophil to the death of the neutrophil. We highlight neutrophil recruitment to both infected and injured tissues and outline differences in recruitment of neutrophils between different tissues. Finally, we examine how neutrophils use different mechanisms to either bolster protective immune responses or negatively cause pathological outcomes at different locations.

Immune sensitization during 1 year in the Antarctic high-altitude Concordia Environment

BACKGROUND

Antarctica is a challenging environment for humans. It serves as a spaceflight ground analog, reflecting some conditions of long-duration exploration class space missions. The French-Italian Concordia station in interior Antarctica is a high-fidelity analog, located 1000 km from the coast, at an altitude of 3232 m. The aim of this field study was to characterize the extent, dynamics, and key mechanisms of the immune adaptation in humans overwintering at Concordia for 1 year.

METHODS

This study assessed immune functions in fourteen crewmembers. Quantitative and phenotypic analyses from human blood were performed using onsite flow cytometry together with specific tests on receptor-dependent and receptor-independent functional innate and adaptive immune responses. Transcriptome analyses and quantitative identification of key response genes were assessed.

RESULTS

Dynamic immune activation and a two-step escalation/activation pattern were observed. The early phase was characterized by moderately sensitized global immune responses, while after 3-4 months, immune responses were highly upregulated. The cytokine responses to an ex vivo stimulation were markedly raised above baseline levels. These functional observations were reflected at the gene transcriptional level in particular through the modulation of hypoxia-driven pathways.

CONCLUSIONS

This study revealed unique insights into the extent, dynamics, and genetics of immune dysfunctions in humans exposed for 1 year to the Antarctic environment at the Concordia station. The scale of immune function was imbalanced toward a sensitizing of inflammatory pathways.

The Pathogenic Involvement of Neutrophils in Acute Respiratory Distress Syndrome and Transfusion-Related Acute Lung Injury

The acute respiratory distress syndrome (ARDS) is a serious and common complication of multiple medical and surgical interventions, with sepsis, pneumonia, and aspiration of gastric contents being common risk factors. ARDS develops within 1 week of a known clinical insult or presents with new/worsening respiratory symptoms if the clinical insult is unknown. Approximately 40% of the ARDS cases have a fatal outcome. Transfusion-related acute lung injury (TRALI), on the other hand, is characterized by the occurrence of respiratory distress and acute lung injury, which presents within 6 h after administration of a blood transfusion. In contrast to ARDS, acute lung injury in TRALI is not attributable to another risk factor for acute lung injury. 'Possible TRALI', however, may have a clear temporal relationship to an alternative risk factor for acute lung injury. Risk factors for TRALI include chronic alcohol abuse and systemic inflammation. TRALI is the leading cause of transfusion-related fatalities. There are no specific therapies available for ARDS or TRALI as both have a complex and incompletely understood pathogenesis. Neutrophils (polymorphonuclear leukocytes; PMNs) have been suggested to be key effector cells in the pathogenesis of both syndromes. In the present paper, we summarize the literature with regard to PMN involvement in the pathogenesis of both ARDS and TRALI based on both human data as well as on animal models. The evidence generally supports a strong role for PMNs in both ARDS and TRALI. More research is required to shed light on the pathogenesis of these respiratory syndromes and to more thoroughly establish the nature of the PMN involvement, especially considering the heterogeneous etiologies of ARDS.

Differential Regulation of Zfp30 Expression in Murine Airway Epithelia Through Altered Binding of ZFP148 to rs51434084

Neutrophil chemotaxis to the airways is a key aspect of host response to microbes and a feature of multiple pulmonary diseases including asthma. Tight regulation of this recruitment is critical to prevent unwanted host tissue damage and inflammation. Using a mouse (Mus musculus) model of asthma applied to the Collaborative Cross population, we previously identified a lung gene expression quantitative trait locus (eQTL) for Zinc finger protein 30 (Zfp30) that was also a QTL for neutrophil recruitment and the hallmark neutrophil chemokine CXCL1. The Zfp30 eQTL is defined by three functionally distinct haplotypes. In this study, we searched for causal genetic variants that underlie the Zfp30 eQTL to gain a better understanding of this candidate repressor's regulation. First, we identified a putative regulatory region spanning 500 bp upstream of Zfp30, which contains 10 SNPs that form five haplotypes. In reporter gene assays in vitro, these haplotypes recapitulated the three previously identified in vivo expression patterns. Second, using site-directed mutagenesis followed by reporter gene assays, we identified a single variant, rs51434084, which explained the majority of variation in expression between two out of three haplotype groups. Finally, using a combination of in silico predictions and electrophoretic mobility shift assays, we identified ZFP148 as a transcription factor that differentially binds to the Zfp30 promoter region harboring rs51434084. In conclusion, we provide evidence in support of rs51434084 being a causal variant for the Zfp30 eQTL, and have identified a mechanism by which this variant alters Zfp30 expression, namely differential binding of ZFP148.

Priming of the neutrophil respiratory burst: role in host defense and inflammation

Neutrophils are the major circulating white blood cells in humans. They play an essential role in host defense against pathogens. In healthy individuals, circulating neutrophils are in a dormant state with very low efficiency of capture and arrest on the quiescent endothelium. Upon infection and subsequent release of pro-inflammatory mediators, the vascular endothelium signals to circulating neutrophils to roll, adhere, and cross the endothelial barrier. Neutrophils migrate toward the infection site along a gradient of chemo-attractants, then recognize and engulf the pathogen. To kill this pathogen entrapped inside the vacuole, neutrophils produce and release high quantities of antibacterial peptides, proteases, and reactive oxygen species (ROS). The robust ROS production is also called 'the respiratory burst', and the NADPH oxidase or NOX2 is the enzyme responsible for the production of superoxide anion, leading to other ROS. In vitro, several soluble and particulate agonists induce neutrophil ROS production. This process can be enhanced by prior neutrophil treatment with 'priming' agents, which alone do not induce a respiratory burst. In this review, we will describe the priming process and discuss the beneficial role of controlled neutrophil priming in host defense and the detrimental effect of excessive neutrophil priming in inflammatory diseases.

Heterogeneity Among Neutrophils

Neutrophils (PMNs) play a key role in innate defence mechanisms. Generally, PMNs were considered to have a homogeneous population of mature and diversified cells. It seems, however, that their pleiotropic action results from the existence of different subpopulations in this group of cells. There are data that confirm the involvement of PMNs in the direct activation of other cells in non-specific response, as well as specialised cells in specific response. For example, there have been observations of PMNs with different levels of activity in relation to lymphocytes, and a population was identified which had characteristics similar to those of cells which are capable of presenting antigens. There are also reports of PMNs which demonstrate different survival time or capacity for chemotaxis. Other studies suggest that the neutrophil response to Staphylococcus aureus is diverse (not identical among all neutrophil). There are also reports of PMNs with varying activity during inflammation, which might explain many as yet unknown pathophysiological aspects of their hyperreactivity. The functional dualism of PMNs in the course of neoplastic disorders raises a lot of controversy. This paper presents the current state of knowledge of the heterogeneity of PMNs and their potential roles in different stages of disease.

Kinetics and Role of Plasma Matrix Metalloproteinase-9 Expression in Acute Lung Injury and the Acute Respiratory Distress Syndrome

Primed neutrophils that are capable of releasing matrix metalloproteinases (MMPs) into the circulation are thought to play a significant role in the pathophysiology of acute respiratory distress syndrome (ARDS). We hypothesized that direct measurement of plasma MMP-9 activity may be a predictor of incipient tissue damage and subsequent lung injury, which was investigated in both an animal model of ARDS and a small cohort of 38 critically ill human patients. In a mouse model of ARDS involving instillation of intratracheal lipopolysaccharide (LPS) to induce lung inflammation, we measured neutrophil-mediated inflammation, along with MMP-9 activity in the airways and lung tissue and MMP-9 expression in the plasma. Neutrophil recruitment, inflammation, and MMP-9 activity in the airways and lung tissue increased throughout the 72 h after LPS instillation, whereas plasma MMP-9 expression was greatest at 12 to 24 h after LPS instillation. The results suggest that the peak in plasma MMP-9 activity may precede the peak of neutrophil inflammation in the airways and lung tissue in the setting of ARDS. Based on this animal study, a retrospective observational cohort study involving 38 patients admitted to a surgical intensive care unit at a tertiary care university hospital with acute respiratory failure requiring intubation and mechanical ventilation was conducted. Plasma samples were collected daily, and MMP-9 activity was compared with lung function as determined by the PaO2/FiO2 ratio. In patients who developed ARDS, a notable increase in plasma MMP-9 activity on a particular day correlated with a decrease in the PaO2/FiO2 ratio on the following day (r = -0.503, P < 0.006). Taken together, these results suggest that plasma MMP-9 activity changes, as a surrogate for primed neutrophils may have predictive value for the development of ARDS in a selected subset of critically ill patients.

The effect of a selective CXCR2 antagonist (AZD5069) on human blood neutrophil count and innate immune functions

AIMS

The aim of the present study was to investigate whether selective antagonism of the cysteine-X-cysteine chemokine receptor-2 (CXCR2) receptor has any adverse effects on the key innate effector functions of human neutrophils for defence against microbial pathogens.

METHODS

In a double-blind, crossover study, 30 healthy volunteers were randomized to treatment with the CXCR2 antagonist AZD5069 (100 mg) or placebo, twice daily orally for 6 days. The peripheral blood neutrophil count was assessed at baseline, daily during treatment and in response to exercise challenge and subcutaneous injection of granulocyte-colony stimulating factor (G-CSF). Neutrophil function was evaluated by phagocytosis of Escherichia coli and by the oxidative burst response to E. coli.

RESULTS

AZD5069 treatment reversibly reduced circulating neutrophil count from baseline by a mean [standard deviation (SD)] of -1.67 (0.67) ×10(9) l(-1) vs. 0.19 (0.78) ×10(9) l(-1) for placebo on day 2, returning to baseline by day 7 after the last dose. Despite low counts on day 4, a 10-min exercise challenge increased absolute blood neutrophil count, but the effect with AZD5069 was smaller and not sustained, compared with placebo treatment. Subcutaneous G-CSF on day 5 caused a substantial increase in blood neutrophil count in both placebo- and AZD5069-treated subjects. Superoxide anion production in E. coli-stimulated neutrophils and phagocytosis of E. coli were unaffected by AZD5069 (P = 0.375, P = 0.721, respectively vs. baseline, Day 4). AZD5069 was well tolerated.

CONCLUSIONS

CXCR2 antagonism did not appear adversely to affect the mobilization of neutrophils from bone marrow into the peripheral circulation, phagocytosis or the oxidative burst response to bacterial pathogens. This supports the potential of CXCR2 antagonists as a treatment option for diseases in which neutrophils play a pathological role.

Contrasting inflammatory responses in severe and non-severe community-acquired pneumonia

The objective of this study was to compare systemic and local cytokine profiles and neutrophil responses in patients with severe versus non-severe community-acquired pneumonia (CAP). Hospitalized patients with CAP were grouped according to the pneumonia severity index (PSI), as non-severe (PSI < 91 points) or severe (PSI ≥ 91 points). Blood and sputum samples were collected upon admission. Compared to non-severe CAP patients, the severe CAP group showed higher plasma levels of pro- and anti-inflammatory cytokines but in contrast, lower sputum concentrations of pro-inflammatory cytokines. Blood neutrophil functional responses were elevated in CAP patients compared to healthy controls. However, neutrophils from severe CAP patients showed reduced respiratory burst activity compared to the non-severe group. Results indicate that patients with severe CAP fail to mount a robust local pro-inflammatory response but exhibit instead a more substantial systemic inflammatory response, suggesting that a key driver of CAP severity may be the ability of the patient to generate an optimal local inflammatory response.

Pulmonary retention of primed neutrophils: a novel protective host response, which is impaired in the acute respiratory distress syndrome

Rationale

Acute respiratory distress syndrome (ARDS) affects over 200 000 people annually in the USA. Despite causing severe, and often refractory, hypoxaemia, the high mortality and long-term morbidity of ARDS results mainly from extra-pulmonary organ failure; however the mechanism for this organ crosstalk has not been determined.

Methods

Using autologous radiolabelled neutrophils we investigated the pulmonary transit of primed and unprimed neutrophils in humans. Flow cytometry of whole blood samples was used to assess transpulmonary neutrophil priming gradients in patients with ARDS, sepsis and perioperative controls.

Main results

Unprimed neutrophils passed through the lungs with a transit time of 14.2 s, only 2.3 s slower than erythrocytes, and with <5% first-pass retention. Over 97% of neutrophils primed ex vivo with granulocyte macrophage colony-stimulating factor were retained on first pass, with 48% still remaining in the lungs at 40 min. Neutrophils exposed to platelet-activating factor were initially retained but subsequently released such that only 14% remained in the lungs at 40 min. Significant transpulmonary gradients of neutrophil CD62L cell surface expression were observed in ARDS compared with perioperative controls and patients with sepsis.

Conclusions

We demonstrated minimal delay and retention of unprimed neutrophils transiting the healthy human pulmonary vasculature, but marked retention of primed neutrophils; these latter cells then ‘deprime’ and are re-released into the systemic circulation. Further, we show that this physiological depriming mechanism may fail in patients with ARDS, resulting in increased numbers of primed neutrophils within the systemic circulation. This identifies a potential mechanism for the remote organ damage observed in patients with ARDS.

Assessment of priming of the human neutrophil respiratory burst

Neutrophils play an essential role in host defense against microbial pathogens and in the inflammatory reaction. Upon activation, neutrophils produce reactive oxygen species (ROS) such as superoxide anion (O2 (∙-)), hydrogen peroxide (H2O2), and hypochlorous acid (HOCl), a process referred to as the respiratory burst. The enzyme responsible for this process is called the NADPH oxidase or respiratory burst oxidase. This multicomponent enzyme system is composed of two transmembrane proteins (p22phox and gp91phox/NOX2, which form the cytochrome b558), three cytosolic proteins (p47phox, p67phox, p40phox), and a GTPase (Rac1 or Rac2), which assemble at membrane sites upon cell activation. The NADPH oxidase is in a resting state in circulating neutrophils, and its activation can be induced by a large number of soluble and particulate agents such as the formylated peptide, formyl-methionyl-leucyl-phenylalanine (fMLF). This activation can be enhanced or "primed" by pro-inflammatory cytokines, LPS and other agents. Priming is a "double-edged sword" process as it contributes to a rapid and efficient elimination of the pathogens but can also induce the generation of large quantities of toxic ROS that can damage surrounding tissues and participate to inflammation. In this chapter, we describe the techniques used to measure priming of the NADPH oxidase in human neutrophils.

Cytokines and neutrophils responses in influenza pneumonia

This case report shows a striking correlation of remarkable brief high levels of pro- and anti-inflammatory cytokines coupled with increased neutrophil activation, followed by a sharp decrease in cytokine levels and increased neutrophil apoptosis associated with the favorable clinical outcomes of a patient with severe influenza infection. The host response examined in our case is not complete, given it did not assess the full spectrum of host response. The brief neutrophil and cytokine response seen in our case in the absence of antiviral therapy and in the presence of methotrexate immunosuppressive therapy rise the question as to whether the latter optimally modulated the macrophage function, resulting in a favorable outcome of severe influenza viral infection.

Acute lung injury results from failure of neutrophil de-priming: a new hypothesis

Neutrophils are the most abundant circulating white cell in humans and play a crucial role in the innate immune response. Accumulation and activation of neutrophils, together with delayed clearance, have been shown to be a key event in the pathogenesis of acute lung injury. Previously, it has been proposed that there is substantial pooling of neutrophils within the pulmonary vasculature, even under physiological conditions, making the lung especially vulnerable to neutrophil-mediated tissue injury. However, more recent evidence suggests that only primed neutrophils accumulate in the pulmonary vasculature. This article examines the evidence for these two opposing views and proposes a new two-step model for the recruitment of neutrophils into the lung. Firstly, neutrophils that become primed, by exposure to a range of inflammatory mediators or physicochemical perturbations, become shape changed and stiff because of alterations in their cytoskeleton, and as a result, accumulate within the pulmonary circulation. In the absence of further stimuli, the healthy pulmonary vasculature is able to selectively retained these primed cells, allow them to 'de-prime' and be released back into the circulation in a quiescent, state. If this pulmonary 'de-priming' mechanism fails, or a second insult occurs, such as ventilator-associated barotrauma, which causes loss of alveolar integrity, primed neutrophils migrate from the pulmonary vasculature into the interstitial space with resultant lung injury. This canonical 'two step' model highlights the importance of neutrophil priming in the genesis of lung injury and the importance of adopting strategies to minimise alveolar injury.

Endotoxin priming of neutrophils requires endocytosis and NADPH oxidase-dependent endosomal reactive oxygen species

NADPH oxidase 2 (Nox2)-generated reactive oxygen species (ROS) are critical for neutrophil (polymorphonuclear leukocyte (PMN)) microbicidal function. Nox2 also plays a role in intracellular signaling, but the site of oxidase assembly is unknown. It has been proposed to occur on secondary granules. We previously demonstrated that intracellular NADPH oxidase-derived ROS production is required for endotoxin priming. We hypothesized that endotoxin drives Nox2 assembly on endosomes. Endotoxin induced ROS generation within an endosomal compartment as quantified by flow cytometry (dihydrorhodamine 123 and Oxyburst Green). Inhibition of endocytosis by the dynamin-II inhibitor Dynasore blocked endocytosis of dextran, intracellular generation of ROS, and priming of PMN by endotoxin. Confocal microscopy demonstrated a ROS-containing endosomal compartment that co-labeled with gp91(phox), p40(phox), p67(phox), and Rab5, but not with the secondary granule marker CD66b. To further characterize this compartment, PMNs were fractionated by nitrogen cavitation and differential centrifugation, followed by free flow electrophoresis. Specific subfractions made superoxide in the presence of NADPH by cell-free assay (cytochrome c). Subfraction content of membrane and cytosolic subunits of Nox2 correlated with ROS production. Following priming, there was a shift in the light membrane subfractions where ROS production was highest. CD66b was not mobilized from the secondary granule compartment. These data demonstrate a novel, nonphagosomal intracellular site for Nox2 assembly. This compartment is endocytic in origin and is required for PMN priming by endotoxin.

Priming of neutrophils and differentiated PLB-985 cells by pathophysiological concentrations of TNF-α is partially oxygen dependent

Activation of polymorphonuclear leukocytes (PMN) can be modulated to intermediate 'primed' states characterized by enhanced responsiveness to subsequent stimuli. We studied priming in response to TNF-α in human PMN and PLB-985 cells, a myeloid cell line differentiated to a neutrophilic phenotype (PLB-D). PMN generated reactive oxygen species (ROS) in response to TNF-α alone, and NADPH oxidase activity increased in response to stimulation with formyl-Met-Leu-Phe after priming. PLB-D cells also demonstrated priming of NADPH oxidase activity. Similar to priming by endotoxin, priming of the respiratory burst by TNF-α was predominantly oxygen dependent, with marked attenuation of ROS generation if primed anaerobically. Both PMN and PLB-D cells displayed significant increases in cell surface CD11b and gp91(phox) expression after TNF-α priming and PMN displayed activation of MAPK. In response to TNF-α priming, neither mobilization of intracellular proteins nor activation of MAPK pathways was NADPH oxidase dependent. Priming of PMN and PLB-D cells by low TNF-α concentrations enhanced chemotaxis. These data demonstrate that pathophysiological concentrations of TNF-α elicit NADPH oxidase-derived ROS and prime cells for enhanced surface protein expression, activation of p38 and ERK1/2 MAPK pathways, and increased chemotaxis. Furthermore, PLB-D cells undergo TNF-α priming and provide a genetically modifiable model to study priming mechanisms.

Regulation of phagocyte NADPH oxidase by hydrogen peroxide through a Ca(2+)/c-Abl signaling pathway

The importance of H(2)O(2) as a cellular signaling molecule has been demonstrated in a number of cell types and pathways. Here we explore a positive feedback mechanism of H(2)O(2)-mediated regulation of the phagocyte respiratory burst NADPH oxidase (NOX2). H(2)O(2) induced a dose-dependent stimulation of superoxide production in human neutrophils, as well as in K562 leukemia cells overexpressing NOX2 system components. Stimulation was abrogated by the addition of catalase, the extracellular Ca(2+) chelator BAPTA, the T-type Ca(2+) channel inhibitor mibefradil, the PKCdelta inhibitor rottlerin, or the c-Abl nonreceptor tyrosine kinase inhibitor imatinib mesylate or by overexpression of a dominant-negative form of c-Abl. H(2)O(2) induced phosphorylation of tyrosine 311 on PKCdelta and this activating phosphorylation was blocked by treatment with rottlerin, imatinib mesylate, or BAPTA. Rac GTPase activation in response to H(2)O(2) was abrogated by BAPTA, imatinib mesylate, or rottlerin. In conclusion, H(2)O(2) stimulates NOX2-mediated superoxide generation in neutrophils and K562/NOX2 cells via a signaling pathway involving Ca(2+) influx and c-Abl tyrosine kinase acting upstream of PKCdelta. This positive feedback regulatory pathway has important implications for amplifying the innate immune response and contributing to oxidative stress in inflammatory disorders.

Flow cytometric investigation of neutrophil oxidative burst and apoptosis in physiological and pathological situations

Flow cytometric analysis provides a rapid screen for abnormalities of polymorphonuclear neutrophils (PMN) function and reflect their behavior in vivo more accurately. This review summarizes the major fluorescent probes used to study PMN oxidative burst and apoptosis using flow cytometry (FCM). We also provide examples of FCM studies in physiological and pathological situations, illustrating the advantages of FCM for assessment of PMN oxidative burst and PMN apoptosis. These data point to the role of FCM in detecting primary immunodeficiencies such as IRAK4 deficiency and support the use of the assessment of the PMN oxidative burst for routine testing in patients with bacterial infections. We also demonstrate the utility of whole-blood analysis using FCM for a better understanding of PMN functionality, i.e., tuning PMN responses to inflammatory stimuli. Finally, FCM permits a simultaneous analysis of phenotypic, functional and morphometric parameters assessing whole-blood PMN apoptosis, in particular in response to Toll-like receptor agonists and during simian immunodeficiency virus infection.

Plasma granulocyte colony-stimulating factor levels correlate with clinical outcomes in patients with acute lung injury

OBJECTIVES

To evaluate the association between plasma granulocyte colony-stimulating factor (G-CSF) levels and clinical outcomes including mortality in patients with acute lung injury (ALI), and to determine whether lower tidal volume ventilation was associated with a more rapid decrease in plasma G-CSF over time in patients with ALI.

DESIGN

Retrospective measurement of G-CSF levels in plasma samples that were collected prospectively as part of a large multicenter clinical trial.

SETTING

Intensive care units in ten university centers.

PATIENTS

The study included 645 patients enrolled in the National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Clinical Network trial of lower tidal volumes compared with traditional tidal volumes for ALI.

MEASUREMENTS AND MAIN RESULTS

Baseline plasma levels of G-CSF were associated with an increased risk of death and a decrease in ventilator-free days and organ failure-free days in multivariate analyses controlling for ventilation strategy, age, and sex (Odds ratio death 1.2/log10 increment G-CSF, 95% confidence interval 1.01 to 1.4). Stratification of G-CSF levels into quartiles revealed a strong association between the highest levels of G-CSF and an increased risk of death and decreased ventilator-free days and organ failure-free days in multivariate analyses controlling for ventilation strategy, Acute Physiology and Chronic Health Evaluation III score, Pao2/Fio2 ratio, creatinine, and platelet count (p < 0.05). Subgroup multivariate analysis of patients with sepsis as their risk factor for ALI revealed a U-shaped association between mortality and G-CSF levels such that risk increased linearly from the second through fourth (highest) quartiles, yet also increased in the first (lowest) quartile. G-CSF levels decreased over time in both tidal volume groups, and there was no statistical difference in the extent of decrease between ventilator strategies.

CONCLUSIONS

In patients with ALI, plasma G-CSF levels are associated with morbidity and mortality, but these levels are not influenced by tidal volume strategy. In patients with sepsis-related ALI, a bimodal association between baseline plasma G-CSF levels and subsequent morbidity and mortality from this disease was found.

Hypercapnic acidosis attenuates severe acute bacterial pneumonia-induced lung injury by a neutrophil-independent mechanism

OBJECTIVE

Deliberate induction of hypercapnic acidosis protects against lung injury after nonseptic lung injury. In contrast, concerns exist regarding the effects of hypercapnic acidosis in the setting of severe pulmonary sepsis. The potential for the effects of hypercapnic acidosis to be neutrophil-mediated remains to be determined. We investigated whether hypercapnic acidosis--induced by adding CO2 to inspired gas--would protect against severe acute lung injury induced by pulmonary Escherichia coli instillation and the role of neutrophils in mediating this effect.

DESIGN

Prospective randomized animal study.

SETTING

University Research Laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

In series 1, after induction of anesthesia and tracheostomy placement, animals were randomized to normocapnia (FICO2 0.00, n = 12) or hypercapnic acidosis (FICO2 0.05, n = 12). E. coli (0.5-3.0 x 10(15) colony-forming units) was instilled intratracheally and the animals were ventilated for 6 hrs to allow a severe acute lung injury to evolve. In series 2, animals were randomized to neutrophil depletion or nondepletion before bacterial instillation, in a three-group design: normocapnia alone (Normo + polymorphonuclear neutrophils [PMN], n = 9), normocapnia with neutrophil depletion (Normo - PMN, n = 9), or hypercapnic acidosis with neutrophil depletion (hypercapnic acidosis - PMN, n = 9). After intratracheal E. coli administration these animals were also ventilated for 6 hrs.

RESULTS

Hypercapnic acidosis protected against evolving pneumonia-induced acute lung injury, attenuating the increase in airway pressure, and the decrement in lung compliance and arterial PO2. However, hypercapnic acidosis did not reduce histologic injury. Hypercapnic acidosis also protected against evolving pneumonia-induced acute lung injury in the presence of neutrophil depletion, reducing both physiologic and histologic indices of lung injury.

CONCLUSIONS

Hypercapnic acidosis reduces indices of intratracheal E. coli induced lung injury by a mechanism that seems to be neutrophil-independent.

Priming of the neutrophil NADPH oxidase activation: role of p47phox phosphorylation and NOX2 mobilization to the plasma membrane

Neutrophils play an essential role in host defense against microbial pathogens and in the inflammatory reaction. Upon activation, neutrophils produce superoxide anion (O*2), which generates other reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), hydroxyl radical (OH*) and hypochlorous acid (HOCl), together with microbicidal peptides and proteases. The enzyme responsible for O2* production is called the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase or respiratory burst oxidase. This multicomponent enzyme system is composed of two trans-membrane proteins (p22phox and gp91phox/NOX2, which form the cytochrome b558), three cytosolic proteins (p47phox, p67phox, p40phox) and a GTPase (Rac1 or Rac2), which assemble at membrane sites upon cell activation. NADPH oxidase activation in phagocytes can be induced by a large number of soluble and particulate factors. Three major events accompany NAPDH oxidase activation: (1) protein phosphorylation, (2) GTPase activation, and (3) translocation of cytosolic components to the plasma membrane to form the active enzyme. Actually, the neutrophil NADPH oxidase exists in different states: resting, primed, activated, or inactivated. The resting state is found in circulating blood neutrophils. The primed state can be induced by neutrophil adhesion, pro-inflammatory cytokines, lipopolysaccharide, and other agents and has been characterized as a "ready to go" state, which results in a faster and higher response upon exposure to a second stimulus. The active state is found at the inflammatory or infection site. Activation is induced by the pathogen itself or by pathogen-derived formylated peptides and other agents. Finally, inactivation of NADPH oxidase is induced by anti-inflammatory agents to limit inflammation. Priming is a "double-edged sword" process as it contributes to a rapid and efficient elimination of the pathogens but can also induce the generation of large quantities of toxic ROS by hyperactivation of the NADPH oxidase, which can damage surrounding tissues and participate to inflammation. In order to avoid extensive damage to host tissues, NADPH oxidase priming and activation must be tightly regulated. In this review, we will discuss some of the mechanisms of NADPH oxidase priming in neutrophils and the relevance of this process to physiology and pathology.

Endotoxin priming of neutrophils requires NADPH oxidase-generated oxidants and is regulated by the anion transporter ClC-3

Several soluble mediators, including endotoxin, prime neutrophils for an enhanced respiratory burst in response to subsequent stimulation. Priming of neutrophils occurs in vitro, and primed neutrophils are found in vivo. We previously localized the anion transporter ClC-3 to polymorphonuclear leukocytes (PMN) secretory vesicles and demonstrated that it is required for normal NADPH oxidase activation in response to both particulate and soluble stimuli. We now explore the contribution of the NADPH oxidase and ClC-3 to endotoxin-mediated priming. Lipooligosaccharide (LOS) from Neisseria meningitidis enhances the respiratory burst in response to formyl-Met-Leu-Phe, an effect that was impaired in PMNs lacking functional ClC-3 and under anaerobic conditions. Mobilization of receptors to the cell surface and phosphorylation of p38 MAPK by LOS were both impaired in PMN with the NADPH oxidase chemically inhibited or genetically absent and in cells lacking functional ClC-3. Furthermore, inhibition of the NADPH oxidase or ClC-3 in otherwise unstimulated cells elicited a phenotype similar to that seen after endotoxin priming, suggesting that basal oxidant production helps to maintain cellular quiescence. In summary, NADPH oxidase activation was required for LOS-mediated priming, but basal oxidants kept unstimulated cells from becoming primed. ClC-3 contributes to both of these processes.

Pulmonary stromal-derived factor-1 expression and effect on neutrophil recruitment during acute lung injury

The severe and protracted inflammation that characterizes acute lung injury (ALI) is driven by the ongoing recruitment of neutrophils to the lung. Although much of the cytokine signaling responsible for the initial phase of ALI has been elaborated, relatively little is known about the mechanisms governing the recruitment of neutrophils from the bone marrow to the lung in the later period of this disease. Given its previously described chemoattractant effects on marrow neutrophils, we investigated whether stromal-derived factor-1 (SDF-1) (CXCL12) might participate in this later phase of recruitment. Using immunohistochemistry to examine both banked human lung specimens from patients with ALI and lungs from mice with LPS-induced pneumonitis, we found that pulmonary SDF-1 expression increases during ALI. We further determined that both lung SDF-1 protein expression and mRNA expression rise in a delayed but sustained pattern in this mouse model and that the major source of the increase in expression appears to be the lung epithelium. Lastly, we found that expression of the SDF-1 receptor CXCR4 rises in a similar temporal pattern on neutrophils in both the blood and airspace of LPS-injured mice and that Ab-mediated SDF-1 blockade significantly attenuates late but not early pulmonary neutrophilia in this model. These results implicate SDF-1 in neutrophil recruitment to the lung in the later period of acute lung injury and suggest a novel role for this cytokine in coordinating the transition from the inflammatory response to the initiation of tissue repair.

Severe X-linked chronic granulomatous disease in two unrelated females

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency caused by mutations of one of the subunits of phagocyte reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase leading to decreased or complete absence of neutrophil oxidative burst. We report the clinical and laboratory findings in two young unrelated females 14 and 9 years of age and natives of Tahiti and Reunion Islands, respectively, with severe X-linked granulomatous disease. In both cases, the infectious pattern was unusual, with convergent symptoms suggesting underlying mycobacterial infection. Functional analysis revealed low residual NADPH oxidase activity with about 5-10% of normal neutrophil population. De novo null mutations affecting the CYBB gene that encodes the gp91 protein were found in both cases in the heterozygous state (in patient 1, p.Arg130X in exon 5, and in patient 2, a novel insertion in exon 6, c.632_633insCATC). Methylation analysis confirmed that phenotype expression was linked to skewed X inactivation and showed that the de novo mutation arose on the maternally inherited chromosome in one case and on the paternally inherited chromosome in the other case. In conclusion, X-linked CGD carriers could therefore be at risk for severe infectious diseases depending on the skewed X inactivation pattern and the infectious context.

Ventilator-associated pneumonia: diagnosis, treatment, and prevention

While critically ill patients experience a life-threatening illness, they commonly contract ventilator-associated pneumonia. This nosocomial infection increases morbidity and likely mortality as well as the cost of health care. This article reviews the literature with regard to diagnosis, treatment, and prevention. It provides conclusions that can be implemented in practice as well as an algorithm for the bedside clinician and also focuses on the controversies with regard to diagnostic tools and approaches, treatment plans, and prevention strategies.

Isolation of neutrophils from mouse liver: A novel method to study effector leukocytes during inflammation

Neutrophils are phagocytic leukocytes that represent one of the first lines of defense during infection and injury. Neutrophils emigrate into tissues during inflammation and are phenotypically different compared to cells in the circulation. To further understand the biology of tissue-recruited neutrophils, we have developed a reliable method to isolate these cells from inflamed liver. Acute liver inflammation was induced in mice by systemic treatment with adenovirus vectors. Two hours following adenovirus treatment, livers were enzymatically digested and leukocytes isolated by Percoll density gradient centrifugation. Neutrophils were then purified by negative immunomagnetic separation. Neutrophils isolated in this manner were 95% pure as determined by flow cytometry and more than 97% viable by propidium iodide staining. In order to carry out molecular studies, we extracted high quality genomic DNA and RNA from isolated neutrophils. PCR was used to successfully amplify sample genes from isolated neutrophil DNA. Isolated neutrophil RNA was used in a ribonuclease protection assay to evaluate chemokine gene expression. Neutrophils were shown to express multiple chemokine mRNA transcripts including MIP-1 beta, MIP-2 and IP-10. This work describes a novel method to isolate highly pure, viable neutrophils from pathologically inflamed tissue for subsequent detailed cellular and molecular analysis.

Protective role of metallothionein in acute lung injury induced by bacterial endotoxin

BACKGROUND

Metallothionein (MT) is a protein that can be induced by inflammatory mediators and participate in cytoprotection. However, its role in inflammation remains to be established. A study was undertaken to determine whether intrinsic MT protects against acute inflammatory lung injury induced by bacterial endotoxin in MT-I/II knock out (-/-) and wild type (WT) mice.

METHODS

MT (-/-) and WT mice were given vehicle or lipopolysaccharide (LPS, 125 microg/kg) intratracheally and the cellular profile of the bronchoalveolar lavage (BAL) fluid, pulmonary oedema, lung histology, expression of proinflammatory molecules, and nuclear localisation of nuclear factor-kappaB (NF-kappaB) in the lung were evaluated.

RESULTS

MT (-/-) mice were more susceptible than WT mice to lung inflammation, especially to lung oedema induced by intratracheal challenge with LPS. After LPS challenge, MT deficiency enhanced vacuolar degeneration of pulmonary endothelial cells and type I alveolar epithelial cells and caused focal loss of the basement membrane. LPS treatment caused no significant differences in the enhanced expression of proinflammatory cytokines and chemokines nor in the activation of the NF-kappaB pathway in the lung between the two genotypes. Lipid peroxide levels in the lungs were significantly higher in LPS treated MT (-/-) mice than in LPS treated WT mice.

CONCLUSIONS

Endogenous MT protects against acute lung injury related to LPS. The effects are possibly mediated by the enhancement of pulmonary endothelial and epithelial integrity, not by the inhibition of the NF-kappaB pathway.

Effect of 15-deoxy-delta 12,14-prostaglandin J2 on acute lung injury induced by lipopolysaccharide in mice

15-Deoxy-delta(12,14)-prostaglandin J(2) (15d-prostaglandin J(2)) has received attention for its anti-inflammatory properties. The present study investigated the efficacy of 15d-prostaglandin J(2) on acute lung injury induced by lipopolysaccharide in mice. ICR mice were administered with 15d-prostaglandin J(2) (10 microg/kg, 100 microg/kg, or 1 mg/kg) before intratracheal challenge with lipopolysaccharide (125 microg/kg). Treatment with 15d-prostaglandin J(2) did not ameliorate rather enhanced at a dose of 1 mg/kg the neutrophilic lung inflammation and pulmonary edema by lipopolysaccharide. The enhancement was concomitant with the increased lung expression of interleukin-1 beta, macrophage inflammatory protein-1 alpha, and macrophage chemoattractant protein-1. 15d-prostaglandin J(2) increased the nuclear protein expression of peroxisome proliferator-activated receptor (PPAR)-gamma and inhibited the nuclear localization of nuclear factor-kappa B related to lipopolysaccharide. 15d-prostaglandin J(2) increased the phosphorylation of c-Jun in the presence or absence of lipopolysaccharide. Our data suggest that 15d-prostaglandin J(2) may not be useful but potentially harmful for the therapeutic option of acute lung injury.

Cytokine-mediated inflammation in acute lung injury

Clinical acute lung injury (ALI) is a major cause of acute respiratory failure in critically ill patients. There is considerable experimental and clinical evidence that pro- and anti-inflammatory cytokines play a major role in the pathogenesis of inflammatory-induced lung injury from sepsis, pneumonia, aspiration, and shock. A recent multi-center clinical trial found that a lung-protective ventilatory strategy reduces mortality by 22% in patients with ALI. Interestingly, this protective ventilatory strategy was associated with a marked reduction in the number of neutrophils and the concentration of pro-inflammatory cytokines released into the airspaces of the injured lung. Further research is needed to establish the contribution of cytokines to both the pathogenesis and resolution of ALI.

Distinct ligand-dependent roles for p38 MAPK in priming and activation of the neutrophil NADPH oxidase

In response to certain cytokines and inflammatory mediators, the activity of the neutrophil NADPH oxidase enzyme is primed for enhanced superoxide production when the cells receive a subsequent oxidase-activating stimulus. The relative role of p38 MAPK in the priming and activation processes is incompletely understood. We have developed a 2-step assay that allows the relative contributions of p38 MAPK activity in priming to be distinguished from those involved in oxidase activation. Using this assay, together with in vitro kinase assays and immunochemical studies, we report that p38 MAPK plays a critical role in TNFalpha priming of the human and porcine NADPH oxidase for superoxide production in response to complement-opsonized zymosan (OpZ), but little, if any, role in neutrophil priming by platelet-activating factor (PAF) for OpZ-dependent responses. The OpZ-mediated activation process per se is independent of p38 MAPK activity, in contrast to oxidase activation by fMLP, where 70% of the response is eliminated by p38 MAPK inhibitors regardless of the priming agent. We further report that incubation of neutrophils with TNFalpha results in the p38 MAPK-dependent phosphorylation of a subpopulation of p47(phox) and p67(phox) molecules, whereas PAF priming results in phosphorylation only of p67(phox). Despite these phosphorylations, TNFalpha priming does not result in significant association of either of these oxidase subunits with neutrophil membranes, demonstrating that the molecular basis for priming does not appear to involve preassembly of the NADPH oxidase holoenzyme/cytochrome complex prior to oxidase activation.

[A new role for neutrophils during sepsis: target and source of interleukin-12]

The immune response against a bacterial aggression involves the monocytes-macrophages and polymorphonuclear neutrophils (PMN) in the first line of defense. This natural or innate immunity controls the proliferation of micro-organisms while waiting for the development of aspecific immunity related to lymphocytes. Establishing a link between innate and specific immunity, interleukin-12 (IL-12) is an essential cytokine of the inflammatory response. In a first in vitro study, we showed that IL-12 potentiates the effect of LPS on the production of IL-8 by stimulated PMN, the main chemotactic and activating cytokine of neutrophils. IL-12 would thus support the local recruitment of PMN via an autocrine loop of amplification. In a second in vivo study in septic patients, we noted a defect in the pulmonary and systemic production of IL-12, suggesting a dysregulation of innate immunity during the course of sepsis.

Vascular endothelial growth factor VEGF189 induces human neutrophil chemotaxis in extravascular tissue via an autocrine amplification mechanism

Vascular endothelial growth factor (VEGF) is a potent and specific endothelial cell mitogen involved in normal and pathological angiogenesis. Our group recently reported that, among the several VEGF isoforms, VEGF189 (V189) is selectively induced in decidual endometrial cells during the mid-late phase of the menstrual cycle, together with polymorphonuclear neutrophil (PMN) influx. We thus compared the effects of various VEGF isoforms on PMN migration in vitro, and the mechanisms involved. In transmigration and under-agarose assays, V189 was both chemotactic and chemokinetic for PMN, while VEGF165 (V165) was only chemokinetic. The chemokinetic effect of V189 for PMN was blocked by neutralizing anti-VEGF antibodies, but not by neutralizing anti-KDR antibodies, suggesting that the Flt-1 VEGF receptor that is expressed in PMN mediates these effects. Flow cytometric analysis of several adhesion molecules at the PMN surface showed that all VEGF isoforms slightly upregulated beta1- and beta2-integrins and PECAM, and downregulated L-selectin; all these molecules are activation markers. The involvement of beta1-integrins was further supported by the ability of blocking antibodies to reduce VEGF-induced PMN migration. As human PMN can secrete several cytokines and growth factors, the selective secretion of VEGF isoforms was also further examined. RT-PCR analysis showed that V165 mRNA was more strongly expressed than V189 mRNA. Conversely, the major protein isoform secreted after optimal PMN degranulation was V189, which was located in both azurophilic and specific granules. PMN-derived VEGF can thus modulate PMN migration. This autocrine amplification mechanism would allow sustained VEGF release to occur at inflammatory sites, and may contribute to both normal and pathological angiogenesis.

The Effects of S(???)-, R(+)-, and Racemic Bupivacaine on Lysophosphatidate-Induced Priming of Human Neutrophils

Local anesthetics modulate inflammatory responses and may therefore be potentially useful in mitigating perioperative inflammatory injury. The inflammatory modulating effects of S(-)-bupivacaine are not known. Therefore, we compared the effects of S(-)-bupivacaine, R(+)-bupivacaine, and racemic bupivacaine on neutrophil function and receptor signaling. Priming (by lysophosphatidic acid [LPA]) and activation (by N-formylmethionine-leucyl-phenylalanine) of superoxide release by isolated human neutrophils was studied by using a cytochrome c-reduction assay. LPA receptor signaling in Xenopus oocytes was studied by using voltage clamp. All three local anesthetics were without effect on activation. S(-)-Bupivacaine inhibited priming more than did racemic bupivacaine; R(+)-bupivacaine was without effect. At 10(-4) M, S(-)-bupivacaine inhibited approximately 50%. Comparable results were obtained in our recombinant model, where S(-)-bupivacaine most effectively inhibited LPA signaling. Compared with racemic bupivacaine and other anesthetics, S(-)-bupivacaine appears particularly effective in suppressing neutrophil priming, a process responsible in part for the overactive neutrophil response.

IMPLICATIONS

Overactive inflammatory responses underlie several perioperative disorders. Compared with racemic bupivacaine and other anesthetics, S(-)-bupivacaine appears particularly effective in suppressing neutrophil priming, a process responsible in part for the overactive neutrophil response.

Deactivation of alveolar macrophages in septic neutropenic ARDS

STUDY OBJECTIVES

Neutrophils often have been involved in the pathophysiology of ARDS. However, authentic ARDS has been described in patients with severe neutropenia, suggesting the presence of other potential mechanisms that are responsible of this syndrome. Alveolar macrophages (AMs) could be involved in the development of ARDS, and so we decided to study AM activation in neutropenic patients.

PATIENTS

We designed a prospective study and enrolled two subgroups of consecutive patients (group A, 18 patients; group B, 22 patients) with septic ARDS. In the first period, 7 of 18 patients were neutropenic, and in the second period 10 of 22 patients were neutropenic. All neutropenic patients were treated with granulocyte colony-stimulating factor (G-CSF).

MEASUREMENTS AND RESULTS

In group A, BAL fluid samples were analyzed for differential and total cell counts, and alveolar activation marker expression (ie, human leukocyte antigen [HLA]-DR locus) was determined. Basal and lipopolysaccharide (LPS)-stimulated production of tumor necrosis factor, interleukin (IL)-1 beta, IL-6, and IL-10 was evaluated in group B. In neutropenic patients, the BAL fluid total cell count and the neutrophil absolute count was significantly lower compared to those in nonneutropenic patients (p = 0.029 and p = 0.046, respectively). HLA-DR expression on AMs was significantly decreased (p = 0.016), and the percentage of AMs expressing HLA-DR was also significantly lower (p = 0.041). In neutropenic patients, the mean percentage of AMs expressing HLA-DR was significantly lower in deceased patients compared to survivors (30 +/- 7 vs 43 +/- 1, respectively; p = 0.047). Basal AMs released cytokines was comparable between the two groups; however, LPS stimulation yielded a deactivation of AMs in neutropenic patients.

CONCLUSION

These results suggest a deactivation and/or hypoactivation of AMs in septic ARDS patients. This deactivation/hypoactivation could be linked to the use of G-CSF as this molecule has been shown to generate a down-regulation of HLA-DR expression.

Enteral nutrition with eicosapentaenoic acid, gamma-linolenic acid, and antioxidants reduces alveolar inflammatory mediators and protein influx in patients with acute respiratory distress syndrome

OBJECTIVE

Previously, we showed that acute respiratory distress syndrome patients fed an enteral diet containing eicosapentaenoic acid and gamma-linolenic acid and elevated antioxidants (EPA+GLA; Oxepa) had significantly reduced pulmonary inflammation, increased oxygenation, and improved clinical outcomes. In a subset of acute respiratory distress syndrome patients from this trial, we performed a preliminary examination of the potential mechanisms underlying these clinical improvements by retrospectively testing the hypothesis that enteral feeding with EPA+GLA could reduce alveolar-capillary membrane protein permeability and the production of interleukin (IL)-8, IL-6, tumor necrosis factor-alpha, and leukotriene B4 that are responsible, in part, for pulmonary inflammation.

DESIGN

Prospective, randomized, double-blind, controlled clinical trial.

SETTING

Intensive Care Unit of the Ohio State University Medical Center.

PATIENTS

A total of 67 patients were enrolled who met defined criteria for acute lung injury/acute respiratory distress syndrome.

INTERVENTIONS

A total of 43 of 67 evaluable patients randomly received either EPA+GLA or an isonitrogenous, isocaloric standard diet that was tube fed at a minimum caloric delivery of 75% of basal energy expenditure times 1.33 for at least 4 to 7 days.

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavage (BAL) was performed at baseline and study days 4 and 7 to obtain BAL fluid (BALF) for measurement of total protein, ceruloplasmin, and transferrin, total neutrophil count, IL-8, IL-6, tumor necrosis factor-alpha, and leukotriene B4. Oxygenation, measured as Pao2/Fio2, was assessed before BAL. Patients fed EPA+GLA had a significant reduction in BALF ceruloplasmin and IL-8 during the study as compared with patients fed the control diet. BALF levels of total protein, neutrophils, and leukotriene B4 tended to decrease in EPA+GLA patients over the course of the study as compared with control patients. BALF levels of IL-6 declined similarly during the study in both groups. A trend toward a reduction in BALF tumor necrosis factor-alpha was observed on study day 7 in the EPA+GLA group as compared with control patients. Significant improvements in oxygenation (Pao2/Fio2) occurred in EPA+GLA patients on study day 4 as compared with controls. Correlation analysis revealed significant relationships between BALF neutrophil counts and indices of alveolar-capillary membrane protein permeability, IL-8, and leukotriene B4.

CONCLUSIONS

This preliminary investigation showing a decrease in BALF levels of IL-8 and leukotriene B4 and the associated reduction of BALF neutrophils and alveolar membrane protein permeability in acute respiratory distress syndrome patients fed EPA+GLA support, in part, the potential mechanisms underlying the previously described clinical improvements with this diet. Additional controlled studies are needed to confirm these findings.

Oncostatin M production by blood and alveolar neutrophils during acute lung injury

Polymorphonuclear neutrophils (PMN) are involved in the pathogenesis of acute lung injury (ALI), secreting numerous mediators such as proteases, reactive oxygen species, and cytokines. Because we had recently observed the ability of normal human PMN to degranulate and synthesize oncostatin M (OSM), an IL-6-family cytokine, we quantified OSM production ex vivo by highly purified blood and alveolar PMN from 24 ventilated patients with ALI, including some patients with severe pneumonia. Most of the patients had no detectable OSM in plasma, and OSM production by cultured blood PMN was similar to that of healthy controls. However, OSM was present in bronchoalveolar lavage (BAL) fluid supernatant, with significantly higher levels during pneumonia. In addition, alveolar OSM levels correlated with the number of PMN obtained by BAL, suggesting that PMN are an important source of OSM within the alveoli. Indeed, purified alveolar PMN from all of the patients, especially those with pneumonia, strongly produced OSM. Interestingly, in the latter patients, alveolar PMN always produced more OSM than autologous blood PMN. These results document the functional duality of PMN in ALI by showing the participation of PMN in the modulation of lung inflammation.

Oxidant-increased endothelial permeability: prevention with phosphodiesterase inhibition vs. cAMP production

The present objective was to determine whether hydrogen peroxide (H(2)O(2)) increases transvascular albumin clearance and lung weight in an isolated rat lung and whether posttreatment with cAMP-enhancing agents can prevent these increases. Transvascular albumin clearance was assessed by (125)I-labeled albumin clearance ((125)I-albumin flux/perfusate concentration of (125)I-albumin) at a given fluid filtration. Nonlinear regression analysis of transvascular albumin clearance vs. fluid filtration yielded values for the permeability-surface area product (PS) and the reflection coefficient (sigma). H(2)O(2) decreased sigma from a control value of 0.93 to 0.38, did not change PS, and increased lung weight. Posttreatment with isoproterenol, a beta(2)-adrenergic-receptor agonist, reduced the H(2)O(2)-induced decrease in sigma to 0.65 and augmented the increase in lung weight. Posttreatment with CP-80633, a phosphodiesterase 4 inhibitor, further reduced the H(2)O(2)-induced decrease in sigma to 0.79 and blocked the rise in lung weight. In the presence of isoproterenol or CP-80633, H(2)O(2) increased PS. Therefore, H(2)O(2) increased the convective and diffusive clearances of albumin across an intact pulmonary vasculature. Furthermore, inhibition of cAMP metabolism more effectively attenuated the H(2)O(2)-induced increases in convective albumin clearance and lung weight as compared with stimulation of cAMP production.

Adrenaline upregulates monocyte L-selectin in vitro

OBJECTIVE

Although surface adhesion molecules mediate leucocyte-endothelial interactions at sites of inflammation, relatively little is known of the factors which increase the expression of L-selectin in circulating leucocytes. The expression of leucocyte L-selectin increases during acute stress events such as injury and is temporally related to an early neuroendocrine response. This study investigates whether adrenaline increases the expression of L-selectin on monocytes, neutrophils and lymphocytes in vitro and whether these effects are mediated via beta-adrenoceptors.

METHODS

A total of 20 ml of blood was withdrawn from 28 healthy volunteers (21 males) with a mean age of 29 years (range 23-67 years). Adrenaline at physiological doses mimicking trauma (0-200 nmol/l) was added to whole blood prior to immunofluorescent staining and analysis by flow cytometry. Propranolol (50 microl of 2 x 10(-5) M) was also added to separate tubes prior to incubation with adrenaline. Saline (40 microl 0.9% solution) was used as a control. Expression is described firstly as percentage of cells expressing L-selectin and secondly as average intensity (mean channel fluorescence, mcf) per cell expressing CD62L. Summary measures were used to analyse the data.

RESULTS

A significant increase in both the percentage of monocytes expressing L-selectin and mean channel fluorescence of L-selectin was evident with adrenaline in vitro (P < 0.0001). Maximal increases occurred at 100 nmol/l adrenaline when a 9% increase in the percentage of monocytes expressing L-selectin and a 23% increase in mean channel fluorescence were observed. These effects were both blocked by propranolol (P < 0.0001). No significant differences were observed for neutrophils or lymphocytes except for a slight increase in the percent neutrophils expressing L-selectin, and a small decreasing trend in percent lymphocytes expressing L-selectin.

CONCLUSIONS

Adrenaline upregulates the surface expression of L-selectin on monocytes in vitro, an effect which is partially mediated by beta-adrenoceptors. As monocytes initiate early aspects of the inflammatory response, these findings suggest that beta-blockade may have an inhibitory role for certain aspects of leucocyte trafficking.